Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Method and device for charging a fibre material suspension
The invention relates to a method for loading of a fibrous stock suspension
with calcium
carbonate.
Several methods for loading chemical pulp fibers with calcium carbonate are
already
known. A method is described in US 6,413,365 B1 where the fibrous material is
transported via a supply line together with calcium oxide and/or calcium
hydroxide which
are contained in said 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 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
Fiber
Loading Process.
A method for loading a fibrous stock suspension is known from DE 101 07 448 Al
whereby the fibrous stock suspension is fed into a crystallizer and is treated
in said
crystallizer by shear forces in order to break down larger fiber agglomerates
into smaller
ones, or even into individual fibers, and whereby the crystallizer is utilized
at the same
time as reactor for the chemical precipitation reaction.
It is the objective of the current invention to further simplify a method of
the type
referred to at the beginning.
In accordance with the current invention this objective is met by a method
comprising the
following process steps:
- Adding of calcium hydroxide in liquid or dry form, or of calcium oxide into
the
fibrous stock suspension,
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- Adding of carbon dioxide into the fibrous stock suspension,
- Precipitation of calcium carbonate from the calcium hydroxide through the
carbon
dioxide in a pressurized pressure vessel.
The current invention describes a method for the production of fiber loaded
precipitated
calcium carbonate (FLPCC), whereby 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
which can be
utilized on a paper machine.
With the method according to the current invention the currently used filler
material is
replaced, supplemented or activated by the filler material which is produced
by the fiber
loading process technology. Activation means that the already existing filler
particles are
superimposed by the fiber loading process or serve as a crystallization
nucleus, thereby
providing improved optical characteristics.
The method is also especially suitable if paper which is printed with flexo-
ink (water
based printing ink) - especially news print - is used for the production of
the fiber raw
material. The print particles consisting of flexo-ink cannot be removed
through a
floatation process, or can be removed only with great difficulty. With the
current
invention it is now possible to integrate fillers and foreign substances such
as printing
ink, contaminants, stickies, etc. which are inherently present in DIP papers
into the fiber
loading-crystallization process whereby the already present filler particles
are being
superimposed by the fiber loading process, or serve as crystallization
nucleus.
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The method is independent of whether or not the fiber raw material contains a
filler that
was produced by a precipitation process in a batch reactor or by a refining
process, or
whether talcum, titanium dioxide (TiO2), silicon, etc are used. The refining
process is
also referred to as GCC-process (GCC = ground calcium carbonate).
When a fibrous stock suspension is processed with the fiber loading technology
a
completely new product for application in paper production will result, with
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
fibers directly
in the stock preparation of a paper mill.
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 and
cardboard and
packaging papers including those with which recycling paper types and DIP
papers are
used. Packaging papers of this type can have a filler content of between 1 and
60%
and/or can possess a white liner having a filler content of between I and 60%.
The
loaded and manufactured 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.
Fibrous stock produced according to the fiber loading combination process
technology
generally possesses a superior dewatering characteristic compared to a fibrous
stock
produced according to another method; the dewatering capacity is between 5 to
100 ml
CSF or 0.2 to 15 SR, depending upon the required freeness. The stock or pulp
produced
according to the fiber loading process further possesses a lower water
retention value of
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2 to 25% depending upon the raw material used in the production process. 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 accordingly faster.
When a fibrous stock suspension is processed with the fiber loading technology
a
completely new product results which possesses new and improved
characteristics
compared to the papers available on the market. The fiber loading process
which is
described below permits precipitation of a filler - especially calcium
carbonate - which is
uniformly distributed and adhered to, in and between the fibers directly in
the stock
preparation of a paper mill.
By means of a combination or by means of an individual application of the
measures in
accordance with the current invention described below only precipitated
calcium
carbonate for the fiber loading process is produced and already present filler
material is
activated.
By utilizing the fiber loading technology in the pulper or in the batch-
container the
optical characteristics of the paper suspension and the raw material can be
improved by
0.5 to 30 lightness points, preferably by 1 to 25 lightness points -
predominantly through
masking of the contaminants such as ink particles and dirt. In addition, a
conversion of
non-activated fiber stock components, for example non-converted calcium
hydroxide,
PCC (precipitated calcium carbonate), GCC (ground calcium carbonate), lime
components, etc. which are embedded in the recycled paper raw material or in
the DIP-
pulp occurs.
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Advantageous design forms of the current invention result from the sub-claims,
the
description and the drawing.
In accordance with one design form aqueous fiber raw material, especially
aqueous paper
raw material having a consistency of between 1 and 20% of fibrous stock
content is fed
into the pressure vessel, whereby LC-fiber stock material (low consistency) is
used at a
content of between 1 and 6%, MC-fiber stock material (medium consistency) is
used at
a content of between 6 and 10% and HC-fiber stock material (high consistency)
is used at
a content of between 10 and 20%.
It is advantageous if the aqueous fiber raw material is diluted to a fibrous
stock
suspension having a consistency of between 0.1 and 20%, especially diluted to
a
consistency of between 2 and 18%.
In a suitable embodiment of the method the pressure vessel is closed by a
sluice after
supplying the aqueous fiber stock material and/or the dilution water.
It is advantageous if the calcium hydroxide or the calcium oxide is mixed into
the
aqueous fiber stock in a range of between 0.1 and 60% of the existing solids
content of
the volume of the dry fiber stock.
The pH value is preferably between 6 and 11, especially between 6.5 and 10.5.
The reaction time is between 0.0005 and 30 minutes, especially in a range of
between
0.05 and 10 minutes.
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The calcium carbonate can be precipitated advantageously through adding the
carbon
dioxide in a pressure range of between 0 and 15 bar, especially between 0 and
6 bar.
One design form of the method provides that the fibrous stock suspension
and/or the
carbon dioxide is heated by means of process water or dilution water or steam
during its
dissolution in the fibrous stock suspension, or by means of the fiber loading
process or
through introducing heat energy from the outside, especially by means of steam
energy or
electrical energy.
The carbon dioxide can be added prior to, during or after the addition of the
carbon
dioxide or the calcium hydroxide or the calcium oxide.
In this connection it is advantageous if the pressure vessel is opened by a
valve or a sluice
before the fiber loading reaction, or after the reaction.
The energy expenditure for the precipitation of the loaded fibers is between
0.3 and 8
kWh/t, especially between 0.5 and 4 kWh/t, if no refiner for the fiber stock
is used. A
refiner may also be installed before the vessel if the fiber pulp is already
sufficiently
dissolved. In an alternative embodiment of the current invention the refiner
may also be
installed downstream from the pressure vessel.
The process temperature is preferably between -15 and 120 , especially
between 20 and
90 C.
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Due to the fiber loading process rhombohedral, scalenohedron and spherical
crystals are
formed.
Due to this process crystals having dimensions preferably of between 0.05 and
5gm,
especially between 0.3 and 2.5 m can be produced.
Static and/or moving, especially rotating mixing elements can be utilized for
the purpose
of mixing the fibrous stock suspension.
The process is preferably conducted in a pressure range of between 0 and 15
bar,
especially between 0 and 6 bar.
In a preferred embodiment according to the invention it is also possible to
conduct a
refining process in the pressure vessel, at the same time as the precipitation
process.
The invention also relates to a device for the implementation of the method.
In accordance with the invention the device is characterized in that it
comprises an infeed
device for the supply of the fiber raw material, as well as a pressure vessel.
An advantageous embodiment of the method provides that the pressure vessel
comprises
a sluice or a valve through which the fiber raw material is fed for the
production of the
fibrous stock suspension with loaded fibers. The pressure vessel is preferably
equipped
with inlets for dilution or press water, for calcium oxide or calcium
hydroxide and for
carbon dioxide.
In addition the pressure vessel comprises a rotor for mixing the fibrous stock
suspension.
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The current invention is described in further detail below, citing a design
example and
with the assistance of the only drawing. This illustrates a schematic view of
a device for
loading a fibrous stock suspension.
A fiber raw material is supplied to a pressure vessel 2 through a supply pipe
1(Drawing).
In order to be able to establish and limit the supply volume a sluice 3 which
is opened
and closed via a motor driven closing mechanism is located between the supply
pipe I
and the pressure vessel 2.
Dilution water, calcium hydroxide in liquid or solid form or calcium oxide or
chemicals
are added through additional supply line connections 4, 5, 6 so that - if the
raw fiber stock
was initially supplied to a fill level 7 - a filling of the pressure container
2 above this fill
level 7 is formed, consisting of the calcium hydroxide which serves the fiber
loading
process, together with the water and/or the dilution water in which it is
dissolved.
In order to mix the fiber raw stock with the calcium hydroxide so that this
penetrates into
the fibers a rotor 8 is supplied which comprises a propeller wheel or similar
device at the
bottom and/or at a higher level of the pressure container 2. The rotor 8 is
driven via a
motor 9.
Preferably at least one inlet 10 is provided in the lower area of the pressure
container 2
for carbon dioxide through which the calcium hydroxide reacts to calcium
carbonate.
After the fiber raw material has been dissolved and loaded with calcium
carbonate it is
routed to a machine for the production of a fibrous web, through a discharge
pipe 12
which is equipped with a valve 11.
In addition a measuring location 13 is also preferably provided on pressure
container 2 in
order to measure the chemical composition of the content in said pressure
container 2,
especially to measure the pH value.
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Component Identification
1 Supply pipe
2 Pressure container
3 Sluice
4 Supply line connection
Supply line connection
6 Supply line connection
7 Filling level
8 Rotor
9 Motor
Inlet for carbon dioxide
11 Discharge pipe
12 Valve
13 Measuring location
