Hydrogen-nitrogen-based shaft furnace direct reduction ironmaking system and process method

Abstract

The application provides a hydrogen-nitrogen-based shaft furnace direct reduction ironmaking system and process method, and the ironmaking system comprises a shaft furnace, the shaft furnace has a reduction zone, a constant pressure zone and a cooling zone from top to bottom; a cooling and heat recovery unit, the cooling and heat recovery unit has a low-temperature process gas supply pipe connected with the lower part of the cooling zone, and a heat recovery pipe connected with the constant pressure zone and the upper part of the reduction zone; and a process gas circulation treatment unit, the process gas circulation treatment unit has a process gas circulation pipe connected with the top flue gas outlet of the shaft furnace and the reduction zone, and the process gas circulation pipe is provided with a first dust remover, a dehydrator and a nitrogen removal device. The application can solve the problems of uneven gas distribution and low heat utilization efficiency in the existing hydrogen-nitrogen-based shaft furnace process, effectively control the nitrogen concentration in the process, efficiently recover and utilize the system energy, and optimize the product cooling and the heat distribution in the furnace.

Description

Technical Field

[0001] This invention relates to the field of blast furnace ironmaking technology, and in particular to a hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system and process. Background Technology

[0002] Direct reduction ironmaking in shaft furnaces, as a low-carbon ironmaking process, has been widely used globally. Among them, shaft furnace processes using natural gas as the primary reducing gas source, such as the MIDREX and HYL-Energiron processes, have achieved large-scale commercial operation due to their mature processes and stable product quality. However, these processes generally rely on natural gas resources, and carbon emissions remain significant, making them difficult to promote in resource-scarce regions.

[0003] With the global steel industry's push towards "dual carbon" goals, hydrogen metallurgy, which replaces hydrocarbon gases with hydrogen, has become a key area of ​​research and industrialization. In recent years, some studies have explored the possibility of using hydrogen as a reducing agent in direct reduction in shaft furnaces, a system that theoretically can achieve near-zero carbon emissions in ironmaking. However, numerous engineering challenges remain in hydrogen reduction, such as uneven gas distribution within the furnace, low heat utilization efficiency, and the high requirements for equipment safety and system integrity in hydrogen-nitrogen processes. Furthermore, if the introduced nitrogen is used to control the pressure inside and outside the furnace, nitrogen can easily accumulate in the system, diluting the reducing atmosphere, reducing the reaction rate, and even affecting product quality.

[0004] Therefore, it is necessary to develop a hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system and process to achieve effective control of nitrogen concentration and efficient recovery and utilization of system energy, while also taking into account product cooling and optimization of heat distribution within the furnace. Summary of the Invention

[0005] The purpose of this invention is to provide a hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system and process, which solves the problems of uneven gas distribution and low heat utilization efficiency in existing hydrogen-nitrogen-based vertical shaft furnace processes, achieves effective control of nitrogen concentration in the process, efficient recovery and utilization of system energy, and optimizes product cooling and furnace heat distribution.

[0006] The above-mentioned technical objectives of the present invention are mainly achieved through the following technical solutions.

[0007] On one hand, the present invention provides a hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system, which includes:

[0008] A vertical furnace, which from top to bottom has a reduction zone, a constant pressure zone, and a cooling zone;

[0009] A cooling and heat recovery unit, the cooling and heat recovery unit having a low-temperature process gas supply pipe connected to the lower part of the cooling zone, and a heat recovery pipe connecting the upper part of the constant pressure zone and the reduction zone;

[0010] The process gas circulation treatment unit has a process gas circulation pipe connecting the flue gas outlet at the top of the vertical furnace and the reduction zone. The process gas circulation pipe is equipped with a first dust collector, a dehydrator, and a denitrification device.

[0011] In a preferred embodiment of the present invention, the reduction zone comprises a preheating reduction zone and a high-temperature reduction zone from top to bottom;

[0012] The top of the vertical furnace is provided with a flue gas outlet, and the side wall of the vertical furnace is provided with a cooling exhaust gas inlet that connects to the preheating reduction zone, a high temperature reducing gas inlet that connects to the high temperature reduction zone, a cooling exhaust gas outlet that connects to the constant pressure zone, and a low temperature reducing gas inlet that connects to the lower part of the cooling zone.

[0013] The outlet end of the low-temperature process gas supply pipe is connected to the low-temperature reducing gas inlet, the two ends of the regenerating pipe are respectively connected to the cooling tail gas outlet and the cooling tail gas inlet, and the two ends of the process gas circulation pipe are respectively connected to the flue gas outlet and the high-temperature reducing gas inlet.

[0014] In a preferred embodiment of the present invention, the process gas circulation pipe has a branch parallel section, the branch parallel section having two process gas branch pipes arranged in parallel, and the denitrification device is disposed on one of the process gas branch pipes.

[0015] In a preferred embodiment of the present invention, two denitrification devices are provided in parallel on the process gas branch pipe.

[0016] In a preferred embodiment of the present invention, a heat exchanger is provided between a portion of the process gas circulation pipe upstream of the denitrification device and a portion of the process gas circulation pipe downstream of the denitrification device.

[0017] In a preferred embodiment of the present invention, a compressor is further provided on the process gas circulation pipe, and the first dust collector, the dehydrator and the compressor are arranged sequentially on the process gas circulation pipe between the downstream of the heat exchanger and the upstream of the denitrification device.

[0018] In a preferred embodiment of the present invention, a heating furnace is provided at one end of the process gas circulation pipe connected to the reduction zone.

[0019] In a preferred embodiment of the present invention, the cryogenic process gas supply pipe is equipped with a hydrogen storage tank and a pressure regulator.

[0020] In a preferred embodiment of the present invention, a second dust collector is provided on the heat recovery pipe.

[0021] In a preferred embodiment of the present invention, the regenerating pipe downstream of the second dust collector has a branched parallel section, the branched parallel section having two regenerating branch pipes arranged in parallel, one of which is provided with a heater.

[0022] In a preferred embodiment of the present invention, the top and bottom of the vertical furnace are respectively provided with a feeding port and a discharging port.

[0023] On the other hand, the present invention also provides a hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process, which includes:

[0024] Iron-containing furnace charge is fed into the upper part of the vertical furnace through the charging port, and high-temperature reducing gas is sent into the middle part of the vertical furnace to reduce the iron-containing furnace charge in the reduction zone to generate direct reduced iron.

[0025] Hydrogen-rich cooling gas is fed into the lower part of the vertical furnace to exchange heat with the direct reduced iron in the cooling zone in a countercurrent manner. After the heat exchange, the hydrogen-rich cooling gas is exported from the constant pressure zone and introduced into the reduction zone to preheat and pre-reduce the iron-containing furnace charge.

[0026] The flue gas produced by the reaction of the high-temperature reducing gas and the hydrogen-rich cooling gas is discharged from the top outlet of the vertical furnace and subjected to dust removal, dehydration and denitrification treatment. Then, the flue gas is used as the high-temperature reducing gas and introduced into the middle of the vertical furnace.

[0027] In a preferred embodiment of the present invention, the reduction zone comprises a preheating reduction zone and a high-temperature reduction zone from top to bottom. The hydrogen-rich cooling gas exported from the constant pressure zone is introduced into the preheating reduction zone to preheat and pre-reduce the iron-containing furnace charge. The treated flue gas is introduced into the high-temperature reduction zone to reduce the iron-containing furnace charge.

[0028] In a preferred embodiment of the present invention, the flue gas after dust removal and dehydration is pressurized and then partially subjected to denitrification treatment, while the other part of the flue gas that has not undergone denitrification treatment is mixed with the denitrified flue gas and then introduced into the vertical furnace.

[0029] In a preferred embodiment of the present invention, the flue gas after denitrification and mixing is subjected to heat exchange treatment with the flue gas before dust removal.

[0030] In a preferred embodiment of the present invention, the flue gas is heated before being introduced into the vertical furnace as the high-temperature reducing gas.

[0031] In a preferred embodiment of the present invention, the hydrogen-rich cooling gas is pressure-regulated before being introduced into the cooling zone of the vertical furnace.

[0032] In a preferred embodiment of the present invention, the hydrogen-rich cooling gas is subjected to dust removal treatment before being introduced into the reduction zone of the vertical furnace after heat exchange and heating.

[0033] In a preferred embodiment of the present invention, the hydrogen-rich cooling gas is heated before being sent into the reduction zone after dust removal.

[0034] Compared with the prior art, the technical solution of the present invention has the following characteristics and advantages:

[0035] This invention constructs a hydrogen-nitrogen-based vertical shaft furnace reduction ironmaking system and process, combining key technologies such as nitrogen removal, cooling gas reflux, and electric heating, to achieve stable control of the atmosphere in the ironmaking system and efficient utilization of energy.

[0036] First, by setting a nitrogen removal branch pipe after the compressor, the problem of nitrogen enrichment in the system caused by the introduction of nitrogen due to the equalization of feeding pressure is effectively avoided, ensuring that the nitrogen content in the circulating gas remains stable at less than 40 vol.% for a long time, thereby maintaining a high hydrogen partial pressure and ensuring the efficiency of the reduction reaction and the metallization rate.

[0037] Secondly, this invention employs a dual-path feeding of process gas into the vertical shaft furnace. On one hand, the high-temperature reducing gas, after heating, enters the high-temperature reduction zone of the furnace, providing the main heat and reducing atmosphere. On the other hand, the low-temperature reducing gas, acting as cooling gas, enters from the bottom of the furnace to cool the directly reduced iron and then flows back to the upper part of the furnace body, participating again in the pellet preheating process. This achieves cascade utilization of sensible heat, effectively reducing the total energy consumption of the system. Compared to the existing technology where cooling gas is emitted separately and requires a separate tail gas treatment device, this invention unifies its recirculation and treats it together with the main gas, simplifying the tail gas system and reducing equipment investment and operating costs.

[0038] In summary, this invention not only has significant advantages in terms of process stability, energy efficiency, and system safety, but also possesses great potential for industrial application and promotional value. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0040] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. Those skilled in the art, guided by the teachings of this invention, can select various possible shapes and proportions to implement the invention according to specific circumstances.

[0041] Figure 1 This is a schematic diagram of the structure of the hydrogen-nitrogen-based vertical shaft furnace reduction ironmaking system described in this invention.

[0042] Explanation of reference numerals in the attached figures:

[0043] 10. Vertical shaft furnace; 11. Flue gas outlet; 12. Cooling exhaust gas inlet; 13. High-temperature reducing gas inlet; 14. Cooling exhaust gas outlet; 15. Low-temperature reducing gas inlet; 16. Charging port; 17. Discharge port;

[0044] 20. Cryogenic process gas supply pipe; 21. Hydrogen storage tank; 22. Pressure regulator;

[0045] 30. Heat recovery pipe; 31. Second dust collector; 32. Heater;

[0046] 40. Process gas circulation pipe; 41. Heat exchanger; 42. First dust collector; 43. Dehydrator; 44. Pressurizer; 45. Denitrification device; 46. Heating furnace. Detailed Implementation

[0047] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0048] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0050] Implementation Method 1:

[0051] This invention provides a hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system, such as... Figure 1 As shown, it includes: a vertical furnace 10, which has a reduction zone, a constant pressure zone and a cooling zone from top to bottom; a cooling and heat recovery unit, which has a low-temperature process gas supply pipe 20 connected to the lower part of the cooling zone and a heat recovery pipe 30 connecting the upper part of the constant pressure zone and the reduction zone; and a process gas circulation treatment unit, which has a process gas circulation pipe 40 connecting the flue gas outlet 11 at the top of the vertical furnace 10 and the reduction zone, and the process gas circulation pipe 40 is equipped with a first dust collector 42, a dehydrator 43 and a denitrification device 45.

[0052] The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system of the present invention adopts a dual-path feeding of process gas into the vertical shaft furnace 10. On the one hand, the flue gas generated at the top of the furnace is treated and enters the reduction zone of the vertical shaft furnace 10 as high-temperature reducing gas, providing the main heat and reducing atmosphere. On the other hand, the low-temperature reducing gas, as cooling gas, enters from the bottom of the furnace to cool the direct reduced iron and then flows back to the upper part of the furnace body to participate in the preheating process of the iron-containing furnace charge again, realizing the cascade utilization of sensible heat and effectively reducing the total energy consumption of the system.

[0053] The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system of the present invention is equipped with a denitrification device 45 for removing nitrogen on the process gas circulation pipe 40. This effectively avoids the problem of nitrogen enrichment in the system caused by the introduction of nitrogen due to the equalization of the charging pressure, and ensures that the nitrogen content in the circulating gas is stable within a predetermined range for a long period of time, thereby maintaining a high hydrogen partial pressure and ensuring the efficiency of the reduction reaction and the metallization rate.

[0054] The following section will provide a detailed description of the specific structure of each part of the hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system described in this invention, as well as the positional relationships and pipeline connections between each part.

[0055] It should be noted that the descriptions of "low temperature", "high temperature" and "hydrogen-rich" in this invention are only relative. Since the temperature is different at different locations within the vertical furnace 10, the distinction is made based on the temperature differences between different areas. This is not a limitation on the scope of protection of the invention. Furthermore, the specification of this invention provides the corresponding temperature and content selection range. Therefore, the above descriptions do not lead to any ambiguity in this invention.

[0056] The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system has a vertical shaft furnace 10, such as Figure 1 As shown, the vertical shaft furnace 10 is the core of the entire system. From top to bottom, the furnace consists of a reduction zone, a constant pressure zone, and a cooling zone, used to complete the gas-solid reduction reaction of the oxide pellets (containing iron charge), and the cooling and discharge of the direct reduced iron (DRI) product. In the reduction zone, the oxide pellets react with the reducing agent (hydrogen) to produce elemental iron (direct reduced iron). In the cooling zone, the DRI produced by the reaction is cooled in various ways to prevent it from re-oxidizing after being tapped from the furnace. The inner wall of the vertical shaft furnace 10 is constructed of refractory material to withstand the high-temperature reaction environment and provide insulation; the outer shell is a steel structure to provide sufficient mechanical strength.

[0057] Furthermore, such as Figure 1 As shown, the top and bottom of the vertical shaft furnace 10 are respectively equipped with a charging port 16 and a discharging port 17. The charging port 16 is connected to a sealed charging device, which can realize continuous and uniform distribution of oxidized pellets, ensuring that the material is evenly distributed inside the furnace, thereby maintaining the thermodynamic and kinetic stability of the reaction process. The discharging port 17 is connected to a direct reduced iron storage and transportation device, which can realize the continuous outward transportation of direct reduced iron.

[0058] The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system also includes a cooling and heat recovery unit for cooling and recovering heat from the direct reduction of iron. The cooling and heat recovery unit has a low-temperature process gas supply pipe 20 and a regenerator pipe 30 connected to the vertical shaft furnace 10.

[0059] like Figure 1 As shown, a low-temperature reducing gas inlet 15, connecting to the lower part of the cooling zone, is provided on the side wall of the vertical furnace 10. The outlet end of the low-temperature process gas supply pipe 20 is connected to the low-temperature reducing gas inlet 15, which is used to introduce low-temperature reducing gas (usually low-temperature hydrogen-rich reducing gas, i.e., hydrogen-rich cooling gas as described below) into the cooling zone. The low-temperature reducing gas entering the cooling zone can cool the direct reduced iron generated above, thereby reducing the temperature of the direct reduced iron. The low-temperature reducing gas is selected as room-temperature hydrogen gas with a temperature of about 25°C and a purity of 99.99%.

[0060] like Figure 1As shown, the side wall of the vertical furnace 10 has a cooling exhaust gas outlet 14 connecting to the constant pressure zone and a cooling exhaust gas inlet 12 connecting to the reduction zone; the inlet and outlet ends of the regenerator pipe 30 are connected to the cooling exhaust gas outlet 14 and the cooling exhaust gas inlet 12, respectively. The cooling exhaust gas (heated hydrogen-rich reducing gas) generated after heat exchange and heating in the cooling zone enters the constant pressure zone and can be discharged from the cooling exhaust gas outlet 14 into the regenerator pipe 30. Then, it re-enters the vertical furnace 10 through the cooling exhaust gas inlet 12 and comes into contact with the falling iron-containing furnace charge in the upper reduction zone to preheat and pre-reduce the iron-containing furnace charge. After that, it is discharged from the top of the furnace, thereby realizing the recovery and utilization of heat.

[0061] The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system also includes a process gas circulation treatment unit for treating the flue gas generated by the vertical shaft furnace 10 to recycle the flue gas as process gas. The process gas circulation treatment unit mainly includes a process gas circulation pipe 40 connected to the vertical shaft furnace 10.

[0062] like Figure 1 As shown, the top of the vertical shaft furnace 10 has a flue gas outlet 11, and the side wall of the vertical shaft furnace 10 has a high-temperature reducing gas inlet 13 that connects to the reduction zone; the inlet and outlet ends of the process gas circulation pipe 40 are connected to the flue gas outlet 11 and the high-temperature reducing gas inlet 13, respectively. The flue gas generated after the reduction reaction in the reduction zone of the vertical shaft furnace 10 can enter the process gas circulation pipe 40 through the flue gas outlet 11. The sources of the flue gas are the cooling tail gas entering the reduction zone from the cooling tail gas inlet 12, the high-temperature reducing gas entering the reduction zone from the high-temperature reducing gas inlet 13, and a portion of nitrogen introduced as equalizing gas during the charging process.

[0063] like Figure 1 As shown, the process gas circulation pipe 40 is equipped with a first dust collector 42, a dehydrator 43, and a denitrification device 45. The first dust collector 42 uses wet dust removal to remove dust particles and some water vapor from the flue gas; the dehydrator 43 removes liquid water from the flue gas; the denitrification device 45 removes nitrogen that gradually accumulates in the system, controlling the nitrogen content to within 40 vol.%. The purified flue gas, as a high-temperature reducing gas, re-enters the reduction zone of the vertical furnace 10 through the high-temperature reducing gas inlet 13, realizing a closed-loop circulation of high-temperature reducing gas and flue gas; the denitrification device 45 can separate some nitrogen from the flue gas using pressure swing adsorption or membrane separation. The main component of the high-temperature reducing gas produced after flue gas treatment is hydrogen, and its temperature needs to reach the reaction temperature required by the reduction zone in the vertical furnace 10, typically around 1000℃.

[0064] This invention achieves efficient utilization of hydrogen resources, step-by-step recovery and utilization of heat, and stable control of the atmosphere in the vertical furnace 10 by setting up a dual-flow circulation path and a denitrification device 45, while reducing system complexity and operating costs, and has good prospects for engineering applications.

[0065] The following will further explain the structure and technical effects of the preferred embodiment of the hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system described in this invention.

[0066] According to one embodiment of the present invention, such as Figure 1 As shown, the reduction zone consists of a preheating reduction zone and a high-temperature reduction zone from top to bottom; the cooling exhaust gas inlet 12 on the side wall of the vertical furnace 10 is connected to the preheating reduction zone, and the high-temperature reducing gas inlet 13 on the side wall of the vertical furnace 10 is connected to the high-temperature reduction zone.

[0067] Since the heat generated by the cooling exhaust gas after heat exchange in the cooling zone is slightly less than the heat of the high-temperature reducing gas introduced into the high-temperature reduction zone, it is introduced into the preheating reduction zone for preheating and pre-reduction to ensure the high-temperature environment in the high-temperature reduction zone and to ensure the efficient reduction reaction and product quality of the iron-containing furnace charge in the high-temperature reduction zone.

[0068] According to one embodiment of the present invention, such as Figure 1 As shown, the process gas circulation pipe 40 has a branch parallel section, which has two process gas branch pipes arranged in parallel, and the denitrification device 45 is installed on one of the process gas branch pipes.

[0069] Specifically, the flue gas is divided into two parts after dust removal and dehydration. A small portion enters the denitrification device 45 to remove the nitrogen that gradually accumulates in the system and control the nitrogen content to within 40 vol.%. The remaining majority of the flue gas is combined with the denitrified flue gas and then fed into the vertical furnace 10.

[0070] It should be noted that although this nitrogen removal process cannot completely remove nitrogen from the system, it can achieve dynamic control of nitrogen concentration, keeping the nitrogen content in the circulating gas stably below 40 vol.%, thus ensuring the reactivity of the reducing atmosphere and the stability of system operation.

[0071] Better, such as Figure 1 As shown, two denitrification devices 45 are connected in parallel on the process gas branch pipe; one of the two denitrification devices 45 is used as a backup to facilitate its maintenance and ensure the continuous and stable operation of the system.

[0072] According to one embodiment of the present invention, such as Figure 1 As shown, a heat exchanger 41 is provided between a portion of the process gas circulation pipe 40 upstream of the denitrification unit 45 and a portion of the process gas circulation pipe 40 downstream of the denitrification unit 45.

[0073] The flue gas before dust removal and dehydration and the flue gas after denitrification in the process gas circulation pipe 40 are subjected to heat exchange treatment. The flue gas before dust removal and dehydration has a high temperature, and its temperature decreases after passing through the heat exchanger 41, which facilitates the subsequent dust removal, dehydration and denitrification processes. At the same time, the denitrified flue gas is reintroduced into the heat exchanger 41, so that the heat is transferred back into the flue gas. The flue gas is cooled down and then heated up again to ensure that the gas introduced into the high-temperature reduction zone has a high temperature and avoids temperature fluctuations in the vertical furnace 10.

[0074] According to one embodiment of the present invention, such as Figure 1 As shown, a compressor 44 is also provided on the process gas circulation pipe 40. The first dust collector 42, the dehydrator 43 and the compressor 44 are arranged in sequence on the process gas circulation pipe 40 between the downstream of the heat exchanger 41 and the upstream of the denitrification device 45.

[0075] The first dust collector 42 is placed before the dehydrator 43 and the pressurizer 44 to prevent dust in the flue gas from damaging the dehydrator 43 and the pressurizer 44; the flue gas after dust removal and dehydration is pressurized by the pressurizer 44 to increase the pressure of the flue gas and keep it in balance with the gas pressure in the vertical furnace 10, so as to avoid significant pressure fluctuations in the vertical furnace 10 due to the introduction of flue gas.

[0076] According to one embodiment of the present invention, such as Figure 1 As shown, a heating furnace 46 is provided at one end of the process gas circulation pipe 40 that is connected to the high-temperature reduction zone.

[0077] After pressurization and denitrification, the flue gas enters the heating furnace 46 and is heated to 950℃-1050℃, so that the temperature of the flue gas is consistent with the temperature inside the vertical furnace 10. This avoids significant temperature fluctuations inside the vertical furnace 10 caused by the introduction of flue gas, thereby ensuring the high-temperature environment of the high-temperature reduction zone and ensuring the efficient reduction reaction and product quality of the iron-containing furnace charge in the high-temperature reduction zone.

[0078] According to one embodiment of the present invention, such as Figure 1 As shown, the cryogenic process gas supply pipe 20 is equipped with a hydrogen storage tank 21 and a pressure regulator 22.

[0079] The hydrogen storage tank 21 contains room temperature hydrogen (about 25°C). The room temperature hydrogen is sent to the lower part of the cooling zone of the vertical furnace 10 after passing through the pressure regulator 22 as a low temperature process gas (cooling gas). It comes into countercurrent contact with the downward high temperature direct reduced iron to complete the cooling process.

[0080] According to one embodiment of the present invention, such as Figure 1 As shown, a second dust collector 31 is installed on the regenerator pipe 30. The cooling exhaust gas generated after heat exchange with the direct reduced iron in the cooling zone is treated to remove dust before being introduced into the preheating reduction zone, thereby avoiding pipe blockage and reducing impurities in the material.

[0081] According to one embodiment of the present invention, such as Figure 1 As shown, the regenerating pipe 30 downstream of the second dust collector 31 has a branch parallel section, which has two regenerating branch pipes arranged in parallel, one of which is equipped with a heater 32.

[0082] If the temperature of the high-temperature reducing gas entering the furnace is limited, or if the effective height of the high-temperature reduction zone is reduced due to furnace condition fluctuations, the heater 32 is started. Part of the cooling exhaust gas in the heat recovery pipe 30 can be quickly heated to the target temperature through the heater 32 and sent into the reduction zone for supplemental heating, thereby ensuring the residence time of the oxide pellets in the reduction zone and the metallization rate of the product, making reasonable use of resources and reducing energy consumption.

[0083] Implementation Method Two:

[0084] This invention also provides a hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process, which includes the following steps:

[0085] Step S1: The iron-containing furnace charge is fed into the upper part of the vertical furnace 10 through the charging port 16, and at the same time, high-temperature reducing gas is sent into the middle part of the vertical furnace 10 to reduce the iron-containing furnace charge in the reduction zone to generate direct reduced iron.

[0086] Step S2: The hydrogen-rich cooling gas is fed into the lower part of the vertical furnace 10 to exchange heat with the direct reduced iron in the cooling zone in a countercurrent manner. After the heat exchange, the hydrogen-rich cooling gas is discharged from the constant pressure zone and introduced into the reduction zone to preheat and pre-reduce the iron-containing furnace charge.

[0087] Step S3: The flue gas generated after the reaction of high-temperature reducing gas and hydrogen-rich cooling gas is discharged from the top outlet of vertical furnace 10 and subjected to dust removal, dehydration and denitrification treatment. Then, the flue gas is introduced into the middle of vertical furnace 10 as high-temperature reducing gas.

[0088] It should be noted that the above steps are described in sequence according to the process of the iron-containing furnace charge falling in the vertical furnace 10. In actual production, the ironmaking process in the vertical furnace 10 is a continuous process, and the above steps are all carried out simultaneously.

[0089] The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process described in this invention employs a dual-pathway feeding of process gas into the vertical shaft furnace 10. On one hand, the flue gas generated at the furnace top is treated and then enters the reduction zone of the vertical shaft furnace 10 as high-temperature reducing gas, providing the main heat and reducing atmosphere. On the other hand, the hydrogen-rich cooling gas, which serves as cooling gas, enters from the furnace bottom to cool the direct reduced iron and then flows back to the upper part of the furnace body to participate in the pellet preheating process again. This achieves the cascade utilization of sensible heat and effectively reduces the total energy consumption of the process.

[0090] The following section will provide a detailed description of the specific process steps of the hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process described in this invention.

[0091] In step S1, the feeding and reduction processes are carried out.

[0092] High-grade oxidized pellets, after pelletizing and roasting, are used as furnace charge and loaded into the vertical furnace 10 from the top using the charging system. Nitrogen is used to equalize the pressure during the charging process to maintain the pressure difference between the inside and outside of the furnace and to prevent hydrogen leakage.

[0093] It should be noted that during the initial startup of the system, the air inside the furnace must first be replaced with nitrogen, followed by hydrogen to replace the nitrogen, ensuring the establishment of a safe atmosphere inside the furnace. During this stage, the nitrogen content is relatively low. Subsequently, during continuous operation of the system, nitrogen will be gradually introduced into the system through the pressure equalization process during loading and unloading. If this is not controlled, nitrogen enrichment in the circulating gas will occur.

[0094] High-temperature reducing gas enters the middle of the vertical furnace 10 through high-temperature reducing gas inlet 13, maintaining a stable atmosphere and temperature field in the reduction zone and providing the necessary heat and reducing agent for the reduction of the furnace charge. The iron-containing furnace charge forms a continuous column of charge falling from top to bottom, and undergoes a reduction reaction with the high-temperature reducing gas in the reduction zone to generate high-temperature direct reduced iron.

[0095] In step S2, a cooling and waste heat recovery and reuse process is carried out.

[0096] Hydrogen-rich cooling gas (selected as ambient temperature hydrogen, around 25°C, with a purity of around 99.99%) enters the cooling zone from the bottom of the vertical furnace 10, coming into countercurrent contact with the high-temperature direct reduced iron already reduced in the lower part of the furnace 10, absorbing its sensible heat to achieve product cooling and gas heating. The cooled direct reduced iron is discharged from the bottom of the vertical furnace 10 and sent to the storage and transportation system.

[0097] After being heated, the hydrogen-rich cooling gas (cooling tail gas) is discharged from the constant pressure zone and sent to the upper part of the reduction zone to mix with the high-temperature reducing gas, thereby preheating and pre-reducing the oxidized pellets and realizing the cascade utilization of sensible heat.

[0098] In step S3, the purification and circulation process of the flue gas from the furnace top is carried out.

[0099] The flue gas from the furnace top is a mixture containing water vapor, dust, and some unreacted hydrogen and nitrogen. After passing through a wet dust collector to remove water vapor and dust, a dehydrator to remove liquid water, and a denitrifier to remove some nitrogen, the gas is then introduced back into the reduction zone of the vertical furnace 10 as high-temperature reducing gas, thus achieving a closed-loop circulation of high-temperature reducing gas and flue gas.

[0100] After cooling, the temperature of the direct reduced iron is less than 200℃. It is discharged through the discharge port 17 at the bottom of the vertical furnace 10 and enters a closed conveying or storage system to prevent re-oxidation or spontaneous combustion. The final product can be directly sent to the electric furnace or other subsequent smelting processes.

[0101] The following will provide a detailed description of the preferred embodiment of the hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process described in this invention.

[0102] According to one embodiment of the present invention, the reduction zone has a preheating reduction zone and a high-temperature reduction zone from top to bottom. The hydrogen-rich cooling gas exported from the constant pressure zone is introduced into the preheating reduction zone to preheat and pre-reduce the iron-containing furnace charge. The treated flue gas is introduced into the high-temperature reduction zone as high-temperature reducing gas to reduce the iron-containing furnace charge.

[0103] Since the heat generated by the cooling exhaust gas after heat exchange in the cooling zone is slightly less than the heat of the high-temperature reducing gas introduced into the high-temperature reduction zone, it is introduced into the preheating reduction zone for preheating and pre-reduction to ensure the high-temperature environment in the high-temperature reduction zone and to ensure the efficient reduction reaction and product quality of the iron-containing furnace charge in the high-temperature reduction zone.

[0104] According to one embodiment of the present invention, after the flue gas has undergone dust removal and dehydration treatment, it is pressurized and then partially denitrified, while the other part of the flue gas that has not undergone denitrification treatment is mixed with the denitrified flue gas and then fed into the vertical furnace 10.

[0105] After dust removal and dehydration, the flue gas is divided into two parts. A small portion removes the nitrogen that gradually accumulates in the system through pressure swing adsorption or membrane separation, controlling the nitrogen content to within 40 vol.%. The remaining majority of the flue gas is combined with the denitrified flue gas and then fed into the vertical furnace 10.

[0106] It should be noted that although this nitrogen removal process cannot completely remove nitrogen from the system, it can achieve dynamic control of nitrogen concentration, keeping the nitrogen content in the circulating gas stably below 40 vol.%, thus ensuring the reactivity of the reducing atmosphere and the stability of system operation.

[0107] In a preferred embodiment of the present invention, the flue gas after denitrification and mixing is subjected to heat exchange treatment with the flue gas before dust removal.

[0108] The flue gas before dust removal and dehydration and the flue gas after denitrification are subjected to heat exchange treatment. The flue gas before dust removal and dehydration has a higher temperature, while the flue gas after denitrification has a lower temperature. After heat exchange, the cooled flue gas is easier to process in subsequent dust removal, dehydration and denitrification processes. The heated flue gas is introduced into the high-temperature reduction zone to maintain a high temperature in the high-temperature reduction zone.

[0109] In a preferred embodiment of the present invention, the flue gas is heated before being introduced into the vertical furnace 10 as a high-temperature reducing gas.

[0110] Before the pressurized and denitrified flue gas enters the vertical furnace 10, it is heated to 950℃-1050℃ to keep the temperature of the flue gas consistent with the temperature inside the vertical furnace 10. This avoids significant temperature fluctuations inside the vertical furnace 10 caused by the introduction of flue gas, thereby ensuring the high-temperature environment of the high-temperature reduction zone and ensuring the efficient reduction reaction of iron-containing furnace charge and product quality in the high-temperature reduction zone.

[0111] In a preferred embodiment of the present invention, the hydrogen-rich cooling gas is pressure-regulated before being introduced into the cooling zone of the vertical furnace 10. The pressure of the hydrogen-rich cooling gas, after pressure regulation, is kept consistent with the pressure inside the vertical furnace 10, thus preventing significant pressure fluctuations within the furnace 10 caused by the introduction of the hydrogen-rich cooling gas.

[0112] In a preferred embodiment of the present invention, the hydrogen-rich cooling gas, after heat exchange and heating, is subjected to dust removal treatment before being introduced into the reduction zone of the vertical furnace 10. The cooling exhaust gas (hydrogen-rich cooling gas after heat exchange and heating) generated after heat exchange with direct reduced iron in the cooling zone is subjected to dust removal treatment before being introduced into the preheating reduction zone, thereby avoiding pipe blockage and reducing impurities in the material.

[0113] In a preferred embodiment of the present invention, the hydrogen-rich cooling gas is heated before being sent into the reduction zone after dust removal.

[0114] If the effective height of the high-temperature reduction zone is reduced due to factors such as limited temperature of the high-temperature reducing gas entering the furnace or fluctuations in furnace conditions, some of the cooling exhaust gas is heated to the target temperature and sent into the reduction zone for reheating. This ensures the residence time of the oxidized pellets in the reduction zone and the metallization rate of the product, making reasonable use of resources and reducing energy consumption.

[0115] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system, characterized in that, include: A vertical furnace (10) has a reduction zone, a constant pressure zone and a cooling zone from top to bottom; The cooling and heat recovery unit has a low-temperature process gas supply pipe (20) connected to the lower part of the cooling zone, and a heat recovery pipe (30) connecting the upper part of the constant pressure zone and the reduction zone. The process gas circulation treatment unit has a process gas circulation pipe (40) connecting the flue gas outlet (11) at the top of the vertical furnace (10) and the reduction zone. The process gas circulation pipe (40) is equipped with a first dust collector (42), a dehydrator (43) and a denitrification device (45).

2. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system according to claim 1, characterized in that, The reduction zone consists of a preheating reduction zone and a high-temperature reduction zone from top to bottom; The top of the vertical furnace (10) is provided with a flue gas outlet (11), and the side wall of the vertical furnace (10) is provided with a cooling exhaust gas inlet (12) that connects to the preheating reduction zone, a high temperature reducing gas inlet (13) that connects to the high temperature reduction zone, a cooling exhaust gas outlet (14) that connects to the constant pressure zone, and a low temperature reducing gas inlet (15) that connects to the lower part of the cooling zone. The outlet end of the low-temperature process gas supply pipe (20) is connected to the low-temperature reducing gas inlet (15), the two ends of the heat recovery pipe (30) are connected to the cooling tail gas outlet (14) and the cooling tail gas inlet (12) respectively, and the two ends of the process gas circulation pipe (40) are connected to the flue gas outlet (11) and the high-temperature reducing gas inlet (13) respectively.

3. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system according to claim 1 or 2, characterized in that, The process gas circulation pipe (40) has a branch parallel section, the branch parallel section has two process gas branch pipes arranged in parallel, and the denitrification device (45) is installed on one of the process gas branch pipes.

4. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system according to claim 3, characterized in that, The process gas branch pipe is equipped with two denitrification devices (45) connected in parallel.

5. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system according to claim 3, characterized in that, A heat exchanger (41) is provided between the upstream portion of the process gas circulation pipe (40) of the denitrification device (45) and the downstream portion of the process gas circulation pipe (40).

6. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system according to claim 5, characterized in that, A compressor (44) is also provided on the process gas circulation pipe (40). On the process gas circulation pipe (40) between the downstream of the heat exchanger (41) and the upstream of the denitrification device (45), the first dust collector (42), the dehydrator (43) and the compressor (44) are arranged in sequence.

7. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system according to claim 6, characterized in that, A heating furnace (46) is provided at one end of the process gas circulation pipe (40) that is connected to the reduction zone.

8. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system according to claim 1 or 2, characterized in that, The cryogenic process gas supply pipe (20) is equipped with a hydrogen storage tank (21) and a pressure regulator (22).

9. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system according to claim 1 or 2, characterized in that, The heat recovery pipe (30) is equipped with a second dust collector (31).

10. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system according to claim 9, characterized in that, The regenerating pipe (30) downstream of the second dust collector (31) has a branch parallel section, which has two regenerating branch pipes arranged in parallel, one of which is equipped with a heater (32).

11. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking system according to claim 1, characterized in that, The top and bottom of the vertical furnace (10) are respectively provided with a feeding port (16) and a discharging port (17).

12. A direct reduction ironmaking process using a hydrogen-nitrogen-based vertical shaft furnace, characterized in that, include: Iron-containing furnace charge is fed into the upper part of the vertical furnace (10) through the charging port (16), and high-temperature reducing gas is sent into the middle part of the vertical furnace (10) to reduce the iron-containing furnace charge in the reduction zone to generate direct reduced iron. Hydrogen-rich cooling gas is fed into the lower part of the vertical furnace (10) to exchange heat with the direct reduced iron in the cooling zone in a countercurrent manner. After the heat exchange, the hydrogen-rich cooling gas is discharged from the constant pressure zone and introduced into the reduction zone to preheat and pre-reduce the iron-containing furnace charge. The flue gas generated after the reaction of the high-temperature reducing gas and the hydrogen-rich cooling gas is discharged from the top outlet of the vertical furnace (10) and subjected to dust removal, dehydration and denitrification treatment. Then the flue gas is introduced into the middle of the vertical furnace (10) as the high-temperature reducing gas.

13. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process according to claim 12, characterized in that, The reduction zone consists of a preheating reduction zone and a high-temperature reduction zone from top to bottom. The hydrogen-rich cooling gas exported from the constant pressure zone is introduced into the preheating reduction zone to preheat and pre-reduce the iron-containing furnace charge. The treated flue gas is introduced into the high-temperature reduction zone to reduce the iron-containing furnace charge.

14. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process according to claim 12 or 13, characterized in that, After dust removal and dehydration, the flue gas is pressurized, and a portion of it undergoes denitrification treatment. The remaining portion of the flue gas that has not undergone denitrification treatment is mixed with the denitrified flue gas and then introduced into the vertical furnace (10).

15. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process according to claim 14, characterized in that, The flue gas after denitrification and mixing is subjected to heat exchange treatment with the flue gas before dust removal.

16. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process according to claim 15, characterized in that, Before the treated flue gas is introduced into the vertical furnace (10) as the high-temperature reducing gas, the flue gas is heated.

17. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process according to claim 12 or 13, characterized in that, Before the hydrogen-rich cooling gas is introduced into the cooling zone of the vertical furnace (10), the hydrogen-rich cooling gas is subjected to pressure regulation.

18. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process according to claim 12 or 13, characterized in that, Before the hydrogen-rich cooling gas, after heat exchange and heating, is introduced into the reduction zone of the vertical furnace (10), the hydrogen-rich cooling gas is subjected to dust removal treatment.

19. The hydrogen-nitrogen-based vertical shaft furnace direct reduction ironmaking process according to claim 18, characterized in that, Before the hydrogen-rich cooling gas after dust removal is sent into the reduction zone, the hydrogen-rich cooling gas is heated.

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