Analysis of elementary process steps in industrial glass melting tanks: some ideas on innovations in industrial glass melting

Conventional industrial glass furnaces show broad glass melt residence time distributions in the melting tanks and average residence times may be up to more than two days for high quality glass products, such as float glass or TV glass, despite the minimum residence times of 8-10 hours (or even less than 4 hours for container glass furnaces). Long residence times are associated with large melt tank volume/pull rate ratios and high structural heat losses. The recirculation flows, necessary to supply the batch blanket with sufficient energy for the fusion processes of the batch materials, are often poorly controlled and cause these shown residence time differences. For each elementary process step the most relevant process parameters in terms of desired flow patterns, mixing behavior, temperature, chemistry and required time for completion of the process step are analyzed. From this analysis, it is concluded that the different steps need very different conditions comparing the processes with each other. Therefore glass furnace design modifications should be focused on the development of furnaces with segments, each of them dedicated and optimized for the a certain stage of the melting process: melting-in of batch, sand grain dissolution, removal of gases (bubbles and dissolved gases), re-absorption of residual bubbles and glass melt (chemical and thermal) homogenization. Some developments in fast fining and rapid melting-in of batch will be shown and shortly discussed