Internal filtration

R. Reidy, Profde of the International Filtration and Separation Industry, Elsevier, Oxford, 1993. 

In operating a pressure leaf filter, the sludge is fed under pressure from the bottom and equally distributed. The clear filtrate from each leaf is collected in a common manifold and carried away. In filters with an external filtrate manifold (refer to the sketch in Figure 12), the filtrate from each leaf is visible through a respective sightglass. This is not possible when the leaves are mounted on a hollow shaft that serves as an internal filtrate collecting manifold. Tlie filter cakes are built on each side... 

Park, B. G., Lee, W. G., Chang, Y. K., Chang, H. N. (1997). Effects of periodic backflushing with filtrate on filtration performance in an internal-filtration bioreactor. Bioprocess Engineering, 16, 253—256. 

If the reaction products absorb light at the wavelength being used, then the quantum yield will decrease as the reaction proceeds because reactants are not absorbing all the light. This is called internal filtration. To minimize the problem, only the initial stages of the photochemical process are studied. 

Dr Stein has eight patents to his name and has held the Presidency of the South Texas Chapter of the International Filtration Society. His interests include math and science tutoring, guitar playing and building and repairing personal computers. He is married to Doris and has 3 children and 2 grandchildren. 

While current therapy is believed to be effective in the clearance of small solutes such as urea, improved removal of middle molecules and protein-bound solutes is desirable. Henderson et al. (2001) point to the importance of quantifying the removal of larger toxic solutes in the fight of increasing evidence that shows a positive correlation between survival and middle molecule clearance in hemodialysis patients. A number of studies are underway to enhance the removal of middle molecules. These studies include (1) variations in modes of dialysis, (2) changes in dialyzer design to improve internal filtration, (3) targeted removal of specific molecules, and (4) increased frequency of dialysis. 

Fujimura, T., Uchi, Y., Fukuda, M., Miyazaki, M., Uezumi, S., and Hiyoshi, T. (2004). Development of a dialyzer with enhanced internal filtration to increase the clearance of low molecular weight proteins. J. Artif. Organs 7, 149. 

Ronco, C., Orlandini, G., Brendolan, A., Lupi, A., and La Greca, G. (1998). Enhancement of convective transport by internal filtration in a modified experimental hemodialyzer Technical note. Kidney Int. 54, 979. 

Sato, Y., Mineshima, M., Ishimori, I., Kaneko, I., Akiba, T., and Teraoka, S. (2003). Effect of hollow fiber length on solute removal and quantification of internal filtration rate by Doppler ultrasound. Int. J. Artif. Organs 26, 129. 

A filter that resembles a candle filter is the Cricket filter (from Amafilter), which is so-named because the elements, rather than being cylindrical, are flattened so as to resemble a cricket bat in shape. Each element was suspended from a filtrate collection manifold to which was connected an internal filtrate pipe rising from the bottom of the element. The small volume of each element and the flat surface ensmed complete cake removal during blow-back. 

Hannon, D. and B. Damin (1993), New diesel low temperature operability. AGELFl filtration test . CEC 4th International Symposium, Birmingham. 

After heating to 50 °C in a water bath, the sample was cooled to below room temperature and filtered. The residue was washed with two 5-mL portions of CCI4, and the combined filtrates were collected in a 25-mL volumetric flask. After adding 2.00 mL of the internal standard solution, the contents of the flask were diluted to volume with CCI4. Analysis of an approximately 2- tL sample gave LfD signals of f3.5 for the terpene hydrate and 24.9 for the camphor. Report the %w/w camphor in the analgesic ointment. 

Filtered valves contain a fine internal filter, typically below the body orifice. This filter prevents clogging by the debris sometimes found in product and package. The use of filtration is recommended with any valve systems containing body, stem, or actuator orifices of 0.25-mm (or smaller) diameter unless exceptional care is taken in the cleaning of product and package components. Valves containing these small orifices are used for products propelled by compressed gas. 

No internal piping and no conventional filter valve are needed with single-cell dmm filters where the entire dmm also operates under vacuum. The cake discharge is effected by air blowback from an internal stationary shoe mounted inside the dmm at the point of discharge. There are very close tolerances between the inside surface of the dmm and the shoe in order to minimize the leakage. The inside of the dmm acts as a receiver for the separation of air and filtrate conventional multicompartment dmm filters require a separate external receiver. This type of filter permits operation of the filter with thin cakes so that high dmm speeds, up to 26 rpm, can be used and high capacities can be achieved. Sizes up to 14 m are available. 

Mechanical Cake Removal. This method is used in the American version of the dynamic filter described under cross-flow filtration with rotating elements, where turbine-type rotors are used to limit the cake thickness at low speeds. The Exxflow filter, introduced in the United Kingdom, is described in more detail under cross-flow filtration in porous pipes. It uses, among other means, a roUer cleaning system which periodically roUs over a curtain of flexible pipes and dislodges any cake on the inside of the pipes. The cake is then flushed out of the curtain by the internal flow. 

Membrane filtration has been used in the laboratory for over a century. The earliest membranes were homogeneous stmctures of purified coUagen or 2ein. The first synthetic membranes were nitrocellulose (collodion) cast from ether in the 1850s. By the early 1900s, standard graded nitrocellulose membranes were commercially available (1). Their utihty was limited to laboratory research because of low transport rates and susceptibiUty to internal plugging. They did, however, serve a useflil role in the separation and purification of coUoids, proteins, blood sera, enzymes, toxins, bacteria, and vimses (2). 

Booker Morey, Ph.D., Senior Consultant, SRI International Member, Society of Mining, Metallurgy and Exploration (SME of AIME), The Filtration Society, Air and Waste Management Association Registered Professional Engineer (California and Massachusetts) (Section 18, Liquid-Solid Operations and Equipment)... 

Feed Slurry Temperature Temperature can be both an aid and a limitation. As temperature of the feed slurry is increased, the viscosity of the hquid phase is decreased, causing an increase in filtration rate and a decrease in cake moisture content. The limit to the benefits of increased temperature occurs when the vapor pressure of the hquid phase starts to materially reduce the allowable vacuum. If the hquid phase is permitted to flash within the filter internals, various undesired resiilts may ensue disruption in cake formation adjacent to the medium, scale deposit on the filter internals, a sharp rise in pressure drop within the filter drainage passages due to increased vapor flow, or decreased vacuum pump capacity. In most cases, the vacuum system should be designed so that the liquid phase does not boil. 

All drum filters (except the single-compartment filter) utilize a rotary-valve arrangement in the drum-axis support trunnion to facih-tate removal of filtrate and wash hquid and to allow introduction of air or gas for cake blowback if needed. The valve controls the relative duration of each cycle as well as providing dead portions of the cycle through the use of bridge blocks. A typical valve design is shown in Fig. 18-121. Internal piping manifolds connect the valve with various sections of the drum. 

Pressure build-up Provide adequate venting and dust filtration on downstream of receiving vessel vent mill (risk of com-, Where liquefied gas (nitrogen or CO9 ) is used ponent failure, ensure adequate vent sizing and limit particularly in gas liquefied gas feed-rate to mill conveying systems). Internal pressure may also force product out of the mill. CCPS G-11 CCPS G-22 CCPS G-23 CCPS G-29... 

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