JP2002340320A - Electrode elevation control method and device thereof in plasma type melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode elevation control method in a plasma type melting furnace capable of stabilizing an arc upon starting the plasma, etc. SOLUTION: Upon starting the operation of the melting furnace by charging metal into the plasma type melting furnace and impressing a predetermined voltage between both electrodes 4, 5 to form the arc A while lifting a cathode electrode 4 from the metal M, the potential gradient of the arc is measured. After the measured value is decreased from the initial potential gradient measured during a predetermined period of time immediately after the starting of lifting of the cathode electrode 4, the cathode electrode is stopped when the measuring potential gradient is restored to the initial potential gradient.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode elevation control method and an electrode elevation control device in a plasma melting furnace.

[0002]

2. Description of the Related Art For example, in a plasma type melting furnace for melting ash, when the melting furnace is operated for the first time, or when the operation is restarted after maintenance of the furnace wall, first, the furnace is put into the furnace.
The operation is started or restarted after a metal ball (or a metal plate or the like) is put in and melted by a plasma arc.

When a metal ball is put into a furnace to start melting, the surface of the metal ball is not flat, so that the metal that has started to melt enters the gap between the metal balls and solidifies again.
Therefore, where the temperature is high due to the plasma arc,
The arc melts and becomes depressed, and the arc flies not only downward but also sideways, causing a state of arc rampage.

Conventionally, when such an arc rampage has occurred, an operator temporarily moves to the height position of the cathode electrode where the arc rampage subsides by experience, and from here, the voltage is also stabilized based on the experience. The height of the electrode was finely adjusted as described above.

[0005]

As described above, when an arc rampage occurs, the height of the cathode electrode is adjusted so that the voltage becomes constant, based on the experience of the operator. In addition, it is difficult to make adjustments.Therefore, there is a problem that power fluctuates due to a change in the arc length that occurs at the time of arc striking, which affects the entire facility. As a result, there is a problem that re-ignition is required, and a wasteful working time is generated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrode raising / lowering control method and an electrode raising / lowering control device in a plasma type melting furnace which can stabilize a plasma arc when starting or resuming the arc.

[0007]

According to a first aspect of the present invention, there is provided a method for controlling the elevation of an electrode in a plasma melting furnace, wherein a metal is charged into the plasma melting furnace and a predetermined distance is set between both electrodes. When starting operation of the melting furnace by forming an arc while applying a voltage and raising the cathode electrode from the metal, the potential gradient of the arc is measured and measured over a predetermined time immediately after the start of the raising of the cathode electrode. This is a method in which the cathode electrode is stopped when the measured potential gradient recovers to the initial potential gradient after decreasing from the initial potential gradient.

[0008] Further, the first electrode elevation control device in the plasma type melting furnace of the present invention is characterized in that a metal is charged into the plasma type melting furnace and a predetermined voltage is applied between both electrodes to pull up the cathode electrode from the metal. An electrode elevation control device for forming an arc, comprising: a voltage detector that detects a voltage of a cathode electrode; an electrode height detector that detects a height of a cathode electrode from a reference position; and both of these detectors. A voltage gradient measurement unit for measuring the potential gradient at predetermined intervals by inputting a voltage detection value and a height detection value of the same, and inputting a cathode voltage command value and a cathode voltage detection value from the voltage detector. A control unit that outputs a control signal based on the deviation and a measured potential gradient measured by the potential gradient measuring unit are input, and the measured potential gradient is used to pull up and open the cathode electrode. After reduction than the initial potential gradient which is measured for a predetermined time immediately after it is obtained by including a determination unit for outputting an instruction for stopping the cathode electrode upon the return to the initial potential gradient.

According to the first electrode elevation control method and the configuration of the electrode elevation control device described above, the potential gradient at the cathode electrode is input to the determination unit and compared with the initial potential gradient to determine whether or not the range of the arc rampage has been eliminated. Since the determination is made, it is possible to quickly and reliably control the arc rampage.

Further, in order to solve the above-mentioned problem, a second method for controlling the elevation of an electrode in a plasma melting furnace according to the present invention is characterized in that a predetermined voltage is applied between both electrodes when the operation is restarted after the operation of the plasma melting furnace is stopped. This is a method for controlling the elevation of the electrode when forming an arc while pulling up the cathode electrode from the metal by applying an electric potential, wherein the potential gradient of the arc and the height of the cathode electrode during operation are stored in a storage unit, and after the operation is stopped. In the re-ignition, the height of the cathode electrode stored in the storage unit is read, and the cathode electrode is raised to the height.

[0011] Further, according to a second aspect of the present invention, there is provided an apparatus for raising and lowering an electrode in a plasma-type melting furnace, wherein a metal is charged into the plasma-type melting furnace and a predetermined voltage is applied between the two electrodes to raise the cathode from the metal. An electrode elevation control device for forming an arc, comprising: a voltage detector that detects a voltage of a cathode electrode; an electrode height detector that detects a height of a cathode electrode from a reference position; and both of these detectors. A voltage gradient measurement unit for measuring a potential gradient at predetermined intervals by inputting a voltage detection value and a height detection value of the same, and inputting a cathode voltage command value and a cathode voltage detection value from the voltage detector. A control unit that outputs a control signal based on the deviation and a measured potential gradient measured by the potential gradient measuring unit are input and stored. To the height of the cathode electrode at the time the cut has occurred, it is obtained; and a re-ignition command unit to raise the cathode electrode.

According to the second electrode elevation control method and the configuration of the electrode elevation control device, during the re-ignition operation, the electrode is immediately returned to the height of the cathode electrode immediately before the occurrence of the arc interruption. It is possible to return to the original height position more quickly and accurately than when returning.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electrode control apparatus and an electrode control method in a plasma melting furnace according to a first embodiment of the present invention will be described with reference to FIGS.

By the way, the gist of the present invention lies in the control of raising and lowering the electrode at the start of operation. Therefore, the following description will focus on this part, and the plasma type melting furnace will be of the twin torch type. explain.

As shown in FIG. 1, one of a furnace body 1 of a plasma melting furnace is provided with an ash inlet 2 for charging ash, which is a material to be melted, and the other is for taking out molten slag. Slag outlet 3 is provided. Also, at the position near the slag outlet 3 on the upper wall of the furnace body 1,
For example, a rod-shaped cathode electrode 4 made of graphite is
At a position near the ash inlet 2 on the upper wall portion, a rod-shaped anode electrode 5 also made of graphite is provided with a lifting device (for example, a driving source such as a servomotor is used).
6 and 7, the power supply 8 is provided to supply power between the electrodes 4 and 5, and the power (voltage and current) to be supplied to the electrodes 4 and 5 and each electrode 4 , 5 is provided with an operation control device 9 for controlling the elevation amount.

The lifting devices 6 and 7 are described below.
Although the drawing is simply depicted as a box in the drawing, specifically, the supporting members are provided upright in parallel with the respective electrodes 4 and 5, and the supporting members are respectively provided so as to be movable up and down by, for example, a motor drive. It comprises a lifting body and a gripping arm protruding from each lifting body and gripping a corresponding electrode. When the lifting body moves up and down, each of the electrodes 4 and 5 is moved through the gripping arm. Is raised and lowered.

As shown in FIG. 2, the operation control device 9 includes a voltage / current pattern setting unit 11 for setting a voltage / current ratio applied to the electrodes, a plasma power setting unit 12 for setting plasma power, A voltage / current calculator 13 for inputting a set voltage / current ratio and a set plasma power, calculating a voltage and a current to be applied, and outputting the calculated voltage and current to a control unit of the power supply 8, and a voltage from the voltage / current calculator 13 A voltage distribution unit 14 for inputting a value and distributing a voltage to the cathode electrode 4 and the anode electrode 5, and a cathode for inputting the cathode voltage obtained by the voltage distribution unit 14 and controlling the lifting / lowering device 6 of the cathode electrode 4 A lifting control device 15 and an anode lifting control device 16 for inputting the anode voltage obtained by the voltage distribution unit 14 and controlling the lifting device 7 of the anode electrode 5 are also provided. There.

The above-mentioned cathode elevation control device (electrode elevation control device) 15 includes a voltage detector 21 for detecting a voltage applied to the cathode electrode 4 and a predetermined reference position of the cathode electrode 4 (for example, a contact with an input metal). An electrode height detector (for example, an encoder or the like is used) 22 for detecting the height with respect to the position, and the cathode voltage detected by the voltage detector 21 and the target cathode voltage from the voltage distributor 14 are subtracted. A first subtraction unit 23 for obtaining a deviation signal from the voltage detector 21 and a feedforward control unit 24 for inputting a cathode voltage (detection voltage signal) from the voltage detector 21 to a lead unit 24a and a lag unit 24b to obtain a feedforward signal.
A first PID processing unit 25 that performs PID processing on the deviation signal obtained by the first subtraction unit 23, an addition unit 26 that adds the feedforward signal to the signal processed by the first PID processing unit 25, A second subtraction unit 27 that subtracts the height signal obtained by the addition unit 26 from the detection height detected by the electrode height detector 22 to obtain a deviation signal; A PID process is further performed on the obtained deviation signal, and a control signal is supplied to a cathode lifting device (electrode lifting device).
6 and the detection values from the voltage detector 21 and the height detector 22 which are output to the second PID processing unit 28 to be output to
A potential gradient measuring unit 29 that measures a potential gradient (V / mm) at predetermined time intervals, and a switch unit 30a that is disposed before the first subtraction unit 23, switches an input signal to the first subtraction unit 23. The first switch 30 that switches between a normal command position (a) as a voltage command from the voltage distribution unit 14 and a detection position (b) as a detected voltage value from the voltage detector 21.
And the potential gradient measured by the potential gradient measuring unit 29, the change in the potential gradient is detected, and in response to the change in the potential gradient, the switch unit 30a is set to the normal command position (a) side or to the detection position. The determination unit 31 outputs a signal connected to the position (b) to the first switch 30.

Here, the judgment by the judgment section 31 will be described. The value of the measured potential gradient decreases from the initial potential gradient measured over a predetermined time immediately after the start of pulling up of the cathode electrode 4, and then the initial potential gradient is measured. When the potential gradient is recovered, it is determined that the range of the arc rampage has been escaped. In this case, in order to stop the rise of the cathode electrode 4,
The switch unit 30a is switched to the detection position (b).

In the lead portion 24a, a differentiation process is performed on the original voltage signal, and in the lag portion 24b, the differentiated signal is subjected to a primary sending process to smooth the signal.

Next, a method of controlling the electrodes at the start of the operation of the plasma melting furnace will be described. First, the furnace body 1
After the metal M is put into the inside, both electrodes 4 and 5 are lowered, and the lower ends thereof are brought into contact with the metal M.

Then, a predetermined voltage is applied between the electrodes 4 and 5, the cathode electrode 4 is slowly pulled up, and a spark is generated between the cathode 4 and the metal M to form an arc (arc column) A. Thereafter, the cathode electrode 4 is slowly pulled up, but the amount of elevation is controlled so that arc rampage does not occur on the way.

The reference position of the amount of elevation of the cathode electrode 4 is usually a contact position with the metal M. The control at the time of raising and lowering is intended to prevent the adverse effects caused by the arc rampage. Since the cause of the arc rampage is based on the following reason,
That is what came to mind.

Normally, as the electrode is pulled up, the voltage changes in accordance with the amount of pulling up (potential gradient). Then, it is known that, after being raised to a certain extent, the potential gradient decreases to almost zero (the voltage rise stops), and if the pulling is further continued, the voltage starts to rise and returns to the original potential gradient.

That is, in a state in which the arc is violent, the slag or metal is molten and thus not static, and the slag melted by the impact of the arc or by, for example, the ejection pressure of an inert gas rises or scatters around. For example, a change in the arc length caused by other than moving the electrode up and down occurs, and power is consumed by this change, so that the potential gradient is considered to be substantially zero.

Therefore, after the potential gradient initially transitions at the predetermined gradient, once becomes near zero, and then returns to the original potential gradient, it is out of the range where the arc rampage occurs.

Hereinafter, a method of controlling the elevation of the electrode will be described based on the above. First, from the voltage / current pattern setting unit 11 and the plasma power setting unit 12,
The voltage / current ratio and the plasma power are calculated by the voltage / current calculation unit 1.
3, a plasma current is output according to the plasma power, and the voltage is supplied to the voltage distribution unit 14.
To output a cathode voltage and an anode voltage.

Then, with the predetermined voltage and current applied to each of the electrodes 4 and 5, the cathode electrode 4 starts to rise. That is, a command is issued to raise the cathode electrode 4 at a predetermined speed.

At the time of this rising operation, the potential gradient measuring section 29 calculates the potential gradient at predetermined time intervals, and the measured value is input to the determination section 31. The potential gradient is determined by moving the value measured at predetermined time intervals by, for example, four values (the number is not limited to four, but may be three or less or five or more). Obtained by average.

In the determination section 31, the potential gradient is compared with the potential gradient immediately before it. If the change is constant, the switch section 30a of the first switch 30 is switched to the normal command position. (B), the normal control is performed.

That is, the cathode electrode 4 is controlled by the two PID processing units 25 and 28 and the feedforward control unit 24 provided in cascade so as to have a predetermined height according to the command voltage.

When the potential gradient becomes smaller than the previously measured value, that is, the initial potential gradient and becomes almost zero in the determination section 31, and then becomes large again, the range of the arc rampage is reduced. Judging that it has come off,
The switch unit 30a of the first switch 30 is switched to the detection position (b) to set the deviation signal to zero and maintain the current height.

That is, as compared with the conventional case in which the height of the cathode electrode is adjusted based on the experience of the worker so as to stop the arc rampage, the cathode electrode 4 is automatically and in real time. Is obtained, and the potential gradient is input to the determination unit 31 to determine whether or not it has escaped from the range of the arc rampage, so that the arc rampage can be quickly and reliably controlled. Therefore, it is possible to prevent adverse effects on other facilities due to a change in power.

In the case of escape from the arc rampage, the control by the determination unit 31 is ended in hardware or software. Next, an electrode lifting control apparatus and an electrode lifting control method in a plasma melting furnace according to a second embodiment of the present invention will be described with reference to FIG.

The difference between the first embodiment and the second embodiment is that the relationship between the potential gradient at the cathode electrode and the height of the cathode electrode from the reference position is always grasped. The point is that, after the operation is stopped due to the break of the arc, the height is returned to the state where the break of the arc has occurred at the time of re-ignition.

Therefore, in the second embodiment, the description will focus on only the points different from the first embodiment, and the same components as those in the first embodiment will be the same. And description thereof is omitted.

That is, a normal command position (c) C for transmitting a normal target height command (target voltage command) and a forced height are provided between the addition unit 26 and the second subtraction unit 27 of the cathode lifting control device 15. Second switch 4 having switch portion 41a for switching to any of forced command positions (d) for transmitting commands
1 and a data storage unit (connected to the forced command position (d) side of the second switch 41) for storing the potential gradient and the voltage / electrode height obtained by the potential gradient measuring unit 29 in a database. A re-ignition command unit 43 having a memory unit 42 and outputting at least the electrode height value immediately before the arc is cut off from the data storage unit 42 by a re-ignition command;
A switching command section 44 for outputting a switching signal to the second switching device 41 at the time of re-ignition is provided.

Next, a description will be given of a method of controlling the lifting and lowering of the electrode at the time of re-ignition in the event that the arc is cut off due to arc rampage during the operation of the plasma melting furnace. Immediately before the arc break occurs, the potential gradient value measured by the potential gradient measuring unit 29 is stored in the potential gradient data storage unit 42.

When an instruction for re-ignition operation is issued,
After a signal for connecting the switch unit 41a to the compulsory command position (d) is output from the switching command unit 44 to the second switch 41, the re-ignition command unit 43 outputs the cathode electrode immediately before the arc break occurs. The forced height command indicating the height position of No. 4 is input to the second subtraction unit 27, and the height of the cathode electrode 4 is returned to the original height position at a stretch.

The difference between the forced height command from the re-ignition command section 43, ie, the voltage corresponding to this height, and the original set voltage at the cathode electrode 4 is ± 1 of the set voltage.
If it exceeds 0%, the reset signal
And the switch section 41a is connected to the normal command (C) side, and is configured to return to the normal control.

As described above, at the time of the re-ignition operation, the cathode electrode is returned to the height position of the cathode electrode immediately before the occurrence of the arc interruption, so that it is necessary for the operator to contact the metal and raise it again as in the conventional case. It is possible to quickly and accurately return to the original height position as compared with the case of returning by experience.

[0042]

As described above, according to the electrode lifting control method and the electrode lifting control device according to the first and second aspects of the present invention, the potential gradient at the cathode electrode is measured and the measured potential gradient is measured. By inputting to the determination unit and comparing it with the initial potential gradient, it is determined whether or not the arc is out of the range of the arc rampage, so that the arc rampage subsides based on the experience of the worker as in the past. As compared to the case where the height of the cathode electrode was adjusted,
The arc rampage can be quickly and reliably controlled, and thus a change in electric power can be prevented from adversely affecting other facilities.

Further, according to the electrode lifting control method and the electrode lifting control device according to the third and fourth aspects of the present invention, during the re-ignition operation, the electrode up to the height position of the cathode electrode immediately before the arc break occurs. Because it is returned at once, as in the past, when it comes in contact with metal and rises again,
It is possible to quickly and accurately return to the original height position as compared with the case of returning by the experience of the worker.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic overall configuration of a plasma melting furnace according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of an electrode elevation control device in the plasma melting furnace of the first embodiment.

FIG. 3 is a block diagram showing a schematic configuration of an electrode elevation control device in a plasma melting furnace according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace main body 4 Cathode electrode 6 Electrode raising / lowering device 15 Cathode raising / lowering control device 21 Voltage detector 22 Electrode height detector 23 1st subtraction part 24 Feedforward control part 25 1st PID processing part 26 Addition part 27 Second subtraction part 28 No. 2PID processing unit 29 Potential gradient measuring unit 30 First switch 30a Switch unit 31 Judgment unit 41 Second switch 42 Data storage unit 43 Re-ignition command unit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Toshiyuki Minano, Inventor 1-7-89, Minami Kohoku, Suminoe-ku, Osaka-shi, Osaka Inside Hitachi Zosen Corporation (72) Masakazu Saruwatari 1 Minami-Kohoku, Suminoe-ku, Osaka-shi, Osaka No.7-89 F-term in Hitachi Zosen Corporation 3K061 NB02 NB30 4K045 AA04 BA07 DA01 RB02 4K056 AA05 BA02 BB08 CA20 FA04 FA11 4K063 AA04 AA12 BA13 CA06 CA09 FA56 FA66 FA78

Claims (4)

[Claims] When a metal is charged into a plasma type melting furnace and a predetermined voltage is applied between the two electrodes to form an arc while pulling up a cathode electrode from the metal, an arc is formed. The potential gradient is measured, and the cathode electrode is stopped when the measured potential gradient recovers to the initial potential gradient after decreasing from the initial potential gradient measured for a predetermined time immediately after the start of pulling up the cathode electrode. An electrode lifting and lowering control method in a plasma melting furnace. 2. An electrode elevation control device for charging a metal into a plasma type melting furnace and applying a predetermined voltage between the two electrodes to form an arc while pulling up the cathode electrode from the metal. A voltage detector that detects voltage, an electrode height detector that detects the height of the cathode electrode from a reference position, and a voltage gradient and a height detected value that are input from both detectors to determine the potential gradient A potential gradient measuring unit that measures at every interval; a control unit that inputs a cathode voltage command value and a cathode voltage detection value from the voltage detector and outputs a control signal based on a deviation thereof; The measured potential gradient measured by the section is input, and the measured potential gradient is smaller than the initial potential gradient measured over a predetermined time immediately after the start of the pulling up of the cathode electrode. , Electrode elevation control device in a plasma melting furnace, characterized by comprising a determination unit for outputting an instruction for stopping the cathode electrode upon the return to the initial potential gradient. 3. An electrode lifting / lowering control method for forming an arc by applying a predetermined voltage between both electrodes and forming an arc while pulling up a cathode electrode from a metal when the operation is restarted after the operation of the plasma melting furnace is stopped. The potential gradient of the arc during operation and the height of the cathode electrode are stored in the storage unit, and upon re-ignition after the operation is stopped, the height of the cathode electrode stored in the storage unit is read out, and the cathode is read up to that height. An electrode raising and lowering control method in a plasma type melting furnace, comprising raising an electrode. 4. An electrode elevation control device for forming an arc while charging a metal into a plasma-type melting furnace and applying a predetermined voltage between the two electrodes to raise the cathode from the metal. A voltage detector that detects voltage, an electrode height detector that detects the height of the cathode electrode from a reference position, and a voltage gradient and a height detected value that are input from both detectors to determine the potential gradient A potential gradient measuring unit that measures at every interval; a control unit that inputs a cathode voltage command value and a cathode voltage detection value from the voltage detector and outputs a control signal based on a deviation thereof; In addition to inputting and storing the measured potential gradient measured by the unit, when an arc break occurs, the cathode electrode up to the height of the cathode electrode at the time when the arc break occurs. Electrode elevation control device in a plasma melting furnace, characterized by comprising a re-ignition command section to raise.