Dow cell

There are different ways of producing chlorine from brine, for example, Dow cells, Hooker cells, and mercury cells. Which process is to be used must be known in order to make an accurate economic evaluation, since the capital costs and operating costs are different for each of these processes. The process engineer may have to investigate the different processes and economically evaluate each before deciding which process is best. 

Electrolysis of hydrous cell feed (MgCl2 1.5 H20) in the so-called Dow cell requires graphite anodes which can be lowered into the cell to compensate for graphite consumed by the electrolytic decomposition of water. 

There are two bipolar filter-press cell designs for manufacturing chlorine, the Dow cell and the Glanor cell. Both use finger-type electrodes, as opposed to flat plates. The Dow cells, developed over the past eighty years [76-79] are simple and rugged. They employ... 

Fig. 9. Dow diaphragm cell, section view a, perforated steel back plate b, cathode pocket c, asbestos diaphragm d, DSA anode e, copper back plate f,...

Fig. 2. The Dow magnesium cell. The steel container. A, is equipped with a ceramic cover, B, through which graphite anodes, C, pass. The magnesium is deposited on the cathode, D, and is diverted as it rises into the collection sump, E. The chlorine is withdrawn through a vent, F.

Electrochemical cells may be used in either active or passive modes, depending on whether or not a signal, typically a current or voltage, must be actively appHed to the cell in order to evoke an analytically usehil response. Electroanalytical techniques have also been divided into two broad categories, static and dynamic, depending on whether or not current dows in the external circuit (1). In the static case, the system is assumed to be at equilibrium. The term dynamic indicates that the system has been disturbed and is not at equilibrium when the measurement is made. These definitions are often inappropriate because active measurements can be made that hardly disturb the system and passive measurements can be made on systems that are far from equilibrium. The terms static and dynamic also imply some sort of artificial time constraints on the measurement. Active and passive are terms that nonelectrochemists seem to understand more readily than static and dynamic. 

Later, Du Pont in America developed its own ionically conducting membrane, mainly for large-scale electrolysis of sodium chloride to manufacture chlorine, Nafion , (the US Navy also used it on board submarines to generate oxygen by electrolysis of water), while Dow Chemical, also in America, developed its own even more efficient version in the 1980s, while another version will be described below in connection with fuel cells. Meanwhile, Fenton et al. (1973) discovered the first of a... 

Fig. 5-5. Dow automatic x-ray recording spectrometer, front view. Note cell on spectrometer case, which extends off photograph to right. Driving mechanism (left front) and vertical x-ray tube (center) are shown. (Liebhafsky, Ann. N.Y. Acad. Sci., 53, 997. Courtesy of Dow Chemical,Company.)...

FIGURE 12.12 A schematic representation of the electrolytic cell used in the Dow process for magnesium. The electrolyte is molten magnesium chloride. As the current generated by the external source passes through the cell, magnesium ions are reduced to magnesium metal at the cathode and chloride ions are oxidized to chlorine gas at the anode. 

Organic carboxylic acids are commonly found in foods, in the adipate process stream, and as pollutants. Fatty acids are the lipophilic portion of glycerides and a major component of the cell membrane. Phenols are widely used in polymers, as wood preservatives, and as disinfectants. Chloro-phenols such as 4-chlorophenol, two isomeric dichlorophenols, 2,4,6-tri-chlorophenol, three isomeric tetrachlorophenols, and pentachlorophenol were separated on a Dowex (The Dow Chemical Co. Midland, MI) 2-X8 anion exchange resin using an acetic acid-methanol gradient.138... 

Figure 10 Separation of monochloroacetate, dichloroacetate, and trichloroacetate on a sulfonated poly(styrene-divinyl benzene) column with suppressed conductivity detection. Column 2% cross-linked sulfonated poly(styrene-divinyl benzene) capacity 0.02 meq/g. Flow rate 64 ml/hr. Eluant 15 mM sodium phenate. Suppressor 0.28 x 25 cm Dowex 50W X8 column (200-400 mesh). Detector Chromatronix conductivity cell connected to a Dow conductivity meter. (Reprinted with permission from Small, H., Stevens, T. S., and Bauman, W. C., Anal. Chem., 47,1801,1975. 1975 Analytical Chemistry.)...

Several chlor-alkali producers have some control over surplus caustic inasmuch as they use large quantities in-house. In some cases, if caustic is tight then the weak cell liquor can be upgraded and placed on the market. Dow s propylene oxide (PO)... 

Dow Chemical and General Motors are installing up to 400 fuel cells at Dow plants. Hydrogen is a natural byproduct at Dow and will provide 35 megawatts at its facilities. 

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