Oxygen Stage Advanced Control Using On-Line Kappa Sensors, 1991 Pulping Conference Proceedings

Recent advances in Kappa analysis, dynamic simulation, and adaptive/predictive process control technologies are combined to help provide a practical solution to meeting stringent Kappa control requirements. Many production staff face increasingly tighter Kappa control requirements because of environmental pressures on bleach plant operations, more rigid quality specifications, and economic pressures from worldwide competition. This paper presents an advanced control strategy for oxygen delignification that incorporates a combination of modeling, control analysis and sensor technologies. This approach provides more accurate prediction and control of Kappa under real world operating conditions than provided by other approaches or any single technique alone. It’s practicality results from incorporating an embedded kinetic model of the oxygen delignification process coupled with an adaptive module that continuously "learns" from the process. This knowledge is used to compensate for dead time variations, and model inaccuracies that often occur with fixed process models. On-line Kappa sensors continuously validate and calibrate the model to maintain accuracy over time. This results in tighter control of outlet Kappa even with large incoming variations from the digester(s). The resulting self-tuning strategy can be implemented with most DCS systems, is easy to use, and will work with any manufacturer’s Kappa sensor. It also has application to continuous digesters and the bleach plant.