NZ591346A

NZ591346A - Improved method of producing pulp from pinus radiata

Info

Publication number: NZ591346A
Application number: NZ59134611A
Authority: NZ
Inventors: Andrew James Chamley; Ronald James Erickson; Srecko Krajcic; Paul Morton Saunders
Original assignee: Wpi Internat Ltd
Priority date: 2011-02-28
Filing date: 2011-02-28
Publication date: 2011-10-28
Also published as: WO2012115526A1

Abstract

Disclosed is a thermo mechanical method of producing pulp from Pinus Radiata wood chips including the steps of: introducing the Pinus Radiata wood chips into a refiner system including one or more refiners where at least one of the refiners has a set of refining discs with an angled bar unidirectional configuration, grinding the wood chips in between the refining discs within the refiners, wherein the set of refining discs are configured to produce pulp that has a final freeness value of between 300 ml (CSF) and 450 ml (CSF), and an average fibre length of between 1.1 mm and 1.7 mm. Also disclosed is the pulp made by the method described above.

Description

<div class="application article clearfix" id="description"> RECEIVED at IPONZ on 8 September 2011 1 5 10 15 20 25 Our Ref: WPI001 Patents Form No. 5 PATENTS ACT 1953 30 Complete After Provisional No. 591346 Filed 24 February 2011 35 COMPLETE SPECIFICATION IMPROVED METHOD OF PRODUCING PULP FROM PINUS RADIATA 40 We, WPI International Ltd, a New Zealand company of Pulpmill, State Highway 49, Ohakune, New Zealand, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: RECEIVED at IPONZ on 8 September 2011 2 IMPROVED METHOD OF PRODUCING PULP FROM PINUS RADIATA FIELD OF THE INVENTION 5 The present invention relates to a thermo mechanical method of producing pulp from Pinus Radiata wood chips. BACKGROUND 10 According to one form of the paper making process, wood chips obtained from trees are refined in between refining plates (made up of several refining segments) to break down the fibres in the wood in order to create paper based products. 15 Pinus Radiata is one type of wood that is used to make these paper based products. Pinus Radiata is a softwood tree from the Pine family and is also known as the Monterey Pine, Radiata Pine or Insignis Pine. As with other wood, Pinus Radiata is made of three main constituents. It includes 20 the cellulose fibres that are desired for making paper products. It also includes lignin, which is a complex polymer that helps bind the fibres; and hemicelluloses, which is a mixture of several plant polysaccharides. The refining process attempts to separate the cellulose fibres from the lignin and hemicelluloses. Pinus Radiata is known to have a very long natural fibre length. 25 Known refining processes for Pinus Radiata generally result in a final pulp product that includes fibres of an excessive average fibre length. On average, the fibre length in the pulp produced after the primary refining stage using known methods is around 2.3 mm with a freeness value of around 630 ml CSF 30 (Canadian Standard Freeness). The freeness value is effectively a measure of how fast water flows through the pulp. These known primary refining stages operate at approximately 55% moisture content, or at 45% consistency. Following further steps of the pulp process (including secondary refining and 35 screening stages) the final resultant pulp is known to have an average fibre length of approximately 2.0 mm with a freeness value of around 350 ml CSF. RECEIVED at IPONZ on 8 September 2011 3 Due to the length of the fibres in the pulp produced using known methods, during the paperboard or paper manufacturing process the fibres interweave so that they tangle together and flocculate to produce paper board or paper with poor 5 formation. This provides a poor quality product with low smoothness and printability properties. Therefore, Pinus Radiata pulp produced that has these parameters is generally considered low quality and not particularly suitable for paper products. 10 Further, as freeness has a linear relationship with bulk, these known refining processes have produced relatively low bulk pulp values. Bulk is effectively a measurement of the inverted density of the pulp, i.e. the amount of volume per unit weight. Producing pulp having a greater bulk value is advantageous to the paper maker as this enables less resources and energy to be consumed for a 15 particular pulp thickness compared with the resources and energy required for pulp having a lesser bulk value. These known processes using Pinus Radiata utilise one or more refining plates that have fibre cutting geometries where the bars and grooves on the plates are 20 orientated such that they extend out from the refining plate from the centre along the plate's radius at substantially a zero degree angle. That is, the bars and grooves do not substantially deviate away from the radial path of the plate. Although refining plates have been developed utilising angled bar configurations, 25 these have been predominantly directed at non Pinus Radiata pulp processing techniques. These configurations were developed to reduce the energy consumption during the pulp process, but were not been able to produce the required quality pulp in terms of fibre length, freeness and bulk. 30 An object of the present invention is to produce an improved quality pulp made from Pinus Radiata, or to at least provide the public with a useful choice. The present invention aims to overcome, or at least alleviate, some or all of the afore-mentioned problems. 35 RECEIVED at IPONZ on 8 September 2011 4 SUMMARY OF THE INVENTION It is acknowledged that the terms "comprise", "comprises" and "comprising" may, under varying jurisdictions, be attributed with either an exclusive or an inclusive 5 meaning. For the purpose of this specification, and unless otherwise noted, these terms are intended to have an inclusive meaning - i.e. they will be taken to mean an inclusion of the listed components that the use directly references, but optionally also the inclusion of other non-specified components or elements. 10 According to one aspect, the present invention provides a thermo mechanical method of producing pulp from Pinus Radiata wood chips including the steps of: introducing the Pinus Radiata wood chips into a refiner system including one or more refiners where at least one of the refiners has a set of refining discs with an angled bar unidirectional configuration, grinding the wood chips in between the 15 refining discs within the refiners, wherein the set of refining discs are configured to produce pulp that has a final freeness value of between 300 ml (CSF) and 450 ml (CSF), and an average fibre length of between 1.1 mm and 1.7 mm. BRIEF DESCRIPTION OF THE DRAWINGS 20 Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a diagrammatic representation of the refiner system according to 25 an embodiment of the present invention; Figure 2A shows a simple representation of the angle of the bars with respect to the direction of rotation of the plate for a known refiner plate configuration; 30 Figure 2B shows a simple representation of the angle of the bars with respect to the direction of rotation of the plate for a plate configuration according to an embodiment of the present invention; Figure 3 shows an example of a refiner plate that may be used in a primary 35 refiner according to an embodiment of the present invention; RECEIVED at IPONZ on 8 September 2011 5 Figure 4 shows a graph indicating the measured fibre length of final pulp product produced using a method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION 5 First Embodiment The following description describes an embodiment of a process for producing improved thermo-mechanical pulp (TMP) from Pinus Radiata. 10 The initial stage of producing pulp involves the removal of the bark from the Pinus Radiata logs using a bark removal machine (debarker drum). Once the bark is removed, the logs are transformed into wood chips by a wood chipping machine (chipper). 15 The wood chips are first screened by removing any oversize and undersize chips. The chips are then pre-heated with steam in an atmospheric vessel. 20 The preheated chips are submerged in hot process water to remove any debris. After removal, they are squeezed in a compaction screw to remove moisture and extractives. Prior to being fed to a series of refiners, the chips are heated in a pressurized 25 vessel. AH the steps prior to the refiner stages use standard process parameters, as will be understood by a skilled person. 30 The chips are then fed to a refining system, which consists of one or more refiners that are used to turn the wood chips into a pulp mixture. According to this embodiment of the present invention, the refining system includes multiple refiners. In particular, there are three refiners (R1, R2, R5) in a 35 primary refining stage, two refiners (R3, R4) in a secondary refining stage and a further reject refiner (R6) as explained in more detail below. RECEIVED at IPONZ on 8 September 2011 6 However, it will be understood that as an alternative, the refining system may include as a minimum a single primary refiner utilising the herein described refiner plate configuration and having sufficient capacity to produce the required 5 pulp. According to a further alternative, the refining system may include two or more primary refiners utilising the herein described refiner plate configuration. According to yet a further alternative, one or more secondary refiners utilising the herein described refiner plate configuration may be used. 10 According to this embodiment, each of the refiners (whether primary, secondary or a reject refiner) include a single rotating refining plate (consisting of one or more refining segments) and a fixed refining plate such that the plates oppose each other and rotate relative to each other. The wood chips are fed in to a gap in between the refining plates through a central aperture in one of the plates. 15 The single rotating plate is caused to rotate adjacent the static plate while an axial force is applied to either or both of the rotating and static plates. The applied axial force causes the rotating plate and static plates to move towards each other and so enable the wood chips to be broken down in between the relatively rotating plates into the fibre components. 20 As an alternative, the system may incorporate a double disc refining system where any of the refiners in any of the refining stages may include two rotating refining plates that oppose each other and rotate in opposite directions to each other. The wood chips are fed in between the refining plates through a central 25 aperture in one or both of the plates. The plates are caused to rotate in opposite directions while they are also forced together. Each refiner plate may be made from twelve refiner segments that join together to form the complete plate. As is known in the industry, a refiner plate may 30 consist of an inner segment, a four piece (i.e. four segments) ring placed around the inner segment, an eight piece ring placed around the inner ring and an outer ring consisting of twelve segments. It will be understood that, as an alternative, the plate may also be made from a single piece or two or more segments. 35 According to this embodiment the wood chips are passed through several stages of refining to produce the refined pulp. RECEIVED at IPONZ on 8 September 2011 7 A primary refining stage refines the new wood chips. A secondary refining stage refines the pulp that comes from the primary refining 5 stage. This secondary stage provides a higher quality pulp than that produced solely by the primary refining stage. The secondary refining stage also reduces the shive content (i.e. bundles of unrefined fibre) in the pulp mixture. According to this embodiment, the pulp from the primary refining stage is processed by the secondary refining stage with minimal energy application. That is, the majority of 10 the processing energy is utilised by the primary refining stage. It will be understood that the amount of the primary refined pulp forwarded to the secondary refiners may depend on the amount of shive content found in the pulp coming from the primary stage. That is, the pulp from the primary stage may be 15 monitored to determine the level of shive content and the system adjusted accordingly to apply the required amount of energy to the secondary refining stage dependent on the amount of shive content found. As a minimum, zero energy being applied to the secondary refining stage means the secondary stage is bypassed. 20 The pulp output from the secondary stage is fed to a pressure screening stage which screens the secondary pulp to ensure only the high quality pulp is allowed through. That is, only the refined pulp that passes through the pressure screens is passed on to the further processing stages. The rejected pulp (i.e. the pulp 25 that does not pass through the screens) is fed to a reject refining stage to be refined again. This further refined pulp is then passed back to the screening stage. According to an alternative method, the secondary refining stage is not used and 30 the pulp from the primary stage is fed from the primary stage direct to the pressure screening stage, where the rejected pulp is fed to the reject refiner. Ail refined pulp that passes through the pressure screens is passed on to the further processing stages. RECEIVED at IPONZ on 8 September 2011 8 According to a further alternative method, a separate reject refiner stage may further refine the rejected pulp before applying the refined pulp to the pressure screening stage. 5 According to yet a further embodiment, the refining stage may be comprised of just the primary refining stage without any secondary refining. Optionally, pulp from the primary refining stage may be fed back through a reject refiner via a screening system if the pulp is not of sufficient quality. 10 Figure 1 shows a diagrammatic representation of the refiner system according to this embodiment According to this embodiment, the primary refining stage uses three separate primary refiners (R1, R2, R5) all of which process the wood chips in parallel. 15 Refiners R1, R2 and R5 all use a specifically designed refiner disc/segment as described in more detail below. The refiner R5 has slightly more capacity for refining the wood chips than R1 and R2 combined. In particular, according to this embodiment, the outer rings of the refiner plates are specifically designed having a bar and groove configuration as defined below. As an alternative, the two outer 20 rings of the refiner plates may have the configuration defined below. According to this embodiment, all three of the primary refiners R1, R2 and R5 include a modified refiner plate made up of segments that have an angled bar unidirectional configuration. The term unidirectional indicates that the refiner 25 plate is configured to be rotated during a pulp refining operation in a single direction. The bars and grooves on the plate are offset or angled away from the radial path of the refiner plate such that rotation of the plate not only cuts the fibres in the mixture being processed but also allows the mixture to more easily pass from the centre of the plate to its outer radial edge as well as keeping the 30 pulp in the gap between the bars so that it is subjected to impact as the plate is rotated in one direction. This is compared to the known refiner plate configuration that has bars and grooves that are substantially parallel to the radial path of the refiner plate. That is, according to this embodiment, the bars in the refiner plate lie in a direction that is not perpendicular to the angle of rotation, 35 instead the bars are offset so that the direction of the bar (from the outer edge to RECEIVED at IPONZ on 8 September 2011 9 the centre of the plate) does not pass through the centre of the refiner plate. In other words, they are orientated obliquely in relation to the radius of the segment. This form of refining plate segment in the primary refining stage provides a refiner 5 plate that reduces energy usage while maintaining the quality of the pulp with respect to fibre length, bulk and shive content. That is, the specific quality requirement for Pinus Radiata is maintained while allowing the pulp mixture to move across the plate surface. 10 Figures 2A and 2B show a simple representation of the angle of the bars (and so the grooves) with respect to the direction of rotation of the plate for a prior known configuration (Figure 2A) and a configuration according to this embodiment (Figure 2B). 15 Figure 2A shows a prior known bar configuration in a bi-directional refiner plate used for refining Pinus Radiata. The bars 201 are configured so that they are perpendicular to the direction of rotation of the refiner plate 203. The plate can therefore operate in a clockwise or anti-clockwise manner. The projected line of the bars and grooves passes through the centre of the refiner plate. 20 Figure 2B shows the bar configuration of an angled bar uni-directional refiner plate according to this embodiment used for refining Pinus Radiata. The bars 205 are configured so that they are offset from an angle which is perpendicular to the direction of rotation of the refiner plate 207. The plate can therefore only 25 operate in an anti-clockwise manner (as indicated by the arrows). The projected line of the bars and grooves do not pass through the centre of the refiner plate. Therefore, the mixture that enters the refiner plate at the centre, marked with a +, can more easily travel from the centre of the refiner plate out to the radial outer edge of the plate. 30 Figure 3 shows one such example of the configuration of an angled bar unidirectional refiner plate segment that could be used in the primary refiners R1, R2 and R5 according to this embodiment. 35 The refiner plate segment 301 includes a number of adjacent bars 303 which form grooves in between. As can be seen from figure 3, the bars 303 are not RECEIVED at IPONZ on 8 September 2011 10 parallel with the radial path 305 from the refiner plate centre to the refiner plate edge. Instead, the bars are oriented obliquely in relation to this radial path. A skilled person will understand that alternative configurations may also be used 5 where the segment has an angled bar unidirectional configuration. According to this example, the refiner segment has multiple regions (inner, central and outer) where the angle of orientation of the bars varies in each region. However, it will be understood that the bars may be orientated at an angle that is the same in each of these regions. 10 Referring back to figure 1, the secondary refining stage includes two refiners R3 and R4 which process the pulp from the primary refiners in parallel. According to this embodiment, both R3 and R4 use standard refining segments/discs, as will be understood by a skilled person. However, as an alternative, one or both of the 15 secondary refiners may use an angled bar unidirectional refiner plate as described above with reference to figures 2B or 3. The pulp from the secondary refiners is fed to a set of pressure screens 101. If the pulp does not pass through the screens it is fed to a reject refining stage. 20 According to this embodiment, the reject refiner stage includes a single refiner R6, which also uses an angled bar unidirectional refiner plate as described above. As an alternative, the reject refiner stage may use standard refining segments discs as will be understood by a skilled person. 25 In each of the refiners R1 to R6 a single rotating disc is used against a stationary disc. That is, the discs rotate relative to each other with one being stationary. It will be understood that, as an alternative, one or more of the refiners may incorporate a dual disc rotation system as mentioned above. 30 Each plate generally includes three zones, an inner zone, a central zone and an outer zone. Each zone may have a number of bars and grooves that have defined dimensions and orientations in order to refine the wood chips. 35 As an example, each zone may have bar widths that range from 3.5 to 1.5 mm, groove widths from 4.5 to 2.0 mm, and a groove depth from 5.0 mm to 10.0 mm. RECEIVED at IPONZ on 8 September 2011 11 As an alternative, the inlet zone may include dams that are located in between adjacent bars. As a further alternative, these dams may be sub surface dams that have a height less than the height of the bars. For example, the dams may be at a height that is half that of the bar height. 5 After the secondary refinement stage has taken place, a latency removal stage may be used where twirling is removed from the fibre. After the latency removal stage, the pulp may be passed through a series of 10 pressure screens to screen out any parts of the pulp that are not of the required quality. That is, long and/or coarse fibres and/or stiff fibres and shive (bundles of fibre) are removed (rejected) from the main pulp stream. These rejected components may then be fed through a reject refiner before being fed back through the pressure screens or forward to the next process. 15 The screened pulp may then be cleaned in bydracyclones to remove debris, bark and shive that have passed through the screening stage. Extractives are then removed from the diluted pulp using a compaction screw. 20 The extraction screw also increases consistency prior to bleaching. The pulp is then bleached to increase the pulp brightness using a peroxide/alkali process. 25 The bleaching process affects the bulk properties of the final pulp product. For example, at 350 CSF the bleaching process may produce a bleached final pulp product that has an ISO brightness of 80 and a bulk value of 2.7 m3/kg x 1CT3. Alternatively, the bleaching process may produce a bleached final pulp product that has an ISO brightness of 70 and a bulk value of 3.1 m3/kg x 10"3. In general, 30 the bulk values of the final pulp product are between 2.7 m3/kg x 10~3 and 3.3 m3/kg x 10"3. Free water is then removed from the pulp, after which the pulp is then dried in a hot air flash dryer, 35 RECEIVED at IPONZ on 8 September 2011 12 The pulp may be tested at this point to provide a final quality measurement. It will be understood that the quality of the pulp may be tested throughout the process steps described above. 5 The properties of the pulp produced using the above described method were measured as follows. Using an optical fibre analyser on a Pulp Expert (an automated analyser) the average fibre length of the final pulp product at 350 CSF was measured as 1.25 10 mm. Figure 4 shows a distribution of the fibre lengths in the sample measured. It can be seen from this distribution that the longest fibre is approx 4.0 mm and the shortest fibres are approx 0.4 mm. 15 In general the average fibre length of the final pulp mixture was found to be between 1.15 and 1.3 mm. Even more generally, the average fibre length of the final pulp mixture was found to be between 1.1 and 1.7 mm. 20 Importantly, the freeness of the pulp is also controlled in the refining stages and measured using a standard Tappi drainage test (T227 om-92). The freeness value of the final pulp product measured was between 300 ml and 450 ml (CSF). More specifically, the freeness value obtained may be between 315 ml (CSF) and 25 400 ml (CSF), or more specifically between 330 ml (CSF) and 390 ml (CSF). According to this embodiment, the consistency of the mixture provided to the primary refiners may be adjusted within the range 25% to 30%, which is equivalent to a moisture content range of between 70% and 75%. By controlling 30 the mixture of wood chips and water content (i.e. the consistency), control in the amount of energy used to convert the wood chip into pulp is provided. That is, as the amount of water used in the refining process is increased (i.e. the consistency is lowered) the amount of electrical energy required for the refining process is reduced. 35 RECEIVED at IPONZ on 8 September 2011 13 A standard Tappi procedure is used to determine the bulk value of the final pulp product. A Tappi meter T220 om - 88 was used to make a sheet made out of pulp (i.e. a hand sheet, which is a round disc of the pulp). A micrometer is then used to make a physical thickness measurement. Based on this thickness 5 measurement, a calculation is performed using the known weight, size and volume of the round disc to determine the bulk value. The pulp produced using the herein described method has a value of between 2.7 and 3.3 m3/kg x 10-3. More specifically, the pulp produced may have a bulk value of between 2.9 and 3.2 m3/kg x 10-3. 10 A further measurement used to test the quality of the final pulp product is a strength measurement. A standard Tappi procedure is used to determine the strength of the final pulp 15 product. The Tappi procedure used for measuring tensile strength is T494: Tensile Breaking Properties of Paper and Faperboard. The pulp produced using the herein described methods produces a final product pulp that has a tensile strength range of between 1900 and 2800 meters. 20 A table of the various approximate process parameters used in the above described method is now provided. Consistency Freeness Temp Disc Speed Disc force Chip Flow -mi CSF °C RPM Tonnes Oven Dry Tonnes/hr R1 25-30% 400 - 570 1500 40 6.756 R2 25-30% 400 - 570 1500 40 6.756 R5 25-30% 400 - 570 1500 50-90 15.765 Pre Heater 110 RECEIVED at IPONZ on 8 September 2011 14 It will be understood that other parameters may also vary the quality of the final pulp product. For example, the age of the refining plates, the quality of the wood chip and how stable the machines are during operation. 5 During the primary refining stage, the process aims include having a freeness value in the ranges described above. The freeness value may be controlled by adjusting the plate gap between the refining plates. That is, the axial load applied to the refining plates may be adjusted to force the plates closer together. 10 In the primary refining stage, according to this embodiment, the freeness value of the pulp exiting this stage may be- monitored to check the average freeness values. For example, R1 and R2 refiners may be set to produce a pulp having a freeness value of up to 600 ml (CSF), whereas the R5 refiner may be controlled so that the pulp produced by R5 has a freeness value of 400 ml (CSF), or 15 possibly lower. As a further example, the R5 refiner may be controlled so that the pulp produced by R5 has a freeness value of 600 ml CSF, and the R1 and R2 refiners are controlled so that the pulp produced by R1 and R2 is 400 ml CSF. By combining the pulp from these refiners, depending on the volume produced by each of the refiners, the average freeness value is configured to be around 500 20 ml (CSF). By adjusting the various parameters, the CSF values can be adjusted up and down so that they fall in range of the desired quality of the end product pulp. Further, the pulp quality may be monitored after the primary refining stage to 25 determine the average fibre length at this stage. A target average fibre length may be, for example, 1.3 mm. After the secondary refining and additional processes, the final product pulp average length will then fall within the desired range as described above. 30 As a secondary control parameter, the energy input may be adjusted by varying the plate gap. After the final testing stage, the pulp is packaged by baling, wrapping, and tying with wire prior to it being despatched. 35 RECEIVED at IPONZ on 8 September 2011 15 The pulp bale that is produced by the above described process may then be used to form various types of product, such as paper and paperboard products. Further Embodiments 5 It will be understood that the embodiments of the present invention described herein are by way of example only, and that various changes and modifications may be made without departing from the scope of invention. 10 It will be understood that the primary refining stage may be modified to include a single refiner utilising one of the refining segment forms as described herein. Alternatively, the primary refining stage may be modified to include more than three refiners, with one or more of those refiners utilising an angled bar unidirectional refining segment form as described herein. 15 Further, it will be understood that the secondary refining stage, if used, could be modified to include a single refiner, or three or more refiners. Further, it will be understood that the secondary and/or reject refining stages may 20 implement low consistency refining techniques for the refining process. For example, the secondary and/or reject refining stages may use up to or greater than 90% moisture content. Further, it will be understood that any of the refiners may use a combination of 25 two differently configured refining segments for each plate. For example, one or more of the primary refiners may use an angled bar unidirectional refiner plate that opposes a standard (i.e. bi-directional parallel bar) refiner plate. 30 RECEIVED at IPONZ on 8 September 2011 16 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> CLAIMS:

1. A thermo mechanical method of producing pulp from Pinus Radiata wood chips including the steps of: 5 introducing the Pinus Radiata wood chips into a refiner system including one or more refiners where at least one of the refiners has a set of refining discs with an angled bar unidirectional configuration, grinding the wood chips in between the refining discs within the refiners, wherein the set of refining discs are configured to produce pulp that has a 10 final freeness value of between 300 ml (CSF) and 450 ml (CSF), and an average fibre length of between 1.1 mm and 1.7 mm.

2. The method of claim 1, wherein the freeness value is between 315 ml (CSF) and 400 ml (CSF). 15

3. The method of claim 2, wherein the freeness value is between 330 ml (CSF) and 390 ml (CSF).

4. The method of claim 1, wherein the average fibre length is between 1.15 20 and 1.3 mm.

5. The method of claim 4, wherein the average fibre length is substantially 1.25 mm. 25

6. The method of claim 1, wherein the average fibre length is between 1.3 and 1.7 mm.

7. The method of claim 1» wherein the bulk value of the puip is between 2.7 and 3.3 m3/kg x 10"3. 30

8. The method of claim 7, wherein the bulk value of the pulp is between 2.9 and 3.2 m3/kg x 10"3 RECEIVED at IPONZ on 8 September 2011 17

9. The method of claim 1, wherein the one or more refiners are primary refiners. 5

10. The method of claim 1, wherein the refiner system includes one or more primary refiners and a reject refiner.

11. The method of claim 1, wherein the refiner system further includes one or more secondary refiners. 10

12. The method of claim 1, wherein the pulp is passed through one or more pressure screens.

13. The method of claim 12, wherein the pulp is passed though one or more 15 pressure screens after passing through a primary refiner or a reject refiner.

14. The method of claim 1, wherein the pulp is further processed in one or more hydracyclones. 20

15. The method of claim 1, wherein the refining discs are rotated relative to each other at a speed of between 1400 and 1600 rpm.

16. The method of claim 1, wherein an axial force is applied to the refining discs at a force of between 50 and 90 tonnes. 25

17. The method of claim 1, wherein the wood chips are processed in the refiner system with a moisture content of between 70% and 75%.

18. The method of claim 1, wherein the at least one refiner includes a set of 30 refiner discs including two different types of disc.

19. The method of claim 1, wherein the at least one refiner includes a set of refiner discs of the same type. 35

20. Pulp made from the method of any one of claims 1 to 19. RECEIVED at IPONZ on 8 September 2011 18 21, A method of producing pulp from Pinus Radiata wood chips substantially as herein described with reference to figures 1, 2B, 3 and 4. WPI International Ltd f / By 1 heir Attorneys ELLIS TERRY </div>