JP2004196637A - Monolithic refractory for waste melting furnace and waste melting furnace lined with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a monolithic refractory which has a comparable durability to a refractory containing chromium oxide such as an alumina-chromium oxide-based refractory even not substantially containing chromium oxide, when it is used for a lining of a waste melting furnace. <P>SOLUTION: The monolithic refractory which is very excellent in anti-corrosive properties as the lining of the waste melting furnace contains tin oxide of 0.5-40 mass% in terms of SnO<SB>2</SB>. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００５４】
【表2】

試験結果が示すとおり、本発明の実施例はいずれも優れた耐食性を示す。その耐食性は酸化クロム含有のアルミナ−酸化クロム質の比較例７にくらべても遜色がない。また、中でも結合剤にアルミナセメントを使用したものが耐食性に優れている。
【００５５】
これに対し、酸化スズを添加していない比較例１、酸化スズ添加量が多過ぎる比較例２は耐食性に劣る。アルミナ−炭化系素質の比較例３、アルミナ−マグネシア質の比較例４は、アルミナ−ジルコニア質の比較例５についても、本発明の実施例に比較して耐食性に劣る。
【００５６】
比較例７はアルミナ−酸化クロム質不定形耐火物である。良好な耐食性を示すものの、酸化クロムを10質量％含み、使用後の耐火物中に環境上有害な六価クロムが多量に生成する。
【００５７】
図２は、酸化スズを10質量％含む実施例2の不定形耐火物をベースにアルミナ原料の増減で耐火性配合物中のＡｌ₂Ｏ₃成分の割合を変化させ、Ａｌ₂Ｏ₃の割合と不定形耐火物の耐食性との関係を試験し、その結果をグラフに示したものである。また、耐食性は実施例2（Ａｌ_２Ｏ_３：88.7％）の侵食寸法を100とした指数で表した。
【００５８】
同グラフの結果から、酸化スズを本発明の範囲内で含む不定形耐火物の耐食性において、Ａｌ₂Ｏ₃成分の割合が55質量％以上、さらには60質量％以上の材質が好ましいことが確認される。
【００５９】
また、以上の本発明実施例での優れた耐食性向上の効果は実機試験においても同様である。
【００６０】
【発明の効果】
廃棄物溶融炉特有のスラグ成分、超高温操業に対し、本発明の耐火物は以上の試験結果が示とおり、優れた耐食性を発揮する。また、本発明は実質的に酸化クロムを含まない材質であっても、酸化クロムを含む材質に匹敵する耐用性を示す。
【００６１】
ガス化溶融炉、灰溶融炉等の廃棄物溶融炉は廃棄物の減容化に効果的である反面、その過酷な操業条件のために高耐用の耐火物が求められる。本発明はこれに対応できる耐火物として、また環境面で好適な耐火物として、その産業的価値はきわめて高い。
【図面の簡単な説明】
【図１】アルミナ質不定形耐火物において、酸化スズの割合と耐火物の耐食性との関係を示したグラフである。
【図２】耐火性配合物中のＡｌ₂Ｏ₃の割合と不定形耐火物の耐食性との関係を示したグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an amorphous refractory for a waste melting furnace and a waste melting furnace lined with the same.
[0002]
[Prior art]
In recent years, the amount of generated waste has been increasing steadily, and its disposal has become a major social problem. Landfilling of waste requires a huge land area, and it is not easy to secure the land. Conventionally, the volume of waste has been reduced by incinerators, but it is difficult to secure even land for reclaiming the incinerated ash. Therefore, in order to further reduce the volume of waste, a gasification melting furnace for directly melting waste or an ash melting furnace for melting incineration ash of waste has appeared.
[0003]
The waste melting furnace is operated continuously for a long time, and its operating temperature is extremely high, over 1300 ℃. In addition, the slag of the furnace contents has a low basicity with a CaO / SiO ₂ weight ratio of 0.5 to 1.5, and has a high content of alkali components represented by K ₂ O and Na ₂ O. It is a severe use condition.
[0004]
In particular, refractories containing a basic refractory raw material or a neutral refractory raw material have poor corrosion resistance to this low basicity slag. Further, the slag having a low basicity has low viscosity and the alkali component of the slag easily penetrates into the refractory structure, thereby reducing the corrosion resistance of the refractory.
[0005]
Refractories used in waste melting furnaces are broadly classified into fixed refractories and irregular refractories. The construction of fixed refractories is brickwork, requires heavy labor and requires a high level of skill. In recent years, lining with irregular shaped refractories has been widely used.
[0006]
A material conventionally used as an amorphous refractory for a waste melting furnace is an alumina-chromium oxide amorphous refractory containing chromium oxide. This material exhibits excellent corrosion resistance in combination with the volume stability of alumina and the slag resistance of chromium oxide. However, there has been a problem that chromium oxide generates hexavalent chromium harmful to the human body, and slag and refractory waste after use cause environmental pollution.
[0007]
Therefore, there has been proposed an amorphous refractory for a waste melting furnace which does not contain chromium oxide and has excellent corrosion resistance. For example, ZrO ₂ -SiC material (for example, Patent Document 1), ZrB ₂ -SiC material (for example, Patent Document 2), ZrO ₂ -ZrB ₂ -SiC material (for example, Patent Document 3), MgO-Al ₂ O ₃ .MgO material (Eg, Patent Document 4), MgO—Al ₂ O ₃ .MgO—ZrO ₂ (for example, Patent Document 5), and Al ₂ O ₃ —MgO (for example, Patent Document 6).
[0008]
[Patent Document 1]
JP 2000-239072 A (pages 1-7)
[0009]
[Patent Document 2]
JP 2000-327436 A (pages 1-6)
[0010]
[Patent Document 3]
JP-A-2000-335969 (pages 1-7)
[0011]
[Patent Document 4]
JP 2001-253782 A (pages 1-7)
[0012]
[Patent Document 5]
JP 2002-128573 A (pages 1-6)
[0013]
[Patent Document 6]
JP 2001-153321 A (pages 1-9)
[0014]
[Problems to be solved by the invention]
However, none of the above-mentioned conventional materials has sufficient corrosion resistance. The components of ZrO ₂ and MgO are easily eluted into slag of low basicity, and are poor in alkali erosion resistance. In the case of a material containing ZrB _{2 and} silicon carbide, the waste melting furnace operates in an oxidizing atmosphere, so that the ZrB ₂ and silicon carbide components are oxidized, and the corrosion resistance is reduced.
[0015]
SUMMARY OF THE INVENTION It is an object of the present invention to obtain a chromium oxide-containing, amorphous, refractory material having a service life comparable to that of, for example, alumina-chromium oxide, which is substantially free of chromium oxide, as a lining of a waste melting furnace.
[0016]
[Means for Solving the Problems]
The amorphous refractory of the present invention exhibits extremely excellent corrosion resistance as a lining of a waste melting furnace by containing 0.5 to 40% of tin oxide in terms of SnO ₂ in mass ratio. Since there is almost no viscosity and thermodynamic data of the tin oxide-containing melt, the mechanism of improving the corrosion resistance of the present invention by tin oxide is not necessarily clear, but from the experiments and observations of the present inventors, the following is considered. .
[0017]
For example, amorphous refractories based on alumina raw materials are easily eroded to low basicity slag of waste melting furnaces, and tin oxide was added to this within the range limited by the present invention. In this case, the slag erosion resistance is significantly improved.
[0018]
The low basicity slag of the waste melting furnace has low viscosity, but the tin oxide contained in the refractory dissolves in the slag at the site of contact with the refractory, so that the viscosity of the slag increases. The high viscosity of the slag adheres to the refractory surface, forms a high-viscosity slag coating on the refractory surface, and protects the refractory structure and prevents the entry of alkali components into the refractory structure. And the corrosion resistance is improved.
[0019]
Tin oxide has a lower melting point than general refractory raw materials, and is incompatible with the formulation of refractory for waste melting furnaces under severe operating conditions from technical common sense. Therefore, by using tin oxide within the range limited in the present invention, the effect of improving the corrosion resistance obtained by increasing the viscosity of the low basicity slag specific to the waste melting furnace can be easily predicted from the prior art. Not something.
[0020]
The refractory aggregate in the amorphous refractory of the present invention is, for example, one or two or more selected from alumina raw materials, alumina-silica raw materials, silica raw materials, spinel raw materials, and magnesia raw materials. When the main component is alumina, the effect of improving the corrosion resistance by adding tin oxide becomes more remarkable. This is considered to be because the alumina raw material is excellent in volume stability and relatively difficult to react with tin oxide, and thus tin oxide, which increases the viscosity of slag, is likely to elute from the refractory structure.
[0021]
Further, even if the amorphous refractory of the present invention is made of a material substantially free of chromium oxide, it can obtain corrosion resistance comparable to that of a conventional chromium oxide-containing product. By using a material substantially free of chromium oxide, there is no generation of hexavalent chromium harmful to the human body, and the problem of environmental pollution is solved.
[0022]
FIG. 1 is a graph showing the relationship between the ratio of tin oxide and the corrosion resistance of a refractory, taking an alumina refractory as an example. Here, the corrosion resistance was measured by changing the ratio of tin oxide based on the amorphous refractory having the composition of Example 2 described later. The measurement of the corrosion resistance was carried out based on the test method shown in the section of Examples, and was represented by an index with the erosion dimension of a material not containing tin oxide being 100.
[0023]
From the graph, it is confirmed that the amorphous refractory containing tin oxide in a ratio limited in the present invention has excellent corrosion resistance to slag of a waste melting furnace.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Tin oxide includes stannous oxide (SnO) and stannic oxide (SnO ₂ ). In the present invention, it is preferable to use stannic oxide which is stable in an oxidizing atmosphere which is the operating condition of the waste melting furnace. The purity is preferably high so that it works effectively even when a small amount is added, and is, for example, 80% by mass or more, more preferably 95% by mass or more in terms of SnO ₂ .
[0025]
The ratio of tin oxide in the amorphous refractory is 0.5 to 40% by mass, more preferably 1 to 30% by mass. In accordance with this, tin oxide is used at a ratio of, for example, 0.5 to 40%, more preferably 1 to 30% in the refractory composition when producing an amorphous refractory.
[0026]
If the proportion of tin oxide is small, the effect of improving corrosion resistance of the present invention cannot be obtained. If the amount is too large, the tin oxide reacts with the refractory raw material or the binder component, generates a large amount of low melting point substances, and deteriorates the corrosion resistance.
[0027]
The particle diameter of tin oxide is, for example, 1 mm or less, more preferably 0.5 mm or less in the JIS sieve opening, in order to sufficiently enhance the effect of improving the corrosion resistance of the present invention by using tin oxide. Is preferred. When the amount of tin oxide used is large, a combination of particles having a particle size exceeding 1 mm may be used in view of the balance of the particle size composition of the entire refractory composition in order to achieve a dense packing of the amorphous refractory.
[0028]
Specific examples of the alumina raw material used as the refractory raw material in the present invention include sintered alumina, fused alumina, shale, bauxite, and the like. Above all, synthetic products such as sintered alumina and electrofused alumina having high Al ₂ O ₃ purity are preferable. Calcined alumina may be used for the fine powder portion.
[0029]
When the alumina material is mainly used as the refractory raw material, the amorphous refractory of the present invention has a remarkable improvement in corrosion resistance in relation to tin oxide. Specifically, it is 55% by mass or more, more preferably 65% by mass or more of Al ₂ O ₃ in the chemical composition in proportion to the refractory composition. The Al ₂ O ₃ component is supplied not only from a refractory raw material such as an alumina raw material, an alumina-silica raw material, or a MgO.Al ₂ O ₃ -based spinel raw material (hereinafter referred to as a spinel raw material), but also, for example, an alumina cement. It becomes.
[0030]
As the refractory raw material other than the alumina raw material, for example, one or more selected from alumina-silica raw material, spinel raw material, zirconia raw material, and magnesia raw material can be used.
[0031]
Alumina-siliceous raw materials include electrofused mullite and sintered mullite, as well as natural mullite and pyroxene. In addition, a raw material containing andalusite, sillimanite, kyanite and the like as main minerals can also be used.
[0032]
Specific examples of the spinel raw material are, for example, an electrofused spinel or a sintered spinel. From an economical point of view, spinel slag produced as a by-product during vanadium refining may be used. A calcined spinel may be used for the fine powder portion. The component (MgO.Al ₂ O ₃ ) of the spinel is not limited to the theoretical value of the spinel, but may be, for example, an alumina-rich spinel having a large Al ₂ O ₃ value.
[0033]
Examples of zirconia raw materials include zircon and zirconia. Specific examples of zirconia include, for example, stabilized zirconia or partially stabilized zirconia to which CaO, MgO, Y ₂ O _3, etc. are added.
[0034]
Examples of the magnesia raw material include electrofused or sintered magnesia and magnesia-calcia as synthetic products. Natural magnesia may be used. Light burned magnesia can also be used as fine powder. When the alumina raw material and this magnesia raw material are used together, spinel is generated at high temperature when using the refractory, and the volume expansion accompanying the spinel generation densifies the refractory structure, prevents slag penetration and prevents corrosion of the refractory. Is further improved.
[0035]
Since the magnesia raw material is a refractory raw material having a large thermal expansion property, the amount of the magnesia raw material is preferably not more than 20% by mass in the refractory compound so as not to impair the spalling resistance of the amorphous refractory.
[0036]
When the amorphous refractory of the present invention is made of a material substantially free of chromium oxide, the problem of environmental pollution can be solved. The phrase “substantially not contained” includes not only the case where chromium oxide is not contained at all but also the case where chromium oxide is contained as an unavoidable impurity, and a small amount of magnesia raw material is added as a digestion inhibitor.
[0037]
The content of chromium oxide in a conventional refractory containing chromium oxide is 10 to 60% by mass. On the other hand, chromium oxide used as an antidigestion agent for magnesia raw material is usually 1 to 3% by mass in the magnesia raw material. In addition, the preferred amount of the magnesia raw material is 20% by mass or less, and the amount of chromium oxide in this case is 0.6% by mass or less when converted to the proportion of the refractory composition. As described above, the use of chromium oxide as an antidigestion agent for magnesia raw materials is extremely small, and has little effect on environmental pollution.
[0038]
Further, chromium oxide may be further added to the amorphous refractory of the present invention, but chromium oxide has a problem of environmental pollution as described above. Therefore, even when chromium oxide is added, it is preferable to minimize the amount.
[0039]
The particle size of the refractory raw material is adjusted, for example, to a coarse particle, a medium particle, or a fine particle, for example, with a maximum particle diameter of 3 to 10 mm. For the purpose of imparting spalling resistance to the amorphous refractory, in addition to the coarse, medium, and fine particles described above, a refractory aggregate having a large particle diameter of, for example, 10 to 50 mm may be combined. The refractory raw material may be used after refractory use, refractory waste material, or the like, and the particle size of which is adjusted.
[0040]
To the extent that the effects of the present invention are not impaired, silica, volatile silica, clay, carbon, glass, slaked lime, silicon nitride, silicon nitride, and the like may be used in an amount of, for example, 20% by mass or less, in addition to the above as a refractory raw material. , More preferably 10% by mass or less. In particular, volatile silica is excellent in imparting fluidity during construction of a refractory and is effective in densifying the construction body structure.
[0041]
The specific type and amount of the binder are not particularly different from those used for conventional amorphous refractories. For example, alumina cement, magnesia cement, phosphate, silicate, colloidal silica, colloidal alumina and the like can be used. Among them, alumina cement is preferred. The amount of the binder used is preferably 0.5 to 10% by mass in the refractory composition. Colloidal silica, colloidal alumina and the like are aqueous solutions. In the case of an aqueous binder, the amount used in the present invention is in terms of solids.
[0042]
Alumina cement is excellent in imparting strength to the construction body structure. Further, the Al ₂ O ₃ component contained therein hardly reacts with tin oxide, and the Al ₂ O ₃ component which hardly reacts with the tin oxide due to ultrafine powder intervenes in the matrix of the amorphous refractory structure, Tin oxide is easily eluted during use. Thus, the use of alumina cement as a binder effectively affects the improvement of the corrosion resistance of the present invention by tin oxide.
[0043]
The dispersant imparts fluidity during construction of the amorphous refractory. Specific examples are not limited at all, for example, sodium tripolyphosphate, sodium hexametaphosphate, sodium polypolyphosphate, sodium acid hexametaphosphate, sodium borate, sodium carbonate, inorganic salts such as polymetaphosphate, sodium citrate Sodium tartrate, sodium polyacrylate, sodium sulfonate, polycarboxylates, β-naphthalene sulfonates, naphthalenesulfonic acid, and carboxyl group-containing polyether dispersants. The addition amount is preferably 0.01 to 1% by mass, more preferably 0.03 to 0.5% by mass, based on 100% by mass of the refractory composition.
[0044]
In addition to the above refractory raw materials, binders and dispersants, if necessary, known as additives for amorphous refractories, drying accelerators, metal powders such as Al and Si, metal fibers, organic fibers, ceramics Fibers, basic aluminum lactate, antioxidants, thickeners, curing agents, curing retarders and the like may be added.
[0045]
Construction of the refractory of the present invention is performed by pouring, press-fitting, spraying, or the like. In the spraying, a part or all of the binder or a quick-setting binder may be added at the nozzle portion. The working moisture is, for example, 3 to 13% by mass, and more preferably 3 to 7% by mass, based on the entire amorphous refractory. In addition, this construction is not limited to new construction of a furnace wall or the like, but may be additional construction for repair.
[0046]
In the pouring work, a formwork is used. The working moisture is preferably, for example, 3 to 7% by mass with respect to the entire amorphous refractory. At the time of construction, it is preferable to apply vibration to promote filling. After construction, cure and dry.
[0047]
For the construction, in addition to the direct construction to the waste melting furnace, a precast product obtained in advance at another place may be used. A combination of both the direct construction and the precast product may be used.
[0048]
Even when the lining of the waste melting furnace is constructed of irregular refractories, refractory bricks may be used partially. In addition, in places where the type of the refractory is not in direct contact with the slag, a refractory of a different material such as an adiabatic refractory may be used. In a waste melting furnace in which a refractory of a different material is used for each of such zones, the amorphous refractory of the present invention exerts its excellent corrosion resistance as a lining at a site where the use conditions are strictest.
[0049]
【Example】
The composition and test results of Examples of the present invention and Comparative Examples are shown below. The test method is as follows. In each of the tests, the working water was added in an amount of 4% by mass, and after kneading, the mixture was poured into a vibrating mold and molded. Next, curing and drying were performed to obtain a test sample.
[0050]
Flexural strength: A test sample of 40 × 40 × 160 mm was measured according to JIS R2205.
[0051]
Corrosion resistance: A test sample molded into a regular brick shape was lined in a rotary erosion furnace to measure corrosion resistance. The slag (CaO / SiO ₂ : 0.74) discharged from the gasification and melting furnace was used as an erosion agent, and after erosion was performed at 1500 ° C. for 20 hours, the erosion dimension was measured. did. The smaller the value, the better the corrosion resistance.
[0052]
Actual machine test: A garbage melting furnace with a garbage disposal rate of 100 tons per day was lined, and the wear rate (mm / month) was measured after 12 months of use. The operating temperature of this gasification and melting furnace is 1400 ° C., and its slag component is mass%, SiO ₂ : 42.8, CaO: 31.7, Al ₂ O ₃ : 12.4, Fe ₂ O ₃ : 4.8, Na ₂ O: 3.7, ( CaO / SiO ₂ : 0.74).
[0053]
【table 1】

[0054]
[Table 2]

As shown by the test results, all of the examples of the present invention show excellent corrosion resistance. Its corrosion resistance is not inferior to Comparative Example 7 of alumina-chromium oxide containing chromium oxide. In particular, those using alumina cement as a binder are excellent in corrosion resistance.
[0055]
In contrast, Comparative Example 1 in which tin oxide was not added and Comparative Example 2 in which the amount of tin oxide added was too large were inferior in corrosion resistance. Comparative Example 3 of the alumina-carbide material and Comparative Example 4 of the alumina-magnesia material are also inferior in corrosion resistance to Comparative Example 5 of the alumina-zirconia material as compared with the examples of the present invention.
[0056]
Comparative Example 7 is an alumina-chromium oxide amorphous refractory. Although exhibiting good corrosion resistance, it contains 10% by mass of chromium oxide and generates a large amount of environmentally harmful hexavalent chromium in refractories after use.
[0057]
2 changes the ratio of Al ₂ O ₃ component in refractory formulations in decreasing the alumina raw material based monolithic refractory of Example 2 containing tin oxide 10 wt%, the proportion of Al ₂ O ₃ The relationship between the corrosion resistance of the refractory and the amorphous refractory was tested, and the results are shown in the graph. Further, the corrosion resistance was represented by an index with the erosion dimension of Example 2 (Al ₂ O ₃ : 88.7%) being 100.
[0058]
From the results of the graph, it was confirmed that, in the corrosion resistance of the amorphous refractory containing tin oxide within the scope of the present invention, a material having an Al ₂ O ₃ component ratio of 55% by mass or more, and more preferably 60% by mass or more is preferable. Is done.
[0059]
Further, the excellent effect of improving the corrosion resistance in the embodiment of the present invention described above is the same in the actual machine test.
[0060]
【The invention's effect】
As shown in the above test results, the refractory of the present invention exhibits excellent corrosion resistance to slag components specific to waste melting furnaces and ultrahigh-temperature operation. In addition, the present invention shows a durability comparable to a material containing chromium oxide even if the material does not substantially contain chromium oxide.
[0061]
Waste melting furnaces such as gasification melting furnaces and ash melting furnaces are effective in reducing the volume of waste, but are required to have high durability refractories due to their severe operating conditions. The present invention has a very high industrial value as a refractory that can cope with this and as a refractory suitable for the environment.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the ratio of tin oxide and the corrosion resistance of a refractory in an alumina-based amorphous refractory.
FIG. 2 is a graph showing the relationship between the proportion of Al ₂ O ₃ in the refractory composition and the corrosion resistance of the amorphous refractory.

Claims (10)

An amorphous refractory for waste melting furnaces containing 0.5 to 40% tin oxide by mass. An amorphous refractory for a waste melting furnace containing a refractory composition containing 0.5 to 40% of tin oxide in mass ratio, the balance being a refractory raw material and a binder, and a dispersant. _3. The waste according to claim 2, wherein the refractory raw material is mainly one or two or more selected from an alumina raw material, an alumina-silica raw material, a MgO.Al ₂ O ₃ spinel raw material, a zirconia raw material, and a magnesia raw material. Irregular refractories for melting furnaces. 3. The amorphous refractory for a waste melting furnace according to claim 2, wherein the refractory raw material is mainly composed of an alumina raw material. 5. The amorphous refractory for a waste melting furnace according to claim 4, wherein the content of Al ₂ O ₃ in the chemical composition is 55% by mass or more as a percentage of the refractory composition. 6. The amorphous refractory for a waste melting furnace according to any one of claims 1 to 5, substantially not containing chromium oxide. 7. The amorphous refractory for a waste melting furnace according to claim 1, wherein the magnesia raw material contains chromium oxide as a digestion inhibitor. 8. The amorphous refractory for a waste melting furnace according to claim 1, wherein the binder is alumina cement. A waste melting furnace lined with the amorphous refractory according to any one of claims 1 to 8. 10. The waste melting furnace according to claim 9, wherein the lining of the amorphous refractory is direct application to the furnace, use of a precast product obtained in advance at another location, or a combination of both.

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