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In this paper, the influence of inclining angle of turbine blades on classification results was studied employing mica as the experimental materials. Based on the experimental results, the fish-hook effect in air classification appearing in Tromp curve was explained and discussed in term of particle agglomeration. The results obtained showed that the smaller the inclining angle of the blades, the smaller the classified particle cut size was, but the lower the classification precision was. The fish-hook effect decreased and the classification precision increased with the increase in inclining angle of blades, which may be attributed to decrease in the critical agglomerated particle size.

Based on the pneumatic mechanics and the gas-solid two-phase fluid theory, a model of gas-solid two-phase flow speed field was set up for horizontal turbines during the classifying process, and the formula of classified particle cut size in irregular speed fields was deduced. In order to evaluate the model, a number of experiments were carried out in a fluidized-bed jet-mill using samples such as calcium carbonate, carbon silicon, alumina, etc. It was found that the formula of classified particle cut size agreed with the experimental results very well. Furthermore, the relationship between the structural parameters of turbine and the classifying results was discussed, and the turbine structure was optimized according to the formula of classified particle cut size.