A pellet cooling-hydrogen pre-reduction-shaft furnace reduction combined production system and method

Abstract

The present application relates to oxidized pellet cooling, shaft furnace reduction technical field, specifically relates to a kind of pellet cooling-hydrogen pre-reduction-shaft furnace reduction combined production system and method.The combined production system includes cooling-hydrogen pre-reduction stage and reduction stage;The reduction section gas inlet of the reduction stage is connected with the gas outlet pipeline of cooling-pre-reduction III section of the cooling-hydrogen pre-reduction stage;The gas outlet of shaft furnace reduction section is connected with the gas inlet pipeline of cooling-pre-reduction I section of the cooling-hydrogen pre-reduction stage by hydrogen-rich gas heat exchanger.The present application combines oxidized pellet cooling and shaft furnace hydrogen reduction process, uses hydrogen-rich gas discharged from shaft furnace top to cool and pre-reduce pellet in oxidized pellet cooling process, improves hydrogen utilization and hydrogen shaft furnace reduction process production efficiency, significantly speeds up the cooling speed of pellet, shortens pellet cooling time and pellet shaft furnace reduction time, and improves the energy utilization efficiency of whole process.

Description

Technical Field

[0001] This invention relates to the field of oxide pellet cooling and vertical shaft furnace reduction technology, specifically to a combined production system and method for pellet cooling-hydrogen pre-reduction-vertical shaft furnace reduction. Background Technology

[0002] Traditional iron and steel metallurgy mainly uses carbon as a reducing agent to reduce iron oxides into metallic iron, resulting in a large amount of carbon dioxide emissions.

[0003] To reduce carbon dioxide emissions during steel smelting, research has proposed hydrogen metallurgy, which uses hydrogen instead of carbon as a reducing agent. Studies have shown that increasing the proportion of hydrogen in the gaseous reducing agent during the gas-solid reduction reaction of iron oxides can significantly improve the reduction rate and efficiency. Furthermore, the only byproduct of hydrogen reduction of iron oxides is water vapor, thus avoiding carbon dioxide emissions.

[0004] Currently, hydrogen metallurgy technology is divided into hydrogen-rich metallurgy and pure hydrogen metallurgy, and the reactors that can be used are mainly the relatively mature gas-based vertical shaft furnaces. Moreover, in terms of carbon reduction effect, pure hydrogen vertical shaft furnace reduction has great potential for development.

[0005] However, the existing pure hydrogen vertical shaft furnace reduction process, which uses room-temperature oxidized pellets followed by hot hydrogen reduction, has two main drawbacks. First, the current process uses the physical heat of hydrogen as the heat source for the reduction reaction. However, hydrogen has a low specific heat coefficient, and the reduction of iron oxides by hydrogen is a strongly endothermic reaction. Given that the current heat exchanger's heating limit for hydrogen is no higher than 950℃, the hydrogen circulation volume is large, and the primary utilization rate is generally no more than 30%, resulting in low efficiency. Second, the current cooling of oxidized pellets uses cross-flow air heat exchange, a process that lasts 40-60 minutes until the pellet temperature drops to <150℃. The pellets then reheat and reduce in the vertical shaft furnace. This cooling process is lengthy and inefficient, and may also result in the discharge of high-temperature waste gas and low waste heat utilization, leading to significant energy waste throughout the process.

[0006] To address the aforementioned issues, CN114107590A discloses a pellet oxidation roasting-pure hydrogen reduction cooling system and method. This system integrates the oxidation roasting and reduction cooling processes of green pellets within the same reactor. The reactor comprises a heating roasting section, a temperature regulation section, an isobaric section, and a reduction cooling section, connected sequentially from top to bottom. In the heating roasting section, the green pellets are in countercurrent contact with a mixture of hot flue gas and superheated steam from the temperature regulation section, heating and oxidizing the green pellets into oxidized pellets. The oxidized pellets then enter the temperature regulation section, where they are contacted with superheated steam for temperature regulation before entering the isobaric section for transition. Finally, they enter the reduction cooling section where they are simultaneously reduced and cooled with hydrogen from the hydrogen inlet, yielding the solid product, sponge iron.

[0007] CN113881842A discloses a system and method for producing metallized pellets through integrated pellet roasting and reduction, which has similar features to CN114107590A. The system includes a chain grate machine, a rotary kiln, a reduction zone, and a finished product conveyor. After the pellets are roasted, their heat is directly used for reduction to achieve integrated production.

[0008] The above-mentioned scheme improves the production process of pellets and the gas-based shaft furnace process to a certain extent, thereby increasing the hydrogen utilization rate, shortening the pellet cooling process, and saving energy. However, it involves significant changes to the existing pellet production process and gas-based shaft furnace process, resulting in high modification costs and making it difficult to implement and promote in the existing pellet production process and gas-based shaft furnace process. Summary of the Invention

[0009] To address the aforementioned problems, this invention provides a combined production system and method for pellet cooling, hydrogen pre-reduction, and vertical shaft furnace reduction. This method solves the problems of low hydrogen utilization, long cooling process in the production of oxidized pellets, and high energy waste in the gas-based vertical shaft furnace reduction process.

[0010] In a first aspect, the present invention provides a combined production system for pellet cooling-hydrogen pre-reduction-vertical furnace reduction, which includes a cooling-hydrogen pre-reduction stage and a reduction stage. The cooling-hydrogen pre-reduction stage includes: cooling equipment and a cooler; according to the flow of high-temperature pellets after roasting in production, the cooling equipment includes: cooling-pre-reduction stage III, cooling-pre-reduction stage II, and cooling-pre-reduction stage I in sequence. The reduction stage includes: a hydrogen-rich gas heat exchanger, a vertical furnace, and a condenser; the vertical furnace includes: a reduction section and a cooling section. The inlet of the reduction section is connected to the outlet pipe of the cooling-pre-reduction III section; the outlet of the reduction section is connected to the inlet pipe of the cooling-pre-reduction I section via a hydrogen-rich gas heat exchanger.

[0011] This invention rationally divides the cooling equipment and connects the cooling-pre-reduction III section and the cooling-pre-reduction I section to the reduction section of the vertical shaft furnace to form a circulating path for hydrogen-rich gas. Thus, in the cooling-hydrogen pre-reduction stage, the hydrogen-rich gas discharged from the top of the hydrogen vertical shaft furnace replaces air as the cooling medium for the pellets. The heat of the pellets themselves is used to heat the reduction reaction between iron oxides and H2 in the hydrogen-rich gas. While cooling the pellets, the pellets are also reduced to obtain pre-reduced pellets with a certain degree of reduction. This can improve the utilization efficiency of hydrogen, shorten the reduction process in the hydrogen vertical shaft furnace, and improve production efficiency.

[0012] In addition to cooling the pellets through gas-solid heat exchange, this invention also utilizes the strong endothermic effect of the reduction reaction between iron oxides and H2, which can significantly accelerate the cooling rate and shorten the cooling time of the pellets.

[0013] Meanwhile, by utilizing the cascade convection of hydrogen-rich gas, the physical heat of the pellets is fully utilized. While the pellets are being cooled, the pre-reduction degree of the pellets is increased and high-temperature hydrogen-rich gas is obtained. This gas is used for subsequent hydrogen vertical furnace reduction, which can reduce the energy consumption of the hydrogen-rich gas heat exchanger when heating the hydrogen-rich gas and improve the energy utilization efficiency of the entire process.

[0014] Furthermore, in the cooling-hydrogen pre-reduction stage, the cooling-pre-reduction stage III is provided with a gas outlet, and the cooling-pre-reduction stage I is provided with a gas inlet. The cooling gas medium used in the cooling-pre-reduction stage III, cooling-pre-reduction stage II, and cooling-pre-reduction stage I is hydrogen-rich gas; the hydrogen-rich gas can be a mixture of hydrogen, nitrogen, and water vapor containing different mass or volume percentages.

[0015] The cooling equipment further includes a cooling-protection section and a cooling final section. The cooling-protection section is located at the front end of the cooling-pre-reduction section I to prevent hydrogen-rich gas from entering the material layer and causing deflagration, thus improving system safety. The cooling final section is located at the rear end of the cooling-pre-reduction section III to provide final cooling to the pre-reduced pellets while preventing the metallic iron in the pre-reduced pellets from being oxidized again by air. The cooling gas medium used in the cooling-protection section and the cooling final section is an inert gas, such as nitrogen (N2) or argon (Ar) (G1, G5).

[0016] In the cooling-hydrogen pre-reduction stage, the cooling equipment can be a pellet ring cooler, a belt roaster cooling section, etc., and the cooler can be a water-cooled cooler, an air heat exchange cooler, etc.

[0017] Furthermore, in the reduction section, both the reduction section and the metallized pellet cooling section are provided with gas inlets and outlets. The gas used in the reduction section is a mixture of hydrogen-rich gas from the outlet of the cooling-pre-reduction III section and hydrogen-rich gas used for reduction, heated by a hydrogen-rich gas heat exchanger. The cooling medium used in the metallized pellet cooling section is an inert gas, such as nitrogen (N2) or argon (Ar). The hydrogen-rich gases (G4, G6, G7) can be mixtures containing different mass or volume percentages of hydrogen, nitrogen, and water vapor.

[0018] Secondly, the present invention also provides a combined production method for pellet cooling-hydrogen pre-reduction-vertical furnace reduction, comprising: a cooling-hydrogen pre-reduction stage and a hydrogen vertical furnace reduction stage; In the cooling-hydrogen pre-reduction stage, hydrogen-rich gas is used to replace air to cool the pellets. By using the cascade convection of hydrogen-rich gas, the pellets are rapidly cooled from >1000℃ to <150℃. The pellets are partially reduced by hydrogen, and high-temperature hydrogen-rich gas with a temperature of >400℃ is obtained at the same time. In the hydrogen reduction stage of the vertical shaft furnace, the high-temperature hydrogen-rich gas from the outlet of the cooling-hydrogen pre-reduction stage is mixed with the hydrogen-rich gas used for reduction and then heated to 900℃-950℃ by a hydrogen-rich gas heat exchanger. It then enters the reduction section of the vertical shaft furnace to further reduce the pre-reduced pellets into metallized pellets. The metallized pellets are cooled in the cooling section of the vertical shaft furnace to obtain the metallized pellet product. At the same time, the hydrogen-rich gas discharged from the outlet of the reduction section is returned to the cooling-hydrogen pre-reduction stage for recycling after the water vapor is removed and the temperature is lowered by the condenser.

[0019] Furthermore, in the cooling-hydrogen pre-reduction stage, the cooling-protection section uses a forced draft method to allow cooling gas G1 to pass through the burden layer from bottom to top, mainly to vent the air within the pellet ore burden layer; the cooling-pre-reduction III, cooling-pre-reduction II, and cooling-pre-reduction I stages recycle the hydrogen-rich gas discharged from the top of the reduction shaft furnace and cooled by condensation and dehydration, using a cascade utilization method to penetrate the burden layer; specifically as follows: Hydrogen-rich gas G2 first enters the cooling-pre-reduction stage I via a blower, passing through the pellet ore layer from bottom to top. The temperature of the pellet ore decreases while the hydrogen-rich gas G2 is heated. Hydrogen-rich gas G2, which penetrates and is heated through the pellet bed in the cooling-pre-reduction stage I, enters the cooling-pre-reduction stage II through the reheat air duct and passes through the pellet bed from bottom to top. During this process, the temperature of the pellet decreases and it undergoes a reduction reaction with H2 in the hydrogen-rich gas. A small amount of iron oxides in the pellet are reduced, and the water vapor, a byproduct of the reduction reaction, enters the hydrogen-rich gas G3. At the same time, the temperature of the hydrogen-rich gas G3 is further increased. The hydrogen-rich gas G3 penetrates the cooling-pre-reduction II stage and enters the cooling-pre-reduction III stage through the reheat air duct, passing through the pellet ore layer from bottom to top. During this process, the pellets undergo a reduction reaction with H2 in the hydrogen-rich gas, and a large amount of iron oxides in the pellets are reduced. The water vapor generated by the reduction reaction enters the hydrogen-rich gas G4, and at the same time, the temperature of the hydrogen-rich gas G4 increases to over 400°C. In the final cooling stage, the cooling gas G5 is forced through the material layer from bottom to top by a blower. The hot waste gas is collected and cooled by a cooler before being combined with the cooling gas G5 and re-entering the material layer for recycling. After cooling, the temperature of the pellets drops to ≤50℃, and the pre-reduced pellets are obtained by unloading.

[0020] As a specific embodiment of the present invention, the combined production method of pellet cooling-hydrogen pre-reduction-vertical furnace reduction includes the following steps: (1) When the roasted high-temperature pellets move forward on the cooling equipment, they pass through the cooling-protection section, the cooling-pre-reduction III section, the cooling-pre-reduction II section, the cooling-pre-reduction I section, and the final cooling section in sequence; Meanwhile, the hydrogen-rich gas discharged from the top of the vertical furnace and cooled by condensation and dehydration is used in a cascade manner to pass through the pellet ore layer in the cooling-pre-reduction section I, cooling-pre-reduction section II, and cooling-pre-reduction section III. Finally, the high-temperature ore pellets are cooled and pre-reduced to obtain pre-reduced pellets; (2) The pre-reduced pellets discharged from the cooling end section enter the reduction vertical furnace from the top and exchange gas-solid heat with the high-temperature hydrogen-rich gas running from bottom to top. While the temperature rises, a further reduction reaction occurs to generate metallized pellets. The metallized pellets enter the cooling section and are cooled by the cooling gas to obtain the metallized pellet product. Meanwhile, the high-temperature hydrogen-rich gas G4 discharged from the cooling-pre-reduction III section is mixed with the hydrogen-rich gas G6 used for reduction to form hydrogen-rich gas G7. After being heated to 900℃-950℃ by a hydrogen-rich gas heat exchanger, it enters the reduction shaft furnace from the bottom of the reduction section and is discharged from the top of the reduction shaft furnace. The discharged hydrogen-rich gas G2 passes through a condenser to remove water vapor and is cooled to <30℃, and is then recycled to the cooling-pre-reduction I section for reuse.

[0021] In the above production method, an inert gas cooling-protection (11) is set at the front end of the cooling-pre-reduction section (12, 13, 14) to prevent hydrogen-rich gas in the cooling-pre-reduction section (12, 13, 14) from entering the material layer and causing deflagration, thereby improving system safety. A circulating inert gas cooling final section (15) is set at the rear end of the cooling-pre-reduction section (12, 13, 14), and a cooler (2) is used to cool the circulating inert gas. This prevents the metal iron in the pre-reduction pellets from being oxidized again by the air while finally cooling the pre-reduced pellets produced in the cooling-pre-reduction section (12, 13, 14). The hydrogen-rich gas passes through the cooling-pre-reduction I section (14), cooling-pre-reduction II section (13), and cooling-pre-reduction III section (12) of the material layer in a cascade manner. The physical heat of the increased cooling-pre-reduction I section (14) and cooling-pre-reduction II section (13) of the pellet material layer can be fully utilized to continuously heat the hydrogen-rich gas, thereby increasing the reduction reaction rate of iron oxides in the pellets and H2 in the cooling-pre-reduction III section (12). The high-temperature hydrogen-rich gas discharged from the cooling-pre-reduction III stage (12) is mixed with the hydrogen-rich gas for reduction and then heated through heat exchange before entering the vertical furnace, which can reduce the energy consumption of the heat exchanger and make full use of the heat of the pellet itself.

[0022] The beneficial effects of this invention are as follows: (1) This invention combines the oxidation pellet cooling process with the vertical furnace hydrogen reduction process. During the oxidation pellet cooling process, the hydrogen-rich gas discharged from the top of the vertical furnace is used to pre-reduce the pellets, thereby improving the hydrogen utilization rate and the production efficiency of the hydrogen vertical furnace reduction process.

[0023] (2) The present invention uses hydrogen-rich gas instead of air as the cooling medium for high-temperature pellets. In addition to cooling the pellets through gas-solid heat exchange, it also utilizes the strong endothermic effect of the reduction reaction of iron oxides and H2, which can significantly accelerate the cooling rate of the pellets and shorten the cooling time of the pellets.

[0024] (3) This invention fully utilizes the physical heat of the pellet ore through cascade convection, improves the pre-reduction degree of the pellet ore while cooling the pellet ore and obtains high-temperature hydrogen-rich gas. This gas is used for subsequent hydrogen vertical furnace reduction, which can reduce the energy consumption of the hydrogen-rich gas heat exchanger when heating the hydrogen-rich gas and improve the energy utilization efficiency of the whole process. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process flow of the combined production system and method for pellet cooling-hydrogen pre-reduction-vertical furnace reduction of the present invention.

[0026] In the diagram: 1-Cooling equipment, 11-Cooling-protection section, 12-Cooling pre-reduction section III, 13-Cooling pre-reduction section II, 14-Cooling pre-reduction section I, 15-Cooling final section, 2-Refrigerator, 3-Hydrogen-rich gas heat exchanger, 4-Reduction shaft furnace, 41-Reduction section, 42-Cooling section for metallized pellets, G1, G5-Cooling gas, G2, G3, G4, G6, G7-Hydrogen-rich gas.

[0027] Figure 2 This is the gas-phase equilibrium diagram of CO (solid line) and H2 (dashed line) reducing iron oxides. Detailed Implementation

[0028] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0029] Example 1 This embodiment provides a combined production system for pellet cooling, hydrogen pre-reduction, and vertical shaft furnace reduction, such as... Figure 1 As shown, it includes two sections: a pellet cooling-hydrogen pre-reduction section and a reduction section; (1) The cooling-hydrogen pre-reduction section mainly includes cooling equipment (1) and cooler (2); cooling equipment (1) can be a pellet ring cooler, a belt roaster cooling section, etc.; cooler (2) can be a water-cooled cooler, an air heat exchange cooler, etc.

[0030] in: The cooling equipment (1) is divided into 5 sections according to the flow of high-temperature pellets after roasting in production. Specifically, it includes the cooling-protection section (11), the cooling-pre-reduction III section (12), the cooling-pre-reduction II section (13), the cooling-pre-reduction I section (14), and the cooling final section (15). The cooling-pre-reduction III section (12) is equipped with a gas outlet, and the cooling-pre-reduction I section (14) is equipped with a gas inlet.

[0031] Among them, the cooling gas medium used in the cooling-pre-reduction stage III (12), cooling-pre-reduction stage II (13), and cooling-pre-reduction stage I (14) is hydrogen-rich gas (G2, G3); the hydrogen-rich gas (G2, G3) can be a mixture of hydrogen, nitrogen, and water vapor containing different mass or volume percentages. The cooling gas medium used in the cooling-protection section (11) and the cooling terminal section (15) is an inert gas such as nitrogen (N2) or argon (Ar) (G1, G5).

[0032] (2) The reduction section mainly includes a hydrogen-rich gas heat exchanger (3), a reduction shaft furnace (4), and a condenser (5); The reduction shaft furnace is divided into a reduction section (41) and a metallization pellet cooling section (42), each with a gas inlet and outlet.

[0033] The gas used in the reduction section (41) is a mixture of hydrogen-rich gas (G4) from the outlet of the cooling-pre-reduction III section (12) and hydrogen-rich gas for reduction (G6), which is then heated by a hydrogen-rich gas heat exchanger. The hydrogen-rich gas (G4, G6, G7) can be a mixture of hydrogen, nitrogen and water vapor with different mass or volume percentages. The cooling medium used in the metallized pellet cooling section (42) is an inert gas, such as nitrogen (N2) or argon (Ar).

[0034] In the above production system, the inlet of the reduction section (41) is connected to the outlet of the cooling-pre-reduction III section (12); the outlet of the reduction section (41) is connected to the inlet of the cooling-pre-reduction I section (14) via a hydrogen-rich gas heat exchanger (3).

[0035] Through the above connections, the cooling-hydrogen pre-reduction stage and the reduction stage can be combined for production, forming a circulating pathway for hydrogen-rich gas. This allows the hydrogen-rich gas discharged from the top of the hydrogen shaft furnace to replace air as the cooling medium for the pellets. The heat from the pellets themselves provides heat for the reduction reaction between iron oxides and H2 in the hydrogen-rich gas. While cooling the pellets, they are simultaneously reduced to obtain pre-reduced pellets with a certain degree of reduction. This improves hydrogen utilization efficiency, shortens the reduction process in the hydrogen shaft furnace, and increases production efficiency. It also significantly accelerates the cooling rate and reduces the cooling time of the pellets. Furthermore, the obtained high-temperature hydrogen-rich gas can be used for subsequent hydrogen shaft furnace reduction, reducing energy consumption when heating the hydrogen-rich gas in the heat exchanger and improving the overall energy utilization efficiency.

[0036] Example 2 This embodiment provides a combined production method for pellet cooling-hydrogen pre-reduction-vertical furnace reduction, such as... Figure 1 As shown, it includes: (1) Cooling-hydrogen pre-reduction stage: When the roasted high-temperature pellets advance on the cooling equipment (1), they pass through the cooling-protection section (11), the cooling-pre-reduction III section (12), the cooling-pre-reduction II section (13), the cooling-pre-reduction I section (14), and the final cooling section (15) in sequence. In the cooling-protection section (11), the cooling gas G1 is blown through the material layer from bottom to top by a blower. Its main function is to vent the air in the pellet ore layer. Cooling-pre-reduction stage III (12), cooling-pre-reduction stage II (13), and cooling-pre-reduction stage I (14) recycle the hydrogen-rich gas discharged from the top of the reduction shaft furnace and cooled by condensation and dehydration, and use a cascade utilization method to penetrate the furnace charge layer: Hydrogen-rich gas G2 first enters the cooling-pre-reduction stage I (14) by a blower, and passes through the pellet ore layer from bottom to top. The temperature of the pellet ore drops while the hydrogen-rich gas G2 is heated. The hydrogen-rich gas G2, which penetrates the pellet bed in the cooling-pre-reduction I section (14) and is heated, enters the cooling-pre-reduction II section (13) through the reheat air pipe and passes through the pellet bed from bottom to top. During this process, the temperature of the pellet decreases and it undergoes a reduction reaction with H2 in the hydrogen-rich gas. A small amount of iron oxides in the pellet are reduced, and the water vapor (H2O) byproduct of the reduction reaction enters the hydrogen-rich gas G3. At the same time, the temperature of the hydrogen-rich gas G3 is further increased. The hydrogen-rich gas G3, which penetrates the cooling-pre-reduction II section (13), enters the cooling-pre-reduction III section (12) through the reheat air pipe and passes through the pellet ore layer from bottom to top. During this process, the pellet ore undergoes a reduction reaction with H2 in the hydrogen-rich gas, and a large amount of iron oxide in the pellet ore is reduced. The water vapor (H2O) generated by the reduction reaction enters the hydrogen-rich gas G4, and at the same time, the temperature of the hydrogen-rich gas G4 increases to above 400°C. In the final cooling section (15), the cooling gas G5 is passed through the material layer from bottom to top by a blower. After the hot waste gas is collected, it is cooled by a cooler (2) and then merged with the cooling gas G5 before entering the material layer again for recycling. After cooling, the temperature of the pellets drops to ≤50℃, and the pre-reduced pellets are obtained by unloading.

[0037] Analysis and explanation: During the above-mentioned cooling process of pellets, the temperature of the roasted high-temperature pellets can reach 1200℃~1300℃, and must be reduced to <100℃ after cooling.

[0038] According to the equilibrium diagram of H2 reduction of iron oxide ( Figure 2 As shown by the dotted line, within the temperature range of 100℃ to 1300℃ during the cooling of iron pellets, regardless of the stage, H2 in the hydrogen-rich gas can transform iron oxides according to the process Fe2O3 → Fe3O4 → Fe x The reduction proceeds in the order of O→Fe or Fe2O3→Fe3O4→Fe, and the higher the temperature and the higher the H2 content in the hydrogen-rich gas, the more favorable it is for the reduction of iron oxides. Therefore, this invention utilizes the hydrogen-rich gas discharged from the top of the hydrogen shaft furnace to replace air as the cooling medium for the pellets. The heat of the pellets themselves is used to heat the reduction reaction between the iron oxides and the H2 in the hydrogen-rich gas. While cooling the pellets, the reduction of the pellets is carried out simultaneously to obtain pre-reduced pellets with a certain degree of reduction. This can improve the utilization efficiency of hydrogen, shorten the reduction process in the hydrogen shaft furnace, and improve production efficiency.

[0039] Simultaneously, iron oxides undergo a reduction reaction with H2 at high temperatures: Reactions that occur when T > 570℃ include: 3 Fe₂O₃ + H₂ = 2Fe₃O₄ + H₂O, ΔG θ =-15547-74.40TJ·mol-1 (1) Fe3O4 + H2 = 3FeO + H2O, ΔG θ =71940-73.62TJ·mol-1 (2) FeO + H2 = Fe + H2O, ΔG θ =23430-16.16TJ·mol-1 (3) Reactions that occur when T < 570℃ include: 3 Fe₂O₃ + H₂ = 2Fe₃O₄ + H₂O, ΔG θ =-15547-74.40TJ·mol-1 (1) 1 / 4 Fe3O4 + H2 = 3 / 4 Fe + H2O, ΔG θ =35550-30.40TJ·mol-1 (4) In the above reactions, reaction (1) is an exothermic reaction, and reactions (2) to (4) are all endothermic reactions. The overall reaction effect is endothermic. Therefore, in the scheme proposed in this invention, when the pellets are in the cooling-pre-reduction section and are in convection with hydrogen-rich gas, not only is physical heat exchange between gas and solid carried out, but also heat is absorbed by the reduction reaction of iron oxides and H2, thereby accelerating the cooling rate of the pellets.

[0040] (2) Vertical shaft furnace reduction stage: The high-temperature hydrogen-rich gas G4 discharged from the cooling-pre-reduction III section (12) is mixed with the hydrogen-rich gas G6 for reduction to form hydrogen-rich gas G7. After being heated to 900℃-950℃ by the hydrogen-rich gas heat exchanger (3), it enters the reduction shaft furnace (4) from the bottom of the reduction section (41). Meanwhile, the pre-reduced pellets discharged from the cooling terminal section (15) enter the reduction vertical furnace (4) from the top and exchange gas-solid heat with the high-temperature hydrogen-rich gas running from bottom to top. While the temperature rises, a further reduction reaction occurs to generate metallized pellets. The metallized pellets enter the cooling section (42) and are cooled by the cooling gas to obtain the metallized pellet product. The hydrogen-rich gas G2 discharged from the top of the reducing furnace is cooled to <30°C by removing water vapor in the condenser (5) and then recycled to the cooling-pre-reduction stage I (14) for reuse.

[0041] In the above system and method, an inert gas cooling-protection (11) is set at the front end of the cooling-pre-reduction section (12, 13, 14) to prevent the hydrogen-rich gas in the cooling-pre-reduction section (12, 13, 14) from entering the material layer and causing deflagration, thereby improving system safety; a circulating inert gas cooling final section (15) is set at the rear end of the cooling-pre-reduction section (12, 13, 14), and a cooler (2) is used to cool the circulating inert gas, so as to prevent the metallic iron in the pre-reduced pellets from being oxidized again by air while performing final cooling on the pre-reduced pellets produced in the cooling-pre-reduction section (12, 13, 14); the hydrogen-rich gas is utilized in cascade. The material passes through the cooling-pre-reduction I section (14), cooling-pre-reduction II section (13), and cooling-pre-reduction III section (12) in sequence, with the material layer temperature gradually increasing. This method can make full use of the physical heat of the increased cooling-pre-reduction I section (14) and cooling-pre-reduction II section (13) pellet material layer to continuously heat the hydrogen-rich gas, thereby increasing the reduction reaction rate of iron oxides and H2 in the cooling-pre-reduction III section (12) pellets. The high-temperature hydrogen-rich gas discharged from the cooling-pre-reduction III section (12) is mixed with the hydrogen-rich gas for reduction and then heated through heat exchange before entering the vertical furnace, which can reduce the energy consumption of the heat exchanger and make full use of the heat of the pellets themselves.

[0042] This invention uses cascade convection to allow hydrogen-rich gas to pass through the gradually increasing temperature of the cooling-pre-reduction section pellet bed, extending the gas-solid heat exchange time between the hydrogen-rich gas and the high-temperature pellets. This fully utilizes the physical sensible heat of the pellets and increases the temperature of the hydrogen-rich gas, thereby improving the pre-reduction degree of the pellets in the cooling-pre-reduction III section (12) and obtaining high-temperature hydrogen-rich gas with a temperature ≥400℃. This reduces the energy consumption of the subsequent heat exchanger when heating the hydrogen-rich gas, resulting in a higher energy utilization rate compared to the conventional pellet cooling-heating-reduction process.

[0043] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A combined production system for pellet cooling-hydrogen pre-reduction-vertical furnace reduction, characterized in that, Includes a cooling-hydrogen pre-reduction stage and a reduction stage; The cooling-hydrogen pre-reduction stage includes: cooling equipment and a cooler; according to the flow of high-temperature pellets after roasting in production, the cooling equipment includes: cooling-pre-reduction stage III, cooling-pre-reduction stage II, and cooling-pre-reduction stage I in sequence. The reduction stage includes: a hydrogen-rich gas heat exchanger, a vertical furnace, and a condenser; the vertical furnace includes: a reduction section and a cooling section. The cooling-pre-reduction stage III is provided with a gas outlet, and the cooling-pre-reduction stage I is provided with a gas inlet; The cooling gas medium used in the cooling-pre-reduction stage III, cooling-pre-reduction stage II, and cooling-pre-reduction stage I is hydrogen-rich gas. The hydrogen-rich gas passes through the pellet ore layer of the cooling-pre-reduction stage I, cooling-pre-reduction stage II, and cooling-pre-reduction stage III in a cascade convection manner. The outlet of the cooling-pre-reduction III section is connected to the pipeline of the hydrogen-rich gas heat exchanger. The gas used in the reduction section is a mixture of high-temperature hydrogen-rich gas discharged from the outlet of the cooling-pre-reduction III section and hydrogen-rich gas for reduction, which is then heated by the hydrogen-rich gas heat exchanger. The outlet of the reduction section is connected to the condenser pipe. The hydrogen-rich gas discharged from the top of the reduction furnace is cooled down by removing water vapor in the condenser and then circulated to the inlet of the cooling-pre-reduction section I for reuse.

2. The pellet cooling-hydrogen pre-reduction-vertical furnace reduction combined production system according to claim 1, characterized in that, The cooling equipment also includes a cooling-protection section and a final cooling section; The cooling-protection section is located at the front end of the cooling-pre-reduction section I; The cooling terminal section is located at the rear end of the cooling-pre-reduction III section; The cooling gas medium used in the cooling-protection section and the final cooling section is an inert gas.

3. A production method using the pellet cooling-hydrogen pre-reduction-vertical furnace reduction combined production system as described in claim 1 or 2, characterized in that, include: Cooling-hydrogen pre-reduction stage and hydrogen shaft furnace reduction stage; In the cooling-hydrogen pre-reduction stage, hydrogen-rich gas is used to replace air to cool the pellets. The pellets are cooled and partially reduced by hydrogen through the cascade convection of hydrogen-rich gas, while obtaining high-temperature hydrogen-rich gas with a temperature of >400℃. In the hydrogen reduction stage of the vertical shaft furnace, the high-temperature hydrogen-rich gas from the outlet of the cooling-hydrogen pre-reduction stage is mixed with the hydrogen-rich gas used for reduction. After being heated by the hydrogen-rich gas heat exchanger, it enters the reduction section of the vertical shaft furnace, reducing the pre-reduced pellets into metallized pellets. The metallized pellets are then cooled in the cooling section of the vertical shaft furnace to obtain the metallized pellet product. At the same time, the hydrogen-rich gas discharged from the outlet of the reduction section is cooled by the condenser to remove water vapor and is then returned to the cooling-hydrogen pre-reduction stage for recycling.

4. The combined production method of pellet cooling-hydrogen pre-reduction-vertical furnace reduction according to claim 3, characterized in that, During the cooling-hydrogen pre-reduction stage: Hydrogen-rich gas G2 first enters the cooling-pre-reduction stage I via a blower, passing through the pellet ore layer from bottom to top. The temperature of the pellet ore decreases while the hydrogen-rich gas G2 is heated. Hydrogen-rich gas G2, which penetrates and is heated through the pellet bed in the cooling-pre-reduction stage I, enters the cooling-pre-reduction stage II through the reheat air duct and passes through the pellet bed from bottom to top. During this process, the temperature of the pellet decreases and it undergoes a reduction reaction with H2 in the hydrogen-rich gas. A small amount of iron oxides in the pellet are reduced, and the water vapor, a byproduct of the reduction reaction, enters the hydrogen-rich gas G3. At the same time, the temperature of the hydrogen-rich gas G3 is further increased. The hydrogen-rich gas G3 penetrates the cooling-pre-reduction II stage and enters the cooling-pre-reduction III stage through the reheat air duct, passing through the pellet ore layer from bottom to top. During this process, the pellets undergo a reduction reaction with H2 in the hydrogen-rich gas, and the iron oxides in the pellets are reduced. The water vapor generated by the reduction reaction enters the hydrogen-rich gas G4, and at the same time, the temperature of the hydrogen-rich gas G4 increases to over 400°C. In the final cooling stage, the cooling gas G5 is forced through the material layer from bottom to top by a blower. The hot waste gas is collected and cooled by a cooler before being combined with the cooling gas G5 and re-entering the material layer for recycling. After cooling, the temperature of the pellets drops to ≤50℃, and the pre-reduced pellets are obtained by unloading.

5. The combined production method of pellet cooling-hydrogen pre-reduction-vertical furnace reduction according to claim 3, characterized in that, include: (1) When the roasted high-temperature pellets move forward on the cooling equipment, they pass through the cooling-protection section, the cooling-pre-reduction III section, the cooling-pre-reduction II section, the cooling-pre-reduction I section, and the final cooling section in sequence; Meanwhile, the hydrogen-rich gas discharged from the top of the vertical furnace and cooled by condensation and dehydration is used in a cascade manner to pass through the pellet ore layer in the cooling-pre-reduction section I, cooling-pre-reduction section II, and cooling-pre-reduction section III. Finally, the high-temperature ore pellets are cooled and pre-reduced to obtain pre-reduced pellets; (2) The pre-reduced pellets discharged from the cooling end section enter the reduction vertical furnace from the top and exchange gas-solid heat with the high-temperature hydrogen-rich gas running from bottom to top. While the temperature rises, a further reduction reaction occurs to generate metallized pellets. The metallized pellets enter the cooling section and are cooled by the cooling gas to obtain the metallized pellet product. Meanwhile, the high-temperature hydrogen-rich gas G4 discharged from the cooling-pre-reduction III section is mixed with the hydrogen-rich gas G6 used for reduction to form hydrogen-rich gas G7. After being heated to 900℃-950℃ by a hydrogen-rich gas heat exchanger, it enters the reduction shaft furnace from the bottom of the reduction section and is discharged from the top of the reduction shaft furnace. The discharged hydrogen-rich gas G2 passes through a condenser to remove water vapor and is cooled to <30℃, and is then recycled to the cooling-pre-reduction I section for reuse.

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