Refractory ceramic gas purging element

Abstract

The invention relates to a refractory ceramic gas purging element featuring an insert which was cast into a blind hole within a refractory gas permeable body, which insert is made of a refractory ceramic material and has a density different to that of the body.

Claims

1. A refractory ceramic gas purging element, featuring a) an axial extension between a first end, which provides means to supply a gas into the gas purging element, and a second end, at which the gas may leave the gas purging element and enter into an adjacent metal melt, b) a body, made of a pressed MgO based refractory ceramic material, comprising more than 80% by weight of MgO, and designed to allow the gas supplied at the first end of the gas purging element, to pass through the body and to leave the body at the second end of the gas purging element, wherein c) the body extends from the second end of the gas purging element towards the first end of the gas purging element, thereby defining an axial height HB of the body, with a first end, adjacent to the first end of the gas purging element, and a second end, corresponding to the second end of the gas purging element, d) a blind hole, which extends from the first end of the body towards its second end, thereby defining an axial height HH of the blind hole, with HB being larger than HH, wherein e) the blind hole is filled with an insert, made of a refractory ceramic material, comprising more than 80% by weight of Al.sub.2O.sub.3, which features a density different to that of the body and which is in-situ cast into said blind hole.

2. The gas purging element of claim 1, wherein the axial height HH of the blind hole corresponds to at most 50% of the axial height HB of the body.

3. The gas purging element of claim 1, wherein the blind hole and the insert feature a cylindrical or frustoconical common wall.

4. The gas purging element of claim 1, wherein the blind hole features a cross section along a plane, which extends perpendicular to the axial extension of the gas purging element, from the group comprising: circular, rectangular, oval, star-like and polygonal.

5. The gas purging element of claim 1, wherein the body features a random porosity of 10 to 50% by volume with respect to a total volume of the body.

6. The gas purging element of claim 1, wherein the body features a directed porosity, provided by channels, which extend between the first and second end of the body.

7. The gas purging element of claim 1, further comprising a gas distribution chamber, which is arranged adjacent to the first end of the body and fluidicly connectable to corresponding gas supply means.

8. The gas purging element of claim 1, wherein the body is made of a refractory ceramic material, comprising MgO and Cr.sub.2O.sub.3 in a total amount of more than 80% by weight.

9. The gas purging element of claim 1, wherein the insert is made of a cement castable.

10. The gas purging element of claim 1, wherein the insert was tempered after casting into the blind hole.

11. The gas purging element of claim 1, wherein the density of the insert differs from that of the body by at least 8%.

12. The gas purging element of claim 1, wherein the insert has an open porosity which differs from that of the body by at least 30%.

13. The gas purging element of claim 1, wherein the insert differs from the body by at least one of the following: a higher density, a lower open porosity a smaller gas permeability.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described by a way of example with respect to the attached drawing, featuring

(2) FIG. 1: A sectional view of a first embodiment of the refractory gas purging element.

(3) FIG. 2: A sectional view of a second embodiment of the refractory gas purging element.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(4) According to FIG. 1 the refractory ceramic gas purging element features an axial extension (A-A) between a first end (lower end) E1 and a second (upper) end E2.

(5) The gas purging element comprises a gas permeable body 10, which is made of a pressed MgO-based refractory ceramic material with an open random porosity of about 25% by volume, featuring a density of 2.8 g/cm.sup.3. This allows a gas, supplied at the first end E1 via a gas feeding pipe F, to pass through the open pores of said body 10 and to leave the body 10 at the second end E2 via an uncovered upper surface 12 of said body 10.

(6) The body 10 itself is peripherally covered by a steel envelope S, which also covers the lower first end E1 and comprises one opening O, from which the gas feeding pipe F extends outwardly, i.e. in the Figures, downwardly.

(7) The body 10 extends from the second end E2 of the gas purging element towards the first end E1 but ends at a distance to said first end E1, thereby providing a gas distribution chamber 14. The overall height of body 10 is identified as HB, its first, lower end as 10F and its second, upper end as 10S.

(8) The gas distribution chamber 14 is limited at its upper end by a steel plate 14s, which is welded to the outer steel envelope S and which abuts the first end 10F of said body 10.

(9) Body 10 further features a blind hole 16 of frustoconical shape at its lower end 10F (adjacent to E1), which blind hole 16 extends from the first, lower end 10F of body 10 towards its second end 10S with an axial height HH being approximately 0.4 of the axial height HB of body 10.

(10) The blind hole 16 is filled with a monolithic insert 18, which is substantially gas tight (3% by volume open porosity) and made of a refractory ceramic Alumina based castable, which was in-situ cast into said blind hole 16. Thereafter the insert unit was tempered at 200 C. for 3 hours, finally featuring a density of 3.1 g/cm.sup.3, i.e. ca. 11% higher than that of the body.

(11) The lower first end 10F of body 10 abuts against the steel plate 14s as does the lower end of insert 18. While the steel plate 14s is perforated in its ring shaped contact zone vis-a-vis body 10 (to allow the gas to enter the porous body 10), said steel plate 14s is not perforated in its contact zone vis--vis the gas-tight insert 18.

(12) The gas, fed via the gas feeding pipe F into gas distribution chamber 14, thereafter penetrates the open porosity of body 10 before leaving said body 10 via its surface 12 into an adjacent metal melt.

(13) The embodiment according to FIG. 2 is similar to that of FIG. 1. Insofar only characteristic differences are mentioned hereinafter:

(14) While the overall shape of the gas purging element according to FIG. 1 is cylindrical and insert 18 features a frustoconical shape, FIG. 2 presents a frustoconical gas purging element comprising a cylindrical insert 18.

(15) Insert 18 is made of a low cement castable (comprising 94% by weight Al.sub.2O.sub.3, requiring 5% by weight water), which was poured in-situ into a corresponding blind hole 16 at the first end 10F of body 10 and then tempered as in the previous example.

(16) Insert 18 according to FIG. 2 has a density of about 3.1 g/cm.sup.3 and an open porosity of about 14 by volume.

(17) Body 10, which according to this embodiment is a cast item comprising gas channels 22 (so-called directed porosity), features a density of only 2.6 g/cm.sup.3 and a total open porosity of 27% by volume.

(18) The gas permeability of the body is ca. 150 nPerm and that of the insert about 2 nPerm.

(19) The gas permeability is always identified according to ASTM C577-07.sup.2.