TY - JOUR
T1 - Discrete element method simulation of a conical screen mill
T2 - A continuous dry coating device
AU - Deng, Xiaoliang
AU - Scicolone, James
AU - Han, Xi
AU - Davé, Rajesh N.
N1 - Funding Information:
The authors gratefully acknowledge partial financial support from the National Science Foundation (NSF) through grants # EEC-0540855 and EEC-0951845 . The authors would like to thank the support from EDEM solutions by providing an academic license.
Publisher Copyright:
© 2014 Elsevier Ltd.
PY - 2015/3/4
Y1 - 2015/3/4
N2 - A conical screen mill or a comil is a frequently used device for powder delumping. It has been recently shown as a promising continuously operating device for powder dry coating. In order to examine the influence of the operating parameters of comil, which has rather complex geometry, discrete element method (DEM) modeling was carried out and the residence time distribution (RTD) and mean residence time (MRT) were computed. The simulation results show that MRT increases with increasing impeller speeds, an outcome that is counter-intuitive. Limited experimental investigation showed a qualitative agreement with corresponding simulation results. Simulation results also showed that MRT increases with decreasing feed rates, decreasing open areas, and decreasing screen hole sizes. In addition to computing the RTD and MRT, the relationship between average collision number (ACN), number of particles inside the transition zone (region above the conical part), and MRT was examined indicating that higher impeller speed leads to longer MRT and larger ACNs. In contrast, the equilibrium number of particles inside the comil decreases with increasing feed rate, open area, and screen hole size, therefore, leading to a decrease in both MRT and ACNs. Such analysis shows that increasing impeller speed forces more particles to stay in the transition zone, leading to increased MRT; hence increased MRT may not always lead to improved dry coating. Overall, the results demonstrate the relationship between MRT and various operating parameters, while shedding light on the impact of ACNs on MRT, hence providing better understanding of the complex dynamic process and the selection of experimental conditions.
AB - A conical screen mill or a comil is a frequently used device for powder delumping. It has been recently shown as a promising continuously operating device for powder dry coating. In order to examine the influence of the operating parameters of comil, which has rather complex geometry, discrete element method (DEM) modeling was carried out and the residence time distribution (RTD) and mean residence time (MRT) were computed. The simulation results show that MRT increases with increasing impeller speeds, an outcome that is counter-intuitive. Limited experimental investigation showed a qualitative agreement with corresponding simulation results. Simulation results also showed that MRT increases with decreasing feed rates, decreasing open areas, and decreasing screen hole sizes. In addition to computing the RTD and MRT, the relationship between average collision number (ACN), number of particles inside the transition zone (region above the conical part), and MRT was examined indicating that higher impeller speed leads to longer MRT and larger ACNs. In contrast, the equilibrium number of particles inside the comil decreases with increasing feed rate, open area, and screen hole size, therefore, leading to a decrease in both MRT and ACNs. Such analysis shows that increasing impeller speed forces more particles to stay in the transition zone, leading to increased MRT; hence increased MRT may not always lead to improved dry coating. Overall, the results demonstrate the relationship between MRT and various operating parameters, while shedding light on the impact of ACNs on MRT, hence providing better understanding of the complex dynamic process and the selection of experimental conditions.
KW - Average collision number
KW - Comil
KW - Discrete element method (DEM)
KW - Dry coating
KW - Residence time
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U2 - 10.1016/j.ces.2014.08.051
DO - 10.1016/j.ces.2014.08.051
M3 - Article
AN - SCOPUS:84922331981
SN - 0009-2509
VL - 125
SP - 58
EP - 74
JO - Chemical Engineering Science
JF - Chemical Engineering Science
ER -