Refining characteristics of Northern and Southern bleached Softwood Kraft B. Palmer Tappsa Conference October 2010

[SA Technology Centre, Sappi Manufacturing] Slide 2 Objectives  Compare wood and fibre characteristics of Northern and Southern bleached Softwood Kraft  Highlight key differentiating features  Determine the individual refining characteristics

[SA Technology Centre, Sappi Manufacturing] Slide 3 Selected fully bleached softwood samples 1.A rich blend of Pinus patula with the balance Pinus elliotii from Mpumalanga, SA (Classified as P. patula in this study) 2.A rich blend of Spruce with the balance a mixture of Pines from Scandinavia (Classified as P. mariana in the study) 3.A rich blend of Douglas Fir with the balance Western Hemlock / Balsam Fir – Canada (Classified as P. menziesii in this study)

[SA Technology Centre, Sappi Manufacturing] Slide 4 Work Scope  Stage 1 Determine the anatomy of the predominant wood species and fibre characteristics of the respective pulp samples after Kraft cooking and bleaching.  Stage 2 Compare the refining characteristics of each sample using a standard refining programme  Stage 3 Identify the optimum refining energy and intensity of each sample

[SA Technology Centre, Sappi Manufacturing] Slide 5 Stage 1- Introduction to Wood Anatomy Juvenile and mature wood  Plantation grown trees such as P. patula in the Southern Hemisphere grow rapidly and are harvested at a younger age so that the juvenile portion of the tree is significant.  Saw-mill chips will be sourced from the outer portion of the tree (mature wood)  (a) juvenile core located in interior of tree bole;  (b) properties that increase from juvenile to mature wood; and  (c) properties that decrease from juvenile to mature wood.

[SA Technology Centre, Sappi Manufacturing] Slide 6 Stage 1 – Introduction to Wood Anatomy Earlywood and latewood  Each annual growth ring contains earlywood, which is laid down in the early part of the growing season and is characterized by large cells with thin cell walls.  Latewood is characterized by small cells with thick cell walls.  Earlywood is low density, latewood is high density wood.  Slow growing softwoods, P. mariana and P. menziesii have a high proportion of latewood.

[SA Technology Centre, Sappi Manufacturing] Slide 7 Stage 1- Wood Anatomy results Fibre diameter P. patula has a relatively high fibre width increasing from pith to bark

[SA Technology Centre, Sappi Manufacturing] Slide 8 Stage 1 - Wood Anatomy results Cell wall thickness Juvenile wood with a high ratio of earlywood Increased latewood growth as tree ages

[SA Technology Centre, Sappi Manufacturing] Slide 9 Stage 1 - Wood Anatomy results Summary  Significant difference in anatomy noted with the P. patula from the inner to outer tree diameter.  Fibres from the outer diameter will be more difficult to refine than those from the inner diameter.  Important to know the ratio of saw mill chips to whole tree or roundwood in a pulp sample.

[SA Technology Centre, Sappi Manufacturing] Slide 10 Stage 1 - Gamma ray densitometry from the bark to the pith  P. patula has a low and consistent density at the pith (early wood) with an increased frequency of peaks at the middle to outer layer (late wood)  The P. mariana and P. menziesii also had annual peaks of wood density from the pith to the bark but proportionally there was more latewood than with the P. patula g.cm g.cm g.cm 3

[SA Technology Centre, Sappi Manufacturing] Slide 11 Stage 1 - Fibre characteristics – bleached Kraft

[SA Technology Centre, Sappi Manufacturing] Slide 12 Stage 1 - Fibre characteristics – bleached Kraft

[SA Technology Centre, Sappi Manufacturing] Slide 13 Number of fibres per gram of pulp Number (10e6/g) P. patula3.7 P. menziesii5.7 P. mariana4.6 Stage 1 - Fibre characteristics – bleached Kraft

[SA Technology Centre, Sappi Manufacturing] Slide 14 Results – Stage 1 Summary of fibre dimensions for each of the pulps SpeciesAvg. Weighted fibre length Avg. weighted fibre width Avg. cell wall thickness Lumen Width Unit(µm) P. patula P. menziesii P. mariana  P. patula  P. menziesii  P. mariana

[SA Technology Centre, Sappi Manufacturing] Slide 15 Evaluate the comparative refining characteristics of the 3 samples using a laboratory single disc refiner under identical and controlled refining conditions.  12” single disc pilot refiner  300 lt 3.5% consistency, 1.2 Ws.m, 0 kWh/t – 220 kWh/t  Hydra cycle mode: Fixed intensity (auto gap adjustment), several passes  Ability to establish a refining curve at 5 different energy levels Stage 2 - Refining equipment Pilot refiner details

[SA Technology Centre, Sappi Manufacturing] Slide 16 Stage 2 – Refining results Freeness vs. refining energy and associated costs P. Patula exhibits a relatively fast freeness development

[SA Technology Centre, Sappi Manufacturing] Slide 17 P. menziesii exhibits a higher unrefined tensile Index P. mariana and P. menziesii show a sharp increase in the Tensile index at a higher freeness when compared to the P. patula At a freeness of 450 ml the P. menziesii exhibits a tensile Index 60% higher than that of P. patula Stage 2 – Refining results Comparative refined strengths

[SA Technology Centre, Sappi Manufacturing] Slide 18 Stage 2 – Refining results Comparative refined strengths  With refining, there is always a compromise between the tear and tensile result.  Ideally, both the tear and tensile should be as high as possible however only one of these two properties can be developed, usually one at the expense of the other.  It is possible to develop P. patula to a similar tear as the other two but not tensile.

[SA Technology Centre, Sappi Manufacturing] Slide 19 Stage 2 – Refining results Comparative refined bulk properties P. patula has the highest bulk as a result of its comparatively high coarseness

[SA Technology Centre, Sappi Manufacturing] Slide 20 Stage 3 – Determine Optimum refining for P. patula  Low intensity refining (0.8 Ws.m) of the P. patula produces the best tensile result for a given tear

[SA Technology Centre, Sappi Manufacturing] Slide 21  When refining the P. mariana, an intensity of 1.6 Ws.m produces the best tear and tensile result  An intensity of 0.8 Ws.m appears to be too low to develop tensile with P. mariana Stage 3 – Determine optimum refining for P. mariana

[SA Technology Centre, Sappi Manufacturing] Slide 22  When refining the P. menziesii, an intensity of 1.6 Ws.m produces the best tear result and an intensity of 1.2 Ws.m produces the highest tensile. Stage 3 – Determine optimum refining for P. menziesii

[SA Technology Centre, Sappi Manufacturing] Slide 23 Stage 3 – Summary of refined properties at 450 ml CSF O.8 Ws/m1.2 Ws/m1.6 Ws/m EnergyCostTensileTearEnergyCostTensileTearEnergyCostTensileTear Kwh/tR m paNm/gmNm 2 /gKwh/tR m paNm/gmNm 2 /gKwh/tR m paNm/gmNm 2 /g P. patula P. menziesii P. mariana

[SA Technology Centre, Sappi Manufacturing] Slide 24 Conclusion  significant differences exist in the wood anatomy and fibre characteristics of the pulp samples both between the three different species and between the two Hemispheres.  Fibre characteristics dictate the manner in which a fibre responds to refining which defines the specific refined pulp properties.  P. patula exhibited a relatively fast freeness development. Conventional thinking would suggest that this was an indication of a weaker fibre. However, this species had a robust morphology compared to the Northern Hemisphere woods. The theory developed in this study suggests that the effect of coarseness and the concomitant number of fibres per gram plays a significant role.