Apparatus and method for preparing pre-reduced pellets based on a fire grate rotary kiln

Abstract

The present disclosure provides a pre-reduced pellet preparation apparatus and method based on a grate rotary kiln. The pre-reduced pellet preparation apparatus includes a grate rotary kiln pellet oxidation system and a hydrogen-based shaft furnace reduction system. In the pre-reduced pellet preparation method, the roasting process and the reduction process in iron-containing green pellets are organically combined, the pellet cooling process after roasting and the heating process before pellet reduction are eliminated, and the physical heat of the roasted pellets is used to meet the heat required in the heating and reduction process, solving the technical problems of low hydrogen utilization rate and high energy consumption of the pellets in the traditional direct reduction process of oxidation roasting and direct reduction process, and reducing pellets with a certain metallization rate are obtained, and the prepared pre-reduced pellets are used as blast furnace load, thereby greatly reducing the fuel consumption and carbon emission of the blast furnace, and the method is a novel low-carbon and green pre-reduced pellet preparation process.

Description

Technical Field

[0001] The present disclosure relates to a pretreatment technology for ferrous metallurgical raw materials in the field of steelmaking, and particularly to a device and method for preparing pre-reduced pellets.

Background Art

[0002] Steel production in China mainly adopts the long-flow process of blast furnace-converter. Due to the constraints of process characteristics, it is necessary to use a large amount of fossil energy mainly composed of coal, thereby discharging a large amount of greenhouse gases. According to statistics, the carbon dioxide emissions from steel production in China account for 15% of the total social emissions. Therefore, steel production is an industry with a large amount of greenhouse gas emissions. As an important process step in the whole process, the energy consumption and carbon emissions of blast furnace smelting and the pretreatment of raw materials before ironmaking account for 70-80% of the total energy consumption and carbon emissions of the whole process. Therefore, how to reduce the carbon emissions in the ironmaking process is the key to solving the green development of the steel industry. With the enlargement of blast furnaces and the progress of operation technology, the thermal efficiency and gas utilization rate of blast furnaces are approaching the theoretical optimum values, and the room for emission reduction and consumption reduction in the blast furnace smelting process is becoming smaller and smaller. The hot spot of energy-saving research in ironmaking is increasingly concentrated on the agglomeration process of ore and coal before ironmaking. The amounts of pollutants such as SO2, NO X and dioxin generated in the sintering and agglomeration processes of iron ore are more than 60%, 50% and 90% of the whole process respectively, and the CO2 emissions account for 15%. The pelletizing process, in which the generation amount of pollutants and the energy consumption are only 20% and 50% of the sintering process respectively, has made great progress in recent years.

[0003] According to Mysteel's calculations, pellet production in China mainly based on the traveling grate rotary kiln process reached 225 million tons in 2020. Pellets are mainly used as raw materials in blast furnaces and direct reduction furnaces. Usually, they are roasted to 1200 - 1300 °C in an oxidizing atmosphere, cooled to room temperature, and then added to blast furnaces or direct reduction furnaces, where they are heated to 1500 °C or 900 °C while being reduced to molten iron or direct reduced iron. To reduce the energy consumption of high-temperature roasting of pellets and improve energy utilization efficiency, researchers have proposed various technical solutions.

[0004] In "Technical Concept of Pellet Traveling Grate Rotary Kiln Shaft Cooling Kiln" (Metallurgical Equipment, Volume 5, 2020), Luo Hao et al. proposed the concept of shaft cooling kiln ventilation cooling instead of the conventional ring cooler or belt machine considering that this solution has the characteristics of high waste heat utilization rate and small plant area.

[0005] Chinese Patent Publication No. 111380366A discloses a waste heat recycling system for sintered hot ore and pellet coolers, and proposes the idea of dividing the cooler into a high-temperature flue gas area, a medium-temperature flue gas area, and a low-temperature flue gas area and matching it with a residual heat boiler.

[0006] Chinese Patent Publication No. 112161260A discloses a method for sintered ore and pellet cooling, waste heat recovery, and a boiler, and proposes using a solid heat exchange waste heat recovery device. The boiler includes a solid-solid heat exchanger, and the solid-solid heat exchanger includes a start-up protection device of the solid-solid heat exchanger, a primary evaporator, and a secondary evaporator.

[0007] Chinese Utility Model Patent No. 202465830U discloses a waste heat recovery system for pellets and sintered ore, which consists of a feeding device, a tank cooling bin, a heat-resistant dust collector, a heat exchanger, a normal-temperature dust collector, and an induced draft fan.

[0008] In addition, using a pellet direct reduction process to prepare direct reduced iron for use in a converter or an electric furnace is also a technical direction for reducing carbon emissions in a steel plant. Chinese Patent Publication No. 111534659 discloses a parallel regenerative gas-based shaft furnace and a method for manufacturing direct reduced iron. The top gas, high-temperature reducing gas, intermediate gas, and cooling gas of the two shaft furnaces communicate with each other. Iron-containing green pellets or lump ores are continuously supplied to the two shaft furnaces, and the high-temperature reducing gas is periodically supplied to the shaft furnaces under the switching of a reversing valve group. Along the direction of the gas flow, parallel flow heating and countercurrent heat storage are simultaneously performed in the two shaft furnaces to carry out a reduction reaction to produce direct reduced iron and top gas.

[0009] Chinese Patent No. 104195278B discloses a method for manufacturing iron powder by directly reducing iron ore through a shaft furnace-rotary kiln. After pelletizing the iron concentrate, the green pellets are roasted in a shaft furnace, coal particles are added to a direct reduction furnace for reduction, and the reduced product is magnetically separated to obtain metallic iron powder.

[0010] Chinese Patent Publication No. 111910072A discloses a method for preparing and using pre-reduced flux-containing pellets by using steel slag as part of the raw materials. This method includes screening the steel slag, taking out steel slag particles with a particle size of 2-4 mm as the core for pelletization, pulverizing the remaining steel slag into steel slag powder, pelletizing the steel slag powder together with fly ash, iron oxide red, iron concentrate powder, and a composite binder, and performing drying, preheating, and roasting to obtain the completed pre-reduced flux-containing pellets.

[0011] Chinese Patent Specification No. 103261446 discloses a method and an apparatus for producing direct reduced iron by using a reducing gas source containing hydrogen and CO. DRI (Direct Reduced Iron) is produced by using pellets and lump ores as iron raw materials and a reducing gas prepared by coal gasification containing highly oxidized CO and hydrogen (CO2 and H2O). This method overcomes the limitations of using natural gas in previous gas-based direct reduction shaft furnaces.

[0012] Chinese Patent Publication No. 105408500A discloses a method for reducing iron oxide to metallic iron by using natural gas. Purified or raw natural gas, purified or contaminated coke oven gas, etc. are converted into a reducing gas / synthesis gas suitable for direct reduction with minimal treatment or purification. Hydrocarbons, etc. are converted to H2 and CO by reduction. This method has the typical characteristics of adding iron oxide into a shaft furnace at normal temperature, converting and heating the gas to obtain a reducing gas, and providing the high temperature required for the reaction. In order to solve the problem of low utilization rate, purification, heating, and circulation are carried out cyclically many times.

[0013] Chinese Patent Specification No. 103898265 discloses a system device and method for reforming coke oven gas for directly reducing iron ore. The coke oven gas generated in the coking process is reformed and converted into a hydrogen-rich reducing gas (H2 and CO), and then the hydrogen-rich reducing gas is introduced into the shaft furnace to directly reduce the iron ore. This solution can reduce carbon dioxide emissions during iron ore reduction and can better conform to the energy resource characteristics of China, different from the direct reduction of iron by natural gas.

[0014] Specification of Chinese Patent Publication No. 110484672A discloses a method for producing direct reduced iron by a gas-based shaft furnace. According to the method for producing direct reduced iron by a gas-based shaft furnace, heat is absorbed by the Boudouard reaction between blast furnace undersize coke and CO2, so that the temperature in the shaft furnace can be effectively reduced, the occurrence of thermal compaction of the furnace load is reduced, at the same time, the energy released from reduction is effectively used, the overall energy utilization rate is improved, the generated CO raises the reduction potential in the furnace and promotes the reduction of iron ore, which is beneficial to promoting the application of the direct reduction technology of iron ore in a gas-based shaft furnace. The iron ore is pellet or lump ore, or a mixture thereof.

[0015] The above technical method has the problem of high carbon emissions when using coal particles, and the gas-based direct reduction process has inherent thermodynamic limitations mainly due to the large specific heat capacity of iron oxide. Also, after the reforming of natural gas or coke oven gas, hydrogen is mainly used as a reducing agent, which absorbs a lot of heat during the reduction process and makes it difficult to maintain the reduction temperature, so it is often necessary to heat and circulate the gas. In the whole process, the hydrogen utilization rate is relatively low, usually about 30%, so it is difficult to promote the gas-based direct reduction process worldwide, and it has only been developed in countries where natural gas is cheap, such as the Middle East and South America.

[0016] Considering the above situation, there is an urgent need in the industry to develop a new iron-containing green pellet sintering and reduction technology that can solve the technical problems of low hydrogen reduction utilization rate during the direct reduction of conventional pellets, and high energy consumption caused by repeated heating such as heating (about 1250 °C), cooling (about 25 °C), and reheating (820 - 1050 °C) of pellets during oxidative roasting and direct reduction.

Prior Art Documents

Patent Documents

[0017]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Non-Patent Document

[0018]

Non-Patent Document 1

Summary of the Invention

[0019] In view of the above drawbacks in the prior art, an object of the present disclosure is to provide a preliminary reduction pellet preparation apparatus and method based on a fire grate rotary kiln. By utilizing a fire grate rotary kiln and a hydrogen shaft furnace, the roasting process and the reduction process in the pellet are organically combined, the pellet cooling process after roasting and the heating process before pellet reduction are eliminated, and the physical heat of the roasted pellet is used to meet the heat required for the heating and reduction processes, solving the technical problems of low hydrogen utilization rate and high energy consumption in the direct reduction process of pellets in the oxidation roasting and conventional direct reduction processes, obtaining reduction pellets with a specific metallization rate, and using the prepared preliminary reduction pellets as a blast furnace burden, thereby significantly reducing the fuel consumption and carbon emissions of the blast furnace. Therefore, this method is a novel low-carbon and green preliminary reduction pellet preparation process.

[0020] To achieve the above object, the present disclosure adopts the following technical solutions. In a first aspect of the present disclosure, a preliminary reduction pellet preparation apparatus including a fire grate rotary kiln pellet oxidation system and a hydrogen shaft furnace reduction system is provided. The fire grate rotary kiln pellet oxidation system includes a fire grate system and a rotary kiln system connected to the fire grate system. In the fire grate system, in order to obtain preheated pellets, iron-containing green pellets are sequentially dried and preheated. In the rotary kiln system, in order to obtain roasted pellets, the preheated pellets are roasted at a temperature of 1170 - 1300 °C. The hydrogen shaft furnace reduction system includes a hydrogen shaft furnace, a supply system, a reduction gas system, a cooling system, and an exhaust system. The supply system is arranged at the upper part of the hydrogen shaft furnace, and the roasted pellets from the rotary kiln system are directly conveyed to the supply system. The reduction gas system processes the flue gas from the hydrogen shaft furnace and supplies reduction gas to the hydrogen shaft furnace to obtain pre-reduced pellets. The roasted pellets from the supply system are reduced in the hydrogen shaft furnace. The cooling system cools the pre-reduced pellets in the hydrogen shaft furnace to obtain cooled pre-reduced pellets. The exhaust system is arranged at the bottom of the hydrogen shaft furnace and discharges the cooled pre-reduced pellets.

[0021] Preferably, the grate system is provided with a drying section I, a drying section II, a preheating section I, and a preheating section II in order in the moving direction of the iron-containing green pellets. The preheating section II communicates with the rotary kiln system and is connected to the drying section II via a first reheating fan. The preheating section I is connected to the tubular heat exchanger of the reduction gas system, connected to the rotary kiln system via a combustion fan, and connected to the drying section I via a second reheating fan. The drying section I and the drying section II are each connected to a bag dust collector via a main exhaust fan.

[0022] Preferably, the supply system includes an upper hopper, an intermediate hopper, and a lower hopper, and valves are arranged between the upper hopper and the intermediate hopper and between the intermediate hopper and the lower hopper, and / or The reducing gas system includes a tubular heat exchanger, a residual heat boiler, a first scrubber, a circulation fan, and a pressurizing fan. The tubular heat exchanger is provided with a flue gas inlet, a flue gas outlet, an air inlet, and an air outlet. The flue gas inlet is connected to the flue gas port at the upper end of the hydrogen shaft furnace. The flue gas outlet is connected to the residual heat boiler. The air inlet is connected to a fan. The air outlet is connected to the preheating section I of the fire grate system. The air outlet of the residual heat boiler is connected to the air inlet of the first scrubber. One end of the circulation fan is connected to the air outlet of the first scrubber, and the other end communicates with the annular tuyere in the middle part of the hydrogen shaft furnace. The pressurizing fan pressurizes the reducing gas from the circulation fan and / or The cooling system includes an oxy-fuel combustion unit, a waste heat recovery unit, a second scrubber, and a cooling fan. The oxy-fuel combustion unit is connected to the air outlet at the lower part of the hydrogen shaft furnace. One end of the waste heat recovery unit is connected to the oxy-fuel combustion unit, and the other end is connected to the air inlet of the second scrubber. One end of the cooling fan is connected to the air outlet of the second scrubber, and the other end communicates with the air inlet at the lower part of the hydrogen shaft furnace. The air outlet at the lower part of the hydrogen shaft furnace is arranged above the air inlet at the lower part of the hydrogen shaft furnace.

[0023] Preferably, an air duct is provided in the upper hopper, a pressure equalizing device is provided in the middle hopper, and a universal distributor is provided in the lower hopper.

[0024] In a second aspect of the present disclosure, a method for preparing pre-reduced pellets is provided. The method for preparing pre-reduced pellets uses the apparatus for preparing pre-reduced pellets according to the first aspect of the present disclosure to obtain roasted pellets having a temperature of 1170 - 1300 °C in the fire grate rotary kiln pellet oxidation system of the apparatus for preparing pre-reduced pellets. Then, in order to obtain pre-reduced pellets, the roasted pellets are directly supplied to the hydrogen shaft furnace reduction system of the apparatus for preparing pre-reduced pellets for reduction.

[0025] Preferably, the method for preparing pre-reduced pellets (1) After mixing bentonite and finely pulverized limestone / hydrated lime with an iron ore raw material to obtain a mixed material, water is mixed with this mixed material and pelletized to obtain an iron-containing green pellet; (2) Distributing the iron-containing green pellets to a fire grate system to form a material layer of the iron-containing green pellets, continuously subjecting the material layer of the iron-containing green pellets to blast drying, exhaust drying, primary preheating, and secondary preheating to obtain preheated pellets, and then supplying the preheated pellets to a rotary kiln system and roasting at 1170 - 1300 °C to obtain roasted pellets at a temperature of 1170 - 1300 °C; (3) Supplying the roasted pellets to a hydrogen-based shaft furnace reduction system, causing the roasted pellets to undergo a reduction reaction with a reducing gas, and then cooling with a cooling gas to obtain preliminarily reduced pellets. It includes.

[0026] Preferably, in step (1), the iron ore raw material is selected from one or more of magnetite, hematite, and limonite, and / or The iron ore raw material has a Blaine specific surface area of 1500 cm 2 / g or more, and / or The blending amount of bentonite is 0.7 - 1.5 wt% of the iron ore raw material, and / or The mixed material has a binary alkalinity of 0.3 - 0.5 or 0.8 - 1.2, and / or The particle size of the iron-containing green pellets is 8 - 20 mm, and / or In step (2), in the fire grate system, the material layer of the iron-containing green pellets has a height of 250 - 400 mm, and / or The blast drying is carried out in the drying section I of the fire grate system at a temperature of 170 - 240 °C and an air velocity of 0.8 - 1.4 m / s for 1.5 - 2.5 minutes, and / or The exhaust drying is carried out in the drying section II of the fire grate system at a temperature of 300 - 400 °C and an air velocity of 0.8 - 1.4 m / s for 4 - 6 minutes, and / or The primary preheating is carried out in the preheating section I of the checker system at a temperature of 600 - 800 °C and an air velocity of 0.8 - 1.4 m / s for 4 - 6 minutes, and / or The secondary preheating is carried out in the preheating section II of the checker system at a temperature of 900 - 1100 °C and an air velocity of 0.8 - 1.4 m / s for 4 - 6 minutes, and / or The fuel of the rotary kiln system includes natural gas, coke oven gas, pyrolysis gas, pyrolysis oil, biomass oil, or biomass carbon, and / or The rotary kiln system uses high-temperature air to support combustion, and the high-temperature air is from the mixed gas composed of the air and high-temperature exhaust gas of the checker system, and / or In the roasting process, the roasting temperature is controlled to be 1170 - 1300 °C, and the roasting time is controlled to be 8 - 12 minutes, and / or In step (3), the pressure of the hydrogen shaft furnace in the hydrogen shaft furnace reduction system is 200 - 250 kPa, and / or The reducing gas is pure hydrogen or coke oven gas, and / or During the reduction reaction, the consumption of the reducing gas is 800 - 1200 m 3 / t, and the reduction reaction time is 40 - 100 minutes, and / or The cooling gas contains nitrogen and natural gas, and / or During the cooling process, the flow rate of the cooling gas is 1200 - 1800 m 3 / t, and / or The discharge temperature of the pre-reduced pellets is less than 150 °C, and The metallization rate of the pre-reduced pellets is 40% or more.

[0027] Preferably, in step (2), in the blast drying process, the blast drying temperature is 190 - 210 °C, and the air velocity is 0.9 - 1.2 m / s, and / or In the exhaust drying process, the exhaust drying temperature is 330 - 350 °C, and the air velocity is 0.9 - 1.2 m / s, and / or In the primary preheating process, the air velocity is 0.9 to 1.2 m / s, and / or In the secondary preheating process, the air velocity is 0.9 to 1.2 m / s, and / or In step (3), the metallization rate of the preliminary reduction pellets is 40 to 62%, and The reducing gas is pure hydrogen, and during the reduction reaction, the hydrogen utilization rate is 50% or more.

[0028] Preferably, in step (3), the reducing gas is pure hydrogen, and during the reduction reaction, the hydrogen utilization rate is 55% or more, and / or After the roasted pellets are conveyed into the supply system of the hydrogen shaft furnace reduction system through a high-temperature resistant tank, they are distributed into the hydrogen shaft furnace of the hydrogen shaft furnace reduction system through the supply system and participate in the reduction reaction in the middle part of the hydrogen shaft furnace. The reducing gas enters the hydrogen shaft furnace through the reducing gas system and participates in the reduction reaction. The flue gas after the reaction enters the reducing gas system from the flue gas outlet at the upper end of the hydrogen shaft furnace, is subjected to heat exchange, waste heat recovery, and scrubbing, and then enters the middle part of the hydrogen shaft furnace and participates in the reduction reaction, and The cooling gas enters the hydrogen shaft furnace through the cooling system and participates in the cooling process. The treated mixed gas enters the cooling system from the air outlet at the lower part of the hydrogen shaft furnace, is subjected to oxy-combustion, waste heat recovery, and scrubbing, and then enters the lower part of the hydrogen shaft furnace and participates in the cooling process.

[0029] Preferably, in step (3), the distribution in the supply system is performed as follows. The roasted pellets are introduced into the supply system, pass through the upper hopper, middle hopper, and lower hopper of the supply system in sequence, and then are distributed into the hydrogen shaft furnace through a universal distributor. After the roasted pellets are charged into the upper hopper, steam or nitrogen is introduced to replace oxygen so that the oxygen content in the upper hopper becomes 1% or less. The valve below the upper hopper is opened, whereby the roasted pellets completely flow into the intermediate hopper. The valve below the upper hopper is closed, and the equalizing process is completed using a gas having the same composition as the top gas in the hydrogen shaft furnace. After the equalizing is completed, the valve below the intermediate hopper is opened. After the roasted pellets completely flow into the lower hopper, the valve below the intermediate hopper is closed. Then, the valve below the lower hopper is opened to distribute the roasted pellets into the hydrogen shaft furnace.

[0030] The beneficial effects of the present disclosure are as follows.

[0031] 1. According to the pre-reduced pellet preparation apparatus and method provided by the present disclosure, by utilizing the fire grate system, rotary kiln system, and hydrogen shaft furnace reduction system, the roasting step and the reduction step in the pellets are organically combined, the pellet cooling process after roasting and the heating process before reduction treatment are eliminated, and the physical heat of the roasted pellets is used to meet the heat required in the heating and reduction processes, solving the technical problems of low hydrogen utilization rate and high energy consumption in the direct reduction process of pellets in the oxidation roasting and conventional direct reduction processes, obtaining reduced pellets with a specific metallization rate, and using the prepared pre-reduced pellets as a blast furnace burden, thereby significantly reducing the fuel consumption and carbon emissions of the blast furnace. This method is a novel low-carbon and green pre-reduced pellet preparation process.

[0032] 2. According to the pre-reduced pellet preparation apparatus and method provided by the present disclosure, by using pure hydrogen or hydrogen-enriched gas for cooling and reduction, the process becomes simpler and the energy utilization efficiency is improved.

[0033] 3. According to the pre-reduced pellet preparation apparatus and method provided by the present disclosure, the physical heat of the roasted pellets is used to meet the heat required for hydrogen reduction and gas heating. As a result, the thermodynamic conditions for hydrogen reduction are more rationalized, and the hydrogen utilization rate is significantly improved.

[0034] 4. According to the pre-reduced pellet preparation apparatus and method provided by the present disclosure, the entire process preferably employs the combustion of non-fossil energy sources such as pyrolysis gas, pyrolysis oil, biomass oil, and biomass carbon, green electric drive devices, and pure hydrogen or hydrogen-enriched gas reduction. As a result, the production of pre-reduced pellets by a carbon-free or low-carbon process can be realized. Moreover, by using pre-reduced pellets in a conventional blast furnace or converter, the carbon emissions in the steelmaking process can be significantly reduced.

Brief Description of the Drawings

[0035] Other features, objectives, and advantages of the present disclosure will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings.

Figure 1

Embodiments for Carrying Out the Invention

[0036] To better understand the above technical solutions of the present disclosure, the technical solutions of the present disclosure will be further described below together with the accompanying drawings and embodiments.

[0037] Referring to FIG. 1, the pre-reduced pellet preparation apparatus provided by the present disclosure includes a fire grate rotary kiln pellet oxidation system 1 and a hydrogen-based shaft furnace reduction system 2. Referring to FIG. 1, the fire grate kiln pellet oxidation system 1 includes a fire grate system 18 and a rotary kiln system 16 connected to the fire grate system 18, and is used to sequentially dry, preheat, and perform high-temperature roasting on iron-containing green pellets, and Referring to FIG. 1, the grate system 18 sequentially dries and preheats the iron-containing green pellets to obtain preheated pellets. The grate system 18 is provided with a drying section I, a drying section II, a preheating section I, and a preheating section II in sequence in the moving direction of the green pellets. The preheating section II communicates with the rotary kiln system 16. The preheating section II is connected to the drying section II via the first reheating fan 14. The preheating section I is connected to the tubular heat exchanger 235 of the reducing gas system 23. The preheating section I is connected to the rotary kiln system 16 via the combustion fan 17 and is also connected to the drying section I via the second reheating fan 15. The drying section I and the drying section II are each connected to the bag dust collector 12 via the main exhaust fan 11. The rotary kiln system 16 is used for the high-temperature roasting of the preheated pellets in the grate system 18. The rotary kiln system 16 burns fuel using a burner to supply the heat required in the high-temperature roasting process. The roasted pellets obtained after roasting in the grate rotary kiln pellet oxidation system 1 are conveyed to the supply system of the hydrogen-based shaft furnace reduction system 2 via the high-temperature resistant tank.

[0038] Referring to FIG. 1, the hydrogen shaft furnace reduction system 2 includes a hydrogen shaft furnace 22, a supply system 21, a reducing gas system 23, a cooling system 24, and an exhaust system, and is used to reduce the roasted pellets obtained by roasting in the fire grate rotary kiln pellet oxidation system 2. The supply system 21 is arranged above the hydrogen shaft furnace 22 to receive the roasted pellets from the rotary kiln system 16. The reducing gas system 23 supplies reducing gas to the hydrogen shaft furnace 22. Further, the reducing gas system 23 processes the flue gas generated by the reduction reaction in the hydrogen shaft furnace 22 to reduce the roasted pellets from the supply system 21 in the hydrogen shaft furnace 22 and can also obtain pre-reduced pellets. The cooling system 24 supplies cooling gas, performs a cooling process on the pre-reduced pellets obtained in the hydrogen shaft furnace 22 to obtain cooled pre-reduced pellets, and can further process the mixed gas generated after cooling. The exhaust system is arranged at the bottom of the hydrogen shaft furnace 22 to discharge the cooled pre-reduced pellets.

[0039] Referring to FIG. 1, the supply system 21 includes an upper hopper 211, an intermediate hopper 212, and a lower hopper 213. In order to maintain a closed environment in each part of the hopper, valves are arranged between the upper hopper 211 and the intermediate hopper 212, and between the intermediate hopper 212 and the lower hopper 213. In a specific embodiment, after the upper hopper 211 is filled with roasted pellets (up to 1200°C), in order to make the oxygen content in the upper hopper 211 be 1% or less, the upper hopper 211 is further provided with an air duct for facilitating the introduction of steam (preferably high-temperature and high-pressure) or nitrogen (preferably high-temperature and high-pressure) for replacing the oxygen in the air. In order to ensure pressure equalization in the intermediate hopper, the intermediate hopper 212 is provided with a pressure equalizing device. The pressure equalizing process can be completed using a gas with the same composition as the top gas in the shaft furnace. A universal distributor is arranged under the lower hopper 213 to facilitate the distribution of the roasted pellets to the hydrogen shaft furnace 22.

[0040] Referring to FIG. 1, the reducing gas system 23 is used to supply the reducing gas necessary for the reduction reaction to the hydrogen-based shaft furnace 22, and includes a tubular heat exchanger 235, a residual heat boiler 231, a first scrubber 232, a circulation fan 233, and a pressurizing fan 234. The tubular heat exchanger 235 is provided with a flue gas inlet, a flue gas outlet, an air inlet, and an air outlet. The flue gas inlet is connected to the flue gas port at the upper end of the hydrogen-based shaft furnace 22, the flue gas outlet is connected to the residual heat boiler 231, the air inlet is connected to the heat exchange fan 236, and the air outlet is connected to the preheating section I of the fire grate system 18. The other end of the residual heat boiler 231 is connected to the air inlet of the first scrubber 232. One end of the circulation fan 233 communicates with the air outlet of the first scrubber 232, and the other end of the circulation fan 233 communicates with the annular tuyere in the middle of the hydrogen-based shaft furnace 22. The pressurizing fan 234 pressurizes the reducing gas from the circulation fan 233. In a specific application, the reducing gas enters from the annular tuyere of the hydrogen-based shaft furnace 22 and contacts the roasted pellets from the supply system 21 in the middle of the hydrogen-based shaft furnace 22, and while undergoing a reduction reaction with the roasted pellets, it is heated by the roasted pellets (absorbing the heat of the roasted pellets to cool the roasted pellets). After the reaction, the reducing gas flows out from the flue gas outlet at the upper end of the hydrogen-based shaft furnace 22, is heat-exchanged in the tubular heat exchanger 235, has its waste heat recovered in the residual heat boiler 231, is scrubbed in the first scrubber 232, and passes through the annular tuyere under the action of the circulation fan 233 and the pressurizing fan 234 to participate in the reduction reaction.

[0041] Referring to FIG. 1, the cooling system 24 includes an oxygenated combustion unit 241, a waste heat recovery unit 242, a second scrubber 243, and a cooling fan 244. The oxygenated combustion unit 241 is connected to the air outlet at the lower part of the hydrogen shaft furnace 22. One end of the waste heat recovery unit 242 is connected to the oxygenated combustion unit 241, and the other end is connected to the air inlet of the second scrubber 243. One end of the cooling fan 244 is connected to the air outlet of the second scrubber 243, and the other end communicates with the air inlet at the lower part of the hydrogen shaft furnace 22. The air outlet at the lower part of the hydrogen shaft furnace is arranged above the air inlet at the lower part of the hydrogen shaft furnace. In a specific application, the cooling gas enters the hydrogen shaft furnace 22 from the air inlet at the lower part of the hydrogen shaft furnace, cools the pre-reduced pellets after the reduction reaction at the lower part of the hydrogen shaft furnace 22. The mixed gas after the cooling treatment is oxygenated and burned in the oxygenated combustion unit 241, the waste heat is recovered in the waste heat recovery unit 242, scrubbed in the second scrubber 243, and then participates in the cooling treatment through the air inlet at the lower part of the hydrogen shaft furnace 22 under the action of the cooling fan 244.

[0042] The discharge system discharges the cooled pre-reduced pellets.

[0043] Referring to FIG. 1, the method for preparing pre-reduced pellets provided by the present disclosure uses the above-mentioned pre-reduced pellet preparation device, supplies iron-containing green pellets to the furnace kiln pellet oxidation system 18 of the stove and bakes them at a high temperature, and then directly supplies them to the hydrogen shaft furnace reduction system 2 for reduction. Specifically, this method includes the following steps.

[0044] (1) After mixing bentonite and finely ground limestone / hydrated lime with the iron ore raw material to obtain a mixed material, the mixed material is mixed with water and pelletized to obtain iron-containing green pellets. After the pretreatment of ball milling or high-pressure roll milling, the specific surface area of the bran is 1500 cm 2After obtaining an iron ore raw material by mixing one or more of magnetite, hematite, and limonite with a content of / g or more, bentonite is added, and finely pulverized limestone or slaked lime is added to obtain a mixed material with a binary alkalinity (CaO / SiO2) of 0.3 to 0.5 or 0.8 to 1.2. The blending amount of bentonite is 0.7 to 1.5% by weight of the iron ore raw material, and the binary alkalinity of the mixed material is adjusted according to the actual usage situation using finely pulverized limestone or slaked lime. Then, an appropriate amount of water is added and pelletized using a disk pelletizer or a drum pelletizer to obtain iron-containing green pellets with a particle size of 8 to 20 mm.

[0045] (2) The iron-containing green pellets are put into the fire grate system 18, and blast drying, exhaust drying, primary preheating, and secondary preheating are sequentially performed to obtain preheated pellets. Then, the preheated pellets are supplied to the rotary kiln system 16 and roasted at a high temperature of 1170 to 1300 °C to obtain roasted pellets. The iron-containing green pellets prepared in step (1) are distributed to the fire grate system 18 through a conventional distribution device to obtain a material layer of iron-containing green pellets with a total height of 250 to 400 mm. Then, the material layer of iron-containing green pellets is sequentially subjected to blast drying, exhaust drying, primary preheating, and secondary preheating through the drying section I, drying section II, preheating section I, and preheating section II of the fire grate system 18 to obtain preheated pellets. Then, the preheated pellets are roasted in the rotary kiln system 16 by burning a combustible substance using a burner to provide heat to obtain roasted pellets. Blast drying is carried out in the drying section I by using the high-temperature exhaust gas from the preheating section I and blowing it into the iron-containing green pellets through the second reheating fan 15 from the bottom of the layer of iron-containing green pellets. Blast drying is carried out at a temperature controlled at 170 to 240 °C, preferably 190 to 210 °C, at an air velocity of 0.8 to 1.4 m / s, preferably 0.9 to 1.2 m / s, for a time of 1.5 to 2.5 minutes. Exhaust drying is carried out in the drying section II using the high-temperature exhaust gas from the preheating section II introduced at a position above the surface of the pellet layer that has undergone the above blast drying by the first reheating fan 14. The exhaust drying temperature is adjusted according to the explosion temperature of the green pellets and is controlled to be below the explosion temperature of the pellets. The exhaust drying is carried out at a temperature of 300 - 400 °C, preferably 330 - 350 °C, and an air velocity of 0.8 - 1.4 m / s, preferably 0.9 - 1.2 m / s, for 4 - 6 minutes. The primary preheating is carried out in the preheating section I, and high-temperature air is obtained by indirectly heat-exchanging the air and flue gas after the reduction reaction in the tubular heat exchanger 235 of the reduction gas system 23. The primary preheating is carried out at a temperature of 600 - 800 °C and an air velocity of 0.8 - 1.4 m / s, preferably 0.9 - 1.2 m / s, for 4 - 6 minutes. The secondary preheating is carried out in the preheating section II, and as the high-temperature air, the high-temperature exhaust gas generated by roasting in the rotary kiln is used. The secondary preheating is carried out at a temperature controlled to 900 - 1100 °C and an air velocity of 0.8 - 1.4 m / s, preferably 0.9 - 1.2 m / s, for 4 - 6 minutes.

[0046] Roasting is carried out in the rotary kiln system 16, using the heat provided by the combustion of fuel in the burner. The fuel may be combustible oil or combustible gas (including natural gas, coke oven gas, pyrolysis gas, pyrolysis oil, biomass oil, or biomass carbon), preferably gas from non-fossil energy sources such as pyrolysis gas, pyrolysis oil, or biomass oil. In order to increase the combustion temperature, high-temperature air is used to assist combustion, and the high-temperature air is from the mixed gas composed of air and the high-temperature exhaust gas from the preheating section I. Roasting is carried out at a temperature controlled to 1170 - 1300 °C for a time controlled to 8 - 12 minutes, and the roasted pellets have a cold compressive strength of 2200 N / pellet or more.

[0047] In the fire grate system 18, after blast drying and exhaust drying the iron-containing green pellets, the exhaust gas passes through the main exhaust fan 11, the bag filter 12 and the dust removal, desulfurization and denitrification system, and is discharged from the chimney 13 after meeting the ultra-low emission standards.

[0048] (3) The roasted pellets enter the hydrogen shaft furnace reduction system, undergo a reduction reaction with the reducing gas, and are cooled by the cooling gas to obtain cooled pre-reduced pellets. The roasted pellets enter the supply system 21 of the hydrogen shaft furnace reduction system 2 through the high-temperature resistant tank, and then enter the hydrogen shaft furnace 22 of the hydrogen shaft furnace reduction system 2 through the supply system 21. A reduction reaction takes place in the middle part of the hydrogen shaft furnace 22. After the reduction reaction, a cooling process is carried out at the lower part of the hydrogen shaft furnace 22 to obtain cooled pre-reduced pellets. The flue gas after the reduction reaction enters the reduction gas system 23 from the flue gas outlet at the upper end of the hydrogen shaft furnace 22. After being subjected to heat exchange, waste heat recovery, and scrubbing, it enters the middle part of the hydrogen shaft furnace 22 through the reduction gas system 23 and participates in the reduction reaction. The mixed gas after the cooling process enters the cooling system 24 from the air outlet at the lower part of the hydrogen shaft furnace 22, undergoes oxy-fuel combustion, waste heat recovery, and scrubbing, and enters the lower part of the hydrogen shaft furnace 22 through the cooling system 24 and participates in the cooling process. Specifically, step (3) includes the following sub-steps:

[0049] (3.1) Distribution: The roasted pellets prepared in step (2) are introduced into the supply system 21 of the hydrogen shaft furnace reduction system 2 through a high-temperature resistant tank, and after sequentially entering the upper hopper 211, intermediate hopper 212, and lower hopper 213 of the supply system 21, they are distributed into the hydrogen shaft furnace 22. Also, during the process, after the roasted pellets are charged into the upper hopper 211, steam (preferably high-temperature and high-pressure) or nitrogen (preferably high-temperature and high-pressure) is introduced to replace the oxygen content in the upper hopper 211 to be 1% or less. Then, after the roasted pellets are completely in the intermediate hopper 212, the valve below the upper hopper 211 is opened, and then the valve below the upper hopper 211 is closed. A gas having the same composition as the top gas in the hydrogen shaft furnace 22 is used to complete the equalizing process. After the equalizing is completed, the valve below the intermediate hopper 212 is opened. After the roasted pellets are completely in the lower hopper 213, the valve below the intermediate hopper 212 is closed, and the valve below the lower hopper 213 is opened to distribute the roasted pellets into the hydrogen shaft furnace 22 through a universal distributor.

[0050] (3.2) Reduction reaction: The roasted pellets undergo a reduction reaction in the middle part of the hydrogen shaft furnace 22. The reducing gas is pure hydrogen or coke oven gas, preferably pure hydrogen. The reducing gas enters the hydrogen shaft furnace 22 from the annular tuyere in the middle part of the hydrogen shaft furnace 22, contacts the high-temperature roasted pellets at about 500 °C, and while undergoing a reduction reaction with the roasted pellets, the reducing gas is heated by the roasted pellets (absorbing the heat of the roasted pellets and thus cooling the roasted pellets). As the reducing gas rises, its concentration gradually decreases. However, because the temperature of the roasted pellets is gradually rising, the reduction reaction is proceeding. After the flue gas that has undergone the reduction reaction is discharged from the flue gas outlet at the upper end of the hydrogen shaft furnace 22, the temperature of the flue gas is raised to 1000 °C or above by heating. The flue gas is further heat-exchanged in the tubular heat exchanger 235 (the primary preheating is carried out with the physical heat of the top gas), the waste heat is recovered in the residual heat boiler 231, and scrubbed in the first scrubber 232 to remove H2O and dust from the flue gas. Alternatively, a small amount of aqueous ammonia can be injected into the first scrubber 232 to remove CO2 and SO2 from the flue gas according to the process requirements. As a result, the flue gas becomes a high-reducing-potential gas mainly composed of H2 and CO after simple scrubbing treatment. The obtained reducing gas participates in the reduction reaction again through the circulation fan 233. During the reduction reaction, the consumption of the reducing gas is 800 - 1200 m 3 / t, the reduction reaction time is 40 - 100 minutes, and the pressure of the hydrogen shaft furnace 22 in the hydrogen shaft furnace reduction system 2 is controlled at 200 - 250 kPa.

[0051] (3.3) Cooling treatment: The roasted pellets after the reduction reaction are subjected to cooling treatment by the cooling gas at the lower part of the hydrogen shaft furnace 22. The mixed gas after the cooling treatment enters the cooling system 24 from the air outlet at the lower part of the hydrogen shaft furnace 22. After undergoing oxy-fuel combustion, waste heat recovery, and scrubbing, it enters the hydrogen shaft furnace 22 from the air inlet at the lower part of the cooling system 24 through the cooling system 24 and participates in the cooling treatment again. In the cooling treatment, nitrogen and a small amount of natural gas are used. While cooling, the direct reduced iron (DRI) contained in the reduction material can catalyze the CH4 decomposition, and a small amount of Fe3C is formed, thereby completing the carbonization process to prevent the reoxidation of DRI. In the above process, the flow rate of the cooling gas is 1200 - 1800 m 3 / t. In the process of cooling the pellets, a small amount of H2 is derived by the cooling gas. To ensure safety, after oxy-fuel combustion of the mixed gas, waste heat is utilized, and H2O is removed by a scrubber to obtain a mixed gas containing N2 and a small amount of CO2. The mixed gas is recycled. The final discharge from the hydrogen shaft furnace 22 is the cooled pre-reduced pellets discharged at a temperature below 150°C. The metallization rate of the product is determined according to the requirements of the subsequent process.

[0052] In the above method for preparing the pre-reduced pellets, the metallization rate of the prepared pre-reduced pellets is 40% or more, and the hydrogen utilization rate is up to 40% or more. In a preferred embodiment, the metallization rate of the pre-reduced pellets is 40 - 62%, and the hydrogen utilization rate is 50% or more at most.

[0053] The pre-reduced pellet preparation apparatus and method of the present disclosure will be further described below with reference to specific examples. Also, the pre-reduced pellet preparation apparatus and method in the following embodiments use the aforementioned apparatus and method.

Example

[0054] Examples 1 - 5 The iron ore raw materials in Examples 1-5 are as shown in Table 1. After adding bentonite and finely ground limestone to the iron ore raw materials to form a mixed material, it is mixed with water, and the obtained mixed material is pelletized to form iron-containing green pellets. Then, these iron-containing green pellets are transferred to a fire grate system, and subjected to blast drying, exhaust drying, primary preheating, and secondary preheating in sequence to obtain preheated pellets. After that, they are charged into a rotary kiln system for roasting to obtain roasted pellets. The roasting parameters are shown in Table 1 below.

Table 1

[0055] The roasted pellets are transferred to a hydrogen-based shaft furnace reduction system for reduction using pure hydrogen or coke oven gas. After that, the pellets are cooled by nitrogen and methane and carbonized to obtain pre-reduced pellets. The reduction parameters are shown in Table 2 below.

Table 2

[0056] In Example 1, the binary alkalinity of the iron-containing green pellets is 1.0. By using the processing parameters shown in Table 1, the cold compressive strength of the obtained roasted pellets is high. The roasted pellets are cooled and reduced by introducing pure hydrogen, and the hydrogen utilization rate is 50%. The pre-reduced pellets obtained after cooling have a metallization rate of up to 62%.

[0057] In Example 2, the binary alkalinity of the iron-containing green pellets is 0.3. By using the processing parameters shown in Table 1, since the magnetite ratio is high, the preheating temperature and roasting temperature are suitably reduced. The roasted pellets are cooled and reduced by introducing pure hydrogen, and the hydrogen utilization rate is 61%. The metallization rate of the pre-reduced pellets obtained after cooling is up to 54%.

[0058] In Example 3, the binary basicity of the iron-containing green pellet is 0.9. By using the processing parameters shown in Table 1, the roasted pellet was cooled and reduced by introducing pure hydrogen, and the hydrogen utilization rate was 65%. The metallization rate of the pre-reduced pellet obtained after cooling is at most 60%.

[0059] In Example 4, the binary basicity of the iron-containing green pellet is 0.4. By using the processing parameters shown in Table 1, since the blending amount of the alkaline flux (finely pulverized limestone) decreases, the preheating temperature and the roasting temperature are suitably lowered, and pure hydrogen was introduced at a hydrogen utilization rate of 55% to cool and reduce the roasted pellet. The metallization rate of the pre-reduced pellet obtained after cooling is at most 56%.

[0060] In Example 5, the binary basicity of the iron-containing green pellet is 1.0, and by using the processing parameters shown in Table 1, the cold compressive strength of the obtained roasted pellet is high. The roasted pellet was cooled and reduced by introducing coke oven gas. The hydrogen utilization rate is relatively lower than when pure hydrogen is used because CO, CH4, and H2O undergo a water gas reaction at high temperatures. The hydrogen utilization rate in this example is only 42%. The metallization rate of the pre-reduced pellet is at most 51%.

[0061] In summary, according to the pre-reduced pellet preparation apparatus and method based on the fire grate rotary kiln provided by the present disclosure, by utilizing a fire grate system, a rotary kiln system, and a hydrogen-based shaft furnace reduction system, the roasting process and the reduction process in the pellets are organically combined, the cooling process of the roasted pellets and the heating process of the pellets before reduction are eliminated, the physical heat of the roasted pellets is used to meet the heat required in the heating and reduction processes, and the technical problems of low hydrogen utilization rate and high energy consumption in the direct reduction process of pellets in the oxidation roasting and conventional direct reduction processes are solved, reduced pellets with a specific metallization rate are obtained, and the prepared pre-reduced pellets are used as a blast furnace burden, whereby the fuel consumption and carbon emissions of the blast furnace can be significantly reduced. The present method is a novel low-carbon and green pre-reduced pellet preparation process. By using pure hydrogen or hydrogen-enriched gas for cooling and reduction, the process becomes simpler, the energy utilization efficiency is improved, the physical heat of the roasted pellets is used to meet the heat required for hydrogen reduction and gas heating. As a result, the thermodynamic conditions for hydrogen reduction are more rationalized, and the hydrogen utilization rate is significantly improved. The entire process preferably employs the combustion of non-fossil energy sources such as pyrolysis gas, pyrolysis oil, biomass oil, and biomass carbon, green electric drive devices, and pure hydrogen or hydrogen-enriched gas reduction. As a result, it is possible to realize the production of pre-reduced pellets by a carbon-free or low-carbon process, and by using pre-reduced pellets in a conventional blast furnace or converter, the carbon emissions from the steelmaking process can be significantly reduced.

[0062] Those skilled in the art should recognize that the above embodiments are merely examples of the present disclosure and should not be construed as limiting the present disclosure. It is intended that variations and modifications of the above embodiments fall within the scope of the appended claims of the present disclosure as long as they are within the scope of the true technical concept of the present disclosure.

Claims

1. A preliminary reduction pellet preparation apparatus comprising a fire grate rotary kiln pellet oxidation system and a hydrogen shaft furnace reduction system, wherein the fire grate rotary kiln pellet oxidation system comprises a fire grate system and a rotary kiln system connected to the fire grate system. In the fire grate system, iron-containing green pellets are sequentially dried and preheated to obtain preheated pellets. In the rotary kiln system, the preheated pellets are roasted at a temperature of 1170 to 1300 °C to obtain roasted pellets, the hydrogen shaft furnace reduction system comprises a hydrogen shaft furnace, a supply system, a reducing gas system, a cooling system, and an exhaust system. The supply system is disposed above the hydrogen shaft furnace, and the roasted pellets from the rotary kiln system are directly conveyed to the supply system. The reducing gas system processes flue gas from the hydrogen shaft furnace and supplies reducing gas to the hydrogen shaft furnace. The roasted pellets from the supply system are reduced in the hydrogen shaft furnace to obtain preliminary reduction pellets. The cooling system cools the preliminary reduction pellets in the hydrogen shaft furnace to obtain cooled preliminary reduction pellets. The exhaust system is disposed at the bottom of the hydrogen shaft furnace and discharges the cooled preliminary reduction pellets, the reducing gas is hydrogen gas, and the reducing gas is not heated before entering the hydrogen shaft furnace, the fire grate system is provided with a drying section I, a drying section II, a preheating section I, and a preheating section II in order in the moving direction of the iron-containing green pellets, the preheating section II communicates with the rotary kiln system and is connected to the drying section II via a first reheating fan, the preheating section I is connected to a tubular heat exchanger of the reducing gas system, is connected to the rotary kiln system via a combustion fan, and is connected to the drying section I via a second reheating fan, the drying section I and the drying section II are each connected to a bag dust collector via a main exhaust fan, A preliminary reduction pellet preparation apparatus characterized by the above.

2. The supply system includes an upper hopper, an intermediate hopper, and a lower hopper, and valves are arranged between the upper hopper and the intermediate hopper, and between the intermediate hopper and the lower hopper, and / or The reducing gas system includes a tubular heat exchanger, a residual heat boiler, a first scrubber, a circulation fan, and a pressurizing fan. The tubular heat exchanger is provided with a flue gas inlet, a flue gas outlet, an air inlet, and an air outlet. The flue gas inlet is connected to the flue gas port at the upper end of the hydrogen shaft furnace, the flue gas outlet is connected to the residual heat boiler, the air inlet is connected to a fan, the air outlet is connected to the preheating section I of the fire grate system, the air outlet of the residual heat boiler is connected to the air inlet of the first scrubber, one end of the circulation fan is connected to the air outlet of the first scrubber, and the other end communicates with the annular tuyere at the middle part of the hydrogen shaft furnace. The pressurizing fan pressurizes the reducing gas from the circulation fan, and / or The cooling system includes an oxy-fuel combustion unit, a waste heat recovery unit, a second scrubber, and a cooling fan. The oxy-fuel combustion unit is connected to the air outlet at the lower part of the hydrogen shaft furnace. One end of the waste heat recovery unit is connected to the oxy-fuel combustion unit, and the other end is connected to the air inlet of the second scrubber. One end of the cooling fan is connected to the air outlet of the second scrubber, and the other end communicates with the air inlet at the lower part of the hydrogen shaft furnace. The air outlet at the lower part of the hydrogen shaft furnace is arranged above the air inlet at the lower part of the hydrogen shaft furnace. The preliminary reduction pellet preparation device according to claim 1, characterized in that.

3. The preliminary reduction pellet preparation device according to claim 2, characterized in that an air duct is provided in the upper hopper, a pressure equalizing device is provided in the intermediate hopper, and a universal distributor is provided in the lower hopper.

4. A step of preparing pre-reduced pellets by using the pre-reduced pellet preparation apparatus according to any one of claims 1 to 3; a step of roasting the pellets at a temperature of 1170 to 1300 °C in the fire grate rotary kiln pellet oxidation system of the pre-reduced pellet preparation apparatus to obtain roasted pellets having a temperature of 1170 to 1300 °C; and then, a step of directly supplying the roasted pellets to the hydrogen shaft furnace reduction system of the pre-reduced pellet preparation apparatus for reduction to obtain pre-reduced pellets. A method for preparing pre-reduced pellets.

5. (1) After mixing bentonite and finely pulverized limestone / hydrated lime with an iron ore raw material to obtain a mixed material, water is mixed with this mixed material and pelletized to obtain iron-containing green pellets; (2) Distributing the iron-containing green pellets to a fire grate system to form a material layer of the iron-containing green pellets, continuously subjecting the material layer of the iron-containing green pellets to blast drying, exhaust drying, primary preheating, and secondary preheating to obtain preheated pellets, and then supplying the preheated pellets to a rotary kiln system for roasting at 1170 to 1300 °C to obtain roasted pellets having a temperature of 1170 to 1300 °C; (3) Supplying the roasted pellets to a hydrogen shaft furnace reduction system, causing the roasted pellets to undergo a reduction reaction with a reducing gas, and then cooling with a cooling gas to obtain pre-reduced pellets. The method for preparing pre-reduced pellets according to claim 4, characterized by including the above steps.

6. In the step (1), the iron ore raw material is selected from one or more of magnetite, hematite, and limonite, and / or The iron ore raw material has a Blaine specific surface area of 1500 cm ２ / g or more, and / or the blending amount of bentonite is 0.7 to 1.5% by weight of the iron ore raw material, and / or the mixed material has a binary alkalinity of 0.3 to 0.5 or 0.8 to 1.2, and / or the particle size of the iron-containing green pellets is 8 to 20 mm, and / or In the step (2), in the fire grate system, the material layer of the iron-containing green pellets has a height of 250 to 400 mm, and / or the blast drying is carried out in the drying section I of the fire grate system at a temperature of 170 to 240 °C and an air velocity of 0.8 to 1.4 m / s for 1.5 to 2.5 minutes, and / or The exhaust drying is carried out in the drying section II of the fire grate system at a temperature of 300 to 400 °C and an air velocity of 0.8 to 1.4 m / s for 4 to 6 minutes, and / or The primary preheating is carried out in the preheating section I of the fire grate system at a temperature of 600 to 800 °C and an air velocity of 0.8 to 1.4 m / s for 4 to 6 minutes, and / or The secondary preheating is carried out in the preheating section II of the fire grate system at a temperature of 900 to 1100 °C and an air velocity of 0.8 to 1.4 m / s for 4 to 6 minutes, and / or The fuel used in the rotary kiln system includes natural gas, coke oven gas, pyrolysis gas, pyrolysis oil, biomass oil, or biomass carbon, and / or The rotary kiln system uses high-temperature air to support combustion, and the high-temperature air is from a mixed gas composed of the air and high-temperature exhaust gas of the fire grate system, and / or In the roasting process, roasting is carried out for 8 to 12 minutes, and / or In step (3), the pressure of the hydrogen shaft furnace in the hydrogen-based shaft furnace reduction system is 200 to 250 kPa, and / or The reducing gas is pure hydrogen or coke oven gas, and / or During the reduction reaction, the consumption amount of the reducing gas is 800 to 1200 m ３ / t, the reduction reaction is carried out for a time of 40 to 100 minutes, and / or The cooling gas contains nitrogen and natural gas, and / or During the cooling process, the flow rate of the cooling gas is 1200 to 1800 m ３ / t, and / or The pre-reduced pellets are discharged at a temperature of less than 150 °C, and The metallization rate of the pre-reduced pellets is 40% or more. The method for preparing pre-reduced pellets according to claim 5, characterized in that.

7. In step (2), in the process of the blast drying, the blast drying is carried out at a temperature of 190 to 210 °C and an air velocity of 0.9 to 1.2 m / s, and / or In the process of the exhaust drying, the exhaust drying is carried out at a temperature of 330 to 350 °C and an air velocity of 0.9 to 1.2 m / s, and / or In the process of the primary preheating, the air velocity is 0.9 to 1.2 m / s, and / or In the process of the secondary preheating, the air velocity is 0.9 to 1.2 m / s, and / or In step (3), the metallization rate of the pre-reduced pellets is 40 to 62%, The reducing gas is pure hydrogen, and during the reduction reaction, the hydrogen utilization rate is 50% or more. The method for preparing pre-reduced pellets according to claim 6, characterized in that.

8. In step (3), the reducing gas is pure hydrogen, and during the reduction reaction, the hydrogen utilization rate reaches 55% or more, and / or The roasted pellets are conveyed into the supply system of the hydrogen shaft furnace reduction system through a high-temperature resistant tank, and then distributed into the hydrogen shaft furnace of the hydrogen shaft furnace reduction system through the supply system, and participate in the reduction reaction in the middle part of the hydrogen shaft furnace. The reducing gas enters the hydrogen shaft furnace through the reducing gas system and participates in the reduction reaction. The flue gas after the reduction reaction enters the reducing gas system from the flue gas outlet at the upper end of the hydrogen shaft furnace, and after being subjected to heat exchange, waste heat recovery, and scrubbing, enters the middle part of the hydrogen shaft furnace and participates in the reduction reaction. And The cooling gas enters the hydrogen shaft furnace through the cooling system and participates in the cooling process. The mixed gas after the treatment enters the cooling system from the air outlet at the lower part of the hydrogen shaft furnace, and after being subjected to oxygen combustion, waste heat recovery, and scrubbing, enters the lower part of the hydrogen shaft furnace and participates in the cooling process. The method for preparing pre-reduced pellets according to claim 5, characterized in that.

9. In step (3), the distribution in the supply system is carried out as follows: The roasted pellets are introduced into the supply system, pass through the upper hopper, intermediate hopper, and lower hopper of the supply system in sequence, and then are distributed into the hydrogen shaft furnace through a universal distributor. After the roasted pellets are charged into the upper hopper, steam or nitrogen is introduced to replace oxygen so that the oxygen content in the upper hopper is 1% or less. Then, the valve below the upper hopper is opened. As a result, after the roasted pellets completely enter the intermediate hopper, the valve below the upper hopper is closed. A gas having the same composition as the top gas in the hydrogen shaft furnace is used to complete the equalization process. After the equalization is completed, the valve below the intermediate hopper is opened. After the roasted pellets completely enter the lower hopper, the valve below the intermediate hopper is closed. Then, the valve below the lower hopper is opened to distribute the roasted pellets into the hydrogen shaft furnace. The method for preparing pre-reduced pellets according to claim 8, characterized in that.

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