Study on thermal conversion and detoxification mechanism of fluorine during co-combustion of meager coal and spent cathode carbon block

Abstract

Fluoride is a toxic and harmful ingredient in the spent cathode carbon blocks (SCCB). Gaseous fluoride pollution is a significant potential pollution source in the process of boiler collaborative disposal of SCCB. In this paper, meager coal and SCCB were used as fuel, the mixing ratio and temperature were variables, the law of thermal conversion of fluorine during the co-combustion process was studied, and the properties of ash residue were discussed. At the same time, CaO was added to the furnace to reveal the influence of temperature on the effect of fluorine fixation in the furnace. The results showed that combustion was the most suitable method for removing soluble fluorine from SCCB, and the thermal conversion rate of soluble fluorine was up to 99.68–99.98%. The higher the combustion temperature, the higher the conversion of gaseous fluoride, and the worse the effect of fluorine fixation in the furnace. It is not suitable for fluorine fixation in the furnace when the furnace temperature exceeded 1100 ℃. The higher the mixing ratio of SCCB, the higher the production of gaseous fluoride, and a proper mixing ratio is vital for co-combustion. Ash residue after mixing 10% SCCB combustion belongs to general industrial solid waste. This study has important theoretical significance for determining the applicable furnace type, the appropriate mixing ratio and effective fluoride treatment measures in the co-combustion process of coal and SCCB.