2 replies to this topic

[Truck]

Dear all,

 

I am now simulating a biogas plant with an amine upgrading unit (MEA, 30%) by a superpro designer.  As I understand, the CO₂ loading in lean amine is around 0.3 mol CO₂/mol MEA. Thus, I am wondering if lean amine contains CO₂, do we need to increase amine solution so that it will meet CO₂ loading in rich amine is 0.5mol CO₂/mol MEA?

 

Thanks for your help!

[Art Montemayor]

Truck:

 

Your questions indicate that you haven’t done the study and homework required to undertake your project.  You should have already read and studied such material as  “Gas Purification” by Kohl & Nielsen, the NGPSA Engineering Databook, and “Gas Conditioning and Processing” by John Campbell.  Have you done this?

 

The best way for me to help you out is to pass on many years of field experience in designing, building, installing, and operating Amine systems for CO₂ removal:

• How did you arrive at a decision to employ a 30% weight MEA solution for absorbing CO₂?  I would not employ any solution over 15% weight.  Corrosion will eat up your process in no time at all.
• Design for a Rich MEA solution with 0.30 mole CO₂/mole MEA; Lean MEA should be 0.10 mole CO₂/mole MEA.  Where do you obtain your "understanding" of CO₂ loading?
• The Lean solution will ALWAYS have some CO₂ loading.  You increase this loading by subjecting it to CO₂ in the MEA absorber.  You subsequently regenerate the enriched Rich solution and recirculate the resulting lean solution.  What is it about this process that you don’t understand?

Many students have come to this Forum in the past 20 years seeking help but seldom answering our direct questions.  Please answer any questions given you if you wish to continue to receive free help.

[Truck]

Dear Art Montemayor,

 

Thank you very much for your answer. Yes, I have not read and studied those books yet as I am not chemical processing student. I am studying biogas, and biogas contains 35-55% CO₂ and 55% -35% CH₄. Thus, I want to use a model to simulate a biogas plant with an upgrading biogas by amine scrubber. I learn how to do it by reading previous journal papers.

 

- The decision to use 30% of MEA  are: (i) high concentration of CO₂ in biogas (45% CO2 in biogas for my stimulation) and low water will be used if I use high MEA;  (ii) reference [1] states that "Fluor Daniel uses 30% w/w MEA solvent with the help of some corrosion inhibitors".

 

- The upgrading methane requires less than 6% vol of CO2, therefore, it requires removing 96% CO₂ from biogas. If high CO₂ needs to be absorbed, rich amine solution should be 0.5mol CO₂/mol MEA. In addition to this, those references [2, 3] also used 0.5mol CO₂/mol MEA for their studies. Beside that, the lowest energy requirement of 176 kJ/mol CO₂ (4 GJ/ton CO₂) can be achieved

at lean solvent loading between 0.25 and 0.30 mol CO₂/ mol MEA [2, 3, 4].

 

-  At first if you design the plant and you know that for 1kg of CO₂ input (to an absorber) you needs 2.77kg MEA + 6.47kg H₂O (30%MEA solution, 96% CO₂ removal). Then if 0.3 mol CO₂/mol MEA lean amine is circulated back to the absorber, the total solution now are 1.598kg CO₂ (1kg in put + 0.548g circulated) + 4.426kg MEA (2.77kg circulated +1.656 kg new) + 10.3kg H₂O. Thus my question is: Do I need to redesign the columns for the new mass?

 

Kind regards,

 

 

 

 

References:

 

[1] A Technical, Economic and Environmental Assessment of Amine-based CO2 Capture Technology for Power Plant Greenhouse Gas Control. https://www.cmu.edu/... June 2012.pdf;

 

[2] Systematic study of aqueous monoethanolamine-based CO2 capture process: model development and process improvement. http://onlinelibrary...2/ese3.101/full

 

[3] CO2 capture from power plants Part I. A parametric study of the technical performance based on monoethanolamine. http://www.sciencedi...750583606000077

 

[4] Energy saving in a CO2 capture plant by MEA scrubbing. http://www.sciencedi...263876210002959