CN117795155A - Methods, uses thereof, slurry compositions and systems - Google Patents

Methods, uses thereof, slurry compositions and systems Download PDF

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Publication number
CN117795155A
CN117795155A CN202280054667.2A CN202280054667A CN117795155A CN 117795155 A CN117795155 A CN 117795155A CN 202280054667 A CN202280054667 A CN 202280054667A CN 117795155 A CN117795155 A CN 117795155A
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China
Prior art keywords
slurry composition
reject
fraction
screening
composition
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CN202280054667.2A
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Chinese (zh)
Inventor
米克·尼卡马
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Metsa Board Oyj
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Metsa Board Oyj
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Publication of CN117795155A publication Critical patent/CN117795155A/en
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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D1/00—Methods of beating or refining; Beaters of the Hollander type
    • D21D1/20—Methods of refining
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/08—Mechanical or thermomechanical pulp
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/02—Pretreatment of the raw materials by chemical or physical means
    • D21B1/021—Pretreatment of the raw materials by chemical or physical means by chemical means
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
    • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
    • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
    • D21B1/14—Disintegrating in mills
    • D21B1/16—Disintegrating in mills in the presence of chemical agents
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/18—De-watering; Elimination of cooking or pulp-treating liquors from the pulp
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D99/00—Subject matter not provided for in other groups of this subclass

Abstract

According to an example aspect of the invention, there is provided a method comprising: providing wood chips; impregnating wood chips with an impregnating composition to obtain impregnated wood chips; refining the impregnated wood chips in at least one refiner to obtain a refined slurry composition; screening the refined slurry composition to obtain a selected fraction and a reject fraction; at least part of the reject fraction of the screening step is directed back to the impregnation step or to a step preceding the impregnation step.

Description

Methods, uses thereof, slurry compositions and systems
Technical Field
The present invention relates to a method used in the manufacture of a slurry.
Background
In the known pulping process, the chopped wood may first be impregnated with chemicals. The impregnated wood chips are then fed to a primary refiner, which may consist of several consecutive primary refiners. After refining, the consistency of the slurry is typically reduced and inclusions (impurities) are removed. After removal of the inclusions, the slurry is screened into a selected (accept) fraction and a reject (reject) fraction. The selected portion may be fed to a disc filter where the consistency of the slurry is increased and then further bleached and washed. The reject fraction is typically stored in reject storage bins and is processed in a separate reject processing line involving one or more reject refiners.
The present invention aims to improve the known pulping process.
Disclosure of Invention
The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.
According to a first aspect of the present invention there is provided a method comprising: providing wood chips; impregnating wood chips with an impregnating composition to obtain impregnated wood chips; refining the impregnated wood chips in at least one refiner to obtain a refined slurry composition; screening the refined slurry composition to obtain a selected fraction and a reject fraction; and directing at least part of the reject fraction from the screening step back to the impregnation step or to a step preceding the impregnation step.
Various embodiments of the first aspect may include one or more features in the following list:
the impregnating composition is an aqueous composition comprisingOr a plurality of: naOH, na 2 SO 3 White liquor such as oxidized white liquor, green liquor such as oxidized green liquor, and H 2 O 2 。
In the refining, the refining energy consumption is in the range of 0.2 to 1.5 MWh/t.
After the refining step, the pulp composition has a Pulmac chip content of less than 10%, such as less than 5%.
After the refining step, the slurry composition has a Canadian Standard Freeness (CSF) in the range of 285 to 750, e.g., 285 to 470, or 350 to 750.
In the screening step, at least 80wt-%, such as at least 95wt-% of the refined slurry composition is directed to the selected fraction.
The selected portion has a Pulmac chip content no more than 10 percent, such as no more than 5 percent, lower than the Pulmac chip content of the feed to the screened refined slurry composition.
The CSF of the selected fraction differs by no more than + -20% from the CSF of the feed to the screened refined slurry composition.
The method further comprises dewatering the selected portion output from the screening.
Dewatering is performed by means of a screw press and/or a disc filter.
Dewatering includes dewatering by a screw press.
The consistency of the slurry composition (such as the selected fraction) fed to the spiral press is at least 2%, such as at least 3%, for example 2% to 5%, preferably 3% to 4%.
Dehydration includes dehydration by a disc filter.
The consistency of the slurry composition (such as the selected portion) fed to the disc filter is at least 0.5%, such as 1.0% to 1.5%.
During dewatering, the slurry composition is dewatered to a consistency of at least 20%, such as at least 30%.
Optionally after reducing the consistency of the slurry composition to less than 15%, such as less than 10%, the dewatered slurry composition is fed to a bleaching step.
The consistency of the selected fraction is first increased to more than 20% and then reduced to about 8% to 12%, preferably about 10%, for example to clean up the slurry.
The reject fraction is fed to the impregnation step at a consistency ranging from 4% to 20%, such as from 4% to 10%.
According to a second aspect of the present invention there is provided the use of a method according to the first aspect in the manufacture of a bleached or unbleached thermomechanical pulp.
According to a third aspect of the present invention, there is provided a slurry composition obtainable by the method according to the first aspect. Preferably, the slurry composition comprises BCTMP.
According to a fourth aspect of the present invention there is provided a system for performing the method according to the first aspect.
According to a fifth aspect of the invention there is provided a method comprising: providing a slurry composition; screening the slurry composition to obtain a selected fraction and a reject fraction; and dewatering the selected fraction output from the screening by a screw press.
Various embodiments of the fifth aspect may include one or more of the following features in the following list:
the method comprises, prior to the screening step: providing wood chips; refining wood chips in at least one refiner to obtain a refined slurry composition; directing the refined slurry composition to the screen.
The method comprises: prior to the screening step, providing a slurry composition comprising a mechanical slurry, such as groundwood slurry; a slurry composition comprising a mechanical slurry is directed to the screen.
The consistency of the slurry composition (such as the selected fraction) fed to the spiral press is at least 2%, such as at least 3%, for example 2% to 5%, preferably 3% to 4%.
Dewatering takes place during screening and in a subsequent screw press.
During dewatering, the slurry composition is dewatered to a consistency of at least 20%, such as at least 30%.
Optionally after reducing the consistency of the slurry composition to less than 15%, such as less than 10%, the dewatered slurry composition is fed to a bleaching step.
The consistency of the selected fraction is first increased to greater than 20% and then reduced to about 8% to 12%, preferably about 10%, for example to clean the slurry composition.
Screening includes screening performed by a first screening device and screening performed by a subsequent second screening device.
The consistency of the slurry composition in the output of the first screening device is lower than the consistency of the slurry composition in the output of the second screening device.
In the screening step, at least 50wt-%, such as at least 80wt-% of the refined slurry composition is directed to the selected fraction.
The method comprises directing the reject fraction from the screening step to a reject handling line.
The reject treatment line comprises at least the step of refining the reject fraction by a reject refiner.
The method comprises directing the output of the reject treatment line to the screw press, and preferably the consistency of the output is at least 2%, such as at least 3%, for example 2% to 5%, preferably 3% to 4%.
The method further comprises, prior to the screening step, impregnating the wood chips with an impregnating composition to obtain impregnated wood chips, and refining the impregnated wood chips in at least one refiner.
The impregnating composition is an aqueous composition comprising one or more of the following: naOH, na 2 SO 3 White liquor such as, for example, oxidized white liquor, green liquor such as oxidized green liquor, and H 2 O 2 。
The method comprises directing at least part of the reject fraction from the screening step back to the impregnation step or to a step preceding the impregnation step.
According to a sixth aspect of the present invention there is provided the use of the method according to the fifth aspect in the manufacture of a chemical thermo-mechanical pulp or a bleached chemical thermo-mechanical pulp.
According to a seventh aspect of the present invention there is provided the use of a method according to the fifth aspect in the manufacture of a mechanical pulp, such as groundwood, pressure groundwood, stone groundwood or thermo-mechanical pulp.
According to an eighth aspect of the present invention there is provided a slurry composition obtained by the method according to the fifth aspect. Preferably, the slurry composition comprises BCTMP.
According to a ninth aspect of the present invention there is provided a system configured to perform the method according to the fifth aspect.
THE ADVANTAGES OF THE PRESENT INVENTION
An advantage of the present invention is that the amount of reject generated during the screening step can be reduced.
Another advantage of the present invention is that relatively high CSF levels can be employed throughout the process.
Another advantage of the present invention is that a disc filter can be omitted.
Another advantage of the present invention is that the pulping process for the purpose of preparing various slurry end compositions can be conveniently tailored.
An advantage of the present invention is that energy savings can be achieved due to the fewer equipment involved in the process.
Drawings
FIGS. 1 and 2 illustrate methods according to at least some embodiments of the invention; and
fig. 3 illustrates a screening step in a method according to at least some embodiments of the invention.
Detailed Description
In this context, the term "pulp" generally refers to wood pulp.
In this context, the term "selected" refers to a portion that has been accepted into the next step of the process, such as into the next step of the mainline process.
In this context, the term "reject" refers to a portion that is not accepted into the next step of the process, such as the portion that is abandoned from continuing the main line process.
In this context, the term "reject fraction" generally refers to the reject fraction from the screening step.
In this context, canadian Standard Freeness (CSF) is measured according to ISO 5267-2 standard.
In this context, the brightness is measured according to the 457nm brightness of the ISO 2470 standard.
In this context, the chip content refers to the chip content of "Pulmac (0.1 mm)".
In some embodiments of the present invention, it has surprisingly been observed that a separate reject handling line may not be required at all in the pulping process.
In some embodiments of the invention, it has surprisingly been observed that a screw press may be used instead of a disc filter in the dewatering step of the pulping process.
Typically, the present method may be incorporated into a slurry manufacturing process.
In one embodiment, the method of the invention comprises: providing wood chips; impregnating wood chips with an impregnating composition to obtain impregnated wood chips; refining the impregnated wood chips in at least one refiner to obtain a refined slurry composition; screening the refined slurry composition to obtain a selected fraction and a reject fraction; and directing at least a portion of the reject fraction from the screening step back to the impregnation step or to a step preceding the impregnation step.
In another embodiment, the method of the invention comprises: providing wood chips; refining wood chips in at least one refiner to obtain a refined slurry composition; screening the refined slurry composition to obtain a selected fraction and a reject fraction; and dewatering the selected portion by a screw press.
The wood to be cut may include: softwood, such as spruce or pine, or mixtures thereof; or hardwoods such as birch, aspen, alder, maple, eucalyptus, tropical hardwoods or mixtures thereof, or it may comprise a mixture of softwood and hardwoods.
The impregnating composition may be an aqueous composition comprising one or more of the following: naOH, na 2 SO 3 White liquor such as oxidized white liquor, green liquor such as oxidized green liquor, and H 2 O 2 。
During refining, wood fibers are released from the wood material softened in the impregnation step. Due to mechanical forces in refining, the fibers are shortened, the fiber diameter is reduced, and the fibers become fibrillated (fibrillated). Fibrillation (external fibrillation) involves breaking the smooth fiber surface and roughening it by introducing microfibers on the fiber surface. Internal fibrillation will also typically occur, which increases the flexibility of the fibers. With respect to the quality of the refined material obtained, a low chip content, high strength and sufficient fiber length may be pursued.
The refiner used for refining wood chips may be a high consistency refiner or a low consistency refiner. In the case of high consistency refiners, the consistency of the slurry to be refined is typically 20% to 60%. In the case of low consistency refiners, the consistency of the slurry to be refined is typically 3% to 5%.
The refiner may be a flat disc refiner or a conical disc refiner.
The refiner may be a single-disc or a double-disc refiner. Preferably, the refiner is a single disc refiner comprising a stator and a rotor.
The distance between the blades of the refiner may be in the range of 0.1mm to 1.0 mm.
In the refining, the refining energy consumption may be in the range of 0.2 to 1.5 MWh/t.
After the refining step, the pulp may have a Pulmac chip content of less than 20%, such as less than 10%, for example less than 5%.
After the refining step, i.e. in the output of the last refiner, the refined slurry may have a Canadian Standard Freeness (CSF) of at least 285, such as at least 350, e.g. at least 400. In certain embodiments, the refined slurry may have a canadian standard freeness of less than 750, such as less than 470.
In one embodiment, the refined slurry may have a Canadian Standard Freeness (CSF) in the range of 285 to 470. Such a slurry may be suitable for use in the manufacture of CTMP which may be used as a material for light-weight coated printing paper.
In one embodiment, the refined slurry may have a Canadian Standard Freeness (CSF) in the range of 350 to 750. Such a slurry may be suitable for use in the manufacture of BCTMP that may be used as a folding carton board material.
There is typically an inclusion removal step prior to directing the refined slurry to screening. During inclusion removal, the curl of the fibers is reduced and the fibers become straightened.
In one embodiment, the consistency of the refined slurry composition fed to the screening step is at least 2%, such as at least 3%, for example 2% to 5%, preferably 3% to 4%.
The consistency of the slurry is at least 2%, such as at least 3%, e.g. 2% to 5%, preferably 3% to 4%, during the screening step or at least in the selected output of the screening step. One advantage of having such a high consistency at least in the selected output of the screening is that the selected fraction can be fed directly into the screw press after screening. At lower consistencies, the mass flow may be too high to be handled by the screw press.
In the screening step, at least 50wt-%, for example at least 80wt-%, such as at least 90wt-%, preferably at least 95wt-% of the refined slurry composition is directed to the selected fraction.
Preferably, the composition and properties of the refined slurry are not substantially altered by the screening. In other words, the amount of reject separated from the slurry in the screening step is preferably minimized.
The Pulmac chip content of the selected portion is preferably no more than 50 percentage points, such as no more than 10 percentage points, for example no more than 5 percentage points, lower than the Pulmac chip content of the feed to the screened refined slurry feed.
For example, the Pulmac fragment content of the selected portion may be less than 10%, such as less than 5%, preferably less than 1%.
The CSF of the selected portion may differ by no more than ±20% from the CSF of the incoming refined slurry feed to the screen.
In certain embodiments, in steps subsequent to the screening step, no new slurry feed is combined to the selected portion output from the screening step. Thus, the steps downstream of the screening step, typically dewatering and bleaching, accept only the selected fraction from the screening as input. Thus, if the input to the post-screening step requires adjustment, then only the nature and composition of this unique selected portion need be adjusted.
In one embodiment, the dewatering may be performed in a screw press. In this embodiment, the consistency of the fraction fed from the screening to the dewatering step is preferably at least 2%, such as at least 3%, for example 2% to 5%, preferably 3% to 4%. Preferably, the moiety consists of selected moieties from the screen.
In one embodiment, the dewatering may be performed by a disc filter. In this embodiment, the consistency of the fraction fed from the screening to the dewatering step is preferably 0.5% to 2%, such as 1.0% to 1.5%. Preferably, the moiety consists of selected moieties from the screen.
In one embodiment, dewatering may be performed during the screening and in a subsequent screw press or disc filter. Thus, the removal of a portion of the water may already take place in the screening step, for example by using at least two screening apparatuses arranged in series, and the latter screening apparatuses being configured to partially dewater the slurry composition.
In a preferred embodiment, a disc filter is not used in the step following the screening step to dewater the selected portion. One advantage of not using a disc filter is that the CSF of the slurry can be adjusted to a higher level throughout the process, as cake formation problems can be avoided. Such cake formation problems may be encountered in methods using disc filters.
One advantage of dewatering using a screw press is that the consistency can be increased to a high level, such as to 15% to 40%, for example to at least 20%, preferably to at least 30%. It may be advantageous to be able to effectively remove moisture from the screened slurry if desired.
The selected fraction from the screening may be dewatered to a consistency of at least 20%, for example at least 30%.
The method may include: providing wood chips; impregnating wood chips with an impregnating composition to obtain impregnated wood chips; refining the impregnated wood chips in at least one refiner to obtain a refined slurry composition; screening the refined slurry composition to obtain a selected fraction and a reject fraction; and dewatering the selected portion from the screening by a screw press, wherein the consistency of the selected portion fed to the screw press is at least 3%, and wherein in dewatering the slurry composition is typically dewatered to a consistency of at least 20%.
The dewatered selected fraction may be fed to a bleaching step, optionally after reducing the consistency of the selected fraction to less than 15%, such as to less than 10%.
In some embodiments, the consistency of the selected portion is first increased to greater than 20% and then reduced to about 8% to 12%, preferably about 10%, for example, to clean up the slurry.
The reject fraction from the screening may be fed back to the dipping step or to a step preceding the dipping step. Preferably, the reject fraction is fed to the impregnation step or to a step preceding the impregnation step at a consistency in the range of 2% to 45%. In one embodiment, the slurry composition (such as the reject fraction) fed to the impregnation step has a consistency in the range of 4% to 10%.
Advantageously, the reject fraction is not fed directly to the refining step, but to a step preceding the refining step. This avoids the problems associated with maintaining a proper consistency in the refiner. In such embodiments, the consistency of the reject fraction may vary within a wider range.
One advantage of feeding the reject fraction to or before the impregnation step is that the reject fraction may be further impregnated before continuing the refining.
In a preferred embodiment, the reject fraction is fed to the impregnation step or to a step preceding the impregnation step, without separate dewatering of the reject fraction and/or without separate refining of the reject fraction. For example, the reject fraction may be fed directly from the reject output of the screening to the impregnation step or to a step preceding the impregnation step.
In some embodiments, the reject fraction is fed to the impregnation step or to a step immediately preceding the impregnation step, typically without any refining of the reject fraction.
The step preceding the impregnation step may be a step of washing the wood chips.
The method may comprise directing at least a portion of the reject fraction, preferably substantially all of the reject fraction, directly back to the impregnation step or to a step immediately preceding the impregnation step.
The method may comprise directing substantially all of the reject fraction back to the impregnation step, preferably without any refining of the reject fraction.
In some embodiments, at least a portion of the reject fraction, such as substantially all of the reject fraction, may be directed from the screening directly to a reject handling line separate from the main line, i.e. not forming part of the main line.
The reject treatment line may comprise a reject refiner.
The reject process may include one or more of the following steps: dewatering the reject, refining the reject by a reject refiner, and screening the reject to obtain a selected portion and a reject portion of the reject treatment line.
The reject handling line may comprise one or more screening devices, such as at least two screening devices.
The consistency of the slurry composition input to the reject handling line screening step may be at least 2%, such as at least 3%, for example 2% to 5%, preferably 3% to 4%.
The output (such as the reject of the reject handling line) may be fed back to the main line, for example to the main line dewatering step, to be combined with the selected output from the main line screening.
In one embodiment, the output of the reject handling line may have a consistency of at least 2%, such as at least 3%, for example 2% to 5%, preferably 3% to 4%. The advantage is that the reject of the reject handling line can then be fed directly to the screw press in the main line.
In one embodiment, the reject from the reject handling line is directed to a main line dewatering step, such as to a screw press, for example, at a consistency of at least 2%.
Preferably, the consistency of the reject outputted from the reject handling line is adjusted to a range of 2% to 5%.
In one embodiment, a portion of the reject from the screening step is directed back to the impregnation step and another portion of the reject from the screening step is directed to the reject handling line.
The present invention may be applied to the manufacture of a slurry selected from the group consisting of: mechanical pulp, thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), bleached chemi-thermomechanical pulp (BCTMP), semi-chemical pulp, groundwood pulp (GW), pressure groundwood Pulp (PGW), stone groundwood pulp (SGW), and combinations thereof.
The pulp may be bleached or unbleached.
Preferably, the method is used to make a chemi-thermo-mechanical pulp or a bleached chemi-thermo-mechanical pulp.
In some embodiments, the method is used to make mechanical pulp, groundwood pulp (GW), pressure groundwood Pulp (PGW), stone groundwood pulp (SGW), or thermo-mechanical pulp (TMP).
BCTMP obtained by some embodiments of the present invention may be provided as a material of one or more layers of paperboard (such as folded box paperboard) or paper (such as printing paper, writing paper or tissue).
In one embodiment, the method is for preparing a slurry suitable for use in making paperboard having the following characteristics:
preferably, the density of the board is between 0.5 and 1.3g/cm 3 Within a range of (2). Preferably, the brightness of the paperboard is greater than 84%.
In another embodiment, the method is for preparing a slurry suitable for use in making paper having the following characteristics:
preferably, the density of the paper is in the range of 0.7-1.4g/cm 3 Within a range of (2). Preferably, the brightness of the paper is greater than 77%.
The invention also relates to a system configured to perform a method according to any of the embodiments described above or any combination thereof. The system may be part of a pulp mill. The system may include one or more of the following devices: wood cutting equipment, chip impregnation systems, one or more primary refiners, one or more pulp screening equipment, one or more reject refiners, reject screening equipment, pulp dewatering equipment (such as disc filters or screw presses), pulp bleaching systems.
Referring now to the drawings:
fig. 1 illustrates process steps in a method according to at least some embodiments of the invention. The process comprises the following steps: cutting 10, dipping 11, refining 12, screening 13, dewatering 14, optional bleaching 15 and optional washing 16. The filtering produces as outputs a selected portion and a reject portion. The selected fraction continues on the main line and is led from the screening 13 to the dewatering 14. The reject fraction (if present), or at least part of the reject fraction, is fed back from the screening 13 to a step preceding the refining step, for example to the impregnation step 11, as indicated by the arrow in fig. 1. Here, the dehydration 14 may include a screw press or a disc filter.
Fig. 2 illustrates process steps in a method according to at least some embodiments of the invention. Here, the main line comprises the steps of cutting 20, optional impregnation 21, refining 22, screening 23, dewatering 24, optional bleaching 25 and optional washing 26. The method further comprises a reject handling line 27, which is independent of the main line. The reject fraction obtained in the screening 23 is led to a reject handling line 27. The reject treatment line may comprise a reject refining step and/or a reject screening step. The output from the reject handling line 27, such as the selected portion, may be redirected back to the main line, such as to the dewatering 24 step. Here, the dewatering 24 preferably comprises a screw press.
Fig. 3 illustrates a screening step in a method according to at least some embodiments of the invention. The incoming slurry composition P is fed to the screening step 33. The resulting selected portion a and reject portion R are filtered as outputs. The accept selected portion a proceeds to the next step of the main line process, dewatering 34 by a screw press. The reject fraction R then does not continue the main line process any more but is sent to the reject handling line or back in the main line, for example back to the impregnation step (not shown here).
The consistency of the incoming slurry P (which may be a refined slurry) is preferably at least 3.5%, for example 3.5% to 4.5%.
The consistency of the selected fraction a is preferably at least 3%, for example 3.5% to 4%.
The consistency of the reject fraction is preferably at least 4%, for example at least 4.5%.
Examples
The test involved feeding reject from the screen directly into a pulping process of impregnation. The process main line comprises cutting, dipping, refining, screening, dewatering through a disc filter, and bleaching. The consistency of the stock composition input to bleaching is about 10%. The selection from the screen is directed to a disc filter. Reject from the screening is either directed to a conventional reject handling line or alternatively directed back to the impregnation step.
In the process of test 1 and test 2, the conventional reject handling line was skipped and the reject from the screening was returned to the impregnation step. Test 1 and test 2 were performed on different dates.
The reference process does not include any reject feedback, but instead directs reject from the screen directly to a conventional reject processing line containing a reject refiner.
We measured the Canadian Standard Freeness (CSF) of the slurry composition output from the disc filter (i.e., at some point between the disc filter and bleaching). The results are shown in Table 1. The results show that the CSF of the slurry compositions in the test 1 and test 2 processes were successfully maintained at the same level as the CSF of the slurry composition in the reference process.
It is to be understood that the disclosed embodiments are not limited to the specific structures, process steps, or materials disclosed herein, but extend to equivalents thereof as would normally be recognized by one of ordinary skill in the relevant art. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.
As used per se, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a list for convenience. However, these drafts should be understood as if each member of the list was individually identified as an independent and unique member. Thus, unless indicated to the contrary, no individual member of such a list should be construed as being virtually identical to any other member of the same list based solely on their presentation in a common group. In addition, various implementations and examples of the invention, as well as alternatives to the various components thereof, may be mentioned herein. It should be understood that such embodiments, examples and alternatives are not to be considered as actual equivalents of each other, but rather as independent and autonomous representations of the invention.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
While the above embodiments illustrate the principles of the invention in one or more specific applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and implementation details can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as set forth in the following claims.
The verbs "comprise" and "comprise" as used in this document are used as open-ended constraints that neither preclude nor require the presence of unrecited features. The features recited in the dependent claims may be freely combined with each other unless explicitly stated otherwise. Furthermore, it should be understood that the use of "a" or "an" throughout this document, i.e., in the singular, does not exclude a plurality.
Industrial application
The invention is applicable at least industrially to the production of slurries such as CTMP or BCTMP.
List of abbreviations
TMP thermomechanical slurry
CTMP chemical-thermal-mechanical slurry
BCTMP bleached chemi-thermo-mechanical pulp
GW wood grinding pulp material
PGW pressure wood grinding material
SGW stone mill wood pulp
CSF Canadian standard freeness
List of reference numerals
10. 20 cutting
11. 21 impregnation
12. 22 refining
13. 23, 33 screening
14. 24, 34 dehydration
15. 25 bleaching of
16. 26 washing
27. Reject treatment

Claims (26)

1. A method, comprising:
-providing wood chips;
-impregnating the wood chips with an impregnating composition to obtain impregnated wood chips;
-refining the impregnated wood chips in at least one refiner to obtain a refined slurry composition;
-screening the refined slurry composition to obtain a selected fraction and a reject fraction; and is also provided with
-directing at least part of the reject fraction from the screening step back to the impregnation step or to a step preceding the impregnation step.
2. The method of any of the preceding claims, wherein the impregnating composition is an aqueous composition comprising one or more of the following: naOH, na 2 SO 3 White liquor such as oxidized white liquor, green liquor such as oxidized green liquor, and H 2 O 2 。
3. A process according to any one of the preceding claims, wherein in the refining energy consumption is in the range of 0.2 to 1.5 MWh/t.
4. The method according to any of the preceding claims, wherein after the refining step the pulp composition has a Pulmac chip content of less than 10%, such as less than 5%.
5. The method of any of the preceding claims, wherein, after the refining step, the slurry composition has a Canadian Standard Freeness (CSF) in the range of 285 to 750, such as 285 to 470, or 350 to 750.
6. A method according to any of the preceding claims, wherein in the screening step at least 80wt-%, such as at least 95wt-% of the refined slurry composition is directed to the selected fraction.
7. A method according to any one of the preceding claims, wherein the Pulmac chip content of the selected fraction is no more than 10 percentage points, such as no more than 5 percentage points, lower than the Pulmac chip content of the incoming refined slurry composition fed to the screen.
8. The method of any of the preceding claims, wherein the CSF value of the selected fraction differs by no more than ±20% from the CSF value of the incoming refined slurry composition fed to the screen.
9. The method of any one of the preceding claims, further comprising dewatering the selected portion output from the screening.
10. The method according to any of the preceding claims, wherein the dewatering is performed by a screw press and/or by a disc filter.
11. The method of any of the preceding claims, wherein:
the dehydration includes dehydration by a screw press
Preferably, the consistency of the slurry composition, such as the selected fraction, fed to the spiral press is at least 2%, such as at least 3%, for example 2% to 5%, preferably 3% to 4%.
12. The method of any of the preceding claims, wherein:
the dewatering includes dewatering by a disc filter
Preferably, the consistency of the slurry composition, such as the selected portion, fed to the disc filter is at least 0.5%, such as 1.0% to 1.5%.
13. A method according to any of the preceding claims, wherein during dewatering the slurry composition is dewatered to a consistency of at least 20%, such as at least 30%.
14. A method according to any of the preceding claims, wherein the dewatered pulp composition is fed to a bleaching step, optionally after reducing the consistency of the pulp composition to less than 15%, such as less than 10%.
15. A method according to any of the preceding claims, wherein the consistency of the selected fraction is first increased to more than 20% and then reduced to about 8% to 12%, preferably about 10%, for example for cleaning of the slurry.
16. The method of any of the preceding claims, wherein the reject fraction is fed to the impregnation step at a consistency ranging from 4% to 10%.
17. The method according to any of the preceding claims, comprising the step of directing at least part of the reject fraction, preferably substantially all of the reject fraction, directly back to the impregnation step or immediately before the impregnation step.
18. The method according to any of the preceding claims, comprising directing substantially all of the reject fraction back to the impregnation step, preferably without any refining of the reject fraction.
19. The method of any one of the preceding claims, further comprising dewatering the selected portion to obtain a slurry composition.
20. Use of the method according to any of the preceding claims for the manufacture of bleached or unbleached thermo-mechanical pulp.
21. Slurry composition obtainable by the process according to any one of claims 1 to 19.
22. The slurry composition of claim 21, wherein the slurry composition comprises BCTMP.
23. A slurry composition obtained by a slurry manufacturing process in combination with the method according to any one of claims 1 to 19.
24. The method of claim 23, wherein the slurry composition is CTMP, such as BCTMP.
25. A system configured to perform the method of any one of claims 1 to 19.
26. The system of claim 25, forming part of a pulp mill, and comprising: a wood cutting apparatus, a chip impregnation system, one or more primary refiners, one or more pulp screening apparatuses, a pulp dewatering apparatus, and optionally, a pulp bleaching system.
CN202280054667.2A 2021-08-17 2022-08-17 Methods, uses thereof, slurry compositions and systems Pending CN117795155A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FI20215861 2021-08-17
FI20215861A FI20215861A1 (en) 2021-08-17 2021-08-17 A method, use of the same, a pulp composition, and a system
PCT/FI2022/050535 WO2023021243A1 (en) 2021-08-17 2022-08-17 A method, use of the same, a pulp composition, and a system

Publications (1)

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CN117795155A true CN117795155A (en) 2024-03-29

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CA (1) CA3228121A1 (en)
FI (1) FI20215861A1 (en)
SE (1) SE2430124A1 (en)
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Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3073737A (en) * 1958-10-08 1963-01-15 Dorr Oliver Inc Wood pulp and process for producing same
US4502918A (en) * 1981-06-10 1985-03-05 Macmillan Bloedel Limited Two-stage chemical treatment of mechanical wood pulp with sodium sulfite
SE9402101L (en) * 1994-06-15 1995-12-16 Moelnlycke Ab Light dewatering, bulky, chemical-mechanical pulp with low tip and fine material content
SE517297C2 (en) * 1999-09-10 2002-05-21 Stora Kopparbergs Bergslags Ab Method for producing mechanical pulp from a cellulose-containing material, pulp made according to the method and carton produced from the pulp
FI121311B (en) * 2005-05-03 2010-09-30 M Real Oyj A process for the preparation of a mechanical pulp for use in the manufacture of paper and board

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