Introduction

Calumite is a glassy calcium-alumino-silicate, produced from granulated blast furnace slag. Calumite offers similar benefits to cullet with the additional benefits of a refining agent.

Calumite is used in all types of soda- lime-silica glass production and is used in all glass colours at between 1-4% (of dry sand weight) in extra clear flint and up to 30% in amber glass.

Benefits of Calumite

CO2 Reduction - Limestone and dolomite is partial replaced, reducing process CO2 emissions by up to 400 kg per tonne of Calumite used. Combustion CO2 savings are also seen with savings of up to 300 kg per tonne of Calumite used.

Energy Saving - Calumite is 99% glass so behaves in a similar way to cullet with the associated energy saving benefits. Typically, between 0.25% and 0.36% energy savings per 1% Calumite addition. Calumite can also be used to reduce furnace temperatures or increase furnace pull.

Glass Quality - Improvements in glass quality are always seen when Calumite is introduced with seed reduction of up to 70% seen due to the fining process starting earlier in the furnace melt. Improved redox control and amber colour stability are also seen.

Batch Simplification - Calumite can remove the need for multiple raw material sources whilst improving colour stability and defect levels.