Upgrading the Disposal of Mswi Fly Ash with Compaction: Feasibility Exploration and Advantage

Abstract

The landfilling is the mainstream disposal pathway for fly ash derived from municipal solid waste incineration, after the stabilization/solidification. However, the stabilized fly ash (SFA) has been generated in increasingly more amount, which quickens the depletion of landfilling capacity. Moreover, the small size and low density endue the SFA with high environmental risk during the processing and subsequent transportation. To address this issue, cost-effective compaction is introduced into the SFA disposal process. It is found that SFA from both grate furnace and fluidized bed are of high porosity, loose structure, and irregular shape, which indicate the high potential of compaction. The applied pressure, holding duration, and moisture content are the main influencing factors, and the optimal values are 100-200 MPa, 20 s, and 10-15%, respectively, which are also dependent on the incinerator type. As a result, density of the SFA can be more than doubled, and >60% of the volume can be reduced, leading to the saving of landfilling capacity for more SFA. Three classical equations are adopted to explore the compaction process, and Huang Peiyun and Heckel equations are the most suitable and can be used for further investigation. After compaction, the axial compressive strength and three-point bending of green compact can meet the MU10 class lime-sand brick standard, which is favorable for transportation and landfilling. The compaction-mediated process is finally presented, highlighting the advantage and application potential.

Keywords: Stabilized fly ash, Compaction, Volume reduction, Disposal upgrading, Advantage