Equilibrium is a state of balance between opposing forces such that the net force or change is zero, including static equilibrium where the resultant force is zero and dynamic equilibrium where the rates of opposing reactions are equal. There are different types of equilibrium such as chemical, dynamic, and ionic equilibrium. A contact equilibrium separation process aims to reduce the concentration of a component in one phase or stream and increase it in another, typically calling one stream the overflow and the other the underflow.

1. EQUILIBRIUM
 Equilibrium is a state of rest or balance due to the equal action of
opposing forces.
 It is a state of balance between opposing forces or actions that is
either static (as in a body acted on by forces whose resultant is
zero) or dynamic (as in a reversible chemical reaction when the
rates of reaction in both directions are equal).
Types of Equilibrium:
 Chemical equilibrium
 Dynamic equilibrium
 Ionic equilibrium

3. Contact Equilibrium Separation
• A contact equilibrium separation process
is designed to reduce the concentration of a
component in one phase, or flowing stream in
a continuous process, and increase it in
another. Conventionally, and just to
distinguish one stream from another, one is
called the overflow and the other the
underflow.

4. PHASE TRANSFORMATION