Solidification and heat transfer of an air-cooling molten blast furnace slag droplet is numerically simulated by the volume of fluid (VOF) method coupling with the solidification/melting model. The effects of droplet diameter and air velocity are investigated on the dynamic solidification evolution and heat transfer of the slag droplet

respectively. The results show that it is available for the air-cooling technique to realize fast solidification of the molten slag droplet surface

while non-uniform solidification evolution is found to occur inside the slag droplet. The solidification process of the molten slag droplet is expedited with decreasing droplet diameter and increasing air velocity due to the enhancement in the heat transfer. The optimum slag droplet diameter and air velocity should be comprehensively determined for a practical heat recovery system. As for a droplet with diameter of 0.5-2 mm at initial temperature of 1673.15 K

it releases the heat of solidification within 2 s under air velocity of 1-5 m·s-1

and the highest air outflow temperature as a result can reach above 900 K.