11 replies to this topic

[piolin]

Hello, I'm making a simulation of gas sweetening plant. This plant treat a gas stream to come to high-pressure system of a HDS plant, this stream don't contain CO2, it only contain H2, H2S and light HC's. I have used the amine package, but I have some doubts.

I don't know when I should use Li-Mather or Kent-Eisenberg model. I have read that I should use Li-Mather for VLE and Kent-Eisenberg for LLE, but I'm not sure. I'd like to know when should I use each one and why.

I'd like to know too when should I use non-ideal or ideal termodynamic model and why.

So that I have made the simulation with Li-Mather/non-ideal thermodinamyc model as HYSYS manual advices.

Thanks.

Li-Mather is a more fundamental and rigorous model as opposed to the older and empiricaql Kent-Eisenberg method. The non-ideal themo package accounts for the kinetic effects which for just H2S absorption are minimal as the reaction is fast.

[piolin]

Thanks Frank, I'm grateful to you

[Ingegnè]

I'm studying a similar case of Pioline. CO2 sweetening without H2S.

My problem is that:

I'm not able to understand how to size the column. Once I have run the calculation and obtained the %CO2 required, I go for sizing the column (TRAY sizing utility). I insert Diameter, packed tower internal, type of packings and I start with a certain heigh of bed.
I can apprechiate that whatever height I insert and run again the calculation, the final result in %CO2 is always the same.
how is it possible?

[Padmakar Katre]

Dear,
Please be specific about what are you telling because your statements are not clear.First could you tell me what is your active spec(Tray Sizing-Design-Specs-Mode-Design/Rating).If mode is design then you need not to insert the dia of the section let the Hysys to calculate these all design parameters and in case of rating of an existing tower then you have to vary the dia and check for flooding and related consequences.
Waiting for your comment.

[Padmakar Katre]

Li-Mather is a more fundamental and rigorous model as opposed to the older and empiricaql Kent-Eisenberg method. The non-ideal themo package accounts for the kinetic effects which for just H2S absorption are minimal as the reaction is fast.

Addition to the above,
Kent And Eisenberg Model

-A model based on the Kent and Eisenberg approach is used to correlate the equilibrium solubility of acid gases in the amine solutions. The reference articles contain experimental data that were used to validate the solubility model The model is used to interpolate and extrapolate the available experimental solubility data in the Amines Property Package. For tertiary amines that do not form carbamate, the equations involving that ionic species are eliminated from the model.

Li-Mather Model-

The Amines property package is modified to simulate three phase behaviour. For the three phase simulation, the K values from the Peng-Robinson property package were combined with the K values from the Amines LLE and VLE package.

The Li-Mather model shows a strong predictive capability over a wide range of temperatures, pressures, acid gas loadings, and amine concentrations. The framework of the thermodynamic model is based on two types of equilibria: vapour-liquid phase equilibria and liquidphase chemical equilibria.

[Ingegnè]

perhaps my desription is not that clear.
If you would like to know the height of the packed tower you are rating and to appreciate how height influences the CO2% at the outlet, how could you do?

[Zauberberg]

Ingegnè,

It is still not clear - are you designing a completely new tower, or you want from Hysys to perform rating calculations of an existing amine absorber?
Please be more specific.

Regards,

[abhi_agrawa]

Ingegnè,

From the information you have provided, it seems that you wish to fix the height of packing required. To this I can say that HYSYS can not provide you the answer. HYSYS simulates on the number of theoretical tray that you input. Now, if you multiply this number of theoretical trays with HETP (height equivalent of theoretical plate), you would get the packing height needed.

As the name suggests, HETP is the height of packing required for achieving separation that would have been achieved in 1 theoretical stage. HETP (or some people call it HETS: height equivalent of theoretical stage), is a strong function of the fluid properties, type of packing etc.

Hope this helps,
abhishek

PS:Suggest you have a look at http://www.cheresour...packcolzz.shtml
The HETP values given in the article are indicative.

[Ingegnè]

Oh, thank you so much for your clear reply. I was looking for that answer for so long. I couldn't find any confirmation of what you answered on none of tutorials or manuals.
Thank you so much

[Lukas]

Is this topic still ON?

I have a different problem with amine absorption.

I have to sweet a C2 gas stream from CO2, that is present as 0.7% in molar basis.
Sweet gas shall have max 0.2% of CO2.

I'm using DEA acqous solution, 25% weight basis.

I could not reach the outlet spec.
Hysys don't succed to go under 0.5% CO2 content.

Is there any one that faced this problem too?

[Zauberberg]

1. Check lean amine loading - if equilibrium CO2 content in lean amine is such it cannot pick up more CO2 from the gas, increasing reboiler temperature will solve the problem.
2. Check amine circulation rate - if lean amine loading is OK, maybe you are not circulating sufficient amount of solvent.
3. Check number of stages in absorber - if both issues described above are OK, check if there is any improvement when you increase the number of theoretical plates in the absorber tower.

One recommendation: for all future queries you may have, it is always better to start the new topic instead of posting question under the existing one. That way you'll get more attention to your question.

Good luck,