Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Distillation Tower Flooding 1
- Thread starter Falcon03
- Start date
-
1
- #2
Flooding = accumulation of liquid within the column.
If liquid accumulation occurs below the feed you could observe erratic level in the column sump. If liquid accumulation occurs near top of column, you may see erratic level in reflux drum. A further symptom of flooding is poor separation due to poor vapor/liquid contact. Depending on how many of the trays are flooded, you may be able to see that the temperature profile is flat in the region where flooding has occured. Consider also the value of the total column pressure drop. Typical tray DP's are 0.7 to 1 kPa/tray. If average tray DP is much higher than this it would also be indicative of tray flooding.
A good check to see if your column DP is faulty or if the problem is flooding would be to back-off on column loads to see if DP behaves better at lower loads. DP should increase proportionately with loads and at flood point there should be a sudden sharp increase in gradient.
Flooding could also be liquid or vapor sensitive. There are tests you can perform to determine which it is and also what the flooding mechanism is (i.e. downcomer backup flooding / downcomer choke flooding / jet flooding). For more on these techniques refer to "Distillation Operation" by H.Z. Kister.
Lastly, you could take column hydraulic data from steady state column simulation and ask a reputable tray vendor to rate the column internals.
Hope this helps..
Greg
If liquid accumulation occurs below the feed you could observe erratic level in the column sump. If liquid accumulation occurs near top of column, you may see erratic level in reflux drum. A further symptom of flooding is poor separation due to poor vapor/liquid contact. Depending on how many of the trays are flooded, you may be able to see that the temperature profile is flat in the region where flooding has occured. Consider also the value of the total column pressure drop. Typical tray DP's are 0.7 to 1 kPa/tray. If average tray DP is much higher than this it would also be indicative of tray flooding.
A good check to see if your column DP is faulty or if the problem is flooding would be to back-off on column loads to see if DP behaves better at lower loads. DP should increase proportionately with loads and at flood point there should be a sudden sharp increase in gradient.
Flooding could also be liquid or vapor sensitive. There are tests you can perform to determine which it is and also what the flooding mechanism is (i.e. downcomer backup flooding / downcomer choke flooding / jet flooding). For more on these techniques refer to "Distillation Operation" by H.Z. Kister.
Lastly, you could take column hydraulic data from steady state column simulation and ask a reputable tray vendor to rate the column internals.
Hope this helps..
Greg
First check your DP indication
Best method I have found is to use two seperate (Independent) pressure transmitters & do the DP calulation via a moore card in your DCS.
Your are basically going to have to do a set of trials to map a pressure profile of your tower.(ensure the readings are taken directly off the tower at sample connections etc and not at a common header at the base of the tower)This chould give you a "magic number" the operators can keep the DP below. (also give them a simple mass balance spreadsheet)
Best method I have found is to use two seperate (Independent) pressure transmitters & do the DP calulation via a moore card in your DCS.
Your are basically going to have to do a set of trials to map a pressure profile of your tower.(ensure the readings are taken directly off the tower at sample connections etc and not at a common header at the base of the tower)This chould give you a "magic number" the operators can keep the DP below. (also give them a simple mass balance spreadsheet)
b4 flooding level rises ... as level rises ... as level increased (if the distillation tower has a side draw-off's) the properties of draw-off's differs (if petroleum industry the collours become darkers @the upper trays) & down trays become colder...
the main indication for level increasing is the increase of pressure.
by the way under any adoubt of flooding watch:
1-High levels of bottom..
2-Pressure increase of the collumn.
3-Temp.'s of trays become colder.
the main indication for level increasing is the increase of pressure.
by the way under any adoubt of flooding watch:
1-High levels of bottom..
2-Pressure increase of the collumn.
3-Temp.'s of trays become colder.
DMcMahan is right, this service can and will fast and accurately pinpoint flooding as well as many other process related problems and internal damage. check it ouit here for more info.
maybe we can help.
maybe we can help.
- Status
Similar threads
- Locked
- Question