Detailed performance analysis of the wet extractive grinding process for higher calcium yields from steelmaking slags

Abstract

In this paper, the wet extractive grinding method for efficient recovery of calcium from steelmaking slags was studied. This work supports the Sustainable Development Goal of UN, SDG12: Responsible Consumption and Production by reducing the need for virgin limestone and aiming to circular solutions. The extraction is the first step in our pH-swing process, wherein CaO from the slag using a NH4Cl-water solvent is dissolved. After filtering the solid phase, CO2 is bubbled into the Ca-rich solution to produce precipitated calcium carbonate (PCC). Traditional mechanical mixing for extraction stage is found problematic since it requires energy intensive preliminary fine-grinding to be effective. Effects of the processing time (1.25–20 min), and the slag-to-solvent ratio (SLR = 30–120 g/L) were studied here in detail in the extractive grinding process. Inductively coupled plasma-atomic emission spectroscopy (ICP-OES), energy-dispersive X-ray spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses were used for the detailed physical and chemical characterization of raw and residual slag powders. Results showed that Ca-yield increases from 35 to ~70% via the EG process as comparison with mechanical mixing. Results also show that the rate of the process also significantly increased.