JPH0128803B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention is a blast furnace operating method in which iron oxide is injected into the blast furnace from the blast tuyeres to control the Si concentration in the hot metal. The present invention also relates to a blast furnace operating method for stabilizing unloading. Prior art and its problems Si migration into hot metal in a blast furnace is caused by SiO2 rather than slag metal reaction in the hearth sump.
Gas-metal reactions mediated by gases play a major role. Into hot metal using SiO gas as a medium
The transition of Si can be roughly divided into the following two processes (Tetsu to Hagane Vol. 58, 1972, p. 219). In other words, the main source of coke is ash in the high temperature, low oxygen partial pressure region near the raceway.
SiO by reaction of SiO ₂ with solid carbon in coke
The gas generation process and the Si transfer process into the hot metal due to the reaction between the SiO gas contained in the rising gas flow below the softening cohesive zone and the carbon in the dripping hot metal, and these two processes can be expressed by a reaction equation. The expression is as follows. (SiO ₂ ) + C = SiO (g) + CO (g) SiO (g) + C = Si + CO (g) where () is a conventional notation to indicate that the compound is present in the slag, and is an element The underlined name is a common notation to indicate that the component is present in the hot metal. Further, (g) is a common notation indicating that the compound is a gas. Therefore, methods for controlling the Si concentration in hot metal include controlling the SiO gas generation reaction and controlling the Si transfer reaction into the hot metal. In actual blast furnace operation, the former control means include controlling the amount of SiO ₂ brought in before the tuyere by controlling the ash content in the coke, and controlling the SiO gas generation rate by controlling the temperature before the tuyere. The latter control means include controlling the cohesive zone level by controlling the coke ratio based on charge distribution control, and controlling the cohesive zone level by controlling the reducibility and softening and cohesive properties of sintered ore ( Iron and Steel Vol・68 1982 A129
page). In addition to the above-mentioned control method based on the Si transfer mechanism into the hot metal in the blast furnace, methods for controlling the Si concentration in the hot metal include injecting iron oxide into the furnace through the blast tuyere and using the following reaction. A so-called in-furnace desiliconization method for oxidizing Si in hot metal has been developed (Japanese Patent Application Laid-open No. 53-87908, JP-A No. 56-29601, JP-A No. 58-
77508). Si + 2FeO = (SiO ₂ ) + 2Fe In the case of this control means, if the above reaction is appropriately controlled, the Si concentration can be controlled immediately before tapping, and the Si concentration in the hot metal can be easily managed. However, the conventional method of controlling the Si concentration in hot metal by blowing iron oxide has the following drawbacks. First of all, iron oxide is injected into the furnace using a method that maintains the flow rate per unit time at a constant value, but in actual operation, there are unpredictable changes in the physical and chemical properties of the charge. Disturbance factors such as anomalies in the fall of the burden in the furnace can cause changes in the gas flow distribution in the furnace,
As the temperature distribution of the solid changes and the cohesive zone level fluctuates, the Si concentration in the hot metal dripping into the hearth changes. Since the amount of Si in the hot metal that is discharged from the blast furnace is almost constant, the Si concentration in the hot metal discharged from the blast furnace fluctuates. The second problem is that the amount of iron oxide blown into the furnace is not managed at each blowing tuyere, but is managed based on the total amount blown into the furnace. In other words, in normal iron oxide injection operations, when a small amount of iron oxide is being injected, an equal amount of iron oxide is injected from the tuyeres that are equally divided in the circumferential direction, and when a large amount of iron oxide is being injected, the same amount of iron oxide is injected from all the tuyeres. Although it is blown in through the mouth, the piping is designed so that the amount blown in from each tuyere is equal, and the total flow rate of iron oxide is simply controlled under the collective piping. However, with this method, the refractory wears out unevenly in the circumferential direction at the end of the life of the blast furnace, deposits are formed unevenly in the circumferential direction, or the charging If the charge is eccentrically charged into the furnace, or if the rate of descent of the charge is uneven in the circumferential direction, the Si concentration in the hot metal dripping onto the hearth may vary in the circumferential direction. The disadvantage is that it varies. In addition, as a method to alleviate the variation in Si concentration depending on the taphole when there is no iron oxide injection, a method has been proposed in which the amount of fuel injected from the tuyeres is adjusted depending on the direction of the taphole (Unexamined Japanese Patent Publication No. 117805). In iron oxide injection, when the Si concentration in the hot metal dripping into the hearth varies in the circumferential direction as described above, if iron oxide injection is performed evenly in the circumferential direction as in the past, This results in variations in the Si concentration in the hot metal discharged from each taphole. Therefore, the inventors actually measured the Si concentration in hot metal discharged from the taphole as a method to alleviate the variation in Si concentration for each tap due to disturbance during iron oxide injection operation from the tuyere. previously proposed a method of calculating the amount of iron oxide injected from the difference from the target Si concentration and controlling the amount of iron oxide injected from the tuyere in the relevant taphole direction through feedback control (Japanese Patent Laid-Open No. 59-64733). . This method solves all the problems caused by the conventional iron oxide injection described above, and makes it possible to maintain the Si concentration in the hot metal tapped from the blast furnace within a certain range. However, when the deviation in the amount of iron oxide injected in the circumferential direction is large, the variation in hot metal temperature becomes large.
A new problem has arisen that may also affect the unloading situation. In other words, the injection of iron oxide from the tuyere has the so-called in-furnace desiliconization effect, which oxidizes Si in the hot metal through the reaction described above, but at the same time, a part of the injected iron oxide is oxidized by the reaction described below. It is directly reduced by the solid carbon in the coke in the coke zone at the tip of the way. FeO + C = Fe + CO (g) The above reaction is an endothermic reaction, and especially if the deviation in the amount of iron oxide injected in the circumferential direction is increased, the heat balance in the circumferential direction in the lower part of the furnace will be disrupted, resulting in variations in hot metal temperature. As the becomes larger,
Heat flow ratio (solid heat capacity flow rate/gas heat capacity flow rate)
This may also affect the unloading situation in the circumferential direction, which may lead to deterioration of furnace conditions such as slips and tuyere breakage. Purpose of the Invention The present invention aims to reduce the variation in Si concentration in hot metal from tap hole to taphole by adjusting the amount of iron oxide injected in each direction in the circumferential direction, as described above. When the iron injection amount deviation is large, the fact that the injection amount can be divided and controlled for each direction of the taphole can be used to adjust the fuel injection amount in the circumferential direction as heat compensation, or to control the steam injection in the circumferential direction. By adjusting the charging amount at the same time, the purpose is to reduce variations in hot metal temperature from tap hole to tap hole and to stabilize unloading. Structure and operation of the invention In the current blast furnace operation, fluctuations in the condition inside the furnace due to disturbance factors and non-uniformity in the condition inside the furnace in the circumferential direction inevitably occur. The change in Si concentration is measured for each taphole, and depending on the difference from the target Si concentration, the amount of iron oxide injected from the blast tuyeres in the relevant taphole direction is changed.
Calculate the amount of fuel or steam injected from the tuyere in the direction of the taphole, which is necessary for heat compensation corresponding to the amount of iron oxide injected, and This method maintains the Si concentration and temperature of hot metal tapped from a blast furnace within a certain range by feedback controlling the amount of fuel or steam injected. Hereinafter, the blast furnace operating method according to the present invention will be explained based on FIG. 1. FIG. 1 shows the configuration of an apparatus for implementing the method of the present invention. Iron oxide is injected into a blast furnace 1 from an iron oxide storage tank 2 through a flow control valve 3 and a flow meter 4 through a blowing tuyere 5. is blown into the furnace. On the other hand, the auxiliary fuel storage tank 6 also has a flow control valve 7,
A flow meter 8 is installed, and a flow control valve 9 and a flow meter 10 are also installed in the steam piping. Although not shown, flow rate control valves 3, 7, 9 and flow meters 4, 8, 10 are installed at each ventilation tuyere. The iron oxide storage tank 2 has the number of tap holes depending on the direction of the tap hole,
Or more than one tuyere is installed. The amount of iron oxide blown into each of the above-mentioned blast tuyeres is determined by the amount of iron oxide in the hot metal measured at each taphole 18 by a known optical emission spectrometry method, or by rapid analysis using a concentration cell, for example, at the cast bed.
Si concentration and target Si set by the method described below
Input the concentration into the calculator 11, calculate the required amount of iron oxide injection based on the difference in the Si concentration between the two, and control the opening degree of the flow rate control valve 3 with reference to the actual measured value of the current injection amount. Do by doing. At the same time, the adjustment of the amount of fuel injection or the amount of steam injection necessary for heat compensation corresponding to the injection of iron oxide is carried out in the calculation unit 12 by adjusting the heat balance at the tuyere level based on the amount of iron oxide injection. - The amount of fuel or steam injected necessary for heat compensation is determined by calculating the material balance, and this is done by controlling the opening degree of the flow rate control valve 7 or 9 in the relevant direction. The target Si concentration can be input manually via the input data setting device 17 or by inputting the blast furnace exhaust gas data 1.
3. Based on the charge data 14, air blowing data 15, and tap iron data 16, a mathematical simulation model built into the calculator 12 (for example, iron and steel vol.
68 1982 A129 page) and input continuously automatically. Next, a method of calculating the amount of iron oxide blown and the amount of fuel blown or steam blown necessary for heat compensation will be explained. Figure 2 shows that in blast furnace A (inner volume 2700m ³ ),
Si in hot metal when the amount of steam injection in the relevant direction is simultaneously adjusted with reference to the amount of steam injection necessary for heat compensation calculated using the method described below with respect to the amount of iron oxide injection per tuyere. Indicates the actual concentration value. In other words, Si in the hot metal discharged from a certain taphole
From the difference between the measured concentration value and the target Si concentration, it is possible to determine the amount of change in the amount of iron oxide injected into each tuyere in the direction of the tap hole. The relationship shown in FIG. 2 is built into the calculator 11, and by inputting the current Si concentration in hot metal and the target Si concentration,
The amount of iron oxide blown is automatically calculated, and the opening degree of the flow rate regulating valve 3 is controlled according to the calculated value. At the same time, the amount of steam injection required for heat compensation accompanying the injection of iron oxide can be calculated using the same figure 2, using the amount of change in the amount of iron oxide injection as input. The amount of change in the actual amount of steam injection can be determined. Regarding this steam injection amount, the relationship shown in Fig. 2 is built into the calculator 11, and by inputting the previously calculated iron oxide injection amount, the steam injection amount is automatically calculated. , controls the opening degree of the flow rate adjustment valve 9. The relationship shown in FIG. 2 can be similarly obtained when the amount of fuel injection is adjusted as a means for compensating for the heat accompanying the injection of iron oxide. The amount of steam injection necessary for heat compensation accompanying iron oxide injection is calculated in the computing unit 12 based on the blast furnace exhaust gas data 13, charge data 14, ventilation data 15, and tap iron data 16. Built-in mathematical simulation model (e.g. Tetsu to Hagane vol.68 1982
A129) is calculated. Example The results of implementing the present invention in a blast furnace A (inner volume 2700 m ³ ) are shown in Tables 1 and 2. In other words, during period A in Table 1, the Si concentration in the hot metal discharged from the No. 2 taphole was high, and the variation in Si in the hot metal (V _si ) was as large as 0.121%, but the variation in hot metal temperature (V _TPig ) was 9.1°C. Therefore, No.2
The amount of iron oxide injected from the tuyere in the direction of the taphole is 290.
As a result of increasing the Si concentration in hot metal discharged from the No. 2 taphole by increasing Kg/hr, the variation in Si concentration in hot metal (V _si ) decreased to 0.060%, but iron oxide injection Because of the large amount of action, the temperature of the hot metal discharged from the No. 2 taphole decreased, and as a result, the variation in hot metal temperature (V _TPig ) increased to 17.6°C. In addition, unloading worsened at the No. 2 taphole direction, and tuyere damage due to slips and unloading of raw ore occurred frequently, leading to deterioration of furnace conditions. In period B of Table 2, the Si concentration in the hot metal discharged from the No. 3 taphole was high, and the variation in Si in the hot metal (V _si ) was as large as 0.129%, but the variation in hot metal temperature (V si ) was large. _TPig ) was 9.3℃. Therefore, No.
The amount of iron oxide injected from the tuyere in the direction of the 3 taphole is 340.
As a result of increasing the amount of steam injected in this direction by 93 kg/hr based on the relationship shown in Figure 2, the Si concentration in the hot metal discharged from the No. 3 taphole As a result, the variation in Si concentration in hot metal (V _si ) decreased to 0.056%. At the same time, thermal compensation suppressed the drop in the temperature of hot metal discharged from the No. 3 taphole, and the hot metal The temperature variation (V _TPig ) also did not increase, at 9.7°C. In addition, unloading was good, and there was no damage to the tuyere due to slips or falling raw ore.

【table】

【table】

[Table] Effects of the Invention As is clear from the above examples, according to the method of the present invention, the Si concentration of each taphole is actually measured, and the impeller of the taphole direction is adjusted according to the difference from the target Si concentration. By controlling the amount of iron oxide injected from the mouth and at the same time controlling the amount of steam or fuel injected as heat compensation, even if the action amount of iron oxide injection is large, the temperature of hot metal in the relevant direction can be reduced. Therefore, it is possible to reduce the variation in the Si concentration in the hot metal discharged from the blast furnace under stable unloading conditions.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an apparatus for implementing the method of the present invention, and FIG. 2 is a chart showing the relationship between changes in the amount of iron oxide blown, changes in Si concentration, and amount of steam blown in the same. 1...Blast furnace, 2...Iron oxide storage tank, 3,
7, 9... Flow control valve, 4, 8, 10... Flow meter, 5... Blowing tuyere, 6... Auxiliary fuel storage tank, 11, 12... Arithmetic unit, 13... Exhaust gas data, 14... ...Charge data, 15...Blowing data, 16...Tapping data, 17...Input data setting device, 18...Tapping port.

Claims (1)

[Claims] 1 In the blast furnace operation method in which iron oxide is injected into the blast furnace from the blast tuyere, the Si concentration in the hot metal for each taphole is actually measured, and depending on the difference from the target Si concentration, the blast tuyere of the relevant taphole direction is By changing the amount of iron oxide injected from the blast furnace and adjusting the amount of fuel or steam injected in the direction of the taphole in accordance with the amount of iron oxide injected, the amount of hot metal tapped from the blast furnace can be changed. A blast furnace operating method characterized by maintaining Si concentration and temperature within a certain range.