Filtration technology has been used in ancient China for production, and paper made from plant fibers was available in 200 BC. In 105 AD Cai Lun improved the papermaking method. During the papermaking process, he dangled the plant fiber pulp on the dense fine bamboo curtains. Water is filtered through the gap of the bamboo curtain, and a thin layer of wet pulp is left on the surface of the bamboo curtain, and dried to form paper. Most of the earliest filtration was gravity filtration. Later, pressure filtration was used to increase the filtration speed, and then vacuum filtration appeared. The rotary vacuum filter invented in the early 20th century realized the continuous operation of filtering. Since then, various types of continuous filters have appeared successively. Filters that operate intermittently (such as plate and frame filter presses) have been developed because they can achieve automatic operation, and the filtering area is getting larger and larger. To obtain filter residues with low moisture content, mechanically pressed filters have been developed.
