In the SAMEX project ArcelorMittal, Tecnalia and KU Leuven are upscaling an ammoniacal leaching-based flowsheet to remove and recover zinc from fine BOF steelmaking sludge, so that the residual sludge can be internally recycled to the Blast Furnace, via the sinter plant. However, fine BOF steelmaking sludge is just one of several by-products generated in a steelmaking plant. In reality the Blast Furnace, the Basic Oxygen Furnace and the Electric Arc Furnace generate a multitude of other types of slags, sludges and dusts.
Recently, an excellent review paper by Johannes Rieger and Johannes Schenk was published in the Journal of Sustainable Metallurgy. The paper provides a clear overview of the amounts of steelmaking residuals generated in Europe and describes several pyrometallurgical processes to valorise various steelmaking by-products.
These processes include the OxyCup® shaft furnace, the integrated DK recycling route, and the Befesa Waelz rolling tube furnace process in detail; these are operating state-of-the-art treatment technologies. The review paper corroborates that combined these processes can deal with a large fraction of these by-products.
BOF sludge remains a challenge
However, with respect to BOF sludge, the paper acknowledges that landfilling is still the dominant “utilisation” route (see Table 5 in the paper). This confirms the ambitious goal of the SAMEX project to develop a cost-effective, environmentally-friendly flowsheet to valorise fine BOF steelmaking sludge.
Abstract review paper
A circular economy is one of the important pillars of a sustainable iron and steel industry. Solid and sludgy residuals from steelmaking processes represent secondary resources with considerable amounts of valuable materials such as metals and minerals. Therefore, several treatment technologies for dusts and sludges target material recovery. The main benefits are a lower demand for primary resources and a reduced landfill volume as well as economic savings for steel plant operators.
The current review article gives an overview of the amounts of steelmaking residuals generated in Europe and describes the OxyCup® shaft furnace, the integrated DK recycling route, and the Befesa Waelz rolling tube furnace process in detail, which represent currently operating state-of-the-art treatment technologies in detail. Nowadays, European steel producers reach a byproduct recycling rate of up to 95% (including onsite recycling and residual utilization performed by external companies).
A benefit analysis was performed by several experts from Germany comparing different residual-treatment processes in terms of feed flexibility, product recovery, and material cycle closure. The study revealed that the OxyCup ® shaft furnace and the DK route are more favorable compared to the Befesa Waelz process. However, moderate effort is required to implement the Befesa Waelz process in an existing steelmaking process chain, which is one of the advantages of this technology.
Full reference paper
Johannes Rieger, Johannes Schenk, Residual Processing in the European Steel Industry: A Technological Overview, Journal of Sustainable Metallurgy, (2019) 5, 295–309, https://doi.org/10.1007/s40831-019-00220-2
More info about SAMEX?
SAMEX is an upscaling project funded under the ‘KAVA Call 6’, in the framework of the 'Innovation Theme’ No.3 of EIT Raw Materials Project Number 19205.
In SAMEX, AM, Tecnalia (TEC) & KU Leuven (KUL) will upscale an ammoniacal leaching process from TRL5 to TRL7. To do so, TEC, AM and KUL aim to check at pilot plant level the capability to treat AM’s Zn-rich, fine BOF sludge, generating a cleaned Fe-rich residue that can be internally recycled in the sinter plant (and fed to the BF) and a ZnS precipitate product that can be sold to the zinc industry, thereby providing a nucleus for industrial symbiosis.
The SAMEX flowsheet and the to be built pilot plant will consist of several units: (a) dewatering unit, (b) leaching reactor incl. air injection and NH3 regeneration, (c) solid/liquid (filter press) separation, (d) ZnS precipitation. The pilot plant will be used to test fine BOF sludges from different AM plants in Europe. As such, the SAMEX flowsheet is demonstrated and validated, allowing the replication of the flowsheet to a larger set of AM plants in Europe, who are thus the users of the SAMEX end results and provide the required market uptake.
SAMEX LinkedIn page: https://www.linkedin.com/company/37549689