VakETO, Moscow, Russia:

O. B. Minkov, Director

National University of Science and Technology MISiS, Moscow, Russia:
I. O. Minkova, Postgraduate Student
V. P. Tarasov, Head of Department
E. V. Chukina, Senior Lecturer, e-mail: chukina_e@mail.ru

When calcium wire is used in the ferrous metals industry, its cost is of particular relevance. The cost of calcium can be reduced by reducing the temperature and duration of aluminothermic reduction. Due to low heat conductivity, CaO and Al containing briquettes require a longer heat-up time thus impeding temperature reduction. The presence of CaCO₃ and Ca(OH)₂ in CaO justifies the need for costly carbon materials that are used to make high-temperature heat units of vacuum reduction furnaces. To reduce the external heat generated by the furnace, it is proposed to use a thermal additive for the aluminothermic reduction of Ca. Al and Fe₂O₃ powders were used as thermal additives. It was demonstrated that the use of pressed CaO, Fe₂O₃ and Al mixture as burden, after it has been vacuum heated to 1,000 ^oC and soaked for 1 hour, helps achieve up to 50% of calcium recovery. The following mixture of the burden (briquettes) was found to result in the maximum recovery of calcium, %: 20 Al; 15 Fe₂O₃; 65 CaO. The authors of this paper established that calcium can be produced by aluminothermic reduction of CaO containing burden at the temperatures exceeding 1115 К (842 ^oC). At this temperature the decomposition of calcium hydroxide and that of calcium carbonate are “separated” in time from the aluminothermic reduction of calcium. A design of industrial furnace is proposed that consists of a sealed vessel, a heat unit, a vacuum system and a water-cooled capacitor.

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