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Патент USA US3076749

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Feb. 5, ‘1963'
F. NETTEL
MANUFACTURE OF PULP mou FIBROUS SUBSTANCES
Filed Aug. 11, 1958
3,076,739
United States Patent O?ice
,
3,076,739
Patented Feb. 5, 1963
1
2
3,076,739
digester and to the hopper were kept closed, however,
when the impregnation in the ?rst chamber starts, the
valve of the second chamber to the hopper is opened and
MANUFACTURE OF PULP FROM FIBROUS
SUBSTANCES
‘ Frederick Nettel, 173 Chapel Road, Manhasset, N.Y.
Filed Aug. 11, 1958, Ser. No. 754,317
7 Claims. (Cl. 162--17)
?lling starts, and when completed, impregnation in the
second chamber proceeds in the same manner as described
for the ?rst chamber. In the meantime impregnation in
the ?rst chamber has been completed to a desired degree,
This invention deals with improvements in the conver
whereupon surplus liquor is drained from it and then its
sion of ?brous substances, in particular wood, straw,
bagasse for examples, into pulp. Known processes work
valved connection to the ?rst digester tube of the con
either on the batch system or the continuous system. In
the batch system the raw material in form of chips or
cuttings is fed into large so-called digester containers
where it is subjected to the action of suitable chemicals
tinuous digester is opened and the contents discharged
into the latter. When this discharge is completed, the
impregnation in the second chamber has also been com
pleted and surplus liquor is drained from it. Then the
valved connection of the ?rst chamber with the digester
(liquor) in the presence of steam at pressures mostly above 15 is closed and the valved connection of the second chamber
atmospheric for long periods, being discharged periodical
with the digester tube is opened and feeding of the latter
ly. Continuous digesters use tubes through which the raw
material is moved by mechanical means, mostly screws.
The disadvantages of the batch digesters are principally
in the slowness of the action, the losses incurred in steam—— 20
from the second chamber begins. Now the pressure in
the ?rst chamber is suitably relieved, its valved connection
and time-when ?lling them, heating them and discharging
same manner over and over again, resulting in a substan
them.
with the hopper opened and ?lling from the hopper is
repeated. The cycle is now closed and is repeated in the
tially continuous feeding of the digester, because the
switching over of feeding from one chamber to the other
which by themselves operate on the batch principles can be
give more uniform pulp, but they require complicated, ex
pensive and often unreliable means for feeding the raw 25 completed in a few seconds. It is another object of my in
vention to provide the valves for the material, liquor and
material into the pressure space of the digesters consisting
steam with controls which operate these elements in the
of one or more tubes through which the processed ma
' The continuous digesters are more flexible in operation,
terial is moved mostly by screws arranged inside the
digester tubes. The devices used for bringing the raw
material into the pressure space are either power-driven
screws, or power-driven multi-cell rotary feeders. Such
devices require much power and have to be designed to
operate at widely different speeds to regulate the digester
output, which makes them unduly expensive in ?rst costs
sequence indicated above, completing the operating cycle
in a predetermined and adjustable time, called for the pur
poses of this speci?cation the “cycle time.”
It is a further object of my invention to vary the cycle
tilme in relationship with the required output of the digester
p ant.
The volume (chip capacity) of the sluice-impregnation
35 chambers is determined by the nature of the raw material
and in maintenance, because of wear.
to be processed, the type of liquor used, and the product
It is known to be advantageous, and even necessary in
quality desired. At present an impregnation period, i.e. a
some cases, to impregnate the raw chips before cooking.
residence time of the chips in each chamber, of not less
This is done in known continuous digesters either by pre
than ten percent of the whole pulping cycle time is pre
soaking the chips or cuttings with liquor prior to pressing
ferred.
the material into the pressure zone, or by using the ?rst
It is immaterial for the purposes of my invention
tube as impregnating tube into which liquor is fed together
whether impregnation takes place at the same or a pressure
with steam. Pre-soaking at atmospheric pressure does
di?erent from that which prevails in the digester tubes.
not give satisfactory results because the liquor generally
Obviously, the pressure in the chambers will be equalized
has to be at elevated temperatures to be chemically really
with that in the digester tubes when the valved con
effective.
45 nections to the latter are opened. It is also immaterial for
Using the ?rst tube as impregnating tube is expensive
in the sense that the chips or cuttings do not have to be
the purposes of my invention what ?brous raw material is
used and what chemical composition the liquor has.
In the drawing af?xed to this speci?cation and forming
ging in the piping is known to cause dif?culties. Re-circu 50 part thereof, an embodiment of this invention is illustrated
diagrammatically by way of non-limiting example as
lating the liquid after re-forti?cating it during the impreg
follows:
nation is known to be advantageous, economical and be
It shows a digester with two closed sluicing and im
cause it shortens the necessary cooking time.
pregnation chambers and two cooking tubes. 1 is the
‘It is the main object of this invention to provide in
substantially continuous digesters simple and cheap means 55 open hopper with outlet conduits 2 and 3‘ and interposed
moved for good impregnation. Besides, the recovery of
surplus liquor from the impregnating tube without clog
for impregnating the raw material, while at the same time
gate valves 4 and 5. v6 and 7 are the two closed sluicing
eliminating the complicated and costly devices for bring
and impregnation chambers with outlet conduits 8 and 9
with interposed gate valves Y10 and 11. Conduits 8i and
9 discharge into conduit 12 which is connected to the
ing the material from a space (hopper) under atmospheric
pressure into the pressure zone or zones of the digesters.
In general it may be said that I attain this principal ob 60 one end of the ?rst cooking tube 13 with internal screw
14- which is driven by a motor 15. At the other end of
ject of my invention, as well the other objects thereof
tube 13 a conduit 16 connects with the second cooking
which will hereinafter appear, by providing a plurality of
tube 17 which is essentially of the same design as the tube
closed chambers, preferably two in number, each with
13, also driven by a motor 18. The conduit 19 is con
valved connections with a source of raw material, for ex
ample an open hopper, and with the pressure zone of the 65 nected with the discharger 26 for the cooked pulp which
leaves the plant through pipe 21. At the lower end of
digester. The raw material is fed into said chambers in
‘the hopper 1 two valved steam pipes 21 and 22 are pro
sequence, beginning with the ?rst chamber with its valve
vided to facilitate the discharge of the raw chips from
to the digester closed. After ?lling is completed, the
the hopper. The valved pipes 23 and 24 serve to admit
valve to the hopper is also closed and steam is admitted
and liquor circulated through said chamber so that im 70 steam under pressure into the chambers 6 and 7, and the
valved pipe 25 permits to connect the chambers 6 and
pregnation of the raw material is achieved. While this
7 with the atmosphere. Also connected with both cham
takes place, the valves of the second chamber to the
3,076,739
3
bars are liquor impregnating and circulating means con
sisting of liquor tanks 26 and 27 from which liquor can
be pumped by pumps 28 and 29 driven by motors 28’
and 29' through the pipes 30 and 31 with valves 30’ and
31' into the upper parts of the chambers 6 and 7. The
liquor returns to said tanks via the pipes 32 and 33.
Fresh (white) liquor is fed into said tanks through the
valved pipes 34 and 35. All the valves shown, with the
4
power demand for operating known devices such as screw
feeders or multi-cell feeders.
Manifestly, variations may be resorted to, equivalents
of parts introduced, and parts may be used without others
Within the broad scope of my invention and its features.
Having now described my invention, I claim:
1. Method of producing pulp from ?brous materials in
a continuous digester by subjecting them to the chemi
exception of those in pipes 21, 22, 34 and 35, are power
cal action of a liquor and steam, comprising the steps of
operated ‘from a common control cylinder 36, driven by 10 charging the comminuted raw material into the inlet of
a motor 37. This cylinder receives an operating medi
a ?rst chamber, thereafter closing the inlet and outlet of
um, for example oil under pressure, at 38. The control
said ?rst chamber so as to isolate it, admitting steam
connections to each of said valves are indicated diagram
and liquor under pressure into said isolated chamber,
matically only by broken lines. Steam may also be ad
circulating the liquor through said ?rst chamber in a
mitted to the ?rst cooking tube through the valved pipe
substantially closed ?rst circuit so as to impregnate the
3?. The drawing shows the plant {at a moment when the
raw material therein, then draining surplus liquor from
chamber 7 is discharging into the digester While the cham
said ?rst isolated chamber while maintaining the inlet
her 6 is being ?lled. Obviously the valves in pipes 21,
closed, then opening the outlet of said ?rst isolated cham
22., 34 and 35 may also be power operated from the cyl
ber, then discharge the contents of said ?rst chamber
inder 36, if desired. Starting, and operating of the plant,
into the pressure zone of the digester, repeating said steps
assuming both chambers 6 and 7 empty and the gate
with a second chamber and the same digester, the ?lling
valves 4, 5, 10 and 11 closed, proceeds after starting the
of the second chamber with said raw material being timed
motor 37 of the control as follows; gate valve 4 is
to occur during the impregnation of said raw material in
opened and chamber 6 ?lled, assisted by steam jet from
the ?rst isolated chamber, and thereafter repeating the
pipe 21. Gate valve 4 closed, steam admitted through 25 cycle alternatingly with the ?rst and second chambers
pipe 23, pump 23 started by motor 28' [and valve 30'
and with the same relative timing, with the liquor circu
opened, so that impregnation of the chips in the
lating through said second chamber means in a second
chamber 6 can proceed, and by keeping the pump in op
substantially closed circuit.
eration recirculation of the liquor impregnation is
2. Method of producing pulp from ?brous raw ma
speeded and improved. In the meantime, after starting 30 terials in a high pressure continuous digester by subject
impregnation in chamber 6, gate valve 5 is opened and
ing them to the chemical action of a liquor and steam,
?lling of chamber 7 starts in the same way, and when
comprising the steps of closing the outlet of a ?rst cham—
completed, gate valve 5 is closed, steam admitted through
ber, charging the comminuted raw material into the inlet
pipe 24, pump 29 started by motor 29' and valve 31’
of said ?rst chamber, thereafter closing the inlet of said
opened, so that impregnation in the chamber 7 proceeds
?rst chamber so as to isolate it, admitting steam and
in the same manner as described above for chamber 6.
liquor under low pressure into said isolated ?rst cham
In the meantime impregnation in the chamber 6 has been
ber, circulating the liquor through said ?rst chamber in
completed, whereupon the pump 28 is stopped, valve 30’
a ?rst substantially closed circuit so as to impregnate the
closed, so that surplus liquor is drained from chamber 6
raw material therein, then draining surplus liquor from
40
via pipe 32 into the liquor tank. Thereafter gate valve
said ?rst isolated chamber while maintaining the inlet
10 is opened and the impregnated chips are discharged
closed, opening the outlet of said ?rst isolated chamber
into the cooking tube 13, assisted by steam jet from pipe
23. After the chamber 6 is empty, the impregnation
to the higher pressure zone of the digester so as to admit
gate valve 10 is closed and the steam pressure in the
chamber with said raw material being timed to occur dur
this higher pressure to the ?rst chamber, then discharge
which has been proceeding in the chamber 7', is also
the contents of said ?rst chamber into the digester under
completed so that surplus liquor is drained from it via 45 the higher pressure, repeating said steps with the second
pipe 33 by stopping pump 29 and closing valve 31’. Now
chamber ‘and the same digester, the ?lling of the second
chamber 6 is relieved either to the atmosphere via pipe
25 with 3-way valve or by opening gate valve 4 slowly,
thereby loosening and moistening the chips at the en
trance of chamber 3, making it ready for the next ?lling.
After gate valve 10 has been closed, the gate valve 11
is opened and discharge of the chamber 7 into the digester
ing the impregnation of said raw material in the ?rst iso
lated chamber, and thereafter repeating the cycle alter
natingly with the ?rst and second chambers and with the
same relative timing with the liquor circulating through
said isolated second chamber in a second ‘substantially
closed circuit.
begins immediately, practically without interruption of
3. In a continuous digester for comminuted ?brous
the feeding of the digester. The feeding and impregna 55 material, the combination of a digester in which the
tion cycle is now completed and is repeated by the ?lling
?brous material is subjected to the action of steam and
of the chamber 6.
liquor under pressure for chemical treatment of said
For regulating the output in continuous digesters it is
material, open container means for the raw material,
known to regulate the speed of the motors 15 and 18 and
two chambers each having an inlet and outlet, conduit
thereby the speed at which the pulp is moved through the
means including ?rst valve means for connecting selec
cooking tubes by the screws 14. Obviously, it is neces
tively each of the said inlets of said two chambers with
said open container means, conduit means including sec
sary to correlate the feeding from the chambers 6 and 7
ond valve means for selectively connecting each of the
with the required output and this is achieved by my in
vention by regulating the speed of the motor 37 driving 65 outlets of said two chambers with the digester, a source
of liquor, conduit means including third valve means
the control cylinder 36.
The use of sluices to introduce materials into a pres
sure zone is known per se. This invention teaches ‘as new
forming a ?rst substantially closed circulatory path for
said liquor through the said ?rst chamber and a second
substantially closed circulatory path for said liquor
the combination of special sluice chambers With continu
through
said second chamber, pumping means for circu
ous digesters, and effecting an important part of the pulp 70
lating the liquor separately through each of said circula
ing process, i.e. the impregnation of the raw material,
tory paths, conduit means including fourth valve means
under the simultaneous application of liquor and steam
for introducing steam under pressure into, and for with
under pressure Within two or more alternatingly operat
drawing steam from said chambers, control means for
ing sluice chambers, with predetermined time intervals
operating the valve means and pumping means in said
provided for the impregnation, eliminating also the heavy 75 conduit means in predetermined sequence and in repeti
3,076,739
6
tive cyclic order, said control means including means for
closing the second valve means, means for opening the
while the impregnation of the raw material is proceed
ing in said second chamber.
?rst valve means between said open container means and
said ?rst chamber vfor ?lling it with raw material, means
4. In a continuous digester as set forth in claim 3,
valved conduit means for introducing into said closed
chambers steam of di?erent pressure than prevails in the
digester tubes and to maintain said different pressure at
for then closing the ?rst valve means serving said ?rst
chamber, means for then opening the third and fourth
valve means to the ?rst chamber for liquor and steam,
means for then energizing the pumping means serving
least during part of the time While impregnation takes
place in said chambers.
5. In a continuous digester as set forth in claim 3,
the ?rst chamber for circulating liquor through said
chamber so as to effect impregnation of the raw material 10 valved steam conduits connectable to both said chambers,
during a predetermined period, means for then opening
to relieve rcssure in the said chambers to a space of
said ?rst valve means between said open container means
lower pressure.
6. In a continuous digester as set forth in claim 3, a
and the second chamber for ?lling said second chamber
liquor tank interposed in the circuit of liquor circulation
with raw material while impregnation is proceeding in
said ?rst chamber, means for then closing said ?rst valve 15' and valved conduit means for introducing fresh liquor
means to said second chamber ‘after filling of said second
into the said circuit.
7. In a continuous digester as set forth in claim 3,
chamber with raw material, means for then opening the
means for regulating the digester output by valve con
third and fourth valve means serving the second chamber
trol means disposed to complete the cycling operation of
for introducing liquor and steam into said second cham
the valves in time intervals decreasing with increasing
ber, means for then energizing the liquor pumping means
serving the second chamber so as to effect impregnation
output of the digester.
of the raw material therein during a predetermined
References Cited in the ?le of this patent
period, means for then closing said third and fourth
valve means serving said second chamber, means for then
UNITED STATES PATENTS
deenergizing said pumping means for the second cham 25
‘1,882,391
Morterud ____________ __ Oct. 11, 1932
ber, means for then opening the second valve means from
the ?rst chamber so- as to discharge the contents of said
?rst chamber into the digester, means for then closing
said second valve means from the ?rst chamber, means
for then opening the second valve means serving the sec
ond chamber so as to discharge the contents of the sec
ond chamber into the digester, mean-s for then closing
said second valve means for the second chamber, means
for opening the ?rst valve means to the ?rst chamber
1,904,894
1,975,255
Westad _____________ __ Apr. 18, 1933
Decker _______________ __ Oct. 2, 1934
2,799,579
Messing _____________ _.. July 16, 1957
2,803,540
2,886,483
Durant _____________ __ Aug. 20, 1957
Rosenblad ___________ __ May 12, 1959
2,905,240
Sandberg ___________ _.. Sept. 22, 1959
589,751
Germany ____________ _._ Dec. 13, 1933
FOREIGN PATENTS
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