Feasibility of Rotary Cup Atomizer for slag granulation

At the present molten slag from a blast furnace (B.F.) is granulated by impinging much water without any recovery of its much sensible heat (1 823 K), polluting water and atmosphere. To solve these problems, we studied the dry granulation of molten slag by Rotary Cup Atomizer (RCA), in which the influence of the rotating speed of the RCA on slag drop size was mainly examined. In the experiment, the molten B.F. slag was supplied to the center of RCA with air blast. Slag drops flown from the cup lip due to centrifugal force were collected and examined from viewpoints of shape, dimension and the flown distance of the drop. Most significantly, molten slag was successfully granulated under the dry conditions without water impingement. The rotating speed of the RCA influenced the diameter and shape of slag drop very strongly. The higher rotating speed made the slag drops smaller, more spherical and more uniform. Drops with 5 to 6 mm of average dimension were obtained at the rotating speed of 15 rps (900 rpm), and drops with less than 1 mm, at that of 50 rps (3 000 rpm). In the former case, the shape of drop obtained was distributed, changing from sphere to stick at the further place from the center of RCA. The results revealed a possibility of alternative, new slag granulation process with many benefits.