Lesson 5 Overview

Hello. In lesson five, we will pick up the second part of the separation processes. Remember in lesson four, we've talked about distillation as perhaps the most significant separation process.

In this lesson, we will start with the light ends unit. You know that the light ends unit process the lightest fraction of crude oil. We call it the overhead from the distillation column. It ends up as LPG. That is propylene and butane, and the naphtha fractions that are very important for producing gasoline.

Now, since this is the lightest fraction of crude oil, it's simpler in its molecular makeup, so we can begin actually to see individual compounds. So we can use analytical data, like vapor liquid equilibrium, and we could use analytics expressions, equations like Fenske equations to make calculations about the separation of these components, like propane from butane and so forth.

Now, distillation is, of course, one and the most important separation process, but there are other processes that would use other physical properties like the solvent power of compounds, of chemicals. Now, one such technique is called solvent extraction. We could use solvent extraction to fraction the residue that comes from distillation rather than this atmospheric or vacuum distillation residue. It is more common to have the vacuum distillation residue that goes into the solvent fractionation processes.

One important solvent technique is deasphalting, which is done to remove asphalt, the stuff that you put on the road for pavement, and the function, the principal objective of deasphalting is not to make asphalt, really. It is a byproduct, but it to remove asphalt, so what remains after removing the asphalt from the residue could be used for producing more fuels and other more relevant products in downstream processing in a petroleum refinery.

Here you'll see a sample of asphalt that is produced by the deasphalting process by rejecting it from the crude oil using the anti-solvent behavior for anti-solvent phenomenon in the deasphalting process. You can see this is pure asphalt. You need to mix that with aggregates to pave the roads so the bottom of the barrel is solid form here.

Another solvent extraction process is called dewaxing. That removes wax. This is the candle wax, the paraffin wax that we know. Again, the purpose here is not to make candle wax but to remove wax from this heavy fraction of crude oil so that what is left over is a good base stock to make lubricating oils or engine oils.