What to do if the liquid level at the bottom of the distillation tower cannot be lowered?
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When our catalytic unit’s salt-washing system was restarted, the slurry pump experienced vacuum conditions, and the backup pump could not be switched in, resulting in a high liquid level. One wants to cut off the feed, but is concerned that a high liquid level in the bottom of the distillation tower could cause oil from the upper part of the tower to flow down, thereby flooding the gas-oil inlet and preventing the reactor from venting pressure through a flare. What should I do? Please give your support, colleagues. Thank you!
Fix the backup pump as soon as possible. This situation is dangerous whether the machine is parked or not: pressure builds up if it is parked, and coking occurs in the slurry system if it is not parked.
The main thing for the person in charge is to find a way to increase the flow rate of the slurry pump or switch to a backup pump; if that doesn’t work, they can consider manually shutting off the feed stream, without using the emergency bypass line. The device I used to work on could send the raw material back to the oil slurry reprocessing line for discharge. There should be other off-line raw materials as well. At this point, the operator must increase the recycle oil return to the tower as well as the mid-stage reflux, in order to prevent the catalyst from reaching the upper part of the distillation tower.
I wonder if you have a connection line between the inlet of the slurry pump and the inlet of the re-refining pump! If a re-refining pump is borrowed to pump the slurry from the bottom of the distillation tower.
As you said, if the feed is cut off and steam supply is also stopped, where would the pressure in the reaction section come from to rise? At this point, it is necessary to actively cut off the feed, reduce the steam entering the settler, or directly transfer the catalyst from the settler to the regenerator for single-vessel fluidization; meanwhile, the distillation system just needs to have its pumps repaired as soon as possible. If the liquid level at the bottom of the tower is high, so be it; without feed and steam, pressure cannot build up. This post was last edited by mjl25mp6 on 2008-2-23 14:00]
The priority is to identify the cause of the fault and repair the slurry pump as soon as possible! If the indication of the bottom of tower liquid level is faulty and the low liquid level at the bottom of the tower prevents the slurry pump from operating properly, production can be maintained for a short period of time by promptly fixing the liquid level gauge, increasing the amount of material sent back to the tower, and using raw materials to restore the liquid level at the bottom of the tower, thereby enabling the slurry pump to function again. If recovery is not possible or the slurry pump fails and cannot be repaired in a short time, immediately cut off the feed! Single-unit fluidization is carried out. The feedstock can be circulated or the feed pump can be stopped; priority should be given to dealing with the slurry pump, and the steam used for lifting should be reduced. Since the slurry pump cannot deliver enough flow, the temperature at the upper part of the baffle will rise rapidly. In this case, the bottom of the tower will not become full, but oil and gas will rush up to the upper trays, causing contamination of the product. It is possible to increase the circulation in the middle section as well as the amount of reflux sent back to the tower, by utilizing the oil refined and returned to the tower. After the feed is cut off, the distillation column lacks sufficient heat source, causing the temperature at the bottom of the column to drop. However, due to the circulation of the feed, no feed reaches the bottom of the column, so this does not lead to pressure buildup in the reaction vessel. It’s just that if the slurry pump isn’t repaired for a long time, it can be quite troublesome.
What was said upstairs is correct – “the key is to find the cause of the problem.” The vacuum condition in the slurry pump may be caused by too low a processing rate when dealing with salt accumulation in the distillation tower, which results in an excess of light components in the slurry at the bottom of the tower. Treatment: The bottom of the fractionation tower should be equipped with pipelines for emergency discharge of slurry, allowing such slurry to be discharged externally. At the same time, increase the temperature in the middle section of the fractionation tower as well as the gas phase temperature, in order to vaporize the light components in the slurry.
The slurry pump has been emptied – how can it be drained? The startup cycle line using slurry oil and reprocessed oil is acceptable; increasing the amount of reprocessed oil fed back to the tower works as well, but how can we ensure that there is no condensate in the slurry oil pipeline? How to discharge the slurry?