JP5315732B2 - Blast furnace operation method - Google Patents

Description

  The present invention relates to a method of 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. As a result, the shaft temperature 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 that increases 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.
In addition, the raw materials used in the blast furnace include raw materials that are manufactured in a sintering machine or coke oven and directly sent to the blast furnace raw material tank after particle size adjustment. After being stored, this material is recovered and sent to the blast furnace raw material tank. Furthermore, some of the iron ore is stored in the yard in granular form after it arrives at the factory. Some raw materials are later sent to the blast furnace raw material tank. Among these raw materials, those that are sent to the blast furnace raw material tank after being stored in the yard are inevitably wet with rainwater when stored in the yard, and the moisture content becomes several mass%. Some raw materials have a water content exceeding 10 mass%.

When such a raw material with a large amount of moisture is charged into the blast furnace, heat for the latent heat of evaporation of the water is required, sensible heat of the blast furnace gas in the upper part of the blast furnace is taken, and the temperature of the upper part of the blast furnace becomes lower. In addition, the use of a large amount of hydrogen-based fuel and the introduction of a high-moisture raw material further promotes a lower temperature.
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.
(A) A blast furnace operation method characterized by charging a preheated raw material from the top of a blast furnace in a blast furnace operation in which a reducing material containing 10% by mass or more of H is blown from a tuyere.
(B) The blast furnace operating method according to (A), wherein the preheated raw material is charged so that the top gas temperature of the blast furnace is 110 ° C. or higher.
(C) According to (A) or (B), the raw material is preheated and charged to a charging raw material temperature at which the furnace top gas temperature obtained by the following formula (1) becomes 110 ° C. or higher. Blast furnace operation method.
Furnace top gas temperature (° C.) = 0.68 × (charging raw material temperature (° C.)) + 55.8 (1)
(D) Preheating of the raw material is performed in a preheating facility provided in the upper part of the blast furnace with a heated gas introduced into the preheating facility, as described in any one of (A) to (C) Blast furnace operation method.
(E) The blast furnace operating method according to (D), wherein the temperature of the preheated raw material discharged from the preheating facility and charged into the blast furnace is adjusted by adjusting the temperature of the heated gas.

  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 blast furnace charging raw materials such as iron ore, sintered ore, coke, etc. are preheated, the temperature is increased and charged into the blast furnace from the top of the furnace, thereby increasing the temperature in the furnace and having a high hydrogen content. Prevents the expansion of the low temperature range and the drop in the furnace top temperature, which are problems when reducing materials are blown in.

  The temperature of the charging raw material such as iron ore, sintered ore, and coke charged to the blast furnace may be preheated to a temperature at which moisture in the blast furnace gas is not condensed. Specifically, the temperature of the top gas of the blast furnace is 110. What is necessary is just to preheat a charging raw material to the temperature which becomes more than degreeC. For this purpose, it is preferable that the temperature of the charged raw material is preheated to 110 ° C. or higher and charged. The higher the temperature, the higher the effect of preventing the temperature drop at the top of the furnace, but if it is 800 ° C. or higher, the equipment may be damaged due to heat resistance. Therefore, the upper limit of the charging raw material temperature is determined by the heat resistance temperature of the charging device at the top of the blast furnace.

  By using the pre-charged raw material, the temperature in the furnace rises, and even when blast furnace operation in which a reducing material with a high hydrogen content is blown, the expansion of the low temperature region is suppressed, and the furnace top temperature is reduced. Can be prevented. Since the charged raw material is dried by being preheated, the raw material with a large amount of water is not charged into the blast furnace, and the amount of heat input into the furnace during blast furnace operation can be reduced. In addition, the preheated and dried charge material is sieved to remove the powdery part, and then charged into the blast furnace, thereby reducing the amount of powder material brought into the blast furnace and reducing the gas flow in the furnace. There is also an effect that the operation of the blast furnace can be stabilized by making it appropriate.

  Although all of the charged raw materials may be preheated, the preheating of a part of the charged raw materials has an effect of increasing the temperature of the furnace top gas. When preheating a part of the charged raw material, it is preferable to preheat iron ore and sintered ore with a high proportion of the powdery part removed by drying by preheating.

  Preheating of the blast furnace charging material can be performed in a hopper at the top of the blast furnace. It is preferable to preheat the charged raw material by introducing a heating gas into the hopper. It is also effective to preheat in a hopper called a storage tank or a storage tank for storing ore and coke before charging the hopper at the top of the blast furnace.

As the heating gas used for preheating the charged raw materials, various heating gases generated in the factory can be used. In particular, exhaust gas that is discharged at a relatively low temperature of about 300 ° C. or less and difficult to recover heat can be used effectively. In the case of blast furnace storage tanks and storage tanks, a sintering machine is usually installed in the vicinity, so using the cooler exhaust gas from the sintering machine is optimal because the air supply path is short and heat dissipation is low. And particularly preferred. In addition, heating gas can be appropriately selected according to the location conditions of each factory such as blast furnace hot stove exhaust gas and rolling heating furnace exhaust gas. Of course, a combustion furnace, an electric furnace or the like may be installed for generating heated gas, and a dedicated hot air generation source may be used.
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 performing the operation of blowing a reducing material having a high hydrogen content from the tuyere 2 of the blast furnace 1, the blast furnace charging raw material 3 is preheated by the preheating equipment 4 and charged into 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.

  FIG. 2 shows an embodiment of the preheating facility 4 in FIG. The charging raw material 3a is charged into the preheating tank 8 from above. The heated gas generated by the heated gas generator 10 is supplied from the air supply port 9 at the lower part of the preheating tank 8 to heat the raw material charged in the preheating tank 8. The heated gas is discharged as exhaust gas 12 from the exhaust port 11 at the top of the preheating tank 8. The temperature of the charged raw material 3b discharged from the lower part of the preheating tank 8 is measured with the thermometer 13, and the heated gas generator 10 is used to adjust the temperature of the heated gas so that the charged raw material charged into the blast furnace has an arbitrary temperature. Adjust the 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.

  Invention Examples 1 and 2 are examples corresponding to Comparative Example 1, in which iron ore, sintered ore, and coke as charging raw materials were heated to 200 ° C. and 400 ° C. and charged. Similarly, Examples 3 and 4 correspond to Comparative Example 2, Examples 5 and 6 correspond to Comparative Example 3, and Examples 7 and 8 correspond to Comparative Example 4. Table 1 shows the operation conditions for each operation.

  Table 1 shows the amount of the top gas of the blast furnace, the calorific value, the composition, and the temperature in each operating condition. Moreover, the relationship between the charging raw material temperature and furnace top gas temperature (TGT) in each operation is collectively shown in FIG.

According to FIG. 3, it is understood that the charging raw material temperature may be 110 ° C. or higher in order to ensure the furnace top gas temperature of 110 ° C. or higher. In addition, the average relationship between the charging raw material temperature and the furnace top gas temperature is
Furnace top gas temperature (° C.) = 0.68 × (charging raw material temperature (° C.)) + 55.8
It can be expressed by the relationship.

  As described above, it can be seen that, by preheating and charging the charged raw material, it is possible to prevent a decrease in the furnace top gas temperature during the operation of blowing the hydrogen-containing reducing material.

Schematic which shows one Embodiment of this invention. Schematic which shows one Embodiment of the preheating equipment of this invention. The graph which shows the relationship between charging raw material temperature and furnace top gas temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 tuyere 3 (3a, 3b) Charge raw material 4 Preheating equipment 5 Blowing 6 Reducing material with high hydrogen content 7 Pulverized coal 8 Preheating tank 9 Air supply port 10 Heating gas generator 11 Exhaust port 12 Exhaust gas 13 Thermometer

Claims (5)

In the blast furnace operation where a reducing material containing 10 mass% or more of H is blown from the tuyere,
From the furnace top of the blast furnace, and charged raw material preheated to above 110 ° C., blast furnace operation wherein the Rukoto raise the furnace top gas temperature of the blast furnace above 110 ° C.. The blast furnace operating method according to claim 1, wherein the reducing material includes pulverized coal, and a basic unit of the pulverized coal is over 150 kg / t . Blast furnace method according to 請 Motomeko 2 you, characterized in that blown into 7 kg / t-pig or blast furnace as a hydrogen content derived from the reducing material containing the H 10 mass% or more. The blast furnace operating method according to any one of claims 1 to 3, wherein the raw material is preheated by a heated gas introduced into the preheating equipment in a preheating equipment provided in an upper part of the blast furnace. The blast furnace operating method according to claim 4, wherein the temperature of the preheated raw material discharged from the preheating facility and charged into the blast furnace is adjusted by adjusting the temperature of the heated gas.

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