Estimation method of dropping molten iron temperature in blast furnace and operation method of blast furnace

Abstract

To improve the estimation accuracy of a dropping molten iron temperature.SOLUTION: An estimation method of a dropping molten iron temperature in a blast furnace includes: a relational information acquisition step of acquiring in advance relational information between a temperature measurement time and a molten iron temperature in a non-operation period in which an operation of the blast furnace is not performed, when an elapsed time from the start of tapping to the measurement of the molten iron temperature is defined as the temperature measurement time; a regression coefficient acquisition step of acquiring a slope of a regression line of the temperature measurement time and the molten iron temperature based on the relationship information acquired in the relational information acquisition step; and a correction step of correcting the measured molten iron temperature to the molten iron temperature when the tapping completion time has elapsed based on the slope acquired in the regression coefficient acquisition step to obtain the dropping molten iron temperature.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for estimating the temperature of dripping molten iron in a blast furnace. [Background technology]

[0002] In recent years, blast furnace processes have been required to reduce CO2 emissions in order to prevent global warming, and blast furnace operation under low reducing agent ratio conditions is being promoted. However, operation under low reducing agent ratio conditions can easily lead to instability in the furnace, which can result in fluctuations in production volume and a decrease in furnace heat.

[0003] For this reason, there is an ever-increasing need for stabilization of blast furnace conditions, and methods are being implemented and considered to predict instability in advance by improving the accuracy of molten iron temperature measurement or prediction, detecting abnormalities, etc. In addition, because raising the molten iron temperature above the control value means that the reducing agent ratio is excessive, there is an increasing need to accurately control the molten iron temperature from the perspective of reducing CO2 emissions.

[0004] The furnace heat (heat level) inside the blast furnace that should be kept constant during furnace start-up is the temperature of the dripping molten iron before it reaches the molten iron reservoir at the hearth. Maintaining a constant heat level inside the blast furnace stabilizes the reactions inside the furnace, ultimately achieving stable operation. However, because there is no established method for directly measuring the dripping molten iron temperature, the measured molten iron temperature is used as a management indicator for blast furnace operation.

[0005] In an actual blast furnace, the molten iron temperature is measured using an immersion expendable thermocouple after it has been retained in the molten iron basin at the hearth for a certain period of time and then tapped out of the taphole. The measured molten iron temperature decreases due to heat removal from the blast furnace hearth, sidewalls, and tapping lane, as well as heat radiation to the atmosphere. This can result in a low temperature being measured regardless of the temperature of the dripping molten iron. In this case, if the reducing agent rate is increased because the molten iron temperature is low, the dripping molten iron temperature may rise above the control value. Therefore, such an operational action is unnecessary from the perspective of controlling the dripping molten iron temperature and undesirable from the perspectives of reducing CO2 emissions and stabilizing the furnace interior.

[0006] Patent Document 1 discloses a method of attaching a temperature sensor to the drilling pit of a drilling machine and measuring the molten iron temperature at the drilling position in a blast furnace. Patent Document 2 discloses a method of continuously capturing images of the iron flowing out of the tap hole, determining the molten iron temperature from the brightness of the molten iron in the captured images, and calculating the average molten iron temperature. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2023-131619 A [Patent Document 2] Patent No. 4580466 [Non-patent literature]

[0008] [Non-Patent Document 1] "Three-dimensional Dynamic Simulator for Blast Furnace", ISIJ International, Vol. 39 (1999), No. 1, p. 15-22 (Koji TAKATANI et al.) [Non-patent document 2] "Development of a Blast Furnace Mathematical Model" (Nippon Steel Sumitomo Metal Technical Report, No. 410, pp. 73-79, 2018) (Nishioka et al.) Summary of the Invention [Problem to be solved by the invention]

[0009] However, because the molten iron temperature changes from moment to moment due to factors such as heat transfer from the hearth and its side walls, the degree of deviation between the measured molten iron temperature and the dripping molten iron temperature is not constant. In addition, the time required to measure the molten iron temperature varies depending on the worker, working environment, and temperature measurement method. Therefore, a means is needed to accurately estimate the dripping molten iron temperature regardless of the measurement time or method. [Means for solving the problem]

[0010] As mentioned above, the amount of heat removed at the hearth is thought to be affected by the residence time of the molten iron at the hearth, but the molten iron temperature is affected by operational controls, various disturbances, measurement errors, etc. Therefore, it has not been possible to clearly understand the relationship between the molten iron temperature and the temperature measurement time based on data acquired over a long period of time. In addition, because the disturbances are large, there have been few precedents for operating a furnace without any operational controls. As a result, it has been difficult to clearly understand the effect of the temperature measurement time on the molten iron temperature.

[0011] In order to solve the above-mentioned problems, the method of estimating the dripping hot metal temperature according to the present invention is characterized by comprising: (1) a relationship information acquisition step of acquiring in advance relationship information between the temperature measurement time and the hot metal temperature during a non-operation period in which the blast furnace is not operated, where the temperature measurement time is defined as the time elapsed from the start of tapping until the hot metal temperature is measured; a regression coefficient acquisition step of calculating the slope of a regression line of the temperature measurement time and the hot metal temperature based on the relationship information acquired in the relationship information acquisition step; and a correction step of calculating the dripping hot metal temperature by correcting the measured hot metal temperature to the hot metal temperature when the tapping completion time has elapsed based on the slope acquired in the regression coefficient acquisition step.

[0012] (2) The method for estimating the temperature of dripping molten iron in a blast furnace according to (1) above, characterized in that the relevant information acquisition step is a step of acquiring the relevant information based on actual measurement data of an actual blast furnace.

[0013] (3) The method for estimating the temperature of dripping molten iron in a blast furnace according to (2) above, characterized in that the non-operation period is at least 24 hours or more.

[0014] (4) The method for estimating the temperature of dripping molten iron in a blast furnace according to (1) above, characterized in that the relevant information acquisition step is a step of acquiring the relevant information based on analytical processing using a blast furnace mathematical model.

[0015] (5) The method for estimating the dripping hot metal temperature of a blast furnace according to (4) above, characterized in that the analytical processing using the blast furnace mathematical model comprises: a first processing step of acquiring information on the change in the hot metal temperature over time when the operation is carried out after performing parameter adjustment using data corresponding to the operation data for a period for which the slope of the regression line is desired as input conditions; a second processing step of correcting the hot metal temperature measured during the operation period to a hot metal temperature from which the influence of the operation has been removed, based on the information acquired in the first processing step; and a third processing step of acquiring the relationship information based on the hot metal temperature measured during a period when the operation is not carried out and the hot metal temperature obtained in the second processing step.

[0016] (6) A method for estimating the temperature of dripping molten iron in a blast furnace according to any one of (1) to (3) above, characterized in that the tapping completion time is an arithmetic mean value of the tapping completion times during the non-operation period.

[0017] (7) A method for estimating the dripping hot metal temperature in a blast furnace according to any one of (1) to (3) above, characterized in that the correction step is a step of calculating the dripping hot metal temperature based on the following formula (1), where Tmeasure is the measured hot metal temperature, t is the time for temperature measurement, t is the time for completion of tapping, and a is the slope obtained in the regression coefficient obtaining step: T=a*(tave-t)+Tmeasure...Equation (1)

[0018] (8) A method for operating a blast furnace, characterized in that, when the dripping molten iron temperature estimated using the estimation method according to any one of (1) to (3) above differs from a control value, an operation is carried out to bring the dripping molten iron temperature closer to the control value. [Effects of the Invention]

[0019] According to the present invention, by clarifying the relationship between the temperature measurement time and the molten iron temperature in advance, the measured molten iron temperature can be corrected to a value close to the actual dripping molten iron temperature regardless of the temperature measurement time or method. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic cross-sectional view of a blast furnace. [Figure 2] FIG. 10 is a scatter diagram showing an example of relationship information. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0022] 1 is a schematic diagram of the vicinity of a tap hole 2 and a tap runner 3 in a blast furnace 1 of this embodiment. The blast furnace 1 is provided with approximately three to five tap holes 2 in the circumferential direction for discharging molten metal and slag from the lower part of the blast furnace, and a tap runner 3 for flowing the molten metal and slag is provided ahead of the tap holes 2. A skimmer 4 is provided in the tap runner 3, and the molten metal and slag that flow from the tap hole 2 into the tap runner 3 are gravity-separated by the skimmer 4 into molten metal M and slag SL. Since the molten metal M has a larger specific gravity than the slag SL, it passes under the skimmer 4 and is discharged into a torpedo car (not shown).

[0023] Generally, once the tap hole 2 is opened (tapping begins), tapping continues for about 2 to 3 hours. However, towards the end of tapping, it becomes difficult to remove the molten metal and slag, so after about 2 to 3 hours, the tap hole 2 is closed (tapping completed) and a new tap hole 2 is opened in a different or the same direction. The process from opening the tap hole 2 to closing it is sometimes referred to as "TAP." Depending on the blast furnace and the operating conditions, the taps of the two tap holes 2 may overlap in time.

[0024] The temperature of the molten pig iron is generally measured at point D on the outlet side of the skimmed iron 4. An immersion expendable thermocouple is generally used as the temperature measuring device. However, as described in Patent Document 1, the temperature may be measured using a temperature sensor attached to the drilling pit, or as described in Patent Document 2, the molten pig iron temperature may be determined based on the brightness of an image of the molten pig iron. The frequency of temperature measurement varies depending on the blast furnace and measuring equipment, but with immersion expendable thermocouples it is often measured about once every 30 minutes.

[0025] In blast furnace operation, "set values" include blast conditions (e.g., blast volume, oxygen enrichment amount, blast moisture, amount of material injected from the tuyere, such as pulverized coal injection amount, and type of pulverized coal), raw material charging conditions (amount of material charged from the furnace top, such as ore charging amount and coke charging amount, and components of ore and coke), and pressure conditions (furnace top pressure, etc.). However, even if the set values ​​are constant, fluctuations often occur in practice due to some factor, and this is defined as "disturbance fluctuation" in this specification. In addition, intentionally changing the above-mentioned "set values" is defined as "operational manipulation."

[0026] Based on the above definitions, a method for estimating the dripping hot metal temperature according to this embodiment will be described. The method for estimating the dripping hot metal temperature includes a related information acquisition step, a regression coefficient acquisition step, and a correction step. Each step will be described in detail below.

[0027] >Related information acquisition step< In the relation information acquisition step, relation information between the temperature measurement time and the molten iron temperature during a non-operation period when no operation was performed is acquired based on the actual measurement data of the blast furnace. The relevant information may be obtained by analytical processing using a blast furnace mathematical model. The reason for targeting the non-operation period is that by eliminating the influence of operational operations on the molten iron temperature, the accuracy of estimating the molten iron dripping temperature based on the regression coefficients described below can be improved. Here, even if a period includes the time during which an operation is performed, if the time during which the operation is performed is short, the period can be regarded as a "non-operation period." For example, if the five minutes immediately after the start of an operation are defined as the time during which an operation is performed, and if no operation is performed during 99% or more of period A and no operation that exceeds ±2% of the original set value is performed, period A can be regarded as a "non-operation period." In other words, even if no operation is performed during 99% or more of period A, it is desirable not to regard period A as a "non-operation period" if even one major operation is performed. The temperature measurement time is the time elapsed from the start of tapping to the time the molten iron temperature is measured. The non-operation period is preferably at least 24 hours or more. If the non-operation period is too short, appropriate related information cannot be obtained, and since the impact on the operation of some blast furnaces remains for about 8 hours, a certain period of time must pass in order to minimize the impact on operation.

[0028] Figure 2 is an example of relational information (scatter diagram), and shows actual furnace data for a certain blast furnace during a non-operation period (approximately one week). The vertical axis represents the measured molten iron temperature (°C), and the horizontal axis represents the temperature measurement time (min). The relational information is obtained by measuring the temperature several times during one tap and plotting the measured molten iron temperatures sequentially for each tap hole 2. Since the temperature measurement time is not fixed, the relational information shown in the figure can be obtained. The temperature was measured according to the method shown in Figure 1. However, as mentioned above, the temperature measurement method is not limited to this.

[0029] >Regression coefficient acquisition step< After creating a scatter diagram, the data plotted on the scatter diagram is fitted to a linear function using, for example, the least squares method, to determine the slope (regression coefficient) of the regression line for the temperature measurement time and molten iron temperature. In the example in Figure 2, the slope of the regression line is 0.2, and although the effects of disturbance fluctuations and measurement errors that do not require operational control remain, the R 2 The coefficient of determination was 0.2947. Therefore, a correlation was found between the temperature measurement time and the molten iron temperature. 2 If the coefficient of determination is 0.2947, it can be assessed that there is a correlation.

[0030] >Correction Step< The regression line confirmed a "positive correlation" in which the longer the temperature measurement time, the higher the molten iron temperature. As time passes from the start of tapping, the amount of molten iron that had accumulated near tap hole 2 before tapping decreases, and it is thought that the proportion of molten iron that has dripped during tapping increases relatively. Since the molten iron that has dripped during tapping has a short period of time to be affected by heat removal, it is presumed that the longer the temperature measurement time, the closer the measured molten iron temperature will be to the desired dripping molten iron temperature.

[0031] There are many factors that lower the molten iron temperature, including external disturbances, but factors that raise the molten iron temperature are unlikely to occur other than measurement errors in the temperature measuring equipment, so it can be assumed that the measured molten iron temperature just before the end of tapping is close to the dripping molten iron temperature.

[0032] Based on the above considerations, the measured molten iron temperature is corrected to the molten iron temperature when the tapping completion time has elapsed based on the slope of the regression line obtained in the regression coefficient acquisition step, to determine the dripping molten iron temperature T (corresponding to the correction step). Specifically, the dripping molten iron temperature T can be estimated based on the following equation (1). T=a*(tave-t)+Tmeasure...Equation (1) a: Slope of the regression line tave: Tapping completion time t: Temperature measurement time Tmeasure: The temperature of the molten iron measured at the temperature measurement time t

[0033] The tapping completion time tave may be the arithmetic average of the tapping completion times during the non-operation period. For example, for each tap hole 2, the tapping completion time is counted for the number of TAPs performed during the non-operation period, and the tapping completion time tave can be determined by dividing the total of these tapping completion times by the total number of TAPs. However, the median or mode may also be used as the tapping completion time tave.

[0034] In the example shown in Figure 2, the tapping completion time tave is 140 min (arithmetic mean value). As mentioned above, the slope a is 0.2. Therefore, when estimating the dripping hot metal temperature T by correcting the hot metal temperature Tmeasure: 1510°C obtained at the temperature measurement time t: 30 min, the dripping hot metal temperature T can be estimated as 1532°C by substituting these parameters into equation (1).

[0035] >Blast furnace operation method< If the estimated dripping hot metal temperature differs from the control value, it is advisable to carry out an operation to bring the dripping hot metal temperature closer to the control value. Here, the "control value" is not a fixed value but a range value. For example, if the difference between the target dripping hot metal temperature and the estimated dripping hot metal temperature is about ±5°C, this is not considered an operational fluctuation that requires operation, and no operation is necessary. Therefore, the control value may be, for example, a range of about ±5°C of the target dripping hot metal temperature.

[0036] (Variation 1) In the above-described embodiment, the temperature measurement data for all tap holes 2 are collected and the dripping molten iron temperature is estimated using the same slope a of the regression line, but the present invention is not limited to this. For example, depending on the blast furnace, there may be a steady temperature difference depending on the orientation of the tap holes 2. In this case, related information may be acquired for each tap hole 2, the slope a of the regression line may be found, and the dripping molten iron temperature T may be estimated. In this case, it goes without saying that the tapping completion time tave can be found for each orientation of the tap hole 2.

[0037] It is also desirable to determine the slope a of the regression line for each blast furnace. For example, if the size or shape of the blast furnace changes, the amount of heat removal will change, and the slope a is expected to change. By determining the slope a of the regression line for each blast furnace, the accuracy of estimating the dripping molten iron temperature T can be improved.

[0038] (Variation 2) In the above-described embodiment, the scatter diagram of Fig. 2 was obtained from temperature measurement data of an actual furnace, but the present invention is not limited to this, and the scatter diagram may be obtained by analytical processing using a blast furnace mathematical model. The blast furnace mathematical model divides the inside of a blast furnace into small regions, and simulates the time development of behavior in each small region based on calculation formulas for physicochemical phenomena such as mass transfer, reaction, and heat transfer in the lumpy zone and cohesive zone, and is used to understand or predict furnace conditions from blast furnace operating conditions and raw material properties.

[0039] For example, in the case of a three-dimensional blast furnace mathematical model, the internal region of the blast furnace can be divided in the height direction, the radial direction, and the circumferential direction to define a plurality of meshes (small regions), and the behavior within each mesh can be simulated. Various papers and the like have been published on blast furnace mathematical models, and for example, the blast furnace mathematical models described in Non-Patent Documents 1 and 2 can be suitably used.

[0040] For example, by using a blast furnace mathematical model capable of performing non-steady-state calculations such as those described above, it is possible to calculate the time changes in the iron production rate (t / d), coke ratio CR (kg / tp), pulverized coal ratio PCR (kg / tp), blast pressure (hPa), furnace top pressure (hPa), furnace top temperature (°C), gas utilization rate ηCO (%), and molten iron temperature (°C), etc., for settings of various boundary conditions (in other words, blast furnace specifications) such as the various model parameters used in the blast furnace mathematical model, the blast furnace raw material charging conditions, and the blast conditions.

[0041] Mathematical blast furnace models take into account various chemical reactions that occur in the blast furnace. To effectively use the mathematical blast furnace model, it is desirable to appropriately adjust the various chemical reactions that occur in the blast furnace and the parameters within the model so that the measured values ​​of various physical quantities match the calculated values ​​of the model. Measured values ​​of physical quantities include blast pressure, CO utilization rate, H utilization rate, FeO concentration in the slag, solution loss reaction rate, Si concentration in the molten iron, C concentration in the molten iron, and molten iron temperature. Parameter adjustments include adjustments of correction coefficients for reaction rate constants of chemical reactions such as ore reduction, coke gasification, SiO reduction, carburization, and water-gas shift reaction, as well as correction coefficients for solid-liquid heat exchange coefficients and furnace void fraction correction parameters (see, for example, Non-Patent Document 2).

[0042] Based on the above assumptions, the analysis process using the blast furnace mathematical model carried out in this embodiment will be specifically described. Parameter adjustment is performed (hereinafter also referred to as a reference setting process) using data corresponding to the operation data for the period for which the regression line of the blast furnace is desired to be calculated (hereinafter also referred to as corresponding data) as input conditions. The corresponding data may be average operation data for the period for which the regression line of the blast furnace is desired to be calculated. However, the corresponding data and the average operation data do not necessarily need to match, as long as the deviation is small. As described above, the blast furnace mathematical model can simulate how the molten iron temperature changes when, for example, the blast conditions change. However, if parameters that deviate from the parameters for the period for which the regression line is desired to be calculated are set, it is not possible to accurately simulate the change in the molten iron temperature due to the influence of operational operations. Therefore, parameter adjustment is performed as a reference setting process.

[0043] After the reference setting process is completed, the influence of operational procedures on the molten pig iron temperature is calculated by a non-steady-state calculation. Specifically, the change in the molten pig iron temperature over time when blast conditions (blast flow rate, oxygen enrichment rate, blast moisture content, amount of material injected from the tuyere such as pulverized coal injection rate, type of pulverized coal, etc.), raw material charging conditions (ore charging rate, coke charging rate, amount of material charged from the furnace top such as ore and coke composition), and pressure conditions are changed is simulated (corresponding to the first processing step).

[0044] The molten pig iron temperature measured during the operation period is corrected to a molten pig iron temperature from which the influence of the operation has been removed, based on the information acquired in the first processing step (corresponding to the second processing step). For example, if an operation that changes the blast volume has been carried out during the period for which the regression line is to be calculated, the relationship between the blast volume and the molten pig iron temperature when the blast volume is changed has been calculated by the above-mentioned simulation, and the actually measured molten pig iron temperature can be corrected to the molten pig iron temperature when the blast volume is not changed (in other words, the molten pig iron temperature from which the influence of the operation has been removed) based on this relationship.

[0045] Based on the molten iron temperature measured during the period when no operation is being performed and the molten iron temperature determined in the second processing step, information (relationship information) corresponding to Figure 2 is obtained (corresponding to the third processing step).

[0046] The processing performed after obtaining the scatter plot will not be described again.

[0047] The method of Modification 2, which utilizes analytical processing using a blast furnace mathematical model, is a suitable technique when the non-operation period is short (for example, less than 24 hours). [Explanation of symbols]

[0048] 1 blast furnace 2 Taphole 3 Tapping bucket 4 Skinma

Claims

1. When the time elapsed from the start of tapping to the measurement of the molten iron temperature is defined as the temperature measurement time, a relationship information acquisition step of acquiring in advance relationship information between temperature measurement times and molten iron temperatures during non-operation periods when the blast furnace is not operated; a regression coefficient acquisition step of calculating a slope of a regression line of the temperature measurement time and the molten iron temperature based on the relationship information acquired in the relationship information acquisition step; a correction step of correcting the measured molten iron temperature to the molten iron temperature at the time when the tapping completion time has elapsed, based on the slope obtained in the regression coefficient obtaining step, to obtain the dripping molten iron temperature; A method for estimating the temperature of dripping molten iron in a blast furnace, comprising:

2. The related information acquisition step is a step of acquiring the related information based on actual measurement data of an actual blast furnace.

2. The method for estimating the temperature of dripping molten iron in a blast furnace according to claim 1.

3. The non-operation period is at least 24 hours or more.

3. The method for estimating the temperature of dripping molten iron in a blast furnace according to claim 2.

4. The related information acquisition step is a step of acquiring the related information based on an analysis process using a blast furnace mathematical model.

2. The method for estimating the temperature of dripping molten iron in a blast furnace according to claim 1.

5. The analysis process using the blast furnace mathematical model is a first processing step of adjusting parameters using data corresponding to operational data for a period for which the slope of the regression line is desired as an input condition, and then acquiring information on changes in molten iron temperature over time when operational operations are performed; a second processing step of correcting the molten iron temperature measured during the operation to a molten iron temperature that is free from the influence of the operation, based on the information acquired in the first processing step; a third processing step of acquiring the relationship information based on the molten iron temperature measured during a period when no operation is being performed and the molten iron temperature determined in the second processing step; 5. The method for estimating the temperature of dripping molten iron in a blast furnace according to claim 4, further comprising:

6. The tapping completion time is the arithmetic average value of the tapping completion time during the non-operation period.

4. The method for estimating the temperature of dripping molten iron in a blast furnace according to claim 1, wherein the method comprises:

7. When the measured molten iron temperature is Tmeasure, the temperature measurement time is t, the tapping completion time is tave, and the slope acquired in the regression coefficient acquisition step is a, 4. The method for estimating the temperature of dripping molten iron in a blast furnace according to claim 1, wherein the correction step is a step of calculating the dripping molten iron temperature based on the following formula (1): T=a*(tave-t)+Tmeasure...Formula (1)

8. A method for operating a blast furnace, comprising, when a dripping molten iron temperature estimated using the estimation method according to any one of claims 1 to 3 differs from a control value, carrying out an operation to bring the dripping molten iron temperature closer to the control value.

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