Evolution characteristics of gases during pyrolysis of maceral concentrates of Russian coking coals

The major constituents that control the properties of coking coals are vitrinite and fusinite. Thus, for better understanding of the thermochemical reactions during the carbonisation of coking coals, the evolution characteristics of gaseous products during pyrolysis were studied with four samples of vitrinite-rich and four samples of fusinite-rich concentrates of Russian coking coals of rank (Ro) varying from 0.80 to 1.54. Maceral concentrates were generated by repeated cycles of float-sink separation under centrifugal force. The gases evolved during thermogravimetric analysis of the maceral concentrates were analysed by gas chromatography for the content of methane, hydrogen, carbon dioxide and carbon monoxide. The major constituents of gaseous products were methane, carbon monoxide and hydrogen. The amount of carbon dioxide evolved was observed to be insignificant compared to the amounts of hydrogen, methane and carbon monoxide. Graphs were plotted between the rates of evolution of the above gaseous components and temperature for different maceral concentrates to study their evolution characteristics. A clear difference in yields of methane, carbon monoxide and hydrogen in vitrinite- and fusinite-rich concentrates could be observed from the study. Content of hydrogen, methane and carbon monoxide varied from 55 to 65, 29 to 37 and 6 to 12%, respectively, in vitrinite-rich concentrates and from 57 to 70, 19 to 22 and 11 to 22%, respectively. in fusinite-rich concentrates. The evolution behaviour of gaseous products during primary devolatilisation (260-550 degreesC) and secondary devolatilisation (550-850 degreesC) was also discussed. Mathematical analysis was carried out to identify the significant factors and regression equations for prediction of the yield and composition of the gaseous products. Some of the most distinguishing features of this study are: (a) use of a broad range of coking coals; (b) study of the gas evolution pattern for both vitrinite- and fusinite-rich concentrates at a heating rate of 5 degreesC min(-1), which is very close to the standard carbonisation practice of 3 degreesC min(-1), and the temperature range of heating was from room temperature to 900 degreesC, which is close to the high-temperature carbonisation of 1000 degreesC, and (d) the study of the gas evolution behaviour during primary and secondary devolatilisation. (C) 2001 Elsevier Science Ltd. Ail rights reserved.