Nonlinear model predictive control of energy-integrated process systems

Abstract

Improving energy efficiency has become particularly important in chemical processes in view of recent increases in energy prices, growing environmental concerns, and regulatory pressure. In this paper, we consider a class of process systems with significant energy recovery. Extending our previous results concerning the two time scale dynamics of such systems, we demonstrate that the fast component of the dynamics is asymptotically stable in practical cases. Using this result, we develop a hierarchical control framework, consisting of a linear control system for the fast dynamics and a MISO nonlinear model predictive controller for the slow dynamics, and prove that it guarantees exponential stability for the overall system. Subsequently, we explore the implications of this approach in economic model predictive control and optimal energy management. We illustrate our theoretical developments with a benchmark chemical process application.