Use of the Magnetic Fraction of Fly Ash as a Heavy Medium Material in Coal Washing

摘要

Several bituminous coal fly ashes were fractionated in a dry state using a moving-field electromagnetic separator. The sedimentation and rheological characteristics of suspensions of the magnetic fraction recovered from one of these ashes were determined and compared with those of suspensions prepared from an industrial grade magnetite sample. Effects of grinding and washing the magnetic fraction and of the addition of contaminants were also evaluated. Results indicated that the magnetic fraction of power plant fly ashes compares favorably with industrial grade magnetite as a heavy medium material. Preliminary studies with heavy medium beneficiation of a coal sample using the magnetic fraction of a typical fly ash confirmed that this material is quite suitable in coal washing. A cost analysis showed that a modest investment in magnetic separation and grinding equipment could result in recovery of a significant amount of marketable heavy medium material from the waste coal ashes of many large U.S. power plants burning bituminous coals. In addition, the amount of plant fly ash for disposal would be reduced by about 15 percent. (ERA citation 04:021296)