SYSTEM AND METHOD FOR REFINING AGRICULTURAL FIBERS TO A PULP SPECIFICATION
20220389657 · 2022-12-08
Inventors
Cpc classification
D21H11/12
TEXTILES; PAPER
International classification
D21H11/12
TEXTILES; PAPER
D21C3/02
TEXTILES; PAPER
Abstract
Methods and systems for preparing non-wood agricultural feedstock material for use as a pulp, and making a paper product therefrom. The method includes providing non-wood agricultural feedstock material (e.g., corn stover) that includes agricultural fibers, chemically pulping the agricultural fibers at a low temperature of less than 100° C., refining the agricultural fibers (either before or after cooking), and introducing the produced agricultural fiber pulp into a papermaking machine to make liner, medium, tissue, towel, cardstock or other paper product (e.g., tubes, cores, chipboard, grayboard, or other rigid container board). The agricultural pulp fibers can also be introduced into a molded pulp products manufacturing machine, to make egg cartons, molded paper plates, molded single use packaging, or the like.
Claims
1. A method comprising: providing non-wood agricultural feedstock material that includes agricultural fibers, and reducing the size of such agricultural fibers to a desired length, and mechanically refining such agricultural fibers; chemically pulping the agricultural fibers in an alkaline chemical pulping process to produce an agricultural fiber pulp, wherein chemically pulping the agricultural fibers is achieved at a temperature of less than 100° C. and at atmospheric pressure; and introducing the agricultural fiber pulp into a papermaking machine to make liner, medium, tissue, towel, cardstock, chipboard, or other paper product from the agricultural fiber pulp.
2. The method of claim 1, wherein reducing the size of the agricultural fibers to a desired length and mechanically refining such fibers occurs before, during or after chemical pulping.
3. (canceled)
4. The method of claim 1, wherein the non-wood agricultural feedstock material comprises at least one of corn stover, hemp, wheat straw, rice straw, soybean residue, cotton residue, switchgrass, miscanthus, DDGS, bamboo, or sugarcane bagasse.
5. The method of claim 1, wherein the agricultural fiber pulp is combined with at least one of OCC pulp or virgin wood pulp to make the liner, medium, tissue, towel, cardstock, chipboard, or other paper product.
6. The method of claim 1, wherein chemically pulping the agricultural fibers is achieved without addition of any acids, and wherein the method is performed without the use of ozone, and without any bleaching.
7. The method of claim 1, wherein chemically pulping the agricultural fibers is achieved in a 2-step cooking process, comprising: introducing the agricultural fibers into a first reactor, wherein the first reactor operates at a low temperature of less than 100° C.; introducing the agricultural fibers from the first reactor into a second reactor, where the second reactor operates at a low temperature, of less than 100° C., the second reactor operating at a higher temperature than the first reactor, to produce the agricultural fiber pulp.
8. (canceled)
9. (canceled)
10. (canceled)
11. The method of claim 1, wherein chemically pulping the agricultural fibers includes chemically pulping with a sodium hydroxide or other active alkali concentration of from 4 g/L to less than 40 g/L, from 4 g/L to 20 g/L, or from 4 g/L to 10 g/L, or an active alkali (relative to the agricultural feedstock material) value of from 10% to 30%, for a period of time of from 1 hour to 5 hours, at a temperature of less than 100° C.
12. (canceled)
13. The method of claim 1, wherein a yield of the agricultural fibers in the liner, medium, tissue, towel, cardstock, chipboard, or other paper product is at least 40%, at least 50%, at least 60%, at least 70%, or at least 80% by weight.
14. The method of claim 1, wherein the liner, medium, tissue, towel, cardstock, chipboard, or other paper product includes at least 3% by weight of agricultural fibers.
15. (canceled)
16. (canceled)
17. The method of claim 1, wherein the liner, medium, tissue, towel, cardstock, chipboard, or other paper product is at least one of liner or medium, and is incorporated into a corrugated paper container.
18. The method of claim 17, wherein the corrugated paper container includes both liner and medium, wherein the liner and medium both include agricultural fibers, and wherein the liner and medium include different weight fractions of agricultural fiber therein, or wherein the corrugated paper container includes both liner and medium, wherein only one of the liner or medium include agricultural fibers therein.
19. (canceled)
20. The method of claim 1, wherein reducing the size of such agricultural fibers to a desired length, and mechanically refining such agricultural fibers in preparation for pulping comprises (i) chopping or shredding, (2) milling, and/or (3) screening such agricultural fibers, wherein such (i) chopping or shredding, (2) milling, and/or (3) screening such agricultural fibers is achieved in a low consistency pulper.
21. (canceled)
22. (canceled)
23. The method of claim 1, wherein the agricultural fibers are incorporated into containerboard, chipboard, grayboard, or another rigid container board.
24. A method comprising: providing non-wood agricultural feedstock material that includes agricultural fibers, and reducing the size of such agricultural fibers to a desired length, and mechanically refining such agricultural fibers; chemically pulping the agricultural fibers in an alkaline chemical pulping process to produce an agricultural fiber pulp, wherein chemically pulping the agricultural fibers is achieved at a temperature of less than 100° C. and at atmospheric pressure; and introducing the agricultural fiber pulp into a molded pulp product manufacturing machine to make a molded pulp product from the agricultural fiber pulp.
25. The method of claim 24, wherein the molded pulp manufacturing machine performs at least one of wet pressing or thermoforming of the agricultural fiber pulp to form the molded pulp product.
26. The method of claim 25, wherein the molded pulp product comprises at least one of an egg carton, a molded disposable “paper” plate, a food container, or a molded pulp product used for packaging consumer goods, wherein the molded pulp product is a disposable single use product.
27. A product, comprising the liner, medium, tissue, towel, cardstock, chipboard, or other paper product formed by the method of claim 1.
28. The product as recited in claim 27, wherein the product comprises liner, medium, cardstock or chipboard, and is in the form of a box.
29. The product as recited in claim 27, wherein the product comprises liner and medium and is in the form of a container that includes a corrugated portion.
30. (canceled)
31. (canceled)
32. (canceled)
33. (canceled)
34. (canceled)
35. (canceled)
36. (canceled)
37. A system comprising: a separation and size reduction module configured to reduce the size of agricultural fibers within provided non-wood agricultural feedstock material to a desired fiber length, the separation and size reduction module being configured to cut, mill and/or screen the agricultural feedstock material; a chemical pulping module configured to chemically pulp the agricultural fibers in an alkaline chemical pulping process to produce an agricultural fiber pulp, wherein the chemical pulping module operates at a temperature of less than 100° C. and at atmospheric pressure; and a papermaking machine configured to make liner, medium, tissue, towel, cardstock, chipboard, or other paper product from the agricultural fiber pulp.
38. (canceled)
39. (canceled)
40. (canceled)
41. The system of claim 37, wherein the provided non-wood agricultural feedstock material comprises at least one of corn stover, hemp, wheat straw, rice straw, soybean residue, cotton residue, switchgrass, miscanthus, DDGS, bamboo, or sugarcane bagasse, and wherein the system is further configured to combine the agricultural fiber pulp with at least one of OCC pulp, other recycled paper, or virgin wood pulp to make the liner, medium, tissue, towel, cardstock, chipboard, or other paper product.
42. The system of claim 37, wherein the chemical pulping module comprises a 2-step cooking system, comprising: a first reactor that operates at a low temperature of less than 100° C.; wherein the system includes a screw press between the first reactor and a second reactor for removing at least a portion of black liquor generated in the first reactor; the second reactor, where the second reactor operates at a low temperature of less than 100° C., the second reactor operating at a higher temperature than the first reactor, to produce the agricultural fiber pulp.
43. (canceled)
44. (canceled)
45. (canceled)
46. (canceled)
47. (canceled)
48. (canceled)
49. (canceled)
50. (canceled)
51. (canceled)
52. (canceled)
53. (canceled)
54. (canceled)
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0081] The appended drawings contain figures of example embodiments to further illustrate and clarify the above and other aspects, advantages and features of the present invention. It will be appreciated that these drawings depict only example embodiments of the invention and are not intended to limit its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings.
[0082]
[0083]
[0084]
[0085]
[0086]
[0087]
[0088]
[0089]
[0090]
[0091]
[0092]
[0093]
[0094]
[0095]
DETAILED DESCRIPTION
[0096] Various disclosed embodiments are generally concerned with the production and use of feedstock blends, and products such as cardboard, paperboard, kraft paper or the like, made from feedstock blends, that may include one or more types of agricultural fibers and/or other non-wood fibers in various quantities. Example feedstock blends may additionally, or alternatively, include recycled paper and/or recycled cardboard, and forest products such as wood fibers. Unless specified in a particular claim, the scope of the invention is not limited to any particular feedstock blend or components however.
[0097] In some particular example embodiments, a system for producing containerboard is provided that fractionates and refines agricultural feedstocks to a pulp specification that may be useful in applications such as, but not limited to: blending with OCC (old corrugated containers which may or may not include wood fibers) and/or other recycled papers; blending with non-wood fibers, such as agricultural fibers; and, use as a pure species of one agricultural fiber.
[0098] In a first example embodiment, corn stover pulps are blended with OCC to produce a new pulp blend for use in producing containerboard. A second example embodiment of the invention uses a pulp of both corn stover and wheat straw, blended with OCC. In a third example embodiment, bast fibers from hemp straw are introduced to the corn stover-OCC blend of the first example embodiment noted above. These embodiments are presented only by way of example, and are not intended to limit the scope of the invention in any way. A wide variety of possible non-wood agricultural fibers are possible, including but not limited to corn stover, hemp, wheat straw, soybean residue, switchgrass, or DDGS (Distillers Dried Grains w/Solubles).
[0099] Example embodiments of the invention may provide various features, although no particular feature or group of features is required to be implemented in any particular embodiment. Following is a brief discussion of features, any one or more of which may be incorporated in an embodiment of the invention. The features noted in the following discussion are provided by way of illustration and are not intended to limit the scope of the invention in any way.
[0100] One or more example embodiments of the invention are directed to various types of containerboard that can be made by the processing of various non-wood feedstocks, such as one or more agricultural fibers for example, with or without being combined with traditional wood-based paper pulp, and without regard to whether or not the traditional wood-based paper pulp is recycled.
[0101] As another example, embodiments of the invention may enhance the performance characteristics of containerboard made with recycled materials. Embodiments of the invention may present alternatives to the use of trees as a feedstock for containerboard. Even where mechanical performance characteristics may not necessarily be enhanced as compared to use of conventional pulp materials (e.g., virgin wood pulp or OCC), the present embodiments provide a sustainability advantage, reducing use of wood and forest resources, allowing such materials to be put to higher use.
[0102] Example embodiments may provide a commercially viable use for agricultural residues that are left over from various types of grain farming such as corn, wheat, and soy beans, for example. Implementing this approach may provide a new income stream for the grower of those crops who might otherwise destroy those residues, or plow them under. Further, embodiments of the invention may enable the use of cover crops, as well as the ability to harvest and process the cover crops in an industrial setting. Implementation of this approach may further incentivize growers of these crops to increase the soil health of their fields.
[0103] The use of non-wood agricultural residues or other non-wood agricultural feedstock materials and fibers and other non-wood fibers in processes for producing is products which may have to be relatively strong to perform their intended function, such as containerboard used to make boxes for example, may be counterintuitive. This is a because agricultural materials and other non-wood fibers typically lack the strength and durability of wood fibers and other wood-based materials (e.g., houses are framed with wood, not corn stalks). Thus, the partial replacement, in some example embodiments of the invention, of relatively stronger wood based materials with relatively weaker agricultural feedstock materials runs counter to conventional wisdom. In still other embodiments, wood based fibers may be completely omitted, and such embodiments may include only agricultural materials and/or other non-wood fibers. In addition non-wood agricultural feedstock materials exhibit other significantly different characteristics from wood chips or fibers derived therefrom, e.g., as they are significantly less homogenous, containing a variety of structures making it further counter intuitive to process such materials together in a large batch.
[0104] Example embodiments of the invention embrace a production system which may implement particular conditions (e.g., chemical pulping conditions and other treatments, to preserve fiber length and strength) needed to enable effective processing to achieve the required physical, chemical, and/or performance characteristics of containerboard, and products made of containerboard. Embodiments of the invention may provide for a system and process that may include a production sequence of size reduction, mechanical refining, and an alkaline chemical pulping process, where the production sequence may serve to enhance the natural strength of the non-wood fiber inputs that are used to produce containerboard and products that include containerboard. In some embodiments, size reduction, mechanical refining and the like may be minimal before subjection to the alkaline chemical pulping process (cooking). In an embodiment, such size reduction, fractionating, and/or refining may be achieved within the modules associated with the papermaking machine, rather than in the pulp preparation process. For example, a relatively unrefined or “rough” pulp as produced by the present process may simply be fed into a pulper (skipping the detrashing module to which OCC may be fed) of the paper making process, joining with OCC coming from the detrashing module (should detrashing of the OCC be needed). Such a pulper may achieve the desired size reduction, fractionation, and/or refining, without the entity running the cooking process that produces the agricultural pulp fiber from having to perform such steps (which would be redundant), given the contemplated downstream use of the pulp product. In addition, embodiments of the invention embrace production processes that may limit the amount of water used in production by using closed loop circulation technologies.
A. Overview
[0105] The physical components of a corrugated paper container may include two types of paperboard, which may collectively be referred to as ‘containerboard.’ The two types of containerboard are testliner (also referred to simply as liner) and corrugated medium. Both types of containerboard are typically manufactured at paperboard mills out of either recycled wood pulp, virgin wood pulp, or a combination of recycled wood pulp and virgin wood pulp.
[0106] Industry data indicates that virgin wood pulps can maintain strength through multiple recycling processes (e.g., 7 recycles). However, the quality of recycled wood fibers diminishes with each re-pulping process, e.g., due to fiber shortening and other effects. To prolong the lifetime of the recycled material, a percentage of virgin fibers may be introduced which may help the finished containerboard meet performance characteristics acceptable in the market.
[0107] Thus, example embodiments of the invention include a wide variety of containerboard compositions that use virgin (or recycled) non-wood fibers as an alternative to virgin wood fibers. Such embodiments may, for example, enable reduced consumption of forest resources, such as wood fiber, while also providing for a relative improvement in the quality and longevity of the containerboard through the inclusion of non-wood fibers as a component of the containerboard.
B. General Aspects of Some Example Embodiments
[0108] Containerboard, example embodiments of which are disclosed herein, may be used in the manufacture of various types of corrugated materials and containers made of corrugated materials. The desired properties of containerboard may vary based on a number of considerations, such as the purpose of the corrugated container that is being produced. Corrugated containers are widely used for packing, storage, and transportation of goods. In one example application, corrugated containers intended for storage may need to have sufficient strength to accommodate stacking and resistance to crushing under an applied load.
[0109] In another example application, a box used for an e-commerce delivery in the mail system would need durability to withstand punctures and tears, while also being relatively lightweight so as to keep shipment costs down. Thus, such boxes and containers may have a relatively high strength-to-weight ratio.
[0110] In a third example application, corrugated containers used for transporting frozen foods would need insulative properties, and the ability to contain any fluid leakage without becoming saturated. Thus, some such frozen food containers may require the ability to be impregnated with, or otherwise accept, materials such as wax or another waterproofing agent which may serve to prevent leakage into, and out of, the container, while also preventing saturation of the box itself that could cause the corrugated material to fail.
[0111] Processes according to example embodiments of the invention that employ one or more types of non-wood fibers, may enable the production of containerboard and containerboard products to meet market demands such as those noted above.
C. Detailed Aspects of Some Example Embodiments
[0112] Recovering paper from a recycling stream may involve three major processes, namely, collection (whether residential or business), separation and sorting, and baling those materials of certain categories. These processes may be undertaken by one waste collection company, or by a waste collection company in conjunction with a specialized recycling company that handles the sorting and baling, and has ability to sell into the markets. According to the Institute of Scrap Recycling Industries, “Guidelines for Paper Stock: PS-2013-Export Transactions”, herein incorporated by reference in its entirety, there are 52 different categories of waste paper. The highest volume of waste paper (g comes from category #11 Old Corrugated Containers, also referred to as “OCC” which is commonly traded in the market in large square bales, typically ranging from 700-2000 lbs.
[0113] As category #11 OCC may be the most commonly available type of recycled paper product, that material may be particularly well suited for use in various embodiments of the invention. However, in addition, or as an alternative, to the use of OCC, embodiments of the invention may use recyclable paper and paper products of any grade (e.g., pulp thereof), and/or may use any paper or paper products that have already been recycled using conventional recycling processes (e.g., recycled pulp). Examples of other typically encountered recycled paper products include category #12 DS OCC (double sorted OCC), category #13 DLK (double lined kraft), category #36 UOP (unsorted office paper), and category #37 SOP (sorted office paper). Other categories are also possible, examples of which are found in “Guidelines for Paper Stock: PS-2013-Export Transactions”, already incorporated by reference in its entirety.
[0114] At least some embodiments may comprise unbleached products, such as containerboard for example, that are produced by processes and methods that do not use ozone, or other bleaching agents (e.g., no oxygen, chlorine, or other bleaching). The omission of bleaching agents from processes and products according to example embodiments of the invention may reduce production expenses, and may also contribute to production of a product with relatively greater strength and durability as compared with a product, such as printer paper and copier paper for example, that was produced in part with the use of a bleaching agent, where a high degree of whiteness or brightness is important. Embodiments of products that were produced without the use of ozone or other bleaching agents may be referred to herein as “unbleached”.
[0115] It was noted earlier herein that example embodiments of the invention may employ non-wood components, such as agricultural fibers for example, which may also be referred to herein as “agricultural feedstock material” or “agricultural residue”. Recovering agricultural residue is a process that takes place in a specific period of time after the harvest of the primary crop (e.g., corn). Typically, during the harvest of the main crop, the rest of the plant is cut from the ground. These materials can be gathered and baled in the field using techniques and equipment common to hay farmers and other agricultural baling operators. Some agricultural residues, such as wheat straw, already have a market. Wheat straw may be used, for example, for animal bedding or further processed in animal feed.
[0116] Note that as used herein, “agricultural residue” embraces, but is not limited to any portion of a primary crop that remains in/on/under a field after the primary crop has been harvested. In some cases, agricultural residue may consist only of portions of a primary crop, while in other cases, agricultural reside may also include, as a minority component, other plant material such as weeds and/or other non-crop plants. “Agricultural feedstock material” is a broader term, and would include non-wood agricultural materials that may be grown specifically for use as described herein (e.g., such as switchgrass, or other crops, that are not simply residues. All such materials may be used, as described herein.
[0117] In some cases, embodiments of the invention may employ one or more purposely grown fiber crops such as perennial grasses. Examples of such may include, but are not limited to miscanthus and/or switchgrass. Harvesting of such purposely grown fiber crops can involve the simultaneous process of cutting and baling at the time of harvest. Once the materials have been baled, they are ready for use in the production processes as described herein to become containerboard or other paper products as described herein (e.g., kraft paper).
[0118] With the foregoing in view, details are now provided concerning some particular illustrative embodiments of the invention. Such embodiments may include feedstock mixtures and blends, production processes, and intermediate and final products such as containerboard and products made of containerboard. Some example production processes may comprise three stages. Depending on the needs of the end user, one or more such stages may be omitted.
[0119] The first stage of some example production processes according to embodiments of the invention is fiber preparation. In the fiber preparation stage, bales of raw materials such as one or more agricultural feedstock materials that comprise, or consists of, fibers/fibrous material, may be run through up to three primary processes to reduce the fibers to a suitable size for pulping. These primary processes may comprise chopping or shredding, milling such as hammermilling, and screening. The processes of chopping, shredding and hammermilling will reduce the size of the fibers and/or the degree to which such fibers adhere to one another. Each of these three primary processes involves a cutting process, and at the end of each process is a screen with perforations or other openings which may be set at different sizes, such as from ⅛″ to 2″, so that the fiber lengths of the material that is being processed become smaller and more uniform with each successive process. It is noted that agricultural feedstock materials also contain a certain amount of ash, both extrinsic and intrinsic, which is not needed in the production of containerboard. The shredding and milling processes may help to remove ash, dirt, and other contaminants from the agricultural feedstock materials. Retention of some such materials in fibers, e.g., silica which may be present in corn stover or other agricultural feedstocks, may be desirable in some embodiments, e.g., for increased insulative value. After the milling and screening processes have been performed, it may or may not be necessary to perform additional screening to obtain optimal fiber lengths. By way of example, corn or wheat fibers from corn stover, wheat straw or similar cereals may have a fiber length that is relatively short, such as about 1 mm (e.g., 0.1 mm to 1.5 mm, or 0.5 mm to 1 mm). Hemp fibers may be significantly longer, e.g., from 3-6 mm in length. Hemp fibers may thus be similar in length to some soft-wood fibers (e.g., varieties of pine), while cereal fibers may be similar in length to some hard-wood fibers. It can be important to maintain a desired average fiber length, as decreasing fiber length through cutting or other processing can decrease strength properties of the finished containerboard. Pith materials (e.g., from the inside of stalks) may typically be shorter than the surrounding bast or other more exterior structural portions of the agricultural feedstock material. Such pith materials may be sufficiently short that they are screened out, as dust fines (e.g., particle sizes of less than 1 mm, less than 0.5 mm, less than 0.25 mm, or less than 0.1 mm). In an embodiment, such could be reintroduced into the papermaking process later (e.g., with pulp fibers, during production of liner or medium). By way of example, pith may account for 15-20% by weight of a given stalk's agricultural fibers. Pith size and concentration may of course depend on the identity of the agricultural feedstock material. Reintroduction of such fines at some point during papermaking can advantageously increase yield (usage of a greater fraction of the corn stover or other agricultural feedstock material).
[0120] The second stage of some example production processes may comprise pulping of the agricultural fibers, e.g., after any preliminary the fiber preparation stage has been completed. The pulping may involve chemical pulping and/or mechanical pulping. Certain fibers such as corn stover and wheat straw for example, may be pulped through a chemical process. One example chemical pulping process for agricultural fibers may comprise the following operations: [0121] Washing the fibers with water. [0122] impregnating the fibers with alkaline chemicals, such as sodium hydroxide at about 4 g/L to 40 g/L, 4 g/L to 20 g/L, 4 g/L to 10 g/L, 4 g/L to 9 g/L, 4 g/L to 8 g/L, or 8 g/L to about 20 g/L concentration within the alkaline liquor used to pulp the prepared agricultural feedstock material. Relatively lower concentrations, coupled with longer cooking times and relatively lower cooking temperatures, may be advantageous for providing overall higher yields, lower cost, and reduction in waste stream generation. Any of various additives may be included within the alkaline pulping liquor (e.g., sodium sulphide), although in an embodiment, no such additives other than the hydroxide (e.g., sodium hydroxide) or other alkali for extracting the lignin and hemicellulose are present (e.g., no peroxides, acids, enzymes, alcohols, etc.) The weight ratio of alkali to the agricultural feedstock material in the digester may be any suitable ratio, such as from 1:1 to 50:1, from 1:1 to 25:1, from 1:1 to 20:1, or 5:1 to 20:1. The weight ratio of active alkali to agricultural feedstock material may be from 5% to 50%, from 10% to 30%, from 15% to 25%, from 5% to 20%, or from 5% to 12% (e.g., 8% to 12%). In an embodiment, it is advantageous to extract the most lignin possible, with the least amount of alkali. [0123] Cooking into a pulp, e.g., with a continuous screw digester, such as a vertical or horizontal screw digester. A continuous screw digester may be advantageous, as compared to a batch cooking digester process, although batch processes are also contemplated and within the scope of the present disclosure. In an embodiment, out of service bleaching towers (e.g., from shut-down copy paper or similar mills) could be used for pulping. Although cooking conditions may vary generally from about 60° C. to 180° C., from 60° C. to 150° C., or from 60° C. to 120° C., an advantageous aspect of some embodiments of the present disclosure is that cooking occurs at less than 100° C., such as from 60° C. to 100° C., from 60° C. to 99° C. from 65° C. to 99° C. or from 65° C. to about 95° C. In an embodiment, the cooking temperature may be less than 100° C., which may advantageously eliminate the need for a cold blow discharge tank (a blow tank), because the temperature exiting the digester is less than 100° C., particularly where the cooking is carried out at atmospheric pressure. Above such temperatures and under pressurized conditions, a steam explosion associated with exiting the digester can damage particularly non-wood fiber cellular structures, due to differences between non-wood cell structures and wood cell structures. The elimination of a blow tank and similar expensive components is an important aspect of the present disclosure, which seeks to eliminate the need for such expensive components, insofar as possible. The residence time in the digester may range from about 15 minutes to about 10 hours, from 30 minutes to about 5 hours, from 1 hour to 5 hours, or from 1 hour to 3 hours. Relatively shorter times may be used at relatively higher temperatures, and longer times at lower temperatures. As noted, relatively longer residence times at lower temperatures (e.g., less than 100° C.) may be advantageous, for increasing overall yield. In an embodiment, the cooking process is carried out in 2-steps, within 2 reactors, with a screw press therebetween, as described in applicant's U.S. Application No. 63/280,855, already incorporated by reference in its entirety. [0124] refining at low consistency; and [0125] screen, press, and discharge the final pulp to storage tanks.
[0126] Where the alkali cooking process is carried out at moderate temperature and pressure (e.g., at atmospheric pressure, rather than under pressurized conditions) yield may actually be improved, and such conditions may negate the need for the typical cold blow discharge. Alternative systems and methods that include relatively high temperatures under pressurized conditions and inclusion of a cold blow discharge step result in significantly increased cost to the system. The elimination of such is an advantage of at least some embodiments according to the present disclosure.
[0127] In an embodiment, the yield of the agricultural fibers useable in liner, medium, or other paper product as compared to the starting agricultural feedstock material may be at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 85%, or at least 90% by weight. In an embodiment, yield may be from 60-65%. Yield can be increased as described herein (e.g., using relatively lower cooking temperature and longer residence times, reintroducing fines that may be screened out and later reintroduced during papermaking, etc.).
[0128] A mechanical pulping process may be used in place of, or in addition to, a chemical pulping process, and may take place before, simultaneously, or after, a chemical pulping process. Mechanical pulping processes may be employed for re-pulping OCC and other types of recovered paper. Of course, agricultural feedstock materials can also be processed by such methods. As noted above, a pulper may be used after chemical pulping/cooking of the agricultural feedstock fiber material to aid in achieving desired size and refinement characteristics, e.g., by introducing such agricultural pulp material into the pulper, with OCC, before processing through the papermaking machine. One example of a mechanical pulping process that may be employed in some embodiments of the invention may comprise the following operations: [0129] pulper/de-trashing performed by a pulper/de-trashing module (detrashing may only be needed for the OCC inputs) [0130] high density cleaning, such as with a grit separator; [0131] screening—using a coarse screen, and then a fine screen; [0132] cleaning, such as with two-stage fine cleaner banks; [0133] thickening, such as with a disc filter or side hill screen; [0134] fractionation, such as with fractionation screens or double nip thickeners; [0135] refining, which may comprise either disc or conical refining; and/or [0136] discharging of the material to storage tanks.
[0137]
[0138] By way of example, the low consistency pulping module of
[0139] The low consistency pulping module of
[0140] Removal of the lignin and hemicellulose from the pulp as quickly as possible, e.g., which is aided by inclusion of 3 modules (low consistency pulping, reactor 1, reactor 2) which perform such is beneficial in minimizing caustic consumption, as caustic in the presence of lignin (or hemicellulose) will continue to be consumed, even after the lignin or hemicellulose has already been separated from the pulp fibers. It is therefore beneficial to remove and separate the lignin and hemicellulose from the pulp structures as quickly as possible, to maximize efficient use of the caustic alkali material.
[0141] The low consistency pulping module may not operate as a pulper in the traditional sense, as it does not actually produce a pulp, but instead produces a material that requires further processing, to actually be considered a pulp (e.g., in reactors 1 and 2). Rather, this preliminary module serves to condition the corn stover or other non-wood agricultural feedstock material, shredding it to a smaller size (although still relatively large), creating a slurry in which the corn stover or similar material is shredded, and wetted, e.g., with average fragments being reduced in length or other size dimension to perhaps 0.5 to 1.5 inch (1.3 to 3.8 cm), creating a slurry having a consistency that is pumpable through the remainder of the system. Such a low consistency pulping module is an example of the first stage described herein, for reducing the size of the agricultural fibers to a desired length, and performing some degree of mechanical refining, preparatory to chemical pulping to be performed thereafter. As some caustic can be present in this module, a significant portion of the “fast” lignin, that portion which is most easily extracted, can be extracted from the corn stover or other agricultural feedstock in this stage of the process as well. The low consistency pulping module can include an extraction plate having holes formed therein, a rotor, stator (with the extraction plate positioned therebetween), as will be appreciated by those of skill in the art. The extraction plate openings may be configured to allow passage of materials with a size, e.g., from 0.25 inch to 1 inch (e.g., about 0.5 inch). Desired operation of the low consistency pulping module can be adjusted by adjusting various parameters for components of this module, such as extraction plate hole size or shape, density of holes in the plate, the gap between the plate and the rotor, as well as other parameters that effect the degree of shredding, how much lignin is extracted, and the like. The low consistency pulper differs from the subsequent reactor in that the pulper is particularly configured to wet the agricultural fiber feedstock material, mix the materials, and impregnate the feedstock material with the alkali liquor. The pulper is well agitated, providing a vortex, to sink the lightweight corn stover or similar feedstock material. While the pulper may include alkali caustic material to begin removal of the lignin, the pulper does not provide a reliable, well defined residence time, as does the reactor. In addition, the pulper is well agitated, while the reactor (e.g., a downflow reactor) may not be mixed. Rather, feedstock material simply exits the pulper once it is small enough to pass through the extraction plate (e.g., about 0.5 inch). The average residence time of the pulper may be, for example, 6-8 minutes, although this of course varies for individual volumes of feedstock material, depending on when the needed size reduction is achieved.
[0142] The pulp materials separated from the lignin and hemicellulose can be fed into reactor module 1, as shown in
[0143] The material exiting from reactor 1 is fed into a screw press, as shown in
[0144] Pulp exiting the screw press can be sent to a mixing conveyor, as shown in
[0145] Although the data in
[0146] The first reactor may be agitated, while the second reactor may provide pulping without agitation.
[0147] The coarse screening, refining, and/or fine screening modules may serve to fractionate the pulp materials, based on fiber length, or diameter. By way of example, refining may be achieved with a double disk refiner with low intensity refining plates, as will be appreciated by those of skill in the art. The coarse screening step may serve to separate that portion of the pulp that should be sent to the refiner. The small fraction passing through the coarse screen may not necessarily be fed into the refiner, as the small components do not need refining. Because corn stover and similar agricultural feedstock materials are not homogenous, as would be a wood feedstock, various different fiber lengths, as well as even non-fiber structures may be present in the pulp before fractionation. It may be desirable to remove some such structures, during screening, for example. For example, cobs are largely formed from nonfibrous material, including a large fraction of parenchyma cells, which appear rather as generally spherical or rounded particulates. Cobs may account for at least 10% by weight of some corn stover. In an embodiment, it would be advantageous to harvest corn stover in a way that would leave the cobs on the field. Where cob particulates (e.g., in the form of parenchyma cells) are included in the pulp material exiting the chemiwasher (or a screw press) with the pulp, they can be separated from the pulp, as fines, using washing, if desired. Such materials can be added back into the pulp before introduction of pulp into the blend chest, to increase yield, if desired. By way of example, a given pulp product prepared from corn stover included a size distribution where 23% by weight of the material passed through a 200 mesh (75 micron opening) screen. Most if not all of these fines are believed to be parenchyma. In an embodiment, it may be beneficial to maintain such parenchyma in larger chunks (e.g., 10-20 parenchyma cells), rather than having them be present as smaller fines, as individual parenchyma cells. Such may aid in increasing the freeness value, e.g., to greater than 300, or greater than 400 mL CSF.
[0148] While
[0149]
[0150] Depending upon the embodiment, multiple types of pulp may be produced in either parallel or staggered production lines, and combined together later. Such may be particularly advantageous where the different types of pulp require different processing (e.g., relatively short fiber cereal agricultural feedstock materials, as compared to long fiber hemp agricultural material). After the pulping process, if multiple types of pulp are combined, the relative amounts of the different pulps can be adjusted at variable percentages, in a stock preparation system. In an example mixing process in which pulps of two or more different types are combined together, a first operation may involve the use of an agitated blend chest that can mix multiple pulps, at various percentages depending on desired containerboard characteristics. The blended stock may then pass to a machine chest, and is then diluted just before being discharged across a wire screen to the headbox of a paper production machine.
[0151] The third stage of some example production processes may comprise production of a product, such as containerboard for example, on paper machines which may, or may not be conventional paper machines typically used in the industry today. Example paper machines that may be employed in connection with some embodiments of the invention may comprise multiple sections, listed hereafter in order from upstream to downstream in the production process: headbox; forming section; press section; drying section; and, reel section.
[0152] In the production process, water from the pulps is drained and the material is then pressed into a continuous sheet that winds onto a reel at the end of the paper machine. The resulting product from this paper machine may be a jumbo roll of containerboard, such as testliner, medium (e.g., for corrugation), or even a corrugated multi-layer material (liner+corrugated medium). These paper machines can produce either a single-ply or multi-ply sheet. In a multi-ply sheet the different plies may be provided with different compositional characteristics (e.g., greater fraction of agricultural fibers in one ply than another). When producing a corrugated container, the liner may similarly have different compositional characteristics than the corrugated medium (e.g., greater fraction of agricultural fibers in one layer than the other). The roll widths may vary in length from about 90″ to about 250,″ although larger or smaller widths may be employed. The basis weights of this paper generally range from about 100 gsm to about 250 gsm, or from 20.5# to 51.2#. In an embodiment, the basis weight is greater than that of typical copy paper, e.g., at least 100 gsm. In further contrast relative to a typical copy paper process, there is typically no need for any acid treatments, oxidation (e.g., ozone) or bleaching treatments for the pulp (e.g., in contrast to U.S. Pat. No. 6,302,997 to Hurter, as well as other processes that require relatively high whiteness or brightness).
[0153] At this point, the containerboard is now ready for use in a corrugation process, and can be made into a box or other product that includes a corrugated portion. The containerboard may also be used for other paper products such as, but not limited to, protective inserts, sacks and bags, mailing envelopes, and cards and tags. Some example container products that may be produced using the pulp blends and processes of example embodiments are shown in
D. Further Aspects of Some Example Processes
[0154] With reference next to
TABLE-US-00001 TABLE 1 Wheat Distillers or rice Dried Other residue Corn Soybean Non- Grains (bamboo, (wheat residue or Virgin virgin w/ Switchgrass sugarcane or rice (corn Hemp cotton wood wood Solubles or bagasse, OCC straw) stover) fiber residue pulp pulp (DDGS) miscanthus etc.) OCC X X X X X X X X X Wheat or X X X X X X X X X rice residue (wheat or rice straw) Corn X X X X X X X X X residue (corn stover) Hemp fiber X X X X X X X X X Soybean or X X X X X X X X X cotton residue Virgin X X X X X X X X X wood pulp Non-virgin X X X X X X X X X wood pulp Distillers X X X X X X X X X Dried Grains w/Solubles (DDGS) Switchgrass X X X X X X X X X or miscanthus Other X X X X X X X X X X (bamboo, sugarcane bagasse, etc.)
[0155] In an example embodiment, the feedstock percentages for various agricultural fiber materials may be as follows: corn=30% (+/−5%); wheat=20% (+/−5%); and, OCC=50% (+/−5%). Note that these percentages may refer to weight percentages of the raw materials, as measured prior to commencement of a paper production process. Any of the selected feedstocks may range from, for example, at least 3%, 5% to 95%, 10% to 90%, 15% to 85%, 20% to 80%, 25% to 75%, 30% to 70%, 35% to 65%, 40% to 60%, or 45% to 55%. Exemplary values for any feedstock may include 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%. Additional ranges may be formed by selecting any 2 of such values.
[0156] The components and associated reference numbers for
[0157]
[0185]
[0213]
[0249]
[0271] Some of the examples shown in
[0272] For example,
[0273] By way of example, in the case of a corn stover process similar to that seen in
[0274] The freeness of the employed pulps, or pulp blends may be any desired value. By way of example, the freeness of such may be from 200 to 500 mL CSF, 200 to 450 mL CSF, 200 to 300 mL CSF, at least 300 mL CSF, such as 300-500 mL CSF, from 350-400 mL CSF, or 375-425 mL CSF. Higher freeness values correspond to faster drainage of the water from the paper making pulp mixture. Where freeness is too low, this may interfere with the ability to effectively form the desired containerboard. Where freeness is too high, drainage may be so fast that it can result in a product with poor strength characteristics, and uneven dispersion of pulp fibers.
[0275] Advantageously, any residual alkali (e.g., hydroxide) within the pulp may be removed through a washing or other suitable step, so that the final produced containerboard, and the pulp fibers from which such is formed may have a pH value of about 7 (e.g., 6 to 8, such as 6.5 to 7.5).
E. Testing, Experiments, and Trials
[0276] Any reference to ASTM, ISO, TAPPI or other standards refers to the latest update to any such standard, unless otherwise indicated. Any such referenced standards are herein incorporated by reference in their entirety.
Trial 1.
[0277] An exemplary fiber preparation process for hemp and corn stover was evaluated. A standard silage chopper with a 2″ screen was used for fiber preparation of both hemp and corn stover materials. The goal of the trial was to test pure hemp, pure corn stover, and OCC at various levels of refinement, as well as to evaluate a range of blends of such raw materials for testing. When testing hemp, it was found that the long fibers roped around the agitator, which may have been responsible at least in part for lower than optimum strength results for hemp. A total of 17 blends were prepared and tested. It was observed at the end of the first complete set that the freeness of the OCC was abnormally high, about 700 mL CSF. Reducing the freeness may improve homogenous dispersion of fibers, and the strength of the paper product. A second batch formed from the same blends was prepared, using OCC that had been refined down to a freeness value of about 450 mL CSF.
[0278] Trial 1 Corn Stover Digester
[0279] A shipment of raw chopped hemp stalks (cat. 1) and corn stover from Murray State University in Kentucky was used for Trial 1. 350 g of oven dried corn stover was alkali digested in a 5 L batch digester with 20% active alkali (relative to the hemp, by weight), at a liquor to chip ratio of 6:1 (no sodium sulfide added). The digester used a small pump to recirculate liquor through the bed of chips. One corn stover cook was also completed with this batch digester setup, but recirculation problems were observed on the second attempt. To reduce this problem, in the next batch, the corn stover was first wet de-pithed by soaking the chips in hot water (approx. 115° F.) and refining them in a chip refiner with the gap set to 0.060 inch. Resultant chips were collected, air dried, and sifted through a 1/16th inch mesh screen. A cook with the de-pithed chips was attempted, but abandoned early due to continued poor liquor recirculation.
[0280] The corn stover cooks were completed by decreasing the amount of chips in the digester to 200 g (on an oven dried basis), and increasing the liquor to chip ratio (L:C or L:W) to 9:1. For each cook, the pH was monitored before and after each cook, and the liquor tested for residual alkali. The first corn stover cook had a calculated H-factor of 245 and a residual alkali (RA) of 10.9 g/L Na.sub.2O. H-factor is a pulping variable measurement that combines cooking temperature and time into a single variable, and its calculation will be apparent to those of skill in the art. There was concern that the fibers were over-cooked, and precipitation of lignin may be occurring. The remaining cooks were lowered to a calculated H-factor of 132 and the active alkali percentage lowered to 15% (relative to the corn stover, by weight), as shown in Table 2. The corn stover cook temperature was 160° C.
TABLE-US-00002 TABLE 2 % Active Alkali Residual Residual Chips (g) Digester (relative Calc. Alkali Alkali Sample OD (L) to Chips) L:W H-Factor (#/ft.sup.3 Na.sub.2O) (g/L Na.sub.2O) Corn 350 5 20 6 245 0.682 10.93 Stover 1 Corn 200 5 20 9 132 0.461 7.39 Stover 2 Corn 200 5 20 9 132 0.447 7.16 Stover 3 Corn 450 10 15 9 132 0.248 3.97 Stover 4 Corn 450 10 15 9 132 0.171 2.75 Stover 5 Corn 450 10 15 9 132 0.234 3.75 Stover 6
[0281] Trial 1 Hemp Digester
[0282] For the hemp digestion. Trial 1 started with Category 1 hemp: rough chopped stalks—pre CBD extraction. While these broke down well in the digester, the bast fibers were very long and screened out. The bast fibers would be expected to increase the tear strength of paper with proper distribution (i.e., minimal or no clumping) in the sheet. Traditional papermaking does not handle long fibers (>5 mm length) well and can result in roping of fibers in the stock approach system or poor dispersion during sheet formation. After testing the residual alkali from the first sample (Hemp Cat. 1-1) it was observed that there was alkali left, and that the cook time should be increased. The cooking conditions and residual alkali testing for the hemp fibers are referenced in Table 3. The hemp cook temperature was 170° C.
TABLE-US-00003 TABLE 3 % Active Alkali Residual Residual Chips Digester (relative Calc. Alkali Alkali Sample (g) OD (L) to Chips) L:W H-Factor (#/ft.sup.3 Na.sub.2O) (g/L Na.sub.2O) Hemp Cat. 1-1 350 5 20 5 132 0.899 14.39 Hemp Cat. 1-2 350 5 20 5 397 0.790 12.65 Hemp Cat. 1-3 350 5 20 5 397 0.828 13.26 Hemp Cat. 4-1 635.5 10 20 6 627 0.599 9.60 Hemp Cat. 4-2 650 10 20 6 704 0.589 9.43 Hemp Cat. 4-3 650 10 20 6 704 0.560 8.97
[0283] After each cook, the free-flowing black liquor was collected for further analysis. The chips were washed with a known amount of hot tap water and the filtrate collected. Chips were refined in a Sprout-Waldron 105-A 12″ Refiner with a 0.010″ gap. Before every refining, the refiner was heated, and the gap checked using a feeler gauge. Resultant fibers were screened for 20 minutes through an 0.008″ Somerville flat screen, with the cuts parallel to the direction of flow. Accept and reject fibers were collected; yield, Kappa, and percent Ash were determined on the accept fibers (Table 4). From the yield and collected black liquor and wash, the amount of black liquor, total suspended solids, and total dissolved solids in a sample from each type of fiber were calculated (Table 5).
TABLE-US-00004 TABLE 4 Yield-Overall Yield-Collected Sample Accept (%) Reject (%) Accept (%)2 Reject (%)3 Freeness Kappa Ash (%) Corn Stover 37.53 0.15 99.61 0.39 294.17 11.02 6.08 std.dev 1.76 0.20 0.51 0.51 60.45 3.52 Hemp Cat-1 42.09 2.93 93.33 6.67 573.33 89.40 3.41 std.dev 4.30 1.72 4.34 4.34 20.82 19.03 Hemp Cat-4 39.60 0.50 98.73 1.27 568.33 99.00 7.64 std.dev 2.99 0.25 0.70 0.70 30.14 5.03
TABLE-US-00005 TABLE 5 Black Liquor Total Total Suspended Total Dissolved Sample Solids (%) Solids Solids Corn Stover 7.88 247.81 35.52 Hemp Cat-1 11.81 378.88 — Hemp Cat-4 11.17 596.21 46.53
[0284] After producing more than 700 g of accept hemp and corn stover fibers, a PFI mill study was performed on each fiber type to test freeness vs handsheet physical strength. Each fiber was refined at 0, 250, 500, and 1000 revolutions (e.g., in the PFI mill). If the freeness dropped below 200, the study was stopped. Table 6 reports the fiber refining vs. freeness, with each fiber type being tested in duplicate.
TABLE-US-00006 TABLE 6 Sample Revolutions Average Freeness Corn Stover 0 310 Corn Stover 250 180 Hemp Cat-1 0 485 Hemp Cat-1 250 395 Hemp Cat-1 500 390 Hemp Cat-1 1000 345 Hemp Cat-4 0 475 Hemp Cat-4 250 365 Hemp Cat-4 500 355 Hemp Cat-4 1000 320
[0285] The fibers from each revolution point were formed into handsheets following the procedure written in TAPPI T205. After the handsheets dried and cured to 73° F. and 50% relative humidity, the paper was tested for its physical properties: basis weight, caliper, density, tear, tensile, burst, and taber stiffness, following TAPPI Standards T220 and T566. Table 7 reports the average results from testing. From this data, it was concluded that separate refining of the fiber types may be helpful in achieving optimal strength properties in a mixed fiber paper.
TABLE-US-00007 TABLE 7 Basis Taber Tensile weight Caliper Density Stiffness Tear Index Burst Index Index Sample (gsm) (0.001″) (g/cm.sup.3) (TSU) (m•Nm.sup.2/g) (kPa•m.sup.2/g) (N•m/g) Hemp 62.88 5.59 0.443 0.498 4.88 1.67 37.21 Cat-4 0 Rev Hemp 63.29 5.31 0.469 0.586 4.36 2.19 47.30 Cat-4 250 Rev Hemp 63.21 4.88 0.510 0.606 4.63 2.31 47.46 Cat-4 500 Rev Hemp 64.93 4.82 0.530 0.637 4.63 2.77 52.22 Cat-4 1000 Rev Hemp 67.35 4.84 0.548 0.571 4.40 3.26 62.85 Cat-4 3000 Rev Corn 65.05 4.84 0.529 0.509 6.95 4.85 87.90 Stover 0 Rev Corn 66.76 4.49 0.586 0.528 6.17 5.14 82.67 Stover 250 Rev Hemp 59.35 4.86 0.481 0.436667 6.15 2.75 52.38 Cat-1 0 Rev Hemp 59.76 4.80 0.490 0.521667 5.44 3.33 57.30 Cat-1 250 Rev Hemp 57.46 4.38 0.517 0.6 6.03 3.68 61.45 Cat-1 500 Rev Hemp 55.78 4.24 0.518 0.503333 5.23 3.79 67.07 Cat-1 1000 Rev
[0286] 17 handsheet samples including varying amounts of OCC, corn stover, and hemp were formed, outlined in Table 8. The OCC and corn stover were un-refined, and the hemp was refined in the PFI mill for 250 revolutions. Sample 9 was a control, formed from 100% OCC.
TABLE-US-00008 TABLE 8 OCC Hemp Corn Sample (%) (%) (%) 1 75.0 25.0 0.0 2 75.0 0.0 25.0 3 50.0 0.0 50.0 4 50.0 25.0 25.0 5 58.3 33.3 8.3 6 66.7 16.7 16.7 7 75.0 0.0 25.0 8 50.0 50.0 0.0 9 100.0 0.0 0.0 10 83.3 0.0 16.7 11 58.3 8.3 33.3 12 83.3 16.7 0.0 13 66.7 16.7 16.7 14 66.7 16.7 16.7 15 50.0 25.0 25.0 16 66.7 33.3 0.0 17 66.7 16.7 16.7
[0287] 15 handsheets were produced from each set of blended fibers. The 10 best handsheets were tested for physical strength properties. The best handsheets were chosen from a standard deviation of the grammage, with no damage to the sheets. These properties were used to determine how adding hemp or corn stover fibers to the OCC would affect the strength properties of the product.
[0288] The first blended handsheet study used OCC as received from a local papermill. After the first set was tested, it was found that the provided OCC had a higher freeness (755 mL CSF) than expected for typical OCC. The trial was redone with the OCC refined to a freeness of 435 mL CSF. The same blends and testing procedures were used.
[0289] Table 9 shows grammage, basis weight, caliper and density measurements for each of the first 17 samples (where the OCC exhibited higher freeness).
TABLE-US-00009 TABLE 9 Grammage Basis Wt. Caliper Density Sample g (gsm) (0.001″) g/cm.sup.3 1 1.251 62.56 6.60 0.371 2 1.256 62.81 5.69 0.435 3 1.266 63.28 5.49 0.453 4 1.241 62.05 5.51 0.448 5 1.234 61.69 5.48 0.445 6 1.227 61.36 5.72 0.425 7 1.240 62.02 5.94 0.409 8 1.206 60.29 5.28 0.448 9 1.327 66.33 6.77 0.386 10 1.269 63.45 6.15 0.403 11 1.260 63.02 5.46 0.456 12 1.245 62.27 6.35 0.387 13 1.182 59.09 5.24 0.447 14 1.278 63.89 5.66 0.444 15 1.196 59.79 5.55 0.426 16 1.216 60.78 5.40 0.447 17 1.260 63.00 5.54 0.446
[0290] Tables 10-11 report various characteristics for the paper formed from the blends of Table 9.
TABLE-US-00010 TABLE 10 Tear Tensile Tensile Index Strength Index Freeness Sample Tear (mN) mN.m.sup.2/g Tensile N kN/m N.m/g Stretch % TEA J/m.sup.2 CSF 1 923.37 14.77 28.14 1.88 29.98 1.63 20.58 690 2 937.21 14.93 38.54 2.57 40.89 1.95 32.84 625 3 886.74 14.01 47.63 3.18 50.18 2.09 43.89 535 4 769.17 12.40 40.73 2.72 43.75 1.98 36.97 580 5 780.62 12.65 36.32 2.42 39.25 1.97 30.31 580 6 896.73 14.61 37.79 2.52 41.06 1.79 28.87 620 7 911.1 14.69 34.87 2.32 37.48 1.85 28.60 640 8 777.94 12.93 39.14 2.61 43.29 2.02 34.67 590 9 880.8 13.28 24.76 1.65 24.88 1.36 13.84 755 10 934.24 14.62 32.46 2.16 34.11 1.79 23.73 675 11 826.15 13.11 46.31 3.09 49.00 2.00 41.31 560 12 859.5 13.82 27.82 1.85 29.80 1.47 18.31 695 13 815.46 13.80 35.32 2.35 39.85 1.67 26.36 605 14 883.73 13.83 35.85 2.39 37.42 1.96 30.28 620 15 737.1 12.32 36.01 2.40 40.17 1.85 30.43 565 16 772.73 12.71 32.75 2.18 35.93 1.75 26.00 580 17 852.09 13.52 36.08 2.41 38.18 1.93 31.51 605
TABLE-US-00011 TABLE 11 Burst Index Stiffness Sample Burst PSI Burst kPa kPa.m.sup.2/g Taber left Taber Right Taber Average TSU (mN m) 1 14.91 102.81 1.64 6.66 4.84 5.75 0.58 56387.95 2 21.33 147.07 2.34 6.04 4.74 5.39 0.54 52857.57 3 27.49 189.52 3.00 6.24 5.14 5.69 0.57 55799.55 4 22.58 155.68 2.51 6.38 5.02 5.7 0.57 55897.62 5 19.94 137.49 2.23 6.98 4.1 5.54 0.55 54328.56 6 20.94 144.36 2.35 6.86 4.52 5.69 0.57 55799.55 7 18.57 128.01 2.06 6.72 4.14 5.43 0.54 53249.84 8 21.43 147.78 2.45 6.18 4.06 5.12 0.51 50209.79 9 12.00 82.76 1.25 7.34 4.3 5.82 0.58 57074.41 10 17.71 122.09 1.92 6.44 4.12 5.28 0.53 51778.85 11 26.95 185.81 2.95 6.32 4.18 5.25 0.53 51484.65 12 15.29 105.41 1.69 5.98 4.48 5.23 0.52 51288.52 13 21.34 147.10 2.49 4.18 2.94 3.56 0.36 34911.50 14 20.71 142.80 2.23 6.32 3.62 4.97 0.50 48738.80 15 19.84 136.79 2.29 6.56 3.42 4.99 0.50 48934.93 16 18.33 126.40 2.08 7.28 3.84 5.56 0.56 54524.70 17 20.12 138.72 2.20 6.94 2.82 4.88 0.49 47856.21
[0291] Table 12 shows grammage, basis weight, caliper and density measurements for each of the second 17 samples (where the OCC exhibited lower freeness).
TABLE-US-00012 TABLE 12 Grammage Basis Wt. Caliper Density Sample g (gsm) (0.001″) g/cm.sup.3 1* 1.271 63.56 5.09 0.491 2* 1.258 62.89 4.85 0.508 3* 1.250 62.49 4.87 0.502 4* 1.168 58.42 4.91 0.471 5* 1.208 60.41 4.74 0.509 6* 1.274 63.71 5.33 0.472 7* 1.194 59.68 4.80 0.492 8* 1.186 59.30 4.85 0.482 9* 1.227 61.33 4.97 0.486 10* 1.224 61.18 4.86 0.497 11* 1.277 63.87 4.93 0.509 12* 1.187 59.37 5.17 0.456 13* 1.251 62.55 4.93 0.496 14* 1.192 59.59 4.74 0.498 15* 1.158 57.90 4.93 0.467 16* 1.217 60.86 5.01 0.479 17* 1.195 59.77 4.77 0.494
[0292] Tables 13-14 reports various characteristics for the paper formed from the blends of Table 12.
TABLE-US-00013 TABLE 13 Tear Tensile Tensile Index Strength Index Sample Tear (mN) mN.m.sup.2/g Tensile N kN/m N.m/g Stretch % TEA J/m.sup.2 Freeness CSF 1* 817.82 12.90 55.53 3.70 58.21 2.55 64.77 470.00 2* 736.29 11.70 57.84 3.86 61.29 2.47 67.55 410.00 3* 608.60 9.74 64.13 4.28 68.41 2.36 65.82 415.00 4* 605.77 10.37 49.46 3.30 56.40 2.26 50.78 420.00 5* 665.39 11.02 53.35 3.56 58.90 2.68 65.32 405.00 6* 723.69 11.36 55.56 3.70 58.12 2.23 55.42 415.00 7* 656.10 10.99 58.60 3.91 65.47 2.19 55.92 350.00 8* 615.99 10.39 50.79 3.39 57.10 2.24 51.04 455.00 9* 762.76 12.44 59.96 4.00 65.19 2.47 64.94 435.00 10* 769.87 12.58 58.64 3.91 63.91 2.53 65.79 420.00 11* 689.59 10.80 60.09 4.01 62.70 2.12 56.41 385.00 12* 779.40 13.12 53.83 3.59 60.48 2.47 50.05 475.00 13* 672.09 10.75 53.70 3.58 57.24 2.41 59.00 360.00 14* 723.49 12.15 48.30 3.22 54.03 2.42 53.19 405.00 15* 659.51 11.40 48.70 3.25 56.07 2.13 49.58 340.00 16* 679.42 11.17 50.68 3.38 55.51 2.32 53.26 460.00 17* 688.50 11.52 54.63 3.64 60.94 2.21 53.98 405.00
TABLE-US-00014 TABLE 14 Burst Index Taber Stiffness Sample Burst PSI Burst kPa kPa.m.sup.2/g Taber left Taber Right Average TSU (mN m) 1* 36.26 249.99 3.93 4.68 3.46 4.07 0.41 39912.9 2* 39.63 273.25 4.35 6.56 2.76 4.66 0.47 45698.8 3* 33.32 229.76 3.68 5.32 2.48 3.90 0.39 38245.7 4* 30.39 209.54 3.58 3.32 4.16 3.74 0.37 36676.7 5* 34.12 235.28 3.89 3.08 3.64 3.36 0.34 32950.2 6* 33.86 233.43 3.66 5.90 4.08 4.99 0.50 48934.9 7* 39.43 271.86 4.56 4.64 4.86 4.75 0.48 46581.4 8* 30.91 213.10 3.59 4.68 4.16 4.42 0.44 43345.2 9* 38.00 261.99 4.27 6.96 4.04 5.50 0.55 53936.3 10* 38.70 266.82 4.36 6.48 3.76 5.12 0.51 50209.8 11* 36.93 254.60 3.99 6.04 2.44 4.24 0.42 41580.0 12* 34.49 237.79 4.01 6.44 2.98 4.71 0.47 46189.1 13* 36.24 249.84 4.00 6.26 2.82 4.54 0.45 44522.0 14* 29.91 206.19 3.46 5.62 1.78 3.70 0.37 36284.4 15* 29.86 205.85 3.55 3.74 3.26 3.50 0.35 34323.1 16* 32.09 221.27 3.64 6.10 3.36 4.73 0.47 46385.2 17* 33.11 228.28 3.82 5.12 3.86 4.49 0.45 44031.6
[0293] Even after refining the OCC down to a more typical value of 435 mL CSF freeness, several of the samples show similar strength characteristics as compared to the OCC control, showing that non-wood agricultural fibers can be incorporated into the paper product, while generally maintaining desired mechanical and physical properties. As noted herein, where care is taken in the chemical pulping and other processes used to prepare the agricultural fiber pulp material, to ensure that fiber length and strength of such fibers are maintained, further improvements and better yields can be achieved. For example, it can be important to limit the use of high temperatures, high pressures, and the use of certain chemicals (e.g., ozone, acids, peroxides, etc.), to maintain or increase strength, while at the same time minimizing generation of hazardous waste streams for which disposal accommodations must be made.
Trial 2.
[0294] For trial 2, the fiber preparation process was further developed, including shredding, hammermilling, and screening. In addition, the cooking temperature was reduced to 150° C., compared to trial 1 (where it was 160° C. for the corn stover and 170° C. for the hemp). As noted herein. Applicant has found that even lower temperatures (less than 100° C.) are even better suited to producing desired results.
[0295] Material Preparation
Hammermill
[0296] 2.5×50 mm slotted screen
[0297] Digester Cook 1:
Process Run ID: CS-1150° C. 30 minutes
10 g/L NaOH—1200 g 50% NaOH solution+58.8 L RO water
3500 g corn stover (94.6% csy=3312.4 g od)
Liquor heating to 150° C.—14 minutes
Ramping time for material to reach 150° C.—5 minutes
Cooking time—30 minutes. Black liquor samples taken every 5 minutes during run, 6 Samples in total
Maximum temperature during cook—150.9° C.
Average temperature during cook—150.3° C.
Cooling time at end of run—18 minutes to 60° C.
Steam wash—5 minutes
Final Material Weight—8239.1 g @ 22.0% csy=1812.60 g OD 54.7% Yield
[0298] Digester Cook 2:
Process Run ID: WS-1150° C. 30 minutes
10 g/L NaOH—1200 g 50% NaOH solution+58.8 L RO water
3500 g wheat straw (95.2% csy=3332.0 g od)
Liquor heating to 150° C.—10 minutes
Ramping time for material to reach 150° C.—4 minutes
Cooking time—30 minutes. Black liquor samples taken every 5 minutes during run, 6 samples in total
Maximum temperature during cook—151.0° C.
Average temperature during cook—150.6° C.
Cooling time at end of run—20 minutes to 60° C.
Steam wash—5 minutes
Final Material Weight—7198.2 g @ 22.6% csy=1628.23 g OD
48.9% Yield
[0299] Digester Cook 3:
Process Run CS-2 150° C. 30 minutes
8 g/L NaOH—960 g 50% NaOH solution+59.04 L RO water
3500 g corn stover (94.64% csy=3312.4 g od)
Liquor heating to 150° C.—12 minutes
Ramping time for material to reach 150° C.—4 minutes
Cooking time—30 minutes. Black liquor samples taken every 5 minutes during run, 6 samples in total
Maximum temperature during cook—151.1° C.
Average temperature during cook—150.7° C.
Cooling time at end of run—16 minutes to 60° C.
Steam wash—5 minutes
Final Material Weight—8635.8 g @ 27.7% csy=2392.13 g OD 72.2% Yield
[0300] Digester Cook 4:
Process Run ID: WS-2 150° C. 30 minutes
8 g/L NaOH—960 g 50% NaOH solution+59.04 L RO water
3500 g wheat straw (95.2% csy=3332.0 g od)
Liquor heating to 150° C.—10 minutes
Ramping time for material to reach 150° C.-4 minutes
Cooking time—30 minutes. Black liquor samples taken every 5 minutes during run, 6 samples in total
Maximum temperature during cook—150.6° C.
Average temperature during cook—150.4° C.
Cooling time at end of run—18 minutes to 60° C.
Steam wash—5 minutes
Final Material Weight—8515.5 g @ 24.4% csy=2075.02 g OD 62.3% Yield
[0301] Digester Cook 5:
Process Run ID: CS-3 150° C. 30 minutes
9 g/L NaOH—1080 g 50% NaOH solution+58.92 L RO water
3500 g corn stover (94.64% csy=3312.4 g od)
Liquor heating to 150° C.—12 minutes
Ramping time for material to reach 150° C.—4 minutes
Cooking time—30 minutes. Black liquor samples taken every 5 minutes during run, 6 samples in total
Maximum temperature during cook—150.6° C.
Average temperature during cook—150.4° C.
Cooling time at end of run—18 minutes to 60° C.
Steam wash—5 minutes
Final Material Weight—7499.0 g @ 22.8% csy=1712.77 g OD 51.7% Yield
[0302] Digester Cook 6:
Process Run ID: WS-3 150° C. 30 minutes
9 g/L NaOH—1080 g 50% NaOH solution+58.92 L RO water
3500 g wheat straw (95.2% csy=3332.0 g od)
Liquor heating to 150° C.—10 minutes
Ramping time for material to reach 150° C.—4 minutes
Cooking time—30 minutes. Black liquor samples taken every 5 minutes during run, 6 samples in total
Maximum temperature during cook—150.7° C.
Average temperature during cook—150.5° C.
Cooling time at end of run—18 minutes to 60° C.
Steam wash—5 minutes
Final Material Weight—7802.4 g @ 22.1% csy=1722.77 g OD 51.7% Yield
[0303] Table 15 shows data for hammer milling and screening of wheat straw.
TABLE-US-00015 TABLE 15 Hammermill Processing of Wheat Straw Screen type Slotted screen Screen size 2.5 mm/50 mm Mass Before Hammer After Hammer material- Milling Milling 14.1 kg 13.4 kg Rotary Drum Screen Size 1/32 inch Run time for each batch 2 minutes Wheat Straw Batch weight Dust Collected Batch 1 2 kg 0.130 kg Batch 2 2 kg 0.105 kg Batch 3 2 kg 0.101 kg Batch 4 2 kg 0.104 kg Batch 5 2 kg 0.114 kg Batch 6 2 kg 0.111 kg Batch 7 2.1kg 0.135 kg Initial weight Final weight Total dust before screening after screening Collected 14.1 kg 13.2 kg 0.800 kg
[0304] Table 16 shows data for hammer milling and screening of corn stover.
TABLE-US-00016 TABLE 16 Hammermill Processing of Corn Stover Screen type Slotted screen Screen size 2.5 mm/50 mm Mass material - Before Hammer After Hammer Milling Milling 14.6 kg 11.9 kg Rotary Drum Screen Size 1/32 inch .sup. Run time for each batch 2 minutes Corn Stover Weight for each batch Dust Collected Batch 1 2 kg 0.225 kg Batch 2 2 kg 0.195 kg Batch 3 2 kg 0.190 kg Batch 4 2 kg 0.167 kg Batch 5 2 kg 0.195 kg Batch 6 1.9 kg 0.212 kg Initial weight Final weight Total dust before screening after screening Collected 11.9 kg 10.6 kg 1.184 kg
[0305] Table 17 shows corn stover soda pulp handsheet data for different samples, (e.g., how many g/L of NaOH used in pulping, how many revolutions milled in the PFI mill).
TABLE-US-00017 TABLE 17 Corn Corn Corn Corn Stover Stover Stover Stover 10 g/L 8 g/L 8 g/L 9 g/L Sample Number unmilled unmilled 250 rev unmilled Freeness, ml 330 376 208 330 Moisture, % 9.25 9.14 10.06 9.25 Oven dry Grammage, g/m.sup.2 59.7 62.0 61.3 59.7 Bulk, cm.sup.3/g 1.82 2.44 2.30 1.82 Tear Index, mN*m.sup.2/g 7.15 5.28 7.41 7.15 Breaking length, km 4.52 2.96 3.99 4.52 Tensile Index, N m/g 44.3 29.1 39.1 44.3 Stretch, % 2.09 2.19 2.70 2.09 Burst Index, kPa*m.sup.2/g 2.08 1.19 1.68 2.08 Energy@break (J/m.sup.2) 31.0 15.3 24.7 31.0 Final Strain (%) 2.10 2.21 2.47 2.10
[0306] All handsheets were formed according to TAPPI T205 sp-18 Forming Handsheets for Physical Tests of Pulp and tested according to TAPPI T200 sp-16 Physical Testing of Pulp Handsheets. Any pulps with Freeness values below 200 mL CSF were not formed into handsheets.
[0307] Tables 18A-18B show wheat straw soda pulp handsheet data for various samples.
TABLE-US-00018 TABLE 18A Wheat Wheat Wheat Wheat Wheat straw straw straw Straw straw 9 g/L 9 g/L 9 g/L 9 g/L 10 g/L Sample Number unmilled 250 rev 500 rev 1000 rev unmilled Freeness, ml 522 313 280 220 612 Moisture, % 9.82 9.17 9.50 9.74 9.85 Oven dry Grammage, g/m.sup.2 59.0 63.4 63.5 68.5 60.3 Bulk, cm.sup.3/g 1.82 1.64 1.60 1.52 1.80 Tear Index, mN*m.sup.2/g 8.20 8.67 8.35 8.67 7.08 Breaking length, km 4.85 6.88 7.66 9.13 4.03 Tensile Index, N m/g 47.6 67.5 75.1 89.5 39.5 Stretch, % 2.42 2.56 3.09 4.85 2.45 Burst Index, kPa*m.sup.2/g 1.91 3.77 4.20 4.86 1.70 Energy@break (J/m.sup.2) 22.2 71.3 78.3 168.2 20.4 Final Strain (%) 2.45 2.58 3.11 4.89 2.47
TABLE-US-00019 TABLE 18B Wheat Wheat Wheat Wheat Straw Straw Straw Straw 10 g/L 10 g/L 8 g/L 8 g/L Sample Number 250 rev 500 rev unmilled 250 rev Freeness, ml 293 254 532 207 Moisture, % 9.46 9.25 9.48 10.11 Oven dry Grammage, g/m.sup.2 61.4 64.4 61.0 63.7 Bulk, cm.sup.3/g 1.66 1.59 1.95 1.73 Tear Index, mN*m.sup.2/g 8.57 7.87 5.82 7.20 Breaking length, km 7.16 7.67 2.83 4.73 Tensile Index, N m/g 70.2 75.2 27.8 46.3 Stretch, % 3.04 3.07 1.32 1.72 Burst Index, kPa*m.sup.2/g 4.03 4.42 0.90 2.11 Energy@break (J/m.sup.2) 73.9 93.8 9.2 29.2 Final Strain (%) 3.05 3.07 1.33 1.72
[0308] All handsheets were formed according to TAPPI T205 sp-18 Forming Handsheets for Physical Tests of Pulp and tested according to TAPPI T200 sp-16 Physical Testing of Pulp Handsheets. Any pulps with Freeness values below 200 mL were not formed into handsheets.
[0309] Table 19A shows compositional characteristics of blends 1-7 and blend X that were prepared, while Table 19B shows pulp blends handsheet data for blends 1-7.
TABLE-US-00020 TABLE 19A Blend # OCC Hemp Corn Wheat 1 40 0 60 0 2 40 10 50 0 3 45 5 50 0 4 90 10 0 0 5 100 0 0 0 6 40 0 40 20 7 40 10 30 20 X 0 0 100 0
TABLE-US-00021 TABLE 19B Blend Blend Blend Blend Blend Blend Blend Sample Number 1 2 3 4 5 6 7 Freeness, ml 403 407 393 490 437 353 400 Moisture, % 9.41 9.60 9.48 8.93 8.84 9.41 9.07 Oven dry 64.6 66.5 61.4 61.7 61.1 58.7 61.3 Grammage, g/m.sup.2 Bulk, cm.sup.3/g 1.88 1.98 1.94 1.95 1.86 1.82 1.98 Tear Index, mN*m.sup.2/g 9.99 8.85 8.80 13.12 13.15 9.64 10.52 Breaking length, km 4.33 4.30 4.32 4.00 4.34 5.06 4.62 Tensile Index, N m/g 42.5 42.2 42.3 39.2 42.5 49.7 45.3 Stretch, % 2.68 2.84 3.13 3.21 3.83 3.04 2.90 Burst Index, kPa*m.sup.2/g 2.08 2.08 2.08 2.12 2.44 2.44 2.38 Energy @ break (J/m.sup.2) 37.8 36.7 35.0 35.8 50.1 38.7 36.5 Final Strain (%) 2.70 2.87 3.16 3.24 3.87 3.04 2.90
[0310] All handsheets were formed according to TAPPI T205 sp-18 Forming Handsheets for Physical Tests of Pulp and tested according to TAPPI T200 sp-16 Physical Testing of Pulp Handsheets. Any pulps with Freeness values below 200 mL were not formed into handsheets.
[0311] Table 20 shows OCC and hemp handsheet data, where the freeness target was 400 mL CSF after the Valley Beater (another type of refiner).
TABLE-US-00022 TABLE 20 OCC @ Hemp Freeness @ 437 mL 453 mL Sample Number CSF Freeness CSF Freeness, ml 437 453 Moisture, % 8.84 8.39 Oven dry Grammage, g/m.sup.2 61.1 59.6 Bulk, cm.sup.3/g 1.86 2.92 Tear Index, mN*m.sup.2/g 13.15 25.16 Breaking length, km 4.34 2.77 Tensile Index, N m/g 42.5 27.1 Stretch, % 3.83 2.97 Burst Index, kPa*m.sup.2/g 2.44 2.66 Energy@break (J/m.sup.2) 50.1 22.1 Final Strain (%) 3.87 3.00 Note: OCC @ 437 mL CSF freeness is also the sample used for Blend 5.
[0312] Table 21 shows CSF and Kappa number for corn stover soda pulp.
TABLE-US-00023 TABLE 21 CSF Freeness Consistency Temp Kappa Sample ID (mL, corrected) (%) (° C.) Number Corn stover 376 0.30 22 29.6 8 g/L unmilled Corn Stover 208 0.31 19 8 g/L 250 rev Corn Stover 115 0.30 20 8 g/L 500 rev Corn Stover 387 0.32 22 13.5 9 g/L unmilled Corn Stover 137 0.30 21 9 g/L 250 rev Corn Stover 330 0.28 22 14.6 10 g/L unmilled Corn Stover 162 0.28 18 10 g/L 250 rev
[0313] All Freeness testing was done according to TAPPI T227 om-17 Freeness of Pulp (Canadian Standard Method). All Kappa numbers were done according to TAPPI T236 om-13 Kappa Number of Pulp.
[0314] Table 22 shows CSF and Kappa number for wheat straw soda pulp.
TABLE-US-00024 TABLE 22 CSF Freeness Consistency Temp Kappa Sample ID (mL, corrected) (%) (° C.) Number Wheat straw 532 0.31 21 27.0 8 g/L unmilled Wheat straw 207 0.28 21 8 g/L 250 rev Wheat straw 144 0.28 21 8 g/L 500 rev Wheat straw 522 0.31 20 21.6 9 g/L unmilled Wheat straw 313 0.28 21 9 g/L 250 rev Wheat Straw 280 0.28 21 9 g/L 500 rev Wheat Straw 220 0.30 21 9 g/L 1000 rev Wheat Straw 110 0.28 20 9 g/L 3000 rev Wheat straw 612 0.30 20 17.7 10 g/L unmilled Wheat straw 293 0.30 21 10 g/L 250 rev Wheat straw 254 0.28 21 10 g/L 500 rev Wheat Straw 194 0.29 21 10 g/L 1000 rev
[0315] All Freeness testing was done according to TAPPI T227 om-17 Freeness of Pulp (Canadian Standard Method). All Kappa numbers were done according to TAPPI T236 om-13 Kappa Number of Pulp.
[0316] Table 23 shows UV visible spectrophotometer measurements for corn stover digester process liquor.
TABLE-US-00025 TABLE 23 Corn Stover Absorbance Dilution Wavelength - Wavelength - Sample ID Factor 205 nm 280 nm 10 g NaOH/Liter CS -1 (5 minute) 350 1.74 0.506 CS-1 (10 minute) 450 1.53 0.474 CS-1 (15 minute) 550 1.41 0.445 CS-1 (20 minute) 700 1.03 0.330 CS-1 (25 minute) 750 1.04 0.322 CS-1 (30 minute) 800 0.97 0.310 9 g NaOH/Liter CS -3 (5 minute) 160 1.46 0.346 CS-3 (10 minute) 220 1.50 0.403 CS-3 (15 minute) 250 1.65 0.471 CS-3 (20 minute) 300 1.51 0.444 CS-3 (25 minute) 400 1.30 0.393 CS-3 (30 minute) 500 1.07 0.328 8 g NaOH/Liter CS-2 (5 minute) 50 1.34 0.041 CS-2 (10 minute) 55 1.62 0.166 CS-2 (15 minute) 65 1.67 0.331 CS-2 (20 minute) 77 2.58 0.640 CS-2 (25 minute) 160 1.87 0.511 CS-2 (30 minute) 190 1.74 0.497
[0317] Table 24 shows UV visible spectrophotometer measurements for wheat straw digester process liquor.
TABLE-US-00026 TABLE 24 Wheat Straw Absorbance Dilution Wavelength - Wavelength - Sample ID Factor 205 nm 280 nm 10 g NaOH/Liter WS -1 (5 minute) 100 1.29 0.023 WS -1 (10 minute) 200 0.48 0.057 WS -1 (15 minute) 200 0.82 0.168 WS -1 (20 minute) 200 1.03 0.241 WS -1 (25 minute) 200 1.27 0.313 WS -1 (30 minute) 200 1.49 0.385 9 g NaOH/Liter WS -3 (5 minute) 200 1.53 0.373 WS -3 (10 minute) 300 1.36 0.352 WS -3 (15 minute) 350 1.49 0.388 WS -3 (20 minute) 400 1.42 0.370 WS -3 (25 minute) 450 1.42 0.370 WS -3 (30 minute) 500 1.43 0.366 8 g NaOH/Liter WS -2 (5 minute) 100 0.82 0.009 WS -2 (10 minute) 200 0.60 0.060 WS -2 (15 minute) 200 0.81 0.153 WS -2 (20 minute) 200 1.06 0.233 WS -2 (25 minute) 200 1.26 0.300 WS -2 (30 minute) 200 1.60 0.395
[0318] FIGS. 18-19 show photographs of paper formed from pulp processed at 8 g/L, and 10 g/L of NaOH, as described herein. In
Trial 3.
[0319] The handsheets evaluated above during trial 2 were made to a weight of about 60 gsm. During trial 2, handsheets at a higher weight, of about 127 gsm were also made, and were sent for further paper testing. Table 25A shows test results for blends 1, 2, and 5, while Table 25B shows results for blends 3, 4, and X, for samples at 127 gsm.
TABLE-US-00027 TABLE 25A Analysis Units Blend 1 Blend 2 Blend 5 Basis weight, (conditioned) g/m.sup.2 147.95 150.26 140.20 Bulk cc/g 1.66 1.79 1.63 Burst index kPa .Math. m.sup.2/g 2.16 2.31 2.43 Tear index (1-ply) mN .Math. m.sup.2/g 7.75 9.98 9.66 Tensile index N .Math. m/g 34.7 35.3 35.1 Tensile km 3.54 3.59 3.57 Stretch % 2.67 2.26 3.06 Tensile Energy Absorption J/m.sup.2 101 86.7 106 Ring Crush kN/m 1.41 1.62 1.27 Fold count 89 124 122 Stiffness, Taber g .Math. cm 7.46 8.93 7.67 Short Span Compression, STFI kN/m 2.88 3.06 2.50 Absorption, water drop seconds 8.0 10.0 63.6
TABLE-US-00028 TABLE 25B Analysis Units Blend 3 Blend 4 Blend X Basis weight, (conditioned) g/m.sup.2 145.90 146.87 147.33 Bulk cc/g 1.59 1.63 1.66 Burst index kPa .Math. m.sup.2/g 2.41 2.27 2.33 Tear index (1-ply) mN .Math. m.sup.2/g 6.05 8.30 9.89 Tensile index N .Math. m/g 41.0 40.4 39.7 Tensile Stiffness kN/m 666 750 703 Tensile km 4.17 4.12 4.05 Stretch % 2.10 1.77 2.09 Tensile Energy Absorption J/m.sup.2 89.3 74.4 86.4 Ring Crush kN/m 1.54 1.48 1.52 Fold count 165 126 228 Stiffness, Taber g .Math. cm 8.00 14.7 19.7 Short Span Compression, STFI kN/m 3.68 3.21 2.75
Trial 4.
[0320] While the previously described trials were on lab scale equipment, trial 4 was on commercial scale equipment. 2 tons of corn stover, 2 tons of OCC, and about 450 pounds of hemp were processed as described herein. Cooking/pulp digesting was performed at 150° C. for 30 minutes, similar to trial 2. The results of trial 4 show a 50/50 blend of non-wood agricultural fiber with OCC outperforms 100% OCC in many respects, although yield was relatively low. The more gentle cooking procedure described herein (e.g., temperature of less than 100° C., for a longer period of time) will help to improve yield, and may also better preserve fiber length, so as to increase strength properties. A portion of the pulp from trial 4 was used to make handsheets, for testing. Another portion of the pulp from trial 4 was used in trial 5, for papermaking on a papermaking machine. The results for the handsheets of trial 4 are shown in Tables 26A-26C, below. The comparison provided between samples C1 and P8 is exemplary.
TABLE-US-00029 TABLE 26A Freeness Shives (%) LWAFL Sample Comments (mL) 0.15 mm (mm) OCC 1 Foundry 432 0.18 1.126 OCC 2 Floor 500 0.02 1.338 P1-3 OCC 420 0.00 R1 Digester Discharge 271 0.06 0.807 T7 Coarse Screen Accepts 170 0.00 0.813 G2A Micra Sieve Long Fiber 429 2.52 0.928 P5 TWP discharge 360 1.40 0.879 P6 TWP discharge 332 1.50 0.861 P7 TWP discharge 324 1.34 1.135 C1 50/50 Composite 365 1.42 1.119 P8 Final OCC 434 0.34 1.539
TABLE-US-00030 TABLE 26B Burst Tear Tensile Bulk Index Index Index Stretch TEA Sample (cm.sup.3/g) (kPa•m.sup.2/g) (mNm.sup.2/g) (Nm/g) (%) (J/m.sup.2) OCC 1 1.80 1.69 8.3 31.3 2.28 31.84 OCC 2 1.74 2.22 10.8 40.2 2.37 38.93 P1-3 1.81 2.49 11.3 43.4 2.78 49.91 R1 1.41 2.07 7.1 47.1 2.24 119.62 T7 1.28 2.97 6.2 47.0 2.34 127.18 G2A 1.59 2.51 11.9 47.9 3.07 191.84 P5 1.57 3.78 8.9 56.1 3.44 238.06 P6 1.59 3.51 8.9 51.6 2.87 187.32 P7 1.58 3.42 8.6 59.3 3.66 263.13 C1 1.60 3.26 12.2 56.9 3.07 194.47 P8 1.66 3.07 17.8 45.9 3.03 159.50
TABLE-US-00031 TABLE 26C CMT Index Ring Crush Index SCT Sample (Nm.sup.2/g) (Nm.sup.2/g) (Nm.sup.2/g) OCC 1 0.00 0.00 16.57 OCC 2 0.00 0.00 18.20 P1-3 1.36 8.33 19.31 R1 1.16 12.68 26.40 T7 1.18 12.92 27.03 G2A 1.42 0.00 23.47 P5 1.32 27.87 P6 1.42 31.50 P7 1.39 29.18 C1 1.86 25.05 P8 1.22 20.26
Trial 5.
[0321] Pulps resulting from trial 4 were sent for papermaking trials. A successful production run with a blend of OCC and corn stover fibers was made. A fraction of corn dust (fines) was brought forward from the fiber preparation stage, and added to the pulp, for inclusion in the sheet of paper formed, increasing the yield (see the medium shown in
TABLE-US-00032 TABLE 26D Sieve Size Opening U.S. Standard (mm) (μm) Mesh Size 5.60 5600 3.5 4.75 4750 4 4.00 4000 5 3.35 3350 6 2.80 2800 7 2.36 2360 8 2.00 2000 10 1.70 1700 12 1.40 1400 14 1.18 1180 16 1.00 1000 18 0.85 850 20 0.71 710 25 0.60 600 30 0.50 500 35 0.425 425 40 0.355 355 45 0.300 300 50 0.25 250 60 0.212 212 70 0.180 180 80 0.15 150 100 0.125 125 120 0.105 105 140 0.090 90 170 0.075 75 200
[0322] The plan for trial 5 was as follows:
7:00 Machine warm up.
9:00 Medium run start with 127 g/m with OCC & Fines (Corn dust).
[0323] Chemicals «as is»:
[0324] CFennoPol K 2813 (Polyacrylamide, drainage & dewatering aid)—0.35 Kg/Ton
[0325] FennoSil 2185 (Colloidal Silica, micro particles, drainage & dewatering aid)—3 Kg/Ton
[0326] FennoBond 3300 (GPAM, Dry Strength)—20 Kg/Ton
9:20 Stabilize basis weight at 127 g/m.sup.2 and 4% moisture for 30 minutes.
9:50 Produce Medium 127 g/m.sup.2 for 20 minutes
10:10 Change production to make Liner
[0327] Chemicals «as is»:
[0328] FennoSize KD 544M (AKD, Sizing)—10 Kg/Ton
10:15 Increase basis weight to 171 g/m.sup.2 and stabilize moisture to 8-10%.
10:45 Increase corn flow and decrease total debit to add 25% corn to the recipe
10:50 Increase corn flow and decrease total debit to add 43% corn to the recipe
11:00 Produce Liner 171 g/m.sup.2 for 25 minutes
11:30 Add 5% of Hemp pulp to the machine chest.
11:33 Produce Liner (with Hemp) 171 g/m.sup.2 until the sheet breaks
11:40 End
[0329] Trial 5 proceeded as follows:
At 8:30, the machine warm up was going well.
At 9:00, the machine was in startup and the team was getting ready to start the chemicals.
9:20 the fan pump was started on water and the stock was added soon after.
9:25 Pulp buildup under the Fourdrinier deckle (drive side).
9:29, the drainage was almost too good. The water line did not advance very far on the drainage table.
[0330] Trial 5 continued as follows:
9:33, treading the wet sheet to the presses section went well.
9:40, treading the sheet through the dryer was more difficult and took about 10 minutes.
9:33, the sheet broke.
9:45, the sheet was on the drum reel.
[0331] 10:09, working on the sheet formation. The sheet drained really fast, by looking at the position of the water line. Drainage that is too fast (freeness value too high) can cause poor sheet formation.
[0332] Trial 5 continued as follows.
10:42, medium production began. 900 Kg of OCC remained.
11:00, medium production completed. The basis weight was increased to prepare for the liner run.
11:07, started adding corn pulp. 475 Kg of OCC pulp remaining.
11:10, 25% corn pulp. The water line moved further and the water level increased in the top former vacuum box.
11:10, the liner recipe is on the machine (50% OCC/50% Corn). The drainage is much slower than before, and the sheet formation is better (
Trial 6.
[0334] Paper produced in trial 5 was sent for corrugation trials. 16 inch rolls of B-flute single face (including liner and corrugated medium) containerboard were produced. The B-flute single face product exhibited ECT (edge crush test) values of 30-31 lb/in, similar to similar product formed from recycled OCC, even given that this trial was made using a Langston corrugator which uses a pressure roll instead of a belted singlefacer. Use of the pressure roll causes slightly more crushing during lamination which can reduce the ECT of the product. As such, use of a belted singlefacer would likely result in somewhat higher ECT values. In addition, as noted herein, use of lower cooking temperatures, and selection of other process parameters as described herein will also increase strength, and other desired performance characteristics.
Trial 7.
[0335] The production of the single face B-flute made in Trial 6 at commercial scale was monitored, and this material was used in a lab environment to produce corrugate structures by gluing the double face to complete the corrugate structure.
[0336] While the present disclosure largely focuses on manufacture of liner and medium for construction of corrugated containerboard, it will be appreciated that the present disclosure is applicable to manufacture of a variety of other products, including, but not limited to brown kraft paper, assorted paper towels (e.g., brown paper towel material often used for hand drying in bathrooms), as well as assorted bags and sacks including but not limited to cement bags, feed bags, SOS bags, shopping bags, die-cut handle bags, liquor bags, and lawn and leaf bags. Such paper materials may typically have a basis weight of 30 to 120 gsm, 30 to 90 gsm, 30 to 70 gsm, 70-120 gsm, 70-110 gsm, 70-90 gsm, or 110-120 gsm, depending on the particular application. Brown paper towel material (e.g., as used for hand drying in commercial bathrooms) may often have a basis weight of 20-30 lbs (e.g., 75 to 120 gsm). Those of skill in the art will be familiar with conversion between lb and gsm basis weight values.
[0337] Another advantage of using the present non-wood agricultural fiber pulp materials is that such materials include negligible if any sulfur, in contrast to wood fiber materials, which include significant sulfur.
[0338] In addition to kraft paper, liner and medium as described herein, the present non-wood pulp materials can also be used in the molding or thermoforming of molded pulp products, such as egg cartons, molded disposable “paper” plates, other food related containers, or various molded pulp products used for packaging consumer goods. Such molded pulp products are disposable single use products. Such molded pulp products have historically been formed from recycled newsprint, although the volume of available newsprint has drastically declined in recent years. Use of the present non-wood agricultural feedstock pulp materials can be used for molded pulp products, and will provide greater rigidity than comparable materials currently used in the manufacture of such products. For example, the agricultural fiber pulp can be introduced into a molded pulp product manufacturing machine (e.g., a pulp chest thereof) to make a molded pulp product from the agricultural fiber pulp. Such a process may include wet pressing and/or thermoforming. Another example product that can be formed using the present processes is cardboard tubes and cores (e.g., for rolls of toilet paper, rolls of paper towels, mailing tubes, as well as chipboard or grayboard (i.e., rigid container board). Such products may typically have a thickness from 0.5 mm to 5 mm.
[0339] In an embodiment, blending of corn stover pulp or another agricultural pulp fiber pulp material with OCC may serve to preserve a desired freeness value of the corn stover pulp or other agricultural pulp material, where the OCC is included as a majority of the blend. For example, when running 100% corn stover pulp through a refiner, the corn stover fibers are significantly damaged, resulting in significant loss of freeness. Applicant has found though that where such corn stover pulp material is run through a refiner as a minority component of a blend with OCC, that the freeness of the corn stover pulp material is surprisingly protected and preserved. For example, in an embodiment, the corn stover run through a refiner in such a blend may be present at less than 50%, less than 40%, less than 30%, less than 20%, less than 10%, at least 3%, at least 5%, such as from 3% to 25%. Such is another advantage of preparing a corn stover or similar non-wood agricultural pulp material through a cooking process as described herein, and then blending such pulp material with OCC or a similar wood pulp material, and then refining such blend (e.g., in a pulper).
[0340] In addition, unless otherwise indicated, numbers expressing quantities, constituents, distances, or other measurements used in the specification and claims are to be understood as optionally being modified by the term “about” or its synonyms. When the terms “about,” “approximately,” “substantially,” or the like are used in conjunction with a stated amount, value, or condition, it may be taken to mean an amount, value or condition that deviates by less than 20%, less than 10%, less than 5%, less than 1%, less than 0.1%, or less than 0.01% of the stated amount, value, or condition.
[0341] As used herein, the term “between” includes any referenced endpoints. For example, “between 2 and 10” includes both 2 and 10.
[0342] Although this disclosure has been described in terms of certain embodiments, other embodiments apparent to those of ordinary skill in the art are also within the scope of this disclosure. Accordingly, the scope of the disclosure is intended to be defined only by the claims which follow.