Filter press cell

Fig. 4. Types of ElectroCell Systems AB modular filter press cells commerically available...

The filter press cell is composed of a series of iron ates, which are recessed on either side as shown in the ag am, from which it will be seen that, if two of these ates are put together, a space will be enclosed by them f virtue of the recess... 

The simplest kind of cell construction, shown in Figure 19.19(d), suffices for the production of hydrogen by electrolysis of water and for the recovery of chlorine from waste HC1. The term filter-press cell is applied to this kind of equipment because of the layered construction. These two electrolyses are economically feasible under some conditions. Some details are given by Hine (1985). 

Bipolar electrodes are suspended or inserted into an oblong vessel of rectangular cross section or arranged to form the so called filter press cell. The first method is used mainly for the electrolytical refining of metals where the crude... 

A transfer of this definition of the cross-flow term to the chemical reactor field implies that the so-called cell reactor [26], consisting of thin, porous catalyst plates mounted in a rack like a filter press, should also be of interest to describe here. The same may apply to the great number of different electrochemical filter-press cell reactors [27]. It may be noted that the cell reactor principle is, however, not valid for the so-called parallel-passage reactor [28,29]. In this case the same fluid flows on both sides of the catalyst plates without any need for communication and exchange between the fluids through the plates. The advantage of this reactor is its being dust-proof, since dust present... 

The three kinds of reactors already described in this section are all traditional cross-flow reactors with permeable plates or membranes. The electrochemical filter-press cell reactors used, e.g., for electrosynthesis, are equipped with cation-selective membranes to prevent mixing of the anolyte and the catholyte. These cell reactors are therefore good examples of the extended type of cross-flow reactors according to the definition transferred from the filtration field. The application of the electrochemical filter-press cell reactor technique... 

It should also be observed that the catalytic cell reactor (described in Section II.D), which is intended to be an alternative reactor to trickle beds for liquid-phase hydrogenations, is a further-developed electrochemical filter-press cell based on the firm Electro Cell AB s concept with respect to the preparation of thin, porous electrodes. 

Divided Flow Cells. Filter press (plate and frame) (Fig. 6) cells may be used with and without diaphragm this type of cell is treated in Chapter 31. Filter press cells for laboratory-scale work are now available commercially. It might be pointed out that when commercializing a process is a possibility, it might save time to switch early to a cell type akin to those usually employed in large-scale operations. 

It has been recommended that one reduce nitromethane to methylhydroxylamine in dilute hydrochloric acid at constant current in a divided filter press cell with a nickel, stainless steel, or Monel 400 cathode unreacted nitromethane was distilled off and the water removed at 30mmHg at t < 50°C to avoid decomposition [9]. 

Eour-electron reductions of aromatic carboxylic acids occur when reactions are carried out in strongly acidic solutions at lead or mercury cathodes, giving excellent yields of the corresponding benzyl alcohols [23,34-36]. The reaction is easily performed on a large scale. For example, the adaptation of a filter press cell for continuous reduction of benzoic acid has been described [37]. 

Some filter-press type electrochemical reactors can be used both in a divided and undivided mode. This is illustrated in Ref. 51. The ICI filter-press cell system FM 21 is discussed in the context of several pilot-plant applications, most of them organic. 

In the case of well-known electrochemical reactions, as well as for electrolyses where larger scales are involved, two-electrode cells (connected to a galvanostat) can be used with continuous feed of the reactant to the working electrode. This type of electrolysis is suitable for industrial purposes where specific devices and cells are utilized. Since electrodes of large areas are necessary, the distance between the anode and the cathode is small and determines the cell geometry (e.g. capillary-gap cell or filter-press cell). The use of cells equipped of porous electrodes (materials like graphite or carbon moss, platinum, nickel) have also been developed to perform electrocatalytic reactions at very large surfaces. Some typical cells used in the laboratory and in industry are presented at the end of this review. 

Among the exotic cells for the laboratory, flow cells (filter press cells) require an external loop with a pump to recirculate the electrolyte. Also, solid polymer electrode (SPE) cells have been described.16-19 The electrode material is deposited on both sides of a membrane (Nafion) or pressed against the membrane. An advantage is that the ionic conduction takes place in the membrane so that no supporting electrolyte is required. Moreover, this cell can work with gaseous reactants. 

FIGURE 21.19 Schematic representation of the filter press cell used to carry out the electrooxidation of carbohydrates. 

The electrolysis of sucrose was performed in a filter press cell (micro-flow cell, electro-cell AB) (Figure 21.19). The working electrode was platinum deposited electrochemically on a titanium plate. The counter electrode was a plate of stainless steel. The two compartments of the cell were separated by an ion-exchange membrane (Nation 423). A part of this membrane immersed in a saturated potassium sulfate permitted to connect by capillarity the MSE. The electrolyte in the cell was circulated by an external peristaltic pump (1 cm3 min-1) and passed through a reservoir (100 cm3). 

Filter-press cell is fastened on the supporting gummed frame and insulators. 

Figure 5.6 Comparison of I-V characteristics for a solid electrolyte and conventional bipolar filter press cell Temperature SO C,...

Such cells do not permit continuous operation and have a very low space time yield. This has led to the study of cells where the Mn02 is formed as a slurry in the anolyte in which case the manganese dioxide may be formed in a flow system, e.g. a filter press cell. Usually such systems use a lower temperature and a higher pH but, although successful in the laboratory, are probably not yet used in commercial practice. 

BASF in Germany considered the use of the capillary gap cell (see Fig. 2.16 in Chapter 2) for this electrolysis. The cell consists of a stack of carbon discs closely spaced by 0.2 mm thick strips of an insulator. The electrolyte is pumped through the inter-electrode gaps and a voltage is applied to endplates so that a bipolar cell is formed. The cell design is compact, simple and cheap compared with a filter press cell and the tetraalkylammonium concentration could be reduced to below 0.5% without loss of yield and with an energy consumption below 3000 kWh ton . ... 

The electrode is set into a bipolar element, which consists of a channel frame surrounding the anodes, lined with titanium for protection against corrosion in the anolyte environment. The elements, with the anode side of one facing the cathode side of another, thereby forming a cell, are clamped together with tie-rods. The resulting assemblage has the appearance of a plate and frame filter-press—a commonly used piece of equipment for filtration operations. Hence, the term bipolar filter-press cell. ... 

FIGURE 2.8. Dow filter-press cell of Hunter-Otis and Blue. A basic cell configuration B horizontal cross-sectional view. 

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