Effect of bar edge conditions on fibre trapping in low consistency refining

摘要

In a low consistency refiner pulp fibres are trapped between the bar edges of the rotor and stator and worked into the narrow gap between rotor and stator. No refining occurs if the fibres are not trapped. A reduction in fibre trapping is believed to be in the common observation that refining becomes less efficient as the bars wear and lose their sharpness.rnThis paper examines the effect of bar edge sharpness on relative fibre trapping in low consistency refining. The measurements were made on a bleached softwood kraft pulp at consistencies ranging from 1-6% using a conical laboratory refiner. Three sets of trials were done. One set of trials was done with a set fillings that had been worn in number of previous refining trials, while a second set of trials were done with a set of fillings where the bar edge had been sharpened by running the refiner with quartz sand. A third set of trials was done with fillings in which the bar edges had been manually rounded with abrasive paper.rnThe results showed that the fraction of the refiner bar length that trapped fibres was approximately proportional to pulp consistency for all three trials, independent of bar edge sharpness. The reduction in fibre trapping, with lower consistency, increases the harshness of the refining on the fibres, at a given level of refining power. The results also showed that the artificially treated bars trapped generally had a lower fraction of the bar surface trapping fibres, which also increased the harshness of the refining process.