Metal production is one of the most energy-intensive industrial sectors. At the same time, climate change, scarcity of raw materials, decreasing landfill capacities and considerable disposal costs are leading to increased interest in innovative recovery concepts for secondary raw materials from iron and steel production. However, the processes for recovering metals and other valuable materials are complex.
Hydromallurgical processes
Pyrometallurgical processes separate metallic from non-metallic materials at high temperatures of 800 to 1,500 degrees Celsius. The mass melts to form an alloy containing the desired metals such as iron, chromium, nickel, zinc and others. Further processes are required to separate these valuable materials. This consumes a lot of energy. Less energy is required for the hydrometallurgical process. Here, the metallic source material or dust is immersed in acid to dissolve metals. Further processes such as electrolysis can be used to separate and purify the metals.
“We need to improve the technologies and think even more about circular engineering solutions so that we can overcome the challenges facing the domestic industry,” emphasized Helmut Antrekowitsch, Vice Rector for Research and Sustainability at Montanuniversität Leoben. “Andritz is working hard to ensure that by-products from metal production are not seen as waste, but as a resource and an opportunity. To do this, we need the strong university units to help us drive forward the circular economy through innovative, sustainable solutions,” said Arthur Stingl, Senior Vice President Processing Lines and Strip Furnaces at Andritz. Over the past two years, the Graz-based technology group has been researching energy-efficient hydrometallurgical recovery of valuable metals together with the Chair of Nonferrous Metallurgy at Montanuni Leoben, the K1-Met competence center and voestalpine.
Hydrochloric acid wins the race
The first step was to characterize the dusts from stainless steel production. “We then evaluated which of the various leaching media – including hydrochloric acid, acetic acid and citric acid – works best to recover chromium, nickel and zinc from the steel mill dust,” explained Stefan Steinlechner, project manager from the Chair of Nonferrous Metallurgy. Hydrochloric acid won the race. “In the course of the experiments to optimize the extraction, it was shown that extraction rates of around 70 percent could be achieved for chromium and over 95 percent for zinc and nickel,” Steinlechner explained. He named the evaluation of economic efficiency and upscaling as the next steps.
“We don’t just talk about green technology, we live it,” emphasized Willibald Ehrenhöfer (ÖVP), State Councillor for Economic Affairs and Research. As part of the “Green Tech X” tender, the Styrian Future Fund (Province of Styria), the Austrian Society for Metallurgy and Materials (ASMET) and individual industrial companies (voestalpine High Performance Metals, Marienhütte, Andritz, Primetals Technologies and Saubermacher) have made a total of EUR 2.5 million available for the years 2022 and 2023 to promote projects in the field of the circular economy and climate protection.
It was also announced on Tuesday that Andritz has started up another shoe press at Lee & Man Paper, Malaysia. The press is integrated into a packaging paper machine and is already the ninth shoe press that Andritz has supplied to Lee & Man Paper. According to the Graz-based company, it leads to considerable energy savings, improved machine runability and better strength of the end product.
[Source: APA-Science, 06.05.2025]
