13 replies to this topic

[nooru]

Hi all,

I was trying to converge a distillation column that has a top pump around rather then
a reflux , how can this be done in HYSYS

need help

Regads
nooru

[Zauberberg]

There is a "reboiler absorber" template within available unit operations in Hysys - that's the distillation tower without reflux facilities. Once when you plug this Unit Op into the flowsheet and start defining column configuration, you'll be provided with an option to install a pumparound circuit where exact location (tray No.) of P/A draw and return can be entered.

[nooru]

thanks for ur reply .
actually the case i am trying to deal here is the one that doesnt operate with a reboiler and
at the same time with no reflux but top pump around. instead of reboiler it has an Stripping steam
option. one more thing what i am doing is to start with HYSYS column template {3sscrude.col} so by
simply deleting un wanted operations like that of reboiler i have converged the tower but I am facing
difficulty in getting rid from the Reflux.

Regards

NOORU

[Zauberberg]

Then you can use "Absorber" template, and define pumparound within Column Side Ops window. Depending on the actual feed stream location (my guess is that it should be top feed), you may need to do a small trick and add a dummy top feed stream (e.g. 1kg/h flow) in case that the actual column feed is somewhere in the middle of tower.

[nooru]

i tried that absorber template its really upto my requirement but i am still confused to what
exactly HYSYS requires to converge a column I have following as my active specs
> Top pump around return temp & flow rate
> inter pump around return temp & flow rate
> bottom flow
> side draw rate

but it never converges .
secondly after all the frustration i start to over specify HYSYS and end up with an head ache

waiting for your response

Regards

NOORU

[Zauberberg]

Can you upload the model (as ZIP file), and give us feed conditions and product specifications?

[Chellani]

Noru,

Welcome to the great world of simulation. Take a tea / coffee break to avoid headache.

[Zauberberg]

Upload the model or the system PFD with all process information, and take the advice to make a break from time to time. And avoid specifying bottom flowrate as it doesn't make a lot of sense - you are usually interested in product quality, not the flowrate.

[nooru]

THANKS FOR UR REPLIES
See, the column overhead is the stream having ( Gas + LPG + NAPTHA + Kerosene )
the side draw to stripper is the GAs Oil product + it splits to Inter PA
and the bottom is the residue
I never thought of defining product quality specs and i am not sure what are the option
available in HYSYS .

I am facing problems in attachment option its not uploading HYSYS file
so I have managed to put a brief information in excel file thats attached

Regards

NOORU

Attached Files

•  COLUMN DISCRIPTION.xlsx   9.98KB   141 downloads

[Padmakar Katre]

THANKS FOR UR REPLIES
See, the column overhead is the stream having ( Gas + LPG + NAPTHA + Kerosene )
the side draw to stripper is the GAs Oil product + it splits to Inter PA
and the bottom is the residue

Dear,
Check the feed split across your column, the material balance doesn't close(an error of 300 TPD). From your input it seems that the you have a single side stripper and that is the Gas Oil. I am just giving some steps which may help you to solve your problem

1. I presume that the assay is characterized in Hysys Sim Basis Manager and you have predefined composition stream in the main environment. Now you can input your temperature of 360 C and 2 Kg/cm2 pressure and feed stream will be converged.

2.Get an absorber from the object palette to main environment. Once you double click on the absorber icon , you will have absorber column input expert. For the top stage reflux you have two options there i.e. the first one is Liquid Inlet(which you don't have), so select the second option of the Pump around.
3. Give names to the stream to be connected at Ovhd Vap Outlet, Bottoms Liquid Outlet and bottom stage inlet as the stripping steam stream. No need to give the top stage inlet stream. Important thing to keep in mind here is that leave the optional side draws blank for a while.
4.On the Next page of the column input expert give top and bottom pressures. (Pressure you have given seems to be unrealistic as 20 theoretical trays with say 50% efficiency (need to check)will have 40 actual trays and column will have higher pressure drop than your specified value of 0.1 kg/cm2)

5. On the next page give the optional temperature estimate values (good starting point for the column matrix solver to initiate the solution).

6. You have a fully defined column and with no active specification needed. Just run the column and you will get the the column converged with column feed flow split in top and bottom outlets.

7. Now you configure the intermediate PA with 2 active specifications i.e. circulation flow and return temperature. For better and speedy convergence start with the smaller number e.g. 500 kg/hr and return temperature same as the draw temperature.

8. Now in the column window, go to the side options tab (Side Ops) and add GO stripper (here you forgot to give us input about the type of side stripper i.e. is it steam stripped or reboiled stripper choose one which you have).

9. It will give another active specification where you can define the draw rate of the GO and run the column. I am sure it will converge.

10. Now you try meeting your specifications i.e. product quality and all by altering the active specifications values (need to be gentle to enough here for not to have a large change in the spec value from earlier value) as well the inputs such as the feed temperature, stripping steam conditions.

I never thought of defining product quality specs and i am not sure what are the option
available in HYSYS .

Without monitoring the quality of the product,converging a column and accepting the solution is not proper way of conduction the simulations. So you need to open your design basis and get the product quality such as the Ovhd vapor min/max FBP temperature value, or D86 recovery temperatures of the GO and many others. There might be some constraints/product quality in your design basis which you have to achieve.

I am facing problems in attachment option its not uploading HYSYS file
so I have managed to put a brief information in excel file thats attached

Regards

NOORU

Before you reply, please go through the suggestions by the members. As suggested by Zauberberg you can zip the files (Hysys file, PFD, Product quality or any constraints to meet or special requirement)
Hope this helps. Let us know if the problem still persists.

P.S.- In case of advanced columns options like column with SS,PA and custom columns always keep in mind that if it doesn't converge with 2-3 trails, delete that object and start with a new one, as even after reseting the column runner window, it doesn't converge. This is my experience, others may or may not agree.

Edited by Padmakar S Katre, 20 October 2010 - 01:05 PM.

[Zauberberg]

Thank you for uploading process data (is it Design or Actual tower data?) but for reviewing the model we need the Hysys file as well. If you have problems with uploading .HSC type of files, I'd suggest you to zip the simulation file and try re-uploading.

Thanks,

[nooru]

it really helped by doing step by step somehow i was doing the same with bundle of loads and demanding high variation from HYSYS simultaneously.the case I am trying to converge is a real an existing Tower operating with 20 trays ( the top trays are sieve and the rest 8 trays are bubble cap ) I guess this justifies the pressure profile .
I started the same way you said by defining Components > fliud package > oil manager > calculated Assay > cut / blend > simulation environment and so on
now coming to the Absorber template i did the same avoiding the side options converging the case with GO stripper and pump around Rate and return Temp.
Now comes the stage when I try to bring up the specs to my desired values as soon as i shift the feed tray to 16 stage ( my required feed inlet ) it shows error and do not converge.

By now i have repeated this case multiple times and got it converged and I did not even realize how it actually did !
: )

after converging it i wish to tune it to my specs as you ppl said like IBP, FBP and so on ...... But !

I am still facing problem with uploading the file it shows error " you are not permitted to upload this kind of file"

[nooru]

any ways thanks a lot ! guys for giving your kind suggestions and inputs and keeping in touch

it all kept me intact and motivated till the end and i am still looking forward for this great leaning and valuable exchanges with you ppl .

thanks



Regards

nooru

[nooru]

Hi

after quite long i am finally having that green strip !
the case has been converged successfully
now I was wondering about the quality specs and their fine tunning.

please see the attachment. its 3.2 version

Regards

NOORU

Attached Files

•  COLUMN.zip   136.59KB   148 downloads