Drum Filter consists of a drum rotating in a tub of liquid to be filtered. The liquid to be filtered is in the tub below the drum and agitated to keep the particle in suspension.
The rotary drum is divided into compartments which can be under vacuum or can be supplied with gas under pressure depending on the position. While rotating, a constant position of the rotary drum is submerged in the slurry.
The cake is formed while the drum is submerged and under vacuum. The solids adhere to the outside of the drum while the liquid filtrate is draw by the vacuum through the filter media to the internal portion of the drum, and pumped away.
The vacuum drum filter provides a continuous discharge of the solids and the cake can usually be dewatered. Some cake washing is often possible although it is not usually possible to get a clean separation of the different filtrates.
The vacuum is then released and the gas pressure may be applied so that the cake can be discharged. æThe solids can also be discharged using a knife, cutting off the solids and a small portion of the filter media to reveal a fresh media surface.
The drum can be pre-coated with a filter aid. These are generally open but can be enclosed for handling hazardous material or for operation at temperature away from ambient.