Modify recycling line inlet tie in point

[Tafouteistik]

Since we do not have gas cooler on recycling line of our reciprocating compressor, I'd like to know what could be the risks if instead of keeping recycling line connected to the outlet of 3rd stage before cooler and scrubber, we connect it to the 3rd stage after cooler knock out. Like this, we will not recycle hot gas but fresh cooled and probably dried gas.
Could you help me by telling me what are the drawbacks?
thank you in advance

 

[pmover]

Cooled, dry gas is the better option. Otherwise, hot wet gas may be problematic.

 

[georgeverghese]

There must be a reason why the recycle line takeoff is currently upstream of the gas cooler - I would guess this hot gas recycle was selected to avoid low temperatures/hydrates downstream of the recycle valve. And would also guess you want to relocate this take off downstream of the gas cooler because you're currently getting high 1st stage suction temp, which then exacerbates discharge temperatures.
Have you run a simulation of this compressor's performance with this relocation with the compressor in full recycle mode, and with the current estimated compression efficiency?

 

[gwalkerb]

Typically I see a hot recycle on a compressor when the combination of aftercooling and JT cooling would drop it to a temperature that either drops out unwanted liquid, or creates methane hydates. For any other application, a cold post-AC recycle is used.

If you have a scrubber after your cooler section, that implies to me that you must be close to the phase boundary. So although you would be removing any condensed liquids that dropped out during aftercooling, your gas would still be right on that boundary, and any additional cooling (in this case JT through the recycle valve) would probably condense more liquids. Usually this doesn't cause operational issues as your recycle is returning upstream of a inlet scrubber, but it's going to depend on what the liquids are and what your intent is with them.