Studies into the kinetic compensation effects of Loy Yang Brown coal during gasification in a steam environment – A mechanistic view

Abstract

This study aims to investigate the kinetic compensation effects (KCE) and gain insights into the mechanisms, during gasification of Loy Yang brown coal char with steam, in an in-situ fluidized bed gasification operation for two-particle size ranges (106–150 and 180–212 µm). The instantaneous rate of char gasification and CO, CO₂, and H₂ formation was measured by continuous monitoring of product gas composition through a quadrupole mass spectrometer. Gasification of the smaller particle size range (106–150 µm) in kinetics-controlled regime shows less importance of char-catalyzed element on the WGS reaction, as revealed by the apparent activation energy and apparent frequency factor for CO and CO₂ formation. However, the study of kinetic parameters of char consumption on gasification using coal char with larger particle sizes (180–212 µm) indicated the limitations of intraparticle diffusion. That potentially affects the CO₂ formation by catalyzed WGS through re-adsorption of CO on catalytic char surface at a higher conversion level (> 0.3) as revealed by the difference in the extent of KCE for CO and CO₂ formation. The difference in the extent of KCE for char consumption and H₂ formation for bigger particles indicates the intraparticle diffusion limitations also appear to affect the route of H₂ formation, i.e., significantly produced through adsorption on catalytical active site with less involving the carbon active sites on char surface.