JP3164976B2 - Method for predicting slopping in a converter and its prevention - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method useful for the operation of a converter, and more particularly, to a method for predicting slopping which, if generated during blowing, is a major obstacle to the operation and a method for preventing slopping.

[0002]

2. Description of the Related Art Refining of hot metal and molten steel in a converter involves purging pure oxygen gas from a lance inserted into the furnace from the furnace opening of the converter into the molten steel to decarburize the molten steel while stirring the molten steel.
Furthermore, desiliconization and dephosphorization and desulfurization are performed by the reaction of the molten slag that forms slag with the slag material charged into the converter. In the process of slag formation, the slag composition, viscosity, and oxygen content in the slag If the slag is formed by various conditions such as these, and the slag is excessively advanced, so-called slopping may occur, in which the slag and even molten steel overflow from the furnace port.

[0003] The occurrence of such slopping has a great effect on the molten steel composition, the molten steel yield, etc., as well as a decrease in work efficiency, a decrease in calorie of collected gas, generation of red smoke, deterioration of the work environment, breakage of equipment, and the like. It causes various problems. Therefore, it is necessary to predict the situation inside the converter immediately and to operate the converter properly, for example, to minimize the occurrence of slopping.

Conventionally, various proposals have been made for grasping the condition of the converter furnace. As a method for grasping the slag state in the furnace, for example, in Japanese Patent Application Laid-Open No. 52-101618,
In the converter steelmaking method, a method is disclosed in which oxygen balance is calculated based on information on exhaust gas during blowing to estimate the amount of generated oxides, that is, slag, in the furnace. In this method, a time delay due to the analysis is unavoidable, and the slapping prediction accuracy is low because the slapping is not caused solely by the amount of slag.

Various attempts have been made to detect the slag level by a physical measurement method, such as an acoustic measurement method (JP-A-54-33790), a vibration measurement method (JP-A-54-114414), and a furnace. Internal pressure measurement method
104417), a microwave measurement method (Japanese Patent Laid-Open No.
No. 40812), a furnace body surface temperature measuring method (JP-A-58-4)
No. 8615).

[0006] The vibration measurement method, the furnace pressure measurement method, and the furnace body surface temperature measurement method are all indirect measurement methods, and the slag level and the slag state cannot be quantitatively grasped. Low. The microwave measurement method can directly measure the slag level, but since the molten steel, slag, gas, etc. move extremely complicated inside the converter during blowing, it is necessary to detect or estimate abnormalities. Is not easy, and high technology is required for signal processing and the like, so that it is inevitable that the apparatus becomes expensive. For each of the above-described methods, there are problems in terms of accuracy and investment amount when applied to actual operations for the reasons described above.

[0007] The acoustic measurement method aims to predict the occurrence of slopping by estimating the slag level by capturing changes in the frequency and intensity of the sound generated from the furnace during blowing. Since it is simple and the equipment cost is low, it is an effective means for preventing slopping in a top-blowing converter. However, because of the principle of detecting a specific frequency and predicting slopping based on a change in the intensity of the frequency sound, in an upper-bottom blower using bottom-blown gas, noise is affected by the bottom-blown gas. Increased, making it difficult to predict slopping.

Further, when determining the measurement frequency, there is no knowledge about the sound source, and conventionally, various frequencies are investigated to determine empirically the frequency which can reflect the tendency of the slopping. However, there is a problem in that the sound collection frequency is not set, and thus the accuracy of the slopping detection is deteriorated.

[0009] Further, since the sound source reflecting the slopping has not been clarified, there is no knowledge about the installation position of the microphone used for sound collection. It was determined empirically based on that. For this reason, this is not always optimal as a sound collection position, and causes deterioration in accuracy.

[0010] Furthermore, there is no effective knowledge disclosed quantitatively about the judgment of the slopping prediction, and considerable skill and experience are required to predict the slopping from an acoustic signal that fluctuates each time due to different blowing conditions. However, due to poor accuracy, it is impossible to implement effective anti-sloping means based on information from an acoustic measurement device (hereinafter referred to as a sound meter), and therefore, there is almost no application of the sound meter to actual operation. Was the actual situation.

Further, as a method of preventing slopping, a method in which a waste rubber product is introduced in Japanese Patent Application Laid-Open No. Sho 59-133309, and a sedative containing calcium aluminate as a main component in Japanese Patent Application Laid-Open No. 61-96021 are disclosed. Method, JP-A-61
A method of blowing an inert gas into JP-149417, a method of adding a soothing material containing dust, sludge, mill scale, etc. to JP-A-62-86110;
No. 810 discloses a method of blowing a reducing agent into a slag from a lance, and the like. However, these methods aim to break the foamed slag by rapidly generating a large amount of gas in the slag, but in the actual operation, the generated slag was generated near the end of the highly viscous de-Si phase. Injecting the large amount of gas generated during the forming slag, on the contrary, promotes the forming and may worsen the slopping.

[0012]

As described above, in order to solve the problem of the sound meter, the present invention aims at optimizing the frequency and the installation position to dramatically improve the accuracy of the sound meter in predicting the slipping. It is an object of the present invention to provide a judgment condition for accurately predicting the slopping from the information, and to provide a method for taking an effective anti-slopping means based on the slipping prediction information by the sound meter.

[0013]

SUMMARY OF THE INVENTION The present invention provides a method for predicting the occurrence of slopping in a refining reaction vessel by collecting the sound generated in a furnace and predicting the upper blowing oxygen discharge sound during blowing. run
Through the circumference of the top opening of the reaction vessel
The sound is collected by the microphone installed inside the extension of the inverted conical shape.
The base sound pressure is determined from the time of 20 to 50% of the de-Si time in the required time from the start of blowing and the end time of de-Si removal, and the base sound pressure level is reduced by 5% or more. To predict the occurrence of slopping
It is characterized by.

Further, according to the present invention, there is provided a method for preventing slopping, comprising blowing powdery carbon material into the upper surface of the furnace slag and / or into the slag based on the above-mentioned slopping prediction signal. Is a method of preventing slopping, wherein the carbon material to be blown is a carbon material having a maximum particle size of 3 mm or less.

[0015]

First, a method of predicting slopping will be described. Conventionally, there is no clear principle for detecting the degree of slag forming by a sound meter. Therefore, as mentioned above, its measurement frequency,
The installation position is determined empirically, and there is a problem that accuracy is deteriorated. The present inventors have sought to optimize the measurement frequency and frequency by elucidating the mechanism of detecting the degree of slag forming by the sound meter, and to further elucidate the transmission and absorption mechanism of the sound generated in the furnace to collect the slag. The accuracy was improved by optimizing the sound position.

The details will be described below with reference to actual examples. The sound meter continuously measures the behavior of the specific frequency, focusing on the fact that the specific frequency reflects the forming behavior in the furnace. Conventionally, since there is no knowledge about the characteristic frequency, various frequencies were experimentally sampled and the frequency to be adopted was determined empirically. However, in the furnace, various sounds from various sound sources are mixed and resonate, for example, a top blowing discharge sound, a sound at the time of adding a sub-quantity, a bottom blowing gas boiling sound, a furnace peripheral device operation sound, and the like. I have. Therefore, it has not been possible to identify the sound source that reflects the forming so far, and the frequency was set empirically.However, since the optimal frequency could not be identified, especially after the upper-bottom blowing converter, It was considered impossible to apply the sound meter under actual operating conditions because the required accuracy could not be secured.

The present inventors have paid attention to the fact that each sound has a natural frequency for various sounds generated from each sound source, and have clarified a sound source having a frequency that reflects forming. That is, the time, frequency, and sound pressure intensity during blowing are analyzed at the same time by three-dimensional data to find a specific frequency that fluctuates when forming occurs. The sound source was analyzed by continuously measuring the change in strength from the steel and the waste to the next hot metal charging. as a result,
It was clarified that the sound source of the specific frequency reflecting the forming is the upper blowing oxygen discharge sound, and thus it was found that the upper blowing oxygen discharge sound is optimal as the sound collection frequency in the sound meter.

This will be described in more detail with reference to an example. FIG. 3 shows frequency analysis data in the vicinity of the time of occurrence of slopping. Sounds of various frequencies are observed during blowing, but a characteristic behavior that the sound pressure level decreases at a frequency near 1500 Hz in the figure during slopping is observed. Next, FIG. 2 shows the results of continuously measuring the change in strength from the hot metal charging to blowing, tapping, and slagging to the next hot metal charging in the converter at the frequency at which the slopping behavior was observed. The sound pressure intensity sharply increased at the same time as the start of blowing, and decreased several times by slag forming until the end of blowing. From this feature, it was found that the sound source for detecting the forming by the sound meter was the sound of oxygen discharge from the upper lance.

Next, the mechanism of reduction in sound pressure intensity during slopping was examined. In general, sound propagates as a spherical wave, and if there is an obstacle or a change in density in the course of traveling, the sound is partially or mostly reflected and apparently behaves as if absorbed. The present inventors have focused on this transmission mechanism of the sound from the upper blowing lance discharge port, and have formed a forming slag, an iron plate,
The mechanism of sound absorption by refractories was clarified. When the reflection ratio of sound due to an obstacle or a change in density is calculated as R, and the transmission ratio as T, the transmittance is as shown in Table 1.

[0020]

[Table 1]

Here, R. T is defined as in the following equations (1) and (2). R = (ρ ₁ c ₁ −ρ ₂ c ₂ ) ² / (ρ ₁ c ₁ + ρ ₂ c ₂ ) ² (1) T = 1−R (2) ρ ₁ , ρ ₂ : substance Density of substance 1 and substance 2 c ₁ , c ₂ : sound velocity in substance 1 and substance 2

It is considered that the above-described upper-blowing oxygen discharge sound is generated at the tip of the upper-blowing nozzle. Normally, when there is no slopping, the sound propagates through the CO gas, which is an atmospheric gas, and is observed at the sound meter sound collection position. Is done. Regarding the propagation through the CO gas, the sound intensity does not decrease due to the obstacle. However, if the molten slag or the iron plate interrupts the progress of the sound, the sound transmittance drops sharply. For example, if the sound transmittance in CO gas is 100%, the molten slag is 0.04%,
Only 0.006% is transmitted through an iron plate. In other words, the decrease in sound pressure level during slopping occurs because the forming slug rises between the sound source position (the tip of the lance) and the sound collection position, impeding the passage of sound, so that the sound is apparently absorbed. Is done. Therefore, the in-furnace slag level at the time when the sound pressure level is reduced in the sound meter can be determined that the slag has formed near the furnace port beyond the position of the lance tip (discharge port).

When an obstacle made of a material such as a refractory or iron is located between the tip of the lance and the sound collection position, the sound almost completely passes through the same mechanism as the sound absorption by the slag. (See Table 1 above), the sound collection level is extremely reduced. As a result, the S / N ratio (the sound pressure ratio between the upper-blown oxygen discharge sound and other noise) decreases, and the accuracy of predicting the slopping deteriorates.

If a sound collecting position (particularly a sound collecting position below the tip of the upper blowing acid lance for the purpose of predicting early slopping) is installed in the furnace, dust and spitting in the furnace can be obtained. This often causes blockage of the sound collecting tube or breakage of the sound collecting microphone, which makes application to actual operation impossible. Therefore, as the sound collection position,
It must be located outside the converter (including above the converter furnace opening) and at a position where it is possible to directly collect the upper blowing oxygen discharge sound. Considering that the sound propagates as a spherical wave from the point of generation, the sound collection position is an inverted conical extension extending from the top of the upper blowing acid lance during blowing and passing through the circumference of the upper opening of the reaction vessel. Inside is optimal.

In order to predict slopping due to fluctuations in sound pressure level, it is necessary to determine a reference sound pressure level and to determine a sound pressure fluctuation amount during forming. During blowing, the level of the oxygen-absorbing sound of the upper blowing oxygen fluctuates intermittently due to dust and spitting in the furnace. Among them, the frequency of occurrence of the slopping is the highest, and the time at which the slopping occurs at the earliest timing during the blowing is near the end point of the removal of Si. Therefore, the reference sound pressure level must be determined before the end of the Si removal. As a method of this determination, the present inventors set the sound pressure level at a time point of 20% to 50% of the Si removal time in the required time (Si removal time) from the blowing start time to the estimated Si removal end time. It has been found that the reference sound pressure level is optimal.

If the time is less than 20% of the Si removal time, disturbance factors such as fluctuations in the amount of exhaust gas due to the input of auxiliary materials and fluctuations in the transmittance of the upper blowing oxygen discharge sound due to the auxiliary materials input from the furnace are large.
Since the sound collection level is not stable, it is inappropriate as a reference sound pressure level. Further, if the time exceeds 50% of the Si removal time, the frequency of occurrence of the slopping rises sharply as compared to before, and there is a possibility that the slopping prediction may not be in time, which is also inappropriate.

It is desirable that the sampling of the sound pressure level be performed at intervals of 5 to 30 seconds. Even if the calculation is performed in a short cycle of 5 seconds or less, a dramatic improvement in accuracy cannot be expected, and conversely, only the calculation load is increased. On the other hand, if the time exceeds 30 seconds, the accuracy of the sloping judgment is deteriorated. For example, the sound pressure fluctuation immediately before the occurrence of the slopping in the 340T converter operation is 5 to the reference sound pressure level.
8% decrease in sound pressure level. If it is less than 5% (for example, 2%), there is a low possibility that the forming level in the furnace will be ejected from the furnace port, and the frequency of over-forecasting will increase sharply.
If a value higher than 8% (for example, 10%) is used as the prediction criterion, the action for preventing the slapping cannot be made in time even if the prediction is made, and the function as the slopping prediction device is not performed. This threshold is the sound collection energy level,
An appropriate value may be selected according to the furnace shape, capacity, and the like. Further, a value obtained by multiplying the base sound pressure level by a threshold value may be used as an operation management index (criterion).

Next, a method for preventing slopping will be described. The sounding meter continuously monitors the forming status inside the furnace during blowing, and if a sign of slopping is detected, implements an anti-sloping action. As the anti-slopping action, in the conventional technology, a gas generator is injected, and a large amount of gas generated by decomposition or combustion is injected at the same time as the injection to make the slag penetrate, thereby improving the permeability of exhaust gas generated during blowing. The method is general. However, as described in the related art, the method of breaking the foaming slag with the gas generating material to prevent the slopping may, on the contrary, promote the slopping by the gas generated by itself, There is a drawback that the effect as a prevention means is low.

The present inventors consider that, as a soothing material, a material having a function of reducing foaming time by promoting coalescence and flotation of bubbles and calming foaming, rather than foam breakage by generated gas, is suitable. Was. As a known technique, as a method of promoting the coalescence of the foam, by contacting the formed slag with carbon, the surface tension of the slag on the carbon surface is reduced, and attention is paid to a method of promoting the coalescence of the foam. A method for preventing slopping, characterized by blowing powdered carbonaceous material into the upper surface of the inner slag and / or into the slag, was established.

Conventionally, it has been found that the method of injecting powdery carbonaceous material is effective for slag foaming. However, there has been no effective technique for predicting slopping. Check if the slag overflows and blow it in.Or, if the slapping does not occur during the period when sloping occurs frequently, regardless of whether or not slopping occurs, the heat and oxygen balance may be reduced. It was difficult to apply the method as a method for preventing slopping during industrial production, because it deviated from the relationship expected before the start of blowing and caused deterioration in refining controllability.

According to the present invention, it becomes possible to blow coke breeze only when there is a sign of slopping, and the forming suppression technique using coke breeze can be applied to actual operation. If the coke breeze is blown in an improper direction depending on the blow direction, most of the coke breeze is consumed for scattering loss and secondary combustion, and the suppression effect is reduced. Therefore, it is most effective to directly blow the powdery carbonaceous material into the furnace slag upper surface and / or into the slag.

As the coke powder to be used, coke having a maximum particle size of 3 mm or less is desirable. When it is larger than 3 mm, the effect of suppressing the forming due to the decrease in the reaction surface area is reduced. On the other hand, if fine powder having a maximum particle size of 1 mm or less is used, for example, scattering loss increases, and in this case, the suppression effect also decreases. The amount of blow at one time is about 1 kg / T to 2.5 kg / T, so that the slipping can be prevented by forming suppression (sedation).

Even if the operator instructs the start of the blowing, the sound pressure level is constantly monitored by a computer even if the operator manually gives an instruction, and it is continuously determined whether or not the threshold value is exceeded. The blowing of coke breeze may be automatically started by a slopping prediction signal of the computer. In the case of automatic determination, since the sound pressure level of the sound meter hunts due to dust or the like in the furnace, the determination may be performed using a moving average value for the purpose of preventing erroneous detection.

[0034]

FIG. 1 is a block diagram showing the configuration in which the present invention is implemented. Oxygen is blown from the acid lance 2 to the hot metal 5 charged in the converter 1 to perform blowing. If the slag 6 forms during blowing, the intensity of the oxygen discharge sound collected by the sound collecting microphone 9 changes. The signal is sent to the sound meter 10, only a specific frequency is extracted by the band filter 11, the signal is amplified by the amplifier 12, and the signal is processed by the signal processing computer 13. When it is determined that the signal-processed value exceeds the predetermined threshold of the sound pressure level, a command is sent to the coke breeze blowing control computer 14 so that a predetermined amount of coke breeze is stored in the coke storage hopper. 7 and is blown into a converter by a coke breeze blowing lance 8.

The blowing of coke breeze can be manually performed by an operator according to the information of the sound meter. The amplifier 12 may be provided between the band filter 11 and the sound collecting microphone 9. The collection frequency extracted by the band filter may be set to a collection width in accordance with the required accuracy of predicting the slopping. At this time, it is desirable that the upper blowing sound is near the center of the collection frequency, but it may be near the boundary. The sound meter is 1500 Hz, which is the top-blown oxygen discharge sound whose frequency has been analyzed in advance.
It is set to collect sound in the vicinity.

The sound-collecting microphone 9 is installed at the top of the top of the acid lance at the top of the converter. The dust collecting duct 3 and the dust collecting hood 4 were installed at a position where there was no obstacle between them, about 1.2 m above the furnace port, between the outer circumference of the exhaust gas dust collecting duct 3 and the inner circumference of the dust collecting hood 4. 300T hot metal was charged into a converter equipped with such a slopping prediction device. Table 2 shows an example of blowing conditions.

[0037]

[Table 2]

The hot metal mixing ratio is 79% and the cold iron mixing ratio is 10%
The average deoxidation oxygen efficiency was determined, and based on the result, the amount of supplied oxygen required until the end of desiliconization was determined. During blowing, the integrated oxygen amount sent from the start of blowing is monitored, the sound pressure level of the integrated oxygen amount from 20% to 50% is sampled every 20 seconds, and the average value is calculated. Determined level. As a threshold value of the sound pressure level in the judgment of the prediction of the occurrence of the slopping, 6% of the base sound pressure level was set.

The sound pressure level of the sound meter was continuously monitored, and at 5 minutes after the start of the blowing acid, the sound pressure level dropped below the threshold value, so coke breeze was blown at 450 kg / min. The coke breeze has a maximum particle size of 3 mm and the blowing rate is 0.9 kg / T. As a result, forming slag did not overflow or flow out of the furnace vent, and the slag was favorable. In order to prevent dust from adhering to the sound collecting microphone, purging with gas may be performed in the vicinity of the sound collecting microphone. The purge gas may be air or nitrogen. If the sound meter accuracy deteriorates due to purge noise,
Purging may be stopped during blowing, and purging may be performed only during non-blowing.

[0040]

[Table 3]

Prior to the implementation, as shown in Table 3, the input amount of quicklime was reduced as compared with the conventional method, but there was no problem in operation. As described above, conventionally, since slopping is often caused by low basicity and high viscosity slag especially near the end of the de-Si phase, the quick lime is originally dephosphorized for the purpose of increasing the basicity charged in the initial stage of blowing. It was no longer necessary to respond by supplying more than necessary.

[0042]

In the past, since it was difficult to predict and prevent slapping, operation measures were implemented to avoid adverse effects on operation when slopping occurred. The present invention makes it possible to predict and prevent slopping, so that it is not necessary to add excess lime for the purpose of preventing slopping, and it is possible to greatly reduce steelmaking costs.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a control system configuration according to the present invention.

FIG. 2 is a diagram showing an example of a measurement result of a sound intensity change during blowing.

FIG. 3 is a diagram showing an example of a frequency analysis result of a sound during blowing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Converter furnace body 2 Acid lance 3 Dust collecting duct 4 Dust collecting hood 5 Hot metal (molten steel) 6 Forming slag 7 Powder coke hopper 8 Powder coke blowing lance 9 Sound collecting microphone 10 Sound meter 11 Band filter 12 Amplifier 13 Signal processing Computer 14 Injection control computer for coke breeze 15 In the extension of inverted cone

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Koichi Endo, Oita-shi, Oita-shi, 1 Nishinosu, Nippon Steel Co., Ltd. Inside the Oita Works (72) Inventor, Yasuo Obana 1-inch, Nishi-nosu, Oita-shi, Oita, New Japan (72) Inventor: Tatsuro Hirata, Oita, Oita, Oita, 1-fig., Nishi-nosu, Nippon Steel Corporation (56) References JP-A-51-67202 (JP, A) JP-A-53-45615 (JP, A) JP-A-62-196314 (JP, A) JP-A-62-202013 (JP, A) JP-A-63-123655 (JP, U) (58) Int.Cl. ⁷ , DB name) C21C 5 / 28,5 / 46

Claims (3)

(57) [Claims] 1. A method for predicting the occurrence of slopping in a refining reaction vessel by collecting a sound generated in a furnace, wherein a blowing oxygen blowing sound for blowing is blown with the tip of an upper blowing acid lance being blown up. It collected by established were collected microphone reverse conical shape in extension through the circumference of the reaction vessel upper opening, from blowing start time
Of the estimated required time until the end of Si removal,
From 20 to 50% of the time i, the base sound pressure is determined,
A method for predicting slopping in a converter, wherein the occurrence of slopping is predicted when the base sound pressure level drops by 5% or more . 2. A method for preventing slopping in a converter based on the slopping prediction signal according to claim 1, wherein a powdery carbon material is blown into the upper surface of the furnace slag and / or into the slag. . 3. The method for preventing slopping in a converter according to claim 2, wherein the carbon material to be blown is a carbon material having a maximum particle size of 3 mm or less.