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Gas Turbine FR9E High Exhaust Pressure
Gas Turbine GE Frame 9E in combined cycle operation is experiencing high exhaust pressure reaching 15Kpa.

Gas Turbine GE Frame 9E in combined cycle operation is experiencing high exhaust pressure reaching 15Kpa. Following is the concern:

1. What can be the reason for high exhaust pressure

2. What impact it can cause on Gas Turbine performance.

1 out of 1 members thought this post was helpful...

>1. What can be the reason for high exhaust pressure
Most likely is an obstruction in the exhaust path. Potential obstructions include fouling of the HRSG tubes, improper damper or stack closure position (if dampers or stack closure are present), catalytic converter fouling (if you have these). What kind of fuel are you burning?

>2. What impact it can cause on Gas Turbine performance.
It will definitely have a negative impact on performance - both output and efficiency.

0 out of 1 members thought this post was helpful...

Thank you for the response.

As per your questions:
We are burning Low BTU gas, and stack is equipped with exhaust damper and is in full open condition.

If HRSG tubes are being fouled, it should have impact on steam generation.
I will check it from DCS historian since this issue was identified back in 2013 and still persisting.

1 out of 1 members thought this post was helpful...

>I will check it from DCS historian since this issue was
>identified back in 2013 and still persisting.

What instrument are you measuring exhaust back pressure with? If you are relying on the pressure transmitter supplied with the gas turbine, have you verified its calibration? And, are you sure the instrument tubing lines are clear? They have been known to plug up.

0 out of 1 members thought this post was helpful...

We are relying on pressure transmitter supplied by GE. We have not verified its calibration since plant is in running condition.
But yes, it is possible that its tubes are chocked but we have two transmitters giving same high value.

>>I will check it from DCS historian since this issue was
>>identified back in 2013 and still persisting.
>
>What instrument are you measuring exhaust back pressure
>with? If you are relying on the pressure transmitter
>supplied with the gas turbine, have you verified its
>calibration? And, are you sure the instrument tubing lines
>are clear? They have been known to plug up.

1 out of 1 members thought this post was helpful...

Do you have any history on the Exhaust Press. drop? When did this increase happen, was it sudden or progressive?

Has there been any boiler or exhaust maintenance been done recently?

Has anyone done any visual or boroscope loo to see if there is any simple obstruction?

0 out of 1 members thought this post was helpful...

>Do you have any history on the Exhaust Press. drop? When
>did this increase happen, was it sudden or progressive?

It started increasing in 2013 and still persisting. I

>Has there been any boiler or exhaust maintenance been done
>recently?

Yes we have done visual inspection of HRSG and have found sulfur deposits on tubes in later stages. We have planned to perform Dry Ice Blast. Will it have affect on increasing back pressure

>Has anyone done any visual or boroscope loo to see if there
>is any simple obstruction?

Yes visual inspection carried out and no obstruction.

Is this boiler re-fired? You say that you are getting sulfur deposits, where are you operating vs. the gas dew point temperature and what is your gas supply temp. (has it changed?) If your gas temp. has been reduced that is maybe why you are getting mineral sulfur deposits. If you can get it cleaned, try increasing your Fuel Gas Supply temp.to inhibit sulfur formation.

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>Is this boiler re-fired? You say that you are getting
>sulfur deposits, where are you operating vs. the gas dew
>point temperature and what is your gas supply temp. (has it
>changed?) If your gas temp. has been reduced that is maybe
>why you are getting mineral sulfur deposits. If you can get
>it cleaned, try increasing your Fuel Gas Supply temp.to
>inhibit sulfur formation.

Yes we have after burners equipped in HRSG.

The gas fuel used have high sulphur and is considered as permeate gas. I can check the temperatures of gas and will let you know.

Will it play role in producing high exhaust pressure?

If you have high sulfur gas, the production of mineral sulfur is tied to gas temperature. If this is causing higher sulfur deposition it is possible it is causing blockage. I'm only guessing and, like you, looking for a cause.