JP2022148377A - Blast furnace operation method - Google Patents

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

The present invention relates to a method of operating a blast furnace.

In general, in blast furnace operation, blast furnace raw materials (ore raw materials, coke and auxiliary raw materials, and in some cases scrap, unburned coal-containing agglomerate ore, ferro-coke, etc.) are conveyed to the furnace top charging device by a conveyor, and Charge into the blast furnace. The top charging device is configured so that the uppermost surface of the charge in the blast furnace can be maintained at a predetermined height position, and if the uppermost surface of the charge drops, it compensates for the drop. Blast furnace raw material is charged into the blast furnace as follows. The ore raw material and the coke are alternately stacked to form layers in the blast furnace, and descend in the furnace while maintaining the layered form. Hot air and pulverized coal as a reducing agent are blown into the blast furnace from the blower tuyere at the bottom of the blast furnace. Pulverized coal and coke are combusted by hot air blown from the blower tuyeres to generate high-temperature reducing gases such as carbon monoxide and hydrogen. Further, gas such as coke oven gas (COG) or natural gas (NG) may be blown from the blower tuyeres (or other tuyeres).

The reducing gas turns into a violent rising air current and blows up in the furnace, and reduces the ore raw material descending in the furnace while raising the temperature of the ore raw material (indirect reduction). The FeO generated as a result drips inside the coke layer in a molten state, contacts with the carbon of the coke and is further reduced (direct reduction), and becomes hot metal containing less than 5% carbon and accumulates in the hot water pool at the bottom of the furnace. . This molten iron is taken out from the tap hole provided on the side of the hearth and carried to the next steelmaking process.

Conventionally, in the operation of a blast furnace, an operational management index is set, and the furnace condition is controlled by monitoring the time transition of the operational management index and executing the corresponding operational action. Therefore, setting an appropriate operation control index is extremely important for stable operation of a blast furnace. In particular, when automating the operation of a blast furnace, it is important to appropriately define an operation control index that can be a target variable for automatic control.

Operation management indicators include hot metal temperature, hot metal Si content, solution loss carbon content, furnace top gas composition (CO concentration, CO ₂ concentration, CO + CO ₂ concentration, ηCO (= CO ₂ / (CO + CO ₂ )), etc.), heat load etc. Conventionally, after monitoring these values, the operator has made appropriate and comprehensive judgments to carry out operational actions (for example, adjustment of pulverized coal injection amount, blast humidity, etc.). In addition, when performing constant adjustment of the production volume, in addition to the calculated iron tapping amount, solution loss carbon amount, and reducing material ratio, Tf (theoretical combustion temperature at the tuyere tip) is also taken into account, has been adjusted.

Various methods of setting operational management indexes and selecting operational conditions based thereon have been proposed in the past. For example, Patent Document 1 classifies the heat balance change and the hot metal temperature obtained from a heat balance model that estimates the heat balance in the lower part of the furnace into predetermined ranges, determines the furnace heat trend rank, and operates in advance for each furnace heat trend rank. In addition to setting the conditions, the operating conditions are selected from the amount of heat balance change at the time of furnace heat judgment and the hot metal temperature, history information of hot metal temperature until furnace heat judgment, coke ratio, moisture content, blast temperature, blast volume A method of operating a blast furnace, characterized in that operating conditions are selected from operating conditions before and after including the reference based on the operating conditions according to each history information of the operating conditions already implemented, and the blast furnace is operated. do.

Further, Patent Document 2 describes a. determining the furnace heat level from the temperature of the hot metal tapped from the blast furnace; b. Determining the 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 the furnace heat index obtained from the sensor data; c. A furnace heat control method for a blast furnace, characterized in that an operational action is performed according to the furnace heat level and the furnace heat transition level.

Further, Patent Document 3 discloses a hot metal temperature prediction method for predicting the hot metal temperature in a blast furnace using a physical model capable of calculating the state in the blast furnace in an unsteady state, and describes 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 heat loss amount of the furnace body, the sensitivity between the values calculated by the physical model and the actual value of the actual operation data a step of optimizing the parameters related to the gas reduction rate or the furnace body heat loss amount in the physical model so that the sensitivities of the blast furnaces match each other, and predicting the hot metal temperature in the blast furnace using the physical model with the optimized parameters. A hot metal temperature prediction method is described, comprising:

In addition, Patent Document 4 discloses a furnace heat management method during blast furnace operation, in which the auxiliary fuel injection amount is added to the calculated coke ratio obtained by dividing the coke consumption rate obtained from the furnace top gas component etc. by the pig iron production rate. Calculate the calculated fuel ratio by adding the value obtained by dividing by the production speed and multiplying the replacement rate, calculate the calculated corrected fuel ratio by correcting the calculated fuel ratio with the air temperature and air humidity, and calculate the calculated corrected fuel ratio describes a blast furnace heat management method characterized by controlling the heat balance in the furnace by adjusting the blast humidity, the amount of pulverized coal injected, the blast temperature, and the charged coke ratio so that the is a predetermined set value. .

JP-A-1-319616 JP 2014-118599 A JP 2018-24936 A JP-A-10-46215

Patent Documents 1 to 3 are techniques for determining operation actions using the hot metal temperature as a furnace heat index, and Patent Document 4 uses a calculated fuel ratio or a calculated corrected fuel ratio as a furnace heat index to determine operation actions. Technology. However, these indices are not sufficiently effective for improving the stability of blast furnace operation to a satisfactory level. ) required further investigation of the furnace heat index.

For example, in the monitoring of hot metal temperature and/or hot metal Si content as described in Patent Documents 1 to 3, the frequency of measurement is low (usually about once an hour), so the measurement results are reflected in operational actions. The time lag was large, and it was insufficient for precise reactor condition control. In addition, the hot metal temperature and hot metal Si content are greatly influenced by the gas flow when FeO is dripped from the cohesive zone, the state of filling of the furnace bottom and core, slag metal reaction, etc., and the state of the tap hole and trough. Therefore, there is a problem that the control of the molten iron temperature and/or the molten iron Si content does not necessarily lead to the stabilization of the blast furnace operation by stabilizing the state of the cohesive zone (especially the position of the cohesive zone).

On the other hand, according to gas chromatographic analysis values of furnace top gas components as described in Patent Document 4, short-period data can be obtained. However, the analytical value alone is not sufficient for precise control of the blast furnace because it only considers the heat according to the reduction state.

An object of one aspect of the present invention is to solve the above problems and provide a blast furnace operating method that enables precise control of the blast furnace heat level.

[1] In the method of operating a blast furnace,
The input heat on the tuyere including the blast sensible heat of the gas blown from the tuyere and the combustion heat of the carbon burned on the raceway,
Output heat on the tuyere including heat of decomposition of blast moisture possessed by 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;
A method of operating a blast furnace, characterized in that a heat balance on the tuyere defined as the difference between is used as an operation control index.
[2] The method of operating a blast furnace according to [1] above, wherein the heat balance on the tuyeres is defined by the following formula (1).
Heat balance on 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) h) (1)
[3] The method for operating a blast furnace according to [1] above, wherein the heat balance on the tuyere is defined by the following formula (2).
Tuyere heat balance (GJ/h) = [carbon combustion heat + blast sensible heat + indirect reduction heat - furnace 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) (2)
[4] In the method of operating a blast furnace,
The input heat amount including the sensible heat of the gas blown from the tuyere and the combustion heat of the carbon burned on the raceway,
Output heat including decomposition heat of blast moisture possessed by gas blown from tuyeres, decomposition heat of pulverized coal, and reaction heat due to solution loss reaction and direct reduction reaction;
A method of operating a blast furnace, characterized in that a heat balance on the tuyere per tapped amount defined as a value obtained by dividing the difference of the calculated tapped amount by the calculated tapped amount is used as an operation control index.
[5] The method for operating a blast furnace according to [4] above, wherein the heat balance on the tuyere per amount of tapped iron is defined by the following formula (3).
Tuyere top heat balance (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 output (tp/h) (3)
[6] The method for operating a blast furnace according to [4] above, wherein the heat balance on the tuyere per amount of tapped iron is defined by the following formula (4).
Tuyere heat balance (GJ/tp) = [carbon combustion heat + blast sensible heat + indirect reduction heat - furnace top gas sensible heat - furnace body heat removal - blast moisture decomposition heat - pulverized coal decomposition heat - solution loss reaction heat - heat of direct reduction - heat of hydrogen reduction] (GJ/h)/calculated iron output (tp/h) (4)

According to one aspect of the present invention, a method of operating a blast furnace can be provided that allows for precise control of the blast furnace heat level.

FIG. 4 is a diagram explaining a furnace heat index used for controlling the heat balance on the tuyere in the operating method of the blast furnace according to one aspect of the present invention. 4 is a flow chart showing processing performed in a method for operating a blast furnace according to one aspect of the present invention. 2 is a diagram showing the relationship between the tapping ratio (that is, the amount of tapped iron per day per 1 m ³ of blast furnace internal volume) and the position of the cohesive zone in Example 1. FIG. 2 is a diagram showing the relationship between the tapping ratio (that is, the amount of tapped iron per day per 1 m ³ of blast furnace internal volume) and the position of the cohesive zone in Comparative Example 1. FIG.

Illustrative embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

One aspect of the present invention is a method for operating a blast furnace, in which sensible heat of the blast of gas blown from the tuyere (also simply referred to as "sensible heat of the blast" in the present disclosure), combustion heat of carbon burned on the raceway (this (also referred to simply as "carbon combustion heat" in the disclosure), and reaction heat due to the indirect reduction reaction by carbon monoxide (also referred to as simply "indirect reduction heat" in the present disclosure) on the tuyere (i.e., at tuyere level and The input heat generated above this), the decomposition heat of the blast moisture possessed by the gas blown from the tuyere (also referred to simply as the “blast moisture decomposition heat” in this disclosure), the decomposition heat of pulverized coal (in this disclosure Also simply referred to as "pulverized coal decomposition heat".), reaction heat due to an endothermic solution loss reaction (also simply referred to as "solution loss reaction heat" in the present disclosure), and reaction heat due to direct reduction reaction (simply referred to as " Also referred to as “direct reduction heat”), 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). Provided is a method of operating a blast furnace using the heat balance above the tuyere (that is, the heat balance above the tuyere) defined as the difference between , as an operational control index.

Here, the solution loss reaction heat and the direct reduction reaction heat may be collectively referred to as "solution loss carbon reaction heat". Solution loss carbon refers to the carbon other than the carbon burned on the raceway out of all the carbon supplied into the furnace. carbon that reacted with CO ₂ and FeO as it descended in the atmosphere. The reaction between carbon and CO ₂ (C+CO ₂ →2CO) is a solution loss reaction, and the reaction between carbon and FeO (C+FeO→CO+Fe) is a direct reduction reaction, but the two reactions cannot be clearly distinguished. Therefore, 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 "solution loss carbon reaction heat".

In the present disclosure, "using a certain furnace heat index as an operational management index" means observing changes in the furnace heat index over time and taking operational actions according to the changes. Further, in the present disclosure, the gas blown from the tuyere is not limited to air that is oxygen-enriched and humidity-controlled and blown from the hot blast stove, that is, hot air, but also includes the gas if a reducing gas is separately blown.

In general, the furnace heat index is controlled by adjusting the tuyere tip conditions such as the amount of pulverized coal injected, the blast moisture content, and the blast temperature. do. The production volume is adjusted mainly by adjusting the air flow rate and the oxygen enrichment rate. The present inventors have found that it is possible to collect data in a short period that can reduce the time lag until the measurement result of the furnace heat index is reflected in the operational action, but the data is sufficient for appropriate operational action. We considered a method to include such information. As a result, it has been found that certain combinations of a number of blast furnace operating parameters above the tuyere level are useful in the above approach, allowing for precise control of the blast furnace heat balance. Further, the inventors have found that by using the combination of the specific parameters as target variables for automatic blast furnace control, it becomes possible to determine appropriate operational actions even in automatic control.

Normally, the sensible heat of molten iron (that is, the sensible heat of pig iron tapped from a blast furnace) is the largest output heat quantity, but it is difficult to measure the molten iron temperature in a short period. The molten iron temperature can be obtained by a known method from the hearth temperature, the amount of heat removed by the stave, etc. However, since the conditions in the lower part of the blast furnace are not constant and it is difficult to grasp, it is necessary to obtain a certain degree of accuracy in a short period. cannot be known by Therefore, the present inventors monitor the heat balance above the blast furnace tuyere level as described above, and control the difference between the heat input (input heat amount) and the heat output (output heat amount) to be constant. Focused on stabilizing the cohesive zone level. The input heat quantity and the output heat quantity above the blast furnace tuyere level are parameters that can be grasped in a short period and can be measured with relatively high accuracy. Therefore, by controlling the heat balance above the tuyere level to be constant, short-cycle and highly accurate blast furnace condition control becomes possible.

If the tuyere heat balance is constant, it can be assumed that the cohesive zone level remains converged within the operationally assumed range. In the method of this embodiment, the heat balance on the tuyere defined as the difference between the input heat quantity on the tuyere obtained from the combination of specific parameters and the output heat quantity on the tuyere obtained from the combination of specific parameters is used as an operation management index. to optimize the amount and timing of fishing actions so that this difference is constant.

FIG. 1 is a diagram illustrating a furnace heat index used for controlling the heat balance on the tuyere in the blast furnace operating method according to one aspect of the present invention. In general blast furnace operation, the input heat is mainly 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, and slag generation heat. 105 etc. Among them, the amount of heat of carbon combustion heat and air sensible heat is large. In addition, the output heat amount is mainly radiated heat 201 (for example, heat removal from the furnace body), hydrogen reduction heat 202, furnace top gas sensible heat 203, pulverized coal decomposition heat 204, blast moisture decomposition heat 205, and solution loss reaction heat 206. , direct reduction heat 207, molten iron sensible heat 208, molten iron component reduction heat 209, etc. Among them, solution loss reaction heat and direct reduction heat (that is, reaction heat of solution loss carbon) are large. In the method of the present embodiment, the heat input and the heat output on the tuyere (i.e., occurring at the tuyere level and above), i.e. Input heat and output heat on the tuyeres including hydrogen reduction heat 202, pulverized coal decomposition heat 204, blast moisture decomposition heat 205, solution loss reaction heat 206 and direct reduction heat 207 are used as furnace heat indices. In another aspect, the input heat on the tuyere may not include the indirect reduction heat 104 and the output heat on the tuyere may not include the hydrogen reduction heat 202 . In another aspect, the furnace heat index further includes the furnace top gas sensible heat 203 and/or the furnace body heat removal on the tuyere among the heat dissipation 201 as the output heat amount on the tuyere. In still another aspect, when a reducing gas or a non-reducing gas is blown from the shaft tuyeres in the shaft of the blast furnace, the sensible heat and reaction heat of these gases are also included in the furnace heat index. be able to.

Here, the sensible heat of blast is a value obtained as sensible heat of nitrogen, oxygen, and blast moisture up to the blast temperature, and the carbon combustion heat is a value obtained from the amount of oxygen supplied to the tip of the tuyere. Solution loss reaction heat and direct reduction heat (that is, solution loss carbon reaction heat) are the amount of carbon charged from the furnace top and tuyeres, the amount of burned carbon, and the amount of carbon in the furnace top gas (specifically, It is a value obtained from the amount of solution loss carbon, which is the difference from the amount of carbon obtained by gas chromatography analysis of CO and _CO2 in the furnace top gas.

The heat balance on the tuyere used in the method of the present embodiment can be calculated based on information that can be sequentially measured in a short period, such as charging conditions at the furnace top, tuyere tip conditions, gas components at the furnace top, etc. This is advantageous in that there is little time lag until measurement results are reflected in operational actions. In addition, according to the method of the present embodiment, the furnace heat index, which is not special, can be used as an individual heat index, so heat balance control is simpler and more accurate than, for example, estimation based on an unknown index. But it is advantageous. In particular, since the method of the present embodiment does not require the measured value of the hot metal temperature, the calculation period of the furnace heat index can be set to a short period, for example, seconds at the shortest. In a typical embodiment, the operational data measurement cycle may be, for example, every 5 minutes for reasons of process such as gas chromatography measurement cycle.

According to the method of the present embodiment, the heat balance can be almost calculated based only on the three elements of oxygen, nitrogen, and hydrogen. Conventionally, the amount of solution loss carbon is used as a furnace heat index other than the hot metal temperature, but in the method of the present embodiment, the amount of solution loss carbon is also used indirectly. For example, if only the amount of solution loss carbon is used as a furnace heat index, changes in heat such as sensible heat generated by changing the blowing operation (blowing volume, etc.) for furnace heat control are not taken into account as an index. However, there was a problem that it was difficult to carry out effective operation actions. However, according to the method of the present embodiment, the heat balance on the tuyere is calculated in consideration of the heat index related to the tuyere tip condition as well as the solution loss carbon, so that the blast furnace can be operated more precisely, and the operation is stable. can be made.

The method of this embodiment can have the following advantages.
(1) Since it is possible to control the blast furnace by collecting only the furnace heat index of the tuyere and above, for example, compared to the method of using the hot metal temperature as the furnace heat index, operation data can be obtained in a short period. Furnace heat control of the blast furnace in cycles is possible.
(2) Conditions below the cohesive zone (pig iron and slag dripping liquid flow, gas flow, filling condition of furnace bottom and core, slag metal reaction, taphole and trough conditions, etc.) affect Since the molten iron temperature, which is an index, can be excluded from the furnace heat index, it is possible to grasp the heat balance based on the reactions actually occurring from the cohesive zone to the upper part of the furnace.
In other words, the control using the hot metal temperature as a furnace heat index is greatly affected by changes in the filling structure of the furnace bottom and the conditions near the tap hole. It is difficult to determine which one of the changes in the situation is caused by the change, and it may rather induce furnace heat fluctuations (thus, ventilation and heat load fluctuations). Since the method of the present embodiment comprehensively considers the main heat balance on the tuyere to control the blast furnace, at least the heat level on the tuyere (that is, the area above the core) is stabilized. controllable, thus stably maintaining the position of the cohesive zone.
(3) In addition to the heat of reaction and heat of reduction of coke and pulverized coal, it is possible to control the blast furnace more precisely by using the sensible heat of air and oxygen, which are simultaneously used as actions, as indices.
That is, since the furnace heat index almost covers the main heat balance above the tuyere (including the sensible heat of the blast in addition to the heat corresponding to the reduction state), the cohesive zone level and above the tuyere Precise control of heat balance is possible.

In one aspect, the heat balance on the tuyere is represented by the following formula (1):
Heat balance on 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) h) (1)
is the heat balance on the tuyere per hour (unit: GJ/h) (hereinafter also simply referred to as the heat balance on the tuyere (GJ/h)) per hour.

Equation (1) above is a heat balance equation that takes into consideration both the heat of reaction at the tuyeres and the heat of reaction due to reduction. Referring to FIG. 1 again, from various furnace heat indices of the blast furnace, carbon combustion heat 101, blast sensible heat 102, indirect reduction heat 104, hydrogen reduction heat 202, pulverized coal decomposition heat 204, blast moisture content Decomposition heat 205, solution loss reaction heat 206, and direct reduction heat 207 are selected to acquire operation data (step S10 described later), and the acquired operation data is used to calculate the heat balance on the tuyere according to equation (1). A calculated value is obtained (step S12 to be described later). A decrease in the above-tuyere heat balance value means that the heat level in the furnace is expected to decrease in the future, thereby lowering the hot metal temperature. Therefore, when the upper tuyere heat balance value is lowered, an operation action is executed to increase the upper tuyere heat balance value (step S16, which will be described later). On the other hand, an increase in the tuyere heat balance value means that the heat level in the furnace will increase in the future, which will lead to an increase in the hot metal temperature and/or the furnace top temperature, which in turn will lead to deterioration of ventilation. . Therefore, when the tuyere heat balance value rises, an operational action is executed to reduce the tuyere heat balance value (step S16, which will be described later).

In one aspect, a target range of tuyere heat balance (GJ/h) is preset as a reference value, and some operational action is taken when the calculated tuyere heat balance (GJ/h) deviates from the reference value. do.

In one aspect, the target range for tuyere heat balance (GJ/h) may be set to a specific numerical range, e.g.
The formula below:
A ₁ ≤ tuyere upper heat balance (GJ/h) calculated value ≤ A ₂
(In the formula, A ₁ and A ₂ are each a value of 600 GJ/h to 2000 GJ/h. However, it varies depending on the volume inside the blast furnace and the level of tapping amount.)
may be determined by In this case, if the calculated tuyere heat balance (GJ/h) is less than A ₁ or greater than A ₂ , take some operational action. A ₁ may preferably be 800 GJ/h or more, or 1000 GJ/h or more, or 1200 GJ/h or more. _A2 may preferably be 1800 GJ/h or less, or 1600 GJ/h or less, or 1400 GJ/h or less. In a preferred example for a 5000 m ³ class blast furnace, A ₁ is 1500 GJ/h and A ₂ is 1700 GJ/h. In another preferred example for a 5000 m ³ class blast furnace, A ₁ is 1300 GJ/h and A ₂ is 1450 GJ/h. In a preferred example in a ³⁰⁰⁰ m3 _class blast furnace, A1 is 820 GJ/h and _A2 is 850 GJ/h.
When determining A ₁ and A ₂ , the furnace volume may be multiplied by a coefficient, and according to this, an operation design using a common coefficient can be performed for a plurality of blast furnaces having different furnace volumes. For example, the value obtained by multiplying the furnace volume (m ³ ) by 0.25 to 0.35 is A ₁ (GJ/h), and the value obtained by multiplying the furnace volume (m ³ ) by 0.28 to 0.40 is A ₂ (GJ/h).

In one aspect, the target range of the tuyere heat balance (GJ/h) is the degree of deviation from a predetermined tuyere heat balance (GJ/h) set value (also referred to as the set balance value in the present disclosure). may be defined by, for example, the following formula:
Set balance value × B ₁ ≤ Heat balance on tuyere (GJ/h) calculated value ≤ Set balance value × B ₂
may be determined by In this case, if the calculated tuyere heat balance (GJ/h) is _less than the set balance value times B1 or _more than the set balance value times B2, then some operational action is taken. B ₁ has a value of less than 1.00, preferably 0.95 or more, or 0.98 or more, or 0.99 or more. B2 has a value greater _than 1.00, preferably 1.05 or less, or 1.02 or less, or 1.01 or less.
In addition, the target range of the heat balance on the tuyere (GJ/h) is not based on the set balance value, but the calculated value of the heat balance on the tuyere (GJ/h) calculated from the operation data at the start of control (in the present disclosure, the initial balance It may also be determined by the degree of divergence from the value.

A person skilled in the art knows the relationship between a furnace heat index measured as operational data and an operational action corresponding to the furnace heat index. For example, the carbon combustion heat can be controlled by increasing or decreasing the amount of coke charged, increasing or decreasing the amount of pulverized coal blown, selection of each coal type of coke and pulverized coal, etc. It can be controlled by changing blast conditions such as blast moisture, oxygen enrichment, hydrogen gas blow rate, liquefied natural gas blow rate, and the like. Operational actions that increase or decrease carbon combustion heat and blast sensible heat, which are furnace heat indices with large amounts of heat, are useful for controlling the heat balance on the tuyere. Examples of operational actions to be taken when the calculated tuyere heat balance falls below the reference value include increasing coke charge, increasing pulverized coal injection, increasing blast temperature, reducing blast moisture, etc. , and the operation action when the calculated value of heat balance on the tuyere exceeds the reference value is the opposite operation to the above.

In the method of the present embodiment, instead of the heat balance on the tuyere (GJ/h), the heat balance on the tuyere per amount of tapped iron (GJ/tp) can be used as an operation control index. When the heat balance above the tuyere (GJ/h) is used as an operational management index, the operation action does not take into account the amount of iron output. It may not take action. By using the tuyere heat balance per tapped amount (GJ/tp) as an operation management index, the blast furnace can be operated more strictly while varying the tapped amount. The tuyere heat balance per tapped amount (GJ/tp) is particularly advantageous in automating blast furnace operations.

That is, one aspect of the present invention is a method for operating a blast furnace, in which the sensible heat of the blown air of the gas blown from the tuyere, the combustion heat of the carbon burned on the raceway, and the reaction heat due to the indirect reduction reaction by carbon monoxide are combined. The input heat on the tuyeres including the heat of decomposition of the blast moisture possessed by the gas blown from the tuyeres, the reaction heat due to the endothermic solution loss reaction and direct reduction reaction, the hydrogen reduction reaction (that is, the reduction reaction of iron ore with hydrogen ) and the heat output above the tuyere including the heat of decomposition of pulverized coal is divided by the calculated amount of tapped iron. A method of operating a blast furnace is provided.

The calculated amount of pig iron is an estimated amount of pig iron that can be calculated from the material balance of the charge from the top of the blast furnace, the components of the top gas, and the like. The calculation method of the calculated iron tapping amount is not particularly limited. For example, in the method of estimating the amount of tapped iron from the oxygen balance, it is possible to calculate the amount of tapped iron from the gas components at the top of the 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 hot metal. Further, for example, in the method of estimating the amount of tapped iron from the amount charged into the furnace, the amount of tapped iron is calculated from the amount of ore charged from the top of the furnace per unit time. The weighted average of the value obtained by the method of estimating the amount of tapped iron from the oxygen balance and the value obtained by the method of estimating the amount of tapped iron from the amount of charging into the furnace may be adopted as the calculated amount of tapped iron. .

In one aspect, the heat balance on the tuyere per tapped amount (GJ/tp) is given by the following formula (3):
Heat balance on the tuyere per amount of tapped iron (GJ/tp) = [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)/calculated iron output (tp/h) (3)
i.e.
Heat balance on the tuyere per amount of tapped iron (GJ/tp) = Heat balance on the tuyere (GJ/h)/calculated amount of tapped iron (tp/h)
Defined in
In this aspect, the target range of the heat balance on the tuyere per amount of tapped iron (GJ/tp) is set in advance as a reference value, and the calculated value of the heat balance on the tuyere per amount of iron tapped (GJ/tp) deviates from the reference value. perform some operational action when

In one aspect, the target range for tuyere heat balance per tap (GJ/tp) may be set to a specific numerical range, such as the following formula:
C ₁ ≦ Calculated value of heat balance on tuyere per amount of tapped iron (GJ/tp) ≦ C ₂
(Wherein, C ₁ and C ₂ each have a value of 2.80 GJ/tp to 4.00 GJ/tp.)
may be determined by In this case, if the calculated tuyere heat balance _per tap (GJ/tp) is less than C1 or greater than _C2 , then some operational action is taken. C ₁ may preferably be 3.00 GJ/tp or more, or 3.20 GJ/tp or more. _C2 may preferably be 3.80 GJ/tp or less, or 3.60 GJ/tp or less, or 3.40 GJ/tp or less. In _one preferred example, C1 is 3.00 GJ/tp and _C2 is 3.40 GJ/tp.

In one aspect, the target range for heat balance on tuyere per tapped amount (GJ/tp) is a predetermined heat balance on tuyere per tapped amount (GJ/tp) set value (in this disclosure, set balance value It may be determined by the degree of divergence from ), for example, the following formula:
Set balance value x D1 ≤ Calculated value of heat balance on tuyere _per tapping amount (GJ/tp) ≤ Set balance value _x D2
may be determined by In this case, if the calculated tuyere heat balance _per tapped amount (GJ/tp) is less than the set balance value x D1 or greater _than the set balance value x D2, then some operational action is taken. D ₁ has a value of less than 1, preferably 0.95 or more, or 0.98 or more, or 0.99 or more. D2 is a value greater _than 1, preferably 1.05 or less, or 1.02 or less, or 1.01 or less.
In addition, the target range of the heat balance on the tuyere per amount of tapping (GJ/tp) is not based on the set balance value. It may be determined by the degree of deviation from the value (also referred to as the initial balance value in the present disclosure).

In both the embodiment in which the tuyere heat balance (GJ/h) is used as an operational management index and the embodiment in which the tuyere heat balance per tapped amount (GJ/tp) is used as an operational management index, the output calorie is the top gas. It may further include sensible heat and/or furnace body heat removal in the tuyere region. As is known to those skilled in the art, the top gas sensible heat is obtained by multiplying the top gas flow rate by the average temperature of the top gas and the specific heat of the gas, and the heat removal from the furnace body is the heat load. Calculated by dividing by the amount. The heat load is obtained by multiplying the water supply and discharge temperature difference of the stave by the amount of water supply. The output calorie may be calculated simply by setting the top gas sensible heat and the furnace body heat removal amount to zero or fixed values, but if the top gas sensible heat and the furnace body heat removal amount are calculated as described above, It is preferable because the heat balance can be managed more appropriately.

Therefore, in one aspect, the tuyere heat balance (GJ/h) can be defined by the following equation (2).
Tuyere heat balance (GJ/h) = [carbon combustion heat + blast sensible heat + indirect reduction heat - furnace 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) (2)

In one aspect, the heat balance on the tuyere per calculated amount of tapped iron (GJ/tp) can be defined by the following equation (4).
Heat balance on the tuyere per amount of iron output (GJ/tp) = [carbon combustion heat + sensible heat from blast + indirect reduction heat - sensible heat from top gas - heat removal from furnace body - blast moisture decomposition heat - pulverized coal decomposition heat - solution loss reaction heat - direct reduction heat - hydrogen reduction heat]/calculated pig iron output (tp/h) (4)

Each of the tuyere input heat quantity and the tuyere output heat quantity used to calculate the tuyere heat balance further includes a furnace heat index other than those mentioned above for the purpose of more precise control of the tuyere heat balance. and such additional furnace heat indices may be selected arbitrarily. From the viewpoint of significantly obtaining the advantage of the method of the present embodiment that the blast furnace can be precisely controlled only with the furnace heat index above the tuyere, the furnace heat index used as the operation management index in the method of the present embodiment is It is preferable that it is only related to the input heat quantity and/or the output heat quantity above. Therefore, in a typical aspect, the furnace heat index used as an operation management index in the method of the present embodiment does not include the furnace lower heat removal amount (for example, the stave heat removal amount).

Next, a specific implementation procedure of the method of this embodiment will be described. FIG. 2 is a flow chart showing the processing performed in the blast furnace operating method according to one aspect of the present invention. Referring to FIG. 2, first, operation data of the furnace heat index exemplified above is acquired (step S10). Next, based on the acquired operation data, a calculated value of heat balance on the tuyere, specifically, heat balance on the tuyere (GJ/h) or heat balance on the tuyere per amount of tapped iron (GJ/tp) is obtained (step S12 ).

Next, the calculated value of the heat balance on the tuyere is compared with a preset reference value of the heat balance on the tuyere, and it is determined whether or not the calculated value of the heat balance on the tuyere satisfies the reference value (step S14). As a result of the determination in step S14, if the tuyere top heat balance calculated value does not satisfy the reference value, the process proceeds to step S16. In step S16, an operation action is performed so that the heat balance on the tuyere approaches the reference value. On the other hand, in step S14, when the tuyere top heat balance calculated value satisfies the reference value, the process in this control cycle is terminated without performing the process of step S16. As described above, feedback control can be performed so that the tuyere upper heat balance calculated value satisfies the reference value.

EXAMPLES 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.

[Example 1]
A blast furnace operation simulation was performed for an actual blast furnace with a furnace volume of 5000 m ³ and a reducing agent ratio of about 330 kg/t. The model used for the simulation is a one-dimensional unsteady model.

By a known method (Akitoshi Shigemi Ironmaking Handbook P186-Chapter 6 Blast Furnace Operation Theory "6.3 Blast Furnace Heat Calculation"), carbon combustion heat, blast sensible heat, indirect reduction heat, blast moisture decomposition heat, The heat of decomposition of pulverized coal, the heat of reaction of solution loss carbon, and the heat of hydrogen reduction were calculated.
Based on the obtained values, the following formula (1):
Heat balance on 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) h) (1)
When the heat balance (GJ/h) on the tuyere was calculated according to the above, it was 1375 (GJ/h). Based on this, the target range of tuyere heat balance (GJ/h) was set to 1361 to 1389 (GJ/h) of ±1%, which was set as the reference value.

Data for each of the above parameters were then acquired 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, solution loss carbon reaction heat, and hydrogen reduction heat are calculated by the above method, and the above formula (1 ) to obtain the calculated tuyere heat balance (GJ/h).

Whether the calculated tuyere heat balance (GJ/h) calculated value satisfies the above reference value is determined each time data is acquired (that is, every 60 seconds), and if it satisfies the above, the operating conditions are not changed. If not, the blast furnace was operated so that the heat balance above the tuyere was kept constant by increasing or decreasing the pulverized coal injection amount among the operating conditions.

On the other hand, the estimated cohesive zone position from the tuyere was calculated using a one-dimensional unsteady model each time the above data was obtained. Fig. 3 shows the tapping ratio (i.e., the amount of tapped iron per day per ^1m3 of the internal volume of the blast furnace) (horizontal axis) and the estimated cohesive zone position from the tuyere (vertical axis) from the start to the end of the simulation operation. plotted the relationship between

[Comparative Example 1]
The results of a conventional run in which heat action was performed based on the hot metal temperature without using the tuyere heat balance are plotted in FIG.

As shown in FIGS. 3 and 4, in Example 1 using the blast furnace operating method according to the present invention, compared with Comparative Example 1, the variation in the position of the cohesive zone when the tapping ratio varies is remarkable. It was less. More specifically, the estimated cohesive zone position from the tuyere in the tapping ratio range of about 2.0 t/day/m ³ to about 2.4 t/day/m ³ is from about 0 m to about 3.0 m (the central portion of the distribution ranged from about 0.9 m to about 2.6 m), whereas Example 1 ranged from about 1.0 m to about 2.0 m (the range of the distribution The central portion was within a range of about 1.1 m to about 1.5 m). Moreover, in Example 1, as compared with Comparative Example 1, the variation in the estimated cohesive zone position from the tuyere at a certain tapping ratio was remarkably small. More specifically, for example, at a tapping ratio of 2.2 t/day/m ³ , in Comparative Example 1, the estimated cohesive zone position from the tuyere is about 0.8 m to about 2.5 m (about ±0.5 m), whereas in Example 1, it fell within a range of approximately 1.1 m to approximately 1.4 m (approximately ±0.1 m at the center of the distribution). Thus, in Example 1, a remarkable effect of stabilizing the operation was obtained.

101 Carbon combustion heat 102 Air sensible heat 103 Other sensible heat 104 Indirect reduction heat 105 Slag generation heat 201 Dissipated heat 202 Hydrogen reduction heat 203 Top gas sensible heat 204 Pulverized coal decomposition heat 205 Air moisture decomposition heat 206 Solution loss reaction heat 207 Direct reduction heat 208 Hot metal sensible heat 209 Hot metal component reduction heat

Claims (6)

In the method of operating a blast furnace,
The input heat on the tuyere including the blast sensible heat of the gas blown from the tuyere and the combustion heat of the carbon burned on the raceway,
Output heat on the tuyere including heat of decomposition of blast moisture possessed by 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;
A method of operating a blast furnace, characterized in that a heat balance on the tuyere defined as the difference between is used as an operation control index. The method of operating a blast furnace according to claim 1, wherein the heat balance on the tuyere is defined by the following formula (1).
Heat balance on 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) h) (1) The method of operating a blast furnace according to claim 1, wherein the heat balance on the tuyere is defined by the following formula (2).
Tuyere heat balance (GJ/h) = [carbon combustion heat + blast sensible heat + indirect reduction heat - furnace 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) (2) In the method of operating a blast furnace,
The input heat amount including the sensible heat of the gas blown from the tuyere and the combustion heat of the carbon burned on the raceway,
Output heat including decomposition heat of blast moisture possessed by gas blown from tuyeres, decomposition heat of pulverized coal, and reaction heat due to solution loss reaction and direct reduction reaction;
A method of operating a blast furnace, characterized in that a heat balance on the tuyere per tapped amount defined as a value obtained by dividing the difference of the calculated tapped amount by the calculated tapped amount is used as an operation control index. 5. The method of operating a blast furnace according to claim 4, wherein the heat balance on the tuyere per amount of tapped iron is defined by the following formula (3).
Tuyere top heat balance (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 output (tp/h) (3) 5. The method of operating a blast furnace according to claim 4, wherein the heat balance on the tuyere per amount of tapped iron is defined by the following formula (4).
Tuyere heat balance (GJ/tp) = [carbon combustion heat + blast sensible heat + indirect reduction heat - furnace top gas sensible heat - furnace body heat removal - blast moisture decomposition heat - pulverized coal decomposition heat - solution loss reaction heat - heat of direct reduction - heat of hydrogen reduction] (GJ/h)/calculated iron output (tp/h) (4)

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