Method for producing oxidized pellets through wet ball-milling classification of magnetic separation powder

Abstract

The invention discloses a method for producing oxidized pellets through wet ball-milling classification of magnetic separation powder. The method comprises the following steps that S1, after steel slag is subjected to rod milling and magnetic separation, the magnetic separation powder is obtained; s2, the magnetic separation powder is subjected to ball milling and screening to obtain flaky elemental iron, and other materials are subjected to rotational flow classification to obtain first ore pulp; s3, the hematite and limonite coarse powder is directly subjected to tower grinding and rotational flow classification, and second ore pulp is obtained; s4, the first ore pulp and the second ore pulp are conveyed to a mixed ore pulp pool through a pipeline to be mixed; s5, after mixing, flocculating in a concentration sedimentation tank to obtain mixed ore pulp; s6, the mixed ore pulp is subjected to concentration and plate-frame pressure filtration, and autogenous grinding fine powder is obtained; s7, the autogenous grinding fine powder, the coking fly ash and the bentonite enter a batching bin according to the proportion to be mixed; s8, the mixture is subjected to mixing, roller milling and pelletizing, and green pellets are obtained; and S9, the green pellets pass through a belt type roasting machine, and then oxidized pellets are obtained. The method has the advantages that the method for applying the steel slag solid waste magnetic separation powder to the belt type roasting machine to produce the mixture is achieved, and meanwhile the metallurgical performance index of oxidized pellets is improved.

Description

Technical Field

[0001] The invention relates to the technical field of pellet preparation, and in particular to a method for producing oxidation pellets using wet ball milling and classification of magnetic separation powder. Background Art

[0002] Each ton of steel is accompanied by about 100 kg of steel slag as a by-product. At present, the comprehensive resource utilization rate of steel slag in my country is still at a low level, only about 30%. In the existing domestic processing process, the molten steel slag is pre-treated, crushed, magnetically separated, and screened to obtain slag steel and tailings of a certain particle size. Among them, slag steel is basically directly recycled and reused in the sintering process; tailings are prepared into different performance materials according to the specific needs of the application field. However, slag steel contains some elemental iron (iron particles), Fe3O4 and CaO, which is only used in sintering, which limits its scope of use. Combined with the need to use a certain proportion of magnetic fine powder in conventional pellet production, the slag steel is used for pelletizing after a certain process treatment, which can alleviate the pelletizing plant's dependence on magnetic fine powder and realize the diversification of pelletizing raw material structure.

[0003] Among the raw materials for pelletizing, the demand for raw material varieties is different due to different pelletizing equipment. At present, high-priced magnetic concentrate accounts for more than 80% of the raw material structure of domestic pelletizing. The use of belt roasting machine to realize the full hematite production mode requires matching adjustments in process parameters. For example, processes such as graded carbon matching and zoned oxygen control can reduce the proportion of magnetic concentrate in the pelletizing ingredients. However, by using the by-product of the full-process steel enterprise - steel slag, after a certain process treatment, magnetic separation powder containing elemental iron (iron particles), Fe3O4, CaO, and MgO components is obtained. However, due to its coarse particle size, it cannot be used directly in pelletizing. Therefore, long-process enterprises generally use it in sintering. At present, the technology of slag-free steel-magnetic separation powder is used as a technical reference for pelletizing. Summary of the invention

[0004] The purpose of the present invention is to provide a method for wet ball milling classification of magnetic powder for oxidized pellet production, realize the method of using magnetic powder of steel slag solid waste to produce mixed materials in a belt roaster, and improve the metallurgical performance indicators of oxidized pellet ore.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A method for producing oxidized pellets by wet ball milling and classification of magnetic powder, characterized in that it comprises the following steps:

[0007] S1, steel slag is rod-milled and magnetically separated to obtain magnetic separation powder;

[0008] S2, the magnetic powder is ball-milled according to the material ratio, and the flake elemental iron formed is screened and dehydrated for use in the converter, and the remaining materials are cyclone-classified to obtain the first slurry;

[0009] S3, the coarse hematite powder is directly subjected to tower grinding and cyclone classification according to the material ratio to obtain the second slurry;

[0010] S4, transporting the first ore pulp and the second ore pulp to a mixed ore pulp pool through a pipeline for mixing;

[0011] S5, after mixing, it enters the concentration sedimentation tank, where flocculants are added and the pH value of the water is controlled to obtain mixed slurry;

[0012] S6, the mixed slurry is concentrated and plate-and-frame filtered to obtain autogenous fine powder;

[0013] S7, the self-grinding powder, coking dust removal ash and bentonite are mixed in a batching bin according to the proportion;

[0014] S8, after intensive mixing and high-pressure roller grinding, the mixed material enters the ball making system to obtain raw balls;

[0015] S9, the green balls are passed through a belt roaster to obtain oxidized pellets.

[0016] Preferably, the magnetically separated powder in S1 has a particle size range of less than 8 mm accounting for more than 90%.

[0017] Preferably, a cylindrical screen is provided at the tail of the ball mill in S2, the circular hole size of the cylindrical screen is 4 mm, the particle size range of -200 mesh in the first slurry accounts for 75-85%, and the concentration of the first slurry is 20-25%.

[0018] Preferably, in the second slurry in S3, the particle size range of -200 mesh accounts for 70-75%, and the concentration of the second slurry is 20-25%.

[0019] Preferably, the feed ratio of the magnetic powder to the hematite is: magnetic powder ≤ 8%: hematite ≥ 92%.

[0020] Preferably, in said S4, the inflow angle of the first slurry and the second slurry is 180°, and the mixed slurry pool is further provided with spiral blades.

[0021] Preferably, the flocculant in S5 is alkaline flocculant polyacrylamide, the molecular weight of polyacrylamide is ≥10 million, the input amount of flocculant per ton of ore is 0.03 kg / t, the pH value of the water body is controlled at 8-9, and the concentration of the mixed ore pulp is 65-70%.

[0022] Preferably, the proportion of coking dust in S7 accounts for 0.30-0.45% of the self-ground fine powder, and the proportion of bentonite accounts for 0.2-0.4% of the self-ground fine powder.

[0023] Preferably, water is added to the pelletizing system in S8 to moisten the pellets to obtain green pellets, and the particle size of the green pellets is in the range of 10-16 mm.

[0024] Preferably, in the oxidized pellets in S9, CaO / SiO2≤0.4, MgO content≥0.5%, compressive strength≥2300N / P, reduction expansion≤17%, and reducibility≥65%.

[0025] In summary, the beneficial effects of the present invention are as follows: the present invention expands the resources for pelletizing, and the magnetic separation powder of steel slag, a by-product of steel, is successfully applied to the production of pelletizing after being treated by a certain process, thus realizing the high-value utilization of steel slag by-products; the elemental iron (iron particles) is ball-milled to form flaky iron, which can be directly used as scrap steel raw material to enter the converter; other materials are ball-milled to form slurry, which is used as the raw material for producing pellets, thus providing another path for promoting the production mode of reducing the proportion of magnetic concentrate in pelletizing, and having great significance for the expansion of resources for pelletizing; the magnetic separation powder after the by-product steel slag is treated, because it contains Fe3O4, CaO and MgO, thus realizing the oxidation and heat generation of Fe3O4 under zero magnetic concentrate, and solidifying with Fe2O3 solid phase to form a paste, and at the same time controlling the interval of CaO / SiO2≤0.4, forming a partial low-melting-point liquid phase, which plays a role in strengthening the compressive strength of the pellets, and utilizing the MgO in the magnetic separation powder to improve the metallurgical performance indicators such as the reduction expansion of the pellet ore, finally realizing another breakthrough in preparing pellets under the stable metallurgical performance indicators of the pellet ore to reduce the production of magnetic concentrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The invention is a schematic flow chart of a method for producing oxidation pellets by wet ball milling and classification of magnetic powder. DETAILED DESCRIPTION

[0027] The specific implementation manner of the present invention is further described below in conjunction with the accompanying drawings, and this embodiment does not constitute a limitation of the present invention.

[0028] Example 1

[0029] like Figure 1 As shown, a method for producing oxidized pellets by wet ball milling of magnetic powder comprises the following steps:

[0030] S1, steel slag is rod-milled and magnetically separated to obtain magnetic separation powder with a particle size range of less than 8 mm and a proportion of more than 90%;

[0031] S2, after the magnetic powder is ball-milled according to the material ratio, the formed flake elemental iron is screened and dehydrated for use in the converter, and the remaining materials are subjected to cyclone classification to obtain the first slurry, in which the particle size range of -200 mesh accounts for 75%, and the concentration of the first slurry is 25%. A cylindrical screen is set at the end of the ball mill, and the circular hole size of the cylindrical screen is 4mm;

[0032] S3, the coarse hematite powder is directly subjected to tower grinding and cyclone classification according to the material ratio to obtain the second slurry, in which the particle size range of -200 mesh accounts for 70%, and the concentration of the second slurry is 25%;

[0033] S4, transporting the first ore pulp and the second ore pulp to a mixed ore pulp pool through a pipeline for mixing, wherein the inflow angle of the first ore pulp and the second ore pulp is 180°, and the mixed ore pulp pool is further provided with a spiral blade, and the feeding ratio of the magnetic separation powder and the hematite is: 8% of the magnetic separation powder: 92% of the hematite;

[0034] S5, after mixing, enters the concentration sedimentation tank, and the alkaline flocculant polyacrylamide is added at a rate of 0.03kg / t per ton of ore, and the pH value of the water body is controlled at 8.4 to obtain a mixed slurry. The molecular weight of polyacrylamide is ≥10 million. Polyacrylamide can promote the precipitation of slurry and increase the concentration. The concentration of the mixed slurry is 68%. Since the surface potential of hematite gradually increases in negative charge with the increase of pH, the electrostatic attraction between polyacrylamide and hematite increases significantly with the increase of slurry pH. The pH is selected at 8.4, firstly to enhance the flocculation effect, and secondly to extend the service life of the equipment;

[0035] S6, the mixed slurry is concentrated and plate-and-frame filtered to obtain autogenous fine powder;

[0036] S7, the self-ground fine powder, coking dust ash and bentonite are mixed in a batching bin according to a proportion, the proportion of coking dust ash accounts for 0.30% of the self-ground fine powder, and the proportion of bentonite accounts for 0.2% of the self-ground fine powder;

[0037] S8, after intensive mixing and high-pressure roller milling, the mixed material enters the ball making system and is moistened with water to obtain green balls, the particle size of which ranges from 10 to 16 mm;

[0038] S9, the raw balls are passed through a belt roaster to obtain oxidized pellets, in which the CaO / SiO2 ratio is 0.4, the MgO content is ≥0.5%, the compressive strength is 2460N / P, the reduction expansion is 13.6%, and the reducibility is 67.1%.

[0039] The specific ratios and ingredients are shown in Table 1 below:

[0040] Table 1 Specific ratio and composition of materials in Example 1

[0041]

[0042] Example 2

[0043] like Figure 1 As shown, a method for producing oxidized pellets by wet ball milling of magnetic powder comprises the following steps:

[0044] S1, steel slag is rod-milled and magnetically separated to obtain magnetic separation powder with a particle size range of less than 8 mm and a proportion of more than 90%;

[0045] S2, after the magnetic powder is ball-milled according to the material ratio, the formed flake elemental iron is screened and dehydrated for use in the converter, and the remaining materials are subjected to cyclone classification to obtain the first slurry, in which the particle size range of -200 mesh accounts for 80%, and the concentration of the first slurry is 22%. A cylindrical screen is set at the end of the ball mill, and the circular hole size of the cylindrical screen is 4mm;

[0046] S3, the coarse hematite powder is directly subjected to tower grinding and cyclone classification according to the material ratio to obtain the second slurry, in which the particle size range of -200 mesh accounts for 72%, and the concentration of the second slurry is 23%;

[0047] S4, transporting the first ore pulp and the second ore pulp to a mixed ore pulp pool through a pipeline for mixing, wherein the inflow angle of the first ore pulp and the second ore pulp is 180°, and the mixed ore pulp pool is further provided with a spiral blade, and the feeding ratio of the magnetic separation powder and the hematite is: 5% magnetic separation powder: 95% hematite;

[0048] S5, after mixing, enters the concentration sedimentation tank, and the alkaline flocculant polyacrylamide is added at a rate of 0.03kg / t per ton of ore, and the pH value of the water body is controlled at 8.3 to obtain a mixed slurry. The molecular weight of polyacrylamide is ≥10 million. Polyacrylamide can promote the precipitation of slurry and increase the concentration. The concentration of the mixed slurry is 65%. Since the surface potential of hematite gradually increases in negative charge with the increase of pH, the electrostatic attraction between polyacrylamide and hematite increases significantly with the increase of slurry pH. The pH is selected at 8.3, firstly to enhance the flocculation effect, and secondly to extend the service life of the equipment;

[0049] S6, the mixed slurry is concentrated and plate-and-frame filtered to obtain autogenous fine powder;

[0050] S7, the self-ground powder, coking dust ash and bentonite are mixed in a batching bin according to a proportion, the proportion of coking dust ash accounts for 0.45% of the self-ground powder, and the proportion of bentonite accounts for 0.2% of the self-ground powder;

[0051] S8, after intensive mixing and high-pressure roller milling, the mixed material enters the ball making system and is moistened with water to obtain green balls, the particle size of which ranges from 10 to 16 mm;

[0052] S9, the green balls are roasted in a belt roaster to obtain oxidized pellets, in which CaO / SiO2 is 0.33, MgO content is ≥0.5%, compressive strength is 2390N / P, reduction expansion is 14.9%, and reducibility is 72.7%.

[0053] The specific ratios and ingredients are shown in Table 2 below:

[0054] Table 2 Specific ratios and ingredients of materials in Example 2

[0055]

[0056]

[0057] Example 3

[0058] like Figure 1 As shown, a method for producing oxidized pellets by wet ball milling of magnetic powder comprises the following steps:

[0059] S1, steel slag is rod-milled and magnetically separated to obtain magnetic separation powder with a particle size range of less than 8 mm and a proportion of more than 90%;

[0060] S2, after the magnetic powder is ball-milled according to the material ratio, the formed flake elemental iron is screened and dehydrated for use in the converter, and the remaining materials are subjected to cyclone classification to obtain the first slurry, in which the particle size range of -200 mesh accounts for 85%, and the concentration of the first slurry is 20%. A cylindrical screen is set at the end of the ball mill, and the circular hole size of the cylindrical screen is 4mm;

[0061] S3, the coarse hematite powder is directly subjected to tower grinding and cyclone classification according to the material ratio to obtain the second slurry, in which the particle size range of -200 mesh accounts for 75%, and the concentration of the second slurry is 20%;

[0062] S4, transporting the first ore pulp and the second ore pulp to a mixed ore pulp pool through a pipeline for mixing, wherein the inflow angle of the first ore pulp and the second ore pulp is 180°, and the mixed ore pulp pool is further provided with a spiral blade, and the feeding ratio of the magnetic separation powder and the hematite is: 8% of the magnetic separation powder: 92% of the hematite;

[0063] S5, after mixing, enters the concentration sedimentation tank, and the alkaline flocculant polyacrylamide is added at a rate of 0.03kg / t per ton of ore, and the pH value of the water body is controlled at 8.4 to obtain a mixed slurry. The molecular weight of polyacrylamide is ≥10 million. Polyacrylamide can promote the precipitation of slurry and increase the concentration. The concentration of the mixed slurry is 68%. Since the surface potential of hematite gradually increases in negative charge with the increase of pH, the electrostatic attraction between polyacrylamide and hematite increases significantly with the increase of slurry pH. The pH is selected at 8.4, firstly to enhance the flocculation effect, and secondly to extend the service life of the equipment;

[0064] S6, the mixed slurry is concentrated and plate-and-frame filtered to obtain autogenous fine powder;

[0065] S7, the self-ground powder, coking dust ash and bentonite are mixed in a batching bin according to a proportion, the proportion of coking dust ash accounts for 0.45% of the self-ground powder, and the proportion of bentonite accounts for 0.2% of the self-ground powder;

[0066] S8, after intensive mixing and high-pressure roller milling, the mixed material enters the ball making system and is moistened with water to obtain green balls, the particle size of which ranges from 10 to 16 mm;

[0067] S9, the raw balls are passed through a belt roaster to obtain oxidized pellets, in which the CaO / SiO2 ratio is 0.4, the MgO content is ≥0.5%, the compressive strength is 2480N / P, the reduction expansion is 13.8%, and the reducibility is 70.0%.

[0068] The specific ratios and ingredients are shown in Table 1 below:

[0069] Table 3 Specific ratios and ingredients of materials in Example 3

[0070]

[0071] Example 4

[0072] like Figure 1 As shown, a method for producing oxidized pellets by wet ball milling of magnetic powder comprises the following steps:

[0073] S1, steel slag is rod-milled and magnetically separated to obtain magnetic separation powder with a particle size range of less than 8 mm and a proportion of more than 90%;

[0074] S2, after the magnetic powder is ball-milled according to the material ratio, the formed flake elemental iron is screened and dehydrated for use in the converter, and the remaining materials are subjected to cyclone classification to obtain the first slurry, in which the particle size range of -200 mesh accounts for 80%, and the concentration of the first slurry is 24%. A cylindrical screen is set at the end of the ball mill, and the circular hole size of the cylindrical screen is 4mm;

[0075] S3, the coarse hematite powder is directly subjected to tower grinding and cyclone classification according to the material ratio to obtain the second slurry, in which the particle size range of -200 mesh accounts for 72%, and the concentration of the second slurry is 20%;

[0076] S4, transporting the first ore pulp and the second ore pulp to a mixed ore pulp pool through a pipeline for mixing, wherein the inflow angle of the first ore pulp and the second ore pulp is 180°, and the mixed ore pulp pool is further provided with a spiral blade, and the feeding ratio of the magnetic separation powder and the hematite is: 8% of the magnetic separation powder: 92% of the hematite;

[0077] S5, after mixing, enters the concentration sedimentation tank, and the alkaline flocculant polyacrylamide is added at a rate of 0.03kg / t per ton of ore, and the pH value of the water body is controlled at 8.2 to obtain a mixed slurry. The molecular weight of polyacrylamide is ≥10 million. Polyacrylamide can promote the precipitation of slurry and increase the concentration. The concentration of the mixed slurry is 70%. Since the surface potential of hematite gradually increases in negative charge with the increase of pH, the electrostatic attraction between polyacrylamide and hematite increases significantly with the increase of slurry pH. The pH is selected at 8.2, firstly to enhance the flocculation effect, and secondly to extend the service life of the equipment;

[0078] S6, the mixed slurry is concentrated and plate-and-frame filtered to obtain autogenous fine powder;

[0079] S7, the self-ground fine powder, coking dust ash and bentonite are mixed in a batching bin according to a proportion, the proportion of coking dust ash accounts for 0.3% of the self-ground fine powder, and the proportion of bentonite accounts for 0.4% of the self-ground fine powder;

[0080] S8, after intensive mixing and high-pressure roller milling, the mixed material enters the ball making system and is moistened with water to obtain green balls, the particle size of which ranges from 10 to 16 mm;

[0081] S9, the green balls are roasted in a belt roaster to obtain oxidized pellets, in which CaO / SiO2 is 0.3, MgO content is ≥0.5%, compressive strength is 2310N / P, reduction expansion is 15.7%, and reducibility is 72.83%.

[0082] The specific ratios and ingredients are shown in Table 4 below:

[0083] Table 4 Specific ratios and ingredients of materials in Example 4

[0084]

[0085] The present invention expands the resources for pelletizing. After the magnetic separation powder of steel slag, a by-product of steel, is treated by a certain process, it is successfully applied to the production of pelletizing, thus realizing the high-value utilization of the steel slag by-product. The elemental iron (iron particles) is ball-milled to form flaky iron, which can be directly used as a scrap steel raw material to enter the converter. Other materials are ball-milled to form slurry, which is used as the raw material for producing pellets, thus providing another path for promoting the production mode of reducing the proportion of magnetic concentrate in pelletizing, and having great significance for the expansion of resources for pelletizing. The magnetic separation powder after the by-product steel slag is treated, because it contains Fe3O4, CaO and MgO, thus realizing the oxidation and heat generation of Fe3O4 under zero magnetic concentrate, solidifying with Fe2O3 solid phase to form a paste, and at the same time controlling the interval of CaO / SiO2≤0.4 to form a partial low-melting point liquid phase, which plays a role in strengthening the compressive strength of the pellets, and utilizing the MgO in the magnetic separation powder to improve the metallurgical performance indicators such as the reduction expansion of the pellet ore, finally realizing another breakthrough in preparing pellets under the stable metallurgical performance indicators of the pellet ore to reduce the production of magnetic concentrate.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions should also be deemed to fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for producing oxidized pellets by wet ball milling of magnetic powder, characterized in that: The steps include: S1, steel slag is rod-milled and magnetically separated to obtain magnetic separation powder; S2, the magnetic powder is ball-milled according to the material ratio, and the flake elemental iron formed is screened and dehydrated for use in the converter, and the remaining materials are cyclone-classified to obtain the first slurry; S3, the coarse hematite powder is directly subjected to tower grinding and cyclone classification according to the material ratio to obtain the second slurry; S4, transporting the first ore pulp and the second ore pulp to a mixed ore pulp pool through a pipeline for mixing; S5, after mixing, it enters the concentration sedimentation tank, where flocculants are added and the pH value of the water is controlled to obtain mixed slurry; S6, the mixed slurry is concentrated and plate-and-frame filtered to obtain autogenous fine powder; S7, the self-grinding powder, coking dust removal ash and bentonite are mixed in a batching bin according to the proportion; S8, after intensive mixing and high-pressure roller grinding, the mixed material enters the ball making system to obtain raw balls; S9, the green balls are passed through a belt roaster to obtain oxidized pellets.

2. The method for producing oxidation pellets by wet ball milling of magnetic powder according to claim 1, characterized in that: The particle size range of the magnetically separated powder in S1 is greater than 90% of that of the magnetically separated powder less than 8 mm.

3. The method for producing oxidation pellets by wet ball milling of magnetic powder according to claim 1, characterized in that: A cylindrical screen is arranged at the tail of the ball mill in S2, the circular hole size of the cylindrical screen is 4 mm, the particle size range of -200 mesh in the first slurry accounts for 75-85%, and the concentration of the first slurry is 20-25%.

4. The method for producing oxidation pellets by wet ball milling of magnetic powder according to claim 1, characterized in that: In the second slurry in S3, the particle size range of -200 mesh accounts for 70-75%, and the concentration of the second slurry is 20-25%.

5. The method for producing oxidation pellets by wet ball milling of magnetic powder according to claim 1, characterized in that: The feed ratio of the magnetic powder to the hematite is: magnetic powder ≤ 8%: hematite ≥ 92%.

6. The method for producing oxidation pellets by wet ball milling of magnetic powder according to claim 1, characterized in that: In the S4, the inflow angle of the first ore pulp and the second ore pulp is 180°, and the mixing ore pulp pool is provided with spiral blades.

7. The method for producing oxidation pellets by wet ball milling of magnetic powder according to claim 1, characterized in that: The flocculant in S5 is alkaline flocculant polyacrylamide, the molecular weight of polyacrylamide is ≥10 million, the input amount of flocculant per ton of ore is 0.03kg / t, the pH value of the water body is controlled at 8-9, and the concentration of the mixed ore pulp is 65-70%.

8. The method for producing oxidation pellets by wet ball milling of magnetic powder according to claim 1, characterized in that: In the S7, the proportion of coking dust ash accounts for 0.30-0.45% of the self-ground fine powder, and the proportion of bentonite accounts for 0.2-0.4% of the self-ground fine powder.

9. The method for producing oxidation pellets by wet ball milling of magnetic powder according to claim 1, characterized in that: In the ball making system in S8, water is added to moisten the ball making system to obtain green balls, and the particle size of the green balls ranges from 10 to 16 mm.

10. The method for producing oxidation pellets by wet ball milling of magnetic powder according to claim 1, characterized in that: The oxidized pellets in S9 have CaO / SiO2≤0.4, MgO content≥0.5%, compressive strength≥2300N / P, reduction expansion≤17%, and reducibility≥65%.

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