Rotary filter aids

In the precoat mode, filter aids allow filtration of very fine or compressible soHds from suspensions of 5% or lower soHds concentration on a rotary dmm precoat filter. This modification of the rotary dmm vacuum filter uses an advancing knife continuously to skim off the separated soHds and the... 

This type of filter can be used for removal of Penicillium and Streptomyces mycelia in the production of penicillin and streptomycin, respectively.5 In these processes the rotary drum filter is used with a pre-coated cloth filter with filter aid the filter cake is removed by a knife blade which scrapes the cake from the rotating drum. 

A fermentation broth containing Streptomyces kanamyceticus cells is filtered by a vacuum rotary filter. The feed rate is 120kg h1 each kilogram of broth contains 60g of cells. To improve filtration, filter aids are added at a rate of 10kg-h. The concentration of kanamycin in the broth is 0.05%. The filtrate is collected at a rate of 112 kg h. The concentration of kanamycin in the filtrate is 0.045%. The filter cake contains cells, and filter aid is continuously removed from the filter cloth. 

A rotary filter which operates at a fixed vacuum gives a desired rate of filtration of a slurry when rotating at 0.033 Hz. By suitable treatment of the filter cloth with a filter aid, its effective resistance is halved and the required filtration rate is now achieved at a rotational speed of 0.0167 Hz (1 rpm). If, by further treatment, it is possible to reduce the effective cloth resistance to a quarter of the original value, what rotational speed is required If the filter is now operated again at its original speed of 0.033 Hz, by what factor will the filtration rate be increased ... 

A 2-1. two-necked round-bottomed flask fitted with a mechanical stirrer and a reflux condenser is charged with 40.0 g. (0.22 mole) of p-cyanobenzenesulfonamide (Note 1), 600 ml. of 75% (v/v) formic acid, and 40 g. of Raney nickel alloy (Note 2). The stirred mixture is heated under reflux for 1 hour (Note 3). The mixture is filtered with suction through a Buchner funnel coated with a filter aid (Note 4), and the residue on the funnel is washed with two 160-ml. portions of 95% ethanol. The combined filtrates are evaporated under reduced pressure with a rotary evaporator (Note 5). The solid residue (Note 6) is heated in 400 ml. of boiling water and freed from a small amount of insoluble material by decantation through a plug of glass wool placed in a filter funnel. The filtrate is chilled in an ice bath and the precipitate is collected by filtration with miction, washed with a small amount of cold water and dried at 50°... 

The mixture is shaken vigorously, and the lower layer is separated and stored in ice. The aqueous layer is extracted with two 50-ml. portions of dichloromethane. The organic extracts are combined and shaken with 100 ml. of ice-cold, concentrated aqueous ammonia (35% w/w), and this mixture is filtered through a filter-aid cake and separated (Note 12). The extraction and filtration are repeated with fresh ammonia solution using the same filter (Note 13). The filter is washed with 50 ml. of dichloromethane, and the organic layer is separated and dried over anhydrous magnesium sulfate. The dried solution is filtered, the filter is washed with 50 ml. of dichloromethane, and the solvent is removed on a rotary evaporator at 30°. The flask containing, the residual oil after removal of the dichloromethane is cooled to 0° before exposure to air (Note 14). 

A filtered solution of Na[Mn(CO)5], prepared from 2.42g (6.21 mmol) of Mn2(CO)10 (Strem) in freshly distilled dry tetrahydrofuran (THF) (50mL),7 is treated with benzyl chloride (1.70g, 13.49mmol). The mixture is stirred for 2h at room temperature and then refluxed for lOmin. After cooling, the solution is filtered through a pad of filter aid (2cm), which is then washed with three 10-mL portions of dry diethyl ether. The solvent is then removed from the combined filtrate and washings under reduced pressure (rotary evaporator) until 5 mL remain. Silica gel (3 g, 200-325 mesh, Ajax) is then added and the... 

Whole-broth clarification Rotary vacuum drum filtration Centrifugation Crossflow MF, UF Maintains high throughput Does not require filter aids... 

Filtration. Filtration can include filter presses, rotary drum vacuum filters (RDVF), belt filters, and variations on synthetic membrane filtration equipment, such as filter cartridges, pancake filters, or plate and frame filter presses. These processes typically operate in a batch mode when the filter chamber is filled up or the vacuum drum cake is exhausted, a new batch must be started. This type of filtration is also called dead-end filtration because the only fluid flow is through the membrane itself. Due to the small size of cells and their compressible nature, typical cell cakes have low permeability and filter aids, such as diatomaceous earths, perlite, or other mined materials are added to overcome this limitation. Moreover, the presence of high solids and viscous polymeric fermentation byproducts can limit filtration fluxes without the use of filter aids. 

A mixture of the hydrolyzate with diatomaceous earth, added as a filter aid, is then filtered on rotary, vacuum, precoated filters. The filtrate is a clear, slightly yellow, sweet-tasting liquor containing about 0.1% of protein and 0.2% of ash. The rest is carbohydrate, made up of 95.0% of D-glucose, 2.0% of maltose, 1.6% of isomaltose, and 1.4% of tri- and higher saccharides. 

The crude product is dissolved in 800 ml. of hot 95% ethanol, 15.5 g. of activated carbon (Note 7) is added, and the mixture is swirled periodically while it is allowed to cool for 1 hour. The activated carbon is recovered by filtration with suction through a bed of filter aid (Note 4), the filter cake is washed with 50 ml. of 95% ethanol, and the combined filtrates are evaporated under vacuum with a rotary evaporator. The residue is dissolved in 225 ml. of boiling water, and the hot solution is decanted through glass wool placed in a filter funnel. The filtrate is cooled to 0° and the product is collected by filtration with suction, washed with a small amount of cold water, and dried in a vacuum oven at 50°. The yield of p-formylbenzenesulfon-amide is 25.6-28.0 g. (62.9-68.8%), m.p. 117-118° (Note 8). 

To minimize degradation of impurities, low-speed (1800 rpm) pumps with open impellers should be used. Where solids are large and floc-like, it may be advisable to use a recessed impeller centrifugal pump or a multistage piston pump with suitable aircushioning chambers. Reciprocating pumps should have ball valves. Gear or rotary pumps may be used where solids are not abrasive and filter aid is not present. 

RVPF (Rotary Vacuum Precoat Filter) A drum filter that is coated with a thick (up to 6 in.) precoat of filter aid, such as CELITE or equivalent. 

The solution is then filtered through a No. 3 sintered funnel containing Celite as a filter aid and the THF is removed using the rotary evaporator to give a white residue. 

Precoated rotary vacuum drum filters (Fig. 6) are used by filtering a slurry of filter aid and water first, then subsequent product filtration. Difficult filtering materials, which have a tendency to blind, are removed with a doctor blade. Precoat is removed along with the slurry to expose a new filtration surface each cycle. 

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