(55e) A Simple Model to Account Particle Breakage in Pneumatic Conveying
Breakage of particles in pneumatic conveying is an important phenomenon that should be considered during design or operation. As the particles being conveyed through a pipeline, they are always subjected to collisions at different velocities and angles resulting the particles to break. It follows that various flow and structural parameters affect the breakage, such as: fluid velocity, pipeline geometry, different types of bends, etc. In order to predict the final size distribution of the conveyed material, complicated numerical simulations, such as: DEM-CFD, which require high computation time since they track and treat the particles as individuals, are commonly used. In the present study we suggest a simple model to account for particle breakage in pneumatic conveying. The proposed model calculates a change in particle size by tracking a constant layer of a conveyed material in a pipe cross section. Since most of the damage occurs in bends, the model calculates the breakage as a result of collisions between the particles and the bend walls only. For a certain material, particle size and gas velocity, the particle velocity distribution was predicted by empirical model recently developed in our lab. Then, assuming this velocity as the impact velocity and the collision angle defined by a bend geometry, the breakage of the particles was calculated using five empirical comminution functions, namely: strength distribution function, selection function, breakage function, fatigue function and equivalence function. Finally, the results of the calculations show a fair agreement with experimental ones conducted with salt particles in a 2 inch pneumatic conveying pipe line. The computation time was significantly reduced with respect to standard numerical simulations.