CA2046717A1 - Method and apparatus for treating fibrous materials with a gaseous reagent - Google Patents
Method and apparatus for treating fibrous materials with a gaseous reagentInfo
- Publication number
- CA2046717A1 CA2046717A1 CA002046717A CA2046717A CA2046717A1 CA 2046717 A1 CA2046717 A1 CA 2046717A1 CA 002046717 A CA002046717 A CA 002046717A CA 2046717 A CA2046717 A CA 2046717A CA 2046717 A1 CA2046717 A1 CA 2046717A1
- Authority
- CA
- Canada
- Prior art keywords
- fibrous material
- gaseous reagent
- pulp
- mixing chamber
- gas
- 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.)
- Abandoned
Links
- 239000003153 chemical reaction reagent Substances 0.000 title claims abstract description 42
- 239000002657 fibrous material Substances 0.000 title claims abstract description 39
- 238000000034 method Methods 0.000 title claims abstract description 6
- 238000006243 chemical reaction Methods 0.000 claims abstract description 34
- 239000000203 mixture Substances 0.000 claims abstract description 18
- 238000007872 degassing Methods 0.000 claims abstract description 6
- 239000007789 gas Substances 0.000 claims description 73
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 43
- 239000000725 suspension Substances 0.000 claims description 23
- 238000004061 bleaching Methods 0.000 claims description 21
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 13
- 239000001301 oxygen Substances 0.000 claims description 13
- 229910052760 oxygen Inorganic materials 0.000 claims description 13
- 229920001131 Pulp (paper) Polymers 0.000 claims description 10
- 239000012042 active reagent Substances 0.000 abstract 1
- 239000012159 carrier gas Substances 0.000 description 11
- 238000000926 separation method Methods 0.000 description 6
- 230000009471 action Effects 0.000 description 5
- 239000000835 fiber Substances 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 238000004076 pulp bleaching Methods 0.000 description 3
- 238000007664 blowing Methods 0.000 description 2
- 238000005056 compaction Methods 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 description 2
- 239000004155 Chlorine dioxide Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 235000019398 chlorine dioxide Nutrition 0.000 description 1
- 230000002301 combined effect Effects 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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
- D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone
-
- 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
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
- Treatment Of Fiber Materials (AREA)
- Inorganic Fibers (AREA)
Abstract
Docket No. 1197-IR-PA
ABSTRACT OF THE DISCLOSURE
A method and apparatus for treating fluffed high consistency fibrous materials with gaseous reagents provides a mechanical mixing chamber with a dwell time sufficient to allow reaction of a substantial majority of the gaseous reagent prior to dispensing the mixture into a porous bed reaction and degasification chamber. The gas flows through the porous bed of fibrous material in the reaction chamber until virtually all the active reagent has been consumed. This results in uniformly treated fibrous materials and efficient reagent utilization.
ABSTRACT OF THE DISCLOSURE
A method and apparatus for treating fluffed high consistency fibrous materials with gaseous reagents provides a mechanical mixing chamber with a dwell time sufficient to allow reaction of a substantial majority of the gaseous reagent prior to dispensing the mixture into a porous bed reaction and degasification chamber. The gas flows through the porous bed of fibrous material in the reaction chamber until virtually all the active reagent has been consumed. This results in uniformly treated fibrous materials and efficient reagent utilization.
Description
20~6717 Docket No. 1197-IR-PA
METHOD AND APPARATUS FOR TREATING FIBROUS
MATERIALS WITH A GASEOUS REAGENT
BACKGROUND OF THE INVENTION
This invention relates generally to pulp processing for papermaking and more particularly to pulp bleaching using a gaseous bleaching reagent.
Bleaching of wood pulp using gaseous reagents 05 such as chlorine dioxide or ozone involves a large volume percentage of carrier gas along with the reactive gas. This results from the methods of preparation of such gaseous bleaching reagents.
Ozone is generated by passing air, or oxygen, l~ through an electrical field of sufficient intensity to generate a corona discharge which converts a portion of the oxygen into ozone. For example, passing oxygen through the corona, in some ozone generators, will result in conversion of as much as six percent of the oxygen into ozone. The remaining oxygen passes into the bleaching process with the ozone as a "carrier gas". When reacted with the pulp, the ozone fraction will be substantially 2n~67l7 Docket No. 1197-IR-PA
consumed and the oxygen must be removed from the pulp as it is not reactive under the bleaching conditions used and its recovery is important to the economics of ozone generation.
05 One currently available ozone bleaching apparatus treats pulp at a high consistency of 20 to 50 percent. The pulp is fluffed by a mechanical fluffer in the presence of the reacting gas, is transported by the gas through a conduit; and is dropped onto 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/carrier gas mixture is initially mixed with the pulp in the fluffer to form a gas suspended mixture for transport and initiation of reaction, which then passes through a conduit to the top of the tower.
The ozone and carrier gas flows through the porous bed at a substantially higher velocity than that at which the bed moves down through the reaction tower. The carrier gas leaves the pulp bed peripherally into the gas separation chamber from which it is recycled to the ozone generator.
Bleaching in this type reactor frequently results in a mottled appearance due to the variable 20467~7 Docket No. 1197-IR-PA
permeability of the fluffed pulp agglomerations.
This variability is also attributed to non-uniform compaction of the porous pulp bed which results from localized impact of the falling pulp. Greater local 05 depth of the pulp bed also increases local compaction. These compacting factors are further aggravated by the pressure drop of the ozone and carrier gas through the pulp bed. Since the pressure drop is proportional to the compacted density of the pulp bed, the aggravating character of the gas flow is clear. In addition, the exothermic bleaching reaction produces higher temperatures in the zones of lower density and thus higher bleaching rates in those zones. Since the ozone/pulp reaction is very fast, and since the rate decreases rapidly with concentration decrease, the non-uniform bleaching effects of prior art reactors have been further aggravated because a large fraction of the ozone is consumed before it has an opportunity to reach the fibers in more densely packed zones of the pulp bed.
One important characteristic of the porous bed type reactor is that it has proved highly efficient in removing the ozone from its oxygen carrier gas.
Measurements of the gas leaving the porous bed into Docket No. 1197-IR-P~
the gas separation chamber have shown a very low residual ozone content, for example 30 parts per million (when the feed gas contained 4% ozone in oxygen at the top of the reactor). This high 05 utilization of the ozone gas is important to the economics of ozone bleaching as ozone is a relatively expensive chemical. It is believed that this high efficiency in ozone utilization is the result of the fact that the bulk density of the pulp bed is substantially increased near the gas separation zone by the combined effects of weight of the pulp above and pressure drop of the gas flowing through the entire height of the bed. For example, in a reactor operating with eight feet of pulp bed above the separation zone, and a gas velocity in the upper portion of the porous bed reactor of about 40 ft./minute, the bulk density of the pulp at the gas separation zone will have risen to about 40 lbs./cu.ft. and the porosity will have been reduced to about 36% of the bulk volume.
In this zone of reduced porosity, the ozone gas is forced into intimate contact with the pulp fibers, and the last traces of ozone are consumed in bleaching rather than passing through the porous bed and being destroyed in the recycling system used to recover the oxygen carrier gas.
METHOD AND APPARATUS FOR TREATING FIBROUS
MATERIALS WITH A GASEOUS REAGENT
BACKGROUND OF THE INVENTION
This invention relates generally to pulp processing for papermaking and more particularly to pulp bleaching using a gaseous bleaching reagent.
Bleaching of wood pulp using gaseous reagents 05 such as chlorine dioxide or ozone involves a large volume percentage of carrier gas along with the reactive gas. This results from the methods of preparation of such gaseous bleaching reagents.
Ozone is generated by passing air, or oxygen, l~ through an electrical field of sufficient intensity to generate a corona discharge which converts a portion of the oxygen into ozone. For example, passing oxygen through the corona, in some ozone generators, will result in conversion of as much as six percent of the oxygen into ozone. The remaining oxygen passes into the bleaching process with the ozone as a "carrier gas". When reacted with the pulp, the ozone fraction will be substantially 2n~67l7 Docket No. 1197-IR-PA
consumed and the oxygen must be removed from the pulp as it is not reactive under the bleaching conditions used and its recovery is important to the economics of ozone generation.
05 One currently available ozone bleaching apparatus treats pulp at a high consistency of 20 to 50 percent. The pulp is fluffed by a mechanical fluffer in the presence of the reacting gas, is transported by the gas through a conduit; and is dropped onto 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/carrier gas mixture is initially mixed with the pulp in the fluffer to form a gas suspended mixture for transport and initiation of reaction, which then passes through a conduit to the top of the tower.
The ozone and carrier gas flows through the porous bed at a substantially higher velocity than that at which the bed moves down through the reaction tower. The carrier gas leaves the pulp bed peripherally into the gas separation chamber from which it is recycled to the ozone generator.
Bleaching in this type reactor frequently results in a mottled appearance due to the variable 20467~7 Docket No. 1197-IR-PA
permeability of the fluffed pulp agglomerations.
This variability is also attributed to non-uniform compaction of the porous pulp bed which results from localized impact of the falling pulp. Greater local 05 depth of the pulp bed also increases local compaction. These compacting factors are further aggravated by the pressure drop of the ozone and carrier gas through the pulp bed. Since the pressure drop is proportional to the compacted density of the pulp bed, the aggravating character of the gas flow is clear. In addition, the exothermic bleaching reaction produces higher temperatures in the zones of lower density and thus higher bleaching rates in those zones. Since the ozone/pulp reaction is very fast, and since the rate decreases rapidly with concentration decrease, the non-uniform bleaching effects of prior art reactors have been further aggravated because a large fraction of the ozone is consumed before it has an opportunity to reach the fibers in more densely packed zones of the pulp bed.
One important characteristic of the porous bed type reactor is that it has proved highly efficient in removing the ozone from its oxygen carrier gas.
Measurements of the gas leaving the porous bed into Docket No. 1197-IR-P~
the gas separation chamber have shown a very low residual ozone content, for example 30 parts per million (when the feed gas contained 4% ozone in oxygen at the top of the reactor). This high 05 utilization of the ozone gas is important to the economics of ozone bleaching as ozone is a relatively expensive chemical. It is believed that this high efficiency in ozone utilization is the result of the fact that the bulk density of the pulp bed is substantially increased near the gas separation zone by the combined effects of weight of the pulp above and pressure drop of the gas flowing through the entire height of the bed. For example, in a reactor operating with eight feet of pulp bed above the separation zone, and a gas velocity in the upper portion of the porous bed reactor of about 40 ft./minute, the bulk density of the pulp at the gas separation zone will have risen to about 40 lbs./cu.ft. and the porosity will have been reduced to about 36% of the bulk volume.
In this zone of reduced porosity, the ozone gas is forced into intimate contact with the pulp fibers, and the last traces of ozone are consumed in bleaching rather than passing through the porous bed and being destroyed in the recycling system used to recover the oxygen carrier gas.
2~46717 Docket No. 1197-I~-PA
The foregoing illustrates limitations known to exist in present gaseous reagent pulp bleaching reactors. Thus, it is apparent that it would be advantageous to provide an alternative directed to 05 overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided, including features more fully disclosed hereinafter.
SUMMARY OF THE INVENTION
In one aspect of the present invention, this is accomplished by providing an apparatus for treating fibrous material with a gaseous reagent having provision for fluffing the fibrous material in the presence of the gaseous reagent to form a gas suspension of the fibrous material and a device for receiving and agitating said gas suspension of fibrous material to mechanically maintain the fibrous material in suspension in the gaseous reagent until the gaseous reagent has substantially reacted with the fibrous material. The mixture is then dispensed into-a porous bed reaction and degasification chamber wherein the reaction is completed and the remaining reaction gases are removed from the fibrous material.
Docket No. 1197-IR-PA
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing 05 figures.
BRIEF DESCRIPTION OF T~E DRAWING FIGURES
Fig. 1 is a schematic partially sectional view of an apparatus which embodies the features of the present invention;
Fig. 2 is a fragmentary partially sectional view of the apparatus as seen from line 2-2 of Fig. l;
Fig. 3 is a graphic presentation of the reaction rate of ozone with wood pulp in a porous bed reactor; and Fig. 4 is a fragmentary partially sectional view of the apparatus of another embodiment of the present invention in which the reagent gas is introduced into the feed hopper of the mixing chamber rather than into the fluffer.
204671~
Docket No. 1197-IR-PA
DET~ILED DESC~IPTION
Fig. 1 shows the preferred embodiment of a gas/solid reactor system 20 of the present invention. It consists principally of a fluffer/blower 60, which forms the gas suspended 05 mixture of the fibrous solid as previously described, a mixing chamber 40, and a porous bed reactor 30. The fluffer/blower 60 and porous bed reactor 30 are well-known in the art, but are described here in order to illustrate the function of the present invention within the system.
Fluffer/blower 60 receives high consistency pulp 5 (20% to 50% consistency) from a dewatering pres-c, not shown, through conduit 66. It also receives a gas mixture 71 of feed gas 70 and excess 15 blowing gas 76 through gas loop 50. Feed gas 70 is composed of a gaseous reagent and, depending upon the reaction desired, the gaseous reagent may be mixed with any appropriate substantially non-reactive carrier gas. For purposes of this description, a wood pulp bleaching operation using ozone as the gaseous reagent and oxygen as the carrier gas will be used. Feed gas mixture 70 is injected through valve 77 into gas loop 50 where it Docket No. 1197-IR-PA
mixes with excess blowlng gas 76 and forms gas mixture 71. It enters fluffer/blower 60 where it is mixed with pulp 5 to form a gas suspended pulp fluff mixture and provides the mass flow necessary to 05 transport gas/fluff mixture 54 which is discharged through conduit 51 into fluff discharge cyclone 52.
From there pulp 5 falls into mixing chamber feed hopper 46 and is fed into mixing chamber 40 by auger 43.
Within mixing chamber 40, the gas suspended pulp fluff mixture is mechanically agitated by the intense action of paddle blades 44 on rotor shaft 42 which is driven by motor 41. The velocities of the fluffed pulp and the contacting gas 69, which is composed of the remaining gaseous reagent in combination with the non-reactive carrier gas plus the developing gases resulting from the progressive bleaching reaction, through the mixing chamber are not the same. Usually the gas is traveling faster.
The intense mechanical action of the paddle blades maintains the pulp fluff in suspension in the contacting gas 69 and, thus, ensures intimate contact between the contacting gas 69 and the fluffed pulp so that no portion of the fluffed pulp leaves the mixing chamber without contacting the Docket No. 1197-IR-PA
gaseous reagent. This ensures uniform bleaching during the high rate portion of the bleaching reaction. The mixture is discharged from the mixing chamber 40 through discharge neck 45 into the porous 05 bed reactor 30. The action of the paddle blades 44 at the entrance to discharge neck 45 prevents plugging of the neck by the pulp exiting the mixing chamber 40.
The fluffed pulp, having formed a porous bed, moves slowly downward through the porous bed reactor 30 and becomes more compacted toward the bottom as previously described.
The contacting gas 69 passes down through the permeable pulp bed 7, since lt has a much higher velocity than that of the pulp through the reactor 30, until it reaches gas exit 37 where it escapes peripherally to the annular gas exit chamber 32.
The contacting gas 69, by this time stripped of all but a trace of ozone and predominantly composed of oxygen plus yases produced as a by-product of the bleaching reaction, is vented through nozzle 75 and recycled to the ozone generator system. Bleached pulp 10 at the bottom of porous bed reactor 30 is diluted with recycled filtrate through dilution Docket No. 1197-IR-PA
nozzle 34 and is discharged through pulp discharge 36 as dilute bleached pulp 15.
Fig. 2 shows a partially sectioned schematic view from line 2-2 of Fig. l of fluffer/blower 60 05 and its associated equipment. Pulp 5 from the dewatering press enters compression screw feeder 62 through conduit 66 and from there is fed into fluffer/blower 60. The compression screw feeder compacts the pulp into a substantially impermeable plug 99 which prevents backward flow of the mixed gas from reactor system 20. Mixed gas 71 is fed into fluffer/blower 60 through gas loop 50. It is mixed with the fluffed pulp which it conveys as a gas suspension of fluffed pulp by entrainment into pulp and gas discharge conduit 51.
Referring to Figs. l and 2, the novel features of the invention can best be understood. The functions of the fluffer/blower 60 and its related equipment, as well as the porous bed reactor 30, are well-known in the art. Despite the shortcomings of the prior art porous bed reactor, already described, its high efficiency of ozone removal makes it a desirable element, in combination with the present invention, as explained below. The bleaching 204671~
Docket No. 1197-IR-PA
reaction of ozone with pulp is very fast. Fig. 3 shows a graphic representation of the concentration of ozone (in percent) versus time (in seconds) in contact with fluffed pulp under conditions such as 05 those previously described for a porous bed reactor. The concentration of ozone in oxygen coming out of an ozone generator is shown as being approximately 4%. It can be seen, that for a porous bed reactor, approximatel~ 60% of the ozone is consumed in less than one second of contact with the pulp, while at six seconds, over 9G% of the ozone is consumed. For this reason, thorough mixing of the ozone with the pulp fibers is imperative in order to avoid wide variations in bleached lS brightness of the pulp. Thus, mechanical mixing chamber 40 is provided between fluffer/blower 60 and porous bed reactor 30.
The fluffed pulp/gas mixture 54 is injected through fluff discharge cyclone 52 and mixing chamber hopper 46 into auger 43 which conveys it to the mixing paddles 44 mounted on rotor shaft 42.
The feed rate is maintained so that the bulk density of the intensely agitated pulp in the substantially horizontal mixing chamber is the maximum possible which will not result in plugging of the chamber.
Docket No. 1197-IR-PA
This ensures that all of the fluffed pulp passing through chamber 40 is exposed, to the maximum possible extent, to the gaseous reagent in the chamber. Paddles 44 provide intensive mixing action 05 between the pulp fluff and the gas to maintain the gas suspension of the pulp fluff which was formed in the fluffer/blower 60 during the dwell time in the mixing chamber 40. The mixing paddles closest to discharge neck 45 prevent plugging of the neck by the pulp exiting the mixing chamber 40 and dropping into reactor 30 on top of pulp bed 7. The contacting gas 69 which, after six seconds mixing, contains less than half its initial ozone, continues downward through the porous pulp bed until it reaches gas exit 37 at which time its concentration is typically less than 30 parts per million ozone.
The mixing chamber provides a pulp fluff dwell time in the range of approximately 10 seconds while maintaining the pulp in suspension in the contacting gas 69 through intimate intensive mechanical mixing of the gas and pulp fluff. This ensures the maximum practical reaction extent prior to discharge of the mixture into the porous bed reactor. Since the ozone concentration entering the porous bed reactor 2~46717 Docket No. 1197-IR-PA
is suhstantially less than half its initial concentration, the reaction rate is considerably slower, and non-uniformity of bleaching due to variable porosity of the pulp bed is further 05 mitigated.
Fig. 4 shows an alternative em~odiment of the present invention which is similar to that of Fig.
1, except that, here, fluffer/blower 60 has been replaced by fluffer 90 which, without any blowing action, deposits fluffed pulp fibers directly into mixing chamber hopper 46. Gas loop 50 has also been eliminated in this embodiment, since the reagent gas mixture is introduced in the mixing chamber hopper rather than in the fluffer.
This invention, in its preferred embodiment, provides the advantage of attaining uniform bleaching reaction results in the example considered without wasting expensive ozone or other gaseous reagent. By providing the mechanical mixing chamber prior to the porous bed reactor chamber, the desired gas/pulp contact time is achieved while intimate mixing is maintained. Thus, the invention provides uniform substantially complete reaction under commercially practical conditions over a wide range of capacities.
Docket No. 1197-IR-PA
The ozone/wood pulp reaction is used as an example to illustrate the features of this invention. Any gas/solid reaction in which the reaction kinetics are similar to those of 05 ozone/wood pulp and in which the solid has fluffy fibrous characteristics similar to wood pulp is an appropriate application for this invention.
The foregoing illustrates limitations known to exist in present gaseous reagent pulp bleaching reactors. Thus, it is apparent that it would be advantageous to provide an alternative directed to 05 overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided, including features more fully disclosed hereinafter.
SUMMARY OF THE INVENTION
In one aspect of the present invention, this is accomplished by providing an apparatus for treating fibrous material with a gaseous reagent having provision for fluffing the fibrous material in the presence of the gaseous reagent to form a gas suspension of the fibrous material and a device for receiving and agitating said gas suspension of fibrous material to mechanically maintain the fibrous material in suspension in the gaseous reagent until the gaseous reagent has substantially reacted with the fibrous material. The mixture is then dispensed into-a porous bed reaction and degasification chamber wherein the reaction is completed and the remaining reaction gases are removed from the fibrous material.
Docket No. 1197-IR-PA
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing 05 figures.
BRIEF DESCRIPTION OF T~E DRAWING FIGURES
Fig. 1 is a schematic partially sectional view of an apparatus which embodies the features of the present invention;
Fig. 2 is a fragmentary partially sectional view of the apparatus as seen from line 2-2 of Fig. l;
Fig. 3 is a graphic presentation of the reaction rate of ozone with wood pulp in a porous bed reactor; and Fig. 4 is a fragmentary partially sectional view of the apparatus of another embodiment of the present invention in which the reagent gas is introduced into the feed hopper of the mixing chamber rather than into the fluffer.
204671~
Docket No. 1197-IR-PA
DET~ILED DESC~IPTION
Fig. 1 shows the preferred embodiment of a gas/solid reactor system 20 of the present invention. It consists principally of a fluffer/blower 60, which forms the gas suspended 05 mixture of the fibrous solid as previously described, a mixing chamber 40, and a porous bed reactor 30. The fluffer/blower 60 and porous bed reactor 30 are well-known in the art, but are described here in order to illustrate the function of the present invention within the system.
Fluffer/blower 60 receives high consistency pulp 5 (20% to 50% consistency) from a dewatering pres-c, not shown, through conduit 66. It also receives a gas mixture 71 of feed gas 70 and excess 15 blowing gas 76 through gas loop 50. Feed gas 70 is composed of a gaseous reagent and, depending upon the reaction desired, the gaseous reagent may be mixed with any appropriate substantially non-reactive carrier gas. For purposes of this description, a wood pulp bleaching operation using ozone as the gaseous reagent and oxygen as the carrier gas will be used. Feed gas mixture 70 is injected through valve 77 into gas loop 50 where it Docket No. 1197-IR-PA
mixes with excess blowlng gas 76 and forms gas mixture 71. It enters fluffer/blower 60 where it is mixed with pulp 5 to form a gas suspended pulp fluff mixture and provides the mass flow necessary to 05 transport gas/fluff mixture 54 which is discharged through conduit 51 into fluff discharge cyclone 52.
From there pulp 5 falls into mixing chamber feed hopper 46 and is fed into mixing chamber 40 by auger 43.
Within mixing chamber 40, the gas suspended pulp fluff mixture is mechanically agitated by the intense action of paddle blades 44 on rotor shaft 42 which is driven by motor 41. The velocities of the fluffed pulp and the contacting gas 69, which is composed of the remaining gaseous reagent in combination with the non-reactive carrier gas plus the developing gases resulting from the progressive bleaching reaction, through the mixing chamber are not the same. Usually the gas is traveling faster.
The intense mechanical action of the paddle blades maintains the pulp fluff in suspension in the contacting gas 69 and, thus, ensures intimate contact between the contacting gas 69 and the fluffed pulp so that no portion of the fluffed pulp leaves the mixing chamber without contacting the Docket No. 1197-IR-PA
gaseous reagent. This ensures uniform bleaching during the high rate portion of the bleaching reaction. The mixture is discharged from the mixing chamber 40 through discharge neck 45 into the porous 05 bed reactor 30. The action of the paddle blades 44 at the entrance to discharge neck 45 prevents plugging of the neck by the pulp exiting the mixing chamber 40.
The fluffed pulp, having formed a porous bed, moves slowly downward through the porous bed reactor 30 and becomes more compacted toward the bottom as previously described.
The contacting gas 69 passes down through the permeable pulp bed 7, since lt has a much higher velocity than that of the pulp through the reactor 30, until it reaches gas exit 37 where it escapes peripherally to the annular gas exit chamber 32.
The contacting gas 69, by this time stripped of all but a trace of ozone and predominantly composed of oxygen plus yases produced as a by-product of the bleaching reaction, is vented through nozzle 75 and recycled to the ozone generator system. Bleached pulp 10 at the bottom of porous bed reactor 30 is diluted with recycled filtrate through dilution Docket No. 1197-IR-PA
nozzle 34 and is discharged through pulp discharge 36 as dilute bleached pulp 15.
Fig. 2 shows a partially sectioned schematic view from line 2-2 of Fig. l of fluffer/blower 60 05 and its associated equipment. Pulp 5 from the dewatering press enters compression screw feeder 62 through conduit 66 and from there is fed into fluffer/blower 60. The compression screw feeder compacts the pulp into a substantially impermeable plug 99 which prevents backward flow of the mixed gas from reactor system 20. Mixed gas 71 is fed into fluffer/blower 60 through gas loop 50. It is mixed with the fluffed pulp which it conveys as a gas suspension of fluffed pulp by entrainment into pulp and gas discharge conduit 51.
Referring to Figs. l and 2, the novel features of the invention can best be understood. The functions of the fluffer/blower 60 and its related equipment, as well as the porous bed reactor 30, are well-known in the art. Despite the shortcomings of the prior art porous bed reactor, already described, its high efficiency of ozone removal makes it a desirable element, in combination with the present invention, as explained below. The bleaching 204671~
Docket No. 1197-IR-PA
reaction of ozone with pulp is very fast. Fig. 3 shows a graphic representation of the concentration of ozone (in percent) versus time (in seconds) in contact with fluffed pulp under conditions such as 05 those previously described for a porous bed reactor. The concentration of ozone in oxygen coming out of an ozone generator is shown as being approximately 4%. It can be seen, that for a porous bed reactor, approximatel~ 60% of the ozone is consumed in less than one second of contact with the pulp, while at six seconds, over 9G% of the ozone is consumed. For this reason, thorough mixing of the ozone with the pulp fibers is imperative in order to avoid wide variations in bleached lS brightness of the pulp. Thus, mechanical mixing chamber 40 is provided between fluffer/blower 60 and porous bed reactor 30.
The fluffed pulp/gas mixture 54 is injected through fluff discharge cyclone 52 and mixing chamber hopper 46 into auger 43 which conveys it to the mixing paddles 44 mounted on rotor shaft 42.
The feed rate is maintained so that the bulk density of the intensely agitated pulp in the substantially horizontal mixing chamber is the maximum possible which will not result in plugging of the chamber.
Docket No. 1197-IR-PA
This ensures that all of the fluffed pulp passing through chamber 40 is exposed, to the maximum possible extent, to the gaseous reagent in the chamber. Paddles 44 provide intensive mixing action 05 between the pulp fluff and the gas to maintain the gas suspension of the pulp fluff which was formed in the fluffer/blower 60 during the dwell time in the mixing chamber 40. The mixing paddles closest to discharge neck 45 prevent plugging of the neck by the pulp exiting the mixing chamber 40 and dropping into reactor 30 on top of pulp bed 7. The contacting gas 69 which, after six seconds mixing, contains less than half its initial ozone, continues downward through the porous pulp bed until it reaches gas exit 37 at which time its concentration is typically less than 30 parts per million ozone.
The mixing chamber provides a pulp fluff dwell time in the range of approximately 10 seconds while maintaining the pulp in suspension in the contacting gas 69 through intimate intensive mechanical mixing of the gas and pulp fluff. This ensures the maximum practical reaction extent prior to discharge of the mixture into the porous bed reactor. Since the ozone concentration entering the porous bed reactor 2~46717 Docket No. 1197-IR-PA
is suhstantially less than half its initial concentration, the reaction rate is considerably slower, and non-uniformity of bleaching due to variable porosity of the pulp bed is further 05 mitigated.
Fig. 4 shows an alternative em~odiment of the present invention which is similar to that of Fig.
1, except that, here, fluffer/blower 60 has been replaced by fluffer 90 which, without any blowing action, deposits fluffed pulp fibers directly into mixing chamber hopper 46. Gas loop 50 has also been eliminated in this embodiment, since the reagent gas mixture is introduced in the mixing chamber hopper rather than in the fluffer.
This invention, in its preferred embodiment, provides the advantage of attaining uniform bleaching reaction results in the example considered without wasting expensive ozone or other gaseous reagent. By providing the mechanical mixing chamber prior to the porous bed reactor chamber, the desired gas/pulp contact time is achieved while intimate mixing is maintained. Thus, the invention provides uniform substantially complete reaction under commercially practical conditions over a wide range of capacities.
Docket No. 1197-IR-PA
The ozone/wood pulp reaction is used as an example to illustrate the features of this invention. Any gas/solid reaction in which the reaction kinetics are similar to those of 05 ozone/wood pulp and in which the solid has fluffy fibrous characteristics similar to wood pulp is an appropriate application for this invention.
Claims (14)
1. An apparatus for treating fibrous material with a gaseous reagent comprising:
means for fluffing the fibrous material in the presence of the gaseous reagent to form a gas suspension of the fibrous material;
means for receiving and agitating said gas suspension of fibrous material to mechanically maintain the fibrous material in suspension until the gaseous reagent has substantially reacted with said fibrous material; and means for receiving said gas suspension of fibrous material wherein the reaction is completed and the remaining reaction gases are removed from the fibrous material.
means for fluffing the fibrous material in the presence of the gaseous reagent to form a gas suspension of the fibrous material;
means for receiving and agitating said gas suspension of fibrous material to mechanically maintain the fibrous material in suspension until the gaseous reagent has substantially reacted with said fibrous material; and means for receiving said gas suspension of fibrous material wherein the reaction is completed and the remaining reaction gases are removed from the fibrous material.
2. The apparatus of claim 1, wherein the means for agitating the gas suspension of fibrous material comprises an elongate mixing chamber having a plurality of mixing paddles mounted on an axially oriented rotatably driven shaft.
3. The apparatus of claim 2, further comprising:
Docket No. 1197-IR-PA
feed auger means at a receiving portion of said mixing chamber for conveying the gas suspension of fluffed fibrous material into the mixing chamber.
Docket No. 1197-IR-PA
feed auger means at a receiving portion of said mixing chamber for conveying the gas suspension of fluffed fibrous material into the mixing chamber.
4. The apparatus of claim 1, wherein the means for receiving and agitating the gas suspension of fibrous material is operated at a speed which provides a suspension dwell time of up to approximately ten seconds.
5. An apparatus for treating a fluffed fibrous material with a gaseous reagent comprising:
means for introducing a gas suspension of fluffed fibrous material into a mixing chamber;
means within said mixing chamber for mechanically agitating to maintain the fibrous material in suspension in the gaseous reagent for a dwell time sufficient that a substantial majority of the gaseous reagent has reacted with the fibrous material; and means for dispensing the mixture of fibrous material and gaseous reagent into a reaction and degasification chamber to form a porous bed in which the reaction can continue until the gaseous reagent is substantially completely consumed.
Docket No. 1197-IR-PA
means for introducing a gas suspension of fluffed fibrous material into a mixing chamber;
means within said mixing chamber for mechanically agitating to maintain the fibrous material in suspension in the gaseous reagent for a dwell time sufficient that a substantial majority of the gaseous reagent has reacted with the fibrous material; and means for dispensing the mixture of fibrous material and gaseous reagent into a reaction and degasification chamber to form a porous bed in which the reaction can continue until the gaseous reagent is substantially completely consumed.
Docket No. 1197-IR-PA
6. The apparatus of claim 5, wherein said means for introducing the fibrous material and gaseous reagent into a mixing chamber comprises means for fluffing the fibrous material in the presence of the gaseous reagent.
7. The apparatus of claim 5, wherein the means for mechanically mixing the fibrous material and the gaseous reagent comprises an elongate mixing chamber having a plurality of mixing paddles mounted on an axially oriented rotatably driven shaft.
8. The apparatus of claim 7, further comprising:
feed auger means at a receiving portion of said mixing chamber for conveying the gas suspension of fluffed fibrous material into the mixing chamber.
feed auger means at a receiving portion of said mixing chamber for conveying the gas suspension of fluffed fibrous material into the mixing chamber.
9. The apparatus of claim 7, wherein the fibrous material is wood pulp of 20% to 50%
consistency, the gaseous reagent is a mixture of ozone in oxygen, and the dwell time within said mixing chamber is approximately ten seconds.
Docket No. 1197-IR-PA
consistency, the gaseous reagent is a mixture of ozone in oxygen, and the dwell time within said mixing chamber is approximately ten seconds.
Docket No. 1197-IR-PA
10. In an apparatus, for bleaching wood pulp with a gaseous reagent, of the type having a mechanical pulp fluffer which fluffs the pulp in the presence of the gaseous reagent to form a gas suspension of pulp and a porous bed reaction and degasification chamber, the improvement comprising:
a mechanical mixing chamber having a rotor with a plurality of mixing paddles, and means for conveying the pulp and gaseous reagent, as a gas suspension of pulp, through the mixing chamber at a rate such that a substantial majority of said gaseous reagent is consumed in the mixer, said mixing chamber being positioned between said mechanical pulp fluffer and said porous bed reaction and degasification chamber.
a mechanical mixing chamber having a rotor with a plurality of mixing paddles, and means for conveying the pulp and gaseous reagent, as a gas suspension of pulp, through the mixing chamber at a rate such that a substantial majority of said gaseous reagent is consumed in the mixer, said mixing chamber being positioned between said mechanical pulp fluffer and said porous bed reaction and degasification chamber.
11. The apparatus of claim 10, wherein said means for conveying comprises an auger at the entrance of said mixing chamber.
12. The apparatus of claim 10, wherein said means for conveying comprises a bias on the mixing paddles.
Docket No. 1197-IR-PA
Docket No. 1197-IR-PA
13. A method for treating fibrous material with a gaseous reagent comprising the steps of:
fluffing the fibrous material in the presence of the gaseous reagent to form a gas suspension of the fibrous material;
agitating to mechanically maintain the fibrous material in suspension in the gaseous reagent until said gaseous reagent has substantially reacted with said fibrous material; and dispensing the mixture into a porous bed reaction and degasification chamber to complete the reaction and remove the remaining reaction gases from the fibrous material.
fluffing the fibrous material in the presence of the gaseous reagent to form a gas suspension of the fibrous material;
agitating to mechanically maintain the fibrous material in suspension in the gaseous reagent until said gaseous reagent has substantially reacted with said fibrous material; and dispensing the mixture into a porous bed reaction and degasification chamber to complete the reaction and remove the remaining reaction gases from the fibrous material.
14. The bleaching apparatus of claim 10, wherein said means for conveying provides a dwell time for the gas suspension of pulp in the mixing chamber of approximately 10 seconds.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US65158691A | 1991-02-06 | 1991-02-06 | |
| US651,586 | 1991-02-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2046717A1 true CA2046717A1 (en) | 1992-08-07 |
Family
ID=24613432
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002046717A Abandoned CA2046717A1 (en) | 1991-02-06 | 1991-07-10 | Method and apparatus for treating fibrous materials with a gaseous reagent |
Country Status (12)
| Country | Link |
|---|---|
| JP (1) | JPH0657672A (en) |
| CN (1) | CN1063915A (en) |
| AT (1) | ATA139491A (en) |
| AU (1) | AU646267B2 (en) |
| BR (1) | BR9103446A (en) |
| CA (1) | CA2046717A1 (en) |
| DE (1) | DE4203131A1 (en) |
| ES (1) | ES2050566B1 (en) |
| FI (1) | FI913382A (en) |
| FR (1) | FR2672314B1 (en) |
| IT (1) | IT1250690B (en) |
| SE (1) | SE9102209L (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5810973A (en) * | 1993-09-21 | 1998-09-22 | Beloit Technologies, Inc. | Apparatus for producing small particles from high consistency wood pulp |
| US5942088A (en) * | 1995-07-26 | 1999-08-24 | Beloit Technologies, Inc. | Apparatus for bleaching high consistency pulp with a gaseous bleaching reagent |
| US6077396A (en) * | 1997-05-16 | 2000-06-20 | Lariviere; Christopher J. | Apparatus for fluffing and contacting high consistancy wood pulp with a gaseous bleaching reagent |
| US6210532B1 (en) | 1994-08-11 | 2001-04-03 | Lewis D. Shackford | Means for conveying pulp having differential pressure control |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5181989A (en) * | 1990-10-26 | 1993-01-26 | Union Camp Patent Holdings, Inc. | Reactor for bleaching high consistency pulp with ozone |
| US5409570A (en) * | 1989-02-15 | 1995-04-25 | Union Camp Patent Holding, Inc. | Process for ozone bleaching of oxygen delignified pulp while conveying the pulp through a reaction zone |
| US5520783A (en) * | 1990-10-26 | 1996-05-28 | Union Camp Patent Holding, Inc. | Apparatus for bleaching high consistency pulp with ozone |
| NZ242792A (en) * | 1991-05-24 | 1993-12-23 | Union Camp Patent Holding | Two-stage pulp bleaching reactor: pulp mixed with ozone in first stage. |
| CA2151814A1 (en) * | 1992-12-18 | 1994-07-07 | Beloit Technologies, Inc. | Pulp and bleach reagent mixer and method |
| US5554259A (en) * | 1993-10-01 | 1996-09-10 | Union Camp Patent Holdings, Inc. | Reduction of salt scale precipitation by control of process stream Ph and salt concentration |
| AT402077B (en) * | 1995-03-10 | 1997-01-27 | Andritz Patentverwaltung | METHOD AND DEVICE FOR TREATING FIBER FABRIC, ESPECIALLY BLEACHING |
| CA2227690A1 (en) * | 1995-07-26 | 1997-02-13 | L. Allan Carlsmith | Method and apparatus for bleaching pulp with a gaseous bleaching reagent |
| SE514416C2 (en) * | 1999-06-10 | 2001-02-19 | Valmet Fibertech Ab | Method and system for gas-tight feed of pulp to an ozone bleaching reactor |
| DE10349120A1 (en) * | 2003-10-22 | 2005-05-25 | Voith Paper Patent Gmbh | System for continuous coating of material strip with a liquid or viscous product has a collecting trough for excess fluid at the start and end of the process and with active removal of the fluid from the trough |
| CN103439216B (en) * | 2013-07-22 | 2015-04-22 | 广东轻工职业技术学院 | Apparatus for determining gas content in paper-pulp fiber suspension |
| CN111556967B (en) * | 2017-12-20 | 2023-04-04 | 尤妮佳股份有限公司 | Method for producing recycled pulp fibers |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3041233A (en) * | 1957-12-17 | 1962-06-26 | Kamyr Ab | Method of introducing high density pulp into a pressure vessel |
| NO137651C (en) * | 1975-10-31 | 1978-03-29 | Myrens Verksted As | PROCEDURE AND APPARATUS FOR CONTINUOUS TREATMENT OF FINDEL FIBER MATERIAL OR CELLULOSIZED MASS WITH GAS WITHOUT COVER. |
| US4303470A (en) * | 1979-06-15 | 1981-12-01 | Weyerhaeuser Company | Method and apparatus for mixing gases with a wood pulp slurry |
| US4363697A (en) * | 1979-12-03 | 1982-12-14 | The Black Clawson Company | Method for medium consistency oxygen delignification of pulp |
| US4426256A (en) * | 1982-03-09 | 1984-01-17 | Myrens Verksted A/S | Apparatus for treating fibrous material with a gas |
| CA1300322C (en) * | 1987-06-08 | 1992-05-12 | Derek Hornsey | Method of bleaching or delignification of cellulose pulp with oxygen |
| FI89516B (en) * | 1989-05-10 | 1993-06-30 | Ahlstroem Oy | Foerfarande Foer blekning av cellulosamassa med Otson |
| 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 |
-
1991
- 1991-07-10 CA CA002046717A patent/CA2046717A1/en not_active Abandoned
- 1991-07-11 AT AT0139491A patent/ATA139491A/en not_active IP Right Cessation
- 1991-07-12 FI FI913382A patent/FI913382A/en not_active Application Discontinuation
- 1991-07-16 AU AU80441/91A patent/AU646267B2/en not_active Ceased
- 1991-07-16 CN CN91105630.0A patent/CN1063915A/en active Pending
- 1991-07-19 SE SE9102209A patent/SE9102209L/en not_active Application Discontinuation
- 1991-07-22 IT ITMI912023A patent/IT1250690B/en active IP Right Grant
- 1991-08-06 ES ES09101835A patent/ES2050566B1/en not_active Expired - Fee Related
- 1991-08-07 JP JP3197543A patent/JPH0657672A/en active Pending
- 1991-08-12 BR BR919103446A patent/BR9103446A/en not_active Application Discontinuation
- 1991-11-13 FR FR9113942A patent/FR2672314B1/en not_active Expired - Fee Related
-
1992
- 1992-02-04 DE DE4203131A patent/DE4203131A1/en not_active Withdrawn
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5810973A (en) * | 1993-09-21 | 1998-09-22 | Beloit Technologies, Inc. | Apparatus for producing small particles from high consistency wood pulp |
| US6210532B1 (en) | 1994-08-11 | 2001-04-03 | Lewis D. Shackford | Means for conveying pulp having differential pressure control |
| US5942088A (en) * | 1995-07-26 | 1999-08-24 | Beloit Technologies, Inc. | Apparatus for bleaching high consistency pulp with a gaseous bleaching reagent |
| US6077396A (en) * | 1997-05-16 | 2000-06-20 | Lariviere; Christopher J. | Apparatus for fluffing and contacting high consistancy wood pulp with a gaseous bleaching reagent |
Also Published As
| Publication number | Publication date |
|---|---|
| BR9103446A (en) | 1992-09-29 |
| ATA139491A (en) | 1995-06-15 |
| DE4203131A1 (en) | 1992-08-13 |
| FI913382A0 (en) | 1991-07-12 |
| IT1250690B (en) | 1995-04-21 |
| ES2050566A1 (en) | 1994-05-16 |
| CN1063915A (en) | 1992-08-26 |
| ES2050566B1 (en) | 1994-12-01 |
| AU8044191A (en) | 1992-08-13 |
| JPH0657672A (en) | 1994-03-01 |
| SE9102209D0 (en) | 1991-07-19 |
| FI913382A (en) | 1992-08-07 |
| ITMI912023A0 (en) | 1991-07-22 |
| ITMI912023A1 (en) | 1993-01-22 |
| FR2672314B1 (en) | 1994-01-14 |
| AU646267B2 (en) | 1994-02-17 |
| SE9102209L (en) | 1992-08-07 |
| FR2672314A1 (en) | 1992-08-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |