JPH0849008A - Prediction of slopping in converter and prevention of the same - Google Patents

Abstract

PURPOSE:To prevent the development of slopping in a converter by measuring a sound of a specific frequency caused by oxygen jet form a top-blowing lance during the converter operation, predicting a time of the slopping and additing pulverized carbonaceous material into the furnace. CONSTITUTION:At the time of producing molten steel by refining molten iron 5 in the converter 1 by the oxygen top-blown refining form an oxygen-blowing lance 2 which executes decarburization as the main reaction, a sound collecting microphone 9 is arranged on a reverse conical extending line 15 with which the tip part of the lance 2 becomes an apex shape and which passes through the circular circumference of the upper opening part of the converter 1. A base sound pressure is decided by starting from the time point of 20-50% de-Si, in the necessary time from the starting time of the oxygen-blowing to the estimated time of completing the de-Si. At the time of lowering the sound pressure level by >=5&, the development of the slopping in the furnace is predicted with a around meter 10. The carbonaceous material such as coke, etc., having <=3mm sizes in a holder 7 is charged into foaming slag 6 from the lance 2. The development of the slopping phenomenon such as overflowing of the foaming slag 6, and in some case, that of the molten iron 5 from the converter is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method useful in the operation of a converter, and more particularly to a method of predicting sloping and a method of preventing sloping, which would be a major obstacle to the operation if they occur during blowing.

[0002]

BACKGROUND ART Refining of hot metal and molten steel in a converter decarburizes pure oxygen gas ejected from a lance inserted into the furnace from the furnace mouth of the converter by spraying the molten steel with stirring to melt the molten steel.
Further, the slag material charged into the converter is used for desulfurization and dephosphorization desulfurization by the reaction of the molten slag that forms slag, and the slag composition, viscosity, and oxygen content in the slag during this slag conversion process. The slag forms due to various conditions such as the above, and if it progresses excessively, so-called sloping may occur in which slag and even molten steel overflow from the furnace port.

When this sloping occurs, it has a great influence on the molten steel composition, the molten steel yield, etc., and also reduces the working efficiency, the calorie of the recovered gas, the deterioration of the working environment such as the generation of red smoke, and the damage of the equipment. It causes various problems. Therefore, it is necessary to predict the situation inside the converter as soon as possible and to carry out proper converter operation by preventing the occurrence of sloping as much as possible.

Various proposals have heretofore been made to grasp the condition of the converter. As a method for grasping the slag condition in the furnace, for example, in JP-A-52-101618,
In the converter steelmaking method, a method is disclosed in which oxygen balance is calculated based on exhaust gas information during blowing to estimate the amount of oxides produced in the furnace, that is, the amount of slag. This method inevitably causes a delay in analysis and analysis, and since the cause of sloping is not solely due to the amount of slag, the sloping prediction accuracy is low.

Various attempts have been made to detect the slag level by a physical measuring method, such as an acoustic measuring method (Japanese Patent Laid-Open No. 54-33790), a vibration measuring method (Japanese Patent Laid-Open No. 54-114414), a furnace. Internal pressure measurement method (JP-A-55-55)
104417), a microwave measurement method (JP-A-57-1).
40812), a method for measuring the temperature of the surface of the furnace body (JP-A-58-4)
No. 8615) has been proposed.

The vibration measuring method, the furnace pressure measuring method, and the furnace body surface temperature measuring method are all indirect measuring methods, and the slag level and the state of the slag cannot be quantitatively grasped, and the sloping prediction accuracy is Low. The microwave measurement method can directly measure the slag level, but since molten steel, slag, gas, etc. move extremely complicatedly in the converter during blowing, anomalies should be detected or estimated. Since it is not easy and requires high technology for signal processing and the like, it is inevitable that the device becomes expensive. Due to the above-mentioned reasons, there is a problem in applying such a method to actual operation in terms of accuracy and investment amount.

Further, the acoustic measurement method is intended to predict the occurrence of sloping by estimating the slag level by catching the changes in the frequency and intensity of the sound generated in the furnace during blowing, and the measurement principle is Since it is simple and the equipment cost is low, it is an effective slopping prevention means in the top blowing converter. However, because it is a principle that detects a specific frequency and predicts sloping by the intensity change of the frequency sound, in the case of a bottom-blown converter that uses bottom-blown gas, noise due to the bottom-blown gas causes noise. Has increased, making it difficult to predict sloping.

Further, when determining the measurement frequency, there is no knowledge about the sound source, and conventionally, various frequencies have been investigated and the frequency capable of reflecting the sloping tendency has been empirically determined. Therefore, it cannot be said that the sound collection frequency is set, so that there is a problem that the deterioration of the sloping detection accuracy is caused.

Further, due to the fact that the sound source that reflects sloping has not been clarified, there is no knowledge of the installation position of the microphone used for sound collection. Conventionally, the sound collection test was conducted at several locations. It was decided based on experience. Therefore, that position is not always the optimum sound collection position, which causes deterioration in accuracy.

Further, regarding the determination of sloping prediction, there is no effective quantitatively disclosed knowledge, and considerable skill and experience are required to predict sloping from an acoustic signal that fluctuates due to different blowing conditions each time. However, since the accuracy is poor, it is impossible to implement effective sloping prevention means based on the information of the acoustic measurement device (hereinafter referred to as the sound meter), and therefore the sound meter is hardly applied to the actual operation. Was the reality.

Further, as a method for preventing slopping, a method in which a waste rubber product is put in is conventionally disclosed in JP-A-59-133309, and a soothing material containing calcium aluminate as a main component is introduced in JP-A-61-96021. Method, JP-A-61
No. 149417, a method of blowing an inert gas, JP-A No. 62-86110, a method of adding a calming material containing dust, sludge, mill scale, etc., JP-A No. 63-72.
No. 810 discloses a method of blowing a reducing agent into a slag from a lance. However, these methods aim to break the foamed slag by rapidly generating a large amount of gas in the slag, but in actual operation, it occurred in the vicinity of the end point of the de-Si phase, which has a particularly high viscosity. Introducing the large amount of gas generating product into the forming slag, on the contrary, promotes forming and may worsen sloping.

[0012]

As described above, in order to solve the problem of the sound meter, according to the present invention, the frequency and the installation position are optimized to drastically improve the sloping prediction accuracy of the sound meter. The present invention provides a method for indicating an effective sloping prevention means based on the sloping prediction information by a sound meter, showing a judgment condition for accurately predicting sloping from the information.

[0013]

DISCLOSURE OF THE INVENTION The present invention is characterized in that when sloping generation in a refining reaction vessel is predicted by collecting sound generated in a furnace, an upper blowing oxygen discharge sound for blowing is collected. It was estimated from the start of blowing, that the sound collecting microphone was installed in an inverted cone-shaped extension line passing through the circumference of the upper opening of the reaction vessel with the tip of the upper blown acid lance during blowing as the apex. Of the required time until the end of Si removal (Si removal time), the bass sound pressure is determined from the time of 20 to 50% of the Si removal time, and sloping is detected when the bass sound pressure level drops by 5% or more This is achieved by a sloping prediction method characterized by:

Further, according to the present invention, there is provided a slopping preventing method characterized by blowing powdery carbonaceous material into the upper surface of the furnace slag and / or into the slag based on the sloping prediction signal. Is a carbon material having a maximum particle diameter of 3 mm or less.

[0015]

First, a method for predicting sloping will be described. Conventionally, there is no clearly understood principle for detecting the degree of slag forming by a sound meter. Therefore, as mentioned above, the measured frequency,
The installation position has been empirically determined, and there was a problem that accuracy deteriorated. The present inventors have attempted to optimize the measurement frequency and frequency by elucidating the mechanism of detecting the degree of slag foaming by a sound meter, and further elucidating the transmission / absorption mechanism of the sound generated in the furnace. The accuracy has been improved by optimizing the sound position.

A detailed description will be given 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 have been experimentally sampled and the frequency to be adopted has been empirically determined. However, in the furnace, various sounds from various sound sources such as top blowing discharge sound, sound when sub-amount was input, bottom blowing gas boiling sound, operation noise of peripheral equipment, etc. were mixed and resonated. There is. Therefore, until now it was impossible to identify the sound source that reflects the forming, and the frequency was set empirically, but since the optimum frequency could not be identified, especially after becoming a top-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 inventors of the present invention have clarified a sound source having a frequency that reflects forming, paying attention to the fact that each sound has a natural frequency with respect to various sounds generated from each sound source. That is, by simultaneously analyzing three-dimensional data of time, frequency, and sound pressure intensity during blowing, a specific frequency that fluctuates when forming occurs is found, and that frequency is further changed from molten iron charging to blowing and discharging in the converter. The sound source was analyzed by continuously measuring the strength change from steel and slag to the next hot metal charging. as a result,
It was clarified that the sound source of the specific frequency that reflects the forming was the upward blowing oxygen discharge sound, and therefore it was found that the upward blowing oxygen discharge sound is the optimum sound collection frequency in the sound meter.

A more detailed description will be given with an example. FIG. 3 shows frequency analysis data near the time when sloping occurs. Sounds of various frequencies are observed during blowing, but a characteristic behavior of decreasing sound pressure level is observed at a frequency near 1500 Hz in the figure during slopping. Next, FIG. 2 shows the results of continuous measurement of the strength change from the molten iron charging to the next molten iron charging through the blowing, smelting, tapping, and slag with respect to the frequency at which this sloping behavior was observed. At the same time as the start of blowing, the sound pressure intensity rises sharply, and during the period until the end of blowing, it drops sharply several times due to slag foaming. From this feature, it was found that the sound source that detects the forming with the sound meter is the oxygen discharge sound from the top blowing lance.

Next, the mechanism of the sound pressure intensity reduction during sloping was examined. In general, sound propagates as a spherical wave, and if there is an obstacle or density change in the course of the sound, it partially or largely reflects and apparently behaves as if absorbed. The inventors of the present invention focused on this transmission mechanism of the sound from the top blowing lance discharge port, forming slag, iron plate,
The mechanism of sound absorption by refractory materials was clarified. When the reflection ratio of sound due to an obstacle or density change 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 by 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 Densities of 1 and substance 2 c ₁ and c ₂ : speed of sound in substance 1 and substance 2

It is considered that the above-mentioned blown oxygen discharge sound is generated at the tip of the blown nozzle, and normally propagates through the CO gas, which is the atmospheric gas, and is observed at the sound meter sound collecting position in the absence of sloping. To be done. When propagating in CO gas, there is no reduction in sound intensity due to obstacles. However, when the molten slag or the iron plate interrupts the progress of the sound, the sound transmittance sharply decreases. For example, assuming that the sound transmittance in CO gas is 100%, the molten slag is 0.04%,
With an iron plate, only 0.006% is transmitted. In other words, when the sound pressure level drops during sloping, the forming slug rises between the sound source position (lance tip) and the sound collection position, blocking the passage of sound. To be done. Therefore, it can be judged that the slag level in the furnace at the time when the sound pressure level is lowered in the sound meter is forming near the furnace port beyond the lance tip (discharge port) position.

By the same mechanism as the sound absorption by the slag, when an obstacle composed of a refractory and iron or the like is located between the tip of the lance and the sound collecting position, the sound is almost transmitted by the obstacle. No (see Table 1 above), the sound collection level is extremely reduced. As a result, the SN ratio (sound pressure ratio of the upper-blown oxygen discharge sound and other noise) is lowered, and the accuracy of sloping prediction is deteriorated, which is unsuitable as a sound collection position.

If a sound collecting position (particularly, a sound collecting position below the tip of the upper blown acid lance for the purpose of predicting early slopping) is installed in the furnace, dust and spatter inside the furnace will be generated. This often causes clogging of the sound collection tube or damage to the sound collection microphone, and cannot be applied to actual operation. Therefore, as the sound collection position,
It is necessary to be outside the converter (including above the converter throat) and to be able to directly collect the upper blowing oxygen discharge sound. Considering that the sound propagates as a spherical wave from the generation point, the sound collection position is an inverted conical extension line that passes through the circumference of the upper opening of the reaction vessel with the tip of the upper blown acid lance during blowing as the apex. The best is inside.

In order to predict sloping due to variations in sound pressure level, it is necessary to determine a reference sound pressure level and a criterion for determining a sound pressure variation amount during forming. During blowing, the dust collection level in the furnace and the spitting cause the top blowing oxygen discharge sound collection level to fluctuate intermittently. Among them, the slopping occurrence frequency is the highest, and the sloping occurrence time at the earliest timing during blowing is near the end of Si removal. Therefore, the reference sound pressure level must be determined before the end of Si removal. As the determination method, the present inventors set the sound pressure level at a time 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. We found that it was optimal to use the standard sound pressure level.

If it is before 20% of the Si removal time, the disturbance factors such as the fluctuation of the exhaust gas amount due to the injection of the auxiliary material and the fluctuation of the upper blown oxygen discharge sound transmittance due to the auxiliary material injected from the furnace are large,
Since the sound collection level is not stable, it is not suitable as the reference sound pressure level. Further, if the desiliconization time exceeds 50%, the slopping occurrence frequency rises sharply compared with that before, and there is a possibility that the slopping prediction will not be in time, which is also inappropriate.

The sound pressure level sampling is preferably 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 on the contrary, only the calculation load is increased. Further, if it exceeds 30 seconds, the sloping determination accuracy deteriorates. For example, in 340T converter operation, the sound pressure fluctuation immediately before the occurrence of sloping is 5 to the reference sound pressure level.
8% Sound pressure level decreases. If it is less than 5% (for example, 2%, etc.), it is unlikely that the forming level in the furnace will be ejected from the furnace mouth, and the over-prediction frequency will sharply increase.
Further, if a value higher than 8% (for example, 10%) is used as the prediction criterion, the action for preventing slopping will not be in time even if the prediction is made, and the function as the sloping prediction device will not be achieved. This threshold is the sound collection energy level,
An appropriate value may be selected according to the furnace shape, capacity, etc. Further, a value obtained by multiplying the base sound pressure level by a threshold value may be used as an operation management index (determination criterion).

Next, a method of preventing sloping will be described. The sound meter continuously monitors the forming conditions in the furnace during blowing, and if sloping signs are detected, sloping prevention action is taken. As a slopping prevention action, in the conventional technology, a gas generation product is injected, and at the same time as the injection, a large amount of gas generated by decomposition or combustion penetrates the slag to improve the air permeability of exhaust gas generated during blowing. The method is common. However, as described in the above-mentioned conventional technique, the method of defoaming the forming slag with a gas generation product to prevent sloping may, on the contrary, promote the sloping by the gas generated by itself. There is a drawback that the effect as a preventive measure is low.

The present inventors believe that a suitable calming material is not a foam that is broken by generated gas, but a material that has a function of calming foaming by shortening a bubble existence period by promoting coalescence / floating of bubbles. It was As a known technique, as a method of promoting the coalescence of bubbles, by contacting the formed slag and carbon, to reduce the surface tension of the slag on the carbon surface, focusing on the method of promoting the coalescence of bubbles, furnace A method for preventing sloping, which is characterized by blowing powdery carbonaceous material into the upper surface of the inner slag and / or into the slag, has been established.

Conventionally, it has been known that the method of blowing powdery carbonaceous material is effective for breaking the slag, but since there is no effective sloping prediction technology, it is possible to use the steel exit from the converter or the furnace mouth. Make sure that the slag overflows and blow it, or if you do not have sloping and blow carbonaceous material during the period when sloping frequently occurs, if slopping does not occur, heat and oxygen balance are It was difficult to apply it as a method for preventing sloping during industrial production, because it deviated from the relationship expected before the start of blowing and deteriorated refining controllability.

According to the present invention, it becomes possible to blow coke powder only when there is a sloping sign, and the forming suppression technology by coke powder can be applied to actual operations. Depending on the blowing direction, if the coke dust is blown toward the improper direction, most of the coke is consumed for the scattering loss and the secondary combustion, and the suppressing effect is reduced. Therefore, it is most effective to directly blow powdery carbonaceous material into the upper surface of the slag in the furnace and / or into the slag.

Further, 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 of 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, scattering loss increases, and in this case also, the suppressing effect decreases. The amount of air blown once is about 1 kg / T to 2.5 kg / T, and slopping can be prevented by suppressing forming (sedation).

Even if the operator manually gives the instruction to start blowing, if the sound pressure level is constantly monitored by the computer and it is judged that the sound pressure level is exceeded, the sound pressure level is continuously judged. The coke blowing may be automatically started by the sloping prediction signal of the computer. In the case of automatic determination, since the sound pressure level of the sound meter hunts due to the influence of dust and the like in the furnace, determination may be performed using a moving average value for the purpose of preventing erroneous detection.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram in which the present invention is implemented. Oxygen is blown from the acid feeding lance 2 to the hot metal 5 charged in the converter 1 to perform blowing. When the slag 6 is formed 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 processed by the signal processing computer 13. When it is determined that the signal-processed value exceeds the predetermined sound pressure level threshold value, a command is sent to the powder coke blowing control computer 14 to supply a predetermined amount of powder coke to the powder coke storage hopper. 7 is cut out and blown into the converter by a coke blowing lance 8.

It is also possible for an operator to manually blow in the coke dust according to the information on the sound meter. Further, the amplifier 12 may be installed between the band filter 11 and the sound collecting microphone 9. For the sampling frequency extracted by the band filter, the sampling width may be set according to the required sloping prediction accuracy. At this time, it is desirable that the top blowing discharge 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 blowing oxygen discharge sound whose frequency has been analyzed in advance.
It is set to collect sound in the vicinity.

The position of the sound collecting microphone 9 is set at 15 in the inverted conical extension line passing through the circumference of the converter furnace, with the top of the converter upper blowing acid lance tip as the apex, and the upper blowing acid lance tip and the sound collecting microphone. It was installed between the outer circumference of the exhaust gas dust collection duct 3 and the inner circumference of the dust collection hood 4 approximately 1.2 m above the furnace opening so that there was no obstacle between them. 300 T of hot metal was loaded into a converter equipped with such a sloping prediction device. Table 2 shows an example of blowing conditions.

[0037]

[Table 2]

The hot metal mixing ratio is 79% and the cold hot metal mixing ratio is 10%.
The average oxygen removal efficiency for Si was determined, and based on the result, the amount of oxygen supply required to complete the removal of Si was determined. During blowing, the cumulative amount of oxygen sent from the start of blowing is monitored, the sound pressure level from 20% to 50% of cumulative oxygen is sampled every 20 seconds, the average value is calculated, and the base sound pressure is calculated. Determined the level. As the threshold value of the sound pressure level in the determination of the prediction of occurrence of sloping, 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 fell below the threshold value, so coke powder was blown at 450 kg / min. The powder coke has a maximum particle size of 3 mm and a blow rate of 0.9 kg / T. As a result, forming slag overflow and outflow from the furnace mouth were not observed, and the situation was favorable. In addition, for the purpose of preventing dust from adhering to the sound collecting microphone, a page using 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 only during non-blowing.

[0040]

[Table 3]

Prior to the implementation, this time, as shown in Table 3, the amount of quicklime added was reduced as compared with the conventional method, but there was no problem in operation. Thus, in the past, since sloping was often caused by low basicity and high viscosity slag especially near the end of the de-Si period, quick lime was originally dephosphorized for the purpose of increasing the basicity of initial charging in blowing. It was no longer necessary to deal with it by overfilling it with the necessary amount.

[0042]

Since it has been difficult to predict and prevent sloping in the past, operation measures have been implemented for the purpose of avoiding adverse effects on operation when sloping occurs. Since the present invention makes it possible to predict and prevent slopping, it is not necessary to add excess lime for the purpose of preventing slopping, and it is possible to significantly reduce the steelmaking cost.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an example of measurement results of changes in sound intensity during blowing.

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

[Explanation of symbols]

 1 Converter furnace body 2 Acid transfer 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 Calculator 14 Powder coke blowing control computer 15 Inside inverted cone extension line

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Endo 1 Nishinosu, Oita-shi, Oita Pref., Nippon Steel Co., Ltd. Oita Works (72) Inventor Yasuo Obana 1-prefecture Nishinosu, Oita, Oita Prefecture New Japan Oita Steel Works, Ltd. (72) Inventor Tatsuro Hirata No. 1 Nishinosu, Oita-shi, Oita Prefecture Shin-Nippon Steel Co., Ltd. Oita Works, Ltd.

Claims (4)

[Claims] 1. When detecting the sloping prediction in the refining reaction container by sampling the sound generated in the furnace, the upper blowing oxygen discharge sound for blowing is peaked at the tip of the upper blowing acid lance during blowing. Collecting sound with a sound collecting microphone installed in an inverted conical extension line passing through the circumference of the upper opening of the reaction vessel, and predicting sloping occurrence based on that sound Lopping prediction method. 2. Out of the required time from the start of blowing to the estimated end of Si removal, 20 to 50% of the Si removal time.
2. The method for predicting sloping in a converter according to claim 1, wherein the base sound pressure is determined from the point of time, and the occurrence of sloping is predicted when the base sound pressure level decreases by 5% or more. 3. Based on the sloping prediction signal according to claim 1 or 2, powdery carbonaceous material is blown into the upper surface of the furnace slag and / or the slag. Anti-slopping method. 4. The method for preventing slopping in a converter according to claim 3, wherein the carbonaceous material to be blown is a carbonaceous material having a maximum particle size of 3 mm or less.