Preparation method of high-silicon magnetite pellets added with biomass
By adding biomass to high-silicon magnetite, using the volatile components of the biomass and the residual carbon after high-temperature roasting, the reduction and adhesion of pellets are promoted, and the problem of poor metallurgy performance of high-silicon ore in blast furnace smelting is solved, the compressive strength and metallurgy of the pellets are improved, and the low-carbon green metallurgy of steel enterprises is promoted.
Patent Information
- Application Number
- CN202411975656.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-04-04
AI Technical Summary
In blast furnace smelting, high SiO2 content leads to high slag viscosity and poor desulfurization capacity, which affects metallurgy performance and airflow resistance, increasing the difficulty of the iron smelting process.
By adding biomass to high-silicon magnetite, the volatile components of the biomass and the residual carbon after high-temperature roasting can be used to promote the reduction and adhesion inhibition of the pellets, and the compressive strength and metallurgical properties of the pellets are improved.
It has achieved effective utilization of high-silicon magnetite, improved the compressive strength and metallurgical performance of the pellets, reduced dependence on fossil energy, and promoted low-carbon green metallurgy of steel enterprises.
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Figure CN119753317A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of ironmaking raw material preparation, and in particular relates to a method for preparing high-silicon magnetite pellets added with biomass. Background Art
[0002] High-silicon iron ore is a type of iron ore resource with the advantages of low ignition loss, low price and large storage capacity. China's high-silicon iron ore reserves exceed 55 billion tons, but the SiO2 content of the ore is too high, and some even reach more than 10%. When it is used in blast furnace smelting, the blast furnace slag has low basicity, high viscosity and poor desulfurization ability, which can increase the air flow resistance in the upper part of the blast furnace, directly affecting the gas dynamic conditions during the smelting process of the blast furnace charge, and reducing the metallurgical properties such as the ore reduction degree. Therefore, this type of iron ore is difficult to utilize.
[0003] Pellets are one of the main raw materials in blast furnace ironmaking. Made by rolling various types of fine-grained iron ore concentrates with a small amount of binder into balls and then roasting them, pellets are required to have a high TFe content, low silica content, and low levels of harmful elements such as sulfur and phosphorus. Biomass, a renewable resource known as a "carbon-neutral resource," can be added to high-silicon magnetite concentrate powder to produce blast furnace pellets. Biomass can partially replace fossil fuels, and the micropores formed by its volatiles and the residual carbon after high-temperature roasting can promote the reduction of the high-silicon pellets and inhibit their adhesion, thereby addressing the tight iron ore supply issues facing steel companies. Summary of the Invention
[0004] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a method for preparing high-silicon magnetite pellets with added biomass, so as to realize the utilization of high-silicon magnetite, and the compressive strength of the prepared high-silicon magnetite pellets meets production requirements, ensures metallurgical properties, and improves the utilization rate of biomass and high-silicon magnetite.
[0005] To achieve the above object, the present invention is implemented through the following technical solutions:
[0006] A method for preparing high-silicon magnetite pellets with biomass addition comprises the following steps:
[0007] S1) drying and sieving high silicon magnetite concentrate, biomass, and bentonite to remove coarse particles and impurities in the raw materials; mixing the high silicon magnetite concentrate, biomass, and bentonite in a mixer, and then adding water to the mixture to a water content of 6% to 8% by mass of the total mixture, mixing again and then stewing;
[0008] S2) adding the stewed mixture in batches to a disc pelletizer for pelletizing, completing the mother ball formation stage, mother ball growth stage and green ball compaction stage by spraying water, and controlling the moisture content of the green balls to be 8.0% to 8.5% by mass;
[0009] S3) Screening and roasting the green balls in sequence to obtain finished pellets.
[0010] The biomass is one or more of waste wood chips and bamboo.
[0011] The drying temperature in S1) is 105-110° C., and the drying time is 4-6 h. The sieved raw materials in S1) contain particles with a diameter of less than 200 mesh, accounting for more than 95 wt %.
[0012] The mass content of SiO2 in the high-silicon magnetite concentrate is not less than 5%.
[0013] The components of the bentonite are calculated by mass percentage:
[0014] SiO2: 55.96%, Al2O3: 11.73%, MgO: 2.1%, CaO: 4.16%.
[0015] In step S1), the mass ratio of the high silicon magnetite concentrate, biomass and bentonite is 100:(3-7):1.5.
[0016] In step 2), water is sprayed in a manner that drops of water form balls and grows in a mist-like manner.
[0017] In step S2), the mother ball forming stage: the ball forming time is 2 to 5 minutes, and the mother ball particle size is 2 to 4 mm;
[0018] Cue ball growth stage: the ball making time is 6 to 8 minutes, and the raw ball particle size is 8 to 10 mm;
[0019] Green ball compaction stage: the ball making time is 4 to 6 minutes, and the green ball particle size is 12.5 to 14 mm. At this time, stop adding materials and spraying water.
[0020] The inner diameter of the disc of the disc pelletizing machine is 1.2m, the disc rotation speed is 30r / min, and the disc inclination angle is controlled at 45°.
[0021] In step S3), the calcination is a three-stage calcination:
[0022] The first stage: the temperature is raised from room temperature to 450°C at a rate of 9-10°C / min, while air is introduced at a rate of 2.4-3.0 L / min;
[0023] The second stage: the temperature is raised from 450°C to 925°C at a rate of 7-8°C / min, then kept at that temperature for 35-40 minutes, while air is introduced at a rate of 2.4-3.0 L / min;
[0024] The third stage: the temperature is raised from 925°C to 1250°C at a rate of 4-5°C / min, then kept at that temperature for 35-40 minutes, while air is introduced at a rate of 2.4-3.0L / min; finally, the temperature is cooled with the furnace temperature.
[0025] Compared with the prior art, the present invention has the following beneficial effects:
[0026] 1. The present invention establishes a method of producing iron ore pellets using pure biomass as raw material and high-silicon magnetite. While leveraging the advantages of biomass, it also improves the metallurgical properties of high-silicon magnetite, enabling metallurgical enterprises to reduce their dependence on fossil energy, and has certain significance for steel enterprises to achieve low-carbon green metallurgy.
[0027] 2. The high-temperature pyrolysis of the biomass in the present invention produces a reducing atmosphere of volatiles and hydrocarbons such as CnHm. These substances form a large number of gas channels as they escape from the pellets. This increases the porosity of the pellets, accelerates the conversion of solid-solid reactions to gas-solid reactions, facilitates the transfer of heat radiation into the pellets, and provides favorable thermodynamic and kinetic conditions. After high temperatures, the biomass produces reducing gases and biochar. These volatile gases and the residual biochar produced, acting as a reducing agent, form a local reducing atmosphere and react with the magnetite particles, enabling the pellets to undergo self-reduction reactions and achieving the purpose of pre-reduction.
[0028] 3. High-silicon magnetite produces a liquid phase at high temperatures. The addition of biomass increases the uniform porosity of the pellets, creating a liquid phase that is evenly distributed throughout the pores, providing support for pellet strength. Overall, biomass high-silicon pellets utilize low-quality ore and replace the non-renewable energy of coal with renewable energy biomass, providing a solution for economic benefits, energy conservation, and emission reduction in pellet production.
[0029] 4. According to different pelletizing stages, the present invention puts the raw materials into the disc of the disc pelletizing machine in batches for screening and pelletizing, sprays water in the form of dripping water into balls and mist growth, and completes the mother ball formation stage, mother ball growth stage and green ball compaction stage accordingly, and finally obtains biomass high-silicon magnetite pellets, which are obtained after oxidative roasting and have metallurgical properties that meet the requirements of smelting production. This is of great significance to the further development and full utilization of biomass in high-silicon pellets, and can make good use of high-silicon iron ore, a relatively inferior iron ore resource.
[0030] 5. The high silicon magnetite pellets prepared by the present invention with biomass addition have a compressive strength of up to 3058N, a pellet reduction expansion rate of less than 15%, and a pellet RDI of +3.15 The indexes are all above 90%, which is in line with the national pellet ore use standards and meets the use requirements of steel enterprises. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 This is a flow chart for the preparation of high-silicon magnetite pellets with added biomass. DETAILED DESCRIPTION
[0032] The present invention will be described in detail below with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.
[0033] A method for preparing high-silicon magnetite pellets with biomass addition comprises the following steps:
[0034] S1) drying and sieving high silicon magnetite concentrate, biomass, and bentonite to remove coarse particles and impurities in the raw materials; mixing the high silicon magnetite concentrate, biomass, and bentonite in a mass ratio of 100:(3-7):1.5 in a mixer, and then adding water to the mixture in a water percentage of 6% to 8% of the total mixture mass, mixing again and stewing (at room temperature);
[0035] The biomass is waste sawdust or bamboo. The SiO2 content in the high-silicon magnetite concentrate is not less than 5%. The composition of the bentonite by mass is: SiO2: 55.96%, Al2O3: 11.73%, MgO: 2.1%, and CaO: 4.16%.
[0036] The temperature during the drying process is 105-110° C., and the drying time is 4-6 hours; the particle size of the raw materials after screening is less than 200 mesh, accounting for more than 95wt%.
[0037] S2) adding the stewed mixture in batches to a disc pelletizer for pelletization, conveniently controlling the particle size of the pellets, spraying water in a dripping manner and mist-like growth manner, completing the mother ball formation stage, mother ball growth stage, and green ball compaction stage, and controlling the moisture content of the resulting green balls to be between 8.0% and 8.5% by mass. The disc of the disc pelletizer has an inner diameter of 1.2 m, a disc rotation speed of 30 r / min, and a disc inclination angle of 45°.
[0038] Ball making process at each stage:
[0039] Cue ball formation stage: the ball-making time is 2 to 5 minutes, and the cue ball particle size is 2 to 4 mm;
[0040] Cue ball growth stage: the ball making time is 6 to 8 minutes, and the raw ball particle size is 8 to 10 mm;
[0041] Green ball compaction stage: the ball making time is 4 to 6 minutes, and the green ball particle size is 12.5 to 14 mm. At this time, stop adding materials and spraying water.
[0042] S3) Screening and roasting the green balls in sequence to obtain finished pellets.
[0043] The roasting is a three-stage roasting:
[0044] The first stage: the temperature is raised from room temperature to 450°C at a rate of 9-10°C / min, while air is introduced at a rate of 2.4-3.0 L / min;
[0045] The second stage: the temperature is raised from 450°C to 925°C at a rate of 7-8°C / min, then kept at that temperature for 35-40 minutes, while air is introduced at a rate of 2.4-3.0 L / min;
[0046] The third stage: the temperature is raised from 925°C to 1250°C at a rate of 4-5°C / min, then kept at that temperature for 35-40 minutes, while air is introduced at a rate of 2.4-3.0L / min; finally, the temperature is cooled with the furnace temperature.
[0047] Example 1
[0048] See Figure 1 The method for preparing high silicon magnetite pellets with biomass includes the following steps:
[0049] S1: Pour 5000g of magnetite, 150g of waste sawdust, and 75g of bentonite into a mixer. Start stirring and then pour in 314±0.5g of water. Stir for 5 minutes to obtain a uniform mixture, which is then stewed for later use.
[0050] S2: The mixture after cooking is divided into three batches. The first batch is sent to the disc pelletizer for pelletization. Core pellets with a particle size of 2-4 mm are obtained through screening. Under the premise of controlling the moisture content, the mixture of the previous batch that does not meet the particle size requirements is dried again and watered, mixed evenly, and then recycled for pelletization.
[0051] S3: Put the core pellets with a particle size of 2 to 4 mm into the disc pelletizer, and add the second batch of materials into the disc pelletizer by adding materials while spraying water to make balls, and obtain grown pellets with a particle size of 8 to 10 mm by screening.
[0052] S4: Put the grown pellets with a particle size of 8 to 10 mm into the disc pelletizer, and add the third batch of materials into the disc pelletizer by adding materials while spraying mist water to make balls, and obtain green pellets with a particle size of 12.5 to 14 mm by screening.
[0053] S5: Dry the green pellets with a particle size of 12.5 to 14 mm and send them into a muffle furnace for three-stage roasting to obtain high-silicon magnetite pellets with waste sawdust.
[0054] Example 2
[0055] See Figure 1 The method for preparing high silicon magnetite pellets with biomass includes the following steps:
[0056] S1: Pour 5000g of magnetite, 250g of waste sawdust, and 75g of bentonite into a mixer. Start stirring and then pour in 320±0.5g of water. Stir for 5 minutes to obtain a uniform mixture, which is then stewed for later use.
[0057] S2: The mixture after stewing is divided into 3 batches. The first batch is sent to the disc pelletizing machine for pelletizing, and core pellets with a particle size of 2 to 4 mm are obtained by screening.
[0058] S3: Put the core pellets with a particle size of 2 to 4 mm into the disc pelletizer, and add the second batch of materials into the disc pelletizer by adding materials while spraying mist water to make balls, and obtain grown pellets with a particle size of 8 to 10 mm by screening.
[0059] S4: Put the grown pellets with a particle size of 8 to 10 mm into the disc pelletizer, and add the third batch of materials into the disc pelletizer by adding materials while spraying mist water to make balls, and obtain green pellets with a particle size of 12.5 to 14 mm by screening.
[0060] S5: Dry the green pellets with a particle size of 12.5 to 14 mm and send them into a muffle furnace for three-stage roasting to obtain high-silicon magnetite pellets with waste sawdust.
[0061] Example 3
[0062] See Figure 1 The method for preparing high silicon magnetite pellets with biomass includes the following steps:
[0063] S1: Pour 5000g of magnetite, 350g of waste sawdust, and 75g of bentonite into a mixer. Start stirring and then pour in 326±0.5g of water. Stir for 5 minutes to obtain a uniform mixture, which is then stewed for later use.
[0064] S2: The mixture after stewing is divided into 3 batches. The first batch is sent to the disc pelletizing machine for pelletizing, and core pellets with a particle size of 2 to 4 mm are obtained by screening.
[0065] S3: Put the core pellets with a particle size of 2 to 4 mm into the disc pelletizer, and add the second batch of materials into the disc pelletizer by adding materials while spraying mist water to make balls, and obtain grown pellets with a particle size of 8 to 10 mm by screening.
[0066] S4: Put the grown pellets with a particle size of 8 to 10 mm into the disc pelletizer, and add the third batch of materials into the disc pelletizer by adding materials while spraying mist water to make balls, and obtain green pellets with a particle size of 12.5 to 14 mm by screening.
[0067] S5: Dry the green pellets with a particle size of 12.5 to 14 mm and send them into a muffle furnace for three-stage roasting to obtain high-silicon magnetite pellets with waste sawdust.
[0068] Example 4
[0069] See Figure 1 The method for preparing high silicon magnetite pellets with biomass includes the following steps:
[0070] S1: Pour 5000g of magnetite, 150g of bamboo, and 75g of bentonite into a mixer. Start stirring and then pour in 314±0.5g of water. Stir for 5 minutes to obtain a uniform mixture, which is then stewed for later use.
[0071] S2: The mixture after stewing is divided into 3 batches. The first batch is sent to the disc pelletizing machine for pelletizing, and core pellets with a particle size of 2 to 4 mm are obtained by screening.
[0072] S3: Put the core pellets with a particle size of 2 to 4 mm into the disc pelletizer, and add the second batch of materials into the disc pelletizer by adding materials while spraying mist water to make balls, and obtain grown pellets with a particle size of 8 to 10 mm by screening.
[0073] S4: Put the grown pellets with a particle size of 8 to 10 mm into the disc pelletizer, and add the third batch of materials into the disc pelletizer by adding materials while spraying mist water to make balls, and obtain green pellets with a particle size of 12.5 to 14 mm by screening.
[0074] S5: Drying the green pellets with a particle size of 12.5 to 14 mm and feeding them into a muffle furnace, and roasting them in three stages to obtain high-silicon magnetite pellets with bamboo added.
[0075] Example 5
[0076] See Figure 1 The method for preparing high silicon magnetite pellets with biomass includes the following steps:
[0077] S1: Pour 5000g of magnetite, 250g of bamboo, and 75g of bentonite into a mixer. Start stirring and then pour in 320±0.5g of water. Stir for 5 minutes to obtain a uniform mixture, which is then stewed for later use.
[0078] S2: The mixture after stewing is divided into 3 batches. The first batch is sent to the disc pelletizing machine for pelletizing, and core pellets with a particle size of 2 to 4 mm are obtained by screening.
[0079] S3: Put the core pellets with a particle size of 2 to 4 mm into the disc pelletizer, and add the second batch of materials into the disc pelletizer by adding materials while spraying mist water to make balls, and obtain grown pellets with a particle size of 8 to 10 mm by screening.
[0080] S4: Put the grown pellets with a particle size of 8 to 10 mm into the disc pelletizer, and add the third batch of materials into the disc pelletizer by adding materials while spraying mist water to make balls, and obtain green pellets with a particle size of 12.5 to 14 mm by screening.
[0081] S5: Drying the green pellets with a particle size of 12.5 to 14 mm and feeding them into a muffle furnace, and roasting them in three stages to obtain high-silicon magnetite pellets with bamboo added.
[0082] Example 6
[0083] See Figure 1 The method for preparing high silicon magnetite pellets with biomass includes the following steps:
[0084] S1: Pour 5000g of magnetite, 350g of bamboo, and 75g of bentonite into a mixer. Start stirring and then pour in 326±0.5g of water. Stir for 5 minutes to obtain a uniform mixture, which is then stewed for later use.
[0085] S2: The mixture after stewing is divided into 3 batches. The first batch is sent to the disc pelletizing machine for pelletizing, and core pellets with a particle size of 2 to 4 mm are obtained by screening.
[0086] S3: Put the core pellets with a particle size of 2 to 4 mm into the disc pelletizer, and add the second batch of materials into the disc pelletizer by adding materials while spraying mist water to make balls, and obtain grown pellets with a particle size of 8 to 10 mm by screening.
[0087] S4: Put the grown pellets with a particle size of 8 to 10 mm into the disc pelletizer, and add the third batch of materials into the disc pelletizer by adding materials while spraying mist water to make balls, and obtain green pellets with a particle size of 12.5 to 14 mm by screening.
[0088] S5: Drying the green pellets with a particle size of 12.5 to 14 mm and feeding them into a muffle furnace, and roasting them in three stages to obtain high-silicon magnetite pellets with bamboo added.
[0089] The high silicon magnetite pellets obtained in Examples 1 to 6 above and supplemented with biomass were tested for basic metallurgical properties, and the results are as follows:
[0090]
[0091] Through the basic metallurgical performance test, it can be seen that the pure biomass high silicon magnetite pellets obtained by the preparation method of this application have a significant increase in the reduction index of the pellets when the biomass ratio increases, and the reducibility is significantly improved; the reduction expansion performance of the pellets is relatively good, the reduction expansion index RSI is between 10% and 13%, and the RDI +3.15 The indexes are all above 90%, and the pellets have good performance and meet the standards for use in the furnace. Among them, the high-silicon magnetite pellets added with waste sawdust have better performance, the finished balls have higher compressive strength, and have the advantages of lower N and S content, so they can be used first.
[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, corresponding technical personnel in this technical field should understand that they can still modify the technical solutions of the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements cannot cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing high silicon magnetite pellets with biomass, characterized in that: The following steps are involved: S1) drying and sieving high silicon magnetite concentrate, biomass and bentonite to remove coarse particles and impurities in the raw materials; mixing the high silicon magnetite concentrate, biomass and bentonite in a mixer, and then adding water to the mixture, the mass percentage of the added water is 6% to 8% of the total mass of the mixture, and then mixing again and stewing the mixture; S2) adding the stewed mixture in batches into a disc pelletizer for pelleting, completing the mother ball formation stage, mother ball growth stage and green ball compaction stage by spraying water, and controlling the water mass percentage of the green balls to be obtained to be 8.0% to 8.5%; S3) Screening and roasting the raw balls in sequence to obtain finished pellets.
2. The method for preparing high silicon magnetite pellets with biomass added according to claim 1, characterized in that: The biomass is one or more of waste wood chips and bamboo.
3. The method for preparing high silicon magnetite pellets with biomass added according to claim 1, characterized in that: The drying temperature in S1) is 105-110° C. and the drying time is 4-6 hours; the particle size of the sieved raw materials in S1) is greater than 95wt%.
4. The method for preparing high silicon magnetite pellets with biomass addition according to claim 1, characterized in that: The mass content of SiO2 in the high silicon magnetite concentrate is not less than 5%.
5. The method for preparing high silicon magnetite pellets with biomass added according to claim 1, characterized in that: The components of the bentonite are calculated by mass percentage: SiO2: 55.96%, Al2O3: 11.73%, MgO: 2.1%, CaO: 4.16%.
6. The method for preparing high silicon magnetite pellets with biomass added according to claim 1, characterized in that: In step S1), the mass ratio of the high silicon magnetite concentrate, biomass and bentonite is 100:(3-7):1.
5.
7. The method for preparing high silicon magnetite pellets with biomass added according to claim 1, characterized in that: In step 2), water is sprayed in a manner that drops of water form balls and grows in a mist-like manner.
8. The method for preparing high silicon magnetite pellets with biomass added according to claim 1, characterized in that: In step S2), the mother ball forming stage: the ball making time is 2 to 5 minutes, and the mother ball particle size is 2 to 4 mm; Cue ball growth stage: ball making time is 6 to 8 minutes, and the raw ball size is 8 to 10 mm; Green ball compaction stage: the ball making time is 4 to 6 minutes, and the green ball particle size is 12.5 to 14 mm. At this time, stop adding materials and spraying water.
9. The method for preparing high silicon magnetite pellets with biomass added according to claim 1, characterized in that: The inner diameter of the disc of the disc pelletizing machine is 1.2 m, the disc speed is 30 r / min, and the disc inclination angle is controlled at 45°.
10. The method for preparing high silicon magnetite pellets with biomass added according to claim 1, characterized in that: In step S3), the calcination is a three-stage calcination: The first stage: the temperature is raised from room temperature to 450°C at a rate of 9-10°C / min, while air is introduced at a rate of 2.4-3.0L / min; The second stage: the temperature is raised from 450℃ to 925℃ at a rate of 7-8℃ / min, and then kept at this temperature for 35-40min, while air is introduced at a rate of 2.4-3.0L / min; The third stage: the temperature is raised from 925°C to 1250°C at a rate of 4-5°C / min, then kept at that temperature for 35-40min, while air is introduced at a rate of 2.4-3.0L / min; finally, it is cooled with the furnace temperature.