FIBRE PAD DENSITY PROFILES OF A HIGH-CONSISTENCY TMP REFINER

In studies of TMP refining phenomena, the refiner is often called a "black box" because the actual mechanisms inside the refiner are unknown. This study brings new information on fibre pad density in the refining zone. When developing more energy-efficient refiner plates, this information is very important. The fibre-pad density profile in a thermo-mechanical pulp (TMP) refiner was determined by combining in-situ shear force data from the TMP refiner refining zone with off-line disruptive shear stress data using TMP pulp samples taken at the corresponding plate gap. The fibre-pad density in a 44-inch single-rotating disc refiner at a production rate of 700 kg/h was found to vary between 200 and 450 kg/m(3). This value is lower than in mill refiners, which are typically at least 65 inches in diameter and have a production rate of over 8 tons/h. There, the fibre-pad density can reach 600 kg/m(3). The fibre-pad density quantifies the amount of pulp in the total plate-gap volume. In this study, it was possible, for the first time, to measure and determine the density profile for a relatively large TMP refiner. With the help of this density profile, refiner plate development can focus on the most crucial regions of the pattern.