Method for producing iron ore briquettes for direct reduction reaction furnace and briquette product

Abstract

The invention discloses a production method of an iron ore block mass for a direct reduction reaction furnace. The production method comprises the following steps: dispersing a nano material in a binder; mixing with iron ore powder and / or steelmaking byproducts and additives; adjusting moisture; carrying out agglomeration; solidifying the block mass; the surface of the briquette is coated with a coating to reduce blocking effects in a direct reduction reaction furnace.

Description

Technical Field

[0001] The present invention belongs to the technical field of mining and metallurgy, and relates to a method for producing iron ore agglomerates for replacing pellets and lump ore conventionally used in direct reduction (DR) reactors. Background Art

[0002] A direct reduction reactor is characterized by its ability to reduce iron ore to metallic iron without melting the reactor charge. The resulting metallic product in the solid phase is called sponge iron (also known as direct reduced iron (DRI)), which can be hot-pressed into briquettes, producing hot briquetted iron (HBI).

[0003] Direct reduction (DR) is an alternative to using blast furnaces to produce an intermediate product that essentially functions like pig iron. Both intermediate products (pig iron and sponge iron) are used in steel mills to produce steel, with sponge iron primarily used in electric furnaces. The best-known DRM processes include Midrex, HyL (Hayata y Lamina), Armco, H.Iron, SL-RN, and Purofer.

[0004] In order to ensure that the direct reduction reactor performs optimally and obtains a high-quality final product (sponge iron), the iron ore agglomerates to be fed need to have specific physical, chemical and metallurgical properties.

[0005] The prior art provides several technologies for agglomerating ores for use in direct reduction reactors. However, as described in the present invention, these technologies are unable to produce agglomerates with specific metallurgical properties, and therefore cannot achieve optimal performance in direct reduction reactors.

[0006] Brazilian patent BR102019023195-5, filed in the name of Vale SA, describes a type of iron ore briquette used to replace metallic charge in blast furnaces. Unlike the present invention, the briquette produced in this patent lacks specific properties and cannot be directly used in reduction reactors such as Midrex and HyL. Furthermore, Brazilian patent BR102019023195-5 uses different raw materials, such as flux, than the present invention. Furthermore, this patent does not address the coating application step encompassed by the present invention.

[0007] Brazilian patent BR112014005488-6, also filed in the name of Vale SA, describes a process for producing agglomerates that differs from the present invention in several respects, including (i) the use of different raw materials, (ii) the absence of a coating step, (iii) its suitability for agglomerates produced by granulation techniques (e.g., small pellets), and (iv) the product protected by this patent does not meet the physical and chemical requirements required for direct reduction processes.

[0008] Brazilian Patent BR102022006033-9, also filed in the name of Vale SA, describes a briquette production method that differs from the present invention in: (i) using different raw materials; (ii) employing microwave reduction; and (iii) using biomass as a reducing agent. BR102022006033-9 describes a method for obtaining reduced materials using microwave technology and biomass. The resulting pre-reduced briquettes (>60% metallic iron) are merely an intermediate step for subsequent use in various reactors.

[0009] Kleiton Lovati's 2019 master's thesis, "Development of self-reducing briquets with coating agents" (Desenvolvimento de briquetes autorredutores com agente de recobrimento), describes a method for producing self-reducing briquets using coating agents such as dolomitic limestone, bentonite, serpentinite, and steelmaking slag. The present invention differs from this document primarily in the product, which cannot be considered a self-reducing briquet. Self-reducing briquets are composed of iron ore and a significant amount of carbonaceous material, which imparts their self-reducing properties. These briquets are specifically designed for reduction and smelting technologies (e.g., Corex, Finex, Hismelt, Tecnored, Oxicup), whereas the present invention focuses on direct reduction technologies (e.g., Midrex, HyL, Fastmet, Jindal, etc.).

[0010] Renata Penna published a paper in 2010 entitled "Development of a method to assess the reoxidation tendency of iron ore pellets in the direct reduction gas process" à tendênciaà de pelotas de minério de ferro reduzidas em processo de A master's thesis by [author] Direta a Gás describes the effects of degradation on iron ore pellets during direct reduction. This document differs from the present invention in the type of pellets used. Specifically, the document describes pellets produced using a high-temperature agglomeration process (>1300°C), while the present invention deals with low-temperature pellets produced at approximately 250°C.

[0011] Compared to blast furnace production, direct reduction agglomerates must have a higher iron content (>60%) and lower levels of harmful components (Na2O, SiO2, and Al2O3) (<10%). Furthermore, agglomerates for direct reduction must have lower disintegration and higher metallization (>90%) than blast furnace products.

[0012] The present invention relates to a method for producing low-temperature iron ore agglomerates for a direct reduction (DR) reactor. Compared with the prior art, the method has the following advantages:

[0013] 1. Controlling the porosity of the agglomerate by adding organic additives and curing at slightly higher temperatures (burning the added organic material);

[0014] 2. Control bulk density by reducing the compaction pressure and apparent density of the agglomerate;

[0015] 3. Use higher-grade feed (i.e., ore with higher iron content);

[0016] 4. Use single or combined adhesives;

[0017] 5. The final agglomerates obtained have a standard size, which has an important impact on the performance of the final product;

[0018] 6. The final agglomerates obtained have good physical strength, including resistance to weathering, and are suitable for long-distance transportation and loading and unloading;

[0019] 7. The final agglomerates obtained produce less dust in the reduction reactor and have a high metallization rate;

[0020] 8.CO2 emissions are reduced because the curing process occurs at room temperature or low temperature.

[0021] For this type of agglomerate, porosity is crucial for its subsequent use in a direct reduction reactor. Therefore, controlling porosity and bulk density is a key factor in improving the product's performance in a direct reduction reactor.

[0022] For example, controlling porosity ensures that during the direct reduction process, gases can freely flow into and out of the agglomerate structure without compromising its physical properties, i.e., causing it to disintegrate. Otherwise, the product strength would be significantly reduced, failing to meet the minimum performance standards for the process.

[0023] The packing density of the agglomerates can be controlled in a variety of ways, such as adjusting the process conditions, improving the agglomerate surface finish and using (chemical or mineral) additives to ensure optimal porosity.

[0024] Therefore, the present invention is significantly different from the known literature in the prior art. The importance of porosity to the direct reduction product has been confirmed through laboratory scale tests and direct reduction process basket tests of some customers.

[0025] Regarding the production raw materials, it is worth noting that one of the purposes of using a combination of multiple binders is to reduce the content of harmful components (Na2O, SiO2 and Al2O3) in the briquette product.

[0026] Purpose of the Invention

[0027] The general object of the present invention is to provide a novel method for producing iron ore briquettes with high metallurgical properties for use as an alternative to pellets and lump ore in direct reduction reactors. The main characteristics of the resulting briquettes include high physical strength, low fines generation, and high metallization during direct reduction reactor operation.

[0028] Another object of the present invention is to provide a more sustainable method for reducing CO2 emissions in mining-metallurgical production chains. Summary of the Invention

[0029] In its preferred embodiment, the present invention discloses a method for producing iron ore agglomerates for use in direct reduction furnaces as an alternative to pellets and lumps, the method comprising the following steps:

[0030] a) dispersing 0.05 to 2 weight percent of nanomaterial in a binder to obtain a "binder mixture";

[0031] b) mixing 1% to 10% of the binder mixture obtained in step a) with 70% to 99% of iron ore fines and / or steelmaking by-products, and 0% to 5% of chemical and / or mineral additives having properties that promote plasticity and / or improve the porosity of the agglomerates;

[0032] c) adjusting the water content of the mixture so that the water content is 0% to 25% by weight;

[0033] d) agglomeration by briquetting or extrusion;

[0034] e) solidifying the mass;

[0035] f) Applying a coating on the surface of the agglomerates to reduce the sticking effect in the DR reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention is described in detail below with reference to the accompanying drawings:

[0037] Figure 1 is a simplified block diagram of a briquette production method for a direct reduction reactor furnace according to the present invention.

[0038] Figure 2 The comparison shows the evolution of the disintegration results of the obtained agglomerates.

[0039] Figure 3 Shown is an image of agglomerates produced according to the method of the invention after application of a coating that reduces the sticking effect.

[0040] Figure 4 Shown are images of briquettes obtained after basket trials in an industrial-scale direct reduction furnace (DRI).

[0041] Figure 5 A graph showing the pellet (DRI) metallization and carburization rate data obtained after basket testing various pellet samples in Midrex and HyL reactors.

[0042] Figure 6 Shown is a graph of disintegration of briquettes (DRI) data obtained after basket testing of various briquettes samples in Midrex and HyL reactors. DETAILED DESCRIPTION

[0043] Although the present invention may have different embodiments, preferred embodiments have been described in the drawings and explained in the following detailed discussion. It should be understood that this description is intended to illustrate the principles of the invention and is not intended to limit the invention to the contents described herein.

[0044] The subject matter of the present invention will be described in detail below by way of example and not limitation. The materials and methods disclosed herein may include different details and procedures without departing from the scope of the present invention. Unless otherwise indicated, all components and percentages disclosed below are by weight.

[0045] The main method of the present invention relates to a method for producing iron ore briquettes for replacing pellets and lump ore in a direct reduction furnace, the method comprising the following steps:

[0046] a) dispersing 0.05 to 2 weight percent of nanomaterial in a binder to obtain a "binder mixture";

[0047] b) mixing 1% to 10% of the binder mixture obtained in step a) with 70% to 99% of iron ore fines and / or steelmaking by-products, and 0% to 5% of chemical and / or mineral additives having properties that promote plasticity and / or improve the porosity of the agglomerates;

[0048] c) adjusting the water content of the mixture so that the water content is 0% to 25% by weight;

[0049] d) agglomeration by briquetting or extrusion;

[0050] e) solidifying the mass;

[0051] f) Applying a coating on the surface of the agglomerates to reduce the sticking effect in the DR reactor.

[0052] like Figure 1 As shown in the block diagram, the agglomerate production method preferably begins by dispersing the nanomaterial in a binder under mechanical stirring. The nanomaterial is used in an amount, by weight, of 0.05% to 2% of the binder in the mixture. The nanomaterial used in step a) can include carbon nanotubes, exfoliated graphite, functionalized microsilicates, tubular nanosilica, tubular halloysite, carbon nanofibers, graphene, and the like.

[0053] The binder used in step a) may be composed of sodium silicate, plant tar, asphalt, starch, phenolic resin, molasses, etc. Such binders bind particles by adhesion and / or chemical interaction and can be used alone or in combination to improve the strength of the agglomerate.

[0054] Step b) of the method of the present invention comprises adding 1% to 10% of the binder mixture obtained in step a) to 70% to 99% by weight of iron ore fines and / or steelmaking by-products, and adding 0% to 5% by weight of chemical and / or mineral additives, followed by mixing in an intensive mixer for up to 4 minutes. Additives used as plasticizers include bentonite, asphalt, tar, starch, and slaked lime, which have the property of improving plastic forming ability in the subsequent agglomeration step. Pore-forming agents such as asphalt, tar, phenolic resin, glucose, starch, molasses, glycerol, carboxymethyl cellulose (CMC), and biomass are also used as additives to increase the porosity of the solidified agglomerates.

[0055] The iron ore fines and steelmaking by-products used in step b) of the method of the present invention preferably meet the following conditions: Fe 总含量 >60%, SiO2 <5%, Al2O3 <2%, 98% particle size <6mm, and a maximum moisture content of 25%. Steel by-products used may consist of pellet fines, DRI (direct reduced iron) fines, sludge, scale (accumulation), etc. The quality of these by-products may vary from plant to plant, so their use as raw materials must meet the aforementioned conditions and be previously laboratory tested.

[0056] In step c) of the method of the present invention, water is added to adjust the moisture content of the mixture so as to reach the optimum moisture content of 0% to 25% required for the agglomeration step.

[0057] Step d) of the process of the present invention involves agglomeration by briquetting or extrusion.

[0058] For extrusion briquetting, the optimal moisture content should be controlled within the range of 8% to 25%. In addition to adding binders and additives, the strength and porosity of the raw briquette can be adjusted during the production process by adjusting the negative pressure of the equipment (i.e., the extruder). The resulting extrudate is a cylindrical tube with a diameter of 5mm to 50mm and a length of 50mm to 200mm.

[0059] For briquetting, the moisture content of the mixture is preferably controlled between 1% and 7%. Briquetting is performed in a roller press with an appropriate cavity to produce pillow-shaped briquettes with geometric dimensions of 15-50 mm x 10-40 mm x 5-25 mm. This geometry and proper control of its dimensions, combined with the raw materials used and process conditions, result in briquettes with increased mechanical strength, resulting in superior performance.

[0060] During the briquetting process, the roller pressure and speed, the roller spacing (maintaining a minimum spacing to prevent cracking and / or burring of the briquette), and the feed rate must be controlled to obtain an apparent density of less than 3.8 g / cm 3 And the bulk density does not exceed 50% of the briquette, thus meeting the metallurgical performance requirements.

[0061] Roller pressure and speed control is achieved by adjusting the current intensity of the briquetting machine, and the specific adjustment method depends on the machine model. Due to the significant differences in the type, brand and capacity of briquetting machines, it is impossible to preset a unified current intensity range. Therefore, the best and reproducible control method applicable to different machine models is to calculate the linear force, with a recommended value of 15kN / cm3 to 30kN / cm3. The higher the current intensity, the stronger the bonding between the particles, resulting in higher compaction (bulk density and apparent density) and lower porosity. However, it is necessary to find an optimal balance between the bulk density, apparent density, porosity and physical quality of the agglomerate.

[0062] Step e) of the present method involves curing the agglomerate, which can be accomplished in a gas furnace, electric furnace, infrared furnace, electromagnetic furnace, or at room temperature. The curing temperature and time for different furnace types are determined by the type of binder or binder mixture used. If pure sodium silicate is used as the binder, curing in an electric furnace, infrared furnace, or gas furnace at 100°C to 550°C for 10 to 30 minutes is recommended. For electromagnetic microwave ovens, the curing time is 2 to 15 minutes. For room temperature curing, the curing time can be up to 15 days.

[0063] Step f) applies a layer of chemical or mineral additives by dipping, spraying, or other techniques to reduce sticking of the agglomerates in the direct reduction reactor. Examples of such additives include bauxite, bentonite, serpentine, cement, magnesium hydroxide, limestone, and combinations thereof. The amount of coating agent used per ton of agglomerates ranges from 1 kg to 10 kg. The coating is applied as a water-based suspension.

[0064] The iron ore agglomerates produced by the method of the present invention have excellent physical, chemical and metallurgical properties and can replace pellets and lump ore in direct reduction furnaces, improving the efficiency and production capacity of the metallurgical chain. The characteristics of the final agglomerates include:

[0065] High iron content (Fe > 60%)

[0066] ●Low content of harmful ingredients (Na2O, SiO2 and Al2O3 <5%)

[0067] Low disintegration (<10%, can be <5%)

[0068] ●High metallization rate (>90%, up to 99.5%)

[0069] The excellent performance of the briquettes obtained by the present invention in a direct reduction reactor is attributed to the strict control of three key parameters throughout the production process:

[0070] ●Bulk density <50%

[0071] Apparent density <3.8 g / cm 3

[0072] ●Porosity>40%, pores are interconnected

[0073] For this type of briquettes, porosity is crucial for their subsequent use in the direct reduction reactor. Controlling porosity ensures that gases can freely flow into and out of the briquettes during the direct reduction process without affecting their physical quality. Otherwise, the product's strength will be significantly reduced during the reduction phase, failing to meet the minimum performance requirements of the production process. Furthermore, the briquettes will disintegrate, generating fines that can negatively impact the production process within the direct reduction reactor.

[0074] Figure 2 The comparison shows the evolution of the disintegration results obtained during the research and development (R&D) carried out to optimize the present invention. Figure 2 A shows a briquette obtained using a method known in the art, which briquette exhibits high disintegration values of about 40% to 65%. Figure 2 B shows the first stage of evolution results obtained during the research and development (R&D) process, with disintegration values falling to between 20% and 30%. Figure 2 C shows a briquette obtained by the process described in the present invention, with a disintegration value lower than 10%.

[0075] The bulk density (or compaction) of the particles directly affects the disintegration of the agglomerates in the DR reactor and also improves the metallization rate. As mentioned above, lower density agglomerates have higher porosity, which allows for a more uniform (and gentler) flow of gases into and out of the DR reactor during metallurgical operations.

[0076] The present invention achieves optimal bulk density and porosity parameters by adjusting agglomeration conditions, optimizing agglomerate surface smoothness, and using (chemical or mineral) additives to increase porosity.

[0077] Example

[0078] The method according to the present invention produces iron ore fines agglomerates specifically for use in a direct reduction reactor.

[0079] The iron ore feedstock used was 96% pellets by weight, with an iron content of 68.5% and a particle size of <0.15 mm. Sodium silicate and nanomaterials were used as binders. Starch and slaked lime were used as additives. A briquetting process was used to produce pillow-shaped briquettes with the following dimensions: 25 x 20 x 15 mm.

[0080] The briquetting press uses a current between 30 and 40 amps, corresponding to a linear force of approximately 15.7 to 29.4 kN / cm. The briquettes are cured in a gas-fired furnace at temperatures between 250°C and 350°C for 30 minutes. After curing, the briquettes are coated with cement by spraying.

[0081] like Figure 3 As shown in , chemical-physical-metallurgical tests were performed on the obtained briquettes to verify the quality of the final briquettes. The following Table 1 lists the chemical and physical quality test results of different briquettes samples:

[0082]

[0083] The images of DRI agglomerates obtained after Midrex and HyL industrial reactor basket tests are shown below. Figure 4 As shown, the quality data of DRI agglomerates (metallization rate and carburization rate) are as follows Figure 5 As shown, the disintegration data under reducing conditions are as follows Figure 6 shown.

[0084] Therefore, although only some embodiments of the present invention are shown, it should be understood that those skilled in the art can make various omissions, substitutions or modifications without departing from the spirit and scope of the present invention. In any respect, the embodiments are only for illustrative and non-restrictive interpretation.

[0085] It should be clearly stated that any combination of elements that achieve the same function and obtain the same effect in substantially the same manner is within the scope of the present invention. Replacing certain elements in one embodiment with other elements is also within the scope of the present invention.

Claims

1. A method for producing iron ore agglomerates for a direct reduction reactor, characterized in that: The method comprises the following steps: a) dispersing 0.05 to 2 weight percent of a nanomaterial in a binder to obtain a binder mixture; b) mixing 1% to 10% of the binder mixture obtained in step a) with 70% to 99% of iron ore fines and / or steelmaking by-products and 0% to 5% of additives in an intensive mixer; c) adjusting the water content of the mixture so that the water content is 0% to 25% by weight; d) agglomeration by briquetting or extrusion; e) solidifying the mass; f) applying a coating on the surface of the agglomerates to reduce the sticking effect in the direct reduction reactor.

2. The method according to claim 1, characterized in that The nanomaterial used in step a) is selected from the group consisting of carbon nanotubes, exfoliated graphite, functionalized microsilicate, tubular nanosilica, tubular halloysite, carbon nanofibers and graphene.

3. The method according to claim 1, characterized in that The binder used in step a) is selected from the group consisting of sodium silicate, vegetable tar, asphalt, starch, phenolic resin and molasses.

4. The method according to claim 1, wherein The iron ore powder and steelmaking by-products used in step b) meet the following conditions: Fe 总含量 >60%, SiO2<5%, Al2O3<2%, and 98% particle size <6mm.

5. The method according to claim 1, wherein The additive used in step b) is selected from the group consisting of bentonite, asphalt, tar, slaked lime, phenolic resin, glucose, starch, molasses, glycerol, carboxymethyl cellulose (CMC) and biomass.

6. The method according to claim 1, characterized in that The mixing in step b) is carried out in an intensive mixer for a maximum time of 4 minutes.

7. The method according to claim 1, characterized in that The agglomeration in step d) is carried out in an extruder, and the obtained extrudate is a cylindrical tube with a diameter of 5 mm to 50 mm and a length of 50 mm to 200 mm.

8. The method according to claim 1, characterized in that The agglomeration in step d) is carried out in a roller press to produce pillow-shaped briquettes with geometric dimensions of 15-50 mm x 10-40 mm x 5-25 mm.

9. The method according to claim 1, characterized in that The agglomeration in step d) is carried out in a roller press, and the bulk density of the obtained agglomerates is less than 50%, and the apparent density is less than 3.8 g / cm 3 , porosity>40%, and the pores are interconnected.

10. The method according to claim 1, characterized in that The briquetting in step d) is performed in a briquetting machine, and the linear force is controlled in the range of 15 kN / cm to 30 kN / cm.

11. The method according to claim 1, wherein The curing in step e) can be performed in a gas furnace, an electric furnace, an infrared furnace, an induction furnace or at room temperature.

12. The method according to claim 11, characterized in that The curing performed in the gas furnace, the electric furnace or the infrared furnace is performed at a temperature of 100° C. to 550° C. for 10 to 30 minutes.

13. The method according to claim 11, characterized in that The curing is performed in the induction cooker for 2 minutes to 15 minutes.

14. The method according to claim 11, characterized in that The curing performed at room temperature can last up to 15 days.

15. The method according to claim 1, wherein The coating agent in step f) is applied by dipping or spraying using a chemical additive or mineral additive having surface coating properties, wherein the additive is selected from the group consisting of bauxite, bentonite, serpentine, cement, magnesium hydroxide, limestone, and combinations thereof.

16. The method according to claim 1, wherein The amount of the coating agent in step f) is 1 kg to 10 kg per ton of agglomerates.

17. An iron ore agglomerate produced according to the method of claims 1 to 16, characterized in that The iron ore agglomerates have ideal physical, chemical and metallurgical properties for replacing pellets and lump ores in direct reduction furnaces, namely: Fe>60%, harmful components (Na2O, SiO2 and Al2O3)<10%, disintegration<10%, metallization>90%, bulk density<50%, and apparent density<3.8g / cm 3 , porosity>40%, and the pores are interconnected.

18. The agglomerate according to claim 17, wherein The iron content of the agglomerate is between 65.1% and 67.5%, the content of harmful components (Na2O, SiO2 and Al2O3) is less than 5%, the disintegration degree is less than 5%, and the metallization rate is between 91.2% and 99.5%.

Images