JPH1019230A - Method for melting treatment of refuse inclineration ash and melting furnace therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a melting method and a melting furnace capable of stably melting refuse incineration ash without damaging refractories of a refuse incineration ash melting furnace and without abrasion of electrodes of an arc heating device. Is what you do. SOLUTION: A furnace wall (1) provided with a slag tap hole (2) and a molten salt overflow hole (3), a gutter (4a, 4b) connected to each hole, and a furnace wall (1) are separated. In the furnace, each of the hearths (5) is made of a water-cooled metal member, and the municipal solid waste incineration ash (12) is melted by generating an arc on a molten salt by an arc generator to form an arc. While forming the self-coating layer (13), the generated molten slag (9) is discharged from the slag tap hole (2) through the gutters (4a, 4b), and the generated molten salt is discharged from the overflow hole (3). Gutter (4
a, 4b), and the generated metal is solidified on the hearth and taken out by lowering the hearth (5).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detoxifies and reduces the volume of refuse incineration ash, especially fly ash and electric furnace dust collected when incinerating municipal waste, sewage sludge, industrial waste, etc. And a melting furnace thereof.

[0002]

2. Description of the Related Art Waste incineration ash such as municipal waste contains harmful substances such as dioxins and heavy metals. In addition, there is a problem that the incineration ash has a low specific gravity and is bulky.
In the case of dumping in a landfill as it is, not only is it costly to take measures to prevent elution of harmful substances, but in recent years, it has become difficult to secure a space for dumping.

[0003] Therefore, as a method of detoxifying garbage incineration ash and greatly reducing its volume, its effective utilization is as follows.
Various methods of making molten slag have been developed, some of which have been adopted by local governments.

[0004] However, two types of incineration ash are usually generated, main ash and fly ash, and the conventional method of melting incineration ash has reached a practical level with respect to the melting of main ash. Some have done it.

[0005] However, a practical method has not yet been established for fly ash. The reason will be described below.

Generally, fly ash contains a large amount of salts mainly containing chlorides of sodium and potassium. When this is melted, a molten salt mainly containing the above-mentioned salts and a salt mainly containing other oxides are contained. The molten slag is completely detoxified. However, since the molten salt contains some leaching harmful substances, it is necessary to separate and extract the molten slag and the molten salt.

Therefore, a melting method using electric power is known as a melting method in which a molten salt is generated in an upper layer portion by a difference in specific gravity and a molten slag is generated in a lower layer portion to separate and extract the two.

[0008] However, since the melting by the conventional melting furnace using electric power is melting in a furnace in which the furnace body is entirely lined with a refractory, the molten salt only intensely erodes the refractory of the furnace body. In addition, because the molten salt has extremely high fluidity, it can penetrate into refractories, and in addition to the characteristics of the molten salt having a low electrical resistance, a leakage phenomenon and a short-circuit phenomenon can occur, and stable operation can be continued. It was not a practical melting method.

However, fly ash contains a large amount of heavy metals and harmful substances that are particularly easy to elute, so fly ash is designated as a specially controlled general waste. Therefore, a practical melting method has been strongly established. Was desired.

In view of the above, the melting treatment method of Japanese Patent Application No. 6-300272 filed by one of the applicants of the present invention is practically applicable when the fly ash is melted in a single-phase electric resistance melting furnace that does not use refractories. Fly ash melting was realized.

FIG. 3 is a longitudinal sectional view of an embodiment of a single-phase electric resistance melting furnace not using a refractory in the above-mentioned application, in which a bottom electrode is provided at the center of the hearth. A furnace wall 1 made of a water-cooled metal member having a slag tap hole 2 and a gutter 4a made of a water-cooled metal member connected to the hole 2 and provided with an electric insulator 14 interposed therebetween. It is composed of a hearth 5 made of a water-cooled metal member provided with a bottom electrode 6 and a hearth elevating device 7, and an upper electrode 11.

In the above configuration, when the upper electrode 11 is lowered, the refuse incineration ash 12 is charged and energized, an arc is generated, the refuse incineration ash 12 is melted, and the upper electrode 11 is raised as the melting progresses.

In the steady melting state, the refuse incineration ash 12 is melted to form a molten slag layer 9, a molten salt layer 10, and an ingot 8 in which the metal contained in the refuse incineration ash is melted and dropped to form an ingot 8, which is cooled with water. Self-coating layer 1 where molten slag and molten salt solidify and replace refractory
3 is formed.

The metal contained in the refuse incineration ash is melted, dropped on the hearth 5 and solidified to form an ingot, and the refuse incineration ash is lowered by the hearth elevating device 7 in accordance with the growth thereof. 12 is melted.

When the ingot has grown to a predetermined size,
After the melting is interrupted and the molten slag 9 and the molten salt 10 are discharged, the water-cooled hearth 5 is lowered by the hearth lifting device 7 to take out the ingot 8.

Since the self-coating layer 13 has a function as a heat and electric insulator, in the type in which the hearth electrode is provided in the center of the hearth, even in the fly ash containing a large amount of salt, electrically stable melting is achieved. It becomes possible.

FIG. 4 is a longitudinal sectional view of an embodiment of the three-phase electric resistance melting furnace which does not use a refractory in the above-mentioned application and which does not have a bottom electrode in the center of the hearth. A gutter 4a made of a water-cooled metal member is connected to a slag tap hole 2 provided on a furnace wall 1 made of water. At the lower part of the furnace wall 1, a furnace floor 5 made of a water-cooled metal member is provided separately from the furnace wall 1. The hearth 5 is provided so as to be able to ascend and descend by a hearth elevating device 7, and three arc electrode rods 11 using three phases are arranged on the upper part of the furnace body. At the start of the furnace, a scrap iron layer 12b is formed on the refuse incineration ash slag 12a, on which the waste incineration ash is charged.

Incidentally, when fly ash is melted in this three-phase electric resistance melting furnace, molten salt having high conductivity is generated around the electrodes, and current flows between the electrodes, so that continuous melting is difficult. Was.

[0019]

In the above single-phase electric resistance melting furnace, a large amount of molten salt precipitates as the fly ash melting is continued, so that the furnace wall must be made higher than necessary. Further, since the melting proceeds while the upper electrode 11 is immersed in the molten salt layer 10 and the molten slag layer 9, the molten salt layer 1
The electrode part immersed in 0 has an anomalous wear and is liable to break the tip of the upper electrode from the wear part 15, and has a drawback that the amount of wear is large.

Further, as a feature of the electric resistance melting method, most of the salts contained in the fly ash are formed as a molten salt in a large amount, instead of generating little molten fly ash. This molten salt contains some eluting harmful substances, and requires subsequent treatment. On the other hand, in the molten fly ash, lead, zinc and the like are concentrated, and these can be used as non-ferrous raw materials. Therefore, it is advisable to suppress the generation of molten salt as much as possible and to concentrate heavy metals in molten fly ash. From this, since the molten salt temperature is slightly lowered because the salt is melted by the heat of the molten slag, it is disadvantageous to actively volatilize the molten salt.

Therefore, the present invention provides a method for stably incinerating refuse incineration ash without damaging the refractory of the refuse incineration ash melting furnace and without abrasion of the electrodes of the arc heating device, and actively volatilizing the molten salt. An object of the present invention is to provide a melting method capable of melting and a melting furnace thereof.

[0022]

SUMMARY OF THE INVENTION The melting treatment method of the present invention comprises a furnace wall having a slag tap hole and a molten salt overflow hole, a gutter connected to each hole, and a hearth separated from the furnace wall. In the furnace made of water-cooled metal members, the incinerated municipal incineration ash is melted by generating an arc on the molten salt by an arc generator and forming a self-coating layer on the inner surface of the furnace body. The molten slag is discharged from the slag tap hole via a gutter, the generated molten salt is discharged from the overflow hole via a gutter so that a large amount of molten salt is not stored, and the generated metal solidifies on the hearth. Then, it is taken out by lowering the hearth.

Further, the melting furnace of the present invention has a furnace wall provided with a slag tap hole and a molten salt overflow hole, a gutter connected to each hole, and a metal floor which is separated from the furnace wall by water cooling. A furnace body formed by the member;
A heating device provided with a hearth raising / lowering means and an arc generator for generating an arc on the molten salt is provided.

As the arc generator, a transfer type plasma torch or an arc generator having a non-consumable arc electrode rod is used.

In the present invention, since the electrodes are melted in the water-cooled furnace without being immersed in the molten salt layer, the electrodes can be protected from the molten salt layer without the furnace body being eroded by the molten salt. Further, since the high-heat arc contacts the thin-layer molten salt, the molten salt can be forcibly volatilized.

[0026]

FIG. 1 is a sectional view of a melting apparatus using a non-consumable electrode for performing a melting method of the present invention.

In FIG. 1, a slag tap hole 2 and a molten salt overflow hole 3 are provided on a furnace wall 1 made of a water-cooled metal member, and a gutter 4a made of a water-cooled metal member is provided in each of the holes 2 and 3. , 4b are connected.
At the lower part of the furnace wall 1, a furnace floor 5 made of a water-cooled metal member is provided separately from the furnace wall 1. The hearth 5 is provided so as to be able to move up and down by a hearth lifting device 7.

The heating device includes an arc electrode rod 16 above the furnace body.
And an arc generator in which a hearth bottom electrode 6 is provided on a hearth 5 via an electrical insulator 14. The arc electrode rod 16 and the furnace bottom electrode 6 are connected to a power supply 17.

In the above configuration, the arc electrode rod 16 and the furnace bottom electrode 6 are short-circuited, an arc is generated, and the incineration ash is melted by arc heat.

In a steady state, the metal contained in the molten slag layer 9, the molten salt layer 10, and the incineration ash is melted and dropped to form an ingot 8, and the furnace wall 1, the gutters 4a, 4b,
On the surface of the hearth 5, the molten slag and the molten salt are solidified to form a self-coating layer 13 that substitutes for a refractory.

During the melting, the arc electrode rod 16 generates an arc without being immersed in the molten salt layer 10.

When the molten slag layer 9 and the molten salt layer 10 become deeper due to the melting of the refuse incineration ash, the molten slag layer 9 and the molten salt layer 10 are discharged from the slag tap hole 2 and the molten salt overflow hole 3, and the respective layers 9, 1
0 is maintained at a predetermined level.

The metal contained in the refuse incineration ash is melted, dropped on the hearth 5 and solidified to form an ingot, and the incineration ash is lowered while lowering the hearth 5 by the hearth lifting device 7 in accordance with the growth. 12 is melted.

When the ingot has grown to a predetermined size,
After the melting is interrupted and the molten slag 9 and the molten salt 10 are discharged, the water-cooled hearth 5 is lowered by the hearth lifting device 7 to take out the ingot 8.

In the present invention, the self-coating layer 13 is adhered to the porous dry incineration ash layer formed on the surface of the water-cooled furnace wall, the solid layer of the molten salt formed on the surface thereof, and the surface of the solid layer. The slag layer is layered, the incinerated ash layer has high heat insulation and insulation properties, and the solid layer has high insulation properties.Furthermore, since the arc electrode rod is not immersed in molten salt, the arc electrode rod is made of molten salt. No damage,
The melting furnace can be operated in an electrically stable state.

FIG. 2 is a longitudinal sectional view of a melting furnace using a transfer type plasma torch for carrying out the melting method of the present invention.

In FIG. 2, the slag tap hole 2 and the molten salt overflow hole 3 are provided on a furnace wall 1 made of a water-cooled metal member, as in the above-described embodiment. Are connected to gutters 4a and 4b made of a water-cooled metal member. In the lower part of the furnace wall 1,
A hearth 5 made of a water-cooled metal member separated from the furnace wall 1
Is provided. The hearth 5 is provided so as to be able to move up and down by a hearth lifting device 7.

The heating device includes a plasma gas 2 at the upper part of the furnace body.
A plasma torch 19 which is activated by zero is provided, and a plasma generator is provided in which the hearth electrode 5 is provided on the hearth 5 via an electrical insulator 14. Plasma torch 19
The furnace bottom electrode 6 is connected to a power supply 17.

In the above configuration, after incineration ash is charged into the furnace body, a plasma arc is generated in the plasma torch 19 by the plasma gas 20 and a plasma initial ignition power supply (not shown), and the radiant heat generated by the plasma flame 21 and the Joule generated by the energization. Melt incineration ash by heat.

In a steady state, the metal contained in the molten slag layer 9, the molten salt layer 10, and the incineration ash is melted and dropped to form an ingot 8, and the furnace wall 1, the gutters 4a, 4b,
On the surface of the hearth 5, the molten slag and the molten salt are solidified to form a self-coating layer 13 that substitutes for a refractory.

During the melting, the plasma torch 19 generates the plasma flame 21 without being immersed in the molten salt layer 10.

The subsequent operation is similar to that of the above embodiment, and the molten slag layer 9 and the molten salt layer 10 are melted by melting the incineration ash.
Is deeper, the water is discharged from the slag tap hole 2 and the molten salt overflow hole 3 to maintain each of the layers 9 and 10 at a predetermined level.

The metal contained in the refuse incineration ash is melted, dropped on the hearth 5 and solidified to form an ingot, and in accordance with its growth, the refuse incineration ash 12 Is melted.

When the ingot has grown to a predetermined size,
After the melting is interrupted and the molten slag 9 and the molten salt 10 are discharged, the water-cooled hearth 5 is lowered by the hearth lifting device 7 to take out the ingot 8.

Also in this embodiment, since the self-coating layer 13 is formed on the wall surface of the water-cooled furnace and the plasma torch is not immersed in the molten salt, the plasma torch is not damaged by the molten salt and the melting furnace is electrically connected. Operation can be performed in a stable state.

In the method using plasma, current flows through the molten salt layer or molten slag layer through the plasma arc through the electrode, so that there is no fear of abnormal melting of the plasma torch and the amount of wear can be reduced. It is.

[0047]

【The invention's effect】

(1) The present invention does not immerse the plasma torch and the arc electrode rod, which are the plasma flame and the arc generating electrode, in the molten salt. There is no worry about damage to the arc generating electrode. In the case of the arc electrode rod, the electrode consumption is small, the unit price of the electrode is reduced, and
There is an effect that the trouble of adding the electrodes is largely omitted.

(2) Since the furnace wall and hearth have a water-cooled structure without using refractories, not only incineration ash which is a mixture of fly ash containing a large amount of salt and main ash but also fly ash alone can be melted. There is no severe erosion of the refractory due to salt, and there is no electrical trouble such as short circuit or short circuit due to the formation of the self-coating layer. Therefore, there is an effect that practical melting of incineration ash can be realized.

(3) Advantageously, heavy metals can be concentrated in the molten fly ash, and the recovery and utilization of molten metals can be achieved by minimizing the amount of molten salt required for post-treatment and volatilizing the molten salt positively. Melting can be realized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a melting apparatus using a non-consumable electrode rod for performing a melting method of the present invention.

FIG. 2 is a sectional view of a melting furnace using a plasma arc torch for performing the melting method of the present invention.

FIG. 3 is a longitudinal sectional view of a single-phase electric resistance melting furnace using no refractory, in which a bottom electrode is provided at the center of the hearth.

FIG. 4 is a vertical sectional view of an electric resistance melting furnace not using a refractory and having no furnace bottom electrode.

[Description of Signs] 1 furnace wall 2 slag tap hole 3 molten salt overflow hole 4a, 4b gutter 5 hearth 6 hearth electrode 7 hearth lifting / lowering device 8 ingot 9 molten slag (layer) 10 molten salt (layer) 11 upper electrode REFERENCE SIGNS LIST 12 refuse incineration ash 12 a litter 12 b scrap iron 13 self-coating layer 14 electrical insulator 15 worn part 16 arc electrode rod 17 power supply 19 plasma torch 20 plasma gas 21 plasma flame

Claims (3)

[Claims] 1. A furnace wall provided with a slag tap hole and a molten salt overflow hole, a gutter connected to each hole, and a furnace floor separated from the furnace wall are charged in a furnace body made of a water-cooled metal member. The generated garbage incineration ash is melted by generating an arc on the molten salt by an arc generator, forming a self-coating layer on the inner surface of the furnace body, and discharging the generated slag from the slag tap hole via a gutter. A method for melting refuse incineration ash, wherein generated molten salt is discharged from an overflow hole via a gutter, and generated metal is solidified on a hearth and taken out by lowering the hearth. 2. A furnace body including a furnace wall having a slag tap hole and a molten salt overflow hole, a gutter connected to each hole, and a furnace floor separated from the furnace wall, each being formed of a water-cooled metal member. A refuse incineration ash melting furnace, comprising: a furnace floor raising / lowering means; and a heating device having an arc generator for generating an arc on the molten salt. 3. The incineration ash melting furnace according to claim 2, wherein the arc generator is an arc generator having a transfer type plasma torch.