# Thread: Fractionating process to obtain fractions with a boiling point between -160 C to +20 C ?

1. I know about fractional distillation columns for separation of crude oil. I assume this must be for separating oil which are gases at room temp.

What is this process called and how does it work?

Thanks.

2.

3. Originally Posted by JackAnimated
I know about fractional distillation columns for separation of crude oil. I assume this must be for separating oil which are gases at room temp.

What is this process called and how does it work?

Thanks.
So far as I know it is essentially the same, except that you have to liquify the gas mixture first by cooling: Air separation - Wikipedia, the free encyclopedia

4. The towers work by condensing hot vapours after they have been heated far above their boiling points. As the vaporized petrolium profuct goes up the tower the temperature drops.
The heavier tarlike products condense first near the bottom of the tower.

It can get much more complicated with cracking towers, vacuum towers, stripper columns, cokers, hydrotreaters, hydrogen furnaces and catalytic reformers.

Edit. Oh, what are they called? Frac towers.

(How much detail do you need?)

5. Your question is not stated clearly.

As exchemist says, fractionation of low boiling materials is much the same as fractionation of higher boiling fractions, except the process is carried out at low temperatures. Air is separated into nitrogen, oxygen and argon by this type of process. The air is first liquified.

6. Would a fractionating column be used in this instance?

7. Originally Posted by JackAnimated
Would a fractionating column be used in this instance?
Yes. The physics is fundamentally the same. The materials are selected to deal with the low temperatures. Aluminium alloys are used for air separation.

8. The question I've been set asked for a labeled diagram to accompany my explanation. I cannot find one on the internet. Should I just draw a standard fractional distillation column, but with different temperatures and fractions?

9. I didn't realise this was an assignment question. Try using the term 'cryogenic fractionation'.

10. A discussion about fractional distillation wouldn't be complete without mentioning theoretical plates.

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