Identification, control and optimization strategies for thermo-mechanical pulping (TMP) processes

The focus of this thesis is to develop an advanced control sys tem for existing and tobe developed Thermo-Mechanical Pulping (TMP) refining proc esses. Therefore, the thesis has two parts. The first part developed two differe nt but yet complementary closed-loop identification methods to update the model s used in the low-level control layer of the current advanced control systems for TM P refiners. These newly developed identification methods are specific to close d-loop systems controlled by Model Predictive Control (MPC) techniques, and s uccessfully tailored to the presence of the MPC. By updating the existing process models, the current advanc ed control systems can be operated to give better performance. However, these c ontrol systems may not be able to provide optimal performance due to process dis turbances. Hence, a novel economically oriented advanced control system is dev eloped for the existing two-stage TMP refiner processes for their optimal operation when disturbances are present. This novel technique dynamically optimizes th TMP processes as opposed to conventional two-layer methods which perform pr ocess optimization at steady-state, and has shown a potential economical benefi t through reduction of total specific energy of a two-stage TMP process in a simulati on study. In the second part, a novel TMP process with multi-stages of L ow Consistency (LC) refining is studied for its optimal operation. The proposed Nonlinear Model Predictive Control (NMPC) technique dynamically opt imizes the process and provides better performance when disturbances are pres nt. This economically oriented NMPC (econNMPC) minimizes the total specific energy consumption of the process while respecting all the process constra i ts nd achieving final desired pulp quality. In simulation studies, a TMP process w ith multiple stages of LC refining was able to save significant specific energy cons umption with setpoint tracking control when disturbances are present. More over, further reduction ii Abstract of specific energy has been achieved with the developed econN MPC technique.of specific energy has been achieved with the developed econN MPC technique.