Distillation-related questions – Basic Examination for Registered Chemical Engineers

Choose A – increase it. That’s how I understand it: when the descending reflux liquid has more opportunities to come into contact with the rising steam, there are also more chances for purification, so Xd increases. There is a question regarding determining the optimal feeding point in a distillation tower; one can refer to textbooks on chemical engineering principles, and everyone can also discuss this topic

I also think it’s A; the answer chosen is actually B

Choose A. The feed position is lowered, the number of theoretical plates in the distillation section increases, and the concentration of the effluent rises.

The distillation column is divided into two sections by the feed plate; the section of the column above the feed plate, that is, the upper half of the column, is where the rising vapor is purified, that is, where the less volatile components are removed, and therefore it is called the rectifying section. The lower half of the column, below the feed plate (including the feed plate), carries out the concentration of the less volatile components in the descending liquid; that is, the more volatile components are removed, which is why it is called the stripping section. A complete distillation column should include a rectifying section and a stripping section. If the feed inlet is set at a high level, it will contribute to the quality of the heavier components in the bottom of the tower; conversely, it favors an increase in the yield of lighter components at the top of the tower. The height of the stripping section and the location of the feed plates are determined based on the composition of the feed and its temperature.

The composition of the distillate – it’s necessary to know what this refers to: does it mean the quantity or the components? If it’s the components, they might become more concentrated or remain unchanged; but if it’s the quantity, then it definitely decreases