Heavy metal enrichment characteristics and environmental risk assessment of MSW pyrolysis char and coal co-incineration fly ash

Co-incineration of municipal solid waste (MSW) in coal-fired power plants is increasingly recognized for its potential benefits. Pre-carbonization of MSW substantially enhances its calorific value compared to direct co-incineration. However, the heterogeneous composition of MSW poses challenges in managing heavy metal emissions, particularly in fly ash. This study investigates the enrichment characteristics of heavy metals during the incineration of MSW pyrolysis char using a drop tube furnace experimental setup, along with an environmental risk assessment. The results show that mixing more MSW pyrolysis char with coal enhances the ability of fly ash to capture heavy metals. This is due to the smaller particle size of fly ash from the char, which effectively adsorb heavy metals released during incineration. The heavy metal concentration in fly ash was significantly higher than in char, for the reason that heavy metals tend to volatilize and condense on fly ash at high temperatures. Additionally, heavy metal concentrations in leachate were substantially lower than in solid samples, suggesting that these metals in MSW pyrolysis char and fly ash are not readily dissolved in water, thereby reducing the risk of environmental pollution. However, the hazard level of different heavy metals in fly ash increased with the increase of co-incineration temperature, with more consideration on process temperature control. These findings provide valuable insights into the disposal of heavy metals in pyrolyzed carbon and fly ash from municipal solid waste incineration.