2 replies to this topic

[Djvu]

Dear All

I have Hysys simulation with a recycle loop.
The simulation has a splitter for purge and recycle. My aim is to reduce the purge from the system, so I vary the split ratio.
But I have noticed that even though I vary the split ratio the purge value is constant and the recycle varies according to the split ratio.
like the purge value is a constant 57 kgmol/hr and recycle flow varies with split ratio.
Is this a flaw? How can I get the purge to change from this constant value and what actually made this number come up?

Thanks

[Padmakar Katre]

Dear All

I have Hysys simulation with a recycle loop.
The simulation has a splitter for purge and recycle. My aim is to reduce the purge from the system, so I vary the split ratio.
But I have noticed that even though I vary the split ratio the purge value is constant and the recycle varies according to the split ratio.
like the purge value is a constant 57 kgmol/hr and recycle flow varies with split ratio.
Is this a flaw? How can I get the purge to change from this constant value and what actually made this number come up?

Thanks

Dear,
The purge in case of steady state simulation going to be a constant value whereas in case of transient operation you will get the range of flows and I think this is a simple understanding. Unless you don't redefine the basis for the purge, the value will not change. To see the different flows of purge you need to run a case study with the split ratio as an dependent variable and the parameter which is basis of purge as independent parameter and check the effect over the range. This is in general reply to a general query and yes if you give us the operations details or background of the plant/process, may we can put some value addition.

[abhi_agrawa]

Djvu,

If you try to do an overall material balance, then at steady state, Mass in = Mass Out.

For your flowsheet:
Mass In = sum of flow rates of streams 1, 9, 10, 11, 20
Mass out = sum of flow rates of streams 15, 17, 19

Depending on how you have set up the simulation and what you are trying to do, the flow rates of 15 and 19 may or may not depend on the recycle. If they do not, then we can say that the flow rates of stream 15 and 19 are constant irrespective of the amount of recycle. In such a situation, no matter how much you change your recycle flow rate of stream 17 is fixed. Only if the recycle has an effect on flow rates of stream 15 and 19, will 17 change with recycle.

Hope this helps,
Abhishek