Carbon sequestration via steel slag accelerated carbonation. The influence of operating conditions on process evolution and yield

A factorial study was conducted on steelmaking basic oxygen furnace slag to identify the individual and joint effects of total pressure, CO2 concentration in the gas phase and temperature on the CO2 sequestration yield through direct aqueous carbonation. The operating parameters were fixed at three levels according to a 33 factorial design, resulting in a set of 27 batch carbonation experiments. The carbonation performance and the changes in the mineralogical characteristics of the slag were investigated in detail. Large effects of the operating factors were observed for CO2 uptake, ranging from 6.7 to 53.6 g CO2/100 g slag. The analysis of the solid and liquid phases at the end of the carbonation treatment showed significant changes in the physical, chemical and mineralogical composition of the material. In particular, evidence was gained of other elements (Mg, Fe, Mn, Zn) in addition to Ca being intensively involved in the carbonation reactions, with a variety of carbonate phases being produced in addition to calcium carbonate forms. © 2015 The Authors.