| Electro-fused magnesia has a wide range of applications in basic fields such as electronics and metallurgy.In-depth exploration of various physical phenomena and laws in the electro-fused magnesia furnace will help improve the smelting process,thereby improving the quality and output of the electro-fused magnesia.The environment for smelting electro-fused magnesia is harsh and the process is complicated.This makes it difficult and costly to monitor many process parameters through experiments.In order to understand the law of heat and mass transfer dominated by electromagnetic fields in the electro-fused magnesia furnace.In this paper,a fluid dynamics model is established for the main internal processes of the electro-fused magnesia furnace,and numerical simulation calculations are performed to solve the above problems.DC electric arc furnace has the advantages of low power consumption,low voltage fluctuation and simple electromagnetic environment.It is widely used in the field of iron and steel smelting,and there is no report of industrialized production in the field of magnesia smelting.Refractory materials are different from conductive metals.In order to allow continuous smelting of MgO,it is necessary to design an experimental platform for a small-scale DC electro-fused magnesia furnace and to study the characteristics of its smelting process.Based on the assumption that the arc plasma is in a local thermodynamic equilibrium,a three-dimensional finite element model of the arc is established in this paper.The simulation results of a single arc are compared with the measured and numerical model data recorded in the literature,and the agreement is good.For double arcs,the effects of current,electrode axis spacing and arc length on the arc multiphysics are analyzed using multi-field coupling numerical simulation technology.The results show that when the current is 500 A,the arc length is 3 cm,and the electrode axis spacing is 10 cm,the temperature,velocity and current density all reach the maximum near the sheath area at the bottom of the electrode.There is an obvious repulsion phenomenon between the double arcs,which makes the two arcs incline to the outside respectively.The greater the current,the stronger the repulsion.This is consistent with the fact that the severely ablated area of the electrode in the experiment is inclined to the outside.For the double arc and molten bath inside the DC electro-fused magnesia furnace,a unified three-dimensional magnetic fluid finite element model is established.In order to verify the reliability of the algorithm,the double electrodes tungsten inert gas-metal inert gas(DE-TIG)model was first established in this paper.It can be concluded that the simulation results in this paper are more consistent with the literature records.Furthermore,the calculation algorithm of momentum in the magnetic field is changed to make it suitable for the calculation of the DC electro-fused magnesia furnace.After the simulation results of the double arcs and the molten bath are stable,the heat transfer law,flow field characteristics and electromagnetic phenomena of the arcs and the molten bath are analyzed.The conclusion can be obtained: under the action of electromagnetic force,two eddy currents opposite to each other will be generated on both sides of the molten bath.The shape of the solid-liquid interface will therefore be greatly affected.At present,three-phase AC electro-fused magnesia furnace are still used in the industrial preparation of fused magnesia.The problem of eddy current loss caused by high AC current is very serious.Based on the assumption that the magnetic field is time-harmonic and stable,a three-dimensional finite element model of an AC electro-fused magnesia furnace with a capacity of 3000 k VA is established in this paper.ANSYS Maxwell software was used to analyze the magnetic field distribution and eddy current loss during the refining period.On the basis of considering the error,the numerical results are more consistent with the experimental results.Furthermore,the influence of four factors,namely the current size,the height of the conductive cross arm,the different material of the furnace cover and the thickness of the furnace body,on the electromagnetic field distribution and the eddy current loss is quantitatively analyzed.The results show that the smaller the current and the higher the position of the conductive cross arm,the smaller the eddy current loss at each part and the weaker the magnetic field strength around the magnesia furnace.For the furnace cover with the most serious eddy current loss,replacing the local area with large eddy current loss with non-magnetic high-speed steel can reduce the overall eddy current loss. |
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