Claims
- 1. A method for producing thermomechanical and chemi-thermomechanical pulp effective for use as a raw material for printing paper, the method comprising:refining wood raw material in a refiner to form a refined stock which has a consistency of at least 20% and not more than 90%; and screening the refined stock at a consistency which is about the same as it is as it came from refining in a plurality of stages into accept stock portions and reject stock portions to form a ready made stock having a freeness value of 30 to 70 ml CSF.
- 2. The method of claim 1, wherein the refined stock is screened at a consistency of 30 to 60%.
- 3. The method of claim 2, wherein the screening is carried out by a screen having a diameter to length of housing ratio of 1 to 10.
- 4. The method of claim 1, wherein wood raw material is refined at a superatmospheric pressure of over 400 kPa, and at a superatmospheric pressure of 600 to 700 kpa.
- 5. The method of claim 4, wherein the freeness value of the refined stock is 250 to 700 ml CSF.
- 6. The method of claim 1, wherein after refining, the refined stock is screened into a first accept and a first reject stock portion.
- 7. The method of claim 6, wherein the freeness value of the first accept stock portion is 20 to 50 ml CSF.
- 8. The method of claim 6, wherein the first accept stock portion is taken out of the process.
- 9. The method of claim 6, wherein the first accept stock portion is conveyed to re-screening.
- 10. The method of claim 9, wherein the first accept stock portion is re-screened to form a secondary accept stock portion and a secondary reject stock portion.
- 11. The method of claim 10, wherein the secondary accept stock portion is taken out of the process.
- 12. The method of claim 10, wherein the secondary reject stock portion is conveyed to refining, after which it is screened to form a third accept stock portion and a third reject stock portion.
- 13. The method of claim 12, wherein the third accept stock portion is taken out of the process.
- 14. The method of claim 13, wherein the third reject portion is conveyed back to refining.
- 15. The method of claim 9, wherein the first accept stock portion is screened to produce a fourth accept stock portion and a fourth reject stock portion.
- 16. The method of claim 15, wherein the fourth accept stock portion is taken out of the process.
- 17. The method of claim 15, wherein the fourth reject stock portion is conveyed to a third refining stage.
- 18. The method of claim 6, wherein the first reject stock portion comprises 60 to 90% by weight of the refined stock.
- 19. The method of claim 6, wherein the first reject stock portion is fed into a second refining stage, and stock obtained from said second refining stage is screened to produce a second accept stock portion and a second reject stock portion.
- 20. The method of claim 19, wherein the second reject stock portion comprises between 60 and 80% by weight of the stock in the second screening.
- 21. The method of claim 20, wherein the second reject stock portion is taken to a third refining stage to produce a third refined stock and the stock obtained from said third refining stage is screened so as to form a fifth accept stock potion and a fifth reject stock portion.
- 22. The method of claim 21, wherein the fifth accept stock portion is taken out of the process.
- 23. The method of claim 22, wherein the secondary accept stock portion, third accept stock portion and fifth accept stock portion are combined and mixed to form a ready-made stock.
- 24. The method of claim 22, wherein the first accept stock portion, second accept stock portion and fifth stock portion are combined and mixed to form a ready-made stock.
- 25. The method of claim 22, wherein the second accept stock, fourth accept stock and fifth accept stock are combined and mixed to form a ready-made stock.
- 26. The method of claim 21, wherein the fifth reject stock portion is conveyed back to the third phase of refining.
- 27. The method of claim 21, wherein the fifth reject stock portion is conveyed to a fourth phase of refining, and the stock from said fourth stage of refining is screened to form a sixth accept stock and sixth reject stock.
- 28. The method of claim 27, wherein the sixth accept stock is taken out of the process.
- 29. The method of claim 28, wherein the first accept stock portion, second accept stock portion, fifth accept stock portion and sixth accept stock portion are combined and mixed to form a ready-made stock.
- 30. The method of claim 27, wherein the sixth reject stock is conveyed back into the fourth phase of refining.
- 31. The method of claim 27, wherein the sixth rejected stock portion is conveyed to a low consistency refiner.
- 32. The method of claim 31, wherein a seventh accept stock portion refined in the low consistency refiner, is taken out of the process.
- 33. The method of claim 32, wherein the first accept stock portion, second stock portion, fifth accept stock portion, sixth accept stock portion and seventh accept stock portion are combined and mixed to form a ready-made stock.
- 34. The method of claim 19, wherein the second reject stock portion is conveyed back into the second refining stage.
- 35. The method of claim 19, wherein the second accept stock portion is taken cut of the process.
- 36. A method for producing thermomechanical and chemi-thermomechanical pulp effective for use as a raw material for printing papers the method comprising:refining wood raw material in a refiner to form a refined stock; and screening the refined stock in a plurality of stages into accept stock portions and reject stock portions to form a ready made stock having a freeness value of 30 to 70 ml CSF, wherein the stock is screened at a consistency of at least 20% and not more than 90%, the method effective for providing a stock with 40 to 50% of the fibers having an average fiber length of greater than 2.0 mm.
- 37. A method for producing thermomechanical and chemi-thermomechanical pulp effective for use as a raw material for printing paper, the method comprising:refining wood raw material in a refiner at a super-atmospheric pressure of over 400 kPa at from 165° C. to 175° C. to form a refined stock which has a consistency of from 40% to 90%; and screening the refined stock at a consistency at about the same as it came from refining in a plurality of stages into accept stock portions and reject stock portions to form a ready made stock having a freeness value of 30 to 70 ml CSF, wherein the stock is screened at a consistency of at least 20% and not more than 90%, the method effective for providing a stock with 40 to 50% of the fibers having an average fiber length of greater than 2.0 mm.
- 38. The method as recited in claim 37, wherein the pressure, temperature and average time of each of the refining steps are effective to provide the ready made stock with 40 to 50% of the fibers do not pass through screens of 16 and 28 mesh and 35-40% of the fibers pass through screens of 48 and 200 mesh.
- 39. A method for producing thermomechanical and chemi-thermomechanical pulp effective for use as a raw material for printing paper, the method comprising;refining wood raw material in a refiner to form a refined stock; and screening the refined stock in a plurality of stages into accept stock portions and reject stack portions to form a ready made stock having a freeness value of 30 to 70 ml CSF, wherein the stock is screened at a consistency of at least 20% and not more than 90% and the refining and screening are done at the same consistency in more than one of the plurality of stages, the method effective for providing a stock with 40 to 50% of the fibers having an average fiber length of greater than 2.0 mm.
Parent Case Info
This application is a Continuation of PCT/F100/01054 filed on Dec. 1, 2000.
US Referenced Citations (20)
Foreign Referenced Citations (3)
Number |
Date |
Country |
2714730 |
Oct 1977 |
DE |
0138484 |
Apr 1985 |
EP |
397851 |
Nov 1977 |
SE |
Non-Patent Literature Citations (3)
Entry |
International Search Report for International application No. PCT/FI00/01054, mailed on Mar. 16, 2001. |
International Search Report for International application No. PCT/FI00/01055, mailed on May 17, 2001. |
Printout from Dialog(R) File 351 is provided for Finnish publication which supplies relevant patent information, and English language title and abstract. |
Continuations (1)
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Number |
Date |
Country |
Parent |
PCT/FI00/01054 |
Dec 2000 |
US |
Child |
10/165191 |
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US |