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To solve the problems of poor mixing effect and poor sphericity for the silicon nitride particles in the dry granulation chamber, the influence of the inclination parameters for the open turbine typed axial‒radial combined structure on the mixing effect of silicon nitride particles prepared by dry method was studied. The mathematical model of Eulerian‒Eulerian gas‒solid two phase flow was established, and the physical model of the axial‒diameter combined structure granulation chamber was simplified. The computational fluid dynamics (CFD) method was used to analyze the volume distribution and velocity field of silicon nitride particles in granulation chamber in the axial structure under the different inclined angles. The sphericity of silicon nitride particles was tested by experiments, and the accuracy of numerical simulation results was verified. The numerical analysis results show that, when the inclination angle is 45°, the volume fraction of silicon nitride particles is 0.3~0.7 (accounting for 28%), showing the better circulating fluidity and the best mixing effect, compared with the inclination angle of 30° and 60°. The experimental results show that, the best average sphericity of the silicon nitride particles is 0.72 when the inclination angle of the axis‒diameter combined structure is 45°, which can effectively improve the mixing effect of silicon nitride particles.

In order to explore the effect of dry granulation time on the compactness of silicon nitride ceramic particles, the water content, micro-morphology and particles strength of the particles under different granulation time were compared and analyzed base on the self-design granulation time-particle compactness experimental platform. The results show that with the increase of granulation time, the moisture content of silicon nitride particles decreased linearly, and the micro-morphology of silicon nitride particles showed three states; rough, smooth and cracky. When the granulation time was 5 min, the water content of the form silicon nitride particles was about 9%, which reached the optimal production value. SEM images show that the surface of the silicon nitride particles was smooth and crackless. and the particles strength reached the maximum value of 2.5 N measured by experiment. [ABSTRACT FROM AUTHOR]