Electrical connections bipolar

There are two varieties of diaphragm and membrane cells. They are equally used. Monopolar cells are connected in parallel using external electrical connections. Bipolar cells are connected in series, with the anode of a cell directly connected to the cathode of the adjacent cell. This makes bipolar cells more compact than monopolar cells. °... 

The electrolytic cells shown ia Figures 2—7 represent both monopolar and bipolar types. The Chemetics chlorate cell (Fig. 2) contains bipolar anode/cathode assembhes. The cathodes are Stahrmet, a registered trademark of Chemetics International Co., and the anodes are titanium [7440-32-6] Ti, coated either with mthenium dioxide [12036-10-17, RUO2, or platinum [7440-06-4] Pt—indium [7439-88-5] Ir (see Metal anodes). Anodes and cathodes are joined to carrier plates of explosion-bonded titanium and Stahrmet, respectively. Several individual cells electrically connected in series are associated with one reaction vessel. 

Eig. 6. Options for electrical connections to parallel plate cells (a), monopolar and (b), bipolar connection. 

Design Principles An individual fuel cell will generate an electrical potential of about 1 V or less, as discussed above, and a current that is proportional to the external load demand. For practical apph-cations, the voltage of an individual fuel cell is obviously too small, and cells are therefore stacked up as shown in Fig. 27-61. Anode/ electrolyte/cathode assemblies are electrically connected in series by inserting a bipolar plate between the cathode of one cell and the anode of the next. The bipolar plate must be impervious to the fuel... 

II. Ease of electrical connection Here the main problem is that of efficient electrical current collection, ideally with only two electrical leads entering the reactor and without an excessive number of interconnects, as in fuel cells. This is because the competitor of an electrochemically promoted chemical reactor is not a fuel cell but a classical chemical reactor. The main breakthrough here is the recent discovery of bipolar or wireless NEMCA,8 11 i.e. electrochemical promotion induced on catalyst films deposited on a solid electrolyte but not directly connected to an electronic conductor (wire). 

Either parallel, called monopolar, or series, called bipolar, electrical connections can be made to the pairs of electrodes in a complete cell. The monopolar types have individual connections to each electrode and thus require only individual pair potential to be applied to the cell assembly. The bipolar mode has electrical connections only to the terminal electrodes. One design such as Figure 19.16(f) has 48 pairs of electrodes in series and requires 600 V. The equipment of Figure 19.19(a) also has bipolar connections. The voltage profile in such equipment is indicated schematically in Figure 19.17(d). Bipolar equipment is favored because of its compactness and, of course, the simplicity of the electrical connections. No adverse comments appear to be made about the high voltages needed. 

Figure 19.16. Basic designs of electrolytic cells, (a) Basic type of two-compartment cell used when mixing of anolyte and catholyte is to be minimized the partition may be a porous diaphragm or an ion exchange membrane that allows only selected ions to pass, (b) Mercury cell for brine electrolysis. The released Na dissolves in the Hg and is withdrawn to another zone where it forms salt-free NaOH with water, (c) Monopolar electrical connections each cell is connected separately to the power supply so they are in parallel at low voltage, (d) Bipolar electrical connections 50 or more cells may be series and may require supply at several hundred volts, (e) Bipolar-connected cells for the Monsanto adiponitrile process. Spacings between electrodes and membrane are 0.8-3.2 mm. (f) New type of cell for the Monsanto adiponitrile process, without partitions the stack consists of 50-200 steel plates with 0.0-0.2 ram coating of Cd. Electrolyte velocity of l-2 m/sec sweeps out generated Oz.

In bipolar electrolyzer stacks, the face of the electrode to the left can be negative, whereas its other side, facing the next cell to the right can be positive. Naturally, these electrodes are separated and their electrical connections are provided by a metal separator plate (separation diaphragm). These units require less floor space and can operate at higher temperatures and pressures. 

In a bipolar arrangement, the sacrificial electrodes are placed between the two parallel electrodes without any electrical connection. The two monopolar electrodes are connected to the electric power source with no interconnections between the sacrificial electrodes. This cell arrangement provides a simple setup, which facilitates easy maintenance. When an electric current is passed through the two electrodes, the neutral sides of the conductive plate will be transformed to charged sides, which have opposite charge compared with the parallel side beside it. The sacrificial electrodes are known as bipolar electrodes. It has been reported that EC cell with monopolar electrodes in series connection was more effective where aluminum electrodes were used as sacrificial and iron was used as anode and cathode. And, electrocoagulation with Fe/Al (anode/cathode) was more effective for the treatment process than Fe/Fe electrode pair (Modirshahla et al. 2007). 

Capillary gap cell — The undivided capillary gap (or disc-stack) cell design is frequently used in industrial-scale electroorganic syntheses, but is also applicable for laboratory-scale experiments when a large space-time yield is required. Only the top and bottom electrodes of c.g.c. (see Figure) are electrically connected to - anode and cathode, respectively, whereas the other electrodes are polarized in the electrical field and act as -> bipolar electrodes. This makes c.g.c. s appropriate for dual electrosynthesis, i.e., pro duct-generating on both electrodes. 

Either parallel, called monopolar, or series, called bipolar, electrical connections can be made to the pairs of electrodes in a complete cell. The monopolar types have individual connections to each electrode and thus require only individual pair potential to be applied to the cell assembly. The bipolar mode has electrical connections only to the terminal electrodes. One design such as... 

Figure 3. Electrical connections in multielectrode cells, (a) Monopolar, (b) Bipolar...

Electrolyzers for the membrane cell electrolysis process are a filter press arrangement of cell units electrically arranged in two different cell configurations, mono-polar and bipolar. Figure 13 illustrates the examples of the electrical connection of the cells (65). Figure 14 illustrates the electrolysis... 

---