EP0199481B1 - A process for the manufacture of cellulose pulps - Google Patents
A process for the manufacture of cellulose pulps Download PDFInfo
- Publication number
- EP0199481B1 EP0199481B1 EP86302491A EP86302491A EP0199481B1 EP 0199481 B1 EP0199481 B1 EP 0199481B1 EP 86302491 A EP86302491 A EP 86302491A EP 86302491 A EP86302491 A EP 86302491A EP 0199481 B1 EP0199481 B1 EP 0199481B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- pulp
- mixture
- process according
- range
- refined
- 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.)
- Expired
Links
- 238000000034 method Methods 0.000 title claims description 63
- 230000008569 process Effects 0.000 title claims description 57
- 229920002678 cellulose Polymers 0.000 title claims description 11
- 239000001913 cellulose Substances 0.000 title claims description 11
- 238000004519 manufacturing process Methods 0.000 title claims description 10
- 239000000126 substance Substances 0.000 claims description 31
- 230000029087 digestion Effects 0.000 claims description 26
- 239000000203 mixture Substances 0.000 claims description 18
- 239000000835 fiber Substances 0.000 claims description 13
- 238000005470 impregnation Methods 0.000 claims description 11
- 239000000463 material Substances 0.000 claims description 11
- 239000002023 wood Substances 0.000 claims description 10
- 210000000988 bone and bone Anatomy 0.000 claims description 5
- 230000009471 action Effects 0.000 claims description 3
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical compound [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 claims description 2
- 239000011236 particulate material Substances 0.000 claims 2
- 229920001131 Pulp (paper) Polymers 0.000 description 27
- 238000007670 refining Methods 0.000 description 21
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 description 16
- 235000010265 sodium sulphite Nutrition 0.000 description 8
- 238000004537 pulping Methods 0.000 description 6
- 238000010411 cooking Methods 0.000 description 5
- 238000010297 mechanical methods and process Methods 0.000 description 5
- 239000011122 softwood Substances 0.000 description 5
- 235000008577 Pinus radiata Nutrition 0.000 description 4
- 241000218621 Pinus radiata Species 0.000 description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 4
- 239000005864 Sulphur Substances 0.000 description 4
- 241000894007 species Species 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 238000010793 Steam injection (oil industry) Methods 0.000 description 3
- 230000006835 compression Effects 0.000 description 3
- 238000007906 compression Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 230000018109 developmental process Effects 0.000 description 3
- 239000011121 hardwood Substances 0.000 description 3
- 230000005226 mechanical processes and functions Effects 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 238000010025 steaming Methods 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- 238000004061 bleaching Methods 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000012216 screening Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 241000609240 Ambelania acida Species 0.000 description 1
- 235000017166 Bambusa arundinacea Nutrition 0.000 description 1
- 235000017491 Bambusa tulda Nutrition 0.000 description 1
- 229920003043 Cellulose fiber Polymers 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- 244000166124 Eucalyptus globulus Species 0.000 description 1
- 244000082204 Phyllostachys viridis Species 0.000 description 1
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 1
- 241000018646 Pinus brutia Species 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000010905 bagasse Substances 0.000 description 1
- 239000011425 bamboo Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000012634 fragment Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000011369 resultant mixture Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000000930 thermomechanical effect Effects 0.000 description 1
- 210000001519 tissue Anatomy 0.000 description 1
Images
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C3/00—Pulping cellulose-containing materials
- D21C3/22—Other features of pulping processes
- D21C3/26—Multistage processes
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C3/00—Pulping cellulose-containing materials
- D21C3/22—Other features of pulping processes
- D21C3/26—Multistage processes
- D21C3/266—Multistage processes the same pulping agent being used in all stages
Definitions
- This invention relates to a process for the manufacturing of cellulose mechanical pulps.
- Mechanical pulp plants typically have a lower specific capital cost to build and mechanical pulps typically have a high yield and can be cheaper to produce than chemical pulps.
- mechanical pulps do not provide the pollution problems which are associated with chemical pulps.
- mechanical pulps have not been of the same high quality as chemical pulps and thus to achieve an end pulp which is of the required quality but at the same time economic to produce it is a well known technique to combine mechanical and chemical pulps.
- the aforementioned developments in mechanical pulp processes which stem from the basic RMP process have led to some mechanical pulps having the characteristics of a chemical pulp and they can thus be used as a replacement, in whole or in part, for chemical pulps in those applications where chemical pulps have traditionally been used.
- the present invention has its basis in the surprising discovery that the whole pulp can be subjected to a two stage digestion and refining process with the second addition of an aqueous sodium sulphite solution taking place prior to or with the cellulose material entering or after the first refining stage followed by digestion after the chemical addition.
- the process can be carried out with significant savings in energy requirements even though the whole pulp is processed in the two digestion and refining steps whilst increase in many of the desirable properties of the pulp for end use applications are obtained.
- the process has particular application either singly or in combination for pinus radiata corewood and/or pinus radiata slab wood, eucalyptus and New Zealand hardwoods but it is believed that it has similar application to other wood types and species.
- the present invention requires a relatively high total charge of digestion chemicals the total charge is split into two separate charges of which the first charge is preferably lower but preferably in an impregnation process rather than a simple mixing stage.
- the resultant pulp is low in fines, has high strength characteristics and is produced with low energy requirements.
- the total chemical charge in the present invention may be in the order of that required in a CMP process but does not require the high energy demands of a CMP process for some wood types, particularly pine species and hardwood/softwood blends.
- FR-A-2 544 757 describes a process of formation of pulp from fibre, such as bagasse and bamboo, involving at least two digestion stages, with addition of digestion chemicals before each stage. « Blowdown » i. e. decompression, occurs between two digestion stages, in order to separate the fibre bundles.
- the object of the present invention is to provide a process for the manufacture of cellulose mechanical pulps which provides a high yield pulp of improved quality which can be used as a substitute for chemical pulps and is achieved without increases or at lesser increases in refining energy inputs.
- the invention is set out in claim 1.
- the invention can be said to consist of a process for the manufacturing of cellulose pulp using two or more chemical addition and digestion stages in conjunction with mechanical pulping techniques.
- mechanical pulping has its normal meaning in the art and refers to the process of disruption of a cellulose substance by mechanical action to yield a product consisting mainly of liberated and separated single cellulose fibres and their fragments and which is suitable for use in the manufacture of paper and other products.
- the invention consists of a process for the manufacturing of a cellulose pulp from material in particulate form comprising the steps of impregnating the material with digestion chemicals, digesting the impregnated material, adding further digesting chemicals and mechanically refining the resultant mixture to reduce the material to predominantly whole fibres, digesting the impregnated and refined mixture and then further refining the resulting pulp product, if required.
- wood chips are washed in washer 10 and conveyed to a surge/pre-steaming vessel 11.
- live steam is added to remove air and preheat the chips to a temperature in the range of 80-100 °C.
- Discharge of chips from vessel 11 is maintained at a controlled rate to a compression screw feeder 12 wherein excess liquid is removed and the chips are dewatered to over 20 % dryness. In the preferred form the chips are dewatered to over 40 % dryness.
- the chips are then delivered to an impregnation device 13 (preferably an inclined screw conveyor).
- Digestion chemicals are delivered to or between the feeder device 12 and/or the impregnation device 13 with delivery being at a temperature below 100 °C, preferably under 50 °C.
- These delignifying chemicals in aqueous form are of known composition, primarily of the sodium sulphite family, and are added at a level of 0,5 to 5 % active chemical on bone dried fibre. Condensation of steam within the chips causes the liquor to be absorbed into the chips. Retention time within the liquor zone of the impregnation device 13 is 5 to 20 minutes but preferably over 7 minutes.
- the chips On leaving the liquor zone of the impregnation device 13 the chips may be subjected to direct steam heating to raise the temperature of the chips to within the range of 80-100 °C.
- the impregnated chips are then fed to a primary digester 14 by a pressure sealing device 13a such as a compression screw, rotary valve or similar.
- the residence time within the digester 14 is in the range of 3 to 20 minutes, but preferably 5 to 10 minutes, with heating by direct steam injection to give a vapour phase reaction.
- the pressure of the primary digester 14 is in the range of 0-800 kPa overpressure, but more preferably 200 to 400 kPa overpressure.
- Product from primary digester 14 is controlled by metering in accordance with known procedures and fed via feeder/pressure seal 15 to a primary refiner 16 (such as a disc refiner) operating at 0 to 600 kPa overpressure but more preferably 200 to 300 kPa overpressure.
- Further digestion or cooking chemicals of known composition are added to the product feed to the primary refiner 16 for subsequent reaction in the secondary digester 19.
- the cooking chemicals are mixed with the chip/pulp mixture present in the primary refiner 16 by the refiner action.
- Addition of the sulphite based cooking chemicals is in the range of 2 to 20 % active chemical on bone dried fibre preferably 5 % to 10 % on bone dried fibre.
- the pulp and steam generated in the primary refiner 16 are discharged through a common blowline to a cyclone 17 where water and/or spent process liquor is added for consistency control during the subsequent digestion phase.
- Pulp and liquor is discharged from cyclone 17 by a feeder/pressure seal device 18 (preferably a compression screw) and enters the secondary digester 19.
- the residence time within the secondary digester 19 is in the range of 20 to 120 minutes but more preferably 30 to 60 minutes at an overpressure in the range of 100 to 800 kPa but more preferably 300 to 600 kPa overpressure.
- Discharge from the secondary digester 19 is achieved by injecting water/spent liquor through lines 20 and 21 into the base of the secondary digester 19 and mixing this with the pulp.
- the motive force for discharging the pulp is provided by the internal pressure in the digester.
- the digester may be discharged by screw conveyor or other methods.
- Discharged pulp is passed to a washer 22, preferably a press washing system, wherein it is washed and pressed and passed by a feeder/pressure seal 23 to a secondary refiner 24.
- the secondary refiner 24 may operate at a pressure in the range 0 to 600 kPa overpressure but preferably 200 to 300 kPa overpressure.
- Steam and pulp are discharged from secondary refiner 24 through a common blowline to a cyclone 25 where they are separated and discharged in substantially the same manner as that from the primary refiner 16.
- the resultant pulp may then be treated in accordance with accepted pulping practices, such as latency removal, screening, cleaning and bleaching.
- accepted pulping practices such as latency removal, screening, cleaning and bleaching.
- the resulting pulp product may be dried or used directly or indirectly for its intended end use.
- either or both the refining stages in refiners 16 and 24 may take place at atmospheric pressure with screws or other discharge and conveying devices ; two or more stages of refining may be present prior to or after the secondary digester 19 ; pulp from the secondary digester 19 may be discharged directly from the pulping process outlined as being an inter- or post- refining stage ; inter-stage washing and de-watering could be included between first stage digesting and first stage refining ; a further stage or stages of chemical addition, refining, digesting with or without inter-stage washing and de-watering could be added.
- Impregnation/cooking chemicals for the first digestion stage may be added via a mechanical mixing system, similarly for the second digestion stage they may be added to the cellulose material after the primary refiner in a mechanical mixing system.
- the effect of the inter-stage or post-digesting stage is to give a change in fibre properties, improving some, but what is of significance, is a major reduction in refining energy requirements to achieve the desired end use properties.
- the process according to the present invention results in a high-yield mechanical pulp of at least a similar but generally improved quality over pulps obtained with similar known process but without increases or at lesser increases in refining energy inputs.
- High levels of combined sulphur at the same freeness level can thus be achieved without higher power usage as is normally the case with some chemi-mechanical (CMP) or chemi-thermomechanical (CTMP) processes.
- CMP chemi-mechanical
- CMP chemi-thermomechanical
- SCTMP sulphonated chemi-thermomechanical pulp
- the digestion/refining process treatment allows high sulphonation to be achieved giving better brightness, absorbency, softness and fibre flexibility with a major reduction in refining energy requirements.
- the process results in clean fibre separation, improved fibre yield with reduced fines and improved bulk, tear index, tensile index, stretch, burst and other wet and dry web properties.
- Test runs of the process of the present invention have been carried out and the results of the properties of the process and RMP and CTMP pulp for unbleached screened and cleaned pulp (tested to SCAN standards using a 60 g/m 2 handsheet) are set out below.
- the pulp product prior to bleaching stage (s) contains a low quantity of fibre bundles, that .is less than substantially 10 % and preferably substantially none.
- the process can be used for soft woods, blends of soft woods and blends of softwoods and hardwoods. For the last case superior quality is obtained than when using other high yield processes.
- CTMP chemi-thermomechanical pulp process
- RMP refiner mechanical pulp process
- a conventional CTMP process was carried out. Blends of chips of different wood species and single species (see first line in the following table) were treated in a steaming vessel for 10 minutes at about 95 degrees centigrade, condensate was drained and the vessel charged with cold impregnation chemical, sodium sulphite, of sufficient concentration to give the desired final sulphur content.
- the impregnation liquor was heated by recirculation through an external heat exchanger to about 95 degrees centigrade and the liquor then drained.
- the impregnated chips were digested at about 130 degrees centigrade using direct steam injection for 5 minutes.
- the digested chips were discharged by screw conveyor and fed to a pressurized double disc refiner operating at about 2 bar overpressure. The resulting pulp was again refined by a second pass through the same refiner under the same pressure conditions.
- Blends of chips of different wood species and single species were treated in a steaming vessel for 10 minutes at about 95 degrees centigrade, condensate was drained and the vessel charged with cold impregnation chemical, sodium sulphite, of sufficient concentration to give the desired final sulphur content.
- the impregnation liquor was heated by recirculation through an external heat exchanger to about 95 degrees centigrade and the liquor then drained.
- the impregnated chips were digested at about 130 degrees centigrade using direct steam injection for 5 minutes.
- the digested chips were discharged by screw conveyor and fed to a pressurized double disc refiner.
- the refiner secondary digestion chemical sodium sulphite liquor
- the pulp/liquor mixture was conveyed by refiner generated steam (blown) back to the primary cooking vessel and digested at 160 degrees centigrade for about 60 minutes.
- Digested pulp was discharged and refined for a second time. Both refining stages were pressurised at about 2 bar overpressure.
- Example 3 The process of Example 3 was carried out.
- the pulp had further digestion chemicals added at the entry to the second stage refiner and a third stage of digestion was carried out followed by a third stage of refining at atmospheric pressure.
- the results of this process are shown in the extreme right hand column marked « SCTMP » in the table which follows.
- the resultant pulp from the process according to the invention is unexpectedly suitable for further refining development to improve various properties, in particular tensile index, burst, air resistance, that will enhance its performance in its selected end use.
Description
- This invention relates to a process for the manufacturing of cellulose mechanical pulps.
- There are many known processes for the manufacture of cellulose pulps and, more particularly, high-yield cellulose mechanical pulps. These processes include but are not confined to refiner mechanical processes (RMP), thermo-mechanical processes (TMP), chemi-mechanical processes (CMP), thermo- chemi mechanical process (TCMP) and chemi-thermo mechanical processes (CTMP). These processes which have been developed over the years are essentially developments of the basic RMP process and whilst the differences between processes appear to be small they do represent improvements which lead to the production of improved pulp quality (often but not always coupled with reduced pulp yield). Generally, however, most of the improved processes have been at the expense of an increase in refining energy required to meet the requisite paper making or other end use properties.
- Mechanical pulp plants typically have a lower specific capital cost to build and mechanical pulps typically have a high yield and can be cheaper to produce than chemical pulps. In addition mechanical pulps do not provide the pollution problems which are associated with chemical pulps. Generally mechanical pulps have not been of the same high quality as chemical pulps and thus to achieve an end pulp which is of the required quality but at the same time economic to produce it is a well known technique to combine mechanical and chemical pulps. The aforementioned developments in mechanical pulp processes which stem from the basic RMP process have led to some mechanical pulps having the characteristics of a chemical pulp and they can thus be used as a replacement, in whole or in part, for chemical pulps in those applications where chemical pulps have traditionally been used.
- For example, there is disclosed in Canadian patent specifications 1 071 805, 1 145 106 and 1 145 107 to Ontario Paper Company Ltd processes for the production of mechanical pulps which are claimed to be useful as substitutes for chemical pulps. These processes require a mechanical pulp of the TMP, RMP, or TCMP type to be treated or mixed with a relatively high charge of digestion chemicals e. g. an aqueous sodium sulphite solution after the refining stage and the thus treated pulp to be pressure digested with optionally further refining taking place after the digestion stage.
- In U.S. patent specification 4 502 918 of MacMillan Bloedel Ltd there is disclosed a pulping process in which wood particles are treated with an aqueous solution of sodium sulphite, the treated particles are then digested and refined following which the resultant pulp is separated into an accepts fraction and a rejects or long fibre fraction. The rejects fraction is then further treated with a sodium sulphite solution, digested and refined where upon the or at least part of the accepts and rejects fractions are combined to form the final pulp.
- The present invention has its basis in the surprising discovery that the whole pulp can be subjected to a two stage digestion and refining process with the second addition of an aqueous sodium sulphite solution taking place prior to or with the cellulose material entering or after the first refining stage followed by digestion after the chemical addition. The process can be carried out with significant savings in energy requirements even though the whole pulp is processed in the two digestion and refining steps whilst increase in many of the desirable properties of the pulp for end use applications are obtained. The process has particular application either singly or in combination for pinus radiata corewood and/or pinus radiata slab wood, eucalyptus and New Zealand hardwoods but it is believed that it has similar application to other wood types and species.
- Whilst the present invention requires a relatively high total charge of digestion chemicals the total charge is split into two separate charges of which the first charge is preferably lower but preferably in an impregnation process rather than a simple mixing stage. The resultant pulp is low in fines, has high strength characteristics and is produced with low energy requirements. For example, the total chemical charge in the present invention may be in the order of that required in a CMP process but does not require the high energy demands of a CMP process for some wood types, particularly pine species and hardwood/softwood blends.
- FR-A-2 544 757 describes a process of formation of pulp from fibre, such as bagasse and bamboo, involving at least two digestion stages, with addition of digestion chemicals before each stage. « Blowdown », i. e. decompression, occurs between two digestion stages, in order to separate the fibre bundles.
- The object of the present invention is to provide a process for the manufacture of cellulose mechanical pulps which provides a high yield pulp of improved quality which can be used as a substitute for chemical pulps and is achieved without increases or at lesser increases in refining energy inputs.
- The invention is set out in claim 1.
- Broadly, the invention can be said to consist of a process for the manufacturing of cellulose pulp using two or more chemical addition and digestion stages in conjunction with mechanical pulping techniques.
- The term « mechanical pulping as used herein has its normal meaning in the art and refers to the process of disruption of a cellulose substance by mechanical action to yield a product consisting mainly of liberated and separated single cellulose fibres and their fragments and which is suitable for use in the manufacture of paper and other products.
- More specifically the invention consists of a process for the manufacturing of a cellulose pulp from material in particulate form comprising the steps of impregnating the material with digestion chemicals, digesting the impregnated material, adding further digesting chemicals and mechanically refining the resultant mixture to reduce the material to predominantly whole fibres, digesting the impregnated and refined mixture and then further refining the resulting pulp product, if required.
- The following is a more detailed description of an embodiment of the invention, with reference to the accompanying drawing which is a schematic flow diagram of a process of the invention.
- According to the process shown in the drawing, wood chips are washed in
washer 10 and conveyed to a surge/pre-steamingvessel 11. In this vessel live steam is added to remove air and preheat the chips to a temperature in the range of 80-100 °C. Discharge of chips fromvessel 11 is maintained at a controlled rate to acompression screw feeder 12 wherein excess liquid is removed and the chips are dewatered to over 20 % dryness. In the preferred form the chips are dewatered to over 40 % dryness. The chips are then delivered to an impregnation device 13 (preferably an inclined screw conveyor). - Digestion chemicals are delivered to or between the
feeder device 12 and/or theimpregnation device 13 with delivery being at a temperature below 100 °C, preferably under 50 °C. These delignifying chemicals in aqueous form are of known composition, primarily of the sodium sulphite family, and are added at a level of 0,5 to 5 % active chemical on bone dried fibre. Condensation of steam within the chips causes the liquor to be absorbed into the chips. Retention time within the liquor zone of theimpregnation device 13 is 5 to 20 minutes but preferably over 7 minutes. - On leaving the liquor zone of the
impregnation device 13 the chips may be subjected to direct steam heating to raise the temperature of the chips to within the range of 80-100 °C. The impregnated chips are then fed to aprimary digester 14 by apressure sealing device 13a such as a compression screw, rotary valve or similar. The residence time within thedigester 14 is in the range of 3 to 20 minutes, but preferably 5 to 10 minutes, with heating by direct steam injection to give a vapour phase reaction. The pressure of theprimary digester 14 is in the range of 0-800 kPa overpressure, but more preferably 200 to 400 kPa overpressure. - Product from
primary digester 14 is controlled by metering in accordance with known procedures and fed via feeder/pressure seal 15 to a primary refiner 16 (such as a disc refiner) operating at 0 to 600 kPa overpressure but more preferably 200 to 300 kPa overpressure. Further digestion or cooking chemicals of known composition are added to the product feed to theprimary refiner 16 for subsequent reaction in thesecondary digester 19. The cooking chemicals are mixed with the chip/pulp mixture present in theprimary refiner 16 by the refiner action. Addition of the sulphite based cooking chemicals is in the range of 2 to 20 % active chemical on bone dried fibre preferably 5 % to 10 % on bone dried fibre. - . The pulp and steam generated in the
primary refiner 16 are discharged through a common blowline to acyclone 17 where water and/or spent process liquor is added for consistency control during the subsequent digestion phase. Pulp and liquor is discharged fromcyclone 17 by a feeder/pressure seal device 18 (preferably a compression screw) and enters thesecondary digester 19. The residence time within thesecondary digester 19 is in the range of 20 to 120 minutes but more preferably 30 to 60 minutes at an overpressure in the range of 100 to 800 kPa but more preferably 300 to 600 kPa overpressure. - Discharge from the
secondary digester 19 is achieved by injecting water/spent liquor throughlines secondary digester 19 and mixing this with the pulp. The motive force for discharging the pulp is provided by the internal pressure in the digester. Alternatively the digester may be discharged by screw conveyor or other methods. - Discharged pulp is passed to a
washer 22, preferably a press washing system, wherein it is washed and pressed and passed by a feeder/pressure seal 23 to asecondary refiner 24. Thesecondary refiner 24 may operate at a pressure in the range 0 to 600 kPa overpressure but preferably 200 to 300 kPa overpressure. Steam and pulp are discharged fromsecondary refiner 24 through a common blowline to acyclone 25 where they are separated and discharged in substantially the same manner as that from theprimary refiner 16. - The resultant pulp may then be treated in accordance with accepted pulping practices, such as latency removal, screening, cleaning and bleaching. The resulting pulp product may be dried or used directly or indirectly for its intended end use.
- The process as described above is open to modification. For example, either or both the refining stages in
refiners secondary digester 19 ; pulp from thesecondary digester 19 may be discharged directly from the pulping process outlined as being an inter- or post- refining stage ; inter-stage washing and de-watering could be included between first stage digesting and first stage refining ; a further stage or stages of chemical addition, refining, digesting with or without inter-stage washing and de-watering could be added. - Impregnation/cooking chemicals for the first digestion stage may be added via a mechanical mixing system, similarly for the second digestion stage they may be added to the cellulose material after the primary refiner in a mechanical mixing system.
- The effect of the inter-stage or post-digesting stage is to give a change in fibre properties, improving some, but what is of significance, is a major reduction in refining energy requirements to achieve the desired end use properties.
- The process according to the present invention results in a high-yield mechanical pulp of at least a similar but generally improved quality over pulps obtained with similar known process but without increases or at lesser increases in refining energy inputs. High levels of combined sulphur at the same freeness level can thus be achieved without higher power usage as is normally the case with some chemi-mechanical (CMP) or chemi-thermomechanical (CTMP) processes. The pulp is referred to in the following tables as sulphonated chemi-thermomechanical pulp (SCTMP).
- The digestion/refining process treatment allows high sulphonation to be achieved giving better brightness, absorbency, softness and fibre flexibility with a major reduction in refining energy requirements. In addition the process results in clean fibre separation, improved fibre yield with reduced fines and improved bulk, tear index, tensile index, stretch, burst and other wet and dry web properties.
- Test runs of the process of the present invention have been carried out and the results of the properties of the process and RMP and CTMP pulp for unbleached screened and cleaned pulp (tested to SCAN standards using a 60 g/m2 handsheet) are set out below.
- The pulp product prior to bleaching stage (s) contains a low quantity of fibre bundles, that .is less than substantially 10 % and preferably substantially none.
- The process can be used for soft woods, blends of soft woods and blends of softwoods and hardwoods. For the last case superior quality is obtained than when using other high yield processes.
- Mesh sizes in the table below are measured according to the Bauer McNett method. Shive content is measured by the Sommerville method. All results in the table are test results for Pinus Radiata slab wood (sawmill residue) chips. All tests are carried out on 60 g/m2 hand sheets according to ISO standards.
- The following examples of the present invention and conventional chemi-thermomechanical pulp process (CTMP) and refiner mechanical pulp process (RMP) were carried out in a pilot plant using commonly available New Zealand wood species.
- An RMP process was carried out on softwood chips (Pinus Radiata, sawmill slab residue) at about 60 % moisture content, the chips being refined with two passes through a double disc refiner at atmospheric pressure. The results are shown in the table in the column headed « RMP » and establish a base for comparison with other pulping processes.
- A conventional CTMP process was carried out. Blends of chips of different wood species and single species (see first line in the following table) were treated in a steaming vessel for 10 minutes at about 95 degrees centigrade, condensate was drained and the vessel charged with cold impregnation chemical, sodium sulphite, of sufficient concentration to give the desired final sulphur content. The impregnation liquor was heated by recirculation through an external heat exchanger to about 95 degrees centigrade and the liquor then drained. The impregnated chips were digested at about 130 degrees centigrade using direct steam injection for 5 minutes. The digested chips were discharged by screw conveyor and fed to a pressurized double disc refiner operating at about 2 bar overpressure. The resulting pulp was again refined by a second pass through the same refiner under the same pressure conditions.
- The results of the processes were listed under the columns CTMP in the following table.
- A process according to the present invention was carried out. Blends of chips of different wood species and single species (see first line in the following table) were treated in a steaming vessel for 10 minutes at about 95 degrees centigrade, condensate was drained and the vessel charged with cold impregnation chemical, sodium sulphite, of sufficient concentration to give the desired final sulphur content. The impregnation liquor was heated by recirculation through an external heat exchanger to about 95 degrees centigrade and the liquor then drained. The impregnated chips were digested at about 130 degrees centigrade using direct steam injection for 5 minutes.
- The digested chips were discharged by screw conveyor and fed to a pressurized double disc refiner. At the point of feeding the refiner secondary digestion chemical (sodium sulphite liquor) was added at the required concentration to give the desired final pulp sulphur content. The pulp/liquor mixture was conveyed by refiner generated steam (blown) back to the primary cooking vessel and digested at 160 degrees centigrade for about 60 minutes. Digested pulp was discharged and refined for a second time. Both refining stages were pressurised at about 2 bar overpressure.
- The results of the processes are shown in columns (marked SCTMP) in the following table.
- The process of Example 3 was carried out. The pulp had further digestion chemicals added at the entry to the second stage refiner and a third stage of digestion was carried out followed by a third stage of refining at atmospheric pressure. The results of this process are shown in the extreme right hand column marked « SCTMP » in the table which follows.
- In the foregoing examples all final pulp was washed and screened through a 0.16mm flat screen prior to property testing to simulate the screening/cleaning function of a typical mechanical pulp mill.
- The resultant pulp from the process according to the invention is unexpectedly suitable for further refining development to improve various properties, in particular tensile index, burst, air resistance, that will enhance its performance in its selected end use.
-
Claims (9)
characterised in that, before, simultaneously with or after step (c), the mixture is mechanically refined to reduce the material to predominantly whole fibres so that step (d) is performed on a refined mixture.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NZ211684A NZ211684A (en) | 1985-04-04 | 1985-04-04 | Manufacture of cellulose pulp: second digestion step follows initial digestion and refining steps |
NZ211684 | 1985-04-04 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0199481A1 EP0199481A1 (en) | 1986-10-29 |
EP0199481B1 true EP0199481B1 (en) | 1989-12-13 |
Family
ID=19921155
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP86302491A Expired EP0199481B1 (en) | 1985-04-04 | 1986-04-04 | A process for the manufacture of cellulose pulps |
Country Status (15)
Country | Link |
---|---|
EP (1) | EP0199481B1 (en) |
JP (1) | JPS61282491A (en) |
KR (1) | KR930003394B1 (en) |
AR (1) | AR243623A1 (en) |
AU (1) | AU585331B2 (en) |
BR (1) | BR8601558A (en) |
CA (1) | CA1273454A (en) |
DE (1) | DE3667515D1 (en) |
ES (1) | ES8705940A1 (en) |
FI (1) | FI83238C (en) |
MY (1) | MY102502A (en) |
NO (1) | NO167159C (en) |
NZ (1) | NZ211684A (en) |
PT (1) | PT82341B (en) |
ZA (1) | ZA862454B (en) |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
USH1672H (en) * | 1988-03-28 | 1997-08-05 | Kimberly-Clark Corporation | Tissue products made from low-coarseness fibers |
FI126694B (en) * | 2005-12-02 | 2017-04-13 | Metsä Board Oyj | Chemical-mechanical pulp and process for producing chemical-mechanical pulp |
CN102561094B (en) * | 2012-01-06 | 2015-04-15 | 黑龙江浩源生物科技有限公司 | Method for making pulp and paper by using cornstalk xylose residue |
CN103410036B (en) * | 2013-08-15 | 2015-11-18 | 齐鲁工业大学 | A kind of production method of high-yield hardwood pulp |
CN104928958A (en) * | 2015-05-25 | 2015-09-23 | 张家港市欣发包装有限责任公司 | Method of producing corrugated paper with straw |
AT518800B1 (en) * | 2016-06-17 | 2019-09-15 | Andritz Ag Maschf | METHOD FOR PRODUCING FIBROUS MATERIAL |
CN112342814B (en) * | 2020-11-19 | 2023-03-31 | 横县东糖糖业有限公司纸业分公司 | Method for producing high-strength natural-color paper pulp by taking eucalyptus bark as raw material |
CN113481741B (en) * | 2021-07-27 | 2023-05-09 | 中福海峡(平潭)发展股份有限公司 | Fungus grass chemical machine pulp and preparation method and application thereof |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CA1145106A (en) * | 1980-07-11 | 1983-04-26 | Alan C. Shaw | Procedure for improving properties of mechanical wood pulps |
US4502918A (en) * | 1981-06-10 | 1985-03-05 | Macmillan Bloedel Limited | Two-stage chemical treatment of mechanical wood pulp with sodium sulfite |
AU570034B2 (en) * | 1983-04-20 | 1988-03-03 | Process Evaluation And Development Corp. | Continuous pulp digester |
-
1985
- 1985-04-04 NZ NZ211684A patent/NZ211684A/en unknown
-
1986
- 1986-04-03 ZA ZA862454A patent/ZA862454B/en unknown
- 1986-04-03 NO NO861307A patent/NO167159C/en not_active IP Right Cessation
- 1986-04-03 CA CA000505773A patent/CA1273454A/en not_active Expired - Lifetime
- 1986-04-04 EP EP86302491A patent/EP0199481B1/en not_active Expired
- 1986-04-04 JP JP61079058A patent/JPS61282491A/en active Pending
- 1986-04-04 AR AR86303572A patent/AR243623A1/en active
- 1986-04-04 AU AU55650/86A patent/AU585331B2/en not_active Ceased
- 1986-04-04 DE DE8686302491T patent/DE3667515D1/en not_active Expired - Lifetime
- 1986-04-04 KR KR1019860002568A patent/KR930003394B1/en not_active IP Right Cessation
- 1986-04-04 FI FI861453A patent/FI83238C/en not_active IP Right Cessation
- 1986-04-04 ES ES554182A patent/ES8705940A1/en not_active Expired
- 1986-04-04 BR BR8601558A patent/BR8601558A/en not_active IP Right Cessation
- 1986-04-04 PT PT82341A patent/PT82341B/en not_active IP Right Cessation
-
1987
- 1987-10-10 MY MYPI87002889A patent/MY102502A/en unknown
Also Published As
Publication number | Publication date |
---|---|
PT82341A (en) | 1986-05-01 |
NO861307L (en) | 1986-10-06 |
NO167159C (en) | 1991-10-09 |
KR930003394B1 (en) | 1993-04-26 |
BR8601558A (en) | 1986-12-09 |
AU5565086A (en) | 1986-10-16 |
FI861453A (en) | 1986-10-05 |
FI861453A0 (en) | 1986-04-04 |
AR243623A1 (en) | 1993-08-31 |
FI83238C (en) | 1991-06-10 |
JPS61282491A (en) | 1986-12-12 |
NO167159B (en) | 1991-07-01 |
ES8705940A1 (en) | 1987-06-01 |
ES554182A0 (en) | 1987-06-01 |
KR860008339A (en) | 1986-11-14 |
AU585331B2 (en) | 1989-06-15 |
EP0199481A1 (en) | 1986-10-29 |
ZA862454B (en) | 1986-11-26 |
DE3667515D1 (en) | 1990-01-18 |
NZ211684A (en) | 1989-07-27 |
PT82341B (en) | 1988-12-15 |
FI83238B (en) | 1991-02-28 |
MY102502A (en) | 1992-06-30 |
CA1273454A (en) | 1990-09-04 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP2915576B2 (en) | CTMP process | |
US4152197A (en) | Process for preparing high-yield cellulose pulps by vapor phase pulping an unpulped portion of lignocellulosic material and a partially chemically pulped portion | |
EP0764225B1 (en) | A light drainability, bulky chemimechanical pulp that has a low shive content and a low fine-material content | |
US4087317A (en) | High yield, low cost cellulosic pulp and hydrated gels therefrom | |
US20080035286A1 (en) | Processes and systems for the pulping of lignocellulosic materials | |
US4116758A (en) | Method of producing high yield chemimechanical pulps | |
US2169473A (en) | Method of producing cellulose pulp | |
EP0056263B1 (en) | A method for improving the washing of cellulose pulps produced from lignocellulosic material | |
EP0199481B1 (en) | A process for the manufacture of cellulose pulps | |
US3919041A (en) | Multi-stage chlorine dioxide delignification of wood pulp | |
US5089089A (en) | System for sulfonating mechanical pulp fibers | |
CA2440789C (en) | Method for producing pulp | |
US3013931A (en) | Printing paper and process of making the same | |
Veisi et al. | Mixing bleached white poplar and wheat straw chemimechanical pulps to improve the mechanical and optical characteristics | |
AU2002244309A1 (en) | Method for producing pulp | |
US3013932A (en) | Printing paper and process of making the same | |
EP0030778B1 (en) | Process for the formation of refiner pulp | |
US3591451A (en) | Pretreatment of vegetable matter and delignification of the refined matter with chloring dioxide | |
US2862814A (en) | Utilization of pith in the manufacture of pulp | |
US4836892A (en) | Pulp blends for linerboards | |
FI57454C (en) | FRAMSTAELLNING AV FOERBAETTRAD HOEGUTBYTESMASSA | |
Bocianowski et al. | Miscanthus giganteus as an auxiliary raw material in NSSC birch pulp production | |
Biswas et al. | Kraft pulping of Albizia richardiana wood species in a mixture with Bambusa vulgaris. | |
De Groot et al. | Alkaline pulping of fiber hemp | |
DAR | PULPING PROCESSES---PRESENT STATUS AND TREND |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): DE FR GB SE |
|
17P | Request for examination filed |
Effective date: 19870130 |
|
17Q | First examination report despatched |
Effective date: 19871123 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: YHTYNEET PAPERITEHTAAT OY Owner name: CAXTON PAPER LIMITED |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR GB SE |
|
REF | Corresponds to: |
Ref document number: 3667515 Country of ref document: DE Date of ref document: 19900118 |
|
ET | Fr: translation filed | ||
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed | ||
EAL | Se: european patent in force in sweden |
Ref document number: 86302491.5 |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: IF02 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20020410 Year of fee payment: 17 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 20020417 Year of fee payment: 17 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20020425 Year of fee payment: 17 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: SE Payment date: 20020426 Year of fee payment: 17 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20030404 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20030405 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20031101 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20030404 |
|
EUG | Se: european patent has lapsed | ||
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20031231 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |