Near Infrared Spectroscopy : An Introductory Study On Measurement Techniques And Tools For Analysing Moisture Content In Pulp And Paper Media

Abstract: The growing technique of near infrared spectroscopy is used to build fundamental knowledge of how the method might be applied for moisture determination in pulp and paper media. Filter paper was used to investigate the angle and distance dependence, otherwise obscured by the uneven surface of pulp or dry fibers. For contact measurements both filter paper and CTMP-fibers were used. The angle and distance evaluation is based on visual spectral interpretation to later incorporate preprocessing methods of the data followed by a multivariate analysis using PLS. With the knowledge built before the experimental startup, the acquired spectra are known to have many co-linearities and hence, for the purpose of determining the moisture content abundant information which might enable the reduction of data points for evaluation. The distance and angle experiments gave results indicating that the intensity of the reflected light change the information gathered and must be accounted for in calibration. Turning the measuring probe 30 degrees or more at 5 mm distance reduced the effect of high intensity specular reflection. Temperature displayed differences in the spectra, cold samples giving less response than warm samples although no clear correlation was found. Multivariate analysis of the contact measurement samples gave most accurate result after multiple signal correction preprocessing. Distance measurements on fiber rendered models with high RMSEC values and gave no reasonable base for prediction.