JP2004257679A - Device and method for collecting dust of arc furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for collecting dust of an arc furnace capable of effectively changing pressure fluctuation caused by change of exhaust gas generation stemming from change of operational conditions in the arc furnace for preventing dispersing the exhaust gas out of the arc. <P>SOLUTION: In the arc furnace dust collecting device having a furnace pressure setting device 16 for setting furnace pressure of the arc furnace 1 and a detecting device 13 for detecting the furnace pressure of the arc furnace, a moving duct 4 is arranged downstream side of a furnace cover side duct. The device comprises a moving duct control device 17 for controlling speed of the moving duct, a comparison operator for comparing/operating pressure difference between a target value of the furnace pressure set by the furnace pressure setting device and a measured value of the furnace pressure detecting device, and a moving duct control device for controlling a space s between the furnace cover side duct and the moving duct side by the comparison operator. In the method for collecting dust of the arc furnace, the furnace pressure setting device 16 sets the furnace target pressure of the arc furnace 1 and the furnace pressure detecting device 13 provided in the arc furnace detects the furnace pressure. In this method, the moving duct 4 is arranged downstream side of the furnace cover side duct 3, the pressure difference between the furnace target pressure set by the furnace pressure setting device 16 and the measured value of the furnace pressure detecting device 13 is compared/operated, and the space s between the furnace cover side duct 3 and the moving duct side 4 is controlled based on the operation result. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an arc furnace dust collector and a method for effectively collecting and discharging dust and the like generated from exhaust gas generated during melting operation in an arc furnace.
[0002]
[Prior art]
In order to effectively suppress the flue gas and dust generated during the melting operation in the arc furnace from scattering outside the arc furnace, the pressure inside the arc furnace is maintained negative by setting the furnace pressure. For this reason, in consideration of the predicted exhaust gas amount generated during the melting operation of the arc furnace and the pressure loss of the dust collector, a suction fan having the ability to maintain the furnace pressure in the arc furnace at a negative value has been selected. However, since the amount of exhaust gas generated varies depending on the state of the melting operation of the arc furnace, the heat generated in the arc furnace is taken out together with the exhaust gas, and the thermal efficiency of the arc furnace decreases. In order to suppress such a decrease in thermal efficiency and to reduce the power consumption of the fan itself, a method of pattern-controlling the number of revolutions of the suction fan to a preset air flow based on the predicted exhaust gas amount has been adopted. I have.
[0003]
However, when exhaust gas is generated from the arc furnace at a speed higher than the predicted generation rate, the pressure inside the arc furnace cannot be maintained at a negative value, and it is not possible to prevent the exhaust gas, dust and the like from scattering outside the arc furnace.
[0004]
Therefore, the pressure inside the arc furnace is detected by a pressure detector, converted into an electric signal, and applied to the control mechanism of the damper placed in front of the suction fan, and the pressure inside the arc furnace is adjusted by opening and closing the damper. It has been proposed to.
[0005]
However, with a butterfly valve or louver valve damper installed in a large-diameter duct, there is almost no change in the furnace pressure even if the opening is changed near full opening, and if the opening is changed near the middle opening, Since it has characteristics such as a large change in the furnace pressure, it is difficult to finely adjust the furnace pressure.
[0006]
In addition, it is generally known that the effect of reducing the power consumption of the suction fan itself by opening and closing the damper is low, and the effects in terms of fine adjustment of the furnace pressure in the arc furnace, responsiveness, power consumption, etc. are still sufficient. Not. Therefore, in Patent Literature 1, the gas pressure in a processing apparatus such as an electric furnace is detected by a pressure detector and converted into an electric signal, which is applied to a pressure regulator to obtain a difference from a preset internal pressure of the apparatus. A suction pressure control method for a processing device has been proposed, wherein a deviation value corresponding to this difference is applied to a drive motor rotation speed control mechanism of the suction fan for the processing device, and the suction fan is controlled to a required rotation speed. ing.
[0007]
[Patent Document]
Japanese Patent Application Laid-Open No. Sho 62-125290
[Problems to be solved by the invention]
However, the generation rate of exhaust gas increases in the arc furnace, the amount of exhaust gas increases in a short time, and the furnace pressure increases, or the generation of exhaust gas stops in the arc furnace, and the amount of exhaust gas decreases in a short time. The response is slow when the pressure in the furnace decreases, and the fluctuations in the pressure in the arc furnace increase, so that it is not sufficiently effective in terms of scattering of exhaust gas and dust outside the arc furnace. There's a problem.
[0009]
[Means for Solving the Problems]
The present invention is to solve such a problem, the pressure in the arc furnace is controlled by controlling the gap between the furnace lid side duct and the moving duct, and an arc furnace that efficiently collects and discharges the exhaust gas. The present invention provides a dust collecting device and a dust collecting method thereof, and has the following configuration.
(1) In an arc furnace dust collector having a furnace pressure setting device 16 for setting the furnace pressure of the arc furnace 1 and a detector 13 for detecting the furnace pressure of the arc furnace, downstream of the furnace lid side duct 3 The moving duct 4 is arranged on the side, a moving duct control device 17 for controlling the speed of the moving duct, a target value of the furnace pressure set by the furnace pressure setting device 16 and a measured value of the furnace pressure detector 13 are provided. A dust collection device for an arc furnace, comprising: a comparison operation device 18 for comparing and calculating the pressure difference between the furnace and the moving duct control device 17 for controlling a gap s between the furnace lid side duct 3 and the moving duct 4 by the comparison operation device. apparatus.
[0010]
(2) The moving duct control device 17 performs a comparison operation for calculating a pressure difference between a target value of the furnace pressure set by the furnace pressure setting device 16 of the arc furnace and a measurement value of the furnace pressure detector 13. A speed reference judging device 19 for judging the speed reference of the moving duct 4 from the pressure difference, and comparing the measured value of the speed detector 15 of the moving duct 4 with the speed reference of the speed reference judging device 19 to determine the speed. The dust collecting device for an arc furnace according to the above item (1), comprising a speed control device 20 for controlling the speed of the moving duct 4 based on a standard.
[0011]
(3) Even if the pressure difference is the same, a different speed reference is determined depending on the direction of the pressure difference, and comparison is performed based on a speed reference graph having a speed reference zero range with respect to the pressure difference in order to maintain the position of the moving duct. The dust collecting device for an arc furnace according to (1) or (2), further including a moving duct control device 17 that determines a speed reference from the pressure difference calculated by the arithmetic device 18.
[0012]
(4) Dust collection of the arc furnace in which the furnace pressure of the arc furnace 1 is set to a target pressure in the furnace by the furnace pressure setter 16 and the furnace pressure detector 13 installed in the arc furnace detects the furnace pressure. In the apparatus, a moving duct is arranged downstream of the furnace lid side duct 3 and a pressure difference between a target value of the furnace pressure set by the furnace pressure setting device 16 and a measured value of the furnace pressure detector 13 is compared. A dust collecting method for an arc furnace, wherein the method calculates the gap s between the furnace lid side duct 3 and the moving duct 4 based on the calculation result.
[0013]
(5) The control of the gap s between the furnace lid side duct 3 and the moving duct 4 is performed by controlling the target value of the furnace pressure set by the furnace pressure setting device 16 of the arc furnace and the measurement value of the furnace pressure detector 13. And a speed reference determining device 19 that determines the speed reference of the moving duct 4 from the pressure difference compares the measured value of the speed detector 15 of the moving duct 4 with the speed reference of the speed reference determining device 19. The method according to (4), wherein the speed of the moving duct 4 is controlled based on a speed reference.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
【Example】
Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.
The drawings show a preferred embodiment of the dust collecting apparatus for an arc furnace according to the present invention. FIG. 1 is a schematic explanatory view of an arc furnace provided with the present invention, and FIG. FIG. 3 is a specific explanatory diagram of a speed reference graph of the moving duct.
[0015]
In FIG. 1, exhaust gas and dust generated during melting work in the arc furnace 1 pass through the furnace lid side duct 3, the moving duct 4, the fixed duct 5a, the combustion tower 6, and the fixed duct 5b when the furnace lid 2 is closed. After being sent to the fixed duct 5c by the suction fan 7, the dust passes through the fixed duct 5e, is removed by the dust collector 9, is passed through the fixed duct 5f, passes through the fixed duct 5g by the main fan 10, and is discharged to the chimney 11 as dust-removed exhaust gas. You. The moving duct 4 is installed at the upstream end of the fixed duct 5a via a driving device such as an electric cylinder, and is configured so that a gap s formed between the moving duct 4 and the furnace lid side duct 3 can be adjusted.
[0016]
Further, when the furnace lid 2 is opened for an operation such as charging a material to be melted such as scrap into the arc furnace 1, dust and exhaust gas generated are collected by the dust collecting hood 8, the fixed duct 5 d, and the fixed duct 5 e. Then, the main fan 10 passes through the fixed duct 5g through the dust collector 9 and the setting duct 5f, and is discharged to the chimney 11 as exhaust gas from which dust is removed by the dust collector 9.
[0017]
The suction fan 7 and the main fan 10 are provided in consideration of the predicted exhaust gas generation amount from the arc furnace 1 and the pressure loss of the furnace lid side duct 3, the moving duct 4, the fixed ducts 5a to 5g, the combustion tower 6, the dust collector 9, and the like. The capacity is selected, and the rotation speeds of the suction fan 7 and the main fan 10 are pattern-controlled so that the air volume becomes a preset air volume based on the predicted exhaust gas volume.
[0018]
As shown in FIG. 2, the moving duct control device 17 includes a comparison operation unit 18, a speed reference determination unit 19, and a speed control unit 20.
In the comparison operation unit 18, the target value of the furnace pressure: Ps (kpa) set by the furnace pressure setting unit 16 and the arc furnace 1 measured by the furnace pressure detector 13 through the pressure guiding tube 12 from the furnace lid 2. The measured value of the pressure in the furnace: Pa (kpa) is compared by the comparison operation unit,
Pressure difference △ Pa (kpa) = Ps (kpa) -Pa (kpa)
Is calculated. Further, based on the reference pressure difference: △ Ps (kpa), the pressure difference: （Pa (%) = △ Pa (kpa) / △ Ps (kpa) × 100
Is calculated. The measured value △ Pa (kpa), which varies depending on the capacity of the arc furnace 1 and the capacity of the suction fan 7, is indexed using a reference pressure difference: △ Ps (kpa).
[0019]
The speed reference determining unit 19 determines the speed reference Vs (%) of the moving duct 4 from the indexed pressure difference: △ Pa (%). In order to determine an appropriate speed reference in accordance with the characteristics of the arc furnace 1, several speed reference graphs are used as shown in FIG. In the speed reference graph, a positive speed reference indicates a direction in which the gap s between the furnace lid side duct 3 and the moving duct 4 is widened, and a negative speed reference indicates a direction in which the gap s is reduced.
[0020]
The speed reference graph 1 is a method of determining the speed reference Vs (%) at a ratio of 1: 1 with respect to the pressure difference ΔPa (%). The gap s is determined according to the magnitude of the pressure difference ΔPa (%). Is controlled at a speed of 1: 1 ratio in both directions of increasing and decreasing. However, in the speed reference zero range ΔP ₀ with respect to the pressure difference ΔPa (%), the speed reference is set to zero because there is no need to change the gap.
[0021]
The speed reference graph 2 determines the speed reference Vs (%) at a ratio of 1: 0.5 with respect to the positive pressure difference ΔPa (%), and determines the speed reference Vs (%) with respect to the negative pressure difference ΔPa (%). A method of determining the speed reference Vs (%) by the ratio of 2 to decrease the speed when the gap is widened in a state where the furnace pressure is negative and increasing the speed when the gap is narrowed when the furnace pressure is positive. It is. However, in the speed reference zero range ΔP ₀ with respect to the pressure difference ΔPa (%), it is not necessary to change the gap, so that the speed reference is set to zero as in the speed reference graph 1.
[0022]
The speed reference graph 3 determines the speed reference Vs (%) at a ratio of 1: 2 with respect to the positive pressure difference ΔPa (%), and sets the speed reference Vs (%) to 1: 0. A method of determining the speed reference Vs (%) at a ratio of 5 to increase the speed when the gap is widened when the furnace pressure is negative and decrease the speed when narrowing the gap when the furnace pressure is positive. It is. However, in the speed reference zero range ΔP ₀ with respect to the pressure difference ΔPa (%), it is not necessary to change the gap, so that the speed reference is set to zero as in the speed reference graph 1.
[0023]
In the present invention, a speed reference graph suitable for the characteristics of the arc furnace 1 is selected and used to determine a speed reference Vs (%) with respect to a pressure difference ΔPa (%). Further, it is possible to set a speed reference graph having characteristics other than the above three characteristics. For example, 1: 1.5, 1: 2.5 and 1: 0.25.
[0024]
The speed control unit 20 compares the measured value Va (rpm) of the speed detector 15 of the moving duct 4 with the speed reference Vs (%) of the speed reference determination unit 19, and determines that the measured value Va (rpm) is the speed reference Vs. The control is performed so as to be the speed reference Vs (rpm) given by (%).
First, a speed reference Vs (rpm) is calculated from the speed reference Vs (%) and the maximum speed Vamax (rpm) of the moving duct drive device 14.
Vs (rpm) = Vamax (rpm) × Vs (%) / 100
Next, the speed of the moving duct driving device 14 is controlled so that the measured value Va (rpm) matches the speed reference Vs (rpm). Here, it goes without saying that a system such as an electric system or a hydraulic system can be used as the system of the moving duct driving device 14.
[0025]
In order to suppress the fluctuation of the pressure inside the furnace against the unpredictable change in the generation rate of the exhaust gas in the arc furnace 1 and keep the fluctuation constant, a moving duct 4 is disposed downstream of the furnace lid side duct 3 immediately adjacent to the arc furnace. It is effective to control the furnace pressure by controlling the gap s between the furnace-side duct 3 and the moving duct 4. In view of the pressure balance from the arc furnace 1 to the suction fan 7, the gap s between the furnace lid side duct 3 and the moving duct 4 immediately behind the arc furnace directly affects the furnace pressure of the arc furnace, and finely adjusts the furnace pressure. Is possible and responsive. In order to effectively adjust the furnace pressure by the moving duct 4, even in the same gap s, the furnace pressure fluctuates due to the amount of exhaust gas from the arc furnace, so that the pressure difference between the target value and the measured value of the furnace pressure is reduced. It is necessary to change the position of the moving duct accordingly. That is, when the pressure difference increases, the moving duct 4 is moved quickly to adjust the gap s, and when the pressure difference decreases and approaches the target value, the speed of the moving duct 4 can be reduced. Control is required.
[0026]
A comparison operation unit for calculating a pressure difference between a target value of the furnace pressure set by the furnace pressure setter of the arc furnace and a measured value of the furnace pressure detector, The speed reference determining unit 19 that determines the speed reference of the moving duct 4 from the pressure difference, compares the measured value of the speed detector 15 of the moving duct with the speed reference of the speed reference determining unit 19, and determines the speed reference of the moving duct 4 based on the speed reference. The speed control unit 20 for controlling the speed determines a different speed reference depending on the direction of the pressure difference even if the pressure difference is the same, and sets a speed reference zero for the pressure difference to maintain the position of the moving duct. By determining the speed reference from the pressure difference calculated by the comparison operation unit based on the speed reference graph having a range, the gap s between the furnace-side duct 3 and the moving duct 4 is controlled to thereby control the pressure inside the arc furnace. Reduce fluctuations It is possible to maintain constant.
[0027]
【The invention's effect】
As described above, according to the present invention, for an unpredictable fluctuation in the furnace pressure in an arc furnace, a moving duct is disposed on the downstream side of the furnace-side duct to control a gap between the furnace-side duct and the moving duct. Thus, fluctuations in the furnace pressure can be suppressed and kept constant. Scattering of exhaust gas and dust outside the arc furnace can be prevented, and the effect of improving the environment of the arc furnace is great.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view of an arc furnace provided with the present invention.
FIG. 2 is a configuration diagram of a moving duct control device of the present invention.
FIG. 3 is a specific explanatory diagram of a moving speed reference graph for moving the moving duct of the present invention.
[Explanation of symbols]
1: Arc furnace 2: Furnace lid 3: Furnace lid side duct 4: Moving duct 5a to 5g: Fixed duct 6: Combustion tower 7: Suction fan 8: Dust collection hood 9: Dust collector 10: Main fan 11: Chimney 12: Induction Pressure tube 13: Furnace pressure detector 14: Moving duct driving device 15: Speed detector 16: Furnace pressure setting device 17: Moving duct control device 18: Comparison operation unit 19: Speed reference determination unit 20: Speed control unit s: Gap

Claims (5)

In the arc furnace dust collector having the furnace pressure setting device 16 for setting the furnace pressure of the arc furnace 1 and the detector 13 for detecting the furnace pressure of the arc furnace, the dust collector moves to the downstream side of the furnace lid side duct 3. A moving duct control device 17 that arranges the duct 4 and controls the speed of the moving duct, and a pressure difference between a target value of the furnace pressure set by the furnace pressure setting device 16 and a measurement value of the furnace pressure detector 13 And a moving duct control device 17 for controlling the gap s between the furnace-side duct 3 and the moving duct 4 by the comparing and calculating device. The moving duct control device 17 includes a comparison operation device 18 that calculates a pressure difference between a target value of the furnace pressure set by the furnace pressure setting device 16 of the arc furnace and a measurement value of the furnace pressure detector 13. A speed reference judging device 19 for judging a speed reference of the moving duct 4 from the pressure difference, and comparing a measured value of the speed detector 15 of the moving duct 4 with a speed reference of the speed reference judging device 19, based on the speed standard. The dust collector of an arc furnace according to claim 1, comprising a speed control device (20) for controlling a speed of the moving duct (4). Even if the pressure difference is the same, a different speed reference is determined depending on the direction of the pressure difference, and based on a speed reference graph having a speed reference zero range with respect to the pressure difference in order to maintain the position of the moving duct, the comparison arithmetic unit 18 is used. The dust collector for an arc furnace according to claim 1 or 2, further comprising a moving duct control device (17) for determining a speed reference from the pressure difference calculated in (1). In a dust collector for an arc furnace in which the furnace pressure of the arc furnace 1 is set to a furnace target pressure by a furnace pressure setting device 16 and the furnace pressure is detected by a furnace pressure detector 13 installed in the arc furnace, The moving duct 4 is arranged on the downstream side of the furnace lid side duct 3, and a pressure difference between a target value of the furnace pressure set by the furnace pressure setting device 16 and a measured value of the furnace pressure detector 13 is calculated. And a method of controlling a gap s between the furnace lid side duct 3 and the moving duct 4 based on the calculation result. The control of the gap s between the furnace lid side duct 3 and the moving duct 4 is performed by controlling the pressure between the target value of the furnace pressure set by the furnace pressure setting device 16 of the arc furnace and the measurement value of the furnace pressure detector 13. The difference is calculated, and the speed reference determining device 19 that determines the speed reference of the moving duct 4 from the pressure difference compares the measured value of the speed detector 15 of the moving duct 4 with the speed reference of the speed reference determining device 19 to determine the speed. The method according to claim 4, wherein the speed of the moving duct (4) is controlled based on a criterion.

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