Vacuum disc filter

Disc filters are similar in principle to rotary filters, but consist of several thin discs mounted on a shaft, in place of the drum. This gives a larger effective filtering area on a given floor area, and vacuum disc filters are used in preference to drum filters where space is restricted. At sizes above approximately 25 m2 filtration area, disc filters are cheaper but their applications are more restricted, as they are not as suitable for the application of wash water, or precoating. 

Fig. 2.4. Rotary vacuum disc filter (Automatic Coal Cleaning Co. Ltd. and Davey, Paxman and Co. Ltd.).

The most common types of filters used in industrial processing are pressure filters such filter presses, leaf filters, and cartridge filters, as well as vacuum filters like the rotary drum vacuum filter, and the rotary vacuum disc filter. Most filtration units produce a cake, which at long cycles may become reasonably dry at the expense of declining the flow rafes. Keeping consfanf... 

Hydrate product Rotary vacuum disc filter Crystalline/coarse 5, 9, 14 Resists stretch and abrasion. 

Total submergence is used in the vacuum disc filter thickener (Figure 13.12), in which case the cake discharge, by backwashing with filtrate, occurs as each sector passes through the lowest point of the slurry tank. 

Figure 5 Rotary vacuum disc filter (Eimco). (From Osborne, 1990.)...

The capillary disc filter looks like any other standard rotary vacuum disc filter, as can be seen in Figure 3.25, but the filter medium is a finely porous ceramic disc, which draws filtrate through the disc material by capillary action, under the applied vacuum. The filter discs are made of sintered alumina with uniform micropores less than 1 pm in size, which allows only liquid to flow through it. Despite an almost absolute vacuum, no air penetrates the filter material. The disc material is inert,... 

A valve with bridges and internal compartments for form and dry under vacuum and cake discharge under pressure with 2-2.5 bar snap or 0.2-0.25 bar constant blow. Most disc filters are fitted with one valve only however two valves are often mounted on both drive and nondrive ends with long barreled filters or when the hydraulic loadings are high. 

Disc Filters A disc filter is a vacuum filter consisting of a number of vertical discs attached at intervals on a continuously rotating... 

Of all continuous filters, the vacuum disc is the lowest in cost per unit area of filter when mild steel, cast iron, or similar materials of construction may be used. It provides a large filtering area with minimum floor space, and it is used mostly in high-tonnage dewatering applications in sizes up to about 300 m (3300 ft ) of filter area. 

Small disc filters and small single-use slacked disc filters in plastic housings are avail le and have the appearance of cartridge filters but consist of a series of separate membranes rather than of one continuous pleated membrane. This added complexity may make sterilization by saturated steam more difficult. Deep vacuums intended to ensure effective air removal from the filter media... 

Figure 11.14 Ceramic disc filters c jillary pressure control (Outokumpu Mintech Oy, Espoo, Finland) Table 11.4 Vacuum filter productivity ...

Continuous filtration is discussed by Coulson and Richardson.. It commonly employs rotary vacuum filters. These are usually cylindrical in shape, rotating about a horizontal axis with a filter medium on the curved surface and a vacuum applied from inside. Rotating disc filters are less frequently employed (see Fig. 2.4). These have a number of discs on the same shaft with vacuum applied from inside but the flat surfaces of the discs hold the filter medium. The methods of continuous discharge of the filter cake during operation, and of replacement of the filter medium at intervals, are less elegant than those applicable to rotating cylinders. 

Figure 1.27 Schematic side view of a rotary disc vacuum filter [left) and photograph, with permission from Ceramec, of a multiple disc filter installation fitted with ceramic elements (right).

Another variation of the same principle is the DDS vacuum pressure filter which has a number of small discs mounted on a shaft which rotates discontinuously. The cake is formed on both sides of the discs when they are at the bottom position, i.e. dipped in the slurry. When the discs come out of the slurry and reach the top position, hydraulically driven pistons squeeze the cake and the extra liquid then drains from both sides of the cake. The cake is removed by blow-back with compressed air. 

---