What is a distillation tower?

Fractionating column is a tower-type vapor-liquid contact device for rectification, also called a distillation tower. There are two main types: plate tower and packed tower. According to the operation mode, it can be divided into continuous distillation tower and batch distillation tower. 　　The steam enters from the bottom of the tower and comes into countercurrent contact with the descending liquid. During the two-phase contact, the volatile (low boiling point) components in the descending liquid are continuously transferred to the steam, and the non-volatile (high boiling point) components in the steam are continuously transferred to the descending liquid. The closer the steam is to the top of the tower, the higher the concentration of its volatile components. The closer the descending liquid is to the bottom of the tower, the more enriched its non-volatile components are, achieving the purpose of component separation. The vapor rising from the top of the tower enters the condenser, part of the condensed liquid returns to the top of the tower as reflux liquid and enters the distillation tower, and the rest is taken out as distillate. Part of the liquid flowing out from the bottom of the tower is sent to the reboiler. After thermal evaporation, the vapor returns to the tower, and the other part of the liquid is taken out as the remaining liquid in the kettle. 　　Principle of Rectify The basic principle of distillation is to partially vaporize a liquid mixture and utilize the characteristics of different volatilities (relative volatility, α) of each component to achieve unit operations for separation purposes. Distillation can be divided into: Simple distillation, flash distillation, rectification and special distillation, etc. This section takes the two-component mixture system as the research object. Based on the analysis of simple distillation, through comparison and extension, it explains the operating principle of distillation and its implementation method, so as to understand and master the difference between rectification and simple distillation (including: principles, operations, results, etc.). 　　6.2.1 Distillation operation and results Taking benzene-toluene mixture as an example, Figure 6-1 is a schematic diagram of its device and process, and its txy phase diagram is shown in Figure 6-2. When the mixed liquid with composition xF and temperature t1 is heated to t3 to partially vaporize, and the gas phase and liquid phase are separated, the resulting gas phase composition is y3 and the liquid phase composition is x3. It can be seen that y3>xF>x3. The main internal components are: Tray, feed distribution pipe, overflow weir, downcomer, bubble cap, etc. This post was last edited by qlasd on 2009-4-5 01:47 ]