Basket

Typical uses Recovery and concentration of solid sludges. 

Typical particle size and feed concentration range 0.1-100 pm and 5% w/w. 

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The cryptophane is typical of the chiral resolution of methane derivatives (eg, CHFClBr) (146) and the basket-shaped host of Figure 23d exhibits extremely high enantioselectivity for various peptides (144). 

The centrifuge is a horizontal basket designed to operate so that the cake formed on the screen is pushed as an increment from the loading end of the basket to the discharge end by a pusher plate operating on a timed cycle. On completion, the nitrocellulose cake is discharged into water in a slurry tub on a lower floor, and purified by conventional procedures. 

Fixed-Bed Centrifuges. The simplest of the fixed-bed centrifuges is the perforated basket centrifuge (Fig. 31) which has a vertical axis, a closed bottom, and a Hp or overflow dam at the top end. Some domestic machines of this type are ia use for straining vegetable or fmit juices. Ia the iadustrial versioas, the basket housiag is oftea supported by a three-point suspeasioa called the three-column centrifuge. 

The plough cannot be allowed to reach too close to the cloth and some residual cake remains. Where this is not acceptable, the cake may be removed by a pneumatic system, by vacuum, or by reslurrying. The cycle can be automated and controlled by timers. The maximum speeds of basket centrifuges vary from 800 to 1500 rpm, and basket diameters are in the range from 10 to 1400 mm. A 1200-mm diameter, 750-mm long basket may handle as much as 200 kg of cake in one charge. 

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. 

In some cases, particularly with iaactive metals, electrolytic cells are the primary method of manufacture of the fluoroborate solution. The manufacture of Sn, Pb, Cu, and Ni fluoroborates by electrolytic dissolution (87,88) is patented. A typical cell for continous production consists of a polyethylene-lined tank with tin anodes at the bottom and a mercury pool (ia a porous basket) cathode near the top (88). Pluoroboric acid is added to the cell and electrolysis is begun. As tin fluoroborate is generated, differences ia specific gravity cause the product to layer at the bottom of the cell. When the desired concentration is reached ia this layer, the heavy solution is drawn from the bottom and fresh HBP is added to the top of the cell continuously. The direct reaction of tin with HBP is slow but can be accelerated by passiag air or oxygen through the solution (89). The stannic fluoroborate is reduced by reaction with mossy tin under an iaert atmosphere. In earlier procedures, HBP reacted with hydrated stannous oxide. 

The electrolyte is prepared by dipping granulated lead, suspended in a basket, into and out of the fluosUicic acid. The lead oxidizes during the operation and lead fluosUicate is formed ... 

Fuel Dissolution. In the American and British plants, LWR fuel pieces typically fall directly from the shear into a dissolver basket, which fits inside the dissolver vessel. A soluble poison such as gadolinium is added to the nitric acid to prevent criticahty. The massive end fittings are sometimes separated from the fuel pieces before the latter enter the dissolver. The French have installed continuous rotary dissolvers in the UP3 and UP2-800 plants at La Hague. The units each consist of a dmm rotating within a geometrically favorable slab tank (13). 

The NFS shear successfully processed irradiated LWR fuel between 1966 and 1972. Among the lessons learned were that the chute that channeled sheared fuel pieces to the dissolver basket was susceptible to bridging, the gag drives required a disproportionate amount of maintenance, and insufficient throat clearance led to jamming of chopped fuel. 

Pubhc concerns about pesticides in the diet of infants and children resulted in an expert committee convened by the U.S. National Academy of Sciences which devoted four years to the review of all available data. A consensus report was issued in 1993 (80). A number of recommendations for further work to more precisely define what constitutes the diet of infants and children were made. No risk could be estimated. The residue data reviewed by the panel were mainly from monitoring studies conducted by the PDA using multiresidue methods to analyze fresh produce and market basket samples collected from various geographic areas (81,82). These and other rehable scientific studies have demonstrated that relatively few food samples contain detectable residues. Most residues are far below estabhshed tolerances which are set above the maximum residue found in treated raw agricultural... 

Fig. 17. (a) Kellogg vertical quench converter (b) Ammonia Casale converter basket modification. 

The Imperforate Bowl Centrifuge. In an imperforate bowl centrifuge the dow of the continuous Hquid phase is nominally axial, except for areas immediately adjacent to the feed inlet and efduent oudet. Tubular soHd-bowl basket and imperforate bowl conveyor-discharge centrifuges satisfy this definition. 

Fig. 2. Sepaiation in a basket 01 tubulai centrifuge, where X is the initial position. Other terms are defined in the text.

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