JP2014005510A - Blast furnace operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blast furnace operation method which, when COgenerated in an iron mill is reformed and used as a reducing agent in a blast furnace, can efficiently reduce the amount of the generated COat a low cost without performing separation operation twice.SOLUTION: A blast furnace operation method includes: a COseparation step where COis separated and recovered from exhaust gas of an air heating furnace 2; a step of reforming COto CHwhere His added to the COseparated and recovered in the COseparation step to reform the COto CHand CO; and a step of blowing CHinto a blast furnace where the CHand CO obtained by reforming in the step of reforming COto CHare blown into a blast furnace 1.

Description

The present invention, modifying the separated recovered CO ₂ from a gas mixture containing CO _2, about blast furnace operation method using the reformed gas as a reducing agent for blast furnace.

Global warming due to an increase in CO ₂ has been widely taken up as an international problem, and reducing its emissions has become a global issue. Various technological developments have been attempted to separate and recover CO ₂ from the generated gas, but no effective means has been proposed for how to use the recovered CO ₂ . A technique for burying the recovered CO ₂ in the ground, so-called carbon dioxide capture and storage (CCS), has been actively researched mainly in Europe, the United States, Japan and the like. However, this method is not only difficult to obtain social consensus in Japan, which is an earthquake country, from the viewpoint of safety after CO ₂ is buried in the ground. According to a trial calculation by the Organization (RITE), the value obtained by dividing the CO ₂ embeddable amount in the vicinity of Japan including the near sea by the emission amount, that is, the lifetime is only about 50 to 100 years. Therefore, at least in Japan, CCS is unlikely to be a fundamental solution for reducing CO ₂ emissions.

According to statistics, Japan's CO ₂ emissions are about 30% due to power generation, 10% due to steel production, and in other areas, the transportation and civilian sectors account for a large proportion.

In the power plant, CO ₂ is emitted in order to convert chemical energy of coal, oil, and natural gas into electric energy by complete oxidation of these fossil fuels. Therefore, an amount of CO ₂ commensurate with the use of fossil fuel is inevitably generated, but such fossil fuel power generation is so-called soft power generation such as solar power generation, wind power generation, tidal power generation in the long term.・ It is thought that the number will gradually decrease with the spread of energy use, biomass power generation, and nuclear power generation.

On the other hand, in steel production, CO ₂ is generated in various processes, but the largest source is the blast furnace process. The generation of CO ₂ in this blast furnace process results from the reduction of oxygen in the iron ore by reducing iron ore, which is iron oxide, with the reducing material CO. For this reason, in steel production, it can be said that generation of CO ₂ is inevitable.

  That is, in the blast furnace process, hot air of 1000 ° C. or higher generated in the hot blast furnace is blown from the lower part of the blast furnace, the coke is burned, the heat necessary for the reduction and melting of iron ore is supplied, and the reducing gas (CO) is supplied. The iron ore is reduced with this reducing gas (CO) to obtain hot metal.

  The reduction of iron ore with the reducing gas (CO) is represented by the following formula (1).

Fe ₂ O ₃ + 3CO = 2Fe + 3CO ₂ ΔH = -23.4kJ / mol (exotherm) (1)

  Conventionally, as shown in FIG. 1, in the hot stove 2, the byproduct gas (blast furnace gas) of the blast furnace 1 is used as a part or all of the fuel.

On the other hand, as a method for reducing iron ore without generating CO ₂ , it is conceivable to use hydrogen as a reducing gas. However, when hydrogen is blown into the blast furnace, the reduction of the iron ore by hydrogen is expressed by the following equation (2) and becomes an endothermic reaction.

Fe ₂ O ₃ + 3H ₂ = 2Fe + 3H ₂ O ΔH = 100.1kJ / mol (endothermic) ・ ・ ・ (2)

  In this way, since reduction by hydrogen is an endothermic reaction, when hydrogen is blown into the blast furnace, the heat at the bottom of the blast furnace may be taken away, and there is a risk that the heat necessary for the reduction or dissolution of iron ore may be insufficient. Compensation is required.

On the other hand, in Patent Document 1, as shown in FIG. 2, CO ₂ is separated from blast furnace gas, and a hydrogen-containing substance (here, H ₂ ) is added to the CO _{2 so as} to be converted to methane CH ₄ . A technique for reusing as a reducing gas in a blast furnace is disclosed.

When CH ₄ is blown into the blast furnace, it is converted into CO and H ₂ by the reaction of the following formula (3) in the blast furnace.

CH ₄ + 1 / 2O ₂ = CO + 2H ₂ ΔH = -8.5kJ / mol (exotherm) (3)

The above formula (3) is an exothermic reaction and can supply heat necessary for the reduction and dissolution of iron ore. The resulting reducing gas (CO, _{H 2)} is to reduce iron ore as shown in the following equation (4).

Fe ₂ O ₃ + CO + 2H ₂ = 2Fe + CO ₂ + 2H ₂ O ΔH = 58.9kJ / mol (endothermic) (4)

Thus, since the combustion heat of CH _{4 represented by} the above formula (3) can be used for the reduction and dissolution of iron ore in the blast furnace, the reduction of iron ore by hydrogen as represented by the above formula (2) Thermal compensation at the bottom of the blast furnace is not necessary.

JP2011-225969A

When the method of Patent Document 1 is carried out, CO and N ₂ remain after separating CO ₂ from the blast furnace gas. At that time, CO has a reducing power, whereas N ₂ is an inert gas. Therefore, in order to utilize CO, it is necessary to further separate CO and N ₂ . That is, as shown in FIG. 2, two (two stages) separation work of separating CO after separating CO ₂ is indispensable.

The _two separation operations of CO ₂ separation and CO separation for blast furnace gas require about twice as much equipment and energy for that purpose, so the cost is inevitably increased and there is also energy loss. Will increase.

The present invention has been made in view of the above circumstances, and performs two (two-stage) separation operations when reforming CO ₂ generated in an ironworks and using it as a reducing agent in a blast furnace. Therefore, an object of the present invention is to provide a blast furnace operating method capable of efficiently reducing the amount of CO ₂ generated at low cost.

As a result of intensive studies to solve the above problems, the inventors of the present invention focused on the fact that the composition of the exhaust gas of the hot stove consists mainly of CO ₂ and N ₂ and hardly contains CO and O _2. By separating and recovering CO ₂ from the exhaust gas from the furnace, reforming the CO ₂ to methane to obtain a reformed reducing material, and blowing this reformed reducing material into the blast furnace, one time (one stage) A new blast furnace operation method has been conceived, which requires only a separation operation and can efficiently reduce the amount of CO ₂ generated at low cost.

Since a general combustion burner has a short combustion zone, it needs to be burned at an air ratio of more than 1.1 and not more than 1.5 for complete combustion. When the hydrocarbon fuel is burned at an air ratio of more than 1.1 and less than 1.5, the CO ₂ concentration in the exhaust gas is as low as 10 to 14 vol%, and the CO ₂ recovery rate is low even if CO ₂ is separated and recovered. On the other hand, with a general combustion burner, the CO ₂ concentration in the exhaust gas when the hydrocarbon fuel is burned at an air ratio of 1.0 to 1.1 is as high as 14 to 15 vol%. The concentration becomes high.

On the other hand, in the case of a hot stove, it burns in a combustion chamber surrounded by high-temperature bricks of 1000 ° C. or higher, so even if the air ratio is 1.0 to 1.1, CO in exhaust gas is less than 100 ppm. CO separation after the CO ₂ separation from the exhaust gas becomes unnecessary.

Further, in the hot-air oven, the sum of CO ₂ and CO are 30～50Vol% and high blast furnace gas _{(CO 2: 15~25vol%, CO} : 15~25vol%, N 2: 45~55vol%, H 2: 0 ˜5 vol%) as the main fuel, the CO ₂ concentration in the exhaust gas is a high concentration of 20% or more, which is suitable for separating and reforming CO ₂ .

  In addition to the exhaust gas from the hot stove, the above effect can be obtained if the exhaust gas is from a combustion furnace that uses blast furnace gas as part or all of the fuel.

  The present invention is based on the above idea and has the following features.

[1] Characteristically, CO ₂ is separated from exhaust gas from a combustion furnace that uses blast furnace gas as part or all of fuel, and reducing gas obtained by reforming the separated CO ₂ into methane is injected into the blast furnace. Blast furnace operation method.

  [2] The blast furnace operating method according to [1], wherein the combustion furnace is a blast furnace hot stove.

In the present invention, when CO ₂ generated at a steel works is reformed and used as a reducing agent in a blast furnace, CO _{2 in} the exhaust gas of a combustion furnace that uses blast furnace gas as part or all of the fuel is separated and recovered. Then, the CO ₂ is reformed into methane to obtain a reformed reducing material, and this reformed and reducing material is blown into the blast furnace. Without providing, CO ₂ reduction can be achieved efficiently at low cost.

It is a figure which shows the conventional blast furnace operating method (conventional example). It is a figure which shows the blast furnace operating method (comparative example) of patent document 1. FIG. It is a figure which shows the blast furnace operating method (example of this invention) which concerns on one Embodiment of this invention.

  A blast furnace operating method according to an embodiment of the present invention will be described.

FIG. 3 shows a blast furnace operating method according to an embodiment of the present invention. In the CO ₂ separation process the CO ₂ is separated and recovered from the hot air oven 2 gas, hydrogen-containing material to CO ₂ which is separated and recovered in the CO ₂ separation process blast furnace operation method according to this embodiment (in this case, H ₂₎ CO ₂ / CH ₄ reforming step for reforming (converting) CO ₂ to CH ₄ and CO by adding NO, and CH ₄ and CO obtained by reforming in the CO ₂ / CH ₄ reforming step And a CH ₄ blast furnace blowing process for blowing into the blast furnace 1.

Here, the exhaust gas from the hot stove is composed of CO ₂ , N ₂ , and H ₂ O, and hardly contains CO and O ₂ . For _{example, CO 2: 22vol%, N} 2: 68vol%, H 2 O: a 10 vol%.

Therefore, the carbon-containing gas contained in the exhaust gas of the hot stove is only CO ₂ , and in Patent Document 1, as shown in FIG. 2, two times of CO ₂ separation and CO separation (2 However, the carbon-containing gas in the exhaust gas can be recovered by only one (one stage) separation operation of CO ₂ separation.

Incidentally, for modifying the separated recovered CO ₂ to CH ₄ (conversion) is, (3) as in equation is because as the heat generation and the heat source at the moment when blown into a blast furnace, if Fukikome the CO ₂ This is because heat is absorbed by the reaction of the following formula (5) that consumes coke in the furnace.

CO ₂ + C = 2CO ΔH = 171.5kJ / mol (endothermic) (5)

  Hereinafter, this embodiment will be described in detail.

As described above, CO ₂ separated and recovered in the separation step is reformed (converted) into CH ₄ and CO by reacting with hydrogen in the reforming step.

At that time, in order to reform (convert) the separated and recovered CO ₂ to CH ₄ , a known method in which reforming is performed using a catalyst by adding hydrogen can be employed.

The methanation reaction of CO ₂ with hydrogen is shown in the following formula (6). Depending on the reforming conditions, a part of CO ₂ becomes CO (the following formula (7)), but CO further reacts with hydrogen to generate CH ₄ (the following formula (8)).

CO ₂ + 4H ₂ = CH ₄ + 2H ₂ O ΔH = -39.4kJ / mol (exotherm) (6)
CO ₂ + H ₂ = CO + H ₂ O ΔH = 9.9kJ / mol (endothermic) (7)
CO + 3H ₂ = CH ₄ + H ₂ O ΔH = -49.3kJ / mol (exotherm) (8)

The above formulas (6) and (8) are exothermic reactions. In equation (6), low temperature is advantageous in equilibrium, and the CO ₂ equilibrium conversion at 300 ° C. is about 95%. In addition, the low temperature is advantageous in the equation (8) as well, and the CO equilibrium conversion rate at 300 ° C. is about 98%. For these reactions, a methanation catalyst usually used can be used. Specifically, CO ₂ or CO can be reformed to CH ₄ by using a transition metal catalyst such as Fe, Ni, Co, or Ru. Among these, Ni-based catalysts are particularly preferable because they have high activity and high heat resistance and can be used up to a temperature of about 500 ° C. Further, iron ore may be used as a catalyst. Particularly, the high crystal water ore after crystallization water desorption has a large specific surface area and can be suitably used as a catalyst.

The amount of hydrogen added to the CO ₂ is preferably in the molar ratio of CO ₂ is 2.5 to 5. If the molar ratio is less than 2.5, there is a problem that the production ratio of CH ₄ is low. On the other hand, when the molar ratio exceeds 5, no adverse effect on the reaction is observed, but the unreacted H ₂ remaining increases and the economic efficiency decreases, and the methane ratio in the reducing gas obtained by reforming decreases. To do. As for the ratio of CH ₄ and CO in the reformed gas, a reducing gas having a desired composition can be obtained by adjusting the molar ratio of hydrogen mixed in CO ₂ , the catalyst type, and the reaction temperature.

Although the supply source of hydrogen added to CO ₂ is arbitrary, for example, hydrogen generated by decomposing a hydrogen-containing compound such as ammonia can be used. Ammonia is generated when producing coke for carbonization of coal (ammonia generation amount is about 3.3 Nm ³ / t-coal), and currently recovered as liquid ammonium or ammonium sulfate.

  Examples of other hydrogen-containing compounds for obtaining hydrogen include coke oven gas. When obtaining hydrogen from coke oven gas, a method of separating and recovering hydrogen in coke oven gas by PSA (physical adsorption), etc., reforming hydrocarbons in coke oven gas (partial oxidation), and hydrogen from this reformed gas A method such as a method of separating and recovering PSA (physical adsorption) or the like can be employed.

  In this embodiment, if ammonia or coke oven gas can be used as a hydrogen supply source, it is not necessary to procure a hydrogen supply source from outside the steelworks, or the amount procured from outside the steelworks can be reduced.

  Alternatively, the biomass may be partially oxidized, and hydrogen may be separated and recovered from the obtained gas by PSA (physical adsorption) or the like.

  Examples of hydrogen obtained from other sources include hydrogen produced by reforming hydrocarbons such as natural gas by steam reforming, hydrogen obtained by vaporizing liquefied hydrogen, and organic hydride. And hydrogen produced by dehydrogenation, hydrogen produced by electrolysis of water, and the like.

As a reactor for reforming (converting) CO ₂ to CH ₄ , a fixed bed reactor, a fluidized bed reactor, a gas bed reactor, or the like can be used. The physical properties of the catalyst are appropriately selected depending on the type of the reactor.

  Among these, as the methanation reactor, an adiabatic fixed bed reactor filled with a catalyst such as a Ni-based catalyst having excellent heat resistance is particularly preferable.

  A heat exchanger is disposed in the gas flow path on the downstream side of the methanation reactor, and the reaction heat of the methanation reaction in the methanation reactor is appropriately recovered by the heat exchanger.

It is preferable to separate and remove H ₂ O contained in the reformed gas by a known method. As a separation method, a cooling method, an adsorption method, or the like can be applied. In the cooling method, the reformed gas is cooled to a dew point temperature or lower, and H ₂ O is condensed and removed. Although the dew point temperature is determined by the concentration of H ₂ O in the reformed gas, normally, if the reformed gas is cooled to 30 ° C. or less, H ₂ O can be appropriately condensed and removed, and air blown into a normal blast furnace. Since it becomes comparable to the air moisture concentration, it is preferable for blast furnace operation. In addition, the adsorption method uses a dehumidifying adsorbent such as silica gel, but repeats adsorption and regeneration in an adsorption tower, and a honeycomb rotor that repeats regeneration and adsorption continuously while the adsorbent formed in a honeycomb shape rotates. A system etc. can be suitably adopted.

Furthermore, when CO _{2 that} has not been reformed into CH ₄ or CO remains in the reformed gas, for example, CO ₂ may be separated and removed by the method described above.

Thus, in this embodiment, in modifying CO ₂ generated in an ironworks and using it as a reducing agent in a blast furnace, the composition of the exhaust gas from the hot stove mainly consists of CO ₂ and N ₂ , and CO 2 Focusing on the fact that NO and O ₂ are hardly contained, CO _{2 in} the exhaust gas of the hot stove is separated and recovered, and the CO ₂ is reformed into CH ₄ and CO to obtain a reformed reducing material. Since the material is blown into the blast furnace, only one separation operation is required, and CO ₂ reduction can be achieved efficiently at low cost without providing a CO separation facility.

In this embodiment, the case where exhaust gas from a hot stove is used has been described. However, exhaust gas from a combustion facility (combustion furnace) that uses blast furnace gas in an ironworks, particularly exhaust gas containing almost no CO or O ₂ is used. Thus, it is possible to obtain the same effect as this embodiment.

Examples of the present invention will be described. The internal volume of the target blast furnace was 5000 m ³ .

  First, operating conditions in the conventional blast furnace operating method (conventional example) shown in FIG. 1 are shown below.

・ Air flow rate: 1054 Nm ³ / tp
-Oxygen enrichment: 27.4 Nm ³ / tp
-Humidity during blowing: 25 g / Nm ³
・ Blower temperature: 1150 ℃
-Reducing material ratio: 495 kg / tp (coke ratio: 365 kg / tp, pulverized coal ratio: 130 kg / tp)
・ Blast furnace gas generation amount (dry): 1587 Nm ³ / tp (N ₂ : 52.8 vol%, CO ₂ : 22.7 vol%, CO: 20.7 vol%, H ₂ : 3.8 vol%)
-CO ₂ emissions (C supplied to steelworks is converted to CO ₂ ): 2052 kg / t

On the other hand, as a comparative example, the blast furnace operating method described in Patent Document 1 as shown in FIG. 2 was performed. That is, the blast furnace gas is separated by two separation operations, and the CO ₂ separated in the first separation operation is charged into the stationary phase reforming reactor together with H ₂ which is 4.2 times the molar ratio to CO ₂ , and CH 2 ₄ was blown from the blast furnace tuyere together with the CO separated in the second separation operation.

In this comparative example, Table 1 shows the operation results when 50 Nm ³ / tp of reducing gas composed of 50% CH _{4 and} 50% CO was blown into the blast furnace.

As an example of the present invention, a blast furnace operating method based on an embodiment of the present invention as shown in FIG. 3 was performed. That is, the exhaust gas from the hot stove is separated by a single separation operation, and the separated CO ₂ is charged into the stationary phase reforming reactor together with H ₂ having a molar ratio to CO ₂ of 2.6 times, and is converted into CH ₄ and CO. It was reformed and blown from the blast furnace tuyeres.

Table 1 shows the operation results when reducing gas composed of 50% CH _{4 and} 50% CO was blown into the blast furnace at 50 Nm ³ / tp in this example of the present invention.

  Here, based on Table 1, the example of the present invention will be compared with the comparative example.

First, the blast furnace exhaust CO _2, in any of the present invention and comparative example Example was also decreased 4.2 percent from _2052kg-CO 2 / t to _1966kg-CO 2 / t in the conventional example. This is because if the composition of the introduced reducing gas (reformed gas) is the same, the difference between the source gas of the reducing gas (reformed gas) being the exhaust gas of the hot stove or the blast furnace gas is In order not to affect the operation, the reduction effect of CO ₂ emission from the blast furnace was the same between the inventive example and the comparative example.

Next, the amount of hydrogen necessary to produce the reducing gas (reformed gas) to be blown into the blast furnace is _2.5 Nm ³ —H ₂ / Nm ³ —reducing gas in the example of the present invention. 0Nm ³ -H ₂ / Nm ³ - as compared to the reducing gas 0.5Nm ³ -H ₂ / Nm ³ - was to increase by reducing gas.

However, in the comparative example, CO ₂ separated from the blast furnace gas and reducing gas modified by CO are blown into the blast furnace, so if a part of CO of the blast furnace gas supplied to the hot stove is consumed, There will be a shortage of CO. That is, the reformed gas 1Nm ³ requires 0.5 Nm ³ of CO, and this amount of CO is insufficient in the hot stove. Therefore, the total amount of hydrogen was calculated assuming that the shortage of CO in the hot stove was compensated by reforming CO ₂ with H ₂ . To produce CO of 0.5 Nm ³ is required supplement of _{H 2} 0.5 Nm ^3, Part 0.5Nm ³ -H ₂ / Nm ³ - a reducing gas, to produce the reducing gas When added to the reducing gas, 2.5Nm ³ -H ₂ / Nm ³ is required hydrogen amount at substantially invention sample _{^{- - 2.0Nm 3 -H 2 / Nm}} 3 is hydrogen amount required for the reduction gas It turns out that it is the same.

In addition, when hydrogen (3026 kcal / Nm ³ ) is directly supplied as a combustible gas instead of reforming, the calorific value per unit volume is almost the same as that of CO (3018 kcal / Nm ³ ), so that 0.5 Nm ³ of CO is supplemented. Still needs to be supplemented with 0.5 Nm ³ of H ₂ .

It is also possible to replace the CO to be insufficient in a hot air oven at CO is used under process and power, due to the lack of CO used under process and power generation that case, the H ₂ CO ₂ sources H ₂ is necessary to substitute for the flammable gas that does not become or to reform and supply CO ₂ to CO.

The electric power required for CO ₂ separation was 400 kWh / t-CO ₂ in the comparative example, but it was halved to 200 kWh / t-CO _{2 in the} example of the present invention. This is because the comparative example requires two separation steps, whereas the present invention requires one separation step.

As described above, in the example of the present invention, the same amount of hydrogen is used and the same CO ₂ reduction effect as in the comparative example, but the electric power required for the separation is reduced by half, so that the CO 2 can be efficiently produced at low cost. ₂ reductions can be made.

1 Blast furnace 2 Hot stove

Claims (2)

A blast furnace characterized in that CO ₂ is separated from exhaust gas of a combustion furnace using blast furnace gas as part or all of fuel, and a reducing gas obtained by reforming the separated CO ₂ into methane is injected into the blast furnace. Operation method.   The blast furnace operating method according to claim 1, wherein the combustion furnace is a blast furnace hot stove.

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