JP3027287B2 - Electric resistance type melting furnace and its operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric resistance type melting furnace for suitably melting a material to be melted, such as fly ash or incinerated ash generated when incineration of municipal waste or industrial waste, and its operation. It is about the method.

[0002]

2. Description of the Related Art Generally, most of molten materials such as fly ash and incinerated ash generated when municipal waste and industrial waste are incinerated are landfilled. However, it is becoming increasingly difficult to secure landfill sites every year, and there is a demand for effective use and volume reduction of the material to be melted. In addition, melted materials such as fly ash
Because it contains harmful substances such as dioxins and heavy metals,
Landfilling may cause environmental pollution due to elution of heavy metals and the like, and intermediate treatment for detoxification is required for final disposal.

[0003] In recent years, as a method for solving these problems, melting treatment of a material to be melted such as fly ash has been performed. Thus, when the material to be melted is melted, it becomes slag and the volume is greatly reduced. Further, when the material to be melted is converted into a slag, it becomes a physically and chemically stable substance, which can be effectively used for aggregates, roadbed materials, and the like, and elution of heavy metals and the like in landfills is eliminated. As described above, the melting treatment is one of the best methods for treating a material to be melted such as fly ash.

[0004] Conventionally, as a method for melting a material to be melted such as fly ash, melting by a burner or melting by electricity has been known. Above all, an electric resistance type melting method is widely used. FIG. 3 is a schematic longitudinal sectional view of a conventional electric resistance type melting furnace using an electric resistance type melting method. The melting furnace has an inlet 30a, an exhaust gas outlet 30b and a tap 30.
and a plurality of electrodes 31 and the like suspended from the ceiling wall of the furnace body 30 into the furnace. The carbon-based electrode 31 has a high melting point.
Is used. Thus, the molten material such as fly ash generated in a refuse incinerator or the like is charged into the furnace from the charging port 30a,
By flowing an electric current between the electrodes 31, the object to be melted is heated to about 1300 ° C. to 1400 ° C. by the Joule heat of the object itself and melted. The melt 34 is appropriately extracted from a tap hole formed on the peripheral wall of the furnace body 30. During operation of the electric resistance melting furnace, the inside of the furnace is operated in a reducing atmosphere in order to prevent the electrode 31 from being oxidized and consumed.

[0005]

However, the material to be melted, such as fly ash and incinerated ash, contains a large amount of unburned carbon having a high melting point and a small specific gravity in a ratio of several percent to several tens percent. May be. Thus, when the material to be melted containing unburned carbon is melted in a conventional electric resistance melting furnace, the unburned carbon has a high melting point and a low specific gravity. To form a layer floating on the surface.
As a result, when a new material to be melted is introduced into the furnace main body 30 to perform the melting process, the unburned carbon layer prevents the unburned carbon layer from melting into the melt 34, and the melting process is significantly reduced. was there. In particular, as the operation time elapses, the unburned carbon layer also becomes thicker in order to further promote the above problem. In order to solve this problem, there is a method in which air is blown into the furnace to burn unburned carbon contained in the material to be melted in the furnace, but in this case, the material to be melted does not sufficiently contact the air. Therefore, it is necessary to blow a large amount of air into the furnace. As a result, oxidation and depletion of the electrode 31 are promoted, and another problem arises in that the amount of exhaust gas and the amount of dust accompanying the exhaust gas increase.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is intended to be able to satisfactorily melt even a material containing a large amount of unburned carbon without deteriorating the processing capacity. And a method of operating the same.

[0007]

In order to achieve the above object, an electric resistance melting furnace according to the present invention comprises a method of supplying a melted material such as fly ash containing unburned carbon to a furnace body through a melt supply passage. The molten metal is melted by applying a voltage to the electrodes after being charged into the furnace, and the melt is discharged from a tap hole formed in the furnace body, and exhaust gas in the furnace is discharged from an exhaust gas outlet formed in the furnace body. in resistance type melting furnace, the object to be melt
In the supply path of the melt to be supplied by pneumatic transportation,
A part is supplied as combustion air, and unburned carbon contained in the material to be melted is radiated from inside the furnace body or radiated from the furnace.
It is characterized by providing the primary combustion chamber for burning by over Na. In addition, the method for operating the electric resistance melting furnace of the present invention is characterized in that a molten material such as fly ash containing unburned carbon is charged into the furnace main body from a molten material supply passage and a voltage is applied to the electrode. melted, while tapping the melt from the pouring port formed in the furnace body, in the operating method of the electric resistance type melting furnace to discharge from the exhaust gas outlet gas was formed in the furnace body of the furnace, the Melted material supplied by pneumatic transportation
A primary combustion chamber is provided in the material supply path, and the primary combustion chamber
Supply a part of the transportation air with the goods as combustion air,
The unburned carbon contained in the material to be melted in the primary combustion chamber
It is characterized in that after being burned by radiant heat or a burner from within the furnace body, the material to be melted is charged into the furnace body and melted.

[0008]

The material to be melted containing unburned carbon is supplied to the primary combustion chamber from the material supply passage, where the unburned carbon is burned and then injected into the furnace body to be melted.
Even when the material to be melted is melted, the unburned carbon is already burned, so that the carbon does not float on the surface of the melt to form a layer. After the unburned carbon is burned in the primary combustion chamber, the melt to be subsequently charged is charged into the furnace main body to be melted. At this time, the material to be melted quickly melts into the melt, and is rapidly melted, due to the fact that the carbon layer is not formed on the surface of the melt in the furnace. Needless to say, since the unfused carbon is not contained in the material to be melted, it does not mean that the carbon floats on the surface of the melt to form a layer.

During operation of the electric resistance type melting furnace, a material containing unburned carbon is charged into the furnace body after burning the unburned carbon in the primary combustion chamber. Since the melting process is performed, even when the material to be melted containing a large amount of unburned carbon is melted, the unburned carbon is prevented from floating on the melt and forming a layer. be able to. As a result, the material to be melted which is sequentially charged into the furnace body immediately receives heat from the melt and is rapidly melted.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic system diagram of a melting processing system using an electric resistance melting furnace according to an embodiment of the present invention.
Is an electric resistance type melting furnace composed of a furnace body 2, an electrode 3 and a primary combustion chamber 4, etc., 5 is a melt storage tank for storing a melt 6 such as fly ash and incineration ash, and 7 is a melt supply passage. , 8 is a blower for transporting the molten material, 9 is a cyclone separator, 10 is a branch for air, 11 is an exhaust gas discharge channel, 12 is a gas cooling tower, 13
Is a dust collector, 14 is an exhaust gas treatment device, 15 is a damper, 1
6 is an induction ventilator, 17 is a chimney, 18 is a controller, 19 is an oxygen concentration detector (or carbon monoxide concentration detector), 20
Is a pressure detector.

The furnace body 2 of the electric resistance type melting furnace 1 is formed in a cylindrical box shape by a peripheral wall 2a, a ceiling wall 2b, and a bottom wall 2c formed of a steel plate and a refractory material such as a refractory brick. The molten material 6 such as fly ash is introduced into the periphery of the wall 2b.
And an exhaust gas outlet 2e for discharging exhaust gas in the furnace are formed at the periphery of the ceiling wall 2b opposite to the injection port 2d. Furthermore, the peripheral wall 2a
Is formed with a tap hole (not shown) for extracting the melt 21 in the furnace.

The electrode 3 is disposed so as to be inserted through the center of the ceiling wall 2b of the furnace main body 2, and is generally hung from the ceiling wall 2b into the furnace. The electrode 3 is automatically raised and lowered by an appropriate lifting device (not shown), and the immersion depth of the electrode 3 in the melt 21 layer is adjusted according to the amount of melting of the material 6 to be melted or the amount of current. It can be adjusted.
Note that a plurality of carbon-based electrodes are used for the electrode 3.

The primary combustion chamber 4 is provided in a melt supply path 7 extending from the melt storage tank 5 to the inlet 2d of the furnace body 2, and the melt 6 is supplied from the inlet 2d to the furnace body 2 through the inlet 2d. The unburned carbon contained therein is burned before being introduced into the inside. In the present embodiment, the primary combustion chamber 4 is provided in a portion of the melt supply passage 7 directly above the ceiling wall 2 b of the furnace main body 2, and is formed by surrounding the inlet 2 d of the ceiling wall 2 b with the fireproof wall 22. Have been. Also, the primary combustion chamber 4
Is in communication with the inside of the furnace through the inlet 2d,
Radiant heat is received from inside the furnace body 2. Further, a part of the air for transporting the molten material is used as the combustion air supplied to the primary combustion chamber 4, and this air is sucked into the primary combustion chamber 4 by the induction ventilator 16. . The amount of combustion air sucked into the primary combustion chamber 4 is adjusted by controlling the damper 15 by the controller 18. That is, the controller 18 includes the oxygen concentration detector 19
Is controlled based on the oxygen concentration of the exhaust gas outlet 2e detected by the pressure sensor and the pressure in the furnace main body 2 detected by the pressure detector 20, and the controller 18 maintains a predetermined pressure and a reducing atmosphere in the furnace, In addition, damper 15 is drawn into primary combustion chamber 4 so that air enough to burn unburned carbon is sucked.
Is controlling.

Next, a description will be given of a case where the melted material 6 such as fly ash is melted using the melting system configured as described above. The molten material 6 such as fly ash stored in the molten material storage tank 5 is transported in the molten material supply path 7 by air blown from the blower 8 for transporting the molten material, and is pneumatically transported to the cyclone separator 9. And after separating the air here,
After passing through the primary combustion chamber 4, it is charged into the furnace main body 2 from the charging port 2d.

The material 6 to be melted introduced into the furnace main body 2 is heated to about 1400 ° C. by the Joule heat of the material to be melted 6 and melted by passing a current between the electrodes 3. Thereby, 21 layers of the melt are formed in the furnace main body 2. Since the amount of the melt 6 to be initially charged into the furnace body 2 is relatively small, the amount of unburned carbon contained in the melt 6 is also small. As a result, the carbon layer does not float on the melt 21 layer.

When the melt 21 layer is formed in the furnace body 2, the melts 6 in the melt storage tank 5 are successively charged into the furnace body 2. That is, the molten material 6 in the molten material storage tank 5 is pneumatically transported to the cyclone separator 9 by blowing air from the blower 8 for transporting the molten material in the same manner as described above. It is sequentially supplied to the combustion chamber 4.

The molten material 6 supplied into the primary combustion chamber 4
The unburned carbon contained in the material to be melted 6 is instantaneously burned in the primary combustion chamber 4 by radiant heat from inside the furnace body 2. At this time, a part of the air for transporting the molten material is used as the combustion air, and this air is
Is drawn into the primary combustion chamber 4. The amount of combustion air is adjusted by the controller 18 controlling the damper 15 based on the oxygen concentration at the exhaust gas outlet 2 e and the pressure in the furnace body 2. It is set so that unburned carbon can be burned in the primary combustion chamber 4 while maintaining a reducing atmosphere.

Molten material 6 from which unburned carbon is burned
Fall from the primary combustion chamber 4 into the furnace main body 2 through the charging port 2d, and are sequentially melted. At this time, the material to be melted 6 immediately dissolves into the melt 21, due to the fact that the carbon layer is not formed on the surface of the melt 21, and is rapidly melted. Of course, the unburned carbon contained in the material to be melted 6 has already been burned in the primary combustion chamber 4, and thus does not float on the surface of the melt 21 to form a carbon layer.

On the other hand, the exhaust gas generated in the furnace main body 2 is discharged from an exhaust gas outlet 2e, cooled in a gas cooling tower 12, collected by a dust collector 13 to collect volatile matters, etc. After that, it is discharged from the chimney 17. Further, the melt 21 accumulated in the furnace main body 2 with the elapse of the operation time is appropriately discharged from the tap hole.

During operation of the electric resistance melting furnace 1,
Since the unburned material 6 containing unburned carbon is incinerated by radiant heat in the primary combustion chamber 4 and then put into the furnace main body 2 for melting treatment, Even in the case where the molten material 6 containing a large amount of combustible carbon is melted, it is possible to prevent unburned carbon from floating on the molten material 21 to form a layer. As a result, the material to be melted 6 sequentially injected into the furnace body 2 receives heat immediately from the melt 21 and is rapidly melted.
Further, since carbon is burned by radiant heat from the furnace main body 2, a fuel such as oil or gas is not required, and it is possible to prevent an increase in processing cost.

In the above embodiment, unburned carbon contained in the melt 6 is incinerated by radiant heat in the primary combustion chamber 4, but in other embodiments, it is incinerated. Alternatively, a burner (not shown) may be provided in the primary combustion chamber 4, and the unburned carbon contained in the material 6 to be melted may be burned in the primary combustion chamber 4 using the burner. Further, the burner is used only when the electric resistance type melting furnace 1 is started to operate, and the unburned carbon in the molten material 6 charged first is burned by the burner. The unburned carbon inside may be burned by radiant heat.
This makes it possible to burn all unburned carbon in the melt 6 to be charged into the furnace, which is extremely convenient.

FIG. 2 is a schematic system diagram of a melting processing system using an electric resistance melting furnace 1 according to another embodiment of the present invention. In addition to being installed in the vicinity, a combustion air supply passage 23 is connected to the primary combustion chamber 4 so that the material 6 to be melted and the combustion air are separately supplied into the primary combustion chamber 4. In the primary combustion chamber 4, unburned carbon contained in the material 6 to be melted is burned by radiant heat from the furnace or by a burner provided in the primary combustion chamber 4. In this case, the same operation and effect as the above embodiment can be obtained.

[0023]

As described above, according to the present invention, the primary combustion chamber is provided in the molten material supply passage for supplying the molten material into the furnace body, and the unburned material contained in the molten material in the primary combustion chamber is provided. After the carbon is burned, the material to be melted is put into the furnace body for melting, so even if the material to be melted containing a large amount of unburned carbon is melted, The burning carbon does not float above the melt to form a layer. As a result, the material to be melted sequentially charged into the furnace body immediately receives heat from the melt in the furnace, and is rapidly melted. As a result, the melt processing capacity is greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a melting processing system using an electric resistance melting furnace according to an embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view of a melting processing system using an electric resistance melting furnace according to another embodiment of the present invention.

FIG. 3 is a schematic longitudinal sectional view of a conventional electric resistance melting furnace.

[Explanation of symbols]

1 is an electric resistance melting furnace, 2 is a furnace main body, 3 is an electrode, 4 is a primary combustion chamber, 6 is a material to be melted, 7 is a supply path for a material to be melted, and 21 is a melt.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kiyoyuki Kitayama 978 Ono, Ono, Itoigawa, Niigata Prefecture Incorporated Tanabe Co., Ltd. (72) Inventor Kenzo Rokumachi 978, Ono, Ono, Itoigawa, Niigata Pref. Reference JP-A-55-67396 (JP, A) JP-A-57-24687 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23J 1/00 F23G 5/00 115 F23G 7 / 00 103

Claims (2)

(57) [Claims] An object to be melted such as fly ash containing unburned carbon is introduced into a furnace main body from a melt supply path and is melted by applying a voltage to an electrode. The molten material is supplied by pneumatic transportation in an electric resistance melting furnace in which the hot water is discharged from the formed tap hole and the exhaust gas in the furnace is discharged from an exhaust gas outlet formed in the furnace main body .
A part of the transportation air and combustion air
And an unburned carbon contained in the material to be melted is provided with a primary combustion chamber for burning the unburned carbon by radiant heat from the furnace body or a burner . 2. A material to be melted such as fly ash containing unburned carbon is introduced into a furnace body from a material supply passage and is melted by applying a voltage to an electrode. In the method for operating an electric resistance type melting furnace, in which the molten metal is discharged from the formed tap hole and the exhaust gas in the furnace is discharged from an exhaust gas outlet formed in the furnace body, the molten material is transported by air.
A primary combustion chamber is provided in the supply path
For burning part of the transport air together with the melt in the primary combustion chamber
It is supplied as air, and the unburned carbon contained in the material to be melted in the primary combustion chamber is radiated from the furnace body to radiant heat or a burner.
A method for operating an electric resistance type melting furnace, wherein a material to be melted is put into a furnace body and then melted after further burning.