Particles' degradation and dynamics in conveying systems

Abstract

The attrition process of particles in conveying systems is a common problem in many industrial applications. The current study adopts a new approach to modeling particle breakage by implementing one-dimensional breakage algorithm (ODBA) in a one-dimensional flow model (Uzi et al., 2016). This method is used for the first time in two-way coupling, i.e. when the breakage affects the flow dynamics and vice versa. The one-dimensional flow model uses conventional balances of mass, momentum and energy. Moreover, the ODBA exploits empirical correlations for particle characteristics (i.e. breakage, equivalence and fatigue functions), and dynamic behavior (i.e. impact velocity and frequency) obtained from a coupled 3D CFD and Discrete Element Method (DEM) simulations. Both the dynamics of the particles and the attrition of the particles were validated using the proposed approach. A dilute pneumatic conveying system was considered, which comprises of 1in. pipe and 5 straight sections and 4 bends (R/D=1) with a total length of 14.5m. CFD-DEM results served as the basis for the velocity validation, satisfying a good agreement along the conveying line. In this system, the attrition of Potash particles was simulated and compared with the experimental measurements of Kalman et al. (2004), showing an excellent agreement. This comparison consists of inlet gas superficial velocity of 40m/s and is comprised of ten conveying cycles in order to emphasize the fatigue phenomena. The investigated case was also analyzed to provide the dynamic parameters of the two-phase flow with regard to the coupling with the breakage algorithm. It was well established that the flow parameters are sensitive to particle size. In the pressure variation, it was prominent that larger particles resolve a larger pressure drop, while the differences between the cycles in the velocity were more extensive. These differences were caused by the changes in particle size distribution and actualized due to the two-way coupling approach.