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Date submitted2015-10-25
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Date accepted2015-12-04
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Date published2016-08-22
Regularities of selenium and chromium behavior in redox processes during hydrometallurgic treatment of solid phase products of rhenium extraction
- Authors:
- G. V. Petrov
- M. I. Kalashnikova
- S. B. Fokina
The main source of selenium is copper anode slime. But during the pyrometallurgical treatment of sulphide polymetallic ores significant amount of selenium along with radiogenic osmium and rhenium is concentrated in the solid-phase products of acid wash extraction and cannot be extracted, as gets lost with discharged chromium-containing solutions of osmium stage. The paper presents results of research into selenium reduction in the chromium-containing sulfuric acid medium by sulfurous gas and sodium sulphite. The use of the above reducers in optimum conditions leads to almost complete recovery of selenium (VI) while selenium (IV) extraction rate is not exceeding 60 %. The chrome (III) present in solutions has no impact on the selenium extraction rate. Chrome (VI) is almost completely reduced to a trivalent state, thus its negative impact on subsequent rhenium sorption from solutions purified from selenium is excluded. In view of a high rate of selenium extraction from chromium-containing sulfuric acid solutions formed in the process of radiogenic osmium production using sulfurous gas and sodium sulphite, choice of a method for selenium reduction is to a great extent dependent on the company’s profile.
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Date submitted2014-07-21
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Date accepted2014-09-19
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Date published2014-12-22
Preliminary preparation of oil for primary processing
Oil supplied for primary processing always undergoes preliminary preparation, the purpose of which is to eliminate the harmful effect of water and salt contained in the oil. It is thought that corrosion of the equipment is connected mainly with chlorides of magnesium and calcium, which are subjected to hydrolysis with the formation of hydrochloric acid. Under the influence of hydrochloric acid the destruction (corrosion) of metal equipment at technological plants occurs (especially refrigerating-condensing and heatexchange equipment, furnaces of rectification units etc.). The authors of the article, on the basis of thermodynamic calculations, provide their point of view on this process and give a methodology by which the process of preliminary oil dehydration and desalting can be controlled. The thermodynamic calculations executed for standard conditions on the basis of refer-enced data confirm a high probability of chemical interaction of iron with hydrogen ions, hy-drogen sulphide and especially with carbonic acid. This testifies to high activity of the carbon dioxide dissolved in water and the impossibility of hydrolysis of ions of magnesium, calcium and iron. The calculations show that only the hydrolysis of magnesium chloride is possible tak-ing into account the ionic composition of the water phase in the oil. It should be noted that the presence of ions of chlorine shifts the iron potential in a nega-tive direction and increases the speed of corrosion of petrochemical equipment. The solution of this problem is in the development of modern methods of crude oil dehydration and desalting. It is also, however, in an intensification of the processes of mixing water-oil emulsions with wash-ing water by using various physical fields (for example, ultrasound) and creating new effective mixing devices on the basis of them.