Determining Flash Point of Pentane/Water Mixture

[VTB001]

Hello; I have a theoretical waste stream (125F / 52 oC) that contains water with an extremely small amount of pentane in it. The stream has the potential to become open to atmosphere. I am trying to determine if I can calcualte the flash point (since I cannot open/close cup measure it) based on the amount of pentane vs water at this temperature and pressure.

I am concerned with the potential for this miniscule amount of pentane to be a flammable concern if opened to atmosphere(assuming the low C5 / H2O ratio is maintained). Although insoluable in water, I do not think using the flash point of pentane is correct for this mixture but am not sure.

The flash point for pentane is -56F / -49 oC.
The boiling point is 97F /36 oC .
Vapour density is 2.5 (vs 1 for air)

I believe that there will be vapours produced wtih these temperatures (operating @ 125F with hydrocarbon flash point of -56F) which can be released when open to atmosphere.

I have not been able to find any reference to this in NFPA references but I may have missed it. Any advise would be appreciated. Thank you.

 

[dcasto]

Since pentane can come out of the water phase solution over time and float, then for an open tank the flash point of the mixture is that of pure hydrocarbon.

I practicle use, if the holding tank is opened to the atmosphere, the rate of the Hydrocarbon release is very slow and dependant on variables like, wind, humidity, solar, temperature. With this, unless you are in the artic with no wind, the HC's will stay in the water phase longer.