Effect of Char Temperature on CO2 Gasification of High Ash Coal and Biomass

Information on comparative gasification reactivity of high temperature chars in CO2 with high ash coal (C), sawdust (SD) and rice husk (RH) under identical condition is important for clean energy development drive particularly in countries like India, where energy matrix is dominated by coal and introduction of larger quantity of biomass in energy-mix is attracting global interests. Therefore, TGA-studies on char-gasification reactivity using CO2 as a gasifying agent were performed at temperatures 850-1000 degrees C. In case of coal and RH-chars, CO2 reactivity found to increase with increasing the BET surface area and reverse trend was observed with SD-chars. Both the biomass-chars showed increased specific micro pore surface area with increasing char preparation temperature through t-plot analysis, still keeping unusual behavior of CO2 reactivity of SD-char unexplained. The estimations indicating the presence of catalytically active alkali and alkaline earth metals in substantial quantity is only important criteria found to explain the decreasing trend of gasification reactivity of SD-char prepared at various temperatures despite the increase in surface area. Catalytic activity of the components decreases with the rise in char preparation temperature. Kinetic analysis reveal that activation energy values of SD-chars varied in the range123-182 kJ mole(-1), whereas those for coal- and RH-chars remained in the range 204-214 kJ mole(-1).

Automated summary

This study aimed to compare the gasification reactivity of different char samples in CO2. The results showed that the gasification reactivity of coal and rice husk chars increased with increasing BET surface area, while sawdust char exhibited the opposite trend. The specific micro pore surface area of both biomass chars increased with the char preparation temperature, but the unusual behavior of CO2 reactivity in sawdust char was not explained.