Paper Brightness Optimizer

Chemicals to control paper brightness are often added prior to pulp storage tanks in order to ensure enough reaction time. This means there are long delays between chemical addition and feedback from the paper machine brightness sensors. This often results in high chemical consumption to ensure that paper brightness specifications are met. The Paper Brightness Controller uses multivariable model predictive control (MPC) to account for the long delays.


  • The Paper Brightness Controller utilizes the Paper Quality Software Sensors to predict the pulp and paper brightness before it is measured on the machine for feedforward control. Software sensors compensate for disturbances such as: pulp blend ratios, broke addition, chemical charge, white water changes and dye applications. The final brightness measurement signal comes from the paper machine QCS scanner.
  • Since the relationships between chemical addition and brightness can change with pulp inventory the paper brightness control utilizes the MPC software feature to automatically make on-line changes to model gain and deadtime with changing pulp inventories.
  • A cascaded MPC control approach is used to control intermediate brightness points if applicable with chemical dosages (volume per tonne pulp) as the control handles. The set points for the intermediate brightness points are manipulated by MPC to control final paper brightness.


  • Implementation of the Paper Brightness Optimizer has achieved reduction of paper brightness variability by 50% and reduced trim chemical cost by 54%.