Conversion of ppmv's from real to STP 1

[lfbg]

Hello,

Can anyone please help me? I need to convert the ppmv value that I measure at an extraction point of gas at a given temperature and pressure to Standard Temperature and Pressure. I thougt it was an easy operation but I found myself in quite a trouble. I'll apreciate any help.
thank you


lfbg

 

[katmar]

If your contaminant is a gas, then unless either the contaminant gas or the bulk gas are significantly non-ideal there should not be any difference between the ppmv at the measured conditions and at STP. If both gases are measured in volumetric terms they will both change by the same fraction as the P and T change, and the ratio (ppm) will stay the same.

I presume the contaminant is not a solid because then you would not be expressing it as ppm - rather as mass per volume.



Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[mbeychok]

lfbg:

Where you may have a problem (other than those pointed out in Katmar's excellent response) is in determining what Standard Temperature and Pressure to use ... unless it is spelled out in some pertinent document involved in your work. See

http://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressure

<== click here

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[lfbg]

Thanks for your help,
In fact, I am dealing with biogas. I am extracting about 5000 Nm3/h and my contaminant is hydrogen sulfide (H2S). I get a value of around 1300ppm (I am assuming that it is in volumetric terms because my company assumes so).
So if I understand well, this value can be considered as already at STP, even if the measuring devices do not do this conversion?
Thanks again


lfbg

 

[25362]

As Katmar has clearly explained, yes. Another designation sometimes used instead of ppmv is [&mu;]mol/mol.