JP2002340322A - Twin torch type plasma melting furnace and method for operation therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for starting operation of a twin torch type plasma melting furnace, which enables starting of operation on plasma melting in a stable condition. SOLUTION: An initial ignition operation is performed in a single mode in which an anode electrode 5 is permitted to contact a melt, and a plasma arc is generated between a cathode electrode 4 and the melt. At the same time, with the instructions from a polarity switch command part 15, positive voltage is impressed on the cathode electrode 4, which is disposed at a slag outlet, to permit the electrode to serve as an instant anode electrode for starting melting. When the instant anode electrode has descended during conversion to a twin mode, the polarity of voltage being impressed on both of the electrodes 4, 5, is switched to a proper one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a twin-torch type plasma melting furnace and a method of operating the same.

[0002]

2. Description of the Related Art In a twin torch type plasma melting furnace, when starting operation, first, an electrode is brought into contact with a material to be melted, and after energization, a cathode is slowly pulled up to generate a plasma arc, thereby causing a single arc. Melting was started in the mode, and thereafter, the anode electrode was pulled up to shift to the twin mode.

[0003]

By the way, when the operation is switched from the single mode to the twin mode, there is a problem that the plasma arc on the anode electrode side becomes unstable and it takes time to operate.

Accordingly, an object of the present invention is to provide a twin torch type plasma melting furnace capable of stably starting the operation of plasma melting and a method of starting the operation.

[0005]

In order to solve the above problems, a twin torch type plasma melting furnace according to the present invention is a twin torch type plasma melting furnace having a furnace body provided with a cathode electrode and an anode electrode, A furnace body provided with polarity switching means for switching the voltage polarity applied to the cathode electrode and the anode electrode, and more specifically, a furnace body in which the cathode electrode and the anode electrode are respectively provided so as to be vertically movable via a lifting device. And a power supply device for applying a DC voltage to both electrodes, and a twin torch type plasma melting furnace having an operation control device for controlling the power supply device and the elevating device, wherein a voltage applied to the cathode electrode and the anode electrode A polarity switching means for switching polarity is provided, and the operation control device includes an initial ignition operation or a re-ignition operation. A polarity switching timing determination unit that determines the switching timing of the voltage polarity by the ignition status determination unit and the polarity switching unit that determines whether the initial ignition operation, or during re-ignition operation, When the temperature is low, the polarity switching means applies a voltage having a polarity opposite to the voltage polarity applied during normal operation by the switching instruction from the polarity switching timing determination unit.

The method of operating a twin torch type plasma melting furnace of the present invention is a method of operating a twin torch type plasma melting furnace having a furnace body provided with a cathode electrode and an anode electrode. After starting melting in a single mode in which a plasma arc is generated between the cathode electrode and the material to be melted while being in contact with the top, the voltage is applied to the electrodes when transitioning to the twin mode in which a plasma arc is generated in both electrodes In the initial ignition operation in the single mode in the above-described operation method, the positive electrode voltage is applied to the cathode electrode arranged on the slag outlet side to start melting as a temporary anode electrode. , When the temporary anode electrode falls or the anode voltage rises during the transition to the twin mode. When detecting, a method of switching the voltage polarity applied to the electrodes, further during re-ignition operation by the single mode in the above operation method,
While applying a positive voltage to the cathode electrode disposed on the slag port side to start melting as a temporary anode electrode, and at the time of transition to the twin mode, when the arc in the temporary cathode electrode becomes stable, This is a method of switching the voltage polarity to be applied.

According to each of the above-mentioned plasma melting furnaces and their operating methods, the voltage polarity applied to the cathode electrode and the anode electrode is switched, so that, for example, during the initial ignition operation or the re-ignition operation of the melting furnace, the material to be melted is changed. When the temperature is low, the operation is started by applying a voltage opposite to the voltage polarity applied during normal operation, that is, by operating the anode electrode side where melting does not proceed so much as a cathode electrode which is easy to melt. It is possible to prevent the occurrence of a poor melting state, for example, a plasma arc rampage, which has sometimes occurred on the anode electrode side, and a state in which the electrode is fixed to the melt.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A twin torch type plasma melting furnace and an operation method thereof according to an embodiment of the present invention will be described below with reference to FIGS.

First, a schematic configuration of a twin torch type plasma melting furnace will be described with reference to FIG. In the plasma melting furnace, one of a furnace body 1 having a melting chamber 1a is provided with an ash inlet 2 for charging a material to be melted, for example, ash, and the other is for taking out a molten slag S as a melt. Is provided. Further, a rod-shaped cathode electrode 4 made of, for example, graphite is formed at a position of the upper wall of the furnace body 1 near the slag outlet 3, and a graphite electrode is formed of graphite at a position of the upper wall near the ash inlet 2. The rod-shaped anode electrode 5 is provided so as to be able to move up and down by respective lifting devices 6 and 7, and a DC power supply 8 for supplying electric power between the electrodes 4 and 5 is provided. An operation control device 9 for controlling the power (voltage and current) supplied to the electrodes 4 and 5 from the device 8 and the elevating operation of the electrodes 4 and 5 is provided.

The lifting devices 6 and 7 are simply drawn as boxes in the drawing.
A column member standing in parallel with each of the electrodes 4 and 5;
For example, each of the support members is provided with an elevating body provided so as to be able to move up and down by a motor drive, and a gripping arm protruding from each of the elevating bodies and holding a corresponding electrode. By doing so, each of the electrodes 4 and 5 is moved up and down via the gripping arm.

In this plasma melting furnace, the voltage control at each electrode is controlled by the amount of elevation of each electrode (accurately,
The height of the molten slag from the surface is adjusted.

As shown in FIG. 2, the operation control device 9 includes at least lifting devices 6 and 7 for the electrodes 4 and 5.
Height adjusting unit 11 for controlling the height position of each electrode 4 and 5 by controlling the voltage, and adjusting the voltage applied to each electrode 4 and 5 and applying the adjusted voltage to the electrode height adjusting unit 11.
And a circuit (electrical wiring) 13 for supplying a high voltage from the power supply device 8 to each of the electrodes 4 and 5.
A polarity switching switch (polarity switching means) 14 for switching the polarity of the voltage to be applied and a polarity switching instruction unit 15 for outputting a switching signal to the polarity switching switch 14 are provided.

A voltage signal (cathode voltage, anode voltage) of a voltage applied to each of the electrodes 4 and 5 in the power supply device 8 is input to the voltage adjustment unit 12, and this voltage signal is input to the voltage adjustment unit 12. Voltage signal input circuit 16
A voltage signal changeover switch (voltage signal changeover means) 17 for switching the signal line in accordance with the changeover instruction signal from the polarity changeover instruction section 15 is provided in the middle of the operation.
In FIG. 2, reference numerals 18 and 19 denote height position detectors for detecting the amount of elevation of each of the electrodes 4 and 5, that is, the elevation position, and specifically, are provided in each of the elevating devices 6 and 7. An encoder or the like for detecting the amount of lifting of the lifted body is used. Although not shown, a cathode voltage determination unit that detects an arc state at the cathode electrode via a voltage is provided.

The operation control device 9 further includes an automatic operation control unit (for example, an automatic operation program) for controlling the two electrodes 4 and 5 to automatically perform ash melting by the plasma arc. I have.

By the way, since the gist of the present invention lies in the place where the operation is started, the operation start method in the automatic operation control unit will be described based on the flowchart shown in FIG. 3 together with the configuration of the operation control device. .

The operation start portion of the automatic operation control section is roughly divided into an initial ignition operation (also referred to as a cold start) in which the operation is started from the beginning and an operation after the operation is temporarily stopped for some reason during the melting operation. Restart operation (also called hot start).

First, as shown in step 1, the operation start state judging section 21 judges whether the operation start state is the initial ignition operation or the re-ignition operation. Specifically, it is determined whether or not the elapsed time from the start of operation to the present time exceeds a preset initial ignition determination time. The initial ignition determination time is a power-on time to the furnace (electrode), and may be any time as long as it is possible to determine whether the operation is the initial ignition operation or the re-ignition operation.
For example, it is set to a relatively short time.

On the other hand, if the elapsed time from the start of the operation is within the initial ignition determination time, that is, if it is determined that the operation has been started, or if almost no time has passed since the start of the operation, as shown in step 2, the electrode The polarity determination unit 22 determines whether the electrode on the side of the slag outlet 3 is a cathode electrode.

When the electrode polarity judging section 22 judges that the electrode on the side of the slag outlet 3 is the cathode electrode, the process proceeds to step 3, and in accordance with an instruction from the polarity switching instructing section 15, a polarity switching switch. 14 is operated to switch the polarity (reverse the polarity). That is, the original cathode electrode (hereinafter, also referred to as a real cathode electrode) is used as a temporary anode electrode (hereinafter, also referred to as a temporary anode electrode), and the original anode electrode (hereinafter, also referred to as a real anode electrode) is used as a temporary anode electrode. The electrodes are used as cathode electrodes (hereinafter also referred to as temporary cathode electrodes), and the polarities of these temporary electrodes are stored in the storage unit. The current polarity of the electrode is displayed on, for example, an operation panel (or a control panel) or the like so that the operator can confirm the polarity.

Then, the routine proceeds to step 4, where ignition is performed. That is, a high DC voltage is applied to both electrodes 4 and 5 by the power supply device 8. If it is determined in step 2 that the electrode on the side of the slag outlet 3 is not the cathode electrode but the anode electrode (temporary anode electrode), the process proceeds to ignition in step 4 as it is.

After the ignition has been performed, as shown in step 5, the polarity switching timing determination unit 23 determines whether or not the two electrodes 4 and 5, which have been provisionally polarized, may be returned to the original actual polarity. Is determined. That is, the timing of switching from the single mode to the twin mode is determined.

More specifically, the amount by which the temporary anode electrode 4 is lowered is detected via the height position detector 18, and a determination is made based on this amount of lowering. The reason for determining the switching timing, that is, the melting state of the material to be melted at the temporary anode electrode, based on the amount of elevation of the temporary anode electrode is as follows.

That is, when the metal to be melted is melted at the anode electrode portion, its surface is almost always lowered (when the metal is in a solid state and stacked, a gap is formed between the metals. Since the surface of the anode electrode goes down when it melts, the anode electrode is always controlled to zero volt so that the anode electrode is in contact with the metal, that is, the anode voltage becomes zero. It is. Therefore, when the lowering of the anode electrode is detected, it can be understood that the melting in the anode electrode portion has advanced to some extent.

If the polarity switching timing judging section 23 detects that the temporary anode electrode 4 has fallen and determines that the melting of the metal in the temporary anode electrode section has advanced, the process proceeds to step 6 where a polarity switching instruction is issued. The polarity switch 14 is operated by an instruction from the unit 15, and the polarity is switched to the original actual polarity. After that, the normal operation is started. If it is determined in step 5 that the timing is not the switching timing, the state is maintained until the switching timing condition is detected.

On the other hand, when the operation start state judging section 21 (step 1) judges that the elapsed time from the start of operation exceeds the initial ignition judgment time, that is, it is considered that the furnace has been operated. If it is determined that the current operation is re-ignition, as shown in step 7, the re-ignition determination unit 2
At 4, it is determined whether or not the elapsed time from when the power is cut off to the present time exceeds the re-ignition determination time, that is, the degree of cooling (melting state) of the material to be melted is determined based on the elapsed time since the power was cut off. You. The re-ignition determination time is also determined by experience based on the size of the furnace body and the like, similarly to the initial ignition determination time.

If it is determined that the re-ignition determination time has elapsed and the temperature of the material to be melted has decreased, as shown in step 8, the electrode polarity determination unit 25 (described in step 2) The determination unit may be the same as the electrode polarity determination unit 22), and similarly to step 2, it is determined whether the electrode on the side of the slag outlet 3 is a cathode electrode.

If the electrode polarity determining section 25 determines that the electrode is the cathode electrode 4, the process proceeds to step 9, and
The polarity switching switch 4 is operated by an instruction from the polarity switching instruction unit 15 to switch the polarity to the temporary anode electrode, and the state of the temporary polarity is stored in the storage unit. Thereafter, the process proceeds to step 10, where the power supply device 8 applies a voltage to both temporary electrodes, that is, ignition is performed.

When the ignition is performed, the process proceeds to the cathode voltage determination section 26 as shown in step 11, where it is determined whether or not the voltage of the temporary cathode electrode is stable. Proceeds to step 6 described in the above initial ignition operation, and after the polarities of both temporary electrodes are switched back to the original actual polarities, the normal operation is started.

By the way, the cathode voltage determination section 26 calculates a potential gradient, which is a time variation of the voltage, and determines whether the potential gradient is within a predetermined range.
For example, in an arc rampage, the potential gradient approaches zero,
When a predetermined potential gradient is detected after approaching zero, it is determined that the cathode voltage is stable.

If it is determined in step 11 that the cathode voltage is not stable, the state is maintained until it is stabilized. If it is determined in step 8 that the electrode on the side of the slag outlet 3 is not the cathode electrode (actual electrode) but the anode electrode (temporary electrode), the ignition in step 10 is performed. Proceed to.

Further, when the re-ignition judging section 24 judges in step 7 that the re-ignition judgment time has not been exceeded,
That is, when it is determined that the material to be melted is not cooled but warm, as shown in step 12, the electrode polarity determination unit 27 (the electrode polarity determination unit 2 described in step 2).
2 and may determine whether the electrode on the side of the slag outlet 3 is a cathode electrode (actual electrode).

If it is determined in step 12 that the electrode is the cathode electrode, the process proceeds to step 13, where ignition (reignition) is performed, and then normal operation is started. If it is determined that the electrode is not the cathode electrode, step 14
After the voltage polarity is switched, the ignition is performed and the normal operation starts.

As described above, when the temperature of the material to be melted is low during the initial ignition operation or the re-ignition operation of the melting furnace, the switching instruction from the polarity switching timing judging unit makes it possible to perform the normal operation via the polarity switching means. Since a voltage having a polarity opposite to the voltage polarity to be applied is applied, that is, the anode electrode side where melting does not proceed so much is operated as a cathode electrode which is easy to melt, conventionally, the anode electrode side is conventionally used. Since the occurrence of a poor melting state, that is, a plasma arc runaway and a state in which the electrode is fixed to the object to be melted, is prevented, and the melting operation can be started quickly in a stable state of the plasma arc, the reliability is improved. And a plasma melting furnace having a high melting point can be provided.

[0034]

As described above, according to the plasma melting furnace and the method of operating the same according to the present invention, the polarity of the voltage applied to the cathode electrode and the anode electrode is switched, for example, during the initial ignition operation or re-ignition of the melting furnace. When the temperature of the material to be melted during operation is low, by applying a voltage opposite to the voltage polarity applied during normal operation, that is, the anode electrode side where melting does not proceed so much is operated as a cathode electrode that is easy to melt. By doing, conventionally,
Insufficient melting state, such as plasma arc runaway, which has occurred on the anode electrode side at the start of operation, and the occurrence of a state of sticking of the electrode to the melted object are prevented. Therefore, the melting operation is started quickly and in a stable plasma arc state. be able to.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a schematic configuration of an operation control device in the plasma melting furnace.

FIG. 3 is a flowchart showing an operation control method in the plasma melting furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace main body 2 Ash inlet 3 Slag outlet 4 Cathode electrode 5 Anode electrode 6, 7 Elevating device 8 Power supply device 9 Operation control device 11 Electrode height adjustment part 12 Voltage adjustment part 14 Polarity change switch 15 Polarity change instruction part 21 Operation Start state determination unit 22 Electrode polarity determination unit 23 Polarity switching timing determination unit 24 Re-ignition determination unit 25 Electrode polarity determination unit 26 Cathode state determination unit 27 Electrode polarity determination unit

Continuing from the front page (72) Inventor Toshiyuki Minano 1-7-89 Minami Kohoku, Suminoe-ku, Osaka-shi, Osaka Inside Hitachi Zosen Corporation (72) Inventor Masakazu Saruwatari 1-7-7 Minami-Kohoku, Suminoe-ku, Osaka-shi, Osaka No. 89 F-term in Hitachi Zosen Corporation (reference) 3K061 NB02 NB30 3K062 BA02 DB14 4K045 AA04 RB02 4K063 AA04 CA03 CA06 FA56 FA72

Claims (5)

[Claims] 1. A twin torch type plasma melting furnace having a furnace body provided with a cathode electrode and an anode electrode, comprising a polarity switching means for switching a voltage polarity applied to the cathode electrode and the anode electrode. Characteristic twin torch type plasma melting furnace. 2. A furnace body in which a cathode electrode and an anode electrode are respectively provided so as to be movable up and down via a lifting device, a power supply device for applying a DC voltage to both electrodes, and an operation for controlling the power supply device and the lifting device. A twin torch type plasma melting furnace having a control device, comprising: a polarity switching means for switching a voltage polarity applied to the cathode electrode and the anode electrode; and the operation control device includes an initial ignition operation or a re-ignition. An operation state determination unit for determining whether the operation is performed and a polarity switching timing determination unit for determining a switching timing of the voltage polarity by the polarity switching unit are provided.When the initial ignition operation is performed or the re-ignition operation is performed, When the temperature is low, the polarity switching means determines the voltage polarity applied during normal operation by the switching instruction from the polarity switching timing determination unit. Twin Torch type plasma melting furnace, characterized by being configured to apply a voltage of opposite polarity. 3. A method for operating a twin torch type plasma melting furnace in which a furnace body is provided with a cathode electrode and an anode electrode, wherein the anode electrode is brought into contact with the material to be melted, After starting melting in a single mode that generates a plasma arc, when transitioning to twin mode in which a plasma arc is generated on both electrodes,
A method for operating a twin torch type plasma melting furnace, comprising switching a voltage polarity applied to an electrode. 4. During an initial ignition operation in a single mode, a positive electrode voltage is applied to a cathode electrode arranged on a slag port side to start melting as a temporary anode electrode, and at the time of shifting to a twin mode, The method of operating a twin torch type plasma melting furnace according to claim 3, wherein the polarity of the voltage applied to both electrodes is switched when the temporary anode electrode falls or when the anode voltage is detected. 5. A re-ignition operation in a single mode, a positive electrode voltage is applied to a cathode electrode disposed on a slag port side to start melting as a temporary anode electrode, and at the time of shifting to a twin mode, 4. The operating method of the twin torch type plasma melting furnace according to claim 3, wherein the polarity of the voltage applied to both electrodes is switched when the arc at the temporary cathode electrode is stabilized.