Device system for preparing metal oxide particles

Abstract

The utility model provides a device system for preparing metal oxide particles, which comprises an evaporation concentration device, a spray drying device and a thermal decomposition device, a bottom discharge port of the spray drying device is communicated with a feed port of the thermal decomposition device, and a bottom discharge port of the thermal decomposition device is communicated with the evaporation concentration device. An outlet of the evaporation concentration device is communicated with an atomization device at the top of the spray drying device, a hot air outlet of the thermal decomposition device is communicated with a hot air inlet of the spray drying device through a first induced draft fan and a heating device in sequence, and the upper portion of a sealed heating cavity in the thermal decomposition device is a constant-temperature heating area. And heating assemblies of independent control switches are arranged on the inner wall of the cavity of the constant-temperature heating area at intervals in the vertical direction. The device system provided by the utility model can accurately control the retention time of materials, ensures that the materials are completely decomposed, is good in sealing performance, does not have the problem that the materials are adhered to walls, and reduces the energy consumption and the cost of production.

Description

Technical Field

[0001] This utility model relates to the field of metal oxide powder preparation technology, and specifically to an apparatus system for preparing metal oxide particles. Background Technology

[0002] Compared to metal sulfates and chlorides, metal nitrates have lower thermal decomposition temperatures. Upon reaching these temperatures, metal nitrates decompose into metal oxides, oxygen, and nitrogen dioxide. Notably, oxygen and nitrogen dioxide can be regenerated into nitric acid through water absorption; therefore, using nitrates to prepare metal oxides has significant application potential.

[0003] In current industrial production, roller kilns or rotary kilns are commonly used for the high-temperature pyrolysis of nitrate raw materials. However, during operation, the insufficient airtightness of traditional kilns leads to frequent dust and gas leaks, causing environmental pollution. In rotary kilns, materials tend to stick to the walls as they roll within the kiln, which, over long-term operation, affects the uniformity of heating and consequently impacts product quality. In addition, spray pyrolysis equipment can also be used for production. Usually, the metal nitrate solution is sprayed into the pyrolysis furnace in a mist and pyrolyzed in a high-temperature environment to obtain metal oxide particles. However, the problems with this type of device are: (1) It is difficult to control the residence time of the material in the spray pyrolysis furnace. If the residence time is too short, the metal nitrate solution will not be completely decomposed. If the residence time is too long, the particle size may be too large. (2) This device couples spray drying and high-temperature pyrolysis, resulting in uneven reaction temperature and atmosphere. The nitrogen oxides generated by decomposition are uncontrollable and are prone to producing nitric oxide, which is not conducive to the spray recovery of nitric acid. The remaining nitrogen oxides require additional denitrification treatment, and the cost of the recovery device is high. (3) It increases gas consumption, thereby increasing production costs. (4) The material universality of this device is insufficient. The equipment suitable for light metal oxides cannot be used to produce heavy metal oxides. In addition, some nitrates have a high endothermic enthalpy, and the airflow speed is too fast, which can also lead to the incomplete decomposition of the raw materials.

[0004] For example, CN109539792A discloses a spray pyrolysis device for preparing ternary cathode precursors and its usage method. The device includes a first spray pyrolysis device and a second spray pyrolysis device. The outlet of the first spray pyrolysis device is connected to a conveying device, and the outlet of the conveying device is located in the cavity of the second spray pyrolysis device. The method includes: (1) spraying a ternary mixed salt solution into the first spray pyrolysis device to generate a pre-product; (2) the pre-product enters the second spray pyrolysis device through the conveying device, where solid and gas are separated. The solid is the ternary cathode precursor for lithium batteries, and the gas is discharged and then processed or recycled. Although this method ensures residence time by setting up two spray pyrolysis devices, as the pyrolysis temperature increases, the two sets of spray pyrolysis devices need to consume a large amount of thermal energy to maintain the temperature, resulting in high operating costs. Furthermore, the dust and gas passing through the U-shaped pipe inevitably cause problems such as material blockage and wall adhesion, leading to uneven material decomposition.

[0005] Therefore, developing a device for preparing metal oxide particulate materials that can fully guarantee the pyrolysis temperature and residence time, while avoiding problems such as wall adhesion and dust leakage, and reducing production costs and energy consumption, is a technical problem that needs to be solved in this field. Utility Model Content

[0006] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide a device system for preparing metal oxide particles. The device system can accurately control the residence time of the material, ensure complete decomposition of the material, and has good sealing performance, so as to prevent the material from sticking to the wall and reduce the energy consumption and cost of production.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides an apparatus system for preparing metal oxide particles, the apparatus system comprising an evaporation and concentration device, a spray drying device, and a thermal decomposition device;

[0009] The bottom outlet of the spray drying device is connected to the inlet of the pyrolysis device.

[0010] The top of the cavity of the spray drying device is equipped with an atomizing device, and the outlet of the evaporation and concentration device is connected to the feed liquid inlet of the atomizing device;

[0011] The top of the cavity of the spray drying device is also provided with a hot air inlet, and the hot air outlet of the pyrolysis device is connected to the hot air inlet of the spray drying device in sequence via the first induced draft fan and the heating device.

[0012] The pyrolysis device is equipped with a sealed heating chamber. The upper part of the sealed heating chamber is a constant temperature heating zone. The inner wall of the constant temperature heating zone is equipped with heating components with independent control switches at intervals along the vertical direction.

[0013] Compared to existing spray pyrolysis equipment, the device system provided by this invention adopts a separate design for the spray drying device and the pyrolysis device. This allows the feed liquid (generally a metal nitrate solution) to first be spray-dried into micron-sized particles, and then pyrolyzed into metal oxide particles. This ensures uniform particle size and pyrolysis uniformity of the product, and results in a denser structure, significantly reducing the energy consumption cost of the pyrolysis process. Furthermore, the hot air discharged from the pyrolysis device is reheated by a heater and then reused in the spray drying device, further reducing heat loss and energy consumption. In addition, the sealed heating chamber has excellent airtightness, avoiding dust leakage problems that occur with rotary kilns and other similar devices, resulting in less heat loss and higher thermal efficiency.

[0014] It is worth noting that in this invention, a constant-temperature heating zone is provided at the upper part of the sealed heating chamber. Heating components with independent control switches are arranged at intervals along the vertical direction on the inner wall of the chamber. At least two sets of heating components are arranged (opened) at intervals from top to bottom along the vertical direction on the inner wall of the chamber. For example, there can be 2, 3, 4, 5, or 6 sets, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable. In this invention, by controlling the number of heating components that are turned on, the range of the constant-temperature heating zone is controlled, achieving the effect of precisely controlling the residence time of materials according to the physical properties of different liquids, thereby ensuring complete pyrolysis of the raw materials and saving energy costs.

[0015] Furthermore, in this invention, controlling the number of heating components that open vertically from top to bottom effectively controls the proportion of the height of the constant-temperature heating zone to the height of the sealed heating chamber. This ensures the universality of the constant-temperature heating zone for different materials, avoiding problems such as excessively short material residence time (resulting in incomplete decomposition of metallic nitrates and the generation of nitric oxide) or excessively long residence time (resulting in excessively large particle sizes), as seen in existing spray pyrolysis devices. Specifically, taking magnesium nitrate, praseodymium nitrate, and cerium nitrate as examples, by controlling the number of heating components that open, the height of the constant-temperature heating zone is made to occupy 1 / 3, 1 / 2, and 2 / 5 of the height of the sealed heating chamber, respectively, thereby precisely controlling the material residence time.

[0016] In this invention, the spacing between adjacent heating components is not specifically limited and can be set according to actual needs; each heating component generally includes at least one heater, and the type of heater is not specifically limited, and any heater commonly used in the art can be used, such as an electric heater or a flame jet heater; each heater in the same heating component is independently controlled; when the number of heaters in the same heating component is ≥2, the position and layout of the heaters can be set according to requirements, ensuring the required thermal decomposition temperature of the metal oxide while ensuring the temperature uniformity of the constant temperature heating zone and low heating power, thereby saving energy consumption, for example, the heaters can be set at equal intervals along the circumferential direction of the inner wall of the cavity.

[0017] In this invention, the atomizing device can be any atomizing device commonly used in spray drying in the art, and can be selected according to the required particle size range of the metal oxide particles.

[0018] Preferably, the feed inlet of the pyrolysis device is located at the top of the pyrolysis device; the bottom outlet of the spray drying device is located above the feed inlet of the pyrolysis device.

[0019] Preferably, the bottom outlet of the spray drying device and the inlet of the pyrolysis device further include a storage device and a feeding device connected sequentially in the direction of material flow.

[0020] Preferably, the storage device includes a storage bin; the feeding device includes a guide screw.

[0021] Preferably, the sealed heating chamber of the pyrolysis device is a vertical chamber.

[0022] In this invention, on the one hand, by placing both the atomizing device and the hot air inlet at the top of the spray drying device's cavity, the dried material can fall under the influence of gravity and hot air, and be discharged from the bottom outlet of the spray drying device. On the other hand, by incorporating a storage device and a feeding device, the material can be temporarily stored in the storage device, and the feeding device can control the material's feed rate and quantity. Furthermore, the thermal decomposition device provided by this invention uses a vertical cavity, enabling the material to undergo thermal decomposition during its descent under gravity, thus preventing significant wall adhesion.

[0023] Preferably, the hot air outlet of the pyrolysis device is located on the upper side of the pyrolysis device.

[0024] In this invention, by setting the hot air outlet of the thermal decomposition device to one side of the upper part of the thermal decomposition device, it is possible to ensure that the material is separated into solid and gas in a timely manner after being decomposed into solid and gas in the thermal decomposition device.

[0025] Preferably, the device system further includes a first gas-solid separation device; the hot air outlet of the pyrolysis device is connected to the first gas-solid separation device; and the gas phase outlet of the first gas-solid separation device is connected to a first induced draft fan.

[0026] Preferably, the device system further includes a second gas-solid separation device; the inlet of the second gas-solid separation device is connected to the gas phase outlet of the spray drying device; the solid phase outlet of the second gas-solid separation device is connected to the inlet of the storage device.

[0027] In this invention, the first and second gas-solid separation devices are not particularly limited and can be any device commonly used in the art for separating gases and solid particles, such as a bag filter. The solid phase outlets of the first and second gas-solid separation devices are generally located at the bottom of the device, and the gas phase outlets are generally located on the side wall of the device. In this invention, the gas phase outlet of the spray drying device is generally located on the side wall of the device.

[0028] Preferably, the device system further includes a second induced draft fan and an exhaust gas absorption device; the gas phase outlet of the second gas-solid separation device is connected to the exhaust gas absorption device via the second induced draft fan.

[0029] In this invention, the exhaust gas absorption device absorbs nitrogen dioxide and prepares nitric acid, thereby improving the recovery rate of nitric acid.

[0030] The apparatus system provided by this utility model is used to prepare metal oxides and nitric acid from metal nitrate solutions. The operation process is as follows:

[0031] (1) The metal nitrate solution is concentrated in an evaporation and concentration device. According to the needs of subsequent spray drying, the metal nitrate solution is concentrated to the target concentration to obtain a concentrated solution.

[0032] Specifically, the metal nitrate solution may be, for example, any one or a combination of at least two of nickel nitrate, cobalt nitrate, manganese nitrate, lanthanum nitrate, cerium nitrate, praseodymium nitrate, neodymium nitrate, magnesium nitrate, aluminum nitrate, zirconium nitrate, yttrium nitrate, or calcium nitrate;

[0033] (2) The concentrated solution obtained in step (1) is sprayed into the top atomizing device of the spray drying device to atomize the concentrated solution into micron-sized droplets. Hot air is introduced into the hot air inlet at the top of the spray drying device to control the temperature inside the spray drying device so that the water in the droplets evaporates, and metal nitrate solid powder and first dust-containing tail gas are obtained. The first dust-containing tail gas enters the second gas-solid separation device. The separated solid phase and metal nitrate solid powder enter the storage bin together. The separated gas phase is sent into the tail gas absorption device by the second induced draft fan.

[0034] Specifically, the reaction temperature in the spray drying device can be, for example, 200-500°C, the reaction time can be, for example, 0.5-2h, and the atomization method of the atomizing device can be, for example, any one or a combination of at least two of pressure atomization, two-fluid atomization, or centrifugal atomization.

[0035] (3) The solid metal nitrate powder in the storage bin described in step (2) is fed into the thermal decomposition device by the guide screw. The residence time of the material is controlled by controlling the number of heating components turned on in the constant temperature heating zone, while meeting the temperature required for nitrate decomposition. The solid metal oxide powder is obtained and discharged from the oxide product outlet at the bottom of the thermal decomposition device under the action of gravity. At the same time, a second dust-containing tail gas is also obtained. The second dust-containing tail gas enters the first gas-solid separation device for deep dust removal through the hot air outlet. The separated gas phase enters the heating device for supplementary heating through the first induced draft fan, and finally returns to the hot air inlet of the spray drying device for recycling to provide the heat required for drying.

[0036] Specifically, the reaction temperature of the thermal decomposition device can be, for example, 500-1200℃, and the reaction time can be, for example, 0.5-2h.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The sealed heating chamber in the device system provided by this utility model has good airtightness, no dust leakage, avoids environmental pollution, has little heat loss and high thermal efficiency.

[0039] (2) The device system provided by this utility model divides the spray drying molding and high-temperature pyrolysis into two thermal processes, which ensures the uniformity of particle size and pyrolysis of the product, and the structure is more compact, which can significantly reduce the energy consumption cost of the thermal decomposition process.

[0040] (3) The device system provided by this utility model controls the atomizing device and the hot air inlet to be located at the top of the cavity of the spray drying device. It can use gravity and the driving force of the spray drying hot air to discharge the dried material from the bottom outlet of the spray drying device and enter the vertical cavity of the thermal decomposition device from the top through the feeding device. This allows the material to undergo thermal decomposition under the action of gravity and avoids obvious wall sticking problems.

[0041] (4) The hot air discharged from the thermal decomposition device in the device system provided by this utility model is reheated by the heater and then reused in the spray drying device, which can reduce the heat loss and energy consumption of the device system.

[0042] (5) The device system provided by this utility model has heating components with independent control switches arranged vertically on the inner wall of the cavity of the constant temperature heating zone. By controlling the number of heating components turned on from top to bottom, the range of the constant temperature heating zone can be controlled, so as to achieve the effect of accurately controlling the residence time of materials according to the physical properties of different liquids, thereby ensuring complete pyrolysis of raw materials and saving energy costs. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the device system provided in Embodiment 1 of this utility model;

[0044] In the diagram: 1-Evaporation and concentration device; 2-Spray drying device; 3-Storage silo; 4-Feeding screw; 5-Thermal decomposition device; 6-First gas-solid separation device; 7-First induced draft fan; 8-Heating device; 9-Second gas-solid separation device; 10-Second induced draft fan; 11-Tail gas absorption device. Detailed Implementation

[0045] It should be understood that in the description of this utility model, the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model 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 utility model.

[0046] It should be noted that, in the description of this utility model, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0047] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments.

[0048] Example 1

[0049] This embodiment provides an apparatus system for preparing metal oxide particles, such as... Figure 1As shown, the device system includes an evaporation and concentration unit 1, a spray drying unit 2, and a pyrolysis unit 5. The bottom outlet of the spray drying unit 2 is connected to the inlet of the pyrolysis unit 5 via a storage bin 3 and a guide screw 4 in the direction of material flow. The inlet of the pyrolysis unit 5 is located at the top of the pyrolysis unit 5, and the bottom outlet of the spray drying unit 2 is located above the inlet of the pyrolysis unit 5. An atomizing device is installed at the top of the cavity of the spray drying unit 2. The outlet of the evaporation and concentration unit 1 is connected to the liquid inlet of the atomizing device. A hot air inlet is also provided at the top of the cavity of the spray drying unit 2. The pyrolysis unit... The hot air outlet of the 5 is located on the upper side of the pyrolysis device 5. The hot air outlet is connected to the first gas-solid separation device 6. The gas phase outlet of the first gas-solid separation device 6 is connected to the first induced draft fan 7. The outlet of the first induced draft fan 7 is connected to the hot air inlet of the spray drying device 2 via the heating device 8. The gas phase outlet of the spray drying device 2 is connected to the inlet of the second gas-solid separation device 9. The solid phase outlet of the second gas-solid separation device 9 is connected to the inlet of the storage device. The gas phase outlet of the second gas-solid separation device 9 is connected to the tail gas absorption device 11 via the second induced draft fan 10. Both the first gas-solid separation device 6 and the second gas-solid separation device 9 are bag filters.

[0050] The thermal decomposition device 5 is equipped with a sealed heating chamber with a vertical cavity. The upper part of the sealed heating chamber is a constant temperature heating zone. The inner wall of the constant temperature heating zone is equipped with heating components with independent control switches at intervals along the vertical direction. The number of heating components that are turned on is adjusted so that the height of the constant temperature heating zone is 1 / 3 of the height of the sealed heating chamber.

[0051] The apparatus system provided in this embodiment is used to prepare magnesium oxide from magnesium nitrate solution. The operation process is as follows:

[0052] (1) A 1 mol / L magnesium nitrate solution is concentrated to a concentration of 5 mol / L in an evaporation and concentration apparatus 1 at 80°C to obtain a concentrated solution;

[0053] (2) The concentrated solution obtained in step (1) is sprayed into the top atomizing device of the spray drying device 2 to atomize the concentrated solution into micron-sized droplets. Hot air is introduced into the hot air inlet at the top of the spray drying device 2 to control the temperature inside the spray drying device 2 to 200°C, so that the water in the droplets evaporates to obtain magnesium nitrate solid powder and the first dust-containing tail gas. The first dust-containing tail gas enters the bag filter. The separated solid phase and magnesium nitrate solid powder enter the storage bin 3 together. The separated gas phase is sent to the tail gas absorption device 11 by the second induced draft fan 10.

[0054] (3) The magnesium nitrate solid powder in the storage bin 3 described in step (2) is fed into the thermal decomposition device 5 via the guide screw 4. The residence time of the material is controlled by controlling the number of heating components turned on in the constant temperature heating zone. At the same time, the temperature of the constant temperature heating zone is controlled at 600℃ to meet the needs of magnesium nitrate decomposition. Magnesium oxide solid powder is obtained and discharged from the oxide product outlet at the bottom of the thermal decomposition device 5 under the action of gravity. The average size of the primary particles is 580nm, and the particle size of the secondary particles is D. 50 The dust concentration is 3.48 μm. At the same time, a second dust-laden exhaust gas is also obtained. The second dust-laden exhaust gas enters the bag filter for deep dust removal through the hot air outlet. The separated gas phase enters the heating device 8 through the first induced draft fan 7 for supplemental heating, and finally returns to the hot air inlet of the spray drying device 2 for recycling, providing the heat required for drying.

[0055] In this embodiment, the magnesium oxide yield is 99.5%, the nitric acid recovery rate in the tail gas absorption device 11 is 97%, and the nitric acid concentration is 51%.

[0056] Example 2

[0057] This embodiment provides an apparatus system for preparing metal oxide particles. The only difference from Embodiment 1 is that the number of heating components turned on is adjusted so that the height of the constant temperature heating zone is 2 / 5 of the height of the sealed heating chamber.

[0058] The apparatus system provided in this embodiment is used to prepare cerium oxide from cerium nitrate solution. The operation process is as follows:

[0059] (1) A 1 mol / L cerium nitrate solution was concentrated to a concentration of 4.5 mol / L in an evaporation and concentration apparatus at 85°C to obtain a concentrated solution;

[0060] (2) The concentrated solution obtained in step (1) is sprayed into the top atomizing device of the spray drying device to atomize the concentrated solution into micron-sized droplets. Hot air is introduced into the hot air inlet at the top of the spray drying device to control the temperature inside the spray drying device to 230°C, so that the water in the droplets evaporates to obtain cerium nitrate solid powder and the first dust-containing tail gas. The first dust-containing tail gas enters the bag filter. The separated solid phase and cerium nitrate solid powder enter the storage bin together. The separated gas phase is sent into the tail gas absorption device by the second induced draft fan.

[0061] (3) The cerium nitrate solid powder in the storage bin described in step (2) is fed into the thermal decomposition device via a guide screw. The residence time of the material is controlled by controlling the number of heating components turned on in the constant temperature heating zone. At the same time, the temperature of the constant temperature heating zone is controlled at 650℃ to meet the needs of cerium nitrate decomposition. Cerium oxide solid powder is obtained and discharged from the oxide product outlet at the bottom of the thermal decomposition device under the action of gravity. The average size of the primary particles is 520nm, and the secondary particle size D50 The dust concentration is 3.23 μm. At the same time, a second dust-laden exhaust gas is also obtained. The second dust-laden exhaust gas enters the bag filter for deep dust removal through the hot air outlet. The separated gas phase enters the heating device through the first induced draft fan for supplemental heating, and finally returns to the hot air inlet of the spray drying device for recycling, providing the heat required for drying.

[0062] In this embodiment, the cerium oxide yield is 99.7%, the nitric acid recovery rate in the tail gas absorption device is 96%, and the nitric acid concentration is 50%.

[0063] Example 3

[0064] This embodiment provides an apparatus system for preparing metal oxide particles. The only difference from Embodiment 1 is that the number of heating components turned on is adjusted so that the height of the constant temperature heating zone is 1 / 2 of the height of the sealed heating chamber.

[0065] The apparatus system provided in this embodiment is used to prepare praseodymium oxide from praseodymium nitrate solution. The operation process is as follows:

[0066] (1) A 1 mol / L praseodymium nitrate solution was concentrated to a concentration of 4 mol / L in an evaporation and concentration apparatus at 90°C to obtain a concentrated solution;

[0067] (2) The concentrated solution obtained in step (1) is sprayed into the top atomizing device of the spray drying device to atomize the concentrated solution into micron-sized droplets. Hot air is introduced into the hot air inlet at the top of the spray drying device to control the temperature inside the spray drying device to 250°C, so that the water in the droplets evaporates to obtain praseodymium nitrate solid powder and the first dust-laden exhaust gas. The first dust-laden exhaust gas enters the bag filter. The separated solid phase and praseodymium nitrate solid powder enter the storage bin together. The separated gas phase is sent into the exhaust gas absorption device by the second induced draft fan.

[0068] (3) In step (2), the praseodymium nitrate solid powder in the storage silo is fed into the thermal decomposition device via a guide screw. The residence time of the material is controlled by controlling the number of heating components turned on in the constant temperature heating zone. At the same time, the temperature of the constant temperature heating zone is controlled at 700℃ to meet the needs of praseodymium nitrate decomposition. Praseodymium oxide solid powder is obtained and discharged from the oxide product outlet at the bottom of the thermal decomposition device under the action of gravity. The average size of the primary particles is 570nm, and the secondary particle size D 50 The dust concentration is 3.41 μm. At the same time, a second dust-laden exhaust gas is also obtained. The second dust-laden exhaust gas enters the bag filter for deep dust removal through the hot air outlet. The separated gas phase enters the heating device through the first induced draft fan for supplemental heating, and finally returns to the hot air inlet of the spray drying device for recycling, providing the heat required for drying.

[0069] In this embodiment, the yield of praseodymium oxide is 99.6%, the recovery rate of nitric acid in the tail gas absorption device is 96%, and the concentration of nitric acid is 51%.

[0070] Example 4

[0071] This embodiment provides an apparatus system for preparing metal oxide particles. The only difference from Embodiment 3 is that the number of heating components turned on is adjusted so that the height of the constant temperature heating zone is 1 / 3 of the height of the sealed heating chamber.

[0072] The device system provided in this embodiment is used to prepare praseodymium oxide from praseodymium nitrate solution. The operation process is the same as in Example 3, and the temperature of the constant temperature heating zone remains unchanged at 700°C.

[0073] In this embodiment, the yield of praseodymium oxide is 93.2%, the average size of primary particles is 530 nm, the particle size D50 of secondary particles is 3.30 μm, the recovery rate of nitric acid in the tail gas absorption device is 80%, and the concentration of nitric acid is 40%.

[0074] Example 5

[0075] This embodiment provides an apparatus system for preparing metal oxide particles. The only difference from Embodiment 3 is that the number of heating components turned on is adjusted so that the height of the constant temperature heating zone is 1 / 3 of the height of the sealed heating chamber.

[0076] The apparatus system provided in this embodiment is the same as in Example 3, except that the temperature of the constant temperature heating zone is controlled at 800°C.

[0077] In this embodiment, the yield of praseodymium oxide is 98.7%, the average size of primary particles is 560 nm, the particle size D50 of secondary particles is 3.39 μm, the recovery rate of nitric acid in the tail gas absorption device is 85%, and the concentration of nitric acid is 43%.

[0078] Compared to Example 3, Examples 4 and 5, conducted at the same pyrolysis temperature, show that in Example 4, the isothermal heating zone was too short, resulting in insufficient residence time and the collected product containing undecomposed praseodymium nitrate. In Example 5, although the pyrolysis temperature was further increased to 800°C, the reaction time was still insufficient due to the short isothermal heating zone, leading to low nitrogen dioxide content in the reaction product and low nitric acid recovery. Therefore, this invention can precisely adjust the proportion of the isothermal heating zone's height to the sealed heating chamber's height based on the material's characteristics, ensuring complete pyrolysis, improving product yield, and maintaining low energy consumption.

[0079] Comparative Example 1

[0080] This comparative example provides an apparatus system for preparing metal oxide particles. The only difference from Example 1 is that the spray drying device and the pyrolysis device are replaced with a spray pyrolysis device. The feed inlet of the atomizing device in the spray pyrolysis device is connected to the outlet of the evaporation and concentration device. An oxide product outlet is provided at the bottom of the spray pyrolysis device. A dust-containing exhaust gas outlet is provided on the side wall of the spray pyrolysis device. The dust-containing exhaust gas outlet is connected to an exhaust gas absorption device through a bag filter.

[0081] The apparatus system provided in this comparative example for preparing magnesium oxide from magnesium nitrate solution differs from that in Example 1 only in that the concentrated solution is fed into a spray pyrolysis device and spray pyrolysis is performed at 600°C to obtain magnesium oxide solid powder. The average primary particle size is 565 nm, and the secondary particle size D... 50 The dust concentration was 3.39 μm. Dust-laden exhaust gas was also obtained, which was then sent to the exhaust gas absorption device after deep dust removal by a bag filter to obtain nitric acid.

[0082] In this comparative example, the magnesium oxide recovery rate was 85%, the nitric acid recovery rate in the tail gas absorption device was 83%, and the nitric acid concentration was 43%.

[0083] Comparative Example 2

[0084] This comparative example provides an apparatus system for preparing metal oxide particles, which is the same as that in Comparative Example 1.

[0085] The apparatus system provided in this comparative example for preparing magnesium oxide from magnesium nitrate solution differs from that in Example 1 only in that the concentrated solution is fed into a spray pyrolysis device and spray pyrolysis is performed at 750°C to obtain magnesium oxide solid powder. The average primary particle size is 550 nm, and the secondary particle size D... 50 The dust concentration was 3.37 μm. Dust-laden exhaust gas was also obtained, which was then sent to the exhaust gas absorption device after deep dust removal by a bag filter to obtain nitric acid.

[0086] In this comparative example, the recovery rate of magnesium oxide was 94.1%, the recovery rate of nitric acid in the tail gas absorption device was 88%, and the concentration of nitric acid was 46%.

[0087] Compared to Example 1, Comparative Examples 1 and 2, at the same pyrolysis temperature, showed insufficient heat supply in Comparative Example 1, failing to fully pyrolyze magnesium nitrate, resulting in undecomposed magnesium nitrate in the product. Although the pyrolysis temperature was further increased in Comparative Example 2, it still could not achieve the magnesium oxide and nitric acid yields of Example 1, even at a higher temperature. Therefore, the device system provided by this invention, by dividing spray drying and high-temperature pyrolysis into two thermal processes, preheats the material before pyrolysis, reducing the temperature requirements for pyrolysis. Furthermore, spray drying ensures uniform particle size, and the independent pyrolysis process makes decomposition more uniform, significantly reducing the energy consumption cost of the pyrolysis process.

[0088] In summary, the device system provided by this utility model can accurately control the residence time of materials, ensure complete material decomposition, and has good sealing performance, preventing material from sticking to the wall and reducing energy consumption and costs in production.

[0089] The applicant declares that the above description is only a specific embodiment of the present utility model, but the protection scope of the present utility model 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 utility model fall within the protection and disclosure scope of the present utility model.

Claims

1. An apparatus system for preparing metal oxide particles, characterized in that, The device system includes an evaporation and concentration device, a spray drying device, and a thermal decomposition device; The bottom outlet of the spray drying device is connected to the inlet of the pyrolysis device. The top of the cavity of the spray drying device is equipped with an atomizing device, and the outlet of the evaporation and concentration device is connected to the feed liquid inlet of the atomizing device; The top of the cavity of the spray drying device is also provided with a hot air inlet, and the hot air outlet of the pyrolysis device is connected to the hot air inlet of the spray drying device in sequence via the first induced draft fan and the heating device. The pyrolysis device is equipped with a sealed heating chamber. The upper part of the sealed heating chamber is a constant temperature heating zone. The inner wall of the constant temperature heating zone is equipped with heating components with independent control switches at intervals along the vertical direction.

2. The apparatus system for preparing metal oxide particles according to claim 1, characterized in that, The bottom of the pyrolysis device is provided with an oxide product outlet.

3. The apparatus system for preparing metal oxide particles according to claim 1, characterized in that, The feed inlet of the pyrolysis device is located at the top of the pyrolysis device; The bottom outlet of the spray drying device is located above the inlet of the pyrolysis device.

4. The apparatus system for preparing metal oxide particles according to claim 3, characterized in that, The bottom outlet of the spray drying device and the inlet of the pyrolysis device are connected in sequence according to the material flow direction, including a storage device and a feeding device.

5. The apparatus system for preparing metal oxide particles according to claim 4, characterized in that, The storage device includes a storage bin; The feeding device includes a guide screw.

6. The apparatus system for preparing metal oxide particles according to claim 1, characterized in that, The sealed heating chamber of the pyrolysis device is a vertical chamber.

7. The apparatus system for preparing metal oxide particles according to claim 1, characterized in that, The hot air outlet of the pyrolysis device is located on one side of the upper part of the pyrolysis device.

8. The apparatus system for preparing metal oxide particles according to claim 1, characterized in that, The device system also includes a first gas-solid separation device; The hot air outlet of the pyrolysis device is connected to the first gas-solid separation device. The gas phase outlet of the first gas-solid separation device is connected to the first induced draft fan.

9. The apparatus system for preparing metal oxide particles according to claim 4, characterized in that, The device system also includes a second gas-solid separation device; The inlet of the second gas-solid separation device is connected to the gas phase outlet of the spray drying device; The solid phase outlet of the second gas-solid separation device is connected to the inlet of the storage device.

10. The apparatus system for preparing metal oxide particles according to claim 9, characterized in that, The device system also includes a second induced draft fan and an exhaust gas absorption device; The gas phase outlet of the second gas-solid separation device is connected to the tail gas absorption device via the second induced draft fan.

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