Exhaust gas reforming method, blast furnace operation method, and exhaust gas temperature-raising reforming equipment

Abstract

To provide a method for reforming blast furnace exhaust gas, a blast furnace operation method, and an exhaust gas temperature-raising reforming facility that are superior in terms of production cost and production efficiency without using large-scale heat exchangers. [Solution] A method for reforming exhaust gas, which reforms CO2 gas contained in the exhaust gas of a blast furnace into a reformed gas containing CO and H2, comprising: a combustion step in which a combustible gas and air are supplied to a hot blast furnace 51 and the hot blast furnace 51 is heated by combustion in the hot blast furnace 51; and a heating and reforming step in which CO2 gas is supplied to the heated hot blast furnace 51, the CO2 gas is heated in the hot blast furnace 51 and the heated CO2 gas is reacted with a hydrocarbon gas to reform the CO2 gas into a reformed gas.

Description

Technical Field

[0001] The present invention relates to a method for reforming exhaust gas, an operation method for a blast furnace, and equipment for heating and reforming exhaust gas.

Background Art

[0002] In the operation of a blast furnace, for the purpose of reducing CO2 emissions, a technology for reforming CO2 in the exhaust gas generated in the blast furnace and reusing it is used. For example, Patent Document 1 discloses a technology for separating CO2 in the gas generated in a blast furnace, reacting it with CH4 to generate a reformed gas containing CO and H2, and blowing the generated reformed gas into the tuyere of the blast furnace.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the technology of Patent Document 1 has problems in installation space and installation cost because a large-scale heat exchanger is required when heating and raising the temperature of the reformed gas.

[0005] As a technology for solving the above problems, there is also known a technology that uses the hot blast stove of a blast furnace as heating and reforming equipment and raises the temperature of the reformed gas in addition to reforming CO2. In this technology, CO2 gas and CH4 gas are passed through the regenerator bricks of the hot blast stove heated by the combustion of combustible gas, thereby reforming and raising the temperature of the CO2 gas. However, this technology using the hot blast stove of a blast furnace has the following problems.

[0006] The hot blast stove of a blast furnace needs to alternately repeat a process of burning combustible gas to raise the temperature of the regenerator bricks (combustion process) and a process of passing the gas to be heated through the regenerator bricks to raise the temperature (blowing process).

[0007] This is also true when using a hot blast furnace to reform and heat exhaust gas. In other words, it is necessary to alternate between a process of burning combustible gas to heat the heat storage bricks (combustion process) and a process of passing CO2 gas and CH4 gas through the heat storage bricks to heat them and reform them (heating and reforming process). Furthermore, when using a hot blast furnace to reform and heat exhaust gas, after the heating and reforming process the furnace is filled with combustible gas produced by the reforming. For this reason, in order to prevent explosions in the combustion process, it is necessary to replace (purge) the furnace with an inert gas such as N2 gas before proceeding to the combustion process. In short, when using a hot blast furnace to reform and heat exhaust gas, there was a problem of increased production costs because a large amount of inert gas was required, and the refractory material inside the furnace was cooled and lost heat. In addition, the time required for the purging process also led to a decrease in production efficiency.

[0008] Therefore, the present invention has been made in view of the above-mentioned problems, and aims to provide a method for reforming exhaust gas from a blast furnace, a method for operating a blast furnace, and an exhaust gas temperature-raising reforming facility that are excellent in terms of production cost and production efficiency, without using a large-scale heat exchanger when reforming exhaust gas from a blast furnace. [Means for solving the problem]

[0009] (1) According to one aspect of the present invention, there is a method for modifying exhaust gas, which modifies CO2 gas contained in the exhaust gas of a blast furnace into a modified gas containing CO and H2, comprising: a combustion step of supplying a combustible gas and air to a hot blast furnace and burning them in the hot blast furnace to raise the temperature of the hot blast furnace; and a temperature-boosting modification step of supplying the CO2 gas to the heated hot blast furnace, raising the temperature of the CO2 gas in the hot blast furnace, and reacting the heated CO2 gas with a hydrocarbon gas to modify the CO2 gas into the modified gas.

[0010] (2) According to one aspect of the present invention, in the exhaust gas reforming method described in (1) above, in the temperature rise reforming step, only the CO2 gas contained in the exhaust gas discharged from the blast furnace is supplied to the hot blast furnace. (3) According to one aspect of the present invention, a method for operating a blast furnace is provided, which involves reforming CO2 gas contained in exhaust gas discharged from a blast furnace into a reformed gas using the exhaust gas reforming method described in (1) or (2) above, and blowing the reformed gas into the tuyeres of the blast furnace.

[0011] (4) According to one aspect of the present invention, an exhaust gas temperature-raising and reforming apparatus is provided for reforming CO2 gas contained in the exhaust gas of a blast furnace into a reformed gas containing CO and H2, comprising a hot blast furnace, a reforming device, and a control device for controlling the hot blast furnace and the reforming device, wherein the control device supplies combustible gas and air to the hot blast furnace and burns them in the hot blast furnace to raise the temperature of the hot blast furnace, supplies the CO2 gas to the heated hot blast furnace to raise the temperature of the CO2 gas in the hot blast furnace, supplies the heated CO2 gas and hydrocarbon gas to the reforming device and reacts them to reform the CO2 gas into the reformed gas. [Effects of the Invention]

[0012] According to one aspect of the present invention, a method for reforming exhaust gas from a blast furnace, a method for operating a blast furnace, and an exhaust gas temperature-raising reforming facility are provided that offer excellent production cost and production efficiency without using a large-scale heat exchanger. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing a blast furnace facility according to one embodiment of the present invention. [Figure 2] This is a schematic diagram of a hot air furnace. [Figure 3] This is an explanatory diagram showing an exhaust gas reforming method according to one embodiment of the present invention. [Figure 4] This is a schematic diagram showing a conventional blast furnace facility. [Figure 5] This is an explanatory diagram showing a conventional exhaust gas reforming method. [Modes for carrying out the invention]

[0014] The following detailed description will illustrate embodiments of the present invention with reference to the drawings. In the drawings, identical or similar parts are denoted by the same or similar reference numerals, and redundant descriptions are omitted. Each drawing is schematic and may differ from reality. Furthermore, the embodiments shown below are illustrative of apparatus and methods for realizing the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not limited to the materials, structure, arrangement, etc., of the components described below. The technical idea of ​​the present invention can be modified in various ways within the technical scope defined by the claims described in the patent claims.

[0015] <Equipment configuration> A blast furnace facility according to one embodiment of the present invention will be described with reference to the drawings. As shown in Figure 1, the blast furnace facility 1 comprises a blast furnace 2, a CO2 separation and recovery unit 3, a pressurization unit 4, and a temperature-boosting reforming unit 5.

[0016] Blast furnace 2 is a blast furnace that produces pig iron using iron ore and coke as raw materials. In blast furnace 2, raw materials such as coke and iron ore are charged from the top of the furnace, and pure oxygen gas and a reformed gas (described later) are blown in from tuyeres at the bottom of the furnace to melt and reduce the iron ore, and a refining process is carried out to obtain molten iron from the tap. In blast furnace 2, exhaust gas containing CO2 is generated as a result of this refining process. At least a portion of the exhaust gas is recovered at the top of blast furnace 2 and reformed by the method described later.

[0017] The CO₂ separation and recovery device 3 is a device that separates and recovers CO₂ gas from the exhaust gas generated in the blast furnace 2 and recovered. The method of separation and recovery is not particularly limited and can be performed using known methods. For example, the CO₂ separation and recovery device 3 may separate and recover CO₂ gas using an amine. The CO₂ gas separated and recovered by the CO₂ separation and recovery device 3 is sent to the pressure boosting equipment 4. The CO₂ gas separated and recovered by the CO₂ separation and recovery device 3 only needs to be a gas containing CO₂ as the main component, and may contain steam or the like. Further, the separated and recovered CO₂ gas does not contain combustible gas. Furthermore, the exhaust gas from which the CO₂ gas has been separated is a combustible gas containing CO and H₂ and is reused within the steelworks.

[0018] The pressure boosting equipment 4 is equipment that boosts the pressure of the CO₂ gas separated and recovered from the exhaust gas. The CO₂ gas boosted by the pressure boosting equipment 4 is sent to the temperature raising and reforming equipment 5. For example, the pressure boosting equipment 4 boosts the pressure of the separated and recovered CO₂ gas to a pressure above the pressure loss in the blast furnace hearth, usually to about 0.3 to 0.5 MPa. Also, in order to improve the reforming efficiency of the CO₂ gas in the temperature raising and reforming equipment 5, the CO₂ gas may be further pressurized.

[0019] The temperature raising and reforming equipment 5 is equipment that raises the temperature of the boosted CO₂ gas and reforms it. The temperature raising and reforming equipment 5 includes a hot blast stove 51, a reforming device 52, and a control device 53.

[0020] As shown in Figure 2, the hot blast stove 51 has a combustion chamber 511 connected at the upper part and a regenerator 512. The combustion chamber 511 and the regenerator 512 are such that the gas supplied from the lower part of one is sent to the other through the upper connection path and discharged from the lower part of the other. Also, the hot blast stove 51 has heat storage bricks 513 inside the regenerator 512. The heat storage bricks 513 are bricks that store the heat generated by the combustion of combustible gas in the combustion process described later. In the present embodiment, the hot blast stove 51 is a device that raises the temperature of the CO₂ gas sent from the pressure boosting equipment 4 and sends the heated CO₂ gas to the reforming device 52. The blast furnace equipment 1 is provided with a plurality of hot blast stoves 51, for example, 3 to 4 hot blast stoves 51.

[0021] The reforming device 52 is a device that reforms the heated CO2 gas to produce a reformed gas. The reforming device 52 reacts CH4 gas supplied separately from the CO2 gas with the high-temperature CO2 gas heated in the hot blast stove 51 using a catalyst to produce a reformed gas containing CO and H2. The produced reformed gas is sent to the tuyere of the blast furnace 2 and used for refining in the blast furnace 2. A plurality of reforming devices 52 may be provided corresponding to the plurality of hot blast stoves 51, or one reforming device 52 may be provided for the plurality of hot blast stoves 51.

[0022] The control device 53 is a device that controls the operations of the hot blast stove 51 and the reforming device 52. Specifically, the control device 53 controls the supply and discharge of various gases to and from the hot blast stove 51 and the reforming device 52. Thereby, the reforming of the exhaust gas in the reforming facility 5 is performed. Details of the control of the hot blast stove 51 and the reforming device 52 by the control device 53 will be described later.

[0023] <Exhaust gas reforming method> Next, the exhaust gas reforming method according to the present embodiment will be described. In the present embodiment, as shown in FIG. 3, after the combustion process is performed, the temperature-raising reforming process is performed. Thereafter, the combustion process and the temperature-raising reforming process are repeated in order again.

[0024] In the combustion process, as shown in FIG. 3(A), combustible gas and air are supplied to the combustion chamber 511 of the hot blast stove 51, and the combustible gas and air are burned in the hot blast stove 51. Thereby, the heat storage bricks 513 of the hot blast stove 51 are heated. Also, exhaust gas is discharged from the lower part of the heat storage chamber 512. The combustion process is performed until a predetermined time elapses, for example, until the heat storage bricks are about 1300°C.

[0025] In the temperature-boosting reforming process, as shown in Figure 3(B), CO2 gas is first supplied from the pressurization equipment 4 to the heat storage chamber 512 of the hot blast furnace 51. The supplied CO2 gas is separated and recovered from the exhaust gas and is a gas that mainly contains CO2. The supplied CO2 gas may contain steam, etc., but it does not contain flammable gases. In the temperature-boosting reforming process, it is preferable that only CO2 gas is supplied to the heat storage chamber 512. The supplied CO2 gas is heated by the heat storage bricks 513 that have been heated in the combustion process. At this time, the CO2 gas is heated to, for example, about 1100°C. The heated CO2 gas is supplied to the reforming device 52 from the bottom of the combustion chamber 511. Next, in the reforming device 52, the CO2 gas supplied from the hot blast furnace 51 is reacted with CH4 gas supplied separately from the CO2 gas to produce a reformed gas containing CO and H2. In other words, in the reforming unit 52, CO2 gas is reformed into reformed gas. The generated reformed gas is supplied to the tuyeres of the blast furnace 2 and used in the refining process of the blast furnace 2 together with pure oxygen gas. The temperature-raising reforming process is carried out until a predetermined time has elapsed.

[0026] Furthermore, the control of the supply and discharge of various gases during the combustion process and the temperature-raising reforming process is performed by the control device 53.

[0027] In this embodiment, the combustion process and the temperature-raising reforming process are repeated. During the temperature-raising reforming process, CO2 gas is supplied to the hot blast furnace 51, so after the temperature-raising reforming process, the hot blast furnace 51 is filled with CO2 gas, which is a non-combustible gas. Therefore, after the temperature-raising reforming process, the combustion process can be carried out continuously without replacing the inside of the hot blast furnace 51 with an inert gas such as N2 gas to prevent explosions.

[0028] Here, with reference to Figures 4 and 5, a conventional exhaust gas reforming method using a hot blast furnace as the reforming and heating equipment 5a will be described. As shown in Figure 4, in the conventional exhaust gas reforming method, the blast furnace equipment 1a comprises a blast furnace 2a, a CO2 separation and recovery unit 3a, a pressurization unit 4a, and a reforming and heating equipment 5a. The blast furnace 2a, the CO2 separation and recovery unit 3a, and the pressurization unit 4a have the same configuration as those in this embodiment.

[0029] As shown in Figure 5, the reforming and heating equipment 5a uses a hot air furnace and has a combustion chamber 54a, a heat storage chamber 55a, and a heat storage brick 56a. The combustion chamber 54a and the heat storage chamber 55a are the same as the combustion chamber 511 and the heat storage chamber 512 in this embodiment. On the other hand, unlike the heat storage brick 513 in this embodiment, the heat storage brick 56a needs to have a reforming function in addition to a heat storage function. For this reason, it is necessary to have a brick with a catalytic function, or to provide a catalyst separately from the brick.

[0030] As shown in Figure 5, the exhaust gas reforming in the reforming and heating equipment 5a involves a combustion process, a reforming and heating process, and a purging process, which are repeated in sequence. In the combustion process, as shown in Figure 5(A), combustible gas and air are supplied to the combustion chamber 54a, similar to the combustion process in this embodiment, and the combustible gas and air are burned in the hot air furnace. This raises the temperature of the heat storage bricks 56a.

[0031] Next, in the reforming and heating process, as shown in Figure 5(B), CO2 gas is supplied to the heat storage chamber 55a from the pressurization equipment 4a, and CH4 gas is further supplied from another supply route. The CO2 gas and CH4 gas supplied to the heat storage chamber 55a react with the heat storage bricks 56a within the heat storage chamber 55a to form a reformed gas, which is then heated and discharged from the combustion chamber 54a. The reformed gas discharged from the combustion chamber 54a is supplied to the tuyeres of the blast furnace 2a and, together with the pure oxygen gas supplied from another supply route, is used in the refining process of the blast furnace 2a. After the reforming and heating process, the inside of the reforming and heating equipment 5a is filled with furnace gas containing combustible reformed gases of CO and H2.

[0032] Subsequently, during the purging process, N2 gas is supplied to the combustion chamber 54a, as shown in Figure 5(C). During the purging process, the flammable furnace gas inside the reforming and heating equipment 5a is discharged from the bottom of the heat storage chamber 55a along with the N2 gas, and the inside of the reforming and heating equipment 5a is replaced with non-flammable N2 gas. This prevents explosions from occurring in the next combustion process.

[0033] Conventional modification methods required the use of large amounts of N2 gas for the purging process. Furthermore, the purging process caused heat loss, as the N2 gas cooled the heat storage bricks 56a, removing heat. Additionally, the purging process reduced production efficiency. Moreover, the need to provide not only heat storage but also modification capabilities for the heat storage bricks 56a resulted in higher manufacturing costs.

[0034] In contrast to conventional exhaust gas reforming methods, the exhaust gas reforming method according to this embodiment eliminates the need for a purging process, thus suppressing the increase in production costs and decrease in production efficiency caused by the use of N2 gas. Furthermore, since it is not necessary to provide reforming functionality to the heat storage bricks 513 and existing hot air furnaces can be used, construction costs for the equipment can also be reduced. Moreover, there is no need to use a large-scale heat exchanger, as described in Patent Document 1.

[0035] <Blast furnace operation method> In this embodiment, the operation method of the blast furnace 2 involves reforming the CO2 gas contained in the exhaust gas discharged from the blast furnace 2 into a reformed gas using the exhaust gas reforming method described above, and then blowing the reformed gas into the blast furnace 2 from the tuyeres of the blast furnace 2. At this time, pure oxygen gas is also blown in from the tuyeres along with the reformed gas, thereby carrying out the refining process of the blast furnace 2. Furthermore, the timing of the combustion process and the temperature rise reforming process are staggered for each of the multiple hot blast furnaces 51. This ensures that the reformed gas is continuously supplied to the blast furnace 2.

[0036] <Variation> Although the present invention has been described above with reference to specific embodiments, this description is not intended to limit the invention. By referring to the description of the present invention, those skilled in the art will also see other embodiments of the invention, including various modifications, in addition to the disclosed embodiments. Accordingly, the embodiments of the invention described in the claims should be understood to include embodiments that include these modifications described herein, either individually or in combination.

[0037] For example, in the above embodiment, CH4 gas was used in the temperature-reforming step, but the present invention is not limited to such examples. In the temperature-reforming step, hydrocarbon gases other than CH4 may be used, as long as they can reform CO2 gas.

[0038] Furthermore, although the above embodiment assumes that pure oxygen gas is injected into the blast furnace 2 along with the reformed gas, the present invention is not limited to this example. For example, a gas with a high oxygen concentration may be used instead of pure oxygen gas.

[0039] Furthermore, in the above embodiment, the hot blast furnace 51 was assumed to be an external combustion type in which the combustion chamber 511 and the heat storage chamber 512 are independent, but the present invention is not limited to such examples. The hot blast furnace may be an internal combustion type or a top combustion type in which the combustion chamber and the heat storage chamber are built into the same iron shell. [Explanation of Symbols]

[0040] 1,1a Blast furnace equipment 2,2a blast furnace 3,3a CO2 Separation and Recovery Machine 4,4a Booster equipment 5. Temperature-Increasing Reformation Equipment 51 Hot stove 511 Combustion chamber 512 Heat storage chamber 513 Heat-storage bricks 52 Reforming device 53 Control device 5a Reforming and heating equipment 54a Combustion chamber 55a Heat storage chamber 56a Heat storage brick

Claims

1. CO2 contained in blast furnace exhaust gas ２ The gas is CO and H ２ A method for reforming exhaust gas, which reforms it into a reformed gas containing the following: A combustion process involves supplying combustible gas and air to a hot air furnace and burning them within the hot air furnace to raise the temperature of the hot air furnace, The CO2 is added to the heated hot air furnace. ２ The gas is supplied, and the CO is released in the hot air furnace. ２ The gas is heated, and the heated CO ２ By reacting the gas with the hydrocarbon gas, the CO ２ A temperature-increasing reforming step for reforming the gas into the reformed gas, A method for reforming exhaust gas, comprising the following features.

2. In the aforementioned heating and reforming process, the CO2 is supplied to the hot air furnace. ２ The exhaust gas reforming method according to claim 1, wherein only gas is supplied.

3. CO2 is contained in the exhaust gas emitted from blast furnaces. ２ The gas is reformed into a reformed gas by the exhaust gas reforming method described in claim 1 or 2. A method for operating a blast furnace, comprising injecting the reformed gas from the tuyeres of the blast furnace.

4. CO contained in the exhaust gas of the blast furnace ２ The gas is reformed into a reformed gas containing CO and H ２ It is exhaust gas temperature-raising reforming equipment that reforms the gas into a reformed gas containing CO and H The system comprises a hot air furnace, a modification device, and a control device for controlling the hot air furnace and the modification device. The control device is By supplying combustible gas and air to the hot blast furnace and burning them within the hot blast furnace, the temperature of the hot blast furnace is raised. The CO2 is added to the heated hot air furnace. ２ The gas is supplied, and the CO is released in the hot air furnace. ２ Heat the gas, The heated CO ２ By supplying the gas and hydrocarbon gas to the reforming apparatus and reacting them, the CO ２ A temperature-controlled exhaust gas reforming apparatus for reforming gas into the aforementioned reformed gas.

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