Aplicação do sistema online NIR no controle de qualidade dos cavacos em uma indústria de papel e celulose

Abstract

This study presents the implementation and evaluation of an online near infrared spectroscopy system for the real-time monitoring of wood chip properties in a large-scale Kraft pulp mill. The research was motivated by the high variability of wood supplied from different regions and forest origins, which generates significant fluctuations in the cooking and bleaching performance. The main objective was to determine whether continuous monitoring of moisture, bulk density, extractives, lignin and other chemical properties could improve digester stability, enhance operational efficiency and reduce chemical consumption in downstream processes. The methodology involved the use of a Fourier transform near infrared analyzer equipped with chemometric models based on partial least squares and validated according to consolidated multivariate calibration standards. The system was initially started with historical laboratory data and continuously updated with new samples to increase model robustness and coverage of wood variability. Operational results demonstrated significant improvements, including increased stability of the Kappa number in both production lines evaluated and measurable gains in digester yield, indicating reduction of fiber losses and lower specific wood consumption. These operational gains directly affected the bleaching plant, enabling more controlled oxygen delignification and contributing to reduced consumption of bleaching chemicals such as chlorine dioxide and hydrogen peroxide. The study confirms that near infrared spectroscopy provides a valuable predictive tool for process optimization, allowing faster operational responses compared to traditional laboratory analyses. The conclusions emphasize the potential for further application of the technique to additional chemometric properties and to the production of dissolving pulp, strengthening the relevance of online near infrared monitoring as an advanced control strategy for pulp manufacturing.