Abstract: To provide a vacuum-degassing method and a vacuum degassing apparatus excellent in the effect of vacuum-degassing molten glass, more specifically, a method for vacuum-degassing molten glass and a vacuum degassing apparatus, capable of effectively suppressing formation of reboil bubbles. A method for vacuum-degassing molten glass, which comprises melting glass materials to be silicate glass and passing the resulting molten glass in a flow passage in a vacuum degassing vessel, the interior of which is maintained in a reduced pressure state, to vacuum-degas the molten glass, wherein vacuum-degassing is carried out under conditions satisfying the following formula (1) at a bottom portion of the vacuum degassing vessel: SS=pSO2/Pabs <2.0??(1) wherein SS is the supersaturation degree of SO2 in the molten glass, pSO2 is the partial pressure (Pa) of SO2, and Pabs is the pressure (Pa) at the bottom portion of the glass flow passage of the vacuum degassing vessel.

Abstract: A vacuum degassing apparatus having a throughput of at least 200 tons/day without causing problems such as a stagnation of molten glass flow in the molten glass flow path, an increment of flow rate of the molten glass flow in a local area, an excessive increment of pressure loss of the molten glass flow. A vacuum degassing apparatus comprises a vacuum degassing vessel, and an uprising pipe and a downfalling pipe which are connected with the vacuum degassing vessel, wherein the vacuum degassing vessel includes a wide portion for providing a molten glass flow path, and in the wide portion, the proportion W1/L1 of the breadth of molten glass flow path W1 to the length of molten glass flow path L1 is at least 0.

Abstract: To provide a vacuum-degassing method and a vacuum degassing apparatus excellent in the effect of vacuum-degassing molten glass, more specifically, a method for vacuum-degassing molten glass and a vacuum degassing apparatus, capable of effectively suppressing formation of reboil bubbles. A method for vacuum-degassing molten glass, which comprises melting glass materials to be silicate glass and passing the resulting molten glass in a flow passage in a vacuum degassing vessel, the interior of which is maintained in a reduced pressure state, to vacuum-degas the molten glass, wherein vacuum-degassing is carried out under conditions satisfying the following formula (1) at a bottom portion of the vacuum degassing vessel: SS=pSO2/Pabs<2.0??(1) wherein SS is the supersaturation degree of SO2 in the molten glass, pSO2 is the partial pressure (Pa) of SO2, and Pabs is the pressure (Pa) at the bottom portion of the glass flow passage of the vacuum degassing vessel.

Abstract: A vacuum degassing apparatus having a throughput of at least 200 tons/day without causing problems such as a stagnation of molten glass flow in the molten glass flow path, an increment of flow rate of the molten glass flow in a local area, an excessive increment of pressure loss of the molten glass flow. A vacuum degassing apparatus comprises a vacuum degassing vessel, and an uprising pipe and a downfalling pipe which are connected with the vacuum degassing vessel, wherein the vacuum degassing vessel includes a wide portion for providing a molten glass flow path, and in the wide portion, the proportion W1/L1 of the breadth of molten glass flow path W1 to the length of molten glass flow path L1 is at least 0.

Abstract: A vacuum degassing apparatus for molten glass includes a vacuum housing which is evacuated to be depressurized therein; a vacuum degassing vessel which is provided in the vacuum housing to vacuum-degas molten glass as the molten glass flows therein; an uprising pipe which connects to the vacuum degassing vessel, and sucks and draws up undegassed molten glass to introduce the undegassed molten glass into the vacuum degassing vessel; and a downfalling pipe which connects to the vacuum degassing vessel and draws down the degassed molten glass from the vacuum degassing vessel to discharge the degassed molten glass. The cross sectional area of the path at the upper end portion of the uprising pipe is larger than the cross sectional area of the path at the lower end portion of the uprising pipe.

Abstract: A vacuum degassing apparatus for molten glass includes a vacuum housing which is evacuated to be depressurized therein; a vacuum degassing vessel which is provided in the vacuum housing to vacuum-degas molten glass as the molten glass flows therein; an uprising pipe which connects to the vacuum degassing vessel, and sucks and draws up undegassed molten glass to introduce the undegassed molten glass into the vacuum degassing vessel; and a downfalling pipe which connects to the vacuum degassing vessel and draws down the degassed molten glass from the vacuum degassing vessel to discharge the degassed molten glass. The cross sectional area of the path at the upper end portion of the uprising pipe is larger than the cross sectional area of the path at the lower end portion of the uprising pipe.

Abstract: A process for producing a glass for cathode ray tubes, having a Sb2O3 content of from 0 to 0.19% as represented by mass percentage and containing H2O, which process comprises a step of melting a raw material in an atmosphere under a pressure of P0 to obtain a molten glass, and a step of vacuum degassing the molten glass in an atmosphere under a pressure PA which is lower than P0, wherein the pressure P of the molten glass is made to be at most (6.1 W+0.06) atm in the vacuum degassing step, wherein W is the content of said H2O as represented by mass percentage.

Abstract: A vacuum degassing apparatus for molten glass, comprising: a vacuum housing which is evacuated to be depressurized therein; a vacuum degassing vessel which is provided in the vacuum housing to vacuum-degas molten glass as the molten glass flows therein; an uprising pipe which connects to the vacuum degassing vessel, and sucks and draws up undegassed molten glass to introduce the undegassed molten glass into the vacuum degassing vessel; and a downfalling pipe which connects to the vacuum degassing vessel and draws down the degassed molten glass from the vacuum degassing vessel to discharge the degassed molten glass; wherein the cross sectional area of the path at the upper end portion of said uprising pipe is larger than the cross sectional area of the path at the lower end portion of said uprising pipe.

Abstract: A vacuum degassing apparatus for molten glass, comprising:

Abstract: A process for producing a glass for cathode ray tubes, having a Sb2O3 content of from 0 to 0.19% as represented by mass percentage and containing H2O, which process comprises a step of melting a raw material in an atmosphere under a pressure of P0 to obtain a molten glass, and a step of vacuum degassing the molten glass in an atmosphere under a pressure PA which is lower than P0, wherein the pressure P of the molten glass is made to be at most (6.1 W+0.06) atm in the vacuum degassing step, wherein W is the content of said H2O as represented by mass percentage.