Chlor-alkali cells

Chlor-alkali cell Chlor-alkali industry... 

Table 7. Thermodynamic Decomposition Voltage of Chlor—Alkali Cells at 25°C...

Overvoltages for various types of chlor—alkali cells are given in Table 8. A typical example of the overvoltage effect is in the operation of a mercury cell where Hg is used as the cathode material. The overpotential of the H2 evolution reaction on Hg is high hence it is possible to form sodium amalgam without H2 generation, thereby eliminating the need for a separator in the cell. 

Table 8. Components of Chlor—Alkali Cell Voltages...

Sodium was made from amalgam ia Germany duriag World War II (68). The only other commercial appHcation appears to be the Tekkosha process (74—76). In this method, preheated amalgam from a chlor—alkali cell is suppHed as anode to a second cell operating at 220—240°C. This cell has an electrolyte of fused sodium hydroxide, sodium iodide, and sodium cyanide and an iron cathode. Operating conditions are given ia Table 6. 

Electrochemical processes require feedstock preparation for the electrolytic cells. Additionally, the electrolysis product usually requires further processing. This often involves additional equipment, as is demonstrated by the flow diagram shown in Figure 1 for a membrane chlor-alkali cell process (see Alkali AND chlorine products). Only the electrolytic cells and components ate discussed herein. 

Figure 10.2 Arrangement of a typical electrolytic chlor-alkali cell...

Chlor-alkali cell gas effluent, gas purification, l 618t Chlor-alkali electrolytic process, 13 809 Chlor-alkali processes, 13 775... 

However, the published corrosion rates of Ru from oxygen evolution are not reliable, as they forecast [50] Ru losses as high as 40 g cm-2 h, which is inconsistent with the anode lifetimes observed in commercial chlor-alkali cells. 

Electric energy is the predominant cost in the manufacture of chlorine and is the driver for most of the technical progress in the chlor-alkali industry. The busiest areas of development over the past 20 or 30 years have been related to reductions in energy consumption. Approximately 60% of the papers presented in this book deal with improvements in chlor-alkali cell internals, namely the anolyte/catholyte separator (primarily membranes) and the electrodes. 

The chlor-alkali cell in this diagram electrolyzes an aqueous solution of sodium chloride to produce chlorine gas, hydrogen gas, and aqueous sodium hydroxide. The asbestos diaphragm stops the chlorine gas produced at the anode from mixing with the hydrogen gas produced at the cathode. Sodium hydroxide solution is removed from the cell periodically, and fresh brine is added to the cell. 

O In a chlor-alkali cell, the current is very high. A typical current would be about 100 000 A. Calculate the mass of sodium hydroxide, in kilograms, that a cell using this current can produce in one minute. 

Write a descriptive paragraph to compare the reactions that occur in a Downs cell and a chlor-alkali cell. Describe the similarities and differences. 

Early experimental versions of Nafion within the context of chlor-alkali cells consisted of SO2F precursor forms that were first reacted on only one side with ethylenediamine (EDA) before the conversion of the remainder of the membrane to the sulfonate form took place. The result was a well-defined stratum of sulfonamide cross-links, that were formed upon heating after reaction, that served to reduce swelling at the catholyte interface, which, in turn, reduced OH back migration. However, these EDA-modified membranes proved inadequate in chlor-alkali cells due to the chemical degradation of these cross-links... 

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. 

In 1972, when the main thrust for these then-new materials was the development of efficient polymer membranes for chlor-alkali cells, the F. I. du Pont Co. reported much information, mostly in the form of product literature, in the form of empirical equations regarding the water mass and volume uptake of sulfonate form Nafion as a function of FW (in the range 1000—1400), some alkali metal counterion... 

As mentioned, this review is focused primarily on a survey of the vast literature dealing with the structure and properties of Nafion in the sulfonic acid and cation exchanged sulfonate forms. The literature on the carboxylate version is sparse and currently of lesser interest, as its application seems to be limited to membranes in chlor-alkali cells, and since it is a... 

The first electrochemical application of the D -statistic deals with the lack- of-association (i.e. independence) hypothesis concerning current efficiency and current load in diaphragm-type industrial scale chlor-alkali cells [18], Table 5 demonstrates that the two factors are independent with the understanding that the current efficiency/current load relationship may indirectly be influenced by other technical variables, e g. cell potential, and impurities. 

Table 5. Testing the independence of current efficiency and current load via eight different diaphragm-type chlor-alkali cells [18]...

The Spearman-Hotelling-Pabst test may be used for determining if a Z)-type statistic in Eq.(15) is significant, by comparing the computed D, D, etc. to lower quantiles of the statistic, tabulated e g. in [31], The diaphragm-type chlor-alkali cells in Section II.3 with rs =... 

Monopolar electrodes have a direct electrical connection with an external power supply. This requires the distribution of current over the total area of one monopolar electrode, collecting the current from the other monopolar electrode for conduction to the next cell through intercell busbars. Monopolar cells operate at low voltages, and may require high amperages. Industrial circuits of cells may consist of one hundred or more monopolar cells in series. Monopolar electrodes are used in some membrane chlor-alkali cells (Figs. 4 and 5), fluorine cells (Fig. 6), and in metal electrowinning cells (Fig. 7). 

S02/Vent Streams Hg/Chlor-Alkali Cell Gas Effluent... 

TABLE III Components of the Applied Potential in a Chlor-Alkali Cell... 

The commercial importance of this metal was first recognized in 1950s when its high strength/density ratios were found attractive in aerospace applications. The corrosion resistance in a variety of conditions led to its use in wet chlorine gas coolers for chlor-alkali cells, chlorine and chlorine dioxide bleaching equipment in pulp/paper mills, and reactor interiors for pressure acid leaching of metallic ores. The metal and its alloys were used in seawater power plant condensers, with over 400 million feet installed in application.65,66 The most commonly used alloys and their composition are given in Table 4.48. 

The heart of the chlor-alkali process is a cell in which saturated, purified NaCl is electrolytically decomposed. The three types of chlor-alkali cells currently in use are... 

The rapidly growing use of C102 in the pulp and paper industry has led to the rapid growth of sodium chlorate, NaC103, production in recent years. Sodium chlorate is produced by the electrolysis of NaCl brine in a cell that is very similar to a diaphragm chlor-alkali cell, except that it has no diaphragm. The overall reaction is as follows ... 

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