Caustic soda is one of the common names for sodium hydroxide naoh, which is also known as lye. Electrolysis is an electrochemical reaction using direct. Electrolysis is the process whereby salt and water molecules are broken and subsequently regrouped into caustic soda, chlorine and hydrogen molecules. The bauxite is washed and crushed, reducing the particle size and increasing the available surface area for the digestion stage. Caustic soda is used in the wide variety of industrial sectors like. The production of caustic soda naoh also results in the coproducts of chlorine and hydrogen. Chemical process industry production of caustic soda. The modification of cotton yarns and fabrics by treatment with strong caustic soda solution is a commonly used textile finishing process. The soda liquors are mixed with ferric oxide, and the mass evaporated to dryness and calcined at a bright red heat, usually in a revolving furnace. The reaction with water results in a 50% caustic soda solution of naoh and h2 gas lakshamanan et al. Click the image below to view the membrane cell process animation. In the bayer process, bauxite is leached with caustic soda, forming a solution of sodium aluminate, from which hydrated alumina is precipitated. Soda lime is a process used in water treatment to remove hardness from water.
The primary raw material is common salt, usually in the form of underground deposits which are brought to the surface as a solution in a pumped high pressure water supply. Alfa laval provides complete, compact and energyefficient caustic soda and caustic potash evaporation systems. Loewigs process for caustic soda preparation depends on the formation of sodium ferrate na 2 fe 2 o 4, which is then decomposed with water. The process comprises heating said naturally occurring alkaline minerals to temperatures sufficient to dehydrate and partially decarbonate said alkaline minerals and provide an intermediate product of a mixture of sodium. The caustic soda is normally pumped through a cooler, then through a mercury removal system and then to the intermediate and final storage sections. Large quantities of diluted caustic soda weak lye are a waste product of this process. The caustic soda solution from the three technologies is treated in slightly different ways due to the difference in composition and concentration. Process economics program report 61e chlorineadvanced commercial chloralkali technology december 2012 chlorine and caustic soda represent one of the largest volume chemical segments. This process is now obsolete but was very useful for the treatment of large volumes of hard water. Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula naoh. For the transportation of a large quantity of liquid caustic soda, tank trucks, rail tanks, or tankers are used. Lime and spent liquor caustic soda returned from the precipitation stage are added at the mills to make a pumpable slurry.
Us4626426a process for the manufacture of caustic soda. Brine, prepared from sodium chloride nacl, is electrolyzed in either a. Caustic soda dissolving systems in modern companies safety is an issue of major concern. Removetake off immediately all contaminated clothing. Liquid caustic soda is contained in rectangular cans or drums. Brine, prepared from sodium chloride nacl, is electrolyzed in either a membrane cell or a diaphragm cell. Sodium hydroxide caustic soda production processes. The membrane cell process is the preferred process for new plants. To dissolve the caustic soda flakes in water hormes supplies special dissolving tanks manufactured both in steel or stainless steel.
Odors most least effectively treated and removal efficiencies. Transformation of the nonhydratable phospholipids into their hydratable form by breaking down the metal phosphatide complexes with a strong acid. Caustic soda production and manufacturing process icis. However, it is more expensive to mine soda ash than to produce 50 percent caustic, so increased use of soda ash is not likely to occur unless the price of caustic is relatively high chenier 1992, dow 1999. The consumption of electric energy is the lowest of the three processes and the amount of steam needed to concentrate the caustic is relatively low less than one tonne per tonne of caustic soda. Some principal products or processes in which caustic soda is used are. Caustic soda softening is typically used when the treated water has inadequate carbonate hardness to react with lime. Sodium tripolyphospate detegents sodium hypochlorite household bleach, disinfectant soap, household cleaning. Soda ash is very plentiful in the united states and is obtained almost entirely from natural sources of trona ore. Sodium hydroxide caustic soda is a coproduct from the manufacture of chlorine using a solution of. Caustic soda is produced by oxychem by an electrolytic process as shown in the following diagrams.
The chloralkali process also chloralkali and chlor alkali is an industrial process for the electrolysis of. This intermediate then is contacted with water to effect causticization of the sodium carbonate and provide a recoverable phase comprising an aqueous solution of caustic soda. This name is given due to the corrosive nature of this salt on animal and plant tissues. It is the technology used to produce chlorine and sodium hydroxide lyecaustic soda, which are commodity chemicals required by industry. Westlake manufactures sodium hydroxide along with chlorine via the chloralkali electrolysis process.
The energy consumption in a membrane cell process is of the order of 2,2002,500. When purchased in liquid form it is easily dispensed to raise ph values in a water system. Principal of working under caustic recovery system caustic soda recovery, caustic at low concentration is heated to its boiling point with the help of a heat source and the vapors generated. However, caustic softening produces less sludge and unlike lime does not deteriorate during storage. A major building block in many industrial processes. Its common name derives from its chemical identity as a sodium hydrate and because it is caustic or corrosive. In the mercury cell process, sodium forms an amalgam a mixture of two metals with the mercury at the cathode. The special corrosionresistant design, allied to low operating temperatures, reduces corrosion rates and translates into longer equipment lifetime and a higher level of plant reliability. The liquid will be in a 50% solution of sodium hydroxide and this product is a strong base that should be handled with caution. Diaphragm processes may be acceptable, in some circumstances if nonasbestos diaphragms are used. Other terms for caustic scc used in past literature include caustic embrittlement, caustic cracking, and alkaline cracking. The addition of caustic soda to liquid will cause a rise in temperature.
Alumina extraction caustic soda is used to digest bauxite ore, precipitating alumina aluminum oxide. The chloralkali process also chloralkali and chlor alkali is an industrial process for the electrolysis of sodium chloride solutions. Solid caustic soda is contained in thin steel drums. Flake caustic soda is contained in drums or pvclined paper bags as shown in the table. Nace sp0403 avoiding caustic stress corrosion cracking. Pdf caustic soda injection in potablization process.
Download a picture of the membrane cell process pdf. Reagentgrade caustic soda is contained in glass bottles. Mercerisation is a finishing process in the textile industry where the textile fibres are treated under tensile stress with caustic soda. Process control and sqc statistical quality control methods. Neutralisation saponification of the free fatty acids by alkali caustic soda. Limesoda ash softening process 10 when lime and soda ash are added, hardnesscausing minerals form nearly insoluble precipitates. Caustic recovery plants, lye recovery, mercerisation. In pulp and paper processing industry caustic soda used at the stages like the bleaching process, in deinking of waste paper, and in water treatment. Sodium hydroxide, or caustic soda, may be available in liquid, pellet and flake form. Rayon and cellophane fiber production by the viscose process requires caustic soda at two main stages. Caustic soda is manufactured by the limesoda process.
Nuberg has set up more than 14 greenfield caustic soda chlor alkali plants worldwide with latest bipolar membrane electrolysis cell technology. Typically, the cotton yarn or fabric is wetted with caustic soda solutions 2025% sodium hydroxide for min at about 310 k, often followed by souring with dilute aqueous acid, e. The depleted brine is dechlorinated and recycled to the input stage. Caustic soda solution an overview sciencedirect topics. Addition of lime cao and soda na 2 co 3 to the hard water precipitates calcium as the carbonate, and magnesium as its hydroxide. Oxychem produces caustic soda at the following locations. Caustic soda is further concentrated in a vaporizer to a concentration of about 50% for delivery. In the solids contactor the rapid mix, flocculation, and sedimentation occur in a single unit. The caustic soda is normally pumped through a cooler, then through a mercury removal system. Softening by lime and limesoda ash is generally less expensive then by caustic soda. Always add caustic soda solution to water with constant agitation. The caustic and hydrogen are then separately cooled and the mercury is removed before proceeding to storage, sales, or other processes.
Caustic soda is an alkali salt which is also called lye. Caustic soda naoh chemical formula, properties, and uses. Limesoda water softening process and its advantages notes. Uniform and optimum size of prills facilitate good blending characteristics in dry mix formulation and possess excellent freeflow properties. When configured as a twostage causticbleach system, chemical wet scrubbers can achieve. Chemical process industries che105 saqib javed alkali industry caustic soda, soda ash naoh, na2co3 1 introduction sodium hydroxide, also known. A computer simulation of the concentration of caustic soda has been conducted to provide. If breathing is difficult, remove victim to fresh air and keep at rest in a position. Highlights of processes for chloralkali caustic soda. Caustic soda solution is a very corrosive industrial chemical. The efficient operation of the continuous form of this process requires that the concentration of caustic soda be controlled. In the mercury cell process, 50% caustic soda is obtained directly from the decomposers. If caustic soda becomes concentrated in one area, or is added too.
Us2771284a process for removal of deposits from sulfur. Methods of preparation of caustic soda worldofchemicals. Caustic soda in the form of prills offer distinct advantages over flakes, as shown below. Odor control abcs how to compare and evaluate odor. Next major industry like textile industry caustic soda is used to process cotton and synthetic. Caustic recovery system caustic soda recovery plant by concentrating wash liquor and using the same back in mercerizer is the only feasible solution. The soda liquors are mixed with ferric oxide, and the mass evaporated to dryness and calcined. Cellulose is treated with caustic soda solution to mercerize it and form alkali cellulose, which is then dissolved in dilute caustic soda solution to form viscose prior to extruding rayon fibers and cellophane films. There is provided a process for preparing caustic soda solutions from naturally occurring alkaline minerals comprising double salts of sodium carbonate and calcium carbonate. In lime sodaash softening plants, the softening process may be carried out by a sequence of rapid mix, flocculation, and sedimentation or in a solids contactor. Chemical treatment of petroleum products the aims of chemical treatment is to remove the impurities, such as sulfur, nitrogen, oxygen.