Filtration disk filter

Total submergence is used in the vacuum disk filter thickener (Eig. 13) in which the cake discharge, by backwashing with filtrate, occurs as each sector passes through the lowest point of the slurry tank. 

Horizontal or vertical vessel filters, especially those with vertical rotating elements, have undergone rapid development with the aim of making truly continuous pressure filters, particularly but not exclusively for the filtration of fine coal. There are basically three categories of continuous pressure filters available, ie, disk filters, dmm filters, and belt filters including both hydrauHc and compression varieties. 

There are many technical problems to be considered when developing a new commercial and viable filter. However, the filtration hardware in itself is not enough, as the control of a continuous pressure filter is much more difficult than that of its equivalents in vacuum filtration the necessary development may also include an automatic, computerized control system. This moves pressure filtration from low to medium or even high technology. Disk Filters. 

The disk filter is similar to the dmm in operation, but filtration is conducted using a series of large diameter filter disks that carry the filter medium on both sides of the disk. They are connected to the main horizontal shaft and partly immersed in the feed slurry. The central shaft is connected by a set of valves which serve to provide vacuum and air as in dmm filters. As the disk sections submerge during rotation, vacuum is appHed to form a cake on both sides of the disk. The cycle of operation is similar to that in a dmm filter. One unit can have as many as 12 disks of up to 5-m diameter. Disk filters, both compact and cost effective, are used extensively in the iron ore industry to dewater magnetite concentrates. 

Continuous Pressure Filters These filters consist of conventional drum or disk filters totally enclosed in pressure vessels. Filtration takes place with the vessel pressurized up to 6 bar and the filtrate discharging either at atmospheric pressure or into a receiver maintained at a suitable backpressure. Cake discharge is facilitated through a dual valve and lock-hopper arrangement in order to maintain vessel pressure. Alternatively, the discharged filter cake can be reslurried within the filter or in an adjoining pressure vessel and removed through a control valve. 

Plate pr esses. Sometimes called sheet filters, these are assemblies of plates, sheets of filter media, and sometimes screens or frames. Thev are essentially modified filter presses with practically no cakeholding capacity. A press may consist of many plates or of a single filter sheet between two plates, the plates may be rectangular or circular, and the sheets may lie in a horizontal or vertical plane. The operation is similar to that of a filter press, and the flow rates are about the same as for disk filters. The operating pressure usually does not exceed 138 kPa (20 psig). The presses are used most frequently for low-viscosity liqmds, but an ordinaiy filter press with thin frames is commonly used as a clarifier for 100-Pa s (1000-P) rayon-spinning solution. Here the filtration pressure may be 6900 kPa (1000 psig). 

For example, if a 293-mm-diameter disk filter system having an EFA of 530 cm2 is challenged and the 107/cm2 level is used, the total challenge to the filter is 5.3 x 109 organisms. If a sterile filtrate is assumed the LRV would be calculated and reported as follows ... 

As for filtration times of less than 120 s—for instance, with continuous drum or disk filters, where filtration time would normally be less than 60 s—the initial aav of 0.11 x 10n m/kg and the true R, of 0.24 x 10n m 1 will yield a reasonable representation of the data. Thus the equations become t = 402u2 + 348u and t = (1.86 x 106)L2 + (2.4 x 104)L. 

Fig. 6. Sketch of apparatus for the filtration of oxygen-sensitive materials. (A, B), 250-ml. flash equipped with 24/40 joint and 5-mm.-i.d. sidearm (C—E), vacuum stopcocks, 2-mm. bore (F), vacuum stopcock, 6-mm, bore G), fritted disk filter, coarse, 40-mm.-diam. (R), filtration chamber with 45/50 Joint, volume to bottom of Joint 100 ml.

Membranes are available in sheet, roll, disk, capsule, cartridge, and hollow-fiber formats. For sample filtration, disk-format membranes are the most popular devices. Disks are sold in loose form or packed in disposable syringe filters or cartridges common diameters commercially available are 3, 7, 13, 25, 47, and 96 mm, or even larger. Samples are filtered by manually applying a positive pressure or in a vacuum manifold. 

FIGURE 58.15 Vacuum disk filter (a) side view, (b) top view. (From Shirato, M. et al., eds. M.J. Matteson and C. Orr, in Filtration-Principles and Practice, Marcel Dekker, New York, pp. 299-423, 1987. With permission.)... 

The process begins with a weak acid leach (pH 1.5-1.8) followed by a pH bump to 3.8-4.0 for iron, silica, arsenic and antimony precipitation. The slurry is thickened, and the solid residues are filtered and washed to recover water-soluble zinc in two stages of American disk filters. This filtration step is being upgraded as described in a following section. These iron-rich residues are then repulped and combed with the residue slurry from the oxide leaching circuit and are pumped to the smelter where the slurry is filtered, combined with other materials and process in the JCIVCET furnace. 

Rotary disk filter, vacuum, c/s, heavy duty mineral processing with filter and agitator but exduding vacuum system and vacuum recdver, filtrate pump, moisture trap and scrubber condenser. FOB cost = 265 000 for a total disk, number X 2nD, area = 100 m with n = 0.38 for the range 8-100 and n = 0.55 for the range 100-250. TM = 4 if installed on floor 4.5 if installed devated. 

Centrifugation or filtration in candle filters or in disk filters precoated with charcoal gives sodium hydroxide solutions containing mercury concentrations of < 0.05 ppm (mgAg of 50 % caustic soda). 

Filtration only filter washed with MeOH Soxhlet extraction with MeOH SPE on anion exchanger (elution with 95 5 MeOH/con HCl) derivatization further cleanup with alumina, silica, copper SPE on graphitized carbon black (elution with 9 1 CH2Cl2/MeOH,0.01 M in tetra-methylammonium hydroxide) derivatization further cleanup with alumina SPE on graphitized carbon black (elution with 9 1 CH2Cl2/MeOH, 0.02 M in tetra-butylammonium bisulfate) butyl esters formed in GC injection port Liquids. SPE on Cm resin for the lower concentrations and Cm disks for the higher solids MeOH extraction extracts were cleaned up by anion exchange and additional SPE on Cm... 

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