Anti-Surge Valve Arrangement 1

[cderin2000]

Hello Friends,

Can you help solve the question below (diagram attached):
After a trip of compressor, which of the arrangement in the attached diagram is better to avoid compressor surging during the turndown period and why? Help with the advantages and disadvantages of both arrangements.
If you have any better arrangement for compressor mechanical safety during the turndown period for the arrangements, it will be helpful too.
Thanks.

 

[rotw]

You need to indicate the type of driver. Do you size the Anti-surge system just for trip (not usual) or do you consider continuous recycle and start up. How you size the anti-surge valve (what is your cv selection approach) ?

2nd arrangement, all thing being equal, the valve gets hot gas so valve inlet volume flow gets higher, the price of the valve goes slightly up but it is more the addition of a cooler that is much of an issue cost wise (while just putting a hot gas by pass might be an option).

So on the 2nd arrangement you get rid of the scrubber volume at the discharge, volume of the dedicated heat exchanger on the anti-surge loop should be lower than cooler of arrangement#1, all in all that should help for trip as general rule when you have bigger volume at the discharge it takes 'a while' to see the downstream pressure getting lower hence system will create more resistance which plays in favor of surging the compressor while this one decelerates. From this stand point the quicker you get rid of the pressure in the downstream system the better it is. So high volume at the inlet and low volumes at discharge, and ultimately a by-pass big enough and fast enough. Another important point to look at, assuming your deceleration rate is known in advance (inertia of the shaft), is the closure time of the ESD valve.

Have a dynamic simulation performed.

 

[cderin2000]

Thanks rotaryw,

Your reply is appreciated.
This question is just for educational purpose. We assume both arrangement are under the same conditions; drivers, inlet flow, piping sizes etc.
Thanks