9 replies to this topic

[apis]

Hi everybody,

I have a little bit problem here about the rigorous distillation column.I already had a data about the distillation column from shortcut distillation column.But, when i put the data into the rigorous distillation column, i had encounter with unconverging matter.I don't know where is my mistake.I had put all the specs needed such as no of stages,number of feed stage,reboiler and condenser pressure,reflux ratio and distillate rate.What is make me become more weird is,when i did my short cut distillation column,everything is alright and converge.People outhere,please help me.I really2 need some precious information about this matter from you all.Please guide me.Thanks in advance.

[Padmakar Katre]

Dear,
Hysys has this problem.Once we choose the short-cut column to find number of stages and then to use the same number of stages in other case column doesnot converge.So my advice to you is to get the column design by other softwares like DISTILL or any other which is recommended for and then simulate it into Hysys.
You can try on option if the simulation does not converge as of a start approach you can go for Ranged Specification than fixed which you can change in the spec summary of the design tab of the column runner window.
Waiting for your comments.

[joerd]

Apis,

If this is the same column you had on January 7th, you can get it converged (which I did for you at the time.) No need for other software.
The shortcut column is really a shortcut, no iterations, or advanced specs. So it will solve as long as there is a solution with your specs. The rigorous model takes more effort, but there are a number of ways to "help" the solver get to a solution. More easily achieved specs is one of those.

[apis]

Dear joerd and padmakar,

Thank you very2 much for your greatest information.Sory i'm late because i had a lil' bit problems with my internet.Joerd,padmakar, i'm really2 happy now because i already had converge my rigorous distillation column too.Million thank you to both of you for helping me in this matter.Now, i'm really2 enjoying in this learning process.Oh,thanks god.But, i know i still have a lot of weaknesses and lack a lot of information about this simulation.I hope both of you and all people outhere are willing to guide and shared all information with me again in my next learning process after this.Thousand thank you first to both of you joerd and padmakar and to all my beloved friends:-)But, a lil' bit question here,emm,how far we can trust about the result of shortcut distillation column?

[joerd]

If you read the Hysys documentation, you'll find the answer:

The Shortcut Column performs Fenske-Underwood short cut calculations for simple refluxed towers. The Fenske minimum number of trays and the Underwood minimum reflux are calculated. A specified reflux ratio can then be used to calculate the vapour and liquid traffic rates in the enriching and stripping sections, the condenser duty and reboiler duty, the number of ideal trays, and the optimal feed location.
The Shortcut Column is only an estimate of the Column performance and is restricted to simple refluxed Columns. For more realistic results the rigorous Column operation should be used. This operation can provide initial estimates for most simple Columns.

BTW, it seems that your "2" key is stuck, and your space bar isn't working properly.

[apis]

Dear joerd,

Thank you very much for your information joerd.Ooo,i see.So, the short cut column is the simple distillation that only use the estimation for their results.Joerd, do you know how to use optimizer in HYSYS?can you share that precious information with me?Do you have the important note or information or other sources that i can refer to in my study process?"BTW, it seems that your "2" key is stuck, and your space bar isn't working properly." what do you mean joerd?can you explain it to me again?

[Zauberberg]

Hello Apis,


Running optimizer in Hysys is very simple: you need to define your Independent variables (the ones that are subject to change during optimization process), your Object function (what is going to be optimized) and your Constraints as well (there are always some logical or process constraints that restrict your optimization process). You can find in Hysys manuals how this works. There is a good example how you can optimize surface area of heat exchanger network for a given (fixed) duty required. You should be familiar with using Spreadsheets in Hysys for doing this the way it should be.

Regarding the column case: be sure to specify correct range of tray efficiency and don't squeeze your tower from all sides. If model is set properly, once when you reached convergence it should be flexible enough to respond on every change of input data. I've seen people doing rigorous models of different towers and getting the results for a given set of column specifications, but once when they change these specs, the model was not able to predict column behaviour in a correct manner.

For Hysys tutorials related to Optimizer function, go to: http://prosys.korea....e/hysys/manual/
and read about this topic in "Operations guide".

Best of luck,

[apis]

Hi Zauberberg,

Thank you very much for your optimizing step.But,what do you mean by 'your Object function (what is going to be optimized)' in your optimization steps that you had told me.Can you elaborate it more detail because i have a little bit difficulties when i want to select the things that i want to optimize in the optimizer.Zauberberg,i also have several problems here.I really hope you can help me.First, i have a little bit confuse about the result that i had have in my rigorous distillation solution.The problems is the result that i have is different from the mass balance calculation that i did in my manual calculation.Refer to your url="http://prosys.korea....r/~tclee/hysys/
manual/"]http://prosys.korea.ac.kr/~tclee/hysys/manual/,i failed to open and download that HYSYS tutorial.Do you have other sources that can make me understand better in this optimizer?Another one question, how to do distillation with side stream output?what the things that we need to consider in this matter?Thanks in advance.I hope you can help and share with me with your precious information.

[Zauberberg]

Hello Apis,

Regarding the Optimizer: objective function is process variable that is going to be optimized. You have one good example related to minimizing total UA factor for heat exchanger network. Optimizer spreadsheet is the place where you import and define all variables that are subjects or objects of optimization process. If that PDF tutorial file is unavailable for direct view, try the good old method - right click on the link and choose "save as".

For the column: once when you put the column template into the main flowsheet, introducing side streams is done through the column window where you define the number of pumparounds, side reboilers etc. The streams should be defined at the first place in the main flowsheet. For example, if you have crude distillation column or FCC main fractionator, in the main flowsheet you should enter all inlet and outlet streams from the tower: feed, stripping steam, residue, overhead product, kerosene, LGO, HGO (for atmospheric tower). The rest is simple and it can be viewed in related tutorials file.

Regards,

[apis]

Hi Zauberberg and everybody,

Thank you very much for your willingness to help me to explain briefly about the optimization and side stream matter.I'll try it.Refer to the URL that you had give to me,I still cannot download that tutorial although i had using your method.Any other suggestion for me to get that precious tutorial?Please I reall2 need it.Please help me.Another one,about my simulation problem,what do you think about the reboiler and condenser pressure?Is it supposed to be same with the pressure in the column(1.2 mbar) or not?In my opinion,it supposed to be different because to let the liquid and vapour flow(in my logic).Please guide me if i'm wrong.But, from my reading, i still can't found how to calculate the reboiler and condenser pressure.Did you know any source that tell us how to determine and calculate the pressure of condenser and reboiler?Please share it with me.I'll find it.It's very important to me.About the product that produce in my distillation column,how can i increase my product composition(bottom product).What i already know now is reboiler duty will influence the bottom product composition(Please guide me if i'm wrong).What else the things that you think will influence bottom product composition(Based on you working experience)?If you have any sources that i need to read to find this relationship,please let me know.I'll find it.I really2 want to learn about this distillation problem in detail.Please help me.