Numerical Simulation Of Air Classifier Classification Process

With the development of ultra-fine powder technology, the requirements of silicon carbide abrasive particle size for modern industry become more and more small, and particle size distribution should be narrower. The performance of grading equipment require more strictly. FL450 type air classifier as a common grading machine equipment silicon carbide particles, find out how it works, the impact of operating parameters, device structure parameters, materials and equipment as well as the nature of the amplification effect of media law airflow Classifier effect on classifier optimize the structure and operating conditions, and it is important to improving the efficiency of the device classificatiom.In this paper, using numerical simulation method, using the fluent software to simulate process of FL450 type air classifier to carry on the research analysis of silicon carbide. By using the discrete phase model to simulate the air flow inside the gas-solid flow classifier, using the stochastic model to simulate different trajectories in the particle size classifier. The use of air classifier model constructed, different speed and air flow, the influence of different impeller structure and different density of the material guiding cone structure, the internal flow field of the velocity distribution of the classifier and classification process of simulation, using its influence to the results of the classification, according to the production requirements to make reasonable and optimized design of the existing classification operation. Get conclusions as follows:(1) Using the discrete phase model and the stochastic model to describe the process of air classifier classification is feasible.(2) In this paper, ignoring the interaction between particles, the classification process of particles with different diameters in the classifier, classification of particles is still the "fish hook effect". That "fish hook effect" relates to the force on particles classification process, which needs to be further studied. This paper does not support the "fish hook effect" in the process of the classification of particles agglomeration of the conclusion.(3) Fixed air volume adjustment grading impeller speed, improve the speed of the concentration and the yield ofproduct is high grade change and does not affect the classification results in a proper range. When the speed exceeds the proper range, product cut size d50 will decline, grading effect becomes worse; fixed grading impeller speed to adjust the air volume, air seriously affect the yield of product.(4) Leaf blade number which too small and too thick leaves can make the classification performance and classification process variation or no classification effect. Under the premise of ensuring the classification effect, vane number is 72, the recovery of product grading impeller with thickness of 4mm than that of the original production process using rate is high; the guiding cone diameter on the classification results are affected, there exists an optimal diameter makes the classification effect is the best.(5) In the classifier classification efficiency in different density of the material is not the same, the density of 2300kg/m3-4000kg/m3 material between the better classification effect, higher density, smaller density fractionation effect is poor.(6) When the medium temperature from 15 degrees to 145 degrees, will increase the proportion of large particles through the grading impeller, is not conducive to the classification.(7) Classification of equipment will lead to classification of amplification product yield decreased, less impact on the classification of products.