Branch of Ural Federal University named after the first President of Russia B. N. Yeltsin, Krasnoturinsk, Russia:

M. V. Belousov, Senior Lecturer of a Chair of Aluminium Metallurgy

Saint Petersburg State Polytechnical University, Saint Petersburg, Russia:
I. V. Butorina, Professor of a Chair of Technology and Research of Materials, e-mail: butorina_irina@mail.ru

Ural Federal University named after the first President of Russia B. N. Yeltsin, Ekaterinburg, Russia:
D. F. Rakipov, Assistant Professor of a Chair of Light Metals Metallurgy

Along with other branches of non-ferrous metallurgy, manufacturing of magnesium is an environmentally hazardous production, where is formed a significant amount of wastes, including the toxic ones. The amount of wastes, along with their variety and severity, are determined by the applied magnesium manufacturing technology. There exist the fundamentally different electrolytic and silicothermic methods of industrial production. Authors of this paper have proposed a project of organization of magnesium plant in Sverdlovsk Oblast, with application of silicothermal technology of manufacturing of magnesium from dolomite, according to the Pidgeon process. This paper presents the results of comparison of environmental indices of these two magnesium manufacturing methods for the purpose of determination of the most efficient method, which should ensure the least impact on the environment. The electrolysis process includes both the recovery of magnesium by a constant electric current on the steel cathode, and the release of chlorine on the graphite anode from the chloride molten salt at a temperature of 680–700 ^оC. The silicothermic process is based on the reduction of magnesium from its oxide by silicon at the temperatures of 1200 ^оC. The proposed technology is close to the Pidgeon process, but has a number of technological distinctive features, which reduce the consumption of energy and emissions of greenhouse gases into the environment (by up to 15 kg/kg of Mg). Such a result is achieved due to the usage of a heat energy of waste gases of a magnesium reduction furnace. These gases are directed to the dolomite burning furnace and magnesium condensate melting furnace. Usage of waste gases according to the proposed scheme made it possible to reduce the total consumption of natural gas for the creation of the required thermal conditions in two production stages, i.e. during the roasting of dolomite and smelting of magnesium condensate (by 46–48%). This paper presents the data about the environmental indices of magnesium manufacturing by electrolytic and proposed technologies (specific energy consumption, water consumption, emissions and waste). Comparison of these technologies shows that the proposed silicothermal technology of magnesium manufacturing has the best environmental indices. During the usage of this method, chlorine emissions are completely absent. At the same time, emissions and effluents from this production do not require the high technological purification. Wastes of storage do not require the costly processing.

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