Filter is a device that uses a porous filter to achieve solid-liquid separation. Filters are used in chemical, petroleum, pharmaceutical, light industry, food, mineral processing, coal and water treatment sectors. The filter is a new type of filter system with novel structure, small size, easy and flexible operation, high efficiency, and closed work. It is a multi-purpose filter device with strong applicability. 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.