Supersonic drying system for particles and particle dehydration method

Abstract

The invention discloses a supersonic drying system for particles and a particle dehydration method, and relates to the technical field of particle drying. The heat-sensitive polymer particles are guided into the vortex flow field and suspend and spirally rise under dynamic balance of centrifugal force and airflow drag force, at the moment, the low-pressure environment generated by the vortex flow field reduces the boiling point of water on the surface of the vortex flow field, and water evaporation can be achieved at the low temperature in combination with the heat generation unit. Then, a high-energy electron beam excited by the plasma generator promotes moisture migration and evaporation of the particles, and the drying effect of the particles is enhanced; dehydrated particles automatically break away from a vortex flow field and enter a collecting area due to density change, nitrogen flow carries evaporated water vapor to enter a discharging area, automatic separation of the particles and the nitrogen flow is achieved, through the unique structural design and the particle movement drying process, the device is suitable for heat-sensitive polymer particles, thermal degradation of the heat-sensitive polymer particles is avoided, and the service life of the heat-sensitive polymer particles is prolonged. And efficient particle drying is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of particle drying, and in particular to a supersonic drying system for particles and a particle dehydration method. Background Art

[0002] In the field of polymer particle drying, hot air drying relies on high-temperature gas to conduct heat. Although it can quickly evaporate free water on the surface, it is easy to destroy the physical form of heat-sensitive polymer (such as PLA, PVA) particles and easily cause them to chemically degrade, and cannot meet the drying needs of such materials.

[0003] In addition to 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, and heat conduction and convection heat transfer are inefficient. After the water evaporates, the lack of sufficient airflow slows its diffusion, making the overall drying process time-consuming.

[0004] The current drying scheme for thermosensitive polymer particles is difficult to promote rapid evaporation of surface moisture of thermosensitive polymer particles under mild conditions to achieve efficient drying. Summary of the Invention

[0005] One of the purposes of the present invention is to solve the problem that the conventional drying scheme for thermosensitive polymer particles is difficult to promote rapid evaporation of surface moisture of thermosensitive polymer particles under mild conditions to achieve efficient drying.

[0006] A second object of the present invention is to provide a particle dehydration method.

[0007] To achieve one of the above-mentioned purposes, the present invention adopts the following technical solution: a supersonic drying system for particles, comprising a collecting cylinder sleeved outside an accelerating cylinder, the gap between the two forming a collecting area, and the discharge area at the upper end of the collecting cylinder is higher than the upper end outlet of the accelerating cylinder.

[0008] Multiple Laval nozzles are arranged on the inner wall of the accelerator tube in a spiral trajectory, with their outlet directions tangent to the inner wall of the accelerator tube, guiding the supersonic nitrogen flow to spiral upward around the central axis of the accelerator tube in a tangential direction, entraining the surrounding gas to form a vortex flow field; A guide tube extending from the outside of the collecting cylinder to the accelerating cylinder guides the thermosensitive polymer particles to the vortex flow field, so that the particles are suspended and spirally ascend under the centrifugal force and drag force of the vortex flow field.

[0009] The vortex flow field with low pressure in the center and high pressure at the edge places the particles in a low-pressure environment, lowering the boiling point of water on their surface, and evaporating through the heat generating unit in the acceleration cylinder.

[0010] The plasma generator installed on the inner wall of the acceleration cylinder excites a high-energy electron beam in the nitrogen flow, destroying the hydrogen bonds between the water in the particle pores and the polymer chains, and using the low-pressure environment to accelerate the migration of the water to the particle surface, and then evaporated through the heat generation unit; After dehydration, the particle density changes, causing the centrifugal force and the drag force to become unbalanced, and the particles migrate toward the inner wall of the collection tube, escape 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.

[0011] The beneficial effects of the present invention are as follows: by guiding the thermosensitive polymer particles into the vortex flow field, they are suspended and spirally ascended under the dynamic balance of centrifugal force and airflow drag. At this time, the low-pressure environment generated by the vortex flow field reduces the boiling point of water on its surface. Combined with the heat generating unit, water evaporation can be achieved at a lower temperature. Then, the high-energy electron beam excited by the plasma generator promotes the migration and evaporation of water in the particles, thereby enhancing the drying effect of the particles. After dehydration, the particles automatically separate 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, thereby achieving automatic separation of the particles and the nitrogen flow. The present invention is suitable for thermosensitive polymer particles through its unique structural design and particle motion drying process, avoids thermal degradation, and achieves efficient particle drying.

[0012] Furthermore, in an embodiment of the present invention, an air pipe connected to the Laval nozzle is provided on the outer wall of the acceleration cylinder. The air pipe is connected to the magnetic levitation turbine, and the nitrogen flow is sucked and pressurized by the magnetic levitation turbine, and then transported to the Laval nozzle through the air pipe, so that the Laval nozzle ejects a supersonic nitrogen flow.

[0013] Furthermore, in an embodiment of the present invention, the magnetic levitation turbine pressurizes the nitrogen flow to 1.5 MPa and then delivers it to the Laval nozzle.

[0014] Furthermore, in an embodiment of the present invention, the velocity of the nitrogen flow along the tangential direction is maintained in the range of 100-150 m / s, and the ratio of the central pressure to the edge pressure of the vortex flow field is 20%-40%.

[0015] Furthermore, in an embodiment of the present invention, the angle between the tangent of the guide tube and the inner wall of the acceleration cylinder is 70°-80°, which is used to tangentially guide the thermosensitive polymer particles into the vortex flow field.

[0016] Furthermore, in an embodiment of the present 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 10-15 MHz, so that the plasma electron density reaches 10¹ 0 -10¹² cm⁻³.

[0017] Furthermore, in an embodiment of the present invention, a sawtooth guide groove is provided on the inner wall of the collecting cylinder, the groove depth is 0.5-1.5 times the diameter of the particle, and the groove spacing is 2-3 times the diameter of the particle.

[0018] Furthermore, in an embodiment of the present invention, the heat generating unit is frictional heat between the particles and the supersonic nitrogen flow, or is a heat source conducted by the electric thermal resistance in the acceleration cylinder to the supersonic nitrogen flow.

[0019] Furthermore, in an embodiment of the present invention, the heat generating unit maintains the temperature of the nitrogen flow in the acceleration cylinder in the range of 40-60°C.

[0020] To achieve the second of the above objectives, the present invention adopts the following technical solution: a particle dehydration method, which is based on the supersonic drying system for particles described in one of the above objectives of the invention and includes the following steps: Step 1: The particles are introduced tangentially into the vortex flow field formed by the supersonic nitrogen flow, and suspension is achieved through the dynamic balance between the centrifugal force and the drag force in the vortex flow field.

[0021] Step 2: Plasma is excited in the vortex flow field, allowing high-energy electrons to penetrate the pores of the particles and destroy the hydrogen bonds between the water and the polymer chains in the pores of the particles.

[0022] Step 3: 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 the surface. The water on the particle surface is evaporated through frictional heat between the particles and the supersonic nitrogen flow or heat conducted to the supersonic nitrogen flow.

[0023] Step 4: After dehydration, the density of the particles increases, triggering an imbalance between the centrifugal force and the drag force, driving the particles to migrate to the collection area.

[0024] Furthermore, in an embodiment of the present invention, the energy of the plasma high-energy electrons in step 2 is 5-10 eV, and the boiling point of water on the particle surface in step 3 is reduced to 45-50°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of the supersonic drying system according to an embodiment of the present invention.

[0026] Figure 2 Schematic diagram of the detailed structure of the supersonic drying system according to an embodiment of the present invention.

[0027] Figure 3 Schematic diagram of particle size distribution in the vortex flow field according to an embodiment of the present invention.

[0028] Figure 4 Schematic diagram of the process of particles adhering to water in the prior art.

[0029] Figure 5This is a schematic diagram of the movement process of particles before and after they attach to water in a vortex in the prior art.

[0030] 10. Accelerator, 11. Laval nozzle, 12. Plasma generator; 20. Collection cylinder, 21. Collection area, 22. Discharge area; 30. Guide tube; 40. Magnetic levitation turbine, 41. Trachea. DETAILED DESCRIPTION

[0031] In order to clearly and completely describe the objectives and technical solutions of the present invention and make the advantages more clearly understood, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are part of the embodiments of the present invention, not all of them, and are only used to explain the embodiments of the present invention, not to limit 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.

[0032] In the description of the present invention, it should be noted that the terms "center," "middle," "upper," "lower," "left," "right," "inner," "outer," "top," "bottom," "side," "vertical," "horizontal," and the like, indicating positions or location relationships, are based on the positions or location relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "one," "first," "second," "third," "fourth," "fifth," and "sixth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0034] For the purposes of simplicity and illustration, the principles of the embodiments are described primarily with reference to examples. In the following description, numerous specific details are provided to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that the embodiments may not be limited to these specific details in practice. In some instances, well-known particle dehydration methods and structures are not described in detail to avoid unnecessarily obscuring the embodiments. Furthermore, all embodiments may be used in combination with one another.

[0035] It should be noted that the drawings in the specification are the contents of the specification. The structural shapes, connection relationships, coordination relationships, and positional relationships that can be obtained without any doubt in the drawings in the specification should be understood as the contents of the specification.

[0036] A supersonic drying system for granules, such as Figure 1 and Figure 2 As shown, it includes a collection tube 20 that is sleeved on the outside of the accelerator tube 10, forming a collection area 21 between the two. The discharge area 22 at the upper end of the collection tube 20 is higher than the outlet of the accelerator tube 10. Multiple Laval nozzles 11 are arranged in a spiral trajectory along the inner wall of the accelerator tube 10, with their outlet direction tangent to the inner wall of the accelerator tube 10, and are used to generate a supersonic nitrogen vortex flow field. The guide tube 30 that runs through the collection tube 20 to the interior of the accelerator tube 10 is used to transport heat-sensitive polymer particles. The plasma generator 12 installed on the inner wall of the accelerator tube 10 is used to excite a high-energy electron beam. And the heat generation unit in the accelerator tube 10 is used to evaporate water on the surface of the particles.

[0037] The guide tube 30 guides the thermosensitive polymer particles into the vortex flow field generated by the Laval nozzle 11. Under the action of the centrifugal force and drag force of the vortex flow field, the particles are suspended and spiral upward. Since the vortex flow field is in a state of low pressure in the center and high pressure at the edge, the particles are in a low-pressure environment, the boiling point of the water on their surface is reduced, and it evaporates through the heat generating unit in the acceleration cylinder 10. At the same time, the plasma generator 12 on the inner wall of the acceleration cylinder 10 excites a high-energy electron beam in the nitrogen flow, destroying the hydrogen bonds between the water and the polymer chains in the pores of the particles, and using the low-pressure environment to accelerate the migration of water to the surface of the particles, and then evaporates through the heat generating unit. After dehydration, the change in particle density causes an imbalance between the centrifugal force and the drag force. During the upward process, the particles migrate toward the inner wall of the collection cylinder 20, break away from the vortex flow field, and fall into the collection area 21 under the action of gravity, while the vortex flow field is discharged from the discharge area 22.

[0038] Specifically, the present application limits the airflow in the vortex flow field to a nitrogen flow, which excites a high-energy electron beam to destroy the hydrogen bonds between water and polymer chains in the pores of the PLA particles. The low-pressure environment is used to accelerate the migration of water to the surface of the particles, which is then evaporated through the heat generation unit. At this time, the PLA particles have no water attached, and they shrink due to heat, and their density also increases. The reduction in the centrifugal force of the vortex flow field on them is greater than the reduction in the airflow drag force. At this time, the particles will break the original balance and move to the outside of the vortex flow field.

[0039] The vortex flow field can be simply referred to as vortex.

[0040] The supersonic drying system for particles disclosed in this application is derived from the "Study on the Induced Nucleation and Coagulation Mechanism and Enhanced Separation Performance in Supersonic Cyclone Separators", with reference to the published Figure 4 and Figure 5 This study innovatively proposed a new strategy of introducing solid particles into the supersonic cyclone separator to carry out heterogeneous induced condensation nucleation during the dehydration and dehydrogenation process of natural gas: the particles introduced in the process of the vortex-shaped natural gas (gas phase) quickly passing through the shrinking neck (the air flow accelerates, the pressure decreases, and the temperature also decreases accordingly, achieving condensation) will affect the radius of the droplets produced 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.

[0041] The above research plan first introduces solid particles without water attached. The particles are suspended and moved forward under the dynamic balance of the centrifugal force and drag of the vortex (particles without water attached are suspended under the dynamic balance of the centrifugal force and the drag of the airflow). After that, the particles are attached with water molecules formed by condensation, breaking the dynamic balance of centrifugal force and drag. Under the action of centrifugal force, they are thrown to the wall and discharged through the moisture outlet.

[0042] The research proposal is a technology that introduces dry particles into the vortex to remove the attached water and increase its shape, thereby achieving separation of particles and water together.

[0043] Based on the above research plan, the applicant conducted reverse utilization. First, water-attached particles were introduced into the vortex, so that the particles were suspended under the dynamic balance between the centrifugal force of the vortex and the drag force of the airflow. After they were dehydrated (breaking the dynamic balance), the centrifugal force was used to separate them from the vortex.

[0044] The present application is a technology that introduces attached water particles into a vortex to dehydrate and reduce their shape, thereby achieving separation of particles and water.

[0045] Based on the reverse deduction of the theory and model disclosed in the above research plan, it is concluded that eddy currents can be used to suspend particles attached to water, and after they are dehydrated, the centrifugal force of the eddy currents can be used to separate them.

[0046] The advantage of the present invention is that by guiding the thermosensitive polymer particles into the vortex flow field, they are suspended and spirally ascended under the dynamic balance of centrifugal force and airflow drag. At this time, the low-pressure environment generated by the vortex flow field reduces the boiling point of water on the surface. Combined with the heat generating unit, water evaporation can be achieved at a lower temperature. Then, the high-energy electron beam excited by the plasma generator 12 promotes the migration and evaporation of water in the particles, thereby enhancing the drying effect of the particles. After dehydration, the particles automatically separate from the vortex flow field due to density changes and enter the collection area 21, while the nitrogen flow carries the evaporated water vapor into the discharge area 22, thereby achieving automatic separation of the particles and the nitrogen flow. The present invention is suitable for thermosensitive polymer particles through its unique structural design and particle motion drying process, avoids their thermal degradation, and achieves efficient particle drying.

[0047] Furthermore, in an embodiment of the present invention, an air pipe 41 connected to the Laval nozzle 11 is provided on the outer wall of the acceleration cylinder 10. The air pipe 41 is connected to the magnetic levitation turbine 40, and the nitrogen flow is sucked and pressurized by the magnetic levitation turbine 40, and then transported to the Laval nozzle 11 through the air pipe 41, so that the Laval nozzle 11 ejects a supersonic nitrogen flow.

[0048] Furthermore, in the embodiment of the present invention, the magnetic levitation turbine 40 pressurizes the nitrogen flow to 1.5 MPa and then delivers it to the Laval nozzle 11 .

[0049] Furthermore, in an embodiment of the present invention, the velocity of the nitrogen flow along the tangential direction is maintained in the range of 100-150 m / s, and the ratio of the central pressure to the edge pressure of the vortex flow field is 20%-40%.

[0050] Furthermore, in the embodiment of the present invention, the included angle between the tangent of the guide tube 30 and the inner wall of the acceleration cylinder 10 is 70°-80°, which is used to tangentially guide the thermosensitive polymer particles into the vortex flow field.

[0051] Furthermore, in the embodiment of the present invention, the plasma generator 12 is a radio frequency electrode group connected to a radio frequency current, and the operating frequency of the radio frequency electrode group is 10-15 MHz, so that the plasma electron density reaches 10¹ 0 -10¹² cm⁻³.

[0052] Furthermore, in an embodiment of the present invention, a sawtooth guide groove is provided on the inner wall of the collecting cylinder 20 , the groove depth is 0.5-1.5 times the particle diameter, and the groove spacing is 2-3 times the particle diameter.

[0053] When particles collide with the inner wall of the collecting tube 20 with a serrated guide groove, the contact situation changes significantly compared to the smooth inner wall. The presence of the serrated guide groove means that the particles are no longer in a simple plane collision. The particles will contact the groove wall, and the direction of the force during the collision becomes complicated. For example, the particles may slide along the inclined surface of the groove wall. In this process, 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 direction that causes the particles to rebound will be reduced, thereby reducing the possibility of the particles rebounding after colliding with the inner wall of the collecting tube 20 and rebounding back into the vortex flow field.

[0054] Furthermore, in the embodiment of the present invention, the heat generating unit is the friction heat between the particles and the supersonic nitrogen flow, or the heat source conducted by the electric thermal resistance in the acceleration tube 10 to the supersonic nitrogen flow.

[0055] There are generally two reasons for the generation of frictional heat. The first reason is that although the particles are driven by the airflow in the vortex flow field, the particles have a certain mass and inertia, and their motion response speed lags behind the airflow. The airflow passes through the supersonic vortex flow field formed by the Laval nozzle 11, and the speed changes rapidly and complexly. At a certain moment, the airflow speed may suddenly change direction or accelerate, and the particles cannot immediately make corresponding adjustments due to inertia. For example, when the airflow turns quickly, the particles tend to maintain their original direction of movement, resulting in a change in the relative speed between the particles and the surrounding airflow, and then forming a velocity gradient between the particle surface and the airflow, thereby generating friction-generated heat.

[0056] The second reason is that the vortex flow field itself has the characteristic of uneven velocity distribution. The airflow velocity and direction in the central area and the edge area are different. When particles move in the vortex flow field, they will pass through different speed areas. When particles enter the high-speed area from the low-speed area, or from the high-speed area to the low-speed area, the speed difference between the particles and the surrounding airflow will change, thus forming a velocity gradient. Even at the same radial position, due to the rotational characteristics of the vortex, the tangential velocity of the airflow will also change with time and spatial position. The relative motion of the particles and the airflow at different positions produces a velocity gradient, which generates friction and generates heat.

[0057] Furthermore, in the embodiment of the present invention, the heat generating unit maintains the temperature of the nitrogen flow in the acceleration cylinder 10 in the range of 40-60°C.

[0058] A particle dehydration method, based on the above-mentioned supersonic drying system for particles, comprises the following steps: Step 1: The particles are introduced tangentially into the vortex flow field formed by the supersonic nitrogen flow, and suspension is achieved through the dynamic balance between the centrifugal force and the drag force in the vortex flow field.

[0059] Step 2: Plasma is excited in the vortex flow field, allowing high-energy electrons to penetrate the pores of the particles and destroy the hydrogen bonds between the water and the polymer chains in the pores of the particles.

[0060] Step 3: 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 the surface. The water on the particle surface is evaporated through frictional heat between the particles and the supersonic nitrogen flow or heat conducted to the supersonic nitrogen flow.

[0061] Step 4: After dehydration, the density of the particles increases, triggering an imbalance between the centrifugal force and the drag force, driving the particles to migrate to the collection area 21 .

[0062] Furthermore, in an embodiment of the present invention, the energy of the plasma high-energy electrons in step 2 is 5-10 eV, and the boiling point of water on the particle surface in step 3 is reduced to 45-50°C.

[0063] The specific particle dehydration process based on the above system is as follows: Several Laval nozzles 11 are arranged in a spaced spiral pattern along the inner wall of the acceleration cylinder 10. The external airflow is boosted to 1.5 MPa by the magnetic levitation turbine 40. Then, a supersonic nitrogen flow is injected through the array of 12 Laval nozzles 11 at a tangential angle of 75°, creating a gradient vortex flow field within the acceleration chamber with a central pressure of 5 kPa and an edge pressure of 20 kPa. The pressure distribution exhibits a gradient characteristic of low pressure at the center and high pressure at the edge.

[0064] Thermosensitive polymer particles are transported into the accelerating cylinder 10 through the guide tube 30. The outlet direction of the guide tube 30 forms a 75° angle with the tangent line of the inner wall of the accelerating cylinder 10, so that the particles enter the vortex flow field. Driven by the tangential airflow in the vortex flow field, the particles spiral upward along the cavity wall. Based on the principle of dynamic balance between centrifugal force and airflow drag, the particles can be suspended in an annular zone 10-15 mm from the central axis of the accelerator cylinder 10. Specifically, taking a thermosensitive polymer (PLA) particle with a diameter of 3 mm as an example, with a tangential velocity of 120 meters per second in the vortex flow field and a rotation radius of 0.5 meters, the centrifugal force is calculated to be approximately 0.024 Newtons based on the centrifugal force calculation method (first calculate the mass of the PLA particle, assuming a density of 1250 kilograms per cubic meter and approximating the particle as a sphere). The formula for the volume of a sphere is four-thirds times pi times the radius cubed. In this case, the radius is half the 3 mm diameter. After calculating the mass, the centrifugal force is equal to the mass times the square of the tangential velocity, divided by the rotation radius).

[0065] At the same time, calculate the drag force on the particle. Drag is the resistance exerted by the nitrogen on the particle, and its direction is opposite to the object's motion relative to the nitrogen. Given that the ambient gas is nitrogen, with a density of 1.25 kilograms per cubic meter, the drag coefficient is approximately 0.5, and the particle's frontal area is equal to pi times the square of the radius. The airflow drag is 0.5 times the drag coefficient times the nitrogen density times the frontal area times the square of the tangential velocity. This calculation yields a drag force of approximately 0.023 Newtons.

[0066] The nitrogen flow is designed as a spiral upflow pattern. The direction of the centrifugal force is radially outward, and the PLA particles are pushed upward by the vertical component of the airflow drag force. In this case, the component of the resultant force of the centrifugal force and the airflow drag force in a specific direction (vertical) is equal to the gravity. In other words, the resultant force of the centrifugal force and the airflow drag force is almost equal to the gravity acting on the PLA particles, but in the opposite direction.

[0067] The gravitational force on PLA particles is equal to their mass multiplied by the acceleration due to gravity (assuming the acceleration due to gravity is 9.8 meters per second squared), which is approximately 0.0011 Newtons. This allows the PLA particles to remain stably suspended. Conversely, knowing the gravitational force on the PLA particles allows for the selection of appropriate nitrogen flow parameters, ensuring stable suspension of the PLA particles under the dynamic balance between the centrifugal force of the vortex flow field and the drag force of the airflow. This principle is a mature technical principle that can be understood by those skilled in the art without requiring any ingenuity.

[0068] In the supersonic drying system's annular accelerating chamber, the water-laden PLA particles are subjected to a low pressure of approximately 10 kPa, which reduces the boiling point of water on their surface to 45-50°C (calculated according to the Clausius-Clapeyron equation). The PLA particles are propelled tangentially by the high-speed airflow, where moisture on their surfaces evaporates through frictional heat generated by the particles' own high-speed motion in the supersonic airflow, or through heating from the heating unit at the bottom of the accelerating chamber.

[0069] The water evaporation temperature is lower than the glass transition temperature of PLA and PVA, ensuring that the material does not undergo thermal degradation.

[0070] At the same time, the radio frequency electrode (13.56MHz) excites the nitrogen plasma flow, generating high-energy electrons (5-10eV), which bombard the water molecules in the pores inside the polymer particles, destroying the hydrogen bonds between them and the polymer chains. Then, driven by the low-pressure environment and the centrifugal force of the vortex flow field in the acceleration cylinder 10, the water migrates along the pores to the surface of the PLA particles. Then, it evaporates and dehydrates through the friction heat generated by the high-speed movement of the PLA particles themselves in the supersonic airflow or through the heating of the electric thermal resistor in the acceleration cylinder 10.

[0071] After dehydration, the density of the 1.25 g / cm³ PLA particles increases to 1.28 g / cm³, breaking the mechanical equilibrium. At this time, the centrifugal force exceeds the drag force and the gravity of the PLA particles, pushing the PLA particles to migrate toward the inner wall of the acceleration cylinder 10.

[0072] After the spiraling nitrogen flow leaves the acceleration cylinder 10, the PLA particles are subjected to centrifugal force and migrate toward the inner wall of the collection cylinder 20, causing the dehydrated PLA particles to escape from the vortex flow field. The dehydrated PLA particles fall to the collection area 21 under their own gravity for collection, while the nitrogen flow carries the evaporated water vapor through the discharge area 22 above the collection cylinder 20 for discharge.

[0073] Finally, during the particle drying process, considering the impact of particles with different moisture contents or different sizes on the drying results, the following adjustment scheme is adopted: like Figure 3 As shown, the full-field three-dimensional velocity field and particle size analyzer illuminates the vortex flow field through the pulsed laser at the bottom of the accelerator tube 10, and then uses the cross-frame CCD camera at the bottom of the accelerator tube 10 to capture the image of the particles in the vortex flow field. By processing the image using the autocorrelation or cross-correlation principle, 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.

[0074] The nitrogen gas flow rate or pressure of the Laval nozzle 11 is adjusted according to the measured particle size and distribution information.

[0075] Pressure Adjustment: If large particles are predominant, increase the inlet pressure to the Laval nozzle 11 to increase the nitrogen flow velocity. For example, increasing the inlet pressure from 1.5 MPa to 1.8 MPa will enhance the drag force of the nitrogen flow on large particles, ensuring they are better suspended in the vortex flow field, increasing their contact time with the hot airflow and promoting drying. If small particles predominate, reduce the inlet pressure to prevent them from rapidly leaving the drying area (low pressure environment) due to excessive airflow velocity, resulting in incomplete drying.

[0076] Flow Control: For large particles, increase the nitrogen flow rate to increase the turbulence in the vortex flow field, which helps disperse large particles, prevent agglomeration, and improve drying uniformity. When the proportion of large particles is high, increase the nitrogen flow rate. For small particles, reduce the nitrogen flow rate to slow their movement in the flow field, allowing them to have sufficient residence time in the drying area.

[0077] By continuously monitoring the movement of particles in the vortex flow field and combining this with information about their particle size, the water content can be indirectly inferred (generally, under the same conditions, particles with high water content will have different movement speeds and trajectories). When an increase in the proportion of particles with high water content is detected, the heat generation unit power (i.e., the electric thermal resistance power) is increased or the particle residence time in the vortex flow field is extended.

[0078] The drying area is then subdivided based on the particle distribution and moisture content in the vortex flow field. In areas with high moisture content, the plasma generator 12's energy output is increased to strengthen the destruction of hydrogen bonds between water and polymer chains, accelerating water migration and evaporation. In areas with low moisture content, the energy input is reduced to prevent over-drying of the particles.

[0079] Although the above describes the illustrative specific embodiments of the present invention so that those skilled in the art can understand the present invention, the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, all inventions and creations based on the concepts of the present invention are protected.

Claims

1. A supersonic drying system for particles, characterized in that: The collecting cylinder includes a collecting cylinder sleeved outside the accelerating cylinder, the gap between the two constitutes a collecting area, and the discharge area at the upper end of the collecting cylinder is higher than the upper end outlet of the accelerating cylinder; Multiple Laval nozzles are arranged on the inner wall of the accelerator tube in a spiral trajectory, with their outlet directions tangent to the inner wall of the accelerator tube, guiding the supersonic nitrogen flow to spiral upward around the central axis of the accelerator tube in a tangential direction, entraining the surrounding gas to form a vortex flow field; A guide tube extending from the outside of the collecting cylinder to the inside of the accelerating cylinder guides the thermosensitive polymer particles to the vortex flow field, so that the particles are suspended and spirally ascend under the action of the centrifugal force and drag force of the vortex flow field; The vortex flow field with low pressure in 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 evaporating through the heat generating unit in the acceleration cylinder; The plasma generator installed on the inner wall of the acceleration cylinder excites a high-energy electron beam in the nitrogen flow, destroying the hydrogen bonds between the water in the particle pores and the polymer chains, and using the low-pressure environment to accelerate the migration of the water to the particle surface, and then evaporated through the heat generation unit; After dehydration, the particle density changes, causing the centrifugal force and the drag force to become unbalanced, and the particles migrate toward the inner wall of the collection tube, escape 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 an air pipe connected to the Laval nozzle. The air pipe is connected to the magnetic levitation turbine, and the nitrogen flow is sucked and pressurized by the magnetic levitation turbine, and then transported to the Laval nozzle through the air pipe, so that the Laval nozzle ejects a supersonic nitrogen flow.

3. The supersonic drying system for particles according to claim 2, characterized in that: The magnetic levitation turbine pressurizes the nitrogen 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 nitrogen flow velocity along the tangential direction 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 group connected to a radio frequency current, the operating frequency of the radio frequency electrode group is 10-15 MHz, and the plasma electron density reaches 10¹ 0 -10¹² cm⁻³.

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

7. The supersonic drying system for particles according to claim 1, characterized in that: The heat generating unit is the friction heat between the particles and the supersonic nitrogen flow, or the heat source conducted by the electric thermal resistance in the acceleration cylinder to the supersonic nitrogen flow.

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

9. A particle dehydration method, characterized in that: The method is based on the supersonic drying system for particles according to any one of claims 1 to 8, and comprises the following steps: Step 1: The thermosensitive polymer particles are introduced tangentially into the vortex flow field formed by the supersonic nitrogen flow, and suspension is achieved through the dynamic balance between the centrifugal force and the drag force of the vortex flow field; Step 2: Plasma is excited in the vortex flow field, allowing high-energy electrons to penetrate the pores of the particles and destroy the hydrogen bonds between the water and the polymer chains in the pores of the particles; Step 3: 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 the particle surface. The frictional heat between the particles and the supersonic nitrogen flow or the heat transferred to the supersonic nitrogen flow evaporates the water on the particle surface. Step 4: After dehydration, the density of the particles increases, triggering an imbalance between the centrifugal force and the drag force, driving the particles to migrate to the collection area.

10. The particle dehydration method according to claim 9, characterized in that: The energy of the plasma high-energy electrons in step 2 is 5-10 eV, and the boiling point of water on the particle surface in step 3 is reduced to 45-50°C.

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