Hi

I have a problem with power not being available at the GT's during hot summer days.  Fogging has been suggested to improve the situation.

The required water quality is the (traditional !) DMW with < 10 ppm of TDS, <3 SiO2, pH bet 6.5 to 7.5, conductance < 11x10^(-6) mho/cm.

I have the following water available...
TDS 38 ppms, sulphide 26ppm, hardness (Ca) Nil, pH 3 to 4.5,CO2 100ppm - rarely some traces of light hydrocarbons (evaporatable...) conductnce at about 50 or so...

Normally used fuel gas contains much higher H2S - about 1000 ppms, about 4% CO2.

My query is - (leaving traditional DMW quality specifications aside, which are written around ground water treatment) - can we look at the contaminants in the water (instead of the conventional markers of contamination like TDS / conductance) and evaluate their effect for use in fogging ?  

TDS in this supply is due to H2S dissolved...and low pH a result of CO2 / H2S again... There is no conventional scalants (Ca/Mg...).  What exactly is the effect on the (initial stages of) air compressor / GT if this quality of water is used for fogging ?

I would prefer not to treat (except for filtration) this water...as some of the treatment options (like de-aeration) is likely to create some additional problems (of disposal of H2S laden air...)

Comments are welcome....

Thanks

   

The unfortunate fact is that the carbon dioxide comes out of solution much more easily than the more soluble hydrogen sulfide. As it comes out, the pH value rises and this upsets the equilibrium between alkaline sulfides and hydrogen sulfide so that the reaction proceeds in the wrong direction for the removal of hydrogen sulfide.

The end result would be that the remaining dissolved sulfide would end up coating the GT blades.

Lots of luck trying to convince your CT supplier that you alternative water is good enough to fog into their machine. What motivation do they have to accept something else? If they approve it and you scatter the machine you might have recourse; if they don’t approve the alternative water and you scatter the machine it will be you fault. Are you prepared for that to occur? You have to do your own evaluation of the risks and the rewards for using the alternative water supply and proceed on that basis.

That said; fogging a small amount of water into a high volume air steam would appear to be analogous to an evaporative stripper process. The H2S and CO2 have to enter the compressor in the gas phase. Any entrained water droplets would eventually evaporate as the air is compressed and the temperature increases.

You might want to run the calculation to have on-hand should your local air regulators question the increased emission of SO2/SO3.