What could be the cause of elevated calcium levels in the brine used in the chlor-alkali industry, while magnesium levels remain within normal limits?
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Recently, after passing through the Jiusi membrane, the calcium level detected by ICP was nearly 20 (the standard is below 3), while the magnesium level was within the acceptable range. Additionally, an excessive amount of sodium carbonate was added during the process. What could be the cause of this problem? Where might calcium ions have been introduced?
In the chlor-alkali industry, if the calcium ion level is too high while the magnesium ion level is within normal limits, and an excessive amount of sodium carbonate is used, the possible problems and sources of calcium ions can be attributed to the following aspects: 1. Quality issues with the raw salt: The salt used may already contain a high level of calcium ions. It is recommended to check the quality of the raw salt or switch suppliers. 2. Sodium carbonate content: Although an excess amount of sodium carbonate is added, if the sodium carbonate itself contains high levels of calcium salt impurities, it can still lead to excessive calcium ions. Quality testing of sodium carbonate can be considered. 3. Membrane treatment system issues: The treatment efficiency of the Jiusi membrane may be problematic. Check the membrane system for any damage or decline in performance, and clean, maintain it regularly, or replace it with new membranes. 4. Operational issues: During the operation process, improper procedures may also lead to the introduction of calcium ions. Pay attention to strengthening employee training and operational monitoring. It is recommended to start from these aspects, conduct a thorough inspection and check each item in detail, identify the root cause of the excessive calcium ion levels, and take corrective actions. .
Thank you for your reply. The calcium ion level exceeds the limit quite often, but there are also times when it is within the acceptable range. The calcium and magnesium content in crude brine is usually in the range of several hundred, and it drops below 20; in some cases it is still within acceptable limits. After all these years of operation, factories generally do not consider issues related to the quality of the raw materials or the effectiveness of sodium carbonate. As the processing capacity of the Jiusi membrane declines, all indicators are likely to show abnormalities. In terms of operational issues, apart from adding salt, there is no one else to carry out the necessary operations.
Excess calcium ions in the raw salt: If the calcium ion content in the raw salt exceeds the specified range, then even with the addition of an excessive amount of sodium carbonate during the salt purification process, it may not be possible to reduce the calcium ion levels to below the standard values. Pollution during brine purification: During the brine purification process, if there are issues such as corrosion or damage to the equipment or pipelines, it may allow calcium ions from the external environment to enter the brine system. Furthermore, if the membrane modules in use are damaged or aged, it may also lead to the leakage of impurities such as calcium ions. Improper method of adding sodium carbonate: If sodium carbonate is added in an improper manner, such as at too fast a rate or with uneven mixing, it may affect its reaction with calcium ions, resulting in incomplete removal of those ions. Detection error: Although this situation is rare, it is not possible to completely rule out errors that may occur during the detection process or instrument failures, which could lead to abnormally high calcium levels.
Is the reaction time after adding the refined substance sufficient?
Where are the sampling points? Are there any other chemicals added before those sampling points, such as hydrochloric acid or hydrazine? Analyze these two situations in detail. Another aspect is reaction time; it’s necessary to analyze the amount of excess alkali and the calcium content in the raw salt, and to estimate these values roughly.