Tubular pressure filter

The pressure filter with tubular elements has also been used as a thickener, when the cake, backwashed by intermittent reverse flow, is redispersed by an agitator at the bottom of the vessel and discharged continuously as a slurry. In some cases the filter cake builds up to a critical thickness and then falls away without bio whack. 

Figure 4-78. Tubular in-line pressure filter with reusable elements. The flow unfiltered liquid enters the inlet port, flows upward, around, and through the media, which is a stainless steel or fabric screen reinforced by a perforated stainless steel backing. Filtered liquid disch lrges through the outlet (top) port. Because of outside-to-lnside flow path, solids collect on the outside of the element so screens are easy to clean. By permission, Ronningen-Petter Engineered Filter Systems, Bulletin RP-2.

Slow filtering 0.1-10 cm/hr pressure filters disc and tubular centrifuges sedimenting centrifuges... 

Various pressure filters — Continuous drum Botch leaf Botch ptote Botch tubular element Batch cortridge Botch plote ond frome... 

Batch vacuum leaf Batch nutsche Batch pressure filters plate-and-fi ame vertical leaf tubular... 

Pressure filters are usually operated batch-wise. The batch pressure filters can be classified as tank (pressure vessel) filters or presses. Tank filters have filter elements of different types mounted in pressure vessels. Tank filters are divided into pressure nutsches, leaf filters, candle or tubular filters, bag filters, and cartridge filters. Presses (see Figure 22.38) consist of a series of filter surfaces (plates). The elements are mounted on a frame and are pressed together mechanically. 

Slow separation cm/h Pressure filters Disc and tubular centrifuge... 

Control of the back-pressure level required for efllbctive back-flushing has bear claimed with the use of flat perforated plate elements in the Cricket filter [Filtration and Separation, Sep/Oct., 1991]. Automatic, semicontinuous cleaning of tubular candle filters can also be realised by momentary reversal of the filtrate flow a resulting bump is defivered to the cake, which is dModged and Ds to the cone-shaped bottom of the unit, Bgure 11.53. The effectiveness of these filters is inproved by the use of filter media whkh can handle veiy dilute suspensions of fine (< 0.5 pm) particles, e.g. PIPE membranes). 

Pressure filter 6 Solvent recovery 7 Tubular furnace 8 Vacuum distillation 9 Gas purification 10 Gas separation... 

A multi-element pressure filter comprises a cyhndrical vessel inside which a number of horizontal or vertical porous elements covered by filter cloths are placed (see Figures 1.29 and 1.30). The process suspension, which may be toxic, volatile or flammable, is pumped into the vessel at pressures up to 500 kPa. The positive pressure induces cakes to form on the outer surfaces of the cloths and filtrate is transported away through the elements and a suitable manifold system. Either flat elements, in the form of square, circular or rectangular leaves, or tubular candles are used. They are spaced sufficiently to avoid the possibility of cakes touching on adjacent elements. The pressure... 

Multi (tubular) element leaf pressure filter (Sections 1.4.2.2 and 6.1.3)... 

Sawyer has patented a similar pressure filter, also tubular, in which the filter blanket in the form of a membrane is constantly cleaned by a sonic sinusoidal wave. This is induced by a transducer which is affixed to the tubular wall at an antinodal point and which causes cavitation and continuous cake removal within the annular filtration chamber. This invention is specifically related to the membrane process of filtration, such as ultra-filtration reported in the following section. 

The so-called axial filter , developed in the Oak Ridge National Laboratory, is remarkably similar to Morton s and Kaspar s dynamic filter in that the filter leaf is in the tubular form and the outer shell is also cylindrical. An ultra-filtration module based on this principle has also been described more recently. Unlike the European dynamic filters referred to in the previous paragraph, however, this filter is not suitable for scale-up because it poorly utilizes the available space. The Escher-Wyss pressure filter described (identical copy of this paper also appeared subsequently in Filtration and Separation ) takes the idea of axial filtration a step further in... 

A Venturi-scrabber with downstream cyclone for collection of the dust loaded water drops will be built. By conversion, the ionization unit which is used for the tubular fabric filter will be connected upstream to the Yenturi-scrubber. The throat cross-section will be dimensioned in such a way that the max. pressure loss in the scrubber will be 85 mbar. A second construction will be made with a larger throat cross-section. In a thiid variation the unit will be run as a scrabbing tower, i.e. without constriction of the gas flow. 

Two types of precoat filters (tubular and filter leaf) have been used for amine filtration. Typical sizing criteria and performance data are summarized in Table 3-7. A review of experience with several precoat filters in DBA plants located in Canada and the United States has been presented by Scheirman (1973A, B), Combined use of filter aid and activated carbon in a precoat filter of the pressure leaf type has been reported by Dailey (1970). Such a system removes suspended solids and undesirable dissolved compounds in one operation. However, Smith and Younger (1972) report that precoat filters using both activated carbon and filteraid are not as effective as a precoat filter combined with a dedicated activated carbon filter. 

The advantage of candle filters is that as the cake grows on the tubular elements the filtration area increases and the thickness of a given volume of cake is therefore less than it would be on a flat element. This is of importance where a thick cake is being formed the rate of increase in the pressure drop is less with tubular elements. 

External-Cake Tubular Filters Several filter designs are available with vertical tubes supported by a filtrate-chamber tube sheet in a vertical cylindrical vessel (Fig. 18-115). The tubes may be made of wire cloth porous ceramic, carbon, plastic, or metal or closely wound wire. The tubes may have a filter cloth on the outside. Frequently a filter-aid precoat will be applied to the tubes. The prefilt slurry is fed near the bottom of the vertical vessel. The filtrate passes from the outside to the inside of the tubes and into a filtrate chamber at the top or the bottom of the vessel. The sohds form a cake on the outside ofthe tubes with the filter area actually increasing as the cake builds up, partially compensating for the increased flow resistance of the thicker cake. The filtration cycle continues until the differential pressure reaches a specified level, or until about 25 mm (1 in) of cake thickness is obtainea... 

The concept of cross-flow microfiltration is shown in Figure 16.11, which represents a cross-section through a rectangular or tubular membrane module. The particle-containing fluid to be filtered is pumped at a velocity in the range 1-8 m/s parallel to the face of the membrane and with a pressure difference of 0.1-0.5 MN/m2 (MPa) across the membrane. The liquid penneates through the membrane and the feed emerges in a more concentrated form at the exit of the module.1617 All of the membrane processes are listed in Table 16.2. Membrane processes are operated with such a cross-flow of the process feed. 

Glomerular filtration rate (GFR) is the volume of plasma-like fluid that is filtered per unit time across the glomerular capillary membranes to enter the tubular space. Filtrate formation is driven by the net filtration pressure that is equal to the capillary hydrostatic pressure diminished by the sum of capillary oncotic... 

The experiments on the iodine separation were conducted as follows. A tubular vessel of pyrex glass, having at one end a plane window and at the other end a conical light-trap, was evacuated and then filled with iodine at about 0.17 mm. pressure, and then with hexene at about 6 mm. partial pressure. The tube was then subjected to the intense light from two Cooper-Hewitt glass mercury arcs, using a filter of 0.05 molal potassium dichromate 2 cm. in thickness to cut off all radiations on the violet side of the green mercury line. The lamps were rim at considerably below the rated capacity, and were cooled by a blast of air to keep the emission lines as narrow as possible. 

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