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I. Principle of DMF recovery (1) Principle of DMF distillation DMF and water are separated by means of distillation. Distillation is a process used to separate components in a solution by taking advantage of the differences in their vapor pressures or boiling points. The thermodynamic equilibrium relationship between the gas and liquid phases is the basis for the separation of the two components. From an equilibrium perspective, the two phases are in a non-equilibrium state when they first come into contact. If the composition of the liquid phase on the plate is taken as the reference condition, then the concentration of volatile components in the gas phase in contact with it is lower than that at equilibrium; as a result, the volatile components in the liquid phase will transfer into the gas phase. At the same time, the poorly volatile components in the gas phase transfer to the liquid phase until equilibrium is reached. Thus, on each tray of the tower, there is both heat transfer and mass transfer; the gas and liquid phases come into counterflow contact within the tower, undergoing multiple instances of partial vaporization and partial condensation, which enables the separation of the mixed fluids. In the aforementioned distillation process, introducing reflux liquid to the tower top and steam generated by the reboiler at the bottom of the tower are essential conditions for the continuous operation of distillation. In distillation operations, the reflux ratio is a key technical parameter that directly affects equipment costs, operating costs, and product quality.