Near infrared process sensors for pulp mill applications

摘要

Process analyzers utilizing near infrared (NIR) reflectance spectroscopy are being used increasingly to provide information necessary to optimize the pulp making process. Material properties of interest are related to measured NIR reflectance using statistical techniques. The advantage of the technique is the speed of measurement and the ability to perform non-contact measurements. Analyzer systems have been developed for both at-line and over-the-conveyor on-line installations. The development of an NIR calibration involves five steps: 1) a set of samples with known physical or chemical properties is assembled; 2) the NIR reflectance spectra of this sample set are collected; 3) calibrations are developed from the spectra and the properties of interest using one of several multivariate techniques; 4) the reliability of each calibration is validated; 5) the validated calibrations are used to predict properties of interest for unknown samples. Examples presented include: at-line analysis of pulp kappa and brightness; on-line analysis of lime mud moisture and color; on-line analysis of wood chip moisture; and, on-line analysis of wood chip resin content in and OSB application.