Explain the McCabe-Thiele method for distillation column design.

The McCabe-Thiele method is a graphical technique for determining the number of theoretical stages in a binary distillation column. It involves plotting the equilibrium curve (y vs x), operating lines for rectifying and stripping sections, and stepping off stages between them. Key assumptions include constant molar overflow and binary mixture. The method determines minimum reflux ratio, actual stages needed, and optimal feed stage location.