JP2011195955A - Blast furnace operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blast furnace operation method which can detect collision of a charged material with a furnace wall upon charging of a raw material near the furnace wall, and enables improvement of the deposition state of the raw material near the furnace wall while protecting a furnace body by charging the raw material directly from a rotating chute to the vicinity of the furnace wall on the basis of the detection.SOLUTION: When charging the raw material into the blast furnace 1 using the rotating chute 2, the vibration of the furnace wall is measured by a vibration pickup 4, and the frequency of vibration is analyzed. After deciding a specific frequency at which a difference occurs in vibration acceleration by collision of the raw material with the furnace wall, the peak value of vibration acceleration at the specific frequency is detected and the collision is detected. It is preferable to: previously detect the minimum value of a tilting angle θ of the rotating chute at which the raw material collides with the furnace wall; set the upper limit value of the angle θ of the rotating chute 2; and then adjust the falling position of the raw material. It is also preferable to use 200 to 2,000 Hz as the specific frequency.

Description

  The present invention relates to a charge fall position detection in a blast furnace, and relates to a blast furnace operating method for performing charge distribution control based thereon.

  When using a bell-less charging device with a swirl chute, when charging the raw material from the top of the blast furnace, the tilt angle of the swirl chute is hard or soft so that it does not collide with the furnace wall. Measures such as setting are taken. This is to prevent wear of the furnace wall due to the collision of the raw material with the furnace wall.

  However, depending on the properties of the raw material, such as the mixing ratio, particle size, and moisture, even if the raw material is charged at the same tilt angle, the flight distance changes and the actual raw material falling point changes. Therefore, the upper limit of the tilt angle is set with a sufficient margin with respect to the angle at which the raw material actually collides with the furnace wall.

  Until now, as a method of grasping the behavior of falling raw materials when charging using a swivel chute, multiple microwave rangefinders have been installed at the blast furnace furnace port, and the distance meter installation position and detection distance are Based on this, a method for detecting a material falling position from a bell-less charging device is known, which detects the material falling position in the circumferential direction and the radial direction in the blast furnace (see, for example, Patent Document 1).

  In addition, as a method of estimating the in-furnace situation using the frequency, an acoustic detector is installed by drilling holes in the furnace wall, the sound inside the furnace is detected, and the frequency distribution and sound pressure distribution. There is known a technique for detecting the state of gas flow in the furnace in the vicinity of the furnace wall and the generation state of deposits on the inner surface of the furnace wall based on the change with time (see, for example, Patent Document 2).

JP-A-3-111504 JP 59-173212 A

  However, in the method using the microwave distance meter described in Patent Document 1, it is not possible to detect a collision between the charged raw material and the furnace wall when the raw material is charged in the vicinity of the furnace wall. Further, even with the method described in Patent Document 2, it is difficult to detect a collision between the charged raw material and the furnace wall. Therefore, as described above, it is necessary to provide an upper limit having a sufficient margin for the tilt angle of the turning chute to prevent the raw material furnace wall from colliding.

  On the other hand, for stable operation and energy saving of the blast furnace, the gas flow rate in the vicinity of the furnace wall is maintained to prevent deposits from growing on the furnace wall, and in the middle part of the furnace, the gas flow rate is reduced to iron ore. It is important to reduce to the minimum necessary for the reduction of gas and maximize the gas utilization rate.

  However, since the upper limit of the tilt angle of the turning chute is set as described above, the raw material cannot be constantly dropped to the vicinity of the furnace wall (for example, within about 1 m from the furnace wall). In order to adjust the mass ratio of ore and coke in the vicinity of the furnace wall (hereinafter referred to as “O / C”) necessary to maintain the gas flow rate on the side, the raw material is positioned away from the furnace wall. It must be done indirectly due to the shape of the deposit caused by dropping.

Therefore, it affects not only the vicinity of the furnace wall but also the O / C in the middle part of the furnace. As a result, when the O / C in the vicinity of the furnace wall is reduced, the gas utilization rate in the middle part of the furnace is deteriorated. Along with this, there are cases where the reducing material ratio increases and the CO ₂ emission increases.

  Therefore, the object of the present invention is to solve such problems of the prior art, and to detect a collision between the charged raw material and the furnace wall when charging the raw material in the vicinity of the furnace wall. An object of the present invention is to provide a method for operating a blast furnace capable of improving the raw material deposition state in the vicinity of the furnace wall while protecting the furnace body by directly charging the raw material from the chute.

The features of the present invention for solving such problems are as follows.
(1) When the raw material is charged into the blast furnace using the swivel chute, vibration of the blast furnace wall is measured, frequency analysis of the vibration is performed, and the presence or absence of collision of the raw material with the blast furnace wall After determining a specific frequency, which is a frequency at which a difference in vibration acceleration of vibration occurs, detecting a peak value of the vibration acceleration at the specific frequency to detect a collision of the charged material to the furnace wall How to operate the blast furnace.
(2) detecting the minimum value of the tilt angle of the swivel chute where the charged material collides with the furnace wall in advance, and setting the upper limit value of the tilt angle of the swirl chute to adjust the fall position of the charged material. A method for operating a blast furnace as described in (1) above.
(3) Described in (1) or (2), wherein the presence or absence of a collision is detected by obtaining a temporal change in vibration acceleration with a specific frequency in a part or all of the frequency band of 200 to 2000 Hz. Blast furnace operation method.

According to the present invention, the collision between the charged raw material and the furnace wall can be detected with higher accuracy than before, and the swirl chute closer to the furnace wall than before can be prevented while preventing the wear due to the raw material collision to the furnace wall. It becomes possible to charge the raw material. Thereby, the deposition state of the raw material in the blast furnace is improved, the gas utilization rate is improved, and the reduction of the reducing material ratio and the reduction of CO ₂ emission can be achieved.

Schematic which shows one Embodiment of this invention. Change of vibration acceleration with time (no charge material collision). Changes in vibration acceleration over time (with charging material collision). The graph which shows the result of frequency analysis. The schematic diagram which shows the coke layer around a furnace wall. Time change of vibration acceleration only in a frequency band (specific frequency) of 200 to 700 Hz (no collision of charged raw materials). Time change of vibration acceleration only in a frequency band (specific frequency) of 200 to 700 Hz (with charging material collision). The schematic of the upper part of a blast furnace which shows the measurement position of the vibration of a furnace wall.

  In the present invention, the collision between the charged raw material and the furnace wall is detected by measuring the vibration of the furnace wall of the blast furnace. The vibration of the furnace wall can be measured using a vibrometer. As a result of analyzing the vibration signal (generally acceleration of vibration) obtained using a vibrometer, the vibration component obtained by the vibration of the furnace wall is due to the impact of the charged raw material on the furnace wall, Vibration caused by other factors such as vibration transmitted to the furnace wall when the charged raw material falls on the raw material deposition surface can be identified by the difference in vibration frequency. And it can detect accurately and accurately that the raw material with which the furnace was charged from the turning chute collided with the furnace wall.

  Although it has been difficult to detect the collision of raw materials accurately and directly with conventional microwave rangefinders and acoustic measurement techniques, the present inventors use a vibrometer as described in the following examples. When wall vibration acceleration was measured and frequency analysis was performed, it was found that a significant difference appears in vibration acceleration at a specific frequency due to the collision of the charged material with the furnace wall. Completed the invention. The frequency in a specific range in which a difference in vibration acceleration occurs depending on whether or not the raw material collides with the blast furnace wall is hereinafter referred to as “specific frequency”. The larger the difference in vibration acceleration at a specific frequency, the better. However, in terms of detection accuracy, it is sufficient that the ratio of vibration acceleration with collision / vibration acceleration without collision is 2 or more. It is preferable to use, as the specific frequency, a frequency at which the ratio of vibration acceleration / vibration acceleration without collision is 3 or more.

  Specifically, a vibration pickup (sensor that detects vibration and converts it into an electrical signal) is installed on the outer surface of the blast furnace's iron shell, and the charged material is charged most into the furnace wall. Measure the time change of the vibration during the operation. When the charged raw material directly collides with the furnace wall, the vibration acceleration at a specific frequency becomes larger than when the charged raw material does not directly collide with the furnace wall. When the vibration acceleration peak at a specific frequency is greater than the reference value, it can be determined that the charged raw material has directly collided with the furnace wall. The reference value may be determined as appropriate so that the presence / absence of collision can be detected with a value larger than the vibration acceleration peak intensity at a specific frequency when the charged raw material does not directly collide with the furnace wall.

  It is preferable to avoid the collision of the charged raw material with the furnace wall at a high frequency from the viewpoint of equipment protection, and it is preferable to set the maximum tilt angle that does not collide.

  Therefore, a value smaller than the tilt angle when the charged raw material directly collides with the furnace wall is set as the maximum value of the tilt angle of the turning chute.

  Since the specific frequency varies depending on the blast furnace in which the operation is performed, it is desirable to obtain it by conducting a test in advance. In a normally used large blast furnace, the specific frequency is in the range of 200 to 2000 Hz. The presence or absence of a collision can be clearly detected by determining the time change of vibration acceleration limited to only a specific frequency by determining a part or all of the frequency band of this range as a specific frequency and detecting the peak value.

  The uppermost part (raw material deposition surface) of the raw material charged into the blast furnace descends when the charged raw material is unloaded, and rises when the charged raw material is newly charged. In actual operation, the timing (descent distance) at which the raw material is charged into the blast furnace is adjusted in order to adjust the raw material deposition surface to an almost constant height level. The reference surface is called the stock line. Yes. The stock line is established at the blast furnace design stage and remains unchanged during operation.

  The vibration pickup, which is the measurement unit of the vibrometer, is preferably installed on the outer surface of the iron skin near the raw material charging reference level (stock line) of the blast furnace, and is preferably installed in a highly rigid part without a cooling stave. . Moreover, it is preferable to install 4-16 places at equal intervals in the circumferential direction.

  For example, the stock line is a position indicated by 10 in FIG. As shown in the examples below, it was possible to detect a material collision on the furnace wall by installing a vibration pickup in the range of 0.8 m above the stock line and 2.3 m below the vibrometer, The installation position of the vibration pickup is preferably in the range of 1.5 m above the stock line to 3.0 m below the stock line. Further, considering the vertical movement of the material deposition surface as shown by 11a and 11b, a plurality of heights are taken into consideration. More preferably, it is installed at the position.

  Although the above method can detect the impact of the charged raw material on the furnace wall, the specific frequency varies depending on the type of charged raw material (for example, coke, lump ore, sintered ore, pellets, etc.) Since the fall trajectory from the swivel chute differs depending on the type of charging material, the tilt angle of the swirling chute is measured in advance with a vibrometer for each type of charging material until the charging material collides with the furnace wall (vibration). It is preferable that the tilt angle at the time of operation is adjusted by gradually increasing the vibration acceleration (measured by the meter) until the minimum tilt angle at which the raw material collides with the furnace wall is obtained. In addition, if the vibration acceleration at the maximum tilt angle during operation increases, this indicates that the charged material has collided with the furnace wall, so the tilt angle during operation should be adjusted to the smaller side. Is preferred. In addition, the tilt angle of the swivel chute is periodically increased while measuring with a vibrometer until the charged material collides with the furnace wall, and the minimum tilt angle at which the raw material collides with the furnace wall is obtained to determine the tilt angle during operation. Is preferably adjusted.

By using the above-described method of the present invention, when a raw material, particularly coke having a large particle size, is charged in the vicinity of the furnace wall, it can be directly charged within 1 m from the furnace wall. By controlling the thickness more precisely, the gas flow rate near the furnace wall can be sharply increased in a narrow range, the gas utilization rate is lowered at the furnace wall part, and the gas is locally routed inside the furnace so that Increase gas utilization. This makes it possible to reduce the reducing material ratio and CO ₂ emissions in the ironmaking process.

  An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram of a longitudinal section of the upper part of the blast furnace. A swirl chute 2 of a bell-less charging device installed at the upper part of the blast furnace 1 charges the raw material 3 into the blast furnace while rotating at a tilt angle θ. Vibration of the blast furnace wall is detected by a vibration pickup 4 installed on the outer surface of the iron skin of the blast furnace 1, and frequency analysis is performed by the detection unit 5 to detect a collision of the raw material with the furnace wall. Reference numeral 6 denotes a tilt angle setting device, which controls the tilt angle θ of the swivel chute 2 with the maximum value of the tilt angle θ as the maximum value at which the raw material does not collide with the furnace wall in response to the analysis result of the detection unit 5. .

In a blast furnace (blast furnace) with a tapping ratio of 2.3 t / m ³ / day having the same equipment as shown in FIG. 1, the raw material (coke) is charged by changing the tilt angle of the turning chute. The vibration of the blast furnace wall was measured.

  As shown in FIG. 8, the vibration meter has four height positions with reference to the stock line 10, 0.8 m above the stock line (SL + 0.8 m), 0.3 m above the stock line (SL + 0.3 m), and 1 below the stock line. A total of 16 pieces were installed in a circumferential direction of 4 points (every 90 degrees) at 2.4 m (SL-1.4 m) and 2.3 m (SL-2.3 m) below the stock line. 0.8 m above the stock line and 2.3 m below the stock line are the height positions where the sensitivity of the vibrometer was the best in the preliminary test.

  As for the sensitivity of the vibrometer, if the structure of the blast furnace wall is uniform in the height direction, the distance between the installation height position and the position where the coke collides should be better. Since there is a part of the furnace wall where vibration is difficult to transmit structurally, it is only necessary to find an appropriate installation position according to the blast furnace.

  During operation, since the height of the raw material surface changes sequentially, in order to complement the vibration meter between 0.8 m above the stock line and 2.3 m below the stock line, 0.3 m above the stock line and 1 below the stock line. A vibration meter was also installed at 4m. In addition, the result shown below is a case where the vibrometer is installed at a position 1.4 m below the stock line.

  FIG. 2 shows the time change of the vibration acceleration when there is no material collision with the furnace wall, and FIG. 3 shows the time change of the vibration acceleration at the time of the collision. In addition, the presence or absence of the collision was confirmed by the simulation of the fall trajectory.

  Since the charging of the raw material by the turning chute was performed with a setting of making one turn in about 6 seconds, a vibration peak was measured every about 6 seconds. FIG. 3 in which the charged raw material collides with the furnace wall is substantially larger in vibration acceleration than FIG. 2 in which the charged raw material does not collide with the furnace wall, but the value of the vibration acceleration changes with time. There was no difference in the value of vibration acceleration so that the presence or absence of a collision could be judged by setting a threshold value.

  The results of the frequency analysis of FIGS. 2 and 3 are also shown in FIG. In FIG. 4, a is a case where there is no collision of the charged raw material to the furnace wall, and b is a case where there is a collision of the charged raw material. It can be seen that the vibration acceleration b is 2 to 10 times greater in the frequency range 200 to 2000 Hz than in the other frequency bands in the frequency range 200 to 2000 Hz.

FIGS. 6 and 7 show changes in vibration acceleration over time using only a frequency band (specific frequency) of 200 to 700 Hz of the measurement results of FIGS. The vibration acceleration peak value in FIG. 6 is 0.2 m / s ² at the maximum, but the vibration acceleration peak value in FIG. 7 is 0.4 m / s ² at the minimum. Therefore, by setting the threshold value to 0.3 m / s ² , it is possible to detect the collision of the charged raw material with the furnace wall.

  Using the results of the above measurement, the setting of the upper limit value of the tilt angle of the swivel chute, which was conventionally set to 54 degrees in order to surely avoid the collision of the charged raw material with the furnace wall, has been relaxed. The unit was increased by one unit amount to 55 degrees as the upper limit value, and charging was performed with improved controllability so that the coke layer thickness would be a predetermined thickness at the periphery of the furnace. FIG. 5 shows a schematic view of the coke layer charged in this way around the furnace wall. It becomes possible to provide a local thickness portion of the coke 8 around the furnace wall 7, and it is possible to control the layer thickness of the raw material even within a range of 1 m from the furnace wall, which has been difficult to control so far. It was. Although the possibility of a collision is increased at an inclination angle of 55 degrees or more, it is possible to review the upper limit value successively by detecting vibration.

As a result, the gas utilization rate was improved by 0.2% as a whole, and the reducing agent ratio, which was 487.5 kg / tp, decreased to 486.5 kg / tp. Therefore, the reducing material ratio could be reduced by 1.0 kg / tp. Also, the CO ₂ emission amount decreased by 3.2 kg / tp.

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 Swivel chute 3 Raw material 4 Vibration pickup 5 Detection part 6 Tilt angle setting device 7 Furnace wall 8 Coke 9 Ore 10 Stock line 11 (11a, 11b) Raw material deposition surface θ Tilt angle

Claims (3)

  When the raw material is charged into the blast furnace using the swivel chute, the vibration of the blast furnace wall is measured, the frequency of the vibration is analyzed, and the vibration of the vibration depends on whether the raw material collides with the blast furnace wall. Operation of a blast furnace characterized by detecting a collision of a charged raw material to a furnace wall by detecting a peak value of vibration acceleration at the specific frequency after determining a specific frequency that causes a difference in acceleration Method.   Detecting the minimum value of the tilt angle of the swivel chute where the charged raw material collides with the furnace wall in advance, setting the upper limit value of the tilt angle of the swivel chute, and adjusting the fall position of the charged raw material The method for operating a blast furnace according to claim 1.   The blast furnace according to claim 1 or 2, wherein the presence or absence of a collision is detected by obtaining a temporal change in vibration acceleration with a specific frequency in a part or all of a frequency band in a range of 200 to 2000 Hz. Operation method.