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.
Keywords: catalytic; desulfurized fly ash; pyrolysis; pyrolysis gas upgrading; sawdust.