Amine Regenerator vertical thermosyphon reboiler not flowing properly 2

[kalinjm]

We have a thermosyphon reboiler on our amine regenerator that has not been flowing properly since turn around. The bottom sump of the regenerator has a auxiliary baffle and a preferential baffle. In fig 19-37 of the GPSA manual, it is baffle orientation b. We think it might be pluggage, but we can't conclusively verify that. I was wondering if anyone had any experience with this problem, any ideas how to conclusively verify pluggage, or any other potential causes?

Thanks

 

[pmover]

i presume the reboiler and regenerator operated satisfactorily before turnaround? if true, then i'd be asking what is different to reboiler before and after turnaround? any work done on reboiler or amine regenerator during turnaround activities?

fyi, which edition of gpsa manual is applicable? the 12th edition has fig 19-37 as the design parameters for top feed nozzles. using fig 19-42 does have the various configurations for bottom sumps.

-pmover

 

[grampi1]

Is there a high point vent to remove non-condensables from the steam side? Is it open?

 

[kalinjm]

The GPSA Edition that I am refering to is the 10th Edition. I wasn't here for the turnaround, but the reboiler was working properly before the turnaround. The reboiler didn't have any work done to it during turnaround other then inspection. The regenerator had alot of work done to it. We changed out all of the trays. We have two identical regenerator systems and the other one is working fine. Grampi1 I will see about the non-condesables. Thanks for all the help and any more advice or ideas will be appreciated.

Thanks

 

[kalinjm]

Our high point vent is open on the steam side. Our thermal scan does show signs of possible pluggage on the process stream. We are in the process of removing the insulation to get a full scan.

 

[sshep]

Is the problem that you can't get heat into the reboiler and you infer a process side problem- i.e. steam wide open with chest pressure at steam supply pressure, but no steam flow? By pluggage you hypothesize material blocking the inlet tube sheet or in the nozzle/inlet line. Other potential causes are loss of level on the reboiler side of the baffle due to leakage (raise bottoms level), foaming (shake test of bottoms material), film boiling (usually there is a cycling), a layer of floating hydrocarbons in the bottom (drain the tower).

A bit more on the symptoms might be nice as a "flow problem" is pretty non-specific. Opening up the system is likely to be disappointing, I have several times had this come up with nothing useful found inside. On the otherhand shooting some steam (or N2, steam is nice for an aqueous system) just long enough into the reboiler to intitate the thermosyphon, opening equalization between the bottoms compartments, closing the inlet butterfly valve (if you have one) and boiling down the reboiler then opening it, or other kicks to the system have mysteriously started the thermosyphon with the root cause remaining unexplained.

best wishes,
sshep

 

[kalinjm]

The main symptom that we have noticed is that the temperature going to the reboiler is 10 oF higher than it should be. To my understanding the temperature going to the reboiler should be the same as the bubble point of the liquid which is 264 oF. Also, our capacity on the tower is down approx. 40%. We have tried to use lift steam, add antifoam, and lower steam flow with no success in getting these temperatures back up in line. We are thinking that possible construction debris is clogging the reboiler inlet tube sheet or nozzle inlet lines. I don't know if we have tried opening the equalization valves between the bottoms compartments, but I will look into that one. We don't have any way to isolate the reboilers.

Thanks for all the advice. I will keep ya'll posted and if any body else has any more useful advice I am all ears.

 

[sshep]

The bottoms temperature should be the bubblepoint of your lean amine- the fact that it isn't is a clue. If your pressure at the tower bottoms is normal, and the temperature is true, then indications are that something is compositionally not right with your amine.

When you say tower capacity is down, is this due to higher bottoms temperature limiting the reboiler, or is there something else?

best wishes,
sshep

 

[kalinjm]

I am sorry I haven't responded lately to my thread. The limiting factor is the higher temperature of the amine causing us to be steam limiting. I wanted to thank everyone for there helpful post. We haven't fixed the reboiler problem completely but with other problems being addressed and fixed, the amine system is running good now. It is no longer the bottleneck to our facility. If anyone has any ideas on causes for SO2 spikes in the TGU incinerator, check my new thread out and please respond.

Thanks