Researchers at TU Bergakademie Freiberg are testing how glass can be produced without carbon-containing raw materials. As a replacement for the carbonate raw materials, they are testing the use of oxidie or hydroxide raw materials in a new research project.

If the tested methods find usage, carbon dioxide emissions in the container and plate glass industry could be significantly reduced.

In addition to recycled shards, glass has so far been produced from sand, sodium carbonate (soda) and calcium carbonate (lime). When heated, these carbonates form the corresponding oxides and thereby release carbon dioxide. The oxides react with one another at temperatures of up to 1.550 degrees Celsius and form a vitreous melt.

But why are the carbonate-free raw materials not already being used in the glass industry? "The oxidie and hydroxide raw materials tend to collect dust in the so-called glass melting tank and cake beforehand during storage. This makes handling the mixture more difficult,” explains Dr. Khaled Al Hamdan, a research associate at the Institute of Glass and Glass Technology at the TU Bergakademie Freiberg. The researchers are now investigating how the process can be optimised to minimise caking, sticking and dust-collecting in the new research project.

Further reduce emissions through the use of fine cullets

In addition, the team is testing how the proportion of waste glass, in particular fine cullets, can be further increased in the process using the oxide or hydroxide raw materials. "If fine cullets are used, the melt in the glass tank trough tends to foam. We suspect that the carbon-free, alternative raw materials reduce this tendency to foam and therefore allow a higher proportion of fine shards, ”says Dr. Khaled Al Hamdan.

Over the next 18 months, the researchers plan to carry out the new process in a laboratory-scale test facility as well as at the industrial partners involved. If the tested measures for decarbonisation in glass production prove to be suitable, about 0,66 million tonnes of carbon dioxide could be saved in the future. This is roughly equivalent to the average annual turnover of 137.500 people. Due to the increased use of fine cullet, valuable primary resources can be conserved and the CO2- emissions associated with the melting process can be further reduced.

Background: Research project funded by the German Federal Environmental Foundation

The Deutsche Bundesstiftung Umwelt is funding the new research project at the TU Bergakademie Freiberg and the Technische Hochschule Nürnberg Georg Simon Ohm (Prof. Dr. Ing. Sven Wiltzsch) with a total of 346.000 euros. Project partners from the glass industry and plant construction are Glashütte Freital GmbH and Zippe Industrieanlagen GmbH.

Fragen beantwortet / Contact: 
 Dr.-Ing. Khaled Al Hamdan,

Researchers in front of a furnace in the experimental facilities for glass technology. Photo: TU Bergakademie Freiberg / D. Müller