Process for the explosion pulping of grasses and pulp

Abstract

The application provides a steam explosion pulping method and pulp for gramineae. The method comprises the following steps: cutting gramineae to a predetermined size, and then humidifying to a predetermined moisture content to obtain a material to be exploded; loading the material to be exploded into a steam explosion reaction device, vacuumizing to a first pressure, then atomizing an alkali catalyst or an alkali catalyst precursor into an aerosol, and introducing the aerosol into the steam explosion reaction device; after the introduction of the aerosol is completed, introducing water vapor with a temperature higher than 120 DEG C into the steam explosion reaction device, so that the pressure in the steam explosion reaction device is increased to a second pressure, and pressure maintaining is performed for a first predetermined time; after the pressure maintaining is completed, cutting off the water vapor source, introducing preheated inert gas into the steam explosion reaction device, so that the pressure in the steam explosion reaction device is increased to a target explosion pressure, and then explosion is performed to obtain a flocculent fiber material. The application can realize uniform dissociation of gramineae without high chemical pretreatment cost.

Description

Technical Field

[0001] This application relates to the field of pulp and paper making, specifically to a steam explosion pulping method and pulp for gramineous plants. Background Technology

[0002] my country has abundant resources of gramineous plants (such as straw), with a huge annual output, but their efficient and high-value utilization has always been a challenge for the industry. Traditional straw fiberization methods mainly include mechanical, chemical, and chemimechanical methods. Mechanical methods are energy-intensive, cause severe fiber damage, and have low yields; chemical methods (such as the alkali process) are heavily polluting and difficult to treat wastewater; while chemimechanical methods have improved somewhat, they still have problems such as chemical residues and fiber strength loss. These methods struggle to achieve clean and low-energy production goals while ensuring fiber quality.

[0003] Gas-phase explosion, as a highly efficient physical-chemical pretreatment technology, can destroy the dense structure of lignocellulose and separate its three major components, making it a preferred method for straw pulping. However, existing technologies have significant drawbacks: First, when processing high-silica straw, lignin removal is incomplete, leading to high energy consumption and significant equipment wear in subsequent pulping. Second, simple steam explosion relies solely on physical action and cannot regulate the chemical properties of the fiber surface. Third, high temperatures easily induce fiber oxidative browning, making it difficult to produce high-brightness pulp. Fourth, fibers are prone to excessive degradation, making it difficult to balance yield and strength. Fifth, the process is lengthy and highly polluting, making it unsuitable for small-scale, distributed production needs.

[0004] To address the aforementioned issues, the industry has attempted to soften the straw surface using chemical spraying (spraying dilute alkali or ammonia). However, due to surface tension, the droplets cannot penetrate the material, only forming a water film on the surface, resulting in poor softening and generating a large amount of wastewater. Other scholars have proposed a prolonged soaking pretreatment before steam explosion, but this would negate the advantages of the steam explosion process itself, such as its short process flow and high intensity.

[0005] The content of the background section is merely the technology known to the inventor and does not necessarily represent the prior art in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, the first aspect of this application provides a method for steam explosion pulping of gramineous plants, comprising: The grass plants are cut to a predetermined size and then conditioned to a predetermined moisture content to obtain the material to be blasted. After the material to be blasted is loaded into the steam explosion reaction device, a vacuum is drawn to the first pressure, and then the alkaline catalyst or alkaline catalyst precursor is atomized into an aerosol and introduced into the steam explosion reaction device. After the aerosol is introduced, water vapor at a temperature higher than 120°C is introduced into the steam explosion reaction device, so that the pressure inside the steam explosion reaction device rises to a second pressure and is maintained at the pressure for a first predetermined time. After the pressure holding is completed, the steam source is cut off, and preheated inert gas is introduced into the steam explosion reactor to raise the pressure inside the steam explosion reactor to the target explosion pressure, and then the explosion is carried out to obtain flocculent fiber material.

[0007] In some embodiments of this application, after the pressure inside the steam explosion reaction device rises to the target explosion pressure, while maintaining the pressure inside the steam explosion reaction device at no less than 95% of the target explosion pressure, the steam explosion reaction device is vented for a second predetermined time before the explosion is carried out.

[0008] In some embodiments of this application, the steam explosion pulping method further includes: heating the exhaust component during the exhaust process, with a heating temperature ≥160°C.

[0009] In some embodiments of this application, the second predetermined time is 5 to 10 seconds.

[0010] In some embodiments of this application, the predetermined size is 1-5 cm and the predetermined moisture content is 30-40%.

[0011] In some embodiments of this application, the first pressure is <0.02MPa, the second pressure is 0.8~1.2MPa, and the first predetermined time is 30~600s.

[0012] In some embodiments of this application, the alkaline catalyst or alkaline catalyst precursor is selected from sodium carbonate solution, sodium hydroxide solution, ammonia solution or urea solution with a mass concentration of 0.5~5.0%, the median particle size of the aerosol is <1μm, and the liquid-solid ratio of the alkaline catalyst or alkaline catalyst precursor to the oven-dry mass of the material to be blasted is 1:1 to 2:1 L / kg.

[0013] In some embodiments of this application, the temperature of the steam is 150~190°C, and the temperature of the preheated inert gas is 0~5% higher than the temperature inside the steam explosion reaction device.

[0014] In some embodiments of this application, the steam explosion pulping method further includes: The flocculent fiber material is milled, graded, washed, and dewatered to obtain a dry pulp with a moisture content of <10%.

[0015] A second aspect of this application provides a slurry obtained by any of the steam explosion slurry preparation methods described above.

[0016] The technical solution provided in this application achieves targeted in-situ deep catalysis of the catalyst without the need for long-term pre-soaking, eliminating the "external decay and internal growth" phenomenon caused by uneven penetration from the root. Moreover, no soaking waste liquid is generated throughout the process. It can achieve uniform dissociation of gramineous plants without paying high costs for chemical pretreatment, thereby improving the whiteness and strength properties of the pulp.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The embodiments of this application are described in detail below with reference to the accompanying drawings. These drawings, which form part of this application, are used to provide a further understanding of the application. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application.

[0019] Figure 1 A flow chart of a steam explosion pulping process according to an embodiment of this application is shown. Detailed Implementation

[0020] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this application. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0021] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0022] The specific embodiments of this application will be described in more detail below with reference to the accompanying drawings and examples, so as to better understand the solution of this application and its advantages in various aspects. However, the specific embodiments and examples described below are for illustrative purposes only and are not intended to limit this application.

[0023] Through research, the inventors discovered a long-neglected physical bottleneck in existing steam explosion processes: the capillaries and pores inside plant stems are filled with air. These "air barriers" severely hinder the penetration of steam and chemical agents. Traditional steam explosions rely solely on positive pressure differentials to propel the medium into the material, resulting in limited and highly uneven penetration depth. This leads to varying degrees of dissociation between the inside and outside of the material, resulting in a "raw flake" phenomenon where the material is "rotten on the outside and raw on the inside."

[0024] Figure 1 An embodiment of this application illustrates a steam explosion pulping method for gramineous plants, comprising the following steps S10 to S40.

[0025] S10: After cutting the grass plants to a predetermined size, adjust the moisture content to a predetermined level to obtain the material to be blasted.

[0026] This step pre-treats the gramineous plants to make them more suitable for the steam explosion process. Optionally, the predetermined size is 1-5 cm. Optionally, the predetermined moisture content is 30-40%. If the moisture content is too low, the internal heat transfer medium in subsequent processes will be insufficient, which may lead to fiber pyrolysis and carbonization; if it is too high, the evaporation of free water during vacuuming will lead to excessive pumping load and affect the "dry phase" frictional tearing effect at the moment of explosion.

[0027] S20: After loading the material to be blasted into the steam explosion reactor, evacuate to the first pressure, and then atomize the alkaline catalyst or alkaline catalyst precursor into an aerosol and introduce it into the steam explosion reactor.

[0028] Taking a steam explosion reactor as an example, the material to be exploded can be loaded into the reactor, and then the Roots-water ring vacuum pump unit connected to the reactor body can be started to evacuate to the first pressure. Optionally, the first pressure is <0.02MPa. The Roots-water ring vacuum pump unit completes the evacuation in about 5 to 15 minutes.

[0029] During the vacuuming process, the continuous strong pressure difference between the inside and outside of the device can forcibly extract the free air from the deep pores and capillaries of the plant tissue, eliminating the "gas resistance" that would hinder the subsequent entry of aerosols. At the same time, the moderate drop in material temperature after vacuuming causes the high-temperature water vapor introduced later to condense and release heat at the capillary orifice, enhancing the swelling effect.

[0030] After vacuuming, while maintaining the current pressure (negative pressure) inside the device, the alkaline catalyst or alkaline catalyst precursor is atomized into an aerosol and introduced into the steam explosion reaction device. Because free air in the deep pores and capillaries of the plant tissue is removed during the vacuuming process, the aerosol produced at atmospheric pressure is injected at high speed through the pipes under the suction effect of the negative pressure inside the device. Under the huge negative pressure difference between the inside and outside of the device, the extremely small aerosol particles are instantly "re-absorbed" and penetrate deeply into the pores inside the plant.

[0031] A pneumatic ultrasonic atomization device can be used to atomize alkaline catalysts or alkaline catalyst precursors into nano- and submicron-sized aerosols. Optionally, the median particle size (D) of the aerosol can be... 50 <1μm. Optionally, the alkaline catalyst or alkaline catalyst precursor is selected from sodium carbonate solution, sodium hydroxide solution, ammonia solution, or urea solution with a mass concentration of 0.5~5.0%. Optionally, the liquid-solid ratio of the alkaline catalyst or alkaline catalyst precursor to the oven-dry mass of the material to be blasted is 1:1 to 2:1 L / kg. Further optionally, when using sodium carbonate solution, the ratio of sodium carbonate in the sodium carbonate solution to the oven-dry mass of the material to be blasted is (1~5):50; when using sodium hydroxide solution, the ratio of sodium hydroxide in the sodium hydroxide solution to the oven-dry mass of the material to be blasted is (1~4):100; when using ammonia solution, the ratio of ammonia in the ammonia solution to the oven-dry mass of the material to be blasted is (1~3):50; when using urea solution, the ratio of urea in the urea solution to the oven-dry mass of the material to be blasted is (3~8):100. Urea will hydrolyze to produce ammonia under the high temperature conditions of steam explosion, thus exerting an alkaline catalytic effect.

[0032] This application reveals for the first time that "air resistance" within plant tissues is the core physical bottleneck hindering media penetration, and innovatively employs a negative pressure strategy of "vacuuming before entering the reactor." This operation forcibly removes free air from the capillary and utilizes the subsequent huge pressure difference potential energy to instantly reverse-absorb the aerosol into the deep layers of the material. Targeted in-situ deep catalysis of the catalyst is achieved without the need for prolonged pre-soaking, fundamentally eliminating the "external rot and internal growth" phenomenon caused by uneven penetration, and generating no soaking waste liquid throughout the entire process.

[0033] S30: After the aerosol is introduced, water vapor at a temperature higher than 120°C is introduced into the steam explosion reaction device, so that the pressure in the steam explosion reaction device rises to the second pressure and is maintained for the first predetermined time.

[0034] This step introduces high-temperature steam for hydrothermal synergistic softening, causing the plant tissue to swell. Simultaneously, under the pressure within the device, the alkaline catalyst or alkaline catalyst precursor, deeply embedded in the tissue, targets and weakens the crosslinking of lignin and hemicellulose, resulting in uniform softening of the material as a whole. Furthermore, while existing technologies require the use of biological enzymes to weaken the crosslinking of lignin and hemicellulose, this application does not employ biological enzymes, completely avoiding the risk of high-temperature catalyst deactivation.

[0035] Optionally, the second pressure is 0.8~1.2MPa. Optionally, the holding time (first predetermined time) is 30~600s. This application can achieve uniform softening of the material through short-term holding. Further optionally, the temperature of the steam used is 150~190℃, which provides better softening effect and allows the temperature inside the device to be controlled below the cellulose decomposition temperature, ensuring the integrity of the cellulose.

[0036] S40: After the pressure holding is completed, the steam source is cut off, and the preheated inert gas is introduced into the steam explosion reactor to raise the pressure in the steam explosion reactor to the target explosion pressure, and then the explosion is carried out to obtain flocculent fiber material.

[0037] After pressure holding is completed, the high-temperature steam source is cut off. An inert gas (such as nitrogen or industrial compressed air) is preheated through a heat exchanger, and then the preheated high-pressure inert gas is injected into the reactor, rapidly increasing the pressure inside to the target explosion pressure. Optionally, the temperature of the preheated inert gas is 0-5% higher than the temperature inside the steam explosion reactor to maintain the temperature within the reactor. All temperatures referred to here are in Celsius.

[0038] Optionally, the target burst pressure is 1.5~2.0MPa, which is sufficient to achieve physical tearing of the fibers. During the burst, the main discharge valve at the bottom of the vessel is opened instantly and completely (opening time <0.1s), and the material is ejected and disintegrated in one blow using the pressure energy maintained at the peak value.

[0039] In this application, steam serves only as a heat medium for softening, while preheated inert gas provides the explosive pressure energy, completely decoupling the temperature and pressure fields physically. The thermal decomposition temperature of cellulose is approximately 220°C. In this application, since the temperature field within the device is provided by the high-temperature steam in step S30, the temperature inside the device is lower than the thermal decomposition temperature of cellulose at the target explosive pressure. Therefore, only physical tearing of the fibers occurs during the explosion, without cellulose decomposition, achieving a balance between physical tearing efficiency and chemical structural integrity during the explosion process. Furthermore, the preheated inert gas completely avoids the wet-packing phenomenon caused by the condensation and back-absorption of room-temperature gas. This enables the steam explosion process to achieve a perfect unity of "high-pressure strong tearing" and "low-temperature preservation of integrity" for the first time, greatly improving the yield of long fibers and the physical strength of the slurry.

[0040] The inventors further discovered that in traditional steam explosion processes, impurities such as acetic acid and free waxes generated after the high-temperature and high-pressure treatment of gramineous plants are ejected from the main valve along with the fibrous material. These impurities affect the properties of the slurry, especially its whiteness. Furthermore, the waxes can condense and accumulate in subsequent pipes and components, posing both safety hazards and impacting production progress. In traditional steam explosion processes, releasing these impurities requires opening the valve, which affects the pressure within the equipment.

[0041] To address the issues of reduced blasting power and wax condensation blockage caused by impurity removal during traditional multi-stage blasting processes, in some embodiments of this application, after the pressure within the steam explosion reactor reaches the target blasting pressure in step S40, venting is required before blasting. This involves directional airflow to remove volatilized acetic acid and trace amounts of free wax. However, the venting time should not be too long, otherwise it will affect the blasting potential energy. Optionally, the second predetermined venting time is 5-10 seconds.

[0042] During venting, the pressure inside the steam explosion reactor must be maintained at no less than 95% of the target explosion pressure, and the pressure inside the reactor should not change too much. To maintain the pressure and preserve the explosion potential energy, the venting components (venting valve and venting pipeline) of the steam explosion reactor can be slightly opened to vent, and then preheated inert gas can be simultaneously introduced into the reactor. If a steam explosion reactor is used, the bypass venting valve at the top of the reactor can be slightly opened. The pressure transmitter inside the reactor and the inert gas inlet regulating valve form a closed-loop PID control, and a small amount of preheated inert gas is simultaneously added to ensure that the total pressure drop inside the reactor during venting does not exceed 5% of the target explosion pressure, thus maintaining the explosion potential energy.

[0043] In some embodiments of this application, the exhaust components are heated during the exhaust process to prevent waxes and other substances from solidifying and clogging them. The heating temperature needs to be higher than the melting point / dew point of plant waxes and lignin; in this application, it is set to ≥160°C. Heating can be achieved by using full-process electric heating or steam jacket heating on the exterior of the exhaust components. Simultaneously, the exhaust valve can be entirely made of a weak acid-resistant alloy to completely prevent molten wax from condensing and clogging the exhaust channel.

[0044] By employing a combined "heat tracing-impurity removal-pressure compensation" control scheme, three major engineering obstacles in traditional multi-stage pressure relief designs have been overcome: attenuation of explosive power, condensation and blockage of wax, and valve wear. This approach not only removes impurities but also ensures explosive potential energy and fundamentally eliminates condensation and blockage of molten wax at valves, thereby improving the feasibility of continuous industrial production.

[0045] After the flocculent fiber material is prepared, it can be further processed through grinding, grading, washing, etc., according to requirements. The specific operations will not be described in detail here. Optionally, in one embodiment of this application, the finished product is a dry pulp with a moisture content of <10%, which is obtained by grinding, grading, washing, and dewatering the aforementioned flocculent fiber material.

[0046] This application further provides a pulp prepared by the aforementioned method. The pulp provided by this application has fully and uniformly dissociated fibers, with no "green sheet" residue, and at the same time, the fiber length is intact and the specific surface area is large, resulting in paper with high strength properties.

[0047] The present invention will now be described with reference to specific embodiments. The process conditions and values ​​used in the following embodiments and comparative examples are exemplary, and their possible ranges are as shown in the foregoing description of the invention. For process parameters not specifically noted, conventional techniques can be used. Unless otherwise specified, the reagents and instruments used in the technical solutions provided by the present invention can all be purchased from conventional channels or the market. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0048] Example 1 This embodiment prepares a dry pulp for papermaking, and the specific process is as follows: 100 kg of bagasse (oven dry) is chopped to 2-3 cm after dust and impurity removal, and the wet basis moisture content is adjusted to 35-40% to obtain the material to be blasted.

[0049] The material to be blasted was loaded into the steam explosion reactor and sealed. The Roots-water ring vacuum pump unit was started and continuously pumped for 8 minutes to reduce the absolute pressure inside the reactor to below 0.02 MPa. While maintaining the pressure inside the reactor, the pneumatic ultrasonic atomizing device was instantly activated, using the pressure difference to atomize a 1.0% sodium carbonate solution into particles with a median particle size (D). 50 Aerosols with a diameter of <1μm are injected into the reactor. The liquid-solid ratio of sodium carbonate solution used for atomization to raw material is 1.5:1 (L / kg), and the effective amount of sodium carbonate accounts for 1.5% of the oven-dry mass of the raw material.

[0050] Then, high-temperature steam at 180°C was immediately introduced into the reactor to pressurize it to 1.0 MPa for hydrothermal synergistic softening. The pressure was maintained at 1.0 MPa for 120 seconds, allowing the sodium carbonate catalyst to target and weaken the crosslinking of lignin and hemicellulose in situ within the plant tissue.

[0051] After the pressure holding is completed, the high-temperature steam source is cut off, and nitrogen gas preheated to 185°C by the heat exchanger is injected into the reactor to rapidly increase the total pressure to the explosion target pressure of 2.0 MPa.

[0052] The bypass vent valve at the top of the reactor is slightly opened for approximately 6 seconds to discharge the volatilized acetic acid and trace amounts of free wax. During this process, the pressure transmitter inside the reactor and the inert gas inlet regulating valve form a PID closed-loop control, simultaneously supplementing a small amount of preheated inert gas to ensure that the total pressure drop inside the reactor during venting does not exceed 5% of the target burst pressure, maintaining the peak burst potential energy. The bypass vent valve and venting pipeline are equipped with full-process electric heating, with the heating temperature set at approximately 170℃. After the impurities are discharged, the bypass valve is closed, and the main discharge valve at the bottom of the reactor is instantly and fully opened (opening time <0.1s), releasing and dissociating the material in one burst to obtain flocculent fibrous material.

[0053] The blasted flocculent fiber material is sequentially subjected to water washing, high-consistency refining, graded washing, and dewatering and drying to obtain finished dry pulp for papermaking. Specifically, water washing involves a 1:10 solid-liquid ratio countercurrent washing for 20 minutes to remove leachables; high-consistency refining uses a 30% pulp concentration and a three-stage fine refining process with a coarse refining gap of 2.5 mm, a medium-coarse refining gap of 1.0 mm, and a fine refining gap of 0.2 mm; graded washing uses a four-stage countercurrent deep washing process to remove lignin leachables and fine fibers; and dewatering and drying involves mechanical dewatering to a moisture content of 50% and hot air drying at 80℃ to a moisture content below 10%.

[0054] The properties of the prepared slurry are shown in Table 1.

[0055] Comparative Example 1-1 This comparative example prepares a dry pulp for papermaking, and the specific process is as follows: 100 kg of bagasse (oven dry) is chopped to 2-3 cm after dust and impurity removal, and the wet basis moisture content is adjusted to 35-40% to obtain the material to be blasted.

[0056] The material to be blasted is loaded into a steam explosion reactor and sealed. High-temperature steam at 180°C is introduced to pressurize the reactor to 1.5 MPa. The pressure is maintained for 300 seconds, and then the pressure is released instantaneously within 0.1 seconds to blast the material, thus obtaining flocculent fiber material.

[0057] The blasted flocculent fiber material is sequentially subjected to water washing, high-consistency refining, graded washing, and dewatering and drying to obtain finished dry pulp for papermaking. Specifically, water washing involves a 1:10 solid-liquid ratio countercurrent washing for 20 minutes to remove leachables; high-consistency refining uses a 30% pulp concentration and a three-stage fine refining process with a coarse refining gap of 2.5 mm, a medium-coarse refining gap of 1.0 mm, and a fine refining gap of 0.2 mm; graded washing uses a four-stage countercurrent deep washing process to remove lignin leachables and fine fibers; and dewatering and drying involves mechanical dewatering to a moisture content of 50% and hot air drying at 80℃ to a moisture content below 10%.

[0058] The properties of the prepared slurry are shown in Table 1.

[0059] Comparative Examples 1-2 This comparative example prepares a dry pulp for papermaking, and the specific process is as follows: 100 kg of bagasse (oven dry) is chopped to 2-3 cm after dust and impurity removal, and the wet basis moisture content is adjusted to 35-40% to obtain the material to be blasted.

[0060] The material to be blasted was loaded into the steam explosion reactor and sealed. The Roots-water ring vacuum pump unit was started and continuously pumped for 8 minutes to reduce the absolute pressure inside the reactor to below 0.02 MPa. Then, high-temperature steam at 180°C was immediately introduced into the reactor to increase the pressure to 1.0 MPa for hydrothermal softening. The pressure was maintained at 1.0 MPa for 120 seconds.

[0061] After the pressure holding is completed, high-temperature steam at 180℃ is continuously introduced to increase the pressure inside the reactor to 1.5MPa. Then, the pressure is released instantaneously within 0.1s to burst the reactor and obtain flocculent fiber material.

[0062] The blasted flocculent fiber material is sequentially subjected to water washing, high-consistency refining, graded washing, and dewatering and drying to obtain finished dry pulp for papermaking. Specifically, water washing involves a 1:10 solid-liquid ratio countercurrent washing for 20 minutes to remove leachables; high-consistency refining uses a 30% pulp concentration and a three-stage fine refining process with a coarse refining gap of 2.5 mm, a medium-coarse refining gap of 1.0 mm, and a fine refining gap of 0.2 mm; graded washing uses a four-stage countercurrent deep washing process to remove lignin leachables and fine fibers; and dewatering and drying involves mechanical dewatering to a moisture content of 50% and hot air drying at 80℃ to a moisture content below 10%.

[0063] The properties of the prepared slurry are shown in Table 1.

[0064] Comparative Examples 1-3 This comparative example prepares a dry pulp for papermaking, and the specific process is as follows: 100 kg of bagasse (oven dry) is chopped to 2-3 cm after dust and impurity removal, and the wet basis moisture content is adjusted to 35-40% to obtain the material to be blasted.

[0065] The material to be blasted was loaded into the steam explosion reactor and sealed. The Roots-water ring vacuum pump unit was started and continuously pumped for 8 minutes to reduce the absolute pressure inside the reactor to below 0.02 MPa. While maintaining the pressure inside the reactor, the pneumatic ultrasonic atomizing device was instantly activated, using the pressure difference to atomize a 1.0% sodium carbonate solution into particles with a median particle size (D). 50 Aerosols with a diameter of <1μm are injected into the reactor. The liquid-solid ratio of sodium carbonate solution used for atomization to raw material is 1.5:1 (L / kg), and the effective amount of sodium carbonate accounts for 1.5% of the oven-dry mass of the raw material.

[0066] Then, high-temperature steam at 180°C was immediately introduced into the reactor to pressurize it to 1.0 MPa for hydrothermal synergistic softening. The pressure was maintained at 1.0 MPa for 120 seconds, allowing the sodium carbonate catalyst to target and weaken the crosslinking of lignin and hemicellulose in situ within the plant tissue.

[0067] After the pressure holding is completed, high-temperature steam at 180℃ is continuously introduced to rapidly increase the total pressure to the explosion target pressure of 1.5MPa. Then, the pressure is released and the material explodes instantaneously within 0.1s to obtain flocculent fiber material.

[0068] The blasted flocculent fiber material is sequentially subjected to water washing, high-consistency refining, graded washing, and dewatering and drying to obtain finished dry pulp for papermaking. Specifically, water washing involves a 1:10 solid-liquid ratio countercurrent washing for 20 minutes to remove leachables; high-consistency refining uses a 30% pulp concentration and a three-stage fine refining process with a coarse refining gap of 2.5 mm, a medium-coarse refining gap of 1.0 mm, and a fine refining gap of 0.2 mm; graded washing uses a four-stage countercurrent deep washing process to remove lignin leachables and fine fibers; and dewatering and drying involves mechanical dewatering to a moisture content of 50% and hot air drying at 80℃ to a moisture content below 10%.

[0069] The properties of the prepared slurry are shown in Table 1.

[0070] Comparative Examples 1-4 This comparative example prepares a dry pulp for papermaking, and the specific process is as follows: 100 kg of bagasse (oven dry) is chopped to 2-3 cm after dust and impurity removal, and the wet basis moisture content is adjusted to 35-40% to obtain the material to be blasted.

[0071] The material to be blasted is loaded into a steam explosion reactor and sealed. High-temperature steam at 180°C is introduced into the reactor to pressurize it to 1.0 MPa for hydrothermal softening. The pressure is maintained at 1.0 MPa for 120 seconds.

[0072] After the pressure holding is completed, the high-temperature steam source is cut off, and nitrogen gas preheated to 185°C by the heat exchanger is injected into the reactor to rapidly increase the total pressure to the explosion target pressure of 2.0 MPa.

[0073] The bypass vent valve at the top of the reactor is slightly opened for approximately 6 seconds to discharge the volatilized acetic acid and trace amounts of free wax. During this process, the pressure transmitter inside the reactor and the inert gas inlet regulating valve form a PID closed-loop control, simultaneously supplementing a small amount of preheated inert gas to ensure that the total pressure drop inside the reactor during venting does not exceed 5% of the target burst pressure, maintaining the peak burst potential energy. The bypass vent valve and venting pipeline are equipped with full-process electric heating, with the heating temperature set at approximately 170℃. After the impurities are discharged, the bypass valve is closed, and the main discharge valve at the bottom of the reactor is instantly and fully opened (opening time <0.1s), releasing and dissociating the material in one burst to obtain flocculent fibrous material.

[0074] The blasted flocculent fiber material is sequentially subjected to water washing, high-consistency refining, graded washing, and dewatering and drying to obtain finished dry pulp for papermaking. Specifically, water washing involves a 1:10 solid-liquid ratio countercurrent washing for 20 minutes to remove leachables; high-consistency refining uses a 30% pulp concentration and a three-stage fine refining process with a coarse refining gap of 2.5 mm, a medium-coarse refining gap of 1.0 mm, and a fine refining gap of 0.2 mm; graded washing uses a four-stage countercurrent deep washing process to remove lignin leachables and fine fibers; and dewatering and drying involves mechanical dewatering to a moisture content of 50% and hot air drying at 80℃ to a moisture content below 10%.

[0075] The properties of the prepared slurry are shown in Table 1.

[0076] Table 1

[0077] Comparative Example 1-1 is a traditional steam explosion method. As can be seen from Table 1, its raw flake rate is ≥5%, and there are many obvious hard core particles remaining visible to the naked eye, with poor dissociation uniformity.

[0078] Comparative Example 1-2 added a vacuuming step to Comparative Example 1-1. The vacuuming operation removed free air from the capillaries and pores inside the material, eliminating the gas barrier that hindered vapor permeation. Compared to Comparative Example 1-1, the green sheet yield of Comparative Example 1-2 decreased from ≥5% to 2~3%, the ash content decreased from 2.1% to 1.8% (a decrease of 14%), the whiteness increased from 58% to 61% ISO, and the fiber wet weight slightly increased from 1.5g to 1.6g.

[0079] Comparative Examples 1-3, based on Comparative Examples 1-2, added sodium carbonate aerosol, reducing ash content from 1.8% to 1.0% (an additional reduction of 44%). The aerosol successfully penetrated deep into the material and exerted an in-situ desilication effect; the green sheet rate decreased from 2-3% to 1-2%, and the targeted weakening of cross-links by the catalyst resulted in more thorough dissociation; the freeness increased from 39°SR to 42°SR, indicating more complete fiber fibrillation. The grinding disc wear decreased sharply from 0.13 mm to 0.08 mm (a reduction of 38%), and the weakening of the silica layer by the catalyst significantly reduced grinding disc wear during the grinding process.

[0080] Comparative Examples 1-4, without vacuuming and without using alkaline catalysts or alkaline catalyst precursors, only achieved complete physical decoupling of the temperature and pressure fields. Compared to Comparative Example 1-1, the brightness increased from 58% to 65% ISO (an increase of 7 percentage points), and the fiber wet weight increased from 1.5g to 1.7g (an increase of 13%). These improvements are directly attributed to the low-temperature environment (approximately 185℃) of the temperature-pressure decoupling, which significantly reduced fiber thermal degradation and browning reactions. However, lacking a catalyst to target and weaken cross-links, and without pre-impregnation or vacuuming to improve vapor penetration, the ash content increased to 2.2%, the green sheet rate remained at 3-5%, and the freeness decreased from 38°SR to 33°SR, indicating insufficient fiber softening, inadequate weakening of cross-links, and poor fluffing during refining. This demonstrates that temperature-pressure decoupling alone can improve fiber quality indicators (brightness and wet weight), but its improvement on dissociation uniformity is extremely limited.

[0081] Example 1, compared to Comparative Examples 1-3, achieved a complete physical decoupling of the temperature and pressure fields. The burst pressure increased from 1.5 MPa (saturated steam) to 2.0 MPa (nitrogen pressurization), while the system temperature decreased from approximately 201°C to approximately 185°C. Fiber wet weight increased from 1.6 g to 1.9 g (a 19% increase), whiteness increased from 62% to 72% ISO (a 10 percentage point increase), and freeness slightly increased from 42°SR to 44°SR. With the same catalyst dosage, more thorough fiber separation and less chemical damage were achieved simply by decoupling the temperature and pressure fields, directly quantifying the significant gains of temperature-pressure decoupling under aerosol conditions.

[0082] Example 1, compared to Comparative Examples 1-4, added negative pressure evacuation and aerosol-targeted catalysis. Ash content decreased from 2.2% to 0.8% (a 64% reduction), green sheet yield plummeted from 3-5% to <1%, and freeness recovered from 33°SR to 44°SR. Based on the excellent physical conditions provided by the complete physical decoupling of the temperature and pressure fields, the targeted weakening and desilication of cross-linking bonds by the aerosol catalyst is an irreplaceable chemical means of transforming physical accessibility into complete dissociation. Furthermore, its synergistic effect resulted in better desilication of the prepared pulp and more complete fiber retention. Especially for the parameters of ash content and fiber weight loss, the synergistic effect of the three factors resulted in an improvement rate exceeding the sum of their individual effects.

[0083] Experimental Example 1 The dry pulp obtained from Examples 1 to Comparative Examples 1-4 was used to prepare laboratory hand-made sheets with a basis weight of approximately 80 g / m² according to GB / T24324-2009 "Preparation of Laboratory Paper Sheets from Pulp - Conventional Sheet Forming Method". The physical strength properties of the paper were then tested, and the results are shown in Table 2.

[0084] Table 2

[0085] Comparative Example 1-1: High ash content impurities interfere with the hydrogen bonding between fibers. The high green sheet rate means that a large number of undissociated fiber bundles exist in the paper sheet as defect points. The tensile index, tear index, bursting index and folding endurance of the paper are the lowest among all groups.

[0086] The pulp obtained in Example 1 significantly outperformed the comparative examples in all paper strength indicators. The tensile index was approximately 58 N·m / g, an increase of about 53% compared to Comparative Example 1-1 (38 N·m / g). This gain mainly stemmed from two aspects: firstly, the ash content was only 0.8%, allowing for sufficient removal of the silica coating on the fiber surface and complete exposure of hydrogen bond sites; secondly, the freeness of 44°SR provided sufficient fibrillation while maintaining a high fiber wet weight of 1.9g, avoiding the excessive fiber cutting problem associated with traditional high freeness and ensuring a balance between bonding area and fiber skeleton strength. The tear index was approximately 5.5 mN·m² / g, an increase of about 72% compared to Comparative Example 1-1 (3.2 mN·m² / g). The fiber wet weight of 1.9g was the highest among all groups, indicating that the longer fibers formed more interlacing points in the paper sheet, which was the dominant factor in the improved tear strength. The burst strength index was approximately 4.2 kPa·m² / g, representing an improvement of about 110% compared to Comparative Example 1-1 (2.0 kPa·m² / g), the largest improvement among the four indicators. Bursting strength depends on both the interfiber bonding strength and the fiber length itself. Example 1 achieved optimal performance in both aspects, and the green sheet rate of <1% eliminated weak points in the paper sheet, resulting in a significant increase in burst strength.

[0087] The MIT (Made in Taiwan) folding endurance is approximately 160 cycles, representing a 540% improvement compared to Comparative Example 1-1 (25 cycles), a significant improvement far exceeding other strength indicators. Folding endurance is most sensitive to fiber flexibility and the degree of keratinization. Low-temperature, high-pressure, and gentle bursting controls the system temperature below the critical point of cellulose thermal degradation, effectively preventing overheating and keratinization of the fibers. This maintains the fibers' good flexibility, resulting in a significant leap in folding endurance.

[0088] Comparative Examples 1-2 had a fiber wet weight of 1.6g and a raw sheet rate of 2-3%, showing some improvement in dissociation uniformity, but the ash content was still as high as 1.8%, and the improvement in fiber length retention was limited. Therefore, their paper strength index was only slightly better than that of Comparative Example 1-1.

[0089] Comparative Examples 1-3 had an ash content of 1.0% and a freeness of 42°SR. The silica coating on the fiber surface was effectively removed, and the hydrogen bond sites were more fully exposed. The tensile index and bursting index of the resulting paper were significantly better than those of Comparative Examples 1-2. However, the wet weight of the fiber was only 1.6g, and the improvement in the tear index was limited.

[0090] Comparative Example 1-4 has a fiber wet weight of 1.7g. Low-temperature bursting protects the fiber length, but the ash content is 2.2% and the green sheet rate is 3~5%. Therefore, its paper tear index is relatively high (thanks to the longer fiber). However, the tensile index and burst index are dragged down by the ash content and green sheet rate. The improvement is even slightly lower than that of Comparative Example 1-1, which only uses vacuum. Although the burst index has improved, the improvement is limited.

[0091] Example 2 This embodiment prepares a high-toughness slurry for molding, and the specific process is as follows: 100 kg of wheat straw (dry) is chopped to 2-3 cm after dust and impurities are removed, and the moisture content is adjusted to 35-40% on a wet basis.

[0092] The material to be blasted was loaded into the steam explosion reactor and sealed. The Roots-water ring vacuum pump unit was started and continuously pumped for 8 minutes to reduce the absolute pressure inside the reactor to below 0.02 MPa. While maintaining the pressure inside the reactor, the pneumatic ultrasonic atomizing device was instantly activated, using the pressure difference to atomize a 1.0% sodium carbonate solution into particles with a median particle size (D). 50 Aerosols with a diameter of <1μm are injected into the reactor. The liquid-solid ratio of sodium carbonate solution used for atomization to raw material is 1.5:1 (L / kg), and the effective amount of sodium carbonate accounts for 1.5% of the oven-dry mass of the raw material.

[0093] Then, high-temperature steam at 180°C was immediately introduced into the reactor to pressurize it to 1.0 MPa for hydrothermal synergistic softening. The pressure was maintained at 1.0 MPa for 120 seconds, allowing the sodium carbonate catalyst to target and weaken the crosslinking of lignin and hemicellulose in situ within the plant tissue.

[0094] After the pressure holding is completed, the high-temperature steam source is cut off, and nitrogen gas preheated to 185°C by the heat exchanger is injected into the vessel to rapidly increase the total pressure to the explosion target pressure of 1.8 MPa.

[0095] The bypass vent valve at the top of the reactor is slightly opened for approximately 6 seconds to discharge the volatilized acetic acid and trace amounts of free wax. During this process, the pressure transmitter inside the reactor and the inert gas inlet regulating valve form a PID closed-loop control, simultaneously supplementing a small amount of preheated inert gas to ensure that the total pressure drop inside the reactor during venting does not exceed 5% of the target burst pressure, maintaining the peak burst potential energy. The bypass vent valve and venting pipeline are equipped with full-process electric heating, with the heating temperature set at approximately 170℃. After the impurities are discharged, the bypass valve is closed, and the main discharge valve at the bottom of the reactor is instantly and fully opened (opening time <0.1s), releasing and dissociating the material in one burst to obtain flocculent fibrous material.

[0096] The blasted flocculent fiber material was subjected to sequential washing, high-consistency refining, light washing, and dehydration drying to obtain the finished product. The washing process involved a 1:10 solid-liquid ratio countercurrent washing for 15 minutes to remove leachates; high-consistency refining was performed with a 25% concentration using a single-stage fine refining process with a 4.0mm gap between the grinding discs; light washing was performed in a single stage to retain most of the hemicellulose leachates as a natural binder; and dehydration drying involved mechanical dehydration to a moisture content of 50%, followed by hot air drying at 75℃ to a moisture content below 10%.

[0097] The properties of the prepared slurry are shown in Table 3.

[0098] Comparative Example 2-1 This comparative example demonstrates the preparation of a high-toughness molding slurry, and the specific process is as follows: 100 kg of wheat straw (dry) is chopped to 2-3 cm after dust and impurities are removed, and the moisture content is adjusted to 35-40% on a wet basis.

[0099] The material to be blasted is loaded into a steam explosion reactor and sealed. High-temperature steam at 180°C is introduced to pressurize the reactor to 1.3 MPa. The pressure is maintained for 400 seconds, and then the pressure is released instantaneously within 0.1 seconds to blast the material, thus obtaining flocculent fiber material.

[0100] The blasted flocculent fiber material was subjected to sequential washing, high-consistency refining, light washing, and dehydration drying to obtain the finished product. The washing process involved a 1:10 solid-liquid ratio countercurrent washing for 15 minutes to remove leachates; high-consistency refining was performed with a 25% concentration using a single-stage fine refining process with a 4.0mm gap between the grinding discs; light washing was performed in a single stage to retain most of the hemicellulose leachates as a natural binder; and dehydration drying involved mechanical dehydration to a moisture content of 50%, followed by hot air drying at 75℃ to a moisture content below 10%.

[0101] The properties of the prepared slurry are shown in Table 3.

[0102] Comparative Example 2-2 This comparative example demonstrates the preparation of a high-toughness molding slurry, and the specific process is as follows: 100 kg of wheat straw (dry) is chopped to 2-3 cm after dust and impurities are removed, and the moisture content is adjusted to 35-40% on a wet basis.

[0103] The material to be blasted was loaded into the steam explosion reactor and sealed. The Roots-water ring vacuum pump unit was started and continuously pumped for 8 minutes to reduce the absolute pressure inside the reactor to below 0.02 MPa. Then, high-temperature steam at 180°C was immediately introduced into the reactor to increase the pressure to 1.0 MPa for hydrothermal softening. The pressure was maintained at 1.0 MPa for 120 seconds.

[0104] After the pressure holding is completed, high-temperature steam at 180℃ is continuously introduced to increase the pressure inside the reactor to 1.3MPa. Then, the pressure is released and the reactor explodes instantaneously within 0.1s to obtain flocculent fiber material.

[0105] The blasted flocculent fibrous material is sequentially subjected to water washing, high-consistency refining, light washing, and dehydration and drying to obtain finished dry pulp for papermaking. The water washing process involves a 1:10 solid-liquid ratio countercurrent water washing for 15 minutes to remove leachates; high-consistency refining uses a 25% pulp concentration and a single-stage fine refining process with a 4.0mm gap between the refining discs; light washing is performed in a single stage to retain most of the hemicellulose leachates as a natural binder; and dehydration and drying involves mechanical dehydration to a moisture content of 50% and hot air drying at 75℃ to a moisture content below 10%.

[0106] The properties of the prepared slurry are shown in Table 3.

[0107] Comparative Examples 2-3 This comparative example demonstrates the preparation of a high-toughness molding slurry, and the specific process is as follows: 100 kg of wheat straw (dry) is chopped to 2-3 cm after dust and impurities are removed, and the moisture content is adjusted to 35-40% on a wet basis.

[0108] The material to be blasted was loaded into the steam explosion reactor and sealed. The Roots-water ring vacuum pump unit was started and continuously pumped for 8 minutes to reduce the absolute pressure inside the reactor to below 0.02 MPa. While maintaining the pressure inside the reactor, the pneumatic ultrasonic atomizing device was instantly activated, using the pressure difference to atomize a 1.0% sodium carbonate solution into particles with a median particle size (D). 50 Aerosols with a diameter of <1μm are injected into the reactor. The liquid-solid ratio of sodium carbonate solution used for atomization to raw material is 1.5:1 (L / kg), and the effective amount of sodium carbonate accounts for 1.5% of the oven-dry mass of the raw material.

[0109] Then, high-temperature steam at 180°C was immediately introduced into the reactor to pressurize it to 1.0 MPa for hydrothermal synergistic softening. The pressure was maintained at 1.0 MPa for 120 seconds, allowing the sodium carbonate catalyst to target and weaken the crosslinking of lignin and hemicellulose in situ within the plant tissue.

[0110] After the pressure holding is completed, high-temperature steam at 180℃ is continuously introduced to rapidly increase the total pressure to the explosion target pressure of 1.3MPa. Then, the pressure is released and the material explodes instantaneously within 0.1s to obtain flocculent fiber material.

[0111] The blasted flocculent fibrous material is sequentially subjected to water washing, high-consistency refining, light washing, and dehydration and drying to obtain finished dry pulp for papermaking. The water washing process involves a 1:10 solid-liquid ratio countercurrent water washing for 15 minutes to remove leachates; high-consistency refining uses a 25% pulp concentration and a single-stage fine refining process with a 4.0mm gap between the refining discs; light washing is performed in a single stage to retain most of the hemicellulose leachates as a natural binder; and dehydration and drying involves mechanical dehydration to a moisture content of 50% and hot air drying at 75℃ to a moisture content below 10%.

[0112] The properties of the prepared slurry are shown in Table 3.

[0113] Comparative Examples 2-4 This comparative example demonstrates the preparation of a high-toughness molding slurry, and the specific process is as follows: 100 kg of wheat straw (dry) is chopped to 2-3 cm after dust and impurities are removed, and the moisture content is adjusted to 35-40% on a wet basis.

[0114] The material to be blasted is loaded into a steam explosion reactor and sealed. High-temperature steam at 180°C is introduced into the reactor to pressurize it to 1.0 MPa for hydrothermal softening. The pressure is maintained at 1.0 MPa for 120 seconds.

[0115] After the pressure holding is completed, the high-temperature steam source is cut off, and nitrogen gas preheated to 185°C by the heat exchanger is injected into the vessel to rapidly increase the total pressure to the explosion target pressure of 1.8 MPa.

[0116] The bypass vent valve at the top of the reactor is slightly opened for approximately 6 seconds to discharge the volatilized acetic acid and trace amounts of free wax. During this process, the pressure transmitter inside the reactor and the inert gas inlet regulating valve form a PID closed-loop control, simultaneously supplementing a small amount of preheated inert gas to ensure that the total pressure drop inside the reactor during venting does not exceed 5% of the target burst pressure, maintaining the peak burst potential energy. The bypass vent valve and venting pipeline are equipped with full-process electric heating, with the heating temperature set at approximately 170℃. After the impurities are discharged, the bypass valve is closed, and the main discharge valve at the bottom of the reactor is instantly and fully opened (opening time <0.1s), releasing and dissociating the material in one burst to obtain flocculent fibrous material.

[0117] The blasted flocculent fibrous material is sequentially subjected to water washing, high-consistency refining, light washing, and dehydration and drying to obtain finished dry pulp for papermaking. The water washing process involves a 1:10 solid-liquid ratio countercurrent water washing for 15 minutes to remove leachates; high-consistency refining uses a 25% pulp concentration and a single-stage fine refining process with a 4.0mm gap between the refining discs; light washing is performed in a single stage to retain most of the hemicellulose leachates as a natural binder; and dehydration and drying involves mechanical dehydration to a moisture content of 50% and hot air drying at 75℃ to a moisture content below 10%.

[0118] The properties of the prepared slurry are shown in Table 3.

[0119] Table 3

[0120] Comparative Example 2-1 is the traditional steam explosion method. As can be seen from Table 3, its raw fragment rate is 3-5%.

[0121] Comparative Example 2-2, based on Comparative Example 2-1, added a vacuuming step. The green sheet yield decreased from 3-5% to 1.5-2.5%, ash content decreased from 2.5% to 2.1% (a decrease of 16%), pentosan content slightly increased from 18% to 19%, and fiber wet weight slightly increased from 4.0g to 4.2g. After breaking down the internal air resistance of the material, the vapor penetration depth increased, the fiber swelling was more complete, and some surface silica dissolved out during the swelling process.

[0122] Comparative Examples 2-3, based on Comparative Example 2-2, added sodium carbonate aerosol, resulting in a decrease in ash content from 2.1% to 1.5% (an additional reduction of 29%), an increase in pentosan content from 19% to 22% (an increase of 3 percentage points), a further decrease in green sheet yield from 1.5-2.5% to 1-2%, and an increase in fiber wet weight from 4.2g to 4.5g. The catalyst penetrated deep into the material to weaken cross-linking bonds, allowing for more complete fiber dissociation while more completely preserving the natural adhesive components of hemicellulose on the fiber surface.

[0123] Comparative Examples 2-4, without vacuuming and without using alkaline catalysts or alkaline catalyst precursors, only achieved complete physical decoupling of the temperature and pressure fields. Compared to Comparative Example 2-1, the fiber wet weight increased from 4.0g to 4.3g (an increase of 7.5%), and the whiteness increased from 54% to 59% ISO (an increase of 5 percentage points). However, the ash content increased from 2.5% to 2.6%, the pentosan content remained unchanged at 18%, the green sheet rate remained at 3-5%, and the freeness decreased from 19°SR to 17°SR. This demonstrates that simple temperature-pressure decoupling cannot independently solve the problem of dissociation uniformity in the molding process.

[0124] Example 2, compared to Comparative Examples 2-3, achieved a complete physical decoupling of the temperature and pressure fields, reducing the burst temperature from approximately 195°C to approximately 185°C and increasing the burst pressure from 1.3 MPa to 1.8 MPa. The fiber wet weight increased significantly from 4.5 g to 5.0 g (an increase of 11%), whiteness increased from 62% to 70% ISO (an increase of 8 percentage points), and pentosan content increased from 22% to 24% (an increase of 2 percentage points). Low-temperature, high-pressure bursting demonstrated significant advantages in preserving fiber length and natural adhesive components.

[0125] Example 2, compared to Comparative Examples 2-4, added negative pressure evacuation and aerosol-targeted catalysis. Ash content decreased from 2.6% to 1.2% (a 54% reduction), pentosan content jumped from 18% to 24% (a 6 percentage point increase), and the green flake rate decreased from 3-5% to <1%. The core contributions of aerosol catalysis in the molding pathway—desilication, weakened crosslinking, and promotion of hemicellulose retention—were clearly quantified.

[0126] As can be seen from the examples and comparative examples, negative pressure evacuation, aerosol-targeted catalysis, and complete physical decoupling of the temperature field and pressure field have a synergistic effect. Negative pressure evacuation is beneficial to aerosol catalysis, aerosol catalysis selectively weakens hemicellulose-crosslinking bonds, and the low temperature environment reduces the thermal degradation of hemicellulose. In particular, for the pentosan content and fiber wet weight, the synergistic effect of the three factors makes the improvement rate of these two parameters exceed the sum of their individual effects.

[0127] Experiment Example 2 The dry pulp obtained in Examples 2 to 2-4 was vacuum filtered and hot-pressed to dry in a laboratory pulp molding machine to prepare standard molding samples (square, basis weight approximately 500 g / m³). 2 The physical strength properties of the finished product were tested, and the results are shown in Table 4.

[0128] Table 4

[0129] Comparative Example 2-1 had a fiber wet weight of 4.0 g and a pentosan content of 18%. Due to limited fiber length and partial loss of natural adhesive components, the molded product exhibited the lowest dry compressive strength among all groups. Regarding wet strength, the limited number of inter-fiber bonding points resulted in rapid collapse of the hydrogen bond network upon immersion in water, leading to low wet strength.

[0130] The molded articles prepared from the slurry obtained in Example 2 showed significantly better performance than the comparative examples and intermediate examples in all performance indicators. The dry compressive strength is approximately 340 kPa, an increase of approximately 89% compared to Comparative Example 2-1 (180 kPa). Hemicellulose acts as a natural binder in pulp molding, and its retention directly affects the self-bonding strength between fibers. Example 2, with a pentosan content of 24% (the highest among all groups), provides the most abundant natural binder component; simultaneously, the fiber wet weight is 5.0 g, and the three-dimensional network formed by the long fibers provides solid skeletal support. The synergistic effect of both makes the dry compressive strength approach the level of traditional chemical pulp molded products. The wet compressive strength is approximately 95 kPa (approximately 28% of the dry strength), an increase of approximately 138% compared to Comparative Example 2-1 (40 kPa). The wet strength of pulp molded products is one of the key shortcomings in their engineering applications. The high pentosan content of Example 2 provides more hydrogen bond binding sites between fibers, retaining more effective binding points even when some hydrogen bonds are broken by water molecules after immersion; at the same time, the long fiber network can maintain a more complete structural skeleton in the wet state, delaying the collapse of strength. Apparent density is approximately 0.50 g / cm³. 3 Compared with Comparative Example 2-1 (0.38 g / cm³), 3 The ash content is increased by about 32%. The low ash content (1.2%) makes the fiber surface clean and free of impurities. The beating degree of 22°SR is moderate, and the fibers are more likely to be tightly packed during the suction filtration molding process, forming a denser product structure.

[0131] Comparative Example 2-2 showed a fiber wet weight of 4.2g and pentosan content of 19%, with limited improvement; its dry and wet strengths were only slightly improved.

[0132] Comparative Examples 2-3 showed an increased pentosan content of 22% (hemicellulose retention increased by 3 percentage points), a fiber wet weight of 4.5g, more abundant natural adhesive components, and tighter inter-fiber bonding. The dry compressive strength and apparent density were significantly better than Comparative Example 2-1. Regarding wet strength, the abundant arabinose and glucuronic acid groups in hemicellulose provided additional hydrogen bonding sites, resulting in a significant improvement in wet strength.

[0133] Comparative Examples 2-4 had a fiber wet weight of 4.3g, but the pentosan content was only 18%, hemicellulose was not retained, and the green sheet rate was as high as 3-5%. The undissociated fiber bundles formed local weak areas in the molded products, and the expected dry compressive strength was inferior to that of Intermediate Examples 2-3.

[0134] The above analysis shows that the synergistic effect of low-temperature high-pressure explosion and negative pressure, and catalyst-targeted weakening in Example 2 not only improves the fiber integrity and hemicellulose retention rate of the slurry, but more importantly, it significantly improves the final mechanical properties of the molded product through the combined advantages of "long fiber skeleton + sufficient natural adhesive + clean fiber surface".

[0135] Obviously, the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for steam-explosion pulping of gramineous plants, characterized in that, include: The grass plants are cut to a predetermined size and then conditioned to a predetermined moisture content to obtain the material to be blasted. After the material to be blasted is loaded into the steam explosion reaction device, a vacuum is drawn to the first pressure, and then the alkaline catalyst or alkaline catalyst precursor is atomized into an aerosol and introduced into the steam explosion reaction device. After the aerosol is introduced, water vapor at a temperature higher than 120°C is introduced into the steam explosion reaction device, so that the pressure inside the steam explosion reaction device rises to a second pressure and is maintained at the pressure for a first predetermined time. After the pressure holding is completed, the steam source is cut off, and preheated inert gas is introduced into the steam explosion reactor to raise the pressure inside the steam explosion reactor to the target explosion pressure, and then the explosion is carried out to obtain flocculent fiber material.

2. The steam explosion pulping method according to claim 1, characterized in that, After the pressure inside the steam explosion reaction device rises to the target explosion pressure, while maintaining the pressure inside the steam explosion reaction device at no less than 95% of the target explosion pressure, the steam explosion reaction device is vented for a second predetermined time before the explosion is carried out.

3. The steam explosion pulping method according to claim 2, characterized in that, Also includes: During the exhaust process, the exhaust components are heated to a temperature ≥160℃.

4. The steam explosion pulping method according to claim 2, characterized in that, The second predetermined time is 5~10 seconds.

5. The steam explosion pulping method according to claim 1, characterized in that, The predetermined size is 1~5cm, and the predetermined moisture content is 30~40%.

6. The steam explosion pulping method according to claim 1, characterized in that, The first pressure is <0.02MPa, the second pressure is 0.8~1.2MPa, and the first predetermined time is 30~600s.

7. The steam explosion pulping method according to claim 1, characterized in that, The alkaline catalyst or alkaline catalyst precursor is selected from sodium carbonate solution, sodium hydroxide solution, ammonia solution or urea solution with a mass concentration of 0.5~5.0%. The median particle size of the aerosol is <1μm. The liquid-solid ratio of the alkaline catalyst or alkaline catalyst precursor to the oven-dry mass of the material to be blasted is 1:1 to 2:1 L / kg.

8. The steam explosion pulping method according to claim 1, characterized in that, The temperature of the steam is 150~190℃, and the temperature of the preheated inert gas is 0~5% higher than the temperature inside the steam explosion reaction device.

9. The steam explosion pulping method according to claim 1, characterized in that, Also includes: The flocculent fiber material is milled, graded, washed, and dewatered to obtain a dry pulp with a moisture content of <10%.

10. A slurry, characterized in that, Obtained by the steam explosion pulping method according to any one of claims 1 to 9.

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