SEM-EDS Analysis of Fly Ash from One Shanghai Municipal Solid Waste Incineration Plant during Heating Process

This study aims to explore microstructure and elementary variation of fly ash from one Shanghai municipal solid waste incineration (MSWI) plant on the one hand and analyze leaching toxicity of Zn, Pb, Cd and Cu during heating process. SEM-EDS was performed on fly ash of room temperature and those sintered at 700□, 800□, 90□0, 1,000□, and 1,100□ respectively, and leaching toxicity of four heavy metals analyzed by horizontal vibration extraction procedure (HVEP). It is found that structure of fly ash is strengthened with increase of temperature, which is conducive to stabilization of heavy metals. Crystal content increases from room temperature to 800□ and then decreases in the heating process, while content of glass phases has a reverse trend. Ca and O content variation has a similar trend, while Cl has a reverse trend with them. Their leaching toxicity in fly ash sintered at temperatures over 900□ is lower than the limit value described in “Identification Standard of Hazardous Waste—Identification of Leaching Toxicity”. Finally, 1000□ is recommended to treat MSWI fly ash.

I. Introduction

The disposal of fly ash generated during municipal solid waste incineration (MSWI) may pose a significant risk to the environment due to the possible leaching of hazardous pollutants, such as toxic metals. It is regarded as a hazardous material because concentrations of TCLP leaching solution exceeded standards. Thermal treatment is one of the most important methods, which involves sintering technology and vitrification process. The former attracted more attention than the latter because of its low energy needed [1]. No matter which one is used, a clear understanding of its thermal characterization is of great importance.