Amine Contactor Off gas cooler
Amine Contactor Off gas cooler
(OP)
Some debate at our plant regarding cooling of the sweet gas from the contactor.
Original design of the plant was (following sweet gas flow) contactor --> knockout (to recover amine) --> Dehydration (glycol, Refrigeration, and Lean Oil)
We are installing two new contactors, and the operations asked the question why we would not install an off gas cooler upstream of the amine knockout to help recover more amine.
My response was that cooling was not necessary as amine carryover due to evaporation was negligable compared to entrainment losses, and the only way to reduce entrainment was to slow the velocity of the gas ie. make the knock out wider.
they doubt my answer as they have worked in another plant that had upstream (of the knock out) off gas coolers. Hard to argue facts like that, but I am not convinced that the other plant installed off gas coolers for amine recovery my suspicion is that they had other motives. Any thoughts?
Original design of the plant was (following sweet gas flow) contactor --> knockout (to recover amine) --> Dehydration (glycol, Refrigeration, and Lean Oil)
We are installing two new contactors, and the operations asked the question why we would not install an off gas cooler upstream of the amine knockout to help recover more amine.
My response was that cooling was not necessary as amine carryover due to evaporation was negligable compared to entrainment losses, and the only way to reduce entrainment was to slow the velocity of the gas ie. make the knock out wider.
they doubt my answer as they have worked in another plant that had upstream (of the knock out) off gas coolers. Hard to argue facts like that, but I am not convinced that the other plant installed off gas coolers for amine recovery my suspicion is that they had other motives. Any thoughts?





RE: Amine Contactor Off gas cooler
I would however install a sweet gas cooler and KO drum. Cooling will also condense water, which cleans up the fuel gas.
In addition, the key is that your KO drum has a demister pad, which provide most of the benefit. Without cooling you can just as well add the demister to the top of the absorber.
RE: Amine Contactor Off gas cooler
The temperature reduction reduces water content in a big way, and reduces the amount of glycol circulation that may be required.
A sweet gas scrubber is really a serious requirement - all it takes is one foaming incident with amine carryover and it's justified to prevent amine losses and downstream contamination.
RE: Amine Contactor Off gas cooler
It is my understanding that temperature plays a very small role in reducing amine entrainment therefore a cooler would not help, at least not a whole lot.
I would disagree CJKruger's comment of "just as well add a demister to the top of the contactor" as a knock out helps separate the entrained liquid by slowing down the vapour (larger diameter than the tower). A demister helps but the key is fluid velocity.
Our design is not for high CO2 loading, also we run split flow to the tower (lean + semi lean, the gas off the contactor is only about 55oC. The refrige/dehy system is nowhere near loaded so the benefit of adding cooling upstream of the knockout is lost on me.
I appreciate both your timely responses. Thanks
RE: Amine Contactor Off gas cooler