WO2023021243A1 - Procédé, utilisation associée, composition de pâte, et système associé - Google Patents

Procédé, utilisation associée, composition de pâte, et système associé Download PDF

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Publication number
WO2023021243A1
WO2023021243A1 PCT/FI2022/050535 FI2022050535W WO2023021243A1 WO 2023021243 A1 WO2023021243 A1 WO 2023021243A1 FI 2022050535 W FI2022050535 W FI 2022050535W WO 2023021243 A1 WO2023021243 A1 WO 2023021243A1
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WO
WIPO (PCT)
Prior art keywords
pulp
fraction
screening
composition
reject
Prior art date
Application number
PCT/FI2022/050535
Other languages
English (en)
Inventor
Mikko NIKAMAA
Original Assignee
Metsä Board Oyj
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Metsä Board Oyj filed Critical Metsä Board Oyj
Priority to CN202280054667.2A priority Critical patent/CN117795155A/zh
Priority to SE2430124A priority patent/SE2430124A1/en
Priority to DE112022003992.2T priority patent/DE112022003992T5/de
Priority to CA3228121A priority patent/CA3228121A1/fr
Publication of WO2023021243A1 publication Critical patent/WO2023021243A1/fr

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Classifications

    • 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
    • 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
    • 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

Definitions

  • the present invention relates to processes used in manufacturing of pulp.
  • chipped wood may first be impregnated with chemicals.
  • the impregnated chips are then directed to primary refining, which may consist of several consecutive primary refiners.
  • primary refining which may consist of several consecutive primary refiners.
  • the consistency of the pulp is typically decreased and latency removed.
  • the pulp is screened to an accept and a reject fraction.
  • the accept fraction may be directed to a disc filter, wherein the consistency of the pulp is increased, and then further to bleaching and washing steps.
  • the reject fraction is typically stored in reject storage silos and treated in a separate reject treatment line involving one or more reject refiners.
  • the present invention is aimed at improving the known pulping methods.
  • 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 pulp composition; screening the refined pulp composition to obtain an accept fraction and a reject fraction; and directing at least part of the reject fraction from the screening step back to said impregnating step or to a step preceding said impregnating step.
  • the impregnating composition is an aqueous composition comprising one or more of the following: NaOH, ISfeSCh, white liquor, such as oxidised white liquor, green liquor, such as oxidised green liquor, and H2O2.
  • the refining energy consumption is in the range 0.2 to 1.5 MWh/t.
  • the pulp composition has a Pulmac shive content of less than 10%, such as less than 5%.
  • the pulp composition has Canadian Standard Freeness (CSF) in the range 285 to 750, for example 285 to 470, or 350 to 750.
  • CSF Canadian Standard Freeness
  • the Pulmac shive content of the accept fraction is not more than 10 percentage points lower, such as not more than 5 percentage points lower than the Pulmac shive content of the incoming refined pulp composition fed to the screening.
  • the CSF of the accept fraction differs from the CSF of the incoming refined pulp composition fed to the screening by not more than ⁇ 20%.
  • the method further comprises dewatering the accept fraction output from the screening.
  • Said dewatering is carried out by a screw press and/or by a disc filter.
  • the dewatering comprises dewatering carried out by a screw press.
  • the pulp composition, such as the accept fraction, that is fed to the screw press has a consistency of at least 2%, such as at least 3%, for example 2 to 5%, preferably 3 to 4%.
  • the dewatering comprises dewatering carried out by a disc filter.
  • the pulp composition, such as the accept fraction, that is fed to the disc filter has a consistency of at least 0.5%, such as 1.0 to 1.5%.
  • the pulp composition is dewatered to a consistency of at least 20%, such as at least 30%.
  • the dewatered pulp composition is fed to a bleaching step, optionally after decreasing the consistency of the pulp composition to less than 15%, such as to less than 10%.
  • the consistency of the accept fraction is first increased to above 20% and then decreased to about 8 to 12%, preferably to about 10%, for example to clean the pulp.
  • the reject fraction is fed to the impregnating step at a consistency in the range 4 to 20%, such as 4 to 10%.
  • thermomechanical pulp According to a second aspect of the present invention, there is provided use of the method according to the first aspect in the manufacturing of bleached or unbleached thermomechanical pulp.
  • a pulp composition obtained by the method according to the first aspect.
  • the pulp composition comprises BCTMP.
  • a system configured to execute the method according to the first aspect.
  • a method comprising: providing a pulp composition; screening the pulp composition to obtain an accept fraction and a reject fraction; and dewatering the accept fraction output from the screening by a screw press.
  • Various embodiments of the fifth aspect may comprise one or more features from the following bulleted list:
  • the method comprises before the screening step: providing wood chips; refining the wood chips in at least one refiner to obtain a refined pulp composition; directing the refined pulp composition to said screening.
  • the method comprises before the screening step: providing a pulp composition comprising mechanical pulp, such as groundwood pulp; directing the pulp composition comprising mechanical pulp to said screening.
  • the pulp composition, such as the accept fraction, that is fed to the screw press has a consistency of at least 2%, such as at least 3%, for example 2 to 5%, preferably 3 to 4%.
  • the pulp composition is dewatered to a consistency of at least 20%, such as at least 30%.
  • the dewatered pulp composition is fed to a bleaching step, optionally after decreasing the consistency of the pulp composition to less than 15%, such as to less than 10%.
  • the consistency of the accept fraction is first increased to above 20% and then decreased to about 8 to 12%, preferably to about 10%, for example to clean the pulp composition.
  • the screening comprises screening carried out by a first screening device and screening carried out by a subsequent second screening device.
  • At least 50 wt-%, such as at least 80 wt-% of the refined pulp composition becomes directed to the accept fraction.
  • the method comprises directing the reject fraction from the screening step to a reject treatment line.
  • the reject treatment line comprises at least a step of refining the reject fraction by a reject refiner.
  • the method comprises directing an output of the reject treatment line to said screw press, and preferably said output has a consistency of at least 2%, such as at least 3%, for example 2 to 5%, preferably 3 to 4%.
  • the method further comprises, before 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, Na2SCh, white liquor, such as oxidised white liquor, green liquor, such as oxidised green liquor, and H2O2.
  • the method comprises directing at least part of the reject fraction from the screening step back to said impregnating step or to a step preceding said impregnating step.
  • a seventh aspect of the present invention there is provided use of the method according to the fifth aspect in the manufacturing of mechanical pulp, such as groundwood pulp, pressure groundwood pulp, stone groundwood pulp, or thermomechanical pulp.
  • the pulp composition obtained by the method according to the fifth aspect.
  • the pulp composition comprises BCTMP.
  • a ninth aspect of the present invention there is provided a system configured to execute the method according to the fifth aspect.
  • An advantage of the present invention is that the amount of reject generated in the screening step may be decreased.
  • a further advantage of the present invention is that relatively high CSF levels may be used throughout the process.
  • a further advantage of the present invention is that a disc filter may be dispensed with. [0020] A further advantage of the present invention is that tailoring of the pulping process for the purpose of preparing various pulp end compositions may be facilitated.
  • An advantage of the present invention is that energy savings may be attained as the process involves less equipment.
  • FIGURES 1 and 2 illustrate the method in accordance with at least some embodiments of the present invention.
  • FIGURE 3 illustrates the screening step in the method in accordance with at least some embodiments of the present invention.
  • pulp typically refers to wood pulp.
  • accept refers to the fraction that has been accepted to be fed to the succeeding step in the process, such as to the succeeding step in the main line process.
  • reject refers to the fraction that has not been accepted to be fed to the succeeding step in the process, such as to the fraction that has been rejected from continuing in the main line process.
  • reject fraction typically refers to the reject fraction from the screening step.
  • CSF Canadian Standard Freeness
  • brightness is measured according to brightness 457 nm, ISO 2470.
  • shive content refers to shive content “Pulmac (0.1 mm)”.
  • Pulmac 0.1 mm
  • a disc filter may be replaced by a screw press in a dewatering step of a pulping process.
  • the present method may be incorporated in a pulp manufacturing process.
  • the present method comprises: 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 pulp composition; screening the refined pulp composition to obtain an accept fraction and a reject fraction; and directing at least part of the reject fraction from the screening step back to said impregnating step or to a step preceding said impregnating step.
  • the present method comprises: providing wood chips; refining the wood chips in at least one refiner to obtain a refined pulp composition; screening the refined pulp composition to obtain an accept fraction and a reject fraction; and dewatering the accept fraction by a screw press.
  • the wood to be chipped may comprise softwood, such as spruce or pine or mixtures thereof, or hardwood, such as birch, poplar, aspen, alder, maple, eucalypt tropical hardwood, or mixtures thereof, or it may comprise a mixture of softwood and hardwood.
  • the impregnating composition may be an aqueous composition comprising one or more of the following: NaOH, ISfeSCh, white liquor, such as oxidised white liquor, green liquor, such as oxidised green liquor, and H2O2.
  • the wood fibres become released from the wood material that has been softened in the impregnating step.
  • the fibres are shortened, the fibre diameter is decreased, and the fibres become fibrillated.
  • the fibrillating involves breaking of the smooth fibre surface to make it hairy by introduction of microfibrils on the fibre surface. Also internal fibrillating typically occurs, which increases flexibility of the fibres. As to the quality of the obtained refined mass, a low shive content, high strength, and a sufficient fibre length may be aimed at.
  • the refiner that is used for refining the wood chips may be a high- consistency refiner or a low-consistency refiner.
  • the consistency of the pulp to be refined is typically 20 to 60%.
  • the consistency of the pulp 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 one-disc or a two-disc refiner.
  • the refiner is a one-disc refiner comprising a stator and a rotor.
  • the distance between the blades of the refiner may be in the range 0.1 to 1.0 mm.
  • the refining energy consumption may be in the range 0.2 to 1.5 MWh/t.
  • the pulp may have a Pulmac shive content of less than 20%, such as less than 10%, for example less than 5%.
  • the refined pulp may have Canadian Standard Freeness (CSF) of at least 285, such as at least 350, for example at least 400. In some embodiments, the refined pulp may have Canadian Standard Freeness of less than 750, such as less than 470.
  • CSF Canadian Standard Freeness
  • the refined pulp may have Canadian Standard Freeness (CSF) in the range 285 to 470.
  • CSF Canadian Standard Freeness
  • Such pulp may be suitable for the manufacturing of CTMP that is usable as a material of lightweight coated printing paper.
  • the refined pulp may have Canadian Standard Freeness (CSF) in the range 350 to 750.
  • CSF Canadian Standard Freeness
  • Such pulp may be suitable for the manufacturing of BCTMP that is usable as a material of folding boxboard.
  • the refined pulp composition that is fed to the screening step may have a consistency of at least 2%, such as at least 3%, for example 2 to 5%, preferably 3 to 4%.
  • the pulp has a consistency of at least 2%, such as at least 3%, for example 2 to 5%, preferably 3 to 4%.
  • An advantage of having such a high consistency at least in the accept output of the screening is that the accept fraction may be directly feedable to a screw press after the screening. In lower consistencies, the mass flow rate might be too high to be handled by a screw press.
  • At least 50 wt-%, for example at least 80 wt-%, such as at least 90 wt-%, preferably at least 95 wt-% of the refined pulp composition becomes directed to the accept fraction.
  • composition and properties of the refined pulp are not substantially altered as a result of the screening.
  • the amount of reject separated from the pulp in the screening step is preferably minimised.
  • the Pulmac shive content of the accept fraction is preferably not more than 50 percentage points lower, such as not more than 10 percentage points lower, for example not more than 5 percentage points lower than the Pulmac shive content of the incoming refined pulp fed to the screening.
  • the Pulmac shive content of the accept fraction may be less than 10%, such as less than 5%, preferably less than 1%.
  • the CSF of the accept fraction may differ from the CSF of the incoming refined pulp fed to the screening by not more than ⁇ 20%,
  • the dewatering may be carried out in a screw press.
  • the fraction that is fed from the screening to the dewatering step preferably has a consistency of at least 2%, such as at least 3%, for example 2 to 5%, preferably 3 to 4%.
  • said fraction consists of the accept fraction from the screening.
  • the dewatering may be carried out by a disc filter.
  • the fraction that is fed from the screening to the dewatering step preferably has a consistency of 0.5 to 2%, such as 1.0 to 1.5%.
  • said fraction consists of the accept fraction from the screening.
  • the dewatering may be carried out both during the screening and in a subsequent screw press or disc filter.
  • part of water removal may take place already in the screening step, for example by using at least two screening devices arranged in series and by configuring the latter screening device to partly dewater the pulp composition.
  • a disc filter is not used for dewatering the accept fraction in steps succeeding the screening step.
  • An advantage of not using a disc filter is that CSF of the pulp may be adjusted to higher levels throughout the process, as cakeforming problems may be avoided. Such cake-forming problems might be encountered in methods that use a disc filter.
  • An advantage of using a screw press for the dewatering is that the consistency may be increased to high levels, such as to 15 to 40%, for example to at least 20%, preferably to at least 30%.
  • the ability to effectively remove water from the screened pulp, if needed, may be advantageous.
  • the accept fraction from the screening may be dewatered to a consistency of at least 20%, such as at least 30%.
  • the method may comprise: 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 pulp composition; screening the refined pulp composition to obtain an accept fraction and a reject fraction; and dewatering the accept fraction output from the screening by a screw press, wherein the accept fraction that is fed to the screw press has a consistency of at least 3%, and wherein in the dewatering, the pulp composition is typically dewatered to a consistency of at least 20%.
  • the dewatered accept fraction may be fed to a bleaching step, optionally after decreasing the consistency of the accept fraction to less than 15%, such as to less than 10%.
  • the consistency of the accept fraction is first increased to above 20% and then decreased to about 8 to 12%, preferably to about 10%, for example to clean the pulp.
  • the reject fraction from the screening may be fed back to the impregnating step or to a step preceding the impregnating step.
  • the reject fraction is fed to the impregnating step or to a step preceding the impregnating step at a consistency in the range 2 to 45%.
  • the pulp composition, such as the reject fraction, fed to the impregnating step has a consistency in the range 4 to 10%.
  • the reject is not fed directly to the refining step but instead to a step preceding the refining step. In that way problems related to maintaining an appropriate consistency in the refiner may be avoided.
  • the consistency of the reject may be allowed to vary in a broader range.
  • An advantage related to feeding the reject to the impregnating step or to a step preceding the impregnating step is that the reject fraction may receive a further impregnation before continuing to the refining.
  • the reject fraction is fed to the impregnating step or to a step preceding the impregnating step without separate dewatering of the reject fraction and/or without separate refining of the reject fraction.
  • the reject fraction may be fed directly from the screening reject output to the impregnating step or to a step preceding the impregnating step.
  • the reject fraction is fed to the impregnating step or to a step immediately preceding the impregnating step, typically without any refining of the reject fraction.
  • the step preceding the impregnating step may be a step of washing the wood chips.
  • the method may comprise leading at least a part of the reject fraction, preferably substantially all of it, directly back to the impregnating step or to a step immediately preceding the impregnating step.
  • the method may comprise leading substantially all of the reject fraction directly back to the impregnating step, preferably without any refining of said reject fraction.
  • At least part of the reject fraction may be directed from the screening to a reject treatment line that is separate from the main line, i.e. does not form part of the main line.
  • the reject treatment line may include a reject refiner.
  • the reject treatment may comprise one or more of the following steps: dewatering the reject, refining the reject by the reject refiner, and screening the reject to an accept and a reject of the reject treatment line.
  • the reject treatment line may comprise one or more screening devices, such as at least two screening devices.
  • the pulp composition input to the screening step of the reject treatment line may have a consistency of at least 2%, such as at least 3%, for example 2 to 5%, preferably 3 to 4%.
  • An output, such as an accept of the reject treatment line may be fed back to the main line, for example to the main line dewatering step, thus to become combined with the accept output from the main line screening.
  • the accept that is output from the reject treatment line may have a consistency of at least 2%, such as at least 3%, for example 2 to 5%, preferably 3 to 4%.
  • an accept from a reject treatment line is directed to the main line dewatering step, such as to the screw press for example at a consistency of at least 2%. [0082] It is preferred to adjust the consistency of the accept that is output from the reject treatment line to the range 2 to 5%.
  • a part of the reject from the screening step is directed back to the impregnating step and another part of the reject from the screening step is directed to the reject treatment line.
  • the present invention may be applicable for the manufacturing of pulp selected from the following group: mechanical pulp, thermomechanical pulp (TMP) chemithermomechanical pulp (CTMP), bleached chemithermomechanical pulp (BCTMP), semichemical pulp, groundwood pulp (GW), pressure groundwood pulp (PGW), stone groundwood pulp (SGW), and combinations thereof
  • TMP thermomechanical pulp
  • CTMP bleached chemithermomechanical pulp
  • GW groundwood pulp
  • PGW pressure groundwood pulp
  • SGW stone groundwood pulp
  • the pulp may be bleached or unbleached.
  • the method is for the manufacturing of chemithermomechanical pulp or bleached chemithermomechanical pulp.
  • the method is for the manufacturing of mechanical pulp, groundwood pulp (GW), pressure groundwood pulp (PGW), stone groundwood pulp (SGW) or thermo mechanical pulp (TMP).
  • GW groundwood pulp
  • PGW pressure groundwood pulp
  • SGW stone groundwood pulp
  • TMP thermo mechanical pulp
  • BCTMP obtained by some embodiments of the present method may be applicable as a material of one or more layers of paperboard, such as folding boxboard, or of paper, such as printing paper or writing paper or tissue paper.
  • the method is for preparation of such pulp that is adapted for the manufacturing of paperboard with the following characteristics:
  • the density of the paperboard is in the range 0.5 - 1.3 g/cm 3 .
  • the brightness of the paperboard is larger than 84%.
  • the method is for preparation of such pulp that is adapted for the manufacturing of paper with the following characteristics:
  • the density of the paper is in the range 0.7 - 1.4 g/cm 3 .
  • the brightness of the paper is larger than 77%.
  • the present invention also concerns a system configured to execute the method according to any of the embodiments described above or their any combinations.
  • the system may form part of a pulp mill.
  • the system may comprise one or more of the following devices: a wood chipping device, a wood chip impregnating system, one or more primary refiners, one or more pulp screening devices, one or more reject refiners, a reject screening device, a pulp dewatering device, such as a disc filter or a screw press, a pulp bleaching system.
  • FIGURE 1 illustrates process steps in a method in accordance with at least some embodiments of the present invention.
  • the process comprises the following steps: chipping 10, impregnating 11, refining 12, screening 13, dewatering 14, optional bleaching 15, and optional washing 16.
  • the screening produces as outputs an accept fraction and a reject fraction.
  • the accept fraction continues in the main line and is directed from the screening 13 to the dewatering 14.
  • the reject fraction if existing, or at least a part of the reject fraction, is fed from the screening 13 back to a step preceding the refining step, for example to the impregnating step 11, as shown by an arrow in FIG. 1.
  • the dewatering 14 may comprise a screw press or a disc filter.
  • FIGURE 2 illustrates process steps in a method in accordance with at least some embodiments of the present invention.
  • the main line comprises the steps of chipping 20, optional impregnating 21, refining 22, screening 23, dewatering 24, optional bleaching 25, and optional washing 26.
  • the method further includes a reject treatment line 27 which is separate from the main line.
  • the reject fraction obtained in the screening 23 is directed to the reject treatment line 27.
  • the reject treatment line may comprise a reject refining step and/or a reject screening step.
  • An output, such as an accept fraction from the reject treatment line 27 may be directed back to the main line, such as to the dewatering 24.
  • the dewatering 24 preferably comprises a screw press.
  • FIGURE 3 illustrates the screening step in the method in accordance with at least some embodiments of the present invention.
  • the incoming pulp composition P is fed to the screening step 33.
  • the screening produces as outputs an accept fraction A and a reject fraction R.
  • the accept fraction A is accepted to continue in the mainline process to the next step, the dewatering by a screw press 34.
  • the reject fraction R is rejected from continuing in the mainline process and instead directed either to a reject treatment line or backwards in the mainline, for example to an impregnating step (not shown here).
  • the consistency of the incoming pulp P which may be refined pulp, is preferably at least 3.5%, for example 3.5 to 4.5%.
  • the consistency of the accept fraction A is preferably at least 3%, such as 3.5 to 4%.
  • the consistency of the reject fraction is preferably at least 4%, such as at least 4.5%.
  • a pulping process comprising direct feeding of the reject from the screening to the impregnating was tested.
  • the process main line included chipping, impregnating, refining, screening, dewatering by a disc filter, and bleaching.
  • the consistency of the pulp composition input to the bleaching was about 10%.
  • the accept from the screening was directed to the disc filter.
  • the reject from the screening was directed either to a conventional reject treatment line or alternatively back to the impregnating step.
  • Test 1 and Test 2 processes, the conventional reject treatment line was bypassed and the reject from the screening was fed back to the impregnating step. Tests 1 and 2 were conducted on different days.
  • the Reference process did not include any back- feeding of the reject but instead the reject from the screening was directed to the conventional reject treatment line comprising a reject refiner.
  • the present invention is industrially applicable at least in the manufacturing of pulp, such as CTMP or BCTMP.

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
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Abstract

Dans un aspect donné à titre d'exemple, l'invention concerne un procédé consistant : à obtenir des copeaux de bois ; à imprégner les copeaux de bois avec une composition d'imprégnation pour obtenir des copeaux de bois imprégnés ; à raffiner les copeaux de bois imprégnés dans au moins un raffineur afin d'obtenir une composition de pâte raffinée ; à tamiser la composition de pâte raffinée afin d'obtenir une fraction acceptée et une fraction rejetée ; et à diriger au moins une partie de la fraction rejetée de l'étape de tamisage à ladite étape d'imprégnation ou à une étape précédant ladite étape d'imprégnation.
PCT/FI2022/050535 2021-08-17 2022-08-17 Procédé, utilisation associée, composition de pâte, et système associé WO2023021243A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
CN202280054667.2A CN117795155A (zh) 2021-08-17 2022-08-17 方法、其用途，浆料组合物和系统
SE2430124A SE2430124A1 (en) 2021-08-17 2022-08-17 A method, use of the same, a pulp composition, and a system
DE112022003992.2T DE112022003992T5 (de) 2021-08-17 2022-08-17 Verfahren, Verwendung desselben, eine Zellstoffzusammensetzung und ein System
CA3228121A CA3228121A1 (fr) 2021-08-17 2022-08-17 Procede, utilisation associee, composition de pate, et systeme associe

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Citations (5)

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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
EP0096548A1 (fr) * 1982-06-04 1983-12-21 Macmillan Bloedel Limited Traitement chimique en deux étapes d'une pâte de bois mécanique
EP0764225A1 (fr) * 1994-06-15 1997-03-26 SCA Mölnlycke AB Pate de cellulose chimico-mecanique volumineuse a faible indice d'egouttage et a faible teneur en buchettes et en matieres a grains fins
WO2001020074A1 (fr) * 1999-09-10 2001-03-22 Stora Kopparbergs Bergslags Aktiebolag (Publ) Procede lie a la production de pate mecanique
WO2006128950A1 (fr) * 2005-05-03 2006-12-07 M-Real Oyj Procede de fabrication de pate mecanique destinee a produire du papier ou du carton

Patent Citations (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
EP0096548A1 (fr) * 1982-06-04 1983-12-21 Macmillan Bloedel Limited Traitement chimique en deux étapes d'une pâte de bois mécanique
EP0764225A1 (fr) * 1994-06-15 1997-03-26 SCA Mölnlycke AB Pate de cellulose chimico-mecanique volumineuse a faible indice d'egouttage et a faible teneur en buchettes et en matieres a grains fins
WO2001020074A1 (fr) * 1999-09-10 2001-03-22 Stora Kopparbergs Bergslags Aktiebolag (Publ) Procede lie a la production de pate mecanique
WO2006128950A1 (fr) * 2005-05-03 2006-12-07 M-Real Oyj Procede de fabrication de pate mecanique destinee a produire du papier ou du carton

Non-Patent Citations (1)

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Title
GOEL K: "UPGRADING MECHANICAL PULPS BY CHEMICAL TREATMENT OF REJECTS PRIOR TO REFINING", ABSTRACT BULLETIN OF THE INSTITUTE OF PAPER CHEMISTRY, THE INSTITUTE OF PAPER CHEMISTRY-LIBRARY. APPLETON, US, vol. 58, no. 8, 1 February 1988 (1988-02-01), pages 1064, XP000028413 *

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CA3228121A1 (fr) 2023-02-23
SE2430124A1 (en) 2024-03-13

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