Determination of Technological Parameters of Selenium Recovery from Metallurgical Production Middlings in a Vacuum-Distillation Unit

The paper demonstrates the results of technological tests conducted with a representative rough selenium sample, obtained at Kazakhmys Smelting LLP to prepare refined selenium using vacuum-distillation technology, developed at the Institute of Metallurgy and Ore Beneficiation JSC, using the vapor phase filtration method on the existing process equipment. The technological scheme provides for preliminary melting of rough selenium in a receiving melting furnace and subsequent vacuum distillation of selenium. The vacuum-distillation recovery technological parameters are determined for selenium obtained from selenium-containing middlings produced by Kazakhmys Smelting LLP under conditions close to the production. We carried out the tests using the only industrial vacuum distillation unit prototype in the Republic of Kazakhstan. These tests enabled us to obtain refined selenium containing more than 99.5% of the main component with the throughout recovery 94.1%. The unit consists of the source material receiving smelting furnace and a vacuum distillation apparatus. The source material segregation process was implemented at atmospheric pressure and at 475 °c, and the resulting melt was filtered through a metal grid located on a false bottom in the receiving smelting furnace. Then, the ingots of selenium melted were sent to a vacuum distillation apparatus consisting of an evaporator and a condenser. We carried out the vacuum distillation of selenium remolded under optimal conditionsan evaporator temperature is 425 °c, a condenser temperature is 165 °c and residual pressure in the system is 0.4–1.1 kpa. Heating the condenser provided liquid-phase condensation of selenium vapor. The resulting refined selenium was cast into 5.0 kg bars. besides, we obtained the free-flowing residuals enriched with precious metals during vacuum distillation with a silver content of 13 400 g/t. the free-flowing residue was 8.1%.