But glass melting and forming is a system, not one isolated unit. Once the glass is melted by a particular mechanism, it must be delivered in suitable and appropriate condition to the forming mechanism, whatever that might be. Since the SCM is a rapid melting process, it could produce a melt with substantial bubbles. However, the glass will be homogeneous and in an ideal condition for bubble removal by a rapid refining process. Plasma melting could also require additional downstream refining and/or mixing. And for an oxy-fuel forehearth (front end) to operate effectively, it must receive high-quality molten glass that has the requisite qualities needed for a particular forming process.
As a result, an additional step between the melting process and the forehearth-a refining and/or conditioning process-will be needed before any "next-generation melting system" (or series of systems) is finalized. This process is a crucial link between these innovative glass melting and delivering processes to achieve the ultimate goal-efficiently and cost effectively producing high-quality glass. Without an integrated, robust refining process, all of the expected energy, capital and environmental savings can be quickly wiped out by defective end products.
A half-day workshop hosted by the Glass Manufacturing Industry Council (GMIC) on October 29, 2003, in conjunction with the Glass Problems Conference in Champaign, Ill., gave participants an opportunity to discuss the need for refining/conditioning for the next generation glass melting system in an open forum. The workshop identified the parameters, criteria and barriers that will likely be encountered in attempting to refine glass produced by these two melting technologies, as well as entities (individuals or corporations) that might be interested in pursuing advanced technologies in the refining/ conditioning area. Fifty glass industry professionals from all over the world discussed a number of existing and potential refining technologies, including vacuum, sonic (with and without shear), centrifugal, inert gas diffusion and bubbling, shelf or shallow fining, deep refiner, microwave, high temperature and slip stream/recirculation. They also discussed raw materials such as Synsil (supplied by Minerals Technologies Inc.), or burnt or hydrated lime, which can remove gas from the mix; and refining agents, such as cerium oxide. The possibility also exists to identify technologies used by other industries that could be relevant to glass.
The October event was a stepping stone to a one-day workshop that will be held in Pittsburgh, Pa., on May 20, 2004, at the end of the Glassman 2004 session, which will also be hosted by GMIC. This follow-up event is expected to produce specific proposals for research projects, including coalitions of companies and possible funding sources.
More information about the GMIC's workshops, as well as the progress made on the DOE/glass industry research projects, can be obtained from the GMIC.