Effects of Pulp Furnish and Refiner Speed on Residence Time in a High Consistency Refiner, 1996 Pulping Conference Proceedings

J. J. Senger, D. Ouellet, C. P. J. Bennington--Pulp residence time in the refining zone of a high consistency laboratory refiner was measured at different rotational speeds for CTMP at 20% consistency using a technique developed by Ouellet et al. (Proceedings of 1995 Intl. Mech. Pulp. Conf., 171-176). The results were compared to previous results obtained with kraft pulp, as well as predictions from the mathematical model developed by Miles and May (J. Pulp Paper Sci. 16(2), .J63-J7l, 1990). Lower rotational speeds produced larger residence times, as espected from the theory. The residence time of CTMP was found to be much lower than that of kraft pulp under similar operating conditions. The CTMP results were also in better agreement with the theory. The discrepancy between kraft and CTMP was explained through high- speed video observations observations of pulp flow in the refiner. which showed that two distinct flow regimes existed. The radial location where the transition from one regime to the other takes p1ace was found to depend on furnish properties and rotational speed, and theoretical considerations allowed us to use this information to estimate the ratio of friction coefficients in Miles and May’s theory.