FUSED RAW MATERIAL FOR THE PRODUCTION OF A REFRACTORY PRODUCT, A METHOD FOR THE PRODUCTION OF THE FUSED RAW MATERIAL AND A USE OF THE FUSED RAW MATERIAL

Abstract

The invention concerns a fused raw material for the production of a refractory product, a method for the production of the fused raw material and a use of the fused raw material.

Claims

1. Fused raw material for the production of a refractory product comprising the following mineralogical phases: Magnesia spinel with a hyperstoichiometric proportion of Al.sub.2O.sub.3; and Al.sub.4O.sub.4C.

2. Fused raw material according to claim 1, comprising the following mineralogical phases in the following proportions: Magnesia spinel with a hyperstoichiometric proportion of Al.sub.2O.sub.3:50 to 99% by mass; and Al.sub.4O.sub.4C: 1 to 50% by mass.

3. Fused raw material according to claim 1, comprising the following mineralogical phases in the following proportions: Magnesia spinel with a hyperstoichiometric proportion of Al.sub.2O.sub.3:70 to 90% by mass; and Al.sub.4O.sub.4C: 10 to 30% by mass.

4. Fused raw material according to claim 1, wherein the magnesia spinel with a hyperstoichiometric proportion of Al.sub.2O.sub.3 has a proportion of Al.sub.2O.sub.3 in the range from 77 to 97% by mass.

5. Fused raw material according to claim 1, comprising magnesia spinel with a hyperstoichiometric proportion of Al.sub.2O.sub.3 and Al.sub.4O.sub.4C in a total mass of at least 95% by mass.

6. Fused raw material according to claim 1, comprising magnesia spinel with a hyperstoichiometric proportion of Al.sub.2O.sub.3 and Al.sub.4O.sub.4C in a total mass of at least 99% by mass.

7. Fused raw material according to claim 1, having a thermal expansion of at most 8.0 ppm/K.

8. Method for producing a fused raw material according to claim 1, comprising the following steps: providing a batch having a chemical composition which comprises: Al.sub.2O.sub.3; MgO; and C; forming a melt from the batch; and cooling the melt; wherein Al.sub.2O.sub.3, MgO and C are present in such proportions that, when the melt is formed and cooled, a portion of the Al.sub.2O.sub.3 with MgO forms magnesia spinel with a hyperstoichiometric proportion of Al.sub.2O.sub.3 and a portion of the Al.sub.2O.sub.3 with C forms Al.sub.4O.sub.4C.

9. The method according to claim 8, wherein the batch has a chemical composition comprising the following substances in the following proportions: Al.sub.2O.sub.3: 77.5 to 98.5% by mass; MgO: 1 to 22% by mass; and C: 0.5 to 15% by mass.

10. The method according to claim 8, wherein the batch has a chemical composition comprising the following substances in the following proportions: Al.sub.2O.sub.3: 78 to 85% by mass; MgO: 6 to 15% by mass; C: 8 to 12% by mass.

11. Use of the fused raw material according to claim 1 for the production of a refractory product with the following proportions: provision of a fused raw material according to claim 1; mixing the fused raw material with at least one additional raw material to produce a refractory batch; and application of temperature to the batch.

Description

EXEMPLRY EMBODIMENT

[0116] In the following description of the exemplary embodiment FIG. 1 shows a scanning electron microscope image of a section of the fused raw material produced according to the exemplary embodiment

[0117] First, a synthetic raw material based on the oxides MgO and Al.sub.2O.sub.3 was produced. For this purpose, the starting raw materials 9% by mass caustic magnesia (with a purity of more than 99% by mass MgO) and 91% by mass calcined alumina (with a purity of more than 99% by mass Al.sub.2O.sub.3) were mixed together. The mixture was granulated and then subjected to a temperature of 1,700 C. for five hours. During this temperature exposure, a synthetic raw material with the following chemical composition was formed from the starting raw materials: 8.77% by mass MgO; 90.56% by mass Al.sub.2O.sub.3; 0.67% by mass other oxides (especially SiO.sub.2, CaO, Fe.sub.2O.sub.3 and Na.sub.2O).

[0118] This synthetic raw material was processed into a grain mixture with a grain size in the range of >0 to 1 mm.

[0119] To carry out the method in accordance with the invention, a batch was provided which contained 90% by mass of this synthetic raw material and 10% by mass of petroleum coke (with a purity of over 99% by mass carbon).

[0120] Afterwards, the batch had the following chemical composition:

[0121] Al.sub.2O.sub.3: 81.5% by mass;

[0122] MgO: 7.9% by mass;

[0123] C: 9.9% by mass;

[0124] Remainder: 0.7% by mass.

[0125] This batch was then melted in an electric arc furnace at a temperature of 2,100 C. The formed melt was then cooled down to room temperature. The melt cooled down to room temperature represented an exemplary embodiment of a fused raw material according to the invention.

[0126] The resulting raw material had a mineralogical composition of 79.8% by mass of magnesia spinel with a hyperstoichiometric proportion of Al.sub.2O.sub.3 and 19.6% by mass of Al.sub.4O.sub.4C, in addition to a remainder (especially SiO.sub.2, CaO, Fe.sub.2O.sub.3 and Na.sub.2O) with a proportion of 0.6% by mass.

[0127] The magnesia spinel with a hyperstoichiometric proportion of Al.sub.2O.sub.3 had, based on the mass of the magnesia spinel, a proportion of MgO of 6.76% by mass and a proportion of Al.sub.2O.sub.3 of 93.24% by mass. Expressed in moles and normalized to 4 moles of oxygen, this results in a mineralogical phase Mg.sub.0.23Al.sub.2.51O.sub.4.

[0128] The thermal expansion of the fused raw material was determined according to DIN 51045-4:2007-01 at 1,000 C. at 5.92 ppm/K (average value from three measurements).

[0129] A scanning electron microscope image of a section of the fused raw material produced according to this example was taken. This image is shown in FIG. 1. The black bar at the bottom right of the image corresponds to a length of 100 m.

[0130] The matrix of hyperstoichiometric spinel, which appears as a darker area and is marked with the reference symbol 1, is clearly visible. In this matrix 1 the phase Al.sub.4O.sub.4C, which is marked with the reference sign 2, is embedded, which appears as a brighter area.