Abstract: Modeling of batch distillation has been mostly based on equilibrium model in previous studies.It leads to a large-scale differential algebraic equations (DAEs) system.Due to its dynamic nature,initialization of the system has been a problem.Batch distillation columns are frequently started up with different initial reboiler charges.A model to express startup behavior of batch columns starting from an empty cold state is proposed to handle this issue.Each tray will be described from a non-equilibrium phase in which only mass and energy transfer are taking place to an equilibrium phase in which the vapor-liquid equilibrium is reached.The switching point between these two phases is decided by the relationship of bubble-point temperature at the operating pressure.The liquid holdup of each tray is related to the geometry of the trays.The model is verified through experiment on a pilot batch plant with a bubble-cap tray column to separate a methanol-water mixture.