Method for preparing high-strength and high-yield pulp through biological enzyme treatment and recycling separation liquid

Abstract

The invention discloses a method for preparing high-strength and high-yield pulp through biological enzyme treatment and recycling separation liquid, which comprises the following steps: taking wood and bamboo as fiber raw materials; the high-strength and high-yield pulp is obtained through material preparation, spiral extrusion, deep eutectic solvent treatment, solid-liquid separation and lignin recovery, biological enzyme treatment, solid-liquid separation and sugar liquid recovery, two-stage high-concentration pulp grinding and inter-stage retention reaction. According to the method, lignin and carbohydrates are recycled respectively through step-by-step pretreatment of deep eutectic solvent treatment and biological enzyme treatment on the wood fibers, meanwhile, the high-tensile-strength paper pulp is prepared under the conditions of low pulping energy consumption and low dipping reagent dosage, and the deep eutectic solvent can be recycled. According to the high-strength and high-yield pulping method adopting the deep eutectic solvent and the biological enzyme for treatment, the resource utilization rate in the pulping process is 90%, the pulping specific energy consumption is reduced by 30%-50%, and the tensile index is increased by more than one time.

Description

Technical Field

[0001] The invention belongs to the field of pulping and papermaking, relates to a high-yield clean pulping technology, and particularly to a method for preparing high-strength and high-yield pulp and separating lignin and sugar solution for resource utilization based on biological enzyme treatment. Background Art

[0002] At present, my country's annual production of high-yield pulp is nearly 10 million tons, which is used to make various paper and paperboard products, alleviating the shortage of fiber resources in the papermaking industry. However, there are shortcomings in the production of high-yield pulp, such as high pulping energy consumption, low pulp strength and high wastewater treatment costs. Developing high-yield clean pulping energy-saving processes and comprehensively utilizing pretreatment liquids are important ways for the papermaking industry to achieve energy conservation, emission reduction and high-quality development.

[0003] Biopulping has the characteristics of reducing pulping energy consumption, saving pulping chemicals, improving pulp fiber quality, and a clean and environmentally friendly pulping process. It is a pulping technology with good development prospects. Wood chips are treated with fungi (mainly white rot fungi) to partially or completely remove lignin from plant tissues for pulping. However, the treatment cycle is too long (more than 2 weeks or even several months), and the strain culture requires prior sterilization, addition of corn steep liquor, temperature control, humidity control, and oxygenation. The expansion conditions are strict and industrialization has not been achieved. Pulping with biological enzymes such as xylanase, cellulase, laccase, and manganese peroxidase after pretreatment of wood / bamboo fiber raw materials has a short treatment time and is easy to match with existing production processes, which has attracted the attention of pulp and paper researchers.

[0004] Patent ZL20211130437.5 provides a method for using a compound biological enzyme preparation and its preparation method and application. The compound biological enzyme preparation of the invention is used to treat wood chips. The patent uses a compound enzyme preparation to treat wood chips. Because the dense structure of the wood chips limits the treatment efficiency of the enzyme preparation, and the enzyme preparation ingredients need to be compounded with laccase that degrades lignin, the enzyme treatment cost is high. Patent 202011050725.3 provides a method for treating wood chips, a wood chip treatment system and a chemical-mechanical pulp product. The composite enzyme liquid is sprayed on the wood chips through a liquid spray pipe during the screening, sampling and transportation of the wood chips to relax the internal tissue of the wood chip fiber cell wall and decompose and remove the xylan, hemicellulose and pectin adhesives in the wood chips. Also, because the treatment object is wood chips, there is a long treatment time (>48h), a complicated treatment procedure, and the power saving effect is not significant (37kW·h / t).

[0005] The physicochemical properties of deep eutectic solvents (DESs) are very similar to those of ionic liquids. They have good swelling and component dissolution effects on cellulosic biomass, and can be used as pretreatment reagents to assist pulping (Chinese Patent 202011327992.0, Patent Publication CN 117166276A, etc.), providing good conditions for subsequent cooking delignification or enzyme treatment. There are large differences in the dissolution effects of different deep eutectic solvents on the chemical components in wood fibers. Among them, organic acid-based low eutectic solvents such as lactic acid / choline chloride (10:1) and oxalic acid / choline chloride (1:1) have good removal effects on lignin, and the lignin dissolution rate for wood and bamboo fiber raw materials is more than 90%. The use of this low eutectic solvent for dissolving lignin for pretreatment is expected to significantly reduce the inhibitory effect of lignin in the material on enzyme treatment.

[0006] The production process of high-yield pulp involves the use of a disc refiner to dissociate the fiber raw materials. In order to reduce the energy consumption of pulping and improve the mechanical strength of the pulp, chemical impregnation is generally required before pulping, which consumes a large amount of impregnation chemicals. In addition, the chemical components dissolved from the fiber raw materials are complex in composition (lignin, hemicellulose and degradation products of cellulose) and the concentration of organic matter is low, making resource utilization difficult.

[0007] In the high-yield pulping process, mechanical extrusion, low eutectic solvents, biological enzymes, etc. are used for pretreatment. Through the extrusion crushing and size reduction of wood chips and bamboo chips, the moderate dissolution of lignin by low eutectic solvent treatment, and the partial degradation and dissolution of hemicellulose and cellulose by biological enzyme treatment, on the one hand, the resource utilization of the dissolved components of lignin, hemicellulose and cellulose can be achieved. On the other hand, it can replace the traditional chemical impregnation treatment to produce higher strength pulp, so as to break through the technical bottleneck existing in the production of high-yield pulp in the industry. Summary of the invention

[0008] The present invention provides a bio-enzyme mechanical pulping method, which uses a low eutectic solvent and a bio-enzyme to pretreat wood fibers, replacing the conventional chemical impregnation method, dissociating fibers with lower energy consumption to produce high-strength pulp, and realizing the recovery and utilization of dissolved lignin and sugar solution.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A method for preparing high-strength and high-yield pulp and separated liquid resource utilization by biological enzyme treatment, the processing steps are as follows: (1) material preparation: wood and bamboo fiber raw materials are chipped, washed, and steamed to obtain wood chips or bamboo chips with a length of 20 to 40 mm and a thickness of 3 to 5 mm, and debris such as sand and stones are removed and the moisture content of the chips is adjusted for standby use; (2) screw extrusion: the chips are mechanically extruded pre-treated by a screw extrusion device to reduce their size to obtain the extruded material, which is in the shape of a rod or a filament with a length of 1 to 40 mm and a width of 100 to 500 μm; (3) low eutectic solvent treatment: the extruded material is treated with a low eutectic solvent prepared from lactic acid and choline chloride at a temperature of 80 to 110° C., a time of 60 to 120 min, and a solid-liquid ratio of 1:4 to 1:10; (4) solid-liquid separation I: solid-liquid separation is achieved by centrifugation followed by extrusion to obtain solid material I and liquid I. Solid material I is washed with water until it is neutral, and the separated liquid I is used to recover the low eutectic solvent and lignin; (5) Bioenzyme treatment: The solid material I is treated with a composite enzyme solution composed of cellulase and xylanase, with a treatment temperature of 45-55°C, a pH of 5.5, a time of 60-120 min, and a solid-liquid ratio of 1:4-1:10; (6) Solid-liquid separation II: The material obtained by bioenzyme treatment is subjected to solid-liquid separation by a method of first centrifugation and then extrusion to obtain solid material II and liquid II. The separated liquid II is used to recover the sugar solution; (7) High-concentration refining I: The solid material II is subjected to normal pressure refining and dissociation by a high-concentration disc mill, with a refining slurry concentration of 20%-40% and a refining gap of 0.3-0.5 mm. Add impregnation reagent to the pulping feed port, with the dosage of 20-40 kg / t; (8) Stay reaction: After the pulping is completed, adjust the pulp concentration to 20%-40% and the temperature to 70-95°C, and carry out stay reaction for 45-90 minutes; (9) High-concentration pulping II: After the stay reaction, use a high-concentration disc mill to perform normal pressure pulping and dissociation. The pulp after grinding is washed with clean water, and the washing water is filtered and purified for reuse. Among them:

[0011] In step (1), the wood and bamboo fiber raw materials include broad-leaved wood such as poplar and eucalyptus and their mixed wood chips, as well as bamboo such as bamboo and moso bamboo and their mixed bamboo chips; it can also be wood, bamboo or their processing residues.

[0012] In the step (3) of treating with a low eutectic solvent, the low eutectic solvent used is a mixed solution of choline chloride and lactic acid in a molar ratio of 1:10.

[0013] In step (4) solid-liquid separation I, liquid I is refrigerated overnight by adding 3 times the volume of water, precipitated and filtered to obtain lignin, and the amount of lignin recovered is 20 to 70 kg / t dry material; the filtrate is concentrated to the original volume by low-temperature heating at 60° C. and recycled.

[0014] In the biological enzyme treatment of step (5), the mass ratio of xylanase to cellulase is 2:1, and the amount of enzyme solution is 20-40 U / g.

[0015] In step (6) solid-liquid separation II, liquid II is concentrated to obtain sugar solution, the amount of recovered sugar solution is 100-500 L / t dry material, the solid content is 20%, and the main components are xylooligosaccharides, xylose and glucose.

[0016] In step (7) high-concentration refining I, the impregnation agent added in the refining process is composed of MgO and NaOH, the ratio of which is 1:3, the amount of the impregnation agent is 20-40 kg / t, the refining specific energy consumption is 100-200 kW·h / t, the refining slurry concentration is 20%-40%, the refining gap is 0.3-0.5 mm, and the refining specific energy consumption is 150 kW·h / t. In a further scheme, when the fiber raw material is a hardwood raw material, 3-5 kg / t of DTPA and 20-40 kg / t of H2O2 are added simultaneously in the high-concentration refining I process, and the prepared pulp is a high-strength bleached pulp with a pulp yield of 80%-85%. The main parameters of the finished pulp are: fiber bundle content <0.08%, tensile index 30-50 N·m / g, and pulp whiteness of 74%-86% ISO.

[0017] In step (9) high-concentration refining II, the refining slurry concentration is 20% to 40%, the refining gap is 0.2 to 0.3 mm, and the refining specific energy consumption is 300 to 400 kW·h / t. The prepared pulp is a natural color, high-strength, high-yield pulp (yield 80% to 85%, fiber bundle content <0.08%, tensile index 30 to 50 N·m / g).

[0018] The beneficial effects of the present invention are embodied in:

[0019] The present invention adopts a pretreatment method of spiral extrusion, low eutectic solvent treatment, biological enzyme treatment and other steps to achieve the separate recycling of lignin and sugar substances, and has significant high resource utilization and green environmental protection characteristics. Lignin and sugar substances are recovered in the pretreatment process, and the recovery amounts are 20-70 kg / t of lignin and 100-500 L / t of sugar solution (solid content 20%), plus 800-850 kg / t of finished high-yield pulp, and the total resource utilization rate is more than 90%; the sugar solution mainly contains oligoxylose, xylose and glucose, which can be used as a raw material for the preparation of functional health products and animal feed additives.

[0020] The present invention adopts pretreatment such as low eutectic solvent treatment and biological enzyme treatment, and has significant energy-saving effect in pulping. The specific energy consumption of two-stage pulping is 400-600kW·h / t, and compared with the traditional pulping method, the power consumption of pulping is saved by 35%-50%.

[0021] The pulp produced by the present invention is natural color, high strength and high yield pulp, with a pulp yield of 80% to 85%. The main parameters of the finished pulp are: fiber bundle content <0.08%, tensile index 30 to 50 N·m / g. The tensile strength is nearly doubled compared with the traditional method (tensile index 15 to 30 N·m / g). BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Flow chart of bio-enzyme treatment to produce high-strength and high-yield pulp and resource utilization of separation liquid. DETAILED DESCRIPTION

[0023] The following is a clear and complete description of the technical solution of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The preparation method of the low eutectic solvent used in the following examples is as follows: 26 kg of lactic acid and 4 kg of choline chloride (molar ratio 10:1) are weighed and mixed, and reacted at 60° C. and 200 rpm for 2 h to form a uniform transparent liquid, which is used as a low eutectic solvent.

[0025] Example 1

[0026] 1. Using eucalyptus as raw material Figure 1 The process of making high-strength and high-yield natural color pulp is as follows:

[0027] (1) Material preparation: Eucalyptus logs are chipped, washed, and steamed to obtain wood chips with a length of 20 to 40 mm and a thickness of 3 to 5 mm. Sand and other debris are removed and the moisture content of the chips is adjusted to 10% for later use.

[0028] (2) Screw extrusion: 2.5 kg of eucalyptus wood chips (water content 2.78 kg) were mechanically extruded using a twin screw extruder (Jiangsu Jinwo, model TSP65, screw speed 450 rpm) to reduce the size of the extruded material to obtain a rod-shaped or filament-shaped material with a material specification of 1 to 40 mm in length and 100 to 300 μm in width. During the extrusion process, a low eutectic solvent (7.5 kg) with a volume three times that of the material was used to replace and remove the water in the material, and the extruded liquid was dehydrated and reused to reduce the water content of the material to less than 3.5%.

[0029] (3) Low eutectic solvent treatment: The extruded material was treated with a low eutectic solvent at a temperature of 90°C, a time of 120 min, a solid-liquid ratio of the material to the low eutectic solvent of 1:8, and a total weight of 22.5 kg.

[0030] (4) Solid-liquid separation I: First centrifuge and then squeeze to achieve solid-liquid separation, and obtain solid material I and liquid I. The solid material I is washed with water until it is neutral for the next step of enzyme treatment. The low eutectic solvent and lignin are recovered from the separated liquid I. The specific method is as follows: the separated liquid I is mixed with 10 times the volume of water and placed in a 0-4°C cold storage overnight. After the solid is precipitated, the lignin is filtered out by centrifugation. The crude lignin is about 128.5g after purification; the filtrate is evaporated to anhydrous in a rotary vacuum dryer at 60°C and -0.98MPa vacuum degree, and is used for the recovery and recycling of the low eutectic solvent.

[0031] (5) Biological enzyme treatment: The solid material I was treated with a composite enzyme solution composed of cellulase and xylanase, the mass ratio of xylanase to cellulase was 2:1, the enzyme solution dosage was 30 U / g, the treatment temperature was 50°C, the pH was 5.5, the treatment time was 120 min, and the solid-liquid ratio was 1:8.

[0032] (6) Solid-liquid separation II: Solid-liquid separation is achieved by centrifugation followed by extrusion to obtain solid material II and liquid II. Solid material II is used for the next step of high-concentration refining I, and separated liquid II is used for sugar liquid recovery. The amount of recovered sugar liquid is 200 L / t dry material, and the solid content is 20%. HPLC analysis shows that the main components are oligoxylose, xylose and glucose.

[0033] (7) High-concentration refining I: A high-concentration disc mill is used to perform normal pressure refining and dissociation of solid material II. An impregnation agent is added to the refining feed port. The impregnation agent is composed of MgO and NaOH in a mass ratio of 1:3, and the amount of the impregnation agent is 40 kg / t. The refining slurry concentration is 25%, the refining gap is 0.3-0.5 mm, and the refining specific energy consumption is 150 kW·h / t.

[0034] (8) Stay reaction: After refining, the pulp concentration was adjusted to 25% and the temperature to 95°C, and the stay reaction was carried out for 60 minutes.

[0035] (9) High-concentration refining II: After the retention reaction is completed, the slurry is refined and dissociated at normal pressure using a high-concentration disc refiner. The refining slurry is washed with clean water, and the washing water is filtered and purified for reuse. The refining slurry concentration is 25%, the refining gap is 0.2-0.3 mm, and the refining specific energy consumption is 350 kW·h / t.

[0036] The pretreatment process of each ton of dry eucalyptus wood chips recovers 51.4kg of lignin, 200L of sugar solution (solid content 20%), 865kg of finished high-yield pulp, and the total resource utilization rate is 92.6%; the specific energy consumption of pulping is 500kW·h / t, and the main quality indicators of the finished pulp are: 300mL CSF, fiber bundle content 0.06%, bulk thickness 2.12cm 3 / g, tensile index 43.6N·m / g.

[0037] Example 2

[0038] 1. Using eucalyptus as raw material to produce high-strength and high-yield bleached pulp, the specific process is as follows:

[0039] (1) Preparation: Same as the method in Example 1.

[0040] (2) Screw extrusion: the same method as in Example 1.

[0041] (3) Low eutectic solvent treatment: the same as the method in Example 1.

[0042] (4) Solid-liquid separation I: The method is the same as in Example 1.

[0043] (5) Bio-enzyme treatment: the same as in Example 1.

[0044] (6) Solid-liquid separation II: the same method as in Example 1.

[0045] (7) High-concentration refining I: When adding the impregnation reagent to the refining feed port, 3kg / t of DTPA and 40kg / t of H2O2 were added at the same time, and the specific energy consumption of refining was 150kW·h / t.

[0046] (8) Stay reaction: the same as the method in Example 1.

[0047] (9) High-concentration refining II: The method is the same as that in Example 1, and the specific energy consumption of refining is 320 kW·h / t.

[0048] The pretreatment process of each ton of dry eucalyptus wood chips recovers 51.4kg of lignin, 200L of sugar solution (solid content 20%), 846kg of finished high-yield pulp, and the total resource utilization rate is 90.7%; the specific energy consumption of pulping is 470kW·h / t, and the main quality indicators of the finished pulp are: 290mLCSF, fiber bundle content 0.05%, bulk thickness 1.95m 3 / g, tensile index 46.2N·m / g, pulp whiteness 81.3%ISO.

[0049] Comparative Example 1

[0050] 1. Using eucalyptus as raw material to make high-yield pulp, the specific process is as follows:

[0051] (1) Preparation: Same as the method in Example 1.

[0052] (2) Screw extrusion: 2.5 kg of eucalyptus wood chips (water content 2.78 kg) were mechanically extruded and pre-treated using a twin screw extruder (Jiangsu Jinwo, model TSP65, screw speed 450 rpm) to reduce the size of the extruded material to obtain a rod-shaped or filament-shaped material with a length of 1 to 40 mm and a width of 100 to 300 μm. During the extrusion process, water equivalent to 3 times the amount of the absolute dry material was added and directly sent to high-concentration pulping I.

[0053] (3) Low eutectic solvent treatment: No such step.

[0054] (4) Solid-liquid separation I: No such step.

[0055] (5) Biological enzyme treatment: No such step.

[0056] (6) Solid-liquid separation II: No such step.

[0057] (7) High-concentration refining I: A high-concentration disc refiner was used for normal pressure refining and dissociation. An impregnation agent was added to the refining feed port. The impregnation agent consisted of MgO and NaOH in a mass ratio of 1:3. The amount of the impregnation agent was 40 kg / t. The refining slurry concentration was 25%, the refining gap was 0.3-0.5 mm, and the refining specific energy consumption was 354 kW·h / t.

[0058] (8) Stay reaction: slurry concentration 25%, temperature 95°C, time 60 min.

[0059] (9) High-concentration refining II: A high-concentration disc mill is used for normal pressure refining and dissociation. The refining pulp is washed with clean water, and the washing water is filtered and purified for reuse. The refining pulp concentration is 25%, the refining gap is 0.2-0.3 mm, and the refining specific energy consumption is 452 kW·h / t.

[0060] 862kg of pulp can be produced from each ton of dry eucalyptus wood chips; the specific energy consumption of pulping is 806kW·h / t. The main quality indicators of the finished pulp are: freeness 310mLCSF, fiber bundle content 0.05%, bulk thickness 2.46cm 3 / g, tensile index 18.2N·m / g.

[0061] Example 3

[0062] 1. Using bamboo as fiber raw material to produce natural color, high strength and high yield bamboo pulp, the specific process is as follows:

[0063] (1) Preparation: Same as the method in Example 1.

[0064] (2) Screw extrusion: the same method as in Example 1.

[0065] (3) Low eutectic solvent treatment: the same as the method in Example 1.

[0066] (4) Solid-liquid separation I: First centrifuge and then squeeze to achieve solid-liquid separation to obtain solid material and liquid. The solid material is washed with water until neutral for the next step of enzyme treatment. The low eutectic solvent and lignin are recovered from the separated liquid. The specific method is as follows: add 25 kg of water to the separated liquid, place it in a 0-4°C cold storage overnight, and centrifuge and filter out lignin after the solid is precipitated. The crude lignin is about 154.8 g after purification; the filtrate is evaporated to anhydrous in a rotary vacuum dryer at 60°C and -0.98MPa vacuum degree, and used for the recovery and recycling of the low eutectic solvent. The solvent recovery rate is 91%.

[0067] (5) Bio-enzyme treatment: the same as in Example 1.

[0068] (6) Solid-liquid separation II: Solid-liquid separation is achieved by centrifugation followed by extrusion to obtain solid material and liquid. The fiber material is used for the next step of high-concentration refining I, and the separated liquid is used for sugar liquid recovery. The amount of recovered sugar liquid is 260L / t dry material, the solid content is 20%, and the main components of HPLC analysis are oligoxylose, xylose and glucose.

[0069] (7) High-concentration refining I: A high-concentration disc refiner was used for normal pressure refining and dissociation, with a refining slurry concentration of 25% and a refining gap of 0.3-0.5 mm. An impregnation agent was added to the refining feed port, the impregnation agent was composed of MgO and NaOH, the mass ratio of which was 1:3, the amount of the impregnation agent was 40 kg / t, the refining slurry concentration was 25%, the refining gap was 0.3-0.5 mm, and the refining specific energy consumption was 140 kW·h / t.

[0070] (8) Stay reaction: the same as the method in Example 1.

[0071] (9) High-concentration refining II: A high-concentration disc refiner is used for normal pressure refining and dissociation. The refining pulp is washed with clean water, and the washing water is filtered and purified for reuse. The refining pulp concentration is 25%, the refining gap is 0.2-0.3 mm, and the refining specific energy consumption is 345 kW·h / t.

[0072] During the pretreatment process, 61.9 kg of lignin and 260 L of sugar solution (20% solid content) were recovered per ton of dried bamboo chips. 802 kg of high-yield pulp was produced, and the total resource utilization rate was 91.6%. The specific energy consumption of pulping was 485 kW·h / t. The main quality indicators of the finished pulp were: 290 mL CSF, fiber bundle content 0.05%, and bulk thickness 2.07 cm 3 / g, tensile index 38.3N·m / g.

[0073] Comparative Example 2

[0074] 1. Using bamboo as raw material to make natural color high yield pulp, the specific process is as follows:

[0075] (1) Preparation: Same as the method in Example 1.

[0076] (2) Screw extrusion: 2.5 kg of bamboo slices were mechanically extruded and pre-treated using a twin screw extruder (Jiangsu Jinwo, model TSP65, screw speed 450 rpm) to reduce the size of the extruded material to obtain a rod-shaped or filament-shaped material with a length of 1 to 40 mm and a width of 100 to 300 μm. During the extrusion process, 3 times the amount of water was added to the material and then directly sent to high-concentration pulping I.

[0077] (3) Low eutectic solvent treatment: No such step.

[0078] (4) Solid-liquid separation I: No such step.

[0079] (5) Biological enzyme treatment: No such step.

[0080] (6) Solid-liquid separation II: No such step.

[0081] (7) High-concentration refining I: A high-concentration disc refiner was used for normal pressure refining and dissociation, with a refining slurry concentration of 25% and a refining gap of 0.3-0.5 mm. An impregnation agent was added to the refining feed port, the impregnation agent was composed of MgO and NaOH, the mass ratio of which was 1:3, the amount of the impregnation agent was 40 kg / t, the refining slurry concentration was 25%, the refining gap was 0.3-0.5 mm, and the refining specific energy consumption was 330 kW·h / t.

[0082] (8) Stay reaction: the same as the method in Example 1.

[0083] (9) High-concentration refining II: A high-concentration disc mill is used for normal pressure refining and dissociation. The refining pulp is washed with clean water, and the washing water is filtered and purified for reuse. The refining pulp concentration is 25%, the refining gap is 0.2-0.3 mm, and the refining specific energy consumption is 450 kW·h / t.

[0084] 837kg of pulp can be produced from each ton of absolutely dry bamboo chips, and the specific energy consumption of pulping is 780kW·h / t. The main quality indicators of the finished pulp are: freeness 320mL CSF, fiber bundle content 0.07%, bulk thickness 2.25cm 3 / g, tensile index 17.6N·m / g.

[0085] The pulping results of each embodiment and comparative example and the main quality indicators of pulp are compared in Table 1 below:

[0086] Table 1 Pulping results and main quality index comparison of pulp in various embodiments and comparative examples

[0087]

[0088] According to the above table, the pulping methods provided in the examples all have the characteristics of high resource utilization (more than 90%), low pulping specific energy consumption (<500kW·h / t) and high tensile strength (>30N·m / g). Under similar freeness (290-310mLCSF), compared with comparative example 1, Example 1 and Example 2 using eucalyptus as raw material, the resource utilization is 5.5% and 9.1% higher, the pulping specific energy consumption is reduced by 37.9% and 41.7%, and the tensile strength is increased by 139% and 154% respectively; compared with comparative example 2, Example 3 using bamboo as raw material has a resource utilization rate of 7.9% higher, the pulping specific energy consumption is reduced by 37.8%, and the tensile strength is increased by 85.9%.

[0089] In summary, it can be seen from the comparative experimental results that the method for preparing high-strength and high-yield pulp and separation liquid resource utilization using the bio-enzyme treatment of the present invention can maximize the utilization of fiber resources and produce high-strength pulp with lower energy consumption.

[0090] Obviously, the above described embodiments are only some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing high-strength and high-yield pulp and separating liquid resource utilization by biological enzyme treatment, characterized in that: The following steps are involved: (1) Material preparation: chipping, washing and steaming the wood or bamboo fiber raw materials to obtain wood chips or bamboo chips, and adjusting the moisture content of the chips to be used for later use; (2) Screw extrusion: Use screw extrusion equipment to mechanically extrude the sheet to pre-treat it, reduce its size, and obtain the extruded material; (3) Deep eutectic solvent treatment: The extruded material is treated with a deep eutectic solvent prepared from lactic acid and choline chloride; (4) solid-liquid separation I: performing solid-liquid separation on the material obtained by the treatment with the low eutectic solvent to obtain a solid material I and a liquid I; the solid material I is washed with water until it is neutral, and the liquid I is used to recover the low eutectic solvent and lignin; (5) Bioenzyme treatment: using a composite enzyme solution composed of cellulase and xylanase to treat the solid material I with bioenzyme; (6) Solid-liquid separation II: solid-liquid separation of the material obtained by the enzyme treatment to obtain solid material II and liquid II; liquid II is used for sugar solution recovery; (7) High-concentration refining I: using a high-concentration disc mill to perform normal pressure refining and dissociation of solid material II; adding an impregnation agent at the refining feed inlet, with the dosage being 2% to 6%; (8) Stay reaction: After refining, the slurry concentration is adjusted to 20% to 40% and the temperature is adjusted to 70 to 95° C., and the stay reaction is carried out for 45 to 90 minutes; (9) High-concentration refining II: After the residence reaction is completed, the slurry is refined and dissociated at normal pressure using a high-concentration disc mill. The slurry after refining is washed with clean water to obtain a finished high-yield slurry. The washing water is filtered and purified for reuse.

2. The method for preparing high-strength and high-yield pulp and separating liquid resource utilization by biological enzyme treatment according to claim 1, characterized in that: In step (3) the low eutectic solvent treatment, the low eutectic solvent is a mixed solution composed of choline chloride and lactic acid in a molar ratio of 1:10; the temperature of the low eutectic solvent treatment is 80 to 110° C., the time is 60 to 120 min, and the solid-liquid ratio is 1:4 to 1:

10.

3. The method for preparing high-strength and high-yield pulp and separating liquid resource utilization by biological enzyme treatment according to claim 1, characterized in that: In step (4) solid-liquid separation I, liquid I is refrigerated overnight by adding 3 times the volume of water, precipitated and filtered to obtain lignin; the filtrate is concentrated to the original volume by heating and recycled.

4. The method for preparing high-strength and high-yield pulp and separating liquid resource utilization by biological enzyme treatment according to claim 1, characterized in that: In step (5) of the biological enzyme treatment, the mass ratio of xylanase to cellulase is 2:1, the dosage of the complex enzyme solution is 20-40 U / g; the temperature of the biological enzyme treatment is 45-55°C, the pH is 5.5, the time is 60-120 min, and the solid-liquid ratio is 1:4-1:

10.

5. The method for preparing high-strength and high-yield pulp and separating liquid resource utilization by biological enzyme treatment according to claim 1, characterized in that: In step (6) solid-liquid separation II, liquid II is concentrated to obtain sugar solution, and the amount of recovered sugar solution is 100-500 L / t dry material, and the main components are xylooligosaccharides, xylose and glucose.

6. The method for preparing high-strength and high-yield pulp and separating liquid resource utilization by biological enzyme treatment according to claim 1, characterized in that: In step (7) high-concentration refining I, the impregnation reagent includes MgO and NaOH in a mass ratio of 1:3, and the amount of the impregnation reagent is 20-40 kg / t; the concentration of the refining slurry in the normal pressure refining dissociation is 20%-40%, the refining gap is 0.3-0.5 mm, and the refining specific energy consumption is 100-200 kW·h / t.

7. The method for preparing high-strength and high-yield pulp and separating liquid resource utilization by biological enzyme treatment according to claim 6, characterized in that: In step (7) high-concentration refining I, the impregnation reagent also includes DTPA and H2O2, and the amount of DTPA is 3-5 kg / t and the amount of H2O2 is 20-40 kg / t.

8. The method for preparing high-strength and high-yield pulp and separating liquid resource utilization by biological enzyme treatment according to claim 1, characterized in that: In step (9) high-concentration refining II, the concentration of the refining slurry in the normal pressure refining dissociation is 20% to 30%, the refining gap is 0.2 to 0.3 mm, and the refining specific energy consumption is 300 to 400 kW·h / t.

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