Prediction of Concentration Profiles of a Particle - Laden Slurry Flow in Horizontal and Vertical Pipes

Abstract

The effect of particle diameter and initial solids concentration on the concentration profiles of a Xylene - 2 amino, 4, 6 dimethyl pyrimidine (ADP) slurry flowing in horizontal pipe, vertical pipe, and vertical pipe with a branch (sampling pipe) was simulated using computational fluid dynamics. ANSYS FLUENT 12.0 was used as the computational fluid dynamic software. The k-epsilon turbulence model with standard wall functions coupled with the mixture multi-phase model was used to simulate all the test cases. A grid independence study was performed and fully-developed flow regions are predicted for horizontal and vertical pipes. The model was validated with experimental data sets available in the literature. The concentration profiles at the fully-developed region of the horizontal and vertical pipes are compared. The concentration profiles in the sampling pipe are compared with those registered at the fully-developed region of the vertical pipe. The present computational model predicts the velocity and the concentration profiles of a slurry flowing in horizontal and vertical pipes with an acceptable degree of accuracy. It was found that the concentration profiles in the horizontal pipe displayed greater spatial variation, whereas the concentration profiles in the vertical pipe displayed reduced spatial variation; they are almost uniform. Owing to this, the fully-developed region of the vertical pipe will serve as a good location for performing off-line sampling and near infra-red spectroscopic analysis of a particle-laden slurry. It was found that the concentration profiles in the sampling pipe and the fully-developed region of the vertical pipe are almost uniform and similar for 30 and 100 m ADP particles. For bigger particles (300 m ADP particles), the concentration profiles in the sampling pipe displayed greater spatial variation with higher concentration of particles observed at the bottom wall of the sampling pipe because of the effect of gravity. Owing to this, the off-line sampling method is suitable for sampling slurries with less than 100 m particles using the modeled parameters, avoiding effects of strongly non-uniform concentration profiles