BiChlor

If bipolar membrane electrolysers are installed (Fig. 15.10), such as the ICI BiChlor, then even less floor area is required for the same production capacity. In both membrane cases the space available also depends on the chosen operating current density. Utilising the 150 kA available, nine bipolar electrolysers can operate up to 16.7 kA each. This would require 112 anodes per electrolyser to manufacture the 200 000 tonnes per year of caustic soda, utilising about 360 V of the 450 V available. With bipolar electrolyser centres of 6.5 m, including operator walkways, an area of around 60 m by 14 m or 840 m2 will be required. However, more extensive pipework modifications are required with bipolar arrangements. 

Several years ago, ICI ETB looked at the total market for chlor-alkali membrane technology and considered how to develop an electrolyser that would extend its product and market range. A detailed analysis was carried out and many chlor-alkali producers were consulted. As a result of this work ICI ETB has developed an electrolyser called BiChlor. 

Set out in the sections below are the stages that ICI ETB went through in developing BiChlor. Some of the features of BiChlor are also discussed and finally the performance of the technology is displayed. 

Given the analysis described in Section 18.2.2, it was decided to develop an electrolyser that was capable of running comfortably at 6kA m-2. To ensure this requirement, BiChlor is designed for 8 kA m-2. This provides the flexibility to use BiChlor at very high current densities to suit the needs of particular clients and allows for advances in membranes which might move the optimum current density upwards. 

Figure 18.3 illustrates how a BiChlor Nestpak can be removed from and returned to the electrolyser. 

Fig. 18.3 Schematic of the removal of a Nestpak from a BiChlor electrolyser. 

To remove gas from an electrolyser compartment the obvious choice is to take it out at the top. In addition, it is important that the gas can leave the compartment along its entire length in order to avoid any back pressure. This is exactly the way BiChlor is designed, which is illustrated in Fig. 18.4. 

In order to ensure that the liquor level in the BiChlor is always higher than the top of the membrane and the membrane is fully flooded during operation, the gas exit header also acts as the liquor outlet header. Liquors overflow from the outlet header of each compartment as shown in Fig. 18.4. 

BiChlor contains mesh electrodes, the design of which has been carefully selected to have the most beneficial combination of gas and liquor transport, membrane support and high current-carrying capability. 

Fig. 18.5 Specialised BiChlor mesh electrode design incorporating spider current distributors.

BiChlor contains a number of features to lower the electrolyser voltage by reducing the resistance. One of these features is the design for zero gap operation. This lowers the electrolyser resistance by keeping the distance from the electrodes to the membrane at a minimum. 

Fig. 18.6 Distribution pattern of the cathode and anode spiders to minimise resistance to current flow across the membrane area of the BiChlor electrode. 

This leads on to an explanation of the reason for each BiChlor Nestpak containing a number of dimples . These dimples can be seen in the cut-away drawing of a BiChlor electrolyser (Fig. 18.7). The circular dimples on the cathode side point outwards and on the anode side point inwards. These dimples fit into one another when the Nestpaks of BiChlor are pushed together. 

Each Nestpak module in the BiChlor electrolyser is sealed along its perimeter by a combination of a bolted flange and gaskets. This allows the sealing pressure to be controlled around all of the perimeter of each individual Nestpak. In a large-area bipolar filter-press electrolyser, sealing is only achieved with massive compression equipment and even then a variable sealing pressure is likely to exist around the module perimeter. 

After conducting trials on various prototypes and testing a large number of components over many years, ICIETB installed a BiChlor demonstration electrolyser at Id s Lostock Plant in the UK. The BiChlor electrolyser achieved an oxygen content of approximately 1.5% in chlorine with alkaline feed brine. 

Fig. 18.8 Plot of power consumption of the BiChlor electrolyser for different membranes. Data breakdown is given in Table 18.1.

Table 18.1 Typical performance data of the BiChlor electrolyser operating at 5 kA m 2 (taken from Fig. 18.8).

With FM1500 and BiChlor, ICI ETB has the technology to suit all project needs... 

BiChlor is the result of extensive market research and operating experience... 

BiChlor contains a unique combination of features which offer considerable benefits to the chlor-alkali producer... 

BiChlor delivers Lowest Lifetime Costs By Design... 

The enzymes that are involved in the conversion of tyrosine to the aldoximes, 25 and 26 02.105 pj tryptophan , phenylalanine , valine and isoleucine " to the corresponding aldoximes are the multifunction cytochrome P450. CYP79A1, that hydroxylates tyrosine, was isolated from Sorghum bichlor and subsequently cloned". These oximes are the building blocks of plant glucosinolates, 15, and glycosides, 16. 

BICHLOR Not a process, but the trade name for a design of bipolar cell for electrolyzing brine. Offered by INEOS Chlor, UK. 

Application BICHLOR electrolysers are used to produce chlorine, sodium hydroxide (or potassium hydroxide) and hydrogen by the electrolysis of sodium chloride (or potassium chloride) solutions. BICHLOR electrolysers are state-of-the art, having zero electrode gap and separate anode and cathode compartments ensuring the highest product quality at the lowest electrical energy usage. 

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... 

FIGURE 5.30. INEOS BiChlor electrolyzer. (With permission from INEOS Chlor Ltd.)... 

UhdeNora, Company Information, Mai 2003 Company Pamphlet, 2002 a) Asahi-Kasei, Company Information, July 2003 Company Pamphlet, 2003 b) Chlorine Engineers Corp., Company Information, June 2003 Company Pamphlet, 2003 c) www.dtechsystems.com/mcre.html, 2003 www.dtechsystems.com/3-lm2mcre. html, 2003 d) Electrochemical Technology Business, www.etbusiness.com/html/chlor-tech/frn 1500.htm www.etbusiness.com/ html/chlor-tech/bichlor.htm. 

Bichlor-athyll-benzol 6, 364. 3.4.DiQhlor-o-zylol 6 II283. 

Bichlor>dibeii ]amin 12 II574. 2.4 Diehlor-dib izy]amin 12II574. 3.3 -Diehlor-dibenzyl in 12,1074, 1465,... 

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