Filter small-scale

The oxime is freely soluble in water and in most organic liquids. Recrystallise the crude dry product from a minimum of 60-80 petrol or (less suitably) cyclohexane for this purpose first determine approximately, by means of a small-scale test-tube experiment, the minimum proportion of the hot solvent required to dissolve the oxime from about 0-5 g. of the crude material. Then place the bulk of the crude product in a small (100 ml.) round-bottomed or conical flask fitted with a reflux water-condenser, add the required amount of the solvent and boil the mixture on a water-bath. Then turn out the gas, and quickly filter the hot mixture through a fluted filter-paper into a conical flask the sodium chloride remains on the filter, whilst the filtrate on cooling in ice-water deposits the acetoxime as colourless crystals. These, when filtered anddried (either by pressing between drying-paper or by placing in an atmospheric desiccator) have m.p. 60 . Acetoxime sublimes rather readily when exposed to the air, and rapidly when warmed or when placed in a vacuum. Hence the necessity for an atmospheric desiccator for drying purposes. 

In general, pan filters are selected for freely filtering soHds and thick filter cakes. Cake washing can be introduced easily. Most appHcations are in the mining and metallurgical industries for small-scale batch filtration. 

The scale-up of filtration centrifuges is usually done on an area basis, based on small-scale tests. Buchner funnel-type tests are not of much value here because the driving force for filtration is not only due to the static head but also due to the centrifugal forces on the Hquid in the cake. A test procedure has been described with a specially designed filter beaker to measure the intrinsic permeabiHty of the cake (7). The best test is, of course, with a small-scale model, using the actual suspension. Many manufacturers offer small laboratory models for such tests. The scale-up is most reHable if the basket diameter does not increase by a factor of more than 2.5 from the small scale. 

Dust Separation It is usuaUy necessaiy to recover the solids carried by the gas leaving the disengaging space or freeboard of the fluidized becl GeneraUy, cyclones are used to remove the major portion of these sohds (see Gas-Sohds Separation ). However, in a few cases, usuaUy on small-scale units, filters are employed without the use of cyclones to reduce the loading of solids in the gas. For high-temperature usage, either porous ceramic or sintered metal has been employed. Multiple units must be provided so that one unit can be blown back with clean gas while one or more are filtering. 

While research has developed a significant and detailed filtration theory, it is still so difficult to define a given liquid-solid system that it is both faster and more accurate to determine filter requirements by performing small-scale tests. Filtration theoiy does, however, show how the test data can best be correlated, and extrapolated when necessary, for use in scale-up calculations. 

Leaf Tests A bomb filter is used for small-scale leaf tests to simulate the performance of pressure-leaf (leaf-in-shell) filters. The equipment used is a small [50.8- by 50.8-mm (2- by 2-in)] leaf, covered with appropriate filter medium, suspended in a cell large enough to contain sufficient shiny to form the desired cake (Fig. 18-108). The shiny may be agitated gently, for example, by an air sparger. 

FIG. 18-108 Bomb filter for small-scale pressure filtration tests. [Silverhlatt etal., Cbem. Eng., 81(9), 132 (1974), hy permission.]... 

Scaling Up Test Results The results of small-scale tests are determined as dry weight of sohds or volume of filtrate per unit of area per cycle. This quantity multiplied by the number of cycles per day permits the calculation of either the filter area reqiiired for a stipulated daily capacity or the daily capacity of a specified plant filter. The scaled-up filtration area should be increased by 25 percent as a factor of uncertainty. In the calculation of cycle length, proper account must be made of the downtime of a batch filter. 

For estimating filtration rate (therefore, operating pressure and size of the filter), washing characteristics, and other important features, small-scale tests such as the leaf or pressure bomb tests described earlier are usually essential. In the conduct and interpretation of such tests, and for advice on labor requirements, maintenance schedule, and selection of accessory equipment the assistance of a dependable equipment vendor is advisable. 

More detailea descriptions of small-scale sedimentation and filtration tests are presented in other parts of this section. Interpretation of the results and their conversion into preliminary estimates of such quantities as thickener size, centrifuge capacity, filter area, sludge density, cake diyness, and wash requirements also are discussed. Both the tests and the data treatment must be in experienced hands if error is to be avoided. 

It may be purified by recrystallization from hot hydrochloric add, as recommended in Org. Syn. 3, 87, but on account of the difficulty of filtration this procedure is satisfactory on a small scale only. It is preferably distilled in 200-g. lots from a 500-cc. Claisen flask under 10-15 mm. pressure, b.p. 160-165V12 mm. It is important that no air inlet be used to prevent bumping, since under these conditions it partly sublimes and causes trouble by stopping up the connections. A filter or distilling flask is used as a receiver and only a short but wide bore (10 mm.) air condenser is necessary. This product is pale yellow and melts at 95-96°. The yield from 200 g. of crude product is 180-185 g-... 

A filter pump discharging into an aspirator, fitted with an outlet at the top for air and an outlet at the bottom for water, will give enough air for small-scale operations of glass-working. W. A. Shenstone (1889) described this device. 

Ultrafiltration processes (commonly UF or UF/DF) employ pressure driving forces of 0.2 to 1.0 MPa to drive liquid solvents (primarily water) and small solutes through membranes while retaining solutes of 10 to 1000 A diameter (roughly 300 to 1000 kDa). Commercial operation is almost exclusively run as TFF with water treatment applications run as NFF. Virus-retaining filters are on the most open end of UF and can be run as NFF or TFF. Small-scale sample preparation in dilute solutions can be run as NFF in centrifuge tubes. 

One of the more important considerations in determining the end use of synthetic graphite is its contamination with metallic components Metals such as iron, vanadium, and especially in nuclear applications, boron are deleterious to the performance of graphite Table 3 presented the extraction yields of NMP-soluble material for three bituminous coals. For these coals, mineral matter and insoluble coal residue were separated from the extract by simple filtration through 1-2 pm filter paper fable 13 lists the high-temperature ash content in the dry coal, and in their corresponding NMP-insoluble and NMP-soluble products. The reduced ash content of the extract is typically between 0.1 to 0.3 wt% using traditional filtration techniques for the small-scaled extraction experiments... 

The filtrate is collected in a filter flash of a size appropriate to the volume of the solution. The very useful filter tube (Fig. 8) in its various sizes is also employed when filtering on a small scale. Such tubes stand in a lead support or in a wooden block bored with holes of various diameters. 

A simple qualitative test of the purity of the indigo obtained can be carried out as follows A little of the material is heated for some time (with shaking) in a test tube with pyridine and some drops of the liquid are then poured on to a filter paper. If the indigotin is pure the pyridine is not coloured, whereas impurities which may be formed when working on a small scale confer on it a more or less dirty brown colour, as shown by a spot test. If it is desired to purify the whole of the indigo with pyridine, the dye is collected at the pump after boiling with the liquid, washed with pure hot pyridine, boiled once more with hydrochloric acid, collected at the pump, washed with hot water, and dried.2... 

Deo et al. [13] proposed an empirical model based on experimental results obtained with a small-scale spin-filter based bioreactor. They observed that the perfusion flux capacity, which was defined as the perfusion flux at which fouling begun to occur, was proportional to the inverse of the cell concentration and to the square of the tangential velocity at the screen surface (Eq. 21) ... 

Shock-Pass-Heat-Filter (SPHF) Sensitiviry Test (Vbl 4, p D316 with Fig 1 and p DJ99-1) Small Scale Gap Test (SSGT) (Vol 4, p D343-R D344 with Fig 35)... 

The alkali sulphates can also be made by neutralizing, say, a soln. of 5 grms. of sulphuric acid in 30 c.c. of water with the alkali hydroxide or carbonate, and evaporating the soln. until crystals begin to form. The process is not economical except on a small scale. It is used mainly for lithium, rubidium, and caesium sulphates. H. Erdmann 20 treated a hot soln. of crude rubidium iron alum with milk of lime made from purified lime, and filtered the liquid from the excess of lime, calcium sulphate, and ferric hydroxide, by suction. The small amount of lime in soln. is precipitated by adding rubidium carbonate. The filtrate is neutralized with sulphuric acid, and evaporated to the point of crystallization. 

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