Method for direct reduction of iron ore in a shaft furnace by plasma heating and iron production by reduction

Abstract

This invention proposes a plasma-heated direct reduction vertical shaft furnace and a method for reduction ironmaking. The vertical shaft furnace has a furnace body and a hopper. The furnace body includes an independent cylinder and a furnace cooling section. The independent cylinder is connected to the hopper, and hollow graphite electrodes are installed on the independent cylinder. The hollow graphite electrodes are connected to a reducing gas source device to ionize a first portion of the reducing gas supplied by the reducing gas source device and generate high-temperature ionized gas. The furnace cooling section is located below the independent cylinder and is connected to the reducing gas source device. A second portion of the reducing gas supplied by the reducing gas source device enters the furnace cooling section and is preheated by the high-temperature reduced iron therein. The preheated second portion of the reducing gas enters the independent cylinder and, together with the high-temperature ionized gas, reduces the green pellets that have entered the independent cylinder. This invention avoids the safety hazards associated with heating outside the vertical shaft furnace and the transportation of high-temperature reducing gas.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a plasma-heated direct reduction vertical furnace and a method for reduction ironmaking. Background Technology

[0002] Developing hydrogen metallurgical processes that replace carbon with hydrogen is an important way for China's steel industry to achieve carbon emission reduction. Currently, with the continuous maturation of green hydrogen production processes such as water electrolysis, biological methods, and nuclear power, the development of direct hydrogen reduction shaft furnaces has become a consensus in the steel industry, and is of great significance for carbon neutrality in the steel industry.

[0003] However, due to hydrogen's flammable and explosive nature, safety requirements for hydrogen use in traditional vertical shaft furnaces are very high. Traditional vertical shaft furnace reduction processes (such as Midrex and HYL) require heating hydrogen to a reduction temperature of over 1000°C using an electric furnace outside the furnace body before introducing the high-temperature hydrogen into the furnace to react with the low-temperature pellets inside. Such high hydrogen temperatures pose significant challenges to hydrogen detection, pipeline and valve sealing, and lifespan. Therefore, developing a vertical shaft furnace system that allows low-temperature hydrogen to enter and react with preheated high-temperature pellets is crucial for the development and safety of all-hydrogen vertical shaft furnaces.

[0004] Hydrogen plasma is an ionized gas composed of hydrogen atoms, hydrogen ions, and electrons. It possesses strong reducing properties and high thermal efficiency, making it a promising candidate for application in the field of direct reduction shaft furnaces in hydrogen metallurgy. For example, Chinese invention patent application number 202311543312.2, entitled "A System and Method for Direct Reduction Ironmaking with Hydrogen-Rich Plasma Heating," discloses a system for direct reduction ironmaking with hydrogen-rich plasma heating. In this system, the plasma shaft furnace comprises, from top to bottom, a feeding zone, a reduction zone, a feeding zone, and a plasma heating zone. The plasma heating zone is equipped with a hydrogen plasma torch, a hot reducing gas circulation outlet, and a hydrogen inlet. The inlet hydrogen gas is heated and ionized by the plasma torch, then enters the upper reduction zone through an inner tube and a conical feeding device vent to reduce the iron ore. The technical solution in this application eliminates the cooling section of a traditional shaft furnace, allowing hot sponge iron to directly enter the plasma heating zone and melt into molten iron. However, for most steel companies, this method requires consideration of the compatibility of the ironmaking-steelmaking-rolling processes. It cannot achieve 100% hot charging and hot delivery of molten iron from hot sponge iron, necessitating the storage of some cold sponge iron, thus preventing the production of cold sponge iron. Furthermore, introducing hydrogen into the molten iron, heating it, and causing it to overflow and rise through an inner pipe to the reduction zone, results in a situation where the temperature of the molten iron is much higher than the temperature at which sponge iron is reduced from iron ore (approximately 1000°C). Consequently, the temperature of the hydrogen must also be higher than the reduction temperature. Such a high temperature will cause the sponge iron to partially clump together during its descent, potentially disrupting the entire process.

[0005] For example, Chinese invention patent application number 202411012337.4, entitled "A Hydrogen-Based Vertical Furnace Direct Reduction Iron Energy Storage Device and Method," provides a hydrogen-based vertical furnace direct reduction iron energy storage device. The outlet of the hydrogen supply device is connected to the inlet of an arc plasma heater, and the outlet of the plasma heater is connected to the gas inlet at the bottom of the vertical furnace. High-temperature hydrogen enters the bottom of the vertical furnace through the gas inlet, heating and reducing the oxidized pellets into metallic iron during its ascent. Because an arc plasma heater is used outside the vertical furnace to heat the reducing gas (hydrogen), the heated hydrogen enters from the bottom of the furnace to heat and reduce the oxidized pellets into metallic iron. Such a high hydrogen temperature outside the furnace poses significant challenges to hydrogen detection, pipeline and valve sealing, and lifespan, posing a potential safety hazard for hydrogen use. Furthermore, there is no heat exchange between the gas and the reduced hot direct reduced iron in the furnace cooling section, causing the hot reduced iron to be directly discharged outside the furnace, resulting in significant heat loss.

[0006] For example, Chinese invention patent application number 202210658048.6, entitled "A Method and Apparatus for Heating DRI Reducing Gas Using Plasma," provides a method and apparatus for heating DRI reducing gas using plasma. This method involves inputting reducing gas into a plasma heating device and heating it to 900-1100°C. The heated reducing gas then enters a vertical shaft furnace and reacts with the ore pellets to produce reduced iron. However, this technology still uses a plasma heater outside the vertical shaft furnace to heat the reducing gas to its reduction temperature. The heated gas enters from the bottom of the furnace to heat and reduce the oxidized pellets into metallic iron. Such a high reducing gas temperature outside the furnace poses significant challenges to the detection of reducing gas (especially hydrogen), the sealing and lifespan of pipelines and valves, and also presents safety hazards related to hydrogen use. Furthermore, there is no heat exchange between the gas and the reduced, hot direct reduced iron in the furnace cooling section, causing the hot reduced iron to be directly discharged outside the furnace, resulting in significant heat loss.

[0007] As can be seen from the above, existing reduction shaft furnaces all use plasma to heat the reducing gas (oxygen or other hydrogen-rich reducing gas) to the reduction temperature (around 1000℃), and then introduce the high-temperature reducing gas into the shaft furnace. The high-temperature reducing gas heats the pellets in the shaft furnace and causes a reduction reaction to obtain direct reduced iron. This method has very high requirements for the sealing of the high-temperature hydrogen delivery pipelines and valves, posing a safety hazard in the use of hydrogen at high temperatures.

[0008] Therefore, this invention proposes a plasma-heated direct reduction vertical furnace and a method for reduction ironmaking to overcome the shortcomings of the prior art. Summary of the Invention

[0009] The purpose of this invention is to provide a plasma-heated direct reduction vertical furnace and a method for reduction ironmaking. The method uses room temperature reducing gas (hydrogen) to pass through a hollow graphite electrode, ionizing the reducing gas and generating a high-temperature ionized gas, thereby enabling the reducing gas introduced into the vertical furnace to reach the reduction temperature. This avoids heating outside the vertical furnace and transporting the high-temperature reducing gas, and provides a novel reducing gas heating device and method for direct reduction vertical furnaces, solving the safety hazards such as pipeline and valve sealing caused by transporting high-temperature reducing gas.

[0010] The objective of this invention can be achieved through the following methods: This invention provides a plasma-heated direct reduction vertical furnace, which has a furnace body and a hopper for storing green pellets, the hopper being located above the furnace body. The vertical furnace body includes: At least one independent cylinder, the top of which is detachably connected to the hopper, and a hollow graphite electrode is provided at the bottom of the independent cylinder. The two ends of the hollow graphite electrode are respectively connected to the independent cylinder and the reducing gas source device, so as to ionize the first part of the reducing gas supplied by the reducing gas source device through the hollow graphite electrode and generate high-temperature ionized gas. At least one furnace cooling section is provided, located below the independent cylinder, with its top connected to the bottom of the independent cylinder. The furnace cooling section is connected to the reducing gas source device. A second portion of reducing gas supplied by the reducing gas source device enters the furnace cooling section and is preheated by the high-temperature reduced iron therein. The preheated second portion of reducing gas enters the independent cylinder and, together with the high-temperature ionized gas, reduces the green pellets that have entered the independent cylinder.

[0011] In a preferred embodiment of the present invention, there are multiple independent cylinders, the tops of the multiple independent cylinders are respectively connected to the bottoms of corresponding feed pipes, and the tops of the feed pipes are connected to the outlets of the hoppers. The feed pipe is equipped with a furnace charge regulating valve.

[0012] In a preferred embodiment of the present invention, a temperature measuring element is provided on the independent cylinder and near the position where it is connected to the hollow graphite electrode.

[0013] In a preferred embodiment of the present invention, the reducing gas source device and the hollow graphite electrode are connected sequentially through a first delivery pipeline and a second delivery pipeline. The first conveying pipeline is provided with a first regulating valve, and / or the second conveying pipeline is provided with a second regulating valve.

[0014] In a preferred embodiment of the present invention, the reducing gas source device and the furnace cooling section are connected sequentially through a first conveying pipeline and a third conveying pipeline; The first conveying pipeline is equipped with a first regulating valve, and / or the third conveying pipeline is equipped with a flow meter.

[0015] In a preferred embodiment of the present invention, the top of the independent cylinder is connected to the first conveying pipeline so that the reducing gas in the independent cylinder can flow back into the first conveying pipeline and enter the furnace cooling section together with the second part of the reducing gas.

[0016] In a preferred embodiment of the present invention, a furnace top gas circulation outlet pipe is provided at the top of the independent cylinder, the furnace top gas circulation outlet pipe is connected to the inlet of the purification and pressurization device, the outlet of the purification and pressurization device is connected to one end of the furnace top gas circulation pipeline, and the other end of the furnace top gas circulation pipeline is connected to the first conveying pipeline.

[0017] In a preferred embodiment of the present invention, the bottom of the furnace cooling section has a discharge port, through which the reduced iron after the second part has been preheated is discharged.

[0018] In a preferred embodiment of the present invention, the hollow graphite electrode has a hollow cylindrical structure. The axial length of the hollow graphite electrode is 1500 mm to 2000 mm; and / or, The outer diameter of the hollow graphite electrode is 300 mm to 400 mm; and / or, The inner diameter of the hollow graphite electrode is 50 mm to 80 mm; and / or, The flow rate of the first portion of reducing gas in the hollow graphite electrode is 50 Nm³ / h to 70 Nm³ / h.

[0019] This invention provides a method for reduction ironmaking, which employs the aforementioned plasma-heated direct reduction shaft furnace. The method for reduction ironmaking includes the following steps: Step S1: Quantitatively discharge the green pellets from the silo into the independent cylinder; Step S2: Start the reducing gas source device, which supplies a first portion of reducing gas to the hollow graphite electrode, and at the same time supplies a second portion of reducing gas to the furnace cooling section. Step S3: The hollow graphite electrode ionizes the first part of the reducing gas and generates high-temperature ionized gas; at the same time, the high-temperature reduced iron in the furnace cooling section preheats the second part of the reducing gas. Step S4: Both the ionized gas and the preheated second part of the reducing gas enter the independent cylinder and reduce the green pellets inside the independent cylinder.

[0020] In a preferred embodiment of the present invention, in step S4, after both the ionized gas and the preheated second portion of reducing gas enter the independent cylinder, the ionized gas further heats the preheated second portion of reducing gas to 850°C to 1100°C.

[0021] In a preferred embodiment of the present invention, in step S4, the temperature of the independent cylinder is detected by a temperature sensing element, and the temperature inside the hollow graphite electrode is controlled by the magnitude of the current supplied to the hollow graphite electrode and / or the flow rate of the first portion of reducing gas.

[0022] In a preferred embodiment of the present invention, after step S4, step S5 is further included: the remaining reducing gas after the green pellets are reduced in the independent cylinder is returned to the furnace cooling section to replenish the flow of the second part of the reducing gas.

[0023] In a preferred embodiment of the present invention, the reduction ironmaking method further includes: Step S6: Repeat steps S2 to S5; When the temperature of the high-temperature reduced iron in the furnace cooling section drops below 100°C, it is discharged to the outside.

[0024] Based on the above, the characteristics and advantages of the plasma-heated direct reduction shaft furnace and the reduction ironmaking method of the present invention are as follows: A hopper is installed above the independent cylinder, while a furnace cooling section is located below the independent cylinder. A hollow graphite electrode is installed at the bottom of the independent cylinder, with its two ends connected to the independent cylinder and a reducing gas source device, respectively. During operation, room temperature reducing gas can be supplied through the reducing gas source device. The hollow graphite electrode ionizes the reducing gas supplied by the reducing gas source device to generate high-temperature ionized gas. The furnace cooling section can inject reducing gas preheated by high-temperature reduced iron into the bottom of the independent cylinder. This preheated reducing gas is heated to the reduction temperature by the high-temperature ionized gas upon entering the independent cylinder. The preheated reducing gas and the high-temperature ionized gas together reduce the green pellets fed into the independent cylinder from the hopper. The resulting direct reduced iron can enter the furnace cooling section to participate in the preheating of the reducing gas. The hollow graphite electrodes enable in-furnace heating of the reducing gas in the vertical furnace, thus avoiding the need for external heating and transportation of the reducing gas. This solves the safety hazards associated with transporting high-temperature reducing gas, such as the sealing of pipelines and valves. Furthermore, the combination of highly reducing ionized gas and reducing gas at the reduction temperature improves the reduction efficiency of the pellets in the vertical furnace. Attached Figure Description

[0025] The following figures are intended only to illustrate and explain the present invention and do not limit the scope of the invention. Wherein: Figure 1 This is a schematic diagram of the structure of the hydrogen plasma heating direct reduction vertical furnace of the present invention.

[0026] The reference numerals in the accompanying drawings of this invention are: 1. Feed hopper; 2. Green pellets; 3. Vertical shaft furnace body; 301. Independent cylinder; 302. Feed pipe; 303. Furnace body cooling section; 304. Discharge port; 4. Furnace charge regulating valve; 5. Insulation layer; 6. Reducing gas source device; 7. Hollow graphite electrode; 8. Power supply device; 9. First conveying pipeline; 10. Second conveying pipeline; 11. Third conveying pipeline; 12. First regulating valve; 13. Second regulating valve; 14. Flow meter; 15. Purification and pressurization device; 1501. Filter element; 16. Furnace top gas circulation pipeline; 17. Furnace top gas circulation outlet pipe; 18. Temperature measuring element; 19. Reduced iron. Detailed Implementation

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Implementation Method 1

[0031] like Figure 1 As shown, the present invention provides a plasma-heated direct reduction vertical furnace, which has a furnace body 3 and a hopper 1 for storing green pellets 2, the hopper 1 being located above the furnace body 3. The furnace body 3 includes at least one independent cylinder 301 and at least one furnace cooling section 303. The independent cylinder 301 serves as the main body of the reduced green pellets 2. The top of the independent cylinder 301 is detachably connected to the hopper 1. A hollow graphite electrode 7 is disposed at the lower part of the independent cylinder 301. The two ends of the hollow graphite electrode 7 are respectively connected to the independent cylinder 301 and a reducing gas source device 6, so as to ionize the first portion of reducing gas supplied by the reducing gas source device 6 through the hollow graphite electrode 7 and generate a high-temperature electrode. The furnace cooling section 303 is located below the independent cylinder 301, and the top of the furnace cooling section 303 is connected to the bottom of the independent cylinder 301. The furnace cooling section 303 is connected to the reducing gas source device 6. The second part of the reducing gas supplied by the reducing gas source device 6 enters the furnace cooling section 303 and is preheated by the high-temperature reduced iron 19 therein. The preheated second part of the reducing gas enters the independent cylinder 301 and together with the high-temperature ionized gas, reduces the green pellets 2 that enter the independent cylinder 301.

[0032] In this invention, a hopper 1 is provided above the independent cylinder 301, and a furnace cooling section 303 is provided below the independent cylinder 301. A hollow graphite electrode 7 is provided at the lower part of the independent cylinder 301. One end of the hollow graphite electrode 7 is connected to the independent cylinder 301, and the other end of the hollow graphite electrode 7 is connected to the reducing gas source device 6. During operation, room temperature reducing gas can be supplied through the reducing gas source device 6, and the reducing gas supplied by the reducing gas source device 6 is absorbed by the hollow graphite electrode 7. The process involves ionization to generate high-temperature ionized gas. The reducing gas, preheated by the high-temperature reduced iron, can be injected into the bottom of the independent cylinder 301 through the furnace cooling section 303. This preheated reducing gas can be heated to the reduction temperature by the high-temperature ionized gas when it enters the independent cylinder 301. The preheated reducing gas and the high-temperature ionized gas together reduce the green pellets fed into the independent cylinder 301 from the hopper 1. The resulting direct reduced iron can enter the furnace cooling section 303 to participate in the preheating of the reducing gas.

[0033] In this invention, the hollow graphite electrode 7 enables the vertical furnace to heat the reducing gas inside the furnace, thereby avoiding the heating and transportation of the reducing gas outside the furnace and solving the safety hazards such as pipe and valve sealing caused by the transportation of high-temperature reducing gas; and the strong reducing ionized gas combined with the reducing gas that has reached the reduction temperature improves the reduction efficiency of the pellets in the vertical furnace.

[0034] In this invention, green pellet 2 is iron ore pellet. The reducing gas source device 6 can be a hydrogen source device that supplies hydrogen. During operation, a first portion of hydrogen at room temperature can be supplied through the hydrogen source device. The first portion of hydrogen supplied by the hydrogen source device is ionized through the hollow graphite electrode 7 to generate high-temperature ionized gas. A second portion of hydrogen (supplied by the hydrogen source device), preheated by high-temperature reduced iron, can be injected into the bottom of the independent cylinder 301 through the furnace cooling section 303. This preheated second portion of hydrogen, upon entering the independent cylinder 301, can be heated to the reduction temperature by the high-temperature ionized gas. The preheated second portion of hydrogen and the high-temperature ionized gas together reduce the iron ore pellets fed into the independent cylinder 301 from the hopper 1. The resulting direct reduced iron can enter the furnace cooling section 303 to participate in the preheating of the second portion of hydrogen.

[0035] In an optional embodiment of the present invention, such as Figure 1As shown, there can be one independent cylinder 301. Alternatively, there can be multiple independent cylinders 301, spaced apart and evenly distributed along the circumference of the vertical furnace body 3. These cylinders 301 are connected to the hopper 1 via multiple feeding pipes 302. Specifically, the top of each independent cylinder 301 is connected to the bottom of its corresponding feeding pipe 302, and the top of each feeding pipe 302 is connected to the outlet of the hopper 1. A furnace charge regulating valve 4 is installed on each feeding pipe 302, which controls the feeding of green pellets 2 from the hopper 1 into the independent cylinder 301.

[0036] Specifically, there can be 5 independent cylinders 301. Each independent cylinder 301 is a vertically arranged cylindrical structure. The inner diameter of the independent cylinder 301 can be, but is not limited to, 1.0m to 1.5m, and the height of the independent cylinder 301 can be, but is not limited to, 4m to 10m.

[0037] Preferably, the inner diameter of the independent cylinder 301 is 1.2m and the height of the independent cylinder 301 is 8m.

[0038] In an optional embodiment of the present invention, such as Figure 1 As shown, the outer wall of the independent cylinder 301 is covered with a thermal insulation layer 5 to improve the thermal insulation performance of the independent cylinder 301 and ensure the stable progress of the reduction reaction. The thermal insulation layer 5 can be made of, but is not limited to, ceramic fiber materials or lightweight refractory castables.

[0039] Furthermore, the thickness of the insulation layer 5 can be, but is not limited to, 200mm to 300mm. Preferably, the thickness of the insulation layer 5 is 250mm.

[0040] In embodiments of the present invention, the number of furnace cooling sections 303 is not limited. That is, the number of furnace cooling sections 303 is one, in which case multiple independent cylinders 301 share one furnace cooling section 303. Of course, the number of furnace cooling sections 303 can also be multiple, and multiple furnace cooling sections 303 correspond one-to-one with multiple independent cylinders 301, with each independent cylinder 301 connected to its corresponding furnace cooling section 303.

[0041] In an optional embodiment of the present invention, such as Figure 1 As shown, a temperature sensing element 18 is installed in the independent cylinder 301 near its connection with the hollow graphite electrode 7. The temperature sensing element 18 monitors the actual temperature inside the independent cylinder 301 near the location where the reduction reaction occurs in real time. Based on the detected temperature, the temperature inside the independent cylinder 301 can be controlled by adjusting the current supplied to the hollow graphite electrode 7 and / or regulating the flow rate of the first portion of reducing gas, thereby ensuring that the temperature inside the independent cylinder 301 can stably reach the reduction temperature (approximately 1000℃). The temperature sensing element 18 can be, but is not limited to, a temperature sensor.

[0042] In an optional embodiment of the present invention, such as Figure 1 As shown, the reducing gas source device 6 and the hollow graphite electrode 7 are connected in sequence through a first conveying pipe 9 and a second conveying pipe 10. That is, the gas supply port of the reducing gas source device 6 is connected to one end of the first conveying pipe 9, the other end of the first conveying pipe 9 is connected to one end of the second conveying pipe 10, and the other end of the second conveying pipe 10 is connected to the hollow graphite electrode 7. The first part of the reducing gas provided by the reducing gas source device 6 enters the hollow graphite electrode 7 after passing through the first conveying pipe 9 and the second conveying pipe 10 in sequence.

[0043] Furthermore, such as Figure 1 As shown, a first regulating valve 12 is provided on the first conveying pipeline 9. The amount of reducing gas supplied by the reducing gas source device 6 can be controlled by the first regulating valve 12 to ensure that the reduction of the pellets 2 inside the independent cylinder 301 can be met.

[0044] Furthermore, such as Figure 1 As shown, a second regulating valve 13 is provided on the second conveying pipeline 10. The amount of first reducing gas supplied to the hollow graphite electrode 7 by the reducing gas source device 6 can be controlled by the cooperation of the first regulating valve 12 and the second regulating valve 13. In turn, the temperature inside the independent cylinder 301 can be controlled by controlling the flow rate of the first part of the reducing gas to ensure that the reduction temperature can be reached.

[0045] In an optional embodiment of the present invention, such as Figure 1 As shown, the reducing gas source device 6 and the furnace cooling section 303 are connected in sequence through a first conveying pipeline 9 and a third conveying pipeline 11. That is, the gas supply port of the reducing gas source device 6 is connected to one end of the first conveying pipeline 9, and the other end of the first conveying pipeline 9 is also connected to one end of the third conveying pipeline 11. The other end of the third conveying pipeline 11 is connected to the furnace cooling section 303. The second part of reducing gas provided by the reducing gas source device 6 enters the furnace cooling section 303 after passing through the first conveying pipeline 9 and the third conveying pipeline 11 in sequence. After being preheated in the furnace cooling section 303, the second part of reducing gas enters the independent cylinder 301 to participate in the reduction reaction.

[0046] Furthermore, such as Figure 1 As shown, a flow meter 14 is installed on the third delivery pipeline 11. The flow meter 14 is used to detect the amount of reducing gas entering the furnace cooling section 303 in real time to ensure that there is enough reducing gas to participate in the reaction. The flow meter 14 is a gas flow meter.

[0047] In an optional embodiment of the present invention, such as Figure 1As shown, the top of the independent cylinder 301 is connected to the first conveying pipeline 9, thereby forming a circulating return path between the independent cylinder 301 and the furnace cooling section 303. Through this circulating return path, the reducing gas in the independent cylinder 301 can flow back to the first conveying pipeline 9 and enter the furnace cooling section 303 together with the second part of reducing gas supplied by the reducing gas source device 6. This part of the reducing gas that flows back through the independent cylinder 301 can be used as a supplement to the second part of the reducing gas. This not only makes full use of the remaining reducing gas in the independent cylinder 301 and avoids waste, but also ensures that there is enough reducing gas to participate in the reduction reaction, so as to ensure the reaction is complete.

[0048] In this embodiment, the flow rate of the reducing gas returning from the independent cylinder 301 to the furnace cooling section 303 can be, but is not limited to, 450 Nm³ / h to 650 Nm³ / h.

[0049] Specifically, such as Figure 1 As shown, the top of the independent cylinder 301 is provided with a furnace top gas circulation outlet pipe 17, which is connected to the inlet of the purification and pressurization device 15. The outlet of the purification and pressurization device 15 is connected to one end of the furnace top gas circulation pipeline 16, and the other end of the furnace top gas circulation pipeline 16 is connected to the first conveying pipeline 9. The purification and pressurization device 15 can be equipped with a filter screen and a fan, etc., to filter the reducing gas circulating back to the furnace cooling section 303 to remove impurities, while providing backflow pressure to ensure that the remaining reducing gas in the independent cylinder 301 can smoothly flow back to the furnace cooling section 303.

[0050] In an optional embodiment of the present invention, such as Figure 1 As shown, the bottom of the furnace cooling section 303 has a discharge port 304, through which the reduced iron 19, after being preheated by the second part of the reducing gas, is discharged.

[0051] In an optional embodiment of the present invention, such as Figure 1 As shown, the hollow graphite electrode 7 is electrically connected to the power supply device 8 to control the working state of the hollow graphite electrode 7.

[0052] In an optional embodiment of the present invention, a mesh baffle (not shown) that can be opened and closed can be provided between the furnace cooling section 303 and the independent cylinder 301. When the green pellets 2 in the independent cylinder 301 are reduced, the baffle is closed. At this time, the baffle only allows the reducing gas to pass through, while the green pellets 2 in the independent cylinder 301 are intercepted inside the independent cylinder 301. After the reduction is completed, the baffle can be opened, and the obtained high-temperature direct reduced iron 19 can enter the furnace cooling section 303 from the independent cylinder 301 for heat exchange and exhaust.

[0053] In an optional embodiment of the present invention, the hollow graphite electrode 7 has a hollow cylindrical structure.

[0054] The axial length of the hollow graphite electrode 7 can be, but is not limited to, 1500 mm to 2000 mm. Preferably, the axial length of the hollow graphite electrode 7 is 1500 mm.

[0055] The outer diameter of the hollow graphite electrode 7 can be, but is not limited to, 300 mm to 400 mm. Preferably, the outer diameter of the hollow graphite electrode 7 is 400 mm.

[0056] The inner diameter of the hollow graphite electrode 7 can be, but is not limited to, 50 mm to 80 mm. Preferably, the inner diameter of the hollow graphite electrode 7 is 80 mm.

[0057] The flow rate of the first portion of reducing gas in the hollow graphite electrode 7 can be, but is not limited to, 50 Nm³ / h to 70 Nm³ / h. Specifically, the flow rate of the first portion of reducing gas in the hollow graphite electrode 7 is 60 Nm³ / h.

[0058] In this invention, the gas ionized inside the hollow graphite electrode 7 can be hydrogen, or argon, nitrogen, or a mixture of multiple gases can be used for ionization.

[0059] The plasma-heated direct reduction vertical furnace of the present invention comprises multiple independent cylinders 301 arranged within the furnace. Each cylinder 301 has an insulation layer 5 covering its outer wall. Hollow graphite electrodes 7 are inserted into the lower part of each cylinder 301. These electrodes are electrically connected to a power supply device 8, and room-temperature hydrogen gas is introduced into them via a hydrogen gas source. The electrodes ionize this hydrogen gas, forming a high-temperature ionized gas (containing hydrogen ions, ground-state and excited-state hydrogen atoms and molecules). Therefore, the high-temperature ionized gas exhibits strong reducing properties. This high-temperature ionized gas heats another portion of the hydrogen gas (as reducing gas) rising from the furnace cooling section 303 into the independent cylinders 301 to the reduction temperature, and simultaneously heats the green pellets 2 introduced into the independent cylinders 301 to the reduction temperature, thereby causing a reaction within the independent cylinders 301 to produce directly reduced iron 19. In addition, the strongly reducing ionized gas produced by ionization helps the reduction reaction of green pellet 2 and can improve the efficiency of the reduction reaction.

[0060] The features and advantages of the plasma-heated direct reduction vertical furnace of the present invention are as follows: I. This plasma-heated direct reduction vertical furnace has a hollow graphite electrode 7 installed at the lower part of the independent cylinder 301. A room-temperature reducing gas can be supplied through a reducing gas source device 6. The hollow graphite electrode 7 ionizes the reducing gas supplied by the reducing gas source device 6 to generate a high-temperature ionized gas. Due to the installation of the hollow graphite electrode 7, the furnace can heat the reducing gas inside the furnace, thus avoiding the need for heating and transporting the reducing gas outside the furnace. This solves the safety hazards such as pipe and valve sealing issues associated with transporting high-temperature reducing gas. Furthermore, the strong reducing ionized gas, combined with the reducing gas reaching the reduction temperature, improves the reduction efficiency of the pellets inside the furnace.

[0061] Second, the plasma heating direct reduction vertical furnace can be modularly configured, which facilitates quick replacement and maintenance, ensuring production efficiency.

[0062] Implementation Method 2

[0063] This invention provides a method for reduction ironmaking, which employs the aforementioned plasma-heated direct reduction shaft furnace. The method includes the following steps: Step S1: Open the furnace charge regulating valve 4 and quantitatively output the green pellets 2 in the hopper 1 to the independent cylinder 301 through the feed pipe 302; Step S2: Start the reducing gas source device 6 and simultaneously open the first regulating valve 12 and the second regulating valve 13. The reducing gas source device 6 supplies the first part of the reducing gas to the hollow graphite electrode 7, and at the same time, the reducing gas source device 6 supplies the second part of the reducing gas to the furnace cooling section 303. Step S3: Start the power supply device 8 to supply power to the hollow graphite electrode 7. The hollow graphite electrode 7 ionizes the first part of the reducing gas and generates high-temperature ionized gas. At the same time, the high-temperature reduced iron 19 in the furnace cooling section 303 preheats the second part of the reducing gas. Step S4: Both the ionized gas and the preheated second part of the reducing gas enter the independent cylinder 301 and reduce the green pellets 2 inside the independent cylinder 301; Step S5: The remaining reducing gas after the green pellets 2 are reduced in the independent cylinder 301 is returned to the furnace cooling section 303 to replenish the flow of the second part of the reducing gas. Step S6: Repeat steps S2 to S5 above.

[0064] When the temperature of the high-temperature reduced iron 19 in the furnace cooling section 303 drops below 100°C, it is discharged to the outside.

[0065] In an optional embodiment of the present invention, before performing step S1, green pellets 2 are added to the silo 1 until the green pellets 2 in the silo 1 reach a preset material level. The green pellets 2 are iron ore pellets with a particle size of 8 mm to 16 mm.

[0066] In an optional embodiment of the present invention, in step S4 above, after both the ionized gas and the preheated second part of the reducing gas enter the independent cylinder 301, the ionized gas further heats the preheated second part of the reducing gas to 850°C to 1100°C, preferably 1000°C.

[0067] In an optional embodiment of the present invention, in step S4 above, the temperature of the independent cylinder 301 is detected by the temperature sensing element 18, and the temperature inside the hollow graphite electrode 7 is controlled by the magnitude of the current supplied to the hollow graphite electrode 7 and / or the flow rate of the first portion of the reducing gas.

[0068] In an optional embodiment of the present invention, the flow rate of the reducing gas returned from the independent cylinder 301 to the furnace cooling section 303 is 450 Nm³ / h to 650 Nm³ / h.

[0069] Furthermore, the total flow rate of the second part of reducing gas and the reducing gas returning from the independent cylinder 301 to the furnace cooling section 303 (i.e. the flow rate of the reducing gas entering the independent cylinder 301 from the furnace cooling section 303) is 9000 Nm³ / h.

[0070] The reduction ironmaking method of this invention addresses the safety hazards associated with poor sealing of high-temperature hydrogen pipelines and valves outside the vertical shaft furnace during the reduction ironmaking process. This invention proposes placing a hollow graphite electrode 7 on an independent cylinder 301, introducing room-temperature hydrogen gas into the hollow graphite electrode 7. Upon energization, the hollow graphite electrode 7 ionizes the hydrogen gas into a high-temperature ionized gas. This high-temperature ionized gas simultaneously heats the preheated reducing gas entering the independent cylinder 301 and the green pellets 2 introduced into the independent cylinder 301 to the reduction temperature. The high-temperature ionized gas and the reducing gas together reduce the green pellets 2 to direct reduced iron, avoiding the heating and transportation of the reducing gas outside the vertical shaft furnace and solving the safety hazards associated with pipeline and valve sealing during the transportation of high-temperature reducing gas.

[0071] It has the same characteristics and advantages as the plasma-heated direct reduction vertical furnace mentioned above, which will not be repeated here.

[0072] It should be noted that in the description of this application, the terms "first," "second," etc., are used only for descriptive purposes and to distinguish similar objects; there is no order between them, nor should they be construed as indicating or implying relative importance. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0073] The various embodiments described in this specification are presented in a progressive manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0074] The above are merely a few embodiments of the present invention. Although the embodiments disclosed in the present invention are as described above, the content is only for the purpose of facilitating understanding of the present invention and is not intended to limit the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A plasma-heated direct reduction vertical furnace, characterized in that, The plasma-heated direct reduction vertical furnace has a furnace body and a hopper for storing green pellets, the hopper being located above the furnace body. The vertical furnace body includes: At least one independent cylinder, the top of which is detachably connected to the hopper, and a hollow graphite electrode is provided at the bottom of the independent cylinder. The two ends of the hollow graphite electrode are respectively connected to the independent cylinder and the reducing gas source device, so as to ionize the first part of the reducing gas supplied by the reducing gas source device through the hollow graphite electrode and generate high-temperature ionized gas. At least one furnace cooling section is provided, located below the independent cylinder, with its top connected to the bottom of the independent cylinder. The furnace cooling section is connected to the reducing gas source device. A second portion of reducing gas supplied by the reducing gas source device enters the furnace cooling section and is preheated by the high-temperature reduced iron therein. The preheated second portion of reducing gas enters the independent cylinder and, together with the high-temperature ionized gas, reduces the green pellets that have entered the independent cylinder.

2. The plasma-heated direct reduction vertical furnace as described in claim 1, characterized in that, The number of independent cylinders is multiple, and the top of each independent cylinder is connected to the bottom of a corresponding feed pipe. The top of the feed pipe is connected to the outlet of the hopper. The feed pipe is equipped with a furnace charge regulating valve.

3. The plasma-heated direct reduction vertical furnace as described in claim 1 or 2, characterized in that, A temperature measuring element is provided on the independent cylinder near the position where it is connected to the hollow graphite electrode.

4. The plasma-heated direct reduction vertical furnace as described in claim 1 or 2, characterized in that, The reducing gas source device and the hollow graphite electrode are connected sequentially through a first delivery pipeline and a second delivery pipeline. The first conveying pipeline is provided with a first regulating valve, and / or the second conveying pipeline is provided with a second regulating valve.

5. The plasma-heated direct reduction vertical furnace as described in claim 1 or 2, characterized in that, The reducing gas source device and the furnace cooling section are connected sequentially through a first conveying pipeline and a third conveying pipeline; The first conveying pipeline is equipped with a first regulating valve, and / or the third conveying pipeline is equipped with a flow meter.

6. The plasma-heated direct reduction vertical furnace as described in claim 5, characterized in that, The top of the independent cylinder is connected to the first conveying pipeline so that the reducing gas in the independent cylinder can flow back into the first conveying pipeline and enter the furnace cooling section together with the second part of the reducing gas.

7. The plasma-heated direct reduction vertical furnace as described in claim 6, characterized in that, The top of the independent cylinder is provided with a furnace top gas circulation outlet pipe, which is connected to the inlet of the purification and pressurization device. The outlet of the purification and pressurization device is connected to one end of the furnace top gas circulation pipeline, and the other end of the furnace top gas circulation pipeline is connected to the first conveying pipeline.

8. The plasma-heated direct reduction vertical furnace as described in claim 1, characterized in that, The hollow graphite electrode has a hollow cylindrical structure. The axial length of the hollow graphite electrode is 1500 mm to 2000 mm; and / or, The outer diameter of the hollow graphite electrode is 300 mm to 400 mm; and / or, The inner diameter of the hollow graphite electrode is 50 mm to 80 mm; and / or, The flow rate of the first portion of reducing gas in the hollow graphite electrode is 50 Nm³ / h to 70 Nm³ / h.

9. A method for reduction ironmaking, implemented using a plasma-heated direct reduction shaft furnace as described in any one of claims 1 to 8, characterized in that, The reduction iron smelting method includes the following steps: Step S1: Quantitatively discharge the green pellets from the silo into the independent cylinder; Step S2: Start the reducing gas source device, which supplies a first portion of reducing gas to the hollow graphite electrode, and at the same time supplies a second portion of reducing gas to the furnace cooling section. Step S3: The hollow graphite electrode ionizes the first part of the reducing gas and generates high-temperature ionized gas; at the same time, the high-temperature reduced iron in the furnace cooling section preheats the second part of the reducing gas. Step S4: Both the ionized gas and the preheated second part of the reducing gas enter the independent cylinder and reduce the green pellets inside the independent cylinder.

10. The method for reduction iron smelting as described in claim 9, characterized in that, In step S4, after both the ionized gas and the preheated second part of the reducing gas enter the independent cylinder, the ionized gas further heats the preheated second part of the reducing gas to 850°C to 1100°C.

11. The method for reduction iron smelting as described in claim 9, characterized in that, In step S4, the temperature of the independent cylinder is detected by a temperature sensing element, and the temperature inside the hollow graphite electrode is controlled by the magnitude of the current supplied to the hollow graphite electrode and / or the flow rate of the first portion of reducing gas.

12. The method for reduction iron smelting as described in claim 9, characterized in that, After step S4, step S5 is also included: the remaining reducing gas after the green pellets are reduced in the independent cylinder is returned to the furnace cooling section to replenish the flow of the second part of the reducing gas.

13. The method for reduction iron smelting as described in claim 12, characterized in that, The reduction ironmaking method further includes: Step S6: Repeat steps S2 to S5; When the temperature of the high-temperature reduced iron in the furnace cooling section drops below 100°C, it is discharged to the outside.

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