Rapid on-site assessment of wood quality can significantly enhance decision-making and operational efficiency in the pulp and paper industry. Spectroscopic techniques, including near-infrared (NIR) spectroscopy, can be used to characterise wood, but there is a need for development to use these methods in the field, especially for optimising the continuous kraft pulping process. This study focused on using a portable NIR spectrometer to measure lignin and moisture content in Nordic softwood chips, while also distinguishing between bound and free water, with particular focus on challenges related to field-based measurements and process-relevant information. Partial Least Square Regression (PLSR) effectively reduced data dimensionality and simultaneously performed the regression. The performance of portable NIR model was found to be comparable with models based on data from a traditional benchtop NIR. However, several portable NIR spectra need to be acquired and averaged to achieve predictive capability. The results confirm that robustness of benchtop systems for accurate moisture determination. Portable NIR may be useful at kraft pulp mills during disturbance situations, when rapid information about chip quality is necessary.
Klečina et al. (2026) studied this question.