PRODUCT CATEGORIES
A plate filter often used to filtrate the silver/gold/zinc precipitate generated in a Merrill Crowe process. These filter filters have the advantage of low cost, great strength and ease of internal inspection.
Plate and frame filters are made in every conceivable combination of inlet and outlet positions. Bottom inlet and top outlet positions are considered best for precoating and filter aid suspension. In larger sizes it is preferable that these are at opposite ends of the filter. All air should be purged from the filter before precoating is completed. This may be difficult if gasketed filter septa are used.
There are two basic types of filters. One is the plate-and-frame, the other is the recessed-plate type, also called as chamber type. The plate-and-frame filter press consists of a skeleton framework made up to two end supports connected by two horizontal parallel bars.
On the bars a varying number of filter chambers are assembled which consist of medium-covered plates alternating with frames which provide space for the cake. The chambers are closed and tightened by a screw or hydraulic ram, which forces the Filter Press plates and frames together, making a gasket of the filter cloth. The charge enters the filter press under pressure and fills each chamber approximately simultaneously. The liquid passes through the filter medium, which in turn retains the solids.
The clear filtrate is removed at a discharge outlet. The filter cake builds up until the frames are full-judging by filtering time, decrease in feed rate, or rise in back-pressure. Once the frames are full of cake, filtering is stopped and wash liquid applied if necessary; this may be followed by deliquoring the cake.
There arc various ways of arranging feed inlet, filtrate outlet, and wash-liquor inlet port. For example, in simple washing the wash liquor follows the same path as filtrate, while in thorough washing the liquid is admitted to the faces of alternate plates and then passes through the entire cake thickness to drain away on the other plates.
The recessed-plate filter has no frame; each plate serves as both plate and frame. The feed slurry enters through a larger central port, and filter cake begins to form in the recess in each side of the plate. In order to minimize the strain on the filter cloth, the depth of the recess is usually about 16 mm. giving a maximum cake thickness of about 32 mm.
The advantages of our filter press are adaptability to high pressures, production of a dry washed cake, durability, easy alterability of media and frames, and flexibility. Disadvantages include high labor cost unless mechanized, leakage, and exposure of product to air during discharge. The provision of mechanized systems to move the filter plates and to open and close the filter press at the end and commencement of the filtration cycle can reduce operating manpower requirements. Filter press materials of construction include cast iron, wood, stainless steel, glass-filled polyester, polypropylene without fillers, and aluminum; metal plates and frames may have a rubber or phenolic coating, or they may be entirely of plastic.
