Interphase mass transfers material balances

If the T and P of a multiphase system are constant, then the quantities capable of change are the individual mole numbers rf of the various chemical species i in the various phases p. In the absence of chemical reactions, which is assumed here, the ft may change only by interphase mass transfer, and not (because the system is closed) by the transfer of matter across the boundaries of the system. Hence, for phase equilibrium in a 7T-phase system, equation 212 is subject to a set of material balance constraints ... 

In this case, as shown in Figure 4, the subsystems are stoichiometry, material balance, energy balance, chemical kinetics, and interphase mass transfer. The mass transfer phenomena can be subdivided into (1) phase equilibrium which defines the driving force and (2) the transport model. In a general problem, chemical kinetics may be subdivided into (1) the rate process and (2) the chemical equilibrium. The next step is to develop models to describe the subsystems. Except for chemical kinetics, generally applicable mathematical equations based on fundamental principles of physics and chemistry are available for describing the subsystems. 

Understand the importance of material balances in interphase mass-transfer calculations. 

Combine material-balances information from the McCabe-Thiele graphical method with interphase mass-transfer considerations to determine the packed height of the rectifying and stripping sections of a continuous-contact binary distillation tower. 

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