Entrained-flow pyrolysis and (co-)gasification characteristics of Indian high-ash coals

Co-utilization in entrained-flow gasifiers is a potential solution to address the high ash-related problems persistent in fluidized-bed gasifiers. This work presents the hitherto unreported high-temperature (1000-1400 degrees C) entrained-flow pyrolysis and (co-) gasification characteristics of Indian high-ash coals and two candidate fuels (indigenous bituminous coal and petcoke) for possible co-utilization. Char analyses - TGA, FTIR, Raman, and SEM - are also performed to characterize the pyrolysis-induced structural changes. Volatile yields of candidate fuels matched with proximate values while those of high-ash coal exceeded by similar to 12 wt%. Thermal deactivation was more pronounced for coal chars. High-ash coals achieved 100% carbon conversion at conditions exceeding 1300 degrees C and 20 vol% CO2. Bituminous coal showed comparable conversions, 70-90%, at identical conditions; further increase in conversion potential may be possible through steam addition due to enhanced char deactivation and pore diffusion effects at higher temperatures. Petcoke achieved lowest conversion of similar to 30% even at the severest conditions; decreasing the average particle size by half showed an improvement of only similar to 15%. Co-gasification of high-ash coal and petcoke blends showed no synergy. Considering closely matching carbon conversion, volatile release potential, and industry-standard slag tapping temperatures (1300-1500 degrees C), indigenous bituminous coals are more promising for co-utilization with high-ash coals in autothermal entrained-flow gasifiers.