Sodium chromite preparation device and preparation method based on mechanochemical method

Abstract

The invention relates to the technical field of sodium ion electronics, and particularly discloses a sodium chromite preparation device and method based on a mechanochemical method.The sodium chromite preparation device comprises a base, a driving disc is rotationally arranged on the base, a main ball milling tank is rotationally arranged in the middle of the driving disc, and two symmetrically-arranged auxiliary ball milling tanks are rotationally arranged on the driving disc. Through the synergistic effect of the main ball-milling tank and the auxiliary ball-milling tank, argon serving as protective gas serves as a carrier to continuously flow and dynamically carry refined chromic oxide and sodium carbonate in the auxiliary ball-milling tank into the main ball-milling tank, the continuous process of raw material pretreatment and mechanochemical reaction is achieved, material accumulation is avoided, real-time contact of reactants is ensured, and the production efficiency is improved. And the product is the sodium chromite powder under high-energy ball milling, and mechanical crushing and secondary ball milling are not required to be performed on the product, so that the production period can be greatly shortened, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a device and method for preparing sodium chromite based on a mechanochemical method. Background Art

[0002] Sodium-ion batteries are secondary batteries (rechargeable batteries) that rely primarily on the movement of sodium ions between the positive and negative electrodes, similar to the working principles of lithium-ion batteries. Sodium chromite, a layered oxide material with a stable crystal structure and extremely high reversible capacity, is considered an ideal cathode material for sodium-ion batteries. The use of layered sodium chromite in the cathode material of sodium-ion batteries can give them high reversible capacity, high electrochemical activity, and excellent cycling stability.

[0003] Currently, sodium chromite is prepared using sodium carbonate and chromium oxide, which are mixed, pressed, sintered, and ground to produce sodium chromite powder. Patent No. CN114180628A also discloses a vacuum method for preparing sodium chromite, specifically: the raw materials are first heated, dried, and mixed in appropriate proportions, followed by ball milling, tableting, and finally calcination in a vacuum reactor to produce the sodium chromite.

[0004] The above-mentioned method for preparing sodium chromite from sodium carbonate and chromium oxide has the following disadvantages: 1. It requires high-temperature continuous calcination, which consumes a lot of energy and increases costs; 2. Product densification: The calcined product is a flaky, dense block that requires additional mechanical crushing and ball milling, which increases the complexity of the process and the production cycle of the entire sodium chromite powder, reducing production efficiency.

[0005] In view of the above problems, the present invention provides a sodium chromite preparation device and preparation method based on a mechanochemical method. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the existing defects and provide a sodium chromite preparation device and preparation method based on a mechanochemical method. Through the synergistic effect of the main ball mill and the auxiliary ball mill, and the continuous flow of argon as a protective gas as a carrier, the refined chromium oxide and sodium carbonate in the auxiliary ball mill are dynamically carried into the main ball mill, thereby realizing a continuous process of raw material pretreatment and mechanochemical reaction, avoiding material accumulation, ensuring real-time contact between reactants, and facilitating increased reaction rate. It can also significantly shorten the interval time of multiple steps such as mixing, tableting, and calcination in the traditional process, reduce process complexity, and improve production efficiency, which can effectively solve the problems in the background technology.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a sodium chromite preparation device based on a mechanochemical method, comprising a base, a drive disk rotatably disposed on the base, a main ball mill rotatably disposed in the middle of the drive disk, and two symmetrically arranged auxiliary ball mills rotatably disposed on the drive disk, a main turntable rotatably disposed in the middle of the lid of the main ball mill, and an auxiliary turntable rotatably disposed in the middle of the lid of the auxiliary ball mill; The upper surface of the main turntable is provided with a main shaft, and the middle part of the side of the main shaft is provided with evenly distributed feed holes. The lower end of the main shaft is provided with an annular hole, and the feed hole is connected with the inner cavity of the main ball mill through the annular hole. The side of the main shaft corresponding to the feed hole is provided with an annular sleeve, and the side of the annular sleeve is provided with a feed pipe that passes through the auxiliary turntable, and the feed port of the feed pipe is provided with a first-level screen. The upper end of the side of the main shaft is provided with a ventilation pipe group connected to the inner cavity of the auxiliary ball mill, and the main shaft is a hollow structure. The internal thread of the main shaft is connected to a hollow screw, and a secondary screen is installed at the bottom of the hollow screw through a connecting rod.

[0008] As a preferred technical solution of the present invention, a telescopic rod is provided on the edge of the upper surface of the base, and a fixing plate connected to the upper end of the side surface of the main shaft is provided on the top of the telescopic rod.

[0009] As a preferred technical solution of the present invention, the ventilation pipe group includes a distribution ring installed at the upper end of the side of the main shaft. The distribution ring is a hollow structure, and an annular sealing plate is rotatably provided at the bottom of the distribution ring. An air outlet pipe is provided on the annular sealing plate. The air outlet of the air outlet pipe passes through the auxiliary turntable and extends to the inner cavity of the auxiliary ball mill. An air inlet pipe is provided on the side of the distribution ring.

[0010] As a preferred technical solution of the present invention, the peripheral side of the driving disc is provided with a belt groove, and the inner side of the base is provided with a gear ring, and the bottom of the auxiliary ball mill is provided with a secondary gear meshing with the gear ring.

[0011] As a preferred technical solution of the present invention, a main gear is provided at the bottom of the main ball mill, a transmission gear set is provided at the bottom of the driving disc, and the gear ring drives the main gear to rotate through the transmission gear set.

[0012] A method for preparing a sodium chromite preparation device based on a mechanochemical method, comprising the following steps: S1, heating and drying the chromium oxide powder and the sodium carbonate powder respectively, and placing the dried chromium oxide powder and the sodium carbonate powder into different auxiliary ball mill jars according to proportion; S2. First, argon gas is introduced to exhaust the residual air in the auxiliary ball mill and the primary ball mill. Then, an external drive motor is controlled to operate. The external drive motor controls the rotation of a drive disk via a belt. The drive disk drives the primary ball mill and the auxiliary ball mill to rotate. Under the action of the meshing of the gear ring and the secondary gear, the auxiliary ball mill rotates while revolving, thereby ball milling the chromium oxide powder and the sodium carbonate powder. S3. Under the carrying effect of argon gas, chromium oxide powder and sodium carbonate powder with particle size smaller than the aperture of the first-level sieve enter the main ball mill through the feed pipe. Under the action of the gear ring, transmission gear set and main gear, the main ball mill rotates at high speed to produce high-energy ball milling. The high-energy ball milling promotes atomic-level diffusion between chromium oxide particles and sodium carbonate particles, forming an amorphous interface layer and directly generating sodium chromite. At the same time, under the action of the continuous inflow and discharge of argon gas, the by-product carbon dioxide is discharged through the hollow screw along with the argon gas, and the secondary sieve blocks the material in the main ball mill.

[0013] As a preferred technical solution of the present invention, in S1, the heating temperature of the chromium oxide powder and the sodium carbonate powder is 300-600°C, the heating time is 2-3h, and the molar ratio of the chromium oxide powder to the sodium carbonate powder is 1:1-1.2.

[0014] As a preferred technical solution of the present invention, silicon carbide grinding balls are used in both the main ball mill and the auxiliary ball mill; wherein, the diameter of the large balls in the main ball mill is 5-10 mm, the diameter of the small balls is 2-5 mm, and the mass ratio of the large balls to the small balls is 3-4:1; the diameter of the large balls in the auxiliary ball mill is 10-20 mm, the diameter of the small balls is 5-10 mm, and the mass ratio of the large balls to the small balls is 1-1.5:1.

[0015] As a preferred technical solution of the present invention, in S3, the first-level sieve adopts a 150-200 mesh sieve, and the second-level sieve adopts a 400-600 mesh sieve.

[0016] As a preferred technical solution of the present invention, the rotation speed of the main ball mill is in the range of 600-1000 rpm, the rotation speed of the auxiliary ball mill is in the range of 250-400 rpm, and the revolution speed of the auxiliary ball mill is in the range of 100-200 rpm.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The sodium chromite preparation device and preparation method based on the mechanochemical method illustrated in the present invention adopts the synergistic effect of the main ball mill and the auxiliary ball mill to realize the continuous process of raw material pretreatment and mechanochemical reaction, which can greatly shorten the interval time of multiple steps such as mixing, tableting, and calcination in the traditional process, thereby improving production efficiency.

[0018] 2. The sodium chromite preparation device and preparation method based on the mechanochemical method illustrated in the present invention uses argon as a protective gas to continuously flow as a carrier, dynamically carrying the refined chromium oxide and sodium carbonate in the secondary ball mill into the primary ball mill, avoiding material accumulation and ensuring real-time contact between the reactants, which is beneficial to increasing the reaction rate.

[0019] 3. The sodium chromite preparation device and preparation method based on the mechanochemical method exemplified in the present invention directly drives the solid-state reaction through high-energy ball milling, eliminating the need for high-temperature calcination in traditional processes, thereby reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 It is a bottom view structural schematic diagram of the present invention; Figure 3 It is a schematic diagram of the local structure of the present invention; Figure 4 for Figure 3 Schematic diagram of the structure viewed from above; Figure 5 It is a structural diagram of the distribution ring in the present invention.

[0021] In the figure: 1 base, 2 telescopic rod, 21 fixed plate, 3 drive plate, 4 main ball mill, 41 main turntable, 5 auxiliary ball mill, 51 auxiliary turntable, 6 main shaft, 61 annular hole, 62 feed hole, 63 hollow screw, 64 connecting rod, 65 secondary screen, 7 annular sleeve, 71 feed pipe, 72 primary screen, 8 distribution ring, 81 air inlet pipe, 82 air outlet pipe. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] See also Figure 1-5The present invention provides a technical solution: a sodium chromite preparation device based on a mechanochemical method, comprising a base 1, a driving disk 3 is rotatably provided on the base 1, a main ball mill 4 is rotatably provided in the middle of the driving disk 3, and two symmetrically arranged auxiliary ball mills 5 are rotatably provided on the driving disk 3. Through the cooperation of the main ball mill 4 and the auxiliary ball mill 5, during the ball milling process of the raw materials, the raw materials entering the main ball mill 4 can be directly subjected to high-energy ball milling, and mechanical energy is used to induce chemical reactions or induce changes in the organization, structure and performance of the materials, so that chromium oxide and sodium carbonate are generated to generate sodium chromite. A main turntable 41 is rotatably provided in the middle of the lid of the main ball mill 4, and an auxiliary turntable 51 is rotatably provided in the middle of the lid of the auxiliary ball mill 5. The solid-state reaction is directly driven by high-energy ball milling, and high-temperature calcination in traditional processes is unnecessary, which can reduce energy consumption.

[0024] A main shaft 6 is provided on the upper surface of the main turntable 41, and evenly distributed feed holes 62 are provided in the middle of the side of the main shaft 6. An annular hole 61 is provided at the lower end of the main shaft 6. The feed hole 62 is connected to the inner cavity of the main ball mill 4 through the annular hole 61. An annular sleeve 7 is provided on the side of the main shaft 6 corresponding to the feed hole 62. A feed pipe 71 is provided on the side of the annular sleeve 7 that passes through the auxiliary turntable 51, and a first-level screen 72 is provided at the feed port of the feed pipe 71. The raw materials after ball milling in the auxiliary ball mill 5 are filtered through the first-level screen 72 and then follow the argon gas into the main ball mill 4 for high-energy ball milling.

[0025] The upper end of the side of the main shaft 6 is provided with a ventilation pipe group connected to the inner cavity of the auxiliary ball mill 5, and the main shaft 6 is a hollow structure. The internal thread of the main shaft 6 is connected to a hollow screw 63. The bottom of the hollow screw 63 is installed with a secondary screen 65 through a connecting rod 64. The secondary screen 65 is used to filter the material in the main ball mill 4 to prevent the material from being discharged.

[0026] Furthermore, a telescopic rod 2 is provided on the edge of the upper surface of the base 1 , and a fixing plate 21 connected to the upper end of the side of the main shaft 6 is provided on the top of the telescopic rod 2 to fix the main shaft 6 .

[0027] Furthermore, the ventilation pipe group includes a distribution ring 8 installed at the upper end of the side of the main shaft 6. The distribution ring 8 is a hollow structure, and an annular sealing plate is rotatably provided at the bottom of the distribution ring 8. An air outlet pipe 82 is provided on the annular sealing plate. The air outlet of the air outlet pipe 82 passes through the auxiliary turntable 51 and extends to the inner cavity of the auxiliary ball mill 5. An air inlet pipe 81 is provided on the side of the distribution ring 8, and the connection between the air outlet pipe 82 and the auxiliary ball mill 5 can be maintained by the rotating annular sealing plate.

[0028] Furthermore, a belt groove is provided on the peripheral side of the driving disk 3, and a gear ring is provided on the inner side of the base 1. The bottom of the auxiliary ball mill 5 is provided with a secondary gear meshing with the gear ring. When the driving disk 3 rotates, the auxiliary ball mill 5 is driven to rotate. Under the meshing action of the secondary gear and the gear ring, the auxiliary ball mill jar 5 can rotate on its own, thereby improving the ball milling effect.

[0029] Furthermore, a main gear is provided at the bottom of the main ball mill 4, and a transmission gear set is provided at the bottom of the drive disc 3. The gear ring drives the main gear to rotate through the transmission gear set. The transmission gear set includes a first gear meshed with the gear ring, a second gear meshed with the first gear, and a third gear arranged at the bottom of the second gear. The third gear is meshed with the main gear, and the diameter of the third gear is larger than that of the second gear. The gear set increases the speed of the main gear, and high-energy ball milling is achieved by increasing the rotational speed of the main ball mill 4.

[0030] A method for preparing a sodium chromite preparation device based on a mechanochemical method, comprising the following steps: S1, heating and drying the chromium oxide powder and the sodium carbonate powder separately, the heating temperature of the chromium oxide powder and the sodium carbonate powder is 300-600 ° C, the heating time is 2-3 hours, and the dried chromium oxide powder and the sodium carbonate powder are placed in different auxiliary ball mill 5 according to the molar ratio of the chromium oxide powder to the sodium carbonate powder of 1:1-1.2; S2. First, argon gas is introduced to exhaust the residual air in the auxiliary ball mill 5 and the primary ball mill 4. Then, the external drive motor is controlled to operate. The external drive motor controls the rotation of the drive disk 3 via a belt. The drive disk 3 drives the primary ball mill 4 and the auxiliary ball mill 5 to rotate. Under the action of the meshing of the gear ring and the secondary gear, the auxiliary ball mill 5 rotates while revolving, thereby ball milling the chromium oxide powder and the sodium carbonate powder. S3. Under the carrying effect of argon gas, chromium oxide powder and sodium carbonate powder with a particle size smaller than the aperture of the first-level screen 72 enter the main ball mill 4 through the feed pipe 71. Under the action of the gear ring, the transmission gear set and the main gear, the main ball mill 4 rotates at a high speed to produce high-energy ball milling. The high-energy ball milling promotes atomic-level diffusion between the chromium oxide particles and the sodium carbonate particles, forming an amorphous interface layer and directly generating sodium chromite. At the same time, under the action of the continuous inflow and discharge of argon gas, the by-product carbon dioxide is discharged along with the argon gas through the hollow screw 63, and the secondary screen 65 blocks the material in the main ball mill 4.

[0031] The present invention uses argon as a protective gas as a carrier to continuously flow, dynamically carrying the refined chromium oxide and sodium carbonate in the auxiliary ball mill 5 into the main ball mill 4, avoiding material accumulation, ensuring real-time contact between reactants, and facilitating increased reaction rate.

[0032] Furthermore, silicon carbide grinding balls are used in both the main ball mill 4 and the auxiliary ball mill 5; wherein, the diameter of the large balls in the main ball mill 4 is 5-10 mm, the diameter of the small balls is 2-5 mm, and the mass ratio of large balls to small balls is 3-4:1; the diameter of the large balls in the auxiliary ball mill 5 is 10-20 mm, the diameter of the small balls is 5-10 mm, and the mass ratio of large balls to small balls is 1-1.5:1.

[0033] Furthermore, in S3, the first-level screen 72 uses a 150-200 mesh screen, and the second-level screen 65 uses a 400-600 mesh screen.

[0034] Furthermore, the rotation speed of the main ball mill 4 is in the range of 600-1000 rpm, the rotation speed of the auxiliary ball mill is in the range of 250-400 rpm, and the revolution speed of the auxiliary ball mill is in the range of 100-200 rpm.

[0035] The principle of preparing sodium chromite by mechanochemical method is: First, the grinding balls and the raw material powders (Cr2O3 and Na2CO3) collide and rub violently under high-speed rotation, generating high energy input. The mechanical force causes the crystal structure of Cr2O3 and Na2CO3 to distort, resulting in a large number of grain boundaries, dislocations, and surface defects. The atomic activity at the defects is significantly increased, providing activation sites for ion diffusion and chemical reactions. Then: During the ball milling process, the raw material powder is repeatedly crushed to the nanometer level (50-100 nm), and the specific surface area increases (up to 20-50 m 2 / g), Cr 3+ and Na + The contact probability is greatly improved. The local high pressure (instantaneous pressure reaches several GPa) and instantaneous high temperature (local micro-area temperature can reach 500-1000℃) induced by mechanical force accelerates ion diffusion and drives the following reactions: Cr2O3+Na2CO3 →2NaCrO2+CO2↑; Mechanical force directly destroys the Cr-O and Na-O bonds, promotes the formation of new bonds (Cr-O-Na), and generates layered NaCrO2.

[0036] The mechanochemical method replaces thermal energy with mechanical energy input, and the reaction can be completed at room temperature.

[0037] Furthermore, after the equipment has been running for 4-6 hours, the chromium oxide is completely reacted. At this point, sodium chromite is mixed with sodium carbonate powder. The hollow screw 63 is rotated, and the secondary screen 65 is driven downward by the hollow screw 63 via the connecting rod 64. The external negative pressure extraction device is connected to the hollow screw 63. Argon gas carrying the sodium chromite powder and sodium carbonate powder is discharged through the gap between the secondary screen 65 and the main shaft 6 and enters the storage chamber of the external negative pressure device. The mixture of sodium chromite powder and sodium carbonate powder is placed in oxygen-free water (boiled and cooled distilled water) and stirred. Sodium carbonate is highly water-soluble (35.7 g / 100 g H2O at 20°C) and sodium chromite is virtually insoluble in water for separation. The solid-to-liquid ratio is controlled at 1:8-1:10, and the washing temperature is maintained at 50-60°C (to enhance the dissolution kinetics of sodium carbonate). Centrifugal separation combined with vacuum filtration is used to obtain the sodium chromite powder.

[0038] The present invention realizes the efficient, high-purity and low-energy preparation of sodium chromite by designing a main ball mill 4 and an auxiliary ball mill 5 that act in synergistic manner, and by adopting a design of step-by-step ball milling, argon gas carrying and mechanochemical drive. The synergistic effect of the main ball mill 4 and the auxiliary ball mill 5 realizes a continuous process of raw material pretreatment and mechanochemical reaction, which can greatly shorten the interval time of multiple steps such as mixing, tableting and calcination in the traditional process, reduce the process complexity and improve the production efficiency.

[0039] The present invention realizes the synergistic effect of the main ball mill 4 and the auxiliary ball mill 5, and uses argon as a protective gas to continuously flow as a carrier, dynamically carrying the refined chromium oxide and sodium carbonate in the auxiliary ball mill 5 into the main ball mill 4, thereby realizing a continuous process of raw material pretreatment and mechanochemical reaction, avoiding material accumulation, ensuring real-time contact between reactants, and facilitating an increase in reaction rate. The product is sodium chromite powder produced by high-energy ball milling, and there is no need for mechanical crushing and secondary ball milling of the product, which can greatly shorten the production cycle and thus improve production efficiency.

[0040] Any undisclosed portions of the present invention are prior art, and their specific structures, materials, and operating principles will not be described in detail. Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A sodium chromite preparation device based on a mechanochemical method, comprising a base (1), characterized in that: A driving disk (3) is rotatably provided on the base (1), a main ball mill (4) is rotatably provided in the middle of the driving disk (3), and two symmetrically arranged auxiliary ball mills (5) are rotatably provided on the driving disk (3), a main turntable (41) is rotatably provided in the middle of the lid of the main ball mill (4), and an auxiliary turntable (51) is rotatably provided in the middle of the lid of the auxiliary ball mill (5); The upper surface of the main turntable (41) is provided with a main shaft (6), and the middle part of the side of the main shaft (6) is provided with evenly distributed feed holes (62), and the lower end of the main shaft (6) is provided with an annular hole (61), and the feed hole (62) is communicated with the inner cavity of the main ball mill (4) through the annular hole (61). The side of the main shaft (6) corresponding to the feed hole (62) is provided with an annular sleeve (7), and the side of the annular sleeve (7) is provided with a feed pipe (71) that passes through the auxiliary turntable (51), and the feed port of the feed pipe (71) is provided with a first-level screen (72). The upper end of the side of the main shaft (6) is provided with a ventilation pipe group connected to the inner cavity of the auxiliary ball mill (5), and the main shaft (6) is a hollow structure. The internal thread of the main shaft (6) is connected to a hollow screw (63), and the bottom of the hollow screw (63) is installed with a secondary screen (65) through a connecting rod (64).

2. The sodium chromite preparation device based on the mechanochemical method according to claim 1, characterized in that: A telescopic rod (2) is provided on the edge of the upper surface of the base (1), and a fixing plate (21) connected to the upper end of the side surface of the main shaft (6) is provided on the top of the telescopic rod (2).

3. The sodium chromite preparation device based on the mechanochemical method according to claim 1, characterized in that: The ventilation pipe group includes a distribution ring (8) installed at the upper end of the side of the main shaft (6), the distribution ring (8) is a hollow structure, and an annular sealing plate is rotatably provided at the bottom of the distribution ring (8), and an air outlet pipe (82) is provided on the annular sealing plate. The air outlet of the air outlet pipe (82) passes through the auxiliary turntable (51) and extends to the inner cavity of the auxiliary ball mill (5), and an air inlet pipe (81) is provided on the side of the distribution ring (8).

4. The sodium chromite preparation device based on the mechanochemical method according to claim 1, characterized in that: The peripheral side surface of the driving disc (3) is provided with a belt groove, and the inner side surface of the base (1) is provided with a gear ring, and the bottom of the auxiliary ball mill (5) is provided with a secondary gear meshing with the gear ring.

5. The sodium chromite preparation device based on the mechanochemical method according to claim 4, characterized in that: A main gear is provided at the bottom of the main ball mill (4), and a transmission gear set is provided at the bottom of the drive disc (3). The gear ring drives the main gear to rotate via the transmission gear set.

6. A method for preparing sodium chromite based on the mechanochemical method according to claim 1, characterized in that: Follow these steps: S1, heating and drying the chromium oxide powder and the sodium carbonate powder respectively, and placing the dried chromium oxide powder and the sodium carbonate powder into different auxiliary ball mill jars (5) according to the proportion; S2, firstly introduce argon gas to discharge the residual air in the auxiliary ball mill (5) and the main ball mill (4), then control the external drive motor to work, the external drive motor controls the drive disc (3) to rotate through the belt, the drive disc (3) drives the main ball mill (4) and the auxiliary ball mill (5) to rotate, under the action of the meshing of the gear ring and the auxiliary gear, the auxiliary ball mill (5) rotates while revolving, thereby ball milling the chromium oxide powder and the sodium carbonate powder; S3. Under the carrying effect of argon gas, chromium oxide powder and sodium carbonate powder with a particle size smaller than the aperture of the first-level sieve (72) enter the main ball mill (4) through the feed pipe (71). Under the action of the gear ring, the transmission gear set and the main gear, the main ball mill (4) rotates at a high speed to produce high-energy ball milling. The high-energy ball milling promotes atomic-level diffusion between the chromium oxide particles and the sodium carbonate particles, forming an amorphous interface layer and directly generating sodium chromite. At the same time, under the action of the continuous discharge of argon gas, the by-product carbon dioxide is discharged along with the argon gas through the hollow screw (63), and the secondary sieve (65) blocks the material in the main ball mill (4).

7. The method for preparing sodium chromite based on a mechanochemical method according to claim 6, characterized in that: In S1, the heating temperature of the chromium oxide powder and the sodium carbonate powder is 300-600° C., the heating time is 2-3 hours, and the molar ratio of the chromium oxide powder to the sodium carbonate powder is 1:1-1.

2.

8. The method for preparing sodium chromite based on a mechanochemical method according to claim 6, characterized in that: Silicon carbide grinding balls are used in both the main ball mill (4) and the auxiliary ball mill (5); wherein, the diameter of the large ball in the main ball mill (4) is 5-10 mm, the diameter of the small ball is 2-5 mm, and the mass ratio of the large ball to the small ball is 3-4:1; the diameter of the large ball in the auxiliary ball mill (5) is 10-20 mm, the diameter of the small ball is 5-10 mm, and the mass ratio of the large ball to the small ball is 1-1.5:

1.

9. The method for preparing sodium chromite based on a mechanochemical method according to claim 6, characterized in that: In S3, the first-level screen (72) uses a 150-200 mesh screen, and the second-level screen (65) uses a 400-600 mesh screen.

10. The method for preparing sodium chromite based on a mechanochemical method according to claim 6, characterized in that: The rotation speed range of the main ball mill (4) is 600-1000 rpm, the rotation speed range of the auxiliary ball mill is 250-400 rpm, and the revolution speed range of the auxiliary ball mill is 100-200 rpm.

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