Blast furnace operation methods

Abstract

To provide an operation method for a blast furnace capable of enhancing reduction effect of CO2 while reducing pressure loss in the furnace.SOLUTION: In an operating method for a blast furnace in which ore and coke, which are blast furnace raw materials, are alternately charged, a first furnace diameter region is defined as the area with the non-dimensional radius of the blast furnace of 0 to less than 0.2, and a second furnace diameter region is defined as the area with the non-dimensional radius of the blast furnace of 0.2 to less than 1, assuming that the diameter of the blast furnace is 1. The charging of raw materials into the blast furnace is performed so that, when the dimensionless O / C obtained by substituting 1 for the weight ratio (O / C) of coke and ore charged into the blast furnace is expressed as the O / C at each furnace diameter position of the first furnace diameter region and the second furnace diameter region, the dimensionless O / C at each furnace diameter position of the first furnace diameter region is 0.00 or more, and the difference between the maximum value and the minimum value of the dimensionless O / C at each furnace diameter position of the second furnace diameter region is 0.35 or less. Hydrogen-based reducing gas is blown from the tuyere under the blowing condition that the hydrogen gas blowing amount is 75 (Nm3 / t) or more.SELECTED DRAWING: Figure 2b

Description

[Technical Field]

[0001] This invention relates to a method for operating a blast furnace in which ore and coke, which are blast furnace raw materials, are charged alternately. [Background technology]

[0002] In blast furnace operation, reducing agents such as coke and pulverized coal are used to raise the temperature of the ore charged into the furnace and to reduce the ore inside the furnace. Reducing the reducing agent ratio (weight of reducing agent per ton of molten iron) is an effective method for reducing CO2 emissions during pig iron production. In order to reduce the reducing agent ratio, it is necessary to increase the reduction efficiency inside the furnace. Among the reduction reactions that occur inside the furnace, the reduction reaction represented by the chemical formula: FeO + C → Fe + CO (direct reduction) is an endothermic reaction with a large amount of heat absorbed, and it is important to suppress this endothermic reaction in order to improve the reduction efficiency inside the furnace.

[0003] Here, the direct reduction reaction described above is a reduction reaction that occurs when molten ore comes into direct contact with coke, and therefore the reaction mainly takes place in the lower part of the furnace. For this reason, by sufficiently reducing the ore with a hydrogen-based reducing gas containing H2, etc., before the molten ore reaches the lower part of the furnace, the amount of unreduced ore in contact with the coke is reduced, and the direct reduction reaction can be suppressed.

[0004] Conventionally, a technique has been proposed to suppress the direct reduction reaction by blowing in hydrogen-based reducing gases (gases containing C and H, such as COG, natural gas, and city gas) from tuyeres located at the bottom of the furnace. Patent Document 1 discloses a blast furnace operation method in which a gaseous reducing agent with an H / C (molar ratio of hydrogen to carbon) of 1.5 or higher is blown in along with a solid reducing agent. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 4984396 [Overview of the project] [Problems that the invention aims to solve]

[0006] As disclosed in Patent Document 1, the pressure loss inside the furnace can be reduced by blowing hydrogen gas through the tuyeres. However, while the method disclosed in Patent Document 1 can reduce the pressure loss inside the furnace, there were issues with the amount of CO2 reduction.

[0007] In view of the above problems, the present invention aims to further enhance the CO2 reduction effect while reducing pressure loss in the furnace. [Means for solving the problem]

[0008] To solve the above problems, the blast furnace operation method according to the present invention is (1) a blast furnace operation method in which ore and coke, which are blast furnace raw materials, are charged alternately, wherein the region of the blast furnace with a blast furnace diameter of 1 and a blast furnace dimensionless radius of 0 or more and less than 0.2 is defined as the first furnace diameter region, and the region of the blast furnace with a blast furnace dimensionless radius of 0.2 or more and less than 1 is defined as the second furnace diameter region, and when the weight ratio (O / C) of coke and ore charged into the blast furnace is replaced with 1 and the weight ratio (O / C) at each furnace diameter position in the first furnace diameter region and the second furnace diameter region is expressed as the dimensionless O / C, the dimensionless O / C at each furnace diameter position in the first furnace diameter region is 0.00 or more, and the difference between the maximum and minimum values ​​of the dimensionless O / C at each furnace diameter position in the second furnace diameter region is 0.35 or less, and the blast furnace raw materials are charged in such a way that the hydrogen gas injection amount is 75 (Nm 3 The method is characterized by blowing a hydrogen-based reducing gas from the tuyer under blowing conditions of 1 / t or higher.

[0009] (2) The method for operating a blast furnace according to (1) above, characterized in that blast furnace raw materials are charged in such a way that the dimensionless O / C at each furnace diameter position in the first furnace diameter region is greater than 0.00.

[0010] (3) The method for operating a blast furnace according to (2) above, characterized in that in the second furnace diameter region, the difference between the maximum and minimum values ​​of the dimensionless O / C is 0.20 or less.

[0011] (4) In the second furnace diameter region, the difference between the maximum value and the minimum value of the dimensionless O / C is more than 0.00, and the maximum value is more than 1.00. The operation method of the blast furnace according to (3) above is characterized by this.

[0012] (5) The operation method of the blast furnace according to (1) above is characterized in that the charging of blast furnace raw materials is carried out so that the dimensionless O / C in the second furnace diameter region is 0.95 or more and 1.3 or less.

Effect of the Invention

[0013] According to the present invention, while reducing the pressure loss in the furnace, the CO2 reduction effect can be further enhanced.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic diagram of a blast furnace (bell-less blast furnace). [Figure 2a] It is the charging distribution condition of Example 1. [Figure 2b] It is the charging distribution condition of Example 2. [Figure 2c] It is the charging distribution condition of Example 3. [Figure 2d] It is the charging distribution condition of Example 4. [Figure 2e] It is the charging distribution condition of Example 5. [Figure 2f] It is the charging distribution condition of the comparative example. [Figure 2g] It is the charging distribution condition of the conventional operation. [Figure 3] It shows the change in the pressure loss in the furnace when the amount of hydrogen gas injection is variously changed in the "conventional operation" and "Example 1" shown in FIGS. 2g and 2a. [Figure 4] It shows the change in the CO gas utilization rate in the furnace when the amount of hydrogen gas injection is variously changed in the "conventional operation" and "Example 1" shown in FIGS. 2g and 2a. [Figure 5] It shows the change in the H2 gas utilization rate in the furnace when the amount of hydrogen gas injection is variously changed in the "conventional operation" and "Example 1" shown in FIGS. 2g and 2a. [Figure 6] Figure 2g and Figure 2a show the changes in the carbon reduction effect when the hydrogen gas injection volume is variously changed in the "conventional operation" and "Example 1". [Figure 7] Figure 2a to Figure 2g show the pressure loss reduction effect (kPa) for each of the "conventional operation", "Example 1" to "Example 5", and "Comparative Example" when the hydrogen gas injection volume is fixed at 200 (Nm3 / t). [Figure 8] Figure 2a to Figure 2g show the carbon reduction effect (%) for each of the "conventional operation", "Example 1" to "Example 5", and "Comparative Example" when the hydrogen gas injection volume is fixed at 200 (Nm3 / t).

Mode for Carrying Out the Invention

[0015] Figure 1 is a schematic view of a blast furnace used in the operation method of a blast furnace according to an embodiment of the present invention. The blast furnace 1 is a bell-less blast furnace and includes tuyeres 2, an annular pipe 3, a blow pipe 4, and a swivel chute 5. A plurality of tuyeres 2 are provided at the lower part of the furnace along the furnace circumferential direction of the blast furnace 1. The annular pipe 3 is disposed so as to surround the lower part of the blast furnace 1. The blow pipe 4 is intermittently provided in the circumferential direction of the annular pipe 3, and each is connected to a different tuyere 2.

[0016] The swivel chute 5 rotates around an axis extending in the vertical direction, and alternately charges ore and coke, which are blast furnace raw materials, into the furnace in layers to form an ore layer and a coke layer. The ore and coke may be charged in a plurality of times respectively, or may be charged once each. Sintered ore, pellets, lump ore, and uncalcined carbonaceous lump ore can be used for the ore. Further, the ore may contain a reduction aid such as small lump coke. The coke may contain ferrocoke. By controlling the drive conditions such as the notch of the swivel chute 6, a desired layer structure described later is realized. Note that the present invention can also be applied to a bell-type blast furnace having no swivel chute.

[0017] (Background of the Present Invention) Before describing the desired layer structure mentioned above, the history of the invention will be explained. In this specification, "pressure loss (in the blast furnace)" refers to the difference between the pressure at the tip of the tuyere 2 and the pressure at the top of the blast furnace 1, excluding the pressure loss in the piping from the blower (not shown) to the tip of the tuyere 2. When a blast furnace mathematical model for simulating an actual furnace is used (see Examples for specific examples), the pressure loss is calculated using the Ergun formula, and in the case of an actual furnace, it is measured by a pressure gauge installed on the furnace wall.

[0018] By using a hydrogen-based reducing gas as the reducing gas blown in from the tuyeres of the blast furnace, pressure loss inside the blast furnace can be reduced due to the following reasons: (1) hydrogen gas has low density and low viscosity, (2) the potential of the reducing gas is improved, which reduces the amount of Bosch gas, (3) the properties of ore melting in the fusion zone are improved, and (4) the amount of coke pulverization is reduced due to a decrease in the amount of sol-ross carbon.

[0019] In other words, by injecting a large amount of hydrogen-based reducing gas into the furnace, the pressure loss inside the furnace can be reduced. However, in conventional blast furnace operation, in order to reduce the pressure loss inside the blast furnace, an operating method is adopted in which no ore is charged into the center of the furnace (i.e., an operating method in which a layer of coke alone is deposited in the center of the furnace, hereinafter also referred to as "coke-only layer formation operation"). Therefore, in inventing a novel blast furnace operating method, the inventors reduced the pressure loss in base operation (coke-only layer formation operation, by setting the hydrogen gas injection amount to 0 (Nm 3 It was considered necessary to keep the hydrogen gas injection rate at or below the rate of operation (per ton). The hydrogen gas injection rate was calculated based on the amount of hydrogen (Nm³) required to produce 1 ton of molten iron. 3 ) refers to this.

[0020] On the other hand, with the worsening of global warming in recent years, reducing CO2 emissions, which have the greatest impact on global warming as a greenhouse gas, is also required in blast furnace operations. In order to reduce CO2 emissions in blast furnace operations, reducing the carbon consumption intensity (carbon consumption per ton of molten iron) is an effective measure.

[0021] Therefore, the inventors diligently studied a blast furnace operating method that would further enhance the carbon reduction effect while keeping pressure loss at or below the level of base operation, and discovered a blast furnace operating method that satisfies the following (A) and (B).

[0022] Regarding (A) Blast furnace dimensionless radius: Ore and coke are charged so that the dimensionless O / C ratio at each furnace diameter position in the region between 0 and 0.2 (first furnace diameter region) is 0.00 or greater. The blast furnace dimensionless radius is the dimensionless radius obtained by converting the furnace diameter (furnace radius) of the blast furnace to 1. In other words, the layer structure of ore and coke is not limited in the first furnace diameter region. The layer structure of the blast furnace raw materials deposited in the first furnace diameter region may be a two-layer structure in which an ore layer and a coke layer are stacked vertically over the entire furnace diameter direction, or it may be a layer structure consisting of a coke-only layer in part and the remainder consisting of the aforementioned two-layer structure, or it may be an ore-only layer consisting of ore.

[0023] Furthermore, as shown in the above configuration (A), a charging method that results in a dimensionless O / C ratio of 0.00 or more at each furnace diameter position in the first furnace diameter region can be used, for example, by separately preparing a batch containing predetermined amounts of ore and coke, and charging the batch into the first furnace diameter region. However, it is not limited to this method.

[0024] (B) In the region of the blast furnace dimensionless radius: 0.2 to 1 (second furnace diameter region), ore and coke are charged in such a way that the variation in O / C in the furnace radial direction is minimized. Specifically, when the O / C ratio (O / C) of ore and coke charged into the blast furnace from the top is replaced with a dimensionless O / C ratio of 1, and the O / C ratio at each furnace diameter position in the second furnace diameter region is expressed, the blast furnace raw materials are charged in such a way that the difference between the maximum and minimum values ​​of the dimensionless O / C at each furnace diameter position is within 0.35. If it exceeds 0.35, the bias of the reducing gas in the furnace diameter direction becomes large, and the carbon reduction effect becomes insufficient. Preferably, the difference between the maximum and minimum values ​​of the dimensionless O / C at each furnace diameter position in the second furnace diameter region is 0.2 or less.

[0025] For example, in the case of a two-dump charging process where ore and coke are charged in one step, the O / C ratio at each furnace diameter position is expressed as a dimensionless O / C based on a dimensionless O / C obtained by substituting the weight ratio of these ore and coke (O / C) to 1. The weight ratio of ore and coke charged into the blast furnace from the top can be determined by pre-measuring the weights of the ore and coke transported to the blast furnace's top hopper. If the ore contains carbon-containing ore such as uncalcined coal-containing agglomerated ore, the weight ratio may be determined by allocating the uncalcined coal-containing agglomerated ore to the ore component and the coke component. Similarly, if the coke contains coke with ore components such as ferrocoke, the weight ratio may be determined by allocating the ferrocoke to the ore component and the coke component.

[0026] According to the above configuration (B), it is possible to suppress the uneven flow of reducing gas caused by the bias of dimensionless O / C in the radial direction of the furnace. As a result, the reducing gas can be utilized more effectively, the reduction efficiency can be improved, and the carbon reduction effect can be enhanced. While there are no particular limitations on the maximum and minimum values ​​of the dimensionless O / C in the second furnace diameter region, it is desirable to set the maximum value to 1.3 or less and the minimum value to 0.95 or more. That is, it is desirable to charge the ore and coke so that the dimensionless O / C in the second furnace diameter region is between 0.95 and 1.3.

[0027] Furthermore, as shown in the above configuration (B), in the second furnace diameter region, charging methods that reduce the variation in dimensionless O / C in the furnace diameter direction include, for example, a method of appropriately adjusting the amount of ore and coke charged by grasping the trend of variation in dimensionless O / C in advance through numerical calculations or model experiments, or a method of grasping the distribution of ore and coke based on the measurement results of a profile meter measured during operation, converting the result to dimensionless O / C, and appropriately adjusting the amount of ore and coke charged. However, these methods are not limited to these.

[0028] (C) A large amount of hydrogen-based reducing gas is injected from tuyer 2 of blast furnace 1. The hydrogen-based reducing gas may be hydrogen gas itself, or it may be COG containing hydrogen gas, natural gas, city gas, etc. The amount of hydrogen-based reducing gas injected should be equivalent to the amount of hydrogen gas injected, which is 75 (Nm³). 3 The amount is greater than / pig-ton). Under conditions that satisfy the above configurations (A) and (B), by injecting a large amount of hydrogen-based reducing gas of configuration (C), the carbon reduction effect can be further enhanced while keeping the pressure loss at or below that of base operation.

[0029] A blast furnace operation method that satisfies the above (A) to (C) preferably satisfies the following (A') instead of (A) with respect to the dimensionless O / C at each furnace diameter position in the first furnace diameter region.

[0030] Regarding (A') Ore and coke are charged in such a way that the dimensionless O / C ratio at each furnace diameter position in the region of blast furnace dimensionless radius: 0 or greater and less than 0.2 (first furnace diameter region) is greater than 0.00. The layer structure of the blast furnace raw materials deposited in the first furnace diameter region may be a two-layer structure in which an ore layer and a coke layer are stacked vertically over the entire furnace diameter, or it may be a single layer of ore consisting only of ore.

[0031] Furthermore, regarding the charging method such that the dimensionless O / C at each furnace diameter position in the first furnace diameter region is greater than 0.00, as in the above configuration (A'), the explanation is omitted as it is the same as the method described in (A).

[0032] The present invention will be described in detail with reference to examples.

[0033] (Examples) The distribution conditions of the charge material deposited in the furnace and the amount of hydrogen gas injected from the tuyeres were varied, and the effects on the pressure loss in the furnace and the carbon reduction effect were simulated using a blast furnace mathematical model. Hydrogen gas was used as the reducing gas. The charge material distribution conditions assumed in this embodiment are shown in Figures 2a to 2g. In Figures 2a to 2g, the vertical axis is dimensionless O / C(-), and the horizontal axis is dimensionless radius position(-). The definitions of "dimensionless O / C" and "dimensionless radius" have already been described, so the explanation is omitted. "Example 1" to "Example 4" shown in Figures 2a to 2d are embodiments that satisfy the configurations (A'), (B), and (C) shown in the above embodiments, and "Example 5" shown in Figure 2e is an embodiment that satisfies the configurations (A) to (C) shown in the above embodiments. "Comparative Example" shown in Figure 2f is a charge material distribution condition that does not satisfy any of the configurations (A) to (C) and (A') shown in the above embodiments. The "conventional operation" shown in Figure 2g corresponds to the coke single-layer formation operation described above, and is a charge distribution in which a single layer of coke is formed in the center of the furnace. The "Example 1" shown in Figure 2a is a charge distribution in which the dimensionless O / C is 1.0 (constant in the furnace radial direction), and is hereafter referred to as a perfectly flat charge.

[0034] The mathematical model used for the blast furnace was the one described in "Three-dimensional Dynamic Simulator for Blast Furnace" by Kouji TAKATANI, Takanobu INADA, and Yutaka UJISAWA, ISIJ International, Vol.39 (1999), No.1, pp.15-22. The simulation parameters are shown in Table 1. [Table 1]

[0035] (Regarding changes in internal pressure loss) Figure 3 shows the change in furnace pressure loss when the hydrogen gas injection rate is varied in the charge distribution for "Conventional Operation" and "Example 1" shown in Figures 2g and 2a. In Figure 3, the vertical axis represents the change in pressure loss (kPa), and the horizontal axis represents the hydrogen injection rate (Nm³). 3(t). Here, the "pressure loss change (kPa)" is the difference between the pressure loss under each condition and the pressure loss in the base operation (in the operation of forming a single layer of coke, with the hydrogen gas injection amount set to 0 (Nm 3 / t)). When the "pressure loss change (kPa)" is 0 or less, it can be evaluated that the pressure loss is reduced.

[0036] From Figure 3, in the case of complete flat charging, it was found that by setting the hydrogen gas injection amount to 75 (Nm 3 / t) or more, the pressure loss can be suppressed to be equal to or lower than that in the base operation.

[0037] (Regarding the change in the in - furnace reduction gas utilization rate) In the charge distributions of the "conventional operation" and "Example 1" shown in Figures 2g and 2a, the changes in the in - furnace reduction gas utilization rate when the hydrogen gas injection amount is variously changed are shown in Figures 4 and 5. Figure 4 shows the change in the in - furnace CO gas utilization rate. The vertical axis is the CO gas utilization rate (%), and the horizontal axis is the hydrogen injection amount (Nm 3 / t). Here, the "CO gas utilization rate (%)" is a value calculated based on the blast furnace gas discharged from the top of the furnace, obtained by dividing the CO2 gas concentration by the sum of the CO2 gas and CO gas concentrations. Figure 5 shows the change in the in - furnace H2 gas utilization rate. The vertical axis is the H2 gas utilization rate (%), and the horizontal axis is the hydrogen injection amount (Nm 3 / t). Here, the "H2 gas utilization rate (%)" is a value calculated based on the blast furnace gas discharged from the top of the furnace, obtained by dividing the H2O gas concentration by the sum of the H2O gas and H2 gas concentrations.

[0038] From Figures 4 and 5, it was found that by performing complete flat charging, the reduction gas in the furnace can be utilized more effectively compared to the conventional operation, and the reduction efficiency is improved.

[0039] (Regarding the change in the carbon reduction effect) In the charge distributions of the "conventional operation" and "Example 1" shown in Figures 2g and 2a, the change in the carbon reduction effect when the hydrogen gas injection amount is variously changed is shown in Figure 6. In Figure 6, the vertical axis is the carbon reduction effect (%), and the horizontal axis is the hydrogen injection amount (Nm3 / t) Here, "carbon reduction effect (%)" refers to the reduction in carbon consumption per unit, and the amount of hydrogen gas injected is 0 (Nm³ in base operation (coke single layer formation operation). 3 This was calculated as the reduction rate of CO2 emissions relative to the operating rate (per t).

[0040] Figure 6 shows that, when comparing with the same hydrogen gas injection rate, fully flat charging can achieve a greater carbon reduction effect compared to conventional operation.

[0041] For "Conventional Operation," "Example 1" to "Example 5," and "Comparative Example" shown in Figures 2a to 2g, the hydrogen gas injection rate was set to 200 (Nm³). 3 Figures 7 and 8 show the pressure loss reduction effect (kPa) and carbon reduction effect (%) for each case when the pressure is fixed at / t. The "pressure loss reduction effect (kPa)" in Figure 7 has the same definition as the "pressure loss change (kPa)" in Figure 3. If the pressure loss reduction effect (%) is 0% or less and the carbon reduction effect (%) is 12% or more, it is evaluated as "both the pressure loss reduction effect and the carbon reduction effect are excellent" and is marked with "○". If the pressure loss reduction effect (%) is 0% or less and the carbon reduction effect (%) is 12.8% or more, it is evaluated as "the pressure loss reduction effect is excellent and the carbon reduction effect is particularly excellent" and is marked with "◎". On the other hand, if the carbon reduction effect (%) is less than 12%, it is evaluated as "the carbon reduction effect is low" and is marked with "×". The evaluation results are shown in Table 2. [Table 2]

[0042] Referring to Table 2, Examples 1 to 4, which satisfy the above configurations (A'), (B), and (C), and Example 5, which satisfies the above configurations (A) to (C), received an evaluation of "○" or higher. Examples 2 to 4, in addition to satisfying the above configurations (A'), (B), and (C), received an evaluation of "◎" because the difference between the maximum and minimum values ​​of dimensionless O / C at each furnace diameter position in the second furnace diameter region was 0.2 or less. On the other hand, in the comparative example, although the pressure loss was sufficiently reduced, the difference between the maximum and minimum values ​​of dimensionless O / C in the furnace diameter direction in the second furnace diameter region was greater than 0.35 (minimum value approximately 0.5, maximum value approximately 1.4), so the carbon consumption could not be sufficiently reduced, and received an evaluation of "×". Furthermore, in conventional operation, the difference between the maximum and minimum values ​​of dimensionless O / C in the radial direction is greater than 0.35 (minimum value approximately 0.1, maximum value approximately 1.6), so carbon consumption could not be sufficiently reduced, resulting in a "×" rating. [Explanation of Symbols]

[0043] 1. Blast furnace 2. Tuyeres 3. Ring pipe 4. Blowpipe 5. Swivel chute

Claims

1. A method of operating a blast furnace in which ore and coke, which are blast furnace raw materials, are charged alternately, The region with a blast furnace diameter of 1 and a blast furnace dimensionless radius of 0 or more and less than 0.2 is defined as the first furnace diameter region, and the region with a blast furnace dimensionless radius of 0.2 or more and less than or equal to 1 is defined as the second furnace diameter region. When the weight ratio (O / C) of coke and ore charged into the blast furnace is replaced with a dimensionless O / C of 1, and the weight ratio (O / C) at each furnace diameter position in the first and second furnace diameter regions is expressed, The blast furnace raw materials are charged such that the dimensionless O / C at each furnace diameter position in the first furnace diameter region is 0.00 or greater, and the difference between the maximum and minimum values ​​of the dimensionless O / C at each furnace diameter position in the second furnace diameter region is within 0.

35. Hydrogen gas injection rate: 75 (Nm³) 3 Under blowing conditions of t or higher, a hydrogen-based reducing gas is blown in from the tuyer. A method for operating a blast furnace, characterized by the following.

2. A method for operating a blast furnace according to claim 1, characterized in that blast furnace raw materials are charged such that the dimensionless O / C at each furnace diameter position in the first furnace diameter region is greater than 0.

00.

3. In the second furnace diameter region, the difference between the maximum and minimum values ​​of the dimensionless O / C is 0.20 or less. The method for operating a blast furnace according to claim 2, characterized in that...

4. In the second furnace diameter region, the difference between the maximum and minimum values ​​of the dimensionless O / C is greater than 0.00, and the maximum value is greater than 1.

00. A method for operating a blast furnace according to claim 3, characterized in that it is a method for operating a blast furnace according to claim 3.

5. The blast furnace raw materials are charged in such a way that the dimensionless O / C ratio in the second furnace diameter region is between 0.95 and 1.

3. A method for operating a blast furnace according to claim 1, characterized in that...

Images