HYSYS Dynamic for reducing feed pressure with time

[Z_Z]

Hi there, I would like to learn something in dynamic hysys.

Specifically having pressure in the FEED decrease with time (For example starts at 250bar and with time goes down gradually to 20bar). Is that even possible?

The pressure reduction is to depict how a trailer carrying compressed natural gas at 250bar being the "FEED" but then as it feeds the process it reduces gradually to 20 or 30 bar which it will be replaced with another trailer. I want to depict that process and was wondering if Hysys Dynamic does that. At the moment when I hit "run" in Dynamic Hysys nothing happens (Pressure remains at 250bar)

Any help is appreciated

 

[LittleInch]

Why not model the Feed as a tank instead?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

If tha pressure reduction occurs slower than the control valve's response time, successive steady state snapshots are all you need to do.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[Z_Z]

Happy new year guys.

@LittleInch That is a great idea, the only issue is a tank requires both gas and liquid outlet streams, and I got only one gas outlet stream which is the compressed natural gas so I wasn't able to do it. If you have any idea how I can solve this please do let me know

@1503-44 I kind of need to show how it works under "dynamic mode", if you have any suggestions on how to reduce the pressure as it depicts CNG from trailer is being consumed would be great

 

[LittleInch]

I don't know enough about HYSYS but I'm very surprised by that statement. You just set the contents surely. The will be no liquid component.

I think you might need to read the manual...

Or ask someone close to you to show you how to set up the analysis properly.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

This is a VERY simple model that could easily be done in Excel, or any one phase gas flow analysis program. No need to be delayed by Hysis learning curve.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[georgeverghese]

Use the batch depressure routine which is available in both Hysis and Pro-II. Run a cold blowdown. Many options are possible in this utility routine. If you need higher fidelity with low metal wall temperatures at and around the exit nozzle, consult Simulation Sciences in the US for Pro-II - their helpdesk folks have experts on all sorts of topics.

 

[1503-44]

Oh. I finally get it. You have modeled a constant pressure feed source. Of course nothing will happen until you introduce some dynamics somewhere.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[Z_Z]

Sorry for the late reply, just wanted to update you guys.

@LittleInch, There has to be a Feed to the Tank, a vapor product and liquid product stream, however it seems having a product stream with zero flow is possible.
Also I added a valve before the feed enters the tank, and once the dynamic simulation starts the valve closes completely, leaving the tank to deplete as time passes and the pressure gradual decrease is displayed.
Mission accomplished

Thank you all for your contribution. It helped me get what I wanted.

Enjoy your weekend
Z