Modern Bleach Plant Advanced Process Control utilizing Inline Sensors and Model Predictive Control

摘要

During the past two decades there have been significant changes to operating conditions of fiber lines and bleach plants, in particular. In addition to major mechanical modifications, environmentally driven changes have resulted in the elimination of chlorine for most Kraft bleached grades. However, many of the norms or control philosophies have not changed and are in fact rooted in the theories related to the characteristics of chlorine bleaching. Very small amounts of lignin remain in lower Kappa Number pulp entering the brightening stage. The traditional location of sensors needs to be changed as the reaction rates of chlorine dioxide are much different than chlorine. Brightness control becomes more appropriate than the traditional kappa factor control and evidence will be presented that shows DEK levels less than 2 have a high degree of testing error and potential variability when compared to a brightness measurement.