JP2001316172A - Alumina-chromia based refractory for ash melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a alumina-chromia based refractory suitable for a lining material being in contact with molten slag which is generated in a digestant melting facility for industrial waste, daily living sludge and municipal refuse. SOLUTION: The alumina-chromia based refractory for the ash melting furnace is so constituted that 70-95 wt.% of an alumina raw material in which Al2O3 value is >=99.0 wt.%, and grain diameter is 0.044-5 mm, 5-23 wt.% of chromia fine powder raw material in which Cr2O3 value is >=99.0 %, grain diameter is <=3 μm, and 0.5-10 wt.% of a silica raw material in which SiO2 value is >=99.0 wt.%, grain diameter is <=0.015 mm, and its mineral composition is consisting of two phases of corundum and alumina-chromia solid solution, and their composing ranges are represented by 0.65-0.85, and 0.15-0.31 in X-ray relative intensity ratio respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chromia refractory suitable as a lining material in contact with molten slag of an incineration melting facility for industrial waste, domestic sludge and municipal waste.

[0002]

2. Description of the Related Art Chromia-based refractory materials, in particular, alumina-chromia refractory materials, are excellent in corrosion resistance at high temperatures, and therefore are currently used as refractory materials for incineration and melting equipment for many industrial wastes, household sludge and municipal waste. Adaptation is being considered. In addition, the effect on the life of refractory materials has been increased by increasing the operating temperature and throwing in fly ash due to dioxin emission regulations and reducing the amount of refuse, and the demand for refractory materials with higher corrosion resistance has been increasing. For this reason, the corrosion resistance is improved by increasing the chromia content or adding a zirconia-based raw material. However, when the chromia content is increased, the spalling resistance tends to decrease. Attempts have been made at grain size blending, such as the use of chromia coarse angles, but the blending is complicated and tends to result in lower productivity and higher costs.

[0003] For example, JP-A-6-321628 discloses a sintering of a refractory composed of 10 to 50% by weight of a chromia raw material mainly composed of chromia coarse angle, 5 to 30% by weight of a zircon raw material, and a balance of an alumina raw material. be those, alumina and wherein the sum of the _{Al 2 O 3, Cr 2 O} 3 and ZrO ₂ other components in the sinter is 10 wt% or less - chromia - zircon-based refractories are disclosed However, chromia coarse angle is used as a raw material. In the detailed description of the invention, the coarse angle uses chromium oxide having a content of about 90 to 99% by weight, and Cr ₂ in the refractory brick. The O ₃ content is expected to be about 10 to 50% by weight. Therefore, since the content of Cr ₂ O ₃ is large, the spall resistance is inferior, and the coarse chromia angle is described as being obtained by pulverizing the material once sintered, which increases the cost.

Next, Japanese Patent Application Laid-Open No. 8-48574 discloses that Al ₂
In O ₃ content of 99.0 wt% or more, a particle size 0.044~5m
alumina raw material 30 to 75% by weight of m, _Al 2 _{O 3} content 9
9.0 wt% or more, calcined alumina 10-20% by weight of particle size less than 0.03 mm, with _Cr 2 _{O 3} content of 90 wt% or more chromium material 5 to 20 wt% of the particle size 0.03 to 3 mm, and Alumina-chromium-zirconia refractories for ash melting furnaces containing 10 to 30% by weight of a zirconia raw material having a particle size of 1 mm or less are disclosed. However, in the detailed description of the invention, it is described that by using a chromium raw material together with the chromium raw material, a high expansion property by the zirconia raw material and a microcrack are generated in the refractory structure by the shrinkage by the chromium raw material to reduce elasticity. Thus, the generation of cracks in the tissue may promote slag infiltration.

[0005]

In the current ash melting furnace,
It is melted in a wide variety of areas such as sewage sludge, municipal waste incineration ash, fly ash, and shredder dust, and has low to high basicity, and the melting conditions are not specified. In addition, due to the reduction of garbage and the regulation of dioxin emission, the usage conditions are becoming more severe, and fire-resistant materials with excellent corrosion resistance are required. Such a medium alumina-chromia refractory material has excellent corrosion resistance, but tends to have high chromia for further imparting corrosion resistance. Further, the corrosion resistance is improved by adding a zirconia-based raw material.

Accordingly, an object of the present invention is to add a high-purity silica raw material as compared with an alumina-chromia-based refractory material used in an ash melting furnace, and to use a chromia raw material having a fine particle size of 3 μm or less. Another object of the present invention is to provide an alumina-chromia refractory having improved infiltration resistance and erosion resistance at low cost. In other words, by using a chromia raw material of 3 μm or less, the reactivity with slag is further increased by forming a fine powder of alumina-chromia solid solution, and a highly viscous slag melt is generated.
When high-purity silica is added, slag infiltration into the refractory structure can be suppressed by increasing the viscosity of the slag melt that has penetrated by being present as a glass phase between grains in the refractory structure.

[0007]

Means for Solving the Problems The alumina-chromia refractory of the present invention is obtained by converting an alumina raw material having an Al ₂ O ₃ value of 99.0% by weight or more and a particle size of 0.044 to 5 mm to 70 to 95.
% By weight, Cr ₂ O ₃ value 99.0% by weight or more and particle size 3 μm
Ash melting furnace, characterized in that the following chromia pulverized raw materials 5 to 23 wt% and a particle size 0.015mm following silica raw materials SiO ₂ value 99.0% by weight or more consisting of 0.5 to 10 wt% Alumina-chromia refractories for industrial use.

[0008]

The present inventors have found that the addition of a high-purity silica material as appropriate and the use of fine powdered chromia of 3 μm or less in the alumina-chromia refractory for ash melting furnaces results in the interface between the brick structure and the molten slag. By generating a highly viscous melt by improving the reactivity of, and by suppressing the infiltration of slag into the brick tissue, found that it is possible to improve the corrosion resistance, and completed the present invention. is there.

The alumina raw material used in the present invention is Al
A high purity product having a ₂ O ₃ value of 99.0% by weight or more, for example, fused alumina. The particle size ranges from 0.044 to 5 mm, preferably from 0.044 to 3 mm. Further, if the Al ₂ O ₃ value of the alumina raw material is less than 99.0% by weight, it is not preferable because the corrosion resistance is reduced. The particle size is 0.044m
If it is less than m, undesirably, the spalling resistance decreases. Further, if it exceeds 5 mm, it is not preferable because the corrosion resistance is reduced. The added amount of the alumina raw material is 70 to 9
It is in the range of 5% by weight, preferably 70-80% by weight. If the amount is less than 70% by weight, the structure is poor, and the infiltration resistance is lowered, which is not preferable. If it exceeds 95% by weight, the corrosion resistance is lowered, which is not preferable. Further, the fused alumina used in the present invention can be replaced with sintered alumina.

Next, the chromium raw material used in the present invention is:
The Cr ₂ O ₃ value is preferably 99.0% by weight or more, and the particle size is preferably 3 μm or less, more preferably 2 μm or less. When the chromia raw material has a Cr ₂ O ₃ value of less than 99% by weight, impurities such as Al ₂ O ₃ , TiO ₂ , and FeO contained therein lower the viscosity of the melt produced by the reaction with the slag, thereby reducing erosion resistance. And the spalling property is lowered due to the progress of sintering. The particle size is 3μ
If it exceeds m, the reactivity of forming a highly viscous melt with the slag decreases, and the infiltration resistance decreases, which is not preferable. Also, since the particle size of the chromia raw material to be used is a fine powder of 3 μm or less, the amount to be added is preferably 23% by weight or less in consideration of moldability, sinterability and spall resistance. If it is less than 5% by weight, the corrosion resistance is undesirably reduced. Therefore, the mixing amount of the chromia raw material is 5 to 20.
%, More preferably from 10 to 20% by weight.
% By weight.

The silica raw material used in the present invention is S
The iO ₂ value is preferably 99.0% by weight or more, for example, white silica. If the SiO ₂ value is less than 99.0% by weight, the viscosity at high temperatures is undesirably reduced due to Al ₂ O ₃ , TiO ₂ , FeO, etc. contained as impurity components. The amount of the silica material added is in the range of 0.5 to 10% by weight, and preferably in the range of 1 to 7% by weight. The amount is 1
If it exceeds 0%, sintering occurs, and the spall resistance decreases, which is not preferable. In the alumina-chromia refractory,
Since the chromia raw material to be added and mixed has a small particle size of 3 μm or less, a highly viscous melt is likely to be generated by the reaction with the slag. In some cases, the silica content may be set to 0% by weight. In the case of slag, since a large amount of alkali is contained, it is preferable to add and mix 1 to 5% by weight of a silica material. Al ₂ O as a silica raw material
₃ and addition of mullite or clay containing TiO ₂ , FeO, etc. is not preferred.

The alumina-chromia refractory of the present invention is prepared by adding a predetermined amount of a binder to a raw material mixture having the above-described composition, kneading the mixture, and molding the mixture by a conventional method.
It is obtained by baking in a temperature range of 00 to 1820 ° C. The mineral composition of the obtained refractory is preferably composed of only corundum and alumina-chromia solid solution. In the mineral composition range, corundum and alumina-chromia solid solutions are preferably 0.65 to 0.85 and 0.15 to 0.31 in X-ray relative intensity ratio, respectively.

Here, as the binder, molasses, lignin sulfonate solution, or the like can be used, and a suitable binder can be obtained by appropriately mixing the two to adjust the viscosity. An organic binder such as methyl cellulose can also be used, but the cost increases.
The added amount of the mixed binder is preferably in the range of 2 to 4% by weight, based on the total amount of the above-mentioned blend. In addition, an inorganic binder such as clay is not preferable because it reduces corrosion resistance.

The molding method is not particularly limited, but is, for example, 1 ton / cm ² or more, preferably 1.
It is preferable to reduce the porosity by high-pressure molding into a predetermined shape at a pressure of 5 ton / cm ² .

After being formed into a predetermined shape as described above, baking is performed after drying at a temperature range of 50 to 150 ° C. for 15 to 30 hours, preferably about 20 to 30 hours.
The firing temperature is 1500 to 1820 ° C., preferably 160
It is preferable to bake in the range of 0 to 1820 ° C for 10 to 30 hours, preferably in the range of 20 to 30 hours. If the firing temperature is lower than 1500 ° C., the mechanical strength is insufficient and the structure is not densified, and the corrosion resistance is undesirably reduced.

[0017]

EXAMPLES The alumina-chromia refractory of the present invention will be further described below with reference to examples and comparative examples. Examples Table 1 below shows Examples and Comparative Examples of the refractories obtained.
Of the raw materials described in Table 1, first, a coarse particle portion of 5 to 1 mm was put into a mixer, and then a mixed solution of molasses and a lignin sulfonic acid solution was added and mixed.
The following fine powder parts were charged and mixed for 10 minutes. The obtained mixture was molded by hydraulic pressing at a pressure of 1000 Kg / cm ² , and the obtained molded body was dried at 100 ° C. for 24 hours and fired at 1820 ° C. for 24 hours to obtain a specimen. Various properties of the obtained specimen are also shown in Table 1.

[0018] The composition of the raw material powder used is such that the fused alumina has an Al ₂ O ₃ value of 99.5% by weight and the chromium oxide has a Cr ₂ O ₃ value of 99.6% by weight. Further, quartz having a SiO ₂ value of 99.4% by weight was used.

In Table 1, the room temperature bending strength is JIS.
The erosion test was performed under the following conditions based on R2213. The sample was heated by an oxygen-propane burner, the test temperature was 1600 ° C., and the test time was 4 hours. The erosion agent is Ca
Actual furnace slag having an O / SiO ₂ ratio of 0.54 was used. In addition, in order to see the effect of the CaO / SiO ₂ ratio, slaked lime was added to adjust the CaO / SiO ₂ ratio to 0.8, and a test was carried out even with a different basicity. Erosives are
After the furnace temperature reaches the predetermined temperature, 1.2kg
After holding for 0 minutes, the mixture was discharged, and the next erosion agent was charged. This operation was repeated eight times. The evaluation test results were obtained by cutting the test sample and measuring the erosion depth and the infiltration depth of the cut surface. 1 and 2 show schematic diagrams of an erosion test device for reference.

In addition, the alumina-chromia refractory obtained in the present invention was subjected to an insertion test of a real furnace, and as a result, no erosion due to slag and no crack due to heating were observed.
It turned out to be extremely excellent in corrosion resistance and spall resistance.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an erosion test device heated by an oxygen-propane burner.

FIG. 2 Method of lining test pieces

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B09B 3/00 303M (72) Inventor Issei Uchida 1406, Nishikatagami, Bizen City, Okayama Prefecture 18 Okayama Ceramics Technology Promotion Inside the Foundation (72) Inventor Yasuo Mizota 1406-18 Nishikatagami, Nishikatagami, Bizen City, Okayama Prefecture Inside the Okayama Ceramics Technology Promotion Foundation (72) Inventor Akira Yamaguchi Nagoya Institute of Technology, Materials Engineering, Nagoya Institute of Technology, Nagoya-shi, Aichi F Terms (reference) 3K061 NB28 4D004 AA02 AA46 CA29 CB01 DA03 DA10 4D059 AA03 BB04 BB11 4G030 AA22 AA36 AA37 BA25 CA01 HA01 HA04 HA05 4K051 BE03

Claims (2)

[Claims] 1. An alumina raw material having an Al ₂ O ₃ value of 99.0% by weight or more and a particle size of 0.044 to 5 mm is 70 to 95% by weight, and a Cr ₂ O ₃ value of 99.0% by weight or more and a particle size of 3 μm. The following chromia fine powder raw material is composed of 5 to 23% by weight, the mineral composition is composed of two phases of corundum and alumina-chromia solid solution, and the composition range is 0.65 to 0.85 and the relative intensity ratio of X-ray is 0.65 to 0.85, respectively. An alumina-chromia refractory for an ash melting furnace, comprising 0.15 to 0.31. 2. An alumina raw material having an Al ₂ O ₃ value of 99.0% by weight or more and a particle diameter of 0.044 to 5 mm is 70 to 95% by weight, and a Cr ₂ O ₃ value of 99.0% by weight or more and a particle diameter of 3 μm. 5 to 23% by weight of the following chromia fine powder raw material and SiO ₂ value 9
The silica raw material having a particle size of not less than 9.0% by weight and not more than 0.015 mm is composed of 0.5 to 10% by weight, the mineral composition is composed of two phases of corundum and alumina-chromia solid solution, and the composition range is X-ray. 0.6 in relative intensity ratio
Alumina-chromia refractories for ash melting furnaces, comprising 5 to 0.85 and 0.15 to 0.31.