An ultrasonic drying system for particles and a method of dehydrating particles

Abstract

This invention discloses a supersonic drying system and dehydration method for particles, relating to the field of particle drying technology. The system includes a collection cylinder fitted outside an accelerating cylinder. By guiding thermosensitive polymer particles into a vortex flow field, they are suspended and spirally ascended under the dynamic balance of centrifugal force and airflow drag. The low-pressure environment generated by the vortex flow field lowers the boiling point of water on the particle surface, and combined with a heat-generating unit, moisture evaporation can be achieved at a relatively low temperature. Subsequently, a high-energy electron beam excited by a plasma generator promotes the migration and evaporation of moisture from the particles, enhancing the drying effect. After dehydration, the particles automatically detach from the vortex flow field due to density changes and enter the collection zone, while the nitrogen flow carries the evaporated water vapor into the discharge zone, achieving automatic separation of the particles and the nitrogen flow. This invention, through its unique structural design and particle motion drying process, is suitable for thermosensitive polymer particles, avoiding thermal degradation and achieving highly efficient particle drying.

Description

Technical Field

[0001] This invention relates to the field of particle drying technology, and in particular to an ultrasonic drying system and a particle dehydration method for particles. Background Technology

[0002] In the field of polymer particle drying, hot air drying relies on high-temperature gas to conduct heat. Although it can quickly evaporate surface free water, it easily damages the physical morphology of heat-sensitive polymer (such as PLA and PVA) particles and causes them to undergo chemical degradation, thus failing to meet the drying requirements of such materials.

[0003] Besides hot air drying, vacuum drying can lower the boiling point of heat-sensitive polymer particles and reduce thermal damage. However, in a vacuum environment, the number of gas molecules is small, resulting in low efficiency in heat conduction and convection. After moisture evaporates, the diffusion rate is slow due to the lack of sufficient airflow, leading to a longer overall drying process.

[0004] Current drying methods for thermosensitive polymer particles struggle to achieve efficient drying by rapidly evaporating surface moisture under mild conditions. Summary of the Invention

[0005] One of the objectives of this invention is to solve the problem that existing drying methods for thermosensitive polymer particles are difficult to achieve efficient drying by rapidly evaporating surface moisture under mild conditions.

[0006] The second objective of this invention is to provide a method for dehydrating particles.

[0007] To achieve one of the above objectives, the present invention adopts the following technical solution: a supersonic drying system for particles, comprising a collecting cylinder fitted outside an accelerating cylinder, the gap between the two forming a collecting area, and the upper discharge area of ​​the collecting cylinder being higher than the upper outlet of the accelerating cylinder.

[0008] Multiple Laval nozzles, inclined in a spiral trajectory on the inner wall of the accelerator, have their outlet direction tangential to the inner wall of the accelerator, guiding the supersonic nitrogen gas flow to spiral upward along the central axis of the accelerator in a tangential direction, entraining surrounding gas to form a vortex flow field;

[0009] A guide tube extending from the outside of the collection cylinder into the acceleration cylinder guides the thermosensitive polymer particles into a vortex flow field, causing them to suspend and spiral upward under the centrifugal force and drag force of the vortex flow field.

[0010] The vortex flow field with low pressure at the center and high pressure at the edges puts the particles in a low-pressure environment, lowering the boiling point of water on their surface, and causing them to evaporate through the heat-generating unit inside the accelerating cylinder.

[0011] The plasma generator located on the inner wall of the accelerating cylinder excites a high-energy electron beam in the nitrogen gas flow, which breaks the hydrogen bonds between water and polymer chains in the particle pores, and uses the low-pressure environment to accelerate the migration of the water to the particle surface, and then evaporates it through the heat generation unit.

[0012] The change in particle density after dehydration causes an imbalance between centrifugal force and drag force, causing the particles to migrate towards the inner wall of the collection cylinder, break away from the vortex flow field, and fall into the collection area under the action of gravity. The vortex flow field is then discharged from the discharge area.

[0013] The beneficial effects of this invention are as follows: By guiding thermosensitive polymer particles into a vortex flow field, they are suspended and spirally ascended under the dynamic balance of centrifugal force and airflow drag. The low-pressure environment generated by the vortex flow field lowers the boiling point of water on their surface, and combined with the heat-generating unit, moisture evaporation can be achieved at a lower temperature. Subsequently, a high-energy electron beam excited by a plasma generator promotes the migration and evaporation of moisture from the particles, enhancing the drying effect. After dehydration, the particles automatically detach from the vortex flow field due to density changes and enter the collection area, while the nitrogen flow carries the evaporated water vapor into the discharge area, achieving automatic separation of the particles and the nitrogen flow. This invention, through its unique structural design and particle motion drying process, is suitable for thermosensitive polymer particles, avoiding their thermal degradation and achieving highly efficient particle drying.

[0014] Furthermore, in this embodiment of the invention, the outer wall of the acceleration cylinder is provided with a gas pipe communicating with the Laval nozzle. The gas pipe is connected to a magnetic levitation turbine. The magnetic levitation turbine draws in nitrogen gas flow and pressurizes it, and then delivers it to the Laval nozzle through the gas pipe, so that the Laval nozzle ejects supersonic nitrogen gas flow.

[0015] Furthermore, in this embodiment of the invention, the magnetic levitation turbine pressurizes the nitrogen gas flow to 1.5 MPa and then delivers it to the Laval nozzle.

[0016] Furthermore, in this embodiment of the invention, the velocity of the nitrogen gas flowing tangentially is maintained in the range of 100-150 m / s, and the ratio of the center pressure to the edge pressure of the vortex flow field is 20%-40%.

[0017] Furthermore, in this embodiment of the invention, the angle between the guide tube and the tangent of the inner wall of the acceleration cylinder is 70°-80°, which is used to tangentially guide the heat-sensitive polymer particles into the vortex flow field.

[0018] Furthermore, in this embodiment of the invention, the plasma generator is a radio frequency electrode group connected to a radio frequency current, and the operating frequency of the radio frequency electrode group is 10-15MHz, so that the plasma electron density reaches 10¹. 0 -10¹² cm⁻³.

[0019] Furthermore, in this embodiment of the invention, the inner wall of the collecting cylinder is provided with a serrated guide groove, the groove depth being 0.5-1.5 times the particle diameter, and the groove spacing being 2-3 times the particle diameter.

[0020] Furthermore, in this embodiment of the invention, the heat-generating unit is the frictional heat between the particles and the supersonic nitrogen gas flow, or the heat source for the conduction of the supersonic nitrogen gas flow by the thermal resistor inside the acceleration cylinder.

[0021] Furthermore, in this embodiment of the invention, the heat-generating unit maintains the temperature of the nitrogen gas flow inside the acceleration cylinder in the range of 40-60°C.

[0022] To achieve the second objective mentioned above, the present invention adopts the following technical solution: a particle dehydration method, which, based on the supersonic drying system for particles described in one of the above objectives, includes the following steps:

[0023] Step 1: The particles are tangentially introduced into the vortex flow field formed by the supersonic nitrogen gas flow, and suspension is achieved through the dynamic balance between the centrifugal force and the drag force of the vortex flow field.

[0024] Step 2: Excite plasma in a vortex flow field to allow high-energy electrons to penetrate the particle pores and break the hydrogen bonds between water and polymer chains within the particle pores.

[0025] Step 3: Simultaneously, the low-pressure environment of the vortex flow field is used to lower the boiling point of water on the particle surface and accelerate the migration of water from the particle pores to the surface. The water on the particle surface is evaporated by the frictional heat between the particle and the supersonic nitrogen flow or by the heat conducted to the supersonic nitrogen flow.

[0026] Step 4: After dehydration, the density of the particles increases, triggering an imbalance between centrifugal force and drag force, driving the particles to migrate to the collection area.

[0027] Furthermore, in this embodiment of the invention, the plasma high-energy electron energy in step two is 5-10 eV, and the boiling point of water on the particle surface in step three is reduced to 45-50℃. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the supersonic drying system according to an embodiment of the present invention.

[0029] Figure 2 This is a detailed structural diagram of the supersonic drying system according to an embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of the particle size distribution in the vortex flow field according to an embodiment of the present invention.

[0031] Figure 4 This is a schematic diagram of the process of water adhering to particles in the prior art.

[0032] Figure 5 This is a schematic diagram illustrating the changes in the motion of particles before and after water adheres to them in a vortex, as described in existing technologies.

[0033] 10. Accelerator tube; 11. Laval nozzle; 12. Plasma generator;

[0034] 20. Collection cylinder; 21. Collection area; 22. Discharge area;

[0035] 30. Guiding tube;

[0036] 40. Magnetic levitation turbine; 41. Air pipe. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clear and complete, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some, not all, embodiments of the present invention, and are merely illustrative of the embodiments of the present invention. They are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] In the description of this invention, it should be noted that the terms "center," "middle," "upper," "lower," "left," "right," "inner," "outer," "top," "bottom," "side," "vertical," and "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "a," "first," "second," "third," "fourth," "fifth," and "sixth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] For purposes of simplicity and illustration, the principles of the embodiments are described primarily by way of example. In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that these embodiments may not be limited to these specific details in practice. In some instances, well-known particle dehydration methods and structures have not been described in detail to avoid unnecessarily obscuring these embodiments. Furthermore, all embodiments can be used in combination with each other.

[0041] It should be noted that the accompanying drawings are part of the content of the instruction manual. The structural shapes, connections, fits, and positional relationships that can be clearly seen in the accompanying drawings should all be understood as part of the content of the instruction manual.

[0042] An ultrasonic drying system for particles, such as Figure 1 and Figure 2 As shown, the system includes a collection cylinder 20 fitted around the outside of the accelerator cylinder 10, forming a collection zone 21 between them. The discharge zone 22 at the upper end of the collection cylinder 20 is higher than the outlet of the accelerator cylinder 10. Multiple Laval nozzles 11, arranged obliquely along the inner wall of the accelerator cylinder 10 in a spiral trajectory, have their outlet directions tangential to the inner wall of the accelerator cylinder 10, and are used to generate a supersonic nitrogen vortex flow field. A guide tube 30 penetrating the collection cylinder 20 into the interior of the accelerator cylinder 10 is used to transport heat-sensitive polymer particles. A plasma generator 12 installed on the inner wall of the accelerator cylinder 10 is used to excite a high-energy electron beam. A heat-generating unit within the accelerator cylinder 10 is also included for evaporating moisture from the particle surface.

[0043] The guide tube 30 guides the heat-sensitive polymer particles into the vortex flow field generated by the Laval nozzle 11. Under the centrifugal force and drag force of the vortex flow field, the particles are suspended and spiral upward. Due to the low pressure at the center and high pressure at the edge of the vortex flow field, the particles are in a low-pressure environment, and the boiling point of water on their surface decreases, evaporating through the heat-generating unit inside the accelerating cylinder 10. At the same time, the plasma generator 12 on the inner wall of the accelerating cylinder 10 excites a high-energy electron beam in the nitrogen gas flow, breaking the hydrogen bonds between water and polymer chains in the particle pores, and using the low-pressure environment to accelerate the migration of water to the particle surface, which is then evaporated through the heat-generating unit. After dehydration, the change in particle density causes an imbalance between centrifugal force and drag force. During the upward process, the particles migrate towards the inner wall of the collecting cylinder 20, detach from the vortex flow field, and fall into the collecting area 21 under the action of gravity, while the vortex flow field is discharged from the discharge area 22.

[0044] Specifically, this application restricts the airflow of the vortex flow field to nitrogen flow. A high-energy electron beam is excited in the nitrogen flow to break the hydrogen bonds between water and polymer chains in the pores of PLA particles. The low-pressure environment accelerates the migration of water to the particle surface, and then the water evaporates through the heat-generating unit. At this time, the PLA particles have no water attached and shrink due to heat, and their density also increases. The centrifugal force of the vortex flow field on them decreases more than the decrease in airflow drag. At this time, the particles will break the original equilibrium and move to the outside of the vortex flow field.

[0045] A vortex flow field can be simply referred to as a vortex.

[0046] The supersonic drying system for particles disclosed in this application originates from "Research on the Induced Nucleation and Condensation Mechanism and Enhanced Separation Performance in a Supersonic Cyclone Separator," and is based on its disclosure. Figure 4 and Figure 5 This study innovatively proposes a new strategy for introducing solid particles into a supersonic cyclone separator to induce heterogeneous condensation and nucleation during the natural gas dehydration and dehydrocarbonization process. The particles introduced during the rapid passage of vortex-shaped natural gas (gas phase) through the narrowed neck (where the gas flow accelerates, the pressure decreases, and the temperature also decreases, resulting in condensation) affect the radius of the droplets generated by condensation. As the particle size increases, the particles that were originally stably suspended and moving in the supersonic cyclone are thrown to the wall under the action of the cyclone and discharged through the wet gas outlet.

[0047] The above research scheme first introduces solid particles without water attachment. These particles are suspended and moved forward under the dynamic balance of centrifugal force and drag force of the eddy (particles without water attachment are suspended under the dynamic balance of centrifugal force and airflow drag force of the eddy). After the particles are attached with water molecules formed by condensation, the dynamic balance of centrifugal force and drag force is broken. Under the action of centrifugal force, they are thrown to the wall and discharged through the moisture outlet.

[0048] The research scheme is a technique that introduces dry particles into a vortex to remove water and promote their formation, thereby achieving the separation of particles and water together.

[0049] The applicant reversed the above research plan by first introducing water-attached particles into the eddy, suspending the particles under the dynamic balance of centrifugal force and airflow drag. After the particles dehydrate (breaking the dynamic balance), they were freed from the eddy by using centrifugal force.

[0050] This application relates to a technology that introduces attached water particles into a vortex for dehydration and shape reduction, thereby achieving separation of particles and water.

[0051] Based on the theoretical and model-backward derivation of the above research scheme, it is concluded that eddies can be used to suspend water-bearing particles, and after they are dehydrated, they can be separated by the centrifugal force of the eddies.

[0052] The advantage of this invention lies in guiding the thermosensitive polymer particles into a vortex flow field, where they are suspended and spirally ascended under the dynamic balance of centrifugal force and airflow drag. The low-pressure environment generated by the vortex flow field lowers the boiling point of water on the particle surface, and combined with the heat-generating unit, moisture evaporation can be achieved at a lower temperature. Subsequently, a high-energy electron beam excited by the plasma generator 12 promotes the migration and evaporation of moisture from the particles, enhancing the drying effect. After dehydration, the particles automatically detach from the vortex flow field due to density changes and enter the collection zone 21, while the nitrogen flow carries the evaporated water vapor into the discharge zone 22, achieving automatic separation of the particles and the nitrogen flow. This invention, through its unique structural design and particle movement drying process, is suitable for thermosensitive polymer particles, avoiding their thermal degradation and achieving highly efficient particle drying.

[0053] Furthermore, in this embodiment of the invention, the outer wall of the acceleration cylinder 10 is provided with an air pipe 41 that communicates with the Laval nozzle 11. The air pipe 41 is connected to the magnetic levitation turbine 40. The magnetic levitation turbine 40 draws in nitrogen gas and pressurizes it, and then delivers it to the Laval nozzle 11 through the air pipe 41, so that the Laval nozzle 11 ejects supersonic nitrogen gas.

[0054] Furthermore, in this embodiment of the invention, the magnetic levitation turbine 40 pressurizes the nitrogen gas flow to 1.5 MPa and then delivers it to the Laval nozzle 11.

[0055] Furthermore, in this embodiment of the invention, the velocity of the nitrogen gas flowing tangentially is maintained in the range of 100-150 m / s, and the ratio of the center pressure to the edge pressure of the vortex flow field is 20%-40%.

[0056] Furthermore, in this embodiment of the invention, the tangent angle between the guide tube 30 and the inner wall of the acceleration cylinder 10 is 70°-80°, which is used to tangentially guide the heat-sensitive polymer particles into the vortex flow field.

[0057] Furthermore, in this embodiment of the invention, the plasma generator 12 is a radio frequency electrode group connected to a radio frequency current. The operating frequency of this radio frequency electrode group is 10-15MHz, so that the plasma electron density reaches 10¹. 0 -10¹² cm⁻³.

[0058] Furthermore, in this embodiment of the invention, the inner wall of the collecting cylinder 20 is provided with a serrated guide groove, the groove depth is 0.5-1.5 times the particle diameter, and the groove spacing is 2-3 times the particle diameter.

[0059] When particles collide with the inner wall of the collecting cylinder 20 with serrated guide grooves, the contact situation changes significantly compared to a smooth inner wall. The presence of the serrated guide grooves means that the particle collision is no longer a simple planar collision. The particles come into contact with the groove wall, and the direction of the force during the collision becomes complex. For example, particles may slide along the inclined surface of the groove wall, in which the impact force generated by the collision is dispersed and guided. According to the principles of mechanics, when the force is decomposed along the direction of the groove wall, the force component perpendicular to the inner wall that causes the particles to rebound decreases, thereby reducing the likelihood of particles rebounding after colliding with the inner wall of the collecting cylinder 20 and returning to the vortex flow field.

[0060] Furthermore, in this embodiment of the invention, the heat-generating unit is the frictional heat between the particles and the supersonic nitrogen gas flow, or the heat source for the conduction of the supersonic nitrogen gas flow by the thermal resistance inside the acceleration cylinder 10.

[0061] Frictional heat generation generally has two causes. First, although particles are carried by the airflow in the vortex flow field, the particles possess a certain mass and inertia, causing their motion response speed to lag behind the airflow. The supersonic vortex flow field formed by the Laval nozzle 11 experiences rapid and complex velocity changes. At any given moment, the airflow velocity may suddenly change direction or accelerate, and the particles, due to inertia, cannot immediately adjust accordingly. For example, when the airflow makes a rapid turn, the particles tend to maintain their original direction of motion, causing a change in the relative velocity between the particles and the surrounding airflow. This creates a velocity gradient between the particle surface and the airflow, thereby generating frictional heat.

[0062] The second reason is that vortex flow fields inherently possess uneven velocity distribution; the magnitude and direction of airflow velocity differ between the central and peripheral regions. When particles move within a vortex flow field, they traverse different velocity regions. When a particle moves from a low-speed region to a high-speed region, or vice versa, the velocity difference between the particle and the surrounding airflow changes, creating a velocity gradient. Even at the same radial position, due to the rotational characteristics of the vortex, the tangential velocity of the airflow varies with time and spatial location. The relative motion between the particle and the airflow at different locations generates a velocity gradient, thus producing friction and generating heat.

[0063] Furthermore, in this embodiment of the invention, the heat-generating unit maintains the temperature of the nitrogen gas flow inside the accelerating cylinder 10 in the range of 40-60°C.

[0064] A method for dehydrating particles, based on the aforementioned supersonic drying system for particles, includes the following steps:

[0065] Step 1: The particles are tangentially introduced into the vortex flow field formed by the supersonic nitrogen gas flow, and suspension is achieved through the dynamic balance between the centrifugal force and the drag force of the vortex flow field.

[0066] Step 2: Excite plasma in a vortex flow field to allow high-energy electrons to penetrate the particle pores and break the hydrogen bonds between water and polymer chains within the particle pores.

[0067] Step 3: Simultaneously, the low-pressure environment of the vortex flow field is used to lower the boiling point of water on the particle surface and accelerate the migration of water from the particle pores to the surface. The water on the particle surface is evaporated by the frictional heat between the particle and the supersonic nitrogen flow or by the heat conducted to the supersonic nitrogen flow.

[0068] Step 4: After dehydration, the density of the particles increases, triggering an imbalance between centrifugal force and drag force, driving the particles to migrate to the collection area 21.

[0069] Furthermore, in this embodiment of the invention, the plasma high-energy electron energy in step two is 5-10 eV, and the boiling point of water on the particle surface in step three is reduced to 45-50℃.

[0070] The specific particle dehydration process based on the above system is as follows:

[0071] A number of Laval nozzles 11 are arranged in a spaced spiral pattern along the inner wall of the acceleration cylinder 10. The external airflow is pressurized to 1.5 MPa by the magnetic levitation turbine 40 and then injected with supersonic nitrogen gas at a tangential angle of 75° through the array of 12 Laval nozzles 11, so that a gradient vortex flow field with a central pressure of 5 kPa and an edge pressure of 20 kPa is formed in the acceleration chamber. Its pressure distribution shows a gradient characteristic of low pressure in the center and high pressure at the edge.

[0072] Thermosensitive polymer particles are conveyed into the accelerator cylinder 10 through the guide tube 30. The outlet direction of the guide tube 30 forms a 75° angle with the tangent of the inner wall of the accelerator cylinder 10, so that the particles are cut into the vortex flow field.

[0073] Driven by the tangential airflow in the vortex flow field, the particles spiral upward along the cavity wall. According to the dynamic balance principle of centrifugal force and airflow drag, the particles can be suspended in an annular zone 10-15 mm from the central axis of the acceleration cylinder. Specifically, let's take a thermosensitive polymer, PLA particles with a diameter of 3 mm, as an example. With a tangential velocity of 120 m / s and a rotation radius of 0.5 m, the centrifugal force is calculated as follows (first calculate the mass of the PLA particle, assuming the PLA density is 1250 kg / m³, approximating the particle as a sphere, the mass equals the density multiplied by the sphere's volume, the sphere's volume formula is four-thirds multiplied by pi multiplied by the cube of the radius, here the radius is half the diameter of 3 mm; after calculating the mass, the centrifugal force equals the mass multiplied by the square of the tangential velocity and then divided by the rotation radius). The calculated centrifugal force is approximately 0.024 N.

[0074] Meanwhile, the drag force acting on the particle is calculated. The drag force is the resistance exerted by nitrogen on the particle, and its direction is opposite to the direction of the object's motion relative to the nitrogen. Given that the gas in the environment is nitrogen, with a density of 1.25 kg / m³, a drag coefficient of approximately 0.5, and the particle's frontal area being pi multiplied by the square of its radius, the airflow drag force is calculated as 0.5 multiplied by the drag coefficient, the nitrogen density, the frontal area, and the square of the tangential velocity. This yields an airflow drag force of approximately 0.023 Newtons.

[0075] The nitrogen flow is designed as a spiral upward flow pattern, with the centrifugal force directed radially outward. PLA particles are propelled upward by the vertical component of the airflow drag force. In this case, the resultant force of the centrifugal force and the airflow drag force in a specific direction (vertical) is equal to the gravity. That is to say, the magnitude of the resultant force of the centrifugal force and the airflow drag force is approximately equal to the gravity acting on the PLA particles, and the direction is opposite.

[0076] The gravity acting on a PLA particle is equal to its mass multiplied by the acceleration due to gravity (taken as 9.8 m / s²), approximately 0.0011 Newtons. This allows the PLA particle to remain stably suspended. Conversely, knowing the gravity acting on the PLA particle allows for the selection of appropriate nitrogen flow parameters, enabling the PLA particle to remain stably suspended under the dynamic balance between the centrifugal force and the airflow drag in the vortex flow field. This principle is a mature technology, readily understood by those skilled in the art without any creative effort.

[0077] In the annular acceleration chamber of the supersonic drying system, the water-containing PLA particles are in a low-pressure environment of approximately 10 kPa, which lowers the boiling point of the water on their surface to 45-50 °C (calculated according to the Clausius-Clapeyron equation). The PLA particles are propelled by the high-speed airflow, generating tangential motion. The moisture on the surface of the polymer particles is evaporated and dehydrated through frictional heat generated by the high-speed motion of the polymer particles in the supersonic airflow or through heating by the heating unit at the bottom of the acceleration chamber.

[0078] The water evaporation temperature is lower than the glass transition temperature of PLA and PVA, ensuring that the material does not undergo thermal degradation.

[0079] Simultaneously, the radio frequency electrode (13.56MHz) excites nitrogen gas plasma, generating high-energy electrons (5-10eV) that bombard water molecules in the pores inside the polymer particles, breaking their hydrogen bonds with the polymer chains. Then, driven by the low-pressure environment and centrifugal force of the vortex flow field inside the accelerator cylinder 10, the water migrates along the pores to the surface of the PLA particles. It is then evaporated and dehydrated by the frictional heat generated by the high-speed motion of the PLA particles in the supersonic gas flow or by the heating of the thermal resistance inside the accelerator cylinder 10.

[0080] After dehydration, the density of PLA particles with a density of 1.25 g / cm³ increases to 1.28 g / cm³, breaking the mechanical balance. At this point, the centrifugal force exceeds the drag force and the gravity of the PLA particles, pushing the PLA particles to migrate towards the inner wall of the acceleration cylinder 10.

[0081] After the spiraling nitrogen gas flow leaves the acceleration cylinder 10, the PLA particles are subjected to centrifugal force and migrate towards the inner wall of the collection cylinder 20, causing the dehydrated PLA particles to leave the vortex flow field. The dehydrated PLA particles fall into the collection area 21 under their own gravity for collection, while the nitrogen gas flow carries the evaporated water vapor and is discharged through the discharge area 22 above the collection cylinder 20.

[0082] Finally, considering the impact of particles with different moisture contents or different sizes on the drying results during the particle drying process, the following adjustment scheme is adopted:

[0083] like Figure 3 As shown, the full-field three-dimensional velocity field and particle size analyzer illuminates the vortex flow field by emitting laser light from the pulsed laser at the bottom of the accelerator tube 10. Then, the cross-frame CCD camera at the bottom of the accelerator tube 10 captures the particle images in the vortex flow field. By processing the images using the principles of autocorrelation or cross-correlation, the velocity field distribution in the vortex flow field can be obtained, and the particle size and distribution information can be measured at the same time.

[0084] Based on the measured particle size and its distribution information, adjust the nitrogen gas flow rate or pressure of the Laval nozzle 11.

[0085] Pressure regulation: If there are many large-diameter particles, increase the inlet pressure of Laval nozzle 11 to increase the nitrogen flow velocity. For example, increase the inlet pressure from 1.5 MPa to 1.8 MPa to enhance the drag force of the nitrogen flow on large particles, ensuring that large particles can be better suspended in the vortex flow field, increasing the contact time with the hot airflow, and promoting drying. If small-diameter particles are dominant, reduce the inlet pressure to prevent small particles from leaving the drying area (low-pressure environment) too quickly due to excessive airflow velocity, resulting in insufficient drying.

[0086] Flow rate adjustment: For large particles, increasing the nitrogen gas flow rate increases the turbulence of the vortex flow field, which helps disperse large particles, avoids agglomeration, and improves drying uniformity. When the proportion of large particles is high, the nitrogen gas flow rate can be increased. For small particles, reducing the nitrogen gas flow rate lowers their velocity in the flow field, allowing them sufficient residence time in the drying region.

[0087] By continuously monitoring the motion of particles in the vortex flow field and combining it with their particle size information, the water content can be indirectly inferred (generally, under the same conditions, particles with high water content will have different motion speeds and trajectories). When an increase in the proportion of high water content particles is detected, the power of the heat-generating unit (i.e., the power of the electrothermal resistance) is increased or the residence time of the particles in the vortex flow field is extended.

[0088] Based on the particle distribution and moisture content in the vortex flow field, the drying area is further subdivided. For areas with high moisture content and particle aggregation, the energy output of plasma generator 12 is increased to enhance the disruption of hydrogen bonds between moisture and polymer chains, thereby accelerating moisture migration and evaporation. For areas with low moisture content, the energy input is reduced to prevent excessive drying of particles.

[0089] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, the invention is not limited to the scope of the specific embodiments. For those skilled in the art, all inventions utilizing the concept of the present invention are protected as long as various variations are within the spirit and scope of the invention as defined and determined by the appended claims.

Claims

1. A supersonic drying system for particles, characterized in that, It includes a collection cylinder fitted outside the acceleration cylinder, the gap between the two forming a collection area, and the upper discharge area of ​​the collection cylinder is higher than the upper outlet of the acceleration cylinder; Multiple Laval nozzles, inclined in a spiral trajectory on the inner wall of the accelerator, have their outlet direction tangential to the inner wall of the accelerator, guiding the supersonic nitrogen gas flow to spiral upward along the central axis of the accelerator in a tangential direction, entraining surrounding gas to form a vortex flow field; A guide tube extending from the outside of the collection cylinder into the acceleration cylinder guides the thermosensitive polymer particles into the vortex flow field, causing them to suspend and spiral upward under the action of centrifugal force and drag force in the vortex flow field. The vortex flow field with low pressure at the center and high pressure at the edge puts the particles in a low-pressure environment, lowering the boiling point of water on their surface, and they evaporate through the heat-generating unit inside the acceleration cylinder. The plasma generator located on the inner wall of the accelerating cylinder excites a high-energy electron beam in the nitrogen gas flow, which breaks the hydrogen bonds between water and polymer chains in the particle pores, and uses the low-pressure environment to accelerate the migration of the water to the particle surface, and then evaporates it through the heat generation unit. The change in particle density after dehydration causes an imbalance between centrifugal force and drag force, causing the particles to migrate towards the inner wall of the collection cylinder, break away from the vortex flow field, and fall into the collection area under the action of gravity. The vortex flow field is then discharged from the discharge area.

2. The supersonic drying system for particles according to claim 1, characterized in that, The outer wall of the acceleration cylinder is provided with a gas pipe that communicates with the Laval nozzle. The gas pipe is connected to a magnetic levitation turbine. The magnetic levitation turbine draws in nitrogen gas and pressurizes it, and then delivers it to the Laval nozzle through the gas pipe, so that the Laval nozzle ejects supersonic nitrogen gas.

3. The supersonic drying system for particles according to claim 2, characterized in that, The magnetic levitation turbine pressurizes the nitrogen gas flow to 1.5 MPa and then delivers it to the Laval nozzle.

4. The supersonic drying system for particles according to claim 1, characterized in that, The velocity of the nitrogen gas flowing tangentially is maintained in the range of 100-150 m / s.

5. The supersonic drying system for particles according to claim 1, characterized in that, The plasma generator is a radio frequency electrode assembly connected to a radio frequency current. The operating frequency of this radio frequency electrode assembly is 10-15MHz, enabling the plasma electron density to reach 10¹⁰. 0 -10¹² cm⁻³.

6. The supersonic drying system for particles according to claim 1, characterized in that, The inner wall of the collection cylinder is provided with a serrated guide groove, the groove depth is 0.5-1.5 times the particle diameter, and the groove spacing is 2-3 times the particle diameter.

7. The supersonic drying system for particles according to claim 1, characterized in that, The heat-generating unit is the frictional heat between the particles and the supersonic nitrogen gas flow, or the heat source for the conduction of the supersonic nitrogen gas flow by the thermal resistor inside the acceleration cylinder.

8. The supersonic drying system for particles according to claim 1, characterized in that, The heat generation unit maintains the temperature of the nitrogen gas flow inside the acceleration cylinder within the range of 40-60°C.

9. A method for dehydrating particles, characterized in that, This method, based on the supersonic drying system for particles according to any one of claims 1-8, includes the following steps: Step 1: Thermosensitive polymer particles are tangentially introduced into the vortex flow field formed by the supersonic nitrogen gas flow, and suspension is achieved through the dynamic balance between centrifugal force and drag force in the vortex flow field; Step 2: Excite plasma in the vortex flow field to allow high-energy electrons to penetrate the particle pores and break the hydrogen bonds between water and polymer chains in the particle pores; Step 3: Simultaneously, the low-pressure environment of the vortex flow field is used to reduce the boiling point of water on the particle surface and accelerate the migration of water in the particle pores to its surface. The water on the particle surface is evaporated by the frictional heat between the particle and the supersonic nitrogen flow or by the heat conducted to the supersonic nitrogen flow. Step 4: After dehydration, the density of the particles increases, triggering an imbalance between centrifugal force and drag force, driving the particles to migrate to the collection area.

10. The particle dehydration method according to claim 9, characterized in that, In step two, the high-energy electrons in the plasma have an energy of 5-10 eV, and in step three, the boiling point of water on the particle surface drops to 45-50℃.

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