Iron ore carbon-containing pellet as raw material for iron making by belt roaster

Abstract

The application discloses a kind of iron ore carbon-containing pellets, comprising: iron ore powder, flux, binder, solid reducing agent and moisture, wherein the mass ratio of the iron ore powder, flux and binder is 100:0-10:0.5-5, the addition amount of solid reducing agent is such that the molar ratio of carbon element and oxygen element in the mixture of iron ore powder, flux, binder and solid reducing agent is 0.7-1.3, and the mass of moisture is 5-15% of the total mass of iron ore powder, flux, binder and solid reducing agent.The application further discloses a belt-type roaster ironmaking method using the iron ore carbon-containing pellets as raw material.The application solves the problems of reduction degree and green ball strength by adjusting the raw material, and solves the problems of uneven product ball quality and high energy consumption by adjusting the belt-type roaster process.

Description

Technical Field

[0001] This invention relates to the technical fields of iron and steel metallurgy and pellet production. More specifically, this invention relates to a belt roasting method for ironmaking using carbon-containing iron ore pellets as raw material. Background Technology

[0002] Currently, my country has a huge demand for steel.

[0003] my country's steel industry primarily employs the long-process steel production process, which involves grinding and beneficiating iron ore into iron concentrate, sintering it into sinter or pellets, and then using coke from a coke oven and flux as raw materials in a blast furnace to produce pig iron with a high carbon content. This blast furnace pig iron is then refined in an oxygen converter and a refining furnace to produce qualified steel. The qualified steel is then cast or continuously cast into steel ingots or billets, and finally rolled into finished steel products. The long-process steel production process involves numerous steps, large-scale equipment, high energy consumption, severe pollution, and long production cycles. In contrast, the short-process steel production process uses scrap steel or direct reduced iron as raw materials, directly smelting it in an electric furnace to obtain qualified steel, which is then rolled. This process is simpler, more efficient, environmentally friendly, and has a shorter production cycle.

[0004] Direct reduced iron, one of the main raw materials for electric arc furnace steelmaking, has the characteristics of extremely low levels of harmful elements and stable and uniform chemical composition. It can partially or completely replace scrap steel in electric arc furnace smelting to produce high-value-added special steel, clean steel and high-quality steel, and can achieve good technical and economic indicators.

[0005] Direct reduction processes can be divided into gas-based direct reduction processes using natural gas as the reducing agent and coal-based direct reduction processes using coal as the reducing agent, depending on the reducing agent used. However, my country's natural gas reserves are relatively scarce and expensive, thus greatly limiting the development of gas-based direct reduction processes in my country. Domestically, coal-based direct reduction processes are mainly used, including tunnel kiln processes, rotary kiln processes, and rotary hearth furnace processes. For example, invention patent CN115612774A, published on January 17, 2023, entitled "A New Method for Direct Reduction Ironmaking in a Hydrogen-Based Vertical Furnace," uses a vertical furnace to prepare metallized pellets; similarly, invention patent CN115354148A, published on November 18, 2022, entitled "A Cooling System and Method for Metallized Pelletizing in a Rotary Hearth Furnace," uses a rotary hearth furnace to prepare metallized pellets. Among them, rotary kiln technology has high requirements for raw materials and fuels and high operating costs, and poor production stability; tunnel kiln has problems such as small single-unit capacity, high energy consumption, serious pollution and poor product quality; rotary hearth furnace is mostly used for dust treatment and comprehensive utilization of compound minerals, and the processing capacity is relatively small.

[0006] In my country, belt calciner technology is a very mature pellet production process with the advantages of simple process, compact layout and large processing capacity. Belt calciners are mostly used in the preparation of oxidized pellets, but rarely in the field of direct reduction to prepare metallized pellets. Summary of the Invention

[0007] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0008] Another objective of this invention is to provide a belt roasting method for ironmaking using carbon-containing iron ore pellets as raw material. This method solves the problems of reduction degree and green pellet strength by adjusting the raw material formulation, and solves the problems of uneven quality of finished pellets and high energy consumption by adjusting the belt roasting process.

[0009] To achieve these objectives and other advantages according to the present invention, a carbon-containing iron ore pellet is provided, comprising: iron ore powder, flux, binder, solid reducing agent, and water, wherein the mass ratio of the iron ore powder, flux, and binder is 100:0 to 10:0.5 to 5, the amount of solid reducing agent added is such that the molar ratio of carbon to oxygen in the mixture of iron ore powder, flux, binder, and solid reducing agent is 0.7 to 1.3, and the mass of water is 5 to 15% of the total mass of iron ore powder, flux, binder, and solid reducing agent.

[0010] Preferably, the content of iron ore powder with a particle size of less than 0.044 μm is >50%, and the specific surface area is >1200 cm². 2 / g, iron content >50%.

[0011] Preferably, the flux includes one or more of limestone, dolomite, lightly calcined dolomite, and slaked lime.

[0012] Preferably, the binder comprises one or more of bentonite, cement, geopolymer, water glass, or sodium carboxymethyl cellulose.

[0013] Preferably, the solid reducing agent is a carbon-containing material with a fixed carbon mass fraction >30%.

[0014] Preferably, the carbon-containing material with a fixed carbon mass fraction >30% includes one or more of anthracite, bituminous coal, coke powder, and coal gangue with a particle size of less than 1 mm.

[0015] Preferably, the iron ore carbon-containing pellets are prepared into spherical shapes using a pelletizing disc, roller, or briquetting machine.

[0016] This invention further claims a belt roasting ironmaking method using the aforementioned carbon-containing iron ore pellets as raw material, comprising:

[0017] Step 1, Material spreading: The iron ore carbon-containing pellets with a thickness of 200-600 mm are evenly spread on the head of the belt roaster using the material spreading system of the belt roaster.

[0018] Step 2: After removing moisture from the flue gas in the second cooling section, blow it into the forced-air drying section for drying; control the hot air temperature in the forced-air drying section to be 100-350℃; introduce the flue gas from the roasting section and the homogenizing section into the exhaust drying section, control the hot air temperature in the exhaust drying section to be 200-500℃; introduce the high-temperature flue gas from the first cooling section into the preheating section through the furnace hood, control the hot air temperature in the preheating section to be 400-900℃; heat the tail gas from the first cooling section through a burner or heat exchanger and then introduce it into the roasting section, control the hot air temperature in the roasting section to be 800-1300℃, and roast for 10-50 minutes; and control the wind speed above the material layer throughout the entire section to be 1m / s-5m / s;

[0019] Step 3: After dehydrating the exhaust gas, mix it with an appropriate amount of room temperature nitrogen and blow it into the first and second cooling sections through a cooler. In the second cooling section, water is also sprayed to cool the temperature of the iron ore carbon pellets to below 150°C, thus obtaining the finished metallized pellets.

[0020] Preferably, the exhaust gas in step three is one or more of the following: exhaust gas from the blower drying section, exhaust gas from the ventilation drying section, exhaust gas from the preheating section, exhaust gas from the first cooling section, and exhaust gas from the second cooling section.

[0021] Preferably, before step one, a base material of 50-120 mm thickness and an edge material of 50-100 mm thickness are pre-laid on the belt roasting machine trolley using finished metallized pellets.

[0022] The present invention has at least the following beneficial effects:

[0023] 1. The iron ore carbon-containing pellets provided by this invention are scientific and efficient in their formulation, balancing the carbon content, binary basicity and binder dosage, solving the problems of raw material reduction degree and green pellet strength, and overcoming the problem of belt roasting machines being constrained by raw materials.

[0024] 2. The carbon in the iron ore carbon pellets provided by this invention can both act as a reducing agent in the reduction process and supply heat, thereby significantly reducing energy consumption and pollutant emissions.

[0025] 3. The belt roasting ironmaking method using the aforementioned carbon-containing iron ore pellets as raw material, provided by this invention, solves the problem of uneven quality of the finished pellets;

[0026] 4. The belt roasting ironmaking method using the carbon-containing iron ore pellets as raw material provided by the present invention can shorten the direct reduced iron preparation process.

[0027] 5. The belt roasting ironmaking method provided by the present invention, which uses the carbon-containing iron ore pellets as raw materials, supplements the heat through multiple pairs of burners or heat exchangers, flexibly adjusts the temperature, realizes the self-circulation of high-temperature flue gas, and reduces resource consumption.

[0028] 6. The belt roaster ironmaking method using the aforementioned carbon-containing iron ore pellets as raw material provided by the present invention realizes thick-layer ironmaking, and the production process is completed on a single piece of equipment, which greatly improves the scale and automation of production and meets the needs of industrialization.

[0029] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of a belt roaster ironmaking method using carbon-containing iron ore pellets as raw material, as described in one embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of the ironmaking process using a belt roaster with carbon-containing iron ore pellets as raw material, as described in another embodiment of the present invention. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can implement it based on the description.

[0033] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not imply the presence or addition of one or more other elements or combinations thereof.

[0034] Example 1

[0035] Preparation of carbon-containing iron ore pellets (excluding flux):

[0036] Iron ore powder and anthracite were dried in a multi-functional drying oven (temperature set at 105℃), and then mixed at a mass ratio of 100:28.17 to achieve a carbon-oxygen molar ratio of 1.2. Bentonite and water were then added at 0.8 wt% and 8 wt% of the mixture, respectively. The selected iron ore powder had a particle size of less than 0.044 μm, a content of >50%, and a specific surface area >1200 cm². 2 Iron ore powder with an iron content greater than 50% by mass and anthracite particle size less than 1 mm were used. The mixture was then homogenized in a high-speed mixer and pelletized using a disc pelletizer. Green pellets with a particle size of 8–16 mm were screened out as qualified carbon-containing iron ore pellets. The compositions of the iron ore powder and anthracite are shown in Tables 1 and 2, respectively.

[0037] Table 1 Chemical composition of iron ore powder (mass fraction)

[0038] Element TFe FeO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> CaO MgO <![CDATA[TiO2]]> Quality fraction (%) 62.81 21.50 3.47 2.07 2.01 2.95 0.23

[0039] Table 2. Industrial composition of anthracite (mass fraction)

[0040] Element Fixed carbon Industrial moisture Ash Volatile matter Quality fraction (%) 82.43 1.65 11.41 5.94

[0041] Example 2

[0042] Preparation of carbon-containing iron ore pellets (including flux)

[0043] Iron ore powder, anthracite, and limestone are dried in a multi-functional drying oven (temperature set at 105℃), and then mixed according to a certain mass ratio to achieve a carbon-oxygen molar ratio of 1.2. Bentonite and water are then added at 0.8 wt% and 8 wt% of the mixture, respectively. The selected iron ore powder has a particle size of less than 0.044 μm, a content of >50%, and a specific surface area >1200 cm². 2 The mixture consists of iron ore powder with an iron content greater than 50% by mass and anthracite coal with a particle size less than 1 mm. After being mixed in a high-speed mixer, the mixture is pelletized using a disc pelletizer. Green pellets with a particle size of 8–16 mm are selected as qualified carbon-containing iron ore pellets. The composition of the iron ore powder and anthracite coal is the same as in Example 1.

[0044] Example 3

[0045] like Figure 1 and Figure 2 As shown, the preparation of the finished metallized pellets:

[0046] Step 1: The qualified iron ore carbon-containing pellets obtained in Example 1 are evenly spread in a 200mm thickness on the head of the belt roaster through the feeding system of the belt roaster.

[0047] Step 2: After removing moisture from the flue gas in the second cooling section, blow it into the forced-air drying section for drying; control the hot air temperature in the forced-air drying section at 250℃; introduce the flue gas from the roasting section and the homogenizing section into the exhaust drying section, control the hot air temperature in the exhaust drying section at 400℃, introduce the high-temperature flue gas from the first cooling section into the preheating section through the furnace hood, and slowly raise the pellet temperature to 750℃ through the preheating section; heat the tail gas from the first cooling section through the burner or heat exchanger and then introduce it into the roasting section, control the hot air temperature in the roasting section at 1200℃, and roast for 30 minutes; and control the wind speed above the material layer in the entire section at 3m / s.

[0048] Step 3: After dehydrating the exhaust gas, mix it with an appropriate amount of room temperature nitrogen and blow it into the first and second cooling sections through a cooler. In the second cooling section, water is also sprayed to cool the iron ore carbon-containing pellets to 120°C, thus obtaining the finished metallized pellets.

[0049] Example 4

[0050] Step 1: The qualified iron ore carbon-containing pellets obtained in Example 2 are evenly spread in a 200mm thickness on the head of the belt roaster through the feeding system of the belt roaster.

[0051] Step 2: After removing moisture from the flue gas in the second cooling section, blow it into the forced-air drying section for drying; control the hot air temperature in the forced-air drying section at 250℃; introduce the flue gas from the roasting section and the homogenizing section into the exhaust drying section, control the hot air temperature in the exhaust drying section at 400℃, introduce the high-temperature flue gas from the first cooling section into the preheating section through the furnace hood, and slowly raise the pellet temperature to 750℃ through the preheating section; heat the tail gas from the first cooling section through the burner or heat exchanger and then introduce it into the roasting section, control the hot air temperature in the roasting section at 1200℃, and roast for 30 minutes; and control the wind speed above the material layer in the entire section at 3m / s.

[0052] Step 3: After dehydrating the exhaust gas, mix it with an appropriate amount of room temperature nitrogen and blow it into the first and second cooling sections through a cooler. In the second cooling section, water is also sprayed to cool the iron ore carbon-containing pellets to 120°C, thus obtaining the finished metallized pellets.

[0053] Example 5

[0054] Step 1: First, evenly lay a 120mm thick base material and a 100mm thick edge material with finished metallized pellets at the head of the belt roaster. Then, evenly lay a 600mm thick layer of the qualified iron ore carbon-containing pellets obtained in Example 1 at the head of the belt roaster through the feeding system of the belt roaster.

[0055] Step 2: After removing moisture from the flue gas in the second cooling section, blow it into the forced-air drying section for drying; control the hot air temperature in the forced-air drying section at 350℃; introduce the flue gas from the roasting section and the homogenizing section into the exhaust drying section, control the hot air temperature in the exhaust drying section at 500℃, introduce the high-temperature flue gas from the first cooling section into the preheating section through the furnace hood, and slowly raise the pellet temperature to 900℃ in the preheating section; heat the tail gas from the first cooling section through a burner or heat exchanger and then introduce it into the roasting section, control the hot air temperature in the roasting section at 1300℃, and roast for 50 minutes; and control the wind speed above the material layer in the entire section at 5m / s.

[0056] Step 3: After dehydrating the exhaust gas (including exhaust gas from the blower drying section, exhaust gas from the preheating section, exhaust gas from the first cooling section, and exhaust gas from the second cooling section), mix it with an appropriate amount of room temperature nitrogen and blow it into the first and second cooling sections through a cooler. In the second cooling section, water is also sprayed to cool the temperature of the carbon-containing iron ore pellets to 130°C, thus obtaining the finished metallized pellets.

[0057] Example 6

[0058] Step 1: First, evenly lay a 50mm thick base material and a 50mm thick edge material on the head of the belt roaster using finished metallized pellets. Then, evenly lay a 400mm thick layer of the qualified iron ore carbon-containing pellets obtained in Example 1 on the head of the belt roaster using the feeding system of the belt roaster.

[0059] Step 2: After removing moisture from the flue gas in the second cooling section, blow it into the forced-air drying section for drying; control the hot air temperature in the forced-air drying section at 100℃; introduce the flue gas from the roasting section and the homogenizing section into the exhaust drying section, control the hot air temperature in the exhaust drying section at 200℃, introduce the high-temperature flue gas from the first cooling section into the preheating section through the furnace hood, and slowly raise the pellet temperature to 400℃ through the preheating section; heat the tail gas from the first cooling section through the burner or heat exchanger and then introduce it into the roasting section, control the hot air temperature in the roasting section at 800℃, and roast for 10 minutes; and control the wind speed above the material layer in the entire section at 1m / s.

[0060] Step 3: After dehydrating the exhaust gas (including exhaust gas from the blower drying section, exhaust gas from the ventilation drying section, exhaust gas from the preheating section, exhaust gas from the first cooling section, and exhaust gas from the second cooling section), mix it with an appropriate amount of room temperature nitrogen and blow it into the first and second cooling sections through a cooler. In the second cooling section, water is also sprayed to cool the temperature of the carbon-containing iron ore pellets to 140°C, thus obtaining the finished metallized pellets.

[0061] Example 7

[0062] Step 1: First, evenly lay a 100mm thick base material and an 80mm thick edge material with finished metallized pellets at the head of the belt roaster. Then, evenly lay a 500mm thick layer of the qualified iron ore carbon-containing pellets obtained in Example 1 at the head of the belt roaster through the feeding system of the belt roaster.

[0063] Step 2: After removing moisture from the flue gas from the second cooling section, blow it into the forced-air drying section for drying; control the hot air temperature in the forced-air drying section at 200℃; introduce the flue gas from the roasting section and the homogenizing section into the exhaust drying section, control the hot air temperature in the exhaust drying section at 400℃, introduce the high-temperature flue gas from the first cooling section into the preheating section through the furnace hood, and slowly raise the pellet temperature to 800℃ through the preheating section; heat the tail gas from the first cooling section through the burner or heat exchanger and then introduce it into the roasting section, control the hot air temperature in the roasting section at 800℃, and roast for 30 minutes; and control the wind speed above the material layer in the entire section at 3m / s.

[0064] Step 3: After dehydrating the exhaust gas (including exhaust gas from the blower drying section, exhaust gas from the ventilation drying section, exhaust gas from the preheating section, exhaust gas from the first cooling section, and exhaust gas from the second cooling section), mix it with an appropriate amount of room temperature nitrogen and blow it into the first and second cooling sections through a cooler. In the second cooling section, water is also sprayed to cool the temperature of the iron ore carbon-containing pellets to 135°C, thus obtaining the finished metallized pellets.

[0065] Comparative Example 1

[0066] pellet preparation

[0067] According to the invention patent with publication number CN115478158A, publication date of 2022.12.16, entitled "A Method for Pelletizing", the green pellet preparation method is as follows: anthracite (same as in Example 1) is added to iron ore powder raw material (same as in Example 1) to obtain a mixture, and the pellets are obtained by a disc pelletizing mechanism. Green pellets with a particle size of 8-16 mm are screened as qualified pellets, wherein the amount of anthracite added is 30 wt%.

[0068] Comparative Example 2

[0069] According to the invention patent CN115491455A, published on December 20, 2022, entitled "A Pre-reduced Pellet Preparation Device and Method Based on a Belt Calcination Machine," the specific steps of the reduced pellet preparation method are as follows:

[0070] Step 1: The qualified iron-containing pellets obtained from Comparative Example 1 are transferred into a belt roasting machine system and subjected to forced air drying, exhaust drying, first-stage preheating, second-stage preheating, and high-temperature roasting to obtain high-temperature pellets.

[0071] Step 2: The high-temperature pellets obtained in Step 1 are transferred to a hydrogen-based vertical shaft furnace reduction system for reduction. After reduction using pure hydrogen or coke oven gas, the pellets are cooled with nitrogen and methane and then carburized to obtain pre-reduced pellets.

[0072] Comparative Example 3

[0073] Preparation of finished iron-containing pellets:

[0074] Step 1: The qualified carbon-containing pellets obtained in Comparative Example 1 are evenly spread in a 200mm thickness on the head of the belt roaster using the feeding system of the belt roaster.

[0075] Step 2, same as in Example 3;

[0076] Step 3: Same as in Example 3, to obtain the finished pellets.

[0077] Comparative Example 4

[0078] Using the iron ore carbon-containing pellets obtained in Example 1 as raw materials, pre-reduced pellets were prepared using the reduction pellet preparation method disclosed in the invention patent with publication number CN115491455A, publication date of 2022.12.20, entitled "A Pre-reduced Pellet Preparation Device and Method Based on a Belt Roasting Machine".

[0079] Table 3. Average metallization rate (%) of finished pellets

[0080] Group Example 3 Example 4 Comparative Example 2 Comparative Example 3 Comparative Example 4 Average metallization 91.7 92.3 65.8 74.1 77.6

[0081] As can be seen from the data in Table 3, the raw materials of Examples 3 and 4 are different, but the preparation methods are the same. The raw materials of both Examples 3 and 4 are prepared using the iron ore carbon-containing pellet preparation method provided by this invention. The only difference is that the raw materials of Example 3 do not contain flux, while the raw materials of Example 4 contain flux. The average metallization rate of the finished pellets obtained from Examples 3 and 4 is not significantly different, indicating that the addition of flux has little effect on the average metallization rate of the finished pellets. The average metallization rate of the finished pellets obtained from Examples 3 and 4 is much higher than the average metallization rate of the finished pellets obtained from Comparative Examples 2-4. Comparative Example 2 and Example 3 use different raw materials and preparation methods. In Comparative Example 2, green pellets were prepared using existing technology, and the finished reduced pellets were prepared using existing methods. The average metallization rate was 65.8%, only about 70% of the average metallization rate of the finished reduced pellets obtained using the raw materials and preparation method provided by this invention. Comparative Example 3 and Example 3 use different raw materials but the same preparation method. The raw material used in Comparative Example 3 is green pellets prepared using existing technology, while the preparation method is the same as that provided in this application. The average metallization rate of the finished reduced pellets obtained in Comparative Example 3 can reach about 80% of the average metallization rate of the finished reduced pellets obtained using the raw materials and preparation method provided by this invention. Comparative Example 4 and Example 3 use the same raw materials but different preparation methods. Comparative Example 4 uses the green pellets provided by this invention as raw materials and prepares reduced pellets using existing methods. The average metallization rate of the finished reduced pellets obtained in Comparative Example 4 can reach about 85% of the average metallization rate of the finished reduced pellets obtained using the raw materials and preparation method provided by this invention. The average metallization rate is a quality indicator for measuring the degree of reduction of direct reduced iron; the higher the value, the higher the metallic iron content in the direct reduced iron product. Comparing Example 3 and Comparative Example 4, it can be seen that, with the same raw materials, the preparation method provided by this invention is beneficial to improving the average metallization rate of the reduced pellets. Comparing Example 3 and Comparative Example 3, it can be seen that, with the same reduction pellet preparation method, using the green pellets provided by this invention is also beneficial to improving the average metallization rate of the reduced pellets. Comparing Example 3, Comparative Example 3, and Comparative Example 4, it can be seen that the reduction pellet preparation method has a much greater impact on the average metallization rate of the reduced pellets than the green pellet ratio. Comparing Example 3 and Comparative Example 2, it can be seen that, with different raw materials and preparation methods, the reduced pellets obtained in Example 3 have a better average metallization rate. Comparing Example 3 and Comparative Examples 2-4, it can be seen that the adjustment of the green pellet raw material ratio and the adjustment of the belt calciner preparation process in this application have a positive impact on the average metallization rate of the obtained reduced pellets, and the combined effect of the two on the average metallization rate of the reduced pellets is much greater than the sum of the individual improvements on the average metallization rate of the reduced pellets.

[0082] During the preparation process, the maximum compressive strength of the high-temperature pellets of Examples 3 and 4, and Comparative Examples 2 to 4 was measured and the results are shown in Table 4.

[0083] Table 4 Compressive strength of high-temperature pellets (N / pellet)

[0084] Group Example 3 Example 4 Comparative Example 2 Comparative Example 3 Comparative Example 4 compressive strength 3246 3178 2159 2435 2584

[0085] The compressive strength of the reduced pellets characterizes their mechanical strength; a higher value indicates a greater maximum crushing load. As shown in Table 4, the compressive strength of the reduced pellets obtained in Examples 3 and 4 is significantly better than that obtained in Comparative Examples 2-4. Comparative Example 2 shows the lowest compressive strength. Comparing Example 3 and Comparative Example 3, the compressive strength of the reduced pellets obtained using the preparation method provided by this invention from green pellets obtained with existing technology only reaches 75% of the compressive strength of the reduced pellets obtained in this application. Comparing Example 3 and Comparative Example 4, the compressive strength of the reduced pellets obtained using the preparation method provided by this invention from green pellets obtained with existing technology reaches approximately 80% of the strength of the reduced pellets obtained in this application. Therefore, the preparation method provided by this invention significantly improves the compressive strength of the reduced pellets. The impact of green pellet quality on the compressive strength of reduced pellets is far greater than that on the compressive strength of green pellets. Furthermore, it can be observed that the improvement in compressive strength resulting from improvements in both green pellet quality and preparation method is greater than the sum of the improvements in compressive strength resulting from improvements in green pellet quality and preparation method alone. This is because the green pellet formulation method provided by this invention is scientifically efficient, balancing carbon content, binary basicity, and binder dosage, thus solving the problems of raw material reduction degree and green pellet strength. It overcomes the difficulty of belt roasters being constrained by raw materials. The reduced pellet preparation method provided by this invention uses multiple burners or heat exchangers for supplementary heating, flexibly adjusting the temperature and solving the problem of uneven finished pellet quality. The energy consumption per ton of metallized pellets obtained using the carbon-containing pellet formulation and the finished pellet preparation method provided in this application is 70%–89% of the energy consumption per ton of finished pellets produced by existing vertical shaft furnace processes using existing green pellet formulations.

[0086] Meanwhile, the method for preparing reduced pellets provided by this invention uses carbon-containing pellets as a reducing agent in the reduction process, which greatly reduces the amount of reducing agent used. The carbon-containing pellets also participate in the heat supply, which greatly reduces energy consumption and pollutant emissions. Furthermore, the method for preparing reduced pellets provided by this invention realizes the self-circulation of high-temperature flue gas, which reduces resource consumption.

[0087] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the present invention's iron ore carbon-containing pellets and the belt roasting method using them as raw materials will be readily apparent to those skilled in the art.

[0088] As described above, according to the present invention, the present invention includes at least the following beneficial effects:

[0089] 1. The iron ore carbon-containing pellets provided by this invention are scientific and efficient in their formulation, balancing the carbon content, binary basicity and binder dosage, solving the problems of raw material reduction degree and green pellet strength, and overcoming the problem of belt roasting machines being constrained by raw materials.

[0090] 2. The carbon in the iron ore carbon pellets provided by this invention can both act as a reducing agent in the reduction process and supply heat, thereby significantly reducing energy consumption and pollutant emissions.

[0091] 3. The belt roasting ironmaking method using the aforementioned carbon-containing iron ore pellets as raw material, provided by this invention, solves the problem of uneven quality of the finished pellets;

[0092] 4. The belt roasting ironmaking method using the carbon-containing iron ore pellets as raw material provided by the present invention can shorten the direct reduced iron preparation process.

[0093] 5. The belt roasting ironmaking method provided by the present invention, which uses the carbon-containing iron ore pellets as raw materials, supplements the heat through multiple pairs of burners or heat exchangers, flexibly adjusts the temperature, realizes the self-circulation of high-temperature flue gas, and reduces resource consumption.

[0094] 6. The belt roaster ironmaking method using the aforementioned carbon-containing iron ore pellets as raw material provided by the present invention realizes thick-layer ironmaking, and the production process is completed on a single piece of equipment, which greatly improves the scale and automation of production and meets the needs of industrialization.

[0095] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A belt roasting method for ironmaking using carbon-containing iron ore pellets as raw material, characterized in that, include: Step 1, Material spreading: The iron ore carbon-containing pellets with a thickness of 200-600mm are evenly spread on the head of the belt roaster using the material spreading system of the belt roaster. The carbon-containing iron ore pellets comprise: iron ore powder, flux, binder, solid reducing agent, and water. The mass ratio of the iron ore powder, flux, and binder is 100:0~10:0.5~5. The amount of solid reducing agent added ensures that the molar ratio of carbon to oxygen in the mixture of iron ore powder, flux, binder, and solid reducing agent is 0.7~1.

3. The mass of water is 5~15% of the total mass of the iron ore powder, flux, binder, and solid reducing agent. The iron ore powder contains >50% iron ore with a particle size less than 0.044 μm and has a specific surface area >1200 cm². 2 / g, iron content > 50%; the solid reducing agent is a carbon-containing material with a fixed carbon content > 30%; the carbon-containing material with a fixed carbon content > 30% includes one or more of anthracite, bituminous coal, coke powder, and coal gangue with a particle size of less than 1mm; Step 2: After removing moisture from the flue gas from the second cooling section, blow it into the forced-air drying section for drying; control the hot air temperature in the forced-air drying section to be 100~350℃; introduce the flue gas from the roasting section and the homogenizing section into the exhaust drying section, control the hot air temperature in the exhaust drying section to be 200~500℃; introduce the high-temperature flue gas from the first cooling section into the preheating section through the furnace hood, control the hot air temperature in the preheating section to be 400~900℃; heat the tail gas from the first cooling section through a burner or heat exchanger and then introduce it into the roasting section, control the hot air temperature in the roasting section to be 800~1300℃, and roast for 10~50 minutes; and control the wind speed above the material layer throughout the entire section to be 1m / s~5m / s; Step 3: After dehydrating the exhaust gas, mix it with an appropriate amount of room temperature nitrogen and blow it into the first and second cooling sections through a cooler. In the second cooling section, water is also sprayed to cool the temperature of the iron ore carbon pellets to below 150°C, thus obtaining the finished metallized pellets.

2. The belt roasting ironmaking method using carbon-containing iron ore pellets as raw material as described in claim 1, characterized in that, The flux includes one or more of limestone, dolomite, lightly calcined dolomite, and slaked lime.

3. The belt roasting ironmaking method using carbon-containing iron ore pellets as raw material as described in claim 2, characterized in that, The binder includes one or more of bentonite, cement, geopolymer, water glass, or sodium carboxymethyl cellulose.

4. The belt roasting ironmaking method using carbon-containing iron ore pellets as raw material as described in claim 3, characterized in that, The iron ore carbonaceous pellets are prepared into spherical shapes using a pelletizing disc, roller, or briquetting machine.

5. The belt roasting ironmaking method using carbon-containing iron ore pellets as raw material as described in claim 4, characterized in that, The exhaust gas mentioned in step three is one or more of the following: exhaust gas from the blower drying section, exhaust gas from the ventilation drying section, exhaust gas from the preheating section, exhaust gas from the first cooling section, and exhaust gas from the second cooling section.

6. The belt roasting ironmaking method using carbon-containing iron ore pellets as raw material as described in claim 5, characterized in that, Before step one, a base material of 50-120 mm thickness and an edge material of 50-100 mm thickness are pre-laid on the belt roasting machine trolley using finished metallized pellets.

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