A Fast and Accurate near Infrared Spectroscopy Method for the Determination of Cellulose Content of Alkali Cellulose Applicable for Process Control

Abstract

A novel near infrared (NIR) spectroscopy method for the determination of the cellulose content of alkali cellulose, an intermediate product in viscose fibre production, is presented. This method is especially suitable for the purpose of process control. The method is realised in diffuse reflectance mode. A fast sample preparation step consisting of the compression of the coarse bulky alkali cellulose is introduced, in order to homogenise the sample material. The measurement takes 10 min, including the preparation step. For calibration of the method, samples taken directly from the production line have been used in combination with samples prepared in the laboratory. Validation conducted in a production environment yields a root mean square error of prediction of 0.36% w/w for cellulose content, which is sufficient for the detection of deviation from standard production parameters. It is found that the source material for the alkali cellulose influences the NIR spectra. Analysis of the source material indicates that the hemicellulose composition, i.e. a poly- or oligosaccharide dissolvable in caustic lye, has an impact on the NIR spectra. Different types of source materials can be discerned from their NIR spectra.