Structural evolution of a bituminous coal char related to its synchronized gasification behavior with H2O and/or CO2

This work aims to investigate the structural evolution of the char during gasification under a single or mixed atmosphere of H2O and/or CO2 with the synchronized investigation of the effect of the varying char structure on the gasification reactivity. The experimental char was prepared from a bituminous coal at 1000°C. The changes of the char structure along with the progress of the carbon conversion during gasification were characterized using N2 adsorption, SEM, and Raman spectroscopy. The results revealed that H2O showed a more dramatically change on the char structure than CO2 and two reactants had different reaction pathways. The different pathways of reactants affected the evolution manners of the char structure and different gasification reactivity of char was related to structural evolution. The specific reaction rate between the char and CO2 decreased monotonously with increasing carbon conversion. However, the opposite trends are observed when H2O exist, either H2O alone or the mixtures of H2O and CO2. The char gasification reactivity was under the common effect of physical and chemical structure. In terms of the mixture of H2O and CO2, the significant specific surface area caused by H2O provided more active sites for CO2. The interactions between H2O and CO2 promoted reaction between C and CO2 (C + CO2 → CO) in mixtures of H2O and CO2, leading to higher amount of CO and higher specific reaction rate than calculated.