JP2005314144A - Chromium-free monolithic refractory for waste material melting furnace and waste material melting furnace lined with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chromium-free monolithic refractory which exhibits a service life comparable to that of the chromia-containing monolithic refractory as the lining of a waste material melting furnace; and to provide the melting furnace lined with the same. <P>SOLUTION: The raw material composition of the chromium-free monolithic refractory for the waste material melting furnace contains ≤20 mass% yttria-based raw material and the remainder mainly comprising a magnesia-based raw material. The content of the yttria-based raw material in the raw material composition of the refractory is set to be 0.3-20 mass% expressed in terms of Y<SB>2</SB>O<SB>3</SB>component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a chromium-free amorphous refractory for a waste melting furnace substantially free of chromia components, and a waste melting furnace lined with the amorphous refractory.

  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.

  The slag component of these waste melting furnaces (hereinafter referred to as melting furnaces) contains a large amount of alkali derived from the waste components, and the operation of the melting furnace is extremely high temperature of 1300 ° C. or higher due to severe use conditions. The wear of the refractory lining it is significant.

  The refractories used in the melting furnace are roughly classified into regular refractories and irregular refractories. The construction of regular refractories involves brickwork and is labor intensive and requires advanced technology. In recent years, therefore, lining with an irregular refractory has been widely used.

  Conventionally, the amorphous refractory used for a melting furnace is a chromia-containing product typified by alumina-chromia (see, for example, 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 problem that chromia, which is a part of the refractory component, changes 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 (for example, see Patent Document 2), alumina-magnesia (for example, see Patent Document 3), and alumina-silicon carbide (for example, Patent Document 4).
JP-A-10-324562 JP 2000-281455 A JP 2001-153321 A JP 2000-203952 A

  However, the above conventional chromium-free material is greatly inferior in durability to a chromia-containing product when used as a melting furnace. Since the slag of the melting furnace is multi-alkali, the alumina-zirconia or alumina-magnesia is inferior in corrosion resistance because the zirconia component and the magnesia component are eluted in the slag. Alumina-silicon carbide is inferior in corrosion resistance because silicon carbide is oxidized in the oxidizing atmosphere of the melting furnace.

  Therefore, the present invention provides an excellent durable chromium-free amorphous refractory equivalent to a chromia-containing product as a lining of a melting furnace and a melting furnace lining the same.

In the present invention, the refractory raw material composition is 20 mass% or less of yttria raw material, the remainder is mainly magnesia raw material, and the proportion of yttria raw material in the refractory raw material composition is 0.3 to 20 in terms of Y ₂ O ₃ component. It is a chromium-free amorphous refractory for waste melting furnaces with a mass%.

The components of the melting furnace slag are derived from waste components and contain a large amount of alkali (Na ₂ O + K ₂ O) as 1.5 to 15% by mass. The refractories for melting furnaces are markedly worn due to the conditions specific to the melting furnace due to the operation of the multi-alkali slag and the ultra-high temperature furnace.

  In the conventional amorphous refractories of alumina-zirconia, alumina-magnesia, and alumina-silicon carbide, the main material is an alumina material. The alumina material is excellent in fire resistance and volume stability, but easily reacts with alkali, reacts with the alkali component of the melting furnace slag to produce a low melting point alkali compound, and lowers corrosion resistance.

On the other hand, the amorphous refractory of the present invention is improved in the erosion property to the multi-alkali slag peculiar to the melting furnace by combining a specific amount of yttria raw material with a composition mainly composed of magnesia raw material. To do. The reason is that MgO component of yttria raw material and MgO of magnesia raw material react to form MgO—Y ₂ O ₃ spinel, and this MgO—Y ₂ O ₃ spinel has high corrosion resistance against multi-alkali slag. Indicates.

The melting furnace slag is extremely low in viscosity due to many alkalis. Y ₂ O ₃ promotes grain growth of MgO fine powder, densifies the matrix of the refractory structure, and also prevents the penetration of melting furnace slag having a low viscosity, greatly contributing to the improvement of corrosion resistance.

  Conventional alumina-magnesia is mainly composed of alumina, and the upper limit is about 20% by mass even when the proportion of magnesia is large. The magnesia raw material itself is also excellent in alkali resistance. It is not fully demonstrated.

The refractory for a melting furnace of the present invention is a ratio of the refractory raw material composition, and may further combine alumina raw materials in a range of 30% by mass or less. The Al ₂ O ₃ component reacts with the Y ₂ O ₃ component from the yttria raw material to form YAG, densify the refractory structure, and prevent slag infiltration.

However, when the alumina starting material is too high, _Al 2 _{O 3} component inhibits generation of the _MgO-Y 2 _{O 3} spinel, the effect of corrosion resistance decreases to the molten slag. For this reason, when using it combining an alumina raw material, 30 mass% or less is preferable in the ratio occupied to a refractory raw material composition.

In the present invention, a part of the magnesia material may be used as an Al ₂ O ₃ —MgO-based spinel material. However, also in this case, if the proportion of the Al ₂ O ₃ —MgO-based spinel material is too large, the formation of the MgO—Y ₂ O ₃ -based spinel is inhibited, so the proportion of the refractory material is preferably 20% by mass or less.

In addition to yttria with high Y ₂ O ₃ purity, yttrium-rich mixed rare earth oxides may be used as the yttria-based raw material. As the yttrium-rich rare earth oxide, for example, a crude rare earth oxide raw material in the course of refining rare earth elements from rare earth ores can be used.

The magnesia material preferably has an organosilicon compound film. Formation of the organosilicon compound coating is known as a digestion-resistant treatment method for magnesia raw materials, but in the present invention, the effect of corrosion resistance against multi-alkali slag is further improved. This is presumably because the organosilicon compound film becomes SiO _{2 at a} high temperature and reacts with the MgO component of the yttria raw material and MgO of the magnesia raw material to promote the formation of the MgO—Y ₂ O ₃ spinel.

  The refractory material of the present invention is a chromium-free material substantially free of chromia components, and exhibits a sufficient corrosion resistance effect under severe use conditions such as a multi-alkali slag peculiar to a melting furnace and ultrahigh temperature operation. As a result, the refractory of the present invention improves the melting furnace operation rate and the refractory unit by extending the refractory life, and solves the problem of environmental pollution by being a chromium-free material.

Specific examples of the yttria-based raw material used in the present invention are one or more selected from yttria and yttrium-rich mixed rare earth oxides. The ratio of the yttria raw material is 20% by mass or less and 0.3 to 20% by mass in terms of Y ₂ O ₃ component in the ratio of the refractory raw material composition. More preferably, it is 0.5 to 10% by mass in terms of Y ₂ O ₃ component. When the amount is small, the slag resistance is inferior to the multi-alkali melting furnace slag, and the effect of the present invention cannot be obtained. On the other hand, when the amount is too large, the corrosion resistance is lowered and the yttria-based raw material is expensive, which is economically undesirable. Specific examples of the yttrium-rich rare earth oxide include synthetic products and crude rare earth oxides. The crude rare earth oxide contains _, for example, Gd ₂ O ₃ , Er ₂ O ₃ , Dy ₂ O ₃ , Yb ₂ O _{3 and the} like in addition to Y ₂ O ₃ . The Y ₂ O ₃ component purity of the yttrium-rich rare earth oxide is preferably 50% by mass or more, and more preferably 60% by mass.

  The yttria raw material is preferably used as fine particles having an average particle size of 1 to 45 μm in order to increase the reactivity with the magnesia raw material.

  Specific examples of the magnesia material are sintered magnesia, electrofused magnesia, and natural magnesite (magnesium carbonate). Since natural magnesite has a high porosity, it is preferably used in combination with other magnesia raw materials only in a small amount when used. Moreover, you may use the light-burning magnesia which is easy to obtain as a fine powder.

  The magnesia raw material is the main component of the refractory raw material composition, and its proportion occupies the remainder of the yttria raw material and further the alumina raw material, but is preferably at least 60% by mass of the refractory raw material composition.

  As a method for forming an organic silicon compound film on a magnesia material, for example, an organic silicon compound or the organic silicon compound is dissolved in an organic solvent such as an alcohol and added to and mixed with the magnesia material, followed by drying at 120 ° C. or higher, for example. If necessary, heat treatment is further performed at 200 to 500 ° C.

Specific examples of the organosilicon compound include silicone, silane coupling agent, alkoxysilane, silylating agent and the like. In particular, it is preferable to use a silicone oil that has a large amount of residual SiO ₂ and can form a strong coating layer. Examples of silicone include methyl hydrogen silicone oil and dimethyl silicone oil.

  Examples of silane coupling agents include vinyltrichlorosilane, pinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (βmethoxysilane) silane, γ- (methacryloxypropyl) trimethoxysilane, γ-aminopropylethoxysilane, γ- Mercaptopropyltri, methoxysilane and the like.

  Examples of the alkoxysilane include tetraethoxysilane, tetramethoxysilane, and methyltriethoxysilane. Examples of the silylating agent include trimethylchlorosilane and hexamethyldisilazane.

  The surface coating of the organosilicon compound is not necessarily performed on the entire magnesia material. When the magnesia material used in the present invention is 100 mass%, preferably 60 mass% or more, more preferably 80 mass%. The above is used as a magnesia material having the surface coated with this organosilicon compound.

Specific examples of the alumina raw material include fused alumina, sintered alumina, bauxite and the like. Among them, fused alumina and sintered alumina having high purity of Al ₂ O ₃ are preferable. The Al ₂ O ₃ —MgO-based spinel may be a sintered product or an electrofused product. The Al ₂ O ₃ : MgO ratio is not limited to a theoretical value and can be used. For example, Al ₂ O ₃ : MgO having a weight ratio of 1: 1 to 10: 1 can be used.

The particle sizes of the magnesia material, the alumina material, and the Al ₂ O ₃ —MgO-based spinel material are appropriately adjusted to coarse particles, medium particles, and fine particles so as to obtain a tightly packed structure. For the fine powder part of the alumina raw material, calcined alumina that is easily available as ultrafine particles may be used. When the amount of the alumina material and the Al ₂ O ₃ —MgO-based spinel material is small, it is preferable to mainly use fine particles or ultrafine particles.

The proportion of the alumina raw material in the refractory raw material composition is preferably 30% by mass or less, more preferably 20% by mass or less. Al ₂ O ₃ feedstocks has the effect of reacting with Y ₂ O ₃ component of yttria feedstock densified refractory tissue to form a YAG prevent slag penetration. However, when the _Al 2 _{O 3} feedstocks is too large, _Al 2 _{O 3} component inhibits generation of the _MgO-Y 2 _{O 3} spinel, resulting in a decrease in corrosion resistance to the molten slag. Moreover, in order to fully exhibit the effect of slag penetration prevention, at least 3 mass% is used.

Also for the amount of Al ₂ O ₃ —MgO-based spinel material used, the amount of Al ₂ O ₃ component in the refractory material composition is 20% by mass in order not to inhibit the formation of MgO—Y ₂ O ₃ -based spinel in the present invention. It is preferable to adjust so that it may become below.

As long as the effect of the present invention is not impaired, as a refractory raw material, further, using one or more selected from silica, mullite, calcia, dolomite, zircon, zirconia, titania, silicon carbide, carbon, etc. Also good. These are preferably in a range of less than 10% by mass, more preferably 5% by mass or less, in order to inhibit the formation of MgO—Y ₂ O ₃ spinel in the refractory of the present invention.

  The amorphous refractory of the present invention is substantially free of chromia to prevent environmental pollution. Here, “substantially free” means, for example, an amount of 0.1 mass% or less of impurities or magnesia material as a digestive inhibitor even if chromia is included.

  For the refractory material having a fixed shape, a binder and a dispersant are added as technical common sense for workability. However, the material and the added amount thereof are not particularly different from those of conventional refractories. The binder is, for example, one or more selected from alumina cement, magnesia cement, Portland cement, hydraulic alumina, aluminum oxycarboxylate, phosphate, silicate, silica sol, phenol resin, and the like. Among these, alumina cement excellent in imparting construction body strength is preferable. The addition amount of the binder is an outer coating with respect to 100% by mass of the refractory raw material composition, 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. 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 100% by mass of the refractory raw material. More preferably, it is 0.03-0.5 mass%.

  In addition to the above, the amorphous refractory of the present invention may be a curing regulator, aluminum lactate, organic fiber, drying accelerator, rare earth oxide other than yttria, metal silicon, nickel, aluminum, volatile silica, glass, etc. May be added. When these are added, the addition amount is adjusted in the range of, for example, 5% by mass or less, more preferably 5% by mass or less as an outer coating with respect to 100% by mass of the refractory raw material composition.

  In the construction, about 3 to 5% by mass of water is added and kneaded with the outer coating on the entire blended composition described above, and then cast 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 may be lined by a precast method using a precast product obtained by pouring into a formwork at another location.

Tables 1 and 2 show examples of the present invention, comparative examples thereof, and test results of the respective examples.

Yttria were used _Y 2 _{O 3} 99.9% by weight products. As the yttrium-rich rare earth oxide, a crude rare earth oxide raw material having a Y ₂ O ₃ purity of 72.2% by mass was used.

A magnesia material having an organosilicon compound coating (indicated as coated sintered magnesia in the table) was coated with silicone oil as the organosilicon compound. Specifically, methylhydrogen silicone was used by dissolving it in 3% by mass of ethanol in advance. The coating was made by adding an organosilicon compound to sintered magnesia, carrying it in a Henschel mixer for 5 minutes under heating at 50 ° C., drying at 120 ° C., and then heat-treating at 400 ° C. The coverage of the organic silicon compound to the magnesia particles was 0.08 to 0.15 wt% in terms of SiO _2.

  The refractory in each example was poured into the refractory blend composition by adding 5% by mass of construction water, mixing, and pouring while applying vibration. Furthermore, what was cured and dried at 120 ° C. for 24 hours was used as a test piece. The test method is as follows.

Slag erosion resistance: 1400 ° C. with erosion of municipal waste slag with CaO / SiO _{2 of} 0.65 and alkali content of 5% by mass discharged from the gasification melting furnace assuming erosion in the waste melting furnace A rotary erosion test was conducted. In each test, the wear size was measured. The wear size is indicated by an index with the test value of Comparative Example 1 as 100, and the larger the value, the worse the corrosion resistance.

  Actual machine test: An example and a part of the comparative example were poured into a gasification melting furnace having a waste disposal amount of about 80 t per day and an operation temperature of about 1400 ° C. using a core. The construction promoted filling with a vibrator. After curing and drying, it was used for 3 months. As the durability, the amount of wear (mm / month) was measured.

  As the test results show, all of the examples of the present invention exhibit an excellent corrosion resistance against melting furnace slag. In particular, the slag erosion resistance is further improved in an example in which coated sintered magnesia is used as a magnesia material.

On the other hand, in Comparative Example 1, the yttria material is combined with the magnesia material, but Y ₂ O ₃ in the refractory material composition exceeds the ratio limited to the present invention, and the slag erosion resistance is poor. Alumina-zirconia comparative example 2 and alumina-silicon carbide comparative example 3 are also inferior in slag erosion resistance compared to the examples of the present invention. Comparative Example 4 uses a yttria-based raw material, but if the coverage is alumina-zirconia, the effect of improving the slag erosion resistance cannot be obtained.

Claims (7)

The composition of the refractory raw material is 20% by mass or less of the yttria raw material, the remainder is mainly the magnesia raw material, and the proportion of the yttria raw material in the refractory raw material composition is 0.3 to 20% by mass in terms of Y ₂ O ₃ component. Chrome-free amorphous refractories for waste melting furnaces. The composition of the refractory material is 20% by mass or less of the yttria material, 30% by mass or less of the alumina material, the remainder is mainly magnesia material, and the proportion of the yttria material in the refractory material composition is 0 in terms of Y ₂ O ₃ component .3-20 mass% chromium-free amorphous refractories for waste melting furnaces. Refractory raw material composition further Al ₂ O ₃ -MgO based spinel waste melting furnace for chrome-free monolithic refractory of raw materials containing more than 20 wt% claim 1 or 2, wherein.   The chromium-free amorphous refractory for a waste melting furnace according to any one of claims 1 to 3, wherein the yttria raw material is at least one selected from yttria and yttrium rich rare earth oxides.   The chromium-free amorphous refractory for a waste melting furnace according to any one of claims 1 to 3, wherein the magnesia material has an organic silicon compound coating. 6. The waste melting furnace according to claim 1, wherein a slag containing alkali (Na ₂ O + K ₂ O): 1.5 to 15% by mass passes through the furnace while the waste melting furnace is in operation. A chrome-free amorphous refractory for a waste melting furnace lining according to any one of the above items.   A waste melting furnace formed by lining the chromium-free amorphous refractory according to any one of claims 1 to 6 by pouring and / or precasting.