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EP0226495B1 - Procédé et appareil pour le blanchiment de la pâte à papier - Google Patents

Procédé et appareil pour le blanchiment de la pâte à papier Download PDF

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Publication number
EP0226495B1
EP0226495B1 EP86402533A EP86402533A EP0226495B1 EP 0226495 B1 EP0226495 B1 EP 0226495B1 EP 86402533 A EP86402533 A EP 86402533A EP 86402533 A EP86402533 A EP 86402533A EP 0226495 B1 EP0226495 B1 EP 0226495B1
Authority
EP
European Patent Office
Prior art keywords
suspension
oxygen
passage
pulp
diffuser
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
EP86402533A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0226495A1 (fr
Inventor
Arthur S. Perkins
Jack A. Davidson
Robert Gum Hong Lee
Derek Horney
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.)
Air Liquide Canada Inc
Original Assignee
Air Liquide Canada 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
Priority claimed from CA000507000A external-priority patent/CA1300320C/en
Application filed by Air Liquide Canada Inc filed Critical Air Liquide Canada Inc
Priority to AT86402533T priority Critical patent/ATE54476T1/de
Publication of EP0226495A1 publication Critical patent/EP0226495A1/fr
Application granted granted Critical
Publication of EP0226495B1 publication Critical patent/EP0226495B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/20—Mixing gases with liquids
    • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
    • B01F23/232—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using flow-mixing means for introducing the gases, e.g. baffles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/20—Mixing gases with liquids
    • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
    • B01F23/237—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids characterised by the physical or chemical properties of gases or vapours introduced in the liquid media
    • B01F23/2376—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids characterised by the physical or chemical properties of gases or vapours introduced in the liquid media characterised by the gas being introduced
    • B01F23/23761—Aerating, i.e. introducing oxygen containing gas in liquids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/20—Mixing gases with liquids
    • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
    • B01F23/237—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids characterised by the physical or chemical properties of gases or vapours introduced in the liquid media
    • B01F23/2376—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids characterised by the physical or chemical properties of gases or vapours introduced in the liquid media characterised by the gas being introduced
    • B01F23/23761—Aerating, i.e. introducing oxygen containing gas in liquids
    • B01F23/237612—Oxygen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/30—Injector mixers
    • B01F25/31—Injector mixers in conduits or tubes through which the main component flows
    • B01F25/313—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced in the centre of the conduit
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/30—Injector mixers
    • B01F25/31—Injector mixers in conduits or tubes through which the main component flows
    • B01F25/313—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced in the centre of the conduit
    • B01F25/3133—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced in the centre of the conduit characterised by the specific design of the injector
    • B01F25/31331—Perforated, multi-opening, with a plurality of holes
    • B01F25/313311—Porous injectors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/30—Injector mixers
    • B01F25/31—Injector mixers in conduits or tubes through which the main component flows
    • B01F25/314—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced at the circumference of the conduit
    • B01F25/3142—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced at the circumference of the conduit the conduit having a plurality of openings in the axial direction or in the circumferential direction
    • B01F25/31421—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced at the circumference of the conduit the conduit having a plurality of openings in the axial direction or in the circumferential direction the conduit being porous
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/40—Static mixers
    • B01F25/42—Static mixers in which the mixing is affected by moving the components jointly in changing directions, e.g. in tubes provided with baffles or obstructions
    • B01F25/43—Mixing tubes, e.g. wherein the material is moved in a radial or partly reversed direction
    • B01F25/433—Mixing tubes wherein the shape of the tube influences the mixing, e.g. mixing tubes with varying cross-section or provided with inwardly extending profiles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/40—Static mixers
    • B01F25/42—Static mixers in which the mixing is affected by moving the components jointly in changing directions, e.g. in tubes provided with baffles or obstructions
    • B01F25/43—Mixing tubes, e.g. wherein the material is moved in a radial or partly reversed direction
    • B01F25/433—Mixing tubes wherein the shape of the tube influences the mixing, e.g. mixing tubes with varying cross-section or provided with inwardly extending profiles
    • B01F25/4335—Mixers with a converging-diverging cross-section
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/40—Static mixers
    • B01F25/42—Static mixers in which the mixing is affected by moving the components jointly in changing directions, e.g. in tubes provided with baffles or obstructions
    • B01F25/43—Mixing tubes, e.g. wherein the material is moved in a radial or partly reversed direction
    • B01F25/433—Mixing tubes wherein the shape of the tube influences the mixing, e.g. mixing tubes with varying cross-section or provided with inwardly extending profiles
    • B01F25/4337—Mixers with a diverging-converging cross-section
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F33/00—Other mixers; Mixing plants; Combinations of mixers
    • B01F33/80—Mixing plants; Combinations of mixers
    • B01F33/834—Mixing in several steps, e.g. successive steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F35/00—Accessories for mixers; Auxiliary operations or auxiliary devices; Parts or details of general application
    • B01F35/71—Feed mechanisms
    • B01F35/715—Feeding the components in several steps, e.g. successive steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F2025/91—Direction of flow or arrangement of feed and discharge openings
    • B01F2025/919—Direction of flow or arrangement of feed and discharge openings characterised by the disposition of the feed and discharge openings
    • B01F2025/9191—Direction of flow or arrangement of feed and discharge openings characterised by the disposition of the feed and discharge openings characterised by the arrangement of the feed openings for one or more flows, e.g. for the mainflow and the flow of an additional component
    • B01F2025/91911—Direction of flow or arrangement of feed and discharge openings characterised by the disposition of the feed and discharge openings characterised by the arrangement of the feed openings for one or more flows, e.g. for the mainflow and the flow of an additional component with feed openings in the center of the main flow
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F2025/91—Direction of flow or arrangement of feed and discharge openings
    • B01F2025/919—Direction of flow or arrangement of feed and discharge openings characterised by the disposition of the feed and discharge openings
    • B01F2025/9191—Direction of flow or arrangement of feed and discharge openings characterised by the disposition of the feed and discharge openings characterised by the arrangement of the feed openings for one or more flows, e.g. for the mainflow and the flow of an additional component
    • B01F2025/91912—Direction of flow or arrangement of feed and discharge openings characterised by the disposition of the feed and discharge openings characterised by the arrangement of the feed openings for one or more flows, e.g. for the mainflow and the flow of an additional component with feed openings at the circumference of the main flow
    • B01F2025/919121—Direction of flow or arrangement of feed and discharge openings characterised by the disposition of the feed and discharge openings characterised by the arrangement of the feed openings for one or more flows, e.g. for the mainflow and the flow of an additional component with feed openings at the circumference of the main flow with feed openings around the complete circumference of the main flow, e.g. being a perforated or porous part
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F2025/91—Direction of flow or arrangement of feed and discharge openings
    • B01F2025/919—Direction of flow or arrangement of feed and discharge openings characterised by the disposition of the feed and discharge openings
    • B01F2025/9191—Direction of flow or arrangement of feed and discharge openings characterised by the disposition of the feed and discharge openings characterised by the arrangement of the feed openings for one or more flows, e.g. for the mainflow and the flow of an additional component
    • B01F2025/919125—Direction of flow or arrangement of feed and discharge openings characterised by the disposition of the feed and discharge openings characterised by the arrangement of the feed openings for one or more flows, e.g. for the mainflow and the flow of an additional component with feed openings in the center and at the circumference of the main flow

Definitions

  • the invention relates to the dispersion and dissolution of one or more gases in a pulp suspension.
  • It relates more particularly to a method according to the preamble of claim 1, as well as an apparatus for reacting oxygen in an oxygen-containing gas with a cellulose paste.
  • the mixing apparatus described in these patents is relatively complicated and expensive, and has moving parts which can cause breakdowns or static parts located in the flow path, which can lead to blockage.
  • GB-A-2 006 852 describes the addition of gaseous oxygen in any form in a dough (slurry). Despite the suggestion to use turbulence, not all of the oxygen can react to delignify the pulp.
  • US-A-3,545,731 describes an apparatus which can only be used with a liquid but cannot be used with a pulp such as a paper pulp.
  • An object of the present invention is therefore to provide an apparatus capable of efficiently dispersing and kneading oxygen in a pulp suspension, simplified and economical compared to the already existing apparatus.
  • the method according to the invention conforms to the characteristic of claim 1.
  • aqueous cellulose pulp suspension having a consistency of about 8 to about 16%, preferably 10 to 12%, by defining for the pulp a relatively unobstructed flow path passing through and past an oxygen introduction zone and circulating the suspension over the flow path at a rate at which it is fully fluidized and completely turbulent , so as to present substantially "Newtonian" properties, conditions in which it behaves substantially like water, and which produces a very effective mixing.
  • the oxygen is introduced into the suspension through diffusion means which have a fixed porous surface in contact with the rapidly moving suspension, in the oxygen introduction zone, in a finely divided form, of preferably in the form of a mass of fine bubbles having a diameter at most equal to about 2 to about 10 ⁇ m, for example. This causes the bubbles to disperse throughout the suspension without noticeable coalescence as it would occur with larger bubbles.
  • the apparatus according to the invention conforms to the characteristic of claim 11.
  • Preferred means for diffusing oxygen includes a sintered metal element of the type normally used for filtration.
  • a typical diffuser consists of a sintered stainless steel element produced by the process of US patent ⁇ A ⁇ 2,554,343. According to this process, the alloyed metal powder is passed through a particle size chosen in a sintering controlled atmosphere to produce sheets or shaped bodies made of porous media. The powdery metal particles melt at their contact points, resulting in a bonded mass with a homogeneous crystal structure. No binders or other foreign materials are introduced, which retains the basic properties of the metals or alloys used.
  • the element preferably has a thickness in the range of from about 0.8 mm to about 6.5 mm.
  • the pores must have a diameter less than about 10 ⁇ m, preferably in the range of from about 2 to about 10 ⁇ m, and the porosity should be substantially uniform over the entire surface of the porous wall and preferably in the range of about 40 to about 50%.
  • a widely used type is 316 L stainless steel (0.03% carbon maximum). Variable pore sizes are suitable.
  • the action of the diffusing device is to produce a mass of very fine bubbles in accordance with the principle set out in US patent ⁇ A ⁇ 3,545,731, with the exception that, to properly mix oxygen in a pulp suspension, special conditions must be observed which have been discovered and which are described in the present invention.
  • the diffuser element preferably includes a cylinder through which the suspension passes, and the walls of the cylinder define the flow path.
  • the diffuser element can form part of the cylinder wall, it can take the form of a porous tube placed transversely to the axis of the cylinder, or it can take the form of a porous tube along the axis of the cylinder .
  • the suspension path is relatively unobstructed.
  • the suspension passes directly through the cylinder without any obstruction.
  • this tube occupies a small space, so that most of the interior space of the cylinder is occupied by the suspension which passes through it while remaining in contact with the surface of the porous diffuser .
  • the diffusing apparatus comprises a duct having a cylindrical wall which defines the external limits of the passage and a closed capacity maintained inside the duct, and having a cylindrical wall which defines the internal limits of the passage .
  • a bubble producing surface having a large number of gas outlets, of microscopic dimensions is arranged on the wall of the duct as well as on the wall of the container.
  • a gas manifold surrounds the outer face of the wall of the duct and is connected to a source of pressurized gas which supplies the gas.
  • the closed capacity is also connected to a gas source.
  • the decrease in the friction curve indicates another change in the flow mechanism.
  • a continuous and purely liquid annular body was formed between the stopper and the wall. The flow in this ring is laminar.
  • a speed is reached beyond which the flow becomes turbulent.
  • the increase in speed intensifies the turbulence and the fiber plug decreases in size.
  • New fibers detach from the plug.
  • the whole suspension becomes turbulent when the speed is increased beyond the point where the flow curves of the fiber suspension and the water, after crossing, become parallel. All speed and consistency gradients have disappeared and the suspension behaves like a turbulent liquid.
  • the shear field imposed in the entire mass of fibers now exceeds the value of shear stress which is necessary to completely disintegrate the fibrous network.
  • the invention lends itself particularly well to a dosage of oxygen in stages in the suspension of pâté. This is obtained by introducing a stream of a suspension of cellulose pulp under pressure, supplied by a feed, into a reaction system composed of a plurality of successive stages, in each of which the stream first flows in a restricted section in which it acquires an appropriate speed to fluidize it and give it a liquid flow and, then, it circulates in an enlarged section in which it acquires a speed such that a plug flow occurs.
  • oxygen is injected into the flow of liquid under pressure, in the form of a large quantity of small bubbles to disperse these bubbles throughout the mass of the liquid, and as a result, most of oxygen reacts with the pulp in the plug flow at this point.
  • the treated suspension is then recovered at the exit from the final stage.
  • Another subject of the invention is another preferred method of kneading the suspension which leaves the oxygen diffuser by passing it through a dough fluidization mixer.
  • This mixer can be placed adjacent to the diffuser or placed some distance downstream. This mixer effectively ensures a new mixing and a new dispersion of the possible agglomerations of oxygen, so that the oxygen remains in a finely divided form and is mixed more intimately with the suspension.
  • a preferred static mixer consists of a tube which narrows to form a constriction, followed by a tube which widens to reach the diameter of the tube in which the dough suspension circulates. The speed through the throttle will be roughly the same as that seen in the diffuser.
  • the invention also relates to means for coordinating the flow of oxygen with the flow of the pulp suspension so as to maintain the appropriate dosage of oxygen.
  • a device for measuring the flow rate for example an orifice plate inserted in the path of the suspension, upstream of the diffuser, the orifice plate being connected to a differential pressure cell which, at in turn, is connected to a controller.
  • the controller sends a signal to an oxygen flow control valve, which regulates the supply of oxygen to the diffuser.
  • an orifice plate or other device in the oxygen supply line to measure the flow of oxygen.
  • the adjustment mechanism may include a computer which maintains a constant, predetermined and fixed ratio between oxygen and the dough, so as to increase or reduce the dosage to compensate for variations in the flow rate of the dough suspension.
  • the injection of oxygen into a suspension of cellulose pulp according to the invention can be used at different stages of the delignification and bleaching processes.
  • the aim is to decrease the Kappa index of the dough.
  • the Kappa index can be reduced from the range of 50 to 60 to the interval from 20 to 30.
  • the Kappa index can be reduced from the interval from 5 to 10 to the range 2.3 to 3.5.
  • the speed of the dough passing through the oxygen introduction zone is 0.5 to 50 meters per second, a preferred interval being 5 to 40 meters per second.
  • the surface of the fixed diffuser can have an area of approximately 0.0033 to 0.00033 dm 2 per unit of oxygen gas flow of 1 dm 3 per minute, or a flow of 30 to 300 normal cubic meters of oxygen per meter square of porous surface.
  • the dosage rate can vary from 2.5 to 25 kg, preferably from 5 to 7.5 kg per tonne of dough, on the basis of dry air (AD) for bleaching and from 10 to 50 kg per tonne for delignification.
  • AD dry air
  • the oxygen used can be molecular oxygen, as found commercially, which contains 90% or more and preferably 98% or more oxygen.
  • the oxygen can be in the form of a gas containing more than 50% oxygen.
  • the starting paste suspension can contain about 10 to about 20% air by volume of dispersed paste, which dilutes the added oxygen.
  • concentration of the gas containing added oxygen can be at the lower end of the oxygen content range and, for a dough containing a lot of air, the added gas may contain oxygen near the upper limit of the oxygen content range.
  • the oxygen content of the residual gas leaving the vent of the final treatment tank is measured. Based on this content, it can be determined whether a good mixing has been obtained. Adjustments can be made accordingly and the dosage can be changed in stages to obtain the best results.
  • the dosage can be uniformly proportioned at each stage or it can be modified to adapt to variations in conditions such as variations in the nature of the dough, or otherwise.
  • the invention is particularly flexible with regard to the equipment and the process, so that it can be used to economically equip a stationery after the fact.
  • the diffuser elements are relatively uncomplicated and inexpensive and can be easily installed in the installation.
  • Each factory has a certain nominal production capacity.
  • the present invention lends itself to being adjusted to suit this nominal capacity.
  • the variations in the flow rates of the pulp suspension and, therefore, of the oxygen, are related to the variations in the pulp demand, so the flow rate can be reduced due to a shutdown when the dough tanks are full .
  • the pulp suspension passes through a first oxygen diffuser and a plurality of reactors, each of which is preceded by an oxygen diffuser.
  • a fraction or all of the suspension can be introduced into a reaction tower to allow additional extraction with caustic soda.
  • Figs. 3,4, 5, and 7 are views showing variants of dough fluidizing diffusers.
  • the typical installation shown will be understood on reading the description of the path of the pulp suspension which circulates in this installation.
  • the particular stage represented in the bleaching process is the first stage of alkaline extraction.
  • An aqueous suspension of cellulose pulp containing caustic soda is pumped at a high surface speed, which arrives through the tube 15 from a supply source (not shown), through the pump A, in a line 17 which enters an oxygen diffuser B pulp fluidizer in which oxygen is diffused and dispersed in fine bubbles in the suspension stream.
  • the suspension current is pumped from a power source, via line 17, by pump A, at a speed such that the current behaves like water and that there is a strong turbulence in any mass. .
  • the oxygen is diffused in the stream through a diffuser B, in fine bubbles, as described below, in more detail, and it provides rapid mixing of the oxygen throughout the dough stream.
  • the stream of rapidly moving pulp which circulates in line 17 downstream of the oxygen diffuser, and which now contains dispersed oxygen, is introduced into the bottom of a first vertical reaction chamber C, in which it circulates at a much lower speed in the form of a plug. At this lower speed, the suspension loses its fluidity, trapping the oxygen dispersed in the stopper, which allows the oxygen and the caustic soda to react with the paste during the time when the suspension containing oxygen stay in room C.
  • the suspension is then sent rapidly, in turbulent flow, through a tube 19, into a second oxygen diffuser B, which it passes through and into the bottom of a second reaction chamber C, in which it remains for a certain period. to allow oxygen and bleaching chemicals to continue to react with cellulose.
  • the suspension is sent, by a tube 21 and through a third oxygen diffuser B 2 , to a third reaction chamber C 2 .
  • the dough then passes through a pressure adjustment valve 23 and, in a tube 24, to enter the upper end of a reaction tower D.
  • the dough stays in the tower D to give more time to the product bleaching chemical to react with cellulose.
  • the dough can flow in the opposite direction, that is to say from top to bottom through the chambers to reach the base or at the top of the reaction tower, or some or all of the reaction can be horizontal.
  • the pulp suspension leaving tower D is then collected at the outlet of an outlet tube 25 and it is washed to remove bleaching chemicals and impurities, or alternatively, depending on the stage of the bleaching process, the suspension processed can be sent to another processing.
  • a vent 29 for the gaseous effluents makes it possible to monitor the excess oxygen, with a view to regulating the process so as to ensure greater efficiency.
  • FIG. 2 there is a static mixer fluidizing dough or throttle E, in series with the diffuser B, between this diffuser and the first reaction column through which the suspension stream containing oxygen is passed.
  • the constriction has a constricted neck which narrows the current and increases its speed. This ensures better dispersion of the oxygen gas bubbles throughout the mass of pulp suspension.
  • the paste fluidiser oxygen diffuser B is composed, as shown on a larger scale in FIG. 3, a cylinder 31 which forms a passage 32 for the suspension of dough.
  • the cylinder has flanges 33, 34 on its ends, for connection to a pipe.
  • a porous metal tube 35 is placed diametrically across the passage 32 which, with this exception, is free; this tube enters an opening in the side of the cylinder 31, through a connector 31a which is fixed and sealed in place by a tube connector 6 of the "SWAGELOK" type (registered trademark).
  • the wall of the tube 35 is preferably made of sintered metal.
  • the paste is continuously introduced at high speed through the passage 32 while oxygen is supplied to the porous tube 35 and it diffuses into the paste through the wall of this tube.
  • FIG. 4 A variant of the diffuser is shown in FIG. 4.
  • the wall of the cylinder 41 has a porous cylindrical central section 45.
  • a manifold 47 encloses this section from the outside and an oxygen connection 48 is provided leading to the manifold. The passage of the paste suspension is thus entirely free.
  • FIG. 5 Another form of diffuser is shown in FIG. 5.
  • a device 55 in the form of an annular crown is placed against the cylinder 51 and surrounds the passage 52.
  • the tube 55 is provided with suitable small orifices 56 through which the oxygen is diffused.
  • the passage 52 is entirely free.
  • FIG. 6 Another form of diffuser is shown in FIG. 6.
  • a porous tube 65 extends axially and in a central position along the passage 62 and is held in this passage by suitable supports or cross-pieces 69 which are connected inside the wall of the cylinder 61.
  • a tube oxygen 68 is placed from the outside of the cylinder at the end of the diffusion tube 65.
  • FIG. 7 shows yet another preferred form of diffuser.
  • This diffuser is mounted between mounting flanges 100 and 101, from which start short sections of cylindrical tubes 102 and 103 respectively, which are connected to oblique tapered flanges 104 and 105.
  • a double wall J composed of a wall cylindrical inner wall 111, is placed between the ends of the flanges 104 and 105, a cylindrical outer wall 107 without perforation and the annular walls of perforated ends 108 and 109.
  • the microporous inner wall 111 is preferably made of sintered metal, as before described.
  • the tube sections 102 and 103, the flanges 104 and 105 and the porous wall 111 form an enclosure.
  • a cylinder K having a microporous wall 113 (preferably made of sintered metal), capped at its ends with impermeable frustoconical caps 115 and 117.
  • the cylinder K is suitably supported by a cross device S not shown, to maintain its position in the duct.
  • the wall 113 of the cylinder K and the wall 111 of the double wall J form between them an annular passage P.
  • a pipe 119 for supplying oxidizing gas connects a source of oxidizing gas under pressure to the interior space of the double wall J
  • An oxidizing gas supply tube 121 connects a source of oxidizing gas under pressure to the interior volume of the cylinder K.
  • the diffuser is connected, in the same way as in the connection of the other embodiments described above, by the flange 100, to an inlet tube for the paste suspension and, by the flange 101, to a tube which transports the outgoing dough suspension.
  • the paste suspension is introduced into the left end of the device, at a fluidization speed, and flows at high speed through the passage P between the microporous walls 111 and 113, and it exits through the far right.
  • An oxidizing gas under pressure is introduced through the tubes 119 and 121 and diffused in fine bubbles through the opposite porous walls 111 and 113, in the suspension of fluidized paste which circulates rapidly in the passge C, as previously described.
  • the diffusion of the gas in the suspension is extremely efficient due to the large diffusion surface formed at the two limits of the fluidized pulp stream.
  • the static dough fluidizer mixer E shown in FIG. 2, connected in series with the oxygen diffuser B, comprises an elongated tube in one piece of circular cross section, between the flanges 81 and 82.
  • a first frustoconical part 83 narrows from the flange 81 to be connected, at a neck 84, at the small end of a longer frusto-conical part 85, which flares, and which ends at the flange 82.
  • the mixer E is connected to a connection piece F which has an upstream flange 90 connected to the flange 34 with the interposition of a seal.
  • the transition piece F has a downstream flange 91 assembled to the flange 81 of the mixer.
  • the paste suspension momentarily circulates in a wider section then in a restricted section substantially to the section of the diffuser tube.
  • the size (the inside diameter) of the cylinder 31 into which the pulp suspension is pumped and brought into contact with oxygen varies according to the capacity of the pulp mill. Typical diameters range from about 50 to about 300 mm and usually from about 75 to about 150 mm.
  • reaction chambers C, C, and C 2 Three reaction chambers C, C, and C 2 are shown .
  • a greater or lesser number of reaction chambers can be used, depending on the material to be treated, the amount of oxygen added and the desired bleaching effect.
  • the effects of several diffusers, each of which is equipped with a reaction chamber, consist in adding in stages large additions of oxygen, by adding small amounts to each diffuser, so as to obtain: This expression is calculated at the pressure of the particular stage considered.
  • the speed at which the slurry suspension is discharged through the diffuser cylinder 31 is a high velocity which makes the current behave like water and makes it easier to disperse small bubbles of oxygen which are mixed throughout the mass of the current.
  • the pressure of the pulp suspension may be about 0.1 to 1 megapascals (MPa), and the oxygen pressure of about 0.14 to 1.4 MPa.
  • the residence time of the paste in the cylinder 31 of the diffuser is usually in the range of about 0.001 to about 0.120 seconds.
  • the residence time in each of reactors C, C 1 and C 2 is usually in the range of about 1 minute to about 5 minutes and the residence time in tower D is in the range of about 30 to about 90 minutes.
  • the pressure in each reactor is approximately 0.1 to 1 MPa.
  • the invention does not exclude the use or the combination with the diffusers for the introduction of oxygen into the dough, of high speed mixers such as, for example, those described in US patent brevet A ⁇ 4,295,926, in the name of WEYERHAEUSER, or of a "KAMYR MC" registered trademark pump).
  • the nature of the treated pulp can be wood softwoods, hardwoods or a mixture having a consistency in the range of 5 to 16%.
  • Pasta can be treated according to the invention at different stages of the delignification-bleaching process.
  • the starting dough in the caustic extraction stage of a bleaching operation may have a Kappa number in the range of 5.0 to 10.0 and the bleached dough exiting from tank D may have, after washing, an index of 2.5 to 3.5.
  • the suspension takes on the characteristics of water.
  • the suspension passes in close contact with the diffusing element and the oxygen leaves through the pores of this element in the form of bubbles of very small diameter.
  • These bubbles are well dispersed due to the turbulence of the dough and they have a large specific surface, compared to their volume, to ensure mass transfer through the gas / liquid interface.
  • the mass transfer of oxygen is considerably enhanced by this dispersing process with fluidization.
  • the suspension can be subjected to a pre and post-treatment before being pushed back into the first diffuser B, the suspension has undergone normal treatments in a delignification-bleaching operation.
  • the suspension contains small concentrations of other bleaching chemicals.
  • the suspension is provided at a temperature in the range of about 40 ° C to about 90 ° C.
  • the suspension leaving the bleaching tower D will be washed to remove bleaching chemicals and other impurities.
  • a typical bleaching facility could have a processing capacity of 1000 tonnes of pulp per day, 10% consistency with an oxygen quantity of 5 kg per ton, or 5000 kg of oxygen. Under these conditions, this flow could be 6.321 liters per minute, with a speed of circulation of the suspension through the diffuser of 40 meters per second, and an oxygen flow of 3.13 kg per minute. The diffusion surface would be around 0.26 square decimetres.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Dispersion Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
EP86402533A 1985-11-15 1986-11-14 Procédé et appareil pour le blanchiment de la pâte à papier Expired - Lifetime EP0226495B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT86402533T ATE54476T1 (de) 1985-11-15 1986-11-14 Verfahren und vorrichtung zum bleichen von papierpulpe.

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US79828685A 1985-11-15 1985-11-15
US798286 1985-11-15
CA000507000A CA1300320C (en) 1985-11-15 1986-04-18 Pulp bleaching
CA507000 1986-04-18

Publications (2)

Publication Number Publication Date
EP0226495A1 EP0226495A1 (fr) 1987-06-24
EP0226495B1 true EP0226495B1 (fr) 1990-07-11

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EP (1) EP0226495B1 (pt)
AU (1) AU595842B2 (pt)
BR (1) BR8605636A (pt)
DE (1) DE3672580D1 (pt)
NZ (1) NZ218294A (pt)
PT (1) PT83745B (pt)

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CA1300322C (en) * 1987-06-08 1992-05-12 Derek Hornsey Method of bleaching or delignification of cellulose pulp with oxygen
FR2617736A1 (fr) * 1987-07-08 1989-01-13 Sampson Cat Dispositif de production d'emulsion, en vue du nettoyage et de la desinfection
RU2103433C1 (ru) * 1995-01-16 1998-01-27 Грудинин Владимир Павлович Способ обработки волокнистой массы химическим реагентом и установка для его осуществления
SE505141C2 (sv) * 1995-10-23 1997-06-30 Sunds Defibrator Ind Ab Syrgasdelignifiering av massa i två steg med hög satsning av alkali och syrgas och temperatur under 90 C i första steget
NO962328L (no) * 1996-06-05 1997-12-08 Aga Ab Fremgangsmåte og anordning for innföring av gass i en væske
DE19849628A1 (de) * 1998-10-28 2000-05-04 Margret Spiegel Verfahren und Anordnung zum Einbringen von Gas in eine Flüssigkeit
EP1319435A3 (de) * 2001-12-12 2004-10-06 Collectplan GmbH Method and apparatus for introducing a first medium in a second medium
DE102004059934A1 (de) * 2004-12-09 2006-06-22 Würdig, Uwe, Dipl.-Ing. Einrichtung zur Anreicherung flüssiger Medien mit Gas
SE528449C2 (sv) * 2005-09-28 2006-11-14 Kvaerner Pulping Tech Apparat för inblandning av ånga till ett flöde av cellulosamassa
KR101358512B1 (ko) 2007-03-15 2014-02-06 다우 글로벌 테크놀로지스 엘엘씨 연속 흐름 반응기용 혼합기, 연속 흐름 반응기, 상기 혼합기 형성 방법 및 상기 반응기 작동 방법
JP5301225B2 (ja) * 2007-09-20 2013-09-25 富士フイルム株式会社 ドープ混合方法、溶液製膜方法、ドープ混合装置、及び溶液製膜設備
KR101351302B1 (ko) * 2012-10-23 2014-01-15 주식회사 디섹 선박의 밸러스트수 처리시스템
MY191545A (en) 2016-06-15 2022-06-30 Anzai Satoshi Ultrafine bubble generation device for aquaculture or wastewater treatment
US20200330936A1 (en) * 2018-10-05 2020-10-22 University Of Baltimore Systems, Methods, and Apparatus for Utilizing a Resuspension Tank
SE545007C2 (en) * 2021-01-18 2023-02-28 Valmet Oy Mixing device and method for mixing a fluid into a fiber pulp
CN115448440B (zh) * 2022-07-25 2023-10-24 中石化宁波工程有限公司 一种分形氧化装置

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Also Published As

Publication number Publication date
DE3672580D1 (de) 1990-08-16
AU595842B2 (en) 1990-04-12
BR8605636A (pt) 1987-08-18
PT83745A (en) 1986-12-01
NZ218294A (en) 1990-05-28
PT83745B (pt) 1988-08-17
EP0226495A1 (fr) 1987-06-24
AU6467186A (en) 1987-05-21

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