US20190284760A1

US20190284760A1 - Method And System For Producing Market Pulp And Products Thereof

Info

Publication number: US20190284760A1
Application number: US16/293,678
Authority: US
Inventors: Philip M. Hoekstra; Srinivas Hanumansetty
Original assignee: Buckman Laboratories International Inc
Current assignee: Buckman Laboratories International Inc
Priority date: 2018-03-15
Filing date: 2019-03-06
Publication date: 2019-09-19
Also published as: CN111868328A; BR112020018123A2; JP2021518492A; ZA202005145B; EP3743558A1; AU2019236073A1; CA3092934A1; WO2019177826A1; MX2020009594A

Abstract

Methods and systems are provided for producing market pulp which include treatment of pulp before pulp drying. An anionically charged compound and enzyme are used to treat pulp before pulp drying to improve pulp dewatering performance and efficiency in the production of market pulp. Market pulp products containing the treatment compounds are also described.

Description

This application claims the benefit under 35 U.S.C. § 119(e) of prior U.S. Provisional Patent Application Nos. 62/643,224, filed Mar. 15, 2018, and 62/702,395, filed Jul. 24, 2018, which are incorporated in their entireties by reference herein.

BACKGROUND OF THE INVENTION

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.
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.
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 U.S. Pat. No. 8,916,024, pulp is treated with a combination of cationically and anionically charged compounds 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. Pat. 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.
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

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.
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.
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.
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.
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.
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.
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.
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 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.
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.
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.
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

FIG. 1 is a process flow chart for producing market pulp according to an example of the present application.

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.

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.

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.

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.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

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.
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 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.
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.
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 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 C4-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.
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, β-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).
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 plants. The pectinases generally are enzymes involved in the degradation of pectin, a carbohydrate whose main component is a sugar acid. β-glucanases are enzymes involved in the hydrolysis of β-glucans which are also similar to cellulose in that they are linear polymers of glucose.
The following paragraphs provide examples of enzymes that can be used alone or in any combination in the present invention.
Endo-cellulases that can be used, for example, are endoglucanase with binding domain (e.g., NOVOZYM® 476, Novozymes), endoglucanase enriched with high cellulase units (e.g., NOVOZYM® 51081, Novozymes), or combinations thereof, or other known or useful endo-cellulases.
Liquid enzymatic compositions containing cellulases are available under the names Celluclast® and Novozym® 188, which are both supplied by Novo Nordisk.
PULPZYM® product, available from Novo Nordisk, and ECOPULP® product, from Alko Biotechnology, are two examples of commercially available liquid enzymatic compositions containing xylanase-based bleaching enzymes.
As a class, hemicellulases can include hemicellulase mixture and galactomannanase. Commercial liquid enzymatic compositions containing hemicellulases are available as PULPZYM® from Novo, ECOPULP® from Alko Biotechnology and Novozym® 280 and Gamanase™, which are both products of Novo Nordisk. The mannanases can be, for example, endo-mannanases, such as endo-β-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).
Pectinases comprise endopolygalacturonase, exopolygalacturonase, endopectate lyase (transeliminase), exopectate lyase (transeliminase), and endopectin lyase (transeliminase). Commercial liquid enzymatic compositions containing pectinases are available under the names Pectinex™ Ultra SP and Pectinex™*, both supplied by Novo Nordisk.
β-glucanases are comprised of lichenase, laminarinase, and exoglucanase. Commercial liquid enzymatic compositions containing β-glucanases are available under the names Novozym® 234, Cereflo®, BAN, Finizym®, and Ceremix®, all of which are supplied by Novo Nordisk.
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.
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.
Other suitable enzymes and enzyme-containing compositions include those such as described in U.S. Pat. Nos. 5,356,800, 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 BUZYME® 2523 and BUZYME® 2524, both available from Buckman Laboratories International, Inc., Memphis, Tenn.
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.
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 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 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.
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 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 Mütek DFR-05 drainage/retention tester. The Mütek DFR-05 drainage freeness retention simulates the retention and drainage conditions prevailing in a pulp or paper machine.
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 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.
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, organosols 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 refiners only for defibration of feedstock, also can be processed with the indicated pulp treatment.
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.
“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.
“Enzyme” refers to a protein that is capable of catalyzing a chemical reaction.
“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.
“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.
“Nonionic compound” refers to a compound that is amphiphilic and has no charge group at either terminal end group thereof.
“Nonionic surfactant” refers to a surfactant that is amphiphilic and has no charge group at either terminal end group thereof.
“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.
“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 as the charged groups thereon or may be amphoteric with a net cationic charge for the overall molecule.
“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.
“Kraft pulp” refers to chemical wood pulp produced by digesting wood by the sulfate process.
“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.
“Dissolving pulp” refers to a higher purity, special grade pulp made for processing into cellulose derivatives including rayon and acetate.
“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.
“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.
“Defibration” refers to separation of wood fibers by mechanical means, chemical means, or combinations of both.
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 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 haft 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 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.
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.
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 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.
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 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.
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 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.
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.
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 centriscreen 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 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.
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.
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 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.
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 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.
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.
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, 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 H₂O 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).
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).
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.
As an option, inorganic anionic coagulants can be used, such as polyphosphates, anionic silica sol, or any combinations thereof.
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 10 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 compound/ton dry fiber, or from about 0.5 to about 3 lb. anionically charged compound/ton dry fiber (on a solids/solids basis).
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.
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.
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 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.
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.
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.
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.
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 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.
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

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.
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.
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 pulp. The dosage rate of enzyme, for each of enzyme X and enzyme Y, was 1 g of enzyme/kg dry fiber pulp.
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 Mütek 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.
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 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

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

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 and also a separate combination of the anionic surfactant with a different enzyme, and water drainage of untreated pulp.
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.
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.
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.
The results of these experiments are shown in FIGS. 4 and 5. FIG. 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.
These same data are shown in FIG. 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.
The benefit of this invention is demonstrated another way in Table 3. The “final pad consistency” is the percent fiber in the final 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.

	TABLE 3

	final pad consistency	% improvement

Blank	4.90	—
surfactant only	5.78	18
enzyme only	5.68	16
surfactant + enzyme	6.06	24

Again, 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.
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.
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 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, β-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 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 10 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);
(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;
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.
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).
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.
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 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.
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.

Claims

What is claimed is:

1. 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 claim 1, 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.

3. The method of claim 1, 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 claim 1, wherein the anionically charged compound is an organic anionically charged compound.

5. The method of claim 1, wherein the enzyme is a hydrolytic enzyme.

6. The method of claim 1, 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;

thermally drying said mechanically dewatered pulp to form market pulp.

8. The method of claim 7, 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 claim 7, 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 claim 7, further 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 claim 7, wherein the anionic surfactant is a sulfate surfactant, a sulfonate surfactant, a sulfosuccinate surfactant, or any combinations thereof.

12. The method of claim 7, 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 claim 7, wherein the enzyme is cellulase, hemicellulase, pectinase, cellobiase, xylanase, mannanase, β-glucanase, carboxymethylcellulase, amylase, glucosidase, galactosidase, laccase, or any combinations thereof.

14. The method of claim 7, wherein said forming provides kraft pulp, sulfite pulp, fluff pulp, dissolving pulp, bleached chemothermomechanical pulp, or any combinations thereof.

15. The method of claim 7, 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 claim 7, 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 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 claim 7, 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 claim 7, wherein the anionic surfactant is added to the pulp in an amount of from about 0.1 lb./ton dry fiber to about 10 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 claim 7, further comprising unitizing said market pulp to form unitized market pulp.

20. The method of claim 7, wherein the cellulosic particulates are hardwood chips, softwood chips, recycled paper fiber, or any combinations thereof.

21. The method of claim 7, 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);

(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 individually in the pulp (without the enzyme).

22. The method of claim 7, 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 claim 7, 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 claim 1 containing said anionically charged compound and said enzyme.

25. A market pulp made by the method of claim 7 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;

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 claim 26, 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 claim 26, wherein said pulp forming unit is a digester capable of receiving at least one chemical for digesting the cellulosic particulates.

29. The system of claim 26, 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 claim 26, 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.

31. The system of claim 26, 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:

(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).