how to simulate absorption tower with reaction?

[sahil]

Nitric Acid process.

1. How to find interaction parameter for Peng Robinson equation?
2. How to find the k(equilibrium and kinetics) equation in reaction section?
3. And also the A,B, C etc in the equation?

[jasper]

1) a literature search for the binary interaction parameters. If that fails, you would have to fit them to e.g. VLE data, which also should come from literature (or measurement)

2) from literature (or measurement)

3) which equation?

Note that most processes involving nitric acid and water will likely require an electrolyte based thermodynamics package for an accurate description. But Peng Robinson could do a reasonable job with proper interaction parameters.

[arvind.prasad]

We are trying to simulate a nitric acid process. The process is a medium pressure process. We have been able to so far simulate the reactor. Here the gases coming out from the Nitrogen dioxide reactor are absorbed in a absorption tower. This is obviously absorption with reaction. For this we are using Chemsep. We have decided to use NRTL for liquid phase, since we believe that NO2 will get dissolved in the water, and will from HNO3. The gas phase will be taken as Ideal, for the pressure of absorption is below 10 bar. Also we are unable to figure out how to configure Chemsep for Absorption with reaction. Since there is no example, we are a bit stuck. Is there any reference paper that we can simulate??

[hkooijman]

You can find the proper modeling of nitric acid absorption columns in:
* Ind. Eng. Chem. Res., 1997, 36 (10), pp 4325–4334 (http://pubs.acs.org/doi/abs/10.1021/ie970186j)
* Computers & Chemical Engineering Volume 20, Supplement 2, 1996, Pages S1425-S1430 (http://www.sciencedirect.com/science/ar ... 549600244X)
* Chemical Engineering Science Volume 60, Issue 22, November 2005, Pages 6462-6471 (http://www.sciencedirect.com/science/ar ... 0905003726)
There are probably a few more publications from the hand of Professor Gorak and his coworkers you can find with a Scholar search.

As you will be able to read in these publications, there are gas phase as well as liquid phase reactions, and the mass transfer can be affected by the reactions. To properly model the acid formed, an electrolyte model is the proper way of modeling. Typically, the absorption columns also have cooling equipment on the trays so you need a tool which can handle all this. ChemSep LITE doesn't have the capability to do all that. Of course, for the sake of getting an approximate plant simulation going, it is possible to "cheat" and use Henry's law and assume no reactions, but this would need tuning to a particular plant, and would not transfer to differently sized columns. Henry's law data are here http://webbook.nist.gov/cgi/cbook.cgi?I ... Solubility However, these would have to fit the Henry coefficients to a form required by ChemSep since it does not come with a Henry for NO2.

-Harry

[sahil]

We read the papers it was helpful , but it didn't help us to simulate the reactive absorption in COCO. Do u have any example or flowsheet which we can solve it in COCO?
Also the Henry law shortcut is good but right now we are keeping is as last minute option.
And we are trying to solve our NO2 absorption tower with reaction using DECHEMA thermodynamic package and activity coefficient using NRTL model. The problem in NRTL model is that we aren't able to get the binary interaction parameters like aij, Aij, Aji. So if u have any idea on how to find them or how to calculate them please share.

[jasper]

Neither ChemSep's thermo, nor COCO's thermo is able to provide electrolyte models. You can do it in COFE, but you will need an external thermodynamics package that does provide you with the electrolyte thermo, or make some assumptions on basis of which you do not need electrolyte thermo (for example the Henry assumption).

[arvind.prasad]

[jasper]

If your question is whether you can set up reactions in ChemSep, the answer is yes.

[colancto]

My recollection is that the thermodynamic/reaction modelling involved is rather complex. I think it is why there is for example a version of ProSim Plus which was tailored (a long time ago) to whatever fertilizer manufacturers were looking for.