MEASUREMENT OF NORMAL AND SHEAR FORCES DURING REFINING USING A PIEZOELECTRIC FORCE SENSOR

摘要

The normal and shear forces acting locally on pulp flocs and wood chips have been measured over a 5 mm section of an individual bar in the stationary plate of a laboratory single-disc refiner, using a novel piezoelectric force sensor. Softwood TMP at 20% consistency was fed into the refiner in some trials, while others used softwood chips. The rotational speed of the refiner was varied from 700 to 2550 rpm. The results of this preliminary study indicate that the forces on pulp flocs at 20% consistency are qualitatively similar to those at low consistency, measured in a previous study [Goncharov. V.N.. "Force Factors in a Disk Refiner and Their Effect on the Beating Process." Buzmah. Prom. No.5:12-14. English Trans.. (1971)]. There is a large peak in both the normal and shear forces occurring over the initial part of an impact that reduces significantly over the final portion of the impact. For wood chips, it was observed that impacts would last for several bar crossings, and occur periodically with each rotation of the refiner. This is in accordance with earlier high-speed video observations of the flow of chips in RMP refiners [Atack. D.. Towards a Theory of Refiner Mechanical Pulping." APPITA. 34(3):pp 223-227. (1980)]. The results indicate that the piezoelectric force sensor can be a valuable tool for elucidating mechanisms of the refining process, and ultimately for controlling refiner operation.