Electrolysis system brine level balance

I am not from the chlor-alkali industry, but I am very interested in the technological advancements in this sector. The sodium chloride concentration in concentrated brine is 300–310 grams per liter, while it drops to 200–210 grams per liter in the diluted brine after electrolysis. Therefore, I recommend chlorinating-freeing the brackish water and concentrating it to 270–280 grams per liter of sodium chloride, without using vacuum or sodium sulfite techniques for chlorination removal. We have a membrane technology that can economically and efficiently concentrate solutions containing 200–210 grams per liter of sodium chloride to 270–280 grams per liter, while ensuring that the free chlorine concentration in the resulting dilute brine remains below 10 ppm, or even lower. The by-product water obtained contains almost no impurities (aside from a very low chlorine content), and it might have better uses. Of course, this technology can also be used to concentrate weaker sodium hydroxide and dilute hydrochloric acid. Its cost efficiency is far higher than that of conventional six-effect evaporation. Please see my topic post “Non-traditional brackish water chlorination removal techniques””

The reason for the imbalance is that water moves to the cathode along with sodium ions, while chlorine carries away a portion of it; if these two amounts are added together, the overall amount of water satisfies the material balance equation.

I observed the operation of my plant; the flow rate of the brackish water returning from the electrolysis process was approximately 0.77 times the flow rate of the salt water entering that same process. I wonder if it’s normal?

Regarding the water balance in the cycle of primary brine → secondary brine → weak brine → primary brine, it is as follows: moisture content in raw salt + makeup water + moisture content in additives (soda ash, caustic soda, barium chloride, sedimentation aids, etc.) + water reused for regeneration + moisture content in sodium sulfite + moisture content in alkalis and acids used by the ion exchange membrane = amount of water that penetrates from the anode to the cathode in the electrolyzer + moisture content in salt sludge. Depending on the process, other components such as steam and moisture content in brine may also be present. The amount of water that penetrates into the electrolyzer can be calculated by considering the concentration of the brine and weak brine entering the electrolyzer, along with factors such as current efficiency and operating current, based on sodium ion balances.

The water loss in the saline solution occurs mainly as part of the brackish water leaving the system, with another portion passing through the membrane to the cathode. If a mass balance is performed solely on the water at the cathode, it will be found that there is an excess of water there – this water has moved from the anode to the cathode. The amount of this water depends on operational conditions, including the concentration of the saline solution, the concentration of the circulating alkali, temperature, and the condition of the membrane

This question is too general. The salt balance is related to the brine raw materials used by your company. If only salt is used, with only the ion-exchange membrane process, the equilibrium is very simple. If a combination of brine, ion-exchange membranes, and diaphragm systems is used, equilibrium calculations are required.

When calculating the water balance, it is also necessary to take into account the loss of hydrogen and hydroxide ions generated by water electrolysis in the cathode chamber!

For concentrated salt water and diluted salt water, since they are composed of salt and water, the volume measured is the volume of the solution. The mass flow rate is the same. The same is true for bases; therefore, when considering balance issues, the entire system must be taken into account to achieve equilibrium.

Who can calculate the flow rate of the brackish water leaving the tank?