Study On The Application Of Electromagnetic Driving In Conducting Fluids

With the explosive growth of steel production in China,the annual output of steel slag from the steel industry is also very huge.In order to protect the environment and save resources,steel slag must be recycled.Since the metal iron content of steel slag is about 10%,the recovery of metal iron in steel slag becomes an inevitable part of steel slag resource recycling.However,the current prevailing metallic iron recovery method is complicated and energy-consuming,according to which,this paper proposes to use the characteristics of good fluidity of steel slag at high temperature before the slag is discharged from the converter,and separate the slag and steel by applying electromagnetic force generated by high-frequency traveling wave magnetic field and electrocapillary force generated by DC electric field,respectively,according to the difference of physical properties of the two phases of steel and slag.However,considering the difficulty of high-temperature industrial tests,this paper explores laboratory prototype experiments at room temperature based on the principle of magnetohydrodynamics.The research of the paper is divided into two parts: the first part introduces the theory,numerical simulations and model experiments of driving low conductivity liquids by high-frequency traveling wave magnetic fields;the second part introduces the principle of driving metal droplets by using electrocapillary action and the implementation method.The main work is as follows:The first part focuses on the driving of low conductivity liquids by highfrequency traveling wave magnetic fields.Firstly,the electromagnetic induction principle of two-phase driving of low conductivity liquids by high-frequency traveling wave magnetic field is described,and a numerical model of multi-physical field coupling including electromagnetic field,temperature field,and flow field is established.The main results of the numerical simulation are: the magnetic field strength and electromagnetic force are mainly distributed at the edges of the vessel,and the electromagnetic force is proportional to the square of the current,is a sinusoidal function of the phase difference of the current,is proportional to the frequency of the current,and is exponentially related to the radial position in the vessel.The average flow rate and the average temperature of the solution are linearly related to the current magnitude and frequency,while the average flow rate of the fluid shows a law of increasing and then decreasing with the increase of the phase difference of the current,and reaches a maximum near the phase difference of 90°.Then,the analytical solutions of current phase difference,current amplitude ratio and total impedance of the driving and induced phases at the operating frequency of the loop system are obtained by analyzing the circuit of high-frequency traveling wave magnetic field,and the numerical solutions of current phase difference,current amplitude ratio and total impedance of the driving and induced phases are obtained by substituting the relevant electrical parameters.Finally,the effectiveness of using a high-frequency traveling wave magnetic field to drive a low conductivity solution is experimentally verified.The second part focuses on the study of driving a metal droplet in a weakly conducting liquid by applying a direct current using the electrocapillary principle.First,the principle of electrocapillary motion of metal droplets is explained.Then,the equations for the electrocapillary motion are derived from the Lippmann equation in combination with the relevant equations of electromagnetism,electrochemistry,and hydrodynamics.In the light of the fact that the viscosity of the slag is much larger than that of the steel,the formula for the electrocapillary motion is simplified to make it more practical after examining the degree of influence of specific parameters.Finally,the electrocapillary motion of metal droplets in Na OH-starch mixture was investigated by an experimental setup designed and built.The results show that the horizontal velocity component of the droplet undergoes three stages: rapid increase to a great value,slow decrease to a stable value and maintenance of the stable velocity after the electric field is applied.When the viscosity of the mixture is between 853 m Pa-s and 1760 m Pa-s,the electric field strength is between 90 V/m and 135 V/m or the droplet radius is between 0.91 mm and 1.31 mm,the droplet velocity satisfies the electrocapillary motion equation,i.e.,the electrocapillary motion velocity is proportional to the electric field strength and droplet radius,and inversely proportional to the mixture viscosity.The experiment also proved the feasibility of using the electroapillary phenomenon to separate the metal droplets in slag.