A Fluent Software-based Study Of The Numerical Simulation For Mechanisms Of Dry Magnetic Separation

With the acceleration of China's industrialization, the discharge, gas and dust produced in production process do great harms to environment. Therefore, more and more attentions are paid to the possible ways of controlling the bad influence of industrial wastes. But the fact that the particles contained in the waste water, gas and dust is magnetic can help us get out of this problem. It is indicated by some experiments that: it is a good way to deal with the harmful particles in the waste water, gas and dust by high gradient magnetic separation technology. However, high gradient magnetic separation theory is rather complicated, although some mathematical models have been set up already by some scholars. In addition, the fluid-solid two-phase of the fluid dynamics equations are even more complex, some of which are non-linear equations, as a result, to get the solution of the equation is by no means an easy work. But numerical simulation for the process of high-gradient magnetic separation can be done by means of computer. Thereafter, the mechanism and affecting factors of the high gradient magnetic separation can be revealed through analysis of the results. Viewing the fluid as continuous medium and the magnetic particle as discrete systems, the dynamical model for collecting the magnetic particles in the high gradient magnetic field is established on the basis of the single-wire mode at the beginning of this thesis with the consideration of the fluid drag force and the force borne by the particles, based on which the multi-wire calculation model which is the theoretical basis for further calculations and experiments is proposed based on analysis of the particle movement in the process of the high gradient magnetic separation. Then, with the help of the FLUENT software, numerical simulation for the gas-solid two-phase flow in the process of the high gradient magnetic separation is set up regarding the air speed, magnetic field strength, particle diameter, particle magnetic and medium fill rate and other factors on the efficiency of catching. Finally, the acceptability, reliability and accuracy of the numerical simulations proposed in this thesis are proved by a comparison between the data of the calculation and the experiments.The results show that: magnetic force and fluid drag force are the dominant forces for the magnetic medium catching the magnetic particles in the process of high gradient magnetic separation; in a particle diameter range of 0 to 60, the collecting efficiency decreases as the particle size decreases; when the particle diameter is greater than 60, the fluid drag force suffered by particles will also increase accordingly, which makes the collection efficiency decreased; in high gradient magnetic separation process it is good to catch the particle in a situation that the out magnetic field and the particle are magnetically strong enough, but the gas fluid speed is slow enough. Meanwhile, the fill rate of the magnetic particles is another influencing factor for catching the particles; the catching efficiency is greater if the fill rate is greater. But it does not mean that the fill rate is the bigger the better, too great a fill rate will result in gaps which will influence the efficiency of the separation process.