JP2014005482A - Operating method of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable manufacturing pig iron stably by preventing certainly a decrease of air permeability in a blast furnace even at the time of manufacturing of the pig iron with blowing dust coal including low volatile component coal.SOLUTION: Dust coal including low volatile component coal is blown to satisfy PCR×V/100≤273P (however, P>0), PCR×V/100≥90 where PCR is a blowing amount of the dust coal per 1 t of pig iron (kg/t of molten iron), V is a blending ratio of the low volatile component coal in total blown dust coal (%) and P is a blending amount of a self-fluxing pellet in all iron source (T/t of molten iron), at the time of manufacturing pig iron with blowing the dust coal including the low volatile component coal with a hot wind from a tuyere of a blast furnace.

Description

  The present invention relates to a method of operating a blast furnace in which pig iron is produced while blowing pulverized coal containing low-volatile coal together with hot air from the tuyere of the blast furnace.

Conventionally, in a blast furnace, iron ore, coke, limestone and other raw materials are charged in layers from the top, and hot air is blown from the bottom to produce a series of reactions such as reduction and melting of iron ore to produce pig iron doing. In the operation of the blast furnace, pulverized coal is blown together with hot air from the tuyere of the blast furnace as a reducing material, and this technique is disclosed in Patent Documents 1 to 4.
In Patent Document 1, in the operation of injecting pulverized coal into a blast furnace where the amount of pulverized coal injection exceeds 120 kg / t, when using low volatile coal having a volatile content of 20% by mass or less, 10 to 38% by mass of the total pulverized coal. The low volatile coal is mixed with 62 to 90% by mass of high volatile coal having a volatile content of 30% by mass or more and blown from the tuyere.

In Patent Document 2, in a blast furnace operation method in which pulverized coal is blown from a blast furnace tuyere at a blowing amount of 160 kg / pt or more, pulverized coal having a volatile content of any of the blended coal types of 25% by mass or less is blown. A sintered ore having an Al ₂ O ₃ content of 1.75% by mass or more and a value obtained by subtracting the MgO content from the sum of the CaO content and the SiO ₂ content of 11% by mass or less is loaded from the top of the furnace. It has entered.

Patent Document 3 discloses that in a blast furnace operation method in which pulverized coal is blown together with hot air from a blast furnace blower tuyere, the allowable volatile content of pulverized coal is −0.2 × (PC / R) +60, provided that PC / R ( Coal is blended and blown into the blast furnace so that the ratio is equal to or less than the value indicated by pulverized coal ratio) = pulverized coal amount (kg / hr) / output.
In Patent Document 4, in a blast furnace operation method in which pulverized coal is blown into the interior of a blast furnace from a tuyere, high volatile content pulverized coal is blown from before the low volatile content pulverized coal blowing position.

Japanese Patent No. 4224218 JP 4572734 A JP 2000-282112 A Japanese Patent Laid-Open No. 06-128614

Patent Documents 1 to 4 described above are techniques for operating a blast furnace by blowing pulverized coal, and a technique for blowing low-volatile coal among pulverized coal is also disclosed, but even if these techniques are used, In some cases, the air permeability of the blast furnace decreased.
Therefore, in view of the above problems, the present invention reliably prevents the deterioration of air permeability in the blast furnace and stably manufactures pig iron even if the pig iron is manufactured while blowing pulverized coal containing low-volatile coal. It aims at providing the operation method of the blast furnace which can do.

In order to achieve the above-described object, the present invention takes the following technical means.
The method of operating a blast furnace according to the present invention is such that, when producing pig iron while blowing pulverized coal containing low-volatile coal together with hot air from the tuyeres of the blast furnace, the low blast furnace satisfies the formulas (1) to (2). It is characterized by blowing pulverized coal containing volatile coal.
PCR × V / 100 ≦ 273P (1)
PCR × V / 100 ≧ 90 (2)
However,
PCR: Amount of pulverized coal blown per ton of pig iron (kg / molten iron ton)
V: Mixing ratio (%) of low volatile coal in all pulverized coal injected
P: Compounding amount of self-soluble pellet in total iron source (ton / molten iron ton)
P = Ore ratio (ton / molten iron ton) × self-fluxing pellet mixing ratio (%)
P> 0
Note that “ton / molten iron t” is the number of tons per ton of molten iron. Hereinafter, “ton / molten iron t” is expressed as “T / molten iron t”. In accordance with this notation, “kg / molten metal ton” is represented as “kg / molten metal t”.

  According to the present invention, even if pig iron is produced while blowing pulverized coal containing low-volatile coal, pig iron can be stably produced while reliably preventing a decrease in air permeability in the blast furnace.

It shows a conceptual diagram of the entire blast furnace. It is a related figure of the amount of low volatile coal injection, and the lower ventilation resistance index of a blast furnace. The low volatile coal injection rate used for the operation of the blast furnace is 90 kg / t or more, the ratio of low volatile coal injection rate to the self-soluble pellet (volatile coal injection rate / self-soluble pellet), and lower ventilation resistance It is a relationship figure with an index.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a blast furnace operating method according to the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic view of the entire blast furnace.
As shown in FIG. 1, a blast furnace 1 has a furnace body 2 whose outside is covered with a steel plate-made iron skin and whose inside is lined with a refractory. The furnace body 2 of the blast furnace 1 is spread downward from the upper part to the lower part, the shaft part 3 from the top, the straight barrel-like berry part 4, further below it, the Bosch part 5 spreading upward, and the bottom furnace It has a floor 6. The side wall of the hearth part 6 is provided with an opening (a tuyere 7) through which hot air or pulverized coal is blown into the furnace. In addition, an outlet 8 for taking out pig iron (hot metal) is provided on the side wall of the hearth.

In such a blast furnace 1, raw materials such as sintered ore, pelletized ore, coke, limestone and the like are introduced from above the furnace body 2, and hot air is blown from the tuyere 7 and pulverized coal is blown. Produces pig iron.
In recent years, the global production of crude steel has increased, so the demand for pulverized coal used as part of blast furnace reducing material has increased, and the tendency for flammable highly volatile coal to decrease is increasing. It is in. Meanwhile, the use of low-volatile coal with low combustibility is also being considered. For example, in Japanese Patent No. 4224218, combustion efficiency is improved by defining the proportion of low-volatile coal in the total pulverized coal, or in Japanese Patent No. 4572734, the proportion of CaO or the like to be added is adjusted. Thus, unburned low-volatile coal is eliminated, or JP 2000-282112 discloses coal blending by regulating the allowable volatile content. However, even if these technologies are used, it is difficult to ensure air permeability while promoting consumption of unburned pulverized coal, and in order to use low-volatile coal, it is necessary to develop a new technology.

Therefore, the inventors first investigated the air permeability of the blast furnace using low volatile coal. The air permeability of the blast furnace is evaluated by the value of the airflow resistance index as shown in paragraph 0011 of JP 2004-263258 A. When the airflow resistance index is small, the reducing gas generated in the lower part of the furnace Is stable and the operation is stable (reduction of the ore and the temperature rise of the charge are stable), the smaller the ventilation resistance index, the better. The ventilation resistance index is such that the absolute pressure of the blast furnace is Pb (g / cm ² ), the absolute pressure at the top of the furnace is Pb (g / cm ² ), and the amount of gas generated in the lower part of the furnace is Vb (Nm ³ / min). And [(Pb ² −Pt ² ) / Vb ^1.7 ].

Incidentally, Pb (g / cm ²⁾ and, as shown in paragraph 0014 of JP-A-2004-263258, since the amount of gas in the Bosch portion of blast furnace (Vb), _{N 2} of the blown in air Amount (N _air × 0.79) and the amount of CO generated by the combustion reaction (O ₂ + 2C → 2CO) between O ₂ in the blown air and O ₂ enriched in the blown air and pulverized coal (2 × N _air × 0.21 + 2 × NO ₂ ). Specifically, it is represented by [Vb = N _air × 0.79 + 2 × N _air × 0.21 + 2 × NO ₂ ]. N _air is the blown air amount (Nm ³ / min), and NO ₂ is the oxygen enrichment amount (Nm ³ / min) into the blown air.

  Here, since it is considered that unburned low volatile coal stays in the lower part of the blast furnace and impairs the air permeability of the blast furnace, in the present invention, the air permeability of the blast furnace is not the top of the blast furnace but the blast furnace. Evaluation was made using the absolute pressure of the pressure gauge provided in the middle stage (two stages of shafts). In addition, since the air permeability in the lower stage of the blast furnace and the two-stage shaft was evaluated, the air flow resistance index is expressed as a “lower air flow resistance index”. If the lower ventilation resistance index is greater than 2.0, wind reduction due to ventilation failure occurs, and therefore the lower ventilation resistance index is preferably 2.0 or less. In this embodiment, a pressure gauge is provided on the second stage of the shaft, which is the middle stage of the blast furnace, and the air permeability is evaluated. However, the position of the pressure gauge and the numerical value of the lower ventilation resistance index are not limited. For example, the position of the pressure gauge is preferably set to a position where the lower ventilation resistance of the blast furnace can be measured and includes the fusion zone 10 of the blast furnace. Further, since the lower ventilation resistance index indicates the degree of air permeability, its own numerical value is not limited. For example, in the operation of the blast furnace, an upper limit value of the lower ventilation resistance index may be set to be equal to or lower than the upper limit value.

  FIG. 2 summarizes the relationship between the amount of low volatile coal injected and the lower ventilation resistance index of the blast furnace. As shown in FIG. 2, the lower ventilation resistance index tends to increase as the amount of low-volatile coal injection increases. When the amount of low volatile coal injected is 90 kg / molten iron or more, the lower ventilation resistance index tends to exceed 2.0. However, in actual operations, as described above, many low-volatile coals are used instead of high-volatile coals in response to the decrease in high-volatile coals as crude steel production increases worldwide. For example, as described above, even if the amount of low volatile coal injected is 90 kg / molt or more, the lower ventilation resistance index is not lowered, that is, the lower ventilation resistance index is 2.0 or less. It is necessary to make it.

  Therefore, the inventors have verified from various angles whether there is a method for reducing the lower ventilation resistance index to 2.0 or less even when the amount of low volatile coal injected is 90 kg / molten iron or more. As a result, as will be described later, by considering the balance between the self-fluxing pellets, the amount of pulverized coal blown, and the blending ratio of the low volatile coal in the total pulverized coal, the amount of low volatile coal blown is 90 kg. / It has been found that the lower airflow resistance index can be made 2.0 or less even when the hot metal is made t or more. As described in Japanese Patent No. 4224218, the low volatility coal has a volatile content of 20% or less, and the high volatility coal has a volatile content of 30% or more. It is. Volatiles can be determined by industrial analysis of coals (JIS M 8812).

  Pellets are often used as iron ore materials (iron source). Since this pellet has fewer pores than the sintered ore, the interfacial area is small, and the indirect reduction ratio tends to be low while the direct reduction ratio tends to be high. Therefore, when pellets are used, a large amount of carbon for direct reduction is required, and it becomes easy to consume more pulverized coal. The pellets are classified into non-self-soluble pellets (non-self-soluble pellets) and self-soluble pellets, both of which tend to consume pulverized coal, but each has the following tendency.

Many non-self-soluble pellets have poor high-temperature reducibility and low CaO / SiO ₂ (C / S). When this is used, many secondary additives for C / S adjustment of blast furnace discharge slag are used. Raw materials are required. In addition, since non-self-soluble pellets are difficult to melt, the width of the cohesive zone 10 is increased, which may reduce the air permeability of the blast furnace.
On the other hand, self-fluxing pellets have higher meltability and higher direct reduction than non-self-fluxing pellets, so pulverized coal, especially low volatility low-volatile coal, remains unburned pulverized coal. Even if it is easy to consume at the lower part of the blast furnace, expansion of the width of the cohesive zone 10 can be suppressed, and the air permeability of the blast furnace can be improved. For this reason, in the present invention, when operating using low volatile coal, the amount (supply amount) of the self-soluble pellet is used among the pellets, and the low volatile coal and the self-soluble pellet are used. By using it at the same time, it was decided to ensure the air permeability of the blast furnace even with many low-volatile coals.

Specifically, the amount of pulverized coal injected per ton of pig iron is PCR (kg / molten iron t), the blending ratio of low-volatile coal in the total pulverized coal injected is V (%), and the total iron source Assuming that the blending amount of the self-fluxing pellets is P (T / molten iron t), the low-volatile coal and the self-fluxing pellets are used so as to satisfy the formulas (1) and (2). Yes.
PCR × V / 100 ≦ 273P (1)
PCR × V / 100 ≧ 90 (2)
However,
P> 0
The blending ratio V (%) of the low volatile coal in the total pulverized coal is the low volatile coal blending ratio contained in the total pulverized coal when the total amount of the pulverized coal is 100%. When the amount of blown coal is 60 t / h and 30 t / h of low-volatile coal is used, 30/60 × 100, which is 50%.

  The blending amount P (T / molten iron t) of self-fluxing pellets in the total iron source is expressed as ore ratio (T / molten iron t) × self-solubilizing pellet blending ratio (%). / The amount of self-fluxing pellets in molten iron t). Here, the ore ratio is a basic unit of ore used per ton of hot metal (T / hot metal t). The self-fluxing pellet blending ratio (%) is the blending ratio of self-fluxing pellets when the raw material that is the iron source is 100% of the raw material of the blast furnace. For example, when the raw material serving as the iron source is 16000 t / day and the self-soluble pellet is used at 1600 t / day, the self-soluble pellet blending ratio (%) is 10% at 1600/16000 × 100. In addition, when the ore ratio is 1.6 (T / molten iron t) and 10% self-fluxing pellets are used, the blending amount P (T / molten iron t) of the self-fluxing pellets in the total iron source is 0.16 (T / Molten iron t).

In addition, “PCR × V / 100” in the formulas (1) and (2) is the amount of low volatile coal blown, and the formula (1) is the amount of low volatile coal blown and self-soluble. The relationship with the pellet, equation (2), indicates that the amount of low-volatile coal blown is 90 kg / molten iron or more.
FIG. 3 shows the ratio of the amount of low volatile coal injected to the self-soluble pellets (the amount of volatile coal injected / self-soluble pellets), assuming that the amount of low-volatile coal used in the operation of the blast furnace is 90 kg / t or more. It summarizes the relationship with the lower ventilation resistance index. As shown in FIG. 3, when satisfy | filling the ratio of the blowing amount of the volatile coal with respect to a self-fluxing pellet, ie, Formula (1), a lower ventilation resistance index can be 2.0 or less.

  Tables 1 and 2 show examples in which the blast furnace was operated by the method of operating the blast furnace of the present invention and comparative examples in which the blast furnace was operated by a method different from the present invention.

First, implementation conditions in Examples and Comparative Examples will be described.
A blast furnace having a furnace internal volume of 5400 m ³ was used. As the reducing material, pulverized coal and coke were used, the pulverized coal ratio was 144 to 203 kg / molten metal t, and the coke ratio was 300 to 361 kg / molten metal t.
As the iron source, self-fluxing pellets, sintered ore, lump ore, and non-self-fluxing pellets were used. The blending ratio of the self-fluxing pellets was 21.9 to 29.1%, the blending ratio of the sintered ore was 42 to 51%, the lump ore was 20 to 21%, and the non-self-fluxing pellets were 0 to 15.1%. The total ratio of self-fluxing pellets and non-self-fluxing pellets was 28 to 38%. In addition, conditions other than a self-fluxing pellet may be anything. Further, as shown in Japanese Patent No. 4418836, self-fluxing pellets are 0.8 ≦ CaO / SiO ₂ (C / S) ≦ 2.0 and 0.4 ≦ MgO / SiO ₂ (Mg / S ) ≦ 1.1, and the pressure loss rapid increase temperature (Ts) of the high temperature load reduction test is 1310 ° C. higher. The pressure loss rapid increase temperature (Ts) is determined by Ts = 110 × C / S + 100 × M / S + 25 ×% TFe-480, where% TFe is the total iron content (mass%). The auxiliary materials used were those according to ordinary methods in the art. The amount of tapping was 9577 to 10784 t / day. The production amount and auxiliary materials are not limited.

  The low volatile coal ratio (low VM ratio) was greater than 0 and 70% or less, and the high volatile coal ratio (high VM ratio) was 30 or more and less than 100%. The low volatile coal VM was 13 to 20%, and the high volatile coal VM was 32 to 44.3%. The blowing pressure was measured using the pressure of the hot air blown from the hot blast furnace into the blast furnace, and the lower pressure of the furnace was measured at a position including the cohesive zone 10 in the normal operation in the middle stage (two stages) of the shaft. Was used.

  In Examples 1 to 31, the value in the column of “low VM amount (left side value of Equation 1)” indicating the amount of low volatile coal blown is 90 kg / molten iron t or more and satisfies Equation (2). The blast furnace is operated with a lot of low volatile coal. After such operation, in Examples 1 to 31, the amount of low volatile coal injected (low VM amount) is greater than the value (index) of the “right side value of Formula 1” indicating the index of the self-soluble pellet. Since the formula (1) is small, the lower ventilation resistance index can be made 2.0 or less.

On the other hand, in Comparative Examples 1 to 25, the low VM amount is larger than the value (index) of the “right side value of Formula 1” and does not satisfy Formula (1), so the lower ventilation resistance index is larger than 2.0. became.
As described above, according to the present invention, since the formulas (1) and (2) are satisfied, even if pig iron is produced while blowing pulverized coal containing low-volatile coal, it is possible to reliably reduce the air permeability in the blast furnace. It is possible to prevent and stably manufacture pig iron.

  In the embodiment disclosed herein, matters not explicitly disclosed, for example, operating conditions, various parameters, dimensions, weights, volumes, etc. of the components do not deviate from the range normally practiced by those skilled in the art. However, matters that can be easily assumed by those skilled in the art are employed.

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 Furnace body 3 Shaft part 4 Berry part 5 Bosch part 6 Hearth part 7 tuyere 8 Outlet 10 Fusion zone

Claims (1)

When producing pig iron while blowing pulverized coal containing low volatile coal together with hot air from the tuyeres of the blast furnace, blowing pulverized coal containing the low volatile coal so as to satisfy Equation (1) and Equation (2). A blast furnace operating method characterized by
PCR × V / 100 ≦ 273P (1)
PCR × V / 100 ≧ 90 (2)
However,
PCR: Amount of pulverized coal blown per ton of pig iron (kg / molten iron ton)
V: Mixing ratio (%) of low volatile coal in all pulverized coal injected
P: Compounding amount of self-soluble pellet in total iron source (ton / molten iron ton)
P = Ore ratio (ton / molten iron ton) × self-fluxing pellet mixing ratio (%)
P> 0

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