Recovery of fly ash carbon by carbochlorination via phosgene route

Coal fly ash consists mainly of unburned carbon and minerals. It also contains phosphorus with a concentration much higher than that acceptable for the metallurgical coke or boiler fuel. By flotation process, a large portion of the inorganic materials can be separated. However, further treatment is necessary before the fly ash carbon can be reused as a fuel or metallurgical coke. In our study, chlorination method was attempted using phosgene as a chlorinating agent. Our thermodynamic simulation shows that, by using phosgene, the minerals can be converted completely already at the temperature 200 °C. However, the experimental results showed that the reactivity of minerals with phosgene depends strongly on the reaction temperature; the reactivity is high in the first 10 min. Within 10 min, 80% of the minerals can be extracted from the fly ash at 1050 °C. Chlorination is also effective in removing phosphorus from fly ash. At 1000 °C, the content of phosphorus can be reduced from 2100 to 24 ppm in 10 min.