1. COST Action 2015, San Sebastian
Understanding Internal Fiber Development During TMP Refining of Sulfite Pre-treated Spruce Chips
Dinesh Fernando, Erik Nelsson & Geoffrey Daniel
Deptartment of Forest Products
Swedish University of Agricultural Sciences (SLU)
Uppsala, Sweden.
26 May Dinesh Fernando

2. Results and Discussions
Objectives : To investigate effects of low dosage sulfite pre-treatment combined with modern high consistency double disc (DD) refining & to understand TMP fiber development determining pulp & paper properties.
Pulp & Paper Properties
Figure 1. Tensile index vs. SEC for pulps produced with/without sulfite pre-treatment.
Figure 2. Tensile index vs. sulfonate content at a constant SEC of 1950 kWh/bdt.
Table 1. Pulp properties for different refining energies & dosages of Na2SO3 .
Prominent effects of sulfite chip pre-treatment;
- increasing tensile index (TI), density, elongation, brightness etc (Fig. 1 & Table 1).
- lowering shive content, freeness & light scattering (Table 1).
- Proportional increase in tensile index with the amount of Na2SO3 added & was 7.6 Nm/g (~18%) for the highest dosage (1.2% Na2SO3), Fig. 2.
- Improved energy efficiency by lowering ~320 kWh/bdt (~15%) SEC at a TI of 47 Nm/g compared with untreated pulp (Fig. 1 & Table 1).
26 May Dinesh Fernando

3. Degree of fiber wall delamination/internal fibrillation (D/IF)
Table 2. LR statistics for type 3 analysis of ordinal logistic regression test for significant differences in the degree of D/IF of pulps from sulfonated and/or unsulfonated TMPs.
Figure 3. Degree of delamination/internal fibrillation (D/IF) development in double-disc refined TMP pulps produced with different sulfite addition and SEC.
D/IF developed differently with increasing SEC & sulfite addition i.e. internal fiber development (IFD) varied depending on the treatment & SEC.
Sulfite treatment & increasing SEC effectively induces D/IF (Fig. 3);
- Pulp 1.21(2040) dominated by treated fibers (65%) & “high D/IF” fibers (39%) representing most flexible TMPs,
Statistical analyses (Table 2) showed SEC & sulfite treatment significantly induced D/IF.
No significant difference between the pulps 0.00(2080) & 1.21(1780). - i.e. similar IFD between the two pulps.
SS method revealing changes in D/IF development explained property development of the pulps & the improved energy efficiency associated with sulfite pretreatment.
26 May Dinesh Fernando