The importance of coalescence for efficient application of extraction and reaction engineering involving liquid–liquid mixtures is reviewed, with an emphasis on the role of intensification techniques for improvement. Discussion of gravity settling is used as a starting point, which then extends into the role of solid surfaces, such as fibers, in promoting coalescence. The physical mechanisms which control interactions between drops that then lead to coalescence are then reviewed. These include collision frequency, interfacial drainage, the role of van der Waals forces, and dynamic changes in drop geometry. A brief introduction to population balance modeling for prediction of coalescence rates is presented. The application of electrostatics to intensification of coalescence is analyzed, with a short summary of the controlling relationships. Recent developments in the application of surfactants and electrolytes for the enhancement of coalescence are also reviewed, together with an overview of controlling equations. Other intensification techniques that are briefly reviewed include the application of ultrasonic fields, phase-inversion techniques, and the use of membranes.

Enhancement of mass transfer is one the most important factors in the intensification of liquid–liquid processes. The fundamentals of interphase mass transfer for single drops are reviewed, with summary of the important correlations developed to date. The cases of single oscillating drops and of droplets experiencing circulation are discussed with presentation of important correlations for mass-transfer coefficients. The discussion of single drops is extended to describe a quantitative approach to describing mass-transfer rates for liquid–liquid systems based on solution of the Navier–Stokes equations, continuity equations, and Fick’s law. The phenomena of time-dependent mass transfer, the role of interfacial instability, and Marangoni convection are described with presentation of the controlling equations. Comparisons between experimental mass-transfer data and predictions are shown. More complex cases involving swarming drops are considered, with a review of correlations for the calculation of mass-transfer rates in various continuous column contactors, including spray columns, pulsed packed columns, pulsed plate columns, and rotating disk columns.

The principles of process intensification and the positive impacts for process safety, economics, and the exploitation of novel chemistry are described. The nexus between process intensification and sustainability is explained. The role of novel solvents such as ionic liquids in process intensification is discussed. The principles of liquid–liquid contact and phase separation are described, followed by a review of current engineering technologies for liquid–liquid processes which embrace the principles of process intensification. A brief overview of state-of-the-art mixing technology for liquid–liquid systems and for mixer settlers precedes a summary of current column contactor types and rotary contactors. Established designs of column contactors are briefly reviewed. The chapter includes some description of industrial coalescence equipment, showing how the design of coalescence equipment has been improved to enhance performance. A final section dealing with recent oscillatory baffled contactor technology is included, demonstrating how they meet the criteria for process intensification.

The fundamentals of droplet formation and motion are discussed, highlighting the importance to intensification of contactor hydraulic performance and mass transfer kinetics. A detailed review of the relationships dictating drop formation, drop size, and velocity in liquid–liquid systems is included. Dynamic behavior during drop formation and the mode of drop detachment from a nozzle are described. The behavior of single discrete drops in unhindered motion is considered, and then developed into the analysis of swarms of drops in hindered motion and in sprays. Key literature discussing droplet behavior is reviewed, with presentation of correlations for prediction of drop size and velocity in these cases. An overview of drop size correlations for liquid–liquid mixtures in stirred vessels is presented. This is followed by a review of correlations developed for drop size in continuous column contactors of various types. These include the Kühni column, the pulsed Karr column, packed columns, spray columns, and rotating disk columns. Quantitative modeling of dispersion and coalescence in stirred vessels based on a population balance approach is also described.

THIS IS ONE OF THE LONGER chapters in this book and should be revisited many times at various levels. To cover in detail the subject of the properties of gases and liquids would take an entire book. Reference [1] is a classic example of such a book. We begin our study of properties by defining a few basic terms and concepts. We follow this by examining ideal-gas properties that originate from the equation of state and calorific equations of state. Various approaches for obtaining properties of nonideal gases, liquids, and solids follow. We emphasize the properties of substances that have coexisting liquid and vapor phases. The concept of illustrating processes graphically, using thermodynamic property coordinates (i.e., T– and P– coordinates), is developed.

IN THIS CHAPTER, we extend the overarching mass and energy conservation principles to reacting systems. In addition to conserving mass in an overall sense, the mass of individual elements must also be conserved in the transformation of reactants to products. Complicating energy conservation (the first law of thermodynamics) is the need to account for the potential energies associated with the making and breaking of chemical bonds. To accomplish this, we introduce the concept of standardized enthalpies. We introduce other new concepts related to mass conservation (e.g., various measures of stoichiometry) and energy conservation (e.g., adiabatic flame temperatures and fuel heating values). The chapter also applies the theoretical developments to practical steady-flow systems (e.g., furnaces, boilers, and combustors). Although the chapter focuses on combustion, the ideas developed here apply to other reacting systems as well.

CHAPTER 10 CONSIDERED MIXTURES OF ideal gases. In this chapter, we will apply a mixture analysis to investigate air–water mixtures, referred to as moist air. Since the water content in the air is relatively low, the partial pressure of the water is low. At low partial pressures, the water vapor can be approximated as an ideal gas and the moist air is an ideal-gas mixture. This chapter will first define some terms commonly used for moist air: specific humidity, relative humidity, and dew point. The analysis of moist air will then be used in several common applications: evaporative coolers, humidifiers, air conditioners, dehumidifiers, and cooling towers.

CHAPTER 10 CONSIDERS IDEAL gas mixtures. We will apply the ideal-gas properties from Chapter 2 to calculate the thermodynamic properties of nonreacting ideal-gas mixtures. These mixture properties will then be used in the conservation equations from Chapter 5 and entropy calculations from Chapter 7. With this analysis, we can study the mixing of two or more gases, the heating/cooling or compression/expansion of a mixture, and the operation of steady-state devices that use a mixture of ideal gases. Until this point, we have considered air as a simple ideal gas. In this chapter, we will look at the air properties considering the composition of the air.