Blast furnace operation method

Abstract

To provide a blast furnace operation method that allows precise control of blast furnace heat levels.SOLUTION: In a blast furnace operation method of one embodiment of the present invention, a heat balance at a tuyere defined as a difference between an input heating value on the tuyere including the blast sensible heat of gas blown through the tuyere and the combustion heat of carbon burned in a raceway, and an output heating value on the tuyere including the decomposition heat of blast moisture included in the gas blown through the tuyere, the decomposition heat of pulverized coal, and the reaction heat by solution loss reaction and direct reduction reaction, is used as an operation control index.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for operating a blast furnace. [Background technology]

[0002] In general, in blast furnace operation, blast furnace raw materials (ore raw materials, coke and auxiliary materials, and sometimes scrap, unburned carbon-containing agglomerates, ferro-coke, etc.) are transported by a conveyor to a furnace top charging device and charged into the blast furnace from the furnace top. The furnace top charging device is configured to maintain the top surface of the charge materials in the blast furnace at a predetermined height, and when the top surface position of the charge materials drops, the blast furnace raw materials are charged into the blast furnace to replenish the dropped amount. The ore raw materials and coke are alternately stacked in layers in the blast furnace, and they descend inside the furnace while maintaining the layered form. Hot air, pulverized coal as a reducing agent, etc. are blown in from the blast tuyeres at the bottom of the blast furnace. The pulverized coal and coke are burned by the hot air blown in from the blast tuyeres, generating high-temperature reducing gases such as carbon monoxide and hydrogen. In addition, gases such as coke oven gas (COG) or natural gas (NG) may be blown into the blast tuyere (or other tuyere).

[0003] The reducing gas rises in the furnace as a strong updraft, raising the temperature of the ore falling through the furnace while reducing the ore (indirect reduction). The FeO produced drips through the coke layer in a molten state and is further reduced when it comes into contact with the carbon in the coke (direct reduction), becoming molten iron containing just under 5% carbon and accumulating in the basin at the bottom of the furnace. This molten iron is removed from a tap hole installed next to the bottom of the furnace and transported to the next steelmaking process.

[0004] Conventionally, in blast furnace operation, operation control indices are set, and the furnace status is controlled by monitoring the time transition of the operation control indices and executing operation actions corresponding to the time transition. Therefore, setting appropriate operation control indices is extremely important for stable operation of the blast furnace. In particular, when automating the operation of a blast furnace, it is important to appropriately define operation control indices that can be target variables for automatic control.

[0005] The operation control indicators are the molten iron temperature, the amount of molten iron Si, the amount of solution loss carbon, the furnace top gas composition (CO concentration, CO 2 Concentration, CO+CO 2 Concentration, ηCO(=CO 2 / (CO+CO 2 )), heat load, etc. Conventionally, these values ​​were monitored and operational actions (e.g., adjustment of pulverized coal injection amount, blast moisture, etc.) were taken based on the operator's appropriate and comprehensive judgment. When a certain amount of production was also adjusted, the blast amount, oxygen enrichment amount, etc. were adjusted taking into account Tf (theoretical combustion temperature at the tuyere tip) in addition to the calculated pig iron production amount, solution loss carbon amount, and reducing agent ratio.

[0006] Various methods for setting operation management indexes and selecting operation conditions based on the indexes have been proposed. For example, Patent Document 1 describes a method for operating a blast furnace, which comprises dividing the heat balance change and molten iron temperature obtained from a heat balance model for estimating the heat balance in the lower part of the furnace into predetermined ranges, determining furnace heat trend ranks, setting operation conditions in advance for each furnace heat trend rank, selecting the operation conditions from the amount of heat balance change and the molten iron temperature at the time of furnace heat judgment, and selecting operation conditions from among operation conditions before and after the reference, based on the operation conditions according to historical information on the molten iron temperature and historical information on the previously implemented operation conditions of the coke ratio, moisture, blast temperature, and blast volume until the furnace heat judgment is reached, to operate the blast furnace.

[0007] Furthermore, Patent Document 2 describes a method for controlling furnace heat in a blast furnace, characterized by: a. determining a furnace heat level from the temperature of molten metal tapped from the blast furnace, b. determining a furnace heat transition level based on sensor data obtained from a sensor attached to the blast furnace or the amount of change over time in a furnace heat index calculated from the sensor data, and c. performing operational actions in accordance with the furnace heat level and the furnace heat transition level.

[0008] Patent Document 3 describes a molten iron temperature prediction method for predicting the molten iron temperature in a blast furnace using a physical model capable of calculating the state inside the blast furnace in an unsteady state, characterized in that the method includes a step of optimizing a parameter in the physical model related to the gas reduction rate or the amount of furnace body heat loss so that the sensitivity between values ​​calculated by the physical model matches the sensitivity between actual values ​​of actual operation data for at least one of the relationship between the reducing agent ratio and the amount of solution loss carbon, the relationship between the reducing agent ratio and the gas utilization rate, and the relationship between the reducing agent ratio and the amount of furnace body heat loss, and predicting the molten iron temperature in the blast furnace using the physical model with the optimized parameters.

[0009] Patent Document 4 describes a blast furnace heat management method for a furnace during operation, which is characterized in that a calculated coke ratio is calculated by dividing the coke consumption rate, determined from the furnace top gas components, etc., by the pig iron production rate, and a value obtained by multiplying the value obtained by dividing the auxiliary fuel injection amount by the pig iron production rate by the replacement rate is added to obtain a calculated fuel ratio, and the calculated fuel ratio is corrected by the blast temperature and blast humidity to obtain a calculated corrected fuel ratio, and the heat balance in the furnace is controlled by adjusting the blast humidity, pulverized coal injection amount, blast temperature, and charged coke rate so that the calculated corrected fuel ratio becomes a predetermined set value. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 1-319616 [Patent Document 2] JP 2014-118599 A [Patent Document 3] JP 2018-24936 A [Patent Document 4] Japanese Patent Application Publication No. 10-46215 Summary of the Invention [Problem to be solved by the invention]

[0011] Patent Documents 1 to 3 are techniques for determining operation actions using molten iron temperature as a furnace heat index, and Patent Document 4 is a technique for determining operation actions using a calculated fuel ratio or a calculated corrected fuel ratio as a furnace heat index. However, these indexes are not sufficiently effective for improving the stability of blast furnace operation to a satisfactory level, and further study of the furnace heat index was necessary, particularly for use in automatic control of a blast furnace (for example, automatic control involving switching of operation actions every few tens of minutes).

[0012] For example, in the monitoring of the molten iron temperature and / or the amount of silicon in the molten iron as described in Patent Documents 1 to 3, the measurement frequency is low (usually about once an hour), so there is a large time lag until the measurement results are reflected in operational actions, and this is insufficient for precise furnace condition control. In addition, since the molten iron temperature and the amount of silicon in the molten iron are greatly affected by the gas flow when FeO drips from the cohesive zone, the filling state of the hearth and the deadman, the slag metal reaction, and the like, as well as the state of the tap hole and the runner, there is a problem that control of the molten iron temperature and / or the amount of silicon in the molten iron does not necessarily lead to stabilization of the blast furnace operation by stabilizing the state of the cohesive zone (especially the position of the cohesive zone).

[0013] On the other hand, short-period data can be obtained by gas chromatography analysis of furnace gas components as described in Patent Document 4. However, the analysis value alone only takes into account heat depending on the reduction state, and is not sufficient for precise control of the blast furnace.

[0014] An object of one aspect of the present invention is to provide a blast furnace operation method that solves the above problems and enables precise control of the blast furnace heat level. [Means for solving the problem]

[0015] [1] In the method of operating a blast furnace, The input heat quantity on the tuyere includes the sensible heat of the gas blown from the tuyere and the heat of combustion of carbon burning in the raceway; An output heat quantity on the tuyere including the decomposition heat of the blast moisture contained in the gas blown from the tuyere, the decomposition heat of the pulverized coal, and the reaction heat due to the solution loss reaction and the direct reduction reaction; A method for operating a blast furnace, comprising the steps of: [2] The method for operating a blast furnace according to the above-mentioned [1], characterized in that the heat balance above the tuyere is defined by the following formula (1). Heat balance above the tuyere (GJ / h) = [carbon combustion heat + blast sensible heat + indirect reduction heat - blast moisture decomposition heat - pulverized coal decomposition heat - solution loss reaction heat - direct reduction heat - hydrogen reduction heat] (GJ / h) (1) [3] The method for operating a blast furnace according to the above [1], characterized in that the heat balance above the tuyere is defined by the following formula (2): Heat balance above the tuyere (GJ / h) = [Carbon combustion heat + sensible heat of blast + indirect reduction heat – sensible heat of top gas – heat removal from furnace body – heat of blast moisture decomposition – heat of pulverized coal decomposition – solution loss reaction heat – direct reduction heat – hydrogen reduction heat] (GJ / h) (2) [4] In the method of operating a blast furnace, An input heat amount including the sensible heat of the gas blown from the tuyere and the combustion heat of carbon burning in the raceway; Output heat including heat of decomposition of blast moisture contained in the gas blown from the tuyere, heat of decomposition of pulverized coal, and heat of reaction due to solution loss reaction and direct reduction reaction; The present invention relates to a blast furnace operating method, and a heat balance above the tuyere per iron production amount, which is defined as a value obtained by dividing the difference between the calculated iron production amount and the actual iron production amount, as an operation control index. [5] The method for operating a blast furnace according to the above [4], characterized in that the heat balance above the tuyere per unit of iron production is defined by the following equation (3): Heat balance above the tuyere (GJ / tp) = [carbon combustion heat + blast sensible heat + indirect reduction heat - blast moisture decomposition heat - pulverized coal decomposition heat - solution loss reaction heat - direct reduction heat - hydrogen reduction heat] (GJ / h) / calculated pig iron production (tp / h) (3) [6] The method for operating a blast furnace according to the above item [4], characterized in that the heat balance above the tuyere per unit of iron production is defined by the following equation (4): Heat balance above the tuyere (GJ / tp) = [Carbon combustion heat + blast sensible heat + indirect reduction heat – top gas sensible heat – furnace body heat removal – blast moisture decomposition heat – pulverized coal decomposition heat – solution loss reaction heat – direct reduction heat – hydrogen reduction heat] (GJ / h) / calculated iron production (tp / h) (4) Effect of the Invention

[0016] According to one aspect of the present invention, a method of operating a blast furnace may be provided that allows precise control of blast furnace heat levels. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a diagram illustrating a furnace heat index used for controlling the heat balance above the tuyere in a blast furnace operation method according to one embodiment of the present invention. [Diagram 2] 1 is a flowchart showing a process performed in a blast furnace operation method according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram showing the relationship between the productivity (i.e., the amount of pig iron produced per m3 of the inner volume of the blast furnace per day) and the position of the cohesive zone in Example 1. [Figure 4] FIG. 2 is a diagram showing the relationship between the productivity (i.e., the amount of pig iron produced per m3 of the inner volume of the blast furnace per day) and the position of the cohesive zone in Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, exemplary embodiments of the present invention will be described, however, the present invention is not limited to the following embodiments.

[0019] One aspect of the present invention is a method for operating a blast furnace, comprising the steps of: calculating input heat quantities above the tuyere (i.e., generated at the tuyere level and above), including sensible blast heat (also referred to simply as "sensible blast heat" in this disclosure) of gas blown through the tuyere, combustion heat of carbon burning in the raceway (also referred to simply as "carbon combustion heat" in this disclosure), and reaction heat due to an indirect reduction reaction by carbon monoxide (also referred to simply as "indirect reduction heat" in this disclosure); and calculating heat quantities above the tuyere level and above the tuyere, including decomposition heat of blast moisture (also referred to simply as "blast moisture decomposition heat" in this disclosure) of gas blown through the tuyere, decomposition heat of pulverized coal (also referred to simply as "indirect reduction heat" in this disclosure). The present invention provides a blast furnace operation method that uses, as an operation management index, the heat balance above the tuyere (i.e., the heat balance above the tuyere), which is defined as the difference between the output heat quantity above the tuyere, including the reaction heat due to the solution loss reaction, which is an endothermic reaction (also referred to simply as "solution loss reaction heat" in this disclosure), the reaction heat due to the direct reduction reaction (also referred to simply as "direct reduction heat" in this disclosure), and the reaction heat due to the hydrogen reduction reaction (i.e., the reduction reaction of iron ore with hydrogen) (also referred to simply as "hydrogen reduction heat" in this disclosure).

[0020] Here, the solution loss reaction heat and the direct reduction reaction heat are sometimes collectively referred to as "solution loss carbon reaction heat." Solution loss carbon refers to all the carbon fed into the furnace other than the carbon burned in the raceway. Specifically, it refers to the carbon in the coke charged from the top of the furnace that is converted into CO as it descends in the furnace. 2 Carbon reacted with FeO. Carbon and CO 2 Reaction with (C+CO 2 The reaction of carbon with FeO (C+FeO→CO+Fe) is a direct reduction reaction, but the two reactions cannot be clearly distinguished. For this reason, the total amount of carbon that contributed to both reactions is called solution loss carbon, and the reaction heat of both reactions is sometimes collectively called "reaction heat of solution loss carbon."

[0021] In this disclosure, "using a furnace heat index as an operation management index" means observing the increase or decrease in the furnace heat index over time and taking operational action according to the increase or decrease. In addition, in this disclosure, the gas blown from the tuyere is not limited to the oxygen-enriched, humidity-controlled air blown from the hot stove, i.e., hot air, but also includes the reducing gas blown separately when the reducing gas is blown.

[0022] In general, furnace heat indexes are controlled by adjusting tuyere conditions such as pulverized coal injection amount, blast moisture amount, and blast temperature, and when a large furnace heat drop occurs, the coke is increased. Also, production volume is adjusted mainly by adjusting the blast volume and oxygen enrichment amount. The inventors have studied a method for collecting data in a short period that can reduce the time lag until the measurement results of the furnace heat index are reflected in the operation action, while making the data contain sufficient information for appropriate operation action. As a result, it was found that a combination of specific parameters above the tuyere level among many operation parameters of a blast furnace is useful for the above method and enables precise control of the blast furnace heat balance. It was also found that by using the combination of the specific parameters as a target variable for automatic blast furnace control, it is possible to determine appropriate operation actions even in automatic control.

[0023] Usually, in the output heat quantity, the sensible heat of the molten pig iron (i.e., the sensible heat of the pig iron tapped from the blast furnace) is the maximum, but it is difficult to measure the molten pig iron temperature in a short cycle. The molten pig iron temperature can be obtained by a known method from the hearth temperature, the amount of heat removed by the stave, etc., but since the conditions in the lower part of the blast furnace are not constant and difficult to grasp, it is not possible to know the temperature with a certain degree of accuracy in a short cycle. Therefore, the inventors of the present invention have focused on stabilizing the cohesive zone level by monitoring the heat balance above the blast furnace tuyere level as described above and controlling the difference between the heat input (input heat quantity) and the heat output (output heat quantity) to be constant. The input heat quantity and output heat quantity above the blast furnace tuyere level are parameters that can be grasped in a short cycle and can be measured with relatively high accuracy. Therefore, by controlling the heat balance above the tuyere level to be constant, it is possible to control the blast furnace condition in a short cycle and with high accuracy.

[0024] If the heat balance above the tuyere is constant, it can be assumed that the cohesive zone level is kept in a converged state within an assumed operational range. In the method of this embodiment, the heat balance above the tuyere, which is defined as the difference between the input heat amount above the tuyere obtained from a combination of specific parameters and the output heat amount above the tuyere obtained from a combination of specific parameters, is used as an operational management index, and the amount and timing of operational actions are optimized so that this difference is constant.

[0025] 1 is a diagram for explaining furnace heat indexes used to control the heat balance above the tuyere in a blast furnace operation method according to one embodiment of the present invention. In general blast furnace operation, the input heat is mainly provided by carbon combustion heat 101 (specifically, coke combustion heat and pulverized coal combustion heat), blast sensible heat 102, other sensible heat 103, indirect reduction heat 104, slag formation heat 105, etc., among which the heat of carbon combustion heat and blast sensible heat are large. The output heat is mainly provided by dissipation heat 201 (for example, furnace body heat extraction), hydrogen reduction heat 202, furnace top gas sensible heat 203, pulverized coal decomposition heat 204, blast moisture decomposition heat 205, solution loss reaction heat 206, direct reduction heat 207, molten iron sensible heat 208, molten iron component reduction heat 209, etc., among which the heat of solution loss reaction and direct reduction heat (i.e., solution loss carbon reaction heat) are large. In the method of the present embodiment, the input heat amount and output heat amount on the tuyere (i.e., generated at the tuyere level and above), i.e., the input heat amount on the tuyere including the carbon combustion heat 101, the blast sensible heat 102, and the indirect reduction heat 104, and the output heat amount on the tuyere including the hydrogen reduction heat 202, the pulverized coal decomposition heat 204, the blast moisture decomposition heat 205, the solution loss reaction heat 206, and the direct reduction heat 207, are used as the furnace heat index. In another aspect, the input heat amount on the tuyere may not include the indirect reduction heat 104, and the output heat amount on the tuyere may not include the hydrogen reduction heat 202. In yet another aspect, the furnace top gas sensible heat 203 and / or the heat dissipated from the furnace body on the tuyere among the heat dissipation 201 as the output heat amount on the tuyere are further included in the furnace heat index. In yet another embodiment, when reducing gas or non-reducing gas is injected from a shaft tuyere in the shaft section of the blast furnace, the sensible heat and reaction heat from these gases can be further included in the furnace heat index.

[0026] Here, the sensible heat of blast is the value obtained as the sensible heat of nitrogen, oxygen and blast moisture up to the blast temperature, and the heat of carbon combustion is the value obtained from the amount of oxygen fed to the tuyere. The solution loss reaction heat and direct reduction heat (i.e., the reaction heat of solution loss carbon) are calculated by multiplying the amount of carbon fed from the furnace top and tuyere, the amount of burned carbon and the amount of carbon in the top gas (specifically, the amount of CO and CO in the top gas).2 This value is obtained from the solution loss carbon amount, which is the difference between the amount of solution loss carbon obtained by gas chromatography analysis of the raw material.

[0027] The heat balance above the tuyere used in the method of this embodiment can be calculated based on information that can be measured sequentially in a short period, such as the charging conditions at the furnace top, the tuyere tip conditions, and the gas components at the furnace top. This is advantageous in that there is little time lag until the measurement results are reflected in the operation action. In addition, the method of this embodiment is advantageous in that heat balance control is simple and accurate compared to estimation based on unknown indices, since furnace heat indices that are not special as individual heat indices can be utilized. In particular, since the method of this embodiment does not require a measured value of the molten iron temperature, it is possible to set the calculation period of the furnace heat indices to a short period, for example, in units of seconds at the shortest. In a typical embodiment, the measurement period of the operation data may be, for example, every 5 minutes, for process reasons such as the measurement period of gas chromatography.

[0028] According to the method of this embodiment, the heat balance can be calculated almost based on only three elements, oxygen, nitrogen, and hydrogen, and the heat balance can be calculated in a short period of, for example, minutes. Conventionally, the solution loss carbon amount has been used as a furnace heat index other than the molten iron temperature, but in the method of this embodiment, this solution loss carbon amount is also used indirectly. For example, when only the solution loss carbon amount is used as the furnace heat index, there is a problem that precise operation action is difficult because the change in heat, such as sensible heat of blast caused by changing the blast operation (blast amount, etc.) for furnace heat control, is not taken into account as an index. However, according to the method of this embodiment, the heat balance above the tuyere is calculated taking into account the solution loss carbon as well as the heat index related to the tuyere tip condition, so that more precise operation of the blast furnace is possible and operation can be stabilized.

[0029] The method of this embodiment can have the following advantages. (1) Since blast furnace control is possible by collecting only furnace heat indicators at the tuyere and above, it is possible to obtain operating data in a short period and therefore control the furnace heat of the blast furnace in a short period, compared to a method that uses, for example, the molten iron temperature as the furnace heat indicator. (2) The molten iron temperature, which is an index that is affected by conditions below the cohesive zone (liquid flow when pig iron and slag are dripped, gas flow, the filling condition of the hearth and deadman, slag-metal reaction, the condition of the tap hole and launder, etc.), can be excluded from the furnace heat index. Therefore, it is possible to grasp the heat balance based on the reactions that are actually occurring from the cohesive zone to the upper part of the furnace. That is, control using the molten iron temperature as a furnace heat index is significantly affected by changes in the filling structure at the hearth and the state near the tap hole, making it difficult to determine whether fluctuations in heat balance are due to reactions above the cohesive zone or changes in the hearth condition, and may instead induce furnace heat fluctuations (and therefore fluctuations in ventilation and heat load).The method of this embodiment controls the blast furnace by comprehensively considering the main heat balance above the tuyere, so that the heat level at least above the tuyere (i.e., the region roughly above the deadman) can be stably controlled, and therefore the position of the cohesive zone can be stably maintained. (3) By using the sensible heat of the air and oxygen, which are used as actions at the same time, in addition to the reaction heat and reduction heat of the coke and pulverized coal, as indicators, more precise control of the blast furnace is possible. In other words, since the furnace heat index almost covers the main heat balance above the tuyere (including not only the heat corresponding to the reduction state but also the sensible heat of the blast), precise control of the cohesive zone level and the heat balance above the tuyere is possible.

[0030] In one embodiment, the heat balance above the tuyere is calculated according to the following formula (1): Heat balance above the tuyere (GJ / h) = [carbon combustion heat + blast sensible heat + indirect reduction heat - blast moisture decomposition heat - pulverized coal decomposition heat - solution loss reaction heat - direct reduction heat - hydrogen reduction heat] (GJ / h) (1) This is the heat balance above the tuyere per hour (unit: GJ / h) (hereinafter simply referred to as the heat balance above the tuyere (GJ / h)).

[0031] The above formula (1) is a heat balance formula that takes into account both the heat of reaction at the tuyere and the heat of reaction by reduction. Referring again to FIG. 1, from various furnace heat indicators of the blast furnace, the carbon combustion heat 101, the blast sensible heat 102, the indirect reduction heat 104, the hydrogen reduction heat 202, the pulverized coal decomposition heat 204, the blast moisture decomposition heat 205, the solution loss reaction heat 206, and the direct reduction heat 207 are selected and operation data is acquired (step S10 described later), and a heat balance calculation value above the tuyere is obtained according to formula (1) using the acquired operation data (step S12 described later). The decrease in the heat balance value above the tuyere means that the heat level in the furnace will decrease in the future, which is expected to result in a decrease in the molten iron temperature. Therefore, when the heat balance value above the tuyere decreases, the operation action is executed to increase the heat balance value above the tuyere (step S16 described later). On the other hand, an increase in the heat balance value above the tuyere means that the heat level in the furnace will increase in the future, which will lead to an increase in the molten iron temperature and / or the furnace top temperature, and ultimately to a deterioration in ventilation. Therefore, when the heat balance value above the tuyere increases, the process proceeds to execute an operational action to reduce the heat balance value above the tuyere (step S16 described later).

[0032] In one embodiment, a target range for the heat balance above the tuyere (GJ / h) is preset as a reference value, and some operational action is taken if the calculated value of the heat balance above the tuyere (GJ / h) deviates from the reference value.

[0033] In one embodiment, the target range for the heat balance above the tuyere (GJ / h) may be set to a specific range of values, for example: The formula: A 1 ≦Calculated heat balance above the tuyere (GJ / h)≦A 2 (In the formula, A 1 and A 2 are between 600GJ / h and 2000GJ / h, respectively. However, this varies depending on the blast furnace's internal volume and production level.) In this case, the calculated heat balance above the tuyere (GJ / h) may be determined as follows: 1 Less than or A 2If the target is greater than 1, perform some operational action. 1 may preferably be 800 GJ / h or more, or 1000 GJ / h or more, or 1200 GJ / h or more. 2 may preferably be 1800 GJ / h or less, or 1600 GJ / h or less, or 1400 GJ / h or less. 3 In a preferred example of a class A blast furnace, 1 is 1500GJ / h, and A 2 is 1700GJ / h. 5000m 3 In another preferred example of a class A blast furnace, 1 is 1300GJ / h, and A 2 is 1450GJ / h. 3000m 3 In a preferred example of a class A blast furnace, 1 is 820GJ / h, and A 2 is 850GJ / h. A 1 and A 2 When determining the capacity of a blast furnace, a coefficient may be multiplied by the capacity of the furnace. This allows operation design using a common coefficient for multiple blast furnaces with different capacities. For example, 3 ) multiplied by 0.25 to 0.35 to get A 1 (GJ / h) and the furnace volume (m 3 ) multiplied by 0.28 to 0.40 to obtain A 2 (GJ / h).

[0034] In one embodiment, the target range of the heat balance above the tuyere (GJ / h) may be determined by the degree of deviation from a predetermined heat balance above the tuyere (GJ / h) set value (also referred to as a set balance value in this disclosure), for example, by the following formula: Set balance value x B 1 ≦Calculated heat balance above the tuyere (GJ / h) ≦Set balance value × B 2 In this case, the calculated heat balance above the tuyere (GJ / h) is the set balance value x B 1 Less than or set balance value × B 2 If the value is greater than the threshold, perform some operational action.1 is a value less than 1.00, and is preferably 0.95 or more, or 0.98 or more, or 0.99 or more. 2 is a value greater than 1.00, and is preferably 1.05 or less, or 1.02 or less, or 1.01 or less. In addition, the target range of the heat balance above the tuyere (GJ / h) may be determined not based on the set balance value, but based on the degree of deviation from the calculated value of the heat balance above the tuyere (GJ / h) calculated from the operational data at the start of control (also referred to as the initial balance value in this disclosure).

[0035] The relationship between the furnace heat index measured as the operation data and the operation action corresponding to the furnace heat index is known to those skilled in the art. For example, the carbon combustion heat can be controlled by increasing or decreasing the coke charge amount, increasing or decreasing the pulverized coal injection amount, selecting each of the coal types of coke and pulverized coal, and the like, and the blast sensible heat can be controlled by changing the blast conditions such as the blast volume, blast temperature, blast moisture, oxygen enrichment amount, hydrogen gas injection amount, and liquefied natural gas injection amount. Operational actions that increase or decrease the carbon combustion heat and blast sensible heat, which are furnace heat indexes with large heat amounts, are useful for controlling the heat balance above the tuyere. Examples of operational actions that are executed when the calculated value of the heat balance above the tuyere falls below the reference value include increasing the coke charge amount, increasing the pulverized coal injection amount, increasing the blast temperature, and reducing the blast moisture, and the operational action when the calculated value of the heat balance above the tuyere exceeds the reference value is the opposite operation to the above.

[0036] In the method of this embodiment, instead of the above-mentioned heat balance above the tuyere (GJ / h), the heat balance above the tuyere per pig iron output (GJ / tp) can also be used as an operation control index. When the heat balance above the tuyere (GJ / h) is used as an operation control index, the operation action does not take into account the pig iron output, and therefore, when operating a blast furnace while varying the pig iron output, the operation action may not necessarily be ideal. By using the heat balance above the tuyere per pig iron output (GJ / tp) as an operation control index, the blast furnace can be operated more strictly while varying the pig iron output. The heat balance above the tuyere per pig iron output (GJ / tp) is particularly advantageous in automating the operation of a blast furnace.

[0037] That is, one aspect of the present invention provides a method for operating a blast furnace, which uses, as an operational management index, a heat balance above the tuyere per iron production, which is defined as the difference between the input heat quantity above the tuyere, which includes the sensible heat of the blast of the gas blown through the tuyere, the heat of combustion of carbon burning in the raceway, and the reaction heat due to the indirect reduction reaction by carbon monoxide, and the output heat quantity above the tuyere, which includes the decomposition heat of the blast moisture of the gas blown through the tuyere, the reaction heat due to the endothermic solution loss reaction and the direct reduction reaction, the reaction heat due to the hydrogen reduction reaction (i.e., the reduction reaction of iron ore by hydrogen), and the decomposition heat of pulverized coal, divided by the calculated iron production.

[0038] The calculated iron production rate is an estimated iron production rate that can be calculated from the material balance of the charge from the top of the blast furnace, the top gas components, and the like. The calculation method of the calculated iron production rate is not particularly limited. For example, in a method of estimating the iron production rate from the oxygen balance, the iron production rate can be calculated from the gas components at the top of the blast furnace based on the fact that the oxygen brought in by the ore is reduced and removed by the CO generated at the tuyere to produce molten iron. In addition, for example, in a method of estimating the iron production rate from the amount of ore charged into the furnace, the iron production rate is calculated from the amount of ore charged from the top of the furnace per unit time. The calculated iron production rate may be a weighted average of the value obtained by the method of estimating the iron production rate from the oxygen balance and the value obtained by the method of estimating the iron production rate from the amount of iron charged into the furnace.

[0039] In one embodiment, the heat balance above the tuyere per unit of hot metal production (GJ / tp) is calculated according to the following formula (3): Heat balance above the tuyere per iron production (GJ / tp) = [carbon combustion heat + blast sensible heat + indirect reduction heat - blast moisture decomposition heat - pulverized coal decomposition heat - solution loss reaction heat - direct reduction heat - hydrogen reduction heat] (GJ / h) / calculated iron production (tp / h) (3) That is, Heat balance above the tuyere per iron production (GJ / tp) = Heat balance above the tuyere (GJ / h) / Calculated iron production (tp / h) It is defined as: In this embodiment, a target range for the heat balance above the tuyere per pig iron production rate (GJ / tp) is preset as a reference value, and some operational action is taken if the calculated value of the heat balance above the tuyere per pig iron production rate (GJ / tp) deviates from the reference value.

[0040] In one embodiment, the target range of the heat balance above the tuyere per tonne (GJ / tp) may be set to a specific range of values, for example, as defined by the following formula: C 1 ≦Calculated value of heat balance above the tuyere per production amount (GJ / tp)≦C 2 (In the formula, C 1 and C 2 are between 2.80GJ / tp and 4.00GJ / tp, respectively.) In this case, the calculated heat balance above the tuyere per unit of production (GJ / tp) may be determined as follows: 1 Less than or C 2 If the value is greater than the threshold, perform some operational action. 1 may preferably be 3.00 GJ / tp or more, or 3.20 GJ / tp or more. 2 may be preferably 3.80 GJ / tp or less, or 3.60 GJ / tp or less, or 3.40 GJ / tp or less. In a preferred example, C 1 is 3.00GJ / tp, and C 2 is 3.40GJ / tp.

[0041] In one embodiment, the target range of the heat balance above the tuyere per unit of pig iron production (GJ / tp) may be determined by the degree of deviation from a predetermined heat balance above the tuyere per unit of pig iron production (GJ / tp) set value (also referred to as a set balance value in this disclosure), for example, by the following formula: Set balance value x D 1 ≦Calculated value of heat balance above the tuyere per amount of hot metal produced (GJ / tp) ≦Set balance value × D 2 In this case, the calculated heat balance above the tuyere per unit of iron production (GJ / tp) is the set balance value x D 1 Less than or set balance value x D 2If the value is greater than 1, perform some operational action. 1 is a value less than 1, and is preferably 0.95 or more, or 0.98 or more, or 0.99 or more. D 2 is a value greater than 1, and is preferably 1.05 or less, or 1.02 or less, or 1.01 or less. In addition, the target range of the heat balance above the tuyere per iron production rate (GJ / tp) may be determined not based on the set balance value, but based on the degree of deviation from the calculated value of the heat balance above the tuyere per iron production rate (GJ / tp) calculated from the operating data at the start of control (also referred to as the initial balance value in this disclosure).

[0042] In both the embodiment in which the heat balance above the tuyere (GJ / h) is the operation management index and the embodiment in which the heat balance above the tuyere per iron output (GJ / tp) is the operation management index, the output heat quantity may further include the sensible heat of the furnace top gas and / or the heat extraction amount of the furnace body in the region above the tuyere. As is known to those skilled in the art, the sensible heat of the furnace top gas is calculated by multiplying the flow rate of the furnace top gas by the average temperature and the gas specific heat of the furnace top gas, and the heat extraction amount of the furnace body is calculated by dividing the heat load by the iron output. The heat load is calculated by multiplying the temperature difference between the supply and discharge water of the stave by the amount of feed water. The output heat quantity may be calculated by simply setting the sensible heat of the furnace top gas and the heat extraction amount of the furnace body to zero or a fixed value, but it is preferable to calculate the sensible heat of the furnace top gas and the heat extraction amount of the furnace body as described above, since the heat balance above the tuyere can be more appropriately managed.

[0043] Therefore, in one embodiment, the heat balance above the tuyere (GJ / h) can be defined by the following equation (2): Heat balance above the tuyere (GJ / h) = [Carbon combustion heat + sensible heat of blast + indirect reduction heat – sensible heat of top gas – heat removal from furnace body – heat of blast moisture decomposition – heat of pulverized coal decomposition – solution loss reaction heat – direct reduction heat – hydrogen reduction heat] (GJ / h) (2)

[0044] In one embodiment, the heat balance above the tuyere per calculated pig iron production (GJ / tp) can be defined by the following formula (4). Heat balance above the tuyere per iron production (GJ / tp) = [Carbon combustion heat + blast sensible heat + indirect reduction heat – top gas sensible heat – furnace body heat removal – blast moisture decomposition heat – pulverized coal decomposition heat – solution loss reaction heat – direct reduction heat – hydrogen reduction heat] / calculated iron production (tp / h) (4)

[0045] The input heat quantity above the tuyere and the output heat quantity above the tuyere used to calculate the heat balance above the tuyere may further include furnace heat indicators other than those described above for the purpose of more precisely managing the heat balance above the tuyere, and such additional furnace heat indicators may be selected arbitrarily. From the viewpoint of significantly obtaining the advantage of the method of this embodiment that the blast furnace can be precisely controlled only by the furnace heat indicator above the tuyere, it is preferable that the furnace heat indicators used as operation management indicators in the method of this embodiment are only those related to the input heat quantity and / or output heat quantity above the tuyere. Therefore, in a typical aspect, the furnace heat indicators used as operation management indicators in the method of this embodiment do not include the lower furnace heat extraction amount (e.g., stave heat extraction amount).

[0046] Next, a specific procedure for carrying out the method of this embodiment will be described. Fig. 2 is a flow chart showing the processing carried out in the blast furnace operation method according to one aspect of the present invention. Referring to Fig. 2, first, the operation data of the furnace heat index exemplified above is acquired (step S10). Next, based on the acquired operation data, a calculated value of the heat balance above the tuyere, specifically, the heat balance above the tuyere (GJ / h) or the heat balance above the tuyere per iron tapping rate (GJ / tp) is obtained (step S12).

[0047] Next, the calculated value of the heat balance above the tuyere is compared with a preset reference value of the heat balance above the tuyere to determine whether or not the calculated value of the heat balance above the tuyere satisfies the reference value (step S14). If the result of the determination in step S14 is that the calculated value of the heat balance above the tuyere does not satisfy the reference value, the process proceeds to step S16. In step S16, an operational action is executed to bring the heat balance above the tuyere closer to the reference value. On the other hand, if the calculated value of the heat balance above the tuyere satisfies the reference value in step S14, the process in this control cycle is terminated without performing the process in step S16. In this manner, feedback control can be performed so that the calculated value of the heat balance above the tuyere satisfies the reference value. EXAMPLES

[0048] The exemplary embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0049] [Example 1] Furnace capacity 5000m 3 A simulation of blast furnace operation was carried out for an actual blast furnace with a reducing agent rate of about 330 kg / t. The model used in the simulation was a one-dimensional unsteady model.

[0050] The carbon combustion heat, blast sensible heat, indirect reduction heat, blast moisture decomposition heat, pulverized coal decomposition heat, solution loss carbon reaction heat, and hydrogen reduction heat were calculated using a known method (see Shigemi Akitoshi's Ironmaking Handbook, p. 186 - Chapter 6, Blast Furnace Operation Theory, "6.3 Heat Calculation for Blast Furnaces"). Based on the obtained values, the following formula (1): Heat balance above the tuyere (GJ / h) = [carbon combustion heat + blast sensible heat + indirect reduction heat - blast moisture decomposition heat - pulverized coal decomposition heat - solution loss reaction heat - direct reduction heat - hydrogen reduction heat] (GJ / h) (1) According to the above, the heat balance above the tuyere (GJ / h) was calculated to be 1375 (GJ / h). Based on this, the target range of the heat balance above the tuyere (GJ / h) was set to 1361 to 1389 (GJ / h) with a ±1% margin, and this was set as the standard value.

[0051] Next, data for each of the above parameters was obtained every 60 seconds while the blast furnace was operating. From the obtained data, the carbon combustion heat, blast sensible heat, indirect reduction heat, blast moisture decomposition heat, pulverized coal decomposition heat, reaction heat of solution loss carbon, and hydrogen reduction heat were calculated by the above method, and the heat balance above the tuyere (GJ / h) was calculated according to the above formula (1).

[0052] Whether the calculated heat balance above the tuyere (GJ / h) met the above-mentioned standard value was judged each time data was acquired (i.e., every 60 seconds as mentioned above). If it met the standard value, the operating conditions were not changed. If it did not, the blast furnace was operated so that the heat balance above the tuyere was kept constant by increasing or decreasing the operating conditions, for example, the amount of pulverized coal injection.

[0053] On the other hand, the estimated position of the cohesive zone from the tuyere was calculated using a one-dimensional unsteady model for each data acquisition. 3 The relationship between the amount of hot metal produced per day (horizontal axis) and the estimated location of the cohesive zone from the tuyere (vertical axis) is plotted.

[0054] [Comparative Example 1] The results of conventional operation, in which thermal action was carried out based on the molten iron temperature without using the heat balance above the tuyere, are plotted in Figure 4.

[0055] 3 and 4, in Example 1, in which the blast furnace operation method according to the present invention was used, the fluctuation of the cohesive zone position when the productivity fluctuated was significantly smaller than in Comparative Example 1. More specifically, when the productivity was about 2.0 t / day / m 3 ~About 2.4t / day / m 3In Comparative Example 1, the estimated cohesive zone position from the tuyere in the range was widely distributed over a range of about 0 m to about 3.0 m (the center of the distribution was in the range of about 0.9 m to about 2.6 m), whereas in Example 1, it was within a range of about 1.0 m to about 2.0 m (the center of the distribution was in the range of about 1.1 m to about 1.5 m). Furthermore, in Example 1, the variation in the estimated cohesive zone position from the tuyere at a certain productivity was significantly smaller than in Comparative Example 1. More specifically, for example, at a productivity of 2.2 t / day / m 3 In the comparative example 1, the estimated cohesive zone position from the tuyere varied from about 0.8 m to about 2.5 m (about ±0.5 m at the center of the distribution), whereas in the example 1, it was within the range of about 1.1 m to about 1.4 m (about ±0.1 m at the center of the distribution). Thus, in the example 1, a remarkable operation stabilization effect was obtained. [Explanation of symbols]

[0056] 101 Carbon Combustion Heat 102 Sensible heat of ventilation 103 Other sensible heat 104 Indirect reduction heat 105 Heat of slag formation 201 Dissipated heat 202 Hydrogen reduction heat 203 Top gas sensible heat 204 Heat of decomposition of pulverized coal 205 Blow moisture decomposition heat 206 Solution loss reaction heat 207 Direct reduction heat 208 Molten iron sensible heat 209 Heat of reduction of molten iron components

Claims

1. In the operation of a blast furnace, The input heat quantity on the tuyere includes the sensible heat of the gas blown from the tuyere and the heat of combustion of carbon burning in the raceway; An output heat quantity on the tuyere including the decomposition heat of the blast moisture contained in the gas blown from the tuyere, the decomposition heat of the pulverized coal, and the reaction heat due to the solution loss reaction and the direct reduction reaction; The heat balance above the tuyere, defined as the difference between A method for operating a blast furnace, comprising: setting a target range for the heat balance above the tuyere as a reference value in advance; and implementing an operational action when the calculated value of the heat balance above the tuyere deviates from the reference value.

2. The method for operating a blast furnace according to claim 1, characterized in that the heat balance above the tuyere is defined by the following formula (1). Heat balance above the tuyere (GJ / h) = [carbon combustion heat + sensible heat of blast + indirect reduction heat - blast moisture decomposition heat - pulverized coal decomposition heat - solution loss reaction heat - direct reduction heat - hydrogen reduction heat] (GJ / h) ... (1)

3. The method for operating a blast furnace according to claim 1, characterized in that the heat balance above the tuyere is defined by the following formula (2). Heat balance above the tuyere (GJ / h) = [carbon combustion heat + sensible heat of blast + indirect reduction heat - sensible heat of furnace top gas - heat extraction from furnace body - heat of blast moisture decomposition - heat of pulverized coal decomposition - solution loss reaction heat - direct reduction heat - hydrogen reduction heat] (GJ / h) ... (2)

4. In the operation of a blast furnace, An input heat amount including the sensible heat of the gas blown from the tuyere and the combustion heat of carbon burning in the raceway; Output heat including heat of decomposition of blast moisture contained in the gas blown from the tuyere, heat of decomposition of pulverized coal, and heat of reaction due to solution loss reaction and direct reduction reaction; The heat balance above the tuyere per unit of iron production, defined as the difference between the calculated iron production and the actual iron production, is used as an operational management index. A method for operating a blast furnace, comprising: setting a target range for the heat balance above the tuyere per iron output as a reference value in advance; and implementing operational action if the calculated value of the heat balance above the tuyere per iron output deviates from the reference value.

5. The method for operating a blast furnace according to claim 4, characterized in that the heat balance above the tuyere per unit of iron production is defined by the following formula (3): Heat balance above the tuyere (GJ / tp) = [carbon combustion heat + blast sensible heat + indirect reduction heat - blast moisture decomposition heat - pulverized coal decomposition heat - solution loss reaction heat - direct reduction heat - hydrogen reduction heat] (GJ / h) / calculated pig iron production (tp / h) ... (3)

6. The method for operating a blast furnace according to claim 4, characterized in that the heat balance above the tuyere per unit of iron production is defined by the following formula (4): Heat balance above the tuyere (GJ / tp) = [carbon combustion heat + sensible heat of blast + indirect reduction heat - sensible heat of furnace top gas - heat removal from furnace body - heat of blast moisture decomposition - heat of pulverized coal decomposition - solution loss reaction heat - direct reduction heat - hydrogen reduction heat] (GJ / h) / calculated pig iron production (tp / h) ... (4)

Images