Vertical automatic filter press

Figure 12.4 Scheme to show the vertical automatic filter press... 

Classification of automatic filter presses now in practical use are as follows recessed-plate type and plate-and-frame type lateral type and vertical type fixed filter-cloth type and filter cloth-traveling type. 

FIGURE 58.12 Vertical, recessed-plate, endless filter clothtraveling, expression-type automatic filter press. (From Shirato, M. et al., Filtration—Principles and Practice, eds. M.J. Matteson and C. Orr, Marcel Dekker, New York, pp. 299 23, 1987. With permission.)... 

The vertical recessed plate automatic press is shown schematically in Figure 15. Unlike the conventional filter press with plates hanging down and linked in a horizontal direction, this filter press has the plates in a horizontal plane placed one upon another. This design offers semicontinuous operation, saving in floor space, and easy cleaning of the cloth, but it allows only the lower face of each chamber to be used for filtration. 

These weaves are frequently, though not exclusively, found in belt filters, either of the vacuum, continuous multi-roll press or of the vertical automatic pressure type. Owing to the interlacing pattern of the threads, it is possible to create fabrics with a measure of a solidity and stability that are ideally suited to filters of the types identified. On the debit side, the cost of weaving such high-density fabrics tends to preclude their use in all but a limited number of niche appUcations. 

The vertical filter press is a very effective unit, fully automatic in operation, though somewhat expensive. It occupies less floor space than a horizontal filter press of the same filtration area. 

The vertical recessed plate automatic press, shown schematically in Figure 15 and described previously, is another example of a horizontal belt pressure filter. Cycle times ate short, typically between 10 and 30 minutes, and the operation is fully automated. The maximum cake thickness is about 35 mm washing and dewatering (by air displacement) of cakes is possible. Apphcations include treatment of mineral slurries, sugar, sewage sludge, and fillers like talc, clay, and whiting. 

The testing for evaluating the horizontal diaphragm press is the same as that described above for the (vertical) diaphragm presses. To ensure automatic operation, the cake solids should not stick to the seal of the filter chamber and need to be carefully evaluated during testing. 

A Japanese firm, Kuri Chemical Engineers, has a vertical screw press, with the dewatered solids discharging at the bottom. A scraper part of the screw leaves a thin heel of cake which acts as a precoat, which is either formed directly from the process slurry or from a filter aid such as diatomite. The filtration screen (wedge wire screen of 25 pm aperture) is cleaned automatically by back-washing. The tests reported were with potassium chloride crystals in a solution of PVC in acetone, and with activated carbon in an aqueous solution of alanine. Particle size ranged from 1 to 100 pm. 

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