CA1055754A - Method of liquid treating cellulose fibres and a device for carrying out the method - Google Patents
Method of liquid treating cellulose fibres and a device for carrying out the methodInfo
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- CA1055754A CA1055754A CA265,428A CA265428A CA1055754A CA 1055754 A CA1055754 A CA 1055754A CA 265428 A CA265428 A CA 265428A CA 1055754 A CA1055754 A CA 1055754A
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- pulp
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- pressure
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Abstract
ABSTRACT OF THE DISCLOSURE
A method and apparatus of treating cellulose fibres in a cellulose pulp with a concentration of 10-90% with a liquid is disclosed. The pulp is intermittently given elastic compression forces and the cellulose fibres are subjected to pressure shocks with a duration not exceeding 1 second and of such a magnitude that the pressure in the interior of the fibres is increased to a valve exceeding 0.2 atmospheres excess pressure. The fibres are allowed to expand between the pressure shocks without remaining deformation and the treatment is maintained until complete impreg-nation and/or exchange of liquid enclosed in the fibres has been accomplished.
A method and apparatus of treating cellulose fibres in a cellulose pulp with a concentration of 10-90% with a liquid is disclosed. The pulp is intermittently given elastic compression forces and the cellulose fibres are subjected to pressure shocks with a duration not exceeding 1 second and of such a magnitude that the pressure in the interior of the fibres is increased to a valve exceeding 0.2 atmospheres excess pressure. The fibres are allowed to expand between the pressure shocks without remaining deformation and the treatment is maintained until complete impreg-nation and/or exchange of liquid enclosed in the fibres has been accomplished.
Description
~S5754 This invention relates to a method of treating cellulose fi~res in a cellulose pulp with a liquid, and an apparatus for use in carrying out this method.
In different types of treatment of cellulose pulp, such as defibration, paper production, de-inking, bleaching, etherific-ation, and esteriication, it is of extremely great importance that the individual fibres take up a suficient amount of liquid for them to swell.
The term "cellulose pulp" is here intended to embrace chemical, semichemical and mechanical pulp as well as shredded paper waste.
- Fibre knots can occur when mechanical, semichemical and chemical pulp is dried and pressure dewatered to pulp concentra-tions above 15%, and the insolubility of these fibre knots is amplified during subsequent drying of the cellulose pulp. Pulp with fibre knots is less suitable for producing paper. This formation of fibre knots is caused to a large extent by the cavit-ies of the cellulose fibres containing air, hindering the entry of water or other liquid into the fibres.
A well-impregnated fibre contains adsorbed water, i.e.
water which has been taken up in the cellulose itself, and enclosed water, while a poorly impregnated fibre only contains a smaller amount of enclosed water. It is the adsorbed water which causes the cellulose fibre to swell and it is the enclosed water which is -pressed out of the fibres when these are subjected to pressure, for example in a pressure water extractor. If the fibres only contain a small amount of enclosed water or other liquid, they become strip-like during compression. Such flat fibres form ` fibre knots in the cellulose pulp, and on passage through drying ; 30 cylinders, for example in a papermaking machine, these knots are overdried and become horny.
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Knot formation also occurs in pressure water extraction and drying of well-impregnated pulps, due to the occurrence of cellulose with low density as is found in certain thin-walled springwood fibres.
When such a fibre is treated with a chemical li~uid, the pores are filled with the chemical liquid which subsequently pushes out the washing water during washing. When the water in such a fibre is pressed out of the fibre before drying, the fibre is flattened, thus causing knotting on subsequent drying.
An object of the method of the invention is therefore to provide a dispersal of these fibre knots and the bindings --occurring between the fibres, by causing all the fibres to reach ~ -a completely swollen condition.
Another problem arises in reactions such as de-inking, bleaching, etherification, and esterification, this being to prov- ~
ide such liquid supply to the individual fibres and uncovering of -them that the reaction chemicals are given a very high efficiency. -; It is therefore a further object of the method of the ; invention to provide separation of the fibres in the pulp and selectively to provide exchange of enclosed liquid.
According to the present invention there is provided . . .
a method of treating cellulose fibres in a cellulose pulp with a concentration of 10-90% with a liquid wherein the pulp is inter- - -mittently given elastic compression forces, comprising subjecting the cellulose fibres to pressure shocks with a duration not . .
- exceeding 1 second and of such a magnitude that the pressure in the interior of the fibres is increased to a value exceeding 0.2 atmospheres excess pressure, allowing the fibres to expan~ without remaining deformation, between the pressure shocks, and maintaining this treatment until substantially complete impregnation and/or exchange of liquid enclosed in the fibres has been accomplished.
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~055~S4 Thus the method subjects the cellulose fibres to pressure shocks of such magnitude and duration that the ~ibres are alternatingly compressed and expand without remaining de~ormation until complete impregnation and/or exchange of enclosed liquid has been achieved.
Such pressure shock treatment is not to be confused with known pressure shock treatment oE fibre suspensions, e.g.
in a rod mill according to United States patent specification
In different types of treatment of cellulose pulp, such as defibration, paper production, de-inking, bleaching, etherific-ation, and esteriication, it is of extremely great importance that the individual fibres take up a suficient amount of liquid for them to swell.
The term "cellulose pulp" is here intended to embrace chemical, semichemical and mechanical pulp as well as shredded paper waste.
- Fibre knots can occur when mechanical, semichemical and chemical pulp is dried and pressure dewatered to pulp concentra-tions above 15%, and the insolubility of these fibre knots is amplified during subsequent drying of the cellulose pulp. Pulp with fibre knots is less suitable for producing paper. This formation of fibre knots is caused to a large extent by the cavit-ies of the cellulose fibres containing air, hindering the entry of water or other liquid into the fibres.
A well-impregnated fibre contains adsorbed water, i.e.
water which has been taken up in the cellulose itself, and enclosed water, while a poorly impregnated fibre only contains a smaller amount of enclosed water. It is the adsorbed water which causes the cellulose fibre to swell and it is the enclosed water which is -pressed out of the fibres when these are subjected to pressure, for example in a pressure water extractor. If the fibres only contain a small amount of enclosed water or other liquid, they become strip-like during compression. Such flat fibres form ` fibre knots in the cellulose pulp, and on passage through drying ; 30 cylinders, for example in a papermaking machine, these knots are overdried and become horny.
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Knot formation also occurs in pressure water extraction and drying of well-impregnated pulps, due to the occurrence of cellulose with low density as is found in certain thin-walled springwood fibres.
When such a fibre is treated with a chemical li~uid, the pores are filled with the chemical liquid which subsequently pushes out the washing water during washing. When the water in such a fibre is pressed out of the fibre before drying, the fibre is flattened, thus causing knotting on subsequent drying.
An object of the method of the invention is therefore to provide a dispersal of these fibre knots and the bindings --occurring between the fibres, by causing all the fibres to reach ~ -a completely swollen condition.
Another problem arises in reactions such as de-inking, bleaching, etherification, and esterification, this being to prov- ~
ide such liquid supply to the individual fibres and uncovering of -them that the reaction chemicals are given a very high efficiency. -; It is therefore a further object of the method of the ; invention to provide separation of the fibres in the pulp and selectively to provide exchange of enclosed liquid.
According to the present invention there is provided . . .
a method of treating cellulose fibres in a cellulose pulp with a concentration of 10-90% with a liquid wherein the pulp is inter- - -mittently given elastic compression forces, comprising subjecting the cellulose fibres to pressure shocks with a duration not . .
- exceeding 1 second and of such a magnitude that the pressure in the interior of the fibres is increased to a value exceeding 0.2 atmospheres excess pressure, allowing the fibres to expan~ without remaining deformation, between the pressure shocks, and maintaining this treatment until substantially complete impregnation and/or exchange of liquid enclosed in the fibres has been accomplished.
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~055~S4 Thus the method subjects the cellulose fibres to pressure shocks of such magnitude and duration that the ~ibres are alternatingly compressed and expand without remaining de~ormation until complete impregnation and/or exchange of enclosed liquid has been achieved.
Such pressure shock treatment is not to be confused with known pressure shock treatment oE fibre suspensions, e.g.
in a rod mill according to United States patent specification
2,116,511. In the apparatus described therein, fibres in suspen-sion are pressed for long periods against a wall of soft rubber to amplify the rubbing effect between the fibres, but the fibres are not compressed to any measurable extent and the necessary interior excess pressure in the fibres is not obtained. In contrast to this, the pressure shock periods, the duration o which is preferably only some tenths of a second but can extend up to about 1 second depending on the type of pulp employed, of the method of the invention are extremely short.
From Swedish patent specification 316,362 it is further known to subject a fibre suspension to pressure shocks by reducing the liquid volume for the purpose of increasing rubbing between ;
the individual fibres in the suspension, but the effects of the invention, namely impregnation and/or exchange of liquid in the interior of the fibres, are not obtained in this case either because a prerequisite for such exchange or impregnation is a high -pulp concentration, i.e. a concentration of the order of magnitude 10-90~, preferably exceeding 15~. -Treatment according to the invention allows poorly impregnated fibres, for example, to receive such good impregnation that they can be worked in a beating machine to produce high quality paper. Poorly impregnated fibres become strip-like when they are subjected to hi~h pressure in a worm press or a disc ~3~
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-`` lOS5754 refiner, and they make a rolling movement which causes the flattened fibres to entangle themselves with each other and form fibre knots at concentrations of the order of magnitude of 15%. Even though these fibres are unimpregnated to a large extent, a small amount o~ hemicellulose is released, which during subsequent drying causes the ~ibre knots to be united very closely together by the formation of hydrogen bonds. These ibre knots cannot be dispersed with conventional pulp dispersing methods.
The invention enables dispersion of such ~ibre knots by means o the short heavy pressure shocks in combination with a small supply of liquid. The favourable effect according to the invention would appear to be caused by the fibres being flattened during the `
pressure shock and that during the subsequent expansion they suck in liquid, preferably alkaline, into the cavities in the fibres, the liquid there being bonded to the OH groups o~ the cellulose.
The fibre thus begins to swell and straighten out. Together with the high interior fibre pressure, this causes the remaining hydrogen bonds between the ~ibres to rupture. A knot~free and well-impregnated swollen fibre is obtained, which gives a paper witll very high quality in subsequent beating treatment.
The method of the invention and consequent pump effect, indicated above, between the fibre and liquid can be advantag-eously employed for de-inking.
The invention also prQvides apparatus for use in carrying out the method recited above, comprising a p~oessin~ v~ssel includ - ing a wall having spaced apart therein an inlet and an outlet for the cellulose pulp, and a driven planetary mixing paddle accommodated in the vessel and arranged to move towards and away from the wall repeatedly to throw a part of the cellulose pulp against the wall.
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The invention will be further understood from the following description by way of example with re~erence to the accompanying drawings, in which:-Fig. 1 shows a flow dia~ram of a plant selected as anexample of the application of the invention, for de-inking printing paper waste;
Fig. 2 shows a modi~ication of the plant according to Fig. l;
Fig. 3 shows a flow diagram of a plant for flake-drying of cellulose pulp, embodying the invention;
Fig. 4 shows a flow diagram of a plant for peroxide bleaching, oxygen gas bleaching or pulp colouring, embodying the invention; and Figs. 5 and 6 show a planetary mixer, used in the plant to which Figs. 1 to 4 relate, arranged to treat cellulose pulp according to the invention.
A plant is schematically illustrated in Fig. 1 for de-inking newspaper waste. The waste is fed from a shredder 1 to an apparatus 2, in which the cellulose pulp, to which water has - -been added so that a concentration of at least 30% dry content has been obtained, is defibrated by the fibres being subjected to pressure shocks according to the invention. The treatment takes place with conventional de-inking chemicals and chemicals to keep ~ -the liberated ink suspended. The apparatus 2, consisting for example of a planetary mixer according to Figs. 5 and 6, provides the pressure shock treatment as described in conjunction with ;-Figs. 5 and 6.
The treated pulp is transferred from said appara~us 2 to an apparatus 3, e.g. another planetary mixer according to Figs. 5 and 6, or a conventional disintegrator, in which the pulp ts diluted to a dry content of about 4%.
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The diluted pulp is transferred from apparatus 3 to a screw water extractor 4, which presses out so much o~ the ink-containing water that the dry content of the pulp rises to about 35%.
The dewatered pulp is transferred to an apparatus 5 of the same kind as apparatus 2, and the pulp isance again treated in the apparatus 5 according to the present invention with de-inking chemicals and suspending agent, whereafter it is transferred -~to a corresponding apparatus or a disintegrator 6, in which it is once again diluted with water to about 4% dry content.
The pulp is transferred from the apparatus 6 to a fur-ther screw water extractor 7, which presses out so much water that the dry content of the pulp rises to 35%. The pulp, now free from ink, is finally diluted in a disintegrator 8 to about 4% dry content and is taken into paper production.
The water coming from the screw water extractors 4 and 7, blackened by ink, is taken to a microscreen 9 which separates the accompanying cellulose fibres, which are returned to the apparatus 2. The printing ink suspension liberated from fibres is treated, for example in a flotation plant (not shown), in which the ink is removed together with humus and heavy metals present in the raw water.
The embodiment shown in Fig. 2 differs from the .; .
embodiment described above in that the printing paper waste from -the shredder 1 is transferred to a drum 10, provided with feed ~-screw and bumping rods, where it is p~ovided with water and de-inking and suspending agents.
From tllis drum 10 the pulp is transferred to the screw water extractor 4, whereafter the de-inking process continues ~as ln the embodiment of Flg. 1.
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- 1~3557~4 In Fig. 3 there is shown a plant for preventing fibre knotting when flake-drying cellulose.
Cellulose pulp with a dry content of about 4% is taken from a storage container to a conventional water extraction app-aratus 11, e.g. a rotating vacuum filter, where the dry content is brought up to about 30~. From the apparatus 11 the cellulose pulp is taken to an apparatus 12, e.g. a planetary mixer according to Figs. 5 and 6, for treatment according to the present invention for homogenization. This homogenization can suitably be acceler~
ated by adding sufficient sodium peroxide so that the pH of the pulp is brought up to about 8.
After this homogenization the pulp is taken to a conventional screw water extractor 13, in which its dry content `
is increased to about 45%, whereafter it is taken to a still fur-ther apparatus 14 according to the present invention, wherein it is worked to disperse the knots formed in the screw water extrac~
tor. It has been found advantageous to add a small amount of sodium peroxide here as well.
From the apparatus 14 the pulp is taken to a convention-al flake drier 15. It has been found that the thus-treated pulp is practically free from fibre knots after drying, whereas the pulp supplied to the same flake drier 15 from the storage container directly via the water extracting apparatuses 11 and 1~ has so many fibre knots that it was practically unusable for manufacturing paper. ~ -Fig. 4 illustrates a plant for peroxide bleaching, oxygen gas bleaching, paper pulp colouring and printing paper ` decolouring.
Pulp with a dry content of about 4% from a pulp contain~
` 30 er (not shown~ is fed to a conventional water extraction apparatus : ,' . ~
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': ,'' ' :' ~SS754 16, e.g. a rotating vacuum filter, where its dry content is increased to 15-20%. The pulp is taken ~rom the appara us 16 to a conventional screw water extractor 17, where its dry content is increased to about 35%. From the water extractor 17 the pulp is taken by a screw conveyor 18, wherein it is suitably provided with colouring matter, de-inking chemica]s or bleaching reagents, to an apparatus 19 according to the present invention. After treatment in the apparatus 19, the now ready~treated pulp is taken to a papermaking machine (not shown), possibly via a pulp container.
An embodiment of an apparatus for providing the neces-sary pressure shock treatment of the cellulose fibres is illustrated in a simplified form in Figs. 5 and 6.
A container 20~ made as an upright cylinder with a flat bottom 22, is provided with a connection for a feed screw 21 close to its bottom 22 and a connection for a discharge screw 23 close to its top. The container 20 is provided with at least three pivot-ally mounted supporting wheels 24, and is accommodated inside a cylindrical wall 25 with a greater inside diameter than the outside diameter of the container 20. The wall 25 is rigidly connected with a substructure, e.g. a floor 26, and lS made from a rigid and very stable material, e.g. reinforced concrete. On its inside it is provided with buffers 27, made from elastic material such as -~
rubber, which are made as rings accommodated in recesses in the wall 25. The buffers 27 are arranged to keep the container 20 centrally within the wall 25.
A structure 28, placed adjacent the wall ~5, is provided with means for ra:ising and lowerihg a planetary mixer paddle 29 ~-~
with its driving arrangement 30, said paddle 29 being arranged to strike the inner wall of the container 20 during its planetary movement so that the conta~ner during this action, counteracted by ~ - : .
the buffers 27, is given a rotating oscillation.
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~55754 Every time a paddle edge strikes or at least comes very close to the inner wall of the container 20, a part of the pulp, and thereby the cellulose fibres, is compressed between the wall and the paddle edge, and as soon as the pressure shock generated thereby ceases, the fibres elastically return to an expanded condition, liquid being partly adsorbed and partly enclosed in unswollen fibres. The take-up of liquid presumably takes place through deformation during compression by the pressure shock and by suction during expansion, but which factor is the deciding one is difficult to say.
During the pressure shock, heat, inter alia, is formed, which contributes to rupturing the hydrogen bonds between the fibres and thereby achieving defibration and dispersion of fibre knots. Shearing forces acting between the cellulose fibres during the pressure shock also contribute to causing defibration and dis-persion of the fibre knots. As the fibres are subjected to the pressure shocks, swelling is completed and the enclosed liquid is "pumped" out of the cavities and is replaced by new li~uid, which causes the good effect in de-inking, bleaching, colouring etc.
The pressure shocks are so short-lived that the fibres can return to an expanded state after compression. If the pres-sure shocks are made too long and heavy, there is the risk of exploding the cell walls and causing permanent deformation of the fibres. This applies essentially to the originally poorly impreg-nated fibres.
It has been found advantageous to provide either the paddle 29 or the container 20, or both, with a covering of elastic -~
material. It has also been found advantageous to provide the shaft i 31 carrying the paddle 29 with means for imparting to the pulp in the container a vertical circulatory movement, said means being for example formed as a verticai screw 32 or as propellers mounted ~;
on the shaft 31.
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The apparatus described above for providing pressure shocks can be replaced with other suitable apparatus, e.g. rollers with a mutual reciprocatory movement, ~hrough which the pulp is passed. The pressure shocks can also be achieved by enclosing the pulp in a container wherein the pressure can be varied. A number of trials which have been carried out with pressure shock treatment of cellulose pulp in comparison with conventional treatment are accounted for in the following.
Trial 1 A flake-dried semichemical beech paper pulp in the form of bales was provided with water to 4% pulp concentration and beaten in a hollander beater. The fibre suspension obtained gave a very poor quality paper due to the abundant presence of fibre knots and poor liquid impregnation of the fibres. The paper strength was also of poor standard.
The beech cellulose fibres contain a high percentage of cellulose with low density. When drying of this cellulose pulp is preceded by a heavy dewatering pressure, for example in a screw water extractor, these fibres are flattened and form fibre knots 20 which are extremely difficult to disperse.
For some reason unknown up to now, the flattened fibres -appear not to be able to adsorb water and only contain insignifi-cant amounts of enclosed water, which is the main reason for a paper, manufactured from cellulose with a high content of such ` fibres, being so sub-standard.
On the other hand, a well-impregnated fibre containing -both adsorbed and enclosed water gives an impeccable paper.
Trial 2 The s~ne paper pulp as in Trail 1 was provided with 30 water to 6% pulp concentration and was beaten and defibrated in an . . ' .
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l(~S57~4 ordinary beater. As was expected, the suspension obtained gave a paper very rich in knots with the same poor strenyth ~ualities as in Trial 1.
Trial 3 The same paper pulp as in Trials 1 and 2 was subjected to combined pressure shock and mixing treatment according to the invention during simultaneous liquid feed up to about 30~ pulp concentration. After dilution the paper pulp obtained gave a first~class knot~free paper with good strength qualities.
When the cellulose fibre is thrashed against the yield-ing container wall so much heat energy is generated locally and for such a short time that the hydrogen bonds keeping the fibres and fibre knots together are ruptured.
After the cellulose fibre has been repeatedly subjected to such yielding and shearing pressure shocks, this hydrogen bonding has been completely eliminated. As soon as contact is released between the mixing and defibrating means, the cellulose `;
fibre and the yielding container wall, the fibre begins to straigh-ten itself out both with regard to length and width. Consequently a suction action occurs inside the fibres. Supplied liquid is then sucked into the cavities of the fibres where it is chemically bound to the OH groups of the cellulose.
The liquid thus adsorbed in the cellulose can naturally not be repressed out of the fibre at the next contact between the container wall, fibre and defibrating/mixing means. On the other hand, however, at every such contact the liquid enclosed in the fibre will be pressed out, whereafter new liquid is sucked in so that from the intèrior it can react with and swell the cellulose of the fibre. Through this swelling together with the homogeniza_ tion of the cellulose with low density which takes place in conjun-ction with the shearing pressure of the mixing means against the : - .. .
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~oss754 container wall, the cellulose fibre can be given the strength characteristics desired for the paper formation during ater~
treatment in the beating means.
Trial 4 A flake~dried, unbleached sulphite pulp in compressed baled form was provided with water t:o 4% pulp concentration and beaten in a hollander. The fibre suspension obtained gave a very poor paper with low strength characteristics due to the abundant presence of fibre knots and unsatisfactory liquid impregnation of the fibres.
Trials 5-6 . ~.
The same paper pulp as in Trial 4 was treated in the same way as the semichemical pulp according to Trials 2-3, these trials with the unbleached sulphite pulp giving corresponding final results as the Trials 2-3 gave with the semichemical pulp.
Trial 7 Certain qualities of certain paper colourings were added to a bleached sulphite pulp with a 4% pulp concentration, and the colourings were mixed with the pulp in a laboratory pulper, whereafter the pulp solution was diluted to about 0.5% pulp concentration for the formation of she~ts. The water departing ~ -on sheet formation was heavily coloured.
Trial 8 The same sulphite pulp at about 30% pulp concentration was provided with the same amount of the same paper colourings as in Trial 7 and was mixed in an apparatus according to Figures 5 and 6. Thereafter the pulp was diluted to about 0.5% pulp con-centration for the formation of eheets. The water departing on sheet formation was slightly coloured.
The reason for this is that in pulp concentrations over ~ 30% there is practically no liquid around the fibres, it being : ', ..
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~05575~a instead adsorbed in the cellulose and enclosed in the caVities in the cellulose fibre. If paper colourings are added to such a cellulose pulp while it is treated according to the invention, the colour will be partly "pumped" into the flbre and partly dispersed in the swollen cellulose, whereby the amount o~ colour in the water departing from sheet formation will be very small.
Trials show that pulp concentrations up to 90% can be used.
Trial 9 Mechanical wood pulp was provided with ~ater in a mix-ing hollander to a pulp concentration of about 4%, whereafter it ~'was provided with 3% peroxide solution in the necessary amount for bleaching. The pulp was ready-bleached after six hours, and had a whiteness of 70% G.E.
Trial 10 The same mechanical pulp as in Trial 9 was provided with water in a hydrapulper to 10-12% pulp concentration, where-after it was supplied with the same amount of 3% peroxide solu- -tion as in Trial 9. After 3 hours the pulp was ready-bleached and had a whiteness of about 70% G.E.
Trial 11 ~ ....
The same mechanical pulp as in Trials 9 and 10 was provided with water in a structure according to the invention and to a pulp concentration of 30~35%, whereafter it was supplied with the same amount of 3% peroxide solution. After 45 minutes the pulp was ready-bleached to a whiteness of 72% G.E. ,~
Through the treatment according to the invention the peroxide solution is quickly pumped into the cavlties of the fibres, which together with the high concentration on reduced water content is the reason for a somewhat higher whlteness be-ing obtained in Trial 11 than in Trials 9 and 10, and for the ~13~
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increased bleaching speed.
The higher pulp concentration, which can reach 90%, also results in smaller apparatus volume, whereby plant costs will be smaller.
Trial 12 A sulphite pulp was provided with water to a pùlp con~
centration of between 30 and 35%, whereafter during treatment ac~
cording to the invention it was simultaneously treated with ch~
lorine gas. After about 5 minutes the chlorine bleaching was completed. In the conventional methods, chlorine bleaching is carried out at a pulp concentration of about 4%, It then takes between 60 and 90 minutes before bleaching is terminated, It has been found that chlorine is very quickly in~
corporated by substitution in the li~nin~ At a pH of 2~3 and a -pulp concentration of about 4%, which is most usual in practical operation, the substitution reaction is completed after between 60 and 90 minutes and terminates thereafter completely independent-ly of how great the chlorine excess is and whether there is lig~
nin left to chlorinate. -At a lower pH the chlorine substitution can be termina~
ted after 5-10 minutes. It has however been found th~t it is not possible to increase the reaction speed by adding more chlo-rine to the pulp suspension than what has been determined by lab~
oratory experiments for the respective pulp qualities, as an ad~
dition of chlorine above the a unt determined in the laboratory ; does not react with the lignin, which will remain in the pulp after the chlorine treatment, An increased reaction time must thus be achie~ed in .:
some othPr way, preferably by reducing the amount of water in the cellulose so that the pulp concentration is increased above -:
: . ..
~55754 30%, which to advantage can be carried out accoxdin~ to the invention.
During recent years, a new method has been worked out which enables recovery of bleaching li~uors, namely the oxy~
gen gas bleaching method~ In this bleaching method it is neces~
sary to work with pulp concentrations above 30~ to prevent a heavy reduction of the strength qualities of the cellulose, This is facilitated by simultaneously defibrating and alkali treating the cellulose with pressure shocks according to the invention before oxygen gas bleaching. Other suitable bleaching agents are, for example, chlorine dioxide, hypochlorite or hydrosulphite. -Trial 13 Printing paper waste in an undefibrated ~orm was treated in a mixing drum with an aqueous solution of de~inking chemicals, whereb~ the major part o~ the printing ink was dis~
solved, and the liquid was removed from the paper waste in a sub~
sequent screw water extractor.
Thereafter the printing paper waste was defibrated according to the invention while simultaneously adding de-inking chemicals plus a dirt absorbing agent, After dilution with sub-; sequent screw water extraction the pulp from the printing paper waste had regained the whiteness of 62% G.E. of the original .
pulps (unbleached sulphite and mechanical pulpl. In a subsequent peroxide bleaching according to the invention whiteness of bet.
ween 70 and 74% G.E. were obtained.
` 3ust de~inking of the printing paper waste according to conventional methods gives a whiteness of between 53 and 56%
C.E. With a subsequent peroxlde ble~ching a whiteness of 57~60%
~ G.E. is obtained. m us, with these conventional methods the - 30 whiteness of the original pulps is not obtained. The reason is i . . ' .. . .
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that the liberated printing ink pushe~ into the cavities ~n the fibres, from which it is not possible to remove ~t other than by the fibre pumping technique according to the in~ention.
In the conventional de~-inking methods, printin~
paper waste is defibrated in a hydrapulper at a pulp concentra-tion of about 10% while simultaneousl~ adding de~inking chemi~
cals and preferably an agent for lowering surface tension, There~
after the precipitated printing ink is removed from the pulp sus~
pension by a flotation process. To do this, dilution to a pulp concentration of about 0.1% is carried out, said concentration rising to a few percent in the subsequent filter ~ashing of the de-inked pulp. Large amounts of water are thus employed to re~
move the dissolved ink from the paper fibres. It has therefore not been economically possible to remove ink from the e~luent in flotation an~ washing filter plants, and these pollutants have - therefore been allowed to accompany the effluent into the recip~
ient water.
As ~ result of the high pulp concentrations at which the de-inking plant according to the invention works, i~e. up to a concentration of 90%, it becomes possible to remove nearly all the printing ink from the de~inking plant effluent, whereby it becomes possible and economically adv~ntageous to reflux the major part of this water to the de~inking process.
This reuse also results in unused chemicals being re~
turned to the process, whereby costs are further reduced.
By this reuse of the effluent there will be a consid- -erable reduction of the a unt of fresh water supplied and at the same time a considerable reduction in the cost of purifying it from humus and heavy metals.
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1~557~4 From the above trials it is apparent that the pres-sure treatment according to the invention results in a substan-tial improvement of the convention,al methods.
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From Swedish patent specification 316,362 it is further known to subject a fibre suspension to pressure shocks by reducing the liquid volume for the purpose of increasing rubbing between ;
the individual fibres in the suspension, but the effects of the invention, namely impregnation and/or exchange of liquid in the interior of the fibres, are not obtained in this case either because a prerequisite for such exchange or impregnation is a high -pulp concentration, i.e. a concentration of the order of magnitude 10-90~, preferably exceeding 15~. -Treatment according to the invention allows poorly impregnated fibres, for example, to receive such good impregnation that they can be worked in a beating machine to produce high quality paper. Poorly impregnated fibres become strip-like when they are subjected to hi~h pressure in a worm press or a disc ~3~
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.... . . . . .. . . . . . . .. . .
-`` lOS5754 refiner, and they make a rolling movement which causes the flattened fibres to entangle themselves with each other and form fibre knots at concentrations of the order of magnitude of 15%. Even though these fibres are unimpregnated to a large extent, a small amount o~ hemicellulose is released, which during subsequent drying causes the ~ibre knots to be united very closely together by the formation of hydrogen bonds. These ibre knots cannot be dispersed with conventional pulp dispersing methods.
The invention enables dispersion of such ~ibre knots by means o the short heavy pressure shocks in combination with a small supply of liquid. The favourable effect according to the invention would appear to be caused by the fibres being flattened during the `
pressure shock and that during the subsequent expansion they suck in liquid, preferably alkaline, into the cavities in the fibres, the liquid there being bonded to the OH groups o~ the cellulose.
The fibre thus begins to swell and straighten out. Together with the high interior fibre pressure, this causes the remaining hydrogen bonds between the ~ibres to rupture. A knot~free and well-impregnated swollen fibre is obtained, which gives a paper witll very high quality in subsequent beating treatment.
The method of the invention and consequent pump effect, indicated above, between the fibre and liquid can be advantag-eously employed for de-inking.
The invention also prQvides apparatus for use in carrying out the method recited above, comprising a p~oessin~ v~ssel includ - ing a wall having spaced apart therein an inlet and an outlet for the cellulose pulp, and a driven planetary mixing paddle accommodated in the vessel and arranged to move towards and away from the wall repeatedly to throw a part of the cellulose pulp against the wall.
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The invention will be further understood from the following description by way of example with re~erence to the accompanying drawings, in which:-Fig. 1 shows a flow dia~ram of a plant selected as anexample of the application of the invention, for de-inking printing paper waste;
Fig. 2 shows a modi~ication of the plant according to Fig. l;
Fig. 3 shows a flow diagram of a plant for flake-drying of cellulose pulp, embodying the invention;
Fig. 4 shows a flow diagram of a plant for peroxide bleaching, oxygen gas bleaching or pulp colouring, embodying the invention; and Figs. 5 and 6 show a planetary mixer, used in the plant to which Figs. 1 to 4 relate, arranged to treat cellulose pulp according to the invention.
A plant is schematically illustrated in Fig. 1 for de-inking newspaper waste. The waste is fed from a shredder 1 to an apparatus 2, in which the cellulose pulp, to which water has - -been added so that a concentration of at least 30% dry content has been obtained, is defibrated by the fibres being subjected to pressure shocks according to the invention. The treatment takes place with conventional de-inking chemicals and chemicals to keep ~ -the liberated ink suspended. The apparatus 2, consisting for example of a planetary mixer according to Figs. 5 and 6, provides the pressure shock treatment as described in conjunction with ;-Figs. 5 and 6.
The treated pulp is transferred from said appara~us 2 to an apparatus 3, e.g. another planetary mixer according to Figs. 5 and 6, or a conventional disintegrator, in which the pulp ts diluted to a dry content of about 4%.
- , ~-.; .' ', lOS~75~L
The diluted pulp is transferred from apparatus 3 to a screw water extractor 4, which presses out so much o~ the ink-containing water that the dry content of the pulp rises to about 35%.
The dewatered pulp is transferred to an apparatus 5 of the same kind as apparatus 2, and the pulp isance again treated in the apparatus 5 according to the present invention with de-inking chemicals and suspending agent, whereafter it is transferred -~to a corresponding apparatus or a disintegrator 6, in which it is once again diluted with water to about 4% dry content.
The pulp is transferred from the apparatus 6 to a fur-ther screw water extractor 7, which presses out so much water that the dry content of the pulp rises to 35%. The pulp, now free from ink, is finally diluted in a disintegrator 8 to about 4% dry content and is taken into paper production.
The water coming from the screw water extractors 4 and 7, blackened by ink, is taken to a microscreen 9 which separates the accompanying cellulose fibres, which are returned to the apparatus 2. The printing ink suspension liberated from fibres is treated, for example in a flotation plant (not shown), in which the ink is removed together with humus and heavy metals present in the raw water.
The embodiment shown in Fig. 2 differs from the .; .
embodiment described above in that the printing paper waste from -the shredder 1 is transferred to a drum 10, provided with feed ~-screw and bumping rods, where it is p~ovided with water and de-inking and suspending agents.
From tllis drum 10 the pulp is transferred to the screw water extractor 4, whereafter the de-inking process continues ~as ln the embodiment of Flg. 1.
..
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- 1~3557~4 In Fig. 3 there is shown a plant for preventing fibre knotting when flake-drying cellulose.
Cellulose pulp with a dry content of about 4% is taken from a storage container to a conventional water extraction app-aratus 11, e.g. a rotating vacuum filter, where the dry content is brought up to about 30~. From the apparatus 11 the cellulose pulp is taken to an apparatus 12, e.g. a planetary mixer according to Figs. 5 and 6, for treatment according to the present invention for homogenization. This homogenization can suitably be acceler~
ated by adding sufficient sodium peroxide so that the pH of the pulp is brought up to about 8.
After this homogenization the pulp is taken to a conventional screw water extractor 13, in which its dry content `
is increased to about 45%, whereafter it is taken to a still fur-ther apparatus 14 according to the present invention, wherein it is worked to disperse the knots formed in the screw water extrac~
tor. It has been found advantageous to add a small amount of sodium peroxide here as well.
From the apparatus 14 the pulp is taken to a convention-al flake drier 15. It has been found that the thus-treated pulp is practically free from fibre knots after drying, whereas the pulp supplied to the same flake drier 15 from the storage container directly via the water extracting apparatuses 11 and 1~ has so many fibre knots that it was practically unusable for manufacturing paper. ~ -Fig. 4 illustrates a plant for peroxide bleaching, oxygen gas bleaching, paper pulp colouring and printing paper ` decolouring.
Pulp with a dry content of about 4% from a pulp contain~
` 30 er (not shown~ is fed to a conventional water extraction apparatus : ,' . ~
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': ,'' ' :' ~SS754 16, e.g. a rotating vacuum filter, where its dry content is increased to 15-20%. The pulp is taken ~rom the appara us 16 to a conventional screw water extractor 17, where its dry content is increased to about 35%. From the water extractor 17 the pulp is taken by a screw conveyor 18, wherein it is suitably provided with colouring matter, de-inking chemica]s or bleaching reagents, to an apparatus 19 according to the present invention. After treatment in the apparatus 19, the now ready~treated pulp is taken to a papermaking machine (not shown), possibly via a pulp container.
An embodiment of an apparatus for providing the neces-sary pressure shock treatment of the cellulose fibres is illustrated in a simplified form in Figs. 5 and 6.
A container 20~ made as an upright cylinder with a flat bottom 22, is provided with a connection for a feed screw 21 close to its bottom 22 and a connection for a discharge screw 23 close to its top. The container 20 is provided with at least three pivot-ally mounted supporting wheels 24, and is accommodated inside a cylindrical wall 25 with a greater inside diameter than the outside diameter of the container 20. The wall 25 is rigidly connected with a substructure, e.g. a floor 26, and lS made from a rigid and very stable material, e.g. reinforced concrete. On its inside it is provided with buffers 27, made from elastic material such as -~
rubber, which are made as rings accommodated in recesses in the wall 25. The buffers 27 are arranged to keep the container 20 centrally within the wall 25.
A structure 28, placed adjacent the wall ~5, is provided with means for ra:ising and lowerihg a planetary mixer paddle 29 ~-~
with its driving arrangement 30, said paddle 29 being arranged to strike the inner wall of the container 20 during its planetary movement so that the conta~ner during this action, counteracted by ~ - : .
the buffers 27, is given a rotating oscillation.
-8~
~ ' ' ' .. . ... . .. .... .. .. ..
~55754 Every time a paddle edge strikes or at least comes very close to the inner wall of the container 20, a part of the pulp, and thereby the cellulose fibres, is compressed between the wall and the paddle edge, and as soon as the pressure shock generated thereby ceases, the fibres elastically return to an expanded condition, liquid being partly adsorbed and partly enclosed in unswollen fibres. The take-up of liquid presumably takes place through deformation during compression by the pressure shock and by suction during expansion, but which factor is the deciding one is difficult to say.
During the pressure shock, heat, inter alia, is formed, which contributes to rupturing the hydrogen bonds between the fibres and thereby achieving defibration and dispersion of fibre knots. Shearing forces acting between the cellulose fibres during the pressure shock also contribute to causing defibration and dis-persion of the fibre knots. As the fibres are subjected to the pressure shocks, swelling is completed and the enclosed liquid is "pumped" out of the cavities and is replaced by new li~uid, which causes the good effect in de-inking, bleaching, colouring etc.
The pressure shocks are so short-lived that the fibres can return to an expanded state after compression. If the pres-sure shocks are made too long and heavy, there is the risk of exploding the cell walls and causing permanent deformation of the fibres. This applies essentially to the originally poorly impreg-nated fibres.
It has been found advantageous to provide either the paddle 29 or the container 20, or both, with a covering of elastic -~
material. It has also been found advantageous to provide the shaft i 31 carrying the paddle 29 with means for imparting to the pulp in the container a vertical circulatory movement, said means being for example formed as a verticai screw 32 or as propellers mounted ~;
on the shaft 31.
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The apparatus described above for providing pressure shocks can be replaced with other suitable apparatus, e.g. rollers with a mutual reciprocatory movement, ~hrough which the pulp is passed. The pressure shocks can also be achieved by enclosing the pulp in a container wherein the pressure can be varied. A number of trials which have been carried out with pressure shock treatment of cellulose pulp in comparison with conventional treatment are accounted for in the following.
Trial 1 A flake-dried semichemical beech paper pulp in the form of bales was provided with water to 4% pulp concentration and beaten in a hollander beater. The fibre suspension obtained gave a very poor quality paper due to the abundant presence of fibre knots and poor liquid impregnation of the fibres. The paper strength was also of poor standard.
The beech cellulose fibres contain a high percentage of cellulose with low density. When drying of this cellulose pulp is preceded by a heavy dewatering pressure, for example in a screw water extractor, these fibres are flattened and form fibre knots 20 which are extremely difficult to disperse.
For some reason unknown up to now, the flattened fibres -appear not to be able to adsorb water and only contain insignifi-cant amounts of enclosed water, which is the main reason for a paper, manufactured from cellulose with a high content of such ` fibres, being so sub-standard.
On the other hand, a well-impregnated fibre containing -both adsorbed and enclosed water gives an impeccable paper.
Trial 2 The s~ne paper pulp as in Trail 1 was provided with 30 water to 6% pulp concentration and was beaten and defibrated in an . . ' .
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l(~S57~4 ordinary beater. As was expected, the suspension obtained gave a paper very rich in knots with the same poor strenyth ~ualities as in Trial 1.
Trial 3 The same paper pulp as in Trials 1 and 2 was subjected to combined pressure shock and mixing treatment according to the invention during simultaneous liquid feed up to about 30~ pulp concentration. After dilution the paper pulp obtained gave a first~class knot~free paper with good strength qualities.
When the cellulose fibre is thrashed against the yield-ing container wall so much heat energy is generated locally and for such a short time that the hydrogen bonds keeping the fibres and fibre knots together are ruptured.
After the cellulose fibre has been repeatedly subjected to such yielding and shearing pressure shocks, this hydrogen bonding has been completely eliminated. As soon as contact is released between the mixing and defibrating means, the cellulose `;
fibre and the yielding container wall, the fibre begins to straigh-ten itself out both with regard to length and width. Consequently a suction action occurs inside the fibres. Supplied liquid is then sucked into the cavities of the fibres where it is chemically bound to the OH groups of the cellulose.
The liquid thus adsorbed in the cellulose can naturally not be repressed out of the fibre at the next contact between the container wall, fibre and defibrating/mixing means. On the other hand, however, at every such contact the liquid enclosed in the fibre will be pressed out, whereafter new liquid is sucked in so that from the intèrior it can react with and swell the cellulose of the fibre. Through this swelling together with the homogeniza_ tion of the cellulose with low density which takes place in conjun-ction with the shearing pressure of the mixing means against the : - .. .
... .
~oss754 container wall, the cellulose fibre can be given the strength characteristics desired for the paper formation during ater~
treatment in the beating means.
Trial 4 A flake~dried, unbleached sulphite pulp in compressed baled form was provided with water t:o 4% pulp concentration and beaten in a hollander. The fibre suspension obtained gave a very poor paper with low strength characteristics due to the abundant presence of fibre knots and unsatisfactory liquid impregnation of the fibres.
Trials 5-6 . ~.
The same paper pulp as in Trial 4 was treated in the same way as the semichemical pulp according to Trials 2-3, these trials with the unbleached sulphite pulp giving corresponding final results as the Trials 2-3 gave with the semichemical pulp.
Trial 7 Certain qualities of certain paper colourings were added to a bleached sulphite pulp with a 4% pulp concentration, and the colourings were mixed with the pulp in a laboratory pulper, whereafter the pulp solution was diluted to about 0.5% pulp concentration for the formation of she~ts. The water departing ~ -on sheet formation was heavily coloured.
Trial 8 The same sulphite pulp at about 30% pulp concentration was provided with the same amount of the same paper colourings as in Trial 7 and was mixed in an apparatus according to Figures 5 and 6. Thereafter the pulp was diluted to about 0.5% pulp con-centration for the formation of eheets. The water departing on sheet formation was slightly coloured.
The reason for this is that in pulp concentrations over ~ 30% there is practically no liquid around the fibres, it being : ', ..
~12~
~05575~a instead adsorbed in the cellulose and enclosed in the caVities in the cellulose fibre. If paper colourings are added to such a cellulose pulp while it is treated according to the invention, the colour will be partly "pumped" into the flbre and partly dispersed in the swollen cellulose, whereby the amount o~ colour in the water departing from sheet formation will be very small.
Trials show that pulp concentrations up to 90% can be used.
Trial 9 Mechanical wood pulp was provided with ~ater in a mix-ing hollander to a pulp concentration of about 4%, whereafter it ~'was provided with 3% peroxide solution in the necessary amount for bleaching. The pulp was ready-bleached after six hours, and had a whiteness of 70% G.E.
Trial 10 The same mechanical pulp as in Trial 9 was provided with water in a hydrapulper to 10-12% pulp concentration, where-after it was supplied with the same amount of 3% peroxide solu- -tion as in Trial 9. After 3 hours the pulp was ready-bleached and had a whiteness of about 70% G.E.
Trial 11 ~ ....
The same mechanical pulp as in Trials 9 and 10 was provided with water in a structure according to the invention and to a pulp concentration of 30~35%, whereafter it was supplied with the same amount of 3% peroxide solution. After 45 minutes the pulp was ready-bleached to a whiteness of 72% G.E. ,~
Through the treatment according to the invention the peroxide solution is quickly pumped into the cavlties of the fibres, which together with the high concentration on reduced water content is the reason for a somewhat higher whlteness be-ing obtained in Trial 11 than in Trials 9 and 10, and for the ~13~
~ ., .
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increased bleaching speed.
The higher pulp concentration, which can reach 90%, also results in smaller apparatus volume, whereby plant costs will be smaller.
Trial 12 A sulphite pulp was provided with water to a pùlp con~
centration of between 30 and 35%, whereafter during treatment ac~
cording to the invention it was simultaneously treated with ch~
lorine gas. After about 5 minutes the chlorine bleaching was completed. In the conventional methods, chlorine bleaching is carried out at a pulp concentration of about 4%, It then takes between 60 and 90 minutes before bleaching is terminated, It has been found that chlorine is very quickly in~
corporated by substitution in the li~nin~ At a pH of 2~3 and a -pulp concentration of about 4%, which is most usual in practical operation, the substitution reaction is completed after between 60 and 90 minutes and terminates thereafter completely independent-ly of how great the chlorine excess is and whether there is lig~
nin left to chlorinate. -At a lower pH the chlorine substitution can be termina~
ted after 5-10 minutes. It has however been found th~t it is not possible to increase the reaction speed by adding more chlo-rine to the pulp suspension than what has been determined by lab~
oratory experiments for the respective pulp qualities, as an ad~
dition of chlorine above the a unt determined in the laboratory ; does not react with the lignin, which will remain in the pulp after the chlorine treatment, An increased reaction time must thus be achie~ed in .:
some othPr way, preferably by reducing the amount of water in the cellulose so that the pulp concentration is increased above -:
: . ..
~55754 30%, which to advantage can be carried out accoxdin~ to the invention.
During recent years, a new method has been worked out which enables recovery of bleaching li~uors, namely the oxy~
gen gas bleaching method~ In this bleaching method it is neces~
sary to work with pulp concentrations above 30~ to prevent a heavy reduction of the strength qualities of the cellulose, This is facilitated by simultaneously defibrating and alkali treating the cellulose with pressure shocks according to the invention before oxygen gas bleaching. Other suitable bleaching agents are, for example, chlorine dioxide, hypochlorite or hydrosulphite. -Trial 13 Printing paper waste in an undefibrated ~orm was treated in a mixing drum with an aqueous solution of de~inking chemicals, whereb~ the major part o~ the printing ink was dis~
solved, and the liquid was removed from the paper waste in a sub~
sequent screw water extractor.
Thereafter the printing paper waste was defibrated according to the invention while simultaneously adding de-inking chemicals plus a dirt absorbing agent, After dilution with sub-; sequent screw water extraction the pulp from the printing paper waste had regained the whiteness of 62% G.E. of the original .
pulps (unbleached sulphite and mechanical pulpl. In a subsequent peroxide bleaching according to the invention whiteness of bet.
ween 70 and 74% G.E. were obtained.
` 3ust de~inking of the printing paper waste according to conventional methods gives a whiteness of between 53 and 56%
C.E. With a subsequent peroxlde ble~ching a whiteness of 57~60%
~ G.E. is obtained. m us, with these conventional methods the - 30 whiteness of the original pulps is not obtained. The reason is i . . ' .. . .
~15~ -, ~ . .': ' B ~
:' :
1~557~ :
that the liberated printing ink pushe~ into the cavities ~n the fibres, from which it is not possible to remove ~t other than by the fibre pumping technique according to the in~ention.
In the conventional de~-inking methods, printin~
paper waste is defibrated in a hydrapulper at a pulp concentra-tion of about 10% while simultaneousl~ adding de~inking chemi~
cals and preferably an agent for lowering surface tension, There~
after the precipitated printing ink is removed from the pulp sus~
pension by a flotation process. To do this, dilution to a pulp concentration of about 0.1% is carried out, said concentration rising to a few percent in the subsequent filter ~ashing of the de-inked pulp. Large amounts of water are thus employed to re~
move the dissolved ink from the paper fibres. It has therefore not been economically possible to remove ink from the e~luent in flotation an~ washing filter plants, and these pollutants have - therefore been allowed to accompany the effluent into the recip~
ient water.
As ~ result of the high pulp concentrations at which the de-inking plant according to the invention works, i~e. up to a concentration of 90%, it becomes possible to remove nearly all the printing ink from the de~inking plant effluent, whereby it becomes possible and economically adv~ntageous to reflux the major part of this water to the de~inking process.
This reuse also results in unused chemicals being re~
turned to the process, whereby costs are further reduced.
By this reuse of the effluent there will be a consid- -erable reduction of the a unt of fresh water supplied and at the same time a considerable reduction in the cost of purifying it from humus and heavy metals.
~16-' ' ~ ' .:
1~557~4 From the above trials it is apparent that the pres-sure treatment according to the invention results in a substan-tial improvement of the convention,al methods.
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Claims (11)
1. A method of treating cellulose fibres in a cellu-lose pulp with a concentration of 10-90% with a liquid wherein the pulp is intermittently given elastic compresssion forces, comprising subjecting the cellulose fibres to pressure shocks with a duration not exceeding 1 second and of such a magnitude that the pressure in the interior of the fibres is increased to a value exceeding 0.2 atmospheres excess pressure, allowing the fibres to expand, without remaining deformation, between the pres-sure shocks, and maintaining this treatment until substantially complete impregnation and/or exchange of liquid enclosed in the fibres has been accomplished.
2. A method as claimed in claim 1 and comprising simultaneously heavily agitating the cellulose fibres to give them a movement relative to each other.
3. A method as claimed in claim 1 or 2 wherein the pressure shocks are generated by the cellulose pulp being thrown and/or pressed against an elastic surface.
4. A method as claimed in claim 1 for decolouring cellulose pulp, wherein the liquid comprises de-inking chemicals and a dirt absorbing agent.
5. A method as claimed in claim 4 wherein the liquid contains an agent for reducing surface tension.
6. A method as claimed in claim 1 or 2 fox colouring cellulose pulp, wherein the liquid comprises water and colouring pigment providing a pulp concentration of up to 90% and wherein after the pressure shock treatment water is added for obtaining a suspension suitable for the formation of sheets.
7. A method as claimed in claim 1 for bleaching cel-lulose pulp, wherein the pulp is brought to a concentration of up to 90% by the addition of liquid and bleaching agent.
8. A method as claimed in claim 7 wherein the bleach-ing agent consists of peroxide, chlorine, chlorine dioxide, hypochlorite, or hydrosulphite.
9. Apparatus for use in carrying out the method of claim 1, comprising a processing vessel including a wall having spaced apart therein an inlet and an outlet for the cellulose pulp, and a driven planetary mixing paddle accommodated in the vessel and arranged to move towards and away from the wall re-peatedly to throw a part of the cellulose pulp against the wall.
10. Apparatus as claimed in claim 9 wherein the wall of the vessel is in the form of an upright cylinder having the inlet and outlet provided towards the opposite ends thereof.
11. Apparatus as claimed in claim 9 or 10 wherein the wall and/or the planetary mixing paddle is/are provided with a covering of elastic material.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA265,428A CA1055754A (en) | 1976-11-12 | 1976-11-12 | Method of liquid treating cellulose fibres and a device for carrying out the method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA265,428A CA1055754A (en) | 1976-11-12 | 1976-11-12 | Method of liquid treating cellulose fibres and a device for carrying out the method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1055754A true CA1055754A (en) | 1979-06-05 |
Family
ID=4107244
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA265,428A Expired CA1055754A (en) | 1976-11-12 | 1976-11-12 | Method of liquid treating cellulose fibres and a device for carrying out the method |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1055754A (en) |
-
1976
- 1976-11-12 CA CA265,428A patent/CA1055754A/en not_active Expired
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