EFFECTS OF PULP FURNISH AND REFINER SPEED ON RESIDENCE TIME IN A HIGH-CONSISTENCY REFINER

Pulp residence time in the refining zone of a high-consistency laborat ory refiner was measured at different rotational speeds for chemitermo nechanical pulp (CTMP) at 20% consistency using a technique developed by Ouellet et al. [J. Pulp Paper Sci. 22(8): J301(1996)]. The results were with (a) previous results obtained with kraft pulp and (b) predic tions from the mathematical model developed by Miles and May [J. Pulp Sci. 16(2): J63(1990)]. Lower rotational speeds produced longer reside nce times as expected from the theory. However, the residence time of was found to be much lower that of kraft pulp under similar operating conditions. The CTMP results also were in better agreement the theory. The discrepancy between kraft and CTMP was explained high-speed video observations pulp flow in the refiner, which two distinct flow regime s. The radial location where transition from one to the other takes pl ace was found to depend on furnish properties and rotational speed-and theoretical considerations allowed us to use this information to esti mate the ratio of friction coefficients in Miles and May's theory.