Filtration is the process of separating solid particles from fluid. Under the effect of pressure difference, the solid-liquid and gas-solid two-phase mixture is forced to pass through the porous medium, and the solid particles are trapped on the medium, so as to achieve the purpose of separating liquid and solid, and gas and solid. Realize the method of solid-liquid separation operation, sedimentation, hydraulic rotation and centrifugal separation in industry. In general, filtration is more economical than centrifugal separation, but the solid product obtained has a high moisture content. For fine particle suspensions or suspensions with low solids content, centrifugal separation is not suitable, and pressure filtration is preferred.