CA1051151A - Apparatus and process for producing kraft type pulp - Google Patents
Apparatus and process for producing kraft type pulpInfo
- Publication number
- CA1051151A CA1051151A CA217,492A CA217492A CA1051151A CA 1051151 A CA1051151 A CA 1051151A CA 217492 A CA217492 A CA 217492A CA 1051151 A CA1051151 A CA 1051151A
- Authority
- CA
- Canada
- Prior art keywords
- hot
- pulp
- kraft
- disc
- black liquor
- 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
- D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21B1/00—Fibrous raw materials or their mechanical treatment
- D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
- D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
Abstract
ABSTRACT OF THE DISCLOSURE
Method for producing pulp for use in the manufacture of kraft type products such as linerboard and bag grade paper comprising the steps of steaming small segments of fibrous material, defiberizing the same in a pressurized atmosphere and at an elevated temperature and, while the resultant fiber products are still hot, mixing them with hot kraft pulp and then refining the mixture so obtained, and improved apparatus for practicing said method in a simple and efficient manner.
Method for producing pulp for use in the manufacture of kraft type products such as linerboard and bag grade paper comprising the steps of steaming small segments of fibrous material, defiberizing the same in a pressurized atmosphere and at an elevated temperature and, while the resultant fiber products are still hot, mixing them with hot kraft pulp and then refining the mixture so obtained, and improved apparatus for practicing said method in a simple and efficient manner.
Description
Serial No. 217~492 Charters ~.~S~S~
BACKGROUND OF THE IN~7ENTION
This invention relates to new and unique means and methods for producing a relatively low cost, hi~h quality pulp for use in making kraft type products such as liner-board and bag grade paper.
The kraft pulp industry has been beset with manylprob-lems. A baslc and continuing problem is the ever increasing cost of production. ~owever, thi~ problem is over~hado~ed by the more serious problem that the supply of wood of the quality normally required for the production of kraft pulp is limited. Efforts to heretofore find a satisfactory solution have met with little success.
SUMMARY OF THE INVENTION
The pre~ent invention not only pxovide~ means and meth-ods ~or extending the available supply o pulp for kraft type products but also enables a substantial reduction in the cost o~ producing such a pulp and improves its quality.
The method of the invention provides a process for pro-ducing a pulp suited for use in the manufacture of kraft type products comprising the steps of steaming small segments of fibrous material, db~i~erizing the steamed segments and elevating the temperature of the resultant defiberized materials, applying hot black liquor and mixing the defiberized materials with a hot kraf~ pulp and thereafter mechanically refining the mixture so obtained while the defiberized materials are still at an elevated temperature.
The apparatus of the invention for producing a pulp suited for use in the manufacture of kraft type products
BACKGROUND OF THE IN~7ENTION
This invention relates to new and unique means and methods for producing a relatively low cost, hi~h quality pulp for use in making kraft type products such as liner-board and bag grade paper.
The kraft pulp industry has been beset with manylprob-lems. A baslc and continuing problem is the ever increasing cost of production. ~owever, thi~ problem is over~hado~ed by the more serious problem that the supply of wood of the quality normally required for the production of kraft pulp is limited. Efforts to heretofore find a satisfactory solution have met with little success.
SUMMARY OF THE INVENTION
The pre~ent invention not only pxovide~ means and meth-ods ~or extending the available supply o pulp for kraft type products but also enables a substantial reduction in the cost o~ producing such a pulp and improves its quality.
The method of the invention provides a process for pro-ducing a pulp suited for use in the manufacture of kraft type products comprising the steps of steaming small segments of fibrous material, db~i~erizing the steamed segments and elevating the temperature of the resultant defiberized materials, applying hot black liquor and mixing the defiberized materials with a hot kraf~ pulp and thereafter mechanically refining the mixture so obtained while the defiberized materials are still at an elevated temperature.
The apparatus of the invention for producing a pulp suited for use in the manufacture of kraft type products
- 2 -~ '"' .
. ,,~ ,' '.
Serial No~ 217,492 Charters ~as~S~
comprises a steaming vessel and a disc type refiner in a ~eries relation, for steaming segments of fibrous material and reducing the same to their fibrous content. The appar-atus also includes means for subjecting the disc refined fibrous material to an application of hot black liquor and means providing for a combining of hot kraft pulp with the disc refined fibrous material and hot black liquor to thereby produce a composite pulp mixture ideally suited for kraft type products.
The method and appaxatus 50 provided enable a pulping process featuring a mixture of defiberized wood chips with a conventional kraft stock. The wood chips may be derived from a variety of waste type materials. In accordance with a preferred procedure, the wood chips, either in a raw or weakly impregnated condition~ are steamed, pressure refined in a disc refiner, and, while still hot, mixed with hot kraft pulp and hot black liquor. As a consequence of this mixture, the lignin which coats the disc refined fibers is reacted with ~he unused chemicals remaining in the black liquor. The composite fiber mixture so obtained can then be conventionally refined and screened and washed either before or after refining.
The equipment and controls of the invention system are so arranged as to minimize the production of steam and the use of chemical liquors. The net result is a ~ _ 3 _ . .
Serial No. 217,492 Charters ~5~
most economical and effective procedure for providing a homogeneous pulp mixture eminently suited for u~e in making high quality kraft type products which have improved strength characteristics.
A primary object of the invention is to provide improvements in apparatus and procedures for produc-ing a quality pulp suited for use in making kraft type products such as linerboard and bag type paper.
~ nother object of the invention is to provide a kraft quality pulp product comprising a mixture of conventional kraft fibers and fibers derived from woods not normally accepted or workable as kraft materials.
A ~urther object of the invention is to provide means and methods of making kraft quality pulp which are economical to employ, more efficient and satis-factory in use and adaptable to a wide variety of applications.
~ nother object of the invention is to provide a workahle procedure for employing low cost groundwood type materials in producing a kraft quality pulp.
An additional object of the invention is to pro- ;
vide means and methods for producing a new pulp ," '' ' - 3a ' Charters Docket ~o. 74068 1(~5~1~5il suitable or use in kraft type products po~essing the advantageou~ features, the inherent meritorious character-istics and the means and mode of use herein described~
With the above and other incidental objects in view as will more fully appear in the specification, the in-vention intended to be protected by Lettexs Patent consists of the features of construction~ the parts and combinations thereof, and the mode of operation as hereinafter described or illustr~ted in the accompanying drawings, or their equivalents.
Referring to the accompanying drawings wherein is sh~wn one but obviously not necessarily the only form of embodiment of the i~vention~
Fig. 1 is a diagrammatic showing of a preferred in-stallation for practicing a process embodying the con-cepts of the present invention;
Fig. 2 shows a modification of the installation and procedure illustrated in Fig. l; and ~ igs. 3-5 diagrammatically illustrate-further modi-ficatio~s of the installation and procedure of Fig~ 1which employ basic concepts of the present invention.
Like parts are indicated by similar characters of reference throughout the several views.
The invention system illustrated in Fig. 1 of the accompanying drawings includes, in part and in series relation, a screw press 10, a steaming vessel 12, a disc type refiner 14, a centrifugal separator 16 and a mixing tank 18.
.
Charters Docket No. 74068 ~ .
~al5~
A blow tank 20 is csnnected to receive hot kraf t stoclc and attendant black li~uoD :Erom a ~atch type digester ~not sh~wn) and to diqcharge such stock to the :~
mixing tank 18 by way of a conduit 22. The latter incorpora~e~ a pump 24, the control of which will deter~
mine the rate of f~ed of the hot kraft stoGk and black li~uo~ to the tank 18.
A p~mp 26 is incorporated in a oonduit 28 which connects at its enkrance end to the mixing tank 18.
The discharge end of the conduit 28 connects to a disc type refiner 30 which is in a series relation with a:~:
screen 32 and a washer 34. There may be one or more series related refiners 30, screens 32 or washers 34.
This will depend on the particular application of the :. :
inve~tion system.
- In the practicP of ~he invention per Fig~ 1, raw wood chips, which may be derived from what is normally considered as scrap or waste materials, are first fed . -into the screw press 10. .In the case illustrated, a conventional screw press may be employed but it i5 pre-ferred that ~he press 10 be one such as known as an "Impressafiner", a product manufactured by The Bauer Bros. Co. of Springfield, Ohio, U.S.A. In the "Impxessafiner" the wood chips are successively com~
pressed and e~panded to remove resins and contained liquids and partially defiberized by this procPdure~
Then, at the discharge end of the press, the pressed chips are subjected to an application of a small amount of liquid conditioning chemical, the nature of 5 - :
:'' Charter~
Docket No. 74068 which depend~ on the desired physic;~ Larac'ceri~tics of the end product sought. T}le conditioning chemical employed may be NaO~l, Na2S, NaOH ~ Na2S, Na2Sx (polysulfide), or the like. The fact that the chip~ read~ ly expand in the pre~ence of liquor after they leave the pressure zor~e of the pres~ contributes to a most effective pre-trea~ment of th ir fiber content.
Free of extracted effluent, 'che pre-treated ohips are then moved thrvuyh ~ pre~sure se;~ling valve 11 ~o the st~am cha~er defined in ~ vessel 12~ The c:hips are retained in the ~team chamber for a period of two to ten minutes during which they are continuously advanc~d to a disc}large ~tation from which they are directed to: the inlet of the di~c re~iner 14 . In the preferred esribodimerlt illu3trated the refiner 14 will provide a pres~urized environment for the partially defi~erized and pre~
conditioned chîps. It i~; noted that a doubïe re~rolving disc refiner is preferred, though a single disc refiner will function satisfaetorily fox 90m& applications vf ~he invention system and process. In passing through the steam chaniber in the vessel 12 the chips will be sub~ected to elevated pres-sure~ from 10 ~o 150 p.s.i.g. and correspondingly to elevated temperatures and at consi~te~cie~ from 15 to 40~. A similar environment will prevail in the refiner 14 as the chip~ are passed ~etween opposed refiner discs (not shown), one of which revolves relative ~he other.
Under influence of the discs and the pressurized con-ditions in the refiner 14, maintained by the provision of a valve 13 in a discharge line 15 extending from the Charters Docket NOD 74068 lOS~ S~
refiner to the tàngen~ial inlet of the centrifugal separator 16, the chips are converted primarily into individual fibers coated with lignin and small fiber bundles loosely held together by a lignin bond. As the chips are reduced, the resultant fibers and f iber bundles and attendant free liquor are blown past the valve 13 to the inlet of the separator 16. ~nter-ing the inlet of the separator 16 together with these fibers is a measured amount of black liquor delivered by way of a conduit 17 and through the medium of a pump 19. The suction side of pump 19 connects with a liquor recovery line 21 which connects in turn with the washer or washers 34 at the ena of the invention system. The liquor will cause the pulp fibers which enter the sep-arator to assume a dilute slurry form.
For best results, the temperature of the liquorintroduced to the separator should be maintained bet ween 140F.and 212F. It is most important for best performance to keep the temperature of the liquor within the se~arator close to 212Fo ~ to insure an optimal reaction on the fibers by the residual chemicals in the hot black liquor and the maintenance of the fib-ers at an elevated temperature durlng and a~ter the conventional cyclone separating procedure in the sep-2 5 arator 16.
By keeping the liquor at the noted temper-ature level heat is retained and the production and ' escape of steam minimized. Such steam as is produced is directed from the overflow end of the separator to a Charters Docket No. 74068 ~ S~S~ ~
heat recovery system (not shown~.
Accordingly, the fibers produced in the refiner 14 are further chemically treated in the separator 16 by ~
hot black liquor which moves therewith from the under- -S flow end of the ~eparator to the mixing tank 18.
As noted previously,the blow tank 20 is connected with a digester containing a batch of conventional kraft pulp. Once the kraft materials in the digester are properly digested, the resultant pulp stock is de-livered to the blow tank. The tem~erature of thisstock and that in the mixing tank 18 is controlled by the delivering of metered amounts of hot black liquor.
This liquor has its source in the li~uor recovery line 21 and is furnished under the influence of pump 19 .. . .. ..
through branches 23 and 25 of the conduit 17. As noted in Fig. 1, a ~ranch 27 of conduit 17 can be used to supply black liquor to the refiner 14, if 50 desired.
. As they reach the tank 18, the pressure refined fiber products originating in the refiner 14 will be continuously mixed with the hot kraft pulp. The latter is delivered from the blow tank 20 at a unifonm rate so as to achieve a desired proportion of conventional kraft pulp to the disc refined pulp. As will be ob-vious the mixing takes place in the presence of hot black liquor, the temperature of which~ as noted pre-viously, is kept close tv 212~. It is significant that the pressure refined pulp will essentially be individual fibers, so that they are continuously ex-posed to the rPsidual chemical in the hot black liquor Charters Docket No. 74068 ~S~S~ .
and the reaction thereon by the chemical will be con-tinuous throughout the entire process.
The proportion of the disc refined pulp mixed with the conventional hot kraft pulp will preferably be con- :
S trolled so that.it will be between 5% and 25% of the total pulp productionO The-amounts cQmbined will depend on the required end product strength, bulk, brightness, print-ability~ stiffness, etc. Practice indicates that the mos~ practical pulp produced per the invention will have a disc refinad fiber content of 10~ to 15%. It appears at this time that if this aisc refinea fiber content is in~
creased to 25%, a new line of kraft type proaucts will be enabled by the present invention.
To pGint out the benefits of the invention as to yield and savings, reference is had to the following illustration of the economics of usin~ a mixture of 10%
pressure refined pulp fibers and 90% kraft type pulp in a 1000 ton per day kraft type linerboard mill.
Assume the following conditions:
Kraft Pulp Yield 55 Pressure Refined - Black Liquor treated Pulp Yield 9o%
Raw Wood required for 1,000 ~ons of 55% Yield Kraft Pulp1,818 Ton Raw Wood required for 900 Tons of 55% Yield Kraft Pulp1,636 Ton : Raw Wood required for 100 Tons :
; of 90% Refined Pulp 111 Ton Raw Wood required for 1,000 Tons of Mixed Pulp 1,747 Ton Wood Savings Per Day using 10% .
Refined Pulp 71 Ton "'''~
_ 9 _ Charters Docket No. 74068 ~S~
The resulting savings o 71 ton of wood per day represents a 3~9% wood savings. At a wood cost of $23 per ton, this repre~ents a yearly (350 days) saving~ of approximately $571, 000 . ~igher percentages of high yield pulp would~ of ourse, increase the saving in wood usaga.
The high black liquor temperatures employed per the invention not only improve the conditioning of the pres-sure refined fibers but they also improve the economics of operating evaporators in a conventionally associated chemical recovery system.
Thus, by reason of the invention, the problem of a limited supply of the raw materials normally required for producing kraft pulp is considerably diminished, if not eliminated. Moreover the cost of producing a pulp capable of use for kraft type products has become sig-nificantly reduced. Add to this the high quality of this newly conceived homogeneous pulp mixture and the net result is a substantial advantage to and advance in the pulping art and installations therefor.
Fig. 2 of the drawings shows an installation which is identical to that shown in and described with refer-ence to Fig. 1 except that the screw press 10 and the pre~impregnation procedure effected therein is elimin-ated. Here the raw chips will be first steamed and the rest of the procedure will be as previously de~cribed.
ThP system will be completely adequate for preparing pulp for use in kraft type products. This is due to the fact the chemical reaction enabled by use and Charters Docket No, 74 0 6 8 ~5~
application of hot black liquor a~ described is highly effective to control the physical characteristics of the desired end product.
Fig. 3 shows a modi~ication of the system of Fig. 1 wherein the screw press 13 and mixing tank lB are both eliminated. In this system the centriugal or cyclone separator 16 is so placed that its underflow ~nd dis-charges the disc refined materials in the form of fibers chemically treat~3d by hot black liquor, as previously de~cribed, directly to the blow tank 20.
In thi5 embodiment of the invention the rate of feed of hot kraft pulp from the.kraft ~igester to the blow tank 20 will be maintained at a uniform level.
As the disc refined chemically treated fibers flow into the hot kraft pulp, an automatic mixture will inherently :
take place. A continuous cooking e~fect results as ..
the residual chemicals in the black liquor in the bl~w tank react on the intermixed fibers. In this case the black liquor should ba kept at a temperature in the range - .
from about 140F. to 250F.
The embodiment o~ Fig. 3 is not preferred since the control ~actors are not as well defined as in the other :
described embodiments of the invention. Howeverr the resultant pulp will be well suited for lesser quality kraft type products and advantages of the bas~c concept of the invention are still retained. :
It is noted that where the kraft pulp is produced in .
a ~ystem which discharges the cooked pulp at atmospheric pressure, the conventional blow tanX 20 would not be Charters Docket NOD 74068 . ~
5~
required for steam separation. In ~uch case the kraft pulp could be discharg~d, in a metered flow, directly to the tank 18.
The system of ~g. 4 of the drawings differ~ from that of Fig. 2 only in that the hot kraft stock is not combined wi~h the disc refined stock in the tank 18 but in the course of a merging . low in the conduit 28. In.this case conduit 22 is eliminated and replaced by a conduit 32 which directs the hot kraft stock from the blow tank 20 to the discharge conduit 28 at a p~int immediately following a pump 27. The latter is incorporated in the conduit 28 to induce a pressured flow of stock from the tank 18 to the following disc refiner 30. Thus, as disc refined stock, diluted by hot black liquor in the tank 18, is drawn from the.mixing tank and moved with the hot liquor, under pressure, to the refiner 30~ the hot kraft stock is discharged into the body thereof by way of the conduit 32 and so mixed in the course of a continuous flow. In the course of the movement of this mixture to and through the di~c refiner 30, $he liquor content, still hot, con-tinues to react on the disc refined fibers. The process ~nd e~uipment employed in the system of Fig. 4 is other-wise as previously described.
The installation of Fig. 5 of the drawings differs from that o~ Fig. 4 in that the cyclone separator 16 and the mixing tank 18 have been eliminated and replaced by a dilution tank 40,..In this embodiment of the invention the delivery lïne 17, which carries hot black liquor, is provided with two branches 42 and 44 which connect the line . , .. , .. . . . ~.
Charters Docket No.74068 3L~5~S~L
with the tank 40. The branches 42 and 44 embody control valves 41 and 43 and are connected to respectively dis- ~.
charge into the upper and lower ends of the tank 4 0 .
With a ~ys~em so modified as shown in Fig. 5, ~e fiber s~ock created in the refiner 14, as previously described, is discharged directly to the tank 40 wherein pressure is carefully coIl.trolled. In thi~ in~tance black liquor of a.proper temperature must be introduced to the case of the refiner 14, in the course of the disc refin-ing procedure, in an amount sufficient to cause conden-sation of most o~ the steam which may occur during the refining operation. This will obviate the need for a separator 16 in following relation to the disc refiner.
In the tank 40 which constitutes a dilution tank, the . ..
disc refined fibers are embodied in a body of hot black liquor to which liquor may be aaded, as required, below the level of the liquid in the tank, by way of the ~ :
branches 42 and 44. With this arrangement there is a .. -controlled consistency of the material in the tank 40 ~ -~
and the heat lost as steam is reduced to a minimum.
Utilizing the pump 27, the dilute slurry form ~f the disc refined fibers which have been reacted with hot liquor in the dilution tank is channeled to the conduit 28 to be flowed therethrough under pressure. A control valve 29 is incorporated in the conduit 28 in a following re-lation to the pump 27. In the embodiment of Fig. 5 t~e blow tank 20 is connected to the conduit 28 by w~y of a conduit 45 in which is incorporated the pump 24 followed by a control valve 46~ The discharge end of the conduit Charters Docket No, 74068 ~S~
45 connects into the conduit 28 immediately following the valve 29. It may thus be seen that in this embodi-ment of the invention there is a metered control of the disc refined stock as well as.a metered control of the S hot kraft stock. The respective disc refined stock and hot kraft stock may thu~ be caused to merge in a continu-ing flow in the conduit 28 following the valve 29 and in proportions which may be precisely arranged. The so merged portions of the respective stocks will be thoroughly intermixed in the.course of flow .and there will be a continuing reaction of the hot black liquor forming part of the flow on the disc refined fibers which is continued as the fibers and the hot kraft stock are intermixed in a further refining procedure in a disc re-finer or refiners 30.
Of course, as in each descri~ed em~odiment of theinvention, this last de~cribed disc refining is followed by screening and washing of a suitable and conventional natuxe~ The resultant stock mixture, as washed, is directed to storage and/or immediately forwarded for further use while the hot black li~uor remaining after washing is recovered and transmitted from the washers by way of a line 21 int~ which is connected the hot liquor delivery line 17.
In ~his last described embodiment of the invention it may be necessary to bleed some steam from the top of the tank 40 in order to control the pressure in this tank and within the case of the disc refiner 14. The mechanics of this are believed quite obvious and need not be specifically described.
-.14 -Charter~
Docket No.74068 1~5~
From the foregoing it ~ill be clear that the in-vention provides a simple but uni~ue proces~ of extending conventional kraft stock which results in a high quality pulp usable for a great variety of kraft type products. '- ' Not only are economie3 inherent in the sy~tem and answers to problems which have.been prevalent in the art as ':
describsd, hut the invention appears to have''developed the possibility of new products Which are ba~ically kraft type products.
Various installations have been suggested to embody ': . .
the invention concept and illustrated in generally descending order of preference. The differences in the ; ~.
installations as here proposed are with a practical ';' recognition of the fact that differences in available equipment or the nature of the end product desired may make it more reasonable or suitable that one installation may be preferred in preference to others, ' From the ab~ve description it will be apparent that there is thus,provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is sus-ceptible of modiication in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.
While in order to comply with the statute the in-vention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to ~he spe~ific features shown, - Charter~
Docket No. 74068 .
~51~
but that the means and con~truction herein disclosed comprise but one of several modes of putting the invention into effect and the inven~ion is therefore claimed in any of its forms or modifications within ~he legitimate and valid scope of the appended claims.
::'
. ,,~ ,' '.
Serial No~ 217,492 Charters ~as~S~
comprises a steaming vessel and a disc type refiner in a ~eries relation, for steaming segments of fibrous material and reducing the same to their fibrous content. The appar-atus also includes means for subjecting the disc refined fibrous material to an application of hot black liquor and means providing for a combining of hot kraft pulp with the disc refined fibrous material and hot black liquor to thereby produce a composite pulp mixture ideally suited for kraft type products.
The method and appaxatus 50 provided enable a pulping process featuring a mixture of defiberized wood chips with a conventional kraft stock. The wood chips may be derived from a variety of waste type materials. In accordance with a preferred procedure, the wood chips, either in a raw or weakly impregnated condition~ are steamed, pressure refined in a disc refiner, and, while still hot, mixed with hot kraft pulp and hot black liquor. As a consequence of this mixture, the lignin which coats the disc refined fibers is reacted with ~he unused chemicals remaining in the black liquor. The composite fiber mixture so obtained can then be conventionally refined and screened and washed either before or after refining.
The equipment and controls of the invention system are so arranged as to minimize the production of steam and the use of chemical liquors. The net result is a ~ _ 3 _ . .
Serial No. 217,492 Charters ~5~
most economical and effective procedure for providing a homogeneous pulp mixture eminently suited for u~e in making high quality kraft type products which have improved strength characteristics.
A primary object of the invention is to provide improvements in apparatus and procedures for produc-ing a quality pulp suited for use in making kraft type products such as linerboard and bag type paper.
~ nother object of the invention is to provide a kraft quality pulp product comprising a mixture of conventional kraft fibers and fibers derived from woods not normally accepted or workable as kraft materials.
A ~urther object of the invention is to provide means and methods of making kraft quality pulp which are economical to employ, more efficient and satis-factory in use and adaptable to a wide variety of applications.
~ nother object of the invention is to provide a workahle procedure for employing low cost groundwood type materials in producing a kraft quality pulp.
An additional object of the invention is to pro- ;
vide means and methods for producing a new pulp ," '' ' - 3a ' Charters Docket ~o. 74068 1(~5~1~5il suitable or use in kraft type products po~essing the advantageou~ features, the inherent meritorious character-istics and the means and mode of use herein described~
With the above and other incidental objects in view as will more fully appear in the specification, the in-vention intended to be protected by Lettexs Patent consists of the features of construction~ the parts and combinations thereof, and the mode of operation as hereinafter described or illustr~ted in the accompanying drawings, or their equivalents.
Referring to the accompanying drawings wherein is sh~wn one but obviously not necessarily the only form of embodiment of the i~vention~
Fig. 1 is a diagrammatic showing of a preferred in-stallation for practicing a process embodying the con-cepts of the present invention;
Fig. 2 shows a modification of the installation and procedure illustrated in Fig. l; and ~ igs. 3-5 diagrammatically illustrate-further modi-ficatio~s of the installation and procedure of Fig~ 1which employ basic concepts of the present invention.
Like parts are indicated by similar characters of reference throughout the several views.
The invention system illustrated in Fig. 1 of the accompanying drawings includes, in part and in series relation, a screw press 10, a steaming vessel 12, a disc type refiner 14, a centrifugal separator 16 and a mixing tank 18.
.
Charters Docket No. 74068 ~ .
~al5~
A blow tank 20 is csnnected to receive hot kraf t stoclc and attendant black li~uoD :Erom a ~atch type digester ~not sh~wn) and to diqcharge such stock to the :~
mixing tank 18 by way of a conduit 22. The latter incorpora~e~ a pump 24, the control of which will deter~
mine the rate of f~ed of the hot kraft stoGk and black li~uo~ to the tank 18.
A p~mp 26 is incorporated in a oonduit 28 which connects at its enkrance end to the mixing tank 18.
The discharge end of the conduit 28 connects to a disc type refiner 30 which is in a series relation with a:~:
screen 32 and a washer 34. There may be one or more series related refiners 30, screens 32 or washers 34.
This will depend on the particular application of the :. :
inve~tion system.
- In the practicP of ~he invention per Fig~ 1, raw wood chips, which may be derived from what is normally considered as scrap or waste materials, are first fed . -into the screw press 10. .In the case illustrated, a conventional screw press may be employed but it i5 pre-ferred that ~he press 10 be one such as known as an "Impressafiner", a product manufactured by The Bauer Bros. Co. of Springfield, Ohio, U.S.A. In the "Impxessafiner" the wood chips are successively com~
pressed and e~panded to remove resins and contained liquids and partially defiberized by this procPdure~
Then, at the discharge end of the press, the pressed chips are subjected to an application of a small amount of liquid conditioning chemical, the nature of 5 - :
:'' Charter~
Docket No. 74068 which depend~ on the desired physic;~ Larac'ceri~tics of the end product sought. T}le conditioning chemical employed may be NaO~l, Na2S, NaOH ~ Na2S, Na2Sx (polysulfide), or the like. The fact that the chip~ read~ ly expand in the pre~ence of liquor after they leave the pressure zor~e of the pres~ contributes to a most effective pre-trea~ment of th ir fiber content.
Free of extracted effluent, 'che pre-treated ohips are then moved thrvuyh ~ pre~sure se;~ling valve 11 ~o the st~am cha~er defined in ~ vessel 12~ The c:hips are retained in the ~team chamber for a period of two to ten minutes during which they are continuously advanc~d to a disc}large ~tation from which they are directed to: the inlet of the di~c re~iner 14 . In the preferred esribodimerlt illu3trated the refiner 14 will provide a pres~urized environment for the partially defi~erized and pre~
conditioned chîps. It i~; noted that a doubïe re~rolving disc refiner is preferred, though a single disc refiner will function satisfaetorily fox 90m& applications vf ~he invention system and process. In passing through the steam chaniber in the vessel 12 the chips will be sub~ected to elevated pres-sure~ from 10 ~o 150 p.s.i.g. and correspondingly to elevated temperatures and at consi~te~cie~ from 15 to 40~. A similar environment will prevail in the refiner 14 as the chip~ are passed ~etween opposed refiner discs (not shown), one of which revolves relative ~he other.
Under influence of the discs and the pressurized con-ditions in the refiner 14, maintained by the provision of a valve 13 in a discharge line 15 extending from the Charters Docket NOD 74068 lOS~ S~
refiner to the tàngen~ial inlet of the centrifugal separator 16, the chips are converted primarily into individual fibers coated with lignin and small fiber bundles loosely held together by a lignin bond. As the chips are reduced, the resultant fibers and f iber bundles and attendant free liquor are blown past the valve 13 to the inlet of the separator 16. ~nter-ing the inlet of the separator 16 together with these fibers is a measured amount of black liquor delivered by way of a conduit 17 and through the medium of a pump 19. The suction side of pump 19 connects with a liquor recovery line 21 which connects in turn with the washer or washers 34 at the ena of the invention system. The liquor will cause the pulp fibers which enter the sep-arator to assume a dilute slurry form.
For best results, the temperature of the liquorintroduced to the separator should be maintained bet ween 140F.and 212F. It is most important for best performance to keep the temperature of the liquor within the se~arator close to 212Fo ~ to insure an optimal reaction on the fibers by the residual chemicals in the hot black liquor and the maintenance of the fib-ers at an elevated temperature durlng and a~ter the conventional cyclone separating procedure in the sep-2 5 arator 16.
By keeping the liquor at the noted temper-ature level heat is retained and the production and ' escape of steam minimized. Such steam as is produced is directed from the overflow end of the separator to a Charters Docket No. 74068 ~ S~S~ ~
heat recovery system (not shown~.
Accordingly, the fibers produced in the refiner 14 are further chemically treated in the separator 16 by ~
hot black liquor which moves therewith from the under- -S flow end of the ~eparator to the mixing tank 18.
As noted previously,the blow tank 20 is connected with a digester containing a batch of conventional kraft pulp. Once the kraft materials in the digester are properly digested, the resultant pulp stock is de-livered to the blow tank. The tem~erature of thisstock and that in the mixing tank 18 is controlled by the delivering of metered amounts of hot black liquor.
This liquor has its source in the li~uor recovery line 21 and is furnished under the influence of pump 19 .. . .. ..
through branches 23 and 25 of the conduit 17. As noted in Fig. 1, a ~ranch 27 of conduit 17 can be used to supply black liquor to the refiner 14, if 50 desired.
. As they reach the tank 18, the pressure refined fiber products originating in the refiner 14 will be continuously mixed with the hot kraft pulp. The latter is delivered from the blow tank 20 at a unifonm rate so as to achieve a desired proportion of conventional kraft pulp to the disc refined pulp. As will be ob-vious the mixing takes place in the presence of hot black liquor, the temperature of which~ as noted pre-viously, is kept close tv 212~. It is significant that the pressure refined pulp will essentially be individual fibers, so that they are continuously ex-posed to the rPsidual chemical in the hot black liquor Charters Docket No. 74068 ~S~S~ .
and the reaction thereon by the chemical will be con-tinuous throughout the entire process.
The proportion of the disc refined pulp mixed with the conventional hot kraft pulp will preferably be con- :
S trolled so that.it will be between 5% and 25% of the total pulp productionO The-amounts cQmbined will depend on the required end product strength, bulk, brightness, print-ability~ stiffness, etc. Practice indicates that the mos~ practical pulp produced per the invention will have a disc refinad fiber content of 10~ to 15%. It appears at this time that if this aisc refinea fiber content is in~
creased to 25%, a new line of kraft type proaucts will be enabled by the present invention.
To pGint out the benefits of the invention as to yield and savings, reference is had to the following illustration of the economics of usin~ a mixture of 10%
pressure refined pulp fibers and 90% kraft type pulp in a 1000 ton per day kraft type linerboard mill.
Assume the following conditions:
Kraft Pulp Yield 55 Pressure Refined - Black Liquor treated Pulp Yield 9o%
Raw Wood required for 1,000 ~ons of 55% Yield Kraft Pulp1,818 Ton Raw Wood required for 900 Tons of 55% Yield Kraft Pulp1,636 Ton : Raw Wood required for 100 Tons :
; of 90% Refined Pulp 111 Ton Raw Wood required for 1,000 Tons of Mixed Pulp 1,747 Ton Wood Savings Per Day using 10% .
Refined Pulp 71 Ton "'''~
_ 9 _ Charters Docket No. 74068 ~S~
The resulting savings o 71 ton of wood per day represents a 3~9% wood savings. At a wood cost of $23 per ton, this repre~ents a yearly (350 days) saving~ of approximately $571, 000 . ~igher percentages of high yield pulp would~ of ourse, increase the saving in wood usaga.
The high black liquor temperatures employed per the invention not only improve the conditioning of the pres-sure refined fibers but they also improve the economics of operating evaporators in a conventionally associated chemical recovery system.
Thus, by reason of the invention, the problem of a limited supply of the raw materials normally required for producing kraft pulp is considerably diminished, if not eliminated. Moreover the cost of producing a pulp capable of use for kraft type products has become sig-nificantly reduced. Add to this the high quality of this newly conceived homogeneous pulp mixture and the net result is a substantial advantage to and advance in the pulping art and installations therefor.
Fig. 2 of the drawings shows an installation which is identical to that shown in and described with refer-ence to Fig. 1 except that the screw press 10 and the pre~impregnation procedure effected therein is elimin-ated. Here the raw chips will be first steamed and the rest of the procedure will be as previously de~cribed.
ThP system will be completely adequate for preparing pulp for use in kraft type products. This is due to the fact the chemical reaction enabled by use and Charters Docket No, 74 0 6 8 ~5~
application of hot black liquor a~ described is highly effective to control the physical characteristics of the desired end product.
Fig. 3 shows a modi~ication of the system of Fig. 1 wherein the screw press 13 and mixing tank lB are both eliminated. In this system the centriugal or cyclone separator 16 is so placed that its underflow ~nd dis-charges the disc refined materials in the form of fibers chemically treat~3d by hot black liquor, as previously de~cribed, directly to the blow tank 20.
In thi5 embodiment of the invention the rate of feed of hot kraft pulp from the.kraft ~igester to the blow tank 20 will be maintained at a uniform level.
As the disc refined chemically treated fibers flow into the hot kraft pulp, an automatic mixture will inherently :
take place. A continuous cooking e~fect results as ..
the residual chemicals in the black liquor in the bl~w tank react on the intermixed fibers. In this case the black liquor should ba kept at a temperature in the range - .
from about 140F. to 250F.
The embodiment o~ Fig. 3 is not preferred since the control ~actors are not as well defined as in the other :
described embodiments of the invention. Howeverr the resultant pulp will be well suited for lesser quality kraft type products and advantages of the bas~c concept of the invention are still retained. :
It is noted that where the kraft pulp is produced in .
a ~ystem which discharges the cooked pulp at atmospheric pressure, the conventional blow tanX 20 would not be Charters Docket NOD 74068 . ~
5~
required for steam separation. In ~uch case the kraft pulp could be discharg~d, in a metered flow, directly to the tank 18.
The system of ~g. 4 of the drawings differ~ from that of Fig. 2 only in that the hot kraft stock is not combined wi~h the disc refined stock in the tank 18 but in the course of a merging . low in the conduit 28. In.this case conduit 22 is eliminated and replaced by a conduit 32 which directs the hot kraft stock from the blow tank 20 to the discharge conduit 28 at a p~int immediately following a pump 27. The latter is incorporated in the conduit 28 to induce a pressured flow of stock from the tank 18 to the following disc refiner 30. Thus, as disc refined stock, diluted by hot black liquor in the tank 18, is drawn from the.mixing tank and moved with the hot liquor, under pressure, to the refiner 30~ the hot kraft stock is discharged into the body thereof by way of the conduit 32 and so mixed in the course of a continuous flow. In the course of the movement of this mixture to and through the di~c refiner 30, $he liquor content, still hot, con-tinues to react on the disc refined fibers. The process ~nd e~uipment employed in the system of Fig. 4 is other-wise as previously described.
The installation of Fig. 5 of the drawings differs from that o~ Fig. 4 in that the cyclone separator 16 and the mixing tank 18 have been eliminated and replaced by a dilution tank 40,..In this embodiment of the invention the delivery lïne 17, which carries hot black liquor, is provided with two branches 42 and 44 which connect the line . , .. , .. . . . ~.
Charters Docket No.74068 3L~5~S~L
with the tank 40. The branches 42 and 44 embody control valves 41 and 43 and are connected to respectively dis- ~.
charge into the upper and lower ends of the tank 4 0 .
With a ~ys~em so modified as shown in Fig. 5, ~e fiber s~ock created in the refiner 14, as previously described, is discharged directly to the tank 40 wherein pressure is carefully coIl.trolled. In thi~ in~tance black liquor of a.proper temperature must be introduced to the case of the refiner 14, in the course of the disc refin-ing procedure, in an amount sufficient to cause conden-sation of most o~ the steam which may occur during the refining operation. This will obviate the need for a separator 16 in following relation to the disc refiner.
In the tank 40 which constitutes a dilution tank, the . ..
disc refined fibers are embodied in a body of hot black liquor to which liquor may be aaded, as required, below the level of the liquid in the tank, by way of the ~ :
branches 42 and 44. With this arrangement there is a .. -controlled consistency of the material in the tank 40 ~ -~
and the heat lost as steam is reduced to a minimum.
Utilizing the pump 27, the dilute slurry form ~f the disc refined fibers which have been reacted with hot liquor in the dilution tank is channeled to the conduit 28 to be flowed therethrough under pressure. A control valve 29 is incorporated in the conduit 28 in a following re-lation to the pump 27. In the embodiment of Fig. 5 t~e blow tank 20 is connected to the conduit 28 by w~y of a conduit 45 in which is incorporated the pump 24 followed by a control valve 46~ The discharge end of the conduit Charters Docket No, 74068 ~S~
45 connects into the conduit 28 immediately following the valve 29. It may thus be seen that in this embodi-ment of the invention there is a metered control of the disc refined stock as well as.a metered control of the S hot kraft stock. The respective disc refined stock and hot kraft stock may thu~ be caused to merge in a continu-ing flow in the conduit 28 following the valve 29 and in proportions which may be precisely arranged. The so merged portions of the respective stocks will be thoroughly intermixed in the.course of flow .and there will be a continuing reaction of the hot black liquor forming part of the flow on the disc refined fibers which is continued as the fibers and the hot kraft stock are intermixed in a further refining procedure in a disc re-finer or refiners 30.
Of course, as in each descri~ed em~odiment of theinvention, this last de~cribed disc refining is followed by screening and washing of a suitable and conventional natuxe~ The resultant stock mixture, as washed, is directed to storage and/or immediately forwarded for further use while the hot black li~uor remaining after washing is recovered and transmitted from the washers by way of a line 21 int~ which is connected the hot liquor delivery line 17.
In ~his last described embodiment of the invention it may be necessary to bleed some steam from the top of the tank 40 in order to control the pressure in this tank and within the case of the disc refiner 14. The mechanics of this are believed quite obvious and need not be specifically described.
-.14 -Charter~
Docket No.74068 1~5~
From the foregoing it ~ill be clear that the in-vention provides a simple but uni~ue proces~ of extending conventional kraft stock which results in a high quality pulp usable for a great variety of kraft type products. '- ' Not only are economie3 inherent in the sy~tem and answers to problems which have.been prevalent in the art as ':
describsd, hut the invention appears to have''developed the possibility of new products Which are ba~ically kraft type products.
Various installations have been suggested to embody ': . .
the invention concept and illustrated in generally descending order of preference. The differences in the ; ~.
installations as here proposed are with a practical ';' recognition of the fact that differences in available equipment or the nature of the end product desired may make it more reasonable or suitable that one installation may be preferred in preference to others, ' From the ab~ve description it will be apparent that there is thus,provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is sus-ceptible of modiication in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.
While in order to comply with the statute the in-vention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to ~he spe~ific features shown, - Charter~
Docket No. 74068 .
~51~
but that the means and con~truction herein disclosed comprise but one of several modes of putting the invention into effect and the inven~ion is therefore claimed in any of its forms or modifications within ~he legitimate and valid scope of the appended claims.
::'
Claims (19)
1. A process of producing a pulp suited for use in the manufacture of kraft type products comprising the steps of steaming small segments of fibrous material, defiber-izing the same and elevating the temperature thereof, applying hot black liquor and mixing the defiberized ma-terials with a hot kraft pulp and mechanically refining the mixture so obtained while the defiberized materials are still at an elevated temperature.
2. A process of producing pulp as in Claim 1 char-acterized by elevating the temperature of said defiberized material by subjecting the same to a hot black liquor having a temperature in the range of 140°F. to 250°F. prior to mixing thereof with said hot kraft stock.
3. A process of producing pulp as in Claim 2 characterized by applying said hot black liquor at a temperature in the neighborhood of 212°F.
4. A process of producing pulp as in Claim 2 wherein the step of defiberizing said segments is carried out by disc refining said steamed segments.
5. A process of producing pulp as in Claim 4 wherein said disc refining step is carried out in a pres-surized environment.
6. A process of producing pulp as in Claim 1 wherein, immediately following the defiberizing of said steamed segments, the said defiberized material is introduced to a vessel with the hot black liquor and in said vessel subjected with said liquor to a centrifugal separation action, in the course of which the fibers of said de-fiberized material are subjected to the chemical content of said liquor and caused to achieve and maintain an elevated temperature and then discharged and in con-tinuing movement thereof combined with the hot kraft stock to produce said mixture which is then further refined.
7. A process of producing pulp as in Claim 6 wherein following the centrifugal separating action said defiber-ized material at an elevated temperature is introduced to a vessel wherein the hot kraft stock is also introduced and mixed therewith in the presence of hot black liquor prior to refining the resultant mixture.
8. A process of producing pulp as in Claim 1 wherein the said segments of fibrous material, following de-fiberizing thereof, are discharged to a blow tank which commonly receives said hot kraft stock and the mixture so produced is subjected to an application of the hot black liquor at a temperature in the range of 140°F. to 250°F.
to maintain the temperature of said defiberized material and react thereon in the course of flow therewith to re-finer means wherein the mixture so obtained is subjected to a further refining procedure and the resultant stock forwarded for screening and washing.
to maintain the temperature of said defiberized material and react thereon in the course of flow therewith to re-finer means wherein the mixture so obtained is subjected to a further refining procedure and the resultant stock forwarded for screening and washing.
9. A process of producing pulp as in Claim 6 wherein following the centrifugal separating action said defiber-ized material at elevated temperature is introduced to a vessel wherein additional hot black liquor is added to maintain it at an elevated temperature and have the chemical content react thereon and then the resultant mixture is flowed to a further refiner means and in the course of its flow the hot kraft stock is introduced thereto to merge and mix therewith in movement to said further refiner means wherein the resulting mixture is subjected to refining as a composite to result in an intermingled pulp product.
10. A process of producing pulp according to Claim 1 wherein prior to being steamed said segments are pressed and subjected upon release from the pressing action to an application of chemicals NaOH, Na2S, NaOH + Na2S or Na2Sx (polysulfide) or the equivalent.
11. A process for producing pulp as in Claim 1 wherein said segments are steamed for a period up to ten minutes at pressures of 10 to 150 p.s.i.g. and at consistencies from 15% to 40% before defiberizing and the defiberizing is effected under conditions of elevated pressure.
12. A process of producing pulp as in Claim 11 characterized by mixing the defiberized segments with hot kraft pulp in hot black liquor at a temperature of 140°F. to 250°F.
13. A process of producing pulp suited for use in the manufacture of kraft type products comprising the steps of steaming small segments of fibrous material, defiberizing the same, elevating and maintaining an elevated temperature thereof, applying hot black liquor and in the course of movement of said defiberized ma-terial blending in hot kraft stock to produce a composite pulp mixture and thereafter refining the composite pulp mixture so resulting.
14. Apparatus for producing a pulp suited for use in the manufacture of kraft type products comprising a steam-ing vessel and a disc type refiner in series relation for steaming segments of fibrous material and reducing the same to its fiber content, means for subjecting said disc refined fibrous material to an application of hot black liquor and means providing for a combining of hot kraft pulp with the disc refined fibrous material and the hot black liquor to produce a composite pulp mixture ideally suited for kraft type products.
15. Apparatus as set forth in Claim 14 wherein a centrifugal separator is arranged in series and in follow-ing relation to said disc refiner and means are connected therewith for an application therein of hot black liquor with the disc refined material to be jointly subjected to a centrifugal separating action therein prior to mixing of the hot kraft material with the disc refined fibrous material.
16. Apparatus as in Claim 15 characterized by said centrifugal separator being connected to discharge the centrifugally separated disc refined fibrous material and attendant hot black liquor to a blow tank for mixture of said disc refined material with said hot kraft stock in said blow tank and further refiner means connected in following relation to further refine the composite mixture of said disc refined fibrous material and said hot kraft stock.
17. Apparatus as in Claim 14 characterized by further vessel means following said disc refiner to receive the disc refined material, said further vessel means having, in connection therewith, means to apply hot black liquor therein to have the chemical content thereof react on said disc refined material and cause said material to maintain an elevated temperature, and a further refiner following said further vessel means and connected thereto by conduit means and said means for combining hot kraft pulp including means in connection with one of said further vessel means and said conduit means to deliver therein a flow of hot kraft pulp for mixture thereof with the hot disc refined material prior to said disc refined material reaching said further refiner.
18. Apparatus as in Claim 17 wherein said further vessel means includes a second vessel connected to receive said material from said disc refiner and connected in turn to discharge said disc refined material to a mixing tank constituting a third vessel into which is connected the delivery means for the hot kraft stock.
19. Apparatus as set forth in Claim 15 wherein a mixing tank is connected in following relation to said centrifugal separator to receive therefrom the disc refined material and said mixing tank has means in connection therewith for delivery thereto of the hot kraft stock and further disc refiner means in following relation to said mixing tank to receive therefrom the composite of the disc refined material and hot kraft stock and to refine the same as a composite mixture.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US456455A US3873412A (en) | 1974-04-01 | 1974-04-01 | Mechanically refining a mixture of kraft and semichemical pulp |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1051151A true CA1051151A (en) | 1979-03-27 |
Family
ID=23812830
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA217,492A Expired CA1051151A (en) | 1974-04-01 | 1975-01-07 | Apparatus and process for producing kraft type pulp |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US3873412A (en) |
| JP (1) | JPS5313001B2 (en) |
| CA (1) | CA1051151A (en) |
| FI (1) | FI750031A (en) |
| SE (1) | SE7500167L (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4060450A (en) * | 1972-09-01 | 1977-11-29 | Westinghouse Electric Corporation | High yield saturating paper |
| SE413684C (en) * | 1974-09-23 | 1987-05-07 | Mo Och Domsjoe Ab | PROCEDURE FOR PREPARING CELLULOSAMASSA IN THE REPLACEMENT AREA 65-95% |
| US4145246A (en) * | 1976-07-19 | 1979-03-20 | Crown Zellerbach Corporation | Process for making high-strength, high-yield sulfite-modified thermomechanical pulp and a linerboard composition produced therefrom |
| US4836892A (en) * | 1986-10-09 | 1989-06-06 | Union Camp Corporation | Pulp blends for linerboards |
| FI81396C (en) * | 1988-10-25 | 1990-10-10 | Enso Gutzeit Oy | FOERFARANDE FOER BEHANDLING AV AVFALLSVATTEN FRAON TRAEFOERAEDLINGSINDUSTRINS MASSAFRAMSTAELLNINGSPROCESSER. |
| FR2785917B1 (en) * | 1998-11-16 | 2001-01-12 | Wood & Pulp Ltd | PROCESS AND PLANT FOR PRODUCING PAPER PULP |
| US6899790B2 (en) * | 2000-03-06 | 2005-05-31 | Georgia-Pacific Corporation | Method of providing papermaking fibers with durable curl |
| US6627041B2 (en) * | 2000-03-06 | 2003-09-30 | Georgia-Pacific Corporation | Method of bleaching and providing papermaking fibers with durable curl |
| US7967948B2 (en) * | 2006-06-02 | 2011-06-28 | International Paper Company | Process for non-chlorine oxidative bleaching of mechanical pulp in the presence of optical brightening agents |
| CA2979048C (en) | 2015-03-11 | 2021-03-16 | Andritz Inc. | Processes and systems for the pulping of lignocellulosic materials |
| WO2019152969A1 (en) * | 2018-02-05 | 2019-08-08 | Pande Harshad | Paper products and pulps with surface enhanced pulp fibers and increased absorbency, and methods of making same |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1372640A (en) * | 1919-11-17 | 1921-03-22 | Flintkote Co | Paper felt |
| US1847326A (en) * | 1928-01-28 | 1932-03-01 | Lewis L Alsted | Paper pulp and process of making same |
| US2660097A (en) * | 1949-04-16 | 1953-11-24 | Price Brothers & Company Ltd | Method of processing wood pulp |
| US3202569A (en) * | 1961-06-22 | 1965-08-24 | Johns Manville | Cold caustic fiberboard manufacture |
| US3827934A (en) * | 1971-06-28 | 1974-08-06 | Westvaco Corp | Process for producing high strength,high yield hardwood pulp |
| US3811995A (en) * | 1972-09-05 | 1974-05-21 | Westvaco Corp | Method of high yield semichemical pulp production |
-
1974
- 1974-04-01 US US456455A patent/US3873412A/en not_active Expired - Lifetime
-
1975
- 1975-01-07 FI FI750031A patent/FI750031A/fi not_active Application Discontinuation
- 1975-01-07 CA CA217,492A patent/CA1051151A/en not_active Expired
- 1975-01-08 SE SE7500167A patent/SE7500167L/xx not_active Application Discontinuation
- 1975-01-22 JP JP966375A patent/JPS5313001B2/ja not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FI750031A (en) | 1975-10-02 |
| JPS50126901A (en) | 1975-10-06 |
| SE7500167L (en) | 1975-10-02 |
| JPS5313001B2 (en) | 1978-05-06 |
| US3873412A (en) | 1975-03-25 |
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