The High Vacuum Oil Purifiers create negative pressure at the filtrate outlet as the driving force for filtration. This oil purifier is divided into batch operation and continuous operation. The intermittently operated vacuum oil purifiers can purify suspensions of various concentrations, and the continuously operated vacuum oil purifiers are suitable for filtering thick suspensions containing more solid particles.

The intermittent operation purifier has been developed due to the automatic operation, and the filter area is getting larger and larger. In order to obtain filter residues with low moisture content, mechanically pressed filters have been developed.

The container is divided into upper and lower chambers with filter media, which constitutes a simple filter. Suspension is added to the upper cavity, enters the lower cavity through the filter medium under pressure to become filtrate. The solid particles are trapped on the surface of the filter medium to form filter residue (or filter cake).

During the Oil Filtration Process, the filter residue layer on the surface of the filter medium gradually thickens, the resistance of the liquid through the filter residue layer increases and the filtration speed decreases. When the filter chamber is full of filter residue or the filtering speed is too low, stop filtering, remove the filter residue, and regenerate the filter medium to complete one oil filtration process cycle.

The resistance must be overcome when the liquid passes through the filter residue layer and the filter medium. Therefore, there must be a pressure difference on both sides of the filter medium, which is the driving force for filtration. Increasing the pressure difference can speed up the filtration, but the deformed particles under pressure will easily block the pores of the filter medium when the pressure difference is large, and the filtration will slow down instead.

Suspension filtration has three methods: filter residue layer filtration, deep layer filtration and sieving filtration. The filter residue layer filtration means that the initial filter residue layer is formed after the initial stage of filtration. After that, the filter residue layer plays a major role in filtering. At this time, both large and small particles are intercepted; deep filtration means that the filter medium is thick and the suspension contains solid particles, and the particles are smaller than the pores of the filter medium. When oil filtration process, the particles are adsorbed in the pores after entering, sieve filtration means that the solid particles trapped by the filter are larger than the pores of the filter medium, and the inside of the filter medium does not absorb solid particles. Filtration methods, such as rotating drum filter sieve to filter out coarse particles in sewage. Besides removing the particles, the Vacuum Oil Purifier also can remove water and gas by vacuum dehydration and degassing.