Effect of red mud on combustion behavior and heavy metal stabilization of Refuse Derived Fuel (RDF)

Abstract

Refused Derived Fuel (RDF) from municipal solid waste has become a promising and effective approach for waste storage and utilization. However, the poor combustion performance and heavy metals (HMs) emission limit the development of this technology. In this study, red mud (RM), an industrial waste from the alumina extraction process, was used as an additive to improve the combustion behavior of RDF. The results show that 10 wt% of red mud addition can increase the flammability index (F) and the comprehensive combustion characteristic index (S) by 91% and 156%, respectively. It significantly reduced the burnout temperature of RDF by 59 °C. Moreover, RM also promoted the transformation of HMs into more stable forms. The proportion of F4 speciation for Cr, Ni, Cu, Zn Cd, and Pb in ash residues increased by 6.42%, 50.91%, 92.48%, 43.77%, 15.77%, and 4.53%, respectively, while the leaching rate of Cr, Ni, and Cd decreased by 1.7%, 0.99%, and 1.31%. The findings proved that RM could serve as an efficient additive for enhancing RDF combustion and stabilizing the HMs in ash residues, which would provide new insight into the co-utilization of wastes and the contribution to the clean combustion of RDF.