Disc filter

O For solids that are fast settling and cannot be kept as a homogenous slurry in bottom or side feed filters such as Drum or Disc Filters. 

The Disc Filters belong to the side feed group of filtering machines. They are generally used in heavy duty applications such as the dewatering of iron ore. 

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. 

Table 20.5 Effect of membrane disc filter diameter on filtration volumes... 

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. 

Figure 6.24 Photographic representation of a range of filter types and their stainless steel housing. Most filters used on an industrial scale are of a pleated cartridge design, which facilitates housing of maximum filter area within a compact space (a). These are generally housed in stainless steel housing units (b). Some process operations, however, still make use of flat (disc) filters, which are housed in a tripod-based stainless steel housing (c). All photographs courtesy of Pall Life Sciences, Ireland...

Dissolution Measurement. Resist solutions 1n mixtures of Isoamyl acetate/cyclohexanone/methyl Isobutyl ketone (90 5 5 by volume) were filtered through 0.45 pm disc filters, then spin-coated onto silicon wafers at about 2000 rpm. The coated wafers were prebaked 1n a convection oven at 90°C for 1 hour, then stored 1n a desiccator. The basicities of the alkaline solutions were titrated by a standard HC1 solution with a Fisher Accument pH meter, Model 805 MP. The film thickness 1s about 2 pm. Resist dissolution was measured by a He-Ne laser Interferometer 1n a thermostated bath at the desired temperatures (12.131-... 

In essence, the disc filter operates in a manner similar to a bottom-feed drum filter. The principal differences to be noted are the compartments which are formed on both faces of vertical discs. These comprise eight or more segments, each of which is connected to the horizontal shaft of the machine. The filtrate and air are drawn through the filter medium, into the drainage system of the segments, and finally through passages in the rotary shaft to a valve located at one or both ends. 

Kempken et al. [113] employed a rotating disc filter to harvest CHO cells, and observed that the filter could be operated at low transmembrane-pressure with high wall shear rates, leading to high filtrate flow rates, high product yields and minimum fouling. They concluded that their system offered a powerful alternative to conventional tangential flow filtration. 

Fig. 6. Rotating disc filter designed using computational fluid dynamics [114]...

Shelf 3 12 Gassing assembly (disc filters and silicon hoses) RF TC13... 

Disc filters F G PtoF medium — fine high medium medium med- to high high medium... 

The bubble point test is a popular single-point physical integrity test for disc filter membranes based on Eq. (21). A fdter medium is wetted with a liquid, and test gas pressure is slowly raised until a steady stream of bubbles appears from a tube or hose attached to the downstream side of the filter and immersed in water (Fig. 9). The pressure at which the bubbles first appear is recorded as the bubble point and is related to the largest pores in the fdter medium. A pore size can be calculated from Eq. (21) however, it must be realized that the bubble point test does not measure the actual pore size, but only allows correla-... 

The bubble point test, while popular, has some deficiencies that must be realized. First, there is variation in the operator detection of the test end point that is, the first appearance of gas bubbles rising in the liquid. Some operators are able to see smaller bubbles than others. In a recent study, a panel of seven observers recorded the initial detection of a steady stream of air bubbles rising from a capillary held under water as the air pressure was gradually increased. The observers, who had received different degrees of training, identified the simulated bubble point as occurring at air flows of 5 to 50 mL/min corresponding to air pressures of 34 and 38 psi, respectively, for a 90-mm disc filter membrane [56]. 

Dynamic filtration modules are basically of two types rotating disc filter (RDF) and vortex flow filter (VFF). In the latter, the filtration module has a cylindrical shape and has a rotating concentric cylindrical mesh in its interior. The rotational movement of the internal cylinder generates a Taylor-Couette flow in the annular gap (Roth et al., 1997), creating Taylor vortices that minimize concentration polarization and mesh fouling. Continuous perfusion processes based on this type of filter and operating continuously for up to 100 days have been reported (Mercille et al., 1994). 

Rotating disc filter developed by Castilho and Anpach (2003). 

Assay Solution Transfer 0.1 g of sample, accurately weighed, into a 100-mL volumetric flask, and dilute to volume with deionized water. Transfer approximately 10 mL of this solution into a separate container, and add approximately 0.2 g of an MB-1 mixed-bed resin. Shake this mixture for 30 s, and filter through a 0.45-micron nylon disc filter. 

Filter the black slurry on a sintered disc filter funnel (of very fine porosity) and wash the filter cake thoroughly at least 5 times with CH2CI2 (5 x 40 mL). 

Sintered disc filter funnel (medium porosity)... 

Filter the large amount of precipitated sodium toluenesulfonate on a sintered disc filter funnel and wash it with Et20 (3 x 100 mL). 

Dry the organic colourless Et20 layer over MgS04, filter it on a sintered disc filter funnel and evaporate the solvent on a rotary evaporator to yield 18.4 g of pure diiodo derivative 7 (pale-yellow liquid, 99% yield). 

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