Method for extracting iron from gasified slag

Abstract

The invention relates to a method for extracting iron from gasified slag, and belongs to the technical field of solid waste resource utilization. The method for extracting the iron from the gasified slag comprises the following steps: mixing the gasified slag, a first additive and a second additive, and carrying out gradient roasting, crushing and grinding and magnetic separation to extract the iron, so as to realize the extraction of the iron, the first additive is an inorganic alkali salt, and the second additive is selected from carbon powder and / or a palladium compound. The gasified slag is directionally modified by the first additive (inorganic alkali salt) and the second additive (carbon powder and / or palladium compound) at a lower temperature, the process for extracting iron from gasified slag, which has the advantages of cheap raw materials, simple equipment, convenient process, low energy consumption and low cost, is provided, and the large-scale industrial requirement for extracting iron from gasified slag is met.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization, and in particular relates to a method for extracting iron from gasified slag. Background Art

[0002] As an important clean coal utilization technology, coal gasification technology has been growing rapidly at a compound annual growth rate of 25%-30%, and a new coal chemical industry with regional agglomeration has been formed in areas rich in coal resources. A large amount of coal gasification slag is produced in the coal gasification process. With the rapid increase in the emission of gasification slag, and due to many factors such as high overburned carbon, many aromatic impurities, high water content, and mixed inorganic metal compound components, the current comprehensive utilization rate is low. Open-air storage and pit landfill are still the main disposal methods for coal gasification slag. This traditional treatment method occupies land and dusts, soaks into the ground, and seriously affects the local ecological environment. Enterprises need to invest a lot of money every year but still cannot effectively deal with the growing amount of gasification slag. Under the current situation of increasingly severe environmental carrying capacity, it has become a top priority for the sustainable development of coal enterprises to make high-value resource utilization of gasification slag, complete solid waste reduction, and large-scale disposal, which is also an urgent need for the high-quality development of the national ecological environment.

[0003] The main metal contained in gasification slag in my country is iron. How to achieve low energy consumption, low cost and high efficiency in iron extraction is the key step in the resource utilization of gasification slag. In the existing technology, there are mainly the following processes for extracting iron from gasification slag:

[0004] Patent CN115582215A discloses a gasification slag separation process method, which uses two permanent magnetic flat plate magnetic separators to achieve gasification slag separation under a high magnetic field of 12,000 Gauss. The iron extraction rate is low, and the iron-rich part is only used as a cement additive. Patent CN111057810A discloses a method for removing impurity iron from gasification slag, which is achieved by roasting the gasification slag at a high temperature of 1150-1350 degrees and then achieving an iron removal rate of about 80% in the gasification slag in a strong magnetic field with a magnetic field strength of 2000-6000 Gauss. Patent CN114480745A discloses a method for recovering iron from steel slag using coal gasification slag, which uses coal gasification slag as a reducing agent to achieve a molten reduction ironmaking process at a high temperature of 1400 degrees. Patent CN116574910A discloses a method for preparing ferrosilicon-aluminum-calcium alloy by high-temperature smelting of coal gasification slag, using SiO2 and NaCl as additives to prepare ferrosilicon-aluminum-calcium alloy by high-temperature smelting in a resistance furnace at 1800°C. Patent CN116078348A discloses a comprehensive utilization method of coal gasification slag, using traditional acid leaching and alkali leaching processes to achieve the separation of ferroalloys and water purifiers. Patent CN115583655A discloses a method for graded extraction, utilization and conversion of high-calcium and high-iron gasification slag elements, after magnetizing the gasification slag with high-cost titanium magnetite ore, the highest iron content obtained by screening through a magnetic separation device is only 50.3%. However, the above existing technologies basically have several common problems: (1) High magnetic fields are required for iron selection, resulting in high costs in the iron selection process; (2) The use of titanium magnetite ore to magnetize the gasified slag will also lead to high costs and insufficient magnetic susceptibility, resulting in low iron selection rates; (3) If the gasified slag needs to be modified, extremely high temperatures are often required, making the modification process require expensive equipment and high energy consumption; (4) Traditional iron extraction processes such as molten reduction ironmaking require high energy consumption, and acid and alkali dissolution processes often result in a large amount of waste due to complex processes, etc. All these high energy consumption and high cost problems make it difficult to achieve large-scale and sustainable iron extraction from gasified slag.

[0005] Therefore, how to achieve low-energy consumption, low-cost and high-efficiency iron extraction remains the key to the resource utilization of gasification slag, which poses great challenges. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for extracting iron from gasified slag, which directionally modifies the gasified slag at a relatively low temperature by using a first additive (inorganic alkali salt) and a second additive (carbon powder and / or palladium compound), thereby providing a gasified slag iron extraction process with cheap raw materials, simple equipment, convenient process, low energy consumption and low cost, thereby meeting the large-scale industrialization needs of gasified slag iron extraction.

[0007] The object of the present invention is to provide a method for extracting iron from gasified slag, comprising the following steps: mixing gasified slag, a first additive and a second additive, extracting iron through gradient roasting, crushing and grinding, and magnetic separation to achieve iron extraction; the first additive is an inorganic alkali salt, and the second additive is selected from carbon powder and / or palladium compounds.

[0008] In one embodiment of the present invention, the water content of the gasified slag is less than 5%, and the iron content is less than 12%.

[0009] In one embodiment of the present invention, the inorganic alkali salt is selected from sodium carbonate and / or sodium bicarbonate.

[0010] In one embodiment of the present invention, the palladium compound is selected from palladium chloride and / or palladium acetate.

[0011] In one embodiment of the present invention, the mass ratio of the gasified slag, the first additive and the second additive is 100:(4.8-5.2):(5-5.2).

[0012] In one embodiment of the present invention, the gradient calcination includes two stages. The first stage is heating to 580°C-620°C at a rate of 8°C / min-12°C / min and keeping warm for 30min-60min; the second stage is heating to 950°C-1000°C at a rate of 4°C / min-5°C / min and keeping warm for 50min-70min.

[0013] In one embodiment of the present invention, the gradient roasting is carried out by electric heating, natural gas heating or steam heating.

[0014] In one embodiment of the present invention, the passing rate of the crushed and ground powder is above 90% under the condition of 200 mesh.

[0015] In one embodiment of the present invention, the magnetic induction intensity of the magnetic separation iron extraction is 1800G-2000G, and the time is 25min-35min.

[0016] In one embodiment of the present invention, the iron ore concentrate recovery rate of the method is 74%-94%.

[0017] The technical solution of the present invention has the following advantages over the prior art:

[0018] (1) The method for extracting iron from gasified slag described in the present invention uses a cheap and readily available first additive (inorganic alkali salt) and a second additive (carbon powder and / or palladium compound), and performs temperature control during the roasting and modification process of the gasified slag to directionally transform non-magnetic or weakly magnetic ferric oxide and ferrous oxide into ferroferric oxide with strong magnetism. The second additive is equivalent to a catalyst, which can adjust the valence state of iron in the gasified slag to ferroferric oxide. The carbon dioxide produced by the decomposition of the added first additive and the carbon monoxide produced by the second additive during the roasting and modification process have good reducibility and coordination, and can stabilize the catalyst and allow the catalyst to maintain continuous catalytic activity. By regulating the temperature of the gradient roasting, the iron in the gasified slag can be converted into ferroferric oxide with strong magnetism at the maximum conversion rate, thereby realizing efficient iron extraction from the gasified slag in a relatively low magnetic induction intensity environment. Compared with the existing process, the magnetic induction intensity of 2000G required by the present invention is the lowest magnetic field in the existing gasified slag magnetic separation and iron extraction process.

[0019] (2) The high-activity additive used in the method for extracting iron from gasified slag of the present invention improves the efficiency of directionally converting weakly magnetic ferric oxide and ferrous oxide in the gasified slag into strongly magnetic ferroferric oxide, so that the magnetization of iron in the gasified slag can be completed at a temperature not higher than 1000°C, which is the lowest temperature in the current gasified slag magnetic separation iron extraction process, and significantly reduces the temperature compared with the melting iron extraction process.

[0020] (3) The method for extracting iron from gasified slag described in the present invention uses cheap raw materials, has a convenient process, low cost, low equipment requirements, no waste liquid discharge, is environmentally friendly, has a low modification temperature, and a high iron extraction rate. It meets the requirements of green and sustainable development and can meet the needs of large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0022] Figure 1 The process flow chart of extracting iron from gasified slag of the present invention is as follows;

[0023] Figure 2 The composition analysis results of the initial sample of gasified slag used in the embodiment of the present invention;

[0024] Figure 3 The iron extraction analysis results of Example 1 of the present invention are as follows;

[0025] Figure 4 The iron extraction analysis results of Example 2 of the present invention are as follows;

[0026] Figure 5 The iron extraction analysis results of Example 3 of the present invention are as follows;

[0027] Figure 6 The figure is the iron extraction analysis result of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0029] In the present invention, unless otherwise defined, technical and scientific terms used in the present invention have the same meanings as commonly understood by those skilled in the art to which the present invention belongs.

[0030] In the present invention, unless otherwise stated, the term "and / or" used in the present invention includes any and all combinations of one or more of the associated listed items.

[0031] In the present invention, unless otherwise stated, the experimental methods used in the embodiments of the present invention are conventional methods unless otherwise stated, and the materials, reagents, etc. used are all commercially available unless otherwise stated.

[0032] Example 1

[0033] Reference Figure 1 As shown, the method for extracting iron from gasified slag in this embodiment specifically includes the following steps:

[0034] S1. 1000 g of gasified slag sample with a water content of less than 5% and an iron content of 11.10% (theoretical iron content is 111.0 g) and 50 g of sodium carbonate, 50 g of carbon powder and 50 mg of palladium chloride are fully mixed in a mixing system and then loaded into a crucible for secondary gradient roasting modification by natural gas heating. First, the temperature is raised to 600°C within 60 minutes and maintained at 600°C for 45 minutes; then the temperature is continued to be raised to 1000°C within 90 minutes and maintained at 1000°C for 60 minutes; finally, it is cooled by water quenching.

[0035] S2. The khaki slag after secondary gradient roasting modification is conveyed to a crusher for crushing and grinding. The crushing and grinding is performed until the pass rate of 200 mesh reaches more than 90%. Then, it is conveyed to a magnetic separator with a magnetic induction intensity of 2000G, and the iron is extracted by shaking for 30 minutes to obtain 103.70g of iron concentrate, and the iron concentrate selection rate is 93.42%.

[0036] The composition and iron extraction results of the initial sample of gasification slag were tested. The results are as follows: Figure 2-Figure 3As shown, the iron content of the iron concentrate is 81.62%, and the total iron extraction rate of the original gasified slag is 76.97%.

[0037] Example 2

[0038] The method for extracting iron from gasified slag in this embodiment specifically comprises the following steps:

[0039] S1, 1000g of gasified slag sample with a water content of less than 5% and an iron content of 11.10% (theoretical iron content is 111.0g), 50g of sodium carbonate and 50g of carbon powder are fully mixed in a mixing system and loaded into a crucible, and subjected to secondary gradient roasting modification by natural gas heating. First, the temperature is raised to 600°C within 60min and maintained at 600°C for 45min; then the temperature is continued to be raised to 1000°C within 90min and maintained at 1000°C for 60min; finally, it is cooled by water quenching.

[0040] S2. The khaki slag after secondary gradient roasting modification is conveyed to a crusher for crushing and grinding. The crushing and grinding is performed until the pass rate of 200 mesh reaches more than 90%. Then, it is conveyed to a magnetic separator with a magnetic induction intensity of 2000G, and the iron is extracted by shaking for 30 minutes to obtain 87.44g of iron concentrate, and the iron concentrate selection rate is 78.77%.

[0041] The iron extraction results were tested and the results were as follows Figure 4 As shown, the iron content of the iron concentrate is 58.05%, and the total iron extraction rate of the original gasified slag is 45.73%.

[0042] Example 3

[0043] The method for extracting iron from gasified slag in this embodiment specifically comprises the following steps:

[0044] S1, 1000g of gasified slag sample with a water content of less than 5% and an iron content of 11.10% (theoretical iron content is 111.0g), 50g of sodium bicarbonate and 50g of carbon powder are fully mixed in a mixing system and loaded into a crucible, and subjected to secondary gradient roasting modification by natural gas heating. First, the temperature is raised to 600°C within 60min and maintained at 600°C for 45min; then the temperature is continued to be raised to 1000°C within 90min and maintained at 1000°C for 60min; finally, it is cooled by water quenching.

[0045] S2. The khaki slag after secondary gradient roasting modification is conveyed to a crusher for crushing and grinding. The crushing and grinding is performed until the pass rate of 200 mesh reaches more than 90%. Then, it is conveyed to a magnetic separator with a magnetic induction intensity of 2000G, and the iron is extracted by shaking for 30 minutes to obtain 82.17g of iron concentrate, and the iron concentrate selection rate is 74.03%.

[0046] The iron extraction results were tested and the results were as follows Figure 5As shown, the iron content of the iron concentrate is 43.06%, and the total iron extraction rate of the original gasified slag is 31.88%.

[0047] Example 4

[0048] The method for extracting iron from gasified slag in this embodiment specifically comprises the following steps:

[0049] S1. 1000 g of gasified slag sample with a water content of less than 5% and an iron content of 11.10% (theoretical iron content is 111.0 g) and 50 g of sodium carbonate, 50 g of carbon powder and 50 mg of palladium acetate are fully mixed in a mixing system and then loaded into a crucible for secondary gradient roasting modification by natural gas heating. First, the temperature is raised to 600°C within 60 minutes and maintained at 600°C for 45 minutes; then the temperature is continued to be raised to 1000°C within 90 minutes and maintained at 1000°C for 60 minutes; finally, it is cooled by water quenching.

[0050] S2. The khaki slag after secondary gradient roasting modification is conveyed to a crusher for crushing and grinding. The crushing and grinding is performed until the pass rate of 200 mesh reaches more than 90%. Then, it is conveyed to a magnetic separator with a magnetic induction intensity of 2000G, and the iron is extracted by shaking for 30 minutes to obtain 91.17g of iron concentrate, and the iron concentrate selection rate is 82.14%.

[0051] The iron extraction results were tested and the iron content of the iron concentrate was 73.31%, and the total iron extraction rate of the original gasified slag was 60.21%.

[0052] Comparative Example 1 is basically the same as Example 1, except that no sodium carbonate is added

[0053] S1. 1000 g of a gasified slag sample with a water content of less than 5% and an iron content of 11.10% (theoretical iron content is 111.0 g), 50 g of carbon powder and 50 mg of palladium chloride are fully mixed in a mixing system and then loaded into a crucible for secondary gradient roasting modification by natural gas heating. First, the temperature is raised to 600°C within 60 minutes and maintained at 600°C for 45 minutes; then the temperature is continued to be raised to 1000°C within 90 minutes and maintained at 1000°C for 60 minutes; finally, it is cooled by water quenching.

[0054] S2. The khaki slag after secondary gradient roasting modification is conveyed to a crusher for crushing and grinding. The crushing and grinding is performed until the pass rate of 200 mesh reaches more than 90%. Then, it is conveyed to a magnetic separator with a magnetic induction intensity of 2000G, and the iron is extracted by vibration for 30 minutes to obtain 44.47g of iron concentrate, and the iron concentrate selection rate is 40.06%.

[0055] The iron extraction results were tested and the iron content of the iron concentrate was 47.52%, and the total iron extraction rate of the original gasified slag was 19.04%.

[0056] Comparative Example 2 is basically the same as Example 1, except that sodium carbonate, carbon powder and palladium chloride are not added.

[0057] S1. 1000g of gasified slag sample with a water content of less than 5% and an iron content of 11.10% (theoretical iron content is 111.0g) was placed in a crucible and subjected to secondary gradient roasting modification by natural gas heating. The temperature was first raised to 600°C within 60min and maintained at 600°C for 45min; then the temperature was continued to be raised to 1000°C within 90min and maintained at 1000°C for 60min; finally, it was cooled by water quenching.

[0058] S2. The khaki slag after secondary gradient roasting modification is conveyed to a crusher for crushing and grinding. The crushing and grinding is performed until the pass rate of 200 mesh reaches more than 90%. Then, it is conveyed to a magnetic separator with a magnetic induction intensity of 2000G, and the iron is extracted by shaking for 30 minutes to obtain 13.24g of iron concentrate, and the iron concentrate selection rate is 11.93%.

[0059] The iron extraction results were tested and the results were as follows Figure 6 As shown, the iron content of the iron concentrate is 28.15%, and the total iron extraction rate of the original gasified slag is 3.36%.

[0060] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for extracting iron from gasified slag, characterized in that: The method comprises the following steps: mixing gasified slag, a first additive and a second additive, and extracting iron through gradient roasting, crushing and grinding, and magnetic separation; the first additive is an inorganic alkali salt, and the second additive is selected from carbon powder and / or palladium compound.

2. The method for extracting iron from gasified slag according to claim 1, characterized in that: The water content of the gasified slag is less than 5%, and the iron content is less than 12%.

3. The method for extracting iron from gasified slag according to claim 1, characterized in that: The inorganic alkali salt is selected from sodium carbonate and / or sodium bicarbonate.

4. The method for extracting iron from gasified slag according to claim 1, characterized in that: The palladium compound is selected from palladium chloride and / or palladium acetate.

5. The method for extracting iron from gasified slag according to claim 1, characterized in that: The mass ratio of the gasified slag, the first additive and the second additive is 100:(4.8-5.2):(5-5.2).

6. The method for extracting iron from gasified slag according to claim 1, characterized in that: The gradient calcination includes two stages. The first stage is heating to 580-620°C at a rate of 8-12°C / min and keeping warm for 30-60 minutes. The second stage is heating to 950-1000°C at a rate of 4-5°C / min and keeping warm for 50-70 minutes.

7. The method for extracting iron from gasified slag according to claim 1, characterized in that: The gradient roasting method is electric heating, natural gas heating or steam heating.

8. The method for extracting iron from gasified slag according to claim 1, characterized in that: After crushing and grinding, the passing rate of the powder under 200 mesh conditions is more than 90%.

9. The method for extracting iron from gasified slag according to claim 1, characterized in that: The magnetic induction intensity of the magnetic separation iron extraction is 1800G-2000G, and the time is 25min-35min.

10. The method for extracting iron from gasified slag according to claim 1, characterized in that: The iron concentrate recovery rate of the method is 74%-94%.

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