Refining intensity was determined directly from measured residence times and energy data. However, the refining intensity did not correlate with pulp freeness and long fibre content (Bauer McNett). In contrast, the refiner plate gap correlated well with the pulp quality. It appears that the refining zone pulp pad characteristics play an important role in the energy transfer and thus development of pulp quality. Both the wood and fibre network properties should be considered to link the current intensity explanation to pulp quality. The residence time of pulp within a refining zone was measured for the key process conditions of energy input, production rate and refining consistency using a radioactive isotope. The measurements allow the pulp velocities within the refiner to be determined and thus enable a greater understanding of the refining mechanism(s). The chip/pulp residence time within a primary-stage TMP refiner were found to range from 3 to 15 seconds depending on the process conditions. For "normal" TMP process conditions, pulp remained within the refining zone for approximately 0.5 seconds and within the refiner system (ribbon screw to blow valve) for approximately 3 seconds. Altering the process conditions demonstrated that: 1. Increased specific energy input and production rate both caused the refining zone residence time to increase 2. Increased refining consistency did not change the refining zone residence time.
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