Competition between H2O and CO2 for active sites during co-gasification of bituminous coal and pineapple sawdust in an atmosphere containing H2O, CO2, H2, and CO

Abstract

The competition between the H2O and CO2 for the active sites during gasification remains a controversial issue in the literature. In this study, the competition between the H2O and CO2 for the active sites during gasification of coal, biomass, and a mixture of coal and biomass using the Langmuir–Hinshelwood (L–H) kinetic parameters obtained in our previous two papers (Massoudi Farid et al., 2016, 2017) was investigated. It was found that the char–H2O and char–CO2 reactions occurred on separate active sites for all samples. For a constant CO2 concentration, increasing the H2O concentration caused an increase in the kinetic coefficient. The extent to which the kinetic coefficient increased became less pronounced as the amount of biomass in the co-gasified mixture increased. For a constant H2O concentration, increasing the CO2 concentration also increased the kinetic coefficient; however, the extent to which the kinetic coefficient increased was greater when the amount of biomass was higher. Additional experiments were conducted to study the effect of the co-existence of H2 and CO on the competition between the char–H2O and char–CO2 reactions for the active sites. It was found that the char–H2O and char–CO2 reactions also occurred on separate active sites, even in the presence of both H2 and CO.