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U.S. Department of Energy
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Direct utilization- recovery of minerals from coal fly asy. Fossil energy program technical progress report, 1 January 1984 - 31 March 1984

Technical Report ·
OSTI ID:6687286

Research is reported for two methods for extracting metal values from power plant fly ash. In the first method (HiChlor process), a carbochlorination reaction is used to produce a mixture of volatile metal chlorides from the oxides in the ash. Fractional condensation of the mixed chlorides is being investigated as the first step in their recovery and separation. This effort is accompanied by work on a unique slurry reactor in which the ash is contacted by gaseous chlorine while suspended with finely divided carbon in a molten salt mixture consisting of NaCl and AlCl/sub 3/. In the second method, a lime-sinter solid state reaction is used to selectively convert the alumina in the ash to a soluble form. The alumina is recovered by leaching the finely divided clinker. The effects of mineralizers on the sinter reaction are being investigated as a means for increasing alumina yield and reducing the temperature required. A similar study is underway to determine the degree to which the limestone required can be replaced by flue gas scrubber sludge which also has mineralizer properties. Preliminary results show that at least 30% of the limestone can be replaced. Attempts to reduce the sintering temperature required have also been carried out using a laboratory scale rotary kiln. Through kiln modifications, residence time has been increased so that lower temperatures can be used. The alumina-containing extract from the leaching of the clinker will occasionally contain excessive amounts of silica. To meet electrolytic cell feed specifications, the silica content is reduced by digestion with a small amount of lime. Work has been completed on an update of an economic feasibility study of the lime-sinter process. 13 figures, 8 tables.

Research Organization:
Ames Lab., IA (USA)
DOE Contract Number:
W-7405-ENG-82
OSTI ID:
6687286
Report Number(s):
IS-4860; ON: DE84015006
Country of Publication:
United States
Language:
English