Method for improving vanadium yield in nitridation reduction process of vanadium-nitrogen alloy

Abstract

The invention discloses a method for improving vanadium yield in a vanadium-nitrogen alloy nitridation reduction process, which comprises the following steps: (1) uniformly mixing vanadium trioxide, ammonium polyvanadate, a carbonaceous reducing agent, iron powder, a binder and an auxiliary inhibitor in proportion to obtain a mixed material; (2) carrying out compression molding on the mixed material, and drying to obtain raw material balls; and (3) the raw material balls are subjected to a programmed heating nitridation reduction reaction in the nitrogen atmosphere, cooling is conducted after the reaction is finished, and the vanadium-nitrogen alloy is obtained. By controlling the ratio of vanadium trioxide to ammonium polyvanadate and designing a temperature programming curve matched with the reaction kinetics of the double-vanadium-source system, before the vanadium trioxide is subjected to violent carbon thermal reduction and volatile vanadium oxide is generated, the vanadium oxide is converted into the volatile vanadium oxide by utilizing the preferential decomposition and reaction of the ammonium polyvanadate; a protective layer for inhibiting vanadium volatilization is formed in material particles, and the vanadium recovery rate can reach 97% or above.

Description

Technical Field

[0001] This invention belongs to the field of vanadium metallurgy, and specifically relates to a method for improving the vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys. Background Technology

[0002] Vanadium-nitrogen alloys are important microalloying additives in the steel industry, which can significantly improve the strength, toughness, wear resistance, and weldability of steel. Currently, the mainstream method for industrial production of vanadium-nitrogen alloys is to mix vanadium-containing oxides (such as vanadium pentoxide and vanadium trioxide) with carbonaceous reducing agents and carry out a carbothermic reduction nitriding reaction under a high-temperature nitrogen atmosphere.

[0003] However, this process suffers from a long-standing and unresolved technical challenge: during the high-temperature reaction stage (1400-1600℃), vanadium in the raw materials volatilizes in large quantities as low-valence oxides (such as VO and V₂O), resulting in significant losses in vanadium yield. In existing technologies, the total vanadium yield is typically only 90%-92%, which not only wastes precious metal resources and increases production costs, but also causes the volatilized vanadium compounds to condense on the inner wall of the kiln, affecting equipment lifespan and operational stability.

[0004] To reduce volatilization, existing technologies often employ methods such as lowering the maximum reaction temperature, extending the reaction time, or adding excessive carbonaceous reducing agents. However, this leads to problems such as increased energy consumption, decreased production efficiency, and increased carbon content in the products, failing to fundamentally resolve the contradiction between yield and efficiency.

[0005] Therefore, developing a novel preparation method that can effectively suppress vanadium volatilization and significantly improve vanadium yield without sacrificing reaction efficiency is of great significance for cost reduction, efficiency improvement, and green development of the vanadium-nitrogen alloy industry. Summary of the Invention

[0006] The purpose of this invention is to provide a method for improving the vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys, which can significantly suppress vanadium volatilization and increase the vanadium yield of vanadium-nitrogen alloys to over 97%.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A method for improving vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys includes the following steps: (1) Raw material preparation and mixing: Vanadium trioxide as the main vanadium source, ammonium polyvanadate as an auxiliary vanadium source and structural agent, carbonaceous reducing agent, iron powder, binder and auxiliary inhibitor are mixed evenly to obtain a mixture. (2) Molding and drying: The mixture is pressed into shape and dried to obtain raw material balls; (3) Temperature-controlled nitriding reduction: The raw material balls are placed in a nitrogen atmosphere and subjected to a temperature-controlled nitriding reduction reaction. After the reaction is completed, the mixture is cooled to obtain the vanadium-nitrogen alloy product.

[0008] Furthermore, the programmed temperature-increasing nitridation reduction reaction comprises three stages: First stage (pre-nitriding and decomposition stage): The temperature is raised from room temperature to 500-700℃ at the first heating rate and held for 10-60 minutes to allow ammonium polyvanadate to fully decompose and initiate surface pre-nitriding.

[0009] The second stage (protective layer construction and main reduction stage): The temperature is increased to 1000-1250℃ at the second heating rate and held for 1-3 hours. This slow heating stage is the key period for the full development and densification of the protective layer.

[0010] The third stage (deep nitriding and sintering stage): The temperature is raised to 1250-1550℃ at the first heating rate and held for 1-4 hours to complete deep nitriding and product densification.

[0011] Furthermore, the second heating rate of the present invention is less than the first heating rate.

[0012] Furthermore, the first heating rate of the present invention is 3-8°C / minute.

[0013] Furthermore, the second heating rate of the present invention is 1-3°C / minute.

[0014] Furthermore, the third heating rate described in this invention is 3-8°C / minute.

[0015] Furthermore, in the mixture of the present invention, the molar ratio of vanadium trioxide to vanadium in ammonium polyvanadate is 1:0.2 to 1:0.6.

[0016] Furthermore, in the mixture of the present invention, based on the total mass of vanadium trioxide and ammonium polyvanadate, the amount of carbonaceous reducing agent added is 24-30% of the total mass of vanadium raw materials; the amount of iron powder added is 0.5-2% of the total mass of vanadium raw materials; the amount of binder added is 0.1-1.5% of the total mass of vanadium raw materials; and the amount of auxiliary inhibitor added is 0.1-1.5% of the total mass of vanadium raw materials.

[0017] Furthermore, the carbonaceous reducing agent described in this invention is one or more of graphite or carbon black.

[0018] Furthermore, the binder of the present invention is selected from one or more of cellulose or starch.

[0019] Furthermore, the auxiliary inhibitor described in this invention is selected from one or more of boron nitride, silicon carbide, and silicon nitride.

[0020] The vanadium-nitrogen alloy prepared by the method of the present invention has a vanadium element yield of not less than 97%.

[0021] The inventive principle of the technical solution of this invention lies in: This invention controls the ratio of vanadium trioxide to ammonium polyvanadate and designs a programmed temperature rise curve that matches the reaction kinetics of the dual vanadium source system. This allows for the preferential decomposition and reaction of ammonium polyvanadate to preferentially decompose and react with the vanadium before the critical temperature window (800-1300℃) when vanadium trioxide undergoes severe carbothermic reduction and readily produces volatile vanadium oxides. This constructs a dense intermediate protective layer in situ within and on the surface of the material particles, physically blocking and chemically locking in vanadium, thus inhibiting its volatilization. The molar ratio of vanadium in vanadium trioxide to ammonium polyvanadate is controlled to be 1:0.2 to 1:0.6; this ratio range is crucial for ensuring the formation of an effective protective layer. The auxiliary inhibitor in the mixture further strengthens the grain boundaries and stabilizes the protective layer.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects: (1) Vanadium yield is significantly improved: Through the "dual vanadium source synergistic shell formation" mechanism, the volatilization of vanadium at high temperature is fundamentally suppressed, so that the total vanadium yield can stably reach 97% to 99%, which is 5-8 percentage points higher than the traditional process, resulting in significant economic benefits.

[0023] (2) Energy saving and consumption reduction: Due to the reduction of volatilization loss, there is no need to make up for the yield by excessively extending the high temperature holding time. The total reaction cycle can be shortened by 10%-20%, and the furnace cleaning and maintenance costs caused by the condensation of volatiles are reduced, resulting in a reduction in overall energy consumption.

[0024] (3) Stable product quality: The presence of the protective layer makes the reaction environment more uniform, reduces the phenomenon of local over-reduction or insufficient nitriding, and the resulting vanadium-nitrogen alloy product has a more uniform composition, small nitrogen content fluctuation, and stable quality.

[0025] (4) Strong process adaptability: The method of the present invention has good adaptability to raw materials and can be achieved by optimizing the temperature control program, with low modification cost. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be further described in detail with reference to specific embodiments. Example 1

[0027] The method for preparing the vanadium-nitrogen alloy in this embodiment is as follows: (1) Mix 150Kg vanadium trioxide, 120Kg ammonium polyvanadate, 67.5Kg graphite powder, 2.7Kg iron powder, 3.4Kg starch and 3.4Kg silicon nitride evenly to obtain a mixture; the molar ratio of vanadium trioxide to vanadium in ammonium polyvanadate in the mixture is 1:0.6.

[0028] (2) Use a briquetting machine to press the mixture into pellets with a diameter of 30-40 mm, and dry them at 160°C for 14 hours to obtain raw material pellets.

[0029] (3) Load the raw material pellets into the feed hopper and send them into the pusher kiln. Under the protection of flowing nitrogen, perform the following heating program: raise the temperature to 600℃ at 5℃ / min and hold for 30 minutes (first stage); then slowly raise the temperature to 1250℃ at 1℃ / min (second stage) and hold for 1.5 hours; finally raise the temperature to 1500℃ at 5℃ / min and hold for 2 hours (third stage). After the reaction is completed, cool the furnace to obtain the vanadium-nitrogen alloy.

[0030] Testing revealed that the vanadium-nitrogen alloy product prepared in this embodiment contained 78.60% vanadium and 15.62% nitrogen. Calculations showed that the vanadium yield was 98.83%. Example 2

[0031] The method for preparing the vanadium-nitrogen alloy in this embodiment is as follows: (1) Mix 150 kg of vanadium trioxide, 79.5 kg of ammonium polyvanadate, 57.4 kg of graphite powder, 2.3 kg of iron powder, 2.9 kg of cellulose and 2.9 kg of silicon carbide evenly to obtain a mixture; the molar ratio of vanadium trioxide to vanadium in ammonium polyvanadate in the mixture is 1:0.4.

[0032] (2) Use a briquetting machine to press the mixture into pellets with a diameter of 30-40 mm, and dry them at 150°C for 16 hours to obtain raw material pellets.

[0033] (3) Load the raw material pellets into the feed hopper and send them into the pusher kiln. Under the protection of flowing nitrogen, perform the following heating program: heat to 500℃ at 8℃ / min and hold for 60 minutes (first stage); then slowly heat to 1050℃ at 3℃ / min (second stage) and hold for 2 hours; finally heat to 1400℃ at 3℃ / min and hold for 1 hour (third stage). After the reaction is completed, cool with the furnace to obtain the vanadium-nitrogen alloy.

[0034] Testing revealed that the vanadium-nitrogen alloy product prepared in this embodiment contained 78.36% vanadium and 15.18% nitrogen. Calculations showed that the vanadium yield was 98.76%. Example 3

[0035] The method for preparing the vanadium-nitrogen alloy in this embodiment is as follows: (1) Mix 150 kg of vanadium trioxide, 40 kg of ammonium polyvanadate, 47.5 kg of carbon black, 2 kg of iron powder, 2.4 kg of cellulose and 2.4 kg of boron nitride evenly to obtain a mixture; the molar ratio of vanadium trioxide to vanadium in ammonium polyvanadate in the mixture is 1:0.2.

[0036] (2) Use a briquetting machine to press the mixture into pellets with a diameter of 30-40 mm, and dry them at 160°C for 14 hours to obtain raw material pellets.

[0037] (3) Load the raw material pellets into the feed hopper and send them into the pusher kiln. Under the protection of flowing nitrogen, perform the following heating program: heat to 700℃ at 3℃ / min and hold for 20 minutes (first stage); then slowly heat to 1000℃ at 2℃ / min (second stage) and hold for 1.5 hours; finally heat to 1350℃ at 8℃ / min and hold for 3 hours (third stage). After the reaction is completed, cool with the furnace to obtain the vanadium-nitrogen alloy.

[0038] Testing revealed that the vanadium-nitrogen alloy product prepared in this embodiment contained 78.28% vanadium and 15.26% nitrogen. Calculations showed that the vanadium yield was 98.69%. Example 4

[0039] (1) Mix 150 kg of vanadium trioxide, 120 kg of ammonium polyvanadate, 64.8 kg of carbon powder, 1.5 kg of iron powder, 0.35 kg of starch, and 0.35 kg of boron nitride evenly to obtain a mixture; the molar ratio of vanadium trioxide to vanadium in the mixture is 1:0.6.

[0040] (2) Use a briquetting machine to press the mixture into pellets with a diameter of 30-40 mm, and dry them at 155°C for 15 hours to obtain raw material pellets.

[0041] (3) Load the raw material pellets into the feed hopper and send them into the pusher kiln. Under the protection of flowing nitrogen, perform the following heating program: raise the temperature to 600℃ at 5℃ / min and hold for 30 minutes (first stage); then slowly raise the temperature to 1200℃ at 1℃ / min (second stage) and hold for 2 hours; finally raise the temperature to 1480℃ at 5℃ / min and hold for 2.5 hours (third stage). After the reaction is completed, cool the furnace to obtain the vanadium-nitrogen alloy.

[0042] Testing revealed that the vanadium-nitrogen alloy product prepared in this embodiment contained 78.52% vanadium and 15.51% nitrogen. Calculations showed that the vanadium yield was 98.69%. Example 5

[0043] (1) Mix 150 kg of vanadium trioxide, 120 kg of ammonium polyvanadate, 80 kg of carbon powder, 5.4 kg of iron powder, 4.0 kg of cellulose, and 4.0 kg of silicon carbide evenly to obtain a mixture; the molar ratio of vanadium trioxide to vanadium in the mixture is 1:0.6.

[0044] (2) Use a briquetting machine to press the mixture into pellets with a diameter of 30-40 mm, and dry them at 165°C for 13 hours to obtain raw material pellets.

[0045] (3) Load the raw material pellets into the feed hopper and send them into the pusher kiln. Under the protection of flowing nitrogen, perform the following heating program: raise the temperature to 650°C at 5°C / min and hold for 20 minutes (first stage); then slowly raise the temperature to 1250°C at 1.5°C / min (second stage) and hold for 1 hour; finally raise the temperature to 1520°C at 5°C / min and hold for 2 hours (third stage). After the reaction is completed, cool the furnace to obtain the vanadium-nitrogen alloy.

[0046] Testing revealed that the vanadium-nitrogen alloy product prepared in this embodiment contained 78.45% vanadium and 15.47% nitrogen. Calculations showed that the vanadium yield was 98.62%.

[0047] Comparative Example 1 The preparation method of the vanadium-nitrogen alloy in this comparative example is as follows: (1) Mix 150 kg of vanadium trioxide, 120 kg of ammonium polyvanadate, 67.5 kg of graphite powder, 2.7 kg of iron powder and 3.4 kg of cellulose evenly to obtain a mixture. The molar ratio of vanadium trioxide to vanadium in ammonium polyvanadate is 1:0.6.

[0048] (2) Use a briquetting machine to press the mixture into pellets with a diameter of 30-40 mm, and dry them at 160°C for 14 hours to obtain raw material pellets.

[0049] (3) Load the raw material pellets into the feed hopper and send them into the pusher kiln. Under the protection of flowing nitrogen, perform the following heating program: heat to 600℃ at 5℃ / min and hold for 30 minutes (first stage); then slowly heat to 1250℃ at 1℃ / min (second stage) and hold for 1.5 hours; finally heat to 1500℃ at 5℃ / min and hold for 2 hours (third stage). After the reaction is completed, cool with the furnace to obtain the vanadium-nitrogen alloy.

[0050] Testing revealed that the vanadium-nitrogen alloy product prepared in this comparative example contained 78.10% vanadium and 15.12% nitrogen. Calculations showed a vanadium yield of 95.5%. This indicates that even with dual vanadium sources and programmed temperature rise, the lack of auxiliary inhibitors to strengthen the grain boundaries of the protective layer leads to increased vanadium volatilization loss and a decreased vanadium yield.

[0051] Comparative Example 2 The preparation method of the vanadium-nitrogen alloy in this comparative example is as follows: (1) Mix 150 kg of vanadium trioxide, 37.5 kg of graphite powder, 1.5 kg of iron powder and 3.4 kg of cellulose evenly to obtain a mixture.

[0052] (2) Use a briquetting machine to press the mixture into pellets with a diameter of 30-40 mm, and dry them at 160°C for 14 hours to obtain raw material pellets.

[0053] (3) Load the raw material pellets into the feed tank and send them into the pusher kiln. Under the protection of flowing nitrogen, heat the temperature from room temperature to 1500℃ at a rate of 5℃ / min and hold for 3 hours. After the reaction is completed, cool the furnace to obtain the vanadium-nitrogen alloy.

[0054] Testing revealed a vanadium yield of 90.1%, and obvious yellow condensate (vanadium pentoxide) was observed in the kiln cooling zone, indicating that the traditional process resulted in significant vanadium volatilization and a low vanadium yield.

[0055] In summary, this invention, through innovative raw material combinations and precise process control, successfully solves the core problem of low vanadium yield in vanadium-nitrogen alloy production, and has extremely high industrial application value.

Claims

1. A method for improving the vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys, characterized in that, Includes the following steps: Vanadium trioxide, ammonium polyvanadate, carbonaceous reducing agent, iron powder, binder and auxiliary inhibitor are mixed evenly according to the specified ratio to obtain a mixture. The mixture is pressed into shape and dried to obtain raw material balls; The raw material pellets were subjected to a programmed temperature-increasing nitriding reduction reaction under a nitrogen atmosphere. After the reaction was completed, the pellets were cooled to obtain a vanadium-nitrogen alloy.

2. The method for improving vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys according to claim 1, characterized in that, In the mixture, the molar ratio of vanadium trioxide to vanadium in ammonium polyvanadate is 1:0.2 to 1:0.

6.

3. The method for improving vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys according to claim 1, characterized in that, The programmed temperature-controlled nitridation reduction reaction includes: (1) First stage: heating from room temperature to 500-700℃ at the first heating rate and holding for 10-60 minutes; (2) Second stage: heating to 1000-1250℃ at the second heating rate and holding for 1-3 hours; (3) Third stage: heating to 1250-1550℃ at the third heating rate and holding for 1-4 hours to complete the nitridation reduction.

4. The method for improving vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys according to claim 3, characterized in that, The second heating rate is less than the first heating rate.

5. The method for improving vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys according to claim 3 or 4, characterized in that, The first heating rate is 3-8℃ / minute.

6. The method for improving vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys according to claim 3 or 4, characterized in that, The second heating rate is 1-3℃ / minute.

7. The method for improving vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys according to claim 3 or 4, characterized in that, The third heating rate is 3-8℃ / minute.

8. The method for improving vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys according to claim 1, characterized in that, The mixture comprises, based on the total mass of vanadium trioxide and ammonium polyvanadate, the following additives: carbonaceous reducing agent at 24-30% of the total mass of vanadium raw materials; iron powder at 0.5-2% of the total mass of vanadium raw materials; binder at 0.1-1.5% of the total mass of vanadium raw materials; and auxiliary inhibitor at 0.1-1.5% of the total mass of vanadium raw materials.

9. The method for improving vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys according to claim 1, characterized in that, The auxiliary inhibitor is selected from one or more of boron nitride, silicon carbide, and silicon nitride.

10. The method for improving vanadium yield during the nitriding reduction process of vanadium-nitrogen alloys according to any one of claims 1-9, characterized in that, The vanadium-nitrogen alloy prepared by the method has a vanadium yield of not less than 97%.