Chemical potential gradient driven phase-equilibrium systems

2 Chemical potential gradient driven phase-equilibrium systems 

We consider here the role of bulk flow parallel to the direction of the chemical potential gradient based force in phetse-equilibrium based open two-phase systems. Vapor-liquid systems of flash vaporization, flash devolatilization and batch distillation are considered first, followed by a liquid-liquid system for extraction. Solid-liquid systems for zone melting and normal freezing are studied thereafter to explore how bulk flow parallel to the force direction is essential to considerable purifleation of solid systems followed by solid-vapor systems as in drying. 

1 Vapor-liquid systems flash vaporization, devolatilization and batch distillation 

Distillation based separation of a liquid mixture exploiting the inherent separation achieved in a closed vessel due to vapor-liquid equilibrium (Section 4.1.2) is implemented in an open separator vessel in a variety of ways. The variations are primarily due to the nature and origin of the bulk flows of the liquid and the vapor streams, and to the manner of feed introduction. Here we wiU consider only 

In reality, the design of the flash drum has to be such that the upward vapor velocity is low enough not to entrain 

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The interface between two polymers, whether compatible or incompatible, is a region of finite thickness within which the composition varies continuously from one bulk phase to the other [44]. This interfacial region is formed by interdiffusion of the two continuous phases, driven by the chemical potential gradient. In an incompatible system, the equilibrium interfacial thickness is attained when the entropy effect equals the enthalpy effect [45—48], giving a thickness of typically 1-20 nm, depending... 

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