What is use of both cold fuel gas temp control valve and hot fuel gas temp control valve in GE frame 9FA machine?

 

Ramanath,

From my somewhat limited experience with F-class machines, the use of heated fuels is not that common but is becoming more common. The installations I have worked on or visited with heated fuel (usually only a single gas fuel, natural gas), there has not been a need for independent gas- or gas temperature control valves.

Are these valves at your site actually controlling gas fuel temperature, or are they controlling the flow-rates of the cold- and heated gas fuels?

Heated natural gas fuel is usually done to improve the overall efficiency of the power plant (fractional percentage efficiency performance improvement, but with such a large machine, over time the savings adds up).

It does so, I'm told, by not quenching the combustion gas temperatures as the introduction of cold fuel does, thereby saving a small amount of fuel.

I would imagine that if the unit(s) at your site had two different control valves, or even temperature control valves, it would be because of some very unusual fuels in use at your site. Or, possibly because the volumes of the unheated fuel versus the heated fuel would be very different, possibly requiring different-sized valves or different valve components because of the temperature differentials, or both.

Or, there may be other considerations, since we don't know what kinds of fuels the unit(s) at your site burn.

I'm also aware that some turbines are now being configured to burn what are commonly referred to as "by-product" gases, or "tail gases" from some process. These are sometimes low BTU fuels that are hot from the process they are being produced by. They may need cooling.

But, we don't really have enough information about your site, the fuels, and the configuration. We would likely need to see the P&IDs for the fuel- and related systems to make a better analysis.

I'm aware that many sites with F-class turbines have what are called "Contractual Service Agreements" with GE or other vendors of such services. If your site is one of them, you should be able to ask the representative from the Company providing the services to help you understand why these valves are necessary for the unit(s) at your site.