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[cat]

Dear all,

I am trying to simulate a PID control on chemcad, schematics are given in the attached file.

Stream 1 is the outgoing stream of a vessel which needs to be maintained at a certain pressure, say 120 kPa. The pressure control valve is actuated when the vessel pressure exceeds its setpoint, thus, stream is split to 2 and 4. I have placed a PID to control the subsequent control valve. Current tuning parameters used were also included as well as valve specifications (Cv).

My dilemma:

I have set stream 1 pressure at 130 kPa, so I'd expect the control valve to actuate, thus the flow rates for streams 4 and 2 will be dependent on the action of the controller. However, I cannot determine the "settings at the node/divider (unit OP 2)". Should I remove this? But, if I do this I cannot split the flow. Or is my schematic wrong?

I know that this is a simple mass balance and I can compute overall mass flow in streams 2 and 4 if I have the valve opening. But this is a multicomponent system and downstream of stream 2 is a complex system, thus, I'd opted to do a simulation.

Thanks.  1.pdf   19.3KB   31 downloads

Edited by cat, 20 July 2011 - 11:15 PM.