EP1540073A1 - Method of manufacturing mechanical or chemi-mechanical pulp and an apparatus for manufacturing the same - Google Patents
Method of manufacturing mechanical or chemi-mechanical pulp and an apparatus for manufacturing the sameInfo
- Publication number
- EP1540073A1 EP1540073A1 EP03761888A EP03761888A EP1540073A1 EP 1540073 A1 EP1540073 A1 EP 1540073A1 EP 03761888 A EP03761888 A EP 03761888A EP 03761888 A EP03761888 A EP 03761888A EP 1540073 A1 EP1540073 A1 EP 1540073A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- reject
- refining
- wood material
- accept
- defibrated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 229920001131 Pulp (paper) Polymers 0.000 title claims abstract description 12
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 12
- 238000000034 method Methods 0.000 claims abstract description 50
- 238000007670 refining Methods 0.000 claims abstract description 36
- 239000000463 material Substances 0.000 claims abstract description 27
- 239000002023 wood Substances 0.000 claims abstract description 25
- 238000012216 screening Methods 0.000 claims abstract description 15
- 238000005265 energy consumption Methods 0.000 abstract description 9
- 239000007795 chemical reaction product Substances 0.000 abstract description 2
- 239000000047 product Substances 0.000 abstract 1
- 239000000835 fiber Substances 0.000 description 7
- 102000004190 Enzymes Human genes 0.000 description 2
- 108090000790 Enzymes Proteins 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229920005610 lignin Polymers 0.000 description 2
- 101001132883 Homo sapiens Mitoregulin Proteins 0.000 description 1
- 102100033799 Mitoregulin Human genes 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000005381 potential energy Methods 0.000 description 1
- 238000004537 pulping Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
- D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
- D21D5/02—Straining or screening the pulp
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21B1/00—Fibrous raw materials or their mechanical treatment
- D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
- D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
Definitions
- the invention relates to a method of manufacturing mechanical and chemi- mechanical pulp by disintegrating and treating wood material.
- the invention also relates to an apparatus for manufacturing mechanical or chemi-mechanical pulp.
- One object of the invention is to carry out the disintegration and refining of the pulp in such a manner, that the total energy consumption is substantially reduced, as will be described in the following.
- thermo-mechanical pulp is conventionally manufactured with high consistency- technology (HC-technology).
- TMP thermo-mechanical pulp
- the refining process is often divided into two HC-refining steps with a total energy consumption of about 2000-2500 kWh/ton including reject refining.
- As a rule 2/3 (1200-1700 kWh/ton) of the energy is consumed in the primary step and 1/3 (600-800 kWh/ton) in the secondary step.
- US 6267841 Bl discloses a pulping process where the wood material after a primary refining step is treated with enzymes and is further treated in a secondary refining step. By using enzymes it is possible to use low-energy refining in both refining steps.
- WO 8906717 Al discloses a method of making mechanical pulp. After a high- energy refining step of approximately 2000 kWh/ton the pulp is screened and the reject is further refined in two steps before its reunited with the rest of the pulp. During this process chemicals are added at different stages to further grind and improve the pulp quality.
- a conventional process for making pulp for newspaper use comprises high- energy refining steps approximately using 2000-2500 kWh/t. This is to improve pulp properties and make sure that the shives are reduced to a satisfactory content. This is a high energy consumption and it is an object of this invention to substantially reduce it.
- This invention relates to a new method and a new apparatus for removing the problems and drawbacks with known techniques according to the objects of the invention mentioned above.
- the new method is characterized by the following steps:
- wood material is defibrated in a first step with a low energy input and then
- reject is screened from the accept (main part of the defibrated wood material) and then
- a preferred embodiment of the method is further characterized by that the accept is refined after the screening.
- Another preferred embodiment of the method is further characterized by that the refining of the accept is performed in a low consistency (LC) refining process.
- LC low consistency
- Another preferred embodiment of the method is further characterized by that the first step defibration is performed at a high rotation speed.
- Another preferred embodiment of the method is further characterized by that the reject is refined in a high consistency process.
- Another preferred embodiment of the method is further characterized by that the reject after refining is screened and possible remaining reject is fed back for further refining.
- Another preferred embodiment of the method is further characterized by that the reject is mixed with the accept before this second screening step.
- the new apparatus is characterized by a defibration device with a low energy input defibrating the wood material, a screening device separating reject from the accept, a reject refining device and a mixing stage, mixing the refined reject with the accept.
- a preferred embodiment of the apparatus is further characterized by that it comprises a refiner stage refining the accept.
- Another preferred embodiment of the apparatus is further characterized by that the accept refiner is refining at low consistency, 2-6%.
- Another preferred embodiment of the apparatus is further characterized by that the reject refiner is refining at low consistency.
- Another preferred embodiment of the apparatus is further characterized by that it after the reject refiner comprises, devices for screening the reject and feeding possible remaining reject back to the reject refiner.
- Figure 1 discloses a schematic view of the steps of the process according to the invention.
- Figure 2 discloses a diagram showing tensile strength as a function of energy input per ton.
- Fig. 1 a first embodiment of the process of the invention. A first
- Step 1 of the process comprises a defibration step, preferably at a high speed (approximately 1500 rpm or higher), defibrating the wood material.
- Defibration at high speed has proven to be very effective in reducing the amount of shives in the defibrated material.
- This first defibration step is using a very low energy input of 400-900 kWh/t at high consistency as it has been shown that 65-95% of the wood material is aheady defibrated to fibers at this low energy input.
- An alternative to high speed defibration is to use double-disc refiners. Two discs are then rotating in opposite directions. The rotating speed can then be kept lower with the same effect because of the relative movement of the discs.
- Another conventional way of lowering the energy input is to increase the grinding gap.
- a common practice to use a higher energy input in the defibration (primary refiner) with the purpose to decrease the shive content gives the result that already defibrated fibers are only to a small degree further treated. Most of this extra higher energy input is namely mostly consumed by decreasing residual content of shives. Because of the high content of already defibrated fibers achieved already at a very low energy input, further energy input in the the primary refiner does not lead to treatment of the defibrated fibers. The shives are bigger in size compared to the smaller size of defibrated fibers. Therefore, further energy input is consumed for the defibration of shives.
- Step 2 of the process is a screening step where the shives are screened from the coarse defibrated pulp and thus become reject.
- This screening can be performed in two steps to make sure that the capacity is sufficient to screen all the coarse defibrated pulp from shives.
- the screening is performed after two steps of refining when the pulp contains only a few percent shives and after a substantial energy consumption.
- the shives (reject) and the accept are treated separately. To treat the accept and reject separately makes it possible to adapt the treatment for the respective type and this results in a more energy effective process.
- the accept is after Step 2 treated in a low consistency refiner 3.
- the low consistency refining is preferably performed at an energy effort of about 200-400 kWh/ton at 85-95°C and at a pulp concentration of 2-6%.
- the increased LC-refining temperature is due to more softening of the lignin. Because of the technology in low consistency refining with a smaller plate gap makes the process intensive and energy effective. This results in an intensive and very effective processing of the pulp.
- a reliable measure of the low energy exploitation in conventional processes compared to the process of the present invention is the tensile index as a function of the energy input per ton.
- the diagram in Fig. 2 shows in curve 1 (LEMP) how the tensile index of the process of the present invention shows a more or less linear character and therefore shows a favourable development of the tensile strength against energy consumption while curve 2 (Reference) representing the conventional processes very soon deviate from the linear curve due to akeady refined fibers remaining with the shives causing an excessive amount of energy to be needed to reach the same tensile strength.
- the reject (shives) from Step 2 is processed in either a conventional HC-reject refiner 4 or a LC-refmer. It is preferred that this process takes place in a pressurized environment, e.g. 15-20% more than the atmospheric pressure. This is to achieve a more lenient processing due to softening of the lignin. It is further preferred if the reject pulp is screened again in a screening device 5 with a feed-back of possible remaining shives to the reject refining step. A hydrocyclone may be used to further separate remaining shives from the pulp. LC-processed accept and the reject are finally mixed at the end of the process 6. The different characteristics of the reject and accept can then by changing ingoing proportions be used to obtain pulps with desired properties blended into a desired mix.
- the accept is after the LC-refining, led to the reject just after the reject refining 4 but before the screening 5.
- the advantage of this alternative process is that an extra safety feature is added in that the accept will be screened once more together with the reject and the process is thus taking care of eventual deficiencies in earlier screening 2 and refining steps 3.
- the total energy consumption of the process according to this invention can in an industrial application be 1000-1400 kWh/ton or even lower. With a conventional process the energy consumption varies from 2000 to 2500 kWh/ton. It is thus possible to reduce the energy consumption to 50% with the process according to this invention.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
Abstract
The present invention relates to a method for manufacturing mechanical or chemi-mechanical pulp by disintegrating and treating wood material. The wood material is defibrated in a first step with a low energy input compared to conventional processes. Then the reject is screened from the defibrated wood material. The reject is then refined separately and mixed again with the rest defibrated material to a final pulp product. The invention also relates to an apparatus for manufacturing mechanical or chemi-mechanical pulp by disintegrating and treating wood based material. The apparatus comprises a defibration device (1) with a low energy input, a screening device (2) separating reject from the main part of the defibrated wood material, a reject refining device (4) and a device for (6) mixing the refined reject with the rest of the wood based material.One object of the invention is to carry out the disintegration and the refining of the pulp in such a manner, that the total energy consumption is substantially reduced relative to common practice.It is a further object of the invention to provide a method and apparatus by which it is easy to control through choice of energy inputs the characteristics of the end product by controlling the properties of the defibrated wood material through the process.
Description
METHOD OF MANUFACTURING MECHANICAL OR CHEMI-MECHANICAL PULP AND AN APPARATUS FOR MANUFACTURING THE SAME
BACKGROUND AND TECHNICAL FIELD The invention relates to a method of manufacturing mechanical and chemi- mechanical pulp by disintegrating and treating wood material. The invention also relates to an apparatus for manufacturing mechanical or chemi-mechanical pulp.
One object of the invention is to carry out the disintegration and refining of the pulp in such a manner, that the total energy consumption is substantially reduced, as will be described in the following.
It is a further object of the invention to provide a method and apparatus by which it is easy to control the characteristics of the end product by controlling the properties of the wood material through the process.
Mechanical pulp is conventionally manufactured with high consistency- technology (HC-technology). When manufacturing thermo-mechanical pulp (TMP) the refining process is often divided into two HC-refining steps with a total energy consumption of about 2000-2500 kWh/ton including reject refining. As a rule 2/3 (1200-1700 kWh/ton) of the energy is consumed in the primary step and 1/3 (600-800 kWh/ton) in the secondary step.
US 6267841 Bl discloses a pulping process where the wood material after a primary refining step is treated with enzymes and is further treated in a secondary refining step. By using enzymes it is possible to use low-energy refining in both refining steps.
WO 8906717 Al discloses a method of making mechanical pulp. After a high- energy refining step of approximately 2000 kWh/ton the pulp is screened and the reject is further refined in two steps before its reunited with the rest of the pulp. During this process chemicals are added at different stages to further grind and improve the pulp quality.
A conventional process for making pulp for newspaper use comprises high- energy refining steps approximately using 2000-2500 kWh/t. This is to improve pulp properties and make sure that the shives are reduced to a satisfactory content. This is a high energy consumption and it is an object of this invention to substantially reduce it.
SUMMARY OF THE INVENTION
This invention relates to a new method and a new apparatus for removing the problems and drawbacks with known techniques according to the objects of the invention
mentioned above. According to the invention, the new method is characterized by the following steps:
(1) wood material is defibrated in a first step with a low energy input and then
(2) reject is screened from the accept (main part of the defibrated wood material) and then
(3) the reject is refined separately and then
(4) the refined reject is mixed again with the accept (main part of the defibrated wood material) to a final product.
A preferred embodiment of the method is further characterized by that the accept is refined after the screening.
Another preferred embodiment of the method is further characterized by that the refining of the accept is performed in a low consistency (LC) refining process.
Another preferred embodiment of the method is further characterized by that the first step defibration is performed at a high rotation speed. Another preferred embodiment of the method is further characterized by that the reject is refined in a high consistency process.
Another preferred embodiment of the method is further characterized by that the reject after refining is screened and possible remaining reject is fed back for further refining.
Another preferred embodiment of the method is further characterized by that the reject is mixed with the accept before this second screening step.
The new apparatus according to the invention is characterized by a defibration device with a low energy input defibrating the wood material, a screening device separating reject from the accept, a reject refining device and a mixing stage, mixing the refined reject with the accept. A preferred embodiment of the apparatus is further characterized by that it comprises a refiner stage refining the accept.
Another preferred embodiment of the apparatus is further characterized by that the accept refiner is refining at low consistency, 2-6%.
Another preferred embodiment of the apparatus is further characterized by that the reject refiner is refining at low consistency.
Another preferred embodiment of the apparatus is further characterized by that it after the reject refiner comprises, devices for screening the reject and feeding possible remaining reject back to the reject refiner.
BRIEF DESCRIPTION OF THE DRAWINGS
Special embodiments of the invention will be described in the following detailed description of the invention with reference to the drawing.
Figure 1 discloses a schematic view of the steps of the process according to the invention.
Figure 2 discloses a diagram showing tensile strength as a function of energy input per ton.
DETAILED DESCRIPTION OF THE INVENTION In Fig. 1 is shown a first embodiment of the process of the invention. A first
Step 1 of the process comprises a defibration step, preferably at a high speed (approximately 1500 rpm or higher), defibrating the wood material. Defibration at high speed has proven to be very effective in reducing the amount of shives in the defibrated material. This first defibration step is using a very low energy input of 400-900 kWh/t at high consistency as it has been shown that 65-95% of the wood material is aheady defibrated to fibers at this low energy input. An alternative to high speed defibration is to use double-disc refiners. Two discs are then rotating in opposite directions. The rotating speed can then be kept lower with the same effect because of the relative movement of the discs. Another conventional way of lowering the energy input is to increase the grinding gap. A common practice to use a higher energy input in the defibration (primary refiner) with the purpose to decrease the shive content gives the result that already defibrated fibers are only to a small degree further treated. Most of this extra higher energy input is namely mostly consumed by decreasing residual content of shives. Because of the high content of already defibrated fibers achieved already at a very low energy input, further energy input in the the primary refiner does not lead to treatment of the defibrated fibers. The shives are bigger in size compared to the smaller size of defibrated fibers. Therefore, further energy input is consumed for the defibration of shives. The defibrated wood material is at this stage of the process typically containing 5-35 % shives. Step 2 of the process is a screening step where the shives are screened from the coarse defibrated pulp and thus become reject. This screening can be performed in two steps to make sure that the capacity is sufficient to screen all the coarse defibrated pulp from shives. In conventional processes, the screening is performed after two steps of refining when the pulp contains only a few percent shives and after a substantial energy consumption. After Step 2 the shives (reject) and the accept are treated separately. To treat the accept and reject separately makes it possible to adapt the
treatment for the respective type and this results in a more energy effective process. The accept is after Step 2 treated in a low consistency refiner 3. The accept which contains 65- 95% defibrated fibers practically without shives only needs a light processing to develop the desired paper making characteristics. The low consistency refining is preferably performed at an energy effort of about 200-400 kWh/ton at 85-95°C and at a pulp concentration of 2-6%. The increased LC-refining temperature is due to more softening of the lignin. Because of the technology in low consistency refining with a smaller plate gap makes the process intensive and energy effective. This results in an intensive and very effective processing of the pulp.
A reliable measure of the low energy exploitation in conventional processes compared to the process of the present invention is the tensile index as a function of the energy input per ton. The diagram in Fig. 2 shows in curve 1 (LEMP) how the tensile index of the process of the present invention shows a more or less linear character and therefore shows a favourable development of the tensile strength against energy consumption while curve 2 (Reference) representing the conventional processes very soon deviate from the linear curve due to akeady refined fibers remaining with the shives causing an excessive amount of energy to be needed to reach the same tensile strength.
The reject (shives) from Step 2 is processed in either a conventional HC-reject refiner 4 or a LC-refmer. It is preferred that this process takes place in a pressurized environment, e.g. 15-20% more than the atmospheric pressure. This is to achieve a more lenient processing due to softening of the lignin. It is further preferred if the reject pulp is screened again in a screening device 5 with a feed-back of possible remaining shives to the reject refining step. A hydrocyclone may be used to further separate remaining shives from the pulp. LC-processed accept and the reject are finally mixed at the end of the process 6. The different characteristics of the reject and accept can then by changing ingoing proportions be used to obtain pulps with desired properties blended into a desired mix.
In a different embodiment of the invention (not shown) the accept is after the LC-refining, led to the reject just after the reject refining 4 but before the screening 5. The advantage of this alternative process is that an extra safety feature is added in that the accept will be screened once more together with the reject and the process is thus taking care of eventual deficiencies in earlier screening 2 and refining steps 3.
With this concept, according to the embodiment of Fig. 1, it is possible to control the characteristics of the pulp in an easy way by varying the energy input in the different refining steps. The potential energy reduction with this process is very high. The total energy consumption of the process according to this invention can in an industrial
application be 1000-1400 kWh/ton or even lower. With a conventional process the energy consumption varies from 2000 to 2500 kWh/ton. It is thus possible to reduce the energy consumption to 50% with the process according to this invention.
Claims
1. Method for manufacturing mechanical or chemi-mechanical pulp by disintegrating and treating wood material, comprising the following steps (1) wood material is defibrated in a first step with a low energy input and then
(2) resulting reject is screened from the accept (main part of the defibrated wood material) and then
(3) the reject is refined separately and then
(4) the refined reject is mixed with the accept (main part of the defibrated wood material) to a final pulp product.
2. Method according to claim 1, wherein the accept is also refined after the screening.
3. Method according to claim 2, wherein the refining of the accept is performed in a low consistency (LC) refining process.
4. Method according to any one of the preceding claims, wherein the first step defibration is performed at a high rotation speed.
5. Method according to any one of the preceding claims, wherein the reject is refined in a high consistency process.
6. Method according to any one of the preceding claims, wherein the reject after refining is screened and any remaining reject is fed back to the reject refiner.
7. Method according to claim 6, wherein the reject is mixed with the accept before this second screening step.
8. Apparatus for manufacturing mechanical or chemi-mechanical pulp by disintegrating and treating wood material comprising a defibration device (1) with a low energy input for defibrating the wood material, followed by a screening device (2) separating reject from the accept (main part of the defibrated wood material), a reject refining device (4) and a device (6) for mixing the refined reject with the accept (main part of the defibrated wood material).
9. Apparatus according to claim 8 comprising a further refiner (3) for refining the accept.
10. Apparatus according to claim 9, wherein the accept refiner (3) is refining at low consistency, 2-6%.
11. Apparatus according to any of the claims 8-10, wherein the reject refiner (4) is refining at low consistency.
12. Apparatus according to any of the claims 8-11 further comprising after the reject refiner (4), device (5) for screening the reject and feeding any remaining reject back to the reject refiner (4).
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE0202032A SE0202032D0 (en) | 2002-07-01 | 2002-07-01 | Method for manufacturing mechanical or chemical-mechanical pulp and a device for manufacturing the same |
SE0202032 | 2002-07-01 | ||
PCT/SE2003/001146 WO2004003288A1 (en) | 2002-07-01 | 2003-07-01 | Method of manufacturing mechanical or chemi-mechanical pulp and an apparatus for manufacturing the same |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1540073A1 true EP1540073A1 (en) | 2005-06-15 |
Family
ID=20288382
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP03761888A Withdrawn EP1540073A1 (en) | 2002-07-01 | 2003-07-01 | Method of manufacturing mechanical or chemi-mechanical pulp and an apparatus for manufacturing the same |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1540073A1 (en) |
AU (1) | AU2003243114A1 (en) |
CA (1) | CA2491533A1 (en) |
SE (1) | SE0202032D0 (en) |
WO (1) | WO2004003288A1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FI121311B (en) * | 2005-05-03 | 2010-09-30 | M Real Oyj | A process for the preparation of a mechanical pulp for use in the manufacture of paper and board |
DE102007036379A1 (en) * | 2007-07-31 | 2009-02-05 | Voith Patent Gmbh | Process for producing fines from pulp reject |
CA2824076A1 (en) | 2012-08-21 | 2014-02-21 | University Of New Brunswick | System and method for reclaiming rejects in sulfite pulping |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
SE459924B (en) * | 1988-01-22 | 1989-08-21 | Sunds Defibrator | SET FOR MANUFACTURE OF MECHANICAL MASS |
SE513140C2 (en) * | 1998-11-19 | 2000-07-10 | Valmet Fibertech Ab | Procedure for producing upgraded newsprint pulp to SC / LWC quality |
-
2002
- 2002-07-01 SE SE0202032A patent/SE0202032D0/en unknown
-
2003
- 2003-07-01 WO PCT/SE2003/001146 patent/WO2004003288A1/en not_active Application Discontinuation
- 2003-07-01 AU AU2003243114A patent/AU2003243114A1/en not_active Abandoned
- 2003-07-01 EP EP03761888A patent/EP1540073A1/en not_active Withdrawn
- 2003-07-01 CA CA002491533A patent/CA2491533A1/en not_active Abandoned
Non-Patent Citations (1)
Title |
---|
See references of WO2004003288A1 * |
Also Published As
Publication number | Publication date |
---|---|
CA2491533A1 (en) | 2004-01-08 |
WO2004003288A1 (en) | 2004-01-08 |
SE0202032D0 (en) | 2002-07-01 |
AU2003243114A1 (en) | 2004-01-19 |
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