Abstract:
Samples of Douglas-fir chips and western hemlock/true fir chips were pulped by the kraft and sulfite processes respectively. The spent liquors were analyzed for fluorescent response, and the fluorescent intensities of each liquor sample correlated with yields, Kappa numbers, and lignin contents of the pulps. Linear relationships were seen between fluorescent intensities and the pulp properties of kraft samples, while the sulfite samples demonstrated a maximum fluorescent intensity in the region of a 40% yield. It is postulated that the nonlinear relationship between fluorescence and sulfite pulp properties is due to lignin condensation reactions. Industrial samples were obtained from one sulfite and three kraft pulp mills. Nonlinear relationships were found between liquor fluorescences and Kappa numbers for the kraft mill samples, due to alterations in production parameters between samples. The results from the analysis of the sulfite mill samples verify the laboratory findings that a maximum fluorescent intensity is attained near the end of a normal sulfite cook. A comparison was made between a Turner model 111 filter fluoromter and a Turner model 210 spectrofluorometer, to determine whether the less expensive filter fluorometer would suffice for the monitoring of delignification in a mill. The results suggest that with the correct filters and light source, the model 111 is an accurate tool for the measurement of spent pulping liquor fluorescence.
