JPS6224487B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention relates to a method for suppressing slopping in converter operation. Conventional technology The purpose of converter operation is to reduce the carbon contained in the molten metal using oxygen supplied during converter blowing, and to turn the slag-forming agent introduced into the furnace into sludge, thereby reducing the generated molten slag. The purpose is to cause dephosphorization, desulfurization, etc. to occur through the reaction between the molten metal and the molten metal. In this case, the slagging state of the slag is a major factor that determines the operational results.If the slag slag progresses excessively, it will promote the forming state of the slag and eventually cause an abnormal reaction in which the slag overflows outside the furnace, that is, slopping. Various problems arise, such as reduced work efficiency, reduced iron yield, deterioration of the working environment, and damage to equipment. On the other hand, in the case of poor slag formation, the dephosphorization effect and the like deteriorate, making it impossible to obtain the desired quality. Therefore, it is necessary to adopt an operating method that does not cause slopping while allowing sufficient slag formation.
To this end, it is necessary to clarify the first method of predicting sloping and the second method of suppressing sloping. The two are closely related, and it goes without saying that unless there is an accurate way to predict sloping, it is impossible to find a specific method to suppress sloping. Various proposals have been made to understand the status of converters. In other words, converter exhaust gas analysis method (Japanese Patent Application Laid-Open No. 52-101618
), acoustic measurement method (JP-A-54-33790), vibration measurement method (JP-A-54-114414), furnace pressure measurement method (JP-A-55-104417), microwave measurement method (JP-A-54-104417), Akira
No. 57-140812), Furnace Surface Temperature Measuring Method (Unexamined Japanese Patent Publication No. 58
-48615) etc. have been disclosed. However, with these known methods, no suggestion has been made regarding an accurate method for predicting the occurrence of sloping and suppressing sloping, such as a specific method for introducing a sloping suppressing material, which is considered to be the most effective method for suppressing sloping. Not yet.
The reason for this is presumed to be that the various methods of sloping prediction proposed above are not necessarily easy to implement and highly accurate. Problems to be Solved by the Invention In view of the above circumstances, the present invention provides a specific method for suppressing slopping using a converter sloping detection device, which was filed by the applicant (Japanese Patent Laid-Open No. 60-228931). be. Means/effect for solving the problem The present invention provides two or more through holes in the side wall of the converter,
A photodetection device is provided on at least one side, and a sloping suppressing material rapid injection device is provided on the other side.
This is a converter operating method characterized by injecting a slopping suppressant into the furnace at a rate exceeding 0.3 kg per minute per ton of furnace volume within 15 seconds. The present invention will be explained below using the drawings. FIG. 1 is an explanatory diagram schematically showing an example of an apparatus for implementing the method of the present invention. As shown in FIG.
Through-holes 4, 4' are provided that penetrate up to the point. At least two through holes may be provided, one of which may be a tapping hole. In order to prevent blockage, the through holes other than the tapping hole can be selected at any location on the side wall of the furnace body that is not easily immersed in molten metal during blowing, tapping, charging of hot metal, etc. A photodetector is installed in at least one of the through holes. The optical detection device refers to a series of devices including an optical probe for observing the furnace condition and analyzing and processing the obtained images to determine the presence or absence of slopping. FIG. 1 shows an example of this, in which a support pedestal 5 is provided near the converter, an optical probe 7 is placed on a movable pedestal 82 that is placed astride a rail 81 attached to the support pedestal 5, and the optical probe 7 is mounted on a movable device 8. Therefore, the optical probe is installed so that it can be inserted into and removed from the through hole. The reason why the optical probe can be freely inserted and removed from the through hole is that the optical probe can be inserted only when it is actually necessary to detect the situation inside the furnace, and the waiting time between tapping and next blowing can be reduced. Alternatively, the tapping hole is also used as a through hole in the method of the present invention, as mentioned above, to avoid unnecessary heat load and bad environment such as dust during raw material charging time, etc., and because it can be completely removed during tapping. It can be done. An optical probe is a cylindrical object containing a light guide. Here, the optical conductor refers to a conductor, such as a quartz-based optical fiber, that transmits radiation light emitted from a high-temperature object with low loss. As mentioned above, the optical probe is inserted into the through-hole and faces the inside of the high-temperature furnace, so there is a risk of wear and tear, so at least its tip must be protected by some means of cooling, and it is also necessary to take measures to prevent the through-hole from clogging. It is usually equipped with a device that cools it with an inert gas and then discharges it into the furnace. The optical image captured at the tip of the photoconductor is converted into a photoelectric conversion image signal by a photoelectric conversion element 10 attached via a connector 9. Here, the photoelectric conversion element has a function of converting light into an electric signal for each wavelength in proportion to its intensity, and is, for example, an ITV camera, a photomultiplier tube combined with a spectrometer, or the like. These are located at a sufficient distance from the light-receiving surface of the light guide, which is under severe conditions, and are therefore in a favorable environment to perform their functions. By the way, after the start of converter operation, when slag formation in the furnace progresses to a certain extent and the temperature of the gas 18 above the slag 16 becomes higher than the temperature of the slag, the wavelengths of the light emitted by the gas atmosphere and the light emitted by the slag become different. A clear difference appears in the strength relationship, and by specifically extracting this difference, it is possible to detect the occurrence of sloping. This is shown as a sorting device 11, a computing device 12, and a determining device 13 in FIG. 1, and the process from receiving the in-furnace light to outputting the slopping detection signal will be described in more detail with reference to the block diagram in FIG. The image of the light inside the furnace captured by the tip of the light guide is
As mentioned above, the photoelectric conversion element 10 converts the photoelectric conversion signal 6 into
1, and the signal is separated by wavelength into B (blue), G (green), and R (red) by the separation device 11, and output as three types of photoelectric conversion signals 62.
Since this signal is an analog signal, it is binarized by a binarization circuit 51 at an appropriate threshold level in order to be applied to the next arithmetic unit. It is thought that the occurrence of sloping is correlated with the amount of slag and the magnitude of the change in the amount of slag, so first, from the three types of binary signals, the area calculation device 12 calculates
The area amount of each color that occupies in the total image area is extracted as a color-specific area amount signal 63, and is passed through a binarization circuit 55 and sent to the determination device 13 as a color-specific area amount binary signal 64 for convenience in judgment. input. The above-mentioned area amount for each color can be determined by, for example, setting the vertical synchronization signal as a reset pulse (16.7 msec) and the count pulse as 0.143 μsec (7 MHz), and adding the above-mentioned binary R signal, binary G signal, and binary For example, for yellow, R・Gon,
Obtained by counting the number of Boff pulses. Next, in order to capture the change in area amount, the area amount signal 63 for each color from the above-mentioned area calculation device is passed through a high-pass transmission filter 52, a positive value conversion circuit 53, and a binarization circuit 5.
4, and is inputted to the determination device 13 as a binarized color-by-color area amount change amount signal 65. The slopping judgment criteria are as shown in Table 1, based on the combination of the color-based area amount binary signal and the color-based area amount binary signal that emphasizes the amount of change.

[Table] However, in reality, it is necessary to consider the operational status of the converter at the time of judgment. That is, in the early stage of blowing, slopping cannot occur and the gas temperature in the furnace is low, so the judgment in the previous table is not accurate. Furthermore, when the input of ore and the addition of auxiliary materials such as quicklime and dolomite have been incorporated into the operation sequence, there is no need to issue an alarm, and if the amount of silicon in the hot metal is higher than a predetermined value, The possibility of slopping is large. These are shown in FIG. 2 as a converter process 56 and an input signal 66 for ore auxiliary materials, etc.
When such judgment logic is added and the cases in Table 1 where there is a high possibility of slopping occurring are expanded, the result is as shown in Table 2. In any case, the basis of judgment is where to set the threshold level that serves as the standard for the area amount binary signal for each color and the area amount change amount for each color binary signal. must be determined from a large number of operating records and the correlation of these signals from the equipment.

[Table] The criteria for judgment as described above is determined in advance, and this criterion is compared with the two types of area binary signals described above, and the sloping is determined depending on whether the possibility of sloping occurring is high, low, or absent. The detection signal 67 is determined by the determination device 1
It can be output from 3. An example of the results of slopping detection conducted in an actual reactor in this manner will be described below. A through hole was made in the side wall of the furnace body at a height of approximately 4 m from the bottom of the 170 t/CH top-bottom blowing converter, and a light detection device was installed to determine the possibility of slopping according to the criteria in Table 1. The results shown in Table 3 were obtained. The hot metal conditions at this time are that the [Si] content is 0.30 to 0.50%.

[Table] As is clear from Table 3, sloping did not actually occur even though there was a sloping warning.
The overdetection rate was 5.3% out of 95, and there were no alarms and no slopping occurred. The slopping suppression operations were carried out using known methods such as increasing the bottom blowing rate, increasing the amount of oxygen being fed, and adding suppressants such as coke powder and coal powder.
The success rate of the slopping suppression operation in this table is 60%
It is. Based on the results described above, the above-mentioned sloping prediction method has sufficient accuracy, and since the conventional sloping suppression operation is insufficient, various studies were conducted on sloping suppression operations using the sloping prediction method. In other words, in the case of a top-blown or top-bottom blown converter, the most common control is to adjust the lance top-blown jet and bottom-blown gas, both of which change the state of agitation between slag and metal. In order to change the balance of oxidation reaction and ring element reaction and gradually balance out the oxygen potential in the slag,
Changes in response after manipulation are slow, and rapid onset of appropriate effects cannot be expected. On the other hand, materials containing carbon sources such as ring agents such as coke and coal react with FeO in the slag.
It is expected to have an immediate effect on suppressing slopping by reducing the amount of slag by reducing it to Fe. Furthermore, in order to start the reaction quickly,
In order to link the slopping suppressant feeding device and the sloping detection device, and to bring the suppressant into contact with the contents of the furnace quickly and evenly, the suppressant is transported in the form of a powder by air flow, and is deposited on the side wall of the converter. Based on the judgment that it would be preferable to blow the material together with a carrier gas through a nozzle through the provided through hole, a device for rapidly blowing the slopping suppressant material was provided. To explain with reference to FIG. 1, a slopping detection signal 67 issued from the determining device 13 is input to the blowing control device 14. The blow control device includes a stop valve 25
to allow gas from the inert gas source 30 to flow into the suppressant supply tank 70 to pressurize the tank, to adjust the opening of the supply tank outlet valve 71, and to open the suppressant carrier gas piping system 21. The flow rate adjustment device 23 is controlled to adjust the amount of the suppressing material and carrier gas blown into the flow control device 23 . The suppressant entrained in the carrier gas is blown into the furnace by a nozzle inserted into the through hole 4'. In the present invention, the slopping suppressing material rapid blowing device refers to a series of suppressing material blowing devices from the blowing control device 14 to the nozzle, and the device illustrated in FIG. 3 is a preferred example. That is, the suppressor injection nozzle 90 is also inserted into the through hole in the same way as the optical probe, and the slopping suppressant is injected together with the carrier gas while being exposed to high heat, so at least the tip of the nozzle is cooled by the cooling gas. is desirable. In this case, slag and the above-mentioned suppressing material may adhere and grow on the tip of the nozzle 90 and the inner wall of the through hole due to the carrier gas and cooling gas at room temperature, and the through hole may become clogged. In order to prevent this adhesion growth, according to the experience of the present inventor, it is effective to add O ₂ to the nozzle cooling gas flowing into the outer cylinder 91 of the nozzle. That is, as illustrated in FIG. 3, in addition to the nozzle outer cylinder cooling gas piping system 40, the O ₂ piping system 45
If the amount of O ₂ added is about 30 to 55% of the total amount of gas after mixing with the cooling gas, the opening degree of the flow rate control valves 41 and 46 can be adjusted using the ratio setting device 15 to prevent blockage. I was able to reach my goal. The addition of O ₂ to the cooling gas also functions in exactly the same way in preventing the through hole for insertion of the optical probe from being clogged. Further, it is preferable that the nozzle 90 can be inserted into or removed from the through hole for exactly the same reason as the optical probe, and this device is similar to the optical probe. Insertion/removal displacements can thus be easily absorbed by partially using flexible pipes between the piping system and the nozzle connection. Using the above-described sloping detection device, slopping detection method, and sloping suppressant rapid injection device, it is possible to obtain specific guidelines regarding the sloping suppressing material injection method, that is, the time required to inject the suppressing material after sloping detection, and the sloping material blowing speed. I conducted a test. First, preliminary tests showed that there is no big difference whether the slopping suppressant is a cyclic material, whether it is coke or coal, and that the particle size of the suppressant depends on the reactivity in the furnace and the efficiency of air transport. From the above, it was concluded that 5 mm or less is preferable. The carrier gas is preferably a gas that does not react with the above-mentioned suppressor, does not easily react with the contents of the furnace when blown into the furnace, and does not affect the components of the target steel.
Examples of this include CO ₂ , Ar, and N ₂ , but CO ₂ was used in the test. A 170-ton top-bottom blowing converter was used as the test furnace, and first, after the occurrence of sloping was predicted, the frequency distribution of the time until slag overflowed from the furnace mouth was determined when no sloping suppression action was taken. This is shown in Figure 4. Although this result suggests that it is necessary to take action within 10 minutes after predicting the occurrence of slopping, we conducted a more detailed examination of the influence of the above two factors on the sloping suppression effect, and the results are shown in Table 4. Got results. In other words, the time tm from when the occurrence of slopping is predicted until the start of the injection of the suppressor is within 15 seconds, preferably within 10 seconds, and the injection speed of the sloping suppressor is Vm.
is an amount exceeding 0.3 kg per minute per ton of converter furnace volume,
It has become clear that an extremely good success rate in suppressing slopping can be obtained when the amount is preferably over 0.6 kg, and the present invention has been completed. The injection of suppressant should continue until the end of the slopping alarm, and the duration should be 0.5 minutes or more.
It was approximately 1.0 minutes, and there was a tendency that the smaller the tm and the larger the Vm, the shorter the blowing duration time. Based on this result, we attempted to suppress slopping in a 100t converter and a 300t converter, and obtained similar results. Note that if the furnace volume is large and the amount of suppressant injected per unit time is large, the number of through holes and nozzles can be increased to cope with the problem.

[Table] Effects of the Invention As described in detail above, the method of the present invention makes it possible to greatly suppress the occurrence of slopping, and has an extremely large effect on converter operation.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of the present invention, Fig. 2 is a block diagram of a photodetection device, Fig. 3 is an explanatory diagram showing an example of a sloping suppressing material rapid injection device, and Fig. 4 is a diagram showing a sloping occurrence frequency distribution. It is. 1... Converter, 2... Side wall, 3... Furnace interior, 4,
4'...Through hole, 5...Support frame, 7...Optical probe, 8...Movement device, 81...Rail, 82...
...Moving frame, 9...Connector, 10...Photoelectric conversion element, 11...Separation device, 12...Arithmetic device, 1
3...determination device, 14...blow control device, 15...
... Ratio setting device, 16 ... Slag, 17 ... Molten metal,
18... Gas, 19... Lance, 20... Carrier gas piping system, 21... Stop valve, 22... Pressure reducing valve, 23... Flow rate adjustment device, 24... Stop valve, 25
... Stop valve, 30 ... Inert gas source, 40 ... Cooling gas piping system, 41 ... Flow rate control valve, 45 ... O ₂
Gas piping system, 46...flow control valve, 51...binarization circuit, 52...high-pass transmission filter, 53...
Positive value conversion circuit, 54... Binarization circuit, 55... Binarization circuit, 56... Converter process, 61... Photoelectric conversion video signal, 62... Video signal for each wavelength range, 63
... Area amount signal for each color, 64... Binarized area amount signal for each color, 65... Binarized signal for amount of change in area amount for each color, 6
6...Input signal for ore, auxiliary materials, etc., 67...Slopping detection signal, 70...Supply tank, 71...Outlet valve, 72...Receiving tank, 90...Blowing nozzle, 91...Outer cylinder.

Claims (1)

[Claims] 1. Two or more through holes are provided in the side wall of the converter, a photodetection device is provided in at least one, and a rapid injection device for slopping suppressant is provided in the other, and within 15 seconds at the most after the photodetection device detects the occurrence of slopping, A converter operating method characterized by injecting a slopping suppressant into the furnace at a rate exceeding 0.3 kg per minute per ton of furnace volume.