Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND SYSTEM FOR PRODUCING MARKET PULP
AND PRODUCTS THEREOF
BACKGROUND OF THE INVENTION
[0001] This application claims the benefit under 35 U.S.C. 119(e) of prior
U.S. Provisional
Patent Application Nos. 62/643,224, filed March 15, 2018, and 62/702,395,
filed July 24, 2018,
which are incorporated in their entireties by reference herein.
[0002] The present invention relates to the production of market pulp. More
particularly,
methods and systems are provided for producing market pulp which include
treatment of pulp
with one or more anionic surfactants or compounds and one or more enzymes
before pulp drying.
[0003] In the pulp making industry, cellulose-containing feed material has
been defibrated
chemically, mechanically, or both, and then typically is washed and at least
partly dewatered after
such operations. In pulping processes in which the pulp is chemically treated,
such as by chemical
digestion, bleaching, or other chemical treatments, dewatering can be used to
drain water and
separate free chemical from the fibers. Some pulp mills may be integrated with
a paper making
plant, wherein the dewatering of the product pulp may be limited such that
slurry pulp or wet laid
pulp can be directly advanced to a papermaking machine at the same production
site. Other pulp
mills produce market pulp in non-integrated production operations. Market pulp
can be pulp
product which has been significantly dewatered in the final stages of pulp
processing. Market
pulp further may be formed into bales or rolls of dewatered pulp. The market
pulp can be
transported to other locations for later use.
[0004] A particular process for producing market pulp which uses diverse
ionic compounds
before pulp drying is described in U.S. Pat. No. 8,916,024. According to the
process of USP
8,916,024, pulp is treated with a combination of cationically and anionically
charged compounds
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before drying, and more particularly, the treatment involves treating pulp
with a combination of at
least one cationic polymer and at least one anionic polymer effective to form
a polyelectrolyte
complex in the treated pulp. U.S. Patent No. 6,706,144 shows a method of
dewatering of
dewatering an aqueous cellulosic pulp slurry, which may be a market pulp
slurry, wherein a
mixture of one or more nonionic surfactants and one or more anionic
surfactants is added to the
slurry.
100051 The present investigators have realized that the rate at which pulp
dewatering can be
accomplished in a pulp mill in the production of market pulp can significantly
affect the overall
line speed and production capacity of the pulp mill or similar production
facility. The present
investigators have realized that there is a need for new methods and systems
for producing market
pulp with enhanced pulp-dewatering performance and efficiencies.
SUMMARY OF THE PRESENT INVENTION
[0006] A feature of the present invention is to provide a method for
producing market pulp
with treatment of pulp with one or more anionically charged compounds and with
one or more
enzymes to improve one or more properties of the market pulp or process to
produce the market
pulp, such as, improving dewatering performance and efficiency.
[0007] Another feature of the present invention is to provide a method for
producing market
pulp by sequentially adding anionic surfactant(s) and one or more enzymes to
pulp before
dewatering to improve pulp drainage.
[0008] An additional feature of the present invention is to provide a
system for producing
market pulp capable of using one or more anionically charged compounds and one
or more
enzymes before pulp drying to improve pulp drainage.
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[0009] A further feature of the present invention is to provide a market
pulp comprising
dewatered pulp which contains one or more anionically charged compounds and
one or more
enzymes from the pulp treatment method.
[0010] Additional features and advantages of the present invention will be
set forth in part in
the description that follows, and in part will be apparent from the
description, or may be learned
by practice of the present invention. The objectives and other advantages of
the present invention
will be realized and attained by means of the elements and combinations
particularly pointed out
in the description and appended claims.
[0011] To achieve these and other advantages, and in accordance with the
purposes of the
present invention, as embodied and broadly described herein, the present
invention relates, in one
embodiment, to a method for producing market pulp comprising forming
cellulosic particulates
into pulp; adding at least one anionically charged compound and adding at
least one enzyme to the
pulp to provide treated pulp; mechanically dewatering the treated pulp to
provide mechanically
dewatered pulp; and thermally drying the mechanically dewatered pulp to form
market pulp.
[0012] The present invention further relates to a method for producing
market pulp
comprising forming cellulosic particulates into pulp; adding at least one
anionic surfactant and
adding at least one enzyme to the pulp before dewatering; mechanically
dewatering the pulp; and
thermally drying the dewatered pulp to form market pulp.
[0013] The present invention further relates to a system for producing
market pulp comprising
a supply of cellulosic fibers; at least one pulp forming unit for forming pulp
from the cellulosic
fibers; at least one feeding device for feeding at least one anionically
charged compound, such as
an anionic surfactant, to the pulp; at least one feeding device for feeding at
least one enzyme to the
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pulp; a dewatering device for mechanically removing water from the pulp; and a
dryer for
thermally removing water from the pulp to provide market pulp.
[0014] The present invention further relates to a market pulp comprising
dewatered pulp
which contains at least one anionically charged compound and at least one
enzyme from the
indicated treatment method.
[0015] It is to be understood that both the foregoing general description
and the following
detailed description are exemplary and explanatory only and are intended to
provide a further
explanation of the present invention, as claimed.
[0016] The accompanying drawings, which are incorporated in and constitute
a part of this
application, illustrate some of the embodiments of the present invention and
together with the
description, serve to explain the principles of the present invention.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a process flow chart for producing market pulp according
to an example of
the present application.
[0018] FIG. 2 is a schematic showing a portion of the system in FIG. 1
which includes a pulp
dryer for bleached pulp according to an example of the present application.
[0019] FIG. 3 is a schematic of a pulp dryer which can be used in the
system shown in FIG. 1
according to an example of the present application.
[0020] FIG. 4 is a graph showing the amount of water removed (in grams)
from wet pulp over
time for several examples, including an example of the present invention.
[0021] FIG. 5 is a bar graph showing the volume of water drained (in ml)
from wet pulp for
three drain times for several examples, including an example of the present
invention.
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DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0022] The present invention relates to production of market pulp which has
been treated with
one or more anionically charged compounds and with one or more enzymes to
improve pulp
dewatering performance and efficiency thereof and/or other properties. As used
herein, "market
pulp" refers to mechanically dewatered pulps which are thermally dried. The
market pulp provides
a dry form of product material which has useful storage stability and can be
more easily shipped
and handled than bulkier aqueous forms of pulp product. The market pulp can be
stored,
transported, or both for subsequent use as a process material used in other
production processes.
The market pulp optionally can be securely wrapped as a unitized product for
shipping or
transport for further processing, such as papermaking. As an option, market
pulp, as referenced
herein, can be a product of a modified type of pulp mill which is adapted
according to options of
the present invention for treatment of the pulp after any bleaching and before
final dewatering
with the anionically charged compound(s) and one or more enzymes.
[0023] These treatment additives impact the dewatering performance in
significant and
beneficial ways which would not be expected from the use of either the
anionically charged
compound and enzyme individually, and in some options may exceed additive
expected effects
from the individual component. The combined treatment of pulp with the
anionically charged
compound and enzyme can provide a synergistic effect on water removal which is
much better
than either treatment alone and much better than the additive effect expected.
It has been observed
that the high basis weight of some pulp sheets on a pulp dryer, for example,
can be an impediment
to good drainage. It has been found that significant improvements in
dewatering performance at a
pulp dryer can be provided in the production of market pulp by treatment of
pulps after digestion
or other mode of defibration, and any bleaching, and before pulp drying, with
the anionically
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charged compound and enzyme used in combined treatment of pulps. Treatment of
the pulp prior
to the pulp dryer with the combination of the anionically charged compound and
with the
enzyme(s), for example, can increase the free drainage rate of the pulp.
Increasing the free
drainage rate of the pulp makes it feasible to increase the production speed
and capacity of the
process for producing market pulp. As an option, the pulp treatment methods
and systems of the
present invention are not part of, nor integrated with, a paper making
machine.
[0024] Though not desiring to be bound to any theory, enzymes may provide
other
mechanisms to improve water removal from the pulp in the methods and systems
of the present
invention. The surface of the fiber is hydrophilic, and so there is a portion
of the water in the
slurry that is tightly bound to the fiber surface, and not easily removed by
gravity drainage, nor by
applied vacuum, nor by pressing. A cellulase enzyme, for example, may remove
the amount of
tightly-bound water by removing some portion of fibrils from the fiber
surface, thus reducing the
effective surface area that can bind water. The fiber surface also is
comprised of hemicelluloses, in
addition to cellulose. These hemicellulose compounds are especially likely to
bind water to the
fiber surface. Use of a hemicellulase enzyme may remove a portion of
hemicellulose (xylan or
mannan, for example) from the fiber surface, and thus also reduce the affinity
of water to the fiber.
[0025] The anionically charged compound(s) can be one or more anionic
compounds and/or
can be one or more anionic surfactants. Examples include, but are not limited
to, an alcohol
sulfate, an alcohol alkoxy sulfate, a sulfonate, a sulfosuccinate, a
sulfosuccinic acid ester with an
ethoxylated alcohol, and any soluble or dispersible salts thereof, or any
combinations thereof. A
sulfonate refers to a salt or ester of a sulfonic acid. A sulfosuccinate
refers to a sulfonate derivative
of succinate (e.g., a salt or ester of sulfosuccinic acid). For salts thereof,
the counterion can be a
metal ion, such as an alkali metal (e.g., sodium, potassium). More specific
examples include, but
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are not limited to, a fatty alcohol sulfate (e.g., C12-18 fatty alcohol
sulfate), an alkyl alcohol
sulfate (e.g., C10-C16 alkyl alcohol sulfate), an ethoxylated alcohol sulfate
(e.g., ethoxylated
C12 alcohol sulfate), a sulfonated fatty acid alkyl ester, an olefin
sulfonate, a paraffin sulfonate, an
alkylbenzylsulfonate, and a dialkyl sulfosuccinate. Additional examples
include dodecyl alcohol
sulfate, hexadecyl alcohol sulfate, dodecyl ethoxy sulfate, tetradecyl ethoxy
sulfate, decylbenzene
sulfonate, tetradecyl benzene sulfonate, tetradecyl sulfonate, octadecyl
sulfonate, 3-hydroxy- 1 -
hexadecane sulfonate, 2-hexadecene- 1 -sulfonate, dioctylsulfosuccinate sodium
salt, or others.
The anionically charged compound can be an anionic surfactant, which is a
sulfate surfactant, a
sulfonate surfactant, a sulfosuccinate surfactant, or any combinations
thereof.
[0026] The enzyme component of the enzyme used with the anionically charged
compound(s)
to treat the pulp according to this invention can include, for example, an
enzyme having
cellulolytic activity, hemi-cellulolytic activity, pectinolytic activity, or
glycosidasic activity. The
enzyme can be a hydrolytic enzyme which has activity that affects the
hydrolysis of fiber (e.g.,
hydrolytic activity), such as to accelerate the hydrolysis of a chemical bond.
The enzyme can be,
for example, cellulase, hemicellulase, lipase, pectinase, cellobiase,
xylanase, protease, mannanase,
13-glucanase, carboxymethylcellulase (CMCase), amylase, glucosidase,
galactosidase, laccase, or
any combinations thereof A single type of enzyme or a combination of two or
more different
types of enzymes can be used jointly with the anionically charged compound(s).
[0027] Cellulases generally are enzymes that degrade cellulose, a linear
glucose polymer
occurring in the cell walls of plants. The cellulase enzyme can be, for
example, a cellulase, such as
an endo-cellulase, exo-cellulase, cellobiase, oxidative cellulase, cellulose
phosphorylases, or any
combinations thereof Hemicellulases (e.g., xylanase, arabinase mannanase)
generally are
involved in the hydrolysis of hemicellulose, which, like cellulose, is a
polysaccharide found in
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plants. The pectinases generally are enzymes involved in the degradation of
pectin, a carbohydrate
whose main component is a sugar acid. P-glucanases are enzymes involved in the
hydrolysis of 13-
glucans which are also similar to cellulose in that they are linear polymers
of glucose.
[0028] The following paragraphs provide examples of enzymes that can be
used alone or in
any combination in the present invention.
[0029] Endo-cellulases that can be used, for example, are endoglucanase
with binding domain
(e.g., NOVOZYMS 476, Novozymes), endoglucanase enriched with high cellulase
units (e.g.,
NOVOZYMO 51081, Novozymes), or combinations thereof, or other known or useful
endo-
cellulases.
[0030] Liquid enzymatic compositions containing cellulases are available
under the names
Celluclaste and Novozyme 188, which are both supplied by Novo Nordisk.
[0031] PULPZYMO product, available from Novo Nordisk, and ECOPULPO product,
from
Alko Biotechnology, are two examples of commercially available liquid
enzymatic compositions
containing xylanase-based bleaching enzymes.
[0032] As a class, hetnicellulases can include hemicellulase mixture and
galactomannanase.
Commercial liquid enzymatic compositions containing hemicellulases are
available as
PULPZYMO from Novo, ECOPULP from Alko Biotechnology and NovozymCD 280 and
GamanaseTM, which are both products of Novo Nordisk. The mannanases can be,
for example,
endo-mannanases, such as endo-13-mannanase. Mannanase preparations, for
example, are
commercially available, including types which may be manufactured with the aid
of genetically
modified microorganisms (e.g.. Bacillus- and Trichoderma-types).
[0033] Pectinases comprise endopolygalacturonase, exopolygalacturonase,
endopectate lyase
(transeliminase), exopectate lyase (transeliminase), and endopectin lyase
(transeliminase).
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Commercial liquid enzymatic compositions containing pectinases are available
under the names
PectinexTM Ultra SP and PectinexTm*, both supplied by Novo Nordisk.
[0034] 13-glucanases are comprised of lichenase, laminarinase, and
exoglucanase. Commercial
liquid enzymatic compositions containing 13-glucanases are available under the
names Novozym
234, Cereflog, BAN, Finizym , and Ceremix , all of which are supplied by Novo
Nordisk.
[0035] The enzymes can be commercially obtained in ready-to-use
preparations, from
suppliers such as indicated herein or other suppliers. The enzymes can be a
dry powder or
granulate, a non-dusting granulate, a liquid, a stabilized liquid, or a
stabilized protected enzyme,
or other forms suitable for addition to a fiber slurry or similar fiber-
containing material. Liquid
enzyme preparations may, for instance, be stabilized by adding stabilizers
such as a sugar, a sugar
alcohol or another polyol, and/or lactic acid or another organic acid
according to established
processes. Dry powder forms may be lyophilized and include substrates.
[0036] The enzyme and anionically charged compound(s) components can be
premixed into a
common composition used to treat a pulp, or they can be separately added. If
premixed, an
enzyme preformulated in a liquid composition can be used as the source of the
enzyme combined
with the anionically charged compound(s) component. A cellulolytic enzyme
composition can
contain, for example, from about 5% by weight to about 20% by weight enzyme.
These enzyme
compositions can further contain, for example, polyethylene glycol, hexylene
glycol,
polyvinylpyrrolidone, tetrahydrofuryl alcohol, glycerine, and/or water, and/or
other conventional
enzyme composition additives, as for example, described in U.S. Pat. No.
5,356,800, which is
incorporated herein in its entirety by reference. If enzyme substrates are
present with dry powder
forms of the enzymes, the substrates should not adversely interact with or
interfere with the pulp
treatment or other papermaking processes.
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100371 Other suitable enzymes and enzyme-containing compositions include
those such as
described in U.S. Pat. No. 5,356,800, U.S. Pat. No. 4,923,565, and
International Patent
Application Publication No. WO 99/43780, all incorporated herein in their
entireties by reference.
Other exemplary paper making pulp-treating enzymes are BUZYMEO 2523 and
BUZYMES
2524, both available from Buckman Laboratories International, Inc., Memphis,
Tenn.
100381 The enzyme can be added in an amount, for example, of from about
0.0001% by
weight to about 5% by weight enzyme based on the dry weight of the pulp, or
from about
0.0005% by weight to about 4.5% by weight, or from about 0.001% to about 4% by
weight, or
from about 0.005% to about 3.5% by weight, or from about 0.01% to about 3% by
weight, or
from about 0.05% by weight to about 2.75% by weight, or from about 0.1% by
weight to about
2.5% by weight, or from about 0.2% by weight to about 1.5% by weight, or from
about 0.001% to
about 0.1% by weight, or from about 0.005% to about 0.5% by weight enzyme
based on dry
weight of the pulp, though other amounts can be used. These addition amounts
of the enzyme
relative to pulp can apply to use of pre-mixtures of the enzyme and
anionically charged
compound(s) in a common composition, and also the other addition options
indicated herein for
introducing the enzyme and anionically charged compound(s) separately to pulp
(simultaneously
or sequentially). Any amount, percentage, or proportion of enzyme described
herein can be on an
active enzyme basis. For example, an enzyme amount referred to as 1% by weight
enzyme can
refer to 1% by weight active enzyme.
[0039] The combination of treating the pulp with at least one anionically
charged compound
and at least one enzyme before dewatering beneficially influences the drainage
and dewatering
behavior of the treated pulps. The at least one anionically charged compound
and at least one
enzyme, for example, can be added to pulp sequentially by separate additions
thereof at different
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process locations or at different times at the same process location, or they
can be added
concurrently at least in part at the same process location (e.g., as separate
feeds or as a pre-
mixture). As an option, market pulp can be produced by sequentially adding at
least about 80% up
to 100% by weight of the total added amount of the anionically charged
compound after addition
of the at least one enzyme to the pulp before dewatering the pulp. In such an
option, the enzyme
is given the opportunity to interact first with the pulp fibers before
interactions are made with the
anionically charged compound. The addition of the at least one anionically
charged compound and
at least one enzyme in this sequence can magnify the enhancements in
dewatering performance
that can be achieved. As another option, at least a portion or all of the
anionically charged
compound can be added to the pulp before the enzyme is added to the pulp. With
the present
invention, compared to pulp drainage seen without the addition of any
anionically charged
compound or enzyme, or using just the anionically charged compound alone or
using the enzyme
alone, to the pulp, pulp drainage performance in the production of market pulp
can be
significantly increased, such as by a factor of one, two, or three or more
with processes of the
present invention. Further, as compared to use of only an anionically charged
compound alone or
the use of an enzyme alone, to treat the pulp, drainage efficiencies can be
significantly increased,
such as by about 60% to about 200%, or other increases, by the combined
addition of at least one
anionically charged compound and at least one enzyme to the pulp. In addition,
drainage rates can
be achieved that exceed the sum of the individual drainage rates obtained from
use of the
anionically charged compound alone or the enzyme individually to treat a pulp.
Better drainage in
the wire section of the pulp dryer can lead to reduced moisture of pulp in the
press section, and as
a result, steam consumption in the drying section can be significantly
reduced, which can provide
energy savings. Further, improvements of pulp dewatering provided by treatment
of digested pulp
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with the present invention prior to pulp drying can allow for faster pulp
throughout rates or speeds
in the pulp mill, whereby the productivity of the pulp mill can be increased.
A suitable amount of
pulp dewatering may be provided at a reduced total polymer addition rate as
compared to what
may be predicted as needed if using an anionically charged compound alone.
Free drainage
properties of the pulps treated with the present invention before pulp drying
can demonstrate good
correlations with water retention properties, such as in terms of water
retention values or WRV, of
the treated pulps, which indicates that the treatment can yield reliable
nonrandomized results.
[0040] As an option, the combination of treating the pulp with at least one
anionically charged
compound and at least one enzyme before dewatering in the production of market
pulp is effective
to provide at least one of the following:
(i) increased pulp free drainage (g/90 sec) to a value which is at least
7.5%
greater, or at least 10% greater, or at least 15% greater, or at least 25%
greater, or at least 50%
greater, or at least 75% greater, or at least 100% (one time) greater, or at
least 200% (two times)
greater, or at least 300% (three times) greater, or at least 400% (four times)
greater, or at least
500% (five times) greater, than free drainage value obtained without any
treatment in the pulp;
(ii) increased pulp free drainage to a value which is at least about 3%, or
at least
about 10%, or at least about 30%, or at least about 40%, or at least about
50%, or at least about
60%, or at least about 75%, or at least about 100% greater than free drainage
value obtained
with using the anionically charged compound (e.g., an anionic surfactant)
individually in the
pulp (without the enzyme);
(iii) increased pulp free drainage to a value which is at least about 10%
greater,
or at least about 15% greater, or at least about 20% greater, or at least
about 25% greater, or at
least about 30% greater, or at least about 40% greater, or least about 50%
greater, or at least
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about 60% greater, than a free drainage value calculated as a sum of the free
drainage increases
obtained from using the anionically charged compound (e.g., an anionic
surfactant) and enzyme
separately and individually in the pulp; and
(iv) reducing pulp water retention value (WRV) to a value which is at
least about
10% less, or at least 15% less, or at least about 20% less, or at least about
25% less than WRV
obtained with using the anionically charged compound (e.g., an anionic
surfactant) individually
in the pulp (without the enzyme). In calculating the percentage values for
(i), (ii), (iii), and (iv),
the denominator values of the fractions are based on the values for the pulps
treated with only
one or none of the anionically charged compound or enzyme, and the numerator
values are the
absolute values of the difference between the property value for the dual
treated anionically
charged compound/enzyme treated pulp and the pulp treated with only one or
none of the
anionically charged compound/enzyme. Water removal measurements for (i), (ii),
(iii), and (iv)
can be obtained using a Matek DFR-05 drainage/retention tester. The Matek DFR-
05 drainage
freeness retention simulates the retention and drainage conditions prevailing
in a pulp or paper
machine.
100411 These and/or other effects of the present invention can be provided
by treatment of the
pulp with the one or more anionically charged compounds and one or more
enzymes without the
need for co-addition or the co-presence in the pulp under treatment of any
nonionic or cationically
charged compounds, such as a nonionic surfactant, a cationic surfactant, a
cationic polymer, or a
cationic flocculant. As an option, a pulp slurry undergoing treatment with the
anionically charged
compound and enzyme can be free or essentially free of nonionic surfactant
and/or cationically
charged compounds, since the beneficial effects obtained by the present
invention do not rely on
the co-presence of such nonionic surfactant or cationically charged compounds.
With regard to
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added nonionic surfactants, as an option, the pulp can be treated with less
than 0.1 kg/metric ton
dry fiber, or less than 0.05 kg/metric ton dry fiber, or less than 0.01
kg/metric ton dry fiber, or less
than 0.001 kg/metric ton dry fiber, or less than 0.0001 kg/metric ton dry
fiber or in the absence of
nonionic surfactant, based on total nonionic surfactants. With regard to added
cationically charged
compounds, as an option, the pulp can be treated with less than 0.1 kg/metric
ton dry fiber, or less
than 0.05 kg/metric ton dry fiber, or less than 0.01 kg/metric ton dry fiber,
or less than 0.001
kg/metric ton dry fiber, or less than 0.0001 kg/metric ton dry fiber or in the
absence of cationically
charged compounds (e.g., cationic surfactant(s), cationic polymer(s)),
cationic flocculant(s), and
the like), based on total cationically charged compounds.
[0042] The methods of the present invention can be used to improve
dewatering of pulpable
materials, including cellulosic pulpable materials, noncellulosic pulpable
materials, recycled paper
waste pulpable materials, or any combinations thereof. As an option, the
cellulosic pulpable
materials can be lignocellulosic. The drainage and dewatering improvements due
to the pulp
treatment according to methods and systems of the present invention is not
limited to treating any
particular type of pulp and can find application in all grades of pulp. The
treatable pulps can be
chemical pulps, mechanical pulps, or combinations of these types of pulps. As
an option, the
treatable pulp is a chemical pulp at least in part. The treatable pulp can be
bleached or unbleached
when treated. The treatable pulp can include, for example, Kraft pulp,
dissolving pulp, fluff pulp,
semichemical pulps (e.g., bleached chemothermomechanical pulp or BCTMP),
sulfite pulp, soda
pulp, organosolv pulp, polysulfide pulp, or other pulps, and any combinations
thereof.
Nonchemical mechanical pulps, such as pulps mechanically defibrated only, such
as by use of
disk or conical refmers only for defibration of feedstock, also can be
processed with the indicated
pulp treatment.
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[0043] As used herein, "dried pulp" refers to laid, stacked, piled or
otherwise physically
accumulated pulp which is sufficiently dewatered to be exposed to air and
unsuspended and non-
immersed in aqueous medium.
[0044] "Anionically charged compound" refers to a compound having a net
negative charge
on the molecule in aqueous solution. The anionically charged compound can be
organic or
inorganic. "Organic" means the compound contains at least one C-H bond.
[0045] "Enzyme" refers to a protein that is capable of catalyzing a
chemical reaction.
[0046] "Surfactant" refers to an organic compound which can lower the
surface tension of a
liquid, the interfacial tension between two liquids, or that between a liquid
and a solid.
[0047] "Anionic surfactant" refers to a surfactant having a net negative
charge on the
molecule in aqueous solution. Accordingly, the anionic surfactant can have
only anionic moieties
as the charged groups thereon or may be amphoteric with a net anionic charge
for the overall
molecule.
[0048] "Nonionic compound" refers to a compound that is amphiphilic and has
no charge
group at either terminal end group thereof
[0049] "Nonionic surfactant" refers to a surfactant that is amphiphilic and
has no charge
group at either terminal end group thereof
[0050] "Cationically charged compound" refers to a compound having a net
positive charge
on the molecule in aqueous solution. The cationically charged compound can be
organic or
inorganic.
[0051] "Cationic surfactant" refers to a surfactant having a net positive
charge on the
molecule in aqueous solution. Accordingly, the cationic surfactant can have
only cationic moieties
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as the charged groups thereon or may be amphoteric with a net cationic charge
for the overall
molecule.
[0052] "Cationic polymer" refers to a polymer having a net positive charge
on the molecule in
aqueous solution. Accordingly, the cationic polymer can have only cationic
moieties as the
charged groups thereon or may be amphoteric with a net cationic charge for the
overall molecule.
[0053] "Kraft pulp" refers to chemical wood pulp produced by digesting wood
by the sulfate
process.
[0054] "Fluff pulp" refers to a chemical, mechanical or combination of
chemical/mechanical
pulp, usually bleached, used as an absorbent medium in disposable diapers, bed
pads, and other
hygienic personal products. Fluff pulp is also known as "fluffing" or
"comminution" pulp.
[0055] "Dissolving pulp" refers to a higher purity, special grade pulp made
for processing into
cellulose derivatives including rayon and acetate.
[0056] "Bleached chemothermomechanical pulp" or "BCTMP" refers to bleached
CTMP.
"CTMP" refers to chemical-mechanical pulp produced by treating wood chips with
chemicals
(e.g., sodium sulfite) and steam before mechanical defibration.
[0057] "Unitize" refers to a process by which a plurality of market fibers
can be bundled or
packaged together as a single unitary product for handling.
[0058] "Defibration" refers to separation of wood fibers by mechanical
means, chemical
means, or combinations of both.
[0059] Referring first to FIG. 1, wood chips, or other comminuted
cellulosic or noncellulosic
fibrous material, are fed by line 10 to a continuous digester 12 or one or
several batch digesters
wherein the pulp is subjected to the pulping action of pulping liquor fed
thereto by line 14. This
option can be described, for example, with particular reference to a kraft
process applied to virgin
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lignocellulosic fibrous material, wherein digested and optionally bleached
pulp is treated with an
anionically charged compound or surfactant and enzyme before the kraft pulp is
dried and
unitized. It will be understood that the invention also is applicable to other
pulping procedures
with appropriate modification to take into account the treatment of the pulp
with anionically
charged compound or surfactant and enzyme before the pulp is dried. As an
option, in the lcraft
process, the active pulping chemicals can be sodium hydroxide and sodium
sulfide, which is also
known as white liquor, and these chemicals can be contained in the pulping
liquor fed by line 14.
The digester can operate in batch or continuous manner. There are generally
known variations of
the cooking processes both for the batch and the continuous digesters which
can be applied. In a
continuous digester, for example, the wood chips or other particulated
feedstock materials can be
fed at a rate which allows the pulping reaction to be complete by the time the
materials exit the
reactor. As an option, delignification may require, for example, cooking at
several hours, such as
at about 100 C to about 200 C (266 F to 356 F), or other temperature and
cooking time
conditions suitable for the feedstock and digestion chemicals used for
digestion. Typically, the
finished cooked wood chips are blown by reducing the pressure to atmospheric
pressure. This
releases steam and volatiles. As an option, after the digestion, the resulting
cooked wood pulp
containing residual spent pulping liquor can pass by line 16 to a brown stock
washing zone 18.
The washing zone 18 can be used for washing the digested chips free from
entrained spent
pulping liquor and screening out unwanted material. Screening of the pulp
after pulping can be a
process whereby the pulp is separated from large shives, knots, dirt and other
debris. The "accept"
is the pulp which can be further processed according to the present invention,
and the material
separated from the pulp is "reject." The brown stock from the blowing can go
to washing stages
where the used cooking liquors are separated from the cellulose fibers.
Typically, a pulp mill may
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have multiple washing stages in series. The spent pulping liquor, or black
liquor 15, may be fed to
a recovery and regeneration zone (not shown), which can be operated according
to conventional
methods.
[0060] As an option, the pulp in line 16 can be subjected to washing in the
brown stock
washing zone 17, such as, for example, by successive passage through washers
and screens before
discharge of the unbleached pulp 19 from the brown stock washing zone 17 by
line 18. As an
option, the unbleached pulp can be bleached at a bleach plant 22 before the
resulting bleached
pulp is dried at a pulp dryer 24 to provide market pulp 26. In the bleach
option, unbleached pulp
19 is fed to a bleach plant 22 through line 20. As an option, pulp leaving a
digester wash unit may
retain a dark brown color due to residual lignin content that it is desired to
bleach out, which can
depend on the intended end use. If bleached, conventional bleaching processes
can be used on the
pulp. As an option, in the bleach plant 22, the pulp can be subjected to one
or a plurality of
bleaching, caustic extraction, and washing operations, which can result in
further delignified and
bleached pulp of an increased brightness. The bleaching treatment chemicals
can be, for example,
oxygen gas, ozone, chlorine dioxide, chlorine, peroxide, pure acid or a
suitable alkali for an
extraction step, or a mixture of these, and possibly other bleaching chemicals
or additives. For
example, pairs of chlorine dioxide and caustic extraction towers followed by
pulp washing stages
may be used for bleaching, or other conventional pulp bleaching arrangements
may be applied to
the pulp.
[0061] The bleached pulp can be discharged from the bleach plant 22 by line
23 for passage to
the pulp dryer 24. As another option, as indicated by line 21 in FIG. 1, the
unbleached pulp can be
fed directly from the washing zone 17 to the pulp dryer 24 without any
intervening bleaching of
the pulp. For example, in the case of a plant designed to produce pulp to make
brown sack paper
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or linerboard for boxes and packaging, and the like, the pulp may not need to
be bleached to a
high brightness. The pulp dryer 24 can dewater and thermally dry the bleached
or unbleached pulp
to provide dried pulp in line 25 which is market pulp. The pulp dryer 24 can
include, for example,
a mechanical dewatering section and a thermal drying section, which are
described in further
details and illustrations with respect to other figures herein. The market
pulp 26 can be in the
form of continuous dried pulp sheets, for example, or other dried forms of
pulp discharged from
the pulp dryer 24.
100621 As an option, at least one anionically charged compound and at least
one enzyme are
added to treat the pulp before the pulp is dewatered and dried in pulp dryer
24. As an option,
enzyme can be added to the pulp at feed line 27 and the anionically charged
compound can be
added at feed line 28 at the inlet side of the pulp dryer 24. The addition of
at least one anionically
charged compound and at least one enzyme to the pulp before dryer 24 can
improve dewatering
performance at the dryer 24. As an option, for bleached pulp, at least one
anionically charged
compound and at least one enzyme can be added to the pulp anywhere after the
bleach plant 22
and before dryer 24. As another option, for unbleached pulp, at least one
anionically charged
compound and at least one enzyme can be added to the pulp anywhere after the
digester 12 and
before dryer 24. As an option, the anionically charged compound is added to
the pulp no earlier
than the addition of the enzyme to the pulp. As an option, the anionically
charged compound is
added to the pulp at times which can partially overlap with the addition times
of the enzyme. As
an option, all amounts of the enzyme are added to the pulp before the addition
of all amounts of
the anionically charged compound to the pulp. As an option, about 80% to 100%,
or from about
85% to 100%, or from about 90% to 100%, or from about 95% to 100% by weight,
of the total
weight amount of enzyme is added to the pulp prior to the earliest adding of
the anionically
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charged compound to the pulp. Additional details and illustrations on the
addition of the indicated
treatment compounds to the pulp before the dryer are provided in discussions
of other figures
herein.
[0063] The market pulp 26 discharged from pulp dryer 24 optionally can be
unitized at station
or stations 29. As an option, to unitize the market pulp, the dried pulp from
the pulp dryer is
formed into bales or rolls, or other securable large scale units of the pulp
fibers. The mode of
unitization of the market pulp is not necessarily limited as long as a bale,
roll or other bundle of
dried pulp fibers is secured together as a single unitary product for
transport and handling. As an
option, continuous dried pulp sheets can be produced by the pulp dryer which
can be formed into
bales or rolls. As an option, continuous dried pulp sheets formed at a pulp
dryer can be cut into
pieces and stacked into bales. The pulp bales can be compressed, wrapped, and
tied into secure
bundles for storage and transport. Both sheeted bales and flash dried bales
can be unitized for
handling and shipment. As an option, the unitizing can comprise wire or strap-
tying bales of cut
sheets of the dried pulp, or wire or strap-tying flash-dried bales of the
dried pulp. For example, as
an option, a unit of about 7 to 9 bales can be securely wire-tied with 6 to 9
strands of heavy steel
wire. The unitized sheeted bales or flash dried bales of dried pulp provide
unitized market pulp. A
sheeted bale may have a weight of about 250 kg or other weights, which may
measure
approximately 27 to 32 inches wide, 35 to 37 inches long, and 17 to 18 inches
high, or other
dimensions. Flash dried bales that are less densely pressed also may be
provided which may
weigh about 195 to about 200 kg, or other weights. Other sizes and weights of
bales of dried pulp
may be unitized. As another option, as indicated, market pulp can be unitized
as rolls or reels. For
example, rolls of the market pulp can be formed which may measure from about 7
to about 55
inches in width and from about 58 to 60 inches in diameter, or other
dimensions. The rolls of
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pulp optionally can be wrapped with removable cover sheeting, wire or strap
tied, or both. As an
option, the market pulp can be stored and/or transported in a non-unitized or
a unitized form to
paper mills which are on-site or off-site with respect to the pulp mill where
the market pulp is
produced. The market pulp can be used in paper manufacture, such as by
reslurrying the dried
pulp for papermaking processing or other uses.
100641 FIG. 2 shows further details on a portion of a bleached pulp dryer
224 and an
associated pulp feeding and pretreatment system according to an option of the
present invention.
Bleached pulp is drawn from one or more bleach towers 222A, 222B at the bleach
plant (e.g.,
bleach plant 22 in FIG. 1), and transmitted through line 223 to a surge chest
227 and from there to
a machine chest 229. The bleached pulp can be mixed in surge chest 227 until a
substantially
uniform dispersion is achieved. The bleached pulp in surge chest 227 can be
transmitted to the
machine chest 229. The machine chest 229 can be a consistency leveling chest
which provides a
retention time for the pulp which can be enough to allow variations in
consistency entering the
chest to be leveled out in a generally known manner. The pulp contents of the
machine chest 229
can be feed into a pulp dryer section 224 via a machine chest pump 231.
100651 The pulp dryer section 224 can include a mechanical dewatering
section 224A and a
thermal drying section (not shown in this figure). Of these sections, only a
portion of the
mechanical dewatering section 224A is shown in FIG. 2 with additional
information on this
section and other subsequent processing sections provided in the discussion of
other figures
herein. As an option, the pulp pumped from the machine chest pump 231 can be
mixed and
diluted with white water 233 from a white water silo 201 to form a stream of
diluted pulp 226.
The pulp 226 is pumped by pump 203 through a centiscreen 235 to a head box 205
from which
pulp is sprayed or otherwise deposited onto wire 207. As an option, the pump
203 can be a
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centrifugal pump known as a fan pump. The pulp 208 collected on the wire 207
is advanced onto
a wet press (not shown) for further dewatering of process water, and then
thermal drying and
unitization, which are described in greater detail with respect to other
figures herein. As an option,
the white water silo 201 can form part a white water recirculation loop
including lines 206 and
233 and silo 201, such as shown in FIG. 2, which is integrated with the
mechanical dewatering
section 224A of the pulp dryer 224. For example, filtrate 206, also referred
to herein as the white
water, which is drained from the wire 207 can be recirculated to the white
water silo 201 for reuse
as the whitewater 233 combined with fresh pulp to form the combined stream of
pulp 226.
[0066] The treatment of the pulp 226 can include one or more introduction
point or points for
each of the at least one anionically charged compound and at least one enzyme,
before the
resulting treated 236 pulp reaches the head box 205 and wire 207. As an
option, the anionically
charged compound is added to the pulp before the enzyme, such as illustrated
in FIG. 2. For
example, the enzyme can be added at the inlet side of the fan pump 203 using
feeding device 202,
and the anionically charged compound can be added at the discharge side of the
fan pump 203
using feeding device 204. As an option, this sequence of addition of at least
one anionically
charged compound and at least one enzyme can be provided at other locations
between the bleach
towers 222A, 222B and the head box 205 of the mechanical dewatering section
224A. As
indicated, the wet fiber sheet formed from the treated pulp as collected on
the wire 207 can be
further drained and mechanically pressed as part of the mechanical dewatering
section, and then
the screened and pressed pulp can be thermally dried, before the resulting
dried pulp is conveyed
to a unitizing station or stations.
[0067] Referring to FIG. 3, as an option, digested and optionally bleached
pulp slurry 323 is
combined with white water from a white water silo 306 and the resulting
diluted pulp 326 can be
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pumped via a fan pump 303 to head box 305. As an option, enzyme from supply
and feeding
device 302 can be added to the pulp 326 at the inlet side of the pump 303 and
anionically charged
compound from supply and feeding device 304 can be added at the outlet side of
the fan pump
303. The at least one anionically charged compound and at least one enzyme can
interact with
pulp fibers and contents while the pulp is fed towards the head box by the
pumping action of the
fan pump and before being discharged from the head box onto the wire or screen
for dewatering.
The at least one anionically charged compound and at least one enzyme can
interact with pulp
fibers sufficient to significantly improve drainage and dewatering
efficiencies of the pulp on the
wire as compared to the same pulp without at least one anionically charged
compound and at least
one enzyme or the pulp treated with only one of at least one anionically
charged compound and at
least one enzyme.
[0068] From the headbox 305, the pulp can be sprayed onto wire 307 where
the pulp slurry is
dewatered and forms a wet sheet of pulp fiber. As an option, the pulp can be
supplied to the
headbox at consistencies between 0.1% and 5% solids, or from about 0.5% to
about 3% solids, or
from about 1% to about 2.5% by weight solids. The pH of the treated pulp
supplied to head box
305 can be, for example, from about 4 to about 9, or from about 4.5 to about
8.0, and can be
controlled within these ranges with addition of pH modifiers, if desired or
necessary. As an
option, the pulp can exit the headbox 305 through a rectangular opening of
adjustable height
called the slice, which stream lands and spreads on wire 307. The wire may be
a foraminous
continuous metal screen or plastic mesh which travels in a loop. The wire can
be, for example, a
flat wire Fourdrinier, a twin wire former, or any combinations of these. Low
vacuum boxes and
suction boxes may be used with the wire in conventional manners. As an option,
the sheet
consistency of the pulp after dewatering on the wire may be for example, from
about 2% to about
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35%, or from about 10% to about 30% by weight, based on % solids content, or
other values.
Conventional wire or screen devices for dewatering pulp may be adapted for use
in the methods
and systems of the present invention. The filtrate portion 306, also referred
to herein as white
water, which is drawn and drains through the wire 307 can be recirculated to
the white water silo
301, as indicated, and then can be combined with fresh pulp 323 before the
resulting diluted pulp
326 is pumped to the head box 305.
[0069] The pulp 308 which is collected on wire 307 can be passed forward to
a wet-press
section 309. Additional water can be pressed and vacuumed from the pulp 308 at
wet-press
section 309. As an option, press section 309 can remove water from the pulp
with a system of
nips formed by rolls pressing against each other aided by press felts that
support the pulp sheet
and can absorb the pressed water. A vacuum box, such as a Uhle box, optionally
can be used, for
example, to apply vacuum to the press felt to remove the moisture so that when
the felt returns to
the nip on the next cycle, it does not add moisture to the sheet. As an
option, the pulp sheet can be
passed through a series of rotating rolls ("presses") that squeeze out water
and air until the fiber
consistency of the pulp sheet is from about 40% to about 50% by weight. As an
option, the
pressed pulp can comprise up to about 50% solids after pressing, or from about
20% to about 45%
solids, or other values.
[0070] The screened and pressed pulp 310 can be moved to a thermal dryer
section 311 for
evaporative drying. Heat can be used at thermal dryer section 311 to remove
additional water,
such as by evaporation. As an option, the pulp 310 can be dried in the thermal
dryer section 311 at
a temperature in the range of 60 C to 127 C (140 F to 260 F) to remove more
water. As an
option, the thermal dryer can have, for example, a series of internally steam-
heated cylinders that
evaporate the moisture of the pulp as the pulp is advanced over the heated
cylinders. As an option,
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a pressed pulp sheet can be floated through a multi-story sequence of hot-air
dryers until the
consistency is from about 80% to about 97% by weight consistency, or from
about 85% to about
95% by weight, or other values. As an option, the dried pulp leaving the pulp
dryer has an
absolute moisture content (i.e., total H20 content based on total weight of
pulp) of less than about
20% by weight, or less than about 15% by weight, or less than about 10% by
weight, or from
about 5% to about 20% by weight, or from about 5% to about 10% by weight. For
example, dried
pulp containing 12 total parts by weight water (all forms) and 100 parts by
weight dry pulp fiber
has an absolute moisture content of 10% by weight (i.e., 12/(12+100)*100).
[0071] The dried pulp 325 exiting the thermal dryer 311 is market pulp 326.
As an option,
market pulp 326 provided by the thermal drying can be in the form of
continuous dried pulp
sheets. The market pulp 326 can optionally be unitized at station or stations
327 as in FIG. 1 to
obtain a unitized market pulp 329 (e.g., bales, rolls, or other forms).
[0072] As an option, the indicated at least one anionically charged
compound and at least one
enzyme used to treat the pulp to improve dewatering performance can be water
soluble or water
dispersible compounds.
[0073] As an option, inorganic anionic coagulants can be used, such as
polyphosphates,
anionic silica sol, or any combinations thereof.
[0074] As an option, at least one anionically charged compound can be added
to the pulp in
processes of the present invention, such as at the approach to the pulp dryer
as illustrated or
elsewhere after any bleaching and before the pulp dryer, in an amount from
about 0.1 lb. to about
pounds (lb.) anionically charged compound/ton dry fiber, or from about 0.2 to
about 8 lb.
charged compound/ton dry fiber, or from about 0.3 to about 4 lb. anionically
charged
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compound/ton dry fiber, or from about 0.5 to about 3 lb. anionically charged
compoundAon dry
fiber (on a solids/solids basis).
[0075] The enzyme can be added to pulp in an amount from about 0.001 to
about 2 pounds
(lb.) active enzyme/ton dry fiber, or from about 0.01 to about 1.5 lb./ton dry
fiber, or from about
0.1 to about 1 lb./ton dry fiber, or other amounts.
[0076] As an option, at least one anionically charged compound and at least
one enzyme can
be added to the pulp in a total amount of from about 0.2 lb./ton dry fiber to
about 12 lb./ton dry
fiber, or from about 0.4 to about 10 lb./ton dry fiber, or from about 0.6 to
about 8 lb./ton dry fiber,
or from about 1 to about 6 lb./ton dry fiber (on a solids/solids basis), or
other values. As an option,
at least one anionic compound and at least one enzyme can be added to the pulp
in a weight ratio
(w:w) of from about 10,000:1 to 1:10, or from about 1000:1 to about 1:5, or
from about 100:1 to
about 1:1, or from about 10:1 to about 2:1, or other ratios.
[0077] Wood chips suitable for use in the production of market pulp in the
present invention
can be derived from hardwood tree species, softwood tree species, or
combinations thereof.
Softwood tree species include, but not limited to: fir (such as Douglas fir
and balsam fir), pine
(such as Eastern white pine and Loblolly pine), spruce (such as white spruce),
larch (such as
Eastern larch), cedar, and hemlock (such as Eastern and Western hemlock).
Examples of
hardwood tree species include, but are not limited to: acacia, alder (such as
red alder and
European black alder), aspen (such as quaking aspen), beech, birch, oak (such
as white oak), gum
trees (such as eucalyptus and sweet gum), poplar (such as balsam poplar,
Eastern cottonwood,
black cottonwood, and yellow poplar), maple (such as sugar maple, red maple,
silver maple, and
big leaf maple). These types of woods can be used individually or in any
combinations thereof. As
an option, a combination of hemlock and cottonwood particulates can be used.
As an option, the
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wood chips to be pulped include virgin wood material, such as at least 50% by
weight up to 100%
by weight virgin wood material. As an option, other pulpable material may be
used or included in
the feedstock, such as recycled fiber materials, such as recycled fiber from
post-consumer waste,
or non-wood materials, such as grasses, agricultural residues, bamboo, Bast
materials (e.g.,
Ramie, flax, hemp), or any combinations thereof.
[0078] In addition to at least one anionically charged compound and at
least one enzyme, the
pulps may be treated with one or more optional additives within the market
pulp making system
as long as they do not interfere with the indicated function of at least one
anionically charged
compound and at least one enzyme to improve dewatering performance of the
treated pulps. A list
of optional chemical additives that can be used in conjunction with the
present invention include,
for example, pH modifiers, dry strength agents, wet strength agents, softening
agents, debonding
agents, adsorbency agents, sizing agents, dyes, optical brighteners, chemical
tracers, opacifiers,
dryer adhesive chemicals, and the like. Additional optional chemical additives
may include, for
example, pigments, emollients, humectants, viricides, bactericides, buffers,
waxes,
fluoropolymers, odor control materials and deodorants, zeolites, perfumes,
vegetable and mineral
oils, polysiloxane compounds, other surfactants, moisturizers, UV blockers,
antibiotic agents,
lotions, fungicides, preservatives, aloe-vera extract, vitamin E, or the like.
Suitable optional
chemical additives can be retained by the pulp fibers and may or may not be
water soluble or
water dispersible. As indicated, cationically charged compounds are not
required to be
additionally added or present in a pulp treatment of the present invention
which uses at least one
anionically charged compound and at least one enzyme to obtain improvements in
dewatering
performance.
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[0079] As indicated, the combined treatment of the pulp with the at least
one anionically
charged compound and at least one enzyme can provide significantly higher
dewatering
performance than when using either single chemistry treatment. In some
options, though
correlation of water retention with free drainage can vary with ionically
charged compound type
and application process, free drainage generally can demonstrate good
correlation with water
retention. In some options, increasing the dosage of the ionically charged
compounds in the pulp
can slightly reduce WRV and increase dewatering wherein the improvements
ultimately can peak
or level off with progressively increased dosages.
[0080] A market pulp product can be provided that includes the market pulp
or unitized pulp
which has at least one anionically charged compound and at least one enzyme
retained at least in
part to the pulp fibers from the indicated treatment method. The market pulp
made in processes
according to the present invention can comprise, for example, from about 0.001
to about 5 pounds
(lb.) anionically charged compound/ton dry fiber, or from about 0.01 to about
3 lb. anionically
charged compound/ton dry fiber, or from about 0.1 to about 2 lb. anionically
charged
compound/ton dry fiber, or from about 0.2 to about 1 lb. anionically charged
compound/ton dry
fiber (on a solids/solids basis), and the enzyme can be contained in the
market pulp in an amount
of from about 0.000001 lb. to about 1 lb./ton dry fiber or from about 0.00001
lb. to about 0.1
lb./ton dry fiber.
[0081] In an industrial situation where market pulp is produced, a large
capital expenditure to
build a massive steam-operated dryer usually is needed. Once that is in place,
a large amount of
energy is required to remove the water from the pulp. An improvement in the
water removal from
the fiber pad, as can be provided by the present invention, can be leveraged
to benefit the producer
in several ways. If a sheet with less moisture enters the dryer, less steam is
required to dry the
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sheet to the point where it can be shipped. At the same time, an alternative
is to limit the reduction
in steam usage and instead speed up the machine. The benefit then is an
increase in production,
which can be provided by the present invention.
[0082] The present invention will be further clarified by the following
examples, which are
intended to be only exemplary of the present invention. Unless indicated
otherwise, all amounts,
percentages, ratios and the like used herein are by weight.
EXAMPLES
Example 1:
[0083] Experiments were conducted to compare water drainage of pulp treated
using an
anionic surfactant alone, an enzyme alone, and their combination as added to
the pulp and also a
separate combination of the anionic surfactant with a different enzyme, and
water drainage of
untreated pulp.
[0084] A laboratory test was conducted for the evaluation. As indicated,
separate experiments
were run on pulps to compare the effects of using the anionic surfactant and
an enzyme
individually and in combinations of the anionic surfactant and an enzyme. A
control test also was
conducted with no chemical additive used on the pulp.
[0085] The enzymes used for these experiments were BLX-14303 from Buckman
Laboratories, containing a xylanase enzyme as the active component ("enzyme
X"), and BLX-
14350 from Buckman Laboratories, containing a completely different xylanase
enzyme as the
active component ("enzyme Y"). The anionic surfactant was sodium lauryl ether
sulfate (3 moles
EO), which was used in an aqueous solution at a 30% (wt.) concentration of the
anionic
surfactant. The dosage rate of anionic surfactant used was 2 g of anionic
surfactant/kg dry fiber
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pulp. The dosage rate of enzyme, for each of enzyme X and enzyme Y, was 1 g of
enzyme/kg dry
fiber pulp.
[0086] The following testing procedure was applied. A slurry of bleached
pulp to be tested
was prepared with a consistency of about 1 percent by weight in tap water.
Water removal from
the slurry was evaluated using a Miitek DFR-05 drainage/retention tester. A
selected volume of
this slurry (500 mL) was added into a chamber which has a screen at the
bottom. Any anionic
surfactant and/or enzyme included in a test sample was pre-mixed with the
slurry before addition
to the chamber. The screen was a metallic mesh screen (mesh size = 600 mesh).
When the test
was initiated, the water was allowed to drain from the slurry through the
screen. The amount of
water that drained freely from the sample, and the rate of drainage was
monitored. No vacuum nor
pressure was applied for the first 30 seconds after initiating drainage from
the chamber. At 30
seconds after the drainage is initiated, the testing apparatus (i.e., a DFR
with forced dewatering
(controlled mechanical level)) was used to apply pressure to the pad (i.e.,
the fiber mat collected
on the screen). Again the rate of water being removed from the pad was
measured. At 50 seconds
additional pressure was applied, and at 70 seconds again additional pressure
was applied. This
procedure, including the amount of pressure applied at each stage, mimics the
dewatering and
pressing that occurs on a paper machine or on a pulp dryer. Free drainage
rates in g/30 sec and
g/90 sec were determined based on the measurements.
[0087] The results of these experiments are shown in Tables 1 and 2. Table
1 below shows
raw data from a set of tests, and Table 2 shows the deviations in results for
the samples which
contained an anionic surfactant, an enzyme, or both, from the control. The
numbers in Tables 1
and 2 are grams of water drained from a sample. The result after 30 seconds is
free drainage, 30
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seconds after drainage is initiated. The result after 90 seconds is for the
total water removed after
free drainage and 3 additional pressings.
Table 1 ¨ raw data
Time
Sample 30 sec. 90 sec.
Control 345 385.5
anionic surfactant A (30%) 349 404.5
anionic surfactant A (30%) +
358 419
enzyme X
anionic surfactant A (30%) +
359 420.5
enzyme Y
enzyme Y 348.5 387
Table 2 ¨ water removal: change vs. control
30 sec. 90 sec.
anionic surfactant A (30%) 4 19
anionic surfactant A (30%) +
13 33.5
enzyme X
anionic surfactant A (30%) +
14 35
enzyme Y
enzyme Y 3.5 1.5
[0088] These experimental results show that treating a pulp slurry with the
combination of
anionic surfactant and enzyme, e.g., a cellulolytic or hemicellulolytic
enzyme, together provides
an unexpected better-than-additive result to improve the removal of water. It
is apparent from the
data that the combination provides a synergistic effect on water removal, much
better than either
treatment alone, and much better than the additive effect expected.
Example 2:
[0089] An additional experiment was conducted to compare water removal from
pulp treated
using an anionic surfactant alone, an enzyme alone, and their combination as
added to the pulp
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and also a separate combination of the anionic surfactant with a different
enzyme, and water
drainage of untreated pulp.
[0090] The laboratory test conducted is similar to that shown in Example 1.
Again, separate
experiments were run on pulps to compare the effects of using the anionic
surfactant and an
enzyme individually and in combinations of the anionic surfactant and an
enzyme. A control test
also was conducted with no chemical additive used on the pulp.
[0091] The enzyme used for these experiments was a formula prepared from
enzyme NS-
51121 available from Novozymes ("enzyme"), which contains a xylanase enzyme,
and an anionic
surfactant (sodium lauryl ether sulfate (3 moles EO) (designated
"surfactant"), which was used in
an aqueous solution in a 30% active aqueous formula. The dosage rate of
anionic surfactant used
was 2 g of 30% active formula/kg of dry fiber pulp. The dosage rate of enzyme
was 1 g of enzyme
formula/kg of dry fiber pulp.
[0092] The testing procedure applied is as described in Example 1. A slurry
of bleached pulp
to be tested was prepared with a consistency of about 1 percent by weight in
tap water. A selected
volume of this slurry (500 mL) was added into a chamber which has a screen at
the bottom. Any
anionic surfactant and/or enzyme included in a test sample was pre-mixed with
the slurry before
addition to the chamber. When the test was initiated, the water was allowed to
drain from the
slurry through the screen. The amount of water that drained freely from the
sample, and the rate of
drainage was monitored. No vacuum nor pressure was applied for the first 30
seconds after
initiating drainage from the chamber. At 30 seconds after the drainage is
initiated, pressure was
applied to the pad, followed by pressure applied again at 50 seconds, and once
more at 70 seconds.
The rate of water being removed from the pad was measured. Total water removed
from the pad
was measured.
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[0093] The results of these experiments are shown in Figures 4 and 5.
Figure 4 records the
total water removed from the sample through the 90-second test. From the
results, the addition of
the surfactant improves water removal, and the application of the enzyme also
improves water
removal. The data also show that there is a difference in the effect from the
enzyme compared to
that for the surfactant. The data also demonstrate that with the combination
of enzyme and
surfactant, the total water removed is greater than the benefit that can be
achieved with either
component alone. Further, there is some difference in the effect of each
component. The enzyme
provides the effect of faster initial ("free") drainage. The advantage of this
effect is that more
water is removed prior to the presses. The surfactant provides the advantage
of better water
removal in the pressing. The combination of the two mechanisms provide the
best result.
[0094] These same data are shown in Figure 5. The total water removed at
the 8-second point
shows the effect on initial free drainage. The total at the 30-second point is
the final free drainage.
The positive effect especially of the enzyme is shown. The final measurement
at the 90-second
point gives the total water removed. For reference, the initial total volume
of water is 495 mL.
[0095] The benefit of this invention is demonstrated another way in Table
3. The "fmal pad
consistency" is the percent fiber in the fmal pad after pressing. The goal is
to maximize the pad
consistency. If less water remains after pressing, less heat and steam is
required to dry the pad to
its final specification. A general rule on a pulp dryer is that a 1 percent
increase in pad
consistency entering the drying process results in a 4 percent reduction in
energy required to dry
the pad. Addition of surfactant alone or enzyme alone give similar benefits,
but the combination
gives a much better result.
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Table 3
final pad consistency % improvement
Blank 4.90
surfactant only 5.78 18
enzyme only 5.68 16
surfactant + enzyme 6.06 24
[0096] Again, these experimental results show that treating a pulp slurry
with the combination
of anionic surfactant and enzyme, e.g., a cellulolytic or hetnicellulolytic
enzyme, together provides
an unexpected better-than-additive result to improve the removal of water. It
is apparent from the
data that the combination provides a synergistic effect on water removal, much
better than either
treatment alone, and much better than the additive effect expected.
[0097] The present invention includes the following
aspects/embodiments/features in any
order and/or in any combination:
1. The present invention relates to a method for producing market pulp,
comprising:
forming cellulosic particulates into pulp;
adding at least one anionically charged compound and at least one enzyme to
said pulp
to provide treated pulp;
mechanically dewatering said treated pulp to provide mechanically dewatered
pulp; and
thermally drying said mechanically dewatered pulp to form market pulp.
2. The method of any preceding or following embodiment/feature/aspect,
wherein at least
part of said adding of said enzyme to said pulp occurs prior to said adding of
said anionically
charged compound to said pulp.
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3. The method of any preceding or following embodiment/feature/aspect,
wherein about
80% to 100% by weight of said adding of said enzyme to said pulp occurs prior
to said adding
of said anionically charged compound to said pulp.
4. The method of any preceding or following embodiment/feature/aspect,
wherein the
anionically charged compound is an organic anionically charged compound.
5. The method of any preceding or following embodiment/feature/aspect,
wherein the
enzyme is a hydrolytic enzyme.
6. The method of any preceding or following embodiment/feature/aspect,
further
comprising bleaching the pulp after the pulp forming and before the adding of
the anionically
charged compound and enzyme to said pulp.
7. A method for producing market pulp, comprising:
forming cellulosic particulates into pulp;
adding at least one anionic surfactant and at least one enzyme to said pulp to
provide
treated pulp;
mechanically dewatering said treated pulp to provide mechanically dewatered
pulp; and
thermally drying said mechanically dewatered pulp to form market pulp.
8. The method of any preceding or following embodiment/feature/aspect,
wherein at least
part of said adding of said enzyme to said pulp occurs prior to said adding of
said anionic
surfactant to said pulp.
9. The method of any preceding or following embodiment/feature/aspect,
wherein about
80% to 100% by weight of said adding of said enzyme to said pulp occurs prior
to said adding
of said anionic surfactant to said pulp.
10. The method of any preceding or following embodiment/feature/aspect,
further
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comprising bleaching the pulp after the pulp forming and before the adding of
the anionic
surfactant and enzyme to said pulp.
11. The method of any preceding or following embodiment/feature/aspect,
wherein the
anionic surfactant is a sulfate surfactant, a sulfonate surfactant, a
sulfosuccinate surfactant or
any combinations thereof.
12. The method of any preceding or following embodiment/feature/aspect,
wherein the
anionic surfactant is an alcohol sulfate, an alcohol alkoxy sulfate, a
sulfonate, a dialkyl
sulfosuccinate, an sulfosuccinic acid ester with an ethoxylated alcohol, or a
soluble or dispersible
salt thereof, or any combinations thereof.
13. The method of any preceding or following embodiment/feature/aspect,
wherein the
enzyme is cellulase, hemicellulase, pectinase, cellobiase, xylanase,
mannanase, 13-glucanase,
carboxymethylcellulase, amylase, glucosidase, galactosidase, laccase, or any
combinations
thereof.
14. The method of any preceding or following embodiment/feature/aspect,
wherein said
forming provides kraft pulp, sulfite pulp, fluff pulp, dissolving pulp,
bleached
chemothermomechanical pulp, or any combinations thereof.
15. The method of any preceding or following embodiment/feature/aspect,
further
comprising bleaching the pulp after the pulp forming and before the adding of
the anionic
surfactant and enzyme to said pulp.
16. The method of any preceding or following embodiment/feature/aspect,
wherein said
mechanically dewatering comprises screening and pressing of the pulp, wherein
drained white
water from said screening is combined with fresh pulp and pumped with a fan
pump to a head
box for the screening, wherein said enzyme is fed into the combined fresh pulp
and white water
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before entering the fan pump, and said anionic surfactant is fed into said
combined fresh pulp
and white water after exiting said fan pump and before reaching the headbox.
17. The method of any preceding or following embodiment/feature/aspect,
wherein the
anionic surfactant and enzyme are added to the pulp in a ratio of from about
10,000:1 to about
1:10.
18. The method of any preceding or following embodiment/feature/aspect,
wherein the
anionic surfactant is added to the pulp in an amount of from about 0.1 lb./ton
dry fiber to about
lb./ton dry fiber, and the enzyme is added to the pulp in an amount of from
about 0.001
lb./ton dry fiber to about 2 lb./ton dry fiber.
19. The method of any preceding or following embodiment/feature/aspect,
further
comprising unitizing said market pulp to form unitized market pulp.
20. The method of any preceding or following embodiment/feature/aspect,
wherein the
cellulosic particulates are hardwood chips, softwood chips, recycled paper
fiber, or any
combinations thereof.
21. The method of any preceding or following embodiment/feature/aspect,
wherein the
combination of treating the pulp with the at least one anionic surfactant and
at least one enzyme
before dewatering in the production of market pulp is effective to provide at
least one of the
following:
(i) increased pulp free drainage (g/90 sec) to a value which is at least
7.5%
times greater than free drainage value obtained without any treatment in the
pulp;
(ii) increased pulp free drainage to a value which is at least about 3%
greater
than free drainage value obtained with using the anionic surfactant
individually in the pulp
(without the enzyme);
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(iii) increased pulp free drainage to a value which is at least about 10%
greater
than a free drainage value calculated as a sum of the free drainage increases
obtained from
using the anionic surfactant and enzyme separately and individually in the
pulp; and
(iv) reducing pulp water retention value (WRV) to a value which is at least
about
10% less than WRV obtained with using the anionic surfactant separately and
individually in
the pulp (without the enzyme).
22. The method of any preceding or following embodiment/feature/aspect,
wherein the
treating is effective for increasing obtained free drainage to a value which
is at least five times
greater than free drainage value obtained without any treatment of the pulp.
23. The method of any preceding or following embodiment/feature/aspect,
wherein the
treating is effective for increasing obtained free drainage to a value which
is from about 60% to
about 200% greater than free drainage value obtained with using the anionic
surfactant
individually in the pulp.
24. A market pulp made by the method of any preceding or following
embodiment/feature/aspect containing said anionically charged compound and
said enzyme.
25. A market pulp made by the method of any preceding or following
embodiment/feature/aspect containing said anionic surfactant and said enzyme.
26. A system for producing market pulp comprising:
a supply of cellulosic particulates;
at least one pulp forming unit for forming pulp from said cellulosic
particulates;
at least one feeding device for feeding at least one anionically charged
compound to said
pulp;
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at least one feeding device for feeding at least one enzyme to said pulp to
provide
treated pulp after addition of both the anionically charged compound and the
enzyme;
a mechanical dewatering device for mechanically removing water from said
treated pulp
to provide mechanically dewatered pulp; and
a thermal drying device for thermally removing water from said mechanically
dewatered
pulp to provide market pulp.
27. The system of any preceding or following embodiment/feature/aspect,
wherein said at
least one feeding device for feeding anionically charged compound feeds
anionic surfactant and
said at least one feeding device for feeding enzyme feeds hydrolytic enzyme.
28. The system of any preceding or following embodiment/feature/aspect,
wherein said pulp
forming unit is a digester capable of receiving at least one chemical for
digesting the cellulosic
particulates.
29. The system of any preceding or following embodiment/feature/aspect,
wherein said
mechanical dewatering device comprises screen and press sections, wherein
drained white
water from the screen section is combinable with fresh pulp and pumpable with
a fan pump to a
head box of the mechanical dewatering device, wherein said at least one
feeding device for said
enzyme is capable of feeding said enzyme into the combined fresh pulp and
white water before
entering said fan pump, and said at least one feeding device for said
anionically charged
compound is capable of feeding said anionically charged compound into said
combined fresh
pulp and white water after exiting said fan pump and before reaching the
headbox.
30. The system of any preceding or following embodiment/feature/aspect,
further
comprising a bleaching unit for bleaching the pulp after the pulp forming unit
and before the
adding of the anionically charged compound and enzyme to said pulp with said
feeding devices.
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31.
The system of any preceding or following embodiment/feature/aspect, wherein
the first
and second feeding devices being capable of introducing respective first and
second amounts of
the anionically charged compound and enzyme to pulp drawn from the pulp
forming unit to
provide at least one of the following:
(i) increased pulp free drainage (g/90 sec) to a value which is at least
7.5%
times greater than free drainage value obtained without any treatment in the
pulp;
(ii) increased pulp free drainage to a value which is at least about 3%
greater
than free drainage value obtained with using the anionically charged compound
individually in
the pulp (without the enzyme);
(iii) increased pulp free drainage to a value which is at least about 10%
greater
than a free drainage value calculated as a sum of the free drainage increases
obtained from
using the anionically charged compound and enzyme separately and individually
in the pulp;
and
(iv) reducing pulp water retention value (WRV) to a value which is at least
about
10% less than WRV obtained with using the anionically charged compound
individually in the
pulp (without the enzyme).
[0098]
The present invention can include any combination of these various features or
embodiments above and/or below as set forth in sentences and/or paragraphs.
Any combination of
disclosed features herein is considered part of the present invention and no
limitation is intended
with respect to combinable features.
[0099]
Applicant specifically incorporates the entire contents of all cited
references in this
disclosure. Further, when an amount, concentration, or other value or
parameter is given as either
a range, preferred range, or a list of upper preferable values and lower
preferable values, this is to
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be understood as specifically disclosing all ranges formed from any pair of
any upper range limit
or preferred value and any lower range limit or preferred value, regardless of
whether ranges are
separately disclosed. Where a range of numerical values is recited herein,
unless otherwise stated,
the range is intended to include the endpoints thereof, and all integers and
fractions within the
range. It is not intended that the scope of the invention be limited to the
specific values recited
when defining a range.
[00100] Other embodiments of the present invention will be apparent to
those skilled in the art
from consideration of the present specification and practice of the present
invention disclosed
herein. It is intended that the present specification and examples be
considered as exemplary only
with a true scope and spirit of the invention being indicated by the following
claims and
equivalents thereof.
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