Compaction as a cost-effective strategy to upgrade the disposal of MSWI fly ash: feasibility and potential

Landfilling remains the primary disposal method for fly ash produced from municipal solid waste incineration (MSWI) following stabilization/solidification. However, the increasing generation of stabilized fly ash (SFA) is accelerating the depletion of landfill capacity. Furthermore, the small particle size and low bulk density of SFA present significant environmental risks during handling and transportation. To mitigate these issues, a cost-effective compaction method was introduced into the SFA disposal process. The results show that SFA from both grate furnaces and fluidized bed incinerators exhibited high porosity, loose structure, and irregular particle morphology, indicating substantial potential for compaction. Key parameters influencing compaction effectiveness included compaction pressure, holding duration, and moisture content, with optimal values identified as 100-200 MPa, 20 s, and 10%-15% moisture, respectively, depending on the incinerator type. After compaction treatment, the density of SFA more than doubled, while its volume was reduced by over 60%, significantly increasing landfill capacity and enhancing the efficiency of SFA disposal. The compaction process was effectively modeled using the Huang Peiyun equation for gerate furnace ash and the Heckel equation for fluidized bed ash. Furthermore, the unconfined compressive strength and three-point bending strength of compacted SFA met the MU10 standard for lime-sand bricks, making the material suitable for transportation and disposal. Finally, the compaction-based disposal method for SFA demonstrated clear techno-economic advantages and significant potential for broader application in waste management strategies.