Gas-based shaft furnace ironmaking system and method based on CO2 and steam cyclic reforming

Abstract

This invention discloses a gas-based vertical shaft furnace ironmaking system and method based on CO2 and steam cyclic reforming. The system includes a gas-based vertical shaft furnace (1), a CO2 / steam high-temperature gasification reforming furnace (2), a scrubbing tower (4), a condenser (5), a gas-liquid separator (6), a circulating fan (7), a gas mixer (11), a liquid slag discharge device (12), and a wet gas bypass / non-dehydration circulating branch (14). In this invention, the top gas generated by the gas-based vertical shaft furnace is purified and reintroduced into the CO2 / steam high-temperature gasification reforming furnace, so that CO2 and H2O in the top gas undergo a high-temperature gasification reforming reaction with carbon-containing raw materials, realizing the regeneration conversion of CO2 to CO and H2O to CO and H2. This changes the existing process where CO2 and H2O mainly rely on removal or direct emission, and improves the overall carbon and hydrogen resource recycling efficiency of the system.

Description

Technical Field

[0001] This invention relates to the field of ironmaking technology, and in particular to a gas-based vertical shaft furnace ironmaking system and method based on CO2 and steam circulation reforming. Background Technology

[0002] The steel industry is a crucial foundation of the national economy, but it is also a major consumer of energy and emitters of carbon dioxide. The traditional blast furnace-converter long-process ironmaking process uses coke as the primary reducing agent and heat source, generating significant carbon dioxide emissions during iron ore reduction. Statistics show that carbon emissions from the ironmaking process account for over 70% of the steel industry's total carbon emissions. Therefore, developing low-carbon, green, and efficient new ironmaking processes has become an important development direction for the metallurgical industry.

[0003] Currently, gas-based direct reduction ironmaking technology is gradually attracting widespread attention due to its advantages such as low carbon emissions, short process, and high energy efficiency. Existing gas-based direct reduction processes such as MIDREX and HYL / Energiron mainly use natural gas reformed gas or hydrogen-rich reducing gas as reducing agents to complete the reduction reaction of iron oxides in a vertical shaft furnace.

[0004] While existing gas-based direct reduction and coal gasification ironmaking processes can reduce carbon emissions from traditional blast furnace processes to some extent, they still generally suffer from problems such as heavy reliance on high-quality energy sources like natural gas, insufficient utilization of carbon dioxide and H2O resources in the furnace top gas, high energy consumption in the reducing gas preparation process, and low efficiency in utilizing high-temperature sensible heat. Specifically, existing carbon dioxide gasification or steam gasification technologies typically suffer from insufficient reaction temperature, limited endothermic reaction enhancement capabilities, low carbon conversion efficiency, insufficient H2 / CO ratio adjustment capabilities, and low system thermal efficiency. Furthermore, existing coal gasification and vertical shaft furnace reduction processes often operate relatively independently, requiring high-temperature gasification products to undergo cooling, purification, and reheating before entering the vertical shaft furnace, resulting in significant system energy losses. In addition, in the existing process, most of the carbon dioxide and H2O in the furnace top gas are only removed or partially recycled. A highly efficient recycling system with "carbon dioxide / H2O conversion - CO-H2 reducing gas regeneration - vertical furnace utilization" as the core and necessary external transmission / venting as an auxiliary is not yet formed. Therefore, there is still much room for improvement in terms of efficient utilization of carbon resources, control of reducing gas composition, system decarbonization and overall energy efficiency improvement. Summary of the Invention

[0005] The purpose of this invention is to provide a gas-based vertical shaft furnace ironmaking system and method based on CO2 and steam cyclic reforming, so as to at least partially solve the above-mentioned problems of the prior art.

[0006] One aspect of the present invention provides a gas-based vertical shaft furnace ironmaking system based on CO2 and steam circulating reforming, comprising: a gas-based vertical shaft furnace 1, a carbon dioxide / steam high-temperature gasification reformer 2, a scrubbing tower 4, a condenser 5, a gas-liquid separator 6, a circulating fan 7, a gas mixer 11, a liquid slag discharge device 12, and a wet gas bypass / non-dehydration circulating branch 14, wherein... The top outlet of the gas-based vertical shaft furnace 1 outputs top gas, and the bottom outlet outputs direct reduced iron; The scrubbing tower 4 is connected to the top outlet of the gas-based vertical shaft furnace 1 to remove dust and perform preliminary cooling treatment on the received furnace top gas. The first outlet of the scrubbing tower 4 is connected to the condenser 5, allowing the gas to enter the condenser 5 for cooling treatment. The cooled gas enters the gas-liquid separator 6 to separate the gas from the condensate. The separated gas is then transported to the carbon dioxide / steam high-temperature gasification reformer 2 by the circulating fan 7. The second outlet of the scrubbing tower 4 is connected to the wet gas bypass / non-dehydration circulation branch 14, which is connected to the carbon dioxide / steam high-temperature gasification reformer 2 to send the scrubbed gas into the carbon dioxide / steam high-temperature gasification reformer 2. The carbon dioxide / steam high-temperature gasification reformer 2 includes: a top gas inlet, which is connected to the circulating fan 7 and the wet gas bypass / non-dehydration circulating branch 14 respectively; a carbon-containing raw material inlet, which is used to receive carbon-containing raw materials; a gas outlet, which is used to output high-temperature gas to the gas mixer 11; and a bottom slag discharge device 12, which is used to discharge the molten ash generated during the gasification process. The gas mixer 11 includes: a gas inlet connected to the gas outlet of the carbon dioxide / steam high-temperature gasification reformer 2; a gas supply inlet connected to a gas supply device to receive the input reducing gas in order to adjust the ratio and / or temperature of carbon monoxide and hydrogen in the gas; and a gas outlet connected to the reducing gas inlet of the gas-based vertical shaft furnace 1.

[0007] Preferably, the system also includes a plasma torch 3 for providing a high-temperature heat source to the carbon dioxide / water vapor high-temperature gasification reformer 2.

[0008] Preferably, the outlet temperature of the plasma torch 3 is 3000℃, the in-furnace gasification and reforming reaction temperature of the carbon dioxide / water vapor high-temperature gasification and reforming furnace 2 is 1300℃, and the working pressure is 1.0MPa.

[0009] Preferably, the system also includes a fresh carbon dioxide replenishment branch 13, which is connected to the gas mixer 11 to input carbon dioxide into the gas mixer 11 or the gas output pipe of the gas mixer 11.

[0010] Preferably, the system further includes a dust removal device, a desulfurization device, and a temperature control device connected in sequence. The inlet of the dust removal device is connected to the gas outlet of the carbon dioxide / water vapor high-temperature gasification reformer 2, and the outlet of the temperature control device is connected to the gas mixer 11.

[0011] Preferably, the system also includes a pulverized coal silo 8, a metering feeder 9, and a pulverized coal spray gun 10. The pulverized coal spray gun 10 is connected to the carbon-containing raw material inlet of the carbon dioxide / steam high-temperature gasification reformer 2. The pulverized coal spray gun 10 is also connected to the pulverized coal silo 8 and the metering feeder 9 to receive the carbon-containing raw materials provided by the pulverized coal silo 8 and the metering feeder 9.

[0012] Preferably, the system further includes a first controller for controlling the opening and closing of the first outlet and / or the second outlet of the washing tower 4.

[0013] Preferably, the system also includes valves, flow meters, thermometers, pressure detection devices, online gas composition analyzers, and a second controller installed on each gas pipeline. The second controller adjusts the opening and closing degree of the valves on each gas pipeline based on the data from the flow meters, thermometers, pressure detection devices, and online gas composition analyzers on each gas pipeline.

[0014] Another aspect of the present invention provides a gas-based shaft furnace ironmaking method based on CO2 and steam cyclic reforming, applied to the gas-based shaft furnace ironmaking system provided in the above aspects and any preferred embodiments, comprising: The top gas output from the gas-based vertical furnace 1 is washed using a scrubbing tower 4. The first part of the furnace top gas after washing is sequentially fed into the condenser 5 and the gas-liquid separator 6, and the gas output from the gas-liquid separator 6 is transported to the carbon dioxide / water vapor high temperature gasification reformer 2 by the circulating fan 7. The second part of the top gas after washing is transported to the carbon dioxide / water vapor high-temperature gasification reformer 2 through the wet gas bypass / non-dehydration circulation branch 14. The carbon dioxide / steam high-temperature gasification reformer 2 receives the first part of the top gas and / or the second part of the top gas after washing treatment, and receives carbon-containing raw materials. The carbon-containing raw materials are used to react with the first part of the top gas and / or the second part of the top gas at high temperature to obtain high-temperature gas. The ratio and / or temperature of carbon monoxide and hydrogen in the gas are adjusted by the gas mixer 11 and then delivered to the gas-based vertical furnace 1.

[0015] Compared with the prior art, the present invention has at least the following advantages: This invention purifies the top gas generated by a gas-based vertical shaft furnace and reintroduces it into a CO2 / steam high-temperature gasification reformer. This allows the CO2 and H2O in the top gas to undergo a high-temperature gasification reforming reaction with the carbon-containing raw materials, achieving the regeneration and conversion of CO2 to CO and H2O to CO and H2. This changes the existing technical route where CO2 and H2O mainly rely on removal or direct emission, and improves the overall carbon and hydrogen resource recycling efficiency of the system. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a gas-based vertical shaft furnace ironmaking system based on CO2 and steam cyclic reforming, provided for an embodiment of the present invention.

[0017] Figure 2 A schematic diagram of the process for a gas-based vertical shaft furnace ironmaking method based on CO2 and steam circulating gasification reforming, provided in an embodiment of the present invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate to understand the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a product or device comprising a series of units is not necessarily limited to those explicitly listed, but may include other units not explicitly listed or inherent to such product or device.

[0020] In this invention, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation.

[0021] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain situations to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0022] Furthermore, the terms "installation," "setup," "equipped with," "connection," "joint," and "socket" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] Example 1 This invention provides a gas-based vertical shaft furnace ironmaking system based on CO2 and steam cyclic reforming. Figure 1 A schematic diagram of the system is shown. (Reference) Figure 1 As shown, the system includes: a gas-based vertical shaft furnace 1, a carbon dioxide / steam high-temperature gasification reformer 2, a scrubbing tower 4, a condenser 5, a gas-liquid separator 6, a circulating fan 7, a gas mixer 11, a liquid ash discharge device 12, and a wet gas bypass / non-dehydration circulating branch 14, wherein... The gas-based shaft furnace 1 outputs top gas from its top outlet and direct reduced iron (DRI) from its bottom outlet. The gas-based shaft furnace 1 is used for the gas-based direct reduction of iron oxide charge. Iron-containing charge is added from the top of the gas-based shaft furnace 1 and moves downwards under gravity; reducing gas is introduced through the lower sidewall of the gas-based shaft furnace 1 and forms a counter-current contact with the descending charge. The iron-containing charge can be oxide pellets, lump ore, sinter, or a mixture thereof; the reducing gas mainly includes reducing gases such as CO and H2. Inside the furnace, iron oxides undergo a step-by-step reduction reaction, ultimately producing metallized DRI. The reduced DRI is discharged from the bottom of the gas-based shaft furnace 1, while the top gas is exported from the top. The top gas contains CO, CO2, H2, H2O, and a small amount of dust impurities, with CO2 and H2O being the main target components for recycling.

[0025] The scrubbing tower 4 is connected to the top outlet of the gas-based vertical shaft furnace 1, and performs dust removal and preliminary cooling treatment on the received furnace top gas. The first outlet of the scrubbing tower 4 is connected to the condenser 5, allowing the gas to enter the condenser 5 for cooling. The cooled gas then enters the gas-liquid separator 6 to separate the gas from the condensate. The separated gas is then transported to the carbon dioxide / steam high-temperature gasification reformer 2 by the circulating fan 7. The second outlet of the scrubbing tower 4 is connected to the wet gas bypass / non-dehydration circulation branch 14, which is connected to the carbon dioxide / steam high-temperature gasification reformer 2, sending the scrubbed gas into the carbon dioxide / steam high-temperature gasification reformer 2. In a preferred embodiment, the system further includes a first controller for controlling the opening and closing of the first and / or second outlets of the scrubbing tower 4.

[0026] The scrubbing tower 4 performs dust removal and preliminary cooling treatment on the top gas from the gas-based vertical shaft furnace 1. By contacting the gas with the spray liquid, dust and some impurities in the gas are removed. Subsequently, two circulation routes can be selected according to the operating objectives: one is the condensation and dehydration circulation route, in which the gas enters the condenser 5 for further cooling, causing the water vapor in the gas to condense and precipitate. The cooled gas enters the gas-liquid separator 6 to separate the gas from the condensate. The purified gas after separation is pressurized and transported to the CO2 / water vapor high-temperature gasification reformer 2 under the action of the circulating fan 7; the other is the wet gas non-dehydration circulation route, in which the top gas, after dust removal and necessary cooling, is directly or indirectly sent to the CO2 / water vapor high-temperature gasification reformer 2 through the wet gas bypass / non-dehydration circulation branch 14, so that the water vapor in it is retained and participates in the subsequent gasification and reforming. The condensation and dehydration circulation route is beneficial for reducing the temperature rating, material grade, and equipment cost of the circulating fan or compressor; the wet gas non-dehydration circulation route is beneficial for improving the water vapor recycling rate, improving the H2 / CO ratio, and reducing the external high H2 gas supplementation.

[0027] The CO2 / steam high-temperature gasification reformer 2 includes: a top gas inlet connected to a circulating fan 7 and a wet gas bypass / non-dehydration circulating branch 14; a carbon-containing raw material inlet for receiving carbon-containing raw materials; a gas outlet for outputting high-temperature gas to a gas mixer 11; and a bottom slag discharge device 12 for discharging molten ash generated during the gasification process. In one embodiment, the system further includes a pulverized coal silo 8, a metering feeder 9, and a pulverized coal spray gun 10. The pulverized coal spray gun 10 is connected to the carbon-containing raw material inlet of the CO2 / steam high-temperature gasification reformer 2, and is also connected to the pulverized coal silo 8 and the metering feeder 9 to receive carbon-containing raw materials provided by the pulverized coal silo 8 and the metering feeder 9. The CO2 / steam high-temperature gasification reformer 2 is a high-temperature gasification reforming reaction device used to realize the high-temperature gasification reforming reaction between CO2, H2O in the circulating gas and carbon-containing raw materials. Circulating gas is introduced from the side or bottom of the CO2 / steam high-temperature gasification reformer 2. Carbonaceous raw materials are stored in the pulverized coal silo 8, quantitatively conveyed by the metering feeder 9, and then injected into the CO2 / steam high-temperature gasification reformer 2 through the pulverized coal injection gun 10. The carbonaceous raw materials can be pulverized coal, coke powder, semi-coke powder, biomass charcoal powder, or other carbonaceous solid fuels. In one embodiment, a liquid slag discharge device 12 is installed at the bottom of the CO2 / steam high-temperature gasification reformer 2 to discharge the molten ash generated during the gasification process. The liquid slag discharge device 12 can adopt a water-sealed slag outlet, a continuous slag discharge trough (low pressure below 0.5 MPa), or an intermittent slag discharge structure (high pressure below 4.0 MPa) to maintain stable operation within the furnace and slag flowability.

[0028] The gas mixer 11 includes: a gas inlet connected to the gas outlet of the CO2 / steam high-temperature gasification reformer 2; a gas replenishment inlet connected to a gas replenishment device to receive the input reducing gas to adjust the ratio and / or temperature of carbon monoxide and hydrogen in the gas; and a gas outlet connected to the reducing gas inlet of the gas-based vertical shaft furnace 1. The high-temperature CO-H2 rich gas generated by the CO2 / steam high-temperature gasification reformer (2) can be discharged from the side of the furnace body and, if necessary, enter the gas mixer 11 after high-temperature dust removal, desulfurization, and temperature adjustment. To adjust the reducing gas temperature and atmosphere composition, supplementary reducing gas can be introduced into the gas mixer 11 through the gas replenishment device. This supplementary reducing gas is preferably unreformed gas, but can also be natural gas reformed gas, hydrogen-rich gas, or other gases containing reducing components. In the condensation and dehydration circulation route, supplemental reducing gas can be used to increase the H2 / CO ratio and improve the smooth operation of the vertical furnace; in the wet gas non-dehydration circulation route, the circulating H2O reacts with carbon in the reformer to generate H2, which can reduce or eliminate the need for high H2 supplemental gas.

[0029] In a preferred embodiment, the system further includes a plasma torch 3 for providing a high-temperature heat source to the CO2 / steam high-temperature gasification reforming furnace 2. Preferably, the outlet temperature of the plasma torch 3 is 3000°C, the in-furnace gasification reforming reaction temperature of the CO2 / steam high-temperature gasification reforming furnace 2 is 1300°C, and the operating pressure is 1.0 MPa. The plasma torch 3 can be installed on the top or side wall of the CO2 / steam high-temperature gasification reforming furnace 2 to provide a high-temperature heat source to the furnace. When the plasma torch 3 is in operation, it generates a high-temperature plasma jet. The outlet temperature of the plasma torch can be 2000–10000℃, preferably about 3000℃. The gasification and reforming reaction temperature inside the furnace can be controlled at 1000–1800℃, preferably about 1300℃, and the working pressure can be 0.1–4.0 MPa(G), for example 1.0 MPa(G), thereby enhancing the endothermic gasification and reforming reactions between CO2 and carbon, and between H2O and carbon: CO2 + C → 2CO, H2O + C → CO + H2. Since the above reactions are endothermic, the high-temperature heat provided by the plasma torch 3 can significantly improve the reaction rate and carbon conversion efficiency, while promoting ash melting and achieving liquid slag discharge. The high-temperature coal gas generated in the CO2 / steam high-temperature gasification reformer 2 mainly contains CO and H2, and may also contain unconverted CO2, H2O and a small amount of inert gas. Its reducing power depends on the CO content, H2 content, CO2 / CO ratio and H2O / H2 ratio. It can be used as the reducing gas source of the gas-based vertical shaft furnace 1 after mixing with supplemental reducing gas, temperature adjustment, fresh CO2 adjustment or partial external delivery.

[0030] In a preferred embodiment, the system further includes a fresh carbon dioxide replenishment branch 13, connected to the gas mixer 11, to input carbon dioxide into the gas mixer 11 or its gas output pipeline. For example, fresh CO2 can be added to the gas mixer 11 or its outlet reducing gas pipeline via the fresh CO2 replenishment branch 13 to adjust the CO / CO2 ratio, H2 / CO ratio, and reduction potential of the mixed reducing gas, so as to meet the target gas utilization rate, temperature, and metallization rate requirements of the vertical shaft furnace. After the high-temperature CO-H2 rich gas, the replenishing reducing gas, and the optional fresh CO2 are uniformly mixed in the gas mixer 11, they are transported to the lower reducing gas inlet of the gas-based vertical shaft furnace 1 via the gas pipeline. When the amount of high-temperature gas exceeds the demand of the vertical shaft furnace or when it is necessary to maintain the material balance of the system, a portion of CO-rich or CO-H2 gas can be output through the external syngas / venting pressure regulating branch.

[0031] The temperature of the mixed reducing gas entering the gas-based shaft furnace 1 is preferably controlled within the range of 700–1000°C, more preferably around 850°C, to improve the reduction rate of iron oxides and reduce external heating energy consumption. The furnace top gas generated after the reduction reaction re-enters the scrubbing tower 4, and is either dehydrated by the condenser 5 and gas-liquid separator 6 and then circulated, or circulated after retaining water vapor through the wet gas bypass / non-dehydrated circulation branch 14, and then returned to the CO2 / water vapor high-temperature gasification reformer 2 under the action of the circulating fan 7 or hot gas compressor, thus forming a circulation process with "furnace top gas circulation—CO2 / H2O high-temperature conversion—CO-H2 reducing gas regeneration—shaft furnace utilization" as the main body; at the same time, the dynamic balance of system pressure, inert components and impurities such as sulfur / chlorine can be maintained by the linkage regulation of fresh CO2 replenishment, replenishment of reducing gas, external syngas delivery or small-stream venting branches, avoiding the accumulation of impurities caused by completely closed-loop circulation, and allowing the shaft furnace gas utilization rate to be adjusted within the range of about 10%–30% according to the production target.

[0032] In a preferred embodiment, the system further includes a dust removal device, a desulfurization device, and a temperature control device connected in sequence. The inlet of the dust removal device is connected to the gas outlet of the carbon dioxide / water vapor high-temperature gasification reformer 2, and the outlet of the temperature control device is connected to the gas mixer 11.

[0033] In a preferred embodiment, the system further includes valves, flow meters, thermometers, pressure detection devices, online gas composition analyzers, and a second controller installed on each gas pipeline. The second controller adjusts the opening and closing degree of the valves on each gas pipeline based on data from the flow meters, thermometers, pressure detection devices, and online gas composition analyzers. The valves, flow meters, thermometers, pressure detection devices, and online gas composition analyzers installed on each gas pipeline are used to achieve system operating parameter adjustment and automatic control. The circulating fan (7) or hot gas compressor can be used to regulate the circulating gas flow rate and system pressure; the metering feeder 9 can be used to control the amount of carbon-containing raw material injected in order to regulate the intensity of CO2 / water vapor gasification reforming reaction and the composition of reducing gas; the fresh CO2 supplementary gas branch 13, the wet gas bypass / non-dehydration circulating branch 14, the supplementary reducing gas branch and the external syngas / venting pressure regulating branch can be closed-loop regulated according to the composition of the vertical furnace inlet gas, the composition of the furnace top gas, the gas utilization rate, the H2 / CO ratio, the water vapor content, the furnace temperature and the system pressure.

[0034] In a typical pilot-scale operation of condensation dehydration-reducing gas replenishment, purified circulating coal gas enters the CO2 / steam high-temperature gasification reformer (2) at a rate of approximately 1000 Nm³ / h and approximately 40°C. Its volumetric composition is approximately 51.6% CO, 18.8% H2, 29.0% CO2, 0% H2O, and 0.6% N2. The carbon-containing raw material can be bituminous coal with a moisture content of approximately 2%, with an injection rate of approximately 0.32 t / h, and is supplemented by coal gas at a rate of approximately 5 Nm³ / h and approximately 80°C. The CO2 / steam high-temperature gasification reformer (2) can operate at a gasification temperature of approximately 0.3 MPa (G) and approximately 1700°C, with a plasma torch outlet temperature of approximately 2912°C, a gasification reaction heat absorption of approximately 1.8 MW, and a bottom liquid slag discharge rate of approximately 19.3 kg / h.

[0035] Under the above operating conditions, the outlet flow rate of high-temperature CO-H2 rich gas at the CO2 / steam high-temperature gasification reformer (2) is approximately 1585 Nm³ / h, and the temperature is approximately 1700℃. Its volume composition is approximately 74.6% CO, approximately 24.7% H2, approximately 0.1% CO2, approximately 0.1% H2O, and approximately 0.5% N2. The high-temperature CO-H2 rich gas is mixed with approximately 1729 Nm³ / h of unreformed gas at approximately 40℃. The volume composition of the unreformed gas is approximately 65% ​​CO, approximately 25% H2, approximately 6% CO2, approximately 3% H2O, and approximately 1% N2. This results in approximately 3314 Nm³ / h of mixed reducing gas entering the vertical furnace at approximately 850℃, with a volume composition of approximately 69.7% CO, approximately 24.8% H2, approximately 3.1% CO2, approximately 1.6% H2O, and approximately 0.8% N2.

[0036] The gas-based vertical shaft furnace (1) can operate at a gas utilization rate of about 10% under this condition. The top gas is about 3314 Nm³ / h at about 450°C, and its volume composition is about 62.1% CO, 22.5% H2, 10.8% CO2, 3.8% H2O, and 0.8% N2. After washing, condensing and gas-liquid separation, the top gas can produce about 101 kg / h of condensate, which is sent back to the CO2 / steam high-temperature gasification reformer (2) by the circulating fan (7). When the gas production of the system exceeds the demand of the vertical shaft furnace, about 2388 Nm³ / h of CO / CO-H2 rich synthesis gas with a calorific value of about 10.7 MJ / Nm³ can be sent out or sent to the flare via the vent branch to maintain the material balance of the system.

[0037] In another optional operating mode, fresh CO2 supplementation can be reduced or eliminated, increasing the gas utilization rate of the vertical shaft furnace to approximately 30%, and the external syngas supply, unconverted gas supply, pulverized coal injection, and condensate supply can be adjusted accordingly. Furthermore, in the wet gas non-dehydration circulation mode, the wet gas bypass / non-dehydration circulation branch (14) can be opened, allowing water vapor in the top gas to enter the CO2 / water vapor high-temperature gasification reformer (2) without condensation removal, and generate H2 through the H2O+C→CO+H2 reaction, thereby increasing the H2 / CO ratio of the circulating reducing gas and reducing or eliminating external high-H2 gas supplementation. This mode can be configured with a high-temperature resistant circulating fan, hot gas compressor, or corresponding heat preservation and temperature control facilities according to the top gas temperature and moisture content. The above parameters are only examples of pilot-scale operating conditions; those skilled in the art can adjust them within an equivalent range based on the vertical shaft furnace scale, raw material grade, target metallization rate, and gas composition.

[0038] Compared with the prior art, the present invention introduces CO2 and H2O from the top gas of the gas-based vertical shaft furnace (1) into the CO2 / steam high-temperature gasification reforming furnace (2) for high-temperature conversion, thereby realizing the resource recycling of CO2 to CO and H2O to CO and H2. At the same time, the plasma torch (3) provides a high-temperature heat source to improve the reaction efficiency and carbon conversion rate of CO2 / steam gasification reforming. Through the condensation dehydration-reducing gas supplementation route, the wet gas non-dehydration circulation route, the fresh CO2 gas adjustment and the external syngas / venting pressure adjustment, the high-temperature reducing gas and the gas-based direct reduction process are directly coupled and the furnace reduction atmosphere is precisely adjusted. This reduces the overall energy consumption of the system, improves the energy utilization efficiency and carbon resource recycling rate, and realizes low-carbon and high-efficiency gas-based direct reduction ironmaking.

[0039] Example 2 Based on the same technical concept as in Example 1, this embodiment of the invention provides a gas-based vertical shaft furnace ironmaking method based on CO2 and steam cyclic reforming, applicable to the gas-based vertical shaft furnace ironmaking system provided in Example 1 and any of its optional embodiments. Figure 2 A flowchart illustrating this method is shown, as follows: Figure 2 As shown, the method includes: Step 201: Use the scrubbing tower 4 to scrub the top gas output from the gas-based vertical furnace 1. Step 202: The first part of the furnace top gas after washing is sequentially input into the condenser 5 and the gas-liquid separator 6, and the gas output from the gas-liquid separator 6 is transported to the carbon dioxide / water vapor high temperature gasification reformer 2 through the circulating fan 7. Step 203: The second part of the top gas after washing is transported to the carbon dioxide / water vapor high temperature gasification reformer 2 through the wet gas bypass / non-dehydration circulation branch 14. Step 204: The first part of the top gas and / or the second part of the top gas after washing are received through the carbon dioxide / steam high-temperature gasification reformer 2, and carbon-containing raw materials are received. High-temperature gas is obtained by reacting the carbon-containing raw materials with the first part of the top gas and / or the second part of the top gas through high-temperature gasification reforming. Step 205: Adjust the ratio and / or temperature of carbon monoxide and hydrogen in the gas through the gas mixer 11, and then deliver it to the gas-based vertical furnace 1.

[0040] Compared with the prior art, the present invention has at least the following advantages: This invention purifies the top gas generated by a gas-based vertical shaft furnace and reintroduces it into a CO2 / steam high-temperature gasification reformer. This allows the CO2 and H2O in the top gas to undergo a high-temperature gasification reforming reaction with the carbon-containing raw materials, achieving the regeneration and conversion of CO2 to CO and H2O to CO and H2. This changes the existing technical route where CO2 and H2O mainly rely on removal or direct emission, and improves the overall carbon and hydrogen resource recycling efficiency of the system.

[0041] This invention addresses the problems of low CO2 and H2O utilization, inflexible H2 / CO ratio adjustment, high system energy consumption, and insufficient thermal efficiency in existing gas-based direct reduction and coal gasification ironmaking processes. It proposes a novel gas-based vertical shaft furnace low-carbon ironmaking process based on CO2 / steam circulating gasification reforming: (1) A circulating ironmaking process with “top gas circulation - CO2 / H2O high-temperature conversion - CO-H2 reducing gas regeneration - vertical furnace utilization” as the main body was proposed.

[0042] This invention purifies the top gas generated by the gas-based vertical shaft furnace (1) and reintroduces it into the CO2 / steam high-temperature gasification reformer (2), so that the CO2 and H2O in the top gas undergo a high-temperature gasification reforming reaction with the carbon-containing raw materials, thereby realizing the regeneration and conversion of CO2 to CO and H2O to CO and H2. This changes the existing technical route in which CO2 and H2O mainly rely on removal or direct emission, and improves the overall carbon and hydrogen resource recycling efficiency of the system.

[0043] (2) A CO2 / steam enhanced gasification reforming technology for producing reduced gas based on plasma high-temperature heating was proposed.

[0044] This invention utilizes a plasma torch (3) to form a high-temperature reaction zone within a CO2 / steam high-temperature gasification reforming furnace (2), providing a high-temperature heat source for the endothermic gasification reforming reactions between CO2 and carbon, and between steam and carbon. This significantly improves the CO2 / steam gasification reforming reaction rate and carbon conversion efficiency, enhancing the following reaction processes: CO2 + C → 2CO, H2O + C → CO + H2. Compared to traditional combustion heating or conventional gasification methods, this invention achieves higher reaction temperatures, faster reaction kinetics, and higher CO-H2 generation efficiency, while also facilitating ash melting and discharge and stable furnace operation.

[0045] (3) Deep thermal coupling of high-temperature gasification gasification and gas-based vertical furnace direct reduction process was achieved.

[0046] In this invention, the high-temperature CO-rich coal gas generated by the CO2 / steam high-temperature gasification reformer (2) does not need to be cooled significantly. After necessary high-temperature dust removal, desulfurization and temperature regulation, it can be directly sent to the gas-based vertical furnace (1) as a reducing gas. This fully utilizes the sensible heat of the high-temperature coal gas, reduces the energy loss caused by coal gas cooling, heat exchange and reheating in traditional processes, and improves the overall thermal efficiency and energy utilization efficiency of the system.

[0047] (4) A flexible reducing gas preparation route that can switch between condensation and dehydration cycle and wet gas non-dehydration cycle was constructed.

[0048] In this invention, either a condensation-dehydration circulation route or a wet gas non-dehydration circulation route can be selected based on equipment investment, circulating compression temperature level, and target H2 / CO ratio. The condensation-dehydration circulation route can reduce the temperature, material, and cost requirements of the circulating fan or compressor, and adjust the H2 / CO ratio by supplementing unreformed gas, hydrogen-rich gas, etc.; the wet gas non-dehydration circulation route allows H2O in the top gas to enter the CO2 / steam high-temperature gasification reformer (2) to participate in the reaction, reducing or eliminating the external high H2 gas supplementation. By adjusting the pulverized coal injection rate, circulating gas rate, plasma heating power, unreformed gas supplementation rate, fresh CO2 supplementation rate, wet gas bypass flow rate, and external syngas supply rate, flexible control of reducing gas composition, CO / CO2 ratio, H2 / CO ratio, temperature, and heat balance can be achieved.

[0049] (5) Low-carbon ironmaking and syngas co-production have been achieved.

[0050] Based on meeting the reduction requirements of the gas-based vertical furnace (1), this invention can output a portion of CO-rich or CO-H2 syngas according to the system operating conditions, thereby realizing the co-production of ironmaking and syngas, improving the comprehensive energy utilization value of the system, and providing a new technical path for metallurgical-chemical coupling low-carbon processes.

[0051] (6) A new process integration method suitable for low-carbon metallurgy was proposed.

[0052] This invention integrates CO2 recycling, high-temperature gasification, plasma-enhanced heating, and gas-based direct reduction into a new low-carbon ironmaking process characterized by high carbon utilization, high thermal efficiency, and low CO2 emissions, providing a new technical solution for the green and low-carbon transformation of the steel industry.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gas-based vertical shaft furnace ironmaking system based on CO2 and steam cyclic reforming, characterized in that, include: The system includes a gas-based vertical shaft furnace (1), a carbon dioxide / steam high-temperature gasification reformer (2), a scrubbing tower (4), a condenser (5), a gas-liquid separator (6), a circulating fan (7), a gas mixer (11), a liquid slag discharge device (12), and a wet gas bypass / non-dehydration circulating branch (14). The top outlet of the gas-based vertical shaft furnace (1) outputs top gas, and the bottom outlet outputs direct reduced iron; The scrubbing tower (4) is connected to the top outlet of the gas-based vertical shaft furnace (1) to remove dust and perform preliminary cooling treatment on the received furnace top gas; the first outlet of the scrubbing tower (4) is connected to the condenser (5) so that the gas enters the condenser (5) for cooling treatment. The cooled gas enters the gas-liquid separator (6) to separate the gas from the condensate. The separated gas is transported to the carbon dioxide / steam high-temperature gasification reformer (2) under the action of the circulating fan (7); the second outlet of the scrubbing tower (4) is connected to the wet gas bypass / non-dehydration circulation branch (14), which is connected to the carbon dioxide / steam high-temperature gasification reformer (2) to send the scrubbed gas into the carbon dioxide / steam high-temperature gasification reformer (2). The carbon dioxide / steam high-temperature gasification reformer (2) includes: a top gas inlet, which is connected to the circulating fan (7) and the wet gas bypass / non-dehydration circulating branch (14); a carbon-containing raw material inlet, which is used to receive carbon-containing raw materials; a gas outlet, which is used to output high-temperature gas to the gas mixer (11); and a bottom slag discharge device (12), which is used to discharge the molten ash generated during the gasification process. The gas mixer (11) includes: a gas inlet connected to the gas outlet of the carbon dioxide / steam high-temperature gasification reformer (2); a gas supply inlet connected to the gas supply device to receive the input reducing gas in order to adjust the ratio and / or temperature of carbon monoxide and hydrogen in the gas; and a gas outlet connected to the reducing gas inlet of the gas-based vertical shaft furnace (1).

2. The gas-based vertical shaft furnace ironmaking system based on CO2 and steam circulation reforming according to claim 1, characterized in that, It also includes a plasma torch (3) for providing a high-temperature heat source to the carbon dioxide / water vapor high-temperature gasification reformer (2).

3. The gas-based vertical shaft furnace ironmaking system based on CO2 and steam circulation reforming according to claim 2, characterized in that, The outlet temperature of the plasma torch (3) is 3000℃, the in-furnace gasification and reforming reaction temperature of the carbon dioxide / water vapor high-temperature gasification reforming furnace (2) is 1300℃, and the working pressure is 1.0MPa.

4. The gas-based vertical shaft furnace ironmaking system based on CO2 and steam circulation reforming according to claim 1, characterized in that, It also includes a fresh carbon dioxide replenishment branch (13), which is connected to the gas mixer (11) to input carbon dioxide into the gas mixer (11) or the gas output pipe of the gas mixer (11).

5. The gas-based vertical shaft furnace ironmaking system based on CO2 and steam circulation reforming according to claim 1, characterized in that, It also includes a dust removal device, a desulfurization device and a temperature control device connected in sequence. The inlet of the dust removal device is connected to the gas outlet of the carbon dioxide / water vapor high-temperature gasification reformer (2), and the outlet of the temperature control device is connected to the gas mixer (11).

6. The gas-based vertical shaft furnace ironmaking system based on CO2 and steam circulation reforming according to claim 1, characterized in that, It also includes a pulverized coal silo (8), a metering feeder (9), and a pulverized coal spray gun (10). The pulverized coal spray gun (10) is connected to the carbon-containing raw material inlet of the carbon dioxide / steam high-temperature gasification reformer (2). The pulverized coal spray gun (10) is also connected to the pulverized coal silo (8) and the metering feeder (9) to receive the carbon-containing raw materials provided by the pulverized coal silo (8) and the metering feeder (9).

7. The gas-based vertical shaft furnace ironmaking system based on CO2 and steam circulation reforming according to any one of claims 1-6, characterized in that, It also includes a first controller for controlling the opening and closing of the first outlet and / or the second outlet of the scrubbing tower (4).

8. The gas-based vertical shaft furnace ironmaking system based on CO2 and steam circulation reforming according to any one of claims 1-6, characterized in that, It also includes valves, flow meters, thermometers, pressure detection devices, online gas composition analyzers, and a second controller installed on each gas transmission pipeline. The second controller adjusts the opening and closing degree of the valves on each gas transmission pipeline based on the data from the flow meters, thermometers, pressure detection devices, and online gas composition analyzers on each gas transmission pipeline.

9. A gas-based vertical shaft furnace ironmaking method based on CO2 and steam cyclic reforming, applied to a gas-based vertical shaft furnace ironmaking system based on CO2 and steam cyclic reforming according to any one of claims 1-8, characterized in that, include: The top gas output from the gas-based vertical furnace (1) is washed using a scrubbing tower (4); The first part of the furnace top gas after washing is sequentially fed into the condenser (5) and the gas-liquid separator (6), and the gas output from the gas-liquid separator (6) is transported to the carbon dioxide / water vapor high temperature gasification reformer (2) by the circulating fan (7). The second part of the top gas after washing is transported to the carbon dioxide / water vapor high-temperature gasification reformer (2) through the wet gas bypass / non-dehydration circulation branch (14). The first part of the top gas and / or the second part of the top gas after washing are received by the carbon dioxide / steam high-temperature gasification reformer (2), and carbon-containing raw materials are received. High-temperature gas is obtained by reacting the carbon-containing raw materials with the first part of the top gas and / or the second part of the top gas in a high-temperature gasification reforming reaction. The ratio and / or temperature of carbon monoxide and hydrogen in the gas are adjusted by a gas mixer (11) and then conveyed to the gas-based vertical furnace (1).

Images