Utilization of atmospheric fluidized bed combustion ash

The American Coal Ash Association reports that in 1993 over 88.5 million tons of coal combustion byproducts (ash, boiler slag and scrubber residue) was generated in the United States by utilities in traditional combustion systems. Historically, these combustion byproducts (open-quotes ashclose quotes) have been treated as a waste product and disposed of by placing in landfills. With increased environmental awareness and recognizing that the ash represents, in many cases, a usable product, increased emphasis has been placed on utilizing the ash. Today, approximately 22% of ash generated by the utilities is commercially utilized. The commercial use of each of the four major coal combustion byproducts varies, for instance about 22% of the fly ash is utilized while only about 6% of the scrubber residue is utilized. Not included in the above ash total is an estimate of about 11.5 million tons of atmospheric fluidized bed combustion (AFBC) ash that is generated each year by non-utility generators. Of this total, approximately 8.3 million tons are generated by plants from waste coal fuels. The majority of this waste coal fired plant ash is used in mine reclamation projects in Pennsylvania and West Virginia. For the balance of 3.2 million tons, roughly 600,000 tons is being utilized as a commercial product. This reduced usage AFBC residue as a commercial product, when compared to traditional coal combustion residue, results from unfamiliarity with the product due to the short time the material has been available in significant quantity. Before examining how AFBC ash can be beneficially utilized, one must understand some of the basic properties of the ash material and how it differs from ash generated from traditional coal combustion boilers