Membrane cells commercial electrolyzers

Also, discussions of a number of applications of Nafion are not included in this document and are, at most, mentioned within the context of a particular study of fundamental properties. A number of these systems are simply proposed rather than in actual commercial applications. Membranes in fuel cells, electrochemical energy storage systems, chlor-alkali cells, water electrolyzers, Donnan dialysis cells, elec-trochromic devices, and sensors, including ion selective electrodes, and the use of these membranes as a strong acid catalyst can be found in the above-mentioned reviews. 

The electrolysis of potassium chloride [7447-40-7], KQ, to produce chlorine and potassium hydroxide in membrane cells requires similar but unique membranes. Commercial membranes currendy employed in high performance membrane electrolyzers include E)u Pont s Nation 900 series and Asahi Glass s Flemion 700 series. 

Commercial application of membrane cell technology began in 1975 with the installation of the Nobeoka No 1 (Japan) using Asahi Chemical Co. electrolyzers, Reed Paper (Canada) using Hooker MX electrolyzers and American Can of Canada (Canada) using Ionics Chloromate electrolyzers. By the end of 1982 world capa-... 

After DuPont introduced Nafion membranes. Diamond Shamrock intensified its research efforts in membrane-cell technology. Initial research tests with the membranes began in 1970 using laboratory cells. In 1972, a commercial-size electrolyzer and pilot plant were placed in operation in Painesville, Ohio. Four years later, a 20-ton per day demonstration plant was built in Muscle Shoals, Alabama. Hiis unit was integrated with an existing mercury-cell plant. 

Remarkable advances in ion exchange membranes have been made since their inception and application to chlor-alkali cells in the 1970fs, and since that time many patents have issued on their applications. Several companies besides duPont have developed proprietary membranes and electrolyzers for commercial application. 

A solution of silver nitrate in 8-molar nitric acid is electrolyzed to produce the Ag(II) cations at the anode of a commercially available electrochemical cell. A semi-permeable membrane separates the anode and the cathode compartments of the cell to prevent mixing of the anolyte and catholyte solutions but allowing the passage of cations and water across the membrane. 

Due to the new developments [5] in fuel cell technology—the manufacture of carbon supported platinum catalysts and the use of the Nafion membrane—the cost of bipolar electrolyzers has been reduced a lot, and therefore almost all commercial devices are of this type. In this case, stainless steel or nickel cathodes are used together with nickel anodes in 25%-35% of potassium hydroxide at temperatures between 65°C and 90°C. The hydrogen current density reaches 100-300 mA/cm2 at cell potentials of 1.9-2.2 V, denoting a faradaic efficiency of 80% (losses in peripheries). Usually, a pressurized cell is employed to increase their performance and to reduce the size of the bubbles, thus lowering the overpotential associated with the process. This can be done with appropriate membranes and insulators and by using temperatures near 100°C. 

As mentioned above, the electrolysis of NaCl to from CI2 and NaOH is the largest application of membranes in electrolytic cells. There are also other brine electrolyzes of commercial importance. NaBr brine is electrolyzed to form Br2-(Another method of Br2 formation is to treat bromide brines with CI2 derived from electrolysis.) Electrolysis of KCl brines is the preferred process for making KOH. Because K ions are less hydrated than Na ions, the membrane is more effective at blocking the backdiffusion of KOH, which allows production of KOH in concentrations as high as 47%. 

A commercial membrane plant has multiple cell elements combined into a single unit, called the electrolyzer. The electrolyzers follow two basic designs monopolar and bipolar [148]. 

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