lateral strippers 4

[padovano]

can somebody explain to me in the simplest terminologist possible the use of SIDE STRIPPERS on atmospheric distillation of crude oil. can the by product be obtained without the side strippers?

 

[DickRussell]

A crude column configuration lets one draw multiple products from a single configuration having one heat source (furnace) at the bottom. Each product will not be pure, as in a chemical type process, but will cover a range of distillation temperatures; just how narrow a range depends on the degree of fractionation (number of trays) between product draws. As you go up the column, the liquid has less and less of the heavier ends of the crude feed, so product draws will be lighter and lighter. However, at any particular product draw point, although the liquid will contain a sufficiently low concentration of heavier material not wanted in that product, it also will contain some material that is lighter than is what is wanted. This is because the lighter material must pass through the draw tray on its way higher up, and some will be absorbed in the liquid at that point. The lighter material can be rejected by feeding the liquid draw to the top of a sidestripper, having a reboiler or stripping steam feed at the bottom. The overhead vapor, containing the unwanted lighter material (and of course some of the desired stuff), is returned to the main column, and the stripper bottom product contains just the boiling range desired for that product.

Any good text on petroleum distillation ought to cover this stuff.

 

[25362]

Strippers are used to remove entrained light ends from the draw-off streams. The vapors crossing the draw-off tray contain light components that are partly absorbed -and condensed- in the side-streams.

Strippers usually contain four trays to promote contact between the oil and stripping steam flowing counter-currently. The removed lights and the steam re-enter the main column.

To remove say, 6% by volume, 0.4-0.5 lb steam per US gal of product are used.

 

[reena1957]

Dear padovano,
In addition what others have said above, YES, you can also draw products without side strippers but their flash points will be lower than that if drawn through strippers. If your refinery Crude column has Kero and Diesel side strippers as well as Circulating refluxes, the circulating reflux streams will have lower falsh points compared to the stripped streams, which you can test and find out. I have seen product streams drawn from circulating refluxes when there are limitations on the stripper draws OR there are no strippers forthose streams. You can also strip with hot(preferably)fuel gas(preferably hydrogen rich) in case your column can handle the excess vapor load. In maximizing a particular product from the crude ( say EURO-III Diesel), a well stripped Diesel side cut from the column can lead to higher overall production of blended diesel product than the other way.