7 replies to this topic

[Satyendra Balot]

Dear All,

We have amine absorber in fcc unit, this absorber has wash section of 3 trays. This absorber has kod downstream. I need to know the requirment of amine wash section above amine absorber. If the reason is to recover entrained amine, then still do we need to have downstream kod.

[Bobby Strain]

Surely you must know.

 

Bobby

[Propacket]

That is a very good question. 

 

When you are using a wash water section above absorber and a demister as well, you should expect minimal of amine in downstream KOD (This is from my calculations experience, no operating experience of mine about it). Minimal of amine means losses as low as 100 times lower than conventional value of 0.1 USgal/MMSCF. What you will get in the KOD should be mainly WATER. So no need of a downstream KOD as far as amine entertainment is considered.

[fallah]

Hi,

 

The water wash section at the top of the absorber is there due to following reasons:

-to limit the amine entrainment in the treated gas

-reducing solvent losses

-to prevent product contamination

 

The downstream KOD will serve to separate any possible liquid carry-over from the treated gas and its main function will be to act as a solvent surge drum in the case of accidental severe foaming in the absorber... Therefore, it must be considered to be placed there...

[Satyendra Balot]

Thanks for the reply, one more clarification i need, that is this applicable only for MDEA? As in the old refinery, we r using DEA, and in that we dont have such amine wash section to remove entrained amines. what are the reasons to have amine wash section for MDEA?

[Art Montemayor]

Satyendra:

 

The answer to your question is: Good, experienced design engineering on the part of the client or the engineering contractor.

[RockDock]

amine washes just depend on what you are comfortable with losing. MEA is the least stable amine while MDEA is the most stable. DEA is in between. Most MEA units will have a water wash, while only the very large MDEA units have one usually. That is because MDEA will not lose nearly as much as MEA. A model will predict the losses for you and help you cost the benefits of adding one for an MDEA unit.

 

From my experience, I would always have a water wash for MEA, most times for DEA and sometimes for MDEA.

[ZBR]

Wash water requirement is not just dependent on the type of amine but also on the operating parameters. like i had one unit with MDEA which had the water wash and another with DGA which also had it. But we had a high over head temperature around 140 F so the carry over is more likely, typically if you have low over head temperature less will be carry over. In middle east usually they have high OVHD temperatues and frequently apply wash section. In west you may get low OVHD temperatures but still depending on stability of amine and avoiding product contamination you may still wanna have it.

 

I would agree with fallah on the rest.