(Mainz / Germany) – Mainz-based Schott AG has, for the first time, melted optical glass using hydrogen in a large-scale experiment. "The test with 100 percent hydrogen in the field of advanced optics is pioneering work for the specialty glass industry," says project manager Lenka Deneke.
If the tests showed that the quality was correct and the glass properties remained unchanged, hydrogen would be a suitable technology option for Schott. © Schott AG
The quality of the glass will now be analyzed. If the tests show that this is true “and the glass properties remain unchanged, hydrogen would actually be a suitable technology option.” So far, Schott has been carrying out its tests with gray hydrogen because green hydrogen from renewable energies is not yet available in sufficient quantities. Schott had already tested glass production with 100 percent hydrogen on a laboratory scale last spring. The experience gained with initially up to 35 percent hydrogen by volume “helped a lot” with this year’s project, emphasizes the experiment manager.
Effects of hydrogen on glass quality
However, there are still many open questions for research, such as how hydrogen affects the complex melting processes and the quality of the different products. The problem of infrastructural adaptation must also be solved in order to replace natural gas with hydrogen.
Inspection of a glass bar: The quality of the glass is analyzed during the large-scale experiment. © Schott AG
According to its own information, the group produces over 100 types of optical glass for various areas of application, such as consumer goods and measurement technology, but also optical systems in research and development. The challenge is that “the glasses must have the highest homogeneity and transmission properties”. This also applies to the currently melted glass. If it meets the product requirements, it goes to the customers. “We would then have confirmation that the use of 100 percent hydrogen instead of fossil energy delivers the same quality under industrial conditions,” says Deneke. For a permanent change, further long-term tests would be needed, as well as a continuous supply via a hydrogen pipeline. Only then would the group have taken “another important step towards its strategic goal of climate-neutral glass production by 2030”. Schott has already achieved the switch to 100 percent green electricity and energy efficiency is being continuously and systematically increased.
Tests for several years now
In recent years, Schott had already tested glass production using 100 percent hydrogen on a laboratory scale . For example, in 2021, the melting of three different types of glass using hydrogen was tested over an eight-week period. The result: When firing with hydrogen and oxygen, a similar burner output and temperatures were achieved as with the conventional process using natural gas and oxygen. The quality of the glass was also similar to that of conventional glass. That this would work was not a given, as natural gas cannot simply be substituted for hydrogen. The two gases combust with different reactions.
The following year, Schott, together with the Mainz municipal utility company, launched a pilot project to test the large-scale use of hydrogen in glass production. The largest share of Schott's high energy consumption and CO2 emissions arises from the melting process. Temperatures of up to 1.700 degrees Celsius are required to produce specialty glass for vaccine vials, mobile phone screen protectors, or microchips.
Replace natural gas
The technology change is primarily about replacing natural gas for operating the melting tanks. Either through electrification with green electricity or, in the future, with green hydrogen. However, hydrogen produced with renewable energies is currently still in short supply. “We consciously decided to use it so as not to waste any time testing the technical feasibility,” says Schott CEO Frank Heinricht. “This is sufficient for our experiments, but we urgently need green energy for climate protection.”
Photos
Schott has produced optical glass with 100 percent hydrogen for the first time: a look into the melting tank with liquid glass heated to up to 1.700 degrees. Optical glass is used to manufacture components for commercial, industrial and scientific applications such as microscopy, photography or astronomy. © Schott AG
