Float glass furnaces are the largest type, both with regard to dimensions and to the overall melting output. These furnaces are close to the limit of constructive possibilities. Furnace capacities are usually between 600 – 800 t/d. Of course smaller units with 250 t/d are as possible as larger units up to 1200 t/d.
Float glass furnaces are especially designed for the production of soda lime glass. The requirements concerning glass quality are much stricter and differ from those for container glass.
Float glass furnaces are usually cross fired furnaces. The regenerators, port necks and burners are arranged laterally. For each port neck there is a separate regenerator
chamber together with a slide at the flue gas channel. This allows precise control of the furnace temperature over the entire length of the melting furnace. The firing is usually facilitated with underport burners. Oxyfuel burners installed in the sidewall near the charging zone are called zero-port boosting. This is a measure to increase melting capacity without enlarging the regenerator structure.
Float glass furnaces are constructed as open furnaces. A clear separation of the hot melting part and refining part and of the working end is not possible. This would lead to optical defects in the glass. Since the throat does not exist, it is merely one furnace which is very large. Instead of the throat there is a neck, where also coolers are installed, ensuring the perfect temperature for the subsequent float process. The float process itself starts, when the glass leaves the furnace at an overflow and entering the tin bath.
The adequate furnace insulation and optimal flow profile of the combustion air as well as efficient preheating of the combustion air allow the operation of the furnace with minimum energy consumption. The furnace size is designed in such a way that it produces top-quality glass with the lowest possible energy consumption.