A method for the determination oi the mass-transfer coefficients of vapor and liquid phases on the distillation trays-nonequilibrium-cell method is developed. In the model the tray is divided along the liquid flow direction into a number of cells

in each of which both vapor and liquid phases are assumed to be well mixed and the mass and heat transfer between these two nonequilibrium phases proceeds across the vapor/liquid interface. For each cell the mass and energy balance equations for each phase are connected by the mass and energy conservation relationships around the interface which is assumed to be in therrnodynamic equilibrium. For binary distillation

with given flow rates

compositions and temperatures at the inlet and outlet of tray

the model can be represented by (11×nce+ 2) independent equations with the same number of independent variables. The equations are solved to obtain the individual phase mass-transfer coefficient for both phases on each tray using the hybrid Newton method. The model can be used to determine the transfer coefficient-area products simultaneously for both phases on the basis of a single set of experimental data with both phase rate controlling system. On the other hand

the individual phase coefficients have to bo obtained separately with two sets of data each with one phase rate controlling system by the conventional "efficiency method (e. g. the AIChE model) (nce-number of cells per tray. )