REFRACTORY PRODUCT, A BATCH FOR PRODUCING THE PRODUCT, A METHOD FOR THE PRODUCTION OF THE PRODUCT AND A USE OF THE PRODUCT

Abstract

The invention relates to a refractory product, a batch composition for producing said product, a method for producing the product and the use of the refractory product.

Claims

1. Refractory product comprising the following features: 1.1 the product has a chemical composition according to which the following oxides are present in the following proportions: 1.1.1 MgO: at least 92% by mass; 1.1.2 Al.sub.2O.sub.3: 1.5 to 7% by mass; 1.1.3 Fe.sub.2O.sub.3: less than 3% by mass; 1.1.4 CaO+SiO.sub.2: 1 to 3% by mass; 1.2. the product comprises coated grains having the following features: 1.2.1 the coated grains have a grain size of at least 2 mm; 1.2.2 the coated grains consist of magnesia, the surface of which has a coating of magnesia spinel at least in sections.

2. The product according to claim 1, having a chemical composition with a content of MgO in the range from 92 to 96% by mass.

3. The product according to claim 1, having a chemical composition with a content of Al.sub.2O.sub.3 in the range from 2 to 3.5% by mass.

4. The product according to claim 1, having a chemical composition with a content of Fe.sub.2O.sub.3 of less than 1% by mass.

5. The product according to claim 1, having a dynamic modulus of elasticity of less than 40 GPa.

6. The product according to claim 1, having a temperature T.sub.0.5 for refractoriness under load above 1,700° C.

7. The product according to claim 1, the coating of magnesia spinel having a thickness in the range from 10 to 500 μm.

8. The product according to claim 1, the coated grains having a grain size in the range from 3 to 5 mm.

9. The product according to claim 1, comprising the coated grains in a proportion in the range from 5 and 24% by mass.

10. The product according to claim 1, comprising the coated grains in a proportion in the range from 5 to 24% by mass and further comprising magnesia in a proportion in the range from 76 to 95% by mass.

11. The product according to claim 1 in the form of a shaped fired refractory ceramic product.

12. A batch for producing the product according to claim 1, comprising the following components: 12.1 a first raw material component, consisting of grains of magnesia; 12.2 a second raw material component, consisting of coated grains, comprising the following features: 12.2.1 the coated grains have a grain size of at least 2 mm; 12.2.2 the coated grains consist of magnesia, the surface of which has a coating of alumina at least in sections.

13. The batch according to claim 12, wherein the coated grains have a grain size in the range from 3 to 5 mm.

14. A method for the production of the product according to claim 11, comprising the following steps: 14.1 providing a batch according to at least one of claim 12 or 13; 14.2 shaping the batch into a shaped unfired refractory product; 14.3 firing the shaped unfired refractory product into a shaped fired refractory ceramic product.

15. Use of a product according to claim 1 for the lining of cement rotary kilns.

Description

FIRST COMPARATIVE EXAMPLE

[0177] For comparison purposes, a product was manufactured which did not constitute an example of the invention.

[0178] The product manufactured according to the first comparative example was manufactured according to the second exemplary embodiment, with the only difference that the coated grains of the second raw material component of the batch had a grain size in the range of 0.5 to 1 mm.

[0179] The fired product obtained according to the first comparative example had a chemical composition according to which the following oxides were present in the following proportions:

[0180] MgO: 93.90% by mass;

[0181] Al.sub.2O.sub.3: 3.03% by mass;

[0182] Fe.sub.2O.sub.3: 0.33% by mass,

[0183] CaO: 1.82% by mass;

[0184] SiO.sub.2: 0.69% by mass;

[0185] MnO: 0.03% by mass; and

[0186] Loss on ignition (LOI): 0.20% by mass.

[0187] The product had a structure of sintered grains in the form of magnesia grains and coated grains, the coated grains having a grain size in the range of 0.5 to 1 mm and consisting of magnesia with a surface coated with magnesia spinel.

[0188] The coating of magnesia spinel had a thickness of about 80 μm.

[0189] The physical values of the product were as follows:

[0190] Dynamic modulus of elasticity: 69.3 GPa;

[0191] temperature T.sub.0.5 for refractoriness under load: >1,700° C.;

[0192] cold compressive strength: 96 MPa; and

[0193] bending strength at room temperature: 12.8 MPa.

SECOND COMPARATIVE EXAMPLE

[0194] For comparison purposes, another product was manufactured which was not an example of the invention.

[0195] The product manufactured according to this second comparative example was manufactured according to the second exemplary embodiment, but with the only difference that the first raw material component was present in a proportion of 95% by mass and the second raw material component was present in a proportion of only 5% by mass, both based on the total mass of the displacement.

[0196] The fired product obtained from the second comparative example had a chemical composition according to which the following oxides were present in the following proportions:

[0197] MgO: 95.30% by mass;

[0198] Al.sub.2O.sub.3: 1.43% by mass;

[0199] Fe.sub.2O.sub.3: 0.39% by mass,

[0200] CaO: 1.93% by mass;

[0201] SiO.sub.2: 0.71% by mass;

[0202] MnO: 0.03% by mass; and

[0203] Loss on ignition (LOI): 0.21% by mass.

[0204] The magnesia spinel coating had a thickness of about 130 μm.

[0205] The physical values of the product were as follows:

[0206] Dynamic modulus of elasticity: 48.8 GPa;

[0207] temperature T.sub.0.5 for refractoriness under load: >1,700° C.;

[0208] cold compressive strength: 73 MPa; and

[0209] bending strength at room temperature: 6.2 MPa.

Discussion of the Test Results

[0210] The products manufactured according to the first and second exemplary embodiment each had a very high structural flexibility, indicated by a very low modulus of elasticity of less than 30 GPa, namely 26.6 GPa and 27.9 GPa respectively. At the same time, the products showed good values for refractoriness under load, cold compressive strength and bending strength at room temperature.

[0211] The product manufactured according to the first comparative example had a chemical composition which corresponded to a chemical composition of a product according to the invention. However, with a grain size of the coated grains of 0.5 to 1 mm, the grain size was smaller than the grain size of the coated grains of a product according to the invention. The product according to the first comparative example had a significantly worse structural flexibility than the products according to the first and second exemplary embodiments, indicated by a high modulus of elasticity of 69.3 GPa.

[0212] The product produced according to the second comparative example had a coated grain size which corresponded to a grain size of a product according to the invention. However, (due to the small proportion of coated grains in the product) according to the chemical composition, the proportion of Al.sub.2O.sub.3 was lower than that of a product in accordance with the invention. The product according to the second comparative example had a significantly worse structural flexibility than the products according to the first and second exemplary embodiment, indicated by a high modulus of elasticity of 48.8 GPa.