A closed spray drying system and method of use

Abstract

The application belongs to the technical field of material drying and heat treatment equipment, and discloses a closed spray drying system and a use method. The closed spray drying system comprises, in sequence along a closed circulation carrier gas loop, a gas preparation unit, a heating unit, a spray drying unit, a gas-solid separation assembly, a gas purification unit, a condensation water removal unit, a gas-liquid separation unit and a gas return unit. The gas preparation unit is used for preparing carrier gas, and the heating unit is used for heating the carrier gas to 350-500 DEG C and then sending the carrier gas into the spray drying unit. The spray drying unit is used for receiving and atomizing slurry, so that the slurry is simultaneously dried, granulated and pre-burned in the high-temperature carrier gas to obtain pre-burned particles. The condensation water removal unit and the gas-liquid separation unit are used for condensing and separating water in the carrier gas and recycling the condensed water. The gas return unit is used for sending the carrier gas carrying residual heat after dehydration back to the heating unit for recycling. The system integrates drying, granulation and pre-burning, and can realize circulation of gas, residual heat and water.

Description

Technical Field

[0001] This application relates to the technical field of material drying and heat treatment equipment, specifically to a closed-loop spray drying system and its usage method. Background Technology

[0002] Spray drying technology can transform liquid slurry into spherical particles with uniform particle size and good flowability, and is one of the core processes in the preparation of functional material precursors. The conventional process route typically includes slurry preparation, spray drying, calcination, and obtaining the final product. The spray drying stage is mainly used to remove moisture from the slurry to obtain particles with a specific particle size distribution, providing a precursor for subsequent calcination. The calcination stage is the key step that determines the crystal form and properties of the product, requiring prolonged heating, holding, and cooling to achieve complete decomposition of organic matter and the formation of a carbon coating layer.

[0003] However, traditional spray drying systems are limited to drying and granulation, and their inlet air temperature is typically below 300°C, making it impossible to carbonize and pre-coat the organic components in the precursor materials. Therefore, the subsequent roasting process requires a cycle of 22–30 hours, resulting in extremely low production efficiency and continuous consumption of large amounts of heat energy, leading to energy waste. Furthermore, conventional spray drying systems are mostly open-loop processes using air as the carrier gas; the dried, moist carrier gas is directly discharged, preventing the recovery and reuse of heat and the carrier gas itself. Simultaneously, the condensate generated during the drying process contains trace amounts of material impurities and is discharged directly without treatment, wasting water resources and posing environmental risks.

[0004] Therefore, there is an urgent need for a closed-loop spray drying system and its usage method to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention proposes a closed-loop spray drying system and its usage method, which effectively solves the problems of traditional spray drying systems having limited functionality, high energy consumption, and resource waste.

[0006] To achieve the above objectives, this application adopts the following technical solution: A closed-loop spray drying system includes a closed-loop carrier gas circuit, and a gas generation unit, a heating unit, a spray drying unit, a gas-solid separation component, a gas purification unit, a condensation and dehydration unit, a gas-liquid separation unit, and a gas return unit connected sequentially along the closed-loop carrier gas circuit. The gas generation unit is used to prepare the required gas as a carrier gas for different material systems. The heating unit is used to heat the carrier gas to 350℃-500℃ before sending it into the spray drying unit. The spray drying unit is used to receive and atomize the slurry, so that the slurry can simultaneously complete drying, granulation, and pre-calcination in the high-temperature carrier gas to obtain pre-calcined particles. The condensation and dehydration unit and the gas-liquid separation unit are used to condense and separate the moisture in the carrier gas and recover the condensate. The gas return unit is used to send the dehydrated carrier gas carrying residual heat back to the heating unit for recycling.

[0007] As an optional technical solution for the above-mentioned closed spray drying system, the outlet air temperature of the spray drying unit is 180℃-320℃.

[0008] As an optional technical solution for the above-mentioned closed spray drying system, the gas-solid separation component includes a cyclone separator and a bag filter. The cyclone separator is connected to the outlet of the spray drying unit, the bag filter is connected to the outlet of the cyclone separator, and the gas purification unit is connected to the outlet of the bag filter.

[0009] As an optional technical solution for the above-mentioned closed spray drying system, the gas purification unit includes an activated carbon adsorber, which is used to remove residual organic volatiles in the carrier gas.

[0010] As an optional technical solution for the above-mentioned closed spray drying system, the gas return unit includes a first filter and a blower disposed between the gas-liquid separation unit and the heating unit. After dehydration, the carrier gas carrying residual heat is purified by the first filter and pressurized by the blower. After mixing with the newly produced gas supplemented by the gas production unit, it enters the heating unit.

[0011] As an optional technical solution for the above-mentioned closed spray drying system, the closed spray drying system further includes a condensate recycling unit, which is connected to the gas-liquid separation unit and is used to purify the condensate obtained by the gas-liquid separation unit and reuse it for slurry preparation.

[0012] As an optional technical solution for the above-mentioned closed spray drying system, the condensate recycling unit includes a second filter, a water collection tank, and a recycling pipeline. One end of the recycling pipeline is connected to the gas-liquid separation unit, and the other end is connected to the water collection tank. The second filter is installed in the recycling pipeline.

[0013] As an optional technical solution for the above-mentioned closed spray drying system, an air hammer is provided on the outer wall of the spray drying unit. The air hammer is used to strike the spray drying unit to prevent particles from sticking to the wall.

[0014] As an optional technical solution for the above-mentioned closed spray drying system, the closed spray drying system further includes an induced draft fan, which is installed in the closed-loop carrier gas circuit and is located between the spray drying unit and the gas-liquid separation unit.

[0015] As an optional technical solution for the above-mentioned closed spray drying system, the closed spray drying system further includes a pressure relief unit, which is disposed in the closed-loop carrier gas circuit and located between the first filter and the blower.

[0016] A method of using the above-mentioned closed-loop spray drying system includes the following steps: Step S1: The heating unit heats the gas to 350℃-500℃; Step S2: The atomized slurry is sprayed into high-temperature gas. At an outlet air temperature of 180℃-320℃, drying, granulation and pre-firing are completed simultaneously. During the pre-firing process, the organic matter in the material undergoes preliminary carbonization and forms a carbon coating layer, resulting in blackish-gray granules. Step S3: The high-temperature gas carrying fine particles and volatile organic compounds is subjected to gas-solid separation, adsorption and removal of volatile organic compounds, condensation and dehydration, and gas-liquid separation in sequence to obtain clean gas after dehydration. Step S4: The dehydrated clean gas and residual heat are returned to the heating unit, mixed with the newly added gas, and reheated to 350℃-500℃ for reuse. Step S5: Collect the condensate separated in step S3, purify it, and reuse it in the preparation of slurry in step S2.

[0017] Compared with the prior art, the beneficial effects of this application are as follows: The closed-loop spray drying system provided in this application includes a closed-loop carrier gas circuit, and a gas generation unit, a heating unit, a spray drying unit, a gas-solid separation component, a gas purification unit, a condensation and dehydration unit, a gas-liquid separation unit, and a gas return unit connected sequentially along the closed-loop carrier gas circuit. The gas generation unit is used to prepare the required gas as carrier gas for different material systems. The heating unit is used to heat the carrier gas to 350℃-500℃ and then send it into the spray drying unit. The spray drying unit is used to receive and atomize the slurry, so that the slurry can simultaneously complete drying, granulation, and pre-calcination in the high-temperature carrier gas to obtain pre-calcined particles. The gas-solid separation component is used to separate solid particles in the carrier gas. The gas purification unit is used to remove organic volatiles from the carrier gas. The condensation and dehydration unit and the gas-liquid separation unit are used to condense and separate the moisture in the carrier gas and recover the condensate. The gas return unit is used to send the dehydrated carrier gas carrying residual heat back to the heating unit for recycling.

[0018] This closed-loop spray drying system is a high-temperature closed-loop system integrating drying, granulation, and pre-calcination, and it constructs a circulation system for gas, waste heat, and water resources. Because the carbonization and carbon coating of organic matter are completed simultaneously during the drying stage, the pre-calcination time of the subsequent calcination process is significantly shortened to less than 0.5 hours, resulting in a significant improvement in production efficiency and solving the industry pain point of long calcination in traditional processes. The closed-loop gas circulation reduces carrier gas consumption by more than 95%, waste heat recovery makes the system energy-saving by 30-40%, and the purification and reuse of condensate reduces water waste by more than 85%, thus reducing overall production costs and environmental pressure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the closed spray drying system provided in the embodiments of this application.

[0020] In the picture: 1. Gas generation unit; 2. Heating unit; 3. Spray drying unit; 4. Cyclone separator; 5. Bag filter; 6. Gas purification unit; 7. Exhaust fan; 8. Condensate removal unit; 9. Gas-liquid separation unit; 10. First filter; 11. Blower; 12. Second filter; 13. Water collection tank; 14. Pressure relief unit; 15. Air hammer; 16. Explosion vent; 17. Atomizer; 18. Third filter; 19. Gas storage tank; 20. Fourth filter; 21. Oxygen analyzer; 22. Slurry tank; 23. Diaphragm pump. Detailed Implementation

[0021] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0024] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0026] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0027] The technical solution of this application will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1 As shown, this application provides a closed-loop spray drying system, which includes a closed-loop carrier gas circuit, and a gas generation unit 1, a heating unit 2, a spray drying unit 3, a gas-solid separation component, a gas purification unit 6, a condensation and dehydration unit 8, a gas-liquid separation unit 9, and a gas return unit connected sequentially along the closed-loop carrier gas circuit. The gas generation unit 1 is used to prepare the required gas as a carrier gas for different material systems. The heating unit 2 heats the carrier gas to 350℃-500℃ before sending it to the spray drying unit 3. The spray drying unit 3 receives and atomizes the slurry, allowing the slurry to simultaneously complete drying, granulation, and pre-calcination in the high-temperature carrier gas to obtain pre-calcined particles. The gas-solid separation component separates solid particles from the carrier gas. The gas purification unit 6 removes volatile organic compounds from the carrier gas. The condensation and dehydration unit 8 and the gas-liquid separation unit 9 condense and separate moisture from the carrier gas and recover the condensate. The gas return unit returns the dehydrated carrier gas, carrying residual heat, to the heating unit 2 for recycling.

[0029] Compared to existing technologies, this application proposes a high-temperature closed-loop spray drying system that integrates drying, granulation, and pre-calcination. During the spray drying process, material dehydration and drying, granulation, organic carbonization, and carbon coating pre-calcination are simultaneously achieved. Therefore, the pre-calcination time in the subsequent calcination process is significantly shortened to less than 0.5 hours, or even eliminated entirely, significantly improving production efficiency and solving the industry pain point of long calcination times in traditional processes. Furthermore, a closed-loop circulation system for gas, waste heat, and water resources is constructed. Waste heat from the gas after gas-liquid separation is recycled back to the heater for reuse, requiring only supplemental temperature difference heat energy. The closed-loop gas circulation reduces carrier gas consumption by over 95%, waste heat recovery results in overall system energy savings of 30-40%, and condensate purification and reuse reduce water waste by over 85%, thereby lowering production costs and reducing environmental pressure.

[0030] Optionally, the inlet air temperature of the spray drying unit 3 is 350℃-500℃ and the outlet air temperature is 180℃-320℃, so that the organic matter contained in the material during the pre-calcination stage undergoes preliminary carbonization and forms a carbon coating layer on the particle surface.

[0031] In this embodiment, the closed-loop spray drying system also includes a condensate recycling unit, which is connected to the gas-liquid separation unit 9. This unit purifies the condensate separated by the gas-liquid separation unit 9 and reuses it for slurry preparation. By setting up the condensate recycling unit, the condensate is recycled, thereby reducing water consumption.

[0032] Furthermore, the condensate recycling unit includes a second filter 12, a water collection tank 13, and a recycling pipeline. One end of the recycling pipeline is connected to the gas-liquid separation unit 9, and the other end is connected to the water collection tank 13. The water collection tank 13 is used to store purified water and stably supply it for sample preparation. The second filter 12 is installed in the recycling pipeline and is used to purify the condensate and remove residual impurities. After purification by the condensate removal unit 8, the gas-liquid separation unit 9, the second filter 12, and the water collection tank 13, the condensate is recycled for slurry preparation.

[0033] In this embodiment, the gas purification unit 6 includes an activated carbon adsorber, which is used to remove residual volatile organic compounds from the carrier gas, thereby ensuring gas purity.

[0034] In this embodiment, the gas return unit includes a first filter 10 and a blower 11 disposed between the gas-liquid separation unit 9 and the heating unit 2. The carrier gas, carrying residual heat after dehydration, is purified by the first filter 10 and pressurized by the blower 11 before being mixed with freshly produced gas from the gas production unit 1 and entering the heating unit 2. The first filter 10 is used to filter the circulating gas again to ensure gas cleanliness and avoid affecting the drying effect. The blower 11 is used to drive the closed-loop gas circulation.

[0035] Furthermore, the gas return unit also includes an oxygen analyzer 21, which is located between the first filter 10 and the blower 11 and is used to detect the oxygen content of the circulating gas.

[0036] In this embodiment, the spray drying unit 3 has a tower-shaped structure, i.e., a drying tower. An air hammer 15 is installed on its outer wall. The air hammer 15 periodically vibrates and strikes the spray drying unit 3 to prevent particles from sticking to the wall, and the particles eventually fall into a collection bin at the bottom of the tower. Furthermore, the spray drying unit 3 is also equipped with a pressure relief hole 16 and an atomizer 17. The two ends of the pressure relief hole 16 are connected to the inside of the drying tower and the outside atmosphere, respectively. When the pressure inside the drying tower exceeds a safety threshold, the pressure relief hole 16 opens to release pressure, ensuring production safety. The atomizer 17 is located at the top center of the drying tower and is used to atomize the slurry into fine droplets before spraying it into the drying tower.

[0037] Understandably, the spray drying unit 3 is connected to a slurry tank 22 and a diaphragm pump 23. The slurry tank 22 is used to store the slurry, and the diaphragm pump 23 is located on the pipeline between the slurry tank 22 and the spray drying unit 3. The diaphragm pump 23 is used to stably deliver the slurry, ensure uniform atomization feed, and avoid fluctuations in atomization effect.

[0038] The closed-loop spray drying system in this embodiment also includes an induced draft fan 7, which is installed in the closed-loop carrier gas circuit and located between the spray drying unit 3 and the gas-liquid separation unit 9. Powered by the induced draft fan 7, the airflow flows through the closed-loop carrier gas circuit, sequentially entering the gas-solid separation component and the gas purification unit 6 to complete gas-material separation, and then proceeding to the activated carbon adsorber and the condensate removal unit 8, etc.

[0039] The closed-loop spray drying system in this embodiment also includes a pressure relief unit 14, which is located in the closed-loop carrier gas circuit and between the first filter 10 and the blower 11. When the internal pressure of the system exceeds the safety threshold, the pressure relief unit 14 will automatically start, and the exhaust gas containing trace amounts of volatile organic compounds will be treated by catalytic combustion to meet emission standards. Therefore, the pressure relief unit 14 is used to maintain pressure stability, exhaust gas when there is overpressure, and treat volatile organic compounds.

[0040] The closed-loop spray drying system in this embodiment also includes a third filter 18, a gas storage tank 19, and a fourth filter 20 disposed in a closed-loop carrier gas circuit. The third filter 18 and the gas storage tank 19 are sequentially disposed between the gas generation unit 1 and the heating unit 2. The third filter 18 is used to filter particles and moisture in the gas, ensuring the cleanliness of subsequent equipment and preventing contamination of materials. The gas storage tank 19 is used to store gas and maintain stable circulation pressure. The fourth filter 20 is disposed between the heating unit 2 and the spray drying unit 3. The fourth filter 20 is used to filter impurities in the high-temperature gas and is adaptable to high temperatures of 350℃-500℃, preventing impurities from contaminating materials.

[0041] This embodiment also provides a method of using the above-described closed-loop spray drying system, including the following steps: Step S1: Heating unit 2 heats the gas to 350℃-500℃; Step S2: The atomized slurry is sprayed into high-temperature gas. At an outlet air temperature of 180℃-320℃, drying, granulation and pre-firing are completed simultaneously. During the pre-firing process, the organic matter in the material undergoes preliminary carbonization and forms a carbon coating layer, resulting in blackish-gray granules. Step S3: The high-temperature gas carrying fine particles and volatile organic compounds is subjected to gas-solid separation, adsorption and removal of volatile organic compounds, condensation and dehydration, and gas-liquid separation in sequence to obtain clean gas after dehydration. Step S4: The dehydrated clean gas and residual heat are returned to heating unit 2, mixed with the newly replenished gas, and reheated to 350℃-500℃ for reuse; Step S5: Collect the condensate separated in step S3, purify it, and reuse it in the preparation of slurry in step S2.

[0042] For example, the reactions and changes in the 350℃-500℃ spray drying pre-calcination section include: (1) Rapid removal of moisture and formation of lithium iron phosphate precursor particles. Free water on the surface of the droplets vaporizes instantly. As the moisture is lost, iron phosphate and lithium carbonate form precursor particles with high sphericity and uniform particle size under the viscosity of glucose.

[0043] (2) Pyrolysis of glucose. Glucose first undergoes a dehydration reaction, where the hydroxyl group in the molecule combines with hydrogen atoms to generate H2O. Then, it undergoes deep pyrolysis in an anaerobic environment, removing a large amount of oxygen (CO, CO2) and finally forming a certain amount of elemental carbon.

[0044] (3) Lithium carbonate decomposition. First, Li₂CO₃ begins to decompose slowly, generating Li₂O and CO₂. Subsequently, Li₂O is ionized at high temperature, providing sufficient Li for the formation of LiFePO₄ in the reaction. + source.

[0045] (4) In-situ formation of LiFePO4 crystal nuclei. FePO4, Li + It reacts in concert with the amorphous carbon generated by the pyrolysis of glucose to form the crystal nucleus structure of LiFePO4.

[0046] (5) In-situ coating of elemental carbon. Amorphous carbon is uniformly deposited on the surface of particles and in the internal pores under the drive of surface tension and intermolecular forces, forming a dense carbon coating layer. The coating layer can inhibit the agglomeration of LiFePO4 particles and excessive growth of crystal nuclei during subsequent calcination, and improve the final conductivity of LiFePO4.

[0047] The working process of the closed-loop spray drying system in this embodiment will be briefly described below.

[0048] First, the gas prepared by the gas generation unit 1 is subjected to impurity removal by a third filter 18, then enters a gas storage tank 19 for stable storage. Subsequently, the gas is heated to 350°C-500°C by the heating unit 2, further purified by a fourth filter 20, and then sent to the spray drying unit 3; on the other hand, the slurry formed by mixing water and materials is stably delivered to an atomizer 17 by a diaphragm pump 23, atomized into fine droplets and then sprayed into the spray drying unit 3. Under the action of high-temperature gas, drying, granulation molding and pre-sintering treatment are completed synchronously, wherein the pre-sintering causes organic matters in the materials to undergo preliminary carbonization in this process and form a carbon coating layer, so as to obtain black-gray particles. A pneumatic hammer 15 equipped for the spray drying unit 3 periodically vibrates the tower wall to prevent particles from adhering to the wall, and finally the particles fall into a storage barrel at the bottom of the tower. The high-temperature gas carrying fine particles and organic volatile components (with an outlet air temperature of 180°C-320°C) is pulled by the negative pressure of an induced draft fan 7, and sequentially passes through a gas-solid separation assembly (a cyclone separator 4 and a bag filter 5) and a gas purification unit 6 to complete gas-material separation, and the recovered fine powder returns to the storage barrel; then the gas enters an activated carbon adsorber to remove residual organic volatile components; the purified gas enters a condensation dewatering unit 8, and is subjected to heat exchange and temperature reduction, so that the water vapor therein is sufficiently condensed and precipitated, and gas-liquid separation is realized by a gas-liquid separation unit 9. The condensed water passes through a second filter 12 and enters a water storage tank 13, and is reused for slurry preparation, while the clean gas that still retains certain residual heat after dewatering is purified again by a first filter 10, pushed by a blower 11 to mix with newly prepared gas, and enters the heating unit 2 again. By virtue of the residual heat carried by the circulating gas, the heating unit 2 only needs to supplement a small amount of heat energy to raise the temperature of the mixed gas to the target temperature of 350°C-500°C, which greatly reduces the overall energy consumption of the system; when the internal pressure of the system exceeds the safety threshold, a pressure relief unit 14 will start automatically, and the discharged tail gas containing trace organic volatile components is treated by catalytic combustion and then discharged up to the standard; finally, the black-gray particles in the storage barrel are transferred into saggers for roasting, since pre-sintering has been completed in the spray drying stage, the overall roasting duration can be greatly shortened.

[0049] Obviously, the above description is only the preferred embodiments of the present invention and the applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the inventive concept of the present invention. The scope of the present invention is defined by the scope of the appended claims.

[0050] Note that in the description of this specification, the references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A closed-loop spray drying system, characterized in that, The system includes a closed-loop carrier gas circuit, and a gas generation unit (1), a heating unit (2), a spray drying unit (3), a gas-solid separation component, a gas purification unit (6), a condensation and dehydration unit (8), a gas-liquid separation unit (9), and a gas return unit connected sequentially along the closed-loop carrier gas circuit. The gas generation unit (1) is used to prepare the required gas as a carrier gas for different material systems. The heating unit (2) is used to heat the carrier gas to 350℃-500℃ and then send it into the spray drying unit (3). The spray drying unit (3) is used to receive and atomize the slurry, so that the slurry can be dried, granulated and pre-calcined simultaneously in the high-temperature carrier gas to obtain pre-calcined particles. The gas-solid separation component is used to separate solid particles in the carrier gas. The gas purification unit (6) is used to remove organic volatiles from the carrier gas. The condensation and dehydration unit (8) and the gas-liquid separation unit (9) are used to condense and separate the water in the carrier gas and recover the condensate. The gas return unit is used to send the dehydrated carrier gas carrying residual heat back to the heating unit (2) for recycling.

2. The closed-loop spray drying system according to claim 1, characterized in that, The outlet air temperature of the spray drying unit (3) is 180℃-320℃.

3. The closed-loop spray drying system according to claim 1, characterized in that, The gas-solid separation assembly includes a cyclone separator (4) and a bag filter (5). The cyclone separator (4) is connected to the outlet of the spray drying unit (3), the bag filter (5) is connected to the outlet of the cyclone separator (4), and the gas purification unit (6) is connected to the outlet of the bag filter (5).

4. The closed-loop spray drying system according to claim 1, characterized in that, The gas purification unit (6) includes an activated carbon adsorber, which is used to remove residual organic volatiles in the carrier gas.

5. The closed-loop spray drying system according to claim 1, characterized in that, The gas return unit includes a first filter (10) and a blower (11) disposed between the gas-liquid separation unit (9) and the heating unit (2). After dehydration, the carrier gas carrying residual heat is purified by the first filter (10) and pressurized by the blower (11) in sequence. After mixing with the newly produced gas supplemented by the gas production unit (1), it enters the heating unit (2).

6. The closed-loop spray drying system according to claim 1, characterized in that, The closed-loop spray drying system also includes a condensate recycling unit, which is connected to the gas-liquid separation unit (9) and is used to purify the condensate obtained by the gas-liquid separation unit (9) and reuse it for slurry preparation.

7. The closed-loop spray drying system according to claim 6, characterized in that, The condensate recycling unit includes a second filter (12), a water collection tank (13), and a recycling pipeline. One end of the recycling pipeline is connected to the gas-liquid separation unit (9), and the other end is connected to the water collection tank (13). The second filter (12) is installed in the recycling pipeline.

8. The closed-loop spray drying system according to claim 1, characterized in that, The spray drying unit (3) is provided with an air hammer (15) on its outer wall. The air hammer (15) is used to strike the spray drying unit (3) to prevent particles from sticking to the wall.

9. The closed-loop spray drying system according to claim 1, characterized in that, The closed-loop spray drying system also includes an induced draft fan (7), which is installed in the closed-loop circulating carrier gas circuit and is located between the spray drying unit (3) and the gas-liquid separation unit (9).

10. The closed-loop spray drying system according to claim 5, characterized in that, The closed-loop spray drying system further includes a pressure relief unit (14), which is disposed in the closed-loop carrier gas circuit and located between the first filter (10) and the blower (11).

11. A method of using a closed-loop spray drying system as described in any one of claims 1-10, characterized in that, Includes the following steps: Step S1: The heating unit (2) heats the gas to 350℃-500℃; Step S2: The atomized slurry is sprayed into high-temperature gas. At an outlet air temperature of 180℃-320℃, drying, granulation and pre-firing are completed simultaneously. During the pre-firing process, the organic matter in the material undergoes preliminary carbonization and forms a carbon coating layer, resulting in blackish-gray granules. Step S3: The high-temperature gas carrying fine particles and volatile organic compounds is subjected to gas-solid separation, adsorption and removal of volatile organic compounds, condensation and dehydration, and gas-liquid separation in sequence to obtain clean gas after dehydration. Step S4: The dehydrated clean gas and residual heat are returned to the heating unit (2), mixed with the newly replenished gas, and reheated to 350℃-500℃ for recycling; Step S5: Collect the condensate separated in step S3, purify it, and reuse it in the preparation of slurry in step S2.

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