The chlor-alkali industry produces brine, and in the second half of the year (sometimes in August or September), the level of calcium ions exceeds the allowed limits
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Previously, instances of excessive calcium ion levels occurred for about one to two months; however, there were no cases of excessive magnesium ions. The sodium carbonate used in the processing showed no signs of becoming ineffective, and the amounts added were all in excess. The raw salt used is rock salt transported by rail. The equipment employed for purification is the third-generation Jiusi membrane system, and there’s a buffer tank prior to the Jiusi membranes. In cases where calcium ion levels are excessive, what could be the possible causes—related to the process itself or factors such as water flow rate?
The issue of excessive calcium ions may be related to the following aspects: 1. **Quality of the raw salt**: Although the raw salt is mineral salt transported by rail, its calcium content can vary depending on the mining area. It is recommended to check whether the source of the mineral salts changed in the second half of the year, or whether there are quality differences between different batches. 2. **Efficiency of sodium carbonate usage**: You mentioned that the amount of sodium carbonate added is excessive, but it may be necessary to check the completeness of the reaction between sodium carbonate and calcium ions. If the reaction is incomplete, even with an excessive amount added, it may result in calcium ions not being completely precipitated. 3. **Operation and maintenance status of the equipment**: Is the third-generation Jiusi membrane operating properly? The performance of the membrane deteriorates over time, and it may require inspection and maintenance. In addition, the condition of the buffer tank also needs to be checked for any signs of contamination or scaling. 4. **Water flow rate and treatment speed**: Changes in flow rate can affect the precipitation of calcium ions and the efficiency of filtration. If the flow rate is too high, it may prevent the treatment equipment from effectively removing calcium ions. 5. **Impact of seasonal changes**: Since the problems occur mostly in the second half of the year, they may be related to climate or environmental factors. For example, the rainy season may affect the calcium content during the extraction and transportation of mineral salts. It is recommended to start with these aspects for a thorough examination and analysis, in order to identify the specific reasons for the excessive calcium levels and take appropriate measures for improvement. At the same time, considering increasing the frequency of calcium ion monitoring, especially during seasons when problems occur frequently, can help to adjust the processes and treatment parameters in a timely manner. .
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From a process perspective, increasing the frequency of analysis is used to determine whether it is a process control issue; in fact, raw salt is the most unstable factor. It is determined by the raw salt production process. If the raw salt is sea salt, it is even more unstable. Mineral salts and lake salts are slightly better. Check out the raw salt
You mentioned the \"flow rate of water\"; since that is mentioned, it’s possible that the flow rate of water has changed at this stage. The precipitation that occurs as a result of the reaction between sodium carbonate and calcium ions is highly dependent on the excess amount of these substances as well as the reaction time. A higher flow rate results in a shorter reaction time, which affects the formation of the precipitate and can lead to excessive levels of calcium and magnesium in the brine.