Plant cellulose extraction device

Abstract

The invention relates to the technical field of cellulose extraction, and discloses a plant cellulose extraction device which comprises a slurry preparation unit used for mixing a plant raw material with a suspension medium to prepare slurry and outputting the slurry; the reaction unit comprises a reaction tank, a feeding port of the reaction tank is connected with a discharging port of the slurry preparation unit, the reaction tank is used for containing a mixture formed by the slurry and the supercritical fluid and adjusting the pressure and the temperature in the tank in real time, a first ultrasonic transducer and a second ultrasonic transducer are installed on a tank body of the reaction tank in a surrounding and array mode, and the first ultrasonic transducer and the second ultrasonic transducer are arranged on the tank body of the reaction tank. The first ultrasonic transducer and the second ultrasonic transducer are arranged in a staggered mode and used for applying ultrasonic waves of different frequencies to the mixture, and when the supercritical fluid is in a supercritical state, the first ultrasonic transducer and the second ultrasonic transducer are arranged in a staggered mode. Non-toxic and recyclable supercritical carbon dioxide is used as a main reaction medium and is supplemented with a recyclable mild solvent, so that chemicals such as strong acid and strong alkali are fundamentally replaced, and the generation of high-pollution wastewater is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of cellulose extraction, in particular to a plant cellulose extraction device. Background Art

[0002] Currently, the mainstream plant cellulose extraction technology in the industry mainly relies on chemical methods, such as alkaline and acid methods. It usually uses one or more large reactors as the core equipment. Its typical process flow is as follows: pretreatment, mechanically chopping and grinding the plant raw materials; cooking / hydrolysis, placing the treated raw materials in a reactor, adding high-concentration chemicals, and performing long-term cooking or hydrolysis under high temperature and high pressure conditions. This step is intended to dissolve lignin and hemicellulose; separation and washing, filtering the reaction mixture to separate the crude cellulose, and repeatedly washing it with large amounts of clean water to remove residual chemicals and dissolved impurities; bleaching and purification, multi-stage bleaching of the crude cellulose to further remove residual lignin and improve the purity of the cellulose.

[0003] As the mainstream industrial method for a hundred years, the above scheme has a clear process route and rich equipment and operating experience. However, in the actual operation process, a large amount of wastewater containing high-concentration organic matter and strong acid / strong alkali will be generated, which is difficult and costly to treat. The entire process needs to maintain high temperature and high pressure for a long time, consuming a large amount of steam and electricity. The violent chemical action of strong acids and strong alkalis will cut off the long chains of cellulose, resulting in a decrease in its degree of polymerization and crystallinity, thereby affecting the mechanical strength and functional properties of the final product. The steps of cooking, washing, bleaching, etc. are carried out in batches in different equipment units, occupying a large area, complex process control, and a long production cycle. While removing lignin, part of the cellulose will also be degraded, resulting in a waste of raw materials. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a plant cellulose extraction device, which solves the problems of "high pollution, high energy consumption and cellulose damage" in traditional chemical cellulose extraction.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: A plant cellulose extraction device, comprising: A slurry preparation unit, which is used to mix the plant raw material with the suspension medium, prepare the slurry and output it; A reaction unit, comprising a reaction tank, wherein the inlet of the reaction tank is connected to the outlet of the slurry preparation unit, the reaction tank is used to accommodate a mixture formed by the slurry and the supercritical fluid, and to adjust the pressure and temperature in the tank in real time. The tank body of the reaction tank is surrounded by an ultrasonic transducer 1 and an ultrasonic transducer 2, which are arranged in a staggered manner. The ultrasonic transducer 1 and the ultrasonic transducer 2 are respectively used to apply ultrasonic waves of different frequencies to the mixture. When the supercritical fluid is in a supercritical state, ultrasonic waves are applied through the ultrasonic transducer 1 to cause the supercritical fluid to deeply penetrate into the nanoscale pores of the plant fiber cell wall. When the supercritical fluid is in a metastable state, ultrasonic waves are applied through the ultrasonic transducer 2 to cause the supercritical fluid to produce a cavitation effect at the interface between the fully swollen lignin network structure and the cellulose. a supercritical fluid supply unit, configured to supply supercritical fluid or its precursor to the reaction unit; The multi-stage separation unit has an inlet connected to the outlet of the reaction unit and is used to separate the cellulose from other components in the mixture by reducing the pressure of the mixture in stages and to make the cellulose fluffy and stretched.

[0006] Preferably, the slurry preparation unit includes a mixing and stirring tank, in which the crushed plant raw materials and the suspension medium are injected into the mixing and stirring tank in proportion, and mixed and stirred at normal temperature and pressure to form a fluid slurry. A discharge port is provided at the bottom of the mixing and stirring tank, and the discharge port is opened and closed by a discharge valve and is connected to the input end of the slurry pump.

[0007] Preferably, the extraction device further comprises a solvent recovery module 1, a solvent recovery module 2 and a gas recovery module, wherein the solvent recovery module 1 is used to recover lignin and suspension medium, the solvent recovery module 2 is used to recover cellulose and suspension medium, and the gas recovery module is used to recover supercritical fluid precursor.

[0008] Preferably, a slurry input port, a gas input port and a gas exhaust port are sequentially provided on the top of the reaction tank, and a material exhaust port is provided on the bottom, wherein the slurry input port is connected to the output end of the slurry pump, and a feed valve is provided at the slurry input port. The slurry in the mixing tank enters the reaction tank through the slurry input port through the action of the slurry pump, the gas input port is connected to the exhaust port of the supercritical fluid supply unit, and an electrically controlled valve 1 is provided on the connecting pipeline between the two, the gas exhaust port is connected to the input end of the gas recovery module, and an electrically controlled valve 2 is provided on the connecting pipeline between the two, and an air pressure monitor is also provided in the reaction tank for real-time monitoring of the air pressure in the reaction tank.

[0009] Preferably, the reaction tank adopts a jacketed structure, and the interior of the jacket is connected to an external temperature control circulation device for controlling the internal temperature of the reaction tank.

[0010] Preferably, the multi-stage separation unit includes a Laval nozzle, the input end of the Laval nozzle is connected to the material discharge outlet, and a discharge valve 2 is provided at the connection between the two, the output end of the Laval nozzle is connected to the input end of the hydrocyclone separator, the clear liquid output end of the hydrocyclone separator is connected to the expansion chamber, and the residue discharge end of the hydrocyclone separator is connected to the input end of the solvent recovery module 1.

[0011] Preferably, an exhaust port is provided at the top of the expansion chamber, and the exhaust port is connected to the input end of the gas recovery module. A discharge port is provided at the bottom of the expansion chamber, and the discharge port is connected to the input end of the second solvent recovery module.

[0012] Preferably, the suspension medium is an analytical grade deep eutectic solvent, and the precursor of the supercritical fluid is industrial grade liquid carbon dioxide.

[0013] The present invention provides a plant cellulose extraction device having the following beneficial effects: 1. By using non-toxic, recyclable supercritical carbon dioxide as the primary reaction medium, supplemented by a recyclable mild solvent, this method fundamentally replaces the use of strong acids, bases, and other chemicals, avoiding the generation of highly polluted wastewater. Furthermore, the entire extraction process can be carried out at near-ambient temperatures, relying primarily on precise physical energy input rather than macroscopic heating, significantly reducing energy consumption.

[0014] 2. By utilizing a physical "penetration-stripping" mechanism, this invention avoids chemical damage to the cellulose molecular chains, maximally preserving their natural degree of polymerization and crystalline structure, resulting in high-quality cellulose. Furthermore, the "gas stretching" effect during the second-stage decompression process imparts an excellent physical form to the final product. Furthermore, the gentle extraction process ensures that the structure of separated byproducts, such as lignin, remains intact, increasing their reusability and contributing to the high-value utilization of all plant raw materials, in line with the requirements of a circular economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A perspective view of the present invention; Figure 2 Schematic diagram of the structure of the slurry preparation unit in the present invention; Figure 3 Schematic diagram of the structure of the reaction unit in the present invention; Figure 4 Schematic diagram of the structure of the multi-stage separation unit in the present invention; Figure 5 Schematic diagram of the system of the present invention.

[0016] Among them, 1. Mixing and stirring tank; 2. Discharge valve 1; 3. Slurry pump; 4. Reactor; 401. Slurry input port; 402. Gas input port; 403. Gas discharge port; 404. Material discharge port; 405. Feed valve; 406. Electric control valve 1; 407. Electric control valve 2; 5. Laval nozzle; 6. Discharge valve 2; 7. Hydrocyclone; 8. Expansion chamber. DETAILED DESCRIPTION

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0018] Please see the attached Figure 1 -Attached Figure 5 , an embodiment of the present invention provides a plant cellulose extraction device, comprising: A slurry preparation unit, which is used to mix the plant raw material with the suspension medium, prepare the slurry and output it; The slurry preparation unit includes a mixing and stirring tank 1. The crushed plant raw materials and the suspension medium are injected into the mixing and stirring tank 1 in proportion, and mixed and stirred at normal temperature and pressure to form a fluid slurry. A discharge port is opened at the bottom of the mixing and stirring tank 1, and the discharge port is controlled by a discharge valve 2 and is connected to the input end of the slurry pump 3.

[0019] The plant raw material is a woody or herbaceous plant material that has undergone preliminary mechanical processing (e.g., air-dried and pulverized to a specific mesh size), such as pine sawdust, bamboo powder, or rice straw. The suspending medium is an analytically pure deep eutectic solvent, such as a eutectic mixture prepared by gently heating choline chloride and urea at a specific molar ratio. The eutectic mixture is stirred and mixed in a mixing tank 1 at room temperature and pressure. The mixing ratio is determined to form a slurry with a certain fluidity that can be stably transported by a high-pressure pump.

[0020] It should be noted that this step is not intended to initiate a chemical reaction, but rather to utilize the deep eutectic solvent's affinity for lignin and hemicellulose to achieve initial wetting and pre-swelling, opening a channel for subsequent supercritical medium penetration. Simultaneously, it converts the solid feedstock into a fluid form that can be continuously processed.

[0021] a supercritical fluid supply unit, configured to supply supercritical fluid or its precursor to the reaction unit; The supercritical fluid used is industrial-grade high-purity liquid carbon dioxide.

[0022] The reaction unit includes a reaction tank 4, the feed port of which is connected to the discharge port of the slurry preparation unit. The reaction tank 4 is used to accommodate a mixture formed by the slurry and the supercritical fluid, and to adjust the pressure and temperature in the tank in real time. Ultrasonic transducer 1 and ultrasonic transducer 2 are installed in an array around the tank body of the reaction tank 4, and the two are arranged in a staggered manner. Ultrasonic transducer 1 and ultrasonic transducer 2 are respectively used to apply ultrasonic waves of different frequencies to the mixture. When the supercritical fluid is in a supercritical state, ultrasonic waves are applied through ultrasonic transducer 1 to allow the supercritical fluid to deeply penetrate into the nano-scale pores of the plant fiber cell wall. When the supercritical fluid is in a metastable state, ultrasonic waves are applied through ultrasonic transducer 2 to cause cavitation of the supercritical fluid at the interface between the fully swollen lignin network structure and the cellulose. Effect: The top of the reaction tank 4 is provided with a slurry input port 401, a gas input port 402 and a gas discharge port 403 in sequence, and a material discharge port 404 is provided at the bottom. The slurry input port 401 is connected to the output end of the slurry pump 3, and a feed valve 405 is provided at the slurry input port 401. The slurry in the mixing tank 1 is acted upon by the slurry pump 3 and enters the reaction tank 4 through the slurry input port 401. The gas input port 402 is connected to the exhaust port of the supercritical fluid supply unit, and an electric control valve 1 406 is provided on the connecting pipe between the two. The gas discharge port 403 is connected to the input end of the gas recovery module, and an electric control valve 2 407 is provided on the connecting pipe between the two. An air pressure monitor is also provided in the reaction tank 4 for real-time monitoring of the air pressure in the reaction tank 4. The reaction tank 4 adopts a jacketed structure, and the interior of the jacket is connected to an external temperature control circulation device for controlling the internal temperature of the reaction tank 4.

[0023] The above-described reaction unit scheme aims to create a continuous process from infiltration to exfoliation. Plant material and a suspending medium are mixed in a mixing tank 1 to form a fluid slurry, which is then pumped into a reaction tank 4 via a slurry pump 3. Simultaneously, a supercritical fluid supply unit injects high-pressure carbon dioxide into the reaction tank 4. Pressure and temperature are controlled by a pressure monitor and temperature-controlled circulation equipment, allowing the carbon dioxide to reach and maintain a supercritical state. An array of ultrasonic transducers then applies low-power, low-frequency ultrasonic waves. This acoustic field primarily stimulates an "acoustic streaming" effect, rather than a dramatic cavitation effect. This effect produces microperturbations on a macroscopic scale, which, on a microscopic scale, accelerates the supercritical carbon dioxide, which has both liquid density and gas permeability, to carry deep eutectic solvent molecules, overcoming mass transfer resistance and penetrating deeply into the nanoscale pores of the plant fiber cell walls. This achieves thorough infiltration and swelling of the lignin-hemicellulose-cellulose composite structure, a feat difficult to achieve with traditional methods. After the material has fully swollen, the second electrically controlled valve 407 is controlled to open, allowing some gas to be discharged from the gas outlet 403 to the gas recovery module. The pressure in the reactor 4 is monitored in real time by a pressure monitor, resulting in a controlled, slight decrease in pressure. This pressure remains above the critical pressure of carbon dioxide, but it enters a "metastable state" that is highly sensitive to external disturbances. Within this metastable state, the second array of ultrasonic transducers applies high-power, high-frequency, precisely tuned ultrasonic waves. The frequency of the ultrasonic waves matches the resonant frequency of cavitation bubbles in this specific pressure, temperature, and deep eutectic solvent-carbon dioxide sensitization environment. This eliminates the acoustic cavitation effect as a random macroscopic phenomenon occurring in the fluid, but rather directs it to the interface between the fully swollen lignin network and cellulose, where it undergoes a "precise detonation." The microjets and shock waves generated by the instantaneous collapse of the cavitation bubbles physically "tear" and "peel" the lignin and hemicellulose from the cellulose backbone with powerful microscopic mechanical forces, rather than relying on the rupture of strong chemical bonds. This process is completed at room temperature, which maximizes the protection of the integrity of the cellulose backbone and its natural high-order structure.

[0024] At the same time, it should be noted that the pressure source in the reaction tank 4 is provided by the supercritical fluid supply unit. The supercritical fluid supply unit increases the pressure in the reaction tank 4 by injecting carbon dioxide into the reaction tank 4. The supercritical fluid supply unit cooperates with the second electronically controlled valve 407 and the air pressure monitor to regulate the pressure in the reaction tank 4. This solution not only realizes the supply of supercritical carbon dioxide, but also realizes the regulation of the pressure in the reaction tank 4. It also serves the purpose of purging the entire reaction unit and the multi-stage separation unit. In addition, it also ensures that the material enters the Laval nozzle 5 from the reaction tank 4 at a stable pressure.

[0025] The multi-stage separation unit, whose feed inlet is connected to the discharge outlet of the reaction unit, is used to separate the cellulose from other components in the mixture by gradually reducing the pressure of the mixture, thereby making the cellulose fluffy and stretched. The multi-stage separation unit includes a Laval nozzle 5. The input end of the Laval nozzle 5 is connected to the material discharge outlet 404, and a discharge valve 2 6 is provided at the connection between the two. The output end of the Laval nozzle 5 is connected to the input end of the hydrocyclone 7. The clear liquid output end of the hydrocyclone 7 is connected to the expansion chamber 8. The residue discharge end of the hydrocyclone 7 is connected to the input end of the solvent recovery module 1. The expansion chamber 8 has an exhaust port at the top, which is connected to the input end of the gas recovery module. The expansion chamber 8 has an exhaust port at the bottom, which is connected to the input end of the solvent recovery module 2.

[0026] After the sonochemical reaction, the multiphase mixture leaves the reaction tank 4 and enters a Laval nozzle 5 or a similar rapid decompression structure. The pressure is quickly and precisely reduced to a preset intermediate value. At this intermediate pressure, the density of carbon dioxide drops significantly, resulting in a sharp decrease in its ability to act as a solvent, especially a sharp drop in its ability to dissolve the larger molecular weight lignin-deep eutectic solvent complex. This allows the dissolved lignin to preferentially and selectively nucleate and precipitate from the fluid. The precipitated solid-liquid impurities can be immediately captured and removed by the hydrocyclone 7 immediately downstream. The lighter and larger cellulose remains suspended at this stage. The cellulose suspension, free of most impurities, then enters the expansion chamber 8, where the pressure is completely reduced to atmospheric pressure. The sudden drop in pressure causes the supercritical carbon dioxide-deep eutectic solvent medium remaining between the cellulose micropores and fiber bundles to undergo instantaneous explosive vaporization and volume expansion. This inside-out vaporization process produces a powerful "gas sweeping and mechanical stretching" effect. Its dual functions are: first, to sweep away the last trace impurities from the fiber surface; second, to physically expand and fluff up the cellulose bundles, which were originally tightly entangled due to van der Waals forces, thereby directly obtaining monomeric or oligomeric cellulose products with high dispersion and large specific surface area. This step combines the separation process with the optimization of the product's physical form.

[0027] The extraction device also includes a solvent recovery module 1, a solvent recovery module 2 and a gas recovery module, wherein the solvent recovery module 1 is used to recover lignin and suspension medium, the solvent recovery module 2 is used to recover cellulose and suspension medium, and the gas recovery module is used to recover supercritical fluid precursor.

[0028] Among them, the solvent recovery module 1 is used to collect the lignin-deep eutectic solvent complex discharged from the residue discharge end of the cyclone separator 7, and separate it from the lignin by-products through centralized extraction, sedimentation or membrane separation. The deep eutectic solvent is then purified and returned to the first step of the suspension preparation link for recycling. The separated lignin has not undergone severe chemical degradation and has a more complete structure. It can be used as a high-value-added chemical raw material (such as for the preparation of phenolic resin, carbon fiber, aromatic compounds, etc.).

[0029] The second solvent recovery module is used to collect the mixture of cellulose and deep eutectic solvent, and add one or more "anti-solvents" to it to make the cellulose flocculate and precipitate, and then obtain cellulose solids through filtration or centrifugation. Finally, the cellulose solids are repeatedly washed and dried to obtain dry cellulose products. For the mixture of "anti-solvent" and deep eutectic solvent, the huge difference in boiling points between the two is utilized (the two components of deep eutectic solvent usually have very high boiling points and extremely low vapor pressures, while the boiling point of anti-solvent is much lower). After removing the anti-solvent, the remaining liquid is the regenerated deep eutectic solvent. After testing its purity and component ratio, it can be put back into the next cellulose extraction process to achieve a closed-loop cycle.

[0030] Commonly used anti-solvents include water, ethanol and acetone.

[0031] The gases discharged from the expansion chamber 8 and the reaction tank 4 enter the gas recovery module together. The gas recovery module consists of a filter, a compressor, a condenser and a storage tank. After purifying, compressing and liquefying the gaseous carbon dioxide, it is returned to the supercritical fluid supply unit for recycling.

[0032] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A plant cellulose extraction device, characterized in that: include: A slurry preparation unit, which is used to mix the plant raw material with the suspension medium, prepare the slurry and output it; A reaction unit, comprising a reaction tank (4), wherein the inlet of the reaction tank (4) is connected to the outlet of the slurry preparation unit, the reaction tank (4) is used to accommodate a mixture formed by the slurry and the supercritical fluid, and to adjust the pressure and temperature in the tank in real time, the tank body of the reaction tank (4) is surrounded by an ultrasonic transducer 1 and an ultrasonic transducer 2, which are arranged in a staggered manner, the ultrasonic transducer 1 and the ultrasonic transducer 2 are respectively used to apply ultrasonic waves of different frequencies to the mixture, when the supercritical fluid is in a supercritical state, ultrasonic waves are applied by the ultrasonic transducer 1, so that the supercritical fluid deeply penetrates into the nano-scale pores of the plant fiber cell wall, and when the supercritical fluid is in a metastable state, ultrasonic waves are applied by the ultrasonic transducer 2, so that the supercritical fluid generates a cavitation effect at the interface between the fully swollen lignin network structure and the cellulose; a supercritical fluid supply unit, configured to supply supercritical fluid or its precursor to the reaction unit; The multi-stage separation unit has an inlet connected to the outlet of the reaction unit and is used to separate the cellulose from other components in the mixture by reducing the pressure of the mixture in stages and to make the cellulose fluffy and stretched.

2. A plant cellulose extraction device according to claim 1, characterized in that: The slurry preparation unit comprises a mixing and stirring tank (1), wherein the crushed plant material and the suspension medium are injected into the mixing and stirring tank (1) in proportion, and mixed and stirred at normal temperature and pressure to form a fluid slurry. A discharge port is provided at the bottom of the mixing and stirring tank (1), and the discharge port is opened and closed by a discharge valve (2) and is connected to the input end of a slurry pump (3).

3. A plant cellulose extraction device according to claim 2, characterized in that: The extraction device further comprises a solvent recovery module 1, a solvent recovery module 2 and a gas recovery module, wherein the solvent recovery module 1 is used to recover lignin and suspension medium, the solvent recovery module 2 is used to recover cellulose and suspension medium, and the gas recovery module is used to recover supercritical fluid precursor.

4. A plant cellulose extraction device according to claim 3, characterized in that: The top of the reaction tank (4) is provided with a slurry input port (401), a gas input port (402) and a gas discharge port (403) in sequence, and the bottom is provided with a material discharge port (404), wherein the slurry input port (401) is connected to the output end of the slurry pump (3), and a feed valve (405) is provided at the slurry input port (401). The slurry in the mixing tank (1) enters the reaction tank (4) from the slurry input port (401) through the action of the slurry pump (3). The gas input port (402) is connected to the exhaust port of the supercritical fluid supply unit, and an electric control valve 1 (406) is provided on the connecting pipeline between the two. The gas discharge port (403) is connected to the input end of the gas recovery module, and an electric control valve 2 (407) is provided on the connecting pipeline between the two. An air pressure monitor is also provided in the reaction tank (4) for real-time monitoring of the air pressure in the reaction tank (4).

5. The plant cellulose extraction device according to claim 4, characterized in that: The reaction tank (4) adopts a jacketed structure, and the interior of the jacket is connected to an external temperature control circulation device for controlling the internal temperature of the reaction tank (4).

6. The plant cellulose extraction device according to claim 4, characterized in that: The multi-stage separation unit includes a Laval nozzle (5), the input end of the Laval nozzle (5) is connected to the material discharge port (404), and a discharge valve 2 (6) is provided at the connection between the two, the output end of the Laval nozzle (5) is connected to the input end of the hydrocyclone (7), the clear liquid output end of the hydrocyclone (7) is connected to the expansion chamber (8), and the residue discharge end of the hydrocyclone (7) is connected to the input end of the solvent recovery module 1.

7. The plant cellulose extraction device according to claim 6, characterized in that: An exhaust port is provided at the top of the expansion chamber (8), and the exhaust port is connected to the input end of the gas recovery module. A discharge port is provided at the bottom of the expansion chamber (8), and the discharge port is connected to the input end of the second solvent recovery module.

8. The plant cellulose extraction device according to claim 1, characterized in that: The suspension medium is an analytical grade deep eutectic solvent, and the precursor of the supercritical fluid is industrial grade liquid carbon dioxide.

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