KR101095027B1 - Alumina bonded unshaped refractory and manufacturing method thereof - Google Patents

Abstract

The present invention relates to an alumina binder amorphous refractory and a method for preparing the same, and more particularly to an alumina binder amorphous refractory including Al ₂ O ₃ , SiC, alumina precursor powder and water. It can provide sufficient handling strength without using cement, hardly shrink after heat treatment, and exhibits excellent properties such as low porosity and high strength.

Description

Alumina Binder Indeterminate Refractory and Manufacturing Method Thereof {ALUMINA BONDED UNSHAPED REFRACTORY AND MANUFACTURING METHOD THEREOF}

The present invention relates to an alumina binder amorphous refractory and a method for producing the same, and more particularly, to an alumina binder amorphous refractory that can be used in a furnace, slag contact portion, free form refractory, and a method for producing the same.

Refractories are used to increase resistance to thermal shock, erosion and corrosion in combustion furnaces, gasifiers, furnaces, and in the form of refractory bricks or amorphous refractory materials. Indeterminate refractory materials are generally preferred over refractory bricks, where the gap between bricks is a problem, and improvements have been made in terms of service life, materials and construction methods.

In amorphous refractory materials, refractory aggregates and fine powders are used as binders, and calcium alumina cement has been mainly used as a binder. However, as the use environment is severely affected by high temperature and high pressure, low calcium alumina cement is preferred. In recent years, a low amount of calcium-hydride hydratable alumina is used to improve resistance to thermal abrasion and erosion. It is used for amorphous refractory materials. However, this refractory also has a disadvantage in that the water retaining the bond is dehydrated at 800 ~ 1200 ℃, the bond between the ceramics are not produced, the strength is lowered to 1.2 MPa ~ 2.0 MPa, the bending strength of the sintered body is also 20 MPa or less.

The gasifier of the Integrated Coal Gasification Combined Cycle (IGCC), which has recently gained attention as a highly 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 and should adhere well to the stainless steel pipe, have good thermal conductivity, and have a good first slag layer on the surface.

Amorphous refractory materials generally combine refractory aggregates, abrasive grains and fine powder with alumina cement. The use of less cement results in lower molding density, difficulty in handling, and difficulty in controlling the drying time. It has the advantage of being improved and slowing in penetration. This is because the CaO contained in the cement reacts with the slag at a high temperature to lower the viscosity of the slag, which causes the slag to easily penetrate into the refractory to promote erosion of the refractory. Therefore, there is a tendency to use a small amount of cement. In addition, when the cement is used, the evaporation of moisture is slow, so that room temperature drying takes a long time.

Phosphate amorphous refractory is used instead of cement, which uses mono-aluminum phosphate as a binder and MgO as a curing agent. Difficult to use In addition, low melting point compounds are generated in the P ₂ O ₅ -MgO system, and mono aluminum phosphate is mono-aluminum phosphate, and thus it is continuously moved to the surface, resulting in uneven strength. In addition, there is a problem that P ₂ O ₅ is volatilized in a high-temperature reducing atmosphere, whereby the strength is lowered and becomes uneven. Thus, these refractory materials are not suitable for forming a refractory structure.

Recently, hydrated alumina is used as an inorganic binder, and commercialized examples include Alphabond 100, 300, and 500 of Almatis Alcoa Industrial Chemicals Division. In general, the water-soluble alumina binder has a disadvantage in that it takes a long time to mix. In the case of Alphabond 500, the mixing time is reduced by using alumina particles larger than 300. The flowability of amorphous refractory is greatly influenced by the amount of fine powder. Generally 3 to 7% by weight of the water hydratable alumina binder is used. Hydrated alumina currently used is mainly composed of α-alumina powder, and includes ρ-alumina which reacts easily with water, and a small amount of CaO and SiO ₂ . In the case of Alphabond 300, the average particle size of alumina is 2.3 ㎛, CaO is less than 0.1 wt%, and in case of 500, 5.2 ㎛ is included and 0.6 wt% CaO is included. If the amount of CaO is small, there is a disadvantage that the molding strength is lowered. Hydrated alumina is used by itself or in combination with finely divided silica or small amounts of calcium aluminate cement. Hydrated alumina has a disadvantage in that its performance is degraded when exposed to moisture in the air, and its molding strength is lowered when it is operated at 15 ° C. or lower.

As such, conventional refractory materials have problems such as difficulty in use at high temperatures and pressures, difficulty in handling, and low strength during molding.

Therefore, the present inventors have studied to overcome the problems of the prior art as a result of manufacturing the alumina binder amorphous refractory using alumina precursor powder instead of the cement used in the prior art, can give sufficient handling strength without using cement and After the heat treatment, the shrinkage hardly occurs, and the low porosity and high strength were found to complete the present invention.

The present invention provides an alumina binder amorphous refractory comprising Al ₂ O ₃ , SiC, alumina precursor powder and water and

(a) mixing Al ₂ O ₃ , SiC and alumina precursor powder together to make a mixed refractory;

(b) adding water to the mixed refractory to form a mixture;

(c) curing and drying the mixture; And

(d) heat treating the cured and dried mixture

It relates to a method for producing an alumina binder amorphous refractory comprising a.

The alumina binder amorphous refractory according to the present invention has the advantage of fast drying, cracking does not occur during drying and heat treatment, can be used at high temperature because it does not contain CaO, sintering with the refractory is high strength, sintering Its density is also high, and it is expected that it can be used as an alternative to amorphous refractory using cement.

The present invention relates to an alumina binder amorphous refractory material, and more particularly, the present invention relates to Al ₂ O ₃ And alumina precursors, which are inorganic binder precursors that can give dryness and sintering strength, into powders, so that the powders are evenly distributed on the surface of the refractory, and then water or water and additives are added to the alumina It is characterized by obtaining a binder amorphous refractory material.

Hereinafter, the present invention having the technical features as described above will be described in detail according to the manufacturing steps.

The present invention comprises the steps of mixing together Al ₂ O ₃ , SiC and alumina precursor powder to make a mixed refractory; Adding water to the mixed refractory to form a mixture; Curing and drying the mixture; And heat treating the cured and dried mixture to provide a method for producing an alumina binder amorphous refractory material having high strength.

In the present invention, the mixed refractory is produced by mixing together the alumina precursor powder serving as an inorganic binder precursor to Al ₂ O ₃ (Aluminum oxide) and SiC (Silicon carbide).

Al ₂ O ₃ is one of the aggregate components constituting the skeleton in the refractory is a component that plays an effective role in maintaining a high bending strength in the manufacture of alumina binder amorphous refractory. In the present invention, the particle diameter of the Al ₂ O ₃ and the mixing ratio between the particles are not limited.

The SiC is one of the aggregate components constituting the skeleton in the refractory, and in particular, it is insoluble in water or acid, chemically inert, and has a very hard property. It is a very useful ingredient to prevent the occurrence and maintain durability.

As the SiC, granulated (particle diameter: 6 mm to 1 mm), fine particles (particle diameter: 1 mm to 50 μm) and fine particles (particle diameter: 50 μm or less) may be used, and the mixing ratio between the particles may be used. Is not limited.

In the present invention, the Al ₂ O ₃ and SiC are mixed and used, and the mixing ratio thereof is not limited. Preferably it is good to mix and use so that it may become a weight ratio of 10: 90-30: 70.

Afterwards, the Al ₂ O ₃ The alumina precursor powder is mixed with the mixture of and SiC and then evenly distributed. The alumina precursor powder, which acts as an inorganic binder precursor, is readily dispersed in water at room temperature to form a translucent alumina sol. Therefore, when the alumina precursor powder is mixed with Al ₂ O ₃ and SiC, and then water is added, hydrolysis and polymerization of the alumina precursor occur, which acts as an inorganic binder, thereby making it possible to easily prepare amorphous refractory materials.

As the alumina precursor powder, ρ-alumina or boehmite may be preferably used, and most preferably boehmite is used.

In the present invention, the alumina precursor powder is preferably used to 1 to 10 parts by weight based on 100 parts by weight of the total amount of Al ₂ O ₃ and SiC, more preferably 1 to 6 parts by weight. If the alumina precursor powder is less than 1 part by weight, there is a problem that the bonding strength is lowered. If the alumina precursor powder is more than 10 parts by weight, the amount of water for mixing is increased, the drying time is long, the porosity is increased by volatilization of moisture, porosity This increases, and there is a problem that the bond layer is thickened, so that slag erosion easily occurs.

Spinel, magnesia or zirconia may be additionally included in the mixed refractory material consisting of Al ₂ O _{3 ,} SiC and alumina precursor powder in an amount of 0.1 to 1.0 parts by weight based on 100 parts by weight of the total amount of Al ₂ O ₃ and SiC. In the present invention, by using the spinel, magnesia or zirconia, serves to increase the bending strength of the prepared alumina binder amorphous refractory.

Water is added to the mixed refractory to form a mixture. The water serves to help the hydrolysis and polymerization of the alumina precursor to act as an inorganic binder. In the present invention, the water is preferably used 3 to 15 parts by weight, more preferably 4 to 10 parts by weight based on 100 parts by weight of the total amount of Al ₂ O ₃ and SiC used. When using less than 3 parts by weight of water there is a problem that the mixing and hydrolysis does not occur sufficiently, when using more than 15 parts by weight takes a long drying time, the flow of the refractory agent may occur due to the separation of the layer, There are problems such as higher porosity due to porosity generated by evaporation.

The organic binder may be further included in the mixture to which the water is added. The organic binder serves to assist the bonding, and when used, the handling strength is increased in the present invention, and there is an advantage that an alumina binder amorphous refractory having a more uniform structure can be obtained. The organic binder of the present invention is preferably used 0.01 to 5 parts by weight, more preferably 0.02 to 3 parts by weight based on 100 parts by weight of the total amount of Al ₂ O ₃ and SiC used. When using less than 0.01 parts by weight, there is a problem that the bonding strength is weak, and when using more than 5 parts by weight, there is a problem that the pores generated by decomposition and combustion in the heat treatment process increases.

The organic binder can also be used in the form of an aqueous solution, preferably hydroxyethyl cellulose (Hydroxyethylcellulose, HEC), methyl cellulose (Methylcellulose), hydroxymethyl cellulose (Hydroxymethylcellulose), hydroxypropyl cellulose (Hydroxypropylcellulose) or latex (Latex ) Can be used. Most preferably hydroxyethyl cellulose is used.

Thereafter, the prepared alumina binder amorphous refractory is cured and dried. The curing is performed at room temperature (5 ° C. to 40 ° C.) for 2 to 6 hours. After drying at 60 to 100 ℃ for 3 to 4 hours to give a dosage.

Next, the dried alumina binder amorphous refractory material is heat-treated. The heat treatment is performed for 2 to 4 hours at 1350 ℃ to 1400 ℃ conditions.

Hereinafter, examples of the present invention are shown as follows, but the present invention is not limited to the examples.

< Example  1>

Mixed refractory materials were mixed in a polypropylene container at the composition ratios shown in Table 1 below. 50 g of the following Composition 2 was taken, placed in a paper cup, 6.48 g of distilled water was added, and an amorphous molded body was prepared by tapping. After drying for 2 hours at room temperature (25 ℃), and further dried for 4 hours in a 60 ℃ dryer, and then sintered in air at 1400 ℃ for 2 hours to prepare alumina binder amorphous refractory. The bending strength and density of the prepared alumina binder amorphous refractory were measured and the results are shown in Table 2 below.

Composition ratio of mixed refractory and added Bohemite  amount Al ₂ O ₃ (g) SiC (g) Bohemite (g) d ₅₀ 3-5 mm 0.3 μm 1.25 mm 750㎛ 90 μm 20 탆 5㎛ Composition 1 7 7.6 38 23 3 20 1.4 0 Composition 2 7 7.6 38 23 3 20 1.4 1.96 Composition 3 7 7.6 38 23 3 20 1.4 4.11 Composition 4 7 7.6 38 23 3 21.4 0 6.0

< Example  2>

50 g of Composition 2 was taken in a paper cup, and the alumina binder amorphous form was the same as described in Example 1, except that 8.5 g of 5% by weight aqueous solution of hydroxyethyl cellulose (HEC) was added and sintered at 1400 ° C. for 4 hours. After the refractory was prepared and the bending strength and density were measured, the results are shown in Table 2 below.

< Example  3>

50 g of the composition 3 was added to a paper cup, and 5.89 g of distilled water was added to prepare an alumina binder amorphous refractory material in the same manner as described in Example 1, and the bending strength and density thereof were measured. The results are shown in Table 2 below. .

< Example  4>

50 g of the composition 3 was added to a paper cup, and 5.98 g of distilled water was added to prepare an alumina binder amorphous refractory material in the same manner as described in Example 1, and the bending strength and density thereof were measured. The results are shown in Table 2 below. .

< Example  5>

50 g of the composition 3 was added to a paper cup, 6.33 g of distilled water was added, and the alumina binder amorphous refractory material was prepared in the same manner as in Example 1 except that the mixture was sintered at 1400 ° C. for 4 hours, and the bending strength and density thereof were measured. The results are shown in Table 2 below.

< Example  6>

50 g of Composition 3 was added to a paper cup, and the alumina binder was amorphous in the same manner as described in Example 1, except that 8.55 g of 5 wt% hydroxyethyl cellulose (HEC) aqueous solution was added and sintered at 1400 ° C. for 4 hours. After the refractory was prepared and the bending strength and density were measured, the results are shown in Table 2 below.

< Example  7>

50 g of the composition 4 was added to a paper cup, and 6.81 g of distilled water was added to prepare an alumina binder amorphous refractory material in the same manner as described in Example 1, and the bending strength and density thereof were measured. The results are shown in Table 2 below. .

< Example  8>

50 g of the composition 4 was added to a paper cup, and 7.67 g of distilled water was added thereto, and the alumina binder amorphous refractory material was prepared in the same manner as in Example 1 except that the mixture was sintered at 1400 ° C. for 4 hours. The results are shown in Table 2 below.

< Comparative example  1>

50 g of the composition 1 was taken, placed in a paper cup, and 10 g of 5% by weight aqueous solution of hydroxyethyl cellulose (HEC) was added. The results are shown in Table 2 below.

Bohemite  Effects of and Additives on Alumina Binder Indeterminate Refractory Properties Composition (g of boehmite used) Additive (g)  Sintering temperature (1400 ℃), in air 2 hours 4 hours Distilled water HEC aqueous solution
(5% by weight) density
(g / cm ³⁾ Bending strength
( MPa ) density
(g / cm ³⁾ Bending strength
( MPa ) Composition 1
(0) Comparative Example 1 0 10 2.46 <5 Composition 2
(1.96) Example 1 6.48 0 2.65 52.26 Example 2 0 8.5 2.54 35.14 Composition 3
(4.11) Example 3 5.89 0 2.62 42.49 Example 4 5.98 0 2.63 49.24 Example 5 6.33 0 2.64 42.19 Example 6 0 8.55 2.52 30.55 Composition 4
(6.0) Example 7 6.81 0 2.59 31.94 Example 8 7.67 0 2.58 38.38

※ Bending strength was measured by a three-point method with a span length of 20 mm.

As can be seen in Table 2, in the case of the alumina binder amorphous refractory including the boehmite and water of the present invention, the bending strength is in the range of 30.55 MPa to 52.26 MPa, which is 5 MPa or less in Comparative Example 1 without boehmite Compared with the result is excellent.

< Example  9>

Mixed refractory containing 0.4 g of spinel was mixed in a polypropylene container at the composition ratio shown in Table 3 below. 50 g of the following composition 6 was taken and placed in a paper cup. Then, 0.08 g of polyvinyl alcohol (PVA) was added. Table 4 shows.

Spinel  Composition ratios of mixed refractory materials included and added Bohemite  amount Al ₂ O ₃ (g) SiC (g) Spinel (g) Bohemite
(g) d ₅₀ 3-5 mm 0.3 μm 1.25 mm 750㎛ 90 μm 20 탆 5㎛ <44 μm Composition 5 6.7 7.2 36.5 22.1 2.9 19.2 1.3 0.4 0 Composition 6 7.0 7.2 36.5 22.6 3.0 19.7 1.3 0.4 2.0 Composition 7 6.7 7.2 36.6 22.1 2.9 19.5 1.3 0.4 4.3

< Example  10>

50 g of the composition 6 was added to a paper cup, and 6.66 g of distilled water was added to prepare an alumina binder amorphous refractory material in the same manner as described in Example 1, and the bending strength and density thereof were measured. The results are shown in Table 4 below. .

< Example  11>

50 g of the composition 6 was added to a paper cup, and 6.25 g of distilled water was added to prepare an alumina binder amorphous refractory material in the same manner as described in Example 1, and the bending strength and density thereof were measured. The results are shown in Table 4 below. .

< Example  12>

50 g of the composition 7 was added to a paper cup, and 5.55 g of distilled water was added to prepare an alumina binder amorphous refractory material in the same manner as described in Example 1, and the bending strength and density thereof were measured. The results are shown in Table 4 below. .

< Example  13>

50 g of the composition 7 was taken into a paper cup, and 7.7 g of distilled water and 0.08 g of 5 wt% hydroxyethyl cellulose (HEC) aqueous solution were added to prepare an alumina binder amorphous refractory material in the same manner as described in Example 1. After measuring the density and the results are shown in Table 4 below.

< Comparative example  2>

50 g of the composition 5 without boehmite was added to a paper cup, and 8.8 g of a 5% by weight aqueous solution of hydroxyethyl cellulose (HEC) in distilled water was added. After measuring the bending strength and density, the results are shown in Table 4 below.

Spinel this Included Mixed refractories  Added Bohemite  Sheep
Effect of Alumina Binder on the Physical Properties of Amorphous Refractories Composition (g of boehmite used) Additive (g) Sintering temperature (1400 ℃),
2 hours in air Distilled water HEC aqueous solution
(5% by weight) PVA density
(g / cm ³⁾ Bending strength
(MPa) Composition 5
(0) Comparative Example 2 0 8.8 0 2.55 <5 Composition 6
(2.0) Example 9 6.59 0 0.08 2.66 28.84 Example 10 6.66 0 0 2.63 39.04 Example 11 6.25 0 0 2.61 39.98 Composition 7
(4.3) Example 12 5.55 0 0 2.83 50.71 Example 13 7.7 0.08 0 2.68 52.71

As can be seen in Table 4, the addition of an alumina precursor, that is, boehmite, which is dispersed in water according to the present invention and can be hydrolyzed and polymerized, improves the sintering density by forming an alumina bond with the refractory component during sintering, that is, Porosity is lowered, there is an effect that the strength is increased to 8 to 10 times. In addition, when distilled water was added as an additive in the present invention, it showed superior bending strength, and when the HEC aqueous solution was added as an additive, it showed that excellent bending strength.

Claims (14)

An alumina binder amorphous refractory comprising Al ₂ O ₃ , SiC, alumina precursor powder and water.
The alumina binder amorphous refractory according to claim 1, wherein the alumina precursor powder is p-alumina or boehmite.
The alumina binder amorphous refractory according to claim 1 or 2, wherein the alumina precursor powder is used in an amount of 1 to 10 parts by weight based on 100 parts by weight of the total amount of Al ₂ O ₃ SiC.
The alumina binder amorphous refractory according to claim 1, further comprising spinel, magnesia or zirconia in the alumina binder amorphous refractory.
The alumina binder amorphous refractory according to claim 1, wherein the water is used in an amount of 3 to 15 parts by weight based on 100 parts by weight of the total amount of Al ₂ O ₃ and SiC.
The alumina binder amorphous refractory according to claim 1, further comprising 0.01 to 5 parts by weight of an organic binder based on 100 parts by weight of the total amount of Al ₂ O ₃ and SiC.
7. The alumina binder amorphous refractory according to claim 6, wherein the organic binder is hydroxyethyl cellulose, methyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose or latex.
(a) mixing Al ₂ O ₃ , SiC and alumina precursor powder together to make a mixed refractory;
(b) adding water to the mixed refractory to form a mixture;
(c) curing and drying the mixture; And
(d) heat treating the cured and dried mixture
Method for producing an alumina binder amorphous refractory comprising a.
The method of claim 8, wherein the alumina precursor powder of step (a) is p-alumina or boehmite.
The method of claim 8 or 9, wherein the alumina precursor powder is used in an amount of 1 to 10 parts by weight based on 100 parts by weight of the total amount of Al ₂ O ₃ and SiC used.
The method of claim 8, wherein the mixed refractory of step (a) further comprises spinel, magnesia or zirconia.
The method according to claim 8, wherein the water of step (b) is used in an amount of 3 to 15 parts by weight based on 100 parts by weight of the total amount of Al ₂ O ₃ and SiC.
The alumina binder amorphous refractory according to claim 8, further comprising 0.01 to 5 parts by weight of the organic binder in the mixture of step (b), based on 100 parts by weight of the total amount of Al ₂ O ₃ and SiC. Method of preparation.
The method of claim 13, wherein the organic binder is hydroxyethyl cellulose, methyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, or latex.