Kinetic Study on Low-Rank Coal Char: Characterization and Catalytic CO2 Gasification

Abstract

A kinetic characterization of the CO2 gasification of chars from Chinese low-rank lignite coal is performed by isothermal thermogravimetry. The isothermal condition is 1,073 K, and the CO2 concentration range is 10–90%. Alkali and alkali earth catalysts were used to promote the gasification reactivity. The gasification rate of the char was increased with the carbon dioxide (CO2) concentration. The gasification rate increment was reduced at a higher concentration, which inhibited the CO2 gasification rate. The best CO2 ratio for gasification was 70%. The gasification rate of the char with CO2 is fast and proceeded in the following order: sodium carbonate (Na2CO3)>potassium carbonate (K2CO3)>calcium carbonate (CaCO3)>dolomite. In this study, the following gas–solid reaction models are compared: the shrinking core model, the volumetric reaction model, the modified volumetric reaction model (MVRM), and the random pore model. The correlation coefficient values of the MVRM were the highest of all the models at all concentrations.