Nir-Based Yield Estimation in Semichemical Pulping, 1994 Pulping Conference Proceedings

C. P. Woitkovich, T. J. McDonough, E. W. Malcolm

The semichemical sector of the pulping industry has never had a quick, reliable method for estimating pulping yield. Consequently, it has suffered a serious disadvantage when attempting to define and control pulp quality. This report describes the development and testing of a new method to estimate yield in semichemical pulping. The method is based on near-infrared (NIR) spectroscopic analysis of wood and pulp. Strong correlations have been observed in the laboratory between NIR measurements and gravimetric yield. NIR vs. yield calibrations can be derived from laboratory simulations and applied to mill NIR data to generate yield estimates. Data from three semichemical pulp mills reveal that NIR is a sensitive indicator of relative yield variation. A correlation between pulp NIR measurements and machine runnability is also suggested. It is possible to determine absolute yield levels in a mill if NIR wood chip analysis is included to quantify species composition. NIR vs. yield calibration issues are discussed in detail. Implementation options are also presented.