Inhibition Effect of Coexisting Gas on CO₂ Gasification of Ca-Loaded Coal Char

Abstract

The CO₂ gasification behavior of Ca-loaded Yallourn brown coal char was investigated in the presence of H2 or CO with a thermal balance . The chemical form of Ca catalyst was in situ analyzed with a high temperature X-ray diffraction. In addition, oxygen containing-compounds on Ca-loaded char were evaluated with transient kinetics and temperature programmed desorption techniques. On the basis of these results, the mechanisms of H₂ and CO inhibition on Ca-catalyzed carbon gasification were discussed.
It was found that the presence of H₂ suppresses the formation of surface oxygen containing-compounds as reaction intermediate. Therefore, H₂ inhibition can be attributed mainly to the adsorption of H2 an Ca catalyst or on carbon surface in contact with Ca catalyst. As a result, the following catalytic processes are disturbed; the adsorption of CO₂ on Ca catalyst, and the formation of CaCO₃-C complexes. The temperature dependence of CO inhibition was quite different form the case of H2 inhibition, and this implies that the mechanism may be different in the two inhibition cases.