The use of porous filter media on both sides of the pressure difference, the separation of solid materials and water machinery. Filter is the use of porous filter media, trapping liquid and solid particles in the mixture of solid particles, and solid and liquid separation equipment. Filter is widely used in chemical, petroleum, pharmaceutical, light industry, food, mineral processing, coal and ancient China that has been applied in the production of filter technology, 200 BC has been made of plant fiber paper. In 105 AD, Cai Lun improved the papermaking method. In the papermaking process he planted the plant fiber pulp on a dense bamboo curtain. The first filter is mostly gravity filtering, and later the use of pressure filtration to improve the filtration rate, which in turn appeared a vacuum filter . At the beginning of twentieth Century the invention of the drum vacuum filter to achieve a continuous filter operation. Thereafter, various types of continuous filters appeared successively. Intermittent operation of the filter (such as plate and frame filter press, etc.) can be automated due to the operation and development, increasing the size of the filter. In order to obtain a low moisture content of the filter residue, mechanical press filter has been developed.
