Method for preparing blast furnace burden from sintering return mine at low carbon

Abstract

The invention discloses a low-carbon method for preparing blast furnace burden from sintered return mine, and belongs to the technical field of ferrous metallurgy. The method comprises the following steps: fully and uniformly mixing the sintered return mine with blast furnace lump ore screen underflow, combustible organic waste powder, a fine-fraction metallized material, iron-containing dust, a binder and water, forming through high-pressure double rollers, and carrying out low-temperature drying and consolidation on the obtained wet block mass to obtain the cold-pressed block. According to the method, the whole process is low-carbon, sintering return mine, combustible organic waste resources, fine-fraction metallized materials, iron-containing dust and other resources can be consumed, solid waste accumulation is reduced, and energy consumption and carbon emission of the steel production technological process are reduced.

Description

Technical Field

[0001] The invention relates to a method for preparing blast furnace charge with low carbon content from sintered return ore, and in particular to a method for preparing blast furnace charge with low carbon content by adding fine-grained metallized materials and combustible organic waste powder to sintered return ore for cold pressing, and belongs to the field of iron and steel metallurgy. Background Art

[0002] The 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. At present, as a key industry, the steel industry is facing severe challenges in reducing carbon emissions, optimizing energy utilization, and improving resource recycling efficiency. Therefore, researching and developing low-carbon and efficient blast furnace charge preparation methods to reduce carbon emissions in the ironmaking process has become an important development direction of steel metallurgical technology.

[0003] In the traditional iron-making process, blast furnaces mainly use iron-containing charges such as sintered ore, pelletized ore, and lump ore. Among them, sintered ore accounts for a large proportion of blast furnace charges 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 sintered ore and optimizing the charge structure are of great significance to reducing blast furnace carbon emissions.

[0004] During the sintering and blast furnace smelting process, a large amount of return ore (such as sintering return ore and blast furnace return ore) will be generated. These return ore are mainly composed of incompletely reacted sintering materials, iron ore, iron-containing dust and mud, etc., with a high iron content (generally 40%~60%). At present, most of the return ore is reused by directly returning to the sintering process. On the one hand, repeated sintering of return ore requires additional fuel, electricity and manpower. The energy consumption per ton of sintering ore process is 48.50kgce, and the thermal efficiency of return ore cycle sintering is only 20%~30%, resulting in an increase of more than 70% in comprehensive energy consumption. On the other hand, due to its powdery properties, excessive addition will affect the permeability of the sintering material, thereby reducing the strength and output of the sintered ore. Therefore, how to use sintering return ore efficiently and low-carbon has become an urgent problem for steel companies.

[0005] To solve the above problems, cold-pressed briquette technology has attracted attention due to its characteristics of not requiring high-temperature roasting, low energy consumption, and the ability to absorb 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.) uses sintered return ore with 7% composite binder for extrusion molding, with a molding pressure of 240MPa. The molded briquettes were placed at room temperature for 14 days, and then dried at 130℃ for 12h, with a strength of 2619N / P and a hot strength of 1245N / P. (“Research on the Performance and Reduction Behavior of Cold-Pressed Blocks Prepared from Sintered Return Ore”, Yonggang Zang, Master’s degree thesis, Guizhou University, May 2023) Sintered return ore was used as the iron-containing raw material for extrusion molding, and the bonding effects of corn starch and composite binders were compared, with the binder ratios of 2.5% and 6.15%, respectively. The compressive strength of the cold-pressed block with corn starch was 2915N / P, and the compressive strength of the cold-pressed block with composite binder was 2018N / P. The residual strength after low-temperature reduction pulverization test was 1134N / P, and the strength after reduction test was 336N / P.

[0006] In summary, the sintered ore is currently mainly returned to the sintering process, which has huge carbon emissions and low energy utilization. The sintered ore cold pressing process has not been applied on a large scale, and there are still problems such as high binder prices, high content of harmful elements, and long consolidation time of the formed briquette. Summary of the invention

[0007] In view of the above-mentioned defects of the existing sintered return ore cold pressing process, the purpose of the present invention is to provide a method for preparing blast furnace charge with low carbon from sintered return ore. The method uses sintered return ore as the main raw material, adjusts the raw material composition by adding blast furnace block ore undersize, combustible organic waste powder, fine-grained metallized material, iron-containing dust, etc., and adds a binder for high-pressure molding-low-temperature drying and consolidation to prepare sintered return ore cold pressed blocks that meet the performance requirements of blast furnace charge. The method can utilize sintered return ore, fine-grained metallized material and combustible organic waste resources in a low-carbon and efficient manner. Compared with directly returning the return ore to the sintering process for treatment, the method has the characteristics of simple process, low energy consumption and low carbon emissions.

[0008] In order to achieve the above technical objectives, the present invention provides a method for preparing blast furnace charge with low carbon from sintered return ore, which comprises the following steps: fully mixing the sintered return ore with blast furnace lump ore undersize, combustible organic waste powder, fine-grained metallized material, iron-containing dust, a binder and water, and then forming the mixture through high-pressure rollers. The obtained wet lumps are dried and consolidated at low temperature to obtain cold pressed blocks. The sintered return ore, the blast furnace lump ore undersize, the fine-grained metallized material and the iron-containing dust are composed of the following mass percentages: 92.5%~93.5%: 5%~6%: 1%~2%: 0.5%~1.5%; the mass of the combustible organic waste powder accounts for 0.2%~0.5% of the total mass of the sintered return ore, the blast furnace lump ore undersize, the fine-grained metallized material and the iron-containing dust.

[0009] The key to the technical solution of the present invention is to add a small amount of blast furnace block ore screenings, combustible organic waste powder, fine-grained metallized materials, iron-containing dust and other raw materials to the sintered return ore to control the components, and to prepare iron-containing furnace charge that meets the requirements of the blast furnace in a low-carbon and high-efficiency manner through cold pressing and rapid consolidation under the action of a binder. The key to the present invention's ability to prepare iron-containing furnace charge that meets the requirements of the blast furnace from sintered return ore is to utilize the efficient coupling effect between multiple components in the raw material system, which can improve the strength of the cold pressed block, reduce carbon emissions and improve its metallurgical properties.

[0010] In terms of improving the strength of cold pressed blocks: 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 interface transition layer; at the same time, it has excellent compressibility, and effectively fills 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 caused by excessive porosity during the pressing process; and the organic components in the combustible organic waste powder form chemical bonds with the binder, further strengthening the interface bonding strength and enhancing the strength of the agglomerate. On the other hand, the introduced fine-grained metallized materials have a coupling effect with the iron-containing dust. The fine-grained metallized materials have a high content of metallic iron. The chloride salts in the iron-containing dust can be used as a rusting agent to accelerate the rusting reaction of the metallic iron surface, and improve the strength of the cold pressed blocks through rusting consolidation. The fine-grained metallized materials have good plasticity, and the particles are stretched and deformed during the cold pressing process to achieve densification and filling, which can significantly improve the strength of the cold pressed blocks.

[0011] In terms of low-carbon emissions: combustible organic waste resources can be effectively utilized to reduce the total energy consumption of steel production. Adding combustible organic waste powder to the cold-pressed briquette raw materials can not only utilize the characteristics of combustible organic waste powder containing more organic matter, but also use it to burn and provide heat in the blast furnace reduction process to reduce the consumption of fossil energy. In addition, the combustible organic waste powder will decompose at high temperatures in the blast furnace reduction process to generate a large amount of organic small molecule gases (CO, H2, CH4, etc.), which can be used as a reducing agent to participate in the reduction of iron oxides, further reducing the blast furnace coke ratio.

[0012] In terms of improving the metallurgical properties of cold pressed blocks: the microporous structure formed by the decomposition of combustible organic waste powder at high temperature is conducive to the diffusion of reducing gases, which can improve the metallurgical properties of cold pressed blocks, thereby synergistically absorbing solid waste resources such as sintered return ore, fine-grained metallized materials, and iron-containing dust, and improving energy utilization. The metallic iron in the fine-grained metallized materials can effectively improve the overall reducibility of the cold pressed blocks, and during the reduction process, the metallic iron, as a "skeleton phase", absorbs expansion stress through elastic deformation, which can inhibit crack initiation and expansion, thereby improving the problem of increased pulverization rate caused by volume expansion during the reduction process.

[0013] To sum up, the technical solution of the present invention does not need to return the sintered return ore and the screened undersize of the blast furnace lump ore to the sintering process for repeated sintering, thereby avoiding energy waste and reducing carbon emissions. At the same time, it can also absorb combustible organic waste resources, fine-grained metallized materials, iron-containing dust and other solid waste resources, reduce solid waste accumulation, and further reduce the energy consumption of the steel production process.

[0014] As a preferred solution, the combustible organic waste powder includes at least one of waste biomass, waste rubber, and waste plastic. Waste biomass includes sawdust, bark, rice husk, corn stalks, etc. Waste rubber includes scrapped tires, rubber sealing strips, hoses, industrial rubber product waste, and rubber processing scraps. Waste plastic includes polyethylene (PE) packaging film, polypropylene (PP) container, polyvinyl chloride (PVC) pipe, polyester (PET) bottle, polystyrene (PS) foam, and agricultural film.

[0015] As a preferred solution, the fine-grained metallized material includes the screen undersize of metallized pellets obtained by a direct reduction process or an indirect reduction process. More specifically, the fine-grained metallized material can be the screen undersize of a gas-based shaft furnace reduction product, the screen undersize of a rotary hearth furnace reduction product, the screen undersize of a coal-based rotary kiln reduction product, the screen undersize of a coal-based shaft furnace reduction product, etc.

[0016] As a preferred solution, the proportion of the fine-grained metallized material with a particle size of <5 mm is not less than 90 wt.%. As a preferred solution, the MFe content in the fine-grained metallized material is not less than 50 wt.%. Although fine-grained metallized materials have good plasticity and ductility, if their particle size is too large, they are difficult to be evenly distributed inside the agglomerate, thereby affecting the agglomerate strength and quality stability. If the MFe content of the metallized material is too low, it will affect its plasticity and ductility, thereby affecting the agglomerate 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 organic 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 in the low-temperature drying and consolidation process, the drying temperature is 100℃~180℃, the drying time is 13min~22min; the consolidation temperature is 180℃~280℃, and the consolidation time is 11min~19min. Under the preferred drying and consolidation conditions, the compressive strength of the cold pressed block is not less than 2300N / P, the drum index (+6.3mm) is not less than 80%, the wear resistance index is not higher than 8%, the low-temperature reduction powdering index (+3.15mm) is not less than 70%, and the reduction degree is not less than 75%.

[0025] In the high-pressure roller forming process of the present invention, the obtained forming material is screened, the material under the screen is returned for re-forming, and the material on the screen is the wet agglomerate.

[0026] The method for preparing blast furnace charge with low carbon content by sintering return ore provided by the present invention comprises the following specific steps:

[0027] (1) The sintered return ore is 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 according to 92.5wt.%~93.5wt.%: 5wt.%~6wt.%: 1wt.%~2wt.%: 0.5 wt.%~1.5wt.% to obtain a mixture 1; wherein the proportion of the fine-grained metallized material and the undersize of the blast furnace lump ore <5mm particle size is not less than 90 wt.%, the MFe content in the fine-grained metallized material is not less than 50 wt.%; the proportion of the combustible organic waste powder <1mm particle size 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 iron-containing dust with a particle size of <1mm is not less than 90wt.%, and the chloride content in the iron-containing dust is <0.75wt.%; 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 gas-based vertical furnace reduction product undersize, rotary hearth furnace reduction product undersize, coal-based rotary kiln reduction product undersize, coal-based vertical furnace reduction product undersize, etc.; the iron-containing dust is one or more of sintering dust removal ash, blast furnace secondary dust removal ash, converter dust mud, iron-making 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 blast furnace lump ore screenings, combustible organic waste powder, fine-grained metallized materials, iron-containing dust, etc. to match sintered return ore to prepare cold-pressed blocks. The key is to utilize the efficient coupling effect between multiple components in the raw material system to improve the strength of the cold-pressed blocks, reduce carbon emissions, and improve their metallurgical properties, so as to prepare iron-containing furnace charges that meet the requirements of blast furnaces in a low-carbon and high-efficiency manner. On the one hand, the combustible organic waste powder has a fine particle size and can be evenly distributed on the surface of the return ore particles during the mixing process to form an interface 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 raw material packing density and reduce the stress concentration caused by excessive porosity during the pressing process; and the organic components in the combustible organic waste powder form chemical bonds with the binder, further strengthening the interface bonding strength and enhancing the strength of the agglomerate. On the other hand, there is a coupling effect between fine-grained metallized materials and iron-containing dust. Fine-grained metallized materials have a high content of metallic iron. Chloride salts in iron-containing dust can be used as rusting agents to accelerate the rusting reaction on the surface of metallic iron, thereby improving the strength of cold-pressed blocks through rusting consolidation. In addition, fine-grained metallized materials have good plasticity, and can achieve densification and filling through particle extension and deformation during the cold-pressing process, which can significantly improve the strength of cold-pressed blocks.

[0033] (2) The cold-pressed agglomerates of the present invention can effectively utilize combustible organic waste resources during the preparation process, thereby reducing the total energy consumption of steel production. Combustible organic waste powder is added to the raw materials for cold-pressed blocks. On the one hand, the combustible organic waste powder contains a large amount of organic matter, which can be burned to provide heat during the blast furnace reduction process, thereby reducing the consumption of fossil energy. On the other hand, these substances will decompose under high temperatures during the blast furnace reduction process to generate a large amount of organic small molecule gases (CO, H2, CH4, etc.), which can be used as reducing agents to participate in the reduction of iron oxides, thereby further reducing the blast furnace coke ratio. In addition, the microporous structure formed by the decomposition of the combustible organic waste powder at high temperatures is conducive to the diffusion of reducing gases, thereby improving the metallurgical properties of the cold-pressed blocks.

[0034] (3) The cold-pressed agglomerates of the present invention can be used in a coordinated manner to absorb solid waste resources such as sintered return ore, fine-grained metallized materials, and iron-containing dust during the preparation process, thereby improving energy utilization. On the one hand, both fine-grained metallized materials and iron-containing dust contain a certain amount of iron-containing substances, which 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-pressed blocks; and during the reduction process, the metallic iron, as a "skeleton phase", absorbs expansion stress through elastic deformation, which can inhibit crack initiation and expansion, thereby improving the problem of increased pulverization rate caused by volume expansion during the reduction process. DETAILED DESCRIPTION

[0035] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully in combination with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0036] Unless otherwise defined, all professional terms used below have the same meanings as those generally 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 scope of protection of the present invention.

[0037] Unless otherwise specified, the various reagents and raw materials used in the present invention are commodities that can be purchased from the market or products that can be prepared by known methods.

[0038] The performance test standards of the cold pressed blocks in the following embodiments are as follows: the compressive strength test standard is GB / T 14201-2018, ISO 4700:2015; the drum and wear resistance index test standard is GB / T 24531-2009, ISO 3271:2007; the low temperature reduction powdering index test standard is GB / T 31923-2015.

[0039] Example 1

[0040] The sintered return ore is preliminarily mixed with the blast furnace lump ore undersize, combustible organic waste powder, fine-grained metallized material and iron-containing dust in the ratio of 92.5 wt.%:5 wt.%:1 wt.%:1.5 wt.% to obtain a mixture 1; wherein the proportion of the fine-grained metallized material and the blast furnace lump ore undersize <5 mm is 90 wt.%, and the MFe content in the fine-grained metallized material is 55 wt.%; the proportion of the combustible organic waste powder <1 mm is 93 wt.%, and the calorific value of the combustible organic waste powder is 10 MJ / kg; the proportion of the iron-containing dust particle size <1 mm is 90 wt.%, and the chloride 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 composed of 70 wt.% sintering dust removal ash and 30 wt.% blast furnace secondary dust ash. Then, the mixture 1 is fully mixed with the composite binder and water in a certain proportion to obtain the mixture 2; wherein the addition amount of the composite binder accounts for 3.5 wt.% of the mixture 1; the moisture content of the mixture 2 is 5.0 wt.%; wherein the composite binder is composed of 20 wt.% of the organic binder and 80 wt.% of the inorganic binder; the organic binder is sodium carboxymethyl cellulose; the inorganic binder is sodium silicate; and the mixing equipment is a strong mixer. The mixture 2 is roll-formed by a high-pressure double-roll ball press, and the formed material is screened, and the screened material is the wet mass; wherein the molding line pressure is 1.1t / mm; the wet mass is in the shape of an oblate sphere with a size of 35mm×25mm×18mm. The wet mass is dried and consolidated at low temperature using hot air to obtain a cold pressed block. wherein the drying temperature is 180℃, the drying time is 16min; the consolidation temperature is 280℃, and the consolidation time is 12min.

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

[0042] Example 2

[0043] The sintered return ore is 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 according to 92.5 wt.%: 5 wt.%: 2 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 94 wt.%, and the MFe content in the fine-grained metallized material is 67 wt.%; the proportion of the combustible organic waste powder <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 particle size <1 mm is 94 wt.%, and the chloride content in the iron-containing dust is 0.50 wt.%; the combustible organic waste powder is waste plastic, specifically waste polyethylene (PE) packaging film; the fine-grained metallized material is 25 wt.% of the undersize of the gas-based shaft furnace reduction product and 75 wt.% of the PE packaging film; wt.% mixture of rotary hearth furnace reduction product sieve undersize; iron-containing dust is converter dust mud. Mixture 1 is then fully mixed with composite binder and water in a certain proportion to obtain mixture 2; the addition amount of composite binder accounts for 5 wt.% of mixture 1; the water content of mixture 2 is 6.5 wt.%; the composite binder is composed of 10 wt.% organic binder and 90 wt.% inorganic binder; the organic binder is a mixture of 50 wt.% sodium carboxymethyl cellulose and 50 wt.% phenolic resin; the inorganic binder is a mixture of 20 wt.% bentonite and 80 wt.% sodium water glass (modulus 3.3); the mixing equipment is a wheel mill. Mixture 2 is roll-formed using a high-pressure double-roll ball press, and the formed material is screened, and the screened material is the wet mass; the molding line pressure is 0.9t / mm; the wet mass is in the shape of an oblate sphere with a size of 18mm×14mm×12mm. The wet mass is dried and consolidated at low temperature using hot air to obtain cold pressed blocks, wherein the drying temperature is 150°C and the drying time is 20 minutes; the consolidation temperature is 250°C and the consolidation time is 15 minutes.

[0044] The compressive strength of the cold pressed block is 2470N / P, the drum index (+6.3mm) is 88%, the wear resistance index is 5.4%, the low temperature reduction powdering index (+3.15mm) 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 metallization material is added.

[0053] The compressive strength of the cold pressed block is 2018N / P, the drum index (+6.3mm) is 74%, the wear resistance index is 12%, the low temperature reduction powdering index (+3.15mm) 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-pressed block is 2187N / P, the drum index (+6.3mm) is 80.4%, the wear resistance index is 11.3%, the low-temperature reduction powdering index (+3.15mm) is 71.5%, and the reduction degree is 77%.

Claims

1. A method for preparing blast furnace charge with low carbon by sintering return ore, characterized in that: The sintered return ore, blast furnace block sieves, combustible organic waste powder, fine-grained metallized materials, iron-containing dust, a binder and water are fully mixed, and then formed by high-pressure rollers. The obtained wet agglomerates are dried and consolidated at low temperature to obtain cold pressed blocks; the sintered return ore, the blast furnace block sieves, the fine-grained metallized materials and the iron-containing dust are composed of the following mass percentages: 92.5%~93.5%: 5%~6%: 1%~2%: 0.5%~1.5%; the mass of the combustible organic waste powder accounts for 0.2%~0.5% of the total mass of the sintered return ore, the blast furnace block sieves, the fine-grained metallized materials and the iron-containing dust.

2. The method for preparing blast furnace charge with low carbon from sintered 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. The method for preparing blast furnace charge with low carbon from sintered return ore according to claim 1, characterized in that: The fine-grained metallized material includes the undersize of metallized pellets obtained by direct reduction process or indirect reduction process.

4. The method for preparing blast furnace charge with low carbon from sintered return ore according to any one of claims 1 to 3, characterized in that: The proportion of the fine-grained metallized material having a particle size of <5 mm is not less than 90 wt.%; and / or, The proportion of the particle size of the blast furnace lump ore undersize that meets the particle size of <5mm 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 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.%; and / or, The calorific value of the combustible organic waste powder is not less than 10 MJ / kg.

5. The method for preparing blast furnace charge with low carbon from sintered return ore according to claim 1, characterized in that: The binder is composed of an organic binder and an inorganic binder in a mass percentage of 10% to 20%: 80% to 90%; and / or, 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.

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

7. The method for preparing blast furnace charge with low carbon from sintered 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 dust, iron-making site dust, and cold rolling sludge; and / or, The particle size of the iron-containing dust satisfies that the mass proportion of the particle size <1 mm is not less than 90%, and the chloride content in the iron-containing dust is <0.75wt.%.

8. The method for preparing blast furnace charge with low carbon from sintered return ore according to claim 1, characterized in that: The forming line pressure of the high-pressure roll forming is 0.6t / mm~1.4t / mm; and / or, The moisture content of the wet mass is 4.5 wt.% to 8 wt.%, the shape is oblate spherical, and the dimensions are: major axis×minor axis×height=15mm×13mm×10mm to 35mm×25mm×18mm.

9. The method for preparing blast furnace charge with low carbon from sintered return ore according to claim 1, characterized in that: Hot air is used in the low-temperature drying and consolidation process, the drying temperature is 100°C~180°C, and the drying time is 13min~22min; the consolidation temperature is 180°C~280°C, and the consolidation time is 11min~19min.