Field of Research

Zinc is one of the most important metals in modern society. Its use as a corrosion inhibitor for steel in particular makes it an omnipresent element of everyday life, with demand set to continue rising in the foreseeable future. In addition to its use as corrosion protection, zinc has other important applications in cast products and alloys, in the rubber, ceramics, and fertilizer industries, in pharmaceuticals, and in dietary supplements.

The demand for zinc in Europe is between 2.4 and 2.7 million tons per year. However, only about 27% of this demand can be met by primary production in Europe. This results in a high dependence on imports, especially from Asia and South America. Furthermore, the zinc content in zinc concentrates is generally decreasing, while iron contamination is increasing. This is leading to ever greater landfill problems.

Recycling offers a way out of this situation. However, remelting scrap metal only makes a small contribution of around 6% of demand. Due to its volatile nature, zinc is often found in economically relevant quantities as an oxide in the dust from steel recycling plants. In addition, slag from the lead industry also contains significant amounts of zinc oxide.
Such by-products have the potential to make a much greater contribution to European supply. Zinc from dust from the steel recycling industry and slag from the lead industry could cover around 20% of demand. However, the technologies currently available for processing have significant disadvantages: only zinc is recovered, even though other metals such as iron and lead are also present.

Enormous quantities of new residues are produced, amounting to up to 80% of the input material.
The processes currently in use are based on reduction with fossil carbon carriers, which results in a significant carbon footprint. Based on the current state of the art, in

Proposed solutions

One way to solve the problem of CO2 emissions is to use hydrogen. However, hydrogen is still expensive at present and the necessary technologies for its provision are lacking. A solution that can be implemented in the short term is the use of CO2-neutral biochar, which is comparable to fossil carbon carriers in many respects and could therefore be used in existing processes. However, the influence of its significantly higher reactivity and various impurities must be investigated.

Furthermore, it must be defined whether and how existing processes for the use of biochar need to be optimized. In this context, the possibility of slag optimization must also be considered in order to enable recycling in the construction industry and thus a zero-waste concept.