Study on the structure characteristics and gasification activity of residual carbon in biomass ashes obtained from different gasification technologies

Abstract

The structure characteristics and gasification activity of residual carbons in two rice husk (RH) gasification ashes, a fly ash (FAC) obtained from industrial circulating fluidized bed gasifier (CFBG) and a bottom ash (BAU) obtained from industrial updraft fixed bed gasifier (UFBG), were investigated. Results show that the residual carbon content of FAC (15.93%, dry basis) is much lower than that of BAU (40.27%, dry basis), and the carbon conversion efficiencies of RH in CFBG and UFBG are 93.09% and 74.44%, respectively. The dominant carbon species in RH is oxygen-linked aliphatic carbon (ca. 80%), which disappears in the residual carbons of FAC and BAU. Consequently, the nonprotonated aromatic carbon in RH increases significantly from about 3% to 66–68% during gasification processes, leading to the aromaticity of carbon increases from about 15% to 88–90%. The surface area and pore volume of carbon in RH increase significantly during gasification processes, especially those of FAC, while the gasification activity of carbon in RH decreases slightly due to the increased aromaticity of carbon.