How is Sodium Chlorate made in China?

Sodium chlorate is a strong oxidizing chemical, It is widely used in pulp bleaching, and is a raw material for the production of chlorite, perchlorate, dye industry, etching fluidsand Sodium chlorate is a strong oxidizing chemical. At the same time, it is widely used in the field of metal wet smelting as a heavy metal removal agent.It's a very import chemical material.In the past year, China's sodium chlorate exports have increased by 2-3 times

Today let's talk about the main production methods of sodium chlorate are the chemical method and electrolysis method.

Chemical method: Lime is used as the raw material in the chemical method, where it is converted into lime milk and then chlorinated. The calcium chlorate solution obtained after precipitating calcium chloride crystals undergoes a double decomposition reaction with sodium sulfate or sodium carbonate to produce a solution of sodium amino acid and sodium sulfate products. However, due to its lengthy process, extensive equipment requirements, large footprint, poor operating environment, and high production cost, the chemical production of sodium chlorate is not commonly used domestically or internationally.

Electrolysis method: The electrolysis method is based on raw salt or refined salt as raw material, first made of saturated crude brine, and then added soda ash, caustic soda and barium chloride (can be combined with membrane denitrification technology), remove calcium, iron and sulfate ions in coarse salt water, and filter to obtain a refined brine. The primary purified brine is then treated by ion exchange or membrane to get the secondary purified brine, and then sodium bichromate and hydrochloric acid are added to the secondary purified brine, and the PH value is adjusted and then sent to the electrolytic cell without diaphragm for electrolysis. The sodium chlorate solution obtained by electrolysis is removed from sodium hypochlorite, crystallized, separated and dried to obtain crystalline sodium chlorate. Now all manufacturers are using the electrolysis process to produce sodium chlorate, its process generally includes brine process, electrolytic process, crystallization drying process, etc., are described as follows:

（1）Brine process

In North America and Europe, the chlorination sales used in the production of sodium chlorate are refined sodium chloride, and the brine refining process is often used for secondary purification treatment (using membrane filtration, ion exchange treatment and other technologies to further remove impurity ions in brine). Because the content of impurities in refined salt is less, the production line of brine refining process is short, the amount of slag discharge is less, and the pollution to the environment is reduced. Foreign sodium chlorate manufacturers pay great attention to the purification of salt water, because the quality of salt water directly affects the power consumption and washing cycle (foreign countries basically use refined salt). Domestic sodium chlorate raw materials using mineral salt, brine, seawater, more impurities in the original section, refining production line is long because raw material refining equipment is simple, refined salt water calcium, magnesium content is high, so the tank voltage rises quickly, washing tank cycle is short, generally washed once in three months, brine secondary refining can reduce the brine calcium and magnesium content, but also reduce power consumption, extend the washing tank cycle, improve production efficiency.

(2) Electrolytic process

The electrolytic process is the most important process for the production of sodium chlorate. The cost of electricity is the main cost of sodium chlorate, generally speaking, the production of a ton of sodium chlorate requires more than 5,000 KWH of electricity.

(3) Crystallization process

Almost all production lines use vacuum crystallization technology, there are external circulation type (30,000 tons/year below) and internal circulation type vacuum crystallizer, the heat source is the heat generated by the electrolytic reaction. (more than 30,000 tons/year) vacuum with a ring vacuum pump. MESO, a German company, is the world's largest professional designer and manufacturer of crystallizers, and its equipment is dedicated to the production of large crystals. Horizontal automatic discharge centrifuge is used in the dehydration process. Boiling bed dryer is used in the drying process. Relatively large domestic manufacturers generally use the introduction of technology to produce large crystals.

（4） The main chemical reaction formula in the production process of sodium chlorate is:

Total reaction :NaCL+3H20=NaCLO3+3H21 Anode :2CL--CL2t+2e Cathode :2H20+2e-+H2+20H- 

Liquid phase reaction :CL2+H20=HCLO+H++ CLO-H++CLO 2HCLO+CLO-CLO3-+2CL-+2H+

（5）The main control indicators of electrolysis foreign refined salt water impurity fraction of 2X10 "calcium, magnesium, sulfate, autolide, boride, other impurities, etc.", brine requirements PH6.4-6.8, electric tank temperature of about 50C, electrolyte chlorination sales concentration of 90g/l, sodium chlorate 625g/1.

（6）Main equipment: salt pond, brine preprocessor, brine membrane filter, membrane denitrification device, resin tower device, rectification device, sodium chlorate electrolyzer, vacuum product system, centrifuge, air drying, hydrogen treatment device, plate and frame filter press, water tower, all kinds of storage tanks.

The quality evaluation standard of sodium chlorate products in the Chinese market is GB/T1618-2018.