JP2009221547A - Method for operating blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating a blast furnace, wherein in the case of performing the blast furnace operation for blowing reducing material having high hydrogen content, the enlargement of a low temperature zone in the furnace and the lowering of the furnace top gas temperature are prevented. <P>SOLUTION: The blast furnace operating method, in which preheating gas 4 is blown into the blast furnace 1 from a shaft part in the blast furnace operation for blowing the reducing material containing ≥10 mass% H from a tuyere 2, is used. As the preheating gas, it is desirable that combustion gas obtained by burning the blast furnace gas 8 beforehand removing CO<SB>2</SB>with a de-CO<SB>2</SB>device 11, is used and COG reformed gas as the reducing material containing ≥10 mass% H, is used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for operating a blast furnace in which a reducing material having a high hydrogen content is blown from a tuyere.

In recent years, global warming due to an increase in carbon dioxide emissions has become a problem, and the suppression of emitted CO ₂ is an important issue even in the steel industry. Blast furnaces mainly use coke and pulverized coal as reducing materials, and in order to achieve carbon dioxide emission suppression, measures to replace coke with reducing materials with a high hydrogen content are effective. As a technology to use reducing materials with high hydrogen content in the blast furnace, there is a low carbon dioxide emission steelmaking method that reduces the carbon dioxide emitted in the ironmaking process by blowing LNG (Liquefied Natural Gas) into the blast furnace from the tuyere. It is known (for example, refer to Patent Document 1).

On the other hand, it is known that the reduction reaction of iron oxide with hydrogen is a relatively large endothermic reaction. The reaction and heat of reaction during iron oxide reduction with CO gas and H ₂ gas are shown in the following (a) to (f) (for example, see Non-Patent Document 1).
3Fe ₂ O ₃ + CO → 2Fe ₃ O ₄ + CO ₂ (Reaction heat: +38 kcal / kgFe) (a)
Fe ₃ O ₄ + CO → 3FeO + CO ₂ (heat of reaction: −38 kcal / kg Fe) (b)
FeO + CO → Fe + CO ₂ (Reaction heat: +60 kcal / kgFe) (c)
3Fe ₂ O ₃ + H ₂ → 2Fe ₃ O ₄ + H ₂ O (heat of reaction: +5 kcal / kg Fe) (d)
Fe ₃ O ₄ + H ₂ → 3FeO + H ₂ O (heat of reaction: −96 kcal / kg Fe) (e)
FeO + H ₂ → Fe + H ₂ O (reaction heat: −116 kcal / kg Fe) (f)
In the above reaction formula, the amount of hydrogen input from the tuyere increases, and the ratio of hydrogen reduction in the reduction of iron oxide increases, so the temperature of the shaft portion decreases, and iron ore and sintered ore are charged. This suggests that the residence time of the object in the low temperature region may be extended. The expansion of the low temperature region of the shaft portion means the expansion of the reduced pulverization region of the sintered ore, and the air permeability and the charge lowering behavior are deteriorated by the pulverization of iron ore and the like by the reduction. It has also been pointed out that the temperature of the furnace top gas is also lowered. The furnace top gas temperature is desirably 110 ° C. or higher in terms of blast furnace operation, and when the temperature of the furnace top gas is lowered, moisture in the blast furnace gas condenses, causing problems such as equipment corrosion.

In the first place, in the conventional normal blast furnace operation, the low temperature region was hardly formed. Although there are cases where the amount of hydrogen input to the blast furnace increases due to high pulverized coal ratio operation, generally the coke replacement rate of pulverized coal is normally around 0.9, which is high enough to exceed the injection basic unit of 150 kg / t. In the case of the pulverized coal ratio, the substitution rate further decreases. Therefore, in the case of operation to increase the pulverized coal ratio, the ratio of reducing material increases with the increase in the amount of input hydrogen, and the furnace top temperature generally rises, and the low temperature region is hardly formed. On the other hand, in the method in which LNG is blown from the tuyere as in the method described in Patent Document 1, the coke replacement ratio of natural gas is about 1.1 to 1.2 (see, for example, Non-Patent Document 2). As the natural gas blowing rate increases, the reducing material ratio decreases, so the formation of a low temperature region is actually a problem.
JP-A-3-240906 “Seikan Handbook” Jinjinshokan 1979, p. 78 “Materials and Process 18” Japan Steel Association 2005, p. 984

  As described above, when using a reducing material having a high hydrogen content, such as natural gas, and performing an operation directed to reducing the reducing material ratio, the temperature at the top of the furnace decreases due to the increase in hydrogen input to the blast furnace. There is a problem.

  Therefore, the object of the present invention is to solve such problems of the prior art and to expand the low temperature region in the furnace and lower the furnace top gas temperature when performing a blast furnace operation in which a reducing material having a high hydrogen content is blown. It is to provide a blast furnace operation method that can be prevented.

The features of the present invention for solving such problems are as follows.
(1) A blast furnace operation method in which preheated gas is blown from a shaft portion into a blast furnace furnace in a blast furnace operation in which a reducing material containing 10% by mass or more of H is blown from a tuyere.
(2) The blast furnace operating method according to (1), wherein a combustion gas obtained by burning blast furnace gas from which CO ₂ has been previously removed is used as the preheating gas.
(3) The blast furnace operating method according to (1) or (2), wherein a COG reformed gas is used as a reducing material containing 10% by mass or more of H.

  ADVANTAGE OF THE INVENTION According to this invention, the expansion of the low temperature area | region in a furnace and the temperature fall of furnace top gas can be prevented in the blast furnace operation which blows in a reducing material with a high hydrogen content rate.

  In the present invention, the preheating gas is blown into the furnace of the blast furnace from the shaft portion, thereby preventing the expansion of the low temperature region and the lowering of the furnace top temperature, which are problems when the reducing material having a high hydrogen content is blown.

In the present invention, the reducing material having a high hydrogen content is a substance containing 10% or more of hydrogen (H) as a mass ratio and acting as a reducing material for iron in a blast furnace. Specifically, LNG (H content) About 23% by mass), COG (coke oven gas generated when producing coke: H content: about 25% by mass), BFG (blast furnace gas: H content: 0.2 to 0.5% by mass) containing hydrogen It was obtained by reforming BFG reformed gas, city gas (H content: about 23% by mass), liquefied petroleum gas (LPG: H content: about 23% by mass), and methane, whose amount was increased to 10% by mass or more. Synthesis gas (reducing gas composed of CO and H ₂ gas, H content of about 17% by mass) or the like can be used. The BFG reformed gas is a gas obtained by reforming BFG by a water gas shift reaction (CO + H ₂ O = CO ₂ + H ₂ ) and separating CO ₂ and N ₂ so that the hydrogen content becomes 10% by mass or more. . However, hydrogen in the state of water (H ₂ O) is excluded from the reducing agent having a high hydrogen content used in the present invention. Although hydrogen gas can be used, pure hydrogen gas is difficult to obtain industrially. As the readily available gas, for example, liquefied natural gas or city gas is desirable, and these are often composed mainly of methane (approximately 80% by volume or more of methane). Therefore, the COG reformed gas (H content of about 65% by volume), which has been improved by reforming COG containing about 44% by mass of methane, has a particularly high hydrogen content. It is particularly effective to use the present invention for blast furnace operation that is blown from the outside. By blowing the reducing material having a high hydrogen content into the blast furnace at 3 kg / t-pig or more, more preferably 7 kg / t-pig or more as a hydrogen content derived from blowing the reducing material having a high hydrogen content, the effect of the present invention can be obtained. It can be demonstrated better.

  FIG. 1 is a schematic view showing an embodiment of the present invention. An embodiment of the present invention will be specifically described with reference to FIG. When the operation of blowing a reducing material having a high hydrogen content from the tuyere 2 of the blast furnace 1 is performed, the preheating gas 4 is blown into the furnace using the preheating gas blowing pipe 3 installed in the shaft portion of the blast furnace. It is preferable to blow air from the tuyere and blow pulverized coal 7 or the like which is blown in a normal blast furnace operation in addition to the reducing material 6 having a high hydrogen content.

As the preheating gas 4, a combustion gas (non-reducing gas) obtained by burning BFG, COG, COG reformed gas, LNG, H ₂ gas, LDG or the like with oxygen or air can be used. A gas obtained by indirectly heating a reducing gas containing CO and H ₂ and raising the temperature to a predetermined temperature can also be used. The blowing position of the preheating gas 4 may be any position as long as it is a blast furnace shaft portion.

When the preheating gas 4 is blown into the furnace of the blast furnace 1 from the shaft portion, for example, as shown in FIG. 1, a part of BFG 8 that is the top gas discharged from the blast furnace 1 as a preheating gas is branched, and oxygen 9 Can be burned in the combustion furnace 10 and blown into the blast furnace shaft portion as a combustion gas (non-reducing gas) of about 800 to 1000 ° C. BFG8 with de CO ₂ apparatus 11 for removing CO ₂ from the BFG was removed CO ₂ is burned in the combustion furnace 10, it is preferable to blow the blast furnace shaft portion as a combustion gas. By removing CO ₂ , there is an effect that the amount of oxygen or air necessary for combustion of the preheated gas can be reduced. More preferably, CO ₂ and N ₂ are removed. The CO ₂ removal method may be a chemical absorption method using an alkylamine, or a physical adsorption, physical absorption, or membrane separation method. As a method for removing N ₂ , methods by physical adsorption, physical absorption, and membrane separation can be used.

As an example of injecting reducing gas as the preheating gas 4, for example, when reducing gas of CO: 35 vol% and H ₂ : 65 vol% is blown into the furnace, other combustion gases are burned to enter the furnace It is also possible to inject by heat exchange with the reducing gas to be injected. In that case, it is also convenient to branch a part of the BFG and use it as the other combustion gas. For example, as shown in FIG. 2, the reducing gas 12 can be preheated by exchanging heat with the exhaust gas 13 in which the BFG 8 is burned in the combustion furnace 10 and 14, and can be blown into the furnace as the preheating gas 15. In this case, it is preferable to remove the CO ₂ or CO ₂ and N _2, in the BFG. By blowing preheated reducing gas, iron ore and sintered ore can be pre-reduced while reducing the expansion of the low temperature region of the shaft, specifically, while suppressing pulverization of the charge, It can contribute to the reduction of the reducing material ratio (coke etc.) of the blast furnace. Moreover, oxygen can be added to gas, such as LNG, and it can also be partially oxidized, and can be used as a preheating gas. Further, CO and H ₂ in BFG can be considered as a reducing gas, and preheated and blown into the furnace. In this case, it is preferable to remove the CO ₂ or CO ₂ and N _2, in the BFG.

When a non-reducing gas is used as the preheating gas, particularly when combustion exhaust gas is used, the blowing position may be any position as long as it is a blast furnace shaft portion, and coke charged into the blast furnace and CO ₂ and H ₂ O in the combustion exhaust gas. It is preferable to blow in as a temperature range in which the gasification reaction does not proceed. Specifically, although depending on operating conditions, the P _CO / (P _CO + P _CO2 ) ratio of the blast furnace shaft portion is in the range of 0.3 to 0.7, and the preheating gas temperature is preferably 900 ° C. or lower. Further, since the preheating gas is blown into the furnace from the shaft portion, it is preferable that the preheating gas is blown at a gas velocity equal to or less than the fluidization condition of iron ore and coke so as not to disturb the charge drop in the furnace. . The preheating gas is preferably blown evenly in the circumferential direction, and the preheating gas blowing pipes may be arranged in one or more stages.

When a non-reducing gas is used as the preheating gas, the heat flow ratio around the furnace (heat capacity of falling charge / heat capacity of the furnace top gas) decreases due to the injection of the preheating gas, and the reduction powder temperature range is Since it becomes narrow, powdering is suppressed. Therefore, it is possible to charge highly reduced powder (RDI) sintered ore into the peripheral portion when charging raw materials into the blast furnace as compared with normal operation. For example, the high RDI sintered ore can be charged to the peripheral part by discharging the high RDI sintered ore and charging the rotary chute while rotating (forward tilting) from the outside to the inside. . As the non-reducing gas, it is preferable to use CO ₂ , H ₂ O, N ₂ or the like.

When using reducing gas as the preheating gas, when charging raw materials into the blast furnace, charge low reactive ore such as low reduced powder (RDI) sintered ore or lump ore to the periphery. Is preferred. This is because the gas reduction around the furnace is promoted by blowing the preheating gas. As the reducing gas, CO, H ₂ or the like is preferably used.

  When a reducing gas is used as the preheating gas, it is preferable to further increase the ore layer thickness ratio in the periphery when the raw material is charged into the blast furnace. This is because the reduction of gas in the periphery of the furnace is promoted by blowing the preheating gas, so that the effect of supplementing the reducing property can be obtained.

  When a reducing gas is used as the preheating gas, it is preferable to blow into the furnace temperature range of 700 to 1000 ° C. in order to promote reduction and ensure the furnace upper temperature.

The present invention was applied to various hydrogen-containing reducing material blowing operations in a blast furnace having an internal volume of 5000 m ³ . LNG (CH ₄ : 88.5 vol%, C ₂ H) as a hydrogen-containing reducing material in an operation with a tapping ratio of 2.3 t / m ³ / d, a tuyere tip temperature of 2200 ° C., and a pulverized coal injection amount of 160 kg / t _{6: 4.6vol%, C 3 H} 8: 5.4vol%, others: 1.5 vol%) and _{COG (H 2: 58.45vol%,} CO: 6.35vol%, CH 4: 27.35vol%, CO ₂ : 1.92 vol%, N ₂ : 2.31 vol%, other hydrocarbons: 3.62 vol%), COG reformed gas (H content: about 65 vol%, CO content: 35 vol%: H ₂ content: about 11 .7 mass%) and H ₂ , the operation conditions were changed as appropriate, and an operation test was conducted. Blast furnace gas (BFG) combustion gas, BFG combustion gas from which CO ₂ has been removed (BFG combustion gas de-CO ₂ ), CO, H ₂ gas are used as the preheating gas, and the preheating gas is blown into 38 pipes in the circumferential direction. A blown pipe having a diameter of 20 cm was used. The RDI of sintered ore is 35%.

Examples 1 to 4 of the present invention are examples in which 800 ° C. BFG combustion gas is blown into the shaft portion as a preheating gas, Example 5 of the present invention uses BFG combustion gas of 1000 ° C., and Example 6 of the present invention uses BFG as the preheating gas. In this example, BFG combustion gas was blown to 1000 ° C. by removing CO _2. Example 7 of the present invention was an example in which reducing gas at 800 ° C. of CO: 35 vol% and H ₂ : 65 vol% was blown. Table 1 shows the operation conditions for each operation. Moreover, in the case of normal operation (conventional operation in which no hydrogen-based raw material is intentionally charged into the blast furnace), and in the case of operation in which no preheating gas is injected, Table 1 is shown as Comparative Examples 1 to 4.

Table 1 also shows the amount of top gas of the blast furnace, the calorific value, the composition, the temperature, and the ventilation resistance index (relative values when the corresponding comparative example is 1) under each operating condition. In Comparative Examples 1 to 4, the coke ratio can be reduced by the operation of injecting the hydrogen-containing reducing material, but the full-year resistance index increases and the furnace top gas temperature (TGT) decreases to less than 110 ° C. However, as shown in Examples 1 to 5 of the present invention, it is possible to ensure a furnace top gas temperature (TGT) of 110 ° C. or higher while reducing the coke ratio by blowing the preheating gas from the shaft portion. I understand. Further, as shown in the result of Example 6 of the present invention, by removing CO ₂ from BFG blown into the shaft, the amount of oxygen necessary for combustion can be reduced as compared with using BFG as it is, and the top gas of the blast furnace is further reduced. It was found that calories can be increased. It was found that when reducing gas was blown as the preheating gas (Example 7 of the present invention), the ratio of reducing material could be further reduced, and the operation of the blast furnace was possible with the relative resistance index relative value kept lower than the normal operation.

  As Inventive Example 8, in the condition of Inventive Example 1 of Example 1 above, RDI = 38% sintered ore in a dimensionless radial position in the range of 1/4 from the periphery in the blast furnace radial direction at the dimensionless radial position. From 1/4 to the center, RDI = 35% sintered ore was charged. The relative value of the airflow resistance index with the normal operation was equivalent to that of the normal operation (1.0).

  As Invention Example 9, in the condition of Invention Example 7 of Example 1 above, a sintered ore with RDI = 31% in the range of 1/4 in the dimensionless radial position from the periphery in the blast furnace radial direction, in the dimensionless radial position. From 1/4 to the center, RDI = 35% sintered ore was charged. The relative value of the ventilation resistance index with the normal operation was 0.99 in Invention Example 7 and was 0.97.

Schematic which shows one Embodiment of this invention. Schematic which shows one Embodiment of this invention.

Explanation of symbols

1 Blast Furnace 2 Tuyere 3 Preheating Gas Blowing Pipe 4 Preheating Gas 5 Blowing 6 Reducing Material with High Hydrogen Content 7 Pulverized Coal 8 BFG
9 Oxygen 10 Combustion furnace 11 De-CO ₂ equipment 12 Reducing gas 13 Exhaust gas 14 Heat exchange 15 Preheating gas

Claims (3)

  A blast furnace operation method in which preheating gas is blown into a blast furnace furnace from a shaft portion in a blast furnace operation in which a reducing material containing 10 mass% or more of H is blown from a tuyere. The blast furnace operating method according to claim 1, wherein combustion gas obtained by burning blast furnace gas from which CO ₂ has been removed in advance is used as the preheating gas.   The blast furnace operating method according to claim 1 or 2, wherein COG reformed gas is used as a reducing material containing 10 mass% or more of H.

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