Abstract：By building the classifier model with different grading ring spacing sizes, the flow field characters of different grading ring spacing sizes in SLK5500 type classifier were studied according to the computational fluid dynamics (CFD) theory. The best grading ring spacing size was obtained and a test on the classifier was made. The results show that if grading ring spacing size is too small, the particle concentration of classification area is comparatively higher, which results in much coarser size particle of the products. If grading ring spacing size is too large, the particle concentration of classification area is comparatively lower, and the differential pressure between inlet and outlet is larger, which results in more energy consumption and less finished particle productivity. The SLK5500 type classifier shows the optimum classification performance if the grading ring spacing size is about 250 mm.

Keywords：classifier; grading ring spacing; particle concentration; two phase flow