Evaluation of roll dry granulation process on the high‐viscosity melt solidification and heat recovery

High-viscosity melt with temperature above 1600 K has great potential for energy saving. A mathematical model was proposed on the heat transfer between the rotating roll and melt in a roll dry granulation system, aiming at the efficient granulation and heat recovery of high-viscosity melt. In the model, the relationship between the rotation angle and time was utilized to simplify the three-dimensional dynamic process to a one-dimensional static problem. Then, the influences of the roll material, dimension, rotational speed, and the melt shedding angle on the system performance were investigated. Simulation results indicated that increasing the thermal conductivity or decreasing the wall thickness will result in a higher cooling rate but a more nonuniform heat flux distribution. The possible vibration and thermal fatigue due to the nonuniform heat flux distribution will cause a poor working stability. Heat-resistant steel is a better choice than copper alloy. The optimum wall thickness is about 19 mm, and the rotational speed should be kept below 17 rpm. The overall exergy efficiency increased from 37% to 59%, when the melt shedding angle changed from 120 degrees to 28.8 degrees. This study provides a further feasible method for the efficient granulation and heat recovery of high-viscosity melt.