Abstract: A vacuum degassing apparatus for molten glass according to the present invention comprises a vacuum housing where a vacuum is created; a vacuum degassing vessel housed in the vacuum housing to degas the molten glass; an introduction device communicated to the vacuum degassing vessel so as to introduce untreated molten glass into the vacuum degassing vessel, or preferably an uprising pipe; and a discharge device to discharge treated molten glass from the vacuum degassing vessel, or preferably a downfalling pipe. In the apparatus, at least a portion of at least one of the vacuum degassing vessel, the uprising pipe and the downfalling pipe that directly contact with the molten glass is constituted by refractory material having a porosity of not greater than 5%. The apparatus can increase quantity of flow of the molten glass and consequently a degassing throughput of the molten glass in comparison with prior art, having the same size and the same pressure loss.

Abstract: A vacuum degassing apparatus comprises a path made of dense refractory bricks, the path including an inner surface brick layer, the refractory bricks in the inner surface brick layer having a flatness of 0.5 mm on contacting surfaces with one anther, and the path including a backup brick layer and a ramming material filling layer besides the inner surface brick layer.

Abstract: A vacuum degassing apparatus includes a lifter to absorb deformation in a vertical direction due to thermal expansion of the vacuum degassing, a slider to absorb thermal expansion of the vacuum degassing vessel in a longitudinal direction thereof, or a thermal expansion absorbing layer to absorb thermal expansion of an uprising pipe and a downfalling pipe in a cross-sectional direction, or a thermal expansion absorbing layer provided along a portion of an outer surface of the vacuum degassing vessel in a height direction.

Abstract: A vacuum degassing method for molten glass, which comprises introducing molten glass into a vacuum degassing apparatus, subjecting it to degassing treatment under a predetermined reduced pressure condition and then withdrawing it for a subsequent step, wherein during the degassing treatment, a metal compound which is at least one compound of metal selected from the group consisting of aluminum, titanium, silicon, zinc, magnesium, iron, chromium, cobalt, cerium and calcium, is supplied from outside of the vacuum degassing apparatus to the surface of a bubble layer formed in the molten glass to diminish or extinguish the bubble layer.

Abstract: A vacuum degassing apparatus for molten glass includes a vacuum housing where a vacuum is created; a vacuum degassing vessel housed in the vacuum housing to degas the molten glass; an introduction device communicated to the vacuum degassing vessel so as to introduce untreated molten glass into the vacuum degassing vessel, or preferably an uprising pipe; and a discharge device to discharge treated molten glass from the vacuum degassing vessel, or preferably a downfalling pipe. In the apparatus, at least a portion of at least one of the vacuum degassing vessel, the uprising pipe and the downfalling pipe that directly contact the molten glass is constituted by refractory material having a porosity of not greater than 5%. The apparatus can increase quantity of flow of the molten glass and consequently a degassing throughput of the molten glass, having the same size and the same pressure loss.