Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/001—Injecting additional fuel or reducing agents
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/001—Injecting additional fuel or reducing agents
  • C21B5/003—Injection of pulverulent coal
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/008—Composition or distribution of the charge
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/06—Making pig-iron in the blast furnace using top gas in the blast furnace process
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B7/00—Blast furnaces
  • C21B7/007—Controlling or regulating of the top pressure
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B7/00—Blast furnaces
  • C21B7/16—Tuyéres
  • C21B7/163—Blowpipe assembly
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/001—Injecting additional fuel or reducing agents
  • C21B2005/005—Selection or treatment of the reducing gases

Definitions

• the present invention relates to a blast furnace operation method capable of lowering a reducing agent rate in blast furnace operation.
• a blast furnace operation is performed in such a manner where a ferrous raw material and coke are charged in layers from the furnace top, and hot blast (hot air) and a reducing auxiliary agent such as pulverized coal are blown from tuyeres located at the lower portion of the furnace.
• hot blast hot air
• a reducing auxiliary agent such as pulverized coal
• reducing agents such as coke and pulverized coal are used to reduce the iron source in the furnace.
• the total weight of reducing agents required for producing 1 t of pig iron is called reducing agent rate. If reducing agent rate can be lowered, it is possible to reduce CO 2 emission from the blast furnace and production cost of pig iron; lowering reducing agent rate is a major issue in blast furnace operation, and there have been a number of technical developments in this regard.
• Ferro coke is well known as a typical highly reactive coke.
• Ferro coke is a coke produced by mixing an iron ore powder into coal and performing carbonization; the reactivity of ferro coke is improved as Fe contained therein acts as a catalyst for the coke gasification reaction.
• Patent Literature 3 and Patent Literature 4 and Non-Patent Literature 1 there are descriptions that reducing agent rate can be lowered by using ferro coke.
• This type of blast furnace differs from a conventional and general blast furnace in that a high-concentration oxygen-containing gas is blown from the tuyeres instead of hot air, and that a large amount of methane is blown from the tuyeres as a reducing agent instead of pulverized coal, which requires a set of significantly modified operational conditions.
• a blast furnace operation method in which reducing agent rate is lowered by using a highly reactive coke as typified by ferro coke is known to be effective with respect to a conventional and general blast furnace operated by blowing hot air and a reducing agent mainly composed of pulverized coal from tuyeres.
• Patent Literature 5 detailed examination has not yet been given to the type of blast furnace disclosed in Patent Literature 5, i.e., a blast furnace operated by blowing an oxygen-containing gas with an oxygen concentration close to 100% from the tuyeres as a blast gas, and blowing a hydrocarbon-based reducing agent containing a large amount of hydrogen from the tuyeres other than pulverized coal.
• Patent Literature 6 discloses that when blowing a large amount of a hydrogen-containing gas that contains a hydrogen gas into a blast furnace, lowering coke reactivity is effective to suppress endotherm caused by the coke gasification reaction.
• Patent Literature 6 is targeted at a blast furnace operated by blowing a hot air with a high nitrogen gas concentration from the tuyeres.
• the blast furnace operation method of the present invention was developed to solve the above problems.
• This method includes: charging a ferrous raw material and coke in layers from a furnace top of a blast furnace; and blowing an oxygen-containing gas and a reducing agent containing a hydrocarbon-based gas into the blast furnace from tuyeres of the blast furnace, wherein when the oxygen-containing gas has an oxygen concentration of 80 vol% or more, operation is carried out using a coke with a reaction index CRI of 35 or less.
• a blast furnace operation capable of lowering reducing agent rate can be realized by using a coke having an appropriate reactivity with its reaction index CRI being 35 or less.
• a blast furnace operation method of the present embodiment is described.
• a ferrous raw material and coke are charged in layers from the furnace top of a blast furnace, an oxygen-containing gas with an oxygen concentration of 80 vol% or more is blown from the tuyere(s) of the blast furnace as a blast gas, and a reducing agent containing a hydrocarbon-based gas is blown from the tuyeres.
• the blast furnace operation method of the present invention uses the oxygen-containing gas as a blast gas, instead of hot blast. If using hot blast (air heated to about 1200°C) as a blast gas, since the combustion gas contains about 50 vol% of nitrogen that does not contribute to combustion reaction, it is difficult for the flames in the raceway to reach a high temperature. Thus, if blowing into the blast furnace a large amount of a reducing agent containing a hydrocarbon-based gas, the tuyere-outlet temperature will decrease, which will cause operational troubles.
• the blast furnace operation method of the present invention by using the oxygen-containing gas as a blast gas, nitrogen gas that does not contribute to combustion reaction can be restricted from being mixed thereinto, whereby the tuyere-outlet temperature can be raised to a sufficient temperature. That is, the temperature of the flames in the raceway is higher than if using hot blast.
• the oxygen concentration of the oxygen-containing gas is 80 vol% or more.
• a low oxygen concentration of the oxygen-containing gas may cause operational troubles as a sufficient tuyere-outlet temperature cannot be secured when blowing a large amount of a hydrocarbon-based gas.
• the oxygen concentration of the oxygen-containing gas needs to be 80 vol% or more, preferably 90 vol% or more, more preferably 95 vol% or more.
• the oxygen concentration may even be 100 vol%.
• the remaining gas other than oxygen in the oxygen-containing gas there may be contained, for example, nitrogen, carbon dioxide, argon, water vapor and the like.
• water vapor decreases the tuyere-outlet temperature, it is preferably contained at a low concentration in the oxygen-containing gas; water vapor is preferably contained at a concentration of 10 g/Nm 3 or less, more preferably 5 g/Nm 3 or less, per 1 Nm 3 of the oxygen-containing gas.
• the hydrocarbon-based gas is preferably a hydrogen gas and/or a gas that contains a hydrogen-containing compound.
• the hydrocarbon-based gas may be methane, ethane, propane, ethylene, propylene, methanol, ethanol and the like.
• the hydrocarbon-based gas may be a gas composed by containing even part of these gases, such as a natural gas, city gas, and coke oven gas that are supplied from outside.
• the hydrocarbon-based gas may also be a regenerated gas generated utilizing the blast furnace gas.
• the hydrocarbon-based gas may be a regenerated methane gas obtained by reacting hydrogen with carbon monoxide and/or carbon dioxide contained in the blast furnace gas, via the method described in Patent Literature 5. By utilizing a regenerated gas as the hydrocarbon-based gas, CO 2 emission can be reduced significantly.
• blowing reducing agents including, for example, pulverized coal, waste plastics, and/or a reducing gas such as a carbon monoxide gas may be used together with the hydrocarbon-based gas.
• the amount of such other blowing reducing agents blown into the blast furnace be 20 wt% or less with respect to the total amount of all the blowing reducing agents including the hydrocarbon-based gas.
• a unit "kg/t" indicates the amount of the other blowing reducing agents that are blown into the blast furnace when producing 1 t of hot metal. If using the other blowing reducing agents, these other blowing reducing agents may also be together introduced into a hydrocarbon-based gas supply part.
• a separate reducing agent supply part that is separate from the hydrocarbon-based gas supply part and is configured to pass pulverized coal and/or waste plastics therethrough.
• Non-Patent Literature 2 which was developed by taking reaction, heat transfer, and substance flow into consideration, the inventors used cokes with different reactivities to study changes in the reducing agent rate when operating the blast furnace in such a manner that the hot metal temperature and tapping quantity were constant.
• CRI Coke Reaction Index
• Methane was used as a hydrocarbon-based reducing agent, and study was conducted at a methane rate of 148 kg/t.
• the reducing agent rate decreased as CRI decreased (see FIG.1 ).
• a high-reactive coke which is considered as favorable for use in a conventional and general blast furnace is disadvantageous in lowering the reducing agent rate with regard to the blast furnace of the present invention.
• a low-reactive coke is advantageous in lowering the reducing agent rate.
• the slope of a part of the graph that corresponds to reducing agent rates of 485 kg/t or less is steeper than the slope of a part of the graph that corresponds to reducing agent rates of 487 kg/t or more.
• the goal is set to a reducing agent rate of 485 kg/t or less.
• the hydrogen concentration in the furnace increases as a result of blowing, from the tuyeres, an oxygen-containing gas with a concentration of 100 vol% as a blast gas, and a large amount of a hydrocarbon-based reducing agent containing a large quantity of hydrogen.
• the reducing gas concentration will be relatively high if performing blasting in a nitrogen-less condition.
• a smelting reduction amount decreases as reduction efficiency improves, whereby a decreased coke reactivity will cause the amount of coke gasified to decrease to an extent equal to or greater than an increase in the smelting reduction amount, thus lowering the reducing agent rate (see FIG.2 ).
• Smelting reduction and coke gasification are both significant endothermic reactions, which leads to an increased reducing agent rate.
• a coke reactivity as low as possible is preferred from the perspective of lowering the reducing agent rate, and it is required that CRI be of a certain value or less in order to achieve the reducing agent rate of a given value or less in blast furnace operation.
• Blast furnace operation was carried out under the various operational conditions shown in the following Table 1, where a pulverized coal ratio was set to 0 kg/t, the methane rate was set to 148 kg/t, an oxygen-containing gas unit consumption was set to 316 to 318 Nm 3 /t, the oxygen concentration in the oxygen-containing gas was set to 100%, the temperature of the oxygen-containing gas was set to 25°C, and the moisture of the oxygen-containing gas was set to 0 g/Nm 3 , provided that cokes with various CRIs were used.
• the various operational conditions were determined based on the result shown in FIG.1 .
• Table 1 showing the results of a blast furnace operation where the concentration of the oxygen blown from the tuyeres was 100 vol%, and methane as a hydrocarbon-based gas was blown from the tuyeres, focus was placed on the reducing agent rate (coke rate + pulverized coal rate + methane rate).
• the invention example 1-1 reducing agent rate 479 kg/t
• the invention example 1-2 reducing agent rate 481 kg/t
• the invention example 1-3 reducing agent rate 483 kg/t

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Iron (AREA)

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Publications (1)

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Citations (6)

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• 2023
  • 2023-10-10 JP JP2024502143A patent/JPWO2024171511A1/ja active Pending
  • 2023-10-10 WO PCT/JP2023/036755 patent/WO2024171511A1/fr not_active Ceased
  • 2023-10-10 EP EP23922845.5A patent/EP4653552A1/fr active Pending
  • 2023-10-10 CN CN202380093085.XA patent/CN120584201A/zh active Pending
  • 2023-10-10 KR KR1020257026889A patent/KR20250134667A/ko active Pending
  • 2023-12-28 TW TW112151231A patent/TWI889106B/zh active

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Non-Patent Citations (3)

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