WO2020169772A2 - Refractory compound and binder therefor, method for the production and use thereof - Google Patents

Abstract

The invention relates to an unshaped refractory compound, in particular a casting compound, gunning compound and/or free-flowing compound, comprising a bond system, which forms upon addition of water, and a dry micro-scale amorphous SiO2- binder as the sole binder, which is mixed in a proportion of ≤ 1% by weight of the total mass with the solid components to be bonded and forms the bond system after addition of 1-30% by weight of water. The invention further relates to a method for producing refractory compounds and a use of microcrystalline amorphous silicon dioxide in the production of refractory compounds.

Description

Refractories and binders therefor,

Procedure for their positioning and use

FIELD OF THE INVENTION

The invention relates to a refractory mass, a binding agent for it, a method for fusing a refractory mass and a bonding system and a use of microscale amorphous silicon dioxide according to the preamble of the independent claims. TECHNICAL BACKGROUND

High alumina cements are considered to be the most commonly used conventional binders in refractory unshaped products. The bond is activated by the calcium aluminates contained in these cements by adding water.

In recent years, however, silica sol solutions have increasingly been used as binders. Silica sol solutions are aqueous, colloidal dispersions made from nanoscale amorphous silicon dioxide particles. The refractory products bound with it are characterized by good alkali and acid resistance compared to cement-bound compounds.

Compared to cement-bound materials, the silica sol-bound materials can be heated up quickly due to the lack of hydrate phases, which leads to significant energy and cost savings.

A disadvantage of these binders, however, is that they must be stored in separate containers, protected from frost and light. Due to the sensitivity to frost, special heating devices must be installed.

Alternatively, microscale amorphous silicon dioxide can be mixed as a dry powder with the other components of the mass, so that a silica gel is formed when water is added to the total mass.

From DE 41 09 916 A1 a refractory mortar is known in which a mixture comprising phosphate, clay and lignosulfonate is used as a bin demittel. In DE 10 2014 019 351 A1, tar, pitch, and resin are used as the main binder component.

The binding systems of DE 27 39 767 A1, EP 0 842 910 A2 and DE 30 02 763 A1 are based on clays with the addition of a phosphate acid / hydrochloric acid, and on what serglas / liquid silica sol.

DISCLOSURE OF THE INVENTION

Based on this, the invention is based on the object of creating an improved refractory mass with an improved bonding system, a method for the respective production and a use of microscale amorphous silicon dioxide according to the preamble of the independent claims.

This object is achieved in accordance with the features of the independent claims.

The invention proposes for the first time the use of small amounts (in particular <1% by weight or 0.1-1% by weight) of a microscale amorphous silicon dioxide as the sole binder for bond formation in unshaped refractory materials.

When using a conventional refractory concrete, in which the presence of cement phases (calcium aluminates) can have a disruptive effect (such as in SiC-based kiln furniture), it is advantageous to use a microscale Si0 ₂ system for bond formation instead of water-containing cement phases. This can be done, for example, by using silica sol solutions. For this purpose, the mass to be bound is mixed with the silica sol solution, processed and allowed to harden. Alternatively, microscale amorphous Si0 ₂ can be mixed as a dry powder with the other constituents of the mass, so that a silica gel is formed in the mass when the total mass is mixed with water. The advantage of this procedure is that there is no silica sol solution, the reactivity of which is Storage processes and storage conditions is influenced, must be provided separately.

According to the invention, a binding system is generated by dispersing microscale amorphous silicon oxide under the action of water, which can be used for binding formation in refractory, unshaped products.

The microscale SiO ₂ used for the formation of bonds is a product that can be obtained as an amorphous precipitate via a precipitation reaction and has a purity of approx. 90-99.9% by weight (in the dried state), a mean grain size in the micrometer range ( 1 -50 miti, in particular 1 -10 miti, 1 -20 miti, 1 -30 miti, or 1 -40 miti) and a specific surface area of approx. 50-350 m ² / g, in particular 100-350 m ² / g , 200-350 m ² / g, or 250-300 m ² / g.

The large specific surface of the material causes rapid hydration when mixing the microscale amorphous Si0 ₂ with water to form a silica gel. Silica gels contain (H ₂ Si0 ₅ ) _x units that are held together by van der Waals bonds and hydrogen bonds and between which particles of different chemical composition and different grain sizes can be included. When the gel dries, a Si0 ₂ framework remains which continues to surround the introduced grains.

The method according to the invention relates to the production of a Si0 ₂ binding system by using a dry Si0 ₂ binder, which contains <1% by weight, in particular 0.1-1% by weight, of the total mass with the solid constituents to be bound mixed and, after adding about 1-30% by weight, in particular 1-10% by weight, 10-30% by weight, 15-30% by weight or 20-30% by weight of water, used to form bonds becomes.

The speed of hydration of the Si0 ₂ , the coagulation to the silica gel and the subsequent dehydration of the gel depends on the temperature, pH, material composition and material thickness. The microscale Si0 ₂ -based binding system, however, has a significantly lower reaction dependency with regard to the temperature and the chemical composition than cement-bound binding systems. The bond formation can therefore be used for the production of a variety of refractory masses different raw material composition as spray, vibration, soap flow or casting compound.

The refractory materials produced according to the invention, after they have been cast into cylinders and dried at 110 ° C., alternatively 100-150 ° C., 105-125 ° C., usually have a compressive strength of> 15 MPa. Due to the lower tendency of silica gels to spallate compared to calcium aluminate hydrate phases, the products made with microscale SiO ₂ binders offer the advantage of being able to be heated up more quickly without damage.

Example 1 for refractory masses (given in% by weight):

Aluminum oxide (0-6mm) 80-95%

Spin egg (0-3mm) 5-20%

MgO very fine <1%, especially 0.1% to 1%

Microscale amorphous Si0 ₂ <1%, in particular 0.1% to 1%

Synthetic polyelectrolyte <1%, especially 0.1% to 1%

PE fibers <1%, especially 0.1% to 1%

Example 2 for refractory masses (given in% by weight):

Aluminum oxide (0-6mm) 90-99%

MgO very fine <1%, especially 0.1% to 1%

Microscale amorphous Si0 ₂ <1%, in particular 0.1% to 1%

Synthetic polyelectrolyte <1%, especially 0.1% to 1%

PE fibers <1%, especially 0.1% to 1%

Further details emerge from the subclaims.

Claims

EXPECTATIONS 1. Unshaped refractory mass, in particular casting, spraying and / or self-flowing mass, comprising a binding system that forms when water is added, characterized by a dry microscale amorphous Si0 ₂ binder as the sole binder, which is present in a proportion of <1% by weight of the total mass is mixed with the solid constituents to be bound and, after adding 1-30% by weight of water, forms the binding system. 2. Unshaped refractory mass, in particular according to claim 1, comprising one or more of the following main components or their combination - Up to 99.5 wt .-% (AI203 carriers of different types and grain sizes, for example fused corundum, tabular alumina, andalusite, chamotte, bauxite, mullite, various secondary raw materials, SiC, MgO, quartz, Si0 ₂ , olivine and - Up to 5% by weight of a condenser - Up to 15% by weight of a setting accelerator - Up to 15% by weight of a setting retarder - Up to 1% by weight of a microscale amorphous Si0 ₂ . 3. Refractory material according to claim 1 or 2, characterized in that the microscale Si0 ₂ as an amorphous precipitate via a precipitation reaction it is kept, a purity of>90,>95,> 98 or> 99 wt .-% (in getrockne system state ), an average grain size in the micrometer range (10-50 μm) and / or a specific surface area of approx. 100-300 m ² / g. 4. Refractory material according to one of claims 1 to 3, characterized by forming a silica gel with (H ₂ Si0 ₅ ) _x units that are held together by van der Waals bonds and hydrogen bonds and between which particles of different chemical composition and different grain sizes can be included. 5. Binder for a refractory material, in particular according to one of Ansprü che 1 to 4, characterized in that it contains Si0 ₂ and the Si0 _{2 is} a dry powder and / or with a purity of>90,>95,> 98 or> 99% by weight (in the dried state) and / or with an average grain size in the micrometer range (1-50 gm) and / or with a specific surface area of approx. 50-350 m ² / g. 6. A process for the production of refractory compositions, characterized by the addition of a Si0 ₂ binder, in particular according to claim 5, as the sole binder to form bonds in a composition for a refractory composition. 7. The method according to claim 6, characterized by adding Si0 ₂ as a dry powder. 8. The method according to claim 6 or 7, characterized by dispersing microscale amorphous silicon oxide in water to form a binding system for refractory materials. 9. The method according to any one of claims 6 to 8, characterized in that the Si0 ₂ used for the bond formation is obtained as an amorphous precipitate via a precipitation reaction, a purity of>90,>95,> 98 or> 99 wt .-% ( in the dried state), a mean grain size in the micrometer range (1-50 gm) and / or a specific surface area of about 50-350 m ² / g. 10. The method according to any one of claims 6 to 9, characterized by the formation of a silica gel with (H ₂ Si0 ₅ ) _x units that are held together by van der Waals bonds and hydrogen bonds and between which particles of different chemical composition and different grain sizes can be included. 1 1. The method according to any one of claims 6 to 10, characterized in that after the gel has dried, a SiCV framework remains, which continues to surround the introduced grains. 12. A method for producing a Si0 ₂ binding system by using a dry Si0 ₂ binding agent, which is mixed in a proportion of <1% by weight of the total mass with the solid constituents to be bound and after adding about 1 -30 wt .-% water is used to form bonds, as the sole binder. 13. Use of small amounts, in particular <1% by weight, of a microscale amorphous silicon dioxide in the production of a refractory mass for the formation of bonds in refractory, unshaped materials.