7 replies to this topic

[Ceng]

Dear friends

 

I'm simulating an absorbtion tower in hysys; using 50% wt. MDEA to sweet a sour gas inlet.

I'm using DBR amine package in steady state condition.

The problem is that, when I change the tray efficiencies(overall or component); no change in H2S and CO2 composition in overhead stream occur.

 

Does any one know the reason?

[Chellani]

Not very sure about this but how many trays are you using? Typically these columns have very low efficiency ~ 30%.

 

Use therotical stages rather than actual trays & efficiency. Try reducing theoretical stages rather than changing efficiency and hope you'll see expected results.

[Ceng]

Thanks Chellani

 

I was just changing overall efficiencies. Hysys in all cases calculate equal component efficiencies for H2S and CO2.

[RockDock]

It sounds like your reaction times are too high, probably due to too many trays or too high of an efficiency. I'm only familiar with modeling amine units in ProMax, as it is much more accurate than Hysys. ProMax calculates the residence time. Does Hysys report the residence time? If so, you should be looking at about 40-60 sec. through the column, so roughly 2 sec. per tray.

 

Even if you change the efficiency from 100% to 80%, if the reaction has already reached equilibrium, there will be no change in the sweet gas H2S and CO2 composition.

 

I would also model it on an ideal basis, so 7 stages for 21 actual trays. 

[Ceng]

Thanks RockDock

 

Your right. Promax it is more accurate than Hysys.I haven't seen residence time in hysys.

But new revisions of Hysys software have DBR amine package which is very accurate.

As I understood, in DBR Amine package; Hysys use actual tray efficiencies for CO2 and H2S. changing overall efficiencies have no effect on calculated tray efficiencies for H2S and CO2.

[RockDock]

That is interesting you say that about Hysys's DBR Amine Package. They certainly have a bad reputation they need to overcome for sweetening processes. Would you happen to have any data to share with us about the accuracy? I'm interested, as that would be a major upgrade.

 

Were you able to fix your model?

[IUR]

Ceng 

As far as my experienced on Hysys i will not recomend you to simulate MDEA system on hysys as its results specially for this system are not very accurate, try to use some other simulater like Promax, Win sim design II etc

[Padmakar Katre]

Dear,

Tray with OGTI's Pro-Treat, I used it in past and experience is better than Hysys.