| 摘要 |
Tunnel furnace for foaming glass material, comprising heating elements chosen among electrical and gas based heating elements. The tunnel furnace comprises at least the following temperature zones: a preheating zone ( 8 ) suitable for heating the feed material to a temperature in the range 400-900° C. and a foaming zone ( 9 ) suitable for heating the glass material to a temperature above 900° C. The furnace also typically comprises a cooling zone ( 10 ) suitable for reducing the temperature from the elevated temperature in the foaming zone. According to the present invention the preheating zone ( 8 ) is at least 15% longer than the foaming zone ( 9 ).
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