KR20110104713A - Unshaped refractory composition added with alumina sol binder - Google Patents

Abstract

The present invention relates to an amorphous refractory material in which an alumina sol binder is added to a refractory mixture including Al ₂ O ₃ and SiC. The refractory material of the present invention is alumina sol binder is bonded to the mixed refractory agent, and does not use the cement containing CaO does not cause erosion by CaO even when used at high temperature, maintains the shape after drying, sufficient handling It has strength, hardly shrinkage after heat treatment, low porosity, and high strength, which is particularly useful when used in gasifiers.

Description

Unshaped Refractory Composition Added with Alumina Sol Binder}

The present invention relates to an amorphous refractory to which an alumina sol binder is added, which can be used as a refractory material for gasifier inner walls.

Indefinite refractory materials are preferred to refractory bricks, where the gap between bricks is a problem, and improvements have been made in terms of life, materials, and construction methods. Calcium alumina cement has been mainly used as an inorganic binder, but low calcium alumina cement is preferred due to severe usage conditions such as high temperature and high pressure. Recently, a small amount of calcium is used to improve resistance to thermal abrasion and erosion. Hydratable alumina is used for amorphous refractory materials. However, this refractory has a disadvantage of low strength (1.2-2.0 MPa) at 800 to 1200 ° C. in which water retaining a bond is dehydrated and no bond between ceramics is produced.

The gasifier of the Integrated Coal Gasification Combined Cycle (IGCC), which is recently attracting attention as an efficient and eco-friendly power generation system, operates in harsh environments. The amorphous refractory used for the inner wall of this gasifier is attached to the stainless steel pipe through which the coolant flows, it should be well adhered to the stainless steel pipe, have good thermal conductivity, and the first slag layer should be well formed on the surface. Amorphous refractories generally combine oxides, carbides, or mixtures of these used as a fire retardant with alumina cement, and use less cement, resulting in lower molding densities, handling difficulties, and difficult time control of drying. Corrosion resistance is improved and penetration is slowed down. This is because calcium oxide (CaO) contained in the cement reacts with the slag at a high temperature to lower the viscosity of the slag, thereby facilitating penetration into the refractory, thereby promoting erosion of the refractory. In addition, cement has a disadvantage in that sufficient room temperature drying is required because evaporation of moisture is slow. Instead of cement, phosphate amorphous refractories are used, which use mono-aluminum phosphate as a binder and magnesium oxide (MgO) as a curing agent. It is undesirable in gasifiers that lack oxygen. Low melting point compounds are generated in the P ₂ O ₅ -MgO system, and mono-alumina phosphate is water-soluble, and thus moves to the surface, resulting in uneven strength. In addition, P ₂ O ₅ is volatilized in a high temperature reducing environment, resulting in low strength and non-uniformity. Therefore, such irregularities are not suitable for forming a fireproof structure. Recently, water-soluble alumina is used as an inorganic binder, such as Alphabond 300 and 500 of Almatis Alcoa Industrial Chemicals Division. The refractory to which the water hydratable alumina binder is added has a disadvantage in that it takes a long time to mix. In addition, a method of using finely divided silica and colloidal alumina together with alumina cement has been reported, but the room temperature bending strength is about 5 to 17 MPa.

As described above, the conventional refractory materials have problems in adhesion, thermal conductivity, drying time, or erosion resistance, in addition to strength, and thus are used in gasifiers having high temperature and high pressure.

Accordingly, the present inventors have studied the refractory material that can be used in a gasifier which is a harsh environment at high temperature and high pressure, and have succeeded in completing a refractory material having excellent adhesion and strength, thermal conductivity, and erosion resistance. An object of the present invention is to provide such a refractory.

The present invention relates to an amorphous refractory having an alumina sol binder added to a refractory mixture comprising Al ₂ O ₃ and SiC.

The refractory material of the present invention is alumina sol binder gives the working fluidity to the mixed refractory, does not use cement containing CaO does not cause erosion by CaO even when used at high temperature, maintains the shape after drying, and sufficient handling It has strength, hardly shrinkage after heat treatment, low porosity, and high strength, which is particularly useful when used in gasifiers. The alumina sol is mixed with the fine powder of alumina to act like a paste to coat the surface of the refractory powder to improve the contact between the refractory agents, and unlike the cement used, the sol becomes a gel and the water is volatilized, so it dries quickly. The use of a small amount of alumina sol causes the alumina gel to form a thin film, which does not crack when dried, does not generate gold at a fast temperature increase rate, and also promotes sintering of the finely divided alumina powder to promote ceramic bonding between the refractory materials. Resulting in high strength.

1 is an optical photograph (60 times) of an amorphous refractory prepared by Example 2. FIG.

The present invention relates to an amorphous refractory having an alumina sol binder added to a refractory mixture comprising Al ₂ O ₃ and SiC. The refractory mixture may further include, but is not limited to, magnesium oxide, spinel, zirconia, chromia, hafnium oxide.

A sol, unlike gels, is dispersed in a liquid and exhibits fluidity. Particles refer to an active browning material. Alumina sol is a dispersion of alumina particles in a liquid. The alumina sol binder may be prepared by adding a small amount of acid (nitric acid, hydrochloric acid, acetic acid, formic acid, phosphoric acid, sulfuric acid, etc.) to the boehmite slurry, but is not limited thereto. The alumina sol is mixed with the fine powder of alumina to act like a paste to coat the surface of the refractory powder to improve the contact between the refractory agents, and unlike the cement used, the sol becomes a gel and the water is volatilized, so it dries quickly. The use of a small amount of alumina sol causes the alumina gel to form a thin film, which does not cause gold during drying, does not generate gold with a high temperature increase rate, and promotes sintering of the finely divided alumina powder to promote ceramic bonding between the refractory materials. Resulting in high strength.

The content of the alumina sol binder in the refractory may be 0.2 to 4 parts by weight in an amount of alumina relative to the refractory mixture, and more preferably 0.3 to 1.5 parts by weight. When the content of the alumina sol binder is less than 0.2 in the amount of alumina relative to the refractory mixture, the content of the alumina sol may be low, which may cause a binder role. When the content of the alumina sol binder is greater than 4 parts by weight, the binder phase may increase, resulting in problems of corrosion resistance and thermal conductivity. There may be.

The refractory material of the present invention is alumina sol binder gives the working fluidity to the refractory mixture containing Al ₂ O ₃ , SiC, does not use the cement containing CaO does not cause erosion by CaO even when used at high temperatures, It maintains its shape after drying, has sufficient handling strength, hardly shrinkage after heat treatment, low porosity, and high strength, which is particularly useful when used in gasifiers.

In addition, the present invention, in addition to the inorganic binder such as the alumina sol binder, an organic binder such as hydroxyethyl cellulose (hydroxyethyl cellulose), hydroxypropyl cellulose (methyl cellulose), or latex (latex) is added It can be included as. The content of the organic binder may be 0.03 to 1.0 parts by weight relative to the refractory mixture, preferably 0.05 to 0.5 parts by weight. Organic binders suppress the flow of the refractory agent that may occur during drying and improve the strength of the molded body, but organic binders that decompose during the heat treatment process create pores and may be disadvantageous in terms of strength and thermal conductivity. desirable.

Hereinafter, the present invention will be described in more detail with reference to examples, but the following examples are merely to illustrate the present invention, but it should be understood that the present invention is not limited thereto.

Preparation of Alumina Sol Binder

After boehmite powder was dispersed in distilled water to about 15% by weight, a small amount of nitric acid was added slowly and heated while stirring at 70 to 80 ° C to prepare a semi-transparent sol having a concentration of about 10% by weight with alumina. This sol was coated on a stainless substrate to obtain a thin film by drying at room temperature. The sol was put into a furnace heated at 500 ° C. for about 20 minutes, and taken out to obtain a film having excellent adhesion without cracking.

Example 1

The refractory mixture was mixed in a polypropylene barrel as in Composition 1 in Table 1 below. About 50 g of the mixture was taken and placed in a paper cup. 5.2 parts by weight of the alumina sol (0.52 parts by weight of alumina in the alumina sol) was added to the mixture, followed by tapping to prepare an amorphous molded body. After drying at room temperature for 2 hours, the resultant was placed in a 60 ° C dryer and sintered at 1350 ° C for 2 hours in air. The bending strength and density were measured and the results are shown in Table 2 below.

Example 2

The refractory mixture was mixed in a polypropylene barrel as in Composition 1 in Table 1 below. About 50 g of the mixture was taken into a paper cup, and 6.4 parts by weight of the alumina sol (0.64 parts by weight of alumina in the alumina sol) was added to the mixture, followed by tapping to prepare an amorphous molded body. After drying at room temperature for 2 hours, the resultant was placed in a 60 ° C dryer and sintered at 1350 ° C for 2 hours in air. The bending strength and density were measured and the results are shown in Table 2 below.

Example 3

The refractory mixture was mixed in a polypropylene barrel as in Composition 2 in Table 1 below. About 50 g of the mixture was taken into a paper cup, 6.55 parts by weight of the alumina sol (0.655 parts by weight with alumina in the alumina sol) was added, mixed, and then the amorphous molded body was prepared by tapping. After drying at room temperature for 2 hours, the resultant was placed in a 60 ° C dryer and sintered at 1350 ° C for 2 hours in air. The bending strength and density were measured and the results are shown in Table 2 below.

Example 4

The refractory mixture was mixed in a polypropylene barrel as in Composition 3 in Table 1 below. About 50 g of the mixture was taken into a paper cup, 7.3 parts by weight of the alumina sol (0.73 parts by weight of alumina in the alumina sol) was added to the mixture, followed by tapping to prepare an amorphous molded body. After drying at room temperature for 2 hours, the resultant was placed in a 60 ° C dryer and sintered at 1350 ° C for 2 hours in air. The bending strength and density were measured and the results are shown in Table 2 below.

Example 5

The refractory mixture was mixed in a polypropylene barrel as in Composition 3 in Table 1 below. About 50 g of the mixture was taken into a paper cup, and alumina sol was mixed with 9.8 parts by weight (0.98 parts by weight of alumina in the alumina sol) relative to the mixture, followed by tapping to prepare an amorphous molded body. After drying at room temperature for 2 hours, the resultant was placed in a 60 ° C dryer and sintered at 1350 ° C for 2 hours in air. The bending strength and density were measured and the results are shown in Table 2 below.

Example 6

The refractory mixture was mixed in a polypropylene barrel as in Composition 3 in Table 1 below. Approximately 50 g of the mixture is taken into a paper cup, and the alumina sol is mixed with 8.5 parts by weight (0.85 parts by weight with alumina in the alumina sol), 0.03 parts by weight of hydroxyethyl cellulose (HEC), followed by tapping. ) To form an amorphous molded body. After drying at room temperature for 2 hours, the resultant was placed in a 60 ° C dryer and sintered at 1350 ° C for 2 hours in air. The bending strength and density were measured and the results are shown in Table 2 below.

Comparative Example 1

The refractory mixture was mixed in a polypropylene barrel as in Composition 1 in Table 1 below. About 50 g of the mixture was taken into a paper cup, distilled water was added to 9.52 parts by weight of the mixture, 0.5 parts by weight of hydroxyethyl cellulose (hydroxyethyl cellulose, HEC) was added, and then mixed to form an amorphous molded body by tapping. After drying for 2 hours at room temperature and dried in a 60 ℃ dryer, and then sintered in air at 1350 ℃ for 2 hours. The bending strength and density were measured and the results are shown in Table 2 below.

Comparative Example 2

The refractory mixture was mixed in a polypropylene barrel as in Composition 3 in Table 1 below. About 50 g of the mixture was taken into a paper cup, and distilled water was added to the mixture by adding 8.24 parts by weight of hydroxyethyl cellulose (HEC) and 0.43 parts by weight of hydroxyethyl cellulose (HEC), followed by tapping. After drying at room temperature for 2 hours, the resultant was placed in a 60 ° C dryer and sintered at 1350 ° C for 2 hours in air. The bending strength and density were measured and the results are shown in Table 2 below.

Al ₂ O ₃ (wt%) SiC (% by weight) MgO (% by weight) Average particle size 3-5 mm 0.3 μm 1.25 mm 750㎛ 90 μm 20 탆 5㎛ <44 μm Composition 1 7.0 7.6 38 23 3 20 1.4 0 Composition 2 7.0 7.6 38 23 3 19.6 1.4 0.4 Composition 3 0 7.6 45 23 3 20 1.4 0

Psalter Refractory
Furtherance Additives (parts by weight) density
(g / cm ³⁾ Bending strength
(MPa) Distilled water 10 wt% concentration alumina sol HEC Example 1 Composition 1 0 5.2 0 2.69 45.45 Example 2 0 6.4 0 2.73 46.01 Example 3 Composition 2 0 6.55 0 2.65 55.70 Example 4 Composition 3 0 7.3 0 2.53 46.18 Example 5 0 9.8 0 2.66 53.24 Example 6 0 8.5 0.03 2.64 52.58 Comparative Example 1 Composition 1 9.52 0 0.5 2.46 <5 Comparative Example 2 Composition 3 8.24 0 0.43 2.52 <5

When the alumina sol binder is added as shown in Table 2 (Examples 1 to 6), the alumina sol promotes the sintering of the finely divided alumina to improve the bonding between the refractory agents, thus increasing the sintering density, ie, the porosity, and the high strength. Indicates. When an organic binder is used as a binder without the addition of an alumina sol (Comparative Examples 1 and 2), sintering between the finely divided alumina crystal and the refractory agent does not occur easily, and thus the strength is low. Using alumina sol, it was confirmed that the bending strength increased by about 9 to 11 times compared with the case where it was not used.

Claims (6)

Al ₂ O ₃ and SiC refractory agents monolithic refractory mixture was added to the alumina sol binder comprising a.
The amorphous refractory according to claim 1, wherein the alumina sol binder is prepared by adding an acid to a boehmite slurry.
The amorphous refractory according to claim 1, wherein the refractory mixture comprising Al ₂ O ₃ and SiC further comprises magnesium oxide, spinel, zirconia, chromia, hafnium oxide or a mixture of two or more thereof.
The amorphous refractory according to claim 1, wherein the content of the alumina sol binder is 0.2 to 4 parts by weight in an amount of alumina relative to the refractory mixture including Al ₂ O ₃ and SiC.
The amorphous refractory according to claim 1, further comprising hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, or latex binder.
The fire-resistant of claim 5, wherein the hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, or latex is added to the Al ₂ O ₃ and SiC. Amorphous refractory, characterized in that the addition of 0.03 to 1.0 parts by weight relative to the mixture.

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