The study on the effect of the substitution of K2CO3 with Ca(OH)2 on kinetics on CO2–lignite coal gasification

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Three kinds of lignite were mixed with K2CO3 and Ca(OH)2 and were gasified with CO2 to investigate the effect that the addition of Ca(OH)2 had on the gasification kinetics. K2CO3 and Ca(OH)2 were impregnated and dried, their mixing ratio was varied, and the gasification experiments were conducted over a temperature range from 850 to 950 °C at atmospheric pressure. The modified volumetric reaction model was applied as the gas–solid reaction model to analyze the carbon conversion results and thus obtain the kinetic parameters. The results indicate that the catalytic activity based on carbon conversion followed the order of K2CO3 5 wt% + Ca(OH)2 3 wt% > K2CO3 8 wt% > K2CO3 3 wt% + Ca(OH)2 5 wt% > K2CO3 1 wt% + Ca(OH)2 7 wt%. The reaction rate was also influenced by the type of lignite, with a higher reactivity observed for Adaro lignite. The highest reaction rate constant was of 44.25 min−1 with Adaro lignite and K2CO3 5 wt% + Ca(OH)2 3 wt% at 950 °C. The lowest activation energy of 44.49 kJ/min was calculated for Mongolia lignite with K2CO3 8 wt%. The reaction rate was enhanced by partly substituting K2CO3 with Ca(OH)2, but further substitution resulted in a decrease in the reaction rate compared to that of K2CO3 alone.