Selenium extraction out of metallurgical production middlings

Abstract

A short review of well known and currently used in production sector methods of selenium-containing slurries processing of copper and nickel productions are provided in this paper. The process flow scheme of copper anode slime processing at the Balkhash copper-smelting plant of Kazakhmys Smelting LLP is provided. The copper anode slime obtained after copper electrolysis is processed in the Kaldo furnace at the refining section of the precious metal shop where the metal roasting, smelting and converting are combined. The main product of the Kaldo furnace is the Dore alloy to refine gold and silver. Raw selenium containing ~ 80% of the main component, copper telluride and bag filter fines containing precious metals except for selenium are obtained as a by-product. While Kaldo furnace operation, the exhaust service gases pass through the gas trapping and treatment system. The current gas treatment system consists of three in series connected devices, such as a gas scrubber cooler (a quenching tower or a cooling tower), a Venturi scrubber and a cyclone separator. When gas trapping process the fines is deposited, selenium dioxide and arsenic trioxide are dissolved, and some metal chlorides are absorbed in the circulation solution. The 15 m3 of pulp with 40-50 g/dm3 of solid substance, and 20-50 g/dm3 of selenium in the solution, 2-5 g/dm3 of chlorine, the pH value is from 0 to 1 is formed after all stages of service gases trapping and treatment in the circulation tanks. After the metal hydroxides are deposited, the pulp is going through filter and sent to the selenium sedimentation stage. The precipitate after filtration (Venturi slurry) is a recycled product and is processed in a Kaldo furnace. Selenium precipitation is performed at a 70 °C temperature with sulfur oxide (IV) within 6-10 hours. Selenium obtained under this scheme was segregated in the smelting furnace and then vacuum distillated. As a result of these a brand metal with main component content of more than 99.5 % corresponding to the ST1 brand under GOST 10298-79 intended for export was obtained.