What are the factors contributing to excessive calcium levels in the brine after salting?

In any case, an excess level of calcium ions is definitely abnormal. What does the increase of around 1–4 ppm mentioned by the original poster refer to? What are the standards you have set? Moreover, the excess value is already very high; 0.6 represents the limit, and exceeding it is meaningless. What is the calcium ion content in the industrial salt and brine used by the owner’s company? What is the process control pH? Otherwise, it’s really hard to guess. I wonder if the original poster has an online calcium and magnesium monitor?

Increasing the double-alkali content does not help improve the quality of brine; instead, it affects its quality negatively. The excess alkali index is a metric that has been developed through the experience of many manufacturers both at home and abroad over the years. Some people feel that it isn’t very reasonable and constantly try to change it, for whatever reason, but in the end problems arise that harm them in the end. The issue described by the poster seems to be poor quality of the saltwater resulting from the use of brine. Therefore, here are a few points to keep in mind when using brine: 1. Ensure that the brine is added to the system evenly; if it is added intermittently, changes in the composition of the dissolved saltwater will result in changes in the amount of raw salt required, as well as in the amount of secondary alkalis needed. If it’s difficult to control the addition of these substances properly, then stable control is impossible. So first, it is necessary to stabilize the amount of halogen added; a flow meter should be used to ensure a consistent addition to the system ； 2. The reaction must be complete. The most fundamental reason for the poster’s problem is likely the fluctuations in the amount of di-base added, which results in incomplete reaction of Ca ions; this in turn causes ionic substances to pass through the membrane filter, leading to fluctuations in the Ca content of the water at the outlet ； 3. Regardless of the salt dissolution process used, the key to managing it is stability – including stability in raw materials, stability in flow rates, stability in the amount of additives used, and stability in operations. Only when all these factors are stable can high-quality brine be produced ； 4. The issue raised by the poster is not due to the membrane filtration system; it is mainly caused by the instability in the use of halogenated substances. The above suggestions are for reference only. Feel free to share any feedback on areas that need improvement.

Under normal circumstances, saltwater tests show no presence of calcium or magnesium; however, recently the calcium content in the saltwater has been between 1–4 mg/L. The allowable level of alkalinity is controlled at 0.4–0.6 g/L. The brine supply has been stopped for a week now, and the calcium content fluctuates around 400+50 mg/L. The pH value of the saltwater is 10±5, and there is no online monitoring in place.

The amount of brine added is controlled by a flow meter, with a ratio of 1:0.25 relative to the total amount of saline, and it is added to the primary saline solution. We have also considered the issue you mentioned regarding unstable mixing of brine; as a result, we stopped using brine for a week, and the entire saline system was almost completely replaced. Yet, calcium deposits still appear from time to time.

The calcium content in refined saltwater is between 1 and 4 mg/L – this value is quite normal.

Regarding production, as discussed by the others above, control is important. The ceramic membrane system is less likely to have problems; if there is an issue with the membrane, the water quality should remain above standard levels all the time, rather than fluctuating. I think we can look for the reasons in terms of analysis and testing, such as interference with the readings of the pH meter or whether the reagents used for analysis are of proper quality.

For our brine, a concentration of 1mg or less is required to be considered qualified; I’m not sure what the control criteria are for you

“I have conducted experiments; if salts containing organic compounds enter the desalination tank, they will prevent the precipitation of Ca ions, and it is necessary to extend the retention time for the reaction to proceed completely. ”------Was it done in the laboratory or in production? The fact that a company has the capability to conduct such experiments shows that it is quite strong – at least it was very powerful at that time.

While ruling out the influence of process conditions, we also considered possible factors affecting the analysis. The reagents were prepared anew, and the analysis supervisor carried out the tests personally; yet the problem persisted. As mentioned above, we are now wondering whether organic substances or scale inhibitors present in the saline water might be inhibiting the reaction of calcium.

What design margin is used for your chelating resin columns? Here, the total concentration of calcium and magnesium in the brine is 1 ppm; after 24 hours of operation, it’s necessary to switch over. This is how the process was designed, with a design margin of 1.2, and the system operates with three towers in two series. So, as a precaution, we switch over in advance as soon as the calcium level exceeds the normal range.