KR101247691B1 - Spinel-Silicon Carbide Refractory compositions with High Corrosion Resistivity to Coal Slag and Manufacturing Method thereof - Google Patents

Abstract

The present invention relates to a refractory used in a coal gasifier reactor, alumina surplus spinel solid solution composed of 1: 2-1: 3 in a molar ratio of magnesia and alumina, which is resistant to coal slag and can be used at a high temperature of 1500 ° C or higher. 1-15 parts by weight of finely divided alpha alumina and gamma alumina are added to the refractory material in a refractory material having a ratio of 25: 75-75: 25 by weight of silicon carbide. It relates to a firebrick for a coal gasifier. In addition, according to the method of the present invention, it is possible to provide an environmentally friendly high temperature refractory material that does not contain chromium oxide and can be used at a high temperature of 1500 ° C. or higher without volatilization of chromium.

Description

Spinel / Silicon Carbide Refractory compositions with High Corrosion Resistivity to Coal Slag and Manufacturing Method

The present invention relates to a spinel-silicon carbide refractory composition used in coal gasifiers because of its high corrosion resistance and permeability to slag, and a method for producing the same.

Coal gasifiers are devices that clean and economically produce compounds that can be used as fuels in low-grade coal. The gas obtained at this time is called a synthesis gas, and mainly CO and hydrogen are main components. In the reactor, which is the core of the coal gasifier, oxygen and water are added to carbon-containing raw materials and heated at a high pressure of 30-60 atm. The heating temperature is 1300-1600 ° C. depending on the melting temperature and viscosity of the coal slag generated. Therefore, the fire brick used as lining material inside the reactor requires not only heat resistance, but also permeability, corrosion resistance, thermal shock resistance, repeated oxidation-reduction atmosphere resistance to coal slag, abrasion resistance by coal powder, and resistance to high pressure. . Since the conditions required for refractories in coal gasifiers are so severe, many studies have reported that only high chromium-resistant refractory bricks satisfy this condition.

Refractory with high chromium content is used as a refractory for coal gasifier because of its high slag erosion resistance and spalling resistance. However, since chromium, which is one of environmental regulatory elements, volatilizes in use, there is an urgent need for chromium-free refractory materials that can be used in coal gasifiers.

US Pat. No. 6,815,386 B1 relates to a refractory used in an integrated gasification combined cycle (IGCC) gasifier and is characterized in that the content of chromium oxide (Cr ₂ O ₃ ) is 60% or more. Typical refractory materials that do not contain chromium include Al ₂ O ₃ , MgO, Spinel (MgAl ₂ O ₃ ), and SiC. Alumina-based steel refractories containing up to 85% by weight of alumina (US 4,326,040), refractories using 40-60% by weight of alumina, finely divided silicon carbide, and phosphoric acid-based compounds as binders (US 2009 / 0227441 A1). The MgO system contains 55-95% by weight of MgO and 3-20% by weight of ZiO ₂ (US 2007/0213199 A1), a refractory consisting of MgO and CaZrO ₃ (US 4,849,383), MgO-spinel ( Japanese Patent Application Laid-Open No. 6-100357). The spinel refractory includes a refractory resistant to alkali salts. (US 2007/0042896 A1, US 2008/0254967 A1). Silicon carbide-based refractory materials are widely used in steelmaking and steelmaking, such as silicon carbide-alumina refractories (US 5, 318,932) containing about 10% by weight of alumina, silicon carbide refractories combined with silicon nitride (US 2006/0281625 A1), and the like. have.

However, these refractory materials are known to be less resistant to erosion by coal slag at higher pressure than 1500 ° C. and higher chromium refractory materials.

The present inventors have diligently researched to develop a refractory for petroleum-free coal gasifiers, using alumina excess spinel and silicon carbide as refractory materials, adding finely divided alpha alumina and gamma alumina, and heat-treating them to produce phase transition of gamma alumina. The present invention has been completed by developing a method capable of producing non-chromic refractory materials having excellent heat resistance and excellent corrosion resistance and permeability to coal slag by combining the refractory materials with alpha alumina. When gamma alumina is heat-treated, it becomes alpha alumina which is a high temperature stable phase near 1160 degreeC. Alpha alumina has excellent mechanical properties and strong corrosion resistance. The phase transition from gamma alumina to alpha alumina occurs through nucleation and particle growth. Therefore, additives (eg, V 2 O 5, ZnF 2, Cu, etc.) capable of generating a liquid phase at a temperature lower than the phase transition temperature promote phase transition. In addition, particulate alpha-alumina, which can act as a nucleus, acts as a nucleation seed to promote phase transition.

Accordingly, it is an object of the present invention to provide a non-chromium refractory composition comprising chromium-free alumina excess spinel and silicon carbide and alpha alumina and gamma alumina.

Another object of the present invention is to provide a method for producing the refractory composition.

Other objects and advantages of the present invention will become more apparent from the following detailed description of the invention, claims and drawings.

According to an aspect of the present invention, the present invention provides a mixture of spinel and silicon carbide having a mixing ratio of 25: 75-75: 25% by weight and 1-15 parts by weight of finely divided alpha alumina in a refractory material having a total of 100 parts by weight. A refractory composition comprising -15 parts by weight of gamma alumina.

According to a preferred embodiment of the invention, the spinel is a composition characterized in that the alumina excess spinel.

According to a preferred embodiment of the present invention, the spinel is a composition characterized in that the particle size range is 0.5-10 mm.

According to a preferred embodiment of the present invention, the silicon carbide composition is a composition characterized in that the particle size range is 0.005-5 mm.

According to a preferred embodiment of the present invention, the composition of the alpha-alumina composition is characterized in that the particle size range is 0.01-0.5 mm.

According to a preferred embodiment of the present invention, the gamma alumina is a composition characterized in that the particle size is 0.5 mm or less.

According to a preferred embodiment of the present invention, the gamma alumina is a composition characterized in that the addition form of the composition is added in the form of alumina sol.

In addition,

(i) adding finely divided alpha alumina and 1-15 parts by weight of gamma alumina to a refractory material having a mixing ratio of spinel and silicon carbide of 25: 75-75: 25% by weight, the sum of the mixture being 100 parts by weight, to form a mixture. ;

(ii) adding a small amount of water to the mixture and applying it to a specific form on a material that is poorly shaped or heat resistant;

(iii) a drying step of removing water from the molded body or the applied molded body;

(iv) heat treating the mixture to phase-shift gamma alumina to alpha alumina; And

(v) providing a method for preparing a refractory composition comprising combining gamma alumina phase-transferred with alpha-alumina with a refractory material of the spinel and silicon carbide mixture.

According to a preferred embodiment of the present invention, the spinel is characterized in that the particle size range is 0.5-10 mm.

According to a preferred embodiment of the present invention, the silicon carbide composition is characterized in that the particle size range is 0.005-5 mm.

According to a preferred embodiment of the present invention, the particle size range of the alpha alumina composition is characterized in that the 0.01-0.5 mm.

According to a preferred embodiment of the present invention, the gamma alumina is a method characterized in that the particle size is 0.5 mm or less.

The features and advantages of the present invention are summarized as follows.

(i) The refractory composition according to the present invention has excellent permeability and erosion resistance against coal slag generated as a by-product from coal gasifiers or thermal power plants, thereby increasing the refractory life of the reactors of coal gasifiers or furnaces for thermal power generation.

(ii) The spinel-silicon carbide refractory according to the present invention is an environmentally friendly refractory that does not contain chromium oxide at all and does not cause contamination by chromium volatilization in chromium refractory materials.

1 is a photograph of the microstructure of the spinel-silicon carbide refractory according to the present invention.
Figure 2 is a graph showing the density change of the refractory according to the spinel-silicon carbide ratio in the embodiment of the present invention.
3 is a graph showing the density change of the refractory according to the addition of alumina cement in the embodiment of the present invention.
4 is a graph showing the change in compressive strength of the refractory according to the addition of alumina cement in the embodiment of the present invention.
5 is a graph showing the porosity change of the refractory according to the addition of alumina sol in the embodiment of the present invention.
6 is a graph showing the bending strength change of the refractory according to the addition of alumina sol in the embodiment of the present invention.
7 is a graph showing the degree of erosion resistance of the refractory according to the addition amount of alumina cement in the embodiment of the present invention.

In order to achieve the above object,

25-75% by weight of spinel aggregate (average particle diameter 0.5mm-5mm) excellent in slag erosion, 25-75% by weight of silicon carbide aggregate (0.5mm or more) and silicon carbide fine powder, 2-10% by weight of alpha alumina fine powder %, And gamma alumina relates to a refractory composition for coal gasifiers comprising 1-10% by weight of the total weight of spinel, silicon carbide, alpha alumina.

 Hereinafter, the present invention will be described in more detail.

The spinel is a spinel solid solution assembly containing alumina in excess. Spinel with excess magnesia can be used, but alumina surplus spinel is excellent in corrosion resistance because water is used in coal gasifier. In addition, it is better to use 0.5-10mm assembling than corrosion. However, in order to increase the molding density, it is preferable to mix and use particles having different particle diameters.

The silicon carbide is used by mixing granules of 0.5 mm or more and the following fine particles. If the particle size is large, the corrosion resistance is improved, but if the molding density is low, the permeation resistance of the slag is lowered. Therefore, it is preferable to mix particles having different particle diameters in order to increase the molding density.

The alpha alumina is not intended to be used as an aggregate, but to promote phase transition of gamma alumina to alpha alumina while being very much between the spinel and the silicon carbide aggregate, but powders of 0.2 mm or less may be used, but preferably 0.1 mm or less. It is preferable to use fine powder.

The gamma alumina may be a boehmite powder having an average particle diameter of 0.2 mm, but it is preferable to use fine powder of 0.1 mm or less. Gamma alumina powder not only increases the molding strength of the molded body by reacting with water, but also combines the aggregate after heat treatment to increase the strength of the refractory material, and serves to suppress the penetration of slag between the aggregate and the aggregate. Gamma alumina may also be added in the form of alumina sol as well as in the form of boehmite powder. When added in the form of alumina sol, when the raw material powder is mixed and then kneaded with water, it is added together with water.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are intended to illustrate the present invention in more detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples according to the gist of the present invention.

Example

The refractory composition for coal gasifiers described in Table 1 was prepared. Each of the prepared compositions was dry mixed, and then 3-7% by weight of water was added and kneaded to form a size of 10 × 15 × 120 mm. The molded specimens were dried at room temperature and then removed from the oven at 100 ° C. The dried specimen was heat treated at 1350 ° C. for 3 hours to obtain a fired specimen. The weight change before and after the heat treatment was within 1%, and there was a color change depending on the type and amount of the binder. The density of the specimen was calculated by the Archimedes method, the bending strength was 3 points, and the porosity was calculated from the theoretical and measured densities assuming that the starting materials did not react with each other. The erosion test is the result of erosion in the slag whose composition is shown in Table 3 at 1500 ° C for 12 hours.

For comparison, refractory to which alumina cement was added in addition to gamma alumina as a binder was prepared and compared.

division Fireproof Binders Spinel α-
Al2O3 SiC Sum Bohemite Alumina cement Alumina sol Sum 1.25mm 90 μm 20 μm 5 μm M25 25 8 41 3 21.5 1.5 100 3 - - 3 M25-A2-S3 25 8 41 3 21.5 4.5 103 3 - 2 3.2 * M25-A4-S3 25 8 41 3 21.5 4.5 103 3 - 4 3.4 * M25-C3 25 8 41 3 21.5 1.5 100 3 3 - 6 M25-C5 25 8 41 3 21.5 1.5 100 3 5 - 8 M45 45 8 21 3 21.5 1.5 100 3 - - 3 M45-A2-S3 45 8 21 3 21.5 4.5 103 3 - 2 3.2 * M45-A4-S3 45 8 21 3 21.5 4.5 103 3 - 4 3.4 * M45-C3 45 8 21 3 21.5 1.5 100 3 3 - 6 M45-C5 45 8 21 3 21.5 1.5 100 3 5 - 8 M65 65 8 - 3 21.5 1.5 100 3 - - 3 M65-A2-S3 65 8 - 3 21.5 4.5 103 3 - 2 3.2 * M65-A4-S3 65 8 - 3 21.5 4.5 103 3 - 4 3.4 * M65-C3 65 8 - 3 21.5 1.5 100 3 3 - 6 M65-C5 65 8 - 3 21.5 1.5 100 3 5 - 8 M65-A4-S6 65 8 - 3 21.5 7.5 106 3 - 4 3.4 * M65-A4-S9 65 8 - 3 21.5 10.5 109 3 - 4 3.4 *

division density
(g / cm ³⁾ Porosity
(%) Bending strength
(MPa) Compressive strength
(MPa) corrosion
(mm) Remarks M25 2.62 23 15 127 - M25-A2-S3 2.63 22 20 84 - M25-A4-S3 2.65 21 23 134 2.0 M25-C3 2.66 24 15 89 2.5 M25-C5 2.65 20 2 59 - M45 2.47 28 12 108 - M45-A2-S3 2.53 27 10 99 - M45-A4-S3 2.53 27 15 74 1.5 M45-C3 2.60 24 14 79 - M45-C5 2.55 25 12 48 4.5 M65 2.50 29 11 87 - M65-A2-S3 2.40 32 8 44 - M65-A4-S3 2.48 30 8 50 4.0 M65-C3 2.57 27 13 64 - M65-C5 2.60 25 10 57 4.5 M65-A4-S6 2.39 36 8 62 - M65-A4-S9 2.49 35 10 84 2.0

ingredient ratio SiO ₂ 52.3 Al ₂ O ₃ 21.1 TiO ₂ 1.1 CaO 6.3 Fe ₂ O ₃ 9.7 Na ₂ O 1.1 MgO 1.8 K ₂ O 1.2 MnO 0.1 Cr ₂ O ₃ 4.3 ZrO ₂ 0.9 Total 100

As can be seen in Table 2,

Porosity increased as the amount of spinel increased. Porosity increased from 23% in M25 to 28 and 29% in M45 and M65, respectively. Figure 2 shows the density change of the refractory according to the spinel and silicon carbide ratio of the average particle diameter of 850μm.

Figure 3 shows the density of spinel 65% by weight refractory according to the addition of alumina cement. The density tended to increase as a small amount of alumina cement was added. However, as shown in FIG. 4, the compressive strength decreased as the alumina cement was added.

Figure 5 shows the porosity of the refractory prepared by using only gamma alumina as a binder without using alumina cement. As shown in FIG. 5, as the alumina sol was added, the porosity of the refractory showed a tendency to decrease. 6 shows the bending strength change of the refractory to which alumina sol is added. As shown in FIG. 6, the bending strength increased as the alumina sol was added.

Figure 7 shows the slag penetration depth after impregnated with 1500 ℃ coal slag for 12 hours. As shown in Figure 7, the weight percent of the spinel all 25, 45, 65% was not added to the alumina cement was excellent in the penetration resistance of the refractory bonded with alpha alumina generated from gamma alumina. In addition, it can be seen that the penetration resistance decreases as the amount of alumina cement added increases.

Claims (12)

Refractory composition comprising 1-15 parts by weight of finely divided alpha alumina and 1-15 parts by weight of gamma alumina in a refractory material having a mixing ratio of spinel and silicon carbide of 25: 75-75: 25% by weight and a total of 100 parts by weight of the mixture. .
The composition of claim 1 wherein the spinel is an alumina excess spinel.
The composition of claim 1, wherein the spinel has a particle size range of 0.5-10 mm.
The composition of claim 1, wherein the silicon carbide has a particle size range of 0.005-5 mm.
The composition of claim 1, wherein the alpha alumina has a particle size range of 0.01-0.5 mm.
The composition of claim 1, wherein the gamma alumina has a particle size of 0.5 mm or less.
The composition of claim 1, wherein the gamma alumina is added in the form of an alumina sol.
(i) adding finely divided alpha alumina and 1-15 parts by weight of gamma alumina to a refractory material having a mixing ratio of spinel and silicon carbide of 25: 75-75: 25% by weight, the sum of the mixture being 100 parts by weight, to form a mixture. ;
(ii) adding a small amount of water to the mixture to form a mold or to apply it onto a material having low heat resistance;
(iii) a drying step of removing moisture from the molded article or the applied molded article molded by the method of step (ii);
(iv) heat treating the mixture to phase-shift gamma alumina to alpha alumina; And
(v) combining the gamma alumina phase-transferred with the alpha alumina with the refractory material of the spinel and silicon carbide mixture.
The method of claim 8, wherein the spinel has a particle size range of 0.5-10 mm.
The method of claim 8, wherein the silicon carbide has a particle size range of 0.005-5 mm.
The method of claim 8, wherein the alpha alumina has a particle size range of 0.01-0.5 mm.
The method of claim 8, wherein the gamma alumina has a particle size of 0.5 mm or less.

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