Metallurgy of Tungsten and Molybdenum at Japan New Metals Co., Ltd.

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  • 日本新金属 (株) のタングステン, モリブデン精錬
  • ニホン シン キンゾク カブ ノ タングステン モリブデン セイレン

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Our Japan New Metals Company presently manufactures various intermediates of the tungsten and molybdenum; for example, metals, carbide powders and chemical pure grade oxides, ammonium salts, etc, and is the largest producer of them in Japan. The present production rates of tungsten and molybdenum powder are about 70 tons and 10 tons per month, respectively, and carbide powder 50 tons per month. The raw materials used for these products are refined from high grade tungsten ores (wolframite and scheelite) and crude molybdenum oxide. We report the flow sheets of their extractive metallurgy and processes shown above are discussed.<BR>The tungsten ore is treated with Na2CO3 or NaOH solution in an autoclave to leach tungsten. This Na2WO4 solution is filtered and impurities such as SiO2, As and P are removed by chemical treatment. From this purified solution CaWO4 isprecipitated by addition of CaCl2 or Ca (OH) 2.<BR>This artifically produced CaWO4 or the clean scheelite ore (CaWO4) is decomposed with HCI and is converted to tungstic acid (H2WO4). This tungstic acid is leached as ammonium tungstate with ammonia water and the solution is evaporated to crystallize out the parasalt, impurities being separated during this process. The parasalt is roasted to an oxide (WO3) by a belt type open fumace and feduced tometallic tungsten powder at temperatures of 650-950°C with oxyhydrogen gas, then is carbonized with carbon at 1300-1750°C.<BR>Molybdenum products are manufactured from its crude oxide with a similar process to that for tungsten.<BR>Our new products are ammonium meta-tungstate, hetero-tungstic acid and molybdic acid, etc., for catalyzers.

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