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UBC Theses and Dissertations

The passage of fibres through slots in pulp screening Gooding, Robert William


The screening of wood pulp fibres in aqueous suspension is an important industrial process which involves the passage of "accept" pulp fibres through a perforated or slotted plate, and the retention of larger, coarser fibres on the plate. The influence of fibre, flow, and slot variables on fibre passage was measured in this thesis. These findings were related to the operation of a commercial-scale pressure screen. Also a mechanism of screening was proposed based on fibre trajectories that were observed using high speed cine-photography. This mechanism has two components: 1) a "wall effect" which causes the layer of flow that passes through the slot to be deplete of large fibres, and 2) an "entry effect", which favours the passage of fibres that are short enough and flexible enough to follow the streamlines that turn and pass through the screen plate slot.

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