FAQs on Distillation

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Basic Knowledge of Distillation Operations 1. What are phases and phase equilibrium? Answer: A phase refers to a homogeneous portion within a system that has identical physical and chemical properties. There is usually a phase boundary between different phases, which separates them from one another. The number of phases in a system is independent of the amount of substance. When water and ice are mixed together, water is in the liquid phase while ice is in the solid phase. Under normal conditions, the material in a distillation tower exists in both gas and liquid phases. At a certain temperature and pressure, if there are two or more phases in a material system, and the relative amounts of the material in each phase as well as the concentrations of various components within each phase remain constant over time, we say that the system is in equilibrium. At equilibrium, matter continues to move, but the amounts of each phase and the concentrations of various components remain constant over time. When conditions change, a new phase equilibrium is established; therefore, phase equilibrium is dynamic and relative, rather than static and absolute. For example, in a distillation system, when gases with higher temperatures and liquids with lower temperatures come into contact on the distillation column trays, heat and mass transfer occur; as a result, part of the gas condenses, and the concentration of high-boiling-point components in the resulting liquid phase increases continuously. The liquid portion on the tray vaporizes, and the concentration of low-boiling-point components in the resulting gas phase continues to increase. However, this process of heat and mass transfer does not continue indefinitely; when the gas and liquid phases reach equilibrium, the composition of each component in both phases no longer changes over time. 2、. . . . . . . Sent, please check it.