Ultrafast Carbothermal Process of Municipal Solid Waste Incineration Fly Ash for Purification and Valuable Elements Recovery

Municipal solid waste incineration fly ash (MSWI FA), containing heavy metals and dioxins that can migrate and accumulate in the biosphere, is harmful to human health and the environment. Thermal treatment can effectively purify MSWI FA, but it is not widely used due to high energy consumption and long calcination time. Herein, we report an ultrafast carbothermal process to heat ash to 3600 °C within 0.03 s for FA purification and valuable elements recovery. After one time of ultrafast heating, 99.91% of the dioxins were removed, and the purified ash met the leaching standards. After three ultrafast heating cycles, the removal efficiencies of heavy metals were up to 71% for Zn, 86% for Pb, 71% for Cu, 62% for As, 100% for Hg, 93% for Cd, and 70% for Ni. The ultrafast carbothermal process also promoted chlorine removal by an ash washing process due to the decomposition of CaClOH. The condensate of volatiles was a good urban mining resource, higher than the minimum industrial grade of ore deposit. Compared with the traditional carbothermal treatment, it consumed only 1/110 of energy and needed 1/1920 of the furnace volume. The ultrafast carbothermal process provides an efficient and environmentally friendly way for FA purification and valuable elements recovery.