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Optimized on-line process control of bleaching operations with OptCab


  • Flisberg, Patrik

    () (Department of Mathematics, Linköping University)

  • Nilsson, Stefan

    () (Billerud Skärblacka AB, Sweden)

  • Rönnqvist, Mikael

    () (Dept. of Finance and Management Science, Norwegian School of Economics and Business Administration)


To produce pulp for paper production or as market pulp is a complicated on-line process with many integrated stages that impact the final quality. In the bleaching plant which is at the end of pulp production, the main objective is to increase pulp brightness within specified limits. Here chemical treatments are applied in sequential stages to achieve the right brightness while striving to maintain the pulp strength as unaffected as possible. The raw material, i.e. pulp logs and wood chips from saw mills, differ in quality and properties. Due to this, it is important to continuously update the amount of chemicals added to the pulp in real-time. This is typically done by experienced operators. In this paper, we describe an on-line optimization based decision support system called OptCab that controls the bleaching process at Billerud AB's paper mill in Skärblacka. The solution approach is based on two phases. In phase one, we establish approximations of each of the processes based on process data collected on-line. These approximations are found by solving a set of constrained least square problems and are updated every 15 minutes. In phase two, we formulate an overall nonlinear control problem that links all stages together and aims to minimize the cost of chemicals. This is solved on-line every five minutes. The system has been in operation during the last three years providing a 10% reduction in the use of chemicals. Additional benefits include a more stable brightness quality.

Suggested Citation

  • Flisberg, Patrik & Nilsson, Stefan & Rönnqvist, Mikael, 2007. "Optimized on-line process control of bleaching operations with OptCab," Discussion Papers 2007/9, Norwegian School of Economics, Department of Business and Management Science.
  • Handle: RePEc:hhs:nhhfms:2007_009

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    References listed on IDEAS

    1. P. Spellucci, 1998. "A new technique for inconsistent QP problems in the SQP method," Mathematical Methods of Operations Research, Springer;Gesellschaft für Operations Research (GOR);Nederlands Genootschap voor Besliskunde (NGB), vol. 47(3), pages 355-400, October.
    2. repec:spr:compst:v:47:y:1998:i:3:p:355-400 is not listed on IDEAS
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    Pulp production; on-line optimization based decision support system; nonlinear control problem;

    JEL classification:

    • C61 - Mathematical and Quantitative Methods - - Mathematical Methods; Programming Models; Mathematical and Simulation Modeling - - - Optimization Techniques; Programming Models; Dynamic Analysis

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