Purification of enriched fly ash carbon by chlorination of fly ash in a fluidized bed reactor

Carbon-enriched fly ash containing 80% of carbon and 20% of minerals can be obtained via flotation. The reactivity of this carbon is high; however, phosphorus concentration is much higher than that required by the metallurgical industry. To remove phosphorus and to extract minerals, the fly ash was chlorinated in a fluidized bed with chlorine as the chlorinating agent. Thermodynamic simulation of the “fly ash+Cl2” reaction system shows that a complete conversion of the minerals is feasible in a temperature range of 200°C–1400°C. However, experimental results indicate that the reactivity of minerals with Cl2 depends strongly on the temperature. The rate of chlorination is high during the first 10 min of reaction, afterwards the rate decreases rapidly. The phosphorus content can be reduced from 2100 ppm to less than 200 ppm in 10 min at temperatures above 600°C.