Stabilization of Stainless Steel Slag via Air Granulation
In stainless steel production, slag from argon oxygen decarburization (AOD) converters is dumped on to the ground and then slowly cooled. The slag undergoes phase transformation from β-dicalcium silicate (β-C2S) to γ-dicalcium silicate (γ-C2S) at approximately 500 °C to 450 °C, resulting in slag volume expansion, disintegration, and dust generation. The dusty slag leads to challenges in material handling, metals recovery, and emissions control. Some operations use slag additives to stabilize slag, but this solution is expensive and can limit the end use of slag due to inclusion of toxic elements. Air granulation was hypothesized as a water-free method for stabilizing AOD slag via rapid quenching. Pilot-scale experiments at Sandvik Materials Technology (SMT) with silicon-reduced AOD slags confirmed that air granulation can produce products which are stable and dust free. Mineralogical analyses further indicated that these air-granulated stainless slags contained either no or low content of γ-C2S and are therefore stable.
KeywordsSlag Stainless Argon oxygen decarburization Dry granulation
The authors would like to thank Magnus Eriksson of Harsco and Lennart Johansson of SMT for their support during the execution of the trials. Fredrik Engström of LTU is gratefully acknowledged for support with XRD analysis.
Conflict of interest
The authors Lily Lai Chi So, Mahdi Mahdi, Janice Bolen, Johannes Nell, Isabelle Nolet, and Darryl Metcalfe, declare that there are also no conflicts of interest. The authors disclose their employment with Hatch Ltd., a worldwide leading consulting company which provides a wide range of technology-agnostic studies and engineering services, as demonstrated in their execution of a front-end-loaded engineering approach that often involves scaled testing and various studies to first establish project feasibility, taking into consideration various technology solutions, before making recommendations for full-scale implementation. Air granulation, the subject matter discussed in this paper, is one of various technology solutions being studied and recommended by Hatch Ltd. for slag-handling practices.
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