DD294696A5 - KAOLINSCHAMOTTE STONES WITH HIGH THERMAL AND MECHANICAL STABILITY - Google Patents

Abstract

The invention relates to kaolin chamotte stones with high thermal and mechanical resistance for the delivery of pyrotechnic systems with Formsteinausmauerung. According to the invention, a mass for the production of kaolin chamotte bricks, consisting of various kaolin clay clays and plastic binder in the form of slaked kaolin and / or refractory binding clay, additionally finely ground alumina having an α-Al 2 O 3 content of between 85 and 95% and fumed silica in the form of Accumulation product of dedusting the ferrosilicon production and / or silica sol with an SiO 2 content by 30% and optionally added feinkoerniges silicon carbide and / or silicon. The product firing of the moldings produced from the mass, which is carried out at a cone drop point of preferably PK 146 to 156, is formed from the amorphous SiO 2 of the fumed silica or the silica sol and the finely ground alumina mullite. The alumina with the a-Al 2 O 3 content of between 85 and 95% is on the one hand still so reactive that a good mullite formation can take place, but on the other hand so stable that the grain properties and strengths of the kaolin chamotte stones are not reduced by shrinkage of the clay. The optionally added fine-grained silicon carbide or silicon is partially oxidized at sintering temperature, wherein the SiO2 in statu nascendi additionally strengthened the mullite formation. The forming mullite binder matrix gives the stone a dense structure, high cold-pressure and high-temperature strength and a good pressure fire and thermal shock resistance. {Kaolinschamotte-Steine; pyrotechnic installations; Formsteinausmauerung; alumina; a-Al2O3 content; pyrogenic silicic acid; silica; amorphous SiO2; mullite; silicon carbide; silicon; Structure; Cold compression strength; Heiszbiegefestigkeit}

Description

Field of application of the invention

This invention relates to kaolin chamotte bricks having high thermal and mechanical resistance for the delivery of pyrotechnic plants with a stone lining.

Characteristic of the known state of the art

Kaolin chamotte bricks are known on the basis of densely sintered and less densely sintered kaolin chamotte, being used as a binder kaolin. The corresponding Kaolinschamottekörnungen be mixed with kaolin and molded according to the Trockenpreßverfahren on hydraulic or screw presses. The pressing of kaolingebundenen masses on the one hand is very problematic because kaolin can cause strong layer formation in the compacts, on the other hand, the mechanical and thermal values of the sintered kaolin chamotte stones are relatively low.

thermal and mechanical values are also relatively low.

Furthermore, kaolin chamotte stones are known in which densely sintered kaolin chamotte grains are mixed, shaped and sintered with a binder of conventional refractory binding clay and / or kaolin, the finest corundum and a suspension containing SiO ₂ . Although the thermal and mechanical properties of the kaolin chamotte stones are satisfactory, the technological process step of producing the slip is complicated.

In addition, kaolin chamotte stones are known, which are bound with fine fused corundum and a special refractory binding clay with a high content of fine-grained free üuarz. At the same time, satisfactory thermal and mechanical values are achieved.

Object of the invention

The aim of the invention is to produce kaolin chamotte stones with high thermal and mechanical resistance wedge. The high thermal and mechanical resistance is ensured by very good cold pressure and hot bending strength and high pressure fire and thermal shock resistance.

Explanation of the essence of the invention

Task : The invention is to change the composition of kaolin chamotte stones to achieve the objective.

According to the invention, a mass for the production of kaolin chamotte bricks, consisting of various kaolin chamotte grains and plastic binder in the form of slaked kaolin and / or refractory binding clay, additionally finely ground alumina with an α-Al ₂ O ₃ content between 85 and 95% and fumed silica in the form of the seizure product of dedusting the ferrosilicon production and / or silica sol with an SiO ₂ content by 30% and optionally added fine-grained silicon and / or silicon carbide. The mass is brought to the desired press moisture with sulfite waste liquor and water and / or clay slip and molded by the dry pressing on hydraulic or _i spindle presses. The moldings are preferably sintered at a Kegolfallpunkt between PK146 and PK 156 after drying.

The amorphous SiO _{2 of} the fumed silica or the silica sol reacts at the sintering temperature with the finely ground alumina to MuIMt.

The finely ground alumina with an a-Al ₂ O ₃ content between 85 and 95% is so reactive on the one hand by the remaining content of transitional toners that a good mullite formation btei sintering temperature is guaranteed. On the other hand

However, the a-Al ₂ O ₃ content so high that the Gefeigewerte and strengths of Kaolinschamotte-bteine not be reduced by shrinkage of the clay. A portion of the optionally added fine-grained silicon carbide or silicon is oxidized during sintering. The SiO2 in statu nascendi additionally strengthens mullite formation. The forming mullite binder matrix gives the stone a dense microstructure, high cold-pressure and hot-bending strengths as well as good pressure fire and thermal shock resistance.

By adding the finely ground alumina and the fumed silica or silica sol to the molding compound, the green strength of the molded articles is additionally increased.

Embodiment 1

In a mixing unit, preferably a countercurrent fast mixer

45% by weight of kaolin chamotte, grain fraction 1 to 3 mm and 25% by weight of kaolin shamotto, grain fraction 0 to 1 mm, premixed dry and then mixed with clay slip. Thereafter, 15% by weight of normal corundum, grain fraction <0.2 mm and 15% by weight of special binder clay are mixed in with a proportion of about 40% of fine-grained quartz. The finished mass is processed on a hydraulic press with a specific pressure of 60 MPa to form bricks. The stones are sintered after drying in a tunnel kiln at a cone drop point of PK 150. This conventional kaolin chamotte stone quality has the following quality values:

Al ₂ O ₃ content 45.3%

Cold pressure resistance 55 MPa

Open porosity 17.3%

Bulk density 2.20 g / cm ³

Pressure fire resistance, T _A 1 510 ⁰ C

Embodiment 2

As in example 1, 45.0% by weight of kaolin chamotte, grain fraction 1 to 3 mm, 37.5% by weight kaolin chamotte, grain fraction 0 to 1 mm, 15.0% by weight of refractory binding clay are used in a countercurrent high-speed mixer

0.5% by weight of fumed silica in the form of the precipitate of the ferrosilicon production with the following average properties SiO ₂ content 97.33%

Fe ₂ O ₃ content 0.30%

Al ₂ O ₃ - u. TiO ₂ content 0.31%

Na ₂ O u. K ₂ O content 0.21%

MgO and CaO content 1.32%

P ₂ O ₆ content 0.06%

specific surface area (BET) 20 mVg

and 2.0% by weight of finely ground alumina having an α-Al ₂ O ₃ content of between 85 and 95% mixed with clay slip and processed into shaped bricks on a hydraulic press having a specific compacting pressure of 60 MPa. After drying, the blocks are sintered at a cone drop point of PK 150, the following quality values are obtained:

Al ₂ O ₃ content 41.0%

Cold pressure resistance 57.3 MPa

Open porosity 17.0%

Bulk density 2.21 g / cm ³

Pressure fire resistance, T _A 1 51O ⁰ C

Embodiment 3

As in Working Example 1, 45% by weight of kaolin chamotte, grain fraction 1 to 3 mm 31% by weight kaolin chamotte, grain fraction 0 to 1 mm 10% by weight refractory binding clay 4% by weight fumed silica in the form of the precipitate of the ferrosilicon production with the properties described in Embodiment 2

and 10% by weight of finely ground alumina having an α-Al ₂ O ₃ content of between 85 and 95%

mixed with clay slip and pressed on a hydraulic press with a specific pressing pressure of 60 MPa. After sintering at PK 150, the following quality values are obtained: Al ₂ O ₃ content 43.2%

Cold pressure strength 65.5 MPa

Open porosity 16.0%

Bulk density 2.35 g / cm ³

Pressure Fire Resistance, Ta 1 56O ⁰ C

Embodiment 4

As in Example 1, 45% by weight of kaolin chamotte, grain fraction 1 to 3 mm 17% by weight kaolin chamotte, grain fraction 0 to 1 mm 5% by weight refractory binding clay 8% by weight fumed silica in the form of the precipitate of the ferrosilicon production the properties described in Embodiment 2

and 25% by weight of finely ground alumina with an a-Al ₂ O ₃ content of between 85 and 95%

mixed with water and sulphite liquor and processed on a hydraulic press with 55 MPa into shaped bricks. After firing at PK 150, the kaolin chamotte stones have the following quality values: Al ₂ O ₃ content 51.3%

Cold pressure resistance 63.2 MPa

Open porosity 15.2%

Bulk density 2.40 g / cm ³

Compressive strength, Ta 1 61O ⁰ C

Implementation Example 5

45% by weight kaolin chamotte, grain fraction 1 to 3 mm 30% by weight kaolin chamotte, grain fraction 0 to 1 mm 10% by mass refractory binder clay are used in a countercurrent high-speed mixer

and 10% by weight of finely ground alumina having an α-Al ₂ -O ₃ content of between 85 and 95%

dry premixed. Subsequently, 5% by weight of silica sol with a SiO ₂ content of 30% are mixed in and the finished mass is molded on a hydraulic press with a specific pressure of 60 MPa. The sintering process takes place at a cone drop point of PK 150. The following quality parameters show the resulting stones: Al ₂ O ₃ content 42.3%

Cold pressure resistance 63.3 MPa

Open porosity 16.1%

Bulk density 2.35 g / cm ³

Pressure Fire Resistance, Ta 1 565 ⁰ C

Implementation Example 6

As in Working Example 1, 45% by weight of kaolin chamotte, grain fraction 1 to 3 mm 27% by weight of kaolin shamotto, grain fraction 0 to 1 mm 5% by weight of leached kaolin

4% by weight of fumed silica in the form of the product of the precipitation of the ferrosilicon production

with the properties described in Example 2 15Ma .-% finely ground alumina with an a-Al ₂ O ₃ content between 85 and 95% and 4 Ma. % Silicon carbide ground to a grain fraction with a sieve residue on the 0.063 mm sieve of 31%

mixed with clay slip, pressed on a hydraulic press with a specific pressure of 60 MPa and sintered at a cone drop point of PK 150. The following quality values are obtained: Al ₂ O ₃ content 46.1%

Cold pressure resistance 73.3 MPa

Open porosity 15.9%

Bulk density 2.37 g / cm ³

Pressure Fire Resistance, Ta 1 570 ° C

Implementation Example 7

As in working example 1, 45% by weight of kaolin chamotte, grain fraction 1 to 3 mm, 26% by weight of kaolin chamotte, grain fractions 0 to 1 mm 5% by weight of refractory binding clay

15% by weight of foominated alumina with an a-Al ₂ O ₃ content of between 85 and 95%

5% by weight of silica sol with an SiO ₂ content of 30%

and 4% by weight of FeSi 95 to TGL 6782 (average iron content of 0.5%) ground to a screen residue of 50.2% on the 0.04 mm screen

molded on a hydraulic press with a specific pressing pressure of 60 MPa and sintered at a cone drop product of PK 150, resulting in the following quality values:

Al ₂ O ₃ content <6.3%

Cold pressure strength 75.5 MPa

Open porosity 15.7%

Bulk density 2.38 g / cm ³

Pressure fire resistance, T _A 1 58O ⁰ C

Claims (2)

Kaolinschamottsteine with high thermal and mechanical resistance based on a mass of 60 to 90 Ma .-% of various Kaolinscharrlottekörnungen and 2 to 15 Ma .-% plastic binder in the form of slaked kaolin and / or refractory binding clay and in which the product firing at a cone drop point preferably from PK 146 to PK 156, characterized in that additionally 0.5 to 8% by weight of fumed silica in the form of the product of the dedusting plant of ferrosilicon production
and/
or 1.5 to 6% by weight of silica sol with an SiO ₂ content of 30% 2.0 to 25% by weight of finely ground alumina having an aA.sub.aO content of between 85 to 95% and 0 to 4% by weight of fine-grained silicon carbide
and/ or 0 to 4% by weight of fine-grained silicon
are included.