6 replies to this topic

[Attiq Ahmad]

Dear all,
Can anybody briefly explain me how to simulate Liquid Decanter in Hysis?? I want to simulate a decanter to separate two liquid streams.

Best Regards.

Attiq

[Padmakar Katre]

Dear,
It is not a big deal.If you have the specifications of your feed stream.Just pick the 3 phase sepeartor.Even though you don't have 2 phase flow stream as your problem is to sepearte the 2 liquids based on their density difference i.e. heavy and light liquid.Hysys will perform the calculations only thing is that even though you don't have any flashing so no vapor flow still connect the material stream for the O/H vapor.
This is an additional information,Instead to model the seperators in hysys by the hysys default method i.e. nothing but Hysys always give 100 % sepeartion i.e. your liquid phase vapor fraction equal to 0 (it doesn't account the vapor bubbles/droplets) and vapor stream vapor fraction is equal to 1(it doesn't consider any liquid carryover).But we can simulate the sepeartors as Real seperators which will give an option to put the mesh pad thickness and all releted information.For further information ask Aspen Tech to give the pdf document which I got form their Knowledge database in
their website.

[Attiq Ahmad]

Dear Katre,
first of all, THANX for reply,

I've tried exactly the same as you told me with 3 phase separator. The results don't match with operational experience.

Actually, I've to separate water from Ethylene Dichloride (EDC). Sp. gravity of EDC is 1.26.
In actuall plant we got more than 99% separation, but in Hysys I got only 90% EDC. All parameters including flow rates, separtor size is exactly the same as actual.

Can you please suggest me Property Package which should be used? Currently I am using "UNIQUAC".

Best Regards.

Attiq Ahmad

[JoeWong]

You may used method as proposed by Padmakar by using 3phase separator. If you are at design phase and getting to prepare specification for decanter spec., them you should XXX ppmv (e.g. 500 ppmv) of HC under carried to aqueous phase and XXX ppmvvof aqueous carried over to HC phase.

After that you prepare your decanter datasheet and sent to vendor to select a decanter good for the separation...

HYSYS is process simulator and has quite weak correlation in equipment sizing. Don't rely on HYSYS to sizing decanter for you.



JoeWong

[joerd]

Try NRTL.
If you provide some more detail (flow rate, composition, pressure, temperature) you might get more useful replies.

[Padmakar Katre]

Dear,
Uniquac or NRTL both are good Activity Coeff Models only thing is you have to check the BIP's for both the models if not calculate by Unifac method for unknowns.Even I was just trying to do this simulation by using both models NRTL and Uniquac but I got some absurd results.At least you are getting 90 % purity I found it max 76% even I changed the BIPs and then made the flash calculations but no improvement.
I have a basic question EDC you select as Ethylene Chloride or is there any other sim name for EDC in Hysys.If so let me know because I never had EDC as component.I tried to find the EDC by using all the filters but I found ethylene chloride which I took for the dummy simulation.
Waiting for your comment.

[joerd]

EDC is 1,2-dichloroethane (C2H4Cl2), Hysys component name 12-ClC2 (the second letter is an L). You can look it up by formula.