Determination of Flow Structure in a Gold Leaching Tank by CFD Simulation

Abstract

Experimental residence time distribution (RTD) measurement and computational fluid dynamics (CFD) simulation are the best methods to study the hydrodynamics of process flow systems. However, CFD approach leads to better understanding of the flow structure and extent of mixing in stirred tanks. In the present study, CFD models were used to simulate the flow in an industrial gold leaching tank. The objective of the investigation was to characterize the flowfield generated within the tank after process intensification. The flow was simulated using an Eulerian-Eulerian multi-fluid model where the RANS standard -ε mixture model and a multiple reference frame approach were used to model turbulence and impeller rotation respectively. The simulated flowfield was found to be in agreement with the flow pattern of pitched blade axial-flow impellers that was used for mixing. The leaching tank exhibited good "off-bottom suspension" which reveals minimum deposition of gold ore particles on the bottom of the leaching tanks. Simulation results were consistent with experimental results obtained from a radioactive tracer investigation. CFD approach gave a better description of the flow structure and extent of mixing in a leaching tank. Hence it could be a preferred approach for flow system analysis where the cost of experimentation is high.

Mixing Analysis in a Stirred Tank Using Computational Fluid Dynamics

“…Mixing is by mechanical agitation of two hydrofoil impellers, type A310 mounted on a shaft concentric with the axis of the vessel. Detail description of the domain and all the relevant dimensions, such as tank height and diameter, impeller diameter and clearance, are given in [14]. The MRF approach divides the computational domain into an inner region, in which the governing flow equations (continuity and momentum) are solved in a rotating framework and an outer region, in which the equations are solved in a stationary frame work [15].…”

“…The computational models and their mathematical expressions used in this study are well explained in [14]. An Eulerian-Eulerian multi-fluid model was used to simulate multiphase flow where the liquid and solid phases are all treated as different continua, interpenetrating and interacting with each other everywhere in the computational domain.…”

“…In stirred tanks, the N-S equations are limited to the mass and momentum equations. These equations were used in an earlier study conducted by [14] where appropriate CFD Models were employed to generate the flowfield in an industrial gold leaching tank. As a continuation, the current study was carried out with the objective to simulate the mixing zones in the flowfield generated in the previous investigation.…”

CFD Modelling of Flow and Solids Distribution in Carbon-in-Leach Tanks

“…are still unknown. To address these issues, Dagadu et al [18,19] investigated the mixing in the CIL tanks by conducting CFD simulations and drawing inferences based on the flow field and eddy viscosity. In both of these instances, neither the relationship of the flow field or turbulent viscosity with the solid distribution is quantified, nor the solid distribution in the tanks are presented.…”

Mixing Performance of Counter-Axial Flow Impeller using Computational Fluid Dynamics

“…The standard k-ε model solves for high Reynolds number scenarios. This model is formulated on the assumption that the Reynolds stress is proportional to the mean velocity gradient (Dagadu, et al, 2014).…”