JP2747983B2 - Method and apparatus for melting municipal solid waste incineration ash - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detoxifying and reducing the volume of municipal waste incineration ash (including sewage sludge incineration ash and industrial waste incineration ash).

[0002]

2. Description of the Related Art Municipal waste incineration ash contains harmful substances such as dioxins and heavy metals, and has a problem that its specific gravity is small and bulky. Not only is it costly, but in recent years it has become difficult to secure that dumping space. Therefore, various municipalities have begun to adopt various methods of making molten slag as a method of detoxifying municipal solid waste incineration ash and greatly reducing its volume and effectively utilizing it. The molten slag conversion method is roughly classified into a melting method using electric power and a melting method using a fuel such as coke or petroleum, and when comparing the two, the latter is a new energy source for intermediate treatment of refuse. It is unlikely to be an ideal way to consume. On the other hand, in a garbage incineration plant, power is generated by the combustion energy of garbage, and the surplus power is actually sold. Therefore, the method of melting municipal waste incineration ash using this surplus power does not require a new energy source, and it is more rational because it can complete its own intermediate treatment using only the energy of the refuse to be treated. Can be In addition, the melting method using a fuel is extremely disadvantageous also in collecting secondary fly ash (generally called fly ash) because the amount of exhaust gas is overwhelmingly larger than the melting method using electric power. By the way, in the conventional melting method using electric power, a method using an arc or plasma as a heat source is partially used.However, a method of melting municipal waste incineration ash by these local high-temperature parts is a heating area for municipal waste incineration ash. In addition, the incineration ash and slag of municipal solid waste near the heat source are unnecessarily overheated, making it not only a very efficient method of heating and melting, but also secondary fly ash from the superheated part. There is also a disadvantage that it occurs in large quantities. On the other hand, the so-called electric resistance melting method, in which municipal solid waste incineration ash itself is converted into slag to generate Joule heat in the slag itself through electricity, is capable of widening the heat-generating portion and making it unnecessary to generate unnecessary superheated parts, which is efficient. It is known that municipal solid waste incineration ash can be heated and melted, and there is an advantage that generation of secondary fly ash can be suppressed to a low level. This has been widely experienced in many metallurgical furnaces, especially ferroalloy refining furnaces and glass melting furnaces.

[0003]

However, practical use of a full-fledged electric resistance melting furnace is still rare for the following reasons. In other words, when the electric resistance melting method known as an efficient melting method using electric power as described above is applied to municipal waste incineration ash, the refractory in the melting furnace is immediately eroded, so There was a decisive problem that stable operation could not be continued. This is mainly due to the effects of potassium and sodium oxides contained in municipal solid waste incineration at a fairly high concentration.In addition, in the case of the electric resistance melting method, a fixed amount of molten slag layer is always refractory in principle. If the incineration ash from the municipal solid waste must be melted and the metal mainly composed of iron, which is a by-product of the municipal incineration, must be discharged from the furnace, the conventional type Since there is no method other than discharging in the molten state, the slag must be kept at a high temperature above the melting temperature of the metal, and there is a problem that the refractory is more severely eroded by the high-temperature slag. The present invention has been made in view of such circumstances, and provides a method and apparatus for melting municipal incineration ash that solves the problem of refractory erosion when applying the electric resistance melting method to municipal incineration ash. With the goal.

[0004]

According to the present invention, there is provided a semiconductor device comprising:
The municipal solid waste incineration ash melting treatment method described above is characterized in that a furnace wall provided with a slag tap hole, a gutter connected to the slag tap hole, and a hearth separated from the furnace wall are each a water-cooled metal member. In the furnace body consisting of, the incinerated municipal waste incineration ash is melted by electric resistance using non-consumable electrodes, and the generated slag is discharged from the slag tap hole through the gutter in a molten state, and generated. The metal to be solidified is taken out on the hearth. The municipal solid waste incineration ash melting treatment device according to claim 2 includes a furnace wall having a slag tap hole, a gutter connected to the slag tap hole,
And a furnace body in which a hearth independent of the furnace wall is formed by a water-cooled metal member, an elevating means for the hearth, and a non-electrical heating and melting method for municipal waste incineration ash charged into the furnace body. Heating means using a consumable electrode.

[0005]

[Function] The conventional resistance melting furnace is a method in which municipal solid waste incineration ash is made into slag and tapped, and at the same time the generated metal is tapped in a molten state. Therefore, a refractory must necessarily be used to hold the molten metal. Was. When municipal solid waste incineration ash is melted using refractories, the refractories in the melting furnace are immediately eroded as described above, causing a problem that stable operation of the furnace cannot be continued. The above problem does not occur when the following is adopted. On the other hand, if the means of holding the generated metal in the molten state is stopped and solidified in the furnace bottom in order, and only the slag is held in the molten state, refractory is not required and the molten slag is held in the metal water-cooled furnace What can be achieved has been demonstrated by an electroslag remelting method (hereinafter abbreviated as ESR) known as a remelting and refining method for metals. The above problem can be solved by adopting a means for applying this principle to municipal solid waste incineration ash melting. However, in the case of municipal waste incineration ash melting, the purpose is not to obtain metal unlike ESR, but to obtain slag by melting municipal waste incineration ash.
The amount of slag produced is overwhelmingly large compared to ESR, and the furnace operation method and structure are significantly different from ESR furnaces because non-consumable electrodes are used instead of consumable electrodes like ESR. It will be. Therefore, in the method for melting municipal waste incineration ash according to claim 1 and the apparatus for melting municipal waste incineration ash according to claim 2, a furnace wall having a slag tap hole is connected to the slag tap hole. In a furnace using water-cooled metal members on a gutter, and a furnace floor separated from the furnace wall, municipal solid waste incineration ash is melted by electric resistance by a non-consumable electrode, and the generated slag is tapped from the tap hole. The by-produced metal is solidified and deposited on the hearth. In this case, solidified slag adheres to the furnace wall, hearth, and gutter water-cooled by the operation, plays a role of a refractory, and is thermally insulated from surrounding metal members. When a certain amount of solidified metal is generated, the operation is interrupted, the hearth is lowered, and the metal is discharged. By repeating such operations repeatedly, it is possible to realize the melting of municipal solid waste incineration ash without using refractories.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will now be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIG. 1 is a longitudinal sectional view for explaining a method of starting a municipal solid waste incineration ash melting treatment apparatus according to one embodiment of the present invention, and FIG. 2 is a longitudinal sectional view for explaining a steady state operation of the same apparatus. FIG. 3 is a longitudinal sectional view for explaining a state of discharging a metal lump generated in the apparatus. As shown in FIGS.
The municipal solid waste incineration ash melting treatment apparatus 10 according to one embodiment of the present invention has a furnace body 13 constituted by a cylindrical furnace wall 11 and a furnace floor 12 arranged below the furnace wall 11. A non-consumable electrode 14 is arranged in the furnace body 13. Hereinafter, these will be described.

The furnace wall 11 is made of copper, copper alloy, ordinary steel, alloy steel or a combination thereof (hereinafter, referred to as a metal member) having a water cooling section 15 therein. And cool. The furnace wall 11 includes a slag tap hole 16 and a gutter 1 connected to the slag tap hole 16.
7 is provided. The gutter 17 is also made of a metal member having a water cooling section 18 inside. The inner surface of the furnace wall 11 is provided with a taper slightly expanding downward so that the generated metal can easily fall downward. The hearth 12 is made of a metal member having the same structure as the furnace wall 11 and having a water-cooling portion 19 therein, and is formed independently of the furnace wall 11, and is provided with an elevating device 20 at a lower portion to ascend and descend. Furnace wall 11 in position
Abuts on the lower end. The non-consumable electrode 14 is made of artificial graphite or the like, and it is possible to use a direct current or a single phase. However, since three-phase alternating current is usually used, three electrodes are used in this embodiment. In addition, an electrode gripper not shown,
An electrode raising / lowering device and the like are provided in the same manner as in a normal steelmaking arc furnace.

When the operation of the municipal solid waste incineration ash melting processing apparatus 10 is started, the water cooling section 15 of the furnace wall 11,
After water is passed through the water cooling section 18 of the gutter 17 and the water cooling section 19 of the hearth 12, as shown in FIG. 1, the elevating device 20 is operated to raise the hearth 12 so as to contact the lower end of the furnace wall 11. To form the furnace body 13. A slag 21 made of slag powder (eg, granulated slag) or municipal waste incineration ash is thinly spread, and scrap iron obtained by magnetizing municipal waste incineration ash or fine-sized scrap iron is spread thereon to form an iron scrap layer 22. I do. The iron scrap layer 22 is used to start energization, and it is sufficient that only a small amount is provided below the electrode 14. Next, the electrode 14 is lowered so that the tip of the electrode 14 is in contact with the iron scrap layer 22, and municipal waste incineration ash 23 is charged thereon and covered. When electricity is supplied in this state, an arc is generated between the tip of the electrode 14 and the scrap iron, the scrap iron is melted, and the municipal waste incineration ash 23 is also melted to form a slag layer and the electric resistance melting is started.

In a steady state, the state becomes as shown in FIG.
A molten slag layer 24 is formed, and a solidified slag shell 25 is formed on the inner surface of the furnace wall 11. It is preferable to increase the thickness of the solidified slag shell 25 in order to prevent a decrease in thermal efficiency due to water cooling. To this end, the distance between the electrode 14 and the inner surface of the water-cooled furnace wall 11 is set to be sufficiently large. That is, the size of the water-cooled furnace wall is much larger than in the case of the ESR described above. Municipal solid waste incineration ash 23 melts and molten slag layer 2
4 becomes gradually deeper, so that the molten slag 26 is appropriately discharged from the slag tap hole 16 to maintain an appropriate molten slag layer depth. When the molten slag 26 is tapped,
A thin solidified slag shell 27 is formed on the inner surface of the slag tap hole 16 and the upper surface of the gutter 17 in the same manner as the inner surface of the furnace wall 11 by the water cooling effect.
And the gutter 17 is not eroded by the molten slag 26 and can be used permanently. The discharged molten slag 26 is subjected to a post-process such as water granulation to be used effectively.

The metal by-produced by melting the municipal waste incineration ash 23 is melted and dropped and solidified and deposited on the water-cooled hearth 12 to form a metal lump 28.
2 is lowered by operating the lifting device 20 to hold the molten slag layer 24 at a fixed position. Depending on the electrical conditions, the metal may be solidified and settled in a granular state to form a mixed mass of slag and granular metal. That is, the electrode 14
If the voltage applied to the slag is reduced or the distance between the electrodes is increased, the current density in the molten slag decreases, and the molten slag layer 24 operates at a low temperature. Normally, the current density of the electrode 14 is E
The current density in the slag is higher than that in the case of SR, and the electric condition is set lower, and the temperature of the molten slag layer 24 is set to about 1 ° C. from the melting point of the municipal waste incineration ash 23 of 1200 ° C. to 1300 ° C.
When operating at a temperature higher than 00 to 200 ° C., the fluidity of the slag is good, and a stirring phenomenon similar to convection occurs due to the electromagnetic force. It is possible to In the above embodiment, an example in which three-phase alternating current is used as a power source is shown. However, when direct current is used, three non-consumable electrodes are not required. And the same operation as described above can be performed by applying a current so that the furnace bottom electrode is a positive electrode and the non-consumable electrode is a negative electrode.

In the above operation, secondary fly ash is suppressed low because there is no superheated portion such as arc or plasma.
After all, the incinerated ash of municipal solid waste contains considerable volatile substances such as zinc.
Since a lot of white smoke is generated from above, the secondary fly ash is collected by a dust collector (not shown).

When the solidified metal block 28 has grown to a certain extent, the operation is interrupted as shown in FIG.
Discharge 8. The size of the metal block 28 depends on transportation restrictions, but in the case of normal truck transport, the metal block 28 is discharged when the metal block 28 reaches about 10 tons. Municipal waste incineration ash 2
From No. 3, generally about 10% of metal is generated, so every time about 100 tons of municipal waste incineration ash 23 is melted, a metal lump 28 is discharged. That is, when discharging the metal lump 28, the charging of the municipal waste incineration ash 23 is first stopped, all the charged municipal waste incineration ash 23 is melted, and the molten slag 26 is completely tapped. The cutting / elevating device 20 is contracted to lower the metal lump 28 together with the hearth 12, and the hearth 12 is tilted by tilting means (not shown).
Alternatively, the metal block 28 is moved by a method such as moving the hearth 12 together with a bogie (not shown) and suspending it with a lifting magnet.
To a storage pit. The metal mass 28 is generated in a state of covering the slag shell 29. When cooled, the slag shell 29 is broken and bald.

The metal mass 28 contains many impurities such as phosphorus and is unsuitable as a raw material for steel, but contains several percent of useful nonferrous metals such as copper, tin, lead, nickel, gold and silver. Therefore, it can be separated and reused as a resource. Further, the metal block 28 can be used as it is as a fishing reef or a wave breaking block. When the metal block 28 is used as a wave-dissipating block or the like, it is about four times as heavy as a normal concrete block or the like in the sea. Are suitable.

When the discharge of the metal block 28 is completed, the furnace body 13 is immediately returned to the state shown in FIG. 1 and melting of the municipal waste incineration ash is resumed. By continuing this cycle, stable municipal solid waste incineration ash melting without using refractories is realized. In addition, it is considered that the basic unit of electrode may fluctuate depending on the components of municipal waste incineration ash. . In addition, the power consumption rate is 1000 slag even in the case of a small furnace.
It is about 800 kWh per kg, which is comparable to other melting methods. This is because the resistance melting method is efficient and
The heat loss due to water cooling can be sufficiently compensated for by the heat insulating effect of the solidified slag shell generated on the inner surface of the water cooling furnace wall. Also,
Since no refractory is used, the cost is reduced, and the operation is not stopped for a long time due to furnace repair or rebuilding of the refractory, which is more efficient.

[0015]

According to the method for melting municipal waste incineration ash according to the first aspect and the apparatus for melting municipal incineration ash according to the second aspect, the municipal refuse is not used for the furnace wall and the hearth without using refractories. Since the melting of the incinerated ash is realized, the cost required for refractories and furnaces is unnecessary, and efficient electric resistance melting can be stably continued. In addition, since the generation of secondary fly ash is suppressed to a low level, the melting cost of municipal waste incineration ash is reduced and the melting efficiency is also improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a method for starting a municipal solid waste incineration ash melting apparatus according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view for explaining a steady-state operation of the apparatus.

FIG. 3 is a longitudinal sectional view for explaining a state of discharging a metal lump generated by the apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Melting apparatus of municipal waste incineration ash 11 Furnace wall 12 Hearth 13 Furnace body 14 Electrode 15 Water cooling unit 16 Slag tap hole 17 Gutter 18 Water cooling unit 19 Water cooling unit 20 Lifting device 21 Litter 22 Iron scrap layer 23 24 molten slag layer 25 solidified slag shell 26 molten slag 27 solidified slag shell 28 metal lump 29 slag shell

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B09B 3/00 303K

Claims (2)

(57) [Claims] 1. A furnace wall provided with a slag tap hole, a gutter connected to the slag tap hole, and a hearth separated from the furnace wall are charged in a furnace body made of a water-cooled metal member. The municipal solid waste incineration ash is melted by electric resistance using a non-consumable electrode, and the generated slag is discharged from the slag tap hole through the gutter in a molten state,
A method for melting municipal waste incineration ash, wherein the generated metal is solidified and taken out on the hearth. 2. A furnace wall having a slag tap hole, a gutter connected to the slag tap hole, and a furnace body in which a hearth independent of the furnace wall is formed of a water-cooled metal member. An apparatus for melting municipal waste incineration ash, comprising: means for raising and lowering the hearth; and heating means using a non-consumable electrode for electrically melting the incineration ash introduced into the furnace.