A converter gas cleaning and energy quality recovery system and method

Abstract

This invention provides a converter gas purification and energy recovery system, comprising a moving particle bed, a waste heat boiler, a secondary dust collector, and a gas holder. The moving bed particles are made from compressed converter ash and contain a large amount of iron and iron oxides. The invention also provides a method for using this system, comprising: high-temperature converter gas entering the moving particle bed, filtering most of the dust and purifying the oxygen component in the gas to prevent gas explosions in subsequent operations; the purified gas entering the waste heat boiler to recover waste heat and generate medium- and high-pressure steam; the gas after waste heat recovery undergoes dust removal in the secondary dust collector and then enters the gas holder. When the CO content in the gas is lower than the concentration entering the gas holder, it enters the moving particle bed to reduce the iron oxides in the particles. This method uses a completely dry dust removal process, consumes zero water resources, eliminates gas safety issues, is environmentally friendly, and produces no dust or CO emissions. It can recover the full-temperature sensible heat of the converter gas, release the chemical energy in the gas, and utilize TFe resources in the dust collector ash.

Description

Technical Field

[0001] This invention relates to a converter gas purification and energy recovery system and method, belonging to the technical field of high-temperature flue gas purification and waste heat and energy recovery in industrial furnaces and kilns, and is particularly aimed at converter gas in steel enterprises. Background Technology

[0002] In iron and steel metallurgical production, converters generate a large amount of high-temperature gas, known as converter gas, which is an important secondary energy source for steel enterprises. Converter gas is not only high in temperature but also contains a large amount of dust, with a dust content of approximately 80–150 g / m³. 3 The main components include iron, iron oxide, calcium oxide, manganese monoxide, silicon dioxide, and carbon. Currently, most enterprises use the LF dry dust removal method for converter gas. The main process involves cooling the gas from 1450℃ to 800-900℃ in the vaporization cooling flue, then rapidly reducing the temperature to below 200℃ by spraying water into a steam cooler before entering the dust collector for purification. Further cooling then sends the gas to the converter gas holder. However, the LF dry dust removal method still has some shortcomings: waste heat in the 200℃-900℃ range is not recovered, and a large amount of cooling water (0.2 tons of water / ton of steel) is wasted. The water turns into steam, increasing the humidity of the gas, increasing the load on the dust collector and induced draft fan, and increasing power consumption.

[0003] The "fully dry dust removal + waste heat boiler steam recovery" method ensures full heat recovery and utilization, but its practical application faces many challenges. First, converter blowing is intermittent, with gas temperature and volume fluctuating significantly over time, requiring waste heat recovery equipment capable of withstanding rapid heating and cooling. Second, converter dust has a complex composition and exhibits adhesive properties at high temperatures, leading to high-temperature corrosion and scaling on equipment, making high-temperature dust filtration and purification difficult. Third, the frequent air-gas exchange during converter steelmaking poses a risk of explosion if equipment is not operated properly, as CO-containing gas can mix with oxygen-containing air.

[0004] Converter gas is flammable and explosive, and the safety of gas explosions caused by air intake must be considered during heat recovery. The explosion limits of converter gas are 21.5-71.5%. During converter gas recovery, the concentration of converter gas produced ranges widely. If air is drawn into the pipeline, it may cause an explosion. The minimum ignition temperature of converter gas is approximately 610℃. During normal converter gas recovery, when the temperature exceeds 610℃, if air is drawn into the pipeline, the CO in the converter gas reacts rapidly with the oxygen in the air, quickly consuming the oxygen and preventing its accumulation. Therefore, converter gas is safe above 610℃, and high-temperature converter gas (above 800℃) in the vaporization cooling flue typically does not explode. However, the waste heat recovery process in the intermediate temperature section of the converter gas requires cooling the converter gas to below 610℃, where the possibility of explosion exists.

[0005] According to the three elements of a gas explosion, a combustible gas explosion requires sufficient ignition energy. During the waste heat recovery process of converter gas, sparks from the flue gas or from friction between the flue gas and the recovery equipment can become ignition sources for converter gas explosions. During the oxygen blowing process in a converter, converter splashing produces large-particle, high-heat-content red slag. During the intermediate-temperature recovery process, this red slag enters the waste heat recovery device along with the converter gas, potentially causing a converter gas explosion. Summary of the Invention

[0006] This invention proposes a converter gas purification and energy recovery system for high-temperature, dust-laden converter gas, as well as a method for purifying and recovering energy from converter gas using this system. This method enables full-temperature-range waste heat recovery from converter gas and zero venting of the gas. It eliminates the need for explosion relief valves and also facilitates the resource utilization of converter ash.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] This invention provides a converter gas purification and energy recovery system, the system comprising a moving particle bed, a waste heat boiler, a secondary dust collector, and a gas holder, wherein...

[0009] The moving particle bed includes an upper bed layer, a middle bed layer and a lower bed layer connected in sequence. The lower bed layer is provided with a first air inlet and a first air outlet of the moving particle bed. The middle bed layer is provided with a second air inlet and a third air inlet of the moving particle bed. The upper bed layer is provided with a second air outlet of the moving particle bed.

[0010] The converter gas outlet is connected to the first inlet of the moving particle bed, and the first outlet of the moving particle bed is sequentially connected to the waste heat boiler, the secondary dust collector, and the gas holder, forming a gas passage.

[0011] The gas holder is connected to the third air inlet of the moving particle bed.

[0012] Preferably, the particles filling the moving particle bed are made of iron-containing dust collected from the moving particle bed and / or a secondary dust collector.

[0013] Preferably, copper and tin elements are also added to the particles.

[0014] Preferably, in the moving particle bed, the upper and lower bed layers are vertically arranged, and the middle bed layer is inclined at an angle of 20 to 40°.

[0015] Preferably, an induced draft fan is provided between the secondary dust collector and the gas holder, a first valve is provided between the gas holder and the induced draft fan, a second valve is provided at the second air inlet, and a third valve is provided between the gas holder and the third air inlet.

[0016] The present invention also provides a method for purifying converter gas and recovering energy using the system, comprising the following steps:

[0017] S1. Measure the CO and O2 concentrations in the converter gas at the outlet of the secondary dust collector.

[0018] If the CO concentration at the outlet of the secondary dust collector is higher than or equal to the set concentration value and the O2 concentration is lower than the set concentration value, then proceed to step S2;

[0019] If the CO concentration at the outlet of the secondary dust collector is lower than the set concentration value and / or the O2 concentration is higher than the set value, then proceed to step S3;

[0020] After step S3 is completed, the CO concentration in the converter gas is measured at the gas outlet of the upper bed. If CO is still present, proceed to step S4.

[0021] S2. Open the first valve and close the second and third valves. After the converter gas enters the lower section of the moving particle bed, the dust contained therein is filtered in the lower section of the bed. The dust-removed converter gas is discharged from the gas outlet of the moving particle bed located in the lower section of the bed, and then enters the waste heat boiler for heat exchange, and then enters the secondary dust collector for dust removal, and then enters the gas holder.

[0022] S3. Open the third valve and close the first and second valves. The converter gas passes through the lower section of the moving particle bed, the waste heat boiler, and the secondary dust collector in sequence before entering the middle section of the bed. In the middle section of the bed, the converter gas reduces the iron oxide in the particles to metallic iron. The converter gas after removing CO is discharged from the outlet of the lower section of the moving particle bed. It then passes through the waste heat boiler and the secondary dust collector in sequence before entering the upper section of the bed to exchange heat with the moving bed particles in a countercurrent manner before being discharged.

[0023] S4. During the blowing interval, open the second valve and close the first and third valves to introduce air from the outside into the second air inlet, oxidizing the iron in the particles into iron oxide in the intermediate bed.

[0024] Preferably, in step S1, the CO concentration is set to 20% to 30%, and the O2 concentration is set to 2%, both of which are volume concentrations.

[0025] Preferably, both the middle and lower bed layers have heat storage functions, and the bed temperature is always maintained above 800°C.

[0026] The beneficial effects of the above-described technical solution of the present invention are as follows:

[0027] This invention uses compressed dust particles as filter media and employs a moving particle bed dust collector. While separating the particles from the ignition source, it removes the oxygen component from the coal gas, completely avoiding the risk of coal gas explosion. This method can recover the full-temperature sensible heat of converter gas and release the chemical energy in the gas, achieving converter gas dust filtration, CO purification, and full energy recovery. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the converter gas purification and energy quality system of the invention.

[0030] Wherein: 1-Moving particle bed;

[0031] 1a - Upper bed layer; 1b - Middle bed layer; 1c - Lower bed layer;

[0032] 2- Waste heat boiler; 3- Secondary dust collector; 4- Converter; 5- Gas holder; 6- Induced draft fan;

[0033] 8a - First air intake; 8b - Second air intake; 8c - Third air intake;

[0034] 9a - First valve; 9b - Second valve; 9c - Third valve. Detailed Implementation

[0035] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be described in detail below with reference to specific embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the scope of the invention.

[0036] This invention provides a converter gas purification and energy recovery system. For example... Figure 1 As shown, the system includes a moving particle bed 1, a waste heat boiler 2, a secondary dust collector 3, and a gas holder 5, wherein,

[0037] The moving particle bed 1 includes an upper bed layer 1a, a middle bed layer 1b and a lower bed layer 1c connected in sequence. The lower bed layer 1c is provided with a first air inlet 8a and a first air outlet of the moving particle bed 1. The middle bed layer 1b is provided with a second air inlet 8b and a third air inlet 8c of the moving particle bed 1. The upper bed layer 1a is provided with a second air outlet of the moving particle bed.

[0038] The gas outlet of converter 4 is connected to the first air inlet 8a of the moving particle bed 1, and the first air outlet of the moving particle bed 1 is sequentially connected to the waste heat boiler 2, the secondary dust collector 3, and the gas holder 5, forming a gas passage.

[0039] The gas holder 5 is connected to the third air inlet 8c of the moving particle bed 1, forming a closed loop between the moving particle bed 1, the waste heat boiler 2, the secondary dust collector 3 and the gas holder 5.

[0040] In one embodiment of the present invention, the particles filling the moving particle bed 1 are made of compressed dust and can be recycled. The dust comes from the moving particle bed 1 and / or the secondary dust collector 3, and is rich in metallic iron and iron oxides, which can react with oxygen and CO respectively. The converter dust has the characteristics of high iron content (TFe, above 50%), fine particle size (approximately 5000 mesh), and large specific surface area. It also contains a large amount of alkaline oxides such as CaO (approximately 10%), where iron mainly exists as Fe2O3 and Fe3O4. The dust surface is positively charged and has the ability to adsorb negative ions. In addition to using iron-containing dust, other oxygen carriers such as copper and tin can be added to the particles to achieve oxidation and reduction functions. In the present invention, the particles are spherical with an average particle size of 1-50 mm and have good flowability.

[0041] The particles are loaded from the top of the moving particle bed 1 and can flow continuously from top to bottom within the moving particle bed 1. During stable operation, the TFe composition of the particles in the heat recovery bed 1a is Fe2O3 and Fe3O4. In the reduction bed 1b, the iron oxide in the particles is reduced to metallic iron, while in the oxidation bed 1c, the metallic iron is oxidized again.

[0042] In one embodiment of the present invention, in the moving particle bed 1, the upper bed layer 1a and the lower bed layer 1c are both vertically arranged, while the middle bed layer 1b is inclined, with an inclination angle of 20–40°. The inclined arrangement of the middle bed layer 1b enables automatic stratification of particles of different sizes, i.e., large particles are located on the bed surface while small particles are located at the bottom. The stratified particles flow to the lower bed layer 1c, achieving graded filtration of high-temperature dust-laden converter gas. The structure of the inclined particle bed in the applicant's prior applications CN107096335B and CN110812980B can be referenced.

[0043] Furthermore, the lower bed 1c is an oxidation section. When the converter gas contains oxygen, it is introduced into the lower bed 1c through the first inlet 8a. The iron in the particles reacts with oxygen to form iron oxides, purifying the oxygen content in the converter gas to below the lower explosive limit. The middle bed 1b is a reduction section. When the CO content in the converter gas is lower than a set value, the converter gas is circulated and introduced into the middle bed 1b through the third inlet. The iron oxides in the particles are reduced to elemental iron, and the particles enter the lower bed 1c under gravity. The upper bed 1a is a heat recovery section. When the CO content in the converter gas is greater than or equal to a set value, it is circulated and introduced into the middle bed 1b through the third inlet. Since the reduction reaction in the middle bed 1b is exothermic, a high-temperature gas flow enters the upper bed 1a, where it exchanges heat with the particles in a counter-current manner, leaving the heat of the gas flow in the particle bed and achieving heat recovery. Both the middle bed 1b and the lower bed 1c of the aforementioned moving particle bed 1 have heat storage functions, and the bed temperature is always maintained above 800℃ to ensure the efficient and rapid progress of the redox reaction.

[0044] Furthermore, the relative positions of the oxidation bed and the reduction bed in the moving particle bed 1 can be interchanged, that is, as the particles flow downward, they first enter the oxidation bed and then the reduction bed.

[0045] In one embodiment of the present invention, an induced draft fan 6 is provided between the secondary dust collector 3 and the gas holder 5, a first valve 9a is provided between the gas holder 5 and the induced draft fan 6, a second valve 9b is provided at the second air inlet 8b, and a third valve 9c is provided between the gas holder 5 and the third air inlet 8c. Figure 1 As shown, the gas holder 5 has only one gas inlet and outlet. The pipeline connecting the gas inlet and outlet of the gas holder 5 is divided into two branches: one branch connects to the secondary dust collector 3, and the other branch connects to the third air inlet 8c. The first valve 9a is located at the unbranched end of the pipeline connecting the gas holder 5 to the gas inlet and outlet, and the third valve 9c is located on the branch pipeline connecting the gas holder 5 and the third air inlet 8c.

[0046] The present invention also provides a method for purifying converter gas and recovering energy using the system, comprising the following steps:

[0047] S1. Measure the CO and O2 concentrations in the converter gas at the outlet of the secondary dust collector 3.

[0048] If the CO concentration at the outlet of the secondary dust collector 3 is higher than or equal to the set concentration value and the O2 concentration is lower than the set concentration value (the set concentrations of CO and O2 can be changed according to the actual situation; usually, CO is 20% to 30% and O2 concentration is 2%, both of which are volume concentrations), then proceed to step S2.

[0049] If the CO concentration at the outlet of the secondary dust collector 3 is lower than the set concentration value and / or the O2 concentration is higher than the set value, then proceed to step S3;

[0050] After step S3 is completed, the CO concentration in the converter gas is measured at the gas outlet of the upper bed 1a. If CO is still present, proceed to step S4.

[0051] S2. Open the first valve 9a, close the second valve 9b and the third valve 9c. After the converter gas enters the lower bed 1c of the moving particle bed 1, the dust contained therein is filtered in the lower bed 1c. The dust-removed converter gas is discharged from the gas outlet of the moving particle bed 1 located in the lower bed 1c, and enters the waste heat boiler 2 for heat exchange in sequence, and then enters the secondary dust collector 3 for dust removal, and then enters the gas holder 5.

[0052] S3. Open the third valve 9c, close the first valve 9a and the second valve 9b. The converter gas passes sequentially through the lower bed 1c of the moving particle bed 1, the waste heat boiler 2, and the secondary dust collector 3 before entering the middle bed 1b. In the middle bed 1b, the converter gas reduces the iron oxide in the particles to metallic iron, with the chemical reaction being FeO + CO → Fe + CO2. The converter gas after removing CO is discharged from the outlet of the moving particle bed 1 located in the lower bed 1c, and then passes sequentially through the waste heat boiler and the secondary dust collector before entering the upper bed 1a to exchange heat with the moving bed particles in a countercurrent manner, and then is discharged.

[0053] S4. During the blowing interval, open the second valve 9b and close the first valve 9a and the third valve 9c. Air is introduced from the outside to the second air inlet 8b. In the middle bed 1b, the iron in the particles is oxidized to iron oxide. The chemical reaction is Fe + O2 → FeO.

[0054] In step S2 above, the high-temperature, high-dust-content converter gas enters the oxidation bed of the moving particulate bed, where most of the dust (especially large particles, i.e., the ignition source for gas explosions) is filtered out. The purified gas then enters a waste heat boiler to recover the high-temperature heat from the gas and generate medium- and high-pressure steam. After waste heat recovery, the gas temperature decreases, and it undergoes further purification in a secondary dust collector. Gas with acceptable CO content then enters the gas holder.

[0055] In step S3 above, for coal gas with low CO concentration, i.e., vented coal gas, it enters the reduction bed of the moving particle bed, where iron oxides in the particles are reduced to iron, and the CO concentration is reduced to the ppm level, preventing vented coal gas from polluting the environment. After combustion, the gas leaves the reduction bed and enters the heat recovery bed, where the gas flow exchanges heat with the particles in a counter-current manner, and the recovered heat is then released into the environment.

[0056] When the volume of vented gas is large or the CO concentration is high, iron oxides are insufficient to recover all the CO. In this case, during the blowing interval, an appropriate amount of air is introduced into the bed to oxidize the iron into iron oxides, thereby recovering the CO from the vented gas.

[0057] Combining steps S2 and S4, it can be seen that the oxidation bed of the moving particle bed can not only filter dust (i.e., the ignition source of gas explosion) in the high-temperature gas, but also, in the early and late stages of converter smelting, if the gas contains oxygen, the iron in the moving particle bed and the dust captured in the bed can react with the oxygen, consuming the oxygen component in the gas and ensuring that there is no risk of gas explosion in subsequent processes. In the oxidation bed, the reaction of metallic iron being oxidized into iron oxide is an exothermic reaction, and the large amount of heat released by the oxidation reaction enters the subsequent waste heat boiler with the gas.

[0058] Example 1

[0059] Taking a complete converter blowing process as an example, the working process of this system is as follows:

[0060] During converter blowing

[0061] During converter blowing, a large amount of high-temperature dust-laden gas is generated, reaching a temperature of 1450℃. The main components of the gas are CO, CO2, N2, and H2. At this time, the CO concentration in the converter gas is higher than or equal to the set concentration value, while the O2 concentration is lower than the set concentration value, and step S2 in the aforementioned method is performed. The converter gas enters the oxidation bed 1c of the moving particle bed 1. Most of the dust in the gas, especially large-diameter dust, is filtered by the moving particle bed 1 and adheres to the particle surface. During dust filtration, the high-temperature gas heats the particles. After filtration, the gas temperature decreases only slightly, but the outlet temperature of the lower section of the moving particle bed 1 is still above 1000℃.

[0062] The filtered high-temperature coal gas enters waste heat boiler 2, generating medium- and high-pressure steam. After waste heat recovery, the temperature of the coal gas drops to below 150℃. The cooled coal gas then enters secondary dust collector 3, reducing dust concentration to 50mg / m³. 3 .

[0063] A CO concentration sensor is installed at the outlet of the secondary dust collector 3 to detect the CO content in the gas. When the CO concentration is higher than 20% (this set concentration can be changed according to actual conditions), it meets the requirements for entering the gas holder, and the gas enters the gas holder 5. When the CO concentration is lower than 20%, step S3 in the aforementioned method is performed, the valve is switched, and the gas enters the reduction bed 1b of the moving particle bed 1, where Fe2O3 and Fe3O4 are reduced to metallic iron. In the reduction bed 1b, the CO in the gas burns to generate CO2, and the concentration drops to the ppm level.

[0064] The gas flow after combustion enters the heat recovery bed 1a, where it exchanges heat with the moving bed particles in a countercurrent manner. After heat recovery, the gas is discharged into the atmosphere.

[0065] Early and late stages of refining

[0066] Towards the end of the blowing process, the amount of furnace gas output from converter 4 decreases. If air is mixed in during gas recovery, the oxygen content in the gas will increase. At this point, the oxygen in the gas reacts with the metallic iron in the granular bed to form iron oxides, reducing the oxygen concentration below the gas explosion limit and ensuring that there are no safety hazards during subsequent waste heat recovery.

[0067] Refining interval

[0068] After the vented gas completely reduces all the particles in the reducing bed 1b to metallic iron, vented gas is continued to be introduced, and CO cannot be recovered from the reducing bed. At this point, step S4 of the aforementioned method is performed.

[0069] During the interval between smelting in the converter, a certain amount of air is introduced into the reduction bed 1b. The oxygen in the air reacts with the iron to form iron oxide, which is used to recover the vented gas from the converter.

[0070] In the above scheme, granules compressed from dust collector ash are used as filter media, and a moving particle bed 1 is employed for dust removal. While separating the particles from the sparks, the oxygen component in the coal gas is removed (O2 concentration below the safe value of 2%), completely avoiding the risk of coal gas explosion. This method can recover the sensible heat across the entire temperature range of the converter gas and the chemical energy of CO released from the gas, achieving dust filtration, CO purification, and full energy recovery of the converter gas. It can generate steam at pressures above 2.0 MPa, recover more than 5 kgce of energy per ton of steel, achieve CO emission concentrations below 50 ppm, and dust emission concentrations below 10 mg / m³. 3 .

[0071] Through practical testing and analysis, the process and system of this invention have the following advantages:

[0072] (1) The dry dust removal method is adopted, the water consumption is zero, and the sensible heat recovery of converter gas in the whole temperature range is realized.

[0073] (2) All thermal and chemical energy in the converter gas is recovered, that is, all energy and quality are recovered.

[0074] (3) The particle bed filters out the sparks (large-diameter dust) in the coal gas and removes the oxygen component in the coal gas, so there is no risk of explosion.

[0075] (4) After dust is recovered, it is pressed into balls to obtain iron-containing particles. The particles can be directly fed into the converter as slag-forming agent to realize the recycling of iron resources.

[0076] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this invention, and these modifications or substitutions should all be covered within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope defined in the claims.

Claims

1. A converter gas purification and energy recovery system, characterized in that, The system includes a moving particle bed, a waste heat boiler, a secondary dust collector, and a gas holder, wherein... The moving particle bed includes an upper bed layer, a middle bed layer and a lower bed layer connected in sequence. The lower bed layer is provided with a first air inlet and a first air outlet of the moving particle bed. The middle bed layer is provided with a second air inlet and a third air inlet of the moving particle bed. The upper bed layer is provided with a second air outlet of the moving particle bed. The converter gas outlet is connected to the first inlet of the moving particle bed, and the first outlet of the moving particle bed is sequentially connected to the waste heat boiler, the secondary dust collector, and the gas holder, forming a gas passage. The gas holder has only one gas inlet and outlet. The pipeline connected to the gas inlet and outlet of the gas holder is divided into two branches: one branch is connected to the secondary dust collector, and the other branch is connected to the third air inlet of the moving particle bed.

2. The converter gas purification and energy recovery system according to claim 1, characterized in that, The particles filling the moving particle bed are made of iron-containing dust, which comes from the moving particle bed and / or a secondary dust collector.

3. The converter gas purification and energy recovery system according to claim 2, characterized in that, Copper and tin elements were also added to the particles.

4. The converter gas purification and energy recovery system according to claim 1, characterized in that, In the moving particle bed, the upper and lower bed layers are vertically arranged, while the middle bed layer is inclined.

5. The converter gas purification and energy recovery system according to claim 4, characterized in that, The inclination angle of the middle section of the bed is 20~40°.

6. The converter gas purification and energy recovery system according to any one of claims 1 to 5, characterized in that, An induced draft fan is provided between the secondary dust collector and the gas holder. A first valve is provided between the gas holder and the induced draft fan. A second valve is provided at the second air inlet. A third valve is provided between the gas holder and the third air inlet.

7. A method for purifying and recovering energy from converter gas, characterized in that, The method employs the system described in claim 6 and includes the following steps: S1. Measure the CO and O2 concentrations in the converter gas at the outlet of the secondary dust collector. If the CO concentration at the outlet of the secondary dust collector is higher than or equal to the set concentration value and the O2 concentration is lower than the set concentration value, then proceed to step S2; If the CO concentration at the outlet of the secondary dust collector is lower than the set concentration value and / or the O2 concentration is higher than the set value, then proceed to step S3; After step S3 is completed, the CO concentration in the converter gas is measured at the gas outlet of the upper bed. If CO is still present, proceed to step S4. S2. Open the first valve and close the second and third valves. After the converter gas enters the lower section of the moving particle bed, the dust contained therein is filtered in the lower section of the bed. The dust-removed converter gas is discharged from the gas outlet of the moving particle bed located in the lower section of the bed, and then enters the waste heat boiler for heat exchange, and then enters the secondary dust collector for dust removal, and then enters the gas holder. S3. Open the third valve and close the first and second valves. The converter gas passes through the lower section of the moving particle bed, the waste heat boiler, and the secondary dust collector in sequence before entering the middle section of the bed. In the middle section of the bed, the converter gas reduces the iron oxide in the particles to metallic iron. The converter gas after removing CO is discharged from the outlet of the lower section of the moving particle bed. Then, it passes through the waste heat boiler and the secondary dust collector in sequence before entering the upper section of the bed to exchange heat with the particles in the moving particle bed in a countercurrent manner before being discharged. S4. During the blowing interval, open the second valve and close the first and third valves to introduce air from the outside into the second air inlet, oxidizing the iron in the particles into iron oxide in the intermediate bed.

8. The method according to claim 7, characterized in that, In step S1, the CO concentration is set to 20%~30%, and the O2 concentration is set to 2%, both of which are volume concentrations.

9. The method according to claim 7, characterized in that, Both the middle and lower bed layers have heat storage functions, and the bed temperature is always maintained above 800℃.

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