What are the principles of plantwide control design?

Key principles: 1) Set production rate at bottleneck; 2) Manage inventories systematically (avoid accumulating between units); 3) Handle recycle streams properly (break recycle dynamics with sufficient surge volume); 4) Establish steady-state operating point with degrees of freedom analysis; 5) Select control objectives for quality, environment, safety; 6) Handle disturbances where they enter; 7) Use economic optimization for degree-of-freedom selection. Methodologies: Luyben's 8-step procedure, Skogestad's self-optimizing control. Consider interactions between units, recycle dynamics, and constraint management. MPC often used for coordination.