Bleaching

Kraft pulping produces strong pulp that typically requires further processing by bleaching to provide acceptable brightness. The bleaching process removes the lignin (source of colour) which remains following digester cooking process. This process uses large quantities of expensive bleaching chemicals (usually ClO2) and represents raw material and waste disposal challenges. pH measurement in this area optimizes the efficiency of the bleaching process, lowering bleach consumption, discharge and associated costs.

Accurate controls of pH, wash flows, tower levels, temperatures and dilution flows are critical to overall bleach plant effectiveness. Due to the corrosive nature of the bleaching chemicals, specialized Fisher control valves and Rosemount instrumentation provide best in class reliability and control performance. DeltaV's advanced control strategies also enables the mill to minimize bleaching costs through our multi-stage optimization controls.