Measurement of shear force, temperature profiles and fibre development in mill-scale TMP refiners

Sammanfattning: Two different force sensors have been developed for tangential forcemeasurements in commercial TMP refiners, one is based on the use of piezoelectricsensors and the other on strain gauges. The measurements are used to learn moreabout the refining mechanism in both single-disc (SD) refiners and conical disc(CD) refiners. Despite the large variations observed in both temperature and steampressure, it is possible to measure the force distribution in the plate gap.According to trials in a first-stage SD refiner the tangential force in therefiner gap is highest at the periphery. The tangential forces measured in the flatzone in a CD refiner exhibit a similar profile to the forces in the SD refiner. In bothcases the force is increasing along the plate gap. The tangential force was morescattered at the centre compared to periphery. The temperature profile was alsomeasured and it is important to point out that the temperature profile and thetangential force profile had their maxima at different positions.The fibre characteristics after the flat and CD zones respectively in a CD-82working as a single-stage chip refiner have been studied. A special samplingmethod made it possible to collect pulp sample at the end of the flat zone. Theresults suggest that the flat zone plate gap is important for controlling the long fibrefraction. In general the flat zone had a large influence on the fibre disintegration inthe CD refiner.