JP2001519486A - Method for processing straw into pulp and paper product obtained therefrom - Google Patents

Abstract

  (57) [Summary] The present invention provides a method of pretreating and treating straw pulp and forming by-products suitable for consumption by animals. The present invention also provides a paper product comprising the straw pulp. According to the present invention, straw chips are steam exploded in the absence or presence of small amounts of caustic to form straw pulp.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Technical Field The present invention relates to a method of pretreating and treating lignocellulosic material into pulp.

BACKGROUND INFORMATION There is growing interest in incorporating non-wood cellulose fibers into paper products. Huge amounts of non-wood fibers are available for pulp production. World straw production is estimated to be about 500,000,000 metric tons per year. Only about half of that amount is used for low value purposes such as building materials, fuel, and cattle feed. Most of the remaining amount is wasted by burning or plowing into the soil without recovering energy. However, some of the limitations of making straw into paper include incorporating lower quality fibers from straw into products having sufficient strength, durability, and whiteness for marketable end products. There is a point.

[0003] US Pat. No. 4,040,899, issued to 1977 and issued to Emerson, attempts to address the use of straw pulp in paper. Emerson teaches twisting and crimping the fibers into a paper web.

[0004] According to Pulp and Paper, published in 1952 and 1960 by Interscience Publishers, Inc., "Straws are obtained by chemical treatment or by mechanical and chemical treatments known as mechanochemical processes. Among the various chemicals used to pulp straw are: (1) sodium hydroxide, (2) lime alone or other lime. Combination with alkalis, (3) sodium sulfite plus other alkalis, (4) chlorine, and (5) sodium hydroxide plus sodium sulfide (sulfite method) Other chemicals proposed for pulping straw. The chemicals are nitric acid and sodium chlorite.Sodium carbonate plus sulfur is proposed for the production of crude pulp (straw kraft) used for corrugated paper. The four main processes for producing high quality bleachable straw pulp are:
(1) a soda method, (2) a sulfate method, (3) a neutral sulfite method, and (4) a pomiliochlorine method. The soda and sulfate methods produce good pulp but have relatively low yields. DISCLOSURE OF THE INVENTION The present invention provides a method for pulping straw chips and forming usable by-products. According to the method, the straw chips are mixed with steam and water to form a mixture. The mixture is exposed to a temperature and pressure sufficient to significantly soften the straw chips when exposed to a rapid pressure drop to form straw pulp, lignins, and hemicellulose. The mixture is washed to separate some of the lignins and hemicellulose from the straw pulp, thereby forming water, a usable by-product of the lignins and hemicellulose, called black liquor, and then removing the mechanical refiner. Let it pass.

At temperatures and pressures sufficient to soften the straw chips significantly when exposed to a rapid pressure drop to form straw pulp, lignins and hemicellulose in the mixture,
Before exposing the mixture of straw chips, steam and water, the straw chips may be mixed with caustic. The caustic may be present in the mixture at less than about 2% by weight. More preferably, the caustic is present in the mixture at less than about one-half weight percent. The caustic may include sodium hydroxide. The caustic may also include potassium hydroxide.

In one form of the method, the mixture is brought to a temperature and pressure sufficient to significantly soften the mixture when subjected to a rapid pressure drop, for a period of about two-half minutes to about eight minutes. May be exposed.

In yet another form of the invention, at least about 70% by weight of the straw chips will be straw pulp.

In yet another form of the invention, the pressure sufficient to significantly soften the straw chips when subjected to a rapid pressure drop is between about 140 psig and about 200 psig.

In another form of the invention, the fiber chips may be selected from non-wood fibers such as ryegrass, wheat and mixtures of grain and cereal straw.

The straw is chopped to form a mixture of straw chips, meal, ash and grit, and the mixture is sieved to remove a substantial portion of the straw chips , Ash and grit may be formed to form straw chips for use in the present method. Flour, ash, and coarses may be used as animal feed. In a preferred form of the invention, the meal, ash, and coarse particles are mixed with the black liquor by-product,
Animal feed may be formed.

[0011] The straw pulp formed by this method has a Canadian standard freeness of about 200 and about 60.
It has between 0.

The present invention also provides a paper product made from wood pulp and straw pulp, wherein the straw chips are mixed with steam and water to produce straw pulp. To form a mixture. The mixture is exposed to a temperature and pressure sufficient to significantly soften the straw chips into a straw pulp when subjected to a reduced pressure. The mixture is then refined to separate a significant portion of the straw pulp from the mixture. Some of the wood pulp and paper products were processed and released by consumers (post-c
onsumer) may be obtained from waste.

The straw is chopped to form a mixture of straw chips, meal, ash and coarse particles, and the mixture is sieved to separate a substantial portion of the straw chips from the meal, ash and coarse particles. Then, a straw chip may be formed.

In yet another form of the invention, the straw pulp is a Canadian Standard Freeness (CS)
F) having between about 200 and about 600 and STFI between about 14 and about 21;

[0015] The advantages and features described above, as well as other advantages and features, will be apparent from the detailed description of the best mode for carrying out the invention that follows. In the drawings, the names of similar elements indicate similar parts throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an improved method for pretreating and treating various lignocellulosic feedstocks. Suitable lignocellulosic materials include non-wood fibers such as cereal and cereal straw, and corn stover.
However, it has been found that the method of the present invention is particularly suitable for lignocellulosic materials obtained from grasses and straw, such as annual ryegrass, oxacea, and wheat. Straw chips, as used herein, may refer to chips obtained from any non-wood fiber, such as cereal and cereal straw, grass, and corn stover.
However, for simplicity, all such chips are referred to as straw chips.

Referring first to FIG. 1, ryegrass 10 is shown growing on soil 12 by way of example. Ryegrass 10 has seeds or grains 14 retained within ears 16, hollow stems or internodes 18 between each joint or node 20, and a widely branched whisker system 22. Leaf sheath portion 24 is formed on stem 18 and attaches leaf 26 to stem 18.

During harvesting, ryegrass 10 is cut, bundled and tied, generally below the initial joint or node 20, at about 3-6 inches from the ground. The cut ryegrass is then placed in a field for several weeks and cured. Seeds or grains 14 can be harvested from the harvested plants using a combine. After removing the seeds or grains 14, the combine drops the rest of the ryegrass, commonly known as straw 30, onto the ground. Straw 30 may be recovered from the field and further processed after packing for storage.

Referring to FIG. 2, a straw 30 is fed into a tub grinder 28 for pre-processing. Straw 30 may be packaged and fed into tab grinder 28. The tab grinder 28 shatters the bales and shreds the straw into average 1 inch long pieces. As the shredded straw 32 exits the mill 34, the shredded straw 32
Including nodes 20, leaves 26, leaf sheath portions 24, and internodes 18, as well as ash, silica, and grit.

After exiting the tab grinder 28, the shredded straw 32 is fed into a mill 34, where the shredded straw 32 averages into pieces approximately one-half inch long. Mill 3
4 crushes the nodes 20, leaves 26 and most of the sheath portion 24 into a powder.

If the capacity of the mill 34 does not allow the shredded straw 32 to be fed directly from the tab grinder 28 to the mill 34, the shredded straw 32 is stored in a storage tank 35. , And may then be sent to a mill 34.

After leaving the mill 34, the milled mixture 36 passes through a multilayer screen 37. The pulverized mixture 3 is used to remove and remove the meal 38 from the straw chips 40.
6 is passed through the multilayer screen 37. Rough powder 38 contains non-fibrous particles and ash, and silica and coarse particles are concentrated. Flour 38 may be used as an agricultural by-product for feeding livestock.

The straw chips 40 are thus ready for processing into pulp. Straw chips 40 may be further processed after storage. In addition, if the pulping is to be performed at a location remote from where the straw chips 40 were pre-treated, the straw chips 40 may be used by any method used to transport bulk material, such as by using a container.
May be transported.

Referring to FIG. 3, for processing the straw chips 40 into pulp, the straw chips 40 are fed into a mixer 42 where the straw chips 40 are steamed and water 44, as well as optionally treated. Mix with alkali or cooking additive 46. Typically, the amount of cooking additive 46 utilized is calculated on a weight basis per amount of dry straw chips entering the system. The scale may be incorporated during the pulping process so that the straw chips 40 can be weighed as they enter the system and the amount of cooking additive 46 can be provided at an appropriate rate.

Preferably, cooking additive 4 mixed with steam and water 44 and straw chips 40
The amount of 6 is between about zero and about 2.0% by weight. More preferably, however, the amount of cooking additive 46 is between about zero and about 0.5% by weight. Suitable cooking additives 46 for use in the present invention include sodium hydroxide and potassium hydroxide.

From the mixer 42, a stream 48 composed of straw chips 40, steam and water 44, and optional cooking additives 46 is then fed into a reactor 50. By exposing stream 48 to a temperature and pressure sufficient for water vapor 44 and optional cooking additives 46 to penetrate straw chips 40 in reactor 50, the softened chips, cellulose, A mixture of lignins, hemicellulose and water.

[0027] Suitable reactors for use in the present invention include Stake Technology, Ltd.
d. of Oakville, Canada; and U.S. Patent Nos. 4,798,651 and 4
And continuous feed reactors such as those described in U.S. Pat. The contents of this patent are incorporated herein by reference.

In the present invention, the reactor product 52 can be subjected to a rapid pressure drop by advancing the reactor product 52 into the blow tank 56. Reactor product 52 may be metered from reactor 50 into blow tank 56 by blow valve 54. Reactor product 52 comprises softened straw pulp mixed with lignins, hemicellulose and water. In other words, the straw chips are steam exploded as they exit the reactor 50 and pass through the blow valve 54 to form straw pulp, lignins and hemicellulose.

The stream 58 leaving the blow tank 56 is fed into a screw press 59 in which a stream 126 of the straw pulp mixture is separated from the steam-exploded straw chips. Stream 126 is substantially composed of black liquor and undissolved solids. Generally, stream 126 is substantially comprised of water, reacted lignins, and hemicellulose. Stream 126 is sent to by-product tube 142. Stream 144 exiting by-product tuft 142 passes through filtration system 128. The solids 130 removed in the filtration system 128 are sent to the blow tank 56. Liquid stream 1 exiting filtration system 128
38 is collected in storage tank 140.

The black liquor collected in storage tank 140 is a usable by-product. This by-product has utility as an animal feed additive. In a preferred form of the invention, the by-products are mixed with the meal 38 resulting from the pretreatment to form animal feed. The animal feed is mashed or pelleted by methods well known in the art.

The stream 61 leaving the screw press 59 is then defibrated. Disintegration, Ahlstrom MDR
It may be performed by a mechanical refiner 60 such as a (frotopulper).

The pulp is therefore ready for washing. The pulp may be washed by any method such as dilution and extraction. For example, the refined pulp mixture 62 may be sent to a dilution tank 64 in which the pulp mixture 62 is diluted with water 73. Next, the diluted pulp mixture 66 leaving the tank 64 may be concentrated using a washing press 68. The thin black liquor in stream 69 leaving wash press 68 is sent to blow tank 56.

The concentrated pulp 70 may then be screened to remove unwanted particles. In preparation for screening, the concentrated pulp 70 may be sent to a pre-screening dilution tank 72 where the pulp 70 is mixed with water 73. The diluted pulp 74 exiting the dilution tank 72 is then advanced during primary screening 76. Accepts 78 that exit primary screening 76 may be collected in accept tank 84.

Reject 86 exiting primary screening 76 may be advanced to primary screen reject tank 90. The reject 92 exiting the reject tank 90 may proceed to the secondary screening 80. Accept 82 exited the secondary screening 80
May be collected in an accept tank 84. The reject 88 exiting the secondary screening 80 is sent to the drainer 146.

The dehydrated stream 148 is sent to the secondary reject tank 150. The stream 152 exiting the secondary reject tank 150 is sent to a reject defibrizer 154. Stream 156 exiting reject defibrillator 154 is collected in tertiary screen supply tank 158. Stream 160 exiting tertiary screen supply tank 158
Are passed through a tertiary screen 162. The accepts 164 exiting the tertiary screening 162 are collected in the reject tank 90. Tertiary screening 162
Is sent to the drainer 146.

The nature and nature of the present invention, as well as its objects and advantages, will be more clearly understood with reference to the following specific examples.

Example 1 An annual ryegrass straw is obtained. The measured protein level of the straw is about 3-4 percent (3% -4%). The moisture content of the ryegrass straw is measured to be about 10 percent (10%). Described in the best mode of the present application,
Pretreating annual ryegrass straw according to the method described herein,
Pulping.

The ryegrass straw bales are fed into an agricultural tab grinder where the bales are shattered and the straws are chopped into pieces approximately 1 inch long on average. Agricultural tab grinders have a grid plate with circular holes sized between about one-half (0.5) inch and about two inches.

After leaving the agricultural tab grinder, the shredded straw is fed into a disc mill.
The disc mill is a mill from United Milling Systems, which has a milling gap of about 0.1 mm.
It has between 6 mm and about 1.0 mm. Cut the shredded straw into approximately 1/2 inch pieces in a disc mill. Disc mills also pulverize hard straw knots, leaves and leaf sheaths into large parts. Ash and grit measurements make up about 2-5 percent (2% -5%) of the straw fed into the tab grinder.

After exiting the mill, the straw goes into a 35 mesh vibrating six-deck screen.
The screen is a gyratory screen with a fine mesh and a ball deck to remove fines and dirt from the surface of the screen. About 18 percent (18%) of the mixture is removed as a meal on the screen. Part of the removed flour is the powder formed in the disc mill by the hard nodes, leaves and sheaths of straw. The remainder of the straw chip leaving the screen is on average about one-half (1/2) inch in size.

Flour has a protein level of about 8 to 13 percent (8% to 13%). The silica content is between about 8-15%. The meal removed in the screen is determined to be usable as animal feed.

The pre-treated straw chips are then stored and then pulped. The straw chips are pretreated away from the pulping system. The pretreated straw chips are transported to the pulping system by container trucks.

The pretreated straw chips are supplied to the pulping system at a rate corresponding to the capacity of the pulping system. The pre-treated straw chips are fed into a mixer where the straw chips are mixed with steam and water to achieve a water content of about 40-50% based on the filling of the pre-treated straw chips into the mixer. The pretreated straw chips mixed with steam and water are fed into a Stake Digester steam explosion reactor. In the reactor, the pretreated straw chips are exposed to a pressure of about 160 psig for about 5.5 (5 and 1/2) minutes.

The pulp leaving the reactor is metered into a blow tank by a blow valve. The pulp leaving the blow tank is passed through a screw press, where the black liquor is separated from the pulp. The pulp is then defibrated or refined in an Ahlstrom frotopulper mechanical refiner. The refined pulp is sent to the dilution tank, where the refined pulp has a dilution factor of about 2
. At 5 mix with the liquid. The diluted pulp is then concentrated using a washing press. The concentrated pulp is screened in a two-stage press screen having approximately 0.010 inch slotted plates.

It is determined that at least about 70% by weight of the straw chips will be straw pulp.

After completion of the treatment, the straw pulp has Canadian Standard Freeness (CSF) of about 200 and about 600
And between about 14 and 21 of the Swedish Technical Forestry Institute (STFI). As a comparison, OCC (pulp from recovered cardboard) is determined to have a Canadian Standard Freeness (CSF) between about 200 and about 500 and STFI between about 15 and about 22. The kraft pulp is determined to have a Canadian Standard Freeness (CSF) between about 450 and about 750 and a STFI between about 21 and about 26.

Straw pulp having a Canadian Standard Freeness (CSF) between about 200 and about 600 and STFI between about 14 and about 21 can be blended with kraft pulp and OCC to produce a standard mill grade (standard mill grade). Suitable for manufacturing liner boards with grade). Straw pulp accounts for about 20 percent (20%) of linerboard furnish
Account for less than.

Example 2 Example 1 is repeated using about one-half (0.5) weight percent sodium hydroxide in a mixer.

After the treatment is completed, the straw pulp has a Canadian Standard Freeness (CSF) of about 200 and about 600
And STFI between about 14 and about 21.

Example 3 Example 1 is repeated using about 1% by weight of sodium hydroxide in a mixer.

After the treatment is completed, the straw pulp has a Canadian Standard Freeness (CSF) of about 200 and about 600.
And STFI between about 14 and about 21.

Example 4 Example 1 is repeated using 2% by weight of sodium hydroxide in a mixer.

After completion of the treatment, the straw pulp has a Canadian Standard Freeness (CSF) of about 200 and about 600
And STFI between about 14 and about 21.

Example 5 Example 1 is repeated using about one-half (0.5) weight percent potassium hydroxide in the mixer instead of sodium hydroxide.

After the treatment, the straw pulp has Canadian Standard Freeness (CSF) of about 200 and about 600.
And STFI between about 14 and about 21.

Example 6 Example 1 is repeated using about 1% by weight of potassium hydroxide in the mixer instead of sodium hydroxide.

After the treatment, the straw pulp has Canadian Standard Freeness (CSF) of about 200 and about 600.
And STFI between about 14 and about 21.

Example 7 Example 1 is repeated using about 2% by weight of potassium hydroxide in the mixer instead of sodium hydroxide.

After the treatment, the straw pulp has Canadian Standard Freeness (CSF) of about 200 and about 600
And STFI between about 14 and about 21.

Example 8 Example 1 is repeated except that the pretreated straw chip mixed water is left in the reactor for about two and a half minutes.

After the treatment is completed, the straw pulp has a Canadian Standard Freeness (CSF) of about 200 and about 600.
And STFI between about 14 and about 21.

Example 9 Example 1 is repeated except that the pretreated straw chip mixed water is left in the reactor for about 4 minutes.

After the treatment is completed, the straw pulp has a Canadian Standard Freeness (CSF) of about 200 and about 600.
And STFI between about 14 and about 21.

Example 10 Example 1 is repeated except that the pretreated straw chips mixed with water are left in the reactor for about 6 minutes.

After the treatment is completed, the straw pulp has a Canadian Standard Freeness (CSF) of about 200 and about 600.
And STFI between about 14 and about 21.

Example 11 Example 1 is repeated except that the pretreated straw chip mixed water is left in the reactor for about 8 minutes.

At the end of the treatment, the straw pulp has a Canadian Standard Freeness (CSF) of about 200 and about 600.
And STFI between about 14 and about 21.

Example 12 Example 1 is repeated exposing pretreated straw chips mixed with water to a pressure of about 140 psig in a reactor.

After completion of the treatment, the straw pulp has a Canadian Standard Freeness (CSF) of about 200 and about 600
And STFI between about 14 and about 21.

Example 13 Example 1 is repeated exposing pretreated straw chips mixed with water to a pressure of about 180 psig in a reactor.

At the end of the treatment, the straw pulp has a Canadian Standard Freeness (CSF) of about 200 and about 600.
And STFI between about 14 and about 21.

Example 14 Example 1 is repeated exposing pretreated straw chips mixed with water to a pressure of about 200 psig in a reactor.

At the end of the treatment, the straw pulp has a Canadian Standard Freeness (CSF) of about 200 and about 600.
And STFI between about 14 and about 21.

While specific embodiments of the present invention have been shown and described in detail to exemplify the use of the principles of the invention, such presentation and description have been provided by way of example only, Not for limitation. In all aspects of the invention, protection of the invention by patent is sought in the appended claims and to the fullest extent permitted by the prior art.

[Brief description of the drawings]

FIG. 1 is an elevation view of a ryegrass.

FIG. 2 is a system diagram of a pretreatment plant constructed according to the method of the present invention.

FIG. 3 is a system diagram of a pulping plant constructed according to the method of the present invention.

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] April 5, 2000 (200.4.5)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

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Claims (18)

[Claims] 1. mixing straw chips with water vapor and water to form a mixture; significantly softening said straw chips when subjected to a rapid pressure drop to form straw pulp, lignins and hemicellulose. Exposing the mixture to a temperature and pressure sufficient to remove water, reacted lignin and hemicellulose by passing the mixture through a press to separate some of the lignin and hemicellulose from the straw pulp. Forming a usable straw pulp by passing the straw pulp through a defibrillator to form a usable straw pulp. How to form. 2. A temperature and temperature sufficient to soften said straw chips significantly upon exposure to a rapid pressure drop to form straw pulp, lignins and hemicellulose in said mixture of straw chips, steam and water. Before exposing said mixture of straw chips, steam and water to pressure, said straw chips are mixed with caustic,
The method of claim 1. 3. The caustic alkali is based on the dried straw chips.
3. The method of claim 2, wherein less than about 2% by weight is present in the mixture. 4. The method of claim 3, wherein potassium hydroxide is present in the mixture at less than about one-half (0.5) weight percent based on the dried straw chips. 5. The method of claim 2, wherein said caustic comprises sodium hydroxide. 6. The method of claim 2, wherein said caustic comprises potassium hydroxide. 7. A temperature and pressure sufficient to significantly soften said mixture when subjected to a rapid pressure drop, from about 2 and 2 (2 and 1/2) minutes to about 8 minutes. The method of claim 1, wherein the mixture is exposed. 8. The method of claim 1, wherein said straw chips are selected from the group comprising: ryegrass; wheat; a mixture of cereal and cereal straw. 9. The method of claim 1, wherein at least about 70% by weight of said straw chips becomes straw pulp. 10. The method of claim 1, wherein the pressure is sufficient to significantly soften the straw chips when subjected to a rapid pressure drop from between about 140 psig and about 200 psig to about atmospheric pressure. the method of. 11. The straw chips are obtained by chopping straw to form a mixture of straw chips, flour, ash and coarse particles, and sieving the mixture to remove a substantial portion of the straw chips Formed by separating from flour, ash and coarse particles,
The method of claim 1. 12. The method according to claim 11, wherein the separated meal, ash and coarse particles are used as animal feed. 13. The method of claim 12, wherein the separated meal, ash, and grit are mixed with the usable by-products to form an animal feed. 14. The straw pulp has a Canadian standard freeness of about 200 and about 600.
The method of claim 1, comprising: 15. In a paper product made from wood pulp and straw pulp, the straw pulp mixes the straw chips with steam and water to form a mixture of straw chips, steam and water; Exposing the mixture to a temperature and pressure sufficient to substantially soften the straw chips into straw pulp upon exposure; separating a substantial portion of the straw pulp from the mixture; refining the straw pulp A paper product produced by 16. The paper product of claim 15, wherein a portion of the wood pulp is obtained from processed, consumer-derived waste. 17. The straw chips may be chopped into straw to form a mixture of straw chips, flour, ash, and coarse particles, and the mixture may be sieved to remove a substantial portion of the straw chips from the rough chips. Formed by separating from flour, ash and coarse particles,
A paper product according to claim 15. 18. The straw pulp has a Canadian Standard Freeness (CSF) of about 200.
16. The paper product of claim 15, wherein the paper product has between about and about 600 and between about 14 and about 21 STFI.