Bipolar electrolyzer

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. 

Sudoh M, Kodera T, Hino H, Shimamura H. Effect of anodic and cathodic reactions on oxidative degradation of phenol in an undivided bipolar electrolyzer. J Chem Eng Japan 1988 21(2) 198-203. 

Fig. 79. Bamag type of bipolar electrolyzer with extended electrodes.

As part of the effort to design, build and put into operation a laboratory model of the Sulfur Cycle, a multi-cell, bipolar electrolyzer was constructed. This electrolyzer, shown in Figure 7, contains five cells, each with cross-sectional dimensions of 12.7 by 12.7 cm. 

Fig. 17. Schematic of Asalii Chemical Acilyzer-ML bipolar electrolyzer, (a) View of cell units (b) structure of cell.

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

Oxidation in H2-H2O mixtures could be a long-term problem for uncoated metallic bipolar electrolyzer plates with low H2 content gas. Horita et al. ° documents oxidation in Fe-Cr alloys using 1% H2-Ar (balance) bubbled through water at 50°C (approximately 10% H2 content). A higher H2 content and the use of coatings would greatly lessen this problem. 

Figure 25 shows a single cell of a bipolar electrolyzer, consisting of 26 such elements, for the production of (NH/O2S2O8 from (NH4)2SC>4 as an example [60, 61]. Other cells used today origine from the former Weissenstein process (see next page). Their basic layout is described in [57]. 

In a bipolar electrolyzer, each electrode has both a positive and a negative face, with the positive face in one cell and the negative face in the adjacent cell. Proponents say that bipolar electrolyzers take up less floor space than unipolar ones and that they are better suited to high-pressure and high-temperature operation (which is more efficient). Their drawbacks are that they require much more precise tolerances in construction and that they are more difficult to maintain. (If one cell fails, the entire assembly has to be shut down.)... 

Tokuyama Soda Co., Ltd. has developed a large bipolar electrolyzer that has an electrolysis area of 2.7 m per unit. The cell bodies are metallic. The anode chamber is lined with titanium plating and the cathode chamber and structural frame are carbon steel. The anode surface is titanium mesh with an... 

Figure 15. The Asahi Chemical Company bipolar electrolyzer.

Due to the new developments [5] in fuel cell technology—the manufacture of carbon supported platinum catalysts and the use of the Nafion membrane—the cost of bipolar electrolyzers has been reduced a lot, and therefore almost all commercial devices are of this type. In this case, stainless steel or nickel cathodes are used together with nickel anodes in 25%-35% of potassium hydroxide at temperatures between 65°C and 90°C. The hydrogen current density reaches 100-300 mA/cm2 at cell potentials of 1.9-2.2 V, denoting a faradaic efficiency of 80% (losses in peripheries). Usually, a pressurized cell is employed to increase their performance and to reduce the size of the bubbles, thus lowering the overpotential associated with the process. This can be done with appropriate membranes and insulators and by using temperatures near 100°C. 

Figure 6.22 Example structure of a unit of a bipolar electrolyzer.

Figure 4.5 General arrangement of (a) monopolar and (b) bipolar electrolyzer modules. S denotes separator B denotes bipole.

INEOS BICHLOR Electrolyzers NaCi, Hp, electricity Production of chlorine, hydrogen and 32% NaOH solution by electrolysis of NaCi solution. 97%+ efficiency, very low-power consumption due to zero-gap electode design and modular design provides low-maintenance cost. Bipolar electrolyzer design 33 2009... 

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