4 replies to this topic

[z_kapetaki]

Hi all,

I have the solubility of CO2 in Selexol given in SCF/USGal and I am trying to take out of that mole CO2/mole Selexol. My concern is about the SCF conversion. Do I have to include the temperature term (60 oF) for the SCF to have STP at least as a first result? I would appreciate if anyone could help.

[Zauberberg]

I'm not sure if I understood your question well, but if conversion from SCF to Sm3 is concerned it is very much straightforward since both refer to standard conditions (101.325 kPa, 15.6 degC).

For converting from SCF/gal to mol/mol you need Selexol density and Moleculer weight.

[Art Montemayor]

Having dealt with CO₂ removal processes for a long time, I believe I know what you are faced with. You are probably trying to convert a CO₂ loading given in normal USA units as “SCF/USGal” to “CO2 moles/mole of Selexol”. You need this to relate to published data. Am I correct?

If so, then you should take into consideration that for a gas there are 379.48 ft³/lb-mol at 60 °F and 14.696 psia. These are normal USA units – and they have nothing to do with the term “Normal” as employed in Europe. I try to shy away from using the term “standard”. Every body and his brother has his own “standard” conditions – and more are being fabricated every day. It is safer and more prudent to simply always refer to your base temperature and pressure (you failed to state that you are referring to atmospheric pressure – therefore, I base myself on the stated 14.696 psia).

As Zauberberg states, this is only half of the job. You also need to know the density and the molecular weight of the Selexol solution that you are employing.

[Zauberberg]

Every body and his brother have their own “standard” conditions – and more are being fabricated every day.

Very true, so it is always recommended to quote exact temperature and pressure to which the term "standard" is referred to. Most often - at least in Europe and in projects/plants which have adopted SI units - both "Standard" and "Normal" refer to the same atmospheric pressure 101.325 kPa; "Standard" temperature can be either 15.6 degC or 20 degC, while "Normal" temperature is 0 degC. But, as you said Art, without quoting P,T values, the words "Standard" and "Normal" are quite vague.

[z_kapetaki]

Hello Art,

This is exactly what I am trying to do!

Thank you very much for the reply. So in that case, you think it's more accurate to calculate moles in 60 oF and 1 atm and then make the conversion to any temperature. The densities, though, usually are given in NTP (25 oC and 1 atm). Thank you both for the posts.