Control configurations for an energy integrated distillation column

Abstract

Process integration provides a tool for exploiting significant energy savings in chemical plants. A large part thereof is often realised in distillation columns. An ultimate degree of energy integration for distillation columns is integration of condenser and reboiler of the same column through a direct or indirect heat pump. In this paper the study of a single distillation column integrated with an indirect heat pump reveals some general operational characteristics of energy integrated distillation plants. It is illustrated how a base case design of energy integration may render the integrated plant open loop unstable. The control loop necessary for stabilization influences the set of actuators available for inventory and purity control. It is discussed how the operating region can be covered using the actuators of an integrated plant relative to using standard distillation column actuators. Optimum energy efficiency of the energy integrated column is discussed through comparison to the base case design. Emphasis is placed on design effects upon plant controllability and operability. Finally general design and operational aspects of energy integrated distillation are extracted.