Melting furnace operation method

Abstract

To provide a melting furnace operation method which can remarkably reduce carbon dioxide emission.SOLUTION: A melting furnace operation method according to the present invention has: an ethanol production step of producing ethanol at least using CO and / or CO2 included in an exhaust gas of a melting furnace as a raw material; and a carbon-containing reduced iron production step of producing carbon-containing reduced iron by reducing iron ore using the ethanol produced in the ethanol production step, wherein the carbon-containing reduced iron is used as a raw material charged into the melting furnace.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for operating a melting furnace such as a blast furnace. [Background technology]

[0002] In recent years, there has been a strong demand for reducing carbon dioxide (CO2) emissions against the backdrop of global environmental problems. Therefore, low reducing agent ratio (low RAR) operation is also required for blast furnaces installed in steelworks. In a typical blast furnace, hot air (air heated to about 1200°C) is blown in from the tuyere as blast gas. This causes the oxygen in the hot air to react with the coke and pulverized coal that serve as reducing agents, generating carbon monoxide (CO) gas and hydrogen (H2) gas. The iron ore charged in the blast furnace is reduced by these carbon monoxide and hydrogen gases. In addition, carbon dioxide is generated during the reduction reaction of the iron ore. The blast gas is blown into the blast furnace from the tuyere, and serves to gasify the coke and pulverized coal in the blast furnace.

[0003] As a technology for reducing carbon dioxide emissions in the operation of such a blast furnace, a technology for producing reduced iron from iron ore and charging it into the blast furnace has been studied. For example, Non-Patent Document 1 describes that charging reduced iron into the blast furnace reduces the reducing agent ratio and improves productivity. In addition, as a method for producing reduced iron to be charged into the blast furnace, Patent Document 1 describes a method for directly reducing an iron oxide raw material using natural gas or a gas obtained by reforming natural gas. The reduced iron produced in this way can be charged into the blast furnace together with the ore raw material. In addition, Patent Document 2 describes a method for producing a reducing gas having a H2 / CO ratio within a predetermined range from a by-product gas generated in the iron making process, producing reduced iron by reducing iron ore using the reducing gas, and using the resulting reduced iron in the blast furnace. In addition, Non-Patent Document 2 describes a method for producing carbon-containing reduced iron by reducing iron ore using ethanol as a reducing gas. The carbon-containing reduced iron produced in this way can also be charged into the blast furnace together with the ore raw material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 63-213613 [Patent Document 2] JP 2010-043314 A [Non-patent literature]

[0005] [Non-Patent Document 1] Yu Ujizawa, Kohei Sunahara, Yoshinori Matsukura, Kaoru Nakano, Takafumi Yamamoto, Tetsu-to-Haganen, 92 (2006), pp.591-600 [Non-Patent Document 2] Ade Kurniawan, Keisuke Abe, Kouichi Ohashi, Takahiro Nomura and Tomohiro Akiyama, Fuel Processing Technology, 178(2018), p.156-165 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the methods described in Patent Documents 1 and 2 and Non-Patent Document 1 cannot sufficiently reduce the amount of carbon dioxide emissions. In detail, although the reducing agent ratio is reduced by charging the reduced iron produced by the method described in Patent Document 1 into a blast furnace, the effect is limited. Furthermore, since carbon dioxide is also generated during the production of reduced iron, the effect of reducing carbon dioxide emissions as a whole process cannot be said to be sufficient. On the other hand, by producing reduced iron using by-product gas as in the method described in Patent Document 2, it is possible to reduce the amount of carbon dioxide generated during the production of reduced iron. However, there is still a limit to the effect of reducing the reducing agent ratio by simply charging reduced iron into a blast furnace.

[0007] In contrast, when carbon-containing reduced iron produced by the method described in Non-Patent Document 2 is charged into a blast furnace, the carbon in the carbon-containing reduced iron replaces the function of the reducing agent. For this reason, it is estimated that the effect of reducing the reducing agent ratio is greater than that of the methods described in Patent Documents 1 and 2. However, since carbon dioxide is generated from the carbon in the carbon-containing reduced iron, the amount of carbon dioxide emissions is not significantly improved compared to the methods described in Patent Documents 1 and 2. Furthermore, since carbon dioxide is also generated during the production of carbon-containing reduced iron, the effect of reducing carbon dioxide emissions as a whole process cannot be said to be sufficient.

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for operating a melting furnace that can significantly reduce the amount of carbon dioxide emissions. [Means for solving the problem]

[0009] The method for operating a melting furnace according to the present invention includes an ethanol production process for producing ethanol using at least CO and / or CO2 contained in exhaust gas from the melting furnace as a raw material, and a carbon-containing reduced iron production process for producing carbon-containing reduced iron by reducing iron ore using the ethanol produced in the ethanol production process, and the carbon-containing reduced iron is used as a raw material to be charged into the melting furnace.

[0010] The melting furnace may be a blast furnace.

[0011] In the ethanol production process, the exhaust gas generated in the carbon-containing reduced iron production process may be used as a raw material.

[0012] External hydrogen may be used as a raw material in the ethanol production process.

[0013] The method may further include a step of blowing the ethanol produced in the ethanol production process together with a blast gas from a tuyere of the blast furnace.

[0014] It is preferable to use pure oxygen as the blast gas blown through the tuyere of the blast furnace. Effect of the Invention

[0015] According to the method for operating a melting furnace according to the present invention, it is possible to significantly reduce the amount of carbon dioxide emissions. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a blast furnace according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the configuration of a modified example of the blast furnace shown in FIG. [Diagram 3] FIG. 3 is a schematic diagram showing the configuration of a modified example of the blast furnace shown in FIG. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of a modified example of the blast furnace shown in FIG. [Diagram 5] FIG. 5 is a schematic diagram showing the configuration of a modified example of the blast furnace shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, a method of operating a blast furnace according to one embodiment of the present invention will be described in detail with reference to Figures 1 to 5. In Figures 1 to 5, reference numeral 1 denotes a blast furnace, reference numeral 2 denotes a tuyere, reference numeral 3 denotes an injection device, reference numeral 4 denotes a first dehydration device, reference numeral 5 denotes a gas separation device, reference numeral 6 denotes an ethanol synthesis device, reference numeral 7 denotes a carbon-containing reduced iron manufacturing device, reference numeral 8 denotes a blast furnace raw material charging device, reference numeral 9 denotes a hot air generation device, and reference numeral 10 denotes a second dehydration device.

[0018] As shown in FIG. 1, in a blast furnace operating method according to an embodiment of the present invention, raw materials such as sintered ore, lump ore, pellets (hereinafter also referred to as raw ore materials), and coke are charged into the blast furnace 1 from a raw material charging device 8. A blast gas and a reducing agent are sent to an injection device 3 installed at the bottom of the blast furnace 1, and the blast gas and the reducing agent are injected into the blast furnace 1 through a tuyere 2. The reducing agent injected into the blast furnace 1 from the tuyere 2 is also called an injected reducing agent to distinguish it from coke. The blast gas is a gas injected into the blast furnace 1 from the tuyere 2, and plays a role of gasifying the injected reducing agent and coke in the blast furnace 1. The raw ore materials charged into the blast furnace 1 are reduced by carbon monoxide gas and hydrogen gas generated by the reaction of the blast gas with the injected reducing agent or coke, and molten iron is produced. Carbon dioxide is generated during the reduction process of the raw ore materials. This carbon dioxide is discharged as a by-product gas from the top of the blast furnace 1 together with carbon monoxide and hydrogen that did not react with the raw ore. The top of the blast furnace 1 is under high pressure conditions of about 2 to 4 atmospheres. Therefore, when the blast furnace gas, which is a by-product gas discharged from the top of the blast furnace 1, returns to normal pressure, it expands and cools, causing water vapor to condense. Therefore, the condensed water is removed in the first dehydration device 4.

[0019] Next, at least a part of the dehydrated blast furnace gas is introduced into the gas separator 5 to remove the nitrogen contained in the blast furnace gas. Then, the blast furnace gas from which the nitrogen has been removed is introduced into the ethanol synthesis apparatus 6 as a raw material, and the carbon monoxide, carbon dioxide, and hydrogen in the blast furnace gas are reacted to obtain ethanol (C2H5OH). The ethanol thus produced in the ethanol synthesis apparatus 6 is called regenerated ethanol. When using pure oxygen that does not contain nitrogen as the blast gas, as shown in FIG. 2, a part of the dehydrated blast furnace gas can be directly introduced into the ethanol synthesis apparatus 6 without using the gas separator 5. When using hot air containing nitrogen generated by the hot air generator 9 (see FIG. 1) as the blast gas, a part of the dehydrated blast furnace gas can be directly introduced into the ethanol synthesis apparatus 6, but the inclusion of nitrogen reduces the efficiency of ethanol production. Therefore, when using hot air containing nitrogen as the blast gas, it is preferable to use the gas separator 5.

[0020] When the hydrogen required for ethanol synthesis cannot be provided only by the hydrogen in the blast furnace gas, hydrogen (external hydrogen) may be supplied from the outside as a raw material for the ethanol synthesis unit 6 as shown in FIG. 3. Furthermore, since the exhaust gas generated in the carbon-containing reduced iron production unit 7 described later mainly contains carbon monoxide, carbon dioxide, hydrogen, and water, it is more preferable to recover the exhaust gas as shown in FIG. 4, dehydrate it by the second dehydration unit 10, and then use it as a part of the raw material for the ethanol synthesis unit 6. This makes it possible to reduce energy loss and the amount of external hydrogen charged. The method for synthesizing ethanol by reacting carbon monoxide, carbon dioxide, and hydrogen is not particularly limited, and any generally known synthesis method may be used, for example, a method of biologically synthesizing ethanol using microbial fermentation may be used.

[0021] Hydrogen used to generate regenerated ethanol may be supplied from an external source, but a method that generates as little carbon dioxide as possible is preferred, such as electrolysis of water. In addition, examples of hydrogen supplied from an external source include hydrogen produced by reforming hydrocarbons such as natural gas by steam reforming, hydrogen obtained by vaporizing liquefied hydrogen, and hydrogen produced by dehydrogenating organic hydrides. Hydrogen does not need to be a gas with a hydrogen concentration of 100% by volume, but in order to increase the ethanol concentration in the regenerated ethanol, it is preferable to use a gas with a high hydrogen concentration, specifically a gas with a hydrogen concentration of 80% by volume or more. The hydrogen concentration is more preferably 90% by volume or more, and even more preferably 95% by volume or more. The hydrogen concentration may be 100% by volume. Examples of remaining gases other than hydrogen include CO, CO2, H2S, CH4, and N2.

[0022] Returning to FIG. 1, the obtained regenerated ethanol is introduced into the carbon-containing reduced iron production apparatus 7 and reacted with the raw ore to produce carbon-containing reduced iron. In the carbon-containing reduced iron production apparatus 7, the regenerated ethanol is heated to 700°C to 1000°C and reacted with the charged raw ore to produce carbon-containing reduced iron containing carbon therein. If a reducing agent other than ethanol is used in the carbon-containing reduced iron production apparatus 7, it is difficult to obtain carbon-containing reduced iron containing carbon therein. The higher the carbon concentration in the carbon-containing reduced iron, the greater the effect of reducing carbon dioxide in the blast furnace 1, and therefore it is preferable.

[0023] In addition, exhaust gas mainly composed of carbon monoxide, carbon dioxide, hydrogen, and water is generated as a by-product gas after the reduction reaction with ethanol. The form of the carbon-containing reduced iron manufacturing apparatus 7 is not limited to a reduction apparatus of a specific structure, and a shaft furnace, a rotary kiln, a rotary hearth furnace, etc. can be used. However, since endothermic heat occurs during the reduction reaction with ethanol, there is a possibility that heat is insufficient only with the sensible heat of the introduced ethanol. Therefore, it is preferable to use an apparatus that can indirectly supply heat from the outside of the furnace body using an electric heater or the like, rather than heating only with the sensible heat of gas. Furthermore, since the exhaust gas discharged from the carbon-containing reduced iron manufacturing apparatus 7 mainly consists of carbon monoxide, carbon dioxide, hydrogen, and water, it is preferable to recover all of these, remove water by the second dehydration device 10 (see FIG. 4), and then charge the ethanol synthesis apparatus 6 as a raw material. This makes it possible to reduce energy loss and the amount of external hydrogen charging. The gas separation device 5, the ethanol synthesis device 6, and the carbon-containing reduced iron manufacturing apparatus 7 do not necessarily need to be arranged adjacent to the blast furnace 1. For example, blast furnace gas may be supplied to the outside, nitrogen may be removed from the blast furnace gas in an external gas separation device 5, and the blast furnace gas from which the nitrogen has been removed may be introduced into an external ethanol synthesis device 6 to synthesize regenerated ethanol. Alternatively, carbon-containing reduced iron may be produced using regenerated ethanol in an external carbon-containing reduced iron production device 7, and the obtained carbon-containing reduced iron may be transported and used in the blast furnace 1.

[0024] The obtained carbon-containing reduced iron is charged into the blast furnace 1 together with the raw ore and coke from the blast furnace raw material charging device 8. The carbon-containing reduced iron is iron that has already been partially reduced, so that the amount of reducing gas required in the blast furnace 1 can be reduced by replacing the iron oxide in the raw ore with the reduced iron. This reduces the amount of reducing agent required to generate the reducing gas, and reduces the amount of carbon dioxide emissions. Furthermore, since the carbon-containing reduced iron contains a large amount of carbon, the reducing agent such as coke can be replaced by this carbon, and the reducing agent ratio can be reduced. The blast furnace operation method of this embodiment is characterized in that the carbon in the carbon-containing reduced iron circulates within the process and is not discharged to the outside as carbon dioxide. Therefore, if the reducing agent ratio is reduced by replacing the reducing agent such as coke with the carbon in the carbon-containing reduced iron, the amount of carbon dioxide emissions can be reduced accordingly.

[0025] The amount of carbon-containing reduced iron charged is preferably 50 kg / t or more and 500 kg / t or less. If the amount of carbon-containing reduced iron charged is too small, a sufficient effect of reducing carbon dioxide emissions cannot be obtained. On the other hand, if the amount of carbon-containing reduced iron charged is too large, the effect of reducing carbon dioxide emissions by charging the carbon-containing reduced iron into the blast furnace 1 becomes saturated. Therefore, even though the amount of carbon dioxide emissions does not decrease, the charging energy during the production of the carbon-containing reduced iron increases, which is not preferable. When charging raw materials into the blast furnace 1, the ore raw material and coke are charged alternately, but it is preferable to charge the carbon-containing reduced iron together with the ore raw material.

[0026] [Injected reducing material] Pulverized coal, natural gas, heavy oil, etc. can be used as the injection reducing agent, and recycled ethanol can also be used. In order to further reduce carbon dioxide emissions, it is desirable to introduce a part of the recycled ethanol as part of the injection reducing agent into an injection device 3 and inject it into the blast furnace 1 through a tuyere 2, as shown in Figure 5. By using recycled ethanol as the injection reducing agent, the amount of reducing agents such as coke and pulverized coal can be reduced accordingly. The carbon in the recycled ethanol circulates within the process and is not discharged to the outside as carbon dioxide. Therefore, if the reducing agents such as coke and pulverized coal are replaced by recycled ethanol, the amount of carbon dioxide emissions can be reduced accordingly. When recycled ethanol is used as the injection reducing agent, the injection amount of recycled ethanol is 200 Nm 3 / t. 3 If more than 1 / t is injected, the ethanol will not burn sufficiently at the end of the tuyere 2, generating soot, which may lead to a decrease in the permeability of the blast furnace 1. In addition, since ethanol is liquid at room temperature, it is desirable to preheat it and vaporize it before injecting it into the blast furnace 1.

[0027] [Blow gas] As the blast gas, hot air obtained by heating air enriched with several percent oxygen to about 1200°C can be used, and pure oxygen can also be used as the blast gas. When hot air generated by the hot air generator 9 is used as the blast gas, nitrogen is contained in the blast furnace gas, so a gas separator 5 is required. On the other hand, when pure oxygen is used as the blast gas, nitrogen is not contained in the blast furnace gas, so the gas separator 5 is not required, which is advantageous and desirable in terms of energy efficiency and cost. In addition, when hot air is used as the blast gas, the combustion gas contains about 50% by volume of nitrogen that does not contribute to the combustion reaction, so the temperature of the flame in the raceway is unlikely to become high. Therefore, if a large amount of regenerated ethanol is blown into the blast furnace 1, the tuyere temperature drops and operation trouble occurs. On the other hand, by using pure oxygen as the blast gas, it is possible to suppress the mixing of nitrogen gas that does not contribute to the combustion reaction, so it is possible to raise the tuyere temperature to a sufficient temperature. In other words, it is more preferable because the temperature of the flame in the raceway can be made higher than when hot air is used, and operation troubles can be suppressed.

[0028] Furthermore, when pure oxygen is used as the blast gas, it is desirable to provide a gas injection section in the shaft section or belly section of the blast furnace 1 and inject the preheat gas. When pure oxygen is used as the blast gas, the blast gas does not contain nitrogen, so the gas flow rate flowing through the blast furnace 1 is reduced. Then, the amount of heat supplied from the gas to the raw materials is reduced, so the raw materials are not sufficiently heated, making operation difficult. Therefore, when pure oxygen is used as the blast gas, it is desirable to inject the preheat gas into the shaft section or belly section to compensate for the insufficient amount of heat. As a method for generating the preheat gas, a method in which fuel is burned with oxygen to generate high-temperature gas, and then the gas is mixed with a dilution gas and adjusted to a predetermined temperature and flow rate, or a method in which the gas is directly heated by an electric heater can be used. When generating the preheat gas by combustion, blast furnace gas, coke oven gas, natural gas, propane gas, etc. can be used as the fuel. In addition, blast furnace gas, coke oven gas, nitrogen, etc. can be used as the dilution gas. From the viewpoint of effective energy utilization, it is desirable to recover blast furnace gas, combust a portion of it to generate high-temperature gas, and further mix it with the blast furnace gas before combustion to adjust the temperature and flow rate to a desired level. EXAMPLES

[0029] Table 1 shows examples of the present invention and comparative examples. In Table 1, examples 1 to 4 of the present invention are methods of operating a blast furnace in which carbon-containing reduced iron is produced by reducing iron ore with regenerated ethanol and the carbon-containing reduced iron is used as a raw material in the blast furnace. Comparative example 1 is a normal blast furnace operation method that does not use reduced iron, comparative example 2 is a blast furnace operation method that uses reduced iron produced with natural gas, and comparative example 3 is a blast furnace operation method that uses reduced iron produced with external ethanol. As shown in the bottom row of Table 1, it was confirmed that examples 1 to 4 of the present invention could reduce carbon dioxide emissions significantly compared to comparative examples 1 to 3. The amount of carbon dioxide emissions in each example was calculated based on the amount of carbon charged into the blast furnace and the reduced iron production process.

[0030] [Table 1]

[0031] The above describes the embodiment of the invention made by the present inventors, but the present invention is not limited by the description and drawings that form a part of the disclosure of the present invention according to the present embodiment. The present invention is applicable not only to the operation of a blast furnace, but also to the operation of a melting furnace capable of melting an iron source such as scrap or reduced iron. For example, ethanol can be produced using at least CO and / or CO2 in the exhaust gas generated in the operation of an electric furnace as a raw material, and carbon-containing reduced iron can be produced by reducing iron ore using the produced ethanol, and the produced carbon-containing reduced iron can be charged into an electric furnace for use. Similarly, ethanol can be produced using at least CO and / or CO2 in the exhaust gas generated in the operation of a converter as a raw material, and carbon-containing reduced iron can be produced by reducing iron ore using the produced ethanol, and the produced carbon-containing reduced iron can be charged into a converter for use. In this way, all other embodiments, examples, operation techniques, etc. made by those skilled in the art based on the present embodiment are included in the scope of the present invention. [Explanation of symbols]

[0032] 1 blast furnace 2 Tuyere 3 Blowing device 4 1st dehydration device 5 Gas separation equipment 6. Ethanol synthesis unit 7. Carbon-containing reduced iron manufacturing equipment 8 Blast furnace raw material charging equipment 9 Hot air generator 10 Second dehydration device

Claims

1. At least CO and / or CO contained in the exhaust gas from the melting furnace ２ an ethanol production process for producing ethanol using the above as a raw material; a carbon-containing reduced iron production step of producing carbon-containing reduced iron by reducing iron ore using the ethanol produced in the ethanol production step; Including, A method for operating a melting furnace, comprising using the carbon-containing reduced iron as a raw material to be charged into the melting furnace.

2. 2. The method of claim 1, wherein the melting furnace is a blast furnace.

3. 3. The method for operating a smelting furnace according to claim 2, wherein exhaust gas generated in the carbon-containing reduced iron production process is used as a raw material in the ethanol production process.

4. 3. The method of claim 2, wherein external hydrogen is used as a feedstock in the ethanol production process.

5. 4. The method of claim 3, wherein external hydrogen is used as a feedstock in the ethanol production process.

6. The method for operating a melting furnace according to claim 2, further comprising the step of blowing the ethanol produced in the ethanol production process together with a blast gas from a tuyere of the blast furnace.

7. The method for operating a melting furnace according to claim 3, further comprising the step of blowing the ethanol produced in the ethanol production process together with a blast gas from a tuyere of the blast furnace.

8. The method for operating a melting furnace according to claim 4, further comprising the step of blowing the ethanol produced in the ethanol production process together with a blast gas from a tuyere of the blast furnace.

9. The method for operating a melting furnace according to claim 5, further comprising the step of blowing the ethanol produced in the ethanol production process together with a blast gas from a tuyere of the blast furnace.

10. The method for operating a melting furnace according to any one of claims 2 to 9, wherein pure oxygen is used as the blast gas blown from the tuyere of the blast furnace.

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