What is Caustic Soda?
Sodium hydroxide, also known as caustic soda and caustic soda, has the chemical formula NaOH. It is a highly corrosive strong base, usually in the form of white flakes or granules. It can be mixed with water to form an alkaline solution, and can also be dissolved in methanol and ethanol. This alkaline substance is deliquescent and will absorb water vapor in the air, as well as acidic gases such as carbon dioxide. Sodium hydroxide is one of the commonly used chemicals. It has a wide range of applications and is a necessity in many industrial processes: it is often used in the manufacture of wood pulp paper, textiles, soaps and other detergents, and is also used in household alkaline drain cleaning products.
How is caustic soda made?
The most commonly used industrial method is electrolysis, which is divided into:
◆Diaphragm electrolysis: After salting the raw salt, add soda ash, caustic soda, and barium chloride refiners to remove impurities such as calcium, magnesium, and sulfate ions. Then add sodium polyacrylate or causticized bran to the clarification tank to accelerate precipitation. After sand filtration, add hydrochloric acid to neutralize. The brine is preheated and sent to electrolysis. The electrolyte is preheated, evaporated, salted, and cooled to obtain liquid caustic soda. Further boiling and concentration will obtain the solid caustic soda product. Salt mud washing water is used for salting. Chemical formula: 2NaCl+2H₂O[electrolysis] →2NaOH+Cl₂↑+H₂↑
◆Ion exchange membrane method: After the raw salt is salted, the brine is refined according to the traditional method. The first refined brine is filtered through a microporous sintered carbon tubular filter, and then refined again through a chelating ion exchange resin tower to reduce the calcium and magnesium content in the brine to below 0.002%. The second refined brine is electrolyzed to generate chlorine in the anode chamber. The Na+ in the brine in the anode chamber enters the cathode chamber through the ion membrane and generates sodium hydroxide with the 0H in the cathode chamber. The H+ is directly discharged on the cathode to generate hydrogen. During the electrolysis process, an appropriate amount of high-purity hydrochloric acid is added to the anode chamber to neutralize the OH- that is returned, and the required pure water should be added to the cathode chamber. The concentration of high-purity caustic soda generated in the cathode chamber is 30% to 32% (mass), which can be directly used as a liquid caustic soda product, or it can be further concentrated to obtain a finished product of caustic soda. Chemical formula: 2NaCl+2H₂O→2NaOH+H₂↑+Cl₂↑
Caustic soda upstream products
Raw salt: generally refers to industrial raw salt, which is one of the most important raw materials for caustic soda and soda ash. Its raw salt consumption accounts for 70% of the total annual raw salt production.
Common downstream products
1. Alumina: chemical formula Al2O3. It is a high-hardness compound with a melting point of 2054°C and a boiling point of 2980°C. It is an ion crystal that can be ionized at high temperatures and is widely used in the production of polyaluminium chloride, aluminium sulfate, paint pigments, concrete admixtures, etc.
2. Corrugated paper: a board-shaped material made by gluing noodle paper and corrugated paper formed by corrugating rollers. It is generally divided into single corrugated paperboard and double corrugated paperboard. It has the advantages of low cost, light weight, easy processing, high strength, excellent printing adaptability, and convenient storage and transportation. Caustic soda plays the role of a papermaking auxiliary agent.
3. Formic acid: Formic acid is one of the basic organic chemical raw materials and is widely used in industries such as pesticides, leather, dyes, medicines and rubber.
4. Sodium formate: It is industrially produced by the reaction of carbon monoxide and sodium hydroxide at 150-170°C and about 2MPa. In fact, the production process of sodium formate is part of the production of oxalic acid, and the concentration of the sodium hydroxide solution used for the absorption reaction is 25%-30%.
5. Zirconium oxychloride: The zirconium hydroxide hydrochloric acid method uses zircon and caustic soda to melt, rinse, remove silicon and then react with sulfuric acid, then add ammonia water to obtain zirconium hydroxide precipitate, dissolve the precipitate with hydrochloric acid to obtain zirconium oxychloride, and then obtain zirconium dichloride product through evaporation concentration, cooling crystallization and crystal crushing.
Post time: Dec-11-2024
