Feedstock and Web Analysis Using Mid-Infrared Diffuse Reflectance Spectroscopy and Imaging Spectroradiometry

Abstract

Potential applications of mid-infrared (MIR) spectroscopy in the forest products industry include on-line analysis of feedstock and web materials; these applications differ dramatically in purpose, speed, and overall chemical heterogeneity. Characterization of feedstock will enable sorting of the stock and/or wet chemistry adjustment prior to the web stage of paper production. Sorting will require imaging of the stock as well as classification of the wide variety of chemistry found in recycled stock. At the opposite end of the manufacturing process, on-line analysis of the web will enable adjustment of machine parameters to maximize product quality and minimize waste. Spectroscopic requirements for web analysis include high-speed capability and measurement precision. If successful, both applications could result in a reduction of resource waste, a reduction of plant pollution, and a reduction of energy use while simultaneously improving product quality. Here the progress towards feedstock and web analysis with MIR spectroscopy is presented. To date, work has progressed in three main areas: Diffuse Reflectance mid-Infrared Fourier Transform (DRIFT) spectroscopy of cellulose-based materials, chemometrics analysis, and research of MIR instrumentation for prototype development. The DRIFT spectroscopy data represents a database of the chemistries and spectroscopic signatures of interest to the applications discussed here. Over 50,000 spectra were obtained from cellulose-based materials infised with a wide variety of non-cellulose chemistry. Chemometrics analysis was performed on the DRIFT database to determine the quantitative and qualitative limits of the technique. Emphasis was placed on qualitative evaluation of spectroscopic signatures unique to the particular classes of cellulose-based material; thus, the degree to which classes could be sorted was determined. Finally, investigations of MIR instrumentation suitable for transfer of the technique from the lab-based instrument to a field ready prototype were made.