Analysis and Processing of Low Quality Indigenous Coals for Clean Energy

Home , Coal refuse, Coal slurry, Coal tar, Energy value of coal, Flue gas

ANALYSIS AND PROCESSING OF LOW QUALITY INDIGENOUS COALS FOR CLEAN ENERGY

A thesis submitted

UNIVERSITY OF THE PUNJAB

fulfillment of the requirement for the degree

DOCTOR OF PHILOSOPHY

CHEMISTRY

MUHAMMAD AKBAR

2019

INSTITUTE OF CHEMISTRY UNIVERSITY OF THE PUNJAB LAHORE (PAKISTAN) APPROVAL CERTIFICATE

It is hereby certified that thesis entitled “Analysis and Processing of Low Quality Indigenous Coals for Clean Energy” is based on the results of experiments carried out by Mr. Muhammad Akbar and it has not been previously presented for Ph.D Degree. Mr. Muhammad Akbar has done this research work under my supervision. He has fulfilled all the requirements and is qualified to submit the accompanying thesis for the Degree of Doctor of Philosophy in Chemistry.

Research Supervisor: ______Dr. Muhammad Abdul Qadir Director, Institute of Chemistry, University of the Punjab, Lahore.

Co- Supervisor: ______Dr. Ahmad Adnan Chairman, Department of Chemistry, Government College University, Lahore.

DECLARATION

I, Muhammad Akbar, declare that this dissertation, submitted in fulfillment of the requirement for the award of Doctor of Philosophy, in the Institute of Chemistry, University of the Punjab, is wholly my own work unless otherwise referenced or acknowledged. The document has not been submitted for qualification at any other academic institution.

Muhammad Akbar

DEDICATION

Dedicated to

My Parents

ACKNOWLEDGEMENT

All praise for Almighty Allah alone, the most merciful and compassionate, source of all knowledge and wisdom and creator of the universe with its mysteries of logic. I offer my humblest and sincere words of thanks to Holy prophet Muhammad (SAW) who is the fountain-hearted of every grace for enlightening my conscience with essence of faith and knowledge.

My Profound gratitude is reserved for my supervisor, Dr. Muhammad Abdul Qadir

(Director, Institute of Chemistry, University of the Punjab, Lahore) for providing tremendous insight, guidance and precious suggestions. He has been very kind, and affectionate during the whole research period.

I am really obliged to my respected co-supervisor Dr. Ahmad Adnan (Chairman Department of Chemistry, Government College University, Lahore).His precious suggestions and consistent support helped me a lot to accomplish this task. I am also obliged to Director center of coal technology for providing me the facility of coal analysis .My special words of thanks go to my friend Dr.Waqar Nasir whose extraordinary support remained throughout my studies. I am also thankful to my friends, Dr Muhammad Liaqat, Mr. Haroon Rasheed, Mr. Muhammad Tayyab for their cooperation during my research. My thanks are also to lab. staff especially Muhammad Akram, for providing me lab facilities. I would also specially like to thank to my research fellows Dr. Hajira Rehman and Tanzeela

Shahzadi who remained supportive and co-operative during whole of my research work.

My warmest gratitude goes to my wife, my sons Nouman Akbar, Arsalan Akbar, Hafiz

Muhammad Rizwan Akbar, Tayyab Akbar and my daughter Hafiza Maryam Akbar. I am highly obliged to my elder brothers Muhammad Bashir Aasi and Muhammad Nazir who always supported and encouraged me and my sisters for their love and support .

Muhammad Akbar

TABLE OF CONETNTS CHAPTER No. 1

INTRODUCTION

1.1 The Physical and Chemical Composition of Coal ...... 1

1.2 Formation of coal ...... 1

1.3 Coal Distribution in Pakistan ...... 6

1.4 Uses of Coal ...... 7

1.5 Toxic Effects of Heavy Metals...... 10

1.5.1 Lead...... 10

1.5.2 Mercury ...... 11

1.5.3 Arsenic ...... 11

1.5.4 Cadmium ...... 12

1.5.5 Nickel ...... 13

1.5.6 Copper ...... 14

1.5.7 Chromium ...... 15

1.5.8 Iron ...... 15

1.5.9 Zinc ...... 16

1.6 Desulfurization of Coal ...... 16

1.6.1 Peroxyacetic acid ...... 17

1.6.2 Sodium Hypochlorite ...... 18

1.6.3 Potassium Permanganate ...... 18

1.6.4 Supercritical Fluid Extraction ...... 19

1.6.5 IGT Hydrodesulphurization ...... 19

1.6.6 Magnex Process ...... 19

1.6.7 Chlorinolysis ...... 20

1.6.8 Ferric Chloride ...... 20

1.6.9 Meyers Process ...... 20 1.6.10 Oxydesulphurization ...... 21

1.6.11 Microwave Desulphurization, ...... 21

1.6.12 Sulphur removal by electrolysis...... 21

1.6.13 Microbial Desulfurization ...... 21

1.7 Gasification process ...... 31

1.7.1 Chemical Reactions Involved In Gasification ...... 32

1.7.2 Types of gasifiers ...... 33

1.8 Liquefaction of Coal...... 35

1.8.1 Pyrolysis ...... 35

1.8.2 Direct coal liquefaction ...... 36

1.8.3 Indirect coal liquefaction ...... 36

1.8.4 Bio liquefaction ...... 36

1.8.5 Comparison of DCL and ICL ...... 37

1.9 Aim of present study ...... 39

CHAPTER No.2

EXPERIMENTAL SECTION

2.1 Materials ...... 40

2.2 Analysis ...... 40

2.2.1 Proximate analysis and calorific value determination ...... 40

2.2.2 Moisture content ...... 40

2.2.3 Volatile matter ...... 40

2.2.4 Ash content ...... 41

2.2.5 Fixed carbon...... 41

2.2.6 Calorific value ...... 41

2.2.7 Determination of total Sulfur (Eschka Method) ...... 41

2.2.8 Determination of Sulfate Sulfur ...... 42

2.2.9 Determination of pyritic Sulfur ...... 42 2.2.10 Determination of Organic Sulfur ...... 43

2.2.11 Determination of oxygen content ...... 43

2.2.12 Trace Metal Analysis ...... 43

2.3 Desulphurization of Coal ...... 43

2.3.1 Sulphur leaching with strong acids or alkalis ...... 43

2.3.2 Bio-desulphurization ...... 43

2.3.3 Microorganism ...... 43

2.3.4 Isolation of Ferrous-oxidizing Bacteria ...... 43

2.3.5 Media and conditions of cultivation ...... 44

2.3.6 Methods of bacterial leaching: ...... 44

2.3.7 Determination of Bacterial Biomass ...... 45

2.4 Electrolysis of Coal Slurries ...... 45

2.4.1 Electrolysis of Coal Under Acidic Conditions...... 45

2.4.2 Electrolysis of Lignite Under Alkaline Conditions ...... 45

CHAPTER 3

RESULTS AND DISCUSSION

3.1 Proximate composition of coal ...... 47

3.2 Trace metals content of Coal ...... 47

3.3 Heavy metal Composition of Coal ...... 61

3.4 Removal of sulphur from coal ...... 62

3.4.1 Sulphur leaching with strong acids and alkalis ...... 62

3.4.2 Bioleaching ...... 62

3.4.2.1 Microorganism ...... 63

3.4.2.2 Fermenter ...... 63

3.5 Electrolysis of Coal Slurries ...... 65

3.5.1 Electrolysis of Coal under Acidic Conditions ...... 65

3.5.2 Electrolysis of Lignite Under Alkaline Conditions ...... 80 3.6 Experimental conditions for Electrolysis of coal slurries ...... 97

3.6.1 Electrolysis of Coal under Acidic Conditions ...... 97

3.7 Conclusions ...... 99

REFERENCE

References ...... 100

LIST OF FIGURES Figure 1.1: Location of different coal types...... 1

Figure 1.2: Structure of coal...... 4

Figure 1.3: Hypothetical structure of Lignite...... 5

Figure 1.4: Coal Distribution in Pakistan...... 6

Figure 1.5a: Present Sources of Heat & Power Worldwide ...... 9

Figure 1.5b: Present Sources of Heat and Power in Pakistan...... 9

Figure 1.6: Basic procedure of KMnO4 desulfurization of coal (Attia and Fung, 1993) .... 19

Figure 1.7a: Benzothiophene desulphurization path way (Gilbert et al., 1998)...... 30

Figure 1.7b: 4S Pathway of DBT desulphurization path way (Bresseler et al., 1998)...... 31

Figure 1.8: Gasification reactions...... 33

Figure 3.1: Average percentage moisture content, ash content, volatile matter and fixed Carbon in Duki Coal (Baluchistan), Chamalang Coal (Baluchistan) and Salt Range Coal (Punjab)...... 49

Figure 3.2: Average calorific value (kcal/kg) of Duki, Chamalang coal (Baluchistan) and Salt Range coal (Punjab)...... 50

Figure 3.3: The average levels of trace metals in Duki, Chamalang coal (Baluchistan) and Salt Range coal (Punjab)...... 51

Figure 3.4: The levels of trace metals in Duki Coal (Baluchistan), Chamalang Coal (Baluchistan) and Salt Range Coal (Punjab) on average basis...... 60

Figure 3.5: A comparison predicted and observed values of Hydrogen (mL) ...... 66

Figure 3.6: A three dimension presentation of interaction between potential and temperature observed during the production of hydrogen ...... 68

Figure 3.7: A three dimension presentation of interaction between Ferric concentration and temperature observed during the production of hydrogen...... 69

Figure 3.8: A three dimension presentation of interaction between potential and Ferric concentration observed during the production of hydrogen...... 70

Figure 3.9: A three dimension presentation of interaction between potential and particle size observed during the production of hydrogen...... 71 Figure 3.10: A three dimension presentation of interaction between Ferric and particle size observed during the production of hydrogen...... 72

Figure 3.11: 3-Dimesional graph of interaction b/t Ferric concentration and particle size for the production of Carbon Dioxide...... 73

Figure 3.12: 3-Dimesional graph of interaction b/t potential and particle size for the production of Carbon dioxide ...... 74

Figure 3.13: Dimesional graph of interaction b/t Ferric Ferric concentration and potential for the production of Carbon Dioxide...... 75

Figure 3.14: 3-Dimesional graph of interaction b/t Ferric temperature and particle size for the production of Carbon dioxide...... 76

Figure 3.15: 3-Dimesional graph of interaction b/t Ferric concentration and temperature for the production of Carbon dioxide...... 77

Figure 3.16: 3-Dimesional graph of interaction b/t temperature and potential for the production of Carbon dioxide...... 78

Figure 3.18: A comparison predicted and observed values of Hydrogen (g) ...... 81

Figure 3.19: A three dimension presentation of interaction between potential and temperature observed during the production of hydrogen...... 83

Figure 3.20: A three dimension presentation of interaction between NaOH concentration and temperature observed during the production of hydrogen...... 84

Figure 3.21: A three dimension presentation of interaction between potential and particle size observed during the production of hydrogen...... 85

Figure 3.22: A three dimension presentation of interaction between potential and particle size observed during the production of hydrogen...... 86

Figure 3.23: A three dimension presentation of interaction between NaOH and particle size observed during the production of hydrogen...... 87

Figure 3.24: A three dimension presentation of interaction between potential and temperature observed during the production of humic acid...... 90

Figure 3.25: A three dimension presentation of interaction between NaOH and temperature observed during the production of humic acid...... 91 Figure 3.26: A three dimension presentation of interaction between temperature and particle size observed during the production of humic acid...... 92

Figure 3.27: A three dimension presentation of interaction between NAOH and potential observed during the production of humic acid...... 93

Figure 3.28: A three dimension presentation of interaction between Potential and Particle size observed during the production of humic acid...... 94

Figure 3.29: A three dimension presentation of interaction between Particle size and NaOH observed during the production of humic acid...... 95

Figure 3.30: Desirability ramp of most desirable solution...... 96

LIST OF TABLES Table 1.1: Maceral, Maceral Groups and Plant Component from which Macerals are derived...... 3 Table 1.2: Proximate and Ultimate Analysis for Lignite Coal...... 5 Table 1.3: Comparison of Arsenic retention for the two DECS coals in the PSIT drop tube experiments...... 12 Table 1.4: Bond Strengths in Selected compounds (Bresseler et al.,)...... 27 Table 1.5: Typical properties of DCL and ICL final products...... 38 Table 2.1: Isolation Medium ...... 44 Table 2.2: Basal Salt Solution ...... 44 Table 3.1: Proximate Composition of coal from Duki (Baluchistan)...... 52 Table 3.2: Proximate Composition of coal from Chamalang (Baluchistan) ...... 53 Table 3.3: Proximate Composition of Coal from Salt Range (Punjab)...... 54 Table 3.4: Trace metals Analysis of Coal sample from Duki Coal (Baluchistan)...... 55 Table 3.5 Trace metals content of understudy samples from Chamalang Coal (Baluchistan)...... 56 Table 3.6 Trace metals content of understudy samples from Salt Range Coal (Punjab). ... 57 Table 3.7: Comparison of trace metal content among Duki, Chamalang and Salt range coal with international coal...... 58 Table 3.8: Average values for trace elements in international coals...... 59 Table 3.9: Total sulphur leached...... 62 Table 3.10: Growth of Thiobacillus ferrooxidans ...... 63 Table 3.11: Sulphur leaching ...... 64 Table 3.12: The analysis of variance data for the production of hydrogen under given conditions 67 Table 3.13: The analysis of variance data for the production of hydrogen under given conditions 82 Table 3.14: Analysis of variance of for the production of humic acid ...... 88 Table 3.15: The experimental conditions investigated for the production of hydrogen and Carbon dioxide...... 97 Table 3.16: The experimental conditions investigated for the production of hydrogen and humic acid ...... 98

LIST OF ABBREVIATIONS

UNICEF United Nations International Children's Emergency Fund.

PCRWR Pakistan Council of Research in Water Resources

PHED Public Health Engineering Departmen

EPA Environmental Protection Agency

WHO World Health Organization

NEQS-Pak National Environmental Quality Standards

KPK Khyber PAkhtun khwa

RDA Recommended Dietary Allowance

IARC International Agency for Research on Cancer

NSDWQ-PaK National Standards for Drinking Water Quality Pakistan

EU European Union

GI Gestrointestinal

HDS Hydrodesulphurization

BTU British Thermal Unit

BT Benzothiopene

HBP o-Hydroxybiphenyl

DBT Dibenzothiophene

UCG Underground Coal Liquifaction

DCL Direct Coal Liquifaction

CTL Coal to Liquid

ABSTRACT

Coal is widely distributed on earth and has proven to be the cheapest source of energy and industrial and pharmaceutical raw material.. Pakistan has been gifted by nature by rich coal reserves especially in Thar area where coal reserves have been estimated to about 175 BT with overall coal reserves mounting to 185 BT. Unfortunately these reserves are of low rank , containing heavy metals and sulphur. Most of the Heavy metals are known carcinogen and do not have any harmless limit. These elements are thrown to the atmosphere during combustion and pollute the environment from air to soil. The present study is focused on the proximate analysis, desulphurization of coal using chemical & microbial techniques and electrolysis of coal for obtaining hydrogen . In the first phase of study coal samples were collected from different mines of coal including Chamlang, Duki and Salt range. . Each coal sample was also screened for proximate analysis including moisture, volatile matter and ash content by adopting standard procedures (ASTM D3172, D3173, D3175, and D3174). ASTM D5865 procedure was adopted for the calorific value determination.Trace metal analysis of coal samples were done by first heating coal in mixture of

HCl: HNO3: HF (1:1:2) on hot plate for 6 h and then amount of each metal was determined by ICP. Amount of sulphur in each coal sample was evaluated by Eschka method.Sulphur is present in the coal as pyrite, sulphatic and organic. It is a cause of great concern as it goes to the environment as sulphur dioxide during combustion of fossil fuel. Leaching of sulphur from coal was chemically investigated by using strong acids like H2SO4, HCl and HNO3 or alkalis such as NaOH, KOH or

Na2CO3.Some of the strains of bacteria have been reported to have ability to desulphurize coal. Bacteria utilize energy obtained from ferrous ions and pyritic sulfur oxidation. Thiobacillus ferrooxidans was used to desulphurize coal samples at 28 -30oC and optimal pH range of 1.8 - 2.2. Electrolysis of coal in both acidic and basic media was done .The purpose of this study was to obtain hydrogen for clean energy.In electrolysis of coal done under acidic conditions platinum coated titanium plates were used as electrodes.Two compartments were separated by a glass partition, provided with porous glass frit. Lignite slurry was taken in the anodic compartment. Gas burettes were provided above the electrolyte solution to collect the CO2 gas. Electrolysis was carried out in I.0

o mol/L H2SO4 at 60 C.In case of alkaline electrolysis of coal the same methodology was adopted except that the electrolysis was carried out I.0 mol/L NaOH The solids were separated from the acidified residue by filtration, washed and dried and its humic acid contents were determined.,

CHAPTER No. 1

INTRODUCTION

CHAPTER – 1 INTRODUCTION

1.1 The Physical and Chemical Composition of Coal Coal is combustible, organic sedimentary rock formed from decay of dead plant matter (ancient vegetation) buried beneath earth surface since millions of years due to bacterial action, high pressure and temperature. Basically coal is made up of 50-98% carbon with varying quantities of other elements in smaller quantities, mainly hydrogen (3-13%), sulphur, nitrogen, oxygen, and trace amount of other metals and non-metals.Younger coal has lower carbon content than older coal, dirty, high moisture content and low calorific value.

In geology Hilt's law states “higher rank is related to deepness of coal” (Figure 1.1). By keeping thermal gradient vertical this law is applicable, but due to metamorphism lateral changes of rank are caused regardless of its depth. Coal found at greater depth has low oxygen content. The phenomenon was first witnessed by Professor Carl Hilt in 1873.

Figure 1.1: Location of different coal types. 1.2 Formation of coal By the process of photosynthesis all living plants store energy. Stored energy is released when a plant dies on its decay. Under favorable conditions interruption of this decay process occurs and there is no more release of stored solar energy. This energy is locked in the form of coal. Both physical changes as well as chemical changes in plants change it into peat and then into coal. Over a long period both properties i.e. physical as well as chemical of remains of plants are altered due to geological actions and solid mass of coal is produced. Environmentally ideal conditions of coal formation are wide shallow seas. Other conditions include wimps, coastal

1 CHAPTER – 1 INTRODUCTION plains, river banks, swamps, and lagoons. Coal is known from Precambrian times, the ideal time of coal formation was Carboniferous period. Coal is generally classified into four main types:

Lignite (60-75% Carbon on dry ash free basis, moisture 30-70%): Lignite, often referred to as brown coal is formed from compressed peat. Lignite is considered as low rank coal, highly volatile and its chief consumption is in power stations. It is used to generate electricity. Ornamental stones are also made by polishing “jet” lignite.

Sub-bituminous Coal: (71 to 77% Carbon on a dry ash-free basis): It is dark brown to soft black solid. Moisture content is 15-30 %. Range of heat content of this type of coal is from 8300-11500 BTU/lb. It is used for generation of steam electric power. In this case fossil fuel including oil, gas and coal are utilized to heat water for production of steam that drives a turbine to produce electricity.

Bituminous coal (77-87% carbon on dry ash basis): It is dense black solid with carbon content in the range of 77-87% and 1.5-7% moisture. Bituminous coal formed from compressed lignite is dense and black in color and usually breaks down. These coals are widely used in the manufacturing of briquettes, and power stations, and in the manufacturing of coke. It has two to three times more heat content as compared to lignite coal.

Anthracite (86-97 % carbon on dry ash basis): It is highest quality of ignitable coal with black vitreous gloss. It is the hardest form of coal. It is a smokeless fuel and mainly used for domestic and commercial purpose. It gives good heat output and has long burning times. Its Sulphur content is comparatively low.

It is agreed from different studies that coal is derivative of organic matter of plants (usually higher plants and partly from lower plants). Under different environmental conditions i.e. geologic, hydrologic and climatic conditions plants underwent biochemical decomposition to form humic acids and then peat. Since metamorphic development, or coalification continuous coal series can be obtained by arranging different coals in ascending order of carbon contents present in them and can be written as

Lignite → Sub-bituminous coal → Bituminous coal → Anthracite

On behalf of coal maturation as well as keeping in account its qualitative measure of carbon content, coal is classified as low rank and high rank i.e. Lignite and sub-bituminous are low rank and bituminous and anthracite are high rank. But it should be emphasized that rank should not confused with grades (which effects quality), e.g. low-rank coals are often superior to

2 CHAPTER – 1 INTRODUCTION other members of coal series although not suitable for same uses as mature member of coal. Methods for determination of fixed content by proximate analysis have been specified by American Society for Testing and Materials. Such an analysis defines the fractions of fixed carbon, ash, moisture, and volatile matter. Coal substances are formed by carbon, nitrogen, oxygen, hydrogen and Sulphur, which are analyzed by ultimate or elemental analysis and these analyses are performed by different methods like oxidation, reduction and decomposition. These macerals present themselves in three maceral groups, vitrinite, liptlnite (exinite) and inertinite.1 Table 1.1 lists individual macerals as well as maceral groups now recognized by International Committee for Coal Petrography which indicates plant components from which they are basically derived. Table 1.1: Maceral, Maceral Groups and Plant Component from which Macerals are derived.

Maceral group Symbol Maceral Derived From Collinite Humic gels Vitrinite V Tellinite Wood bark and cortical tissue Vitrodetrinite Sporinite Fungal and other spores Cutinite Leaf cuticles Exinite E Resinite Resin bodies and waxes Alginite Algal remains Liptodetrinite Micrinite Unspecified detrital matter <10 µm Macrinite Similar, but 10-1000 µm grains Intertinite I Semifusinite Carbonized woody tissues Fusinite Carbonized woody tissues Sclerotinite Fungal Sclerota and mycelia Inertodetrinite Information obtained from NMR spectra showed that coal is a extremely cross-linked amorphous, macromolecular structure, comprising of a number of stable units or aggregates. The cluster units include aliphatic carbon, ethers, carboxylic acids and weak hydrogen bonds. Each coal unit consists of an aromatic "core" and an aliphatic exterior part. The low rank coal contains less number of rings present per nucleus. The aliphatic component of each unit is made up of short aliphatic chains and bridges connecting aromatic carbons. These units are joined to each other by methylene, ethylene, sulfide, disulfide, and ether groups. Based on the above chemistry, a typical macromolecular structure of coal is shown in Figure 1.2. Lignite is considered to be low rank coal with large amounts of oxygen. Lignite has also been defined as a gel of humic acid molecules swollen by water. Humic substances are described as high molecular weight polymers with color variations from yellow to black. The abundance of oxygen functionality in lignite can

3 CHAPTER – 1 INTRODUCTION be explained because it represents the first stage of its coalification from plant fragments. A hypothetical structure of lignite is shown in Figure 1.3.proximate and ultimate analysis of lignites was carried out by Oman and Simon,2 statistical results are mentioned in Table 1.1 giving the comparative study of different lignites.

Figure 1.2: Structure of coal.

4 CHAPTER – 1 INTRODUCTION

Table 1.2:Proximate and Ultimate Analysis for Lignite Coal.

Taxas Wilcom Gulf Lignites Proximate Analysis Wt% Moisture 32.2 36.9 Volatile Matter 27.9 25.2 Fixed Carbon 25.0 20.2 Ash 12.5 13.7 Ultimate Analysis Wt% Hydrogen 6.4 6.7 Carbon 38.98 32.1 Nitrogen 0.17 0.5 Oxygen 39.3 42.7 Sulphur 0.73 0.75 Ash Analysis Wt% SiO2 37.0 44.0 Al2O3 11.0 14.0 CaO 11.0 0.5 MgO 2.1 1.73 Na2O 0.37 0.30 K2O 0.53 0.55 Fe2O3 6.98 5.7 MnO 0.15 0.09 TiO2 1.0 1.1 SO3 11.0 7.7

Figure 1.3: Hypothetical structure of Lignite.

5 CHAPTER – 1 INTRODUCTION

1.3 Coal Distribution in Pakistan Pakistan has more than 186 billion tons of coal reserves. (i) Sindh has more than 175 BT (Thar coalfields 160 BT; Badin coalfield 900 MT; Lakhra coalfields 1640 MT; Metting Jhimpir coal field 122 MT). (Figure 1.4) Thar coal field encompasses over 9000 sq. km area. The coal bed thickness of Thar coal bed ranges from 12 - 21meters with 170 meters of average depth. (ii) Balochistan: Duki coal field 50 Million Tonnes; Sor range 34 Million Tonnes; Pir Ismail Ziarat 11 Million Tonnes; Khost Sheikh Harna 76 Million Tonnes; Mach-Abegum coal field 23 Million Tonnes. Chamalang range is located about 40-45 kilometers north of Kohlu (Tehsil Duki, Balochistan). Coal is being mined under an estimate of 30000 tons per month. About 30000 tons of coal is mined per month from this area. (iii) Punjab: Salt range 234 million ton and Makarwal 22 million ton.

Source: PakGeoSurvey.

Figure 1.4: Coal Distribution in Pakistan.

6 CHAPTER – 1 INTRODUCTION

1.4 Uses of Coal Thermal coal or steam coal is chiefly employed in production of electricity. Coking coal is mostly employed in steel manufacturing process. In addition it also found its application in refining of aluminum, paper, pharmaceutical and chemical sector. After refining coal tar is utilized in production of some important and valuable chemicals like; benzene, creosote oil, naphthalene and phenol. Ammonium salts, nitric acid and agricultural fertilizers are manufactured from ammonia gas obtained from coke oven. Several other products like dyes, plastics, aspirins, soap, synthetic fibers and solvents are made from coal or it’s by products. Different means used to produce electricity are hydropower, natural gas, oil, nuclear power, wind, solar and coal.

In Pakistan: Power shortage has become an enduring problem for Pakistan due to its fast growing population and economy. For the past few years, the demand of electricity propagated by 6-8% per annum and overall power shortfall has been estimated between 5,000-8,000 MW [1]. Pakistan is currently counting on furnace oil or natural gas based thermal power generation. However, unpredictable and extraordinary increase in oil prices makes it an expensive and erratic power source on the other hand limited reserves of natural gas make it difficult to meet the energy requirement. Hence, efforts are being made to explore other indigenous resources such as coal, hydropower, solar, wind and nuclear energy generation.3 Coal is an important and most abundant fossil fuel in Pakistan and can play an important role to meet increasing industrial, agricultural and domestic energy demands. According to a report published by Ministry of Water and Power, Pakistan have coal reserves of 186 billion tones. Coal is considered extremely heterogeneous containing organic (C, H, O and N) as well as significant quantities of "inorganic" elements that is why coal combustion in power generation, incineration plants, smelting, and combustion engines is also associated with environmental and health effects including climate change.4 Coal combustion is considered to be major source of trace, minor and major metal releases into the environment.5 Moreover, it has been investigated that emission of trace and heavy metals by coal combustion is higher as compared to fuel oils.6 In order to limit emission of these toxic pollutants, it is necessary to measure the amount of these toxic elements in the coal. A number of methods have been established to measure the emission of these pollutants with high degree of accuracy. Coal contributes about 40% in power generation and in return these coal fired power plants emit CO2, SO2, N2O, NOx, mercury, arsenic, vanadium, molybdenum, cadmium, along with some other hazardous gases. Some heavy metals and trace metals are essential for normal functioning of many biological systems and their deficiency or excess can cause many biological disorders.7 However, the potential accumulation of these heavy metals in bio systems through soil, air and water is one of the major issues of recent times.8,9,10

7 CHAPTER – 1 INTRODUCTION

1- Water Contribution water in electricity production in Pakistan is about 33%. Construction of Dams requires massive funding and long term planning of 10 – 20 years. (Figure 1.5)

2-Oil Oil contributes 30% towards meeting Power requirement. Oil reserves in Pakistan are very scarce and huge foreign exchange is expended in import of oil. It is very expensive source for power production.

3-Natural Gas About 30% of electricity is generated from gas in Pakistan. Reserves of natural gas are depleting and are proving Burden on Pakistan’s limited Foreign Exchange.

4.-Nuclear Only 2% share of nuclear in electricity generation. It is at least 10 to 20 year’s project. Huge initial investment required to start this project.

5-Wind & Solar Contribution of wind and solar is zero percent in generation of power in Pakistan. Expensive technology involving long term planning is required. Huge foreign exchange necessary and it is unable to give a sudden jump. It is a green technology and is more beneficial in conserving environment rather than power generation

6-Coal Coal share in power generation in Pakistan is only 0.2 %. It is primarily used in production of heat. It is economical and not conducive for environment. It can result in a sudden jump if right Coal policies adapted. Coal can be used either as such or can be converted into gas or liquid. Conversion of coal into gas is done underground and is also known as UCG (Underground Coal Gasification). In UCG coal is first converted to gas while still in mine and then used to produce electricity which is finally distributed through the National Grid. This requires the involvement of Government and billions of dollars of investment with execution time of 3 to 4 years. Gasification of coal is also probable on a smaller scale with 2 to 15 MW power or 9000 to 72000 cubic meter/hour of Syngas/Coal Gas to be used for heating purpose. The small scale Coal Gasification is suited to those industries that have big sales and require power at low cost to avoid loss of profits due to shut down. Recently is likely to depend on imported coal $ 180 (Rs. 15,000) per million tons. Power and Heat solutions for Pakistani industries should not be limited only to foreign market. This will

8 CHAPTER – 1 INTRODUCTION lead to incomplete projects left due to very high prices of fuel. Only feasible solution is local coal currently $80 per Million Tons. Price of coal rises in near future but still remains much below the international prices. Business community with Mining Industries and coal Technology should come forward and develop their business for more batter quality Coal Mines.

Figure 1.5a: Present Sources of Heat & Power Worldwide

Figure 1.5b: Present Sources of Heat and Power in Pakistan.

9 CHAPTER – 1 INTRODUCTION

Heavy Metals Contents of Coal

Some of the most frequently existing heavy metals in coal and in waste of coal are listed below: 1.5 Toxic Effects of Heavy Metals

For health trace quantities of heavy metals may be essential, but excess amount might be poisonous I.e. resulting in acute or chronic poisoning. Toxic heavy metals leaching from coal may lead to bio-accumulation of these metals in animals and plants, creating the danger of toxicity11. Toxicity due to heavy metals can damage or retard the functions of nervous system, embalming in composition of blood, dysfunction of kidneys, liver damage, lungs and other vital organs. Exposure to a very long time will also affect progress of muscular, physical and neurological degenerative processes that increase the risk of many dangerous diseases like Parkinson’s disease, Neuro-degenerative disease, multiple-sclerosis and muscular dystrophy. Repeated long-term exposure with these metals may lead to various types of cancers.12 1.5.1 Lead

Lead is soft, dense and moldable blue grey metal (from the Latin name plumbum). Lead is historically used in paints and gasoline. Lead occurs both in inorganic and organic form. Inorganic lead is the most common form of lead is white lead, yellow lead or red lead. In order to increase octane number in leaded gasoline organic lead is used in form of Tetraethyl and tetra methyl lead. Furthermore lead is emitted into atmosphere when fuel having alkyl lead as an additive is burnt. Organic lead is more toxic than inorganic lead as these compounds are absorbed on skin and are very harmful for brain and central nervous system. Burning of fossil fuel, such as coal, in electrical utilities release lead in flue gas which contains lead as a contaminant. Combustion of one million pounds of lignite coal will release about 420 pounds of lead into atmosphere.13

There is no “safe limit” of lead for children, according to American Academy of Pediatrics. In human body Lead has no physiological function. For humans of all ages acceptable lead exposure limits have been repeatedly lowered over years and current scientific understanding recommends that neurological damage due to lead can happen at blood lead levels considerable lower than beforehand described. Lead is amassed in body especially in bones; even very small quantities of lead can be a source of life-long learning and behavior problems. Trace amounts of lead in body can make it problematic for children to learn, pay attention in school. Lead present in mother’s bones can be introduced to fetus via blood stream during pregnancy [420 pounds]. Most of heavy metal poisoning in children is due to lead.

Lead is non-degradable therefore burning of coal and other uses of lead are increasing concentrations of lead in environment of living as well as non-living organisms. Regardless of its

10 CHAPTER – 1 INTRODUCTION source of emission when lead comes down to soil, it sticks powerfully with particles of soil and leftovers in upper layer of soil. Since it does not degrade over a long period of time, this contamination problem is continued. It can be taken up by plants as included in soil and also present in water, and food processing through bronze plumbing parts can often introduce lead contamination in water system and also to other sources. Environmental Law Foundation enlisted a U.S. Environmental Protection Agency lab of US in 2010 curtained 400 samples from 150 trademarked food products promoted to children, including some juices like grape juice, apple juice, packaged peaches and pears, and fruit cocktail mixes. Alarming quantities of lead were present in 125 out of 146 products tested (85 %). 1.5.2 Mercury Mercury is present in many products like batteries, measuring devices, such as thermometers, barometers, electronic switches, lamps, dental amalgams, skin whitening products and pharmaceuticals. During combustion of coal majority of mercury is released. It is ingested by human due to its accumulation and concentration in food chain most common source is by eating fish. Damage of immune system is caused by Mercury due to its high level of toxicity. It can also cause severe damage to nervous system, reproductive system and especially damage of all systems in body of developing fetuses. Coal-fired power plant is main source of mercury into atmosphere, from where it comes back down to earth surface with rain, snow and fog. It then drains into watersheds, rivers, and lakes and settles into sediment where bacteria convert mercury from elemental form into the more toxic methyl mercury.14 This conversion can also take place directly in the seas and oceans, where large amounts of methylmercury are formed. Coal-fired power plants are largest source of mercury in USA which accounts for about 41 percent (48 tons in 1999) of emissions caused by total industries ( Reference: Mercury and coal). This run-off mercury is absorbed by different fish species like Tuna and other fish. Disease Control and Prevention centers have described that eight percent of childbearing age American women had dangerous levels of mercury in their blood system, employing roughly 322,000 neonatal babies at danger of neurological disorder. Introduction to mercury can also rise cardiovascular threat in adults.15,16

U.S. Geological Survey in August 2009 released comprehensive report on mercury contamination in fish in 291 streams in United States. During the study, which was from 1998 to 2005, over 1000 fish were tested and all of them had at least trace amount of toxic mercury.17 1.5.3 Arsenic

Arsenic is highly toxic element and greatly affects the human health because its inorganic compounds are carcinogenic18 whereas organo-arsenic compounds such as mono-methyl and dimethyl arsenic acids are possible carcinogen to humans and are categorized as Group 2 B by International Agency for Research on Cancer19 arsenic exposure will increase risk development of

11 CHAPTER – 1 INTRODUCTION a multiple cancers counting skin cancer and cancers of liver20 bladder, and possibly renal21 and colon.22 Based on information obtained from XAFS arsenic may be present in one or more of

3- three distinct forms: (a) arsenical pyrite; (b) arsenopyrite (FeAsS); and (c) arsenate (AsO4 ), formed probably during combustion. In most of the ash samples studied by XAFS spectroscopy arsenic is predominantly found as arsenate species. Comparison of Arsenic retention for the two DECS coals in the PSIT drop tube experiments is given in Table 1.3.

Table 1.3: Comparison of Arsenic retention for the two DECS coals in the PSIT drop tube experiments. Coal As (Coal) As (Ash) Wt% Ash As cap. eff.* Pittsburgh 70 31 10.0 0.04 Illinois 10 21 14.5 0.30 *Arsenic capture efficiency is defined as: As (Coal)/(As (Ash)/Wt fn. Ash)

During the 1990s, naturally occurring arsenic was found in groundwater in the China, Vietnam, USA, Taiwan, Hungary, Argentina, and the Ganges Plain.23 10 μg/L is arsenic provisional guideline value in water used for drinking purposes which is given by World Health Organization. Similar to neighboring countries Pakistan is also facing severe health problem related to arsenic toxicity.24,25,26 Concentration of arsenic in 3% and 16% water samples of Punjab and Sindh were found above 50 μg/L.27,28 Following the Arsenic crisis in Pakistan and the bordering countries UNICEF and PCRWR have undertaken the valuation of drinking water quality since 1999. For assessment of arsenic, study conducted of showed presence of 10– 200 μg/L in many areas of Pakistan,29,30 in drinking water. According to World Health Organization maximum permissible concentration of As in developed countries is 10 μg/L; however, due to lack of facilities the developing countries 31 are still using the previous guideline value of 50 μg/L. The PHED of Pakistan conducted a survey with the cooperation of UNICEF, for determining the quantity of arsenic in water in 2001 and recognized some areas of arsenic- enriched groundwater in different parts of the Indus basin. Muzaffargarh was identified as one of area in Pakistan which is enriched in arsenic. Contribution of arsenic in surface soils is mainly due to coal combustion and fertilizers.32 The average values of total arsenic in the sediments of Manchar Lake (Sindh) were found in the range of 11.3–55.8.33 1.5.4 Cadmium Cadmium (Cd) is another toxic element found in coal and is well known for its negative effect on endocrine system.34,35 It can contaminate water, soil, and the air through coal mining,

12 CHAPTER – 1 INTRODUCTION combustion, beneficiation, etc. Cadmium presents in coals quite complex form. It exists in coal in sulfides forms and also in form of some organic matter, silicates, and other minerals. Exposure to cadmium can cause chronic and acute health effects in living organisms. Cadmium is found both in earth crust and in water. 36 The mean terrestrial abundance of cadmium is 0.1 to 0.2 mg/kg, and in marine waters, it varies from less than 5ng to 110 ng/L on average.37 Cadmium and its compounds are probable carcinogenic to humans and are classified as Group 1 by International Agency for Research on Cancer, whereas EPA has placed it in Group B1 as probable human carcinogen. Cadmium and its compounds are reported to cause lungs, kidney and prostate cancer. Intoxication due to cadmium can lead to pulmonary, kidney and skeletal damage, and itai-itai diseases.38,39 The tolerable concentration of cadmium in water given by WHO is 0.003 mg/L.40 FAO–WHO had jointly recommended that daily intake of cadmium, should not be more than 11.2 µg per kg body mass.41 In Pakistan, high cadmium concentration in water is from effluent discharges of, steel, marbles and aluminum, industries of mining and metal plating. The concentration of cadmium in ground water samples collected from different areas of Pakistan ranges from 0.1 to 0.221 mg/L.42,43 From industrial Estate of Hayatabad samples of water were collected from different tube showed a highest value of cadmium and reported as (0.21 mg/L), Khyber Pakhtunkhwa (KPK) province has an average of cadmium 0.02 mg/L in water. On other hand concentration of this metal in surface water samples throughout Pakistan was found below 0.2 mg/L.44,45 A number of studies show widespread distribution of cadmium in wastewater samples collected from different zone and regions of Pakistan (Table 1.5). Maximum concentration of 5.35 mg/L cadmium46 was reported in wastewater from Korangi area, Karachi, which is higher than 0.010 mg/L that is a permissible limit which was set by NEQS-Pak for both industrial as well as sewage waste-water. Furthermore for Punjab province and in district Lahore concentration of cadmium was also reported above the safe limit set by NEQS (0.18 to 0.37 mg/L).47 In another study conducted on wetland efficiency for heavy metal removal from industrial wastewater in Gadoon Amazai Industrial Estate, Swabi (KPK province), showed the presence of cadmium in the range of 0.19–0.62 mg/L. Both anthropogenic and natural sources pay much to levels of Cd found in water, soil and sediments, for example, coal, phosphate fertilizers, mine/smelter wastes, sewage sludge, and municipal waste landfills.48 A comprehensive study of coal conducted in China in which 2999 samples were collected from 116 mines (26 provinces). The arithmetic mean concentration of cadmium in Chinese samples was found to be 0.43µg/g. 1.5.5 Nickel Nickel is extensively distributed in living organisms and soil. Its concentration in soil ranges from 4–80 ppm.49 Addition of Ni into atmosphere is due to burning of fossil fuel, process

13 CHAPTER – 1 INTRODUCTION of mining, during smelting, refining process, usage of this metal compounds and alloys containing nickel, and due to incineration.50 Exposure to Ni results from food contaminated with, water, inhalation, and absorption from skin. According to International Agency for Research on Cancer evaluation, Nickel compounds are identified as Group 1 carcinogen to human population. Both metallic Nickel and its compounds cause cancers of the respiratory system including lungs and nasal cavity, dermatitis (nickel itch) and para-nasal sinuses. The permissible concentration of Nickel in water as given by World Health Organization and National Standards for Drinking Water Quality, Pakistan is 0.07and 0.01mg/L respectively.51 Ni concentration differs from <0.0001–3.166 mg/L in ground water to <0.0001–1.552 mg/L in water of in Pakistan region (Table 1). Studies have shown that 75% of surface water samples which were taken from Karachi have exceeded the limit. In a study conducted in Lahore to appraise the impact of waste water irrigation on vegetables showed that the concentration of Nickel in waste water was between 0.91 to 5.94 mg/L which is much higher than the level set by NEQS (National Environmental Quality Standards), Pakistan (1.0 mg/L).52,53 1.5.6 Copper Copper is another important trace element present in liver and food. Copper is a cofactor of many enzymes including lysyl oxidase, superoxide dismutase, cytochrome oxidase, dopamine hydroxylase, and many other oxidase enzymes that reduces oxygen molecule. In the organism it is transported by the ceruloplasmin protein.54 The permitted dietary allowance (RDA) value of copper in grownups is 0.95 mg in whole day. Average intake of copper through die in United States is up to 1.0 mg per day and allowed intake value for young man is 10 mg/day. Most of the studies done in Pakistan conducted on surface or ground water showed that contamination with copper does not pose any significant threat and mostly concentration of copper in water samples is within acceptable standard limits of 2 mg/L as recommended by WHO and NSDWQ-Pak.55,56 The permissible concentration of Cu in soil according to European Standards, (sewage sludge) is 50–140 mg/kg. In many areas of Pakistan, the concentration of copper in soil ranges from less than 6 to 412 mg/kg. A recent study from Lahore, Punjab province, reported the Cu contents in industrial wastewater irrigated vegetables, compared with the clean reference soil (spinach mean 5.77 mg/kg on contaminated soil and 0.44 mg/kg on clean soil, resp.). Leafy vegetables possess greater ability to absorb the heavy metals from soil compared with the other edible plants.57

Acute poisoning caused by ingestion of copper usually includes vomiting, muscular problems, hematemesis, black feces, coma, jaundice, and gastrointestinal disturbances. Those Individuals who have deficiency of glucose-6-phosphate are basically at high risk of hematologic effects caused by copper. Hemolytic anemia is occurring very infrequently which results from when burns are treated with copper compounds. Liver and kidneys are damaged with Long-term

14 CHAPTER – 1 INTRODUCTION exposure of copper. Mammals due to having efficient mechanisms to regulate copper are usually sheltered from excess dietary copper levels.

1.5.7 Chromium Chromium was discovered by Vauquelin in 1797. There are two different oxidation states of chromium, i.e. Cr (III) and Cr (VI), they differ greatly by their impact on environment possibly due to their difference in water solubility. Cr (III) is not much hazardous probably owing to less solubility and not absorbed by the body. Cr (VI) is present in the form of chromates is usually soluble and, because of its oxidizing ability, can have severe harmful effects on our body, including formation of cancerous tumors and damage to gene. Concentration of chromium is normally about 10 ppm in coal; US use about one billion tons of coal annually for generation of electricity. It implies that about 10,000 tons of chromium is poured into environment by US power generation plants alone. There is a great chance of chromium containing coal derived fly ash leach down to ground water and contaminate ground water.58 Due to large number of industrial applications chromium has become an important economic element. Chromium in trivalent state is an essential trace element for living organisms. Metallic chromium has no hazardous effect.59 Large amount of trivalent chromium is toxic. Acute and chronic toxicity is caused by chromium (VI) compounds. The major lethal effects caused by inhalation, contact, or ingestion of Cr (VI) compounds include: allergic and eczematous skin reactions, dermatitis, perforation of the nasal septum, skin ulcerations, mucous membrane ulcerations, bronchial carcinomas, allergic asthmatic reactions, gastro-enteritis, renal oligo-anuric deficiency and hepato-cellular deficiency. Chromium is an important metal used in metallurgy of steel, pigment industry, metal finishing, and as wood preservatives.60 The main source of Cr contamination is from dyestuffs and chromium tanning, when wastes of tanneries are poured direct into water streams without water treatment. Chromium enhances the activity of insulin and has positive effect on glucose tolerance.61 IARC has leveled Cr (VI) compounds as Group 1 carcinogen to humans. The ground water samples studied from various areas of Pakistan showed Cr concentration extending from <0.001 to 9.8 mg/L, well water collected from Kasur showed maximum chromium concentration (mean value 2.12 mg/L) province owing to large number of tanneries.62 1.5.8 Iron It is an important element for body metabolism and is required by the body in greater quantity than any other trace metal. Iron is an important part of number of proteins, enzymes and hemoglobin.63 The Recommended daily intake of iron for adults is 8 mg/day with tolerable maximum intake level is 45 mg/day, which is based on adverse effect and GI distress. WHO, EU or NSDWQ-Pak, have not given any guideline about the value of iron in drinking water.64 Several

15 CHAPTER – 1 INTRODUCTION studies conducted on iron concentrations in ground water showed varying amount of iron from <0.01 to 11.8 mg/L with highest concentration reported in Kasur and Jamshoroo water samples65 followed by 4.28 mg/L from Jamshoro, Sindh. In different localities of Pakistan the concentration of iron in surface water surface water ranges from 0.01 to 5.46 mg/.66 The permissible value of iron in waste water according to NEQS is 8 mg/L. The analysis of data for waste water in various cities of Pakistan revealed that the most areas have Fe content under the safe limits of 8 mg/L with a few exceptions.67 Some common side effects of Iron are diarrhea, constipation; vomiting, nausea, heartburning, stomach pain, black or dark-colored stools, teeth temporary staining, headache, mouth unpleasant taste.

1.5.9 Zinc Zinc is also a vital micronutrient. It controls the activity of enzyme, and has important role in protein structure, and gene expression.68 Although of Zn deficiency harmful effects have been known for many years ago but it can be fatal on exposure to its excess quantity.69 With prolonged intake of supplemental Zn harmful effects associated include headaches, gastrointestinal diseases, impureness in immune function, changes in lipoprotein and cholesterol levels, interactions of zinc-iron and reduction in copper level. RDA of Zn for male and female is 8-11 mg/day, while its tolerable maximum intake value is 40 mg/day for adults, a value based on reduction in erythrocyte copper-zinc superoxide dismutase activity. NSDWQ-Pak has set maximum acceptable concentrations of 5 mg/L for Zn in drinking water.70 Zinc concentration in ground and surface waters of Pakistan, is reported well below the standards fixed by NSDWQ-Pak. Average zinc (Zn) content of the worldwide soils is estimated to be 70 mg/kg that is the same average level of Zn in the earth’s crust.71 In soil the limit of Zn which is allowed for applications of sewage given by EU is 155–300 mg per kilogram. The concentration of zinc in soil/dust of Pakistan varies from less than 0.1 to 1193 mg/kg. In automobile elements Zinc is one of major element; due to its presence in soil samples collected from side of road indicated that vehicular emission is imparting important part in pollution. Background Zn content in lettuce worldwide was found in range of 44–73 m.72 In Pakistan, highest concentration of Zn was reported in vegetables sampled from different parts of Gillgit, Pakistan.73 1.6 Desulfurization of Coal Sulfur compounds are basically present in crude oil and coal and are categorized into two basic groups.  Organic Sulphur  Inorganic Sulphur

16 CHAPTER – 1 INTRODUCTION

Inorganic Sulphur is present in the form of sulphates and sulfides. Sulfate minerals present in coal include barite (BaSO4), anhydrite (CaSO4), gypsum (CaSO4.2H2O), iron sulfates etc.74 The major form of inorganic sulfur compound present in coal matrix is generally pyrite.

Iron pyrites (FeS2), Chalcopyrite (CuFeS2), galena (PbS), Arseno-pyrites (FeAsS), molybdenite (MoS2 ) and covellite (CuS) are included in sulphide minerals. As organic sulfur removal by chemical or physical means is more difficult due to its covalently bounded structure into large intricate coal, in comparison to inorganic sulfur. In coal Organic sulfur occurs as aliphatic, aromatic/heterocyclic forms, which is further categorized into four groups (Prayuenyong, 2002) which are given as follows:  Aliphatic or aromatic thiols  Aliphatic, aromatic, or mixed sulfides  Aliphatic, aromatic, or mixed disulfides  Heterocyclic compounds

Health Hazards of SO2

Coal burning emits SO2. Major health problem associated with SO2 is improper functioning of upper respiratory track. High concentrations of sulfur dioxide in atmosphere can affect breathing process, also effect badly respiratory track, and can be more dangerous for patients already suffering from lung and heart diseases. Bronchitis, irritation of lungs and throat infection can be caused by exposure of very trace amount of Sulphur dioxide. Ability of respiratory system's to defend against bacteria and foreign

particles are lost by exposure to low levels of SO2 over a long period of time. Particularly sensitive groups include children, elderly, people with asthma, and those who are

suffering with heart or lung disease. Chemical, physical and biological processes have been used to remove content of sulphur from coal. Physical methods include grinding followed by screening and washing. Floating heavier particles of pyritic sulphur can be removed from the coal by magnetic separation. Physical cleaning is not much effective for finely divided pyritic and organic sulphur. Process of chemical desulphurization were developed due to deficiency of physical methods in order to remove both type of Sulphur which inorganic and organic in origin These chemical methods majorly accounts for oxidation in air, carbonization, oxidation called as wet oxidation process, Meyer’s process, chlorination and extraction using copper chloride as chlorinating agent, sodium hydroxide and ethanolic solutions.

1.6.1 Peroxyacetic acid Originally peroxyacetic acid extraction of sulphur from coal as single stage technique yielded poor results. This technique converts sulphur compounds into forms that can be easily

17 CHAPTER – 1 INTRODUCTION removed by other desulphurization techniques. Therefore it can be used as pretreatment for alkali extraction of sulphur. The coal is first dispersed in glacial acetic acid and warmed to temperature between 21-104 ˚C and then mixed with 30% H2O2 in 1:3 volume ratios. The coal is then filtered and reacted with sodium carbonate in methanol as solvent at 350 450 ˚C. Peroxy acetic acid removes 85-95% of sulphur when combined with base treatment in organic solvent. This method produces about 80 % of coal without any loss in heat content of coal. 1.6.2 Sodium Hypochlorite Sodium hypochlorite selectively oxidizes organic and sulfatic sulphur present in the coal. 20 gram of 150 μm (100 mesh) coal is treated 100 mL of 5.25 wt% NaOCl at room temperature and 1 atmospheric pressure followed by 0.3 M Na2CO3 wash at 80 C for 1 hour (Brubaker and Stoicos, 1985). This method reduces inorganic sulphur upto 25% and organic sulphur upto 42% with heating value recovery between 81 – 95%. The coal obtained by this method contains 2- 2.7% chlorine. This method is more suitable for removal of sulfatic and organic sulphur. 1.6.3 Potassium Permanganate75 This method is useful for removing both pyritic and organic sulphur. In this method coal is first washed with 1,1,1-trichloroethane and then grinded to 74 μm (200 mesh) followed by oxidation of the coal three times with potassium permanganate with washing between two oxidation stage. In each oxidation state coal is oxidized with 6% KMnO4 solution for about 1.5 hours at room temperature followed by one hour water wash at 80˚ C (Attia and Lei, 1987).76 This method gave better desulphurization than sodium hypochlorite method. Attia and Fung modified this procedure by washing with 16% HCl solution and 15 minutes ultrasonic treatment after each oxidation stage to remove oxidation product layer on coal (Figure 1.6).

18 CHAPTER – 1 INTRODUCTION

77 Figure 1.6: Basic procedure of KMnO4 desulfurization of coal (Attia and Fung, 1993)

1.6.4 Supercritical Fluid Extraction Principle:in this method supercritical fluids such as methanol or ethanol are used to remove organic sulfurfrom coal.High temperature and pressure ar needed for this process.

Supercritical fluid extraction (SFE) of sulphur from coal was performed on a very small

78,79,80 scale with either CO2 in 10% methanol or pure CO2 under supercritical conditions. 1.6.5 IGT Hydrodesulphurization Conventional method used worldwide for desulphurization of coal is hydrodesulphurization (HDS). It is physicochemical technique. It employs use of high-pressure (150-250 psig) and high- temperature (200-425 °C) (Monticello, 1998). Coal is first pulverized and heated with air in fluidized bed reactor at 400 °C one atmospheric pressure. This removes 25 – 30% of the coal producing steam and gas of low BTU. About 8 – 12% coal is destroyed during this step. The coal is then heated in a second fluidized bed reactor at

800 °C and one atmospheric pressure, sulphur is removed as H2S, calcium oxide or iron oxide is used to reduce the consumption of hydrogen. This method provides 83% BTU recovery along with other useful products like fuel gas, light oil and char. 81 1.6.6 Magnex Process Principle:In this process weakly magnetic pyrite and nonmagnetic mineral matter is first converted into paramagnetic material which is then removed by magnetic separation.82,83,84,85 The

19 CHAPTER – 1 INTRODUCTION coal is first ground to less than 1.41 mm and heated to 170 ˚C using 100 Kg steam/ton of coal. The heating of coal removes elemental sulphur and volatile compounds which disrupt the paramagnetic conversion. The coal is then treated with pentacarbonyl iron (0) vapours, which react with the pyrite and mineral matter surfaces. Metallic iron thus formed converts the surface of the pyrite particles into pyrrohotite. Both metallic iron and pyrrohotite are strongly magnetic and thus can be easily removed by using low to medium intensity magnetic separators. 1.6.7 Chlorinolysis This process was developed by Jet Propulsion Laboratory at the California Institute of Technology.86 In this process coal is first pulverized to less than 94 μm and then mixed with 1,1,1-trichloroethane or water in a coal to solvent ratio of 2:1 by weight to form a slurry. The slurry is then treated with chlorine gas for 45 minutes at a temperature between 60-130 ˚C and pressure ranging from 1 – 5 atmospheres. Chlorine reacts with pyrite, iron chloride and S2Cl2 thus produced are decomposed into sulfuric acid and HCl by reaction with water above 50 ˚C. Reaction of chlorine with organic sulphur produces sulfenyl chlorides (RSCl), which are hydrolyzed to sulfonates and sulfuric acid. The total sulphur reduction for water and 1,1,1-trichloroethane are 45-66% and 52-63% respectively but use of 1,1,1-trichloroethane results in greater reduction of organic sulphur and use of water causes greater reduction in pyritic sulphur. The major drawback of this method is poor coal recovery and high chlorine contents of final coal. 1.6.8 Ferric Chloride87 This method was developed by Fan and his coworkers in 1987.88 This method involves heating of 74-38 μm sized coal with 10% by weight of ferric chloride at 300 °C for one hour followed by washing with 2M boiling HCl for 30 minutes. This method is effective for benzothiophene, dibenzothiophene, phenyl disulphide, benzyl methyl sulphide, benzyl phenyl sulphide, benzyl disulphide, 2,5-dimethylthiophene and phenyl sulphide but ineffective for benzothiophene and dibenzothiophene. The major drawback of this method is FeCl3 is unstable at 300 ˚C and decompose to for insoluble iron oxide precipitates on coal. 1.6.9 Meyers Process89 This is the best method for the removal of metallic salt sulphur (pyritic sulphur) but the major limitation is its inability to remove organic sulphur.90 Coal sample is heated with aqueous solution for four to six hours between 90–130 ˚C. Ferrous sulfate formed is re-oxidized with oxygen. The coal is then filtered and washed to remove water soluble sulfates. Acetone extraction is used to remove elemental sulfur. The leach solution is treated with lime to reduce the sulfate concentration down to its original value before recycling. This method removes 83-98% of pyritic sulfur with very little coal loss.

20 CHAPTER – 1 INTRODUCTION

1.6.10 Oxydesulphurization91 This method involves the use of oxygen or air to remove sulphur at elevated temperatures and pressures. This method can be employed both in wet and dry states. In this method coal is slurried in water after pulverizing and pressurized with oxygen or air followed by heating at required temperature. This method is more suitable for removal of pyritic sulphur. Pyritic sulphur is converted into soluble sulphates with the help of dissolved oxygen as shown below. The coal obtained in this method has increased porosity which makes the coal more reactive and decrease in heating value upto 40%. 1.6.11 Microwave Desulphurization92,93 Principle Microwaves selectively heat the pyrite part of the coal and provide energy directly to at the locations where energy is needed for the desulfurization of coal. Microwaves penetrate more quickly in the coal matrix and bring the region high in sulfur to reaction temperature than conventional heating. The best conditions for microwave desulfurization are irradiating 50 gm of coal sample (NaOH to coal ratio of 1:1) with 1.2 kw of microwave for two minutes. The three time treatment results in overall sulfur reduction of 83% with ash reduction of 87%.94 1.6.12 Sulphur removal by electrolysis95969798 Lavlani et al.,99 carried out acidic medium anodic oxidation of coal slurries at potentials 0.8 to 1.0 V, on NHE scale. Pyrite present, during electrolysis, in the coal dissolved in solution, while H2 was released at the cathode. Filtrate will show same electrochemical reactivity if coal is filtered from un-electrolyzed coal slurries. Cyclic voltammetry analysis of slurry and filtrate indicated reversible, one-electron oxidation of Fe (II) to Fe (III), but chemical analysis revealed

2− that sulphide was also oxidized, to SO4 and S⁰ . The electro-chemical reactions involved oxidation of pyrite at anode. Lavlani et al reported that between solid pyrite and the anode dissolved ionic Fe will act as an electron shuttle. Fe (III) can oxidize pyrite and thiophenes were also indicated by Experiments without coal. It is concluded from experiment that by electrolyzing coal slurry in acidic electrolyte employing either platinum or graphite electrodes by electrolyzing coal slurry in acidic electrolyte employing either platinum or graphite electrodes 40% of total sulphur can be removed from lignite and bituminous coal.

1.6.13 Microbial Desulfurization Chemical techniques utilized for desulphurization include comparatively non-specific reactions, which are carried out at high temperatures and high pressures with moderately high utilization of chemicals. Very specific reactions in a simple reactor are major advantage of these type of desulfurization, at normal temperature and pressure, but time require for leaching is very long.

21 CHAPTER – 1 INTRODUCTION

Thiobacillus ferrooxidans Thiobacillus ferrooxidans are chemoautotrophic and aerobic microorganisms which necessitate atmospheric oxygen as well as some inorganic compounds with CO2 for their growth. They are non-speculating gram negative bacteria. They have stick like appearance of average length of 0.9-1.5 μm. By oxidation of sulphur components and Fe2+ Thiobacillus ferrooxidans get energy. 28-30°C is optimal temperature for this bacteria with optimal pH is from 1.8-2.2.

Principle of pyrite oxidation Using Thiobacillus ferrooxidans bacteria100 There are two types of bacterial leaching, direct and indirect. Direct leaching includes bacterial occupation of surface of mineral and metal sulphides and is subsequently oxidized into ferrous sulfate and then to ferric sulfate by enzymatic oxidation. Direct leaching oxidation of pyrite can be illustrated by following Equations 1 & 2:

FeS2 + 3,5 O2 + H2O → FeSO4 + H2SO4 (Equation 1)

2 FeSO4 + 0,5 O2 + H2SO4 → Fe2 (SO4)3 + H2O (Equation 2) A bacterial agent is produced in indirect leaching by which sulphide minerals are oxidized. Fe3+is active agent in this type of oxidation. Mechanism involved in this type of reaction can be illustrated in following ways (Equation 3 & 4):

0 Fe2 (SO4)3 + FeS2 → 3 FeSO4 + 2S (Equation 3)

0 3O2 + 2 H2O → 2 H2SO4 2S + (Equation 4) Methods of bacterial leaching For bacterial leaching test work airlift glass bioreactor of capacity 10 liter was used.101

Prepared samples of coal along with medium 9K without FeSO4 were placed into it, after sterilization of reactor. Mixing and homogenizing of suspension was carried out for a time period of 1 hr., and after that 1,000 ml of 49 bacterial culture Thiobacillus ferrooxidans was acquaint with into reactor. For test programmer Clean bacterial cultures of Thiobacillus ferrooxidans from Czech-Slovak Collection of Micro-organisms in Brno were employed. Concentration of bacteria which was introduced in process was 109 in 1 ml bacterial solution. In order to supply air to reactor, bioreactor was connected to aquarium water aerator. In order to have more moisture and for removal of airborne bacteria air was cleaned in washers in 1 M H2SO4 solution. Mixing of 5% suspension was using air. Measurement of pH was carried out by laboratory pH-meter “RADELKIS”. During whole experiment pH was kept at optimal value 8-2 in order to prevent formation of unwanted jarosite. Temperature was kept in range 26-30°C during leaching, samples of approximately 50 ml were taken from bioreactor for analysis after 1, 2, 3, and 4 weeks,. By taking a part of each sample MPN method was used for measuring biomass growth. Rest was filtered on a Buchner funnel where filtrate and the filter cake were separated; Fe2+ was determined by titration in filtrate. The total Sulphur contents and its separate forms were determined in the

22 CHAPTER – 1 INTRODUCTION filter cake. Cake was washed in 100 ml of 1M HCl and in 200 ml distilled water before determination.102 Test work involving bacterial leaching was conducted by using a 10 liter airlift glass bioreactor. After reactor sterilization prepared samples of coal were placed in it also with medium

9K without involving FeSO4. A time period of 1 hr. was taken in order to mix and homogenize suspension 1,000 ml of 49 bacterial culture Thiobacillus ferrooxidans was introduced into reactor. From Czech-Slovak Collection of Micro-organisms in Brno, Clean bacterial cultures of Thiobacillus ferrooxidans were used for test programmer. Introduced bacterial concentration was 109 in 1 ml bacterial solution. In order to supply air to reactor, aquarium water aerator was connected to bioreactor. By using in 1 M H2SO4 solution air was cleaned in washers to have more moisture and also to remove bacteria. Mixing of 5% suspension was done by using air. pH was demonstrated using laboratory pH-meter “RADELKIS”. Optimal value of pH was kept at 1,8-2 during conduct of whole experiment in order to prevent formation of unwanted jarosite. Temperature was kept in range 26-30°C. Samples of approximately 50 ml were taken from bioreactor, during leaching, after 1, 2, 3, and 4 weeks, for analysis. Biomass growth was evaluated by MPN method by taking a part of each sample. Rest was passed for process of filtration on a Buchner funnel where filtrate and filter cake were separated, concentration of Fe2+ in filtrate were monitored by titration. In filter cake total sulphur contents and its separate forms were founded. Washing of Cake was done in 100 ml of 1M HCl and in 200 ml distilled water before determination. Microbial Desulfurization of Coal103 sulfur is present in coal in three common forms i.e. pyritic, sulfate, and organic sulfur. In-situ oxidation of metal sulfides Originate sulfates which are present in coal at low concentrations. Their leaching from coal is relatively an easy task as they get soluble in water. Oxidative conversion of inorganic sulfur compounds to water-soluble products is accelerated by microbial depyritization. This removal of pyrite results from combined effects of both direct bacterial attack and as well as indirect chemical solubilization. In method mentioned earlier, pyrite (FeS2) is oxidized by bacteria into Fe2(SO4)3 while in second methodology ferric iron is actual oxidizing agent and microorganisms are used for regenerating ferric iron from ferrous iron.

Carbon skeleton of coal is chemically bound to organic sulfur. It is present in forms of organic sulfides, disulfides, thiols and thiophenes. For microbial desulfurization of heterocycles two procedures have been proposed. One method is dependent on oxidation of carbon ring structures to polar derivatives while other methods track sulfur-specific metabolism without carbon skeleton degradation. Both developed methods have been demonstrated with model organosulfur compounds particularly dibenzothiophene (DBT). Reports on organic sulfur removal from coal and water-soluble coal-derived products by microorganisms are also available. Due to

23 CHAPTER – 1 INTRODUCTION difficulty in accurate analysis of organic sulfur content, technical viability of microbial organic sulfur removal from coal is still in dispute.

Expenses of independent microbial depyritization and organic sulfur removal were assessed to be $10–14 and $14 per ton of coal respectively. A cost analysis for a two-step process, which was intended to achieve complete removal of inorganic sulfur and a 40% reduction of organic sulfur, produced $11 per ton of coal.

Bio-desulphurization of inorganic sulphur Desulfurization of inorganic sulphur by techniques involving, microorganism from coal has been working in many laboratory studies (Bos & Kuenen, 1990)104 over the past 50 years.

105 Three-phase system pyrite bioleaching in air stream and CO2 was confirmed by Rossi (1993) was inoculated through suspension of coal in aqueous media with help of appropriate injectors. Presence of definite mesospheric or thermophiles microbial strains can improve dissolution kinetics of pyrite mineral in proper inorganic salt solution. Direct and indirect mechanisms have been predicted for pyrite microbial oxidation involving some catalyst based on Thiobacillus ferrooxidans. For biological oxidation of pyrite, direct technique necessitates physical interaction between particles of pyrite and bacterium for as shown in Equation 5. (Larsson et al., 1994).106

4FeS2 + 15O2 + 2H2O T. ferrooxidans 2Fe2(SO4)3 + 2H2SO4 (Eq 5)

Numerous determinations have been made in order to conduct direct attack on metal sulphides caused by T ferrooxidans. It can also be taken as a heterogeneous process in which bacterial cell attributes it to crystal surface of sulphide which ultimately results in corrosion in a thin film situated between bacterial outer membrane and sulphide surface. There is imperfectness in direct mechanism for oxidation of pyrite for certain coals because of fact that pathogens is too large to enter in pores which are present in coal.

This suggests that in coal pyrite oxidation majorly depend on indirect methods. Because in these mechanism, bacterium oxidizes ferrous iron (Fe2+) to ferric iron (Fe3+); which are than utilized for chemical oxidation of pyrite. Equation 6 and Equation 7 designate indirect oxidation mediated by Fe3+ and one oxidant i.e. T. ferrooxidans.

3+ 2+ + 2- FeS2 + 14 Fe + 8H20 15 Fe + 16 H + 2S04 (Equation 6)

2+ 3+ T. ferrooxidans 2 Fe + 2H+ + 0.5O2 2 Fe + H2O (Equation 7)

In absence of microorganisms oxidation of ferrous iron is a very slow process, may be measured as rate-determining step for oxidation of pyrite with ferric iron. Another possibility for mechanism which is counted as indirect is oxidation by ferric iron of ferrous iron in pyrite,

24 CHAPTER – 1 INTRODUCTION leaving behind elemental sulphur as in Equation 8. This generated Sulphur is then oxidized to sulphate by some suitable microorganisms, as shown in Equation 9.

3+ 2+ FeS2 + 2Fe 3 Fe +2 S° (Equation 8)

T. ferrooxidans 2S° + 3O2 + 2H2O 2 H2SO4 (Equation 9)

For microorganism, rate of pyrite oxidation in coal might be mass-transport-limited rather than substrate-limited. Pyrite oxidation in coal is a first order reaction in pyrite concentration, while pyrite oxidation with pure pyrite is more complex and be contingent on pyrite and ferric iron concentrations. Jarosites formations which are considered as iron precipitate

+ + + + (MFe3(SO4)2(OH)6) where M stands for any one of followings i.e. H , K ,, Na , or NH4 ,is challenging in pyrite oxidation. Chemical reactions are comparatively faster at raised temperatures castoff for thermophiles bacteria, and overall pyrite oxidation rate is greater than at temperatures applied for mesophilic bacteria. Though, eminent temperatures also raise formation of jarosites which are responsive for desulphurization as they stick coal even after complete and suitable washing. Soluble ferric iron amount is also decreased. Influence of these conditions is very pronounced on chemical reactions (Larsson et al., 1994).111 Two indirect oxidation mechanisms have been recently planned by Schippers & Sand for metal sulphides.107 Not only oxidation of pyrite, oxidation of other metal sulphides including molybdenite (MoS2), tungstenite

(WS2), sphalerite (ZnS), chalcopyrite (CuFeS2) and galena (PbS) were considered. First mechanism is exclusively grounded on oxidative attack of ferric iron on acid-insoluble metal sulphides (FeS2, MoS2 and WS2). In this mechanism, main sulphur intermediate is thiosulphate as shown in Equation 10 and Equation 11.

3+ 2- 2+ + FeS2 +6 Fe +3 H2O S203 +7 Fe +6 H (Equation 10) 2- 3+ 2- 2+ + S203 +8 Fe +5 H20 2 SO4 +8 Fe + 10 H (Equation 11)

The second mechanism favours for dissolution of metal sulphides (ZnS, CuFeS2 and PbS) by an attack of ferric iron and/or by protons. In this case main sulphur in the case will be as an intermediate which is shown in Equations 12, 13 and 14.

3+ 2+ 2+ MS + Fe + H+ M + 0.5 H2S + Fe (n > 2) (Equation 12)

3+ 2+ + 0.5H2S + Fe 0.125 S8 + Fe + H (Equation 13)

2- + 0.125S8 + 1.5O2 + H2O SO4 + 2H (Equation 14)

Generation of sulphuric acid is consequently bacterial function biologically to supply protons for hydrolysis attack and/or to keep the iron ions in an oxidized state (Fe+) for an oxidative attack (Figure 2.9). Three species of mesophilic bacteria: T. ferrooxidans (T. f.), T. thiooxidans (T. t.) and Leptospirillum ferrooxidans (L. f) are mainly convoluted. T. ferrooxidans

25 CHAPTER – 1 INTRODUCTION which is basically sulphur and iron oxidizer and another iron oxidizer that is L. ferrooxidans have ability of oxidizing pyrite especially when these are grown up in pure culture. Though T. thiooxidans which plays role as a Sulphur oxidizer is not able to oxidize pyrite alone however it develops its growth on Sulphur which is released when iron is completely oxidized (Rawlings et al., 1999).108

Efficiency of microbial oxidation of pyrite depends on a number of parameters including particle size of pulverized coal, its pyrite content, nutrient media composition, pH, temperature, aeration and also design of reactor. (Klein, 1998) précises some main parameters with indications of optimum conditions for high desulphurization rates.

For large-scale applications different reactor systems have been industrialized. A choice is normally accessible between heap leaching (Beir, 1987)109 and slurry leaching (Beyer et al., 1986)110; earlier one is a cheap approach than slurry leaching. Yet, reaction rates are faster in second one but these involve fine grinding of coal and long residence times with aeration involving large bioreactors. Surface area limits pyrite oxidation rates in heap leaching whereas biomass limits rates in slurry leaching (Olsson, 1994).111 Bond energies of some selected compounds is shown in Table 1.4.

26 CHAPTER – 1 INTRODUCTION

Table 1.4: Bond Strengths in Selected compounds (Bresseler et al.,).112

Bond Bond Strength (KJ/Mole) Reference C-C bonds H3C-CH3 376 Lide, 1995 H2C=CH2 733 Lide, 1995 C-C bond in benzene 505 Sabbah, 1979

C-S bonds C-S 341 Sabbah, 1979 C-S 339 Sabbah, 1979 C-S 338 Sabbah, 1979 HS- CH3 312 Lide, 1995 H3C-S CH3 308 Lide, 1995 H3C-SO2- CH3 280 Lide, 1995 H3C-SCH2C6H5 257 Lide, 1995 H3C- SO2CH2C6H5 221 Lide, 1995

H-C bonds H- CH3 438 Lide, 1995 H- CH2-OH 410 Lide, 1995 H-CHO 364 Lide, 1995

Bio-desulphurization in hydrophobic media Literature describing bio-desulphurization in non-aqueous media is very rare. An unclassified aerobic, gram-positive, soil bacterium, designated as FE-9, was described to desulphurize DBT in 100% dimethylformamide. These pathogenic bacteria transformed under hydrogen DBT to biphenyl and hydrogen sulphide and in air to biphenyl, hydroxyl-biphenyl and sulphate (Finnerty, 1993).113

In recent times DBT desulphurization by Rhodococcus species in two-phase system (solvent: water) was inspected. Obtained results showed augmented DBT desulphurization rates in presence of 45% n-tetrad cane or kerosene (Ohshiro et al., 1996), 95% hexadecane (Kaufman et al., 1998),114 or by use of diesel that 50% (Pacheco et al., 1999).115 DBT desulphurization in Rhodococcus seems to happen intracellularly with DBT uptake from oil phase possibly occurring after transient adsorption to cell (Oldfield et al., 1997). Oil phase and cuff layer emulsions were originate to comprise important quantities of Rhodococcus in 1-10 μm droplets during desulphurization of DBT in hexadecane (Kaufman et al., 1998). Furthermore, Kayser et al. (1993)116 conveyed the relationship between desulphurization activity of R. erythropolis IGTS8 and exterior surface membrane and wall of cell of pathogen. It is evident from literature that membranes are hydrophobic in nature so desulphurization enzymes should work in some organic

27 CHAPTER – 1 INTRODUCTION solvents which in turn will increase mass transfer due to facilitation in contact with coal during process of bio-desulphurization (Patel et al., 1997).117

A substitute method for desulphurization of coal using bacteria and emulsification provided by mineral oil, and solvent mixtures give impression. Lee & Yen (1990) established bio- desulphurization of coal by means of reverse micelle solutions containing T. ferrooxidans cells. Treatment of duration of 24-hour caused a 48% reduction in total sulphur; cell free enzyme excerpts outperformed whole-cell preparations. With long time as much as 70% of total sulphur was detached. Not all sulphur reduction is accredited to biological activity because abiotic controls can reduce total sulphur by as much as 25%. Finnerty (1993) also support this idea, advantages of bio-desulphurization in hydrophobic systems over bio-desulphurization in aqueous systems were anticipated as follows:

1) Enhanced efficiency of biocatalyst in removal of heteroatoms from substrata;

2) Elimination of water-dependent side reactions

3) Improved efficiencies in product recovery by use of low boiling point organic solvents;

4) Process cost benefits

5) Facilitated integration of bioprocessing systems into current fossil industry process infrastructure.

Though, more research is wanted to launch competences, boundaries and optimum conditions for coal biodesulphurisation in hydrophobic media.

Desulphurizing bacteria

More than a few microorganisms have been proposed for process of coal bio desulphurization. Bacteria which are used as Sulphide-reducing were recounted to desulphurize

Sulphur compounds in coal to H2S. Yet, not a weighty reduction in contents of Sulphur of coal was detected in any of reported work (1999 McFarland). Mesoacidophilic, chemolithotropic bacteria have been considered to be the most important organisms for coaldepyritization. Total mainly involved three of species that are T. thiooxidans, Leptospirillum and ferrooxidans (Schippers & Sand, 1999).118 Thiobacillus all species can produce energy from compounds having sulphur in reduce form by process of oxidation. Not like other members of this type of family, ferrous iron can be utilized as electron donor by T. ferrooxidans (Nemati et al., 1998).

L. ferrooxidans in industrial processes is considered to be more potent over T. ferrooxidans for removal of inorganic Sulphur. Major reason associated with it is potential affinity for ferrous and sensitivity to inhibition caused by ferric iron is very low on long time

28 CHAPTER – 1 INTRODUCTION aeration of L. ferrooxidans. Suitable pH for growth of T. ferrooxidans ranges from 1.8-2.5 and on other hand L. ferrooxidans which is in fact acid resistant so it can multiply at acidic pH with value of 1.2. If both species are compared With respect to temperature than T. ferrooxidans is species that accepts low temperature rather than high temperature while that of L. ferrooxidans (Rawlings et al., 1999)119 can grow in high temperature. But some strains of T. ferrooxidans are not able to cause oxidation of pyrite at temperature if low than 10°C (Norris, 1990) so optimal temperature range is 30-35°C. While for L. ferrooxidans upper limit for growth is 45°C (Norris et al., 1986)120 and 20°C is lower limit (Sand et al., 1993).121

Removal of inorganic sulphur is good by use of mesoacidophilic bacteria but not good for if there is concern or removal of sulphur which is organic in nature. Thermoacidophilic bacteria, such as Sulfolobus acidocaldarius, Sulfolobus brierleyi (reclassified as Acidianus brierleyi), Metallo sphaerasedula and Thiobacillus caldus were later recommended for process (Schippers et al., 1999). These bacterial species can cultivate in temperature ranges of 40-90°C, and a pH range of 1.0-5.8 (Karavaiko & Lobyreva, 1994).122 Biodepyritization rates by thermoacidophilic bacteria are advanced than rates by mesoacidophilic bacteria; however, from many results it is acknowledged that mesophiles are more proper for coal depyritization than thermophiles. While S. acidocaldarius and A. brierleyi were conveyed to degrade some organic sulphur compounds, their degradation is in a C-C bond-targeted fashion which is not desirable as sulphur still leftovers in compounds and there is reduction in caloric value of hydrocarbon (Konishi et al., 1997).123

Bioremoval of organic Sulphur was thought not to work at that time. Sulphur removal that is organic in nature was successfully removed by pseudomonas family. For instance, the mutagenically altered bacterium CB 1 isolated from coal contaminated soil, using medium containing DBT for the selection, was reported to remove organic sulphur from model compounds and various coal samples without reduction of the fuel value (Arctech, 1988). Unfortunately due to loss of availability this strain is no longer available to community of research (Oldfield et al., 1998).124 Pseudomonas putida was also claimed to remove both organic and inorganic sulphur. However, conflicting results were obtained from the literature (McFarland et al., 1998).125,126 It seems that there are no well-characterized strains of Pseudomonas species available for further research.

Undeniably aptitude to eliminate both organic and inorganic sulphur has been found in Rhodococcus species which are aerobic, mesophilic, chemo organotropic, and gram positive bacteria (Warhurst & Fewson, 1994).127 A number of DBT-desulphurizing Rhodococcus species have been reported. These include Rhodococcus erythropolis IGTS8 formerly called R. rhodochrous IGTS8 (Kayser et al., 1993),128 R. erythropolis D-1 (Izumi et al., 1994), Rhodococcus sp. SY1 (Omori et al., 1995)129 first reported as Coryne bacterium sp. SY1 (Omori

29 CHAPTER – 1 INTRODUCTION et al., 1992), R. erythropolis H-2 (Ohshiro et al.,1996), R. erythropolis N-36 (Wang & Krawiek, 1996),130 Rhodococcus sp. strain B1, If, Ig and Ih (Denis-Larose et al., 1997) and Rhodococcus sp. ECRD-1 (Grossman et al.,1999)131 which was initially classified as Arthrobacter (Lee et al., 1995)132 and sometimes classified as R. erythropolis X310 (Denis-Larose et al., 1997).133 All these strains are considered very closely related. Among them most studied specie is R. erythropolis IGTS8.

Other DBT-desulphurizing isolates have been classified as Agrobacterium strainMC501 (Constanti et al., 1996),134 Mycobacterium strain G3 (Nekodzuka et al., 1997) and Paenibacillus strain Al 1-2 (Konishi et al., 1997).135 Agrobacterium strain MC501 is the first gram-negative bacterium reported to have DBT desulphurization ability. Paenibacillus sp. strain A11-2 is a thermophile with an apparent maximum specific DBT-desulphurization activity at 50°C. All of these and other isolates were reported to desulphurize DBT to HBP as well, but are then poorly considered. All the above DBT-desulphurizing bacteria seem to have little activity toward thiophenes and benzothiophenes. Gordonia sp. strain 213E able to remove sulphur from BT was later isolated from soil sample (Gilbert et al., 1998)(Figure 1.7). The strain is anaerobic, mesophilic, gram-positive chemoorganotrophic, and recognized as novel species, Gordonia desulfuricans (Kim et al., 1999).136 The Gordonia desulfuricans, however, do not have activity toward DBT.

Figure 1.7a: Benzothiophene desulphurization path way (Gilbert et al., 1998).

30 CHAPTER – 1 INTRODUCTION

S S O O S O - - DBT Sulfone DBT DBT Sulfoxide

2- SO3 + HO Sulphite SOO HO - HBP DBT Sulfinate

Figure 1.7b: 4S Pathway of DBT desulphurization path way (Bresseler et al., 1998).

It can be pointed out from literature, that most fruitful desulphurizing bacterium now a day; are Rhodococcus species, which are talented to selectively remove sulphur from several model compounds. However bacteria are not adaptable for all sulphur compounds. More active microbial cultures are still desirable. Recently, it has been create that when using Shewanella putrefaciens strain NCIMB 8768 in clay bio-desulphurization sulphur odour was reduced (Whittles, personal communication).

Shewanella putrefaciens species are facultatively anaerobic mesophiles, and have several notably properties, e. g. they are versatile with regard to the use of electron acceptors, including oxygen, nitrate, nitrite, dimethyl sulphoxide, thiosulphate, fumarate, and metal oxide. Some strains of S. putrefaciens are iron reducing bacteria, and are able to grow by elemental sulphur reduction (Moser & Nealson, 1996).137

However there is no literature available regarding sulphur removal by the strain NCIMB 8768. This stimulated the work to investigate the desulphurization ability of the strain NCIMB8768, which may provide greater desulphurization efficiency than the current desulphurizing bacteria.

1.7 Gasification process

Thermal process which converts organic or fossil fuel based on carbonaceous into CO2,

H2 and CO without burning is known as gasification. Typically gasification takes place in above ground gasification plant. Reaction can also take place in coal seams below ground. Underground

31 CHAPTER – 1 INTRODUCTION coal gasification technique is used to convert coal into combustible gas. UCG is very much similar to surface gasification. In underground coal gasification cavity below the ground itself becomes reactor for gasification process. Two wells are drilled into the coal, through one well oxidant like water/oxygen or water/air mixture is injected and the product gas formed is brought out to the surface from the other well. Coal present on base of first well is heated to a temperature that burns the coal. By careful regulation of oxidant flow, coal separates into syngas rather than burning. Syngas is then drawn out from second well. Major advantages using this technology are

Low cost of plant, because no gasifiers are needed and no cost of coal transportation. UCG technology also provides the opportunity in reduction of emission because there are fewer surface emissions. UCG also has synergies with CCS as CO2 could be stored in coal cavity after gasification. However before achieving massive deployment a number of issues are to be resolved.

For more than 180 years gasification process is being used for production of energy. In early time’s fuel of these plants were coal and peat. These were established to produce town gas for domestic use. In 1800’s it was replaced by electricity and natural gas and was also used in blast furnaces and for manufacture of synthetic chemicals. During Second World War use of gasification was recurred due to insufficiency of petroleum. Wood gas generators were used to power motor vehicles such as trucks, buses and agricultural machines. It is an estimate that about 9,000,000 vehicles were based on gas all over the world.

1.7.1 Chemical Reactions Involved In Gasification 1. The first step is drying of coal at 100°C. Steam is mixed with gas and then subsequent chemical reactions take place. Water-gas reaction usually takes place if temperature is sufficiently high.

2. Second step is pyrolysis that takes place at temperature of 200-300°C. Volatile matter is released and char is produced, as a result 70% of coal mass is reduced. This process depends upon the properties of carbonaceous materials and determines the properties, structure and composition of char. This undergoes gasification process further.

3. Third process is combustion which occurs as volatile products and char reacts with oxygen to form carbon monoxide and carbon dioxide that supplies heat for gasification process.

4. Process of gasification occurs when char reacts with steam to produce hydrogen and carbon monoxide by this reaction (Figure 1.8).

32 CHAPTER – 1 INTRODUCTION

5. A reversible gas phase reaction of water-gas shift reaction reaches the equilibrium speedily in gasifier. This makes a balance between steam, carbon monoxide, hydrogen and carbon dioxide.

Figure 1.8: Gasification reactions.

A limited amount of oxygen or air is introduced in the reactor to make some of the organic material to burned to product i.e. carbon dioxide and energy. This derives a second reaction which converts more organic matter to carbon monoxide and hydrogen. Further reaction occurs when so produced carbon dioxide and residual water from this react to form methane and excess of carbon dioxide. These reactions occur in reactors and increase the residence time of organic materials, heat and pressure. In more sophisticated reactors catalyst are used to speed up the reactions to achieve the equilibrium more quickly.

1.7.2 Types of gasifiers There are many types of gasifiers which are available commercially; some of them are discussed below:

Counter-current gasifiers

It is a fixed bed of carbonaceous fuel, biomass or coal, which act as gasification agent flows in counter-current pattern. Ash is removed either in the form of slag or in dry condition. Slagging gasifiers have lower steam to carbon ratio gaining a higher temperature than fusion ash temperature. Nature of gasifier means that mechanical strength of fuel must be higher and should be non-cracking so that it may form permeable bed. These restrictions have been reduced by recent developments. This type of gasifier has a low throughput. Tar and methane production is significant typically at operation temperatures. Product gas therefore must be extensively cleaned before using. Tar is then recycled to reactor. In case of fine and undensified biomass gasification such as rice hulls and wheat hulls are necessary to blow with air by using fan. This produces a

33 CHAPTER – 1 INTRODUCTION significantly high gasification temperature as high as 1000°C. A bed of hot and fine char is formed above the gasification zone because gasification is forced through this bed. Mostly complex hydrocarbons are broken down to simpler and smaller components such as carbon monoxide and hydrogen.138

Fluidized bed reactors

Fuel in fluidized is steam and air. Ash from the fuel is removed as heavy agglomerates which defluidize it dry ash gasifiers are of relatively low temperatures so low grade coals are particularly suitable while temperature of agglomerating gasifiers are slightly higher and used for coals of higher rank. Fuel throughput is higher than for fixed bed but less than as for entrained flow gasifiers. Due to elutriation of carbon materials conversion efficiency can be low. This conversion efficiency can be increased by using combustion of solids. For fuels which would damage walls of slagging gasifiers due to formation of corrosive ash fluidized bed gasifiers are more batter to be used. For example corrosive ash level is very high in biomass fuels.

Co-current fixed bed gasifiers

This type of gasifier is similar to counter current type but the flow of gasification agent is in downward direction. Upper part of the bed requires the addition of heat which is provided by some external heat source or by combustion of small amount of fuels. The top of bed contains gasification agent to which heat is transferred which is generated from the produced gas when it leaves the gasifier at a high temperature. This addition of heat will result in the energy efficiency of this bed comparable with the counter-current type. Tar levels for this bed are much lower than counter current type because all tars must have to pass through a hot bed of char.

Entrained flow gasifier

Fuels slurry or atomized liquid fuel, dry pulverized solid, is gasified with oxygen in unidirectional flow. Whole gasification reactions are completed in heavy cloud of small particles. Due to very well separation of coal particles from each other and high operating temperatures this type of gasifier is suitable for most of coal. A higher throughput can be achieved due to high temperature and pressure but on the other hand thermal efficiency is little bit lower, major reason is non-cooling of gas before it is cleaned with existing technology. Higher temperature also shows the non-presence of methane and tar in the final product gas. However oxygen requirements for this type of gasifier are higher than for other types of gasifiers. Operating temperatures for all entrained flow gasifiers is above gas fusion temperature so majority of ash is removed as slag. Consequently a smaller fraction of ash is generated either as a dry fly ash or as ash slurry. Certain types of biomasses contain the fuel which form slag on the inner walls of

34 CHAPTER – 1 INTRODUCTION ceramics, which is acting as a protector to the outer wall of gasifier. However some entrained types of gasifiers are not affected with this slag because they have inner water or steam cooled wall. Some of the fuels produce ashes with very high fusion temperatures. Before gasification usually lime stone is added to the fuel. Lime stone addition is related with lowering of fusion temperatures. Particle size of fuel is much lower than used in other gasifiers. Production of oxygen used in gasification process is more convenient in this process.

Plasma gasifier

High temperature arc is created in this type of gasifier when a high voltage current is fed to a torch. A glass like substrate is generated when inorganic residue retrieved.

1.8 Liquefaction of Coal Our modern world depends upon transportation and electricity. We can’t imagine our lives without both. Transportation and electricity mainly depends on crude oil. But as the demand of crude oil is increasing, prices of oil are also increasing and there is shortage of crude oil. So it has created an interest in alternative fuels. CTL (coal-to-liquid) is the technology which will reduce dependence on crude oil as we will able to produce fuel from coal. In this paper we will be discussing about various technologies from which we can make fuels from coal. The various technologies used are Pyrolysis, Direct Coal Liquefaction, Indirect Coal Liquefaction, and Bio- Liquefaction. CTL is not a feasible solution for the shortage of crude oil but it will be a minor contribution to overcome the shortage of crude oil and will help in dropping down the prices of crude oil.

1.8.1 Pyrolysis High temperature pyrolysis is the oldest method for obtaining liquid from coal. Coal in a closed container is heated up to 950°C. Carbon content is increased by decomposition is carried at high temperature as a result of which volatile matter is removed. This process is much similar to coke making process and a side product is generated which is mostly tar like liquid. This process is based on production of low liquid and upgrading costs are comparatively high. Usually transportation sector does not employ coal tar as fuel however it is globally applicable for production of water proof and insulating products and also used for development of many dyes, paints and drugs. In Pyrolysis with temperature 450-650°C most of volatile matter is removed and some other compounds are generated by thermal decomposition. Maximum of 20% liquid yields are produced when temperature is kept higher than above mentioned temperature. Coke, semi- coke and char are the main products by increasing calorific values and reducing Sulphur content this technique upgrades low rank coals. Karrick process139 is a low temperature carbonization process but semi-coke is the main product. Tar liquids are used as transportation fuel after

35 CHAPTER – 1 INTRODUCTION refining. We can summarize that low liquid yields are provided by pyrolysis and resulting liquid is required before they can be used in existing vehicles. In 1992-1997 a demonstration plant for coal upgrading was established in USA.

1.8.2 Direct coal liquefaction This process is built around Bergius-process which includes desolvation of coal at high temperature and pressure. Hydrocracking is caused by the addition of hydrogen and a catalyst in which long carbon chains are converted into shorter chains furthermore addition of hydrogen improves the H/C ratio of product. Liquid yields with thermal efficiencies of 60-70% can be in excess of dry weight of the coal generated liquids are of higher quality as compared to pyrolysis and can be employed in power generation or can be used as synthetic crude oil. But before as a transport fuel some further treatment and refining stages are needed. Refining can be done by sending the synthetic crude oil to the refinery or at CTL facility.140 Some important products like gasoline, diesel, propane and butane can be obtained from refined oil.

1.8.3 Indirect coal liquefaction In this process by gasification complete breakdown of coal takes place into other compounds resulting Syngas is modified to obtain required balance of carbon monoxide and hydrogen. Syngas is further cleansed by removing Sulphur and other impurities which can cause disturbance in further reactions. By using FT-reactions desired products generated by reaction of Syngas over a catalyst.141 A wide range of different products can be created by altering catalyst and reaction conditions for example methanol product can be produced directly or converted into high quality gasoline via mobile process in additional stages. Here it is summarized that FT synthesis are of two types, one in which gasoline like fuel is generated (high temperature version) and second in which diesel like fuel is generated (low temperature version). More details on FT synthesis via ICL technology have been discussed by others. Sasol in South Africa is only commercial ICL plant which has well established technology and lot of operational experience. It has total 50 years of experience. Different ICL technologies have developed by Sasol but the oldest one was developed in 1950s. Sasol Advanced Synthol High Temperature FT synthesis is advance technology being utilized from 1990s.

1.8.4 Bio liquefaction 70 % of total Chinese fossil fuel energy reserves and 91 % of annual energy consumption is generated from coal. Coal is dominating from a long time to date in Chinese energy markets. Lignite in other coal types is more important fossil energy fuel in China. 1n 1995 Lignite was 130 Billion Tons142 (more than 13 % of total coal reserves in China) and according to third nationwide coal prediction (2005) high ash content, water content, low heating value, degradation under windy conditions and spontaneous combustion are some disadvantages of Lignite over

36 CHAPTER – 1 INTRODUCTION

Bituminous, so the applications of Lignite are limited however lignite is utilized to generate electricity and combustion gas. In these processes sulfides and nitrogen oxides are produced as pollutants and high input energy is required, so it necessity of time a new methodology to utilize lignite by some economical and environment friendly technology. A potential technology (bio liquefaction of lignite) is economical process in which lignite is liquefied by the use of some microorganism and no pollutants are produced. Fakoussa143 reported that microorganisms can liquefy lignite even at room temperature. Later on many organisms were found world widely which can work at room temperature. Through literature it is clear that both fungal and bacterial strains can be utilized in liquefaction of lignite. Bacterial strain include Bacillus cereus and fungal include Streptomyces badius but these microorganisms cannot liquefy Chinese lignite. One research group isolated fungus AH from Fushun mine in China which can liquefy Chinese lignite.144

1.8.5 Comparison of DCL and ICL DCL and ICL are the main candidates for future CTL technology. DCL attempts to make coal liquefaction and reefing similar to that of ordinary crude oil processing. Required amount of liquefaction equipment is reduced by side stepping complete breakdown of coal which results in gaining some efficiency. A large number of different substances are present in coal i.e. many unwanted or toxic substances. Some of these toxic substances can be present in resulting crude oil or may affect catalyst. Ever-changing environmental conditions may force adjustment in DCL process requiring it to meet new regulatory mandates, just as crude oil processing has to be overhauled when new environmental protocols are introduced while a designer fuel strategy is used in ICL.145 Many of various processes will use hydrocarbon fuels which are superior to conventional oil derived products.

Comprehensive comparison between DCL and ICL has been shown in Table 1.5. Generally it is difficult to make a comparison directly because DCL yields unrefined syncrude but ICL produces final products. DCL has not a long history of commercial performance as ICL.

37 CHAPTER – 1 INTRODUCTION

Table 1.5: Typical properties of DCL and ICL final products. DCL ICL Distillable product mix 65% diesel, 35% naphtha 80% diesel, 20% naphtha

Diesel Cetane Number 42-47 70-75

Diesel sulphur Content <5 ppm <1 ppm

Diesel Aromatics 4.8% <4%

Diesel specific Gravity 0.865 0.780

Naphtha octane number >100 45-75 (RON) Naphtha sulphur Content <0.5 ppm Nil

Naphtha Aromatics 5% 2%

Naphtha specific gravity 0.764 0.673

Due to stronger infrastructure batter environmental capabilities and higher flexibility ICL seems to be more batter for future projects. If we consider and use efficiency instead of process efficiencies fuel properties seem to benefit ICL compared to DCL. If we consider estimated cost then both systems are similar in our compilation and analysis we found that coal consumption is major factor for CTL feasibility. We anticipate that only a few countries can realistically develop CTL industry on large scale.

38 CHAPTER – 1 INTRODUCTION

1.9 Aim of present study

The present study is aimed at finding the rank of coal through proximate analysis and determination of calorific values. The heavy metals present in coal are environmental hazard; therefore analysis of trace metals is also needed. Since coal found in Pakistan contains relatively greater amount of sulphur, the aim is to remove sulphur by different sulphur leaching methods to get clean energy from coal.Chemical leaching using different acids and alkalies and biochemical leaching are to be done. In order to get clean energy from coal the electrolysis of coal under acidic and alkaline conditions is designed so that hydrogen can be obtained.

CHAPTER No.2

EXPERIMENTAL SECTION

CHAPTER – 2 EXPERIMENTAL SECTION

2.1 Materials Coal samples were obtained from different areas such as Duki, Chamlang (Baluchistan) and Salt Range (Punjab) of Pakistan. Ten samples were collected from each mining site. All samples were homogenized and desiccated to remove humidity then crushed to fine powder and sieved through 250 µm mesh sieve. These samples were stored in airtight bags of polyethylene before analysis.

Analytical grade reagents including Copper sulphate (CuSO4), potassium sulphate (K2SO4), sodium hydroxide (NaOH), barium chloride (BaCl2), sulphuric acid (H2SO4), nitric acid (HNO3), hydrochloric acid (HCl) and hydrofluoric acid (HF) were purchased from Merck and were used as such without any further purification.

2.2 Analysis Proximate and ultimate analyses were performed according to ASTM (American Society for Testing Materials) guidelines, whereas Ballistic bomb calorimeter was used to investigate calorific value.

2.2.1 Proximate analysis and calorific value determination In proximate analysis, ash, moisture, volatile matter and calorific value of all collected coal samples were determined by using American Standard for Testing and Material ASTM D3174, ASTM D3173, ASTM D3175 and ASTM D3286 respectively.146,147 Value of fixed carbon in analyte was obtained by subtracting % age of ash, moisture and volatile content from 100.148,149,150

2.2.2 Moisture content The moisture contents of all the coal samples were quantified by following ASTM-D3173 standard.151 In this method, weighed crucible was taken and small amount of each sample was put into it and then finally it was placed in a cold muffle furnace. Removal of moisture was done by putting sample to heat at 104°C for one hour. Then the crucible was cooled to room temperature in a desiccator and weighed again. The %age moisture content was calculated as percentage weight loss.

2.2.3 Volatile matter The volatile matter of each coal sample was determined using ASTM-D3175 standard [xxiii15]. Accurately weighed amount (1.0 g) of moisture free sample taken into a crucible which was already weighed having a lid and heating temperature was up to 925°C for a time period of 7 min in a muffle furnace. The sample was removed before reaching the ignition temperature then cooled to room temperature in a desiccator. The sample with crucible was weighed again and volatile matter was calculated as the percentage weight loss.

40 CHAPTER – 2 EXPERIMENTAL SECTION

2.2.4 Ash content ASTM- D3174 standard was followed to determine the ash content of each coal sample.152 Weighed amount of sample was placed in a pre-weighed crucible which was cleaned and then both were placed in furnace at room temperature. Sample temperature was initially raised to high temperature that was 500°C in 1 h initially and finally up to 750°C in next hour. Then it was cooled to room temperature in a desiccator and weighed again. The percentage ash content was then calculated.

2.2.5 Fixed carbon The leftover weight after moisture, volatile matter and ash removal is fixed carbon whose percentage was calculated by the method of difference.

2.2.6 Calorific value ASTM D5865 standard was followed for the estimation of calorific value of all coal samples. Benzoic acid with known calorific value (6.32 kcal/g) was used as standard to calibrate Ballistic bomb calorimeter.153 A known mass (0.5 g) of each sample taken in the crucible was placed in the bomb calorimeter. Oxygen was filled up to pressure of 25 bar and the sample was ignited. Heat released as a result of combustion reaction was noted by the maximum deflection of galvanometer. The energy value of the sample material was estimated by comparing galvanometer deflections for the sample and that for the standard (benzoic acid) and is given in the equation: G. meter deflection calibration Q  Original weight  of  sample Its mathematical form is shown in equation below:    Q31 kcal/ g Z

Where Q is heat released from sample, θ1 is the galvanometer deflection without sample,

θ3 is the galvanometer deflection with sample, Z is the mass of sample in g and γ is the calibration constant.

2.2.7 Determination of total Sulfur (Eschka Method) Coal (1.37 gm) was finely grounded and passed through No. 60 (250 μ) sieve. Coal powder was spread on porcelain crucible and covered with three gram of Eschka mixture (with Eschka mixture containing two parts of light claimed MgO and one part of anhydrous sodium carbonate). Gradual heating of crucible was done by placing it in muffle furnace and heating to 800oC in time of more than one hour till no black particles are left in sample. After cooling the mixture was decanted twice with hot water until filtrate left in beaker is of 200 mL. Sufficient

HCl was added to make the solution acidic, followed by the addition of 10% BaCl2 solution to precipitate sulfate as BaSO4. The resulting solution was allowed to stand for at least two hours at

41 CHAPTER – 2 EXPERIMENTAL SECTION just below the boiling temperature. The solution was then filtered and washed with excess hot water to completely remove BaCl2. Precipitates were then ignited in porcelain crucible in excess air below dull redness. After smoking off the filter paper ppt. of BaSO4 were weighed. percentage of total sulfur in coal sample can be calculated after subtracting amount of barium sulfate and shown in formula given below:

(Weight of BaSO4 in sample − Weight of BaSO4 in Blank) x 13.74 Percentage of Sulfur = Weight of Sample

Sulphur is present in three forms in coal: (1) pyritic sulfur, organic sulfur and sulfate sulfur. Sulfate sulfur is extracted from the coal samples with dilute HCl and pyritic sulfur is extracted from HCl coal residue with dilute HNO3. The pyritic sulfur is determined from HNO3 solution or calculation from pyritic iron which is HNO3 soluble, while sulfate sulfur is determined from HCl solution.

2.2.8 Determination of Sulfate Sulfur Coal sample (2.0 gram) was placed in 250 mL beaker and wetted with 3mL 1:3 ethyl alcohol. Sample was boiled for twenty minutes after adding 50 mL of HCl (1:3). After boiling mixture for twenty minutes mixture was filtered and the coal residue was washed thoroughly six times with cold water and residue was retained for pyritic sulfur determination (2.2.9). To the filtrate was added 10 mL of bromine water and heated to almost boiling. Ammonium hydroxide solution was then added and solution was again heated for twenty minutes. The solution was filtered while hot and the residue was washed five to six times with hot water and volume of filtrate was made 200 mL by adding distilled water.

Solution was neutralized with hydrochloric acid using methyl orange indicator and 10 percent barium chloride solution was slowly added while heating. The solution was allowed to stand for several hours, filtered, washed with excess water to remove any free chlorides and then filter paper was ignited. The weight of barium sulfate was measured in grams and multiplied by 6.868 to obtain the percentage of sulfur as sulfate in coal.’

2.2.9 Determination of pyritic Sulfur Coal residue along with the filter paper from HCl separation in previous procedure (2.2.8) was macerated in 100 mL of 25 percent by volume of HNO3 and allowed to stand 12 to 24 hours with occasional stirring at room temperature. After filtration 3 mL of conc. HCl was added and evaporated to dryness on boiling water bath. Residue was dissolved in 5 mL of concentrated hydrochloric acid and 25 mL water. The solution was transferred to 250 mL beaker excess ammonium hydroxide was added (25 mL). The hot solution was filtered and washed with hot water several times. Sulfur present in the filtrate was determined by the same method as used for sulfate sulfur.

42 CHAPTER – 2 EXPERIMENTAL SECTION

2.2.10 Determination of Organic Sulfur Determination of this type of sulfur was done by subtracting sum of pyritic and sulfate sulfur from total sulfur.

Organic Sulfur = Total Sulfur- (Pyritic Sulfur + Sulfate sulfur)

2.2.11 Determination of oxygen content The oxygen content of the coal samples was determined by the difference as shown in equation below:

%Oxygen 100  C  H  N  S  Moisture  Ash %

2.2.12 Trace Metal Analysis Analytical grade reagents including nitric acid, hydrochloric acid and hydrofluoric acid were purchased from Merck and were used as such without any further purification. Coal sample

(1.0 gm) was digested in a mixture of HCl (10.0 mL), HNO3 (10.0 mL) and HF (20.0 mL) by heating on hot plate for 6 hours. Heating was continued until complete dryness to remove volatile fluorides. Then 5 ml each of HNO3 and H2O were added and contents were filtered out in 50 mL measuring flask and volume was made upto the mark154

2.3 Desulphurization of Coal 2.3.1 Sulphur leaching with strong acids or alkalis

Leaching of sulphur from coal was investigated by using strong acids like H2SO4, HCl and HNO3 or alkalis such as NaOH, KOH or Na2CO3. Unless otherwise stated, the leaching experiments were carried out with 20 g coal powder (≤ 200 micron) in 100cm3 2.0 mol/dm3 solution of an acid or alkali taken in 250 cm3 conical flasks. The flasks were shaken at 100 rpm in

o a shaking incubator at 65 C for 30 minutes

2.3.2 Bio-desulphurization Desulphurization of coal was also studied through microbial bioleaching was achieved

2.3.3 Microorganism The Ferrous-oxidizing bacterium Thiobacillus ferrooxidans was used for microbial desulphurization. The strain was isolated from soil samples.

2.3.4 Isolation of Ferrous-oxidizing Bacteria Ferrous oxidizing bacteria were isolated on following sterilized medium in pre-sterilized Petri plates (Silverman et al).

43 CHAPTER – 2 EXPERIMENTAL SECTION

Table 2.1: Isolation Medium No. Ingredient Amount 1 FeSO4.7H2O 18m.mole 2 Proline 0.4g 3 Agar 1.0g 4 Basal Salt solution 100Ml

The basal salt solution has the following composition (Silverman et al).

Table 2.2: Basal Salt Solution No. Ingredient Amount

1 (NH4)2SO4 3.0 g 2 KCI 0.1 g

3 K2HPO4 0.5 g

4 MgSO4.7H2O 0.5 g

5 Ca(NO3)2 0.01g; 6 Deionized water 1000mL 7 The pH of the medium was set to 2.5 using Conc.

H2SO4 before sterilization 2.3.5 Media and conditions of cultivation A single isolated colony, after positive identification, was taken from the plate and transferred to 250 mL conical flask containing 50 mL sterile salt solution (Table 2.2) with 0.1M

FeSO4. The flasks were incubated for four days in shaking incubator (New Brunswick Classic C24KC) at 30°C and 100 rpm. The growth was harvested and used as inoculums.

The isolated strain was preserved in Fe2+ (0.10 M)-salts medium consisting of Fe2+ (0.108 mol.) and salts solution (1000 ml).

2.3.6 Methods of bacterial leaching: Microbial desulphurization was carried out with Thiobacillus ferrooxidans obtained from Biotechnology and Food Research Centre PCSIR Labs Lahore. The microbial cultivation and leaching were performed in two separate bioreactors. The culture was grown in 7.5 L glass fermenter (New Brunswick) in continuous mode whereas leaching was performed in 15 L locally fabricated stainless steel reactor in repeated fed batch mode.

The medium was transferred to the fermenter 1 and sterilized by placing the bioreactor in autoclave. The fermenter 2 contained 50%coal slurry and was sterilized by passing steam for 30 minutes. The medium was inoculated with 200 mL 72 hours old inoculum developed in shake flasks. The fermentation was carried out at 28oC at constant pH of 2.0±0.1When the bacterial concentration reached 109 per mL, feeding of the sterile medium into the fermenter 1 and culture broth from fermenter 1 to fermenter 2 were started @ 1mL per minute.

44 CHAPTER – 2 EXPERIMENTAL SECTION

2.3.7 Determination of Bacterial Biomass During the growth samples (5 mL) were drawn every 12 hours and analyzed for total cell count by agar plate method.

2.4 Electrolysis of Coal Slurries 2.4.1 Electrolysis of Coal Under Acidic Conditions The electrolysis of lignite slurry was carried out in the presence of sulphuric acid solution in a glass cell (12 cm x 6 cm x6 cm). The anodic and cathode compartments were separated by a glass partition provided with a 4 cm x 4 cm window guarded by porous glass frit to prevent the lignite particles from entering into the cathode chamber. Lignite slurry was taken in the anodic compartment and its contents were stirred magnetically. The anode and cathode were platinum coated 2 cm x 4 cm titanium plates. Above the electrolyte level both the electrodes were connected to gas burettes to collect the produced gases. The cell also contained a thermometer.

Unless otherwise stated each experiment involved 500 mL I.0 mol/L H2SO4 with 50 g lignite powder.

Percentage of coal in the slurry was optimized by classical method and Response Surface Methodology (RSM) was used to optimize four factors i.e. Temperature: Voltage, Ferric concentration and Particle size. Small rotatable central composite design (SRCD) with eight runs for each at axial and factorial points and five replicate runs at center points was augmented to estimate key factors, their respective interactions and pure error. Each factor was investigated at five levels -α, -1, 0, +1, +α (α=1.682) in a randomized order. The whole data was manipulated in Design Expert (Version, 10.0.) statistical software for design selection, robustness, graphical and numerical optimization. The effect of reaction conditions and their interactions were calculated at a 95% confidence interval for means. Two responses including, Hydrogen yield (mL), and Carbon dioxide yield (mL) were modeled by following second order polynomial equation.

Y= 푏 + ∑푘 푏 푋 + ∑푘 푏 푋2 + ∑푘 ∑푘 푏 푋 푋 0 푖=1 푖 푖 푖=1 푖푖 푖>1 푗 푖푗 푖 푗

푘 Where Y denotes response to be optimized;푏0 intercept; ∑푖=1 푏푖푋푖, linear effect of

푘 2 푘 푘 155 variables; ∑푖=1 푏푖푖푋 , quadratic effect and ∑푖>1 ∑푗 푏푖푗푋푖 푋푗 , interaction between these factors.

2.4.2 Electrolysis of Lignite Under Alkaline Conditions The electrolysis of lignite slurry was carried out under alkaline conditions in a glass cell as stated above Unless otherwise stated each experiment involved 500 mL electrolyte (in 0.1 mol/L NaOH) with 50 g lignite powder. The electrolysis was carried out at 60oC and 2.7 volts.

After 15 minutes electrolysis, the whole slurry was treated with 100 mL 1.0 mol/L H2SO4 in a conical flask connected to a delivery tubes. The CO2 gas released on acidification was quantified

45 CHAPTER – 2 EXPERIMENTAL SECTION by back titration method.156 The solids were separated from the acidified residue by filtration, washed and dried and its humic acid contents were determined.157

Percentage of coal in the slurry was optimized by classical method and RSM was used to optimize cell voltage, particle size of coal, Concentration of NaOH and temperature.

CHAPTER 3

RESULTS AND DISCUSSION

CHAPTER – 3 RESULTS AND DISCUSSION

3.1 Proximate composition of coal Proximate analysis involves determination of moisture, ash content, volatile compounds and fixed carbon in coal samples. Coal having less moisture and volatile matter, and higher fixed carbon and calorific values is ranked better in quality. Proximate analysis including the moisture content (%), ash content (%), volatile matter (%), fixed carbon (%) and calorific value (kcal/kg) of coal samples of Duki, Chamalang (Baluchistan) and Salt Range (Punjab) are described in Table 3, 4 and 5, respectively and is also shown in Fig. 3.1 and 3.2. The minimum values of moisture, ash, volatile matter, fixed carbon and calorific values of Duki coal (Table 3.1) are 2.50±0.92, 6.50±0.95, 34.30±1.96, 32.58±1.5, 81.90±0.09 and 5082±24.59, respectively. The maximum values of these parameters for Duki coal are 10.89±2.25, 24.27±3.54, 46.40±1.67, 44.60±3.49 and 6547±29.28 respectively. The average values of these parameters are 6.61, 14.81, 39.48, 39.08 and 5867 respectively. For Chamalang coal (Table 3.2), the minimum values are 1.01±0.02, 6.70±0.57, 34.40±1.42, 33.32±2.51 and 5352±31.09, respectively whereas the maximum values are 5.72±1.28, 23.85±1.34, 45.61±2.27, 52.37±3.67 and 6971±31.69, respectively. The average values are 3.0, 17.63, 38.49, 43.01 and 6125, respectively. In case of Salt Range coal (Table 3.3) the minimum values are 1.90±0.08, 17.29±01.35, 22.70±1.44, 24.40±2.50 and 3890±17.45, respectively and the maximum values are 7.03±1.11, 39.30±02.69, 39.04±2.09, 54.40±3.47 and 6098±36.94, respectively while the average values of these parameters are 4.48, 26.38, 32.54, 36.60 and 5094, respectively. The above stats indicate that the coal belonging to the aforementioned areas of Pakistan is sub- Bituminous. In addition, it also shows that Salt Range coal is low in quality as compared the other two areas.

3.2 Trace metals content of Coal Trace metals are known to exert adverse health effects to the population that is direct in contact with the coal burning or living closer to the coalmines, coal deposits, or coal-burning power stations. The estimation of trace metal level in the coal is therefore very important in order to generate base line data and to plan futuristic strategies to avoid any heath related implication associated with coal burning.158,159 In this study, trace metals including Co, Cr, Cu, Ni, Pb, Zn and Cd were investigated in coal samples from Duki, Chamalang and Salt Range and results are shown in Fig. 3. The trace metal content in Duki coal ranged from 2.55±0.51 to 15.80±2.56 for cobalt, 4.901.57± to 43.05±3.58 for chromium, 2.15±0.08 to 36.55±3.31 for copper, 5.98±1.25 to 21.05±1.25 for nickel, 0.95±0.01 to 3.89±0.33 for lead, 4.86±0.43 to 18.62±2.03 for zinc and 0.05±0.01 to 0.20±0.06 for cadmium. Trace metal values of Duki coal are given in Table 3.4 while those for Chamalang and Salt Range are shown in Table 3.5 and 3.6, respectively.

47 CHAPTER – 3 RESULTS AND DISCUSSION

The trace metal comparison of coal of these areas shows that coal of Salt Range contains greater amount of trace metals than the other two areas located in Baluchistan province (Fig. 3.4). When compared with international coal (Table 3.8) it is found that the coal belonging to these three areas of Pakistan possess comparatively higher values of Co, Cr, Cu, Ni and Cd. However, the value of Zn is higher in Chamalang and Salt Range coal but it is lower for Duki coal than International coal. The lead content is lower in Pakistani coal than international coal.

48 CHAPTER – 3 RESULTS AND DISCUSSION

Figure 3.1: Average percentage moisture content, ash content, volatile matter and fixed Carbon in Duki Coal (Baluchistan), Chamalang Coal (Baluchistan) and Salt Range Coal (Punjab).

49 CHAPTER – 3 RESULTS AND DISCUSSION

Figure 3.2: Average calorific value (kcal/kg) of Duki, Chamalang coal (Baluchistan) and Salt Range coal (Punjab).

50 CHAPTER – 3 RESULTS AND DISCUSSION

Figure 3.3: The average levels of trace metals in Duki, Chamalang coal (Baluchistan) and Salt Range coal (Punjab).

51 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.1: Proximate Composition of coal from Duki (Baluchistan).

Calorific Sampling Moisture Ash Volatile Matter Fixed Value Location (%) (%) (%) Carbon (%) (kcal/kg)

DC1 10.89±2.25 9.73±1.58 38.12±2.77 41.28±3.45 6068±56.00

DC2 4.91±0.97 24.27±3.54 34.10±1.94 36.70±2.15 5226±41.05

DC3 9.71±1.58 10.78±2.15 40.77±2.75 38.74±1.94 5832±37.52

DC4 7.84±1.12 22.74±1.36 36.81±3.04 32.58±1.58 5082±24.59

DC5 4.90±0.81 10.70±1.49 39.80±2.51 44.60±3.49 6245±36.12

DC6 10.80±2.47 15.30±1.80 34.30±1.96 39.60±2.56 5436±31.28

DC7 7.20±1.36 6.50±0.95 42.50±3.57 43.80±2.13 6393±46.70

DC8 2.50±0.92 18.40±2.04 41.4±3.01 37.70±2.05 6547±29.28

DC9 4.80±1.02 14.70±1.45 40.60±2.88 39.90±2.45 5890±39.51

DC10 2.60±0.56 15.01±1.87 46.40±1.67 35.90±1.98 5955±19.58

Mean 6.61 14.81 39.48 39.08 5867

DC= Duki coal

52 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.2: Proximate Composition of coal from Chamalang (Baluchistan)

Calorific Sampling Moisture Ash Volatile Matter Fixed Value Location (%) (%) (%) Carbon (%) (kcal/kg)

CC1 1.92±0.09 14.0±1.61 37.68±1.91 46.40±3.44 6327±22.57

CC2 1.90±0.04 12.51±0.91 38.65±2.36 46.91±2.57 6444±30.56

CC3 4.01±1.00 18.80±2.01 37.20±1.73 39.99±2.12 5742±36.17

CC4 3.80±0.83 21.22±2.34 36.70±2.01 38.30±2.24 5550±22.25

CC5 2.71±0.07 9.61±1.33 38.44±1.55 49.23±3.88 6539±28.37

CC6 1.82±0.05 10.80±1.08 39.61±1.93 52.37±3.67 6971±31.69

CC7 4.31±0.84 16.03±2.34 36.60±2.00 42.98±3.24 5967±38.12

CC8 5.72±1.28 20.01±2.85 34.40±1.42 39.89±2.59 5531±28.21

CC9 1.01±0.02 6.70±0.57 45.61±2.27 40.69±3.61 6825±24.77

CC10 2.80±0.06 23.85±1.34 40.03±1.91 33.32±2.51 5352±31.09

Mean 3.0 17.63 38.49 43.01 6125

CC= Chamalang coal

53 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.3: Proximate Composition of Coal from Salt Range (Punjab).

Calorific Sampling Moisture Ash Volatile Matter Fixed Value Location (%) (%) (%) Carbon (%) (kcal/kg)

SRC1 5.82±1.05 22.75±2.15 32.39±1.74 39.04±1.99 5421±20.89

SRC2 3.96±0.71 23.76±1.78 35.76±2.22 36.52±1.67 5326±18.76

SRC3 1.90±0.08 17.29±1.35 26.40±1.85 54.40±3.47 6098±36.94

SRC4 7.92±2.04 23.52±2.77 33.66±2.05 34.90±2.11 5023±28.25

SRC5 3.20±0.69 26.73±1.95 36.40±1.11 33.67±2.22 5117±22.29

SRC6 2.97±0.51 33.66±2.68 39.04±2.09 24.40±2.50 4491±21.98

SRC7 4.01±0.83 35.21±1.98 30.31±1.15 30.47±2.43 4368±25.53

SRC8 5.01±1.05 23.76±1.54 35.02±1.58 36.21±2.86 5250±30.25

SRC9 7.03±1.11 39.30±2.69 22.70±1.44 30.97±1.79 3890±17.45

SRC10 3.01±0.82 17.82±1.08 33.78±1.96 45.40±3.29 5958±05.38

Mean 4.48 26.38 32.54 36.60 5094

SRC= Salt Range coal

54 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.4: Trace metals Analysis of Coal sample from Duki Coal (Baluchistan).

Location Sampling (Mean±SD) Co (ppm) (Mean±SD) Cr (ppm) (Mean±SD) Cu (ppm) (Mean±SD) Ni (ppm) (Mean±SD) Pb (ppm) (Mean±SD) Zn (ppm) (Mean±SD) Cd (ppm)

DC1 3.0±0.85 19.0±2.05 14.0±2.15 5.98±1.25 1.40±0.05 4.86±0.43 0.15±0.04

DC2 4.60±0.94 13.85±1.86 11.35±0.95 14.45±2.24 1.12±0.24 5.75±0.09 0.20±0.06

DC3 2.55±0.51 4.90±1.57 2.15±0.08 12.60±1.61 0.95±0.01 18.62±2.03 0.05±0.01

DC4 12.0±1.24 42.3±3.56 20.0±2.47 8.95±2.15 1.86±0.06 5.90±0.54 0.09±0.02

DC5 7.41±0.74 22.35±3.15 18.42±2.25 13.60±1.10 1.95±0.08 12.87±1.54 0.12±0.05

DC6 7.20±0.98 25.40±2.25 15.90±1.53 13.05±2.10 1.89±0.12 7.90±1.06 0.16±0.04

DC7 3.30±0.57 7.05±1.11 5.25±1.11 13.25±1.17 2.45±0.05 9.94±2.10 0.07±0.01

DC8 4.40±1.01 7.90±125 9.95±3.12 18.45±2.26 2.83±0.10 11.76±2.31 0.10±0.01

DC9 15.80±2.56 43.05±3.58 36.55±3.31 21.05±1.25 1.03±0.01 12.89±1.95 0.08±0.02

DC10 13.95±1.24 37.75±3.56 50.65±4.51 14.80±1.29 3.89±0.33 7.56±1.34 0.13±0.03

Mean 7.42 22.36 18.42 13.62 1.94 9.80 0.115

DC= Duki coal

55 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.5 Trace metals content of understudy samples from Chamalang Coal (Baluchistan).

Location (Mean±SD)

(Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD)

Cu (ppm) Cd (ppm)

Co (ppm) Zn (ppm)

Sampling

Cr (ppm) Pb (ppm)

Ni (ppm)

CC1 11.35±1.25 46.60±4.18 32.95±3.50 26.60±3.16 2.67±0.35 23.67±3.45 0.09±0.01

CC2 9.95±1.09 26.3±2.74 18.65±2.58 19.5±1.55 4.23±0.48 12.89±2.15 0.25±0.07

CC3 4.55±0.68 6.30±0.57 12.3±1.47 16.1±1.24 3.95±0.25 23.12±3.33 0.17±0.03

CC4 8.55±1.28 44.55±3.88 33.55±3.11 19.90±2.47 3.90±1.0 7.98±1.17 0.12±0.03

CC5 3.00±0.25 7.01±1.02 16.95±1.59 6.12±1.05 1.35±0.05 15.87±2.49 0.05±0.01

CC6 19.85±2.24 5.55±0.54 49.75±2.99 29.3±3.28 2.24±0.19 11.76±1.29 0.08±0.01

CC7 21.55±2.57 31.95±3.25 36.7±3.51 25.95±2.04 3.78±0.67 8.94±1.56 0.14±0.03

CC8 10.75±1.25 32.9±4.11 18.5±2.22 14.6±1.42 3.09±0.25 - 0.09±0.01

CC9 11.19±1.02 25.14±1.28 27.42±1.45 19.76±2.22 3.15±0.39 5.89±0.97 0.15±0.02

CC10 8.56±1.58 22.96±2.38 19.45±2.38 12.03±1.05 2.74±0.11 4.98±0.04 0.07±0.01

Mean 10.93 24.93 26.62 18.99 3.11 13.31 0.12

CC= Chamalang coal

56 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.6 Trace metals content of understudy samples from Salt Range Coal (Punjab).

(Mean±SD) Zn (ppm)

(Mean±SD) (Mean±SD) (Mean±SD) (Mean (Mean±SD) (Mean±SD)

Cu (ppm) Cd (ppm)

Co (ppm)

Sampling

Cr (ppm) Pb (ppm)

Ni (ppm)

Location

±SD)

SRC1 5.0±0.62 20.5±2.82 11.1±2.14 11.4±1.89 10.3 ±1.59 11.1±1.12 0.14±0.02

SRC2 13.45±1.09 14.3±2.02 13.8±1.54 12.9±2.04 12.1±1.26 8.75±2.01 0.09±0.01

SRC3 21.2±2.14 59.8±3.69 37.25±2.45 41.8±3.33 3.91±0.14 33.12±3.07 0.06±0.01

SRC4 5.05±0.57 20.5±2.15 13.6±3.26 21.05±2.73 3.84±0.58 12.98±1.12 0.12±0.03

SRC5 5.85±1.02 22.0±2.22 8.9±2.14 14.25±2.21 0.78±0.01 22.45±3.13 0.17±0.03

SRC6 16.75±2.50 43.8±4.53 35.45±3.65 35.3±2.56 4.07±0.26 16.90±2.45 0.14±0.01

SRC7 9.45±1.47 36.55±3.21 25.85±3.33 23.15±3.53 4.56±0.17 32.21±3.37 0.06±0.01

SRC8 21.05±3.05 39.1±2.58 18.15±2.25 21.35±2.25 2.98±0.34 10.76±1.12 0.08±0.02

SRC9 10.65±1.25 46.15±3.36 23.35±3.26 36.55±2.14 4.09±0.28 9.95±1.16 0.16±0.06

SRC10 3.65±0.69 8.75±1.33 5.7±0.86 7.85±1.21 12.75±1.49 8.43±0.09 0.06±0.01

Mean 11.21 31.14 19.31 22.56 5.94 16.665 0.108

SRC= Salt Range coal

57 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.7: Comparison of trace metal content among Duki, Chamalang and Salt range coal with international coal. Metal Duki Coal Chamalang Salt Range International Energeia Coal Coal coal MinimumValue 2.55 4.55 3.65 1.2 0.5

Maximum Value 15.80 21.55 21.2 7.8 30 Co Average Value 7.42 10.93 11.21 4.5 5 MinimumValue 4.90 6.30 8.75 2.9 0.5

Cr Maximum Value 43.05 46.60 59.8 34.0 60 Average Value 22.36 24.93 31.14 17.6 20 MinimumValue 2.15 12.3 5.7 1.8 -

Cu Maximum Value 36.55 49.75 37.25 20.0 - Average Value 18.42 26.62 19.31 10.8 - MinimumValue 5.98 6.12 7.85 1.5 0.5

Ni Maximum Value 21.05 26.60 36.55 21.0 50 Average Value 13.62 18.99 22.56 11.1 20 MinimumValue 0.95 1.35 0.78 1.1 2

Pb Maximum Value 3.89 4.23 12.75 22.0 80 Average Value 1.94 3.11 5.94 7.0 40 MinimumValue 4.86 4.98 8.43 5.1 -

Zn Maximum Value 18.62 23.67 33.12 18.0 - Average Value 9.805 13.308 16.665 12.7 - MinimumValue 0.05 0.05 0.06 0.01 -

Cd Maximum Value 0.20 0.25 0.17 0.19 - Average Value 0.115 0.17 0.108 0.093 -

58 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.8: Average values for trace elements in international coals.

Element Average, mg/kg Average range, mg/kg Arsenic (As) 2.69 0.36–9.8 Boron (B) 47 11–123 Beryllium (Be) 1.0 0.1–2.0 Cadmium (Cd) 0.093 0.01–0.19 Cobalt (Co) 4.5 1.2–7.8 Mercury (Hg) 0.091 0.03–0.19 Lead (Pb) 7.0 1.1–22 Selenium (Se) 2.15 0.15–5.0 Chromium (Cr) 17.6 2.9–34 Copper (Cu) 10.8 1.8–20 Manganese (Mn) 40 8–93 Nickel (Ni) 11.1 1.5–21 Zinc (Zn) 12.7 5.1–18 Fluorine (F) 120 15–305 Chlorine (Cl) 440 25–1420

59 CHAPTER – 3 RESULTS AND DISCUSSION

20 Duki 15 Chamalang

10 Salt Range Concentration(ppm)

0 Co Cr Cu Ni Pb Zn Cd Metal

Figure 3.4: The levels of trace metals in Duki Coal (Baluchistan), Chamalang Coal (Baluchistan) and Salt Range Coal (Punjab) on average basis.

60 CHAPTER – 3 RESULTS AND DISCUSSION

3.3 Heavy metal Composition of Coal Trace metals are known to exert adverse health effects to the population that is direct in contact with the coal burning or living closer to the coalmines, coal deposits, or coal-burning power stations. The estimation of trace metal level in the coal is therefore very important in order to generate base line data

160,161 and to plan futuristic strategies to avoid any health related implication associated with coal burning.

In this study trace metals including Co, Cr, Cu, Ni, Pb, Zn and Cd were investigated in coal samples from Duki, Chamalang and Salt Range (Table 3.4, 3.5 and & 3.6 and Figure 3.4). The trace metal content in Duki coal (Table 3.4) ranged from Cobalt 2.55±0.51 to 15.80±2.56, chromium 4.901.57± to 43.05±3.58, copper 2.15±0.08 to 36.55±3.31, nickel 5.98±1.25 to 21.05±1.25, lead 0.95±0.01 to 3.89±0.33, zinc 4.86±0.43 to 18.62±2.03 and cadmium 0.05±0.01 to 0.20±0.06. The average values for these trace metals in Duki coal are 7.42, 22.36, 18.42, 13.62, 1.94, 9.805 and 0.115 respectively (Table 3.7).

For Chamalang coal, the minimum and maximum values of these Co, Cr, Cu, Ni, Pb, Zn, and Cd are 4.55 to 21.55, 6.30 to 46.60, 12.3 to 49.75, 6.12 to 26.60, 1.35 to 4.23, 4.98 to 23.67, and 0.05 to 0.25 respectively (Table 3.5). The mean value comes to be 10.93, 24.93, 26.62, 18.99, 3.11, 13.31 and 0.17 respectively.

In case of salt range coal, the minimum values of Co, Cr, Cu, Ni, Pb, Zn, and Cd metals are 3.65±0.69, 8.75±1.33, 5.7±0.86, 7.85±1.21, 0.78±0.01, 8.43±0.09 and 0.06±0.01 respectively. The maximum values are 21.2±2.14, 59.8±3.69, 37.25±2.45, 36.55±2.14, 12.75±33. 12±3.07 and 0.17±0.03 respectively (Table 3.6). The average trace metal content in this area is 11.21, 31.14, 19.31, 22.56, 5.94, 16.66 and 0.108 respectively.

The comparison of trace metal of the selected areas of Pakistan shows that coal of salt range contains greater amount of trace metals than the other two areas located in Baluchistan province (Figure 3).

When compared with international coal (Table 3.8)162,163 it is found that the coal belonging to these three areas of Pakistan possess comparatively higher values of Co, Cr, Cu, Ni and Cd. However, the value of Zn is higher in Chamalang and salt range coal but it is lower for Duki coal than International coal. The lead content is lower in Pakistani coal than international coal.

61 CHAPTER – 3 RESULTS AND DISCUSSION

3.4 Removal of sulphur from coal 3.4.1 Sulphur leaching with strong acids and alkalis

Leaching of sulphur from coal was studied using strong acids like H2SO4, HCl and HNO3 or alkalis such as NaOH, KOH or Na2CO3. Dukki coal containing 5.2 % sulphur, was used for desulphurization experiments. The coal was ground and passed through200 micron sieve. After leaching experiment, the samples were centrifuged; the residue was washed with distilled water and washings were added to the supernatant. The residue was dried and subjected to determine residual sulphur. The results given in the table show percentage of sulphur removed in the experiment (Table 3.9).

Table 3.9: Total sulphur leached. Leaching Total leached agent Sulphur (%) Water 13.5

H2SO4 62.8 HCl 51.6

HNO3 63.5 NaOH 71.2 KOH 78.6

Na2CO3 27.4

NH3 44.5

3.4.2 Bioleaching Desulphurization of coal was also studied through microbial bioleaching was achieved.

62 CHAPTER – 3 RESULTS AND DISCUSSION

3.4.2.1 Microorganism The Ferrous-oxidizing bacterium Thiobacillus ferrooxidans was used throughout this study. Microbial desulphurization was carried out with Thiobacillus ferrooxidans which is a ferrous-oxidizing bacterium. The strain was isolated from soil samples on agar plates where tiny creamy colonies appeared which were brown in colour. Under the microscope these were 0.9 – 1.5 μm non-sporulating rods which were Gram negative.

Thiobacillus ferrooxidans can get energy by oxidation of sulphur components and by oxidation of Fe2+. Optimal temperature for these bacteria is: 28-30°C and optimal pH is in the range 1.8-2.2.

Table 3.10: Growth of Thiobacillus ferrooxidans Time Bacterial count(Cell/mL) Biomass (g/L) (Hours) 0 4.5x 108 0.86 24 1.1x109 2.1 48 3.9x109 7.7 72 5.4x109 10.2 96 6.5x109 12.5 120 7.4x109 14.3 144 8.0x109 15.4 168 8.5x109 16.2 192 8.7x109 16.7 216 8.8x109 16.9 240 8.8x109 16.9

3.4.2.2 Fermenter Principle of pyrite oxidation by Thiobacillus ferrooxidans bacteria.

63 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.11: Sulphur leaching Time (Hours) Total Sulphur Pyritic Organic Sulphatic (%) Sulphur (%) Sulphur (%) Sulphur (%) 0 5.2 3.29 0.61 1.3 24 4.46 2.8 0.56 1.1 48 3.75 2.3 0.53 0.92 72 2.9 1.67 0.48 0.75 96 2.1 0.90 0.44 0.58 120 1.4 0.58 0.4 0.42 144 0.91 0.29 0.35 0.27 168 0.65 0.18 0.31 0.16 192 0.53 0.12 0.27 0.14 216 0.51 0.12 0.25 0.14 240 0.51 0.12 0.25 0.14

64 CHAPTER – 3 RESULTS AND DISCUSSION

3.5 Electrolysis of Coal Slurries 3.5.1 Electrolysis of Coal under Acidic Conditions The analysis of variance data (Table 3.12) indicates the applied experimental layout has good fit over the investigated range of temperature, potential, Ferric concentration and particle size.

The Model F-value of 21.98 implies the model is significant. There is only a 0.05% chance that an F-value this large could occur due to noise. P-values less than 0.0500 indicate model terms are significant. In this case A, B, C, D, D² are significant model terms. Values greater than 0.1000 indicate the model terms are not significant. If there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. The Lack of Fit F-value of 3.50 implies the Lack of Fit is not significant relative to the pure error. There is a 13.21% chance that a Lack of Fit F-value this large could occur due to noise. Non-significant lack of fit is good -- we want the model to fit. In this context, potential (B), Ferric concentration (C), and particle size (D) significantly affect the production of hydrogen and carbon dioxide. Similarly, for quadratic effects applied potential (B²), Ferric concentration (C²) are significant. In contrast, the effect of temperature was found to be non- significant under all the cases.

65 CHAPTER – 3 RESULTS AND DISCUSSION

Fig 3.5: A comparison predicted and observed values of Hydrogen (mL)

66 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.12: The analysis of variance data for the production of hydrogen under given conditions

Sum of Mean Source df F-value p-value Squares Square Model 2.860E+05 14 20431.28 21.98 0.0005 significant

A-Temperature 21632.00 1 21632.00 23.27 0.0029

B-potential 19800.50 1 19800.50 21.30 0.0036

C-Ferric 9556.76 1 9556.76 10.28 0.0184

D-Particle size 35644.50 1 35644.50 38.35 0.0008

AB 672.46 1 672.46 0.7234 0.4276

AC 1.13 1 1.13 0.0012 0.9734

AD 3280.09 1 3280.09 3.53 0.1094

BC 6.13 1 6.13 0.0066 0.9379

BD 578.59 1 578.59 0.6225 0.4602

CD 120.13 1 120.13 0.1292 0.7315

A² 5241.98 1 5241.98 5.64 0.0552

B² 1217.21 1 1217.21 1.31 0.2961

C² 1909.66 1 1909.66 2.05 0.2017

D² 33806.13 1 33806.13 36.37 0.0009

Residual 5577.16 6 929.53

not Lack of Fit 3550.36 2 1775.18 3.50 0.1321 significant

R² 0.9809

C.V. % 6.36

The statistical analysis indicates that selected model can be successfully used to predict the response, so second order polynomial equation (coded) was used to predict the production of hydrogen.

H2 (mL) =+462.30+61.84A+59.16B+26.45C-79.38D+14.25AB-0.3750AC-31.46AD- 0.8750BC+13.21BD+3.88CD-18.73A²+9.03B²-11.30C²+47.56D²

67 CHAPTER – 3 RESULTS AND DISCUSSION

When this equation is used to draw three-dimensional representation of hydrogen production it well elaborated the interaction between various experimental parameters (temperature (A), potential (B), Ferric concentration (C) and Particle size (D).

In this context, data plotted in Figure 3.6 discloses that an increase in applied potential upto 2.5 Design-Expert® Software Trial Version volt causes a sharp increase in hydrogen production but further increase in potential could not increase the Factor Coding: Actual yield of hydrogen at parallel rates. H2 (mL) Design points below predicted value 300 734

750 X1 = A: Temperature X2 = B: potential

Actual Factors C: Ferric = 1.61487 675 D: Particle size = 242.564

600

H2(mL) 525

450

3 86 3 75 3 65 B: potential (volt) 2 55 A: Temperature (ºC) 2 44

Fig 3.6: A three dimension presentation of interaction between potential and temperature observed during the production of hydrogen

68 CHAPTER – 3 RESULTS AND DISCUSSION

Similarly according to Figure 3.7 an increase in temperature improves the production of hydrogen while change in Ferric concentration does not cause notable increase in hydrogen production.

Design-Expert® Software Trial Version Factor Coding: Actual

H2 (mL) 300.0 734.0

X1 = A: Temperature 750.0 X2 = C: Ferric

Actual Factors B: potential = 2.98163 D: Particle size = 242.564 675.0

600.0

H2(mL) 525.0

450.0

1.6 85.8 1.3 75.4 1.0 65.0 C: Ferric (Conc) 0.8 54.6 A: Temperature (ºC) 0.5 44.2

Figure 3.7: A three dimension presentation of interaction between Ferric concentration and temperature observed during the production of hydrogen.

69 CHAPTER – 3 RESULTS AND DISCUSSION

Design-Expert® Software Trial Version Factor Coding: Actual

H2 (mL) 300.0 734.0

X1 = B: potential X2 = C: Ferric

Actual Factors A: Temperature = 81.6489 D: Particle size = 242.563 750.0

675.0

600.0

525.0

H2(mL) 3 450.0

3 1.6

1.3 3

1.0 B: potential (volt) 2 0.8 C: Ferric (Conc) 0.5 2

Figure 3.8: A three dimension presentation of interaction between potential and Ferric concentration observed during the production of hydrogen.

Figure 3.8 describes interaction between Ferric concentration and potential applied for the production of hydrogen. It is obvious from the graph that increase in potential and Ferric concentration improve the production of hydrogen but the effect potential seems more prominent that that of Ferric. In both of the cases potential applied and Ferric concentration higher than 2.5 and 1.5 respectively may not further improve the production of hydrogen. Similar kind of behavior about applied potential can be also seen in Figure 3.9 which indicates that an increase in applied potential upto 2.9 volt improve the production of hydrogen but further increase may impose negative effect on response.

70 CHAPTER – 3 RESULTS AND DISCUSSION

Figure 3.9: A three dimension presentation of interaction between potential and particle size observed during the production of hydrogen.

71 CHAPTER – 3 RESULTS AND DISCUSSION

The data in figure 3.10 indicates variation in particle size along with change in Ferric did not affect the production of hydrogen, however, higher values of alkali and particles may produce higher quantity of hydrogen.

Figure 3.10: A three dimension presentation of interaction between Ferric and particle size observed during the production of hydrogen.

72 CHAPTER – 3 RESULTS AND DISCUSSION

Figure 3.11: 3-Dimesional graph of interaction b/t Ferric concentration and particle size for the production of Carbon Dioxide.

73 CHAPTER – 3 RESULTS AND DISCUSSION

Figure 3.12: 3-Dimesional graph of interaction b/t potential and particle size for the production of Carbon dioxide

74 CHAPTER – 3 RESULTS AND DISCUSSION

Design-Expert® Software Trial Version Factor Coding: Actual

CO2 (mL) Design points above predicted value Design points below predicted value 152 381

X1 = B: potential X2 = C: Ferric 300 Actual Factors A: Temperature = 65 280 D: Particle size = 525 260 240 220

CO2(mL) 200 180 3 1.6 3 1.3 3 1.0

B: potential (volt) 0.8 2 C: Ferric (Conc) 0.5 2

Figure 3.13: Dimesional graph of interaction b/t Ferric Ferric concentration and potential for the production of Carbon Dioxide.

75 CHAPTER – 3 RESULTS AND DISCUSSION

Figure 3.14: 3-Dimesional graph of interaction b/t Ferric temperature and particle size for the production of Carbon dioxide.

76 CHAPTER – 3 RESULTS AND DISCUSSION

Design-Expert® Software Trial Version Factor Coding: Actual

CO2 (mL) Design points above predicted value Design points below predicted value 152 381

X1 = A: Temperature X2 = C: Ferric

Actual Factors B: potential = 2.5 D: Particle size = 525 280 260 240 220

200 85.8

CO2(mL) 180 75.4 1.6

1.3 65.0

1.0 A: Temperature (ºC) 54.6 0.8 C: Ferric (Conc) 0.5 44.2

Figure 3.15: 3-Dimesional graph of interaction b/t Ferric concentration and temperature for the production of Carbon dioxide.

77 CHAPTER – 3 RESULTS AND DISCUSSION

Design-Expert® Software Trial Version Factor Coding: Actual

CO2 (mL) Design points above predicted value Design points below predicted value 152 381

X1 = A: Temperature X2 = B: potential

Actual Factors C: Ferric = 1.05 D: Particle size = 525 320 300 280 260 240 220 200 85.8

CO2(mL) 180 75.4 3

3 65.0

3 A: Temperature (ºC) 54.6 2 B: potential (volt) 2 44.2

Figure 3.16: 3-Dimesional graph of interaction b/t temperature and potential for the production of Carbon dioxide.

78 CHAPTER – 3 RESULTS AND DISCUSSION

44.1889 85.8111 1.60809 3.39191

A:Temperature = 65 B:potential = 2.5

0.485127 1.61487 242.563 807.437

C:Ferric = 1.05 D:Particle size = 525

300.0 734.0 152 381

H2 = 462.3 CO2 = 241.668

Figure 3.17: The desirability ramp for the most suitable set of experimental conditions. Desirability = 0.437 Solution not selected

79 CHAPTER – 3 RESULTS AND DISCUSSION

3.5.2 Electrolysis of Lignite Under Alkaline Conditions Production of hydrogen

The analysis of variance data (Table 3.13) indicates the applied experimental layout has good fit over the investigated range of temperature, potential, alkali concentration and particle size. The Model F- value of 13.38 implies the model is significant. There is only a 0.22% chance that an F-value this large could occur due to noise. In order to screen out various factors, variance in terms of probability (p) was followed i.e., P-values less than 0.0500 indicate model terms are significant and probability p value higher than 0.0500 tells non-significant contribution towards response. In this context, potential (B), Alkali concentration (C), and particle size (D) significantly affect the production of hydrogen and humic acid. Similarly, for quadratic effects applied potential (B²), Alkali concentration (C²) are significant. In contrast, the effect of temperature was found to be non-significant under all the cases. The Lack of Fit F- value of 2.4 implies the Lack of Fit is non-significant, A non-significant lack of fit is desired. Similarly, the value of R2>0.99 indicates there is good correlation between observed and predicted response. The similar can be visualized from figure 3.18. The co-efficient of variation (CV) value 7.63 indicates that results are quite reliable.

80 CHAPTER – 3 RESULTS AND DISCUSSION

Fig 3.18: A comparison predicted and observed values of Hydrogen (g)

81 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.13: The analysis of variance data for the production of hydrogen under given conditions

Source Sum of Squares df Mean Square F-value p-value

Model 1.949E+05 14 13923.80 13.38 0.0022 significant

A-Temperature 5408.00 1 5408.00 5.20 0.0629

B-potential 30504.50 1 30504.50 29.31 0.0016

C-NaOH 12202.40 1 12202.40 11.72 0.0141

D-Particle size 8580.50 1 8580.50 8.24 0.0284

AB 326.65 1 326.65 0.3138 0.5956

AC 780.12 1 780.12 0.7495 0.4199

AD 311.24 1 311.24 0.2990 0.6042

BC 2278.13 1 2278.13 2.19 0.1895

BD 51.85 1 51.85 0.0498 0.8308

CD 2850.12 1 2850.12 2.74 0.1491

A² 1950.26 1 1950.26 1.87 0.2201

B² 37038.66 1 37038.66 35.58 0.0010

C² 13121.58 1 13121.58 12.61 0.0121

D² 972.04 1 972.04 0.9338 0.3712

Residual 6245.44 6 1040.91

Lack of Fit 240.24 2 3120.12 2.4 0.1 Non-significant

C.V. % 7.63 4 1.30

R² 0.9690

The statistical analysis indicates that selected model can be successfully used to predict the response, so second order polynomial equation (coded) was used to predict the production of hydrogen.

H2Yield (mL) =+486.99+30.92A+73.43B+29.89C-38.95D+9.93AB+9.87AC-9.69AD-16.88BC- 3.96BD-18.87CD-11.42A²-49.78B²-29.63C²-8.07D²

82 CHAPTER – 3 RESULTS AND DISCUSSION

In this context, data plotted in figure 3.19 discloses that an increase in applied potential up to 2.5 volt causes a sharp increase in hydrogen production but further increase in potential could not increase the yield of hydrogen at parallel rates.

Fig 3.19: A three dimension presentation of interaction between potential and temperature observed during the production of hydrogen.

83 CHAPTER – 3 RESULTS AND DISCUSSION

Similarly according to figure 3.20 an increase in alkali concentration upto 1.2 % cause notable increase in hydrogen production but further increase could not improve the production of hydrogen at same extent.

Figure 3.20: A three dimension presentation of interaction between NaOH concentration and temperature observed during the production of hydrogen.

84 CHAPTER – 3 RESULTS AND DISCUSSION

Figure 3.21: A three dimension presentation of interaction between potential and particle size observed during the production of hydrogen.

Figure 3.21 describes interaction between alkali concentration and potential applied for the production of hydrogen. It is obvious from the graph that increase in potential and alkali concentration improve the production of hydrogen but the effect potential seems more prominent that that of alkali. In both of the cases potential applied and alkali concentration higher than 2.5 and 1.5 respectively may not further improve the production of hydrogen. Similar kind of behavior about applied potential can be also seen in figure 4.5.which indicates that an increase in applied potential upto 2.9 volt improve the production of hydrogen but further increase may impose negative effect on response.

85 CHAPTER – 3 RESULTS AND DISCUSSION

Figure 3.22: A three dimension presentation of interaction between potential and particle size observed during the production of hydrogen.

86 CHAPTER – 3 RESULTS AND DISCUSSION

The data in figure 3.23 indicates variation in particle size along with change in alkali did not affect the production of hydrogen, however, higher values of alkali and particles may produce higher quantity of hydrogen.

Figure 3.23: A three dimension presentation of interaction between NaOH and particle size observed during the production of hydrogen.

87 CHAPTER – 3 RESULTS AND DISCUSSION

Production of Humic Acid

Table 3.14: Analysis of variance of for the production of humic acid

Source Sum of Squares df Mean Square F-value p-value

Model 7.32 14 0.5230 5.10 0.0359 Significant

A-Temperature 0.0200 1 0.0200 0.1339 0.7270

B-potential 0.9800 1 0.9800 6.56 0.0428

C-NaOH 0.4626 1 0.4626 3.10 0.1289

D-Particle size 0.4050 1 0.4050 2.71 0.1508

AB 0.0010 1 0.0010 0.0068 0.9367

AC 0.0200 1 0.0200 0.1339 0.7270

AD 0.0276 1 0.0276 0.1846 0.6825

BC 0.3200 1 0.3200 2.14 0.1937

BD 0.3299 1 0.3299 2.21 0.1878

CD 0.0450 1 0.0450 0.3012 0.6029

A² 0.6570 1 0.6570 4.40 0.0808

B² 1.84 1 1.84 12.33 0.0126

C² 0.0035 1 0.0035 0.0232 0.8839

D² 0.3667 1 0.3667 2.45 0.1682

Residual 0.8964 6 0.1494

Non- Lack of Fit 0.8244 2 0.4122 2.90 0.065 significant

R² 0.8909

C.V. % 4.44

The analysis of variance data (Table 3.14) indicates the applied experimental layout has good fit over the investigated range of temperature, potential, alkali concentration and particle size. The Model F- value of 5.1 implies the model is significant. There is only a 0.22% chance that an F-value this large could

88 CHAPTER – 3 RESULTS AND DISCUSSION occur due to noise. In order to screen out various factors, variance in terms of probability (p) was followed i.e., P-values less than 0.0500 indicate model terms are significant and probability p value higher than 0.0500 tells non-significant contribution towards response. In this context, potential (B), significantly affect the production of hydrogen and humic acid. Similarly, for quadratic effects applied potential (B²), Alkali concentration (C²) are significant. In contrast, the effect of temperature was found to be non-significant under all the cases. The Lack of Fit F-value of 2.9 implies the Lack of Fit is non- significant, A non-significant lack of fit is desired. Similarly, the value of R2>0.99 indicates there is good correlation between observed and predicted response. The similar can be visualized from figure 3.13. The co-efficient of variation (CV) value 4.44 indicates that results are quite reliable.

Therefore, production of humic acid can be modeled by using second order polynomial equation as:

Humic acid Yield=+3.15+0.0595A+0.4162B+0.1841C-0.2676D-0.0176AB-0.0500AC +0.0912 AD-0.2000BC-0.3155BD+0.0750CD-0.2097A²-0.3511B²-0.0152C²-0.1567D²

If this equation is further used to draw three dimensional presentation of humic acid production for given set of experiments, we can make better understanding about the interaction among various reaction parameters investigated

89 CHAPTER – 3 RESULTS AND DISCUSSION

The data plotted in figure 3.24 discloses that an increase in applied potential upto 2.5 volt causes a sharp increase in humic acid production but further increase in potential could not increase the yield of humic acid at parallel rates.

Design-Expert® Software Trial Version Factor Coding: Actual

Humic acids (g) Design points below predicted value 1.5 3.8

X1 = A: Temperature X2 = B: potential

Actual Factors 4 C: NaOH = 1.63514 D: Particle size = 242.564 3.5

2.5

Humicacids (g) 2 3.4 34.1 2.9 37.0

2.5 40.0

43.0 2.1 B: potential (volt) A: Temperature (ºC) 45.9 1.6

Figure 3.24: A three dimension presentation of interaction between potential and temperature observed during the production of humic acid.

90 CHAPTER – 3 RESULTS AND DISCUSSION

Similarly, figure 3.25 explain that increase in alkali concentration improves the production of humic acid whereas temperature could not affect the reaction significantly. A similar kind of behavior has been shown during the interaction of alkali and potential applied (Figure 3.27).

Design-Expert® Software Trial Version Factor Coding: Actual

H2 (g) 241.0 574.0

X1 = A: Temperature 550.0 X2 = C: NaOH

Actual Factors B: potential = 1.96486 D: Particle size = 242.564 475.0

400.0

H2(g) 325.0

250.0

1.6 45.9 1.4 43.0 1.1 40.0 C: NaOH (Conc) 0.8 37.0 A: Temperature (ºC) 0.6 34.1

Figure 3.25: A three dimension presentation of interaction between NaOH and temperature observed during the production of humic acid.

91 CHAPTER – 3 RESULTS AND DISCUSSION

Figure 3.26: A three dimension presentation of interaction between temperature and particle size observed during the production of humic acid.

92 CHAPTER – 3 RESULTS AND DISCUSSION

Design-Expert® Software Trial Version Factor Coding: Actual

H2 (g) 241.0 574.0

X1 = B: potential X2 = C: NaOH 550.0 Actual Factors A: Temperature = 37.5027 D: Particle size = 242.564 475.0

400.0

H2(g) 325.0

250.0

1.6 3.4 1.4 2.9 1.1 2.5

C: NaOH (Conc) 0.8 2.1 B: potential (volt) 0.6 1.6

Figure 3.27: A three dimension presentation of interaction between NAOH and potential observed during the production of humic acid.

93 CHAPTER – 3 RESULTS AND DISCUSSION

Design-Expert® Software Trial Version Factor Coding: Actual

H2 (g) 241.0 574.0

X1 = B: potential X2 = D: Particle size

Actual Factors 550.0 A: Temperature = 37.5027 C: NaOH = 1.63514 475.0

400.0

H2(g) 325.0

250.0 242.6 3.4 383.8 2.9 525.0 2.5

2.1 666.2 D: Particle size (μm) B: potential (volt) 1.6 807.4

Figure 3.28: A three dimension presentation of interaction between Potential and Particle size observed during the production of humic acid.

94 CHAPTER – 3 RESULTS AND DISCUSSION

Design-Expert® Software Trial Version Factor Coding: Actual

H2 (g) 241.0 574.0

X1 = C: NaOH X2 = D: Particle size

Actual Factors 550.0 A: Temperature = 37.5027 B: potential = 1.96486 475.0

400.0

H2(g) 325.0

250.0 242.6 1.6 383.8 1.4 525.0 1.1

0.8 666.2 D: Particle size (μm) C: NaOH (Conc) 0.6 807.4

Figure 3.29: A three dimension presentation of interaction between Particle size and NaOH observed during the production of humic acid.

95 CHAPTER – 3 RESULTS AND DISCUSSION

Figure 3.30: Desirability ramp of most desirable solution.

96 CHAPTER – 3 RESULTS AND DISCUSSION

3.6 Experimental conditions for Electrolysis of coal slurries 3.6.1 Electrolysis of Coal under Acidic Conditions Table 3.15: The experimental conditions investigated for the production of hydrogen and Carbon dioxide. Factor 1 Factor 2 Factor 3 Factor 4

Run A:Temperature B:potential C:Ferric D:Particle size ºC volt Conc (mol/L) Micron

1 85.8 3.3 1.6 242 2 65.0 2.5 1.0 50 3 65 1 1.0 525 4 65 2.5 0.1 525 5 44.1 1.6 1.6 242.5 6 65 2.5 1.0 525 7 85.8 1.6 0.4 807.4 8 65 2.5 1.0 525 9 100 2.5 1.0 525 10 65 4 1.0 525 11 65 2.5 1.0 525 12 44.1 3.3 0.4 807.4 13 85.8 1.6 1.6 807.4 14 44.1 3.3 1.6 807.4 15 44.1 1.6 0.4 242.5 16 30 2.5 1.0 525 17 65 2.5 1.0 525 18 65 2.5 2 525 19 65 2.5 1.05 525 20 85.8 3.3 0.4 242.5 21 65 2.5 1.05 1000

97 CHAPTER – 3 RESULTS AND DISCUSSION

Table 3.16: The experimental conditions investigated for the production of hydrogen and humic acid Factor 1 Factor 2 Factor 3 Factor 4

Run A: Temperature B: Potential C: NaOH D: Particle size

ºC volt Conc Μm

1 40 4 1.1 525

2 40 2.5 2 525

3 40 2.5 1.1 525

4 40 2.5 0.2 525

5 30 2.5 1.1 525

6 34.054 3.39191 1.63514 807.437

7 40 2.5 1.1 1000

8 40 2.5 1.1 525

9 40 1 1.1 525

10 40 2.5 1.1 525

11 34.054 1.60809 0.564857 242.563

12 40 2.5 1.1 525

13 34.054 3.39191 0.564857 807.437

14 45.946 1.60809 1.63514 807.437

15 34.054 1.60809 1.63514 242.563

16 50 2.5 1.1 525

17 40 2.5 1.1 50

18 45.946 1.60809 0.564857 807.437

19 45.946 3.39191 0.564857 242.563

20 40 2.5 1.1 525

21 45.946 3.39191 1.63514 242.563

98 CHAPTER – 3 RESULTS AND DISCUSSION

3.7 Conclusions

This study revealed the composition of coal samples from different geographical areas of Pakistan. All samples were ranked as sub-bituminous coal from the proximate analysis.and calorific values. Chamalang coal showed higher economic value than Duki and Salt Range coal due to high carbon content and calorific value. But heavy metal contents of all coal samples suggest that their combustion in power generation could be a serious environmental hazard. Leaching of sulphur from coal was studied using strong acids like H2SO4, HCl and HNO3 or alkalis such as NaOH, KOH or Na2CO3. Desulphurization of coal was also studied through microbial bioleaching and good results were obtained. The electrolysis of coal slurries was undertaken under acidic and alkaline conditions. The production of H2 and CO2 was investigated under various conditions of electrical potential, particle size, temperature and Fe+3 and it was observed that electric potential and its interaction with all other factors influenced the reaction yield. It was observed that an increase in applied potential up to 2.5 V increases the production of H2 but further increase in potential does not cause parallel effect. The increase in temperature also increases the yield. The particle size and concentration of Fe+3 has no pronounced effect towards the reaction yield.

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