Document Type

Article

Publication Date

9-2013

Keywords

mineral carbonation, stainless steel slags, carbon sink, waste valorization, mineralogy, heavy metal leaching

Abstract

This work explores the mineral carbonation of stainless steel slags in search for a technically and economically feasible treatment solution that steers these waste residues away from costly disposal in landfills and into valuable applications. Argon Oxygen Decarburization (AOD) and Continuous Casting (CC) slags prove ideal for mineral carbonation as their powdery morphology forgoes the need for milling and provides sufficient surface area for high reactivity towards direct aqueous carbonation. Experiments were undertaken using two methodologies: unpressurized thin-film carbonation, and pressurized slurry carbonation. The influence of process parameters (temperature, CO2 partial pressure, time, solids loading) on the slag carbonation conversion are investigated, seeking the optimal conditions that maximize the potential of the slags as carbon sinks. It was found that CC slag carbonates more extensively than AOD slag at essentially every processing condition due to differences in particle microstructure; still, it was possible to reach up to 0.26 and 0.31 g,CO2/g,slag uptake with AOD and CC slags, respectively, at optimal processing conditions via pressurized slurry carbonation. Mineral carbonation conversion was accompanied by significant reduction in basicity, as much as two pH units, and stabilization of heavy metals leaching, meeting regulatory limits (borderline for Cr) for safe waste materials re-use. Via quantitative mineralogical analyses, it was possible to differentiate the carbonation reactivity of several alkaline mineral phases, and to discern the preferential formation of certain Ca- and Mg-carbonates depending on the processing route and operating conditions. Slurry carbonation was found to deliver greater mineral carbonation conversion and optimal treatment homogeneity, which are required for commercial applications. However, thin-film carbonation may be a more feasible route for the utilization of slags solely as carbon sinks, particularly due to the elimination of several processing steps and reduction of energy demand.

Comments

5 August 2016: At the time of publication, Sheridan College author Rafael M. Santos was associated with the Katholieke Universiteit Leuven in Belgium.

Faculty

Faculty of Applied Science & Technology

School

School of Chemical and Environmental Sciences

Journal

International Journal of Greenhouse Gas Control

Version

Pre-print

Peer Reviewed/Refereed Publication

yes

Terms of Use

Terms of Use for Works posted in SOURCE.

Original Publication Citation

Santos, R. M., Van Bouwel, J., Vandevelde, E., Mertens, G., Elsen, J., & Van Gerven, T. (2013). Accelerated Mineral Carbonation of Stainless Steel Slags for CO2 Storage and Waste Valorization: Effect of Process Parameters on Geochemical Properties. International Journal of Greenhouse Gas Control, 17, 32-45. doi:10.1016/j.ijggc.2013.04.004

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