Grading ring spacing size is one of the important factors affecting classification performance of a classifier.Models of vertical mill classifier with different grading ring spacing sizes were built

and flow field characteristics of different grading ring spacing sizes in vertical mill classifier SMG5500 were studied with the Fluent software.The best grading ring spacing size was obtained by making a comparative analysis of the influence on velocity field

stress field and classification efficiency at different spacing sizes.A test on the classifier was made.Simulated result showed that if grading ring spacing size was too small

most coarse particles larger than 80 μm could enter the cage

resulting in much coarser size particles in the product.If grading ring spacing size was too large

most coarse particles less than 80 μm could not enter the cage

increasing the classifier cycle load and extremely limiting classification efficiency.The vertical mill classifier SMG5500 showed optimal classification performance if grading ring spacing size was around 110 mm.