Method for inhibiting generation of liquid phase in fayalite type slag reduction roasting product

Abstract

The invention provides a method for inhibiting generation of a liquid phase in a fayalite type slag reduction roasting product, which comprises the following steps: mixing fayalite type slag and bentonite for pelletizing to obtain slag pellets; the obtained slag pellets are subjected to first-stage reduction roasting at the temperature of 1000-1100 DEG C; and continuously raising the temperature to 1150-1200 DEG C, and carrying out second-stage reduction roasting. According to the method, under the condition that no additive is added, generation of a liquid phase in the fayalite type slag reduction roasting product can be restrained by changing the heat history, growth of metal iron particles is considered, adhesion and kiln caking cannot be generated in the process, the metallization ratio of the reduction roasting product is high, the metal iron particles in the obtained reduction roasting product are large in particle size, and the metal iron particles are uniform in particle size. The average size reaches 20 microns or above, and subsequent magnetic separation and recovery of metal iron are facilitated.

Description

Technical Field

[0001] This invention belongs to the field of mineral engineering technology, and specifically relates to a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine type slag. Background Technology

[0002] Currently, the comprehensive utilization rate of fir olivine-type slag (such as copper and nickel slag) is about 70%, and its output is increasing year by year. Therefore, the resource-based disposal of fir olivine-type slag has become a major factor limiting the sustainable development of enterprises. Given that the iron content in fir olivine-type slag is between 30% and 45%, iron extraction has become one of the main research directions for its high-value utilization.

[0003] Patent document CN106086276A discloses a method for recovering waste heat from the high-temperature cooling process of molten copper slag, adding solvent, and then reheating and calcining to prepare metallized pellets. This method employs a direct reduction-magnetic separation process. However, this process requires energy-intensive rotary hearth furnaces or vertical shaft furnaces. Using low-energy rotary kilns can easily lead to kiln blockage, and additional flux is required. Patent document CN119571050A discloses a method of mixing copper slag with calcium oxide-based additives, followed by sedimentation and iron extraction from the modified copper slag. This process involves high processing temperatures, high energy consumption, and stringent requirements for raw material composition; the product is an intermediate and requires further processing. Patent document CN119571049A discloses a method of mixing copper slag with additives, obtaining mixed copper slag, and then using self-pulverization for iron extraction. This process involves high processing temperatures, requires ultra-slow and controllable cooling, consumes high energy, and requires excessive amounts of additives. Patent document CN111... Patent document 057858A discloses a process for recovering valuable metals from secondary alkaline leaching solution and residue of copper slag. This process requires microwave alkali dissolution, resulting in energy costs far exceeding those of conventional fuel heating. It also involves high equipment investment and maintenance costs, a lengthy process, and low overall energy efficiency. Patent document CN108676942A discloses a process for separating and recovering valuable metals such as iron, lead, and zinc in a reduction-volatilization smelting furnace using blast furnace, adding fuels such as coal gangue, and fluxes such as high-silicon and high-alumina materials. This process involves high processing temperatures and requires energy to maintain a high-temperature molten pool, as well as oxygen enrichment from blast furnace and injection, resulting in high overall energy consumption. Patent document CN116043018A discloses a combined process of molten chlorination-reduction iron extraction for the comprehensive utilization of valuable elements such as iron, lead, and zinc. This process requires two independent high-temperature smelting stages, leading to cumulative energy consumption and high total energy consumption. Furthermore, the equipment experiences rapid efficiency degradation in corrosive high-temperature environments, has short maintenance cycles, and its long-term operational efficiency is difficult to maintain. Summary of the Invention

[0004] The present invention aims to solve the above-mentioned problems of the prior art. Its purpose is to provide a method for suppressing the formation of liquid phase in the reduction roasting products of ferroolitic slag. This method can suppress the formation of liquid phase in the reduction roasting products of ferroolitic slag without the addition of additives, while taking into account the growth of metallic iron particles, thus creating favorable conditions for the subsequent magnetic separation and recovery of metallic iron.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag includes: Iron olivine-type slag is mixed with bentonite and pelletized to obtain slag pellets; The obtained slag pellets were subjected to a first-stage reduction roasting at 1000~1100℃; Continue heating to 1150~1200℃ for a second-stage reduction roasting.

[0006] Further, the ferrolithic slag in step (1) includes one or more slags whose main phase is ferrolithic, such as copper slag or nickel slag.

[0007] Furthermore, the mass ratio of bentonite to fir olivine slag is 0.5:100 to 5:100.

[0008] Furthermore, the mass ratio of bentonite to fir olivine slag is 1:100 to 3:100.

[0009] Furthermore, the duration of the restoration segment is no less than 60 minutes.

[0010] Furthermore, the duration of the restoration segment is 60-90 minutes.

[0011] Furthermore, the reducing agent in the first-stage reduction roasting and the second-stage reduction roasting is one or more of CO, coke, coal, and charcoal.

[0012] Furthermore, the duration of the two-stage reduction roasting is 30-60 minutes.

[0013] Furthermore, the first-stage reduction roasting and the second-stage reduction roasting are carried out in a rotary kiln.

[0014] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: Existing research promotes the growth of metallic iron particles in copper slag reduction roasting products by introducing additives (CaO, Na2CO3, etc.), but this has problems such as large amounts of secondary tailings that are difficult to dispose of, and it also fails to solve the problem of liquid phase formation. This invention, without the addition of additives, can suppress the formation of the liquid phase in the reduction roasting products of fir olivine-type slag while simultaneously allowing for the growth of metallic iron particles by altering the thermal history, creating favorable conditions for subsequent rotary kiln processing.

[0015] The metallization rate of the product obtained by the present invention in a first-stage reduction roasting at 1000~1100°C for 60~90min can exceed 70%. The second-stage reduction roasting at 1150~1200°C for 30~60min can effectively suppress the formation of liquid phase in the reduction roasting product, and will not produce adhesion or kiln caking. Moreover, the metallization rate in the reduction roasting product exceeds 90%, and the resulting reduction roasting product has a large particle size of metallic iron, with an average size of more than 20μm, which is more conducive to the subsequent magnetic separation and recovery of metallic iron. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the roasting mechanism of the present invention.

[0018] Figure 2 The images show the morphology of the products obtained by different reduction roasting mechanisms, where (a) to (d) correspond to the products obtained by different roasting times in Comparative Example 1, and (e), (f), (g), and (h) correspond to the products obtained by Comparative Example 4, Comparative Example 5, Example 5, and Example 1, respectively.

[0019] Figure 3 The diagram shows the distribution of iron particles in the roasted products obtained in Example 1 and Comparative Example 1, where (a) corresponds to Example 1 and (b) corresponds to Comparative Example 1. Detailed Implementation

[0020] Some embodiments of the present invention provide a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, comprising: Iron olivine-type slag is mixed with bentonite and pelletized to obtain slag pellets; The obtained slag pellets were subjected to a first-stage reduction roasting at 1000~1100℃; Continue heating to 1150~1200℃ for a second-stage reduction roasting.

[0021] The provided technical solution involves transforming iron-containing minerals in fir olivine slag into metallic iron during a low-temperature reduction roasting process. The reduction roasting temperature is further increased, expanding the temperature range while simultaneously promoting the growth of metallic iron particles. This ultimately resolves the contradiction between high-temperature liquid phase generation and metallic iron particle growth during the reduction roasting of fir olivine slag. The resulting reduction roasting product not only boasts a metallization rate exceeding 90% but also avoids adhesion and kiln caking. Furthermore, the average particle size of metallic iron in the product is over 20 μm. Subsequent magnetic separation allows for the selective enrichment of iron particles, ultimately achieving the resource utilization of fir olivine slag.

[0022] In some embodiments, the fir-olive-shaped slag is one or more of slags whose main phase is fir olivine, including copper slag, nickel slag, etc.

[0023] In some preferred embodiments, the mass ratio of bentonite to fir olivine slag is 0.5:100 to 5:100, such as 1:100, 2:100, 3:100, 4:100, 5:100, etc., preferably 1:100 to 3:100.

[0024] In some preferred embodiments, the duration of the restoration segment is not less than 60 minutes; preferably 60 minutes to 90 minutes, such as 60 minutes, 70 minutes, 80 minutes, 90 minutes, etc.

[0025] In some preferred embodiments, the reducing agent in the first-stage reduction roasting and the second-stage reduction roasting is one or more of CO, coke, coal, and charcoal; when a solid reducing agent is used, the reducing atmosphere of the second-stage reduction is generated by the reducing agent added in the first-stage reduction roasting. At this time, the amount of reducing agent added in the first-stage reduction roasting is 1.2 to 1.5 times the theoretical amount, for example, 1.2 times, 1.3 times, 1.4 times, 1.5 times, etc. The theoretical amount is the amount of reducing agent required to reduce iron oxide to metallic iron.

[0026] In some preferred embodiments, the duration of the two-stage reduction calcination is 30-60 minutes, such as 30 minutes, 40 minutes, 50 minutes, 60 minutes, etc.

[0027] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0028] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0030] In the following examples and comparative examples, the metallization rate is the mass ratio of metallic iron to total iron, wherein the content of metallic iron and total iron is tested according to national standards GB / T 38812.2-2020 and GB / T 6730.65-2009, respectively.

[0031] The iron olivine-type slag used in this embodiment of the invention is tailings from copper slag after slow cooling and flotation, with 95% of the particles being -200 mesh. The chemical composition of this iron olivine-type slag is shown in Table 1. The main components are iron and silicon dioxide, with mass contents of 38.48% and 31.65%, respectively. The contents of lead and zinc are 0.78% and 2.31%, respectively. The contents of other elements are low, making it a typical iron olivine-type slag.

[0032] Table 1 Example 1 This embodiment discloses a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, such as... Figure 1 As shown, it includes the following steps: (1) Mix the iron olivine slag and bentonite at a ratio of 100:3 and form balls with a diameter of 8-12 mm; (2) Roast the pellets obtained in step (1) with coal at 1100 °C for 75 min. The amount of coal added is 1.2 times the theoretical amount. Other reducing agents, such as coke, charcoal, CO, etc., can be used to replace the coal. (3) Further heat the reduced roasted material from step (2) to 1150 ℃ and reduce roast for 35 min. The resulting reduced roasted material is shown in the image below. Figure 2 As shown in (h), the product obtained by roasting has rounded particles and does not undergo melting, adhesion, or kiln caking. (4) The reduction calcination product obtained in step (3) was analyzed, and its metallization rate reached 91.25%. The SEM image of the product is shown below. Figure 3 As shown in (a), by Figure 3 (a) It can be seen that the average particle size of iron in the obtained product is relatively large. According to the analysis of Image Pro software, the average particle size of metallic iron particles reaches 23.23 μm.

[0033] Example 2 This embodiment discloses a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, such as... Figure 1 As shown, it includes the following steps: (1) Mix the iron olivine slag and bentonite at a ratio of 100:2 and form them into balls with a diameter of 8-12 mm; (2) The pellets obtained in step (1) are roasted with coal at 1000 °C for 90 min, and the amount of coal added is 1.2 times the theoretical amount; (3) The material from step (2) was further heated to 1150 °C and reductively roasted for 60 min. The resulting product had rounded particles and did not melt, stick together or clump together. (4) The reduction roasting product obtained in step (3) was analyzed and its metallization rate reached 92.89%, and the average particle size of the iron particles reached 28.64 μm.

[0034] Example 3 This embodiment discloses a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, such as... Figure 1 As shown, it includes the following steps: (1) Mix the iron olivine slag and bentonite at a ratio of 100:3 and form them into balls with a diameter of 8-12 mm; (2) The pellets obtained in step (1) are roasted with coal at 1100 °C for 60 min, and the amount of coal added is 1.2 times the theoretical amount; (3) The material from step (2) was further heated to 1200 °C and subjected to reducing roasting for 45 min. The resulting product had rounded particles and did not melt, stick together or clump together. (4) The reduction roasting product obtained in step (3) was analyzed. Its metallization rate reached 91.86%, and the average particle size of the iron particles reached 26.65 μm.

[0035] Example 4 This embodiment discloses a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, such as... Figure 1 As shown, it includes the following steps: (1) Mix the iron olivine slag and bentonite at a ratio of 100:1 and form them into balls with a diameter of 8-12 mm; (2) The pellets obtained in step (1) are roasted with coal at 1050℃ for 90 min, and the amount of coal added is 1.2 times the theoretical amount; (3) The material from step (2) was further heated to 1200℃ and reductively roasted for 60 minutes. The resulting product had rounded particles and did not melt, stick together or clump together. (4) The reduction roasting product obtained in step (3) was analyzed and its metallization rate reached 92.45%, and the average particle size of the iron particles reached 29.85 μm.

[0036] Example 5 This embodiment discloses a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, comprising the following steps: (1) Mix the iron olivine slag and bentonite at a ratio of 100:3 and form them into balls with a diameter of 8-12 mm; (2) The pellets obtained in step (1) are roasted with coal at 1100 °C for 45 min, and the amount of coal added is 1.2 times the theoretical amount; (3) The material from step (2) was further heated to 1150 °C and reductively roasted for 65 min. The roasted product was then analyzed using SEM images. The results are as follows: Figure 2 As shown in (g), the calcined product particles are round and smooth, without melting, sticking, or caking. (4) The reduction roasting product obtained in step (3) was analyzed and its metallization rate reached 91.68%, and the average particle size of the iron particles reached 23.56 μm.

[0037] Comparative Example 1 This comparative example discloses a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, comprising the following steps: (1) Mix the iron olivine slag and bentonite at a ratio of 100:3 and form them into balls with a diameter of 8-12 mm; (2) The pellets obtained in step (1) were roasted with coal at 1150 ℃ for 120 min. The amount of coal added was 1.2 times the theoretical amount. Samples were taken at 30 min, 60 min, 90 min and 120 min of reduction roasting to check the morphology of the roasted pellets. Specifically, as shown in the figure below. Figure 2 As shown in (a) to 2(d), it can be seen from the figure that when reduction roasting is carried out at 1150℃, the roasting material begins to melt and produce liquid substances after 60 minutes of roasting, which causes the roasting material to stick together. After 120 minutes of roasting, severe sticking occurs, leading to kiln clogging and making it difficult to carry out industrial tests smoothly. (3) The product obtained in step (2) after reduction and calcination for 120 min was analyzed. Its metallization rate reached 80.15%. The SEM image of the obtained product is shown below. Figure 3 As shown in (b), it can be seen from the figure that the average particle size of iron in the obtained product is significantly smaller than that of iron in the product of Example 1, and the average particle size of metallic iron particles reaches 8.95 μm.

[0038] Comparative Example 2 This comparative example discloses a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, comprising the following steps: (1) Mix the iron olivine slag and bentonite at a ratio of 100:3 and form them into balls with a diameter of 8-12 mm; (2) The pellets obtained in step (1) were roasted with coal at 1200 °C for 90 min. The amount of coal added was 1.2 times the theoretical amount. The roasting material sticked together, which caused kiln clogging and made it difficult to carry out industrial tests. (3) The reduction roasting product obtained in step (2) was analyzed and its metallization rate reached 71.56%, and the average particle size of the iron particles reached 6.22 μm.

[0039] Comparative Example 3 This comparative example discloses a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, comprising the following steps: (1) Mix the iron olivine slag and bentonite at a ratio of 100:3 and form them into balls with a diameter of 8-12 mm; (2) The pellets obtained in step (1) were roasted with coal at 1100 °C for 240 min. The amount of coal added was 1.2 times the theoretical amount. The roasted product particles were round and did not melt, stick together or clump together. (3) The reduction roasting product obtained in step (2) was analyzed and its metallization rate reached 91.34%, and the average particle size of the iron particles reached 11.12 μm.

[0040] The results show that when a single-stage low-temperature reduction is used instead of a two-stage reduction, extending the reduction roasting time is beneficial for reducing iron-containing minerals in the ferrolithite slag to metallic iron and will not cause kiln caking. However, it is not conducive to the growth of metallic iron particles, which in turn increases the difficulty of subsequent magnetic separation.

[0041] Comparative Example 4 This comparative example discloses a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, comprising the following steps: (1) Mix the iron olivine slag and bentonite at a ratio of 100:3 and form balls with a diameter of 8-12 mm; (2) The pellets obtained in step (1) are roasted with coal at 1100 °C for 30 min, and the amount of coal added is 1.2 times the theoretical amount; (3) The material from step (2) was further heated to 1150 °C and reductively roasted for 80 min. The roasted product was then analyzed using SEM images. The results are as follows: Figure 2 As shown in (e); (4) The reduction roasting product obtained in step (3) was analyzed and its metallization rate reached 80.22%, and the average particle size of the iron particles reached 13.16 μm.

[0042] Comparative Example 5 This comparative example discloses a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, comprising the following steps: (1) Mix the iron olivine slag and bentonite at a ratio of 100:3 and form them into balls with a diameter of 8-12 mm; (2) The pellets obtained in step (1) are roasted with coal at 1100 °C for 45 min, and the amount of coal added is 1.2 times the theoretical amount; (3) The material from step (2) was further heated to 1150 °C and reductively roasted for 65 min. The roasted product was then analyzed using SEM images. The results are as follows: Figure 2 As shown in (f); (4) The reduction roasting product obtained in step (3) was analyzed and its metallization rate reached 84.15%, and the average particle size of the iron particles reached 15.21 μm.

[0043] Comparative Example 6 This comparative example discloses a method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, comprising the following steps: (1) Mix the iron olivine slag and bentonite at a ratio of 100:3 and form balls with a diameter of 8-12 mm; (2) The pellets obtained in step (1) are roasted with coal at 1100 °C for 45 min, and the amount of coal added is 1.2 times the theoretical amount; (3) The material from step (2) was further heated to 1150 °C and reductively roasted for 45 min. The roasted product particles were round and did not melt, stick together or clump together. (4) The reduction roasting product obtained in step (3) was analyzed and its metallization rate reached 81.22%, and the average particle size of the iron particles reached 14.33 μm.

[0044] When the first stage of reduction roasting is short, the metallization rate in the reduction roasting product is low. When the temperature is raised to the second stage of reduction roasting, the initial reaction is dominated by the reduction of iron-containing minerals, resulting in limited growth of the size of the metallic iron particles.

[0045] Comparing Examples 1-5 and Comparative Examples 4-6, it is evident that proper control of the duration of the two-stage reduction roasting is necessary to prevent product adhesion and subsequent kiln clogging. Furthermore, comparing Examples 1, 5, 4, and 5, it is clear that with the same total reduction roasting time, kiln clogging occurs when the first-stage low-temperature roasting time is too short and the second-stage high-temperature roasting time is too long. This also hinders the growth of metallic iron particles and the improvement of metallization rate. Analysis shows that the formation of the liquid phase impedes the contact between the reducing gas and the reactants, resulting in a lower metallization rate and smaller metallic iron particle size. Analysis of Comparative Examples 4 and 5 shows that with the same total roasting time, extending the roasting period reduces the amount of liquid phase generated during the second-stage reduction, thus increasing both the metallization rate and the size of metallic iron particles in the roasted product. Analysis of Comparative Examples 5 and 6 shows that with the same first-stage roasting time, extending the second-stage roasting time also contributes to improving both the metallization rate and the size of metallic iron particles in the roasted product.

[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag, characterized in that, include: Iron olivine-type slag is mixed with bentonite and pelletized to obtain slag pellets; The obtained slag pellets were subjected to a first-stage reduction roasting at 1000~1100℃; Continue heating to 1150~1200℃ for a second-stage reduction roasting.

2. The method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag as described in claim 1, characterized in that, The iron-olive-shaped slag is one or more of the following: copper slag, nickel slag, etc., whose main phase is iron-olive.

3. The method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag as described in claim 1, characterized in that, The mass ratio of bentonite to fir olivine slag is 0.5:100 to 5:

100.

4. The method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag as described in claim 3, characterized in that, The mass ratio of bentonite to fir olivine slag is 1:100 to 3:

100.

5. The method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag as described in claim 1, characterized in that, The duration of the restoration process is no less than 60 minutes.

6. The method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag as described in claim 5, characterized in that, The duration of the restoration is 60-90 minutes.

7. The method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag as described in claim 1, characterized in that, The reducing agent in the first-stage reduction roasting and the second-stage reduction roasting is one or more of CO, coke, coal, and charcoal.

8. The method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag as described in claim 1, characterized in that, The duration of the two-stage reduction roasting is 30-60 minutes.

9. The method for suppressing the formation of liquid phase in the reduction roasting products of fir olivine-type slag as described in claim 1, characterized in that, The first-stage reduction roasting and the second-stage reduction roasting are carried out in a rotary kiln.

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