STATE MODEL OF STEAM REHEATING FOR CONTROL OPTIMIZATION

This paper presents a nonlinear state space model for thermal process of steam reheating. The purpose of the model is to examine existing control system and to support the development of new more efficient control systems for steam reheating units. This model describes countercurrent heat exchanger (biflux) with bypass and two parallel flow heat exchangers with bypasses and spray attemperator. The model includes interconnections of subsystems and the dynamics of all control valves. The model is a state model which enables modeling of power variation from start up to shut down. First, the basic principles of this approach are compared with already published results. Second, the model is calibrated for the newly designed reheating unit for the planned upgrade of a power plant. Both results from static and dynamic characteristic responses, as well as selected control responses in operating range are presented.