Biomass gasification coupling iron ore powder reduction device and method with CO2 circulation

Abstract

The invention provides a biomass gasification coupling iron ore powder reduction device and method with CO2 circulation, and relates to the technical field of direct reduction of iron from biomass gasification products. The biomass gasification coupling iron ore powder reduction device with CO2 circulation comprises a biomass gasification reaction device and a circulating fluidized bed reduction reaction device. The method comprises a method of a biomass gasification reaction device and a method of a circulating fluidized bed reduction reaction device. Through structural arrangement and application of the biomass gasification reaction device and the circulating fluidized bed reduction reaction device, CO2 gas circulation, zero carbon emission and high-purity iron raw material efficient utilization preparation can be achieved; the preparation method is simple and easy to operate, green and environment-friendly, low in cost, short in process, high in efficiency and beneficial to industrial large-scale production and popularization.

Description

Technical Field

[0001] The present invention relates to the technical field of direct reduction of iron by biomass gasification products, and in particular to a biomass gasification coupled iron ore powder reduction device and method with CO2 circulation. Background Art

[0002] With the continuous growth of global energy demand, biomass energy has been proposed and gradually developed as a green and renewable energy source in recent years. Compared with fossil fuels such as oil, coal, and natural gas, biomass energy has the advantages of being green and renewable, having a wide geographical distribution, abundant resources, high activity, and low emissions. Compared with green energy sources such as solar energy, wind energy, and ocean energy, biomass energy stores chemical energy that can be directly converted into chemical products or fuels. Therefore, biomass energy is considered a green alternative to fossil energy.

[0003] As a major agricultural country with vast arable land and economic forests, China generates a significant amount of agricultural and forestry biomass waste annually. Using biomass as an energy source not only effectively disposes of biomass waste but also helps reduce dependence on fossil fuels. With global warming and the 2°C temperature rise target established at the Paris Climate Conference, CO2 capture and storage are also crucial considerations in biomass utilization.

[0004] The steel industry is a major source of carbon dioxide emissions. Globally, it accounts for 5-6% of total carbon emissions, and in China, 15% of carbon dioxide emissions are generated by the steel industry. Currently, smelting one ton of molten iron emits 1.58 tons of carbon dioxide.

[0005] Therefore, in order to achieve the goals of carbon peak and carbon neutrality, the use of a full-process CO2 circulation gasification biomass coupled with iron ore powder reduction process is an effective way to completely solve the high carbon dioxide emission problems of traditional biomass gasification and pig iron smelting processes represented by blast furnaces. Summary of the Invention

[0006] To address the technical problems of existing biomass gasification and gas-based direct iron reduction technologies, which still cannot completely solve carbon dioxide emissions, and the low reduction rate of CO2 direct iron reduction in circulating fluidized bed reactors, the present invention proposes a biomass gasification-coupled iron ore reduction device and method with CO2 circulation that can solve the aforementioned technical problems. The technical solution is as follows:

[0007] A biomass gasification coupled iron ore reduction device with CO2 circulation, the biomass gasification coupled iron ore reduction device with CO2 circulation comprising a biomass gasification reaction device and a circulating fluidized bed reduction reaction device;

[0008] The biomass gasification reaction device mainly includes a gasifying agent mixing device, a gasification furnace, a first gas-solid separation device, a first CO2 gas separation device, a waste residue tank and a first air return device;

[0009] The circulating fluidized bed reduction reaction device mainly includes a gas-solid reduction reaction zone, a second gas-solid separation device, a second CO2 gas separation device, a second return air device, a return material device, a melting pool, a first-stage cyclone preheater, a second-stage cyclone preheater, a third-stage cyclone preheater, a third CO2 gas separation device and a dust collector.

[0010] Optionally, the outlet of the gasifier is connected to the first gas-solid separation device, the heating bottom and top of the first gas-solid separation device are respectively connected to the bottom and waste slag tank of the first CO2 gas separation device, the top of the first CO2 gas separation device is connected to the bottom of the first return air device, the top of the first return air device is connected to the top of the gasifying agent mixing device, and the bottom of the gasifying agent mixing device is connected to the gasifier.

[0011] Optionally, the upper part of the gas-solid reduction reaction zone is connected to the second gas-solid separation device, the lower part of the second gas-solid separation device is connected to the return material device, the return material device is connected to the lower part of the gas-solid reduction reaction zone, and the bottom of the gas-solid reduction reaction zone is connected to the molten pool; the top of the second gas-solid separation device is connected to the bottom of the second CO2 gas separation device, the top and upper part of the second CO2 gas separation device are respectively connected to the second return air device and the upper part of the first-stage cyclone preheater, the top and lower part of the first-stage cyclone preheater are both connected to the upper part of the second-stage cyclone preheater, the top and lower part of the second-stage cyclone preheater are both connected to one end of the upper part of the third-stage cyclone preheater, the other end of the upper part of the third-stage cyclone preheater is connected to the top of the third CO2 gas separation device, and the upper and bottom of the third CO2 gas separation device are respectively connected to the gasification agent mixing device and the dust collector.

[0012] Optionally, the communication between the above devices is carried out through a pipeline.

[0013] Optionally, the upper portion of the first CO2 gas separation device is connected to the connecting pipe between the secondary cyclone preheater and the tertiary cyclone preheater, the connecting pipe between the primary cyclone preheater and the secondary cyclone preheater, and the top of the gas-solid reduction reaction zone.

[0014] A method based on the biomass gasification coupled with iron ore powder reduction device with CO2 circulation, the method of biomass gasification coupled with iron ore powder reduction device with CO2 circulation includes a method of a biomass gasification reaction device and a method of a circulating fluidized bed reduction reaction device.

[0015] Optionally, the method of the biomass gasification reaction device is as follows:

[0016] Water vapor and CO2 are mixed in proportion in the gasifier mixing device, and the preheated biomass particles are sent to the lower part of the gasifier. The mixed gas of fluidized air water vapor and CO2 preheated by the gas preheater is sent to the gasifier through the air distribution plate; after the preheated biomass particles enter the gasifier, they react with water vapor and CO2 under the state of intense gas-solid two-phase flow to generate a large amount of CO, H2 and a small amount of CH4 and other gases. The reaction products enter the first gas-solid separation device with the air flow. In the first gas-solid separation device, ash, residual carbon and other solid products are separated from the gas and enter the waste slag tank. After separation, the gas passes through the first CO2 gas separation device to separate the CO2 alone and enter the first return air device, and then enters the gasifier mixing device to form a CO2 cycle. The remaining gas enters the circulating fluidized bed reduction reaction device.

[0017] Optionally, the method of the circulating fluidized bed reduction reaction device is as follows:

[0018] The preheated iron ore powder is fed into the lower part of the gas-solid reduction reaction zone, and the reducing gas after passing through the second CO2 gas separation device is fed into the gas-solid reduction reaction zone through the air distribution plate; after the preheated high-temperature iron ore powder enters the gas-solid reduction reaction zone, it reacts with the reducing gas under the state of violent gas-solid two-phase flow and is reduced to iron, and a large amount of high-temperature iron ore powder enters the second gas-solid separation device with the air flow. In the second gas-solid separation device, the iron ore powder is separated and enters the return device, and then enters the gas-solid reduction reaction zone, forming a circulation of iron ore powder, and the iron ore powder is eventually reduced to iron through multiple cycles; since the density of iron is greater than that of iron ore powder, the iron and slag generated by the reduction reaction will gradually sink to the bottom of the gas-solid reduction reaction zone, be discharged through the iron discharge port at the bottom, enter the molten pool, and finally form iron billets through slag-iron separation; the post-reduction reaction gas separated by the second gas-solid separation device passes through the second CO2 gas separation device to obtain high-concentration CO2, and enters the gasifying agent mixing device through the second return air device, forming a CO2 circulation;

[0019] The CO2-poor high-temperature gas mainly containing unreacted CO separated from the second CO2 gas separation device is sent to the first-stage cyclone preheater, and iron ore powder and reducing gas are added to the high-temperature reducing gas pipeline; the preheated iron ore powder enters the second-stage cyclone preheater through the lower pipeline of the first-stage cyclone preheater, and the high-temperature flue gas discharged from the top outlet of the first-stage cyclone separator is connected to the pipeline entering the second-stage cyclone preheater, and reducing gas is introduced at the same time; the preheated iron ore powder enters the third-stage cyclone preheater through the lower pipeline of the second-stage cyclone preheater, The high-temperature flue gas discharged from the top outlet of the secondary cyclone separator is connected to the pipeline entering the three-stage cyclone preheater, and reducing gas is introduced at the same time; the preheated iron ore powder is finally connected to the lower part of the gas-solid reduction reaction zone of the circulating fluidized bed reduction reaction device from the bottom of the three-stage cyclone preheater; the high-temperature flue gas discharged from the top outlet of the three-stage cyclone preheater is separated into CO2 by the third CO2 gas separation device, and enters the gasification agent mixing device through the second return air device to form a CO2 circulation, and the remaining gas is discharged into the atmosphere after being treated by the dust collector.

[0020] Optionally, the water vapor comes from the moisture in the biomass itself and steam recovered from waste heat in a steel plant, and the CO2 is obtained through a direct air carbon capture device.

[0021] Optionally, the water vapor is preheated to a temperature of about 200°C.

[0022] Optionally, the temperature of the gasifier is controlled within the range of 800-925°C, the temperature in the entire gasifier is relatively uniform, and the temperature difference between each part is controlled within the range of 0-80°C.

[0023] Optionally, the temperature of the reduction reaction zone is controlled within the range of 700-950°C. Due to the fluidized circulation of a large amount of iron ore powder, the temperature in the entire circulating fluidized bed is relatively uniform, and the temperature difference between each part is controlled within the range of 0-80°C.

[0024] Optionally, the preheated iron ore powder has a particle size range of 0-8 mm and a temperature of 700-950° C.; and the reducing gas comes from a biomass gasification device.

[0025] Optionally, the gas temperature at the top outlet of the first-stage cyclone preheater is controlled at 400-450°C, the gas temperature at the top outlet of the second-stage cyclone preheater is controlled at 650-700°C, and the gas temperature at the top outlet of the third-stage cyclone preheater is controlled at 700-950°C.

[0026] Technical principle of the present invention:

[0027] 1. Existing technologies related to the present invention include air biomass gasification technology; composite gas biomass gasification technology; CO / H2 mixed gas shaft furnace iron ore reduction technology; CO / H2 mixed gas fluidized bed iron ore / powder reduction technology.

[0028] 2. Existing biomass gasification technologies primarily use air, oxygen, water vapor, and mixtures of these gases as gasifying agents. While biomass gasification can help reduce greenhouse gas emissions—for example, the UK's largest 21.5MW waste wood gasification power plant can reduce CO2 emissions by 65,000 tons annually—traditional biomass gasification still produces significant amounts of CO2 due to the use of air as the gasifying agent.

[0029] The reducing agent for existing gas-based direct iron reduction technologies is mainly reducing gas produced by catalytic cracking of natural gas abroad, which consists of CO and H2, with the highest volume fraction of H2 reaching 55%. In China, coal-to-gasification is the main reducing agent, such as coal-to-gasification + reduction shaft furnace process (Baosteel's BL process). Although the above technologies are all gas-based direct iron reduction, they still result in large amounts of carbon dioxide emissions and fail to achieve "green metallurgy."

[0030] 3. This invention uses a CO2-water vapor composite gasifier to gasify biomass and produce reducing gas. The resulting reducing gas (primarily CO and H2) is fed into a circulating fluidized bed reactor to directly reduce iron ore fines, ultimately producing pure iron. The reducing gas at the outlet of the circulating fluidized bed reactor is fed into a multi-stage cyclone separator to heat the iron ore fines and recover the gas's heat energy. The CO2 from both the gasifier and the circulating fluidized bed reactor outlets is fed into the gasifier's gasifying agent inlet for the next biomass gasification cycle. This eliminates the high CO2 emissions associated with CO2 gasification of biomass and CO reduction of iron ore / fines. The entire process is CO2-free, achieving a truly "green metallurgy."

[0031] This method utilizes fine iron ore with a particle size range of 0-8 mm. Compared to conventional blast furnaces, it eliminates the iron ore sintering process. The circulating fluidized bed (CFB) offers efficient heat and mass transfer, long residence time, and high gas-solid reaction rates, resulting in a much higher CO reduction efficiency for fine iron ore than in a shaft furnace. Furthermore, the method utilizes gas recirculation to fully utilize the system's heat, simultaneously increasing both the biomass gasification rate in the gasifier and the iron ore reduction rate in the circulating fluidized bed.

[0032] In the process of preparing reducing gas, the method of using CO2 and steam to gasify biomass can effectively control the production and ratio of CO and H2 in the gasification products. While achieving the reuse of CO2, the gasification products can be directly used for the reduction of iron ore powder, reducing dependence on fossil energy. The circulating fluidized bed is the best reactor for gas-solid reactions. Since the reactor is in a gas-solid two-phase fluidized state, it has the advantages of high heat and mass transfer efficiency, fast chemical reaction rate, and long reaction residence time. It is widely used in chemical processes, coal combustion, coal gasification, etc. The CO2 outlet gas from the gasifier and the reduction reactor is all sent back to the gasifier, turning CO2 from an "emission" into a "reactant", forming a "self-sufficient" carbon cycle, and completely achieving zero carbon dioxide emissions. It is of great significance for the steel industry to achieve carbon neutrality.

[0033] The biomass particles entering the gasifier can quickly react with CO2 and water vapor to form a gasification reaction. The overall reaction equation of the gasification reaction is:

[0034] C x H y O z +wH2O+mCO2→c1H2+c2CO+c3CO2+c4H2O+c5CH4 (1)

[0035] Where w and m are the amount of water and carbon dioxide per mole of biomass fuel, respectively, and c1, c2, c3, c4, and c5 are the coefficients of the gaseous products. The three independent reactions coupled to the global reaction in the equilibrium model are given as follows:

[0036] C + 2H2 → CH4 (2)

[0037] CO + H2O → CO2 + H2 (3)

[0038] C + H2O → CO + H2 (4)

[0039] According to the element balance and equilibrium constant, the coefficient of gaseous products can be calculated. That is:

[0040] Carbon balance: x + m = c2 + c3 + c5 (5)

[0041] Hydrogen balance: y + 2w = 2c1 + 2c4 + 4c5 (6)

[0042] Carbon balance: z + 2m = c2 + 2c3 + c4 (7)

[0043] Equilibrium constant:

[0044] K1=[CH4] / [H2] 2 =c5 / c1 2 (8)

[0045] K2=[CO2][H2] / [CO][H2O]=c1c3 / c2c4 (9)

[0046] K3=[CO][H2] / [H2O]=c1c2 / c4 (10)

[0047] The iron ore powder entering the reduction reaction zone can quickly undergo a reduction reaction with the reducing gas, wherein the overall reaction equation of the reduction reaction is:

[0048] Fe2O3+3CO→2Fe+3CO2 (11)

[0049] Fe2O3+3CH4→2Fe+3CO+6H2 (12)

[0050] Fe2O3+3H2→2Fe+3H2O (13)

[0051] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0052] The above scheme, the present invention proposes a biomass gasification coupled iron ore powder reduction device and method with CO2 circulation, which can solve the technical problems in the existing technology that biomass gasification and gas-based direct iron reduction technology still cannot completely solve the carbon dioxide emissions, and the low reduction rate of CO direct iron reduction in circulating fluidized bed reactors.

[0053] The present invention adopts CO2-water vapor composite gasifying agent to gasify biomass through a biomass gasification reaction device to produce reducing gas CO, and couples it to a circulating fluidized bed reactor to directly reduce iron ore powder, thereby achieving efficient preparation of reducing gas, ironmaking and zero carbon dioxide emissions in the system.

[0054] Replacing coke with gas is a key technological advancement for achieving carbon neutrality in the steel industry. The circulating fluidized bed (CFB) of this invention offers the advantage of good adaptability to iron ore fines, allowing direct use of concentrate without the need for a sintering process. Furthermore, compared to traditional shaft furnaces, CFBs offer the advantages of efficient heat and mass transfer, a fast gas-solid reduction reaction rate, and a high reduction rate for iron ore fines.

[0055] In order to further improve the reduction rate of iron ore powder by hydrogen reduction in a circulating fluidized bed and obtain iron with higher purity, the present invention decouples the two processes of iron ore powder heating and CO reduction, thereby solving the problem of a decrease in the reduction rate of iron ore powder due to an increase in the CO2 partial pressure in the reducing atmosphere caused by CO combustion heating of the iron ore powder.

[0056] The method and device for biomass gasification coupled with iron ore powder reduction with CO2 gas circulation proposed in the present invention have three core advantages: first, zero carbon emissions. By reusing all CO2 products from the gasifier and reduction reactor as gasifying agents, carbon emissions in the process chain are completely eliminated, solving the high-carbon problem of traditional metallurgy; second, efficient resource circulation. Biomass replaces fossil fuels, and CO2 is converted from "waste gas" to "raw material", forming a closed-loop circulation system of "biomass fuel → reducing gas → iron product → CO2 reuse", which greatly reduces energy and carbon costs; third, green metallurgical innovation, breaking through the traditional blast furnace coke dependence, and producing high-purity iron products through the integrated design of the gasification-reduction system, providing the steel industry with a clean production path that can be scalably promoted, which helps to achieve the "dual carbon" goals, has both environmental benefits and economic efficiency, and promotes the steel industry's transformation to "carbon neutrality".

[0057] In summary, compared with other traditional methods, the method of the present invention can achieve CO2 gas circulation, zero carbon emissions and efficient utilization of high-purity iron raw materials through the structural setting and application of the biomass gasification reaction device and the circulating fluidized bed reduction reaction device; the preparation method is simple and easy to operate, green and environmentally friendly, low in cost, short in process, and high in efficiency, which is conducive to large-scale industrial production and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0059] Figure 1 It is a structural schematic diagram of a biomass gasification coupled iron ore powder reduction device with CO2 circulation of the present invention; wherein: label 1' is a gasifying agent mixing device, label 2' is a gasifier, label 3' is a first gas-solid separation device, label 4' is a first CO2 gas separation device, label 5' is a waste slag tank, label 6' is a first return air device 6, label 7' is a gas-solid reduction reaction zone, label 8' is a second gas-solid separation device, label 9' is a second CO2 gas separation device, label 10' is a second return air device, label 11' is a return material device, label 12' is a molten pool, label 13' is a first-stage cyclone preheater, label 14' is a second-stage cyclone preheater, label 15' is a third-stage cyclone preheater, label 16' is a third CO2 gas separation device, and label 17' is a dust collector. DETAILED DESCRIPTION

[0060] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0061] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as an "exemplary" in the present invention should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of the word "exemplary" is intended to present concepts in a concrete manner. Furthermore, in the embodiments of the present invention, "and / or" can mean both or either of the two.

[0062] In the embodiments of the present invention, “image” and “picture” may sometimes be used interchangeably. It should be noted that when the distinction between them is not emphasized, the meanings they intend to express are the same.

[0063] In the embodiments of the present invention, sometimes a subscript such as W1 may be written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0064] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0065] Example 1

[0066] The present embodiment is a biomass gasification coupled iron ore reduction device with CO2 circulation, the biomass gasification coupled iron ore reduction device with CO2 circulation includes a biomass gasification reaction device and a circulating fluidized bed reduction reaction device such as Figure 1 As shown;

[0067] The biomass gasification reaction device mainly includes a gasifying agent mixing device 1', a gasifier 2', a first gas-solid separation device 3', a first CO2 gas separation device 4', a waste residue tank 5' and a first air return device 6'; the outlet of the gasifier 2' is connected to the first gas-solid separation device 3', the heating bottom and top of the first gas-solid separation device 3' are respectively connected to the bottom of the first CO2 gas separation device 4' and the waste residue tank 5', the top of the first CO2 gas separation device 4' is connected to the bottom of the first air return device 6', the top of the first air return device 6' is connected to the top of the gasifying agent mixing device 1', and the bottom of the gasifying agent mixing device 1' is connected to the gasifier 2';

[0068] The circulating fluidized bed reduction reaction device mainly includes a gas-solid reduction reaction zone 7', a second gas-solid separation device 8', a second CO2 gas separation device 9', a second return air device 10', a return material device 11', a molten pool 12', a first-stage cyclone preheater 13', a second-stage cyclone preheater 14', a third-stage cyclone preheater 15', a third CO2 gas separation device 16' and a dust collector 17'; the upper part of the gas-solid reduction reaction zone 7' is connected to the second gas-solid separation device 8', the lower part of the second gas-solid separation device 8' is connected to the return material device 11', the return material device 11' is connected to the lower part of the gas-solid reduction reaction zone 7', and the bottom of the gas-solid reduction reaction zone 7' is connected to the molten pool 12'; The top of the second gas-solid separation device 8' is connected to the bottom of the second CO2 gas separation device 9', the top and upper part of the second CO2 gas separation device 9' are respectively connected to the second air return device 10' and the upper part of the first-stage cyclone preheater 13', the top and lower part of the first-stage cyclone preheater 13' are both connected to the upper part of the second-stage cyclone preheater 14', the top and lower part of the second-stage cyclone preheater 14' are both connected to one end of the upper part of the third-stage cyclone preheater 15', the other end of the upper part of the third-stage cyclone preheater 15' is connected to the top of the third CO2 gas separation device 16', and the upper part and bottom of the third CO2 gas separation device are respectively connected to the gasifying agent mixing device 1' and the dust collector 17';

[0069] The communication between the above devices is carried out through pipelines;

[0070] The upper portion of the first CO2 gas separation device 4' is connected to the connecting pipe between the secondary cyclone preheater 14' and the tertiary cyclone preheater 15', the connecting pipe between the primary cyclone preheater 13' and the secondary cyclone preheater 14', and the top of the gas-solid reduction reaction zone 7'.

[0071] A method based on the biomass gasification coupled with iron ore fines reduction device with CO2 circulation, the method comprising a biomass gasification reaction device and a circulating fluidized bed reduction reaction device;

[0072] The method of the biomass gasification reaction device is as follows:

[0073] Water vapor and CO2 are mixed in proportion in the gasifying agent mixing device 1', and the preheated biomass particles are fed into the lower part of the gasifier 2'. The mixed gas of fluidized air water vapor and CO2 preheated by the gas preheater is fed into the gasifier 2' through the air distribution plate; after the preheated biomass particles enter the gasifier 2', they react with water vapor and CO2 under the state of intense gas-solid two-phase flow to generate a large amount of CO and a small amount of CH4, H2 and other reducing gases. The reaction products enter the first gas-solid separation device 3' with the air flow. In the first gas-solid separation device 3', ash, residual carbon and other solid products are separated from the gas and enter the waste slag tank. After separation, the gas passes through the first CO2 gas separation device 4' to separate the CO2 alone and enter the first return air device 6', and then enters the gasifying agent mixing device 1' to form a CO2 circulation. The remaining gas enters the circulating fluidized bed reduction reaction device;

[0074] The method of the circulating fluidized bed reduction reaction device is as follows:

[0075] The preheated iron ore powder is fed into the lower part of the gas-solid reduction reaction zone 7', and the reducing gas after passing through the second CO2 gas separation device 9' is fed into the gas-solid reduction reaction zone 7' through the air distribution plate; after the preheated high-temperature iron ore powder enters the gas-solid reduction reaction zone 7', it reacts with the reducing gas under the state of violent gas-solid two-phase flow and is reduced to iron. A large amount of high-temperature iron ore powder enters the second gas-solid separation device 8' with the air flow. In the second gas-solid separation device 8', the iron ore powder is separated and enters the return device, and then enters the gas-solid reduction reaction zone 7'. A circulation of iron ore powder is formed, and the iron ore powder is eventually reduced to iron through multiple cycles; since the density of iron is greater than that of iron ore powder, the iron and slag generated by the reduction reaction will gradually sink to the bottom of the gas-solid reduction reaction zone 7', be discharged through the iron discharge port at the bottom, enter the molten pool 12', and finally form iron billets through slag and iron separation; the post-reduction reaction gas separated by the second gas-solid separation device 8' passes through the second CO2 gas separation device 9' to obtain high-concentration CO2, and enters the gasifying agent mixing device 1' through the second return air device 10', forming a CO2 circulation;

[0076] The CO2-poor high-temperature gas mainly containing unreacted CO separated from the second CO2 gas separation device 9' is fed into the primary cyclone preheater 13', and iron ore powder and reducing gas are added to the high-temperature reducing gas pipeline; the preheated iron ore powder enters the secondary cyclone preheater 14' through the lower pipeline of the primary cyclone preheater 13', and the high-temperature flue gas discharged from the top outlet of the primary cyclone separator 13' is connected to the pipeline entering the secondary cyclone preheater 14', and reducing gas is introduced at the same time; the preheated iron ore powder enters the tertiary cyclone preheater 15' through the lower pipeline of the secondary cyclone preheater 14', The high-temperature flue gas discharged from the top outlet of the secondary cyclone separator 14' is connected to the pipeline entering the third-stage cyclone preheater 15', and reducing gas is introduced at the same time; the preheated iron ore powder is finally connected to the lower part of the gas-solid reduction reaction zone 7' of the circulating fluidized bed reduction reaction device from the bottom of the third-stage cyclone preheater 15'; the high-temperature flue gas discharged from the top outlet of the third-stage cyclone preheater 15' is separated into CO2 by the third CO2 gas separation device 16', and enters the gasification agent mixing device 1' through the second return air device to form a CO2 circulation, and the remaining gas is treated by the dust collector 17' and discharged into the atmosphere.

[0077] The water vapor in this embodiment comes from the moisture in the biomass and the steam recovered from the waste heat of the steel plant, and the CO2 is obtained through a direct air carbon capture device.

[0078] The temperature of the water vapor in this embodiment is about 200° C. after preheating.

[0079] The temperature of the gasifier in this embodiment is controlled within the range of 800-925°C. The temperature in the entire gasifier is relatively uniform, and the temperature difference between each part is controlled within the range of 0-80°C.

[0080] The temperature of the reduction reaction zone of this embodiment is controlled within the range of 700-950°C. Due to the fluidized circulation of a large amount of iron ore powder, the temperature in the entire circulating fluidized bed is relatively uniform, and the temperature difference between each part is controlled within the range of 0-80°C.

[0081] In this embodiment, the particle size of the preheated iron ore powder ranges from 0 to 8 mm, and the temperature is 700 to 950° C.; the reducing gas comes from the biomass gasification device.

[0082] In this embodiment, the gas temperature at the top outlet of the first-stage cyclone preheater is controlled at 400-450°C, the gas temperature at the top outlet of the second-stage cyclone preheater is controlled at 650-700°C, and the gas temperature at the top outlet of the third-stage cyclone preheater is controlled at 700-950°C.

[0083] This embodiment takes the production of 1 million tons / year of direct reduced iron as an example. Water vapor and CO2 are mixed in a gasifying agent mixing device at a ratio of 5:1. The temperature of the preheated biomass particles is 250-300°C, the average particle size is 1-5 mm, and the state of intense gas-solid two-phase flow refers to the gas phase flow rate in the gasifier being 74000-76000 Nm 3 / h, the flow rate of solid phase is 18-28Nm 3 / h; the efficiency of the first gas-solid separation device is 90-95%, the efficiency of the first CO2 gas separation device is 80-85%, the efficiency of the first return air device is 95-97%, and the circulation efficiency of CO2 in the biomass gasification reaction device is 80-90%; the efficiency of the second CO2 gas separation device is 85-90%, the efficiency of the second gas-solid separation device is 92-97%, the efficiency of the second return air device is 95-97%, the efficiency of the first-stage cyclone preheater is 80-85%, the efficiency of the second-stage cyclone preheater is 85-90%, the efficiency of the third-stage cyclone preheater is 90-95%, the efficiency of the third CO2 gas separation device is 90-95%, and the circulation efficiency of CO2 in the circulating fluidized bed reduction reaction device is 90-95%.

[0084] Example 2

[0085] This embodiment provides a biomass gasification coupled iron ore powder reduction device with CO2 circulation, and the biomass gasification coupled iron ore powder reduction device with CO2 circulation is shown in Example 1.

[0086] This embodiment takes the production of 1.5 million tons / year of direct reduced iron as an example. Water vapor and CO2 are mixed in a gasifying agent mixing device at a ratio of 5:1. The temperature of the preheated biomass particles is 250-300°C, the average particle size is 1-5 mm, and the state of intense gas-solid two-phase flow refers to the gas phase flow rate in the gasifier being 111,000-113,000 Nm 3 / h, the flow rate of solid phase is 30-40Nm 3 / h; the efficiency of the first gas-solid separation device is 85-90%, the efficiency of the first CO2 gas separation device is 75-80%, the efficiency of the first return air device is 90-92%, and the circulation efficiency of CO2 in the biomass gasification reaction device is 80-90%; the efficiency of the second CO2 gas separation device is 80-85%, the efficiency of the second gas-solid separation device is 87-92%, the efficiency of the second return air device is 90-92%, the efficiency of the first-stage cyclone preheater is 75-80%, the efficiency of the second-stage cyclone preheater is 80-85%, the efficiency of the third-stage cyclone preheater is 85-90%, the efficiency of the third CO2 gas separation device is 85-90%, and the circulation efficiency of CO2 in the circulating fluidized bed reduction reaction device is 85-90%.

[0087] Example 3

[0088] This embodiment provides a biomass gasification coupled iron ore powder reduction device with CO2 circulation, and the biomass gasification coupled iron ore powder reduction device with CO2 circulation is shown in Example 1.

[0089] This embodiment takes the production of 1.2 million tons / year of direct reduced iron as an example. Water vapor and CO2 are mixed in a gasifying agent mixing device at a ratio of 5:1. The temperature of the preheated biomass particles is 250-300°C, the average particle size is 1-5 mm, and the state of intense gas-solid two-phase flow refers to the gas phase flow rate in the gasifier being 89000-91000 Nm 3 / h, the solid phase flow rate is 23-33Nm 3 / h; the efficiency of the first gas-solid separation device is 88-93%, the efficiency of the first CO2 gas separation device is 78-83%, the efficiency of the first return air device is 93-95%, and the circulation efficiency of CO2 in the biomass gasification reaction device is 78-88%; the efficiency of the second CO2 gas separation device is 83-88%, the efficiency of the second gas-solid separation device is 90-95%, the efficiency of the second return air device is 93-95%, the efficiency of the first-stage cyclone preheater is 78-83%, the efficiency of the second-stage cyclone preheater is 83-88%, the efficiency of the third-stage cyclone preheater is 88-93%, the efficiency of the third CO2 gas separation device is 88-93%, and the circulation efficiency of CO2 in the circulating fluidized bed reduction reaction device is 88-93%.

[0090] Example 4

[0091] This embodiment provides a biomass gasification coupled iron ore powder reduction device with CO2 circulation, and the biomass gasification coupled iron ore powder reduction device with CO2 circulation is shown in Example 1.

[0092] This embodiment takes the production of 800,000 tons / year of direct reduced iron as an example. Water vapor and CO2 are mixed in a gasifying agent mixing device at a ratio of 5:1. The temperature of the preheated biomass particles is 250-300°C, the average particle size is 1-5 mm, and the state of intense gas-solid two-phase flow refers to the gas phase flow rate in the gasifier being 59,000-61,000 Nm 3 / h, the solid phase flow rate is 13-23Nm 3 / h; the efficiency of the first gas-solid separation device is 92-97%, the efficiency of the first CO2 gas separation device is 82-87%, the efficiency of the first return air device is 97-99%, and the circulation efficiency of CO2 in the biomass gasification reaction device is 82-92%; the efficiency of the second CO2 gas separation device is 87-92%, the efficiency of the second gas-solid separation device is 94-99%, the efficiency of the second return air device is 97-99%, the efficiency of the first-stage cyclone preheater is 82-87%, the efficiency of the second-stage cyclone preheater is 87-92%, the efficiency of the third-stage cyclone preheater is 92-97%, the efficiency of the third CO2 gas separation device is 92-97%, and the circulation efficiency of CO2 in the circulating fluidized bed reduction reaction device is 92-97%.

[0093] Example 5

[0094] This embodiment provides a biomass gasification coupled iron ore powder reduction device with CO2 circulation, and the biomass gasification coupled iron ore powder reduction device with CO2 circulation is shown in Example 1.

[0095] This embodiment takes the production of 1.2 million tons / year of direct reduced iron as an example. Water vapor and CO2 are mixed in a gasifying agent mixing device at a ratio of 5:1. The temperature of the preheated biomass particles is 250-300°C, the average particle size is 1-5 mm, and the state of intense gas-solid two-phase flow refers to the gas phase flow rate in the gasifier being 89000-91000 Nm 3 / h, the solid phase flow rate is 23-33Nm 3 / h; the efficiency of the first gas-solid separation device is 88-93%, the efficiency of the first CO2 gas separation device is 78-83%, the efficiency of the first return air device is 93-95%, and the circulation efficiency of CO2 in the biomass gasification reaction device is 78-88%; the efficiency of the second CO2 gas separation device is 83-88%, the efficiency of the second gas-solid separation device is 90-95%, the efficiency of the second return air device is 93-95%, the efficiency of the first-stage cyclone preheater is 78-83%, the efficiency of the second-stage cyclone preheater is 83-88%, the efficiency of the third-stage cyclone preheater is 88-93%, the efficiency of the third CO2 gas separation device is 88-93%, and the circulation efficiency of CO2 in the circulating fluidized bed reduction reaction device is 88-93%.

[0096] Example 5

[0097] This embodiment provides a biomass gasification coupled iron ore powder reduction device with CO2 circulation, and the biomass gasification coupled iron ore powder reduction device with CO2 circulation is shown in Example 1.

[0098] This embodiment takes the production of 600,000 tons / year of direct reduced iron as an example. Water vapor and CO2 are mixed in a gasifying agent mixing device at a ratio of 5:1. The temperature of the preheated biomass particles is 250-300°C, the average particle size is 1-5 mm, and the state of intense gas-solid two-phase flow refers to the gas phase flow rate in the gasifier being 44,000-46,000 Nm 3 / h, the solid phase flow rate is 8-18Nm 3 / h; the efficiency of the first gas-solid separation device is 93-98%, the efficiency of the first CO2 gas separation device is 84-89%, the efficiency of the first return air device is 97-99%, and the circulation efficiency of CO2 in the biomass gasification reaction device is 84-94%; the efficiency of the second CO2 gas separation device is 89-94%, the efficiency of the second gas-solid separation device is 94-99%, the efficiency of the second return air device is 97-99%, the efficiency of the first-stage cyclone preheater is 84-89%, the efficiency of the second-stage cyclone preheater is 89-94%, the efficiency of the third-stage cyclone preheater is 94-99%, the efficiency of the third CO2 gas separation device is 94-99%, and the circulation efficiency of CO2 in the circulating fluidized bed reduction reaction device is 94-99%.

[0099] Example 6

[0100] This embodiment provides a biomass gasification coupled iron ore powder reduction device with CO2 circulation, and the biomass gasification coupled iron ore powder reduction device with CO2 circulation is shown in Example 1.

[0101] This embodiment takes the production of 1.3 million tons / year of direct reduced iron as an example. Water vapor and CO2 are mixed in a gasifying agent mixing device at a ratio of 5:1. The temperature of the preheated biomass particles is 250-300°C, the average particle size is 1-5 mm, and the state of intense gas-solid two-phase flow refers to the gas phase flow rate in the gasifier being 96000-98000 Nm 3 / h, the solid phase flow rate is 25-35Nm 3 / h; the efficiency of the first gas-solid separation device is 87-92%, the efficiency of the first CO2 gas separation device is 77-82%, the efficiency of the first return air device is 92-94%, and the circulation efficiency of CO2 in the biomass gasification reaction device is 77-87%; the efficiency of the second CO2 gas separation device is 82-87%, the efficiency of the second gas-solid separation device is 89-94%, the efficiency of the second return air device is 92-94%, the efficiency of the first-stage cyclone preheater is 77-82%, the efficiency of the second-stage cyclone preheater is 82-87%, the efficiency of the third-stage cyclone preheater is 87-92%, the efficiency of the third CO2 gas separation device is 87-92%, and the circulation efficiency of CO2 in the circulating fluidized bed reduction reaction device is 87-92%.

[0102] The above scheme, the present invention proposes a biomass gasification coupled iron ore powder reduction device and method with CO2 circulation, which can solve the technical problems in the existing technology that biomass gasification and gas-based direct iron reduction technology still cannot completely solve the carbon dioxide emissions, and the low reduction rate of CO direct iron reduction in circulating fluidized bed reactors.

[0103] The present invention adopts CO2-water vapor composite gasifying agent to gasify biomass through a biomass gasification reaction device to produce reducing gas CO, and couples it to a circulating fluidized bed reactor to directly reduce iron ore powder, thereby achieving efficient preparation of reducing gas, ironmaking and zero carbon dioxide emissions in the system.

[0104] Replacing coke with gas is a key technological advancement for achieving carbon neutrality in the steel industry. The circulating fluidized bed (CFB) of this invention offers the advantage of good adaptability to iron ore fines, allowing direct use of concentrate without the need for a sintering process. Furthermore, compared to traditional shaft furnaces, CFBs offer the advantages of efficient heat and mass transfer, a fast gas-solid reduction reaction rate, and a high reduction rate for iron ore fines.

[0105] In order to further improve the reduction rate of iron ore powder by hydrogen reduction in a circulating fluidized bed and obtain iron with higher purity, the present invention decouples the two processes of iron ore powder heating and CO reduction, thereby solving the problem of a decrease in the reduction rate of iron ore powder due to an increase in the CO2 partial pressure in the reducing atmosphere caused by CO combustion heating of the iron ore powder.

[0106] The method and device for biomass gasification coupled with iron ore powder reduction with CO2 gas circulation proposed in the present invention have three core advantages: first, zero carbon emissions. By reusing all CO2 products from the gasifier and reduction reactor as gasifying agents, carbon emissions in the process chain are completely eliminated, solving the high-carbon problem of traditional metallurgy; second, efficient resource circulation. Biomass replaces fossil fuels, and CO2 is converted from "waste gas" to "raw material", forming a closed-loop circulation system of "biomass fuel → reducing gas → iron product → CO2 reuse", which greatly reduces energy and carbon costs; third, green metallurgical innovation, breaking through the traditional blast furnace coke dependence, and producing high-purity iron products through the integrated design of the gasification-reduction system, providing the steel industry with a clean production path that can be scalably promoted, which helps to achieve the "dual carbon" goals, has both environmental benefits and economic efficiency, and promotes the steel industry's transformation to "carbon neutrality".

[0107] In summary, compared with other traditional methods, the method of the present invention can achieve CO2 gas circulation, zero carbon emissions and efficient utilization of high-purity iron raw materials through the structural setting and application of the biomass gasification reaction device and the circulating fluidized bed reduction reaction device; the preparation method is simple and easy to operate, green and environmentally friendly, low in cost, short in process, and high in efficiency, which is conducive to large-scale industrial production and promotion.

[0108] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. A and B can be singular or plural. Furthermore, the character " / " as used herein generally indicates an "or" relationship between the associated objects, but it may also indicate an "and / or" relationship. For specific understanding, please refer to the context.

[0109] In this disclosure, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or plural.

[0110] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0111] 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 modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A biomass gasification coupled iron ore powder reduction device with CO2 circulation, characterized in that: The biomass gasification coupled iron ore powder reduction device with CO2 circulation includes a biomass gasification reaction device and a circulating fluidized bed reduction reaction device; The biomass gasification reaction device mainly includes a gasifying agent mixing device, a gasification furnace, a first gas-solid separation device, a first CO2 gas separation device, a waste residue tank and a first air return device; The circulating fluidized bed reduction reaction device mainly includes a gas-solid reduction reaction zone, a second gas-solid separation device, a second CO2 gas separation device, a second return air device, a return material device, a melting pool, a first-stage cyclone preheater, a second-stage cyclone preheater, a third-stage cyclone preheater, a third CO2 gas separation device and a dust collector.

2. The biomass gasification coupled iron ore powder reduction device with CO2 circulation according to claim 1 is characterized in that: The outlet of the gasifier is connected to the first gas-solid separation device, the heating bottom and top of the first gas-solid separation device are respectively connected to the bottom and waste slag tank of the first CO2 gas separation device, the top of the first CO2 gas separation device is connected to the bottom of the first return air device, the top of the first return air device is connected to the top of the gasifying agent mixing device, and the bottom of the gasifying agent mixing device is connected to the gasifier.

3. The biomass gasification coupled iron ore powder reduction device with CO2 circulation according to claim 1 is characterized in that: The upper part of the gas-solid reduction reaction zone is connected to the second gas-solid separation device, the lower part of the second gas-solid separation device is connected to the return material device, the return material device is connected to the lower part of the gas-solid reduction reaction zone, and the bottom of the gas-solid reduction reaction zone is connected to the molten pool; the top of the second gas-solid separation device is connected to the bottom of the second CO2 gas separation device, the top and upper part of the second CO2 gas separation device are respectively connected to the second return air device and the upper part of the first-stage cyclone preheater, the top and lower part of the first-stage cyclone preheater are both connected to the upper part of the second-stage cyclone preheater, the top and lower part of the second-stage cyclone preheater are both connected to one end of the upper part of the third-stage cyclone preheater, the other end of the upper part of the third-stage cyclone preheater is connected to the top of the third CO2 gas separation device, and the upper and bottom of the third CO2 gas separation device are respectively connected to the gasifying agent mixing device and the dust collector.

4. The biomass gasification coupled iron ore powder reduction device with CO2 circulation according to claim 1 is characterized in that: The communication between the above devices is carried out through pipelines.

5. The biomass gasification coupled iron ore powder reduction device with CO2 circulation according to claim 1 is characterized in that: The upper portion of the first CO2 gas separation device is connected to the connecting pipe between the secondary cyclone preheater and the tertiary cyclone preheater, the connecting pipe between the primary cyclone preheater and the secondary cyclone preheater, and the top of the gas-solid reduction reaction zone.

6. A method for coupling the biomass gasification with CO2 circulation to the iron ore fines reduction device according to any one of claims 1 to 5, characterized in that: The method of biomass gasification coupled with iron ore powder reduction device with CO2 circulation includes a method of a biomass gasification reaction device and a method of a circulating fluidized bed reduction reaction device.

7. The method of biomass gasification coupled with iron ore fines reduction device with CO2 circulation according to claim 6, characterized in that: The method of the biomass gasification reaction device is as follows: Water vapor and CO2 are mixed in proportion in the gasifier mixing device, and the preheated biomass particles are sent to the lower part of the gasifier. The mixed gas of fluidized air water vapor and CO2 preheated by the gas preheater is sent to the gasifier through the air distribution plate; after the preheated biomass particles enter the gasifier, they react with water vapor and CO2 under the state of intense gas-solid two-phase flow to generate a large amount of CO, H2 and a small amount of CH4 and other gases. The reaction products enter the first gas-solid separation device with the air flow. In the first gas-solid separation device, ash, residual carbon and other solid products are separated from the gas and enter the waste slag tank. After separation, the gas passes through the first CO2 gas separation device to separate the CO2 alone and enter the first return air device, and then enters the gasifier mixing device to form a CO2 cycle. The remaining gas enters the circulating fluidized bed iron ore powder reduction reaction device.

8. The method of biomass gasification coupled with iron ore fines reduction device with CO2 circulation according to claim 6, characterized in that: The method of the circulating fluidized bed reduction reaction device is as follows: The preheated iron ore powder is fed into the lower part of the gas-solid reduction reaction zone, and the reducing gas after passing through the second CO2 gas separation device is fed into the gas-solid reduction reaction zone through the air distribution plate; after the preheated high-temperature iron ore powder enters the gas-solid reduction reaction zone, it reacts with the reducing gas under the state of violent gas-solid two-phase flow and is reduced to iron, and a large amount of high-temperature iron ore powder enters the second gas-solid separation device with the air flow. In the second gas-solid separation device, the iron ore powder is separated and enters the return device, and then enters the gas-solid reduction reaction zone, forming a circulation of iron ore powder, and the iron ore powder is eventually reduced to iron through multiple cycles; since the density of iron is greater than that of iron ore powder, the iron and slag generated by the reduction reaction will gradually sink to the bottom of the gas-solid reduction reaction zone, be discharged through the iron discharge port at the bottom, enter the molten pool, and finally form iron billets through slag-iron separation; the post-reduction reaction gas separated by the second gas-solid separation device passes through the second CO2 gas separation device to obtain high-concentration CO2, and enters the gasifying agent mixing device through the second return air device, forming a CO2 circulation; The CO2-poor high-temperature gas mainly containing unreacted CO separated from the second CO2 gas separation device is sent to the first-stage cyclone preheater, and iron ore powder and reducing gas are added to the high-temperature reducing gas pipeline; the preheated iron ore powder enters the second-stage cyclone preheater through the lower pipeline of the first-stage cyclone preheater, and the high-temperature flue gas discharged from the top outlet of the first-stage cyclone separator is connected to the pipeline entering the second-stage cyclone preheater, and reducing gas is introduced at the same time; the preheated iron ore powder enters the third-stage cyclone preheater through the lower pipeline of the second-stage cyclone preheater, The high-temperature flue gas discharged from the top outlet of the secondary cyclone separator is connected to the pipeline entering the three-stage cyclone preheater, and reducing gas is introduced at the same time; the preheated iron ore powder is finally connected to the lower part of the gas-solid reduction reaction zone of the circulating fluidized bed reduction reaction device from the bottom of the three-stage cyclone preheater; the high-temperature flue gas discharged from the top outlet of the three-stage cyclone preheater is separated into CO2 by the third CO2 gas separation device, and enters the gasification agent mixing device through the second return air device to form a CO2 circulation, and the remaining gas is discharged into the atmosphere after being treated by the dust collector.

9. The method of biomass gasification coupled with iron ore fines reduction device with CO2 circulation according to claim 7, characterized in that: The water vapor comes from the moisture in the biomass and steam recovered from waste heat in the steel plant, and the CO2 is obtained through a direct air carbon capture device.

10. The method of biomass gasification coupled with iron ore fines reduction device with CO2 circulation according to claim 8, characterized in that: The particle size of the preheated iron ore powder ranges from 0 to 8 mm, and the temperature is 700 to 950°C; the reducing gas comes from the biomass gasification device.

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