Current status of metals recovery from power plant fly ash

The disposal of the large amount of waste coal ash produced today presents both environmental and economic concerns. The full impact of leaching from ash landfills and the cost and complexity of safe disposal only now are being recognized. Utilization of the ash as a mineral resource is receiving increasing attention as an alternative to disposal. Processing methods that have been proposed previously to extract metals from clays and siliceous ores are being adapted to coal ashes. Chemical leaching, sintering processes, and gas-solid reactions are used to extract minerals and other usable by-products so that the coal ash is either entirely consumed or is converted to a residue of reduced volume and environmental impact. The work is being done in the United States at national laboratories and in private industry, and abroad in several other countries. If the work is successful, ash disposal problems will be greatly reduced and a significant new source for important metals such as Al, Ti, and Fe will have been identified.