Investigation on Bauxite Slurry Transportation: Rheological and Pilot Plant Characteristics

Abstract

The current work investigates the transportation of bauxite slurry through rheology as well as experimental pilot plant studies in horizontal pipelines. The work utilizes the sample prepared at a median particle size (d50) of 23.3 mu m, followed by its characterization including temperature-dependent rheology to understand the flow behavior. The tests performed through 50 mm and 100 mm NPS (nominal pipe size) loops on three solids concentrations, 35.2%, 40%, and 45.3% by weight, showed non-Newtonian pseudoplastic behavior with yield stress. The slurry showed a good fit to the Herschel-Bulkley (H-B) model in the tested concentrations. The effect of solids concentration and nominal pipe size on the pressure drop were studied at an operating velocity range of 0.57-1.86 m/s. The semiempirical H-B models developed by Torrance, Wilson and Thomas (W&T), Slatter, Chilton and Stainsby (C&S), along with extended modifications to Tomita and Dodge and Metzner (D&M) models were used to estimate the pressure drop and transition from laminar to turbulent flow regime. The W&T model showed minimum NRMSE (normalized root mean squared error) for all the concentrations in both pipe sizes. The work also estimates the optimum solids concentration for a given throughput of 1,500 tons per hour (TPH) based on the W&T model. Finally, the challenges faced in determining the critical settling velocity and transition point of flow regime were addressed with possible adaptive methods for further investigation.