Металлургия цветных металлов Izvestiya vuzov. Tsvetnaya metallurgiya • 6 • 2015 15 ВведениеОсновным потребителем металлического каль-ция остается черная металлургия, где он и его спла-вы с кремнием и другими элементами, в том числе карбид кальция, применяются в процессах раскис- Thermodynamic investigations and substantiation of the aluminothermic fabrication method of calciumTo search the ways of solving the problem on decreasing the prime cost of producing metallic calcium, it is proposed to consider its aluminothermic production by the example of the CaO-Al system. The thermodynamic analysis implemented for this system showed that the aluminothermic reduction of calcium from its oxide is technically performable under a pressure of 5-10 Pa and temperature of 1200-1500 °C. It is revealed that the implementation of reduction under the residual pressure lower than 1 atm (101,3 Pa) considerably lowers the thermodynamic temperatures of reaction beginning. It is established that only three reactions, in the course of which, calcium aluminates 3CaO ·Al 2 O 3 , 5CaO ·3Al 2 O 3 (12CaO ·7Al 2 O 3 ), and CaO ·Al 2 O 3 are formed, can be used for practical purposes. It is proposed, depending on the final state, to separate the process into the «low-temperature» one (up to 1200 °C, the calcium yield is no higher than 64,3 %) and «high-temperature» one (up to 1500 °C, up to 75 % Ca). It is planned to further confirm these data experimentally. Keywords: calcium, aluminothermic reduction, aluminates, thermodynamics, thermodynamic temperature of reaction beginning, vacuum. Izv. vuzov. Tsvet. metallurgiya. 2015. No. 6. P. 15-22.
The investigation results of the utilization of various-production lithium wastes in the sphere of aluminate synthesis, vacuum aluminothermic lithium production and development of aluminothermic reduction units have been generalized in the study. The flow charts for lithium-bearing waste processing with the production of ecologically clean products have been designed. It was demonstrated that lithium aluminates could be synthesized not only when processing wastes, but also out of marketable lithium and aluminum compounds and could serve as initial materials for the designed technology for the lithium production.Lithium is one the most important metals of the state-of-the-art technology. Fields of its application are continuously extended. It is favored by its unique properties and considerable natural reserves in various fields and salt lake brine. The production of lithium continuously increases. Average annual rates of the increase since 1950 amount to 8.5% and during the past decade to 9.4%. At the present time the world production of lithium is estimated as 16.2 thousand t a year.Lithium metal finds an application in the production of primary lithium current power supplies, lithium accumulators, in the production of synthetic rubber and thermoplastic elastomers, as well as in the production of unique properties-possessing Al-Mg-Li alloys.Due to the development of the newest technology branches a 20-25% annual growth in the lithium consumption, for instance, in the production of LCCSs (lithium-bearing chemical current sources), is expected [1]. At the present time the lithium commercial production is based on the electrolytic production method. LiCl is an initial product. In order to lower the melting point, an equimolar LiCl-KCl mixture is applied that provides the operation regime within the range of working temperatures of 420-430 0 [2]. This process has significant disadvantages that include: application of the most expensive highly hygroscopic and corrosive lithium salt (LiCl), necessity to neutralize escaping chlorine, necessity to utilize spent electrolyte and use of direct current. The necessity to apply alternative methods for obtaining lithium metal is now an urgent task. Metallothermic methods can be such alternative methods. In studies [3,4] the lithium aluminothermic reduction out of its monoaluminate was tried. At 1,000 -1,200 0 and high vacuum a yield of pure metal over 90% could be obtained.During past years we conducted extensive studies of the synthesis of lithium oxide compounds applicable in metallothermic processes of the lithium production and designed high-temperature reduction processes. Lithium aluminates were used that are sufficiently inert, non-volatile and have a high melting point.The formation of three compounds was found out: lithium monoaluminate LiAlO 2 , lithium pentaaluminate LiAl 5 O 8 and pentalithium aluminate Li 5 AlO 4 . Monoaluminate is formed upon heating equimolar mixture of Li 2 3 and gamma-Al 2 3 at 600 0 C. Above that temperature the process of the polymorphic tr...
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