EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

Although its chemistry rich in valuable raw materials: carbon content up to 60% and iron content of up to 30 %, blast furnace sludge cannot be recycled into the sintering process, because of its Zn content which is detrimental for Blast Furnace operation. Without an economically viable solution to the problem, millions of tonnes of sludge goes to landfill, creating costs for steelmakers who are grappling with increasingly stringent environmental regulations around waste management. Hydrometallurgy allows the selective removal of Zn and Pb from the sludge, which can then be recycled at the sinter plant and the heavy metals can be sent to the zinc industry for recycling and reuse. After concluding laboratory tests, one small pilot unit designed by Paul Wurth was used to assess the feasibility of the process a bigger scale. The pilot tests have successfully demonstrated the feasibility of hydrometallurgy treatment for various types of blast furnace sludge. Both concentrates (carbon/ iron and zinc/ lead) produced during hydrometallurgy process met the technical and chemical requirements needed to recycle. For carbon and iron concentrate recycled to the sinter plant, Zn content remains generally below 0,3% and the lead below 0,1%. From an environmental perspective, the results showed that the air pollutants and effluent water from the process after treatment remain below the legal requirements.