Glass Melting Technology: A Technical and Economic ... - OSTI

supplemental energy input in a form more effective than would be possible by increasing
the primary fuel. Traditionally, electric boosting is applied to avoid low bottom
temperatures in a tank in which colored glass is melted.
• Fining zone
In the fining zone, the glass melt should not be exposed to strong mixing effects; a plug
flow regime is preferred. Residence time required in the fining zone depends on the
depth of the melt in this area. A deep melt requires a long residence time and a high
surface temperature, if heated from above, to obtain a sufficiently high temperature level
in the bottom layers of the melt. The temperature gradients from the surface to the bottom
and both ends of the furnace to the hot spot cause glass convective flows to well upward,
resulting in the formation of a spring zone, or spring line, for refining where a line of
bubbles or foam exists near the forward fuel firing port. This defines the end of refining
and the beginning of thermal conditioning, also the highest temperature glass in the
furnace.
Low-pressure will enhance bubble growth and bubble removal, as well as gas stripping.
A plug flow shallow fining zone, using electric energy and low pressure (