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

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.