Advances in Environment Technologies, Agriculture, Food and Animal Science

Reduction of Turceni thermal power plant impact upon environmental by superior valorisation of ash and slag

POPESCU LUMINITA GEORGETA, MIHAI CRUCERU, CRISTINEL RACOCEANU Automatic, Energy and Environmental Department, Constantin Brancusi University of Targu Jiu, Calea Eroilor, no 30, Targu Jiu, Gorj, e-mail: [email protected], [email protected], [email protected], www.utgjiu.ro,

GEORGETA PREDEANU Metallurgical Research Institute Mehadia St., 39, Sector 6, 060543 Bucharest ROMANIA [email protected]

Abstract: In Romania, the energy industry generates yearly great amounts of slag and ash which claims a lot of work for transport and storage by landfill. Ash and slag resulting from steam power plants require approximately 1.2 ha storage space for every million tonnes. With a total installed capacity of 1980 MW, Turceni thermal power plant produces about 7400 m3 of fly-ashes per day using lignite as main fuel. The ash is recovered after the 2-nd gas flow (rotary air preheater) and from the electro filters. Slag and ash from the combustion process are transported hydraulically (1:10 dilution with water) using centrifugal pumps, in series, in deposits designated for this purpose (a natural area with waterproof closure dumps). Currently, new highly cost technologies are foreseen to be applied as the dense water sludge disposal. The principle of “dense sludge technology” consists in continuous mixing with waste water of the coal burning by-products: dry fly ash from the electro filters, slag from Kratzer and eventually the desulfurization by-products, by intense hydraulic circulation, with a rate solid/liquid over 1. This process activates the chemical substances of cemented type existent in fly ashes with the creation of a dense, homogenous sludge, which is pumped in deposit, where, it solidifies after 24 hr. Thus, results a huge solid deposit. The inertization technology transforms the fly ash and slag in an inert waste. But, the main problem remains not solved, because of the long term soil pollution. Thus, having a valuable oxides composition such as SiO2, Al2O3, CaO, Fe2O3, the fly ash could replace up to 30- 50% from the natural sand used in the process of ceramic products manufacturing. In this paper, we will demonstrate how is possible to reduce the environmental impact due to thermal power plant by use the waste from energy industry for producing of new building materials.

Key-Words: environmental impact, ash and slag valorization, wastes, thermal power plant

1. Introduction field of electricity production by burning of fossil fuels represents the activity with the most important In our country is generated millions tons of percentage among the big polluters of the industrial wastes annually. These wastes are stored environment. We refer here to atmospheric pollution in industrial wastes deposits which occupied the through release of large volume of greenhouse gas, large surface of soil and also affects the acidifying gas, dusts or it is about of large amounts environmental quality, in specially the quality of of wastes (ash and slag) deposited in landfills which groundwater and surface water. are occupying large areas of land. Electricity In is produced electricity in two thermo prodsuction in thermal power plant generates the power plants: Turceni, with 2310 MW installed important amounts of ash and slag which are capacity and with 1320 MW installed characterized through low contents of organic capacity. Both thermo power plants use the lignite substance when the burning process has a high as fuel extracted from mining basin of . The

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performance. In this case, the resulted wastes can be between 0,25 – 1 mm. Although they result used in different purposes in the building field [1]. separately, in the technological process, the ash and slag are mixed and hydraulically transported in dumps as a mixture 1:10. The 2. The coal combustion and the ash and slag have a high content of heavy metals and also, the soluble sulphates are secondary products present in a variable concentration, which depends of the coal`s sulphur content. The burn of fossil fuels is associated with the generation of a variety of residues and secondary The other residues generated by the coals products [2]. The term of secondary product is combustion in thermal power plants (which are not generally used for materials that can be sold on the subject of this paper), are: market (for example the gypsum resulted from flue - The residues from the flue gas gas desulphurisation flow) According to their desulphurization flow, provenience, the residues from the burning - The residues from the boiler cleaning, installation can be directly divided in wastes - The rests resulted from the solid fuel corresponding to the burning process or wastes generated from the exploitation of the installation crushing, and its equipment as the coal mills or the water - The mud from the treatment of the process treatment units. The residues directly connected to water, the burning process of the fossil fuels are ash (the - The used resins from the ionic change, ash collected through electric filters and the ash - The mud from wastewater treatment. from the furnace base) and the ashes generated from The most of the residues and secondary products flue gas desulphurization flow: in UE were which are above mentioned from the combustion produced about 55000 Kt of solid wastes from the process (for example ash) and from the gas coal burn. For example in 1999 about 31000 Kt desulphurization flow (for example gypsum) and the were used (55.3%). The rest of 24000 Kt were any other residues from combustion installation deposited permanently controlled [2]. present, generally, a potential environmental risk. The UE actual legislation relates to more of the In the technologic process of the coal burn in boilers residues above mentions, provided from the burning ash and slag result separately [3]: installations. However for the few decades, the • Ash: The ash represent the part of industry made the sustained efforts for development incombustible material which is evicted of the way which leads to reduce the residues from the boiler with the flue gas flow. generating and/or reuse of them in several industrial fields, such as cement industry, building industry, so The ash consists in fine particles with the that the waste quantity which is deposited on the diameter under 0.25 mm (named also flying land has decreased. ash, because it is easily taken by the wind). In accordance with Council Directive no 77/442/EC The ash (over 75%) is captured by the (and changes) stipulations, this is in the benefit of electrostatic dedusters (electric filters) the environmental because the use of the residues as situated at the superior part of the gas raw material help to natural resources conservation circuit. A small part, 2…3% is lost on the and to decrease of wastes produced residues chimney. quantity. Concerning to thermal power ash and slag provided • The ash from the boiler base and/0r the from burning coal, the both of them are composed slag from the boiler: The ash from the base of several elements which are common both soil and is an incombustible material which is coal. deposited at the boiler base and it stays in One of the characteristics is the fact that the mass of shape of unconsolidated ash. If the burning this material is a powder or sintered, the most temperatures exceed the temperature of ash elements being contained in the inert matrices. This fusion, the ash stays as slag in melted state determines the legal classification of them, in the until it is removed from the boiler`s base as national and international waste lists as inert boiler slag. The slag represents the material residue, inactive or not dangerous (for example not that has the particles with a diameter dangerous wastes in the European list of waste - Decision no. 2001/118/EC, and also, forms the part

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of green list from OECD Decision C (92)39/final). of chemical compounds such as: SiO2; CaO; MgO; Also, it is known that some secondary products such Fe2O3; Al2O3, and also of heavy metals. In this as the gypsum from the flue gas desulphurization situation, the most important factors of environment flow are affected. These and also other possible effects of (the gypsum was classified as not dangerous waste them are presented as follows. on the European list - Decision 2001/118/EC) is For the environment protection against highly rated on the gypsum market and is used as contamination with ash or other substances are the most important raw material for production of taken the following measures: gypsum boards. These efforts which are made by • the application of the sodium silicate the industry have helped to reduce the impact risk solution realizes the fixation of the surface upon the environment [3] of the deposit. On the surface of the deposit

is formed a solid film with 2-3 mm weight,

which spread the dissipation of the ash by 3. The environmental impact of wind. Also, the fixation of surface of the ash deposit deposit can be realized through planting of several plants. In absence of these measures, The thermoelectric power plant Turceni is design as the ash from the surface of the deposit with a basic power plant of Energetic National System, a fine grain, is dissipation, as can be seen in with 2310 MW installed capacity. figure no. 2, Ash and slag deposit is formed by solid part decanting (ash and slag) under gravitational effect, • in the running compartment the circulation behind of basic embankments and cant of the means of transport is realized on embankments. By the project, the final height of watered ash, deposit has foreseen at 100 m, so that to occupy the • the protection of the soil and subsoil is all of Valea Ceplea upstream part. realized through sealing works which Cleared technological water and the meteoric water consist in the execution of drainages on ash from the deposit compartments are captured through to the slope in order to reduce the collector intake with variable level, and then it gets, hydrostatic pressure from the ash deposit gravitationally, through recirculation collector pipes situated on the sealing system. The to thermal power plant, being reintroduced in the infiltration water came from the slag and hydraulic circuit. ash deposit Ceplea Valley and has specific pollutants which can influence the quality of From born process of fuel in energetic boiler results underground waters from the nearby zones. ash and slag which are exhausted by hydraulic The most important features of the deposit system to two deposits: one deposit of slag and ash waters are presented in table no. 1 [5]. no.1, which is used in normally function regime, situated in Ceplea Valey at 3,3, km distance from thermoelectric power plant. The area of land affected by compartment no 1 is about 52.64 ha, the volume of deposited ash being of 13.034.470 m3. The area of land affected by compartment no 2 of the same deposit is about 45,4 ha, and the volume is 10.825.795 m3 [4]. Another deposit is deposit no. 2, which is used as Figure no. 2. The ash and slag deposit in a blustery reserve and damage deposit. The deposit is formed day through decanting of solid part (ash and slag) under the gravitational effect, on behind of basic dykes and of cant dykes. The technological decant water Table no. 1. The features of the deposit waters and meteoritic water from the compartments of the Nr. Element UM Value deposit are collected through collecting water intake crt. with variable level, then gravitationally the water is 1 PH 7,1….9 transported through recirculating collected pipes to 2 CO2 free Mg/l 17….30 thermal power plant and reinserted in hydro technic 3 Alkalinity Milival/l 0 circuit. It is known, by analyses, about the presence « p »

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4 Alkalinity Mg/l 1,4… 2 we study within the LIFE project „New building « m » materials by eco-sustainable recycling of 5 Bicarbonates Mg/l 80…130 industrial wastes”, co financed by the European (HCO3) Commission the possibility of use ash, drilling 6 Temporary Mg/l 3,9….6 slurry and metallurgical slag together in order to hardness produce new composite materials that can be used in 7 Permanent G 60…80 material building industry. hardness Having a valuable oxides composition such as SiO2, 8 Calcium Mg/l 400....460 Al2O3, CaO, Fe2O3, the ash could replace up to 30- (Ca 2+) 50% from the natural sand used in the process of 9 Magnesium Mg/l 70....115 ceramic products manufacturing. With an average (Mg 2+) price of 40 €/tone of raw materials used for building 10 Chlorides Mg/l 150....190 bricks manufacturing (clays + clay sands), the (Cl-) valorisation of about 500.000 t/year ashes and about 11 Sulfates Mg/l 1100...1500 100.000 t/year drilled solids, could involve a decrease of the production costs up to 30 mil. €/year, considering that the transport of the raw Ash and slag deposits cover large surface of land materials to the utilization place will be done by the having the negative impact on the environmental wastes suppliers, and the wastes involve NO cost. because of different reasons, that we can summarize as follows: - Ash powder, entrain by wind from dry 4. Chemical composition of ash. surface of deposit affects all environmental Recycle of ash and market factors: water, growth, living bodies, soil, information human settlement. Ash powder with fine grain affects animal bodies and plants even far from deposit. Are affected, also, The chemical composition of ash and slag digestive and respiratory tract of humans considerably varies depending of the source, of and animals. Ash powder with medium or preparation conditions of the coal before burning high grain recover surface of soil and plants process, but depending of fuel combustion near the deposit, technology. - The flora from deposit area both the The minerals that compose ash and slag are spontaneous and the cultivated, specially, silicates, carbonates, sulfates, aluminum oxides, iron suffer negative effects by the fine fractions oxides, calcium oxides, magnesium oxides, fly ash which will lead to reduced plant potassium oxides and sodium oxides. vitality and crop production. Another effect In burning area the mineral substances that compose of pollution is accumulation of increased ash and slag are dehydrating and lose the quantity of heavy metals (chrome, crystallization water, the carbonates are thermally plumbum, arsenic, molybdenum) to dissociated releasing CaO and SO . Due the high toxically level with implication for 3 pass speed of minerals substances though high consumers, temperature area, excepting oxidation and - Because of the absence of impermeability dissociation process, there are no other reactions [3]. and inappropriate drain of deposit tank, the The percent of oxides compounds from ash and slag infiltration from deposit affects ground comparative with clayey soils are present in the water sheet. These have as effect the table no 2. increased mineralization of ground water sheet and soil salinization considering the Silicon dioxide (SiO2) is present in two forms: cumulative aspect. In the case of damage amorphous, which is round and smooth, and and other incidents by overflowing of water crystalline, which is sharp, angular and dangerous. or hydro mixture of water and slag and ash The chemical composition of the ash is generally, is affected quality of surface water. extremely heterogenous, being composed of the mixture of glass particles with several identificable From these reasons but as well as to implementation of community regulations in environmental field,

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crystalline fazes sucha as quartz, mullite and several - The stabilization of waste and solidification, iron oxides. - As replacement material for clay at the The ash produced by the burning coal was released production of clinker cement, in the atmosphere with the flue gas, in the past. This - The filling of disused mines, created environmental and people health issues, fact - The stabilization of soft soils, which determined the elaboration of the regulations - As basic substratum in building roads, with the ash emission reduced under 1% from the - As aggregate substitution (for example for produced ash condition. Worldwide, over than 65% brick production), of the produced ash from the thermal power plants - Agriculture uses: amendment for soil, is eliminated in the waste deposits and sludge bed fertilizer, the stabilization of soil in storage [3]. feed, - Free deposit on the river in order to melt ice

[9]. Table no. 2. The oxide compounds in ash and slag and the oxide compounds in argillaceous soils. Oxide Ash and Argillaceous 5. Conclusion compounds slag soils The production of electricity in power plants SiO2 (%) 47,7 50,20 generates significant quantities of ash and slag,

Al2O3 (%) 21,65 17,00 which are characterized by a very low content of organic substance when the burning process runs Fe2O3 (%) 11,70 7,60 with good performance, and the geotechnical CaO (%) 10,97 5,13 properties are good, so the residues can be used for vary purposes in the field of constructions. MgO (%) 2,65 7,00 The features of the ash depend on the quality of the

SO3 (%) 1,65 0,4 coals (for example, anthracite coal, lignite, oil shale), on the deposit`s geological structure, on the Ash recycling has become an increasing concern in type and specific of the deposit, on the exploitation the last years, due to the storage costs and the mode, on the nature of the sterile intercalations. current interest regarding durable development. For Having a valuable oxides composition such as SiO2, example, since 2005, the thermal power plants from Al2O3, CaO, Fe2O3, the ash could replace up to 30- USA reported the production of 71.1 million tones 50% from the natural sand used in the process of ash, from which 29.1 million tones of ash were ceramic products manufacturing. With an average reused in several applications [6]. The 42 million 3 price of 40 €/tone of raw materials used for building tones ash (33.9 million m ) recycled could be bricks manufacturing (clays + clay sands), the reduced the storage land with 27.500 ha [6,7]. The valorisation of about 500.000 t/year fly ashes and other environmental benefits of the ash recycling about 100.000 t/year drilled solids, could involve a include decrease of natural raw material require, decrease of the production costs up to 30 mil. which would need the quarrying and the replace of €/year, considering that the transport of the raw the high energy consumption material for the materials to the utilization place will be done by the production of Portland cement. Since 2006, wastes suppliers, and the wastes involve NO cost approximately 125 million tones of by-products [10]. resulted from coal burning process, inclusive ash, were produced in USA every year and 43% from these were used in trade applications, in accordance References: with the Coal American Association communications. [1] Luminita Georgeta Popescu, Adrian Gorun, The protection environmental Agency of USA Cristinel Racoceanu, Mihai Cruceru, through that this percent reached 50 % in 2011 [8]. Enviromental impact of ash and slag deposit The used ways of the ash include: Ceplea Valley of Energetic Centre Turceni, 12th - The produce of cement, as replacement International Multidisciplinary Scientific material of Portland cement and sand, GeoConference & EXPO Modern Management - Structural and filling embankments (usually of Mine Producing, Geology and Environmental for building roads), Protection, S G E M 2 0 1 2, CONFERENCE

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PROCEEDINGS, ISSN 1314-2704, pag. 345- 352, [2] Georgeta Predeanu, Study on evaluation of variation limits of fly ash characteristics depending of parent coals and combustion conditions New building materials by eco- sustainable recycling of industrial wastes, Life 10/ENV/RO/729, Inception Report, March – 2012, [3] LF/EIPPCB/LCP_BREF_FINAL, Document de referinta asupra celor mai bune tehnici disponibile (BAT) pentru instalatiile mari de ardere, Ministerul Mediului si Gospodaririi Apelor din Romania, Agentia Nationala de Protectia Mediului, Mai 2005, 638 p. [4] New building materials by eco-sustainable recycling of industrial wastes, Life 10/ENV/RO/729, Inception Report, March – 2012 [5] Studiu privind evaluarea riscurilor de mediu după închiderea Depozitului de zgură şi cenuşă nr.1 – Valea Ceplea, contract de prestări servicii de cercetare ştiinţific 1301/16.12.2010, beneficiar Complexul Energetic Turceni [6] M.Chusid, S. Miller, The Building Brick of Sustainability, Raport The Construction Specifier, May 2009 [7] U.S. Environmental Protection Agency. "Using Coal Ash in Highway Construction - A Guide to Benefits and Impacts". http://www.epa.gov/epaoswer/osw/conserve/c2p 2/pubs/greenbk508.pdf [8] Robert McCabe (March 30, 2008). "Above ground, a golf course. Just beneath it, potential health risks". The Virginian-Pilot. http://hamptonroads.com/2008/03/above-ground- golf-course-just-beneath-it-potential-health-risks, [9] N. Gaarder, Coal ash will fight flooding, Omaha World-Herald, February 17, 2010, [10] New building materials by eco-sustainable recycling of industrial wastes LIFE10 ENV/RO/729 Project, Constantin Brancusi University of Targu Jiu – Beneficiary coordinator.

Acknowledgements The present research has been carried out with the financial support given through LIFE10 ENV/RO/729 Project.

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