PHYSICS AND MATHEMATICS

Heat exchange between the plasma torch jet and the heated surface of the alumina melt for nitrogen, argon and hydrogen

V. E. Kison^a, A. S. Mustafaev^a, V. S. Sukhomlinov<sup>b

a</sup> Saint Petersburg Mining University
^b Saint Petersburg State University

Abstract: The article evaluates the efficiency of heat transfer between the plasma torch jet and the heated surface of the alumina melt in order to select the optimal working gas for the production technology of pure white corundum. This technology is being developed for the purpose of its industrial application with a corundum capacity of 50 kg per hour. According to this technology, corundum crystals are obtained by melting alumina powder in a reactor with a plasma torch jet. Nitrogen, argon, and hydrogen are considered as the working gas of the plasma torch. The calculations use estimates of the thermophysical characteristics of nitrogen, argon, and hydrogen at the operating temperature of the plasma torch, which approximately amounts to 8000K. The jet velocity and Nusselt numbers characterizing heat transfer were calculated taking into account the required performance. According to the results of calculations, the most effective gas for heating and melting alumina is nitrogen because of its incomplete dissociation at the operating temperature of the plasma torch and, as a result, higher thermal conductivity and specific enthalpy.

Keywords: plasma, working gas, plasma torch, corundum.

DOI: 10.23670/IRJ.2021.109.7.006