Method and apparatus for manufacturing high melting point glasses with volatile components

A furnace for manufacturing high melting point glasses, the furnace comprising:

• a superstructure having a combustion chamber disposed over a melting tank, the combustion chamber defining an uninterrupted space without inner dividing walls, the combustion chamber accommodating a plurality of burners,
• the melting tank comprising a melting area, the melting tank further comprising a furnace bottom disposed underneath the melting area, the furnace bottom being connected to a raised bottom area, the raised bottom area extending across the width of the melting tank, the furnace bottom further comprising a row of bubblers extending across the width of the melting tank and in front of the raised bottom area,
• the raised bottom area being disposed between the melting area and a conditioning zone, the conditioning zone being disposed between the raised bottom area and a throat, the throat being disposed between the conditioning zone and an extraction zone,
• the raised bottom area comprising a refining bank having a top and a height defined as a vertical distance between the furnace bottom and the top of the refining bank, the raised bottom area further comprising a step disposed between the refining bank and the melting area, the step having a top and a height defined by the distance between the furnace bottom and the top of the step, the height of the refining bank being greater than the height of the step and is at least 150 mm, the step further comprising at least one row of booster electrodes spaced along the step in a direction parallel to the width of the melting tank and transverse to the length of the melting tank.

A furnace for manufacturing boron glasses and borosilicate glasses having volatile components, the furnace comprising:

• a superstructure having a combustion chamber disposed over a melting tank, the combustion chamber defining an uninterrupted space without inner dividing walls, the combustion chamber accommodating a plurality of burners,
• the furnace further comprising a melting tank with a melting area, the melting tank having a length extending along a longitudinal axis of the melting tank and a width extending transversely to the longitudinal axis of the melting tank, the melting tank further comprising a furnace bottom disposed underneath the melting area, the furnace bottom comprising a field of electrodes and at least one row of bubblers disposed below the melting area, the furnace bottom being connected to a raised bottom area, the raised bottom area extending across the width of the melting tank,
• the raised bottom area being disposed between the melting area and a conditioning zone, the conditioning zone being disposed between the raised bottom area and a throat, the throat being disposed between the conditioning zone and an extraction zone,
• the raised bottom area comprising a refining bank having a top and a height defined as a vertical distance between the furnace bottom and the top of the refining bank, the refining bank comprising a length ranging from about 800 mm to about 2000 mm along the longitudinal axis of the furnace, the raised bottom area further comprising a step disposed between the refining bank and the melting area, the step having a height defined by the distance between the furnace bottom and the top of the step, the height of the step ranging from about 0.3 to about 0.7 times the height of the refining bank, the step further comprising a length disposed along the longitudinal axis of the furnace, a ratio of the length of the step to the length of the refining bank ranging from about 0.4 to about 0.6,
• the step further comprising at least one row of booster electrodes spaced along the step in the direction of the width of the melting tank and transverse to the length of the melting tank, the booster electrodes extend vertically upwards from the step.