JP5427084B2 - Blast furnace operation method - Google Patents

Description

  The present invention relates to a blast furnace operating method using fine-grained sintered ore.

  If the particle size of the sintered ore can be reduced while maintaining the air permeability of the blast furnace, not only the production yield of the sintering plant can be increased, but also the reduction efficiency of the sintered ore in the blast furnace can be increased and the reducing material ratio can be reduced. Therefore, the cost effect is great.

  As a method for maintaining the air permeability of the blast furnace while reducing the particle size of the sintered ore, a method of charging the sintered ore according to the particle size is known. In this method, for example, after sintering the sinter with a 5 mm screen in a sinter factory or blast furnace, coarse sinter over 5 mm on the sieve is charged into the blast furnace, After sieving with a 3 mm screen again for 5 mm or less, the 3-5 mm fine-grained ore is charged into a blast furnace separately from the coarse-grained ore. Usually, fine-grained sintered ore is charged in the peripheral part of the blast furnace and used for adjusting the air permeability and gas amount in the peripheral part (see Non-Patent Document 1).

  However, when the particle size of the fine-grained sinter becomes smaller or the amount increases due to fluctuations in the sinter production conditions, etc., the gas permeability decreases due to the deterioration of the air permeability around the blast furnace, Even fine particles may be delayed in reduction, resulting in insufficient furnace heat. In such a case, it was necessary to reduce the amount of fine-grained sintered ore used or to stop using it.

  Here, in Patent Document 1, the sintered ore is separated into coarse particles and fine particles, and the coarse particles are charged from the central portion of the blast furnace to the intermediate portion, and the fine particles are charged into the peripheral portion of the blast furnace. In the blast furnace operation method adopting the blast furnace operation method, a fine sinter ore and small coke are mixed in advance, and the blast furnace operation method in which the mixture is charged to the periphery of the blast furnace is proposed. It is disclosed that the particle size of the small coke to be mixed is desirably equal to or greater than the particle size of the fine sinter.

According to this method, even if the particle size of the fine-grained sintered ore becomes small, the small coke does not deteriorate the air permeability by acting as a spacer, the surrounding gas flow is maintained, and the fine-grained sintered ore is maintained. The small coke mixed with the ore has a smaller particle size and the small coke mixed with the fine sinter ore has a more active reaction with CO _{2 by} the smaller particle size and the fine sinter ore. The CO ₂ produced by the CO reduction is closer to the coke, and the reaction is fast, so that the reduction efficiency is improved, and the blast furnace can be stably operated with high productivity under high reduction efficiency.

  However, the example only describes an example using a relatively large particle size such as 11 to 15 mm as the average particle size of the fine-grained sintered ore and 20 to 25 mm as the average particle size of the small coke. It was unclear whether this method could be applied to the case of using a fine sinter having a very small particle size.

  Patent Document 2 discloses that in an operation method of a blast furnace in which ore and coke containing sintered ore are alternately charged from the top of the furnace, 1 to 30 wt% of the charged ore is charged with a fine particle size of 1 to 5 mm. When making the grain sintered ore, calculate the reduction rate of the ore layer in the blast furnace by the fine grain sintered ore, and calculate the charging amount of 3 to 25 mm small coke to compensate for the reduction rate reduction amount A method of operating a blast furnace in which the small coke is mixed and charged in the ore layer has been proposed.

  However, this method does not perform the charging method according to the particle size of the sintered ore, but the addition amount is adjusted to 3 to 25 mm depending on the amount of the fine sintered ore having a particle size of 1 to 5 mm in the ore. The small coke is mixed and charged into the entire ore layer.

  Therefore, in a blast furnace that employs a sinter ore particle-size charging method in which coarse sinter of more than 5 mm and fine sinter of 5 mm or less are charged separately, There has not yet been established a blast furnace operation method that can reliably eliminate operational problems caused by fluctuations in particle size and quantity.

Ryuichi Hori et al., Iron and Steel, vol. 78 (1992) No. 8, p. 56-62

JP-A-6-100908 JP-A-8-295907

  Therefore, in the blast furnace operation using the fine-grained sintered ore, the present invention maintains a high production yield in the sintering plant, even if the particle size and amount of the fine-grained sintered ore fluctuate, An object of the present invention is to provide a method for operating a blast furnace capable of preventing a delay in reduction of the ore and maintaining more stable operation by maintaining the air permeability of the blast furnace.

  According to the first aspect of the present invention, the sintered ore is separated into fine-grained sintered ore and coarse-grained sintered ore, and small-grain coke is mixed in advance with the fine-grained sintered ore. In the blast furnace operation method adopting a particle-size charging method for separately charging the grain sintered ore, the average grain size of the fine grain sintered ore is 3 to 5 mm, and the average of the small grain coke The blast furnace operating method is characterized in that the particle size is 1.2 to 2.0 times the average particle size of the fine-grained sintered ore.

In the present invention, the average particle diameter is a mass average particle diameter calculated from the representative diameter between each sieve mesh and the mass between the sieve meshes after classification by a sieving method. For example, when the sieve meshes are classified using a sieve of D ₁ , D ₂ ,..., D _n , D _{n + 1} (D ₁ <D ₂ <... <D _n <D _{n + 1} ), the sieve meshes D _k and D when the mass between the _{k + 1} is _{W k,} mass average particle diameter _{d m} is defined by _{d m = Σ k = 1,} n (W k × d k) / Σ k = 1, n (W k) . Here, d _k is a representative diameter between the meshes D _k and D _{k + 1} , and d _k = (D _k + D _{k + 1} ) / 2.

  The invention described in claim 2 is the blast furnace operating method according to claim 1, wherein the operation is performed at a pulverized coal ratio of 120 kg / t-pig or more.

  The invention according to claim 3 is operated by the coke center charging method in which a part of the lump coke is charged in the center part of the blast furnace and the remainder of the lump coke and ore are charged in layers in the periphery of the blast furnace. It is a blast furnace operating method of Claim 1 or 2 which performs.

  According to the present invention, the sintered ore is separated into fine-grained sintered ore and coarse-grained sintered ore, and small-grain coke is mixed in advance with the fine-grained sintered ore. In the blast furnace operation method adopting a charging method classified by particle size separately charging the ore, the average particle size of the fine-grained sintered ore is 3 to 5 mm, and the average particle size of the small coke, By setting the average particle size of the fine-grained sintered ore to 1.2 to 2.0 times, even if the particle size and amount of the fine-grained sintered ore fluctuate, the production yield in the sintering plant is maintained high. However, it became possible to prevent the delay of reduction of fine-grained sintered ore and maintain the air permeability in the blast furnace, and more stable blast furnace operation could be realized.

It is a graph which shows the relationship between the volume compounding rate of a small grain coke, and the porosity of the packed bed which consists of a mixture of a fine grain sintered ore and a small grain coke. It is a graph which shows the relationship between (average particle diameter of a small coke / average particle diameter of a fine-grain sintered ore) ratio and a relative porosity. In comparative example invention embodiment is a graph showing the relationship between the temperature T and the gasification reaction rate constant k _S.

  Hereinafter, embodiments of the present invention will be described in more detail.

  The present invention separates the sintered ore into fine-grained ore and coarse-grained ore, and previously mixed the fine-grained ore with small-size coke, and the mixture and the coarse-grained ore and In the blast furnace operating method adopting a particle-by-particle charging method for separately charging, the average particle size of the fine-grained sintered ore is 3 to 5 mm, and the average particle size of the small-grain coke is The average particle size of the fine-grained sintered ore is 1.2 to 2.0 times.

  As described above, the average particle diameter of the fine-grained sintered ore used in the present invention is 3 to 5 mm. Here, the lower limit of the average particle size of the fine-grained sinter is set to 3 mm. In addition to the fact that the particle size of the fine-grained sinter is too small, the air permeability cannot be maintained even when mixed with the small-grain coke. This is because, in the first place, there is an increased risk that the fine-grained sintered ore will be scattered as dust during charging into the blast furnace. On the other hand, the upper limit is set to 5 mm because the production yield in the sintering plant decreases if the particle size of the fine-grained sintered ore is too large.

  The average particle size of the small coke is 1.2 to 2.0 times the average particle size of the fine-grained sintered ore based on the following analysis results.

  First, the porosity of a packed bed made of a mixture obtained by mixing three types of small coke with different particle size ranges for fine-grained sintered ore with a particle size range of 4 to 5 mm (average particle size 4.5 mm). Was obtained by calculation using a two-component particle model. The porosity of the packed bed made only of the fine-grained sintered ore was 0.4, and the porosity of the packed bed made only of the small-grain coke was 0.5 regardless of the particle size range.

  FIG. 1 shows the relationship between the volume mixing ratio of small coke in the mixture and the porosity of the packed bed made of the mixture. As seen in the figure, when mixed with small coke having a particle size range of 8 to 20 mm (average particle size 14 mm) (corresponding to “small coke” in the examples described later), small coke (corresponding to small coke) ) Is filled with fine-grained sinter, so the porosity of the packed bed tends to decrease with an increase in the volume mixing ratio of small coke (corresponding to small coke), When small particle coke with a particle size range of 6 to 8 mm (average particle size 7 mm) or 0 to 6 mm (average particle size 3 mm) is mixed, the porosity of the packed bed increases with the volume mixing rate of the small particle coke. Showed a tendency to increase.

  From this result, it was postulated that the porosity of the mixture increased and the air permeability could be maintained by approaching the size of the fine-grained sintered ore rather than using a large-sized coke.

Accordingly, when the data in FIG. 1 is plotted again with the [average particle size of small coke / average particle size of fine sinter] ratio R1 as the horizontal axis and the relative porosity e _M of the mixture as the vertical axis, the data in FIG. was gotten. Here, the relative porosity e _M of the mixture is defined as the volume of small coke, with the porosity ε ₀ of the packed bed made of only fine-grained sinter (that is, no mixing of small coke) as the reference value (1.0). The porosity ε _M of a packed bed made of a mixture mixed by 0.03 at a mixing rate is expressed as a relative value, and is a value defined by e _M = ε _M / ε ₀ .

From FIG. 2, when R1 is in the range of 2.0 or less, the relative porosity exceeds 1.0, the porosity of the packed layer is increased and air permeability can be maintained, whereas R1 exceeds 2.0. It can be seen that the relative porosity is less than 1.0, and the porosity of the packed bed is decreased by mixing small coke, which may deteriorate the air permeability. Moreover, since the gasification reaction rate shown by the reaction formula of C + CO ₂ → 2CO is reduced when the particle size of the small coke is increased, the effect of preventing the reduction delay of the fine-grained sintered ore is reduced. Therefore, the upper limit of R1 is set to 2.0. On the other hand, if R1 is too small, that is, if the particle size of the small coke is too small, the small coke has an apparent density smaller than that of the fine-grained sintered ore, so that it will be scattered as dust when charged into the blast furnace. Problems arise. Therefore, the lower limit of R1 is 1.2, that is, the lower limit of the particle size of the small coke is set slightly larger than the particle size of the fine particle sintering in consideration of the difference in the apparent density.

  As described above, the average particle size of the fine-grained sintered ore is 3 to 5 mm, and the average particle size of the small-grained coke is 1.2 to 2.0 times the average particle size of the fine-grained sintered ore. As a result, the porosity of the packed bed made of a mixture of fine sinter and fine coke can be secured, and the effect of promoting the reduction of fine sinter due to the presence of fine coke can be obtained. Even if the particle size and quantity of the sintered ore fluctuate, it is possible to maintain the air permeability in the blast furnace while maintaining a high production yield in the sintering plant, and more stable blast furnace operation can be realized.

  The present invention is more preferably applied to a blast furnace operation method in which operation is performed at a pulverized coal ratio of 120 kg / t-pig or more.

  When the pulverized coal ratio is 120 kg / t-pig or more, the coke ratio decreases and the O / C increases under the condition of a constant reducing material ratio, so that the air permeability in the portion filled with the fine-grained sintered ore is ensured. Although it becomes more difficult, the application of the present invention can ensure the air permeability of the filling portion more reliably, maintain stable operation, and the cost of replacement of coke and pulverized coal, which is an advantage of high pulverized coal ratio operation. The reduction effect can be enjoyed more reliably.

  Further, the present invention provides a blast furnace in which operation is performed by a coke center charging method in which a part of the lump coke is charged in the center of the blast furnace and the remainder of the lump coke and ore are charged in layers in the periphery of the blast furnace. More preferably, it is applied to the operation method.

  In the blast furnace to which the coke center charging method is applied, the O / C in the peripheral part of the blast furnace is inevitably increased. Therefore, when fine-grained sintered ore is charged in this part, there is a risk that the air permeability may deteriorate. However, by applying the present invention, air permeability in the periphery of the blast furnace can be secured and an appropriate gas flow distribution in the blast furnace can be maintained.

In order to confirm the applicability of the present invention, the amount of fine-grained sintered ore and small-sized coke charged was changed variously in the applicant's Kakogawa Works 1 blast furnace (internal volume: 4550 m ³ ), and the pressure in the blast furnace The effect on loss was investigated. In the same blast furnace, the coke center charging method is adopted throughout the operation period, and ores other than fine sinter (coarse sinter + pellet + lump ore) are combined with small coke. The small amount of coke having a particle size range of 8 to 20 mm (average particle size 17 mm), the amount of which was adjusted so as to be 30 kg / thm (constant), was previously mixed and charged. In addition, when a fine-grained sinter or a mixture of fine-grained sinter and small-grain coke was charged separately, the mixture was charged in the periphery of the blast furnace.

  The results are shown in Table 1 below. In the operation period 1, the effect of mixing the small-grain coke to the fine-grained sintered ore was verified, and in the operation period 2, the influence of the charging amount of the fine-grained sintered ore mixed with the fine-grained coke was verified.

  As is clear from the table, in the operation period 1, the fine-grained sintered ore having an average particle size in the range of 3 to 5 mm based on the operation of Reference Example 1 in which the charging method according to the sintered ore particle size is not applied. In the operation of Comparative Example 1 in which only the pressure was charged separately, the upper pressure loss, the lower pressure loss, and the total pressure loss in the blast furnace increased. On the other hand, the operation of Invention Example 1 in which small-grain coke having an average particle size ratio R1 in the range of 1.2 to 2.0 was mixed with fine-grained sintered ore in the same particle size range and then charged separately. The upper pressure loss, the lower pressure loss, and the total pressure loss in the blast furnace were maintained at almost the same pressure loss as the operation of Reference Example 1. From this result, it was confirmed that the air permeability in the blast furnace can be maintained by mixing small coke having an appropriate particle size with fine-grained sintered ore.

  In operation period 2, the amount of fine-grained sinter mixed with fine-grained coke was increased stepwise, but in the range up to 3.4% by mass of fine-grained sinter, the pressure loss in the blast furnace almost changed. It was confirmed that air permeability was maintained.

In each operation of Reference Example 2 and Invention Example 3, a vertical horizontal sonde with a gas sampling mechanism for measuring the temperature distribution and gas composition distribution in the radial direction and the height direction in the blast furnace from the blast furnace port ( For example, Japanese Unexamined Patent Publication No. 2000-54013 was introduced, and changes in temperature T and CO and CO ₂ gas concentrations in the height direction in the periphery of the blast furnace were measured. Then, using the measurement result, the rate constant k _S of the gasification reaction indicated by the reaction formula of C + CO ₂ → 2CO in the periphery of the blast furnace is obtained, and the relationship between the temperature T and the gasification reaction rate constant k _S is represented by Arrhenius -Figure 3 was obtained by plotting. Note that “k _S (relative value)” on the vertical axis in the figure is a relative value based on the gasification reaction rate constant k _{S · 0} at 1 / T = 0.00070 in Reference Example 2 as a reference (1.0). It is displayed.

  As shown in the figure, compared to the operation of Reference Example 2 in which fine-grained sintered ore is not charged separately, the operation of Invention Example 3 in which small-grained coke is mixed and charged separately compared to the operation of Reference Example 2 However, the gasification reaction rate constant in the periphery of the blast furnace charged with fine-grained sinter was clearly increased, and it was confirmed that the effect of promoting the reduction of fine-grained sinter by mixing fine-grained coke was obtained. .

Claims (3)

  The sintered ore is separated into fine-grained ore and coarse-grained ore, and small-grain coke is mixed in advance with the fine-grained ore, and the mixture and the coarse-grained ore are loaded separately. In the blast furnace operation method adopting the charging method according to particle size, the average particle size of the fine-grained sintered ore is 3 to 5 mm, and the average particle size of the small-grain coke is the fine-grain sintered A blast furnace operating method characterized by being 1.2 to 2.0 times the average particle size of the ore.   The blast furnace operating method according to claim 1, wherein the operation is performed at a pulverized coal ratio of 120 kg / t-pig or more.   3. The operation according to claim 1, wherein the operation is performed by a coke center charging method in which a part of the lump coke is charged in the center portion of the blast furnace and the remainder of the lump coke and ore are charged in layers in the periphery of the blast furnace. Blast furnace operation method.

Images