Causticization of soda ash

PRODUCTION OF CAUSTIC WITHOUT CHLORINE 15.4.1. Causticization of Soda Ash... 

In a process older than the electrochemical route, NaOH is produced by the causticization of soda ash. This is an equilibrium reaction between a solution of carbonate and solid hydrated lime ... 

United States Caustic Soda Production. In 1987 U.S. production of caustic soda increased to 10.4 million tons (fig. 1), more than 10% over that of the previous year, furthermore, 1988 production was up another 6.7% to 11.1 million tons. The demand for caustic soda has been very strong in recent years as evidenced by both increased U.S. consumption and a strong export demand. In 1987 the United States exported 1.5 million tons, 14.5% of the total caustic soda production (6), representing a 25.5% increase over exports in 1986. Then, in 1988, caustic soda exports grew by another 4.1%. A weak doUar helped boost the 1987 exports. Growth slowed in 1988, however, as a result of an industry (and world) wide caustic soda shortage, which was caused by lower U.S. chlorine consumption and forced allocations. Because industries switched from caustic to soda ash where possible, the lower 1988 export growth was not indicative of caustic soda s export potential. 

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). 

The amount of soda ash, Na2C02, produced by the Solvay process has decreased, and most soda ash now comes from the Trona, Wyoming deposits (trona, Na2C02 NaHCO 2H20). Caustic soda, NaOH, solutions may be used ia wet batchiag processes as a source of soda (see Alkali and... 

Other commercial processes ate based on the reaction of sodium sulfide or hydrogen sulfide with sulfur dioxide, and caustic or soda ash ... 

Polymeric coagulants do not affect pH therefore, the need for supplemental alkalinity, such as lime, caustic, or soda ash, is reduced or eliminated. Polymeric coagulants do not add to the total dissolved soHds concentration, eg, 1 ppm of alum adds 0.45 ppm of sulfate ion (expressed as CaCO ) the reduction ia sulfate can significantly extend the capacity of anion-exchange systems. 

Inorga.nicNIa.teria.ls. These include acids (sulfuric, nitric, hydrochloric, and phosphoric), bases (caustic soda, caustic potash, soda ash, sodium carbonate, ammonia, and lime), salts (sodium chloride, sodium nitrite, and sodium sulfide) and other substances such as chlorine, bromine, phosphoms chlorides, and sulfur chlorides. The important point is that there is a significant usage of at least one inorganic material in all processes, and the overall toimage used by, and therefore the cost to, the dye industry is high. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials Solution is acidic and will corrode most metals Stability During Transport Stable Neutralizing Agents for Acids and Caustics Flush with water rinse with dilute solution of sodium bicarbonate of soda ash Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

Carbon dioxide carryover also occurs following the deliberate addition of soda ash (sodium carbonate) directly to the boiler. Where boiler designs provide for a significant internal drum or shell, the use of soda ash and caustic soda to prevent calcium and magnesium scales by precipitation reactions (internal softening) may be employed. 

The most popular form of internal treatment for many years dates from the nineteenth century and is based on a combination of soda ash and caustic. This traditional program, the so-called carbonate-cycle or carbonate treatment, utilizes the addition of sodium carbonate to the BW to deliberately form carbonate sludges that can be removed by BD, rather than permit sulfate scales to develop. If sulfate scales do form in the boiler, the removal process is difficult and very time-consuming, and obviously, boiler operating efficiency will continue to decrease as the sulfate scale increases in thickness. 

In 1968 the average selling costs were 10% of the sales dollar. There is, however, a large variance in this percentage. For basic bulk chemicals such as sulfuric acid, caustic, and soda ash the sales costs are less than 5% of the selling price, while for specialty chemicals having a low sales volume the sales costs may exceed 50% of the selling price. 

The treatment of spent lye consists of a series of operations designed to remove nearly all of the organic impurities (15, 16). The spent lye commonly is treated with mineral or fatty acids to reduce the content of free caustic and soda ash and to reduce the pH to 4.6. 8 (17). Sulfates are to be avoided because they are... 

LYE sometimes refers to solutions of soda ash or potash. It is also used for solutions of CAUSTIC SODA sodium hydroxide) and CAUSTIC POTASH (potassium hydroxide), prepared by mixing milk of lime with soda ash or potash. This mixing produces a solution of caustic soda, or caustic potash, and a limestone precipitate. A medieval recipe for caustic soda crystals calls for 1 part each of slaked lime and soda ash with 7 parts water, boiled until the volume is halved, filtered and decanted 10 times then evapouiated. 

SOda, modified. (neutral soda). A combination of soda ash and bicarbonate of soda in definite proportions for purposes where an alkali is needed, ranging in causticity between bicarbonate of soda and soda ash. White, crystalline powders water-soluble and possessing valuable cleansing and purifying properties. Prepared in various strengths. 

The quantities of chemicals produced from the major mineral constituents of the sea will be extremely large. Fortunately, there are several large chemical industries which could probably consume significant proportions of these quantities. Two examples are the fertilizer industry and the chlor-alkali industry. Currently, 25,000,000 tons of fertilizer are sold each year (9) in the United States, containing 7,600,000 tons of major plant nutrients (2,800,000 tons of N, 2,600,000 tons of P205, and 2,200,000 tons of K20). It has been estimated (4) that by 1965 the chlor-alkali industry will sell 19,000,000 tons of products per year, including 5,700,000 tons of chlorine, 4,700,000 tons of caustic soda, 6,100,000 tons of soda ash, and 1,300,000 tons of hydrochloric acid. 

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