1. IntroductionCaustic soda, scientifically known as sodium hydroxide (NaOH), is a strong alkali with strong corrosiveness. It has two forms: solid and liquid. Solid caustic soda is white and has flakes, granules, etc.; liquid caustic soda is a colorless and transparent liquid. It is easily soluble in water to form an alkaline solution, and it is also hygroscopic and deteriorates when it absorbs carbon dioxide. Caustic soda is a basic chemical raw material, and it is one of the two alkalis in the “three acids and two alkalis” together with soda ash. Caustic soda has a wide range of uses, mainly used in alumina, pulp, dyes, chemical fibers, water treatment, metal smelting, petroleum refining, cotton fabric finishing, purification of coal tar products, as well as food processing, wood processing, machinery industry, chemical industry, etc. According to different forms, caustic soda can be divided into liquid caustic soda and solid caustic soda. Liquid caustic soda is referred to as liquid caustic soda, which is usually a colorless and transparent liquid. According to the mass fraction of sodium hydroxide, liquid caustic soda can be subdivided into 30% liquid caustic soda, 32% liquid caustic soda, 42% liquid caustic soda, 45% liquid caustic soda, 48% liquid caustic soda, 49% liquid caustic soda, 50% liquid caustic soda, etc., of which 32% liquid caustic soda and 50% liquid caustic soda are the mainstream models. Solid caustic soda is referred to as solid caustic soda, including flake caustic soda and granular caustic soda. Flake caustic soda is mainly used in China. According to the mass fraction of sodium hydroxide, solid caustic soda can be subdivided into 73% solid caustic soda, 95% solid caustic soda, 96% solid caustic soda, 99% solid caustic soda, 99.5% solid caustic soda, etc., of which 99% flake caustic soda is the mainstream model.
2. Production process The caustic soda production process includes causticizing method and electrolysis method. The causticizing method is the soda causticizing method, and the electrolysis method can be divided into mercury method, diaphragm method, and ion exchange membrane method. The ion membrane exchange method is the mainstream production process in the world at present, and 99% of caustic soda in my country adopts this production process. Ion exchange membrane electrolysis is a method of obtaining caustic soda and chlorine by using a chemically stable perfluorosulfonic acid cation exchange membrane to separate the anode chamber and cathode chamber of the electrolytic cell. The ion exchange membrane has a special selective permeability, which only allows cations to pass through and blocks anions and gases from passing through. Therefore, after electrolysis, only the anode electrolyte Na+ and H+ ions pass through, while the cathode electrolyte CL-, OH- and the gases produced by electrolysis – hydrogen and chlorine cannot pass through, thereby avoiding the risk of explosion caused by the mixing of the two gases, and also avoiding the generation of impurities that affect the purity of caustic soda. The production process of ion membrane electrolysis is divided into six steps: rectification, brine refining, electrolysis, chlorine and hydrogen treatment, liquid alkali evaporation, and solid alkali production. Its chemical formula is: 2NaCl+2H2O=2NaOH+2H2↑+Cl2↑
3. Introduction to the industrial chain From the perspective of industrial structure, the upstream of caustic soda is electricity and raw salt. It takes 2300-2400 kWh of electricity and 1.4-1.6 tons of raw salt to produce one ton of caustic soda, which account for 60% and 20% of the production cost of caustic soda respectively. Most chlor-alkali enterprises build their own power plants to reduce costs, so coal prices have a certain impact on the cost of caustic soda. Overall, the price trend of industrial electricity and raw salt in my country is relatively stable, so the fluctuation range of caustic soda on the cost side is not large. As an important basic raw material, caustic soda has a wide range of downstream applications, mainly including alumina, printing and dyeing, chemical fiber, chemical industry and other fields. Among them, alumina is the largest consumer industry of caustic soda, accounting for more than 30% of the caustic soda consumption market; printing and dyeing, chemical fiber industry consumption accounts for 12.6%; chemical industry, consumption accounts for about 12%; the remaining industries are relatively scattered, accounting for less than 10%.
Post time: Dec-17-2024
