DE2540917B2 - METHOD AND DEVICE FOR MANUFACTURING IMPROVED HIGH YIELD PULP - Google Patents

Description

25 40 917 4th 3 Attempt 2 Attempt 1

Cooking to various yields with
one and the same type of wood (long-fiber)

Spruce wood chips with a length of approx. 30 mm. Attenuated width 15 mm and thickness approximately 3 mm were washed and at atmospheric pressure for 10 minutes, the chips were de ^r pressed on a laboratory press, and then were allowed to swell in a cooking liquor consisting of NaOH in an amount of 50 g / l ( calculated as Na2O) and SO ₂ in an amount of 65 g / l. The pH of the solution was 6.0. During this impregnation, the wood chips absorbed 1000 ml of solution per 1000 g of absolutely dry wood chips. The impregnated wood chips were placed in a digester and ^{heated to 443 K (170 °} C.) with saturated steam. The overpressure in the digester was 825 kPa (8.4 kp / cm *). A sample (A) was boiled 5 minutes at 443 C (i70 ° C) while another sample (B) for 25 minutes at 443 K (170 ⁰ C) was boiled. The specified cooking times could be viewed as the total cooking time because the heating to the maximum cooking temperature was less than 1 minute. Samples A and B were defibrated, each separately in a disc refiner at digester pressure with the simultaneous addition of dilution water. The defibrated pulp was blown to a hydrocyclone to separate the steam from the pulp suspension. The content of dry cellulose pulp in the resulting pulp suspension was approx. 30%, while the temperature was 360 K (87 ° C). The defibrated mass was refined in a second disc refiner. In this case, dilution water was added in such a way that the refining was carried out at a pulp concentration of approx. 23%. The refined pulp mass was sieved and dewatered to a mass concentration of approx. 35% before it was bleached with 3% hydrogen peroxide and 0.8% sodium ditionite. The samples were ground 1000 revolutions in a laboratory mill and formed into a laboratory sheet prior to paper testing. The following results were obtained:

Sample A Sample B

Pulp yield,% 91.2 84

Grind, ° Schopper-Riegler 56.5 15

Brightness after bleaching, 77.4 70.7
SCAN%

Tear length, m 4200 6800

Friction factor 72 84

Light scattering coefficient, m ² / kg 36.7 21.4

Porosity, Bendtsen ml / min 980 2300

Cooking to various yields with
one and the same type of wood (short grain)

Experiment 1 was repeated with the difference that the spruce wood chips were replaced by birch wood chips were exchanged. The following results were obtained.

Sample A Sample B

93.0 84.2 12.5 18th 81.5 80.7 270 4900 13th 63 37.5 31.3 > 3000 1173

Pulp yield,%

Grind degree, ° Schopper-Riegler
Brightness after bleaching,

SCAN%

Tear length, m

Friction factor

Light scattering coefficient m ² / kg
Porosity, Bendtsen ml / min

The table shows that hardwood treated according to method A gives a mass that is light can be bleached, but has extremely low strength. If the pulp yield is lowered to 84.2%, as with sample B, the strength is considerably improved while the mass remains light remains bleachable and is less difficult to grind than the mass according to sample A.

Attempt 3

Cooking too high yield of

Wood chip mixtures of different types of wood

(long fiber and short fiber)

A wood mixture of 50% birch and 50% spruce, with the same chip dimensions as in experiment 1, with the exception that the chip thickness was 2 mm, was steamed and impregnated with cooking liquid as in experiment 1. The Hatkschnitzelmischung was then cooked at 433 K (160 ⁰ C) for 20 min.. The partially delignified wood chips were defibrated and refined

and bleached as in experiment 1. The pulp obtained is given below with sample 3: A designated. This mass was ground 5000 revolutions in a laboratory mill, whereupon from it Laboratory sheets were produced, which were examined for paper properties. The attempt was repeated with the difference that the spruce wood chips were exchanged for pine wood chips were, the mass obtained being designated as Sample 3: B. The following results were obtain:

A comparison between sample A with a pulp yield of 91.2% and sample B with a Pulp yield of 84% shows that sample A has higher freeness and brightness than sample B, d. That is, the mass produced according to A is easier to grind and to bleach. In addition, sample A has one give better opacity, which is determined by measuring the light scattering coefficient, and directly is proportional to this. In contrast, the method according to B has a mass with better strength than the mass after sample A.

Sample 3: A Sample 3: B

Pulp yield,% 89.0 89.5 Grind degree, ° Schopper-Riegler 40.5 14.5 Brightness according to the 78.4 77.5 Bleaching, SCAN% Tear length, m 3900 3100 Friction factor 68 63 Light scattering coefficient, 36.1 33.4

Porosity, Bendtsen ml / min 1560

> 3000

As can be seen from the table, these pulps are both easily bleachable and proportionate opaque. However, the strength of the masses is less than that of a mass made only of softwood has been produced in an appropriate yield. In addition, in factory papermaking, surface uniformity is increased of the paper is unacceptably low (is due, among other things, to the high porosity emerge). These pulp masses also result in a hard and brittle paper with poor elongation properties.

The present invention aims to obviate the above-mentioned drawbacks and to provide an improved one Producing high-yield pulp in a more economical way than has previously been possible. Accordingly The present invention relates to a process for the production of cellulose from lignocellulosic material! in the Yield range from 70 to 93% with improved quality properties, with at least part of the Lignocellulosic material washed, steamed, impregnated with digesting chemicals and digested and defibrated thereon, which method is characterized in that the lignocellulosic material in at least two different material flows are divided, of which a first material flow according to Washing, steaming and impregnation to a yield of 65 to 92%, preferably 78 to 88%, is digested and a second stream of material is only washed, whereupon the two streams of material mixed directly without intermediate washing and in such a way one in a common pressure vessel Heating to a temperature of 363 to 473 K, preferably 373 to 458 K., that are exposed a further partial delignification and softening of the lignin is achieved, whereupon the product obtained is mechanically defibrated.

According to a preferred embodiment, the second stream of material is also at a temperature steamed from 363 to 383 K for a period of at least 5 minutes. In certain cases it is expedient to impregnate the second material stream with digestion chemicals after steaming, in order to achieve less delignification of the same in the subsequent treatment in the pressure vessel.

The partial delignification in the common pressure vessel should be carried out in such a way that one a final yield of 60 to 88%, if possible 73 to 85%, in the first material stream and a yield from 100 to 85%, preferably 96 to 90%, in the second Material flow received For this, in most cases, a heating time of 1 to 20 minutes, preferably 2 up to 10 minutes, required. It is particularly useful before the digestion of the first stream of material this with To impregnate digestion chemicals and an excess of them before the subsequent digestion to remove in the common pressure vessel.

After the treatment in the pressure vessel, the product obtained is mechanically defibrated and, if necessary a further refining and possibly also bleaching, preferably with lignin-preserving bleaches, exposed

At. the production of pulp according to the present invention is used as the starting material comminuted lignocellulosic material such as Wood chips, chopped straw, sawdust or the like, It is essential according to the invention that the raw material is in the form of smaller pieces is present in order to be able to carry out the process. The comminution of the lignocellulosic material, for example Can be in the form of sticks, can be done in a wood chip chopper that Produces wood chips with a size of 15 to 30 χ 20 to 40 mm and a thickness of 0.5 to 10 mm. the Use of thin wood chips, d. H. Wood chips in the thickness range from 0.5 to 5 mm particularly useful because this prevents the penetration of the

, o Chemicals eased into the lignocellulosic material.

According to the invention, all wood chips are used in one or two wood chip washers Removal of foreign objects such as metal parts, etc., washed. When washing

the wood chips can also be used the excess heat from the pulp process and the frictional heat from the refiners. If the wood chip washing is carried out at an elevated temperature, a more effective washing is achieved and the dwell time in the subsequent steam treatment according to the invention can be reduced. A compensation of the normal moisture variations in the wood chip material supplied, which is desired according to the invention, is also obtained, which brings about greater uniformity in the quality of the pulp mass produced. According to the invention, the washed and preheated wood chips are transported by means of a belt conveyor or screw conveyor to one or two vessels for the steam treatment of the wood chips at atmospheric pressure (steaming). In the method according to the invention, the wood chips are thus divided into two streams either before the wood chip washing or after the wood chip washing or after the steaming, whereupon pulp mass is produced from the respective wood chip flow and the pulp yields in the two wood chip flows are kept different. One stream of wood chips is continuously impregnated with chemicals after washing and steaming and then boiled, whereupon it is fed to a common pressure vessel. The other stream of wood chips can be led to the common pressure vessel directly after the wood chip washing or after the wood chip washing and steaming. Alternatively, this woodchip stream can be impregnated with chemicals after the woodchip washing and steaming before it is fed to the common pressure vessel. A separate boiling of this wood chip flow does not take place. In the common pressure vessel, a further delignification of the supplied material can possibly take place. In the pressure vessel, the material is steamed at an overpressure of 0-981 kPa (O-10kp / cm ² ), preferably at an overpressure of 49-785 kPa (0.5 - 8 kp / cm ² ), and a temperature of 363- 473 K (90-200 ⁰ C), preferably about 373-458 K (100-185 ⁰ C), treated. The heating with steam also came indirectly up to a corresponding Temperatui or lower temperature, if the

Would like to expose pulp to such a pressure that the blowing can take place at one pressure; dei exceeds the saturation pressure of the steam The wood chips can be made from wood chips of the same or different types of wood or from wood chips Schnitzel mixtures of two or more types of wood are formed. The method according to the invention is shown schematically in FIG. 1 explains which dai

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the following embodiment, which explains the invention.

B e i s ρ i e 1 1

Manufacture of nhemimechanical pulp

made of two different types of wood,
one of which is partially delignified

IO

Technical birch wood chips with approximate dimensions of 30 χ 15 mm and a thickness of 5 mm - wood chip stream A - were washed in the wood chip washer 1 and steamed in the steaming vessel 2 at atmospheric pressure and a temperature of 373 K (100 ° C) for 10 minutes. The steamed wood chips were fed to the impregnation chamber 4 via the screw conveyor 3. The screw conveyor was constructed in such a way that it compressed the wood chips during transport and dewatered them from approx. 35% dry matter to approx. 50% dry matter. After passing through the screw conveyor, the wood chips were allowed to swell in the impregnation chamber 4, which contained cooking liquid, which was kept at a constant level and supplied by the chemical preparation 5. When the wood chips swelled in the impregnation chamber, they sucked in cooking liquid in an amount of approx. 1 liter of cooking liquid per kg of dry wood chips. The cooking liquid was prepared from sulfur dioxide mixed with sodium hydroxide, the amount of sodium hydroxide (calculated as Na2O) being 50 g / liter and the amount of sulfur dioxide being 65 g / liter. The cooking liquid had a pH of 6.0. The impregnated wood chips were then transferred to the digester 6, where they ^{were subjected to steam phase boiling by supplying direct steam at an overpressure of 735 kPa (7.5 kp / cm 2} ), the steam being introduced through a line 7. This resulted in a cooking temperature of 443 K (170 ⁰ C). The holding time in the digester 6 was 20 minutes.After digestion of the wood chip stream A in the digester 6, the wood chips were fed to the common pressure vessel 9 with the aid of the screw conveyor 8, which was of the same construction as the screw conveyor 3 and squeezed out excess cooking liquid and steam condensate could be used to impregnate the other woodchip stream B in the impregnation vessel 43 or for the preparation of new cooking liquid in the chemical preparation 5 or be fed directly to a system 10 for the recovery of cooking chemicals. The pulp yield after the dilignification of the wood chip stream A in the digester 6 was 83%. The wood chip flow B was formed by spruce wood chips with the same dimensions as in the wood chip flow A and, after passing through the wood chip washer 11, was fed directly to the common pressure vessel 9, where it was mixed with the wood chip flow A in equal parts. Excess steam with an overpressure of 245 kPa (2 ^ kp / cm ² ) is introduced into the pressure vessel 9 through a line 12 from the screw conveyor 8, the mixture of the wood chip streams A and B being further delignified in the vapor phase at a temperature of 398 K (125 kPa) ° C) was exposed for a period of 3 minutes. The pulp yield of the wood chip stream B was approx. 95% under these conditions. The resulting steam-heated mixture of partially delignified wood chips A and slightly delignified wood chips B was transported with the aid of a screw conveyor 13, which was arranged at the bottom of the pressure vessel, to a defibering device, the disc refiner 14, where the defibration was carried out at an excess pressure of 196 kPa (2nd kp / cm ² ) and a temperature of approx. 393 K (12O ⁰ C), whereupon the pulp mass defibrated in this way was transported to a cyclone 15 for the separation of steam, where cooling water was fed through a line 16. The mass was fed from the cyclone to a second disc refiner 17, where it was further refined at atmospheric pressure and a temperature of approx. 358 K (85 ° C.) and a mass concentration of 25%. The pulp mass obtained was then sieved, while diluting with water, in a pressure sieve 18 at 1% mass concentration. The sieved mass was then treated in a vortex cleaner 19. The residue from the pressure screen 18 and vortex cleaner 19 was dewatered to 20% mass concentration and refined in the refiner 20. The refined residue mass was returned to the pressure screen 18. The accented mass was dehydrated to 20% mass concentration and bleached with hydrogen peroxide. The total yield of the pulp obtained was 87% and the brightness was 78% SCAN. The mass had such strength and optical properties that it could be used for the production of writing and printing paper.

Example 2

Manufacture of chemimechanical pulp

from wood chips from several different types of wood

The process according to Example 1 was repeated with the difference that the wood chip stream / was formed from a mixture of wood chips from birch, Esp <and beech in the ratio 40:40:20 with the same dimensions as in Example 1, while the wood chip stream B was made of pine - Un <spruce wood chips in a ratio of 60: 4C with the same dimensions as in Example 1. The total pulp yield was 87% and the brightness was 77%. The pulp was well suited for the production of writing and printing paper and cardboard.

Example 3

Manufacture of chemimechanical pulp from a single type of wood

The process according to Example 1 was repeated with the difference that both the wood chip flow A and the wood chip flow B from spruce wood chips with the same dimensions as in Example 1 were formed. The total pulp yield was 89% and the brightness after bleaching was 76% SCAN. The pulp had very good strength and good optical properties and was well suited for the production of writing and printing paper, cardboard and soft paper.

709 507 / *

Example 4

Manufacture of chemimechanical pulp

from a stream of wood chips of one and the same type of wood, which is divided into two streams

is divided,
which are partially delignified

Technical birch wood chips of the same length as in example 1 but with a thickness of 3 mm were treated as wood chip stream A according to example 1. The wood chip flow B was formed by birch wood chips of the same dimensions as the wood chip flow A. The wood chip stream B was washed in the wood chip washing machine 11 and steamed in the steaming vessel 21 as in Example 1 and conveyed via the screw conveyor 22 to the impregnation chamber 23, where it was impregnated with the same type of cooking liquid as in the impregnation chamber 4. From the impregnation chamber 23, the wood chip flow B was led directly to the pressure vessel 9, where it was mixed with the wood chip flow A in a ratio of 30:70. Direct steam was then introduced into the pressure vessel 9 through a line 24 at an overpressure of 638 kPa (6.5 kp / cm ² ), which corresponded to a temperature of 433 K (160 ^° C.). The vapor phase cooking took place over a period of 15 minutes. A partial delignification of the entire mixture took place, the yield for woodchip stream A being approx. 79% and for woodchipping stream B approx. 90%. The continued treatment was then carried out as in Example 1. The total pulp yield was 85% and the brightness was 81% SCAN. The pulp obtained had very good strength and optical properties and was well suited for the production of writing and printing paper and cardboard.

Example 5

Manufacture of chemimechanical pulp

from two streams of wood chips of different types of wood, both of which are partially delignified

The process according to Example 4 was repeated with the difference that the wood chip stream A was formed from a mixture of birch and aspen wood chips in a ratio of 50:50 with the length dimensions 50 χ 15 mm and the thickness 1 mm. The wood chip flow B was formed by spruce wood chips of the same dimensions as the wood chip flow A. The total pulp yield was 84% and the brightness was 79% SCAN. The mass obtained was well suited for the production of writing and printing paper, cardboard and soft paper.

Other embodiments of the treatment steps shown in Examples 1 to 5 can also be used in the method according to the invention. In addition to sodium hydroxide, the basic chemicals in the cooking liquid used can also be formed from sodium carbonate, ammonia or magnesium hydroxide or the like. The cooking liquid can also contain only basic chemicals without the presence of sulfur dioxide, which can also be replaced by oxygen. A suitable pH for the cooking liquor used is 2-13 and preferably 5-9. The content of chemicals in the cooking liquid can of course be varied as desired. Instead of carrying out the cooking in the cooker 6 in the vapor phase, the cooking can be carried out in the liquid phase, using a cooking liquid which is significantly less concentrated than in the case of the vapor phase cooking. During the liquid phase boiling, the wood chips are fed directly from the steaming vessel 2 through a line 26 to the digester 6 and the digestion chemicals are fed to the digester 6 from the chemical preparation 5 through a line 27. A suitable temperature range for cooking is 373-453 K (100-180 ° C) and an overpressure of 49-127 kPa (0.5-13 kp / cm ² ). The cooking time is expediently 2-240 minutes The cellulose yield in the delignification of the wood chip stream A in the digester 6 is kept between 65 and 92% and preferably between 78 and 88% according to the invention. As can be seen from the examples, after the wood chip washing, the wood chip stream B can be fed directly to the common pressure vessel 9 for mixing with the wood chip flow A , but it is also possible, after steaming, to add a smaller amount of cooking chemicals to the wood chip flow 5 before it is introduced into the pressure vessel . The residence time in the pressure vessel is expediently kept at a maximum of 20 minutes. A residence time of 2-10 minutes is preferably used. An overpressure of 49-883 kPa (0.5-9 kp / cm ² ) is expediently maintained in the pressure vessel 9. The wood chips treated in the pressure vessel, which are fed to the defibrating device 14, can also be defibrated at atmospheric pressure. The defibering device can also be formed by a cone mill or a screw defibering device.

If two defibrillation devices are used

the, a part of the wood chip flow from the pressure vessel 9 can be defibrated without pressure, while the remaining wood chips are defibrated under pressure. If defibration is carried out without pressure, the wood chips coming from the pressure vessel must first pass through a cyclone 25 for the separation of Steam pass through. The separated steam can be fed to the wood chip washing machine 1 and / or 11, or its heat content can also be used in a chemical recovery system.

z. B. in evaporation. When the wood chips are under Pressure are defibrated, they can after defibrating a cyclone 15 for the separation of Steam can be supplied. In the cyclone can through a line 16, if desired, dilution and

Cooling liquids as well as liquids containing bleach, e.g. bleaching waste liquors, are added will. It is advantageous to adjust the pulp mass according to the dei Further processing of defibrillation in defibrillation or grinding stages, e.g. in a disc refiner, ai Cone mill or a screw defibrator 17, but grinding tools other than those mentioned above can also be used. It is also possible to defibrate the two wood chip streams separately and in this case the following «

Refining also carried out in separate streams leads to be, ie. those wood chips that were used Overpressure can be defibrated, can be regrinded for themselves and those chips that Atmo Spherical pressure can also be defibrated for

be ground. According to another embodiment Approximate form of the invention, the two pulp masses are mixed after defibration and in one common refining device reworked en

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The advantage of the separate grinding of each pulp stream after defibration is that the respective Pulp can be ground to different degrees. When using two defibrillation organs after In addition, different defibrating energies can be used in the pressure vessel. The ground Mass can contain incompletely defibrated small pieces of wood chips, so-called residual particles. Around To separate the remaining particles from the mass, it is advisable to sieve them. Here is a Receive a fraction, which consists of coarse pulp and residual particles. This fraction is called the residue mass and is usually except for a relatively high one Mass concentration, preferably 15-30%, dehydrated and processed in suitable grinding organs, whereby the remaining particles are defibrated into individual fibers. The residual fibers will normally be on it led to the pulp flow that goes to the screening plant. The finished, sieved mass is expediently dewatered, preferably on filters, and can then be bleached or dried directly. In integrated cellulose factories is the bleached or unbleached pulp directly after the screening plant or after The paper mill is fed to the intermediate drainage system. Suitable bleaching agents for bleaching the The resulting pulp are so-called lignin-retaining bleaches such as peroxide and ditionite. Even other bleaching agents such as borohydride, peracetic acid, thioglycolic acid and hydroxylamine can be used will.

In order to compare the method according to the present invention with the prior art, a number of comparative laboratory tests were carried out. The results of these experiments go from the following implementation examples Is 6–8.

Example 6

Method according to the invention,
compared to experiment 3

Spruce wood chips with a length of approx. 30 mm. Width approx. 15 mm and thickness approx. 2 mm - wood chip stream B - were washed, whereupon they were steamed at atmospheric pressure for 10 minutes. The wood chips were pressed out in a laboratory press and then left to swell in a boiling liquid with pH 6.0, consisting of NaOH (50 g / 1, _{calculated as Na 2} O) and SO2 (65 g / l). During this impregnation, the wood chips absorbed 1000 ml of cooking solution per 1000 g of absolutely dry wood chips. In a parallel stream, birch wood chips of the dimensions given above - wood chip stream A - were treated in exactly the same way. In accordance with the invention, the birch wood chips were then cooked separately for 10 minutes, after which they were thoroughly mixed with the impregnated spruce wood chips in a ratio of 1: 1 in a pressure vessel. The chopping mixture was steam-phase cooked for 10 min at a temperature of 433 K (160 ⁰ C) corresponding to an overpressure of 638 kPa (6 ^ kp / cm ²⁾ Boiling) = 20 min. The digested wood chip mixture was defibrated in a disc refiner under digester pressure with the simultaneous addition of dilution water . The dry mass content in the mass suspension was approx. 30%, while the temperature was 360 K (87 ° C). The defibrated pulp was refined in a second disc refiner. In this case, dilution water was added in such a way that the refining was carried out at a mass concentration of approx. 23%. The refined mass was sieved and dehydrated to approx. 35% mass concentration before it was bleached with 3% hydrogen peroxide and 0.8% sodium ditionite. The mass was then ground 500 revolutions in a laboratory mill and formed into laboratory sheets prior to paper testing. In the following, a potting is made between the results of the paper test of the pulp mass according to this example, ie according to the invention, and the mass according to experiment 3 and with the designation sample 3: A, which has already been explained. The difference between the mass according to the invention and the mass 3: A is that, according to the invention, the birch portion on the one hand separately for 10 minutes at a temperature of 433 K (160 ^° C.) and on the other hand together with the spruce portion for 10 minutes at a temperature of 433 ° C K (160 ⁰ C) has been cooked, while with mass 3: A both the birch and the spruce portion have been cooked together for ^{20 minutes at a temperature of 433 K (160 0 C).} The following results were obtained:

40

45

Sample 3: A. According to invention Pulp yield,% 89.0 88.7 Grind, "Schopper-Riegler 40.5 42.0 Brightness after bleaching, 80.4 80.2 SCAN% Tear length, m 3900 4800 Friction factor 68 76 Light scattering coefficient, m ² / kg 36.1 34.8 Porosity, Bendtsen ml / mm 1560 1110 Strain, % 3.4 4.0 Double fold number 6th 18th

As can be seen from the table, in the method of the present invention, a Obtain stronger paper than the conventional method, while retaining the rest desirable properties. Thus, the paper obtained according to the invention has good surface uniformity and good elongation properties as well as good toughness.

Example 7

Method according to the invention,
compared to experiment 3

This experiment was carried out as in Example 6, with the exception that pine wood was used instead of spruce wood. Furthermore, an experiment was carried out in accordance with experiment 3, but with pine wood instead of spruce wood, a pulp mass being obtained which was designated sample 3: B. The difference between the mass according to sample 3: B and the mass according to the invention lies in the fact that in sample 3: B the pine wood chips and birch wood chips have already been mixed at the beginning and thus cooked together for 20 minutes at a temperature of 433 K (160 ° C) ⁰ Q have been exposed.

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while the pine wood chips or birch wood chips according to the invention have been treated in separate streams so that the birch portion on the one hand separately for 10 minutes and on the other hand together with the pine portion for 10 minutes (which was the only boiling to which the pine wood chips were exposed) at a temperature of 433 K (16O ⁰ C) has been boiled. The following results were obtained.

Sample 3: B.

According to
invention

89.5 89.0 14.5 26.0 77.5 77.8 3100 3900 63 70 33.4 33.6 > 3000 1820 2.7 3.3 0 7th

Mechychem. cellulose cellulose Dimensions Dimensions after invention Pulp yield,% 65 88.7 Grind, "Schopper-Riegler 31 42 Brightness, SCAN,% 83 80.2 Tear length, m 3200 4800 Friction factor 76 76 Light scattering coefficient, m ² / kg 41.2 34.8 Porosity, Bendtsen ml / min 1150 1110

15th

Pulp yield,%
Grind degree, ° Schopper-Riegler
Brightness after bleaching,
SCAN%
Tear length, m
Friction factor

Light scattering coefficient, mVkg
Porosity, Bendtsen ml / min
Strain, %
Double fold number

It is clear from this that the preparation of a pulp according to the present invention Surprisingly a stronger paper with good surface uniformity, good extensibility and good toughness while maintaining good optical properties. It is also surprising that when using z. B. a mixture of pine wood chips and birch wood chips one considerably higher freeness obtained with the new process than with the process according to experiment 3.

Example 8

Method according to the invention,

compared to a mix of mechanical and

chemical pulp

In papermaking, mechanical pulp is often mixed to produce wood-containing paper with chemical pulp, whereby the chemical mass gives the paper the strength, while mechanical mass tends to contribute to good formation (i.e. even distribution the fibers in the paper) and gives the paper high opacity. In one experiment a mixture of 35% peroxide bleached mechanical mass with a brightness of 80% SCAN and 65% chemical mass produced with a brightness of 91% SCAN, mixing 500 revolutions in a laboratory mill was ground, after which laboratory sheets were made. These sheets underwent a paper test and compared the results with those results obtained with that of Example 6 paper made according to the invention were obtained. The following test results were obtained:

Show 60 The results indicate that paper, which was produced from a pulp that has been prepared according to the invention has better tensile strength than a conventional wood-containing paper. The only properties that are somewhat degraded are opacity and, to some extent, brightness. It is thus possible, by means of the process according to the invention, to produce a high quality paper, the properties of which are equivalent to those obtained by mixing mechanical and expensive chemical compositions, and this with a total pulp yield which is approximately 24% greater

The reason for the fact that in the process according to the invention a pulp mass is obtained which, in addition to its easy bleachability and easy grindability as well as its acceptable optical properties, also has such a strength that it can be used without admixing a reinforcing mass (with very high strength) for the production of, for example Writing and printing paper that can be used is not known. One explanation could be that milling becomes more efficient in the process of the present invention. The reason why the grinding could be more effective when two types of wood chips with different degrees of delignification are defibrated and refined together may be that the less delignified wood chips, which are simultaneously harder, are defibrated when the softer wood chips, which are more strongly delignified, are defibrated , are helpful. It can also be assumed that the harder wood chips help fibrillate the individual fibers. It is also conceivable that fibrillation in the defibration and refining process occurs at an earlier stage than when relatively soft wood chips are ground separately. Another or simultaneous factor which contributes to the favorable result can be that the softer wood chips fill the disk pattern in the disk refiner faster than relatively hard wood chips. With a more rapid sealing of the disks, on the one hand, better utilization of the supplied energy and, on the other hand, a larger processing zone and a longer dwell time when the cellulose material passes through the grinding element is obtained. Another possible factor or interacting factors may be that the respective range of fibers comes into intimate contact with one another during defibration and binding potentials develop between the fibers that cannot be achieved with separate defibration and grinding.

The method according to the present invention has the significant advantage that it is pulp with high yield, which is essential when there is a lack of wood fiber, and every measure to be taken Obtaining a greater proportion of pulp from the wood is of great importance. Through the invention is it has become possible to produce a pulp pulp in high yield, which paper with good Strength properties, good surface uniformity, good ductility, low brittleness and results in good optical properties. The mass is also easy to grind and easy to bleach. aside from that the method according to the invention results in a lower energy consumption in certain cases. Since you can use different types of wood in the method according to the invention with advantage, offers the Invention also great opportunities for the accessible raw material in forest areas with several types of wood

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and at the same time effectively utilizing the small volume of each type of wood. Another advantage is that the according to the method according to the invention obtained cooking waste liquor has a higher dry content than in the known methods, whereby the heat economy is improved. The cooking liquor also gets higher Extract content than when cooking together, resulting in lower extract content in the finished pulp results

The same equipment can also be used to a very large extent using the present invention be used, in contrast to those cases where pulps of different types of mixed in different factories. An example of this is chemical preparation, the common Pressure vessel and the disc refiner are furthermore a common one according to the invention Sieving, dewatering equipment, bleaching and pulp drying system as well as the same chemical recovery system used

The present invention also relates to a suitable device for carrying out the method according to the invention. The apparatus shown schematically in Figures 2 and 3 comprises a Vertical pressure vessel, in the upper part of which an impregnation chamber provided with vertical transport screws is arranged, which is connected to a damping vessel via a dewatering screw conveyor is, whereby at the bottom of the pressure vessel a screw conveyor for transporting the material under Pressure is arranged from the bottom of the pressure vessel to a defibrator. The inventive The device is characterized in that the pressure vessel has a dewatering screw conveyor is connected to a vertical cooker, in the upper part one with vertical transport screws provided impregnation chamber is attached, the bottom with a draining screw conveyor is connected, which in turn is connected to a damping vessel.

The device according to the invention works in the following way:

After the wood has been chopped into chips and washed, it is fed to the device according to the invention, in two material streams A and B, as shown in FIG. 2 shown. The wood chip stream A is first fed to a steaming vessel 28, where the wood chips are treated with steam which is fed through the line 29, whereupon the wood chips are transported on by means of the screw conveyor 13 with simultaneous dewatering. The water squeezed out of the wood chips is withdrawn through line 31. The wood chips are introduced into the impregnation chamber 32 by means of the screw conveyor 30, into which impregnation chemicals are introduced through the line 33. The wood chips are carried through the impregnation or cooking liquid by means of two vertical screw conveyors 34. After the wood chips have been transported through and impregnated with the cooking liquid, they pass the upper edge 35 of the impregnation vessel and fall down into the digester 36. The placement of the impregnation vessel 32 and the two vertical transport screws 34 in the digester 36 is shown in FIG. 3, which shows a cross-section through the digester along the line III-III. Steam is supplied to digester 36 through a line 37. After the chippings have been digested or cooked to the desired extent, they are transferred from digester 36 to the common pressure vessel 38 transported by means of a screw conveyor 39. When passing through the screw conveyor 39 , a large part of the cooking liquor is pressed out of the softened wood chips. The pressed cooking waste liquor is removed through line 40. The wood chip flow A is mixed with the wood chip flow B in the common pressure vessel 38. Before it is mixed with the wood chips flow A, the wood chip flow B passes through a steaming vessel 41, into which steam is fed through the line 42, and is transported by means of a dewatering screw conveyor 43 to an impregnation chamber 44.The water squeezed out of the wood chips is passed through the line 45 discharged. The impregnation chamber 44 can contain either impregnation chemicals or just water. The required liquid is supplied through line 46. The wood chips are transported through the impregnation chamber 44 by means of two vertical screw conveyors 47, which have the characteristics shown in FIG. 3 shown are similar. The wood chips then pass the upper edge 48 of the impregnation chamber 44 and fall down into the common pressure vessel 38, in which they are mixed with the wood chip flow A. Steam is fed to the pressure vessel 38 through line 49. After the mixture of the wood chip streams A and B has been pressure and heat treated, it is conveyed to a defibering device by means of a screw conveyor 50. The mass obtained can then be fed to a cyclone for vapor separation, whereupon the mass is refined, if necessary, in a second stage and then sieved and bleached. The screw conveyors 30 and 43 are provided with sealing devices at those ends which are connected to the digester 36 or the pressure vessel 38, which prevent the steam from escaping. This is in FIG. 2 not shown.

Here / u 2 sheets of drawings

Claims (10)

Patent claims: 1. A process for the production of pulp from lignocellulose material in the yield range of 70-93% with improved quality properties, wherein at least part of the lignocellulose material is washed, steamed, impregnated with digestion chemicals and digested and defibrated thereon, characterized in that the lignocellulose material is divided into at least two different material flows are divided, of which a first material flow after washing, steaming and impregnation is broken down to a pulp yield of 65-92%, preferably 78-88%, and ^ in the second material flow is only washed, whereupon the two material flows directly without intermediate washing mixed and exposed in a common pressure vessel to heating to a temperature of 363-473 K, preferably 373-458 K, in such a way that a further partial delignification and softening of the lignin is achieved, whereupon the product obtained is mechanically defibrated. 2. The method according to claim 1, characterized in that the second stream of material is also at at a temperature of 363 - 383 K for a period of at least 5 minutes. 3. The method according to claims 1 and 2, characterized in that the second material flow is also impregnated with digestion chemicals. 4. Process according to claims 1 to 3, characterized in that the partial delignification in the common pressure vessel is carried out such that a final pulp yield of 60-88%, preferably 73-85%, in the first material stream and a pulp yield of 100-85%, preferably 96-90%, is obtained in the second material stream. 5. Process according to claims 1 to 4, characterized in that the heating time in the common pressure vessel at 1-20 minutes, preferably 2-10 minutes. 6. The method according to claims 1 to 5, characterized in that the digestion chemicals Sodium hydroxide and / or sulfur dioxide can be used. 7. The method according to claims 1 to 6, characterized in that excess impregnation liquid of the material flow is removed before the joint digestion. 8. The method according to claims 1 to 7, characterized in that the digestion of the first Material flow is carried out as vapor phase boiling. 9. The method according to claims 1 to 8, characterized in that the defibrated product also is refined and bleached. 10. Device for carrying out the method according to claims 1 to 9, comprising a vertical pressure vessel, in the upper part one with vertical transport screw provided impregnation chamber is arranged, which has a dewatering screw conveyor is connected to a damping vessel, being at the bottom of the pressure vessel a screw conveyor for transporting the material under pressure from the bottom of the Pressure vessel is arranged to a defibering device, characterized in that the Pressure vessel (38) via a dewatering screw conveyor (39) with a vertical digester (36) is connected, in the upper part of which is provided with a vertical screw conveyor (34) Impregnation chamber (32) is attached, the bottom of which with a draining screw conveyor (30) is connected, which in turn is connected to a damping vessel (38) The present invention relates to the production of improved high-yield pulp pulps of the semi-chemical, chemimechanical, thermomechanical and mechanical type and a device for Manufacture of such pulps. With the known technology it is possible to get out of Scandinavian Nade'holz contributes strongly to chemimechanical pulp pulp To produce pulp yields of about 85%. The mass obtained in this way has, however, been found to be very proved difficult to bleach. Furthermore, their fibers are very resistant to grinding, which is why it is it is difficult to improve the strength properties in papermaking by milling. That produced paper also gets a rough surface and is therefore less suitable for the Use as writing and printing paper. In addition, such a paper becomes low in opacity; H. high transparency. According to the known technique, the pulp yield increases > than 90% increased, then one mass is obtained consisting of several Is more suitable for paper production and which is also relatively easy to bleach is. However, the increased pulp yield deteriorates the strength to such an extent that the Cellulose pulp without the addition of stronger material for the production of writing and printing paper becomes unsuitable. For high-yield pulps made from hardwood, for pulp yields of ^ 90% obtained an easily bleachable, but extremely weak mass. With pulp yields of S 85% a strong pulp mass is obtained from hardwood, which is also less difficult to grind. Furthermore, such a mass is easily treated with lignin-retaining bleaches such as e.g. B. hydrogen peroxide, too bleaching. It is also known to mix pulps of the types mentioned above, i.e. H. where that The starting material is therefore made of hardwood or softwood. However, this has the disadvantage that the Both pulp pulps must be produced by different methods and the pulp on it before the Paper mix must be mixed, which is why this method is relatively uneconomical. To the Improving the product one has high yields also from mixtures of hardwood and Softwood made. Here, however, it has proven difficult to find sufficiently good properties in terms of strength and surface uniformity. Experiments 1 to 3 are explained below problems mentioned above.