Effect of pyrolysis atmospheres on gaseous products evolution of coal pyrolysis at high temperature

Pyrolysis provides a useful way to develop lignite with low direct economic value, therefore, it is worthwhile to study how to realize efficient pyrolysis and produce more combustible gas components (H-2, CO, CH4). In this paper, high-temperature pyrolysis experiments were carried out on lignite collected from the H-3 coal seam of the Yimin Formation in three mines of the Zhalainuoer Coalfield under different pyrolysis atmospheres (100 % Ar, 25 % CH4 + 75 % Ar, 25 % H-2 + 75 % Ar, 25 % CO + 75 % Ar and 25 % CO2 + 75 % Ar) to investigate the gaseous products evolution with temperature under different atmospheres. Next, multi-peak fitting of pyrolysis gaseous products (H-2, CO, CH4, CO2) yield curves of lignite from different mining areas with 100 % Ar atmosphere were performed to obtain the number of reaction types of H-2, CO, CH4 and CO2 produced during lignite pyrolysis as IV, V, III and VI, respectively. Further, by comparing the gas evolution characteristic under different pyrolysis atmospheres, the following can be obtained: (1) the addition of extra gases to the atmosphere has different effects on the generation of gaseous products at different temperature stages; (2) the addition of CO2 to the atmosphere causes an increase in total CO yield, a decrease in total H-2 yield, and no significant change in CH4 yield of lignite pyrolysis at the final temperature of 1200 degrees C; (3) the addition of either 25 % CH4, 25 % H-2 or 25 % CO to the atmosphere results in a decrease in the yield of other gases except for the added gases. In addition, carbonate minerals and silicate minerals are conducive to the production of CO2 and CH4. This work provides new ideas for the efficient pyrolysis of lignite from the perspectives of atmosphere and temperature, and is conducive to the study of evolution of mineral in coal during pyrolysis.