Pressure filtration alternative

Alternative 2 consists of preliminary treatment followed by dual-media pressure filtration, and two-stage air stripping (Figure 8.4). The preliminary treatment step for iron removal would be exactly the same as specified under Alternative 1. The filters would be recommended to remove suspended matter and particulate iron prior to the air strippers. The required filtration capacity could be provided with either a duplex system of two 60-in.-diameter filters or a triplex system of three 42-in-diameter filters. 

Solvent solubility is widely used to classify coal-derived products (1.,2). The most popular methods are based on some form of Soxhlet extraction. Methods involving Soxhlet extraction are normally time consuming thus complete solvent solubility classification is laborious. An alternate method, used initially by Bertolacini et al. (3.) and modified for our use, employs pressure filtration. Pressure filtrations carried out at room temperature have been used to classify a number of coal-derived products obtained under a variety of liquefaction conditions. 

Soxhlet and the pressure-filtration extraction values obtained with coal-derived products from low-temperature reactions necessitated the development of an alternate pressure-filtration procedure. If cyclohexane cannot swell and penetrate the unreacted coal in the reacted slurry adequately> then THF can be used to swell and penetrate the unreacted coal. All the THF soluble material (vdiich includes the cyclohexane soluble vehicle) can then be efficiently extracted and separated from the unreacted coal matrix. 

The zinc-containing ferredoxin fraction, recognized by the brown color, is diluted twofold with distilled water. This is applied onto a Bio-Rad (Hercules, CA) hydroxylapatite HTP column (equilibrated with Milli-Q water), is equilibrated with Milli-Q-purified distilled water, and is eluted by 2 mM potassium phosphate buffer, pH 6.8 (alternatively, a Toyopearl HW-55C hydrophobic column chromatography (Tosoh Corp, Japan) may be used at this step ). Finally, the pooled fraction is concentrated by pressure filtration through an Amicon (Danvers, MA) YM3 membrane, and passed through a preparative Sephadex G-50 gel filtration column (2.5 X 75 cm Amersham Pharmacia Biotech) equilibrated with 80 mM potassium phosphate buffer, pH 6.8. 

The driving force for filtration in pressure filters is usually the liquid pressure developed by pumping or by the force of gas pressure in the suspension feed vessel. Alternatively, or in addition, the liquid may be squeezed through and out of the cake by the mechanical action of an inflatable membrane, a piston or a porous medium pressed on top of the cake. Pressure filtration is, therefore, defined here as any means of surface filtration where the liquid is driven through the medium by either hydraulic or mechanical pressure, greater than atmospheric. The solids are deposited on top of the filter medium (as in all surface filters), with the possible exception of some cartridge filters which also use a certain amount of depth filtration. In this chapter, the suspension is assumed to approach the medium at 90° and this excludes the so-called dynamic fUter/thickeners or cross-flow filters (also driven by pressure) which are dealt with in a separate chapter (11). 

Apart from the hyperbar vacuum filtration, the work at Karlsruhe also includes fundamental investigations into cake filtration generally, pressure filtration of coal and ore suspensions, and studies of dewatering of cakes. As an alternative to the small drum filter, they have apparently also used a small belt filter in the same pressure vessel. Some commercial developments, like the KHD pressure filter, are reported to have originated from the work at Karlsruhe. 

If the vacuum tests are not successfiil because the rate is too slow or, if the tests are successful but the equipment for vacuum filtration would be too large or too costly, or simply because filtration is not achieved, then one has to look at four possible alternatives. These are a bottom feed vacuum filter with precoating flocculating the feed or adding body feed, either for bottom feed or top feed vacuum filters or pressure filtration in all its ramifications, either with or without flocculation or body feed. In certain cases one can even look at precoating pressure filters. In this respect, of course, pressure filters can equally well be centrifugal filters, or compression filters. 

The alternative pillow test was originated by Tom Stephens of Ten Cate in about 2005 (Ten Cate Geosynthetics, Inc., 2007) and formalized as a standard in 2009 (GRTGT15). The only related references in the open literature are the work of Professor Bhatia and her students at Syracuse University, who developed and conducted research on a similar test which they called the pressure filtration test (Bhatia and Liao, 2004 Satyamurthy et al., 2008, 2009). Hydraulic pressures were measured and quantitative data were produced but the laboratory configuration was different from the field-simulated pillow test, which is described subsequently. 

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. 

Pressure filters are worth noting. These are usually set up in the form of steel cylinders positioned vertically. Another variation consists of using horizontal filtration groups. This has the drawback that the surface loading is variable in the different layers of the filter bed moreover, it increases with greater penetration in the filter bed (the infiltration velocity is lowest at the level of the horizontal diameter of the cylinder). The filter bottom usually consists of a number of screens or mesh sieves that decrease in size from top to bottom or, as an alternative, perforated plates supporting gravel similar to that used in the filter bottoms of an open filter system. 

Hydroxy-B-homo-5a-cholestan-7-one acetate (54b) A solution of 3/3-hydroxy-5a-cholestan-7-one acetate (51b 5 g mp 146-148°) in dioxane-ethanol (100 ml, 1 1) is placed in a 250 ml three-necked flask equipped with a mechanical stirrer and thermometer and is cooled to 0° (iee-salt bath). Powdered potassium cyanide (7.3 g) is added portionwise with stirring. Acetic acid (8 ml) is then added dropwise with constant stirring over 30 min. The resultant mixture is stirred for 1 hr at 0° C and for an additional 2 hr at room temperature. It is then poured into ice water (200 g ice, 100 ml water) and after standing for 1 hr the precipitate is collected by filtration. The product is dissolved in ether (100 ml), the ether solution is washed with 5% sodium bicarbonate, water and dried over anhydrous sodium sulfate. The filtrate is evaporated at reduced pressure and the solid residue (5.1 g) is crystallized from ethyl acetate (30 ml) to yield 2.8 g of cyanohydrin (52b) mp 160-164° repeated crystallization from the same solvent gives a product mp 164-167°. An alternative method of isolation of the cyanohydrin is used when 100 g or larger quantities are worked up. The reaction mixture is poured directly into a mixture of ice water and sodium bicarbonate, the precipitate (mp 155-156°) is washed well with water, dried and used directly for the next step. 

Filtration. The API filtration test for oil-base muds usually gives an all-oil filtrate. The test may not indicate downhole filtration, especially in viscous oils. The alternative high-temperature-high-pressure (HT-HP) filtration test will generally indicate a pending mud problem by amount of fluid loss or water in the filtrate. 

Pressure filters or filter presses are commonly of the batch type, and are characterized by smaller floor area, high filtration rates, and lower capital cost. Dryer cakes are produced. The chemical industry uses these filters more widely than mineral processing industries, mainly because of its batch operation. The most common types of pressure filters used are the plate and frame presses. These comprise a series of vertical, alternating parallel frames and plates, with the filter cloth being held against the plate and the formation of cake occurring in the hollow frame. 

Once the two salts are mixed in solution (acetone is a common solvent for this), the sodium chloride precipitates and is removed by filtration. The solvent is then removed under reduced pressure and, since salts have no vapour pressure, the ionic liquid remains in the flask. The problem with this reaction is that it is almost impossible to remove the last traces of chloride ions. The chloride not only influences the physical properties of the liquid such as melting point and viscosity, but is also a good nucleophile and can deactivate catalysts and affect reproducibility. A great deal of effort has been directed towards removal of the chloride contamination, including washes and chromatography, but none have proved to be completely effective [9], This has led to the development of some alternative synthetic routes. Simply exchanging Na[BF4]... 

For synthesis on a larger scale, it has been found that the workup described by Hart et al is impractical, and an alternative has been published.27 This differs in that aryl halide by-products are removed by distillation under reduced pressure. The residue is then refluxed in EtOH, and filtration effects the recovery of crude halogenated terphenyl product. Sublimation under reduced pressure affords the pure product in up to 75% yield. 

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