Synergistic interactions between biochar reacted with steam and CO2 originating from a diffusion reaction state and intrinsic ash

The interactions between reactions that occur while biochar is gasified in a mixed CO2/H2O(g) atmosphere remain unclear. In the present study, the reactions of palm kernel shell (PKS) biochars with CO2 and H2O(g) were systematically investigated using a thermogravimetric analyzer and a bench-scale tube furnace. The results show that the chemical reaction state and intrinsic ash are primarily responsible for the three interaction effects that have been extensively reported in the literatures. Specifically, an inhibitive effect occurred during D-biochar gasification under the chemical reaction regime, while a transition from independent effect to a competitive effect was observed under the diffusion reaction regime. Micropores suitable for the reaction of biochar with CO2 were found to be produced by H2O(g) in the presence of Ca species, which were representative AAEMs in the intrinsic ash of the PKS biochar. This phenomenon created the desired synergistic effect between the two reactions. The appearance of this synergistic effect was observed only under the diffusion reaction regime and in the presence of intrinsic ash.