Technological innovation in nitrate removal process for alkali production brine
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Technological innovation in the denitration process for alkali production brine, improving upon the previous freezing denitration method to eliminate the risk of floating nitrate. During denitrification, a large amount of floating nitrate causes an excess of it in the upper part of the settler, which affects product separation and leads to frequent tank cleaning cycles. Through the modified process, the problem of floating nitrate was resolved, and the tank cleaning cycle was extended from once every 2–3 hours to 48 hours or even longer.
There are various technologies for nitrate removal from brine; the freezing method is energy-intensive, while a more advanced approach is the use of membranes for nitrate removal. It is widely used in the alkali industry, including soda ash and chlor-alkali products.
The company uses a combined salt and nitrate production process for salt manufacturing, and the nitrate produced can also be sold as a product. Not bad. At the same time, salt and nitrate were taken out from different evaporators. Then separate and dry.
1. Freezing method: In the case of unsaturated saltwater, the solubility of salts in water changes little with temperature. However, the solubility of sodium sulfate changes significantly. Therefore, it is precisely by utilizing this difference that denitrification is achieved. However, in the current production systems of ordinary chlor-alkali enterprises, or in their raw materials, the sodium sulfate content is not very high. Using this method for denitrification results in excessive loss of cooling capacity, making it very uneconomical. Generally, when the mass concentration of sulfate ions reaches 30 g/L or higher, the freezing method is effective for denitrifying such high-nitrate water. Some enterprises use brine re-saturation technology to increase the nitrate concentration in denitration water, but there are the following problems: on the one hand. It can only be implemented in the diaphragm process for alkali production; on the other hand, the production cost remains high and the process is difficult to control. 2. Nitrogen removal by membrane method: This refers to the nitrogen removal process using membranes. It uses saline to remove nitrogen through a selective filtration membrane. As the saline water passes through the membrane filtration unit, sulfate ions and other polyvalent ions are retained, but monovalent ions cannot be separated from the feed saline water. The mass concentration of sulfate in the brine passing through the membrane can be reduced from over 10 L to below 1 g/L, which is referred to as low-nitrate brine ； In the brine that does not pass through the membrane, the mass concentration of sulfate can reach over 30 g/L, and in some cases it can even approach 70 g/L; such brine is referred to as high-nitrate brine. It facilitates further denitration in subsequent processes.