CA1242055A - Sawdust pumping, and processing - Google Patents
Sawdust pumping, and processingInfo
- Publication number
- CA1242055A CA1242055A CA000477850A CA477850A CA1242055A CA 1242055 A CA1242055 A CA 1242055A CA 000477850 A CA000477850 A CA 000477850A CA 477850 A CA477850 A CA 477850A CA 1242055 A CA1242055 A CA 1242055A
- Authority
- CA
- Canada
- Prior art keywords
- slurry
- vessel
- sawdust
- recited
- digester
- 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
Links
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
- D21C7/00—Digesters
- D21C7/06—Feeding devices
Abstract
SAWDUST PUMPING AND PROCESSING
ABSTRACT OF THE DISCLOSURE
A method and apparatus are provided for effecting treatment of sawdust to produce paper pulp in a simplified and efficient manner. The sawdust is entrained with liquid so that it forms a slurry having a consistency of between about 10-25%, and preferably between about 15-22% solids. The slurry consistency is maintained generally constant throughout the treatment process. The slurry at that consistency is pumped by a fluidizing, high speed, degassing, centrifugal pump (22). The pumping action alone provides for transport of the slurry to a digester vessel (26, 40, 46). The digester vessel may be an upflow vessel (26, 46), a hydraulically filled downflow vessel (40), or a superatmospheric vapor phase downflow vessel (40).
Kraft pulping may be practiced in the digester, or a sulfite process may be practiced in the digester (46) and the slurry then passed to a refiner (48) to produce a mechanical pulp. Between the pump and the digester the slurry passes through a heating device (24, 30), which may comprise a fluidizing mixer (24) for directly introducing high pressure steam into the slurry, or a pressure diffuser (30) for effecting indirect heating of the slurry.
ABSTRACT OF THE DISCLOSURE
A method and apparatus are provided for effecting treatment of sawdust to produce paper pulp in a simplified and efficient manner. The sawdust is entrained with liquid so that it forms a slurry having a consistency of between about 10-25%, and preferably between about 15-22% solids. The slurry consistency is maintained generally constant throughout the treatment process. The slurry at that consistency is pumped by a fluidizing, high speed, degassing, centrifugal pump (22). The pumping action alone provides for transport of the slurry to a digester vessel (26, 40, 46). The digester vessel may be an upflow vessel (26, 46), a hydraulically filled downflow vessel (40), or a superatmospheric vapor phase downflow vessel (40).
Kraft pulping may be practiced in the digester, or a sulfite process may be practiced in the digester (46) and the slurry then passed to a refiner (48) to produce a mechanical pulp. Between the pump and the digester the slurry passes through a heating device (24, 30), which may comprise a fluidizing mixer (24) for directly introducing high pressure steam into the slurry, or a pressure diffuser (30) for effecting indirect heating of the slurry.
Description
124205~
SAWDUST PIJMPING A PRO(:ESSING
BACRGROU21D AND SUMMARY OF TIE I2~Vh'~lTION
There are many areas throughout the world where a substantial volume of sawdust and like 5 cellulosic residues are available for the production of paper pulp. While such raw material can effec-tively be utilized to produce paper pulp employing existing technology, the existinq technology is expensive, troublesome, and has very little 10 flexibility. For instance, a typical treatment system utilizable for producing chemical pulp from sawdust is illustrated in U.S. Patent 3,475,271, and a commercial version thereof is shown in a brochure entitled "Kamyr Sawdust Systems Pass the 500,000 15 Tons Per Year Mark". Such systems include an expensive vapor phase feeder, and maintain a substantially atmospheric vapor phase at the top of the digester vessel.
According to the present invention, a 20 method and apparatus are provided that eliminate the vapor phase feeder utilized in conventional sawdust treatment systems, thereby lowering maintenance problems, and providing a number of treatment options. According to the present invention, 25 sawdust may be treated in an upflow digester, or may be treated in a hydraulically filled downflow digester, or may be treated in a downflow digester having a superatmospheric vapor phase. This provides for greater thermal stability, which may be 30 very desirable in many situations.
The term "sawdust" as used in the present specification and claims means sawdust and like cellulosic materials, including wood residues, which
SAWDUST PIJMPING A PRO(:ESSING
BACRGROU21D AND SUMMARY OF TIE I2~Vh'~lTION
There are many areas throughout the world where a substantial volume of sawdust and like 5 cellulosic residues are available for the production of paper pulp. While such raw material can effec-tively be utilized to produce paper pulp employing existing technology, the existinq technology is expensive, troublesome, and has very little 10 flexibility. For instance, a typical treatment system utilizable for producing chemical pulp from sawdust is illustrated in U.S. Patent 3,475,271, and a commercial version thereof is shown in a brochure entitled "Kamyr Sawdust Systems Pass the 500,000 15 Tons Per Year Mark". Such systems include an expensive vapor phase feeder, and maintain a substantially atmospheric vapor phase at the top of the digester vessel.
According to the present invention, a 20 method and apparatus are provided that eliminate the vapor phase feeder utilized in conventional sawdust treatment systems, thereby lowering maintenance problems, and providing a number of treatment options. According to the present invention, 25 sawdust may be treated in an upflow digester, or may be treated in a hydraulically filled downflow digester, or may be treated in a downflow digester having a superatmospheric vapor phase. This provides for greater thermal stability, which may be 30 very desirable in many situations.
The term "sawdust" as used in the present specification and claims means sawdust and like cellulosic materials, including wood residues, which
2 055 are fine enough to react like small particles during handling. This may be contrasted with the way that large comminuted cellulosic particles - such as wood chips - react during handling.
A key to the sawdust treatment process according to the present invention is the unexpected discovery that it is possible to pump sawdust slurries having a consistency high enough to effect practical chemical treatment thereof. That is, 10 according to the present invention it has been found that it is possible to pump sawdust slurries having a solids consistency of between about 10-25%, and more desirably between about 15-22%. Pumping can be accomplished utilizing commercially available 15 fluidizing, high speed, degassing, centrifugal pumps and related systems such as shown in U.S. Patents 4,435,193 and 4,410,337, and sold commercially by Kamyr, Inc. of Glens Falls, New York, and Kamyr AB
of Karlstad, Sweden, under the trademark "MC"
20 pump. The discovery that it is possible to pump medium consistency (e.g. 10-25~) sawdust slurries is surprising since the fine particles tend to act as a solid, as opposed to the situation with pulp or the like wherein the material is more flexible. Further 25 sawdust slurries do not filter well, and a sawdust slurry with a consistency of as little as 10% solids is virtually a semi-solid.
According to the method of the present invention, sawdust is treated by: mixing the sawdust 30 with a liquid to produce a slurry having a solids consistency of between about 10-25~ (preferably about 15-22%); and pumping the slurry, without dilution, to a treatment stage to ultimately produce pulp. At the treatment stage, the slurry is heated 35 (either indirectly, or by direct mixing of high ~;~42055 pressure steam with the slurry - as by utilizing a fluidizing mixer), the slurry is introduced into the vertical vessel, chemical treatment of the slurry within the vessel is practiced, and the slurry is 5 discharged from the vessel. Preferably the vessel is an upflow vessel and the slurry is pumped, without dilution, and under the influence of the fluidizing, high speed, centrifugal pump, up through the vessel. Alternatively, the vessel may be a 10 downflow vessel, either a hydraulically filled vessel or one having a superatmospheric vapor phase.
The chemical treatment in the vessel facilitates breaking down, or effects breaking down, of the lignin in the sawdust. For instance, a 15 sulfite treatment can be provided in the vessel, with the slurry discharged from the vessel then being passed to a refiner to produce a mechanical pulp. Alternatively, the slurry may be subjected to Kraft processing in the vessel, resulting in the 20 production of Kraft pulp. Irrespective of the treatment process, the mixing of the sawdust with liquid is preferably practiced by mixing the sawdust with low pressure steam and a treatment liquid, and then feeding it into a vertical chute, and pumping 25 the slurry from the bottom of the chute. The slurry maintains substantially the same consistency (i.e. a consistency between about 10-25%) without phase separation (solid/liquid) throughout all the treatment procedures.
The apparatus according to the invention comprises: a means for entraining the sawdust in a liquid; a fluidizing, high speed, centrifugal pump such as disclosed in said patents 4,435,193 and 4,410,337; a vertical digester; a conduit between 35 the pump and the digester; and a direct or indirect 4 lX4i:055 heating means for heating the slurry before introduction into the digester. The interconnection between the pump and the digester consists of the conduit, a valve means in the conduit, and the 5 heating means, the force provided by the pump ultimately effecting passage of the slurry through the digester.
It is the primary object of the present invention to provide for the effective, simple, and 10 versatile treatment of sawdust to produce pulp.
This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.
BRIEF DESCRIPTION OF TOE DRAWINGS
FIGURE 1 is a diagrammatic view of exemplary apparatus according to the present invention, for practicing an exemplary method according to the invention;
FIGURE 2 is a diagrammatic view of a second 20 embodiment of apparatus according to the present invention; and FIGURE 3 is a partial, diagrammatic view, showing a third embodiment of exemplary apparatus according to the present invention.
DETAILED DESCRIPTION OF_THE DRAWINGS
FIGURE 1 illustrates a component for a preferred embodiment of an apparatus according to the present invention, for effecting the production of Kraft pulp. The apparatus in this embodiment 12~L2055 comprises a conventional low pressure feeder 10 mounted atop a conventional horizontal steaming vessel 12 (also known as a steam mixer, having a horizontal axis mixing screw therein), having a steam relief pressure con-trolled vent 14. Sawdust is fed from a source to thefeeder 10, and is introduced into the vessel 12 wherein it is entrained in liquid to produce a slurry. The liquid may comprise white liquor from a Kraft process, and additionally low pressure steam is introduced into the vessel 12. The slurry discharged from the vessel 12 is preferably discharged into a vertical chute 16, although it may instead be fed to a conduit connected directly to the pump to be hereinafter described. In the chute 16, a liquid level is maintained utilizing a conventional gamma level indicator 18, which controls a valve means 20 in a conduit 21 leading from the bottom of the chute 16. A liquid, such as white liquor, is preferably introduced into the chute 16.
The structures 10, 12, 14 and 16 comprise means for entraining the sawdust in liquid, to produce a slurry having a solids consistency of between about 10-25% (and preferably between about 15-22%). The slurry has that consistency at the bottom of the chute 16, where the pump 22 is located.
The pump 22 is shown only schematically in FIGURE 1, but in addition to pumping components thereof it will have degassing components, as shown in U.S.
Patents 4,435,193 and 4,410,337. The pump 22 comprises a fluidizing, high speed, degassing, centrifugal pump.
Typically, the impeller thereof _ ~~
'I;
6 ~z42()5S
2000-3400 rpm in order to effect fluidiæation of the slurry. Such a pump 22 is commercially available from Kamyr, Inc. of Glens walls, New York and Kamyr AB of Karlstad, Sweden, under the trademark "MC"
5 pump.
Operatively connected to the conduit 21 is a heating means 24 and a vertical vessel 26. The heating means 24 in the embodiment illustrated in FIGURE 1 comprises a mixer for directly mixing high 10 pressure steam into the slurry. Various forms such a mixer may take are shown in Canadian Patent 1,102,604, such a mixer comprising a fluidizing mixer. A typical mixer that may be utilized for the heating means 24 is sold by Kamyr, Inc. and Kamyr AB
15 under the trademark "MC" mixer.
The vessel 26 comprises a continuous digester, and in the embodiment illustrated in FIGURE 1 is an upflow vessel having a conventional discharge mechanism 28 at the top thereof. In the 20 vessel 26 chemical treatment of the slurry may be practiced. A Kraft delignification process is practiced in the vessel 26, white liquid -introduced during slurrying of the sawdust -providing an active alkali charge which 25 conventionally will be in the range of 9-24~ Na20 on bone dry raw material. The heating means 24 brings the slurry up to optimum cooking temperature normally in the range of 140-175~. The pump 22 brings the slurry up to normal treatment pressure, 30 which is typically 600-1200 kPa, and the slurry is maintained at that pressure, and is maintained in the digester 26 for a time period of about 30-130 minutes. These values are merely exemplary values, and they may vary somewhat depending upon the nature 35 of the sawdust and the particular subsequent 7 1;~g2055 treatment steps to be applied to the pulp, and the ultimate pulp to be produced.
The embodiment illustrated in FIGURE 2 is substantially identical to that illustrated in 5 FIGURE 1 except that heating of the slurry to optimum cooking temperature is accomplished utilizing an indirect heating means 30, and the digester 40 comprises a downflow digester.
The vertical vessel 30 connected to the 10 pump 22 by the conduit 21 preferably comprises an indirect heating vessel with a movable screen, such as shown in u.S. Patent 4,368,628. In such an indirect heating vessel with a movable screen, the A slurry is maintained, without dilution, at 15 substantially the same pressure as it had when discharged from the pump 22. Liquid is withdrawn from the vessel 30 by the pump 32, passes throuqh steam heater 34, and is recirculated back to the vessel to be introduced at inlet 35. Thus, the 20 slurry is indirectly heated as it passes through the vessel 30 and the amount of liquid withdrawn at 31 is substantially the same as the amount of liquid introduced at 35, so that the consistency of the slurry is not significantly changed during heating 25 utilizing vessel 30. The slurry is discharged from conventional discharge mechanism 36 and passes through conduit 37 to be introduced at the top 38 of the downflow digester 40. Pulp as it is produced is discharged from the bottom of the vessel 40 30utilizing a conventional discharge mechanism 42.
According to the present invention, there is a good deal of versatility in the operation of the downflow digester 40. Preferably the downflow digester 40 will be hydraulically filled.
35Alternatively, it may have a superatmospheric vapor 8 lX~0~;5 phase at the top thereof, and noncondensable gases may be vented - in this instance - utilizing vent 43. In either case, the thermal stability of the process is greatly enhanced compared to the 5 substantially atmospheric digester utilized in commercial prior art practices.
The apparatus utilized in FIGURES 1 and 2 is primarily useful for the production of chemical pulp. The apparatus of FIGURE 3 is utilized for the 10 production of mechanical pulp, particularly chemi-mechanical pulp (CMP), or chemithermomechanical (CTMP) pulp. In this embodiment, the chemical treatment vessel 46 is much smaller than the vessels 26, 40, since complete delignification does not take 15 place in the vessel. Typically, sulfite is added to the slurry in the vessel 46 (for example by entraining the sawdust with sulfite in the mixing means and the slurry when discharged from the vessel 46 in discharge line 47 passes to a 20 conventional refiner 48. The mechanical pulp produced is discharged into line 49.
Typically, sodium sulfite at pH 9-10 is the mild pretreatment liquid in the vessel 46, and the temperature therein is at about 130-170C. However, in some situations, no chemical need be added at all, but rather merely by heating of the slurry with high pressure steam (as in fluidiæing mixer 24) to about 110-150C, fibrilization in refiner 48 will be facilitated, producing thermomechanical pulp (TMP).
According to the method of the present invention, sawdust is treated by mixing the sawdust with a liquid (in steam mixer 12 and chute 16) to produce a slurry having a solids consistency of between about 10-25%, and preferably between about 15-22%; and pumping the slurry, utilizing 9 124~05~
fluidizing, high speed, centrifugal pump 22, without dilution, to a treatment stage to ultimately produce pulp. At the treatment stage, the slurry is heated to optimum temperature, and introduced into a 5 treatment vessel. Heating may be accomplished directly - as by mixing high pressure steam directly into the slurry utilizing steam mixer 24 - or indirectly, as by utilizing pressure diffuser 30.
In the treatment vessel, some chemical treatment of the slurry is practiced. The chemical treatment merely facilitates breaking down of the lignin in the sawdust where a mechanical pulp is ultimately to be produced. If a Kraft pulp is ultimately to be produced, in the vessel the chemical treatment breaks down the lignin in the sawdust. The pulp is ultimately discharged from the vessel, whether it be vessel 26, 40 or 46. The chemical treatment takes place during upflow, or hydraulically filled downflow.
Treatment in the vessel 46 may be a sulfite treatment, with the discharge pulp ultimately be refined in refiner 48. Treatment in the vessels 26, 40 is a Kraft treatment, with the Kraft pulp ultimately being produced.
It will thus be seen that according to the present invention a simple, effective, and versatile method and apparatus have been provided for the treatment of sawdust to produce pulp. According to the invention, the vapor phase feeder, and maintenance and cost disadvantages associated therewith, has been eliminated at the same time that versatility of the system has been enhanced.
While the invention has been herein shown and described in what is presently conceived to be ~L24205~
the most practical and preferred embodiment thereof, it will be apparent to those of ordinary skill in the art that many modifications may be made thereof within the scope of the invention, which scope is to be accorded the broadest interpretation of the appended claims so as to encompass all equivalent methods and devices.
A key to the sawdust treatment process according to the present invention is the unexpected discovery that it is possible to pump sawdust slurries having a consistency high enough to effect practical chemical treatment thereof. That is, 10 according to the present invention it has been found that it is possible to pump sawdust slurries having a solids consistency of between about 10-25%, and more desirably between about 15-22%. Pumping can be accomplished utilizing commercially available 15 fluidizing, high speed, degassing, centrifugal pumps and related systems such as shown in U.S. Patents 4,435,193 and 4,410,337, and sold commercially by Kamyr, Inc. of Glens Falls, New York, and Kamyr AB
of Karlstad, Sweden, under the trademark "MC"
20 pump. The discovery that it is possible to pump medium consistency (e.g. 10-25~) sawdust slurries is surprising since the fine particles tend to act as a solid, as opposed to the situation with pulp or the like wherein the material is more flexible. Further 25 sawdust slurries do not filter well, and a sawdust slurry with a consistency of as little as 10% solids is virtually a semi-solid.
According to the method of the present invention, sawdust is treated by: mixing the sawdust 30 with a liquid to produce a slurry having a solids consistency of between about 10-25~ (preferably about 15-22%); and pumping the slurry, without dilution, to a treatment stage to ultimately produce pulp. At the treatment stage, the slurry is heated 35 (either indirectly, or by direct mixing of high ~;~42055 pressure steam with the slurry - as by utilizing a fluidizing mixer), the slurry is introduced into the vertical vessel, chemical treatment of the slurry within the vessel is practiced, and the slurry is 5 discharged from the vessel. Preferably the vessel is an upflow vessel and the slurry is pumped, without dilution, and under the influence of the fluidizing, high speed, centrifugal pump, up through the vessel. Alternatively, the vessel may be a 10 downflow vessel, either a hydraulically filled vessel or one having a superatmospheric vapor phase.
The chemical treatment in the vessel facilitates breaking down, or effects breaking down, of the lignin in the sawdust. For instance, a 15 sulfite treatment can be provided in the vessel, with the slurry discharged from the vessel then being passed to a refiner to produce a mechanical pulp. Alternatively, the slurry may be subjected to Kraft processing in the vessel, resulting in the 20 production of Kraft pulp. Irrespective of the treatment process, the mixing of the sawdust with liquid is preferably practiced by mixing the sawdust with low pressure steam and a treatment liquid, and then feeding it into a vertical chute, and pumping 25 the slurry from the bottom of the chute. The slurry maintains substantially the same consistency (i.e. a consistency between about 10-25%) without phase separation (solid/liquid) throughout all the treatment procedures.
The apparatus according to the invention comprises: a means for entraining the sawdust in a liquid; a fluidizing, high speed, centrifugal pump such as disclosed in said patents 4,435,193 and 4,410,337; a vertical digester; a conduit between 35 the pump and the digester; and a direct or indirect 4 lX4i:055 heating means for heating the slurry before introduction into the digester. The interconnection between the pump and the digester consists of the conduit, a valve means in the conduit, and the 5 heating means, the force provided by the pump ultimately effecting passage of the slurry through the digester.
It is the primary object of the present invention to provide for the effective, simple, and 10 versatile treatment of sawdust to produce pulp.
This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.
BRIEF DESCRIPTION OF TOE DRAWINGS
FIGURE 1 is a diagrammatic view of exemplary apparatus according to the present invention, for practicing an exemplary method according to the invention;
FIGURE 2 is a diagrammatic view of a second 20 embodiment of apparatus according to the present invention; and FIGURE 3 is a partial, diagrammatic view, showing a third embodiment of exemplary apparatus according to the present invention.
DETAILED DESCRIPTION OF_THE DRAWINGS
FIGURE 1 illustrates a component for a preferred embodiment of an apparatus according to the present invention, for effecting the production of Kraft pulp. The apparatus in this embodiment 12~L2055 comprises a conventional low pressure feeder 10 mounted atop a conventional horizontal steaming vessel 12 (also known as a steam mixer, having a horizontal axis mixing screw therein), having a steam relief pressure con-trolled vent 14. Sawdust is fed from a source to thefeeder 10, and is introduced into the vessel 12 wherein it is entrained in liquid to produce a slurry. The liquid may comprise white liquor from a Kraft process, and additionally low pressure steam is introduced into the vessel 12. The slurry discharged from the vessel 12 is preferably discharged into a vertical chute 16, although it may instead be fed to a conduit connected directly to the pump to be hereinafter described. In the chute 16, a liquid level is maintained utilizing a conventional gamma level indicator 18, which controls a valve means 20 in a conduit 21 leading from the bottom of the chute 16. A liquid, such as white liquor, is preferably introduced into the chute 16.
The structures 10, 12, 14 and 16 comprise means for entraining the sawdust in liquid, to produce a slurry having a solids consistency of between about 10-25% (and preferably between about 15-22%). The slurry has that consistency at the bottom of the chute 16, where the pump 22 is located.
The pump 22 is shown only schematically in FIGURE 1, but in addition to pumping components thereof it will have degassing components, as shown in U.S.
Patents 4,435,193 and 4,410,337. The pump 22 comprises a fluidizing, high speed, degassing, centrifugal pump.
Typically, the impeller thereof _ ~~
'I;
6 ~z42()5S
2000-3400 rpm in order to effect fluidiæation of the slurry. Such a pump 22 is commercially available from Kamyr, Inc. of Glens walls, New York and Kamyr AB of Karlstad, Sweden, under the trademark "MC"
5 pump.
Operatively connected to the conduit 21 is a heating means 24 and a vertical vessel 26. The heating means 24 in the embodiment illustrated in FIGURE 1 comprises a mixer for directly mixing high 10 pressure steam into the slurry. Various forms such a mixer may take are shown in Canadian Patent 1,102,604, such a mixer comprising a fluidizing mixer. A typical mixer that may be utilized for the heating means 24 is sold by Kamyr, Inc. and Kamyr AB
15 under the trademark "MC" mixer.
The vessel 26 comprises a continuous digester, and in the embodiment illustrated in FIGURE 1 is an upflow vessel having a conventional discharge mechanism 28 at the top thereof. In the 20 vessel 26 chemical treatment of the slurry may be practiced. A Kraft delignification process is practiced in the vessel 26, white liquid -introduced during slurrying of the sawdust -providing an active alkali charge which 25 conventionally will be in the range of 9-24~ Na20 on bone dry raw material. The heating means 24 brings the slurry up to optimum cooking temperature normally in the range of 140-175~. The pump 22 brings the slurry up to normal treatment pressure, 30 which is typically 600-1200 kPa, and the slurry is maintained at that pressure, and is maintained in the digester 26 for a time period of about 30-130 minutes. These values are merely exemplary values, and they may vary somewhat depending upon the nature 35 of the sawdust and the particular subsequent 7 1;~g2055 treatment steps to be applied to the pulp, and the ultimate pulp to be produced.
The embodiment illustrated in FIGURE 2 is substantially identical to that illustrated in 5 FIGURE 1 except that heating of the slurry to optimum cooking temperature is accomplished utilizing an indirect heating means 30, and the digester 40 comprises a downflow digester.
The vertical vessel 30 connected to the 10 pump 22 by the conduit 21 preferably comprises an indirect heating vessel with a movable screen, such as shown in u.S. Patent 4,368,628. In such an indirect heating vessel with a movable screen, the A slurry is maintained, without dilution, at 15 substantially the same pressure as it had when discharged from the pump 22. Liquid is withdrawn from the vessel 30 by the pump 32, passes throuqh steam heater 34, and is recirculated back to the vessel to be introduced at inlet 35. Thus, the 20 slurry is indirectly heated as it passes through the vessel 30 and the amount of liquid withdrawn at 31 is substantially the same as the amount of liquid introduced at 35, so that the consistency of the slurry is not significantly changed during heating 25 utilizing vessel 30. The slurry is discharged from conventional discharge mechanism 36 and passes through conduit 37 to be introduced at the top 38 of the downflow digester 40. Pulp as it is produced is discharged from the bottom of the vessel 40 30utilizing a conventional discharge mechanism 42.
According to the present invention, there is a good deal of versatility in the operation of the downflow digester 40. Preferably the downflow digester 40 will be hydraulically filled.
35Alternatively, it may have a superatmospheric vapor 8 lX~0~;5 phase at the top thereof, and noncondensable gases may be vented - in this instance - utilizing vent 43. In either case, the thermal stability of the process is greatly enhanced compared to the 5 substantially atmospheric digester utilized in commercial prior art practices.
The apparatus utilized in FIGURES 1 and 2 is primarily useful for the production of chemical pulp. The apparatus of FIGURE 3 is utilized for the 10 production of mechanical pulp, particularly chemi-mechanical pulp (CMP), or chemithermomechanical (CTMP) pulp. In this embodiment, the chemical treatment vessel 46 is much smaller than the vessels 26, 40, since complete delignification does not take 15 place in the vessel. Typically, sulfite is added to the slurry in the vessel 46 (for example by entraining the sawdust with sulfite in the mixing means and the slurry when discharged from the vessel 46 in discharge line 47 passes to a 20 conventional refiner 48. The mechanical pulp produced is discharged into line 49.
Typically, sodium sulfite at pH 9-10 is the mild pretreatment liquid in the vessel 46, and the temperature therein is at about 130-170C. However, in some situations, no chemical need be added at all, but rather merely by heating of the slurry with high pressure steam (as in fluidiæing mixer 24) to about 110-150C, fibrilization in refiner 48 will be facilitated, producing thermomechanical pulp (TMP).
According to the method of the present invention, sawdust is treated by mixing the sawdust with a liquid (in steam mixer 12 and chute 16) to produce a slurry having a solids consistency of between about 10-25%, and preferably between about 15-22%; and pumping the slurry, utilizing 9 124~05~
fluidizing, high speed, centrifugal pump 22, without dilution, to a treatment stage to ultimately produce pulp. At the treatment stage, the slurry is heated to optimum temperature, and introduced into a 5 treatment vessel. Heating may be accomplished directly - as by mixing high pressure steam directly into the slurry utilizing steam mixer 24 - or indirectly, as by utilizing pressure diffuser 30.
In the treatment vessel, some chemical treatment of the slurry is practiced. The chemical treatment merely facilitates breaking down of the lignin in the sawdust where a mechanical pulp is ultimately to be produced. If a Kraft pulp is ultimately to be produced, in the vessel the chemical treatment breaks down the lignin in the sawdust. The pulp is ultimately discharged from the vessel, whether it be vessel 26, 40 or 46. The chemical treatment takes place during upflow, or hydraulically filled downflow.
Treatment in the vessel 46 may be a sulfite treatment, with the discharge pulp ultimately be refined in refiner 48. Treatment in the vessels 26, 40 is a Kraft treatment, with the Kraft pulp ultimately being produced.
It will thus be seen that according to the present invention a simple, effective, and versatile method and apparatus have been provided for the treatment of sawdust to produce pulp. According to the invention, the vapor phase feeder, and maintenance and cost disadvantages associated therewith, has been eliminated at the same time that versatility of the system has been enhanced.
While the invention has been herein shown and described in what is presently conceived to be ~L24205~
the most practical and preferred embodiment thereof, it will be apparent to those of ordinary skill in the art that many modifications may be made thereof within the scope of the invention, which scope is to be accorded the broadest interpretation of the appended claims so as to encompass all equivalent methods and devices.
Claims (30)
1. A method of treating sawdust comprising the steps of:
- mixing the sawdust with a liquid to produce a slurry having a solids consistency of between about 10-25%; and - centrifugally pumping the slurry, without dilution, to a treatment stage to ultimately effect production of pulp, including fluidizing the slurry during centrifugal pumping thereof.
- mixing the sawdust with a liquid to produce a slurry having a solids consistency of between about 10-25%; and - centrifugally pumping the slurry, without dilution, to a treatment stage to ultimately effect production of pulp, including fluidizing the slurry during centrifugal pumping thereof.
2. A method as recited in claim 1 wherein said mixing step is practiced so as to produce a slurry having a solids consistency of between about 15-22%.
3. A method as recited in claim 1 wherein at said treatment stage the following steps are practiced:
(i) heating the slurry to an optimum processing temperature;
(ii) introducing the heated slurry into a continuous treatment vessel as a result of said pumping;
(iii) effecting chemical treatment of the slurry in the vessel to facilitate the breaking down, or to effect the breaking down, of the lignin in the sawdust; and (iv) discharging the treated slurry from the vessel.
(i) heating the slurry to an optimum processing temperature;
(ii) introducing the heated slurry into a continuous treatment vessel as a result of said pumping;
(iii) effecting chemical treatment of the slurry in the vessel to facilitate the breaking down, or to effect the breaking down, of the lignin in the sawdust; and (iv) discharging the treated slurry from the vessel.
4. A method as recited in claim 3 comprising the further step of, substantially coincident with the mixing of liquid with the sawdust, heating the sawdust by introducing low pressure steam into contact therewith.
11 a
11 a
5. A method as recited in claim 3 wherein step (ii) is practiced by introducing the slurry into the bottom of an upflow vessel, the slurry flowing upwardly in the vessel under the influence of said pumping; and wherein step (iv) is practiced by discharging treated slurry from the top of the vessel.
6. A method as recited in claim 5 wherein step (i) is effected by intimately mixing high pressure steam with the slurry immediately prior to step (ii).
.
.
7. A method as recited in claim 5 wherein step (i) is practiced by passing the slurry to an indirect heating vessel, introducing heated liquid under pressure into the indirect heating vessel, removing a volume of liquid generally commensurate with the volume of heated liquid introduced, from the vessel; and heating the removed liquid and circulating it to provide heated introduction liquid; and wherein step (ii) is practiced by passing the heated slurry from the discharge of the indirect-heating vessel to the inlet to the treatment vessel.
8. A method as recited in claim 5 wherein step (iii) is practiced by effecting a sulfite treatment thereof, and wherein the method comprises the further step (v) of passing the slurry discharged from the vessel to a refining stage, and effecting refining of the sawdust slurry to produce mechanical pulp.
9. A method as recited in claim 5 wherein step (iii) is practiced by Kraft treatment of the sawdust slurry so that chemical pulp is discharged in step (iv).
10. A method as recited in claim 3 wherein the vessel is a hydraulically filled downflow vessel, step (ii) being practiced by introducing slurry into the top of the vessel, and step (iv) being practiced by discharging slurry from the bottom of the vessel.
11. A method as recited in claim 3 wherein the vessel is a vertical downflow vessel, having a vapor pressure maintained at the top which is significantly greater than atmosphere pressure, and wherein step (ii) is practiced by feeding the slurry directly to the top of the vessel under the influence of said pumping, and wherein step (iv) is practiced by discharging from the bottom of the vessel.
12. A method as recited in claim 10 wherein step (i) is effected by intimately mixing high pressure steam with the slurry immediately prior to step (ii).
13. A method as recited in claim 10 wherein step (i) is practiced by: passing the slurry to an indirect heating vessel; introducing heated liquid under pressure into the indirect heating vessel; removing a volume of liquid generally commensurate with the volume of heated liquid introduced, from the vessel; and heating the removed liquid and circulating it to provide heated introduction liquid; and wherein step (ii) is practiced by passing the heated slurry from the discharge of the indirect heating vessel to the inlet to the treatment vessel.
14. A method as recited in claim 10 wherein step (iii) is practiced by effecting a -sulfite treatment thereof, and wherein the method comprises the further step (v) of passing the slurry discharged from the vessel to a refining stage, and effecting refining of the sawdust slurry to produce mechanical pulp.
15. A method as recited in claim 10 wherein step (iii) is practiced by Kraft treatment of the sawdust slurry so that chemical pulp is discharged in step (iv).
16. A method as-recited in claim 11 wherein step (i) is effected by intimately mixing high pressure steam with the slurry immediately prior to step (ii).
17. A method as recited in claim 11 wherein step (i) is practiced by:passing the slurry to an indirect heating vessel; introducing heated liquid under pressure into the indirect heating vessel; removing a volume of liquid generally commensurate with the volume of heated liquid introduced, from the vessel; and heating the removed liquid and circulating it to provide heated introduction liquid; and wherein step (ii) is practiced by passing the heated slurry from the discharge of the indirect heating vessel to the inlet to the treatment vessel.
18. A method as recited in claim 11 wherein step (iii) is practiced by effecting a sulfite treatment thereof, and wherein the method comprises the further step (v) of passing the slurry discharged from the vessel to a refining stage, and effecting refining of the sawdust slurry to produce mechanical pulp.
19. A method as recited in claim 11 wherein step (iii) is practiced by Kraft treatment of the sawdust slurry so that chemical pulp is discharged in step (iv).
20. A method as recited in claim 5 comprising the further step of, substantially coincident,with the mixing of liquid with the sawdust, heating the sawdust by introducing low pressure steam into contact therewith.
21. A method as recited in claim 10 comprising the further step of, substantially coincident with the mixing of liquid with the sawdust, heating the sawdust by introducing low pressure steam into contact therewith.
22. A method as recited in claim 11 comprising the further step of, substantially coincident with the mixing of liquid with the sawdust, heating the sawdust by introducing low pressure steam into contact therewith.
23. Apparatus for producing pulp from sawdust comprising:
means for entraining sawdust in liquid to produce a slurry;
a fluidizing, high speed, degassing, centrifugal pump operatively connected to said means for entraining sawdust in liquid to effect pumping of the sawdust slurry;
a digester for effecting chemical treatment of slurry therewithin to facilitate breakdown of, or to effect breakdown of, the lignin in the sawdust;
a conduit interconnecting said pump and said digester, said conduit having valve means disposed therein;
means disposed in said conduit for effecting heating of the slurry pumped from the pump to the digester, for optimum treatment of the slurry in the digester; and said pump connected through said conduit and said heating means to said digester so that said pump provides the motive force for moving the slurry through the digester, and wherein the interconnection between said pump and said digester consists essentially of said conduit, said valve means, and said heating means.
means for entraining sawdust in liquid to produce a slurry;
a fluidizing, high speed, degassing, centrifugal pump operatively connected to said means for entraining sawdust in liquid to effect pumping of the sawdust slurry;
a digester for effecting chemical treatment of slurry therewithin to facilitate breakdown of, or to effect breakdown of, the lignin in the sawdust;
a conduit interconnecting said pump and said digester, said conduit having valve means disposed therein;
means disposed in said conduit for effecting heating of the slurry pumped from the pump to the digester, for optimum treatment of the slurry in the digester; and said pump connected through said conduit and said heating means to said digester so that said pump provides the motive force for moving the slurry through the digester, and wherein the interconnection between said pump and said digester consists essentially of said conduit, said valve means, and said heating means.
24. Apparatus as recited in claim 23 wherein said digester comprises an upflow digester having an inlet at the bottom thereof, and a discharge at the top thereof, and wherein said conduit and said pump are interconnected to said inlet at the bottom of said digester.
25. Apparatus as recited in claim 23 wherein said digester comprises a downflow, hydraulically filled vessel, having an inlet at the top thereof and a discharge at the bottom thereof, and wherein said conduit and said pump are connected to said inlet at the top of said digester.
26. Apparatus as recited in claim 23 wherein said digester comprises a downflow digester having an inlet at the top thereof and a discharge at the bottom thereof, and wherein said digester comprises a superatmospheric vapor phase digester.
27. Apparatus as recited in claim 23 wherein said heating means comprises a fluidizing mixer for mixing high pressure steam directly into said slurry.
28. Apparatus as recited in claim 23 wherein said digester comprises a sulfite digester, and wherein said apparatus further comprises a refiner operatively connected to the discharge from said digester.
29. Apparatus as recited in claim 23 wherein said means for entraining the sawdust in liquid consists of a horizontal steam mixer; a low pressure feeder through which sawdust is fed to said horizontal steam mixer; means for introducing liquid and low pressure steam into said horizontal steam mixer; a vertically extending chute extending downwardly from the discharge from said steam mixer; and means for introducing liquid into said vertical chute; and wherein said fluidizing, high speed, degassing, centrifugal pump is operatively connected to a bottom portion, of said chute.
30. Apparatus as recited in claim 23 wherein said heating means comprises a pressure diffuser, and means for withdrawing liquid from the diffuser, heating the liquid, and recircu-lating liquid back into the diffuser, to effect indirect heating of the slurry therein.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US596,111 | 1975-07-15 | ||
| US59611184A | 1984-04-02 | 1984-04-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1242055A true CA1242055A (en) | 1988-09-20 |
Family
ID=24386023
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000477850A Expired CA1242055A (en) | 1984-04-02 | 1985-03-28 | Sawdust pumping, and processing |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0157279B1 (en) |
| JP (1) | JPH0639755B2 (en) |
| BR (1) | BR8501512A (en) |
| CA (1) | CA1242055A (en) |
| DE (1) | DE3564300D1 (en) |
| FI (1) | FI78745C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6325888B1 (en) | 1995-08-31 | 2001-12-04 | Andritz-Ahlstrom Inc. | Method for pulping sawdust |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI79361B (en) * | 1988-01-05 | 1989-08-31 | Ahlstroem Oy | FOERFARANDE OCH APPARATUR FOER UNDERLAETTANDE AV UTTOEMNING AV FALLROER ELLER LIKNANDE OCH BEHANDLING AV MASSA I SAGDA UTRYMME. |
| US6106668A (en) * | 1996-10-25 | 2000-08-22 | Ahlstrom Machinery Inc. | Method for feeding comminuted fibrous material |
| US5753075A (en) * | 1996-10-25 | 1998-05-19 | Stromberg; C. Bertil | Method and system for feeding comminuted fibrous material |
| SE0201512L (en) * | 2002-05-21 | 2003-03-11 | Kvaerner Pulping Tech | Method for continuous cooking of raw material for cellulose pulp |
| CA2455172C (en) * | 2003-01-30 | 2010-02-23 | Andritz Inc. | Feeding comminuted fibrous material using high pressure screw and centrifugal pumps |
| CN101398262A (en) * | 2007-09-29 | 2009-04-01 | 沈阳铝镁设计研究院 | Direct heating method and apparatus for pulp |
| SE532060C2 (en) | 2008-03-20 | 2009-10-13 | Metso Fiber Karlstad Ab | Supply system including parallel pumps for a continuous boiler |
| US8888954B2 (en) | 2008-03-20 | 2014-11-18 | Valmet Ab | Feeding system having pumps in parallel for a continuous digester |
| SE532083C2 (en) | 2008-03-20 | 2009-10-20 | Metso Fiber Karlstad Ab | Supply system including parallel pumps for a continuous boiler |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR569326A (en) * | 1922-04-27 | 1924-04-10 | Continuous pressure cooker | |
| FR1226093A (en) * | 1958-06-04 | 1960-07-08 | Buss Ag | Process for the continuous supply and removal of solid substances in an apparatus under pressure or under vacuum and device for carrying out the process |
| US3001481A (en) * | 1958-09-02 | 1961-09-26 | Improved Machinery Inc | Pump |
| US3475271A (en) * | 1966-02-07 | 1969-10-28 | Kamyr Ab | Cellulose digester with washing apparatus |
| US3586600A (en) * | 1967-07-27 | 1971-06-22 | Improved Machinery Inc | Continuous digesting apparatus |
| JPS489122U (en) * | 1971-06-11 | 1973-02-01 | ||
| SE390990B (en) * | 1975-06-02 | 1977-01-31 | Kamyr Ab | KIT AND DEVICE FOR IMPREGNATION OF FIBER MATERIALS FOR COOKING BY PULSING PRESSURE BETWEEN BOILER PRESSURE AND A LOWER PRESSURE |
| US4410337A (en) * | 1980-04-07 | 1983-10-18 | A. Ahlstrom Osakeyhtio | Method and an apparatus for separating a gas from a fibre suspension |
| US4370172A (en) * | 1981-03-17 | 1983-01-25 | Compagnie De Construction Mecanique Sulzer, French Societe Anonyme | Controlled vortex pump feed for supplying cellulose-containing material to reaction vessel |
-
1985
- 1985-03-19 DE DE8585103154T patent/DE3564300D1/en not_active Expired
- 1985-03-19 EP EP85103154A patent/EP0157279B1/en not_active Expired
- 1985-03-28 CA CA000477850A patent/CA1242055A/en not_active Expired
- 1985-03-28 FI FI851253A patent/FI78745C/en not_active IP Right Cessation
- 1985-03-29 JP JP60064067A patent/JPH0639755B2/en not_active Expired - Lifetime
- 1985-04-01 BR BR8501512A patent/BR8501512A/en not_active IP Right Cessation
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6325888B1 (en) | 1995-08-31 | 2001-12-04 | Andritz-Ahlstrom Inc. | Method for pulping sawdust |
| US6379504B1 (en) | 1995-08-31 | 2002-04-30 | Andritz Inc. | Apparatus for pulping sawdust |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3564300D1 (en) | 1988-09-15 |
| FI851253L (en) | 1985-10-03 |
| FI851253A0 (en) | 1985-03-28 |
| EP0157279B1 (en) | 1988-08-10 |
| BR8501512A (en) | 1985-11-26 |
| JPS60231890A (en) | 1985-11-18 |
| JPH0639755B2 (en) | 1994-05-25 |
| EP0157279A1 (en) | 1985-10-09 |
| FI78745B (en) | 1989-05-31 |
| FI78745C (en) | 1989-09-11 |
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