The Magnetic Fraction of Coal Fly Ash: Its Separation, Properties, and Utilization

A laboratory-size electromagnetic device has been built to separate the high-iron magnetic fraction from coal fly ash. Fly ash, the fine particulate matter produced when pulverized coal is burned, contains an average of 18 wt. percent iron expressed as Fe2O3 found in a distinctive fraction of finely divided, dense, largely spheroidal particles of high magnetic susceptibility. Seventy to eighty percent of the iron in bituminous coal fly ash is found in this fraction which represents about 20 weight percent or 10 volume percent of the fly ash. In this work the iron-rich fraction has been characterized as to particle size, composition, and density. It appears to have a market potential as a material for preparation of high-density media used in coal washing and other mineral dressing processes. Dense-media material, which costs about $100 per metric ton, is being utilized in increasingly large quantities as the demand for washed coal expands. The magnetic fraction also appears to have potential as a source of iron. If further processing can reduce the silica level found in the fraction as it is separated from the ash, pellets with a composition similar to taconite can be prepared for use as blast furnace feed. Separation and use of this fraction of the coal ash could be profitable for utility companies and could be the beginning of the utilization of the large amount of ash which now constitutes a waste disposal problem