Method for operating a blast furnace

Abstract

The operation method of a blast furnace improves the ventilation of the lower part of the blast furnace by tuyere injection of fine ore. The operation method of the blast furnace (1) of the invention is characterized in that coal is pulverized as fine coal, and an iron ore having a pulverized ignition loss of 9 mass% or more and 12 mass% or less is pulverized as fine ore, the injection rate of the fine coal is 150 kg / tp or more, the injection rate of the fine ore is 2.5 kg / tp or more and 50.0 kg / tp or less, and the fine coal and the fine ore are injected from the tuyere (2). It is preferable that the iron ore and the coal are pulverized together.

Description

[0001] This application is a divisional application of PCT application (PCT / JP2020 / 013733) with application number 202080019705.1, application date 2020.3.26, and invention title "Operating Method of Blast Furnace". Technical Field

[0002] This invention relates to a method for operating a blast furnace. Background Technology

[0003] Traditionally, in blast furnaces, coke and ore raw materials (iron ore, sinter, pellets, etc.) are alternately layered and charged from the top. Pulverized coal and hot air (air, oxygen) are then blown in through the tuyeres, reducing and melting the ore raw materials to produce molten iron. In blast furnaces with such a solid-gas countercurrent moving bed, maintaining good ventilation is crucial for stable operation. This is because poor ventilation can hinder stable operation.

[0004] For example, coke serves a spacer function to ensure ventilation within the furnace, and a certain amount must be used. However, if the use of coke can be suppressed to reduce ventilation within the furnace, the expensive coke can be converted into inexpensive pulverized coal, thus reducing the amount of coke used (coke ratio).

[0005] In recent years, pulverized coal injection (PCO) blast furnace operation, in which pulverized coal is injected through the tuyeres of the blast furnace as a partial substitute fuel (reducing agent) for coke, has become common practice. Recently, high PCO injection rate operations with pulverized coal usage exceeding 150 kg / tp have also been achieved stably.

[0006] Here, the pulverized coal injected into the blast furnace contains approximately 10% by mass (hereinafter referred to as "%"). This ash consists of SiO2: 50%–60%, Al2O3: 20%–30%, and also contains Fe2O3, CaO, etc., and is mainly composed of acidic components.

[0007] Therefore, if the pulverized coal injection rate is high, the acidic slag from the pulverized coal ash increases, and the viscosity and melting point of the slag layer (commonly referred to as "bird's nest slag") retained behind the swirl zone rises. If this is the case, the amount of bird's nest slag retained (hold-up) increases, and the ventilation in the lower part of the blast furnace deteriorates (see reference). Figure 15 ).

[0008] To address the aforementioned deterioration in ventilation at the bottom of the blast furnace, Patent Document 1 discloses a technology that uses iron ore containing 2.0% by weight or more water of crystallization as a raw material in the blast furnace ironmaking process to improve blast furnace productivity and reduce the coke ratio. Specifically, the technology in Patent Document 1 involves reducing iron ore containing 2.0% by weight or more water of crystallization to a reduction rate of 30% or more before charging it into the blast furnace and / or injecting it into the blast furnace. The reduction of the iron ore is carried out in a reducing atmosphere containing hot CO and H2 at temperatures above 400°C.

[0009] Furthermore, Patent Document 2 discloses a technique for operating a blast furnace, particularly concerning the suppression of Si in the released molten iron. Specifically, the technique in Patent Document 2 involves simultaneously injecting fine ore and pulverized coal from each tuyer, ensuring that the ratio of fine ore to pulverized coal at this time is equal to the ratio of ore to coke charged from the top of the blast furnace. In the technique of Patent Document 2, fine ore is injected in addition to pulverized coal, thus suppressing the rise of Si. Furthermore, because the ratio of fine ore to pulverized coal is made equal to the ratio of ore to coke charged from the top of the blast furnace, the distribution of the charge inside the furnace remains unchanged, making it easier to control the charge distribution. It is also noted that because the injection is done separately from each tuyer, the amount of ore injected from each tuyer is small, resulting in a lower risk of equipment failure.

[0010] Prior art literature

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 09-165607

[0013] Patent Document 2: Japanese Patent Application Publication No. 04-002708

[0014] In the method of Patent Document 1, the blowing rate of undehydrated ore is as high as 100 kg / tp, and the temperature drops significantly, so it cannot reduce the amount of slag retained in the Bird's Nest molten slag (retention amount).

[0015] Furthermore, in the method of Patent Document 2, the pulverized coal injection rate is as low as 0-40 kg / tp, which cannot reduce the amount of slag retained in the blast furnace (retention). Additionally, Patent Document 2 does not describe the properties of the ore, and insufficient ore reduction during injection may lead to a decrease in the blast furnace's hot metal temperature, necessitating a further increase in the coke ratio. Moreover, the technology in Patent Document 2 concerns reducing the Si content in the hot metal, unlike this invention, which aims to improve ventilation in the lower part of the blast furnace. Summary of the Invention

[0016] The present invention was developed in view of the above-mentioned problems, and its purpose is to provide a method for operating a blast furnace that can improve ventilation in the lower part of the blast furnace by injecting fine ore through the tuyeres.

[0017] To address the aforementioned issues, the blast furnace operation method of the present invention employs the following technical measures.

[0018] That is, the blast furnace operation method of the present invention is characterized in that coal is pulverized into pulverized coal, and iron ore with a loss on ignition of more than 9% and less than 12% by mass is pulverized as fine powder ore, the injection rate of the pulverized coal is more than 150 kg / tp, and the injection rate of the fine powder ore is more than 2.5 kg / tp and less than 50.0 kg / tp, and the pulverized coal and fine powder ore are injected from the tuyeres.

[0019] Furthermore, it is preferable to crush the iron ore and coal together.

[0020] According to the blast furnace operation method of the present invention, ventilation in the lower part of the blast furnace can be improved by injecting fine ore through the tuyeres. Attached Figure Description

[0021] Figure 1 This diagram schematically illustrates the treatment performed at the tuyeres in the blast furnace operation method of the present invention.

[0022] Figure 2 This is a graph showing how the viscosity characteristics of a slag with 15% Al2O3, 5% MgO, and a basicity of 1.2 change with the FeO content.

[0023] Figure 3 This is a graph showing how the viscosity characteristics of slag containing 40 mol% SiO2 change with the mol% concentration of Fe2O3.

[0024] Figure 4 This is a graph showing the relationship between the loss on ignition of coal used in pulverized coal and the Hardgrove grindability index.

[0025] Figure 5 This is a graph showing the relationship between the loss on ignition and specific surface area of ​​coal used in pulverized coal.

[0026] Figure 6 This is a graph showing the relationship between the injection rate of fine ore and the change in pressure loss of the blast furnace.

[0027] Figure 7 This is a graph showing the results of investigating the relationship between the injection rate of fine ore and the change in pressure loss of the blast furnace using an actual blast furnace.

[0028] Figure 8 This is a block diagram illustrating the steps of the operation method of the present invention.

[0029] Figure 9 This is a block diagram illustrating the steps involved in calculating the change in pressure loss in a blast furnace.

[0030] Figure 10 It is a graph showing the values ​​of various physical properties obtained in the process of calculating the change in pressure loss of a blast furnace.

[0031] Figure 11 This is a diagram showing a rotary torque meter used for measuring the viscosity of molten slag.

[0032] Figure 12 This is a graph showing the temperature dependence of the viscosity of slag with a basicity of 0.6.

[0033] Figure 13 This is a graph showing the temperature dependence of the viscosity of slag with a basicity of 1.0.

[0034] Figure 14 This is a graph showing the relationship between the basicity and viscosity of the slag when the flow ratio is 20 kg / tp.

[0035] Figure 15 This diagram schematically illustrates the treatment performed at the tuyeres in existing blast furnace operation methods. Detailed Implementation

[0036] Hereinafter, based on the accompanying drawings, embodiments of the operation method of the blast furnace 1 of the present invention will be described in detail.

[0037] like Figure 1 As shown, the operation method of blast furnace 1 in this embodiment is characterized by pulverizing coal to obtain pulverized coal, and pulverizing iron ore with a loss on ignition of 9% or more and 12% or less to obtain fine ore, so that the injection rate of pulverized coal is 150 kg / tp or more, and the injection rate of fine ore is 2.5 kg / tp or more and 50.0 kg / tp or less, and pulverized coal and fine ore are injected from tuyeres 2 (the above "kg / tp" refers to the mass (kg) of 1 ton of molten iron, the same below).

[0038] Specifically, in the blast furnace 1 operated by the present invention, coke and ore raw materials (iron ore, sinter, pellets, etc.) are alternately layered and charged from the top of the furnace. Pulverized coal and hot air (air, oxygen) are blown in together from the tuyeres 2 to reduce and melt the ore raw materials to produce molten iron. In the stable operation of the blast furnace 1, which is a solid-gas countercurrent moving bed furnace, it is important to ensure good ventilation within the furnace. This is because poor ventilation hinders stable operation. Coke plays a role in ensuring ventilation within the furnace; if good ventilation can be achieved, the expensive coke can be replaced with inexpensive pulverized coal, reducing the amount of coke used (coke ratio).

[0039] The operation method of the present invention, as described above, involves pulverized coal obtained by injecting air from tuyeres 2 and fine powdered ore obtained by pulverizing iron ore.

[0040] The aforementioned pulverized coal, for example, has a maximum particle size of less than 1000 μm and an average particle size of 50 μm, and is injected into blast furnace 1 at a rate of 150 kg / tp or more. In other words, the operating method of the present invention targets high pulverized coal ratio operation, and is a technique aimed at improving furnace ventilation in high pulverized coal ratio operation, thereby reducing the coke ratio (the mass (kg) of coke required to produce 1 ton of molten iron) in blast furnace 1 operation.

[0041] In addition, the above-mentioned pulverized coal contains about 10% by mass (hereinafter referred to as "%") of ash, which consists of SiO2: 50% to 60%, Al2O3: 20% to 30%, and also Fe2O3, CaO, etc., mainly composed of acidic components.

[0042] Therefore, if the pulverized coal injection rate increases, the amount of acidic slag from the pulverized coal will increase, and the slag will remain in the pulverized coal. Figure 11 As shown, the slag layer (commonly referred to as "bird's nest slag 4") behind the swirling zone (=bird's nest section 3) has increased viscosity and melting point, resulting in decreased ventilation (increased pressure loss). Consequently, the ventilation in the lower part of blast furnace 1 deteriorates.

[0043] However, in the operating method of this invention, in addition to the pulverized coal mentioned above, ore is also injected from the tuyeres 2. Such ore injection is known from publications such as Japanese Patent Application Publication No. 05-214414. For example, as... Figure 2 As shown, it indicates that if ore (Fe2O3) is blown from the tuyeres, when it reaches the nest section, 10%–40% is Fe3O4–FeO, and a portion is reduced to metallic iron. Furthermore, by simultaneously crushing the iron ore and coal, the coal and iron ore are brought closer together, increasing the reduction rate. Additionally, in… Figure 2 and Figure 3 The text also points out that, generally speaking, adding iron oxide components (FeO, Fe2O3) to acidic slag will reduce its viscosity.

[0044] In other words, according to the above Figure 2 If coal and iron ore are injected simultaneously from the tuyeres, a portion of the iron ore is reduced in the vortex zone, and the reduced fine ore is captured by the molten slag behind the vortex zone. As a result, due to the iron oxide composition of the reduced fine ore, the viscosity of the molten slag decreases, and the molten slag in the vortex zone drips more easily. Therefore, it is believed that reducing the amount of molten slag retained in the vortex zone and decreasing the slag retention can improve ventilation in the lower part of the furnace (reducing pressure loss in the lower part of the furnace).

[0045] However, when the iron oxide contained in the fine ore reacts with the coke in the furnace, a direct reduction reaction occurs (e.g., FeO + C → Fe + CO). Because this reaction is accompanied by a large amount of endothermic reaction, it may lower the temperature of the molten iron, thus causing it to cool down. In other words, fine ore cannot be indiscriminately sprayed simply to improve ventilation.

[0046] Therefore, in the operation method of blast furnace 1 of the present invention, the ore properties and injection rate are specified under appropriate conditions so as to achieve both improved ventilation and prevention of cooling.

[0047] Next, the ore properties of the iron ore used as raw material for micronized ore in the operation method of the present invention and the blowing rate of micronized ore will be described.

[0048] Fine powder ore is obtained by crushing iron ore. The iron ore used as raw material for this fine powder ore has a loss on ignition of 9% to 12% by mass. The loss on ignition (LOI) in iron ore is an indicator measured according to JIS M8850, and in the case of iron ore, it mainly represents the content of water of crystallization.

[0049] The specified loss on ignition (LOI) for iron ore is designed to ensure that the grindability of fine iron ore is equivalent to that of coal used for pulverized coal, making it easy to grind (easily become fine), and ensuring that the particle size of both is consistent during grinding. The HGI (Hardgrove Grindability Index) is an indicator of the grindability of coal as shown in the coal HGI strength test (JIS M8801). By measuring the grindability of various iron ores according to this coal HGI strength test method and analyzing its relationship with the loss on ignition (LOI), one can obtain... Figure 4 Such a relationship.

[0050] like Figure 4 As shown, if the loss on ignition (LOI) of iron ore is large, the HGI of iron ore will also be large, making it easier to crush (easier to become fine).

[0051] Here, the HGI of the coal used as pulverized coal in blast furnace 1 is generally between 40 and 90. An HGI of 40 or higher is used because if the HGI is below 40, the pulverability deteriorates, the particle size increases, and equipment wear occurs. Conversely, an HGI below 90 is used because if the HGI is greater than 90, the coal is pulverized too finely, causing pipe blockage.

[0052] When the loss on ignition is 9% or more and 12% or less, the HGI of the iron ore is 40 to 90, which is the same as that of coal used for pulverized coal. When pulverizing iron ore, the particle size of the fine ore becomes comparable to that of pulverized coal (maximum particle size less than 1000 μm, average particle size = 50 μm), thus preventing equipment wear and pipeline rupture.

[0053] In addition, such as Figure 5 As shown, the loss on ignition (LOI) of iron ore is positively correlated with its specific surface area (BET); a larger LOI results in a larger specific surface area. Fine iron ore with a high specific surface area reacts more readily in the vortex zone, thus increasing its reduction rate.

[0054] Based on the above, when the fine ore is captured by the bird's nest slag 4 behind the swirl zone, the viscosity of the bird's nest slag 4 can be reduced, and the amount of bird's nest slag 4 retained can be decreased. As a result, the pressure loss of blast furnace 1 can be reduced, and the ventilation of the lower part of blast furnace 1 can be improved.

[0055] Furthermore, when the loss on ignition (LOI) of iron ore is below 9% by mass, the iron ore with a low HGI is difficult to pulverize because it is used as raw material. Therefore, the particle size of the fine ore increases, leading to greater equipment wear and operational failures such as rupture of conveying pipes, rendering it unusable. Additionally, iron ore with a low LOI has a small specific surface area, resulting in a lower reduction rate in the vortex zone during tuyeres 2. Consequently, the direct reduction reaction with the coke in the furnace core behind the vortex zone leads to greater heat absorption, easily causing a decrease in the temperature of the molten iron (lower furnace heat). As a result, the pressure loss actually increases, and the benefits of fine ore injection are not achieved.

[0056] In addition, when the loss on ignition (LOI) of iron ore is higher than 12% by mass, since there is no ore with such a loss on ignition, the case of loss on ignition higher than 12% by mass is excluded.

[0057] Next, the blowing rate of the fine powder ore will be explained.

[0058] Postscript Figure 9 The calculation process is described to determine the relationship between the blowing rate and pressure loss reduction of fine ore powder. The calculation results are shown in... Figure 6 In the middle section, by increasing the blowing rate of the fine ore, the viscosity of the slag in the Bird's Nest area 4 decreases, the dripping velocity increases, and therefore the slag retention decreases (slag retention is reduced). As a result, the pressure loss reduction increases. However, if the blowing rate of the fine ore reaches 20 kg / tp or higher, the amount of slag in the Bird's Nest area increases, and the pressure loss reduction decreases due to the effect of the lower slag temperature. Furthermore, if the blowing rate of the fine ore is further increased to 50 kg / tp, compared to the condition of a blowing rate of 0 kg / tp (bottom), the pressure loss increases, and the effect disappears.

[0059] Also, the above Figure 6 The result is to follow Figure 9 The calculation process yielded the result, but if an actual blast furnace test is used, the result can be obtained. Figure 7 The result is shown below.

[0060] like Figure 7 As shown, if the actual blast furnace follows Figure 8 When the process is followed, the pressure loss does not decrease when the injection rate of the fine ore is 1.3 kg / tp. However, starting from an injection rate of 2.5 kg / tp, the pressure loss decreases. Figure 6 Similarly, pressure loss is reduced. This is because when the blowing rate is 1.3 kg / tp, the blowing rate is small, and the fine ore cannot be evenly distributed in the 25 vents 2 in the circumferential direction, disrupting the circumferential balance and thus failing to improve ventilation. Therefore, in the operating method of the present invention, the lower limit of the blowing rate of fine ore for which the effect of the present invention is achieved is 2.5 kg / tp or higher.

[0061] Furthermore, when the blowing rate of the fine ore exceeds 50 kg / tp, the sensible heat (heat absorption) of the blowing increases, and the temperature (T) of the molten slag in the bird's nest decreases. In addition, the amount of molten slag flowing in (W) also increases, and the pressure loss increases compared to the bottom before blowing.

[0062] Furthermore, the aforementioned "micronized ore" refers to ore that has undergone pulverization using roller mills, ball mills, etc., and specifically refers to iron ore pulverized to below 1000 μm. Additionally, "pulverized coal" refers to coal that has undergone pulverization using roller mills, ball mills, etc., and specifically refers to coal pulverized to below 1000 μm using the same roller mills or ball mills as coal.

[0063]

Example

[0064] Next, using comparative examples and embodiments, the effects of the operation method of the blast furnace 1 of the present invention will be described in detail.

[0065] First, follow Figure 9 The calculation process yields the change in "reduction in pressure loss" relative to the "injection rate of fine ore." Furthermore, this "reduction in pressure loss" indicates the extent to which pressure loss has decreased compared to before injection; for example, an "increase in the reduction in pressure loss" means a decrease in pressure loss, while a "decrease in the reduction in pressure loss" means an increase in pressure loss. In contrast, the "change in pressure loss" indicates the extent to which pressure loss has increased or decreased compared to before injection. An "increase in the change in pressure loss" means an increase in pressure loss, and a "decrease in the change in pressure loss," as the name suggests, means a decrease in pressure loss.

[0066] Furthermore, the results of the operation method of the present invention will be described thereafter using the symbols defined as shown in Table 1.

[0067] Table 1

[0068]

[0069] First, the upper limit of the blowing rate of fine ore from tuyeres 2 (the upper limit of blowing rate) is explained. First, the changes in the reduction rate, melting rate, and boundary temperature of the vortex zone (equivalent to the temperature of the slag in the bird's nest) within the blowing rate of the fine ore are calculated. This calculation method is based on the mathematical model described in "Iron and Steel, Xiao et al., vol. 78, 1992, p. 1230". The calculation results show... Figure 10 In (a), the calculated elements are shown in Table 2.

[0070] Table 2

[0071] project unit numerical values blower volume <![CDATA[Nm 3 / min]]> 7600 Oxygen <![CDATA[Nm 3 / min]]> 550 wind temperature ℃ 1180 Humidity <![CDATA[g / Nm 3 ]]> 10 Number of wind vents indivual 40 pulverized coal injection rate kg / tp 215 Pulverized coal particle size μm 50 Micronized ore blowing rate kg / tp 0～50 Micronized mineral particle size μm 50

[0072] At this point, only molten ore contributes to reducing the viscosity of the Bird's Nest slag 4. Based on the blowing rate and melting rate of the micronized ore, the relationship between molten ore (flux) and unmolten ore is determined. The determined relationship between molten ore and unmolten ore is shown in... Figure 10 (b) in.

[0073] In addition, the total amount of blown fine ore was accounted for as the slag ratio of Bird's Nest slag 4, and the relationship between the blowing rate of fine ore and the amount (w) of Bird's Nest slag 4 was obtained. The obtained relationship is shown in... Figure 10 (c) Furthermore, the composition of the Bird's Nest slag 4 was calculated based on sampling surveys, with the ratio of the furnace slag composition to the slag composition in the pulverized coal being 0.18:1.00. Additionally, the composition and quantity of the Bird's Nest slag 4 at a blowing rate of 0 were constant at a basicity (C / S) of 0.75, and were calculated as a Bird's Nest slag quantity of 64 kg / tp. Furthermore, basicity (C / S) is the ratio of CaO (mass%) to SiO2 (mass%) contained in the slag.

[0074] Furthermore, all the injected fine ore powder was directly reduced with coke. The relationship between the injection rate of the fine ore powder and the temperature of the molten slag 4 was obtained by subtracting the heat absorbed by the reduction reaction (endothermic portion) from the temperature at the boundary of the vortex zone (temperature of Bird's Nest 3). The obtained relationship is shown in... Figure 10 (d)

[0075] Secondly, the viscosity (μ) of the Bird's Nest slag 4 was determined. The temperature dependence of the viscosity of the Bird's Nest slag 4 at various flow ratios was experimentally determined.

[0076] use Figure 10 (d) The temperature change of the bird's nest section 3 (temperature of the bird's nest slag 4) was used to determine the viscosity (μ) of the bird's nest slag 4 based on the experimental values ​​obtained (details below). Furthermore, the value of the blowing rate of the fine ore = 0 was calculated using the viscosity estimation equation described in "Iron and Steel Sugiyama et al. vol. 73, 1987, p. 2044".

[0077] The relationship between the blowing rate of the fine powder ore obtained from the above steps and the viscosity (μ) of the Bird's Nest slag 4 is shown in the figure. Figure 10 (e) in.

[0078] Furthermore, regarding the dripping linear velocity (u) of the molten slag, based on the relationship described in "Materials and Processes, Kato et al., Vol. 28, 2015, S25," the relationship between the blowing rate of the fine ore and the dripping linear velocity was obtained. The obtained relationship is shown in... Figure 10 (f) in.

[0079] Furthermore, regarding the repression amount (h), based on the relationship described in "Materials and Processes, Kato et al., vol. 28, 2015, S25," the relationship between the blowing rate of the fine ore and the repression amount (h) was obtained. The obtained relationship is shown in... Figure 10 (g) in.

[0080] At this point, the cross-sectional area of ​​the filling layer is S = 6.67 m². 2 (Constant), regarding the amount of slag (W), using Figure 10 The value of (c).

[0081] Finally, the relationship between the blowing rate of the fine ore and the reduction in pressure loss (change in pressure loss) was determined. The pressure loss was calculated according to the formula described in "Iron and Steel, Fukutake et al., vol. 66, 1980, p. 1974". Furthermore, the calculated elements are shown in Table 3. The obtained relationship between the blowing rate of the fine ore and the change in pressure loss is shown in... Figure 10 (h)

[0082] Table 3

[0083] project unit numerical values pulverized coal injection rate kg / tp 215 Micronized ore blowing rate kg / tp 0～50 V: Gas volume in the furnace belly <![CDATA[Nm 3 / min]]> 11340 wind temperature ℃ 1180 Blower pressure kPa 420 S: Cross-sectional area of ​​the filling layer <![CDATA[m 2 ]]> 6.67 L: Bird's Nest height m 7.5 <![CDATA[p g Gas density <![CDATA[kg / m 3 ]]> 0.641 <![CDATA[μ g Gas viscosity Pa·s 0.00000627 ε: Porosity of the filling layer - 0.29 <![CDATA[d W Coke particle size m 0.023

[0084] Furthermore, the "furnace belly gas volume" in Table 3 is a calculated value of the total gas volume generated in front of the tuyere due to the combustion of coke brought in by the air injected from the tuyere, the oxygen used for enrichment and oxidation, the moisture in the blower, and the combustion of auxiliary fuels such as pulverized coal. It is expressed in Nm³. 3 / min represents the quantity of gas in the furnace belly. The method for calculating this "gas volume in the furnace belly" is described, for example, in Iron and Steel, Vol.48 (1962) No.12, p.1606.

[0085] like Figure 10As shown in (h), by increasing the blowing rate of the fine ore, the viscosity of the Bird's Nest slag 4 decreases, and the reduction in pressure loss increases (pressure loss decreases). However, if the blowing rate of the fine ore reaches 20 kg / tp or more, the amount of slag in the Bird's Nest area increases, and due to the decrease in temperature of the Bird's Nest slag 4, the reduction in pressure loss decreases (pressure loss increases). If the blowing rate of the fine ore is further increased to 50 kg / tp, compared to a blowing rate of 0 kg / tp, the pressure loss increases, and the effect of blowing the fine ore is lost.

[0086] However, in order to guide the viscosity of the bird's nest slag 4 by the temperature of the bird's nest section 3, it is preferable to conduct experiments in advance to determine how the mixing ratio of the molten ore (flux) and the slag temperature affect the viscosity of the slag.

[0087] The aforementioned preliminary experiments, as preparations, were conducted in advance. Figure 11 To prevent oxidation, ceramic paste is applied to the pure iron crucible 7 and the pure iron rotor 6 of the rotary torque meter 5. The pure iron rotor 6 of the rotary torque meter 5 is then calibrated using JS1000 calibration fluid, and the relationship between rotational speed and torque is pre-determined. This calibration yields a first-order regression equation, y = ax + b, from which the rotor coefficient (K0) can be calculated. Furthermore, the rotor coefficient can be obtained using K0 = standard viscosity (mPa·s) ÷ regression coefficient b.

[0088] After obtaining the rotor coefficient, a mixture of reagents (slag containing flux) is filled into a pure iron crucible 7 according to the prescribed formulation (shown in Table 4 below). The mixture is heated in an electric furnace to a specific temperature to melt the reagent. The heating temperatures are 1300℃, 1350℃, 1400℃, 1450℃, and 1500℃. The rotor (pure iron rotor 6) mounted on the rotary torque meter 5 is positioned at the center of the molten slag, and rotation begins. Viscosity stability is considered achieved when the measured torque change reaches 0.1% / min. After viscosity stability, measurements are continued for 1 minute, and the measured values ​​within this 1 minute represent the torque measurements. After measurement, rotation is stopped, and the experiment ends. Furthermore, data with unstable viscosity are excluded from the data.

[0089] As mentioned above, the torque is measured at a stable 1-minute interval as the torque value (torque (%)). Substituting the obtained torque (%) into the viscosity η (mPa·s) = torque (%) × K0 ÷ rotational speed (rpm), the viscosity η (mPa·s) of the slag with different flow ratios is calculated. The obtained slag viscosity η (mPa·s) is shown in Table 4.

[0090] Table 4

[0091]

[0092] Under the conditions of slag basicity C / S = 0.6 and C / S = 1.0, the viscosity (μ) of the Bird's Nest slag 4 corresponding to the blowing rate of the fine ore was calculated in a temperature-dependent manner using the above method. If the temperature dependence of the slag viscosity (μ) obtained in this way is summarized, then... Figure 12 and Figure 13 The result.

[0093] Depend on Figure 10 The viscosity values ​​are obtained from equation (d), and the relationship between the basicity and viscosity of the slag is obtained using an exponential function. As an example, the summarized relationship between the basicity and viscosity of the slag under a flow ratio of 20 kg / tp is shown below. Figure 14 In the middle. By Figure 14 The viscosity at alkalinity = 0.75 can be obtained from the relationship.

[0094] If we follow the above method for calculating viscosity and organize the relationship between the blowing rate and viscosity of fine ore powder, we can obtain... Figure 10 (e) is related.

[0095] Based on the steps described above... Figure 10 (e) is the relationship, in other words, based on Figure 6 Based on the relationship, it can be seen that compared with before injection, if the pressure loss decreases (the amount of pressure loss decreases increases, or the amount of pressure loss change is negative), the injection rate of fine ore is above 0 kg / tp and below 50 kg / tp, which can specify the upper limit of the injection rate of fine ore.

[0096] Furthermore, the details of the above calculation steps can be summarized in Table 5.

[0097] Table 5

[0098]

[0099] On the other hand, the lower limit of the injection rate of fine ore can be derived from experiments (actual machine testing) using a real blast furnace.

[0100] Blast furnace 1 used for this actual test is 2112m. 3 A real blast furnace has an iron tapping rate of 1.8 t / m³. 3 / day of blast furnace. With The sequence was changed, and the amount of fine ore injected into blast furnace 1 was changed while the test operation was carried out continuously for 5 days.

[0101] Furthermore, the fine ore injected into the actual blast furnace has the composition shown in Table 6.

[0102] Table 6

[0103]

[0104] Furthermore, the aforementioned micronized ore, after... Figure 8 It is crushed through the process shown.

[0105] The results of the actual test are shown in Table 7 below.

[0106] Table 7

[0107]

[0108] RAR = PC·CR. If the pressure drop is less than the bottom, then it is ○.

[0109]

Example

[0110]

[0111] [Comparative Example]

[0112]

[0113] Referring to Table 7, in both the examples and comparative examples, the pulverized coal ratio (pulverized coal injection rate) is 208 kg / tp (meeting the specification of 150 kg / tp or higher), and the loss on ignition (LOI) of the coal used as raw material for pulverized coal is 11.1 mass% (meeting the specification of 9.0 mass% to 12.0 mass%). Furthermore, the reducing material ratio (the sum of the pulverized coal ratio and the coke ratio) is 524 kg / tp in both the examples and comparative examples.

[0114] Under these conditions of pulverized coal ratio, loss on ignition, and reducing material ratio, the operation was carried out while injecting fine ore, and the pressure loss was measured compared to before injection. The measurement results show... Figure 7 middle.

[0115] like Figure 7 As shown, in the embodiments, the blowing rate of the fine ore is 2.5 kg / tp and 5.0 kg / tp, while in the comparative examples, the blowing rate of the fine ore is 0.0 kg / tp and 1.3 kg / tp.

[0116] Regarding the above embodiments and comparative examples, it can be seen that in the embodiments, the pressure loss changes are -1.72 kPa and -3.33 kPa, respectively. Compared with before the injection, the pressure loss is smaller and the ventilation is better. However, in the comparative examples, the pressure loss changes are 0.00 kPa and 0.73 kPa, respectively. The pressure loss is the same as before the injection, or compared with before the injection, the pressure loss is larger, and the ventilation is not improved.

[0117] Therefore, it can be determined that the ventilation improvement effect can be achieved when the blowing rate of the fine ore is above 2.5 kg / tp.

[0118] Based on a comprehensive assessment of the results of the above embodiments and comparative examples, it can be determined that pulverized coal is used as pulverized coal, and iron ore with a loss on ignition of 9% or more and 12% or less is used as fine ore. The injection rate of pulverized coal is 150 kg / tp or more, and the injection rate of fine ore is 2.5 kg / tp or more and 50.0 kg / tp or less. When pulverized coal and fine ore are injected from tuyeres 2, the ventilation of the lower part of blast furnace 1 can be improved by injecting fine ore from tuyeres 2.

[0119] Furthermore, the embodiments disclosed herein should be considered as illustrative rather than restrictive. In particular, matters not explicitly disclosed in the embodiments herein, such as operating conditions, various parameters, and the dimensions, weight, and volume of structures, do not deviate from the scope of what practitioners would normally implement, and use values ​​that would be easily conceived by a practitioner.

[0120] Symbol Explanation

[0121] 1 Blast Furnace

[0122] 2. Opportunities

[0123] 3. Bird's Nest Section

[0124] 4. Bird's Nest slag

[0125] 5. Rotary Torque Meter

[0126] 6 Pure iron rotor

[0127] 7 Pure iron crucible

Claims

1. A method for operating a blast furnace, characterized in that, Coal with a Hardgrove Grindability Index (HGI) of 40–90 is pulverized coal, and iron ore with a loss on ignition of 9% or more but less than 12% is pulverized fine ore. The pulverized coal injection rate is above 150 kg / tp, and the fine ore injection rate is above 2.5 kg / tp but below 20 kg / tp, with the pulverized coal and fine ore being injected together from the tuyeres. The maximum particle size of the pulverized coal and the fine ore is less than 1000 μm. The coal contains ash of 50%–60% SiO2 and 20%–30% Al2O3. The particle size of the fine ore is made to be consistent with that of the pulverized coal. The change in pressure loss is negative.

2. The blast furnace operation method according to claim 1, characterized in that, The iron ore and coal are crushed together.

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