Influence of rheology on the hydraulic conveying of red mud slurries through the pipeline for eco-friendly and safe disposal

Abstract

The present investigation demonstrates the effect of red mud concentration on the rheological, pipe flow, and pipe wear behavior during slurry pipeline transportation. Rheology data indicate that 40-70 wt.% red mud slurries exhibit shear thinning flow behavior in the shear rate range of 15-300 s-1. Both slurry viscosity and shear stress increase with the increase in red mud concentrations. The yield stress and startup pressure exponentially vary with red mud concentrations. The critical velocity is estimated as 1.5 m/s, above which sedimentation of red mud particles can be avoided in the pipeline. The pipe head loss and specific energy consumption increase with red mud concentration and slurry velocity; however, these parameters decrease with an increase in pipe diameter. Results suggest that the repetitive impingement of the red mud particles on the surface of mild steel specimens causes erosion wear, which intensifies at higher solid loading and velocity. The abrasivity of red mud slurries and the abrasive response of the pipe material are found as a function of red mud concentration. A favorable economic flow condition is achieved, when 60-65 wt.% of red mud slurry is transported at a velocity of 1.5 m/s in a pipe of diameter 0.3 m.