Explain pinch analysis and how it optimizes heat exchanger networks in process plants.

Pinch analysis is a systematic methodology to maximize heat recovery and minimize energy consumption in process plants. It constructs composite curves plotting cumulative heat content versus temperature for all hot and cold streams. The pinch point is where curves are closest, representing the minimum temperature driving force. Key principles: heat should not transfer across the pinch, no external cooling above pinch, no external heating below pinch. The grand composite curve reveals utility requirements. Heat exchanger network design follows rules: maximize matches at pinch, use utilities only where streams cannot be matched. Pinch analysis typically identifies 20-40% energy savings in process plants. Modern extensions include pressure drop considerations, capital-energy tradeoffs, and retrofit scenarios.