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Overview Article on the Production of Caustic Soda
Overview Article on the Production of Caustic Soda
In Russian industry, liquid and solid Caustic soda are distinguished.
By grade, Caustic soda can be classified as:
Grade RR — 47% mercury-cell solution:
- – grade A — for producing ion-exchange resins, chemical solutions and fibers, and in medicine
- – grade B — for producing various metals, in the pulp and paper industry, and in the synthesis of fertilizers
Grade RD — diaphragm-cell solution, not less than 46% — used in soap-making, for bleaching fabrics, producing viscose rayon, in metallurgy, in the chemical and petroleum industries, as well as in many other sectors.
It should be understood that Caustic soda is initially produced in liquid form, while solid grades are obtained by evaporating the solution from the mercury-cell process.
It reacts well with zinc and aluminum. It corrodes glass well. It reacts actively with organic compounds and scale deposits. It reacts with wood, which is used in the pulp and paper industry.
Production Methods:
Production is based on the electrolysis of sodium chloride. Chlorine and Hydrogen are by-products of the reaction.
Caustic soda can be produced by three methods:
- Amalgam (mercury) method
- Diaphragm method
- Membrane method
The amalgam method is based on electrolysis using a mercury cathode. The advantage of the method is producing very pure caustic, free of chlorine.
The diaphragm method gives caustic with a higher chlorine content. But the production cost is significantly lower. The method is based on separating the cathode and anode with a porous diaphragm.
The membrane method is considered the most promising. It is based on separating the cathode and anode with a membrane that allows only sodium ions to pass through. The advantages of the method are the considerable simplicity of the production process compared to the diaphragm method. This method also significantly reduces energy consumption — by 25% compared to the mercury method and by 15% compared to the diaphragm method. The membrane method is the most environmentally friendly of those listed above.
As of 2014, 10 plants in Russia produce Caustic soda. The mercury and diaphragm methods are mainly used. The membrane technology has been implemented at only one enterprise.
Summary table of caustic soda production technology at Russian plants:
By 2015, Europe planned to close all mercury-technology Caustic soda production facilities. For Russian producers, the savings from membrane technology pay for themselves within 2 years, making it the most promising and, moreover, environmentally friendly technology. The main problem is that the membrane needs to be replaced every 3-4 years, and there is no domestic production of membranes in Russia.
See the quality indicators for Caustic soda.
We supply Flaked and Granulated Caustic soda.
To buy Caustic soda you can call us at (495)133-02-40,
or send a request to order@chimko.com or use our contact form.
Sold in 25 kg bags.
