Method for realizing cyclic coating of powder by composite fluidization process

Abstract

The invention discloses a method for realizing cyclic coating of powder by a composite fluidization process. The coating method comprises the following steps: S1, preparing a coating solution; s2, fluidizing gas is introduced; s3, heating the fluidized bed (as required); s4, feeding and fluidizing through ultrasonic vibration; s5, atomizing and spraying the coating solution; s6, carrying out cyclone separation on the primary coated powder; s7, dynamically drying the primary coated powder; s8, vibrating, feeding and fluidizing the primary coated powder again; s9, coating the powder for the second time; and S10, circulating the steps S6 to S9. According to the coating method, circulating continuous coating of the powder can be achieved, meanwhile, the powder is dispersed and distributed in the fluidized bed in a composite fluidization mode combining ultrasonic vibration and gas fluidization, and then a coating layer is more uniform.

Description

Technical Field

[0001] The present invention relates to the technical field of fluidized bed coating, and particularly relates to a method for realizing powder circulation coating by a composite fluidization process. Background Art

[0002] A fluidized bed is a device that uses a fluid such as a gas or a liquid with a certain kinetic energy to suspend solid particles. Since the solid particles are in a suspended state and are in full contact and mixing with the gas or liquid, rapid and full reactions of gas-solid phase or liquid-solid phase can be achieved. Therefore, fluidized beds are widely used in chemical processes, combustion, coal ash treatment, powder treatment, pharmaceutical industry, environmental protection industry, etc.

[0003] The applications of fluidized beds in the powder field mainly include powder drying, cooling, solid separation, granulation, etc. However, there are few literature reports on the application of fluidized beds in powder coating. The main reason is that when a fluidized bed is applied to powder coating, the coating layer is uneven and it is very difficult to achieve continuous cyclic coating.

[0004] CN 118059770 A discloses a powder material coating process based on a fluidized bed, which mainly includes six steps: preparing a coating solution, spraying the coating solution, collecting fluidized coating images, the real-time coating area ratio, determining the drying and curing of the substrate, and completing the preparation of powder material coating. Although this invention gives a method for detecting the coating effect of powder materials, it does not achieve continuous cyclic coating, but only single coating. In addition, the coating process only uses a single fluidization method of gas fluidization, and it is very difficult for the powder to be completely dispersed, and the coating layer cannot be made uniform. The patents of CN 107952402A and CN 117696394A also disclose the processes and devices of fluidized bed coating respectively, but they all have the disadvantages that the single fluidization method makes the coating layer uneven and continuous cyclic coating is not achieved. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a method for realizing powder circulation coating by a composite fluidization process. When the method of the present invention is used for powder material coating, the powder materials are diffusely distributed and are in full contact and mixing with the coating solution, so that the powder coating layer is uniform and cyclic coating of the powder can be achieved multiple times.

[0006] The method for realizing powder circulation coating by the composite fluidization process of the present invention includes the following steps:

[0007] S1. Prepare the coating solution: Prepare the solution for coating according to the requirements of powder coating in a certain proportion;

[0008] S2. Introduce fluidizing gas: Introduce an inert gas with a certain pressure into the air curtain, and the air curtain is located at the bottom of the fluidized bed;

[0009] S3. Heating the fluidized bed (as required): According to the need for powder coating, turn on the heater to heat the inner wall of the fluidized bed to a certain temperature and keep it warm.

[0010] S4. Ultrasonic vibration feeding and fluidization: According to the need for powder coating, select the parameters, turn on the ultrasonic vibrating screen and the electromagnetic feeder. After the powder to be coated undergoes ultrasonic vibration, the powder is evenly dispersed and falls into the fluidized bed through the screen. The powder that has been vibrationally dispersed is blown by the air flow and is diffusely distributed in the fluidized bed.

[0011] S5. Atomizing and spraying the coating solution: Feed the coating solution into the atomizer and spray it into the fluidized bed. The powder and the coating solution come into full contact and mix in the fluidized bed to complete one coating.

[0012] S6. Cyclone separation of the powder after the first coating: The fluidizing gas carrying the coated powder passes through the cyclone separator to separate the powder from the gas.

[0013] S7. Dynamic drying of the powder after the first coating: The separated powder is pneumatically conveyed through the heated pipeline to achieve the drying treatment of the powder.

[0014] S8. Re - vibrating, feeding and fluidizing the powder after the first coating: According to the requirements of powder coating, select the parameters, turn on the ultrasonic vibrating screen and the electromagnetic feeder. The coated powder undergoes ultrasonic vibration, the powder is evenly dispersed and falls into the fluidized bed through the screen. The powder that has been vibrationally dispersed is blown by the air flow and is diffusely distributed in the fluidized bed.

[0015] S9. Secondary coating of the powder: The diffusely distributed powder is further dispersed by the fluidizing gas purge and comes into contact and mix with the coating solution to complete the secondary coating.

[0016] S10. Repeat steps S6 - S9: Implement steps S6 - S9 in a cycle to achieve continuous cyclic coating of the powder until the coating requirements are met.

[0017] The method principle and effects of realizing powder circulation continuous coating by the composite fluidization process of the present invention are as follows: First, the present invention uses two ways of vibration dispersion and gas dispersion to perform composite fluidization on the powder, making the powder distribution dispersed and uniform. When coating, it is fully contacted and uniformly mixed with the coating solution, so that the powder coating layer is more uniform. Among them, each mesh hole of the vibrating screen mesh is equivalent to a channel, and the feeding of the present invention is multi-channel feeding. Compared with single-channel feeding, the powder can be completely dispersed. Second, the present invention realizes the continuous cyclic coating of the powder, avoiding the problem that the coating layer size of single coating does not meet the requirements. The powder and the air flow are separated by a cyclone separator, and the gas is recompressed and recycled as the fluidization gas, while the powder continues to be coated. Before the secondary coating, dynamic drying treatment is added, so that the powder is in a dry state when performing the next coating, which can solidify the powder coating layer. Therefore, when passing through the ultrasonic vibrating screen in the next coating, the coating layer will not fall off or deform. Third, the present invention uses an ultrasonic vibrating screen as the feeding device. In addition to dispersing the powder, it can also control the size of the powder particles, that is, select different mesh numbers of the screen according to the requirements of the powder particle size. Therefore, the selection of parameters such as the mesh number and vibration frequency of the screen before each coating is determined according to the particle size of the powder. Fourth, the judgment condition for stopping coating in the present invention is the number of coatings, which can be determined according to empirical values or obtained through simulation calculations.

[0018] Compared with the existing technology, the present invention combines the two ways of vibration dispersion and gas dispersion to realize the composite fluidization of the powder, making the powder uniformly dispersed, so that the powder coating layer is uniformly distributed. At the same time, the continuous cyclic coating of the powder is realized, making the size of the powder coating layer controllable. Description of the Drawings

[0019] Figure 1 It is the flow chart of the powder cyclic coating by the composite fluidization of the present invention;

[0020] Figure 2 It is the surface morphology photo of the aluminum powder after coating in Example 1;

[0021] Figure 3 It is the surface morphology photo of the aluminum-lithium alloy powder after coating in Example 2. Detailed Embodiments

[0022] In order to better understand the present invention, the method of realizing powder cyclic coating by the composite fluidization process of the present invention will be further described in detail below with reference to the embodiments.

[0023] The method of realizing powder cyclic coating by the composite fluidization process of the present invention includes the following steps:

[0024] S1. Prepare the coating solution: According to the powder coating requirements, prepare the solution for coating according to a certain ratio;

[0025] S2. Introducing fluidizing gas: Introducing a certain pressure of inert gas into the gas curtain, which is located at the bottom of the fluidized bed;

[0026] S3. Heating the fluidized bed (on demand): according to the needs of powder coating, turn on the heater, heat the inner wall of the fluidized bed to a certain temperature and keep it warm;

[0027] S4, Ultrasonic vibration feeding fluidization: According to the needs of powder coating, select parameters, turn on the ultrasonic vibration screen and electromagnetic feeder, and the powder to be coated is subjected to ultrasonic vibration, the powder is evenly dispersed, and falls into the fluidized bed through the screen. The powder that has been vibrated and dispersed is blown away by the airflow and dispersed in the fluidized bed;

[0028] S5, atomization spraying of coating solution: the coating solution is introduced into the atomizer and sprayed into the fluidized bed, the powder and the coating solution are fully contacted and mixed in the fluidized bed, and a coating is completed;

[0029] S6. Cyclone separation of primary coated powder: The fluidizing gas carrying the coated powder passes through the cyclone separator to separate the powder from the gas;

[0030] S7, Dynamic drying of primary coated powder: The separated powder is pneumatically conveyed and passed through a heated pipeline to achieve powder drying;

[0031] S8. Re-vibration and fluidization of the coated powder: According to the requirements of powder coating, select parameters, turn on the ultrasonic vibrating screen and electromagnetic feeder, and the coated powder is ultrasonically vibrated, the powder is evenly dispersed, and falls into the fluidized bed through the screen. The powder that has been vibrated and dispersed is blown away by the airflow and dispersed in the fluidized bed;

[0032] S9, secondary coating of powder: the dispersed powder is further dispersed by fluidizing gas blowing, and is contacted and mixed with the coating solution to complete the secondary coating;

[0033] S10, repeating steps S6 to S9: cyclically implementing steps S6 to S9 to achieve continuous cyclic coating of powders until the coating requirements are met.

[0034] The present invention provides a specific solution as follows: the coating process is completed in an environment protected by an inert gas, that is, the entire fluidized bed device is in an environment protected by an inert gas.

[0035] The present invention provides a specific solution as follows: In step S4, the principle of parameter selection is based on the particle size of the powder to be coated. That is, the size of the powder particles to be coated determines the parameters such as the mesh size, vibration frequency, amplitude, and ultrasonic frequency.

[0036] The specific solution provided by the present invention is as follows: In step S6, the separated gas is recompressed to a certain pressure and introduced into the air curtain, and then enters the fluidized bed through the air curtain and continues to be used as the fluidizing gas.

[0037] The specific solution provided by the present invention is as follows: In step S8, the screen with appropriate mesh number is used, and the principles for selecting the parameters of vibration frequency, amplitude, ultrasonic frequency, and feeding frequency are determined according to the particle size of the powder.

[0038] The specific solution provided by the present invention is as follows: In step S10, the judgment condition for stopping coating is the number of cycles.

[0039] The specific solution provided by the present invention is as follows: In step S10, the number of coating times is determined according to experience or can also be obtained through simulation calculation.

[0040] Example 1

[0041] Aluminum powder with D50 = 8 ± 1 μm is coated with paraffin, and the thickness of the coating layer is required to be not less than 0.01 μm. The coating process includes the following steps:

[0042] S1. Prepare the coating solution: Mix paraffin and petroleum ether in a certain proportion and heat to 60 ± 5 °C;

[0043] S2. Introduce the fluidizing gas: Introduce high-purity argon with a pressure of 0.6 ± 0.1 MPa into the air curtain at the bottom of the fluidized bed;

[0044] S3. Heat the fluidized bed (as required): Turn on the heater, heat the inner wall of the fluidized bed to 80 ± 10 °C and keep it warm;

[0045] S4. Ultrasonic vibration feeding and fluidization: Use a 1000-mesh screen, adjust parameters such as vibration frequency of 20 Hz, amplitude of 3 mm, ultrasonic frequency of 40 Hz, and feeding frequency of 5 Hz, turn on the ultrasonic vibrating screen and the electromagnetic feeder, so that the aluminum powder to be coated is vibrated and dispersed, and then falls into the fluidized bed through the screen. The already vibrated and dispersed powder is blown by the air flow and diffused in the fluidized bed;

[0046] S5. Atomized spraying of the coating solution: Introduce the paraffin solution dissolved in petroleum ether into the atomizer and spray it into the fluidized bed. The powder and the coating solution are in full contact and mixed in the fluidized bed to complete one coating;

[0047] S6. Cyclone separation of the powder coated once: The fluidizing gas carrying the coated aluminum powder passes through the cyclone separator to separate the aluminum powder from the argon. The separated argon is recompressed and introduced into the fluidized bed and continues to be used as the fluidizing gas;

[0048] S7. Dynamic drying of the powder after the first coating: The separated aluminum powder is pneumatically conveyed through a pipeline heated to 100 ± 10 °C to achieve the drying treatment of the aluminum powder.

[0049] S8. Re - vibration feeding and fluidization of the powder after the first coating: Select a 1000 - mesh sieve, adjust parameters such as vibration frequency 20 Hz, amplitude 3 mm, ultrasonic frequency 50 Hz, and feeding frequency 4.5 Hz. Turn on the ultrasonic vibrating sieve and electromagnetic feeder, so that the aluminum powder after the first coating falls into the fluidized bed through the sieve. The already vibration - dispersed powder is blown by the air flow and diffusely distributed in the fluidized bed.

[0050] S9. Secondary coating of the powder: The aluminum powder is dispersed by high - purity argon and contacted and mixed with the coating solution to complete the secondary coating.

[0051] S10. Repeat steps S6 - S9: Implement steps S6 - S9 in a cycle to achieve continuous cyclic coating of the aluminum powder. Stop coating after 27 cycles.

[0052] The photo of the coated aluminum powder in this example is as Figure 2 shown, and it can be seen that the surface coating of the coated aluminum powder is uniform and continuous.

[0053] In this example, the selection basis of the ultrasonic vibrating sieve parameters in steps S4 and S8 is that the particle size of the aluminum powder to be coated is D50 = 8 ± 1 μm, and the requirement of the coating layer thickness is not less than 0.01 μm.

[0054] Example 2

[0055] Use fluororubber to coat aluminum - lithium alloy powder with D50 = 13 ± 1 μm, and the requirement of the coating layer thickness is not less than 0.015 μm. The coating process includes the following steps:

[0056] S1. Prepare the coating solution: Mix fluororubber and ethyl acetate evenly in a certain proportion and heat to 80 ± 5 °C.

[0057] S2. Introduce the fluidizing gas: Introduce high - purity argon with a pressure of 0.8 ± 0.1 MPa into the fluidized bed.

[0058] S3. Heat the fluidized bed (as needed): Turn on the heater, heat the inner wall of the fluidized bed to 100 ± 10 °C and keep it warm.

[0059] S4. Ultrasonic vibration feeding and fluidization: Use a 600 - mesh sieve, adjust parameters such as vibration frequency 18 Hz, amplitude 3.5 mm, ultrasonic frequency 35 Hz, and feeding frequency 5 Hz. Turn on the ultrasonic vibrating sieve and electromagnetic feeder, so that the aluminum - lithium alloy powder to be coated is vibration - dispersed and then falls into the fluidized bed through the sieve. The already vibration - dispersed powder is blown by the air flow and diffusely distributed in the fluidized bed.

[0060] S5. Coating solution atomization spraying: The fluororubber solution dissolved in ethyl acetate is introduced into an atomizer and sprayed into the fluidized bed. The aluminum-lithium alloy powder and the coating solution are in full contact and mixed in the fluidized bed to complete the first coating.

[0061] S6. Cyclone separation of the powder after the first coating: The fluidizing gas carrying the coated aluminum-lithium alloy powder passes through a cyclone separator to separate the powder from argon. The separated argon is recompressed and introduced into the fluidized bed to continue to be used as the fluidizing gas.

[0062] S7. Dynamic drying of the powder after the first coating: The separated aluminum-lithium alloy powder is pneumatically conveyed through a pipe heated to 120 ± 10 °C to achieve the drying treatment of the aluminum-lithium alloy powder.

[0063] S8. Re-vibrating feeding and fluidization of the powder after the first coating: A 600-mesh sieve is selected, and parameters such as the vibration frequency of 22 Hz, the amplitude of 3.5 mm, the ultrasonic frequency of 45 Hz, and the feeding frequency of 4.0 Hz are adjusted. The ultrasonic vibrating screen and the electromagnetic feeder are turned on, so that the aluminum-lithium alloy powder after the first coating falls into the fluidized bed through the sieve. The already vibration-dispersed powder is blown by the airflow and diffusely distributed in the fluidized bed.

[0064] S9. Secondary coating of the powder: The aluminum-lithium alloy powder is dispersed by high-purity argon and contacted and mixed with the fluororubber ethyl acetate solution to complete the secondary coating.

[0065] S10. Repeat steps S6 - S9: Steps S6 - S9 are cyclically implemented to achieve continuous cyclic coating of the aluminum-lithium alloy powder. After 35 cycles, the coating is stopped.

[0066] The photo of the aluminum-lithium alloy powder after coating in this embodiment is as Figure 3 shown. It can be seen that the surface coating of the aluminum-lithium alloy powder after coating is also uniform and continuous.

[0067] In this embodiment, the selection basis of the parameters of the ultrasonic vibrating screen in steps S4 and S8 is the requirement that the particle size of the aluminum powder to be coated is D50 = 13 ± 1 μm and the coating thickness is not less than 0.015 μm.

Claims

1. A method for realizing powder circulation coating by composite fluidization process, characterized in that: The following steps are involved: S1. Prepare coating solution: prepare the coating solution in a certain proportion according to the coating requirements of the powder; S2. Introducing fluidizing gas: Introducing a certain pressure of inert gas into the gas curtain, which is located at the bottom of the fluidized bed; S3, heating the fluidized bed: according to the needs of powder coating, turn on the heater, heat the inner wall of the fluidized bed to a certain temperature and keep it warm; S4, Ultrasonic vibration feeding fluidization: According to the needs of powder coating, select appropriate parameters, turn on the ultrasonic vibration screen and electromagnetic feeder, and the powder to be coated is subjected to ultrasonic vibration, the powder is evenly dispersed, and falls into the fluidized bed through the screen; the powder that has been vibrated and dispersed is blown away by the airflow and dispersed in the fluidized bed; S5, atomization spraying of coating solution: the coating solution is introduced into the atomizer and sprayed into the fluidized bed, the powder and the coating solution are fully contacted and mixed in the fluidized bed, and a coating is completed; S6. Cyclone separation of primary coated powder: The fluidizing gas carrying the coated powder passes through the cyclone separator to separate the powder from the gas; S7, Dynamic drying of primary coated powder: The separated powder is pneumatically conveyed and passed through a heated pipeline to achieve powder drying; S8, once coated powder is re-vibrated and fed into fluidized state: According to the requirements of powder coating, select a screen with a suitable mesh size, adjust the vibration frequency, amplitude, ultrasonic frequency, and feeding frequency parameters, turn on the ultrasonic vibrating screen and electromagnetic feeder, and the coated powder is ultrasonically vibrated, the powder is evenly dispersed, and falls into the fluidized bed through the screen; the powder that has been vibrated and dispersed is blown away by the airflow and dispersed in the fluidized bed; S9, secondary coating of powder: the dispersed powder is further dispersed by fluidizing gas blowing, and is contacted and mixed with the coating solution to complete the secondary coating; S10, repeating steps S6 to S9: cyclically implementing steps S6 to S9 to achieve continuous cyclic coating of powders until the coating requirements are met.

2. The coating method according to claim 1, characterized in that: The coating process is completed in an inert gas protection environment.

3. The coating method according to claim 2, characterized in that: High purity argon was selected as the inert gas.

4. The coating method according to claim 1, characterized in that: In step S4, the parameters are a sieve with a suitable mesh size, and the vibration frequency, amplitude, ultrasonic frequency, and feeding frequency parameters are adjusted.

5. The coating method according to claim 4, characterized in that: In step S4, the principle of parameter selection is based on the particle size of the powder to be coated.

6. The coating method according to claim 1, characterized in that: In step S6, the separated gas is recompressed to a certain pressure and introduced into the air curtain, and then enters the fluidized bed through the air curtain to continue to be used as fluidizing gas.

7. The coating method according to claim 1, characterized in that: In step S8, the parameters are a sieve with a suitable mesh size, and the vibration frequency, amplitude, ultrasonic frequency, and feeding frequency parameters are adjusted.

8. The coating method according to claim 7, characterized in that: In step S8, the principle of parameter selection is based on the particle size of the powder.

9. The coating method according to claim 1, characterized in that: In step S10, the determination condition for stopping the coating is the number of cycles.

10. The coating method according to claim 9, characterized in that: In step S10, the number of coating times is determined based on experience, and can also be obtained based on simulation calculations.

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