JPH0875136A - Incinerated ash melting method and device therefor - Google Patents

Abstract

PURPOSE: To prevent the occurrence of steam explosion which preventing the development of a clog of metal in the gate of a melting furnace, which interrupts continuous melting of incinerated ash. CONSTITUTION: In an incinerated ash melting device, a plurality of nozzles 7 through which plasma to melt and treat incinerated ash generated in a refuse incinerator or oxygen or oxygen enriching gas is blown in a molten metal layer 12 in a melting furnace are formed in a refractory of which a lower side 15 of an arc melting furnace consists. The melting furnace comprises a plasma torch 1, a furnace bottom electrode 2 disposed at a bottom 16 of a furnace body 4, an ash feeding device 3 located at the melting furnace, an ash hopper 8 through which incinerated ash is charged in a water injection device 5 and a melting furnace, and a slug storage tank 9 formed at an outlet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an incinerator ash melting method and apparatus for melting incinerator ash generated in a refuse incinerator in a plasma or arc type melting furnace.

[0002]

2. Description of the Related Art In recent years, the amount of municipal waste generated has been increasing, and it has become difficult to secure landfill sites for garbage in Japan, which has a small land area. Therefore, in order to reduce the amount of landfill waste, it is attempted to burn the waste in a waste incinerator to produce incinerated ash. When garbage is burned into incinerated ash, the volume of incinerated ash is reduced to about 1/20 of that of raw garbage, so many municipalities have started to incinerate garbage. However, even if the volume of the incinerated ash becomes about 1/20 of the garbage, the current situation is that the landfill site for the incinerated ash is still insufficient. Therefore, in recent years, in order to reduce the volume of the incineration ash of the municipal solid waste incinerator and to render it harmless, it has been performed to melt the incineration ash into slag (slag).
When the incinerated ash is melt-processed into slag, the volume thereof can be reduced and harmless, and the slag can be effectively used as a material for roadbed materials, interlocking blocks and the like.

The prior arts for melting incinerated ash have mainly been a burner combustion system and an electric heating system. The burner combustion system is a system in which liquid fuel or gas fuel is burnt by a burner to a high temperature of 1300 ° C. to melt the burned ash. In the case of the burner combustion method, incinerated ash is heated to 1300 ° C.
It cannot be heated any more. Therefore, since metals such as iron contained in the incinerated ash have a melting point of 1500 ° C. or higher, the metals such as iron are removed from the incinerated ash by a magnetic separator or the like, and then the incinerated ash is melted. The current situation is that The metals separated from the incinerated ash are not reused because they are covered with ash and are only landfilled, which is not preferable for the purpose of reducing the volume of the incinerated ash.

Further, the electric heating method is superior to the burner combustion method as a technique for melting the incineration ash, and mainly the plasma melting furnace and the arc furnace, both of which have electric energy of high temperature of 2000 ° C. or higher. This is a method of melting incineration ash into plasma. In the electric heating method, since the temperature can be maintained at the melting point of iron or higher, it is not necessary to separate the metal content of the incineration ash.

[0005]

By the way, when the incineration ash in which the metal is not previously separated is melted, due to the difference in specific gravity,
Separated into a molten metal layer and a slag layer in a melting furnace. Since the molten metal layer has a large specific gravity, it is below the slag layer.
When the incineration ash melting process is continued for a long time, the slag overflows from the melting furnace and is discharged, and the metal settles at the bottom of the melting furnace, so the molten metal layer increases in the melting furnace. .

When the incinerated ash melted is discharged from the gate of an overflow type melting furnace, the slag has a melting point of 1200 to 1300 ° C., so that the slag can be continuously discharged without solidification. However, since the melting point of the main component of the molten metal is 1500 ° C. or higher, the molten metal is cooled and solidified at the sprue of the melting furnace, and the solidified product forms a weir at the sprue to stop continuous discharge of slag and the like. Occurs.

When the molten metal is solidified in the conventional melting furnace and the gate is closed, the operation of the melting furnace is stopped and the melting furnace is tilted to discharge the solidified product, or the molten material in the melting furnace is discharged. After natural cooling, the solidified material is crushed with a drill or the like to remove the crushed material from the melting furnace. The method of tilting the melting furnace is possible in the case of a small melting furnace with a small treatment amount, but the ability to melt the incinerated ash is 10 t /
In a melting furnace with a throughput of one day or more, the weight of the furnace body is too large, and it is difficult to lift and tilt the melting furnace. When the interface of the molten metal layer rises to the level of the sprue in the melting process in the melting furnace, the melting furnace must be stopped, which causes a problem that continuous operation of the melting furnace cannot be performed.

Further, in order to prevent a weir from being formed by a solidified product at the sprue of a melting furnace, a method has conventionally been used in which an auxiliary burner is installed at the sprue part to heat the solidified product. However, after the slag is discharged from the melting furnace by the overflow method, when cooling the slag with a large amount of water, the slag is finely granulated into fine solids without any problems, but it is melted at a high temperature with an auxiliary burner. In the case of metal, steam explosion sometimes occurs due to high temperature and large specific heat, which is a very dangerous process.

It has also been attempted to discharge the molten metal from the melting furnace by a tap method, receive the molten metal in a dry container and air-cool it. However, the temperature of the molten metal in the vicinity of the refractory is increased by heat radiation. It has decreased and is often difficult to discharge. With the tap method, a hole for discharging the melt is opened in the refractory, and a filler of graphite or clay is usually filled in the hole so that the melt is not discharged from the melting furnace.
In this method, when the molten metal is discharged from the melting furnace, the filling material is removed from the hole and the molten material is allowed to flow out from the hole. Although the work of removing the filling from the hole of the melting furnace is performed by a skilled worker, it is a very dangerous work, and the overflow method, which can be remotely operated, is superior in terms of safety. Further, the molten metal smelted by the tap method is generally not useful because iron is mixed with various metals such as copper and zinc.

Even when the method of separating the metal from the incinerated ash is used as the pretreatment of the melting furnace, the metal is removed from the incinerated ash by 100%.
%, It is impossible to solve the problem that when the incineration ash is melted in the melting furnace, the molten metal gradually accumulates in the melting furnace to remove the molten metal from the melting furnace.

Therefore, an object of the present invention is to solve the above problems, and in an incinerator ash melting method for melting and treating the incinerator ash generated in a refuse incinerator in a plasma or arc type melting furnace, A problem that molten metal makes it impossible to perform long-term continuous melting treatment of incineration ash, a problem of clogging the gate of the melting furnace, a method of melting incineration ash that can prevent the occurrence of steam explosion when water granulating the molten metal, and It is to provide the device.

[0012]

The present invention is configured as follows in order to solve the above-mentioned object. That is, the present invention, in the incineration ash melting method for melting and treating the incineration ash generated in the refuse incinerator in the plasma or arc type melting furnace, the molten metal layer and the slag layer formed in the melting treatment process of the incineration ash Among them, the present invention relates to a method for melting incineration ash, which comprises blowing pure oxygen or an oxygen-enriched gas into the molten metal layer to oxidize the molten metal to form slag.

Alternatively, the present invention is a plasma or arc type melting furnace for melting and treating incineration ash generated in a refuse incinerator, and a nozzle for blowing oxygen or oxygen-enriched gas into a molten metal layer in the melting furnace. Is installed in a refractory material that constitutes the bottom portion or the lower side portion of the melting furnace. In this incinerator ash melting apparatus, it is preferable that a plurality of the nozzles be provided in the refractory material.

Alternatively, according to the present invention, in a plasma or arc type melting furnace for melting and treating incineration ash generated in a refuse incinerator, a ceramic supply for feeding oxygen or an oxygen-enriched gas into a molten metal layer in the melting furnace. The incinerator ash melting apparatus is characterized in that a pipe is installed in a refractory material forming a ceiling of the melting furnace, and the supply pipe is opened in the molten metal layer.

[0015]

Since the incineration ash melting method and apparatus according to the present invention are constructed as described above, they operate as follows. That is, this incineration ash melting method, by blowing a pure oxygen or oxygen-enriched gas into the molten metal layer in the plasma or arc type melting furnace, by oxidizing the molten metal to change to metal oxide slag, It is possible to prevent solidification blockage at the sprue of the melting furnace due to the molten metal, and to prevent a steam explosion when the slag discharged from the melting furnace is water granulated. That is, when oxygen or an oxygen-enriched gas is blown into a molten metal in a high temperature state of 1500 ° C. or higher in a melting furnace, an oxidation reaction of the metal occurs and a metal oxide is produced. The slag that has become a metal oxide does not solidify at the sprue of the melting furnace, and since the molten metal does not overflow from the sprue of the melting furnace, the molten metal solidifies at the sprue and may block the sprue. Also, no steam explosion will occur even when the slag is water granulated. Further, oxygen does not have to be pure oxygen, and the same function can be ensured even with an oxygen-enriched gas having a high oxygen concentration in the air.

Further, this incinerator ash melting apparatus uses a melting furnace as a means for blowing pure oxygen or oxygen-enriched gas into the molten metal layer of the molten metal layer and the slag layer formed in the process of melting the incinerated ash. A plurality of nozzles for blowing oxygen or oxygen-enriched gas into the refractory that constitutes the bottom or lower side of the, or oxygen or oxygen-enriched gas to the refractory that constitutes the ceiling of the melting furnace A ceramic supply pipe to be blown in is provided, and the supply pipe is installed so as to open into the molten metal in the melting furnace.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The incineration ash melting method and incinerator ash melting apparatus according to the present invention will be described below with reference to the drawings. An embodiment of the incineration ash melting method according to the present invention will be described. This incineration ash melting method is a method of melting the incineration ash generated in a refuse incinerator in a plasma or arc type melting furnace, and a molten metal layer and slag formed in the incineration ash melting process. Of the layers, pure oxygen or oxygen-enriched gas is blown into the molten metal layer to oxidize the molten metal to form slag. When oxygen or an oxygen-enriched gas is blown into the molten metal layer at a high temperature of 1500 ° C. or higher in the melting furnace, an oxidation reaction of the metal occurs and the metal oxide is converted.

For example, Fe, which is the main component of the molten metal, is oxidized into iron oxide Fe ₂ O ₃ in the presence of oxygen. By converting to metal oxide rather than metal itself, the specific gravity becomes lighter,
The metal oxide floats above the molten metal layer. That is, Fe
Has a specific gravity of 7.86, whereas Fe ₂ O _{3 has} a low specific gravity of 5.2. The metal oxide floating above the molten metal layer is entrained in oxygen and enters the slag layer, where it is mixed with the molten slag. Molten slag is SiO ₂ , Al
Since it is a eutectic of oxides containing ₂ O ₃ , CaO, and Fe ₂ O ₃ as main components, the metal oxide that has entered the slag layer from the molten metal layer is immediately mixed with the original slag to form a homogeneous slag. become. Since the melting point of the slag is the melting point of the eutectic, Fe ₂
Even if the proportion of O ₃ increases, it only increases slightly, the slag does not solidify at the sprue of the melting furnace, and the molten metal does not overflow from the sprue of the melting furnace, so It solidifies, does not block the sprue, and does not cause a steam explosion even when the slag is water granulated.

Further, since the heat of oxidation is generated when the molten metal is oxidized, the temperature of the molten metal layer becomes high. When heated by plasma, the temperature of the slag layer is higher than the temperature of the molten metal layer because the heat of heating the slag layer is transferred to the molten metal layer by heat conduction to be heated. The melting point of slag is lower than that of metal, so at least 13
When the temperature is set to 00 ° C., it is usual to operate while keeping the temperature at which the incineration ash can be melted at 1500 ° C. or higher which is the melting point of iron. Originally, it is desirable to raise the temperature of the molten metal layer and lower the temperature of the slag layer to about 1300 ° C. By blowing oxygen into the molten metal layer, the temperature of the molten metal layer rises, so that it is possible to reduce the energy output of the plasma and operate the slag layer at a temperature slightly higher than the melting point of the slag.

An embodiment of the incineration ash melting apparatus according to the present invention will be described with reference to FIG. As shown in FIG. 1, this incineration ash melting apparatus is mainly used in a plasma or arc type melting furnace for melting incineration ash generated in a refuse incinerator, and a lower side portion 15 forming a furnace body 4 of the melting furnace. A plurality of nozzles 7 for injecting oxygen or oxygen-enriched gas into the molten metal layer 12 in the melting furnace are installed in the refractory constituting the above. The melting furnace includes a plasma torch 1 arranged on a refractory material constituting the ceiling 17, a furnace bottom electrode 2 arranged on the bottom 16 of the furnace body 4, an ash supply device 3 provided on the melting furnace, and an outlet of the melting furnace. The water injection device 5 and the exhaust gas outlet 6 provided,
An oxygen supply port or nozzle 7 formed in the side portion 15 for blowing oxygen or an oxygen-enriched gas into the molten metal layer 12 in the melting furnace, an ash hopper 8 for charging incineration ash into the melting furnace, and a melting furnace It is composed of a slag storage tank 9 provided at the outlet.

Further, the nozzle 7 formed on the side portion 15 of the furnace body 4 is one in which the refractory material on the side portion 15 of the furnace body 4 is perforated and the ceramic supply pipe is embedded, and it is necessary to limit the number to one place. Instead, it can be provided at several places around the side portion 15 of the furnace body 4, and oxygen can be supplied into the melting furnace from several places on the side portion 15 of the furnace body 4. Further, the side portion 15 of the furnace body 4
When oxygen is supplied from the oxygen source, it is necessary to constantly supply oxygen gas in order to prevent the molten metal from flowing back into the oxygen supply port.

The plasma torch 1 and the furnace bottom electrode 2 are connected to the DC power supply device 10. Plasma is generated from the plasma torch 1 by receiving electric power from the DC power supply device 10.
Although not shown, the plasma torch 1 is configured to be cooled with cooling water. The incinerated ash put into the ash hopper 8 is supplied into the melting furnace by the ash supply device 3,
The incineration ash put into the melting furnace is melted by the plasma heat generated in the plasma torch 1, and the slag layer 11 and the molten metal layer 1 are melted.
It is divided into 2 layers. Oxygen or oxygen-enriched gas is supplied into the molten metal layer 12 on the lower side from the nozzle 7 of the oxygen gas supply port. Although not shown, the supply device for oxygen or oxygen-enriched gas is composed of an oxygen cylinder or an oxygen-enriched air production device. The molten metal is oxidized by oxygen and becomes a slag of a metal oxide, so that the interface 1 of the molten metal layer 12
8 never exceeds the level of the gate 13 of the melting furnace.

Since the slag layer 11 in the melting furnace is constantly increased by the supply of incineration ash and the oxidation of the molten metal, the slag overflows from the sprue 13 and the granulation chute 14
Flow out to. In the water granulation chute 14, the slag is rapidly cooled by the water injected from the water injection device 5, and then discharged into the slag storage tank 9. The inner surface of the furnace body 4 is
Protected by refractory. Further, the exhaust gas generated in the melting furnace is exhausted from the exhaust gas discharge port 6 by an induction blower (not shown), and is exhausted to the atmosphere via an exhaust gas treatment device (not shown).

When the incinerator ash is melted by blowing oxygen or oxygen-enriched gas into the molten metal in the melting furnace using the incinerator ash melting apparatus according to the present invention, and in the melting furnace using the conventional incinerator ash melting apparatus. Table 1 shows the characteristics in the case where the incineration ash is melted without blowing oxygen or an oxygen-enriched gas into the molten metal. Table 1 shows the slag composition, the slag melting point, and the slag specific gravity changed by the melting treatment of the incineration ash.

[Table 1]

As can be seen from Table 1, by blowing oxygen or oxygen-enriched gas into the molten metal, the content of Fe ₂ O ₃ was increased and the specific gravity was increased. Although the melting point of slag is slightly higher, the melting point of slag is much lower than that of metallic iron. The amount of abrasion loss is an index of the hardness of slag, but it was confirmed that the amount of abrasion loss was smaller in the molten treatment in which oxygen was blown into the molten metal than in the molten treatment not blown, and it was harder than conventional slag. Was done.

Next, another embodiment of the incineration ash melting apparatus according to the present invention will be described with reference to FIG. The embodiment shown in FIG. 2 has the same configuration and the same function as the above embodiment except that the installation location of the nozzle is different.
The same parts are designated by the same reference numerals, and overlapping description will be omitted. In this incinerator ash melting device, the molten metal layer 1 in the melting furnace is
An oxygen supply port or nozzle 19 is formed in the bottom 16 of the furnace body 4 for blowing oxygen or an oxygen-enriched gas into the furnace 2. The nozzle 19 formed on the bottom portion 16 of the furnace body 4 is
The bottom 16 of the furnace body 4 is made by boring a refractory material and the ceramic supply pipe is embedded in the bottom body 16. It is not necessary to limit to one place, and it can be provided in several places around the bottom part 16 of the furnace body 4. It is also possible to supply oxygen into the melting furnace from several 16 locations. Further, when oxygen is supplied from the bottom 16 of the furnace body 4, it is necessary to constantly flow oxygen gas in order to prevent the molten metal from flowing back into the oxygen supply port.

Another embodiment of the incinerator ash melting apparatus according to the present invention will be described with reference to FIG. The embodiment shown in FIG. 3 has the same configuration and the same function as the above embodiment except that the installation location of the nozzle is different.
The same parts are designated by the same reference numerals, and overlapping description will be omitted. The incinerator ash melting apparatus according to this embodiment has a ceiling 17 of a melting furnace.
A refractory ceramic supply pipe 20 is installed by penetrating the refractory constituting the above, and the supply pipe 20 is opened in the molten metal layer. It is configured to feed oxygen or an oxygen-enriched gas into the molten metal layer in the melting furnace through the supply pipe 20.

When oxygen is supplied to the nozzles 7 and 19 from the side portion 15 or the bottom portion 16 of the furnace body 4 as in the embodiment shown in FIGS. 1 and 2, it is necessary to prevent the molten metal from flowing back into the oxygen supply port. It is necessary to constantly flow the oxygen gas to prevent it, but since it is not necessary to supply oxygen when the interface 18 of the molten metal layer 12 is lowered, it is costly to constantly supply the oxygen gas. On the other hand, in the embodiment shown in FIG. 3, oxygen is supplied from the furnace roof 17, so when the interface 18 of the molten metal layer 12 is lowered and the supply of oxygen is unnecessary, the supply pipe 20 is placed above the slag surface. Even if the oxygen supply is stopped by pulling it up, the molten metal and the slag do not flow back to the oxygen supply port of the supply pipe 20.

The incinerator ash melting apparatus according to the present invention is not limited to each of the above-mentioned embodiments. For example, although not shown, the nozzle installed in the furnace body 4 has a furnace body at the side, bottom or ceiling thereof. It is also possible to configure so as to provide an appropriate number.

[0030]

The incinerator ash melting method and apparatus according to the present invention are configured as described above, and have the following effects. That is, when the conventional incineration ash was melted in the melting furnace, there was a problem that the molten metal solidified in the sprue of the melting furnace to create a weir and interfere with the continuous slag slag, making continuous operation impossible.
According to this invention, the melting point of the slag can be lowered by oxidizing the molten metal in the melting furnace to form a slag of the metal oxide, and the molten metal solidifies at the gate of the melting furnace to form a weir. The effect is that continuous operation becomes possible.

Further, when the temperature of the sprue part is raised by the auxiliary burner to melt the molten metal, the temperature is higher than that of the slag and the specific heat is high, so that there is a problem that steam explosion easily occurs. However, as in the present invention, by slagging the molten metal, the slag can be slagged at a low temperature, so that the effect of reducing the risk of steam explosion is obtained. Moreover, according to the present invention, the conventional incinerator ash melting apparatus, which requires the auxiliary burner at the sprue part, has an effect that continuous slag can be obtained without the auxiliary burner.

In the conventional incineration ash melting apparatus, the temperature of the slag layer had to be set high in order to keep the temperature of the molten metal high, but in the present invention, the molten metal reacts with oxygen in the molten metal layer. Since it can be heated by the generated reaction heat, the temperature of the slag layer can be suppressed to a low level, energy can be saved, and the life of the furnace refractory can be extended.
Further, when slag is formed by using molten metal as an oxide, the content of Fe ₂ O _{3 in} the slag is increased, the specific gravity of the slag is increased, and the hardness is increased. There is an effect that it can be used for such purposes and can increase its value.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of an incinerator ash melting apparatus according to the present invention.

FIG. 2 is a schematic sectional view showing another embodiment of the incineration ash melting apparatus according to the present invention.

FIG. 3 is a schematic sectional view showing still another embodiment of the incineration ash melting apparatus according to the present invention.

[Explanation of symbols]

 1 Plasma torch 4 Furnace body 7,19 Nozzle 11 Slag layer 12 Molten metal layer 13 Gate 15 Side part 16 Bottom part 17 Ceiling 18 Interface 20 Supply pipe

Claims (3)

[Claims] 1. A method for melting incineration ash in which incineration ash generated in a refuse incinerator is melted in a plasma or arc type melting furnace, wherein a molten metal layer and a slag layer formed in the melting process of the incineration ash are included. A method for melting incinerated ash, comprising injecting pure oxygen or an oxygen-enriched gas into the molten metal layer to oxidize the molten metal to form a slag. 2. In a plasma or arc type melting furnace for melting and treating incineration ash generated in a refuse incinerator, a nozzle for blowing oxygen or oxygen-enriched gas into a molten metal layer in the melting furnace is provided in the melting furnace. An incinerator ash melting apparatus, which is installed on a refractory material that constitutes a bottom portion or a lower side portion of the. 3. In a plasma or arc type melting furnace for melting and treating incineration ash generated in a refuse incinerator, a ceramic supply pipe for feeding oxygen or oxygen-enriched gas into a molten metal layer in the melting furnace is melted. An incinerator ash melting apparatus, which is installed on a refractory material that constitutes a ceiling of a furnace, and wherein the supply pipe is opened in the molten metal layer.