What is the reason for poor liquid discharge when starting up the high-pressure separator at the outlet of the methanol synthesis tower?
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In our unit’s methanol synthesis system, two liquid discharge pipelines have been designed from the high-pressure separator to the low-pressure flash tank; both are controlled by control valves and are equipped with Blue-type filters. During startup, it was observed that there was poor liquid discharge as the load was increased – even with both control valves fully open, the liquid level in the high-pressure separator could not be controlled, and the load could not be increased further. We would like to ask the experts the following: 1. What is the purpose of designing two pipelines? 2. What are the possible reasons for poor liquid discharge? A few additional points: this device is new and has never been operated at full capacity. The project has been delayed for a long time, and the original designers from the design institute cannot be reached, so it is not possible to communicate with them. I would like to ask for your advice
Check if the filter is clogged
Is the filter clogged? It tends to get clogged at the beginning of driving. One pipeline is associated with one control valve and one filter; they form a set. During production, one set remains in use while another serves as a backup. When the filter becomes clogged, the backup set takes over, and the set that is in use is taken out for maintenance.
It has been cleaned many times. The filter mesh inside used to have two layers, but now it has been changed to one layer. Previously, a 100-mesh sieve was used; I would like to switch to an 80-mesh sieve. I’m wondering if anyone has any good suggestions
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What is the designed production load? What is the filter pressure difference?
What is blocking the filter? Paraffin or catalyst powder? Or other miscellaneous items? For 2 filters, wouldn’t it work to have one in use and one as a backup? If it’s one in use and one as a backup, it shouldn’t affect production, right?
Check for any blockages; if the filter is clean, there might be a problem with the separator. It’s possible that something was left inside the pipes during installation or during the manufacturing of the equipment. Normally, the designers wouldn’t make such basic mistakes
At first it was catalyst dust, and later paraffin; it’s impossible to control between the operating and standby modes
It is recommended to increase the separator inlet temperature slightly and reduce the filter precision further to see if there is any improvement. Of course, these are all emergency measures; the ultimate solution requires an analysis of the specific causes. It may be due to poor catalyst selectivity or the presence of impurities that result in excessive paraffin; the filter flux is then increased based on the analysis results.
Generally, one of the two pipelines is in operation while the other is in standby mode, which facilitates the removal of the control valve for maintenance. Due to the large pressure difference before and after the control valve, it is easy for the valve element to get damaged, and the liquid level in the separator cannot be controlled; in such cases, the control valve needs to be removed for maintenance. Additionally, the drainage pipeline in the poster’s unit is not functioning properly; check the basket filter, as well as whether the control valves and pipelines are unobstructed, and verify that the control valves are not damaged and thus unable to perform their control function. Once again, it is necessary to analyze the reasons for the high production of paraffin – whether it is a catalyst issue or a problem with the control of process parameters, such as an excessively low temperature at the inlet of the synthesis tower – and to rule out each possible cause one by one.