A hydrocarbon-coupled two-stage gas-circulating high-hydrogen shaft furnace process and system

Abstract

The application belongs to the technical field of iron and steel making, and specifically discloses a carbon-hydrogen coupled two-stage gas circulation high-hydrogen shaft furnace process and system. The process comprises the following steps: spraying main reduction gas into the bottom of the high-hydrogen shaft furnace reduction section through a main channel to perform a high-temperature section reduction reaction; spraying secondary reduction gas into the middle of the reduction section through a secondary channel to perform a middle-low-temperature section reduction reaction; obtaining main process gas and decarburization tail gas by decarburization separation of the top gas; mixing the main process gas with first supplementary gas, heating and raising the temperature to obtain the main reduction gas, and then circulating and introducing the main reduction gas into the main channel; mixing the decarburization tail gas with second supplementary gas, converting CO2 into CO to form the secondary reduction gas, and then circulating and introducing the secondary reduction gas into the secondary channel. Through the synergy of the main and secondary circulation loops and the reaction characteristics of CO and H2 at different temperatures, the application solves the problems of insufficient heat in the middle-low-temperature section of the high-hydrogen shaft furnace and the chemical retention section, significantly improves the product metallization rate, and realizes efficient recycling and emission reduction of CO2.

Description

Technical Field

[0001] This application relates to the field of iron and steelmaking technology, and in particular to a carbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace process and system. Background Technology

[0002] With global warming and the advancement of carbon peaking and carbon neutrality goals, green and low-carbon metallurgy has become an inevitable trend for the transformation and upgrading of the steel industry. Gas-based shaft furnace direct reduction technology, as an important pathway to low-carbon metallurgy, gradually replaces solid carbon with reducing gases such as hydrogen (H2) as a reducing agent, thereby reducing carbon dioxide (CO2) emissions from the steel production process at its source. In the gas-based shaft furnace, iron ore pellets move downwards, while reducing gases flow upwards. The two react countercurrently within the furnace, undergoing a gas-solid phase reduction reaction, ultimately reducing the iron ore to direct reduced iron with a high metallization rate.

[0003] From a thermodynamic perspective, the reduction of iron oxides by hydrogen exhibits a significant endothermic effect, especially in the reduction of ferrous oxide to metallic iron. As the hydrogen concentration in the reducing gas increases, the gas-solid two-phase temperature in the middle and top regions of the shaft furnace decreases due to the vigorous progress of the reduction reaction, thus inhibiting the reduction reaction. This phenomenon causes the reduction reaction zone of iron(III) oxide (Fe3O4) and ferrous oxide (FeO) to shift towards the lower part of the shaft furnace, delaying the formation of metallic iron and creating a large chemical retention zone within the furnace, thereby limiting the overall reduction efficiency and production capacity. From a kinetic perspective, hydrogen has a much higher reduction rate and diffusion capacity than carbon monoxide (CO) at high temperatures; however, under medium and low temperature conditions, carbon monoxide exhibits better reduction characteristics and thermodynamic equilibrium constants than hydrogen. Therefore, the key to improving reduction efficiency lies in how to rationally couple hydrocarbon reduction media to match the reaction characteristics of different temperature ranges within the shaft furnace.

[0004] To improve the reduction efficiency inside the vertical shaft furnace, some related technologies employ segmented circulation processes, such as a two-stage carbon circulation ironmaking process based on an all-oxygen, hydrogen-rich, low-carbon reduction melting furnace disclosed in one related technology. This process obtains reducing gas from the furnace top gas after dust, water, and carbon dioxide removal, and divides it into two parts: the first part, after hydrogen supplementation and heating, enters the melting furnace through the middle reducing gas inlet; the second part, after plasma heating, enters through the lower oxygen inlet. However, in this scheme, because it relies on a reduction melting furnace containing coke combustion and slag-iron melting zones, the system contains a large amount of solid coke, essentially still falling under the category of molten reduction. This fails to address the issues of airflow distribution and heat balance in a pure gas-based vertical shaft furnace under direct gas-phase reduction conditions. Furthermore, the middle circulating gas in this process does not undergo targeted reforming and conditioning, making it impossible to precisely control the CO to H2 ratio of the middle injection gas, thus hindering the full utilization of CO's kinetic advantages in the low-to-medium temperature range and preventing efficient reforming and recycling of CO2. This application addresses these issues with systematic process optimization.

[0005] Furthermore, regarding the preparation of circulating gas in a gas-based vertical shaft furnace, another related technology discloses a method for preparing sponge iron using a gas-based vertical shaft furnace. This method involves hydrogen extraction from reducing gas to obtain hydrogen and carbon monoxide-rich gas. A portion of the carbon monoxide-rich gas is then used as cooling gas, fed into the furnace from the bottom of the cooling section. After heat exchange and carburizing with the sponge iron in the cooling section, it flows upward into the reduction section. However, in this scheme, the system lacks a reforming and conversion cycle for CO2 in the decarburization tail gas, making it impossible to convert the CO2 generated internally into useful reducing gas. This results in the system still needing to emit a large amount of CO2 gas to the outside and requiring a large amount of fresh reducing gas to be added. Simultaneously, this process directly utilizes physically separated carbon monoxide-rich gas for cooling and reduction, failing to construct an independent, precisely controllable secondary reducing gas circulation system outside the furnace, making it difficult to adapt to fluctuations in furnace operation under different raw material conditions. This application improves upon these technical bottlenecks by constructing a carbon-hydrogen coupled dual circulation system. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this application is to provide a carbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace process and system to improve the problem in the related technology where the upper part of the high-hydrogen vertical furnace is affected by the endothermic effect of hydrogen reduction, which leads to a temperature drop and suppression of the reduction reaction, thereby forming a large-scale chemical retention zone in the furnace and causing a delay in the formation of metallic iron, and to reduce the amount of carbon dioxide emitted.

[0007] To achieve the above and other related objectives, this application provides a hydrocarbon-coupled two-stage gas-circulation high-hydrogen vertical furnace process, comprising the following steps: The main reducing gas is injected into the bottom of the reduction section of the high-hydrogen vertical furnace through the main channel to carry out a high-temperature reduction reaction in the furnace. The secondary reducing gas is injected into the middle of the reduction section of the high-hydrogen vertical furnace through a secondary channel to carry out a medium-low temperature reduction reaction within the furnace; wherein, the secondary channel is at a height H from the bottom of the reduction section of the high-hydrogen vertical furnace. x Satisfying H x ≤0.5H, where H is the total height of the restored section; The furnace top gas discharged from the top of the high-hydrogen vertical furnace is subjected to decarbonization treatment to separate the main process gas and decarbonization tail gas. The main process gas is mixed with the first supplementary gas, heated to obtain the main reducing gas, and then circulated into the main channel. Furthermore, the decarbonized tail gas is mixed with the second supplementary gas to convert carbon dioxide into carbon monoxide, forming the secondary reducing gas, which is then circulated into the secondary channel; the secondary reducing gas includes carbon monoxide and hydrogen, the volume percentage of carbon monoxide in the secondary reducing gas is greater than or equal to 50%, and the volume ratio of carbon monoxide to hydrogen in the secondary reducing gas is greater than or equal to 1.

[0008] Optionally, the temperature of the main reducing gas is 950~1050℃.

[0009] Optionally, the temperature of the secondary reducing gas is 600~950℃.

[0010] Optionally, the first replenishing gas is high-hydrogen gas or pure hydrogen.

[0011] Optionally, the second supplementary gas includes methane and / or hydrogen.

[0012] Optionally, the inlet flow rate of the main reducing gas is greater than or equal to 2 / 3 of the total process gas flow rate of the entire system.

[0013] Optionally, the process further includes: adjusting the flow rate of the decarbonized tail gas mixed with the second supplementary gas according to the inlet gas volume requirement of the secondary reduction gas, and venting the excess decarbonized tail gas.

[0014] Optionally, the process further includes: before decarbonizing the top gas of the high-hydrogen vertical furnace, performing gas treatment and first pressurization on the top gas; the gas treatment includes dust removal and gas-water separation.

[0015] Optionally, the process further includes: subjecting the decarbonized tail gas to a second pressurization treatment before mixing the decarbonized tail gas with the second makeup gas.

[0016] Optionally, the heating and temperature-raising process includes gas heating and secondary temperature raising.

[0017] This application also provides a hydrocarbon-coupled two-stage gas circulation high-hydrogen vertical furnace system, comprising: A high-hydrogen vertical shaft furnace has a reduction section. A main channel is provided at the bottom of the reduction section, and a secondary channel is provided in the middle of the reduction section. The height H of the secondary channel from the bottom of the reduction section is [missing information]. x Satisfying H x ≤0.5H, where H is the total height of the restored section; A shared furnace top gas treatment system is provided, the input end of which is connected to the gas outlet at the top of the high-hydrogen vertical furnace. The shared furnace top gas treatment system includes a decarbonization device, which has a main process gas outlet and a decarbonization tail gas outlet. The main reducing gas circulation system includes a first mixing device and a heating and temperature-raising device connected in sequence. The inlet of the first mixing device is connected to the main process gas outlet of the decarbonization device and the first supplementary gas source, respectively. The outlet of the heating and temperature-raising device is connected to the bottom of the reduction section through the main channel. The system includes a secondary reducing gas circulation system, comprising a second mixing device and a reformer connected in sequence. The inlet of the second mixing device is connected to the decarbonization tail gas outlet of the decarbonization device and a second supplementary gas source, respectively. The outlet of the reformer is connected to the middle of the reduction section through the secondary channel.

[0018] Optionally, the shared top gas treatment system includes a gas treatment device, a first pressurization device, and a decarbonization device connected in sequence.

[0019] Optionally, the heating and temperature-raising device includes a gas heating device and a secondary temperature-raising device connected in sequence.

[0020] Optionally, the secondary reducing gas circulation system includes a second pressurizing device, a second mixing device, and a reformer connected in sequence.

[0021] Optionally, the decarbonization device is connected to a venting tower, which is used to selectively discharge the decarbonization tail gas to regulate the inlet gas volume of the secondary reducing gas.

[0022] As described above, the technical solution provided in this application has at least the following beneficial effects: First, by setting up two independent reducing gas circulation loops (primary and secondary), dual independent control of temperature and composition is achieved for different height zones of the reduction section in the high-hydrogen vertical shaft furnace. The primary reducing gas circulation system injects high-temperature, high-hydrogen primary reducing gas (temperature controlled at 950~1050℃) from the main channel at the bottom of the furnace, utilizing the excellent reducing performance of hydrogen at high temperatures to efficiently complete the high-temperature reduction reaction in the lower part of the furnace. The secondary reducing gas circulation system injects high-temperature, high-hydrogen primary reducing gas (temperature controlled at 950~1050℃) from the secondary channel in the middle of the furnace. xA secondary reducing gas rich in carbon monoxide (CO volume percentage ≥ 50%, CO / H2 ≥ 1, temperature 600~950℃, furnace top temperature not exceeding 550℃) is injected into the furnace. Utilizing the excellent reducing performance and exothermic properties of carbon monoxide at medium and low temperatures, it mixes with the rising H2-rich reducing tail gas from the main channel to jointly complete the reduction reaction in the medium and low temperature section. This stepwise matching and synergy of temperature and composition effectively replenishes the heat in the middle of the vertical furnace, alleviates the problem of temperature drop in the middle of the furnace, significantly reduces the chemical retention zone, and improves the overall reduction efficiency.

[0023] Secondly, this application utilizes a decarbonization device within a shared top gas treatment system to efficiently separate CO2 from the top gas. The decarbonized tail gas (mainly composed of CO2+CO) is then introduced into a secondary reducing gas recirculation system. After mixing with a second makeup gas (such as methane and / or hydrogen), it undergoes reforming and / or reverse water-gas shift reaction in a reformer, converting CO2 into useful reducing gases such as CO and H2. This design not only achieves the resource-based recycling and reuse of CO2, significantly reducing CO2 emissions, but also provides a high-reduction-potential reducing medium for the secondary reducing gas recirculation system, realizing a highly efficient closed-loop carbon cycle.

[0024] Furthermore, the inlet flow rate of the main reducing gas is controlled to be greater than or equal to two-thirds of the total process gas flow rate of the entire system. This ensures that the high-temperature section at the bottom of the reduction section of the vertical shaft furnace has sufficient reducing medium flow and heat, guaranteeing the final reduction quality of the iron ore. A venting tower is installed on the decarburization tail gas pipeline, which allows for the selective discharge of a portion of the tail gas based on system pressure and flow rate fluctuations. This flexibly adjusts the gas flow balance and carbon balance of the secondary reducing gas circulation system, improving the safety and stability of system operation.

[0025] Furthermore, in the main reducing gas circulation system, the heating and temperature-raising process employs a two-stage design: gas heating and secondary temperature raising. In the first stage, the gas is preheated to below the safe temperature limit of the metal furnace tubes in the gas heating device. In the second stage, the gas temperature is directly raised to ultra-high temperatures through localized oxygen injection combustion in the secondary temperature-raising device. This synergistic heating method of "external heat + internal combustion" avoids the risks of hydrogen embrittlement and creep failure of metal materials in ultra-high temperature and high-hydrogen environments, significantly extending the service life of the equipment and ensuring the continuous and stable operation of the system. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0027] In the attached diagram: Figure 1 A schematic flow diagram of a hydrocarbon-coupled two-stage gas circulation vertical furnace process provided in some embodiments of this application; Figure 2 This is a schematic diagram of the layout of a hydrocarbon-coupled two-stage gas circulation high-hydrogen vertical furnace system provided in some embodiments of this application.

[0028] The attached figures are labeled as follows: High-hydrogen vertical shaft furnace 1, preheating section 11, reduction section 12, cooling section 13, gas treatment device 21, first pressurization device 22, decarbonization device 23, first supplementary gas source 31, gas heating device 32, secondary temperature raising device 33, main channel 34, second pressurization device 41, second supplementary gas source 42, reformer 43, secondary channel 44, venting tower 5. Detailed Implementation

[0029] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0030] In this application, unless otherwise stated, the term "multiple" means two or more.

[0031] The character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0032] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0033] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0034] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the present application. However, it will be apparent to those skilled in the art that embodiments of the present application may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams, etc., rather than in detail, to avoid making embodiments of the present application difficult to understand.

[0035] Through long-term research and development and in-depth theoretical analysis, the inventors of this application discovered that there are insurmountable thermodynamic and kinetic bottlenecks in the traditional high-hydrogen-based vertical shaft furnace direct reduction process. Firstly, from a reaction thermodynamics perspective, the reduction of iron oxides by hydrogen (e.g., Fe₂O₃→Fe₃O₄→FeO→Fe) is a strongly endothermic reaction, with an endothermic effect higher than that of carbon monoxide reduction. When the hydrogen concentration in the reducing gas increases significantly, the temperature of the gas-solid two-phase system in the furnace drops sharply as the reduction reaction proceeds from bottom to top. When the furnace temperature drops below 820℃, the hydrogen reduction reaction rate is significantly inhibited due to insufficient activation energy. This thermodynamic defect forces the reduction reaction zone of iron(III) oxide and ferrous oxide to shift towards the high-temperature zone at the bottom of the vertical shaft furnace, resulting in a severe lag in the formation of metallic iron. This leads to a large-scale chemical reaction stagnation zone in the upper and middle parts of the vertical shaft furnace, greatly limiting the production efficiency and product metallization rate.

[0036] Secondly, from a reaction kinetics perspective, hydrogen and carbon monoxide exhibit drastically different reduction characteristics across different temperature ranges. In the high-temperature region above 820°C, hydrogen has a high diffusion coefficient and low activation energy, resulting in significantly stronger reduction capacity and reaction rate compared to carbon monoxide. However, in the medium-low temperature region below 820°C, carbon monoxide exhibits significantly stronger reduction characteristics and thermodynamic driving force than hydrogen, and the reduction of iron oxides by carbon monoxide is exothermic or slightly endothermic. High-hydrogen vertical shaft furnaces in related technologies generally employ a single bottom injection channel, which cannot independently adjust the temperature and concentration fields at different heights within the furnace. This results in hydrogen not reaching its maximum efficiency in the high-temperature region, while the medium-low temperature region suffers from a lack of heat and suitable reducing media, creating a reaction bottleneck.

[0037] To address the aforementioned technical deficiencies and bottlenecks, this application provides a hydrocarbon-coupled two-stage gas-circulation high-hydrogen vertical shaft furnace process and system. The core inventive concept of this application lies in: through the middle section of the reduction section of the vertical shaft furnace (height H... x A secondary channel is added for the ≤0.5H content furnace. The carbon dioxide-rich decarbonized tail gas, separated from the furnace top gas after decarbonization, is pressurized and mixed with a second makeup gas (containing methane or pure hydrogen) for reforming to prepare a secondary reducing gas with a CO / H2 ≥ 1 and a temperature of 600~950℃. This secondary reducing gas is injected into the middle of the vertical shaft furnace and mixed with the partially reduced hydrogen-rich tail gas rising from the main channel, jointly completing the reduction reaction in the medium-low temperature section. Simultaneously, the high-hydrogen main process gas separated from the furnace top gas is mixed with the first makeup gas and heated in two stages before being injected as the high-temperature, high-hydrogen main reducing gas from the bottom main channel of the reduction section of the vertical shaft furnace, completing the high-temperature reduction reaction. This process achieves dual control of temperature and composition in both the main and secondary reducing gas circulation systems of the vertical shaft furnace, eliminates the chemical reaction stagnation zone in the upper and middle parts of the high-hydrogen vertical shaft furnace, and realizes the recycling and emission reduction of carbon dioxide.

[0038] See Figure 1 and Figure 2 In some optional embodiments, this application provides a hydrocarbon-coupled two-stage gas circulation high-hydrogen vertical furnace process, which is applied to a low-carbon metallurgical system including a main reducing gas circulation system, a secondary reducing gas circulation system, a shared furnace top gas treatment system, and a high-hydrogen vertical furnace 1. The process specifically includes the following steps: Step 1: The main reducing gas is injected into the bottom of the reduction section 12 of the high-hydrogen shaft furnace 1 through the main channel 34, flowing upwards within the furnace to complete the high-temperature reduction reaction with the iron ore pellets. The main reducing gas is a high-temperature, high-hydrogen reducing gas with an H2 volume percentage ≥60%, and the injection temperature is controlled at 950~1050℃. In the high-temperature zone at the bottom of the reduction section 12 of the high-hydrogen shaft furnace 1, the high concentration of H2 undergoes a rapid reduction reaction with the pellets, efficiently reducing the ferrous oxide in the pellets to metallic iron, ensuring that the final product has an extremely high metallization rate.

[0039] Step 2: The secondary reducing gas is injected into the middle of the reduction section 12 of the high-hydrogen vertical furnace 1 through secondary channel 44 to carry out a medium-low temperature reduction reaction within the furnace. The height H of secondary channel 44 from the bottom of the reduction section 12 of the high-hydrogen vertical furnace 1 is... x Satisfying H x ≤0.5H, where H is the total height of reduction section 12. The secondary reducing gas includes CO and H2, wherein the volume percentage of CO is ≥50%, and the volume ratio of CO to H2 is ≥1, and its injection temperature is controlled at 600~950℃. After the secondary reducing gas is injected, it mixes with the hydrogen-rich tail gas rising from the main channel 34, whose temperature has dropped to about 800℃. Since CO has a stronger reducing ability than H2 at medium and low temperatures, and its reduction reaction is an exothermic reaction, it can effectively compensate for the heat in the furnace, thereby establishing a highly efficient carbon-hydrogen coupling reduction zone in the medium and low temperature zone and eliminating the chemical reaction stagnation zone.

[0040] Step 3: The top gas discharged from the top of the high-hydrogen shaft furnace 1 is introduced into a shared top gas treatment system for decarbonization, separating the main process gas and decarbonized tail gas. The temperature of the top gas discharged from the furnace top is approximately 300~500℃, containing unreacted H2, CO, water vapor, CO2, and a small amount of nitrogen. The top gas is first purified by dust removal and gas-water separation in the gas treatment device 21, then pressurized by the first pressurization device 22 and sent to the decarbonization device 23 for decarbonization treatment (such as pressure swing adsorption decarbonization). The decarbonization treatment separates most of the CO2 from the top gas, thus obtaining a high-hydrogen main process gas rich in H2 and a decarbonized tail gas rich in CO2 at the outlet of the decarbonization device 23.

[0041] Step 4: The main process gas is mixed with the first makeup gas, heated to obtain the main reducing gas, and then circulated into the main channel 34. The separated main process gas enters the main reducing gas circulation system and mixes with the first makeup gas (high-hydrogen gas or pure hydrogen) to replenish the hydrogen consumed by the system during the reduction process. The mixed gas undergoes a two-stage heating process, including gas heating and secondary heating, to obtain a high-temperature, high-hydrogen main reducing gas with a temperature of 950~1050℃, which is then circulated and injected into the bottom of the reduction section 12 of the high-hydrogen vertical furnace 1 through the main channel 34.

[0042] Step 5: The decarbonized tail gas is mixed with the second makeup gas and reformed and / or subjected to a reverse water-gas shift reaction in the reformer 43 to convert CO2 into CO, forming the secondary reducing gas, which is then circulated into the secondary channel 44. The separated decarbonized tail gas enters the secondary reducing gas circulation system, is pressurized by the second pressurizing device 41, and then mixed with the second makeup gas. In the reformer 43, the mixed gas undergoes reforming and / or reverse water-gas shift reaction under high temperature and the action of a catalyst, converting the CO2 in the decarbonized tail gas into highly reducing CO and / or H2, obtaining a secondary reducing gas that satisfies the volume ratio CO / H2≥1 and a temperature of 600~950℃, and is finally circulated and injected into the middle of the reduction section 12 of the high-hydrogen vertical shaft furnace 1 through the secondary channel 44.

[0043] Through the synergistic effect of the above-mentioned process steps, this application successfully achieved adaptive matching of the temperature field and concentration field within the vertical shaft furnace via a dual-channel injection and dual-circulation loop design. Compared to the traditional single-channel high-hydrogen vertical shaft furnace process, this process not only eliminates the chemical reaction stagnation zone in the upper and middle parts of the furnace, significantly improving the metallization rate of the product, but also reforms and reuses all or most of the CO2 separated during decarbonization, achieving high-value utilization and emission reduction of CO2 resources.

[0044] In some optional embodiments, the temperature of the main reducing gas is controlled at 950~1050℃, preferably 950~1000℃. In the high-temperature zone at the bottom of the reduction section 12 of the high-hydrogen shaft furnace 1, the reduction degree of the pellets has reached over 90%. At this point, extremely high temperatures are required to provide the reaction driving force to overcome the resistance of the metallic iron layer to gas diffusion. Controlling the temperature of the main reducing gas at 950~1050℃ maximizes the rapid reduction kinetics of H2 at high temperatures. However, if the injection temperature exceeds 1050℃, the high metallization rate of the pellets in the furnace is prone to softening and agglomeration, leading to deterioration of the material column permeability or even material suspension; if the temperature is below 950℃, the reduction reaction rate slows down significantly, making it impossible to guarantee a high metallization rate of the product.

[0045] Accordingly, the temperature of the secondary reducing gas is controlled at 600~950℃, and the furnace top temperature does not exceed 550℃. In the middle region of the reduction section 12 of the high-hydrogen shaft furnace 1, the pellets are in the pre-reduction stage, and metallic iron begins to precipitate. Since CO has a stronger reducing power than H2 at medium and low temperatures, and the CO reduction reaction is an exothermic reaction, controlling the temperature of the secondary reducing gas at 600~950℃, and the furnace top temperature does not exceed 550℃, can fully utilize the reducing advantage of CO in the medium and low temperature range, supplement the heat in the furnace, and strictly control the temperature of the middle material layer, avoiding the softening and sticking of incompletely reduced pellets due to excessively high local temperatures, thus ensuring the smooth operation of the shaft furnace.

[0046] In some optional embodiments, the first makeup gas is a high-hydrogen gas or pure hydrogen, used to replenish the hydrogen element consumed by the system due to the reduction reaction and maintain the H2 concentration in the main reducing gas circulation loop. The second makeup gas includes methane and / or H2, which can be selected from methane-containing gases (such as natural gas, coke oven gas, or coalbed methane) and / or pure hydrogen. It serves as a reducing medium for chemical reactions, reacting with CO2 in the decarbonization tail gas in the reformer 43 in a reforming reaction (CO2+CH4→2CO+2H2) and / or a reverse water-gas shift reaction (CO2+H2→CO+H2O) to generate a secondary reducing gas rich in CO and / or H2.

[0047] In some optional embodiments, the inlet flow rate of the main reducing gas is controlled to be no less than 2 / 3 of the total process gas flow rate of the entire system. Since the reduction reaction at the bottom of the reduction section 12 of the high-hydrogen shaft furnace 1 is crucial in determining the final product's metallization rate, it is essential to ensure sufficient gas flow in the high-temperature zone at the bottom to carry adequate physical heat and reducing potential. Controlling the inlet flow rate of the main reducing gas to ≥2 / 3 ensures heat balance in the lower high-temperature reduction zone of the shaft furnace, allowing the pellets to be fully reduced before descending to the discharge port. If the main reducing gas flow rate is less than 2 / 3 of the total gas flow rate, insufficient physical heat is carried into the bottom, which can easily lead to a decrease in the hearth temperature, a slower reduction reaction rate, and a lower product metallization rate.

[0048] See also Figure 1 and Figure 2 In some optional embodiments, the process further includes: installing a venting tower 5 on the decarbonization tail gas pipeline; adjusting the flow rate of the decarbonization tail gas mixed with the second makeup gas according to the inlet gas flow rate requirement of the secondary reducing gas; and processing any excess decarbonization tail gas in the venting tower 5. By selectively discharging excess decarbonization tail gas, the inlet gas flow rate of the secondary reducing gas can be adjusted.

[0049] See also Figure 1 and Figure 2In some optional embodiments, the process further includes: treating the top gas of the high-hydrogen shaft furnace 1 with coal gas and performing a first pressurization treatment before decarbonizing it. The coal gas treatment includes, but is not limited to, operations such as dust removal and gas-water separation. The top gas discharged from the furnace top contains a large amount of dust and saturated water vapor. First, the dust content and temperature of the gas are reduced through dry dust removal, wet dust removal, and cooling and dehydration to achieve coal gas purification. The purified top gas is then pressurized for the first time by the first pressurization device 22 to reach the working pressure required by the decarbonization device 23, thereby ensuring the efficient conduct of the decarbonization reaction. Correspondingly, the decarbonization tail gas is subjected to a second pressurization treatment before being mixed with the second makeup gas. The pressure of the decarbonization tail gas discharged from the decarbonization device 23 is relatively low. It is then pressurized a second time by the second pressurization device 41 to increase its pressure to the working pressure of the reformer 43, thereby overcoming the resistance of the reformer 43 and the secondary channel 44, and ensuring that the secondary reducing gas is smoothly injected into the middle of the shaft furnace.

[0050] See also Figure 1 and Figure 2 In some optional embodiments, the heating and temperature-raising process includes gas heating and secondary temperature-raising. After the decarbonized main process gas is mixed with the first supplementary gas, it is first preheated by the gas heating device 32 to raise the gas temperature to 900~950℃; then, the preheated gas enters the secondary temperature-raising device 33 for the second stage of heating, which rapidly raises the gas temperature to the final reduction temperature of 950~1050℃.

[0051] See Figure 2 In some optional embodiments, this application provides a hydrocarbon-coupled two-stage gas circulation high-hydrogen vertical shaft furnace system, which serves as the physical hardware carrier for implementing the above-mentioned process. The system includes a high-hydrogen vertical shaft furnace 1, a shared top gas treatment system, a main reducing gas circulation system, and a secondary reducing gas circulation system.

[0052] The high-hydrogen vertical shaft furnace 1, serving as the core reactor for gas-based reduction, comprises, from top to bottom, a preheating section 11, a reduction section 12, and a cooling section 13. A main channel 34 is located at the bottom of the reduction section 12 for injecting high-temperature, high-hydrogen primary reducing gas; a secondary channel 44 is located in the middle of the reduction section 12 for injecting medium- and low-temperature, CO-rich secondary reducing gas. The secondary channel 44 is installed at a height H. x Satisfying H x ≤0.5H (H is the total height of reduction section 12) to ensure that the secondary reducing gas can accurately enter the medium and low temperature reaction zone inside the furnace.

[0053] The input end of the shared top gas treatment system is connected to the gas outlet at the top of the high-hydrogen vertical shaft furnace 1 via a pipeline for collecting the top gas after the reaction. The shared top gas treatment system includes a gas treatment device 21 (for dust removal, dehydration, etc.), a first pressurization device 22, and a decarbonization device 23 connected in sequence via pipelines. The decarbonization device 23 has a main process gas outlet (outputting high-hydrogen main process gas) and a decarbonization tail gas outlet (outputting CO2-rich decarbonization tail gas).

[0054] The main reducing gas circulation system includes a first mixing device and a heating and temperature-raising device connected in sequence through pipelines. The inlet of the first mixing device is connected to the main process gas outlet of the decarbonization device 23 and the first supplementary gas source 31 (providing the first supplementary gas), respectively. The outlet of the heating and temperature-raising device is connected to the bottom of the reduction section 12 through the main channel 34, thus forming the main reducing gas circulation loop.

[0055] The secondary reducing gas circulation system includes a second mixing device and a reformer 43 connected in sequence by pipelines. The inlet of the second mixing device is connected to the decarbonization tail gas outlet of the decarbonization device 23 and the second supplementary gas source 42 (providing the second supplementary gas). The outlet of the reformer 43 is connected to the middle of the reduction section 12 through a secondary channel 44, thus forming a secondary reducing gas circulation loop.

[0056] This application involves setting a secondary channel 44 in the middle of the vertical furnace body, and setting the height H of the secondary channel 44 from the bottom of the reduction section 12. x Limited to H x Within the range of ≤0.5H, it can ensure the precise injection of secondary reducing gas into the medium-low temperature reduction zone where the temperature has dropped to 600~950℃. Since the secondary reducing gas satisfies a volume ratio of CO / H2≥1, the CO it contains has a stronger reducing capacity than hydrogen in a medium-low temperature environment below 820℃. The exothermic reduction reaction between CO and iron ore pellets not only releases chemical heat to compensate for the furnace temperature drop caused by the endothermic reduction reaction of H2 rising from the bottom, maintaining temperature stability in the middle layer, but also significantly accelerates the reduction process of pellets in the medium-low temperature section, reducing the probability of chemical reaction stagnation zones forming in the upper part of the vertical shaft furnace, and improving the overall reduction efficiency of the vertical shaft furnace and the metallization rate of direct reduced iron.

[0057] Simultaneously, the carbon dioxide in the top gas is efficiently separated by the decarbonization device 23 in the shared top gas treatment system. The separated decarbonization tail gas is then introduced into the secondary reducing gas circulation system, where it is mixed with the second makeup gas (CH4 / H2) and reacted to convert CO2 into useful reducing gases such as CO and H2. This process design not only realizes the resource recycling of CO2 and reduces the overall CO2 emissions, but also allows for flexible control of the composition and temperature of the secondary reducing gas by adjusting the type and flow rate of the second makeup gas. This enables independent dual control of the temperature and composition of the main reducing gas circulation system and the secondary reducing gas circulation system of the vertical shaft furnace, enhancing the system's adaptability to fluctuations in raw material and fuel conditions.

[0058] In summary, the system has a reasonable hardware configuration and can fully support the stable operation of the aforementioned carbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace process.

[0059] See also Figure 2 In some optional embodiments, the heating and temperature-raising device includes a gas heating device 32 and a secondary temperature-raising device 33 connected sequentially via pipelines. In the main reducing gas circulation system, the heating and temperature-raising process employs a two-stage design: gas heating and secondary temperature-raising. In the first stage, the gas is heated to below the safe temperature limit of the metal furnace tube in the gas heating device 32. In the second stage, the gas temperature is directly raised to ultra-high temperatures through localized oxygen injection combustion in the secondary temperature-raising device 33. This synergistic heating method of "external heat + internal combustion" avoids the risks of hydrogen embrittlement and creep failure of metal materials in ultra-high temperature and high-hydrogen environments, significantly extending the service life of the equipment and ensuring the continuous and stable operation of the system.

[0060] See also Figure 2 In some optional embodiments, the secondary reducing gas circulation system includes a second pressurizing device 41, a second mixing device, and a reformer 43 connected in sequence. The decarbonization tail gas is discharged from the decarbonization device 23 at a low pressure. It is pressurized a second time by the second pressurizing device 41 to increase its pressure to the working pressure of the reformer 43, so as to overcome the resistance of the reformer 43 and the secondary channel 44 and ensure that the secondary reducing gas is smoothly injected into the middle of the vertical furnace.

[0061] See also Figure 2 In some optional embodiments, the decarbonization tail gas outlet of the decarbonization device 23 is connected to a venting tower 5 via a pipeline. The venting tower 5 is used to selectively discharge the decarbonization tail gas to regulate the inlet gas flow of the secondary reducing gas. By installing the venting tower 5 on the decarbonization tail gas pipeline, a portion of the tail gas can be selectively discharged according to system pressure and gas flow fluctuations, flexibly adjusting the gas flow balance of the secondary reducing gas circulation system and improving the safety and stability of system operation.

[0062] The technical solution of this application is further illustrated below through specific embodiments. Each embodiment is based on a sponge iron production capacity of 1 million tons per year. It should also be understood that the following embodiments are only for specific illustration of this application and should not be construed as limiting the scope of protection of this application. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of this application fall within the scope of protection of this application. The specific process parameters in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0063] Example 1 See Figure 1 and Figure 2 This embodiment provides a two-stage gas-circulating high-hydrogen vertical shaft furnace process with hydrocarbon coupling. The gas output per ton of iron reduced in the vertical shaft furnace is Q.

[0064] High-hydrogen, high-temperature (1000℃) main reducing gas with a flow rate of 100%Q enters the bottom of the reduction section 12 of the high-hydrogen shaft furnace 1 through the main channel 34. It flows upwards within the furnace, completing the high-temperature reduction reaction with the iron ore pellets. Secondary reducing gas (flow rate approximately 30%Q), in a medium-low temperature state, is injected into the middle of the reduction section 12 of the high-hydrogen shaft furnace 1 through a secondary channel 44 at a height of H / 2 from the bottom of the reduction section 12. This secondary reducing gas mixes with the partially reduced tail gas (rich in H2) rising from the main channel 34, together completing the reduction reaction in the upper and middle-low temperature section of the furnace.

[0065] The top gas discharged from the furnace top enters the shared top gas treatment system. First, it undergoes dust removal and gas-water separation in the gas treatment device 21, and then is pressurized by the first pressurization device 22 before being sent to the decarbonization device 23. The decarbonized high-hydrogen main process gas enters the main reducing gas circulation system and mixes with the first makeup gas (high-hydrogen gas). The mixed gas undergoes a two-stage heating process, namely gas heating and secondary heating, to obtain a high-hydrogen high-temperature main reducing gas at a temperature of 1000℃. This gas is then injected back into the high-hydrogen vertical furnace 1 through the main channel 34.

[0066] The total amount of decarbonized tail gas (mainly CO2 + CO) separated by decarbonization unit 23 is approximately 10%Q. Of this, the majority (approximately 7.5%Q) is introduced into the secondary reduction gas recirculation system, and the remaining portion (approximately 2.5%Q) is selectively discharged through venting tower 5. The decarbonized tail gas entering the secondary reduction gas recirculation system is pressurized by the second pressurization unit 41 and mixed with the second makeup gas (containing methane gas, with a flow rate of approximately 7.5%Q) before entering the reformer 43. The following catalytic reforming reaction occurs within the reformer 43: CO2 + CH4 → 2CO + 2H2 After the reforming reaction, a high-temperature secondary reducing gas with a temperature of 820℃ and a flow rate of approximately 30%Q is obtained. The chemical composition of this gas satisfies CO:H2=1:1 (i.e., CO / H2=1), and it is then injected into the middle of the reduction section 12 of the high-hydrogen shaft furnace 1 through secondary channel 44.

[0067] Example 2 See Figure 1 and Figure 2 This embodiment provides a two-stage gas-circulating high-hydrogen vertical shaft furnace process with hydrocarbon coupling. The gas output per ton of iron reduced in the vertical shaft furnace is Q.

[0068] High-hydrogen, high-temperature (1000℃) main reducing gas, with a flow rate of 100%Q, enters the bottom of the reduction section 12 of the high-hydrogen vertical furnace 1 through the main channel 34, where it completes the high-temperature reduction reaction with the pellets within the furnace. Secondary reducing gas (flow rate approximately 10%Q) is injected into the middle of the reduction section 12 of the high-hydrogen vertical furnace 1 through the secondary channel 44, located at a height of H / 3 from the bottom of the reduction section 12. It mixes with the rising reduction tail gas from the main channel 34, completing the medium-low temperature reduction stage. The furnace top gas is discharged from the furnace top, and after gas treatment (dust removal, gas-water separation) and pressurization by the first pressurization device 22, it enters the decarbonization device 23.

[0069] The decarbonized high-hydrogen main process gas enters the main reducing gas circulation system, mixes with the first makeup gas (pure hydrogen), and after being heated by coal gas and raised to 1000℃ twice, is circulated and injected into the high-hydrogen vertical furnace 1. The decarbonized tail gas (total amount of about 10%Q) generated by the decarbonization unit 23 is all introduced into the secondary reducing gas circulation system and is not discharged externally.

[0070] After being pressurized by the second pressurization device 41, the decarbonized tail gas is mixed with the second makeup gas (pure hydrogen, with a flow rate of approximately 10%Q) and enters the reformer 43. The following reverse water-gas shift reaction occurs within the reformer 43: CO2 + H2 → CO + H2O After reforming, a high-temperature secondary reducing gas with a temperature of 820℃ and a flow rate of approximately 10%Q is obtained, and its chemical composition satisfies CO:H2=1:1. This gas is injected into the middle of the reduction section 12 of the high-hydrogen vertical furnace 1 through secondary channel 44.

[0071] This embodiment achieves a complete closed-loop circulation of carbon elements within the entire system, with no direct CO2 emissions from the system.

[0072] In summary, the hydrocarbon-coupled two-stage gas circulation high-hydrogen vertical furnace process and system provided in this application solves the problems of insufficient heat in the low-temperature zone and chemical retention zone in the high-hydrogen vertical furnace through the synergistic effect of the main and secondary reducing gas dual circulation loops. While significantly improving the metallization rate of the product, it also achieves efficient recycling and emission reduction of CO2, and has extremely high industrial application value.

[0073] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A hydrocarbon-coupled two-stage gas-circulation high-hydrogen vertical shaft furnace process, characterized in that, Includes the following steps: The main reducing gas is injected into the bottom of the reduction section of the high-hydrogen vertical furnace through the main channel to carry out a high-temperature reduction reaction in the furnace. The secondary reducing gas is injected into the middle of the reduction section of the high-hydrogen vertical furnace through a secondary channel to carry out a medium-low temperature reduction reaction within the furnace; wherein, the secondary channel is at a height H from the bottom of the reduction section of the high-hydrogen vertical furnace. x Satisfying H x ≤0.5H, where H is the total height of the restored section; The furnace top gas discharged from the top of the high-hydrogen vertical furnace is subjected to decarbonization treatment to separate the main process gas and decarbonization tail gas. The main process gas is mixed with the first supplementary gas, heated to obtain the main reducing gas, and then circulated into the main channel. Furthermore, the decarbonized tail gas is mixed with the second supplementary gas to convert carbon dioxide into carbon monoxide, forming the secondary reducing gas, which is then circulated into the secondary channel; the secondary reducing gas contains carbon monoxide and hydrogen, the volume percentage of carbon monoxide in the secondary reducing gas is greater than or equal to 50%, and the volume ratio of carbon monoxide to hydrogen in the secondary reducing gas is greater than or equal to 1.

2. The hydrocarbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace process according to claim 1, characterized in that: The temperature of the main reducing gas is 950~1050℃; And / or, the temperature of the secondary reducing gas is 600~950℃.

3. The hydrocarbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace process according to claim 1, characterized in that: The first replenishing gas is high-hydrogen gas or pure hydrogen; And / or, the second supplementary gas includes methane and / or hydrogen.

4. The hydrocarbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace process according to claim 1, characterized in that: The inlet flow rate of the main reducing gas is greater than or equal to 2 / 3 of the total process gas flow rate of the entire system.

5. The hydrocarbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace process according to claim 1, characterized in that, The process also includes: The flow rate of the decarbonized tail gas mixed with the second supplementary gas is adjusted according to the inlet gas volume requirement of the secondary reducing gas, and the excess decarbonized tail gas is released.

6. The hydrocarbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace process according to claim 1, characterized in that, The process also includes: Before decarbonizing the top gas of the high-hydrogen vertical shaft furnace, the top gas undergoes gas treatment and a first pressurization treatment; the gas treatment includes dust removal and gas-water separation. And / or, the decarbonized tail gas is subjected to a second pressurization treatment before being mixed with the second makeup gas.

7. The hydrocarbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace process according to any one of claims 1 to 6, characterized in that: The heating and temperature-raising process includes gas heating and secondary temperature raising.

8. A hydrocarbon-coupled two-stage gas-circulating high-hydrogen vertical shaft furnace system, characterized in that, include: A high-hydrogen vertical shaft furnace has a reduction section. A main channel is provided at the bottom of the reduction section, and a secondary channel is provided in the middle of the reduction section. The height H of the secondary channel from the bottom of the reduction section is [missing information]. x Satisfying H x ≤0.5H, where H is the total height of the restored section; A shared furnace top gas treatment system is provided, the input end of which is connected to the gas outlet at the top of the high-hydrogen vertical furnace. The shared furnace top gas treatment system includes a decarbonization device, which has a main process gas outlet and a decarbonization tail gas outlet. The main reducing gas circulation system includes a first mixing device and a heating and temperature-raising device connected in sequence. The inlet of the first mixing device is connected to the main process gas outlet of the decarbonization device and the first supplementary gas source, respectively. The outlet of the heating and temperature-raising device is connected to the bottom of the reduction section through the main channel. The system includes a secondary reducing gas circulation system, comprising a second mixing device and a reformer connected in sequence. The inlet of the second mixing device is connected to the decarbonization tail gas outlet of the decarbonization device and a second supplementary gas source, respectively. The outlet of the reformer is connected to the middle of the reduction section through the secondary channel.

9. The hydrocarbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace system according to claim 8, characterized in that: The shared furnace top gas treatment system includes a gas treatment device, a first pressurization device, and a decarbonization device connected in sequence.

10. The hydrocarbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace system according to claim 8, characterized in that: The heating and temperature-raising device includes a gas heating device and a secondary temperature-raising device connected in sequence.

11. The hydrocarbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace system according to claim 8, characterized in that: The secondary reducing gas circulation system includes a second pressurizing device, a second mixing device, and a reformer connected in sequence.

12. The hydrocarbon-hydrogen coupled two-stage gas circulation high-hydrogen vertical furnace system according to any one of claims 8 to 11, characterized in that: The decarbonization device is connected to a venting tower, which is used to selectively discharge the decarbonization tail gas to regulate the inlet gas volume of the secondary reducing gas.

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