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Cracked Gas Compressor Query


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#26 PingPong

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Posted 11 May 2020 - 04:33 AM

.... so they talk about wash water adjusted efficiency values here
Who is they ?

#27 chetanhm2

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Posted 12 May 2020 - 01:33 AM

Hi,

 

Water wash adjusted efficiency values will have temp compensation for water wash condensate flow. 



#28 PingPong

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Posted 14 May 2020 - 04:24 AM

Now I still don't know who they are.

 

Water wash adjusted efficiency values will have temp compensation for water wash condensate flow.

That sounds like nonsense, so I'm sure it is.

 

Injecting water will have have only a minor effect on compressor efficiency when comparing with operation without water injection. That effect is only due to moving the operating point on the compressor curves as volumetric flowrate of affected impellers decreases a few percent.

If the effected impellers downstream the injection point(s) in the compressor were operating at a volumetric flowrate below the BEP then the efficiency will drop slightly due to water injection.

If the effected impellers downstream the injection point(s) in the compressor were operating at a volumetric flowrate beyond the BEP then the efficiency will increase slightly due to water injection.

So water injection may increase or decrease efficiency (and power consumption) slightly, depending on the position of the operating point relative to BEP. In any case the effect will be minimal.

 

The efficiency of a compressor is the result of the design of the compressor internals. Fiddling with the gas does not change that. Water injection does not change that. Intercooling by whatever means does not change that.

Fouling or corrosion will make the impellers and diffusers more rough and thereby reduce the efficiency over a long period.

 

Probably the nonsense about "wash water adjusted efficiency" results from a misunderstanding:

Say a compressor with an efficiency of 80 % has a discharge temperature of 105 oC without water injection.

Then water is injected inside the compressor so as to reduce the discharge temperature to 90 oC.

Now a clown may think that the lower discharge temperature must mean that the efficiency must have increased to nearly 100 %, because without water injection it would take an efficiency of nearly 100 % to achieve an outlet temperature of only 90 oC.

But that is nonsense. Discharge temperature only dropped due to intercooling by water injection, not by a change in efficiency. Power consumption will hardly change due to water injection as I already explained above.

 

Don't listen to those clowns.

And don't use Hysys all the time. Hysys keeps young engineers stupid. Start using your brain instead of your fingers.

 

In any case I will not keep reacting to the same nonsense again and again. Read all my posts again and again until you get it.


Edited by PingPong, 14 May 2020 - 04:28 AM.





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