7 replies to this topic

[powerox29]

Hi all,

 

I've been tasked to determine why there is damage to the reciprocating compressor which is downstream of a suction scrubber and its cooler. Recent boroscope findings determine that the vane pack and internals of the scrubber are clean (no damage).

 

I have modeled the simulation via HYSYS and by using the separator carryover setup (with various assumptions), I've found that there is indeed no liquid carryover immediately at the scrubber gas outlet, however from observing the phase envelope the scrubber is actually operating in the two-phase region, hence there is condensation occurring downstream and probably within the scrubber as well.

 

I'd like any opinions on how to mitigate this. Would applying heat tracing at the gas outlet solve this? Or is replacing the coolers into a heater work?

[Pilesar]

If there is no gas-liquid separator at the compressor, then I would consider installing one. Or improve the one you have.

[powerox29]

If there is no gas-liquid separator at the compressor, then I would consider installing one. Or improve the one you have.

As mentioned, there is a scrubber at the compressor suction.

[breizh]

Hi,

How will you be sure there is no liquid carried over? Simulation is just a tool! 

A separator will mitigate risk and prevent trouble coming from the scrubber (mist eliminator, spray nozzles damaged for example).

Continuous monitoring pressure and temperature at the outlet of the scrubber should help.

my view 

Breizh

[powerox29]

Agreed.

 

However, if there were liquid carryover wouldnt there be signs on the internals of the scrubber? As I've mentioned, borescope findings from inspection team conclude that there are no visible damage to the vane pack. If there were liquid carryover, I would expect some signs on the internals i.e. fouling etc.

 

 

Hi,

How will you be sure there is no liquid carried over? Simulation is just a tool! 

A separator will mitigate risk and prevent trouble coming from the scrubber (mist eliminator, spray nozzles damaged for example).

Continuous monitoring pressure and temperature at the outlet of the scrubber should help.

my view 

Breizh

[Alpe]

a gas / liquid separator before the compressor is a common arrangement to protect the equipment from wet gas / liquid / slugging / Hc foaming etc...

it is not clear if existing scrubber has high-level alarms / emergency shutdown system etc...

 

about simulation,  after a scrubber (with some liquid inside) probably you are compressing a saturated or near-dew-point gas...

if you know the exact composition you can calculate the dew point... you don't mention the fluid, for hydrocarbons a EOS such as Peng-Robinson or Soave can be accurate to 1-2 C. for different chemicals make sure to use the correct thermo... 

I use  different tools ( Prode / Excel / Python to simulate real separators)  so I can't comment your results.

 

[powerox29]

Hi,

 

Thanks for this. My understanding was that this scrubber is supposed to act as the final protection in case any liquids comes through before reaching compressor. Hence, there would not be another gas-liquid separator downstream of this. In any case, its not feasible in terms of space to install another equipment on this facility.

 

The dew point is calculated by HYSYS, and the current operation is within the 2-phase region.

 

 

a gas / liquid separator before the compressor is a common arrangement to protect the equipment from wet gas / liquid / slugging / Hc foaming etc...

it is not clear if existing scrubber has high-level alarms / emergency shutdown system etc...

 

about simulation,  after a scrubber (with some liquid inside) probably you are compressing a saturated or near-dew-point gas...

if you know the exact composition you can calculate the dew point... you don't mention the fluid, for hydrocarbons a EOS such as Peng-Robinson or Soave can be accurate to 1-2 C. for different chemicals make sure to use the correct thermo... 

I use  different tools ( Prode / Excel / Python to simulate real separators)  so I can't comment your results.

 

[Alpe]

if you have determined that  damages to compressor are due to liquid / condensate etc.  you can install some additional protection (i.e. sensors etc. to stop compressor) or a liquid separator as already suggested by others...
About simulation probably some  inputs are not correct or the selected thermodynamic package is not suitable for that fluid...

you must be close to dew point (saturated gas)  or above which is a more desirable condition with a reciprocal compressor....