Bipolar Diaphragm Cells

Glanor A Chlor-Alkali process using a bipolar diaphragm cell. Developed by PPG Industries and Oronzio de Nora Impianti Elettrochimic in the early 1970s. 

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

For the membrane cellroom of the same capacity there are two choices of technology type either monopolar or bipolar electrolysers. In the case of monopolar membrane electrolysers (Fig. 15.9), such as the ICI FM1500, one membrane electrolyser can replace one diaphragm cell. Since the membrane electrolyser has smaller dimensions there is an overall space saving. The monopolar membrane electrolysers may use the same pipework galleries and overhead crane from the... 

If the choice is to utilise the full capacity of the existing rectifiers and install more membrane electrolysers then adequate space is available. In the 200 000 tonnes per year example, utilising the voltage saved and adding 16 extra monopolar electrolysers would take less space than the original diaphragm cells. In the case of bipolar electrolysers, the length of the electrolyser could be increased as more anodes and cathodes are added to each electrolyser. The number of electrolysers, however, would stay the same. 

Replacement of diaphragm cells with bipolar membrane electrolysers requires a different electrical layout (Fig. 15.17) since each bipolar membrane electrolyser can only take about 17 kA of the 150 kA available (for a selected current density). This means that all nine electrolysers need to be installed together. The number of anodes in each bipolar electrolyser can be set depending on the number of diaphragm cells left on load, up to the maximum voltage of the rectifiers. 

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 The released Na dissolves in the Hg and is withdrawn to another zone where it forms salt-free NaOH with water, (c) Monopolar electrical connections each cell is connected separately to the power supply so they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.

Figure 6 presents a sketch of a modern monopolar diaphragm cell (there are bipolar arrangements as well). 

Commercial amalgam cells are strictly monopolar, and diaphragm cells exist in monopolar and bipolar variety. This holds for membrane cells, and having presented a monopolar industrial diaphragm cell as... 

PPG and DeNora jointly developed a bipolar filter-press diaphragm cell called the Glanor electrolyzer [32]. The central design feature is the bipolar electrode where one side acts as an anode and the other as a cathode. The electrode consists of a steel plate to which anode fingers are connected on one side and cathode fingers on the other. 

Fig. 1 Scheme of diaphragm cell for hydrochloric acid electrolysis (a) bipolar graphite electrode, (b) resin fiame, (c) diaphragm with gaskets, (d) inlet channels, (e) outlet channels... 

Another type of diaphragm anode is used in the bipolar Ganor cells [169],... 

Figure 12.11 is a schematic of a commercial diaphragm cell, typically operated in the range of 75,000 to 150,000 amperes. Many such cells are connected in series, as shown in Figure 12.12, so that the current leaving at the anode of one cell enters the cathode of the next cell, with the anode terminal cell connected to the positive bus of the rectifier, and the cathode terminal cell connected to the negative bus of the rectifier. Bipolar and monopolar cell circuit layouts are shown in Fig. 12.13. ... 

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