A method for preparing high-strength vanadium-nitrogen alloys based on vanadium ammonium salts

Abstract

This invention discloses a method for preparing a high-strength vanadium-nitrogen alloy based on vanadium ammonium salt, belonging to the field of vanadium-nitrogen alloy preparation technology. The preparation method includes the following steps: vanadium ammonium salt is filtered by plate and frame press, dried, and then dried again. Flaky vanadium pentoxide is added and ground, followed by the addition of graphite, ferric oxide, and water, which are then mixed, ground, and pressed into elliptical green pellets. After drying, the pellets are calcined to obtain the high-strength vanadium-nitrogen alloy based on vanadium ammonium salt. This invention uses vanadium ammonium salt as raw material and employs a direct-heating rotary kiln method to produce high-strength vanadium-nitrogen alloys. This method is low-cost, environmentally friendly, and improves the compressive strength of the vanadium-nitrogen alloy green pellets, effectively solving the problems of poor pelletizing performance and high breakage rate in direct-heating rotary kilns in traditional technologies.

Description

Technical Field

[0001] This invention relates to the field of vanadium-nitrogen alloy preparation technology, and specifically to a method for preparing a high-strength vanadium-nitrogen alloy based on vanadium ammonium salt. Background Technology

[0002] Vanadium-nitrogen alloy (VNOO) is an alloying additive used in steelmaking. Compared to ferrovanadium, VNOO can save 20-40% of vanadium usage at the same strength level, making it highly favored by the steel industry. The mainstream production process for VNOO involves using vanadium pentoxide and vanadium trioxide as raw materials, mixing them with graphite powder to form pellets, and then gradually calcining them in a pusher kiln under a nitrogen atmosphere, including reduction and nitriding reactions. However, the pusher kiln method has the following problems: ① It requires a graphite crucible as a carrier. During VNOO production, the released potassium and sodium gases easily cause the graphite to expand and pulverize. Currently, surface coatings are used to solve this problem, but graphite crucibles are expensive and have a relatively short lifespan; ② The heating elements use silicon carbide rods or silicon molybdenum rods, resulting in relatively high heat loss and long furnace shutdown and startup cycles; ③ The sintered VNOO is prone to caking, requiring manual dispersion and making automated continuous production difficult.

[0003] The direct-heated rotary kiln method for producing vanadium-nitrogen alloys has advantages such as continuous production, convenient start-up and shutdown, low power consumption, and no crucibles / silicon molybdenum rods as consumables. Compared with the traditional pusher kiln method, it has a cost advantage. However, because the material moves dynamically in the rotary kiln, before sintering, the material only has mechanical forces. When using vanadium pentoxide as raw material, even if the compressive strength of the green balls produced by the double-roller briquetting machine is >500N, 10-20% powder will still be generated. Furthermore, when the proportion of recycled material exceeds 5%, the breakage rate of vanadium-nitrogen alloys will increase significantly. The excessively high powder rate is one of the key factors limiting the industrial production of this process.

[0004] Regarding raw materials, most existing research has focused on vanadium pentoxide and vanadium trioxide. In recent years, some studies have used ammonium vanadate as raw material to produce vanadium-nitrogen alloys using the pusher kiln method. This process reduces the number of steps in the preparation of vanadium oxide from ammonium vanadate. Theoretically, it is cheaper than the long process. However, in actual production, this process has low capacity and environmental problems, and has not been successfully converted to other production methods. Existing technology mixes vanadium oxides and carbonaceous reducing agents, presses them into shape using a briquetting machine, and then reacts them at high temperatures in a direct-heated rotary kiln to obtain vanadium-nitrogen alloy products. The vanadium oxides are one or more of vanadium oxides, ammonium metavanadate, ammonium polyvanadate, or red vanadium in various valence states. However, when using ammonium metavanadate or ammonium polyvanadate as raw materials and graphite as a reducing agent, the briquetting performance of the green balls after pressing with a roller briquetting machine is very poor due to the fine grains and light density of the ammonium metavanadate or ammonium polyvanadate. The green balls only have a strength of 40-100N and are severely pulverized during the calcination process, especially in the medium-temperature stage of 800-900℃. The compressive strength of the balls is only 20-40N, resulting in a breakage rate of 30-40% in the finished product. Summary of the Invention

[0005] To address the aforementioned shortcomings in existing technologies, this invention provides a method for preparing high-strength vanadium-nitrogen alloys based on vanadium ammonium salts. This method is low-cost, environmentally friendly, and improves the compressive strength of vanadium-nitrogen alloy green pellets, effectively solving the problems of poor pelletizing performance and high breakage rate in direct-heating rotary kilns in traditional technologies.

[0006] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is: a method for preparing a high-strength vanadium-nitrogen alloy based on vanadium ammonium salt, comprising the following steps: S1, vanadium ammonium salt, after being filtered by plate and frame filter press, dried, and then added with flaky vanadium pentoxide and ground to obtain mixture one; S2. Add graphite and ferric oxide to the mixture obtained in step S1 to obtain mixture two. Then add water, mix and press to obtain raw balls. S3. After drying the green balls obtained in step S2, they are roasted. During roasting, nitrogen gas is continuously introduced into the kiln head. After cooling, vanadium-nitrogen alloy is obtained.

[0007] Furthermore, in step S1, the vanadium ammonium salt is ammonium metavanadate or ammonium polyvanadate.

[0008] Furthermore, in step S1, the moisture content after plate and frame filtration is 35-45%.

[0009] Furthermore, in step S1, the product is dried with compressed air until the moisture content is 20-30%.

[0010] Furthermore, in step S1, the exhaust gas from a direct-heating rotary kiln is used to dry the product in a belt drying kiln until the moisture content is 1-5%.

[0011] Furthermore, in step S1, the exhaust gas from a direct-heating rotary kiln is used to dry the product in a belt drying kiln until the moisture content is 1%.

[0012] Furthermore, in step S1, the temperature of the exhaust gas is 190-210℃.

[0013] Furthermore, in step S1, the exhaust gas includes dust and waste gas.

[0014] Furthermore, in step S1, the dust includes sodium oxide, potassium oxide, ferric oxide, and vanadium pentoxide.

[0015] Furthermore, in step S1, the dust contains 15-16% sodium oxide, 9-10% potassium oxide, 7-8% ferric oxide, and 40-50% vanadium pentoxide.

[0016] Furthermore, in step S1, the dust contains 15.1% sodium oxide, 9.1% potassium oxide, 7.8% ferric oxide, and 46.3% vanadium pentoxide. Furthermore, in step S1, the exhaust gas includes nitrogen, carbon monoxide, carbon dioxide, and ammonia.

[0017] Furthermore, in step S1, the dust collected by the dust collector bag can be directly returned to the leaching process in the sodium vanadium extraction process for further extraction and utilization of vanadium resources; the ammonia in the waste gas, after being absorbed by sulfuric acid, generates ammonium sulfate, which can be returned to the vanadium precipitation process in the sodium vanadium extraction process. The waste gas after being absorbed by sulfuric acid is discharged through an exhaust pipe equipped with an exhaust fan. A burner is installed at the exhaust port to completely burn the carbon monoxide before discharging the gas.

[0018] Furthermore, in step S1, the amount of flaky vanadium pentoxide added is 10-30% of the mass of vanadium ammonium salt.

[0019] Furthermore, in step S1, the amount of flaky vanadium pentoxide added is 10-15% of the mass of vanadium ammonium salt.

[0020] Furthermore, in step S1, the material is ground to a particle size of 180-200 mesh.

[0021] Further, in step S1, grinding is performed using a ball mill.

[0022] The beneficial effects of adopting the above-mentioned further scheme are: by mixing and grinding flake vanadium pentoxide with vanadium ammonium salt, the morphology of the powder is changed and the particle size distribution of the material is increased, thereby improving the intercalation effect between the powders.

[0023] Furthermore, in step S2, the mass ratio of mixture I, graphite, and ferric oxide is 100:25-30:0.5-1.

[0024] Furthermore, in step S2, the mass ratio of mixture I, graphite, and ferric oxide is 100:28:0.5.

[0025] Furthermore, in step S2, the amount of water added is 16-22% of the mass of the mixture.

[0026] Furthermore, in step S2, the amount of water added is 18-20% of the mass of the mixture.

[0027] Furthermore, in step S2, the mixture is ground for 3-4 hours.

[0028] Furthermore, in step S2, the static pressure during pressing is 5-8 MPa.

[0029] Furthermore, in step S2, the raw sphere is an elliptical sphere with a diameter of 30-40 mm.

[0030] Furthermore, in step S2, the molding machine used during pressing is a conventional powder metallurgy molding equipment, which has the functions of automatic loading, automatic unloading and water absorption during the pressing process, and its inner cavity is designed as a hemispherical cavity.

[0031] The beneficial effect of taking the above-mentioned further measures is to improve the fluidity of materials in the rotary kiln.

[0032] Furthermore, in step S2, the angle of repose of the raw ball is 16-22°.

[0033] Furthermore, in step S2, the angle of repose of the raw ball is 18-20°.

[0034] Furthermore, in step S2, the moisture content of the raw pellets is 5-8%.

[0035] Furthermore, in step S3, the raw balls are naturally air-dried until the moisture content does not exceed 3%.

[0036] Furthermore, in step S3, the product is fired in a direct-heating rotary kiln.

[0037] Furthermore, in step S3, the direct-heated rotary kiln has a length of 10m and an internal diameter of 300mm.

[0038] Furthermore, in step S3, the length ratio of the preheating section, high-temperature section, and cooling section of the direct-heating rotary kiln is 4-5:5:3.

[0039] Furthermore, in step S3, the length ratio of the preheating section, high-temperature section, and cooling section of the direct-heating rotary kiln is 4:5:3.

[0040] Furthermore, in step S3, the maximum temperature of the heating section is 1500-1600℃.

[0041] Furthermore, in step S3, during calcination, the tilt angle is 1.5-3° and the rotation speed is 0.3-1m / min.

[0042] Furthermore, in step S3, during calcination, the tilt angle is 2.5° and the rotation speed is 0.5-0.8 m / min.

[0043] Furthermore, in step S3, nitrogen gas is continuously introduced into the kiln head during firing.

[0044] Furthermore, in step S3, the concentration of nitrogen is 99.999%.

[0045] Furthermore, in step S3, the nitrogen flow rate is 80-120 m³ / h. 3 / h.

[0046] Furthermore, in step S3, the nitrogen flow rate is 90-100 m³ / h. 3 / h.

[0047] Furthermore, in step S3, in the direct-heating rotary kiln, the nitrogen gas is introduced in the opposite direction to the material's forward direction, and the resulting exhaust gas passes through the rotary kiln preheating section and enters the belt drying kiln through the flue gas duct.

[0048] Furthermore, in step S3, during firing, a slight positive pressure of 10-20 Pa is maintained inside the kiln.

[0049] Furthermore, in step S3, the temperature is cooled to 65-75°C.

[0050] Furthermore, in step S3, the temperature is cooled to 70°C.

[0051] Furthermore, in step S3, the roasting process lasts for 20-25 hours.

[0052] The high-strength vanadium-nitrogen alloy based on vanadium ammonium salt was prepared by the above-described method for preparing high-strength vanadium-nitrogen alloy based on vanadium ammonium salt.

[0053] The present invention has the following beneficial effects: 1. This invention uses vanadium ammonium salt as raw material and employs a direct-heating rotary kiln energy-saving process, eliminating the need for a vanadium pentoxide preparation step and significantly reducing production costs. Compared with the traditional pusher kiln process, the cost per ton of product is reduced by 4000-4500 yuan.

[0054] 2. In this invention, flake-shaped vanadium pentoxide is added to vanadium ammonium salt and ground. The ground flake-shaped vanadium pentoxide has irregular edges and corners, and the vanadium ammonium salt is crystalline. This makes the powder morphology diverse. At the same time, this method can increase the particle size distribution of the material and improve the interlocking force between the powders during the briquetting process, thereby significantly improving the mechanical strength of the green balls, making the green ball strength as high as 1800-3000N.

[0055] 3. This invention introduces a molding press for briquetting. Compared with traditional roller briquetting machines, the green balls produced by the molding press have controllable ellipticity, are easy to demold, and can reduce the angle of repose of the green balls, thereby increasing the material forward speed in the preheating section of the rotary kiln and avoiding material accumulation. In addition, after static pressing, the material is subjected to uniform stress, the green balls are more dense, and the compressive strength of the green balls is greater than 1000N, effectively avoiding the problem of green ball pulverization in the low and medium temperature sections of the rotary kiln.

[0056] 4. The high-strength vanadium-nitrogen alloy prepared by the method provided in this invention has a vanadium content of 76-78%, a nitrogen content of 16.5-19%, a carbon content of 3.2-4.2%, and a density of 3.8-4.4 g / cm³. 3 No more than 5% of the crushed material has a particle size of less than 10mm.

[0057] 5. This invention utilizes the dust and waste gas generated during the rotary kiln process for resource recovery, making the entire process a green production process. Attached Figure Description

[0058] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0059] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0060] Example 1 A high-strength vanadium-nitrogen alloy based on vanadium ammonium salt is prepared by the following steps: S1. Ammonium polyvanadate, after being filtered by plate and frame press, has a moisture content of 40%. It is then dried to 25% moisture content by compressed air and further dried in a belt dryer using direct-heated rotary kiln exhaust gas at a temperature of 200℃, using direct-heated rotary kiln exhaust gas. Then, flake-shaped vanadium pentoxide is added and ground to a particle size of 180-200 mesh to obtain mixture one. The amount of flake-shaped vanadium pentoxide added is 12% of the mass of ammonium polyvanadate. The exhaust gas includes dust and waste gas. The dust includes sodium oxide, potassium oxide, ferric oxide, and vanadium pentoxide, with sodium oxide accounting for 15.1% and potassium oxide accounting for [missing percentage]. 9.1%, ferric oxide accounts for 7.8%, vanadium pentoxide accounts for 46.3%, and the waste gas includes nitrogen, carbon monoxide, carbon dioxide and ammonia. After the tail gas is dried with ammonium polyvanadate, the dust is collected by the dust collector bag and can be directly returned to the leaching process in the sodium vanadium extraction process for further extraction and utilization of vanadium resources. The ammonia in the waste gas is absorbed by sulfuric acid to generate ammonium sulfate, which can be returned to the vanadium precipitation process in the sodium vanadium extraction process. The waste gas after sulfuric acid absorption is discharged through an exhaust pipe with an exhaust fan. A burner is installed at the exhaust port to completely burn the carbon monoxide before discharging the gas. S2. Add graphite and ferric oxide to the mixture I obtained in step S1 to obtain mixture II. The mass ratio of the above mixture I, graphite and ferric oxide is 100:28:0.5. Then add water, the amount of water added is 19% of the mass of mixture II. Mix and knead for 3.5 hours and press into elliptical spheres of 30-40 mm in a molding press. The static pressure during pressing is 6 MPa to obtain green balls. The angle of repose of the green balls is 20° and the moisture content is 6%. S3. The green balls obtained in step S2 are naturally air-dried until the moisture content is 2%, and then calcined in a direct-heating rotary kiln for 24 hours. The direct-heating rotary kiln is 10m long and 300mm in internal diameter. The length ratio of the preheating section, heating section, and cooling section is 4:5:3. The maximum temperature of the heating section is 1550℃. During calcination, the tilt angle is 2.5°, the rotation speed is 0.6m / min, and 99.999% nitrogen gas is continuously introduced into the kiln head at a flow rate of 95m³ / min. 3 / h, the kiln is kept under a slight positive pressure of 15Pa, and after cooling to 70℃, a high-strength vanadium-nitrogen alloy based on vanadium ammonium salt is obtained.

[0061] Example 2 A high-strength vanadium-nitrogen alloy based on vanadium ammonium salt is prepared by the following steps: S1. Ammonium metavanadate, after being filtered by plate and frame press, has a moisture content of 35%. It is then dried to a moisture content of 20% by compressed air and further dried in a belt dryer using direct-heating rotary kiln exhaust gas at a temperature of 190℃. Flake vanadium pentoxide is then added and ground to a particle size of 180-200 mesh to obtain mixture one. The amount of flake vanadium pentoxide added is 10% of the mass of ammonium metavanadate. The exhaust gas includes dust and waste gas. The dust includes sodium oxide, potassium oxide, ferric oxide, and vanadium pentoxide, with sodium oxide accounting for 15% and potassium oxide accounting for 15%. The waste gas contains nitrogen, carbon monoxide, carbon dioxide, and ammonia. After drying the tail gas with ammonium metavanadate, the dust collected by the dust collector bags can be directly returned to the leaching process in the sodium vanadium extraction process for further extraction and utilization of vanadium resources. The ammonia in the waste gas, after being absorbed by sulfuric acid, generates ammonium sulfate, which can be returned to the vanadium precipitation process in the sodium vanadium extraction process. The waste gas after being absorbed by sulfuric acid is discharged through an exhaust pipe equipped with an exhaust fan. A burner is installed at the exhaust port to completely burn the carbon monoxide before discharging the gas. S2. Add graphite and ferric oxide to the mixture I obtained in step S1 to obtain mixture II. The mass ratio of the above mixture I, graphite and ferric oxide is 100:25:0.5. Then add water, the amount of water added is 16% of the mass of mixture II. Mix and grind for 3 hours and press into elliptical spheres of 30-40 mm in a molding press. The static pressure during pressing is 5 MPa to obtain green balls. The angle of repose of the green balls is 16° and the moisture content is 5%. S3. The green balls obtained in step S2 are naturally air-dried until the moisture content is 1%, and then calcined in a direct-heating rotary kiln for 20 hours. The direct-heating rotary kiln is 10m long and 300mm in internal diameter. The length ratio of the preheating section, heating section, and cooling section is 4:5:3. The maximum temperature of the heating section is 1500℃. During calcination, the tilt angle is 1.5°, the rotation speed is 0.3m / min, and 99.999% nitrogen gas is continuously introduced into the kiln head at a flow rate of 80m³ / min. 3 / h, the kiln is kept under a slight positive pressure of 10Pa, and after cooling to 65℃, a high-strength vanadium-nitrogen alloy based on vanadium ammonium salt is obtained.

[0062] Example 3 A high-strength vanadium-nitrogen alloy based on vanadium ammonium salt is prepared by the following steps: S1. Ammonium polyvanadate, after being filtered by plate and frame press, has a moisture content of 45%. It is then dried to 30% moisture content by compressed air and further dried in a belt dryer using direct-heating rotary kiln exhaust gas at a temperature of 200℃ to a moisture content of 5%. Then, flake-shaped vanadium pentoxide is added and ground to a particle size of 180-200 mesh to obtain mixture one. The amount of flake-shaped vanadium pentoxide added is 15% of the mass of ammonium polyvanadate. The exhaust gas includes dust and waste gas. The dust includes sodium oxide, potassium oxide, ferric oxide, and vanadium pentoxide, with sodium oxide accounting for 16% and potassium oxide accounting for 16%. The waste gas contains nitrogen, carbon monoxide, carbon dioxide, and ammonia. After the tail gas is dried with ammonium polyvanadate, the dust collected by the dust collector bag can be directly returned to the leaching process in the sodium vanadium extraction process for further extraction and utilization of vanadium resources. The ammonia in the waste gas is absorbed by sulfuric acid to generate ammonium sulfate, which can be returned to the vanadium precipitation process in the sodium vanadium extraction process. The waste gas after sulfuric acid absorption is discharged through an exhaust pipe equipped with an exhaust fan. A burner is installed at the exhaust port to completely burn the carbon monoxide before discharging the gas. S2. Add graphite and ferric oxide to the mixture I obtained in step S1 to obtain mixture II. The mass ratio of the above mixture I, graphite and ferric oxide is 100:30:1. Then add water, the amount of water added is 22% of the mass of mixture II. Mix and grind for 4 hours and press into elliptical spheres of 30-40 mm in a molding press. The static pressure during pressing is 8 MPa to obtain green balls. The angle of repose of the green balls is 22° and the moisture content is 8%. S3. The green balls obtained in step S2 are naturally air-dried until the moisture content is 3%, and then calcined in a direct-heating rotary kiln for 25 hours. The direct-heating rotary kiln is 10m long and has an internal diameter of 300mm. The length ratio of the preheating section, heating section, and cooling section is 5:5:3. The maximum temperature of the heating section is 1600℃. During calcination, the tilt angle is 3°, the rotation speed is 1m / min, and 99.999% nitrogen gas is constantly introduced into the kiln head at a flow rate of 120m³ / min. 3 / h, the kiln is kept under a slight positive pressure of 20Pa, and after cooling to 75℃, a high-strength vanadium-nitrogen alloy based on vanadium ammonium salt is obtained.

[0063] Comparative Example 1 A method for producing vanadium-nitrogen alloy includes the following steps: 3000 kg of flake vanadium pentoxide with a content greater than 98%, 855 kg of graphite, and 10 kg of iron oxide scale are mixed and pulverized. The raw materials are then mixed, pressed into pellets, and added intermittently to the feed channel of a direct-heated rotary kiln. When the material level in the feed channel reaches the level detection device, an alarm is triggered, and manual feeding is initiated. Finely crushed material falls through the sieve holes into a fine material storage area in the kiln tail box. As the rotary kiln rotates, the material level in the feed channel decreases, and the pellets sequentially enter the kiln chamber feed inlet, preheating section, heating section, cooling section, kiln chamber discharge outlet, sieve tube feed inlet, sieve tube discharge outlet, and pass over the baffle plate, falling into a large-particle storage area in the kiln tail box. Material is discharged from the kiln tail box every half hour or one hour. The highest temperature the material reaches in the heating section is 1500℃. The direct-heated rotary kiln has a refractory-lined roasting trough. The material pellets fill approximately 45% of the heating section, the voltage between the positive and negative electrodes is approximately 70V, the current is approximately 4500A, and the power is stable at 310-320kW. The equivalent inner diameter of the heating section is 60cm (because there is a roasting trough inside the kiln, the kiln may be cylindrical, prismatic, etc., resulting in a non-regular cylindrical shape, hence the use of equivalent inner diameter), and the length of the heating section is 6.6m.

[0064] Comparative Example 2 A method for producing vanadium-nitrogen alloy includes the following steps: mixing vanadium oxide and a carbonaceous reducing agent, pressing the mixture into shape using a briquetting machine, and then reacting it at high temperature in a direct-heating rotary kiln to obtain the vanadium-nitrogen alloy product, wherein the vanadium oxide is one or more of vanadium oxide in various valence states, ammonium metavanadate, ammonium polyvanadate, or red vanadium.

[0065] Experimental Example 1 The elemental content and density of the high-strength vanadium-nitrogen alloys based on vanadium ammonium salts prepared in Examples 1-3 were tested, and the results are shown in Table 1.

[0066] Table 1 Elemental Content and Density Table

[0067] As shown in Table 1, the high-strength vanadium-nitrogen alloy based on vanadium ammonium salt prepared by the method provided in this invention can achieve a vanadium content of 76-78%, a nitrogen content of 16.5-19%, a carbon content of 3.2-4.2%, and a density of 3.8-4.4 g / cm³. 3 .

[0068] Experimental Example 2 The compressive strength and breakage rate (particle size less than 10 mm is considered as broken material) of the high-strength vanadium-nitrogen alloy green balls based on vanadium ammonium salt prepared in Examples 1-3 were compared with those of Comparative Examples 1-2. The results are shown in Table 2.

[0069] Table 2 Performance Comparison Table

[0070] As shown in Table 2, the high-strength vanadium-nitrogen alloy based on vanadium ammonium salt prepared by the method provided by the present invention has a compressive strength of 1800-3000N, which is much higher than 580N of Comparative Example 1 and 40N of Comparative Example 2. Moreover, the breakage rate of the present invention does not exceed 5%, which is less than 15% of Comparative Example 1 and 35% of Comparative Example 2.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength vanadium-nitrogen alloy based on vanadium ammonium salt, characterized in that, Includes the following steps: S1. Vanadium ammonium salt is filtered by plate and frame filter press, dried, and then vanadium pentoxide flakes are added and ground to obtain mixture one. The vanadium ammonium salt is ammonium metavanadate or ammonium polyvanadate. S2. Add graphite and ferric oxide to the mixture obtained in step S1 to obtain mixture two. Then add water, mix and press to obtain raw balls. S3. After drying the green balls obtained in step S2, they are roasted. During roasting, nitrogen gas is always introduced into the kiln head. After cooling, vanadium-nitrogen alloy is obtained and roasted in a direct-heating rotary kiln. The length ratio of the preheating section, high-temperature section and cooling section of the direct-heating rotary kiln is 4-5:5:

3.

2. The method for preparing high-strength vanadium-nitrogen alloy based on vanadium ammonium salt as described in claim 1, characterized in that, In step S1, the exhaust gas from a direct-heating rotary kiln is used to dry the product in a belt drying kiln until the moisture content is 1-5%.

3. The method for preparing high-strength vanadium-nitrogen alloy based on vanadium ammonium salt as described in claim 1, characterized in that, In step S1, the amount of flake vanadium pentoxide added is 10-30% of the mass of vanadium ammonium salt.

4. The method for preparing high-strength vanadium-nitrogen alloy based on vanadium ammonium salt as described in claim 1, characterized in that, In step S1, the particles are ground to a size of 180-200 mesh.

5. The method for preparing high-strength vanadium-nitrogen alloy based on vanadium ammonium salt as described in claim 1, characterized in that, In step S2, the mass ratio of mixture I, graphite, and ferric oxide is 100:25-30:0.5-1.

6. The method for preparing high-strength vanadium-nitrogen alloy based on vanadium ammonium salt as described in claim 1, characterized in that, In step S2, the static pressure during pressing is 5-8 MPa.

7. The method for preparing high-strength vanadium-nitrogen alloy based on vanadium ammonium salt as described in claim 1, characterized in that, In step S3, during calcination, the tilt angle is 1.5-3° and the rotation speed is 0.3-1m / min.

8. A high-strength vanadium-nitrogen alloy based on vanadium ammonium salt prepared by the preparation method of the high-strength vanadium-nitrogen alloy based on vanadium ammonium salt as described in any one of claims 1-7.

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