Granulation characteristics of molten blast furnace slag by hybrid centrifugal-air blast technique

Of the molten blast furnace (BF) dry granulation techniques that are currently employed, the centrifugal granulation technique is very promising owing to its simple and compact structure, ease of control, and low energy consumption. To better understand the mechanism responsible for the centrifugal granulation of molten BF slag, and to achieve high granulation performance, in the present work, we propose a hybrid technique that combines centrifugal granulation with blast air. We visualize the granulation evolutions under various operating conditions using a high-speed camera. We discuss the effects of the blast air volume flow rate on the granulation characteristics under different granulator rotating speeds and different molten slag mass flow rate conditions. During the granulation process, products including slag particles, slag wool, and coked slag were yielded. The results show that the centrifugal granulation process was accelerated by blast air, and the average particle diameter decreased with an increasing blast air volume flow rate in most operating conditions, achieving a minimum value of 1.06mm. We obtain a less slag block product when we employ blast air, and the greatest reduction reaches 33%. The effect of blast air on the slag wool mass fraction was negligible in most cases. This study highlights a feasible and promising industrial application of the proposed hybrid centrifugal-air blast granulation technique for molten BF slag. [Display omitted] •The influences of blast air on the granulation process was determined.•The centrifugal granulation process was accelerated by blast air.•The average particle diameter was reduced by blast air significantly.•Less slag block product were obtained when blast air was employed.