Numerical investigation of particle motion at the steel—slag interface in continuous casting using VOF method and dynamic overset grids

The capillary interactions are prominent for a micro-sized particle at the steel—slag interface. In this study, the dynamics of a spherical particle interacting with the steel—slag interface is numerically investigated using the volume of fluid method in combination with the overset grid technique to account for particle motion. The simulations have shown the particle’s separation process at the interface and successfully captured the formation and continuous evolution of a meniscus in the course of particle motion. A sensitivity analysis on the effect of different physical parameters in the steel—slag—particle system is also conducted. The result indicates that the wettability of particle with the slag phase is the main factor affecting particle separation behavior (trapped at the interface or fully separated into slag). Higher interfacial tension of fluid interface and smaller particle size can speed up the particle motion but have less effect on the equilibrium position for particle staying at the interface. In comparison, particle density shows a minor influence when the motion is dominated by the capillary effect. By taking account of the effect of meniscus and capillary forces on a particle, this study provides a more accurate simulation of particle motion in the vicinity of the steel—slag interface and enables further investigation of more complex situations.

Effect of basic oxygen furnace slag particle size on sequestration of carbon dioxide from landfill gas

The mineral carbon sequestration capacity of basic oxygen furnace (BOF) slag offers great potential to absorb carbon dioxide (CO2) from landfill emissions. The BOF slag is highly alkaline and rich in calcium (Ca) containing minerals that can react with the CO2 to form stable carbonates. This property of BOF slag makes it appealing for use in CO2 sequestration from landfill gas. In a previous study, CO2 and CH4 removal from the landfill gas was investigated by performing batch and column experiments with BOF slag under different moisture and synthetic landfill gas exposure conditions. The study showed two stage CO2 removal mechanism: (1) initial rapid CO2 removal, which was attributed to the carbonation of free lime (CaO) and portlandite [(Ca(OH)2)], and (2) long-term relatively slower CO2 removal, which was attributed to be the gradual leaching of Ca2+ from minerals (calcium-silicates) present in the BOF slag. Realising that the particle size could be an important factor affecting total CO2 sequestration capacity, this study investigates the effect of gradation on the CO2 sequestration capacity of the BOF slag under simulated landfill gas conditions. Batch and column experiments were performed with BOF slag using three gradations: (1) coarse (D50 = 3.05 mm), (2) original (D50 = 0.47 mm), and (3) fine (D50 = 0.094 mm). The respective CO2 sequestration potentials attained were 255 mg g−1, 155 mg g−1, and 66 mg g−1. The highest CO2 sequestration capacity of fine BOF slag was attributed to the availability of calcium containing minerals on the slag particle surface owing to the highest surface area and shortest leaching path for the Ca2+ from the inner core of the slag particles.