Solubility of Air in Crude Oil 1

[ChEGATOR]

How do I calculate the solubility of air in crude oil at a given temperature and pressure?

Thanks for your help.

 

[25362]

Air solubility in hydrocarbons is frequently expressed by the Ostwald coefficient, which for air at 273 K is 0.095. This coefficient gives the volume of gas per volume of liquid solvent.

I assume that this is not a constant for every crude, but may give you a "grosso modo" idea of the true value.

Correction formulas for other temperatures can be found, for example, in Stachowiak and Batchelor's Engineering Tribology Tribology Series, 24 (Elsevier).

 

[ChEGATOR]

So do you use a formula similar to Henry's Law, but replace Henry's constant with the Ostwald Coefficient?

 

[25362]

There is no formula here, except for the conversion of the Ostwald coefficient at 273 K, C₀, to C_T at temperature T.

Pressure doesn't play a role since gas solubility is generally proportional to gas pressure, and assuming the ideal gas law applies, pressure effects cancel out. Meaning that 95 L of air per 1000 L of hydrocarbon at 1 atm should be the same at 2 or 3 atm, all measured at 0^oC.

According to the reference given above the Ostwald coefficient is evaluated according to ASTM D2779-92(2007). Don't be surprised to find that solubility of air in hydrocarbons may actually increase with temperature to a certain degree.