Accelerated carbonation of municipal solid waste incineration fly ash using CO₂ as an acidic agent for clinker production

An accelerated carbonation pretreatment of municipal solid waste incineration (MSWI) fly ash was investigated for the efficiency of both heavy metal solidification and chloride release in MSWI fly ash. Carbonation was performed with a liquid-to-solid ratio of 5, 10, or 20, during which carbon dioxide was used as the acidic agent. Other properties that were evaluated were the clinker composition, compression strength of the clinker, and setting time of the clinker. Results indicated that the carbonation process was highly efficient for the release of chloride and that the process had a high efficiency for amphoteric heavy metals (Cu, Zn, Pb, and Cd) solidified in the fly ash. The leached amount of Pb, Cu, and Zn in the wastewater effluent after the carbonation process was reduced to 20, 110, and 470 mg/kg compared with the amounts in the wastewater effluent after the single washing process. Major components of ordinary Portland cement (OPC) clinkers are present in the produced clinkers. The properties of the clinker after the addition of the carbonated MSWI fly ash have no obvious changes compared with OPC. Compared with other technologies, this method is helpful in the utilization of MSWI fly ash and to save raw materials in the production of cement.