Process and apparatus for refining molten glass

1. A process for refining molten glass that includes:

(a) providing a flow of molten glass that includes a plurality of gas bubbles;

(b) providing a porous body that has a three-dimensional non-planar shape at least partially submerged within the molten glass, wherein the porous body includes an inlet, an outlet in fluid communication with the inlet, and a plurality of pores through which molten glass can flow between the inlet and the outlet, the plurality of pores being defined by walls having wall surfaces, the porous body having a thickness, a width and a height with the thickness defined as a distance between the inlet and the outlet and wherein at least one of a ratio of the thickness to the height or a ratio of the thickness to the width is greater than 1; and

(c) flowing the molten glass through the porous body and through the plurality of pores such that interaction between the molten glass and the wall surfaces of the pores promotes release of gas bubbles from the molten glass or causes at least some of the gas bubbles within the molten glass to collapse or rupture to reduce the size of the gas bubbles to a commercially acceptable size.

2. The process set forth in claim 1 wherein said step (c) includes flowing the molten glass through the porous body at a flow rate in the range of 18.92-94.64 liters (5-25 gallons) per hour.

3. The process set forth in claim 1 wherein said step (c) includes allowing the molten glass to flow through the porous body by gravity.

4. The process set forth in claim 1 wherein said step (c) includes applying a centrifugal or centripetal force to the molten glass.

5. The process set forth in claim 1 wherein the wall surfaces of the pores includes free carbon or a material that dissociates to provide free carbon, free nitrogen, or both, and said step (c) includes interacting the molten glass with the wall surfaces to produce carbon dioxide gas, nitrogen oxide gas, or both.

6. The process set forth in claim 1 that also includes:

exposing the porous body to a sub-atmospheric pressure environment.

7. The process set forth in claim 1 that also includes:

inducing movement of the porous body to promote bubble release therefrom.

8. The process set forth in claim 1 , wherein the pores range in size from 0.5 to 20 millimeters in diameter.

9. The process set forth in claim 1 , wherein the porous body has from 5 to 100 pores per linear inch.

10. The process set forth in claim 1 , wherein the wall surfaces are concave shaped.

11. The process set forth in claim 1 , wherein in step (c) at least some of the gas bubbles are reduced to a mean diameter of 0.2 millimeters or less.

12. A process for refining molten glass that includes:

(a) providing a flow of molten glass that includes a plurality of bubbles;

(b) providing a porous body that includes an inlet, an outlet in fluid communication with the inlet, and a plurality of pores defining a three-dimensional network of interconnected open pores through which molten glass can flow between the inlet and the outlet, the plurality of pores being defined by walls having wall surfaces; and

(c) flowing the molten glass through the porous body and through the plurality of pores such that between the molten glass and the wall surfaces of the pores promotes release of the gas bubbles from the molten glass or causes at least some of the bubbles within the molten glass to collapse or rupture to reduce the size of the glass bubbles.

13. The process set forth in claim 12 , wherein the plurality of pores have sizes ranging from 0.5 to 20 millimeters in diameter.

14. The process set forth in claim 12 , wherein the wall surfaces include an irregular surface produced by the presence of whiskers or needle-shaped structures on the wall surfaces.

15. The process set forth in claim 12 wherein the wall surfaces have a surface roughness average of greater than 600 microinches.

16. A process for refining molten glass that includes:

(a) providing a flow of molten glass that includes a plurality of bubbles;

(b) providing a porous body having a longitudinal axis that includes an inlet, an outlet in fluid communication with the inlet and spaced apart from the inlet along the longitudinal axis, and a plurality of pores through which molten glass can flow between the inlet and the outlet, wherein the size of pores varies along the longitudinal axis of the porous body; and

(c) flowing the molten glass through the porous body and through the plurality of pores such that between the molten glass and the wall surfaces of the pores promotes release of the gas bubbles from the molten glass or causes at least some of the bubbles within the molten glass to collapse or rupture to reduce the size of the glass bubbles.

17. The process set forth in claim 16 , wherein the pores have a hexagonal shape.

18. The process set forth in claim 16 wherein the porous body comprises at least two serially arranged segments with each segment having pores of a different size from the pores of the other segment.

19. The process set forth in claim 18 wherein the at least two segments are spaced apart by a gap between them.

20. The process set forth in claim 16 wherein the porous body has a width ranging from 4 to 12 inches and a height ranging from 6 to 18 inches.