Thermal Decomposition of Coal from the Tuva Deposit
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Chemistry for Sustainable Development 21 (2013) 303311 303 UDC 662.743 Thermal Decomposition of Coal from the Tuva Deposit N. I. KOPYLOV and YU. D. KAMINSKIY Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences, Ul. Kutateladze 18, Novosibirsk 630128 (Russia) E-mail: [email protected] (Received May 31, 2012; revised November 13, 2012) Abstract The results of research work are reported concerning the thermal decomposition of coal species from the Ulugh and Chadan beds of the Kaa-Khem site of the Tuva deposit as well as an effect of coal activation on the decomposition process. Potentiality is demonstrated for briquetting the coal after removing gaseous and light liquid fractions from the material. Key words: coal, thermal analysis, mechanical activation, thermal decomposition, briquetting, condensable sublimates INTRODUCTION ized by stable properties, whereas the carbon- ization thereof results in producing the gas with The coal species from the Tuva coal basin an increased content of hydrocarbons and hy- and the products of processing thereof repre- drogen. Liquid hydrogenation products contain sent a real and reliable energy source for the a relatively small amount of asphaltenes and industrial development of the Republic of Tyva. heteroatomic compounds. In general, only concerning the coking coal the According to the authors of [16], these coal resource of the Republic of Tyva is estimated species could serve as a valuable raw material as 14.2 billion tons. According to the grade com- for chemical products. The authors of [17] car- position, 88 % of the resources are presented ried out the pyrolysis of the Kaa-Khem coal by GZh grade coal, 12 % being presented by and reference samples (B, G, Zh grade coal G grade coal (according to the State Standard species). They revealed the features of the Kaa- GOST 2554388) [1], so they could be used not Khem coal species, distinguishing the latter only as a raw material for fuel energy, but also from the gas coal of Kuzbass coals close to them in the coke chemistry and chemical industry. in the level of metamorphism. The features of With a view to the practical use, there was the thermochemical transformations of the a great scope of work performed concerning Kaa-Khem coal cause a high sintering ability the determination of the reserves prospected, thereof and the prospects of its use as a raw geological characteristics and classification of material for coking. coal from the mentioned deposit, the composi- However, despite a rather great volume and tion, characteristic properties, quality and cok- wide range of the data obtained, the coal mined at ing behaviour [217 etc.]. For example, the au- the Tuva coal basin continues to be used only as an thors of [16] investigated a number of sam- energy source, without any preliminary treatment. ples taken from the 2-Ulugh bed of the Kaa- A high content of volatile components (non- Khem coal basin in different times. It was dem- condensable gases, coal resins), and caking in onstrated that these coal species are character- the course of coal combustion in the kiln fur- Kopylov N. I. and Kaminskiy Yu. D., 2013 304 N. I. KOPYLOV and YU. D. KAMINSKIY naces and boilers prevent complete carbon burn- rification of solutions. In this regard, one could out, resulting in a systemic release of environ- consider a method of mechanical activation to mentally hazardous products to the atmosphere. be more promising for the activation of coal. In addition, the specific geographical location For the rational use of the Tuva coal spe- of the Tuva region (location of cities and towns cies, of interest is to study their thermal de- in the confined spaces of mountain valleys in a composition with the evolution of gases and wind shadow) and its harsh climatic condi- low-boiling components to apply as intermedi- tions (continental climate, abrupt seasonal vari- ates for chemical industry and with obtaining ations in temperature and dropping the tem- a solid dry fuel and energy product (briquettes). perature in winter with profound anomalies Preliminary experiments [21] concerning the below zero) exacerbate to a great extent the thermolysis of coal from the Kaa-Khem de- mentioned environmentally unfavourable situ- posit demonstrated that in the course of heat- ation. The absence of an adequate circulation ing in a neutral reducing atmosphere at a tem- of atmospheric air above ground contributes perature above 350 °Ñ there occurs mild sin- to smog formation, and, as a result, to air pol- tering the sample material. Subsequent heat- lution with the products of incomplete coal com- ing was followed by distillation of low-boiling bustion, which leads to a significant environ- coal components to the gaseous environment, mental contamination with carcinogens [9]. and then the material exhibited a weakly sin- These factors determine the relevance of tering with becoming porous at first, to be- further research with the purpose to find envi- come loose when the temperature amounted to ronmentally sound technologies for processing about 700 °Ñ and higher. In this case, the mass the coal from the mentioned deposit and ratio- loss (under heat exposure) could reach 6070 % nal use thereof. of the initial value. In order to use coal not only as fuel for power The mechanical activation of original coal generation, but also as a raw material for coke samples during 10 min in an atmosphere of its chemistry and chemical industry, it is neces- own gas medium results in occurring the phase sary to provide them a high reactivity, for ex- transformations with the decomposition and the ample, via activation. formation of active centres, which, to all ap- In the Tyva Institute of Complex Explora- pearance, causes the oxygen saturation of the tion of Natural Resources, SB RAS (Kyzyl, material via sorption process. Under heating fur- Tyva, Russia) there were experiments conduct- ther slow oxidation thereof is observed to form ed concerning the chemical activation of coal carbonates decomposing with the release of CO2. taken from the Elegest open-cast mine of the In order to study the possibility of briquet- Tuva coal basin [1820]. It was demonstrated ting the coal species under investigation, there that the preliminary treatment of coal solu- were experiments carried out to determine the tions of inorganic acids and alkalis exert a sig- character and temperature of sintering and nificant effect on the structure and properties subsequent distillation of low-boiling compo- of coal. It was established that the chemical nents with use of coal samples taken from dif- activation of coal causes decreasing the bond ferent parts of the Ulugh and Chadan beds of strength in the structure of coal with increas- the Kaa-Khem coal basin [22]. ing the coal porosity. In this case, chemical ac- tivation by alkaline solution appeared more ef- ficient. In addition, the chemical activation of EXPERIMENTAL coal promotes increasing the rate and conver- sion level of coal organic matter (COM) into The characteristics of the coal species under liquid and gaseous products, as well as increas- investigation taken from the Ulugh and Chadan ing the yield of the latter. beds of the Kaa-Khem deposit are presented However, this method of activation implies in Table 1. Alongside with the thermal analysis, the use of chemicals, solutions and, therefore, we conducted experiments on determining the requires for corresponding instrumental network temperature limits for he isolation individual scheme for the preparation and subsequent pu- fractions resulting from thermolysis. THERMAL DECOMPOSITION OF COAL FROM THE TUVA DEPOSIT 305 TABLE 1 Technical and chemical characteristics of the coal samples Sites Sampling place Sample Technical analysis, % Elemental analysis, Coal a d daf d index W A V St % with respect to the organic grade matter of coal sample CHNOS Chadan open-cast mine Northern flank 05-03 0.6 10.8 39.8 0.52 87.22 5.61 1.04 5.53 0.60 Zh Chadan coal bed « « 06-03 0.4 9.2 40.8 0.21 88.46 5.58 0.99 4.73 0.24 Zh Southern flank 07-03 0.8 5.2 35.2 0.20 87.66 5.20 0.95 5.97 0.22 Zh Kaa-Khem open-cast Northern flank 08-03 1.2 6.4 47.6 0.17 83.90 5.73 1.11 9.09 0.17 G mine 2-Ulugh coal bed Southern flank 09-03 1.2 5.9 48.9 0.19 84.00 5.52 1.08 9.19 0.21 G-GZh « « 10-03 1.2 9.0 48.6 0.17 83.63 5.70 1.19 9.29 0.19 G-GZh Central part 11-03 1.2 6.0 47.6 0.14 83.02 5.97 1.27 9.59 0.15 G The experiments on thermal investigation permitted the gaseous products of thermolysis were carried out using a MOM-1000 derivato- formed in the bulk of the sample. The mass of graph (MOM, Hungary). The heating rate was the weighed sample portion amounted to 600 maintained at a level of 10 °Ñ/min. The heat- mg. The experiments were repeated for repro- ing was carried out under the conditions of the ducibility. In order activate the original mate- own gas environment and of the free diffusion rial we used an AGO-2 planetary-type mill with of the resulting gas phase throughout the sam- water cooling, at the timing modes of 1, 3 and ple material. To prevent the ignition of the sam- 10 min. The experiments on obtaining the frac- ple and the creation of conditions for the free tions extracted were performed using a setup removal of low-boiling coal components the cru- comprising a muffle furnace, a quartz tubular cible was closed by a carburized lid made of ampoule with a system for suction and trap- foamed corundum that impeded free of air ac- ping of condensable sublimates.