EP0674730A1 - Procede et dispositif de melange de reactif de blanchiment et de pate a papier - Google Patents

Procede et dispositif de melange de reactif de blanchiment et de pate a papier

Info

Publication number
EP0674730A1
EP0674730A1 EP94903584A EP94903584A EP0674730A1 EP 0674730 A1 EP0674730 A1 EP 0674730A1 EP 94903584 A EP94903584 A EP 94903584A EP 94903584 A EP94903584 A EP 94903584A EP 0674730 A1 EP0674730 A1 EP 0674730A1
Authority
EP
European Patent Office
Prior art keywords
pulp
chamber
contactor
bleaching reagent
reagent
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.)
Withdrawn
Application number
EP94903584A
Other languages
German (de)
English (en)
Other versions
EP0674730A4 (fr
Inventor
L. Allan 59 New Boston Road Carlsmith
Patrick D. Murphy
Oscar Luthi
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.)
Ingersoll Rand Co
Original Assignee
Ingersoll Rand Co
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 Ingersoll Rand Co filed Critical Ingersoll Rand Co
Publication of EP0674730A1 publication Critical patent/EP0674730A1/fr
Publication of EP0674730A4 publication Critical patent/EP0674730A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/18—Stationary reactors having moving elements inside
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/60—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis
    • B01F27/70—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis with paddles, blades or arms
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00164—Controlling or regulating processes controlling the flow
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/18—Details relating to the spatial orientation of the reactor
    • B01J2219/182—Details relating to the spatial orientation of the reactor horizontal

Definitions

  • This invention relates generally to pulp manufacturing processes and equipment and more particularly to contactors for promoting intimate contact between high consistency pulp and a gaseous bleaching reagent.
  • Fluffed pulp at 40-45% consistency contains a considerable fraction of individual fibers, but the majority of the fiber is present in agglomerated particles called floes, each containing a substantial number of individual fibers, and measuring about 1/4 to 1/2 inch in diameter, or about 2 - 4 times the fiber length. These particles are porous and permeable to gaseous bleaching reagents.
  • floes agglomerated particles
  • These particles are porous and permeable to gaseous bleaching reagents.
  • flocculation has been widely studied in dilute water suspensions of pulp fibers, it has only recently been recognized that the same phenomenon occurs in gaseous suspensions of moist fibers - for example, at the discharge of a refiner or fluffer used to prepare pulp for gaseous bleaching. (Garner & Kerekes, TAPPI, 63 (6): 103(1980).
  • the floes settle into a bed with a bulk density of about 3.0 pounds (dry fiber weight) per cubic foot.
  • the fluff consists of about 5% fiber and 95% gas (or void) volume, as the water is mostly contained within the fibers.
  • the volume of gas required for bleaching is, however, much larger than the void volume in the fluffed pulp.
  • the fluffed pulp mass is easily compressed by the action of bulk solids handling equipment to form wads and clumps having much higher density and much lower gas permeability.
  • Bleaching gas flows much more slowly through such wads and clumps and much more rapidly through the wad-to-wad contact areas. The result is overbleached contact areas and underbleached wad cores.
  • the delignification (or bleaching) reaction proceeds so quickly that it will be about 90 - 95% completed within the transit chamber between the fluffer and the second chamber, even though the transit chamber is usually fairly small as will be illustrated below.
  • the transit chamber is usually fairly small as will be illustrated below.
  • mixing blades be designed in such a way that the "plug flow" of the wood pulp not be disturbed by the action of the rotor, and that the axial transport of the pulp be achieved without “backmixing” or “forwardmixing” (dispersion) within the mixing chamber.
  • the second disadvantage is that the rotary motion of the mixer causes centrifugal forces to pack the pulp against the wall of the mixer, leaving a clear path for the reagent gas to pass through it without contacting the pulp to any appreciable degree.
  • a contactor for providing intimate contact between pulp and a gaseous bleaching reagent including an elongate substantially cylindrical chamber having an inlet and outlet for pulp and for the gaseous bleaching reagent; a rotatably driven shaft extending along an axial centerline of the chamber; means, mounted on the rotatable shaft, for radially tossing the pulp to maintain a substantially uniform distribution of pulp within successive transverse planes of the cylindrical chamber; and means for regulating flow of gaseous bleaching reagent for transporting the pulp through the contacting chamber to the outlet.
  • Fig. 1 is a general overall fragmentary schematic view of a bleaching system to illustrate the contactor of the present invention in its operating environment;
  • Fig. 2 is a side elevation sectional view of an embodiment of the contactor to show key operating features thereof;
  • Fig. 3 is an end sectional view looking upstream from line 3-3 of Fig. 2;
  • Fig. 4 is a view, as in Fig. 3, to represent the contactor operating with a charge of pulp;
  • Fig. 5 is a fragmentary side elevation sectional view illustrating an alternative contactor blade/arm assembly configuration
  • Fig. 6 is a view, as in Fig. 5, showing a third alternative design of the contactor blade/arm assembly.
  • Fig. 7 is a graphic illustration of the relationship between gas flow velocity and pulp transport velocity through the contactor of the present invention.
  • Fig. 1 shows a pulp bleaching system for bleaching high consistency pulp with a gaseous reagent.
  • the pulp is fluffed in the presence of the reagent/carrier gas mixture in fluffer 10 and fed to inlet 52 of contactor 50. After passing through contactor 50, the pulp and gas mixture pass through discharge outlet 58 and into finishing reactor vessel 100.
  • the relative locations of the system components in this figure are chosen for ease of illustration purposes and are not intended to limit the locations of such components in practice.
  • the contactor 50 consists of a substantially cylindrical chamber 60 having a rotatable shaft 54 extending along the axial centerline of the chamber 60.
  • a number of arms 55 radiate outwardly from the shaft 54 and carry scoop-shaped blades 56 at their outboard ends.
  • Blades 56 are shaped with leading edges closely following the wall of chamber 60 to avoid compacting the pulp while lifting it free of the wall and trailing edges inclined inwardly to toss the fluffed pulp radially inward within a transverse plane and toward shaft 54.
  • the arms 55 and blades 56 are made with no bias so they do not drive the pulp forward or backward but only inwardly from the wall.
  • the "no bias” design significantly reduces dispersion of the pulp within the contactor chamber and improves uniformity of contact time, while the "radial only” tossing behavior of the blades effectively counteracts the centrifugal forces due to rotary motion and results in a fairly uniform dispersion of pulp, across the radial extent of chamber 60.
  • the pulp is transported from inlet 52 to outlet 58 solely by the gas flow through the chamber.
  • the blades 56 are mounted on two arms 55 in a symmetric manner to avoid any axially forward or backward unbalanced influences on the pulp suspension. This also offers increased strength and rigidity by providing support at both axial extremes of each blade. The blades resist axial misalignment due to the improved strength and rigidity. This also permits use of thinner and lighter arms which interfere less with travel of the fluffed pulp through the contactor.
  • the face of the blade 56 which contacts the pulp is either curved or straight. In either case the angle of the face of the blade at its leading edge is very important. On a curved blade, the minimum practical angle for structural strength is about 10 degrees from the tangent to the circle defining the locus of the tip of the blade during operation of the contactor. The blade can then curve inward so that the angle of its heel reaches an angle of about 35 degrees from the same tangent line.
  • a straight blade requires a contacting face which is set at between about 15 degrees and 25 degrees from the tangent.
  • Arms 55 and blades 56 are positioned on the shaft 54 and are spaced apart generally only enough so that they do not overlap adjacent arms and blades. Occasionally, a spacing equal to 1/4 to 1/2 the axial extent of a single blade is allowed as required for contactor performance. In smaller diameter machines it is important that only one arm 55 and blade 56 be positioned at each axial location on the shaft 54, as multiple blades running in one plane impart too much rotary motion and not enough lifting motion to the fluffed pulp as explained below.
  • the blades 56 and arms 55 are arranged at different angular positions on the shaft 54 to balance the rotor against vibration.
  • Fig. 4 is a representation of the action of the scoop-shaped blades 56 on the fluffed high consistency pulp in the contactor 50.
  • the pulp drops to the bottom of chamber 60, blades 56 continuously scoop it up and toss it upward and inward, within a transverse plane, toward the shaft so that the particles 75 follow a transverse flight path across the chamber.
  • the pulp particles 75 are carried axially forward in chamber 60 by the flow of reagent gas mixture until they again hit the chamber wall and are stopped by friction.
  • the pulp particles 75 travel axially through the chamber in a series of short gas borne leaps until they reach discharge outlet 58 and are deposited in finishing reactor 100 where the low-rate portion of the bleaching reaction is carried to its practical limit.
  • the transport mechanism described has been confirmed, in tests using a contactor chamber having transparent walls, by stopping the pulp feed and shaft rotation simultaneously during normal running.
  • the pulp suspension stopped rotating and fell to the bottom of the chamber, filling it to a level between one third and one half full.
  • the bulk density of the pulp at rest is about 3.0 pounds of dry fiber per cubic foot while the bulk density in motion during normal contactor operation is about 1.2 pounds of dry fiber per cubic foot.
  • the gas flow was maintained, the pulp did not move forward again until the rotor was restarted.
  • the rotating pulp suspension continued to fill the chamber but did not travel forward or backward. This demonstrated the "no bias" operation of the blades 56 and arms 55 and confirmed the achievement of controllable gas transport through contactor 50.
  • Fig. 5 shows a contactor 50 with blades 56 each symmetrically mounted on a single arm 55.
  • This is an alternative embodiment of the blade/arm assembly which provides pulp tossing which is virtually bias free in net effect. As a whole, the pulp receives no transport bias from the blades; however there is a slight degree of local forward and backward dispersion due to pulp particles falling off the axial ends of the blades. For this reason, the two arm design of Fig.2 is preferred.
  • Fig. 6 The alternative embodiment shown in Fig. 6 is the same as the embodiment already discussed with respect to Fig. 5 except that blades 56 are attached, at one end extremity, to arms 55 to produce a slight transport bias in the direction of excess projection of the blades. This is also thought to be attributable to some axially forward spillage of pulp from the free ends of the offset mounted blades 56. It is most useful in setting the limits for the gas flow requirements for the desired pulp transport rate in chambers of different sizes.
  • the offset of blades 56 is shown as downstream, but it can be upstream asell, which would create a slight upstream bias.
  • an optimum residence time or dwell time for the pulp in the contactor is determined.
  • the offset of blades 56 the degree of bias is varied and, as a consequence of that bias variation, so is the gas flow required for such pulp dwell time.
  • the relationship between the gas flow velocity and the pulp transport velocity is schematically illustrated in Fig. 7 for a 15 inch diameter contactor at a production rate of 30 TPD (tons per day).
  • the velocity of pulp transport through the contactor is approximately 1/10 of the velocity of the reagent gas mixture. This is due to the interruptions in the flight of the pulp particles each time they hit the chamber wall. Of course, without this velocity difference the bleaching reaction would be much less uniform and much less efficient.
  • the pulp transport is by gas borne jumps accomplished during the transverse flights of the fluffed pulp particles caused by the blades 56. Since forward axial movement of pulp only occurs during those flights, it is clear that, for a given gas flow velocity, the rate of pulp transport is directly proportional to the rotor speed or to the amount of time the pulp particles are in flight due to the action of the blades.
  • Pulp is fed at 500 tons per day (694 pounds per minute dry fiber) to fluffer 10.
  • Gaseous reagent consisting, for example, of ozone at a concentration of 1 3/4% in oxygen carrier gas is injected through valve 102 and pipe 120 into the fluffer where it is mixed with the pulp.
  • the pulp and the gas pass through inlet 52 into contactor 50 and together pass through outlet 58 into finishing reactor 100.
  • a rotor speed of 60 to 90 revolutions per minute is about optimum.
  • the gas flow is about 6000 cubic feet per minute, resulting in a gas velocity through the contactor of about 10 feet per second.
  • the resulting pulp velocity is about 0.9 feet per second, creating a pulp retention time of 12 seconds.
  • This invention eliminates many of the difficulties encountered in bleaching high consistency pulp using ozone in an oxygen carrier gas.
  • the non-uniform brightness caused by overbleaching and underbleaching is greatly reduced by the intimate contact and plug flow of the fluffed pulp provided by the gas transport of the pulp through the contactor.
  • the non-bias design of the blades and the arms assures that only by intimate contact with the transporting reagent gas mixture can the pulp travel through the contactor. Provision of proportioning valves for balancing volumetric flows of bleaching gas and carrier gas to yield a required quantity of gaseous bleaching reagent, determined by pulp transport and pulp bleaching requirements, allows a high degree of adjustability of the reaction within the contactor chamber.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Organic Chemistry (AREA)
  • Paper (AREA)

Abstract

Un appareil (50) permettant de mettre en contact intime la pâte à papier et un agent de blanchiment gazeux comprend une chambre cylindrique sensiblement allongée (60) dont le diamètre interne est proportionnel à la capacité de mélange, et comportant un orifice d'entrée (52) pour la pâte à papier, le gaz porteur et le réactif de blanchiment gazeux; un arbre rotatif (54) s'étendant à travers la chambre le long d'une ligne centrale et axiale de celle-ci; des moyens, montés sur l'arbre rotatif, permettant de lancer radialement la pâte à papier dans des plans transversaux successifs afin de maintenir une répartition sensiblement uniforme de la pâte à travers l'étendue radiale de la chambre cylindrique (60) avec un minimum de mélange axial; ainsi que des moyens supplémentaires permettant de réguler l'écoulement gazeux à travers l'orifice d'entrée (52) afin de transporter la pâte à travers l'appareil mélangeur, cet écoulement étant proportionné de façon à permettre une durée de séjour prédéterminée de la pâte dans la chambre telle que déterminée par les dimensions de la chambre, la vitesse de rotation de l'arbre, la concentration de l'agent de blanchiment, la consistance de la pâte et les impératifs de production de cette dernière.
EP94903584A 1992-12-18 1993-12-09 Procede et dispositif de melange de reactif de blanchiment et de pate a papier. Withdrawn EP0674730A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US99298692A 1992-12-18 1992-12-18
US992986 1992-12-18
PCT/US1993/012035 WO1994015017A1 (fr) 1992-12-18 1993-12-09 Procede et dispositif de melange de reactif de blanchiment et de pate a papier

Publications (2)

Publication Number Publication Date
EP0674730A1 true EP0674730A1 (fr) 1995-10-04
EP0674730A4 EP0674730A4 (fr) 1996-04-10

Family

ID=25538975

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94903584A Withdrawn EP0674730A4 (fr) 1992-12-18 1993-12-09 Procede et dispositif de melange de reactif de blanchiment et de pate a papier.

Country Status (5)

Country Link
EP (1) EP0674730A4 (fr)
CN (1) CN1092833A (fr)
CA (1) CA2151814A1 (fr)
FI (1) FI952998A0 (fr)
WO (1) WO1994015017A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100396079B1 (ko) * 1999-10-26 2003-08-27 주식회사 포스코 폐산탱크의 슬러지 침전 방지장치
CN101550661B (zh) * 2009-05-06 2011-06-15 江苏华机环保设备有限公司 升流漂白塔底的叶轮式纸浆分布器
SE542365C2 (en) * 2018-10-30 2020-04-14 Valmet Oy Mixer for mixing chemicals into pulp
CN114921989B (zh) * 2022-06-08 2024-08-23 浙江临安金洲纸业有限公司 一种造纸的纸浆疏解装置

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2460008A (en) * 1943-10-23 1949-01-25 Bamag Ltd Concurrent flow drier with rotor, stationary casing, and terminal separation means for drying materials and drying fluid
US2627668A (en) * 1949-05-17 1953-02-10 New Jersey Zinc Co Method of contacting solids and gases
SE389351B (sv) * 1975-03-14 1976-11-01 Kamyr Ab Sett och anordning for fordelning och inblandning av gas och/eller vetska i massasuspensioner av hog koncentration.
US5181989A (en) * 1990-10-26 1993-01-26 Union Camp Patent Holdings, Inc. Reactor for bleaching high consistency pulp with ozone
CA2046717A1 (fr) * 1991-02-06 1992-08-07 Beloit Technologies, Inc. Methode de traitement de matieres fibreuses au moyen d'un reactif gazeux et appareil connexe

Also Published As

Publication number Publication date
FI952998A7 (fi) 1995-06-16
FI952998A0 (fi) 1995-06-16
EP0674730A4 (fr) 1996-04-10
CA2151814A1 (fr) 1994-07-07
CN1092833A (zh) 1994-09-28
WO1994015017A1 (fr) 1994-07-07

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