OptCab – control system for bleach plants

A control system that continuously distributes the bleaching between the different bleaching stages can reduce the bleaching costs significantly with a payback time of a couple of months. The system has been running at Billerud’s mill in Skärblacka for two years. Comparisons between periods with OptCab running and with manual operation show that the chemical cost has been reduced by 5-10%.

The control strategy combines flexible process models with advanced and robust control. The process models are updated continuously and use data from a period of one week.

Using the process models an overall optimizing problem including all stages is created and solved. The goal of the optimizing problem is to achieve the lowest bleaching costs with given constraints on chemical charges, kappa number and brightness.