Our two 1994 vintage Westinghouse gas turbines have a premix setup for denox steam and natural gas. Both are combined into one pipe about 30 feet from the combustors. We have been having erratic emissions in one of the machines ever since our gas heater was sent out for repairs. This heater was a retrofit four years ago to improve performance by preheating the natural gas up to 275F from 50F. Currently our NG temperature is 32F which I suspect is causing a loss of too much superheat to the denox steam once its blended. Can anyone tell me what the parameters are of the mixture after it passes through the Y fitting?

Pipe 1 (NG with a 4" ID) = 24.1kpph flow/326.7psig/35.4F

Pipe 2 (steam with a 6" ID) = 37.4kpph flow/393 psig/581F

Pipe 3 (mixture of both above with a 6" ID)

The CT's are designed to run with cold gas but I suspect it shouldn't be this cold.

 

Hello,

Do you have a piping and instrumentation diagram (P&ID) of the controls upstream of the mixing point that show where the sensor readings were taken? Do you also have the pressure and temperature after the mix?

In theory, the down stream temperature of the mixture can be calculated if the properties of the two upstream materials are know. In your case, you are showing an upstream of 326.7 psig for NG and 393 psig for the steam. This tells me that at least one of the pressures, maybe both are taken upstream of a control valve or regulator. This means I have no way of know what the mix pressure is. Without knowing the mix pressure, properties can not be estimated.

Is your gas heater installed and running at this time? I do not know if the 35.4F is upstream of the heater or if it beacause the heater has not been re-installed.

Regards,
James Fountas
[email protected]