Disposal of municipal solid waste incineration fly ash through synergistic in-plant dechlorination and sintering

Abstract

Incineration technology has emerged as the predominant approach for the safe disposal of municipal solid waste in China, generating a significant amount of fly ash as a byproduct. However, the primary landfill method currently employed in China, chelation stabilization coupling, falls short of reliability in terms of environmental standards. Consequently, the safe and effective disposal of fly ash containing high concentrations of chlorine salts, heavy metals, and dioxins is of critical importance. This study proposes a synergistic approach for the dechlorination and sintering of fly ash (FA) generated in waste incineration plants. This method entails the washing of FA with leachate and concentrate, followed by pelletizing and in-furnace sintering. The results indicated that treatment with leachate reduced the residual chlorine concentration in FA to 7 % at a liquid-to-solid ratio of 10 mL g⁻¹, while subsequent treatment with concentrate further lowered it to 4 %. FA also adsorbed impurities from the leachate and concentrate without substantially altering critical water quality parameters, enabling the treated liquids to be reintegrated into the leachate treatment system. Aspen Plus simulations demonstrated that in-furnace sintering had a negligible impact on furnace temperature, even when fly ash constituted 0–3 % of the total waste processed. Additionally, the plant's leachate and concentrate output lives up to FA washing requirements. Overall, our study provides fundamental information and establishes a novel model for a low-cost and eco-friendly “waste to treat waste” approach to dispose FA via leachate/concentrate washing in concert with in-furnace sintering.