Methods for estimating heat supply, devices for estimating heat supply, and operating methods of blast furnaces

Abstract

The method for estimating the supply heat of the present invention is based on the heat supplied to the blast furnace and the manufacturing rate of molten pig iron in the blast furnace. The method includes: an estimation step, wherein the change in sensible heat carried out by the gas passing through the furnace and the change in sensible heat brought in by the raw materials preheated by the gas passing through the furnace are estimated, and the heat supplied to the pig iron in the blast furnace is estimated by taking into account the estimated changes in sensible heat carried out and brought in.

Description

Technical Field

[0001] This invention relates to a method for estimating the heat supply to pig iron in a blast furnace, a heat supply estimation device, and a method for operating the blast furnace. Background Technology

[0002] Typically, to ensure stable operation of a blast furnace, the temperature of molten pig iron needs to be maintained within a specified range. Specifically, when the molten pig iron temperature is low, the viscosity of the molten pig iron and the slag it produces increases, making it difficult for them to exit the taphole. Conversely, when the molten pig iron temperature is high, the Si concentration in the molten pig iron increases, further increasing its viscosity. This increases the risk of the molten pig iron sticking to the tuyeres and causing tuyeres to melt and break. Therefore, to ensure stable blast furnace operation, fluctuations in the molten pig iron temperature need to be suppressed. Against this backdrop, various methods for estimating the heat supplied to the blast furnace and the temperature of the molten pig iron have been proposed. Specifically, Patent Document 1 discloses a blast furnace heat control method, characterized by estimating the molten pig iron temperature after a specific time period based on the current displacement of the furnace heat index from a reference level corresponding to the target molten pig iron temperature, the current displacement of the unloading speed from a reference level of the unloading speed at the furnace top corresponding to the target molten pig iron temperature, and the time of influence of the two displacements on the molten pig iron temperature. Based on this estimation result, furnace heat control operations are performed to reduce fluctuations in the molten pig iron temperature. Patent Document 2 discloses a method that samples gases along the longitudinal direction of the blast furnace, estimates the reaction rate of ore based on the measurement results, uses this value to estimate the internal conditions of the furnace through a model, and thus estimates the thermal state of the lower part of the blast furnace, etc. It also describes how the calculation accuracy of the thermal balance of the lower part of the blast furnace is improved by using the calculated values ​​from the model. Furthermore, Patent Document 3 discloses a method that improves the calculation accuracy of the internal reaction rate by estimating the temperature of the molten pig iron discharged from the blast furnace through a model and considering the composition of gases discharged from the upper part of the blast furnace, etc., thereby changing the main reaction rate used in the model. Furthermore, Patent Documents 4 and 5 disclose a method for predicting the molten pig iron temperature of a blast furnace. This method predicts the future molten pig iron temperature based on operational data including actual values ​​of blast conditions data (at least one of blast furnace blast temperature, blast humidity, blast volume, fine carbon injection amount, and oxygen enrichment), actual values ​​of interference factor data (at least including carbon dissolution amount), and actual values ​​of the molten pig iron temperature. The method is characterized by comprising: a data storage step that stores operational data; a stable-state prediction model construction step that constructs a stable-state prediction model to predict the molten pig iron temperature in a stable state based on the operational data stored in the data storage step; an unstable-state prediction model construction step that reduces the dimensionality of the stable-state prediction model, wherein an unstable-state prediction model is constructed to predict the molten pig iron temperature in an unstable state based on the operational data stored in the data storage step; and a molten pig iron temperature prediction step that predicts the molten pig iron temperature based on the constructed stable-state prediction model and the unstable-state prediction model.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2-115311

[0006] Patent Document 2: Japanese Patent Publication No. 49-20693

[0007] Patent Document 3: Japanese Patent Application Publication No. 10-147804

[0008] Patent Document 4: Japanese Patent Application Publication No. 2008-144265

[0009] Patent Document 5: Japanese Patent Application Publication No. 2018-145520 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The likelihood of significant fluctuations in molten pig iron temperature is high when changes in the amount of molten pig iron produced, such as variations in the blast furnace operating parameters (e.g., the amount of blast furnace feed rate), change relative to the heat supplied to the blast furnace. However, the method described in Patent Document 1 fails to consider factors such as the carry-over of sensible heat caused by blast sensible heat, which is believed to change with varying operating parameters. Therefore, it cannot accurately estimate the heat supplied to the pig iron when operating parameters change significantly. On the other hand, in the methods described in Patent Documents 2 and 3, when operating parameters change significantly without furnace gas sampling, the model cannot reflect changes in the reaction rate, potentially reducing the accuracy of furnace heat prediction. Furthermore, in the methods described in Patent Documents 4 and 5, the accuracy of molten pig iron temperature estimation decreases when previously unrecorded operating changes occur. Moreover, with such low accuracy in molten pig iron temperature estimation, excessive heat supply is often encountered, raising concerns about equipment malfunction. Additionally, from the perspective of reducing carbon dioxide emissions, excessive use of reducing materials as carbon sources is not preferable.

[0012] The present invention was made in view of the above-mentioned problems, and its object is to provide a method and apparatus for estimating the heat supply to the pig iron supplied to the blast furnace with high accuracy even when the operating conditions vary greatly. Another object of the present invention is to provide a method for operating a blast furnace that can appropriately maintain the heat supply to the pig iron in the blast furnace and can control the temperature of the molten pig iron within a specified range with high accuracy even when the operating conditions vary greatly.

[0013] Methods for solving problems

[0014] The method for estimating the supply heat of the present invention is based on the heat supplied to the blast furnace and the production rate of molten pig iron in the blast furnace. The method includes: an estimation step, wherein the change in sensible heat carried out by the gas passing through the furnace and the change in sensible heat carried in by the raw materials preheated by the gas passing through the furnace are estimated, and the heat supplied to the pig iron in the blast furnace is estimated by taking into account the estimated changes in sensible heat carried out and sensible heat carried in.

[0015] It should be noted that the above estimation steps may include the following steps: estimating the heat held by the core coke in the blast furnace, and estimating the heat supplied to the pig iron in the blast furnace based on the estimated heat held by the core coke.

[0016] The supply heat estimation device of the present invention estimates the heat of pig iron supplied to the blast furnace based on the heat supplied to the blast furnace and the production rate of molten pig iron in the blast furnace. It includes: an estimation unit that estimates the change in sensible heat carried out by the gas passing through the furnace and the change in sensible heat brought in by the raw material preheated by the gas passing through the furnace, and estimates the heat of pig iron supplied to the blast furnace by taking into account the estimated changes in sensible heat carried out and brought in.

[0017] It should be noted that the above estimation unit can estimate the heat held by the core coke in the blast furnace, and estimate the heat supplied to the pig iron in the blast furnace by taking into account the estimated heat held by the core coke.

[0018] The blast furnace operation method of the present invention includes the following steps: controlling the heat supplied to the blast furnace based on the heat of pig iron supplied to the blast furnace estimated by the heat supply estimation method of the present invention.

[0019] Invention Effects

[0020] According to the method and apparatus for estimating the heat supply of the present invention, the heat supply to the pig iron supplied to the blast furnace can be estimated with high accuracy even when the operating conditions change significantly. Furthermore, according to the blast furnace operation method of the present invention, the heat supply to the pig iron supplied to the blast furnace can be appropriately maintained even when the operating conditions change significantly, and the temperature of the molten pig iron can be controlled with high accuracy within a specified range. Attached Figure Description

[0021] Figure 1 This is a block diagram showing the configuration of a furnace heat control device as one embodiment of the present invention.

[0022] Figure 2 This is a flowchart illustrating the process of furnace heat control as one embodiment of the present invention.

[0023] Figure 3This is a graph showing an example of the changes in conventional indices and the furnace heat index of the present invention in relation to changes in air supply volume.

[0024] Figure 4 This is a graph illustrating an example of the relationship between conventional indices and the furnace heat index of the present invention and the temperature difference relative to the reference molten pig iron temperature. Detailed Implementation

[0025] Hereinafter, with reference to the accompanying drawings, the configuration and operation of a furnace heat control device, which is an embodiment of the present invention, applies the heat supply estimation method and heat supply estimation device of the present invention.

[0026] [constitute]

[0027] First, refer to Figure 1 The configuration of a furnace heat control device, which is one embodiment of the present invention, will be described. Figure 1 This is a block diagram illustrating the configuration of a furnace heat control device as one embodiment of the present invention. Figure 1 As shown, the furnace heat control device 1, as an embodiment of the present invention, is composed of an information processing device such as a computer. By controlling the heat of the melt supplied to the blast furnace 2 from the tuyeres located at the bottom of the blast furnace 2, the temperature of the molten pig iron produced in the blast furnace 2 is controlled within a specified range.

[0028] The furnace heat control device 1, with this configuration, can accurately estimate the heat of pig iron supplied to the blast furnace 2 even when the operating degree of the blast furnace 2 changes significantly, by performing the furnace heat control process described below. Using the estimation result, it appropriately maintains the heat of pig iron supplied to the blast furnace 2, and accurately controls the temperature of the molten pig iron within a specified range. Hereinafter, refer to... Figure 2 The process of furnace heat control processing as one embodiment of the present invention will be described.

[0029] [Furnace thermal control treatment]

[0030] Figure 2 This is a flowchart illustrating the process of furnace heat control as one embodiment of the present invention. Figure 2In the flowchart shown, starting from the moment the execution command for the furnace heat control process is input to the furnace heat control device 1, the furnace heat control process, in addition to the conventional step S1 which estimates the heat to be supplied to the blast furnace based on the reaction heat balance (heat generated by reaction, heat absorbed by reaction), sensible heat of the blast air, and heat loss (heat removed from the furnace body, etc.), also performs steps S2, S3, and a preferred step S4. These processes are then integrated before proceeding to step S5, which estimates the heat to be supplied. Step S1, which estimates the heat to be supplied to the blast furnace based on the reaction heat balance (heat generated by reaction, heat absorbed by reaction), sensible heat of the blast air, and heat loss (heat removed from the furnace body, etc.), has been performed conventionally, and the heat supplied at this time is set as Q0. A preferred example of the process for step S1 will be explained later.

[0031] In step S2, the furnace heat control device 1 estimates the sensible heat (sensible heat carried out by the gas) Q7 carried out from the lower part of the blast furnace 2 to the upper part (gas passing through the furnace) to the upper part of the blast furnace 2. Specifically, the sensible heat Q7 carried out by the gas (MJ / tp: heat per ton of pig iron. Hereinafter, tp indicates the number of tons of pig iron) can be calculated by multiplying the temperature difference between the estimated temperature of the gas burning in front of the tuyeres and the reference temperature representing the temperature of the upper part of the lower part of the blast furnace by the specific heat of the gas, and is expressed by the mathematical formula (1) shown below. Thus, step S2 is completed, and the process proceeds to step S5.

[0032]

[0033] Here, C i The specific heat (MJ / m³) of gas type i (nitrogen, carbon monoxide, hydrogen) 3 / ℃), V i This indicates the flow rate (m³) of gas type i in Bosch gas. 3 (stp) / minute)(m 3 (stp): Volume at 0℃ and 1 atm (atmosphere), TFT represents the theoretical combustion temperature (℃), T base The reference temperature (°C) is represented as (800–1200°C, preferably 900–1000°C), Pig represents the iron-making rate (tp / minute), and α represents the influence coefficient caused by the blast furnace 2. Their values ​​can be obtained, for example, from a host computer 3 such as a process computer connected to the furnace thermal control device 1 via an electrical communication line.

[0034] In step S3, the furnace heat control device 1 estimates the sensible heat (material-carried sensible heat) Q8 brought into the lower part of the blast furnace 2 by the raw material supplied from the upper part to the lower part. Specifically, the material-carried sensible heat Q8 (MJ / tp) can be expressed as shown in the following mathematical formula (2) by comparing the raw material temperature T1 (=1450~1500℃) at the lower end of the weld band with the reference temperature T base The temperature difference is calculated by multiplying the specific heat of the raw material. Thus, step S3 is completed, and the process proceeds to step S5.

[0035] Q8=β·{∑(C j ·R j )}·(T1-T base (2)

[0036] Here, C j R represents the specific heat (MJ / kg / ℃) of raw material j (coke, pig iron, slag). j T represents the original unit of raw material j (kg / tp), T1 represents the raw material temperature at the lower end of the weld strip (°C), T base β represents the reference temperature (°C), and β represents the influence coefficient caused by the change in blast furnace 2. Their values ​​can be obtained, for example, from the host computer 3.

[0037] In step S4, the furnace thermal control device 1 estimates the heat retained by the coke in the lower part of the blast furnace 2 (coke retention heat) Q9. Specifically, the coke retention heat Q9 (MJ / tp) can be obtained by subtracting the combustion consumption and the amount of carbon discharged in the form of dust from the original coke unit per ton of molten pig iron, multiplied by the difference between the reference temperature and the theoretical combustion temperature and the specific heat C of the coke. coke The result is obtained using the mathematical formula (3) shown below. Thus, step S4 is complete, and we proceed to step S5. It should be noted that step S4 can also be omitted.

[0038]

[0039] Here, C coke T represents the specific heat of coke (MJ / kg / ℃), TFT represents the theoretical combustion temperature (℃), and T represents the theoretical combustion temperature. base CR represents the reference temperature (°C), and CR represents the coke ratio (kg / tp). burn The carbon-to-fuel ratio before the air outlet (the amount of oxygen in the supply air plus the amount of oxygen consumed before the air outlet due to humidification) (kg / tp), PCR represents the carbon-to-fuel ratio of the fine powder (kg / tp), C inPC C represents the carbon ratio in micronized charcoal. sol The carbon solubility ratio (kg / tp) is represented by C, and the dust ratio (kg / tp) is represented by Dust. industγ represents the carbon ratio in the dust, and δ represents the influence coefficients caused by the change in blast furnace 2. Their values ​​can be obtained, for example, from the host computer 3.

[0040] In step S5, the furnace heat control device 1 uses the supplied heat Q0 estimated in step S1, the gas-carried sensible heat Q7 estimated in steps S2-S4, the raw material-carried sensible heat Q8, and the coke retention heat Q9 to estimate the heat of pig iron supplied to the blast furnace 2. Specifically, the furnace heat control device 1 substitutes the supplied heat Q0 estimated in step S1, the gas-carried sensible heat Q7 estimated in steps S2-S4, the raw material-carried sensible heat Q8, and the coke retention heat Q9 into the mathematical formula (4) shown below to calculate the furnace heat index T corresponding to the heat of pig iron supplied to the blast furnace 2. Q (MJ / tp). Thus, step S5 is complete, and the process proceeds to step S6. It should be noted that if step S4 is omitted, the value of the coke retention heat Q9 is set to 0.

[0041] T Q =Q0-Q7+Q8-Q9 …(4)

[0042] Here, Q0 represents the heat supplied to the blast furnace using the reaction heat balance (reaction generation heat, reaction endothermic heat), sensible heat of the blast air, and heat loss (heat removed from the furnace body, etc.). It can be applied to the estimation method used in most cases in the past estimation of the supplied heat, but as a preferred method, a mathematical formula (5) can be listed.

[0043] Q0 = Q1 + Q2 - Q3 - Q4 - Q5 - Q6…(5)

[0044] Here, Q1 represents the heat of combustion of the coke at the tuyeres (MJ / tp). The heat of combustion Q1 can be calculated by dividing the heat generated by the combustion of the coke, calculated based on the amount of oxygen supplied from the tuyeres to the blast furnace per unit time, by the amount of molten pig iron produced per unit time.

[0045] Additionally, Q2 represents the sensible heat of the blast air fed into the blast furnace via the tuyeres (MJ / tp). The sensible heat of the blast air Q2 can be calculated by determining the heat fed into the blast furnace per unit time using the blast air volume and temperature, and then dividing that value by the amount of molten pig iron produced per unit time.

[0046] Additionally, Q3 represents the heat of reaction loss (MJ / tp). This value can be calculated, for example, by determining the amount of carbon lost based on the composition of the gas at the furnace top, as described in Patent Document 1. The heat of reaction loss Q3 can be calculated by dividing this heat of reaction loss by the amount of molten pig iron produced per unit time.

[0047] Additionally, Q4 represents the heat of decomposition (MJ / tp) of the main wet components contained in the supply air. The heat of decomposition Q4 can be calculated by dividing the heat of decomposition obtained from the measured value of the wet components in the supply air by the amount of molten pig iron produced per unit time.

[0048] Additionally, Q5 represents the heat loss from the furnace body (e.g., heat loss due to cooling water) (MJ / tp). As for the heat loss, when the heat loss due to cooling water is calculated, the heat loss Q5 can be calculated by taking into account the amount of heat loss per unit time due to cooling water flow rate and the temperature difference between the inlet and outlet sides of the cooling water in the blast furnace body, and then dividing the calculated heat loss by the amount of molten pig iron produced per unit time.

[0049] Additionally, Q6 represents the heat of decomposition of the reducing material blown in from the duct per unit time (MJ / tp). The heat of decomposition Q6 can be calculated by dividing the heat of decomposition by the amount of molten pig iron produced per unit time.

[0050] In step S6, the furnace heat control device 1 controls the heat supplied from the tuyeres to the blast furnace 2 based on the heat of the pig iron supplied to the blast furnace 2 estimated in step S5, thereby appropriately maintaining the heat of the pig iron supplied to the blast furnace 2 and controlling the temperature of the molten pig iron within a specified range. Thus, step S6 is completed, and the series of furnace heat control processes ends.

[0051] As explained above, in the furnace heat control process of one embodiment of the present invention, the furnace heat control device 1 estimates the change in sensible heat carried out to the upper part of the blast furnace by the gas passing through the furnace and the change in sensible heat carried in to the lower part of the blast furnace by the raw materials preheated by the gas passing through the furnace. Taking into account the estimated changes in sensible heat carried out and carried in, the heat of pig iron supplied to the blast furnace is estimated. Therefore, even when there are large changes in the operating conditions such as the blast rate into the blast furnace, the heat of pig iron supplied to the blast furnace can be estimated with high accuracy. Furthermore, this allows for the appropriate maintenance of the heat of pig iron supplied to the blast furnace even when there are large changes in the operating conditions, and enables the molten pig iron temperature to be controlled with high accuracy within a specified range.

[0052] [Example]

[0053] use Figure 3 The effects of applying the invention of this application will be explained in detail. Figure 3 In the diagram, the horizontal axis represents time, and as an operating condition, it shows the time-dependent changes in the furnace heat index estimated by conventional methods and the furnace heat index estimated using the present invention under conditions of significant changes in air volume. Figure 3In (a), the actual value of the air volume changes over time as an operating condition when the base value of the air volume is set to 1.0. Figure 3 In (b), the actual values ​​of the molten pig iron temperature over time are shown as relative values ​​with the base value set to 0°C. Figure 3 In (c), the estimated value (Q7) of heat removal caused by gas is shown as a relative value when the baseline value of heat removal caused by gas is set to 0 (MJ / tp) over time. Figure 3 In (d), the estimated change in the heat supplied to the blast furnace (furnace heat index) over time is shown as a relative value when the base value of the furnace heat index is set to 0 (MJ / tp). The results estimated using the values ​​of Q1 to Q6 described above are shown in the conventional example (comparative example), while the results estimated using the values ​​of Q1 to Q9 are shown in the present invention example. When managing the heat supplied to the blast furnace using only the values ​​of Q1 to Q6 described above, since the carry-over sensible heat caused by the blast sensible heat, which is believed to change according to the operating degree, is not considered, the heat supplied to the blast furnace cannot be estimated with high accuracy when the operating degree changes significantly. Specifically, as... Figure 3 As shown in (a) to (c), when the temperature of the molten pig iron decreases due to a reduction in the air supply, resulting in an increase in the sensible heat carried out by the gas passing through the furnace (deheating caused by the gas), as follows: Figure 3 As shown in (d), the conventional furnace heat index (comparative example) based on the values ​​of Q1 to Q6 increases and fluctuates significantly. Therefore, when operating a blast furnace according to the conventional furnace heat index, it is impossible to determine the heat exchange required to lower the molten pig iron temperature, potentially leading to poor molten pig iron discharge as the temperature decreases. In contrast, the furnace heat index of the present invention (example of the present invention) takes into account the heat increase or decrease due to blast, thus decreasing with the decrease in molten pig iron temperature and exhibiting minimal fluctuation. Therefore, when operating a blast furnace according to the furnace heat index of the present invention, the molten pig iron temperature can be controlled with high precision within a specified range. Furthermore, more data was collected... Figure 4 The diagram shows a comparison of the furnace heat index (estimated using Q1 to Q6) from previous models and the furnace heat index of this invention (estimated using Q1 to Q9) with the actual molten pig iron temperature (the difference relative to the reference molten pig iron temperature) at more times when the air supply volume is significantly reduced. Figure 4As shown, compared with conventional furnace heat indices, the furnace heat index of the present invention confirms a certain correlation between the furnace heat index and the molten pig iron temperature (the difference relative to the reference molten pig iron temperature). Furthermore, Table 1 shows the results of summarizing the standard deviations of the difference between the estimated and actual molten pig iron temperatures, considering various factors. It can be seen that, compared with the conventional furnace heat index which only uses Q1 to Q6 to estimate the furnace heat index, the estimation accuracy is improved by adding Q7 and Q8 to the estimation (Example 1 of the present invention), and the estimation accuracy is further improved by adding Q9 to the estimation (Example 2 of the present invention). Therefore, by using the furnace heat index of the present invention, it is possible to appropriately maintain the heat supplied to the pig iron in the blast furnace and to control the molten pig iron temperature with high precision within a specified range.

[0054] [Table 1]

[0055] (Table 1)

[0056]

[0057] The embodiments of the invention made by the inventors have been described above, but the present invention is not limited to the description and drawings that constitute a part of the disclosure of the present invention based on these embodiments. That is, all other embodiments, examples, and techniques that can be made by those skilled in the art based on these embodiments are included within the scope of the present invention.

[0058] Industrial availability

[0059] According to the present invention, a method and apparatus for estimating the heat supply to the pig iron supplied to the blast furnace can be provided, even under conditions of significant operational variation. Furthermore, according to the present invention, a method for operating a blast furnace can be provided that appropriately maintains the heat supply to the pig iron in the blast furnace even under conditions of significant operational variation and can precisely control the temperature of the molten pig iron within a specified range.

[0060] Symbol Explanation

[0061] 1. Furnace thermal control device

[0062] 2 Blast Furnace

[0063] 3. Host computer.

Claims

1. A supply heat amount estimation method of estimating a heat amount of hot metal supplied to a blast furnace, from a heat amount supplied to the blast furnace and a production rate of molten hot metal in the blast furnace, comprising: an estimation step of estimating a change in outgoing sensible heat caused by a gas in a furnace and a change in incoming sensible heat supplied from a raw material preheated by the gas in the furnace, and estimating the heat amount of hot metal supplied to the blast furnace, taking into account the changes in outgoing sensible heat and incoming sensible heat estimated, the estimation step including a step of calculating the outgoing sensible heat by multiplying a temperature difference between an estimated temperature of the gas burned in front of a tuyere of the blast furnace and a reference temperature representing a temperature of an upper end of a lower portion of the blast furnace, by a specific heat of the gas in the furnace. The estimation step includes a step of estimating a heat amount held by coke in a hearth present in the blast furnace, and estimating the heat amount of hot metal supplied to the blast furnace, taking into account the heat amount held by the coke in the hearth estimated.

3. A supply heat amount estimation device of estimating a heat amount of hot metal supplied to a blast furnace, from a heat amount supplied to the blast furnace and a production rate of molten hot metal in the blast furnace, comprising: an estimation unit of estimating a change in outgoing sensible heat caused by a gas in a furnace and a change in incoming sensible heat supplied from a raw material preheated by the gas in the furnace, and estimating the heat amount of hot metal supplied to the blast furnace, taking into account the changes in outgoing sensible heat and incoming sensible heat estimated, the estimation unit calculating the outgoing sensible heat by multiplying a temperature difference between an estimated temperature of the gas burned in front of a tuyere of the blast furnace and a reference temperature representing a temperature of an upper end of a lower portion of the blast furnace, by a specific heat of the gas in the furnace.

2. The heat-supply-estimation method according to claim 1, wherein The estimation unit estimates a heat amount held by coke in a hearth present in the blast furnace, and estimates the heat amount of hot metal supplied to the blast furnace, taking into account the heat amount held by the coke in the hearth estimated.

5. An operation method of a blast furnace, comprising a step of controlling a heat amount supplied to the blast furnace, based on a heat amount of hot metal supplied to the blast furnace estimated by the supply heat amount estimation method of claim 1 or 2. ​ ​ 4. The heat-supply-estimating device according to claim 3, wherein ​ ​

Images