中国有色冶金

As the product of wolframite concentrate acidolysis, crude tungstic acid can be used as the raw material to produce ammonium paratungstate and tungsten trioxide. Orthogonal tests are conducted on such processes of crude tungstic acid as dissolution in aqueous ammonia, alkaline leaching of dissolution residue, evaporation and crystallization. Comprehensive tests are carried out on the basis of better orthogonal tests and conclusions are drawn as follow: recommended process flow only adopts dissolution in aqueous ammonia once and that residual tungsten in dissolution residue is recovered by alkaline leaching. The crude tungstic acid produced from wolframite concentrate acidolysis by hydrochloric acid is directly subject to the process flow of dissolution in aqueous ammonia, evaporation and crystallization so as to obtain ammonium paratungstate with 88.46%~88.75% WO₃. The purity of WO₃ can exceed 99.9% after roasting. The residue after dissolution in aqueous ammonia undergoes alkaline leaching to fully recover tungsten. The dissolution rate of WO₃ in aqueous ammonia can exceed 89% and that in alkaline solution can be over 10%. The total recovery rate of WO₃ is over 99% and the direct recovery rate surpasses 75%. After crude tungstic acid is subject to dissolution in aqueous ammonia and alkaline leaching, tantalum, niobium and tin are concentrated in caustic dross that can be used as the raw material to recover tantalum and niobium.