Method for improving quality of acid pellets produced by using Bayan Obo iron ore concentrate through belt type machine

Abstract

The invention discloses a method for improving the quality of acid pellets produced by using bayan obo iron ore concentrate through a belt type machine. The raw materials comprise, by weight, 50% of bayan obo iron ore concentrate, 40% of common magnetite concentrate, 10% of hematite and 2.5% of externally-matched bentonite binder. The invention aims to provide a method for improving the quality of acid pellets produced by using Bayan Obo iron ore concentrate through a belt type machine so as to solve the problems that a black core structure is easily formed, the cold-state strength is low and the FeO content of finished pellets is high when acid pellets are produced by using Bayan Obo iron ore concentrate through a steel-clad belt type machine.

Description

Technical Field

[0001] The invention belongs to the technical field of ironmaking raw material pelletizing, and in particular relates to a method for improving the quality of acidic pellets produced by a belt conveyor using Bayan Obo iron concentrate. Background Art

[0002] Bayan Obo iron concentrate is the main iron material used in the production of acidic pellets of Baotou Steel's belt mill, with a ratio of about 50%, and the remaining 50% are iron concentrates purchased from the surrounding areas. Bayan Obo iron concentrate and iron concentrates purchased from the surrounding areas are all magnetites with high FeO content. Among them, Bayan Obo iron concentrate contains relatively high impurity elements such as potassium, sodium, fluorine, and sulfur. During the oxidation roasting process of the belt mill, potassium and sodium are easy to generate low-melting point liquid phases, and sulfur competes with magnetite for oxygen, which hinders the oxidation inside the pellets, resulting in the formation of a "black heart" structure in the finished pellets, low cold strength, and high FeO in the finished balls. In order to further improve the quality of acidic pellets produced by belt mills using Bayan Obo iron concentrate, the present invention discloses comprehensive technical measures such as using Bayan Obo iron concentrate in belt mills and matching some imported hematite to replace the ore in the area, and simultaneously optimizing the thermal system, so as to achieve the improvement of the cold strength of acidic pellets produced by belt mills. Summary of the invention

[0003] The purpose of the present invention is to provide a method for improving the quality of acidic pellets produced by a belt conveyor using Bayan Obo iron concentrate, so as to solve the problem that the acidic pellets produced by Baosteel belt conveyor using Bayan Obo iron concentrate are prone to form a "black heart" structure, have low cold strength, and have high FeO in the finished balls.

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

[0005] The present invention discloses a method for improving the quality of acidic pellets produced by a belt machine using Bayan Obo iron concentrate. The raw materials include, by weight percentage: 50% Bayan Obo iron concentrate, 40% common magnetite concentrate, 10% hematite, and 2.5% external bentonite binder.

[0006] Furthermore, the Bayan Obo iron concentrate includes Bayan Obo iron concentrate 1# and Bayan Obo iron concentrate 2#.

[0007] Furthermore, the chemical composition of the Bayan Obo iron concentrate 1# includes, by weight percentage: TFe is 65.0-66.0%, FeO is 28.5-29.5%, MgO is 0.80-0.90%, CaO is 1.40%-1.60%, Al2O3≤0.25%, SiO2 is 1.40%-1.60%, S is 0.80-0.90%, F is 0.25%-0.35%, K2O≤0.15%, Na2O≤0.15%; 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 first iron concentrate.

[0008] Furthermore, the chemical composition of the Bayan Obo iron concentrate 2# includes, by weight percentage: TFe is 66.0-67.0%, FeO is 28.5-29.5%, MgO is 0.50-0.70%, CaO is 0.90%-1.10%, Al2O3≤0.40%, SiO2 is 2.20%-2.40%, S is 0.75-0.90%, F is 0.30%-0.40%, K2O≤0.15%, Na2O≤0.25%; 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 first iron concentrate.

[0009] 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.

[0010] Furthermore, the chemical composition of the bentonite includes SiO2 of 58.0% to 60.0% by weight, and Ig≤12.0%.

[0011] Furthermore, the chemical composition of the hematite includes, by weight percentage: TFe is 63.0-63.5%, FeO is <1%, Al2O3≤0.10%, SiO2 is 4.50%-5.500%, and S is 0.005%.

[0012] Further, the production of acid pellets comprises the following steps:

[0013] The mixed iron material is pre-treated by a high-pressure roller mill, and the moisture content of the roller mill feed is controlled at 8.0% to increase the specific surface area of ​​the hematite mixed material. The comparative example is also pre-treated by a high-pressure roller mill;

[0014] The above mixture is pelletized on a pelletizing plate with a diameter of 7.5m, and the falling strength of the raw balls is controlled at 4.5 times / P to 5.0 times / P;

[0015] The green balls are evenly spread on the belt machine trolley through the green ball screening material conveying and material distribution device. The green ball thickness on the belt machine trolley is 340mm-350mm, and the trolley speed is 4.0m / mi;

[0016] The green balls are dried through the belt machine blast drying section and exhaust drying section. The conditions of the blast drying section are: the temperature of the bellows of the blast drying section is controlled at 300℃~320℃, and the time is 3min. The conditions of the exhaust drying section are: the temperature of the smoke hood of the exhaust drying section is controlled at 320℃~350℃, and the time is 3.75min.

[0017] The dry ball is preheated and roasted through a belt machine preheating and roasting section, and the conditions of the preheating and roasting section are as follows: the preheating and roasting hood temperature is gradually increased from 500°C to 1270°C for 16.5 minutes;

[0018] The calcined balls are recrystallized in a belt machine soaking section, wherein the soaking section conditions are as follows: the soaking section hood temperature is 930° C. to 950° C., and the time is 2.25 min;

[0019] The uniformly heated ball is cooled in the belt machine cooling section, and the process conditions of the cooling section are as follows: the range of the hood temperature of the cooling section is 1050°C to 750°C from front to back, and the time is 9.75 minutes; the range of the hood temperature of the cooling section is 330°C to 110°C from front to back, and the time is 3.75 minutes; after cooling, the quality-improved acidic pellets with hematite added are finally obtained.

[0020] Furthermore, the quality indicators of the acidic pellets are: TFe≥63.0%, FeO content<1.5%, achieving a significant improvement in compressive strength and drum strength, and significantly shrinking the "black heart" in the pellets.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are:

[0022] In order to solve the problem that the acidic pellets produced by Baosteel's belt conveyor using Bayan Obo iron concentrate are prone to form a "black heart" structure, have low cold strength and high FeO in the finished pellets, comprehensive technical measures were taken, such as using Bayan Obo iron concentrate and part of imported hematite to replace local ore in the belt conveyor to reduce the FeO content of the mixture, and simultaneously optimizing the thermal system. This has achieved an improvement in the cold strength of the acidic pellets produced by the belt conveyor, creating better raw material conditions for the application of belt acidic pellet smelting in blast furnaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process flow chart for preparing pelletized ore. DETAILED DESCRIPTION

[0024] 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.

[0025] The raw material configuration, process parameters, pellet composition and related properties used in the comparative examples and embodiments of the present invention are shown in Tables 1-3 respectively.

[0026] Table 1 Comparative Examples and Examples Raw Materials Ratios

[0027]

[0028] From Table 1, we can see that:

[0029] Compared with the comparative example, during the implementation of the embodiment, 10% of the ordinary magnetite concentrate was replaced by 10% of hematite.

[0030] Table 2 Changes of main process parameters of belt machine in comparative example and embodiment

[0031]

[0032]

[0033] From Table 3, we can see that:

[0034] Compared with the comparative example, during the implementation of the embodiment, the temperature of the two sections after the high temperature of the roasting section was mainly increased by 10°C.

[0035] Table 3 Cold strength and composition changes of finished balls in the embodiment

[0036] Example No. TFe, % FeO, % Drum, % Compressive strength, N / P Comparative Example 63.41 1.80 95.93 1972 Example 63.56 1.10 96.25 2276 Difference 0.15 -0.70 0.32 304

[0037] From Table 3, we can see that:

[0038] Compared with the comparative example, the FeO content of the finished ball of the embodiment decreased by 0.70%, the compressive strength was 304N / P, the drum strength increased by 0.32 percentage points, and the potassium and sodium contents decreased.

[0039] 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 improving the quality of acid pellets produced by belt conveyor using Bayan Obo iron concentrate, characterized in that: The raw materials include, by weight percentage: 50% Bayan Obo iron concentrate, 40% ordinary magnetite concentrate, 10% hematite, and 2.5% external bentonite binder.

2. The method for improving the quality of acid pellets produced by belt conveyor using Bayan Obo iron concentrate according to claim 1 is characterized in that: The Bayan Obo iron concentrate includes Bayan Obo iron concentrate 1# and Bayan Obo iron concentrate 2#.

3. The method for improving the quality of acid pellets produced by belt conveyor using Bayan Obo iron concentrate according to claim 2 is characterized in that: The chemical composition of the Bayan Obo iron concentrate 1# includes, by weight percentage: TFe is 65.0-66.0%, FeO is 28.5-29.5%, MgO is 0.80-0.90%, CaO is 1.40%-1.60%, Al2O3≤0.25%, SiO2 is 1.40%-1.60%, S is 0.80-0.90%, F is 0.25%-0.35%, K2O≤0.15%, and Na2O≤0.15%; 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 first iron concentrate.

4. The method for improving the quality of acid pellets produced by belt conveyor using Bayan Obo iron concentrate according to claim 3 is characterized in that: The chemical composition of the Bayan Obo iron concentrate 2# includes, by weight percentage: TFe is 66.0-67.0%, FeO is 28.5-29.5%, MgO is 0.50-0.70%, CaO is 0.90%-1.10%, Al2O3≤0.40%, SiO2 is 2.20%-2.40%, S is 0.75-0.90%, F is 0.30%-0.40%, K2O≤0.15%, Na2O≤0.25%; 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 first iron concentrate.

5. The method for improving the quality of acid pellets produced by belt conveyor using Bayan Obo iron concentrate according to claim 4 is characterized in that: The mass ratio of the Bayan Obo iron concentrate 1# and the Bayan Obo iron concentrate 2# is 3:

2.

6. The method for improving the quality of acid pellets produced by belt conveyor using Bayan Obo iron concentrate 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.

7. The method for improving the quality of acid pellets produced by belt conveyor using Bayan Obo iron concentrate 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%.

8. The method for improving the quality of acid pellets produced by belt conveyor using Bayan Obo iron concentrate according to claim 1, characterized in that: The chemical composition of the hematite includes, by weight percentage: TFe is 63.0-63.5%, FeO is less than 1%, Al2O3 is less than or equal to 0.10%, SiO2 is 4.50%-5.500%, and S is 0.005%.

9. The method for improving the quality of acid pellets produced by belt conveyor using Bayan Obo iron concentrate according to claim 1, characterized in that: The production of acid pellets includes the following steps: The mixed iron material is pre-treated by a high-pressure roller mill, and the moisture content of the roller mill feed is controlled at 8.0% to increase the specific surface area of ​​the hematite mixed material. The comparative example is also pre-treated by a high-pressure roller mill; The above mixture is pelletized on a pelletizing plate with a diameter of 7.5m, and the falling strength of the raw balls is controlled at 4.5 times / P to 5.0 times / P; The green balls are evenly spread on the belt machine trolley through the green ball screening material conveying and material distribution device. The green ball thickness on the belt machine trolley is 340mm-350mm, and the trolley speed is 4.0m / mi; The green balls are dried through the belt machine blast drying section and exhaust drying section. The conditions of the blast drying section are: the temperature of the bellows of the blast drying section is controlled at 300℃~320℃, and the time is 3min. The conditions of the exhaust drying section are: the temperature of the smoke hood of the exhaust drying section is controlled at 320℃~350℃, and the time is 3.75min. The dry ball is preheated and roasted through a belt machine preheating and roasting section, and the conditions of the preheating and roasting section are as follows: the preheating and roasting hood temperature is gradually increased from 500°C to 1270°C for 16.5 minutes; The calcined balls are recrystallized in a belt machine soaking section, wherein the soaking section conditions are as follows: the soaking section hood temperature is 930° C. to 950° C., and the time is 2.25 min; The uniformly heated ball is cooled in the belt machine cooling section, and the process conditions of the cooling section are as follows: the range of the hood temperature of the cooling section is 1050°C to 750°C from front to back, and the time is 9.75 minutes; the range of the hood temperature of the cooling section is 330°C to 110°C from front to back, and the time is 3.75 minutes; after cooling, the quality-improved acidic pellets with hematite added are finally obtained.

10. The method for improving the quality of acid pellets produced by belt conveyor using Bayan Obo iron concentrate according to claim 9, characterized in that: The quality indicators of the acidic pellets are: TFe≥63.0%, FeO content<1.5%, which can significantly improve the compressive strength and drum strength, and significantly shrink the "black heart" in the pellets.

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