Method for manufacturing a refractory for an inner lining of a blast furnace and blast furnace having the inner lining

Abstract

A refractory, which is particularly suitable for use in an inner lining of a blast furnace, is obtainable by a process. The process includes providing a mixture containing coke, silicon and a binder. A green block is formed from the mixture. The green block is then baked. The baked block is semi-graphitized at a temperature between 1600 and 2000 C.

Claims

1. A method of manufacturing a refractory, which comprises the steps of: providing a mixture containing coke having an iron content of at most 0.1% by weight, silicon and a binder; forming a green block from the mixture; baking the green block at a temperature between 700 and 1200 C. and resulting in a baked block; and semi-graphitizing the baked block at a temperature between 1600 and 2000 C.

2. The method according to claim 1, which further comprises providing the coke to contain at least 50% by weight of isotropic coke.

3. The method according to claim 1, which further comprises adding graphite to the mixture.

4. The method according to claim 3, which further comprises providing a synthetic graphite as the graphite.

5. The method according to claim 3, which further comprises providing the mixture to contain 60 to 85% by weight of a mixture of the coke and of the graphite based on a dry aggregate of the refractory.

6. The method according to claim 1, which further comprises providing the mixture to contain 5 to 15% by weight of the silicon based on a dry aggregate of the refractory.

7. The method according to claim 1, which further comprises providing the mixture to contain 6 to 14% by weight of titanium dioxide based on a dry aggregate of the refractory.

8. The method according to claim 1, which further comprises providing the mixture to contain 4 to 15% by weight of a silicon carbide-carbon powder mix based on a dry aggregate of the refractory, which contains at least 50% by weight of silicon carbide.

9. The method according to claim 1, which further comprises selecting the binder from the group consisting of coal-tar pitch, petroleum pitch, phenolic resin, furfurylic resin, coal tar, petroleum tar and any mixture of at least two of the aforementioned compounds.

10. The method according to claim 1, which further comprises providing the mixture to contain: 65 to 75% by weight of the coke having the iron content of at most 0.1% by weight and of graphite; 9 to 11% by weight of the silicon; 9 to 11% by weight of titanium dioxide; 8 to 11% by weight of silicon carbide-carbon powder, wherein a sum of the aforementioned ingredients is 100% by weight except for the binder; and the binder.

11. The method according to claim 1, which further comprises performing the forming step by one of block pressing, extrusion, hot pressing or vibro-molding.

12. The method according to claim 1, which further comprises semi-graphitizing the baked block at a temperature between 1700 and 2000 C.

13. The method according to claim 1, which further comprises: impregnating the baked block one of before or after the semi-graphitization step with an impregnation agent selected from the group consisting of coal tar, petroleum tar, coal-tar pitch, petroleum pitch, resin and mixtures of at least two of the aforementioned compounds resulting in an impregnated green block; and rebaking the impregnated green block at a temperature between 700 and 1200 C.

14. The method according to claim 1, which further comprises performing the baking step and the semi-graphitizing step concurrently.

15. The method according to claim 1, which further comprises providing the coke to contain at least 99% of isotropic coke.

16. The method according to claim 1, wherein the coke has an iron content of at most 0.001% by weight.

17. The method according to claim 1, which further comprises providing the mixture to contain: 60 to 80% by weight of the coke having an iron content of at most 0.1% by weight and of graphite; 7 to 12% by weight of the silicon; 8 to 13% by weight of titanium dioxide; 6 to 13% by weight of silicon carbide-carbon powder, wherein a sum of the aforementioned ingredients is 100% by weight except for the binder; and the binder.

18. A blast furnace, comprising: an inner lining containing at least one refractory formed by the process steps of: providing a mixture containing coke having an iron content of at most 0.1% by weight, silicon and a binder; forming a green block from the mixture; baking the green block at a temperature between 700 and 1200 C. and resulting in a baked block; and semi-graphitizing the baked block at a temperature between 1600 and 2000 C.

19. A method of making an inner lining for a blast furnace, which comprises the steps of: forming a refractory by the steps of: providing a mixture containing coke having an iron content of at most 0.1% by weight, silicon and a binder; forming a green block from the mixture; baking the green block at a temperature between 700 and 1200 C. and resulting in a baked block; semi-graphitizing the baked block at a temperature between 1600 and 2000 C. resulting in the refractory; and forming the refractory into a shape of the inner lining for the blast furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) In the following the present invention will be described in more detail by way of a non-limiting example.

(2) A refractory was prepared by first preparing a mixture containing:

(3) 74 parts by weight of a mixture of isotropic coke, such as coal-tar pitch coke, or petroleum coke having an iron content of 0.01% by weight and of synthetic graphite,

(4) 9 parts by weight of metallic silicon powder having a maximum grain size of 63 m,

(5) 9 parts by weight of titanium dioxide (rutilite) having a maximum grain size of 45 m, and

(6) 8 parts by weight of SiC-C powder having a maximum grain size of 63 m.

(7) To this mixture coal-tar pitch was added as a binder in such an amount that a workable paste, i.e. a paste having a suitable viscosity for the forming process, was obtained.

(8) For the mixing step for example a sigma-blade mixer may be used.

(9) Then, the mixture was formed by vibro-molding into green blocks having each a dimension of (WHL) 6306302500 mm, before the blocks were baked in a coke breeze packing at a maximum temperature of 850 to 1000 C.

(10) Afterwards, the baked blocks were semi-graphitized in an Acheson furnace at a final temperature of 2000 C.

(11) The blocks obtained with this method had the following properties:

(12) apparent density: 1.72 g/cm3,

(13) cold crushing strength: 42 MPa,

(14) thermal conductivity: 45 W/m.K, and

(15) pore size distribution: sum of open porosity from pores with a diameter of larger than 1 m equaled 2.7% of the sample volume.

(16) A refractory was prepared as described in example 1, except thatinstead of the semi-graphitization at a final temperature of 2000 C.the baked bodies were submitted to a graphitization treatment at 2500 C. in an Acheson furnace.

(17) The blocks obtained with this method had the following properties:

(18) apparent density: 1.71 g/cm3,

(19) cold crushing strength: 27 MPa,

(20) thermal conductivity: 85 W/m.K, and

(21) pore size distribution: sum of open porosity from pores with a diameter of larger than 1 m equaled 7.0% of sample volume.