DEM analysis of the role of lifter design on performance of rotary cooler

Abstract

Rotary drums are commonly used to dry or cool particulate solids. They are made of a long cylindrical shell that is rotated around the longitudinal axis. The shell is usually slightly inclined to the horizontal to induce flow of solid from one end of the dryer to the other. In case of direct contact dryers and coolers, the air interacts with solids directly. In such cases, the rotary drums are equipped with lifters or flights, placed along the length of the shell to promote gas–solid contact. These lifters carry solids during rotation and shower them across the drum cross section. These lifters are critical to equipment performance. In this particular study, the role of lifter design on equipment capacity, specifically for rotary cooler, is demonstrated using Discrete Element Method (DEM) simulation. Various lifter designs are simulated and validated with experimental studies. In the first step, only the particle dynamics is analyzed. The results are discussed with respect to material hold-up of individual flights and material distribution across the cross-section of the rotary drum. These findings are further substantiated with cooling experiments on gas-solid interaction, where hot sand particles are cooled by driving ambient air through the system. It has been shown that appropriate design modification of lifter can improve the equipment capacity by as much as 30%.