Diaphragm filtering

Fig. 7. Sohds content of sludges dewatered by C, soHd bowl centrifuge VF, vacuum filter BP, belt press FP, filter press, and DFP, diaphragm filter press...

Auxiliary equipment and fittings that require seals, gaskets, diaphragms, filter media, and membranes should exclude materials that permit the possibility of extractable, shedding, and microbial activity. 

All the filters used must comply with the demands made by regulatory authorities. In sterilizable systems, hydrophobic diaphragm filters made of either polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE) with a diaphragm pore width of... 

Figure 26. Cake discharge from a diaphragm filter press.

Variable volume pressure filters and presses Diaphragm filter press 8 8 8 7 1-200 0.1-25... 

Separation is effected by filtration in a diaphragm filter press or in a continuous-belt vacuum filter (Deffense and Tirtiaux, 1982). 

Multi-element candle Multi-element leaf Plate frame press Precoat Nutsche and multielement leaf Precoat plate frame press Recessed plate filter press Sheet filter Single leaf Nutsche Bag Cartridge Dead-end membrane Fibre bed Low shear crossflow Sand bed Simplex strainer Belt press Duplex strainer High shear crossflow Rotary disc Rotary drum Sand bed Tower press Diaphragm filter press Expression (screw) press Horizontal element tube press Vertical diaphragm filter press Vertical element tube press... 

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.

Figure 1.36 Schematic and photograph (Larox), of the vertical diaphragm filter press. A more detailed schematic of the diaphragm press filter cycle is shown in Figure 6.4.

DIAPHRAGM FILTER PRESS (nhrstioniWaahing/deliquoring) Schematic mjjM... 

Vertical diaphragm filter press - single and double-sided Y Y Y... 

The calculations presented in this section illustrate the level of detail that can be achieved when appropriate design equations and procedures are used to predict the performance of batch filters. Although the examples of the diaphragm filter press and the pressure Nutsche filter have been chosen for illustrative purposes, the methodologies can be readily adapted with the aid of the equations shown in Section 6.2 to analyse the performance of most other filters. 

Table 6.3 Pump characteristics for the diaphragm filter press calculation (Example 6.1).

Figure 6.12 Mass balance representation of the diaphragm filter press cycle (from FDS). The values shown for filtrate include the masses of liquid and solute produced during the gas deliquoring phase.

The dispersion model is again used to model the washing phase in the cycle. The initial step, i.e. the calculation of the dispersion number (D ), follows the procedure shown for the diaphragm filter press in Section 6.4.1. 

The calculations presented in Sections 6.4.1 and 6.4.2 illustrate the degree to which the operation of a filter can be predicted from the knowledge of suspension and cake properties as well as basic operational parameters. Simulations develop these procedures to allow the performance of batch filters to be investigated over a wide range of process conditions without the need to perform costly sequences of experiments. While any of the filters shown in Table 6.1 can be simulated with the aid of the equations and procedures presented throughout this chapter, the diaphragm filter press cycle considered in Section 6.4.1 is chosen to illustrate the process. 

Figure 6.1 6 Variation of the total cake thickness during the operating cycle of a diaphragm filter press where the mass of solids per batch is a constant. The legends indicate the maximum thickness of cake on each cloth during filtration with the pump and the chamber thickness is 80 mm.

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