JPH03127486A - Plasma melting device - Google Patents

Abstract

PURPOSE:To prevent a misfire of the plasma arc by controlling the feeding speed of a substance to melt depending on the detected plasma arc voltage. CONSTITUTION:When the composition of a substance to melt to throw in a melting furnace is uneven, or the throwing-in amount of the substance is too much, the plasma arc voltage generates a variation and causes a misfire of the plasma arc. Therefore, the plasma arc voltage is detected by an arc voltage detector 3, and the detected signal is output to a controller 2. The controller 2 outputs a control signal to a feeder device 4 responding to the value of the plasma arc voltage. As a result, the feeding speed of the substance to melt is regulated responding to the value of the plasma arc voltage, and a misfire of the plasma arc is prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to incineration ash generated by incinerating municipal waste, sewage sludge, or other waste in an incinerator, in the technical field of ceramics, refining, etc. ceramics, iron ore,
The present invention relates to a plasma melting apparatus that melts materials to be melted, such as chromite ore and oxide ore, in a melting furnace.

[Conventional technology]

Generally, incineration ash generated by incinerating municipal waste, sewage sludge, or other waste in a waste incinerator is currently disposed of in a landfill in many cases. However, as it becomes more difficult to secure landfill sites year by year, there is a need for a method of reducing the volume of incinerated ash to be landfilled, that is, a volume reduction process. In addition, if incinerated ash is disposed of in a landfill without being treated, the incinerated ash itself contains harmful substances such as various heavy metals.
Harmful substances from incinerated ash elute into rainwater, groundwater, etc., or unburned organic substances in incinerated ash decompose, and these phenomena cause secondary pollution. Therefore, there is a demand for pollution-free treatment of incineration ash discharged from incinerators.

For this reason, various methods for treating incineration ash have been developed. One of the processing methods is a method of charging incinerated ash into an open arc furnace (melting furnace) and melting the incinerated ash. That is, incinerated ash is put into a closed arc furnace in which an arc is constantly generated between an electrode and molten metal, and the organic matter in this incinerated ash is decomposed by arc heat and taken out of the furnace as gas. The inorganic substances inside are melted by arc heat and injected into the molten metal, or taken out of the furnace as molten slag.

However, incineration ash, especially municipal waste incineration ash, contains a large amount of high-melting point substances such as earth and sand, ceramics, and metals, and open arc furnaces have the problem of not being able to completely melt these substances due to insufficient temperature. There is. Therefore, in order to raise the temperature inside the melting furnace to a higher temperature, a plasma melting apparatus has been developed that uses a plasma torch as a melting furnace. The structure of this plasma melting apparatus will be explained with reference to FIG.

This plasma melting device melts incineration ash generated by incinerating municipal waste, sewage sludge, or other waste in a melting furnace, that is, a plasma arc furnace 5, and is mainly used in a plasma arc furnace. 5,
It consists of a plasma torch 8 provided in the plasma arc furnace 5, and a plasma system for generating plasma in the plasma torch 8.

As shown in FIG. 5, the plasma arc furnace 5 includes a furnace body 6.
A fixed water-cooled furnace li7 is provided as the upper part of the furnace. This furnace body 6 is constructed of a refractory material such as carbon, magnesia, alumina, or the like. By tilting the furnace body 6, residual molten slag accumulated in the furnace body 6 can be discharged. Furthermore, a torch lifting device 11, an incineration ash input shade 9, and an ash gas outlet cover 16 for guiding exhaust gas to an exhaust gas duct are attached to the furnace lid 7. plasma torch 8
is installed on the furnace cover 7 by a torch lifting device 11. A graphite electrode serving as a counter electrode 10 of the plasma torch 8 is embedded in the bottom of the furnace body 6, and the electrode (child) built in the plasma torch 8 and the graphite electrode provided at the bottom of the furnace body 6 are connected to each other. A plasma arc is generated between a certain counter electrode 10 (-electrode).

The incinerated ash B generated from the incinerator or the incinerated ash B thinly collected from the dust collector is collected in the ash container.
From the ash container, the ash is fed into the ash hopper 12 of the bushing type feeding device 4 as shown in FIG. The incinerated ash B fed into the ash hopper 12 is continuously (9th
) or intermittently (see FIG. 10) into the plasma arc furnace 5. Due to the thermal energy of the plasma arc, the incinerated ash B containing oxides, highly molten substances, etc. becomes molten slag 13, and the metal is continuously or intermittently discharged from the slag discharge port 15 of the furnace body 6 as molten metal. It is made to flow out and taken out as slag S.

Next, a conventional method of operating a plasma melting apparatus will be explained with reference to the process flow diagram of FIG.

The plasma torch 8 is lowered into the plasma arc furnace 5 and the plasma torch 8 is moved at a predetermined distance (2
00mm~20u), step 40), air,
Plasma generation gas such as argon is supplied to the plasma torch 8.
At the same time, a voltage is applied between the anode of the plasma torch 8, the collimator, and the counter electrode.

In this state, a high-energy pulse is applied between the anode and the collimator of the plasma torch 8 to generate a viroft arc (step 41).

A main arc is then formed from the anode of the plasma torch 8 to the counter electrode 10 (step 42).

After the main termination has been completed, the plasma torch 8 is raised to a predetermined height (step 43), and a predetermined current (for example, 200-300A>) and a predetermined voltage (for example, 4
00 to 500 V), it becomes possible to supply the thermal energy of the plasma arc to the incinerated ash.

At this time, the current is PID%+l'4'n, and the voltage is determined by the distance between the plasma torch 8 and the counter electrode 10. On the other hand, after the main arc is generated, the incinerated ash is transferred to the supply device 4.
, for example, is supplied into the plasma arc furnace 5 using a butcher type supply device or a screw feeder (step 44
), in this case, the bushing type supply device 4 is of a type that is operated independently regardless of the plasma arc voltage.

That is, as can be seen from the operation pattern shown in FIG. 8, the incineration ash supply rate is determined by the moving distance and moving time of the delivery piston. Incineration ash is a non-conductor, and
Due to the rapid generation of gas and dust during supply, a phenomenon occurs in which the plasma arc is interrupted.

Regarding the plasma arc, if the voltage is ■, the current is r, and the resistance is R, then there is a relationship of V=IH, and the current ■ is PID
Since the voltage V is controlled to be constant, when the resistance R becomes large, the voltage V increases. Therefore, the arc voltage detector detects the plasma arc voltage V (step 45).
In step 46), it is determined whether the detected detection signal is lower than the high voltage limit setting value, that is, the protection circuit operating voltage H11L (for example, 700'V), and if the detection signal is lower than the protection circuit Si!
If the circuit operating voltage HHL (for example, 7QOV) is lower, the ash supply device operates continuously (step 47), but if the plasma arc voltage V becomes equal to or higher than the protection circuit operating voltage HHL, the protection circuit operates and the plasma The arc misfires (step 48). When continuing the melting process of the incinerated ash in the plasma arc furnace (step 49), the process returns to step 40.

[Problem to be solved by the invention]

However, in the conventional operating method for plasma melting equipment, when the plasma arc of the plasma arc furnace 5 misfires, the plasma torch 8 must be lowered again and re-ignited according to the above steps, which hinders continuous operation. It turns out.

In the misfire state of the plasma arc furnace 5, if the incinerated ash is already in a molten state, re-ignition is possible because it is electrically conductive, but if the incinerated ash is not melted, or as shown in FIG. In the case of state 14, in which the incinerated ash, which was in a molten state just before a misfire, cools and solidifies before it re-ignites, it becomes impossible to re-ignite, and the operation has to be stopped. When the situation arises, in order to ignite the fire again,
The solidified incineration ash remaining in the furnace must be crushed and taken out from the melting furnace to expose the counter electrode 10, resulting in a heavy workload.

In addition, the conventional method of supplying incinerated ash is an independent and automatic supply method (see Figures 6 and 8), regardless of the plasma arc voltage.
(see figure), the operator must manually turn on and off the ash supply device 4 while visually observing the arc voltmeter to avoid misfires of the plasma arc. , which is very inconvenient.

The purpose of the present invention is to solve the above-mentioned problems, and to explain the plasma arc To avoid solidification of the melted material in the plasma arc furnace and prevent misfire of the plasma arc by controlling the supply speed and supply state of the material to be melted according to fluctuations in the plasma arc voltage of the furnace. An object of the present invention is to provide a plasma melting device characterized by the following.

[Means to solve the problem]

In order to achieve the above object, the present invention is configured as follows.

That is, the present invention provides a plasma arc furnace including a plasma torch and a supply port for a material to be melted, a slag discharge port, and an exhaust gas outlet, a plasma system for generating plasma in the plasma torch, and a plasma arc furnace for supplying the material to be melted. A plasma melting apparatus comprising a supply device that feeds the plasma arc voltage from the mouth to the plasma arc furnace, and includes an arc voltage detector that detects plasma arc voltage, and a plasma arc voltage detector that detects the plasma arc voltage. The present invention relates to a plasma melting apparatus having a controller that controls the amount of linen to be fed.

Further, in this plasma melting apparatus, the controller includes an intermittent operation control circuit that operates the supply device intermittently, and an intermittent operation control circuit that operates the supply device intermittently in response to a detection signal in which a plasma arc voltage is equal to or higher than a set value for supplying the material to be melted. Outputting a signal to stop the supply of the material to be melted to the control circuit, and in response to a detection signal in which the plasma arc voltage is smaller than an optimal limit setting value for supplying the material to be melted, start supplying the material to be melted to the intermittent operation control circuit. It has an arc voltage interlock circuit that outputs a signal.

Furthermore, this plasma melting apparatus includes a protection circuit that causes the plasma arc to misfire in response to a detection signal in which the plasma arc voltage exceeds a high voltage limit setting value.

[Effect]

The plasma melting apparatus according to the present invention is constructed as described above and operates as follows. That is, this plasma melting apparatus can obtain a plasma arc using a plasma torch, and can melt a highly melting material to be melted with the thermal energy of high-temperature plasma. Furthermore, the molten slag in the furnace overflows from the slag discharge port and is continuously discharged outside the furnace, so as long as the material to be melted is fed into the melting furnace to prevent the plasma arc from misfiring, the incinerated ash can be continuously discharged. It can be melt-processed.

If the composition of the material to be melted that is thrown into the melting furnace is uneven, or if the amount of material to be melted is too large, the plasma arc voltage will fluctuate, which can cause the plasma arc to misfire. This plasma arc voltage is detected by an arc voltage detector, and this detection (No. 3) is output to the controller. The controller outputs a control signal to the supply device according to the magnitude of the plasma arc voltage. As a result ,
The supply rate of the material to be melted is adjusted according to the magnitude of the plasma arc voltage, thereby preventing misfire of the plasma arc.

A specific explanation of the control by this controller is as follows.Normally, the supply device intermittently sends the material to be melted to the melting furnace in response to a signal output from the intermittent operation control circuit of the controller. . When the plasma arc voltage detected by the arc voltage detector is input to the arc voltage clock circuit of the controller, the arc voltage clock circuit determines the plasma arc voltage and the supply limit setting value of the material to be melted, that is, the first setting value. When the plasma arc voltage rises and exceeds the first set value, a stop signal is output from the arc voltage increment clock circuit to the intermittent operation control circuit to stop the operation of the supply device. Ru. As a result, new material to be melted is not dropped, so the melting of the material in the plasma arc furnace progresses, and the plasma arc voltage decreases. Then, when the plasma arc voltage becomes smaller than the optimal limit setting value for supplying the material to be melted, that is, the second setting value, a start signal is output from the aliquot voltage ink clock circuit to the intermittent operation control circuit, and the supply device starts the operation. be jealous

In this way, the supply speed of the material to be melted is automatically controlled according to the magnitude of the plasma arc voltage, so it is possible to avoid the plasma arc misfiring due to the plasma arc voltage becoming too large. can.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a plasma melting apparatus according to the present invention will be described below with reference to the drawings. The plasma melting apparatus according to the present invention mixes incinerated ash generated by incinerating waste etc. from an incinerator, and in some cases, dust, that is, incinerated ash collected by the dust collector in the incinerator system. This is a device that is placed in a melting furnace, that is, a plasma arc furnace, and melts and processes the incinerated ash in this plasma arc furnace.

The configuration of this plasma melting apparatus is the same as that of the conventional apparatus already described with reference to FIG. 5, so a description of the apparatus will be omitted.

FIG. 1 is a block diagram showing a control system in a plasma incineration ash melting apparatus according to the present invention. The changeover switch 1 is a switch for switching the control system to either "manual" or "automatic" mode. When switching to "Manual", as in the past, manually operate the supply device 4 while visually observing.
By turning on and off the plasma arc furnace 5.
The rate of supply of incineration ash to can be adjusted. When switched to "automatic", the controller 2 automatically controls the incineration ash supply speed. Controller 2 is
Intermittent operation control circuit 17 and arc voltage ink clock circuit I
8 and 0 intermittent operation control circuit 17 is a circuit for intermittently operating the supply device 4. The arc voltage ink clock circuit 18 outputs an ash supply stop signal to the intermittent operation control circuit 17 when the plasma arc voltage exceeds a first set value, that is, the incinerated ash supply limit set value HL, for example, 550V. Further, when the plasma arc voltage becomes smaller than the second set value, that is, the optimal incinerated ash supply limit set value ML, for example, 500V, an ash supply candy start signal is output to the intermittent operation control circuit 17. Arc voltage detector 3 detects plasma arc voltage and outputs it to arc voltage interlock circuit 18 . As the ash supply device 4, a pusher type ash supply device 4 as shown in FIG. 8 is used here. In the ash supply device 4, the piston pushes the ash to the forward limit E.
and reciprocating movement over the travel distance between I@S and Retraction I@S. This ash supply device 4 has a built-in control circuit that causes the delivery piston to retreat to the backward limit S when it reaches the forward limit E.

Next, an embodiment of the operation of the plasma melting apparatus according to the present invention will be described with reference to FIGS. 2(A) and 2(B). FIG. 2(A) and FIG. 2(B) are process flow diagrams showing one embodiment of the method of operating a plasma melting apparatus according to the present invention. Steps 20 to 24, which are the processes from forming a plasma arc to supplying thermal energy to the incinerated ash, are completely the same as steps 40 to 44 of the conventional operating method shown in FIG. Since this is the process, the explanation will be omitted.

First, the supply device 4 is activated (step 24), and the plasma arc voltage V is detected by the arc voltage detector 3. The plasma arc voltage V is the first set value for stopping the ash supply of the supply device 4, and the incinerated ash supply limit set value HL (
For example, if it is less than 550■), the plasma arc is being generated satisfactorily, so the supply device 4 that supplies incinerated ash to the plasma arc furnace 5 continues to operate, step 32).
The incineration ash will be melted. On the other hand, the detected value of the plasma 7-voltage (■) by the arc voltage detector 3 exceeds the set value HL, and the protection circuit operating voltage, that is, the high voltage limit set value HH.
If it is lower than L (for example, 700■) (step 27
), a timer in the arc voltage ink clock circuit 18 is activated to stop the supply of incinerated ash to the plasma arc furnace 5 for a predetermined period of time (for example, 30 seconds) (step 28);
After the predetermined time has elapsed (step 29), the arc voltage detector 3 detects the plasma arc voltage (2) again (step 30), and the plasma arc voltage V is the second set value, which is the optimal limit set value for the supply of incinerated ash. ML (e.g. 50
Compare and judge whether the voltage is lower than 0V (Step 31), and if it is, operate the rhyme supply device 4 to start supplying incinerated ash into the plasma arc furnace 5 again (Step 32). . However, if the plasma arc voltage (■) does not become equal to or lower than the optimal limit setting value ML for incinerated ash even after the supply of incinerated ash is stopped and a predetermined period of time has elapsed in the comparative judgment in step 31, then the number of times of the comparative judgment is The number of times N is counted is determined in step 34), and the number of times N is compared with a predetermined number Ni1 (for example, three times) in step 35). If it is below, return to step 28 and repeat the process (step 35). Even if the number of counts N exceeds the predetermined number N, the plasma arc voltage V is the optimal limit for supplying incinerated ash. If the value does not fall below the set value ML, there is a possibility that some trouble has occurred in the plasma arc furnace 5, so misfire the plasma arc,
An abnormal signal is generated (step 36). Therefore, by carrying out the above operation, the plasma arc can be processed continuously without misfiring.

Furthermore, in step 27, if the plasma arc voltage exceeds the protection circuit operating voltage, that is, the high voltage limit setting (1iHHL (e.g., 700 V)), there is a possibility that the plasma arc furnace 5 will not be able to operate. The protection circuit of the power supply device is activated and the plasma arc is set to misfire (step 37).

Another embodiment of the operation of the plasma melting apparatus according to the present invention will be described with reference to FIGS. 2(A) and 2(C). FIG. 2(A) and FIG. 2(C) are process flow diagrams showing another embodiment of the method of operating a plasma melting apparatus according to the present invention.

Compared to the operating method of the first embodiment, the operating method of the plasma melting apparatus of this embodiment does not require determining whether the plasma arc voltage V is at the optimum limit setting value ML for the supply of incinerated ash. The operating method is exactly the same, except that a timer is used to set the ash supply stop period to the plasma arc furnace 5 in advance. Therefore, only the different operating steps in the method of operating this plasma melting apparatus will be described here. In the operating process of this embodiment, if the detected value of the plasma arc voltage (■) by the arc voltage detector 3 exceeds the set value HL and is lower than the protection circuit operating voltage, that is, the high voltage limit set value HHL (for example, 700 ■) (step In step 27), the timer in the arc voltage clock circuit 18 is activated to stop the supply of incinerated ash to the plasma arc furnace 5 for a predetermined period of time (for example, 40 seconds). After a predetermined period of time during which the supply of incinerated ash is stopped (step 29), the incinerated ash is again supplied to the plasma arc furnace 5 by the supply device 4 (step 32).

Next, FIG. 3 shows the button type feeding device 4 shown in FIG.
The operating pattern is shown below. When the plasma arc voltage V detected by the arc voltage detector 3 is less than the incinerated ash supply optimum limit setting (tl!ML (for example, 500 V), the signal input from the intermittent operation control circuit 17 of the controller 2 , the piston of the feeder 4 performs normal operation, i.e. moves forward at a time [, S '' S +) and pauses at a time t, S +
-SX), moves forward by time t1 again (sg~S,
), the operation pattern of pausing for time (t (33 to S4) is repeated.

If, at point S, the arc voltage detector 3 becomes equal to or higher than the incinerated ash supply limit set value HL (for example, 550 ■), the supply device 4 stops operating for a predetermined period of time due to the action of the arc voltage increment clock circuit 18. do. However, during the suspension period, the plasma arc voltage is set at the optimal limit setting for incinerated ash supply (IML).
For example, if the voltage does not drop below 500V, the pause period is further extended for a predetermined time (ss x3*).In this way, when the piston of the supply bag W4 reaches the forward/backward position (E),
The control circuit of the feed device 4 is activated and the piston is immediately returned to the retraction limit S.

FIG. 4 compares a conventional plasma melting apparatus (B) and a plasma melting apparatus according to the present invention (A) equipped with the controller 2 with respect to fluctuations in plasma arc voltage. The ash was treated in a conventional manner using a bushing type supply bag W, 4 at an ash feeding rate of 100 kilograms. As a result, 5 minutes after the start of injection: the plasma arc voltage was 700V.
The plasma misfired (D). Thereafter, as a result of repeated ignition and misfire (D), the molten incineration ash was finally cooled and solidified and could no longer be ignited. Therefore, after taking out the solidified slag from inside the plasma arc furnace 5 and exposing the electrode 10 at the bottom of the furnace, the incinerated ash was melted using the operating method of the present invention. As a result, in the operation of the plasma arc furnace 5, the plasma arc does not misfire, and the ash feeding speed by the feeding device 4 is also 1.
A result of 20 kg/h was obtained.

〔Effect of the invention〕

The plasma melting apparatus according to the present invention has the groove bottom as described above, and has the following effects.

That is, the plasma melting apparatus (-2) can automatically control the supply rate of the material to be melted according to fluctuations in the plasma arc voltage, and therefore can prevent misfires of the plasma arc. As a result, not only is there no need for re-ignition work or the work to crush the solidified material to be melted in the melting furnace and take it out of the melting furnace to expose the counter electrode, but it also eliminates the need to visually observe the arc voltmeter. At the same time, it is no longer necessary to manually turn on and off the supply device for the material to be melted, which reduces the workload.

Further, since the melting process of the material to be melted is carried out continuously without interruption, the processing capacity is considerably increased. Furthermore, the controller controls the supply speed of the material to be melted in a manner that suppresses an increase in plasma arc voltage, which has the effect of suppressing power fluctuations and reducing the effect on the power supply. be able to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of a control system in a plasma melting apparatus according to the present invention, FIG.
FIG. 2(B) is a process flow diagram showing one embodiment of the method of operating a plasma melting apparatus according to the present invention, and FIG. 2(C) is a process flow diagram showing another embodiment of the method of operating a plasma melting apparatus according to the present invention. , FIG. 3 is an explanatory diagram illustrating the operation pattern of the bushing type supply device used in the plasma melting apparatus according to the present invention, and FIG. 4 is an explanatory diagram comparing the conventional device and the present invention regarding fluctuations in plasma arc voltage. Fig. 5 is an explanatory diagram showing the structure of the plasma melting device, Fig. 6 is an explanatory diagram showing the conventional operating method of the plasma melting device, and Fig. 7 is an explanatory diagram showing the state in which the object to be melted is solidified in the melting furnace. , 8th
The figure is a schematic diagram showing an example of a button feeder, FIG. 9 is an explanatory diagram illustrating an example of an operation pattern of a conventional buttonhole feeder, and FIG. 10 is another example of an operation pattern of a conventional buttonhole feeder. It is an explanatory diagram explaining an example. l-m-changeover switch, 2-m-controller, 3...
--- Arc voltage detector, 4-- Supply device, 5 Plasma arc furnace (melting furnace), 6-- Furnace body, 7- Furnace'll, 8-- Plasma torch, 9- ... Supply port (
Insertion shoe)), 10--1--1 counter electrode, 11...
---Torch lifting device, 12----Hofva, 13...
...--molten slag, 15--...--slag discharge port,
17-... Intermittent operation control circuit, 18-... Arc voltage ink clock circuit.

Claims (3)

[Claims] (1) A plasma arc furnace equipped with a plasma torch and a supply port for a material to be melted, a slag discharge port, and an exhaust gas outlet;
A plasma melting apparatus including a plasma system that generates plasma in the plasma torch, and a supply device that sends the material to be melted from the supply port to the plasma arc furnace, an arc voltage detector that detects a plasma arc voltage, and an arc voltage detector that detects the plasma arc voltage. A plasma melting apparatus comprising: a controller that controls the supply amount of the material to be melted in response to a detection signal detected by a voltage detector. (2) The controller includes an intermittent operation control circuit that operates the supply device intermittently, and in response to a detection signal in which the plasma arc voltage is equal to or higher than a supply limit value for the material to be melted, the controller causes the intermittent operation control circuit to operate the supply device intermittently. an arc that outputs a signal to stop the supply of the material, and outputs a signal to start supplying the material to be melted to the intermittent operation control circuit in response to a detection signal in which the plasma arc voltage is smaller than an optimum supply limit value for the material to be melted; The plasma melting apparatus according to claim 1, further comprising a voltage interlock circuit. (3) The plasma melting apparatus according to claim 1, further comprising a protection circuit that misfires the plasma arc in response to a detection signal in which the plasma arc voltage is equal to or higher than a high pressure limit setting value.