Elsevier

Minerals Engineering

Volume 20, Issue 1, January 2007, Pages 60-71
Minerals Engineering

CFD simulation and experimental validation studies on hydrocyclone

https://doi.org/10.1016/j.mineng.2006.04.012Get rights and content

Abstract

Hydrocyclone is a key unit operation in mineral process industry and simulation of which using CFD techniques is gaining popularity in process design and optimization. The success of the simulation methodology depends primarily on how best the results are matching with the experimental values and the computational time it requires for obtaining such results. In the present investigation, attempts are made to develop a methodology for simulating the performance of hydrocyclone. Initial work included comparison of experimental and simulated results generated using different turbulence models i.e., standard kε, kε RNG and RSM in terms of water throughput and split with the help of suitably designed experiments. Among the three modeling methods, predictions using RSM model were found better in agreement with experimental results with a marginal error between 4% and 8%. Parametric studies have indicated that a decrease in the spigot opening increased the upward vertical velocity of water more compared to a decrease in the downward vertical velocity. An increase in the inlet pressure has increased the axial velocities of water in both the upward and downward directions and increased the mass flow rates through the cyclone. An increase in the inlet pressure has also increased the static pressure differential along the radius within the cyclone body and hence more water split into overflow. Further, an increase in the inlet pressure has also increased the tangential velocities and reduced the cyclone cut size. The simulated particle distribution values generated using the particle injection technique are found matching with the experimental results while achieving cut sizes between 4.9 and 14.0 μm.

Introduction

Hydrocyclones have been widely accepted in the area of mineral processing due to several advantages, such as ease of operation, high throughput, less maintenance, less floor space requirement etc. Despite its invention in late 18th century, thorough works related to understanding the principles began only in mid fifties (Kelsall, 1952). Kelsall studies on the axial, radial and tangential velocity profiles formed the basis for subsequent research on hydrocyclones. The complex phenomenon involved coupled with non-availability of high-speed computational systems restricted most of the research works focused on the empirical modeling till recent times (Lynch and Rao, 1975, Plitt, 1976). However, the advent of high speed computational systems, in last couple of decades made researchers focus performance simulations using Computational Fluid Dynamics (CFD) techniques (Pericleous and Rhodes, 1986, Hsieh and Rajamani, 1988, Monredon et al., 1992, Rajamani and Milin, 1992, Dyakowski and Williams, 1993, Dyakowski et al., 1994, Malhotra et al., 1994, Hargreaves and Silvester, 1990, Devulapalli and Rajamani, 1996, Griffths and Boysan, 1996, Slack and Wraith, 1997, Slack and Boysan, 1998, Stovin and Saul, 1998, Dyakowski et al., 1999, Suasnabar and Fletcher, 1999, Slack et al., 2000, Ma et al., 2000, Nowakowski et al., 2000, Grady et al., 2002, Slack et al., 2003, Nowakowski and Dyakowski, 2003, Grady et al., 2003, Schuetz et al., 2004, Cullivan et al., 2003, Cullivan et al., 2004, Nowakowski et al., 2004). A numerical technique needs development of suitable methodology and thorough validation with the actual data prior to applications in performance simulation and design. Though most of these studies have validated with water flow characteristics, only few reported simulated results of solids separation behavior. The present study is meant for establishing suitable methodology including turbulence model selection for simulating both water and solid distribution data on different geometries of cyclones. Commercially available CFD software ‘Fluent 6.1.22’ was used. The simulation results carried out on a 76 mm diameter hydrocyclone are validated with experimental data generated in the laboratory in terms of cyclone throughout; water split and solids cut size.

Section snippets

Geometry

The hydrocyclone geometry used for simulation and for experimental studies is presented in Fig. 1. The cylindrical body is 76 mm diameter and 85 mm in length with a closed end at the top surface and bottom face open. A frustum with a larger diameter of 76 mm and smaller diameter of 10 mm maintained at a cone angle of 10° is connected to the main cylindrical body with the face having larger diameter. A cylindrical vortex finder with an inner diameter of 25 mm and outer diameter of 40 mm protrudes into

Simulation

The simulations carried out on hydrocyclone were assumed to be operating without air core. Cartesian coordinate system was used for numerical simulations. Flow simulation was carried out using a 3-D double precision, steady state, and segregated solver. In this method, the governing Navier Stokes equations (Annexure) are solved sequentially using iterative methods till the defined values of convergence are met. Initially, the properties of the water were used along with the pressure and face

Experimental

The experimental setup consisted a slurry tank of 200 liters capacity mounted on a stable platform. A centrifugal pump with 3-phase, 5.5 kW motor was connected to the slurry tank at the bottom. Feed slurry consisting of clay material at 10% solids density was pumped into the cyclone through the pipeline connected to the pump. The other end of the pipeline was connected to the inlet opening of a 76 mm diameter hydrocyclone. The pressure drop inside the cyclone was maintained at required level with

Results and discussion

The simulated results of cyclone throughput (mass flow rate through overflow + mass flow rate through underflow), and on the water-split (percent report of total water entering the cyclone) into overflow product were used for validating the predictions at different test runs with the experimental values. The simulation studies were carried out using standard kε, kε RNG and RSM turbulence models, at three spigot openings, i.e. 10 mm, 15 mm, 20 mm and 25 mm. All these simulations were carried out

Summary

A CFD simulation and supporting validation study on 76 mm hydrocyclone have demonstrated the applicability in the analysis of the water throughput, splits and cyclone cut sizes for various test conditions. Among the turbulence models studied, the simulation results adopting RSM model is found to have better predictions with experimental results. The solid particle distribution simulation through discrete phase modeling technique was found matching with the experimental results at 10% solids by

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