2022 is the International Year of Glass. However, many glass factories are still struggling to survive, and high energy costs and considerable CO₂ emissions mean that glass production faces challenges in the future. Researchers at FAU and Technische Hochschule Nürnberg Georg Simon Ohm are currently conducting research to find a solution to make glass production more sustainable without relying on fossil fuels, their method is based on electric furnaces.
Dr. Dominique de Ligny, President of the FAU Glass and Ceramics Association, said, "We use glass in our daily life more than we realize, sometimes colored, sometimes transparent, because it has a variety of different functions, not only Used in windows, but also our smartphone screens, in storage tanks, in the rotating blades of wind turbines, or the production of lasers."
Producing glass requires a lot of energy. To produce glass, the various raw materials must be heated in a furnace at temperatures exceeding 1,600 degrees Celsius, which is achieved by burning natural gas, but in the process releases a lot of carbon dioxide. Rising natural gas prices mean glass factories are facing significant increases in manufacturing costs. At the same time, energy costs accounted for more than 40% of total costs, up from 14% before 2020, a trend that has brought several glass factories to the brink of closure.
Since 2020, Dr. Dominique de Ligny, together with Dr. Sven Wiltzsch from the Faculty of Materials Engineering at the University of Nuremberg, has been working on ways to make glass production independent of fossil fuels and more sustainable. One option is to heat the furnace with electricity instead of natural gas. To heat the raw material with electricity, electrodes are attached to the edges of the glass furnace, and electricity flows between the electrodes, transferring energy to the material and causing the material to start melting.
Professor Wiltzsch explained, "Imagine that in the future we will be able to use green energy sources, which will be more sustainable. The process will only release very small amounts of carbon dioxide, because the pure electric melting process does not involve any combustion and does not release carbon dioxide or things like carbon monoxide if you run the furnace on electricity, you lose less energy than when you convert hydrogen.
So the system is more efficient.”In their experiments, however, the researchers encountered a problem: Their method was not suitable for producing brown glass, which is critical for some uses. For example, brown glass is needed to store medicines and food because it protects the contents from UV rays.
Figure 1 The sustainable production of glass through electricity 1
The reason this method is not suitable for producing brown glass is the high oxygen concentration in the electric furnace. In a conventional furnace, the oxygen content in the atmosphere is low, but in an electric furnace, it is very high. The high concentration of oxygen in the furnace changes the chemical reaction at the atomic level, resulting in blue rather than brown glass. Nicole Ostermeier studied the special atomic properties of brown glasses in her bachelor thesis. She studied applied materials science at the University of Nuremberg and conducted research at FAU on why brown glass loses its color, and how the melting process changes when electricity is used.
"If we understand the effect of oxygen on glass color, we can also use electrodes to produce brown glass, making the entire glass production process more sustainable," says Prof. Wiltzsch.
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