Linking Char Reactivity to Structural and Morphological Evolution during High Pressure Pyrolysis of Morupule Coal

Abstract Understanding the influence of pressure on char physicochemical properties and reactivity during pyrolysis is principal for the design and optimisation of coal gasification technologies. This work investigated the pyrolysis behaviour of Morupule coal at various pressures and temperatures in a high-pressure wire-mesh reactor (HPWMR). The effect of pressure was pronounced at 600 and 800 °C, resulting in lower total volatile yields at higher pressures due to the repolymerisation of volatiles. Although graphitisation was limited during the heating period, an increase in the concentration of ordered structures was observed during holding at 1000 °C. Marked blowholes on the char surface suggested an explosive bubble transport phenomenon during pyrolysis. Chars produced during the ramping period under high pressure showed higher combustion reactivities than their low-pressure counterparts. However, prolonged holding at peak temperature produced chars of similar reactivity, with their CO2 gasification reactivity found to be independent of pyrolysis pressure.