Jump to content

Featured Articles

Check out the latest featured articles.

File Library

Check out the latest downloads available in the File Library.

New Article

Product Viscosity vs. Shear

Featured File

Vertical Tank Selection

New Blog Entry

Low Flow in Pipes- posted in Ankur's blog


Co2 Absorption Column Using Amdea

absorption co2 amdea mdea

No replies to this topic
Share this topic:
| More

#1 AyrtonB


    Junior Member

  • Members
  • 10 posts

Posted 21 January 2018 - 07:58 PM

Hello everyone,


I'd be grateful for any advice on the design of my CO2 absorption unit within an Ammonia plant, thank you in advance for all replies.




I am using activated MDEA (aMDEA) at a concentration of 30 wt% MDEA, 3 wt% Piperazine (PZ) with the remaining solution being water, it enters the column at 32 degC. The gas stream from which CO2 is being removed enters at 35 degC and contains:

H2O = Neglibile 

CH4 = 0.69%

CO = 0.2%

CO2 = 17.87%

H2 = 61.42%

N2 = 19.5%

Ar = 0.23%

Total Flowrate = 224,910 kg/hr


Much of the literature I have read suggest that both Aspen Plus and HYSYS model the reactions between CO2, MDEA and PZ poorly, as I don't have access to software such as ProMax or ProTreat I have opted to base my design off of experimental data. Using a paper which gave partial pressures and CO2 loading across a range of temperatures I have formed a model in Matlab which accounts for the high heat of reaction, it operates under the assumption that the reaction is thermodynamically rather than mass transfer controlled (literature suggests this is reasonable for a medium conc MDEA & PZ system). 

For a removal of 99% at a column pressure of 25.7 bar my model had a result of 18 trays required and the gas stream leaves at 60 degC. The plot is shown at the bottom of this submission. The CO2 loading is at 0.5 (mol CO2/mol amine) and the lean solvent enters at 508 L/s. Further calculations gave the column diameter to be 3.7m with a height of 12.4m.
Please comment if any of these values seem wildly off.
1) I have opted for a tray column as the high liquid hold-up is recommended for a highly reactive system, I had also seen a Shell CO2 absorption column using the same solvent use trays. My question is whether this is the method that anyone here in industry uses? if you use packing instead why is that?
2) I plan to use a small layer of packing at the bottom of the column to reduce gas entrainment, is this used in industry? if not is this because the carry over is low or do you use another method?
3) Would you use a spray tower or ejector scrubber to add the solvent? I'm currently struggling to understand the pros and cons of each and would appreciate any literature recommendations to help with this.
4) Ullman's Encyclopedia of Industrial Technology suggests using valve plates, specifically varioflex, for the trays, what literature would you recommend to aid with the design of these? Alternatively, are there standard designs used and if so how does one go about the selection process?

5) What is the best way to approach calculating the annual amount of amine make-up required? Presumably the make-up will contain a higher % of PZ as it vaporizes more readily and will therefore carry over at a higher rate, how would I approximate the new make-up ratio? Additionally, what is the average cost for such a make-up?



Edited by AyrtonB, 21 January 2018 - 08:30 PM.

Similar Topics