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

gases leave this compartment and give up their heat in four stages. First they flow upstream
through a preheating zone where they heat the batch floating on the surface. They leave the
furnace through radiant recuperators that heat the combustion air, and then enter convective
recuperators that preheat the gas. Finally, they are passed through a preheater for cullet. A
special tank design includes a shallow melting area with bubblers, a preheating zone with a
sloping bottom, and a deep refiner.
The first installation of the LoNOx melter was a 200-metric ton, natural gas-fired container
furnace at Weigand Glas Steinbach, Germany, in late 1987. This somewhat complex furnace
design has been successfully introduced for tableware and container glass melting. (Moore,
Ronald H., “LoNOx melter shows promise,” Glass Industry, 71[4], 14-18 (1990))
IV.11. Conclusion
Continuous glass melters in operation today have evolved from the basic design of a furnace
created by the Siemens Brothers of Germany in the middle of the 19th century. Improvements to
the melters have been efficient and reliable enough that the Siemens furnace technology has
continued to serve the needs of glassmakers. But the high capital costs for building or
rebuilding, limited flexibility of operation, high costs of fuels, and environmental regulations
have catalyzed efforts to seek new glassmaking technology.
Over the past 30 years, major innovations have been developed for glass melting but with
varying degrees of success. The fragmentation of glass manufacturing into the four major
segments of float glass, container glass, fiberglass, and specialty glasses has made for the
development of numerous technologies. As advancements have been made in refractory
materials, instrumentation and computer modeling, state-of-the-art equipment, firing techniques,
and fuel replacement, many of the technological developments in this area are worthy of
reconsideration. Selected technologies are presented in detail for reference and further study by
glass manufacturers.
The objectives of research and development for innovations in glass manufacturing have been to
replace or renovate combustion heated furnaces to comply with clean air laws; recycle glass
industry wastes and used glass products; develop electric melting facilities with longer furnace
life and improved glass quality; and replace melting tanks with smaller, less expensive, more
flexible melters. Particularly in the last half of the 20th century, glass scientists and engineers
have explored all aspects of the glass melting process—preheating batch and cullet; melting with
preheating systems; nonconventional melting systems, regenerative, recuperative, electric,
oxygen-fuel; waste vitrification; refining; and emission control systems. Of the innovative
technology developed and tested, some has found its way into the mainstream of glass
manufacturing. Others have been set aside for lack of funding for continued development,
inadequate materials for construction, scale-up problems, unreliability, limitation of glass
compositions that could be processed, lack of process control, production of poor glass quality,
safety issues, high net cost or environmental failures.
Innovations in glass melting systems have involved melting and refining by conventional and
non-conventional means. A segmented furnace system has been suggested as the most feasible
alternative to continuous tank furnaces. Segmented systems explored by TNO in the Netherlands
86