U.S. patent application number 10/566046 was filed with the patent office on 2007-06-14 for method for charging a fiber suspension, and arrangement for carrying out said method.
Invention is credited to Klaus Doelle, Oliver Luedtke.
Application Number | 20070131361 10/566046 |
Document ID | / |
Family ID | 34111922 |
Filed Date | 2007-06-14 |
United States Patent
Application |
20070131361 |
Kind Code |
A1 |
Doelle; Klaus ; et
al. |
June 14, 2007 |
Method for charging a fiber suspension, and arrangement for
carrying out said method
Abstract
A method of loading a fibrous stock suspension containing
chemical pulp fibers with calcium carbonate including the steps of:
adding one of calcium oxide and calcium hydroxide in one of a
liquid form and a dry form into the fibrous stock suspension;
adding gaseous carbon dioxide into the fibrous stock suspension;
precipitating of the calcium carbonate through said carbon dioxide;
and refining of the fibrous stock suspension during said
precipitating step.
Inventors: |
Doelle; Klaus; (Kisslegg,
DE) ; Luedtke; Oliver; (Koenigeggwald, DE) |
Correspondence
Address: |
Todd T Taylor;Taylor & Aust
142 S Main Street
P O Box 560
Avilla
IN
46710
US
|
Family ID: |
34111922 |
Appl. No.: |
10/566046 |
Filed: |
August 3, 2004 |
PCT Filed: |
August 3, 2004 |
PCT NO: |
PCT/EP04/51701 |
371 Date: |
January 26, 2006 |
Current U.S.
Class: |
162/9 ;
162/181.2; 162/26; 241/21; 422/129 |
Current CPC
Class: |
D21H 17/70 20130101;
D21H 23/16 20130101; D21H 17/675 20130101; D21B 1/00 20130101; D21H
21/52 20130101 |
Class at
Publication: |
162/009 ;
162/026; 162/181.2; 422/129; 241/021 |
International
Class: |
D21H 17/70 20060101
D21H017/70; D21B 1/00 20060101 D21B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2003 |
DE |
10335751.3 |
Claims
1-18. (canceled)
19. A method of loading a fibrous stock suspension containing
chemical pulp fibers with calcium carbonate, comprising the steps
of: adding one of calcium oxide and calcium hydroxide in one of a
liquid form and a dry form into the fibrous stock suspension;
adding gaseous carbon dioxide into the fibrous stock suspension;
precipitating of the calcium carbonate through said carbon dioxide;
and refining of the fibrous stock suspension during said
precipitating step.
20. The method of claim 19, further comprising the step of applying
a refining force in the range of between approximately 0.1 and 300
kWh per ton of dry paper pulp, said precipitating step and said
refining step are accomplished in a disperger.
21. The method of claim 19, further comprising the step of
providing raw material to the fibrous stock suspension, said raw
material being at least one of aqueous fibrous stock material and
aqueous paper stock, said raw material having a consistency of
between approximately 0.1 to 20%.
22. The method of claim 21, wherein said consistency is between
approximately 2 to 6%.
23. The method of claim 21, wherein said adding one of calcium
oxide and calcium hydroxide step includes the step of mixing said
calcium hydroxide into one of said aqueous fibrous stock material
and said aqueous paper stock thereby forming a mixture having a
solids content of between approximately 0.01 and 60%.
24. The method of claim 23, wherein said mixing step occurs in one
of a static mixer and an intermediate vat.
25. The method of claim 19, wherein said adding gaseous carbon
dioxide includes the step of mixing said carbon dioxide into the
fibrous stock suspension that is moist;
26. The method of claim 19, wherein at least one of a refiner, a
disperger, and a fluffer fiber loaded precipitated calcium
carbonate (FLPCC) reactor are used as at least one of a reactor and
a static mixer.
27. The method of claim 26, wherein the fibrous stock suspension
has one of a fibrous stock content and a paper content of between
approximately 0.01 and 15% while in said static mixer.
28. The method of claim 26, wherein the fibrous stock suspension
has one of a fibrous stock content and a paper content of between
approximately 2 and 40% while in one of said refiner and said
disperger.
29. The method of claim 26, wherein the fibrous stock suspension
has one of a fibrous stock content and a paper content of between
approximately 15 and 60% while in said fluffer-FLPCC-reactor.
30. The method of claim 19, further comprising the step of
supplying dilution water one of prior to, during and after either
of said adding steps.
31. The method of claim 19, wherein energy is expended in the
method of between approximately 0.3 and 8 kWh/t.
32. The method of claim 31, wherein said energy is between
approximately 0.5 and 4 kWh/t.
33. The method of claim 19, wherein a process temperature is
maintained during the method of between approximately -15.degree.
C. and 120.degree. C.
34. The method of claim 33, wherein said process temperature is
between approximately 20.degree. C. and 90.degree. C.
35. The method of claim 19, wherein the method produces calcium
carbonate in at least one of rhombohedral, scalenohedron and
spherical crystals.
36. The method of claim 35, wherein said crystals measure between
approximately 0.05 and 5 .mu.m.
37. The method of claim 36, wherein said crystals measure between
approximately 0.3 and 2.5 .mu.m.
38. The method of claim 19, further comprising the step of using
mixing elements that are one of static, moving and rotating.
39. The method of claim 19, wherein a pressure is maintained in the
range of approximately 0 to 15 bar.
40. The method of claim 39, wherein said pressure is between
approximately 0 and 6 bar.
41. The method of claim 19, wherein a ph is maintained in the
fibrous stock suspension of between approximately 6 and 10.
42. The method of claim 41, wherein said ph is between
approximately 6.5 and 9.5.
43. The method of claim 19, wherein a reaction time is expended of
between approximately 0.01 and 1 minute.
44. The method of claim 19, wherein a reaction time is expended of
between approximately 0.05 and 10 seconds.
45. A fibrous stock suspension loading apparatus, comprising: a
static mixer mixing calcium hydroxide into the fibrous stock
suspension; and at least one of a disperger and a refiner for one
of fluffing and refining of the fibrous stock suspension and to
precipitate the calcium hydroxide in a carbon dioxide atmosphere
while creating fibers that are loaded with calcium carbonate in the
fibrous stock suspension.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to loading of a fibrous stock
suspension with calcium carbonate.
[0003] 2. Description of the Related Art
[0004] Several methods for loading chemical pulp fibers with
calcium carbonate are already known. A method is described in U.S.
Pat. No. 6,413,365 B1, where the fibrous material is transported by
way of a supply line together with calcium oxide and/or calcium
hydroxide which are contained in the suspension. From there, the
fibrous stock suspension is transported into a rotating
distribution device. A reaction gas is fed in a ring shaped pattern
into the fibrous stock suspension; this causes the formation of
calcium carbonate crystals in the fibrous suspension. The calcium
carbonate crystals are distributed in the fibrous stock suspension
through the rotating distributor device. This process is known as a
Fiber Loading Process.
[0005] Additional methods and arrangements for loading fibers in a
fibrous stock suspension with a filler or additives are known from
German Patent Nos. DE 101 07 448 A1 and DE 101 13 998 A1. With the
assistance of these known processes, cigarette paper, cardboard and
all types of packaging papers, all types of Kraft sack paper and
papers containing fillers can be produced. The following applies to
the production of cigarette paper: cigarette paper has a base
weight of 16 to 26g/m.sup.2. It is frequently enhanced with an
impressed watermark and should be very thin, capable of glowing
combustion, and tasteless. It should also possess good optical
values with regard to the brightness. The capability of glowing
combustion is usually achieved by impregnation in order to leave an
attractive white ash.
[0006] Cigarette paper is normally produced from linen or hemp
fibers, cotton, sulfate pulp, paper machine broke, as well as from
other fiber sources. The filler content in cigarette paper is
between 5% and 40%, whereby 30% is considered as a standard
value.
[0007] Packaging papers and cardboards can be divided into three
categories: Container board for packaging purposes, container board
for applications in the field of consumer packaging and specialized
papers such as wallpaper, book spines, etc. Packaging papers are
normally produced as multi-ply products having basis weights higher
than 150 g/m.sup.2. The freeness varies from 600 to 50 CSF or 20 to
80.degree. SR, relative to the produced end product.
[0008] Kraft sack papers require a high porosity and a high
mechanical strength in order to meet the high demands that occur
such as rough handling during the filling process and the duration
of their use, as is the case, for example, with cement bags. The
paper must be strong enough to absorb impacts and must have an
accordingly high energy absorption capacity. The sack paper must
also be porous and sufficiently air permeable in order to
facilitate effortless filling. Sack papers are produced, for
example, from a long fibered Kraft pulp into product having a basis
weight of between 70 and 80 g/m.sup.2, and having a freeness of
between 600 to 425 CSF or 20 to 30.degree. SR. In addition, a
medium freeness, as described above is strived for. This is usually
achieved through high consistency refining whereas in the case of
conventional paper grades, for example, graphic papers, low
consistency refining is utilized. The result of the high
consistency refining is good adhesion of the fibers to each other
as well as a high porosity. The sack paper is predominantly
produced from bleached and unbleached fibers, whereby a filler
content of 5% to 15% may be present in the produced sack paper.
[0009] Filter paper requires a high controlled porosity and pore
distribution. It must have a sufficiently high mechanical strength
to counteract the flow of the medium that is to be filtered. Filter
paper is produced, with a basis weight of 12 to 1200 g/m.sup.2. For
example, an air filter would
[0010] have a basis weight of between 100 and 200 g/m.sup.2, an oil
and fuel filter between 50 and 80 g/m.sup.2, a foodstuff filter to
1000 g/m.sup.2, a coffee filter to 100 g/m.sup.2, a tea bag between
12 and 20 g/m.sup.2 and a vacuum bag between 100 and 150 g/m.sup.2.
All filters are produced from a multitude of fibers, such as
chemical pulp fibers, bleached and unbleached fibers, Kraft pulp,
DIP (deinked) paper, recycled fibers, TMP (thermo mechanical)
paper, etc.
[0011] What is needed in the art is a more efficient, less costly
method of loading a fibrous stock suspension.
SUMMARY OF THE INVENTION
[0012] The present invention provides a method including the
following process steps: [0013] Feeding of calcium hydroxide in
liquid or dry form, or of calcium oxide into the fibrous stock
suspension, [0014] Feeding of gaseous carbon dioxides into the
fibrous stock suspension, [0015] Precipitation of calcium carbonate
through the carbon dioxide and [0016] Refining of the fibrous stock
suspension during the loading process.
[0017] The current invention describes a method for the production
of fiber loaded precipitated calcium carbonate (FLPCC) and to
simultaneously undergo a refining process. The fiber raw material
that is to be loaded may consist of recycling paper, DIP (deinked
paper), secondary fibers, bleached or unbleached pulp, mechanical
pulp, bleached or unbleached sulfate pulp, broke, linen, cotton,
and/or hemp fibers (predominantly cigarette paper) and/or any paper
raw material that can be utilized on a paper machine, irrespective
of whether or not the end product contains a filler that was
produced by a precipitation process in batch reactors or by a
refining process, or whether talcum, titanium dioxide (TiO.sub.2),
silicon, etc. are used. The refining process is also referred to as
GCC process (GCC=ground calcium carbonate).
[0018] When a fibrous stock suspension is processed with a fiber
loading technology a completely new product for application in
paper production results. The new product has new and improved
characteristics compared to a product according to the current
state of the art. The fiber loading technology permits
precipitation of a filler, especially calcium carbonate, that is
uniformly distributed and adhered to, in and between the paper
fibers directly in the stock preparation of a paper mill. It also
allows the treated fibrous stock to undergo a fiber treatment in a
refiner simultaneously with the precipitation process.
[0019] The process for the production of precipitated calcium
carbonate with simultaneous refining with the assistance of the
fiber loading combination process occurs according to the process
data, which is described in further detail below. In this context
please also refer to German Patents DE 101 07 448 A1, DE 101 13 998
A1 and U.S. Pat. No. 6,413,365 B1.
[0020] In accordance with the FLPCC combination process described
under the present invention the filler material utilized according
to the current state of the art is replaced with the filler
material produced according to the fiber loading combination
process technology. The range of application of the filler produced
with the fiber loading combination process technology extends to
applications within the paper production of all paper grades,
including cigarette papers, filter papers, Kraft sack paper grades,
cardboard and packaging papers that have a filler content of
between 1% and 60% and/or a white liner having a filler content of
between 1% and 60%. The loaded and produced paper grades can be
produced on a paper machine from a recycling paper, deinked paper
(DIP), secondary fibers, bleached or unbleached pulp, mechanical
pulp, bleached or unbleached sulfate pulp, broke, linen, cotton,
and/or hemp fibers (predominantly for cigarette paper) and/or any
paper raw material, irrespective of whether or not the end product
contains a filler.
[0021] Fibrous stock produced with the fiber loading combination
process technology generally possesses a superior dewatering
characteristic as compared to a fibrous stock produced according to
another method. The improvement in the dewatering capacity is
between 5 to 100 ml CSF or 0.2 to 15.degree. SR, depending upon the
required freeness. The stock or pulp produced according to the
fiber loading process further possesses a low water retention value
of 2 to 25%, depending upon the raw material that is used in
production. This permits a more effective production of various
paper grades, for example, FL (FL=fiber loaded) copy and printing
paper of all types, FL coating paper of all types, FL news print of
all types and FL cigarette paper of all types, FL B&P paper of
all types, FL Kraft sack paper of all types and FL filter paper,
since the water in the stock suspension can be removed faster. The
stock therefore dries faster.
[0022] In the instance of FL cigarette paper, FL B&P paper, FL
Kraft sack paper and FL filter paper, which do not require fillers,
the exposed filler can be removed by way of an additionally
provided washing process prior to the refining process, following
the refining process, after running through the headbox vat or
prior to feeding into the paper machine. This applies to the filler
that is not deposited in, or on, the fibers and can be washed out
accordingly. The fibers themselves will still contain filler,
inside and out so that the positive effects of the fiber loading
technology can be taken advantage of.
[0023] The fiber loading technology may be utilized, prior to, or
after, the refining process, depending on what requirements are put
upon the end product.
[0024] Compared to the current state of the art, a higher freeness
value can be achieved with the fiber loading combination
technology, since up to 50% of refining energy can be saved. This
has an especially positive influence with all the paper grades,
which pass through a refining process during their production, or
which possess a very high freeness value, for example FL-cigarette
papers, FL B&P papers, FL Kraft sack papers and FL filter
papers. In particular, these are FL
[0025] cigarette papers having 100 to 25 CSF or 68 to 90.degree.
SR, FL B&P papers having 600 to 50 CSF or 20 to 80.degree. SR,
FL sack papers having 600 to 425 CSF or 20 to 30.degree. SR and FL
filter papers having 600 to 350 CSF or 20 to 35.degree. SR.
[0026] The high mechanical strengths in the end product, which are
achieved through the high freeness value, positively affect the
production of FL cigarette papers, FL B&P papers, FL sack
papers and FL filter papers since, due to process based mechanical
loads in the various sections of the paper machine. Process based
mechanical loads exist in the press section, the dryer section and
in the area where the web is wound, the produced intermediate
product and the end product, which is to be produced, bears a high
mechanical load due to the utilization of winders, rewinders and
converting machinery. Great mechanical stresses occur on the paper,
especially in the production of cigarette paper, which are also
partially attributed to the low basis weight and the utilization of
winders.
[0027] More effective drying to a residual moisture content of 1 to
20% permits an increase in efficiency for all paper grades. A
higher water retention capacity, i.e. 1 to 25% results in a
positive influence upon remoistening, which is lower in the
manufacturing process, as well as upon the printability of the
produced web. An additional advantage for all paper grades is the
greater brightness or the higher optical values of around 15 or
more lightness points, which is to be emphasized in the production
of all grades of paper and cardboard, with or without a white
liner. By using the fiber loading technology the optical values,
for example in cigarette papers, are also improved by up to 10
lightness points.
[0028] An additional advantage of fiber loading with the above
referenced paper grades is found in that for special applications
calendering is provided and in doing so the so-called blackening
due to deposits of FL particles in, around, and on, the fibers is
suppressed or eliminated through the utilization of the fiber
loading process of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] 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 an embodiment of the invention
taken in conjunction with the accompanying drawing, wherein:
[0030] FIG. 1 schematically illustrates an embodiment of the
elements and flow of the method of the present invention.
[0031] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplification set out
herein illustrate one preferred embodiment of the invention, in one
form, and such exemplification is not to be construed as limiting
the scope of the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
[0032] In accordance with one embodiment of the current invention
aqueous fibrous stock material, especially aqueous paper stock,
having a consistency of 0.1 to 20%, preferably between 2 and 15% is
used as primary a raw material.
[0033] In accordance with the present invention, calcium hydroxide
is mixed as the preferred filler into the aqueous fiber stock
material, especially into the paper fiber stock, whereby this has a
solids content of between 0.01 and 60%. In accordance with the
current invention utilization of a source material, other than
calcium hydroxide or calcium oxide, for the formation of the filler
is also feasible. The calcium hydroxide is added through a static
mixer or an intermediate vat. The carbon dioxide is preferably
added into a moist fibrous stock suspension having a consistency of
0.1 to 15%, according to the reaction parameters. Calcium carbonate
is precipitated in a carbon dioxide gaseous atmosphere.
[0034] The refining process is carried out simultaneously with the
fiber loading process in an apparatus known as the crystallizer; a
refining energy in the range of between 0.1 and 300 kWh/ton dry
paper pulp is applied; a short reaction time of the calcium
hydroxide and the carbon dioxide is important in this context. The
energy supply or heat volume, or heating of the paper suspension
for the production of crystals in various forms is important for
the present invention.
[0035] Depending upon the application of the respective reaction
machine, aqueous paper stock with a paper content of between 0.01
and 60% is used as the primary raw material.
[0036] An advantageous embodiment of the method of the present
invention provides that a refiner, a disperger and/or a fluffer
FLPCC reactor are utilized as a reactor and/or a static mixer. The
fibrous stock content, especially the paper content used therein is
between 0.01 and 15% in the instance of a static mixer; at between
2 and 40% in the instance of a refiner and a disperger and between
15 and 60% in the instance of a fluffer-FLPCC-reactor.
[0037] The current invention provides that the dilution water is
supplied prior to, during, or after, the addition of carbon
dioxide, calcium hydroxide or calcium oxide. Calcium carbonate
precipitates when adding carbon dioxide into a calcium hydroxide
solution or suspension. Conversely, the precipitative reaction also
occurs, when calcium hydroxide is added to water under a carbon
dioxide atmosphere. Diluting water may be added prior to, during,
or after, the addition of carbon dioxide or calcium hydroxide. An
expenditure of energy of between 0.3 and 8 kWh/t, especially
between 0.5 and 4 kWh/t is preferably used for the precipitation
reaction.
[0038] Likewise it can be provided that the process temperature is
between -15.degree. C. and 120.degree. C., especially between
20.degree. C. and 90.degree. C.
[0039] According to the current invention rhombohedral,
scalenohedron and spherical crystals can be formed.
[0040] Advantageously, the crystals measure between 0.05 and 5
.mu.m, especially between 0.3 and 2.5 .mu.m. Static and/or moving,
especially rotating mixing elements, may be utilized. The process
is carried out in a pressure range of between 0 and 15 bar,
preferably between 0 and 6 bar. The pH value is between 6 and 10,
preferably between 6.5 and 9.5. The reaction time is advantageously
between 0.01 minutes and 1 minute, especially between 0.05 seconds
and 10 seconds.
[0041] The current invention is described in further detail below,
citing a design example and with the assistance of FIG. 1, which
illustrates a schematic view of an apparatus for loading of a
fibrous stock suspension. For the purpose of loading a fibrous
stock suspension with calcium carbonate the suspension is
transported in a device 1 in a pipe line system that is equipped
with control valves 10 and 12. Control valve 10 is located in a
line 14 through which the piping system is connected to a static
mixer 16. Diluting water can be fed to static mixer 16 by way of a
valve 18. Also, the addition of a suspension of calcium hydroxide
is controlled by way of an additional valve 22 that is installed in
a line 20. This is supplied by a preparation apparatus 24, where
solid calcium oxide or calcium hydroxide is fed into water. For
this purpose water is supplied to preparation apparatus 24 by way
of a line that is equipped with a valve 26. The suspension produced
in preparation apparatus 24 is passed into line 20 by a pump
28.
[0042] The diluted fibrous stock suspension, to which calcium
hydroxide was added, flows from mixer 16 into line 30 that is
equipped with valve 32. From line 32 the suspension is immediately
fed into a disperger 42 (crystallizer). For the purpose of
supplying carbon dioxide, this is connected with a carbon dioxide
tank 52 through a line 50, which is equipped with valves 44 and 46,
and a pump 48. Carbon dioxide is fed from carbon dioxide tank 52
into disperger 42 in order to produce the desired precipitation
reaction of calcium hydroxide and carbon dioxide
[0043] for the formation of calcium carbonate as a filler in the
fibers of the fibrous stock. Instead of utilizing a mixer 16, the
calcium hydroxide may also be added from a header tank.
[0044] Line 50 is connected by way of an additional valve 58 with a
static mixer 60 whose purpose it is to add additional carbon
dioxide to the fibrous stock suspension flowing from disperger 42
through line 64 which is equipped with valve 62.
[0045] Fibrous stock suspension that is not treated with calcium
hydroxide can additionally be fed into blend chest 68 by way of the
12 and line 70.
[0046] The fibrous stock suspension flows from static mixer 60 into
blend chest 68, which is equipped with a rotor 66 for the purpose
of thoroughly mixing the fibrous stock suspension. From blend chest
68 the fibrous stock suspension flows either immediately to a
headbox in a paper machine, or it is subjected to additional
mechanical processing, for example in a refiner feed chest.
[0047] In addition, a refiner 80 can be installed in the piping
system for the purpose of improving the fibrous stock suspension
through an additional refining process. Refiner 80 is supplied with
fibrous stock suspension by way of a line 82 that branches off of
line 30. From refiner 80 the repeatedly refined fibrous stock
suspension is brought through line 84 into line 64 and from there,
as described above, into blend chest 68.
[0048] Provisions can additionally be made that carbon dioxide from
carbon dioxide storage tank 52 is supplied to refiner 80 through
line 86 that branches off of line 50 and a static mixer 88 that
connects line 86 with line 82.
[0049] The inventive design of the present invention includes
loading of a fibrous stock suspension with calcium carbonate that
has the advantage, when compared with devices according to the
current state of the art, in that machinery for homogenizing of the
fibrous stock suspension, such as a screw press, and a conditioning
machine for homogenizing of the fibrous suspension (equalizing
reactor) is not required. Refiner 80 having a container/vessel
additionally takes over the refining process, providing a
considerably simpler arrangement of stock preparation compared to
the current state of the art. This refining process serves at the
same time as an agitation process, in order to deposit the calcium
carbonate in the fibers through a shear process.
[0050] In the inventive method, for preparation of the fibrous
stock suspension by way of the fiber loading process, calcium
hydroxide (lime hydrate, lime milk) is used, which has a solubility
in water at 20.degree. C. of 1.65 g/l to 0.7 g/l at 100.degree. C.
A pH value of up to 12.6 is achieved, depending upon how closely
the concentration of the solution reaches the maximum value. In
commercially available lime hydrate concentrations, solids contents
of 0 to 60% can be realized, whereby the suspension has a pH-value
of 12.6 maximum. The actual volume of lime hydrate in the
suspension therefore includes the dissolved component as well as
the solids concentration.
[0051] For a suspension containing 20% calcium hydroxide in one
liter at 20.degree. C. therefore, a dissolved mass of 1.65 g
calcium hydroxide and a solids content of 198.35 g results. Since
in the fiber loading process the conversion or reaction speed
influences the end product of the FL (fiber loading) process every
effort is made to use the lime hydrate for an as short as possible
conversion time. This is achieved in that for the production of the
lime hydrate calcium oxide (CaO), in a medium particle size range
of 0.01 to 100 mm, especially in a size range of 0.05 to 50 mm, is
produced in a slaking process.
[0052] While this invention has been described as having a
preferred design, 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.
* * * * *