Carbonation of BOF Slag in a Rotary Kiln Reactor in View of the Scale-Up of the Wet Route Process

Carbonation of alkaline residues represents a potentially interesting technique for permanently storing in solid form CO 2 contained in flue gas, syngas or biogas, as well as for the valorization of the residues. In particular, the wet carbonation route requires a low amount of water, does not generate wastewater and can be exploited to produce aggregates. The efficacy of this route has been demonstrated at laboratory scale. In view of its scale-up, this study was aimed at evaluating the performance of a wet-route carbonation process applied to Basic Oxygen Furnace (BOF) steel slag employing an operating procedure that could be adopted also at demonstrative or full scale. Dry residues were directly fed by a loading hopper into a rotary kiln reactor, in which gas containing 40% CO 2 and steam were flown through. During the experiments, the flow and composition of the gas phase were continuously monitored, allowing to calculate the amount of CO 2 captured from the gas phase and to compare it with the CO 2 uptake of the solid product. In addition, the leaching behavior of the treated slag was assessed. The results of the tests were close to those obtained in previous experiments performed with pre-humidified BOF slag, both with the same reactor used in this study and at laboratory scale; this suggests that this more automated wet-route process could be employed for demonstration or full scale tests. The set up still needs to be optimized to obtain a product with physical and technical properties suitable for use as aggregate. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13140, 2019.