Catalytic Pyrolysis of Sawdust with Desulfurized Fly Ash for Pyrolysis Gas Upgrading

In this study, the catalytic effects of desulfurized fly ash (DFA) on the gaseous products of sawdust (SD) pyrolysis were investigated in a tubular furnace. The results indicated that DFA catalyzed the process of SD decomposition to improve the hydrogen content and the calorific value of pyrolysis gas. As to its effect on pyrolysis products, DFA increased the non-oxide content of CH₄, C₃H₄, and H₂ in pyrolysis gas by 1.4-, 1.8-, and 2.3-fold, respectively. Meanwhile, the catalytic effect of DFA reduced the CO and CO₂ yields during DFA/SD pyrolysis. Based on the model compound method, CaSO₃ and Ca(OH)₂ in DFA was proved to have quite different catalytic effects on pyrolysis gas components. Ca(OH)₂ accelerated the formation of CH₄ and H₂ through the cracking of methoxyl during lignin and cellulose degradation, while CaSO₃ favored the generation of CO and CO₂ due to the carbonyl and carboxyl of lignin in SD. CaSO₃ also catalyzed SD pyrolysis to promote the C₃H₄ yield in pyrolysis gas. Overall, the catalytic pyrolysis of SD with DFA yielded negative-carbon emission, which upgraded the quality of the pyrolysis gas.