The belt filter (sometimes called a belt filter press) is an industrial machine, used for solid/liquid separation processes, particularly the dewatering of sludges in the chemical industry, mining and water treatment. The process of filtration is primarily obtained by passing a pair of filtering cloths and belts through a system of rollers.

The feed sludge to be dewatered is introduced from a hopper between two filter cloths (supported by perforated belts) which pass through a convoluted arrangement of rollers. As the belts are fed through the rollers, water is squeezed out of the sludge. When the belts pass through the final pair of rollers in the process, the filter cloths are separated and the filter cake is scraped off into a suitable container. Belt filter is generally used in phosphatic fertiliser plant to separate the solid from slurry. It comprises washing to different zone to minimise the product losses. Belt filter are under vacuum system to minimise offgas and effluent during operations. It has application in many areas of industry.

http://en.wikipedia.org/wiki/Belt_filter