Kinetics of Magnesium and Calcium Extraction from Fly Ash by Carbochlorination

In the metal extraction process, recovery of valuable elements from fly ash can have economic benefits and maximize its utilization. Extraction of Mg and Ca from fly ash by the carbochlorination method was studied as a function of carbochlorination temperature, time, carbon content, pellet diameter, and chlorine gas flow rate. The kinetic regime of the carbochlorination of Mg- and Ca-bearing compounds in the fly ash was identified. The carbochlorination residues were analyzed by chemical analysis and scanning electron microscopy. The results showed that chemical reaction control was dominant in carbochlorination of Mg in the temperature range of 800°C to 1050°C. However, for carbochlorination of Ca, the carbochlorination reaction was controlled by the diffusion process. Morphological changes such as the breakage and disappearance of spherical particles showed that the original spherical structure of fly ash was destroyed in the carbochlorination process.