Industrial law
There are three methods of industrial production of caustic soda: causticization, electrolysis and ion exchange membrane.
Causticizing
Soda ash and lime are respectively made into soda ash solution and lime into lime milk, and causticization reaction is carried out at 99-101 ℃. The concentrated solution is further boiled and solidified to obtain a solid caustic soda product. The causticized mud is washed with water, and the washing water is used for alkalization.
Na2CO3+Ca(OH)2= 2NaOH+CaCO3↓
Diaphragm electrolysis
Add soda ash, caustic soda, barium chloride refined preparation to remove calcium, magnesium, sulfate ions and other impurities after the original salt, and then add sodium polyacrylate or caustic bran to the clarification tank to accelerate precipitation, and add hydrochloric acid after sand filtration. And, the brine is preheated and sent to electrolysis, and the electrolyte is preheated, evaporated, salt-separated, and cooled to obtain liquid caustic soda, which is further concentrated to obtain solid caustic soda products. The salt mud washing water is used to dissolve the salt.
2NaCl+2H2O[electrolysis] = 2NaOH+Cl2↑+H2↑
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 to generate chlorine in the anode chamber. Na+ in the brine in the anode chamber enters the cathode chamber and OH in the cathode chamber through the ionic membrane to generate sodium hydroxide, and 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 returned OH-, 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 can be further concentrated to obtain a solid caustic soda product.
2NaCl+2H₂O= 2NaOH+H₂↑+Cl₂↑
