A blast furnace smelting system and method with ultra-low fuel ratio based on the coupling of top gas circulation and CO2 electrocatalytic conversion.

Abstract

The present application relates to a kind of based on top coal gas circulation and CO2 electrocatalytic conversion coupling ultra-low fuel ratio blast furnace smelting system and method, belong to steel smelting technical field.The system includes top coal gas processing, CO2 catalytic conversion, synthesis gas upgrading, excess pressure energy recovery, coal gas heating and energy regulation and control unit.The method is that desorption gas after decarburization of blast furnace top coal gas purification, part is converted into CO+H2 rich reducing gas by electrocatalytic process;The reducing gas is mixed and heated after decarburization gas and is injected into blast furnace;While using the by-product oxygen of electrocatalytic process carries out oxygen-enriched / oxygen blast, and surplus top coal gas is mixed with the remaining desorption gas and is adjusted as fuel in system after heat value, constructs " carbon-gas-energy " closed loop system.The present application breaks through the dependence on external reducing gas;Through green electricity driven CO2 catalytic conversion and system self-circulation, realize blast furnace in no coal injection, ultra-low fuel ratio stable operation, and carbon emission reduction reaches more than 50% in whole life cycle.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel smelting technology, and relates to an ultra-low fuel ratio blast furnace smelting system and method based on the coupling of top gas circulation and CO2 electrocatalytic conversion. Background Technology

[0002] Currently, most steel production capacity utilizes the blast furnace-converter long process, and this will remain the dominant production structure in the short term. This is mainly constrained by two factors: firstly, many steel companies have relatively new equipment and high capacity replacement costs, making it difficult to achieve process substitution in the short term; secondly, the large-scale development of the electric arc furnace short process faces real bottlenecks due to the coal-dominated energy structure and the endowment of low-grade iron ore resources. Against this backdrop, relying solely on energy transition (such as the widespread promotion of hydrogen energy) to achieve deep decarbonization will face challenges such as high technical difficulty and high transformation costs. Therefore, promoting the low-carbon transformation of the dominant blast furnace-converter process has become the core path for the development of the steel industry. It is worth noting that over 70% of the carbon emissions from this process originate from the consumption of carbon-based reducing agents (pulverized coal and coke) during iron ore reduction; therefore, overcoming the blast furnace carbon consumption bottleneck is crucial for achieving deep decarbonization.

[0003] To address these challenges, the "blast furnace top gas recirculation injection" technology has emerged. The core idea of ​​this technology is to purify and separate the blast furnace's self-produced top gas (rich in CO and H2), and then reinject the reducing gas from it back into the blast furnace as an injection medium, replacing part of the purchased fossil fuels. This approach not only helps reduce blast furnace fuel consumption but also effectively reduces CO2 emissions, possessing both economic viability and engineering application potential. However, this technology still faces multiple challenges in its industrialization: First, to achieve deep carbon reduction in blast furnaces, the quantity of reducing gas components in the existing top gas is severely insufficient, requiring additional external reducing gas to support ultra-low fuel ratio smelting conditions. Second, ultra-low fuel ratio operation will lead to a decrease in the blast furnace's own gas production, necessitating the introduction of external blast furnace gas as fuel for the gas heater. However, for enterprises without coking units or other facilities capable of providing reducing gas, gas supply is a practical limitation, especially when the number of blast furnaces within the enterprise is small and gas resources are insufficient. Furthermore, in response to the energy structure transformation and electrification development, it is necessary to further increase the application ratio of new energy sources. In the future, we can explore the use of green gasification technologies such as electrolytic catalytic conversion to produce supplementary reducing gas that meets the requirements of blast furnace smelting, thereby achieving synergistic effects of green electricity consumption and carbon emission reduction.

[0004] Currently, blast furnace smelting technology mainly includes the following methods: Patent application CN121320661A discloses an ultra-low carbon emission blast furnace smelting process and system. This invention proposes a technical approach for ultra-low carbon smelting: decarbonized gas, obtained by treating the blast furnace's self-produced top gas through dust removal, cooling, pressurization, and decarbonization, is mixed with external CO / H2 reducing gas to form a mixed gas. This mixed gas is then heated and injected into the blast furnace as a reducing medium, while simultaneously implementing oxygen-enriched blasting. This process, through synergistic measures such as eliminating pulverized coal injection, injecting high-temperature reducing gas, increasing the amount of gas in the furnace belly, and lowering the theoretical combustion temperature, ensures stable operation of the blast furnace under ultra-low coke ratio conditions, thereby minimizing fossil carbon consumption and ultimately achieving a emission reduction of more than 50% compared to conventional blast furnaces. While this process can achieve the patented goals for integrated steel and coking plants and enterprises with a large number of blast furnaces, it is unsuitable for companies without coking units or other facilities providing reducing gas. Secondly, this process does not achieve green energy consumption or electrification transition. Thirdly, the 50% emission reduction effect of this process is calculated only within the direct fossil fuel consumption of the blast furnace itself. If a life-cycle analysis method is used to include the indirect carbon emission coefficient of externally supplied reducing gas (such as gas from coking or chemical byproducts), the emission reduction effect of this process will decrease to approximately 35%–40%.

[0005] Patent application CN111485044A discloses a method for simulating pure oxygen ironmaking and recycling blast furnace gas. The core idea is to add an oxygen production unit and a CO2 separation unit to the blast furnace ironmaking process. The oxygen produced by the oxygen production unit is mixed with a portion of the separated and recovered CO2 in a certain proportion as blast furnace combustion fuel, replacing traditional air blast, avoiding the introduction of N2, and reducing the difficulty of CO purification. However, this process is not feasible in terms of smelting technology because the oxygen-containing mixed gas injected into the blast furnace contains 30%–80% CO2, which will cause a severe melting reaction with the coke in the blast furnace, rendering the coke's permeability ineffective and ultimately causing the blast furnace to malfunction.

[0006] Patent application CN101638702A discloses a method for recycling blast furnace gas from a direct reduction process. Specifically targeting a vertical shaft furnace direct reduction process, the method involves decarbonizing the discharged gas to obtain CO2-rich desorbed gas and CO+H2-rich decarbonized gas. The CO2-rich desorbed gas is then conditioned and returned to the gas preparation system or used as a material transport medium, thus achieving a physical cycle of CO2. However, this method is limited to the direct reduction process and does not involve the blast furnace ironmaking system. Furthermore, its carbon resource utilization still primarily relies on material recycling, failing to achieve both chemical carbon conversion and system energy efficiency integration.

[0007] To address the aforementioned issues, this invention proposes a process system that integrates reducing gas produced from external renewable energy sources with top coal gas recycling, aiming to synergistically resolve the contradiction between deep decarbonization, system energy consumption, and operational stability. Summary of the Invention

[0008] In view of this, the purpose of this invention is to provide an ultra-low fuel ratio blast furnace smelting system and method based on the coupling of top gas circulation and CO2 electrocatalytic conversion. This system addresses the contradiction between deep decarbonization, system energy consumption, and operational stability by combining deep decarbonization of blast furnace top gas, CO2 electrocatalytic conversion to syngas, syngas to reducing gas, oxygen-enriched injection, and gas circulation injection. Specifically, the system introduces desorbed gas generated from the decarbonization and upgrading of top gas from new energy electrolysis to prepare reducing gas, thus overcoming the bottleneck of insufficient reducing gas in the blast furnace itself. It also constructs a cross-process gas synergistic utilization network, overcoming the gas source limitations for enterprises without coking units or other conditions providing reducing gas when implementing this technology. This system not only achieves efficient purification, circulation injection, and low-carbon smelting of blast furnace gas, but also provides a technically feasible and economically reasonable innovative path for steel enterprises to integrate green energy and promote the low-carbon transformation of blast furnace ironmaking processes.

[0009] To achieve the above objectives, the present invention provides the following technical solution: An ultra-low fuel ratio blast furnace smelting system based on the coupling of top gas circulation and CO2 electrocatalytic conversion is constructed around the blast furnace body, forming an integrated system for efficient material and energy circulation. The system includes the blast furnace and the following six core components: a top gas circulation and processing unit, a desorbed gas diversion device 7, a reducing gas preparation unit, a pulverized coal gas mixing and heating unit, an oxygen-enriched injection unit, and a fuel gas preparation unit.

[0010] The top gas circulation treatment unit is used to sequentially treat the top gas generated by the blast furnace by coarse dust removal, cooling and deep purification, pressure regulation, decarbonization and upgrading, and turbine residual pressure energy recovery, to obtain decarbonized gas and CO2-rich desorbed gas. The desorption gas diversion device 7 is connected to the top coal gas circulation processing unit and is used to divide the desorption gas flow into a first part of desorption gas and a second part of desorption gas. The reducing gas preparation unit is connected to the desorbed gas diversion device 7 and is used to desulfurize and purify the first part of the desorbed gas and perform CO2 electrocatalytic conversion to generate syngas and produce oxygen as a byproduct. The syngas is then upgraded to obtain reducing gas with CO and H2 as the main components. The pulverized gas mixing and heating unit (such as the pulverized gas heater 6) is connected to the top gas circulation treatment unit and the reducing gas preparation unit respectively, and is used to mix the decarbonized gas and the reducing gas and then inject them into the blast furnace after heating. The oxygen-enriched injection unit, connected to the reducing gas preparation unit, is used to mix the oxygen produced by CO2 electrocatalytic conversion with the oxygen-enriched or pure oxygen provided by the external oxygen generation device 24 and then inject it into the blast furnace tuyeres. The fuel gas preparation unit 22 is connected to the desorbed gas diversion device 7 and the surplus top gas pipeline, and is used to mix the second part of the desorbed gas with the surplus top gas that has not participated in the circulation to form fuel gas for heating in the system. The smelting system operates the blast furnace at an ultra-low fuel ratio by stopping the injection of pulverized coal and reducing the amount of coke, and is supplemented with high oxygen-enriched or pure oxygen blast to maintain stable furnace conditions.

[0011] Preferably, the coarse dust removal, cooling and deep purification methods are a combination of processes such as "gravity dust removal + dry dust removal + cooling washing tower" or "gravity dust removal + cyclone separation + wet dust removal".

[0012] Preferably, the top gas circulation treatment unit includes a coarse dust removal device 1, a cooling and deep purification device 2, a top gas pressure regulating device 3, a top gas decarbonization and upgrading device 4, and a turbine residual pressure energy recovery device 5, which are connected in sequence.

[0013] Preferably, the flow rate of the first portion of desorbed gas is dynamically adjusted according to the actual fuel ratio of the blast furnace and the overall fuel demand of the system; the designed processing capacity is determined according to the blast furnace's extreme low fuel ratio operating condition.

[0014] Preferably, the reducing gas preparation unit includes a desorbed gas pressure regulating device 8, a desorbed gas desulfurization and purification device 9, a CO2 electrocatalytic conversion device 10, and a syngas upgrading device arranged sequentially along the process flow.

[0015] Preferably, the CO2 electrocatalytic conversion device 10 includes an integrated power supply facility 17, an electrolyte circulation facility 14, an electrocatalytic reactor 13, a cathode gas purification facility 15, and an anode gas purification facility 16 arranged sequentially. The integrated power supply facility 17 is driven by renewable energy power; the electrocatalytic reactor 13 is used to dynamically adjust the volume ratio of CO to H2 in the syngas to 0.5:1~1:1; the cathode gas purification facility 15 and the anode gas purification facility 16 are respectively used to control the free water content in the syngas and by-product oxygen at the outlet of the CO2 electrocatalytic conversion device 10 to ≤10mg / Nm³.

[0016] Preferably, the syngas upgrading device includes a CO2 thermocatalytic conversion device 11 or a syngas decarbonization upgrading device 12; the CO2 thermocatalytic conversion device 11 uses the fuel gas provided by the fuel gas preparation unit as a process heat source to further convert the residual CO2 in the syngas into CO; the syngas decarbonization upgrading device 12 is used to directly remove CO2 from the syngas to obtain reducing gas and a third part of desorbed gas.

[0017] Preferably, the fuel gas preparation unit 22 includes a mixer, a gas holder, and a fuel gas pipeline, used to mix, store, and adjust the calorific value of the second part of desorbed gas with the surplus top gas, and deliver it to the heating furnace in the injected gas mixing and heating unit and / or the CO2 thermocatalytic conversion device 11 in the reducing gas preparation unit as a heat source.

[0018] Preferably, the smelting method of this system specifically includes the following steps: (1) Top gas circulation treatment: responsible for purifying, separating and recovering energy from the top gas discharged from the blast furnace; its process flow includes the following in sequence: Coarse dust removal and cooling purification: A combination of processes such as "gravity dust removal + dry dust removal + cooling scrubbing tower" or "gravity dust removal + cyclone separation + wet dust removal" is used to perform preliminary purification of the top coal gas to meet the requirements of deep treatment. The specific indicators are: dust content <2mg / Nm³, chloride content ≤20ppm, and temperature reduced to below 40℃.

[0019] Pressure regulation: The pressure of the purified top coal gas is stably increased to 0.5-1.5 MPa to meet the conditions of the decarbonization and upgrading process.

[0020] Decarbonization and upgrading: Pressure swing adsorption (PSA) separation technology is used to separate CO2 from the top coal gas, dividing it into decarbonized gas and CO2-rich desorbed gas. The main components of the decarbonized gas are CO and H2, and the CO2 volume content is reduced to ≤2.0%, with a CO recovery rate of ≥90%. The pressure drop of the entire decarbonization system is controlled within ≤50 kPa to reduce energy consumption.

[0021] Residual pressure energy recovery: Using a turbine-type residual pressure energy recovery device 5, the pressure of the high-pressure decarburization gas is reduced from 0.5-1.45MPa to 0.4-0.6MPa, which is the pressure required by the blast furnace injection system, while recovering its pressure energy and improving the overall energy efficiency of the system; (2) Desorption gas diversion: The CO2-rich desorption gas generated in the decarbonization and upgrading process is distributed; through the flow regulating valve and the control system, the desorption gas is dynamically divided into the first part of desorption gas and the second part of desorption gas; the flow rate of the first part of desorption gas is precisely adjusted according to the fuel ratio of the blast furnace in real time and the overall reducing agent demand of the system. Its design processing capacity is determined according to the extreme low fuel ratio condition of the blast furnace to ensure sufficient supply of reducing gas. (3) Preparation of reducing gas: The CO2 in the first desorbed gas is converted into high-value reducing gas; the process is as follows: Desorption gas pressure regulation and desulfurization: The pressure of the first desorption gas is adjusted to 0.5~1.0MPa and deep desulfurization treatment is carried out to ensure that the sulfur content entering the subsequent unit is ≤1ppm, thus protecting the catalyst; CO2 electrocatalytic conversion: The CO2 electrocatalytic conversion unit 10 is powered by renewable energy. Under mild operating conditions (temperature 70~120℃, pressure 0.5~1.0MPa), it efficiently converts CO2 and H2O into syngas, mainly composed of CO and H2, through electrolysis. The single-pass CO2 conversion rate is ≥80%, and the volume ratio of CO to H2 in the outlet syngas can be flexibly controlled within the ideal range of 0.5:1 to 1:1 by adjusting the electrolysis parameters. The CO2 electrocatalytic conversion unit 10 is equipped with cathode and anode gas purification facilities (15, 16) to ensure that the free water content in the produced syngas and by-product oxygen is ≤10mg / Nm³. Syngas upgrading treatment: To further improve the quality of reducing gas, the syngas produced by electrocatalytic conversion is upgraded and decarbonized; two process routes are adopted: Process Route 1: CO2 thermocatalytic conversion is adopted, using fuel gas combustion to provide a heat source to further convert the residual CO2 in the syngas into CO, ensuring that the CO2 volume content in the final reduced gas is <5.0% and the CO2 conversion rate is ≥55%; Process Route 2: Pressure Swing Adsorption (PSA) is used for decarbonization and upgrading to directly remove CO2 from the syngas, resulting in a CO2 content of <2.0% in the produced reducing gas, while ensuring a CO recovery rate of ≥90%. After the syngas is upgraded, the final product is a reducing gas with CO and H2 as the main components and a low CO2 volume content, as well as a third part of desorption gas.

[0022] (4) Mixing and heating of pulverized coal gas: The decarbonized gas produced by the top coal gas circulation treatment is mixed with the reducing gas produced by the preparation in a certain proportion; the total volume content of CO+H2 in the mixed coal gas is ≥90%, and the volume content of CO2 is <3.0%. Subsequently, the mixed coal gas is sent to the pulverized coal gas mixing and heating unit (i.e., pulverized coal gas heater 6) (using the fuel gas produced by the system as a heat source) and heated to a high temperature of 1200℃~1300℃, and then injected into the blast furnace through the injection system as a chemical reducing agent and part of the heat source; (5) Oxygen-enriched injection: High-purity oxygen produced as a byproduct of the CO2 electrocatalytic conversion process is mixed with oxygen-enriched or pure oxygen provided by the external oxygen generation device 24 to form oxygen-enriched gas with an oxygen volume concentration ≥90%. This gas is then injected into the furnace through an oxygen-enriched injection unit (such as a blast furnace tuyeres) to maintain the theoretical combustion temperature of the blast furnace hearth and ensure stable and smooth furnace operation. (6) Fuel gas preparation: The third part of desorbed gas obtained from the syngas upgrading process (when using the pressure adsorption decarbonization and upgrading process route 2), the second part of desorbed gas separated from the desorbed gas, and the surplus top coal gas that does not participate in the circulation in the system are mixed and stored.

[0023] The second part of the desorbed gas, separated from the desorbed gas diversion, is mixed and stored with the surplus top coal gas that does not participate in the circulation within the system, and its calorific value may be adjusted to form fuel gas for heating within the system. This fuel gas is transported to the CO2 thermocatalytic conversion device 11 (if used) of the pulverized coal gas mixing and heating unit (i.e., pulverized coal gas heater 6) and / or the reducing gas preparation unit as a process heat source, realizing the efficient utilization and complete absorption of low-grade energy within the system.

[0024] The beneficial effects of this invention are as follows: The system is based on the actual situation of the steel industry, fully leveraging its process industry characteristics. This system can collaboratively resolve the structural contradiction between deep decarbonization of blast furnaces and system energy consumption and operational stability. Its core lies in introducing renewable energy-driven electrolysis technology to convert the desorbed gas generated after top gas decarbonization into high-quality reducing gas, thereby effectively compensating for the bottleneck of insufficient reducing gas in the blast furnace itself. Based on this, the system constructs a cross-process gas collaborative utilization network, breaking through the gas source limitations of a single blast furnace implementing top gas recirculation technology. This not only achieves efficient purification, recycling, and low-carbon smelting of blast furnace gas, but also provides a technically feasible and economically reasonable innovative path for steel enterprises to integrate green energy and promote the low-carbon transformation of blast furnace ironmaking processes. Through innovative system integration and optimized design, this solution has achieved significant progress in multiple core dimensions such as energy efficiency, emission reduction, reliability, and economy, specifically reflected in the following aspects: (1) Achieving self-sufficiency in reducing gas, breaking through external dependence and total quantity limitations. This invention treats CO2 in top coal gas as a resource and efficiently converts it into high-quality reducing gas through green electricity-driven electrocatalytic technology. This not only turns emissions into treasure and realizes the "open source" of reducing gas within the system, but also fundamentally breaks through the constraints of traditional technology on ultra-low fuel ratio operation caused by insufficient total amount of reducing gas in top coal gas. The system can obtain sufficient reducing agent without relying on external gas sources, significantly improving the independence and applicability of the technology.

[0025] (2) Constructing an internal energy closed loop to ensure system fuel self-balancing. Addressing the challenge of reduced blast furnace gas production under ultra-low fuel ratios, this invention mixes the diverted desorbed gas with surplus gas to form a stable internal fuel gas, exclusively for use by the gas-fired heaters within the system. This design achieves the recycling of low-grade energy, constructs an energy self-balancing system, and completely eliminates dependence on additional fuel gas sources, making it particularly suitable for production scenarios with limited gas resources.

[0026] (3) Synergistic green electricity consumption and deep decarbonization to lead the transformation of green smelting. This invention converts green electricity into storable chemical energy (reducing gas), which not only provides flexible load for the power grid, but also injects "zero carbon" attributes into the blast furnace process, promoting process decarbonization from the source. This deep synergy between "green electricity consumption" and "carbon recycling" can reduce carbon emissions by more than 50% throughout the entire life cycle.

[0027] (4) Enhance system intelligence and operational flexibility. Through dynamic adjustment of desorbed gas diversion and electrocatalytic conversion, the system can flexibly adjust the output and composition (H2 / CO ratio) of reducing gas according to the green power supply status and blast furnace operating conditions, so as to achieve precise matching of gas production, energy consumption and smelting demand, and ensure the stable and efficient operation of the blast furnace under ultra-low fuel ratio conditions.

[0028] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 A schematic diagram of the process flow of the ultra-low fuel ratio blast furnace smelting system (using CO2 thermocatalytic conversion) provided in Example 1; Figure 2 A schematic diagram of the process flow of the ultra-low fuel ratio blast furnace smelting system (using pressure swing adsorption decarburization and upgrading) provided in Example 2; Figure reference numerals: 1-Coarse dust removal device, 2-Cooling and deep purification device, 3-Top gas pressure regulating device, 4-Top gas decarbonization and upgrading device, 5-Turbine residual pressure energy recovery device, 6-Pulsed gas heating furnace, 7-Desorbed gas diversion device, 8-Desorbed gas pressure regulating device, 9-Desorbed gas desulfurization and purification device, 10-CO2 electrocatalytic conversion device, 11-CO2 thermocatalytic conversion device, 12-Syngas decarbonization and upgrading device, 13-Electrocatalytic reactor, 14-Electrolyte circulation facility, 15-Cathode gas purification facility, 16-Anode gas purification facility, 17-Integrated power supply facility, 18-Syngas preheating facility, 19-Syngas heating furnace facility, 20-Thermocatalytic conversion reactor, 21-Reducing gas purification facility, 22-Fuel gas preparation unit, 23-Reducing gas storage device, 24-Oxygen production device. Detailed Implementation

[0030] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0031] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0032] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0033] Please see Figures 1-2 This invention provides an ultra-low fuel ratio blast furnace smelting system based on the coupling of top gas circulation and CO2 electrocatalytic conversion. Around the blast furnace body, an integrated system for efficient material and energy circulation is constructed, which mainly includes the following six core parts: top gas circulation treatment unit, desorbed gas diversion device 7, reducing gas preparation unit, injected gas mixing and heating unit 22, oxygen-enriched injection unit and fuel gas preparation unit.

[0034] 1) Top gas recirculation processing unit The top gas recirculation treatment unit is responsible for purifying, separating, and recovering energy from the top gas discharged from the blast furnace. Its process flow includes: Coarse dust removal and cooling purification: A combination of processes such as "gravity dust removal + dry dust removal + cooling scrubbing tower" or "gravity dust removal + cyclone separation + wet dust removal" is used to perform preliminary purification of the top coal gas to meet the requirements of deep treatment. The specific indicators are: dust content <2mg / Nm³, chloride content ≤20ppm, and temperature reduced to below 40℃.

[0035] Pressure regulation: The pressure of the purified top coal gas is stably increased to 0.5-1.5 MPa to meet the conditions of the decarbonization and upgrading process.

[0036] Decarbonization and upgrading: Pressure swing adsorption (PSA) separation technology is used to separate CO2 from the top coal gas. This process produces two gases: one is decarbonized gas, whose main components are CO and H2, with the CO2 volume content reduced to ≤2.0% and CO recovery rate ≥90%; the other is desorbed gas rich in CO2. The pressure drop of the decarbonization system is controlled within ≤50 kPa to reduce energy consumption.

[0037] Residual pressure energy recovery: By using a turbine-type residual pressure energy recovery device, the pressure of the high-pressure decarburization gas is reduced from 0.5-1.45MPa to the pressure required by the blast furnace injection system of 0.4-0.6MPa, while recovering its pressure energy, thereby improving the overall energy efficiency of the system.

[0038] 2) Desorption gas splitting unit Connected to the top gas recirculation treatment unit, it distributes the CO2-rich desorbed gas generated during the decarbonization and upgrading process. Through flow regulating valves and a control system, the desorbed gas is dynamically divided into a first part and a second part. The flow rate of the first part of the desorbed gas is precisely adjusted based on the real-time fuel ratio of the blast furnace and the overall reducing agent requirements of the system. Its design processing capacity is determined according to the blast furnace's extreme low fuel ratio operating conditions, ensuring a sufficient supply of reducing gas.

[0039] 3) Reducing gas preparation unit The reducing gas preparation unit includes, sequentially arranged along the process flow, a desorbed gas pressure regulating device 8, a desorbed gas desulfurization and purification device 9, a CO2 electrocatalytic conversion device 10, and a syngas upgrading device. The CO2 electrocatalytic conversion device 10 includes, sequentially arranged, an integrated power supply facility 17, an electrolyte circulation facility 14, an electrocatalytic reactor 13, a cathode gas purification facility 15, and an anode gas purification facility 16. The syngas upgrading device includes a CO2 thermal catalytic conversion device 11 or a syngas decarbonization and upgrading device 12.

[0040] The reducing gas preparation unit converts CO2 into high-value reducing gas. The process flow is as follows: Desorption gas pressure regulation and desulfurization: The pressure of the first part of the desorption gas is adjusted to 0.5~1.0MPa and deep desulfurization treatment is carried out to ensure that the sulfur content entering the subsequent unit is ≤1ppm, thus protecting the catalyst.

[0041] CO2 electrocatalytic conversion: This unit is powered by renewable energy and operates under mild conditions (temperature 70~120℃, pressure 0.5~1.0MPa) to efficiently convert CO2 and H2O into syngas, primarily composed of CO and H2, via electrolysis. The single-pass CO2 conversion rate is ≥80%, and the volume ratio of CO to H2 in the outlet syngas can be flexibly controlled within the ideal range of 0.5:1 to 1:1 by adjusting the electrolysis parameters. The unit is equipped with cathode and anode gas purification facilities to ensure that the free water content in the produced syngas and byproduct oxygen is ≤10mg / Nm³.

[0042] Syngas upgrading treatment: To further improve the quality of reducing gas, the syngas produced by electrocatalytic conversion is upgraded and decarbonized. Two process routes can be adopted: Process Route 1 (see) Figure 1 ): CO2 thermocatalytic conversion is adopted, which uses the heat source provided by fuel gas combustion to further convert CO2 in syngas into CO, ensuring that the CO2 volume content in the final reduced gas is <5.0% and the CO2 conversion rate is ≥55%.

[0043] Process Route 2 (see) Figure 2 ): Pressure swing adsorption is used for decarbonization and upgrading, which directly removes CO2 from the syngas, so that the CO2 volume content in the produced reducing gas is <2.0%, while ensuring a CO recovery rate of ≥90%.

[0044] After the syngas is upgraded, it is finally obtained as a reducing gas with CO and H2 as the main components and a low CO2 volume content.

[0045] 4) Pulverized gas mixing and heating unit The decarbonized gas produced by the top gas recirculation treatment unit is mixed with the reducing gas produced during preparation in a certain proportion. In the mixed gas, the total volume content of CO+H2 is ≥90%, and the volume content of CO2 is ≤3.0%. Subsequently, the mixed gas is sent to the pulverized gas mixing and heating unit (such as pulverized gas heater 6) (using the system's own fuel gas as a heat source) and heated to a high temperature of 1200℃~1300℃. Then, it is injected into the blast furnace through a special pipeline as the main chemical reducing agent and part of the heat source.

[0046] 5) Oxygen-enriched jet cleaning unit The high-purity oxygen produced as a byproduct of the CO2 electrocatalytic conversion process is mixed with oxygen-enriched or pure oxygen provided by the external oxygen generation device 24 to form oxygen-enriched gas with an oxygen volume concentration of ≥90%. This gas is then injected into the blast furnace through the tuyeres to maintain the theoretical combustion temperature of the blast furnace hearth and ensure stable and smooth furnace operation.

[0047] 6) Fuel gas preparation unit The fuel gas preparation unit 22 includes a mixer, a gas holder, and a fuel gas pipeline, which is used to mix, store, and adjust the calorific value of the second part of desorbed gas with the surplus top gas, and deliver it to the heating furnace in the injected gas mixing and heating unit and / or the CO2 thermocatalytic conversion device 11 in the reducing gas preparation unit as a heat source.

[0048] The second portion of desorbed gas, separated by the desorbed gas diversion device 7, is mixed and stored with the surplus top coal gas that is not involved in the circulation within the system. Its calorific value may be adjusted to form fuel gas for internal heating within the system. This fuel gas is then transported to the mixed coal gas heater and / or the CO2 thermocatalytic conversion unit 11 (if used) for reducing gas production as a process heat source, achieving efficient utilization and complete absorption of low-grade energy within the system.

[0049] Specifically, in this invention, the coarse dust removal, cooling and deep purification of top coal gas adopts gravity dust removal + dry dust removal + cooling scrubbing tower or gravity dust removal + cyclone separation + wet dust removal; the coal gas pressure regulation adopts the conventional structure in the existing technology, which usually includes a compressor host, drive motor, gas-liquid separator, cooler, lubrication oil station, dry gas sealing system, etc., so this invention will not elaborate further.

[0050] Example 1: Please see Figure 1 This embodiment provides an ultra-low fuel ratio blast furnace smelting system using CO2 thermocatalytic conversion. The ultra-low fuel ratio blast furnace top gas processed in the following implementation case of this invention is used as an example.

[0051] A certain 1280m 3 The volume fraction of ultra-low fuel ratio blast furnace top gas is shown in Table 1 below: Table 1. Volume fraction of blast furnace top gas

[0052] Other process parameters for top gas: pressure 0.22 MPa, temperature 130℃, gas flow rate 251050 Nm³. 3 / h, calorific value 7196.5kJ / m 3 The amount of top gas participating in the cycle is 207,000 Nm³. 3 / h.

[0053] The smelting system includes a dust removal and purification device 1, a cooling and deep purification device 2, a top gas pressure regulating device 3, a top gas decarbonization and upgrading device 4, a turbine residual pressure energy recovery device 5, a pulverized coal gas heating furnace 6, a desorbed gas diversion device 7, a desorbed gas pressure regulating device 8, a desorbed gas desulfurization and purification device 9, a CO2 electrocatalytic conversion device 10, a CO2 thermal catalytic conversion device 11, a fuel gas preparation unit 22, and a reducing gas storage device 23. The CO2 electrocatalytic conversion device 10 includes an electrocatalytic reactor 13, an electrolyte circulation facility 14, a cathode gas purification facility 15, an anode gas purification facility 16, and an integrated power supply facility 17. The CO2 thermal catalytic conversion device 11 includes a syngas preheating facility 18, a syngas heating furnace facility 19, a thermal catalytic conversion reactor 20, and a reducing gas purification facility 21.

[0054] The smelting process steps of this system are as follows: Step 1: Top gas circulation treatment The top gas recirculation treatment system is responsible for purifying, separating, and recovering energy from the top gas discharged from the blast furnace. Its process flow includes the following steps: Coarse dust removal and cooling purification: A combination of processes such as "gravity dust removal + dry dust removal + cooling scrubbing tower" or "gravity dust removal + cyclone separation + wet dust removal" is used to perform preliminary purification of the top coal gas to meet the requirements of deep treatment. The specific indicators are: dust content <2mg / Nm³, chloride content ≤20ppm, and temperature reduced to below 40℃.

[0055] Pressure regulation: The pressure of the purified top coal gas is stably increased to 0.5-1.5 MPa to meet the conditions of the decarbonization and upgrading process.

[0056] Decarbonization and upgrading: Pressure swing adsorption (PSA) separation technology is used to separate CO2 from the top coal gas. This process produces two gases: one is decarbonized gas, whose main components are CO and H2, with the CO2 volume content reduced to ≤2.0% and CO recovery rate ≥90%; the other is desorbed gas rich in CO2. The pressure drop of the entire decarbonization system is controlled within ≤50 kPa to reduce energy consumption.

[0057] Residual pressure energy recovery: By using a turbine-type residual pressure energy recovery device, the pressure of the high-pressure decarburization gas is reduced from 0.5-1.45MPa to the pressure required by the blast furnace injection system of 0.4-0.6MPa, while recovering its pressure energy, thereby improving the overall energy efficiency of the system.

[0058] Step 2, desorption gas diversion Connected to the top gas recirculation treatment unit, it distributes the CO2-rich desorbed gas generated during the decarbonization and upgrading process. Through flow regulating valves and a control system, the desorbed gas is dynamically divided into a first part and a second part. The flow rate of the first part of the desorbed gas is precisely adjusted based on the real-time fuel ratio of the blast furnace and the overall reducing agent requirements of the system. Its design processing capacity is determined according to the blast furnace's extreme low fuel ratio operating conditions, ensuring a sufficient supply of reducing gas.

[0059] Step 3: Preparation of reducing gas The reducing gas preparation process is responsible for converting CO2 into high-value reducing gases. The process is as follows: Desorption gas pressure regulation and desulfurization: The pressure of the first part of the desorption gas is adjusted to 0.5~1.0MPa and deep desulfurization treatment is carried out to ensure that the sulfur content entering the subsequent unit is ≤1ppm, thus protecting the catalyst.

[0060] CO2 electrocatalytic conversion: This unit is powered by renewable energy and operates under mild conditions (temperature 70~120℃, pressure 0.5~1.0MPa) to efficiently convert CO2 and H2O into syngas, primarily composed of CO and H2, via electrolysis. The single-pass CO2 conversion rate is ≥80%, and the volume ratio of CO to H2 in the outlet syngas can be flexibly controlled within the ideal range of 0.5:1 to 1:1 by adjusting the electrolysis parameters. The unit is equipped with cathode and anode gas purification facilities to ensure that the free water content in the produced syngas and byproduct oxygen is ≤10mg / Nm³.

[0061] Syngas upgrading treatment: To further improve the quality of the reducing gas, the syngas produced by electrocatalytic conversion is upgraded and decarbonized. CO2 thermocatalytic conversion is employed, utilizing fuel gas combustion as a heat source to further convert residual CO2 in the syngas into CO, ensuring that the CO2 volume content in the final reducing gas is <5.0% and the CO2 conversion rate is ≥55%. After upgrading treatment, the syngas ultimately yields a reducing gas with CO and H2 as its main components and a low CO2 volume content.

[0062] Step 4: Mixing and heating of injected coal gas The decarbonized gas produced from the top gas recirculation process is mixed with the high-quality reducing gas produced in the preparation process in a certain proportion. The total volume content of CO and H2 in the mixed gas is ≥90%, and the volume content of CO2 is ≤3.0%. Subsequently, the mixed gas is sent to a heating furnace (using the system's own fuel gas as a heat source) and heated to a high temperature of 1250°C. Then, it is injected into the blast furnace through a pulverized gas injection system as a chemical reducing agent and part of the heat source.

[0063] Step 5: Oxygen-enriched jet blowing The high-purity oxygen produced as a byproduct of the CO2 electrocatalytic conversion process is mixed with oxygen-enriched or pure oxygen provided by the external oxygen generation device 24 to form oxygen-enriched gas with an oxygen volume concentration of ≥90%. This gas is then injected into the blast furnace through the tuyeres to maintain the theoretical combustion temperature of the blast furnace hearth and ensure stable and smooth furnace operation.

[0064] Step 6: Fuel Gas Preparation The second portion of desorbed gas, separated from the desorbed gas stream, is mixed and stored with surplus top coal gas that is not involved in the system's circulation, and its calorific value may be adjusted to form fuel gas for internal heating. This fuel gas is then transported to the pulverized coal gas heater 6 and the CO2 thermocatalytic conversion heater as a process heat source, achieving efficient utilization and complete absorption of low-grade energy within the system.

[0065] The goal of this system and method is to reduce fossil energy consumption in blast furnaces by more than 50% compared to conventional blast furnace processes. Furthermore, by adjusting the amount of reducing gas, it is possible not only to achieve complete self-sufficiency in coal gas, but also to fully utilize surplus low-calorific-value coal gas.

[0066] The results of the example are as follows: (1) The composition of the decarbonized gas is shown in Table 2 below: Table 2 Composition of decarbonized gas

[0067] The flow rate is 113561 Nm 3 / h, calorific value 11882kJ / m 3 The pressure is 0.35~0.45MPa and the temperature is 40℃.

[0068] (2) The composition of the desorbed gas is shown in Table 3 below: Table 3 Desorption Gas Composition

[0069] The total desorption flow rate is 79500 Nm. 3 / h, calorific value 1665kJ / m 3 The pressure is 0.015 MPa and the temperature is 40℃.

[0070] (3) The composition of the synthesis gas is shown in Table 4 below: Table 4 Composition of Syngas

[0071] Syngas flow rate is 49286 Nm 3 / h, pressure is 0.50~0.55MPa, temperature is 40℃.

[0072] (4) The composition of the reducing gas is shown in Table 5 below: Table 5 Composition of reducing gas

[0073] The reducing gas flow rate is 46644 Nm. 3 / h, calorific value 11155kJ / m 3 The pressure is 0.35~0.45MPa and the temperature is 40℃.

[0074] (5) The composition of the fuel gas is shown in Table 6 below: Table 6 Fuel Gas Composition

[0075] The fuel gas flow rate is 94053 Nm 3 / h, calorific value 4226kJ / m 3 The pressure is 0.015 MPa and the temperature is 40℃.

[0076] (6) The composition of the mixed pulverized gas is shown in Table 7 below: Table 7 Composition of Mixed Injected Gas

[0077] The mixed pulverized gas flow rate is 160209 Nm³. 3 / h, calorific value 11670kJ / m 3 The pressure is 0.35~0.45MPa and the temperature is 1250℃.

[0078] Based on the above parameters, the ultra-low fuel ratio blast furnace consumes 265 kg / t iron coke, has a top gas recirculation rate of 82.5%, and requires 46,644 Nm³ of supplementary reducing gas. 3 / h, the pulverized coal gas heating furnace and the syngas heating furnace in the CO2 thermocatalytic conversion process require 93,000 Nm³ of fuel gas. 3 / h.

[0079] Example 2: Please see Figure 2 This embodiment provides an ultra-low fuel ratio blast furnace smelting system that uses pressure swing adsorption for decarbonization and upgrading. The ultra-low fuel ratio blast furnace top gas processed in the following implementation case of this invention is used as an example.

[0080] A certain 1280m 3 The volume fraction of ultra-low fuel ratio blast furnace top gas is shown in Table 8 below: Table 8 Volume fraction of blast furnace top gas

[0081] Other process parameters for top gas: pressure 0.22 MPa, temperature 130℃, gas flow rate 246396 Nm³. 3 / h, calorific value 7056.6kJ / m 3 The amount of top gas participating in the cycle is 209,000 Nm³. 3 / h.

[0082] The smelting system includes: 1. Dust removal and purification; 2. Cooling and deep purification; 3. Top gas pressure regulation; 4. Top gas decarbonization and upgrading; 5. Turbine residual pressure energy recovery; 6. Injected gas heating furnace; 7. Desorbed gas diversion; 8. Desorbed gas pressure regulation; 9. Desorbed gas desulfurization and purification; 10. CO2 electrocatalytic conversion unit; 12. Syngas decarbonization and upgrading unit; 22. Fuel gas preparation unit; and 23. Reducing gas storage unit. The CO2 electrocatalytic conversion unit includes: 13. Electrocatalytic reactor; 14. Electrolyte circulation facility; 15. Cathode gas purification facility; 16. Anode gas purification facility; and 17. Integrated power supply facility.

[0083] The smelting process steps of this system are as follows: Step 1: Top gas circulation treatment The top gas recirculation treatment system is responsible for purifying, separating, and recovering energy from the top gas discharged from the blast furnace. Its process flow includes the following steps: Coarse dust removal and cooling purification: A combination of processes such as "gravity dust removal + dry dust removal + cooling scrubbing tower" or "gravity dust removal + cyclone separation + wet dust removal" is used to perform preliminary purification of the top coal gas to meet the requirements of deep treatment. The specific indicators are: dust content <2mg / Nm³, chloride content ≤20ppm, and temperature reduced to below 40℃.

[0084] Pressure regulation: The pressure of the purified top coal gas is stably increased to 0.5-1.5 MPa to meet the conditions of the decarbonization and upgrading process.

[0085] Decarbonization and upgrading: Pressure swing adsorption (PSA) separation technology is used to separate CO2 from the top coal gas. This process produces two gases: one is decarbonized gas, whose main components are CO and H2, with the CO2 volume content reduced to ≤2.0% and CO recovery rate ≥90%; the other is desorbed gas rich in CO2. The pressure drop of the entire decarbonization system is controlled within ≤50 kPa to reduce energy consumption.

[0086] Residual pressure energy recovery: By using a turbine-type residual pressure energy recovery device, the pressure of the high-pressure decarburization gas is reduced from 0.5-1.45MPa to the pressure required by the blast furnace injection system of 0.4-0.6MPa, while recovering its pressure energy, thereby improving the overall energy efficiency of the system.

[0087] Step 2, desorption gas diversion Connected to the top gas recirculation system, it distributes the CO2-rich desorbed gas generated during the decarbonization and upgrading process. Through flow control valves and a control system, the desorbed gas is dynamically divided into a first part and a second part. The flow rate of the first part of the desorbed gas is precisely adjusted based on the real-time fuel ratio of the blast furnace and the overall reducing agent requirements of the system. Its design processing capacity is determined according to the blast furnace's extreme low fuel ratio operating conditions, ensuring a sufficient supply of reducing gas.

[0088] Step 3: Preparation of reducing gas The reducing gas preparation process is responsible for converting CO2 into high-value reducing gases. The process is as follows: Desorption gas pressure regulation and desulfurization: The pressure of the first part of the desorption gas is adjusted to 0.5~1.0MPa and deep desulfurization treatment is carried out to ensure that the sulfur content entering the subsequent unit is ≤1ppm, thus protecting the catalyst.

[0089] CO2 electrocatalytic conversion: This unit is powered by renewable energy and operates under mild conditions (temperature 70~120℃, pressure 0.5~1.0MPa) to efficiently convert CO2 and H2O into syngas, primarily composed of CO and H2, via electrolysis. The single-pass CO2 conversion rate is ≥80%, and the volume ratio of CO to H2 in the outlet syngas can be flexibly controlled within the ideal range of 0.5:1 to 1:1 by adjusting the electrolysis parameters. The unit is equipped with cathode and anode gas purification facilities to ensure that the free water content in the produced syngas and byproduct oxygen is ≤10mg / Nm³.

[0090] Syngas Upgrading Treatment: To further improve the quality of the reducing gas, the syngas produced by electrocatalytic conversion is upgraded and decarbonized. Pressure Swing Adsorption (PSA) is used for decarbonization and upgrading, directly adsorbing and removing CO2, ensuring that the CO2 volume content in the produced reducing gas is <2.0%, while maintaining a CO recovery rate ≥90%. After upgrading treatment, the syngas ultimately yields a reducing gas with CO and H2 as the main components and a low CO2 volume content, as well as a third-part desorbed gas.

[0091] Step 4: Mixing and heating of injected coal gas The decarbonized gas produced from the top gas recirculation process is mixed with the reducing gas produced during preparation in a certain proportion. The total volume content of CO+H2 in the mixed gas is ≥90%, and the volume content of CO2 is ≤3.0%. Subsequently, the mixed gas is sent to a pulverized coal gas heater (using the system's own fuel gas as a heat source) and heated to a high temperature of 1250℃. Then, it is injected into the blast furnace through the injection system as a chemical reducing agent and part of the heat source.

[0092] Step 5: Oxygen-enriched jet blowing The high-purity oxygen produced as a byproduct of the CO2 electrocatalytic conversion process is mixed with oxygen-enriched or pure oxygen provided by the external oxygen generation device 24 to form oxygen-enriched gas with an oxygen volume concentration of ≥90%. This gas is then injected into the blast furnace through the tuyeres to maintain the theoretical combustion temperature of the blast furnace hearth and ensure stable and smooth furnace operation.

[0093] Step 6: Fuel Gas Preparation The third desorbed gas obtained from syngas upgrading, the second desorbed gas separated from the desorbed gas diversion, the surplus top coal gas that does not participate in the system's circulation, and the desorbed gas discharged from syngas upgrading and decarbonization are mixed, stored, and may undergo calorific value adjustment to form fuel gas for internal system heating. This fuel gas is transported to a pulverized coal gas heater as a process heat source, achieving efficient utilization and complete absorption of low-grade energy within the system.

[0094] The goal of this system and method is to reduce the consumption of solid fossil energy in blast furnaces by more than 50% compared with conventional blast furnace processes. Furthermore, by adjusting the amount of reducing gas, it is possible not only to achieve complete self-sufficiency in coal gas, but also to fully utilize surplus low-calorific-value coal gas.

[0095] The results of the example are as follows: 1. The composition of the decarbonized gas is shown in Table 9 below: Table 9 Composition of decarbonized gas

[0096] The flow rate is 113540 Nm 3 / h, calorific value 11802kJ / m 3 The pressure is 0.35~0.45MPa and the temperature is 40℃.

[0097] 2. The composition of the desorbed gas is shown in Table 10 below: Table 10 Desorbed Gas Composition

[0098] The total desorption flow rate is 78590 Nm. 3 / h, calorific value 1616kJ / m 3 The pressure is 0.015 MPa and the temperature is 40℃.

[0099] 3. The composition of the synthesis gas is shown in Table 11 below: Table 11 Composition of Syngas

[0100] Syngas flow rate is 52373 Nm 3 / h, pressure is 0.50~0.55MPa, temperature is 40℃.

[0101] 4. The composition of the reducing gas is shown in Table 12 below: Table 12 Composition of reducing gas

[0102] The reducing gas flow rate is 43857 Nm. 3 / h, calorific value 11669kJ / m 3 The pressure is 0.35~0.45MPa and the temperature is 40℃.

[0103] 5. The composition of the fuel gas is shown in Table 13 below: Table 13 Fuel Gas Composition

[0104] The total flow rate of fuel gas is 93178 Nm. 3 / h, calorific value 4029kJ / m 3 The pressure is 0.015 MPa and the temperature is 40℃.

[0105] 6. The composition of the mixed pulverized gas is shown in Table 14 below: Table 14 Composition of Mixed Injected Gas

[0106] The total flow rate of the mixed pulverized gas was 157397 Nm³. 3 / h, calorific value 11765kJ / m 3 The pressure is 0.35~0.45MPa and the temperature is 1250℃.

[0107] Based on the above parameters, the coke consumption ratio of the ultra-low fuel ratio blast furnace is 265 kg / t iron, the top gas circulation ratio is 84.8%, and the supplementary reducing gas is 43857 Nm³. 3 / h, the pulverized coal gas heating furnace consumes 91700 Nm³ of fuel gas. 3 / h.

[0108] In summary, the effects of this embodiment are as follows: 1) Achieving a closed-loop carbon resource system and self-sufficiency in reducing gas: CO2 captured in top coal gas is efficiently converted into high-value reducing gas (CO / H2) using green electrocatalytic technology, turning waste into treasure. This not only realizes the recycling of carbon elements within the system, but more importantly, it breaks through the fundamental bottleneck of insufficient reducing gas in traditional top coal gas, enabling the system to achieve self-sufficiency in reducing agents without the need for external gas supply.

[0109] 2) Constructing an integrated and efficient energy balance system: Utilizing oxygen produced by electrocatalytic conversion for high-oxygen injection to enhance the smelting intensity within the furnace; using surplus coal gas within the system as an internal heat source to achieve cascaded and closed-loop utilization of low-grade energy. This solves the problem of heat source shortage under ultra-low fuel ratios and forms a highly efficient and integrated internal energy balance system.

[0110] 3) Significantly reduced fossil fuel consumption and carbon emissions: By implementing a process combination of "stopping pulverized coal injection, significantly reducing the coke ratio (to below 270 kg / t), and injecting circulating reducing gas," dependence on fossil fuels is directly and substantially reduced. Fossil fuel consumption and carbon emissions can be reduced by more than 50% compared to conventional processes.

[0111] 4) Improve smelting efficiency and process stability: The mixed gas injected into the blast furnace has extremely high reducing potential (CO+H2 volume content ≥90%), which significantly enhances the indirect reduction process of the furnace charge, thereby improving smelting efficiency. Combined with high oxygen enrichment, it provides a key guarantee for the long-term stable operation of the blast furnace under ultra-low fuel ratio.

[0112] 5) Collaborative green energy consumption leads to deep decarbonization transformation: Converting green energy into stable and storable chemical energy not only provides high-quality flexible load for the power grid, but also injects the "zero carbon" attribute into the blast furnace process from the source, realizing deep synergy between "green energy consumption" and "carbon recycling", which is a transformative solution that reduces carbon emissions by more than 50% throughout the entire life cycle.

[0113] 6) Possesses flexible intelligent control and full resource utilization capabilities: Through the dynamic adjustment of desorbed gas diversion and electrocatalytic devices, the system can flexibly adjust the reducing gas output and composition (H2 / CO ratio) according to the green electricity supply and blast furnace operating conditions, achieving precise matching between gas production, energy consumption, and smelting needs. Simultaneously, it ensures complete self-sufficiency of the system's process gas and complete utilization of surplus low-calorific-value gas.

[0114] It should be noted that the processes of the systems in Examples 1 and 2 belong to the same concept, and the specific methods of operation of each unit and system have been described in detail in the process examples. Therefore, they will not be listed separately here. In practical applications, the ultra-low fuel ratio blast furnace smelting system and method based on the coupling of top gas circulation and CO2 electrocatalytic conversion provided in the above implementation cases can be assigned to different systems and equipment as needed to complete all or part of the functions described above. This is not a limitation here.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A blast furnace smelting system with ultra-low fuel ratio based on top gas circulation and CO2 electrocatalytic conversion coupling, comprising a blast furnace, characterized in that, Also includes: The top gas circulation treatment unit is used to sequentially treat the top gas generated by the blast furnace by coarse dust removal, cooling and deep purification, pressure regulation, decarbonization and upgrading, and turbine residual pressure energy recovery, to obtain decarbonized gas and CO2-rich desorbed gas. A desorption gas diversion device, connected to the top coal gas circulation processing unit, is used to divide the desorption gas flow into a first part of desorption gas and a second part of desorption gas. The reducing gas preparation unit is connected to the desorbed gas diversion device and is used to desulfurize and purify the first part of the desorbed gas and perform CO2 electrocatalytic conversion to generate syngas and produce oxygen as a byproduct. The syngas is then upgraded to obtain reducing gas. The pulverized coal gas mixing and heating unit is connected to the top coal gas circulation treatment unit and the reducing gas preparation unit, respectively, and is used to mix the decarbonized gas and the reducing gas and then inject them into the blast furnace after heating. The oxygen-enriched injection unit, connected to the reducing gas preparation unit, is used to mix the oxygen produced by CO2 electrocatalytic conversion with the oxygen-enriched or pure oxygen provided by the external oxygen production device and then inject it into the blast furnace tuyeres. The fuel gas preparation unit is connected to the desorbed gas diversion device and the surplus top gas pipeline, and is used to mix the second part of the desorbed gas with the surplus top gas that has not participated in the circulation to form fuel gas for heating in the system. The smelting system operates the blast furnace at an ultra-low fuel ratio by stopping the injection of pulverized coal and reducing the amount of coke, and is supplemented with high oxygen-enriched or pure oxygen blast to maintain stable furnace conditions.

2. The ultra-low fuel ratio blast furnace smelting system based on top gas circulation and CO2 electrocatalytic conversion coupling according to claim 1, characterized in that, The coarse dust removal, cooling and deep purification methods are a combination of "gravity dust removal + dry dust removal + cooling scrubbing tower" or "gravity dust removal + cyclone separation + wet dust removal".

3. The ultra-low fuel ratio blast furnace smelting system based on top gas circulation and CO2 electrocatalytic conversion coupling according to claim 1, characterized in that, The top gas circulation treatment unit includes a coarse dust removal device, a cooling and deep purification device, a top gas pressure regulating device, a top gas decarbonization and upgrading device, and a turbine residual pressure energy recovery device connected in sequence.

4. The ultra-low fuel ratio blast furnace smelting system based on top gas circulation and CO2 electrocatalytic conversion coupling according to claim 1, characterized in that, The flow rate of the first part of the desorbed gas is dynamically adjusted according to the actual fuel ratio of the blast furnace and the overall fuel demand of the system; the designed processing capacity is determined according to the blast furnace's extreme low fuel ratio operating condition.

5. The ultra-low fuel ratio blast furnace smelting system based on top gas circulation and CO2 electrocatalytic conversion coupling according to claim 1, characterized in that, The reducing gas preparation unit includes a desorbed gas pressure regulating device, a desorbed gas desulfurization and purification device, a CO2 electrocatalytic conversion device, and a syngas upgrading device arranged in sequence.

6. The ultra-low fuel ratio blast furnace smelting system based on top gas circulation and CO2 electrocatalytic conversion coupling according to claim 5, characterized in that, The CO2 electrocatalytic conversion device includes an integrated power supply facility, an electrolyte circulation facility, an electrocatalytic reactor, a cathode gas purification facility, and an anode gas purification facility arranged in sequence. The integrated power supply facility is powered by renewable energy; the electrocatalytic reactor is used to dynamically adjust the volume ratio of CO to H2 in the syngas; the cathode gas purification facility and the anode gas purification facility are used to control the free water content in the syngas and by-product oxygen at the outlet of the CO2 electrocatalytic conversion device, respectively.

7. The ultra-low fuel ratio blast furnace smelting system based on top gas circulation and CO2 electrocatalytic conversion coupling according to claim 5, characterized in that, The syngas upgrading device includes a CO2 thermocatalytic conversion device or a syngas decarbonization upgrading device; the CO2 thermocatalytic conversion device uses the fuel gas provided by the fuel gas preparation unit as a process heat source to further convert the residual CO2 in the syngas into CO; the syngas decarbonization upgrading device is used to directly remove CO2 from the syngas to obtain reducing gas and a third part of desorbed gas.

8. The ultra-low fuel ratio blast furnace smelting system based on top gas circulation and CO2 electrocatalytic conversion coupling according to claim 1, characterized in that, The fuel gas preparation unit includes a mixer, a gas holder, and fuel gas pipelines, used to mix, store, and adjust the calorific value of the second part of desorbed gas with the surplus top gas, and deliver it to the heating furnace in the injected gas mixing and heating unit and / or the CO2 thermocatalytic conversion device in the reducing gas preparation unit as a heat source.

9. The ultra-low fuel ratio blast furnace smelting system based on the coupling of top gas circulation and CO2 electrocatalytic conversion according to any one of claims 1 to 8, characterized in that, The smelting method of this system specifically includes: (1) Top gas recirculation treatment: The top gas discharged from the blast furnace will be purified, separated and its energy recovered; the process flow includes the following steps: Coarse dust removal and cooling purification: adopt a combination of "gravity dust removal + dry dust removal + cooling scrubbing tower" or "gravity dust removal + cyclone separation + wet dust removal" processes; Pressure regulation: Stabilize and increase the pressure of the purified top coal gas to meet the conditions of the decarbonization and upgrading process; Decarbonization and upgrading: Pressure swing adsorption separation technology is used to separate CO2 from top coal gas, which is divided into decarbonized gas and CO2-rich desorbed gas; Residual pressure energy recovery: Using a turbine-type residual pressure energy recovery device, the pressure of the high-pressure decarburization gas is reduced to the pressure required by the blast furnace injection system, while recovering its pressure energy. (2) Desorption gas diversion: The CO2-rich desorption gas generated in the decarbonization and upgrading process is distributed; through the flow regulating valve and the control system, the desorption gas is dynamically divided into the first part of desorption gas and the second part of desorption gas; the flow rate of the first part of desorption gas is precisely adjusted according to the fuel ratio of the blast furnace in real time and the overall reducing agent demand of the system. Its design processing capacity is determined according to the extreme low fuel ratio condition of the blast furnace to ensure sufficient supply of reducing gas. (3) Preparation of reducing gas: The CO2 in the first desorbed gas is converted into high-value reducing gas; the process is as follows: Desorption gas pressure regulation and desulfurization: The pressure of the first desorption gas is adjusted to 0.5~1.0MPa and deep desulfurization treatment is carried out to ensure that the sulfur content entering the subsequent unit is ≤1ppm, thus protecting the catalyst; CO2 electrocatalytic conversion: The CO2 electrocatalytic conversion unit is powered by renewable energy electricity. Under mild operating conditions, it efficiently converts CO2 and H2O into syngas, which is mainly composed of CO and H2, through electrolysis. By adjusting the electrolysis parameters, the volume ratio of CO to H2 in the outlet syngas can be flexibly controlled within the ideal range of 0.5:1 to 1:

1. The CO2 electrocatalytic conversion unit is equipped with cathode and anode gas purification facilities to ensure that the free water content in the produced syngas and by-product oxygen is ≤10mg / Nm³. Syngas upgrading treatment: upgrading and decarbonizing syngas produced by electrocatalytic conversion; (4) Mixing and heating of pulverized coal gas: The decarbonized gas produced by the top coal gas circulation treatment is mixed with the reducing gas produced in the preparation in a certain proportion; then, the mixed coal gas is sent to the pulverized coal gas mixing and heating unit and heated to a high temperature, and then injected into the blast furnace through the injection system as a chemical reducing agent and part of the heat source. (5) Oxygen-enriched injection: The high-purity oxygen produced as a byproduct of the CO2 electrocatalytic conversion process is mixed with the oxygen-enriched or pure oxygen provided by the external oxygen production device to form an oxygen-enriched gas with an oxygen volume concentration of ≥90%. This gas is then injected into the furnace through the oxygen-enriched injection unit to maintain the theoretical combustion temperature of the blast furnace hearth and ensure stable and smooth furnace operation. (6) Fuel gas preparation: The second part of desorbed gas separated from the desorbed gas is mixed with the surplus top coal gas that does not participate in the circulation in the system, stored, and the calorific value is adjusted to form fuel gas for heating in the system. The fuel gas is transported to the CO2 thermocatalytic conversion device of the pulverized coal gas mixing and heating unit and / or the reducing gas preparation unit as a process heat source to realize the efficient utilization and complete consumption of low-grade energy in the system.

10. The ultra-low fuel ratio blast furnace smelting system based on top gas circulation and CO2 electrocatalytic conversion coupling according to claim 9, characterized in that, The syngas upgrading process employs two process routes: Process Route 1: CO2 thermocatalytic conversion is adopted, using fuel gas combustion to provide a heat source, and the residual CO2 in the syngas is further converted into CO to obtain reduced gas; Process route 2: Pressure swing adsorption is used for decarbonization and upgrading to directly remove CO2 from the syngas, yielding reducing gas and a third part of desorbed gas; When using process route two, during the fuel gas preparation process, the third part of desorbed gas obtained from the syngas upgrading treatment, the second part of desorbed gas separated from the desorbed gas diversion, and the surplus top coal gas that does not participate in the circulation within the system are mixed and stored.

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