Abnormal pumping vacuum in the middle pump of catalytic fractionation
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During stable operation, the reaction feed rate is 85 T/H. The extraction temperature in Column 1 is between 310 and 320 degrees, while the circulation rate in this column is around 300 t/h. When the pump in Column 1 cannot deliver sufficient flow, the extraction temperature in that section drops below 300 degrees; following this, the temperature rises significantly, and the pressure at the pump outlet fluctuates greatly. Even the backup pump fails to deliver sufficient flow, but normal operation is restored after a short time. I would like to ask everyone about the reasons for this phenomenon, as well as whether there are similar cases.
This post was last edited by buds on 2015-9-14 12:40. Should used oil be reprocessed? Is cold reflux to be injected? Was the mid-range value always this high from the beginning as well? Let’s see if it drops a bit. With such a large volume, there’s a risk of drawing the liquid level down to zero. Has this phenomenon existed before as well? Does it happen often?
There is no reprocessing of contaminated oil, and under normal conditions no cooling reflux is used; this phenomenon is quite occasional – it has occurred three times, with the amount in the intermediate stage remaining consistently high
Does evacuation occur in your operations when the intermediate temperature drops below 300? Or check the trend analysis of DCS to see if such a coincidence exists!
Try reducing the mid-section volume by 30–40 tons.
Check the historical records to see if it coincides with the time when the catalyst was added, and determine whether an excessive amount of catalyst was used, resulting in too high activity and a decrease in the diesel components.
Stable pressure oil, temperature gradient, changes in oil and gas volume, changes in head pressure, salt formation. The circulation volume increases
Does oil come out from the inlet vent when the pump is evacuated?
Regarding this issue with the small wound, I suspect it might be salt deposition. Or it could be due to changes in the properties of the reaction materials
If salt deposition is so severe in the middle section, isn’t it even worse at the top?
It can be assumed with certainty that the gas-liquid contact in this section is not sufficient. If the situation can be restored in a short time, it indicates that the possibility of the tray being overturned is low. In the case of salt formation, it’s likely that the float valve holes in the upper part are blocked, preventing the liquid phase from accumulating properly; as a result, the pump draws air in for a while. When the liquid level rises, some of the liquid is sent out, and once the pressure drops again, local flooding of the tower occurs, creating a vicious cycle.