JP4495011B2 - Control method of hot stove - Google Patents

Description

The present invention relates to a control method for a hot stove that blows hot air into a blast furnace.

Conventionally, the blowing of hot air (high temperature air) to a blast furnace is performed by a plurality of hot air furnaces, a preceding hot air furnace that starts air blowing to the blast furnace first, and a subsequent air that starts air blowing after the preceding hot air furnace. It switches to a hot-air stove sequentially and is performed continuously, and it is required to suppress fluctuations in the temperature and pressure of the hot air when blowing. The fluctuation of the blowing temperature of hot air leads to the fluctuation of temperature in the blast furnace and adversely affects the operation of the blast furnace, and also causes the fluctuation of the volume of hot air and the fluctuation of the blowing pressure. This leads to fluctuations in the reactor pressure and affects the blast core position. For this reason, suppression of fluctuations in the blowing pressure is extremely important for blast furnace operation.
In addition, in the operation of blowing pulverized coal accompanying the low coke ratio operation of the blast furnace, which is regarded as important as a recent operation mode, the pulverized coal that is a cold material is blown into the blast furnace furnace. High temperature as well as stabilization has become an important issue. Furthermore, since the amount of pulverized coal used per ton of hot metal discharged from the blast furnace, that is, the ratio of pulverized coal, is determined by the differential pressure between the carrier gas pressure of pulverized coal and the pressure in the blast furnace, The fluctuation leads to fluctuation of the pulverized coal ratio. Accordingly, in recent operation modes in which the pulverized coal ratio is increased at a low coke ratio, fluctuations in the pulverized coal ratio have come to have a significant adverse effect on blast furnace operation.
From the above, suppression of fluctuations in the blowing pressure is an extremely important issue in the operation of blowing pulverized coal.

As a technique for suppressing fluctuations in the blowing temperature of the hot air described above, for example, the cold parallel method described in the prior art of Patent Document 1, that is, the temperature of hot air by mixing air (cold air) not heated in a hot air furnace with hot air There is a system that blows air to the blast furnace after controlling. When using this cold parallel method, it is possible to suppress fluctuations in the blowing temperature, but basically the cold air is mixed into the hot air, so the blowing temperature cannot be increased, and from the viewpoint of energy saving. There was room for improvement.
For this reason, Patent Document 1 proposes a hot parallel system, that is, a system for supplying hot air to a blast furnace without mixing cold air as a technique for increasing the blowing temperature. When this hot parallel system is used, the blast temperature can be increased, but the opening degree of the air flow control valve of the preceding hot stove is fully opened to be constant, and the opening degree of the succeeding hot stove is opened. As a result, fluctuations occurred in the air temperature.
Therefore, as a technique for preventing fluctuations in the blast temperature, for example, in Patent Document 2, the outlet temperature of each of a plurality of hot stoves is measured, and the blowing rate of hot air sent from the plurality of hot stoves based on the measured temperature A method for determining (mixing ratio) has been disclosed.

JP 55-122813 A JP-A-55-10091

However, in general, the blower that supplies air to the hot stove is controlled so that the blowing pressure to the blast furnace is constant. Therefore, as in Patent Document 2, in order to suppress fluctuations in the blowing temperature, The following inconvenience arises when using the method of controlling the opening degree of the air volume control valve that determines the mixing ratio of hot air while measuring the air temperature of the subsequent hot air furnace.
When the opening change of the air flow control valve provided in the hot stove is abrupt, the air pressure change of the blower may not follow the change of the air flow control valve opening, and the air blowing pressure of the hot air that blows to the blast furnace varies To do. Thus, the fluctuation of the blowing pressure of the blower breaks the mixing balance of the amount of hot air sent out from the two hot air furnaces, resulting in a temperature fluctuation of the hot air blown to the blast furnace.
Moreover, when the opening degree of the air flow control valve becomes too small, it may be necessary to set the air blowing pressure of the air blower within a range that deviates from the air blowing capacity range of the air blower. Leads to fluctuations. Also in this case, since the blowing pressure of the blower cannot be stabilized to a predetermined value, the temperature of the hot air blown to the blast furnace is changed as a result.

Thus, it was confirmed that the fact that the blowing pressure of the blower cannot reach the predetermined value is one of the fluctuation factors of the blowing pressure of the hot air.
In addition, when simultaneously operating the blast volume control valves of the preceding hot stove and the succeeding hot stove, if the opening degree is abrupt as described above, the blast pressure to the blast furnace is ± (20-30) × 10 ² ( It has also been found that fluctuation (hunting) may occur in the range of about Pa).
In particular, under conditions where the pulverized coal injection operation accompanying the low coke ratio operation of the blast furnace, that is, the ratio of the pulverized coal injected into the blast furnace is 150 kg or more per ton of hot metal discharged from the blast furnace and the blast temperature is 1200 ° C. or higher, When hot air that does not mix is blown to the blast furnace, the adverse effect of fluctuations in the blowing pressure on the blast furnace operation becomes more prominent.

The present invention has been made in view of such circumstances, and control of a hot stove capable of suppressing temperature fluctuations and suppressing fluctuations in blowing pressure when blowing hot hot air from a hot stove to a blast furnace. It aims to provide a method.

The control method of the hot stove according to the present invention in accordance with the above object includes a preceding hot stove that starts blowing to the blast furnace first, and a succeeding hot stove that starts blowing to the blast furnace after the preceding hot stove. When supplying hot air to the blast furnace without passing cold air and mixing the air to the base hot air furnace, the mixing ratio of the hot air supplied from each hot air furnace is sent to the hot air furnace provided in each hot air furnace. In the control method of the hot stove determined by the opening of the air volume control valve,
Among the two hot stoves, the change of the air flow control valve in the range in which the air pressure control follows the amount of change per unit time of the opening of the air flow control valve provided in at least one hot air furnace. When the opening degree of the air flow control valve is 90 degrees and the closing position is 0 degrees, the amount of air flow exceeds 0 degree per 30 seconds and 2 degrees or less. The opening degree is operated so that the total value of the opening degree of the blowing amount control valve becomes equal to or more than the lower limit value of the value at which the blowing pressure of the blower for blowing air can be maintained within the blowing capacity range.
Here, as the air flow control valve, for example, a butterfly valve or a ball valve can be used.
Further, the amount of change in the air flow control valve corresponds to the amount of hot air blown from the hot blast furnace provided with the air flow control valve to the blast furnace . In general, the blower controls the blowing pressure so that the amount of blown air blown from the blower is constant, but if the amount of change of the blowing amount control valve changes abruptly, the control of the blowing pressure does not follow this change. There is a case. Therefore, the amount of change of the air flow control valve is set to be equal to or less than the upper limit of a value that enables the change in the air blowing pressure of the blower that performs air flow to follow the change in the opening of the air flow control valve.

In here, the sum value of the degree of opening of the air volume control valve, which corresponds to the total blowing rate of the hot air blowing amount control valve is blown from hot air furnaces provided to the blast furnace.

In the method for controlling a hot stove according to the present invention, it is preferable that the opening degree of the air flow control valve of the preceding hot stove is reduced when the succeeding hot stove starts blowing air to the blast furnace.

In the method for controlling a hot stove according to the present invention, the opening adjustment of the air flow control valve is performed by adjusting the ratio of pulverized coal blown into the blast furnace to 150 kg or more per ton of hot metal discharged from the blast furnace, and the hot air blowing temperature to 1200. It is preferable to carry out it under the condition of at least ° C.

The method for controlling a hot stove according to claims 1 to 3, wherein an upper limit value of a change amount of the air flow control valve in a range in which the air pressure control follows the change amount of the air flow control valve provided in the hot air furnace. Since the upper limit value of the change amount is provided as follows, the change amount of the blower pressure of the blower that blows air can be made to follow the change in the opening degree of the blower amount control valve. Thus, when high-temperature hot air is blown from the hot blast furnace to the blast furnace, fluctuations in the blowing temperature can be suppressed and fluctuations in the blowing pressure can be suppressed, so that stable blast furnace operation is possible.

In particular, in the method for controlling a hot stove according to claim 1, the sum of the opening amounts of the air flow control valves of the two hot stoves allows the air blowing pressure of the blower that performs air blowing to be maintained within the air blowing capacity range. Since the opening degree of the air flow control valve is operated so as to be equal to or higher than the lower limit value , the air blowing pressure of the air blower that performs air blowing can be maintained within the air blowing capacity range, and fluctuations in the air blowing temperature and the air blowing pressure can be suppressed.
Moreover, since the control method of the hot stove of Claim 1 has prescribed | regulated the opening degree of the ventilation volume control valve, the fluctuation | variation of the ventilation temperature and ventilation pressure of a hot air can be suppressed reliably.

The method for controlling a hot stove according to claim 2 is such that, when the succeeding hot stove starts air blowing, the opening degree of the air flow control valve of the preceding hot stove is reduced. Fluctuation in the blowing pressure of the blower due to abrupt closing of the control valve can be suppressed, and fluctuation in the blowing pressure of hot air to the blast furnace can be suppressed.

In the control method of the hot stove according to claim 3 , since each condition of the pulverized coal ratio and the hot air blowing temperature is a condition corresponding to a recent operation mode in which the pulverized coal ratio is increased at a low coke ratio, The cost required can be reduced as compared with the prior art.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is an explanatory view of blast furnace equipment using the control method of a hot stove according to an embodiment of the present invention, and FIG. 2 is an explanation showing the operating state of each hot stove using the control method of the hot stove. FIG.

As shown in FIG. 1 and FIG. 2, a control method for a hot stove according to an embodiment of the present invention includes a preceding hot stove (hereinafter also referred to as a preceding furnace) that starts air blowing to the blast furnace 10 first. Two hot air furnaces 11, 12, hot air furnaces 12, 13, hot air furnaces 13, 14, or hot air of a succeeding hot air furnace (hereinafter also referred to as a succeeding furnace) that starts blowing air to the blast furnace 10 after the preceding furnace When air is passed through each of the furnaces 14 and 11 and hot air is supplied to the blast furnace 10 without mixing cold air, the mixing ratio of the hot air supplied from the preceding furnace and the succeeding furnace is set to each of the hot air furnaces 11 to 14. It is a method of determining by the opening degree of the provided air flow control valves 15 to 18, and the change per unit time of the opening degree of the air flow control valve provided in at least one of the two hot stoves. In this method, the amount is set to a certain value or less.
First, after explaining the blast furnace equipment using the hot stove control method according to an embodiment of the present invention, the hot stove control method will be explained.

As shown in FIG. 1, four hot stoves 11 to 14 are arranged in parallel in the blower main pipe 19 connected to the blast furnace 10, and all these hot stoves 11 to 14 are connected to one blower 20. ing. Each hot stove 11-14 has the thermal storage chamber 21 and the combustion chamber 22, respectively, and the thermal storage chamber 21 and the combustion chamber 22 are sequentially arranged from the blower 20 (upstream) side to the blast furnace 10 (downstream) side. ing. Moreover, each hot stove 11-14 has the ventilation control pipes 23-26 which connect the ventilation main piping 19 and each combustion chamber 22, and the ventilation volume control valve provided sequentially from the blast furnace 10 side of this ventilation control pipe 23-26. 15-18 and on-off valves 27-30. Examples of the air flow control valves 15 to 18 include butterfly valves or ball valves. As the on-off valves 27 to 30, conventionally known on-off valves that can be selected to be fully open or fully closed can be used.

Thereby, for example, after blast furnace gas, coke gas, and air are burned in each combustion chamber 22 to create a heat source, and this combustion gas is stored in bricks arranged in the heat storage chamber 21 (the above, heat storage step), The air blown by the blower 20 is passed through the heat storage chamber 21, and the air is heated to, for example, 1200 ° C. or more and blown to the blast furnace 10 (the blowing process).
The operations of the blower 20, the air flow control valves 15 to 18, and the on-off valves 27 to 30 are controlled by the control device 31. In addition, the temperature and pressure of hot air measured by a sensor 32 arranged immediately before the blast furnace 10 in the blower main pipe 19 are also input to the control device 31.

Subsequently, a hot stove control method according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. Here, the stacking parallel system is applied as a system for blowing hot air from the four hot air furnaces 11 to 14 shown in FIG. 1 to the blast furnace 10. In this stacker parallel system, the four hot air ovens 11 to 14 are alternately and continuously repeated for 90 minutes each for the air blowing process and the heat storage process, and the four hot air ovens 11 to 14 are shifted by 45 minutes. By operating, it is a system which always blows air to the blast furnace 10 from two hot stoves. Of the two hot blast furnaces that perform this blast, the blast furnace 10 starts to be blown first, and the hot blast furnace in the latter half of the blowing process is called the preceding furnace, and the blast furnace 10 is blown after the preceding furnace. The hot stove that starts and is in the first half of the blowing process is called a trailing furnace. In addition, since the preceding furnace consumes heat storage in the first half of the blowing process, its discharge temperature is lower than that of the succeeding furnace, and each discharge temperature of the succeeding furnace and the preceding furnace is time-series in each blowing process. Decline.

First, the opening degree of each of the air flow control valves 15 to 18 will be described with reference to FIG. In FIG. 2, the horizontal axis represents time, and the vertical axis represents the opening degree of each of the air flow control valves 15-18. In FIG. 2, since the corresponding opening / closing valves 27 to 30 are fully opened only when the opening degree of each of the air flow control valves 15 to 18 is 45 degrees or more, the air flow control valves 15 to 18 for performing air blowing. Is in the range of 45 to 90 degrees.

When air blowing is started by such a method, the air flow control valves 15 to 18 are set to 45 degrees while the on-off valves 27 to 30 are closed, and the on-off valves 27 to 30 are opened to start air blowing. To do. On the other hand, when stopping air blowing, the air flow control valves 15 to 18 are closed to 45 degrees, and the on-off valves 27 to 30 that are open at the time of 45 degrees are closed.
In addition, in FIG. 2, the opening degree of the ventilation volume control valves 15-18 of the four hot stove furnaces 11-14 is each shown as the continuous line, the dotted line, the dashed-dotted line, and the long broken line.

At the time (T1) when the hot stove 12 starts to blow air by the control device 31, the opening degree of the air flow control valve 15 of the hot stove 11 starts to decrease (at this stage, the hot stove 11 is the preceding furnace and the hot stove 12). Is equivalent to a trailing furnace). The amount of change in the opening degree of the air flow control valve 15 of the hot stove 11 is set to a certain value or less per unit time.
The amount of change in the opening degree of the air flow control valve needs to be a change amount that can be followed by the change in the air pressure of the blower. This is, for example, related to the air blower or its control specifications, and is therefore generally the upper limit of the amount of change. It is difficult to decide. When actually determining the amount of change in the opening degree of the air flow control valve, the opening degree of the air flow control valve of one of the two hot air furnaces blowing air to the blast furnace is made constant, It can be obtained by changing the amount of change per unit time of the opening degree of the blast volume control valve of the hot stove and investigating the blast pressure fluctuation to the blast furnace.

As described above, in FIG. 2, when the opening degree of the air flow control valve 15 is 90 degrees, the air flow control valve 15 is fully opened, and when the opening degree is 45 degrees, it is fully closed, that is, 0 degrees. The change amount is set to a speed of 90 degrees per 45 minutes, that is, a speed of 1 degree per 30 seconds. However, there is no problem even if the amount of change of the air flow control valve 15 is increased to a speed of 2 degrees per 30 seconds.
Thus, the upper limit of the amount of change of the air flow control valve 15 is set to 2 degrees per 30 seconds when the air flow control valve 15 is fully open 90 degrees and fully closed is 0 degrees. The change in the blowing pressure can follow the amount of change in the opening degree of the blowing amount control valve 15, and the pressure fluctuation of the hot air blown to the blast furnace 10 can be suppressed as compared with the conventional case. The lower limit value of the air flow control valve 15 is a change amount exceeding 0 degrees per 30 seconds. The upper limit value and the lower limit value of the amount of change are the same for the air volume control valves 16 to 18 of the other hot stove 12 to 14 when the preceding furnace is used.

In addition, as the air flow control valve for adjusting the opening degree, it is possible to target either the air flow control valve of the preceding furnace or the succeeding furnace, but to the air flow control valve of the preceding furnace. In this case, the control device closes the blast volume control valve of the preceding furnace based on the above-described upper limit value. At this time, the air flow control valve of the succeeding furnace is adjusted by the control device so that the air temperature fluctuation to the blast furnace input to the control device is suppressed (basically, the air flow control valve is opened. It is desirable to go. It is possible to adjust the air flow temperature to the blast furnace while adjusting the opening of the air flow control valve of the preceding furnace with a known numerical value and starting the air blowing of the succeeding furnace where the detailed value of the temperature is unknown. This is because it contributes to stable operation.

At this time, if the opening amounts of the air volume control valves 15 and 16 of the two hot air furnaces 11 and 12 that are blowing hot air to the blast furnace 10 are too small, the air pressure of the blower 20 is set to an appropriate air pressure. Since it is set to a value that deviates from the capacity range, the total value of the opening amounts of the air flow control valves 11 and 12 is set to be equal to or greater than a preset threshold value. The same applies to the other two hot air furnaces 12 and 13, the hot air furnaces 13 and 14, or the hot air furnaces 14 and 11 that simultaneously blow hot air to the blast furnace 10.
Here, when the total value is less than the threshold value, it may cause an excessive increase in the original pressure of the blower 20, and the blower 20 may cause surging. It may have an adverse effect over temperature fluctuations.

Regarding the setting of this threshold value, for example, it is necessary to consider the blower or its control specifications, for example, similarly to the above-described opening change amount of the air flow control valve, so it is difficult to determine the threshold value in general. However, for example, it is obtained by changing the opening degree of the air flow control valve 16 of the other hot stove 12 while keeping the opening degree of the air blowing control valve 15 of one hot air furnace 11 constant among the two hot stoves. be able to. This threshold value is set so that the air pressure fluctuations to the blast furnace 10 are suppressed to the minimum value when the total opening value is 90 degrees or more when the air flow control valves 15 and 16 are fully opened at 90 degrees and the fully closed state is 0 degrees. it can. Therefore, the upper limit value can be up to 180 degrees.
Thus, if the total value of the opening degree of the air flow control valves 15 and 16 of the two hot stoves 11 and 12 is managed, the air blowing pressure of the air blower 20 can be set within the air blowing capacity range.

Note that the opening degree of the blast volume control valve of the preceding furnace is reduced at the time when the succeeding furnace starts to blow to the blast furnace 10 when blowing air to the blast furnace 10 due to the following circumstances.
The time during which one hot stove 11 (same as the hot stove 12-14) can blow air to the blast furnace 10 strongly depends on the amount of heat stored in the heat storage bricks of the hot stove 11, so that air is blown from the start of air blowing of the single hot stove 11. The time to completion is generally constant. For this reason, if the opening degree of the blast volume control valve of the preceding furnace at the time when the succeeding furnace starts blowing air to the blast furnace 10 (generally, it is often fully open) is maintained for a certain period of time, the opening degree will eventually be reduced. The opening degree of the blast flow control valve of the preceding furnace to be reduced must be reduced in a shorter time. Thus, if it is going to close the ventilation volume control valve rapidly in a short time, the ventilation pressure fluctuation | variation of the air blower 20 will become large, and the original pressure of the air blower 20 will be fluctuate | varied rapidly.

By the above method, the opening / closing valve 27 is closed when the opening degree of the air flow control valve 15 of the hot stove 11 reaches 45 degrees (T2), and then the opening degree of the air flow control valve 17 is set to 45 degrees in advance. The open / close valve 29 of the hot stove 13 is opened, and the opening degree of the air flow control valve 17 is gradually increased by the method described above. At this time, the air flow control valve 16 of the hot stove 12 is fully opened until the opening degree of the air flow control valve 15 of the hot stove 11 decreases to 45 degrees. As described above, the time from T1 to T2 is approximately 45 minutes.
By repeating the above operations in sequence, the change in the blowing pressure of the blower 20 is made to follow the change in the opening degree of the blowing amount control valves 15 to 18 of the respective hot stove furnaces 11 to 14, and the blowing amount of the blower 20 is set to an appropriate blowing capacity. It becomes possible to set the range.

In addition, the opening degree adjustment of the air flow control valves 15 to 18 described above is performed by adjusting the ratio of the pulverized coal blown into the blast furnace 10 to 150 kg (i.e., 150 kg / ton-pig) or more per 1 ton of hot metal discharged from the blast furnace 10. It is preferable to carry out under the condition that the blast temperature is 1200 ° C. or higher.
When pulverized coal is blown into the blast furnace 10, the amount of pulverized coal injected is determined by the carrier gas pressure of the pulverized coal and the pressure in the blast furnace, so that the amount of pulverized coal varies when the pressure in the blast furnace varies. In particular, in the case of low coke ratio operation in which a large amount of pulverized coal ratio of 150 kg / ton-pig or more is blown, fluctuations in the pulverized coal ratio have a significant adverse effect on the stability of the reaction in the blast furnace.

Therefore, the adjustment of the opening amount of the air flow control valve that suppresses fluctuations in the air temperature and pressure of the hot air exhibits its effect remarkably under the conditions of low coke ratio operation, and in particular, the pulverized coal ratio is 170 kg / ton- If it is greater than or equal to pig, the effect appears more remarkably.
In the present embodiment, there is no particular upper limit on the pulverized coal ratio to be applied, and the effect is exhibited even at, for example, about 270 kg / ton-pig, which is currently the highest level.
Moreover, in this Embodiment, the upper limit of the ventilation temperature to the blast furnace 10 to apply depends on the equipment specification of the hot stove 11-11. In addition, even if the blowing temperature of a hot air is the maximum temperature 1260 degreeC in a normal hot stove, an effect is exhibited.

Next, examples carried out for confirming the effects of the present invention will be described.
Here, the hot air sent from the preceding furnace and the succeeding furnace is mixed so that the blowing amount is about 6400 (Nm ³ / min) and the blowing pressure is about 4021 × 10 ² (Pa), and the blast furnace having a furnace volume of 4250 m ³ is mixed. The air was blown to.
When blowing air to the blast furnace, the air flow control valve of the preceding furnace is closed based on the set value in Table 1 to be described later, and the air temperature to the blast furnace is within a range of 1230 ± 10 ° C. (targeting the central value) Then, the opening degree of the blast volume control valve of the succeeding furnace was controlled. In the control, the blowing temperature and blowing amount of hot air sent from the preceding furnace (determined by the opening degree of the blowing amount control valve), the hot blowing temperature sent from the succeeding furnace, the blowing amount, and the mixing to the blast furnace Based on the measured value of the blast temperature, the correction value of the blast amount sent from the succeeding furnace is obtained so that the variation of the blast temperature to the blast furnace is minimized, and the opening degree is controlled.
Based on the above conditions, the operating conditions of Reference Example 1 and Example 2 and Comparative Examples 1 and 2 were set, and the blast furnace operation was carried out for 45 minutes, respectively. Accompanying temperature fluctuations (temperature control is carried out, but pressure fluctuations cause inevitable temperature fluctuations in the control) were measured. Table 1 shows the operation conditions and the operation results.

In Table 1, in both Reference Example 1 and Example 2, the change amount per unit time of the opening amount control valve of the preceding furnace, that is, the opening change speed is set to 1 degree per 30 seconds, and This is a condition in which the air flow control valve opening change speed is set to 1 degree or less per 15 seconds so that the air blowing pressure change of the blower can follow the air flow control valve opening change. In both Reference Example 1 and Example 2, when the succeeding furnace started to send air to the blast furnace, the opening degree of the air volume control valve of the preceding furnace was reduced to suppress the air pressure fluctuation of the blower. Further, in Example 2, the lower limit value of the sum of the opening amounts of the air flow control valves of the preceding furnace and the succeeding furnace is set to 90 degrees, and the air volume is set within an appropriate air blowing capacity range of the blower. is there.

On the other hand, in both Comparative Examples 1 and 2, the change amount per unit time of the opening amount of the blast amount control valve of the preceding furnace is set to 1 degree per 10 seconds, and the change amount is made faster than those in Reference Example 1 and Example 2. The condition is such that the change in the blowing pressure of the blower cannot follow the change in the opening degree of the blowing amount control valve. In addition, Comparative Example 1 is a condition in which the lower limit value of the sum of the opening amounts of the blower amount control valves of the two hot stove furnaces is set to 90 degrees, and the blower amount is set within an appropriate blowing capacity range of the blower. The comparative example 2 is the conditions which set the lower limit to 60 degree | times, and set the ventilation volume outside the suitable ventilation capability range of the air blower.

In the case of Reference Example 1, pressure fluctuation occurred during blast furnace operation, but it was in a range where there was no problem in operation. On the other hand, when the opening degree of the blast volume control valve of the preceding furnace is increased as in Comparative Examples 1 and 2, the blast pressure change of the blower cannot follow the change in the opening degree of the blast volume control valve. The opening change speed of the air flow control valve exceeded 1 degree per 15 seconds, and the pressure fluctuation and temperature fluctuation of the hot air increased.
In addition, as in Example 2, the lower limit value of the sum total of the opening amounts of the air flow control valves provided in the two hot stoves is set to 90 degrees or more, compared with the case of Reference Example 1. It was confirmed that both pressure fluctuation and temperature fluctuation can be reduced. In addition, it turns out that each fluctuation range can be reduced clearly compared with the comparative examples 1 and 2.

Next, the case where the pulverized coal ratio is changed will be described.
In addition, about the blast furnace which blows in hot air, the blowing quantity of hot air, blowing pressure, and the blowing method to a blast furnace, it was set as the conditions similar to the above-mentioned conditions.
Based on the above conditions, the operating conditions of Examples 3 to 5 and Comparative Examples 3 to 5 are set, and the blast furnace operation is performed for 45 minutes, respectively. In addition to measuring fluctuations, the hot metal temperature fluctuations were also measured as a stabilization index for blast furnace operation. Table 2 shows the operation conditions and the operation results.

Here, in Examples 3 to 5, the opening degree change speed of the blast volume control valve of the preceding furnace is 1 degree per 30 seconds, and the opening degree change speed of the blast quantity control valve of the succeeding furnace is 1 degree or less per 15 seconds. The change in the blower air pressure can follow the change in the air flow control valve opening, and the lower limit of the sum of the air flow control valve opening in the preceding and succeeding furnaces is 90 degrees. This is a condition in which the air volume is set within an appropriate blowing capacity range of the blower. In Examples 3 to 5, when the succeeding furnace starts blowing air to the blast furnace, the opening degree of the air volume control valve of the preceding furnace is reduced to suppress fluctuations in the air blowing pressure of the blower. Furthermore, Example 3 is an operation condition for low coke ratio operation with a pulverized coal ratio of 165 (kg / ton-pig) and an air temperature of 1230 ° C., and Example 5 further has a pulverized coal ratio of 175 (kg). / Ton-pig).
On the other hand, Comparative Examples 3 to 5 correspond to Examples 3 to 5, respectively, and the amount of change per unit time of the opening degree of the blast amount control valve of the preceding furnace is assumed to be 1 degree per 10 seconds. Is made faster than Examples 3 to 5 so that the change in the blowing pressure of the blower cannot follow the change in the opening degree of the blowing amount control valve.

Even when the pulverized coal ratio is increased by comparing the conditions of Examples 3 to 5 with the conditions of Comparative Examples 3 to 5 corresponding to the conditions, the air pressure fluctuation and the air temperature fluctuation can be reduced, respectively. As a result, it was confirmed that the fluctuation of the hot metal temperature could be reduced and the blast furnace could be operated stably.
In particular, the fluctuation margin of the hot metal temperature (= example / comparative example × 100%) is 50% in the case of the pulverized coal ratio 140 (kg / ton-pig), and 165 (kg / ton-pig) in the case of the pulverized coal ratio. 39% and pulverized coal ratio of 175 (kg / ton-pig), it can be confirmed that it can be reduced to 28%, respectively, and it can be confirmed that the effect of the present invention appears more remarkably as the pulverized coal ratio increases. It was.

The present invention has been described above with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and is described in the claims. Other embodiments and modifications conceivable within the scope of the above are also included. For example, a case where the control method for a hot stove according to the present invention is configured by combining some or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.
In the above embodiment, the case where four hot stoves are used has been described. However, the present invention is not limited to this, and three or five or more hot stoves can be used. It is also possible to control at least one of the two hot stoves by the method of the above-described embodiment.

And in the said embodiment, although the case where the opening degree of the ventilation volume control valve of each hot stove was shown linearly (the amount of opening change per unit time is constant) was demonstrated, it is limited to this. If it is necessary to adjust the opening of the air flow control valve to suppress fluctuations in the temperature of the air flow to the blast furnace, for example, a curve (change in the amount of opening change per unit time) may be used. Of course it is possible. In addition, although the airflow start time of the hot air from the hot stove has been described with respect to the case where the opening degree of each airflow control valve is 45 degrees and the airflow maximum time point is the opening degree of each airflow control valve 90 degrees, For example, depending on the equipment specifications of the hot stove, the opening degree of the valve at the start of blowing may be made smaller or larger than 45 degrees, or the opening degree of the valve at the highest blowing amount may be made more than 90 degrees. Of course, it is possible to make it small or large. At this time, the opening of each air flow control valve at the start of hot air blowing is fully closed, and the opening of each air flow control valve at the highest air flow is fully opened. The amount of change per unit time and the total value of the opening degree of the blower control valves of the two hot stove furnaces are obtained.

It is explanatory drawing of the blast furnace equipment which uses the control method of the hot stove concerning one embodiment of this invention. It is explanatory drawing which shows the operation state of each hot stove using the control method of the hot stove.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Blast furnace, 11-14: Hot air furnace, 15-18: Blowing amount control valve, 19: Blower main piping, 20: Blower, 21: Heat storage chamber, 22: Combustion chamber, 23-26: Blower control pipe, 27- 30: On-off valve, 31: Control device, 32: Sensor

Claims (3)

Air is passed through each of the two hot air furnaces, the preceding hot air furnace that starts air blowing to the blast furnace, and the subsequent hot air furnace that starts air blowing to the blast furnace after the preceding hot air furnace, and mixes the cold air In the method for controlling a hot stove, the hot air supplied from each hot stove is mixed with the air blow control valve opening degree when the hot air is supplied to the blast furnace. ,
Among the two hot stoves, the change of the air flow control valve in the range in which the air pressure control follows the amount of change per unit time of the opening of the air flow control valve provided in at least one hot air furnace. When the opening degree of the air flow control valve is 90 degrees and the closing position is 0 degrees, the amount of air flow exceeds 0 degree per 30 seconds and 2 degrees or less. It is characterized by operating the opening degree so that the total value of the opening degree of the air flow control valve is equal to or higher than the lower limit value of the value that makes it possible to maintain the blowing pressure of the blower that blows air within the blowing capacity range. To control the hot stove. A method for controlling a hot air furnace of claim 1 Symbol placement, when the trailing hot air oven has started blowing into the blast furnace, that will reduce the degree of opening of the air volume control valve of the prior hot stove A control method of a hot stove. 3. The method of controlling a hot stove according to claim 1 or 2 , wherein the air flow control valve is adjusted by adjusting the opening ratio of the pulverized coal blown into the blast furnace to 150 kg or more per ton of hot metal discharged from the blast furnace. A control method for a hot stove, which is performed under a condition where the temperature is 1200 ° C or higher.

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