Low consistency refining of mechanical pulp : process conditions and energy efficiency
The thesis is focussed on low consistency (LC) refining of mechanical pulp. Theresearch included evaluations of energy efficiency, development of pulpproperties, the influence of fibre concentratio ...
Two-stage low-consistency refining of mechanical pulp
The objective of this study was to reduce energy demand in the mechanical pulp refining process by substituting second stage high consistency (HC) refining with two stages of optimised low consistency (LC) refining. Primary refining of Spruce-Pine-Fir wood chip mix was carried out using the Advanced Thermo-Mechanical Pulp (ATMP) refining process employing mechanical chip pre-treatment in the RT Pressafiner and Fiberizer prior to highintensity refining with the addition of 3.1% bisulphite. A portion of the primary pulp was subjected to a second stage HC refining, and the other part subjected to two stages of LC refining. The results indicate that the two stages of optimised secondary LC refining reduced the gross refining energy by approximately 300 kWh/odt compared to second stage HC refining. The target tensile index of 40 Nm/g required approximately 1450 kWh/odt of gross HC refining energy, and only 1150 kWh/odt using primary HC followed by secondary LC refining. Compared to HC-refined pulps, at a tensile index of 40 Nm/g, the LC-refined pulps had a similar freeness, light scattering coefficient and density, but lower TEA, stretch, tear index and average fibre length. The different pulp properties are believed to originate from the different fibre length distributions resulting from these two refining methods.
SR topography of plastically deformed Fe-Si bicrystals - observation in situ and post mortem
SR reflection topography was applied to study the interaction of slip dislocations with the grain boundaries in Fe-4at%Si bicrystals deformed by compression. Three experimental settings with either a white or monochromatic beam were used and the corresponding orientation contrast analysed. Dislocation transmission through the grain boundary was observed in bicrystals with favourable geometry of the slip systems.