6 replies to this topic

[logan*]

Hi! I'm a chemical engineering student from Italy and I'm working on a project, using Aspen Adsorption, regarding the operation of a packed column that should remove CO2 from a gas stream containing CO2 and N2. The purpose of the project is to find a functional expression of the diffusivity of CO2 as a function of bed coverage (instead of using a fixed one), with the aim of running a simulation and obtain results that fit sperimental data. I've tried to do this using Fortran and the Higashi et al. model (D = D0 * 1/(1-θ)), where D is the diffusivity, θ is the coverage and D0 is a constant. The problem is that I should estimate this constant, but it is not present in the Adsorption estimation module (the software doesn't recognize it as a variable).

Is there anyone who had faced the same problem or knows how to use Fortran to add a variable to the simulation?

Thanks in advance!

[Pingue2008]

Logan,

 

I am not sure I will address your issue but I have been working on a similar column. if your are using Aspen Plus,

you can simulate your column using the Radfrac block. I have not got mine to work as I wish.

http://www.cheresour...-packed-column/

 

Thank you

[logan*]

Pingue,

 

thanks for your answer, but I think we are working on different unit processes. The Radfrac block is for distillation columns, while I'm working with an adsorption column (that's why I'm using Aspen Adsorption instead of Aspen Plus). Correct me if I'm wrong!

 

Thank you

[Pingue2008]

 Logan,

 

In aspen plus there is no block named absorber (adsorption column), but the manual advise to use the Radfrac block and set the condenser and reboiler field to none. If you have access to aspen plus go to the help menu and you will read how to simulate an absorber column using aspen plus. I am not familiar with Aspen Adsorption, but  it sounds like the way to go.

 

Thank you,

[gegio1960]

Going back to the fundamentals:

- adsorption is a gas-solid process (or liquid-solid); you can't simulate it by RadFrac;

- absorption is a gas-liquid process.

In both cases a "packed column" makes sense, but a different one!

 

Logan,

just some brainstorming in absence of more details....

- do you really need a simulator to do that job?

- did you try to make the fitting with "simple" calculation tools (excel) and then connect your spreadsheet to the simulator?

- better to utilize a general-purpose process simulator than a specialized one, not very used in the industry.

My best wishes to you and your research job. Italy needs it.

Good luck

[Pingue2008]

Gegio1960,

 

The Radfrac block that I (pingue2008) proposed is to absorb the CO2 from the gas stream. please read the initial thread. it might have been a spelling error on my part. The Radfrac in Aspen Plus models packed column very well.

 

Thank you

[gegio1960]

Hi dear Pingue,

i don't know if it's useful to go ahead on this way but...

1) the initial thread clearly speaks of aDsorption. A solid aDsorbent. like mole sieves or active carbon, selectively captures the CO2 molecules from the gas stream. This process is realized in a packed column that you can't model with RadFrac.

2) your method speaks of an aBsorption process. A liquid (usually amine or soda soluton), aBsorb the CO2 molecules from the gas stream, flowing countercurrent thru the void spaces created by the inert solid. In this case the solid doesn't directly participate to the process, that you can model with RadFrac.

Incidentally, I've design experience of both the above mentioned processes.... and some additional research activities on the "membrane" alternative, too.

i'm interested in this discussion because, some years ago, I tried to put Aspen Adsorption in the working toolbox of my company... but it was too expensive and not very well developed for the design scopes. Now I see that Aspen Adsorption is included -at limited/no additional cost- in the AspeOne suite, but I don't work anymore on those processes ("simple" adsorption and PSA).

Good luck!