Distribution Characteristics of Heavy Metals in Different Size Fly Ash from a Sewage Sludge Circulating Fluidized Bed Incinerator

Fly ash samples were collected from a sewage sludge incineration power plant in Zhejiang Province, China, where household sludge was mixed with industrial sludge in a ratio of 1:1. A dry-type centrifugal air classifier was used to separate and obtain particles with different sizes. According to the different air flow rates, five size fractions were obtained. The total size distribution of fly ash is described in this paper, and the chemical composition, mineralogical phase, and microstructure of the five fractions of fly ash were detected using X-ray fluorescence spectrometry, X-ray diffractometry, and scanning electron microscopy with energy-dispersive X-ray spectrometry, respectively. The heavy metal content and speciation with various particle sizes were analyzed using a sequential chemical extraction procedure. An integrated evaluation method that considers the type, content, toxicity, and stability of heavy metals was used to evaluate pollutants of the different particle size segments. An attempt was made to correlate the size, toxicity, structure, and properties.