Phase Equilibrium in Chemical Engineering#

Summary#

Chemical Engineers are interested in the amount of stuff in a system, which is described by the various types of balance equations that we introduced earlier. However, they are also interested in the state of stuff in the system, e.g., is stuff a liquid, a gas, or a solid.

Many exciting applications with societal or technological benefits have been developed by exploiting or manipulating the state of a working material in a system. For example, power generation and cooling processes take advantage of the phase change (moving from a liquid to gas, and then back again) as a critical element of the process. Flash separation takes advantage of the phase change (moving from a liquid to a mixture of liquid and gas) to separate chemical mixtures without any moving parts. Similarly, crystallization, often a critical step in many chemical and pharmaceutical processes, involves moving from a liquid mixture to a mixture of solid and a liquid. Finally, many food products, e.g., salad dressings or consumer products such as cosmetics, are emulsions; an emulsion is a mixture of two or more liquids that are usually immiscible on their own but can be mixed with the aid of an emulsifier, a chemical component which stabilizes the mixture. Thus, the state of the working fluid in the system is often a critical component of a process.

Toward understanding the system state in this unit, we will introduce: