A recovery and recycling system for shaft furnace hydrogen smelting tail gas and a method thereof

Abstract

This application relates to a recovery and recycling system and method for tail gas from vertical shaft furnace hydrogen smelting. The system includes: a tail gas supply component, comprising a vertical shaft furnace and a scrubbing tower, wherein the top outlet of the vertical shaft furnace is connected to the scrubbing tower; the vertical shaft furnace generates tail gas, and the scrubbing tower purifies the tail gas; a primary gas treatment component, comprising a heater and a pressure regulating station, wherein the heater is connected to both the pressure regulating station and the scrubbing tower; the heater heats a mixture of purified tail gas and the pressure regulating station adjusts the pressure of the heated tail gas; an electrolysis component, connected to the pressure regulating station, electrolyzes the pressure-adjusted tail gas to generate reducing gas; and a secondary gas treatment component, connected to both the electrolysis component and the vertical shaft furnace, adjusts the physicochemical parameters of the reducing gas to obtain a target reducing gas. This application solves the technical problem of the difficulty in effectively utilizing tail gas generated from existing vertical shaft furnace hydrogen smelting.

Description

Technical Field

[0001] This application relates to the cross-technical fields of waste heat utilization in the steel industry, electrolytic hydrogen production, and low-carbon metallurgy, and particularly to a system and method for waste heat-hydrogen-metallurgy-carbon cyclic coupling production. Background Technology

[0002] Vertical shaft furnaces using hydrogen as the primary reducing gas can reduce sponge iron from pellets at metallurgical reaction temperatures far lower than conventional blast furnaces, producing tail gas primarily composed of water vapor (H2O), rather than the CO2 emitted by blast furnaces. Simultaneously, emissions of pollutants such as dust, sulfur dioxide, and nitrogen oxides are also significantly lower than in traditional processes. While hydrogen-based vertical shaft furnace ironmaking requires hydrogen, and the coking process in steel conglomerates generates substantial amounts of hydrogen-rich coke oven tail gas, the hydrogen produced in this manner has a high carbon emission intensity.

[0003] While vertical shaft furnace hydrogen smelting can significantly reduce CO2 emissions, it is currently impossible to obtain large quantities of low-cost hydrogen. Furthermore, the H2O and CO2 in the smelting tail gas, which contain a certain amount of heat, are difficult to utilize effectively and can only be emitted into the atmosphere. Summary of the Invention

[0004] This application provides a recovery and recycling system and method for tail gas from vertical shaft furnace hydrogen smelting, in order to solve the technical problem that the tail gas generated by existing vertical shaft furnace hydrogen smelting is difficult to utilize effectively.

[0005] In a first aspect, this application provides a recovery and recycling system for tail gas from vertical shaft furnace hydrogen smelting, the system comprising:

[0006] The exhaust gas supply assembly includes a vertical furnace and a scrubbing tower, with the top outlet of the vertical furnace connected to the scrubbing tower; the vertical furnace is used to generate exhaust gas, and the scrubbing tower is used to purify the exhaust gas.

[0007] A primary gas treatment component includes a heater and a pressure regulating station, wherein the heater is connected to both the pressure regulating station and the scrubbing tower; the heater is used to heat the purified exhaust gas mixture, and the pressure regulating station is used to adjust the pressure of the heated exhaust gas.

[0008] An electrolysis unit, connected to the pressure regulating station, is used to electrolyze the tail gas after pressure adjustment to generate reducing gas;

[0009] A secondary gas processing component is connected to both the electrolysis component and the vertical furnace, and is used to adjust the physicochemical parameters of the reducing gas to obtain the target reducing gas.

[0010] Optionally, the electrolysis assembly includes an electrolytic cell, which is connected to the pressure regulating station and the secondary gas treatment unit respectively.

[0011] Connect the components.

[0012] Optionally, the electrolysis assembly further includes an on-site power grid and a rectifier transformer; wherein the rectifier transformer is connected to a branch line.

[0013] Do not connect to the plant's power grid or the electrolytic cell.

[0014] Optionally, the secondary gas treatment component includes a preprocessor, which is connected to both the electrolysis component and the vertical furnace.

[0015] Optionally, the secondary gas treatment assembly further includes a gas separator and a gas holder assembly; wherein the gas holder assembly respectively

[0016] The gas separator is connected to the preprocessor and the electrolysis assembly.

[0017] Optionally, the system further includes:

[0018] A waste heat steam recovery assembly includes a waste heat boiler and a steam pipeline network; wherein the steam pipeline network is respectively connected to the waste heat boiler and the steam pipeline network.

[0019] The waste heat boiler and the heater are connected.

[0020] Optionally, the system further includes a hot press for pressing the sponge iron, the hot press being connected to the vertical...

[0021] The bottom outlet of the furnace is connected to the waste heat steam recovery assembly.

[0022] Secondly, this application provides a method for waste heat-hydrogen production-metallurgy-carbon recycling, the method being adapted to the system described in the first aspect, the method comprising:

[0023] The exhaust gas generated during the production of sponge iron is washed, then heated and pressure regulated to obtain a mixed gas to be electrolyzed.

[0024] The mixed gas to be electrolyzed is electrolyzed to obtain a reducing gas;

[0025] The reducing gas is adjusted in terms of its physicochemical parameters for use in the production of the sponge iron.

[0026] Optionally, by volume fraction, the components of the washed exhaust gas include: H2O content of 50%–90%, CO2 content of 5%–50%, N2 content of <5%, H2 content of <5%, CO content of <3%, O2 content of <2%, SO2 content of <0.1%, NOx content of <0.1%, and dust content of <5 mg / m³. 3 ;

[0027] The composition of the reducing gas after adjusting the physicochemical parameters includes: H2 content of 50%–90%, CO content of 0%–45%, CH4 content of 0%–20%, N2 content of <5%, CO2 content of <2%, H2O content of <2%, SO2 content of <0.1%, the temperature of the reducing gas after adjusting the physicochemical parameters is >700℃, and the pressure of the reducing gas after adjusting the physicochemical parameters is 0.3MPa–0.8MPa;

[0028] The temperature of the sponge iron is >450℃.

[0029] Optionally, the heating endpoint temperature is >600℃, and the electrolysis temperature is 600℃~950℃.

[0030] The technical solutions provided in this application have the following advantages compared with the prior art:

[0031] The waste heat-hydrogen-metallurgy-carbon recycling system provided in this application embodiment involves purifying the exhaust gas from the top of the vertical shaft furnace through a scrubbing tower. The scrubbed exhaust gas is then treated by heaters and a pressure regulating station in the primary gas treatment component, followed by electrolysis to generate reducing gas. Finally, the physicochemical parameters of the reducing gas are adjusted by the secondary gas treatment component, making it suitable for producing sponge iron in the vertical shaft furnace. This solves the technical problem of effectively utilizing the waste gas generated by existing vertical shaft furnace hydrogen smelting. The system significantly improves energy efficiency, reduces production costs, and can also utilize hydrogen-based vertical shaft furnaces for low-carbon metallurgy, recycling CO2 gas and achieving zero emissions, thus achieving comprehensive benefits in terms of low carbon, environmental protection, and economy. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This application provides a schematic diagram of the structure of a waste heat-hydrogen-metallurgy-carbon cyclic coupling production system; wherein,

[0035] 1-Tail gas generation assembly, 11-Vertical furnace, 12-Scrubber, 2-Primary gas treatment assembly, 21-Heater, 22-Pressure regulating station, 3-Electrolysis assembly, 31-Electrolytic cell, 32-Plant power grid, 33-Rectifier transformer, 4-Secondary gas treatment assembly, 41-Pre-processor, 42-Gas separator, 43-Gas holder assembly, 5-Waste heat steam recovery assembly, 51-Waste heat boiler, 52-Steam pipeline network, 6-Hot press, 7-Material car;

[0036] Figure 2 This is a schematic flow diagram of a waste heat-hydrogen-metallurgy-carbon cyclic coupling production method provided in an embodiment of this application. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are partial embodiments of this application, not embodiments of all components. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0039] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the orientation shown in the accompanying drawings. Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to."

[0040] It should be noted that in this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "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 mainly for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0041] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0042] Furthermore, the terms "installation," "setup," "equipped with," "connected," and "linked" 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 application based on the specific circumstances.

[0043] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0044] Currently, vertical shaft furnaces using hydrogen as the primary reducing gas can reduce sponge iron from pellets at metallurgical reaction temperatures far lower than conventional blast furnaces, producing tail gas primarily composed of water vapor (H2O), rather than the CO2 emitted by blast furnaces. Simultaneously, emissions of pollutants such as dust, sulfur dioxide, and nitrogen oxides are also significantly lower than in traditional processes. Hydrogen-based vertical shaft furnace ironmaking requires hydrogen, and the coking process in steel conglomerates generates substantial amounts of hydrogen-rich coke oven tail gas. However, hydrogen produced in this way has a high carbon emission intensity. From a life-cycle perspective, using only hydrogen from coke oven tail gas for smelting cannot reduce the carbon emission intensity of steel production; it necessitates the use of "green electricity"—"green hydrogen" produced through water electrolysis. However, the energy consumption of water electrolysis for hydrogen production is relatively high.

[0045] While vertical shaft furnace hydrogen smelting can significantly reduce CO2 emissions, it currently lacks the availability of large quantities of low-cost hydrogen. Furthermore, the H2O and CO2 in the smelting tail gas, which possess some heat, cannot be utilized and are simply released into the atmosphere. The bottleneck hindering the widespread adoption of SOE electrolysis technology lies in its requirement for additional heat to raise the operating temperature, resulting in a substantial increase in energy consumption and costs. Simultaneously, waste heat resources generated in steel enterprises from processes such as waste heat boilers, heating furnaces, and sintering waste heat are largely wasted, except for a portion used for steam recovery, leading to significant energy and economic losses.

[0046] Therefore, this embodiment utilizes the H2O and CO2 in the top tail gas of the vertical shaft furnace for recycling. Electrolysis of the H2O and CO2 mixture at high temperature directly produces H2 and CO, obtaining high-quality reducing gas for reduction in the vertical shaft furnace. After the reaction in the vertical shaft furnace, H2O and CO2 are generated again and enter the top tail gas to participate in the next cycle. Through this method, multiple process steps, including electrolytic hydrogen production, low-carbon smelting, and tail gas recycling, fully utilize the low-quality waste heat, top tail gas H2O, and CO2, achieving near-zero CO2 emissions.

[0047] Figure 1 A schematic diagram of a vertical shaft furnace hydrogen smelting tail gas recovery and recycling system provided in this application embodiment; please refer to... Figure 1 This application provides a recovery and recycling system for tail gas from vertical shaft furnace hydrogen smelting, the system comprising:

[0048] The exhaust gas supply assembly 1 includes a vertical furnace 11 and a scrubbing tower 12, with the top outlet of the vertical furnace connected to the scrubbing tower; the vertical furnace is used to generate exhaust gas, and the scrubbing tower is used to purify the exhaust gas;

[0049] The primary gas treatment component 2 includes a heater 21 and a pressure regulating station 22. The heater is connected to both the pressure regulating station and the scrubbing tower. The heater is used to heat the purified exhaust gas mixture, and the pressure regulating station is used to adjust the pressure of the heated exhaust gas.

[0050] Electrolysis component 3 is connected to the pressure regulating station 22 and is used to electrolyze the tail gas after pressure adjustment to generate reducing gas;

[0051] The secondary gas processing component 4 is connected to the electrolysis component 3 and the vertical furnace 11 respectively, and is used to adjust the physicochemical parameters of the reducing gas to obtain the target reducing gas.

[0052] In some embodiments, the system further includes:

[0053] The waste heat steam recovery assembly 5 includes a waste heat boiler 51 and a steam pipeline 52; wherein the steam pipeline 52 is connected to the waste heat boiler 51 and the heater 21 respectively.

[0054] In this embodiment, the exhaust gas rich in H2O, CO2, and other substances generated during the smelting process of the vertical shaft furnace 11 enters the scrubbing tower 12. Inside the scrubbing tower 12, the exhaust gas is purified to remove dust, SO2, and other harmful substances before entering the gas heater 21. The purified exhaust gas is heated in the heater 21. The heating method can be direct heating: direct heating of the gas using a resistance wire / rod or a gas radiant tube; or indirect heating: heating the gas flow pipeline, and then transferring heat to the gas through the pipeline. The heated mixed gas enters the pressure regulating station 22, where it is adjusted to the target pressure value. It is then transported via a high-pressure pipeline to the electrolysis unit 3 for electrolysis to produce reducing gas. The reducing gas then undergoes secondary gas treatment unit 4 to adjust its physicochemical parameters to produce sponge iron.

[0055] In this embodiment of the application, the purified exhaust gas and waste heat steam can be mixed together in the heater 21 before heating. The waste heat in the waste heat boiler 51 can come from various sources and equipment: hot pressing waste heat, slag flushing water waste heat, steel slag waste heat, sintering waste heat, coking waste heat, converter exhaust gas waste heat, steel rolling heating furnace waste heat, etc.

[0056] In some embodiments, the electrolysis assembly 3 includes an electrolysis cell 31, which is connected to the pressure regulating station 22 and the secondary gas treatment assembly 4.

[0057] In some embodiments, the electrolysis assembly 3 further includes an internal power grid 32 and a rectifier transformer 32; wherein the rectifier transformer is connected to the internal power grid 32 and the electrolytic cell 31 respectively.

[0058] In this embodiment, the AC power in the plant's power grid 32 is rectified into DC power by the rectifier transformer 32 and adjusted to the target voltage before being supplied to the electrolytic cell 31. The electrolytic cell 31 can be a stacked structure, mainly using solid oxide as the electrolyte, with hydrogen generating electrodes and oxygen generating electrodes formed on both sides.

[0059] In some embodiments, the secondary gas processing component 4 includes a preprocessor 41, which is connected to the electrolysis component 3 and the vertical furnace 11.

[0060] In this embodiment of the application, for example, the secondary gas treatment component 4 includes a pre-processor 41, which is connected to both the cathode outlet of the electrolytic cell 31 and the vertical furnace 11. The H2 and CO gases produced at the cathode of the electrolytic cell 31 can directly enter the pre-processor 41, and after being treated and heated, enter the vertical furnace 11 as reducing gases.

[0061] In some embodiments, the secondary gas processing assembly 4 further includes a gas separator 42 and a gas holder assembly 43; wherein the gas holder assembly 43 is connected to the gas separator 42 and the preprocessor 41 respectively, and the gas separator 42 is connected to the electrolysis assembly 3.

[0062] In this embodiment, the three main components H2, CO, and O2 are separated by a gas separator 42. The separated gases H2, CO, and O2 are then stored independently in a gas holder group 43. The gas holder group 43 can also store natural gas and coke oven tail gas, which, together with the reducing gas generated by electrolysis, enters a preprocessor 41 to adjust the reducing gas composition according to the smelting requirements of the vertical furnace 11, or to provide fuel for gas preheating and heat supply to the vertical furnace 11. The gas holder group 43 collects and stores H2, CO, and O2 generated by the electrolyzer 31, as well as purchased or self-produced CH3 and COG, with each gas stored independently. Exemplarily, the above-mentioned secondary gas processing component 4 also includes a gas separator 42 and a gas holder group 43; wherein the gas holder group 43 is connected to the gas separator 42 and the preprocessor 41 respectively, and the gas separator 42 is connected to the gas outlet of the electrolyzer 31.

[0063] In some embodiments, the system further includes a hot press 6 for pressing the sponge iron, the hot press 6 being connected to the bottom outlet of the vertical furnace 11 and the waste heat steam recovery assembly 2.

[0064] In this embodiment, solid smelting raw materials such as pellets are fed into the vertical furnace 11 from the top by a feeding mechanism. Moving from top to bottom, high-temperature reducing gas passes through the material layer from bottom to top, gradually reducing the raw materials into sponge iron. After smelting, the sponge iron is discharged from the outlet. The sponge iron remains at a high temperature and is easily deformed. It is pressed into iron blocks by a hot press 6 and then enters the material car 7 as raw material for the next stage of steelmaking. Simultaneously, the waste heat of the sponge iron is recovered and fed into the waste heat boiler 51, where the H2O and heat in the waste heat steam are recycled. Alternatively, the hot sponge iron can be directly transported by the material car 7 to the steelmaking workshop for smelting.

[0065] Based on a general inventive concept, Figure 2 A schematic flow chart of a waste heat-hydrogen-metallurgical-carbon cyclic coupling production method provided in this application embodiment; please refer to... Figure 2 This application provides a method for waste heat-hydrogen-metallurgy-carbon recycling, adapted to the system described in the first aspect, the method comprising:

[0066] S11. The exhaust gas generated during the production of sponge iron is washed, then heated and pressure regulated to obtain a mixed gas to be electrolyzed.

[0067] In some embodiments, the components of the washed exhaust gas, by volume fraction, include: 50%–90% H2O, 5%–50% CO2, <5% N2, <5% H2, <3% CO, <2% O2, <0.1% SO2, <0.1% NOx, and <5 mg / m³ of particulate matter. 3 ;

[0068] The final temperature of the heating is >600℃;

[0069] In this embodiment, the composition of the washed tail gas is defined to ensure that the subsequent mixing of the tail gas meets the gas composition requirements of the electrolytic cell 31, generating reducing gas suitable for smelting in the vertical furnace 11. On the other hand, it removes harmful gaseous components such as dust and nitrogen oxides from the vertical furnace 11, preventing certain components in the gas from damaging pipelines and equipment, and avoiding catalyst poisoning and inactivation within the electrolytic cell 31. Since the electrolysis reaction requires high temperatures, ensuring the temperature of the mixed gas accelerates the reaction rate; if the temperature is too low, the reaction efficiency within the electrolytic cell 31 may be too low, failing to meet the required reducing gas consumption for the next step, resulting in unsatisfactory cost and efficiency. For example, the endpoint temperature of the heating can be 605℃, 610℃, 620℃, 630℃, 640℃, etc.

[0070] S21. Electrolyze the mixed gas to be electrolyzed to obtain a reducing gas;

[0071] The electrolysis temperature is 600℃~950℃.

[0072] In this embodiment, the electrolysis temperature is the optimal temperature range for the electrolysis reaction. Excessively high temperatures may limit the reaction rate increase or even have the opposite effect, and require a large amount of additional energy consumption; excessively low temperatures may result in a low reaction rate, failing to guarantee a large yield of reducing gas. For example, the electrolysis temperature can be 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, or 950℃. Furthermore, the electrolysis operating current is set to direct current (DC). DC is the most advantageous power transmission method for the electrolysis reaction in the electrolytic cell 31, ensuring the continuous and efficient reaction of the cathode and anode within the electrolytic cell 31. Additionally, the gas composition, by volume ratio, of the mixed gas entering the electrolytic cell 31 after passing through the pressure regulating station 32 is: H2O: 50–95%, CO2: 5–50%, N2 < 5%, H2 < 5%, CO < 3%. After high-temperature electrolysis, H2O and CO2 are converted into H2, CO, and O2. Electrochemical reactions, depending on the electrode, are as follows: Cathode reaction: 2CO₂ + 4e⁻ → 2CO + 2O₂ 2 -, 2H₂O + 4e- → 2H₂ + 2O 2-Anode reaction formula: 4O 2- →2O2 + 8e-; Overall reaction: H2O + CO2 → H2 + CO + O2. The H2 and CO gases produced at the electrolytic cathode can be directly processed and heated to serve as reducing gases. Alternatively, they can be separated using adsorption, low-temperature distillation, or membrane separation methods. The separated gases H2, CO, and O2 are stored independently.

[0073] S31. Adjust the physicochemical parameters of the reducing gas to produce the sponge iron.

[0074] In some embodiments, the composition of the reducing gas after adjusting the physicochemical parameters includes: H2 content of 50%–90%, CO content of 0%–45%, CH4 content of 0%–20%, N2 content of <5%, CO2 content of <2%, H2O content of <2%, SO2 content of <0.1%, the temperature of the reducing gas after adjusting the physicochemical parameters is >700°C, and the pressure of the reducing gas after adjusting the physicochemical parameters is 0.3 MPa–0.8 MPa;

[0075] The temperature of the sponge iron is >450℃.

[0076] In the embodiments of this application, the composition of the reducing gas is limited. The smelting reaction in the vertical furnace 11 mainly consumes H2 and CO to generate H2O and CO2. On the one hand, it is necessary to ensure that the ratio of H2 and CO reaches a certain value to facilitate the efficient progress of the reduction reaction. On the other hand, gaseous components such as N2 and CO2 do not participate in the smelting reaction. If the ratio is too high, the temperature rise of the gas will consume a lot of energy, and after the reaction is completed, a lot of heat will be taken away, which is not conducive to the energy utilization efficiency of the entire system.

[0077] The optimal temperature for the reduction reaction within the vertical furnace 11 is 700-950℃, and since the reduction reaction is endothermic, it consumes a large amount of heat. Therefore, the reduction temperature must be maintained above 700℃; if the temperature is too low, the reaction rate is low, requiring a large amount of additional heat. For example, the temperature of the reducing gas can be 701℃, 705℃, 710℃, 720℃, 730℃, 740℃, 750℃, etc.

[0078] The pressure of the reducing gas is limited. Within a certain range, the reduction reaction proceeds efficiently while ensuring a high proportion of reducing gas participates in the reaction. Excessive pressure may cause the reducing gas to escape rapidly from the furnace top, resulting in a large amount of gas not participating in the reaction and thus wasting it. Insufficient pressure may lead to low reaction efficiency and affect yield. For example, the temperature of the reducing gas can be 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, etc.

[0079] Limiting and controlling the temperature of sponge iron is beneficial for downstream smelting workshops to directly use the hot sponge iron.

[0080] Sponge iron reduces the initial heating time and energy consumption during smelting. Furthermore, higher temperatures result in lower deformation resistance, allowing the hot press 6 to efficiently press the iron into the required dimensions. Conversely, lower temperatures require additional energy for heating in downstream smelting workshops, and also increase deformation resistance, leading to increased energy consumption and equipment wear on the hot press 6. For example, the temperature of the sponge iron can be 455℃, 460℃, 470℃, 500℃, etc.

[0081] The waste heat-hydrogen-metallurgy-carbon cyclic coupling production method is based on the above-described waste heat-hydrogen-metallurgy-carbon cyclic coupling production system. The specific structure of the waste heat-hydrogen-metallurgy-carbon cyclic coupling production system can be referred to the above embodiments. Since the waste heat-hydrogen-metallurgy-carbon cyclic coupling production method adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0082] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0083] Example 1

[0084] A waste heat-hydrogen-metallurgy-carbon recycling system includes:

[0085] The tail gas generated in the vertical shaft furnace 11 is purified by the scrubbing tower 12 and then enters the heater 21. The waste heat steam in the waste heat boiler 51 and steam network 52 of the waste heat steam recovery assembly 5 enters the heater 21. The mixture of the purified tail gas and waste heat steam after passing through the heater 21 enters the pressure regulating station 22. After being adjusted to the target pressure, it is transported by pipeline to the electrolytic cell 31 of the electrolysis assembly 3 as the raw material for electrolysis gas. The AC power in the plant power grid 31 enters the rectifier transformer 33 and is then transported to the electrolytic cell 31. The reducing gas generated by electrolysis enters the gas holder group 43 through the gas separator 42, and after being processed by the preprocessor 41 to adjust the physicochemical parameters, it is sent to the vertical shaft furnace 11 for smelting. The hot sponge iron at the lower outlet of the vertical shaft furnace 11 enters the hot press 6 to be pressed into iron blocks and then used as the raw material for the next steelmaking step. The waste heat during the hot pressing process is recovered to the waste heat boiler 51.

[0086] Example 2

[0087] A method for waste heat-hydrogen production-metallurgy-carbon recycling coupling production includes:

[0088] The vertical production process involves feeding pellets into the furnace via a feeding mechanism. The Fe content is 63%, the smelting temperature is 850℃, and the reducing gas is a mixture of H2 and CO, with the composition shown in Table 1.

[0089] Table 1. Volume percentage of reducing gas

[0090]

[0091] In the vertical shaft furnace, high-temperature H2 and CO reducing gas are injected from the bottom of the furnace at a pressure of 0.7 MPa and a temperature of 850°C. They pass through the gaps in the pellets from bottom to top, and the pellets move from top to bottom.

[0092] When reducing gas comes into contact with ore pellets, reduction and carburizing reactions occur:

[0093] Fe2O3+3H2= 2Fe+3H2O; Fe2O3+3CO=2Fe+3CO2; 3Fe+2CO=Fe3C+CO2;

[0094] As the iron oxide in the pellets gradually decreases during the descent, the hot metallic iron is discharged from the lower outlet. The sponge iron has a temperature of 520℃, a carbon content of 2.3%, and a metallization rate of 91%. After being collected by the material car, the hot sponge iron is transported to the electric furnace workshop.

[0095] The reduced exhaust gas was washed, and the composition of the washed outlet gas was measured as shown in Table 2.

[0096] Table 2. Components of purified exhaust gas

[0097]

[0098] The purified exhaust gas is transported to the heater via pipeline, while steam from the waste heat boiler and pipeline network is also transported to the heater in a 3:7 ratio. The exhaust gas and steam merge at the front end of the heater and then enter the multi-tube heater for heating, before entering the pressure regulating station for pressure adjustment. The outlet gas temperature of the pressure regulating station is 650℃, and the pressure is 1.6MPa.

[0099] The electrolytic cell uses low-cost nickel electrodes, and the electrolyte material is zirconium dioxide with added yttrium oxide. The operating temperature is 650℃. The cathode reaction is as follows:

[0100] 2CO2 + 4e- → 2CO + 2O 2-

[0101] 2H₂O + 4e⁻ → 2H₂ + 2O 2-

[0102] Anode reaction formula:

[0103] 4O 2- →2O2+8e-

[0104] Adjust the cathode H2 and CO production to 6800–7500 m³ based on the amount of reducing gas used in smelting. 3 / h.

[0105] After electrolysis, the cathode gas mixture, carrying a large amount of heat, directly enters the pre-processor, while the anode O2 gas, after being cooled by heat exchange, enters the gas holder for storage. The pre-processor uses coke oven tail gas to heat to 850°C, and the proportion of each component in the outlet gas is: H2 / CO = 1.4. The gas is then fed into the vertical furnace through the inlet to participate in the next stage of smelting production.

[0106] Example 3

[0107] A method for waste heat-hydrogen production-metallurgy-carbon recycling coupling production includes:

[0108] The vertical shaft furnace production process involves feeding pellets into the furnace via a feeding mechanism. The pellets have a grade of 67%. The reducing gas used is mainly composed of H2 with a small amount of CO. The smelting temperature is 900℃. The composition of the reducing gas entering the furnace is shown in Table 3.

[0109] Table 3. Volume percentage of reducing gas

[0110]

[0111] After the smelting reaction, the H2 and CO in the reducing gas react with the iron oxides in the pellets in a reduction reaction. The specific reaction formula is as follows:

[0112] Fe₂O₃ + 3H₂ = 2Fe + 3H₂O

[0113] F₂O₃ + CO = 2Fe + 3CO₂

[0114] 3Fe + 2CO = Fe3C + CO2

[0115] 3Fe + CO + H₂ = Fe₃C + H₂O

[0116] After the reduction reaction, the exhaust gas from the furnace top, rich in H2O and CO2, enters a scrubbing tower. The composition of the purified gas is shown in Table 4.

[0117] Table 4. Composition of purified exhaust gas from the furnace top

[0118]

[0119] The exhaust gas mixed with steam after washing consists of three parts:

[0120] 10% of the steam comes from the waste heat of the hot press iron, 55% comes from the waste heat boiler, and the remaining 35% comes from the pipeline network.

[0121] The SOE electrolytic cell has a cobalt metal-ceramic composite cathode, a perovskite-type anode, and a scandium-stabilized zirconium oxide as the electrolyte. The operating temperature is 860℃ and the operating current is DC.

[0122] After the electrolysis reaction, the high-temperature H2 and CO mixture is directly fed into the pre-processor, while the O2 generated at the anode is not cooled and is sent to the vertical furnace through a high-temperature pipe as the oxidation reaction gas in the furnace, providing additional heat to the vertical furnace.

[0123] The ratio of H2 to CO in the reducing gas is approximately 9:1, and the hourly flow rate is 3900-5200 m³ / h. 3 .

[0124] High-temperature gas was blown in through multiple tuyeres located at the bottom of the vertical furnace, with a temperature of 830℃ and a pressure of 0.8MPa.

[0125] After hot pressing, the hot sponge iron smelted in the vertical shaft furnace reaches a temperature of 450℃, and the carbon content of the hot-pressed iron is measured to be 0.5%. Steam is generated by heat exchange in the waste heat recovery equipment and then fed into the heater along with steam from the waste heat boiler and pipeline network.

[0126] Example 4

[0127] A method for waste heat-hydrogen production-metallurgy-carbon recycling coupling production includes:

[0128] The vertical production process involves feeding pellets into the furnace via a feeding mechanism. The pellets have a diameter of 10-16 mm and a total iron (TFe) content of 69%. The smelting temperature is 910℃. The reducing gas is mainly composed of a mixture of H2 and CO, with a small amount of natural gas used for auxiliary heating. The ratio of the main components of the reducing gas is controlled to be H2:CO:CH4 = 3.4:1:0.3. All gas components are shown in Table 5.

[0129] Table 5. Volume percentage of reducing gas

[0130]

[0131] The mixture is heated to 750-800℃ using the exhaust gas.

[0132] In the vertical shaft furnace, a mixture of high-temperature H2 and CO gas is injected from the bottom of the furnace at a blowing pressure of 0.5 MPa, passing through the gaps in the pellets from bottom to top, and the pellets move from top to bottom.

[0133] When the reducing gas comes into contact with the ore pellets, a reduction reaction occurs:

[0134] Fe₂O₃ + 3H₂ = 2Fe + 3H₂O

[0135] Fe₂O₃ + 3CO = 2Fe + 3CO₂

[0136] Carburizing reaction:

[0137] 3Fe + 2CO = Fe3C + CO2

[0138] After the pellets are reduced, they still maintain a certain temperature. The spherical reduced iron is discharged from the lower outlet at a temperature of about 470-620℃. After being collected by the material car, the hot sponge iron is conveyed to the electric furnace workshop in a closed manner.

[0139] The chemical composition of the cooled sponge iron sample was measured, and the carbon content was 1.2%, with a metallization rate of approximately 89%.

[0140] The reduced exhaust gas enters a scrubbing tower for cooling and purification. The composition of the scrubbing outlet gas is shown in Table 6.

[0141] Table 6. Components of purified exhaust gas

[0142]

[0143] The purified exhaust gas is transported to the heater via pipeline, while steam from the waste heat boiler and pipeline network is also transported to the heater in a ratio of 1:0.7. The exhaust gas and steam merge at the front end of the heater and then enter the multi-tube heater for heating, before entering the pressure regulating station for pressure adjustment. The outlet gas temperature of the pressure regulating station is 820-850℃, and the pressure is 2.6MPa.

[0144] The electrolytic cell uses nickel alloy and zirconium dioxide electrodes, and operates at a temperature of 820℃. The cathode reaction is as follows:

[0145] 2CO2 + 4e- → 2CO + 2O 2-

[0146] 2H₂O + 4e⁻ → 2H₂ + 2O 2-

[0147] Anode reaction formula:

[0148] 4O 2- →2O2+8e-

[0149] After electrolysis, the cathode gas mixture directly enters the pre-processor, the anode O2 gas is converted into liquid oxygen after heat exchange and deep cooling, and the cathode H2 and CO gas mixture enters the gas holder for storage.

[0150] In summary, this embodiment utilizes the abundant waste heat resources of steel enterprises to increase the temperature of electrolytic cells, significantly reducing electrolysis energy consumption. Simultaneously, H2O and CO2 in the furnace top tail gas are recycled. Electrolysis of the H2O and CO2 mixture at high temperatures can directly produce H2 and CO, obtaining high-quality reducing gas for vertical shaft furnace reduction. After the vertical shaft furnace reaction, H2O and CO2 are generated again and enter the furnace top tail gas to participate in the next cycle. Through this method, multiple process links such as waste heat utilization, electrolytic hydrogen production, low-carbon smelting, and tail gas recycling are coupled, enabling the full utilization of various waste energy sources, including low-quality waste heat, furnace top tail gas H2O, and CO2, achieving near-zero CO2 emissions.

[0151] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A recovery cycle system of a shaft furnace hydrogen smelting offgas, characterized by, The system includes: The exhaust gas supply assembly includes a vertical furnace and a scrubbing tower, with the top outlet of the vertical furnace connected to the scrubbing tower; the vertical furnace is used to generate exhaust gas, and the scrubbing tower is used to purify the exhaust gas. A primary gas treatment component includes a heater and a pressure regulating station. The heater is connected to both the pressure regulating station and the scrubbing tower. The heater is used to heat the purified exhaust gas mixture, and the pressure regulating station is used to adjust the pressure of the heated exhaust gas. The final temperature of the heating is >600°C. An electrolysis unit, connected to the pressure regulating station, is used to electrolyze the tail gas after pressure adjustment to produce reducing gas, and the electrolysis temperature is 600℃~950℃. A secondary gas processing component is connected to both the electrolysis component and the vertical furnace, and is used to adjust the physicochemical parameters of the reducing gas to obtain the target reducing gas. A waste heat steam recovery assembly includes a waste heat boiler and a steam pipeline network; wherein the steam pipeline network is connected to the waste heat boiler and the heater respectively.

2. The system of claim 1, wherein, The electrolysis assembly includes an electrolytic cell, which is connected to the pressure regulating station and the secondary gas processing assembly.

3. The system of claim 2, wherein, The electrolysis assembly also includes an on-site power grid and a rectifier transformer; wherein the rectifier transformer is connected to both the on-site power grid and the electrolytic cell.

4. The system of claim 1, wherein, The secondary gas processing component includes a preprocessor, which is connected to both the electrolysis component and the vertical furnace.

5. The system of claim 4, wherein, The secondary gas processing assembly further includes a gas separator and a gas holder assembly; wherein the gas holder assembly is connected to the gas separator and the preprocessor respectively, and the gas separator is connected to the electrolysis assembly.

6. The system of claim 1, wherein, The system also includes a hot press for pressing sponge iron, and the hot press is connected to the bottom outlet of the vertical furnace and the waste heat steam recovery assembly.

7. A method for producing by coupling waste heat-hydrogen production-metallurgy-carbon cycle, characterized in that, The method is adapted to The system according to any one of claims 1-6, wherein the method comprises: The exhaust gas generated during the production of sponge iron is washed, then heated and pressure regulated to obtain a mixed gas to be electrolyzed. The mixed gas to be electrolyzed is electrolyzed to obtain a reducing gas; The reducing gas is adjusted in terms of its physicochemical parameters for use in the production of the sponge iron.

8. The method of claim 7, wherein, The composition of the scrubbed tail gas, on a volume fraction basis, includes: H2O in an amount of 50% to 90%, CO2 in an amount of 5% to 50%, N2 in an amount of <5%, H2 in an amount of <5%, CO in an amount of <3%, O2 in an amount of <2%, SO2 in an amount of <0.1%, NOx in an amount of <0.1%, and dust in an amount of <5 mg / m3 3 ; The composition of the reducing gas after adjusting the physicochemical parameters includes: H2 content of 50%–90%, CO content of 0%–45%, CH4 content of 0%–20%, N2 content of <5%, CO2 content of <2%, H2O content of <2%, SO2 content of <0.1%, the temperature of the reducing gas after adjusting the physicochemical parameters is >700℃, and the pressure of the reducing gas after adjusting the physicochemical parameters is 0.3MPa–0.8MPa; The temperature of the sponge iron is >450℃.

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