Laboratory Scale Experiments on the Production of Precipitated Calcium Carbonate from Steelmaking Slag via Spray Carbonation

This study investigates a new concept of producing precipitated calcium carbonate (PCC) from steelmaking slag and carbon dioxide via a spray carbonation process. The presented laboratory-scale spray carbonation test reactor uses a spray nozzle to disperse fine droplets of a Ca-rich solution into a spray tower, where calcium carbonate precipitates as a result of the reaction between calcium and the counter flowing CO2 gas. Beside the spray carbonation experiments with the laboratory-scale test plant, a spray analysis was conducted to determine the droplet size of different spray nozzles. This work also presents a comparison between the original X2PCC process and the proposed spray carbonation process and tries to identify its shortcomings and advantages. The feasibility of PCC production from steel slag via spray carbonation was successfully demonstrated at the laboratory-scale. Experiments were conducted at pressures of 5 and 10 bar using nozzles with different capacities and spray angles. All experiments succeeded in producing PCC in the form of rhombohedral calcite with a size of 22.86 to 66.98 μm. The calcite content of the produced PCC was between 80.43 and 96.59 %. Droplet collisions and depositions on the spray tower wall were found to play an important role when trying to produce PCC of a certain size. Experiments also show that it is possible to produce smaller PCC particles with the spray carbonation process compared to the conventional X2PCC process, which makes it a potential alternative and a promising research area in the future.