When it is required that grinding products contain -200 mesh no more than 60~70%, a closed-circuit grinding process can be used.When closed-circuit grinding, the grader returns the sand mostly finer than the original ore particle size.By mixing the returned sand with the newly fed ore in the mill, the average particle size of the ore particle in the mill decreases, and the content of the ore particle close to the particle size of the grinding ore increases. The gap around the coarse ore is filled with fine sand, which is conducive to the formation of a more favorable meshing between the crushing medium and the ore particle.Along the whole length of the mill, the ratio between the size of the ball and the average diameter of the ore particle is relatively stable. The flow speed of the material in the mill is faster. Therefore, the productivity of closed-circuit mill is generally higher than that of open-circuit mill.Closed-circuit grinding can also improve the selective grinding of heavy minerals.The equipment configuration and operation management of closed-circuit grinding process are complicated, but these shortcomings can be made up from the high efficiency and high output of the mill produced by the technical and economic benefits.In conclusion, closed-circuit grinding can control the product size and improve the production capacity by changing the circulating load of the grinding machine, thus bringing a series of benefits conducive to improving the mineral processing index.Structure type and application example of closed-circuit grinding process.