The working principle of GF rotary drum filter is basically the same as that of general vacuum rotary drum filter. The main difference is that the GF filter is pre-coated with filter AIDS (such as diatomite, perlite, etc.) before filtration. During filtration, the filter aid in the tank body forms a pre-coating of the required thickness on the outer surface of the drum under the action of vacuum suction, and then infuses the slurry to be filtered. Under the action of vacuum suction, the separated filtrate passes through the pre-coating and filter cloth, and is discharged through the suction tube, liquid collector tube and gas-liquid separator. The solid particles in the slurry are trapped by the pre-coating and continuously scraped away by the automatic feed scraper along with the filter aid surface. When the residual thickness of the pre-coating is about 10mm, the pre-coating needs to be re-applied for the next working cycle.