Catalytic effect of alkali carbonates on CO2 gasification of Pingshuo coal

Abstract

Na₂CO₃, Li₂CO₃, and K₂CO₃ were used as additives to Pingshuo (PS) coal that was subsequently gasified under a CO₂ stream. The catalytic gasification of coal samples by CO₂ in the presence single or mixed alkali carbonates was investigated by thermogravimetric analysis. The experimental results indicate that the catalytic effect of Li₂CO₃ is significantly larger than that of Na₂CO₃ or K₂CO₃. The catalytic effect of the mixed, bi-metal carbonate containing Li₂CO₃ and Na₂CO₃, or Li₂CO₃, and K₂CO₃, is related to the composition of the catalyst and the proportion of the two components. The bi-metal carbonates having a mole ratio of 9:1 (Li:X) has the largest catalytic effect for PS coal gasification. A synergistic effect between Li and K, or Na, carbonate appears at temperatures greater than 1300 K. An un-reacted shrinking core model is suitable for kinetic analysis of catalytic gasification of coal samples in the presence of alkali carbonates. It is inappropriate, however, to evaluate the catalytic effect only by the activation energy obtained from the kinetic calculations.