Выбор рационального расположения электродов в многоэлектродной дуговой печи постоянного тока

Abstract

One of the main design parameters of multi-electrode furnaces, which largely determines their heat and eco-nomic indicators, is the ratio of the pitch circle diameter of electrodes to the bath diameter Dp/Db. The existing methods for choosing rational design parameters are more relevant to arc furnaces operating on alternating current of industrial frequency. For multi-electrode direct current furnaces, which use magnetohydrodynamic effects to improve mixing conditions and temperature homogenization of the melt, there is no relationship between the heat transfer parameters and the pitch circle diameter of electrodes. This work is a continuation of a number of patents and articles. Elsewhere, the design was justified, a mathematical model of magnetohydrodynamic and thermal processes in the melt of the furnace containing three roof arc and three bottom electrodes was developed, the model was verified through the results of physical experiments, and the parameters of heat transfer in the furnace at Dp/Db ≈ 0,2 were studied. The proposed type of furnace requires the study of the Dp/Db effect on the heat transfer parameters in the melt, which will allow a rational choice of the design parameter. The results were obtained using a three-dimensional mathematical model of magnetohydrodynamic and thermal processes in the steel melt constructed with the non-induction approximation and taking into account the k- turbulence model. The results were processed using methods of analysis of vortex structures and estimation of the integral parameters of hydrodynamic and thermal processes in the molten bath. Numerical experiments have been carried out with the design parameter Dp/Db varying from 0,2 to 0,5. New scientific data on the patterns of changes in the structure of flows and heat transfer parameters in the molten pool of a six-electrode furnace have been obtained. Dp/Db increase within the indicated range causes the increase of intensity of vertical vortex flows circulating between the axis of the corresponding electric arc and the axis of the bath and of the azimuthal flows circulating in horizontal sections of the bath. Vortex flows formed due to natural convection near the side walls of the furnace are suppressed. The maximum value zones of the effective thermal conductivity that reaches 1,8·105 W/(m·K) are redistributed to the central part of the bath, which contributes to increasing temperature distribution efficiency in the bath. The obtained results allow recommending a rational range of values of Dp/Db within 0,4–0,5, which decreases the volume of stagnant zones in the proposed six-electrode furnace by more than 40 % and increases the integral values of the Nusselt number over the depth of the horizontal section of the bath on average by more than 10 %. The obtained data revealing the possibility of improving the mixing conditions and increasing the heat transfer efficiency in the melt of the six-electrode furnace can be recommended for choosing the Dp/Db ratio when designing high power furnace.