JPH0711393B2 - Burner blowout detection method for smelting electric furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention uses a burner to burn fuel and oxygen or an oxygen-containing gas such as oxygen-enriched air in a raw material layer of an electric furnace for smelting, The present invention relates to a method for detecting blower blow-through in an electric furnace in which a raw material is heated and melted by a flame and a combustion gas.

(Prior Art) Conventionally, for example, in an electric furnace for smelting ferro-nickel, as shown in FIG. 1, an electric furnace 2 is charged with a granular material 3 preheated to 800 to 900 ° C. from a throwing tube 4. Then, the three electrodes 5 are energized, and the raw material 3 is heated and melted by Joule heat due to a large current of tens of thousands amperes flowing between the electrodes 5 mainly through the slag layer 6. At that time, the ore in the raw material 3 reacts with the reducing agent to settle as a solution, and the slag layer 6 and the metal layer 7 are formed due to the difference in specific gravity. On the other hand, since the raw material 3 is fed from the throwing tube 4 by the yoke yoke, when the raw material 3 is melted and its volume decreases, the raw material 3 successively flows into the furnace. Then, the slag and the metal are extracted every predetermined time.

By the way, since electric energy is expensive in Japan, a technique for replacing a part of electric energy by using an inexpensive fossil fuel is being developed. As a part of that, raw material 3 in the electric furnace
There is a method of inserting the burner 1 into the high temperature part of the layer and burning the heavy oil or pulverized coal with oxygen or oxygen-containing air at the tip of the burner 1 to promote the dissolution of the raw material 3. In this method, as shown in FIG. 1, a plurality of slender burners 1 having a length of 5 to 6 m are slidably supported by guides 10 outside the furnace, respectively, and slanted into a raw material 3 through holes provided in a furnace lid 8. The fuel is burned in the high temperature part of the raw material 3 above the slag layer 6 by inserting from above. By doing so, the raw material 3 is melted into a solution by electric energy, high-temperature flame and combustion gas, drops into the slag layer 6, is separated into metal and slag, and the metal is deposited in the metal layer 7.

On the other hand, the high-temperature gas generated at the tip of each burner 1 passes through the voids of the powdery raw material 3 and rises while preheating the raw material 3, and is provided on the furnace lid 8 from the entire surface of the raw material 3. It is discharged through the flue 9 and is reused for drying ore and ore and ore materials.

(Problems to be Solved by the Invention) In the above method, in order to heat the raw material most efficiently, the high temperature combustion gas generated at the tip of the burner 1 is in contact with a wide range of the raw material 3 and the raw material layer. It is desirable to raise the voids inside. However, there is a case where the combustion gas is ejected from only one place. In this case, the combustion gas heats only the raw material in a narrow range or hardly contacts the raw material, and is discharged from the raw material layer at a high temperature, resulting in poor thermal efficiency. After a few minutes, some ore in the heated raw material is melted, and a state called blow-by blows out together with the combustion gas.
The molten ore ejected at the time of occurrence of the blow-through increases with time, and not only the thermal efficiency deteriorates as described above, but also local heating to the furnace lid 8 of the electric furnace and adhesion of the molten ore occur. In addition, the molten ore adheres to the lower part of the throwing tube 4 and clogs the throwing tube 4, resulting in adverse effects on various electric furnaces. Further, not only the molten ore adheres to the burner 1 and solidifies to make the burner operation difficult, but in the worst case, the burner and the nozzle at the tip of the burner are melted and damaged. In addition, the molten ore solidifies in a tubular shape in the raw material layer to form a so-called flue, and once the blower combustion operation of the burner has been stopped, the blow-through easily reoccurs even if the burner injection combustion is restarted. Become.

Therefore, if blow-through occurs, it is necessary to remove the burner from the raw material layer at an early stage, reinsert it by changing the angle to eliminate the blow-through, or stop the blow-in combustion once and wait for the recovery of the furnace condition. Is.

However, conventionally, there has been a problem that it is difficult to detect that a blow-through has occurred. Therefore, the worker must frequently inspect the inside of the furnace in order to detect the occurrence of blow-through, which causes a problem that the burden on the worker is large.

The present invention solves the above-mentioned problems, and makes the blow-through state early.
And the task is to make sure to discover it.

(Means for Solving the Problems) In order to solve the above problems, the present invention supplies a fuel and an oxygen-containing gas to a burner inserted in a furnace, and burns the burner in a raw material in the furnace. In the electric furnace,
A burner blowout detection method for an electric furnace for smelting is characterized by detecting vibration of a burner through a vibration sensor and detecting when the vibration intensity exceeds a certain level.

FIG. 1 shows an example of an apparatus for carrying out the method of the present invention. A vibration sensor 11 is provided at the upper end of the guide 10, and a signal of this vibration intensity is amplified by an amplifier 12 and then a bandpass filter 13 extracts only a frequency of 10 dB or more.
It is configured to activate the alarm 16 by comparing with the strength of vibration during normal operation. Note that the burner 1 can be automatically pulled up by interlocking with the drive device of the burner 1 if necessary.

(Operation) According to the above-described method of the present invention, the vibration of the burner 1 detected by the vibration sensor 11 has a strong vibration in a normal state in which no blow-through occurs and in a state in which blow-through occurs. Since the difference is different, it has an effect that the occurrence of blow-by can be easily detected.

(Embodiment) Embodiment 1 As shown in a partially enlarged view of FIG. 2, two vibration sensors 11a and 11b are attached to the upper end of the guide 10 by mounting arms 17 and 18, respectively.
Attached to the vertical axis of the burner 1 (arrow A in FIG. 2).
Is indicated by a vibration sensor 11a, and lateral vibration (indicated by an arrow B in FIG. 2) is detected by a vibration sensor 11b. The burner 1 blows fuel and oxygen into the raw material layer for combustion. While operating the electric furnace.
Tables 1 and 2 show the vibration intensities of frequencies below 10 kHz measured during operation. Table 1 shows a comparison between the vibration intensity a during the 30 minutes before the vertical vibration blow through and the vibration intensity b during the blow through. Table 2 shows a comparison of the vibration intensity c during the 30 minutes before the blow-through and the vibration intensity d during the blow-through for the lateral vibration. The presence / absence of blow-through was visually confirmed at the time of alarm activation and when the recorded vibration intensity was increasing.

30 to 20 minutes, 20 to 10 minutes before blow-through of longitudinal vibration in Table 1, 10
The average of each vibration intensity for 0 min is 6.46dB, 6.34dB,
It was almost the same as 6.89 dB, and the total average was 6.62 dB. On the other hand, the average vibration intensity during blow-through is 14.3 dB, which is 7.68 dB stronger during blow-through. or,
It was 11.89 dB stronger than 18.31 dB, which is the average of the vibration peak values during the void. Next, comparing the lateral vibrations of Table 2 in the same way, it was 16.00dB, 16.14dB,
At 17.65 dB, the overall average is 16.64 dB. On the other hand, it was found that the vibration during blow-through was 25.33 dB, which was 8.69 dB stronger, and was 11.90 dB stronger than the average vibration peak value during blow-through, which was 28.54 dB. Next, for the vibrations in both the vertical and horizontal directions, we tested the difference between the population mean of the vibration intensity for 10 minutes before the occurrence of the blowout and the vibration intensity during the occurrence of the blowout and found that there was a highly significant difference at the significance level of 1%. I understood that I can say.

Example 2 A burner longitudinal direction in which the same electric furnace as in Example 1 was used and the same apparatus was used, the dispersion of vibration intensity was small, and the level difference in vibration intensity before and during blow-through was easy to distinguish. The alarm was activated if there was a difference of 7 dB or more with respect to the vibration, and the relationship between the occurrence of blow-by and the presence or absence of the alarm was investigated. Here, the number of correct reports (there was a blowout and the alarm was activated), the number of false reports (there was no blowout, but the alarm was activated) the number of undetected (the blowout was generated but the alarm did not activate) detection rate ( %) = {/ (+)} × 100 Correct reporting rate (%) = {/ (+)} × 100 The detection rate was about 70% and the correct reporting rate was about 60%. The cause of the false alarm was that there was a momentary difference in vibration intensity of 7 dB or more, and the cause of undetected was that the difference in vibration intensity during the occurrence of blow-through was 7 dB or less. By improving the mounting position of the vibration sensor, it was possible to improve the detection rate and the accuracy rate.

(Effect of the present invention) As described in detail above, according to the present invention, if a blow-through occurs in the burner of the smelting electric furnace, it can be automatically detected, so that the state of blow-through has been delayed. This has the effect of preventing adverse effects on the electric furnace, damage to the burner and nozzle, etc., and improving the operating rate of blow-in combustion.
Further, since the worker can know the occurrence of blow-through remotely (for example, in the operation room where an alarm is installed) without directly monitoring the inside of the furnace, there is an effect that the burden on the worker can be reduced.

[Brief description of drawings]

FIG. 1 is a view showing an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a partially enlarged view showing a mounting portion of a vibration sensor of the apparatus for carrying out the present invention. 1 ... Burner, 2 ... Electric furnace, 3 ... Raw material, 10 ... Guide, 11 ... Vibration sensor.

Claims (1)

[Claims] 1. An electric furnace in which a fuel and an oxygen-containing gas are supplied to a burner inserted in a furnace to burn the burner in a raw material in the furnace, the vibration of the burner is detected through a vibration sensor, A method for detecting burner blow-out in an electric furnace for smelting, which detects when the intensity of vibration exceeds a certain level.