How are the distillation section and the stripping section of a distillation column divided?

When the concentration on a certain tray of the distillation column is close to or equal to that of the feed, the liquid feed is introduced at this point in the column; such a tray is called a feed tray. The section of the tower above the feed tray is the distillation section, while the sections of the tower below or at the feed tray are the stripping section. The function of the distillation section is to concentrate the volatile components in the feedstock. The function of the stripping section is to recover the volatile components in the feedstock. Put simply, using the feed point as a boundary, the distillation section is where the light components are purified; it is located above the feed and contains components that are purer than those in the feed, which is why it is called distillation. The stripping section is used to purify the heavier components; below it, the mixture is even less pure, which is why it is called stripping.

The division between the distillation section and the stripping section of a distillation column is generally made at the feed inlet; the distillation section is used to purify the light components, while the stripping section is used to purify the heavy components

The stripping section includes the feed plate portion.

The upper part of the feed tray is called the distillation section, while the lower part is called the stripping section

There is one issue: currently, propylene columns are generally divided into two sections, with some feed entering at the top of the lower column (for stripping) and some feed entering at the bottom of the upper column (for distillation).

The upper part of the feed tray is called the distillation section, while the lower part is called the stripping section

For multi-stage feeding and discharging, how to confirm it? For example, there are two feed sections, and there is also an intermediate section between the two feed inlets. Is the middle section a distillation section or a stripping section?

There are different feeding sections because the composition of the raw material is not constant; when there is a higher proportion of heavier components, the feeding port moves downward, and when there is a higher proportion of lighter components, the feeding port moves upward. It is not possible to have feeding in both sections at the same time

Yes, that’s the standard procedure. What about unconventional processes? For example, multiple feed streams into the air separation tower. For the air separation upper column, the feed and discharge from top to bottom are: nitrogen gas top outlet, and contaminated nitrogen outlet. Nitrogen-enriched liquid inlet, oxygen-enriched liquid and expanded air inlets, air going to the argon removal tower and liquid returning to the argon removal tower. Gaseous oxygen outlet, liquid oxygen outlet. Sure, please help to divide the rectification section and the stripping section.