Physical chemistry of the reduction of calcium oxide with aluminium in vacuum

Jacob, KT and Srikanth, S (1990) Physical chemistry of the reduction of calcium oxide with aluminium in vacuum. In: High Temperature Materials and Processes, 9 (2-4). pp. 77-92.

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Abstract

The physical chemistry of "aluminothermic" reduction of calcium oxide in vacuum is analyzed. Basic thermodynamic data required for the analysis have been generated by a variety of experiments. These include activity measurements in liquid AI-Ca alloys and determination of the Gibbs energies of formation of calcium aluminates. These data have been correlated with phase relations in the Ca-AI-0 system at 1373 K. The various stages of reduction, the end products and the corresponding equilibrium partial pressures of calcium have been established from thermodynamic considerations. In principle, the recovery of calcium can be improved by reducing the pressure in the reactor. However,, the cost of a high vacuum system and the enhanced time for reduction needed to achieve higher yields makes such a practice uneconomic. Aluminum contamination of calcium also increases at low pressures. The best compromise is to carry the reduction up to the stage where 3CaO-Al,O, is formed as the product. This corresponds to an equilibrium calcium partial pressure of 31.3 Pa at 1373 K and 91.6 Pa at 1460 K. Calcium can be extracted at this pressure using mechanical pumps in approximately 8 to 15 hr, depending on the size and the fill ratio of the retort and porosity of the charge briquettes.

Item Type:	Journal Article
Publication:	High Temperature Materials and Processes
Publisher:	Walter de Gruyter GmbH & Co. KG
Additional Information:	Copyright of this article belongs to Walter de Gruyter GmbH & Co. KG.
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	09 Dec 2011 10:13
Last Modified:	09 Dec 2011 10:13
URI:	http://eprints.iisc.ac.in/id/eprint/42669

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