Gas-to-ash detoxification feasibility and pathways by co-combustion of spent pot lining and food waste shells

Seeking substitutions for Ca-bearing reagents, this study explored the synergistic co-disposal and co-circularity of spent pot lining (SPL) and food waste shells (oyster, clam, and egg shells) in an eco-friendly way. This study is first to evaluate the feasibility of their co-combustions with or without their mechanochemical activation (MCA) toward the gas-to-ash detoxification of fluorine (F). 50% calcined oyster shell fixed about 97.87% of the F content of SPL in the blend ash and outperformed 50% CaO. MCA weakened the diffraction peaks of graphite carbon by favoring the fixation performance through which collisions between particles and the mixing uni-formity were promoted. The combination of 10% SiO2 and 40% calcined clam or egg shells raised the F fixation rate to 98.72 and 99.23%, respectively. F was converted to the complex F-Si-Ca compounds rather than to CaF2. Ca and Si compounds facilitated stabilizing F and Na synchronously and formed NaCa2SiO4F. The leaching F concentration of the ash was less than 100 mg/L, meeting the Chinese criterion (GB 5085.3-2007). The recycling of the food waste shells performed effectively in the cleaner disposal process of SPL by suppressing fluorine emissions.