Discussion and request for help: Analysis of the caustic solution during the alkali washing of olefins
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This post was last edited by qugd on 2023-1-13 at 13:40. Hello, everyone! A few days ago, a friend asked about the current purification processes for ethylene cracking gas in China. Specifically, regarding the alkali washing units used to treat this cracking gas, laboratories are generally used to analyze the waste alkaline solutions from different washing stages. How often is sampling and analysis carried out by these laboratories, i.e., every few hours? What are the requirements for analysis results from a process perspective? Are there any users at home and abroad who use online analysis methods at present, or are there such online analysis techniques for analyzing alkalis and sulfides in alkaline solutions? First, thank you all for your participation.
Why can’t any friends provide some reference information or share their opinions?
Our company conducts alkali solution analysis in the weakly alkaline and strongly alkaline ranges every 8 hours, that is, once per shift. The online alkali concentration analyzer cannot be put into use.
Could we discuss the reasons why the online alkali depth analyzer is not operational? Is it a problem with the testing method, or an obstacle in sample handling during testing?
The alkaline solution contains oil, which affects the on-line analyzer.
Thank you for your reply! That is to say, an online analysis table was installed before, but its performance was not satisfactory. Could you tell me which company’s product it is? I’m causing trouble.
It is impossible to determine whether there is oil in the alkaline solution; I have never seen such a situation. If oil is present, it is necessary to use a sampling pump to carry out intermittent online sampling and flushing. It’s not necessarily true; for reference only
Thank you for your participation. When analyzing certain parameters of aqueous solutions online, if the sample contains oil, especially oil that tends to adhere easily, it is quite difficult to remove this oil. This issue involves not only the problems related to the sampling pump but also the problem of oil contaminating and sticking to the pipelines and various connections; sometimes even enhanced maintenance efforts are not sufficient to resolve this issue. I am considering the analysis of the alkali solution and spent alkali solution in different washing sections of the ethylene caustic scrubber; these factors have a significant impact on the effectiveness of oil removal as well as on the accuracy and reliability of the analyses, and I am looking for ways to improve this situation. Some experiments were conducted, but the results were very unsatisfactory.
This post was last edited by *nht1 on 2023-4-13 at 11:59. If that’s the case, the first step is to use a micro diaphragm pump or centrifugal pump to draw a certain amount of sample and continuously spray it onto the probe or electrode in order to obtain measurement data. The second step involves using another micro pump to deliver an oil-removing cleaning solution onto the electrode, allowing the electrode to be cleaned for a few seconds, with the main purpose being to remove oil. The third step is to use a pure water pump to supply pure water for rinsing the electrode for a few seconds as well. A simple PLC-based control system can be used to manage this process. Since the amount of water generated during rinsing is relatively small, it can be directed into the process water stream – isn’t that more reasonable? Add three micro pumps, a pure water tank, a cleaning reagent tank, and a PLC controller. As I understand it, if electrode-based instruments are used for testing, as long as the electrodes are cleaned thoroughly each time, the test results will definitely be accurate. If other parts become dirty, as long as they are not blocked, it will not affect online sampling or the accuracy of the test results.