Fuel Gas Temperature to GTG 1

[ppmsb]

Hi,

Currently our fuel gas skid got heater to ensure/control fuel gas temp entering GTG combustor at 42 C. If the heater fail/trip & let say the FG temp reduces below 30 C, what is the impact to GTG? Was told the GTG will trip? What the normal criteria of FG temp?

Thanks

ppm

 

[ppmsb]

was informed by my colleague that fuel gas temp needs to be 15 C higher than the hydrocarbon acid dewpoint?

 

[toothless]

We heat our fuel to vaporize any entrained liquids (heavy hydrocarbons). This liquid has a very high heating value that could cause a combustion problem via exhaust spread or high exhaust temperature. It can also damage the fuel nozzles.

We heat our fuel to 150 F.

 

[dcasto]

I believe you need to heat the fuel gas up enough that niether water or hydrocarbons will become liquid. If the gas has CO2 in it, then the CO2 will mix with the water that has condensed to the liquid phase and make an acid.

Adding heat or raising the temperature of the fuel gas will slightly increase the appeant efficiency of the GT. I say appearant because if you burn gas to make the fuel gas warming, you will lose efficency overall.

 

[Romefu12]

ppmsb
The event of the Fuel Gas Heater trip/fail is not necessarily detrimental to the GT if only occurring a few times. If the unit is setup correctly and depending on the unit model, for example a GE 7/ 9FA+e would simply perform a runback to a minimal pre-selected mode and load. However there are users out there that, to save money and not necessarily affect their trip counters for maintenance factors, use this method of shutting off the Fuel gas heaters to respond quickly to dispatch orders giving them the ability to shut the unit down quickly. This method does save time and fuel verses a normally regulated shutdown however they do so at the cost of Combustion Hardware and reliability issues as this practice causes higher than normal thermal stresses in hardware. Many operators assume that the OEM’s do not know that this is becoming a common practice and frequently attempt to blame reliability issues and hardware damage on the OEM’s under the guise of warranty claims. However I can assure you that the OEM’s are aware of this practice and may quickly dismiss warranty claims, as this practice is easy to spot in the control data.

Romefu12

 

[milltir]

The various gas turbine suppliers have differing fuel gas quality specifications, but the temperature requirement is generally around 28°C (50°F) above the hydrocarbon and water dewpoints at the supply point to the package (skid edge).

 

[abeltio]

Most units have now a gas fuel scrubber, the scrubber has liquid level detectors with alarm and trip.

The low fuel temperature alarm and runback is a common practice but most units have only an alarm as the main issue is to avoid slugs of liquid entering the gas fuel and combustion systems - so while the liquid level in the scrubber is below trip level the unit will run safely.

42C is not really heated fuel, it is just to avoid condensations... some units run with 185C fuel

saludos.
a.