Reducing steel industry waste through nickel recovery
Stainless steel is one of the most ubiquitous materials in the modern world, playing an essential role in manufacturing, construction and other sectors. Home to one of the largest steel industries globally, the European Union is at the forefront of efforts to make steel production more efficient, less wasteful and more environmentally friendly.
© tajcikvk - fotolia.com
Working in the EU-funded RECONI project, steel industry researchers have sought to resolve one of the key environmental and resource issues linked to stainless steel production: the nickel-containing waste that usually ends up in landfills.
Generated by metal pickling processes that use strong acids to remove scale from the steel surface, thousands of tonnes of nickel-containing waste are disposed of in European landfill sites each year. This constitutes a lost resource and opportunity for steel manufacturers: the more than 2 500 tonnes of nickel wasted by the stainless steel industry in Europe annually is worth around €25 million at current prices. “The aim of RECONI was to find a technically feasible way to recover nickel from the liquid and solid waste generated by steel pickling processes,” says Andreas Bán, the project coordinator at VDEh-Betriebsforschungsinstitut (BFI) in Germany, a leading European provider of application-focused R&D in the field of steel-making technology.
In collaboration with industrial and research partners from Germany, Italy and Sweden, Bán and his team developed and tested processes to separate nickel from acid sludge and to enrich and refine the metal so that it can be reused in stainless steel manufacturing.
“Liquid or solid pickling waste contains up to 1% nickel. Various hydrometallurgical processes therefore have to be combined and adapted to extract the nickel, concentrate it and refine it,” Bán explains.
In laboratory tests and subsequently in pilot plants the RECONI researchers experimented with various techniques to obtain usable nickel, including leaching to dissolve nickel from the sludge, solvent extraction to remove most non-nickel substances, and a method called ‘electrowinning’ in which electrical currents are passed through a liquid solution to extract the metal. Using another processing technique, the nickel is ‘precipitated’ and compacted into briquettes.
The metallic nickel as well as the briquettes can then be recycled in metallurgical melting plants and reused in stainless steel manufacturing.
Different processes were developed for nickel recovery from liquid waste and solid waste, with varying degrees of performance.
“The comparison of the two processes shows that the nickel recycling from liquid waste is more efficient than from solid waste. Therefore, nickel recovery from liquid waste could be economically viable,” Bán says.
The RECONI project partners are continuing to develop and refine the liquid waste procedure. Meanwhile, the technology developed in RECONI continues to be put to use by BFI, which has received national funding in Germany for a project to recover nickel from landfill waste.
“Every year about 700 000 tonnes of nickel are used across different industries in the EU, and around 24 000 tonnes of that is wasted,” Bán says. “With the processes we developed, a substantial part of that nickel waste could be avoided.”