COMPARISON OF ENERGY EFFICIENCY BETWEEN A ROLLER MILL AND A HAMMER MILL

AIt is generally believed that roller mills utilize energy more efficiently than hammer mills (Silver, 1931;Puckett and Daum, 1968; Appel, 1987). To verify this, a completely randomized factorial experimental design (CRD) withtwo replications was constructed: a total of 72 grinding tests was conducted to compare the energy efficiency between aroller mill and a hammer mill. Energy data were collected using a computerized data acquisition system and a watt-hourmeter for the roller mill and the hammer mill, respectively. A mixture of hard red winter wheat (HRW) varieties was usedto conduct the experiment. To make the comparison meaningful, the parameters for the two machines were set so that theground material characteristics from both were almost identical. For roller mill grinding, roll gap was the mostsignificant factor affecting energy requirement, followed by the roll speed differential. For hammer mill grinding, screenopening size had the most significant effect. For both mills, feed rate was not significant; and energy efficiencies wereabout the same.