Thermal processing of waste material in a rotary kiln
Source: BAM
The melting of the steel in electric arc furnaces is a key process in steelmaking. This enables the production of stainless steels and the recycling of scrap. However, this process produces 10-20 kg of so-called electric arc furnace dust per ton of steel produced, which is deposited from vaporized or swirled-up substances from the furnace exhaust gas. Due to the high material throughput in the steel industry, the worldwide production of this dust adds up to 10 million tons per year. Depending on the input materials, it contains up to 50 % zinc as well as other heavy metals such as lead and cadmium. At present, this material can only be partially reprocessed with a high energy and carbon input or is often disposed in landfills. In contrast, the publication presents a process in which iron chloride solution, which is a by-product of titanium dioxide production, is added to the dust. This leads to the formation of heavy metal chlorides, which vaporize at significantly lower temperatures than the corresponding metals, making it possible to remove over 99 % of the zinc and other heavy metals such as lead, cadmium, and tin from the material in a more energy-efficient thermal process. This means that new products can be manufactured from two residual materials that are suitable for use in the steel and zinc industries. As the process has already been carried out at BAM in a rotary kiln, which is used in industrial applications in a similar design, the recycling process developed has the potential to be carried out on an industrial scale in the future. Based on the results presented in the publication, BAM is currently working on an industrial implementation of the process in a follow-up project together with the medium-sized recycling company Ferro Duo GmbH.
Selective removal of zinc and lead from electric arc furnace dust by chlorination–evaporation reactions
Christopher Hamann, Patrick Piehl, Eric Weingart, Dirk Stolle, Dominik Al-Sabbagh, Markus Ostermann, Gerhard Auer, Christian Adam
Journal of Hazardous Materials, Volume 465, 2024