U.S. patent application number 11/608430 was filed with the patent office on 2007-05-17 for method for producing a paper web, and paper machine.
Invention is credited to Klaus Doelle, Bernd Gueldenberg, Holger Humberg, Volker Niggl.
Application Number | 20070107861 11/608430 |
Document ID | / |
Family ID | 34971102 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070107861 |
Kind Code |
A1 |
Doelle; Klaus ; et
al. |
May 17, 2007 |
METHOD FOR PRODUCING A PAPER WEB, AND PAPER MACHINE
Abstract
The present invention relates to a method and a paper machine
for producing a calendered paper web. The method includes the step
of partially loading with ash a plurality of fibers of a fibrous
stock suspension. The paper machine for the production of a
calendered paper web from a fibrous stock suspension including a
plurality of fibers which are partially loaded with ash includes a
first device for loading a fibrous stock suspension with ash. The
first device can include a first static mixer, a preparation unit
for adding calcium oxide or calcium hydroxide, a press or a
dewatering screw, an equalizing reactor or an equalizing screw, a
container serving as a crystallizer, a second static mixer, and a
carbon dioxide storage tank or a second device for recovering
carbon dioxide.
Inventors: |
Doelle; Klaus; (Kisslegg,
DE) ; Niggl; Volker; (Weingarten, DE) ;
Gueldenberg; Bernd; (Heidenheim, DE) ; Humberg;
Holger; (Nattheim, DE) |
Correspondence
Address: |
Todd T. Taylor;Taylor & Aust, P.C.
142 S. Main Street
P.O. Box 560
Avilla
IN
46710
US
|
Family ID: |
34971102 |
Appl. No.: |
11/608430 |
Filed: |
December 8, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP05/05976 |
Jun 3, 2005 |
|
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|
11608430 |
Dec 8, 2006 |
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Current U.S.
Class: |
162/9 ;
162/181.2; 162/205; 162/265 |
Current CPC
Class: |
D21G 1/00 20130101; D21F
11/00 20130101 |
Class at
Publication: |
162/009 ;
162/205; 162/181.2; 162/265 |
International
Class: |
D21C 9/00 20060101
D21C009/00; D21H 23/16 20060101 D21H023/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 9, 2004 |
DE |
DE 102004028046.0 |
Claims
1. A method for producing a calendered paper web in a paper
machine, said method comprising the step of partially loading with
ash a plurality of fibers of a fibrous stock suspension.
2. The method in accordance with claim 1, further comprising
running the paper web through a calender which is equipped with a
plurality of nips.
3. The method in accordance with claim 2, further comprising
applying a plurality of line loads greater than 50 kN/m to the
paper web in said plurality of nips.
4. The method in accordance with claim 2, further comprising
applying a plurality of line loads greater than 100 kN/m to the
paper web.
5. The method in accordance with claim 2, further comprising
applying a plurality of line loads greater than 350 kN/m to the
paper web.
6. The method in accordance with claim 2, further comprising drying
the paper web to a moisture content of less than 5% and
subsequently remoistening the paper web to a moisture content of
more than 7% prior to said calender.
7. A paper machine for the production of a calendered paper web
from a fibrous stock suspension including a plurality of fibers
which are partially loaded with ash, said paper machine comprising
a first device for loading a fibrous stock suspension with ash.
8. The paper machine in accordance with claim 7, wherein said first
device comprises a first static mixer, a preparation unit for
adding one of calcium oxide and calcium hydroxide, one of a press
and a dewatering screw, one of an equalizing reactor and an
equalizing screw, a container serving as a crystallizer, a second
static mixer, and one of a carbon dioxide storage tank and a second
device for recovering carbon dioxide.
9. The paper machine in accordance with claim 8, further comprising
at least one of a High Consistency Cleaner, a carbon dioxide
heater, and a storage tank one of for a press water and for a water
recovered in said dewatering screw.
10. The paper machine in accordance with claim 8, further
comprising a line and one of a header tank and an upstream third
device, said line configured for returning any filtrate recovered
in said dewatering screw one of to said header tank and to said
upstream third device for preparing the fibrous stock
suspension.
11. The paper machine in accordance with claim 8, further
comprising a washer apparatus for cleaning the fibrous stock
suspension, said washer apparatus located after said container
serving as said crystallizer.
12. The paper machine in accordance with claim 7, further
comprising a twin wire former.
13. The paper machine in accordance with claim 7, further
comprising one press section with at least one shoe press.
14. The paper machine in accordance with claim 7, further
comprising a calender with a plurality of nips.
15. The paper machine in accordance with claim 14, further
comprising an arrangement for remoistening of the paper web, said
arrangement located before said calender.
16. The paper machine in accordance with claim 15, wherein said
arrangement comprises a steam blow box.
17. The paper machine in accordance with claim 7, further
comprising a coating unit.
Description
SUMMARY OF THE INVENTION
[0001] The present invention provides that the paper web is
produced by using a fibrous stock suspension which contains fibers
that are partially loaded with ash.
[0002] When supplying ash with the assistance of the
Fiber-Loading-Process, for example according to DE 102 04 254A1 the
ash is precipitated directly in the fibers and adhered to them. As
detectable through microscope recordings, ash is also deposited in
the cavities of the fiber. Blackening is avoided since even with
collapsed fibers a fiber-ash interface and an ash-fiber interface
exist.
[0003] This means that according to the current invention the
blackening index, however, at the same final roughness is reduced
by at least 10%. Vice versa, the final roughness in the paper is
reduced by at least 12% at the same blackening index.
[0004] One particularly advantageous embodiment provides that the
paper web is run through a calender in the paper machine which is
equipped with a multitude of nips wherein line loads greater than
50 kN/m are applied to the paper web in the nips.
[0005] It is especially advantageous if line loads greater than 100
or greater than 350 kN/m are applied to the web.
[0006] It is also advantageous if the paper web is dried to a
moisture content of less than 5%, and is subsequently remoistened
prior to the calender to a moisture content of more than 7%.
[0007] The invention also relates to a paper machine for the
production of supercalendered paper according to one of the
aforementioned embodiments.
[0008] The paper machine is characterized in that it includes a
device for loading a fibrous stock suspension with ash. The
advantages of said device apply to online as well as to an offline
production of the paper web, in other words, even if the device for
loading the fibrous stock suspension and the machine for the
production of the paper web are not arranged in tandem and the
paper manufacturing process occurs immediately following the
loading of the fibrous stock suspension with ash. Due to the fiber
loading the paper can endure higher line loads in the calender and
a greater smoothness of the paper web can be achieved.
[0009] It is advantageous if the device includes a static mixer, a
processing unit for the addition of calcium oxide or calcium
hydroxide, a press or dewatering screw, an equalizing reactor or an
equalizing screw, a container serving as crystallizer, an
additional static mixer, a carbon dioxide storage tank or an
additional device for the recovery of carbon dioxide.
[0010] One advantageous embodiment provides for a high consistency
cleaner and/or a carbon dioxide heater and/or a storage tank for
press water or for water which was removed in the dewatering
screw.
[0011] It is also advantageous if filtrate from the fiber stock
suspension which is recovered in the dewatering screw is returned
through a line to a header tank or to another upstream device for
processing of the fibrous stock suspension.
[0012] Another advantageous provision would be an additional washer
unit for cleansing of the fibrous stock suspension following the
container that is serving as crystallizer.
[0013] In addition it is also advantageous if the paper machine
also includes a twin wire former. The press section which is
located downstream from said twin wire former would include at
least one shoe press. The paper machine includes one calender with
a multitude of nips in order to reduce roughness and increase
smoothness. An arrangement for remoistening of the paper web is
located before the calender. The remoistening is advantageously
accomplished by way of a steam blow box which also increases the
gloss of the paper.
[0014] In the production of LWC and MWC papers (LWC=light weight
coated; MWC=medium weight coated), a coating unit is of additional
advantage.
[0015] A completely new product possessing new and improved
characteristics compared to products which are already on the
market will result if a fibrous stock suspension is treated with
the fiber loading technology during the paper manufacturing
process. The process described below permits precipitation of a
filler (calcium carbonate) which is evenly distributed and
deposited only on and in the fibrous stock--especially the paper
fiber--to occur directly in the stock preparation in the paper
mill.
[0016] Due to the fact that only fibrous stock loaded with
precipitated calcium carbonate is produced, wherein the calcium
carbonate is attached on or in the fibers, or is embedded in them
the formation of loose precipitated calcium carbonate (PCC) is
prevented. An additional wash cycle before a refining process
and/or after the refining process and/or before the crystallization
process in a crystallizer and/or before a headbox chest or prior to
delivery into the paper machine or recycling the press filtrate to
a header tank or to another storage arrangement located on the
infeed side provides that a constant calcium hydroxide content is
adjusted or regulated in the infeed system of the fiber loading
device. The calcium hydroxide can be added directly in a fiber
stock pulper. The press filtrate can be recycled into the pulper
system. Calcium hydroxide which does not attach on or into the
fibers is recycled back to the upstream process.
[0017] Only that filler which is not attached on or in the fibers,
in other words loose precipitated calcium carbonate, is washed out.
The fibers themselves which are provided with filler on the inside
and the outside do not lose said filler through the wash process
and the recycling of the press filtrate, so that the positive
effects of the fiber loading technology are maintained.
[0018] The present invention especially also provides that the
fibrous stock suspension is fed into a press arrangement intended
to squeeze out a filtrate. Subsequently, the filtrate is recycled
back, at least partially into an arrangement for pulping of the
fibrous stock suspension, specifically into a reservoir which is
located on the infeed side, for example a header tank. The calcium
hydroxide is added at least partially in the arrangement for
pulping of the fiber stock. In the complete pulper system,
specifically in the arrangement for pulping of the fibrous stock, a
pH value of between 7 and 12, especially between 9 and 12 is
maintained.
[0019] Calcium hydroxide in aqueous or in dry form, or calcium
oxide are mixed into the aqueous paper fiber stock in a range of
between 0.01 and 60% of the existing solids content. A static
mixer, a header tank or a pulper system are utilized for the mixing
process; a pH value in the range of between 7 and 12, preferably
between 9 and 12 is applied. The reactivity of the calcium
hydroxide is between 0.01 seconds and 10 minutes, preferably
between 1 second and 3 minutes. Dilution water is added according
to predetermined parameters.
[0020] Carbon dioxide is added into the moist paper stock
suspension according to the reaction parameters. In doing so
calcium carbonate precipitates in the carbon dioxide
atmosphere.
[0021] At the same time a refining energy in the range between 0.1
and 300 kWh/ton dry paper pulp is applied. Compared to conventional
processes for the production of a fibrous stock suspension, the
current invention provides energy efficient attainment of a higher
level of freeness; according to the current invention as much as
50% of refining energy can be saved.
[0022] The high mechanical strengths in the end product which are
achieved through the high freeness value positively affect the
production of all paper grades since, due to process based
mechanical loads in the various sections of the paper machine, such
as in the press section, the dryer section or in the section where
the web is wound, the produced intermediate product and the end
product which is to be produced bear a high mechanical load due to
utilization of winders, rewinders and converting machinery. The
energy supply during the refining process, specifically the heat
volume and the resulting warming effect are controlled. Crystals in
various forms can be produced, according to the control.
[0023] The pre-treatment of the fibrous stock suspension also
creates the basis for improved drying, thereby increasing the
efficiency level in the production of all paper grades. Residual
moisture contents in the range of 1 to 20% are advantageous.
[0024] With the current invention greater brightness and/or higher
optical values with an improved brightness of up to 15 or more
lightness points are also achieved on all grades of paper.
[0025] It may also be provided that an expenditure of energy of
between 0.3 and 8 kWh/t, especially between 0.5 and 4 kWh/t is used
for the precipitation reaction, especially if no refining process
is utilized.
[0026] The process temperature is preferably between -15.degree. C.
and 120.degree. C., especially between 20 and 90.degree. C.
Rhombohedral, scalenohedron and spherical crystals are formed,
wherein the crystals measure between 0.05 and 5 .mu.m, especially
between 0.3 and 2.5 .mu.m.
[0027] Static and/or moving, especially rotating, mixing elements
are utilized for the production of a fibrous stock suspension which
is loaded with calcium carbonate.
[0028] The process may be conducted in a pressure range of between
0 and 15 bar, especially between 0 and 6 bar. Also, the process is
carried out at a pH value that is preferably between 6 and 10,
especially between 6.5 and 8.5. The reaction time is between 0.01
seconds and 1 minute, especially between 0.05 seconds and 10
seconds.
[0029] An additional advantage when utilizing the present invention
with the above referenced paper grades is that these can also be
processed further in a calender. Blackening is avoided due to the
fact that when using the fiber loading technology, fiber loading
particles are deposited in, around and on the fibers.
[0030] Compared to a fibrous stock which is produced according to
conventional methods a fibrous stock produced in accordance with
the fiber loading combination process technology possesses a
superior dewatering capacity which is in the range of between 5 to
100 ml CSF or 0.2 to 15.degree. SR, depending upon the required
level of freeness and filler content. This fibrous stock possesses
a lower water retention capacity of approximately 2 to 25%,
depending upon the raw material that is used in the paper
manufacturing process. Compared to conventional fibrous stock the
water can be removed more quickly from the fibrous stock
suspension, and the fibrous stock dries accordingly faster. This
also has a positive effect on remoistening which, as a result, is
diminished in the paper manufacturing process, and upon the
printability of the produced paper grades.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention will be better understood by reference
to the following description of embodiments of the invention taken
in conjunction with the accompanying drawings, wherein:
[0032] FIG. 1 is a schematic drawing illustrating the preparation
of a fibrous stock suspension for application in a machine for the
production of a fiber web;
[0033] FIG. 2 shows blackening as a function of the roughness in a
paper web; and
[0034] FIG. 3 shows a paper machine for the production of
calendered paper according to the present invention.
[0035] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate an embodiment of the invention, and such
exemplifications are not to be construed as limiting the scope of
the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
[0036] Referring now to the drawings, and more particularly to FIG.
1, there is shown a pipe line system 1 that is equipped with
control valves 2, 3 which is provided for a fibrous stock
suspension. The control valve 2 is located in a line 4 through
which the pipe line system 1 is connected with a static mixer 5.
Dilution water is added to the mixer 5 via a valve 6. A tank 7 or a
container for storage of the fibrous stock suspension is located
following the mixer 5, viewed in a direction of the fiber stock
flow direction. From the tank 7 the fibrous stock suspension is
pumped via a pump 8 to an additional static mixer 9. Dilution water
is also added to the mixer 9 via a valve 10. Likewise, the inflow
of a calcium hydroxide suspension is controlled through a valve 11
which is located in a line 12.
[0037] This is supplied by a processing unit 13 where solid calcium
oxide or calcium hydroxide is added to water. For this purpose the
processing unit 13 is supplied with water via a line 14 which is
equipped with a valve 15. The suspension that is produced in the
processing unit 13 is supplied through a pump 16 into the line
12.
[0038] The fibrous stock suspension to which calcium hydroxide was
added flows from the mixer 9 into a line 17 which is equipped with
a valve 18 to a dewatering screw 19 where water is removed from the
fibrous stock suspension. Said water can, for example, be returned
through a line 20 to the mixer 5 as dilution water. Alternatively,
or in addition the water that was removed in the dewatering screw
19 may also be routed to a storage tank 21 for the fibrous stock
suspension, or it is returned to the mixer 9. Due to the return
flow of calcium hydroxide containing water the pH value can be
increased and adjusted in all instances in the units that are
located preceding the dewatering screw 19.
[0039] In order to equalize the fibrous stock suspension, said
suspension is delivered via a line 22 from the dewatering screw 19
to an equalizing screw 23. A downstream container 25 (crystallizer)
is connected through a line 24 with said equalizing screw. For the
purpose of supplying carbon dioxide this container is connected
with a carbon dioxide storage container 30 via a line 29 which is
equipped with valves 26, 27 and a pump 28. Carbon dioxide is
supplied from this container into the crystallizer 25 in order to
produce the desired precipitation reaction of calcium hydroxide and
carbon dioxide for the formation of calcium carbonate as a filler
in the fibers of the fiber stock.
[0040] In addition the carbon dioxide storage container 30 is
connected with the equalizing screw 23 via an additional line 31
which is equipped with a valve 32 and which branches off line 29.
Carbon dioxide can herewith also be supplied to the equalizing
screw in order to achieve at least a partial precipitation already
at this point.
[0041] Line 29 is also connected via an additional valve 33 with a
static mixer 34. This serves to add additional carbon dioxide to
the fibrous stock suspension which is flowing from the crystallizer
25 via a line 36 which is equipped with a valve 35.
[0042] The fibrous stock suspension flows from the mixer 34 into a
mixing chest 37. A storage tank 38 which additionally serves as a
filtration unit may be provided between the mixer 34 and the mixing
chest 37. From the storage tank 38 the filtrate which has been
enriched with calcium carbonate is recycled back into the header
tank 7 or into another upstream unit for the processing of the
dilution water or the fibrous stock suspension.
[0043] The mixing chest 37 is equipped with a rotor 39 to
thoroughly mix the fibrous stock suspension. The fibrous stock
suspension then flows from the mixing chest 37 either immediately
to a head box in a paper machine, or will be subjected to
additional mechanical processing, for example in a refiner feed
chest.
[0044] Fibrous stock suspension to which calcium hydroxide has not
yet been added can also be supplied to the mixing chest 37 through
a pipe line system 1 via the valve 3 and a line 40 in which said
valve is installed.
[0045] It is further provided that white water or process water
which has been recovered from the machine for the production of the
fibrous stock suspension, especially from the paper machine, for
example in the wire area of the paper machine or, as already
described previously, for the fibrous stock suspension from the
dewatering screw 19, is supplied to the tank 21. Dilution water may
for example be supplied to this tank through a line 41 which is
equipped with a valve 42.
[0046] From the container 21 dilution water which is mixed with
process water flows through a line 43, a pump 44 and a valve 45 to
the crystallizer 25. According to the design of an arrangement for
loading of the fibrous stock suspension with a filler, especially
with calcium carbonate as depicted in FIG. 1, a multitude of
possibilities arises to influence the composition of the fibrous
stock suspension that is being produced in various stages of the
manufacturing process.
[0047] The installation of a high consistency refiner 46 inside
line 4 is advantageous. A heater 47 for the carbon dioxide which is
supplied by the storage tank 30 is optional. The heater 47 operates
with superheated steam which is supplied via an inlet 49 and
discharged via an outlet 48.
[0048] In the production of an SC paper web (SC=super calendered)
(FIG. 2) and depending upon the quality of the paper--SC-A-paper or
SC-B paper--certain upper limits for the roughness R for the
blackening S (blackening index), which is measured in micrometers
according to the PPS measuring method, must be cited as a function
of the roughness. Only papers that have roughness and blackening
values below the limits are usable.
[0049] Calendered papers are especially suitable for the
rotogravure printing process. These papers are calendered in
calender nips in order to achieve the desired smoothness of the
paper surface, since otherwise flaws would occur in the print.
However, if a calender with an insufficient number of nips is
utilized and if excessive nip pressures are applied upon the paper
web, a portion of the fibers would be squeezed in such a way that
they would take on a transparent appearance. In order to achieve a
high paper quality this malfunction must not exceed the limits
illustrated in FIG. 2 which are determined for various paper grades
through the limit curves G which are also depicted in FIG. 2. Also
a too high a waste paper (DIP=deinked paper) component reduces the
paper quality to lower values. Great roughness causes many printing
flaws ("missing dots"). However, the production line becomes
unprofitable if a multitude of nips are utilized during the
printing process while at the same time working at a low pressure
or low line pressure. In accordance with the current invention the
paper quality is therefore improved by loading the cavities of the
fibers with ash. This makes substantially greater line pressures in
the calender nips possible and the number of calender nips can be
reduced compared to the current state of the art. This also permits
an increase in efficiency of the calender and at the same time a
reduction of the blackening.
[0050] A paper machine (FIG. 3) which is suitable for the
production of calendered papers comprises a twin wire former 50, a
press section 51 with two pairs of rolls arranged in tandem,
wherein in each instance one press roll is in the embodiment of a
shoe press roll.
[0051] A single row dryer section 52 is located adjacent to the
press section 51. The paper web is calendered in a calender 53
which is equipped with a multitude of roll pairs. The paper web is
subsequently wound in a winder 54.
[0052] While this invention has been described with respect to at
least one embodiment, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
* * * * *