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WO1999027177A1 - Procede de desencrage et d'elimination des autres contaminants du vieux papier - Google Patents

Procede de desencrage et d'elimination des autres contaminants du vieux papier Download PDF

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Publication number
WO1999027177A1
WO1999027177A1 PCT/US1998/024812 US9824812W WO9927177A1 WO 1999027177 A1 WO1999027177 A1 WO 1999027177A1 US 9824812 W US9824812 W US 9824812W WO 9927177 A1 WO9927177 A1 WO 9927177A1
Authority
WO
WIPO (PCT)
Prior art keywords
flotation
paper
contaminants
repulped
hydrophobic
Prior art date
Application number
PCT/US1998/024812
Other languages
English (en)
Inventor
Peter Seifert
Original Assignee
Thermo Black Clawson Inc.
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 Thermo Black Clawson Inc. filed Critical Thermo Black Clawson Inc.
Publication of WO1999027177A1 publication Critical patent/WO1999027177A1/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00—Flotation
    • B03D1/14—Flotation machines
    • B03D1/1431—Dissolved air flotation machines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00—Flotation
    • B03D1/14—Flotation machines
    • B03D1/1418—Flotation machines using centrifugal forces
    • 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
    • D21B1/30—Defibrating by other means
    • D21B1/32—Defibrating by other means of waste paper
    • D21B1/325—Defibrating by other means of waste paper de-inking devices
    • 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
    • D21C5/02—Working-up waste paper
    • 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
    • D21C9/08—Removal of fats, resins, pitch or waxes; Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/66—Pulp catching, de-watering, or recovering; Re-use of pulp-water
    • D21F1/70—Pulp catching, de-watering, or recovering; Re-use of pulp-water by flotation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/64—Paper recycling

Definitions

  • a sticky can be any tacky impurity in a paper stock suspension, and as such is commonly found as a result of the repulping of old paper material.
  • a sticky is in the form of a discrete particle or groups of such particles clumped together and usually of a size that is visible to the naked eye as well as in any hand sheet made from the pulp containing stickies.
  • stickies may be formed at times by wood resin in new pulp, when old paper is repulped, the stickies are generally very small pieces of plastic materials and, like ink and carbon particles, they are generally of a hydrophobic nature.
  • the hydrophobic contaminants are attached to the paper and must be debonded from it to permit separation and removal from the pulp slurry.
  • the debonding occurs in the pulper, in the presence of chemical additives such as surfactants, detergents, deinking chemicals, and sometimes caustic. These chemicals act similarly to a laundry process.
  • the particles are conventionally separated in a de-ink flotation step, with the aid of air bubbles. The particles attach to the bubbles and are carried to the slurry surface, where they form a foam that can be removed.
  • additional de-ink chemicals may be added ("displectors", saponified fatty acid, or generic nonionic dispersers/collectors, for example).
  • deinking chemicals are required to activate already hydrophobic stickies, so that they can stick to air bubbles. Such attachment should be possible without chemicals.
  • certain deinking chemicals have hydrophobic and hydrophillic ends. If the hydrophobic ends attach themselves to the hydrophobic particle, they actually render it hydrophilic, which is not desirable.
  • deinking flotation chemistry is a poorly understood science and practice. An explanation for the shortfall in removal efficiency may be that the hydrophobic particles (ink, stickies, etc.), which should float easily, lose their hydrophobicity in the wet process before they arrive at the flotation cell. This may be due to the chemicals which are added in the pulper, or afterwards, prior to flotation,
  • the invention includes methods of removal of hydrophobic ink and stickies, or other hydrophobic particles from a suspension of repulped old paper product, whereby the hydrophobic nature of the particle surface is preserved, at least until the flotation deinking step.
  • This objective is achieved by applying one or more of the following principles:
  • deinking is accomplished in hydrocyclone cleaners.
  • Flotation deinking in hydrocyclone cleaners has been proposed and tried on an exploratory basis with air being added at the pump suction feeding the reverse cleaner. No records of such trials are known to exist as these apparently were not successful.
  • a dissolved air step may be added prior to applying material to a hydrocyclone cleaner since the pressure is released during the passage of the pulp through the feed nozzle and into the cleaner itself.
  • bubbles small in diameter migrate quickly toward the central core area of the reverse cleaner, due to the large pressure gradient. Foam and water are removed at the base, at the rejects opening, and a deinked pulp is removed at the apex.
  • Forward and reverse cyclone cleaners are well known in the art, but their use in flotation type deinking is believed to be new, as described herein.
  • the use of a hydrocyclone cleaner for deinking, in the context of this invention has particular merit in view of the relatively short residence time required, permitting the repulped material with hydrophobic contaminants to be quickly subjected to separation with low residence time, in order to take maximum advantage of the inherent hydrophobic nature of the contaminants.
  • Examples of apparatus used in reverse cleaning include Braun U.S. Patent No. 3,912,579 and Braun et al. U.S. Patent No. 3,557,956.
  • the invention may be characterized as a method or process for removing stickies and other hydrophobic contaminants, such as carbon and ink particles, from waste papers including the steps of performing an initial substantially dry repulping and dispersion operation to the waste paper to reduce the size and to disassociate the hydrophobic contaminants from the paper fibers, optionally storing such repulped and dispersed material for further processing, optionally subjecting the repulped and dispersed material to a screening to remove larger clumps therefrom, diluting said material with water to form a pumpable mixture suitable for flotation separation and immediately or as soon as practicable thereafter, subjecting said diluted material to a flotation type separation.
  • the diluted repulped material may be subjected to water with dissolved air therein either as dilution water or as a downstream additive, and the combined streams applied as a slurry to the inlet of a reverse hydrocyclone cleaner so that the air expansion in the slurry entering the cleaner chambers forms bubbles for attachment to the hydrophobic components for delivery through the lightweight overflow port of the hydrocyclone cleaner.
  • the invention may be further characterized as a process of operating a flotation cell system for removing hydrophobic contaminants from a slurry of repulped paper stock in which the holding times in which the stock suspension is subjected to or mixed with water is reduced as far as practical to retain the maximum hydrophobicity of the hydrophobic particles, which may include stickies as well as carbon and ink particles, thereby to increase the efficiency of an existing system.
  • the time interval in which the repulped waste paper material is subjected to wet processing, in which the solid content in the slurry containing such material is less than 20% may be reduced to as low as about five seconds prior to a flotation step.
  • hydrophobic components such as stickies and carbon
  • hydrophobic components are separated from a paper stock slurry containing such components by a process including the steps of applying such slurry to the inlet of a hydrocyclone cleanser such as a reverse type cleaner and simultaneously applying with said slurry dissolved air in water either as part of the slurry or as an adjunct to the slurry, and permitting said air to expand as bubbles within the hydrocyclone to carry off as a foam or a foam rich stream such hydrophobic materials.
  • a hydrocyclone cleanser such as a reverse type cleaner
  • Another object of the invention is to provide systems and methods by which the input parameters including residence time, consistency, and/or chemicals added are optimized with the view of maintaining or enhancing the hydrophobic nature of the contaminants, to the end that bubble attachment is enhanced at the flotation step. More particularly, it is an object of the invention to optimize the conditions that permit the removal of hydrophobic contaminants by taking such steps as to preserve the hydrophobic nature of such contaminants prior to flotation removal.
  • FIG. 1 is a diagram of a system by which the invention may be practiced
  • Fig. 2 is a further diagram showing another form of system by which the method may be practiced
  • Fig. 3 illustrates diagramatically an aspect of the invention.
  • a wastepaper content to be repulped may be treated and handled in accordance with the teachings of co-pending allowed application Serial No. 08/651.812 filed May 25, 1996 as a Continuation-In-Part of Serial No. 08/342,852 filed November 21, 1994 to provide a relatively dry defibered pulp, now U.S. Patent No. 5,762,756 which is incorporated by reference.
  • dry I mean that the product will have a solids content greater than about 20% by weight and preferably between 20%) and up to 80% or more by weight; effectively, a substantially dry product.
  • Such a product may be defibered in a Hi-Con type pulper of Thermo Black Clawson Inc.
  • a twin screw kneading device may be used as shown in U.S. Patent 4,993,649 in which screws rotated in opposite directions and are tapered in diameter, to affect simultaneous pulping kneading and dispersion.
  • Other apparatus which may be employed for essentially dry pulping and dispersion include the Lemort "Betonniere" drum type pulper.
  • the dry pulper or kneader is illustrated at 10 and, as previously described, provides a relatively "dry" defibered pulp containing hydrophobic contaminants which may be subject to rapid dilution in a "zero" level stand pipe or induction pipe 15 where a controlled amount of water may be added from a water source 20.
  • Sufficient water is added to provide a pumpable mixture in the range of about 4-5% solids and is delivered by a pump 21 through a coarse/fine screen 25. At the outlet side of the screen more water may be added to a dilution of about 2% consistency and this product is then delivered by a pump 26 to an air sparger or injector 30 directly to the inlet 32 of a reverse hydrocyclone cleaner 35.
  • the entire residence time of the dry pulp, containing hydrophobic contaminants, from the induction pipe 15 to the inlet of the reverse cyclone 35 may be in the order of as low as 5 seconds, although longer residence times may be required due to particular details of the equipment. In any event, the residence time is substantially less than the one to two hour or more resident time now conventionally employed in flotation systems.
  • the first step is the application of the dry defibered pulp from the defibering apparatus 10 to apparatus in which a sufficient amount of water may be added to provide a pumpable mix, such as 4-5%o solids by weight.
  • the next step is to pump the resulting slurry through a suitable screen, such as a coarse/fine screen 25 for contaminant removal.
  • water may be added to a consistency of about 2% and the suspension is applied through a sparger or air injector 30 to the inlet 32.
  • the inlet consistency will be down to about 1%) solids content.
  • conventional flotation apparatus may be employed.
  • Predominately foam will be separated through the port 40 at a low liquid and solids reject rate or alternatively, the foam may be discharged as a foam laden liquid stream.
  • the latter may be advantageous when the addition of surfactants is minimized and under such conditions, it is possible that the foam particles may be weak, thereby releasing particles back into the fluid and it would therefore be advantageous to remove a fluid stream enriched with rejected particles rather than simply removing the foam content alone.
  • the example including Figure 1 whether the air is added by a sparger or directly to the inlet 32. is characterized by a minimum of dwell time from the dry pulping step, passing directly to a screening step and from there directly to a flotation step with a minimum of residence time.
  • the residence time will be substantially less than the typical one to two hours or more residence time and may be as low as five seconds, although it is believed that quite satisfactory results can be obtained with a minimum of loss of hydrophobicity by times which are in the order of approximately five to approximately twenty minutes.
  • wastepaper containing hydrophobic contaminants is repulped in a "dry" pulper 50 at an extremely high consistency such as about 50%) with a minimum of water and chemicals.
  • the pulper 50 may be the Hi-Con repulper as previously described or the twin screw kneader as previously described or the dry pulper of U.S. Patent 5,762,7566.
  • the repulped material may be deflaked in a deflaker 51. This may be a "Micar" deflaker of Thermo Black Clawson Inc. Then the material is applied to coarse and fine screens 52, respectively. The dry screening is to remove coarse contaminants.
  • the product may be stored in an optional holding bin 55.
  • the dried and screened pulp is delivered from storage or the holding bin 55 in a rapid dilution step, in which water is added sufficient to make a pumpable suspension and delivered by a pump 57 to a conventional flotation tank 60 with a minimum of residence time, such as about five minutes or less.
  • Air may be supplied by a conventional dissolved air applicator 62 at any particular stage in the process.
  • the resulting slurry is subjected to flotation with a absolute minimum delay, with or without added preflotation chemical treatments.
  • the contaminants are able to retain the highest possible degree of natural or inherent hydrophobicity to provide the maximum effective flotation separation.
  • a relatively dry defibered pulp is mixed with water at point A of a process (Fig. 3), such as an existing process, where a slurry is formed which is sent to further process steps including de-ink flotation at point B of the process.
  • the process is controlled so that the residence time between point A and point B is less than 5 minutes, and may be as low as 5 seconds.
  • Wastepaper containing hydrophobic contaminants, is repulped with water containing predominantly only such chemicals which preserve the hydrophobicity of the particles, and only a minimum of chemicals which reduce the hydrophobicity of the particles, over time.
  • the pulp is then mixed with air bubbles, to which particles may attach, for removal from the slurry by flotation.
  • Repulping of wastepaper containing hydrophobic contaminants is performed under such conditions which preserve the hydrophobicity of the particle surfaces up to the flotation deinking step.
  • Other chemicals in the nature of conditioning agents including surfactants, collectors, dispersants, etc., which might reduce the hydrophobicity of the particles, are added immediately before or during the flotation, so that flotation is facilitated, while maintaining the time of exposure of the other chemicals to the hydrophobic particles.
  • Optimized conditions for removal of hydrophobic contaminants by preserving the hydrophobic nature of such contaminants prior to their removal are: — Optimize by reducing the time of contact between contaminant of wastepaper and water.

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Biotechnology (AREA)
  • Mechanical Engineering (AREA)
  • Paper (AREA)

Abstract

Cette invention permet d'éliminer les contaminants hydrophobes du vieux papier désintégré, tout en préservant l'hydrophobie, en ayant recours à un minimum de produits chimiques réactifs, voire aucun, et à un temps de séjour minimum du vieux papier désintégré dans l'eau. On utilise, à cet effet, une désintégration par voie sèche et éventuellement un filtrage par voie sèche (25) et éventuellement le stockage du papier désintégré en vue d'une séparation rapide par dilution et flottation. Cette invention décrit un procédé utilisant un séparateur à flottation à hydrocyclone, grâce auquel la boue de papier désintégré et dilué est appliquée à une entrée d'un hydrocyclone de type inverse (35), et la partie des rebuts riches en air (40) est éliminée au niveau de la sortie des rebuts de l'hydrocyclone avec les contaminants hydrophobes. On peut abaisser le temps de séjour après dilution jusqu'à cinq secondes pour préserver l'hydrophobie.
PCT/US1998/024812 1997-11-21 1998-11-20 Procede de desencrage et d'elimination des autres contaminants du vieux papier WO1999027177A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US6671897P 1997-11-21 1997-11-21
US60/066,718 1997-11-21

Publications (1)

Publication Number Publication Date
WO1999027177A1 true WO1999027177A1 (fr) 1999-06-03

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004010857A1 (de) * 2004-03-05 2005-11-03 Voith Paper Patent Gmbh Vorrichtung zum Pumpen und Entstippen einer störstoffhaltigen Papierstoffsuspension
WO2008144383A1 (fr) * 2007-05-16 2008-11-27 Buckman Laboratories International, Inc. Procédés pour détecter des contaminants organiques dans de la pâte et des fibres

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3557956A (en) * 1970-01-28 1971-01-26 Bergstrom Paper Co Method for de-inking and removal of certain contaminants from reclaimed paper stock
US4797203A (en) * 1986-02-22 1989-01-10 Elp Products Limited Reverse hydrocyclone cleaner for removing light contaminants from pulp slurry
US5273624A (en) * 1986-12-10 1993-12-28 Beloit Technologies, Inc. Pressurized flotation module and method for pressurized foam separation
US5620565A (en) * 1994-06-29 1997-04-15 Kimberly-Clark Corporation Production of soft paper products from high and low coarseness fibers

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3557956A (en) * 1970-01-28 1971-01-26 Bergstrom Paper Co Method for de-inking and removal of certain contaminants from reclaimed paper stock
US4797203A (en) * 1986-02-22 1989-01-10 Elp Products Limited Reverse hydrocyclone cleaner for removing light contaminants from pulp slurry
US5273624A (en) * 1986-12-10 1993-12-28 Beloit Technologies, Inc. Pressurized flotation module and method for pressurized foam separation
US5620565A (en) * 1994-06-29 1997-04-15 Kimberly-Clark Corporation Production of soft paper products from high and low coarseness fibers

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004010857A1 (de) * 2004-03-05 2005-11-03 Voith Paper Patent Gmbh Vorrichtung zum Pumpen und Entstippen einer störstoffhaltigen Papierstoffsuspension
WO2008144383A1 (fr) * 2007-05-16 2008-11-27 Buckman Laboratories International, Inc. Procédés pour détecter des contaminants organiques dans de la pâte et des fibres

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