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UBC Theses and Dissertations

Low consistency refining of mechanical pulp : the relationship between plate pattern, operational variables and pulp properties Elahimehr, Ali


In this dissertation we propose a framework to predict pulp properties of mean fibre length and freeness from low consistency (LC) refiner operating conditions and present correlations between those properties of pulp and hand sheet paper properties of tear, tensile and bulk. This framework is not new and was proposed by Luukkonen [1] however, studying the effect of plate pattern in this work based on the methodology presented in this dissertation is a novel approach. We accomplish this objective through the introduction of two geometrical parameters: Bar Interaction Length, BIL, and Bar Interaction Area, BIA. To do so, a comprehensive modelling of the geometry of disc refiner plates used in LC refining of mechanical pulp is done. We develop analytical and numerical models to estimate important geometrical parameters such as bar crossing area, leading edges of bar crossings and number of crossing points in a disc refiner with parallel distribution of bars. We will then use these models to predict pulp properties of mean fibre length and freeness from refiner operating conditions by running pilotscale refining trials of mechanical pulp over a wide range of plate pattern, rotational speed and gap size. From this stage, we present correlations between hand sheet paper properties of tear, tensile, bulk and pulp properties of freeness and fibre length. We also demonstrate a relationship between net power, plate pattern and refiner operating parameters such as plate gap and rotational speed based upon a classical dimensional analysis in which a reduced parameter space is related to each other through the use of statistical modelling.

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