MODELING AND ADVANCED CONTROL OF IMP REFINER SYSTEM

摘要

It is becoming increasingly important to produce thermo-mechanical pulp (TMP) mat is both uniform and of a high quality. Papermakers desire to optimize paper machine operations, and in some instances to replace the expensive kraft furnish. The highly interactive TMP process necessitates multivariable control. Control of the TMP process is further complicated as blow-line consistency in most cases is not measured using an online sensor. Pulp quality descriptive variables such as fibre length and freeness are measured infrequently. This paper presents a two-level control strategy that stabilizes and optimizes the refining process. The Stabilization layer consists of a multivariable model predictive range controller (MPRC) that regulates the refiner line operations. The Quality Optimization layer provides the pulp quality control as measured by an online pulp quality (freeness, fibre length) sensor. This control strategy leverages the natural decoupling in the process. The modular design technique is able to handle multiple refiner lines that empty into a common latency chest. A global optimizer is also used to integrate and coordinate the two layers for enhanced constraint handling. The control strategy has been implemented at NorskeCanada Elk Falls Operations and significant benefits have been achieved.