Renewable glass manufacturing
Renewable Melting and Conditioning Technology Richard Stormont* outlines how Electroglass furnaces can meet renewable energy targets by improving energy efficiency, reducing emissions and using a hybrid energy approach.
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� Fig 1.The Fuel-Fired Furnace – high heat losses, low thermal efficiency.
� Fig 2. Primary sources of energy.
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lass melting is an energy intensive process. To convert mixed raw materials into melted and refined container glass requires a net energy input of about 2.4 GJ per tonne of glass, with no allowance for the thermal efficiency of the process used. In other words, no allowance for the inevitable heat losses. Melting recycled glass or cullet requires less energy, around 1.7 GJ per tonne or about 30% less than melting pure batch. Again, this takes no account of process heat losses. It is also difficult to meet today’s glass quality expectations using only cullet, meaning that very few products are made with purely recycled glass. It is possible to reduce the net melting energy requirements of our glass products. We can to some extent adjust compositions and the raw materials used to slightly lower the melting and refining temperatures required. We can use more cullet, perhaps accepting less than perfect product colour or consistency of colour. Both these approaches, raw materials adjustments and cullet use, can help towards the key objectives of reducing energy consumption, and conserving scarce raw materials resources. However, in terms of reducing energy consumption, far more can be achieved by focusing on the heat losses in melting processes. In the large majority of fuelfired furnaces, that produce most of the world’s glass, those losses are greater than the net melting energy required by the glass. In other words, the thermal efficiency of the process is less than 50% and in most cases far less. Even if a fuel-fired furnace is capable of operating at a peak thermal efficiency of around 50%, that figure reduces greatly as soon
� Fig 3.The Booster or Hybrid option. Continued>>
33 Glass International December/January 2022
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