Method for producing high-quality alkaline pellets by matching Bayan obo iron ore concentrate with sulfuric acid slag

Abstract

The invention discloses a method for producing high-quality alkaline pellets by matching Bayan obo iron ore concentrate with sulfuric-acid slag. The high-quality alkaline pellets comprise the following raw materials in percentage by weight: 70-75% of Bayan obo iron ore concentrate, 15-25% of common magnetite concentrate, 4-6% of sulfuric-acid slag, 2.2-2.5% of externally matched bentonite and 2.4-2.8% of externally matched limestone. In order to solve the technical problem that the difficulty of comprehensive utilization of the sulfuric-acid slag is large, the invention develops a method for producing high-quality fluorine-containing alkaline pellets by matching a chain grate machine, a rotary kiln and a circular cooler with a high proportion of Bayan Obo iron ore concentrate and matching with the sulfuric-acid slag.

Description

Technical Field

[0001] The invention belongs to the technical field of ironmaking raw material pelletizing, and in particular relates to a method for producing high-quality alkaline pellets by combining Bayan Obo iron concentrate with sulfuric acid slag. Background Art

[0002] Bayan Obo iron concentrate is the main ironmaking material of Baotou Steel. Bayan Obo iron concentrate has the characteristics of "fine particle size, high calcium and low silicon". The natural alkalinity of iron concentrate is about 2.0, which is suitable as a raw material for the production of alkaline pellets. The production of alkaline pellets can achieve high-proportion and high-quality application of Bayan Obo iron concentrate in Baotou Steel's pellet production. Bayan Obo iron concentrate contains relatively high impurity elements such as potassium, sodium, fluorine, and sulfur, especially the sulfur content can reach more than 1%. In order to effectively deal with the impact of the high sulfur content of Bayan Obo iron concentrate on the pelletizing process, high-sulfur ore is often beneficiated and desulfurized to produce high-sulfur tailings for roasting and sulfuric acid production. Sulfate slag is produced after acid production. Therefore, the present invention has developed a method for producing high-quality alkaline pellets using Bayan Obo iron concentrate with sulfuric acid slag using a chain grate-rotary kiln-ring cooler process. Summary of the invention

[0003] In view of the difficulty in comprehensive utilization of sulfate slag, the purpose of the present invention is to provide a method for producing high-quality alkaline pellets by combining Bayan Obo iron concentrate with sulfate slag, and a method for producing high-quality fluorine-containing alkaline pellets by combining a chain grate machine-rotary kiln-ring cooler with a high proportion of Bayan Obo iron concentrate with sulfate slag has been developed.

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

[0005] The invention discloses a method for producing high-quality alkaline pellets by combining Bayan Obo iron concentrate with sulfuric acid slag. The raw materials include, by weight percentage: 70% to 75% of Bayan Obo iron concentrate, 15% to 25% of common magnetite concentrate, 4% to 6% of sulfuric acid slag, 2.2% to 2.5% of external bentonite, and 2.4% to 2.8% of external limestone.

[0006] The mixed material is pre-treated by high-pressure roller mill, and the moisture content of the roller mill feed is controlled at 7.0%-8.0%, so that the specific surface area of ​​the mixed material with sulfuric acid slag is increased by 300cm 2 ·g -1 about;

[0007] The mixed material after high-pressure roller milling is pelletized in a Φ6m pelletizing plate to obtain green balls; the process control parameters of the pelletizing plate are: the moisture content of the green balls is 8.5% to 9.0%, the tilt angle of the ball plate is 45 to 45.5°, the falling strength of the green balls reaches 5.5 times / P or more, and through screening, the proportion of the green ball particle size composition is controlled to be 8mm-16mm to reach more than 95%, and the wet return rate is controlled within 20%;

[0008] The green balls are evenly spread on the chain grate through the green ball distribution device and the screening device. The thickness of the green balls on the chain grate is 175mm-205mm, and the speed of the chain grate is 1.70m / min-1.75m / min.

[0009] Further: the green pellets are dried through the grate blast drying section and the exhaust drying section, the conditions of the blast drying section: the temperature of the air box of the blast drying section is controlled at 200°C to 250°C, and the time is 3.43min to 3.53min. The conditions of the exhaust drying section: the temperature of the smoke hood of the exhaust drying section is controlled at 320°C to 360°C, and the time is 6.86min to 7.05min;

[0010] The dry ball is preheated by the chain grate preheating stage 1 and preheating stage 2. The preheating stage conditions are as follows: the preheating stage hood temperature is controlled at 700±20℃ for 3.43min~3.53min. The preheating stage hood temperature is controlled at 1020℃~1050℃ for 10.29min~10.58min.

[0011] The preheated balls are roasted in a rotary kiln, wherein the roasting conditions of the rotary kiln are as follows: the temperature of the kiln tail hood is controlled at 950°C to 1000°C, and the temperature of the kiln head hood is controlled at 1030°C to 1060°C;

[0012] The roasted balls are cooled and recrystallized by a ring cooler. The process conditions of the ring cooler are as follows: the ring cooler speed is 0.90m / min-0.95m / min, the secondary air temperature is controlled at 980℃-1040℃, the second stage wind temperature of the ring cooling is 820±30℃, and the third stage wind temperature of the ring cooling is 430±40℃. After the roasted balls are cooled, fluorine-containing alkaline pellets with added sulfuric acid slag are finally obtained.

[0013] Furthermore, the raw materials include, by weight percentage: 73% Bayan Obo iron concentrate, 22% ordinary magnetite concentrate, 5% sulfuric acid slag, 2.4% external bentonite, and 2.8% external limestone.

[0014] Furthermore, the quality control of the preheated ball is: compressive strength 600N / P~800N / P.

[0015] Furthermore, the quality control requirements of the calcined balls are: FeO content <5.0%, S content <0.30%, and compressive strength ≥1500N / P.

[0016] Furthermore, the chemical composition of the Bayan Obo iron concentrate includes, by weight percentage: TFe is 64.5-65.0%, 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 first iron concentrate.

[0017] Furthermore, the chemical composition of the ordinary magnetite concentrate includes TFe of 67.0-67.50%, SiO2 of 1.80-2.50%, S of 0.20%-0.30%, F≤0.05%, K2O+Na2O≤0.09% by weight; the concentrate with a particle size of ≤0.074mm in the ordinary magnetite concentrate accounts for at least 90% of the total weight of the fluorine-free magnetite concentrate.

[0018] Furthermore, the chemical composition of the sulfate slag includes TFe of 61.0-61.50%, CaO of 1.50%-1.65%, SiO2 of 5.5-6.0%, and K2O+Na2O≤0.30% in weight percentage; the concentrate with a particle size of ≤0.074mm in the sulfate slag accounts for at least 70% of the total weight of the sulfate slag.

[0019] Furthermore, the chemical composition of the bentonite includes SiO2 of 58.0% to 60.0% by weight, and Ig≤12.0%.

[0020] Furthermore, the chemical composition of the limestone includes, by weight percentage, 50.0% to 52.0% CaO, 2.0% to 4.0% SiO2, 1.0% to 3.0% MgO, and Ig≤42.0%.

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

[0022] The technical problem to be solved by the present invention is the difficulty in comprehensive utilization of sulfuric acid slag. A method for producing high-quality fluorine-containing alkaline pellets by using a chain grate machine, a rotary kiln and annular cooler with a high proportion of Bayan Obo iron concentrate and sulfuric acid slag is developed, thereby realizing the comprehensive utilization of sulfuric acid slag.

[0023] The high-quality fluorine-containing alkaline pellets produced by combining the Bayan Obo iron concentrate with sulfuric acid slag meet the following quality indicators: TFe ≥ 62.5%, FeO content < 1.0%, S content < 0.15%, MgO content ≥ 1.0%, SiO2 content ≤ 3.5%, F content ≤ 0.20%, binary basicity of 1.05-1.20, compressive strength of more than 2300N / P, and reduction expansion rate controlled within 15%. 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 example of producing high-quality fluorine-containing alkaline pellets by adding a high proportion of Bayan Obo iron concentrate and sulfuric acid slag are shown in Tables 1-4 respectively.

[0026] Table 1 Example raw material ratio

[0027]

[0028] Table 2 Main process parameters of chain grate machine-rotary kiln-ring cooler in embodiment

[0029]

[0030]

[0031] Table 3 Chemical composition of pellets in Example

[0032]

[0033] Table 4 Cold strength and reduction performance statistics of finished balls in the embodiment

[0034] Example No. Compressive strength, N / P Reduction expansion rate, % Example 2437 13.50

[0035] It can be seen from Tables 1-4 that the method of using chain grate-rotary kiln-ring cooler with a high proportion of Bayan Obo iron concentrate (73%) and sulfuric acid slag (5%) to produce high-quality fluorine-containing alkaline pellets realizes the comprehensive utilization of sulfuric acid slag.

[0036] 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 producing high-quality alkaline pellets using Bayan Obo iron concentrate and sulfuric acid slag, characterized in that: The raw materials include, by weight percentage: 70% to 75% of Bayan Obo iron concentrate, 15% to 25% of common magnetite concentrate, 4% to 6% of sulfuric acid slag, 2.2% to 2.5% of external bentonite, and 2.4% to 2.8% of external limestone; The mixed material is pre-treated by high-pressure roller mill, and the moisture content of the roller mill feed is controlled at 7.0%-8.0% to increase the specific surface area of ​​the mixed material with sulfuric acid slag; The mixed material after high-pressure roller milling is pelletized in a Φ6m pelletizing plate to obtain green balls; the process control parameters of the pelletizing plate are: the moisture content of the green balls is 8.5% to 9.0%, the tilt angle of the ball plate is 45 to 45.5°, the falling strength of the green balls reaches 5.5 times / P or more, and through screening, the proportion of the green ball particle size composition is controlled to be 8mm-16mm to reach more than 95%, and the wet return rate is controlled within 20%; The green balls are evenly spread on the chain grate through the green ball distribution device and the screening device. The thickness of the green balls on the chain grate is 175mm-205mm, and the speed of the chain grate is 1.70m / min-1.75m / min. Further: the green pellets are dried through the grate blast drying section and the exhaust drying section, the conditions of the blast drying section: the temperature of the air box of the blast drying section is controlled at 200°C to 250°C, and the time is 3.43min to 3.53min. The conditions of the exhaust drying section: the temperature of the smoke hood of the exhaust drying section is controlled at 320°C to 360°C, and the time is 6.86min to 7.05min; The dry ball is preheated by the chain grate preheating stage 1 and preheating stage 2. The preheating stage conditions are as follows: the preheating stage hood temperature is controlled at 700±20℃ for 3.43min~3.53min. The preheating stage hood temperature is controlled at 1020℃~1050℃ for 10.29min~10.58min. The preheated balls are roasted in a rotary kiln, wherein the roasting conditions of the rotary kiln are as follows: the temperature of the kiln tail hood is controlled at 950°C to 1000°C, and the temperature of the kiln head hood is controlled at 1030°C to 1060°C; The roasted balls are cooled and recrystallized by a ring cooler. The process conditions of the ring cooler are as follows: the ring cooler speed is 0.90m / min-0.95m / min, the secondary air temperature is controlled at 980℃-1040℃, the second stage wind temperature of the ring cooling is 820±30℃, and the third stage wind temperature of the ring cooling is 430±40℃. After the roasted balls are cooled, fluorine-containing alkaline pellets with added sulfuric acid slag are finally obtained.

2. The method for producing high-quality alkaline pellets using Bayan Obo iron concentrate and sulfuric acid slag according to claim 1, characterized in that: The raw materials include, by weight percentage: 73% Bayan Obo iron concentrate, 22% ordinary magnetite concentrate, 5% sulfuric acid slag, 2.4% external bentonite, and 2.8% external limestone.

3. The method for producing high-quality alkaline pellets using Bayan Obo iron concentrate and sulfuric acid slag according to claim 1, characterized in that: Preheating ball quality control: compressive strength 600N / P~800N / P.

4. The method for producing high-quality alkaline pellets using Bayan Obo iron concentrate and sulfuric acid slag according to claim 1, characterized in that: Quality control requirements for roasted balls: FeO content <5.0%, S content <0.30%, compressive strength ≥1500N / P.

5. The method for producing high-quality alkaline pellets using Bayan Obo iron concentrate and sulfuric acid slag according to claim 1, characterized in that: The chemical composition of the Bayan Obo iron concentrate includes, by weight percentage: TFe is 64.5-65.0%, 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 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.

6. The method for producing high-quality alkaline pellets using Bayan Obo iron concentrate and sulfuric acid slag according to claim 1, characterized in that: The chemical composition of the ordinary magnetite concentrate includes TFe of 67.0-67.50%, SiO2 of 1.80-2.50%, S of 0.20%-0.30%, F≤0.05%, K2O+Na2O≤0.09% by weight; the concentrate with a particle size of ≤0.074mm in the ordinary magnetite concentrate accounts for at least 90% of the total weight of the fluorine-free magnetite concentrate.

7. The method for producing high-quality alkaline pellets using Bayan Obo iron concentrate and sulfuric acid slag according to claim 1, characterized in that: The chemical composition of the sulfuric acid slag includes TFe of 61.0-61.50%, CaO of 1.50%-1.65%, SiO2 of 5.5-6.0%, and K2O+Na2O≤0.30% in terms of weight percentage; the concentrate with a particle size of ≤0.074mm in the sulfuric acid slag accounts for at least 70% of the total weight of the sulfuric acid slag.

8. The method for producing high-quality alkaline pellets using Bayan Obo iron concentrate and sulfuric acid slag 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%.

9. The method for producing high-quality alkaline pellets using Bayan Obo iron concentrate and sulfuric acid slag according to claim 1, characterized in that: The chemical composition of the limestone includes, by weight percentage, 50.0% to 52.0% CaO, 2.0% to 4.0% SiO2, 1.0% to 3.0% MgO, and Ig≤42.0%.

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