The key step to cause the granulation of gas quenching molten slag is the granulated liquid slag droplet quick cooling and solidifying

and during slag droplet cooling process the main manners of heat transfer are convection and radiation. Based on established mathematical model for slag droplet cooling process

the rule of effect of radiation on slag droplet cooling process is emphasized studied by 4th order Runge-Kutta method. Results show that the slag droplets cooling are undergoing three phases including liquid phase cooling and nucleating

release of latent heat

and solid phase cooling； as the heat transfer through radiation is ignored

it takes 606 ms for temperature of slag droplet (/% : 29. 94FeO

2. 05 Fe

2

O

3

42. 18CaO

9. 33MgO

15. 92SiO

2

2. 09MnO

1. 25 Al

2

O

3

2. 24P

2

O

5

) in nitrogen at 293 K decreasing from 1 723 K to 1 073 K

as compared with that considering the cooling time simultaneously by convection and radiation

it increases by 17. 2%. The results indicate that in calculating cooling rate of slag droplet the heat transfer through radiation can not be ignored.