Float glass production

The most important raw material for the production of float glass is quartz sand, a material that is abundant in nature and will be available in sufficient quantities for future generations. Soda, dolomite (lime) and other raw materials are needed in small quantities. To improve the melting process, approx. 20 % clean glass shards are added to the mixture. These raw materials enter the melting furnace as a mixture and are melted there at a temperature of approx. 1550 °C. The liquid glass is added to the float bath of liquid tin. On the molten tin the glass mass "floats" in the form of an endless band. Due to the surface tension of the glass and the flat surface of the tin bath, a plane-parallel, distortion-free glass ribbon of high optical quality is formed. In the cooling tunnel and in the subsequent open roller conveyor, the glass strip is continuously cooled from 600 to 60 °C, checked for defects by laser and then cut to glass sheets of 6000 x 3210 mm.

 

Scheme of the float glass production

Scheme of the float glass production

1 Batch input

The batch is weighed and filled fully automatically. Depending on the size of the tank, up to 12,000 t of raw materials are filled in every day.

2 Smelting

Melting of the mixture in the tank at a temperature of 1550 °C. This is followed by the refining zone, which leaves the glass at 1100 °C. The melting tank contains up to 1900 t of glass at all times.

3 Float bath

The liquid glass is transferred to a bath of liquid tin. By adapting the lower surface to the completely flat surface of the tin bath and simultaneously heating from above (fire polishing), plane-parallel glass is obtained similar to the mirror glass. The glass thickness is adjusted with so-called top rollers, whereby the equilibrium thickness (= glass thickness, which is adjusted without external intervention) is 6 mm. For a smaller glass thickness, the viscous glass mass must be accelerated, for a larger glass mass, it must be decelerated.

4 Cooling area

After leaving the tin bath, the glass ribbon enters the more than 100 m long annealing furnace. It is cooled from approx. 600 °C to 60 °C. The slow and controlled cooling ensures stress-free solidification of the glass mass. This is important for smooth further processing.

 

 

Project Managment

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