JPH1123164A - Method for detecting damage on wall of plasma melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting damage on the wall of a plasma melting furnace due to corrosion at a refractory wall structure part surely in the early stage without stopping operation of the plasma melting furnace. SOLUTION: The refractory wall structure part 110 of the wall of a furnace comprises an inner circumferential layer 111 of refractory material touching a molten slug 31, and an outer circumferential layer 112 of conductive refractory material surrounding the inner circumferential layer 111 while being insulated electrically therefrom. Damage due to corrosion at the refractory wall structure part 111 is detected by sensing the conducting state of the molten slug 31 interposed between a main electrode and the outer circumferential layer 112. An electrode 140 is embedded in the outer circumferential layer 112 and a current indicator 142 is provided at the earth part 141 thereof. When a corroded part 114 reaches the outer circumferential layer 112, the current indicator 142 senses the conducting state between the main electrode and the outer circumferential layer 112.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to waste (municipal waste,
The present invention relates to a method for detecting damage caused by erosion of a refractory wall structure portion of a furnace wall in a plasma melting furnace for melting and processing incineration ash and fly ash, which are incineration residues of industrial wastes.

[0002]

2. Description of the Related Art In recent years, in order to reduce incineration ash and fly ash (hereinafter abbreviated as "ash") as incineration residues discharged from refuse incinerators and to make them harmless, attention has been paid to ash melting and solidification. And is in practical use. By melting and solidifying the ash, the volume can be reduced to 1/2 to 1/3, while preventing the elution of harmful substances such as heavy metals, reusing molten slag, and extending the life of the final landfill site. Because it becomes.

[0003] As a method of melting and solidifying ash, for example, an arc melting furnace, a plasma arc furnace, an electric resistance furnace or the like is used, and ash is melted and solidified by electric energy; And a method in which ash is melted and solidified by the combustion energy of fuel using a coke bed furnace or the like. In general, when the power generation equipment is co-located with the refuse incineration equipment, the former method using electric energy is adopted, and when the power generation equipment is not co-located, the latter method using combustion energy is adopted. I have.

FIG. 8 shows an example of a plasma melting furnace of a direct current arc discharge graphite electrode type which is juxtaposed with a refuse incineration facility. It is continuously supplied from the hopper 3. In the furnace 1, a graphite main electrode 4 functioning as a negative electrode is hung down from the furnace top, and a furnace bottom electrode 6 functioning as a positive electrode is provided on the furnace bottom. Plasma is generated by the DC power of 600 to 1000 KW (per ton of ash) supplied between the electrodes 4 and 6 by the DC power supply device 8, whereby the ash 30 supplied into the furnace 1 becomes 1400 to 16
The slag is heated to 00 ° C. and becomes a molten slag (hereinafter referred to as “melted slag”) 31. When the furnace 1 is started, since the ash 30 before melting has no conductivity, the start electrode 5 is inserted into the furnace 1 to form a positive electrode, and electricity is supplied to the main electrode 4 via a scrap steel material. Then, after the ash 30 is melted, when the ash 30 is melted, the molten slag 31 has conductivity, so that the positive electrode is switched from the start electrode 5 to the furnace bottom electrode 6. Note that nitrogen gas is supplied from the nitrogen gas supply device 9 into the furnace 1 in order to make the atmosphere a reducing atmosphere. The supply of the nitrogen gas into the furnace 1 is performed through a hollow cylindrical main electrode 4 and a start electrode 5. Further, in the furnace bottom, the furnace bottom electrode 6 and its peripheral portion are air-cooled by the furnace bottom cooling fan 7.

[0005] When the melting of the ash 30 is started, the volatile component and the carbon component contained in the ash 30 become a gas body 34 containing carbon monoxide partially oxidized. The gas body 34 was discharged from the molten slag outlet 10 provided on the furnace wall 1 a, which is the peripheral wall of the furnace 1, into the combustion chamber 12, and was completely burned in the combustion chamber 12 by the supply of combustion air by the combustion air fan 13. Above, it is cooled by the cooling air from the exhaust gas cooling fan 14, and is discharged from the chimney 17 through the bag filter 15 by the induction ventilator 16. The molten fly ash 32 captured by the bag filter 15 is sent to the fly ash reservoir 19 by the molten fly ash conveyor 18. On the other hand, non-combustible components contained in the ash 30 (metals such as iron, glass, sand, etc.)
Is in a molten state, and the molten slag 31 continuously overflows from the molten slag outflow port 10 and falls into a slag water cooling tank 20 filled with water to become granulated slag 33, and the slag storage 22 by the slag unloading conveyor 21. Sent to When the melting furnace 1 is stopped, the molten slag 31 is cooled in order to prevent the molten slag 31 in the furnace 1 from cooling and solidifying.
Hot water is removed by tap holes 11 provided in the furnace wall 1a corresponding to the bottom level of the furnace 1, and the furnace 1 is emptied.

The furnace wall 1a, which is the peripheral wall of the plasma melting furnace 1, generally has a water cooling jacket 120 (or a water spray means, an air cooling means, or the like) on the outer peripheral surface of the refractory wall structure portion 110 in contact with the molten slag 31. Although it is configured to cool, as a conventional typical furnace wall structure, as shown in FIG.
A refractory material (for example, a carbon-based, C-SiC-based, SiC-based, or chromium-based refractory material) capable of withstanding a high temperature of about 600 ° C. and a water-cooling jacket 120 surrounding the refractory material.
With a structure in which cooling water 122 is supplied into a steel plate jacket 121, and further, an electrically insulating heat insulating material layer 130 is interposed between the fire-resistant wall structure portion 110 and the jacket 121 (hereinafter referred to as “conventional”). Furnace walls) are well known.

[0007]

However, in such a conventional furnace wall 1a, there is a problem that the fire wall structure 110 is damaged by erosion.

That is, the refractory wall structure portion 110 is made of a refractory material capable of sufficiently withstanding the high temperature in the furnace 1 as described above, but is exposed to the high temperature and comes into contact with the corrosive molten slag 31. , As shown in FIG.
Easily eroded locally. The damage due to such erosion is particularly remarkable in a portion corresponding to a liquid level of the molten slag 31 (hereinafter, referred to as a “metal surface”) and a peripheral portion of the molten slag outlet 10.

Then, such a fire-resistant wall structure portion 110
Damaged portion due to erosion (hereinafter referred to as “eroded portion”) 11
If operation is continued with 4 left unattended, erosion will progress,
The erosion depth exceeds the thickness of the fire wall structure part 110,
Thermal destruction of the entire melting furnace 1 may occur, or the jacket 121 may be damaged.
May be damaged, causing an extremely dangerous situation such as the internal water 122 leaking and exploding (see the chain line in FIG. 9B). Therefore, the erosion of the refractory wall structure part 110 detects this as early as possible, and
Repair is necessary at a stage where the erosion depth does not reach the thickness of the fire-resistant wall structure portion 110.

However, conventionally, the fire wall structure 110
Since there is no way to detect damage due to erosion during operation, there is no other way than to confirm the furnace wall damage by stopping the operation of the furnace 1. Therefore, in order to detect furnace wall damage early, the operation must be stopped frequently, and continuous operation cannot be performed for a long period of time. . Moreover,
It is difficult to accurately determine the degree of erosion of the refractory wall structure portion 110 depending on the surface (inner peripheral surface) of the refractory wall structure portion 110, etc. It is easy to miss the time.

[0011] The present invention has been made in view of such a point, without stopping the operation of the plasma melting furnace,
An object of the present invention is to provide a furnace wall damage detection method capable of accurately detecting damage caused by erosion of a fire-resistant wall structure portion in a furnace wall at an early stage.

[0012]

According to the present invention, there is provided a method for detecting damage to a furnace wall of a plasma melting furnace, comprising the steps of: forming a refractory wall structure portion of a furnace wall with an inner peripheral layer made of a refractory material in contact with molten slag; It is composed of an outer peripheral layer made of a conductive refractory material surrounding it in an electrically insulated state, and by detecting an energized state through a molten slag between the main electrode and the outer peripheral layer, the refractory This is to detect damage due to erosion of the wall structure. The detection of such a current-carrying state can be performed, for example, by burying a grounded electrode in the outer peripheral layer and using a current indicator provided in the ground portion. Alternatively, a voltage may be applied to a conductor buried in the outer peripheral layer, and the measurement may be performed by a current indicator provided on the conductor. Furthermore, both the inner and outer layers are made of a conductive refractory material, and the inner and outer layers are electrically insulated with an electric insulator, and a voltage is applied between the inner and outer layers to change the current. , The energized state can be sensed.

In other words, when the fire wall structure is damaged by erosion, the erosion depth exceeds the thickness of the inner peripheral layer, and the molten slag enters from the eroded part and comes into contact with the outer peripheral layer, the molten slag is damaged. Has conductivity, a current flows between the main electrode and the conductive outer peripheral layer via the molten slag. On the other hand, it is possible to easily confirm and detect whether or not the energized state is established without stopping the furnace operation by an appropriate method as described above. Therefore, when the erosion exceeds the thickness of the inner layer and reaches the outer layer, damage to the fire-resistant wall structure can be accurately detected, so that the repair time is not missed and continuous operation is safe. Can be performed.

[0014]

FIG. 1 is a block diagram showing an embodiment of the present invention.
3 or 4 to 6 will be described in detail.

FIGS. 1 to 3 show a first embodiment, and FIGS.
FIG. 6 shows the second embodiment, and each embodiment relates to an example in which the present invention is applied to the furnace wall 1a of the plasma melting furnace 1 shown in FIG.

That is, in the first embodiment,
As shown in FIGS. 1 and 2, the furnace wall 1 a, which is the peripheral wall of the plasma melting furnace 1, is formed in a cylindrical shape in which the outer peripheral surface of the fire-resistant wall structure portion 110 is covered with a water-cooling jacket 120. Unlike the conventional furnace wall shown in FIG.
10 has a three-layer structure including an inner peripheral layer 111 in contact with the molten slag 31, an outer peripheral layer 112 surrounding the same, and an electric insulator 113 interposed between the two layers 111 and 112.

The inner peripheral layer 111 is made of a refractory material similar to that used for a conventional furnace wall and has a cylindrical shape. As the refractory material, a material having sufficient heat resistance to a high-temperature atmosphere in the furnace 1, for example, a carbon-based, C-SiC-based, SiC-based, or magnesia-chromium-based material capable of withstanding a high temperature of about 1600 ° C. is used. Is done. The inner peripheral layer 111 and the outer peripheral layer 1
Since an electrical insulator 113 is interposed between the inner peripheral layer 111 and the inner peripheral layer 111, a conductive refractory material (for example, a carbon-based refractory material) is used as a constituent material of the inner peripheral layer 111.

The outer layer 112 is made of a refractory material having excellent conductivity,
For example, it is made of a C-SiC-based or carbon-based refractory material in a cylindrical shape, and surrounds the inner peripheral layer 111 in a state of being electrically insulated by the electric insulator 33 interposed therebetween. The electric insulator 33 is made of an electric insulating material having excellent heat resistance such as spinel and Si ₃ N ₄ .

Incidentally, the thickness of the fire-resistant wall structure portion 110 composed of the inner peripheral layer 111 and the outer peripheral layer 112 is
Similarly to the case where 10 is composed of a single refractory material layer, it is set according to furnace conditions (furnace shape, size, etc.), but the thickness Ta of the inner peripheral layer 111 and the thickness Tb of the outer peripheral layer 112 are different from each other. Usually, it is preferable to set the ratio so that Ta: Tb = 1 to 3: 1. For example, fire wall structure 110
Is 270 mm, Ta = 135-2
It is preferable to set 00 mm and Tb = 70 to 135 mm.

The outer peripheral surface of the outer peripheral layer 112 is covered with a water-cooling jacket 120 with a heat insulating layer 130 having electrical insulation interposed therebetween, similarly to the conventional furnace wall. That is, the outer peripheral layer 112 is in a state of being electrically insulated from both the inner peripheral layer 111 and the water cooling jacket 120 arranged on both sides in the thickness direction. The water cooling jacket 120 has a structure in which cooling water 122 is supplied into a jacket 121 made of a steel plate, similarly to a conventional furnace wall.

1 and FIG.
As shown in the figure, it is arranged at the boundary with the electric insulator 113,
A rod-shaped electrode 140 that is curved along the horizontal is embedded therein. The electrode 140 is grounded, and a current indicator 142 is provided at the ground portion. That is, a ground wire 141 to which a current indicator 142 is attached is connected to the electrode 140, and as described later, the main electrode 4 connected to the cathode of the DC power supply 8 and the conductive outer layer 1
The current indicator 142 is actuated by the current flowing through the electrode 140 when a current flows between the electrodes 12 and 12 via the molten slag 31. In this example, when the current indicator 142 is actuated, it is confirmed by the ammeter pointer that a current has flowed through the electrode 140 (that is, a current is flowing between the main electrode 4 and the outer peripheral layer 112). Yes, and appropriate safety measures are in place.
Specifically, for example, an alarm is issued, and the operation of the plasma melting furnace 1 is urgently stopped.

Thus, in the first embodiment, damage by erosion of the refractory wall structure portion 110 of the furnace wall 1a is detected by the method of the present invention as follows.

That is, the inner peripheral portion of the fire-resistant wall structure portion 110, that is, the inner peripheral layer 111 is exposed to the high-temperature atmosphere in the furnace 1 and comes into contact with the corrosive molten slag 31, so that it mainly corresponds to the molten metal surface. Although it is locally eroded in the height portion and in the peripheral portion of the molten slag outlet 10,
In a state where the depth of the eroded portion 114 does not exceed the thickness Ta of the inner peripheral layer 111, the current is not supplied between the main electrode 4 and the outer peripheral layer 140 and the electrode 140 embedded therein, and the current indicator 142 Does not work (see FIG. 3A).

However, by continuing the furnace operation, the erosion progresses, the depth of the eroded portion 114 exceeds the thickness Ta of the inner peripheral layer 111, and the electric insulator 140 between the inner and outer peripheral layers 111 and 112 is removed. When the slag 31 also erodes and breaks, the molten slag 31 having conductivity invades the eroded portion 114 and comes into contact with the outer peripheral layer 112, so that the main electrode 4 and the outer peripheral layer 14 are in contact with each other.
0 and the electrode 140 embedded therein are energized via the molten slag 31 (see FIG. 3B). As a result, the degree of erosion, that is, the depth of the eroded portion 114 is changed to the thickness Ta of the inner peripheral layer 111 (more precisely, the inner peripheral layer 111 and the electrical insulator 113) by detecting such an energized state by an appropriate detecting means. (Total thickness) can be accurately grasped, and appropriate safety measures can be taken. In this example, the current indicator 142 provided as a detecting means is operated, and as a safety measure, an alarm is issued and the plasma melting furnace 1 is emergency stopped. After the operation is stopped, the inside of the furnace 1 is inspected, and the eroded portion 114 is repaired. At this time, the outer peripheral layer 112 is not eroded, and the inner peripheral layer 1 which is a part of the fire wall structure portion 110 is not eroded.
11 (and the electrical insulator 113) can be repaired economically and easily.

As described above, according to the method of the present invention, the degree of erosion of the refractory wall structure portion 110 can be accurately grasped during the operation of the plasma melting furnace, that is, the eroded portion 114 reaches a certain depth. It is possible to accurately grasp whether or not the erosion is in progress, and if the erosion is not progressing so much, stop the furnace operation unnecessarily to confirm the erosion or proceed to the stage where the erosion induces a dangerous situation Therefore, it is possible to ensure the safe continuous operation of the plasma melting furnace 1 for a long period of time and the appropriate maintenance based on the determination of the appropriate repair time without causing the problem of continuing the furnace operation despite the above.

Also, in the second embodiment, FIG.
As shown in FIG. 5, by forming the inner peripheral layer 111 from a non-conductive refractory material (for example, a chromium-based refractory material),
The outer peripheral layer 11 made of a conductive refractory material without interposing the electric insulator 113 between the two layers 111 and 112.
2 is electrically insulated from the inner peripheral layer 111. Also,
The electrode 140 is buried in a substantially central portion of the outer peripheral layer 112 in the thickness direction. These points, namely, the point that the inner peripheral layer 111 is made of a non-conductive refractory material, the point that both layers 111 and 112 are brought into contact without the interposition of the electric insulator 113, and the electrode 140 is the thickness direction of the outer layer 112 The furnace wall 1a has the same structure as that of the first embodiment except that the furnace wall 1a is buried in a substantially central portion of the furnace wall 1a. The ratio between the thickness Ta of the inner peripheral layer 111 and the thickness Tb of the outer peripheral layer 112 is also the same as in the first embodiment.

Thus, even in the second embodiment, damage due to erosion of the refractory wall structure portion 110 of the furnace wall 1a is detected by the method of the present invention in the same manner as in the first embodiment. Is done.

That is, in a state where the depth of the eroded portion 114 does not exceed the thickness Ta of the inner peripheral layer 111, a current is not conducted between the main electrode 4 and the outer peripheral layer 140 and the electrode 140 embedded therein. The current indicator 142 does not operate (FIG. 6)
(A)). However, the erosion progresses and the erosion portion 114
If the depth exceeds the thickness Ta of the inner peripheral layer 111, the molten slag 31 having conductivity penetrates into the eroded portion 114 and comes into contact with the outer peripheral layer 112, so that the main electrode 4 and the outer peripheral layer 14.
0 and the electrode 140 buried therein are energized via the molten slag 31, the current indicator 142 is activated, an alarm is issued, and the plasma melting furnace 1 is stopped immediately (FIG. 6 ( B)).

It should be noted that the present invention is not limited to the above-described embodiments, and can be appropriately improved and changed without departing from the basic principle of the present invention. In particular, any means may be used to detect that the current is flowing between the main electrode 4 and the outer peripheral layer 112, and the shape of the electrode 140 and the embedding position in the outer peripheral layer 112 are also arbitrary. In short, the eroded portion 114 reaches the inner peripheral surface of the outer layer 112 and the main electrode 4
Any material can be used as long as it can be detected that the state between the outer peripheral layer 112 and the outer peripheral layer 112 is energized via the molten slag 31. For example, when the fire-resistant wall structure portion 110 is configured as in the first embodiment, as shown in FIG.
A current may be sensed by applying a voltage to the conductor 144 embedded in the wire 12 and detecting the change with the current indicator 143. Alternatively, a voltage may be applied between the conductive inner peripheral layer 111 and the electrical insulator 113, and a current change may be detected to detect an energized state.

[0030]

As can be easily understood from the above description, according to the present invention, it is possible to accurately detect the degree of erosion of the refractory wall structure without stopping the furnace operation. It is possible to reliably prevent erosion from progressing to a certain degree or more (more than the thickness of the inner peripheral layer (or the total thickness of the inner peripheral layer and the electrical insulator)). Therefore, the furnace can be operated safely for a long period of time while preventing the danger that the erosion exceeds the fire wall structure portion, and the ash melting process can be performed efficiently. In addition, it is only necessary to repair a part of the fire-resistant wall structure (the inner circumferential layer or the inner circumferential layer and the electrical insulator), and the repair is extremely difficult as compared with the case where the entire fire-resistant wall structure including the outer circumferential layer is repaired. It can be performed economically and easily.

[Brief description of the drawings]

FIG. 1 shows a first example of a furnace wall structure to which the method according to the present invention is applied.
It is a vertical side view of the principal part which shows an example.

FIG. 2 is a cross-sectional plan view taken along the line II-II of FIG.

FIG. 3 is a longitudinal sectional side view corresponding to FIG. 1 showing an eroded state of a fire-resistant wall structure portion.

FIG. 4 shows a second example of the furnace wall structure to which the method according to the present invention is applied.
It is a vertical side view of the principal part which shows an example.

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

FIG. 6 is a longitudinal sectional side view corresponding to FIG. 4, showing an eroded state of a fire-resistant wall structure portion.

FIG. 7 is a vertical sectional side view corresponding to FIG. 1 showing a modification of the energization state sensing means.

FIG. 8 is a vertical sectional side view showing an example of a plasma melting furnace.

FIG. 9 is a vertical sectional side view of a main part showing a conventional furnace wall structure.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Plasma melting furnace, 1a ... Furnace wall, 4 ... Main electrode, 30 ...
Ash, 31: molten slag, 110: fire-resistant wall structure, 11
DESCRIPTION OF SYMBOLS 1 ... Inner peripheral layer, 112 ... Outer peripheral layer, 113 ... Electric insulator, 1
14: eroded portion, 120: water-cooled jacket, 130: electrically insulating and heat-insulating material layer, 140: electrode, 141: ground wire (ground portion), 142: current indicator.

Claims (2)

[Claims] A refractory wall structure portion of a furnace wall is constituted by an inner peripheral layer made of a refractory material in contact with molten slag and an outer peripheral layer made of a conductive refractory material surrounding the inner layer in an electrically insulated state. do it,
Wall damage detection of a plasma melting furnace characterized by detecting damage caused by erosion of a fire-resistant wall structure part by detecting an energized state through a molten slag between a main electrode and an outer peripheral layer. Method. 2. An earthed electrode is buried in the outer peripheral layer,
2. The method according to claim 1, wherein a current indicator provided at the ground portion detects an energized state between the main electrode and the outer peripheral layer.