Hydraulic Transportation of Zinc Suspension Through Pipelines

Abstract

The present investigation was carried out to study the pressure drop characteristics of zinc tailing water slurry in 90˚ pipe bend. Zinc tailing sample was collected from Rampura Agucha mine situated in Rajasthan, India. Before the determination of pressure drop the physical characteristics of zinc tailing sample was determined by various bench scale tests. • It was observe from SEM micrograph that zinc tailing particles are non-spherical in shape and have knife edge structure. The specific gravity of the procured tailing sample was found as 2.87. The maximum static settled concentration of zinc tailing slurry was found as 52.61, 54.02, 61.99 and 65.62% for solid concentration of 25, 35, 45 and 55% respectively. The pH of slurry was lies within the range of 7-7.3. The rheological experiments were carried out to investigate the flow behaviour of zinc tailing water slurry for solid concentration range of 25-55% (by weight). It was found from results that slurry exhibits Newtonian flow behaviour for solid concentration range of 25-35%. Whereas, the increase in solid concentration from 35-55% results in change in flow behaviour to Bingham plastic flow nature. The addition of coarse particles 150-250 μm size results in appreciable decrease in apparent viscosity in fine (<53 μm) particulate slurry. The maximum percentage decrease in apparent viscosity was observed with 20% addition of coarse particles. The pressure drop of slurry through pipe bend at high concentrations was determined using CFD technique. The geometry of pipe bends was varied by modifying the R/d ratio (1.0-3.0). The modeling results were validated with experimental data. The Standard k-ε model shows a most appropriate comparison with experimental results and hence used in the further investigation. The hexagonally shaped cooper type three-dimensional non-uniform grid was chosen to discretize the entire domain. The mesh was refined at the boundaries so as to achieve the y+ value to 30. The contours of turbulence intensity, volume fraction and flow velocity were obtained at the various locations of bend geometry that have never been measured experimentally at such higher concentrations. The solid concentration was varied in the range of 25-55% for flow velocity range of 2-5 m/s. The pressure drop was found to be minimum for bend having R/d ratio 2.0 for low flow rates. For high flow rates pipe bend having R/d ratio 2.5 was optimum. From the results, it was observed that flow velocity dragged the solid particles from the bottom of the pipe along the outer periphery of bend wall.

KEY WORDS: Pressure drop, Zinc tailing, Pipe bend, CFD, Slurry, R/d ratio