Film flow characteristics of molten slag on rotary disk atomizer at commercial scale and implications for slag granule production

Centrifugal-granulation-assisted thermal energy recovery (CGATER), which produces small, hot granules from bulk molten slag for further waste-heat recovery, has emerged as a promising route to treat high-temperature molten slag in the iron and steel industry. However, scaling up CGATER remains challenging due to limited granulation data at the commercial scale. One viable solution is to approach the slag film flow characteristics by modeling and, thus, infer the granulation performance. Herein, we carried out the first computational fluid dynamics modeling of the film flow on the atomizer at the commercial scale, as enabled by the newly developed multiphase, heat transfer model. Orthogonal cases were set for modeling to systematically understand the effects of operation parameters and thermophysical properties on film flow. It is found that heat transfer affects the total film thickness by up to 220.1% but only has a minor effect on the liquid film thickness (13.4% on average). The rotary speed proves the most effective way to adjust the thin liquid thickness at the commercial scale. A cross-validation was implemented to evaluate the correlations comprehensively, which highlights the acceptably good accuracy of our correlation by R2 = 0.85. Finally, we quantified the correlation between the slag film thickness and the slag granule size, enabling fast yet accurate prediction of the centrifugal granulation performance. This work not only explores the film flow characteristics of molten slag at the commercial scale for the first time but also provides a rational pathway to predict granulation performance for the scale-up of CGATER technology.