JP2001280635A - Surface treatment method for material of melting part for waste combustion ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a durability for a heat cycle upon start and stop of an incinerator when the surface of a heat resistant material of a melting part in the inner surface of a melting furnace is coated with a highly corrosion- resistant coating in the furnace in which ash generated by burning a combustion material including waste is heated into a molten slag. SOLUTION: The surface of the outermost layer of the heat resistant material of the melting part in the inner surface of the melting furnace in which the ash obtained by burning the waste is heated into the molten slag is coated with a spinel type compound MCr2O4 (M is Mg or divalent Fe) with a high corrosion resistance, or a mixed material composed of this compound and chromia and zirconia and an intermediate layer having an intermediate composition of a coating material and a base material is formed in a part between the base material and the coating of the outermost layer. Since the intermediate layer is formed so that thermal expansion characteristics gradually change, a thermal stress due to a heat cycle is decreased so that the coating composed of a plurality of layers hardly generating a peeling can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to industrial waste such as waste (general waste such as municipal waste from homes and offices, waste plastic, car shredder dust, waste office equipment, electronic equipment, cosmetics, etc.). The present invention relates to a method for modifying the surface of a molten portion material of a waste fuel ash constituting an inner surface of a melting furnace which heats an ash generated by incineration of a material containing a combustible material) into molten slag.

[0002]

2. Description of the Related Art As one of treatment apparatuses for waste including general waste such as municipal solid waste and combustibles such as waste plastics, waste is put into a thermal decomposition reactor and heated under a low oxygen atmosphere to heat the waste. It decomposes to form a pyrolysis gas (dry distillation gas) and a pyrolysis residue mainly composed of non-volatile components. The pyrolysis gas and the pyrolysis residue are separated in an exhaust device, and the pyrolysis residue is further purified. After cooling with a cooling device of active atmosphere,
It is supplied to a separation device to separate a combustible component mainly composed of pyrolytic carbon and a non-combustible component such as metal, pottery, and gravel, and the combustible component is pulverized into a powder. The combustible component and the pyrolysis gas are introduced into a combustion melting furnace and burned, and the resulting combustion ash is heated by the combustion heat to form molten slag, and the molten slag covers the furnace inner surface covered with a refractory material. There is known a waste treatment apparatus which flows down, discharges from a discharge part to the outside, and cools and solidifies (see Japanese Patent Publication No. 6-56253).

[0003] The high-temperature combustion gas (about 1200 ° C) generated in the combustion-melting furnace is recovered heat energy by a heat exchanger provided at the subsequent stage, is further collected by a dust collector, and finally is cleaned. It is emitted into the atmosphere from the chimney as exhaust gas.

[0004] In industrial kilns, boilers, waste incinerators and the like that require high-temperature treatment, such as steel, non-ferrous, cement, glass, and ceramics, refractories and ceramics with high heat resistance are used. In the use in an environment that comes into contact with the molten slag, it is necessary to consider severe high-temperature corrosion involving the molten slag as well as the gas phase environment such as the oxygen partial pressure and the alkali partial pressure.

In general, when the oxygen partial pressure is high,
Oxide-based heat-resistant materials are used. As a guide for selecting corrosion resistance, a basic material is used when the slag basicity is 1 or more, and a neutral or acidic heat-resistant material is used when the slag is 1 or less. . In the case of oxide-based heat-resistant materials in refuse incineration that burns and melts with air, the slag basicity is often 1 or less,
A neutral heat-resistant material mainly composed of Al ₂ O ₃ is selected.

[0006]

SUMMARY OF THE INVENTION The above ash is melted.
Molten slag is compared to steelmaking slag and other melts.
High content of alkali elements such as Na and K. That
Al₂O₃-SiO ₂, Al₂O₃-S such as SiC
In the case of i-containing heat-resistant material, SiO ₂Ma
Or produced SiO₂But alkali in ash molten slag
Reacts with, to form a low melting point alkali silicate.

[0007] Since this compound is fluidized, refractories such as furnace walls are gradually reduced in thickness. On the other hand, in the case of a high Al ₂ O ₃ refractory material or ceramics, it reacts with components such as alkali, sulfur and chlorine in the ash molten slag to lower the melting point. Therefore, the life of the refractory material or ceramics is shortened. In order to solve this, there is a method of coating the surface with a material having high corrosion resistance, but there is a problem that the material is easily peeled off by a thermal cycle of a refuse incinerator.

SUMMARY OF THE INVENTION An object of the present invention is to improve the corrosion resistance of a material of a molten portion constituting an inner surface of a furnace to ash-melted slag in a melting furnace in which ash generated by burning a combustion product including waste is heated and melted to form a molten slag. The purpose of the present invention is to eliminate the peeling of the film due to thermal cycling.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a method for heating a combustion ash of a combustion product containing a waste and producing a molten slag by melting a combustion ash component of the waste. As a surface treatment of a part material, a spinel type compound (Mg _1-α Fe _α ) _β (Cr
_{1-γ-δ Al γ Fe} σ) 2 O 4 ( provided that, 0 ≦ α ≦
1, 0.714 ≦ β ≦ 1, 0 ≦ γ, 0 ≦ δ, 0 ≦ γ + δ
The material comprising <0.5) is coated.

According to the above surface treatment method, when the ash is heated (about 1300 ° C.) to form a molten slag, the surface of the member that comes into contact with the slag is constructed of a spinel type compound. The effect avoids severe erosion.

[0011] Cr ₂ O ₃ has a large surface tension with molten slag and is hard to wet. Therefore, penetration of the molten slag is suppressed. Cr ₂ O ₃ increases the viscosity of the liquid phase upon dissolution in the molten slag. Therefore, the mass transfer rate in the slag boundary phase in contact with the heat-resistant material is reduced. Since Cr ₂ O ₃ alone is an acidic oxide, its solubility in alkali-containing slag tends to be high. However, a spinel-type substance that is an equimolar compound with a basic oxide such as MgO. When constituted, the solubility in the alkali-containing slag is suppressed.

Representative examples of the spinel-type compound having such characteristics include picrochromite MgCr ₂ O ₄ and chromite FeCr ₂ O ₄ . At this time, the molar ratio between MO and Cr ₂ O ₃ in the spinel-type compound does not need to be 1: 1 (constant ratio), but MgO · n at 1300 ° C.
By analogy with the case of Al ₂ O ₃ , the ratio of Cr ₂ O ₃ is 50.
A spinel structure can be formed in the range of ５８58 mol% (nonstoichiometric). This ratio is expressed by the formula of M _β Cr ₂ O ₄ as follows:
0.714 ≦ β ≦ 1.

Here, the metal element M at the 4-coordinate position in the spinel structure may be either Mg or divalent Fe, or a mixed state of the two at an arbitrary ratio.
Furthermore, as the metal element at the 6-coordinate position in the spinel structure, at least half or more of the metal element is Cr, and the remainder is Al or trivalent Fe. Such a C at the 6-coordinate position
The spinel-type compound in which r accounts for more than half can effectively suppress erosion by molten slag containing a high concentration of an alkali element in both stoichiometric and non-stoichiometric compounds.

When the composition selected as described above is directly formed as a film on the base material of the furnace wall, the film is easily peeled off when a thermal cycle is applied due to a difference from the thermal expansion characteristic of the base material. Therefore, a material having an intermediate composition between the film and the base material is formed as an intermediate layer, and the selected material is formed thereon. With such a multilayer structure, a film that does not peel off due to thermal cycling can be obtained.

Further, the present invention provides not only a single phase of the spinel compound but also a corundum compound (Cr)
_{1-ε-ζ Al ε Fe} ζ) 2 O 3 ( however, 0 ≦ ε 0
≦ ζ, 0 ≦ ε + ζ <0.5), and has a multi-layer structure in which a material consisting of a two-phase mixture with an outermost layer is formed on the intermediate layer. The corundum type compound reacts with the MO component in the raw material refuse in the vicinity of the operating surface during use, and forms a spinel type compound (Cr _1-γ-δ Al _γ F
e _σ ) ₂ O ₄ is generated. As a result of the multilayer structure, heat cycle characteristics are improved.

The present invention also provides a multi-layer structure having not only the single phase of the spinel-type compound but also a two-phase mixture of the spinel type compound and zirconia as an outermost layer film via an intermediate layer. It is a feature. According to the surface, when the ash is heated (about 1300 ° C.) to form a molten slag, a member in contact with the slag is coated with the Cr-containing spinel compound and zirconia, thereby avoiding severe erosion. . And the heat resistant cycle characteristic is improved by the multilayer structure.

Further, the present invention provides not only the single phase of the spinel type compound but also the corundum type compound COR
Layer mixture of zirconia and zirconia ZR (1-η-θ) · S
P + η · COR + θ · ZR (However, 0 <η <1, 0 <
It is characterized in that it has a multilayer structure in which a material consisting of θ <0.5) is provided as an outermost layer film on the intermediate layer. According to such a coating treatment, the effect of adding the above-mentioned corundum type compound COR or zirconia ZR to the spinel type compound SP is superimposed, and as a result, the durability of the member is improved. However, the proportion of zirconia to be added is 5
If it exceeds 0% by weight, it will be combined with various silicates in the molten slag and the durability will be low. And the heat resistant cycle characteristic is improved by the multilayer structure.

Further, the present invention is characterized in that metallic Cr is present in a non-oxidized state in an amount of 40% by weight or less in the material of the outermost layer coating of the multilayer structure of the present invention. During use, near the operating surface, the MO component in the raw material and oxygen in the gas phase react with the metal Cr to generate the spinel compound MCr ₂ O ₄ , thereby improving the corrosion resistance. However, the Cr metal powder to be added is 4% of the entire mixture.
If the content exceeds 0% by weight, local expansion may increase due to an oxidation reaction during use. Therefore, the content is set to 40% by weight or less. And the heat resistant cycle characteristic is improved by the multilayer structure.

Further, the present invention applies the above-mentioned surface treatment method to a protection member of a thermocouple for measuring a temperature, in particular, of a molten portion material of a waste combustion ash. 6 in spinel type compound M (Cr _{1-γ-δ Alγ} Fe _σ ) ₂ O ₄
The addition of a component other than Cr at the coordination position is set so that the total of the additive element Al and trivalent Fe does not exceed the Cr amount so as not to impair the corrosion resistance. And, the molten material of the waste combustion ash treated according to the present invention has improved durability against the thermal cycle as described above.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION <Test Example 1> As a test example 1, a test was performed using a plate-like sample. In the first embodiment, as shown in FIG.
First, as an intermediate layer 2, an aluminum / piclochromite / zirconia mixed composition (alumina / piclochromite /
A film of zirconia (50/43/7) was sprayed, and then picrochromite / zirconia was sprayed as the outermost corrosion-resistant film 4 to form a film having a total thickness of 300 μm. In this environment, the molten slag 2 flows down to the outermost layer coating, and the inside of the furnace is filled with corrosive gas 3.

As Comparative Example 1, a film having no intermediate layer was also formed. The coatings of Example 1 and Comparative Example 1 were reciprocated 10 times between 1450 ° C. and room temperature in the atmosphere to evaluate the number of occurrences of peeling, in a heat cycle, and in an environment simulating the melting part of a refuse incinerator. Was investigated for its ability to react with ash-melted slag and reduce wall thickness.

The latter is N ₂ + 5% O ₂ +1000 ppm
It was immersed in ash molten slag at 1450 ° C. for 20 hours in an HCL atmosphere to give corrosion wear. After withdrawing from the slag,
The amount of erosion was measured and compared. Table 1 shows the results obtained here. The chemical composition of the ash molten slag is shown in Table 2.

According to this, by providing the intermediate layer between the alumina sintered body and the high corrosion resistant film, the resistance to the heat cycle is improved, and the peeling of the high corrosion resistant film can be suppressed. Furthermore, compared to a plate-shaped sintered body having a single-layer structure, a plate-shaped sintered body having a multi-layer structure film as a surface film is inferior to corrosion resistance in an environment in which ash generated during refuse incineration is heated to form molten slag. I knew it wasn't.

[0024]

[Table 1]

[0025]

[Table 2]

<Test Example 2> As Test Example 2, a test was performed using a tubular sample. In the second embodiment, as in the first embodiment, the alumina / piclochromite / zirconia mixed composition (alumina / piclochromite / zirconia 50 / 43 /
7) is sprayed onto the film, and the outermost layer of a mixed powder of picrochromite / zirconia is sprayed onto the film to a total thickness of 300.
A μm film was formed.

On the other hand, as Comparative Example 2, a film having no intermediate layer was formed on a tubular sample. For these two methods, the durability against heat cycles and the amount of erosion due to corrosion and wear were measured and compared in the same manner as in Example 1. As a result, the results shown in Table 3 were obtained. That is, even in a tubular sample,
It was confirmed that the multi-layer coating had higher durability to thermal cycling than the single coating, and that there was no difference between the multi-layer coating and the single coating in corrosion resistance to molten slag.

[0028]

[Table 3]

Next, the operation will be described. By providing an intermediate layer between the base material and the outermost layer coating, the difference in the coefficient of thermal expansion between the base material and the outermost layer coating is reduced, thereby reducing the thermal stress due to the thermal cycle associated with starting and stopping the incinerator. And peeling can be prevented. Also, the formation of the intermediate layer does not affect the corrosion resistance of the entire film. As described above, the durability of the combustion melting furnace is improved, and thus the operation efficiency of the waste treatment apparatus can be improved.

Although the present invention has been described in detail with respect to the formation of a coating by thermal spraying, the present invention is not limited to only those embodiments, and various modifications can be made without departing from the spirit of the present invention. In addition, it goes without saying that a wide variety of surface treatment methods can be employed.

[0031]

As described above, according to the present invention, in a melting furnace in which ash produced by burning a combustion material containing waste is heated to form a molten slag, the melting of the waste combustion ash constituting the inner surface of the furnace is performed. With respect to the component material, it is possible to prevent peeling from the base material by coating the corrosion-resistant coating in a multilayer structure.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a surface treatment according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refractory material, heat-resistant material such as ceramics 2 Molten slag 3 Corrosive gas 4 Corrosion-resistant film 5 Intermediate layer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masakata Hashimoto 3-1-1, Tamano, Tamano-shi, Okayama Mitsui Engineering & Shipbuilding Co., Ltd. Tamano Works F-term (reference) 4K051 AA00 BD01

Claims (7)

[Claims] 1. A surface treatment of a heat-resistant material constituting an inner surface of a melting portion of a melting furnace for generating a molten slag by heating and melting a combustion ash component of a combustion material including a waste, and is formed on the heat-resistant material in advance. An outer layer film made of a spinel-type compound SP represented by the following chemical formula (1) is formed via the intermediate layer, and the intermediate layer has an intermediate composition between the material of the spinel-type compound and the material of the heat-resistant material. A surface treatment method for a molten material of a waste combustion ash, which comprises forming a film of a material. (Mg _1-α Fe _α ) _β (Cr 1 -γ _-δ Al _γ Fe _σ ) ₂ O ₄ (1) where 0 ≦ α ≦ 0.714 ≦ β ≦ 10 0 ≦ γ 0 ≦ δ 0 ≦ γ + δ <0.5 2. A surface treatment of a heat-resistant material constituting an inner surface of a melting portion of a melting furnace which heats and melts a combustion ash of a combustion product including waste to generate a molten slag is formed on the heat-resistant material in advance. Through the intermediate layer, a two-phase mixture (1--) of a spinel-type compound SP represented by the following chemical formula (1) and a corundum-type compound COR represented by the following chemical formula (2)
η) · SP + η · COR (where 0 <η <1), and a film of a material having an intermediate composition between the material of the outer film and the material of the heat-resistant material is formed on the intermediate layer. A surface treatment method for a molten portion material of a waste combustion ash, which is formed. (Mg _1-α Fe _α ) _β (Cr 1 -γ _-δ Al _γ Fe _σ ) ₂ O ₄ (1) where 0 ≦ α ≦ 0.714 ≦ β ≦ 10 0 ≦ γ 0 ≦ δ 0 ≦ γ + δ <0.5 (Cr _1−ε−ζ Al _ε Fe _ζ ) ₂ O ₃ (2) where 0 ≦ ε 0 ≦ ζ 0 ≦ ε + ζ <0.5 3. A surface treatment of a heat-resistant material constituting an inner surface of a melting portion of a melting furnace which heats and melts a combustion ash content of a waste material including a waste to generate a molten slag is formed on the heat-resistant material in advance. An outer layer coating composed of a spinel-type compound SP represented by the following chemical formula (1) and 0.1 to 50% by weight of zirconia is formed via the intermediate layer, and the intermediate layer has a material of the outer layer coating. Forming a film of a material having an intermediate composition between the material and the material of the heat-resistant material. (Mg _1-α Fe _α ) _β (Cr 1 -γ _-δ Al _γ Fe _σ ) ₂ O ₄ (1) where 0 ≦ α ≦ 0.714 ≦ β ≦ 10 0 ≦ γ 0 ≦ δ 0 ≦ γ + δ <0.5 4. A surface treatment of a heat-resistant material constituting an inner surface of a melting portion of a melting furnace for generating a molten slag by heating and melting a combustion ash content of a combustion material including a waste material is formed in advance on the heat-resistant material. Through the intermediate layer, a three-phase mixture (1-η-θ) of a spinel-type compound SP represented by the following chemical formula (1), a corundum-type compound COR represented by the following chemical formula (2), and zirconia ZR: ) ・ SP + η ・ COR + θ
Forming an outer layer coating composed of ZR (0 <η <1, 0 <θ <0.5), wherein the intermediate layer has an intermediate composition between the material of the outer layer coating and the material of the heat resistant material; A surface treatment method for a molten material of a waste combustion ash, which comprises forming a film of a material. (Mg _1-α Fe _α ) _β (Cr 1 -γ _-δ Al _γ Fe _σ ) ₂ O ₄ (1) where 0 ≦ α ≦ 0.714 ≦ β ≦ 10 0 ≦ γ 0 ≦ δ 0 ≦ γ + δ <0.5 (Cr _1−ε−ζ Al _ε Fe _ζ ) ₂ O ₃ (2) where 0 ≦ ε 0 ≦ ζ 0 ≦ ε + ζ <0.5 5. The surface treatment method according to claim 1, wherein 40% by weight or less of metallic Cr is present in the material of the outer layer coating in a non-oxidized state. Surface treatment method for the material of the molten part of waste combustion ash. 6. The surface treatment method according to claim 1, wherein the material to be subjected to the surface treatment is a protection member that protects a thermocouple for performing temperature measurement. Surface treatment method for the material of the molten part of waste combustion ash. 7. A material for a molten portion of waste ash treated by the surface treatment method according to any one of claims 1 to 6.