JPH0694926B2 - Method of melting incineration ash - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to incineration ash for melting and treating incinerator ash generated by incinerating municipal solid waste, sewage sludge, or other waste in an incinerator. Melt processing method.

[Conventional technology]

In general, incinerator ash generated by incinerating municipal solid waste, sewage sludge, or other wastes in a waste incinerator is currently landfilled in most cases.
However, since it is becoming more difficult to secure landfill sites year after year, there is a demand for a method of reducing the volume of incinerated ash to be landfilled, that is, volume reduction treatment.

If the incinerated ash itself is landfilled in a landfill without being treated, the incinerated ash itself contains harmful substances such as various heavy metals. And the like, or the unburned organic substances in the incinerated ash are decomposed, and these phenomena cause secondary pollution. Therefore, there is a demand for pollution-free treatment of incineration ash discharged from the incinerator.

Therefore, various methods for treating incinerated ash have been developed conventionally. For example, a treatment method of mixing incineration ash with cement and solidifying the incineration ash with cement, a treatment method of mixing with asphalt to solidify the incineration ash, a treatment method of mixing with clay or the like to sinter and solidify the incineration ash, etc. It is disclosed. However, the above treatment method has a problem that the treatment cost becomes high and the technical reliability of the treatment state of the incineration ash is lacking.

Another method for treating the incinerated ash is a method of melting the incinerated ash by charging the incinerated ash in a burner furnace, an electric furnace, that is, an open arc furnace. For example, Japanese Unexamined Patent Publication No. 52-86976 discloses a sludge combustion and melting method as a treatment method using an open arc furnace for steelmaking.

The combustion and melting method of the sludge, the sludge is charged into a closed arc furnace in which an arc is constantly generated between the electrode and the molten metal, and the organic matter in the sludge is decomposed by the arc heat of the arc as a gas. It is characterized in that the inorganic substance in the sludge is taken out of the furnace and is melted by the arc heat of the arc to be melted in the molten metal or taken out of the furnace as a molten slag.

Alternatively, JP-A-55-114383 discloses a method for melting incinerated ash.

The melting treatment method of the incineration ash is one in which the incineration ash is sequentially charged onto the molten slag in the submerged arc furnace to form an incineration ash layer, and the incineration ash of the layer is sequentially melted by electric resistance heat of the molten slag. Is. In this case, as the incineration ash, a mixed ash of ash that is incinerated and discharged in the incinerator and dust ash that is collected in the dust collector is used.

[Problems to be Solved by the Invention]

However, since the sludge combustion and melting method disclosed in JP-A-52-86976 uses an open arc furnace using a graphite electrode, a sufficient high temperature cannot be obtained, and therefore the incineration ash is not obtained. , Especially in municipal waste incineration ash, which has a high melting point (eg 1500 ° C or higher),
High melting point materials such as pottery and metal cannot be completely melted. Therefore, in order to put only the substance that can be melted in the open arc furnace into the open arc furnace, after selecting the high melting point substance from the incinerator in advance, it is put into the furnace or the melting point of lime, fluorite, etc. It was necessary to add a depressant to the incineration ash for melt processing.

Further, in the open arc furnace, in order to generate an arc between the electrode and the molten metal, in order to treat waste such as incinerated ash, which is mainly composed of an oxide contained as a slag component, It is necessary to melt a metal such as iron in a furnace in advance to prepare a so-called base metal.

Furthermore, when incinerated ash with a non-uniform composition such as oxide is put on the base metal, the fluctuation of the arc power is large, and
The phenomenon that the arc disappeared occurred. Moreover, when the arc is extinguished, the incinerated ash that is not conductive is covered on the base metal, and the incinerated ash is processed again.Therefore, there is often a problem that the incinerated ash cannot be re-ignited. occured.

Further, in the case of a burner furnace, it is not possible to obtain a higher temperature than in an open arc furnace, and since a large amount of air for fuel combustion is used, the amount of exhaust gas becomes enormous, resulting in a large exhaust gas treatment device. Various problems have arisen such as the necessity.

Generally, plasma is a state in which electrons are ejected from atoms to be ionized, which is high energy generated when electrons are ejected from atoms, and the vicinity of plasma is a high temperature atmosphere. Plasma arc furnaces have been provided to generate this plasma. A plasma torch is provided in this plasma arc furnace. Further, incinerator ash and combustion exhaust gas generated from the incinerator are cleaned by a dust collector such as an electric dust collector, and the cleaned exhaust gas is discharged from the chimney through the induction fan.

The object of the present invention is to solve the above various problems, regardless of the type and composition of the incineration ash, for example, even if the incineration ash contains a high melting point substance such as metal, pottery, earth and sand , Without directly separating and removing the high melting point substances from the incineration ash, directly injecting the incineration ash directly into the melting furnace,
PROBLEM TO BE SOLVED: To provide a melting treatment method of incineration ash, which is capable of generating stable plasma by using a plasma torch which is a plasma generator provided in the melting furnace and melting the incineration ash by the high energy of the plasma to constantly treat it. It is to be.

[Means for Solving the Problems]

The present invention is configured as follows to achieve the above object. That is, the present invention is a method for melting incineration ash containing a high melting point substance discharged from an incinerator, which is charged into a melting furnace to melt the incinerator ash by a plasma arc. At the time of melting, using air as a plasma forming gas, switching the alternating current to direct current by the power supply device and supplying the direct current to the plasma torch, the gas pressure is controlled by the control device to operate in a fluctuating cycle, The present invention relates to a method for melting and treating incineration ash, wherein the plasma arc is controlled so as to be stably supplied.

[Action]

The method for melting incinerated ash according to the present invention is configured as described above, and operates as follows. That is, the melting treatment method of this incineration ash, the incinerator ash containing the high melting point substance discharged from the incinerator is directly charged into the melting furnace, and the air is used as the plasma forming gas in the plasma torch provided in the melting furnace. Since a plasma arc is generated and the incineration ash is melted by the thermal energy of the plasma arc, a plasma arc can be continuously and stably obtained by the plasma torch, and the thermal energy of high temperature plasma is radiated to the incineration ash. Alternatively, the incineration ash can be melted by giving it by conduction.

Further, during the melting treatment of the incineration ash, the heavy metal contained in the incineration ash strongly causes an oxidation reaction with the air which is the plasma forming gas, and the oxidation action changes the oxide to a low volatility to convert it into a heavy metal. Most are fused and fixed in the molten slag. Moreover, by using air, unburned substances such as organic substances, which are usually 5% to 10%, remaining in the incinerated ash can be completely decomposed.

〔Example〕

An embodiment of a method for melting incinerated ash according to the present invention will be described below with reference to the drawings.

The melting treatment method of incineration ash according to the present invention is an incineration ash generated by incinerating wastes in an incinerator, or a mixture of dust collected by a dust collector in exhaust gas treatment with the incineration ash and plasma. This is a method in which the incinerated ash is melted in the plasma arc furnace after being placed in an arc furnace.

FIG. 1 shows a plasma incineration ash melting apparatus for accomplishing the incineration ash melting treatment method. This plasma incineration ash melting apparatus melts incineration ash generated by incinerating municipal waste, sewage sludge, or other wastes in an incinerator in the incinerator, that is, the plasma arc furnace 5, and mainly uses plasma. Arc furnace 5,
It comprises a plasma torch 8 provided in the plasma arc furnace 5 and a plasma system 1 for generating plasma in the plasma torch 8.

As shown in FIG. 1, the plasma arc furnace 5 is provided with a water-cooled fixed-type furnace lid on the upper part of the furnace body. This furnace body
It is constructed of a refractory material such as carbon, magnesia, or alumina, and has a tap 25. Further, a torch lifting device, an incineration ash charging chute 9 and an exhaust gas duct for exhaust gas are attached to the furnace lid. The plasma torch 8 is installed on the furnace lid by a torch lifting device.

Further, as the plasma torch 8 used in this plasma incineration ash melting apparatus, a transfer type as shown in FIG. 2 or a non-transfer type as shown in FIG. 3 is used as the type of arc discharge. be able to. That is, the transfer type plasma torch 8 is composed of a rear electrode 8A which is a + pole and a collimator 8B, and the non-transfer type plasma torch 8 is composed of a rear electrode 8A of a + pole and a front electrode 8C of a − pole. ing. When using the plasma torch 8 of the transfer type arc discharge,
By constructing the structure in which the counter electrode 10 composed of a graphite electrode is embedded in the furnace body and the bottom of the furnace, in the plasma arc furnace 5,
A plasma arc is generated between the rear electrode 8A (+ pole) built in the plasma torch 8 and the counter electrode 10 (− pole) provided at the bottom of the furnace body. When the plasma torch 8 of the non-transfer type arc discharge type is used, it is not necessary to embed the counter electrode 10, and a plasma arc is generated between the rear electrode 8A and the front electrode 8C built in the plasma torch 8. It was

In order to generate plasma in the plasma torch 8, in the case of the transfer type, the positive electrode is connected from the power supply device 4 to the rear electrode 8A built in the plasma torch 8 through the cable 17 by the operation of the plasma system 1. The pole is connected to the counter electrode 10 through the cable 22 and is achieved by applying a voltage between the rear electrode 8A and the counter electrode 10. + For non-transfer type
The connection of the poles is similar to the transfer type, but the-pole is connected to the front electrode 8C through the cable 18 and is achieved by applying a voltage between the rear electrode 8A and the front electrode 8C.

The plasma system 1 is mainly a transfer type or non-transfer type plasma arc torch 8, which switches AC to DC and supplies the DC to the plasma torch 8 so that the current can be stably supplied without the current becoming zero. A power supply device 4, a control device 26 for generating a plasma arc by the plasma torch 8 and controlling for stable supply of the plasma arc, a cooling water supply device 27 for cooling the electrode and the torch body, and plasma formation. It has an air supply device 28 for supplying air to be gas.

Furthermore, the cooling water pump 29 in the cooling water supply device 27 is operated, the cooling water is sent from the water tank 30 to the heat exchanger 38, and after heat exchange in the heat exchanger 33, the heat exchanger 33 to the manifold 34, Then, the plasma torch 8 is supplied through the cooling water pipes 19 and 20 to cool the plasma torch 8 and the furnace lid.

Further, the air compressor of the air supply device 28 is operated to supply compressed air from the manifold 34 to the plasma torch 8 through the plasma forming air pipe 21 as shown by an arrow A.

The incineration ash melting treatment method according to the present invention is achieved by using the above-described incineration ash melting apparatus. In this incineration ash melting apparatus, the incineration ash generated from the incinerator or the incineration ash collected from the dust collector is put into the ash hopper 12. The incinerated ash put into the ash hopper 12 is continuously or intermittently put into the plasma arc furnace 5 through the chute 9. The plasma torch 8 is lowered into the plasma arc furnace 5 under a predetermined setting condition for discharging the plasma arc.

In the transfer type, the plasma torch 8 is set at a predetermined distance from the counter electrode 10, and air, which is a plasma forming gas, is supplied to the plasma torch 8 and then a high voltage is applied between the rear electrode 8A and the collimator 8B. A pulse of energy is applied to generate a pilot arc. Next, plasma torch 8
To a predetermined height and after the main arc is generated, set a predetermined current (for example, 200-300A) and a predetermined voltage (for example, 400-500V) to heat the thermal energy of the plasma arc. It is given to the incineration ash that is a thing by radiation or conduction.

On the other hand, in the case of the non-transfer type, thermal energy is applied to the incineration ash by the same operation as in the transfer type except for the operation of generating a pilot arc by applying a pulse between the rear electrode 8A and the front electrode 8C. That is, a plasma arc is generated by the plasma arc discharge and plasma forming gas, oxide by heat energy of the plasma arc, incineration ash containing a highly molten substance, etc. becomes a molten slag 13 in a molten state, the metal is a molten metal, It flows out continuously or intermittently from the tap hole 25 of the furnace body, and is taken out as slag to the slag receiver 15 to the outside.

Further, the combustion gas generated by melting the incineration ash is sent from the exhaust gas outlet 16 through the exhaust gas duct 23 to, for example, an exhaust gas processing device, and the combustion gas is processed and exhausted from the chimney or the like to the atmosphere.

At this time, the current is PID controlled, and the voltage is determined by the distance between the counter electrodes and the variation cycle of the arc gas pressure in the case of the transfer type plasma torch 8. Further, in the case of the non-transfer type plasma torch, it is determined by the variation cycle of the arc gas pressure. Further, when a non-transfer type plasma torch is used, a plasma arc is generated between the positive electrode and the negative electrode of the plasma torch, and the incinerator ash is melted by the arc heat, that is, plasma energy.

〔The invention's effect〕

The method for melting incinerated ash according to the present invention is configured as described above and has the following effects. That is, the present invention puts incineration ash containing a high melting point substance discharged from an incinerator into a melting furnace, generates a plasma arc by using air as a plasma forming gas in a plasma torch provided in the melting furnace, Since the incineration ash is melted by the thermal energy of the plasma arc, the plasma arc is used instead of the conventional normal arc, so that a stable and stable high temperature can be obtained, the heated portion can be concentrated in a narrow range, and the entire furnace The temperature rise is small, the heat loss from the surface of the furnace is small, and there is almost no fluctuation in the electric power, so there is little effect on the power supply. Further, ignition and extinguishing of the plasma torch can be instantaneously operated, and operation and maintenance management are easy.

Furthermore, by using air as the plasma forming gas, the required air amount is small and the exhaust gas amount is small, so that the melting furnace can be downsized, and the unburned substances (usually 5% to 10%) remaining in the incinerated ash. % Of organic matter remains) can be completely decomposed, and CO,
It is possible to provide a highly safe method for treating incinerated ash that does not emit harmful unburned gas such as hydrocarbons and dioxins and is not discharged.

In particular, since the incineration ash melting treatment method according to the present invention uses plasma arc, it is possible to obtain high thermal energy, and the incineration ash containing high melting point substances such as earth and sand, pottery, and metal is directly charged into the melting furnace. Then, it can be quickly melted as it is, and unlike the conventional burner method, electric furnace method, etc., it is not necessary to selectively remove the high melting point substance from the incineration ash by using a magnetic separator, a vibration conveyor, etc. Not only can the number of working steps be reduced, but the equipment itself can be simplified and compact.

Further, the heavy metal contained in the incinerated ash is usually in the form of chloride with high volatility, but in the present invention, since air is used as the plasma-forming gas, it is volatile due to the strong oxidizing action of the air. It can be converted to low heavy metal oxides, so most of the heavy metals are melted and fixed in the molten slag, do not volatilize in the exhaust gas, and the phenomenon that these heavy metals are eluted from the generated slag occurs. do not do.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an incineration ash melting apparatus for achieving the incineration ash melting treatment method according to the present invention, and FIG. 2 is a transfer type plasma torch used in the incineration ash melting apparatus of FIG. FIG. 3 and FIG. 3 are explanatory views for explaining a non-transfer type plasma torch used in the incinerator ash melting apparatus of FIG. 1 ... Plasma system, 5 ... Plasma arc furnace, 8
...... Plasma torch, 10 …… counter electrode, 13 …… molten slag.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiro Amamiya 1-6-27 Konan, Minato-ku, Tokyo Within EBARA IN FILCO CORPORATION (72) Inventor Akira Miyamura 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa Stock company Ebara Research Institute (56) References JP-A-63-315820 (JP, A)

Claims (1)

[Claims] 1. In a method for melting incineration ash discharged from an incinerator, the incinerator ash containing a high melting point substance is put into a melting furnace and the incinerator ash is melted by a plasma arc. When melting, air is used as a plasma forming gas, alternating current is switched to direct current by a power supply device, and the direct current is supplied to the plasma torch, and a gas pressure is controlled by a control device to operate in a fluctuating cycle. A method for melting and treating incineration ash, characterized by controlling so as to stably supply a plasma arc.