A glass furnace including an additive-containing product including an additive selected from: phosphorus compounds other than glasses and vitroceramics, tungsten compounds other than glasses and vitroceramics, molybdenum compounds other than glasses and vitroceramics, iron in the form of metal, aluminum in the form of metal, silicon in the form of metal, and their mixtures, silicon carbide, boron carbide, silicon nitride, boron nitride, glasses including elemental phosphorus and/or iron and/or tungsten and/or molybdenum, vitroceramics including elemental phosphorus and/or iron and/or tungsten and/or molybdenum, and their mixtures, and having the following chemical analysis, exclusively of the additive, as a percentage by weight on the basis of the oxides: Cr.sub.2O.sub.3?2%, and Cr.sub.2O.sub.3+Al.sub.2O.sub.3+CaO+ZrO.sub.2+MgO+Fe.sub.2O.sub.3+SiO.sub.2+TiO.sub.2?90%, and Cr.sub.2O.sub.3+Al.sub.2O.sub.3+MgO?60%, the content by weight of additive being in the range 0.01% to 6%.

An apparatus and methods of refining glass, in a multi-stage, downwardly cascading manner, include a melting chamber housing molten glass and having an outlet, a first refining chamber downstream from the melting chamber and having a first outlet and a first inlet below the outlet of the melting chamber, and a second refining chamber downstream from the first refining chamber and having a second outlet and a second inlet below the first outlet of the first refining chamber. The first refining chamber has a first negative pressure and the second refining chamber has a second negative pressure.

A process and apparatus for manufacturing glass. A mixture of solid glass-forming materials comprising at least one fining agent are introduced into a doghouse located upstream of an elongated tank. The glass-forming materials are melted in the doghouse at a temperature at or above a fining-onset temperature of the at least one fining agent by application of heat from one or more submerged combustion burners. The resulting molten glass is relatively foamy and may comprise greater than 25 vol. % gas bubbles. The molten glass is directed from the doghouse into an upstream end of the tank where it is refined to produce molten glass having on average less than 20 seeds per ounce.

An apparatus and method of refining molten glass are disclosed. An upstream vessel contains molten glass, a downstream vessel is arranged downstream of the upstream vessel, and vacuum refining vessels are located between the upstream vessel and the downstream vessel and are in separate, alternating fluid communication with the upstream vessel and in separate, alternating fluid communication with the downstream vessel.

A gradient fining tank and a method of operating the tank to refine foamy molten glass is disclosed. The gradient fining tank includes a floor, a roof, and two laterally-spaced sidewalls that at least partially define an interior chamber of the tank. The floor of the tank is profiled to provide the tank with an extended shallow portion that defines an inlet to the interior chamber and a deep holding portion that defines an outlet from the interior chamber. An entry section of the floor provides the extended shallow portion of the tank and a transition section and exit section of the floor provide the deep holding portion. A depth of the interior chamber at an outlet end of the deep holding portion is greater than a depth of the interior chamber at the outlet end of the extended shallow portion.

Processes and systems for producing molten glass using submerged combustion melters, including densifying an initial composition comprising vitrifiable particulate solids and interstitial gas to form a densified composition comprising the solids by removing a portion of the interstitial gas from the composition. The initial composition is passed from an initial environment having a first pressure through a second environment having a second pressure higher than the first pressure to form a composition being densified. Any fugitive particulate solids escaping from the composition being densified are captured and recombined with the composition being densified to form the densified composition. The densified composition is fed into a feed inlet of a turbulent melting zone of a melter vessel and converted into turbulent molten material using at least one submerged combustion burner in the turbulent melting zone.

Processes and systems for producing molten glass using submerged combustion melters, including densifying an initial composition comprising vitrifiable particulate solids and interstitial gas to form a densified composition comprising the solids by removing a portion of the interstitial gas from the composition. The initial composition is passed from an initial environment having a first pressure through a second environment having a second pressure higher than the first pressure to form a composition being densified. Any fugitive particulate solids escaping from the composition being densified are captured and recombined with the composition being densified to form the densified composition. The densified composition is fed into a feed inlet of a turbulent melting zone of a melter vessel and converted into turbulent molten material using at least one submerged combustion burner in the turbulent melting zone.

Systems and methods for controlling the flow of vitrified material. In at least some embodiments, a vitrified material control system comprises a melt chamber (8) configured to contain a molten material (27) during operation of the control system; a siphon valve (11) configured to facilitate a flow of the molten material from the melt chamber; and a vacuum-generation system (26, 15, 16) configured to controllably deliver a vacuum to the molten material in the melt chamber and to thereby regulate a flow of the molten material from the melt chamber. In other embodiments, methods of controlling a flow of molten vitrified material from a heating device are disclosed. The methods may include, for example, applying a vacuum to the molten material to control a dwell time of the molten material in a vessel of the heating device and regulating the vacuum based on a measured temperature of the molten material.

A glass manufacturing apparatus includes a dissolving vessel configured to dissolve a glass raw material to produce a molten glass, a forming vessel configured to form the molten glass into a predetermined shape, and glass supply tubes configured to convey the molten glass from the dissolving vessel to the forming vessel. The glass supply tubes each include a tube body, a flange portion, which is arranged in an outer circumferential portion of the tube body and has first and second parts, an electrode portion arranged in the first part, and a temperature difference setting portion configured to cause a temperature difference between the first and second parts. The temperature difference setting portion sets a temperature of the first part to be higher than that of the second part.

In illustrative implementations of this invention, a crucible kiln heats glass such that the glass becomes or remains molten. A nozzle extrudes the molten glass while one or more actuators actuate movements of the nozzle, a build platform or both. A computer controls these movements such that the extruded molten glass is selectively deposited to form a 3D glass object. The selective deposition of molten glass occurs inside an annealing kiln. The annealing kiln anneals the glass after it is extruded. In some cases, the actuators actuate the crucible kiln and nozzle to move in horizontal x, y directions and actuate the build platform to move in a z-direction. In some cases, fluid flows through a cavity or tubes adjacent to the nozzle tip, in order to cool the nozzle tip and thereby reduce the amount of glass that sticks to the nozzle tip.