Study On Quasi-Particulate Fluidization Classification Of Ultra-Fine Powder Material

Particle classification is usually used to obtain qualified powder product after mill process. Modern industry demand more and more for fine particle size and narrow size distribution. Up to date, the gas-solid classification technologies are hard to reach accuracy standard of liquid-solid classification. Base on characters of liquid-solid classification, a quasi-particulate fluidization state was proposed through strengthening particle decentralization and flow filed uniform to improve gas-solid classification efficiency.Elementary geometric model of classifier was developed based on gas-solid multiphase theory. The flow field and particle movement behavior were simulated by CFD software, according to the simulation results, its structure and operation parameters had been optimized. The experiment was carried out to validate the simulation results. The detailed work and results include:(1) Forces act on particles in new feeding system were analyzed and compared. Particle agglomerate equation indicated that probability to disperse particle sufficient is 99.99%. Feeding system provide sufficiency particle dispersion so as to create quasi-particulate fluidization state. classifier structure parameters were calculated and geometric model required for numerical simulation were obtained by deriving particle velocity formulas.(2) Numerical simulation and analysis of the field inside different inlet and internal structure have been done by adopting the large common hydromechanics calculation software (FLUENT6.2), and the flow field became more symmetry. Based on flow field simulation, moving behavior of particles in the classifier was simulated with discrete phase model, which predicted tracks of particles of different sizes, and the feeding system was improved. Combined numerical simulation with theory calculation result, the final structure of classifier was obtained.(3)The effects of superficial gas velocity and feeding rate on classification accuracy and particle efficiency were studied in monopole classification experiment. Results showed that classification accuracy rose as gas velocity increased and feeding quantity decreased. The clear-cut was hard to achieve for given classification task. There are many fine particles immingled in coarse product, and precise classification can not be achieved by monopole classification device.(4) Repeating classification was carried out ,and the result showed that fine particle content in coarse product decrease to decimus. Based on experiment result, circumfluence was brought in to ameliorate the device. Circulation experiment result indicated that increase segregation time with propriety would enhance classification precision.(5) Experiment data was drawn up and the efficiency equation was obtained. Variance calculation result showed that the model curve is consistent with experiment data.