Calculating Moisture

[ErikHeld]

Task:
Verify the output flow of a flow meter.

Problem:
I don’t know how to begin to calculate the amount of water that can be held in a multi species gas stream. I know all the components, and mass fractions on a “Dry” basis. I also know the temperature and pressure of the gas stream. The gas stream is also at its saturation point “as I was told” Can anybody point me to an online reference to help me with this. Thanks to all.

 

[zdas04]

You didn't say what your species were. If one of them is dominant then you'd probably be reasonably safe using it. For several gases (e.g., CO2, H2S, and "Hydrocarbon Gas" which can be assumed to be a mixture of Methane with other hydrocarbon species that are gaseous at the referenced temperature and pressure), the GPSA Field Data Book has graphs of water content vs. temperature and pressure in Chapter 20.

The "gas saturation point" assumption usually sucks. A gas will be at 100% RH at the surface of the last place there was a coherent gas/liquid interface. A short distance from that coherent surface is less than 100%. As pressure and temperature change, the 100% RH content changes dramatically. If the change puts you over 100% RH then you'll have condensation. If the next change increases the 100% RH point (e.g., the pressure is lower at a constant temperature) then without a coherent gas/liquid interface then the RH will just drop.

 

[ErikHeld]

Sorry. The gas stream is 33.5% H2, 12%CO2, and 53.5% CO with the balance N2, H2S and O2.