A method for recovering iron from copper tailings by microwave roasting

Abstract

This invention belongs to the field of non-ferrous metal tailings extraction technology, specifically relating to a method for recovering iron from copper tailings using microwave roasting. The method involves the following steps: copper tailings and calcareous materials are mixed evenly, then roasted using microwaves while introducing oxygen at 800–1000°C. The roasted residue is crushed and ground, then mixed with an acid solution for iron leaching, achieving an iron leaching rate of not less than 92%. The leachate is concentrated, cooled, and crystallized; after recrystallization to remove impurities, ferrochemical products are obtained. The advantages of this invention are: it effectively converts and decomposes the ferroolitic phase in copper tailings at temperatures below 1000°C; it has low energy consumption; it achieves a high iron leaching rate through wet leaching; the process is short and simple; the iron leaching solution can be used to prepare ferrochemical products; and the leaching residue can be used in the cement industry, effectively recovering and utilizing resources.

Description

Technical Field

[0001] This invention belongs to the field of extracting valuable metals from non-ferrous metal tailings, specifically relating to a method for recovering iron from copper tailings by microwave roasting. Background Technology

[0002] Currently, copper tailings are slag produced during copper smelting and belong to non-ferrous metal slag. Technologies for recovering iron from copper tailings include oxidation / reduction roasting-magnetic separation to obtain iron concentrate, direct reduction-magnetic separation to obtain iron concentrate, and direct reduction smelting to obtain ferroalloys. These technologies are generally carried out at temperatures above 1000℃ and have not been industrialized due to high energy consumption and insignificant economic benefits.

[0003] Existing technologies disclose methods for the comprehensive recovery of Fe, Cu, and Si from copper smelting slag. The copper smelting slag is crushed to a particle size of <5mm and directly leached with hydrochloric acid or inorganic acid at 50-110℃. Although the process is short and energy consumption is low, it has problems such as the stable structure of fir olivine, which is difficult to leach; the reaction of silicates with acid to form colloids; difficulty in solid-liquid separation, which leads to the choice of centrifugal filtration; and low silicon dispersion and recovery rate.

[0004] Existing technologies disclose a method for roasting fir olivine-type metallurgical slag using a mixed gas of SO2 and O2 at temperatures below 1000°C without flux, by controlling the roasting temperature and atmosphere. This converts iron in the slag into Fe2(SO4)3 or Fe2O3, which is then recovered through leaching or strong magnetic separation. While this method lowers the roasting temperature and energy consumption, it uses a high concentration of SO2, making conventional roasting furnaces unusable. It also imposes high requirements on process safety and exhaust gas treatment, and requires strong magnetic separation to recover Fe2O3. Another method involves adding a composite additive of CaO and Fe2O3 to copper slag, roasting it at 700-1100°C with an inert gas atmosphere, and then recovering iron from the copper slag through magnetic separation. Although the magnetic separation rate reaches 86%, the copper slag proportion is less than 20%, while the Fe2O3 addition is as high as 70%, resulting in a small copper slag processing volume. Furthermore, the iron concentrate obtained through magnetic separation often has limited applications due to its high impurity content. Iron powder with low impurity content is obtained through steps such as alkaline roasting, sulfidation reduction and magnetic separation. Although the impurity content is low, the process requires two roasting steps, alkaline roasting and sulfidation reduction, which is a long process and has high energy consumption. Summary of the Invention

[0005] This invention discloses a method for microwave roasting of copper tailings and recovery of iron, to solve any of the above-mentioned and other potential problems in the prior art.

[0006] To achieve the above objectives, the specific solution adopted by the present invention is as follows: a method for microwave roasting of copper tailings and recovery of iron, wherein the copper tailings are mixed evenly with calcareous materials, placed in a microwave oven and oxygen is introduced, and roasted at medium and low temperature by microwave heating, so that the ferroolitic in the copper tailings is converted into ferric oxide and ferric oxide, and the iron is recovered from the liquid after acid leaching, and the slag is recycled as a raw material for cement manufacturing.

[0007] Furthermore, the method specifically includes the following steps:

[0008] S1) Mix copper tailings and calcium materials evenly, roast them using microwave and introduce oxygen to obtain roasted slag;

[0009] S2) The roasted residue is crushed and ground, then mixed with acid solution and oxidant is added to leach iron, resulting in leachate and leaching residue;

[0010] S3) The leachate is concentrated and cooled to crystallize, resulting in a crystallized liquid and crystals. The crystallized liquid is returned to the iron leaching process. The crystals are removed by recrystallization and dried to obtain iron-containing chemical products.

[0011] Further, in S1), the copper tailings are the tailings from pyrometallurgical copper slag after flotation, with the main components being Fe 35-45 wt%, SiO2 25-35 wt%, Al2O3 3-10 wt%, CaO 2-8 wt%, Pb 0.5-1 wt%, and Cu 0.2-0.4 wt%. The calcareous material is one or more of calcium oxide, calcium hydroxide, and calcium carbonate. The copper tailings and calcareous material are mixed at a mass ratio of 1:0.2-0.5 to obtain a mixture. The mixture is then microwave-roasted at a temperature of 800-1000℃, an oxygen flow rate of 0.5-1 L / min, and a roasting time of 5-10 h.

[0012] Furthermore, the acid solution in S2) is any one of sulfuric acid, hydrochloric acid, and nitric acid, and its H... + The concentration is 2-4 mol / L, and the oxidant is one or a combination of sodium chlorate, potassium permanganate, and hydrogen peroxide, with an addition amount of 0.1-0.5 mol / L. First, the roasted slag is crushed and ground to obtain roasted slag powder. Then, the acid solution is mixed with the roasted slag powder at a liquid-to-solid ratio of 3-6:1. The mixture is then leached at a temperature of 25-100℃ for 2-4 hours to obtain a leachate and a leachate residue.

[0013] Furthermore, in step S3), the leachate is concentrated and cooled to crystallize, resulting in a crystallized liquid and crystals. The crystallized liquid is returned to the iron leaching process, and the crystals are removed by recrystallization to obtain iron chemical products.

[0014] The main chemical reactions involved in this invention are as follows:

[0015] 3(Fe2SiO4)+3CaO+O2→2Fe3O4+3CaSiO3 (1)

[0016] 3(Fe2SiO4)+3Ca(OH)2+O2→2Fe3O4+3CaSiO3+3H2O (2)

[0017] 3(Fe2SiO4)+3CaCO3+O2→2Fe3O4+3CaSiO3+3CO2 (3)

[0018] 4Fe3O4 + O2 → 6Fe2O3 (4)

[0019] Furthermore, the following reaction will occur under high temperature conditions:

[0020] 2FeO + SiO2 → 2FeO·SiO2 (5)

[0021] The CaSiO3 formed by adding calcium-containing materials at high temperatures is more stable than 2FeO·SiO2, which can prevent the regeneration of iron oxides into iron silicate, thus solving the problem of effective conversion and decomposition of fir olivine.

[0022] The beneficial effects of this invention are as follows: Due to the adoption of the above technical solution, the method of this invention uses microwaves to effectively transform and decompose the ferroolitic phase in copper tailings at temperatures below 1000℃, resulting in low energy consumption, high iron leaching rate in wet leaching, short process flow, and simple operation. The iron leaching solution can be used to prepare iron chemical products, and the leaching residue can be used in the cement industry, thus effectively recovering resources. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of a method for recovering iron from copper tailings by microwave roasting, according to the present invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments. The specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0025] Example 1:

[0026] like Figure 1 As shown, the specific process is as follows:

[0027] Mix 200g of copper tailings with an iron content of 39.78% with 60g of calcium oxide evenly, put them into a microwave oven with a power of 4000W, control the oxygen flow rate to 1L / min, calcine at 850℃ for 8h, cool to room temperature and then crush and grind into powder.

[0028] The roasted residue powder was leached with 2.5 mol / L hydrochloric acid and 0.2 mol / L sodium chlorate at 60°C, with a liquid-to-solid ratio of 4:1 and a leaching time of 3 hours. After leaching, the residue was filtered and separated, and the iron leaching rate was 93.08%.

[0029] The leachate is concentrated and cooled to crystallize, resulting in a post-crystallized liquid and crystals. The post-crystallized liquid is returned to the iron leaching process, and the crystals are removed by recrystallization to obtain iron chemical products.

[0030] Example 2:

[0031] Mix 400g of copper tailings with an iron content of 40.34% with 160g of calcium hydroxide evenly, put them into a microwave oven with a microwave power of 4000W, control the oxygen flow rate at 0.8L / min, calcine at 900℃ for 6h, cool to room temperature and then crush and grind into powder.

[0032] The calcined residue powder was leached with 1.5 mol / L sulfuric acid and 0.3 mol / L hydrogen peroxide at 80°C, with a liquid-to-solid ratio of 3:1 and a leaching time of 2 hours. After leaching, the residue was filtered and separated, and the iron leaching rate was 92.76%.

[0033] The leachate is concentrated and cooled to crystallize, resulting in a post-crystallized liquid and crystals. The post-crystallized liquid is returned to the iron leaching process, and the crystals are removed by recrystallization to obtain iron chemical products.

[0034] Example 3:

[0035] Mix 300g of copper tailings with an iron content of 38.75% with 200g of calcium carbonate evenly, put them into a microwave oven with a power of 4000W, control the oxygen flow rate to 0.6L / min, calcine at 950℃ for 7h, cool to room temperature and then crush and grind into powder.

[0036] The calcined residue powder was leached with 3 mol / L nitric acid at 25°C, with a liquid-to-solid ratio of 5:1, for 4 hours. After leaching, the residue was filtered and separated, and the iron leaching rate was 93.45%.

[0037] The leachate is concentrated and cooled to crystallize, resulting in a post-crystallized liquid and crystals. The post-crystallized liquid is returned to the iron leaching process, and the crystals are removed by recrystallization to obtain iron chemical products.

[0038] The above provides a detailed description of a method for microwave roasting of copper tailings and iron recovery provided in the embodiments of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and its core ideas; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

[0039] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0040] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0041] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0042] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A method for microwave roasting copper tailings and recovering iron, characterized in that, This method involves mixing copper tailings with calcareous materials, placing them in a microwave oven and introducing oxygen, and then roasting them at a medium to low temperature using microwave heating. This process converts the ferrolithium in the copper tailings into ferric oxide and ferric oxide. After acid leaching, the iron is recovered from the liquid, and the slag is recycled as a raw material for cement manufacturing. Specifically, the following steps are included: S1) Mix copper tailings and calcium materials evenly, roast them using microwave and introduce oxygen to obtain roasted slag; The specific steps are as follows: S1.1) Mix copper tailings and calcareous materials at a mass ratio of 1:0.2 to 0.5 to obtain a mixture. S1.2) The mixture obtained in S1.1) is calcined using microwave at a temperature of 800–1000℃, an oxygen flow rate of 0.5–1 L / min, and a calcination time of 5–10 h. S2) The roasted residue obtained in S1) is crushed and ground, then mixed with acid solution and a certain amount of oxidant is added to leach iron, resulting in leachate and leaching residue. S3) The leachate obtained in S2) is concentrated and cooled to crystallize, resulting in a crystallized liquid and crystals. The crystallized liquid is returned to the iron leaching process, and the crystals are removed by recrystallization and dried to obtain iron chemical products.

2. The method according to claim 1, characterized in that, The copper tailings in S1) are the tailings after flotation of copper slag from pyrometallurgical processes. The composition of the tailings is Fe 35-45wt%, SiO2 25-35wt%, Al2O3 3-10wt%, CaO 2-8wt%, Pb 0.5-1wt%, and Cu 0.2-0.4wt%.

3. The method according to claim 1, characterized in that, The calcium-based material is one or more of calcium oxide, calcium hydroxide, and calcium carbonate.

4. The method according to claim 1, characterized in that, The specific steps in S2) are as follows: S2.1) First, the roasted residue is crushed and ground to obtain roasted residue powder; S2.2) The acid solution and the roasted slag powder are mixed at a liquid-solid ratio of 3 to 6:1, an oxidant is added, and the mixture is leached at a temperature of 25 to 100°C for 2 to 4 hours to obtain a leachate and a leaching residue.

5. The method according to claim 4, characterized in that, The acid solution is any one of sulfuric acid, hydrochloric acid, or nitric acid, and its H+... + The concentration is 2–4 mol / L.

6. The method according to claim 4, characterized in that, The oxidant is one or a combination of sodium chlorate, potassium permanganate, and hydrogen peroxide, and the addition amount is 0.1 to 0.5 mol / L.

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