THERMO-MECHANICAL PULP BLEACHING PROCESS OPTIMIZATION AND BRIGHTNESS VARIABILITY REDUCTION WHILE CONTROLLING TO FINAL PAPER MACHINE BRIGHTNESS AT IRVING PAPER
Final product brightness is of key importance for super calendar paper producers. Manual control of bleaching chemicals typically results in high brightness variability, over-bleaching, and increased chemical costs. High variability leads to elevated bleaching chemical addition to ensure the minimum paper machine brightness is maintained. This action increases overall chemical costs and may even result in brightness reversion. Additionally short-term grade changes to a lower brightness requirement may be effectively ignored due to the difficulty of manually predicting variable storage tower residence times and accounting for non-linear chemical dosage effects on brightness gain. Finally, multiple bleaching chemicals and/or multiple chemical addition points make manual optimization quite difficult. Final product brightness variability can be reduced through the implementation of an advanced control and optimization system. In order to minimize the brightness variability, the advanced control should account for variable residence times, non-linear brightness response curves, grade changes, and the relative effect and cost of multiple brightening agents. Once the pulp brightness variability has been reduced, the average brightness can be shifted lower, closer to target, resulting in a decrease in overall bleaching costs. This paper describes the combined application of advanced control and optimization to achieve the desired paper machine brightness across several brightness grades. The system includes multivariable model predictive control, software sensors for the prediction of residual hydrogen peroxide, and real-time optimization of multiple brightening agents. The mill utilizes sodium hydrosulphite, magnesium hydroxide and hydrogen peroxide for brightening. The control and optimization minimizes off-specification product and reduces overall chemical cost. Both chemical cost savings and variability reduction have been proven in the mill application.
Process optimization paper machine brightness variability reduction thermo-mechanical
Miller Kathleen Hamelin Jean-Francois Fralic Gregory Cole Devin Hohmann Suzanne Dai Zhongguo Court George
Metso, USA2900 Courtyards Drive Norcross, Georgia,30071,USA Irving Paper Ltd.P.O. Box 1900 Saint John,New Brunswick,Canada E2L 4K
国际会议
International Mechanical Pulping Conference 2011(2011国际机械浆学术会议)
西安
英文
283-286
2011-06-26（万方平台首次上网日期，不代表论文的发表时间）