| About Us - Registration/Login - Contact Us - Message Board - Glossary - Features - B-School - Legal - Biz-End - Orange-GTM - WAP |
| STOCK MARKETS | COMPANIES | SECTORS | ECONOMY | MUTUAL FUNDS | ONLINE TRADING | INVESTOR POINTS |
| |
|
| 'This site is a must read for investors ..' Forbes magazine | |
| India Infoline Sector Reports | Mon, 16-Feb-2004 10:46:44 IST (GMT+5:30) | |
| Caustic soda | ||
|
 |
Annexure Technology/ method of production Diaphragm Cell Diaphragm cell contains a diaphragm, usually made of asbestos fibers. This separates the anode from the cathode and allows ions to pass through electrical migration simultaneously reducing the diffusion of products. The diaphragm permits a flow of brine from anode to cathode and prevents side reaction. Sodium ions along with sodium chloride are discharged into the cathode chamber. Thus sodium chloride is separated in evaporators when caustic soda is obtained in the form of aqueous solution. The recycled salt is combined with fresh salt for further use. A major advantage of this cell is that it can run on dilute (20%), fairly impure brine. Such dilute brine produces dilute caustic soda solution (typically 11% caustic with 15% salt) contaminated with salt. Further concentration to 50% solution consumes great deal of energy. Approximately 2600 kg of water is evaporated to produce 1 ton of 50% solution. Units which use this process#include Shriram Industrial Enterprises, Tata Chemicals, Sri Gopal Paper and Sirpur Paper. This process has no significant advantages over other processes, since capital cost is only marginally lower than that for other process. Moreover, asbestos is a major pollutant. Membrane Cell This cell uses a semi-permeable membrane to separate the anode and cathode compartments. Membrane cells separate the compartments with porous chemically active plastic sheets that allow sodium ions to pass, but reject hydroxyl ions. Sodium ions diffuse to the cathode area where they react with de-mineralized water to produce 30-35 % caustic soda and hydrogen gas (The caustic soda is subsequently concentrated to 50 % levels). The salt water is dechlorinated, purified, and recycled in the process. This process has been gaining importance in the country because of number of advantages over the mercury cell process which are as follows; It has lower power of consumption of 2,300-2,500 kwh per ton of caustic soda as compared to 3,200 kwh per ton in the mercury cell process. When a mercury unit is converted from the mercury cell to the membrane cell, it is able to increase its capacity by nearly 20% because the available power can now produce more quantities of caustic soda. It has lower maintenance cost than the mercury cell process and simpler plant operations. Caustic soda produced has high purity. The disadvantages of this process are: It requires higher capital cost. It requires dependence on imports for technology. It requires high quality of salt. Membranes need to be replaced once in every three years. Mercury Cell Mercury cells operate quite differently from the other two types. In this anode (made up of graphite or titanium) remains fixed however a moving pool of mercury acts as cathode. Free sodium from the sodium chloride solution (salt water) forms a sodium mercury amalgam. The amalgam is decomposed using in a separate vessel with soft water producing 50% caustic solution and hydrogen gas. The depleted salt water is cleansed of chlorine, re-saturated with salt, purified and recycled. Discharge of mercury from the plant creates environmental problem. This is an older process and has the advantage of relatively lower capital costs. However, it has two significant disadvantages: Power consumption is high at 3,200 kwh per ton of caustic soda compared to other two cells. Mercury cell plants are pollution hazards since mercury is a major pollutant. Industrial Applications Of Caustic Soda Paper & pulp industry In this industry caustic soda is used for cooking of wood (removal of lignin). Around 120kg of caustic soda is used per ton of paper pulp. Man made fiber industry The industry uses caustic soda to manufacture viscose solution, viscose staple fibres and for mercerization. An average of 600 kg of caustic soda is used per ton of viscose solution. Soaps & detergent industry Soaps are manufactured by saponification of oils and fats with caustic soda. Detergents are produced by neutralization of organic sulphonic acids with caustic soda. Considerable amount of caustic is used indirectly in the form of sodium phosphate in the detergent industry. Other applications In chemical industry caustic soda is used for various purposes such as for pH regulation, for production of nucleophilic anionic intermediates, for etherification and esterification reactions etc. Water treatment industry uses diluted caustic for regeneration of ion exchangers for water purification. In the aluminium industry caustic is used for treatment of bauxite. Apart from these there are various other applications of caustic soda in number of industries. Industrial applications of chlorine
*Note-PVC stands for polyvinyl chloride Cost of power in caustic soda producing regions(FY97)
|
|
|
| 5PAISA | PREMIUM CONTENT | ADVERTISE WITH US | FEEDBACK | DISCLAIMER | PRIVACY POLICY | JOBS | FAQS | SITE MAP | HELP |
