A method for producing nickel matte using laterite nickel ore

Abstract

The present disclosure belongs to the technical field of laterite nickel ore treatment methods, and particularly relates to a method for producing nickel matte using laterite nickel ore. Using laterite nickel ore with high iron, low nickel, and low silicon content (such as limonitic laterite nickel ore) as raw materials, nickel matte is prepared through steps such as reduction roasting, magnetic separation, and reduction sulfidation roasting in sequence. The process route provided by the present disclosure can be produced using existing equipment such as rotary kilns, electric furnaces, and magnetic separators. The process is easy to control and has low costs. The process route provided by the present disclosure also achieves the purpose of directly producing nickel matte using limonitic laterite nickel ore while ensuring the nickel recovery rate.

Description

Technical Field

[0001] This disclosure belongs to the technical field of laterite nickel ore treatment methods. Specifically, it relates to a method for producing nickel matte using laterite nickel ore. Background Art

[0002] With the gradual scarcity of sulfide nickel ore, laterite nickel ore has become an important raw material for smelting nickel products. Currently, the RKEF (Rotary Kiln + Electric Arc Furnace) process is the most widely used laterite nickel ore smelting process. However, due to the lack of high-grade laterite nickel ore, the widespread application of the process is restricted, and the development and utilization of low-cost limonitic laterite nickel ore are urgent.

[0003] Currently, the main process for producing nickel matte from laterite nickel ore is as follows: laterite nickel ore is first smelted to produce low nickel matte, and then the low nickel matte is blown to produce nickel matte. The nickel grade of nickel-iron products obtained by treating low-grade limonitic laterite nickel ore by pyrometallurgical processes is low, the benefit is low, and the efficiency is low. For example, in Patent CN110983043A, a method for preparing high-grade nickel iron from medium and low-grade laterite nickel ore, the crushed laterite nickel ore is mixed with a reducing agent to form pellets, and a self-reduced product is obtained under a protective atmosphere. The self-reduced product is selectively oxidized in a weakly oxidizing atmosphere to obtain an oxidized product. After the oxidized product is smelted and separated, the metal and gangue are separated to obtain a high-grade nickel-iron alloy. This method is for producing high-grade nickel-iron alloy products with a nickel grade of 30%.

[0004] Limonitic laterite nickel ore is a type of laterite nickel ore with high iron, low nickel, and low silicon and magnesium content. Due to the relatively low nickel grade, the economic efficiency of directly producing nickel iron and nickel matte products by pyrometallurgical processes is poor. Therefore, currently, limonitic laterite nickel ore is mainly treated by hydrometallurgical processes. However, hydrometallurgical processes produce a large amount of leaching residues that are difficult to treat. There are no examples of comprehensive recovery and utilization of leaching residues in currently operating laterite nickel ore acid leaching projects globally, and they all adopt the methods of deep-sea landfill and tailings pond storage.

[0005] In view of this, this disclosure is specifically proposed. Summary of the Invention

[0006] The purpose of this disclosure includes providing a method for producing nickel matte using laterite nickel ore, aiming to improve production efficiency and reduce process costs on the premise of ensuring nickel recovery rate.

[0007] To achieve the above purpose of this disclosure, the following technical solutions can be adopted:

[0008] The solution provided by this disclosure includes a method for producing nickel matte using laterite nickel ore, comprising: subjecting the laterite nickel ore to over-reduction roasting at 600°C - 850°C, obtaining nickel-bearing magnetite concentrate by magnetic separation of the roasted product, and subjecting the nickel-bearing magnetite concentrate to reduction sulfidation roasting at 1100°C - 1300°C;

[0009] Among them, the laterite nickel ore is limonitic laterite nickel ore.

[0010] In some embodiments of the present disclosure, it includes: after mixing the laterite nickel ore with a reducing agent, subjecting it to over-reduction roasting at 600°C - 850°C for 40 min - 60 min, subjecting the roasted product to magnetic separation to obtain nickel-bearing magnetite concentrate, subjecting the nickel-bearing magnetite concentrate, the reducing agent and the sulfiding agent to reduction sulfidation roasting at 1100°C - 1300°C for 20 min - 40 min to obtain crude high-nickel matte, and subjecting the crude high-nickel matte to melting and impurity removal to obtain the required high-nickel matte product.

[0011] In some embodiments of the present disclosure, the over-reduction roasting temperature is 750°C - 850°C, and the over-reduction roasting time is 40 min - 120 min.

[0012] In some embodiments of the present disclosure, the mass ratio of the laterite nickel ore to the reducing agent is 1:(0.1 - 0.3).

[0013] In some embodiments of the present disclosure, the reducing agent used in the process of over-reduction roasting is reduction coal.

[0014] In some embodiments of the present disclosure, the over-reduction roasting is carried out in a rotary kiln, and an inert protective gas is introduced during the roasting process.

[0015] In some embodiments of the present disclosure, the magnetic separation intensity is controlled at 1000 GS - 3000 GS.

[0016] In some embodiments of the present disclosure, the roasted product after over-reduction roasting is crushed, ground and then subjected to magnetic separation to obtain nickel-bearing magnetite concentrate and magnetic separation tailings.

[0017] In some embodiments of the present disclosure, crushing is carried out by grinding, and the particle size after crushing is controlled to be less than or equal to 0.075 mm.

[0018] In some embodiments of the present disclosure, it further includes: subjecting the magnetic separation tailings to oxidation roasting and magnetic separation treatment to obtain magnetite and iron-bearing quartz sand.

[0019] In some embodiments of the present disclosure, during the process of subjecting the magnetic separation tailings to oxidation roasting, the roasting temperature is controlled at 500°C - 800°C, and the roasting time is 30 min - 120 min.

[0020] In some embodiments of the present disclosure, when magnetic separation is carried out after oxidation roasting, the magnetic separation intensity is controlled at 800 GS - 1400 GS.

[0021] In some embodiments of the present disclosure, the temperature of the reduction sulfidation roasting is 1200°C - 1250°C, and the time of the reduction sulfidation roasting is 35 min - 40 min.

[0022] In some embodiments of the present disclosure, during the reduction sulfidization roasting process, the mass ratio of nickel-bearing magnetite concentrate to the reducing agent and the sulfiding agent is controlled to be 1:(0.08 - 0.10):(0.30 - 0.50).

[0023] In some embodiments of the present disclosure, the sulfiding agent used in the reduction sulfidization roasting process is sulfur.

[0024] In some embodiments of the present disclosure, the reducing agent used in the reduction sulfidization roasting process is reducing coal.

[0025] In some embodiments of the present disclosure, the reduction sulfidization roasting is carried out in a rotary kiln, and an inert protective gas is introduced during the roasting process.

[0026] In some embodiments of the present disclosure, during the melting and impurity removal process, the operating temperature is controlled to be 1300°C - 1500°C, and the operating time is 10 min - 30 min.

[0027] The present disclosure uses limonitic laterite nickel ore as raw material, and through controlling the reduction temperature, over-reduction roasting is carried out. During this process, the iron oxide in the raw material is first reduced to magnetite and then to wüstite. Then, by utilizing the non-magnetic property of wüstite, wüstite is removed by magnetic separation to obtain nickel-bearing magnetite concentrate. Then, the nickel-bearing magnetite concentrate is subjected to reduction sulfidization roasting and the roasting temperature is controlled, so that sulfur enters the nickel-iron phase to form a solid solution of nickel sulfide and iron sulfide, and matte nickel is obtained. The process route provided by the present disclosure can be produced by using existing equipment such as rotary kilns, electric furnaces, and magnetic separators. The process is easy to control and has low cost. The process route provided by the present disclosure also realizes the purpose of directly producing matte nickel from limonitic laterite nickel ore on the premise of ensuring the nickel recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present disclosure, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 It is a schematic diagram of the main process steps for producing matte nickel from laterite nickel ore provided by the present disclosure;

[0030] Figure 2 It is a process flow diagram for producing matte nickel from laterite nickel ore provided by the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The embodiments of the present disclosure will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present disclosure and should not be regarded as limiting the scope of the present disclosure. For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0032] In the ranges disclosed in the present disclosure, the endpoints and any values of the ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0033] The embodiments of the present disclosure provide a method for producing matte high in nickel from laterite nickel ore. Please refer to Figure 1 , and the main steps include over-reduction roasting, magnetic separation, and reduction-sulfurization roasting carried out in sequence. The laterite nickel ore is subjected to over-reduction roasting at 600°C - 850°C, the roasted product is subjected to magnetic separation to obtain nickel-bearing magnetite concentrate, and the nickel-bearing magnetite concentrate is subjected to reduction-sulfurization roasting at 1100°C - 1300°C.

[0034] It should be noted that using laterite nickel ore with high iron, low nickel, and high silicon and magnesium content (such as limonitic laterite nickel ore) as the raw material, through controlling the reduction temperature for over-reduction roasting, in this process, it is first reduced to magnetite and then to ferrous oxide. Then, taking advantage of the non-magnetic property of ferrous oxide, ferrous oxide is removed through magnetic separation to obtain nickel-bearing magnetite concentrate. Then, the nickel-bearing magnetite concentrate is subjected to reduction-sulfurization roasting and the roasting temperature is controlled to make sulfur enter the nickel-iron phase, generating a solid solution of nickel sulfide and ferrous sulfide to obtain matte high in nickel.

[0035] Specifically, please refer to Figure 2 , the method for producing matte high in nickel from laterite nickel ore provided by the present disclosure includes the following steps:

[0036] S1. Over-reduction roasting

[0037] After mixing the laterite nickel ore with a reducing agent, it is subjected to over-reduction roasting at 600°C - 850°C for 40 min - 120 min. At this reduction temperature, the iron oxide in the laterite nickel ore is first reduced to magnetite and then further reduced to ferrous oxide. If the reduction temperature is too high, such as exceeding 1000°C, it will be directly reduced to iron.

[0038] The so-called "over-reduction roasting" means that by controlling the reduction temperature, the iron oxide in the laterite nickel ore is first reduced to magnetite and then further reduced to ferrous oxide, and the reduction step is in two steps.

[0039] Specifically, during over-reduction roasting, the reduction temperature can be 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, etc., and the time of over-reduction roasting can be 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0040] The method provided by the embodiments of the present disclosure is suitable for treating laterite nickel ores with high iron, low nickel and low silicon contents, such as limonitic laterite nickel ores, but is not limited thereto.

[0041] In a preferred embodiment of the present disclosure, the over-reduction roasting temperature is 750°C - 800°C, and the over-reduction roasting time is 40 min - 120 min. By optimizing the temperature and time of over-reduction roasting, more iron is converted into ferrous oxide and removed by magnetic separation to obtain an intermediate product with a high nickel grade.

[0042] In some embodiments of the present disclosure, the mass ratio of laterite nickel ore to reducing agent is 1:(0.1 - 0.3). It is appropriate to control the dosage of the reducing agent within the above range to make the iron oxide convert more fully. Specifically, the mass ratio of laterite nickel ore to reducing agent can be 1:0.1, 1:0.2, 1:0.3, etc. The reducing agent used during over-reduction roasting can be reducing coal, but is not limited thereto.

[0043] In some embodiments of the present disclosure, over-reduction roasting can be carried out in a rotary kiln, and an inert protective gas is introduced during the roasting process. The type of inert protective gas is not limited and can be nitrogen, argon, etc.

[0044] S2. Magnetic separation

[0045] The roasted product is subjected to magnetic separation to obtain nickel-bearing magnetite concentrate. Most of the iron in S1 is converted into ferrous oxide, and it can be removed by magnetic separation using its non-magnetic property.

[0046] To more fully remove ferrous oxide, the roasted product after over-reduction roasting can be first crushed and ground, and then subjected to magnetic separation to obtain nickel-bearing magnetite concentrate and magnetic separation tailings. During the magnetic separation process, the magnetic separation intensity is controlled at 1000 GS - 3000 GS to fully remove iron impurities and improve the nickel grade of the product. Specifically, the magnetic separation intensity can be 1000 GS, 1500 GS, 2000 GS, 2500 GS, 3000 GS, etc.

[0047] The methods of crushing and grinding and the particle size after grinding are not limited, as long as ferrous oxide can be removed better. In some embodiments of the present disclosure, crushing can be carried out by the methods of crushing and grinding, and the particle size after crushing and grinding is controlled to be less than or equal to 0.075 mm.

[0048] In some embodiments of the present disclosure, the magnetic separation tailings can be further processed to obtain products with market application value. The magnetic separation tailings can be subjected to oxidative roasting and magnetic separation to obtain magnetite and iron-bearing quartz sand, both of which are market-valued products and can be sold externally.

[0049] Furthermore, during the oxidative roasting of the magnetic separation tailings, the roasting temperature is controlled at 500°C - 800°C, and the roasting time is 30 min - 120 min. Through oxidative roasting, ferrous oxide can be oxidized to magnetite.

[0050] Furthermore, when performing magnetic separation after oxidative roasting, the magnetic separation intensity is controlled at 800 GS - 1400 GS to better separate magnetite and iron-bearing quartz sand.

[0051] S3. Reductive sulfidizing roasting

[0052] The nickel-bearing magnetite concentrate is subjected to reductive sulfidizing roasting with a reducing agent and a sulfiding agent at 1100°C - 1300°C for 20 min - 40 min to obtain crude nickel matte. The nickel-bearing magnetite concentrate is subjected to reductive sulfidizing roasting and the roasting temperature is controlled so that sulfur enters the nickel-iron phase to form a solid solution of nickel sulfide and iron sulfide, directly obtaining nickel matte. If the roasting temperature is too high or too low, the target product cannot be obtained.

[0053] Specifically, the temperature of reductive sulfidizing roasting can be 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, etc., and the time of reductive sulfidization can be 20 min, 25 min, 30 min, 35 min, 40 min, etc.

[0054] In a preferred embodiment of the present disclosure, the temperature of reductive sulfidizing roasting is 1200°C - 1250°C, and the time of reductive sulfidizing roasting is 35 min - 40 min. By optimizing the temperature and time of reductive sulfidization, the yield of nickel matte can be further improved.

[0055] Furthermore, during the reductive sulfidizing roasting process, the mass ratio of the nickel-bearing magnetite concentrate to the reducing agent and the sulfiding agent is controlled at 1:(0.08 - 0.10):(0.30 - 0.50). It is appropriate to control the dosage of the raw materials within the above range to further improve the product yield and avoid waste of raw materials. Specifically, the mass ratio of the nickel-bearing magnetite concentrate to the reducing agent and the sulfiding agent can be 1:0.08:0.30, 1:0.09:0.40, 1:0.10:0.50, etc.

[0056] In some embodiments of the present disclosure, the sulfiding agent used in the process of reductive sulfiding roasting is sulfur, and the reducing agent is reducing coal, but it is not limited thereto. The reductive sulfiding roasting can be carried out in a rotary kiln, and an inert protective gas is introduced during the roasting process. The type of the inert protective gas is not limited and can be nitrogen, argon, etc.

[0057] S4. Melting and impurity removal

[0058] The crude nickel matte is subjected to melting and impurity removal to remove impurities such as silicon and aluminum introduced during the magnetic separation process. A small amount of slag produced is general solid waste and can be used as building materials.

[0059] In some embodiments of the present disclosure, during the process of melting and impurity removal, the operating temperature is controlled to be 1300°C - 1500°C, and the operating time is 10 min - 30 min to fully remove impurities and improve the purity of the product. Specifically, the operating temperature can be 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, etc., and the operating time can be 10 min, 20 min, 30 min, etc.

[0060] It should be added that limonitic laterite nickel ore has large reserves, wide raw materials, and is easy to mine. However, the traditional RKEF process is difficult to treat low-grade limonitic laterite nickel ore. The method provided by the embodiments of the present disclosure realizes the feasibility of directly producing nickel matte from limonitic laterite nickel ore. The process is simple, without high-energy-consuming processes, and the nickel matte product is more beneficial to the subsequent hydrometallurgical leaching process. The production can be realized by using existing rotary kilns, electric furnaces, and magnetic separators. The process is easy to control and the cost is low.

[0061] The features and properties of the present disclosure will be further described in detail below in conjunction with embodiments.

[0062] It should be noted that the composition of the limonitic laterite nickel ore processed in the following examples and comparative examples is as follows: by mass fraction, nickel is 1.27%, iron is 48.88%, magnesium is 0.59%, and silicon is 8.23%.

[0063] Example 1

[0064] This example provides a method for producing nickel matte using laterite nickel ore, including the following steps:

[0065] (1) The limonitic laterite nickel ore is mixed with semi-coke according to a mass ratio of 1:0.12, and then subjected to over-reduction roasting in a rotary kiln 1 at 800°C for 50 min, and N2 is introduced as a protective gas during the process.

[0066] (2) Grind the product in step (1) to a particle size of 0.075 mm or less, and then perform magnetic separation under the condition of a magnetic separation intensity of 1100 GS to obtain nickel-containing magnetite concentrate and magnetic separation tailings. The magnetic separation tailings are subjected to oxidative roasting at 700 °C and magnetic separation treatment at 1000 GS to produce magnetite (Fe: 61.2%) and iron-bearing quartz sand (SiO2: 81.3%, Fe3O4: 18.1%).

[0067] (3) Mix the obtained nickel-containing iron concentrate with reducing coal and sulfur in a mass ratio of 1:0.9:0.4, and then add them to rotary kiln 2. Set the temperature to 1200 °C and the reaction time to 40 min. During the process, introduce N2 as a protective gas to obtain crude nickel matte.

[0068] (4) After subjecting the obtained crude nickel matte to melting and impurity removal in an electric furnace, a nickel matte product is obtained. The operating temperature is 1300 °C and the melting and impurity removal time is 10 min.

[0069] After testing, by mass fraction, the obtained nickel matte product contains Ni: 71.41%, S: 24.64%, Fe: 2.82%, Si: 0.09%; the nickel recovery rate is 89.3%.

[0070] Example 2

[0071] This example provides a method for producing nickel matte using laterite nickel ore. The difference from Example 1 is only the following operating parameters: in rotary kiln 1, the over-reduction roasting temperature is 750 °C and the roasting time is 40 min; in rotary kiln 2, the reduction sulfidation roasting temperature is 1250 °C and the reaction time is 35 min; in the electric furnace for melting and impurity removal, the temperature is 1350 °C and the melting and impurity removal time is 15 min.

[0072] After testing, by mass fraction, the obtained nickel matte product contains Ni: 70.28%, S: 25.35%, Fe: 2.61%, Si: 0.12%; the nickel recovery rate is 90.1%.

[0073] Example 3

[0074] This example provides a method for producing nickel matte using laterite nickel ore. The difference from Example 1 is only that: in rotary kiln 1, the over-reduction roasting temperature is 850 °C.

[0075] After testing, by mass fraction, the obtained nickel matte product contains Ni: 72.12%, S: 23.41%, Fe: 1.31%, Si: 0.14%; the nickel recovery rate is 91.2%.

[0076] Comparative Example 1

[0077] This embodiment provides a method for producing nickel matte from laterite nickel ore, which is only different from Embodiment 1 in that the over-reduction roasting temperature in the rotary kiln 1 is 1100 °C.

[0078] After testing, by mass fraction, the obtained nickel matte product contains Ni: 48.24%, S: 17.13%, Fe: 30.26%, Si: 0.08%; the nickel recovery rate is 85.5%.

[0079] Comparative Example 2

[0080] This embodiment provides a method for producing nickel matte from laterite nickel ore, which is only different from Embodiment 1 in that the over-reduction roasting temperature in the rotary kiln 1 is 500 °C.

[0081] After testing, by mass fraction, the obtained nickel matte product contains Ni: 3.56%, S: 6.22%, Fe: 88.78%, Si: 2.14%; the nickel recovery rate is 48.3%.

[0082] Comparative Example 3

[0083] This comparative example provides a traditional method for treating limonitic laterite nickel ore, and the specific steps are as follows:

[0084] (1) Mix limonitic laterite nickel ore with semi-coke and sulfurizing agent according to a mass ratio of 1:0.06:0.1, and then conduct pre-reduction in a rotary kiln at 900 °C for 100 min, and introduce N2 as the protective gas during the process.

[0085] (2) Mix the product in step (1) with semi-coke and sulfurizing agent again according to a mass ratio of 1:0.04:0.1, and then add it to the smelting pool for smelting to obtain a low nickel matte product. The product content is: Ni: 2.57%, S: 13.22%, Fe: 83.98%, Si: 0.12%; the nickel recovery rate is 93.4%.

[0086] (3) Mix the obtained low nickel matte with quartz sand according to a mass ratio of 1:0.5, then add it to the converter for blowing, set the temperature at 1550 °C, and the reaction time at 40 min, and introduce O2 during the process to obtain a high nickel sulfur product.

[0087] After testing, by mass fraction, the obtained high nickel matte product contains Ni: 47.02%, S: 20.38%, Fe: 31.14%, Si: 0.52%; the nickel recovery rate is 75.3%.

[0088] Industrial Applicability

[0089] The present disclosure uses laterite nickel ore with low nickel and low silicon contents in high-speed railways as raw materials, and prepares nickel matte through steps such as reduction roasting, magnetic separation, and reduction sulfidation roasting in sequence. The process route provided by the present disclosure also realizes the purpose of directly producing nickel matte using limonite laterite nickel ore on the premise of ensuring the nickel recovery rate. The process route provided by the present disclosure can be produced using existing equipment such as rotary kilns, electric furnaces, and magnetic separators. The process is easy to control, has low costs, and has very good industrial practicability.

Claims

1. A method for producing nickel matte from laterite nickel ore, characterized in that, Including: After mixing laterite nickel ore with a reducing agent, perform over-reduction roasting at 600°C - 850°C for 40 min - 60 min. Subject the roasted product to magnetic separation to obtain nickel-containing magnetite concentrate. Mix the nickel-containing magnetite concentrate with a reducing agent and a sulfiding agent, and perform reduction-sulfidation roasting at 1100°C - 1300°C for 20 min - 40 min to obtain crude nickel matte. Carry out melting and impurity removal on the crude nickel matte; wherein, the laterite nickel ore is limonite-type laterite nickel ore; the reducing agent used in the over-reduction roasting process is reducing coal; the over-reduction roasting is carried out in a rotary kiln, and an inert protective gas is introduced during the roasting process; The sulfiding agent used in the reduction-sulfidation roasting process is one or both of sulfur and desulfurized gypsum; the reducing agent used in the reduction-sulfidation roasting process is reducing coal; the reduction-sulfidation roasting is carried out in a rotary kiln, and an inert protective gas is introduced during the roasting process.

2. The method according to claim 1, characterized in that, The over-reduction roasting temperature is 750°C - 850°C.

3. The method according to claim 1, wherein The mass ratio of the laterite nickel ore to the reducing agent is 1:(0.1 - 0.3).

4. The method according to claim 1, wherein Control the magnetic separation intensity to be 1000 GS - 3000 GS.

5. The method according to claim 1, wherein Crush the roasted product after the over-reduction roasting and then perform magnetic separation to obtain the nickel-containing magnetite concentrate and magnetic separation tailings.

6. The method according to claim 5, characterized in that, Use the grinding method for crushing, and control the particle size after crushing to be less than or equal to 0.075 mm.

7. The method according to claim 5, wherein Also including: Perform oxidation roasting and magnetic separation treatment on the magnetic separation tailings to obtain magnetite and iron-containing quartz sand.

8. The method according to claim 7, characterized in that During the process of performing oxidation roasting on the magnetic separation tailings, control the roasting temperature to be 500°C - 800°C and the roasting time to be 30 min - 120 min.

9. The method according to claim 7, wherein When performing magnetic separation after the oxidation roasting, control the magnetic separation intensity to be 800 GS - 1400 GS.

10. The method according to claim 1, characterized in that The temperature of the reduction-sulfidation roasting is 1200°C - 1250°C, and the time of the reduction-sulfidation roasting is 35 min - 40 min.

11. The method according to claim 1, characterized in that, During the melting and impurity removal process, control the operating temperature to be 1300°C - 1500°C and the operating time to be 10 min - 30 min.

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