Monopolar

The use of ED with a monopolar membrane for protein separation and acid caseinate production and in bioreactors for organic acid production is a well-proven technology with huge operating systems worldwide. Such ED is applied to different food systems, which include (Bazinet, 2004) 

These applications use the dilution-concentration feature of monopolar ion-exchange membranes. 

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Fig. 8. Anode for monopolar diaphragm cells a, activated (coated) expanded metal b, expanding spring c, titanium-clad copper bar d, copper thread to fix...

In the United States, 76% of the chlorine produced is from diaphragm cells. Production is equally divided between bipolar and monopolar electroly2ers. 

Oy Tech MonopolarE,lectroly rs. OxyTech Systems (a joint venture company of Occidental Chemical and Eltech Systems) suppHes monopolar diaphragm electrolyzers of two designs the OxyTech "Hooker" H-Type (27,28) shown in Figure 11 and the "Diamond" MDC-Type (28,29) in Figure 12. 

Eig. 19. CME monopolar electrolyzer a, membrane b, cathode element c, half-cathode element d, current distributor e. Teflon tube f, CI2 + depleted brine manifold g, conductor rod h, CI2 + depleted brine outlet nozzle i, base frame j, recycled NaOH manifold k, recycled NaOH inlet nozzle 1, gasket (the gasket-to-element ratio is quite small) m, tie rod n, anode element o, H2 + NaOH manifold p, end plate, q, under cell bus bar (simplifies piping... 

ICIFM-21SP Monopolar Electrolyzers. Id s EM-21 SP monopolar electrolyzer incorporates stamped electrodes that are 2 mm thick and of a relatively small (0.2 m ) size (50). The electrolyte compartments are created by molded gaskets between two of the electrode plates the electrode spacing is finite and is estabHshed by gasket thickness. The electrode frames are supported from rails and are compressed between one fixed and one floating end plate by tie rods. Inlet and outlet streams are handled by internal manifolds. A crosscut view of the electrolyzer is shown in Eigure 21. As of 1989, ICI had Hcensed 20 plants having an annual capacity of 468,250 t of NaOH. 

Fig. 24. De Nora Technologies DD-Type monopolar membrane electroly2er.

The De Nora DD-type bipolar electroly2er is similar in constmction to the monopolar electroly2er except that each cell frame is composed of a pair... 

MGC Monopolar Membrane Electrolycyer, OxyTech Systems, Inc., Chardon, Ohio, 1988. 

Ad ceds are bipolar operating at normal, atmospheric pressure unless otherwise noted. Monopolar ceds are used. 

The lshi2uka cell (39—41), another multipolar cell that has been ia use by Showa Titanium (Toyama, Japan), is a cylindrical cell divided ia half by a refractory wall. Each half is further divided iato an electrolysis chamber and a metal collection chamber. The electrolysis chamber contains terminal and center cathodes, with an anode placed between each cathode pair. Several bipolar electrodes are placed between each anode—cathode pair. The cell operates at 670°C and a current of 50 kA, which is equivalent to a 300 kA monopolar cell. 

Germany, Bitterfeld 1920 two-stage rotary kilns heated internally using intermediate grinding of roast oxidation completed within 3—4 h cylindrical monopolar ceUs, 4 m volume undivided con-centric Ni anodes, rod-shaped Fe cathodes unfiltered electrolyte batch operation KMnO crystallizes in ceU electrolysis energy consumption about 700 kWh/1 4,000 27,113... 

The latitude that titanium affords the cell designer has made a wide variety of monopolar and bipolar membrane cell designs possible. 

Cell geometry, such as tab/terminal positioning and battery configuration, strongly influence primary current distribution. The monopolar constmction is most common. Several electrodes of the same polarity may be connected in parallel to increase capacity. The current production concentrates near the tab connections unless special care is exercised in designing the current collector. Bipolar constmction, wherein the terminal or collector of one cell serves as the anode and cathode of the next cell in pile formation, leads to gready improved uniformity of current distribution. Several representations are available to calculate the current distribution across the geometric electrode surface (46—50). 

In the electrolysis zone, the electrochemical reactions take place. Two basic electrode configurations are used (/) monopolar cells where the same cell voltage is appHed to all anode/cathode combinations and (2) bipolar cells where the same current passes through all electrodes (Eig. 4). To minimize the anodic oxidation of OCL , the solution must be quickly moved out of this zone to a reaction zone. Because the reaction to convert OCk to CIO (eq. 

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. 

Monopolar electrodes have a direct electrical connection with an external power supply. This requites the distribution of current over the total area of one monopolar electrode, collecting the current from the other monopolar electrode for conduction to the next cell through interceU busbars. 

Monopolar cells operate at low voltages, and may requite high amperages. Industrial citcuits of cells may consist of one hundred or more monopolar cells in series. Monopolar electrodes are used in some membrane chlor-aLkaU cells (Figs. 4 and 5), fluorine cells (Fig. 6), and in metal electrowinning cells (Fig. 7). 

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

Two-Dimensional Electrode Flow Cells. The simplest and least expensive cell design is the undivided parallel plate cell with electrolyte flow by some form of manifold. Electrical power is monopolar to the cell pack (72). An exploded view of the Foreman and Veatch cell is shown in Figure 7. Note that electrolyte flow is in series and that it is not easily adapted for divided cell operation. 

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