A pulverized coal injection system and method utilizing CO2 separated from furnace top gas as the conveying medium.

Abstract

The application discloses a coal injection system and method using blast furnace top gas as a CO2 separation medium. The system comprises a blast furnace body unit (1), a clean gas decarburization unit (2), and a pulverized coal injection unit (3). The clean gas decarburization unit (2) is connected to the blast furnace body unit (1) at the clean gas outlet, receives blast furnace clean gas, and separates CO2 therefrom, producing enriched gas and high-purity CO2 gas. The pulverized coal injection unit (3) is connected to the clean gas decarburization unit (2) at the CO2 outlet, receives the high-purity CO2 gas, and injects pulverized coal into the blast furnace body unit (1) using the high-purity CO2 gas as the only delivery medium. The application enriches the clean gas produced by the blast furnace by decarburization, and the CO2 gas produced by decarburization is pressurized and used as the delivery gas for the blast furnace. The application recycles and utilizes the CO2 gas produced by decarburization of the blast furnace gas.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to a pulverized coal injection system and method that uses CO2 separated from furnace top gas as the conveying medium. Background Technology

[0002] Pulverized coal injection (PCI) is a core and mature technology in modern ironmaking industry, used to reduce costs, increase efficiency, replace coke, and lower smelting energy consumption. Currently, most blast furnace PCI systems in China use compressed air or nitrogen as the carrier gas for pneumatic conveying of pulverized coal.

[0003] However, with the increasing demands for low-carbon transformation and energy efficiency upgrades in the steel industry, the technological shortcomings of traditional gas transportation methods are becoming increasingly apparent: Compressed air: Contains oxygen, posing safety risks such as coal powder oxidation, spontaneous combustion, and even explosion. It is not suitable for high-volatile coal powder and high-load injection.

[0004] Nitrogen: Although it is highly safe, as an inert gas, it will dilute the concentration of effective reducing gas (CO) in the blast furnace after entering it, which will have a certain negative impact on the furnace condition and smelting efficiency.

[0005] Therefore, there is an urgent need for a new pulverized coal injection conveying process that can balance safety, economy, and environmental protection. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a pulverized coal injection system and method that uses CO2 separated from blast furnace top gas as the conveying medium. By recycling the CO2 gas generated from the decarbonization of blast furnace gas, low-carbon, safe and efficient production of blast furnace ironmaking can be achieved.

[0007] To achieve the above objectives, the present invention provides a pulverized coal injection system that uses CO2 separated from the furnace top gas as the conveying medium, comprising a blast furnace body unit (1), a clean gas decarbonization unit (2), and a pulverized coal injection unit (3). Blast furnace body unit (1) is used to generate clean blast furnace gas; The clean gas decarbonization unit (2) has its inlet connected to the clean gas outlet of the blast furnace body unit (1) for receiving blast furnace clean gas and separating CO2 from it to produce enriched gas and high-purity CO2 gas. The pulverized coal injection unit (3) has its gas source inlet connected to the CO2 outlet of the clean coal gas decarbonization unit (2) for receiving the high-purity CO2 gas; The pulverized coal injection unit (3) is configured to use the high-purity CO2 gas as the only conveying medium to inject pulverized coal into the blast furnace body unit (1).

[0008] Furthermore, the pulverized coal injection unit (3) includes a pulverized coal injection tank (304) and a CO2 pressurizer (302). The CO2 pressurizer (302) is located between the clean coal gas decarbonization unit (2) and the pulverized coal injection tank (304) to pressurize the separated high-purity CO2 gas to the injection pressure and then deliver it to the pulverized coal injection tank (304).

[0009] Furthermore, the pulverized coal injection tank (304) is provided with multiple gas inlets, and the high-purity CO2 gas enters the pulverized coal injection tank (304) as ramming gas, fluidizing gas and conveying gas respectively.

[0010] Furthermore, the pulverized coal injection unit (3) also includes a gas replenisher (307). The outlet of the CO2 compressor (302) is connected to the gas replenisher (307) through a CO2 gas replenishment pipe (305). The high-purity CO2 gas enters the gas replenisher (307) as a pressurizing gas.

[0011] Furthermore, the clean gas decarbonization unit (2) is also equipped with an enriched gas outlet and a CO2 bypass outlet; The enriched gas outlet is used to transport the remaining gas after CO2 separation to the external gas pipeline network. The CO2 bypass outlet is used to export or store excess high-purity CO2 gas.

[0012] Furthermore, the volume purity of the high-purity CO2 gas is greater than 95%.

[0013] To achieve the above objectives, the present invention provides a pulverized coal injection method using the above-described system and employing CO2 separated from furnace top gas as the conveying medium, comprising the following steps: Step S1: Collect the clean blast furnace gas generated by the blast furnace body unit (1); Step S2: The blast furnace clean gas is sent into the clean gas decarbonization unit (2) to separate high-purity CO2 gas and enriched gas; Step S3: Pressurize the high-purity CO2 gas and deliver it to the pulverized coal injection unit (3); Step S4: In the pulverized coal injection unit (3), the high-purity CO2 gas is used as the conveying medium to inject pulverized coal into the blast furnace body unit (1) for combustion and reduction reaction.

[0014] Furthermore, in step S2, the CO concentration in the separated enriched gas is higher than that in the original blast furnace gas, and the enriched gas is transported to an external gas pipeline network for use as fuel.

[0015] Furthermore, in step S4, the high-purity CO2 gas injected into the blast furnace body unit (1) undergoes an endothermic reaction with the hot coke or pulverized coal in the tuyeres swirling zone to generate CO. The reaction equation is: CO2 + C = 2CO.

[0016] The present invention has the following advantages: (1) Achieving deep low-carbon circulation: Unlike existing technologies that use blast furnace gas (containing 50% nitrogen), this invention extracts high-purity CO2 through a decarbonization unit, completely eliminating the introduction of nitrogen from the conveying medium. After entering the blast furnace, CO2 is converted into CO, an effective reducing agent, through an endothermic reaction (CO2+C=2CO), achieving efficient intraplant circulation of carbon elements and significantly reducing carbon emissions.

[0017] (2) Improve the calorific value of coal gas: The enriched coal gas (mainly composed of CO and H2 with low nitrogen content) after CO2 separation has a significantly improved calorific value and can be supplied as high-quality fuel, thus improving energy utilization efficiency.

[0018] (3) High safety: CO2 is an inert gas, which completely eliminates the risk of combustion and explosion caused by the use of compressed air. Its safety is comparable to that of nitrogen and is superior to that of blast furnace gas. At the same time, as a transport gas, CO2 can transport more coal powder per unit volume due to its larger molecular weight, making it easier to achieve dense phase transport.

[0019] (4) Optimize the smelting process: avoid the dilution effect of a large amount of nitrogen on the gas in the furnace, which is conducive to improving the theoretical combustion temperature and gas utilization rate. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a pulverized coal injection system that utilizes CO2 separated from furnace top gas as the conveying medium, according to the present invention. Detailed Implementation

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] like Figure 1 As shown, the present invention provides a pulverized coal injection system that uses CO2 separated from blast furnace top gas as the conveying medium, which mainly includes a blast furnace body unit (1), a clean gas decarbonization unit (2) and a pulverized coal injection unit (3).

[0026] The blast furnace body unit (1) includes a blast furnace body (101), a crude gas dust collector (102), a pulverized coal injection gun (103), and a pulverized coal distributor (104). The dust-laden gas generated by the blast furnace body (101) is purified into clean gas after passing through the crude gas dust collector (102).

[0027] The clean coal gas decarbonization unit (2) includes a decarbonization tank (201), a CO2 pipeline (202), a clean coal gas pipeline (203), an enriched clean coal gas pipeline (204), and a clean coal gas bypass pipeline (205). The decarbonization tank can be a membrane separation type, a pressure swing adsorption type, or a solvent absorption type, as needed. Part of the clean coal gas enters the decarbonization tank (201) through the clean coal gas pipeline (203), where CO2 and enriched coal gas are separated. The enriched coal gas is sent to the external coal gas network through the enriched clean coal gas pipeline (204).

[0028] The pulverized coal injection unit (3) includes a CO2 bypass pipe (301), a CO2 compressor (302), a high-pressure CO2 pipe (303), a pulverized coal injection tank (304), a CO2 make-up gas pipe (305), a pulverized coal conveying main pipe (306), and a make-up gas device (307).

[0029] During operation, in the blast furnace body unit (1), the blast furnace body (101) generates dust-laden blast furnace gas. After being removed by the crude gas dust collector (102), a portion of the gas enters the decarbonization tank (201) of the clean gas decarbonization unit (2). The enriched gas generated enters the external gas pipeline network through the enriched clean gas pipe (204). A portion of the clean gas can also directly enter the external gas pipeline network without passing through the decarbonization tank (201) to remove CO2. After the CO2 gas generated in the decarbonization tank (201) enters the pulverized coal injection unit (3), it is pressurized to a suitable pulverized coal injection conveying pressure by the CO2 pressurizer (302). The high-pressure CO2 gas enters the pulverized coal injection tank (304) through the high-pressure CO2 pipe (303), and is divided into multiple branch pipes, which serve as the ram gas, fluidizing gas and conveying gas for pulverized coal injection, respectively. The pulverized coal gas-solid fluid after high-pressure CO2 fluidization enters the make-up gas device (307) through the pulverized coal conveying main pipe (306). The high-pressure CO2 gas can also be passed through the CO2 pump. 2. The gas supply pipe (305) enters the gas supply device (307) as a pressurizing gas source. After being supplied with gas by the gas supply device (307), the gas-solid coal powder mixture circulates into the blast furnace body unit (1). After being evenly distributed by the coal powder distributor (104), it is injected into the blast furnace body (101) through the coal powder spray gun (103). At the nozzle of the coal powder spray gun (103), the C in the coal powder reacts with the CO2 of the conveying gas under high temperature to generate CO, thereby optimizing the blast furnace reduction kinetics, increasing the coal powder injection rate, and increasing the blast furnace output.

[0030] In addition, if excess CO2 is generated during decarbonization, it can be supplied to other users through the CO2 bypass pipe (301). If the injection distance is short, the make-up gas device (307) may not be required.

[0031] This invention decarbonizes and enriches the clean blast furnace gas, then pressurizes the CO2 produced during decarbonization and uses it as the conveying gas for pulverized coal injection in the blast furnace. By recycling the CO2 generated from blast furnace gas decarbonization, this invention achieves the goal of carbon reduction in blast furnaces. Leveraging the high-temperature reducing environment of the blast furnace, CO2 offers multiple advantages, including safe transportation, participation in in-furnace reactions, low-consumption transportation, and low-carbon recycling. It can simultaneously achieve waste gas disposal, energy saving, and carbon reduction, while increasing pulverized coal injection and blast furnace output. This promotes the transformation of blast furnace ironmaking towards a low-carbon circular production model, demonstrating good policy compatibility and industrial promotion value.

[0032] The present invention has been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described above. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Many other changes and modifications made without departing from the concept and scope of the present invention should be considered within the scope of protection of the present invention.

[0033] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0034] 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 variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A pulverized coal injection system using CO2 separated from furnace top gas as the conveying medium, characterized in that, It includes a blast furnace body unit (1), a clean gas decarbonization unit (2), and a pulverized coal injection unit (3). Blast furnace body unit (1) is used to generate clean blast furnace gas; The clean gas decarbonization unit (2) has its inlet connected to the clean gas outlet of the blast furnace body unit (1) for receiving blast furnace clean gas and separating CO2 from it to produce enriched gas and high-purity CO2 gas. The pulverized coal injection unit (3) has its gas source inlet connected to the CO2 outlet of the clean coal gas decarbonization unit (2) for receiving the high-purity CO2 gas; The pulverized coal injection unit (3) is configured to use the high-purity CO2 gas as the only conveying medium to inject pulverized coal into the blast furnace body unit (1).

2. The pulverized coal injection system using CO2 separated from furnace top gas as the conveying medium according to claim 1, characterized in that, The pulverized coal injection unit (3) includes a pulverized coal injection tank (304) and a CO2 pressurizer (302). The CO2 pressurizer (302) is located between the clean coal gas decarbonization unit (2) and the pulverized coal injection tank (304) to pressurize the separated high-purity CO2 gas to the injection pressure and then deliver it to the pulverized coal injection tank (304).

3. The pulverized coal injection system using CO2 separated from furnace top gas as the conveying medium according to claim 2, characterized in that, The pulverized coal injection tank (304) is provided with multiple gas inlets, and the high-purity CO2 gas enters the pulverized coal injection tank (304) as ramming gas, fluidizing gas and conveying gas respectively.

4. The pulverized coal injection system using CO2 separated from furnace top gas as the conveying medium according to claim 2, characterized in that, The pulverized coal injection unit (3) also includes a gas replenisher (307). The outlet of the CO2 compressor (302) is connected to the gas replenisher (307) through a CO2 gas replenishment pipe (305). The high-purity CO2 gas enters the gas replenisher (307) as a pressurizing gas.

5. The pulverized coal injection system using CO2 separated from furnace top gas as the conveying medium according to claim 1, characterized in that, The clean gas decarbonization unit (2) is also equipped with enriched gas outlet and CO2 bypass outlet; The enriched gas outlet is used to transport the remaining gas after CO2 separation to the external gas pipeline network. The CO2 bypass outlet is used to export or store excess high-purity CO2 gas.

6. The pulverized coal injection system using CO2 separated from furnace top gas as the conveying medium according to claim 1, characterized in that, The volume purity of the high-purity CO2 gas is greater than 95%.

7. A pulverized coal injection method using CO2 separated from furnace top gas as a conveying medium, implemented based on the system described in any one of claims 1-6, characterized in that, Includes the following steps: Step S1: Collect the clean blast furnace gas generated by the blast furnace body unit (1); Step S2: The blast furnace clean gas is sent into the clean gas decarbonization unit (2) to separate high-purity CO2 gas and enriched gas; Step S3: Pressurize the high-purity CO2 gas and deliver it to the pulverized coal injection unit (3); Step S4: In the pulverized coal injection unit (3), the high-purity CO2 gas is used as the conveying medium to inject pulverized coal into the blast furnace body unit (1) for combustion and reduction reaction.

8. The pulverized coal injection method according to claim 7, characterized in that, In step S2, the CO concentration in the separated enriched gas is higher than that in the original blast furnace gas, and the enriched gas is transported to an external gas pipeline network for use as fuel.

9. The pulverized coal injection method according to claim 7, characterized in that, In step S4, the high-purity CO2 gas injected into the blast furnace body unit (1) undergoes an endothermic reaction with the hot coke or pulverized coal in the tuyeres swirling zone to generate CO. The reaction equation is: CO2 + C = 2CO.

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