A system for spray pyrolysis and a method for synthesizing metal oxides

Abstract

The present application relates to a kind of spray pyrolysis device system and the method for synthesizing metal oxide, the device system includes pyrolysis reaction unit, dust collection unit and flue gas recovery unit connected in order along material flow direction;The pyrolysis reaction unit includes automatic feeding device, carrier compression device, atomizing device and pyrolysis device connected in order along material flow direction, and the side wall bottom of the pyrolysis device is connected with combustion device.The present application can ensure that the actual decomposition temperature and residence time of raw material are accurately controlled by setting automatic feeding device, while using reasonable feeding and pyrolysis process parameters;Metal oxide and flue gas can be efficiently separated by using dust collection unit, high-purity metal oxide preparation can be realized, and it can be used for industrial scale production.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, specifically to a spray pyrolysis apparatus system and a method for synthesizing metal oxides. Background Technology

[0002] Micro- and nano-level hierarchical metal oxide materials possess unique physicochemical properties and have broad application prospects in many fields such as energy, environment, catalysis, optics, and electromagnetism. Existing methods for preparing hierarchical metal oxides include sol-gel methods, hydrothermal methods, and template methods, but these often involve complex and cumbersome reagents and procedures, hindering large-scale industrialization. Spray pyrolysis, due to its advantages such as simple process, high production efficiency, and uniform composition of the prepared product, is widely used in the preparation of various metal oxide materials.

[0003] Spray pyrolysis of metal salt solutions occurs in droplet-shaped microreactors, thus readily forming spherical metal oxides with micro / nano structures. However, the relatively low-temperature feed liquid, injected into the pyrolysis furnace with the atomized gas stream, significantly disturbs the temperature distribution within the furnace, leading to uneven decomposition rates. In areas of excessively high temperature, the solvent evaporation rate in the droplets is rapid, often resulting in a hollow, porous structure that is easily broken, leading to low tap density and limited applications. In areas of excessively low temperature, the solvent evaporation rate is slow, which is conducive to the formation of solid spherical structures, but often results in incomplete product decomposition, leading to lower product purity.

[0004] CN 105905935A discloses a method for preparing rare earth oxides or composite oxides with large specific surface area by spray pyrolysis. The method involves dissolving a rare earth chloride or a rare earth chloride and a metal chloride in water to form a solution, adding carboxylic acid and stirring until homogeneous; spraying the mixed solution into a calcining furnace using air as a carrier gas for calcination to generate a carbon-supported rare earth oxide precursor; calcining the precursor at 500–1000℃ for 1–10 h to obtain a specific surface area of ​​26–83 m². 2 ·g -1 Rare earth oxides or rare earth composite oxides. However, the oxides prepared using this invention exhibit a hollow shell structure and are severely fragmented.

[0005] CN 112919552A discloses a high-tap-density multi-component oxide precursor and its preparation method and system. The method involves directly melting a metal salt containing water of crystallization to obtain a sub-molten salt liquid, which is then used as a feedstock for spray pyrolysis. This increases the number of crystallization nuclei within the atomized droplets and reduces solvent evaporation, mitigating the impact on primary particles and facilitating the formation of large-diameter solid particles. A fluidized bed pyrolysis furnace is employed, with a pyrolysis time of 10-50 minutes. While this method improves the tap density of the oxides, the resulting material has excessively large particle size and specific surface area, and relatively few active sites, thus limiting its applications in energy materials, photoelectrocatalysis, and other fields.

[0006] CN 112551601A discloses a method and apparatus for preparing nickel oxide powder by spray pyrolysis. The apparatus involves spraying a raw material liquid into a pyrolysis furnace from a top nozzle, with the oxides discharged from the bottom of the furnace via natural sedimentation, and byproducts recycled into a hydrochloric acid storage tank. However, due to the combined effects of the atomized airflow and gravity, the droplets have a short residence time in the furnace, easily leading to incomplete pyrolysis and making it difficult to guarantee the purity of the oxides.

[0007] In view of the shortcomings of existing technologies, there is an urgent need to provide a device system that enables metal oxides to have high tap density, active sites and purity. Summary of the Invention

[0008] The purpose of this invention is to provide a spray pyrolysis apparatus system and a method for synthesizing metal oxides. By introducing an automatic feeding device and rationally setting the position of the atomizing device, real-time and precise control of the temperature and pressure distribution within the pyrolysis apparatus is achieved. The resulting metal oxides have a micro-nano multi-level structure, possessing both high active sites and high tap density. At the same time, the dust collection unit helps to achieve complete separation of the metal oxides from the flue gas, ensuring the high purity of the metal oxides.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a spray pyrolysis apparatus system, the apparatus system comprising a pyrolysis reaction unit, a dust collection unit and a flue gas recovery unit connected sequentially along the material flow direction;

[0011] The pyrolysis reaction unit includes an automatic feeding device, a carrier compression device, an atomizing device, and a pyrolysis device connected in sequence along the material flow direction. A combustion device is connected to the bottom of the side wall of the pyrolysis device.

[0012] The device system provided by this invention introduces an automatic feeding device that matches the optimal feeding pressure and flow rate based on the real-time temperature and pressure parameters within the pyrolysis device. This ensures continuous, stable, and precise control of the actual reaction temperature and time of the raw materials within the pyrolysis device, effectively preventing the decomposition products from exhibiting hollow or fragmented structures due to excessively high or low local temperatures within the pyrolysis device. The stable and controllable reaction time ensures the complete pyrolysis of the raw materials, thereby producing micro-nano hierarchical metal oxides with high active sites and tap density. Simultaneously, the dust collection unit helps to achieve complete separation of the metal oxides and flue gas, ensuring the high purity of the metal oxide products.

[0013] Preferably, the automatic feeding device includes a raw material storage device, which is connected to a pressurization device via a pipeline.

[0014] Preferably, the automatic feeding device is equipped with a flow meter, a regulating valve, and electrical instruments.

[0015] Preferably, the electrical instruments include a pressure gauge, a hydraulic gauge, and a temperature gauge.

[0016] Preferably, the raw material storage device includes a raw material storage tank.

[0017] Preferably, the booster device includes a booster pump.

[0018] The automatic feeding device is interlocked with the temperature control system and induced draft device of the pyrolysis unit to match the optimal feeding pressure and flow rate according to the real-time temperature and pressure fields inside the pyrolysis unit. This ensures that the actual decomposition temperature and residence time of the raw materials in the pyrolysis unit are continuously and stably controlled, resulting in the prepared metal oxides having a high tap density. At the same time, it enables the pyrolysis unit to operate continuously and stably, achieving remote control and unattended operation.

[0019] Preferably, the outlet of the raw material storage device is connected to the carrier compression device.

[0020] Preferably, the outlet of the atomizing device is connected to the bottom of the inner cavity of the pyrolysis device.

[0021] The atomizing device is located at the bottom of the pyrolysis device. After the raw material is atomized, it moves from the bottom to the top against gravity to complete the pyrolysis reaction. With the parameter settings of the automatic feeding device, the residence time of the material can be flexibly and effectively controlled.

[0022] Preferably, the atomizing device includes any one of single-fluid atomizing, dual-fluid atomizing, pressure atomizing, ultrasonic atomizing, or electrostatic atomizing, and is preferably dual-fluid atomizing.

[0023] Preferably, the atomizing device includes an atomizer.

[0024] Preferably, the nozzle diameter of the atomizing device is 0.5-2mm, for example, it can be 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.8mm or 2mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.8-1mm.

[0025] Preferably, the nozzle of the atomizing device includes a front-end gas-liquid mixing dual-fluid atomizing nozzle.

[0026] The front-end gas-liquid mixing dual-fluid atomizing nozzle has a simple structure and is not easily clogged. It also has a wide range of atomization pressure adjustment, which allows for control of droplet size, size distribution, number of droplets, and droplet velocity, thus helping to improve the atomization effect of the droplets.

[0027] Preferably, the angle between the spray direction of the atomizing device and the height direction of the pyrolysis device is 20-90°, for example, it can be 20°, 30°, 40°, 50°, 60°, 70°, 80° or 90°, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 30-60°.

[0028] The included angle must ensure that the material is evenly dispersed throughout the cavity of the pyrolysis device, while also preventing the spray angle from being too large, which would cause the material to be directly sprayed onto the inner wall of the cavity and result in the loss of effective reactants. Therefore, the present invention controls the included angle within a reasonable range.

[0029] Preferably, the pyrolysis device includes a vertical cavity, and the top of the vertical cavity is provided with a discharge port.

[0030] Preferably, the lining material of the vertical cavity includes heat-resistant corundum castable.

[0031] Compared to heat-resistant metal materials, the heat-resistant corundum castable does not introduce other impurities during the pyrolysis reaction of the material, thus ensuring the purity of the material.

[0032] Preferably, the height of the vertical cavity is 2-10m, for example, it can be 2m, 3m, 5m, 6m, 8m or 10m, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 3-6m.

[0033] Preferably, the diameter of the vertical cavity is 0.1-2m, for example, it can be 0.1m, 0.5m, 0.8m, 1m, 1.5m or 2m, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.5-1m.

[0034] If the diameter of the vertical cavity is too small, a large amount of material sprayed from the nozzle will adhere to the furnace wall, generating a large amount of waste. If the diameter is too large, the temperature and airflow direction distribution inside the vertical cavity will be uneven, resulting in poor material conveying effect.

[0035] Preferably, the vertical cavity is equipped with a temperature and air pressure monitoring device.

[0036] Preferably, the temperature and pressure monitoring device is located at the bottom, middle and top of the vertical cavity.

[0037] The three temperature points set at the bottom, middle and top of the vertical cavity represent the initial temperature, reaction temperature and maximum temperature of the atomized droplets, respectively, which affect the evaporation rate, decomposition rate and decomposition degree of the atomized droplets. The three pressure points are closely related to the initial flow rate of the atomized droplets, the size of the combustion gas flow and the residence time of the material in the cavity. By monitoring the temperature and pressure at multiple locations in the cavity, the pyrolysis process can be more accurately controlled.

[0038] Preferably, the air outlet of the combustion device is equipped with a temperature and air pressure detection device.

[0039] Preferably, along the material flow direction inside the vertical cavity, the combustion device includes a first combustion furnace and a second combustion furnace arranged in sequence.

[0040] The combustion device is equipped with a first combustion furnace and a second combustion furnace, which can better coordinate and control the temperature distribution within the pyrolysis device compared to a single combustion furnace.

[0041] Preferably, the dust collection unit includes a cyclone dust collector and a heat-resistant bag dust collector connected in sequence along the material flow direction.

[0042] The dust collection unit is equipped with a two-stage dust collector, which can effectively prevent the materials and flue gas from reacting again at low temperatures and introducing impurities, while ensuring efficient collection of materials.

[0043] Preferably, the cyclone dust collector is connected to the discharge port of the vertical cavity.

[0044] Preferably, the cyclone dust collector includes any one of the following types: long cone type, cylindrical type, diffusion type, and bypass type, with diffusion type being the most preferred.

[0045] The aforementioned diffusion cyclone dust collector can effectively improve the dust collection efficiency for low-particle-size metal oxides.

[0046] Preferably, the surface of the cyclone dust collector is covered with an insulation layer.

[0047] The insulation layer ensures that the separation process between the metal oxide and the flue gas is completed at high temperature, thereby enabling the collection of high-purity metal oxides.

[0048] Preferably, the interior of the heat-resistant bag filter dust collector is provided with a sintered metal mesh.

[0049] Preferably, the pore size of the sintered metal mesh is 0.01-1μm, for example, it can be 0.01μm, 0.02μm, 0.05μm, 0.1μm, 0.2μm, 0.5μm, 0.8μm or 1μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.05-0.5μm.

[0050] The aperture setting of the sintered metal mesh can further enable the efficient collection of finer-sized metal oxide particles.

[0051] The flue gas recovery unit includes an absorption device, with an exhaust fan connected to the top and a heat exchanger connected to the bottom.

[0052] Preferably, the induced draft device includes an induced draft fan.

[0053] The heat exchange device can further cool the absorbent, thereby improving the regeneration efficiency.

[0054] Preferably, the heat exchange device includes a heat exchanger.

[0055] Preferably, the absorption device is connected to the air outlet of the heat-resistant bag filter.

[0056] Preferably, the absorbent device is made of steel lined with PTFE.

[0057] Preferably, a spiral atomizing nozzle is provided at the bottom of the inner cavity of the absorption device.

[0058] The spiral atomizing nozzle can effectively increase the contact area between the recovered liquid and the flue gas, thereby enhancing the recovery and regeneration effect of acid and alkali gases.

[0059] Preferably, the air inlet material of the absorption device includes heat-resistant and corrosion-resistant brick.

[0060] The heat-resistant and corrosion-resistant bricks can withstand high-temperature flue gas and are resistant to acid and alkali corrosion.

[0061] Preferably, the lining material of the absorption device includes acid and alkali resistant ceramic filler.

[0062] Preferably, the absorption device includes an absorption tower.

[0063] In a second aspect, the present invention provides a method for synthesizing metal oxides using the apparatus system described in the first aspect, the method comprising the following steps:

[0064] A metal salt aqueous solution is fed, transported by carrier gas, atomized, and subjected to pyrolysis to obtain metal oxides and by-product gases. The obtained metal oxides and by-product gases are then separated. Specifically, the metal oxides are collected in stages, and the by-product gases are recovered and treated.

[0065] The method for synthesizing metal oxides provided by this invention allows for adjustable and controllable temperature and reaction time of the raw materials within the pyrolysis apparatus by setting reasonable raw material feed process parameters and spray pyrolysis temperature. The resulting metal oxides can fully utilize their structural characteristics: a one-dimensional nanoscale structure, consisting of 50-200 nm nanocrystalline particles, exposes more surface active sites, improving the performance of the metal oxides; and a secondary particle micron-scale structure, composed of 1-10 μm microspheres, which has a richer pore structure compared to solid spheres, shortening the transport paths of ions and electrons within the material while avoiding the drawbacks of excessive porosity in hollow or multi-shell structures, effectively improving the tap density of the oxides. Therefore, the metal oxides with micro-nano hierarchical structures obtained using the method provided by this invention possess both the advantages of high active sites and high tap density.

[0066] Preferably, the concentration of the metal salt is 10-400 g / L, for example, it can be 10 g / L, 50 g / L, 100 g / L, 200 g / L, 300 g / L or 400 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 100-300 g / L.

[0067] Preferably, the metal salt includes any one or a combination of at least two of metal nitrates, metal chlorides, metal acetates, metal oxalates, or metal ammonium salts. Typical but non-limiting combinations include combinations of metal nitrates and metal chlorides, combinations of metal acetates and metal oxalates, combinations of metal nitrates, metal chlorides, and metal acetates, combinations of metal chlorides, metal acetates, metal oxalates, and metal ammonium salts, or combinations of metal nitrates, metal chlorides, metal acetates, metal oxalates, and metal ammonium salts.

[0068] Preferably, the metal nitrate includes any one or a combination of at least two of nickel nitrate, cobalt nitrate, manganese nitrate, lithium nitrate, magnesium nitrate, cerium nitrate, aluminum nitrate, zirconium nitrate, zinc nitrate, ferric nitrate, molybdenum nitrate, or copper nitrate. Typical but non-limiting combinations include the combination of nickel nitrate and cobalt nitrate, the combination of manganese nitrate, lithium nitrate, magnesium nitrate, and cerium nitrate, the combination of aluminum nitrate, zirconium nitrate, zinc nitrate, and ferric nitrate, the combination of lithium nitrate, magnesium nitrate, cerium nitrate, aluminum nitrate, zirconium nitrate, zinc nitrate, ferric nitrate, molybdenum nitrate, and copper nitrate, or the combination of nickel nitrate, cobalt nitrate, manganese nitrate, lithium nitrate, magnesium nitrate, cerium nitrate, aluminum nitrate, zirconium nitrate, zinc nitrate, ferric nitrate, molybdenum nitrate, and copper nitrate.

[0069] Preferably, the metal chloride salt includes any one or a combination of at least two of nickel chloride, cobalt chloride, manganese chloride, magnesium chloride, lanthanum chloride, cerium chloride, praseodymium chloride, neodymium chloride, aluminum chloride, ferric chloride, or zirconium oxychloride. Typical but non-limiting combinations include the combination of nickel chloride, cobalt chloride, and manganese chloride; the combination of magnesium chloride, lanthanum chloride, cerium chloride, praseodymium chloride, and neodymium chloride; the combination of lanthanum chloride, cerium chloride, praseodymium chloride, neodymium chloride, aluminum chloride, ferric chloride, and zirconium oxychloride; or the combination of nickel chloride, cobalt chloride, manganese chloride, magnesium chloride, lanthanum chloride, cerium chloride, praseodymium chloride, neodymium chloride, aluminum chloride, ferric chloride, and zirconium oxychloride.

[0070] Preferably, the metal acetate includes any one or a combination of at least two of nickel acetate, cobalt acetate, manganese acetate, lithium acetate, magnesium acetate, cerium acetate, or zinc acetate. Typical but non-limiting combinations include a combination of nickel acetate and cobalt acetate, a combination of manganese acetate, lithium acetate, and magnesium acetate, a combination of nickel acetate, cobalt acetate, manganese acetate, lithium acetate, and magnesium acetate, or a combination of nickel acetate, cobalt acetate, manganese acetate, lithium acetate, magnesium acetate, cerium acetate, and zinc acetate.

[0071] Preferably, the metal oxalate includes any one or a combination of at least two of nickel oxalate, cobalt oxalate, manganese oxalate, lithium oxalate, magnesium oxalate, cerium oxalate, lanthanum oxalate, praseodymium oxalate, or neodymium oxalate. Typical but non-limiting combinations include the combination of nickel oxalate and cobalt oxalate, the combination of manganese oxalate, lithium oxalate, magnesium oxalate, and cerium oxalate, the combination of nickel oxalate, cobalt oxalate, manganese oxalate, lithium oxalate, magnesium oxalate, and cerium oxalate, or the combination of nickel oxalate, cobalt oxalate, manganese oxalate, lithium oxalate, magnesium oxalate, cerium oxalate, lanthanum oxalate, praseodymium oxalate, and neodymium oxalate.

[0072] Preferably, the metal ammonium salt includes any one or a combination of at least two of ammonium tungstate, ammonium metatungstate, ammonium metavanadate, or ammonium molybdate. Typical but non-limiting combinations include a combination of ammonium tungstate and ammonium metatungstate, a combination of ammonium metatungstate, ammonium metavanadate, and ammonium molybdate, or a combination of ammonium tungstate, ammonium metatungstate, ammonium metavanadate, and ammonium molybdate.

[0073] Preferably, the feed flow rate is 0.1-100L / h, for example, it can be 0.1L / h, 1L / h, 10L / h, 50L / h or 100L / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] Preferably, the feed pressure is 0.05-1 MPa, for example, it can be 0.05 MPa, 0.1 MPa, 0.4 MPa, 0.7 MPa or 1 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0075] The feed flow rate and pressure are matched to the optimal values ​​based on the real-time conditions of the temperature and pressure fields inside the pyrolysis unit, thereby ensuring that the actual decomposition temperature and residence time of the raw materials in the pyrolysis unit are continuously, stably and precisely controlled.

[0076] Preferably, the pressure of the carrier gas is 0.05-1 MPa, for example, it can be 0.05 MPa, 0.1 MPa, 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa or 1 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.2-0.6 MPa.

[0077] Preferably, the carrier gas includes any one or a combination of at least two of air, oxygen, argon, nitrogen or carbon dioxide. Typical but non-limiting combinations include a combination of air and oxygen, a combination of argon, nitrogen and carbon dioxide, or a combination of air, oxygen, argon, nitrogen and carbon dioxide.

[0078] Preferably, the temperature of the pyrolysis reaction is 500-1000℃, for example, it can be 500℃, 600℃, 700℃, 800℃, 900℃ or 1000℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0079] Preferably, the pyrolysis reaction includes a first reaction section, a second reaction section, and a third reaction section with successively increasing temperatures.

[0080] Preferably, the temperature of the first reaction section is 500-900℃, for example, it can be 500℃, 600℃, 700℃, 800℃ or 900℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0081] Preferably, the temperature of the second reaction section is 550-950℃, for example, it can be 550℃, 650℃, 750℃, 850℃ or 950℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0082] Preferably, the temperature of the third reaction section is 600-1000℃, for example, it can be 600℃, 700℃, 800℃, 900℃ or 1000℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0083] In the first reaction section, the droplet undergoes an initial pyrolysis reaction, and the internal solvent of the droplet gradually evaporates. When it enters the second reaction section, the droplet further decomposes, gradually generating metal oxides and by-product gases. When it enters the third reaction section, the droplet is at its highest pyrolysis temperature, at which point the undecomposed droplet can further complete its decomposition.

[0084] Preferably, the pyrolysis reaction time is 1-60s, for example, it can be 1s, 5s, 10s, 15s, 20s, 30s, 40s, 50s or 60s, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 5-20s.

[0085] Preferably, the pyrolysis reaction uses the combustion of a combustible gas to provide heat. The combustible gas includes any one or a combination of at least two of methane, ethane, propane, acetylene, carbon monoxide, or hydrogen. Typical but non-limiting combinations include a combination of methane and ethane, a combination of propane, acetylene, and carbon monoxide, or a combination of methane, ethane, propane, acetylene, carbon monoxide, and hydrogen.

[0086] Preferably, the recycling process includes: washing and recycling the by-product gas with water before discharging or reusing it.

[0087] As a preferred embodiment of the method described in the second aspect of the present invention, the method includes the following steps:

[0088] A metal salt aqueous solution with a concentration of 10-400 g / L is fed, transported by gas at 0.05-1 MPa, atomized, and pyrolyzed at 500-1000℃ for 1-60 s to obtain metal oxides and by-product gases. The metal oxides and by-product gases are separated. The metal oxides are collected in stages, and the by-product gases are washed with water, recycled, and then discharged or reused.

[0089] The feed flow rate is 0.1-100 L / h, and the pressure is 0.05-1 MPa; the pyrolysis reaction includes a first reaction section, a second reaction section, and a third reaction section with successively increasing temperatures; the temperature of the first reaction section is 500-900℃; the temperature of the second reaction section is 550-950℃; and the temperature of the third reaction section is 600-1000℃; the pyrolysis reaction uses combustible gas combustion to provide heat.

[0090] Compared with the prior art, the present invention has the following beneficial effects:

[0091] The spray pyrolysis apparatus system provided by this invention, by setting up an automatic feeding device and placing the atomizing device at the bottom of the pyrolysis device, can ensure that the actual decomposition temperature and residence time of the raw materials in the pyrolysis device are continuously and stably precisely controlled; the dust collection unit can efficiently separate metal oxides and flue gas to achieve the preparation of high-purity metal oxides; the flue gas recovery unit can realize the recycling and regeneration of flue gas.

[0092] This invention employs reasonable feed parameters and pyrolysis process parameters to effectively control the decomposition temperature and residence time of the raw materials, resulting in a tap density of up to 1.88 g·cm³ for the obtained metal oxides. -3With a purity of up to 99.97%, it can be used for industrial-scale production. Attached Figure Description

[0093] Figure 1 This is a schematic diagram of the spray pyrolysis apparatus system provided in Embodiment 1 of the present invention;

[0094] Figure 2 This is a scanning electron microscope image of cobalt oxide synthesized using the method provided in Application Example 1 of this invention;

[0095] Figure 3 This is a transmission electron microscope (TEM) image of nickel oxide synthesized using the method provided in Application Example 2 of this invention;

[0096] Figure 4 This is a transmission electron microscope (TEM) magnification image of nickel oxide synthesized using the method provided in Application Example 2 of this invention;

[0097] Figure 5 This is a transmission electron microscope (TEM) image of cerium oxide synthesized using the method provided in Application Example 3 of this invention;

[0098] Figure 6 This is a transmission electron microscope (TEM) image of manganese oxide synthesized using the method provided in Application Example 4 of this invention;

[0099] Figure 7 Here is a scanning electron microscope image of cobalt oxide synthesized using the method provided in Comparative Application Example 1 of this invention;

[0100] The components include: 1. Carrier compression device; 2. Dual-fluid atomizer; 3. Raw material storage tank; 4. Booster pump; 5. Vertical cavity; 6. First combustion furnace; 7. Second combustion furnace; 8. Diffusion cyclone dust collector; 9. Heat-resistant bag dust collector; 10. Absorption tower; 11. Exhaust fan; 12. Heat exchanger. Detailed Implementation

[0101] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0102] Example 1

[0103] This embodiment provides a spray pyrolysis apparatus system, such as... Figure 1 As shown, the device system includes a pyrolysis reaction unit, a dust collection unit, and a flue gas recovery unit connected sequentially along the material flow direction;

[0104] The pyrolysis reaction unit includes an automatic feeding device, a carrier compression device 1, a dual-fluid atomizer 2 and a pyrolysis device connected in sequence along the material flow direction. A combustion device is connected to the bottom of the side wall of the pyrolysis device.

[0105] The automatic feeding device includes a raw material storage tank 3, which is connected to a booster pump 4 via a pipeline; the outlet of the raw material storage tank 3 is connected to a carrier compression device 1; the outlet of the dual-fluid atomizer 2 is connected to the bottom of the inner cavity of the pyrolysis device; the nozzle diameter of the dual-fluid atomizer 2 is 0.9 mm; the angle between the spray direction of the dual-fluid atomizer 2 and the height direction of the pyrolysis device is 50°.

[0106] The pyrolysis device includes a vertical cavity 5, with a discharge port at the top; the lining material of the vertical cavity 5 is heat-resistant corundum castable; the vertical cavity 5 has a height of 5m and a diameter of 0.8m; temperature and pressure monitoring devices are installed at the bottom, middle, and top of the vertical cavity 5; the air outlet of the combustion device is equipped with a temperature and pressure detection device; along the material flow direction inside the vertical cavity 5, the combustion device includes a first combustion furnace 6 and a second combustion furnace 7 arranged sequentially.

[0107] The dust collection unit includes a diffusion cyclone dust collector 8 and a heat-resistant bag dust collector 9 connected sequentially along the material flow direction; the diffusion cyclone dust collector 8 is connected to the discharge port of the vertical cavity 5; the surface of the diffusion cyclone dust collector 8 is covered with a heat insulation layer; the interior of the heat-resistant bag dust collector 9 is provided with a sintered metal mesh with a pore size of 0.1μm.

[0108] The flue gas recovery unit includes an absorption tower 10, with an induced draft fan 11 connected to the top and a heat exchanger 12 connected to the bottom. The absorption tower 10 is connected to the outlet of a heat-resistant bag filter 9. A spiral atomizing nozzle is provided at the bottom of the inner cavity of the absorption tower 10. The air inlet of the absorption tower 10 is made of heat-resistant and corrosion-resistant brick, and the inner lining is made of acid and alkali resistant ceramic filler.

[0109] Example 2

[0110] This embodiment provides a spray pyrolysis device system, which differs from Embodiment 1 in that the nozzle diameter of the dual-fluid atomizer 2 is adjusted to 1 mm; the angle between the spray direction of the dual-fluid atomizer 2 and the height direction of the pyrolysis device is adjusted to 30°; the height of the vertical cavity 5 is adjusted to 6 m and the diameter is adjusted to 1 m; the aperture of the sintered metal mesh is adjusted to 0.5 μm, and the rest are the same as in Embodiment 1.

[0111] Example 3

[0112] This embodiment provides a spray pyrolysis device system, which differs from Embodiment 1 in that the nozzle diameter of the dual-fluid atomizer 2 is adjusted to 0.8 mm; the angle between the spray direction of the dual-fluid atomizer 2 and the height direction of the pyrolysis device is adjusted to 60°; the height of the vertical cavity 5 is adjusted to 3 m and the diameter is adjusted to 0.5 m; the aperture of the sintered metal mesh is adjusted to 0.05 μm, and the rest are the same as in Embodiment 1.

[0113] Example 4

[0114] This embodiment provides a spray pyrolysis device system, which differs from Embodiment 1 in that the nozzle diameter of the dual-fluid atomizer 2 is adjusted to 2mm; the angle between the spray direction of the dual-fluid atomizer 2 and the height direction of the pyrolysis device is adjusted to 20°; the height of the vertical cavity 5 is adjusted to 10m and the diameter is adjusted to 2m; the aperture of the sintered metal mesh is adjusted to 1μm, and the rest are the same as in Embodiment 1.

[0115] Example 5

[0116] This embodiment provides a spray pyrolysis device system, which differs from Embodiment 1 in that the nozzle diameter of the dual-fluid atomizer 2 is adjusted to 0.5 mm; the angle between the spray direction of the dual-fluid atomizer 2 and the height direction of the pyrolysis device is adjusted to 90°; the height of the vertical cavity 5 is adjusted to 2 m and the diameter is adjusted to 0.1 m; the aperture of the sintered metal mesh is adjusted to 0.01 μm, and the rest are the same as in Embodiment 1.

[0117] Example 6

[0118] This embodiment provides a spray pyrolysis device system. The difference from Embodiment 1 is that, except for adjusting the nozzle diameter of the dual-fluid atomizer 2 to 0.2 mm, everything else is the same as in Embodiment 1.

[0119] Example 7

[0120] This embodiment provides a spray pyrolysis device system. The difference from Embodiment 1 is that, except for adjusting the nozzle diameter of the dual-fluid atomizer 2 to 2.3 mm, everything else is the same as in Embodiment 1.

[0121] Example 8

[0122] This embodiment provides a spray pyrolysis device system. The difference from Embodiment 1 is that, except that the angle between the spray direction of the dual-fluid atomizer 2 and the height direction of the pyrolysis device is adjusted to 15°, everything else is the same as in Embodiment 1.

[0123] Example 9

[0124] This embodiment provides a spray pyrolysis device system. The difference from Embodiment 1 is that the outlet of the dual-fluid atomizer 2 is connected to the top of the inner cavity of the pyrolysis device, and the outlet of the vertical cavity 5 is adapted to be set at the bottom. All other aspects are the same as in Embodiment 1.

[0125] Example 10

[0126] This embodiment provides a spray pyrolysis device system. The difference from Embodiment 1 is that the surface of the diffusion cyclone dust collector 8 has no heat insulation layer, and the heat-resistant bag dust collector 9 is replaced with a conventional bag dust collector. All other aspects are the same as in Embodiment 1.

[0127] Comparative Example 1

[0128] This comparative example provides a spray pyrolysis apparatus system, which differs from Example 1 in that the automatic feeding device is replaced with a conventional feeding device with constant flow and pressure, while the rest is the same as Example 1.

[0129] Application Example 1

[0130] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Example 1, the method comprising the following steps:

[0131] A 200 g / L cobalt chloride aqueous solution was fed, conveyed by air at 0.3 MPa, atomized, and pyrolyzed for 15 s to obtain cobalt oxide and hydrochloric acid gas. The cobalt oxide and hydrochloric acid gas were separated. The cobalt oxide was collected in stages, and the hydrochloric acid gas was washed with water and recycled to achieve hydrochloric acid reuse.

[0132] The feed flow rate is 5±0.25L / h, and the pressure is 0.4±0.04MPa; the pyrolysis reaction includes a first reaction section, a second reaction section, and a third reaction section with successively increasing temperatures; the temperature of the first reaction section is 700℃; the temperature of the second reaction section is 750℃; and the temperature of the third reaction section is 800℃; the pyrolysis reaction uses a mixture of methane, ethane, and propane for heat generation.

[0133] The scanning electron microscope image of the cobalt oxide is as follows: Figure 2 As shown, the morphology of cobalt oxide consists of secondary microspheres of 4-5 μm in size. These microspheres are formed by the close packing of primary crystal particles of about 100-200 nm in size. The sphericity of the particles is well maintained, and no structural breakage is observed.

[0134] Application Example 2

[0135] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Example 1, the method comprising the following steps:

[0136] A 300 g / L nickel nitrate aqueous solution was fed, conveyed by air at 0.6 MPa, atomized, and pyrolyzed for 5 s to obtain nickel oxide and nitrogen oxides. The obtained nickel oxide and nitrogen oxides were separated. The nickel oxide was collected in stages, and the nitrogen oxides were washed with water and recycled to achieve the reuse of nitric acid.

[0137] The feed flow rate is 10±0.5L / h, and the pressure is 0.7±0.07MPa; the pyrolysis reaction includes a first reaction section, a second reaction section, and a third reaction section with successively increasing temperatures; the temperature of the first reaction section is 800℃; the temperature of the second reaction section is 850℃; and the temperature of the third reaction section is 900℃; the pyrolysis reaction uses a mixture of methane, ethane, and propane for heat generation.

[0138] The transmission electron microscope image of the nickel oxide is as follows: Figure 3 , Figure 4 As shown, nickel oxide consists of secondary microspheres composed of 50-100nm primary crystal particles. The particles have abundant internal pore structures, which can expose more surface active sites, which is beneficial for the physicochemical transport of electrons or ions within the material structure.

[0139] Application Example 3

[0140] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Example 1, the method comprising the following steps:

[0141] A 100 g / L cerium chloride aqueous solution was fed, conveyed by air at 0.2 MPa, atomized, and pyrolyzed for 20 s to obtain cerium oxide and hydrochloric acid gas. The obtained cerium oxide and hydrochloric acid gas were separated. The cerium oxide was collected in stages, and the hydrochloric acid gas was washed with water and recycled to achieve hydrochloric acid reuse.

[0142] The feed flow rate is 2±0.1L / h, and the pressure is 0.2±0.02MPa; the pyrolysis reaction includes a first reaction section, a second reaction section, and a third reaction section with successively increasing temperatures; the temperature of the first reaction section is 600℃; the temperature of the second reaction section is 650℃; and the temperature of the third reaction section is 700℃; the pyrolysis reaction uses a mixture of methane, ethane, and propane for heat generation.

[0143] The transmission electron microscope image of the cerium oxide is as follows: Figure 5 As shown, cerium oxide exhibits a morphology of secondary microspheres approximately 1 μm in size, which are composed of tightly packed primary crystalline particles of approximately 50-100 nm in diameter. It should be noted that since electrons cannot penetrate large particles, their morphology cannot be observed; therefore, smaller particles were specifically selected for morphology characterization.

[0144] Application Example 4

[0145] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Example 1, the method comprising the following steps:

[0146] A 400 g / L manganese acetate aqueous solution is fed, conveyed by air at 1 MPa, atomized, and pyrolyzed for 1 second to obtain manganese oxide, carbon dioxide, and water vapor. The manganese oxide, carbon dioxide, and water vapor are then separated. The manganese oxide is collected in stages, while the carbon dioxide and water vapor are washed with water, recycled, and then discharged.

[0147] The feed flow rate is 100±5 L / h, and the pressure is 1±0.1 MPa; the pyrolysis reaction includes a first reaction section, a second reaction section, and a third reaction section with successively increasing temperatures; the temperature of the first reaction section is 900℃; the temperature of the second reaction section is 950℃; and the temperature of the third reaction section is 1000℃; the pyrolysis reaction uses a mixture of methane, ethane, and propane for heat generation.

[0148] The transmission electron microscope image of the manganese oxide is as follows: Figure 6 As shown, the morphology of manganese oxide is that of secondary microspheres with a size of about 1 μm. It should be noted that the size here is not representative. It can be seen that the primary crystal particles are packed relatively tightly, but the porous structure can still be seen dispersed in the microspheres.

[0149] Application Example 5

[0150] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Example 1, the method comprising the following steps:

[0151] A 10 g / L ammonium tungstate aqueous solution was fed, conveyed by air at 0.05 MPa, atomized, and pyrolyzed for 60 s to obtain tungsten oxide and ammonia. The tungsten oxide and ammonia were then separated. The tungsten oxide was collected in stages, and the ammonia was washed with water and recycled to achieve reuse of the ammonia solution.

[0152] The feed flow rate is 0.1±0.005 L / h, and the pressure is 0.05±0.005 MPa. The pyrolysis reaction includes a first reaction section, a second reaction section, and a third reaction section with successively increasing temperatures. The temperature of the first reaction section is 500℃; the temperature of the second reaction section is 550℃; and the temperature of the third reaction section is 600℃. The pyrolysis reaction uses a mixture of methane, ethane, and propane for combustion to provide heat.

[0153] Application Example 6

[0154] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 1. The difference between this method and Application Example 1 is that, except for adjusting the air delivery pressure to 0.02 MPa, all other aspects are the same as in Application Example 1.

[0155] Application Example 7

[0156] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 1. The difference between this method and Application Example 1 is that, except for adjusting the air delivery pressure to 1.2 MPa, all other aspects are the same as in Application Example 1.

[0157] Application Example 8

[0158] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 1. The difference between this method and Application Example 1 is that the pyrolysis reaction has only one reaction stage, and the temperature of the reaction stage is 800°C. All other aspects are the same as in Application Example 1.

[0159] Application Example 9

[0160] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 2, wherein the steps of the method are the same as those in Application Example 1.

[0161] Application Example 10

[0162] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 3, the steps of which are the same as in Application Example 1.

[0163] Application Example 11

[0164] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 4, wherein the steps of the method are the same as those in Application Example 1.

[0165] Application Example 12

[0166] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 5, wherein the steps of the method are the same as those in Application Example 1.

[0167] Application Example 13

[0168] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 6, the steps of which are the same as in Application Example 1.

[0169] Application Example 14

[0170] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 7, the steps of which are the same as in Application Example 1.

[0171] Application Example 15

[0172] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 8, the steps of which are the same as in Application Example 1.

[0173] Application Example 16

[0174] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 9, the steps of which are the same as in Application Example 1.

[0175] Application Example 17

[0176] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Application Example 10, the steps of which are the same as in Application Example 1.

[0177] Comparative Application Example 1

[0178] This application example provides a method for synthesizing metal oxides using the apparatus system provided in Comparative Example 1. The method differs from Application Example 1 in that the feed flow rate is constant at 5 L / h and the pressure is constant at 0.4 MPa, while all other aspects are the same as in Application Example 1.

[0179] The scanning electron microscope image of the obtained cobalt oxide is shown below. Figure 7 As shown, cobalt oxide exhibits a multi-shell structure and has largely lost the integrity of spherical particles, with severe structural fragmentation.

[0180] The corresponding metal oxides were synthesized using the methods provided in Application Examples 1-17 and Comparative Application Example 1. Purity was tested by titration; particle size was tested by laser diffraction; specific surface area was determined by nitrogen adsorption; and tap density was tested. The results are shown in Table 1.

[0181] Table 1

[0182]

[0183]

[0184] As can be seen from Table 1, and from Application Examples 1-5, the method for synthesizing metal oxides provided by the present invention can obtain metal oxides with high purity and tap density by adjusting the feed pressure and flow rate and controlling the pyrolysis temperature.

[0185] A comparison of Application Example 1 with Application Examples 6 and 7 shows that if the carrier gas pressure is too low or too high, the optimal values ​​for the pyrolysis reaction temperature and residence time of the raw material cannot be guaranteed, resulting in a decrease in the tap density and purity of the obtained metal oxides. A comparison of Application Example 1 with Application Example 8 shows that when the pyrolysis reaction is set to a single reaction temperature range, the raw material directly enters the high-temperature reaction stage. The solvent inside the droplets does not have time to evaporate before forming oxides on its surface, leading to incomplete internal reaction. Subsequent reactions easily form hollow shell structures, significantly reducing the purity and tap density of the metal oxides. A comparison of Application Example 1 with Application Examples 9-12 shows that the spray pyrolysis device system provided by this invention can obtain higher purity and tap density. High-density, low-specific-surface-area micro / nano-level metal oxides; A comparison of Application Example 1 with Application Examples 13 and 14 shows that if the nozzle diameter is too small or too large, it will adversely affect the control of droplet size and quantity, thus affecting the performance of the metal oxides; A comparison of Application Example 1 with Application Example 15 shows that if the spray angle is too small, it cannot be uniformly dispersed in the cavity of the pyrolysis device, resulting in poor particle morphology of the obtained metal oxides; A comparison of Application Example 1 with Application Example 16 shows that placing the atomizer at the top of the pyrolysis device will shorten the residence time of the raw materials, leading to incomplete reaction of the metal oxides and thus reducing purity; A comparison of Application Example 1 with Application Example 17 shows that the dust collection unit provided by this invention can improve the purity of metal oxides;

[0186] As can be seen from the comparison between Application Example 1 and Comparative Application Example 1, the automatic feeding device provided by the present invention plays a role in regulating the temperature distribution and material residence time in the pyrolysis tower, thereby significantly improving the overall performance of the obtained metal oxide.

[0187] In summary, the device system provided by this invention, by setting up an automatic feeding device and placing the atomizing device at the bottom of the pyrolysis device, can ensure that the actual decomposition temperature and residence time of the raw materials in the pyrolysis device are continuously and stably precisely controlled; the dust collection unit can efficiently separate metal oxides and flue gas to achieve the preparation of high-purity metal oxides; and the flue gas recovery unit can realize the recycling and regeneration of flue gas.

[0188] This invention employs reasonable feed parameters and pyrolysis process parameters to effectively control the decomposition temperature and residence time of the raw materials, resulting in a tap density of up to 1.88 g·cm³ for the obtained metal oxides. -3 With a purity of up to 99.97%, it can be used for industrial-scale production.

[0189] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method of synthesizing a metal oxide, characterized by, The method is performed by a spray pyrolysis device system, which comprises a pyrolysis reaction unit, a dust collection unit and a flue gas recovery unit connected in sequence along a material flow direction; The pyrolysis reaction unit comprises an automatic feeding device, a carrier compression device, an atomization device and a pyrolysis device connected in sequence along a material flow direction, and the side wall bottom of the pyrolysis device is connected with a combustion device; the automatic feeding device comprises a raw material storage device connected with a pressure increasing device through a pipeline; the outlet of the raw material storage device is connected with the carrier compression device; The outlet of the atomization device is communicated with the inner cavity bottom of the pyrolysis device; the atomization device is a double-fluid atomization type; the spray head of the atomization device is a front-end gas-liquid mixed double-fluid atomization spray head; The pyrolysis device comprises a vertical cavity, and the top of the vertical cavity is provided with a discharge port; The inside of the vertical cavity is provided with a temperature and air pressure monitoring device; The temperature and air pressure monitoring device is arranged at the bottom, middle and top of the vertical cavity; and the air outlet of the combustion device is provided with a temperature and air pressure detection device; The method comprises the following steps: A metal salt aqueous solution is subjected to feeding, carrier gas delivery, atomization and pyrolysis reaction to obtain metal oxide and by-product gas; the obtained metal oxide and by-product gas are separated; wherein the metal oxide is collected in stages, and the by-product gas is recovered and treated; The flow rate of the feeding is 0.1-100 L / h; the pressure of the feeding is 0.05-1 MPa; and the pressure of the carrier gas delivery is 0.2-0.6 MPa; The temperature of the pyrolysis reaction is 500-1000 ℃, and the time is 1-60 s; the pyrolysis reaction comprises a first reaction section, a second reaction section and a third reaction section with temperature rising in sequence; the temperature of the first reaction section is 500-900 ℃; the temperature of the second reaction section is 550-950 ℃; and the temperature of the third reaction section is 600-1000 ℃.

2. The method of claim 1, wherein, The diameter of the spray head of the atomization device is 0.5-2 mm.

3. The method of claim 2, wherein, The diameter of the spray head of the atomization device is 0.8-1 mm.

4. The method of claim 1, wherein, The included angle between the spray direction of the atomization device and the height direction of the pyrolysis device is 20-90°.

5. The method of claim 4, wherein, The included angle between the spray direction of the atomization device and the height direction of the pyrolysis device is 30-60°.

6. The method of claim 1, wherein, The lining material of the vertical cavity comprises heat-resistant corundum castable.

7. The method of claim 1, wherein, The height of the vertical cavity is 2-10 m.

8. The method of claim 7, wherein, The height of the vertical cavity is 3-6 m.

9. The method of claim 1, wherein, The diameter of the vertical cavity is 0.1-2 m.

10. The method of claim 9, wherein, The diameter of the vertical cavity is 0.5-1 m.

11. The method of claim 1, wherein, Along the material flow direction inside the vertical cavity, the combustion device comprises a first combustion furnace and a second combustion furnace arranged in sequence.

12. The method of claim 1, wherein, The dust collection unit comprises a cyclone dust collector and a heat-resistant cloth bag dust collector connected in sequence along a material flow direction.

13. The method of claim 12, wherein, The cyclone dust collector is connected with the discharge port of the vertical cavity.

14. The method of claim 12, wherein, The type of the cyclone dust collector comprises any one of a long cone type, a cylindrical type, a diffusion type and a bypass type.

15. The method of claim 14, wherein, The type of the cyclone dust collector is a diffusion type.

16. The method of claim 12, wherein, The surface of the cyclone dust collector is coated with a heat preservation layer.

17. The method of claim 12, wherein, The inside of the heat-resistant cloth bag dust collector is provided with a sintered metal mesh.

18. The method of claim 17, wherein, The sintered metal mesh has a pore size of 0.01-1 μm.

19. The method of claim 18, wherein, The sintered metal mesh has a pore size of 0.05-0.5 μm.

20. The method of claim 12, wherein, The flue gas recovery unit comprises an absorption device, the top of the absorption device is connected with an air induction device, and the bottom of the absorption device is connected with a heat exchange device.

21. The method of claim 20, wherein, The absorption device is connected with the gas outlet of the heat-resistant cloth bag dust collector.

22. The method of claim 20, wherein, The inner cavity bottom of the absorption device is provided with a spiral atomizing nozzle.

23. The method of claim 20, wherein, The material of the gas inlet of the absorption device comprises a heat-resistant and corrosion-resistant brick.

24. The method of claim 20, wherein, The material of the inner lining of the absorption device comprises an acid and alkali resistant ceramic filler.

25. The method of claim 1, wherein, The concentration of the metal salt is 10-400 g / L.

26. The method of claim 25, wherein, The concentration of the metal salt is 100-300 g / L.

27. The method of claim 1, wherein, The metal salt comprises any one or a combination of at least two of a metal nitrate, a metal chloride, a metal acetate, a metal oxalate or a metal ammonium acid salt.

28. The method of claim 27, wherein, The metal nitrate comprises any one or a combination of at least two of nickel nitrate, cobalt nitrate, manganese nitrate, lithium nitrate, magnesium nitrate, cerium nitrate, aluminum nitrate, zirconium nitrate, zinc nitrate, iron nitrate, molybdenum nitrate or copper nitrate.

29. The method of claim 27, wherein, The metal chloride comprises any one or a combination of at least two of nickel chloride, cobalt chloride, manganese chloride, magnesium chloride, lanthanum chloride, cerium chloride, praseodymium chloride, neodymium chloride, aluminum chloride, iron chloride or zirconium oxychloride.

30. The method of claim 27, wherein, The metal acetate comprises any one or a combination of at least two of nickel acetate, cobalt acetate, manganese acetate, lithium acetate, magnesium acetate, cerium acetate or zinc acetate.

31. The method of claim 27, wherein, The metal oxalate comprises any one or a combination of at least two of nickel oxalate, cobalt oxalate, manganese oxalate, lithium oxalate, magnesium oxalate, cerium oxalate, lanthanum oxalate, praseodymium oxalate or neodymium oxalate.

32. The method of claim 27, wherein, The metal ammonium acid salt comprises any one or a combination of at least two of ammonium tungstate, ammonium metatungstate, ammonium metavanadate or ammonium molybdate.

33. The method of claim 1, wherein, The carrier gas comprises any one or a combination of at least two of air, oxygen, argon, nitrogen or carbon dioxide.

34. The method of claim 1, wherein, The pyrolysis reaction has a time of 5-20 s.

35. The method of claim 1, wherein, The pyrolysis reaction uses combustion of a combustible gas to provide heat, and the combustible gas comprises any one or a combination of at least two of methane, ethane, propane, acetylene, carbon monoxide or hydrogen.

36. The method of claim 1, wherein, The recovery processing comprises water washing and recycling of the byproduct gas.

37. The method of claim 1, wherein, The method comprises the following steps: A metal salt aqueous solution with a concentration of 10-400 g / L is fed, the carrier gas is delivered at a pressure of 0.2-0.6 MPa, atomization is performed, and pyrolysis is performed at a temperature of 500-1000 ℃ for 1-60 s to obtain metal oxides and byproduct gas; the obtained metal oxides and byproduct gas are separated; the metal oxides are collected in stages, and the byproduct gas is water washed, recycled and then discharged or reused; The flow rate of the feed is 0.1-100 L / h, and the pressure is 0.05-1 MPa; the pyrolysis reaction comprises a first reaction section, a second reaction section and a third reaction section with increasing temperatures; the temperature of the first reaction section is 500-900 ℃; the temperature of the second reaction section is 550-950 ℃; the temperature of the third reaction section is 600-1000 ℃; and the pyrolysis reaction uses combustion of a combustible gas to provide heat.

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