A distillation column is a tower-type gas-liquid contact device used for distillation. It utilizes the different volatility of the components in a mixture-that is, the different vapor pressures of the components at the same temperature-to transfer lighter components (low-boiling-point substances) from the liquid phase to the gas phase, while heavier components (high-boiling-point substances) from the gas phase transfer to the liquid phase, thus achieving separation. Distillation columns are also a widely used mass and heat transfer device in petrochemical production.
While equilibrium distillation and simple distillation can achieve some separation, they cannot separate a mixture into a specific quantity of high-purity product. Petrochemical production often requires products with very high purity, which can be obtained through distillation.
The equipment used in the distillation process is called a distillation column, which can be broadly classified into two categories: ① Plate columns, where the gas and liquid phases generally undergo multiple countercurrent contacts, with cross-flow typically occurring on each plate. ② Packed columns, where the gas and liquid phases undergo continuous countercurrent contact.
A typical distillation unit consists of a distillation column, a condenser, a reflux condenser, and a reboiler. The feed enters the distillation column from a specific tray, called the feed tray. The feed tray divides the distillation column into two sections: the section above the feed tray is called the rectification section, and the section below the feed tray is called the stripping section.
