The isothermal studies of char-CO2 gasification using the high-pressure thermo-gravimetric method

Abstract

The char-CO2 gasification reactions in isothermal and pressurized conditions were studied kinetically by high-pressure thermo-gravimetric analyzer, and the primary objective of this paper was to study the effects of pressure, temperature and char rank on the intrinsic reaction kinetics of the char-CO2 gasification by the Langmuir–Hinshelwood model. The results indicated that the order of reactivity sequence at the same temperature and pressure was Char A > Char B > Char C (Char A from subbituminous coal, and Char B and C from bituminous coals). With the increase in the pressure and temperature, both the intrinsic reaction rate at the same carbon conversion and the carbon conversion efficiency at the same reaction time increased. The results also showed that the gasification rate experienced an initially slow increase, followed by a rapid increase, and finally a decrease corresponding to the increase in the carbon conversion efficiency. It implied that the Langmuir–Hinshelwood model was incompatible to thorough presentation of the complete conversion of the char-CO2 gasification, but was well agreeable to the intrinsic reaction kinetics of char-CO2 gasification when the carbon conversion efficiency was low at the initial stage of the carbon conversion (0–0.6). Based on this, the intrinsic reaction kinetic models of the selected char samples were built.