Soda ash, causticization

A uniform coating of calcium carbonate deposited on the metal surfaces physically segregates the metal from the corrosive environment. To develop the positive LSI required to deposit calcium carbonate, it is usually necessary to adjust the pH or calcium content of the water. Soda ash, caustic soda, or lime (calcium hydroxide) may be used for this adjustment. Lime is usually the most economical alkaH because it raises the calcium content as weU as the alkalinity. 

SpiHs can also be diluted with large volumes of water. Care should be taken, however, because chlorosulfuric acid reacts violentiy with water Hberating heat, hydrochloric acid, and sulfuric acid mists and steam. The water should be appHed from a safe distance upwind of the spiH using a fog no22le. Remaining traces of acid should be neutrali2ed with soda ash, caustic soda, or lime before disposal. 

Fresh water Bentonite extender Bentonite Soda ash Caustic soda... 

The soap maker represents one of the larger consumers of chemicals, especially caustic soda, salt, soda ash, caustic potash, sodium silicate, sodium bicarbonate, and trisodium phosphate. BuUders are inorganic chemicals added to soap. In particular, tetrasodium p5Tophosphate and sodium tripolyphosphate were usually effective soap builders [1-6]. 

The major journals of greatest circulation must present that information which is of greatest interest to most readers. Such chemicals are easily named soda ash, caustic soda, the mineral acids, benzene, phthalic anhydride, aniline, phenol (90 are given in Table I). About 59% of all market news relates to these 90 chemicals. Almost any three of the ten leading journals will contribute information on most of them. The industry report of the Office of Domestic Commerce, Chemicals and Drugs, and the Facts for Industry series of the Tariff Commission and the Bureau of the Census will also contribute information. 

We want to look seriously at several of the services which are offered. But before doing this, it would seem desirable to enumerate the chemicals that are under discussion soda ash, caustic soda, chlorine, bicarbonate of soda,... 

The removal of corrosion products and/or scale from large equipment requires large volumes of cleaning solvents, perhaps 1000 to 100,000 gallons. Much cleaning has been done with diluted solutions of relatively inexpensive acids and alkalis. Solutions of soda ash, caustic soda, phosphates, or... 

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. 

Chlorine Caustic Soda Chlorine Caustic Potash ) Chlorine Sodium Soda Ash ) Chlorine Magnesium Chlorine, Caustic Soda Caustic Potash... 

The only caustic soda production process besides electrolysis is the soda—lime process involving the reaction of lime with soda ash ... 

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). 

Lime Soda. Process. Lime (CaO) reacts with a dilute (10—14%), hot (100°C) soda ash solution in a series of agitated tanks producing caustic and calcium carbonate. Although dilute alkaH solutions increase the conversion, the reaction does not go to completion and, in practice, only about 90% of the stoichiometric amount of lime is added. In this manner the lime is all converted to calcium carbonate and about 10% of the feed alkaH remains. The resulting slurry is sent to a clarifier where the calcium carbonate is removed, then washed to recover the residual alkaH. The clean calcium carbonate is then calcined to lime and recycled while the dilute caustic—soda ash solution is sent to evaporators and concentrated. The concentration process forces precipitation of the residual sodium carbonate from the caustic solution the ash is then removed by centrifugation and recycled. Caustic soda made by this process is comparable to the current electrolytic diaphragm ceU product. 

Sodium fluoride is normally manufactured by the reaction of hydrofluoric acid and soda ash (sodium carbonate), or caustic soda (sodium hydroxide). Control of pH is essential and proper agitation necessary to obtain the desired crystal size. The crystals are centrifuged, dried, sized, and packaged. Reactors are usually constmcted of carbon brick and lead-lined steel, with process lines of stainless, plastic or plastic-lined steel diaphragm, plug cock, or butterfly valves are preferred. 

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... 

Alkalies. In the 1960s, 3.2-34 x 10 t /yr of lime was captively produced by the U.S. alkaH industry for manufacturing soda ash and sodium bicarbonate via the Solvay process. Electrolytic process caustic soda and natural soda ash (trona) from Wyoming have largely replaced the Solvay process. Three of the trona producers in Wyoming now purchase quicklime for producing caustic soda. 

The lower equivalent weight of magnesium hydroxide compared to caustic soda, hydrated lime, and soda ash reduces the stoichiometric amounts necessary to neutralize a given amount of acid. Depending on relative alkah costs, magnesium hydroxide can offer the advantage of lower chemical costs. 

Spills should be picked up before flushing thoroughly with water and neutralizing with soda ash or lime. The introduction of aluminum chloride into any drainage system results in the reduction of effluent pH, which can be adjusted using caustic soda or lime (11). 

Because dimethyl sulfate looks like water, operations are preferably not performed when water is present, eg, wet floors or rain. Any spills or leaks should not be left unattended they should be contained, and mnoff to sewers should be avoided. Minor spills should be flooded with water to dilute and hydroly2e the dimethyl sulfate. The area should then be covered with a dilute (2—5 wt %) caustic solution or a dilute (2—5 wt %) ammonia solution, or soda ash may be sprinkled over the neat liquid and the mix wetted with a gende spray of water. The neutrafi2ing agent should remain on the affected area for 24 h and then should be washed away. Only personnel wearing protective equipment should perform these operations. The product bulletins should be consulted for procedures to be followed for more severe spills. Concentrated ammonia should not be used with neat dimethyl sulfate because explosions have resulted after their contact (128). 

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. 

Sodium and Potassium Benzoate. These salts are available in grades meeting the specifications of the 25ationalVormulary (18) and the Vood Chemicals Codex (19) (Table 7). Sodium benzoate [532-32-1] is produced by the neutralization of benzoic acid with caustic soda and/or soda ash. The resulting solution is then treated to remove trace impurities as weU as color bodies and then dried in steam heated double dmm dryers. The product removed from the dryers is light and fluffy and in order to reduce shipping and storage space the sodium benzoate is normally compacted. It is then milled and classified into various product forms, the names of which often bear Httle relationship to the actual form of the product. 

Sodium sulfite [7757-83-7] which is used in pulp and paper bleaching, is usually produced by the reaction of sulfur dioxide with either caustic soda or soda ash. 

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. 

---