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The principle of a batch preheater for float glass manufacture is virtually identical to that used in container manufacture. The preheater is also modular, but is generally designed for a much higher tonnage as float glass furnaces usually have melting capacities of 600 t/24 h or more. Energy savings of more than 10 % would revolutionise the process and offer a significant improvement in efficiency compared with current heat recovery systems that produce electricity.
One major difference in comparison with systems for container glass applications is the much lower cullet content used. Container operations may melt 80 % or even more cullet with only 20 % or less batch. The situation in float manufacture is almost exactly the opposite, with cullet contents of 15 % or less being common. The prevention of clumping is therefore very important for this type of production, and additional vibrators are provided for this reason. The low cullet content does have one advantage – mechanical wear on the equipment is greatly reduced as this is mainly produced by cullet.
The heat exchangers are also manufactured from special materials to eliminate contamination by unwanted elements such as iron and nickel. Highly transparent and very thin glasses in particular place special demands on the purity of the batch.