A comprehensive deposition velocity model for slurry transport in horizontal pipelines

Abstract

Transportation of solids in form of slurries has become one of the most important unit operations in industries across several disciplines. In fact, the need is more pronounced in industries that are very important for human survival such as food processing, pharmaceuticals and energy (coal, oil and gas). A lot of work has been done in the past 30 years in understanding the factors affecting the deposition velocity of solids in slurries. Experimental observation and theoretical predictions pointed to mixture velocity and solid/fluid properties especially rheology of the resulting slurry to be the most important factors that dramatically affect particle motion and patterning. This paper presents a critical deposition velocity model and a “stability flow map” for complex rheology slurries. The critical deposition model utilizes a more robust generalized two-parameter rheology model to account for any given slurry rheology. The “stability flow map” demarcates the different flow patterns that may be observed at different mixture velocities and rheologies. On this map, the homogeneous slurries are predicted at low rheology and high mixture velocity, whereas heterogeneous slurries (with a concentration gradient) predicted at high rheology (yield stress effects). Sensitivity analysis was conducted on critical Reynolds number, particle density, carrier fluid density, generalized flow behavior index and pipe diameter. It was observed that increase in shear thinning behavior, particle density, pipe diameter and particle diameter led to a decrease in the laminar region and an increased unstable region. The model showed good performance when tested on glass and stainless steel beads test data available in open literature. Preliminary simulation with this map may help engineers select flowline size and carrier fluid rheology for a given type of solid particle.