Traditionally, the teaching of phase equilibria emphasizes the relationships between the thermodynamic variables of each phase in equilibrium rather than its engineering applications. This book changes the focus from the use of thermodynamics relationships to compute phase equilibria to the design and control of the phase conditions that a process needs. Phase Equilibrium Engineering presents a systematic study and application of phase equilibrium tools to the development of chemical processes. The thermodynamic modeling of mixtures for process development, synthesis, simulation, design and optimization is analyzed. The relation between the mixture molecular properties, the selection of the thermodynamic model and the process technology that could be applied are discussed. A classification of mixtures, separation process, thermodynamic models and technologies is presented to guide the engineer in the world of separation processes. The phase condition required for a given reacting system is studied at subcritical and supercritical conditions. The four cardinal points of phase equilibrium engineering are: the chemical plant or process, the laboratory, the modeling of phase equilibria and the simulator. The harmonization of all these components to obtain a better design or operation is the ultimate goal of phase equilibrium engineering. Methodologies are discussed using relevant industrial examples The molecular nature and composition of the process mixture is given a key role in process decisions Phase equilibrium diagrams are used as a drawing board for process implementation

Phase equilibrium knowledge is required for the design of all sorts of chemical processes that may involve separations, reactions, fluids flow, particle micronization, etc. Indeed, different phase behavior scenarios are required for a rational conceptual process design. The aim of this chapter is to present the possible fluid mixture phase behavior that can be found in binary, ternary, and multicomponent systems. Moreover, representation of phase behavior in terms of phase diagrams is discussed. Dealing with phase diagrams of complex mixtures is not an easy task for beginners; however, very simple concepts are behind the rules for their construction. Phase diagrams are essential tools for phase equilibrium engineering as they provide valuable hints to understand the process and to assess the feasible and optimum operating regions. In this chapter, the “phenomenological” meaning of each phase behavior and its relation with molecular properties is discussed. A special attention is given to binary system phase behavior. Even though, in practice we rarely found such simple mixtures, they furnish a great deal of information for the understanding of multicomponent systems.

In this chapter, the basic methodologies of phase equilibrium engineering are introduced through the systematic analysis of several case studies. Some of the thermodynamic tools that have been presented in the previous chapters are applied to illustrate how the phase and conceptual process design of complex engineering problems can be tackled from a phase equilibrium engineering approach. In all the case studies, the first step is to consider in great detail the properties of the process feed, the components, their physical properties, concentrations, and molecular interactions. This information is then used for the selection of thermodynamic models, a suitable technology, pressure, temperature, and compositional operating boundaries. It is shown how the mixture composition and the process goals and specifications determine the process scheme and the unit thermodynamic sensitivity. In addition, the importance of the mixture composition is highlighted in combination with the energy and material balance in the case study for the selection of the desirable natural gas cryogenic technologies. The use of a pressure versus temperature drawing board is used to plot the process trajectory and the mixture phase envelopes from the initial conditions to the key phase engineering design problem. Moreover, the phase design provides also a sound basis for the process initial specification and computer simulation. As another example of phase equilibrium engineering, the heat integration in a complex process is solved by the application of the Gibbs phase rule to the LLV equilibria of a ternary mixture.

Phase Equilibria in Chemical Engineering is devoted to the thermodynamic basis and practical aspects of the calculation of equilibrium conditions of multiple phases that are pertinent to chemical engineering processes. Efforts have been made throughout the book to provide guidance to adequate theory and practice. The book begins with a long chapter on equations of state, since it is intimately bound up with the development of thermodynamics. Following material on basic thermodynamics and nonidealities in terms of fugacities and activities, individual chapters are devoted to equilibria primarily between pairs of phases. A few topics that do not fit into these categories and for which the state of the art is not yet developed quantitatively have been relegated to a separate chapter. The chapter on chemical equilibria is pertinent since many processes involve simultaneous chemical and phase equilibria. Also included are chapters on the evaluation of enthalpy and entropy changes of nonideal substances and mixtures, and on experimental methods. This book is intended as a reference and self-study as well as a textbook either for full courses in phase equilibria or as a supplement to related courses in the chemical engineering curriculum. Practicing engineers concerned with separation technology and process design also may find the book useful.

This volume on phase equilibrium engineering (PEE) aims to fill the gap between the books on reactors and separation process design and the textbooks on chemical engineering thermodynamics. The goal is to change the focus from the use of thermodynamic relationships to compute phase equilibria to the design and control of the phase conditions that a process needs. In this way, phase equilibrium thermodynamics is put to work. The main goal of PEE is the design of the system conditions to achieve the desired phase equilibrium scenario that the process at hand requires. In this chapter, the philosophy of phase equilibrium thermodynamic modeling is discussed in the context of process development and chemical plant operation. Typical phase scenarios that are encountered in separation, materials, and chemical process are presented as well as the problem of phase design and the PEE tools.

This chapter starts with the analysis of the distillation path of binary mixtures on the general phase behavior P–T diagram of binary mixtures. The univariant lines of these diagrams limit the region of vapor–liquid equilibria where binary distillation can be applied. On this basis, the conditions under which distillation is possible for types I, II, IV, and V of binary mixtures are discussed. Furthermore, in this chapter, the principles of fractional distillation, as well as the computational procedures, are discussed. The thermodynamic modeling of a train of distillation columns to separate the components of an ethane-cracked gas mixture is used to develop a strategy for an equation of state parameter tuning. This strategy is based on the analysis of the distillation column phase equilibrium sensitivity and leads to an unique matrix of equation of state dominant binary parameters for the whole fractionation train. The chapter ends with a list of phase equilibrium engineering guidelines to make a realistic design/simulation of distillation columns.

In previous chapters, we have seen the fundamental criteria for phase equilibria and how the phenomenological phase behavior and separation technology of real mixtures are determined by their constituent molecular interactions. Our purpose in this chapter is to present the properties of fluids and the models for the prediction of thermodynamic properties and phase equilibria. These models are classified as predictive models using only pure component properties and semiempirical models based on a molecular thermodynamic approach. Finally, the chapter highlights the importance of the class of mixture and molecular interactions of its components in the selection of thermodynamic models for phase equilibrium calculations.