Abstract:  Aiming at the problem of coarse particles mixed in the overflow product caused by short-circuit flow during the hydrocyclone separation process， a hydrocyclone with a sieve-type overflow pipe is proposed， and the numerical simulation and experimental research was carried out. The simulated results show that compared with the cylindrical overflow pipe， the sieve-type overflow pipe can effectively prolong the separation time of the particles in the hydrocyclone. Therefore the short-circuit flow can re-enter the external swirl and be separated throughly， reducing the coarse particles mixed in the overflow product. The experimental results show that compared with the cylindrical overflow pipe hydrocyclone， the separation efficiency after using the sieve-type overflow pipe is significantly improved. The classification efficiency of -25μm particles increases from 47.59% to 58% by quality and from 48.74% to 60.08% by quantity. The overflow product is finer verifying that the coarse particles mixed in the overflow product is effectively improved. As the opening rate of the overflow pipe increases， the overflow yield increases， and the overflow and underflow product grain sizes tend to become thicker.

Key words:  Hydrocyclone, Short circuit flow, Sieve-type overflow pipe, Separation performance