Types of filter press

Microfiltration. This process is defined as the separation of particulates between 0.1 and 10 p.m by a membrane. Two principal types of membrane filter are used depth filters and screen filters. Typical particulate retention curves for the two types of filter are shown in Figure 26. Screen filters collect retained particulates on the surface depth filters collect them within the membrane. Depth filters, therefore, have a much larger surface area available for filtration and usually have a much larger particulate holding capacity before fouling than screen filters. On the other hand, screen filters generally give a cleaner, sharper separation (8,66). Figure 27 compares typical pore sizes of depth and screen filters.  [c.76]

Various types of filter media and the materials oi which they are constructed are surveyed extensively by Purchas Industrial Filtration of Liquids, CRC Press, Cleveland, 1967, chap. 3), and characterizing measurements (e.g., pore size, permeabihty) are reviewed in detail by Rushton and Griffiths (in Orr, op. cit., chap. 3). Briefer summaries of classification of media and of practical criteria for the selec tion of a filter medium are presented by Shoemaker (op. cit., p. 26) and Purchas [Filtr Sep., 17, 253, 372 (1980)].  [c.1708]

In some ways this chapter is a sidebar discussion, although it would be remiss to treat these systems as miscellaneous. Cartridge filters are so widely used throughout the chemical process industries that, if you are a chemical engineer, it would be amazing that at some point in your career you did not specify or use this type of filter in an application. The other types of filter machines discussed in this chapter are important, but perhaps are not nearly as frequently employed in process and water treatment applications as the cartridge device. In all cases the systems are operated as batch, although there are semi-continuous to continuous operations cropping up all the time.  [c.224]

Several types of aggregate-bed filters are available which provide in-depth filtration. Both gravel and particle-bed filters have been developed for removal of dry particulates but have not been used extensively. Filters have also been developed using a porous ceramic or porous metal filter surface.  [c.403]

In a filtration system (Fig. 1) the porous filtration medium is housed in a housing, with flow of Hquid in and out. A driving force, usually in the form of a static pressure difference, must be appHed to achieve flow through the filter medium. It is immaterial from the fundamental point of view how the pressure difference is generated but there are four main types of driving force, ie, gravity, vacuum, pressure, and centrifugal. The two types of filtration used most often in practice are cake, or surface, filtration and deep bed filtration. This division usually is unambiguous but in some cases, such as in cartridge filters, there is no sharp dividing line.  [c.386]

Solid—Liquid Separation. The separation of proteins by precipitation technology is accompHshed when the soHd and Hquid phases have been separated from one another. Centrifugation, using either tubular bowl or multichamber centrifuges, is used for this purpose (9,35) (see Separation, centrifugal). The machines must be refrigerated to ensure that the correct temperature for precipitation is obtained at the point of separation. Protein precipitates consist of large numbers of small particles, typically 0.1 to 1.0 p.m in diameter, which aggregate together to form a larger particle or floe. This aggregate can be broken down by the shear forces experienced in some types of pump and in the entry region to centrifuges. Consequently, performance of the centrifugation operation is influenced by the shear characteristics of the process equipment as well as by the size, density, and strength of the particles (36). Both of these types of centrifuge function by retaining the soflds within the rotating bowl, while the feed suspension and resultant supernatant flow continuously. One consequence of this mode of operation is a relatively small soflds hoi ding capacity per machine and the need to use a large number of centrifuges to process the contents of a large fractionation vessel. Some manufacturers have introduced depth filtration (qv) for the removal of the soflds at some of the precipitation stages. However, protein precipitates consist of highly compressible particles, and filter aids (37) must be used if blinding of the filter surface is to be avoided.  [c.529]

PIa.te-a.nd-Fra.me Modules. Plate-and-frame modules were among the eadiest types of membrane system the design originates from the conventional filter-press. Membrane, feed spacers, and product spacers are layered together between two end plates. A number of plate-and-frame units have been developed for small-scale appHcations, but these units are expensive compared to the alternatives, and leaks caused by the many gasket seals are a serious problem. Plate-and-frame modules are generally limited to electro dialysis and pervaporation systems and a limited number of highly fouling reverse osmosis and ultrafiltration appHcations.  [c.73]

Pressure filters or filter presses are commonly of the batch type (2,47). These are characterized by high filtration rates, smaller floor area, and lower capital cost. Dryer cakes are produced. These filters are more widely used in the chemical industry than in mineral processing because this is a batch operation. The plate and frame presses (Fig. 22) and the chamber presses are the most common types of pressure filters used. These consist of a series of vertical, alternating parallel frames and plates. The filter cloth is held against the plate. Cake formation occurs in the hoUow frame. The fully automatic Larox chamber filter, reported to reduce dewatering energy requirements, is a more recent development (47). Other developments are the tube press or the pinch press which can operate at 10,000 kPa of dewatering pressure. These units produce very low moisture filter cakes even in the absence of dewatering acids (51).  [c.415]

Air displacement can be accompHshed by using a pressure difference to force the Hquid from the pores in the cake. The types of filters that provide displacement dewatering include virtually all vacuum filters, rotary pressure disk and dmm filters, the Lasta (25), Larox (28), and Vertipress (29) automatic filter presses, hyperbaric filters, tube press filters (23), and a hybrid continuous pressure filter—expression press (30). In a centrifuge, displacement dewatering is accompHshed by applying a body force directly to the Hquid by the spinning motion. The factors that control displacement dewatering are  [c.19]

Cell Geometries. Uniform electrode potential, short interelectrode gaps, and good mixing and mass transport benefit many electrochemical reactions. It is difficult to depart from the narrow spaced rectangular plates with turbulent flow electrolyte to achieve this. Reviews of electrolytic cell design are available in the Hterature (70,71). Several types of cell designs are reviewed herein. Design features in standard chemical engineering hardware are often used in various cell designs found in the Hterature. This is especially tme if that equipment has a desired feature such as mass transfer, heat transfer, or gas absorption. The familiar filter press cells are made more sophisticated with internal manifolds like the plate heat exchanger, the fluidized and packed bed from catalytic reactors, etc.  [c.90]

Filter-medium selection embraces many types of construction fabrics of woven fibers, felts, and nonwoven fibers, porous or sintered solids, polymer membranes, or particulate solids in the form of a permeable bed. Media of all types are available in a wide choice of materials.  [c.1706]

The relatively high prices of pulp and paper filters reflect the construction features that accommodate the veiy high hydraulic capacity that is required. The absence of data for some common types of filters, in particular the filter press, is explained by Hall as due to the complex variety of individual features and materials of construction. For information about missing filters and for firmer estimates for those types presented, vendors should be consulted. In all cases of serious interest, consultation should take place early in the evaluation procedure so that it can yield timely advice on testing, selection, and price.  [c.1723]

Centrifugal Filtration Filtering centrifuges are distinguished from standard centrifugation by a filtering medium incorporated into the design. Slurry is fed to a rotating basket or bowl having a slotted or perforated wall covered with a filtering medium such as canvas or metal- reinforced cloth. The angular acceleration produces a pressure that transports the liquor through the filtering medium, leaving the solids deposited on the filter medium surface as a cake. When the feed stream is stopped and the cake spun for a short time, residual liquid retained by the solids drains off This results in final solids that are considerably drier than those obtained from a filter press or vacuum filter. Principal types of filtering centrifuges are suspended batch machines, automatic short-cycle batch machines and continuous conveyor centrifuges. In suspended centrifuges, the filter medium is usually canvas or a similar fabric, or woven metal cloth. Automatic machines employ fine metal screens. The filter medium in conveyor centrifuges is usually the slotted wall of the bowl itself. Figure 28 provides an example of this machine. The system combines the features of a centrifuge and a screen. Feed enters the unit at the top and is immediately brought up to speed and distributed outward to the screen surface by a set of vanes. Water or other liquid is forced by the sudden centrifugal action through the screen openings into an effluent housing.  [c.367]

In a very general sense, there are two types of wastewater flows - municipal and industrial. Although municipal wastewaters vary in composition, there are ranges of properties that enable filtration equipment to be readily selected and specified. This is not always the situation when treating industrial wastewater streams. The compositions and properties of industrial wastewaters vary significantly, and even within specific industry sectors, these flows can be dramatically different. This is important to realize because although filtration is a physical process, it depends upon and is integrally a part chemical treatment processes such as preconditioning, buffering and filter aid conditioning. These chemical treatment methods must be properly specified along with the filtration equipment itself in order to ensure that a properly designed filtration system is being applied.  [c.78]

There are several types of washing bottoms. One type consists of porous plates which directly support the filter sand, generally without a layer of support gravel. Even if the system has the advantage of being of simple construction, it nevertheless suffers from incrustation. This is the case for softened water or water containing manganese. Porous filters bottoms are also subject to erosion or disintegration upon the filtration of aggressive water.  [c.258]

Forces of physical attraction or adsorption of contaminants to the pore walls is the most important AC filtration process. The amount and distribution of pores play key roles in determining how well contaminants are filtered. The best filtration occurs when pores are barely large enough to admit the contaminant molecule. Because contaminants come in all different sizes, they are attracted differently depending on pore size of the filter. In general AC filters are most effective in removing contaminants that have relatively large molecules (most organic chemicals). Type of raw carbon material and its method of activation will affect types of contaminants that are adsorbed. This is largely due to the influence that raw material and activation have on pore size and distribution.  [c.410]

Processes other than physical attraction also affect AC filtration. The filter surface may actually interact chemically with organic molecules. Also electrical forces between the AC surface and some contaminants may result in adsorption or ion exchange. Adsorption, then, is also affected by the chemical nature of the adsorbing surface. The chemical properties of the adsorbing surface are determined to a large extent by the activation process. AC materials formed from different activation processes will have chemical properties that make them more or less attractive to various contaminants. For example chloroform is adsorbed best by AC that has the least amount of oxygen associated with the pore surfaces. You can t possibly determine the chemical nature of an AC filter. However, this does point out the fact that different types of AC filters will have varying levels of effectiveness in treating different chemicals.  [c.410]

Deep bed filters were developed for potable water treatment as the final polishing process foUowing chemical pretreatment and sedimentation. They are increasingly appHed in industrial wastewater treatment under somewhat harsher operating conditions of higher solids loadings and more difficult backwashing of the media. Most deep bed filters are gravity-fed but some pressure types are used. The most common arrangement is the downflow filter (Fig. 5), with backwash in the upward direction to fluidize the bed.  [c.387]

A number of vacuum filter types use a horizontal filtering surface with the cake forming on top. This arrangement offers a number of advantages gravity settling can take place before the vacuum is appHed, and in many cases may prevent excessive blinding of the cloth due to action of a precoat formed by the coarser particles if heavy or coarse materials setde out from the feed they do so onto the filter surface, and can be filtered and fine particle penetration through the medium can be tolerated because the initial filtrate can be recycled back onto the belt. Top-feed filters are ideal for cake washing, cake dewatering, and other process operations such as leaching.  [c.394]

In the cross-flow mode, fluid is passed across the membrane surface while a portion of the flow is diverted through the filter (permeate). A portion of flow is returned to the central reservoir as retentate. In this process the volume of fluid in the retentate continually decreases as more of the initial volume is collected as permeate. Viral particles are concentrated in the retentate. The advantage of this process is that the cross-flow across the membrane helps extend filter life by reducing gel layer formation. Typically the filtration systems utilizing cross-flow are either in the tangential-type system where fluid passes between two flat sheets of membrane material (Fig. 3) or consist of hoUow-fiber filters where the fluid passes through the middle of hoUow tubes (Fig. 4) (see Hollow-fibermembranes). For tangential flow, the membrane pore sizes range from 70—180 KD (27—29), as well as 100 and 300 KD polyethersulfone membranes. HoUow-fiber ultrafilters between 100 and 6 KF) have been used for vims removal (30—33). These have been constmcted from regenerated cellulose fiber, poly acetalnittile (PAN), and polysulfone (PS). Both types of filters (tangential flow and hoUow fiber) are typicaUy designed for reuse after cleaning and sanitization and thus can be cost effective in terms of the filter cost. On the other hand, these systems may have higher holdup volumes and thus greater loss of production than single-pass systems. The cross-flow system may also be more complex and cosdy to instaU. AdditionaUy, it is necessary to vaUdate the filtration process. In the case of reuse of the filter system the cleaning and sanitization procedures also require vaUdation.  [c.143]

A.queous Jilkaline E.kctrolysis. The traditional process employs potassium hydroxide, KOH, added to the water to improve the conductivity through the ceU. Table 9 shows operating parameters for industrial electrolyzers. All of these systems use a diaphragm to separate the cathode and anode, and keep the product oxygen and hydrogen from mixing. There are basically two types of units offered tank type and filter press. In the tank type, many individual cells are coimected in parallel and fed from one low voltage source. This requires large current flows at low voltage, as well as large transformers and rectifiers. Most commercial electrolyzers are of the filter press type, where cells are stacked and coimected in series. The back side of the cathode for one cell is the anode for the next. This is called a bipolar arrangement. The voltage required to mn the whole module is the sum of the voltages for each individual cell, so low voltages are not needed. However, a series arrangement means that if one cell fails, the module fads. Some units operate at high pressures. This is considered an efficient way to compress hydrogen. Much work is being directed toward improving traditional alkaline electrolysis (157,158). New cell geometries that lower resistances, better electrodes to reduce overvoltages, and better diaphragm materials, so that higher temperatures can be used, are ad. being considered. Higher temperatures enable the electrodes to function more efficiently. Improvements in design and materials are manifested in higher ceU current densities.  [c.425]

From a survey of early 1982, prices of a number of widely used types of process filter were collated by Hall and coworkers [Chem. Eng., 89(7), 80 (1982)]. These data are drawn together in Fig. 18-137, updated to 1995 prices. They have a claimed accuracy of 10 percent, but they should be used confidently only with study-level cost estimations ( 25 percent) at best. Cost of deliveiy to the plant can be approximated as 3 percent of the FOB price [Pikulik anciDiaz, Chem. Eng., 84(21), 106(1977)].  [c.1723]

As in sedimenting centrifuges, heavier solids settle to the bowl to form a cake layer. In filtering centrifuges, the bowl wall is a screen, a perforated surface, or, in general, a filtering medium. Under a centrifugal field, the liquid above, as well as that trapped in the cake, flows through the cake and the filter. Because the solids are coarser as compared to those processed by sedimenting centrifuges, setthng under centrifugal gravity is quick, leaving filtration as the limiting step of the process. Washing and subsequent dewatering of the caJce are very common for filtering centrifuges. Filtering centrifuges are also known as centrifugal filters, wringers, extractors, or diyers. There is a difference in the various types of machines according to whether the feed is batch, intermittent, or continuous, and in the manner in which the cake solids are removed from the basket. The operating range of filtering centrifuges is shown in Table 18-14.  [c.1735]

Continuous is used here to include not only presses that take feed and produce dewatered product in a constant stream, but also automated batch presses that require little or no operator intervention during operadng cvcles. Continuous-expression presses, under this broader operational definition, include variable-volume filter presses (q.v.), which inflate a membrane against the cake to press additional liquid from the solids within the press screw presses, which compress a generally fibrous or polymerized feed in a screw whose diameter increases as the feed progresses through the barrel belt presses, which constrain the feed between two porous belts that are mechanically squeezed together and rigid perforated disk or roll presses, which squeeze solids through a nip formed by converging rotating disks or in the nip between two parallel, closely spaced, porous drums. Many other types of presses are also available, but they are used less frequently. Among them is the tube press, which can exert higher overall pressure on filter cake than any other device. Although the tube press is technically a batch device hke the variable-volume filter press, it can also be automated for continuous cycling.  [c.1744]

Solids Total solids is the residue remaining from a wastewater dried at 103-105° C. It includes the fractions Hiown in Fig. 25-43. The first separation is the portion that passes through a 2- Im filter (dissolved) and those sohds captured on the filter (suspended). Combustion at 500° C further separates the solids into volatile and ash (fixed) sohds. Although ash and volatile solids do not distinguish inorganic from organic solids exactly, due to loss of inorganics on combustion, the volatile fraction is often used as an approximate representation of the organics present. Another type of solids, settleable solids, refers to sohds that settle in an Imhoff cone in one hour. Industrial wastes vaiy substantially in these types of solids and require individual wastewater treatment process analysis. An example of possible variation is given in Table 25-37.  [c.2212]

Rapid FUteration Rapid filtration is a standard unit operation in wastewater treatment. The operation is performed either in open gravitational flow filters or in closed pressure filters. Rapid pressure filters have the advantage of being able to be inserted in the pumping system, thus allowing use of a higher effective loadings. Note that pressure filters are not subject to development of negative pressure in a lower layer of the filter. These filters generally support higher speeds, as the available pressure allows a more rapid flow through the porous medium made up by the filter sand. Pressure filtration is generally less efficient than the rapid open type with free-flow filtration. Pressure filters have the following disadvantages. The injection of reagents is complicated, and it is more complicated to check the efficiency of backwashing. Work on the filter mass is difficult considering the assembly and disassembly required. Also, the risk of breakthrough by suction increases. Another disadvantages is that pressure filters need a longer filtration cycle, due to a high loss of head available to overcome clogging of the filter bed. Another option is to use open filters, which are generally constructed in concrete. They are normally rectangular in configuration. The filter mass is posed on a filter bottom, provided with its own drainage system, including bores that are needed for the flow of filtered water as well as for countercurrent washing with water or air. There are several types of washing bottoms. One type consists of porous plates which directly support the filter sand, generally without a layer of support gravel. Even if the system has the advantage of being of simple construction, it nevertheless suffers from incrustation. This is the case for softened water or water containing manganese. Porous filters bottoms are also subject to erosion or disintegration upon the filtration of aggressive water. The filter bottom is often comprised of pipes provided with perforations that are turned toward the underpart of the filter bottom and embedded in gravel. The lower layers are made up of gravel of approximate diameter 35 - 40 mm, decreasing up to 3 mm. The filter sand layer, located above this gravel layer, serves as a support and equalization zone. Several systems of filter bottoms eomprise perforated self-supporting bottoms or false bottoms laid on a supporting basement layer. The former constitutes a series of glazed tiles, which includes bores above which are a series of gravels in successive layers. All these systems are surpassed to some extent by filter bottoms in concrete provided with strainers. The choice of strainers should in part be based on the dimensions of the slits that make it possible to stop the filter sand, which is selected as a function of tlie filtration goal. Obstruction or clogging occurs only rarely and strainers are sometimes used. Strainers may be of the type with an end that continues under the  [c.368]

Note that RCOOH denotes short chain organic acids such as acetic acid which make up the major fraction of residual oxidation intermediates in a typical wet oxidation effluent. Properties of wet oxidation liquid effluent include negligible NO and SOj, negligible particulate matter, and some VOCs, depending on the waste. Wet oxidation is a mature technology with a long history of development and commercialization. Wet oxidation is applicable to numerous types of waste and is used commercially for the treatment of high strength industrial wastewater, ethylene and refinery spent caustic sludge. There are two other processes that we should mention that are used in conjunction with the WAO process. The first of these is thermal sludge conditioning/low pressure oxidation (LPO). Thermal sludge conditioning is used for the conditioning of biological sludge for dewatering. Thermal conditioning is accomplished using temperatues of 175 to 200 C (350 to 400 F). The low temperature allows for low operating pressures. Thermal conditioning is most commonly used for municipal wastewater treatment sludge. It has also been applied to industrial sludge processing. The technology is applicable to any organic sludge which is difficult to dewater or that contains pathogenic components. The LPO process heats sludge to a point where the biosolids break apart, releasing much of the water trapped within the cell structures, allowing filter presses, vacuum filters, belt presses and other dewatering technologies to perform their jobs more effectively. This process along with dewatering achieves a 90 to 95 % sludge volume reduction, while at the same time destroys any pathogens in the sludge. A schematic of the process is illustrated in Figure 29. The second process used in conjunction with WAO is wet air regeneration. This is a liquid phase reaction in water using dissolved oxygen to oxidize sorbed contaminants and biosolids in a spent carbon slurry, while simultaneously regenerating the powdered activated carbon. The regeneration is conducted at moderate temperatures of 400 to 500 F and at pressures from 700 to 1000 psig. The process converts organic  [c.563]

Many different filter types are used, including horizontal rotary table, belt, in-line pan, and horizontal rotary tilting pan. The dihydrate acid containing 28—32% P2O5 is concentrated further for most uses, usually in single-effect vacuum evaporators. A variety of types are used, including forced circulation, natural circulation, and falling film. Direct-heated spray towers and submerged combustion have also been used but these are no longer preferred. Because corrosion is a serious problem in wet-process acid plants, carbon brick linings and mbber linings are used extensively. Filters, pumps, and agitators are of stainless steel, and piping is made of mbber-lined steel and a variety of plastics.  [c.226]

Filters are grouped according to the capacity by volume as follows small volumes (i.e., below 10,000 acffn), medium volumes (i.e., 10,000 to 100,000 acfm), and large volumes (i.e., >100,000 acfm). The filter-media types include woven and felted media. Temperature capabilities of the media range from higher temperatures ( > 400 °F), to medium temperatures (200 to 400 F) and low temperatures (< 200 °F). The ability of the fabric to collect fine particles and maintain a good cleaning process should serve as the basis in selection of a fabric. As the dust layer or so-called filter cake layer builds up, flow resistance increases. Cleaning reduces the gas flow resistance and maintains the proper pressure drop across the filter.  [c.339]

The size of the filtered sample is established by the anticipated bacterial density. An ideal quantity results in the growth of about 50 colifoim colonies and not more than 200colonies of all types. Often it may be difficult to anticipate the number of bacteria in a sample. Two or three volumes of the same sample must be tested. When the portion being filtered is less than 20 ml, a small amount of sterile dilution water is added to the funnel before filtration. This uniformly disperses the bacterial suspension over the entire surface of the filter. The filter-holding assembly is placed on a suction flask. A sterile filter is placed grid side up over the porous plate of the apparatus using sterile forceps. The funnel is then locked in place holding the membrane. Filtration is performed by passing the sample through the filter under partial vacuum. A culture dish is prepared by placing a sterile absorbent pad in the upper half of the dish and pipetting enough enrichment media on top to saturate the pad. M-Endo medium is used for the coliform group and M-FC for fecal coliforms. The filter is then removed from the filtration apparatus and placed directly on the pad in the dish. The cover is replaced and the culture is incubated (for 24 h at 35 C). For fecal coliforms, incubation is performed by placing the culture dishes in watertight plastic bags and submerging them in a water bath at 44.5 C. Coliform density is calculated in terms of coliforms per 100 ml by multiplying the colonies counted by 100 and dividing this value by the milliliters of the sample filtered.  [c.463]

See pages that mention the term Types of filter press : [c.488]    [c.389]    [c.545]    [c.1748]    [c.355]    [c.360]    [c.240]    [c.1197]   
Crystallization process systems (2002) -- [ c.88 ]