Method for reducing proportion of pellet bentonite by adding superfine mineral powder

Abstract

The invention discloses a method for reducing the proportion of pellet bentonite by adding superfine mineral powder. The method is characterized in that raw materials comprise the following components in percentage by weight: 40% of bayan obo iron ore concentrate, 55% of common magnetite concentrate, 5% of superfine mineral powder and 1.5% of external bentonite. In order to solve the technical problems, the invention discloses a technical scheme for greatly reducing bentonite by adding part of superfine mineral powder to replace peripherally purchased concentrate aiming at the actual conditions of high consumption of bentonite for steel-clad pelletizing and low cold-state strength of finished pellets, and meanwhile, the cold-state strength of the pellets is improved. And a better raw material condition is created for belt type acid pellet smelting applied to a blast furnace.

Description

Technical Field

[0001] The invention belongs to the technical field of ironmaking raw material pelletizing, and in particular relates to a method for reducing the bentonite proportion of pellets by adding ultrafine mineral powder. Background Art

[0002] The iron concentrate used in Baosteel pellets is the Bayan Obo iron concentrate and the iron concentrate purchased from the surrounding areas. The concentrate used has a low specific surface area, poor balling, and low density, which deteriorates the contact between the iron mineral particles during the preheating and roasting process, reduces the crystallization between the iron mineral particles, and increases the porosity of the roasted pellets, thereby reducing the cold strength of the finished pellets. At the same time, the bentonite consumption is high. In view of the above problems, the present invention discloses a technical solution for Baosteel pellets to add part of the ultrafine mineral powder to replace the concentrate purchased from the surrounding areas to significantly reduce the bentonite, while achieving the improvement of the cold strength of the pellets. Summary of the invention

[0003] The purpose of the present invention is to provide a method for reducing the bentonite ratio of pellets by adding ultrafine mineral powder. In view of the actual situation that the bentonite consumption in Baosteel's pelletizing is high and the cold strength of the finished balls is low, a technical solution is disclosed for Baosteel's pelletizing by adding part of ultrafine mineral powder to replace the concentrate purchased from the surrounding areas to significantly reduce the bentonite content, while achieving the improvement of the cold strength of the pellets, thus creating better raw material conditions for the application of belt acid pellet smelting in blast furnaces.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The invention discloses a method for reducing the proportion of pelletized bentonite by adding ultrafine mineral powder. The raw materials include, by weight percentage, 40% of Bayan Obo iron concentrate, 55% of common magnetite concentrate, 5% of ultrafine mineral powder and 1.5% of external bentonite.

[0006] Furthermore, the chemical composition of the Bayan Obo iron concentrate includes, by weight percentage: TFe is 65.0-65.5%, FeO is 28.5-29.5%, MgO is 1.30-1.40%, CaO is 2.0%-2.3%, Al2O3≤0.20%, SiO2 is 0.90%-1.60%, S is 0.70-0.80%, F is 0.25%-0.30%, K2O≤0.10%, Na2O≤0.10%; the percentage of concentrate with a particle size of ≤0.074mm in the Bayan Obo iron concentrate is at least 90% of the total weight of the Bayan Obo iron concentrate.

[0007] Furthermore, the chemical composition of the ordinary magnetite concentrate includes TFe of 64.5-65.50%, SiO2 of 3.5-4.0%, S of 0.20%-0.40%, F≤0.05%, K2O+Na2O≤0.15% by weight; the percentage of concentrate with a particle size of ≤0.074mm in the ordinary magnetite concentrate is at least 70% of the total weight of the ordinary magnetite concentrate.

[0008] Furthermore, the chemical composition of the bentonite includes SiO2 of 58.0% to 60.0% by weight, and Ig≤12.0%.

[0009] Furthermore, the chemical composition of the ultrafine mineral powder includes, by weight percentage: TFe is 46.0-48.0%, FeO is <1%, Al2O3≤5.00%, SiO2≤20.00%, K2O+Na2O≤0.15%, S is 0.03%, and the percentage of concentrate with a particle size of -500 mesh in the ultrafine mineral powder is at least 80% of the total weight of the ultrafine mineral powder.

[0010] Further, the raw material mixture is applied to a pelletizing disk to prepare green balls, and the process parameters of the pelletizing disk are controlled as follows: green ball preparation time is 10 minutes, compaction time is 21 minutes, ball disk speed is 30 r / min, and pellet diameter is 1 meter; the average particle size of the small balls is 11 mm;

[0011] The green balls are dried, preheated, roasted and homogenized to obtain oxidized pellets.

[0012] Furthermore, the drying conditions are: temperature of 200-300°C, time of 10-30 min; the preheating conditions are: temperature of 600-800°C, time of 8-10 min; the calcining conditions are: temperature of 1220-1260°C, time of 8-10 min; the uniform heating conditions are: temperature of 900-1000°C, time of 2-3 min.

[0013] Compared with the prior art, the beneficial technical effects of the present invention are:

[0014] In view of the high bentonite consumption in Baosteel's pelletizing and the low cold strength of the finished balls, a technical solution was disclosed that Baosteel's pelletizing adds part of ultrafine mineral powder to replace the concentrate purchased from surrounding areas, which can significantly reduce the amount of bentonite, while improving the cold strength of the pellets, creating better raw material conditions for the application of belt acid pelletizing in blast furnaces. DETAILED DESCRIPTION

[0015] The specific embodiments of the present invention are further described below by way of examples, but the specific embodiments of the present invention are not limited to the following examples.

[0016] The raw material configurations, raw ball properties, preheated ball properties and finished ball properties used in the comparative examples and embodiments of the present invention are shown in Tables 1-3, respectively.

[0017] Table 1 Comparative Examples and Examples Raw Materials Ratios

[0018]

[0019] From Table 1, we can see that:

[0020] Compared with the comparative example, the embodiment uses 5% ultrafine iron powder to replace 5% of ordinary magnetite concentrate, and the bentonite ratio is reduced by 1 percentage point.

[0021] Table 2 Comparative Examples and Examples Ball Performance

[0022] Example No. Moisture, % Drop strength, times / P Green ball compressive strength, N / P Comparative Example 7.1 5.1 11.7 Example 7.1 5.0 14.3

[0023] From Table 2, we can see that:

[0024] Compared with the comparative example, the embodiment adds 5% of ultrafine mineral powder tailings to replace ordinary magnetite concentrate. Under the premise of stable falling strength of green balls, the bentonite ratio can be reduced from 2.5% to 1.5%, a reduction of about 40%.

[0025] The compressive strength of green balls has a tendency to improve.

[0026] Table 3 Preheated ball performance and finished ball performance of the embodiment

[0027]

[0028] From Table 3, we can see that:

[0029] From the performance of preheated balls, the strength of preheated balls decreased, but the drum strength remained stable; from the results of finished balls, the compressive strength improved.

[0030] In summary, it is feasible to add ultrafine iron ore powder to Baosteel pellets, which is beneficial to reduce the proportion of bentonite and improve the performance of finished balls, while reducing the cost of ore mixing.

[0031] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for reducing the proportion of pelletized bentonite by adding ultrafine mineral powder, characterized in that: The raw materials include, by weight percentage: 40% Bayan Obo iron concentrate, 55% ordinary magnetite concentrate, 5% ultrafine mineral powder, and 1.5% external bentonite.

2. The method for reducing the proportion of pelletized bentonite by adding ultrafine mineral powder according to claim 1, characterized in that: The chemical composition of the Bayan Obo iron concentrate includes, by weight percentage: TFe is 65.0-65.5%, FeO is 28.5-29.5%, MgO is 1.30-1.40%, CaO is 2.0%-2.3%, Al2O3≤0.20%, SiO2 is 0.90%-1.60%, S is 0.70-0.80%, F is 0.25%-0.30%, K2O≤0.10%, and Na2O≤0.10%; the concentrate with a particle size of ≤0.074mm in the Bayan Obo iron concentrate accounts for at least 90% of the total weight of the Bayan Obo iron concentrate.

3. The method for reducing the proportion of pelletized bentonite by adding ultrafine mineral powder according to claim 1, characterized in that: The chemical composition of the ordinary magnetite concentrate includes TFe of 64.5-65.50%, SiO2 of 3.5-4.0%, S of 0.20%-0.40%, F≤0.05%, and K2O+Na2O≤0.15% by weight; the percentage of concentrate with a particle size of ≤0.074mm in the ordinary magnetite concentrate is at least 70% of the total weight of the ordinary magnetite concentrate.

4. The method for reducing the proportion of pelletized bentonite by adding ultrafine mineral powder according to claim 1, characterized in that: The chemical composition of the bentonite includes SiO2 of 58.0% to 60.0% by weight, and Ig≤12.0%.

5. The method for reducing the proportion of pelletized bentonite by adding ultrafine mineral powder according to claim 1, characterized in that: The chemical composition of the ultrafine mineral powder includes, by weight percentage: TFe is 46.0-48.0%, FeO is <1%, Al2O3≤5.00%, SiO2≤20.00%, K2O+Na2O≤0.15%, S is 0.03%, and the percentage of concentrate with a particle size of -500 mesh in the ultrafine mineral powder is at least 80% of the total weight of the ultrafine mineral powder.

6. The method for reducing the proportion of pelletized bentonite by adding ultrafine mineral powder according to claim 1, characterized in that: The raw material mixture is applied to a ball-making disk to prepare green balls. The process parameters of the ball-making disk are as follows: green ball preparation time is 10 minutes, compaction time is 21 minutes, ball disk speed is 30 r / min, and ball diameter is 1 meter; the average particle size of the small balls is 11 mm; The green balls are dried, preheated, roasted and homogenized to obtain oxidized pellets.

7. The method for reducing the proportion of pelletized bentonite by adding ultrafine mineral powder according to claim 6, characterized in that: The drying conditions are as follows: the temperature is 200-300°C and the time is 10-30 minutes; the preheating conditions are as follows: the temperature is 600-800°C and the time is 8-10 minutes; the calcining conditions are as follows: the temperature is 1220-1260°C and the time is 8-10 minutes; the uniform heating conditions are as follows: the temperature is 900-1000°C and the time is 2-3 minutes.

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