JP2005075680A - Chromium free monolithic refractory for waste melting furnace, and waste melting furnace using the same as inner lining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chromium free monolithic refractory having a durability equivalent to or higher than that of an alumina/chromia monolithic refractory and used for an inner lining of a melting furnace. <P>SOLUTION: This chromium free monolithic refractory for the waste melting furnace comprises a compounded composition containing a refractory material mainly comprising an alumina, an alumina cement, and a dispersant, and 0.5-15 mass% tungsten trioxide or molybdenum trioxide added to 100 mass% of the total of the refractory material and the alumina cement. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

   The present invention relates to a chromium-free amorphous refractory used for the lining of a waste melting furnace such as a gasification melting furnace or an ash melting furnace, and a waste melting furnace with the lining thereof.

  In recent years, gasification melting furnaces for directly melting waste or ash melting furnaces for melting incineration ash of waste have emerged as waste processing furnaces excellent in volume reduction of waste and suppression of dioxin generation.

Slag produced in these waste melting furnaces (hereinafter referred to as melting furnaces) is alkali such as sodium (Na ₂ O + K ₂ O: 1 to 15% by mass) derived from waste components, chlorine (Cl: 0.2 to 15% by mass) and a low basicity with a CaO / SiO ₂ mass ratio of 0.3 to 1.5.

  In addition to low basicity, the melting furnace slag has a very low viscosity at the time of melting because the furnace operates at an ultra-high temperature of 1300 ° C. or higher. As a result, the penetration of slag components such as alkali and acid into the refractory structure is promoted, and the wear of the lining refractory is remarkable. In addition, waste and incinerated ash charged into the melting furnace are low-temperature materials in the furnace, and the refractory lining of the lining is spalled by the rapid cooling action.

  The refractories used for the lining of the melting furnace are roughly classified into regular refractories and irregular refractories. Since the construction of the fixed refractory involves brickwork, it requires heavy labor and advanced technology, and in recent years, lining with an irregular refractory has been widely used.

  Conventionally, amorphous refractories known for melting furnaces are chromia-containing products represented by alumina-chromia (see Patent Document 1). This material exhibits excellent corrosion resistance in combination with the fire resistance and volume stability of alumina and the slag resistance of chromia. However, there is a serious problem that chromium oxide, which is a refractory component, is changed to hexavalent chromium which is harmful to the human body, and the slag discharged from the furnace and the refractory after use cause environmental pollution.

Therefore, a chrome-free material substantially free of chromia material has been proposed as an amorphous refractory for a melting furnace. For example, alumina-zirconia (see Patent Document 2), alumina-magnesia (see Patent Document 3), and alumina-silicon carbide (see Patent Document 4).
JP-A-10-324562 JP 2000-281455 A JP 2001-153321 A JP 2000-203952 A

  However, none of the conventional chromium-free amorphous refractories can provide sufficient durability in the lining of the melting furnace. Alumina-zirconia and alumina-magnesia are inferior in corrosion resistance due to the low basicity of the melting furnace slag and the zirconia component or magnesia component eluted into the slag. The operation of the melting furnace is an oxidizing atmosphere, and the alumina-silicon carbide is markedly deteriorated in corrosion resistance due to oxidative decomposition of the silicon carbide component.

  It is an object of the present invention to provide a chromium-free amorphous refractory material that can provide durability equivalent to or higher than that of an alumina-chromia amorphous refractory material in the lining of a melting furnace.

  The chromium-free amorphous refractory for a waste melting furnace of the present invention is a ratio of the above-mentioned refractory raw material and alumina cement to a total amount of 100% by mass in a composition comprising an alumina-based refractory raw material, alumina cement and a dispersant. Thus, tungsten trioxide is added in an amount of 0.5 to 15% by mass. In addition, 0.5 to 15% by mass of molybdenum trioxide is added to a blending composition containing an alumina-based refractory raw material, alumina cement and a dispersant with respect to 100% by mass of the total amount of the refractory raw material and alumina cement. It is characterized by. Furthermore, the total amount of tungsten trioxide and molybdenum trioxide in a ratio of 100 mass% of the total amount of the refractory raw material and the alumina cement is added to the composition containing the refractory raw material mainly composed of alumina, the alumina cement and the dispersant. It is characterized by adding 0.5 to 15% by mass.

  Conventional chromium-free materials combine a substantial amount of zirconia, magnesia or silicon carbide with alumina. On the other hand, in the present invention, an appropriate amount of tungsten trioxide or molybdenum trioxide is added to a refractory raw material mainly composed of alumina.

Both tungsten trioxide and molybdenum trioxide are acidic oxide raw materials that react with alumina raw materials at high temperatures during refractory use, densify the refractory matrix and prevent the penetration of low-viscosity slag. Have. In addition, it reacts with CaO in alumina cement added as a binder to produce CaWO ₄ or CaMnO ₄ which is a crystalline phase with high corrosion resistance, and exhibits excellent corrosion resistance against low basicity slag unique to melting furnaces. .

In other words, the low basicity slag is acidic slag, and the use of tungsten trioxide or molybdenum trioxide which is an acidic oxide raw material is excellent in corrosion resistance against the low basicity slag. Even if it is an acidic oxide raw material, for example, SiO ₂ or the like reacts with other components in the refractory composition to generate a SiO ₂ -based low-melting substance, thereby reducing the corrosion resistance.

The amorphous refractory according to the present invention exhibits durability equal to or higher than that of a conventional chromia-containing product under the use conditions of the melting furnace, despite the chromium-free material due to the above-described effects.

The operation of the waste treatment furnace is a high-temperature operation, and the wear mechanism of the refractory is caused by the low viscosity and low basicity slag derived from the waste components unique to the waste treatment furnace. The amorphous refractory of the present invention can obtain excellent durability comparable to a chromia-containing material as an irregular refractory for a waste treatment furnace. Moreover, the problem of environmental pollution seen in the conventional chromia-containing material is solved by being a chromium-free material.

In the present invention, specific examples of alumina as a main material of the refractory raw material composition include fused alumina, sintered alumina, bauxite and the like. Among them, it is preferable to use fused alumina or sintered alumina having high Al ₂ O ₃ purity. The particle size of alumina is appropriately adjusted to coarse particles, medium particles, and fine particles so that a compact with a tightly packed structure can be obtained. The fine powder part may use calcined alumina that is easily available as ultra fine powder.

  The proportion of alumina used is the proportion of the total amount of refractory raw material and alumina cement, and is preferably 85% by mass or more. If the amount of alumina used is small, the volume stability and fire resistance effects of alumina cannot be fully exhibited.

As long as the effect of the present invention is not impaired, a refractory raw material other than alumina may be further combined as the refractory raw material. For example, it is one or more selected from alumina-silica, silica, mullite, magnesia, calcia, dolomite, zircon, zirconia, silicon carbide, carbon and the like. A specific usage amount is a ratio of the total amount of the refractory raw material and the alumina cement, for example, less than 15% by mass, and more preferably 8% by mass or less.

Tungsten trioxide (WO ₃ ) and molybdenum trioxide (MoO ₃ ) are generally known as raw materials for solid acid catalysts. In the present invention, this tungsten trioxide or molybdenum trioxide which is an acidic oxide is added in an amount of 0.5 to 15% by mass with respect to 100% by mass of the total amount of the refractory raw material and alumina cement. More preferably, 1-10 mass is added. If the proportion of tungsten trioxide or molybdenum trioxide is small, the corrosion resistance effect of the present invention cannot be obtained. Since tungsten trioxide and molybdenum trioxide itself have a low melting point, the corrosion resistance also decreases when the amount added is too large.

Tungsten trioxide and molybdenum trioxide may be used in combination. In this case, the amount used is 0.5 to 15% by mass with respect to 100% by mass of the total amount of the refractory raw material and alumina cement for the same reason as described above. Preferably it is 1-10 mass.

The particle size of tungsten trioxide and molybdenum trioxide is not limited at all. In order to increase the reactivity with the refractory raw material and alumina cement, for example, it is preferably 0.1 mm or less, more preferably 0.045 mm or less.

Alumina cement has a role as a binder, and gives the strength of the irregular refractory construction body. Alumina cement has a large amount of Al ₂ O ₃ component, and it is preferable to use high alumina cement or super high alumina cement having excellent corrosion resistance.

The amount of alumina cement used is not particularly different from conventional amorphous refractories. In the amorphous refractory of the present invention, the proportion of the total amount of the refractory raw material and the alumina cement is, for example, 1 to 15% by mass, preferably 2 to 10% by mass.

  The dispersant is also called a peptizer and has the effect of imparting fluidity during construction of the irregular refractory. Various materials for the dispersant have been proposed. The type of the dispersant in the present invention is not limited. For example, sodium tripolyphosphate, sodium hexametaphosphate, ultrapolyphosphate sodium, acidic hexametaphosphate sodium, carboxyl group-containing polyether, sodium borate, sodium citrate, tartaric acid Soda, sodium polyacrylate, sodium sulfonate and the like.

  The addition amount of the dispersant is preferably 0.01 to 1% by mass as an outer coating with respect to the total amount of the refractory raw material and alumina cement.

  In addition to the above, the amorphous refractory of the present invention is a ratio to the total amount of the refractory raw material and the binder, for example, within a range of 5% by mass or less, a curing regulator, aluminum lactate, organic fiber, A drying accelerator, titanium oxide, metal silicon, nickel, aluminum, volatile silica, glass, or the like may be added.

Slag is generated in the operation of waste melting furnaces such as gasification melting furnaces and ash melting furnaces, which are the objects of construction of irregular refractories, and this is the main cause of refractory wear. The component of the slag is a component specific to a waste melting furnace derived from waste. Low basicity generally containing alkali (Na ₂ O + K ₂ O: 1 to 15% by mass), chlorine (Cl: 0.2 to 15% by mass), and CaO / SiO ₂ mass ratio of 0.3 to 1.5 The slag.

  The lining of the irregular refractory according to the present invention is performed by adding about 3 to 5% by mass of water to the above refractory composition, kneading and pouring it into a waste melting furnace using a mold. When pouring, filling is performed by applying vibration. Curing and drying after construction. This construction may be performed by pouring directly into the furnace, or a precast product obtained by pouring into a formwork in another place may be lined in the furnace.

各例は表に示す不定形耐火物の配合組成物をミキサーにて混練した後、金属製の型枠に流し込んだ。流し込みの際には型枠に振動を付与し、施工体の充填を促進した。ついで２４時間養生し、脱型後、さらに１１０℃×２４時間乾燥した。 Tables 1 and 2 describe examples of the present invention and comparative examples thereof. The test results are also shown in the table.

In each example, the composition of the irregular refractory shown in the table was kneaded with a mixer and then poured into a metal mold. When pouring, the formwork was vibrated to promote the filling of the construction body. Subsequently, it was cured for 24 hours, and after demolding, it was further dried at 110 ° C. for 24 hours.

The apparent porosity of the molded body was measured by a vacuum method in accordance with JIS R22205 after cutting a molded body obtained by applying a normal brick size to a quarter size under the above conditions.

Corrosion resistance was measured by a rotational erosion test using a molded body obtained by applying a normal brick size under the above conditions as a sample. The erodant is gasification melting furnace slag [chemical component values are SiO ₂ : 42.8 mass%, CaO: 31.7 mass%, Al ₂ O ₃ : 12.4 mass%, Fe ₂ O 3: 4.8 mass%. , Na ₂ O: 3.7% by mass, K ₂ O: 1.1% by mass, Cl: 0.9% by mass, (CaO / SiO ₂ : 0.74)]. After erosion at 1600 ° C. for 20 hours, the erosion dimension was measured. As an actual machine test, it was lined in a gasification melting furnace with a daily waste treatment amount of about 70 tons and an operating temperature of about 1500 ° C. The wear rate (mm / month) of the lining refractory was measured after 12 months of use.

  As the test results show, all of the examples of the present invention exhibited an excellent effect comparable to or higher than the chromium oxide-containing product of Comparative Example 7 in the corrosion resistance against the low basicity slag of the melting furnace.

On the other hand, Comparative Example 1 of alumina-silicon carbide, Comparative Example 2 of alumina-zirconia, and Comparative Example 3 of alumina-magnesia are all inferior in corrosion resistance. Comparative Example 4 that does not contain both molybdenum trioxide and tungsten trioxide, Comparative Example 5 and Comparative Example 6 that have more molybdenum trioxide and tungsten trioxide components than the scope of the present invention are similarly poor in corrosion resistance.

  Although Comparative Example 7 contains a large amount of chromium oxide and is excellent in corrosion resistance, the production of hexavalent chromium is concerned, and the effect of the present invention as chromium-free cannot be obtained due to environmental problems.

The amorphous refractory according to the present invention can provide excellent durability comparable to a chromia-containing material as an irregular refractory for a waste treatment furnace.

Claims (6)

  0.5 to 15% by mass of tungsten trioxide is added to the composition containing the alumina-based refractory raw material, alumina cement and a dispersant with respect to 100% by mass of the total amount of the refractory raw material and alumina cement. Chrome-free amorphous refractories for waste melting furnaces.   Add 0.5 to 15% by mass of molybdenum trioxide to the composition containing the alumina-based refractory raw material, alumina cement and a dispersant in a proportion of 100% by mass of the total amount of the refractory raw material and alumina cement. A chrome-free amorphous refractory for waste melting furnaces.   In the composition containing the alumina-based refractory raw material, the alumina cement and the dispersant, the total amount of tungsten trioxide and molybdenum trioxide is 0.5 in a ratio to the total amount of 100% by mass of the refractory raw material and the alumina cement. A chromium-free amorphous refractory for a waste melting furnace, characterized by adding ~ 15% by mass.   The ratio of the refractory raw material and the alumina cement to the total amount of the refractory raw material, the alumina as the refractory raw material has a blending composition of 85% by mass or more. Standard refractory. The waste melting furnace contains alkali (Na ₂ O + K ₂ O: 1 to 15% by mass) and chlorine (Cl: 0.2 to 15% by mass) in the furnace, and the CaO / SiO ₂ mass ratio is 0.3. It is a waste melting furnace which produces | generates slag with a low basicity of -1.5, The chromium free amorphous refractory for waste melting furnaces of any one of Claims 1-4 characterized by the above-mentioned.   A waste melting furnace lined with the chromium-free amorphous refractory according to any one of claims 1 to 5.