Determination of Flow Structure in a Gold Leaching Tank by CFD Simulation
Affiliation(s)
Ghana Atomic Energy Commission, Legon, Accra, Ghana. Faculty of Physics and Applied Computer Science, AGH-UST, Krakow, Poland.
Ghana Atomic Energy Commission, Legon, Accra, Ghana. Faculty of Physics and Applied Computer Science, AGH-UST, Krakow, Poland.
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 kmixture 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.
KEYWORDS
Residence Time Distribution, Computational Fluid Dynamics, Navier Stokes Equations, Eulerian-Eulerian Multi-Fluid Model, RANS Standard k-ε Mixture Model, Multiple Reference Frame
Residence Time Distribution, Computational Fluid Dynamics, Navier Stokes Equations, Eulerian-Eulerian Multi-Fluid Model, RANS Standard k-ε Mixture Model, Multiple Reference Frame
Cite this paper
Dagadu, C. , Stegowski, Z. , Furman, L. , Akaho, E. and Danso, K. (2014) Determination of Flow Structure in a Gold Leaching Tank by CFD Simulation. Journal of Applied Mathematics and Physics, 2, 510-519. doi: 10.4236/jamp.2014.27059.
Dagadu, C. , Stegowski, Z. , Furman, L. , Akaho, E. and Danso, K. (2014) Determination of Flow Structure in a Gold Leaching Tank by CFD Simulation. Journal of Applied Mathematics and Physics, 2, 510-519. doi: 10.4236/jamp.2014.27059.
References
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[1] Delvigne, F., Destain, J. and Thonart, P. (2005) Structured Mixing Model for Stirred Bioreactors: An Extension to the Stochastic Approach. Chemical Engineering Journal, 113, 1-12.
http://dx.doi.org/10.1016/j.cej.2005.06.007 [2] Raju, R., Balachandar, S., Hill, D.F. and Adriana, R.J. (2005) Reynolds Number Scaling of Flow in a Stirred Tank with Rushton Turbine. Part II—Eigen Decomposition of Fluctuation. Chemical Engineering Science, 60, 3185-3198.
http://dx.doi.org/10.1016/j.ces.2004.12.040 [3] Yoon, H.S., Sharp, K.V., Hill, D.F., Adrian, R.J., Balachandar, S., Ha, M.Y. and Kar, K. (2001) Integrated Experimental and Computational Approach to Simulation of Flow in a Stirred Tank. Chemical Engineering Science, 56, 6635-6649. http://dx.doi.org/10.1016/S0009-2509(01)00315-3 [4] Vakili, M.H. and Esfahany, M.N. (2009) CFD Analysis of Turbulence in a Baffled Stirred Tank, a Three-Compartment Model. Chemical Engineering Science, 64, 351-362.
http://dx.doi.org/10.1016/j.ces.2008.10.037 [5] Wang, Z., Mao, Z. and Shen, X. (2006) Numerical Simulation of Macroscopic Mixing in a Rushton Impeller Stirred Tank. The Chinese Journal of Process Engineering, 6, 857-863. [6] Lelinski, D., Allen, J., Redden, L. and Weber, A. (2002) Analysis of the Residence Time Distribution in Large Flotation Machines. Minerals Engineering, 15, 499-505.
http://dx.doi.org/10.1016/S0892-6875(02)00070-5 [7] Furman, L. and Stegowski, Z. (2011) CFD Models of Jet Mixing and Their Validation by Tracer Experiments. Chemical Engineering and Processing, 50, 300-304. http://dx.doi.org/10.1016/j.cep.2011.01.007 [8] Murthy, B.N., Ghadge, R.S. and Joshi, J.B. (2007) CFD Simulations of Gas-Liquid-Solid Stirred Reactor: Prediction of Critical Impeller Speed for Solid Suspension. Chemical Engineering Science, 62, 7184-7195.
http://dx.doi.org/10.1016/j.ces.2007.07.005 [9] Panneerselvam, R., Savithri, S. and Surender, G.D. (2008) CFD Modeling of Gas-Liquid-Solid Mechanically Agitated Contactor. Chemical Engineering Research and Design, 8, 1331-1344.
http://dx.doi.org/10.1016/j.cherd.2008.08.008 [10] Deglon, D.A. and Meyer, C.J. (2006) CFD Modelling of Stirred Tanks: Numerical Considerations. Minerals Engineering, 19, 1059-1068. http://dx.doi.org/10.1016/j.mineng.2006.04.001 [11] Meroney, R.N. and Colorado, P.E. (2009) CFD Simulation of Mechanical Draft Tube Mixing in Anaerobic Digester Tanks. Water Research, 43, 1040-1050. http://dx.doi.org/10.1016/j.watres.2008.11.035 [12] Angst, R., Harnack, E., Singh, M. and Kraume, M. (2003) Grid and Model Dependency of the Solid/Liquid Two-Phase Flow CFD Simulation of Stirred Reactors. Proceedings of 11th European Conference of Mixing, Bambarg, 14-17 October 2003. [13] Barrue, H., Bertrand, J., Cristol, B. and Xuereb, C. (2001) Eulerian Simulation of Dense Solid-Liquid Suspension in Multi-Stage Stirred Reactor. Journal of Chemical Engineering of Japan, 34, 585-594.
http://dx.doi.org/10.1252/jcej.34.585 [14] Lopez de Bertodano, M. (1992) Turbulent Bubbly Two-Phase Flow in a Triangular Duct. Ph.D. Dissertation, Rensselaer Polytechnic Institute, Troy, New York. [15] Cheung, S.C.P., Yeoh, G.H. and Tu, J.Y. (2007) On the Modelling of Population Balance in Isothermal Vertical Bubbly Flows-Average Bubble Number Density Approach. Chemical Engineering Process, 46, 742-756.
http://dx.doi.org/10.1016/j.cep.2006.10.004 [16] Lucas, D., Kreppera, E. and Prasserb, H.M. (2007) Use of Models for Lift, Wall and Turbulent Dispersion Forces Acting on Bubbles for Poly-Disperse Flows. Chemical Engineering Science, 62, 4146-4157.
http://dx.doi.org/10.1016/j.ces.2007.04.035 [17] Khopkar, A.R., Rammohan, A.R., Ranade, V.V. and Dudukovic, M.P. (2005) Gas-Liquid Flow Generated by a Rushton Turbine in Stirred Vessel: CARPT/CT Measurement and CFD Simulations. Chemical Engineering Science, 60, 2215-2229. http://dx.doi.org/10.1016/j.ces.2004.11.044 [18] Montante, G. and Magelli, F. (2005) Modelling of Solids Distribution in Stirred Tanks: Analysis of Simulation Strategies and Comparison with Experimental Data. International Journal of Computational Fluid Dynamics, 19, 253-262.
http://dx.doi.org/10.1080/10618560500081795 [19] Brucato, A., Grisafi, F. and Montante, G. (1998) Particle Drag Coefficient in Turbulent Fluids. Chemical Engineering Science, 45, 3295-3314. http://dx.doi.org/10.1016/S0009-2509(98)00114-6 [20] Khopkar, A.R. and Tanguy, P.A. (2008) CFD Simulation of Gas-Liquid Flows in Stirred Vessel Equipped with Dual Rushtonturbines: Influence of Parallel, Merging and Diverging Flow Configurations. Chemical Engineering Science, 63, 3810-3820. http://dx.doi.org/10.1016/j.ces.2008.04.039 [21] Aubin, J., Kresta, S.M., Bertrand, J., Xuereb, C. and Fletcher, D.F. (2006) Alternate Operating Methods for Improving the Performance of Continuous Stirred Tank Reactors. Chemical Engineering Research and Design, 84, 569-582.
http://dx.doi.org/10.1205/cherd.05216 [22] Khopkar, A.R., Mavros, P., Ranade, V.V. and Bertrand, J. (2004) Simulation of Flow Generated by an Axial Flow Impeller: Batch and Continuous Operation. Chemical Engineering Research and Design, 82, 737-751.
http://dx.doi.org/10.1205/026387604774196028 [23] ANSYS FLUENT Inc. (2006) FLUENT 6.3 User’s Manual. Fluent Inc. Centrera Resource Park, 10 Cavendish Court, Lebanon. [24] Vasquez, S.A. and Ivanov, V.A. (2000) A Phase Coupled Method for Solving Multiphase Problems on Unstructured Meshes. Proceedings of the ASME Fluids Engineering Division Summer Meeting (FEDSM2000), American Society of Mechanical Engineers, 251, 659-664. [25] Bai, H., Stephenson, A., Jimenez, J., Jewell, D. and Gillis, P. (2008) Modeling of Flow and Residence Time Distribution in an Industrial-Scale Reactor with a Plunging Jet Inlet and Optional Agitation. Chemical Engineering Research and Design, 8, 1462-1476. http://dx.doi.org/10.1016/j.cherd.2008.08.012 [26] Jahoda, M., Mostek, M., Kukukova, K.A. and Machon, V. (2007) CFD Modelling of Liquid Homogenization in Stirred Tanks with One and Two Impellers Using Large Eddy Simulation. Chemical Engineering Research and Design, 85, 616-625. http://dx.doi.org/10.1205/cherd06183