There are three methods for industrial production of sodium hydroxide, namely caustic soda, causticization method, electrolysis method and ion exchange membrane method.
1. Causticizing method. Soda ash and lime are respectively made into soda ash solution and lime into milk of lime. The causticization reaction is carried out at 99 to 101 degrees Celsius. The caustic liquid is clarified, evaporated and concentrated to more than 40% to obtain liquid caustic soda. The concentrated solution is further boiled and solidified to obtain a solid caustic soda product.
2. Diaphragm electrolysis. Add soda ash, caustic soda, barium chloride refined preparation to remove ionic impurities after the original salt, then add sodium polyacrylate or caustic bran to the clarification tank to accelerate the precipitation, add hydrochloric acid to neutralize after sand filtration, and the brine is preheated Sent to electrolysis, the electrolyte is preheated, evaporated, salted and cooled to obtain liquid caustic soda, which is further concentrated to obtain solid caustic soda products.
3, ion exchange membrane method. After the original salt is salted, the brine is purified according to the traditional method. After the primary brine is filtered through the microporous sintered carbon tubular filter, the secondary purification is conducted through the chelating ion exchange resin tower to make the calcium and magnesium in the brine. When the content drops below 0.002%, the secondary refined brine is electrolyzed, and the sodium ions in the brine in the anode chamber enter the cathode chamber and the hydroxide in the cathode chamber through the ionic membrane to generate sodium hydroxide.
