Abstract: Granulation of liquid steel slag is the key process during heat recovery.The structure of gas nozzles and their layout should be designed to ensure solidification of slag drops before they falling to the ground.The flow field of gas jet with different structure was simulatd by Fluent software,and the simulation result was compared with that of cold model test.It was concluded that the combined laval-nozzle could provide concentrated and lower-expansion gas jet,and utilized to granulate liquid steel slag by gas quenching.The gas jet out of the combined laval-nozzle could be syncretized and stabilized at 250,265 and 300 mm,repectively,when the Mach numbers of laval-nozzl were 1.0,1.4 and 1.75.Consequently,the liquid steel slag could be granulated to drop and fly steadily when these combined laval-nozzle was utilized.The gas jet velocity at exit increased with the increase of Mach numbers of nozzle.Moreover,the gas jet temperature at exit declined,which could be beneficial to cooling slag drops.