Carbon dioxide reduction is an important problem for steel industries. Steelmakers in Japan are trying to reuse and recycle waste energy and resources. Slag is a potential resource of energy and materials because it contains a lot of elements and is at the high temperature of around 1 500°C when exhausted.The RCA (Rotary Cup Atomizing) method is a popular process in the slag atomizing method. However, when there is a slip between the slag and cup, the energy of cup rotation is not used effectively. In the present study, we developed a rotary cylinder atomizing (RCLA) method that can efficiently use the rotation energy for atomizing the molten slag. Two kinds of RCLA were developed and the slag atomizing behaviors were investigated.The minimum diameter of the slag particle was from 10 to 50 % of the nozzle diameter. The obtained slag particles were amorphous spheres having high sphericity. The higher rotation speed and smaller nozzle diameter could make smaller particles.

Slag is a potential resource of energy and materials because it contains a lot of elements and is at the high temperature of around 1 500°C when exhausted.In the previous study, we developed a rotary cylinder atomizing (RCLA) method that can efficiently use the rotation energy for atomizing the molten slag. The minimum diameter of the slag particle was from 10 to 50 % of the nozzle diameter. The obtained slag particles were amorphous spheres with high aspect ratios. The higher rotation speed and smaller nozzle diameter could make smaller particles. In the present study, the mechanism of slag particle formation from spouting slag string through the nozzle was investigated using the high-speed camera and the theoretical approach was performed.The slag was string-shaped when spouted from the nozzle. The relationship between the particle diameter (d) and nozzle diameter (2a) was derived as follows:Where r is density, L is the distance from the center of rotation to the tip of the slag string, Z is rotation speed and g is surface tension of slag.The flow rate of slag was evaluated using Hagen-Poiseuille's equation and the relationship between the particle diameter and the slag string diameter was obtained using Weber's equation. By comparison between the experimental and calculated results, we concluded that a string diameter of 0.2 mm for a 1.3 mm nozzle diameter was adequate in this experiment.KEY WORDS: mechanism of slag atomizing; slag recycle; amorphous slag; rotary cylinder atomizing.

No abstract