A device and method for preparing porous microspheres with adjustable particle size

Abstract

The invention provides a particle size adjustable porous microsphere preparation device and method, comprising a liquid supply device, an air supply device, a droplet generation device, an annular electrode plate and a particle solidification forming device; the droplet generation device comprises a nozzle, a pneumatic focusing cavity, an adjustable focusing orifice plate and a high-voltage electrostatic generator; the liquid supply device and the air supply device are respectively connected to the pneumatic focusing cavity, the annular electrode plate is located below the droplet generation device, and the particle solidification forming device is located below the annular electrode plate; the invention rationally organizes airflow and liquid flow fields and couples electrostatic technology, so that high-viscosity and easy-to-block liquid can be continuously and stably broken to generate droplets with uniform particle size, avoids fusion of viscoelastic droplets in the dripping process, adhesion in the freezing process, avoids the formation of large-particle porous microsphere particles and adhered porous microsphere particles, reduces the defective rate of porous microspheres, improves the sphericity, and makes the porous microsphere particle size uniform and controllable.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of acoustic microspheres for mobile phone speakers and the field of nano-ceramic materials, and in particular relates to a device and method for preparing porous microspheres with adjustable particle size that rationally organizes gas-liquid flow fields and couples high-voltage electrostatic fields, thereby achieving efficient preparation of microsphere particles with high sphericity, uniform particle size and adjustable particle size. Background Art

[0002] With the development of communication technology, small mobile communication devices have become the mainstream products in the market. The compact internal structure has also attracted widespread attention to micro speakers. However, due to their small size, micro speakers are prone to reduce sound quality. In order to eliminate low-frequency resonance and noise interference inside the speaker, micron-level sound-absorbing microspheres are filled in the back cavity of the speaker to improve acoustic performance.

[0003] At present, the main technologies for preparing micron-scale microspheres include fluidized bed granulation, high shear granulation, hot melt granulation and spray drying. The prepared microspheres have large and uneven particle size distribution, poor sphericity and rough surface of the microspheres. In engineering applications, they are manifested as poor fluidity, low space utilization and poor sound absorption. The droplet size formed by traditional methods is generally distributed in a spectrum. In order to achieve uniform droplet size in the granulation field, the particle size screening link is omitted. The existing technology can obtain a droplet group with uniform particle size based on the liquid droplet fragmentation mode under the action of electrostatics. However, for high-viscosity and easily coagulated base liquids, the nozzle is easily clogged, resulting in the inability to continue granulation. If the clogging problem is solved by increasing the diameter of the capillary nozzle, the droplet size obtained is too large, far exceeding the particle size requirements of the mobile phone speaker resonance cavity. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a particle size adjustable porous microsphere preparation device and method, including an air supply device, a liquid supply device, a droplet generation device and a particle solidification molding device. The droplet generation device reasonably organizes airflow and liquid flow, and the liquid flowing out of the capillary and the airflow in the pneumatic focusing cavity both flow out from the small hole. Due to the interaction between the gas and liquid phases, the liquid forms a stable cone, and a stable microjet is generated at the top of the liquid cone. The diameter of the microjet is much smaller than the capillary nozzle. The capillary nozzle is connected to a high-voltage electrostatic generator so that the liquid is charged when flowing through the capillary nozzle. The high-voltage electrostatic charge voltage is reasonably controlled so that the microjet fragmentation is always in a droplet fragmentation mode. The efficient organization of the airflow and liquid flow forms a finer jet, and a capillary nozzle with a larger diameter can be selected to prevent nozzle clogging, ensuring that the granulation process continues for a long time. The addition of static electricity can further reduce the droplet size, and at the same time, the droplet falling frequency is accelerated, thereby improving the droplet generation efficiency. The present invention is particularly suitable for continuously and stably breaking highly viscous and easily blocked liquids to generate droplets with uniform particle size, avoiding the fusion of viscoelastic droplets during the dripping process and the adhesion during the freezing process, and realizing the efficient preparation of microsphere particles with high sphericity, uniform particle size and adjustable and controllable particle size.

[0005] The technical solution of the present invention is: a particle size adjustable porous microsphere preparation device, comprising a liquid supply device, an air supply device, a droplet generating device, an annular electrode plate and a particle solidification forming device; the droplet generating device comprises a nozzle, a pneumatic focusing cavity, an adjustable focusing orifice plate and a high-voltage electrostatic generator; the nozzle is installed above the pneumatic focusing cavity, the adjustable focusing orifice plate is installed in the through hole at the bottom of the pneumatic focusing cavity, and the nozzle is connected to the high-voltage electrostatic generator; the liquid supply device and the air supply device are respectively connected to the pneumatic focusing cavity, the annular electrode plate is located below the droplet generating device, and the particle solidification forming device is located below the annular electrode plate; the adjustable focusing orifice plate is provided with a focusing circular hole, the annular electrode plate is provided with a circular through hole, and the nozzle, the focusing circular hole and the circular through hole are coaxially installed.

[0006] In the above solution, the droplet generating device further comprises an adjustable nozzle fixing member; a through groove matching the shape of the nozzle is provided at the bottom of the adjustable nozzle fixing member, and the nozzle is installed in the through groove.

[0007] Furthermore, the lower portion of the adjustable nozzle fixing piece is threadedly connected to the upper portion of the pneumatic focusing chamber.

[0008] In the above solution, the droplet generating device is also provided with a fixed bottom plate; the pneumatic focusing cavity is mounted on the fixed bottom plate.

[0009] In the above scheme, the structure of the annular electrode plate from top to bottom is an insulating plate, a conductive aluminum plate and an insulating plate.

[0010] In the above scheme, an air inlet pipe is provided on the side of the pneumatic focusing cavity, the inlet of the air inlet pipe is connected to the air supply device, and the outlet of the air inlet pipe is close to the outlet of the nozzle.

[0011] In the above scheme, the liquid supply device includes a magnetic stirrer, a liquid storage tank and a pressure pump; the liquid storage tank is placed on the magnetic stirrer, and the liquid storage tank is connected to the pressure pump.

[0012] In the above scheme, the particle solidification molding device includes a freezing tank and a filter; the freezing tank is located below the annular electrode plate, the filter is placed in the freezing tank, a low-temperature refrigerant is provided in the freezing tank, and the low-temperature refrigerant immerses the filter; the low-temperature refrigerant is liquid nitrogen.

[0013] In the above scheme, the high-voltage electrostatic generator uses a higher charging voltage of 10kV or more.

[0014] The above scheme further includes a bracket; the bracket is provided with a plurality of longitudinally arranged slots, and the fixed base plate and the annular electrode plate are fixed to the bracket through the plurality of longitudinally arranged slots.

[0015] In the above solution, the inner diameter of the nozzle is 0.3mm-0.7mm, and the outer diameter is 0.6mm-1mm.

[0016] A method for preparing the device for preparing porous microspheres with adjustable particle size comprises the following steps:

[0017] Opening the gas supply device to allow gas to enter the pneumatic focusing cavity of the droplet generation device;

[0018] Starting the liquid supply device to deliver the liquid to the nozzle of the droplet generating device;

[0019] Set the applied voltage value of the high-voltage electrostatic generator, the gas flow rate of the gas supply device, the liquid supply pressure of the liquid supply device, the distance between the nozzle and the adjustable focusing orifice plate, the distance between the nozzle and the annular electrode plate, and the distance between the annular electrode plate and the particle solidification molding device, and select the model of the adjustable focusing orifice plate;

[0020] A particle solidification molding device containing liquid nitrogen is installed under the annular electrode plate. The droplets falling from the adjustable focusing hole plate enter the liquid nitrogen and are frozen and formed. The solid particles are collected and transferred to a collection plate, and liquid nitrogen is poured into it to immerse it. The collection plate is placed in a vacuum freeze dryer and dried to obtain a microsphere product.

[0021] Compared with the prior art, the invention has the following beneficial effects: the invention rationally organizes the airflow and liquid flow field, and couples the electrostatic technology, so that the highly viscous and easily blocked liquid can be continuously and stably broken into droplets with uniform particle size. The fusion of viscoelastic droplets during the dripping process and the adhesion during the freezing process are avoided, and the formation of large-particle porous microsphere particles and adhesion porous microsphere particles are avoided, the defective rate of porous microspheres is reduced, the sphericity is improved, the porous microsphere particle size is uniform and controllable, and the operation is convenient. The droplet particle size can be changed by adjusting the liquid flow rate, gas flow rate or charging voltage, thereby controlling the particle size of the porous microsphere. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a device for preparing porous microspheres with adjustable particle size according to one embodiment of the present invention;

[0023] Figure 2 A droplet generating device according to an embodiment of the present invention;

[0024] Figure 3 It is a magnified scanning electron microscope picture of microspheres formed when two droplets merge in the prior art;

[0025] Figure 4 It is a magnified scanning electron microscope picture of microspheres formed when two liquid droplets are condensed in a freezing liquid obtained in the prior art;

[0026] Figure 5 This is a magnified scanning electron microscope image of microspheres formed when the obtained droplets are swung and dripped according to one embodiment of the present invention.

[0027] In the figure, 1. gas storage tank; 2. pressure reducer; 3. flow meter; 4. droplet generating device; 4-1. adjustable nozzle fixture; 4-2. nozzle; 4-3. pneumatic focusing cavity; 4-4. adjustable focusing orifice plate; 4-5. fixed bottom plate; 4-6. air inlet pipe; 4-7. high-voltage electrostatic generator; 5. annular electrode plate; 6. filter screen; 7. freezing tank; 8. bracket; 9. magnetic stirrer; 10. liquid storage tank; 11. pressure pump. DETAILED DESCRIPTION

[0028] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0030] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] Figure 1 and 2 The figure shows a preferred embodiment of the particle size adjustable porous microsphere preparation device of the present invention, which includes a liquid supply device, an air supply device, a droplet generation device, an annular electrode plate 5 and a particle solidification molding device; the droplet generation device includes a nozzle 4-2, a pneumatic focusing chamber 4-3, an adjustable focusing orifice plate 4-4 and a high-voltage electrostatic generator 4-7; the nozzle 4-2 is installed above the pneumatic focusing chamber 4-3, a through hole of a certain diameter is provided at the bottom of the pneumatic focusing chamber 4-3, the adjustable focusing orifice plate 4-4 is installed in the through hole at the bottom of the pneumatic focusing chamber 4-3, and a sealing rubber ring is provided, which can be replaced according to specific production needs. The nozzle 4-2 is connected to the high-voltage electrostatic generator 4-7, and the high-voltage electrostatic generator 4-7 is grounded. The liquid supply device and the air supply device are respectively connected to the pneumatic focusing chamber 4-3, the annular electrode plate 5 is located below the droplet generation device, and the particle solidification molding device is located below the annular electrode plate 5. The center of the adjustable focusing hole plate 4-4 is provided with a focusing circular hole, the annular electrode plate 5 is provided with a circular through hole, and the nozzle 4-2, the focusing circular hole and the circular through hole are coaxially installed.

[0032] According to this embodiment, preferably, the droplet generating device 4 further includes an adjustable nozzle fixture 4-1; the inner bottom of the adjustable nozzle fixture 4-1 is provided with a through groove matching the shape of the nozzle 4-2, and the nozzle 4-2 is installed in the through groove to prevent the nozzle 4-2 from shaking during use, thereby ensuring the coaxiality of the nozzle of the nozzle, the focusing circular hole of the adjustable focusing orifice plate, and the circular through hole of the annular electrode plate. Preferably, the through groove is a stepped groove.

[0033] The adjustable nozzle fixture 4-1 is divided into two parts, the upper part is a grip handle, the outer wall is smooth, and the lower part of the adjustable nozzle fixture 4-1 is threadedly connected to the upper part of the pneumatic focusing cavity 4-3, thereby adjusting the distance between the nozzle 4-2 and the adjustable focusing orifice plate 4-4. Preferably, the outer wall of the lower part of the adjustable nozzle fixture 4-1 is provided with an external thread, and the upper part of the pneumatic focusing cavity 4-3 is provided with an internal thread. The diameter of the thread can be used as a scale to determine the height of the nozzle fixture 4-1, and the distance between the nozzle 4-2 and the focusing circular hole can be adjusted according to specific production needs.

[0034] According to this embodiment, preferably, the droplet generating device 4 is also provided with a fixed bottom plate 4-5; the pneumatic focusing cavity 4-3 is installed on the fixed bottom plate 4-5, the pneumatic focusing cavity 4-3 is connected to the top of the fixed bottom plate 4-5 by a sealant, and the annular electrode plate 5 is installed below the fixed bottom plate 4-5.

[0035] According to this embodiment, preferably, the structure of the annular electrode plate 5 is an insulating plate, a conductive aluminum plate and an insulating plate from top to bottom. The insulating plate, the conductive aluminum plate and the insulating plate are provided with circular through holes in the center, with diameters of 30 mm, 25 mm and 25 mm respectively, which can realize the electric field effect generated by the annular electrode plate 5 with a diameter of 5 mm, and at the same time prevent air from encountering liquid nitrogen to form water vapor attached to the conductive aluminum plate and affect the electric field effect.

[0036] According to this embodiment, preferably, an air inlet pipe 4-6 is provided on the side of the pneumatic focusing cavity 4-3, and the inlet of the air inlet pipe 4-6 is connected to the air supply device. In order to avoid large disturbances of the air flow at the focusing hole, the outlet of the air inlet pipe 4-6 is close to the outlet of the nozzle 4-2.

[0037] According to this embodiment, preferably, the adjustable focusing hole plate 4-4 is provided with a focusing circular hole with a diameter of 1-5 mm in the center. If the diameter is smaller than this diameter range, the droplets will adhere to the fixed bottom plate 4-5. If the diameter is larger than this diameter range, the airflow has no significant effect on it. The focusing hole plate 4-4 cooperates with the through hole at the bottom of the pneumatic focusing cavity 4-3 and is provided with a sealing rubber ring to ensure sealing. The focusing hole diameter can be adjusted according to specific production requirements.

[0038] According to this embodiment, preferably, the gas supply device includes a gas tank 1, a pressure reducer 2, and a flow meter 3; the gas tank 1 is connected to the pressure reducer 2 and the flow meter 3 through a first connecting pipe. The other end of the first connecting pipe is connected to the air inlet pipe 4-6 on the side of the pneumatic focusing cavity 4-3. Such a setting can ensure stable gas supply and real-time monitoring of the air inlet flow rate; the liquid in the gas tank 1 is helium to ensure operational safety; the flow meter 3 uses a glass rotor and is equipped with a regulating valve.

[0039] According to this embodiment, preferably, the liquid supply device includes a magnetic stirrer 9, a liquid storage tank 10 and a pressure pump 11; the liquid storage tank 10 is placed on the magnetic stirrer 9, the liquid storage tank 10 is connected to the pressure pump 11, and the nozzle 4-2 is connected to the pressure pump 11 through a connecting pipe. The liquid storage tank 10 contains a base liquid of an acoustic material used to prepare porous microspheres, and the magnetic stirrer 9 is placed under the liquid storage tank 10. The liquid is stirred by a rotor to make the particles evenly distributed, so as to avoid the precipitation of suspended particles in the base liquid, change the physical properties of the liquid, and further affect the sound absorption capacity of the microspheres; the pump 11 uses a pressure pump to achieve a large flow rate and stable liquid supply, and the liquid storage tank 10 is connected to the pressure pump 11 through a second connecting pipe.

[0040] According to this embodiment, preferably, the particle solidification molding device includes a freezing tank 7 and a filter 6; the freezing tank 7 is located below the annular electrode plate 5, and the filter 6 is placed in the freezing tank 7. A low-temperature refrigerant is provided in the freezing tank 7, and the low-temperature refrigerant immerses the filter 6. Preferably, the freezing tank 7 and the filter 6 are made of stainless steel, and the filter 6 is suspended in the freezing tank 7 by an insulating hook. The height and diameter of the filter 6 are smaller than the height and diameter of the freezing tank 7 to avoid contact between the filter 6 and the wall of the freezing tank 7, thereby destroying the sphericity and integrity of the microspheres. The low-temperature refrigerant is liquid nitrogen.

[0041] According to this embodiment, preferably, it also includes a bracket 8; the bracket 8 is provided with a plurality of longitudinally arranged slots, and the fixed base plate 4-5 and the annular electrode plate 5 are fixed to the bracket 8 by means of a plurality of longitudinally arranged slots, and their positions can be flexibly changed, so that the inter-electrode distance between the nozzle 4-2 and the annular electrode plate 5 and the distance between the annular electrode plate 5 and the freezing tank 7 can be adjusted according to specific production needs, so that the inter-electrode distance between the nozzle 4-2 and the annular electrode plate 5 and the distance between the annular electrode plate 5 and the freezing tank 7 can be adjusted.

[0042] According to this embodiment, preferably, the inner diameter of the nozzle 4-2 is 0.3mm-0.7mm, and the outer diameter is 0.6mm-1mm. This aperture range can ensure that the problem of nozzle clogging does not occur while producing droplets with the smallest possible particle size, thereby ensuring the feasibility of production; the material is stainless steel.

[0043] The first connecting tube and the second connecting tube are made of silicone hose.

[0044] According to this embodiment, preferably, the high-voltage electrostatic generator 4-7 uses a higher charging voltage of 10kV or more, which can avoid the appearance of large particles and irregular-shaped porous microspheres. Droplets are generated at intervals on both sides of the jet axis and drip in the form of swinging drops, thereby reducing the defective rate of porous microspheres and improving the sphericity.

[0045] A method for preparing the device for preparing porous microspheres with adjustable particle size comprises the following steps:

[0046] Open the gas supply device to allow gas to enter the pneumatic focusing cavity 4-3 of the droplet generation device;

[0047] Start the liquid supply device to deliver the liquid to the nozzle 4-2 of the droplet generating device;

[0048] Set the applied voltage value of the high-voltage electrostatic generator 4-7, the gas flow rate of the gas supply device, the liquid supply pressure of the liquid supply device, the distance between the nozzle 4-2 and the adjustable focusing orifice plate 4-4, the distance between the nozzle 4-2 and the annular electrode plate 5, the distance between the annular electrode plate 5 and the particle solidification molding device, and select the model of the adjustable focusing orifice plate 4-4;

[0049] A particle solidification molding device containing liquid nitrogen is installed under the annular electrode plate 5, and the droplets falling from the adjustable focusing hole plate 4-4 enter the liquid nitrogen to be frozen and formed. The solid particles are collected and transferred to a collection plate, and liquid nitrogen is poured into it to immerse it. The collection plate is placed in a vacuum freeze dryer and dried to obtain a microsphere product.

[0050] According to this embodiment, preferably, the method for preparing the device for preparing porous microspheres with adjustable particle size comprises the following steps:

[0051] Open the valve of the gas storage tank 1 of the gas supply device, and open the pressure reducer 2 and the flow meter 3, and allow the gas to be supplied at a certain flow rate for a period of time until the reading of the flow meter 3 is stable;

[0052] Start the magnetic stirrer 9 to stir the liquid in the liquid storage tank 10. After stirring evenly, start the pressure pump 11 to transport the liquid from the liquid storage tank 10 to the nozzle 4-2;

[0053] According to the requirements of actual production for product parameters, the atomized droplet particle size parameters are precisely controlled by adjusting the height of the annular electrode plate 5, the fixed bottom plate 4-5, the adjustable nozzle fixing part 4-1, the model of the adjustable focusing hole plate 4-4, the applied voltage value of the high-voltage electrostatic generator 4-7, the liquid supply pressure of the pressure pump 11, and the gas supply flow rate of the gas storage tank 1;

[0054] A particle solidification molding device containing liquid nitrogen is installed under the annular electrode plate 5, and the droplets falling from the focusing hole enter the liquid nitrogen to be frozen and formed. After running for a period of time, the high-voltage electrostatic generator 4-7, the valve of the gas tank 1, and the pressure pump 11 are turned off in sequence, and the solid particles collected in the filter screen 6 are transferred to the collection plate and poured with liquid nitrogen to immerse it. The collection plate is placed in a vacuum freeze dryer and dried for 24 hours to obtain the final microsphere product.

[0055] The droplet generation device of the present invention rationally organizes airflow and liquid flow, and the liquid flowing out of the capillary and the airflow in the pneumatic focusing cavity both flow out of the small hole. Due to the interaction between the gas and liquid phases, after the liquid forms a stable cone, a stable microjet is generated at the top of the liquid cone, and the diameter of the microjet is much smaller than the capillary nozzle. In the case of no charge, the droplet size formed is about 1.9 times the diameter of the microjet. The capillary nozzle is connected to a high-voltage electrostatic generator so that the liquid is charged when flowing through the capillary nozzle. The high-voltage electrostatic charge voltage is rationally controlled so that the microjet fragmentation is always in a droplet fragmentation mode. The efficient organization of the airflow and liquid flow forms a finer jet. According to the specific porous microsphere preparation requirements, compared with the prior art, a capillary nozzle with a larger diameter can be selected to prevent nozzle clogging, so as to ensure that the granulation process continues for a long time. The addition of static electricity can further reduce the droplet size, and at the same time, the droplet falling frequency is accelerated, thereby improving the droplet generation efficiency.

[0056] After the droplets are generated, they enter the particle solidification molding device. To ensure that the porous microspheres finally formed have good sphericity, it is also necessary to avoid the fusion of two or more droplets. After the droplets are generated, the downward dripping process is often accompanied by changes in the shape of the droplets. The deformation characteristics of each droplet in the process of water droplets and alcohol droplets falling are similar, and the droplets will not fuse. If the base liquid used to prepare porous microspheres has a certain viscoelasticity, the previous droplet will stretch in the horizontal direction, and the next droplet may stretch in the vertical direction first. When the droplet generation frequency is high, the front and back droplets will often merge to form a large droplet, such as Figure 3 In addition, during the freezing process, if the first drop enters the liquid nitrogen first but has not yet been completely cooled, and the second drop falls to the same position, the two droplets will also be condensed together in the freezing liquid, forming the shape of two microspheres sticking together, as shown in Figure 2. Figure 4 To avoid the above problems, a higher charging voltage is preferred, and the droplets are generated at intervals on both sides of the jet axis and drip in the form of swinging drops, so as to reduce the defective rate of porous microspheres and improve the sphericity, as shown in Figure 1. Figure 5 shown.

[0057] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0058] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A device for preparing porous microspheres with adjustable particle size, characterized in that: It comprises a liquid supply device, a gas supply device, a liquid droplet generating device, a ring-shaped electrode plate (5) and a particle solidification forming device; The droplet generating device comprises a nozzle (4-2), a pneumatic focusing cavity (4-3), an adjustable focusing orifice plate (4-4) and a high-voltage electrostatic generator (4-7); the nozzle (4-2) is installed above the pneumatic focusing cavity (4-3), the adjustable focusing orifice plate (4-4) is installed in a through hole at the bottom of the pneumatic focusing cavity (4-3), and the nozzle (4-2) is connected to the high-voltage electrostatic generator (4-7); a focusing circular hole with a diameter of 1-5 mm is arranged at the center of the adjustable focusing orifice plate (4-4); The liquid supply device and the gas supply device are respectively connected to the pneumatic focusing cavity (4-3); the annular electrode plate (5) is located below the droplet generation device; and the particle solidification forming device is located below the annular electrode plate (5); the adjustable focusing hole plate (4-4) is provided with a focusing circular hole, the annular electrode plate (5) is provided with a circular through hole, and the nozzle (4-2), the focusing circular hole and the circular through hole are coaxially mounted; The droplet generating device (4) further comprises an adjustable nozzle fixing part (4-1); a through groove matching the shape of the nozzle (4-2) is provided at the bottom of the adjustable nozzle fixing part (4-1), and the nozzle (4-2) is installed in the through groove.

2. The device for preparing porous microspheres with adjustable particle size according to claim 1, characterized in that: The lower part of the adjustable nozzle fixing member (4-1) is threadedly connected to the upper part of the pneumatic focusing cavity (4-3).

3. The device for preparing porous microspheres with adjustable particle size according to claim 1, characterized in that: The inner diameter of the nozzle (4-2) is 0.3 mm-0.7 mm, and the outer diameter is 0.6 mm-1 mm.

4. The device for preparing porous microspheres with adjustable particle size according to claim 1, characterized in that: An air inlet pipe (4-6) is provided on the side of the pneumatic focusing cavity (4-3); the inlet of the air inlet pipe (4-6) is connected to the air supply device; and the outlet of the air inlet pipe (4-6) is close to the outlet of the nozzle (4-2).

5. The device for preparing porous microspheres with adjustable particle size according to claim 1, characterized in that: The liquid supply device comprises a magnetic stirrer (9), a liquid storage tank (10) and a pressure pump (11); the liquid storage tank (10) is placed on the magnetic stirrer (9), and the liquid storage tank (10) is connected to the pressure pump (11).

6. The device for preparing porous microspheres with adjustable particle size according to claim 1, characterized in that: The particle solidification molding device comprises a freezing tank (7) and a filter screen (6); the freezing tank (7) is located below the annular electrode plate (5), the filter screen (6) is placed in the freezing tank (7), a low-temperature refrigerant is provided in the freezing tank (7), the low-temperature refrigerant immerses the filter screen (6), and the low-temperature refrigerant is liquid nitrogen.

7. The device for preparing porous microspheres with adjustable particle size according to claim 1, characterized in that: The high-voltage electrostatic generator (4-7) uses a charging voltage of 10 kV or more.

8. The device for preparing porous microspheres with adjustable particle size according to claim 1, characterized in that: It also comprises a bracket (8) and a fixed base plate (4-5); the bracket (8) is provided with a plurality of longitudinally arranged slots, and the fixed base plate (4-5) and the annular electrode plate (5) are fixed to the bracket (8) via the plurality of longitudinally arranged slots.

9. A method for preparing a porous microsphere with adjustable particle size according to any one of claims 1 to 8, characterized in that: The following steps are involved: Opening the gas supply device to allow gas to enter the pneumatic focusing cavity (4-3) of the droplet generation device; Starting the liquid supply device to deliver the liquid to the nozzle (4-2) of the droplet generating device; Setting the applied voltage value of the high-voltage electrostatic generator (4-7), the gas flow rate of the gas supply device, the liquid supply pressure of the liquid supply device, the distance between the nozzle (4-2) and the adjustable focusing orifice plate (4-4), the distance between the nozzle (4-2) and the annular electrode plate (5), and the distance between the annular electrode plate (5) and the particle solidification molding device, and selecting the model of the adjustable focusing orifice plate (4-4); A particle solidification molding device containing liquid nitrogen is installed below the annular electrode plate (5), and the droplets falling from the adjustable focusing hole plate (4-4) enter the liquid nitrogen to be frozen and molded. The solid particles are collected and transferred to a collection plate, and then poured with liquid nitrogen to immerse them. The collection plate is placed in a vacuum freeze dryer for drying to obtain a microsphere product.

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