Stabilization-solidification-utilization of MSWI fly ash coupling CO2 mineralization using a high-gravity rotating packed bed

Abstract

Municipal solid waste incineration fly ash (MSWI-FA) has been regulated as a hazardous waste that needs to treat with stabilization, solidification and landfill due to its amount of heavy metals, chlorides, sulfates and dioxin. While the proper treated MSWI-FA can be utilized as pozzolanic material to reduce the usage of Portland cement. The present article aims to develop an integrated wet-extraction and carbonation process for MSWI-FA stabilization, solidification and utilization via the high-gravity technology. A benchtop experiment demonstrated the dechlorination and CO2 sequestration of MSWI-FA and the carbonated product was applied as a supplementary cementitious material (SCM) in the cement mortar. Physical, chemical and thermal characteristics of raw, wet-extracted, and carbonated MSWI-FA were addressed in terms of the mean diameter, micropore area, micropore volume, chemical compositions, mineralogy and morphology. The effects of the liquid-to-solid ratio and high gravity factor were evaluated. Overall, a chloride extraction ratio of 36.35% and a CO2 capture capacity of 258.5 g-CO2 kg-FA-1 were achieved in the batch experiment. The results of water-energy consumption of chloride removal and CO2 fixation provided a novel insight into the future process criterion. In addition, the carbonated FA was found as binder to partially substitute Portland cement due to its large content of calcium carbonate. The workability and mechanical strength of cement mortar with partial substitution of stabilized FA were evaluated to determine the potential FA utilization pathway. Finally, the continuous process tests determined the key operation indexes for future process scale-up.