Thermodynamic phase-equilibrium mixing process

Thermodynamic models are widely used for the calculation of equilibrium and thermophysical properties of fluid mixtures. Two types of such models will be examined cubic equations of state and activity coefficient models. In this chapter cubic equations of state models are used. Volumetric equations of state (EoS) are employed for the calculation of fluid phase equilibrium and thermophysical properties required in the design of processes involving non-ideal fluid mixtures in the oil and gas and chemical industries. It is well known that the introduction of empirical parameters in equation of state mixing rules enhances the ability of a given EoS as a tool for process design although the number of interaction parameters should be as small as possible. In general, the phase equilibrium calculations with an EoS are very sensitive to the values of the binary interaction parameters. 

For temperatures near the melting point a different thermodynamic analysis becomes useful for characterizing the interaction between blend components (12,14). Because of the lower free energy in the mixed amorphous phase, the crystals of component 2 have a lower equilibrium melting point than pure component 2. The melting point depression stemming from the enthalpic part of the mixing process is... 

In Chap. 6 we treated the thermodynamic properties of constant-composition fluids. However, many applications of chemical-engineering thermodynamics are to systems wherein multicomponent mixtures of gases or liquids undergo composition changes as the result of mixing or separation processes, the transfer of species from one phase to another, or chemical reaction. The properties of such systems depend on composition as well as on temperature and pressure. Our first task in this chapter is therefore to develop a fundamental property relation for homogeneous fluid mixtures of variable composition. We then derive equations applicable to mixtures of ideal gases and ideal solutions. Finally, we treat in detail a particularly simple description of multicomponent vapor/liquid equilibrium known as Raoult s law. 

In contrast to natural structures the morphological features of structures in fabricated foods are in principle within our control. The source of the many structures of foods, even those made from a single raw material (e.g., wheat flour), lies in the ingredient mix and the fact that thermodynamic equilibrium is practically never required or achieved during processing. These metastable structures can be attained because they are favored kinetically, that is, the approach to equilibrium is slow. At any point during the development of a particular structure a process of shape stabilization sets in, usually by vitrification, partial crystallization, phase separation and/or formation of a network (Figure 12.5). 

CVD phase diagrams constructed using the SOLGAS-MIX-PV/FACT program have been shown to be powerful tools in the systematic development of CVD coatings. Their primary benefit is to initially establish the feasibility of a particular system and establish initial process parameters to obtain a particular deposit. Since equilibrium thermodynamics is used to generate CVD phase diagrams, they can only be used to establish trends because CVD process are typically non-equilibrium. With sufficient... 

Extractor equipment considerations are discussed here in the context of their effect on the process performance and not for the purpose of describing detailed design. The main parameter of interest at this point is the number of equilibrium stages that represent the process. Liquid-liquid extraction requires thorough mixing of two liquid phases to achieve thermodynamic equilibrium, followed by complete separation of the phases. The particular equipment selected for a given process is determined, in part, by the mixing and separation characteristics of the phases. 

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