Plants caustic soda

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). 

Suckcharoen, S. and M. Lodenius. 1980. Reduction of mercury pollution in the vicinity of a caustic soda plant in Thailand. Water Air Soil Pollut. 13 221-227. 

Krupp Uhde has more than 40 years of experience in the design and construction of chlorine/caustic soda plants [1]. The company s 150 plants throughout the world have an overall production capacity of approximately 8 million metric tonnes per year of NaOH (100%) and thus make Krupp Uhde unique in its field. 

China s chemical industry began with a 40,000 Ton/per year Caustic Soda Plant in 1914. A few plants producing basic industrial chemicals were built in the 1930 s. By 1949, what the Sino-Japanese War (WW II) did not destroy of China s chemical industry, the Soviets managed to dismantle and remove. 

In years past, caustic soda plants generally prohibited the use of any aluminum parts on any processing equipment, motors, instruments, etc., because aluminum is aggressively attacked by any fumes or drips of caustic soda. However, during a major expansion in the late 1960s, refrigeration units were purchased that were equipped with safety relief valves made with aluminum bodies. During this very active period of construction,... 

Figure 3.3 Cell house in a caustic soda plant...

At the beginning of the war, the manufacture of TNT was poorly understood. The main risk was thought to come from its flammability, and, as a result of the urgency to increase production, some factories were built in inappropriate urban locations. Almost inevitably, this had tragic consequences. For example, a factory in a former textile mill at Ashton-under-Lyme, Greater Manchester, and a factory constructed in a former caustic soda plant at Silvertown, in London, both blew up with heavy loss of life. Less visible as catastrophes were the fatalities and sickness caused by TNT poisoning. 

Provide induced draught fans and scrubbers for necessary equipments to suck out any toxic and inflammable vapours in working areas (e.g. electrolysis cells for chlorine/caustic soda plants). 

Electrolytic plant producing caustic soda, chlorine, and hydrogen from brine. 

Benzene SuIfona.tion. In the benzene sulfonation process, benzene reacts with concentrated sulfuric acid to form benzenesulfonic acid at about 150°C. The benzenesulfonic acid is neutralized with sodium sulfate to produce sodium benzenesulfonate, which is then fused with caustic soda to yield sodium phenate. The sodium phenate is acidified with sulfur dioxide and a small amount of sulfuric acid to release the phenol from the sodium salt. The phenol yield by this process can be as high as 88 mol % to that of the theoretical value based on benzene. Plants employing this technology have been shut down for environmental and economic reasons. 

There are two serious problems associated with continuous tar distillation. Coal tar contains two types of components highly corrosive to ferrous metals. The ammonium salts, mainly ammonium chloride, associated with the entrained Hquor remain in the tar after dehydration, tend to dissociate with the production of hydrochloric acid and cause rapid deterioration of any part of the plant in which these vapors and steam are present above 240°C. Condensers on the dehydration column and fractionation columns are also attacked. This form of corrosion is controlled by the addition of alkaU (10% sodium carbonate solution or 40% caustic soda) to the cmde tar in an amount equivalent to the fixed ammonia content. 

Caustic soda concentrations of 50% are produced directly from equation 11. This advantage is offset by higher operating cell voltages and some mercury contamination of the environment. This latter problem has been diminished or solved to an acceptable extent (31) however, it continues to influence the choice of cells for new plants. No new mercury cells have been installed in the United States since 1970 (32). 

Carbon steel is easily the most commonly used material in process plants despite its somewhat limited corrosion resistance. It is routinely used for most organic chemicals and neutral or basic aqueous solutions at moderate temperatures. It is also used routinely for the storage of concentrated sulfuric acid and caustic soda [up to 50 percent and 55°C (I30°F)]. Because of its availability, low cost, and ease of fabrication steel is frequently used in services with corrosion rates of 0.13 to 0.5 mm/y (5 to 20 mils/y), with added thickness (corrosion allowance) to assure the achievement of desired service life. Product quahty requirements must be considered in such cases. 

In the membrane process, the chlorine (at the anode) and the hydrogen (at the cathode) are kept apart by a selective polymer membrane that allows the sodium ions to pass into the cathodic compartment and react with the hydroxyl ions to form caustic soda. The depleted brine is dechlorinated and recycled to the input stage. As noted already, the membrane cell process is the preferred process for new plants. Diaphragm processes may be acceptable, in some circumstances, but only if nonasbestos diaphragms are used. The energy consumption in a membrane cell process is of the order of 2,200 to 2,500 kilowatt-hours per... 

Aqueous plant effluent and drawoff streams such as steam condensate, sour water, or spent caustic soda solution may require disposal to a disengaging drum. 

It is desired to synthesize a REAMEN for treating the gaseous wastes (Ri and Ra) of a viscose rayon plant. Three MSAs are available to select from. These MSAs are caustic soda, S], (a process stream already existing in the plant with mi = 5.0 kmol/m ), diethanolamine, Sa, (with m2 = 2.0 kmol/m ) and activated carbon, S3. The unit costs for S2 and S3 including stream makeup and subsequent regeneration are 64.9 /m and 169.4 /ro, respectively. Stream data ate given in Table 8.7. 

Fortunately in this case the two materials did not react. People who have emptied acid into alkali tanks have been less fortunate. A plant received caustic soda in tank cars and acid in tank trucks. One day a load of caustic soda andved in a tank truck. It was labeled Caustic Soda, the delivery papers said it was caustic soda, and the hose connections were unusual. But the operators had a mind-set (see Section 3.3.5) that anything in a tank truck was acid, and they spent two hours making an adaptor to enable them to pump the contents of the tank truck into the acid tank. 

A plant worker opened the hatch of a reactor and manually charged it with caustic soda. However, he had failed to check the reactor prior to charging, and the caustic soda reacted with chemicals already present to release a toxic by-product. The worker was overcome, and only survived following emergency treatment. 

The paper and pulp industries consume taif/e quantities of Ca(OH)2 and precipitated (as distinct from naturally occurring) CaCOs. The largest application of lime in pulp manufacture is as a causlicizing agent in sulfate (kraft) plants (p. 89). Here the waste NajC solution is reacted with lime to regenerate the caustic soda used in the process ... 

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