Diaphragm cells operation

In a diaphragm cell operating at 2.3 kA/m2, for example, the percentages of the total cell voltage attributable to these three components are 67 percent thermodynamic, 23 percent IR, and 10 percent overvoltage. Typical voltage distribution in a membrane cell is given in Table 26.9. 

Fig. 6. Energy flow diagram of a typical diaphragm cell operation where numbers represent energy in millions of kilojoules per ton of chlorine. To convert...

Fig. 11. Cut view of OxyTecli H-4 diaphragm cell operating at a nominal load of 150 kA.

Another emission control aspect of diaphragm cell operation concerns the use of the crude cell product, still containing sodium chloride, to carry out base-catalyzed reactions such as ring closure of propylene chlorohydrin (Eq. 8.27) or hydrolysis of chlorobenzene (Eq. 8.45). 

Dimensionally stable anodes (DSAs) made of a corrosion-resistant titanium screening have been adopted by both mercury cell and diaphragm cell operators. A baked-on rutile titanium dioxide paste used with these electrodes decreases the electrochemical overvoltage and raises practical operating current densities. While significantly more expensive than graphite, this anode... 

Comparison of Eq. (94) with Eq. (91) clearly shows that Eq. (92) is a crude approximation for estimating the chlorine current efficiency of diaphragm cells operating with acidic or basic feed brine. Calculations show that the six equation (Eq. 93) overestimates the efficiency by 1-2% compared with the rigorous Eq. (91). 

Diaphragm cell operating at 2.32 kA Membrane cell operating at 3.5 kA Mercury cell operating at lOkA m ... 

In practice, a diaphragm-cell operator varies the difference between the liquid levels in the anolyte and catholyte to keep the flow steady in the face of changes in... 

In spite of the advantages of the membrane technolc, about 75% of all chlorine is produced in mercury and diaphragm cells, operating in ca. 500 plants around the world. Diaphragm technolc prevails in the United States (70%), Russia, and China, and mercury technology in Western Europe (64 %). Continued production from these plants is economical under special circumstances. 

Electrolytic Cell Operating Characteristics. Currently the greatest volume of chlorine production is by the diaphragm ceU process, foUowed by that of the mercury ceU and then the membrane ceU. However, because of the ecological and economic advantages of the membrane process over the other systems, membrane ceUs are currently favored for new production facHities. The basic characteristics of the three ceU processes are shown in Eigure 5. 

Table 10. Operating Capacities and Characteristics of OxyTech Diaphragm Cells...

Table 11. Design and Operating Characteristics of HU Series Diaphragm Cells...

Three forms of caustic soda are produced to meet customer needs purified diaphragm caustic (50% Rayon grade), 73% caustic, and anhydrous caustic. Regular 50% caustic from the diaphragm cell process is suitable for most appHcations and accounts for about 85% of the NaOH consumed in the United States. However, it caimot be used in operations such as the manufacture of rayon, the synthesis of alkyl aryl sulfonates, or the production of anhydrous caustic because of the presence of salt, sodium chlorate, and heavy metals. Membrane and mercury cell caustic, on the other hand, is of superior quaUty and... 

Mr K A Stanley ICI Chlor Chemicals, The Heath, Runcorn, Cheshire, WA7 4QF, UK. Practical Operating Differences in Converting a Diaphragm Cell Chlor-Alkali Plant to a Membrane Electrolyser Plant. E-mail keith stanley ici.com... 

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