Feedback and feedforward control of wet-processed hardboard production using spectroscopy and chemometric modelling

The presented work is concerned with spectroscopy solutions as means for feedback and feedforward control in the production of wet-processed hardboards. For this purpose online UV–vis–NIR spectroscopy was installed on a full-scale industrial hardboard production to collect spectra from fibre materials, intermediate fibremats and from final hardboards. The acquired spectra were subjected to following chemometric methods: (i) principal component analyses (PCA) to characterise raw materials and process variables; and (ii) partial least square (PLS) regression to investigate the linkages between spectral information and technological data that were determined on the final hardboards. The groupings according to different raw material types, fine and coarse fibre furnish, and the “H-factor” a measure that is indicative for the softening of lignin and the hydrolysis of hemicelluloses, clearly demonstrated that UV–vis–NIR spectroscopy is instrumental in feedback and feedforward control throughout the processing stages. Strong relationships were observed between UV–vis-online-spectra of the fibremats and the water uptake of the corresponding fibreboards. Additional plant trials are needed to investigate further applications that lead a full feedback and feedforward control of industrial manufacturing of wood-based panels.