Experimental and kinetic studies of coal–CO2 gasification in isothermal and pressurized conditions

Abstract

This study is to explicate the reaction mechanisms and kinetics of high-pressure char CO₂ gasification via a joint experimental and model simulation approach. The high-pressure char–CO₂ gasification reactions were studied experimentally using a high pressure thermo-gravimetric analyzer (HP-TGA). The results showed that the char CO₂ gasification rate experienced an initially slow increase until the carbon conversion reached 0.6 (Zone I), when a rapid increase in the carbon conversion increased to 0.9 (Zone II). Further gasification reaction, corresponding to a carbon conversion efficiency above 0.9 (Zone III), finally, presented a sharp decrease in kinetics. For more accurate interpretation of the experimental char–CO₂-gasification kinetics and mechanisms, we found a proven kinetic model could be derived based on the random pore model and mixed model, which specifically predicate the studied gasification reaction and its critical kinetics parameters of the Zone I and II, respectively. The developed kinetics model, assembling major parameters (including char structures, pressure order, reaction order, activation energy and pre-exponential factor) was found to be in good agreement with the experimental results, covering wide realistic gasification operation conditions. This study revealed an optimal carbon conversion range with rational gasification kinetics, which can be estimated based on an accurate kinetics model.