Synergistic effects of chemical looping gasification of domestic sludge with corn straw using red mud oxygen carrier for hydrogen-rich syngas production

Abstract

The conversion of domestic sludge into high-value syngas remains challenging because of its low reactivity and high ash content. In this study, a triple-waste chemical looping gasification (CLG) strategy was proposed by integrating domestic sludge, corn straw, and industrial red mud for the production of hydrogen-rich syngas. The effects of key operating parameters, including blending ratio, O/C ratio, reaction temperature, and steam flow rate, on gas composition, total gas yield, cold gas efficiency, carbon conversion rate, effective gas fraction, and lower heating value were systematically evaluated. The optimal conditions were identified as a corn straw/domestic sludge blending ratio of 0.6 (0.5 g sludge), an O/C ratio of 0.3, a reaction temperature of 900 °C, and a steam flow rate of 0.2 mL/min. Under these conditions, a hydrogen fraction of 56% and a total gas yield of 1.23 Nm³/kg were achieved, accompanied by a cold gas efficiency of 93.33%, a carbon conversion of 80.97%, and an effective gas fraction of 81.21%. Additionally, cyclic redox experiments confirmed that the red mud oxygen carrier maintained good reactivity and stability over five consecutive cycles. This work demonstrates a sustainable and efficient strategy for sludge-to-syngas conversion via CLG and highlights the advantages of employing industrial solid waste oxygen carriers and biomass-sludge synergistic gasification.