Method for preparing high-purity iron elementary substance from laterite-nickel ore smelting slag

Abstract

Disclosed in the present invention is a method for preparing a high-purity iron elementary substance from laterite-nickel ore smelting slag, comprising the following steps: ball-milling and mixing laterite-nickel ore smelting slag and a reducing agent to obtain a ball-milled mixture; smelting and slagging the ball-milled mixture to obtain a molten iron-manganese liquid and aluminum-silicon-calcium slag; casting the molten iron-manganese liquid to obtain an iron-manganese alloy; and carrying out electrolytic refining by using the iron-manganese alloy as an anode to obtain a high-purity iron elementary substance. According to the present invention, first, one-step reductive melting is carried out to reduce a trivalent iron oxide present in laterite-nickel ore smelting slag into a liquid metal elementary substance under the action of high temperature and a reducing agent, and the remaining major phases are combined with each other to form calcium aluminosilicate which floats on the surface of the liquid iron elementary substance and is then removed by slagging; and then, iron and manganese in a reduction product are separated by means of electrolytic refining. The effective recovery rate of iron in laterite-nickel ore smelting slag is improved, and the high-purity iron elementary substance can be prepared.

Description

A method for preparing high-purity iron from laterite nickel ore smelting slag Technical Field

[0001] The present invention belongs to the technical field of metal recovery, and in particular relates to a method for preparing high-purity iron from laterite nickel ore smelting slag. Background Art

[0002] Nickel, a pillar of the rapid development of new energy, has become a strategic metal resource. Laterite nickel ore, one of the primary natural occurrences of nickel, is attracting increasing research attention. Hydrometallurgical processes for laterite nickel ore are widely used in industrial production. This hydrometallurgical process produces a large amount of smelting waste slag, containing iron grades exceeding 30%, which can be recycled as a secondary iron resource. Current methods for recovering iron from laterite nickel ore smelting waste slag typically involve reduction roasting, followed by magnetic separation to produce an iron concentrate primarily composed of Fe₃O₄. This concentrate is then further reduced and smelted to produce crude metallic iron. For example, patent CN106893875A discloses a method for processing laterite nickel ore using direct reduction magnetic separation, which includes drying and crushing, mixing, briquetting (balling), carbon thermal direct reduction, and magnetic separation to obtain nickel-iron alloy; for example, patent CN105129831A discloses a comprehensive recycling and utilization method for laterite nickel ore slag, which uses laterite nickel ore slag as raw material, grinds it, mixes it with pulverized coal and water, and presses it into green balls; after drying the green balls, they are roasted, ground, and magnetically separated to obtain iron powder and tailings.

[0003] Since laterite nickel ore smelting slag contains a large amount of silicon, calcium, aluminum and other phases in addition to iron phase, the sample remains a solid phase powder after roasting using the existing reduction roasting and magnetic separation process, resulting in adhesion between the various phases, making it difficult to achieve effective separation between the iron phase reduction product and the silicon, calcium and aluminum phases. In order to reduce the entrainment of silicon, calcium and aluminum, the magnetic separation intensity can only be reduced, resulting in a final iron effective yield of less than 50%, and the obtained iron concentrate needs to be further reduced roasted and smelted.

[0004] Summary of the Invention

[0005] In response to the current problem that it is difficult to effectively recover high-purity iron from laterite nickel ore smelting slag, the purpose of the present invention is to provide a method for preparing high-purity iron from laterite nickel ore smelting slag. The technical route of obtaining crude iron through one-step reduction smelting and then electrolytic refining to prepare high-purity iron achieves efficient preparation and recovery of iron from laterite nickel ore smelting slag.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A method for preparing high-purity iron from laterite nickel ore smelting slag comprises the following steps:

[0008] (1) ball-milling laterite nickel ore smelting slag and a reducing agent to obtain a ball-milled mixture;

[0009] (2) smelting and slagging the ball-milled mixture to obtain an iron-manganese melt and an aluminum-silicon-calcium slag;

[0010] (3) casting the iron-manganese melt to obtain an iron-manganese alloy;

[0011] (4) Using the iron-manganese alloy as the anode for electrolytic refining to obtain high-purity iron.

[0012] Preferably, in step (1), the mass ratio of laterite nickel ore smelting slag to reducing agent is 1:(1-10).

[0013] Preferably, the reducing agent is one or more of coke, petroleum coke, bituminous coal, and lignite.

[0014] Preferably, the smelting and slagging temperature in step (2) is 1200-1600° C., the smelting time is 1-5 hours, and the gas introduced during the smelting process is a mixture of inert gas and oxygen.

[0015] Preferably, the inert gas is N2 or Ar, and the volume proportion of oxygen in the mixed gas is 1-5%.

[0016] Preferably, in step (3), the ferromanganese melt is cast into an ferromanganese alloy anode plate in a mold, and the size of the anode plate is 10 cm×8 cm×5 mm.

[0017] Preferably, the temperature of electrolytic refining in step (4) is 30-80°C, and the current density is 100-800A / m 2 , the electrolysis time is 0.5-5h.

[0018] Preferably, in step (4) electrolytic refining, the cathode is a stainless steel plate and the electrolyte is a sulfate solution.

[0019] Preferably, the electrolyte is a sodium sulfate solution with a concentration of 10-50 g / L, and the pH of the electrolyte is 1-3.

[0020] Preferably, during or after the electrolysis in step (4), the process further includes recovering the manganese salt in the electrolyte.

[0021] The beneficial effects of the present invention are:

[0022] The method for preparing high-purity iron from laterite nickel ore smelting slag provided by the present invention first reduces and smelts the trivalent iron oxide present in the laterite nickel ore smelting slag. Under the action of high temperature and a reducing agent, the iron is reduced to a liquid metal element, while the remaining main phases such as silicon, calcium and aluminum are not reduced, but still exist in the form of oxides and combine with each other to form aluminosilicate calcium, which floats on the surface of the liquid iron element and is removed by slagging; then, electrolytic refining is used to separate the iron and manganese in the reduction product, which not only improves the effective recovery rate of iron in the laterite nickel ore smelting slag, but also prepares high-purity iron element.

[0023] After electrolytic refining, the cathode of the present invention precipitates high-purity metallic iron, while manganese remains in the electrolyte in the form of ions. By regularly opening the electrolyte, the manganese salt therein can be recovered to obtain the corresponding manganese compound product, and the degree of resource utilization is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments are briefly introduced below.

[0025] FIG1 is a flow chart of a method for preparing high-purity iron from laterite nickel ore smelting slag according to the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] Referring to FIG1 , the method for preparing high-purity iron from laterite nickel ore smelting slag provided by the present invention comprises the following steps:

[0028] (1) ball-milling laterite nickel ore smelting slag and a reducing agent in a mass ratio of 1: (1-10) to obtain a ball-milled mixture; the reducing agent is one or more of coke, petroleum coke, bituminous coal, and lignite;

[0029] (2) controlling the smelting and slagging temperature to 1200-1600° C., introducing a mixed gas of N2 or Ar and O2 during the smelting process, wherein the volume proportion of O2 is 1-5%, and the smelting time is 1-5 hours, and slagging is performed on the ball-milled mixture to obtain an iron-manganese melt and an aluminum-silicon-calcium slag;

[0030] (3) casting the molten iron-manganese into an iron-manganese alloy plate in a mold, wherein the size of the iron-manganese alloy plate is 10 cm × 8 cm × 5 mm;

[0031] (4) Electrolytic refining is performed using an iron-manganese alloy plate as the anode, a stainless steel plate of the same size as the cathode, and a sodium sulfate solution with a concentration of 10-50 g / L as the electrolyte; the pH of the electrolyte is 1-3, the electrolysis temperature is controlled at 30-80 ° C, and the current density is 100-800 A / m 2 , electrolysis time 0.5-5h, to obtain high-purity iron;

[0032] (5) During the electrolysis process, manganese remains in the solution in the form of ions, and the manganese salt in the electrolyte is recovered during the electrolysis process or after the electrolysis is completed; further, when the Mn 2+ When the concentration exceeds 20 g / L, the electrolyte is opened and the manganese salt product is recovered by precipitation or extraction.

[0033] In order to improve the effective recovery rate of iron in laterite nickel ore smelting slag and prepare high-purity iron, the present invention proposes a technical route of one-step reduction smelting to obtain crude iron and then electrolytic refining to prepare high-purity iron, which is completely different from the route of the existing technology. The basic principle is: the iron in laterite nickel ore smelting slag exists mainly in the form of trivalent iron oxides. Under the action of high temperature and reducing agent, the iron will be reduced to liquid metal element, while the other main phases such as silicon, calcium and aluminum will not be reduced and still exist in the form of oxides and combine with each other to form aluminum calcium silicate floating on the surface of liquid iron element for slag removal. In addition, since the smelting slag also contains a small amount of manganese, it will be reduced to manganese metal element during the reduction process, thereby forming an iron-manganese melt. Further research found that electrolysis can effectively separate iron and manganese in Fe-Mn alloys. The Fe-Mn melt is cast on the anode to obtain a Fe-Mn alloy anode. Under the action of the electric field, Fe-Mn will dissolve into the electrolyte, and high-purity metallic iron will be precipitated at the cathode, while manganese will remain in the electrolyte in the form of ions. The electrolyte is regularly opened to recover the manganese to obtain the corresponding manganese compound product.

[0034] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0035] The components of the laterite nickel ore smelting slag used in the following examples are shown in Table 1:

[0036] Table 1 Composition of laterite nickel ore smelting slag

[0037] Example 1

[0038] A method for preparing high-purity iron from laterite nickel ore smelting slag comprises the following steps:

[0039] After drying the laterite nickel ore smelting slag, 5kg of it was ball-milled with 10kg of coke and placed in an atmosphere smelting furnace. A mixed gas of N2 and O2 was continuously introduced, with the O2 volume fraction controlled at 1% and the mixed gas flow rate controlled at 500mL / min. The smelting furnace was then heated to 1400°C and kept warm for 3 hours. During this period, the Fe and Mn in the smelting slag were continuously reduced to metal elements and melted into liquid form, while silicon, calcium, and aluminum could not be reduced and still floated on the surface of the molten iron in the form of mixed oxides (CaO·Al2O3·SiO2). The mixed oxides were continuously scraped out using the built-in scraper in the smelting furnace to obtain an iron-manganese mixed melt and an aluminum-silicon-calcium slag, achieving the separation between the target recovered metals Fe and Mn and the non-target elements aluminum, calcium, and silicon. The residual aluminum, silicon, and calcium in the iron-manganese mixed melt were measured to be less than 0.1%. The iron-manganese mixed molten liquid was then poured into a casting mold for casting. An iron-manganese alloy plate with a size of 10 cm × 8 cm × 5 mm was prepared as an electrolytic anode plate, and a stainless steel plate of the same size was used as a cathode. The electrolyte composition was a 30 g / L Na2SO4 solution. During the electrolysis process, 0.1 mol / L H2SO4 was used to adjust the pH of the electrolyte to 2 ± 0.1, and the current density was controlled at 500 A / m 2 , electrolysis temperature 40 ℃, initial cell voltage 1.8 ~ 2.0V, during the electrolysis process, as the anode continues to dissolve, the iron element continues to deposit at the cathode, the cell voltage will continue to rise. When the cell voltage rises to above 4.0V, replace the next anode plate. When the average thickness of the cathode deposited iron exceeds 10mm, remove the cathode plate and peel off the iron element on it. In this embodiment, the cathode plate is removed after 3h of electrolysis. During the electrolysis process, the Mn in the anode plate is also discharged and converted into Mn 2+ Enters the electrolyte, does not precipitate at the cathode, and continues to accumulate in the electrolyte. 2+ When the concentration exceeds 20 g / L, the electrolyte is opened and the pH is adjusted by using liquid alkali to control the pH at 10-11 to obtain Mn(OH)2 by precipitation and filtration.

[0040] After testing, the mass of elemental iron obtained by a single cathode stripping is about 630g, the mass of the theoretically electrodeposited iron is about 675g, the purity of the elemental iron is 99.96%, and the cathode current efficiency is about 93% (calculation formula: actual mass of elemental iron deposited / theoretical mass of elemental iron deposited).

[0041] Example 2

[0042] A method for preparing high-purity iron from laterite nickel ore smelting slag comprises the following steps:

[0043] After drying the laterite nickel ore smelting slag, 5 kg of it was mixed with 5 kg of coke and ball-milled. The mixture was then placed in an atmosphere smelting furnace and continuously introduced with a mixture of N2 and O2, where the volume fraction of O2 was controlled at 5% and the flow rate of the mixed gas was controlled at 500 ml / min. The smelting furnace was then heated to 1200°C and kept warm for 5 hours. The slag produced during the smelting process was continuously scraped out using a scraper built into the smelting furnace to obtain an iron-manganese mixed melt and aluminum-silicon-calcium slag. The residual aluminum, silicon, and calcium in the iron-manganese mixed melt were measured to be less than 0.1%. The iron-manganese mixed melt was then poured into a casting mold for casting. An iron-manganese alloy plate with a size of 10 cm × 8 cm × 5 mm was prepared as the electrolysis anode plate, and a stainless steel plate of the same size was used as the cathode. The electrolyte composition was a 10 g / L Na2SO4 solution. During the electrolysis process, 0.1 mol / L H2SO4 was used to adjust the pH of the electrolyte to a stable value of 1, and the current density was controlled to be 100 A / m 2 , electrolysis temperature is 30℃, electrolysis time is 5h. During the electrolysis process, Mn in the anode plate is also discharged and converted into Mn 2+ Enters the electrolyte, does not precipitate at the cathode, and continues to accumulate in the electrolyte. 2+ After the concentration exceeded 20g / L, the electrolyte was opened and the pH was adjusted with liquid caustic soda to control the pH at 10-11. Mn(OH)2 was obtained by precipitation and filtration. The purity of the elemental iron was 99.93%.

[0044] Example 3

[0045] A method for preparing high-purity iron from laterite nickel ore smelting slag comprises the following steps:

[0046] After drying the laterite nickel ore smelting slag, 5 kg of it was ball-milled with 50 kg of coke and placed in an atmosphere smelting furnace. A mixture of N2 and O2 was continuously introduced, with the O2 volume fraction controlled at 1% and the mixed gas flow rate controlled at 500 ml / min. The smelting furnace was then heated to 1600°C and kept warm for 1 hour. The slag produced during the smelting process was continuously scraped out using a scraper built into the smelting furnace to obtain an iron-manganese mixed melt and aluminum-silicon-calcium slag. The residual aluminum, silicon, and calcium in the iron-manganese mixed melt were measured to be less than 0.1%. The iron-manganese mixed melt was then poured into a casting mold for casting. An iron-manganese alloy plate with a size of 10 cm × 8 cm × 5 mm was prepared as the electrolysis anode plate, and a stainless steel plate of the same size was used as the cathode. The electrolyte composition was a 50 g / L Na2SO4 solution. During the electrolysis process, 0.1 mol / L H2SO4 was used to adjust the electrolyte pH to a stable pH of 3, and the current density was controlled to 800 A / m 2 , electrolysis temperature is 80℃, electrolysis time is 0.5h. During the electrolysis process, Mn in the anode plate is also discharged and converted into Mn 2+ Continuously enriched in the electrolyte, when Mn 2+After the concentration exceeded 20g / L, the electrolyte was opened and the pH was adjusted with liquid caustic soda to control the pH at 10-11. Mn(OH)2 was obtained by precipitation and filtration. The purity of the elemental iron was 99.95%.

[0047] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0048] The above-described embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing high-purity iron from laterite nickel ore smelting slag, characterized in that: The following steps are involved: (1) ball-milling and mixing laterite nickel ore smelting slag and a reducing agent to obtain a ball-milled mixture; (2) smelting and slagging the ball-milled mixture to obtain an iron-manganese melt and an aluminum-silicon-calcium slag; (3) casting the iron-manganese molten liquid to obtain an iron-manganese alloy; (4) Using the iron-manganese alloy as an anode for electrolytic refining to obtain high-purity iron.

2. The method for preparing high-purity iron from laterite nickel ore smelting slag according to claim 1, characterized in that: The mass ratio of the laterite nickel ore smelting slag to the reducing agent in step (1) is 1: (1-10).

3. The method for preparing high-purity iron from laterite nickel ore smelting slag according to claim 1, characterized in that: The reducing agent is one or more of coke, petroleum coke, bituminous coal and lignite.

4. The method for preparing high-purity iron from laterite nickel ore smelting slag according to claim 1, characterized in that: The smelting and slag making temperature in step (2) is 1200-1600° C., the smelting time is 1-5 hours, and the gas introduced during the smelting process is a mixed gas of inert gas and oxygen.

5. The method for preparing high-purity iron from laterite nickel ore smelting slag according to claim 4, characterized in that: The inert gas is N2 or Ar, and the volume proportion of oxygen in the mixed gas is 1-5%.

6. The method for preparing high-purity iron from laterite nickel ore smelting slag according to claim 1, characterized in that: In step (3), the ferromanganese melt is cast in a mold into an ferromanganese alloy anode plate, and the size of the anode plate is 10 cm×8 cm×5 mm.

7. The method for preparing high-purity iron from laterite nickel ore smelting slag according to claim 1, characterized in that: The temperature of the electrolytic refining in step (4) is 30-80°C and the current density is 100-800A / m 2 , the electrolysis time is 0.5-5h.

8. The method for preparing high-purity iron from laterite nickel ore smelting slag according to claim 1, characterized in that: In the electrolytic refining of step (4), the cathode is a stainless steel plate, the electrolyte is a sulfate solution, and the pH of the electrolyte is 1-3.

9. The method for preparing high-purity iron from laterite nickel ore smelting slag according to claim 8, characterized in that: The electrolyte is a sodium sulfate solution with a concentration of 10-50 g / L.

10. The method for preparing high-purity iron from laterite nickel ore smelting slag according to claim 1, characterized in that: During or after the electrolysis in step (4), the process also includes recovering the manganese salt in the electrolyte.

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