Energy-saving method for preparing high-yield pulp by taking wood and bamboo materials as raw materials through two-stage biological enzyme treatment

Abstract

The invention discloses an energy-saving method for preparing high-yield pulp by taking wood and bamboo as raw materials through two-stage bio-enzyme treatment, which comprises the following steps: taking wood and bamboo as fiber raw materials, and carrying out material preparation, spiral extrusion, two-stage bio-enzyme treatment, two-stage pulping and chemical impregnation to obtain low-energy-consumption high-yield pulp. According to the invention, the wood and bamboo fibers are subjected to two-stage biological enzyme treatment and then are subjected to high-temperature disc milling, so that the high-yield pulp with relatively low pulping energy consumption is obtained. The method mainly comprises the following steps: attacking a cellulose amorphous region through a first section of cellulose incision enzyme so as to promote liquid medicine permeation, dissolving out hemicellulose and hydrophilizing lignin after alkaline hydrogen peroxide chemical treatment, and greatly promoting moisture permeation and fiber swelling after xylanase treatment. Or the defect is enlarged through the cellulose incision enzyme, so that the subsequent pulping energy consumption of the high-temperature disc mill is reduced. According to the method, the fiber strength can be well maintained while the energy consumption is reduced, so that the contradiction of an chemi-mechanical pulp production process is balanced.

Description

Technical Field

[0001] This invention belongs to the field of pulp and paper making, specifically relating to a method for preparing high-yield pulp using wood and bamboo as raw materials through a two-stage bio-enzyme treatment process. Background Technology

[0002] Chemimechanical pulp (CMP) has attracted much attention and research in recent years due to its advantages such as high yield and low pollutant emissions. CMP mainly combines chemical pretreatment with mechanical refining to achieve high fiber utilization (typically 85%-90%) while maintaining good paper properties. However, the high energy consumption during refining remains a key bottleneck restricting its further development.

[0003] Biopulping offers advantages such as reduced refining energy consumption, reduced pulping chemicals, improved pulp fiber quality, and a clean and environmentally friendly pulping process, making it a promising pulping technology. Among these technologies, bio-enzyme treatment is highly efficient, specific, and environmentally friendly. By selecting appropriate enzyme preparations and treatment conditions, the chemical composition and physical structure of the fiber surface can be targeted and regulated, further reducing refining energy consumption while maintaining strength. Currently, xylanase and cellulase have become hot topics in chemimechanical pulp modification research.

[0004] Cellulose endonucleases randomly cleave glycosidic bonds in the amorphous regions of cellulose, causing localized weakening of the fiber structure. Under mechanical action, this promotes fiber fibrillation, but excessive treatment leads to decreased fibrillation and increased fine fiber content. The enzymatic mechanism is closely related to the treatment conditions. Xylanase, as a hemicellulose-degrading enzyme, specifically attacks the xylan components in the fiber cell wall. Studies have shown that xylanase treatment primarily improves fiber swelling capacity and accessibility by selectively removing hemicellulose fragments from the fiber surface, promoting fibrillation while avoiding strength loss due to excessive degradation, thus improving subsequent refining efficiency. This not only helps reduce refining energy consumption but also maintains the fiber's bulk strength, keeping the tear index of the finished paper at a high level.

[0005] Current research on bio-assisted mechanical pulping of wood and bamboo fibers mainly focuses on the modification of single enzymes to regulate fiber properties. However, there is still considerable room for research on the synergistic effects of multiple enzymes. By rationally controlling the enzyme treatment process and using the corresponding enzymes, it is possible to maximize energy saving, consumption reduction, and strength maintenance in different processes.

[0006] The invention disclosed in application number CN202411160323.7 is a method for preparing cotton stalk biochemical mechanical pulp. It mainly uses agricultural waste cotton stalks as raw material and employs a process path of pre-steaming, extrusion, cellulase treatment, hot alkali impregnation, refining, and compound treatment with xylanase and pectinase. This method focuses on addressing the problems of high levels of impurities and pectin in cotton stalks, aiming to improve pulp performance and reduce chemical usage. The patent utilizes different bioenzymes for surface treatment and impurity removal of cotton stalk fibers, and removes lignin through simple alkali treatment. However, the use of enzymes is specifically for modifying cotton stalk fibers, and the energy consumption of refining is not quantified.

[0007] The invention disclosed in application number CN201110060169.2 is a chemimechanical pulping process for *Salix psammophila*, which mainly uses fast-growing shrub *Salix psammophila* as raw material. The process involves "steaming-extrusion-cellulase treatment-alkaline hydrogen peroxide impregnation-secondary extrusion-xylanase treatment-secondary impregnation-two-stage refining," emphasizing the synergistic improvement of pulp brightness and strength through the combination of biological enzymes and chemical bleaching. Although energy-saving, the process is complex, involves many steps, and uses a large amount of chemicals, making it only suitable for *Salix psammophila* raw materials with shorter fibers. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention proposes a method for preparing high-yield pulp using a two-stage bio-enzyme treatment of wood and bamboo as raw materials. The method employs a combination of bio-enzymes and chemical impregnation to treat wood and bamboo fibers, thereby dissociating the fibers with lower energy consumption to produce high-yield chemimechanical pulp.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for energy-saving preparation of high-yield pulp using wood and bamboo as raw materials through a two-stage bio-enzyme treatment, characterized by comprising the following steps: (1) Material preparation: Screening, washing and steaming the wood and bamboo fiber raw materials to obtain wood chips with a length of 20~40 mm and a thickness of 3~5 mm. Remove sand and other impurities and adjust the moisture content of the chips for later use. (2) Mechanical extrusion: The steamed wood chips are mechanically extruded to reduce their size and obtain the extruded material, which is in the form of rods or filaments with a length of 1~40 mm and a width of 100~500 μm. (3) Cellulose endopeptidase treatment: Cellulose endopeptidase was used to treat the extruded material; the enzymatic hydrolysis temperature was 50 ℃, the time was 120 min, the solid-liquid ratio was 1:10, and the pH was 4.5. (4) Chemical impregnation: Using alkaline hydrogen peroxide solution as the impregnation solution, the pulp treated with cellulose endopeptidase was thoroughly mixed with the solution and then impregnated at 90 °C for 1 hour. (5) Coarse grinding: The pulp is ground and dissociated under normal pressure using a disc mill. After dissociation, the pulp is adjusted to neutral with a pulp concentration of 20% and a grinding gap of 0.3~0.5mm. (6) Bio-enzyme treatment: The coarsely ground material is treated with xylanase or cellulase, with an enzymatic hydrolysis temperature of 50℃, a time of 120 min, a solid-liquid ratio of 1:10, and a pH of 4.5. (7) High-consistency pulping: A high-consistency disc mill is used for atmospheric pressure pulping and decomposition. The pulp concentration is 23%, and the pulping gap is 0.2~0.3mm. The pulp produced is a low-energy-consumption, high-yield mechanical pulp with a yield of 85-90%.

[0010] The following dosages are all relative to the oven-dry weight of the slurry, as detailed below: In step (3), the amount of cellulase used in the cellulase treatment is 80-100 CMC-U / g.

[0011] In step (4), the amounts of each component in the alkaline hydrogen peroxide solution are as follows: 10% hydrogen peroxide, 8% sodium hydroxide, 2% sodium silicate, and 0.5% DTPA.

[0012] In step (6), the xylanase used is produced by Novozymes, and the amount of xylanase used is 80-100 FXU-S / g; the amount of cellulase used is 80 CMC-U / g.

[0013] The beneficial effects of this invention are reflected in: This invention employs a step-by-step pretreatment method involving spiral extrusion, cellulose endopeptide treatment, alkaline hydrogen peroxide treatment, and two-stage bio-enzyme treatment. This method reduces specific energy consumption throughout the pulping process, resulting in significant energy savings while maintaining high pulp yield and fiber strength. This invention, for the first time, designs a process flow for dense raw materials such as wood and bamboo: "spiral extrusion - cellulose endopeptide treatment - alkaline hydrogen peroxide chemical impregnation - coarse grinding - bio-enzyme treatment (xylanase or cellulose endopeptide) - high-consistency pulping". By promoting the penetration of the chemical solution through cellulose endopeptide, coarse grinding is performed after chemical impregnation, followed by a second bio-enzyme treatment to further enhance fiber swelling and fibrillation capabilities. Finally, high-consistency pulping further facilitates the gradual dissociation of fibers and reduces energy consumption, ultimately achieving a quantitative reduction in pulping energy consumption (up to 34.17%) while maintaining pulp strength at a high yield of over 85%. This forms a high-yield pulp preparation method that combines raw material specificity, energy-saving process, and processing flexibility.

[0014] This invention achieves a significant reduction in pulping energy consumption through the synergistic effect of a first-stage cellulose endonuclease pretreatment, alkaline hydrogen peroxide treatment, and a second-stage specific enzyme treatment. The main working principles of each stage are as follows: The first-stage cellulose endonuclease selectively attacks the amorphous regions of cellulose in the fiber cell wall, initially weakening the overall structural integrity of the fiber and promoting the penetration of the chemical solution; then, alkaline hydrogen peroxide impregnation thoroughly removes lignin and hemicellulose, softening the fiber while increasing its accessibility, making subsequent enzyme reactions easier; the introduced bio-enzyme treatment, xylanase, enhances the fiber's swelling capacity and accessibility by degrading residual hemicellulose fragments and lignin-carbohydrate complexes (LCCs), achieving the most significant reduction in pulping energy consumption; in the bio-enzyme treatment, cellulose endonuclease is used again, continuing to act on the defects formed after the pretreatment and alkaline treatment, further deepening the internal defects of the fiber, weakening the mechanical strength of the fiber, and promoting fibrillation, thereby reducing pulping energy consumption. Attached Figure Description

[0015] Figure 1 A flowchart of the method provided by the present invention. Detailed Implementation

[0016] The present invention will be further described below with reference to embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments are not intended to limit the present invention. In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional methods in the prior art, and therefore will not be described in detail. The raw materials used in the present invention are all commercially available products.

[0017] In the following examples, all percentages are by mass, and all masses are the oven-dry weight of the slurry.

[0018] Example 1 1. Using eucalyptus wood as raw material according to Figure 1 The process for producing low-energy, high-yield pulp is as follows: (1) Material preparation: Screening, washing and steaming the eucalyptus raw materials to obtain wood chips with a length of 20~40 mm and a thickness of 3~5 mm. Remove sand and other impurities and adjust the moisture content of the wood chips for later use.

[0019] (2) Mechanical extrusion: Eucalyptus wood chips are mechanically extruded and pretreated using a twin-screw extrusion machine (Jiangsu Jinwo, model TSP65, screw speed 450 rpm) to reduce their size and obtain the extruded material in the form of rods or filaments. The material specifications are: length 1~40 mm, width 100~300 μm.

[0020] (3) Cellulose endopeptide treatment: 4.5 kg of the extruded material (containing 9.24 kg of water) was treated with cellulose endopeptide. The enzyme dosage was 100 CMC-U / g, the enzymatic hydrolysis temperature was 50 ℃, the time was 120 min, the solid-liquid ratio was 1:10, the pH was 4.5, 150 g of enzyme was added, and the total weight of the material was 45 kg.

[0021] (4) Chemical impregnation: Using alkaline hydrogen peroxide solution as the impregnation solution, 4.3 kg (containing 10.45 kg of water) of cellulose endopeptide-treated slurry was washed with water until neutral and then an impregnation solution of 8% NaOH, 10% H2O2, 2% Na2SiO3 and 0.5% DTPA was added. After the slurry and the solution were mixed evenly, the mixture was impregnated at 90 ℃ for 1 h.

[0022] (5) Coarse grinding: Use a disc mill for atmospheric pressure grinding and dissociation of the slurry. After dissociation, adjust to neutral, with a slurry concentration of 20% and a grinding gap of 0.3~0.5 mm.

[0023] (6) Bio-enzyme treatment: 1.8 kg of coarsely ground material (containing 6.36 kg of water) was treated with xylanase. The enzyme dosage was 80 FXU-S / g, the enzymatic hydrolysis temperature was 50 ℃, the time was 120 min, the solid-liquid ratio was 1:10, the pH was 4.5, 288 g of enzyme solution was added, and the total weight of the material was 18 kg.

[0024] (7) High-consistency refining: The pulp was refining and dissociating under normal pressure using a high-consistency disc mill. The pulp was then washed with clean water. The pulp concentration was 23%, and the refining gap was 0.2~0.3mm.

[0025] The main indicators of the chemimechanical pulp prepared by the process of Example 1 are as follows: the energy consumption of the pulping ratio is 2181.3 kW·h / t, the yield is 88.2% for 150 mL CSF.

[0026] Example 2 1. Using eucalyptus wood as raw material according to Figure 1 The process for producing low-energy, high-yield pulp is as follows: (1) Preparation of materials: The method is the same as in Example 1.

[0027] (2) Screw extrusion: Same as the method in Example 1.

[0028] (3) Cellulose endopeptidase treatment: the same as in Example 1.

[0029] (4) Chemical impregnation: Same as in Example 1.

[0030] (5) Coarse grinding: Same as the method in Example 1.

[0031] (6) Bio-enzyme treatment: 1.8 kg of coarsely ground material (containing 6.36 kg of water) was treated with cellulose endopeptidase. The enzyme dosage was 80 CMC-U / g, the enzymatic hydrolysis temperature was 50 ℃, the time was 120 min, the solid-liquid ratio was 1:10, the pH was 4.5, 48 g of enzyme was added, and the total weight of the material was 18 kg.

[0032] (7) High-concentration pulping: The method is the same as in Example 1.

[0033] The main indicators of the chemimechanical pulp prepared by the process of Example 2 are as follows: the energy consumption of the pulping ratio is 2349.6 kW·h / t, the yield is 85.6% for 150 mL CSF.

[0034] Comparative Example 1 1. The process of producing high-yield pulp from eucalyptus wood is as follows: (1) Preparation of materials: The method is the same as in Example 1.

[0035] (2) Screw extrusion: Same as the method in Example 1.

[0036] (3) Cellulose endopeptidase treatment: the same as in Example 1.

[0037] (4) Chemical impregnation: Same as in Example 1.

[0038] (5) Coarse grinding: Same as the method in Example 1.

[0039] (6) Bioenzyme treatment: This step is not required.

[0040] (7) High-concentration pulping: The method is the same as in Example 1.

[0041] The main indicators of the chemimechanical pulp prepared using the process of Comparative Example 1 are as follows: the energy consumption for refining ratio is 2663.9 kW·h / t, the yield is 86.2% for 150 mL CSF.

[0042] Comparative Example 2 1. The process of producing high-yield pulp from eucalyptus wood is as follows: (1) Preparation of materials: The method is the same as in Example 1.

[0043] (2) Screw extrusion: Same as the method in Example 1. (3) Cellulose endopeptidase treatment: This step is not required.

[0044] (4) Chemical impregnation: Same as in Example 1.

[0045] (5) Coarse grinding: Same as the method in Example 1.

[0046] (6) Bioenzyme treatment: This step is not required.

[0047] (7) High-concentration pulping: The method is the same as in Example 1.

[0048] The main indicators of the chemimechanical pulp prepared by the process of Comparative Example 2 are as follows: the energy consumption of the pulping ratio is 3313.5 kW·h / t, the yield is 85.2% for 150 mL CSF. At a CSF free concentration of 150 mL, the yields of Examples 1 and 2 using eucalyptus wood as raw material were 0.882, 0.856, 0.862, and 0.852, respectively, compared to Comparative Examples 1 and 2. Example 1 showed a 18.12% reduction in grinding energy consumption compared to Comparative Example 1, and a 34.17% reduction compared to Comparative Example 2. Example 2 showed an 11.80% reduction in grinding energy consumption compared to Comparative Example 1, and a 29.09% reduction compared to Comparative Example 2. Compared to chemimechanical pulp obtained without enzyme treatment, the yield can be maintained at over 85-88%.

[0049] Example 3 1. Using poplar wood as raw material according to Figure 1 The process for producing low-energy, high-yield pulp is as follows: (1) Preparation of materials: The method is the same as in Example 1.

[0050] (2) Screw extrusion: Same as the method in Example 1.

[0051] (3) Cellulose endopeptidase treatment: the same as in Example 1.

[0052] (4) Chemical impregnation: Same as in Example 1.

[0053] (5) Coarse grinding: Same as the method in Example 1.

[0054] (6) Bioenzyme treatment: Same as in Example 1.

[0055] (7) High-concentration pulping: The method is the same as in Example 1.

[0056] The main indicators of the chemimechanical pulp prepared by the process of Example 3 are as follows: the energy consumption of the pulping ratio is 1788.0 kW·h / t, the yield is 87.3% with 150 mL CSF.

[0057] Example 4 1. Using poplar wood as raw material according to Figure 1 The process for producing low-energy, high-yield pulp is as follows: (1) Preparation of materials: The method is the same as in Example 1.

[0058] (2) Screw extrusion: Same as the method in Example 1.

[0059] (3) Cellulose endopeptidase treatment: the same as in Example 1.

[0060] (4) Chemical impregnation: Same as in Example 1.

[0061] (5) Coarse grinding: Same as the method in Example 1.

[0062] (6) Bioenzyme treatment: Same as in Example 2. (7) High-concentration pulping: The method is the same as in Example 1.

[0063] The main indicators of the chemimechanical pulp prepared by the process of Example 4 are as follows: the energy consumption of the pulping ratio is 1922.4 kW·h / t, the yield is 85.9% with 150 mL CSF.

[0064] Comparative Example 3 1. The process of producing high-yield pulp from poplar wood is as follows: (1) Preparation of materials: The method is the same as in Example 1.

[0065] (2) Screw extrusion: Same as the method in Example 1.

[0066] (3) Cellulose endopeptidase treatment: the same as in Example 1.

[0067] (4) Chemical impregnation: Same as in Example 1.

[0068] (5) Coarse grinding: Same as the method in Example 1.

[0069] (6) Bioenzyme treatment: This step is not required.

[0070] (7) High-concentration pulping: The method is the same as in Example 1.

[0071] The main indicators of the chemimechanical pulp prepared by the process of Comparative Example 3 are as follows: the energy consumption of the pulping ratio is 2231.8 kW·h / t, the yield is 86.7% for 150 mL CSF.

[0072] Comparative Example 4 1. The process of producing high-yield pulp from poplar wood is as follows: (1) Preparation of materials: The method is the same as in Example 1.

[0073] (2) Screw extrusion: Same as the method in Example 1. (3) Cellulose endopeptidase treatment: This step is not required.

[0074] (4) Chemical impregnation: Same as in Example 1.

[0075] (5) Coarse grinding: Same as the method in Example 1.

[0076] (6) Bioenzyme treatment: This step is not required.

[0077] (7) High-concentration pulping: The method is the same as in Example 1.

[0078] The main indicators of the chemimechanical pulp prepared using the process of Comparative Example 4 are as follows: the energy consumption of the pulping ratio is 2645.8 kW·h / t, the yield is 85.6% for 150 mL CSF. At a CSF free concentration of 150 mL, the yields of Examples 3 and 4, using poplar wood as raw material, were 0.873, 0.859, 0.867, and 0.856, respectively, compared to Comparative Examples 3 and 4. Example 3 showed a 19.88% reduction in grinding energy consumption compared to Comparative Example 3, and a 32.42% reduction compared to Comparative Example 4. Example 4 showed a 13.86% reduction in grinding energy consumption compared to Comparative Example 3, and a 27.34% reduction compared to Comparative Example 4. Example 5 1. Using moso bamboo as raw material, according to Figure 1 The process for producing low-energy, high-yield pulp is as follows: (1) Preparation of materials: The method is the same as in Example 1.

[0079] (2) Screw extrusion: Same as the method in Example 1.

[0080] (3) Cellulose endopeptidase treatment: the same as in Example 1.

[0081] (4) Chemical impregnation: Same as in Example 1.

[0082] (5) Coarse grinding: Same as the method in Example 1.

[0083] (6) Bioenzyme treatment: Same as in Example 1. (7) High-concentration pulping: The method is the same as in Example 1.

[0084] The main indicators of the chemimechanical pulp prepared by the process of Example 5 are as follows: the energy consumption of the pulping ratio is 2446.4 kW·h / t, the yield is 86.5% for 150 mL CSF.

[0085] Example 6 1. Using moso bamboo as raw material, according to Figure 1 The process for producing low-energy, high-yield pulp is as follows: (1) Preparation of materials: The method is the same as in Example 1.

[0086] (2) Screw extrusion: Same as the method in Example 1.

[0087] (3) Cellulose endopeptidase treatment: the same as in Example 1.

[0088] (4) Chemical impregnation: Same as in Example 1.

[0089] (5) Coarse grinding: Same as the method in Example 1.

[0090] (6) Bioenzyme treatment: Same as in Example 2. (7) High-concentration pulping: The method is the same as in Example 1.

[0091] The main indicators of the chemimechanical pulp prepared by the process of Example 6 are as follows: the energy consumption of the pulping ratio is 2617.8 kW·h / t, the yield is 85.7% for 150 mL CSF.

[0092] Comparative Example 5 1. The process of producing high-yield pulp from moso bamboo is as follows: (1) Preparation of materials: The method is the same as in Example 1.

[0093] (2) Screw extrusion: Same as the method in Example 1.

[0094] (3) Cellulose endopeptidase treatment: the same as in Example 1.

[0095] (4) Chemical impregnation: Same as in Example 1.

[0096] (5) Coarse grinding: Same as the method in Example 1.

[0097] (6) Bioenzyme treatment: This step is not required.

[0098] (7) High-concentration pulping: The method is the same as in Example 1.

[0099] The main indicators of the chemimechanical pulp prepared by the process of Comparative Example 5 are as follows: the energy consumption of the pulping ratio is 3056.7 kW·h / t, the yield is 86.0% for 150 mL CSF.

[0100] Comparative Example 6 1. The process of producing high-yield pulp from moso bamboo is as follows: (1) Preparation of materials: The method is the same as in Example 1.

[0101] (2) Screw extrusion: Same as the method in Example 1. (3) Cellulose endopeptidase treatment: This step is not required.

[0102] (4) Chemical impregnation: Same as in Example 1.

[0103] (5) Coarse grinding: Same as the method in Example 1.

[0104] (6) Bioenzyme treatment: This step is not required.

[0105] (7) High-concentration pulping: The method is the same as in Example 1.

[0106] The main parameters of the chemimechanical pulp prepared using the process of Comparative Example 6 are as follows: the energy consumption for refining is 3512.4 kW·h / t, the yield is 85.5% for 150 mL CSF. At a CSF free concentration of 150 mL, the yields of Examples 5 and 6 using moso bamboo as raw material were 0.865, 0.857, 0.860, and 0.855, respectively, compared to Comparative Examples 5 and 6. Compared to Comparative Example 5, Example 5 showed a 19.97% reduction in grinding energy consumption, and compared to Comparative Example 6, a 30.35% reduction in grinding energy consumption. Compared to Comparative Example 5, Example 6 showed a 14.36% reduction in grinding energy consumption, and compared to Comparative Example 6, a 25.47% reduction in grinding energy consumption. In summary, the comparative experimental results show that the two-stage bio-enzyme treatment method of the present invention for energy-saving preparation of high-yield pulp can significantly reduce the grinding energy consumption of wood and bamboo chemimechanical pulp.

[0107] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing high yield pulp by two-stage biological enzyme treatment of wood and bamboo material as raw material, characterized in that, The method comprises the following steps: (1) preparing wood raw materials into wood chips, and screening, washing and steaming treatment; (2) mechanical extrusion: the wood chips are subjected to mechanical extrusion treatment to be in the form of rods or filaments, and extruded materials are obtained; (3) cellulase treatment: cellulase is used to treat the extruded materials; (4) chemical immersion: alkaline hydrogen peroxide solution is used as immersion liquid to chemically immerse the pulp after cellulase treatment, and immersed pulp is obtained; (5) rough grinding: the immersed pulp is subjected to atmospheric grinding and dissociation, and the dissociated pulp is adjusted to neutral; (6) biological enzyme treatment: the dissociated pulp is subjected to biological enzyme treatment with xylanase or cellulase; (7) grinding: the pulp after biological enzyme treatment is subjected to atmospheric grinding and dissociation, and high-yield mechanical pulp is obtained; the yield of the high-yield mechanical pulp is 85-90%.

2. The method of claim 1, wherein, In step (1), the length of the wood chips is 20-40 mm, and the thickness is 3-5 mm.

3. The method of claim 1, wherein, In step (2), the mechanical extrusion device is a double-screw extruder, the length of the extruded materials is 1-40 mm, and the width is 100-500 μm.

4. The method of claim 1, wherein, In step (3), the cellulase treatment temperature is 50 ℃, the time is 120 min, the solid-liquid ratio is 1:10, and the pH is 4.

5.

5. The method of claim 1, wherein, In step (3), the cellulase enzyme dosage in the cellulase treatment is 80-100 CMC-U / g.

6. The method of claim 1, wherein, In step (4), the chemical immersion temperature is 90 ℃, the time is 1 h, and the dosages of the components in the alkaline hydrogen peroxide solution relative to the mass of the wood chips are as follows: hydrogen peroxide 10%, sodium hydroxide 8%, sodium silicate 2%, and DTPA 0.5%.

7. The method of claim 1, wherein, In step (5), the grinding pulp concentration is 20%, and the grinding gap is 0.3-0.5 mm.

8. The method of claim 1, wherein, In step (6), the biological enzyme treatment temperature is 50 ℃, the time is 120 min, the solid-liquid ratio is 1:10, and the pH is 4.

5.

9. The method of claim 1, wherein, In step (6), the dosage of the xylanase is 80-100 FXU-S / g, and the dosage of the cellulase is 80 CMC-U / g.

10. The method of claim 1, wherein, In step (7), the grinding is high-concentration grinding, the grinding pulp concentration is 23%, and the grinding gap is 0.2-0.3 mm.

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