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

control per mixer will optimize the cooling rate and contribute to homogeneity, especially
if cords or knots have been formed by the interaction of molten glass with the refractory
lining.
• Deep refiner
The well de-gassed melt flows on top and then downstream along the bridge wall and
sidewalls into the throat in this deep refiner segment. The melt in the center re-circulates,
allowing small bubbles to be removed in the refiner part. Homogenization occurs
because of the strong re-circulation. The difference between minimum and average
residence time (volume/pull) is still a factor of five but this concept allows a reduction of
the tank volume of about 25 percent compared to conventional furnaces.
Only about 8 percent of the total heat demand must be added in the fining shelf. Instead
of heating the melt by combustion processes, the melt might be heated from 2462 to 2750
˚F (1350 to 1510˚C) by boosting or magnetrons, allowing further reduction in surface
temperatures and good temperature control during fining. Bubbling, weirs, or boosting
electrodes can be used to control the flow regime, to increase mixing, or to limit
backflow. The minimum residence time from chargers to the throat of the segmented
tank is typically low—three to four hours—but all the glass melt volume has been
exposed to temperatures of at least 2678 ˚F (1470 ˚C). Minimum residence time can be
increased by weir walls over the tank width.
Figure 3.D.1. Schematic arrangement of sections of a segmented melter, with typical
temperature levels, residence times, and heating options.
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