Chlorine electrolytic production

Other Chlorine Production Processes. Although electrolytic production of CI2 and NaOH from NaCl accounts for most of the chlorine produced, other commercial processes for chlorine are also in operation. 

Chlorine from Potassium Hydroxide Manufacture. One of the coproducts during the electrolytic production of potassium hydroxide employing mercury and membrane ceHs is chlorine. The combined name plate capacity for caustic potash during 1988 totaled 325,000 t/yr and growth of U.S. demand was expected to be steady at 2% through 1990 (68). 

Sodium Hydroxide. Before World War 1, nearly all sodium hydroxide [1310-93-2], NaOH, was produced by the reaction of soda ash and lime. The subsequent rapid development of electrolytic production processes, resulting from growing demand for chlorine, effectively shut down the old lime—soda plants except in Eastern Europe, the USSR, India, and China. Recent changes in chlorine consumption have reduced demand, putting pressure on the price and availabiHty of caustic soda (NaOH). Because this trend is expected to continue, there is renewed interest in the lime—soda production process. EMC operates a 50,000 t/yr caustic soda plant that uses this technology at Green River it came onstream in mid-1990. Other U.S. soda ash producers have aimounced plans to constmct similar plants (1,5). 

Dead Sea Works Process. The Dead Sea Works, a subsidiary of Israel Chemicals Ltd., aimounced plans ia 1992 to constmct a 25,000 t/yr magnesium plant at Beer-Sheva, Israel. The plant, to be based on Russian camaHite technology, is designed to use an existing potash plant as the source of camaHte. The chlorine by-product can be either Hquefted and sold, or used ia an existing bromine plant. Waste streams from the camaHite process, as well as spent electrolyte from the electrolytic cells, can be returned to the potash plant. 

Regulations. In order to decrease the amount of anthropogenic release of mercury in the United States, the EPA has limited both use and disposal of mercury. In 1992, the EPA banned land disposal of high mercury content wastes generated from the electrolytic production of chlorine—caustic soda (14), accompanied by a one-year variance owing to a lack of available waste treatment faciUties in the United States. A thermal treatment process meeting EPA standards for these wastes was developed by 1993. The use of mercury and mercury compounds as biocides in agricultural products and paints has also been banned by the EPA. 

Chemical Production. Electrolytic production of chemicals is conducted either by solution (water) electrolysis or fused-salt electrolysis. Fluorine, chlorine, chlorate, and manganese dioxide are Hberated from water solutions magnesium and sodium are generated from molten salt solutions. 

FIGURE 14.17 A diaphragm cell tor the electrolytic production of sodium hydroxide from brine (aqueous sodium chloride solution), represented by the blue color. The diaphragm (gold color) prevents the chlorine produced at the titanium anodes from mixing with the hydrogen and the sodium hydroxide formed at the steel cathodes. The liquid (cell liquor) is drawn off and the water is partly evaporated. The unconverted sodium chloride crystallizes, leaving the sodium hydroxide dissolved in the cell liquor. 

One of the major costs in the electrolytic production of chlorine is electrical power. Should the power be purchased, or is a power generating station to be built If a power generator is to be built, should it be built large enough so that it can provide power for future expansions and for other existing plants the company may own in the general area The answers to these questions will greatly affect the amount of capital the company must allocate for the project. 

Carbon is widely used in the catalytic processes of the chemical industry due to its unique characteristics, such as chemical inertness, high surface area and porosity, good mechanical properties and low cost. It is used for the production of chlorine and aluminum, in metal refining (gold, silver, and grain refinement of Mg-Al alloys) as well as for the electrolytic production of hydrogen peroxide and photoelectrochemical water splitting. 

Mercury is mined predominantly as HgS in cinnabar ore and is then converted commercially to a variety of chemical forms. Key industrial and commercial applications of mercury are found in the electrolytic production of chlorine and caustic soda the manufacture of electrical equipment, thermometers, and other instruments fluorescent lamps dental amalgam and artisanal gold production. Use in pharmaceuticals and in biocides has declined substantially in recent years, but occasional use in antiseptics and folk medicines is still encountered. Thimerosal, an organomercurial preservative that is metabolized in part to ethylmercury, has been removed from almost all the vaccines in which it was formerly present. Environmental exposure to mercury from the burning of fossil fuels, or the bioaccumulation of methylmercury in fish, remains a concern in some regions of the world. Low-level exposure to mercury released from dental amalgam fillings occurs, but systemic toxicity from this source has not been established. 

Numerous other types of cell have been devised, and several of these have a much greater efficiency than the Hermite cell—e.g. K. Kellner s,2 Schuckert and Co. s, ML Haas and E. Oettel s, and P. Schoop s systems. The electrolytic production of chlorine and caustic soda, of bleaching liquors, and of disinfecting liquid—e.g. the so-called Dakin s solution—are growing industries. 

Sodium compounds are important largely because they are inexpensive and soluble in water. Sodium chloride is readily mined as rock salt, which is a deposit of sodium chloride left as ancient oceans evaporated and it is also obtained from the evaporation of brine from present-day seas and salt lakes (Fig. 14.19). Sodium chloride is used in large quantities in the electrolytic production of chlorine and sodium hydroxide from brine. 

There have been severe criticisms about the extended use of chlorine gas in industry, owing to concern primarily derived from its ability to form toxic chlorinated organic compounds. In order to avoid its co-production during the electrolytic production of sodium hydroxide, a process has been developed in which a sodium carbonate (soda ash) solution is used as the anolyte in an electrochemical reactor divided by an ion-exchange membrane. Hydrogen gas is produced at the cathode and sent to a gas diffusion anode. Assuming no by-products in the liquid phase and only one by-product in the gas phase ... 

Capodaglio, E., G.Pezzagno, G.C.Bobbio, and F.Cazzoli. 1969. Respiratory function test in workers employed in electrolytic production of chlorine and sodium, [in Italian], Med. Lav. 60 (3) 192—201. 

Cathode in the electrolytic production of chlorine and caustic soda lamps arc rectifiers mercury cells switches thermometers barometers laboratory apparatus dental amalgams raw material for various mercury compounds fungicides antiseptics preservatives pharmaceuticals electrodes reagents... 

In the electrolytic production of sodium at the cathode of an electrolytic cell we may say that the cathode, with its excess of electrons, is the reducing agent which reduces sodium ion to metallic sodium. Similarly we may say that the anode with its deficiency of electrons is the oxidizing agent which oxidizes chloride ion to free chlorine. 

Sodium chloride Sodium chloride is, as a starting material for the electrolytic production of chlorine and sodium hydroxide, available in unlimited quantities. It is either extracted from natural deposits (up to 70%) or from seawater. In the USA, the economically workable deposits of sodium chloride are estimated to be greater than 55 10 t and in the Federal Republic of Germany there is estimated to be 100 10 km of deposits. Extraction is either carried out by mining or leaching (i.e. dissolution of... 

Mercury can be used for the extraction of gold. In hospitals and homes, it is still used in thermometers and blood-pressure cuffs, can be found in batteries, switches, and fluorescent light bulbs. Large amounts of metallic mercury are employed as electrodes in the electrolytic production of chlorine and sodium hydroxide from saline. Today, exposure of the general population comes from three major sources fish consumption, dental amalgams, and vaccines. 

Chlorine-oxygen compounds discussed here are hypochlorite CIO-, chlorite CIO/-, chlorate CIO/", perchlorate CIO]/, and chlorine dioxide CIO2. With the exception of chlorite, all chlorine-oxygen compounds mentioned can be obtained as a direct product of electrolysis, but electrolytic production is not dominating in all cases. There are chemical pathways, too, using molecular chlorine and caustic alkali as basic educts - which have been produced electrolytically before. 

In case of electrolytic production of chlorine oxygen compounds, questions like purification of brine and of products arise, too. These questions are solved in analogy to the means described in Sect. 5.23.4 and shall not be repeated here. 

Consider the sources of some of the common chemical raw materials and relate these to products that are accessible via one or two chemical transformations in a typical chemical complex. Starting with just a few simple components—air, water, salt (NaCl), and ethane—together with an external source of energy, quite a range of finished products is possible (Fig. 1.1). While it is unlikely that all of these will be produced at any one location, many will be, and all are based on commercially feasible processes [1]. Thus, a company which focuses on the electrolytic production of chlorine and sodium hydroxide from salt will often be sited on or near natural salt beds in order to provide a secure source of this raw material. A large source of freshwater, such as a river or a lake will generally be used for feedstock and cooling water... 

The first electrolytic production of chlorine was by the electrolysis of a potassium chloride brine with coproduction of potassium hydroxide by the... 

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