Characteristics of heavy metal migration in the gasification-combustion process of rural solid waste: Influencing factors and mechanisms

Abstract

The miniaturized gasification-combustion model has potential advantages in treatment of rural solid waste (RSW) in China. In this study, the gasification-combustion technology concerning air-staged technology was employed in the treatment of seven combustible components in RSW, focusing on the analysis of heavy metal migration characteristics. Firstly, a comparison was made between combustion and gasification-combustion regarding the migration characteristics of heavy metals, demonstrating that gasification-combustion effectively reduces the volatilization rate of heavy metals. The largest reduction in volatility was 12.99 % for Cu. Secondly, this study explored reaction temperatures and oxygen concentration in the gasification zone, concluding that under experimental conditions mentioned herein, optimal gasification temperatures for curing heavy metals were determined to be 700 °C while maintaining an optimal ratio of air (RA) at 0.5 during gasification. Finally, the interaction of inorganic elements with different components on heavy metal migration was revealed by co-gasification-combustion of equal mass mixture of two components. The P, S, Cl contents and the inorganic mineralogical composition of the RSW are the key factors influencing the transport properties of heavy metals. The two-component synergistic effect of RSW studied in this paper has guiding significance for limiting the proportion of RSW components to control heavy metal emission in gasification-combustion process.