DE3621021A1 - ABRASION RESISTANT FIREPROOF MIXTURE - Google Patents

Description

The invention relates to a refractory mixture, the is characterized by high abrasion resistance and especially a mixture that is used as a casting compound can be used.

Refractory casting compounds are hydraulically setting Mixtures. They contain granular refractories Ingredients and chemical binders.

The refractory casting compounds are in dry form shipped and after being correct with water Consistency can be brought in like concrete be shed, stamped or rammed or with the Trowel or inserted with an air pressure cannon will.

Refractory casting compounds take a strong hydraulic Binding at room temperature and keep the good one Strength until the ceramic bond increasing temperatures.

Casting compounds are particularly suitable for furnace linings with an irregular contour, for patchwork and for casting special moldings that are needed quickly will.

A large number of casting compound mixtures are known each of the known mixtures being different Has properties and each for different Applications.

One of these uses of such refractories Casting compound is the lining of Transfer elements in catalytic Liquid splitting systems in the petrochemical industry.  

In these plants, highly abrasive catalysts are used conveyed at high speeds in the catalytic cracking plant extremely high erosion potentials create. In these systems, they are resistant to abrasion Linings used from phosphate-bonded refractories, which is a very intense anchorage and one require manual insertion.

At the cost of such phosphate-bound refractories in the industry have been casting compounds used, which contain additives of stainless steel fibers, which is less anchored to the Need metal sheath and that relatively quickly can be shed. Although this means the time and Costs could be reduced is one improved abrasion resistance desired.

Abrasion resistant linings in petrochemical Boilers are chemically bound or cement bound refractory mixtures. The abrasion resistance becomes fundamental by using a solid, dense refractory grain, such as fired chamotte and through a strong bond of aluminum orthophosphate or calcium aluminate cement.

In the case of cement, the wear-resistant bond is through a large amount of cement or a combination of Silicon dioxide, cement in an amount less than 10 percent and a surfactant additive achieved a flow of low water content. A improved density by casting with low Water content is reached, a high is unnecessary abrasion-resistant bond with low cement content.  

To further improve profitability at Have been tried by the Plant operators greater transport services applied to the assembly of many small ones Built-in components eliminated. The refractory used Casting compounds for transfer lines have been relative quickly setting cements were made and remained not for a sufficient time for this Flowable applications. Therefore classified cements added to extend the processing time. These Products brought about the desired fluidity and Processing time, but the strength and the Abrasion resistance often became lower than comparable ones Mixtures that are regular calcium aluminate cement contained.

The object of the invention is to create a fireproof mixture, characterized by a good Flowability and a relatively long time Processability time distinguished with improved Density, strength and abrasion resistance.

This is achieved through a refractory mixture that 0.5-5% by weight of evaporated silica, 3.0-15.0% by weight Alumina with a grain size smaller than 0.2 mm, 10-40 wt .-% Calcium aluminum cement and the rest refractory Components such as silica, clay or chamotte contains.

The use of refractory casting mixes in high abrasive devices require casting compounds with excellent abrasion resistant properties.  

If they are also in lines with relatively large Sections are used as in Transfer lines in catalytic Liquid splitting systems, then these should be Casting compounds have a good fluidity and a relative have great processability so that these masses can be introduced.

A first series of mixes was made accordingly Table I prepared. When describing the different mixtures are all percentages Weight basis mentioned unless it's something otherwise has been specified.

These blends indicate the effect of the increase according to Tonddeplatten from 0-15% in one Chamotte casting compound.

It can be observed that the density, strength and abrasion resistance improve with increasing alumina content. Abrasion resistance improved from 8.4 cm ³ loss in the 0% alumina mixture to 7.0 cm ³ loss in a mixture containing 15% alumina. This improvement is remarkable for a refractory product that already had good abrasion resistance before the alumina addition.

Fine synthetic clay is used in the Refractory industry commonly used to do that Heat resistance of the bond in the refractory product too improve and then as a fine material for a correct grain size distribution in refractory products to care.  

Table I

Mixtures with A-17 reactive alumina without evaporated silica

A second batch of mixes was made to make the Effect of the addition of 0-5% evaporated silica towards the same abrasion-resistant, pourable chamotte determine.

Vaporized silica additions of the order of magnitude from 0.5 to 2% lead to an improved density, Strength and abrasion resistance.

At 3 to 5%, the mixture becomes sticky and does not flow as good as before.

The density and strength are increased, but the Improvement in abrasion resistance remains.

Vaporized silica is a submicron, amorphous bi-product of ferro-silicone production and it is known as refractory raw material.

It’s mainly used as an ultrafine particle, as well as reactive silica and additive to Improvement in flow properties.

As Table II shows, only small amounts in Mixtures containing cement are used, or but the flow properties become opposite influenced.  

Table II

Mixtures that contain vaporized silica without fine alumina

A third batch of mixes was made to include the Effect of adding evaporated silica to pourable chamotte, which contained fine alumina examine.

When the alumina is replaced by up to 2% silica then density, firmness and the Abrasion resistance improved.

At 3% silica, the mixture sticky and reduced fluidity. The However, abrasion resistance remains.

The mixture P has excellent abrasion resistance, but the mixture N is preferable because it has excellent flow properties; a necessary Property when the mixture is pourable refractory is used for relatively large applications. The synergistic effect when using evaporated Silica and fine alumina should be considered together will.

The abrasion resistance of the mixtures N and P is excellent based on the mixtures in the tables I and II, each material used separately.  

Table III

Development of the alumina / silica ratio when fine alumina and evaporated silica 10%

A fourth batch of mixtures was made, with each of the mixtures according to the teaching of the invention was composed. Each mixture contained 2% evaporated silica and 8% fine alumina three different types. All four had mixes high resistance to cold pressure and abrasion. The reactive A-17 and A-17 alumina consisted of essentially made of fine, sintered corundum crystal (α-alumina). The big surface and the small one Crystal size make them thermally reactive, i.e. they react or sinter with other compounds relatively low temperatures.

T-61, a tabular alumina, consists essentially of 100% corundum crystals, but this material was fired at a high temperature, so that tabular, non-reactive crystals were formed. A-2 fired alumina contains 90% corundum crystals and 10% alumina crystals (Na ₂ O · llAl ₂ O ₃ ). The thermal reactivity of the A-2 fired alumina lies between the tabular alumina and reactive alumina. Table VIII shows the various properties of these clays.

Table IV

Alumina development

Three more blends were made according to the teaching of the invention with 1% evaporated silica and 9% fine alumina. The mixture T is based on a fired chamotte grain.

This type of mixture was needed wherever good abrasion resistance should be achieved. The mixture U is based on a glassy silica grain, and this Mixture would be used if a combination of good abrasion resistance and lower Thermal conductivity is desired.

Mixture V is based on coarse, tabular Alumina and provide absolute strength and abrasion resistance represents.

Because tabular alumina is more than ten times more expensive the costs have risen like fired chamotte not justified by the modest property improvements.

The three mixtures are supposed to represent the type of base grain, which can be used from 100% silica to a chamotte with approx. 50% silica and 45% 100% alumina. There is a variation of Alumina grain with an alumina content between the chamotte and tabular alumina, such as baked bauxid Kaolin, baked bauxite, kyanite and andalusite, the according to the invention also works well. In addition are silicates not containing aluminum, such as silicon carbide, Silicon nitride or acidic aggregates satisfactory.  

Table V

Basic grain development

The next series should be the effect of change of the cement content.

As can be seen, an increase in the cement of 10 to 40% generally the cold compressive strength and Abrasion resistance (Table VI).  

Table VI

Development of the cement content

The last series of mixes shows the top and lower limits for evaporated silica and fine Alumina and also gives the preferred mixture again, which was chosen because of the good Combination of flow properties and physical Properties.  

Table VII

Fine alumina and evaporated silica areas with preferred mixtures

Table VIII

The composition according to the present invention results in a pourable refractory product that at Applications can be used, the high abrasion resistance or resistance require good flow properties and a long processability. These properties are used for the lining of transfer lines in catalytic liquid splitting plants needed.

While only fired clay to form the refractory Let aggregates be used with each mix other refractories such as silica and Use alumina and other acidic aggregates.

Claims (8)

1. Refractory composition, characterized by 0.5 to 5% by weight of evaporated silica, 3.0 to 15% by weight of alumina smaller than 0.2 mm, 10 to 40% by weight of calcium aluminate cement and the remainder of refractory aggregates. 2. Composition according to claim 1 with the addition of Water to use the mixture as pourable Refractory product with relatively high abrasion resistance. 3. Composition according to claim 1, characterized, that the refractory aggregate is selected from Silica, clay and chamotte. 4. The composition in connection with claim 3, characterized, that the refractory aggregate burned 4.5 to 12 wt .-% Contains clay less than 0.2 mm. 5. The composition in connection with claim 4, characterized, that the alumina content is less than 0.2 mm in is essentially 8% by weight. 6. The composition in connection with claim 5, characterized, that the content of evaporated silica in  is essentially 2% by weight. 7. The composition in connection with claim 1, characterized, that the alumina content less than 0.2 mm in is essentially 8% by weight. 8. The composition in connection with claim 1, characterized, that the content of evaporated silica in is essentially 2% by weight.