WC-Co system hardmetal alloy which has high hardness, high melting temperature, high fracture toughness, high thermal conductivity and low thermal expansion is widely used as a substantial material for molds, oil drilling machines, and cutting and rock crashing tools. Currently, over 1,000 tons of t...
WC-Co system hardmetal alloy which has high hardness, high melting temperature, high fracture toughness, high thermal conductivity and low thermal expansion is widely used as a substantial material for molds, oil drilling machines, and cutting and rock crashing tools. Currently, over 1,000 tons of the cutting sludge of WC-Co system hardmetal alloy are generated in the above manufacture processes each year in Korea, which contains approximately 80% W. Thus, from the view point of the resource recovery, the recovery of tungsten and cobalt form the cutting sludge is one of the important issues especially in Korea since virginal tungsten resource is imported from China mainly. In the study, a process for recovering tungsten and cobalt form the cutting sludge is developed. The process largely consists of two major steps. One is to leach out cobalt from the cutting sludge using aqua regia solution and simultaneously to convert tungsten carbide to tungstic acid(H2WO4), the other to remove impurities contained in the precipitation tungstic acid obtained at the first step by the ammonia water dissolution. For an optimal design of the new process suggested in our research, the effects of various parameters such as concentrate of aqua regia, reaction temperature, time, pulp density, and particle size on the cobalt leaching and tungstic acid formation have been investigated experimentally. From the results, it was found in the first step that an optimum condition is as follows; 100vol.% of aqua regia density, 100℃ of reaction temperature, 1 hour of reaction time, 150g/L of pulp density, and particle size of -500/+250㎛. In the second step, an optimum condition to remove impurities contained in the precipitation tungstic acid obtained was as follows; 60℃ of reaction temperature, 75vol.% of ammonia density and 150g/L of pulp density. Also, 99.85% of ammoniumparatungstate from the purified ammonium polytungstate solution could be manufactured by a conventional evaporation method. The new process suggested in this study could leach out simply cobalt from the cutting sludge compared with conventional processes, and has an additional benefit for converting simultaneously tungsten carbide to tungstic acid. Therefore, it was considered that the process proposed is an alternative process for recovering tungsten and cobalt from the cutting sludge of WC-Co system hardmetal alloy with minimizing the conventional hydrometallurgical problems.
WC-Co system hardmetal alloy which has high hardness, high melting temperature, high fracture toughness, high thermal conductivity and low thermal expansion is widely used as a substantial material for molds, oil drilling machines, and cutting and rock crashing tools. Currently, over 1,000 tons of the cutting sludge of WC-Co system hardmetal alloy are generated in the above manufacture processes each year in Korea, which contains approximately 80% W. Thus, from the view point of the resource recovery, the recovery of tungsten and cobalt form the cutting sludge is one of the important issues especially in Korea since virginal tungsten resource is imported from China mainly. In the study, a process for recovering tungsten and cobalt form the cutting sludge is developed. The process largely consists of two major steps. One is to leach out cobalt from the cutting sludge using aqua regia solution and simultaneously to convert tungsten carbide to tungstic acid(H2WO4), the other to remove impurities contained in the precipitation tungstic acid obtained at the first step by the ammonia water dissolution. For an optimal design of the new process suggested in our research, the effects of various parameters such as concentrate of aqua regia, reaction temperature, time, pulp density, and particle size on the cobalt leaching and tungstic acid formation have been investigated experimentally. From the results, it was found in the first step that an optimum condition is as follows; 100vol.% of aqua regia density, 100℃ of reaction temperature, 1 hour of reaction time, 150g/L of pulp density, and particle size of -500/+250㎛. In the second step, an optimum condition to remove impurities contained in the precipitation tungstic acid obtained was as follows; 60℃ of reaction temperature, 75vol.% of ammonia density and 150g/L of pulp density. Also, 99.85% of ammoniumparatungstate from the purified ammonium polytungstate solution could be manufactured by a conventional evaporation method. The new process suggested in this study could leach out simply cobalt from the cutting sludge compared with conventional processes, and has an additional benefit for converting simultaneously tungsten carbide to tungstic acid. Therefore, it was considered that the process proposed is an alternative process for recovering tungsten and cobalt from the cutting sludge of WC-Co system hardmetal alloy with minimizing the conventional hydrometallurgical problems.
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