Numerical Simulation And Parameter Optimization Of Powder Material Mixing For Iron Concentrate Powder And Bentonite Based On Discrete Element Method

The iron ore pellet method is one of the iron ore agglomeration methods.The pellet ore has the characteristics of high iron content,uniform particle size,good reduction performance and high mechanical strength.The pellet ore is prepared by mixing iron concentrate powder and binder bentonite into a raw ball by a mixer,and then firing at a high temperature or a low temperature.The uniformity of iron concentrate powder and bentonite affects the quality of pellets,which in turn affects the efficiency of iron making.The numerical simulation method is used to study the mixing process of the powder materials in the mixer to optimize the process parameters.Although the Definite Element Method can simulate the stress condition between the material and the cylinder wall,it is difficult to track the movement trajectory of the powder material,and there is contact and separation between the material particles.The Discrete Element Method considers the system to be composed of a myriad of discrete particles,and there is a relationship between contact and separation,mutual motion,and contact force and energy between the particles,which is a problem of powder mechanics.Numerical solutions provide an effective means.Based on the discrete element method,the numerical simulation of the mixing process of steel balls in a vertical spiral mixer is carried out.The variation of the cylinder radius and the cylinder height on the radial speed,tangential speed,vertical velocity and the starter power of the agitator is obtained.The law is in good agreement with the results given in the literature,which shows that it is feasible to use the discrete element method to numerically simulate the material mixing process.The effects of stirrer speed,agitator lead and material filling rate on the mixing uniformity of bentonite and iron concentrate powder in the mixer were studied.The research results show that as the stirring speed increases,the material mixing speed and mixing uniformity increase accordingly.When the material filling rate reaches a certain value,the mixing efficiency decreases,so the proper filling rate can not only improve the mixing efficiency,but also make the mixing more.Uniform;as the mixer lead increases,the mixing efficiency increases,but when equilibrium is reached,the mixing uniformity changes less.In order to improve the mixing efficiency of the mixer,the orthogonal experiment was designed by three factors: stirrer speed,stirrer lead and materialfilling rate.Three experimental indexes were set for the agitator output power,energy loss,particle velocity,and range analysis results.The three factors indicating the influence of the output power of the agitator are: agitator rotation speed> material particle filling rate> agitator lead;the three factors affecting the energy loss are: the filling rate of the material particles> the agitator Speed > agitator lead;the three factors affecting the particle velocity are: agitator speed > agitator lead > material particle filling rate.Finally,according to the order of influence of the experimental factors,combined with the actual demand,we can get the optimal level combination of stirrer speed 42 r / min,stirrer lead 2500 mm,material particle filling rate 0.5.The results obtained in this paper are helpful to improve the mixing uniformity and mixing efficiency of iron concentrate and bentonite powder.