ALL-ELECTRIC FURNACES FOR HIGH QUALITY DEMANDS IN A WIDE RANGE OF GLASS COMPOSITIONS

All-electrically heated furnaces (AEF) are characterized by vertical flow of the melt. The melt itself is continuously and completely covered by a batch layer (cold top). The electric power is released as Joule's heat between the electrodes directly within the glass. The completely covered melt surface by batch excludes evaporation problems concerning B(2)O(3), fluorine, chlorine and so on. Exclusion of evaporation increase the glass quality but also meets environmental regulations to that glass producers get faced more and more of course under consideration of the energy prices. AEF can be utilised for a very wide range of glass types: Soda-lime for tableware but also speciality soda-lime for perfume flacons, STN flat panels and others Borosilicate glass type Boro 3.3 ... 4.9, dependend on requirements from side of the final product. Opal glass (e.g. tableware and perfume flacons) Ophthalmic glass (glass blanks) C glass (fibre glass) Lead glass Non-alkali glass Each glass type needs a tailor made technology and furnace design. Furnace geometry, type and position of electrodes, choice of the appropriate refractory material and others have a highly important influence on glass quality and furnace campaign. Examples for borosilicate glass (alpha 33 10(-7) K(-1)), soda lime and alkali-free glass are announced. With the development for electric melting of non-conductive alkali-free glass for TFT flat panels and others, JSJ passed an apparently non-crossable border in AEF melting technology. The successful commissioning and operation of the world wide first AEF furnace for non-alkali glass for 2 years is a great step ahead. The development of a special electrically heated system that can be operated independently from the electrical resistivity of the melt surrounding, was the key to success. AEF is a very good solution for a wide range of glass compositions if focusing to compact construction due to high specific melting capacity, lowest energy consumption, stable and high glass quality, low emissions as well as comfortable operation.