ROTARY VACUUM DRUM FILTER

Rotary drum filter, vacuum, c/s with swing agitator, panel or wire-wound drum, wash apparatus, variable speed drum drive, trunions, stuffing boxes, scraper discharge, motor and drive excluding vacuum system and vacuum receiver. FOB cost = 210000 for a total drum, nDL, area = 22 m with n = 0.25 for the range 2-22 and n = 0.7 for the range 22-200. FOB cost = 210 000 for an effective filter area =... 

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 ). 

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. 

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. 

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

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... 

A rotary drum filter 6 ft in diameter and 8 ft long is to be used to filter a slurry. The drum rotates at 0.5 rpm, and one-third of the drum s surface is submerged in the slurry. A vacuum is drawn in the drum so that a constant pressure drop of 10 psi is maintained across the drum and filter cake. You test the slurry in the lab by pumping it at a constant filtrate rate of 20 gpm through 1 ft2 of the drum filter screen and find that after 1 min the pressure drop is 8 psi and after 3 min the pressure drop is 12 psi. How long will it take to filter 100,000 gal of filtrate from the slurry using the rotary drum ... 

A slurry is being filtered at a net rate of 10,000 gal/day by a plate and frame filter with 15 frames, with an active filtering area of 1.5 ft2 per frame, fed by a positive displacement pump. The pressure drop varies from 2 psi at start-up to 25 psi after 10 min, at which time it is shut down for cleanup. It takes 10 min to disassemble, clean out, and reassemble the filter. Your boss decides that it would be more economical to replace this filter with a rotary drum filter using the same filter medium. The rotary filter operates at a vacuum of 200 mmHg with 30% of its surface submerged and rotates at a rate of 5 min/rev. If the drum length is equal to its diameter, how big should it be ... 

A slurry is to be filtered with a rotary drum filter that is 5 ft in diameter and 8 ft long, rotates once every 10 s, and has 20% of its surface immersed in the slurry. The drum operates with a vacuum of 20 in.Hg. A lab test was run on a sample of the slurry using 1/4 ft2 of the filter medium at a constant flow rate of 40 cm3/s. After 20 s the pressure drop was 30 psi across the lab filter, and after 40 s it was 35 psi. How many gallons of filtrate can be filtered per day in the rotary drum ... 

A rotary drum filter is to be installed in your plant. You run a lab test on the slurry to be filtered using a 0.1 ft2 sample of the filter medium at a constant pressure drop of 10 psi After 1 min you find that 500 cm3 of filtrate has passed through the filter, and after 2 min the filtrate volume is 715 cm3. If the rotary drum filter operates under a vacuum of 25 in.Hg with 25% of its surface submerged, determine ... 

You want to filter an aqueous slurry using a rotary drum filter, at a total rate (of filtrate) of 10,000 gal/day. The drum rotates at a rate of 0.2 rpm, with 25% of the drum surface submerged in the slurry, at a vacuum of 10 psi. The properties of the slurry are determined from a lab test using a Buchner funnel under a vacuum of 500 mmHg, using a 100 cm2 sample of the filter medium and the slurry, which resulted in the lab data given below. Determine the total filter area of the rotary drum required for this job. 

A slurry containing 50 per cent by mass of solids of density 2600 kg/m3 is to be filtered on a rotary drum filter, 2.25 m in diameter and 2.5 m long, which operates with 35 per cent of its surface immersed in the slurry and under a vacuum of 600 mm Hg. A laboratory test on a sample of the slurry, using a leaf filter with an area of 100 cm2 and covered with a cloth similar to that used on the drum, produced 220 cm3 of filtrate in the first minute and 120 cm3 of filtrate in the next minute when the leaf was under a vacuum of 550 mm Hg. The bulk density of the wet cake was 1600 kg/m3 and the density of the filtrate was 1000 kg/m3. 

Because of its versatility and simplicity, one of the most widely used vacuum filters is the rotary drum filter and a filter of this type was patented in England in 1872 by William and James Hart. The basic design varies with different manufacturers, although essentially all drum type vacuum filters may be divided into two categories ... 

In commercial operations of the dewaxing step, the mixture of wax-bearing oil and solvent is heated to ensure complete solution of the wax and is then passed through exchangers and chillers to totally enclosed rotary drum filters at a temperature about 10° to 15° F. below the desired pour point of the dewaxed oil. Vacuum for filtration is applied to the filtrate receiving vessel. The wax cake on the filter is washed with cold solvent, to remove the occluded oil-solvent solution. Sulfur dioxide superheated gas is used for stripping the solvent from the oil-solution and the wax phase, and the last traces of solvent are removed under vacuum. 

A wide variety of filters are available for the cell recovery. There are generally two major types of filters pressure and vacuum filters. The detailed descriptions of those filter units can be found in Chemical Engineers Handbook (Perry and Chilton, 1973). The two types of filters most used for cell recovery are the filter press and rotary drum filters. A filter press is often employed for the small-scale separation of bacteria and fungi from broths. For large-scale filtration, rotary drum filters are usually used. A common filter medium is the cloth filter made of canvas, wool, synthetic fabrics, metal, or glass fiber. 

Rotary Drum Filters (Usually Vacuum Operation)... 

To obtain a formula for sizing a rotary-drum filter, the mechanism of liquid flow through a porous medium must be considered. As the filter drum rotates through the slurry tank, a porous solid deposits on the surface of the drum, increasing the resistance to liquid flow. The surface of the filter cake is at atmospheric pressure. If it is assumed that the pressure downstream of the filter medium is constant (created by a vacuum pump), then the pressure drop across the filter cake and medium is constant. As the filter cake thickens, the liquid flow rate decreases because of the increasing resistance to flow. 

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