DE3836852A1 - High-strength, abrasion-resistant, refractory castable mixture - Google Patents

Abstract

There is described a refractory mixture which has low porosity, high density, extraordinarily high strength and high abrasion resistance and which is used for lining of plants for catalytic conversion of liquids, such as catalyst transfer lines, rises, J bends, cyclones and other regions for which abrasion resistance at high temperatures and low thermal conductivity are desired. The mixture consists essentially of the following components: a) from 44 to 89% by weight of an abrasion-resistant refractory grain, b) from 10 to 50% by weight of a hydraulic cement, c) from 1 to 6% by weight of a filler comprising very fine, essentially spherical particles of a material selected from the group consisting of Al2O3, Cr2O3, ZrO2, TiO2, clay minerals, carbon and pyrogenic silica, and d) from 0.01 to 1%, based on the total weight of the components a), b) and c), of additives selected from among deflocculants and wetting agents.

Description

The invention relates to refractory pourable mixtures the base of molten oxides including one glassy phase. These mixtures have low porosity, high strength and high heat abrasion resistance.

Refractory fabrics are used in virtually all industrial Oil refining and processing plants used work at elevated temperatures. The temperatures within of plants for the catalytic cracking of liquids can z. B. reach 800 ° C. That's why these or other plants are lined with a fabric that to ensure high resistance to elevated temperatures capable of and against the influences of processing occurring chemical substances and the pressures is stable.

The plants mentioned were refractory for a time Brick lined, but it was found that such Masonry only a low abrasion resistance respectively. Currently, it is common in the industry, the said Installations with a refractory pourable mixture with high insulation value and high abrasion resistance. The facilities are lined by clicking on the inside of metal molds and the fireproof pourable mixture into the molds with vigorous shaking pours, whereby the mixture hardens, after which you finally removed the metal molds.

Although fire-resistant pourable mixtures used for lining The above-mentioned plants are currently suitable available on the market, there is a need  at even more efficient and durable refractories Substances. Refractory linings for catalytic systems Crackers are generally 5.1 to 10.2 mm (2 to 4 inches) thick, and for the lining of a single plant Up to 400 tonnes of refractory pourable mix are required. It goes without saying that the cost of the repair and replacement of such a refractory Lining can be very high. Even more decisive than the cost of replacing the lining is the cost, which are caused by the downtime during which the plant is repaired, which can take several weeks.

Now found a new refractory mixture, the low Porosity, high density, exceptionally high strength and high abrasion resistance and which the life of the strong abrasion exposed surfaces of catalytic Conversion plants for the refining of crude oil extended. This new mixture consists essentially from the following components:

• a) 44 to 89 wt .-% of an abrasion-resistant refractory grain,
• b) 10 to 50% by weight of a hydraulic cement,
• c) 1 to 6 wt .-% of a filler, consisting of very fine, substantially spherical particles a metal oxide selected from the group Al₂O₃, Cr₂O₃, ZrO₂, TiO₂, clay minerals, carbon and fumed silica,
• d) 0.01 to 1%, based on the total weight of the Components a), b) and c), selected from additives under deflocculants and wetting agents.

An abrasion and refractory grain contains 44 to 89% by weight, preferably 54 to 79 wt .-% of the refractory invention pourable mixture. The skilled person is able that for the production of refractory invention  Select mixtures suitable abrasion and refractory grain. The preferred refractory for blends for uses, where low thermal conductivity desired is (as in the above-mentioned facilities for catalytic cracking of liquids) are particles from a mixture of molten clay, zirconium and silica (AZS). The molten AZS refractory contains as main components Al₂O₃, ZrO₂ and SiO₂ or Al₂O₃, ZrO₂, SiO₂ and Cr₂O₃, and usually about 32.5 to 54 wt .-% ZrO₂, about 36 to 51 wt .-% Al₂O₃, about 2 to 16 wt .-% SiO₂, about 0.28 to 1.5 wt .-% Na₂O and less than about 1.5 wt .-% other oxides. Correspondingly suitable substances are used in the PS 12 08 577 and in the corresponding additional patent no. 75 893 described. The chemical composition of the AZS mixtures is not critical, but preferably the AZS grain should have the following composition:

49.0% Al₂O₃,
34.0% ZrO₂,
15.0% SiO₂,
0.1% Fe₂O₃,
0.2% TiO₂,
1.5% Na₂O,
0.2% remaining oxides.

The mineralogical composition of these preferred AZS is 48% corundum, 32% zirconia and 20% vitreous phase.

For use where low thermal conductivity Not required, other abrasion and fire resistant Grains are used. Examples of such substances, alone or in mixture for the production of castings with unique abrasion resistance, strength and compressive strength can be used at room temperature, are without being limited thereto, molten alumina, silicon carbide, molten mullite, molten zirconia and molten clay and zirconia. These substances can be as such  as refractory grains or in admixture with molten ones AZS for the preparation of the refractory mixtures according to the invention be used.

The refractory grain used according to the invention preferably has specific particle size fractions. The particle size distribution is carefully selected so that the finer Pores gradually with increasingly finer particles be filled to the submicron range. this leads to to a mixture with maximum packing density and thus too a casting with low firing, low porosity, high density, extremely high strength and low Erosion loss.

In general, the particle size distribution of the refractory grain to choose so that the particle size distribution within a range of about 44 μm (+325 mesh) and 4760 microns (-4 mesh), which is preferably substantially is consistent. For example, the preferred and particularly preferred refractory grains have a particle size distribution within the following, given in Table 1 Area.

Table 1

The second component of the refractory mixture according to the invention is a hydraulic cement which is 10 to 50% by weight, preferably about 20 to 40 wt .-% of the total amount of the mixture accounts. Such cements are well known. The preferred cement is a high calcium aluminate cement Purity, formed by the conversion of high-purity lime with baked alumina or aluminum hydroxide. calcium aluminate cements of high purity, as currently available are about 80 wt .-% Al₂O₃ and 17.0 wt .-% CaO and have a particle size of about 95 to 97% 44 μm (-325 mesh). But it can also calcium aluminate cements of lesser Purity, d. H. those with about 70% Al₂O₃, are used. Should the pourable refractory mixture in a reducing Atmosphere used, it is important that the Calcium aluminate cement has a low content of silica (about 0.1%) and Fe₂O₃ (about 0.1%).

The filler comprising component c) of the mixture according to the invention represents, is made of very fine, substantially spherical Particles of a substance selected from the Group Al₂O₃, Cr₂O₃, ZrO₂, TiO₂, clay minerals, carbon and fumed silica. The specific surface the materials should generally be above 5 m² / g. They are preferably particles of pyrogenic and glassy Silica with a mean diameter of 0.15 μm and a specific surface area of 18 to 28 m² / g. The said glassy silica has the shape of microspheres and a content of SiO₂ of at least 96.5%, the remainder being Na₂O, Al₂O₃, ZrO₂ and / or carbon eliminated. Silica particles of this type are general known and commercially available. Component c) makes 1 to 6 wt .-% of the total mixture, preferably about 1 to 3 wt .-% of.

Additives such as deflocculants and wetting agents can be 0.01 to 1 % By weight, based on the total weight of components a), b)  and c) make up the refractory pourable mixture. Therefore suitable additives are known and include Calgon®, Polyphosphates, citric acid and Na citrate. The preferred one Deflocculant or wetting agent is the Na salt polymerized substituted Benzoidalkylsulfonsäuren as z. B. under the trade name Darvan® by R. T. Vanderbilt Company, Inc., Norwalk, CT.

The refractory mixtures according to the invention are particularly suitable for the lining of catalytic plants Conversion of liquids, such. B. catalyst transfer lines, Risers, J-headers, cyclones and other areas for high abrasion resistance Temperatures and low thermal conductivity desired are. Is the further processing of the mixtures according to the invention Desired, these are done carefully with a lot Water between about 5.5 and 8, preferably 6.25 and 6.75 Wt .-%, based on the total weight of the mixture, mixed. Best results are obtained with a mixing time of approx. 5 minutes. The mixture must be mixed immediately after mixing to be potted, with the molds used to remove the trapped ones Air and to improve the flow of strong be shaken. The ideal casting temperature is 22 ° C. After initial hardening, the refractory mix must be wet kept to evaporate the water before completion to prevent the implementation. The casting surface can with a fine water jet moistened or with wet sacks off coarse linen or a plastic film for 12 to 24 hours be covered depending on the thickness. The ideal curing temperature is between 21 and 29 ° C.

Table 2 shows the typical physical properties composed of samples of the refractory mixtures according to the invention.

Table 2 Typical physical properties of the mixtures according to the invention (samples fired at 816 ° C.) breaking strength 1758 N / cm² (2500 PSI) Compressive strength at room temperature 8437 N / cm² (12,000 PSI) density 2771 kg / m³ (173 lbs / ft³) erosion loss 4.5 cm³ Linear change - 0.2% Apparent (open) porosity 21% thermal conductivity 1.368 W / m ° K (9.5 BTU / in / hr / ft² / ° F)

Those listed in Table 2 and in the examples below Values were obtained according to the following test methods:

Breaking Strength: ASTM C-133 Compressive strength at room temperature: ASTM C-133 density: ASTM C-20-74 Erosion loss: ASTM C-704

The linear change was detected by measuring a block 24-hour air drying with a caliper with round scale and determined after firing at 816 ° C. Linear change = (Width in the air-dried state - width in the fired Condition) / width in the air-dried state.

The apparent (open) porosity was according to ASTM C-20-74 (modified). The water absorption was carried out by Vacuum impregnation for 30 minutes instead of 2 hours Cook. Sample size: cubes with an edge length of 2.54 cm.

Thermal conductivity: 9 dried blocks of 11.43 cm ×  11,43 cm × 7,62 cm (4,5 "× 4,5" × 3 "), which passes through a 2.54 cm thick heat insulating were separated placed in a gas fired laboratory furnace. This one became then heated to 816 ° C and for 12 hours at this Temperature maintained. Thereafter, the temperatures of the cold outer surfaces using an optical infrared pyrometer measured and used to calculate the thermal conductivity used. Alternatively, the hot wire method may be used become.

Examples 1 to 9

There have been several inventive refractory mixtures mixed and potted to the effect of each component on the pot life, the use properties and the physical properties of the castings obtained demonstrated. The preparation of these mixtures used AZS mixtures had the following chemical composition:

49.0% Al₂O₃,
34.0% ZrO₂,
15.0% SiO₂,
0.1% Fe₂O₃,
0.2% TiO₂,
1.5% Na₂O,
0.2% remaining oxides.

The particle size distribution of the AZS mixtures corresponds to the Column "particularly preferred" in Table 1.

The refractory mixtures were in a mixer of the type Hobart with a capacity of 22 liters (20 quart) mixed, giving first all dry components and 2 minutes were mixed together before you added water. After mixing with water during 5 minutes, the mass was in "shoebox" forms  Lucite 11,43 cm × 11,43 cm × 22,86 cm (4,5 "× 4,5" × 9 ") poured, which you put on a vibrating table, where you 2 to 3 minutes to remove trapped Air at a frequency of 3600 vibrations / minute at low amplitude shook. The potted samples were then left in the molds for 24 hours after which you removed these. The exposed samples were then on The air dried for another 24 hours before getting put them in an oven at 110 ° C for 24 hours.

After drying, the specimens were carried out the measurement of abrasion, the compressive strength at room temperature, density, porosity and thermal conductivity cut out of the shoe box sample. After that were held the specimens at 816 ° C for 5 hours, wherein had heated to this temperature for about 16 hours. The samples were then cooled at firing speed (for about 24 hours).

The mixtures and their physical properties are summarized in Table 3.

water content

As determined by comparison of Example 1 and 2 can, the water content has a strong influence on the compressive strength at room temperature and the abrasion resistance mixtures, wherein a low water content (5 to 3/4%) gives the best results.

cement content

Examples 3 to 5 illustrate the effect of high and low cement content. The high cement content (50%) led to an increase in open porosity to 27.1% and gave a low bulk density of 2451 kg / m3 (153 lbs / ft³) with a short pot life. The low cement content (10%) led to low strength and insufficient mixing and casting properties (honeycomb structure). The preferred one Cement content (30%) gave a mixture with less open Porosity, high bulk density, high strength and excellent Mixing and pouring properties.

Content of fumed silica

The mixture with the high content of fumed silica according to Example 6 gave a mixture which is very sensitive was opposite to the water content. She was sticky, stiff and hard to shed. Except for the high burning fade The physical properties of the castings were approximate the usual. The mixture without fumed silica according to Example 7 showed a higher porosity and a higher one Erosion loss as the preferred embodiment of Example 3.

Melted clay

Example 8 shows that fused alumina deice instead of AZS grain can be used while being appropriate Achieve properties such as abrasion resistance, strength, etc. to let. The thermal conductivity of the refractory product is considerably higher than similar mixtures of AZS Grain.  

Examples 10 and 11

To illustrate the effect of AZS with different Grain size distributions were made in Example 10 and 11 AZS blends used with large and small particle sizes. This AZS Mixtures had the following typical particle size distribution:

These blends and their physical properties are summarized in Table 4.

Table 4

Comparing the results in Table 4 for the examples 10 and 11 with those for Example 3, in which an AZS mixture was used with the preferred particle size distribution, so It can be seen that with coarse AZS grain (Example 10) the pressure resistance noticeably reduced at room temperature is and the cavities in the casting are numerous. In fine AZS grain (Example 11) is slightly higher in abrasion loss, and the mixture is difficult to shed. She has the characteristics of wet sand.

example 12

For comparison with the mixtures according to the invention were two pourable mixtures using conventional, currently on the market. When first comparative mixture (Comparative Example A) became a  Mixture based on Al₂O₃ with a particle size of 6730 microns (-3 mesh) used and second (Comparative Example B) an AZS mixture having a particle size of 4760 microns (-4 mesh). In contrast to the mixtures according to the invention the comparative mixtures do not contain the inventive than Component c) designated microspherical "filler". The mixtures according to Comparative Examples A and B and according to example 12 are the following:

The physical properties of the comparative examples obtained products and the typical properties a mixture according to the invention such. B. according to example 12 are summarized in Table 5.

Table 5

Physical properties after firing at 816 ° C

The results in Table 5 show that the pourable AZS-based product according to Comparative Example B in the physical Properties of the pourable invention Product comes closest. The physical properties the mixture according to Comparative Example B are something worse compared to the mixture according to the invention after Example 12, in particular with regard to the breaking strength, the compressive strength at room temperature and the erosion loss according to ASTM C-704. These properties are ordinary with the life in transfer lines of plants for catalytic Cracking liquids (FCCU) and other, high Abrieb having plants connected. The mixture according to example 12, which has an erosion loss of only 4.5 cc, has, compared with the mixture of Comparative Example B (erosion loss 7.5 cc), almost twice as high Lifetime and compared to the pourable mixture after Comparative Example A based on Al₂O₃ more than twice long life span.

Claims (26)

1. Refractory mixture consisting essentially of the following components:

• a) 44 to 89% by weight of an abrasion-resistant refractory grain,
• b) 10 to 50% by weight of a hydraulic cement,
• c) 1 to 6 wt .-% of a filler consisting of very fine, substantially spherical particles of a substance selected from the group Al₂O₃, Cr₂O₃, ZrO₂, TiO₂, clay minerals, carbon and fumed silica,
• d) 0.01 to 1%, based on the total weight of components a), b) and c), of additives selected from deflocculants and wetting agents.

2. Mixture according to claim 1, characterized that the abrasion and refractory grain is selected  from the group of molten AZS mixture, molten alumina, Silicon carbide, molten mullite, molten Zirconia and molten clay and zirconia. 3. Mixture according to claim 2, characterized that the abrasion and refractory grain is a molten one AZS mixture is 32.5 to 54 wt .-% ZrO₂, 36 to 51 wt .-% Al₂O₃, 2 to 16 wt .-% SiO₂, 0.28 to 1.5 wt .-% Na₂O and less than 1.5 wt .-% of other oxides. 4. Mixture according to claim 3, characterized that the abrasion and refractory grain is a molten one AZS mixture is the 49% Al₂O₃, 34% ZrO₂, 15% SiO₂, 0.1% Fe₂O₃, 0.2% TiO₂, 1.5% Na₂O and 0.2% of others Contains oxides. 5. Mixture according to one of claims 1 to 4, characterized that the particles of the abrasion and refractory grain size of about 44 microns (+325 mesh) to about 4760 μm (-4 mesh). 6. Mixture according to claim 5, characterized that the particle size distribution of the particles within a range of about 44 μm (+325 mesh) to about 4760 μm (-4 mesh) is substantially constant. 7. Mixture according to claim 3, characterized that the particles of the abrasion and refractory grain a size of about 44 microns (+325 mesh) to about 4760 microns (-4 mesh). 8. Mixture according to claim 7, characterized that the particle size distribution of the particles within a range of about 44 μm (+325 mesh) to about 4760 μm (-4 mesh) is substantially constant.   9. Mixture according to claim 6, characterized in that that 0 to 5% of the particles have a size of 4760 microns (+4 mesh), 22-45% has a size of 2380 μm (+8 mesh), 49 to 76% 1190 μm (+14 mesh), 68 to 90% a size of 420 μm (+35 mesh), 85 to 100% a size of 44 μm (+325 mesh) and 0 to 15% one size of 44 μm (-325 mesh). 10. Mixture according to claim 8, characterized 0 to 5% of the particles have a size of 4760 μm (+4 mesh), 22 to 45% a size of 2380 μm (+8 mesh), 49 to 76% a size of 1190 μm (+14 mesh), 68 to 90%, 420 μm (+35 mesh), 85 to 100% a size of 44 μm (+325 mesh) and 0 to 15% one Size of 44 μm (-325 mesh). 11. Mixture according to claim 9, characterized 0 to 1.5% of the particles are one size of 4760 μm (+4 mesh), 32 to 35% one size of 2380 μm (+8 mesh), 59 to 66% a size of 1190 μm (+14 mesh), 78-84%, 420 μm (+35 mesh), 93 to 96% a size of 44 μm (+325 mesh) and 4 to 7% a size of 44 μm (-325 mesh). 12. Mixture according to claim 10, characterized 0 to 1.5% of the particles are one size of 4760 μm (+4 mesh), 32 to 35% one size of 2380 μm (+8 mesh), 59 to 66% a size of 1190 μm (+14 mesh), 78-84%, 420 μm (+35 mesh), 93 to 96% a size of 44 μm (+325 mesh) and 4 to 7% a size of 44 μm (-325 mesh). 13. Mixture according to claim 1, characterized that the hydraulic cement in an amount from 20 to 40 wt .-% is present.   14. Mixture according to one of claims 1 to 13, characterized characterized in that the hydraulic cement is a calcium aluminate cement. 15. Mixture according to claim 14, characterized that the hydraulic cement is a calcium aluminate cement is of high purity. 16. Mixture according to claim 1, characterized that the filler in an amount of 1 to 3 wt .-% is present. 17. Mixture according to claim 3, characterized that the filler in an amount of 1 to 3 wt .-% is present. 18. Mixture according to claim 1, characterized that the filler is fumed silica. 19. Mixture according to claim 3, characterized that the filler is fumed silica. 20. Mixture according to claim 16, characterized that the filler is fumed silica. 21. Mixture according to claim 17, characterized that the filler is fumed silica. 22. Mixture according to claim 8, characterized that the hydraulic cement is a calcium aluminate cement is of high purity and in a crowd from 20 to 40 wt .-% is present and the filler fumed silica is and is present in an amount of 1 to 3 wt .-%. 23. Mixture according to claim 10, characterized that the hydraulic cement is a calcium aluminate cement  is of high purity and in a lot of 20 to 40 wt .-% is present and the filler fumed silica is and is present in an amount of 1 to 3 wt .-%. 24. Mixture according to claim 12, characterized that the hydraulic cement is a calcium aluminate cement is of high purity and in a lot of 20 to 40 wt .-% is present and the filler fumed silica is and is present in an amount of 1 to 3 wt .-%. 25. Mixture according to claim 1, characterized that by adding a lot of water between 5.5 and 8 wt .-%, based on the total weight the components a), b), c) and d), further processed. 26. Mixture according to claim 1, characterized that by adding a lot of water between 6 and 7 wt .-%, based on the total weight of Components a), b), c) and d), further processed.