Note: Descriptions are shown in the official language in which they were submitted.
Serial No. 217~492
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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
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Serial No~ 217,492
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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
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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
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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.
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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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,
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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.
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