(BAT) Reference Document for the Production of Chlor-alkali ...

Chapter 2
Electrolysers containing a multitude of membrane or diaphragm cells are classified as either
monopolar or bipolar. The designation does not refer to the electrochemical reactions that take
place, which of course require two poles or electrodes for all cells, but to the electrolyser
construction or assembly. In a bipolar arrangement, the elements are connected in series with
resultant low current and high voltage (Kirchhoff's circuit laws). The cathode of a cell is
connected directly to the anode of the adjacent cell (Figure 2.13). In the monopolar
arrangement, all anodes and cathodes are connected in parallel, forming an electrolyser with a
high current and low voltage. The current has to be connected to every single anodic and
cathodic element while in a bipolar electrolyser the power supply is connected only to the end
part of the electrolyser. Due to the long current path, ohmic losses in monopolar electrolysers
are much higher than in equivalent bipolar electrolysers leading to increased energy
consumption [ 1, Ullmann's 2006 ].
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Bipolar
electrolyser
Monopolar
electrolyser
Figure 2.13: Simplified scheme of monopolar and bipolar electrolysers
Multiple electrolysers are employed in a single direct current circuit (Figure 2.14). Usually
bipolar electrolysers are connected in parallel with a low current and high voltage. Monopolar
electrolysers are often connected in series, resulting in a high current circuit and low voltage
[ 1, Ullmann's 2006 ]. Table 2.2 shows the differences between typical configurations of a
monopolar and bipolar membrane cell plant with the same production capacity. Monopolar
membrane cell plants are characterised by a larger number of electrolysers while the number of
cells per electrolyser is lower than in a bipolar membrane cell plant.
WORKING DRAFT IN PROGRESS
Source: [ 1, Ullmann's 2006 ]
Figure 2.14: Electrolyser architecture
36 December 2011 TB/EIPPCB/CAK_Draft_1
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