Study on interaction mechanism of steam coupling biomass sludge gasification to syngas with pickling sludge as oxygen carrier

Abstract

A process of producing hydrogen-rich syngas by chemical looping steam gasification is proposed, using pickling sludge (PS) as the oxygen carrier and paper-making sludge(PMS) along with municipal sludge(MS) as the fuel. The reaction characteristics of producing hydrogen-rich syngas through the gasification of PMS and MS were studied. The effects of temperature, steam flow rate and the blended ratio of PS on carbon conversion rate and gasification reaction efficiency were discussed, and the migration mechanisms of the main elements were explained. The results show that FeF₃ in PS exhibits stronger activity than conventional Fe₂O₃ in catalyzing the gasification of PMS and MS at high temperature. With the blended mass ratio of 1:1 of PS, the carbon conversion rate of PMS and MS was increased by 11.8 % and 42.5 %, and the gasification efficiency was increased by 11.1 % and 25.85 %. The Fe³⁺ in PS catalyzed the cleavage of C-H bonds in biomass sludge, and Fe³⁺ was reduced to form the intermediate product FeCr₂O₄ with tar cracking function. After the gasification reaction, the Fe in PS was completely converted to Fe₃O₄ under the action of MS, while the CaO in PMS promoted the valence cycle of Fe to some extent, resulting in partial Fe being fully cycled to Fe³⁺ to form γFe₂O₃. In addition, the CaO can fix the F element in PS to form CaF₂, thus reducing the environmental hazard.