A method for preparing blast furnace burden with low-carbon sinter return fines

Abstract

The invention discloses a method for preparing blast furnace burden with low carbon from sinter return fines, belonging to the technical field of iron and steel metallurgy. The method is to fully mix sinter return fines with undersize of blast furnace lump ore, combustible organic waste powder, fine-grained metallized materials, iron-containing dust, binder and water, and then form them by high-pressure roll compaction. The obtained wet agglomerates are dried and consolidated at low temperature to obtain cold-compressed briquettes. The whole process of this method is low-carbon, which can consume resources such as sinter return fines, combustible organic waste resources, fine-grained metallized materials, iron-containing dust, etc., reduce the accumulation of solid waste, and reduce the energy consumption and carbon emissions in the iron and steel production process.

Description

Technical Field

[0001] The present invention relates to a method for preparing blast furnace burden with low carbon from sinter return fines, and particularly to a method for cold pressing and forming by adding fine-grained metallized materials and combustible organic waste powders to sinter return fines to prepare blast furnace burden with low carbon, belonging to the field of iron and steel metallurgy. Background Art

[0002] The iron and steel industry is one of the main sources of global carbon emissions, especially the blast furnace-converter long process smelting process, whose carbon emissions account for a considerable proportion of the global manufacturing carbon emissions. Currently, as a key industry, the iron and steel industry is facing severe challenges in reducing carbon emissions, optimizing energy utilization, and improving the efficiency of resource recycling. Therefore, researching and developing low-carbon and efficient methods for preparing blast furnace burden to reduce carbon emissions during ironmaking has become an important development direction of iron and steel metallurgy technology.

[0003] In traditional ironmaking processes, blast furnaces mainly use iron-containing burdens such as sinter, pellets, and lump ores. Among them, sinter accounts for a large proportion of the blast furnace burden due to its good metallurgical properties and economy. However, the carbon emissions of the sintering process are relatively high, mainly from fuel combustion (such as coke powder and coal powder). Therefore, reducing the use of sinter and optimizing the burden structure are of great significance for reducing blast furnace carbon emissions.

[0004] During the sintering and blast furnace smelting processes, a large amount of return fines (such as sinter return fines and blast furnace return fines) will be generated. These return fines are mainly composed of unreacted sinter materials, iron ores, iron-containing dust and sludge, etc., and have a relatively high iron content (generally 40% - 60%). Currently, most of the return fines are directly recycled to the sintering process. On the one hand, recycling sinter return fines requires additional fuel, electricity, and labor. The energy consumption per ton of sintering process is up to 48.50 kgce, and the thermal efficiency of recycling sinter return fines is only 20% - 30%, resulting in an increase in comprehensive energy consumption by more than 70%. On the other hand, due to its powdery characteristics, excessive addition will affect the air permeability of the sintering material, thereby reducing the strength and output of sinter. Therefore, how to efficiently and low-carbon utilize sinter return fines has become an urgent problem for iron and steel enterprises to solve.

[0005] To solve the above problems, the cold briquetting technology has attracted attention due to its characteristics of not requiring high-temperature roasting, low energy consumption, and the ability to consume solid waste. The literature ("Effect of Briquetting Pressure on the Properties, Reduction Behavior, and Reduction Kinetics of Cold-Bonded Briquette Prepared From Return Fines of Sinter", Li Y, et al., Metallurgical and Materials Transactions B, 2023, 54(1): 355-369.) used 7% of a composite binder added to sinter return fines for extrusion molding, with a molding pressure of 240 MPa. The formed briquettes were placed at room temperature for 14 days, and then dried at 130 °C for 12 h, with a strength of 2619 N / P and a thermal strength of 1245 N / P. ("Study on the Properties and Reduction Behavior of Cold Briquettes Prepared from Sinter Return Fines", Zang Yonggang, Master's degree thesis, Guizhou University, May 2023) used sinter return fines as the iron-containing raw material for extrusion molding, and compared the bonding effects of corn starch and the composite binder, with binder ratios of 2.5% and 6.15% respectively. The compressive strength of the cold briquettes with corn starch added was 2915 N / P, the compressive strength of the cold briquettes with the composite binder added was 2018 N / P, the residual strength after the low-temperature reduction degradation test was 1134 N / P, and the strength after the reduction test was 336 N / P.

[0006] In summary, currently, sinter return fines are mainly still returned to the sintering process for treatment, resulting in huge carbon emissions and low energy utilization efficiency. The cold briquetting process for sinter return fines has not been applied on a large scale, and there are still problems such as high binder price, high harmful element content, and long consolidation time of the formed briquettes. Summary of the Invention

[0007] Aiming at the above defects existing in the existing cold briquetting process for sinter return fines, the purpose of the present invention is to provide a method for preparing blast furnace burden with low carbon from sinter return fines. This method uses sinter return fines as the main raw material, regulates the raw material composition by adding undersize of blast furnace lump ore, combustible organic waste powder, fine-grained metallized material, iron-containing dust, etc., and adds a binder for high-pressure molding - low-temperature drying consolidation to prepare sinter return fines cold briquettes that meet the performance requirements of blast furnace burden. This method can utilize sinter return fines, fine-grained metallized materials, and combustible organic waste resources with low carbon and high efficiency, and has the characteristics of simple process, low energy consumption, and less carbon emissions compared with directly returning the return fines to the sintering process for treatment.

[0008] In order to achieve the above technical objectives, the present invention provides a method for preparing blast furnace burden with low-carbon sinter return. The method is to fully mix the sinter return with the undersize of blast furnace lump ore, combustible organic waste powder, fine-grained metallized material, iron-containing dust, binder and water, and then form it by high-pressure roll compaction. The obtained wet agglomerate is dried and consolidated at low temperature to obtain a cold-pressed briquette. The sinter return, the undersize of blast furnace lump ore, the combustible organic waste powder, the fine-grained metallized material and the iron-containing dust are composed according to the following mass percentages: 92.5% - 93.5% : 5% - 6% : 1% - 2% : 0.5% - 1.5%.

[0009] The key to the technical solution of the present invention lies in adding a small amount of undersize of blast furnace lump ore, combustible organic waste powder, fine-grained metallized material, iron-containing dust and other raw materials to the sinter return for component regulation, and through cold pressing and rapid consolidation under the action of the binder, preparing an iron-containing burden meeting the requirements of the blast furnace with low carbon and high efficiency. The reason why the present invention can prepare an iron-containing burden meeting the requirements of the blast furnace from the sinter return is mainly due to the efficient coupling effect among multiple components in the raw material system, which can improve the strength of the cold-pressed briquette, reduce carbon emissions and improve its metallurgical properties.

[0010] In terms of improving the strength of the cold-pressed briquette: on the one hand, the introduced combustible organic waste powder can be evenly distributed on the surface of the return ore particles during the mixing process to form an interfacial transition layer; at the same time, it has excellent compressibility and can effectively fill the gaps between the coarse return ore particles through plastic deformation during the forming stage, which can improve the bulk density of the raw materials and reduce the stress concentration phenomenon caused by too high porosity during the pressing process; moreover, the organic components in the combustible organic waste powder form chemical bonding with the binder, further strengthening the interfacial bonding strength and enhancing the strength of the agglomerate. On the other hand, there is a coupling effect between the introduced fine-grained metallized material and the iron-containing dust. The fine-grained metallized material has a relatively high content of metallic iron, and the chloride salt in the iron-containing dust can be used as a rusting agent to accelerate the rusting reaction on the surface of metallic iron. The strength of the cold-pressed briquette is improved through rusting consolidation, and the fine-grained metallized material has good plasticity and can achieve densification filling through particle extension deformation during the cold pressing process, which can significantly improve the strength of the cold-pressed briquette.

[0011] In terms of low carbon emissions: it can effectively utilize the resources of combustible organic waste and reduce the total energy consumption of iron and steel production. Adding combustible organic waste powder to the cold-pressed briquette raw materials not only takes advantage of the characteristics of the combustible organic waste powder having a relatively high content of organic matter, which can burn and supply heat during the blast furnace reduction process, reducing the consumption of fossil energy, but also the combustible organic waste powder will decompose into a large number of organic small molecule gases (such as CO, H2, CH4, etc.) at high temperatures during the blast furnace reduction process and can participate in the reduction of iron oxides as a reducing agent, further reducing the coke ratio of the blast furnace.

[0012] In terms of improving the metallurgical properties of cold-compressed briquettes: The microporous structure formed by the decomposition of combustible organic waste powder at high temperatures is conducive to the diffusion of reducing gases, which can improve the metallurgical properties of cold-compressed briquettes. Thus, it can synergistically consume solid waste resources such as sinter return fines, fine-grained metallized materials, and iron-containing dust, and improve energy utilization efficiency. The metallic iron in the fine-grained metallized materials can effectively improve the overall reducibility of cold-compressed briquettes. Moreover, during the reduction process, the metallic iron acts as a "skeleton phase" and absorbs expansion stress through elastic deformation, which can inhibit the initiation and propagation of cracks, thereby improving the problem of increased powdering rate caused by volume expansion during the reduction process.

[0013] In summary, the technical solution of the present invention does not require the return of sinter return fines and undersize materials of blast furnace lump ore to the sintering process for repeated sintering, thus avoiding energy waste and reducing carbon emissions. At the same time, it can also consume solid waste resources such as combustible organic waste resources, fine-grained metallized materials, and iron-containing dust, reduce solid waste accumulation, and further reduce the energy consumption of the iron and steel production process.

[0014] As a preferred embodiment, the combustible organic waste powder includes at least one of waste biomass, waste rubber, and waste plastic. Waste biomass includes, for example, sawdust, bark, rice husks, corn straw, etc. Waste rubber includes, for example, scrap tires, rubber seals, rubber hoses, waste materials of industrial rubber products, and rubber processing scraps. Waste plastic includes, for example, polyethylene (PE) packaging films, polypropylene (PP) containers, polyvinyl chloride (PVC) pipes, polyester (PET) bottles, polystyrene (PS) foams, and agricultural films.

[0015] As a preferred embodiment, the fine-grained metallized material includes undersize materials obtained from metallized pellets produced by direct reduction processes or indirect reduction processes. More specifically, the fine-grained metallized material can be undersize materials of products reduced in a gas-based shaft furnace, undersize materials of products reduced in a rotary hearth furnace, undersize materials of products reduced in a coal-based rotary kiln, undersize materials of products reduced in a coal-based shaft furnace, etc.

[0016] As a preferred embodiment, the particle size of the fine-grained metallized material satisfies that the proportion of the <5 mm particle size fraction is not less than 90 wt.%. As a preferred embodiment, the MFe content in the fine-grained metallized material is not less than 50 wt.%. Although the fine-grained metallized material has good plasticity and ductility, if its particle size is too large, it is difficult to be evenly distributed inside the briquette, which will affect the briquette strength and quality stability. Moreover, if the MFe content of the metallized material is too low, it will affect its plasticity and ductility, and thus affect the briquette strength.

[0017] As a preferred solution, the particle size of the blast furnace lump ore screening material meets the proportion of <5mm particle size not less than 90wt.%. The blast furnace lump ore screening material refers to the fine particles passing through the screen during the screening process, and these particles are usually produced during the crushing and screening process of the lump ore. The particle size of the blast furnace lump ore screening material needs to be controlled within an appropriate range. If the particle size of the blast furnace lump ore screening material is too large, local stress concentration will occur during molding, resulting in the formation of a microcrack network inside the briquette, which significantly reduces the strength of the agglomerate.

[0018] As a preferred solution, the proportion of the particle size of the combustible organic waste powder that meets the particle size of <1 mm is not less than 93 wt.%. As a preferred solution, the calorific value of the combustible organic waste powder is not less than 10 MJ / kg. If the particle size of the combustible organic waste powder is too large, it will hinder the combination of other material particles, resulting in a loose briquette structure. In addition, during the cold pressing process, large particles of biomass may not be fully compressed, resulting in voids inside the briquette, reducing the compressive strength.

[0019] As a preferred solution, the binder is composed of an organic binder and an inorganic binder in a mass percentage of 10% to 20%: 80% to 90%. As a more preferred solution, the mass of the binder accounts for 2.5% to 5% of the total mass of the sintered return ore, the blast furnace lump ore underscreen, the fine-grained metallized material and the iron-containing dust. As a more preferred solution, the organic binder includes at least one of gelatinized starch, humic acid, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylate, and phenolic resin. As a more preferred solution, the inorganic binder includes at least one of bentonite, sodium silicate, sodium water glass, and silica sol. The amount of binder added and the composite components are optimized based on comprehensive considerations of cost, bonding effect, impurity content, etc. The organic binder in the binder can provide excellent green ball strength and low-temperature strength for the cold-pressed block; the inorganic binder in the binder can provide high-temperature strength for the cold-pressed block, and the organic binder has less impurities and good low-temperature bonding effect, but the price is high and it is not resistant to high temperatures, while the inorganic binder has a lower price and good high-temperature strength, but the impurity content is higher. Therefore, the preferred binder is composed of organic binder and inorganic binder in an appropriate proportion to achieve the best comprehensive effect. In addition, a high amount of binder will increase the cost, while a low amount will affect the strength of the block.

[0020] As a preferred solution, the iron-containing dust includes at least one of sintering dust removal ash, blast furnace secondary dust removal ash, converter dust mud, iron-making field ash, and cold rolling sludge. As a preferred solution, the particle size of the iron-containing dust satisfies that the mass ratio of the particle size <1mm is not less than 90%, and the chloride content in the iron-containing dust is <0.75 wt.%. The role of the iron-containing dust is to fill the pores between large particles, and the particle size should not be too large, otherwise it will affect the molding effect; its chloride content should not be too high, otherwise it will increase the content of harmful elements in the cold pressed block and affect the smooth operation of the blast furnace.

[0021] The raw material ratios of the cold pressed block of the present invention are optimized. Compared with the sintered return ore, the ratio of the blast furnace block ore underscreen, the fine-grained metallized material, and the iron-containing dust should not be too high. For example, the hardness of the blast furnace block ore underscreen is large, and a too high ratio will affect the molding effect; when the fine-grained metallized material ratio is too low, the plastic buffering and filling effects are limited. When the ratio is too high, the cold pressed block will soften prematurely during the blast furnace reduction process, affecting the air permeability; when the iron-containing dust ratio is too low, the chloride salt therein is less, and the strength of the agglomerate obtained by rusting consolidation is limited. When the ratio is too high, the amount of chloride salt introduced is more, which will affect the normal production of the blast furnace. The ratio of combustible organic waste powder should not be too high, otherwise during the cold pressed block reduction process, the combustible organic waste will burn and decompose, significantly increasing the porosity of the cold pressed block and affecting the strength of the cold pressed block.

[0022] As a preferred solution, the molding line pressure of the high-pressure roll forming is 0.6t / mm~1.4t / mm. The molding line pressure should not be too large or too small. If it is too small, the molding pressure is insufficient and the strength of the cold pressed block is low. If it is too large, the original material particle size composition will be destroyed, the strength of the cold pressed block will be reduced, and the energy consumption of the equipment will be increased and the service life will be reduced.

[0023] As a preferred solution, the moisture content of the wet mass is 4.5wt.%~8wt.%, the shape is oblate, and the size is: major axis×minor axis×height=15mm×13mm×10mm~35mm×25mm×18mm. The moisture content in the wet mass needs to be controlled within an appropriate range. Too high or too low moisture is not conducive to the cold pressing of the mass. When the moisture is too low, the binder is difficult to fully dissolve and play a role. When the moisture is too high, the binder will be lost with the water during the pressing process, which will affect the molding effect and the strength of the cold pressed block. The size of the cold pressed block should not be too large or too small. When it is too large, the reducibility of the cold pressed block is poor. When it is too small, the porosity of the blast furnace charge will be reduced and the air permeability will be affected.

[0024] As a preferred solution, hot air is used throughout the process of low-temperature drying and consolidation. The drying temperature is 100°C to 180°C, and the drying time is 13 minutes to 22 minutes; the consolidation temperature is 180°C to 280°C, and the consolidation time is 11 minutes to 19 minutes. Under the preferred drying and consolidation conditions, the compressive strength of the cold briquette is not less than 2300 N / P, the drum index (+6.3 mm) is not less than 80%, the abrasion index is not higher than 8%, the low-temperature reduction degradation index (+3.15 mm) is not less than 70%, and the reducibility is not less than 75%.

[0025] During the high-pressure roll forming process of the present invention, the obtained formed material is screened, and the material passing through the screen is returned for re-forming, while the oversize material is the wet agglomerate.

[0026] The method for preparing a low-carbon blast furnace burden from sinter return ore provided by the present invention includes the following specific steps:

[0027] (1) Sinter return ore is preliminarily mixed with the undersize of the screened blast furnace lump ore, combustible organic waste powder, fine-grained metallized material, and iron-containing dust in a ratio of 92.5 wt.% to 93.5 wt.% : 5 wt.% to 6 wt.%: 1 wt.% to 2 wt.% : 0.5 wt.% to 1.5 wt.% to obtain mixture 1; among them, the proportion of the <5 mm particle size of the fine-grained metallized material and the undersize of the blast furnace lump ore is not less than 90 wt.%, and the MFe content in the fine-grained metallized material is not less than 50 wt.%; the proportion of the <1 mm particle size of the combustible organic waste powder is not less than 93 wt.%, and the calorific value of the combustible organic waste powder is not less than 10 MJ / kg; the proportion of the <1 mm particle size of the iron-containing dust is not less than 90 wt.%, and the chloride salt content in the iron-containing dust is <0.75 wt.%; the combustible organic waste powder is one or more of waste biomass, waste rubber, waste plastic, etc.; the fine-grained metallized material is one or more of the undersize of the products reduced in a gas-based shaft furnace, the undersize of the products reduced in a rotary hearth furnace, the undersize of the products reduced in a coal-based rotary kiln, the undersize of the products reduced in a coal-based shaft furnace, etc.; the iron-containing dust is one or more of sintering dust, blast furnace secondary dust, converter sludge, tapping yard ash, cold rolling sludge, etc.

[0028] (2) Mixture 1 is then mixed with a composite binder and water in a certain proportion to obtain mixture 2; wherein the amount of the composite binder added is 2.5wt.%~5wt.% of mixture 1; the water content of mixture 2 is 4.5wt.%~8wt.%; wherein the composite binder is composed of 10wt.%~20wt.% of an organic binder and 80wt.%~90wt.% of an inorganic binder; the organic binder is one or more of gelatinized starch, humic acid, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylate, phenolic resin, etc.; the inorganic binder is one or more of bentonite, sodium silicate, sodium water glass, silica sol, etc.; the mixing equipment is one or more of a high-power mixer, a horizontal mixer, a wheel mill, etc.

[0029] (3) Use a high-pressure double-roller briquetting machine to roll-form the mixture 2, screen the formed materials, return the screened materials to step (2) for re-forming, and the screened materials are wet agglomerates; wherein the molding line pressure is 0.6 t / mm~1.4 t / mm; the wet agglomerates are oblate spherical in shape, and the dimensions (long axis × short axis × height of the maximum area section) are 15 mm × 13 mm × 10 mm ~ 35 mm × 25 mm × 18 mm.

[0030] (4) Use hot air to dry and consolidate the wet mass at low temperature to obtain cold pressed blocks. The drying temperature is 100℃~180℃, and the drying time is 13min~22min; the consolidation temperature is 180℃~280℃, and the consolidation time is 11min~19min. The compressive strength of the cold pressed blocks shall not be less than 2300N / P, the drum index (+6.3mm) shall not be less than 80%, the wear resistance index shall not be higher than 8%, the low temperature reduction powderization index (+3.15mm) shall not be less than 70%, and the reduction degree shall not be less than 75%.

[0031] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0032] (1) The present invention uses raw materials such as the undersize of blast furnace lump ore, combustible organic waste powder, fine-grained metallized materials, and iron-containing dust to prepare cold-compacted briquettes in combination with sinter return fines. The key lies in the efficient coupling effect among multiple components in the raw material system, which can improve the strength of the cold-compacted briquettes, reduce carbon emissions, and improve their metallurgical properties, and prepare iron-containing burden materials meeting the requirements of blast furnaces in a low-carbon and efficient manner. On the one hand, the particle size of the combustible organic waste powder is relatively fine, and it can be evenly distributed on the surface of the return fines particles during the mixing process to form an interfacial transition layer. At the same time, it has excellent compressibility and can effectively fill the gaps between the coarse return fines particles through plastic deformation during the forming stage, which can improve the bulk density of the raw materials and reduce the stress concentration phenomenon caused by too high porosity during the pressing process. Moreover, the organic components in the combustible organic waste powder form chemical bonds with the binder, further strengthening the interfacial bonding strength and enhancing the strength of the agglomerates. On the other hand, there is a coupling effect between the fine-grained metallized materials and the iron-containing dust. The content of metallic iron in the fine-grained metallized materials is relatively high, and the chlorides in the iron-containing dust can be used as rusting agents to accelerate the rusting reaction on the surface of metallic iron, and improve the strength of the cold-compacted briquettes through rust consolidation. In addition, the fine-grained metallized materials have good plasticity and can achieve densification filling through particle extension deformation during the cold pressing process, which can significantly improve the strength of the cold-compacted briquettes.

[0033] (2) During the preparation process of the cold-compacted briquettes of the present invention, the combustible organic waste resources can be effectively utilized to reduce the total energy consumption of iron and steel production. By adding combustible organic waste powder to the raw materials of the cold-compacted briquettes, on the one hand, the combustible organic waste powder contains more organic substances and can burn to supply heat during the reduction process in the blast furnace, reducing the consumption of fossil energy. On the other hand, these substances will decompose to generate a large amount of organic small molecule gases (such as CO, H2, CH4, etc.) at high temperatures during the reduction process in the blast furnace, which can participate in the reduction of iron oxides as reducing agents and further reduce the coke ratio in the blast furnace. In addition, the microporous structure formed by the decomposition of the combustible organic waste powder at high temperatures is beneficial to the diffusion of reducing gases and can improve the metallurgical properties of the cold-compacted briquettes.

[0034] (3) During the preparation process of the cold-compacted briquettes of the present invention, solid waste resources such as sinter return fines, fine-grained metallized materials, and iron-containing dust can be synergistically disposed of to improve the energy utilization rate. On the one hand, both the fine-grained metallized materials and the iron-containing dust contain a certain amount of iron-containing substances, and this resource can be fully utilized to reduce the accumulation of solid waste. On the other hand, the metallic iron in the fine-grained metallized materials can effectively improve the overall reducibility of the cold-compacted briquettes; and during the reduction process, the metallic iron acts as a "skeleton phase" and absorbs the expansion stress through elastic deformation, which can inhibit the initiation and propagation of cracks, thus improving the problem of increased pulverization rate caused by volume expansion during the reduction process. Specific embodiments

[0035] For the convenience of understanding the present invention, the present invention will be described more comprehensively and in detail below in conjunction with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0036] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The patent terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0037] Unless otherwise specified, various reagents and raw materials used in the present invention are commercially available products or products that can be prepared by well-known methods.

[0038] The relevant standards for the performance testing of cold compacts in the following examples: The detection standard for compressive strength is GB / T 14201-2018, ISO 4700:2015; the detection standards for tumbler and abrasion resistance index are GB / T 24531-2009, ISO 3271:2007; the detection standard for low-temperature reduction degradation index is GB / T 31923-2015.

[0039] Example 1

[0040] The sinter return fines are preliminarily mixed with the undersize of blast furnace lump ore, combustible organic waste powder, fine-grained metallized material, and iron-containing dust in a ratio of 92.5 wt. %: 5 wt. %: 1 wt. %: 1.5 wt. % to obtain mixture 1; among them, the proportion of the <5 mm fraction of the fine-grained metallized material and the undersize of blast furnace lump ore is 90 wt. %, and the MFe content in the fine-grained metallized material is 55 wt. %; the proportion of the <1 mm fraction of the combustible organic waste powder is 93 wt. %, and the calorific value of the combustible organic waste powder is 10 MJ / kg; the proportion of the <1 mm fraction of the iron-containing dust is 90 wt. %, and the chloride salt content in the iron-containing dust is 0.70 wt. %; the combustible organic waste powder is waste biomass, specifically sawdust; the fine-grained metallized material is the undersize of the rotary hearth furnace reduction product; the iron-containing dust is a mixture composed of 70 wt. % sintering dust and 30 wt. % blast furnace secondary dust. Then, mixture 1 is fully mixed with a composite binder and water in a certain ratio to obtain mixture 2; among them, the addition amount of the composite binder accounts for 3.5 wt. % of mixture 1; the moisture content of mixture 2 is 5.0 wt. %; the composite binder is composed of 20 wt. % organic binder and 80 wt. % inorganic binder; the organic binder is sodium carboxymethylcellulose; the inorganic binder is sodium silicate; the mixing equipment is a high-strength mixer. The mixture 2 is subjected to roll forming using a high-pressure roll briquetting machine, and the formed material is screened. The oversize is the wet agglomerate; among them, the forming line pressure is 1.1 t / mm; the shape of the wet agglomerate is a flat sphere, with dimensions of 35 mm × 25 mm × 18 mm. The wet agglomerate is dried and consolidated at a low temperature using hot air to obtain the cold-pressed briquette. Among them, the drying temperature is 180 °C, and the drying time is 16 min; the consolidation temperature is 280 °C, and the consolidation time is 12 min.

[0041] The compressive strength of the cold-pressed briquette is 2330 N / P, the drum index (+6.3 mm) is 82%, the abrasion index is 7%, the low-temperature reduction degradation index (+3.15 mm) is 74%, and the reduction degree is 79%.

[0042] Example 2

[0043] The sinter return fines are preliminarily mixed with the undersize of the blast furnace lump ore, the combustible organic waste powder, the fine-grained metallized material, and the iron-containing dust in a ratio of 92.5 wt. %: 5 wt. %: 2 wt. %: 0.5 wt. % to obtain mixture 1; among them, the proportion of the fine-grained metallized material and the undersize of the blast furnace lump ore with a particle size <5 mm is 94 wt. %, and the MFe content in the fine-grained metallized material is 67 wt. %; the proportion of the combustible organic waste powder with a particle size <1 mm is 96 wt. %, and the calorific value of the combustible organic waste powder is 17 MJ / kg; the proportion of the iron-containing dust with a particle size <1 mm is 94 wt. %, and the chloride salt content in the iron-containing dust is 0.50 wt. %; the combustible organic waste powder is waste plastic, specifically the waste polyethylene (PE) packaging film; the fine-grained metallized material is a mixture of 25 wt. % of the undersize of the shaft furnace reduction product and 75 wt. % of the undersize of the rotary hearth furnace reduction product; the iron-containing dust is converter sludge. Then, mixture 1 is thoroughly mixed with a composite binder and water in a certain ratio to obtain mixture 2; among them, the addition amount of the composite binder accounts for 5 wt. % of mixture 1; the moisture content of mixture 2 is 6.5 wt. %; among them, the composite binder is composed of 10 wt. % of an organic binder and 90 wt. % of an inorganic binder; the organic binder is a mixture of 50 wt. % of sodium carboxymethylcellulose and 50 wt. % of phenolic resin; the inorganic binder is a mixture of 20 wt. % of bentonite and 80 wt. % of sodium silicate (modulus 3.3); the mixing equipment is a pan mill. The mixture 2 is roll formed using a high-pressure roll briquetting machine, and the formed material is screened. The oversize is the wet briquette; among them, the forming line pressure is 0.9 t / mm; the shape of the wet briquette is a flat sphere, with dimensions of 18 mm × 14 mm × 12 mm. The wet briquette is dried and consolidated at a low temperature using hot air to obtain the cold-pressed briquette. Among them, the drying temperature is 150 °C and the drying time is 20 min; the consolidation temperature is 250 °C and the consolidation time is 15 min.

[0044] The compressive strength of the cold-pressed briquette is 2470 N / P, the drum index (+6.3 mm) is 88%, the abrasion index is 5.4%, the low-temperature reduction degradation index (+3.15 mm) is 81%, and the reduction degree is 83%.

[0045] Example 3

[0046] The sintered return ore, the undersize of the blast furnace lump ore, the combustible organic waste powder, the fine-grained metallized material and the iron-containing dust are preliminarily mixed in the ratio of 92.5 wt.%: 6 wt.%: 1 wt.%: 0.5 wt.% to obtain a mixture 1; wherein the proportion of the fine-grained metallized material and the undersize of the blast furnace lump ore <5 mm is 96 wt.%, and the MFe content in the fine-grained metallized material is 77 wt.%; the proportion of the combustible organic waste powder <1 mm is 98 wt.%, and the calorific value of the combustible organic waste powder is 13 MJ / kg; the proportion of the iron-containing dust <1 mm is 97 wt.%, and the chloride content in the iron-containing dust is 0.66 wt.%; the combustible organic waste powder is 50 wt.% of the waste rubber tire and 50 wt.% of the waste rubber tire. wt.% corn stalks; the fine-grained metallized material is the undersize of the gas-based shaft furnace reduction product; the iron-containing dust is the sintering dust ash. Then, the mixture 1 is fully mixed with the composite binder and water in a certain proportion to obtain the mixture 2; the addition amount of the composite binder accounts for 4.5 wt.% of the mixture 1; the water content of the mixture 2 is 6 wt.%; the composite binder is composed of 16 wt.% organic binder and 84 wt.% inorganic binder; the organic binder is a mixture of 20 wt.% humic acid, 60 wt.% sodium carboxymethyl cellulose and 20 wt.% polyacrylate; the inorganic binder is a mixture of 60 wt.% sodium silicate, 20 wt.% sodium water glass (modulus 3.3) and 20 wt.% silica sol (silicon dioxide content 30 wt.%); the mixing equipment is a strong mixer. The mixture 2 was roll-formed by a high-pressure roll-pressing machine, and the formed materials were screened. The screened materials were wet agglomerates. The molding line pressure was 0.8 t / mm. The wet agglomerates were oblate spherical with dimensions of 22 mm × 17 mm × 14 mm. The wet agglomerates were dried and consolidated at low temperature using hot air to obtain cold pressed blocks. The drying temperature was 100 ° C and the drying time was 22 min. The consolidation temperature was 260 ° C and the consolidation time was 19 min.

[0047] The compressive strength of the cold pressed block is 2520N / P, the drum index (+6.3mm) is 90%, the wear resistance index is 4.7%, the low temperature reduction powdering index (+3.15mm) is 80%, and the reduction degree is 81%.

[0048] Comparative Example 1

[0049] Compared with Example 1, the only difference is that no combustible organic waste powder is added.

[0050] The compressive strength of the cold-pressed block is 2051N / P, the drum index (+6.3mm) is 77%, the wear resistance index is 11.5%, the low-temperature reduction powdering index (+3.15mm) is 64%, and the reduction degree is 74.3%.

[0051] Comparative Example 2

[0052] Compared with Example 2, the only difference is that no fine-grained metallized material is added.

[0053] The compressive strength of the cold-compacted briquette is 2018 N / P, the drum index (+6.3 mm) is 74%, the abrasion index is 12%, the low-temperature reduction degradation index (+3.15 mm) is 61.5%, and the reduction degree is 73%.

[0054] Comparative Example 3

[0055] Compared with Example 3, the only difference is that no iron-containing dust is added.

[0056] The compressive strength of the cold-compacted briquette is 2187 N / P, the drum index (+6.3 mm) is 80.4%, the abrasion index is 11.3%, the low-temperature reduction degradation index (+3.15 mm) is 71.5%, and the reduction degree is 77%.

Claims

1. A method for preparing blast furnace burden with low-carbon sinter return ore, characterized in that: After thoroughly mixing sinter return fines with undersize of blast furnace lump ore, combustible organic waste powder, fine-grained metallized material, iron-containing dust, binder and water, it is formed by high-pressure roll pressing. The obtained wet pellets are dried and consolidated at low temperature to obtain cold-compressed briquettes. The sinter return fines, undersize of blast furnace lump ore, combustible organic waste powder, fine-grained metallized material and iron-containing dust are composed according to the following mass percentages: 92.5% - 93.5% : 5% - 6% : 1% - 2% : 0.5% - 1.5%. The fine-grained metallized material includes undersize of metallized pellets obtained by direct reduction process or indirect reduction process.

2. The method for preparing blast furnace burden with low-carbon sinter return ore according to claim 1, characterized in that: The combustible organic waste powder includes at least one of waste biomass, waste rubber and waste plastic.

3. A method for preparing low-carbon blast furnace burden from sinter return fines according to any one of claims 1 - 2, characterized in that: The particle size of the fine-grained metallized material satisfies that the proportion of the <5mm particle size grade is not less than 90 wt.%. and / or, The particle size of the undersize of blast furnace lump ore satisfies that the proportion of the <5mm particle size grade is not less than 90 wt.%. and / or, The MFe content in the fine-grained metallized material is not less than 50 wt.%. and / or, The particle size of the combustible organic waste powder satisfies that the proportion of the <1mm particle size grade is not less than 93 wt.%. and / or, The calorific value of the combustible organic waste powder is not less than 10 MJ / kg.

4. A method for preparing blast furnace burden with low carbon from sinter return fines according to claim 1, characterized in that: The binder is composed of organic binder and inorganic binder according to the mass percentages of 10% - 20%:80% - 90%. and / or, The mass of the binder accounts for 2.5% - 5% of the total mass of the sinter return fines, undersize of blast furnace lump ore, fine-grained metallized material and iron-containing dust.

5. A method for preparing blast furnace burden with low-carbon sinter return ore according to claim 4, characterized in that: The organic binder includes at least one of gelatinized starch, humic acid, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylate, phenolic resin, etc. and / or, The inorganic binder includes at least one of bentonite, sodium silicate, sodium water glass, silica sol, etc.

6. A method for preparing blast furnace burden with low-carbon sinter return ore according to claim 1, characterized in that: The iron-containing dust includes at least one of sintering dust, blast furnace secondary dust, converter sludge, tapping yard ash, cold rolling sludge, etc. and / or, The particle size of the iron-containing dust satisfies that the mass proportion of the <1mm particle size grade is not less than 90%, and the chloride salt content in the iron-containing dust is <0.75wt.%.

7. A method for preparing low-carbon blast furnace burden from sinter return fines according to claim 1, characterized in that: The forming line pressure of the high-pressure roll pressing is 0.6t / mm - 1.4t / mm. and / or, The moisture content of the wet pellets is 4.5 wt.% - 8 wt.%, the shape is flat spherical, and the size is: major axis × minor axis × height = 15mm × 13mm × 10mm - 35mm × 25mm × 18mm.

8. A method for preparing blast furnace burden with low-carbon sinter return ore according to claim 1, characterized in that: Hot air is used during the low-temperature drying and consolidation process. The drying temperature is 100℃ - 180℃, and the drying time is 13min - 22min; the consolidation temperature is 180℃ - 280℃, and the consolidation time is 11min - 19min.