The separation efficiencies were compared under different vortex finder lengths

thickness and flow rates in a small hydrocyclone with the diameter of 50 mm

and the optimal insertion depth

wall thickness of the vortex finder and flow rate were obtained by using the method of orthogonal design. In addition

the influence of vortex finders with tube-in-tube structure in the hydrocyclone on the separation efficiency was investigated. Finally

the relationship between the split ratio and separation efficiency was analyzed on the basis of the optimal structure for the vortex finder. The experimental results show that the cylindrical part of the hydrocyclone plays an important preliminary separation role. For the separation of fine particles

a thin vortex finder which is extended to the junction between the cylindrical and the conical parts is beneficial to the separation efficiency. The results show that the optimum proportion of the vortex finder insertion depth to the hydrocyclone diameter in the small hydrocyclone is bigger than those in the big ones

and it is indicated that there is a remarkable difference of separation between them.