What is vacuum refining
Vacuum refining is a fire refining method to remove impurities from crude metals under or far below atmospheric pressure.
Under certain conditions, this method can also recover valuable elements from crude metals. Vacuum refining can not only prevent the reaction of metal with oxygen and nitrogen in the air and avoid the pollution of gas impurities, but also create thermodynamic and dynamic conditions conducive to the separation of metal and impurities for many refining processes (especially degassing process). Vacuum refining mainly includes vacuum distillation (sublimation) and vacuum degassing. In addition, iodide thermal dissociation, disproportionation metallurgy and chemical vapor deposition under vacuum are often classified as vacuum refining.
Vacuum distillation (sublimation) under the condition of vacuum, using the different vapor pressure and evaporation speed of each substance at the same temperature, controlling the appropriate temperature, making a certain substance volatilize and condense selectively to obtain pure substance. This method is mainly used to purify some metals (or compounds) with lower boiling point, such as mercury, zinc, selenium, tellurium, calcium, magnesium, beryllium and some heavy rare earth metals. The purity of 97.5% metallic zinc can reach 99.94% after one vacuum distillation; the purity of rare earth metal gadolinium can be reduced by 1-2 orders of magnitude under the conditions of vacuum degree 0.133kpa, distillation temperature 2173k and condensation temperature 1373-1473k; the purity of industrial pure magnesium can reach 99.99% after vacuum distillation.
Vacuum distillation can also be used to separate some metallurgical intermediate products to make pure metals. For example, lead-zinc alloy, aluminum magnesium alloy and yttrium magnesium alloy are distilled and separated to produce pure metal, the residual magnesium (or calcium) and its chloride are removed from the product distillation obtained by magnesium chloride reduction or calcium reduction to produce pure rare metal, and the mixed sulfide ore is separated.
One of the key equipments of the vacuum refining system (RH, VD, VOD, etc.) is the vacuum pump. Most of the vacuum pump systems used in the vacuum refining system are steam jet vacuum pumps. The characteristics of steam jet vacuum pump are large air volume, insensitive to dust temperature, high energy consumption, strict requirements on steam quality and large consumption. Water ring vacuum pump has the characteristics of large air volume, low energy consumption and insensitive to dust in low vacuum stage. According to the working characteristics of the water ring vacuum pump, EVP water ring vacuum manufacturer has developed an energy-saving vacuum pump system of the last stage steam jet pump which uses the water ring vacuum pump instead of the steam jet vacuum pump system. It has strong applicability for the new vacuum refining system and the transformation of the original vacuum refining system.
EVP2BE1 series water ring vacuum pump is the single-stage single acting water ring vacuum pump with the widest suction range. Relying on years of rich experience and strong R & D ability in producing water ring vacuum pump, EVP vacuum pump manufacturers have made secondary development. 2BE1 series water ring vacuum pump products have 12 specifications in the initial stage, which have developed into 24 specifications now, with more complete varieties and specifications. Through continuous structural transformation, 2BE1 series vacuum pump products produced by EVP have more stable performance and reliable operation. At present, EVP2BE1 series water ring vacuum pump has been widely used in various industries that need vacuum pumping. EVP2BE1 series water ring vacuum pump has been used in the vacuum refining process of iron and steel works.