Effect of dilution water on pulp consistency in cross-directional basis weight control

Cross-directional basis weight of paper based on hydraulic headbox is adjusted by the opening of dilution water valve. In order to achieve uniform concentration distribution of paper sheet, a research on the effect of dilution water added to the mainstream on concentration and flow was studied by experimental set-up and mathematical modeling in this paper. Based on the numerical simulation results, a scale model of headbox was derived to predict the water content distribution and pulp consistency distribution. Results show that these models could accurately predict the experimental flow characteristics of a pulp suspension with dilution water added. Compared with slice regulation, the inverse response problem and its improvement method were discussed. By parameters improvement of pulp consistency model, the reverse response on both sides can be well eliminated or balanced when the dilution water was adopted to cross-directional profile control system. It ensures that the influence range of a single dilution water valve is controllable, which improves the adjustment accuracy of cross-directional profile control and thus improves the paper quality. © 2019 Korean Technical Assoc. of the Pulp and Paper Industry. All rights reserved.