Distillation is a typical unit operation for separating miscible liquid mixtures in chemical production. Its essence is multi-stage distillation, which uses the different boiling points or saturated vapor pressures of each component in the miscible liquid mixture under a certain pressure to vaporize light components (components with lower boiling points or higher saturated vapor pressures). After multiple partial liquid-phase vaporization and partial gas-phase condensation, the concentration of light components in the gas phase and heavy components in the liquid phase gradually increases, thereby achieving separation. The raw materials are fed into the tower from an appropriate position in the middle, and the tower is divided into two sections. The upper section is the distillation section, which does not contain feed, and the lower section, which contains a feed plate, is the retention section. The condenser provides liquid-phase reflux from the top of the tower, and the reboiler provides gas-phase reflux from the bottom of the tower. Gas and liquid reflux are important characteristics of distillation.