KR101337162B1 - Method for operating blast furnace - Google Patents

Abstract

When ferrocoke is used in a blast furnace, it is possible to provide stable operation by optimizing the amount of ferrocoke used. Coke, including ore, ferrocoke and scilo coke, is charged into the blast furnace. The use ratio of the said ferrocoke is 2 mass% or more and 50 mass% or less of the coke. It is preferable that ferrocoke use ratio is 25 mass% or more. The ferrocoke preferably has a particle size of 15 mm or more and 40 mm or less. The ferrocoke preferably has iron content of 10 mass% or more and 40 mass% or less.

Description

Blast Furnace Operation Method {METHOD FOR OPERATING BLAST FURNACE}

The present invention relates to a blast furnace operating method when using a ferrocoke produced by molding and carbonizing a mixture of coal and iron ore.

In order to reduce the ratio of the reducing material of the blast furnace, a method of lowering the temperature of the heat storage zone formed in the blast furnace is effective (see Non-Patent Document 1, for example).

As a means of reducing the thermal storage zone temperature, the lowering of the start temperature of the gasification reaction of coke (endothermic reaction) shown by following formula (1) is mentioned.

CO ₂ + C → 2CO... (One)

When the gasification reaction start temperature of coke falls, the temperature area | region which this reaction generate | occur | produces expands, and the amount of gasification reactions increases. Ferrocoke produced by distilling the molding formed by mixing coal and iron ore can increase the reactivity of the coke by the catalytic effect of the reduced iron ore, and can reduce the reducing material ratio by lowering the heat preservation temperature. (For example, refer patent document 1).

The method for producing ferrocoke includes, for example, adding a mass of a binder in addition to coal and iron ore, homogenizing the same, press molding by a twin roll molding machine having a recess, and producing briquettes. The process which has the process of distilling this in a water furnace is assumed. In this case, the shape of the ferrocoke becomes a shape having an external shape as shown in FIG. 2, which is suitable for the above roll forming.

In addition, using a mixed raw material of coal and powder ore, a method of producing in the same manner as the present conditions of the actual coke coke is also assumed. Since the conventional coke coke is composed of silica brick, charging iron ore In one case, iron ore reacts with silica, which is a main component of the silica brick, to produce a low melting point pialite, which may cause damage to the silica brick. In this case, the particle shape of ferrocoke becomes indefinite, and the range of a particle size is set by sifting.

On the other hand, the gasification reaction of coke in a blast furnace has reaction of the following (2)-(5) formula other than said (1) formula.

(2) Formula: Reaction with oxygen in the mouth,

(3) formula: reaction with FeO,

(4) Formula: Reaction with water vapor in the shaft portion,

(5) Formula: Reaction with a nonferrous oxide, M in Formula (5) is Si, Mn, Ti, P, etc.

In blast furnace operation, the sum total of gasification reactions other than following (2) Formula is customarily called solution loss carbon amount (it describes as a solose amount hereafter), and is computed by following formula (6). The amount of carbon gasified at the end of the right mouth is calculated by the following equation (2) from the amount of oxygen in the blowing air, and the amount of carbon in the furnace top gas is calculated from the furnace top gas amount and the concentrations of CO and CO _{2 in} the furnace top gas. In the case of using ferrocoke, the reaction of formula (1) is increased, but the reaction of formula (3) is greatly reduced by promoting the following formula (7), which is a gas reduction of iron oxide. I think. In addition, the contribution of the following formula (4) is small in the amount of soluene, and in general, the amount of soluene is understood as the amount of gasification of coke in the furnace top to the fusion zone.

C + 1 / 2O ₂ = CO... (2)

FeO + C = Fe + CO... (3)

H ₂ O + C = H ₂ + CO... (4)

MO _n + C = M + CO _n ... (5)

Solulose amount = amount of carbon in the furnace normal gas-amount of carbonized gas at the end of the right mouth. (6)

FeO + CO = Fe + CO ₂ ... (7)

When increasing the amount of ferrocoke used to reduce the temperature of the heat preservation zone, the amount of solurose, that is, the amount of gasification of coke in the furnace top to the fusion zone decreases, and when a certain condition or more is reached, the amount of carbon in the ferrocoke It is anticipated to exceed Solulus. In the melting zone or less, the so-called dropping zone, it is composed of coke which has been gasified and not extinguished by the solution loss reaction in the top of the furnace to the fusion zone. Ferrocoke is more reactive than coke coke, and even if it is assumed to be preferentially gasified than coke coke, when the amount of carbon in the charged ferrocoke exceeds the gasification amount, the ferrocoke that has not been gasified is left in the dropping zone. Incidentally, the coke coke refers to coke, which is usually produced by coking coal in a coke oven or the like, charged into a blast furnace and used as a coke raw material. If the particle size of the ferrocoke is smaller than that of the coke or the strength is low, if the presence of the ferrocoke in the dropping zone becomes excessive, there is a risk that the air permeability and liquid permeability in the lower part of the furnace may deteriorate. I think there is.

Japanese Laid-Open Patent Publication 2006-28594

 Japan Iron and Steel Institute `` Steel and Steel '' 87, 2001, p.357  Japan Iron and Steel Association "iron and steel" 79, 1993, N618  Kawasaki Seasonal Report, 6 (1974), p.16

As mentioned above, it is thought that the usage-amount of ferrocoke has an upper limit.

Accordingly, an object of the present invention is to provide a stable operation by solving such a problem of the prior art and optimizing the amount of ferrocoke used when ferrocoke is used in a blast furnace.

The characteristics of the present invention for solving such a problem are as follows.

(1) The blast furnace operating method which charges ore and the coke containing ferrocoke and a silo coke to a blast furnace WHEREIN: The use ratio of the said ferrocoke is 2 mass% or more and 50 mass% or less of the said coke.

(2) The blast furnace operating method according to (1), wherein the ferrocoke has a particle size of 15 mm or more and 40 mm or less.

(3) The blast furnace operating method according to (2), wherein the ferrocoke has a particle size of 20 mm or more and 35 mm or less.

(4) The blast furnace operating method according to (1), wherein the use ratio of the ferrocoke is 25% by mass or more and 50% by mass or less of the coke raw material.

(5) The blast furnace operating method according to (4), wherein the use ratio of the ferrocoke is 30% by mass or more and 50% by mass or less of the coke raw material.

(6) The blast furnace operating method according to (1), wherein the ferrocoke has 10 mass% or more and 40 mass% or less of iron powder.

Moreover, the said subject can be solved also by the following invention.

(7) The ferrocoke amount is set to 2 mass% or more and 50 mass% or less of the coke raw material usage when operating the charging of the coke raw material from the top of the furnace by using coke coke as the coke raw material. Blast furnace operation method using ferrocoke to make.

(8) The blast furnace operation method using ferrocoke according to (7), wherein the amount of ferrocoke used is 35 mass% or less of the amount of coke raw material used.

(9) The blast furnace operating method using ferrocoke according to (7) or (8), wherein the particle size of the ferrocoke is smaller than the particle size of the silo coke which is charged alone without mixing with the ore into the blast furnace.

In the present invention, the ore is a generic term for one kind or a mixture of two or more kinds of iron-containing raw materials charged into blast furnaces such as sintered ores, bulk iron ores, and pellets made from iron ores. As an ore layer laminated | stacked in a blast furnace, it may contain subsidiary materials, such as limestone for slag component adjustment other than an ore.

According to the present invention, when using ferrocoke as a part of coke raw material in blast furnace operation, stable operation can be achieved by carrying out the operation which set the upper limit of the usage amount.

BRIEF DESCRIPTION OF THE DRAWINGS It is a graph which shows the relationship between a ferrocoke use ratio and a ventilation resistance (relative pressure loss).
It is a schematic diagram which shows the shape of a ferrocoke.
3 is a graph showing the relationship between the ferrocoke use ratio and the reducing material ratio reduction amount.
4 is a graph showing the relationship between the percentage of ferrocoke used and the amount of carbon in the ferrocoke and the amount of solurose carbon.
5 is a graph showing the relationship between the ferrocoke use ratio and the dropping-rate residual ferrocoke ratio.
6 is a schematic diagram of a ventilation resistance measuring apparatus.
7 is a graph showing the relationship between the ferrocoke use ratio and the ventilation resistance (relative pressure loss) of the mixed packed layer of silocoke and ferrocoke.
8 is a graph showing the particle size distribution of ore.
9 is a graph showing the relationship between the ferrocoke particle diameter and the airflow resistance of the ore + ferrocoke mixed layer.
It is a graph which shows reaction test conditions at the time of measuring coke reaction amount.
11 is a graph showing the relationship between the ferrocoke use ratio and the relative carbon reaction amount.
Fig. 12 is a schematic diagram showing the distribution of charges in the blast furnace when ferrocoke is used.

Ferrocoke is produced by heating a molded product produced by molding a raw material mainly composed of coal and iron ore, and drying the coal in the molded product. In addition, the main component of coal and iron ore means that the raw material of ferrocoke is mainly coal and iron ore, and the ferrocoke is manufactured using a raw material containing 70% by mass or more of coal and iron ore. Raw materials containing more than 80 mass% of coal and iron ore are used.

The higher the iron content in the ferrocoke, the higher the reactivity of the coke. The larger the iron content, the greater the effect is expressed from 10 mass% of the iron content, and the effect is saturated at 40 mass% or more, so 10 to 40 mass% is the preferred iron content.

MEANS TO SOLVE THE PROBLEM The present inventors predict the change of blast furnace operating conditions at the time of using a ferrocoke using the heat-material balance model based on the Rist operation chart (for example, refer nonpatent literature 2), and the amount of solose and blast furnace The amount of ferrocoke remaining in the dropping zone was estimated from the amount of ferrocoke charged in the flask.

Since the ferrocoke is more reactive than the coke coke, if the gas is preferentially gasified than the coke coke, the amount of ferrocoke remaining in the dropping zone is represented by the following formula (8).

The amount of ferrocoke remaining in the dropping zone = (The amount of carbon in the ferrocoke charged into the blast furnace-the amount of solurose carbon). (8)

Here, when the carbon among the ferrocokes charged into the blast furnace is less than or equal to the solenoid carbon, the amount of ferrocoke remaining in the dropping zone is treated as zero. As preconditions for the calculation of these mass balances, iron, 10, 30, and 40 mass% (the remaining coke powder) in ferrocoke and carbon in the coke were 87.5 mass%.

In addition, the dripping zone residual ferrocoke ratio in a dripping zone is represented by following formula (9).

The amount of ferrocoke remaining in the dropping zone / (The amount of ferrocoke remaining in the dropping zone + the amount of coke coke). (9)

The result of examination performed using these formulas is shown in Tables 1-3, and FIGS.

Table 1 shows 10 mass% of iron in ferrocoke, Table 2 shows 30 mass% of iron in ferrocoke, and Table 3 shows examples of 40 mass% of iron in ferrocoke.

In Table 1, when the base does not use ferrocoke, case 1 uses ferrocoke, but when the amount of carbon in the ferrocoke to be charged into the blast furnace is less than the amount of solurose carbon, cases 2 and 3 are charged to the blast furnace. This is the case where the amount of carbon in the ferrocoke is larger than the amount of the solurose carbon. The higher the iron content in the ferrocoke, the higher the reactivity of the ferrocoke and the greater the effect of reducing the temperature of the heat preservation zone. Therefore, also in the same ferrocoke use ratio, the heat preservation zone temperature and the amount of carbon derived from the ferrocoke differ depending on the iron content, and these differences affect the reducing material ratio and the solenoid carbon. In Tables 1-3, these results are added.

3 is a graph showing the relationship between the ferrocoke use ratio and the reducing material ratio reduction amount. It can be seen from FIG. 3 that the higher the iron content in the ferrocoke and the higher the ferrocoke use ratio, the lower the reducing material ratio. For example, when using 25 mass% of ferrocoke with 30% by weight of iron, the reduction material ratio is expected to be reduced by 30 kg / tp. Also, when using 30 mass% of ferrocoke, ferrocoke having 10% by mass of iron In addition, the effect of reducing the reducing material ratio of 20 kg / tp or more is expected. In addition, the ferrocoke use ratio (charged ferrocoke ratio) is a mass ratio of the ferrocoke to the total amount of the ferrocoke and the silocoke to be charged in the blast furnace, as shown in the following formula (10). The mass of the whole ferrocoke shall be used.

Ferrocoke (including iron) / {ferrocoke (including iron) + shilo coke}. (10)

4 and 5, the amount of carbon in the ferrocoke becomes equal to the amount of solulose in the ferrocoke near 30 mass% of the charged ferrocoke use ratio, and when the ferrocoke use ratio charged in the blast furnace is increased, carbon in the ferrocoke is increased. It is understood that ferrocoke remains in the dropping zone in excess of the amount. In addition, the ferrocoke use ratio of the position where a horizontal axis and a line of a graph cross | intersect in FIG. 5 is corresponded to the ferrocoke use ratio whose vertical axis becomes zero in FIG.

Next, the ventilation resistance of the mixed filling layer of coke and ferrocoke was measured using the apparatus shown in FIG. The ventilation resistance measuring apparatus 1 was 400 mm in diameter and 2000 mm in total height, and charged the air permeation measurement sample 2 at 1000 mm height, and measured it. Indeed, the coke had a particle size of 40 to 60 mm, and the ferrocoke used a 18 × 16 × 12 mm (particle size 15 mm) and a 30 × 25 × 18 mm (particle size 24 mm) particle. In the present invention, the particle size of the indicated as A × B × C dimensions are in the Fig of the Faroe and coke, ferro coke is used in the calculation ^{(A × B × C) 1} /3. The ventilation resistance measurement result when the mixing ratio of ferrocoke is changed is shown in FIG. When the ferrocoke mixing ratio exceeds 30 mass%, the air permeation resistance is significantly increased. This is because the particle size of the ferrocoke is smaller than that of the coke coke, and there is no unevenness in shape compared to the coke coke, and thus the filling layer It is assumed that this is due to the effect of lowering the porosity of.

Using the result shown in FIG. 7 as an experimental result which simulated the dropping band, FIG. 1 is obtained by making together the relationship of the ferrocoke usage-amount shown in Tables 1-3 and the residual ferrocoke ratio in a dropping band in FIG.

According to Fig. 1, the air permeation resistance (relative pressure loss) starts to rise from about 10 mass% of the dropping-rate residual ferrocoke ratio, and the iron content of 10 mass% and the use of ferrocoke having a particle diameter of 15 mm correspond to 50 mass%. It can be seen that the air flow resistance rapidly increases from 30 mass% of the dropwise residual ferrocoke ratio. Therefore, even if the ferrocoke use ratio is 50 mass% under the condition that the particle size is larger than the conditions in which the content of the charged ferrocoke having an iron content of 10 mass% and a particle diameter of 15 mm is 50 mass%, or the iron content in the ferrocoke is large. Breathing resistance does not rise. As mentioned above, when using 10-40 mass% of iron content and 15 mm or more of ferrocoke, it found out that the upper limit of the ferrocoke use ratio which avoids the sudden rise of aeration resistance is 50 mass%.

As mentioned above, when ferrocoke use ratio exceeds 50 mass% with respect to the coke usage amount which is a total amount of ferrocoke and a silo coke, the conclusion that the deterioration of the air permeation resistance in a dripping zone will become remarkable is concluded. Therefore, it is necessary to carry out blast furnace operation by adjusting the loading amount so that the use ratio of ferrocoke is 50 mass% or less of the total amount of coke charged into the blast furnace including silo coke, and reducing the reducing material ratio of 20 kg / t or more. In order to obtain the use ratio of 25 mass% or more, preferably 30 mass% or more is preferable.

Ferrocoke is preferably mixed with ore (iron-containing raw material composed of sintered ore, pellets, lump ore, etc.) (for example, see Patent Document 1). At this time, breathability of the mixed layer of ore and ferrocoke Since it is important to operate, the effect of ferrocoke size on the air permeation resistance of the mixed layer of ore and ferrocoke (hereinafter referred to as "ore + ferrocoke mixed layer") was investigated. The particle size distribution of the used ore particle is shown in FIG. The ferrocoke ratio in the ore layer is set to 21 vol% (equivalent to 35 mass% of ferrocoke use ratio), and the effect of the ferrocoke particle diameter mixed in the ore layer on the air permeation resistance is calculated using the following formula (11). Viii).

Ventilation resistance index = (1 / Φd _p ) ^1.3 (1-ε) ^1.3 / ε ³ . (11)

Here, Φ is a shape factor (0.7), d _p is the average particle diameter of the ore + ferrocoke mixed layer, and ε is the porosity of the ore + ferrocoke mixed layer. The average particle diameter of the ore + ferrocoke mixed layer was calculated by correcting the particle size distribution shown in FIG. 8 according to the assumed ferrocoke size, and the porosity was estimated from the particle size distribution after the correction (see Non-Patent Document 3). The results are shown in Fig. It can be seen that the change in the ventilation resistance is small when the particle size of the ferrocoke is between 15 and 40 mm. When the particle size of the ferrocoke is less than 15 mm, the airflow resistance increases by decreasing the average particle diameter of the ore + ferrocoke mixed layer. On the other hand, even if the size of the ferrocoke is large, the ventilation resistance increases, which is due to the decrease in the porosity due to the expansion of the particle size distribution. As mentioned above, it turned out that the ferrocoke particle diameter for avoiding a raise of ventilation resistance is 15-40 mm. If it is a ferrocoke of the shape as shown in FIG. 2 manufactured using a molding machine, it is preferable that the particle diameter (= (A * ^BxC ) ^1/3 ) of the ferrocoke defined above is 15-40 mm. If it is an amorphous ferrocoke manufactured using the coke oven of the present situation, when charging to blast furnace, it is preferable to use what sifted into the range of 15-40 mm of particle diameters.

Next, the gasification reaction test which simulated the conditions in a blast furnace was examined about the usage of ferrocoke which is effective for reaction promotion. Ferrocoke and shilo coke were charged to a crucible having an inner diameter of 76 mm at a predetermined ratio, and tested under gas-temperature conditions as shown in FIG. 10, and the reaction amount of carbon in the coke after the test was measured. Based on the conditions of 100 mass% of coke coke (0 mass% of perco coke), the reaction amount (relative C reaction amount) of the carbon at the time of changing the use rate of ferro coke is shown in FIG. The relative C reaction amount is the sum of the reaction amounts of ferrocoke and silocoke. At 1 mass% of ferrocoke use, no clear difference was found between the base, but at 2 mass% of ferrocoke use, the reaction rate increased with respect to the base, and if the ferrocoke use rate increased, the increase in ferrocoke use rate increased. The reaction amount also increased. If the mixing amount of the ferrocoke is too small, the nonuniformity as the mixed packing layer becomes remarkable, and it is presumed that the reaction promoting effect is hardly exhibited.

Therefore, it is necessary to make ferrocoke use ratio into 2 mass% or more of the coke use amount which is the total coke amount including a coke coke.

Moreover, it is preferable to apply this invention about the particle size of a ferro coke to the case where the ferro coke of the particle size smaller than the particle size of the coke coke inserted alone is mixed with an ore into a blast furnace. In the case of using ferrocoke having a particle size smaller than that of the coke, the air permeability and liquid permeability of the lower part of the furnace may deteriorate, and the effect of the present invention becomes remarkable. When the particle size of the ferrocoke is larger than the coke, the air permeability and liquid permeability of the lower part of the furnace are less likely to deteriorate even when the presence of the ferrocoke becomes excessive. In this case, the ore refers to an iron source raw material charged into a blast furnace such as lump iron ore or sintered ore.

Example 1

The blast furnace use test of ferrocoke was performed. Ferrocokes were prepared by molding a mixture of coal and iron ore into a briquette machine, charging them into a male shaft furnace, and drying them to produce a size of 30 × 25 × 18 mm (particle size 24 mm). Reduction rate of the iron ore of the ferro coke is 80-85%, the drum strength DI _150/15 was 82. The iron content in the ferrocoke was 30 mass%, and the carbon content in the remaining 70 mass% of coke powder was 87.5 mass%. Charging of the raw material into the blast furnace was performed by the method of alternately laminating | stacking the mixed layer of the ferrocoke 10 and the ore 20, and the layer of the alone coke 30 as shown in FIG. In FIG. 8, the left end is a furnace center and 40 is a furnace wall. Indeed, the average particle diameter of the coke 30 was 45 mm. In Fig. 12, the left end is the furnace center, and 40 is the furnace wall. In fact, 5 mass% of coke was used as a small lump coke having a particle diameter of 10 to 25 mm and mixed with ore. Indeed, the average particle diameter of the layer 30 composed of only coke was 45 mm.

When charging a raw material as mentioned above, the operation test was implemented, changing the ratio of the ferrocoke mixed. Table 4 shows changes in the blast furnace reducing material ratio and the ventilation resistance index (relatively the lower ventilation resistance index) when the ferrocoke use ratio is changed. In Table 4, the base is a case which does not use ferrocoke, and cases 1 to 3 are cases in which the ferrocoke use ratio is sequentially increased in the range of 50 mass% or less of the ferrocoke use ratio.

As the use rate of ferrocoke increased, the air resistance increased slightly. Since the ferrocoke ratio was 50 mass% or less, stable operation was continued. As a result of temporarily increasing the use rate of ferrocoke to 55 mass%, it was difficult to continue the operation due to the increase in the ventilation resistance at the bottom of the furnace.

1: ventilation resistance measuring device
2: sample to be measured for ventilation
10: ferrocoke
20: ore
30: coke coke
40: furnace wall

Claims (6)

In the blast furnace operating method which charges ore and the coke containing ferrocoke and a sloppy coke to a blast furnace, the blast furnace operating method whose use rate of the said ferrocoke is 2 mass% or more and 50 mass% or less of the said coke. . The method of claim 1,
The blast furnace operation method in which the said ferrocoke has a particle diameter of 15 mm or more and 40 mm or less. 3. The method of claim 2,
A blast furnace operation method in which the ferrocoke has a particle size of 20 mm or more and 35 mm or less. The method of claim 1,
The blast furnace operating method of the said ferrocoke use ratio is 25 mass% or more and 50 mass% or less of the said coke. The method of claim 3, wherein
The blast furnace operating method of the said ferrocoke use ratio is 30 mass% or more and 50 mass% or less of the said coke. The method of claim 1,
The blast furnace operation method in which the said ferrocoke has 10 mass% or more and 40 mass% or less iron powder.

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