Membrane plate presses

An indatable diaphragm or membrane has been used in membrane plate presses closely related to the conventional plate and frame presses. A pressure filtration period is foUowed by compression with the hydraulically operated membrane or by a hydraulically operated ram if dexible rim seals are fitted. This principle also is used in vertical presses that use either one or two endless cloth belts indexing between plates. Indatable membrane also may be used on a cylindrical filtration surface with or without a preceding pressure filtration stage. 

Other designs squee2e the cake between two permeable belts or between a screw conveyor of diminishing diameter, or pitch, and its permeable enclosure. The available filters which use mechanical compression can be classified into four principal categories, ie, membrane plate presses, tube presses, belt presses, and screw presses. 

Fig. 21. Membrane plate press, ie, recessed plate with variable chamber press.

Membrane plate presses, 11 370-372 Membrane preparation techniques, less widely used, 15 813t Membrane processes. See also Silicone membranes... 

Membrane plate and tube presses are dealt with here belt and screw presses are included in the discussion of continuous pressure filters. 

The introduction of water, or air to a lesser extent, from the backside of flexible membranes reduces chamber volume and squeezes the cake yielding a further lowering of the moisture content. The filter press may be arranged as a mixed pack of flush and membrane plates, full flush or full membrane pack depending on the application. 

A filter press with membrane plates has the following operational sequence ... 

The filter presses play a significant role in the SLS industry, where it is unnecessary to operate in a closed atmosphere. The most typical filter presses is the plate-and-frame filter press. The recessed filter press and the membrane filter press are revised, based on the plate-and-frame filter press. 

Membrane Filter Press. Membrane filter presses use impermeable, flexible membranes, or diaphragms to squeeze the cake for further cake deliquoring, as shown in Fig. 15. This type of filter provides less dead time in a filtration cycle, better washing, and drier cake compared to traditional plate-and-frame and recessed plate filter presses. A comparison of a recessed press operated at 100 psi and a membrane filter operated at 25psi for sludge dewatering is shown in Table 4. ... 

The channels, which had catalyzed electrodes on the surfaces, were covered with Nafion 112 (thickness 50 pm, equivalent weight 1,100 gmoF, ionic conductivity 0.083 S cm" ) to provide ionic conductivity between the anode and the cathode. The Nafion membrane was pressed with a glass plate to avoid solution leakage (Fig. 3.4a). Voltage-current measurements were performed at room temperature with a mass flow control system of fuel and oxidant as shown in Fig. 3.4b. The fuel and oxidant solutions were supplied to the electrodes with the micro-syringe pumps from the outlet of each channel. The flow rate of both the fuel and oxidant solutions was 80 pL miu". Composition of the fuel solution was 2M methanol solution... 

These filters are used on slurries with small amounts of solids, usually less than 0.1%, and ganerally do not form any visible cake. Solids io be removed are usually very small panicles that may be trapped on the surface of the filter medium or within the medium. This typa of filter is usually used in a polishing application where excellent quality liquids are needed as in food or beverage, pharmaceutical, and electronic processing operations. The most common clarifying fillers are disk and plate presses, cartridge filters, precoal pressure filters, deep bed filters, and membrane filters. 

Photographs of one of our STR PEM fuel cells are shown in Figure 3.4.The membrane-electrode-assembly (MEA) was pressed between two machined graphite plates press fit into Teflon blocks and sealed with a silicon rubber gasket. Gas plenums of volume Vg 0.2 cm were machined in graphite plates above a membrane area of lcm. There were several pillars matched between the two plates to apply uniform pressure to the MEA. Hydrogen... 

Figure 1.34 Typical membrane plates showing their general form during the filtration (left) and cake consolidation (right) phases of a diaphragm filter press cycle. Only one corner of each square/rectangular plate is shown.

These machines are similar in form and general operation to filter presses. However, the plate surfaces are modified by the addition of flexible diaphragms to form membrane plates. Although variants exist, feed pumping operations are generally stopped after 80 % of the required volume of filtrate has been produced. The... 

Plate, N. A., Yampolskii, Yu. P. Relationship between structure and transport properties for high free volume polymeric materials. In Paul, D. R., Yampolskii, Y. P. (Eds.) Polymeric gas separation membranes, CRC Press, Boca Raton 1994, 155. 

Sakata et al. made porons carbon membrane plates (PCMP) to separate benzene-cyclohexane azeotrope by pervaporation [9]. PCMPs were prepared from phenol resin powder (BELLPEARL S-870, Kanebo) by pressurizing the powder in a hydraulic press. The disk was heated at 300°C for 1 h in air stream and then carbonized at 800°C in nitrogen stream (A) or CO2 stream at 800°C (B) or at 850°C (C). A had only micro-pores, B had much wider pore size distribution than A and C had both micro- and meso-pores. The separation factor (benzene over cyclohexane) of 2.8 was obtained by pervaporation at 60°C. Flux of pure benzene and pure cyclohexane was 0.34 and 0.57 kg/m h, respectively. 

The main development of the filter press from the simpler versions just described has been to include an impervious elastomeric sheet in each plate compartment (one for each plate on the feed side of the filter medium, butting up against the corresponding sheet of the next plate). These flexible sheets can be inflated pneumatically so as to press down on the drained cake, once filtration is complete, and so dewater it by compression. This type of filter press is then known as the diaphragm filter press (as shown in Figure 3.72). (Initially this sheet was referred to as a membrane, and the term membrane filter press became quite confusingly well-known. 

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