JP4756929B2 - Plasma melting furnace - Google Patents

Description

  The present invention relates to a plasma melting furnace, and more particularly, to a plasma melting furnace for melting incineration ash or incineration fly ash generated by incineration of municipal waste, sewage sludge, or other waste in a waste incineration facility. Is.

  Municipal waste, sewage sludge, or other waste is incinerated at a waste incineration facility to produce incineration ash or incineration fly ash. As a method for reducing the volume of incineration ash and incineration fly ash, there is a method in which ash is introduced into a melting furnace such as a plasma melting furnace and melted (see, for example, Patent Document 1).

Such a plasma melting furnace is provided with a plasma torch for generating arc plasma in the furnace. The tip of the plasma torch, converges the arc plasma, collimator order to further stabilize the plasma gas flow is attached (for example, see Patent Document 2).

  Since incineration ash and incineration fly ash contain corrosive components such as chlorine (Cl) and sulfur (S), incineration ash and incineration fly ash are melted at a high temperature of 1300 ° C. or higher in a plasma melting furnace. Corrosive substances including molten salts such as hydrogen chloride (HCl), sulfur oxide (SOx), and sodium chloride (NaCl) are generated.

  In the plasma torch of a conventional plasma melting furnace, a collimator made of copper or a copper alloy (for example, an alloy of Cu and Zr, an alloy of Cu and Cr) is used. There was a problem that the substance contacted and adhered to the collimator and the collimator was significantly worn out. In particular, when incineration fly ash is melted, more corrosive substances are generated. Therefore, the higher the proportion of incineration fly ash that is introduced, the more the collimator wears out. As a result, the wear of the collimator proceeds significantly.

Japanese Patent Publication No. 5-19277 Japanese Patent Laid-Open No. 3-11598

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a plasma melting furnace capable of suppressing the wear of a collimator in a plasma torch and improving durability. .

In order to achieve the above object, according to one aspect of the present invention, there is provided a plasma melting furnace capable of suppressing wear of a collimator in a plasma torch and improving durability. The plasma melting furnace includes a furnace body, an ash supply device that supplies incineration ash and incineration fly ash to the inside of the furnace body, an incineration ash attached to the furnace body, and supplied to the inside of the furnace body, and A plasma torch having a positive electrode that generates arc plasma that melts incineration fly ash to generate molten slag, a furnace bottom electrode that is a cathode disposed at the bottom of the furnace body, and an electrode of the plasma torch A power source for supplying electric power to the furnace bottom electrode and generating arc plasma between the electrodes . The plasma torch has a collimator for converging arc plasma generated between the electrodes . The collimator is formed on a surface of a collimator body made of copper or a copper alloy having a cooling water passage inside and exposed to an internal atmosphere of the furnace body of the collimator body. A first layer of nickel having a thickness of 0.02 to 0.50 mm to prevent wear of the collimator body due to a corrosive substance generated by melting, and 0.02 to 0.50 mm of chromium on the first layer. And a coating film formed by plating as a second layer having a thickness of .

  According to the present invention, since the wear of the collimator in the plasma torch can be suppressed, the durability of the plasma melting furnace can be improved. Further, since the frequency of replacement of the collimator can be lowered, the cost associated with replacement of the collimator can be reduced.

  Hereinafter, embodiments of the plasma melting furnace according to the present invention will be described in detail with reference to FIGS. 1 to 4. 1 to 4, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic view showing a plasma melting furnace 10 in one embodiment of the present invention. As shown in FIG. 1, the plasma melting furnace 10 includes a furnace main body 12, an ash hopper 14 for injecting incineration ash and incineration fly ash generated in a waste incinerator or the like into the furnace main body 12, and an ash hopper 14. Ash supply device 16 that supplies the incinerated ash that has been charged into the furnace body 12, a plasma torch 20 that is attached to the upper wall 18 of the furnace body 12, and a bottom 22 of the furnace body 12 that faces the plasma torch 20. And a power source 26 for supplying power to the plasma torch 20. The inner surface of the furnace body 12 is protected by a refractory.

  A granulation chute 30 having a water injection device 28 is connected to the furnace body 12, and a slag storage tank 32 is installed at the lower end of the granulation chute 30. Further, an exhaust gas discharge port 34 is provided in the upper part of the granulating chute 30.

Incineration ash and incineration fly ash generated in a garbage incinerator or the like are stored in the ash hopper 14. The ash in the ash hopper 14 is supplied into the furnace body 12 from the supply port 12a by the ash supply device 16 disposed below the ash hopper 14. Then, a direct current voltage is applied between the plasma torch 20 and the furnace bottom electrode 24 by the power source 26 to generate arc plasma between the plasma torch 20 and the furnace bottom electrode 24. As a result, the ash charged into the furnace body 12 is melted by the generated plasma heat, and is divided into two layers, a molten slag layer 40 and a molten metal layer 42.

Since the molten slag layer 40 increases due to the supply of ash and the oxidation of the molten metal, the molten slag layer 40 in the melting furnace overflows the gate 36 and flows out to the granulation chute 30 through the discharge port 12b. In the water granulation chute 30, the molten slag is rapidly cooled by the water ejected from the water ejection device 28, becomes a granulated slag, and is discharged into the slag storage tank 32. The exhaust gas generated in the furnace main body 12 is exhausted from the exhaust gas discharge port 34 by an induction blower (not shown), and is released to the atmosphere through an exhaust gas treatment device (not shown).

  FIG. 2 is a schematic diagram showing the plasma torch 20. As shown in FIG. 2, the plasma torch 20 includes a hollow cylindrical rear electrode 50, a gas introduction port 52 that supplies a plasma generation gas to the internal space of the rear electrode 50, and a converged arc plasma P for converging. And a collimator 54. The rear electrode 50 is connected to the positive electrode of the power source 26, and the furnace bottom electrode 24 facing the plasma torch 20 is connected to the negative electrode of the power source. Further, cooling water flows outside the rear electrode 50.

  FIG. 3 is an enlarged cross-sectional view showing the collimator 54 of the plasma torch 20 of FIG. As shown in FIG. 3, the collimator 54 has a collimator body 56 formed from copper or a copper alloy, and a coating 58 formed on the surface of the collimator body 56. The collimator body 56 is formed with a flow path 60 through which cooling water flows.

The coating 58 is formed on the surface of the collimator body 56 that is exposed to the internal atmosphere of the furnace body 12 and the surface of the collimator body 56 that is in contact with the arc plasma that is ejected. As shown in FIG. 4, a film 58 may be formed on the surface of the collimator body 56 that comes into contact with the arc plasma that is ejected. Further, the film 58 may be formed on both the portion shown in FIG. 3 and the portion shown in FIG.

  Such a film 58 may be made of a metal or may be made of a material other than a metal. By forming such a coating 58, corrosive substances generated in the furnace body 12 are prevented from directly touching copper or a copper alloy which is a base material of the collimator body 56, and wear of the collimator 54 is suppressed. Can do.

  As a method of forming the metal coating 58, a plating process, a thermal spraying process, or a combination of a plating process and a thermal spraying process can be used. As a material to be used, a metal having a corrosion resistance or a metal forming an oxide film having a corrosion resistance is preferable, such as a simple metal such as nickel (Ni) or chromium (Cr), Inconel (trademark) or Hastelloy. Metal alloys such as nickel alloys are also effective.

  For example, in combination with nickel plating treatment and chromium plating treatment, first, a first layer (nickel layer) having a thickness of 0.02 mm to 0.50 mm is formed by nickel plating treatment, and 0 is formed thereon by chromium plating treatment. A second layer (chrome layer) having a thickness of 0.02 mm to 0.50 mm may be formed.

As a method of forming the coating 58 other than the metal, a thermal spraying process can be used. Examples of the material to be used include alumina (Al ₂ O ₃ ), yttria (Y ₂ O ₃ ), zirconia (ZrO), and ceramic containing a part thereof as a constituent component. Since these ceramics have a low density compared to metals formed by metal plating or metal spraying, it is effective to perform sealing treatment.

  It is considered that the wear of the collimator 54 is suppressed by such a coating 58 because an oxide film is formed on the surface of the coating 58. In particular, for chromium (Cr), an oxide film having a high density is formed, so that a high wear suppression effect can be obtained. Although this oxide film is thin in micron units and deteriorates with use, the metal surface that appears after the deterioration is oxidized again to form an oxide film, so that the suppression effect can be maintained.

  Here, with the coating film 58 having a thickness of 0.01 mm or less, a sufficient wear suppression effect by the oxide film cannot be obtained. In addition, the coating 58 having a thickness of 1 mm or more is not particularly easy to form by plating. At the same time, since the surface temperature rises, an effect as a wear margin can be expected, but not so much effect. Therefore, the thickness of the coating 58 is preferably 0.02 mm to 0.50 mm, and more preferably 0.03 mm to 0.20 mm.

The above-described plasma melting furnace was operated under the following conditions, and the incineration ash and incineration fly ash generated when municipal waste was incinerated were melted.
Melting rate: 17t / day Ash properties: Mixed ash of incineration ash and incineration fly ash (incineration ash: incineration fly ash = 85: 15)
Current for plasma generation: 1200A
Voltage for generating plasma: 600V to 1000V
Electric power for generating plasma: 700 kW to 1200 kW
Amount of plasma generation gas: 1100 SLPM to 1500 SLPM
Cooling water flow rate: 36 m ³ / h

The following four types of collimators were prepared, and the depth of wear was measured and compared for each.
1) Collimator without film (hereinafter referred to as conventional collimator)
2) A collimator (hereinafter referred to as a Ni collimator) in which a nickel (Ni) film having a thickness of 0.15 mm is formed by plating.
3) A collimator (hereinafter referred to as Ni-8YZ collimator) in which a nickel (Ni) film having a thickness of 0.15 mm is formed by plating, and a ceramic (8YZ) film having a thickness of 0.20 mm is formed thereon by thermal spraying. Called)
4) A collimator (hereinafter referred to as Ni-Cr collimator) in which a nickel (Ni) film having a thickness of 0.15 mm is formed by plating, and a chromium (Cr) film having a thickness of 0.05 mm is formed thereon by plating. Called)

  In addition, the site | part which measured the wear depth was made into the position where the line extended in the axial direction from the bending part 60a of the flow path 60 in the collimator main body 56 intersects the surface of the film 58 (or collimator main body 56) in FIG. . Since wear at this position is most severe, wear at this position determines the life of the collimator. When the depth of wear reaches 15 mm, the cooling water leaks from the flow path 60, so that the collimator 54 needs to be replaced.

  When the wear of the collimator was compared after operating for 7 days under the above-mentioned conditions, the wear of the conventional collimator was 10 mm, whereas no wear was seen in any of the Ni collimator, Ni-8YZ collimator, and Ni-Cr collimator. It was.

  Next, when the wear start time and the use limit arrival time (the number of useful days) of each collimator when operated under the same conditions as in Example 1, the results shown in Table 1 were obtained. Here, the use limit reaching time is defined as the number of days when the depth of wear becomes 12 mm or more.

  As can be seen from Table 1, the conventional collimator started to wear immediately after the start of operation, whereas the Ni collimator started to wear after 8 days, the Ni-8YZ collimator after 15 days, and the Ni-Cr collimator after 30 days. In addition, when the wear limit is reached, that is, when the wear depth reaches 12 mm (collimator service life), the conventional collimator is 8 days later, the Ni collimator is 16 days later, the Ni-8YZ collimator is 25 days later, and the Ni-Cr collimator is 40 days later. As described above, it has been clarified that by forming a film on the collimator, the service life of the collimator can be extended by 2 to 5 times compared to the conventional collimator.

  Except for the properties of ash, the same conditions as in Example 1 were used, supplying only incineration ash, supplying mixed ash of incineration ash and incineration fly ash (incineration ash: incineration fly ash = 85: 15), and incineration fly ash only For each of the supplies, the wear start time of the Ni—Cr collimator and the use limit arrival time (lifetime) were examined. The results shown in Table 2 were obtained.

Here, the ratio of the corrosive components (Cl and S) contained in the ash is 3% for the incineration ash alone, 15% for the mixed ash, and 30% for the incineration fly ash alone. From the results in Table 2 , it can be seen that the more corrosive components contained in the ash, the shorter the wear start time and the service life.

  In the embodiment described above, an example in which a transfer type plasma torch is used as the plasma torch 20 has been described. However, a non-transfer type plasma torch may be used as the plasma torch 20.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

It is a figure which shows the plasma type melting furnace in one Embodiment of this invention. It is a schematic diagram which shows the plasma torch provided in the plasma type melting furnace of FIG. It is an expanded sectional view which shows the collimator in the plasma torch of FIG. It is an expanded sectional view which shows the modification of the collimator shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Plasma melting furnace 12 Furnace main body 14 Ash hopper 16 Ash supply apparatus 20 Plasma torch 24 Furnace bottom electrode 26 Power supply 28 Water injection apparatus 30 Granulation chute 32 Slag storage tank 40 Molten slag layer 42 Molten metal layer 50 Rear electrode 52 Gas introduction Port 54 Collimator 56 Collimator body 58 Coating 60 Flow path

Claims (1)

A furnace body;
An ash supply device for supplying incineration ash and incineration fly ash to the inside of the furnace body;
A plasma torch that is attached to the furnace body and has an electrode that serves as a positive electrode that generates arc plasma that melts the incineration ash and incineration fly ash supplied to the inside of the furnace body to generate molten slag;
A furnace bottom electrode serving as a cathode disposed at the bottom of the furnace body;
A power source for supplying electric power between the electrode of the plasma torch and the furnace bottom electrode to generate arc plasma between the electrodes ;
With
The plasma torch has a collimator for converging arc plasma generated between the electrodes ,
The collimator is
A collimator body made of copper or copper alloy having a flow path of cooling water inside;
The nickel is formed on the surface of the collimator body exposed to the atmosphere inside the furnace body, and prevents the collimator body from being worn by corrosive substances generated by melting the incineration ash and incineration fly ash. A first layer having a thickness of 0.50 mm, and a coating film formed by plating as a second layer having a thickness of 0.02 to 0.50 mm on the first layer;
A plasma melting furnace characterized by comprising:

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