Vacuum filtration continuous filters

Most continuous pressure filters available (ca 1993) have their roots in vacuum filtration technology. A rotary dmm or rotary disk vacuum filter can be adapted to pressure by enclosing it in a pressure cover however, the disadvantages of this measure are evident. The enclosure is a pressure vessel which is heavy and expensive, the progress of filtration cannot be watched, and the removal of the cake from the vessel is difficult. Other complications of this method are caused by the necessity of arranging for two or more differential pressures between the inside and outside of the filter, which requires a troublesome system of pressure regulating valves. 

There are many technical problems to be considered when developing a new commercial and viable filter. However, the filtration hardware in itself is not enough, as the control of a continuous pressure filter is much more difficult than that of its equivalents in vacuum filtration the necessary development may also include an automatic, computerized control system. This moves pressure filtration from low to medium or even high technology. Disk Filters. 

Vacuum or Pressure The vast majority of all continuous filters use vacuum to provide the driving force for filtration. However, if the feed slurry contains a highly volatile hquid phase, or if it is hot, saturated, and/or near the atmospheric pressure boiling point, the use of pressure for the driving force may be required. Pressure filtration might also be used where the required cake moisture content is lower than that obtainable with vacuum. 

Filtration separates components according to their size. Efficiency depends on the shape and compressibility of the particles, the viscosity of the liquid phase and the driving force, which is the pressure created by overpressure or by vacuum. Filtration can be performed either as dead-end filtration, where the feed stream flows perpendicular to the filter surface (Lee, 1989) or as tangential flow filtration, where the feed stream flows parallel to the filter and the filtrate diffuses across it. Examples of the former are the continuous rotaiy vacuum dram filter, where a rotaiy vacuum filter has a filter medium covering the surface of a rotating drum and the filtrate is drawn through the dram by an... 

Once the proper pH is reached, the slurry can be filtered continuously via a rotary vacuum filtration. A clear KF filtrate can be fed directly to the AQUATECH cell stack. The collected cake is a valuable byproduct. For this case the precipitate is a titanium dioxide which is easily upgraded via washing, drying, grinding and purification to the high value pigment grade Ti0-- Even in the raw form, this byproduct will draw credits of up to 30 /T. 

Assemble the filtration apparatus. Pour sample into the filter funnel and filter the water by creating a vacuum in the collection flask with a hand pump. If the filter becomes clogged with sediment, release the vacuum, replace the filter, and continue filtering. Transfer the filtrate into a preserved sample container. 

Wear breathing apparatus, eye protection, laboratory coat, and butyl rubber gloves. Cover spill with 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand.8 For each 1 mL of iron pentacarbonyl, place 45-50 mL of household bleach (about 5% sodium hypochlorite solution) in a plastic bucket equipped with a stirrer and located in a fume hood. Dilute the bleach with three times its volume of water and, to this solution, slowly add the contaminated spill mix while stirring. Continue the stirring for a period of 48 hours, and then filter the slurry using vacuum filtration. The... 

Vacuum filtration is definitely the method of choice for filtration, and it is the most common method. Vacuum filtration is superior in that suction is used to force the liquid through the filter paper allowing for rapid filtration. Precipitates can be recovered quickly and easily. After the precipitate has been recovered, it can then be vacuum dried. Vacuum drying is simply allowing suction to continue after the liquid has been removed. The suction creates an excellent airflow, which dries the collected precipitate as it flows. Ten to twenty minutes is adequate time to dry any product. 

Vacuum filtration and screen-bowl centrifuges are the principal unit operations used for mechanical dewatering of fine coal. Pressure filtration (plate and frame filter presses and continuous belt filter presses) is used to a much lesser extent to dewater fine... 

Phenyl terminated polybutadiene (M 1300 daltons, 45% vinyl) was reacted with trichlorosilane and chloroplatinic acid and then mixed with a slurry of 105 p particle size silica gel having a 250 A average pore diameter in dry toluene for 24 hours. The quantity of trichlorosilane used was 2 mol per mole of polybutadiene. Pyridine was added to remove HCl, and the slurry was gently shaken for 18 hours at ambient temperature. The surface of the silica was blocked by addition of 1,2-bis(trichlor-osilyl)ethane, and the mixture was treated with pyridine. After three hours of shaking the reaction was worked up by vacuum filtration in a sintered glass funnel and washed with toluene and methanol. The modified silica gel was dried in the filter funnel by continued application of vacuum to the filter funnel. 

FIGURE 7.7 (a) Cross section of a rotary vacuum filter (b) flow sheet for continuous vacuum filtration. 

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