JPS6372812A - Detecting method for slag foaming in converter - Google Patents

Abstract

PURPOSE:To prevent occurrence of slopping caused by foaming slag by transmitting microwave toward a lance from a transmitting part arranged at a converter wall at the time of refining molten steel by the converter, and receiving detecting wave by receivers arranged at the lance to detect the level of foaming slag. CONSTITUTION:The molten iron 11 is charged into the converter 10, and oxygen gas 17 is blown on the surface of molten iron from the tip of lance 16 hanging down in the converter, and C in the molten iron is oxidized, to refine to the molten steel by decarburization. In this case, the horn antenna from a microwave generator 15 is inserted in the converter wall, to transmit the microwave having the prescribed wave length toward the lance 16. When the forming slag develops in the converter and its volume expands so much as to enclosing the lance 16, the ascending position of foaming slag 12 is detected by plural microwave receivers P1-Pn arranged on the lance 16 and is displayed on a display panel 24 and also the treatment for preventing occurrence of the slopping caused by the foaming slag is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for detecting slag foaming in a converter, which grasps the situation inside the furnace during converter blowing and predicts the occurrence of slopping.

[Prior Art] When slopping occurs in converter blowing, it significantly impedes the blowing operation. Slopping is a phenomenon in which slag bubbles (forming) during the slag generation process, and the slag is ejected from the furnace mouth. When this sloping occurs, it causes changes in the molten steel composition and decreases the tapping yield, and also reduces work efficiency. Problems such as a decrease in heat content, a decrease in the calorific value of recovered gas, and smoke generation occur.For this reason, in conventional converter blowing, the situation inside the furnace during blowing is grasped using various detection technologies, and the presence or absence of slag forming is determined. Based on this, the occurrence of slopping is prevented.

Conventional methods for detecting slag forming include exhaust gas analysis, furnace sound measurement, lance and furnace vibration measurement,
There are methods such as furnace body temperature measurement method and microwave projection method. In the exhaust gas analysis method, the exhaust gas composition during blowing is analyzed, the amount of slag produced is estimated based on the analysis results, and slag forging is predicted. In the furnace sound measurement method, the frequency and system width of the sound generated in the furnace during blowing are measured, and slag forming is predicted from changes in the measured values.

In the lance and furnace body vibration measurement method, the lance and furnace body are photographed during the blowwire, and the slag level and slag condition are estimated from changes in the waveform to predict slag forming. In the furnace temperature measurement method, the radiant heat in the upper and lower parts of the furnace body is measured by replacing it with temperature, and the forming of the slag is predicted from the temperature change.

On the other hand, in the microwave projection method, as shown in FIG. Microwaves are projected into the furnace from a microwave generator 7 through a waveguide 6 connected to a protection tube 5. When the projected microwave reaches the slag 3 or hot metal 2 being blown by the lance 4, it is reflected, so this reflected wave is detected by a sensor in the protective tube 5, and this detection signal is transmitted through the waveguide 6. The reflected wave is input to the signal processing device 8 and the intensity of the reflected wave is measured. This allows us to know the slag level and predict the forming of slug 3.

[Problems to be Solved by the Invention] However, in the exhaust gas analysis method, it takes a long time to carry out the analysis operation and analyze the analysis results, so it is not possible to quickly deal with situations where there is a risk of slopping. Since the cause of ropping does not depend only on slag convexity, there is a problem in that the prediction accuracy is low. In addition, with the furnace sound measurement method, it is not always possible to selectively detect only the changes in the sound generated during slag forming, and it is also possible to detect changes in the furnace conditions due to other causes, such as changes in the oxygen supply. There is a problem in that even if the internal pressure of the furnace changes, the sound changes, making it impossible to reliably grasp the situation inside the furnace.

In addition, the lance and furnace body vibration measurement method and the furnace body temperature measurement method are indirect measurement methods, similar to the furnace sound measurement method, and therefore cannot accurately grasp the slag level and slag condition. There is a problem in that the prediction degree of slopping occurrence is low.

On the other hand, in the microwave projection method, since the sensor is installed above the furnace mouth, the tip of the sensor is severely damaged by dust etc. blown out from the furnace mouth, and the sensor deteriorates, resulting in detection failure.
There is a problem that the temperature decreases by 1 degree.

This invention was made in view of such circumstances, and
It is an object of the present invention to provide a method for detecting slag forming in a converter that has high detection accuracy of slag forming and can quickly and reliably predict the occurrence of sloping.

[Means for Solving the Problems] The method for detecting slag forming in a converter according to the present invention includes transmitting a detection wave from a transmitter provided on the furnace wall toward a lance in the converter, and is received by a plurality of receivers provided along the axial direction of the lance, and the level of the formed slag is detected based on these received waves. In this case, the detected wave is
Preferably it is a microwave.

[Operation] In the method for detecting slag foaming in a converter according to the present invention, a lance is lowered into the converter to start blowing, and a detection wave is emitted from a transmitter provided on the furnace wall toward the lance. This detected wave is received by the receiver provided on the lance. Multiple receivers are arranged in sequence along the axial direction of the lance, and when the slag level gradually rises due to forming and the lower part of the lance becomes buried in the slag, the detected waves are scattered by the slag near the receiver. This weakens the strength of the received wave from the bottom of the lance. Based on changes in the strength of these received waves, the ever-changing slag level can be detected, and the situation of slag forming can be grasped.

[Embodiments] Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

The first factor is a schematic diagram showing a converter used in the method for detecting slag foaming in a converter according to an embodiment of the present invention. The converter body 10 is a composite blowing converter having a capacity of about 250 tons, and hot metal 11 covered with slag 12 is accommodated in the furnace body 1o. A plurality of bottom blowing tuyeres (not shown) are provided at the bottom of the furnace body 10, and the bottom blowing tuyere is connected to an oxygen gas or inert gas supply source (not shown) via piping (not shown). ). On the other hand, a horn antenna 13 is fitted into the upper side wall of the furnace body 10 so that its horn faces into the furnace.

The horn antenna 13 is connected to a microwave generator 15 via a waveguide 14, and is a microwave generator! ! !
The microwave generated at t15 is guided to the horn antenna 13 through the waveguide 14, and the microwave of a predetermined wavelength is emitted from the horn antenna 13 toward the inside of the furnace.

On the other hand, a rod-shaped main lance 16 is lowered substantially vertically into the furnace body 10 from the furnace mouth, so that the tip of the lance 16 faces the surface of the hot metal 11 at an appropriate distance. This lance 16 is supported so as to be movable up and down by a lance lifting device (not shown) disposed above the furnace body 10.

The lance 16 is made of substantially pure copper, and has a gas passage (not shown) and a cooling water passage (not shown) each extending in the axial direction. This gas passage is connected to an oxygen gas supply source (not shown) via an IR (not shown), and is directed toward the hot metal 11 from a nozzle hole (not shown) formed at the tip of the lance 16. The system injects high-pressure, high-purity oxygen gas. On the other hand, a multi-point receiving section 18 protrudes from the peripheral wall of the lance 16 so as to face the horn antenna 13.
For example, n pieces (indicated by @P! to Pn in the figure) are arranged at equal intervals along the axial direction of the lance 16.

The distance between mutually adjacent receiving sections 18 is determined by the distance between the horn antennas 1
The length is set to be an odd number multiple of the half wavelength of the microwave transmitted from No. 3.

FIG. 2 is a schematic diagram showing the multi-point receiving section 18. The receiving part 18 is the tip of a metal wire with a substantially uniform diameter, and the part of the metal wire other than this tip is insulated by an insulating tube 19 to prevent the microwaves received by the receiving part 18 from leaking into the lance 16. It's like that. This metal wire is guided into the interior of the lance 16, passes through the lance 16 approximately along the axis of the lance 16, and is connected to one end of the waveguide 20 at the upper end of the lance 16. This waveguide 20 is connected to a demodulation circuit (not shown) of the receiver @ 22, and the n microwaves transmitted through the waveguide 20 are each converted into a voltage signal by the demodulation circuit. It looks like this. Also, the receiver! ! 22 has n filters (not shown) that filter the sinusoidal voltage signal converted by the demodulation circuit into a single-sided flat wave. The output sides of these n filters are each connected to the input side of a comparator (not shown). The n comparators are configured to compare the set value given externally to their input side and the voltage value after passing through the filter.
The output side thereof is connected to n limit switches (not shown) of the display panel 24, respectively. In addition, each of the n limit switches is built into a circuit that lights up an indicator lamp (not shown), and when the voltage difference signal from the comparator exceeds a predetermined value, the limit switch is turned off and current flows through the circuit. It has become. These n display lamps are sequentially labeled with symbols P1 to P1, so that each display lamp corresponds one-to-one to the receiving section 18, respectively.
For example, they are arranged so that Pa corresponds to the receiving section 18 at the top and Pi corresponds to the receiving section 18 at the bottom.

For example, when the voltage value corresponding to the intensity of the received wave from the lowermost receiving section 18 falls below the set value, the indicator lamp corresponding to Pl lights up.

Next, the operation of this practical example will be explained. When hot metal 11 is charged into the furnace body 10, the lance 16 is lowered into the furnace,
High-pressure, high-purity oxygen gas is supplied to the hot metal 11 from the tip of the lance 16.
At the same time, oxygen gas or inert gas is blown into the hot metal 11 through the bottom blowing tuyere to start blowing. During this blowing, an appropriate amount of auxiliary raw material such as quicklime is charged into the furnace, and a large amount of converter slag 12 is produced by a refining reaction between the hot metal 11 and the D1 raw material. Normally, this slag 12 is removed from the furnace solid region toward the furnace wall side by spraying oxygen gas 17 from a lance 16, and the spraying of oxygen gas 17 exposes a portion of the hot metal 11 in the region.

On the other hand, microwaves generated by the microwave generator 15 are transmitted toward the lance 16 via the horn antenna 13. When the emitted microwave propagates through the air and reaches the peripheral wall of the lance 16, a portion of it is received by each of the n receivers 18. Then, the received wave is
Since it is shielded from external 'E1 magnetic waves by the peripheral wall of the lance 16, it is transmitted within the lance 16 without being affected by the reflected liquid in the furnace, and is input to the receiving device 220111 circuit via the waveguide 20. It becomes like this. In converter blowing in a steady state, the receiving part 18 of the lance 16 is exposed to the atmosphere, so the receiving part 1 corresponding to Pt to Pa
The intensity of all the n received waves received at 8 has become strong, and the lamps on the display panel 24 are in a state of being turned off.

In FIG. 3, the horizontal axis shows the elapsed time after the start of blowing, and the vertical axis shows the voltage values corresponding to the intensities of the received waves from Pl to Pa. It is a graph figure which shows a waveform, respectively. When forming occurs in the slag 12, the slag level in the furnace gradually rises and the lance 16
The lower part of the slag becomes buried in the forming slag.

For example, 1. When the lowermost receiving section 18 (Pl) comes to be covered by the slug 12 after a period of time has elapsed, the microwaves reaching the receiving section 18 of Pl are absorbed by the slag 12.
, and the intensity of the received wave at the receiving section 18 of Pl becomes weaker. Therefore, as shown in FIG. 3, the voltage value corresponding to the received wave intensity of Pt rapidly decreases at time t1. Then, the Pl lamp on the display panel 24 lights up, indicating that the slag level in the furnace has risen above the height at which the Pt receiving section 18 is located. In this way, for example, when the indicator lamp P2 lights up after time t2 has elapsed, the converter operator knows the position of the slag level and its rate of rise, indicating that the inside of the furnace is in a situation where slopping may occur. Knowing this, the amount of oxygen gas 17 blown (feed 1! ff1)
Take measures to suppress slopping, such as Section 11 of Section 11, to avoid the occurrence of slopping.

According to the detection II of this embodiment, the slag condition in the furnace can be monitored by blinking the indicator lamp, and the position of the slag level and its rate of rise can be detected. Therefore, when the indicator lamp corresponding to the position where the slag level is high lights up, measures to suppress slopping are taken, and situations where there is a possibility of slopping are quickly dealt with, and slopping is extremely likely to occur. Lopping can be avoided.

Although microwaves are used as detection waves in the above embodiments, the detection wave is not limited to this, and other electromagnetic waves such as light may also be used.

[Effects of the Invention] According to the present invention, a detection wave is transmitted from the transmitting section provided on the furnace wall to the receiving section provided on the lance, so that when the lance is buried in the slag, the detection wave is emitted from the buried portion. It is possible to detect that the received wave intensity has weakened and the slab level has increased.

Therefore, the situation of slag forming during blowing can be quickly grasped, and based on this, slopping can be effectively prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a converter used in a method for detecting slag foaming in a converter according to an embodiment of the present invention;
Figure 2 is a schematic diagram showing the receiving section installed in the lance, Figure 3
The figure is a graph showing the voltage waveform of ngH filtered in the receiver, and FIG. 4 is a schematic diagram showing a converter used in the conventional detection method. 1o; furnace body, 11; hot metal, 12; slag, 13: horn antenna, 14.20; waveguide, 15; microwave generator, 16: lance, 17: oxygen gas, 18: receiving section,
19; Insulating tube, 22; Receiving device, 24: Display panel Applicant's representative Patent attorney Takehiko Suzue No. 1 Mouth Figure 2 Figure 3 t1Miffi -

Claims (2)

[Claims] (1) A detection wave is emitted from a transmitter installed on the furnace wall toward a lance in the converter, and this detection wave is received by multiple receivers installed along the axial direction of the lance. 1. A method for detecting slag forming in a converter, comprising detecting the level of formed slag based on received waves. (2) The method for detecting slag foaming in a converter according to claim 1, wherein the detection wave is a microwave.