Gas-based reduction process, gas-based reduction system and application of particulate iron ore

Abstract

The application provides a gas-based reduction method, a gas-based reduction system and application of a particulate iron ore, and relates to the technical field of smelting. The gas-based reduction method does not need pure oxygen or high-calorific-value gas, and uses natural gas as a raw material. Compressed natural gas is converted into hydrogen-rich gas through desulfurization, steam reforming, shift reaction, first dehydration treatment and first CO2 removal treatment. The hydrogen-rich gas is preheated and countercurrently contacted with particulate iron ore of a specific particle size and at a specific preheating temperature to perform a reduction reaction, so as to obtain particulate direct reduced iron. Since the particle size of the particulate iron ore is small, the reduction reaction speed at the same temperature is faster than that of a traditional pellet, and other binders and a sintering process are not needed, so that pollution is greatly reduced. Meanwhile, the particulate iron ore at the specific preheating temperature is directly subjected to the reduction reaction with the hydrogen-rich gas, and the reduction reaction at low temperature is realized by using the heat of the particulate iron ore and the hydrogen-rich gas.

Description

Technical Field

[0001] This invention relates to the field of smelting technology, and in particular to a gas-based reduction method, gas-based reduction system and application for granular iron ore. Background Technology

[0002] Currently, the global steel smelting industry employs various ironmaking technologies, including blast furnace ironmaking and non-blast furnace ironmaking. Non-blast furnace ironmaking is further divided into direct reduction and smelting reduction, while direct reduction is further divided into gas-based reduction and coal-based reduction. Blast furnace ironmaking technology has the largest production scale and usage. However, the coking and sintering processes in blast furnace ironmaking emit large amounts of dust, carbon dioxide, and other gases, placing significant pressure on the environment. Among non-blast furnace ironmaking technologies, gas-based reduction uses reducing gases to reduce iron oxide in iron ore into metallized pellets. This method is more efficient than the traditional carbon reduction method, eliminates the need for coking and sintering, and is therefore cleaner.

[0003] Currently, gas-based reduction technologies mainly utilize Midrex and HYL gas-based shaft furnaces. Using a gas-based shaft furnace requires first mixing and roasting iron ore and binder to obtain oxide pellets, followed by reduction using reducing gases at high temperatures. In the Midrex gas-based shaft furnace, the reducing gas enters the furnace at 850-950℃, with a reaction pressure of approximately 0.5 MPa, yielding metallized pellets with a metallization rate of 92-93%. In the HYL gas-based shaft furnace, the reducing gas needs to be preheated to 900-960℃, with a reaction pressure of 0.4-0.6 MPa and an H2 / CO ratio of 5.6-5.9, resulting in metallized pellets with an average metallization rate of 91-95%.

[0004] Besides vertical shaft furnace technology, gas-based reduction technologies also include fluidized bed technology. Hydro carbon Research Inc. and Bethlehom Steel Conp jointly developed a hydrogen-fluidized bed technology using a three-stage fluidized bed. The ore powder resides in the reduction bed for a total of 45 hours, yielding reduced iron powder with a metallization rate of 98% and an H2 conversion rate of approximately 5%, operating intermittently. U.S. Steel's HIB fluidized bed technology uses a two-stage fluidized bed to obtain reduced iron powder with a metallization rate of 75% and a temperature of 700℃, with an H2 conversion rate of 32-36%. Exxon Research and Engineering's FIOR technology operates at 1.05 MPa and 880℃, using four fluidized beds to obtain iron powder with a metallization rate >90%.

[0005] Currently, most direct reduction technologies employ vertical shaft furnaces, with a small number using coal-based direct reduction technologies to produce metal pellets with high metallization rates, or to hot-press the pellets into briquettes as the final product. Fluidized bed technology, which produces iron powder, suffers from problems such as long reducing gas residence time, low reducing gas utilization efficiency, low product metallization rate, and the adhesion between iron particles at high temperatures affecting fluidization, resulting in unstable operation and poor economic benefits; therefore, only a very few plants still operate it.

[0006] In view of the above, the present invention is proposed to solve at least one of the above-mentioned technical problems. Summary of the Invention

[0007] The primary objective of this invention is to provide a gas-based reduction method for granular iron ore.

[0008] A second objective of this invention is to provide a gas-based reduction system for granular iron ore.

[0009] A third objective of this invention is to provide the application of the above-mentioned gas-based reduction method and gas-based reduction system for granular iron ore.

[0010] To achieve the above objectives, the following technical solution is proposed:

[0011] This invention provides a gas-based reduction method for granular iron ore, comprising the following steps:

[0012] (a) After desulfurization, compressed natural gas is mixed with steam to carry out a reforming reaction to obtain crude syngas;

[0013] The crude syngas is subjected to a shift reaction to obtain shift gas;

[0014] The shift gas is subjected to a first dehydration treatment and a carbon dioxide removal treatment to obtain a hydrogen-rich gas.

[0015] (b) After being preheated, hydrogen-rich gas is brought into countercurrent contact with preheated granular iron ore to carry out a reduction reaction, thereby obtaining granular direct reduced iron.

[0016] The granular iron ore has an average particle size of 0.015-4.00 mm, a preheated temperature of 500-750°C, a preheated hydrogen-rich gas temperature of 450-650°C, and an average flow rate of less than the minimum fluidization rate of the granular iron ore.

[0017] Furthermore, in step (a), the pressure of the compressed natural gas is 1.5-3.0 MPa;

[0018] Preferably, natural gas is preheated to 200-400℃ and then desulfurized, and the mass fraction of sulfur in the natural gas after desulfurization is not higher than 0.1 ppm;

[0019] Preferably, the volume ratio of compressed natural gas to steam is (2.5-3.6):1;

[0020] Preferably, after mixing natural gas and steam, the mixture is preheated to 450-600°C and then subjected to a reforming reaction at a temperature of 800-900°C.

[0021] Preferably, the dry gas composition of the crude syngas, calculated as 100% by volume, includes: 55-75% H2, 10-20% CO, 10-20% CO2 and 1-3% CH4;

[0022] Preferably, the temperature of the conversion reaction is 200-400℃;

[0023] Preferably, the dry gas composition of the hydrogen-rich gas, based on a volume percentage of 100%, includes: H2 85-99%, CO 0-10%, CO2 0-1%, and CH4 1-10%.

[0024] Furthermore, in step (b), the flow rate ratio of the reducing gas in the hydrogen-rich gas to the particulate iron ore is 500-2000 Nm³. 3 Reducing gas / t granular iron ore;

[0025] Preferably, the pressure of the reduction reaction is 0.05-3.00 MPa;

[0026] Preferably, the reduction reaction time is 1-15 hours.

[0027] Furthermore, step (b) also includes a step of subjecting the reduction tail gas generated during the reduction reaction to a second dehydration treatment to obtain purified tail gas.

[0028] Preferably, at least a portion of the purified exhaust gas is mixed with the shift gas after the first dehydration treatment for reuse; or, at least a portion of the purified exhaust gas is mixed with the hydrogen-rich gas after the first CO2 removal treatment for reuse.

[0029] Preferably, the purified exhaust gas is mixed with fuel gas and oxygen-containing gas for use as fuel, and the heat generated by the combustion of the fuel can be used to preheat granular iron ore.

[0030] Furthermore, step (b) also includes a step of subjecting the reduction tail gas generated during the reduction reaction to a second CO2 removal treatment, followed by a second dehydration treatment to obtain purified tail gas.

[0031] Preferably, the decarbonizing agent used in the second CO2 removal treatment includes calcium oxide;

[0032] Preferably, calcium oxide is subjected to a second CO2 removal treatment to obtain calcium carbonate, and the calcium carbonate is regenerated at 650-950℃. The regenerated calcium oxide can be reused as a decarbonation agent.

[0033] The present invention also provides a gas-based reduction system for granular iron ore, which uses the above-mentioned gas-based reduction method for granular iron ore to produce granular direct reduced iron.

[0034] The gas-based reduction system for granular iron ore includes a desulfurization unit, a reforming unit, a conversion unit, a first dehydration unit, a first CO2 removal unit, a gas preheating unit, a solid preheating unit, and a reduction reaction unit.

[0035] Compressed natural gas is transported to the desulfurization unit via pipeline. The desulfurization unit is connected in sequence to the reforming unit, the conversion unit, the first dehydration unit, and the first CO2 removal unit to convert the compressed natural gas into hydrogen-rich gas.

[0036] Hydrogen-rich gas and granular iron ore are respectively transported to the reduction reaction device through pipelines. A gas preheating device is installed on the pipeline used to transport hydrogen-rich gas, and a solid preheating device is installed on the pipeline used to transport granular iron ore.

[0037] Furthermore, the reduction reaction device is equipped with a rotating component.

[0038] Furthermore, the reduction reaction apparatus includes any one of a through-flow multi-stage furnace reactor, a suspended rotary kiln reactor, or a auger reactor.

[0039] Furthermore, it also includes a second dehydration device, the reduction reaction device is connected to the second dehydration device, and the second dehydration device is connected to the first CO2 removal device; or, it also includes a second CO2 removal device and a second dehydration device, the reduction reaction device is connected in sequence to the second CO2 removal device and the second dehydration device, and the second dehydration device is connected to the first CO2 removal device or to the reduction reaction device.

[0040] Preferably, the gas-based reduction system further includes a hot air furnace, a second dehydration device connected to the hot air furnace, and the hot air furnace connected to the solid preheating device;

[0041] Preferably, the gas-based reduction system further includes a regeneration device, which is connected to the second CO2 removal device.

[0042] The present invention also provides the application of the above-mentioned gas-based reduction method or gas-based reduction system for granular iron ore in the field of direct reduced iron production.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] (1) This invention provides a gas-based reduction method for granular iron ore. Compressed natural gas is converted into hydrogen-rich gas through desulfurization, steam reforming, shift reaction, a first dehydration treatment, and a first CO2 removal treatment. This gas-based reduction method does not require pure oxygen or high-calorific-value fuel gas. Using natural gas as raw material, the natural gas is converted into hydrogen-rich gas, which is then preheated and countercurrently contacted with granular iron ore of a specific particle size and at a specific preheating temperature to carry out a reduction reaction, producing granular direct reduced iron. Due to the smaller particle size of the granular iron ore, the reduction reaction rate at the same temperature is faster than that of traditional pellets, and no other binders or sintering processes are required, greatly reducing pollution. The reduction reaction involves directly reacting granular iron ore with hydrogen-rich gas at a specific preheating temperature. The heat generated by the granular iron ore and the hydrogen-rich gas itself enables the low-temperature reduction reaction. This low-temperature reduction reaction not only eliminates the need for special high-temperature resistant materials but also reduces the probability of iron agglomeration during the reduction process. The average flow rate of the hydrogen-rich gas is lower than the minimum fluidization velocity of the granular iron ore, preventing the gas from passing through the bed (granular iron ore) in the form of bubbles, thus avoiding incomplete gas reaction and low conversion rates. Furthermore, compared to existing iron ore reduction technologies, the gas-based reduction method for granular iron ore provided by this invention has lower CO2 and dust emissions, exhibiting clean and efficient characteristics.

[0045] (2) The present invention provides a gas-based reduction system for granular iron ore. The gas-based reduction system uses the above-mentioned gas-based reduction method for granular iron ore to produce granular direct reduced iron. The gas-based reduction system has a simple process flow and is easy to operate.

[0046] (3) The present invention also provides the application of the above-mentioned gas-based reduction method or gas-based reduction system for granular iron ore. Given the advantages of the above-mentioned gas-based reduction method or gas-based reduction system for granular iron ore, it has good application prospects in the field of direct reduced iron production. Attached Figure Description

[0047] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0048] Figure 1 A gas-based reduction system for granular iron ore according to one embodiment of the present invention;

[0049] Figure 2 A gas-based reduction system for granular iron ore according to another embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of the structure of the suspended rotary kiln reactor provided by the present invention;

[0051] Figure 4 for Figure 3 A schematic diagram of the lifting assembly in the suspended rotary kiln reactor is provided.

[0052] Figure 5 This is a schematic diagram of the structure of the auger-type reactor provided by the present invention;

[0053] Figure 6 for Figure 5 A schematic diagram of the spiral blades in the provided auger reactor;

[0054] Figure 7 This is a schematic diagram of the structure of the cross-flow multi-stage furnace reactor provided by the present invention.

[0055] Icons: R1 - Desulfurization unit; R2 - Reforming unit; R3 - Shift converter; R4 - First CO2 removal unit; R5 - Reduction reaction unit; R6 - Solid preheating unit; R7 - Reduced iron powder hot briquetting machine; R8 - Electric furnace; R9 - Reduced iron powder loading truck; R10 - Hot blast stove; R11 - Second CO2 removal unit; E0 - First dehydration unit; E1 - First heat exchanger; E2 - Second heat exchanger; E3 - Third heat exchanger; E4 - Fourth heat exchanger; E5 - Fifth heat exchanger; E6 - Sixth heat exchanger; E7 - Seventh heat exchanger; E8 - Eighth heat exchanger; E9 - Second dehydration unit; E10 - Gas preheating unit; E11 - Eleventh heat exchanger; E12 - Twelfth heat exchanger; C1 - Compressor;

[0056] 1-Compressed natural gas; 2-Steam; 3-Oxygen-containing gas a; 4-Fuel gas a; 5-Combustion exhaust gas; 6-Condensate a; 7-Decarbonizing agent; 8-Decarbonizing agent absorbing carbon dioxide; 9-Hot pressed sponge iron; 10-Condensate b; 11-Circulating reducing gas exhaust gas; 12-Fuel reducing gas exhaust gas; 13-Fuel gas b; 14-Oxygen-containing gas b; 15-Hot blast furnace combustion exhaust gas; 16-Granular iron ore; 17-Calcium oxide; 18-Calcium carbonate;

[0057] 20-Main cylinder; 21-Reducing diameter; 22-Rotating cylinder section; 23-Sealing mechanism; 24-Lifting assembly; 30-Rotating shaft; 31-Helical blade; 32-Air passage; 33-Seal; 40-Shell; 41-Agitating shaft; 42-Material tray; 43-Discharge pipe; 44-Agitating arm; 45-Scraper; 46-Air hole. Detailed Implementation

[0058] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] According to a first aspect of the present invention, a gas-based reduction method for granular iron ore is provided, comprising the following steps:

[0060] (a) After desulfurization, compressed natural gas is mixed with steam to carry out a reforming reaction to obtain crude syngas;

[0061] The crude syngas is subjected to a shift reaction to obtain shift gas;

[0062] The shift gas is subjected to a first dehydration treatment and a first CO2 removal treatment to obtain a hydrogen-rich gas.

[0063] (b) After being preheated, hydrogen-rich gas is brought into countercurrent contact with preheated granular iron ore to carry out a reduction reaction, thereby obtaining granular direct reduced iron.

[0064] The average particle size of the granular iron ore is 0.015-4.00 mm, the temperature of the preheated granular iron ore is 500-750℃, the temperature of the preheated hydrogen-rich gas is 450-650℃, and the average flow rate of the hydrogen-rich gas is less than the minimum fluidization rate of the granular iron ore.

[0065] Specifically, in step (a), the preparation of particulate direct reduced iron using compressed natural gas is cost-effective and helps reduce carbon dioxide emissions.

[0066] Since natural gas may contain a certain amount of sulfur, the sulfur in the natural gas is removed first before it is mixed with water vapor for reforming. The reforming reaction produces crude syngas, which mainly contains hydrogen, carbon monoxide and other components.

[0067] The crude syngas undergoes a shift reaction to convert most of the carbon monoxide into hydrogen and carbon dioxide, yielding shifted gas.

[0068] The shifted gas undergoes a first dehydration treatment to remove the water vapor it contains by converting it into condensate, and then undergoes a first CO2 removal treatment to remove CO2, resulting in a hydrogen-rich gas.

[0069] In step (b), the reducing gases (hydrogen and carbon monoxide) in the hydrogen-rich gas are mainly used to carry out a reduction reaction with the granular iron ore.

[0070] Using granular iron ore with an average particle size in the specific range of 0.015-4.00 mm as raw material, the reduction reaction rate of granular iron ore at the same temperature is faster than that of traditional oxide pellets or lump ore due to the smaller particle size. Moreover, it does not require the introduction of other binders and sintering processes, which can greatly reduce energy consumption and pollution.

[0071] The average particle size of granular iron ore directly affects the reduction reaction rate. If the average particle size is too low (below 0.015 mm), it can easily lead to excessive dust, low porosity affecting gas passage, and increased pressure drop and energy consumption. If the average particle size is too high (above 4.0 mm), it can easily cause slow reduction rates, low product metallization rates, and blockages in reaction pipelines. Therefore, the average particle size of granular iron ore should be limited to a specific range. Typical, but not limited, granular iron ore has an average particle size of 0.015 mm, 0.02 mm, 0.04 mm, 0.05 mm, 0.08 mm, 0.1 mm, 0.2 mm, 0.4 mm, 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.4 mm, 1.5 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2.4 mm, 2.5 mm, 2.8 mm, 3.0 mm, 3.2 mm, 3.4 mm, 3.5 mm, 3.8 mm, or 4.0 mm.

[0072] Both granular iron ore and hydrogen-rich gas are preheated before the reduction reaction. The reduction reaction can be carried out at a low temperature by utilizing the heat of the materials themselves, reaching temperatures of 450-750℃ (compared to 850-1050℃ in existing technologies). This low-temperature reduction reaction not only eliminates the need for special high-temperature resistant materials but also reduces the probability of agglomeration of granular iron during the reduction process. The preheated temperature of the granular iron ore is 500-750℃, with typical but non-limiting temperatures of 500℃, 550℃, 600℃, 650℃, 700℃, or 750℃. The preheated temperature of the hydrogen-rich gas is 450-650℃, with typical but non-limiting temperatures of 450℃, 480℃, 500℃, 520℃, 550℃, 580℃, 600℃, 620℃, or 650℃.

[0073] By contacting preheated granular iron ore with preheated hydrogen-rich gas in a countercurrent manner, the gas-solid contact efficiency between the hydrogen-rich gas and the granular iron ore can be enhanced, making the reduction reaction more complete and achieving high conversion and metallization rates even at low temperatures.

[0074] In the reduction reaction process of this invention, the average flow rate of the hydrogen-rich gas is lower than the minimum fluidization rate of the granular iron ore (U0). mfThis method keeps the granular iron ore in a non-fluidized state, allowing for more thorough contact between the hydrogen-rich gas and the granular iron ore. Unlike fluidized beds, which require higher gas velocities to maintain fluidization (typically a minimum of 0.8-1 m / s, with shorter residence times and gas passing through the bed as bubbles, resulting in lower conversion rates—around 5% per pass), the utilization efficiency of hydrogen-rich gas is significantly improved compared to fluidized beds, reducing process energy consumption. Furthermore, because the granules do not need to be constantly fluidized, the operational flexibility and stability of this production method are greatly enhanced.

[0075] It should be noted that the minimum fluidization rate (U) of granular iron ore mf It can be obtained through experimental measurement or by calculation using empirical formulas. The commonly used empirical formula is: (Fluidization Engineering Principles, Jin Yong et al., p. 19).

[0076] This invention provides a gas-based reduction method for granular iron ore. Compressed natural gas is converted into hydrogen-rich gas through desulfurization, steam reforming, shift reaction, a first dehydration treatment, and a first CO2 removal treatment. This gas-based reduction method does not require pure oxygen or high-calorific-value fuel gas. Using natural gas as raw material, the natural gas is converted into hydrogen-rich gas, which is then preheated and countercurrently contacted with granular iron ore of a specific particle size and preheating temperature to carry out a reduction reaction, producing granular direct reduced iron. Due to the smaller particle size of the granular iron ore, the reduction reaction rate at the same temperature is faster than that of traditional pellets, and no additional binders or sintering processes are required, significantly reducing pollution. Particulate iron ore at a specific preheating temperature undergoes a direct reduction reaction with hydrogen-rich gas. The heat generated by the granular iron ore and the hydrogen-rich gas itself enables the reduction reaction at a low temperature. This low-temperature reduction reaction not only eliminates the need for special high-temperature resistant materials but also reduces the probability of iron agglomeration during the reduction process. The average flow rate of the hydrogen-rich gas is lower than the minimum fluidization rate of the granular iron ore, preventing the gas from passing through the bed (granular iron ore) in the form of bubbles, thus avoiding incomplete gas reaction and low conversion rate. Furthermore, compared with existing iron ore reduction technologies, the gas-based reduction method for granular iron ore provided by this invention has lower CO2 and dust emissions, making it cleaner and more efficient.

[0077] In a preferred embodiment of the present invention, in step (a), the pressure of the compressed natural gas is 1.5-3.0 MPa; typically, but not limitingly, the pressure of the compressed natural gas is 1.5 MPa, 2.0 MPa, 2.5 MPa or 3.0 MPa.

[0078] The pressure of the natural gas in this invention is the commonly used pressure of pipeline natural gas. The pressure may fluctuate due to pipeline distance. Even if it exceeds the range of 1.5-3.0 MPa described in this invention, the process and technology described in this invention are still within the protection scope of this invention.

[0079] In a preferred embodiment of the present invention, natural gas is preheated to 200-400°C and then desulfurized, and the mass fraction of sulfur in the desulfurized natural gas is not higher than 0.1 ppm. The preheating temperature of the natural gas is 200°C, 220°C, 240°C, 250°C, 260°C, 280°C, 300°C, 320°C, 340°C, 350°C, 360°C, 380°C, or 400°C.

[0080] In a preferred embodiment of the present invention, the volume ratio of compressed natural gas to water vapor is (2.5-3.6):1; typical but non-limiting volume ratios of compressed natural gas to water vapor are 2.5:1, 2.6:1, 2.8:1, 3.0:1, 3.2:1, 3.4:1, 3.5:1 or 3.6:1.

[0081] In a preferred embodiment of the present invention, natural gas is mixed with steam and preheated to 450-600°C before undergoing a reforming reaction. The reforming reaction temperature is 800-900°C. Typical but non-limiting temperatures for the reforming reaction are 800°C, 820°C, 840°C, 850°C, 860°C, 880°C, or 900°C.

[0082] By limiting the volume ratio of compressed natural gas to steam and the temperature of the reforming reaction, the CH4 content in the crude gas is kept as low as possible while the H2 content is kept as high as possible.

[0083] In a preferred embodiment of the present invention, the dry gas composition of the crude syngas, based on a volume percentage of 100%, includes: H2 55-75%, CO 10-20%, CO2 10-20%, and CH4 1-3%.

[0084] Because the crude syngas has a high CO content, it is subjected to a shift reaction to obtain shift gas. The shift gas then undergoes a first dehydration treatment and a first CO2 removal treatment to obtain a hydrogen-rich gas that mainly contains hydrogen and carbon monoxide reducing gas.

[0085] As a preferred embodiment of the present invention, the dry gas composition of the hydrogen-rich gas, based on a volume percentage of 100%, includes: H2 85-99%, CO 0-10%, CO2 0-1%, and CH4 1-10%.

[0086] In a preferred embodiment of the present invention, in step (b), the flow rate ratio of the reducing gas in the hydrogen-rich gas to the particulate iron ore is 500-2000 Nm³. 3Reducing gas / t granular iron ore. Typical but not limiting flow rate is 500 Nm³. 3 Reducing gas / t granular iron ore, 800 Nm 3 Reducing gas / t granular iron ore, 900 Nm 3 Reducing gas / t granular iron ore, 1000 Nm 3 Reducing gas / t granular iron ore, 1500 Nm 3 Reducing gas / t granular iron ore, 1800 Nm 3 Reducing gas / t granular iron ore or 2000 Nm 3 Reducing gas / t granular iron ore.

[0087] It should be noted that, regarding the specific composition of the hydrogen-rich gas in this invention, the reducing gas of the hydrogen-rich gas includes hydrogen and carbon monoxide.

[0088] In a preferred embodiment of the present invention, in step (b), the pressure of the reduction reaction is 0.05-3.00 MPa; typical but non-limiting reduction reaction pressures are 0.05 MPa, 0.06 MPa, 0.08 MPa, 0.10 MPa, 0.2 MPa, 0.4 MPa, 0.5 MPa, 0.8 MPa, 1.00 MPa, 1.20 MPa, 1.40 MPa, 1.50 MPa, 1.80 MPa, 2.00 MPa, 2.20 MPa, 2.40 MPa, 2.50 MPa, 2.80 MPa, or 3.00 MPa.

[0089] By further limiting the pressure of the reduction reaction, natural gas and steam are reformed under appropriate pressure, and the crude syngas does not need to be compressed. After passing through the shift reaction, the first dehydration treatment, and the first CO2 removal treatment, it can be directly fed into the reduction reactor for the reduction reaction.

[0090] In a preferred embodiment of the present invention, the reduction reaction time is 1-15 hours. Typical but non-limiting reduction reaction times are 1 hour, 2 hours, 4 hours, 5 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, or 15 hours.

[0091] By further limiting the reduction reaction time, granular iron ore can have sufficient reduction reaction time to achieve a high metallization rate without inefficient due to excessively long reaction time.

[0092] In a preferred embodiment of the present invention, step (b) further includes a step of subjecting the reduction tail gas generated during the reduction reaction to optional second CO2 removal treatment and second dehydration treatment to obtain purified tail gas.

[0093] It should be noted that "optional second CO2 removal treatment" means that the second CO2 removal treatment may or may not be performed. That is, the reduction tail gas generated during the reduction reaction undergoes a second CO2 removal treatment and a second dehydration treatment to obtain purified tail gas, or the reduction tail gas generated during the reduction reaction undergoes only a second dehydration treatment to obtain purified tail gas.

[0094] In a preferred embodiment of the present invention, in step (b), the decarbonizing agent used in the second CO2 removal process includes calcium oxide;

[0095] Preferably, calcium oxide is subjected to a second CO2 removal treatment to obtain calcium carbonate, and the calcium carbonate is regenerated at 650-950℃. The regenerated calcium oxide can be reused as a decarbonation agent.

[0096] The purified exhaust gas can be recycled in various ways.

[0097] In a preferred embodiment of the present invention, at least a portion of the purified exhaust gas is mixed with the shift gas after the first dehydration treatment for reuse; or, at least a portion of the purified exhaust gas is mixed with the hydrogen-rich gas after the first CO2 removal treatment for reuse.

[0098] In a preferred embodiment of the present invention, the purified exhaust gas is mixed with fuel gas and oxygen-containing gas and used as fuel, and the heat generated by combustion can be used to preheat granular iron ore.

[0099] The gas-based reduction method for granular iron ore provided by this invention can not only achieve the preparation of granular direct reduced iron with a high metallization rate, but also achieve efficient utilization of reducing gas. The energy consumption in the process is greatly reduced, and the heat and materials are fully recycled. It has good application prospects in the field of industrial preparation of granular direct reduced iron.

[0100] According to a second aspect of the present invention, a gas-based reduction system for granular iron ore is also provided, wherein the above-described gas-based reduction method for granular iron ore is used to produce granular direct reduced iron.

[0101] The gas-based reduction system for granular iron ore includes a desulfurization unit R1, a reforming unit R2, a conversion unit R3, a first dehydration unit E0, a first CO2 removal unit R4, a gas preheating unit E10, a solid preheating unit R6, and a reduction reaction unit R5, as detailed below. Figure 1 and Figure 2 As shown.

[0102] Compressed natural gas 1 is transported through a pipeline to the desulfurization unit R1. The desulfurization unit R1 is connected in sequence to the reforming unit R2, the conversion unit R3, the first dehydration unit E0 and the first CO2 removal unit R4, so as to convert the compressed natural gas into hydrogen-rich gas.

[0103] Hydrogen-rich gas and granular iron ore 16 are respectively transported to the reduction reaction unit R5 through pipelines. A gas preheating device E10 is installed on the pipeline used to transport hydrogen-rich gas, and a solid preheating device R6 is installed on the pipeline used to transport granular iron ore.

[0104] Specifically, compressed natural gas 1 undergoes desulfurization in desulfurization unit R1. The desulfurized natural gas is then mixed with water vapor 2 and enters reforming unit R2 for a reforming reaction, converting the natural gas and water vapor into crude syngas, which mainly contains hydrogen and carbon monoxide. The crude syngas then enters shift converter R3 to convert most of the carbon monoxide into hydrogen, yielding shifted gas. The shifted gas passes through a first dehydration unit E0 to remove the water vapor it contains, converting it into condensate a6. Finally, it passes through a first CO2 removal unit R4 to remove carbon dioxide, resulting in hydrogen-rich gas.

[0105] Gas preheating device E10 preheats hydrogen-rich gas, and solid preheating device R6 preheats granular iron ore 16. The preheated hydrogen-rich gas and preheated granular iron ore are then introduced into reduction reaction device R5 and undergo a countercurrent contact for reduction reaction. After the reduction reaction is completed, the reduction tail gas and granular direct reduced iron are discharged from reduction reaction device R5.

[0106] As an optional embodiment of the present invention, the gas-based reduction system further includes a second dehydration device E9, and the reduction reaction device R5 is connected to the second dehydration device E9.

[0107] After the reduction reaction is completed, the reduction tail gas discharged from the reduction reaction device R5 is introduced into the second dehydration device E9 to remove the condensate b 10. After the reduction tail gas is dehydrated, the purified tail gas is obtained.

[0108] In an optional embodiment of the present invention, the second dehydration device E9 is connected to the first CO2 removal device R4.

[0109] When the purified exhaust gas contains a high amount of carbon dioxide, at least a portion of the purified exhaust gas is returned to the first dehydration treatment unit E0 and mixed with the shift gas treated by the first dehydration treatment unit E0 as raw material for reuse, and then enters the first CO2 removal unit R4 for CO2 removal treatment. Alternatively, when the purified exhaust gas contains a low amount of carbon dioxide, at least a portion of the purified exhaust gas is mixed with the hydrogen-rich gas treated by the first CO2 removal unit R4.

[0110] As an optional embodiment of the present invention, the gas-based reduction system further includes a second CO2 removal device R11 and a second dehydration device E9, and the reduction reaction device R5 is connected in sequence to the second CO2 removal device and the second dehydration device E9.

[0111] After the reduction reaction is completed, the reduction tail gas discharged from the reduction reaction device R5 is introduced into the second CO2 removal device R11 to remove CO2, and then passes through the second dehydration device E9 to remove condensate. The reduced tail gas is purified after water removal.

[0112] As an optional embodiment of the present invention, the second dehydration device E9 is connected to the first CO2 removal device R4, or the second dehydration device E9 is connected to the reduction reaction device R5, that is, the purified tail gas is mixed with the hydrogen-rich gas treated by the first CO2 removal device R4.

[0113] Preferably, the decarbonizing agent used in the second CO2 removal unit R11 includes calcium oxide;

[0114] Preferably, the calcium carbonate obtained after carbon dioxide removal is regenerated at 650-950℃, and the regenerated calcium oxide can be reused as a decarbonization agent.

[0115] By using solid calcium oxide as a decarbonizing agent, carbon dioxide can be directly removed from the reduction tail gas without cooling. This differs from existing carbon dioxide removal equipment, which typically uses liquid carbon dioxide absorbents or solid adsorbents to remove carbon dioxide from syngas or reduction tail gas. These methods require cooling the gas, usually to room temperature, and in cases of low-temperature methanol washing, even at -50°C, resulting in significant energy consumption during cooling and heating. This invention uses calcium oxide to directly absorb carbon dioxide from the hot reduction tail gas, eliminating the need for cooling and reducing the required cooling process. Only the temperature required for the second dehydration treatment (around 200°C) needs to be considered. When the dehydrated gas is reused as reducing gas, a significant heating is unnecessary, further reducing energy consumption. This method is particularly suitable when the reduction tail gas contains small amounts of carbon dioxide, requiring only a small amount of calcium oxide or its regeneration to obtain a low-carbon dioxide content gas. Furthermore, using calcium oxide to absorb carbon dioxide eliminates the need for expensive liquid carbon dioxide absorbents (mostly organic amines) or other adsorbents.

[0116] As an optional embodiment of the present invention, the gas-based reduction system further includes a hot blast stove R10, and a second dehydration device E9 is connected in sequence to the hot blast stove R10 and the solid preheating device R6.

[0117] After at least part of the purified exhaust gas is used as fuel reducing gas, exhaust gas 12 is mixed with fuel gas b 13 and then burned with oxygen-containing gas b14 in hot blast stove R10. The resulting combustion exhaust gas is introduced into solid preheating device R6 for heat utilization before being discharged.

[0118] As an optional embodiment of the present invention, the gas-based reduction system further includes a regeneration device (not shown in the figure), which is connected to the first CO2 removal device and / or the second CO2 removal device respectively.

[0119] The regeneration unit is mainly used for the regeneration of the decarbonizing agent in the first and second CO2 removal units.

[0120] In the second CO2 removal unit, calcium oxide can be used as a decarbonating agent. After the calcium oxide is treated to remove CO2, it generates calcium carbonate 18, which is discharged from the second CO2 removal unit and then enters the regeneration unit for regeneration. The calcium oxide 17 obtained from the regeneration treatment can be returned to the second CO2 removal unit as a decarbonating agent for reuse.

[0121] Since each device in the gas-based reduction system for granular iron ore requires a large amount of heat to varying degrees, the heat between the devices is recycled.

[0122] In a preferred embodiment of the present invention, the gas-based reduction system for granular iron ore includes a desulfurization unit R1, a reforming unit R2, a conversion unit R3, a first dehydration unit E0, a first CO2 removal unit R4, a gas preheating unit E10, a solid preheating unit R6, a reduction reaction unit R5, a hot blast stove R10, a reduced iron powder hot briquetting machine R7, an electric furnace R8, and a reduced iron powder loading car R9. Heat exchangers are also provided between the above-mentioned units, including a first heat exchanger E1, a second heat exchanger E2, a third heat exchanger E3, a fourth heat exchanger E4, a fifth heat exchanger E5, a sixth heat exchanger E6, a seventh heat exchanger E7, an eighth heat exchanger E8, an eleventh heat exchanger E11, and a twelfth heat exchanger E12 to achieve heat recycling.

[0123] Compressed natural gas 1 is transported through a pipeline to the desulfurization unit R1. The desulfurization unit R1 is connected in sequence to the reforming unit R2, the conversion unit R3, the first dehydration unit E0 and the first CO2 removal unit R4, so as to convert the compressed natural gas into hydrogen-rich gas.

[0124] Hydrogen-rich gas and granular iron ore 16 are respectively transported to the reduction reaction unit R5 through pipelines. A gas preheating device E10 is installed on the pipeline used to transport hydrogen-rich gas, and a solid preheating device R6 is installed on the pipeline used to transport granular iron ore.

[0125] The reduction reaction unit R5 is also connected to the reduced iron powder hot briquetting machine R7, the electric furnace R8, or the reduced iron powder loading truck R9.

[0126] Specifically, compressed natural gas 1 is preheated in the first heat exchanger E1 and then enters the desulfurization unit R1 for desulfurization. After desulfurization, the natural gas is heat-treated in the second heat exchanger E2 and mixed with steam 2, which has undergone stage-by-stage heat exchange in the fifth heat exchanger E5 and the fourth heat exchanger E4. After being preheated in the third preheater E3, it enters the reforming unit R2 to undergo a reforming reaction, converting the natural gas and steam into crude syngas mainly containing hydrogen and carbon monoxide. Fuel gas a4 is mixed in the seventh heat exchanger E7 with oxygen-containing gas a3, which has undergone stage-by-stage heat exchange in the sixth heat exchanger E6, and then enters the reforming unit R2 as fuel for combustion to provide the heat required for reforming. The combustion exhaust gas 5 formed by fuel combustion undergoes stage-by-stage heat exchange in the third preheater E3, the fourth preheater E4, the fifth preheater E5, the sixth preheater E6, and the seventh preheater E7 before being discharged. Because the temperature of the crude syngas is relatively high (approximately 800-900℃), it undergoes staged heat exchange through the second heat exchanger E2 and the first heat exchanger E1, reducing its temperature to 200-400℃ before entering the shift converter R3. There, most of the carbon monoxide is converted into hydrogen and carbon dioxide, yielding shifted gas. The shifted gas then passes through the first dehydration unit E0 to remove water vapor, converting it into condensate a6. Finally, it passes through the first CO2 removal unit R4 to remove carbon dioxide, resulting in hydrogen-rich gas. In the first CO2 removal unit R4, decarbonizing agent 7 is used to remove carbon dioxide, and the decarbonizing agent 8, which absorbs carbon dioxide, is discharged from the first CO2 removal unit R4.

[0127] After heat exchange in the eighth heat exchanger E8, the hydrogen-rich gas enters the gas preheating device E10 for preheating. The granular iron ore 16 enters the solid preheating device R6 for preheating. The preheated hydrogen-rich gas and the preheated granular iron ore then enter the reduction reaction device R5, where they undergo a countercurrent contact and reduction reaction. After the reduction reaction, the granular iron ore is converted into granular direct reduced iron, and the hydrogen-rich gas is converted into reduction tail gas. The granular direct reduced iron is then fed into the reduced iron powder hot briquetting machine R7 to form hot-pressed iron blocks 9, or directly into the electric furnace R8 for the next smelting step, or into the reduced iron powder loading tanker R9 for the next process.

[0128] Depending on the method of treating the reduction exhaust gas, different process flows can be adopted. For example... Figure 1As shown, the reduction tail gas discharged from the reduction reaction unit R5 enters the second dehydration unit E9 to remove condensate b10, resulting in purified tail gas. Part of the purified tail gas, as circulating reduction tail gas 11, is returned to the first dehydration treatment unit E0 via compressor C1, where it mixes with the shift gas treated in the first dehydration treatment unit E0, and then enters the first CO2 removal unit R4 for carbon dioxide removal. Part of the purified tail gas, as fuel reduction tail gas 12, mixes with fuel gas b13, and then combusts with oxygen-containing gas b14 in the hot blast stove R10. The resulting combustion tail gas is introduced into the solid preheating unit R6 for heat utilization and then discharged as hot blast stove combustion tail gas 15.

[0129] Or, such as Figure 2 As shown, the reduction tail gas discharged from the reduction reaction unit R5 enters the second CO2 removal unit R11 for carbon dioxide removal treatment, and then enters the second dehydration unit E9 to remove condensate b10, resulting in purified tail gas. Part of the purified tail gas, as circulating reduction gas tail gas 11, is returned to the first CO2 removal unit R4 via compressor C1, where it mixes with the hydrogen-rich gas treated in the first CO2 removal unit R4, and then enters the reduction reaction unit R5 for reduction reaction. Part of the purified tail gas, as fuel reduction gas tail gas 12, mixes with fuel gas b13, and then combusts with oxygen-containing gas b14 in the hot blast stove R10. The resulting combustion tail gas is introduced into the solid preheating unit R6 for heat utilization and then discharged as hot blast stove combustion tail gas 15.

[0130] By further defining the specific structure and process flow of the gas-based reduction system for granular iron ore, heat recovery and utilization are fully realized while obtaining granular iron ore.

[0131] It should be noted that the reduction reaction device is an important part of the gas-based reduction system for this granular iron ore.

[0132] As an optional embodiment of the present invention, a rotating component is provided in the reduction reaction device, wherein the rotating component is any one of a spiral, a rotating arm or a rotary cylinder.

[0133] In order to further achieve sufficient contact between granular iron ore and hydrogen-rich gas, so that the reduction reaction can proceed fully, as a preferred embodiment of the present invention, the reduction reaction device includes any one of a suspended rotary kiln reactor, a auger reactor, or a through-flow multi-stage furnace reactor.

[0134] The suspended rotary kiln reactor, the auger reactor, and the through-flow multi-stage furnace reactor are reduction reaction devices independently developed and designed by the inventor based on actual reaction requirements. The structure of each reactor is described below.

[0135] Specifically, suspended rotary kiln reactors such as Figure 3 and Figure 4 As shown, the system includes a rotary kiln shell, comprising a main shell 20 and outwardly contracting reducers 21 connected to both ends of the main shell. Rotary sections 22 are connected to the contracted ends of the reducers 21, and each rotary section 22 is connected to a sealing mechanism 23. A sealing assembly is provided at the junction of the sealing mechanism 23 and the rotary section. Multiple lifting components 24 are installed inside the main shell 20, enabling the granular iron ore to form a multi-layered material curtain as the rotary kiln shell rotates, and allowing hydrogen-rich gas to pass through the multi-layered material curtain and fully contact the granular iron ore. By connecting the sealing mechanism 23 to the necked rotary section 22, the installation difficulty of the sealing assembly between the rotary section 22 and the sealing mechanism 23 is reduced. The resulting multi-layered material curtain effectively increases the contact area between the granular iron ore and the hydrogen-rich gas, allowing for a more complete and thorough reaction.

[0136] Jiaolong reactor, for example Figure 5 and Figure 6 As shown, the reactor includes a shell, with a rotating shaft 30 mounted on its axis. The rotating shaft 30 is connected to spiral blades 31 for conveying solid materials. The spiral blades 31 have multiple gas passages 32 for allowing hydrogen-rich gas to pass through. The solid material fills the reaction chamber of the shell and undergoes a reduction reaction in counter-current contact with the hydrogen-rich gas. The rotating shaft 30 installed inside the auger reactor and the sealing element 33 between the rotating shaft and the shell effectively improve the sealing performance of the auger reactor and enable it to operate under pressure. The spiral blades 31 installed on the rotating shaft 30, combined with the sealed structure of the auger reactor, allow granular iron ore to fill the entire reaction chamber space of the reactor, effectively increasing the filling rate of the granular iron ore.

[0137] Through-flow multi-stage furnace reactor, such as Figure 7 As shown, the system includes: a shell 40, a stirring shaft 41, and multiple material trays 42 spaced apart along the axial direction of the shell 40. Each material tray 42 is connected to a discharge pipe 43 for discharging material. A stirring arm 44 is mounted on the upper part of each material tray 42, and a scraper 45 is connected to the stirring arm 44 for uniformly distributing the granular iron ore on the material tray 42. Each material tray 42 has multiple evenly distributed vents 46 to ensure sufficient contact between the granular iron ore and the reducing gas in the hydrogen-rich gas. The uniform distribution of the hydrogen-rich gas through the multiple evenly distributed vents 46 on the material tray 42 allows the hydrogen-rich gas to flow out layer by layer from bottom to top, ensuring sufficient contact with the granular iron ore on the material tray 42. This effectively increases the contact area between the granular iron ore and the hydrogen-rich gas, enabling a more complete and thorough reaction.

[0138] According to a third aspect of the present invention, the application of the above-described gas-based reduction method or gas-based reduction system for granular iron ore in the field of direct reduced iron production is also provided.

[0139] Given the advantages of the aforementioned gas-based reduction method or system for granular iron ore, it has good application potential in the production of direct reduced iron.

[0140] The technical solution of the present invention will be further described below with reference to embodiments and comparative examples.

[0141] Example 1

[0142] This embodiment provides a gas-based reduction method for granular iron ore, comprising the following steps:

[0143] (a) After desulfurization, liquefied natural gas (LNG) gasified at a pressure of 2.8 MPa is mixed with steam at a volume ratio of (3.5-3.6):1 to carry out a reforming reaction at a temperature of 870 °C to obtain crude syngas; wherein the mass fraction of sulfur in the desulfurized natural gas is less than 1 ppm; the dry gas composition of the crude syngas includes: H2 68-70%, CO 12-13%, CO2 16-18% and CH4 1-1.5%;

[0144] The crude syngas is subjected to a shift reaction at a temperature of 360-380℃ to obtain shifted gas.

[0145] The shifted gas is subjected to a first dehydration treatment and a first CO2 removal treatment to obtain hydrogen-rich gas; wherein the dry gas composition of the hydrogen-rich gas includes: H2 93-96%, CO 3-5%, CO2 0-0.2%, CH4 1.2-1.7%.

[0146] (b) After being preheated, hydrogen-rich gas is brought into countercurrent contact with preheated granular iron ore to carry out a reduction reaction. The reduction reaction pressure is 2.5 MPa and the reduction reaction time is 6 h to obtain granular direct reduced iron.

[0147] After the exhaust gas is cooled to 180-210℃ and the condensate is removed, 95% is returned to the first CO2 removal unit for pretreatment.

[0148] The granular iron ore has the following chemical composition: total iron, FeO, SiO2, CaO, MgO, Al2O3, and MnO, with contents of 62.7%, 27.3%, 1.32%, 1.53%, 3.45%, 0.82%, and 0.28%, respectively. The particle size of the granular iron ore is 48-150 μm, with an average particle size of 0.105 mm. The temperature of the preheated granular iron ore is 650-700℃, and the temperature of the preheated granular iron ore with hydrogen-rich gas is 600-630℃.

[0149] The average flow velocity of hydrogen-rich gas through the bed is 0.065 m / s. Under the conditions of granular iron ore of this particle size, hydrogen-rich gas, and reaction pressure, the minimum fluidization velocity U... mf It is 0.086 m / s.

[0150] In the reduction reactor, the flow rate ratio of the reducing gas in the hydrogen-rich gas to the particulate iron ore is 1400 Nm³. 3 Reducing gas / t granular iron ore.

[0151] The reduction reaction device is a through-flow multi-stage furnace reactor. This process can obtain direct reduced iron powder with a metallization rate of 97.8% and a carbon content of 1.4%, and the single-pass utilization efficiency of reducing gas is 24.2%.

[0152] Example 2

[0153] This embodiment provides a gas-based reduction method for granular iron ore, comprising the following steps:

[0154] (a) After desulfurization, compressed natural gas at a pressure of 2 MPa is mixed with steam at a volume ratio of (3.2-3.3):1 to carry out a reforming reaction at a temperature of 850°C to obtain crude syngas; wherein the mass fraction of sulfur in the desulfurized natural gas is less than 1 ppm; the dry gas composition of the crude syngas includes: H2 63-65%, CO 15-16%, CO2 13-15%, CH4 3-3.5%, N2 2-3%;

[0155] The crude syngas is subjected to a shift reaction at a temperature of 230-250℃ to obtain shifted gas.

[0156] The shifted gas is subjected to a first dehydration treatment and a first CO2 removal treatment to obtain hydrogen-rich gas; wherein the dry gas composition of the hydrogen-rich gas includes: H2 92-94%, CO 0.3-0.5%, CO2 0-0.1%, CH4 3.5-4.1%, N2 2.3-3.5%.

[0157] (b) After being preheated, hydrogen-rich gas is brought into countercurrent contact with preheated granular iron ore to carry out a reduction reaction. The reduction reaction pressure is 1.5 MPa and the reduction reaction time is 3.5 h to obtain granular direct reduced iron.

[0158] The exhaust gas is cooled to 160-190℃, and after the condensate is removed, 90% is returned to the first carbon dioxide removal unit for further treatment.

[0159] The granular iron ore has the following chemical composition: total iron, FeO, SiO2, Al2O3 and MnO, with contents of 66.2%, 1.4%, 5.2%, 0.43% and 0.06%, respectively. The particle size of the granular iron ore is 75-270 μm, with an average particle size of 0.15 mm. The temperature of the preheated granular iron ore is 630-660℃, and the temperature of the preheated granular iron ore with hydrogen-rich gas is 540-560℃.

[0160] The average flow velocity of hydrogen-rich gas through the bed is 0.09 m / s. Under the conditions of granular iron ore of this particle size, hydrogen-rich gas, and reaction pressure, the minimum fluidization velocity U... mf It is 0.13 m / s.

[0161] In the reduction reactor, the flow rate ratio of the reducing gas in the hydrogen-rich gas to the particulate iron ore is 1500 Nm³. 3 Reducing gas / t granular iron ore.

[0162] The reduction reactor is a auger reactor. This process yields granular direct reduced iron with a metallization rate of 98.5% and a carbon content of 0.1%, with a single-pass utilization efficiency of 26.3% for the reducing gas.

[0163] Example 3

[0164] This embodiment provides a gas-based reduction method for granular iron ore, comprising the following steps:

[0165] (a) After desulfurization, compressed natural gas at a pressure of 1 MPa is mixed with steam at a volume ratio of (3.1-3.2):1 to carry out a reforming reaction at a temperature of 860°C to obtain crude syngas; wherein the mass fraction of sulfur in the desulfurized natural gas is less than 1 ppm; the dry gas composition of the crude syngas includes: H2 60-64%, CO 14-15%, CO2 14-16%, CH4 2-2.5%, N2 6-8%;

[0166] The crude syngas is subjected to a shift reaction at a temperature of 260-280℃ to obtain shifted gas.

[0167] The shifted gas is subjected to a first dehydration treatment and a first CO2 removal treatment to obtain hydrogen-rich gas; wherein the dry gas composition of the hydrogen-rich gas includes: H2 85-88%, CO 2-2.2%, CO2 0-0.1%, CH4 2.4-2.9%, N2 7-9.5%.

[0168] (b) After being preheated, hydrogen-rich gas is brought into countercurrent contact with preheated granular iron ore to carry out a reduction reaction. The reduction reaction pressure is 0.6 MPa and the reduction reaction time is 5 h to obtain granular direct reduced iron.

[0169] The exhaust gas first passes through the second CO2 removal unit, where the CO2 content is reduced to below 0.1%. Then it is cooled to 130-150℃, and after removing the condensate, 80% is returned to the first CO2 removal unit for further processing.

[0170] The chemical composition of the granular iron ore is total iron, FeO, SiO2, CaO, MgO, Al2O3, and MnO, with contents of 55.2%, 0.29%, 8.69%, 0.01%, 0.01%, 6.53%, and 0.07%, respectively. The particle size of the granular iron ore is 380-4000 μm, with an average particle size of 1.05 mm. The temperature of the preheated granular iron ore is 710-730℃, and the temperature after preheating with hydrogen-rich gas is 500-520℃.

[0171] The average flow velocity of hydrogen-rich gas through the bed is 0.4 m / s, while the minimum fluidization velocity is 0.63 m / s under the conditions of granular iron ore of this size, hydrogen-rich gas and reaction pressure.

[0172] In the reduction reactor, the flow rate ratio of the reducing gas in the hydrogen-rich gas to the particulate iron ore is 950 Nm³. 3 Reducing gas / t granular iron ore.

[0173] The reduction reactor is a suspended rotary kiln reactor. This process yields direct reduced iron powder with a metallization rate of 96.5% and a carbon content of 0.7%, with a single-pass utilization efficiency of 30.6% for the reducing gas.

[0174] Example 4

[0175] This embodiment provides a gas-based reduction system for granular iron ore corresponding to the gas-based reduction method for granular iron ore in Example 1, specifically as follows: Figure 1 As shown.

[0176] The gas-based reduction system for granular iron ore includes a desulfurization unit R1, a reforming unit R2, a conversion unit R3, a first dehydration unit E0, a first CO2 removal unit R4, a gas preheating unit E10, a solid preheating unit R6, a reduction reaction unit R5, a hot blast stove R10, a reduced iron powder hot briquetting machine R7, an electric furnace R8, and a reduced iron powder loading car R9. Heat exchangers are also provided between the above units, including a first heat exchanger E1, a second heat exchanger E2, a third heat exchanger E3, a fourth heat exchanger E4, a fifth heat exchanger E5, a sixth heat exchanger E6, a seventh heat exchanger E7, an eighth heat exchanger E8, an eleventh heat exchanger E11, and a twelfth heat exchanger E12 to achieve heat recycling.

[0177] Compressed natural gas 1 is transported through a pipeline to the desulfurization unit R1. The desulfurization unit R1 is connected in sequence to the reforming unit R2, the conversion unit R3, the first dehydration unit E0 and the first CO2 removal unit R4, so as to convert the compressed natural gas into hydrogen-rich gas.

[0178] Hydrogen-rich gas and granular iron ore 16 are respectively transported to the reduction reaction unit R5 through pipelines. A gas preheating device E10 is installed on the pipeline used to transport hydrogen-rich gas, and a solid preheating device R6 is installed on the pipeline used to transport granular iron ore.

[0179] The reduction reaction unit R5 is also connected to the reduced iron powder hot briquetting machine R7, the electric furnace R8, or the reduced iron powder loading truck R9.

[0180] Example 5

[0181] This embodiment provides the gas-based reduction system for granular iron ore corresponding to the gas-based reduction method for granular iron ore in Embodiment 2, specifically as follows: Figure 1 As shown.

[0182] The gas-based reduction system for granular iron ore is identical to that in Example 4, except that the pipeline connecting the second dehydration device E9 to the first CO2 removal device R4 allows some of the purified tail gas to mix with the hydrogen-rich gas after the first CO2 removal treatment.

[0183] Example 6

[0184] This embodiment provides the gas-based reduction system for granular iron ore corresponding to the gas-based reduction method for granular iron ore in Example 3, specifically as follows: Figure 2 As shown.

[0185] The gas-based reduction system for granular iron ore, after the reduction tail gas is discharged from the reduction reactor and enters the second CO2 removal unit R11 and the second dehydration unit E9 to remove condensate, yields purified tail gas. The second dehydration unit E9 is connected to the pipeline after the first CO2 removal unit R4 so that part of the purified tail gas is mixed with the hydrogen-rich gas treated by the first CO2 removal unit. The remaining structure and connections are the same as in Example 4.

[0186] The above embodiments demonstrate that the gas-based reduction method for granular iron ore provided by this invention uses natural gas as raw material. Through steam reforming, conversion, dehydration, and decarburization processes, hydrogen-rich gas is obtained. This hydrogen-rich gas can then be used to reduce granular iron ore into granular direct reduced iron (DRI) products, achieving a metallization rate of 96-99%, classifying it as a high-grade DRI product. This process eliminates the need for pelletized raw materials specific to gas-based vertical shaft furnaces and high temperatures exceeding 900°C, and avoids the reaction time of tens of hours required by fluidized beds. It also significantly improves the conversion rate of reducing gas, avoiding excessive gas circulation caused by low conversion rates and reducing power consumption. It is a clean and efficient direct reduced iron method. Systems using this method can reduce energy consumption in the steelmaking process. Furthermore, by using calcium oxide as a decarburizing agent, carbon dioxide can be removed from the reduction tail gas at high temperatures, further reducing energy consumption and improving efficiency.

[0187] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gas-based reduction method for granular iron ore, characterized in that, Includes the following steps: (a) After desulfurization, compressed natural gas at a pressure of 2 MPa is mixed with steam at a volume ratio of (3.2-3.3):1 to carry out a reforming reaction at a temperature of 850°C to obtain crude syngas; wherein the mass fraction of sulfur in the desulfurized natural gas is less than 1 ppm; the crude syngas is subjected to a shift reaction at a temperature of 230-250°C to obtain shift gas; the shift gas is subjected to a first dehydration treatment and a first CO2 removal treatment to obtain hydrogen-rich gas; (b) After preheating, hydrogen-rich gas is countercurrently contacted with preheated granular iron ore to carry out a reduction reaction. The reduction reaction pressure is 1.5 MPa, and the reduction reaction time is 3.5 h, yielding granular direct reduced iron. The reduction tail gas is cooled to 160-190℃, and after removing condensate, 90% is returned to the first carbon dioxide removal unit for further processing. The particle size of the granular iron ore is 75-270 μm, with an average particle size of 0.15 mm. The temperature of the preheated granular iron ore is 630-660℃, and the temperature of the hydrogen-rich gas after preheating is 540-560℃. The average flow velocity of the hydrogen-rich gas through the bed is 0.09 m / s, and under the conditions of granular iron ore of this particle size, hydrogen-rich gas, and reaction pressure, the minimum fluidization velocity Umf is 0.13 m / s. In the reduction reactor, the flow ratio of the reducing gas in the hydrogen-rich gas to the granular iron ore is 1500 Nm³. 3 Reducing gas / t granular iron ore; The reduction reactor is a auger reactor, which includes: a shell, a rotating shaft mounted on the axis of the shell, spiral blades for conveying solid materials connected to the rotating shaft, multiple gas passages for hydrogen-rich gas to pass through on the spiral blades, and a seal installed between the rotating shaft and the shell.

2. A gas-based reduction method for granular iron ore, characterized in that, Includes the following steps: (a) After desulfurization, liquefied natural gas (LNG) gasified at a pressure of 2.8 MPa is mixed with steam at a volume ratio of (3.5-3.6):1 to carry out a reforming reaction at a temperature of 870 °C to obtain crude syngas; wherein the mass fraction of sulfur in the desulfurized natural gas is less than 1 ppm; the crude syngas is subjected to a shift reaction at a temperature of 360-380 °C to obtain shift gas; the shift gas is subjected to a first dehydration treatment and a first CO2 removal treatment to obtain hydrogen-rich gas; (b) After preheating, hydrogen-rich gas is countercurrently contacted with preheated granular iron ore to carry out a reduction reaction. The reduction reaction pressure is 2.5 MPa, and the reduction reaction time is 6 hours, yielding granular direct reduced iron. The reduction tail gas is cooled to 180-210℃, and after removing condensate, 95% is returned to the first CO2 removal unit for pretreatment. The granular iron ore has a particle size of 48-150 μm and an average particle size of 0.105 mm. The temperature of the preheated granular iron ore is 650-700℃, and the temperature of the preheated hydrogen-rich gas is 600-630℃. The average flow velocity of the hydrogen-rich gas through the bed is 0.065 m / s, and under the conditions of granular iron ore of this particle size, hydrogen-rich gas, and reaction pressure, the minimum fluidization velocity Umf is 0.086 m / s. In the reduction reactor, the flow ratio of the reducing gas in the hydrogen-rich gas to the granular iron ore is 1400 Nm³. 3 Reducing gas / t granular iron ore; The reduction reactor is a through-flow multi-stage furnace reactor, which includes: a shell, a stirring shaft, and multiple material trays spaced apart along the axial direction of the shell. The material trays are connected to a discharge pipe for discharging material. Each material tray is equipped with a stirring arm at the top, and a scraper is connected to the stirring arm for uniformly distributing the granular iron ore on the material tray. Each material tray has multiple air holes evenly distributed on it.

3. The gas-based reduction method for granular iron ore according to claim 1 or 2, characterized in that, The mass fraction of sulfur in the natural gas after desulfurization is no higher than 0.1 ppm.

4. The gas-based reduction method for granular iron ore according to claim 1 or 2, characterized in that, The natural gas is mixed with steam and preheated to 450-600℃ for reforming reaction.

5. The gas-based reduction method for granular iron ore according to claim 1 or 2, characterized in that, Based on a volume percentage of 100%, the dry gas composition of the crude syngas includes: H2 55-75%, CO 10-20%, CO2 10-20%, and CH4 1-3%.

6. The gas-based reduction method for granular iron ore according to claim 1 or 2, characterized in that, Based on a volume percentage of 100%, the dry gas composition of the hydrogen-rich gas includes: H2 85-99%, CO 0-10%, CO2 0-1%, and CH4 1-10%.

7. The gas-based reduction method for granular iron ore according to claim 1 or 2, characterized in that, Step (b) also includes a step of subjecting the reduction tail gas generated during the reduction reaction to a second dehydration treatment to obtain purified tail gas.

8. The gas-based reduction method for granular iron ore according to claim 7, characterized in that, The exhaust gas, after at least partial purification, is mixed with the shift gas after the first dehydration treatment for reuse; or, the exhaust gas, after at least partial purification, is mixed with the hydrogen-rich gas after the first CO2 removal treatment for reuse.

9. The gas-based reduction method for granular iron ore according to claim 7, characterized in that, The exhaust gas, after at least partial purification, is mixed with fuel gas and oxygen-containing gas for use as fuel. The heat generated by the combustion of the fuel can be used to preheat granular iron ore.

10. The gas-based reduction method for granular iron ore according to claim 1 or 2, characterized in that, Step (b) also includes a second CO2 removal treatment of the reduction tail gas generated during the reduction reaction, followed by a second dehydration treatment to obtain purified tail gas.

11. The gas-based reduction method for granular iron ore according to claim 10, characterized in that, The decarbonizing agent used in the second CO2 removal process includes calcium oxide.

12. The gas-based reduction method for granular iron ore according to claim 10, characterized in that, After a second CO2 removal process, calcium oxide is converted into calcium carbonate. The calcium carbonate is then regenerated at 650-950℃, and the regenerated calcium oxide can be reused as a decarbonating agent.

13. A gas-based reduction system for granular iron ore, characterized in that, The gas-based reduction method for granular iron ore as described in claim 1 or 2 is used to produce granular direct reduced iron. The gas-based reduction system for granular iron ore includes a desulfurization unit, a reforming unit, a conversion unit, a first dehydration unit, a first CO2 removal unit, a gas preheating unit, a solid preheating unit, and a reduction reaction unit. Compressed natural gas is transported to the desulfurization unit via pipeline. The desulfurization unit is connected in sequence to the reforming unit, the conversion unit, the first dehydration unit, and the first CO2 removal unit to convert the compressed natural gas into hydrogen-rich gas. Hydrogen-rich gas and granular iron ore are respectively transported to the reduction reaction device through pipelines. A gas preheating device is installed on the pipeline used to transport hydrogen-rich gas, and a solid preheating device is installed on the pipeline used to transport granular iron ore.

14. The gas-based reduction system according to claim 13, characterized in that, It also includes a second dehydration device, the reduction reaction device is connected to the second dehydration device, and the second dehydration device is connected to the first CO2 removal device; or, it also includes a second CO2 removal device and a second dehydration device, the reduction reaction device is connected in sequence to the second CO2 removal device and the second dehydration device, and the second dehydration device is connected to the first CO2 removal device or to the reduction reaction device.

15. The gas-based reduction system according to claim 14, characterized in that, The gas-based reduction system also includes a hot air furnace, the second dehydration device is connected to the hot air furnace, and the hot air furnace is connected to the solid preheating device.

16. The gas-based reduction system according to claim 14, characterized in that, The gas-based reduction system also includes a regeneration device, which is connected to the second CO2 removal device.

17. The application of the gas-based reduction method for granular iron ore according to any one of claims 1-12 or the gas-based reduction system for granular iron ore according to any one of claims 13-16 in the field of direct reduced iron production.

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