JPH11237018A - Plasma melting furnace, and its operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma melting furnace which can get an equal and high quality of granulated slug by preventing the mixing of incomplete melted matter into the molten slug overflowing from a furnace without dropping the melting treatment capacity, and its operation method. SOLUTION: This plasma melting furnace performs plasma arc discharge between the main electrode 4 suspended from the furnace top 1b and a start electrode 5c at operation start of a furnace 1, and between the main electrode 4 and a furnace-bottom electrode provided at the bottom 1c of the furnace after start of operation. The interior of the furnace 1 is kept in reductive atmosphere by jetting out inert gas C from the tip of the main electrode 4 and the start electrode 5. This compulsively pushes the incomplete molten matter A floating on the surface of fused slug into molten slug B by lowering the start electrode 5 to the position where the tip sinks into the molten slug B within the furnace 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma melting furnace for melting and processing materials to be melted such as incineration residues and fly ash discharged from an incinerator for municipal waste and industrial waste, and a method of operating the same. is there.

[0002]

2. Description of the Related Art In recent years, in order to reduce the volume and detoxify incineration residues and fly ash (hereinafter referred to as “melted material”) discharged from incinerators for municipal solid waste and industrial waste, the materials to be melted have been Attention has been paid to the melt-solidification method, and it is actually being put to practical use. This is because, by solidifying the material to be melted, it is possible to prevent elution of harmful substances such as heavy metals, reuse molten slag, extend the life of the final landfill site, and the like.

[0003] As a method of melting and solidifying a material to be melted, an arc melting furnace, a plasma arc furnace, an electric resistance furnace, or the like is used, and a method of melting and solidifying the material to be melted by electric energy; And the method of melting and solidifying the material to be melted by the combustion energy of the fuel using a rotary melting furnace, a coke bed furnace, etc. is often used, and when the municipal solid waste incineration equipment is provided with the power generation equipment, The former method using electric energy and the method using combustion energy in the case where a power generation facility is not provided are often used.

FIG. 4 shows an example of a direct current arc discharge graphite electrode type plasma melting furnace which is juxtaposed with a conventional refuse incineration facility. In this plasma melting furnace 1, a material A to be melted is stored in a hopper 3. And supplied continuously into the furnace 1 by the supply device 2. The melting furnace 1 is provided with a graphite main electrode 4 (-pole) inserted vertically from the furnace top 1b and a furnace bottom electrode 6 (+ pole) installed on the furnace bottom 1c. DC power supply 8 (capacity: about 6
An arc is generated between the electrodes 4 and 6 by a DC voltage (200 to 350 V) of 00 to 1000 KW (per ton of the melt), and a plasma P is generated by supplying nitrogen gas as a plasma gas into the arc. Thereby, the material to be melted A is melted by being heated to 1400 to 1500 ° C., and becomes a molten slag B. By the way, since the material to be melted A before melting has low conductivity, the start electrode 5 is dropped into the furnace 1 at the start of the operation of the melting furnace 1 to make it a positive electrode, and electricity is supplied between this and the main electrode 4. As a result, the material to be melted A is melted (see the chain line in FIG. 4). When the material to be melted A melts, its conductivity increases.
Thereafter, the positive electrode is switched from the start electrode 5 to the furnace bottom electrode 6.

On the other hand, the furnace 1 contains molten slag B and main electrodes 4.
Is maintained in a reducing atmosphere to prevent oxidation of the main electrode 4 from the inert gas supply device 9 such as a PSA nitrogen production device.
And, it is continuously supplied into the furnace 1 through a hollow hole of the start electrode 5. Here, inert gas C such as nitrogen gas
Is supplied into the furnace 1 through the hollow holes of the main electrode 4 and the start electrode 5 because "Pb, Zn, etc. are easy to volatilize and the quality of the slag is improved" Filling with active gas C is considered to improve plasma arc generation and stability, and that "the graphite main electrode 4 and graphite start electrode 5 are considered to be less consumed". Things.

The furnace bottom peripheral area of the melting furnace 1 is air-cooled by cool air from a furnace bottom cooling fan 7, thereby preventing an excessive temperature rise near the furnace bottom electrode 6. Further, the furnace wall, that is, the peripheral wall 1a, the furnace top 1b, and the furnace bottom 1c of the melting furnace 1 are all made of a refractory material capable of withstanding a high temperature of 1500 ° C., and the outer periphery thereof is air-cooled or water-cooled as required. doing.

When the melting of the material to be melted A is started, the exhaust gas D containing a high concentration of combustible gas generated in the furnace 1 is discharged.
Is discharged from the molten slag discharge port 10 or the furnace top 1b provided in the peripheral wall portion 1a into the combustion chamber 12 and is completely burned by the supply of combustion air by the combustion air fan 13 in the combustion chamber 12; Cooled by water spray and / or cooling air from an exhaust gas cooling fan 14,
A chimney 17 by a draft ventilator 16 via a bag filter 15
Is discharged from The molten fly ash E captured by the bag filter 15 is collected by the molten fly ash conveyer 18 into the fly ash reservoir 1.
9

On the other hand, non-combustible components (metal such as iron, glass, sand, etc.) contained in the material to be melted A are in a molten state. That is, the melted material A supplied from the hopper 3 to the melting furnace 1
Is heated to a temperature (about 1400 to 1500 ° C.) exceeding its melting point (1200 to 1300 ° C.) by supplying heat generated by the plasma arc discharge, and the liquid molten slag B having fluidity and Become. Then, the molten slag B continuously overflows from the molten slag discharge port 10, falls into a slag water cooling tank 20 filled with water (the slag cooling water is cooled by the cooling device 23), and falls into the granulated slag B.
′, And sent to the slag reservoir 22 by the slag unloading conveyor 21. When the furnace 1 is stopped, if the molten slag B is left in the furnace 1, it takes time to stop and restart the furnace 1. Therefore, the furnace 1 is provided on the peripheral wall 1 a corresponding to the bottom level of the molten slag B. Hot water is removed by the tap hole 11, and the inside of the furnace 1 is emptied.

In this way, the material to be melted A is melted by the plasma melting furnace 1, and the behavior of the molten slag B in the furnace 1 is extremely complicated.
According to the observation of the inside of the actual melting furnace, the flow on the surface layer of the slag is almost like a vortex F as shown in FIG. The vortex F of the molten slag B is not actually an orderly vortex but actually has a complicated turbulence, and the situation of the vortex F is not uniform as it goes deeper from the surface (fluid surface) of the molten slag B. It is assumed that Further, the molten slag B is also convected in the furnace 1 in the vertical direction (vertical direction), the high-temperature slag at the center of the furnace flows in an upward flow, and the low-temperature slag on the peripheral wall flows in a downward flow. It is presumed that it is.

In order to efficiently and uniformly melt the material A to be melted in the furnace 1 without leaving unmelted material or incompletely molten material (hereinafter referred to as “incompletely molten material”). "The furnace 1 is heated substantially uniformly, and the melt A is efficiently heated and melted.""The melt enters the molten slag B and flows with the slag." That the melted material A does not move near the supply port and does not gradually accumulate. "

[0011]

However, in the case of the conventional plasma melting furnace 1 shown in FIG. 4, the furnace 1 has a structure in which the cross section is substantially circular (the peripheral wall 1a is substantially cylindrical). Since the main electrode 4 is vertically arranged on the central axis and the current is passed between the main electrode 4 and the furnace bottom electrode 6, the central axis of the furnace 1 is inevitable. (The core portion) has the highest temperature range, and the vicinity of the peripheral wall portion 1a has a low temperature range due to heat radiation to the outside. "" Specification of the peripheral portion where the low-temperature molten material A is away from the core portion Since the melted material A before melting is at a low temperature and lacks thermal conductivity, the supply region H of the melted material A is in a cold temperature range while the furnace is being melted. Since the temperature distribution in the sample 1 becomes extremely uneven, the molten slag B Temperature distribution also becomes uneven, and has a remote status from the ideal condition for a complete melting of the melt A with high efficiency.

Further, in the above-mentioned conventional plasma melting furnace 1, the material to be melted A is continuously supplied to the furnace 1 by the supply device 2.
A molten material supply port 2a to be supplied into the furnace and a molten slag discharge port 10 for continuously discharging the molten slag B out of the furnace 1 are provided at positions facing the peripheral wall portion 1a. 10 is the inner diameter of the melting furnace 1 (the peripheral wall 1a).
(Inner diameter of the molten slag B), it is difficult for the molten slag B to uniformly flow from the entire area in the furnace 1 toward the molten slag discharge port 10 side, and the flow amount of the molten slag B In other words, there is a region where the amount of slag increases, or conversely, a region where the molten slag hardly flows and stays in a stagnation state, thereby preventing further improvement of the melting processing capacity.

Further, the material to be melted A is usually 5 to 70 μm.
m (in the case of fly ash) or 30 to 50 mm or less (in the case of incineration residue) is supplied into the furnace 1 as fine powder or fine granules having an outer diameter dimension. ,
The porosity and the like vary. For example, the molten slag B may have a good heat receiving property or a bad heat receiving property, or may have a sedimentary property and a floating property. Therefore, the meltable material A having poor heat receptivity and being buoyant does not convect in the vertical direction together with the molten slag B, and remains floating on or in the slag surface layer. The melt is supplied, an incomplete melt layer is formed, and does not completely melt before flowing out of the molten slag discharge port 10, and the incomplete melt mixes into the molten slag B.

As described above, the conventional arc discharge graphite electrode type plasma melting furnace 1 can relatively stably melt the material to be melted A, but still has many problems to be solved. Among them, particularly important problems are the problems of the uniformity of the molten slag B and the melting treatment capacity.

That is, as described above, due to the complicated flow and heat conduction of the molten slag B due to the structure of the furnace 1 itself, the molten slag B remains partially in an incompletely molten state. It is inevitable that the molten slag overflows from the molten slag discharge port 10 together with the molten slag B, and the molten slag B that actually overflows from the molten slag discharge port 10 is considerably dependent on the properties of the material to be melted (the properties of the ash). In addition to the amount of incomplete melt present, the incorporation rate of the incomplete melt varies greatly. As a result, the quality of the molten slag B is lacking in uniformity, and the quality of the granulated slag B 'is inevitably deteriorated, and it is difficult to use the slag B' effectively. Further, if the residence time of the molten slag B in the furnace 1 is increased in order to reduce the mixing ratio of the incomplete molten material in the molten slag B overflowing from the molten slag discharge port 10, the throughput of the molten material A is reduced. As a result, the melting capacity of the melting furnace 1 is reduced.

The present invention has been made in view of the above points, and prevents incomplete molten material from being mixed into molten slag overflowing from a molten slag discharge port without lowering the melting processing capacity. It is an object of the present invention to provide a plasma melting furnace capable of obtaining uniform and high-quality granulated slag and a method of operating the same.

[0017]

SUMMARY OF THE INVENTION According to the present invention, a molten material continuously supplied into a furnace from a molten material supply port is melted by plasma arc discharge, and molten slag is discharged from the molten slag discharge port to the furnace. In order to achieve the above-mentioned purpose, in the plasma melting furnace configured to continuously overflow and discharge outside, the tip can be lowered into the molten slag in the furnace, especially near the supply port of the melt. By providing a rod-shaped elevating body, by lowering the tip of the rod-shaped elevating body into the molten slag, the incomplete molten material floating on the surface of the molten slag is forcibly sunk into the molten slag. Propose to put.

The plasma melting furnace is provided between the main electrode and the start electrode which are suspended from the furnace top at the start of operation of the furnace, and is provided between the main electrode and the furnace bottom after the operation is started. By performing plasma arc discharge between the electrodes and the electrodes, respectively, the molten material continuously supplied into the furnace from the molten material supply port is melted, and the molten slag is continuously discharged from the molten slag discharge port to the outside of the furnace. When the furnace is configured to maintain the inside of the furnace in a reducing atmosphere by overflowing and discharging, and by injecting an inert gas from the tips of the main electrode and the start electrode,
It is preferable to use a start electrode as a rod-shaped elevating body without providing a special rod-shaped elevating body. That is, in the vicinity of the melt supply port, the tip of the start electrode can be lowered into the molten slag in the furnace, and by lowering the tip of the start electrode into the molten slag,
The incomplete molten material floating on the surface of the molten slag is forcibly sunk into the molten slag.

Further, according to the present invention, the molten material continuously supplied into the furnace from the molten material supply port is melted by plasma arc discharge, and the molten slag is continuously discharged from the molten slag discharge port to the outside of the furnace. In order to achieve the above-mentioned object, in the operation method of the plasma melting furnace in which the overflow is caused to overflow and discharge, in particular, in the vicinity of the supply port of the material to be melted, the rod-shaped elevating part whose tip can be lowered into the molten slag in the furnace. By providing a body and repeatedly lowering the tip of this rod-shaped elevating body into the molten slag (including lowering it as necessary and periodically lowering it), incomplete floating on the surface of the molten slag It is proposed to force the melt into the molten slag.

In this operation method, at the time of starting the operation of the furnace, the main electrode and the bottom electrode provided at the bottom of the furnace are placed between the main electrode and the start electrode which are suspended from the top of the furnace. In the meantime, by performing plasma arc discharge, the molten material continuously supplied into the furnace from the molten material supply port is melted, and the molten slag is continuously overflowed from the molten slag discharge port to the outside of the furnace. In the case of a plasma melting furnace operating method in which the furnace is maintained in a reducing atmosphere by discharging the gas and discharging an inert gas from the tip of the main electrode and the start electrode, It is preferable that the incompletely melted material is forced into the molten slag by using the start electrode without providing the rod-shaped lifting element. That is, in the vicinity of the molten material supply port, the tip of the start electrode can be lowered into the molten slag in the furnace, and the tip of the start electrode not used as an electrode is repeatedly lowered into the molten slag. By lowering the molten slag (including the case where it is lowered if necessary and the case where it is lowered periodically), the incomplete molten material floating on the surface of the molten slag is forcibly sunk into the molten slag.

[0021]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be specifically described with reference to FIGS.

As shown in FIGS. 1 to 3, a plasma melting furnace 1 according to the present invention in this embodiment has a furnace wall provided with a cylindrical peripheral wall 1a, a furnace top 1b serving as a ceiling wall, and a furnace bottom electrode 6. This is a fire-resistant wall structure composed of a furnace bottom 1c. The peripheral wall portion 1a is located at a position where the molten material supply port 2a for supplying the molten material A such as incineration residue and fly ash, and a position directly opposed to the molten material supply port 2a in the diameter direction of the furnace 1. A molten slag discharge port 10 and a tap hole 11 located immediately below the melt supply port 2a and near the upper surface of the furnace bottom 1c are provided. An appropriate supply device 2 such as a screw feeder is connected to the melt supply port 2a so that the melt A stored in the hopper 3 is continuously and quantitatively supplied into the furnace 1. . The molten slag discharge port 10 is
This is for discharging the molten slag B and discharging the exhaust gas D, and the molten slag B continuously overflows from the molten slag discharge port 10 to discharge water, similarly to the conventional plasma melting furnace shown in FIG. The slag falls into the filled slag water cooling tank 20 to become granulated slag B ′, and the exhaust gas D is discharged from the molten slag discharge port 1.
From 0 to the combustion chamber 12 where it is completely burned by the supply of combustion air by the combustion air fan 13 in the combustion chamber 12, cooled, removed of molten fly ash and discharged from the chimney (FIG. 4). reference). The furnace walls 1a, 1
b and 1c are made of a refractory material that can sufficiently withstand a high temperature of about 1600 ° C., and a water-cooled jacket is arranged on the outer periphery thereof as necessary. As shown in FIG. 1, the furnace bottom electrode generates a predetermined plasma P between itself and the main electrode 4. Formed. The area around the bottom of the melting furnace 1 is air-cooled by the cool air from the bottom cooling fan 7.

The main electrode 4 is arranged on the center line of the furnace 1 and is supported by penetrating the furnace top 1b so that the main electrode 4 can be raised and lowered according to the liquid level in the furnace 1 (the liquid level of the molten slag B). It has become. The start electrode 5 is vertically and inclinedly inserted through and supported by the furnace top 1 b, and has a standby position (the position shown in FIG. 1) where the lower end does not protrude into the furnace 1, and the front end of the main electrode 4. The portion is raised and lowered over a discharge operation position (position shown in FIG. 2) located at substantially the same height as the portion. Each of the electrodes 4 and 5 is a graphite cylinder having a hollow hole penetrating in the axial direction. The base ends of the electrodes 4 and 5 are connected to an inert gas supply device 9 such as a PSA nitrogen production device, and an inert gas ( Nitrogen gas, etc.) is continuously ejected from the tip. In this embodiment, as shown in FIG. 2, the discharge operation position of the start electrode 5 is the optimal positional relationship between the electrodes 4 and 5 for generating the plasma P necessary for melting the material A to be melted at the start of operation. It is set to be.

The above configuration is the same as that of the conventional plasma melting furnace shown in FIG.
In the above, a rod-shaped elevating body whose tip can be lowered into the molten slag B in the furnace 1 is provided near the molten material supply port, and the tip of the rod-shaped elevating body is lowered into the molten slag B. In this case, the incomplete molten material A ′ floating without settling on the surface of the molten slag is forced into the molten slag B, but in this example, the start electrode 5 is connected to the discharge The start electrode 5 is devised so that it can be lowered further from the position, and the start electrode 5 is used as the above-mentioned rod-shaped elevating body.

That is, the start electrode 5 can be lowered from the standby position to the immersion position (the position shown in FIG. 3) where the tip end immerses in the molten slag B near the melt supply port through the discharge operation position. I have. The start electrode 5 is supplied with power from the DC power supply 8 so as to function as an electrode only when it is located at the discharge operation position at the start of operation, similarly to the conventional plasma melting furnace. In other words, when it is located at the standby position and the immersion position other than the discharge operation position, the power supply from the DC power supply device 8 is cut off and does not function as an electrode, and is maintained in an electrically insulated state. I have. The lowering of the start electrode 5 to the immersion position is performed by the furnace 1 as described later.
Is periodically performed during the operation of the vehicle, and the periodic lowering operation is automatically performed by a lifting device (not shown).

The plasma melting furnace 1 constructed as described above
Is operated according to the invention as follows.

That is, in performing the melting process,
First, at the start of operation, as shown in FIG. 2, the start electrode 5 is lowered from the standby position to the discharge operation position, and plasma P is generated by applying a voltage between the start electrode 5 and the main electrode 4. Thereby, the material A to be melted in the furnace 1 is melted. This is because the conductive molten slag B is not interposed between the main electrode 4 and the furnace bottom electrode 6 and the non-conductive
This is because the plasma P cannot be generated between the electrodes 4 and 6 at the start of the operation when only the gas is interposed.

After the start of the operation in which the molten slag B is generated in the furnace 1 by the plasma P generated between the electrodes 4 and 5, the start electrode 5 is raised to the standby position as shown in FIG. In the state where plasma P is generated by applying a voltage between the main electrode 4 and the furnace bottom electrode 6 while the melted material A is continuously supplied into the furnace 1 by the supply device 2, The melting process of the material to be melted A is performed.
As the material to be melted A is melted by the heating by the plasma P generated between the main electrode 4 and the furnace bottom electrode 6, the molten slag B is continuously dropped and supplied from the molten slag discharge port 10 to the slag water cooling tank 20. Thus, granulated slag B 'is generated. Further, the exhaust gas D is discharged from the molten slag discharge port 10 to the combustion chamber 12.

By the way, the melt A supplied from the melt supply port 2a does not immediately settle into the molten slag B, but floats on the surface of the molten slag. Therefore, in conjunction with the fact that the melted material A is continuously supplied from the melted material supply port 2a, especially in the vicinity of the melted material supply port, the incomplete molten material A is formed on the surface of the molten slag as described above. 'Floats, and there is a possibility that a part of it will be discharged out of the furnace 1 together with the molten slag B overflowing from the molten slag discharge port 10. Therefore, in the operation method according to the present invention, during the operation of the furnace 1, the start electrode 5 which does not function as an electrode except at the start of operation.
Is periodically lowered into the molten slag B,
The incompletely molten material (unmelted or incompletely molten material floating on or near the upper surface of the slag surface) A ′ floating on the surface of the molten slag B in the vicinity of the melt supply port is forcibly melted by the molten slag B. Try to get inside. That is, the start electrode 5 is lowered to the immersion position as shown in FIG. 3 (the tip of the start electrode is immersed in the molten slag B).
And rising from the immersion position (pulling of the start electrode tip from inside the molten slag B) is performed periodically, that is, at predetermined time intervals, and by the tip of the start electrode 5 when descending to the immersion position, The molten material A continuously supplied from the molten material supply port 2a is forcibly pushed into the molten slag B at the earliest possible stage after the supply to the molten slag surface. A situation in which the melt A ′ does not settle in the molten slag B but remains on the surface thereof is prevented as much as possible, and the molten slag B overflowed from the furnace 1 is prevented.
Is almost completely eliminated.

It is also possible to push the incomplete molten material A 'into the molten slag B and to blow the inert gas C into the molten slag B from the tip of the start electrode 5. It is. By blowing the inert gas C into the molten slag B, spontaneous horizontal vortices (see FIG. 5) and vertical convection of the molten slag B in the furnace 1 are forcibly disturbed. Will be. That is, the mixing of the molten slag B becomes more aggressive, the temperature distribution in the furnace 1 becomes more uniform, and the molten slag B
Are heated and melted almost uniformly, and the molten slag B flows from each part in the furnace 1 toward the molten slag discharge port 10 evenly. Therefore, by feeding the molten slag B discharged from the furnace 1 to the slag water cooling tank 20, high-quality and uniform-quality granulated slag B 'containing no incompletely melted material A' can be obtained. Its effective use can be promoted. In addition, since it is not necessary to lengthen the slag residence time in the furnace 1 to reduce the incorporation of the incomplete molten material A ', the melting processing capacity of the furnace 1 decreases and the running cost increases due to the increase in the slag residence time. Can be prevented as much as possible, and the melting treatment of the material to be melted A can be performed effectively. Since the start electrode 5 located at the immersion position is in a completely electrically insulated state where the power is turned off, there is no inconvenience such as energization between the main electrode 4 and the start electrode 5.

The means for blowing the inert gas C into the molten slag B is a start electrode 5 which is not used as an electrode during operation of the furnace 1 and an inert gas for maintaining a reducing atmosphere in the furnace 1. Since the supply device 9 is used as it is, there is no problem such as a case where a special blowing means is newly provided (for example, a problem such as a complicated furnace structure and a rise in initial costs and running costs). Moreover, since an inert gas (nitrogen gas or the like) for maintaining the reducing atmosphere is blown into the molten slag B, the blowing does not have any adverse effect on the reducing atmosphere in the furnace 1.

It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately improved and changed without departing from the basic principle of the present invention. For example, in the above-described example, the incompletely melted material A ′ is sunk into the molten slag B by moving the rod-shaped start electrode 5 up and down. A rod-shaped elevating body which can be lowered to the side, that is, a rod-shaped elevating body exclusively for pushing the incomplete molten material may be separately provided, and the incomplete molten material A 'may be forcibly pushed into the molten slag B by the rod-shaped elevating body. . But,
When the start electrode 5 must be immersed in the molten slag B, for example, when the start electrode 5 is used as a means for blowing inert gas into the molten slag B, the start electrode 5 is incompletely melted. It is advantageous from the viewpoint of the furnace structure and economy from being used also as a rod-shaped elevating body for pushing. That is, the provision of the rod-shaped elevating body for pushing the incomplete molten material does not cause problems such as the furnace structure being complicated and the burden of initial costs and running costs being burdened.

Further, in order to push the incompletely molten material A 'into the molten slag B, a rod-like elevating body (including a case also used as the start electrode 5) is raised and lowered so that the tip thereof is lowered into the molten slag B. The time at which this is performed can be set arbitrarily. That is, the lifting and lowering of the rod-shaped lifting and lowering body for pushing the incomplete molten material A ′ into the molten slag B can be performed as needed, and may be performed intermittently in a predetermined fixed cycle, The melting state in the furnace 1 may be detected, and the melting may be performed according to the detection result. Of course, the lifting and lowering of the rod-shaped lifting body into the molten slag B may be performed automatically or manually.

Further, the present invention is applied to a plasma melting furnace configured to maintain the inside of the furnace in a reducing atmosphere by ejecting an inert gas from the tips of the main electrode and the start electrode. The present invention can be applied to a plasma melting furnace having an arbitrary configuration, such as one having no rod-shaped start electrode. Furthermore, in addition to melting incineration residues and fly ash as described above, the present invention is also applicable to a case where various materials to be melted (for example, industrial waste itself containing ash) are melted in a plasma melting furnace. Can be.

[0035]

As can be easily understood from the above description, according to the first or third aspect of the present invention, the incomplete molten material floating on the surface of the molten slag is forcibly forced into the molten slag. Since the molten slag overflows from the molten slag discharge port, it is possible to almost completely prevent incomplete molten material from entering the molten slag without lowering the melting processing capacity of the plasma melting furnace. Granulated slag of high quality and uniform quality can be obtained and its effective use can be achieved.

According to the second or fourth aspect of the present invention, the incomplete molten material floating on the surface of the molten slag is removed from the molten slag by using the start electrode which is not used after the operation of the furnace is started. In addition to the above-described effects, in addition to the above-described effects, there is an effect that the furnace structure is not complicated and problems such as a burden on initial costs and running costs do not occur.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing an example of a plasma melting furnace according to the present invention.

FIG. 2 is a longitudinal sectional front view corresponding to FIG. 1 and showing an operation state different from that of FIG. 1;

FIG. 3 is a longitudinal sectional front view corresponding to FIG. 1 and showing an operation state different from FIGS. 1 and 2;

FIG. 4 is a vertical sectional side view showing a conventional plasma melting furnace.

FIG. 5 is a cross-sectional plan view taken along the line VV of FIG. 4;

[Brief description of reference numerals]

DESCRIPTION OF SYMBOLS 1 ... Plasma melting furnace, 1a ... Peripheral wall part, 1b ... Furnace top part, 1
c: furnace bottom, 2a: melt supply port, 4: main electrode, 5 ...
Start electrode, 6: current collector, 10: molten slag outlet,
24: gas cooling tower, A: melt, A ': incomplete melt, B: molten slag, B': granulated slag, C: inert gas (nitrogen gas), D: exhaust gas, P: plasma.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05B 7/144 H05B 7/144 Z 7/18 7/18 E

Claims (4)

[Claims] 1. A molten material continuously supplied into a furnace from a molten material supply port is melted by plasma arc discharge, and molten slag is continuously overflowed and discharged from the molten slag discharge port to the outside of the furnace. In the plasma melting furnace configured to cause the melted slag, a rod-shaped elevating body whose tip can be lowered into the molten slag in the furnace is provided in the vicinity of the molten material supply port, and the tip of the rod-shaped elevated body is melted slag. A plasma melting furnace characterized in that the incomplete molten material floating on the surface of the molten slag is forcibly sunk into the molten slag by being lowered into the molten slag. 2. At the start of operation of the furnace, between the main electrode suspended from the furnace top and the start electrode, and after the operation starts, between the main electrode and the furnace bottom electrode provided on the furnace bottom, By performing plasma arc discharge, respectively, the material to be melted continuously supplied into the furnace from the material to be melted is melted, and the molten slag is continuously overflowed and discharged from the furnace through the molten slag discharge port. In the plasma melting furnace, which is configured to maintain the inside of the furnace in a reducing atmosphere by ejecting an inert gas from the tip of the main electrode and the start electrode, the start is performed in the vicinity of the melt supply port. Assuming that the tip of the electrode can be lowered into the molten slag in the furnace, by lowering the tip of the start electrode into the molten slag, unsatisfactory floating on the surface of the molten slag occurs. Plasma melting furnace, characterized by being configured to melt so as to sink into forced into the molten slag. 3. The molten material continuously supplied into the furnace from the molten material supply port is melted by plasma arc discharge, and the molten slag is continuously overflowed from the molten slag discharge port to the outside of the furnace. In the operation method of the plasma melting furnace, a rod-shaped elevating body whose tip can be lowered into the molten slag in the furnace is provided near the melt supply port, and the tip of the rod-shaped elevating body is melted. A method for operating a plasma melting furnace, wherein an incomplete molten material floating on the surface of a molten slag is forced into the molten slag by repeatedly descending into the slag. 4. At the start of operation of the furnace, between the main electrode suspended from the furnace top and the start electrode, and after the operation starts, between the main electrode and the furnace bottom electrode provided at the furnace bottom, By performing plasma arc discharge, respectively, the material to be melted continuously supplied into the furnace from the material to be melted is melted, and the molten slag is continuously overflowed and discharged from the furnace through the molten slag discharge port. In the method for operating a plasma melting furnace in which the inert gas is ejected from the tips of the main electrode and the start electrode so as to maintain the inside of the furnace in a reducing atmosphere, in the vicinity of the melt supply port, The tip of the start electrode can be lowered into the molten slag in the furnace, and the tip of the start electrode not used as an electrode is repeatedly lowered into the molten slag. More, the method of driving a plasma melting furnace, characterized in that so as to sink into force the incompletely melt floating on the molten slag surface into the molten slag.