Method and system for directly reducing iron ore powder through gas-based multi-hearth furnace

Abstract

The invention discloses a method and system for directly reducing iron ore powder through a gas-based multi-hearth furnace, and the method comprises the steps that the iron ore powder and reducing gas are subjected to a reduction reaction in a multi-hearth furnace reactor, and reduced metal iron is obtained; the reducing gas is H2 and / or CO, and the reduction temperature is 700-800 DEG C. According to the method and the system, a multi-hearth furnace is adopted, material flow and high-temperature gas are subjected to countercurrent heat convection exchange reaction from top to bottom through a mechanical transmission device, and the method and the system have the advantages of large hearth area, multiple gas-solid interfaces, long retention time of materials in the furnace, high reduction efficiency and the like; the method is suitable for treating powder substances with low heat value. According to the method and the system, the iron ore powder is directly reduced through the multi-hearth furnace, a pelletizing step necessary for an existing hydrogen-based shaft furnace reduction method is omitted, the problem of particle bonding and flow loss of a fluidized bed hydrogen reduction method is effectively solved, and the method and the system have the advantages of low CO2 emission, low energy consumption, high product metallization ratio and the like.

Description

Technical Field

[0001] The invention relates to the technical field of direct iron reduction, in particular to a method and system for directly reducing iron ore powder in a gas-based multi-hearth furnace. Background Art

[0002] Direct Reduced Iron (DRI) production is one of the important ways for my country to get rid of the constraints of coking coal resource shortage, improve the steel energy structure and product structure, solve the shortage of scrap steel resources, realize comprehensive resource utilization, and adhere to the sustainable development of the steel industry. At present, the direct reduced iron production methods in the world are mainly divided into gas-based method and coal-based method. Compared with the coal-based direct reduced iron process, the gas-based direct reduction method has the advantages of fast reduction speed, stable product quality, low process energy consumption and low CO2 emissions, and has become the mainstream process for producing direct reduced iron in the world.

[0003] At present, the gas-based direct iron reduction technology in industry mainly includes gas-based vertical furnace reduction method and fluidized bed reduction method. The gas-based vertical furnace reduction method is represented by MIDREX method and HYLⅢ method, and the fluidized bed reduction method is represented by Finmet method and Cir-cored method. The reducing gases used mainly include CO, H2, etc.

[0004] Patent publication number CN113930568A discloses a method for preparing direct reduced iron by introducing hydrogen into a reduction shaft furnace, patent publication number CN111926135A discloses a hydrogen-based shaft furnace direct reduction system and reduction method, and patent publication number CN115449580A discloses a zero-carbon emission direct reduction system and process that entirely uses coke oven gas. The above technologies all use a hydrogen-based shaft furnace direct reduction method for ironmaking, and the raw materials are all high-grade oxidized pellets. A pelletizing process must be set up, and the pelletizing process is complicated and the oxidized pellets have high strength requirements.

[0005] Patent publication number CN114941046A discloses a system and method for direct reduction of iron ore by hydrogen based on a circulating fluidized bed, which mainly includes a hydrogen production system, a gas circulation system, a raw material feeding system, and a circulating fluidized bed. The iron ore powder raw material provided by the raw material feeding system is subjected to a reduction reaction by hydrogen provided by the hydrogen production system and fluidizing air provided by the gas circulation system to generate high-temperature flue gas, iron, and slag. This method does not require pelletizing and achieves zero carbon dioxide emissions, but in the high-temperature fluidized bed, the iron ore particles form aggregates due to bonding, causing loss of flow, which will affect the normal progress of the process. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for directly reducing iron ore powder in a gas-based multi-hearth furnace with a simple process; the present invention also provides a system for directly reducing iron ore powder in a gas-based multi-hearth furnace.

[0007] To solve the above technical problems, the technical solution adopted by the method of the present invention is: iron ore powder and reducing gas are subjected to reduction reaction in a multi-chamber furnace reactor to obtain reduced metallic iron; the reducing gas is H2 and / or CO, and the reduction temperature is 700-800°C.

[0008] Furthermore, the particle size of the iron ore powder is ≤5 mm, and the TFe content is ≥65 wt%.

[0009] Furthermore, when the reducing gas is H2, a hydrogen-rich gas with an H2 content ≥ 90 vol% is used; when the reducing gas is CO, a CO-rich gas with a CO content ≥ 90 vol% is used; when the reducing gas is H2 and CO, a reducing gas with an H2+CO content ≥ 90 vol% is used.

[0010] In order to solve the above technical problems, the technical solution adopted by the system of the present invention is: it includes a multi-chamber furnace reactor, a gas supply device and an exhaust gas treatment device; the multi-chamber furnace reactor is provided with a gas inlet and a flue gas outlet; the gas supply device is connected to the gas inlet of the multi-chamber furnace reactor, and the exhaust gas treatment device is connected to the flue gas outlet and the gas supply device of the multi-chamber furnace reactor.

[0011] Furthermore, the tail gas treatment device includes a heat exchange cooling device, a dust removal device, a drying tower, a gas compressor and a CO2 removal system which are connected in sequence; the gas supply device includes a heating device and a gas storage tank.

[0012] Furthermore, the multi-chamber furnace reactor includes a multi-chamber furnace body, a feed port, a gas inlet, a multi-chamber furnace center axis, a material baffle, a multi-chamber furnace rake arm, a discharge port and a smoke outlet; the feed port and the discharge port are respectively arranged at the top and bottom of the multi-chamber furnace body, and the smoke outlet is arranged at the top of the multi-chamber furnace body; the multi-chamber furnace center axis passes through the center of the multi-chamber furnace body up and down; a plurality of furnace chambers are arranged inside the multi-chamber furnace body from top to bottom, each furnace chamber is provided with a material baffle and a multi-chamber furnace rake arm, and the material baffle is located below the multi-chamber furnace rake arm; the multi-chamber furnace rake arm is rotatably connected to the multi-chamber furnace center axis, and the material baffle is annularly connected to the inner wall of the multi-chamber furnace body or is rotatably connected to the multi-chamber furnace center axis in the form of a circular plate.

[0013] Furthermore, each furnace of the multi-hearth furnace reactor is provided with a gas inlet.

[0014] Furthermore, the multi-chamber furnace rake arm is provided with rake teeth for pushing the material on the material baffle.

[0015] The beneficial effects of adopting the above technical solution are: the multi-chamber furnace, also known as a multi-stage furnace, uses a mechanical transmission device to make the logistics flow from top to bottom and the high-temperature gas flow from bottom to top in countercurrent to conduct heat convection exchange reaction, which has the advantages of large furnace area, multiple gas-solid interfaces, long material residence time in the furnace, high reduction efficiency, etc., and can use a variety of reducing gases for reaction, which is suitable for processing powder materials with low calorific value. The method and system directly reduce iron ore powder through a multi-chamber furnace, eliminating the pelletizing step required by the existing hydrogen-based vertical furnace reduction method, effectively solving the problem of particle bonding and loss of flow in the fluidized bed hydrogen reduction method, and has the advantages of low CO2 emissions, low energy consumption and high product metallization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0017] Figure 1 It is a schematic diagram of the process structure of the process of the present invention; Figure 2 It is a structural schematic diagram of the system of the present invention.

[0018] In the figure: multi-chamber furnace reactor 001, heat exchange cooling device 002, dust removal equipment 003, drying tower 004, gas compressor 005, CO2 removal system 006, heating device 007, gas storage tank 008, multi-chamber furnace body 1, feed inlet 2, gas inlet 3, multi-chamber furnace center axis 4, annular material baffle 5, circular plate-shaped material baffle 6, multi-chamber furnace rake arm 7, discharge port 8, flue gas outlet 9. DETAILED DESCRIPTION

[0019] Figure 1 As shown, the method for direct reduction of iron ore powder in a gas-based multi-hearth furnace comprises the following steps: 1) crushing and finely grinding the iron ore into iron ore powder; the particle size of the iron ore powder is ≤5mm, and the TFe content is ≥65wt%.

[0020] 2) The iron ore powder and the reducing gas are subjected to a reduction reaction in a multi-hearth furnace reactor to obtain reduced metallic iron. The reducing gas is H2 and / or CO, and the inlet temperature of the reducing gas entering the multi-hearth furnace reactor is 750-850°C; when the reducing gas is H2, a hydrogen-rich gas with an H2 content of ≥90 vol% is used; when the reducing gas is CO, a CO-rich gas with a CO content of ≥90 vol% is used; when the reducing gas is H2 and CO, a reducing gas with an H2+CO content of ≥90 vol% is used; the reducing gas can also be converted into CO and H2 by a CH4 reforming reaction. The reduction temperature is 700-800°C and the reaction time is 30-120 min. The reduction reaction process is: Fe2O3+3H2→2Fe+3H2O and / or Fe2O3+3CO→2Fe+3CO2.

[0021] 3) The metallization rate of the obtained reduced metallic iron is greater than 92%. The reduced metallic iron can be directly used for electric furnace steelmaking, or enter the molten pool for slag and iron separation to form iron scale.

[0022] Figure 2 As shown, the system for direct reduction of iron ore powder in a gas-based multi-chamber furnace includes a multi-chamber furnace reactor 001, a gas supply device, a tail gas treatment device, a material feeding device, and a product discharging device. The material feeding device and the product discharging device are both sealed silos, and are both equipped with double flap valves to effectively isolate air from entering the furnace. The tail gas treatment device includes a heat exchange cooling device 002, a dust removal device 003, a drying tower 004, a gas compressor 005, and a CO2 removal system 006 connected in sequence; the gas supply device includes a heating device 007 and a gas storage tank 008; the multi-chamber furnace reactor 001 is provided with a gas inlet 3 and a flue gas outlet 9; the gas storage tank 008 is connected to the gas inlet 3 of the multi-chamber furnace reactor through the heating device 007; the flue gas outlet 9 of the multi-chamber furnace reactor is connected to the heat exchange cooling device 002, the dust removal device 003, the drying tower 004, the gas compressor 005, and the CO2 removal system 006 in sequence, and then connected to the gas storage tank 008. In this way, the reducing gas in the gas storage tank 008 is heated by the heating device 007 and then enters the multi-chamber furnace reactor to react with the iron ore powder; the flue gas generated in the reaction process is cooled by the hot cooling device 002, dust removed by the dust removal equipment 003, dried by the drying tower 004, compressed by the gas compressor 005, and the CO2 removal system 006 to remove CO2, and then enters the gas storage tank 008 for recycling.

[0023] Figure 2As shown, the multi-chamber furnace reactor 001 of the gas-based multi-chamber furnace direct reduction system for iron ore powder includes a multi-chamber furnace body 1, a feed port 2, a gas inlet 3, a multi-chamber furnace central axis 4, a material baffle, a multi-chamber furnace rake arm 7, a discharge port 8 and a flue gas outlet 9. The shell of the multi-chamber furnace body 1 is a steel cylinder, and the lining is a refractory material or a heat-insulating material. The feed port 2 is arranged at the top of the multi-chamber furnace body 1, and at least two feed ports 2 can be arranged, which are symmetrically distributed along the central axis at the top of the multi-chamber furnace body 1 or evenly distributed along the circumference of the central axis at the top of the multi-chamber furnace body 1. The discharge port 8 is arranged at the bottom of the multi-chamber furnace body 1, and at least two discharge ports 8 can be arranged, which are symmetrically distributed along the central axis at the bottom of the multi-chamber furnace body 1 or evenly distributed along the circumference of the central axis at the bottom of the multi-chamber furnace body 1. The smoke outlet 9 is arranged at the top of the multi-chamber furnace body 1. At least two smoke outlets 9 can be arranged, which are symmetrically distributed along the central axis at the top of the multi-chamber furnace body 1 or evenly distributed along the circumference of the central axis at the top of the multi-chamber furnace body 1. The multi-chamber furnace central axis 4 passes through the central axis of the multi-chamber furnace body 1 up and down, and is driven by a power device to rotate. At least two furnaces are arranged from top to bottom inside the multi-chamber furnace body 1, and each furnace is provided with a material baffle and a multi-chamber furnace rake arm 7. At least one multi-chamber furnace rake arm 7 is provided in each furnace, and the multi-chamber furnace rake arm 7 is rotatably connected to the multi-chamber furnace central axis 4 and can be tilted outward and downward, and the tilting angle is continuously adjustable within the range of 0 to 8 degrees; when multiple multi-chamber furnace rake arms 7 are arranged, the multi-chamber furnace rake arms 7 are evenly distributed in the circumferential direction; a plurality of rake teeth are fixedly connected below the multi-chamber furnace rake arm 7, and the rake teeth are evenly distributed in the length direction of the multi-chamber furnace rake arm 7. The material baffle is divided into two types, namely, an annular material baffle 5 and a circular material baffle 6; the annular material baffle 5 is connected to the inner wall of the multi-chamber furnace body 1, and can be tilted inward and downward, and the tilt angle is continuously adjustable within the range of 0 to 8 degrees; the circular material baffle 6 is rotatably connected to the multi-chamber furnace center axis 4, and can be tilted outward and downward, and the tilt angle is continuously adjustable within the range of 0 to 8 degrees; the annular material baffle 5 and the circular material baffle 6 are alternately arranged in each furnace from top to bottom; the material baffle is located below the multi-chamber furnace rake arm 7, and the rake teeth on the multi-chamber furnace rake arm can push the material on the material baffle. The spacing of the material baffle when in a horizontal state is preferably 20 mm, and the distance between the rake teeth on the multi-chamber furnace rake arm 7 is 4 mm.

[0024] Figure 2 As shown, in the system for direct reduction of iron ore powder by a gas-based multi-chamber furnace, each furnace of the multi-chamber furnace reactor 001 is provided with a gas inlet 3, and a gas supply device is connected to each gas inlet 3; the heating device is a fuel thermal storage heating device or an electric thermal storage heating device.

[0025] After adopting the above structure, during the use of the system of direct reduction of iron ore powder in the gas-based multi-chamber furnace, the iron oxide material falls into the material baffle of the first layer of the furnace in the multi-chamber furnace body 1 through the feed port 2 of the double flap valve, and the multi-chamber furnace central axis 4 drives the multi-chamber furnace rake arm 7 and rake teeth to push the material to the falling area in the middle or around the material baffle, and fall into the material baffle of the next layer of the furnace; on the material baffle of the second layer of the furnace, the multi-chamber furnace central axis 4 drives the multi-chamber furnace rake arm 7 and rake teeth to push the material to the falling area around or in the middle of the material baffle, and fall into the material baffle of the next layer of the furnace; this is repeated until the reduced metallic iron is pushed out from the bottom discharge port 8; the reducing gas enters from the gas inlet 3 of each furnace and is discharged from the top flue gas outlet 9; the iron oxide solid phase and the reducing gas phase are reduced in the multi-chamber furnace reactor 001 in a countercurrent manner.

[0026] Example 1: Using the above system, the method for direct reduction of iron ore powder in a gas-based multi-hearth furnace is specifically described as follows.

[0027] 1) Crushing and grinding the iron ore into iron ore powder with a particle size of ≤5mm; 2) The iron ore powder and the hydrogen-rich reducing gas are subjected to a reduction reaction in a multi-chamber furnace reactor to obtain metallic iron; wherein the H2 content of the hydrogen-rich reducing gas is 92%, and the reducing gas inlet temperature is 750°C. The reduction process temperature is 700°C, and the reaction time is 120 minutes; 3) The reduced metallic iron is sent to an electric furnace for steelmaking, or enters a molten pool for slag iron separation to prepare iron sheets; the technological rate of the product metallic iron is 92.5%.

[0028] Example 2: Using the above system, the method for direct reduction of iron ore powder in a gas-based multi-hearth furnace is specifically described as follows.

[0029] 1) Crushing and grinding the iron ore into iron ore powder with a particle size of ≤5mm; 2) The iron ore powder and the CO-rich reducing gas are subjected to a reduction reaction in a multi-hearth furnace reactor to obtain metallic iron; wherein the CO content of the CO-rich reducing gas is 91%, and the reducing gas inlet temperature is 850°C. The reduction process temperature is 800°C, and the reaction time is 30 minutes; 3) The reduced metallic iron is sent to an electric furnace for steelmaking, or enters a molten pool for slag iron separation to prepare iron sheets; the technological rate of the product metallic iron is 93.5%.

[0030] Example 3: Using the above system, the method for direct reduction of iron ore powder in a gas-based multi-hearth furnace is specifically described as follows.

[0031] 1) Crushing and grinding the iron ore into iron ore powder with a particle size of ≤5mm; 2) The iron ore powder and the reducing gas mixed with CO and H2 are subjected to reduction reaction in a multi-hearth furnace reactor to obtain metallic iron; wherein the CO content in the reducing gas is 25%, the H2 content is 65%, and the reducing gas inlet temperature is 800°C. The reduction process temperature is 750°C and the reaction time is 100 minutes; 3) The reduced metallic iron is sent to an electric furnace for steelmaking, or enters a molten pool for slag iron separation to prepare iron sheets; the technological rate of the product metallic iron is 94%.

Claims

1. A method for direct reduction of iron ore fines in a gas-based multi-hearth furnace, characterized in that: The iron ore powder and reducing gas are subjected to reduction reaction in a multi-hearth furnace reactor to obtain reduced metallic iron; the reducing gas is H2 and / or CO, and the reduction temperature is 700-800°C.

2. The method for direct reduction of iron ore powder in a gas-based multi-hearth furnace according to claim 1, characterized in that: The iron ore powder has a particle size of ≤5 mm and a TFe content of ≥65 wt %.

3. A method for direct reduction of iron ore fines in a gas-based multi-hearth furnace according to claim 1 or 2, characterized in that: When the reducing gas is H2, a hydrogen-rich gas with an H2 content ≥ 90 vol% is used; when the reducing gas is CO, a CO-rich gas with a CO content ≥ 90 vol% is used; when the reducing gas is H2 and CO, a reducing gas with an H2+CO content ≥ 90 vol% is used.

4. A system for direct reduction of iron ore fines by a gas-based multi-hearth furnace, characterized in that: It comprises a multi-chamber furnace reactor (001), a gas supply device and an exhaust gas treatment device; the multi-chamber furnace reactor (001) is provided with a gas inlet (3) and a flue gas outlet (9); the gas supply device is connected to the gas inlet (3) of the multi-chamber furnace reactor, and the exhaust gas treatment device is connected to the flue gas outlet (9) of the multi-chamber furnace reactor and the gas supply device.

5. A system for direct reduction of iron ore fines by a gas-based multi-hearth furnace according to claim 4, characterized in that: The tail gas treatment device comprises a heat exchange cooling device (002), a dust removal device (003), a drying tower (004), a gas compressor (005) and a CO2 removal system (006) which are connected in sequence; the gas supply device comprises a heating device (007) and a gas storage tank (008).

6. A system for direct reduction of iron ore fines by a gas-based multi-hearth furnace according to claim 4, characterized in that: The multi-chamber furnace reactor (001) comprises a multi-chamber furnace body (1), a feed inlet (2), a gas inlet (3), a multi-chamber furnace center axis (4), a material baffle, a multi-chamber furnace rake arm (7), a material outlet (8) and a smoke outlet (9); the feed inlet (2) and the material outlet (8) are respectively arranged at the top and bottom of the multi-chamber furnace body (1), and the smoke outlet (9) is arranged at the top of the multi-chamber furnace body (1); the multi-chamber furnace center axis (4) passes through the center of the multi-chamber furnace body (1) up and down; a plurality of furnace chambers are arranged inside the multi-chamber furnace body (1) from top to bottom, each furnace chamber is provided with a material baffle and a multi-chamber furnace rake arm (7), and the material baffle is located below the multi-chamber furnace rake arm (7); the multi-chamber furnace rake arm (7) is rotatably connected to the multi-chamber furnace center axis (4), and the material baffle is connected to the inner wall of the multi-chamber furnace body (1) in a ring shape or is rotatably connected to the multi-chamber furnace center axis (4) in a circular plate shape.

7. A system for direct reduction of iron ore fines by a gas-based multi-hearth furnace according to claim 6, characterized in that: Each furnace of the multi-chamber furnace reactor (001) is provided with a gas inlet (3).

8. A system for direct reduction of iron ore fines by a gas-based multi-hearth furnace according to claims 6 and 7, characterized in that: The multi-chamber furnace rake arm (7) is provided with rake teeth for pushing the material on the material baffle.

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