The application of porous media model in numerical calculation of magnesium reduction with thermal process

Abstract

Traditional silicothermic reduction process is in urgent need of improvement due to its high pollution, high energy consumption and high carbon emission defects. The pellet prefabrication-silicon thermal reduction technology has good energy savings and emission reduction effects and has become an important development direction for the magnesium production. However, it is difficult to obtain instantaneous characteristics of temperature rise, high temperature gas flow and reaction conversion extent distribution in the retort through experimental methods for high-temperature chemical reactions interact with complex heat transfer in this process. In this paper, a porous media model which could solve the heat and mass transfer problems of multiphase flow is introduced into the field of numerical calculation of magnesium reduction with thermal process, and it can accurately simulate the process characteristics while greatly reducing the calculation cost. In this model, the entire bed of pellets is treated as porous media and the high temperature gas flowing in the voids of the bed is produced by the chemical reactions in the decomposition and reduction stages of the pellets. The results show that the flow of high-temperature gas can quickly heat the pellets in the central area at the initial stage of the reaction and increase the average reaction conversion extent. The porous media model can also study the axial decomposition extent, reduction extent and temperature distribution difference of the retort. This work explores the future development direction of the numerical calculation of magnesium reduction with thermal process and simultaneously provides a scientific theoretical basis for the industrial production of the pellet prefabrication-silicon thermal reduction technology.