Filter aids handling

Diatomaceous Earth Filtration System Design Diatomaceous Earth Filtration System Operation Diatomaceous Earth Filtration System Maintenance Types of Precoat Filters Auxiliary Parts and Equipment Bulk Filter Aid Handling... 

Filter Aids are porous powders added in small quantities to a soln or suspension to be filtered, in order to increase the efficiency of filtration. They are useful when handling suspensions of finely divided solids or of colloidal materials. The aid should not be much. heavier than die liquids to be filtered, so that it will not settle immediately but will remain in suspension for a while. Kieselguhr and paper pulp are the most widely used filter aids. Others are sawdust, charcoal, Fuller s earth, magnesia, salt, gypsum and some activated charcoals. The charcoals act as decolorizers at the same time... 

Ceramic membrane systems are achieving widespread appheation in the place of centrifuges. These systems do not require filter aid media or a separate follow-on clarification step. HoUow-fiber crossflow modules are preferred for the separation of mammalian cells, which require particularly gentle handling. They can also be used as disposable filters for perfusion and... 

In California, bulk truck shipments are available. These units are provided with self-contained unloading equipment and can be emptied into a storage silo by the driver. A manufacturer s Filtration Specialist should be available to give customers further information on bulk handling systems and on unloading bulk cars. Additional information may be obtained on request from your filter aids suppliers (6). 

Dilute materials that result in high resistance cakes are generally best handled in deep-bed filters or mixed with filter aids. 

Diatomaceous earths (DE) are the skeleton of ancient diatoms (Eigure 22.13a) mined from ancient seabeds, processed, and classified to make different grade of filter aids. Diatomaceous earth is the most commonly used filter aid today. However, the crystalline type DE is a suspicious carcinogen and inhalation needs to be avoided during handling. 

Section 7.5.4.2 discusses filter aids, washing of filter cake to remove occluded liquors, removal and handling of filter cake, and the backwashing of packed bed filters to remove and recover deposited solids. 

Brine polishing filters (Section T.5.4.2) usually employ solid filter aids, which become part of the disposal problem. Their most obvious effect is to add to the volume of solids requiring disposal. Since most filter aids are cellulosic or siliceous, again the toxic hazard is quite low. The operator handling these wastes, however, should be familiar with their detailed analyses, because trace contaminants (e.g., metals in the filter aids) may need special attention. The filtered solids are of approximately the same composition as the clarifier sludges discussed in Section 16.5.1.3. 

Health and safety aspects Handling powdered media (e.g. filter aids) can pose health and safety problems, and disposal of contaminated media may require special considerations. 

Techniques for handling sodium in commercial-scale appHcations have improved (5,23,98,101,102). Contamination by sodium oxide is kept at a minimum by completely welded constmction and inert gas-pressured transfers. Residual oxide is removed by cold traps or micrometallic filters. Special mechanical pumps or leak-free electromagnetic pumps and meters work well with clean Hquid sodium. Corrosion of stainless or carbon steel equipment is minimi2ed by keeping the oxide content low. The 8-h TWA PEL and ceiling TLV for sodium or sodium oxide or hydroxide smoke exposure is 2 mg/m. There is no defined AID for pure sodium, as even the smallest quantity ingested could potentially cause fatal injury. 

For the nitroprusside-cyanide reagent two solutions are prepared. For solution I, sodium nitroferricyanide (sodium nitroprusside, 1.5 g) is dissolved in 2M H2S04 (5mL) to which MeOH (95 mL) and NH4OH (10 mL) is added. A precipitate forms that is discarded. The clear, red solution is refrigerated. For solution II, sodium cyanide (2g) is dissolved in H20 (5 mL) and diluted with MeOH (95 mL), this is filtered if necessary. CAUTION Sodium cyanide can be absorbed through the skin and is extremely toxic. Appropriate safety precautions and first aid procedures should be adopted when handling sodium cyanide. 

An apparatus for the filtration of small to moderate quantities of crystals incorporates the so-called Willstatter filtration nail. The latter consists of a thin glass rod flattened at one end. It is readily constructed by heating the end of a short glass rod in the blowpipe flame and pressing vertically upon an asbestos board. The nail is fitted into small glass funnel it is covered by a circle of a filter paper cut with the aid of a cork borer of appropriate size. A filtration nail r r and funnel, capable of handling up to 1 g. of solid is depicted... 

The recovered oil (reported to contain less than 10% water), can be returned to the oil treating system. However, it would be wise to provide alternate handling for this oil, as the filtration aid chemical may not be compatible with the oil dehydration chemical. Suspended solids are trapped within the interstices of the sand during the filtering step When the accumulation of oil and solids causes an increase in head loss across the media of 10 psi, the media is washed either manually or automatically. 

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