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Aryanpour, Parsa

University of British Columbia

Aperture plugging is a phenomenon that limits both the capacity and efficiency of pulp screens, which are critical components of the papermaking process. An understanding of how pulp plugs are created and how they can be avoided can help enhance the manufacture of paper products globally, providing energy savings, increased productivity, improved product quality and higher levels of paper recycling. Part one of this thesis considers the creation and destruction of plugs in a small, industrial screen. The resistance of the flow through screen apertures provides a means of assessing the presence of plugs and their evolution through their creation: incipient plugging, plug creation and consolidation, and then conversely their elimination: destabilization, disruption and elimination. A structured means of plug elimination was formulated, from which floc strength could be inferred. These measurements provide insight not only into the factors that control plug creation, but into their character. Long-fiber (softwood) plugs were seen to form and consolidate quickly and to achieve high strength. Their low porosity limited flow through the slot soon after creation. Short-fiber (hardwood) plugs formed more slowly, were more porous and weaker. Part two of the thesis focuses on the pressure pulses used to clear plugs from apertures which can, as revealed in this research, also be used to assess the presence and character of the plugs. Key to these observations were fiber-optic pressure sensors installed within the apertures close to where the plug forms. Measurements showed good agreement with past studies where traditional pressure transducers were installed on the screen cylinder feed surface in terms of pulse shape and pressure coefficient. What this novel method revealed, however, was that: 1) plugs were located above the aperture “throat” and 2) pulse variability could indicate incipient plugging and act as an early indicator of plugging.

Text

2024-04-24

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87988

Mechanical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/