Experimental visualization and theoretical analysis of the dynamic impact behavior of a molten blast furnace slag droplet on different surfaces

Highlights: • Experiments are used to investigate the dynamic behavior of slag droplet impact. • The special impact phenomena of molten slag droplets are observed and analyzed. • The effect of the wall materials on the impact process are discussed. • The formulas of the maximum spreading factor and the residence time are determined. -- Abstract: In blast furnace slag dry centrifugal granulation heat recovery systems, the impact of a molten slag droplet on a solid surface is unavoidable because of the device restrictions. To predict the molten slag droplet deposition, the dynamic impact behavior of a high-temperature slag droplet on a solid surface was studied by performing visualization experiments, and the quantitative analysis was analyzed based on the experimental results. Refractory cement and stainless steel were examined as surface materials, and the experimental results from these two surfaces were compared. The droplets spread over a larger area of the refractory cement surface than the stainless steel surface. The refractory cement eroded, and the stainless steel was determined to be a suitable wall material for blast furnace slag dry centrifugal granulation heat recovery systems. On impact, the droplets spread farther if the surface roughness was smaller or if the droplet temperature was higher. A semiempirical model was developed to predict the maximum spreading factor from the initial parameters of the slag droplet. The error of the semiempirical model is within 10%, over a range of Reynold's numbers (33–110) and Weber's numbers (220–1301).