Designing process controller for a continuous bread baking process based on CFD modelling

Temperature is the dominating factor in various physiochemical changes during baking, including starch gelatinization, protein denaturation, enzymatic reactions and browning reactions, which collectively determine the final bread quality. However, often the design and performance of many industrial temperature controllers are not optimized. To circumvent this problem, the possibility of applying a two-dimensional (2D) computational fluid dynamics (CFD) model to the process control design for an industrial continuous bread baking oven was explored in this paper. A feedback control system was incorporated into the CFD model through user-defined functions (UDF). UDF was used to monitor the temperature at specific positions in the oven, and to define the thermal conditions of burner walls according to the control algorithm. A feedback control system with multiple decoupled PI controllers was designed and evaluated. The controller performed satisfactorily in response to disturbances and setpoint changes. With the establishment of the new process control system, the need of a preheating step required in typical industrial operations was re-evaluated. It was found that, under the control system, the elimination of the initial preheating to 550 K would not significantly affect the dough/bread top surface temperature profile across all baking zones.