Someone asked what partial pressures have to do with oil refineries. Everything! Forget the chem text definition…it doesn’t give the whole story for practical applications.
First, understand that a boiling point is defined by a temperature and a pressure. For example, water boils at 212 F and 14.7 psia.
Keeping it simple, the various components of crude oil boil-off at different temps. But, pressure also plays a role in boiling. So, boiling can be hindered by the partial pressure of that component in the vapors about the liquid…even if you’re at the boiling temperature. If you can’t boil off, you can’t separate componentsm, which means you can’t refine the crude oil.
Someone once taught me to think about partial pressure in a practical way. Usually, we say “at what temp will this boil?”. But, in industry, the question often is “I know the temp, but at what pressure do I have to be at?” That’s the partial pressure!
Think of this: A propane tank contains propane in both the liquid and vapor phase. Heat input, such as from a sunny day, allows some liquid propane to “boil-off” as vapor. The vapor pressure increases as “boil-up” continues. Eventually, the “boil-up” will stop when the pressure is equal to the partial pressure. (The terminology is kinda ambiguous, I’ll grant you that!)
That’s a real basic answer about refining. 