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

Abstract

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 °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 ∼12 wt%. Thermal deactivation was more pronounced for coal chars. High-ash coals achieved 100% carbon conversion at conditions exceeding 1300 °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 ∼30% even at the severest conditions; decreasing the average particle size by half showed an improvement of only ∼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 °C), indigenous bituminous coals are more promising for co-utilization with high-ash coals in autothermal entrained-flow gasifiers.