Possibilities and limitations in wet processing of fine IBA
Jonas Boehnke, M.Sc., Sepro Mineral Systems Corp., Canada Gerhard Stockinger, M.Eng., Bran
A recent trend in wet processing of incinerator bottom ash is complemented by the development of a fine ash treatment module for size fractions < 2mm. Options for the extraction of the fine size fractions in both wet or conventional dry process plants is presented and the economical, environmental and health & safety aspects of extracting and processing the fines are discussed. Ash samples are exceptionally heterogenous in their composition and this particularly applies for precious metals. Particle shapes also play a significant role in the selection of suitbale recycling technology. Comprehensive testwork in laboratory scale has identified a compatible gravimetric separation route and it is explained why only a combination of multiple devices satisfies the diverse requirements to produce a marketable heavy non-ferrous metal product. The diverse metal composition and potential precious metal „nugget effect“ poses a sampling challenge. To enhance the confidence level in sampling, pilot scale tests can be considered, for which a practical and cost effective concept is presented. Experience from laboratory and prototype operations has shaped the process and led to the successful launch of a commercial scale plant at Brantner Oesterreich GmbH‘s operation in Austria. Operating data from 2018 allows for a comparison between laboratory experiments and plant operations, which can be applied for scale-up calculations in similar projects.