| 摘要 |
<p>A process for the separation by distillation of small quantities of a middle-boiling fraction from a liquid mixture by means of a distillation column (main column), comprising a rectification and stripping component, where the liquid mixture contains relatively large amounts of higher- and lower-boiling constituents, and the rectification component being connected to the upper end and the stripping component to the lower end of a second distillation column (side column), and the middle-boiling fraction being removed in a vapour or liquid form from its middle region, the concentration of the middle-boiling fraction in the liquid mixture being less than 2 percent, preferably less than 0.1 percent, and the amount of vapour introduced into the side column at its lower end from the main column being 1 - 20 percent, preferably 3 - 10 percent, relative to the amount of vapour in the main column.</p> |
