On the effects of constraints, economics and uncertain disturbances on dynamic operability assessment

It is desirable in chemical process design to select a design which is not only economically competitive but which would also yield satisfactory closed-loop performance. Dynamic operability reflects the ability with which a plant can be controlled and is typically assessed on the basis of the response to specific setpoint or disturbance changes. In this paper, dynamic operability in the face of arbitrary step-like disturbances within a specified range is considered. It is furthermore recognized that the best achievable closed-loop performance is dependent on the proximity of the operating point to the process constraints, which is in turn determined by the process economics and the expected disturbance range. These effects are included in a procedure which extends the operability assessment framework proposed by Swartz (1994). The application of the method is demonstrated on a simple single-input-single-output (SISO) process.