7 replies to this topic

[Bal]

How to ensure the convergence of a recycle stream in HYSYS while optimizing the flow sheet? what tips do usually follow? 

 

Thanks

[Bobby Strain]

You modify the parameters.

 

Bobby

[Bal]

You mean I need to increase the sensitivities of those parameters? 

There are some options within the recycle stream that I would like to know what does it mean, for example:

1. Recycle>> parameters>>variables>>take partial steps

2.The different options within the Numerical tab

3.The different options within the convergence tab

 

The recycle stream in my assignment enters the top of a distillation column, another feed is entering at a higher temperature. When I run the optimizer the temperature of the recycle stream becomes higher than the lower feed..

[Bobby Strain]

So, you should tell us that this is an assignment and you are a student.

 

Bobby

[Bal]

It's not a student forum????????

I'm trying to understand the source of the problem in the simulation..I didn't post the file and ask any1 to solve it for me..

[marchem]

convergence problems are usual with simulators,

you may explore the features of the different tools available in your software reading the operating manual

and by trial and test for your specific case, 

note that changing some settings may accelerate convergence on some test cases but create troubles on others.

 

For optimization you may also consider running specific software such as Matlab or Mathcad which include powerful procedures,

see this example to grasp the idea...

"http://www.harveyhen...chives/07-2014"

[Pilesar]

Break the recycle stream to see what is changing. Follow the calcs by hand around the loop for a cycle or two to understand what is happening and why. Is your reactor unit in balance? Do you have a fixed purge rate? You can often use fundamental material balance equations to determine what your purge rate must be and you can program the equations into the simulation. Sometimes the problem is calculation precision, but most of the time recycle problems are simple material balance issues.

[Bal]

Thanks (Y)