Vacuum filtration plants

Vacuum filtration plants consist not merely of the respective vacuum filter, but much more of a series of complementary units which only make up the effective... 

Additions of new flocculants after conventional thickening produce further dewatering of mineral slimes. A clay flocculated with polyacrylamides and rotated in a dmm can produce a growth of compact kaolin pellets (84), which can easily be wet-screened and dewatered. A device called a Dehydmm, which flocculates and pelletizes thickened sludges into round, 3-mm pellets, was developed for this purpose. Several units reported in commercial operation in Japan thicken fine refuse from coal-preparation plants. The product contains 50% moisture, compared with 3% soflds fed into the Dehydmm from the thickener underflow (85). In Poland, commercial use of the process to treat coal fines has been reported (86), and is said to compare favorably both economically and technically to thickening and vacuum filtration. 

Release protein from plant material into aqueous environment -wet milling, vacuum filtration, centrifugation... 

On cement slurry, ores and flotation concentrates the capacity will range from 200 to 1,300 lb. per 24 hr. per square foot of filter surface. Many plants will run under the smaller of these two figures through overestimation of the size of filter required, irregularities of operating, etc. Where the lower figure is reached with steady operation and giving the filter all the material it will handle and thickened as much as possible the limits of vacuum filtration for the substances mentioned have been... 

A 13.6 kg sample of corn fiber from the plant at 35% solids was mixed with 2.26 kg of deionized water to lower the solids content to 30%. The slurry was loaded into the 50 gallon reactor and hydrolyzed for 30 minutes at 140°C and 1 RPM. The reactor was vented and the hydrolyzed corn fiber was dewatered by processing with vacuum filtration through cheesecloth (Fisher Scientific, Pittsbmgh, PA). The residual hydrolyzed corn fiber was washed twice with a total of 8 gallons of 95°C water and dewatered between washings. 

Pressure filtration differs fi-om vacuum filtration in that the liquid is forced through the filter medium by a positive pressure instead of a vacuum. Among the most widely used in Che chemical process industry (and widely used in Europe for wastewater treatment) is Che filter press. As shown in Figure 3, Che filter press operates by pumping the sludge between plates that are covered with a filter cloth. The liquid seeps throu Che filter cloth leaving the solids bdiind between the plates. Whoi the spaces between the plates are filled, the treatment plant operator separates the plates and removes the solids. 

Vacuum filtration in commercial plants can be likened to the standard operation that is used in any laboratory to separate solids and liquids. In the laboratory the slurry is poured into a Buchner funnel fitted with a filter paper, over a flask that is attached to a vacuum system. The suction draws the liquid through the filter paper, which acts as a support for the crystals the crystals build up on the... 

The KDF filter was first tested in prototype on a coal mine in northern Germany. It was installed in parallel with existing vacuum filters and it produced filter cakes consistendy lower in moisture content by 5 to 7% than the vacuum filters. Two production models have been installed and operated on a coal mine in Belgium. The filter is controlled by a specially developed computer system this consists of two computers, one monitoring the function of the filter and all of the detection devices installed, and the other controlling the filtration process. The system allows optimization of the performance, automatic start-up or shut-down, and can be integrated into the control system of the whole coal washing plant. 

It is advisable to start a constant-pressure filtration test, like a comparable plant operation, at a low pressure, and smoothly increase the pressure to the desired operating level. In such cases, time and filtrate-quantity data shoulci not be taken until the constant operating pressure is reahzed. The value of r calculated from the extrapolated intercept then reflec ts the resistance of both the filter medium and that part of the cake deposited during the pressure-buildup period. When only the total mass of diy cake is measured for the tot cycle time, as is usually true in vacuum leaf tests, at least three runs of different lengths should be made to permit a rehable plot of 0/V against W. If rectification of the resulting three points is dubious, additional runs should be made. 

J. E. Troyan s series of articles on plant startup has a cause/effect table on instrumentation in Part II. This article also has troubleshooting hints for distillation, vacuum systems, heat transfer, and filtration. Here is the table on instrumentation. 

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 ... 

Whilst it may be possible to predict qualitatively the effect of the physical properties of the fluid and the solid on the filtration characteristics of a suspension, it is necessary in all cases to carry out a test on a sample before the large-scale plant can be designed. A simple vacuum filter with a filter area of 0.0065 m2 is used to obtain laboratory data, as illustrated in Figure 7.5. The information on filtration rates and specific resistance obtained in this way can be directly applied to industrial filters provided due account is taken of the compressibility of the filter cake. It cannot be stressed too... 

A third plant uses a chemical precipitation step for removing arsenic and zinc from contaminated surface water runoff. Ferric sulfate and hme are alternately added while the wastewater is vacuum-filtered and sludge is contract-hauled. The entire treatment system consists of dual-media filtration, carbon adsorption, ion exchange, chemical precipitation, and vacuum hltration. Sampling results across the entire treatment system indicated that arsenic was reduced from 6.9 to 0.2 mg/L and zinc from 0.34 to 0.11 mg/L. 

Separate the anthocyanin extract (filtrate) from insoluble plant material by filtering the slurry through a Whatman no. 1 filter paper by vacuum suction using a Buchner funnel. 

Table I shows the properties of the SRC used. This material is produced in the SRC pilot plant by filtration of the solvation reactor effluent and vacuum stripping of process solvent. It contained 93% SRC and 0.11% ASTM ash. For comparison, the ash content of the UOP-filtered SRC filter feed was 0.01%, or 0.03% based on SRC.

A new plant requires a large rotary vacuum filter for the filtration of zinc sulfite from a slurry containing 1 kg of zinc sulfite solid per 20 kg of liquid. The liquid contains water, sodium sulfite, and sodium bisulfite. The filter must handle 8000 kg of slurry per hour. What additional information is necessary to design the rotary vacuum filter How much of this information could be obtained from laboratory or pilot-plant tests Outline the method for converting the test results to the conditions applicable in the final design. 

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