China ancient is application of filtration technology in the production, in the year two hundred BC have been made of plant fiber paper. In 105 AD CAI LUN improved the papermaking process, he swings in dense in papermaking process, plant fiber pulp fine bamboo, water bamboo gap filtration, a thin layer of wet pulp stay on the bamboo surface, dry the paper.

The first filter is mostly gravity filtration, then the pressure filtration, the filtration rate increases, then the vacuum filter. Rotary drum vacuum filter at the beginning of the twentieth Century invention realizes continuous filtering operation. Since then, continuous filter types emerged Filter intermittent operation because it can realize automatic operation and development, more and more filter area. In order to obtain the filter residue low humidity, filter mechanical press have been developed.

Use the filter medium container is divided into the upper lower constitutes a simple filter. Suspension is added on the cavity, filter media into the inferior vena become filtrate through under pressure solid particles are in the filter medium surface residue.

Filtration residue layer dielectric surface deposit gradually thickening filtration process, the liquid through the residue layer resistance increased, the filtration rate decrease When the filter paper is full of residue or the filtration rate is too small, to stop filtering, removing residue, the filter media regeneration, to complete a filter cycle.

Liquid through the residue layer and the filter media must overcome the resistance, so 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 accelerate the filter, but the compressive deformation of the particles in the large pressure difference is easy to plug the porous filter media, filter but slow.

Suspension filtration residue layer filtering, depth filtration and filter screen in three ways. Cake filtration is refers in the filtering phase, formed the initial slag layer, then, the residue layer plays an important role in filtering, this small particles are trapped; deep bed filtration refers to the filter medium thick, less solid particles containing as us pension, and the particles smaller than the filter media pore, filtration, particles into the post is adsorbed on the pore filter; filtration is a solid particle filter are larger than the pore filter media, filter filtration medium no adsorption of solid particles, such as drum screen filter to coarse impurities in sewage.