Experimental Investigation of Lignin Decomposition and Char Structure During CO2 and H2O/N2 Gasification

Characterization of the char pore structure resulting from thermal decomposition of lignin during TGA processing in both CO2 and H2O/N2 media was performed using an Hitachi 4700 scanning electron microscope. Lignin, the more thermally resilient structural component of ligno-cellulosic biomass feedstocks, was found to undergo more complete conversion to volatiles during thermal processing in a CO2 as compared to a H2O/N2 gasification medium. The pyrolytic char created during CO2 thermal treatment exhibited a more porous surface and an intricate channel structure that enabled the CO2 molecules to access the inner volume and provided a channel network for escaping volatiles. This resulted in a more complete solid to gas conversion of the char during CO2 gasification. Both a greater surface pore density and a wider pore size distribution was observed in those chars undergoing thermal decomposition in CO2.