Gasification of a coal char by oxygen and carbon dioxide

The textural changes of coal char upon gasification with either oxygen or carbon dioxide are compared. The comparison is carried out on char samples prepared by gasification with both reactants under conditions satisfying a tentative criterion for kinetic similarity. Accordingly, reaction temperatures and partial pressures of either oxygen or carbon dioxide were selected so as to satisfy the equality of Thiele moduli. Char samples were characterized by porosimetric analysis in order to shed light on pore activation and textural changes induced by the two reactions. Differences in reaction mechanisms associated with the two gasification processes are indirectly assessed. It is inferred that the pathway micropore chemisorption-spillover-desorption at reactive sites plays a much larger role for O(2) than for CO(2) gasification, providing a key for the differences in the observed gasification patterns. (C) 1998 Elsevier Science Ltd. All rights reserved.