A method for efficiently separating niobium from a niobium-containing ore with high calcium oxide content

Abstract

The application discloses a method for efficiently separating niobium from a high-calcium-content niobium-containing ore, and belongs to the technical field of niobium metallurgy. The method comprises the following steps: mixing the high-calcium-content niobium-containing ore with a reducing agent to obtain a first material, taking a sulfidizing agent as a second material, then loading the first material and the second material into a reaction container in a non-mixed manner, so that the second material forms an independent sulfidizing agent area in the reaction container; and heating and reducing smelting to obtain a reduced ore rich in niobium elements and a smelting slag. The method limits the synchronous contact of the calcium-containing mineral, the reducing agent and the sulfidizing agent, suppresses the consumption of the sulfidizing agent by a side reaction, protects the sulfidizing activity of the sulfidizing agent, significantly improves the niobium recovery rate under the same amount of sulfidizing agent, reduces the process cost, and is suitable for processing of high-calcium-type niobium rough concentrates with a calcium oxide content of greater than or equal to 8% measured by chemical analysis.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for separating niobium from niobium ore. Background Technology

[0002] Niobium ore contains a variety of valuable metals, including Fe, Nb, REE, Mg, Ca, Na, and Al, and contains more than ten different niobium-bearing minerals, resulting in a complex composition and fine ore size. Current methods for recovering and enriching niobium from niobium rough and concentrate ore mainly include selective reduction roasting and carbothermic chlorination roasting. To address the problems of these processes, the inventors have designed a method for separating niobium from niobium-bearing ore, as described in Chinese Patent CN119372492B. This method involves adding a sulfiding agent to convert niobium in the slag into niobium-containing sulfides. The converted niobium-containing sulfides are distributed within or around iron sulfides, achieving the separation of niobium from the slag.

[0003] Further research by the inventors revealed that the above process still has the following technical problems when separating niobium ore containing high levels of calcium minerals such as dolomite, apatite, and amphibole:

[0004] During the reaction, the sulfiding agent and calcium-containing minerals are prone to react under the action of the reducing agent, generating byproducts such as calcium sulfide, which reduces the sulfidation efficiency and thus affects the recovery of niobium. If the sulfidation efficiency is to be guaranteed, the amount of sulfiding agent added needs to be further increased, which increases the process operating cost, reduces the economic efficiency of niobium conversion, and restricts its industrial development. Summary of the Invention

[0005] This invention provides a method for efficiently separating niobium from niobium-bearing ores with high calcium oxide content, thereby solving the technical problems mentioned in the background art of reduced sulfidation efficiency and increased costs when separating specific niobium ores in existing separation processes. This method achieves the separation of niobium from slag and the enrichment of niobium while improving the utilization rate of sulfiding agents and economic benefits.

[0006] The technical solution adopted in this invention includes: A method for efficiently separating niobium from niobium-bearing ores with high calcium oxide content includes the following steps: S1. The high-calcium oxide niobium-containing ore is mixed with a reducing agent to obtain a first material, and a sulfiding agent is used as a second material. The first material and the second material are loaded into a reaction vessel in a non-mixed manner, so that the second material forms an independent sulfiding agent region in the reaction vessel; the sulfiding agent includes at least one of sulfur, pyrrhotite and pyrite. S2. The reaction vessel is heated to carry out reduction smelting to obtain reduced ore and slag enriched with niobium.

[0007] In Chinese patent CN119372492B, those skilled in the art generally hold the following preconceived notion: the more uniformly the sulfiding agent, reducing agent, and niobium-containing ore are mixed, the better the subsequent sulfidation effect and the higher the niobium recovery rate. However, the inventors have discovered that this common understanding no longer applies when the process is applied to niobium-containing ore with high calcium content. High-calcium niobium-containing ore reacts with the sulfiding agent and reducing agent during the heating process. Taking pyrite as a sulfiding agent as an example, thermodynamically, ferrous sulfide minerals do not undergo a reduction reaction with carbon at 1500℃. However, if the calcium oxide content in the niobium-containing ore is too high, theoretically, the following reaction occurs at around 656℃: FeS + CaO + C = Fe + CaS + CO (g); The aforementioned reaction competes with the target niobium sulfidation reaction, consuming sulfidation dosage and reducing sulfidation efficiency. This invention addresses this by using a non-mixed loading method, spatially separating the sulfiding agent from the niobium-containing ore and reducing agent. Initially, all three are in solid-phase contact, with the solid-solid reaction interface confined to the junction of the two materials, effectively blocking the solid-phase reaction pathway. When the temperature rises to the reduction smelting temperature and reaches the molten state, the molten sulfiding agent phase settles to the bottom of the slag layer under gravity, maintaining phase separation from the slag phase. Simultaneously, niobium migrates to the molten sulfiding agent phase and undergoes a sulfidation reaction with it at the interface, achieving niobium sulfidation and enrichment. The reaction between calcium oxide and the molten sulfiding agent phase in the slag phase is confined to the interface. The lack of sufficient CaO and C at the interface significantly inhibits side reactions between the sulfiding agent, reducing agent, and calcium oxide.

[0008] As a further preferred embodiment of the above technical solution, the non-hybrid method includes any one of the following two methods: Method 1: Stack the first material and the second material, including two or more alternating layers; Method 2: The first material and the second material are made into composite pellets, wherein the composite pellets have a core-shell structure, the core structure is made of the first material and the shell structure is made of the second material.

[0009] Preferably, in method one, the second material is laid above or below the first material; more preferably, the second material is laid below the first material.

[0010] As a further preferred embodiment of the above technical solution, the calcium oxide mass content of the high-calcium-oxide niobium ore is ≥8%. When the CaO content in the niobium ore is ≥8%, the total amount of free and silicate-bound calcium ions in the ore increases significantly. In traditional homogeneous mixing reduction smelting, CaO, as an alkaline oxide, exhibits a rapid increase in the thermodynamic driving force for the reduction-sulfidation coupled side reaction with FeS and C at high temperatures, as the activity of CaO increases. Experiments show that when the CaO content is below 8%, even with traditional mixing methods, the consumption of sulfiding agent caused by the side reaction is still within a controllable range; however, when the CaO content exceeds 8%, the consumption rate of sulfiding agent by the side reaction increases non-linearly, the sulfidation efficiency decreases significantly, and the economic efficiency deteriorates. Therefore, this invention uses ≥8% as the technical threshold for the applicable object, clearly defining that the technical problem solved by this invention is targeted at the specific scenario of high calcium content.

[0011] As a further preferred embodiment of the above technical solution, the sulfiding agent includes at least one of sulfur and sulfur-containing minerals; the sulfur-containing minerals are one or both of pyrrhotite and pyrite.

[0012] As a further preferred embodiment of the above technical solution, the reducing agent includes at least one of graphite-based reducing agents and coke-based reducing agents.

[0013] As a further preferred embodiment of the above technical solution, the mass ratio of the high calcium oxide content niobium ore, reducing agent and sulfiding agent is 100:(3~12):(5~15).

[0014] As a further preferred embodiment of the above technical solution, in S2, the temperature is raised to 1250~1400℃ for reduction melting, and the holding time for reduction melting is ≥12min.

[0015] As a further preferred embodiment of the above technical solution, the reduced ore is subjected to melting or magnetic separation, followed by further separation to obtain niobium-rich products.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Based on Chinese patent CN119372492B, this invention proposes an improved scheme with material spatial isolation as the core technical means for the specific target of high-calcium oxide type niobium-bearing ore. By using a non-mixed loading method, the sulfiding agent is made to form an independent region in the reactor, which restricts the synchronous contact of the reducing agent, calcium-bearing mineral and sulfiding agent. Kinetically, it suppresses the reduction consumption of the sulfiding agent by side reactions, protects the sulfiding activity of the sulfiding agent, and thus allows more active sulfur to be used for the niobium sulfidation reaction. While achieving the separation of niobium and slag and the enrichment of niobium, it improves the utilization rate of the sulfiding agent, reduces the amount of sulfiding mineral added, and can significantly reduce production costs and improve economic benefits. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the method for efficiently separating niobium from niobium-bearing ore with high calcium oxide content according to the present invention.

[0018] Figure 2 This is an element mapping diagram at the phase interface during the reduction melting process of Example 1.

[0019] Figure 3 This is a photograph of the reduction smelting product of Example 1.

[0020] Figure 4 The image shows the XRD pattern of the product from Comparative Example 1. Detailed Implementation

[0021] The technical solution of the present invention will be further explained and described below with reference to specific embodiments.

[0022] Example 1: like Figure 1 As shown, the method for efficiently separating niobium from niobium-bearing ore with high calcium oxide content in this embodiment uses niobium crude concentrate A as raw material (chemical analysis shows that the Nb2O5 grade in the niobium crude concentrate is 4.6%, the calcium oxide content is 8.9%, and the mass ratio of CaO to SiO2 is 0.7), and includes the following steps: (1) Mix 5g of niobium crude concentrate A with waste graphite that has passed through a 200-mesh sieve at a mass ratio of 100:12 to obtain the first material; (2) Place the first material at the bottom of the alumina crucible, and then spread a layer of the second material (0.75g pyrite) evenly on the top of the first material.

[0023] (3) The reduction smelting was carried out under an argon atmosphere at a temperature of 1400℃ for 20 minutes. After cooling, the reduced ore (including iron, niobium sulfide and iron sulfide) and slag phase were obtained at the bottom of the crucible, thus separating niobium from slag. The reduced ore was chemically analyzed, and the recovery rate of niobium was 91.8%.

[0024] To investigate the reaction mechanism, this embodiment tested the elemental distribution at the phase interface during the reduction melting process in step (3), and the results are as follows: Figure 2 As shown, niobium migrates to the interface between the two phases and undergoes a sulfidation reaction, which is consistent with the reaction mechanism described above.

[0025] In fact, if the stacking order of the first and second materials in step (2) is reversed, so that pyrite is placed at the bottom, the niobium recovery rate is improved after testing.

[0026] The final reduced ore and slag phase photographs are as follows Figure 3As shown, sulfides are separated from the slag phase. This embodiment and the following embodiments can be further processed according to the method disclosed in CN119372492B to obtain further products; for example, by smelting to obtain iron and niobium-rich products, and then sorting the niobium-rich products to obtain the final niobium product; or by crushing, screening, and magnetically separating the reduced ore to obtain niobium-rich products, and then sorting the niobium-rich products to obtain the final niobium product.

[0027] Example 2: The method for efficiently separating niobium from niobium-bearing ore with high calcium oxide content in this embodiment uses the same niobium concentrate A as in Example 1 as raw material, and includes the following steps: (1) Mix 5g of niobium crude concentrate A with waste graphite that has passed through a 200-mesh sieve at a mass ratio of 100:5 to obtain the first material; (2) Place the first material at the bottom of the alumina crucible, and then spread a layer of the second material (0.5g pyrite) on top of the first material.

[0028] (3) The reduction smelting was carried out under an argon atmosphere at a temperature of 1250℃ for 60 minutes. After cooling, the reduced ore (including iron, niobium sulfide and iron sulfide) and slag phase were obtained at the bottom of the crucible, thus separating niobium from slag. The reduced ore was chemically analyzed, and the recovery rate of niobium was 82.4%.

[0029] Example 3: This embodiment describes a method for efficiently separating niobium from niobium-bearing ore with high calcium oxide content. Using niobium rough concentrate B as raw material (chemical analysis shows the Nb₂O₅ grade is 3.7%, the calcium oxide content is 9.65%, and the CaO to SiO₂ mass ratio is 0.43), the method includes the following steps: (1) Mix 5g of niobium crude concentrate B with waste graphite that has passed through a 200-mesh sieve at a mass ratio of 100:3.4 to obtain the first material; (2) Place the first material at the bottom of the alumina crucible, and then spread a layer of the second material (0.25g) pyrite on top of the first material.

[0030] (3) The reduction smelting was carried out under an argon atmosphere at a temperature of 1300℃ for 30 minutes. After cooling, the reduced ore (including iron, niobium sulfide and iron sulfide) and slag phase were obtained at the bottom of the crucible, thus separating niobium from slag. The reduced ore was chemically analyzed, and the recovery rate of niobium was 82.6%.

[0031] Example 4: The method for efficiently separating niobium from niobium-bearing ore with high calcium oxide content in this embodiment uses the same niobium concentrate B as in Example 3 as raw material, and includes the following steps: (1) Mix 5g of niobium crude concentrate B with waste graphite that has passed through a 200-mesh sieve at a mass ratio of 100:9 to obtain the first material. Press the first material into balls to serve as the core structure of the composite pellets. (2) Place the core structure of the composite pellet in a mold, and then press it together with the second material (0.5g pyrite). After pressing, a composite pellet with a core-shell structure is obtained (other conventional pellet preparation processes can also be used). Place the composite pellet in a crucible.

[0032] (3) The reduction smelting was carried out under an argon atmosphere at a temperature of 1330℃ for 30 minutes. After cooling, the reduced ore (including iron, niobium sulfide and iron sulfide) and slag phase were obtained at the bottom of the crucible, thus separating niobium from slag. The reduced ore was chemically analyzed, and the recovery rate of niobium was 86.3%.

[0033] Comparative Example 1: The difference between this comparative example and Example 1 is that niobium crude concentrate A, sieved waste graphite, and pyrite were mixed uniformly in the same proportions as in Example 1 and placed in a crucible for reduction smelting. The reduction smelting process and conditions were the same as in Example 1. Analysis of the reduced ore obtained in this comparative example showed a niobium recovery rate of 80.2%. XRD phase analysis was performed on the product after reduction smelting, as shown... Figure 4 As shown, the CaS phase was formed in the reaction products.

[0034] Comparative Example 2: The difference between this comparative example and Example 2 is that niobium crude concentrate A, sieved waste graphite, and pyrite were mixed evenly in the same proportions as in Example 2 and placed in a crucible for reduction smelting. The reduction smelting process and conditions were the same as in Example 2. Analysis of the reduced ore obtained in this comparative example showed that the niobium recovery rate was 65.8%.

[0035] Comparative Example 3: The difference between this comparative example and Example 3 is that niobium crude concentrate A, sieved waste graphite, and pyrite were mixed evenly in the same proportions as in Example 3 and placed in a crucible for reduction smelting. The reduction smelting process and conditions were the same as in Example 3. Analysis of the reduced ore obtained in this comparative example showed that the niobium recovery rate was 59.5%.

[0036] Comparative Example 4: The difference between this comparative example and Example 4 is that niobium crude concentrate A, sieved waste graphite, and pyrite were mixed evenly in the same proportions as in Example 4 and placed in a crucible for reduction smelting. The reduction smelting process and conditions were the same as in Example 4. Analysis of the reduced ore obtained in this comparative example showed that the niobium recovery rate was 73.4%.

[0037] It should be noted that, in addition to calcium oxide, magnesium oxide reacts with coke, pyrite or ferrous sulfide to form magnesium sulfide during the phase transformation process, thereby consuming the sulfiding agent and reducing the sulfidation efficiency. Therefore, the process of the present invention also has a certain promoting effect on the reduction sulfidation process of niobium ore with high magnesium oxide content.

[0038] The above embodiments are only used to illustrate the technical solutions disclosed in this invention, and are not intended to limit it. It should be noted that the innovation of this invention mainly lies in the use of additives; the selection of other raw materials, process flow, and parameter control can all refer to existing technologies, such as Chinese Patent CN119372492B. Other process details are not listed one by one in the embodiments of this invention. Although this invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions disclosed in the embodiments of this invention, and should all be included within the protection scope disclosed in this invention.

Claims

1. A method for efficiently separating niobium from niobium-bearing ores with high calcium oxide content, characterized in that, Includes the following steps: S1. The high-calcium oxide niobium-containing ore is mixed with a reducing agent to obtain a first material, and a sulfiding agent is used as a second material. The first material and the second material are loaded into a reaction vessel in a non-mixed manner, so that the second material forms an independent sulfiding agent area in the reaction vessel; the sulfiding agent is at least one of sulfur, pyrrhotite and pyrite. S2. The reaction vessel is heated to carry out reduction smelting to obtain reduced ore and slag enriched with niobium.

2. The method for efficiently separating niobium from niobium-bearing ore with high calcium oxide content according to claim 1, characterized in that, The non-mixed approach includes either of the following two approaches: Method 1: Stack the first material and the second material, including two or more alternating layers; Method 2: The first material and the second material are made into composite pellets, wherein the composite pellets have a core-shell structure, the core structure is made of the first material and the shell structure is made of the second material.

3. The method for efficiently separating niobium from niobium-bearing ores with high calcium oxide content according to claim 1 or 2, characterized in that, The calcium oxide content of the high-calcium-oxide niobium-containing ore is ≥8%.

4. The method for efficiently separating niobium from niobium-bearing ores with high calcium oxide content according to claim 1 or 2, characterized in that, The reducing agent includes at least one of graphite-based reducing agents and coke-based reducing agents.

5. The method for efficiently separating niobium from niobium-bearing ores with high calcium oxide content according to claim 1 or 2, characterized in that, The mass ratio of the high calcium oxide content niobium ore, reducing agent and sulfiding agent is 100:(3~12):(5~15).

6. The method for efficiently separating niobium from niobium-bearing ores with high calcium oxide content according to claim 1 or 2, characterized in that, In S2, the temperature is raised to 1200~1400℃ for reduction melting, and the holding time for reduction melting is ≥12min.

7. The method for efficiently separating niobium from niobium-bearing ores with high calcium oxide content according to claim 1 or 2, characterized in that, After the reduced ore is subjected to melting or magnetic separation, it is further separated to obtain niobium-rich products.

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