CA2634378A1 - Method for producing fibrous material - Google Patents
Method for producing fibrous material Download PDFInfo
- Publication number
- CA2634378A1 CA2634378A1 CA002634378A CA2634378A CA2634378A1 CA 2634378 A1 CA2634378 A1 CA 2634378A1 CA 002634378 A CA002634378 A CA 002634378A CA 2634378 A CA2634378 A CA 2634378A CA 2634378 A1 CA2634378 A1 CA 2634378A1
- Authority
- CA
- Canada
- Prior art keywords
- chemicals
- digestion
- wood
- solution
- process according
- 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.)
- Abandoned
Links
- 239000002657 fibrous material Substances 0.000 title claims abstract description 83
- 238000004519 manufacturing process Methods 0.000 title claims description 14
- 239000000126 substance Substances 0.000 claims abstract description 148
- 230000029087 digestion Effects 0.000 claims abstract description 120
- 238000000034 method Methods 0.000 claims abstract description 74
- 239000002023 wood Substances 0.000 claims abstract description 63
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 48
- 229920005610 lignin Polymers 0.000 claims abstract description 47
- 239000011122 softwood Substances 0.000 claims abstract description 32
- 239000011121 hardwood Substances 0.000 claims abstract description 28
- 238000010438 heat treatment Methods 0.000 claims abstract description 11
- 239000007791 liquid phase Substances 0.000 claims abstract description 11
- 239000012071 phase Substances 0.000 claims abstract description 10
- 238000002360 preparation method Methods 0.000 claims abstract description 6
- 238000000926 separation method Methods 0.000 claims abstract description 5
- AZQWKYJCGOJGHM-UHFFFAOYSA-N 1,4-benzoquinone Chemical compound O=C1C=CC(=O)C=C1 AZQWKYJCGOJGHM-UHFFFAOYSA-N 0.000 claims description 26
- 238000010009 beating Methods 0.000 claims description 15
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims description 11
- 239000000203 mixture Substances 0.000 claims description 11
- 230000002378 acidificating effect Effects 0.000 claims description 8
- 239000002253 acid Substances 0.000 claims description 5
- 239000012978 lignocellulosic material Substances 0.000 claims description 5
- 239000004291 sulphur dioxide Substances 0.000 claims description 2
- 235000010269 sulphur dioxide Nutrition 0.000 claims description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical class OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 claims 1
- 150000003568 thioethers Chemical class 0.000 claims 1
- 239000000243 solution Substances 0.000 description 47
- 241000196324 Embryophyta Species 0.000 description 29
- 239000000463 material Substances 0.000 description 20
- 235000019641 whiteness Nutrition 0.000 description 13
- PYKYMHQGRFAEBM-UHFFFAOYSA-N anthraquinone Natural products CCC(=O)c1c(O)c2C(=O)C3C(C=CC=C3O)C(=O)c2cc1CC(=O)OC PYKYMHQGRFAEBM-UHFFFAOYSA-N 0.000 description 11
- 150000004056 anthraquinones Chemical class 0.000 description 11
- 238000005470 impregnation Methods 0.000 description 8
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 description 8
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical compound [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 description 7
- 229920001131 Pulp (paper) Polymers 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000002474 experimental method Methods 0.000 description 6
- 239000000706 filtrate Substances 0.000 description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 5
- 239000000835 fiber Substances 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 239000011368 organic material Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 241000218657 Picea Species 0.000 description 4
- 150000001720 carbohydrates Chemical class 0.000 description 4
- 235000014633 carbohydrates Nutrition 0.000 description 4
- 230000015556 catabolic process Effects 0.000 description 4
- 239000000470 constituent Substances 0.000 description 4
- 238000006731 degradation reaction Methods 0.000 description 4
- 239000000123 paper Substances 0.000 description 4
- 235000010265 sodium sulphite Nutrition 0.000 description 4
- 239000007858 starting material Substances 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 3
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 3
- 230000002411 adverse Effects 0.000 description 3
- 230000036961 partial effect Effects 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 244000166124 Eucalyptus globulus Species 0.000 description 2
- 229920002488 Hemicellulose Polymers 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 239000007844 bleaching agent Substances 0.000 description 2
- 238000005282 brightening Methods 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 238000010411 cooking Methods 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 238000010025 steaming Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 102100031260 Acyl-coenzyme A thioesterase THEM4 Human genes 0.000 description 1
- 241000609240 Ambelania acida Species 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 235000017166 Bambusa arundinacea Nutrition 0.000 description 1
- 235000017491 Bambusa tulda Nutrition 0.000 description 1
- 244000025254 Cannabis sativa Species 0.000 description 1
- 235000012766 Cannabis sativa ssp. sativa var. sativa Nutrition 0.000 description 1
- 235000012765 Cannabis sativa ssp. sativa var. spontanea Nutrition 0.000 description 1
- 235000014466 Douglas bleu Nutrition 0.000 description 1
- 101000638510 Homo sapiens Acyl-coenzyme A thioesterase THEM4 Proteins 0.000 description 1
- 229920001732 Lignosulfonate Polymers 0.000 description 1
- 239000004117 Lignosulphonate Substances 0.000 description 1
- 240000003433 Miscanthus floridulus Species 0.000 description 1
- 240000007594 Oryza sativa Species 0.000 description 1
- 235000007164 Oryza sativa Nutrition 0.000 description 1
- 244000082204 Phyllostachys viridis Species 0.000 description 1
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 1
- 239000004285 Potassium sulphite Substances 0.000 description 1
- 240000001416 Pseudotsuga menziesii Species 0.000 description 1
- 235000005386 Pseudotsuga menziesii var menziesii Nutrition 0.000 description 1
- 241000209140 Triticum Species 0.000 description 1
- 235000021307 Triticum Nutrition 0.000 description 1
- 229920002522 Wood fibre Polymers 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 210000003484 anatomy Anatomy 0.000 description 1
- 239000010905 bagasse Substances 0.000 description 1
- 239000011425 bamboo Substances 0.000 description 1
- 235000009120 camo Nutrition 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 235000005607 chanvre indien Nutrition 0.000 description 1
- 238000004182 chemical digestion Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000013505 freshwater Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000011487 hemp Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000002655 kraft paper Substances 0.000 description 1
- 238000009533 lab test Methods 0.000 description 1
- 235000019357 lignosulphonate Nutrition 0.000 description 1
- LPHFLPKXBKBHRW-UHFFFAOYSA-L magnesium;hydrogen sulfite Chemical compound [Mg+2].OS([O-])=O.OS([O-])=O LPHFLPKXBKBHRW-UHFFFAOYSA-L 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- BHZRJJOHZFYXTO-UHFFFAOYSA-L potassium sulfite Chemical compound [K+].[K+].[O-]S([O-])=O BHZRJJOHZFYXTO-UHFFFAOYSA-L 0.000 description 1
- 235000019252 potassium sulphite Nutrition 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 235000009566 rice Nutrition 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 239000010902 straw Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
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
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
- D21H11/02—Chemical or chemomechanical or chemothermomechanical pulp
- D21H11/06—Sulfite or bisulfite pulp
-
- 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
- D21C3/222—Use of compounds accelerating the pulping processes
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Paper (AREA)
Abstract
The invention relates to a process for producing fibrous material having a lignin content of at least 15% for softwood, of at least 12% for hardwood or at least 10% for annual plants, based in each case on the oven-dry fibrous material, comprising the steps - preparation of a solution of chemicals comprising more than 5% of chemicals (calculated as NaOH) for softwood or comprising more than 3.5% of chemicals (calculated as NaOH) for hardwood or more than 2.5% for annual plants, based in each case on the oven-dry amount of the wood, - mixing of the solution of chemicals with wood or annual plants in a specified liquor ratio, - heating of the solution of chemicals and of the wood or of the annual plants to a temperature above room temperature and then - either (1st alternative) removal of free-flowing solution of chemicals and digestion of the wood or of the annual plants in the vapour phase - or (2nd alternative) digestion of the wood or of the annual plants in the liquid phase and - separation of the free-flowing solution of chemicals and of the wood or of the annual plants.
Description
{ RPV13307 WO
Process for producing fibrous material The invention relates to a process for producing fibrous material from wood or annual plants having a lignin content of more than 15% for softwoods, of more than 12% for hardwoods and of more than 10% for annual plants, based in each case on the oven-dry fibrous material produced, the fibrous material having specified strength properties.
Processes which produce fibrous materials having a relatively high lignin content of more than 15% for softwood and of more than 12% for hardwood are known.
They give a yield of 70% or more, based on the starting material used. These processes are based on chemical andlor on mechanical disintegration of the wood.
In the case of mechanical defibration of the wood, the latter is separated into fibre bundles in beating units - generally after presteaming. These fibre bundles are then defibrillated into individual fibres by further beating. The yield is very high but so is the quantity of beating energy to be applied. The strength of the wood fibres is very low - even after beating - because the fibres contain a large amount of natural lignin and therefore have little binding potential. They are also strongly degraded by the mechanical defibration, which adversely affects their recyclability.
In the case of chemical digestion of the wood, chemicals act on the wood, generally under high pressure and at elevated temperature. The NSSC process may be mentioned as a typical process for high-yield fibrous materials. However, other processes, such as the kraft or the soda process, can also be modified so that high-yield fibrous materials are produced (cf.
"Choosing the best brightening process", N. Liebergott and T. Joachimides, Pulp & Paper Canada, Vol. 80, No.
12, December 1979). If the degradation of the originally used wood is to be limited to a maximum of 30%, far less chemicals are required and used than in the production of chemical pulps which are to be completely freed from lignin. For the production of high-yield chemical puips, the amount of chemicals is metered as a function of the desired yield. In order to achieve a yield of about 70%, based on oven-dry wood use, the prior art recommends using up to 100 of chemicals, based on the starting material. In the case of chemical pulps, the use of chemicals is often 30% or more of chemicals, based on the oven-dry wood.
Chemicals play a role in determining the process costs, i.e. they are used as sparingly as possible. CTMP
fibrous materials are usually produced with amounts of 3% to 5% of chemicals. In known, industrially established processes for producing high-yield fibrous materials, e.g. the NSSC process, up to 10% of chemicals, based on the starting material, are used.
With the use of chemicals limited in this manner, no recovery is as yet installed for recovering the chemicals. In spite of the relatively small amounts of chemicals, this method of fibrous material production leads to considerable pollution of the environment, in particular of bodies of water, not only because of the introduction of chemicals but especially because of the organic load which is released into the main outfall.
Regarding the cost situation, it should be noted that, in the case of mechanically produced fibrous materials, the sharply rising energy prices add to the production costs. In the case of chemically produced high-yield fibrous materials, the production is adversely affected by the costs for the lost chemicals.
High-yield fibrous materials are beaten to high freenesses for the current intended uses. Only then do they reach an acceptable strength level. Here, high freenesses are to be regarded as values of about 300 ml CSF (Canadian Standard Freeness), equivalent to 41 SR
(Schopper-Riegler, see below) and 500 ml CSF, equivalent to 26 SR, as described, for example, in "Choosing the best brightening process", N. Liebergott and T. Joachimides, Pulp & Paper Canada, Vol. 80, No.
12, December 1979, for high-yield fibrous material from softwood. A high freeness is achieved by using mechanical energy. The fibres are rubbed against one another or against a grinder or against a grinding medium and thus changed in their surface properties to achieve better binding behaviour. The high freeness is therefore not an end in itself. Rather, it arises out of the requirements regarding the strength properties of the fibres.
The high-yield fibrous materials produced by a mechanical and/or chemical method are used in particular where high final whiteness and high whiteness stability are not absolutely essential. They could open up numerous further fields of use if the strength level could be increased.
It is therefore an object of the invention to propose a process for producing fibrous material from wood or annual plants having a lignin content of more than 15%
for softwoods, of more than 12% for hardwoods and of more than 10% for annual plants, by means of which fibrous materials of high strength can be produced in an economical manner.
This object is achieved by a process for producing fibrous material from wood or annual plants having a lignin content of at least 15% for softwoods and 12%
for hardwoods and 10o for annual plants, based in each case on the oven-dry fibrous material, comprising the steps:
- preparation of a solution of chemicals comprising more than 5% of chemicals (calculated as NaOH) for softwoods or comprising more than 3.5% of chemicals (calculated as NaOH) for hardwoods or comprising more than 2.5% of chemicals (calculated as NaOH), based in each case on the oven-dry amount of the wood used, - mixing of the solution of chemicals with the wood or annual plants in a specified liquor ratio, - heating of the solution of chemicals and of the wood or annual plants to a temperature above room temperature and then either (lst alternative) - removal of free-flowing solution of chemicals and - digestion of the wood or annual plants in the vapour phase or (2nd alternative) - digestion of the wood or annual plants in the presence of the solution of chemicals in the liquid phase and - separation of the free-flowing solution of chemicals and of the wood or annual plants.
The process according to the invention is based on the fact that larger amounts of chemicals are used for producing high-yield fibrous materials than previously customary. More than 5% of chemicals for softwoods are significantly above the previously customary amounts of chemicals for industrial production of fibrous materials, likewise more than 3.5% of chemicals for hardwoods and 2.5% for annual plants. This high use of chemicals gives fibrous materials in a good yield and with excellent strength properties. Thus, for softwood breaking lengths of more than 8 km, but also breaking lengths of more than 9 km and more than 10 km, are measured at freenesses of only 12 SR to 15 SR. For hardwoods, values of more than 5 km, but also breaking lengths of more than 6 km and more than 7 km, are measured at only 20 SR. Thus, the desired high strength level is achieved.
-It is to be regarded as an extraordinary advantage of the process according to the invention that these strength values are achieved even at extremely low freenesses, as have not been available to date for 5 high-yield fibrous materials. Fibrous materials according to the prior art have an unacceptable strength level at freenesses of 12 SR to 15 SR for softwood fibrous materials or of 20 SR for hardwood. At these low freenesses, known fibrous materials have to date given fibres which have not had sufficient binding power and which accordingly have not had sufficient strength properties for commercial use of such fibrous materials.
Particularly suitable annual plants are bamboo, hemp, rice straw, bagasse, wheat, miscanthus or the like.
In contrast, the fibrous materials produced by the process according to the invention have breaking lengths of more than 8 km to 11 km and tear resistances of more than 70 cN to more than 110 cN, based on a sheet weight of 100 g/m2, even at freenesses in the range from 12 SR to 15 SR. These low freenesses are moreover achieved with a low specific demand for beating energy, which is less than 500 kWh/t of fibrous material for softwood fibrous materials; in the case of hardwood fibrous materials, the demand for beating energy may even be less than 300 kWh/t of fibrous material. The discovery that the high strength level is achieved even at low freenesses of 12 SR to 15 SR for softwood and at 20 SR or less for hardwood is a substantial part of the invention.
These high strength values have not been known to date for fibrous materials having a lignin content of more than 15% for softwood fibrous materials, of more than 12% for hardwood fibrous materials or of more than 10%
for annual plants. The high strength level can, however, also be retained for fibrous materials having an even higher lignin content. The process according to the invention is also suitable for producing softwood fibrous materials having a lignin content of more than 18%, preferably more than 21%, advantageously more than 24%, based on the oven-dry fibre material. Hardwood fibrous materials having a lignin content of more than 14%, preferably more than 16%, particularly preferably more than 18% and annual plants having a lignin content of more than 10%, preferably more than 12%, in particular more than 19%, can likewise be produced by the process according to the invention and show a high strength level.
The composition of the solution of chemicals used for the digestion can be tailored to the wood or the annual plants to be digested and the desired properties of the fibrous material. As a rule, a sulphite component alone is used. Alternatively or in addition, a sulphide component may be added. A digestion with a sulphite component is not disturbed by the presence of sulphide components. Sodium sulphite is generally used industrially, but the use of ammonium or potassium sulphite or of magnesium bisulphite is also possible.
Particularly if large amounts of sulphite are used, it is possible to dispense with the use of an alkaline component because a high pH, which promotes the digestion, is established even without addition of alkaline components.
For establishing the pH and for supporting the delignification, an acidic and/or an alkaline component can be metered in. Industrially, sodium hydroxide (NaOH) is generally used as the alkaline component.
However, the use of carbonates, in particular sodium carbonate, is also possible. All data are in amounts of chemicals in the digestion process in this document, for example on the total use of chemicals or on the division of the sulphite component and the alkaline component, are in each case calculated and stated as sodium hydroxide (NaOH), unless stated otherwise.
Acids can be metered in as the acidic component in order to establish the desired pH. However, the addition of SO2r if appropriate in aqueous solution, is preferred. It is economically and readily available, particularly when the spent solution of chemicals, for example based on sodium sulphite, is prepared for further use after the digestion.
To have recognized the advantages of using a quinone component for the high-yield digestion according to the invention is regarded as an independent inventive performance. Quinone components, in particular anthraquinone, have been used to date in the production of chemical pulps having a minimum lignin content in order to prevent an undesired attack on the carbohydrate towards the end of the digestion. By adding quinone components, it is possible to continue the digestion of wood until almost complete degradation of the lignin. That quinone components significantly increase the rate of the lignin degradation in the production of high-yield chemical pulps has to date proved to be an unrecognized, unexpected property of said quinone components. For example, in the production of softwood fibrous materials, the duration of the digestion can be shortened by more than a half, depending on digestion conditions by more than three quarters. This remarkable effect is achieved with minimum use of quinone. Use of, for example, anthraquinone in an amount of between 0.005% and 0.5%
is optimum. Use of anthraquinone in an amount of up to 1% also has the desired effect. Use of more than 3% of anthraquinone is generally uneconomical.
A solution of chemicals is prepared from individual chemicals or a plurality of chemicals from among the abovementioned chemicals. In general, an aqueous solution is prepared. As an option, the use or the addition of organic solvents can also be provided.
Alcohol, in particular methanol and ethanol, gives, as a mixture with water, particularly effective solutions of chemicals for producing high-quality high-yield fibrous materials. The mixing ratio of water and alcohol can be optimized for the respective raw material in a few experiments.
The amount of chemicals to be used according to the invention for producing a fibrous material having a yield of at least 70% is at least 5% for softwood, at least 3.5% for hardwood and at least 2.5% for annual plants, based in each case on the oven-dry wood or annual plant material to be digested. The quality of the fibrous material produced gives the best results when the chemicals used comprise up to 15% for softwood, up to 10% for hardwood and up to 10% for annual plants. Preferably, between 9% and 11% of chemicals, based on the oven-dry wood, for softwood used, are added. For hardwoods, the use of chemicals tends to be lower, preferably between 4% and 10%, particularly preferably between 6% and 8% and, for annual plants, between 3 and 10%.
As already explained above, it is by no means necessary to establish a specific pH. It may be expedient to add acid or an alkaline component before or during the digestion only if, for example, particular properties of the chemical pulps (particularly high whiteness, a certain ratio of breaking lengths and tear resistance) are to be achieved by the digestion. According to an advantageous embodiment of the process according to the invention, a ratio of an alkaline component to sulphur dioxide (SOZ) can be established within a wide range regardless of the chosen use of chemicals altogether.
SO2 is mentioned here as being representative of the abovementioned acidic component. It is also possible to use an acid instead of SOZ. Since the optionally added quinone component is used only in minimum amounts, generally of substantially less than 1%, it is negligible for establishing this ratio. A ratio of alkaline component:S02 in a range of 4:1 to 1.6:1 is very suitable for carrying out the process according to the invention and for obtaining fibrous materials having good strength properties. A customary, particularly suitable range is between 2:1 and 1.6:1.
The adaptation of the proportioned components is effected as a function of the raw material to be digested and the process management chosen in each case (digestion temperature, duration of digestion, impregnation).
The process according to the invention can be carried out in a wide pH range. The ratio of alkaline component to acidic component and the use of an acidic or of an alkaline component can be established to that a pH
between 6 and 11, preferably between 7 and 11, particularly preferably between 7.5 and 10, is established at the beginning of the process. The more likely alkaline pH of between 8 and 11, which is advantageous for the process according to the invention, also promotes the action of the quinone component. The process according to the invention is tolerant with regard to the pH; a small amount of chemicals is required for pH adjustment. This has an advantageous effect on the costs for chemicals.
Without further addition of acid or alkaline components, a pH of between 8 and 10, in general between 8.5 and 9.5, is established in the free-flowing solution of chemicals and the organic constituents dissolved therein, which were liquefied by the digestion, for example for softwood, at the end of the digestion. The dissolved organic constituents include in particular lignosulphonates.
Process for producing fibrous material The invention relates to a process for producing fibrous material from wood or annual plants having a lignin content of more than 15% for softwoods, of more than 12% for hardwoods and of more than 10% for annual plants, based in each case on the oven-dry fibrous material produced, the fibrous material having specified strength properties.
Processes which produce fibrous materials having a relatively high lignin content of more than 15% for softwood and of more than 12% for hardwood are known.
They give a yield of 70% or more, based on the starting material used. These processes are based on chemical andlor on mechanical disintegration of the wood.
In the case of mechanical defibration of the wood, the latter is separated into fibre bundles in beating units - generally after presteaming. These fibre bundles are then defibrillated into individual fibres by further beating. The yield is very high but so is the quantity of beating energy to be applied. The strength of the wood fibres is very low - even after beating - because the fibres contain a large amount of natural lignin and therefore have little binding potential. They are also strongly degraded by the mechanical defibration, which adversely affects their recyclability.
In the case of chemical digestion of the wood, chemicals act on the wood, generally under high pressure and at elevated temperature. The NSSC process may be mentioned as a typical process for high-yield fibrous materials. However, other processes, such as the kraft or the soda process, can also be modified so that high-yield fibrous materials are produced (cf.
"Choosing the best brightening process", N. Liebergott and T. Joachimides, Pulp & Paper Canada, Vol. 80, No.
12, December 1979). If the degradation of the originally used wood is to be limited to a maximum of 30%, far less chemicals are required and used than in the production of chemical pulps which are to be completely freed from lignin. For the production of high-yield chemical puips, the amount of chemicals is metered as a function of the desired yield. In order to achieve a yield of about 70%, based on oven-dry wood use, the prior art recommends using up to 100 of chemicals, based on the starting material. In the case of chemical pulps, the use of chemicals is often 30% or more of chemicals, based on the oven-dry wood.
Chemicals play a role in determining the process costs, i.e. they are used as sparingly as possible. CTMP
fibrous materials are usually produced with amounts of 3% to 5% of chemicals. In known, industrially established processes for producing high-yield fibrous materials, e.g. the NSSC process, up to 10% of chemicals, based on the starting material, are used.
With the use of chemicals limited in this manner, no recovery is as yet installed for recovering the chemicals. In spite of the relatively small amounts of chemicals, this method of fibrous material production leads to considerable pollution of the environment, in particular of bodies of water, not only because of the introduction of chemicals but especially because of the organic load which is released into the main outfall.
Regarding the cost situation, it should be noted that, in the case of mechanically produced fibrous materials, the sharply rising energy prices add to the production costs. In the case of chemically produced high-yield fibrous materials, the production is adversely affected by the costs for the lost chemicals.
High-yield fibrous materials are beaten to high freenesses for the current intended uses. Only then do they reach an acceptable strength level. Here, high freenesses are to be regarded as values of about 300 ml CSF (Canadian Standard Freeness), equivalent to 41 SR
(Schopper-Riegler, see below) and 500 ml CSF, equivalent to 26 SR, as described, for example, in "Choosing the best brightening process", N. Liebergott and T. Joachimides, Pulp & Paper Canada, Vol. 80, No.
12, December 1979, for high-yield fibrous material from softwood. A high freeness is achieved by using mechanical energy. The fibres are rubbed against one another or against a grinder or against a grinding medium and thus changed in their surface properties to achieve better binding behaviour. The high freeness is therefore not an end in itself. Rather, it arises out of the requirements regarding the strength properties of the fibres.
The high-yield fibrous materials produced by a mechanical and/or chemical method are used in particular where high final whiteness and high whiteness stability are not absolutely essential. They could open up numerous further fields of use if the strength level could be increased.
It is therefore an object of the invention to propose a process for producing fibrous material from wood or annual plants having a lignin content of more than 15%
for softwoods, of more than 12% for hardwoods and of more than 10% for annual plants, by means of which fibrous materials of high strength can be produced in an economical manner.
This object is achieved by a process for producing fibrous material from wood or annual plants having a lignin content of at least 15% for softwoods and 12%
for hardwoods and 10o for annual plants, based in each case on the oven-dry fibrous material, comprising the steps:
- preparation of a solution of chemicals comprising more than 5% of chemicals (calculated as NaOH) for softwoods or comprising more than 3.5% of chemicals (calculated as NaOH) for hardwoods or comprising more than 2.5% of chemicals (calculated as NaOH), based in each case on the oven-dry amount of the wood used, - mixing of the solution of chemicals with the wood or annual plants in a specified liquor ratio, - heating of the solution of chemicals and of the wood or annual plants to a temperature above room temperature and then either (lst alternative) - removal of free-flowing solution of chemicals and - digestion of the wood or annual plants in the vapour phase or (2nd alternative) - digestion of the wood or annual plants in the presence of the solution of chemicals in the liquid phase and - separation of the free-flowing solution of chemicals and of the wood or annual plants.
The process according to the invention is based on the fact that larger amounts of chemicals are used for producing high-yield fibrous materials than previously customary. More than 5% of chemicals for softwoods are significantly above the previously customary amounts of chemicals for industrial production of fibrous materials, likewise more than 3.5% of chemicals for hardwoods and 2.5% for annual plants. This high use of chemicals gives fibrous materials in a good yield and with excellent strength properties. Thus, for softwood breaking lengths of more than 8 km, but also breaking lengths of more than 9 km and more than 10 km, are measured at freenesses of only 12 SR to 15 SR. For hardwoods, values of more than 5 km, but also breaking lengths of more than 6 km and more than 7 km, are measured at only 20 SR. Thus, the desired high strength level is achieved.
-It is to be regarded as an extraordinary advantage of the process according to the invention that these strength values are achieved even at extremely low freenesses, as have not been available to date for 5 high-yield fibrous materials. Fibrous materials according to the prior art have an unacceptable strength level at freenesses of 12 SR to 15 SR for softwood fibrous materials or of 20 SR for hardwood. At these low freenesses, known fibrous materials have to date given fibres which have not had sufficient binding power and which accordingly have not had sufficient strength properties for commercial use of such fibrous materials.
Particularly suitable annual plants are bamboo, hemp, rice straw, bagasse, wheat, miscanthus or the like.
In contrast, the fibrous materials produced by the process according to the invention have breaking lengths of more than 8 km to 11 km and tear resistances of more than 70 cN to more than 110 cN, based on a sheet weight of 100 g/m2, even at freenesses in the range from 12 SR to 15 SR. These low freenesses are moreover achieved with a low specific demand for beating energy, which is less than 500 kWh/t of fibrous material for softwood fibrous materials; in the case of hardwood fibrous materials, the demand for beating energy may even be less than 300 kWh/t of fibrous material. The discovery that the high strength level is achieved even at low freenesses of 12 SR to 15 SR for softwood and at 20 SR or less for hardwood is a substantial part of the invention.
These high strength values have not been known to date for fibrous materials having a lignin content of more than 15% for softwood fibrous materials, of more than 12% for hardwood fibrous materials or of more than 10%
for annual plants. The high strength level can, however, also be retained for fibrous materials having an even higher lignin content. The process according to the invention is also suitable for producing softwood fibrous materials having a lignin content of more than 18%, preferably more than 21%, advantageously more than 24%, based on the oven-dry fibre material. Hardwood fibrous materials having a lignin content of more than 14%, preferably more than 16%, particularly preferably more than 18% and annual plants having a lignin content of more than 10%, preferably more than 12%, in particular more than 19%, can likewise be produced by the process according to the invention and show a high strength level.
The composition of the solution of chemicals used for the digestion can be tailored to the wood or the annual plants to be digested and the desired properties of the fibrous material. As a rule, a sulphite component alone is used. Alternatively or in addition, a sulphide component may be added. A digestion with a sulphite component is not disturbed by the presence of sulphide components. Sodium sulphite is generally used industrially, but the use of ammonium or potassium sulphite or of magnesium bisulphite is also possible.
Particularly if large amounts of sulphite are used, it is possible to dispense with the use of an alkaline component because a high pH, which promotes the digestion, is established even without addition of alkaline components.
For establishing the pH and for supporting the delignification, an acidic and/or an alkaline component can be metered in. Industrially, sodium hydroxide (NaOH) is generally used as the alkaline component.
However, the use of carbonates, in particular sodium carbonate, is also possible. All data are in amounts of chemicals in the digestion process in this document, for example on the total use of chemicals or on the division of the sulphite component and the alkaline component, are in each case calculated and stated as sodium hydroxide (NaOH), unless stated otherwise.
Acids can be metered in as the acidic component in order to establish the desired pH. However, the addition of SO2r if appropriate in aqueous solution, is preferred. It is economically and readily available, particularly when the spent solution of chemicals, for example based on sodium sulphite, is prepared for further use after the digestion.
To have recognized the advantages of using a quinone component for the high-yield digestion according to the invention is regarded as an independent inventive performance. Quinone components, in particular anthraquinone, have been used to date in the production of chemical pulps having a minimum lignin content in order to prevent an undesired attack on the carbohydrate towards the end of the digestion. By adding quinone components, it is possible to continue the digestion of wood until almost complete degradation of the lignin. That quinone components significantly increase the rate of the lignin degradation in the production of high-yield chemical pulps has to date proved to be an unrecognized, unexpected property of said quinone components. For example, in the production of softwood fibrous materials, the duration of the digestion can be shortened by more than a half, depending on digestion conditions by more than three quarters. This remarkable effect is achieved with minimum use of quinone. Use of, for example, anthraquinone in an amount of between 0.005% and 0.5%
is optimum. Use of anthraquinone in an amount of up to 1% also has the desired effect. Use of more than 3% of anthraquinone is generally uneconomical.
A solution of chemicals is prepared from individual chemicals or a plurality of chemicals from among the abovementioned chemicals. In general, an aqueous solution is prepared. As an option, the use or the addition of organic solvents can also be provided.
Alcohol, in particular methanol and ethanol, gives, as a mixture with water, particularly effective solutions of chemicals for producing high-quality high-yield fibrous materials. The mixing ratio of water and alcohol can be optimized for the respective raw material in a few experiments.
The amount of chemicals to be used according to the invention for producing a fibrous material having a yield of at least 70% is at least 5% for softwood, at least 3.5% for hardwood and at least 2.5% for annual plants, based in each case on the oven-dry wood or annual plant material to be digested. The quality of the fibrous material produced gives the best results when the chemicals used comprise up to 15% for softwood, up to 10% for hardwood and up to 10% for annual plants. Preferably, between 9% and 11% of chemicals, based on the oven-dry wood, for softwood used, are added. For hardwoods, the use of chemicals tends to be lower, preferably between 4% and 10%, particularly preferably between 6% and 8% and, for annual plants, between 3 and 10%.
As already explained above, it is by no means necessary to establish a specific pH. It may be expedient to add acid or an alkaline component before or during the digestion only if, for example, particular properties of the chemical pulps (particularly high whiteness, a certain ratio of breaking lengths and tear resistance) are to be achieved by the digestion. According to an advantageous embodiment of the process according to the invention, a ratio of an alkaline component to sulphur dioxide (SOZ) can be established within a wide range regardless of the chosen use of chemicals altogether.
SO2 is mentioned here as being representative of the abovementioned acidic component. It is also possible to use an acid instead of SOZ. Since the optionally added quinone component is used only in minimum amounts, generally of substantially less than 1%, it is negligible for establishing this ratio. A ratio of alkaline component:S02 in a range of 4:1 to 1.6:1 is very suitable for carrying out the process according to the invention and for obtaining fibrous materials having good strength properties. A customary, particularly suitable range is between 2:1 and 1.6:1.
The adaptation of the proportioned components is effected as a function of the raw material to be digested and the process management chosen in each case (digestion temperature, duration of digestion, impregnation).
The process according to the invention can be carried out in a wide pH range. The ratio of alkaline component to acidic component and the use of an acidic or of an alkaline component can be established to that a pH
between 6 and 11, preferably between 7 and 11, particularly preferably between 7.5 and 10, is established at the beginning of the process. The more likely alkaline pH of between 8 and 11, which is advantageous for the process according to the invention, also promotes the action of the quinone component. The process according to the invention is tolerant with regard to the pH; a small amount of chemicals is required for pH adjustment. This has an advantageous effect on the costs for chemicals.
Without further addition of acid or alkaline components, a pH of between 8 and 10, in general between 8.5 and 9.5, is established in the free-flowing solution of chemicals and the organic constituents dissolved therein, which were liquefied by the digestion, for example for softwood, at the end of the digestion. The dissolved organic constituents include in particular lignosulphonates.
The liquor ratio, i.e. the ratio of the amount of the oven-dry wood or annual plants to the solution of chemicals, is adjusted to between 1:1.5 and 1:6. A
liquor ratio of 1:3 to 1:5 is preferred. In this range, good and easy mixing and impregnation of the material to be digested in ensured. For softwood, a liquor ratio of 1:4 is preferred. For wood chips having a large surface area, the liquor ratio may also be substantially higher in order to permit rapid wetting and impregnation. At the same time, the concentration of the solution of chemicals can be kept high so that the amounts of liquid to be circulated are not too large.
The mixing or impregnation of the wood or annual plant digestion material is preferably effected at elevated temperatures. Heating of the wood chips and of the solution of chemicals to 110 C, preferably to 120 C, particularly preferably to 130 C, leads to rapid and uniform digestion of the wood. For the mixing or impregnation of the chips, a period of up to minutes, preferably of up to 60 minutes, particularly preferably of up to 90 minutes, is advantageous. The duration which is optimum in each 25 case depends, inter alia, on the amount of the chemicals and the liquor ratio and the method of digestion (liquid or vapour phase).
The digestion of the lignocellulosic material mixed or 30 impregnated with the solution of chemicals is preferably effected at temperatures between 120 C and 190 C, preferably between 150 C and 180 C. For most timbers, digestion temperatures between 155 C and 170 C
are established. Higher or lower temperatures can be established but, in this temperature range, the energy consumption for the heating and the acceleration of the digestion are economically related to one another.
Higher temperatures can moreover have an adverse effect on the strengths and the whiteness of the fibrous materials. The pressure generated by the high temperatures can be readily absorbed by appropriate design of the digester. The duration of heating is usually only a few minutes, generally up to 30 minutes, advantageously up to 10 minutes, particularly if heating is effected by means of steam. The duration of heating can be up to 90 minutes, preferably up to 60 minutes, e.g. if digestion is effected in the liquid phase and the solution of chemicals is to be heated together with the chips.
The duration of digestion is chosen in particular as a function of the desired properties of the fibrous material. The duration of digestion can be shortened to 2 minutes, for example for the case of a vapour-phase digestion of a hardwood having a low lignin content.
However, it may also be up to 180 minutes if, for example, the digestion temperature is low and the natural lignin content of the wood to be digested is high. Even if the initial pH of the digestion is in the neutral range, a long duration of digestion is required. The duration of digestion is preferably up to 90 minutes, in particular in the case of softwood.
Particularly preferably, the duration of digestion is up to 60 minutes, advantageously up to 30 minutes. A
duration of digestion of up to 60 minutes is suitable especially in the case of hardwoods.
In the case of annual plants, the duration of digestion is up to 90 minutes. The use of a quinone component, in particular anthraquinone, permits a reduction in the duration of digestion to 25% of the time required without addition of anthraquinone. If the use of quinone components is dispensed with, the duration of digestion increases by more than one hour, for example, by 45 minutes to 180 minutes, for comparable digestion results.
liquor ratio of 1:3 to 1:5 is preferred. In this range, good and easy mixing and impregnation of the material to be digested in ensured. For softwood, a liquor ratio of 1:4 is preferred. For wood chips having a large surface area, the liquor ratio may also be substantially higher in order to permit rapid wetting and impregnation. At the same time, the concentration of the solution of chemicals can be kept high so that the amounts of liquid to be circulated are not too large.
The mixing or impregnation of the wood or annual plant digestion material is preferably effected at elevated temperatures. Heating of the wood chips and of the solution of chemicals to 110 C, preferably to 120 C, particularly preferably to 130 C, leads to rapid and uniform digestion of the wood. For the mixing or impregnation of the chips, a period of up to minutes, preferably of up to 60 minutes, particularly preferably of up to 90 minutes, is advantageous. The duration which is optimum in each 25 case depends, inter alia, on the amount of the chemicals and the liquor ratio and the method of digestion (liquid or vapour phase).
The digestion of the lignocellulosic material mixed or 30 impregnated with the solution of chemicals is preferably effected at temperatures between 120 C and 190 C, preferably between 150 C and 180 C. For most timbers, digestion temperatures between 155 C and 170 C
are established. Higher or lower temperatures can be established but, in this temperature range, the energy consumption for the heating and the acceleration of the digestion are economically related to one another.
Higher temperatures can moreover have an adverse effect on the strengths and the whiteness of the fibrous materials. The pressure generated by the high temperatures can be readily absorbed by appropriate design of the digester. The duration of heating is usually only a few minutes, generally up to 30 minutes, advantageously up to 10 minutes, particularly if heating is effected by means of steam. The duration of heating can be up to 90 minutes, preferably up to 60 minutes, e.g. if digestion is effected in the liquid phase and the solution of chemicals is to be heated together with the chips.
The duration of digestion is chosen in particular as a function of the desired properties of the fibrous material. The duration of digestion can be shortened to 2 minutes, for example for the case of a vapour-phase digestion of a hardwood having a low lignin content.
However, it may also be up to 180 minutes if, for example, the digestion temperature is low and the natural lignin content of the wood to be digested is high. Even if the initial pH of the digestion is in the neutral range, a long duration of digestion is required. The duration of digestion is preferably up to 90 minutes, in particular in the case of softwood.
Particularly preferably, the duration of digestion is up to 60 minutes, advantageously up to 30 minutes. A
duration of digestion of up to 60 minutes is suitable especially in the case of hardwoods.
In the case of annual plants, the duration of digestion is up to 90 minutes. The use of a quinone component, in particular anthraquinone, permits a reduction in the duration of digestion to 25% of the time required without addition of anthraquinone. If the use of quinone components is dispensed with, the duration of digestion increases by more than one hour, for example, by 45 minutes to 180 minutes, for comparable digestion results.
According to an advantageous embodiment of the process according to the invention, the duration of digestion is established as a function of the chosen liquor ratio. The lower the liquor ratio, the shorter can the duration of the process be set.
The production of high-yield fibrous material with the use of a large amount of chemicals of more than 5% for softwood, of more than 3.5% for hardwood and at least 2.5% for annual plants initially appears to be uneconomical. However, experiments have shown that only a part of the chemicals is consumed during the partial digestion of the lignocellulosic material. The predominant part of the chemicals is discharged unconsumed, either before the digestion (vapour-phase digestion) or after the digestion (digestion in the liquid phase). The actual consumption of chemicals is below the amounts used in the digestion solution.
The consumption of chemicals is recorded as the amount of chemicals which - based on the originally used amount of chemicals - is measured after removal or separation of the solution of chemicals and optionally the registration of the solution of chemicals, which is measured after the defibration or in combination with the registration of the solution of chemicals. The consumption of chemicals is dependent on the absolute amount of the chemicals used for the digestion, based on the oven-dry wood material to be digested. The greater the use of digestion chemicals, the lower is the direct conversion of chemicals. With the use of 27.5% of chemicals, based on oven-dry wood material, for example, only about 30% of the chemicals used are consumed. With the use of 15% of chemicals, based on oven-dry wood, however, 60% of the chemicals used are consumed, as could be demonstrated in laboratory experiments. According to a preferred embodiment of the process, the consumption of chemicals for the process according to the invention during the digestion is up to 80%, preferably up to 60%, particularly preferably up to 40%, advantageously up to 20%, particularly advantageously up to 10%, of the chemicals used at the beginning of the digestion.
The consumption of chemicals for the production of a metric ton of fibrous material is about 6% to 14% of sulphite and/or sulphide component and, if appropriate, alkaline and/or acidic component and/or if appropriate, quinone component, based on oven-dry fibrous material (soft- and hardwood or annual plants). According to the invention, this amount of chemicals is sufficient for producing a fibrous material having the specified properties. However, in order to ensure a standard process result and, if appropriate, to obtain particular, desired properties of the fibrous material, it may prove to be expedient to use larger amounts of chemicals for the dilution, for example the abovementioned amounts of up to 30% of chemicals, based on oven-dry wood or annual plant material.
The use of these amounts of chemicals at the beginning of the digestion has an advantageous effect, since the fibrous materials obtained in this manner have properties not available to date, in particular good strength properties and good whitenesses. In particular, no digestion process has been available to date which produces fibrous materials having high strengths over a broad pH range from neutral to alkaline range. That the fibrous materials produced according to the invention can be beaten with a far lower energy demand to specified freenesses than known fibrous materials has proved to be economically particularly attractive. Moreover, they develop the high strengths even at unusually low freenesses of 12 SR to 15 SR for softwood and of 20 SR for hardwood.
An excess of chemicals is present in the free-flowing liquid after the mixing and impregnation of the wood with the solution of chemicals or after digestion. This excess is subtracted before the digestion (lst alternative) or after digestion (2nd alternative).
According to an advantageous further development of the process, the composition of the solution of chemicals which is removed is determined and then adjusted to a specified composition for further use for the production of fibres. The solution of chemicals which is removed before or after the digestion of the wood or of the annual plants no longer has the initially established composition. At least a part of the chemicals used for the digestion has - as described above - penetrated into the material to be digested and/or has been consumed during the digestion. The unconsumed chemicals can readily be used again for the next digestion. However, it is proposed according to the invention initially to determine the composition of the removed solution of chemicals and then to replenish the consumed proportions of, for example, sulphite, alkaline component, quinone component or water or alcohol in order to prepare the specified composition again for the next digestion. This replenishment step is also referred to as fortification.
It is to be regarded as a considerable advantage of this measure that the solution of chemicals contains no substances at all or only very few substances which prove to be troublesome in further use of the fortified solution of chemicals for the next digestion only on removal before the digestion but also on removal after the digestion. The process according to the invention which is based on providing an oversupply of digestion chemicals during the impregnation can thus operate extremely economically in spite of the initially apparently uneconomical procedure involving the considerable use of chemicals, since the removal or the separation and the fortification of the solution of chemicals can be carried out simply and economically.
The production of high-yield fibrous material with the use of a large amount of chemicals of more than 5% for softwood, of more than 3.5% for hardwood and at least 2.5% for annual plants initially appears to be uneconomical. However, experiments have shown that only a part of the chemicals is consumed during the partial digestion of the lignocellulosic material. The predominant part of the chemicals is discharged unconsumed, either before the digestion (vapour-phase digestion) or after the digestion (digestion in the liquid phase). The actual consumption of chemicals is below the amounts used in the digestion solution.
The consumption of chemicals is recorded as the amount of chemicals which - based on the originally used amount of chemicals - is measured after removal or separation of the solution of chemicals and optionally the registration of the solution of chemicals, which is measured after the defibration or in combination with the registration of the solution of chemicals. The consumption of chemicals is dependent on the absolute amount of the chemicals used for the digestion, based on the oven-dry wood material to be digested. The greater the use of digestion chemicals, the lower is the direct conversion of chemicals. With the use of 27.5% of chemicals, based on oven-dry wood material, for example, only about 30% of the chemicals used are consumed. With the use of 15% of chemicals, based on oven-dry wood, however, 60% of the chemicals used are consumed, as could be demonstrated in laboratory experiments. According to a preferred embodiment of the process, the consumption of chemicals for the process according to the invention during the digestion is up to 80%, preferably up to 60%, particularly preferably up to 40%, advantageously up to 20%, particularly advantageously up to 10%, of the chemicals used at the beginning of the digestion.
The consumption of chemicals for the production of a metric ton of fibrous material is about 6% to 14% of sulphite and/or sulphide component and, if appropriate, alkaline and/or acidic component and/or if appropriate, quinone component, based on oven-dry fibrous material (soft- and hardwood or annual plants). According to the invention, this amount of chemicals is sufficient for producing a fibrous material having the specified properties. However, in order to ensure a standard process result and, if appropriate, to obtain particular, desired properties of the fibrous material, it may prove to be expedient to use larger amounts of chemicals for the dilution, for example the abovementioned amounts of up to 30% of chemicals, based on oven-dry wood or annual plant material.
The use of these amounts of chemicals at the beginning of the digestion has an advantageous effect, since the fibrous materials obtained in this manner have properties not available to date, in particular good strength properties and good whitenesses. In particular, no digestion process has been available to date which produces fibrous materials having high strengths over a broad pH range from neutral to alkaline range. That the fibrous materials produced according to the invention can be beaten with a far lower energy demand to specified freenesses than known fibrous materials has proved to be economically particularly attractive. Moreover, they develop the high strengths even at unusually low freenesses of 12 SR to 15 SR for softwood and of 20 SR for hardwood.
An excess of chemicals is present in the free-flowing liquid after the mixing and impregnation of the wood with the solution of chemicals or after digestion. This excess is subtracted before the digestion (lst alternative) or after digestion (2nd alternative).
According to an advantageous further development of the process, the composition of the solution of chemicals which is removed is determined and then adjusted to a specified composition for further use for the production of fibres. The solution of chemicals which is removed before or after the digestion of the wood or of the annual plants no longer has the initially established composition. At least a part of the chemicals used for the digestion has - as described above - penetrated into the material to be digested and/or has been consumed during the digestion. The unconsumed chemicals can readily be used again for the next digestion. However, it is proposed according to the invention initially to determine the composition of the removed solution of chemicals and then to replenish the consumed proportions of, for example, sulphite, alkaline component, quinone component or water or alcohol in order to prepare the specified composition again for the next digestion. This replenishment step is also referred to as fortification.
It is to be regarded as a considerable advantage of this measure that the solution of chemicals contains no substances at all or only very few substances which prove to be troublesome in further use of the fortified solution of chemicals for the next digestion only on removal before the digestion but also on removal after the digestion. The process according to the invention which is based on providing an oversupply of digestion chemicals during the impregnation can thus operate extremely economically in spite of the initially apparently uneconomical procedure involving the considerable use of chemicals, since the removal or the separation and the fortification of the solution of chemicals can be carried out simply and economically.
The process according to the invention is controlled in a targeted manner so that only as little as possible of the starting material used is degraded or dissolved. It is desirable to produce a fibrous material which has for softwood a lignin content of at least 15%, based on the oven-dry fibre material, preferably a lignin content of at least 18%, particularly preferably of 21%, advantageously of at least 24%. For hardwood, it is desired to achieve a lignin content of at least 12%, based on the oven-dry fibre material, preferably of at least 14%, particularly preferably of at least 16%, advantageously of at least 18%. In the case of annual plants, the preferred lignin content is between 10 and 28%, in particular between 12 and 26%.
The yield of the process according to the invention is at least 70%, preferably more than 75%, advantageously more than 80%, based in each case on the wood used.
This yield correlates with the abovementioned lignin content of the fibrous material. The original lignin content of wood is specific for the type. In the present process, the loss of yield is predominantly a loss of lignin. In the case of unspecific digestion processes, the proportion of carbohydrates is substantially increased, for example because digestion chemicals also bring cellulose or hemicelluloses into solution in an essentially undesired manner.
A further, advantageous measure is to remove the still remaining solution of chemicals after the defibration and, if appropriate, beating of the lignocellulosic material and to reuse it. This reuse may comprise two aspects in a preferred configuration. Firstly, the organic material, predominantly lignin, degraded or brought into solution during the partial digestion is further used. It is, for example, incinerated in order to obtain process energy. Alternatively, it is processed in order to be otherwise used. Secondly, the spent and unconsumed chemicals are reprocessed so that they can be used for a further, partial digestion of lignocellulosic material. This includes the processing of spent chemicals.
According to a particularly preferred variant of the process according to the invention, the solution of chemicals used is extremely efficiently utilized. After the defibration and, if appropriate, beating, the fibrous material is washed in order to displace the solution of chemicals as far as possible by water. The filtrate forming during this washing and displacement process contains considerable amounts of solution of chemicals and organic material. According to the invention, this filtrate is fed into the removed or separated solution of chemicals before the solution of chemicals is fortified and fed to the next digestion.
The chemicals and organic constituents present in the filtrate do not disturb the digestion. If they make a contribution to the delignification during the next digestion, their content in the solution of chemicals is determined and is taken into account in the determination of the amount of chemicals which is required for this digestion. The further chemicals present in the filtrate are inert during the upcoming digestion. They do not cause problems. The organic constituents present in the filtrate are likewise inert. They are reused after the next digestion in the processing of the solution of chemicals, either to generate process energy or in another manner.
It is regarded as particularly advantageous that, by this management of the filtrate, less fresh water and fewer chemicals are used for the digestion. At the same time, a maximum of dissolved organic material is detected. This improved use of the organic material which has gone into solution also improves the cost-efficiency of the process according to the invention.
= CA 02634378 2008-06-19 Details of the process according to the invention and of the apparatus are explained in more detail below with reference to working examples.
The following experiments were evaluated according to the following specifications:
- The yield was calculated by weighing the raw material used and the chemical pulp obtained after the digestion, in each case dried at 105 C to constant weight (absolutely dry).
- The lignin content was determined as Klason lignin according to TAPPT T 222 om-98. The acid-soluble lignin was determined according to TAPPI UM 250.
- The properties relating to paper technology were determined on test sheets which were produced according to Zellcheming data sheet V/8/76.
- The freeness was determined according to Zellcheming data sheet V/3/62.
- The bulk density was determined according to Zellcheming method V/11/57.
- The breaking length was determined according to Zellcheming method V/12/57.
- The tear resistance was determined according to DIN 53 128 Elmendorf.
- The determination of tensile, tear and burst index was effected according to TAPPI 220 sp-96.
- The whiteness was determined by producing the test sheets according to Zelicheming data sheet V/19/63; measurement was effected according to SCAN C 11:75 using a Datacolor elrepho 450 x photometer; the whiteness is stated in percent according to ISO standard 2470.
- The viscosity was determined according to data sheet IV/36/61 of the Association of the Pulp and Paper Chemists and Engineers (Zellcheming).
- All % data in this document are to be understood as meaning percent by weight, unless specifically stated otherwise.
= CA 02634378 2008-06-19 - The statement "oven-dry" in this document relates to "oven-dry" material which was dried at 105 C to constant weight.
- The chemicals for the digestion are stated in percent by weight as sodium hydroxide, unless explained otherwise.
Example 1 - Digestion of softwood in the liquid phase A sodium sulphite digestion solution was added to a mixture of spruce wood and Douglas fir chips with a liquor ratio of wood:digestion solution 1:3, after steaming (30 minutes with saturated steam at 105 C).
The total use of chemicals was less than 15%, based on oven-dry chips. The pH at the beginning of the digestion was adjusted to pH 6 by addition of SOZ.
The spruce wood chips impregnated with the solution of chemicals were heated to 170 C over a period of 90 minutes and were digested at this maximum temperature over 60 minutes.
Thereafter, the free-flowing liquid was removed by centrifuging, collected and analysed in an arrangement for recycling unconsumed liquid and fortified and thus provided for the next digestion.
The digested chips were defibrated. Portions of the fibrous material thus produced were beaten for different times in order to determine the strength at different freenesses. The energy consumption for defibration of the partly digested chips was less than 300 kWh/t of fibrous material.
In this experiment, the yield was 77%, based on the wood material used.
This corresponds to a fibrous material having a lignin content of well above 20%. The average lignin content for spruce wood is stated as 28%, based on the oven-dry wood material (Wagenfur, Anatomie des Holzes [Anatomy of Wood], VEB Fachbuchverlag Leipzig, 1980). The actual lignin content of the fibrous material is higher than 20% since predominantly, but not exclusively, lignin is degraded during the digestion. Carbohydrates (cellulose and hemicelluloses) are also dissolved in small amounts. The stated values show that the digestion has good selectivity with respect to the lignin and carbohydrate degradation.
The whiteness is unexpectedly high with values above 55% ISO and thus offers a good initial basis for any subsequent bleach in which whitenesses of 75% ISO are achievable.
With an initial freeness of 12 SR, these materials already have a breaking length of 6 km at a density of 1.87 cm3/g.
In order to beat the fibrous materials to a freeness of 15 SR, a duration of beating of 20 to 30 minutes is required. Up to a duration of beating of 20 minutes (freeness 12 SR - 15 SR), the freeness develops independently of the pH at the beginning of the digestion (pH 6 to pH 9.4) within a narrow range.
Likewise independently of the initial pH of the digestion and of the duration of beating required for achieving the freeness, a high strength level is achieved at a freeness of 15 SR.
Example 2 The fibrous material was produced from spruce chips, the pH at the beginning of the digestion being 9.4.
In addition to the 15% of total chemicals (sulphite and NaOH in specified ratio), 0.1% of anthraquinone, based on the amount of wood used, was added to the solution of chemicals.
The duration of the digestion was 60 minutes.
The following values were obtained:
Yield (o): 81.1 Lignin content: 22.7 Whiteness (% ISO): 53.7 Breaking length (km): 9.6 Tear resistance (cN; 100 g/mz): 75.0 By the addition of 0.1% of anthraquinone, the duration of the digestion can be reduced from about 180 minutes to 60 minutes under otherwise unchanged digestion conditions. This time gain is valuable especially because the plants for the production of fibrous materials can be designed with small dimensions. The fact that the temperature required for the digestion need be maintained only over a very much shorter period constitutes a further potential saving.
Furthermore, it was determined that, with decreasing use of total chemicals down to values between 5 and 15%
in the case of softwood, fibrous material having substantially equally good properties is produced.
These results are not dependent on the use of the anthraquinone. The anthraquinone results in an acceleration of the digestion, but the desired fibrous material can also be digested without addition of anthraquinone.
Example 3: Digestion of hardwood in the liquid phase A sodium sulphite digestion solution was added to eucalyptus chips with a liquor ratio of wood:digestion solution 1:3, after steaming. The use of chemicals here was 10.5% (as NaOH), based on oven-dry chips.
= - 21 -In a period of 90 minutes, the material to be digested was impregnated and the material to be cooked was heated to the maximum digestion temperature of 170 C.
The duration of cooking was 50 minutes.
Digestions with eucalyptus wood show that these materials can be produced with a specific energy input of less than 250 KWh/t for defibration.
In these experiments, the yield was 77%, based on the wood material used. At an initial freeness of 14 SR, these materials already have a breaking length of 3.5 km at a density of 2.05 cm3/g. These materials can be bleached in the subsequent bleach to whitenesses of 79.6% ISO.
Experiments have shown that the digestions in the vapour phase show a small overall time requirement.
Compared with the digestion in the liquid phase, the heating to the maximum digestion temperature is effected very much more rapidly. The actual digestion then requires the same duration as cooking in the liquid phase. During the vapour-phase digestion, no free-flowing solution of chemicals is present; such solution is removed after the impregnation and before the digestion. Less organic material is therefore added to it than the solution of chemicals which is removed after the digestion in the liquid phase. However, this has no significant influence on the quality of the fibrous material produced.
While similar values in the case of the yield are achievable in vapour-phase digestions, the whiteness of the fibrous materials produced in the vapour digestion is, however, substantially lower. The reduction of the maximum digestion temperature from 170 C to 155 C has a significant effect: the whiteness increases.
The fibrous materials produced in the vapour phase have outstanding strengths. The breaking length was measured, for example, as 10 km and as 11 km at 15 SR.
The tear resistance was measured, for example, as 82.8 cN and as 91.0 cN. These values correspond to the best values for fibrous materials having a high lignin content which were achieved for digestions in the liquid phase or are even higher. For fibrous materials having a high lignin content from the prior art, comparable strength values are not known.
From the examples, it is particularly clear that the fibrous materials according to the invention require only a small amount of energy during the beating in order to establish large breaking lengths, without the tear resistance being reduced. A freeness of 12 SR was reached in each case in 0-10 minutes; a freeness of 13 SR in 5-30 minutes, generally 10-20 minutes. In order to arrive at a freeness of 14 SR, the Jokro beater had to operate for 30-40 minutes, and between 35 and 40 minutes were required for a freeness of 15 SR.
It is obvious that beating up to freenesses of about 40 SR would require an enormous amount of beating energy. A particular advantage of the process according to the invention is therefore that fibrous materials to be beaten with a small amount of energy and having high strengths are produced.
The yield of the process according to the invention is at least 70%, preferably more than 75%, advantageously more than 80%, based in each case on the wood used.
This yield correlates with the abovementioned lignin content of the fibrous material. The original lignin content of wood is specific for the type. In the present process, the loss of yield is predominantly a loss of lignin. In the case of unspecific digestion processes, the proportion of carbohydrates is substantially increased, for example because digestion chemicals also bring cellulose or hemicelluloses into solution in an essentially undesired manner.
A further, advantageous measure is to remove the still remaining solution of chemicals after the defibration and, if appropriate, beating of the lignocellulosic material and to reuse it. This reuse may comprise two aspects in a preferred configuration. Firstly, the organic material, predominantly lignin, degraded or brought into solution during the partial digestion is further used. It is, for example, incinerated in order to obtain process energy. Alternatively, it is processed in order to be otherwise used. Secondly, the spent and unconsumed chemicals are reprocessed so that they can be used for a further, partial digestion of lignocellulosic material. This includes the processing of spent chemicals.
According to a particularly preferred variant of the process according to the invention, the solution of chemicals used is extremely efficiently utilized. After the defibration and, if appropriate, beating, the fibrous material is washed in order to displace the solution of chemicals as far as possible by water. The filtrate forming during this washing and displacement process contains considerable amounts of solution of chemicals and organic material. According to the invention, this filtrate is fed into the removed or separated solution of chemicals before the solution of chemicals is fortified and fed to the next digestion.
The chemicals and organic constituents present in the filtrate do not disturb the digestion. If they make a contribution to the delignification during the next digestion, their content in the solution of chemicals is determined and is taken into account in the determination of the amount of chemicals which is required for this digestion. The further chemicals present in the filtrate are inert during the upcoming digestion. They do not cause problems. The organic constituents present in the filtrate are likewise inert. They are reused after the next digestion in the processing of the solution of chemicals, either to generate process energy or in another manner.
It is regarded as particularly advantageous that, by this management of the filtrate, less fresh water and fewer chemicals are used for the digestion. At the same time, a maximum of dissolved organic material is detected. This improved use of the organic material which has gone into solution also improves the cost-efficiency of the process according to the invention.
= CA 02634378 2008-06-19 Details of the process according to the invention and of the apparatus are explained in more detail below with reference to working examples.
The following experiments were evaluated according to the following specifications:
- The yield was calculated by weighing the raw material used and the chemical pulp obtained after the digestion, in each case dried at 105 C to constant weight (absolutely dry).
- The lignin content was determined as Klason lignin according to TAPPT T 222 om-98. The acid-soluble lignin was determined according to TAPPI UM 250.
- The properties relating to paper technology were determined on test sheets which were produced according to Zellcheming data sheet V/8/76.
- The freeness was determined according to Zellcheming data sheet V/3/62.
- The bulk density was determined according to Zellcheming method V/11/57.
- The breaking length was determined according to Zellcheming method V/12/57.
- The tear resistance was determined according to DIN 53 128 Elmendorf.
- The determination of tensile, tear and burst index was effected according to TAPPI 220 sp-96.
- The whiteness was determined by producing the test sheets according to Zelicheming data sheet V/19/63; measurement was effected according to SCAN C 11:75 using a Datacolor elrepho 450 x photometer; the whiteness is stated in percent according to ISO standard 2470.
- The viscosity was determined according to data sheet IV/36/61 of the Association of the Pulp and Paper Chemists and Engineers (Zellcheming).
- All % data in this document are to be understood as meaning percent by weight, unless specifically stated otherwise.
= CA 02634378 2008-06-19 - The statement "oven-dry" in this document relates to "oven-dry" material which was dried at 105 C to constant weight.
- The chemicals for the digestion are stated in percent by weight as sodium hydroxide, unless explained otherwise.
Example 1 - Digestion of softwood in the liquid phase A sodium sulphite digestion solution was added to a mixture of spruce wood and Douglas fir chips with a liquor ratio of wood:digestion solution 1:3, after steaming (30 minutes with saturated steam at 105 C).
The total use of chemicals was less than 15%, based on oven-dry chips. The pH at the beginning of the digestion was adjusted to pH 6 by addition of SOZ.
The spruce wood chips impregnated with the solution of chemicals were heated to 170 C over a period of 90 minutes and were digested at this maximum temperature over 60 minutes.
Thereafter, the free-flowing liquid was removed by centrifuging, collected and analysed in an arrangement for recycling unconsumed liquid and fortified and thus provided for the next digestion.
The digested chips were defibrated. Portions of the fibrous material thus produced were beaten for different times in order to determine the strength at different freenesses. The energy consumption for defibration of the partly digested chips was less than 300 kWh/t of fibrous material.
In this experiment, the yield was 77%, based on the wood material used.
This corresponds to a fibrous material having a lignin content of well above 20%. The average lignin content for spruce wood is stated as 28%, based on the oven-dry wood material (Wagenfur, Anatomie des Holzes [Anatomy of Wood], VEB Fachbuchverlag Leipzig, 1980). The actual lignin content of the fibrous material is higher than 20% since predominantly, but not exclusively, lignin is degraded during the digestion. Carbohydrates (cellulose and hemicelluloses) are also dissolved in small amounts. The stated values show that the digestion has good selectivity with respect to the lignin and carbohydrate degradation.
The whiteness is unexpectedly high with values above 55% ISO and thus offers a good initial basis for any subsequent bleach in which whitenesses of 75% ISO are achievable.
With an initial freeness of 12 SR, these materials already have a breaking length of 6 km at a density of 1.87 cm3/g.
In order to beat the fibrous materials to a freeness of 15 SR, a duration of beating of 20 to 30 minutes is required. Up to a duration of beating of 20 minutes (freeness 12 SR - 15 SR), the freeness develops independently of the pH at the beginning of the digestion (pH 6 to pH 9.4) within a narrow range.
Likewise independently of the initial pH of the digestion and of the duration of beating required for achieving the freeness, a high strength level is achieved at a freeness of 15 SR.
Example 2 The fibrous material was produced from spruce chips, the pH at the beginning of the digestion being 9.4.
In addition to the 15% of total chemicals (sulphite and NaOH in specified ratio), 0.1% of anthraquinone, based on the amount of wood used, was added to the solution of chemicals.
The duration of the digestion was 60 minutes.
The following values were obtained:
Yield (o): 81.1 Lignin content: 22.7 Whiteness (% ISO): 53.7 Breaking length (km): 9.6 Tear resistance (cN; 100 g/mz): 75.0 By the addition of 0.1% of anthraquinone, the duration of the digestion can be reduced from about 180 minutes to 60 minutes under otherwise unchanged digestion conditions. This time gain is valuable especially because the plants for the production of fibrous materials can be designed with small dimensions. The fact that the temperature required for the digestion need be maintained only over a very much shorter period constitutes a further potential saving.
Furthermore, it was determined that, with decreasing use of total chemicals down to values between 5 and 15%
in the case of softwood, fibrous material having substantially equally good properties is produced.
These results are not dependent on the use of the anthraquinone. The anthraquinone results in an acceleration of the digestion, but the desired fibrous material can also be digested without addition of anthraquinone.
Example 3: Digestion of hardwood in the liquid phase A sodium sulphite digestion solution was added to eucalyptus chips with a liquor ratio of wood:digestion solution 1:3, after steaming. The use of chemicals here was 10.5% (as NaOH), based on oven-dry chips.
= - 21 -In a period of 90 minutes, the material to be digested was impregnated and the material to be cooked was heated to the maximum digestion temperature of 170 C.
The duration of cooking was 50 minutes.
Digestions with eucalyptus wood show that these materials can be produced with a specific energy input of less than 250 KWh/t for defibration.
In these experiments, the yield was 77%, based on the wood material used. At an initial freeness of 14 SR, these materials already have a breaking length of 3.5 km at a density of 2.05 cm3/g. These materials can be bleached in the subsequent bleach to whitenesses of 79.6% ISO.
Experiments have shown that the digestions in the vapour phase show a small overall time requirement.
Compared with the digestion in the liquid phase, the heating to the maximum digestion temperature is effected very much more rapidly. The actual digestion then requires the same duration as cooking in the liquid phase. During the vapour-phase digestion, no free-flowing solution of chemicals is present; such solution is removed after the impregnation and before the digestion. Less organic material is therefore added to it than the solution of chemicals which is removed after the digestion in the liquid phase. However, this has no significant influence on the quality of the fibrous material produced.
While similar values in the case of the yield are achievable in vapour-phase digestions, the whiteness of the fibrous materials produced in the vapour digestion is, however, substantially lower. The reduction of the maximum digestion temperature from 170 C to 155 C has a significant effect: the whiteness increases.
The fibrous materials produced in the vapour phase have outstanding strengths. The breaking length was measured, for example, as 10 km and as 11 km at 15 SR.
The tear resistance was measured, for example, as 82.8 cN and as 91.0 cN. These values correspond to the best values for fibrous materials having a high lignin content which were achieved for digestions in the liquid phase or are even higher. For fibrous materials having a high lignin content from the prior art, comparable strength values are not known.
From the examples, it is particularly clear that the fibrous materials according to the invention require only a small amount of energy during the beating in order to establish large breaking lengths, without the tear resistance being reduced. A freeness of 12 SR was reached in each case in 0-10 minutes; a freeness of 13 SR in 5-30 minutes, generally 10-20 minutes. In order to arrive at a freeness of 14 SR, the Jokro beater had to operate for 30-40 minutes, and between 35 and 40 minutes were required for a freeness of 15 SR.
It is obvious that beating up to freenesses of about 40 SR would require an enormous amount of beating energy. A particular advantage of the process according to the invention is therefore that fibrous materials to be beaten with a small amount of energy and having high strengths are produced.
Claims (19)
1. Process for producing fibrous material from wood or annual plants having a lignin content of at least 15% for softwood, of at least 12% for hardwood and of at least 10% for annual plants, based in each case on the oven-dry fibrous material, comprising the steps - preparation of a solution of chemicals comprising more than 5% of chemicals (calculated as NaOH) for softwood or comprising more than 3.5% of chemicals (calculated as NaOH) for hardwood or comprising more than 2.5%
of chemicals (calculated as NaOH) for annual plants, based in each case on the oven-dry amount of the wood, - mixing of the solution of chemicals with wood or annual plants in a specified liquor ratio, - heating of the solution of chemicals and of the wood or of the annual plants to a temperature above room temperature and then - either (1st alternative) removal of free-flowing solution of chemicals and digestion of the wood or of the annual plants in the vapour phase or (2nd alternative) digestion of the wood or of the annual plants in the liquid phase and separation of the free-flowing solution of chemicals and of the wood or of the annual plants.
of chemicals (calculated as NaOH) for annual plants, based in each case on the oven-dry amount of the wood, - mixing of the solution of chemicals with wood or annual plants in a specified liquor ratio, - heating of the solution of chemicals and of the wood or of the annual plants to a temperature above room temperature and then - either (1st alternative) removal of free-flowing solution of chemicals and digestion of the wood or of the annual plants in the vapour phase or (2nd alternative) digestion of the wood or of the annual plants in the liquid phase and separation of the free-flowing solution of chemicals and of the wood or of the annual plants.
2. Process according to Claim 1, characterized in that a fibrous material having a content of at least 15% of lignin, preferably at least 18% of lignin, advantageously at least 21% of lignin, in particular at least 24% of lignin, based on oven-dry fibrous material for softwood or having a content of at least 14% of lignin, preferably at least 16% of lignin, particularly preferably at least 18% of lignin, based on oven-dry fibrous material for hardwood or having a content of at least 10% of lignin, preferably at least 12% of lignin, in particular at least 19% of lignin, based on oven-dry fibrous material for annual plants is produced.
3. Process according to Claim 1 or 2, characterized in that a quinone component is used for the preparation of the solution of chemicals.
4. Process according to any of the preceding claims, characterized in that not more than 15% of chemicals, preferably between 9 and 11% of chemicals, are used for the digestion of softwood.
5. Process according to any of the preceding claims, characterized in that not more than 10% of chemicals, preferably between 4 and 10% of chemicals, in particular between 6 and 8% of chemicals, are used for the digestion of hardwood.
6. Process according to any of the preceding claims, characterized in that not more than 10%, preferably between 3 and 10%, of chemicals are used for the digestion of annual plants.
7. Process according any of the preceding claims, characterized in that sulphites and sulphides are used, individually or as a mixture, for the preparation of the solution of chemicals.
8. Process according to Claim 7, characterized in that an acidic and/or an alkaline component, in particular an acid, sulphur dioxide, sodium hydroxide and/or a carbonate are used for the preparation of the solution of chemicals.
9. Process according to any of the preceding claims, characterized in that an alkaline component and an acidic component, in particular SO2, are used for the digestion, the ratio of alkaline component : SO2 being established in the range from 4:1 to 1.6:1, preferably to 2:1.
10. Process according to any of the preceding claims, characterized in that the process is carried out at a pH between 6 and 11, preferably between 7 and
11, particularly preferably between 7.5 and 10.
11. Process according to any of the preceding claims, characterized in that a liquor ratio of wood:solution of chemicals of between 1:1.5 and 1:6, preferably between 1:3 and 1:5, is established.
11. Process according to any of the preceding claims, characterized in that a liquor ratio of wood:solution of chemicals of between 1:1.5 and 1:6, preferably between 1:3 and 1:5, is established.
12. Process according to any of the preceding claims, characterized in that the heating of the solution of chemicals and of the wood or of the annual plants is effected up to 130°C, preferably up to 120°C, advantageously up to 110°C.
13. Process according to any of the preceding claims, characterized in that the heating of the wood or of the annual plants and, if appropriate, of the solution of chemicals lasts up to 90 minutes, preferably up to 60 minutes, advantageously up to 30 minutes, particularly advantageously up to minutes.
14. Process according to any of the preceding claims, characterized in that the digestion of the wood or of the annual plants is carried out at temperatures between 120°C and 190°C, preferably at temperatures between 150°C and 180°C, particularly preferably at temperatures between 160°C and 170°C.
15. Process according to any of the preceding claims, characterized in that the digestion of the wood or of the annual plants lasts up to 180 minutes, preferably up to 90 minutes, particularly preferably up to 60 minutes, advantageously up to 30 minutes, particularly advantageously up to 2 minutes.
16. Process according to Claim 15, characterized in that the duration of the digestion is chosen as a function of the liquor ratio.
17. Process according to any of the preceding claims, characterized in that the consumption of chemicals during the digestion is up to 80%, preferably up to 60%, particularly preferably up to 40%, advantageously up to 20%, particularly advantageously up to 10% of the chemicals used at the beginning of the digestion.
18. Process according to any of the preceding claims, characterized in that the composition of the removed or separated solution of chemicals is determined and is then adjusted to a specified composition for further use for the production of fibres.
19. Process according to any of the preceding claims, characterized in that the solution of chemicals which is released after the defibration and, if appropriate, beating of the digested lignocellulosic material is removed and is further used.
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE200610027006 DE102006027006A1 (en) | 2006-06-08 | 2006-06-08 | Producing fibrous material comprises producing a chemical solution, mixing the chemical solution with wood and/or annual plant; heating the chemical solution and pulping and then separating the woods and the chemical solution |
DE102006027006.1 | 2006-06-08 | ||
DE200610061480 DE102006061480A1 (en) | 2006-12-23 | 2006-12-23 | Producing fibrous material comprises producing a chemical solution, mixing the chemical solution with wood and/or annual plant; heating the chemical solution and pulping and then separating the woods and the chemical solution |
DE102006061480.1 | 2006-12-23 | ||
PCT/EP2007/003012 WO2007140837A2 (en) | 2006-06-08 | 2007-04-04 | Method for producing fibrous material |
Publications (1)
Publication Number | Publication Date |
---|---|
CA2634378A1 true CA2634378A1 (en) | 2007-12-13 |
Family
ID=38801852
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002634378A Abandoned CA2634378A1 (en) | 2006-06-08 | 2007-04-04 | Method for producing fibrous material |
Country Status (6)
Country | Link |
---|---|
US (1) | US20090314443A1 (en) |
EP (1) | EP2029806A2 (en) |
JP (1) | JP2009540132A (en) |
BR (1) | BRPI0712857A2 (en) |
CA (1) | CA2634378A1 (en) |
WO (1) | WO2007140837A2 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2010069151A1 (en) * | 2008-12-19 | 2010-06-24 | 北京英力和泓新材料技术有限公司 | Process for extracting cellulose |
WO2013082735A1 (en) * | 2011-12-07 | 2013-06-13 | 北京英力生科新材料技术有限公司 | Chemical mechanical pulping method |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102007022750A1 (en) * | 2007-05-11 | 2008-11-13 | Voith Patent Gmbh | Process for defibering chemically treated lignocellulosic raw material |
DE102007036382A1 (en) * | 2007-07-31 | 2009-02-05 | Voith Patent Gmbh | Lignocellulosic pulp from annual plants |
DE102007036376A1 (en) * | 2007-07-31 | 2009-02-05 | Voith Patent Gmbh | Bleached pulp |
US20110060077A1 (en) * | 2009-09-10 | 2011-03-10 | Yeng-Fong Shih | Process for Manufacturing High-Performance Natural Fiber Reinforced Composites |
CN102677504B (en) * | 2012-05-29 | 2014-02-26 | 宜宾丝丽雅集团有限公司 | Manufacturing process of antibacterial bamboo pulp used for high-wet-modulus fibre |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB478943A (en) * | 1935-04-24 | 1938-01-24 | Cellulose Res Corp | System of obtaining and treating cellulose and product thereof |
GB885605A (en) * | 1958-09-11 | 1961-12-28 | Stora Kopparbergs Bergslags Ab | Improved method for the production of neutral sulfite pulp |
JPH0931880A (en) * | 1995-07-17 | 1997-02-04 | Mitsubishi Paper Mills Ltd | Bleaching and modification of chemical pulp |
GB2382592A (en) * | 2001-11-30 | 2003-06-04 | Sca Hygiene Prod Gmbh | Use of ozone to enhance the wet strength of fibrous cellulosic material |
CN1177101C (en) * | 2002-07-05 | 2004-11-24 | 岳阳纸业股份有限公司 | Chemical treatment and hot pulping process of wood pulp and dreg pulp with mechanical mill and stone mill |
CN1208519C (en) * | 2003-01-15 | 2005-06-29 | 岳阳纸业股份有限公司 | Surface glued newsprinting paper and manufacturing method thereof |
DE102005036075A1 (en) * | 2005-08-01 | 2007-02-15 | Voith Patent Gmbh | Process for the production of tissue paper |
KR100694840B1 (en) * | 2005-06-09 | 2007-03-14 | 유해일 | Manufacturing method of mechanical pulp from cornstalk |
-
2007
- 2007-04-04 JP JP2009513554A patent/JP2009540132A/en active Pending
- 2007-04-04 CA CA002634378A patent/CA2634378A1/en not_active Abandoned
- 2007-04-04 EP EP07723953A patent/EP2029806A2/en not_active Withdrawn
- 2007-04-04 BR BRPI0712857-6A patent/BRPI0712857A2/en not_active IP Right Cessation
- 2007-04-04 WO PCT/EP2007/003012 patent/WO2007140837A2/en active Application Filing
- 2007-04-07 US US12/161,649 patent/US20090314443A1/en not_active Abandoned
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2010069151A1 (en) * | 2008-12-19 | 2010-06-24 | 北京英力和泓新材料技术有限公司 | Process for extracting cellulose |
WO2013082735A1 (en) * | 2011-12-07 | 2013-06-13 | 北京英力生科新材料技术有限公司 | Chemical mechanical pulping method |
Also Published As
Publication number | Publication date |
---|---|
BRPI0712857A2 (en) | 2012-07-31 |
WO2007140837A3 (en) | 2008-04-03 |
WO2007140837A2 (en) | 2007-12-13 |
US20090314443A1 (en) | 2009-12-24 |
EP2029806A2 (en) | 2009-03-04 |
JP2009540132A (en) | 2009-11-19 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP1541753B1 (en) | Refiner bleaching with magnesium hydroxide or magnesium oxide and perhydroxyl ions | |
US20090314443A1 (en) | Method for producing fibrous material | |
US8152960B2 (en) | Lignocellulosic fibrous material made of wood | |
US20090266500A1 (en) | Process for producing tissue paper | |
CN101466890A (en) | Method for producing fibrous material | |
US4116758A (en) | Method of producing high yield chemimechanical pulps | |
CA1123554A (en) | High yield chemimechanical pulping processes | |
CA2634380C (en) | Process for producing fibrous material from wood | |
US3013931A (en) | Printing paper and process of making the same | |
Gellerstedt et al. | Bleachability of alkaline pulps. Part 1. The importance of β-aryl ether linkages in lignin | |
US3013932A (en) | Printing paper and process of making the same | |
WO2009015699A1 (en) | Lignocellulosic fibrous material from annual plants | |
US4329200A (en) | Method and system for selective alkaline defiberization and delignification | |
Lundqvist et al. | Removal of non-process elements from hardwood chips prior to kraft cooking | |
AU2013357649B2 (en) | Use of sodium dithionite in a cellulose pulping process | |
Kvarnlöf et al. | Oxygen delignification of acid sulfite and bisulfite softwood pulps | |
US8673113B2 (en) | Process for reducing specific energy demand during refining of thermomechanical and chemi-thermomechanical pulp | |
Antes et al. | Effect of Modified Cooking on Bleachability of Eucalyptus globulus and Eucalyptus nitens. | |
Salmén et al. | Improved pulp yield and strength by retained glucomannans in kraft pulping of softwood | |
Jahan et al. | Sodium carbonate pre-extraction of Trema orientalis in the production of paper grade pulp | |
CN113338067B (en) | Environment-friendly color series household paper and preparation method thereof | |
EP0287960A2 (en) | A process for the production of a hemicellulose hydrolysate and special pulp | |
CA1051618A (en) | Method of producing high yield chemimechanical pulps | |
Elhelece | 10596 Rice Straw as a Raw Material for Pulp and Paper Production | |
Mobarak et al. | Newsprint from cotton stalks |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
FZDE | Discontinued |