Numerical Simulation Of Blast Furnace Slag’s Dry Centrifugal Granulation

Blast furnace slag (BF slag) is the main by-product of ironmaking process and has greatrecycling utilization value. At the present the main treatment method of BF slag is waterquenching which not only can’t recover the sensible heat efficiently, but also waste water andpollute the environment with harmful gas. With its own characteristics, dry granulating processcan overcome these shortcomings, and therefore, more and more attentions are paid to it. In thisexperiment, a gas-liquid flow mathematical model of the blast furnace slag is established. Thenumerical simulation and calculation of centrifugal granulating process is done and the influenceof process parameters includes rotary speed, slag temperature, slag flow rate, surface tension,surface roughness of the rotary part, the shape of the rotary part. The results show that:(1) When the rotating speed is slower, the diameter of the granulated slag decreases rapidlywith the increased rotating speed. However, when the rotating speed is faster than a critical value,the diameter varies very slow, even approaches to a constant, indicating that to obtain fine slagparticles,3000rpm is optimum rotating speed for granulation process in this case.(2) Increasing molten slag temperature can reduce its viscosity and improve granulationeffects. When the temperature exceeds1400℃, the slag viscosity and granulation process areinfluenced slightly with the increasing of the slag temperature.(3) A bigger surface tension increases molten slag internal force, leads liquid slag to behardly broken and aggravates granulation process. The slag is subject to greater friction andeasily broken with larger disk surface roughness.(4) Cup and grooved disk is better than flat disk on granulating, but they are expensive anddifficult to be manufactured. Thus, flat disk is more suitable for industrial applications.At the same time, owing to bigger slag flow, granulating more slag in unit time and drycentrifugal granulating effects meeting the needs of recovery, the numerical simulation andcalculation of BF slag’s dry centrifugal granulating process under the industrial scale is studiedin this experiment. The results show that:(1) During the granulating process, smaller average diameter of slag particles can beobtained with a higher slag temperature, a higher rotate speed and a larger diameter of the disk.(2) The factors affecting the cooling rate of the slag particles are given below with adescending order: the diameter of the slag particles, wind speed, thermal conductivity and thecooling medium temperature. During the granulating process, the smaller the diameter of the slagparticles and the higher the wind speed and the higher the thermal conductivity, the higher thecooling rate of the slag particles.(3) The cooling rate of the slag particles is not a constant. It is fast during the early stage ofthe solidification and slows down thereafter.