JP6019893B2 - Blast furnace operation method - Google Patents

Description

  The present invention relates to a method for operating a blast furnace in which one or more of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen are blown into a blast furnace from a tuyere or the like.

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 . Technology for burying the collected 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 carbon as a reducing material. For this reason, in steel production, it can be said that generation of CO ₂ is inevitable.
In the blast furnace process, hot air of 1000 ° C or higher is blown from the bottom of the blast furnace, coke is burned, and heat necessary for the reduction and melting of iron ore is generated and reducing gas (CO) is generated. Reduce stones and get hot metal.

As a method for reducing iron ore without generating CO ₂ , it is conceivable to use hydrogen as a reducing gas. When hydrogen is blown into the blast furnace, the reduction of iron ore with hydrogen is expressed by the following equation (1). Further, reduction by CO generated by combustion of coke or the like is expressed by the following equation (2).
Fe ₂ O ₃ + 3H ₂ = 2Fe + 3H ₂ O ΔH = 100.1kJ / mol (endothermic)… (1)
Fe ₂ O ₃ + 3CO = 2Fe + 3CO ₂ ΔH = -23.4kJ / mol (exothermic)… (2)
Since reduction with hydrogen is an endothermic reaction as described above, when hydrogen is blown directly into the blast furnace, the heat in the lower part of the furnace may be taken away, and there is a risk that the heat necessary for the reduction or dissolution of iron ore will be insufficient. Thermal compensation is required.

On the other hand, Patent Document 1 discloses a blast furnace operating method in which a hydrocarbon-based gas such as LNG is blown in order to reduce the ratio of reducing materials such as coke in a blast furnace.
Further, Patent Document 2 discloses a technique for burning a part of blast furnace gas and injecting it into a blast furnace shaft portion as a high-temperature gas in order to compensate for the heat of the upper part of the furnace when the low reductant ratio operation is directed at the blast furnace. It is disclosed. This document also discloses a technique for removing CO ₂ in the blast furnace gas as necessary.

JP 2006-233332 A JP 2008-214735 A

As described above, generation of CO ₂ is inevitable in steel production. Thus, by utilizing the generated CO ₂ how effectively, or reduces the amount of CO ₂ produced substantially becomes an important issue.
The method of Patent Document 1 can reduce the amount of reducing material (coke etc.) used by blowing LNG into the blast furnace and indirectly reduce the amount of CO ₂ generated in the blast furnace, but effectively use the generated CO _2. However, this does not mean that the actual amount of generated CO ₂ is reduced. Also, the method of Patent Document 2 is not a technique for reducing the substantial amount of CO ₂ generation as in Patent Document 1, and nothing is described about effective use of separated CO ₂ .

Further, in the method of Patent Document 1, hydrogen (hydrocarbon) is blown into a blast furnace to increase hydrogen reduction, and carbon reduction can be reduced to reduce CO _2. However, all of the hydrogen that is input is used for reduction. However, almost half of it is discharged as part of the blast furnace gas composition as hydrogen, and it cannot be said that it is necessarily used effectively for CO ₂ reduction.
Accordingly, an object of the present invention is to provide hydrogen supplied to a blast furnace in a blast furnace operating method in which one or more of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen are blown into the blast furnace. An object of the present invention is to provide a method of operating a blast furnace that can be effectively used and can substantially reduce the amount of CO ₂ generated in the blast furnace.

As a result of intensive studies to solve the problems of the conventional technology as described above, the inventors have found that one or more of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen are contained in a blast furnace. In the operation method of the blast furnace that is blown into the blast furnace gas, out of nitrogen, hydrogen, CO, CO ₂ and H ₂ O, which are the main components of the blast furnace gas, hydrogen and CO ₂ are taken out from the blast furnace gas and converted into CH ₄ (reforming), By blowing this CH ₄ into the blast furnace as a heat source and a reducing agent, a new blast furnace operation method has been devised that can use up the hydrogen introduced into the blast furnace and maximize the CO ₂ reduction effect by the introduction of hydrogen. That is, the gist of the present invention is as follows.

[1] In a method of operating a blast furnace in which one or more of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen are blown into the blast furnace, CO is discharged from the blast furnace gas discharged from the top of the blast furnace. and step (a) to take out ₂ and hydrogen, the CO ₂ and hydrogen extracted in the step (a) and the step (B) to be converted to CH _4, the gas passed through the step (B), step (B) A step (D) of separating and removing CO ₂ remaining without being converted to CH ₄ in step (D), and the gas after separating and removing excess CO ₂ in the step (D) is a reducing gas containing hydrogen. A method of operating a blast furnace, wherein the blast furnace is blown into a blast furnace together with at least one of a liquid fuel containing hydrogen and a solid substance containing hydrogen.
[2] In the operation method of the above-mentioned [1], further have a step process for separating and removing of H _{2 O} from the gas after separating and removing excess CO ₂ by (D) (C), said step (C The gas after separation and removal of H ₂ O by the above is blown into the blast furnace together with one or more of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen. A method for operating a blast furnace according to 1.
[3] The operating method of [1] or [2] above, wherein in step (A), CO is further extracted from the blast furnace gas, and the CO is blown into the blast furnace.

According to the present invention, a reducing gas containing hydrogen from such tuyere, liquid fuel containing hydrogen, the operation method of the blast furnace blowing at least one of the blast furnace of the solid material containing hydrogen, CO ₂ from the blast furnace gas The hydrogen is taken out and converted into CH ₄ , and this CH ₄ is blown into the blast furnace, so that the hydrogen charged into the blast furnace can be used up and the CO ₂ reduction effect by the hydrogen input can be maximized.

Explanatory drawing which shows one embodiment (gas processing flow) of the blast furnace operating method of this invention Explanatory drawing which shows one embodiment of the conventional blast furnace operating method

Hereinafter, the operation method of the blast furnace of this invention is demonstrated.
The present invention is a method of operating a blast furnace in which one or more of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen are blown into the blast furnace from a tuyere or the like. Here, examples of the reducing gas containing hydrogen include natural gas (approximately 100% CH ₄ ), city gas, coke oven gas, propane, and ammonia. Examples of the liquid fuel containing hydrogen include heavy oil, tar, ethanol, methanol, and naphtha. In addition, as a solid substance containing hydrogen, plastic is a typical example, but in addition to this, for example, biomass or the like may be used. This solid substance containing hydrogen is normally blown into the blast furnace as a powdery granule.

One or more of these reducing gases containing hydrogen, liquid fuel, and solid substances can be blown into the blast furnace. Blowing into the blast furnace is usually performed through tuyere, but is not limited thereto. When blowing from a tuyere, it is common to install a blowing lance at the tuyere and blow from this blowing lance.
In a blast furnace operation in which one or more of a reducing gas containing hydrogen from a tuyere, a liquid fuel containing hydrogen, or a solid substance containing hydrogen is blown into the furnace, the composition of the blast furnace gas discharged from the top of the furnace is generally , _CO 2: 20~27vol%, hydrogen: 3~10vol%, CO: 25~30vol% , nitrogen: _50~55vol%, H 2 O: is about 3~10vol%.

The present invention method converts a step (A) to take out CO ₂ and hydrogen from a blast furnace gas discharged from the furnace top of the blast furnace, the CO ₂ and hydrogen retrieved in this step (A) in CH ₄ (modified) The step (B) is performed, and CH ₄ obtained in this step (B) is blown into the blast furnace as a heat source and a reducing agent. As a preferred embodiment, from (i) further having a step separating removal of H _{2 O} from the gas passed through the (B) (C), (ii) Further, through the steps (B) Gas, step ( B) having a step (D) of separating and removing CO ₂ remaining without being converted to CH ₄ ; and (iii) in step (A), CO is further extracted from the blast furnace gas, and the CO is put into the blast furnace. It is preferable to have at least one of blowing.

In the step (A), as a form to take out CO ₂ and hydrogen from a blast furnace gas by using the separating device, but may be separated substantially only CO ₂ and hydrogen from a blast furnace gas, typically, CO ₂ And a gas mainly containing hydrogen (preferably, a gas containing a large amount of CO ₂ and hydrogen and a small amount of CO). The extracted CO ₂ and hydrogen are part or all of CO ₂ and hydrogen contained in the blast furnace gas. Further, nitrogen and H ₂ O contained in the blast furnace gas do not contribute to the reaction in the step (B), and the blast furnace gas after CO ₂ and hydrogen are taken out is usually a fuel such as a reformed blast furnace gas. Therefore, nitrogen and H ₂ O should not be contained as much as possible. For this reason, in the step (A), it is preferable to separate and remove nitrogen and H ₂ O from the blast furnace gas and discharge them out of the system.

In order to extract CO ₂ and hydrogen from the blast furnace gas, for example, the following method can be employed. First, as a method of separating and recovering CO ₂ from a mixed gas, for example, a method of liquefying or solidifying CO ₂ by pressurization or cooling, a method of heating or absorbing CO ₂ in a basic aqueous solution such as caustic soda or amine, etc. A method of separating and recovering by reduced pressure, a method of separating and recovering CO ₂ by adsorption on activated carbon, zeolite, etc., and then separating and recovering by heating or reduced pressure, a method of separating and recovering by a CO ₂ separation membrane, etc. are known. The method can be adopted. In addition, as a method for separating hydrogen, a method such as a PSA (physical adsorption) method can be employed.

In addition, there is no particular limitation on the order of separating CO ₂ and hydrogen from the blast furnace gas, but as will be described later, the amount of hydrogen in the blast furnace gas is to reform the entire amount of CO ₂ contained in the blast furnace gas. Since the amount of hydrogen in the blast furnace gas is usually not sufficient, it is preferable to recover the entire amount of hydrogen in the blast furnace gas. For this reason, hydrogen is first separated and recovered from the blast furnace gas (preferably the entire amount of hydrogen is separated and recovered), and the remaining It is efficient to separate and recover the required amount of CO ₂ from the blast furnace gas.
Note that when ideally remove hydrogen and other than CO ₂ gas from the blast furnace gas, CO ₂ is 70-80% by volume, the remainder is hydrogen.

In the step (B), CO ₂ and hydrogen extracted from the blast furnace gas in the step (A) are converted (reformed) into CH _4. For this reforming, a known method using a specific catalyst or the like is used. Can be applied. The reduction reaction of CO ₂ with hydrogen is shown in the following formula (1).
CO ₂ + 4H ₂ = CH ₄ + 2H ₂ O ΔH = -39.4kJ / mol (exotherm)… (1)
The above is an exothermic reaction. In this reaction, low temperature is advantageous in equilibrium, and the CO ₂ equilibrium conversion at 300 ° C. shows about 95%. For this reaction, a commonly used methanation catalyst can be used. Specifically, CO ₂ can be reformed to CH ₄ by using a transition metal catalyst such as iron, Ni, Co, and 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. In addition, iron ore may be used as a catalyst, and particularly high crystal water ore increases its specific surface area when dehydrated crystal water and can be suitably used as a catalyst.
Obtained in this step (B) gas (hereinafter, referred to as "reformed gas") is usually a gas composed of the gas or substantially CH ₄ as a main component CH _4.

In order to convert (reform) CO ₂ and hydrogen into CH ₄ using a catalyst, a methanation reactor in which CO ₂ and hydrogen (a gas mainly composed of CO ₂ and hydrogen) are usually packed with a catalyst is used. To convert CO ₂ and hydrogen into CH ₄ (reforming). As the reactor, 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.
Here, as shown in the above reaction formula, 4 mol of hydrogen is required for 1 mol of CO ₂ . In general, the amount of hydrogen in the blast furnace gas is insufficient to reform the entire amount of CO ₂ contained in the blast furnace gas. For this reason, it is preferable that excess CO ₂ is discharged while leaving an appropriate amount before reforming or separated and removed after reforming. That is, in the latter case, in the step (D), CO ₂ remaining without being converted into CH ₄ in the step (B) is separated and removed from the reformed gas that has passed through the step (B).

Further, the amount of CO ₂ reformed may be further increased by adding hydrogen procured from other places (for example, hydrogen-based gas blown into the blast furnace) or hydrogen procured from outside to the hydrogen separated from the blast furnace gas. If excess CO ₂ still occurs, it may be discharged with a proper amount before reforming as described above, or separated and removed after reforming.
When CO ₂ is reformed to CH ₄ by hydrogen, H ₂ O is generated. When H ₂ O is introduced into the blast furnace, coke in the blast furnace is consumed, and conversely, CO ₂ emission increases. Therefore, it is preferable to separate and remove H ₂ O from the reformed gas that has undergone the step (B) as the step (C).

As a method for separating and removing H ₂ O from the reformed gas, 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. In addition, as a method of cooling the reformed gas, for example, heat exchange is performed with the reformed gas (usually normal temperature) in the middle of being supplied to the blast furnace through the step (C) of separating and removing H ₂ O. May be.

In the present invention, CH ₄ (reformed gas) obtained by the above reforming is blown into the blast furnace as a heat source and a reducing agent. Blast furnace operation of the present invention has blown "reducing gas containing hydrogen, liquid fuel containing hydrogen, one or more of the solid material containing hydrogen" into the furnace, thus, the CH 4 _(after modification Gas) is blown into the furnace as a substitute for part of “one or more of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen”.

In consideration of blast furnace operation, the reformed gas is preferably blown into the blast furnace after raising the gas temperature. For this reason, after the heat is exchanged with the high-temperature reformed gas immediately after the step (B), the temperature is raised. It may be blown into a blast furnace. Further, the temperature of the reformed gas may be raised by indirect heating using another heat source.
The reformed gas can be blown into the blast furnace in any manner, but usually from the tuyere together with the above-mentioned “one or more of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen”. Infuse.

In the step (A), CO may be further extracted from the blast furnace gas, and this CO may be blown into the blast furnace from a tuyere or the like. The extracted CO is a part or all of the CO contained in the blast furnace gas. The CO taken out from the blast furnace gas is the CH ₄ obtained in the step (B) together with the above-mentioned “one or more kinds of reducing gas containing hydrogen, liquid fuel containing hydrogen, and solid substance containing hydrogen”. It may be blown into the blast furnace together with (the gas after reforming) or may be blown separately.
When CO is not taken out from the blast furnace gas, the corresponding amount of CO is included in the reformed blast furnace gas (usually used as fuel).
In order to extract CO from blast furnace gas, for example, a method in which CO is adsorbed on an adsorbent such as copper / activated carbon, copper / alumina, copper / zeolite, etc., and then separated and recovered by heating or decompression, absorption using copper as a main component. A method of separating and collecting CO by absorbing CO in the liquid and then heating or reducing pressure is known, and any method including these can be adopted.

FIG. 1 shows one embodiment (gas treatment flow) of the present invention.
In this embodiment, first, as a step (A), CO ₂ and hydrogen from a blast furnace gas (CO ₂ and gas mainly composed of hydrogen) is taken out in the separation device. Moreover, since the blast furnace gas contains nitrogen and H ₂ O, these are separated and removed. As a result, the gas components that do not contribute to the reaction in the step (B) can be reduced, and the quality of the remaining gas (reformed blast furnace gas) used as fuel or the like can be improved.

Next, as step (B), CO ₂ and hydrogen (gas mainly composed of CO ₂ and hydrogen) extracted from the blast furnace gas in the step (A) are introduced into a methanation reactor and converted to CH ₄ . (Modify). The reformed gas that has undergone this step (B) is cooled by heat exchange with the reformed gas immediately before being introduced into the blast furnace, and then H ₂ O is separated and removed as step (C). Further, if the CO ₂ that has not been modified in step (B) after the reformed gas is remaining, as a step (D), the CO ₂ may be separated and removed. The reformed gas that has undergone the step (C) (further step (D)) is heated and exchanged with the high-temperature reformed gas immediately after the step (B). It is blown into the blast furnace together with “one or more of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen” (described as “hydrogen-based reducing agent” in FIG. 1). Further, in the step (A), CO may be further taken out from the blast furnace gas, and the CO may be blown into the blast furnace together with the reformed gas as indicated by a broken line in the figure.

In a blast furnace in which natural gas (nearly 100% CH ₄ ) is blown in from a tuyere at 50 kg / tp, a blast furnace gas reforming facility is installed, and the blast furnace according to the present invention conforms to the processing flow shown in FIG. The operation was carried out.
In the present invention example, as for CO ₂ taken out from the blast furnace gas, only 1/4 of the number of moles of hydrogen taken out from the blast furnace gas is supplied to the reformer (methanation reactor), and the rest is the reformed blast furnace. Exhausted as part of the gas. In addition, the CO separated from the blast furnace gas was not returned again to the blast furnace (broken line in FIG. 1), and was also discharged as part of the reformed blast furnace gas. This is because it is necessary to exclude the effect of CO circulation in order to quantitatively evaluate the effect of the present invention.

A part of the blast furnace gas was reformed and circulated according to the processing flow as shown in FIG.
・ Process (A)
The total amount of blast furnace gas generated from the blast furnace, is adsorbed and _{H 2} at an absolute pressure 200kPa is introduced into the adsorption _{tower H 2} adsorbent is filled, thereafter, _H 2 is desorbed the _{H 2} absolute pressure 7 kPa ( to obtain a concentration of H ₂ 99 vol%).
The 10 vol% of the blast furnace gas after separating and recovering of H ₂ was absorbed the CO ₂ in the absolute pressure 200kPa is introduced into the adsorption tower CO ₂ adsorbent is filled, thereafter, desorbing the CO ₂ in the absolute pressure 7kPa And CO ₂ (CO ₂ concentration 99 vol%) was obtained. The remaining 90 vol% of the blast furnace gas was discharged to a conventional blast furnace gas discharge system.

・ Process (B)
The CO ₂ separated and recovered as described above is led to a reformer (reactor), and H ₂ separated and recovered from the blast furnace gas is added to this (H ₂ / CO ₂ : 4 molar ratio), and the Ni-based catalyst Was reformed (converted) to CH ₄ under conditions of reaction temperature: 500 ° C. and SV (Space Velocity): 100 h ⁻¹ . The CO ₂ conversion was about 100%. After the reforming, the gas was cooled with a heat exchanger, H ₂ O was removed with a moisture removing device, and then blown from the blast furnace tuyere.
In the conventional blast furnace operation, only 50 kg / tp of natural gas (almost 100% CH ₄ ) was blown from the tuyere (FIG. 2).

CO ₂ emissions in the present invention and a conventional example of (CO ₂ amount in the blast furnace gas), shown in Table 1 together with the emissions (furnace top exhaust gas amount) and gas composition of the operating conditions and the blast furnace gas.
In the example of the present invention, CH ₄ obtained by the reforming of CO ₂ is replaced with a part of the natural gas blown into the blast furnace, so that the reducing material ratio including the amount of blown reducing gas does not change from the conventional example. Stable operation was possible. In the example of the present invention, part of hydrogen and CO ₂ taken out from the blast furnace gas was converted to CH ₄ and reused in the blast furnace, so the amount of exhaust gas at the top of the furnace was reduced by 11% compared to the conventional example, and from the top of the furnace. The amount of CO ₂ emitted was also reduced by 9%.

Claims (3)

In a method of operating a blast furnace in which one or more of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen are blown into the blast furnace,
A step (A) for extracting CO ₂ and hydrogen from blast furnace gas discharged from the top of the blast furnace, a step (B) for converting CO ₂ and hydrogen extracted in the step (A) into CH ₄ , and the step (B) from the gas passing through the, and a step (B) step (D) for separating and removing the CO ₂ that remained without being converted into CH _4, the separating and removing excess CO ₂ by the step (D) A method of operating a blast furnace, characterized by blowing the gas into the blast furnace together with at least one of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen. Furthermore, it has a step (D) Step (C) separating off of H _{2 O} from the gas after separating and removing excess CO ₂ by, after separating and removing of H _{2 O} by the step (C) Gas The blast furnace operating method according to claim 1, wherein the blast furnace is blown into a blast furnace together with at least one of a reducing gas containing hydrogen, a liquid fuel containing hydrogen, and a solid substance containing hydrogen .   3. The method of operating a blast furnace according to claim 1 or 2, wherein in step (A), CO is further extracted from the blast furnace gas, and the CO is blown into the blast furnace.

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