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Investigation of the Important Parameters in a Gas Sparging Technique for Production of Tungsten Carbide.

Kazonich-G; Raddatz-AE; Carnahan-TG
Proc Pyrometallurgy '87 Symp London 9/21-23/87 Inst Min and Metall 1987 :1075-1105
This paper describes a bench-scale study to delineate the important parameters in a three-step process to produce commercial quality tungsten carbide (wc) directly from tungsten minerals. In the process, tungsten concentrates of wolframite or wolframite and scheelite were decomposed at 1,050 deg c in a molten mixture of nacl and na2sio3 that forms two immiscible phases. Tungsten, as sodium tungstate, reports to the halide phase and is separated from the gangue constituents, which report to the silicate phase. After decanting to separate the two phases, natural gas was sparged into the molten halide phase at 1,070 deg c. Submicrometer crystals of tungsten carbide were initially produced. These crystals grow into thin, triangular-shaped plates up to 100 um on a side or into popcorn-shaped conglomerates. Research was conducted to study sparging chemistry and to determine the effects of operating parameters including time, temperature, and sparging gas composition on the reaction rate, gas utilization efficiency, and wc crystal morphology. This led to a proposed reaction mechanism for the formation of sparged carbide. Wc production rates of 60 g/h wc were obtained in a 76-mm reactor by sparging 1,600 g halide melts containing 32 pct na2wo4 with natural gas at flow rates of 3 l/min. Wc crystals of 10 um or smaller were consistently produced at temperatures between 1,060 deg and 1,070 deg c. Tungsten recovery from the halide phase was 88 pct after 6 h of sparging. Cleaning techniques employing 6m hcl leaches at 65 deg c for 1 h decreased contaminant concentrations to l
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OP 108-87
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Proc. Pyrometallurgy '87 Symp, London, 9/21-23/87. Inst. Min. and Metall., 1987, PP. 1075-1105
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