Rotary drum

Rotary Drum Filters The rotaiy drum filter is the most widely used of the continuous filters. There are many design variations, including operation as either a pressure filter or a vacuum filter. The major difference between designs is in the technique for cake discharge, to be discussed later. All the alternatives are characterized by a horizontal-axis drum covered on the cylindrical portion by filter medium over a grid support structure to allow drainage to manifolds. Basic materials of construc tion may be metals or plastics. Sizes (in terms of filter areas) range from 0.37 to 186 m (4 to 2000 ft ). 

FIG. 18-122 Schematic of a rotary-drum vacuum filter with scraper discharge, showing operating zones. (Schweitzer, Handbook of Separation Techniques for Chemical Engineers, p. 4-38. Copqtight 1979 hq McGraw-Hill, Inc. Used with permission of McGraw-Hill Inc.)... 

Ammonium sulfate is produced as a caprolactam by-product from the petrochemical industry, as a coke by-product, and synthetically through reaction of ammonia with sulfuric acid. Only the third process is covered in our discussion. The reaction between anunonia and sulfuric acid produces an ammonium sulfate solution that is continuously circulated through an evaporator to thicken the solution and to produce ammonium sulfate crystals. The crystals are separated from the liquor in a centrifuge, and the liquor is returned to the evaporator. The crystals are fed either to a fluidized bed or to a rotary drum dryer and are screened before bagging or bulk loading. 

One of the oldest filters applied throughout the chemical processing industry is the rotary vacuum drum filter, which is illustrated in Figure 8. This machine belongs to the group of bottom feed configurations. Rotary drum filters are typically operated in the countercurrent mode of operation. The principle advantage of these machines is the continuity of their operation. 

Figure 13. Cycle sequence of a rotary drum filter.

Internal Rotary-Drum Filters An example of an internal rotary-drum filter is illustrated in Figure 14. The filter medium is contained on the inner periphery. This design is ideal for rapidly settling slurries that do not require a high degree of washing. Tankless filters of this design consist of multiple-compartment drum vacuum filters. 

Disk Filters Disk filters consist of a number of concentric disks mounted on a horizontal rotary shaft. The operating principle is the same as that of rotary-drum vacuum filters. The basic design is illustrated in Figure 22. The disks are formed by using V-shaped hollow sectors assembled radially about a central shaft. Each sector is covered with filter cloth and has an outlet nipple coimected to a manifold... 

In precoating, the prime objective is to prevent the filter medium from fouling. The volume of initial precoat normally applied should be 25 to 50 times greater than that necessary to fill the filter and connecting lines. This amounts to about 5-10 lb/100 fF of filter area, which typically results in a 1/16-in. to 1/8-in. precoat layer over the outer surface of the filter medium. An exception to this rule is in the precoating of continuous rotary drum filters where a 2-in. to 4-in. cake is deposited before filtration. The recommended application method is to mix the precoat material with clear liquor (which may consist of a portion of the filtrate). This mixture should be recycled until all the precoat has been deposited onto the filter medium. The... 

For a 50,000 GPD filtration operation with an average loading 50 mg/L TSS (Total Suspended Solids) determine the optimum flocculant to use in order to achieve at least an 85 % reduction in solids. Assume that a rotary drum filter unit is used. 

From the viewpoint of accommodation to the filter-supporting structure, some cloths cannot be used, even though the filtering characteristics are excellent. For rotary drum filters, for example, the cloth is pressed onto the drum by the caulking method, which uses cords that pass over the drum. In this case, the closely woven cloths manufactured from monofilament polyethylene or polypropylene fiber are less desirable than more flexible cloths of polyfilament fibers or staple cloths. 

Agitated/Monoplate Nutsche Filter/Dryer Horizontal Plate Filter/Dryer Continuous Equipment Rotary Drum Filter Centrifugal Filter Horizontal Belt Filter... 

The resistance of the filter medium is negligible. Determine the filter s capacity in filtrate and the velocity of the belt. To solve this problem take a look at the design criteria for a rotary drum filter - they are very similar. 

A rotary drum vacuum filter is fed with 8.5 m /hr of a suspension containing 17.6% solids by weight. The final wetness of the cake must be 34%. The... 

Rotations-achse, /. axis of rotation, -bewe-guug, /. rotational motion, rotary motion, -druck, m. rotary printing, -filter, n. rotary drum filter. 

Other important separation techniques such as pressure-leaf filtration, centrifugation, rotary drum filtration and others all require technology very specific to the equipment and cannot be generalized in many instances. 

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. 

Sugars are estimated with reducing DNS reagent, based on the colorimetric method developed in an earlier module. Die samples are determined by colour developed, which is detected by a spectrophotometer at a wavelength of 540 nm. In large-scale operations, mycelia are separated by a rotary drum filter. 

For finely ground ores and minerals, rotary drum filtration rates may be 1500 lb/(day)(sqft), at 20 rev/hr and 18-25 In. Hg vacuum. 

Rotary drum filters (usually vacuum operation) (Figure 10.13)... 

For effective volatilization using an enclosed mechanical aeration system, contaminated soil is mixed in a pug mill or rotary drum. The gasoline components are released from the soil matrix by the churning action of the air/soil contact. The induced airflow within the chamber captures the gasoline emissions and passes them through an air pollution control device (e.g., a water scrubber or vapor-phase carbon adsorption system) before they are discharged through a properly sized stack. 

Filters are used only at specific places in the purification of water. Sand filters are used as a final polishing step or prior to a membrane or ion-exchange process, and vacuum rotary-drum filters are used for dewatering sludges. 

A vacuum rotary-drum filter consists of a porous septum that surrounds an empty rotating drum. The bottom of the drum is immersed in the sludge liquor. A vacuum pulled on the inside of the drum causes the water to enter the drum through the filter medium. The solids that cannot pass through are retained on the surface of the medium. As the drum rotates, the solids at the surface of the septum are lifted out of... 

Fig. 16-5). Here the filter medium is attached to a continuous belt instead of directly to the drum. The belt, after leaving the rotary drum, makes some abrupt changes in direction, which loosens and discharges the cake. The septum is then washed from both sides with water52 to remove any remaining material. This wash often is charged to the filter. 

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