Method for granulating and consolidating iron ore feed material for fluidized bed direct reduction

Abstract

The application discloses a method for granulating and consolidating iron ore raw materials for fluidized bed direct reduction. The method mainly comprises the following steps: mixing iron ore powder raw materials with additives, granulating, high-speed whole-granulating, drying and grading, roasting and consolidating, cooling and dedusting, and the like. Specifically, the iron ore powder raw materials are mixed with additives, and after granulation, the near-spherical granulating materials are obtained by high-speed shearing, and after drying and grading, roasting and consolidating and cooling, the iron ore consolidated materials for the fluidized bed direct reduction process are obtained. The granulation and consolidation of the iron ore powder realize the regulation and control of the particle size and structure of the raw materials, greatly improve the adaptability of the raw materials and the reduction efficiency of the fluidized bed direct reduction process, and effectively inhibit the sticking in the reduction process. The balling and high-speed whole-granulating effectively reduce the amount of the binder and improve the yield of the finished products. The drying and grading and the roasting and consolidating produce coarse particles and fine powder circulation return mixing, and the cooling waste heat returns to drying, so that the material and energy are efficiently utilized. The application has the advantages of wide raw material adaptability, high granulation and consolidation efficiency and easy scale application.

Description

Technical Field

[0001] This invention relates to the field of resource utilization, and in particular to a method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction. Background Technology

[0002] As a typical gas-based direct reduction reactor, the fluidized bed reactor boasts advantages such as high gas-solid phase mass and heat transfer efficiency and fast reduction rate, making it a promising iron ore smelting technology. It is well known that the reduction process of iron ore powder is a gradual reduction process from the outside in. From a reaction kinetics perspective, finer iron ore powder particle size is more conducive to reduction, but excessively fine particle size makes it difficult to directly apply to a fluidized bed reactor. Fluidized gas-based direct ironmaking has certain requirements for raw material particle size, typically using iron ore powder / particles of 0.1–3 mm as raw material; otherwise, normal fluidization is difficult or the required gas velocity is too high, resulting in very low reducing gas utilization. Iron ores are diverse in type and shape; not all iron ore raw materials can be directly applied to fluidized bed reactors. Furthermore, a large amount of -400 mesh fine iron ore powder is generated during the iron ore grinding and beneficiation process, which cannot be directly applied to a fluidized bed reactor. For fluidized bed reactors, the most critical issue is that during the fluidized reduction process, iron ore can adhere to the particle surface due to the formation of metallic iron, making normal fluidization difficult or even causing it to lose its fluidization properties. This hinders the large-scale application of fluidized bed ironmaking. Furthermore, the low gas utilization rate is also a factor limiting the development of fluidized bed direct ironmaking technology.

[0003] To address adhesion during the direct reduction process of iron ore gas-based fluidized bed reactors, various methods are employed to prevent adhesion and flow loss. For example, surface coating is used; patents CN107130076B and CN107227383B employ graphite or carbon powder as an anti-adhesion agent, coating the iron ore surface. Furthermore, adding gangue to the fluidized bed reactor can improve the fluidization performance of iron ore particles; for instance, adding coke powder, dolomite powder, or limestone powder (patent CN101624639A). Alternatively, internal structures or auxiliary equipment can be installed within the fluidized bed reactor, such as a stirring device (CN102794456B), or a three-stage fluidized bed reactor can be used, with a cyclone separator installed in each stage (US6585798B2). This technology posits that adhesion in the fluidized bed reactor is caused by fine iron ore powder in the fluidizing gas clogging the air caps; therefore, cyclone dust collectors are installed in each stage of the reactor to prevent adhesion and flow loss caused by fine powder clogging the air caps. Alternatively, the morphology of metallic iron on the particle surface can be controlled by adjusting the composition of the reducing gas to suppress adhesion and flow loss. For example, Japanese patent JP4203090A mixes a small amount of H2S gas into the reducing gas to regulate the structure of iron formed on the particle surface, thereby preventing adhesion during the fluidized reduction process. Although the above technologies have some effect in preventing adhesion and flow loss, most methods rely on physical means to improve fluidization performance, which presents difficulties and risks in industrial implementation. For example, stirring may lead to the leakage of reducing gas and the adhesion of iron ore powder to the surface of the stirring paddle. Surface coating may be uneven, or the dosage may be too high, which could hinder subsequent melting. As for adding dust removal and purification, it does not fundamentally solve the problem of adhesion and flow loss. Ultimately, the main reason is the lack of iron pretreatment technology suitable for fluidized bed ironmaking. Therefore, granulation pretreatment of iron ore to meet the particle size requirements of the fluidized bed reactor, adding anti-adhesion agents to ensure uniform distribution on the surface of iron ore particles, and forming complex salts with iron oxides that are difficult to reduce can fundamentally solve the problem of adhesion and flow loss. In addition, the particles can be restructured and granulated to form porous particles, which facilitates rapid reduction and improves the utilization rate of reducing gas, thereby helping to promote the large-scale application of fluidized bed gas-based direct reduction ironmaking technology.

[0004] For iron ore powder granulation, there are existing patent reports. For example, CN10038502C involves dissolving a polymer compound composed of carboxyl groups, sulfonic acid groups, and their salts in water to form a solution. Then, calcium hydroxide, calcium carbonate, or kaolin particles are added to the water to form a slurry. This slurry is then added to iron ore powder with an average particle size of less than 200 μm in a certain proportion. After processing in a homogenizer, the mixture is dried at 80°C to obtain granules. The granules are then sintered, resulting in a finished product qualification rate of 76.5% and a sintering strength of 83.3%. From the technical implementation process, the preparation of the polymer solution is relatively complex, typically involving multiple substances and multiple steps to obtain a polymer aqueous solution, thus making the entire granulation process complex. The product results show a low qualification rate. Furthermore, the report does not specify the sintering temperature and product particle size distribution, and fails to mention the subsequent adaptation of the granulated material to the reactor. For iron ore that is difficult to granulate, CN102296177B adds biomass fuel with an average particle size of 1-4 mm to iron oxides such as dust and slag, and adds water. After mixing and granulating, it is sintered. Its highest yield is 75.23% and the highest drum strength coefficient is 65.17%. CN103667681B uses methylcellulose as a binder to granulate on a disc granulator and then sinters. However, this patent does not mention the particle size distribution range of the granulated particles or the sintering-related parameters. From the existing technology, there are still the following problems in iron ore powder granulation: (1) The yield is low. According to the reported technology, the yield is about 76%, so about a quarter of them will not be usable or will be returned to the granulation process for granulation, which will increase the granulation cost; (2) There is a lack of granulation technology specifically for fluidized bed reactors. According to the technical background of the existing technology, iron ore pretreatment is mainly aimed at the preparation of pellets for blast furnaces. Generally speaking, blast furnace pellets have a relatively large particle size and cannot be used in fluidized bed reactors.

[0005] Therefore, to fundamentally solve the problems of adhesion and flow loss during the direct reduction of iron ore powder in fluidized bed reactors, as well as the low yield in the granulation process, this invention provides an iron ore powder granulation and consolidation technology with high yield suitable for fluidized bed reactors. This involves refining, granulating, and consolidating the iron ore raw material to obtain a granulated modified material with good fluidization and reduction properties. The basic principle is that under high-temperature conditions, additives can react with iron oxides to form ferrates that are difficult to reduce, which are distributed on the particle surface. This reduces the metallic iron content on the particle surface during reduction, preventing particle adhesion and flow loss. Summary of the Invention

[0006] To address the problems existing in current iron ore powder granulation methods, this invention provides a method for granulating and consolidating iron ore raw materials for fluidized bed direct reduction (FDR). The method mainly includes processes such as mixing, pelletizing, high-speed granulation, drying and classification, roasting and consolidation, cooling, and dust removal. Specifically, iron ore powder raw materials are mixed with additives, pelletized, and then granulated using high-speed shearing to obtain near-spherical granules. After drying, classification, roasting and consolidation, and cooling, the resulting solidified iron ore material for the FDR process is obtained. By granulating and consolidating iron ore powder, the particle size and structure of the raw materials can be controlled, significantly improving the adaptability of the raw materials and the reduction efficiency of the FDR process, and effectively suppressing adhesion during reduction. Pelletizing and high-speed granulation effectively reduce the amount of binder used and increase the yield. The coarse and fine particles produced during drying, classification, and roasting and consolidation are recycled back for mixing, and the residual heat from cooling is returned to drying, achieving efficient utilization of materials and energy.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction, the method comprising the following steps: mixing step 1, pelletizing step 2, high-speed granulation step 3, drying and classification step 4, roasting and consolidation step 5, cooling step 6, dust collection step 7, and dust removal step 8, specifically carried out according to the following steps:

[0009] 1) The iron ore powder raw material and additives are fed into the mixing process 1 together to make them mix evenly;

[0010] 2) The mixture obtained from mixing step 1 and water are fed into pelletizing step 2, where the pelletizing equipment forms near-spherical particles.

[0011] 3) The near-spherical particles obtained in pelletizing step 2 are fed into high-speed pelletizing step 3. A high-speed shearing mixing pelletizing device is used, with a material tray speed of 10-200 rpm, a rotor speed of 100-2500 rpm, and a pelletizing time of 5-30 min to obtain near-spherical fine-diameter particles.

[0012] 4) The fine particles obtained from the high-speed granulation process 3 are fed into the drying and grading process 4, where they are dried under the action of hot air obtained from the cooling process 6. The drying process is carried out using a drum dryer, mechanical vibrating screen, or fluidized bed dryer. The drying temperature is 80-200℃ and the drying time is 10-60 min. The lower limit of the graded particle size is 0.2-0.6 mm and the upper limit is 1.5-3.0 mm. The residue is returned to the mixing process 1. The flue gas is sent to the dust removal process 8 and then discharged after environmental protection treatment to meet the standards.

[0013] 5) The dried material obtained from the drying and grading process 4 is sent to the roasting and consolidation process 5. A rotary kiln or fluidized bed is used, the roasting temperature is 500-1200℃, and the roasting time is 15-60min, so that it can be consolidated under high temperature conditions. The consolidation flue gas is sent to the dust collection process 7 and then to the drying and grading process 4. The dust collection material is returned to the mixing process 1.

[0014] 6) The solidified product obtained from the roasting and solidification step 5 is sent to the cooling step 6 to obtain iron ore solidified material suitable for fluidized bed direct reduction. The iron ore solidified material is cooled by air, and the recovered heat is sent to the drying and grading step 4 to dry the granulated material.

[0015] Preferably, the iron ore powder is one or a combination of magnetite, hematite, and vanadium-titanium magnetite, with a total iron content of ≥50% and a particle size of -0.044mm content of ≥50%.

[0016] Preferably, the mixing process 1 employs one of the following mixing methods: drum milling, ball milling, or high-speed shearing; the additive is a mixed additive composed of inorganic and organic substances, wherein the inorganic additive is one or more of CaO, Ca(OH)2, MgO, Mg(OH)2, lightly calcined dolomite, magnesite, and clay minerals, and its dosage is 0.5-6% of the iron ore powder mass; the organic additive is one or more of the following compounds: carboxymethyl cellulose, starch, sodium alginate, sodium carboxymethyl cellulose, sodium carboxymethyl starch, glucose, sucrose, and fructose, and its dosage is 0.01-2% of the iron ore powder mass.

[0017] Preferably, the pelletizing process 2 uses one of a disc pelletizer, a roller pelletizer, or a briquetting machine, with the amount of water added being 3% to 10% of the iron ore powder mass, and the pelletizing time being 5 to 20 minutes.

[0018] Compared with existing reporting techniques, this invention has the following outstanding advantages:

[0019] (1) High granulation efficiency, high yield, and uniform particle size distribution. The preparation process of this invention is simple and uses relatively inexpensive additives. Relying on high-speed shearing, the binder and iron ore powder are uniformly mixed, which enhances the granulation effect and significantly improves the granulation efficiency and yield. The yield of particles suitable for fluidized bed reactor processing is not less than 85%. In addition, the raw materials are pre-pelleted by a pelletizing device to obtain large spherical materials. Then, under the action of a high-speed shearing device, the large spherical materials are sheared into small spherical materials to obtain spherical particles with a particle size range that meets the requirements of fluidized bed. By combining pelletizing and granulation, the granulation efficiency can be significantly improved and the particle size distribution of the granulated material can be made more uniform.

[0020] (2) Obtaining iron ore particles within the particle size range suitable for fluidized bed direct reduction. According to particle fluidization theory, particles of different sizes exhibit significant differences in fluidization performance under corresponding solid and fluid density differences, and can be classified into four categories: A, B, C, and D. Powders similar to iron concentrate powder with a high proportion below 30μm belong to category C (viscous powder), which is prone to adhesion and channeling, making fluidization difficult. Fluidized bed processing of ultrafine viscous powders is an internationally recognized challenge. Furthermore, the reduced metallic iron exhibits significant viscosity, making it difficult to avoid flow loss and shutdown due to powder adhesion. Therefore, fluidized bed direct reduction of iron should use larger category A or B particles to ensure fluidization quality. Combined with research results on adhesion in fluidized bed direct reduction, slightly larger particles have greater inter-particle collision forces, which is beneficial for suppressing adhesion. This invention modifies iron ore raw materials to obtain iron ore consolidation modified materials similar to category B particles, which are very suitable for use in fluidized bed direct reduction.

[0021] (3) The obtained granulated and consolidated material can effectively suppress adhesion and flow loss during the reduction process. After calcination and consolidation, the granulated material can pass the high-temperature adhesion performance test and shows no adhesion phenomenon in the fluidized bed reactor. As is well known, particles are constantly moving in a fluidized bed reactor, and the collisions between particles and between particles and the reactor wall place high demands on the strength of the particles. This method relies on high-speed shear granulation and calcination consolidation to obtain granulated material with high strength, overcoming the shortcomings of current patented technologies that rely solely on physical barriers with additives and require a large amount of additives. It innovatively uses additives and iron oxides to form ferrates that are difficult to reduce, thereby avoiding the formation of a large amount of metallic iron on the surface during the reduction process, which would lead to flow loss. Therefore, the granulated and consolidated material obtained by this invention is fully applicable to fluidized bed reactors.

[0022] (4) The system energy consumption can be comprehensively utilized, which can reduce energy consumption and reduce costs. The sensible heat of the solidification product is fully utilized and recovered for drying of the granulation raw materials. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0024] Figure 1 This is a schematic diagram of the process for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction according to the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. It should be noted that the embodiments provided in this invention are only for illustrating the technical solutions of the present invention, and are not intended to limit them, nor are they all embodiments.

[0026] Example 1

[0027] Figure 1 This is a schematic flow diagram of a method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction according to the present invention. (Combined with...) Figure 1 The embodiment uses a method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction. The method includes the following steps: mixing step 1, pelletizing step 2, high-speed granulation step 3, drying and classification step 4, roasting and consolidation step 5, cooling step 6, dust collection step 7, and dust removal step 8, specifically carried out according to the following steps:

[0028] 1) The iron ore powder raw material and additives are fed into the mixing process 1 together to make them mix evenly;

[0029] 2) The mixture obtained from mixing step 1 and water are fed into pelletizing step 2, where the pelletizing equipment forms near-spherical particles.

[0030] 3) The near-spherical particles obtained in pelletizing step 2 are fed into high-speed pelletizing step 3. A high-speed shearing mixing pelletizing device is used, with a material tray speed of 10-200 rpm, a rotor speed of 100-2500 rpm, and a pelletizing time of 5-30 min to obtain near-spherical fine-diameter particles.

[0031] 4) The fine particles obtained from the high-speed granulation process 3 are fed into the drying and grading process 4, where they are dried under the action of hot air obtained from the cooling process 6. Drying is performed using a drum dryer, mechanical vibrating screen, or fluidized bed dryer. The drying temperature is 80–200℃, and the drying time is 10–60 min. The lower limit of the graded particle size is 0.2–0.6 mm, and the upper limit is 1.5–3.0 mm. The residue is returned to the mixing process 1. The flue gas is sent to the dust removal process 8, and then discharged after environmental treatment to meet standards.

[0032] 5) The dried material obtained from the drying and grading process 4 is sent to the roasting and consolidation process 5. A rotary kiln or fluidized bed is used, the roasting temperature is 500-1200℃, and the roasting time is 15-60min, so that it can be consolidated under high temperature conditions. The consolidation flue gas is sent to the dust collection process 7 and then to the drying and grading process 4. The dust collection material is returned to the mixing process 1.

[0033] 6) The solidified product obtained from the roasting and solidification step 5 is sent to the cooling step 6 to obtain iron ore solidified material suitable for fluidized bed direct reduction. The iron ore solidified material is cooled by air, and the recovered heat is sent to the drying and grading step 4 to dry the granulated material.

[0034] Example 2

[0035] This embodiment employs the method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction described in Example 1. The method uses magnetite powder with a total iron content of 60.2% and a particle size of -0.044mm of 53.2% as raw material, which is fed into mixing step 1 along with 6.0% magnesite and 0.05% carboxymethyl cellulose. After uniform mixing in a ball mill, the mixture is fed into granulation step 2, where 3% of the iron ore mass of process water is added. The mixture is then processed in a disc granulator for 10 minutes to obtain near-spherical granules. The obtained granules are then fed into a high-speed granulation step 3, where the disc speed is 50 rpm, the rotor speed is 2500 rpm, and the granulation time is 5 minutes. Near-spherical fine granules are obtained under the action of a high-speed shearing mixing granulator. The high-speed granulator... The fine particles obtained in step 3 are sent to the drying and grading process 4, where they are dried in a fluidized bed at 150°C for 50 minutes and graded to obtain particles of 0.2–3.0 mm. These particles are then sent to the roasting and consolidation process 5, where they are roasted in a rotary kiln at 1200°C for 15 minutes. The roasted product is then sent to the cooling process 6, where it is cooled by exchanging heat with air using a fluidized bed cooler to obtain iron ore consolidated material. The air after heat exchange passes through the dust collection process 7 and is then sent to the drying and grading process 4. The sieved material from the drying and grading process 4 is sent to the mixing process 1, while the flue gas is sent to the dust removal process 8. After the flue gas undergoes environmental protection treatment to meet the standards, it is discharged, and the collected dust is returned to the mixing process 1.

[0036] In this embodiment, the yield of the consolidated material was 92.2%, the wear rate of the obtained consolidated material was 2.3%, and the average particle strength was 33.4 N / mm². 2 In a pure hydrogen atmosphere at 850℃, the adhesion test can be passed, meaning that no agglomeration or sticking is observed between the particles.

[0037] Example 3

[0038] This embodiment employs the method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction described in Example 1. The method uses vanadium-titanium magnetite powder with a total iron content of 54.7% and a particle size of -0.044mm of 57.3% as raw material, which is fed into mixing step 1 along with 2.0% MgO and 0.01% starch. After uniform mixing in a ball mill, the mixture is fed into granulation step 2, where 10% of the iron ore mass of process water is added. The mixture is then processed using a briquetting machine for 5 minutes to obtain near-spherical granules. The obtained granules are then fed into a high-speed granulation step 3. The high-speed shear mixing granulator operates at a disc speed of 100 rpm and a rotor speed of 1500 rpm for 6 minutes, obtaining near-spherical fine granules. The high-speed granulation step 3... The fine-diameter particles are sent to the drying and grading process 4, where they are dried at 100°C for 30 minutes in a drum dryer. The particles, ranging from 0.6 to 2.0 mm, are then graded using a vibrating screen and sent to the roasting and consolidation process 5. The particles are roasted at 1000°C for 30 minutes in a fluidized bed. The roasted product is then sent to the cooling process 6, where a three-stage cyclone cooler is used to exchange heat with a mixture of air and nitrogen to obtain the iron ore consolidated material. The air after heat exchange passes through the dust collection process 7 and is then sent to the drying and grading process 4. The sieved material from the drying and grading process 4 is sent to the mixing process 1, while the flue gas is sent to the dust removal process 8. After the flue gas undergoes environmental protection treatment to meet the standards, it is discharged. The collected dust is then returned to the mixing process 1.

[0039] In this embodiment, the yield of the consolidated material was 87.8%, the wear rate of the obtained consolidated material was 3.1%, and the average particle strength was 35.2 N / mm². 2 In a pure hydrogen atmosphere at 850℃, the adhesion test can be passed, meaning that no agglomeration or sticking is observed between the particles.

[0040] Example 4

[0041] This embodiment employs the method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction described in Example 1. The method uses hematite powder with a total iron content of 60.4% and a particle size of -0.044mm of 50.3% as raw material, which is fed into mixing step 1 along with 0.5% CaO and 2% sodium alginate. After uniform mixing under the action of a high-speed shearing machine, it is fed into granulation step 2, where 6% of the iron ore mass of process water is added. The mixture is then processed using a drum granulator for 12 minutes to obtain near-spherical granules. The obtained granules are then fed into a high-speed granulation step 3. The high-speed shearing mixing granulator has a tray speed of 10 rpm, a rotor speed of 100 rpm, and a granulation time of 10 minutes, resulting in near-spherical fine granules. The high-speed granulator... The fine particles obtained in step 3 are sent to the drying and grading process 4, where they are dried in a fluidized bed at 150°C for 20 minutes and graded to obtain particles of 0.2–1.5 mm. These particles are then sent to the roasting and consolidation process 5, where they are roasted in a rotary kiln at 800°C for 30 minutes. The roasted product is then sent to the cooling process 6, where a particle flow cooler is used to exchange heat with air and then with water to obtain iron ore consolidated material. The air after heat exchange passes through the dust collection process 7 and is then sent to the drying and grading process 4. The screened material from the drying and grading process 4 is sent to the mixing process 1, while the flue gas is sent to the dust removal process 8. After the flue gas undergoes environmental protection treatment to meet the standards, it is discharged, and the collected dust is returned to the mixing process 1.

[0042] In this embodiment, the yield of the consolidated material was 91.6%, the wear rate of the obtained consolidated material was 2.8%, and the average particle strength was 33.6 N / mm². 2 In a pure hydrogen atmosphere at 850℃, the adhesion test can be passed, meaning that no agglomeration or sticking is observed between the particles.

[0043] Example 5

[0044] This embodiment employs the method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction described in Example 1. The method uses hematite powder with a total iron content of 50.4% and a particle size of -0.044mm of 54.8% as raw material. This powder, along with 2% bentonite, 0.5% glucose, and 0.02% sodium carboxymethyl cellulose, is fed into mixing step 1. After uniform mixing under the action of a high-speed shearing machine, it is fed into granulation step 2. Process water at 8% of the iron ore mass is added, and the mixture is processed using a disc granulator for 8 minutes to obtain near-spherical granules. The obtained granules are then fed into a high-speed granulation step 3. The high-speed shearing mixing granulator has a disc rotation speed of 200 rpm, a rotor speed of 1000 rpm, and a granulation time of 8 minutes. Near-spherical fine granules are obtained under the action of the high-speed shearing mixing granulator. The fine-diameter particles obtained from the high-speed granulation process 3 are fed into the drying and grading process 4, where they are dried at 200°C for 10 minutes in a drum dryer. The particles, ranging from 0.5 to 1.5 mm, are then graded using a vibrating screen and fed into the roasting and consolidation process 5. The particles are roasted at 1000°C for 25 minutes in a fluidized bed. The roasted product is then fed into the cooling process 6, where it is cooled by exchanging heat with air using a fluidized bed cooler to obtain the iron ore consolidated material. The air after heat exchange passes through the dust collection process 7 and is then fed into the drying and grading process 4. The sieved material from the drying and grading process 4 is fed into the mixing process 1, while the flue gas is fed into the dust removal process 8. The flue gas is then discharged after environmental protection treatment to meet the standards, and the collected dust is returned to the mixing process 1.

[0045] In this embodiment, the yield of the consolidated material was 90.7%, the wear rate of the obtained consolidated material was 3.2%, and the average particle strength was 34.1 N / mm². 2 In a pure hydrogen atmosphere at 850℃, the adhesion test can be passed, meaning that no agglomeration or sticking is observed between the particles.

[0046] Example 6

[0047] This embodiment employs the method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction described in Example 1. The method uses hematite powder with a total iron content of 55.7% and a particle size of -0.044mm of 52.3% as raw material. This powder is fed into a mixing step 1 with 0.5% bentonite, 1.5% Ca(OH), 1.4% sucrose, and 0.05% carboxymethyl cellulose. After uniform mixing in a ball mill, the mixture is fed into a granulation step 2, where 5.5% of the iron ore mass of process water is added. The mixture is then processed using a disc granulator for 12 minutes to obtain near-spherical granules. The obtained granules are then fed into a high-speed granulation step 3, where the disc speed of the high-speed shear mixing granulator is 60 rpm, the rotor speed is 500 rpm, and the granulation time is 8 minutes. Near-spherical fine particles are obtained under the action of the high-speed shear mixing granulator. Granular material: The fine-diameter particles obtained from the high-speed granulation process 3 are sent to the drying and grading process 4, where they are dried at 120°C for 45 minutes in a drum dryer. The particles, ranging from 0.3 to 2.6 mm, are then graded using a vibrating screen and sent to the roasting and consolidation process 5. The particles are roasted at 500°C for 60 minutes in a fluidized bed. The roasted product is then sent to the cooling process 6, where it is cooled by exchanging heat with nitrogen using a three-stage cyclone cooler to obtain iron ore consolidated material. The air after heat exchange passes through the dust collection process 7 and is then sent to the drying and grading process 4. The screened material from the drying and grading process 4 is sent to the mixing process 1, while the flue gas is sent to the dust removal process 8. After environmental treatment to meet the standards, the flue gas is discharged, and the collected dust is returned to the mixing process 1.

[0048] In this embodiment, the yield of the consolidated material was 87.4%, the wear rate of the obtained consolidated material was 2.3%, and the average particle strength was 34.6 N / mm². 2 In a pure hydrogen atmosphere at 850℃, the adhesion test can be passed, meaning that no agglomeration or sticking is observed between the particles.

[0049] Example 7

[0050] This embodiment employs the method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction described in Example 1. The method uses hematite powder with a total iron content of 53.5% and a particle size of -0.044mm of 58.3% as raw material, which is fed into mixing step 1 along with 3% light-burned dolomite, 0.5% Mg(OH), 0.01% fructose, and 0.25% sodium alginate. After uniform mixing in a drum mixer, the mixture is fed into granulation step 2, where 6.7% of the iron ore mass of process water is added. The mixture is then processed in a disc granulator for 18 minutes to obtain near-spherical granules. The obtained granules are then fed into a high-speed granulation step 3, where the disc speed of the high-speed shear mixing granulator is 120 rpm, the rotor speed is 1000 rpm, and the granulation time is 10 minutes. Under the action of the high-speed shear mixing granulator, near-spherical granules are obtained. Spherical fine particulate material: The fine particles obtained from the high-speed granulation process 3 are sent to the drying and grading process 4, where they are dried in a fluidized bed at 180°C for 45 minutes. The particles of 0.2–2.0 mm are then graded by a vibrating screen and sent to the roasting and consolidation process 5, where they are roasted in a rotary kiln at 1200°C for 15 minutes. The roasted product is then sent to the cooling process 6, where it is cooled by exchanging heat with argon gas in a fluidized bed cooler to obtain iron ore consolidated material. The air after heat exchange is sent to the drying and grading process 4 after passing through the dust collection process 7. The screened material from the drying and grading process 4 is sent to the mixing process 1, while the flue gas is sent to the dust removal process 8. The flue gas is discharged after environmental protection treatment to meet the standards, and the collected dust is returned to the mixing process 1.

[0051] In this embodiment, the yield of the consolidated material was 88.3%, the wear rate of the obtained consolidated material was 3.6%, and the average particle strength was 32.8 N / mm². 2 In a pure hydrogen atmosphere at 850℃, the adhesion test can be passed, meaning that no agglomeration or sticking is observed between the particles.

[0052] Unless otherwise specified, "%" in this invention refers to mass percentage.

[0053] The upper and lower limits of the process parameters (such as temperature, time, etc.) and the range values ​​of the present invention can all achieve the method, and examples are not listed here.

[0054] All aspects not described in detail in this invention can be covered using conventional technical knowledge in the field.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction, the method comprising the following steps: mixing step (1), pelletizing step (2), high-speed granulation step (3), drying and grading step (4), roasting and consolidation step (5), cooling step (6), dust collection step (7), and dust removal step (8), specifically carried out according to the following steps: 1) The iron ore powder raw material and the additives are fed into the mixing process (1) together to make them evenly mixed; the additives are a mixed additive composed of inorganic and organic substances, wherein the inorganic additives are one or more of CaO, Ca(OH)2, MgO, Mg(OH)2, lightly calcined dolomite, magnesite, and clay minerals, and the amount of the additives is 0.5~6% of the mass of the iron ore powder; the organic additives are one or more of carboxymethyl cellulose, starch, sodium alginate, sodium carboxymethyl cellulose, sodium carboxymethyl starch, glucose, sucrose, and fructose, and the amount of the additives is 0.01~2% of the mass of the iron ore powder; 2) The mixture obtained in the mixing process (1) and water are fed into the pelletizing process (2), and under the action of the pelletizing equipment, they are formed into near-spherical particles; 3) The near-spherical particles obtained in the pelletizing process (2) are fed into the high-speed granulation process (3). A high-speed shearing mixing granulation equipment is used, with a material tray speed of 10~200 rpm, a rotor speed of 100~2500 rpm, and a granulation time of 5~30 min to obtain near-spherical fine-diameter particles. 4) The fine particles obtained in the high-speed granulation process (3) are sent to the drying and grading process (4), where they are dried using a drum dryer and screened using a mechanical vibrating screen, or screened using a fluidized bed dryer; they are dried under the action of hot air obtained in the cooling process (6), with a drying temperature of 80~200℃ and a drying time of 10~60min; the lower limit of the grading particle size is 0.2~0.6mm and the upper limit is 1.5~3.0mm; the residue is returned to the mixing process (1); the flue gas is sent to the dust removal process (8), and then discharged after environmental protection treatment to meet the standards. 5) The dried material obtained from the drying and grading process (4) is sent to the roasting and consolidation process (5). A rotary kiln or fluidized bed is used for roasting and consolidation. The roasting temperature is 500~1200℃ and the roasting time is 15~60min, so that it can be consolidated under high temperature conditions. The consolidation flue gas is sent to the dust collection process (7) and then to the drying and grading process (4). The dust collection material is returned to the mixing process (1). 6) The solidified product obtained from the roasting and solidification process (5) is sent to the cooling process (6) to obtain iron ore solidified material suitable for fluidized bed direct reduction. The iron ore solidified material is cooled by air, and the recovered heat is sent to the drying and grading process (4) to dry the granulated material.

2. The method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction according to claim 1, characterized in that, The iron ore powder is one or a combination of magnetite and hematite, with a total iron content of ≥50% and a particle size of -0.044mm content of ≥50%.

3. The method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction according to claim 1, characterized in that, The iron ore powder is vanadium-titanium magnetite, with a total iron content of ≥50% and a particle size of -0.044mm content of ≥50%.

4. The method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction according to claim 1, characterized in that, The mixing process (1) adopts a mixing method of ball milling or high-speed shearing.

5. The method for granulation and consolidation of iron ore raw materials for fluidized bed direct reduction according to claim 1, characterized in that, The pelletizing process (2) uses one of a disc pelletizer, a drum pelletizer, or a briquetting machine, with water added at 3% to 10% of the iron ore powder mass, and the pelletizing time is 5 to 20 minutes.

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