Filter press (sometimes called Plate-and-Frame Filter press) which describes the style of filters developed from the 19th century onwards originally for clay. The majority of today's filters are more correctly called "chamber filter press", "Membrane filter press", or "Membrane Plate Filter". Many processes in the food, chemical or pharmaceutical industries make products from liquid-solid suspensions or slurries. These mixtures are like a runny mud or milk shake. The solids in them do not dissolve in the liquid, but are carried along in it. Filter presses separate the solids from the liquids so that the useful part can be processed, packaged or delivered to the next step.
Filter presses generally work in a "batch" manner. The plates are clamped together, then a pump starts feeding the slurry into the filter press to complete a filtering cycle and produce a batch of solid filtered material, called the filter cake. The stack of plates is opened, solid is removed, and the stack of plates is re-clamped and the filtering cycle is repeated.
A filter press uses increased pump pressure to maximize the rate of filtration and produce a final filter cake with a water content under 65%. This is more efficient than regular filtration because of the increased filtration pressure applied by the pump that can reach anywhere between 50-200 PSI.
A filter press consists of a series of filter chambers formed between square, rectangular or round filter plates supported on a metal frame. Once the filter chambers are clamped, the filter press is loaded with slurry. The plates on the filter press are clamped together with hydraulic rams that generate pressures typically in the region of 3000 pounds per square inch.
In addition to the filter plate filtration medium, the growing filter cake enhances removal of fine particles in the slurry. The solution coming through the filter press water bibs, called the filtrate, will be pure.
The filtrate can be drained away for safe disposal, or it can be kept in a water tank for recycled use. At the end of filtration, the solid filter cake can be removed. The whole filtration process is often controlled by electronics to make it automatic or semi-automatic.
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