Rhenium

Rhenium is a refractory metal that looks like steel. The metal powder has black or dark gray color, based on the dispersion. In accordance with a number of physical characteristics rhenium is close to the refractory metals of the sixth group (tungsten, molybdenum), and also to the metals belonging to platinum group. According to melting point rhenium is at the second position among all the metals, and according to strength it has fourth position after iridium, osmium and platinum. Pure metal is ductile at room temperature, but due to the high modulus of elasticity after completed treatment the hardness of rhenium increases due to cold hardening. To restore plasticity, it is annealed in hydrogen, vacuum or inert gas. Rhenium can bear cooling and heating without loss of strength. Its strength at temperatures less than 1200°C is higher than the density of tungsten and molybdenum. The specific electrical resistance of rhenium four times exceeds the density of molybdenum and tungsten.

Rhenium is obtained by processing of raw materials with extremely low percentage of the target elements (mainly copper and molybdenum sulfide material).

Processing of sulfide containing molybdenum and copper materials is based on pyrometallurgical processes (converting, melting, oxidizing roasting). At high temperatures, rhenium is sublimated in the form of higher oxide. Then it is retard in dust and gas separator systems.

During the incomplete rhenium sublimation in the case of molybdenite concentrates roasting its separate part is kept in the cinder and then passes into soda or ammonia leaching solutions of cinders. In this case the sources for the obtaining of rhenium in molybdenum concentrates processing cay be sulfuric acid solutions of dust separator systems and mother waters the hydrometallurgical processing of cinders.

In case of melting of copper concentrates with gases about 56-60% of rhenium is passed away. Remained rhenium is completely converted into matte. In the case of converting the rhenium is removed together with the gases. If the converter and furnace gases are used for the manufacture of sulfuric acid, the concentration of rhenium is observed in sulfuric acid washing the circulation of electrical filters in the form of rhenium acid. As a result, sulfuric acid wash is the main source for rhenium formation of in the processing of copper concentrates.