Ecological awareness and responsibility, increasingly stringent environmental regulations and the more and more critical supply of raw materials make the application of new metal recovery processes a priority. Today the steel industry produces by-products, which are not fully valued. One of them is the sludge produced by the wet gas cleaning system of the blast furnace, with a high lead and zinc content.
Leaching: During this first step, zinc and lead are selectively leached from the BF sludge using hydrochloric acid under oxidising conditions. The leaching step results in a recyclable sludge, a pure iron carbon by-product that can be reintroduced at the sinter plant, replace a part of the anthracite amount, or returned in the form of briquettes directly back to the blast furnace.
Neutralisation: The subsequent neutralisation allows to produce a thoroughly washed Zn/Pb-concentrate that can be recycled in the non-ferrous industry. The remaining salty water that can be recycled internally or in the salt industry.
After successful laboratory tests and the feasibility of the technology being demonstrated at a mobile pilot plant, ArcelorMittal, in a co-development with Paul Wurth, decided to build in Dunkirk the first industrial CIROVAL plant designed for treating 15’000t/year of BF sludge.