JPH09329318A - Separation method of molten salt and molten slag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the qualities molten salt and molten slag in matter melting processed when city garbage burned ash is melted for a processing of making the ash unharmful and for a processing of reutilizing the ash. SOLUTION: The present separation method of molten salt and molten slag is adapted such that city garbage burned ash is melted in a first melting furnace 1 comprising a water cooling metal member to produce molten salt, molten slag 9, and ingot 8 being matter subjected to melting processing, and then the molten salt 10 and the molten slag 9 in the matter are transferred to a second melting furnace 26 comprising a water cooling metal part where the molten salt 10 and the melted slag 9 are separated into two owing to a difference therebetween and are separately independently taken out to the outside of the system.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to incinerated ash generated when incinerating municipal solid waste such as municipal solid waste, sewage sludge, industrial waste, and the like, and particularly to molten salt and molten slag produced when the fly ash is melted. The present invention relates to a method of improving quality and separating.

[0002]

2. Description of the Related Art Municipal solid waste incineration ash contains harmful substances such as dioxins and heavy metals. Moreover, incineration ash has a problem that it has a small specific gravity and is bulky, and when it is dumped directly to a landfill, it is a harmful substance. Not only is it costly to take measures to prevent elution, but in recent years it has become difficult to secure a dumping space.

[0003] Therefore, as a method of making the incinerated ash of municipal solid waste harmless and reducing its volume significantly and making effective use of it, various molten slag forming methods have been developed, and some of them are adopted by local governments. . However, two types of ash and fly ash are usually generated in the incineration ash of municipal solid waste, and the conventional method of melting incinerated ash of municipal solid waste has reached a practical range for melting the main ash. There is also.

However, the actual situation is that a practical method has not yet been established for fly ash. The reason will be described below. Fly ash generally contains a large amount of salts mainly containing chlorides of sodium and potassium. When this is melted, molten salts mainly composed of the above salts and other salts mainly composed of oxides are melted. Although the slag and the molten slag are completely detoxified, the molten salt contains some leaching harmful substances, so it is necessary to separate and take out the molten slag and the molten salt. Therefore, as a melting method in which molten salt is generated in the upper layer portion and molten slag is generated in the lower layer portion due to the difference in specific gravity, and both are separated and taken out, a melting method using electric power is known.

However, conventional melting using a melting furnace using electric power is melting in a furnace in which the entire refractory body is lined with refractory, so the molten salt only erodes the refractory body of the furnace body violently. Not only that, because the molten salt has extremely high fluidity, it penetrates into the refractory and, in addition, the electrical resistance of the molten salt is small, and the leakage and short-circuit phenomena occur, so that stable operation can be continued. No, it was not a practical melting method.

In addition, since fly ash contains a large amount of heavy metals and harmful substances that are particularly liable to be eluted, fly ash is designated as specially controlled general waste, and therefore a practical melting treatment method is strongly established. Was wanted. Therefore, the melting treatment method applied by one of the present applicants and disclosed in Japanese Patent Application No. 6-300272 is a practical fly ash melting method in which the fly ash is melted in a single-phase electric resistance melting furnace that does not use a refractory. Could be realized.

FIG. 2 is a longitudinal sectional view of an embodiment of a single-phase electric resistance melting furnace which does not use a refractory material applied for the above-mentioned application. That is, in FIG. 2, the electric resistance melting furnace includes a furnace wall 1 made of a water-cooled metal member having a slag tap hole 2 and a molten salt overflow hole 3, and each of the holes 2, 2.
3 made of water-cooled metal members connected to 3
And a furnace comprising a water-cooled metal member provided separately from the water-cooled furnace wall 1 and provided with a furnace bottom electrode 6 and a hearth elevating device 7 provided via an electric insulator 14. Floor 5
And the upper electrode 11.

In the above structure, when the upper electrode 11 is lowered, and the municipal solid waste incineration ash 12 is charged to supply electricity, an arc is generated and the municipal solid waste incinerator 12 is melted, and the upper electrode 11 is raised as the melting progresses. . In a steady molten state, the municipal solid waste incineration ash 12 is melted, the molten slag layer 9, the molten salt layer 10, and the metal contained in the municipal solid waste incinerator ash is melted and dropped to form an ingot 8 which is water-cooled. Furnace wall 1
The molten slag or the molten salt is solidified therein to form the self-coating layer 13 as a substitute for the refractory.

When the molten slag layer 9 and the molten salt layer 10 become deep due to the melting of the municipal waste incineration ash, they are discharged from the slag tap hole 2 and the molten salt overflow hole 3 to maintain the respective layers 9 and 10 at a predetermined level. The metal contained in the municipal waste incineration ash is melted and dropped into the furnace floor 5, solidifies to form an ingot, and the furnace floor lifting device 7 lowers the furnace floor 5 in accordance with its growth to incinerate the municipal waste. Melt the ash 12.

When the ingot grows 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 acts as an insulator of heat and electricity, even if fly ash containing a large amount of salts is electrically stable, it can be melted.

[0011]

However, in the above-mentioned electric resistance melting furnace, the molten salt and the molten slag are accompanied by a vigorous stirring phenomenon similar to convection due to electromagnetic force.
0 is always in contact with the unmelted municipal solid waste incineration ash layer 12,
Melting proceeds as it is involved. And part of it sinks into the slag layer and becomes slag.However, since the municipal solid waste incineration ash also generates a large amount of gas in the molten salt layer and the molten slag layer, some of it is contained in the tapped molten salt. Unmelted municipal solid waste incineration ash is suspended, and air bubbles are often discharged into tapped slag. This is not preferable because afterwards, when the recovered salt is treated with water to recover useful substances such as potassium chloride, a large amount of unmelted municipal waste incineration ash becomes sludge and becomes sludge,
There was a problem to obtain only molten salt as much as possible. On the other hand, slag containing bubbles not only has weak strength but also uneven quality, so problems may occur when reusing it, so I would like to obtain completely slag that does not contain bubbles as much as possible. There were challenges. Further, since it is difficult to control the temperature of the slag in the primary melting furnace, it was difficult to obtain a product of a certain quality when processing the slag into slag wool or the like.

[0012]

As described above, when salt and slag are separately tapped in the first melting furnace, incomplete ones are obtained in both cases. Tap salt and slag at the same time to receive in the second melting furnace,
By taking a means to separate the salt and slag into two layers with the edge of the unmelted municipal solid waste incinerated completely cut off, the salt containing almost no unmelted municipal solid waste incinerated ash and the complete mixture containing almost no air bubbles are obtained. It becomes possible to obtain slag that has been slagged. Further, since the temperature control of the slag can be easily performed, it is also convenient when trying to obtain a high value-added product such as slag wool.

That is, according to the present invention, incineration ash of municipal solid waste is melt-processed in a first melting furnace composed of a water-cooled metal member to produce a molten salt, a molten slag and an ingot which are molten products, and then, The molten salt and the molten slag in the molten processed product are transferred to a second melting furnace composed of a water-cooled metal member, and the molten salt and the molten slag are separated by a difference in specific gravity in the second melting furnace. It is a method for separating molten salt and molten slag, which is characterized by separating into layers and taking them out of the system separately.

[0014]

The invention will be explained in more detail by means of an illustrated embodiment. FIG. 1 is a longitudinal sectional view for explaining a first melting furnace (hereinafter referred to as a primary furnace) and a second melting furnace (hereinafter referred to as a secondary furnace) of the present invention, and the left side of the drawing shows the primary furnace.
The symbols of 14 are exactly the same as those described in FIG.
The operation method does not change. The difference from FIG. 2 is that the slag tap hole 2 and the molten salt overflow hole 3 are omitted,
There is one tap hole 21 that taps both at the same time.

Molten salt and slag are tapped at the same time from this tap hole and received by the secondary furnace 26 on the right side of the drawing through the gutter 4. This secondary furnace 26 has a form quite similar to that of the primary furnace, and has a furnace wall made of a water-cooled metal member having a molten salt overflow hole 22 and a slag tap hole 23, and a water-cooled furnace also having a furnace bottom electrode 28. It is composed of a floor 27 and an upper electrode 29. Single-phase power is applied to both electrodes 28, 29 from a power source (not shown).

The salt and slag received from the primary furnace are held in the secondary furnace while forming a self-coating layer and separated into a molten salt layer 30 and a molten slag layer 31 due to a difference in specific gravity.
Since there is no unmelted municipal refuse incineration ash layer in the secondary furnace,
The temperature is raised by the electric power applied from both electrodes 28 and 29, the unmelted ash suspended in the salt is completely melted and separated into salt and slag, and at the same time, the gas component is also removed, and the slag is completely slag. Be converted.

Further, the temperature in the secondary furnace can be arbitrarily increased by adjusting the applied power.
High-quality salt and slag are collected from the overflow hole 22 and the slag tap hole 23, respectively, in the gutters 24a and 2a.
After 4b, it is cast into a form suitable for the subsequent process.

[0018]

The following effects can be obtained by implementing the present invention. That is, (1) high-quality salt containing almost no unmelted municipal solid waste incineration ash can be recovered, which is extremely advantageous when recovering useful substances from the salt by post-treatment. (2) Since the slag is sufficiently slag-free, contains almost no bubbles, has a high strength, and has a specific and constant high quality, it has an effect of broadening the reuse field. (3) Since the temperature of the molten slag can be easily controlled, the slag can be directly processed into slag wool or the like. (4) Since the second melting furnace also has a water-cooled metal wall structure like the first melting furnace, there is no damage to the refractory due to the molten salt,
Further, impurities are not mixed in the slag or the molten salt due to the elution of the refractory.

[Brief description of drawings]

FIG. 1 is an explanatory view of a sectional view showing an example of a melting furnace of the present invention.

FIG. 2 is an explanatory view of a sectional view showing a conventional melting furnace.

[Explanation of symbols]

 1 Furnace wall (primary furnace) 2,23 Slagg tap hole 3,22 Molten salt overflow hole 4,24 Gutter 5,27 Water-cooled hearth 6,28 Hearth bottom electrode 7 Hearth lifting device 8 Ingot 9,31 Molten slag layer 10,30 Molten salt layer 11,29 Upper electrode 12 Incinerated ash 13 Self-coating layer (slag + salt) 14 Electrical insulator 21 Tap hole 26 Secondary furnace

Claims (1)

[Claims] 1. Municipal refuse incineration ash is melted and processed in a first melting furnace composed of water-cooled metal members to produce molten salt, molten slag and ingot which are molten products, and then,
The molten salt and the molten slag in the molten processed product are transferred to a second melting furnace composed of a water-cooled metal member, and the molten salt and the molten slag are separated by a difference in specific gravity in the second melting furnace. A method for separating molten salt and molten slag, which is characterized in that the molten salt and molten slag are separated into layers and taken out of the system separately.