KR100239939B1 - Refractory material and its manufacturing method - Google Patents

Abstract

The present invention relates to a fire-resistant material and its manufacture for improving the service life by increasing wear resistance, heat shock resistance, corrosion resistance and spalling resistance to fire bricks constructed in various industrial furnaces. It consists of a refractory material composed of -71 parts by weight, 22-43 parts by weight of zirconate raw material, 2-7 parts by weight of clay, and in the preparation thereof, the composition is kneaded and calcined at 1630-1670 ° C. for 3 to 6 hours. It is composed of a manufacturing method characterized by.

Description

Refractory material embedded in industrial furnace and manufacturing method thereof

The present invention relates to a fire retardant composed of alumina-zirconia-mullite and a method for manufacturing the same, and more particularly, to a fire retardant having an increased service life due to improved wear resistance, thermal shock resistance, corrosion resistance, and spalling resistance.

In industrial furnaces, such as circulating fluidized bed boilers and various rotary furnaces, refractory bricks are used in parts of the urinary which are subjected to collisions or impacts by powders in charges or hot gas flows.

Circulating fluidized bed boilers burn oil, anthracite or petroleum coke as fuel and limestone as a desulfurizer in a fluidized bed.

The interior of this facility is embedded in refractory to be durable such as temperature load by heat of combustion and abrasion by solid particles produced during combustion.

Solid particles generated in the combustion furnace circulate with the combustion gas at high speed and flow into the cyclone with the combustion gas at high speed.

At this time, the hard solid particles collide with the surface of the refractory interior material with a velocity of about 10 m / sec or more inside the cyclol.

In particular, the target zone of the cyclone is always 20m / sec or more, and the impact angle is larger than the other parts of the cyclone, so that the lifetime of the same refractory lining material is less than ½.

In addition, the internal temperature is 750 ~ 950 ℃, the temperature gradient from the operating surface of the interior material to the steel bar is steep and structurally subjected to compressive stress.

Therefore, it is possible to prevent crack damage during operation only when the thermal shock resistance against temperature change is excellent, and heat loss can be reduced outside the furnace only when the thermal conductivity is as low as possible.

Refractory materials used in this facility include high alumina bricks or phosphate-bonded alumina ramming materials with a certain hardness and strength in addition to relatively high heat resistance.

High alumina brick is used as various bricks with Al ₂ O ₃ content of about 59 ~ 80% by weight. As the alumina content increases, the high alumina brick is fired at high temperature to increase the bond strength of the matrix to increase the fracture strength.

The binding force of the matrix is increased by producing alumina and silica in the raw materials as mullite (3Al ₂ O ₃ · 2SiO ₂ ) during firing.

However, even though mullite is a mineral having excellent volume stability with relatively low thermal expansion, its fracture strength value is limited.

When these bricks are used in the target zone, repairs are frequently caused by wear, which has a fatal effect on facility operation rate.

On the other hand, the phosphate-bonded alumina ramming material achieves high filling density which promotes abrasion resistance, and also has low shrinkage and cold compaction in cold and hot using raw materials such as hot-fired or fused alumina for bulk stability. Do.

This ramming material is made by adding aluminum phosphate as a binder to produce Al ₂ O ₃ · nP ₂ O ₅ compounds in the matrix after construction and drying, and expresses the hot strength up to a relatively high temperature range. To keep abrasion resistance.

However, the phosphate contained in the binder is water soluble and moves the binder to the surface of the construction body as the moisture moves during drying, thereby increasing the P ₂ O ₅ concentration on the surface.

Bond migration caused by incorrect concentration distribution between constructions causes peeling due to the difference in strength between the surface and the inside.

Cyclone structure is a cylindrical structure has a problem that causes fatal damage when partial peeling of the interior material.

In addition, even if the construction and drying is well, the wear resistance at high temperature during use always exists, so when used in the target zone of the cyclone, like the bricks, wear and tear caused by wear is large, there is a problem that frequent maintenance.

Another part of the installation where abrasion resistant refractory is required is the cooler chute of the rotary furnace.

In general, the refractory material used for the cooler chute part of a rotary furnace is different according to the kind of clinker manufactured and the structure of a cooler.

As an example, the cooler chute refractory material of a revolving furnace for cement manufacture suffers from thermal shock damage due to rapid temperature changes of 600 to 1200 ° C, as well as wear caused by dropping impacts of hard clinkers.

Alkaline in the combustion gas components also condenses extensively in the cooler refractory.

Generally, high alumina bricks containing 60 to 85% by weight of Al ₂ O ₃ have been used in this site.

However, high alumina bricks are mostly made of a mullite matrix with a limited fracture strength and are easily damaged by wear.

Moreover, there is a problem that the lifespan is greatly shortened by causing structural spalling due to poor resistance to penetration of alkali compounds.

There is a sintered alumina manufacturing facility as a rotary furnace to produce another clinker.

The cooler chute part of the urinary tract wears excessively due to the thermal shock caused by the temperature change of 600 to 1300 ° C. and the drop impact of the alumina having a high hardness.

The materials used in interior materials are also various, such as cast steel, all-round brick, and hard clay brick.

Cast steel, which is a metal, has less wear and tear due to wear than other materials.

In addition, the main column brick is less hot deformation and wear due to wear is small, but the problem is that it is expensive compared to the life.

Hard clay brick has a problem of reducing the operation efficiency of the furnace because of frequent occurrence of repair due to wear together with high alumina brick in this temperature range.

Generally, silicon carbide (SiC) nitride refractory material is a material having excellent thermal shock resistance and abrasion resistance, but silicon carbide has a problem that the heat dissipation heat loss outside the furnace is large because the thermal conductivity is about 2 to 5 times larger than that of the oxide refractory material. .

The relationship between the degree of wear and the properties of refractory materials in hard charges or high-temperature gas flows under high temperature has not been studied much, but generally the wear resistance is characterized by hot strength, hardness of the aggregate used, and toughness of the matrix. Large refractory is known to be better.

To date, nothing has been introduced as a study on wear resistant alumina-zirconia-mullite bricks.

However, conventionally, alumina-zircon-brick or zircon-mullite brick, commonly referred to as sintered AZS (Bonded Al ₂ O ₃ -ZrO ₂ -SiO ₂ ) brick, has excellent corrosion resistance against the glass melt and is a refractory material for contacting glass with glass. Has been used.

For example, U.S. Patent No. 3,437,499 has a composition of zircon, alumina, molten mullite, calcined Kyanite, clay, etc., and is a sintered body sintered below the dissociation temperature of zircon and has high erosion resistance and high thermal shock resistance. Known for the production of refractory materials, U.S. Patent No. 4,045,233 has a porosity of 8.5 to 15% to satisfy the application to glass melting by using alumino-silicate raw materials, plasticized alumina, zircon, clay, pyrophyllite as a composition. Although fire-resistant compositions have been reported, there is no mention of mechanical properties, and since the aluminosilicate material is used as aggregate, the hardness and mechanical properties are low.

And because these bricks have high porosity and low matrix, they have low strength and hardness, so they have low mechanical properties, and they are mainly composed of zircon, so they cannot be expected to increase the toughness due to the transformation properties of zirconia at high temperatures. It is not expressed.

N.Claussen et al. Are mechanical structural ceramics that disperse zirconia in mullite matrix by improving the strength and toughness by dispersing the mixture of alumina and zircon at high temperature due to the limited mechanical properties of mullite materials. (J. Am. Ceram. Soc., 63, 3-4, p228-229, 1980).

Besides, mullite-zirconia has been studied a lot, but it has not been brought to practical use as a refractory brick with wear resistance.

On the other hand, Korean Patent Publication No. 95-14492 describes the preparation of a small alumina-mullite-zirconia composite of ultra-fine silica sol and boehmite-zirconia powder, which is subjected to heat sintering after filtration, drying, calcination, grinding and compression molding. The method is known but not practical.

In addition, the composite prepared by this method does not have any porosity, so it is impossible to apply it as a refractory material under the conditions of use of the urinary tract requiring heat shock resistance and wear resistance at high temperature.

In addition, zirconia-mullite, which is known to have excellent toughening properties and thermal shock resistance due to transformation of zirconia, has been manufactured and marketed as a refractory raw material. Recently, efforts have been made to improve thermal shock resistance and mechanical properties by using it in refractory materials.

For example, refractory casters used in the urinary tract of hydrocarbon manufacturing industry are required to be more resistant to abrasion, high strength, low thermal conductivity, and thermal shock resistance. (O. Hunter et al, Proceeding UNITECR `95congress, Gyeonggyo, p197-201, 1995).

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. The present invention provides zirconia in the mullite matrix and promotes fracture strength by forming pores and densification of the matrix, thereby providing excellent wear resistance and thermal shock resistance. The purpose of the present invention is to provide a refractory material composed of refractory materials having improved service life due to increased spalling resistance.

1 is a graph showing the apparent porosity and the volume specific gravity according to the Al ₂ O ₃ to ZrSiO ₄ mixing ratio.

2 is a graph showing the apparent porosity and the volume specific gravity according to the Al ₂ O ₃ fine powder ZrSiO ₄ fine powder mixing ratio.

3 is a graph showing the apparent porosity and volume specific gravity according to the particle size of Al ₂ O ₃ .

4 is a graph showing the fracture strength according to the firing temperature.

5 is a graph showing the fracture strength according to the plastic holding time.

The present invention for achieving the above object consists of a refractory composition of 55 to 71 parts by weight of alumina raw material, 22 to 43 parts by weight of zircon raw material, and 2 to 7 parts by weight of clay.

The alumina raw material in the composition may be used one or a mixture of electrolytic alumina or sintered alumina containing 99% by weight or more of Al ₂ O ₃ component quality.

The 55 to 71 parts by weight of the alumina raw material is preferably composed of 8 to 40 parts by weight of particles 5-5 mm, the remainder of the ultra fine powder (having a particle size distribution containing more than 50% 100㎛ or less).

Zircon in a quality raw material 22-43 parts by weight, preferably has a particle size distribution, and material having a goods containing 64-69% by weight of the ZrO ₂ component containing less than 70% by weight 250㎛.

It is preferable that Al ₂ O ₃ have a quality of 29% by weight or more in _{2 to} 7 parts by weight of clay.

In the firing method using the blended raw material, a molded product obtained by adding a binder to the composition, kneading and molding is dried, and fired for 3 to 6 hours at 1630-1670 ° C., which is higher than the dissociation temperature of zircon, and fired for 3 to 6 hours. The same sintered body is obtained.

When explaining the reason for the addition according to the raw material used in the present invention, the alumina raw material uses electrolytic alumina as a raw material that forms zirconia in the mullite matrix by reacting and sintering with the silica component of zircon, as shown in Scheme 1 below.

The reason is that it contains an appropriate amount of alkali and promotes dissociation of zircon without adding a separate mineralizer, making it easier for the reaction to proceed to the right, and the high temperature strength and thermal shock between the mullite and zirconia grain boundaries of the matrix during sintering. It prevents excessive generation of liquid phase that lowers the resistance.

As another reason, electrolytic alumina contains more waste holes and β-Al ₂ O ₃ (Na ₂ O.11Al ₂ O ₃ ) than sintered alumina, so it effectively disperses stress and exhibits excellent thermal shock resistance when present as aggregate in the matrix. This is because the crystal size is large and the hardness and chemical corrosion resistance are large.

In 55 to 71 parts by weight of the molten alumina, the aggregate having a particle size of 5 to 1 mm is preferably composed of 8 to 40 parts by weight, but when the 5 to 1 mm particle size is 8 parts by weight or less, the moldability of the brick is reduced. In the formulation, aggregates are ubiquitous, so that it is difficult to obtain a uniform quality, and when the content is 40 parts by weight or more, aggregates are much higher than the matrix, so the fracture strength is low and the porosity is not high.

Zirconium raw materials are used in the range of 22 to 43 parts by weight, but the ratio of ZrO ₂ is 64 to 69% by weight in a molar ratio of ZrO ₂ and SiO ₂ , and CaO + MgO + Fe ₂ O ₃ as impurities. It is preferable that the content grade is 0.5% by weight or less, and the zirconium raw material particle size contains not less than 250㎛ 70% by weight or more.

The reason why the impurity (CaO + MgO + Fe ₂ O ₃ ) is preferably 0.5% by weight or less is that zircon is bonded with ZrSiO ₄ and heated to have characteristics at around 1580 ° C. without addition of a mineralizer. ZrO ₂ and SiO The impurities other than _{2 do} not dissociate the temperature and produce liquid phase between the matrix of zirconia-mullite after reaction sintering at high temperature. This is because appearance defects are caused.

In addition, when the amount of zirconium raw material used is 43 parts by weight or more, excessive SiO ₂ liquid generated during sintering at high temperature lowers the hot strength and thermal shock resistance, and the volume specific gravity is so high that it acts as a drawback to increase the load of the condenser. .

In addition, when the amount is less than 22 parts by weight, the amount of zirconia and mullite produced by dissociation of zircon in the matrix is so small that the mechanical properties are remarkably deteriorated due to a decrease in the toughness of the matrix, a decrease in strength and an increase in porosity.

The clay is preferably free of residues and salt compounds, which provide good filling between the blends and impart plasticity and formability of the blend.

If the amount is 2 parts by weight or less, the above effect cannot be obtained, and if the amount is more than 7 parts by weight, excessive liquid phase is generated in the zirconia-mullite matrix to lower the mechanical properties.

In the present invention, the compacted zirconia-mullite matrix is maintained at 1630 to 1670 ° C. for 3 to 6 hours as the temperature and time to heat-treat the molded article according to the above-described structure. Preferred to form.

When firing at a temperature below this 1630 ° C., zircon particles of 200 μm or more do not dissociate completely and do not form waste holes around the particles after firing.

Excess liquid phase is present in the matrix, resulting in a decrease in hot strength and thermal shock resistance.

On the other hand, in the case of 1670 ℃ or more, the apparent porosity is not reduced anymore, the liquid component oozes out to the surface of the brick, causing a poor appearance.

In addition, maintaining a calcination time of less than 3 hours at the highest temperature yields a desirable zirconia-mullite matrix structure due to the lack of dissociation time of zircon, and if it is kept too long at the maximum temperature, it also does not help in the formation of pores, but rather a brick surface. Severe liquid exudation occurs.

The following is described according to the embodiment.

Example 1

This Example was adjusted to the molding formulation by adding 3% by weight of molasses as a binder to the refractory brick formulation shown in Table 1 in order to know the densification sintering characteristics according to the particle size and the amount of the alumina and zircon raw materials used as the formulation.

Thereafter, the mold was molded into a size of 230 × 114 × 65 mm using a friction press molding machine having a capacity of 300 tons, dried at 120 ° C. for at least 1 day, and then dried at 120 ° C. for at least 2 days.

1 and 2 show the apparent porosity and the specific gravity of the bricks manufactured in connection with Table 1.

FIG. 1 shows that when the weight ratio (Al ₂ O ₃ / ZrSiO ₄ ) of alumina to zircon is 0.59 to 1.77 (compound Nos. 4, 3, 2, and 1), the amount of zircon fine is fixed and the alumina fine is reduced to (Al ₂ O _{When 3} / ZrSiO ₄ fine fraction is used from 0.19 to 1.03), the excess dissociation of the excessively mixed zircon leads to the formation of a zirconia-mullite matrix, which shows the desirable physical properties by increasing the volume specific gravity and strength and decreasing the apparent porosity.

Also, FIG. 2 shows that when the ratio of total Al ₂ O ₃ / ZrSiO ₄ is 0.59 to 3.61 (compound numbers 4, 5, 6, and 7), the alumina fine fraction increases and the zircon fine fraction decreases (Al ₂ O ₃ / ZrSiO _4). Differential secretion is preferred for increasing the volume specific gravity, strength and decreasing the apparent porosity when 0.19 to 4.60), and it shows that effective sintering is achieved by reducing excess zircon in the matrix without reacting according to the specific surface area of alumina and zircon.

Example 2

This example was to know the type of the alumina raw material and the use characteristics of the fine particle size was prepared in the same manner as in Example 1 for the refractory brick blend shown in Table 2.

Figure 3 shows the apparent porosity and volume specific gravity of the bricks manufactured in connection with Table 2.

The large porosity of the fused alumina fine particles shows a decrease in porosity, which is effective for sintering reaction and matrix densification by dissociation of zircon.

In addition, the same particle size shows that the molten alumina is more effective in densification than the sintered alumina.

Example 3

This example is to know the sintering characteristics according to the firing temperature and the holding time was prepared in the same manner as in Example 1 for the refractory brick blend shown in Table 3, and the appearance and physical property test results after firing.

As shown in Table 3, as the firing temperature and the holding time increase, the densification proceeds and the porosity decreases.

4 and 5 show the constituent minerals of the bricks manufactured in connection with Table 3.

The amount of the constituent minerals is shown by comparing the values measured using the zircon diffraction intensity value of Formulation No. 100 with respect to the diffraction intensity accelerating value of each component measured using an X-ray diffractometer.

As shown in FIG. 4 and FIG. 5, as the firing temperature and the holding time increase, the dissociation of zircon proceeds completely, and the remaining of zircon is not confirmed, and the production of mullite is increased, so that zirconia is dispersed in mullite, which promotes fracture strength. It is effective in organizing.

Example 4

This embodiment is described in detail like the prior art and the comparative example to understand the effect of the present invention in detail.

The formulations shown in Table 4 were prepared in the same manner as in Example 1, and their properties were compared with those of the prior art and comparative examples.

As shown in Table 4, the present invention showed clear results superior in wear resistance, thermal shock resistance, alkali resistance, etc., due to the higher density of bricks and superior cold and hot strength compared to conventional technologies.

In addition, the present invention shows an effect that is more than twice as effective in the actual urinary tract.

As described above, according to the present invention, the composition of alumina raw material, zircon raw material, and clay is appropriately blended, and the particle size of each raw material is adjusted, thereby producing zirconia in the mullite matrix, and at the same time, forming waste pores and matrix densification. Therefore, it is possible to obtain a fire brick having a long service life by increasing wear resistance, thermal shock resistance and spalling resistance.

Claims (3)

Alumina (Al ₂ O ₃₎ is refined 99% by weight or more, yet, 5~1㎜ the particle is 8-40 parts by weight, the fine particles are 47-31 parts by weight of alumina (Al ₂ O ₃₎ raw material to be 55-71 wt. Particles containing zircon (ZrO ₂ ) grade of 64 to 69% by weight, zirconium raw material with a particle size of 250 μm or less and 70% by weight or more and 22 to 43 parts by weight of alumina (Al ₂ O ₃ ) grade of 2% or more by weight A fire resistant material embedded in an industrial furnace, characterized in that it is composed of 2 to 7 parts by weight. The fire resistant material of Claim 1 in which fine alumina fine particle contains 50 micrometers or more of 100 micrometers or less. Alumina (Al ₂ O ₃₎ is refined 99% by weight or more, yet, 5~1㎜ the particle is 8-40 parts by weight, the fine particles are 47-31 parts by weight of alumina (Al ₂ O ₃₎ raw material to be 55-71 wt. Particles containing zircon (ZrO ₂ ) grades of 64 to 69% by weight, 22 to 43 parts by weight of zirconium raw materials having a particle size of 250 μm or less and 70% by weight or more, and alumina (Al ₂ O ₃ ) grades of 29% or more by weight A method of producing a refractory material embedded in an industrial furnace, characterized by kneading and molding a mixture so as to form 2 to 7 parts by weight, and then firing at a temperature of 1630 to 1670 ° C for 3 to 6 hours.

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