Method for producing high-quality alkaline pellets by matching baishan iron ore concentrate with sulfuric acid residue

Abstract

The application discloses a method for producing high-quality alkaline pellets by matching Baiyunebo iron concentrate with sulfuric acid residue, and raw materials include Baiyunebo iron concentrate 70-75%, ordinary magnetite concentrate 15-25%, sulfuric acid residue 4-6%, externally added bentonite 2.2-2.5%, and externally added limestone 2.4-2.8% in percentage by weight. The application aims to solve the problem of difficulty in comprehensive utilization of sulfuric acid residue, and develops a method for producing high-quality fluorine-containing alkaline pellets by matching high-proportion Baiyunebo iron concentrate with sulfuric acid residue in a chain grate-rotary kiln-ring cooler system.

Description

Technical Field

[0001] This invention belongs to the field of iron ore pelletizing technology, and particularly relates to a method for producing high-quality alkaline pellets by combining Bayan Obo iron concentrate with sulfuric acid slag. Background Technology

[0002] Bayan Obo iron ore concentrate is Baogang's primary ironmaking raw material. It is characterized by fine particle size, high calcium content, and low silicon content, with a natural basicity of around 2.0, making it suitable as a raw material for alkaline pellet production. This allows for the high-proportion, high-quality application of Bayan Obo iron ore concentrate in Baogang's pellet production. However, Bayan Obo iron ore concentrate contains high levels of impurities such as potassium, sodium, fluorine, and sulfur, with sulfur content exceeding 1%. To effectively address the impact of the high sulfur content on the pelletizing process, high-sulfur ore is often beneficiated and desulfurized, producing high-sulfur tailings which are then roasted to produce sulfuric acid, resulting in sulfuric acid slag. Therefore, this invention develops a method for producing high-quality alkaline pellets using a chain grate-rotary kiln-annular cooler process with Bayan Obo iron ore concentrate and sulfuric acid slag. Summary of the Invention

[0003] To address the challenge of comprehensive utilization of sulfuric acid slag, the present invention aims to provide a method for producing high-quality alkaline pellets by combining Bayan Obo iron concentrate with sulfuric acid slag. A method has been developed that utilizes a chain grate machine, rotary kiln, and annular cooler with a high proportion of Bayan Obo iron concentrate combined with sulfuric acid slag to produce high-quality fluorine-containing alkaline pellets.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

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

[0006] The mixture was pretreated by high-pressure roller milling, with the moisture content of the roller mill feed controlled at 7.0%-8.0%, resulting in an increase of 300 cm² in the specific surface area of ​​the mixture containing sulfuric acid slag. 2 ·g -1 about;

[0007] The mixture after high-pressure roller milling is pelletized in a Φ6m pelletizing disc to obtain green pellets. The process control parameters of the pelletizing disc are: green pellet moisture content 8.5%~9.0%, disc inclination angle 45~45.5°, green pellet drop strength reaching 5.5 times / P or more, and through sieving, the proportion of green pellets with particle size distribution between 8mm-16mm reaches more than 95%, and the wet return rate is controlled within 20%.

[0008] The raw balls are evenly spread onto the chain grate machine through the raw ball feeding device and screening device. The thickness of the raw balls on the chain grate machine is 175mm to 205mm, and the machine speed of the chain grate machine is 1.70m / min to 1.75m / min.

[0009] Further: The green pellets are dried via a chain grate drying machine with a forced-air drying section and a forced-air drying section. The forced-air drying section conditions are: the air box temperature is controlled at 200℃~250℃, and the time is 3.43min~3.53min. The forced-air drying section conditions are: the fume hood temperature is controlled at 320℃~360℃, and the time is 6.86min~7.05min.

[0010] The dry balls are preheated in two stages using a chain grate machine. The conditions for the first stage of preheating are as follows: the temperature of the fume hood in the first stage is controlled at 700±20℃ for 3.43 min to 3.53 min. The temperature of the fume hood in the second stage of preheating is controlled at 1020℃ to 1050℃ for 10.29 min to 10.58 min.

[0011] The preheated balls are roasted in a rotary kiln under the following conditions: the temperature of the kiln tail hood is controlled at 950℃~1000℃, and the temperature of the kiln head hood is controlled at 1030℃~1060℃.

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

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

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

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

[0016] Furthermore, the chemical composition of the Bayan Obo iron concentrate, by weight percentage, includes: TFe 64.5–65.0%, FeO 28.5–29.5%, MgO 1.30–1.40%, CaO 2.0%–2.3%, Al₂O₃ ≤ 0.20%, SiO₂ 0.90%–1.60%, S 0.70–0.80%, F 0.25%–0.30%, K₂O ≤ 0.10%, and Na₂O ≤ 0.10%; the percentage of concentrate with a particle size ≤ 0.074 mm 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, by weight percentage, includes 67.0-67.50% TFe, 1.80-2.50% SiO2, 0.20%-0.30% S, ≤0.05% F, and ≤0.09% K2O+Na2O; the percentage of concentrate with a particle size ≤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 sulfuric acid slag, by weight percentage, includes 61.0-61.50% TFe, 1.50%-1.65% CaO, 5.5-6.0% SiO2, and ≤0.30% K2O+Na2O; the concentrate with a particle size ≤0.074mm accounts for at least 70% of the total weight of the sulfuric acid slag.

[0019] Furthermore, the chemical composition of the bentonite includes SiO2 of 58.0% to 60.0% by weight, and 1 g ≤ 12.0%.

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

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

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

[0023] The high-quality fluorine-containing alkaline pellets produced from the Bayan Obo iron concentrate and 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 to 1.20, compressive strength of ≥ 2300 N / P, and reduction expansion rate controlled within 15%. Detailed Implementation

[0024] The specific embodiments of the present invention will be further illustrated below, but the specific embodiments of the present invention are not limited to the following embodiments.

[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.

[0026] Table 1. Raw material ratios in the examples

[0027]

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

[0029]

[0030]

[0031] Table 3 Chemical composition of pellets in the examples

[0032]

[0033] Table 4. Statistics on the cold strength and reduction performance of the finished balls in the examples.

[0034] Example 2437 13.50

[0035] As shown in Table 1-4, the method of producing high-quality fluorine-containing alkaline pellets by combining a chain grate machine-rotary kiln-annular cooler with a high proportion of Bayan Obo iron concentrate (73%) and sulfuric acid slag (5%) achieves the comprehensive utilization of sulfuric acid slag.

[0036] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for producing high-quality alkaline pellets from Bayan Obo iron concentrate using sulfuric acid slag, characterized in that: The raw materials, by weight percentage, include: 70%–75% Bayan Obo iron concentrate, 15%–25% ordinary magnetite concentrate, 4–6% sulfuric acid slag, 2.2%–2.5% bentonite, and 2.4%–2.8% limestone. The mixture is pretreated by high-pressure roller mill, and the moisture content of the roller mill feed is controlled at 7.0%-8.0% to improve the specific surface area of ​​the mixture with sulfuric acid residue. The mixture after high-pressure roller milling is pelletized in a Φ6m pelletizing disc to obtain green pellets. The process control parameters of the pelletizing disc are: green pellet moisture content 8.5%~9.0%, disc inclination angle 45~45.5°, green pellet drop strength reaching 5.5 times / P or more, and through sieving, the proportion of green pellets with particle size composition between 8mm-16mm reaches more than 95%, and the wet return rate is controlled within 20%. The raw balls are evenly spread onto the chain grate machine through the raw ball feeding device and screening device. The thickness of the raw balls on the chain grate machine is 175mm to 205mm, and the machine speed of the chain grate machine is 1.70m / min to 1.75m / min. The green balls are dried via a chain grate drying machine with a blower drying section and an exhaust drying section. The conditions for the blower drying section are as follows: the temperature of the blower box is controlled at 200℃~250℃ for 3.43min~3.53min; the conditions for the exhaust drying section are as follows: the temperature of the exhaust hood is controlled at 320℃~360℃ for 6.86min~7.05min. The dry balls are preheated in two stages using a chain grate machine. The conditions for the first stage of preheating are as follows: the temperature of the fume hood in the first stage is controlled at 700±20℃ for 3.43min to 3.53min; the temperature of the fume hood in the second stage of preheating is controlled at 1020℃ to 1050℃ for 10.29min to 10.58min. The preheated balls are roasted in a rotary kiln under the following conditions: the temperature of the kiln tail hood is controlled at 950℃~1000℃, and the temperature of the kiln head hood is controlled at 1030℃~1060℃. The roasted pellets are cooled and recrystallized using an annular cooler. The process conditions of the annular cooler are as follows: the cooler speed is 0.90 m / min to 0.95 m / min, the secondary air temperature is controlled at 980℃ to 1040℃, the second stage air temperature is 820±30℃, and the third stage air temperature is 430±40℃. After cooling, the roasted pellets finally yield fluorine-containing alkaline pellets with added sulfuric acid slag.

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

3. The method for producing high-quality alkaline pellets from Bayan Obo iron concentrate combined with sulfuric acid slag according to claim 1, characterized in that: Quality control of preheated balls: compressive strength 600N / P~800N / P.

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

5. The method for producing high-quality alkaline pellets from Bayan Obo iron concentrate combined with sulfuric acid slag according to claim 1, characterized in that: The chemical composition of the Bayan Obo iron concentrate, by weight percentage, includes: TFe 64.5–65.0%, FeO 28.5–29.5%, MgO 1.30–1.40%, CaO 2.0%–2.3%, Al2O3 ≤0.20%, SiO2 0.90%–1.60%, S 0.70–0.80%, F 0.25%–0.30%, K2O ≤0.10%, and Na2O ≤0.10%.

6. The method for producing high-quality alkaline pellets from Bayan Obo iron concentrate combined with sulfuric acid slag according to claim 1, characterized in that: The chemical composition of the ordinary magnetite concentrate, by weight percentage, includes 67.0-67.50% TFe, 1.80-2.50% SiO2, 0.20%-0.30% S, ≤ 0.05% F, and ≤ 0.09% K2O+Na2O.

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

8. The method for producing high-quality alkaline pellets from Bayan Obo iron concentrate combined with sulfuric acid slag according to claim 1, characterized in that: The chemical composition of the bentonite, by weight percentage, includes 58.0%–60.0% SiO2 and ≤12.0% Ig.

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

Images