Hydrogenation – a strangely high score
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Yesterday, a strange phenomenon occurred in our diesel and gasoline hydrogenation unit: no water could be separated out in the cold high-pressure separator. The water injection rate was 4000 kg/h; the level gauge was functioning properly but showed abnormal readings, staying around 18% with no change. The water is not removed thoroughly enough through low-pressure treatment; some of it enters the stripping tower, resulting in difficulty in controlling the liquid level in that tower. After spending a whole day trying to find the exact cause, I stopped supplying water for an hour, and things returned to normal. Let’s discuss what the reason for this is
What is the inlet temperature at high cold temperatures for you? What was the level of the cold high-pressure liquid before the abnormality occurred? Was the level indicator around 18%, with no change in that level? Was the level control valve still set to automatic mode? It seems that the cold fraction has poor oil-water separation; most of the oil and water end up in the lower fractions, which in turn causes water to be carried into the distillation process. After stopping the water supply for 1 hour, the low temperature and high pressure allow the oil and water to have sufficient time to separate the previous water. Personal opinion. . .
Reply to Floor 2: The inlet is at 45°, the liquid level control is set to automatic mode, and production is proceeding normally. The gas lift liquid level was difficult to control; after thorough investigation, it was found that high pressure was the cause. It was quite sudden. What you say makes some sense, but the high-level gauge didn’t rise after stopping the water injection; around 30 minutes after the injection, the readings were normal, and the low-level gauge stopped increasing further.
Whether the high-pressure cut-off control valve is operating, whether the on-site manual valve is open, whether the path downstream of the high pressure is unobstructed, whether the on-site glass panel displays the correct time, and also the anti-freezing and anti-condensation measures
I think it’s due to an excessive processing volume or high water injection rate, too fast line speed or flow fluctuations, a short residence time at high temperatures, and limited time and space for oil-water separation. Furthermore, it could be that the raw material is relatively heavy and its density is close to that of water, or the oil may emulsify as a result of an increase in feed temperature; it’s also possible that there is a problem with the coalescer.
It’s no big deal; our high-level gauge has been inaccurate, so we’ve been using low-level dehydration, and nothing bad has happened afterward.
Reply to 7# Xiaoyue Xiaoyao, yes
Did you not turn the boundary control valve up or down? Is the boundary meter on site easy to use?
At present, poor high-density separation in hydrogenation units is a significant challenge, especially in units with a single high-density separation process. Issues such as too small a density difference between oil and water, short sedimentation times, and other related problems exist. It is necessary for everyone to work together to accumulate experience in order to ensure the stable and safe operation of these units
The analysis indicates that the processing load is excessive and the separation time is too short. At present, the high-level boundary can only be controlled based on experience; it is necessary to frequently check whether the fluid discharged from the boundary is oil or water in order to determine the appropriate action to take.