4 replies to this topic

[ronaldo115]

I'm a Chemical Engineering Student and i've been assigned a project regarding recovery of ammonia from a gas mixture consisting of 30% ammonia 40% carbon dioxide and the rest water vapor. I'm aware that the best way to do this is by absorption using MEA as solvent and using the AMINE PACKAGE in HYSYS to simulate. But the problem is we are only allowed to use PRSV fluid package for this simulaton project. So i'm stuck on how to start about planning the flowsheet for this problem since it is not possible to simulate absorption with MEA using the PRSV package in HYSYS. Please help me out in this problem. We have been given a target of 99% purity of ammonia in the product. And we dun have to consider costing in this project.

[Andrei]

Ronaldo,

Your known "best way" may not be the best way to perform the separation. Usually the amine absorption is done in a water solution, say 50/50%, and ammonia has a very high water solubility. So you will end up with CO2 absorbed by amine and ammonia by water, no separation. Maybe your professor was right when he forced you not to use amine thermodynamics, he wanted to channel you in another direction.
You should consider some thermal separation process.
Or maybe some thermo-chemical process. Please Google for "chilled ammonia process". It is not yet commercial, but theoretically works. The configuration is similar with an amine plant, but the process involves ammonia bicarbonate and carbonate solution.

Good luck

[smalawi]

Hi,

I'm not sure which process to select to do this separation, there should be many !

I understand that you dont have access to the amine pakcage and only the PRSV. As for using the PRSV it will give you very deferent results

For absorption 30% eff for CO2 and regenration col of 20% and it should work but seems PRSV will still give wrong results totaly !

An alternative is to use the Electrolite package but its not easy to use.

[Andrei]

Gentlemen,

You can try to simulate an Amine system using PRSV, but do not expect to have real results.
I do not want to offend you, but you should read the fundamentals of any equation of state. You will find out the fundamental difference between PRSV and Amine thermodynamic packages.
PRSV, as any equation of state,will consider only the physical CO2/H2S dissolution in the liquid.
As maybe you know, there are some chemical reactions happening in the absorber, reversed in the regenerator of an Amine separation system. There are speed and heat of reaction involved there. An amine package will try to estimate those, while an Eq. of State will ignore them. What you will get is a system with a huge circulation rate, without any connection with the real world.
If your professor told you to forget about amine package, you should do that. And start to think at something else. Did you tried a simple criogenic separation? Or a fractionation,something...

[Zauberberg]

The answer on your query is already contained in the question itself, as suggested by Andrei: if PRSV (or just Peng-Robinson) method is allowed for developing the flowsheet of separation process, then it is obvious that your professor was referring to some king of physical separation. So forget about the amine, and try to think of something else: selective absorption could be a potential answer for separation of these two components.