Preparation of municipal solid waste incineration fly ash/ granite sawing mud ceramsite and the morphological transformation and migration properties of chlorine

Municipal solid waste incineration (MSWI) fly ash is a hazardous waste containing high chlorine and harmful substances generated during the waste incineration disposal, and its resource utilization has a positive effect on reducing environmental pollution. In this study, the feasibility of preparing lightweight MSWI fly ash/granite sawing mud ceramsite (MG ceramsite) was investigated by evaluating the influence of Al2O3 addition, MSWI fly ash content and sintering temperature on the ceramsite properties. The microstructure of MG ceramsite was investigated by using SEM, the chlorine morphological transformation and migration behaviors were simultaneously explored by using the tube furnace experiment, XRD and XRF analyses. The experimental results show that the maximum MSWI fly ash content is about 30 wt%∼35 wt%, with the Al2O3 addition of at least 10 %. By controlling the MSWI fly ash content of 30 wt%, MG ceramsite can be obtained with bulk density of 986 kg/m3, cylindrical compressive strength of 19.67 MPa, 1 h water absorption of 0.31 %, and chlorine content of 0 after sintering at 1150 °C for 20 min. Chlorine in MG ceramsite enters into the tail gas or secondary fly ash in the form of chlorine salts and chlorine-containing gas when the sintering temperature is above 800 °C. The MG ceramsite prepared from MSWI fly ash meets the lightweight aggregate standard and are environmentally friendly. However, the disposal of tail gas and secondary fly ash needs attention when the MSWI fly ash is used as one of the main raw materials to prepare ceramsite.