EP0840820B1 - Method and apparatus for bleaching pulp with a gaseous bleaching reagent - Google Patents

Method and apparatus for bleaching pulp with a gaseous bleaching reagent Download PDF

Info

Publication number
EP0840820B1
EP0840820B1 EP96928093A EP96928093A EP0840820B1 EP 0840820 B1 EP0840820 B1 EP 0840820B1 EP 96928093 A EP96928093 A EP 96928093A EP 96928093 A EP96928093 A EP 96928093A EP 0840820 B1 EP0840820 B1 EP 0840820B1
Authority
EP
European Patent Office
Prior art keywords
pulp
gas
vessel
bleaching
inlet
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
Application number
EP96928093A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0840820A1 (en
Inventor
Walter C. Vliet
Lewis D. Shackford
L. Allan Carlsmith
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Beloit Technologies Inc
Original Assignee
Beloit Technologies 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 Beloit Technologies Inc filed Critical Beloit Technologies Inc
Publication of EP0840820A1 publication Critical patent/EP0840820A1/en
Application granted granted Critical
Publication of EP0840820B1 publication Critical patent/EP0840820B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone

Definitions

  • the present invention relates generally to the bleaching of lignocellulosic materials for use in the pulp and paper industry, and more particularly to a method and apparatus for bleaching pulp with a gaseous bleaching reagent.
  • gaseous reagents including ozone
  • gaseous reagents including ozone
  • ozone gaseous reagents
  • wood pulp is obtained from the digestion of wood chips from repulping of recycled paper or from other sources and is commonly processed in pulp and paper mills in slurry form in water.
  • the term "consistency” is used to express the measured ratio of dry pulp fibers to water, or more specifically, the weight of dry pulp fibers in a given weight of pulp slurry or "pulp stock” as a percentage.
  • Various definitions are used, such as air-dry consistency (a.d.%), or oven-dry (o.d.%), or moisture-free consistency (m.f.%).
  • air-dry consistency a.d.%
  • oven-dry o.d.%
  • moisture-free consistency m.f.%
  • ozone may initially appear to be an ideal material for bleaching lignocellulosic materials, the exceptional oxidative properties of ozone and its relatively high cost have limited the development of satisfactory devices and processes for ozone bleaching of lignocellulosic materials.
  • One known system for bleaching high consistency pulp with ozone includes a device commonly referred to as a fluffer/blower.
  • the pulp is mechanically fluffed within the fluffer/blower in the presence of the ozone and the associated carrier gas (either oxygen or air) so as to form a gas-suspended mixture for transport and initiation of the bleaching reaction.
  • the gas-suspended pulp is then transported through a conduit to the top of a reactor tower, of the porous-bed type.
  • the pulp then drops into the reactor tower to form a porous bed of fluffed pulp which continuously moves downward through a cylindrical reaction tower toward an expanded section which acts as a gas separation chamber.
  • the ozone and carrier gas flow downward through the porous bed at a substantially higher velocity than that at which the pulp bed moves downward through the reactor.
  • the carrier gas then flows into the gas separation chamber within the reactor and is subsequently recycled to an ozone generator.
  • porous-bed reactors of the type just described have proven to be highly efficient with respect to removing or "stripping" the ozone from its carrier gas
  • reactors of this type are subject to the following limitations.
  • the fluffed pulp contains a considerable fraction of individual fibers, a majority of the pulp is present in agglomerated particles called flocs, with each floc containing a substantial number of intertwined individual fibers.
  • flocs are subject to varying permeability which may result in non-uniform bleaching within the reactor due to increased bleaching of outer fibers as compared to that of the inner fibers. This problem may be exacerbated due to local areas of increased pulp density within the reactor.
  • the ozone/pulp reaction is very fast, with the reaction rate being directly proportional to the ozone concentration. This aggravates the non-uniformity of bleaching since a large fraction of the ozone may be consumed prior to reaching the fibers in high density regions within the pulp bed.
  • Other factors contributing to the non-uniformity of pulp bleaching within the reactor include channeling of the gas between pulp particles and the time required for dissolution of the reagent gas in the liquor which surrounds the fibers in the pulp particles.
  • prior systems of this type exhibit limited "turn-down" ratios, i.e. limited flexibility in adjusting to the varying bleaching requirements of different types of pulp (for instance hardwoods versus softwoods) and of varying production rates.
  • the pulp residence time within the fluffer/blower is substantially fixed and is controlled by the fluffer speed required to achieve the desired shredding and fluffing of the pulp.
  • the pulp residence time within the transport conduit interconnecting the fluffer/blower and the bed reactor is also substantially fixed (without an impractical increase in conduit length) due to the transport velocity required within the conduit. Accordingly, the ozone concentration at the inlet to the bed reactor is established by the ozone concentration and flow rate, as well as the pulp input rate, supplied to the fluffer/blower.
  • this is accomplished by providing a method for bleaching pulp with a gaseous bleaching reagent comprising the steps of:
  • this is accomplished by providing a system for bleaching pulp with a gaseous bleaching reagent, with the system comprising:
  • the Figure illustrates a system for bleaching pulp with a gaseous bleaching reagent according to the present invention.
  • System 10 for bleaching lignocellulosic materials, such as high consistency wood pulp, with a gaseous bleaching reagent, according to the present invention.
  • System 10 includes an upstream vessel 12, an intermediate vessel 14 and a downstream vessel 16 which are disposed relative to one another so that lignocellulosic materials, such as high consistency wood pulp, may be reacted with a gaseous bleaching reagent within each of the vessels in succession according to the method of the present invention.
  • the apparatus of the present invention depicted in the illustrative embodiment shown in The Figure will be described in conjunction with a method for bleaching high consistency wood pulp utilizing ozone as the gaseous bleaching reagent, according to the present invention.
  • the apparatus and method of the present invention are not intended to be utilized for the bleaching of either medium consistency or low consistency wood pulp, with the terms high consistency, medium consistency and low consistency referring to the definitions set forth in the Background of this application.
  • the method and apparatus of the present invention may be advantageously utilized in conjunction with gaseous bleaching reagents other than ozone, such as chlorine monoxide, chlorine dioxide, and others.
  • ozone is typically available at a relatively low concentration within a carrier gas, such as oxygen or air.
  • a carrier gas such as oxygen or air.
  • commercially available ozone has a concentration of about 6% to about 10%, by weight, when using oxygen as the carrier gas.
  • contacting gas will refer to the mixture of ozone in an oxygen carrier gas, as well as other gases and vapors, such as by-product gases of reaction, which are present at equilibrium conditions.
  • fresh bleaching gas will be used to denote a mixture of ozone in an oxygen carrier gas supplied from a conventional source, such as a dryer/cleaner and ozone generator, which has not been reacted with the pulp and accordingly does not include reaction by-product gases.
  • High consistency wood pulp 18 is supplied from a conventional dewatering press (not shown) to a compaction feed auger 20.
  • Auger 20 includes a housing 22 having an inlet 24 which is adapted to receive the pulp 18.
  • Feed auger 20 further includes a shaft 26 which is rotatably mounted within housing 22.
  • a screw flight 28 is attached to shaft 26, for rotation therewith, and is effective for compacting the pulp 18 supplied to housing 22 so as to form an impervious pulp plug which is effective for preventing the backflow of gas through feed auger 20.
  • the rotating action of screw 28 causes the pulp plug to advance to a pulp inlet 30 of the upstream vessel 12.
  • upstream vessel 12 comprises a conventional fluffer/blower which functions in a manner well known in the art.
  • Fluffer/blower 12 further includes a means (not shown) for further breaking-up, or fluffing, the disintegrated pulp.
  • This means for fluffing is known in the art and may comprise radially spaced, inner and outer rings of arcuately spaced apart, rotary pins (not shown), mounted for rotation with shaft 34, and a ring of arcuately spaced apart, stationary pins (not shown) attached to housing 36.
  • the disintegrated and fluffed pulp is intensively mixed within fluffer/blower 12 in the presence of a contacting gas, received by a multi-port gas inlet 38.
  • the contacting gas is supplied to inlet 38 from the intermediate vessel 14, in a manner discussed subsequently in greater detail, and includes ozone, oxygen carrier gas, and by-product gases of the reaction occurring within vessel 14.
  • the mixture of the contacting gas and the pulp within fluffer/blower 12 suspends the pulp in the contacting gas and initiates the reaction of the ozone with the pulp.
  • the gas-suspended pulp discharges fluffer/blower 12 through pulp outlet 40 with sufficient velocity so that it is transported to a pulp inlet 42 of the intermediate vessel 14, via conduit 44.
  • the gas-suspended pulp enters an upper portion 41 of the intermediate vessel 14 through inlet 42 in a tangential manner so that the gas-suspended pulp swirls around an inner wall of the upper portion 41 of vessel 14 in a cyclonic fashion.
  • the upper portion 41 of vessel 14 may be referred to in the art as a cyclone.
  • the operation of the fluffer/blower 12 and the gas transport of pulp through conduit 44 to the pulp inlet 42 of vessel 14 requires a volume of gas which is much larger than the total flow of fresh bleaching gas supplied to system 10 from a variety of subsequently discussed sources. As an illustration of this fact, it is noted that for a pulp processing rate of about 500 tons/day, the flowrate of the contacting gas through conduit 44 is about 8,000 cu.
  • the upper portion 41 of vessel 14 includes a gas separator 43 having a generally centrally disposed pipe or conduit 45 which communicates with an upper gas outlet 47 of vessel 14.
  • a significant portion of the contacting gas entering cyclone 41 of vessel 14 is separated from the pulp within separator 43 and is recirculated to one of the ports of the multi-port inlet 38 of the fluffer/blower 12 via conduit 49. It is noted that enriched contacting gas is supplied to a second port of inlet 38 as subsequently described in greater detail.
  • Portion 51 of the contacting gas may be supplied to another portion of the associated bleaching plant for further processing.
  • the intermediate vessel 14 comprises an agitated mixer reactor having a housing 46 and a shaft 48 which is rotatably mounted within housing 46 and driven by conventional means such as a variable speed motor 50. Shaft 48 is sealed as it passes through housing 46 so as to prevent any undesirable leakage of gas externally of reactor 14.
  • the generally centrally disposed pipe 45 of separator 43 is generally concentrically disposed about an upper portion of shaft 48.
  • the agitated mixer reactor 14 further includes a plurality of arms, or paddles 52 which are attached to shaft 48 for rotation therewith, and extend radially outwardly from shaft 48. Additional contacting gas is supplied to the agitated mixer reactor 14 through gas inlet 54 from the downstream vessel 16, in a subsequently described manner.
  • the pulp is agitated within the agitated mixer reactor 14 80 as to maintain the pulp in suspension in the contacting gas and to further react the pulp with the ozone present in reactor 14.
  • the contacting gas flows in co-current relationship with the pulp through the agitated mixer reactor 14, which is preferable.
  • the contacting gas may alternatively flow in countercurrent relationship with the pulp through the agitated mixer reactor 14.
  • the agitated mixer reactor 14 is depicted in a vertical orientation in The Figure, reactor 14 may alternatively be disposed in a horizontal configuration. As discussed previously, a significant portion of the contacting gas entering reactor 14 through inlet 42 is separated from the pulp via separator 43 and recirculated to the fluffer/blower 12 via conduit 49.
  • the gas-suspended pulp, and a first portion of the contacting gas flowing through reactor 14 discharge reactor 14 through a pulp outlet 56 to a pulp inlet 58, comprising an inlet conduit, of the downstream vessel 16 via a conduit 60.
  • the centrifugal action of paddles 52 causes the pulp particles to be flung outward through outlet 56 with a sufficient velocity to travel through conduit 60, which is relatively short in length and horizontally disposed, and into the pulp inlet 58 of vessel 16.
  • the pulp is then gravity-fed through inlet 58.
  • the remaining portion of the contacting gas flowing through reactor 14 discharges through a gas outlet 62 of reactor 14, fpr subsequently described purposes.
  • the downstream vessel 16 comprises a porous bed reactor, with the general function of reactor 16 being well known in the art.
  • the fluffed pulp entering reactor 16 through inlet 58 drops onto a porous bed 64 of fluffed pulp, which moves continuously downward through the porous bed reactor 16.
  • Inlet 58 may include a flow distributor or deflector (not shown) for uniformly distributing the fluffed pulp onto the porous bed 64.
  • the contacting gas flows through the porous bed, so as to further react the pulp with the ozone, at a substantially higher velocity than that of the porous bed.
  • the oxygen carrier gas, and any remaining ozone which has not been consumed, then discharges into an annular gas separation chamber 66 of reactor 16 as indicated by flow arrows 68.
  • the ozone/pulp reaction has been substantially completed and, as known in the art, the concentration of the ozone present in the contacting gas entering gas separation chamber 66 is typically very low.
  • a portion of the contacting gas entering gas separation chamber 66 may be discharged from reactor 16 through a gas outlet 63 of reactor 16, a conduit 65 and a valve 67, as shown by flow arrow 69 so as to off-set the addition of fresh bleaching gas to system 10.
  • valve 55 would be closed.
  • the bleached pulp 70 at the bottom of the porous bed reactor 16 is diluted with recycled filtrate 72 through a dilution nozzle 74 and is then discharged through pulp outlet 76 as dilute, bleached pulp 78.
  • the present invention provides an independent control of the ozone concentration to each of the vessels 12, 14 and 16 while agitating the pulp within vessels 12 and 14 and controlling the pulp residence time within at least vessels 14 and 16 .
  • Fresh bleaching gas comprising freshly generated ozone in an oxygen carrier gas, is supplied to a gas inlet 80 of the porous bed reactor 16 via conduit 82 and control valve 84.
  • Valve 84 is in fluid communication, via conduit 83, with a source 85 of the fresh bleaching gas.
  • Source 85 may comprise an ozone generator and an oxygen dryer/cleaner. Alternatively, fresh bleaching gas may be supplied to conduit 83 from another location within the associated pulp processing plant.
  • the concentration of ozone within the fresh bleaching gas may be in the range of 0.5% to 14% by weight, within the oxygen carrier gas with presently known technology, but is more typically in the range of about 6% to 10% by weight.
  • Valve 84 may be used to control the quantity of fresh bleaching gas supplied to reactor 16, which mixes with the contacting gas entering reactor 16 through pulp inlet 58. Accordingly, a predetermined concentration of ozone within reactor 16 may be independently established, in contrast to those systems wherein the ozone concentration within reactor 16 is determined by the extent of the ozone/pulp reaction within one or more upstream vessels.
  • At least a substantial portion (constituting an entire portion when valve 67 is closed) of the contacting gas entering gas separation chamber 66 of reactor 16 discharges reactor 16 through a gas outlet 86 and a conduit 87 having one end communicating with outlet 86.
  • An opposite end of conduit 87 is attached to a conventional blower 88 which may optionally be used to provide the necessary transport velocity of the contacting gas discharging from outlet 86.
  • the contacting gas then flows through a conduit 89 to a first inlet 90 of a proportioning valve indicated at 92.
  • the concentration of the ozone within the contacting gas discharging from reactor 16 through outlet 86 is determined by a conventional gas analyzer 94 which communicates with the gas outlet 86 of reactor 16 via a conduit 96 and conduit 87.
  • Fresh bleaching gas is supplied to a second inlet 98 of the proportioning valve 92 from a source 100 of the fresh bleaching gas via a conduit 102.
  • source 100 may be separate from the source 85 of fresh bleaching gas discussed previously, or alternatively, may be manifolded together with source 85 so as to provide a common source of fresh bleaching gas.
  • the fresh bleaching gas supplied from source 100 also typically has an ozone concentration of about 6%-10% ozone within an oxygen carrier gas.
  • Valve 92 is used to proportion the amount of fresh bleaching gas from source 100 which is used to enrich the contacting gas discharging from reactor 16 through outlet 86, based on the concentration of the ozone discharging from reactor 16 through outlet 86 as determined by the gas analyzer 94.
  • a desired ozone concentration may be established for the enriched contacting gas discharging from valve 92 through outlet 104 and supplied to the gas inlet 54 of the agitated mixer reactor 14, via conduit 106.
  • a predetermined concentration of ozone may be supplied to the agitated mixer reactor 14, independently of the ozone concentration supplied to the fluffer/blower 12 and porous bed reactor 16.
  • the concentration of ozone provided to the fluffer/blower 12 is also independently controlled in the following manner. As set forth previously, a portion of the contacting gas flowing through the agitated mixer reactor 14 discharges through gas outlet 56 with the suspended, fluffed pulp. The remaining portion of the contacting gas flowing through the agitated mixer reactor 14 discharges reactor 14 through outlet 62 and is supplied to a first inlet 110 of a proportioning valve indicated at 112, via a conduit 114. The concentration of the ozone discharging from outlet 62 of reactor 14 is determined by conventional means such as gas analyzer 116, which communicates with outlet 62 via conduits 118 and 114. Fresh bleaching gas is supplied from a source 120 to a second inlet 122 of valve 112 via a conduit 124.
  • Source 120 may be separate from, or common with, the previously discussed sources 85 and 100 of fresh bleaching gas.
  • Valve 112 proportions the quantities of fresh bleaching gas from source 120 and the contacting gas discharging from outlet 62 of reactor 14, based on the ozone concentration existing at outlet 62 as determined by gas analyzer 116. Accordingly, an enriched contacting gas, having a desired, predetermined ozone concentration, is supplied via an outlet 126 of valve 112 and conduit 128 to the gas inlet 38 of the fluffer/blower 12.
  • Fluffer/blower 12 creates a slight vacuum within conduits 128 and 114 so as to assist in the flow of contacting gas through the gas outlet 62 of the agitated mixer reactor 14.
  • the high consistency wood pulp 18 is supplied to the fluffer/blower 12 via feed auger 20, where it is disintegrated and intensively mixed in the presence of the contacting gas having a selected, predetermined concentration of ozone, so as to suspend the fluffed pulp within the contacting gas and to react the pulp with a portion of the ozone.
  • Some control of the pulp residence time within fluffer/blower 12 may be provided, for instance by using a variable speed motor (not shown) to control the rotating speed of shaft 34.
  • a variable speed motor not shown
  • limited flexibility is available in this regard since, for a given type and consistency of pulp and a given pulp input rate, the speed required to disintegrate and fluff the pulp is somewhat fixed.
  • the fluffed, gas-suspended pulp is then transported to the agitated mixer reactor 14 where it is further agitated so as to maintain the fluffed pulp in suspension in the contacting gas, and to further react the ozone with the pulp.
  • the residence time of the pulp within reactor 14 may be controlled by varying the speed of motor 50, 80 as to vary the rotating, agitating action of paddles 52, and by varying the fill level of pulp within reactor 14.
  • a predetermined concentration of ozone is established within reactor 14 due to the enriched, countercurrent flow of contacting gas supplied from the porous bed reactor 16.
  • the gas-suspended pulp is then transported to the porous bed reactor 16 where it is further reacted with ozone, having a predetermined concentration.
  • the ozone concentration supplied to each of the vessels 12, 14 and 16 is the same and is equal to that which is determined to be required to establish a sufficient driving force to maintain the ozone/pulp reaction, i.e. to sustain a movement of the ozone towards the center of the individual pulp particles. It is noted that this concentration may vary with the type of pulp being processed, for instance whether hardwood or softwood pulps are being bleached. In other instances, it may be determined that it is desirable to provide ozone at different concentrations to vessels 12, 14 and 16.
  • the control of the pulp residence time within at least the agitated mixer reactor 14 and the porous bed reactor 16, in combination with the ability to independently control the ozone concentration supplied to fluffer/blower 12, and reactors 14 and 16 permit increased process flexibility with the present invention and allow the percentage of the ozone/pulp reaction within each vessel to be independently controlled, with the percentage of reaction defined as the percentage of ozone consumed for a given quantity of ozone.
  • the inventor has determined that in order to effect an economy of energy utilization, a minimization of pulp particle damage due to mechanical mixing, and a uniformity of pulp bleaching, that the range of reactions within the various vessels are as follows: about 10% to about 70% within fluffer/blower 12; about 10% to about 70% within agitated mixer reactor 14; and about 10% to about 70% within the porous bed reactor 16. More preferably, the inventor has determined that the range of reaction between the ozone and the pulp within each vessel is as follows: about 30% to about 40% within the fluffer/blower 12; about 30% to about 50% within the agitated mixer reactor 14; and about 10% to about 25% within the porous bed reactor 16.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Apparatus Associated With Microorganisms And Enzymes (AREA)
  • Manipulator (AREA)
EP96928093A 1995-07-26 1996-07-16 Method and apparatus for bleaching pulp with a gaseous bleaching reagent Expired - Lifetime EP0840820B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US144795P 1995-07-26 1995-07-26
US1447P 1995-07-26
PCT/US1996/012902 WO1997005327A1 (en) 1995-07-26 1996-07-16 Method and apparatus for bleaching pulp with a gaseous bleaching reagent

Publications (2)

Publication Number Publication Date
EP0840820A1 EP0840820A1 (en) 1998-05-13
EP0840820B1 true EP0840820B1 (en) 1999-04-28

Family

ID=21696060

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96928093A Expired - Lifetime EP0840820B1 (en) 1995-07-26 1996-07-16 Method and apparatus for bleaching pulp with a gaseous bleaching reagent

Country Status (7)

Country Link
EP (1) EP0840820B1 (pt)
JP (1) JPH10510599A (pt)
AT (1) ATE179469T1 (pt)
BR (1) BR9609840A (pt)
CA (1) CA2227690A1 (pt)
DE (1) DE69602269T2 (pt)
WO (1) WO1997005327A1 (pt)

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0492040A1 (en) * 1990-12-21 1992-07-01 Kamyr, Inc. Tumbling ozone reactor for paper pulp
EP0492039A1 (en) * 1990-12-27 1992-07-01 Kamyr, Inc. Pneumatic reactor ozone bleaching of paper pulp
CA2046717A1 (en) * 1991-02-06 1992-08-07 Beloit Technologies, Inc. Method and apparatus for treating fibrous materials with a gaseous reagent
NZ242792A (en) * 1991-05-24 1993-12-23 Union Camp Patent Holding Two-stage pulp bleaching reactor: pulp mixed with ozone in first stage.
EP0674731A4 (en) * 1992-12-18 1997-06-18 Ingersoll Rand Co METHOD AND APPARATUS FOR REGULATING WOOD PULP BLEACHING.

Also Published As

Publication number Publication date
CA2227690A1 (en) 1997-02-13
ATE179469T1 (de) 1999-05-15
WO1997005327A1 (en) 1997-02-13
DE69602269D1 (de) 1999-06-02
DE69602269T2 (de) 1999-09-16
JPH10510599A (ja) 1998-10-13
BR9609840A (pt) 1999-03-09
EP0840820A1 (en) 1998-05-13

Similar Documents

Publication Publication Date Title
CA1043147A (en) Method and device for distribution and mixing-in of gas and/or liquid in pulp suspensions of high concentration
CA2113450C (en) Method and apparatus for separating gas from a gaseous material
CA2012771C (en) Method of bleaching cellulose pulp with ozone
CA2321863C (en) Method and apparatus for feeding a chemical into a liquid flow
US7758725B2 (en) Method of mixing a paper making chemical into a fiber suspension flow
US4298426A (en) Method and apparatus for treating pulp with oxygen in a multi-stage bleaching sequence
RU2114231C1 (ru) Способ отбелки частиц высококонсистентной целлюлозы (варианты), реактор для отбелки частиц высококонсистентной целлюлозы и система для отбелки целлюлозы озоном
US4295926A (en) Method and apparatus for treating pulp with oxygen
EP0060104B1 (en) Drying wood pulp
EP1409789A1 (en) Method of loading a fiber suspension with calcium carbonate
US4298427A (en) Method and apparatus for intimately mixing oxygen and pulp while using an alkali to extract bleaching by-products
AU646267B2 (en) Method and apparatus for treating fibrous materials with a gaseous reagent
EP0106609A1 (en) Apparatus and method for oxygen extraction of lower consistency pulp
EP0840820B1 (en) Method and apparatus for bleaching pulp with a gaseous bleaching reagent
US4030969A (en) Method of dispersing a bleaching agent into a stream of fibrous cellulosic pulp material in a throttling nozzle
US5942088A (en) Apparatus for bleaching high consistency pulp with a gaseous bleaching reagent
US5562806A (en) Variable angle powered cyclone
US6358363B1 (en) Method and apparatus for bleaching pulp using two fluidizing mixers

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19980102

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT DE ES FI SE

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

17Q First examination report despatched

Effective date: 19980522

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT DE ES FI SE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY

Effective date: 19990428

Ref country code: FI

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19990428

Ref country code: ES

Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY

Effective date: 19990428

Ref country code: AT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 19990428

REF Corresponds to:

Ref document number: 179469

Country of ref document: AT

Date of ref document: 19990515

Kind code of ref document: T

REF Corresponds to:

Ref document number: 69602269

Country of ref document: DE

Date of ref document: 19990602

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000503