Sources and solutions for sodium carbonate in 50% ionic alkali?
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Reasons for the excessively high level of sodium carbonate (Na2CO3) in 50% ionic alkali? What are the normal values, generally? How to resolve this? Please advise!
During production, it’s not merely sodium ions that pass through the ion-exchange membrane; a small amount of salt also enters the catholyte via the channels. This results in a slight presence of salt in the caustic solution. As the efficiency of the ion-exchange membrane decreases, the salt content in the caustic solution increases. Alkali evaporation is a process of concentrating alkali solution; consequently, the salt content in the alkali also increases. I can’t remember the specific indicators. One can start by improving current efficiency, which includes controlling the electrolyte concentration, temperature, start-up and shutdown procedures, current density, and so on.
It is formed by reacting with carbon dioxide in the air.
In 50% ionic alkali, the content of sodium carbonate (Na2CO3) is on the high side. I don’t know exactly how much it is, nor do I know what the normal range should be. So, how can one say that the sodium carbonate content is excessively high?
In 32% of ion-exchange membrane caustic soda samples, the sodium carbonate content is ≤0.1%; extrapolating this to 50% caustic soda, the content should presumably not exceed 0.2%； A higher value is generally attributed to excessive stirring time under compressed air during the alkali dosing process; this causes carbon dioxide in the compressed air to react with sodium hydroxide.
The sodium carbonate in high-concentration alkaline solutions is mainly caused by the absorption of carbon dioxide from the air during concentration, storage, and transportation. This situation is extremely difficult to avoid, unless the environments where large quantities of alkali solutions are exposed to air are completely modified into environments isolated from air and protected by nitrogen gas. This is not easy to achieve; firstly, due to the high costs associated with equipment investment, and secondly, for reasons related to the safety of operators. Of course, it is possible to reduce the carbonate content in concentrated alkali, given that enterprises can achieve a high level of automated control and have made substantial investments in facilities for concentration and drying equipment.