Blast furnace operation method

Abstract

To provide an operation method of a blast furnace that enables proper furnace heat management at start-up after banking of the blast furnace.SOLUTION: An operation method of a blast furnace sets in advance a target numerical condition of a volume evaluation value to evaluate a volume of a SiO gas generation area formed around a raceway, and at least one of a hot metal Si concentration or a hot metal extraction ratio is adjusted so that the volume evaluation value satisfies the target numerical condition.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for operating a blast furnace during start-up after banking of the furnace. [Background technology]

[0002] Furnace heat management is important in blast furnace operation. Furnace heat management during start-up after blast furnace banking (stopping the blowing of air to the blast furnace while leaving the residual materials in the furnace, and shutting down the furnace in a state where it can be restarted) is particularly important from the viewpoint of realizing stable blast furnace operation.

[0003] Conventionally, the molten iron temperature has been widely used as a management index of furnace heat. Patent Document 1 discloses a furnace heat control method in which the temperature of the molten iron during tapping is accurately and precisely measured using an optical fiber covered with a metal tube, and the furnace heat level and furnace heat transition are estimated based on the temperature information. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-222610 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, when starting up a blast furnace after banking, the residues in the furnace are scraped out from the furnace. However, it is difficult to completely remove the residues in the furnace, and the furnace is usually started up with the residual pig iron lump remaining in the hearth.

[0006] The high-temperature molten iron generated by the reduction reaction with the coke and furnace gas drips onto the lump of pig iron at the hearth, and the lump of pig iron melts. In this case, the heat of the molten iron is used as the heat of dissolution of the lump of pig iron, and the temperature of the molten iron drops. On the other hand, the lump of pig iron at the hearth may not be dissolved by the molten iron. In this case, the thermal conductivity of the lump of pig iron is lower than that of the wall bricks of the blast furnace, so the amount of heat removed from the molten iron is small and the temperature of the molten iron hardly drops. As described above, the molten iron temperature varies depending on the amount of the molten pig iron that has melted, and therefore, it is difficult to use the molten iron temperature as a management index for the furnace heat during start-up after banking of the blast furnace.

[0007] In view of the above, an object of the present invention is to provide a method for operating a blast furnace that can appropriately perform furnace heat management during start-up after banking of the blast furnace. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a method for operating a blast furnace, comprising: (1) setting in advance a target numerical condition for a volume evaluation value for evaluating the volume of a SiO gas generation region formed around a raceway; and adjusting at least one of a molten iron Si concentration and a productivity so that the volume evaluation value satisfies the target numerical condition.

[0009] (2) The method for operating a blast furnace according to (1), characterized in that the setting of the target numerical conditions is performed by a relationship defining step of defining, for each volume evaluation value, a relationship between the productivity and the molten iron Si concentration, which varies depending on the volume evaluation value, and a target numerical condition setting step of setting target numerical conditions based on the relationship between the productivity and the molten iron Si concentration obtained in the relationship defining step and on past operating results of the blast furnace.

[0010] (3) A method for operating a blast furnace according to (1) or (2), characterized in that, when the target numerical conditions are not satisfied in the blast furnace operation, operational actions are implemented to improve the same. Effect of the Invention

[0011] According to the present invention, since furnace heat can be appropriately managed during start-up of a blast furnace after banking, rapid and stable start-up operation after banking can be realized. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of a blast furnace according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged view of the vicinity of the tuyere 2 in FIG. [Diagram 3] 1 is a flowchart showing an operation method for start-up after banking of a blast furnace in this embodiment. [Figure 4] 1 is a flowchart showing a procedure for creating a graph showing the relationship between the productivity and the Si concentration in molten iron. [Diagram 5] 1 is a graph showing the relationship between the productivity and the Si concentration of molten iron. [Figure 6] This is an example of a graph showing the relationship between the productivity and the molten iron Si concentration obtained in step 101, in which multiple past operational records of blast furnaces that had good start-ups after banking are plotted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] <About blast furnaces> Fig. 1 is a schematic diagram of a blast furnace according to an embodiment of the present invention. The blast furnace 1 is a bell-less type blast furnace, and includes a tuyere 2, an annular pipe 3, a blowpipe 4, a lance 5 for injecting pulverized coal, a rotating chute 6, and a tap hole 7.

[0014] The tuyere 2 is an inlet for blowing hot air generated in a hot stove (not shown) into the blast furnace 1, and a plurality of tuyere are provided in the lower part of the blast furnace 1 along the circumferential direction of the furnace.

[0015] The annular pipe 3 is disposed so as to surround the lower part of the blast furnace 1. A plurality of blowpipes 4 are provided intermittently in the circumferential direction on the annular pipe 3. The annular pipe 3 supplies hot air sent from the hot stove to the blowpipes 4.

[0016] Each blowpipe 4 is connected to the annular pipe 3 and is also connected to a different tuyere 2. The blowpipe 4 blows hot air sent from the annular pipe 3 into the blast furnace 1 through the tuyere 2.

[0017] The temperature of the hot air blown into the furnace is adjusted by controlling the amount of heat stored in the hot stove and the amount of hot air supplied. The oxygen content of the hot air can be adjusted by mixing air and oxygen in the hot stove. The moisture content of the hot air can be adjusted by dehumidifying or humidifying the hot air before it is blown from the hot stove into the blast furnace 1.

[0018] The lance 5 for injecting pulverized coal into the blowpipe 4. The lance 5 for injecting pulverized coal is inserted through each blowpipe 4, and the tip of the lance 5 for injecting pulverized coal extends into the inside of each blowpipe 4. The pulverized coal injected from the lance 5 for injecting pulverized coal is injected into the blast furnace 1 together with the hot air passing through the blowpipe 4.

[0019] The rotating chute 6 rotates around an axis extending in the vertical direction and charges the ore layer forming raw material and the coke layer forming raw material as blast furnace raw materials so that the ore layer and the coke layer are alternately formed in layers inside the furnace. The ore layer forming raw material can be sintered ore, pellets, lump ore, or unburned carbon-containing agglomerated ore. The ore layer forming raw material can also contain materials other than ore (e.g., reduction assistants such as small lump coke). The coke layer forming raw material may contain ferro coke. The inclination angle and rotation speed of the rotating chute 6 can be controlled to charge the blast furnace raw material at the desired position.

[0020] The tap hole 7 is provided at the bottom of the blast furnace 1 and taps the molten iron produced by the reduction of the raw materials for forming the ore layer. A plurality of tap holes 7 are provided around the periphery of the furnace, and the molten iron can be tapped continuously or intermittently.

[0021] Fig. 2 is an enlarged view of the vicinity of the tuyere 2 in Fig. 1. Referring to Fig. 2, a combustion space (raceway 10) is formed in the furnace by the wind pressure of the hot air blown into the furnace from the tuyere 2. Inside the raceway 10, a group of coke particles burns while swirling, and the ore is reduced. In addition, a SiO gas generation region 100 is formed as a coke packed bed so as to surround the raceway 10. In the SiO gas generation region 100, a high-temperature reaction occurs in which SiO gas and carbon monoxide are generated by the reaction of C and SiO2 contained in the raw material for forming the coke layer (see formula (1) described later for the reaction formula).

[0022] The present inventors have found that rapid and stable start-up operation is possible by controlling the furnace heat during start-up after blast furnace banking based on the volume of the SiO gas generation region 100. Here, during start-up after blast furnace banking, the position of the cohesive zone (see FIG. 1) formed in the blast furnace 1 is high. Therefore, most of the SiO gas generated in the SiO gas generation region 100 is absorbed by the dripping molten iron. From this, it is considered that the molten iron Si concentration (%) is a process determined by the generation rate of SiO gas, that is, the SiO gas generation rate is determined (see Nippon Steel Techniques No. 413, pages 123-129). By controlling the relationship between the production rate theoretically derived from this generation rate limiting and the Si concentration (%) of the molten iron (hereinafter also referred to as the molten iron Si concentration), the volume of the SiO gas generation region 100 can be appropriately controlled.

[0023] In view of these points, the present inventors have found that rapid and stable start-up is possible by setting in advance a target numerical condition for an evaluation value (hereinafter referred to as a volume evaluation value) for evaluating the volume of the SiO gas generation region 100, using the relationship between the productivity and the molten iron Si concentration as an operational management index, and performing an operation to adjust at least one of the productivity or the molten iron Si concentration so that the volume evaluation value satisfies the target numerical condition at the time of start-up after blast furnace banking. Note that "adjusting the molten iron Si concentration so that the volume evaluation value satisfies the target numerical condition" refers to determining an appropriate condition for the molten iron Si concentration based on the productivity and the target numerical condition for the volume evaluation value, and adjusting the molten iron Si concentration so that the appropriate condition is satisfied. In addition, "adjusting the productivity so that the volume evaluation value satisfies the target numerical condition" refers to determining an appropriate condition for the productivity based on the molten iron Si concentration and the target numerical condition for the volume evaluation value, and adjusting the productivity so as to satisfy the appropriate condition.

[0024] Hereinafter, a method for operating a blast furnace at start-up after banking based on the above findings will be described with reference to the flowchart in Fig. 3. Fig. 3 is a flowchart showing a method for operating a blast furnace at start-up after banking in this embodiment. Steps 101 and 102 are performed in advance before start-up after banking of the blast furnace. Note that "start-up" refers to the period from when the blast furnace is restarted (hot air blowing is resumed) until the productivity of the blast furnace during normal operation is reached.

[0025] <Step 101> First, a graph that defines the relationship between the productivity and the Si concentration in the molten iron is created based on the generation rate-limiting theory (step 101). The procedure for creating this graph will be described in more detail with reference to the flowchart shown in FIG.

[0026] As described above, during start-up after blast furnace banking, the position of the cohesive zone (see FIG. 1) formed in the blast furnace 1 is high, so the molten iron Si concentration (%) can be considered to be controlled by the SiO gas generation rate. The reaction in the SiO gas generation region 100 can be defined by the following formula (1). In formula (1), "SiO(g)" refers to SiO gas. SiO2 + C = SiO(g) + CO (1) The forward reaction rate in formula (1) (the reaction rate producing SiO gas) is calculated by the following reaction rate formula: R1 = k1 C SiO2 (2) Here, R1 is the forward reaction rate (mol / (cm 3 s), k1 is the reaction rate constant (s -1 ), C SiO2 is the concentration of SiO2 (mol / cm3) relative to the volume of the SiO gas generation region 100 3 ) and can be calculated from the properties of the coke charged into the top bunker. k1 is calculated by the following formula. k1=2.0×10 4 exp(-69000 / RT) (3) where T is the absolute temperature of the molten iron (K) and R is the gas constant (cal / (mol K)).

[0027] In advance, (A) the value of the molten iron temperature (corresponding to T mentioned above) and (B) the blast furnace volume V f (m 3 ) SiO gas generation region index V, which indicates the volume of the SiO gas generation region 100 SiO (m 3 In other words, in this embodiment, the volume ratio D(%) is used as the volume evaluation value. Here, since the volume of the blast furnace to be started is known, the set volume ratio D is multiplied by the blast furnace volume V f By multiplying by , the SiO gas generation region index V SiO is calculated (step 101a).

[0028] By substituting the preset molten iron temperature T into the above equation (3), the reaction rate constant k1(s -1 ) is calculated (step 101b).

[0029] k1 calculated in step 101b and C SiO2 By substituting into the above equation (2), the forward reaction rate R1 (mol / (cm 3 ·s) is calculated (step 101c).

[0030] R1(mol / (cm 3 s), the SiO gas generation region index V calculated in step 101a SiO Multiplying this by the number of seconds in a day (86400 (s)) gives the number of moles of SiO gas generated per day, n SiO (mol / d) is calculated (step 101d).

[0031] Here, assuming that all of the SiO gas generated per unit time and unit volume is transferred to Si in the molten iron, the n calculated in step 101d SiO The mass of Si contained in the molten iron per day m Si (t / d) is calculated (step 101e).

[0032] m calculated in step 101e Si The molten iron Si concentration (%) is calculated by dividing the amount of iron produced per day (t / d) by the amount of iron produced per day (t / d) (step 101f). f (m 3 ) to obtain the productivity (t / d / m 3 ) is calculated (step 101g).

[0033] The molten iron Si concentration (%) calculated in step 101f and the productivity (t / d / m 3) and a graph is created that defines the relationship between the productivity and the molten iron Si concentration (step 101h). In step 102, which will be described later, a process of selecting an optimal volume fraction D from among a plurality of volume fractions D is required, so in step 101, a graph needs to be created for each of a plurality of predetermined volume fractions D. These plurality of volume fractions D can be set, for example, in a range of 1% to 10% at 1% intervals based on operational performance.

[0034] A graph showing the relationship between the productivity and the molten iron Si concentration, which was created in the above steps 101a to 101h, is shown in FIG. 5. The graph in FIG. 5 shows the relationship between the productivity and the molten iron Si concentration, which was created in the above steps 101a to 101h, when the molten iron temperature T was set to 1510°C and the blast furnace volume V f (m 3 ) SiO gas generation region index V SiO (m 3 The volume fraction D (%) of the molten iron is set to 2% and 6%, respectively. The molten iron temperature T is set to 1530°C, and the blast furnace volume V f (m 3 ) SiO gas generation region index V SiO (m 3 5 shows the results when the volume fraction D (%) of molten iron is set to 2% and 6%, respectively. In FIG. 5, only the graphs for the volume fraction D of 2% and 6% are shown, but as mentioned above, the graphs may be created using other criteria (for example, in the range of 1% to 10% at 1% intervals). Note that as the volume fraction D increases, the molten iron Si concentration for the same productivity inevitably increases.

[0035] From Fig. 5, it can be seen that when the molten iron temperature T and the volume fraction D are constant, the productivity and the molten iron Si concentration are inversely proportional to each other, and the gradient increases as the productivity decreases. Therefore, at low productivity such as immediately after the blast furnace is restarted after banking, the molten iron Si concentration is strongly affected by the productivity. On the other hand, from Fig. 5, it can be seen that the molten iron Si concentration is not easily affected by the molten iron temperature. In view of these points, the present inventor has found that appropriate furnace heat management can be realized by using the productivity and the molten iron Si concentration as operation management indexes and controlling the volume of the SiO gas generation region 100 based on these.

[0036] <Step 102> Next, referring again to Fig. 3, target numerical conditions are set so as to achieve a good start-up after banking based on the graph defining the relationship between the productivity and the molten iron Si concentration obtained in step 101 and the past operational records of the blast furnace (step 102). The four graphs shown in Fig. 6 are graphs of the theoretically derived relationship between the productivity and the molten iron Si concentration according to the procedure of step 101. The preset volume fractions D (%) are 2%, 2.5%, 4% and 6%, respectively, and the preset molten iron temperatures are all 1530°C.

[0037] Among the past operational records of the blast furnace, good operation data in which the start-up after banking was good is plotted on this graph, and the target numerical condition of the volume fraction D (%) can be set based on the volume fraction D (%) of two graphs drawn at positions sandwiching the area where these good operation data are concentrated (this setting method is hereinafter referred to as setting method A). In the illustrated example, when the productivity is 0.5 or more and less than 1.2, the good operation data is concentrated in the area sandwiched between the graphs of D: 4% and D: 6%. Therefore, when the productivity is 0.5 or more and less than 1.2, it is desirable to set the target numerical condition of the volume fraction D (%) to 4% or more and 6% or less. When the productivity is 1.2 or more and less than 1.5, the good operation data is concentrated in the area sandwiched between the graphs of D: 2% and D: 4%. Therefore, when the productivity is 1.2 or more and less than 1.5, it is desirable to set the target numerical condition of the volume fraction D (%) to 2% or more and 4% or less. When the productivity is 1.5 or more and less than 2.0, the good operation data is concentrated in the area between the graphs of D: 2% and D: 2.5%. Therefore, when the productivity is 1.5 or more and less than 2.0, it is desirable to set the target numerical condition of the volume fraction D (%) to 2% or more and 2.5% or less. As shown in Figure 6, once the target numerical condition is determined, the relationship between the corresponding molten iron Si concentration and the productivity can be understood.

[0038] In this embodiment, the target numerical condition of the volume fraction D (%) is set by the above-mentioned setting method A, but the setting method is not limited to this. For example, the target numerical condition may be set so that the target numerical condition of the volume fraction D (%) changes continuously over the entire productivity (0.5 or more and less than 1.5) at the time of startup based on a plot of good operation data in which startup after banking was good among past operation results of the blast furnace (hereinafter, this setting method is referred to as setting method B). The region S that satisfies the target numerical condition set by setting method B is shown by hatching in FIG. 6. Here, "the target numerical condition changes continuously" refers to the fact that the target numerical condition as the left limit of an arbitrary productivity and the target numerical condition as the right limit of the arbitrary productivity are mutually consistent. "The target numerical condition as the left limit of an arbitrary productivity" refers to the target numerical condition when the productivity reaches the arbitrary productivity along the direction of the arrow X shown in FIG. 6 (the direction of increasing the productivity). The "target numerical condition as the right limit of an arbitrary productivity" refers to the target numerical condition when the productivity is made to reach the arbitrary productivity along the direction of the arrow Y shown in FIG. 6 (the direction of reducing the productivity).

[0039] When setting method A is adopted, the target numerical conditions change discontinuously around the productivity of 1.2. In contrast, in setting method B, the target numerical conditions change continuously over the entire productivity range at start-up (0.5 or more and less than 1.5). Therefore, according to setting method B, even if the productivity changes as start-up progresses, no significant improvement action (see step 105 described later) is required, and more stable blast furnace operation can be performed.

[0040] In addition, for example, when the productivity is 1.5 or more and less than 2.0, it can be seen that the good operation data is concentrated in the vicinity of the graph of D: 2%, so the target numerical condition of the volume fraction D (%) may be set to about 2%.

[0041] Fig. 6 is merely an example of the present invention, and the target numerical conditions set in the present invention are not limited to the above-mentioned target numerical conditions. That is, since the graph in Fig. 6 changes depending on the properties of the coke used, the target numerical conditions are not limited to the above-mentioned ranges. In addition, the target numerical conditions can be set to a target value (one value) instead of a range.

[0042] <Step 103> Next, a new blast furnace was started up after banking, and its productivity (t / d / m 3 ) and the molten iron Si concentration (%) are calculated as operation management indexes (step 103). The productivity is roughly proportional to the volume of hot air blown into the blast furnace 1 via the annular pipe 3 → blowpipe 4 → tuyere 2, so the productivity can be estimated by measuring the volume of hot air. The molten iron Si concentration can be calculated by performing a component analysis of the Si concentration of the molten iron tapped from the tap hole 7 of the blast furnace 1. The productivity (t / d / m 3 The method for calculating the Si concentration (%) of the molten iron is not limited to the above method, and various known methods can be used.

[0043] <Step 104, 105> The productivity (t / d / m 3 ) and the target numerical conditions set in step 102, an optimum condition for the molten iron Si concentration (%) is determined, and it is judged whether the molten iron Si concentration (%) calculated in step 103 satisfies the optimum condition (step 104). If the molten iron Si concentration (%) calculated in step 103 satisfies the optimum condition (step 104 Yes), it is judged that "start-up after banking is good" and the furnace thermal management is terminated. On the other hand, if the molten iron Si concentration (%) calculated in step 103 does not satisfy the optimum condition (step 104 No), it is judged that "start-up after banking is poor" and an improvement action is taken to adjust the molten iron Si concentration (step 105).

[0044] The determination in step 104 and the improvement action in step 105 will be described below with reference to Fig. 6. As an example, the calculation results in step 103 are plotted as circled points A and B in Fig. 6.

[0045] When the calculation result in step 103 is point A in FIG. 6, the optimum condition of the molten iron Si concentration (1.8% to 2.8%) is determined based on the productivity (1.1) of point A and the target numerical condition of the volume fraction D (4 to 6%). Since the molten iron Si concentration (4.0%) of point A is higher than the upper limit (2.8%) of the optimum condition, improvement action is taken to lower the molten iron Si concentration while maintaining the productivity to satisfy the optimum condition of the molten iron Si concentration (1.8% to 2.8%). As the improvement action, an action to reduce the heat in the blast furnace 1 (increase the blast moisture, decrease the RAR, decrease the PCR, etc.) is taken.

[0046] When the calculation result in step 103 is point B in FIG. 6, the optimum condition of the molten iron Si concentration (3.4% to 5.0%) is determined based on the productivity of point B (0.6) and the target numerical condition of the volume fraction D (4 to 6%). Since the molten iron Si concentration of point B (3.0%) is lower than the lower limit of the optimum condition (3.4%), improvement action is taken to increase the molten iron Si concentration while maintaining the productivity, so that the optimum condition of the molten iron Si concentration (3.4% to 5.0%) is satisfied. As the improvement action, an action to increase the heat in the blast furnace 1 (reducing the blast moisture, increasing the RAR, increasing the PCR, etc.) is taken.

[0047] After the above-mentioned improvement action (step 105) is implemented, the productivity (t / d / m 3 ) and the molten iron Si concentration (%) are recalculated (step 103), and it is determined again whether the calculated molten iron Si concentration (%) satisfies the optimum conditions (step 104).

[0048] (Example) Blast furnace 1 at steelworks A was started up from banking. Using the above-mentioned setting method B, the region S shown in Fig. 6 was set as the target numerical condition, and furnace heat management was performed using the relationship between the productivity and the molten iron Si concentration as the operational management index.

[0049] During the start-up process of blast furnace 1, the productivity was 0.77 (t / d / m 3 ), the molten iron Si concentration was 4.2% (see point C in Fig. 6). On the other hand, in the region S shown in Fig. 6, when the productivity was 0.77 (t / d / m 3 ), the optimum condition for the molten iron Si content (%) was determined to be 2.5% to 4.0%. Therefore, improvement actions were taken to lower the molten iron Si content while maintaining the same productivity, so that the optimum condition for the molten iron Si content (2.5% to 4.0%) was satisfied. The improvement actions were to reduce the blast moisture to 30 (g / Nm 3 ) to 34(g / Nm 3 As a result, the molten iron Si concentration (%) was reduced to 3.0%, satisfying the optimum conditions.

[0050] During another start-up of blast furnace 1, the productivity was 1.06 (t / d / m 3 ), the molten iron Si concentration was 2.95 (%) (see point D in Fig. 6). On the other hand, in the region S shown in Fig. 6, when the productivity was 1.06 (t / d / m 3 ), the optimum condition for the molten iron Si content (%) was determined to be 1.4% to 2.6%. Therefore, improvement actions were taken to lower the molten iron Si content while maintaining the productivity, so as to satisfy the optimum condition for the molten iron Si content (1.4% to 2.6%). The improvement action was to lower the PCR from 80 (kg / t) to 77 (kg / t). As a result, the molten iron Si content (%) was reduced to 2.5%, and the optimum condition was satisfied.

[0051] As in the above-mentioned embodiment, the start-up of the blast furnace after banking was carried out using the blast furnace operation method according to the present invention. As a result, no troubles such as hanging due to excessive furnace heat or slag discharge problems due to a drop in furnace heat occurred during the start-up process, and the start-up could be completed quickly and stably.

[0052] (Modification) In the above embodiment, a graph is created in step 101 to define the relationship between the productivity and the Si concentration in the molten metal. However, the method for defining the relationship between the productivity and the Si concentration in the molten metal is not limited to this, and a data table such as a table may be created, for example.

[0053] (Modification) In the above embodiment, in step 104, the productivity (t / d / m 3 ) and the target numerical conditions set in step 102, an appropriate condition for the molten iron Si concentration (%) is determined, and it is determined whether the molten iron Si concentration (%) calculated in step 103 satisfies the appropriate condition. However, the present invention is not limited to this, and the tapping rate (t / d / m 3 ) and the optimum conditions are determined, and the productivity (t / d / m 3 ) satisfies the optimum condition. In this case, in step 105, an improvement action is taken to adjust the productivity so that the optimum condition is satisfied. The case where an improvement action is taken to adjust the productivity is described below with reference to Figs. 3 and 6 again. Note that setting method A is adopted for setting the target numerical condition for the volume fraction D (%).

[0054] When the calculation result in step 103 is point A in FIG. 6, the optimum condition for the productivity (0.5-0.8) is determined based on the molten iron Si concentration at point A (4.0%) and the target numerical condition for the volume fraction D (4-6%). Since the productivity at point A (1.1) is higher than the upper limit of the optimum range (0.8), an improvement action is taken to lower the productivity while maintaining the molten iron Si concentration so as to satisfy the optimum condition for the productivity (0.5-0.8). As an improvement action, for example, an action to reduce the blast rate is taken. When the optimum condition for the productivity (0.5-0.8) is satisfied by lowering the productivity while maintaining the molten iron Si concentration at point A, for example, the blast rate is reduced to 3000 (Nm 3 / min) to 2950(Nm 3 / min).

[0055] When the calculation result in step 103 is point B in FIG. 6, the optimum condition for the productivity (0.7 to 1.0) is determined based on the molten iron Si concentration at point B (3.0%) and the target numerical condition for the volume fraction D (4 to 6%). Since the productivity at point B (0.6) is lower than the lower limit (0.7) of the optimum range, improvement action is taken to increase the productivity while maintaining the molten iron Si concentration so as to satisfy the optimum condition for the productivity (0.7 to 1.0). As an improvement action, for example, an action to increase the blast rate is taken. When increasing the productivity while maintaining the molten iron Si concentration at point B to satisfy the optimum condition for the productivity (0.7 to 1.0), for example, the blast rate is increased to 1600 (Nm 3 / min) to 1650(Nm 3 / min).

[0056] Further, as an alternative method of step 104, the productivity (t / d / m 3 ) and the molten iron Si concentration (%), and the target numerical conditions set in step 102, the productivity (t / d / m 3 ) and the optimum conditions for the molten iron Si concentration (%) are determined, and the productivity (t / d / m 3 ) and the molten iron Si concentration (%) may be determined to satisfy the respective optimum conditions. In this case, in step 105, 3 ) improvement action may be taken to adjust the tapping rate so as to satisfy the optimum condition for the molten iron Si concentration (%), and improvement action may be taken to adjust the molten iron Si concentration so as to satisfy the optimum condition for the molten iron Si concentration (%), or improvement action may be taken that can adjust both the tapping rate and the molten iron Si concentration.

[0057] (Modification) In the above embodiment, the volume evaluation value for evaluating the volume of the SiO gas generation region 100 is the blast furnace volume V f (m 3 ) The SiO gas generation region index V indicates the volume of the SiO gas generation region 100 SiO (m 3The volume ratio D (%) of the SiO gas generation region 100 is used, but the present invention is not limited to this. For example, 3 The volume (m 3 ) is calculated by, for example, measuring the temperature inside the blast furnace 1 with a probe inserted into the blast furnace 1 from the outside, and calculating the volume (m ) of the SiO gas generation region 100 based on the measurement results. 3 ) can be used to estimate [Explanation of symbols]

[0058] 1 blast furnace 2 tuyere 3 annular pipe 4 blowpipe 5 lance for pulverized coal injection; 6 swivel chute; 7 tap hole

Claims

[Claim 1] A method for operating a blast furnace during start-up after banking, comprising the steps of: A target numerical condition for a volume evaluation value for evaluating the volume of a SiO gas generation region formed around the raceway is set in advance; The target numerical conditions are set as follows: A relationship defining step of creating a graph defining a relationship between the productivity and the molten iron Si concentration, which varies depending on the volume evaluation value, for each of a plurality of predetermined volume evaluation values; A target numerical condition setting step of plotting good operation data, which is from past operation records of the blast furnace and shows good start-up after banking, on the graph obtained in the relation determination step, and comparing the graph with the good operation data to obtain a volume evaluation value that will result in good start-up after banking, and setting the volume evaluation value as a target numerical condition; It is carried out by If the volume evaluation value is lower than the target numerical condition, an operational action is taken to increase the molten iron Si concentration and / or increase the productivity to increase the volume evaluation value; If the volume evaluation value is higher than the target numerical condition, the molten iron Si concentration is reduced and / or the productivity is reduced, and operational action is taken to reduce the volume evaluation value. A method for operating a blast furnace comprising the steps of:

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