SIC 2812 Alkalies and Chlorine
SIC 2812
This industry classification includes establishments engaged in manufacturing alkalies and chlorine. Examples of products include compressed or liquefied chlorine, sodium or potassium hydroxide, sodium bicarbonate, and soda ash (not produced at mines). Alkalies produced by mining are classified in SIC 1474: Potash, Soda, and Borate Minerals.
325181
Alkalies and Chlorine Manufacturing
The two primary commodities offered by the alkalies and chlorine industry are chlorine and sodium hydroxide (caustic soda), together representing the bulk of all shipments. According to U.S. Census Bureau, the value of shipments by U.S. alkalies and chlorine manufacturers was nearly $6.5 billion in 2005.
Chlorine and caustic soda have consistently appeared on lists of the top ten U.S. chemicals according to production weight. They are co-products of the same chemical process. This means that they are created at the same time and that the production of one results in the production of the other. Although there are several modern procedures used to produce chlorine and caustic soda, most rely on a technique called electrolysis. As electricity is passed through brine (a salt water solution), the brine's components—salt (sodium chloride) and water (made up of hydrogen and oxygen)—recombine to form chlorine and sodium hydroxide (caustic soda) in approximately equal amounts. Some hydrogen gas also results from the process.
Organic chemical manufacturers are the primary chlorine users in the United States. Some examples of chemicals produced with chlorine are ethylene dichloride, carbon tetrachloride, and methylene chloride. These and other chlorinated organic chemicals are used to make many products, including flame retardants, herbicides, solvents, refrigerants, polyvinyl chloride (PVC) pipe, and pigments. The second-largest chlorine user is the pulp and paper industry, which uses chlorine as a bleaching agent. Chlorine products are also used as raw ingredients in household and commercial bleaches, scouring powders, and automatic dishwashing compounds. Other chlorine uses include water treatment, sewage treatment, sanitizing, and metal extracting.
Caustic soda has a wide range of industrial applications. It is used in petroleum exploration and by water treatment facilities, tanneries, and the textile industry. It also plays a role in food processing, metal fabrication, and chemical manufacturing. Caustic soda is also used in industrial complexes to remove boiler scale. Although soda ash has been manufactured synthetically from the evaporation of brines, it is primarily produced from trona, a mined product that is covered in SIC 1474: Potash, Soda, and Borate Minerals. The last synthetic soda ash facility in the United States closed in 1986, idling 700,000 tons of capacity.
Modern methods of chlorine production were developed around electrolysis. The three most-used technologies—diaphragm cells, mercury cells, and membrane cells—produce chlorine and caustic soda by decomposing brine (salt water). Combined, they account for over 90 percent of U.S. chlorine production. Other methods in operation include electrolysis of either molten magnesium chloride or molten sodium chloride; electrolysis of hydrochloric acid; and non-electrolytic processes. The brine used as a raw material is obtained from natural deposits under the earth's surface or is made from salt and water.
Diaphragm cells, the oldest and most widely used of the modern methods, produces more than three-quarters of the nation's chlorine. Direct current is used to separate salt and water into chlorine, hydrogen, and sodium hydroxide (caustic soda). An internal asbestos fiber-coated device called a "diaphragm" keeps the chlorine and caustic soda separate. Manufacturers rely on additional evaporation and drying procedures to create products in marketable concentrations.
Mercury cells employ a different technique for keeping manufactured chlorine and caustic soda separate. Because of the presence of mercury during the application of the cell's electric current, the sodium is isolated and dissolved into the mercury. A secondary process recaptures the mercury and releases the sodium to form...
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