Zinc is one of the most important metals in our society, with the main application being in the corrosion protection of steel. However, zinc also plays an important role in the production of rubber, ceramics and fertilizers. The growing global demand for zinc in 2024 was around 17 million tons, of which Europe accounts for 2.4-2.7 million tons. The emitted CO2 equivalent is 2 tons per ton of primary produced zinc and only about 27% of the European demand for zinc-containing ore is provided by mining areas in Europe. In addition, due to impurities in the ore, large quantities of problematic slag must be dumped in primary zinc production. Only a small proportion of the zinc demand can currently be met by recycling end-of-lifetime products.
By partially replacing primary zinc by extracting zinc from dust from secondary steel production and slag from lead smelters, all these problems of primary zinc production can be addressed. Unfortunately, current extraction technologies for these residues have significant disadvantages, such as selective extraction of zinc without consideration of other valuable ingredients, which hinder this recycling. Also, currently applied recycling processes operate with fossil carbon, resulting in a high CO2 footprint, which is contrary to the goals for sustainable development. Therefore, the aim of this research project is to develop a biochar-based recycling technology in the first step, which can be converted to hydrogen-based in the next step.
Figure 1: Zinc and iron extraction technology for steel mill dust. The dusts are initially agglomerated into larger pellets which, after drying, pass through a pre-evaporation stage before the zinc oxide is separated in the reduction unit. For molten residuals of lead plants only the treatment in the reduction furnace is necessary.
The present research into zinc recycling technology focuses on a range of topics from reducing energy consumption and CO2 emissions to minimizing waste and environmental pollution. The holistic approach includes both the optimization of existing production processes, and the development of innovative processes based on renewable energies. The dedicated team of scientists and students at Montanuniversität Leoben is striving to make zinc production more efficient and environmentally friendly.
At EVT, detailed material and energy flow models of the process route are developed based on detailed process analyses. These models enable technology development in the direction of improved internal waste heat utilization, increased efficiency and reduction of CO2 emissions. In the next step, economic boundary conditions such as investment costs and energy market situations are considered in order to design energy flexibilities and investigate the interplay between efficiency and costs. Based on this, various technology design options can be evaluated in terms of their investment risks, CO2 reduction potential and application locations.
For more information, please visit the website: greenzinc.at/en/.
Figure 2: Methodological steps in the analysis of the zinc recycling and extraction process performed at the Chair of Energy Network Technology
Project Partner:
The COMET- project Green Zinc is funded by COMET – Competence Centres for Excellent Technologies through BMK, BMAW, Standortagentur Tirol, Kärntner Wirtschaftsförderungs Fonds, Steirische Wirtschaftsförderungsgesellschaft m.b.H. and the Province of Styria. COMET is managed by FFG.
