In crude oil refinery, does fractional distillation done in one batch or multiple batches?

Question

Does the plant starts by boiling crude oil in low temperature to extract the "lightest" product first,

and then subsequently increase it's temperature until achieve the "heaviest"?

Or all done in single batch, where it condensed separately?

From what I summarize from multiple video, it seems the latter - It's done in only one batch.

But how come? Since they are differ in boiling point. This really puzzled me

Crude has not been treated in "batches" for a hundred years. Processing is continuous. There area few exceptions such as some cokers are batch ( breaking of the highest boiling material/bitumen.) — blacksmith37, Commented Oct 26, 2021 at 14:39

Solar Mike · Accepted Answer · 2021-10-26 10:53:29Z

2

The process is continuous, crude is fed into the fractional distillation column and the products come out at the relevant temperatures.

answered Oct 26, 2021 at 10:53

Solar Mike

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$\begingroup$ Does boiling point means condensation temperature? $\endgroup$
– Lorenz
Commented Oct 26, 2021 at 11:12
$\begingroup$ @Lorenz consider above boiling point and below boiling point. water to steam and steam to water. Then you could go for latent heat of vaporisation, condensation etc. $\endgroup$
– Solar Mike
Commented Oct 26, 2021 at 11:18
$\begingroup$ @Lorenz - think of it as the temperature at which, for a particular pressure and a particular substance (ie not everything in the mixture going into the still) the liquid and vapor phases of the substance in question are at equilibrium. If you get into great detail, actual boiling may happen above the thermodynamic equilibrium temp etc, and also it will be different depending on whether the liquid has other things in the mixture, but that's not really part of the abstract concept of equilibrium $\endgroup$
– Pete W
Commented Oct 26, 2021 at 12:09

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NMech · Accepted Answer · 2021-10-26 10:58:15Z

0

The following image shows a concept of the fractional distillation process.

Figure: crude oil fractional distillation (source: 123rf.com )

The crude oil is heated, and then as it cools down at higher level you get the different products.

answered Oct 26, 2021 at 10:58

NMech

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$\begingroup$ Actually this is exactly the point of my question, here to ask why. For example "50 C" for gasoline is boiling point, and not condensation temperature. Or am i missed something? $\endgroup$
– Lorenz
Commented Oct 26, 2021 at 11:09
$\begingroup$ @Lorenz I am not sure I follow the question in your comment. I'm not sure, how you differentiate between boliing point and condensation point. . The main difference I see between boiling and condensation is that boiling is the change of a liquid into its vapor phase whereas condensation is the change of vapor into its liquid phase. $\endgroup$
– NMech
Commented Oct 26, 2021 at 11:13
$\begingroup$ Yes I am aware. In diagram, crude is heated to "400 C", and then you were saying as it travel up, it cools down until the point where it condensate to "gasoline", which is "50 C" $\endgroup$
– Lorenz
Commented Oct 26, 2021 at 11:16
$\begingroup$ So boiling point = condensation point? $\endgroup$
– Lorenz
Commented Oct 26, 2021 at 11:17
$\begingroup$ the gasoline is the most easy to evaporate, so it takes lower temperatures to condensate. Is that what you are asking? Fuel oil, or lubricating oil are volatile, so they condensate in earlier in higher temperatures. Is that what you are asking? $\endgroup$
– NMech
Commented Oct 26, 2021 at 11:25

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