How to tell apart Air from Steam in a flowmeter

[jorgerobles]

I need to measure an air& steam stream coming out from a separator at 200 deg C and 600 psig, and to estimate their individual mass rates.
I think this could be done just measuring the volumetric flow rate, pressure, temperature and applying Dalton’s partial pressures law. I would prefer not to have to measure humidity, etc., but I am concern about losing too much accuracy with all the assumptions.
Does anybody have experience with such a situation?
Thanks!
Jorge

 

[25362]

To jorgerobles, let's start by saying that I have no experience with an issue as the one presented by you. It appears, however, that by measuring the density of a slip stream discharging to a lower (measurable) pressure could give you the relative masses of air and steam.
Espero no estar equivocado.

 

[jorgerobles]

Thanks 25362,
I've decided to apply the following approach:
- Since I know that the air at the separator is 100% saturated, this also mean that the partial pressure of the steam (Pv) = Pstautarion a Separation Temp. Whit this I can estimate the molar fraction ratio's for the pseudo components: Nv/N=Pv/Psep, and Na/N=1-Nv/N
- Insulate the line from the Separator to the flow meter. Assuming certain pressure drop in the line and a very small change in temperature, the steam (at a lower pressure and almost the same temperature) will be superheated, therefore the molar ratio’s remain the same. Using Nv/N and Na/N we can estimate the partial pressures under the new conditions, and transform the (volumetric) flow rate measurement in mass flow rate, using the densities at the actual temperature and partial pressures.
- The only pitfall of this approach is that it assume that the gases in the mixture behave as ideal gas. This approach is usually recommended only for low to moderated pressures. I guess I will need to run an additional experiment to verify its validity.
Regards,
Jorge