Boiler Firing Control Design Using Model Predictive Techniques

PI controllers are typically used in industry for boiler firing rate control for their simplicity and ease in tuning; this is the case with the utility boilers at Syncrude Canada’s northern Alberta plant. However, instability often occurs in cases of large (load) disturbances, primarily due to firing rate limit constraints. Using a Syncrude Canada’s utility boiler as an example, we attempt to redesign the firing rate controller. We show that stability and performance of the closed-loop system can be improved to some extent by properly designed PID controllers. For further improvement, we adopt a model predictive control (MPC) scheme which is capable of handling the firing rate constraints directly; a simple MPC algorithm is implemented on a nonlinear simulation package, and significantly better results are achieved. Copyright ©2002 IFAC.