G. Akdogan

Quantification of numerical uncertainty in computational fluid dynamics modelling of hydrocyclones

Abstract Large Eddy Simulations of the flow through a hydrocyclone are used to demonstrate that the Grid Convergence Index (GCI) is a practical method of accounting for numerical uncertainty. The small values of GCI (

CFD Modelling of Global Mixing Parameters in a Peirce-Smith Converter with Comparison to Physical Modelling

The flow pattern and mixing in an industrial Peirce-Smith converter (PSC) has been experimentally and numerically studied using cold model simulations. The effects of air volumetric flow rate and presence of overlaying slag phase on matte on the flow structure and mixing were investigated. The 2-D and 3-D simulations of the three phase system were carried out using volume of fluid (VOF) and realizable k - ɛ turbulence model to account for the multiphase and turbulence nature of the flow respectively. These models were implemented using commercial Computational Fluid Dynamics (CFD) numerical code FLUENT. The cold model for physical simulations was a 1:5 horizontal cylindrical container made of Perspex with seven tuyeres on one side of the cylinder typifying a Peirce-Smith converter. Compressed air was blown into the cylinder through the tuyeres, simulating air or oxygen enriched air injection into the PSC. The matte and slag phases were simulated with water and kerosene respectively in this study. The influence of varying blowing conditions and simulated slag quantities on the bulk mixing was studied with five different air volumetric flow rates and five levels of simulated slag thickness. Mixing time results were evaluated in terms of total specific mixing power and two mixing time correlations were proposed for estimating mixing times in the model of PSC for low slag and high slag volumes. Both numerical and experimental simulations were in good agreement to predict the variation characteristics of the system in relation to global flow field variables set up in the converter through mathematical calculation of relevant integrated quantities of turbulence, Volume Fraction (VF) and velocity magnitudes. The findings revealed that both air volumetric flow rate and presence of the overlaying slag layer have profound effects on the mixing efficiency of the converter.

Modelling of mixing, mass transfer and phase distribution in a Peirce–Smith converter model

Abstract This study presents a numerical and physical modelling study of flow pattern, mixing, solid–liquid mass transfer and slag matte phase distribution in an industrial Peirce–Smith converter (PSC) slice model. The two-dimensional (2D) and three-dimensional (3D) numerical simulations of the three phase system were carried out using volume of fluid (VOF) and realisable k−ϵ (RKE) turbulence model to account for the multiphase and turbulence nature of the flow respectively. These models were implemented using the commercial computational fluid dynamics (CFD) numerical code FLUENT. In physical simulations, water, kerosene, air and sintered benzoic acid compacts were used to simulate matte, slag, injected gas and solid additions into PSC. Both numerical and physical simulations were able to predict, in agreement, the mixing and dispersion characteristics of the system in relation to different blowing conditions employed in this study. Measurement of dimensionless turbulence characteristic values conclusively indicated that fluid flow in PSC is stratified. Ce document présente une étude de modélisation numérique et physique de la configuration de l’écoulement, du mélangeage, du transfert de masse solide-liquide et de la distribution de phase scorie-matte dans un modèle en tranches de convertisseur industriel Peirce–Smith (PSC). On a effectué les simulations numériques 2D et 3D du système à trois phases en utilisant le modèle du Volume de Fluide (VOF) et de la turbulence réalisable (RKE) pour tenir compte des phases multiples et de la nature turbulente de l’écoulement, respectivement. On a exécuté ces modèles en utilisant le code numérique commercial de la dynamique numérique des fluides (CFD) FLUENT. Dans les simulations physiques, on a utilisé de l’eau, du kérosène, de l’air et des compacts frittés d’acide benzoïque pour la simulation de la matte, de la scorie, du gaz d’injection et des additions de solide dans le PSC. Les simulations numériques et physiques étaient toutes deux capables de prédire, en accord, les caractéristiques de mélangeage et de dispersion du système en relation avec les différentes conditions de soufflage utilisées dans cette étude. La mesure des valeurs caractéristiques sans dimension de la turbulence indiquait décisivement que l’écoulement du fluide dans le PSC était stratifié.

INVESTIGATING OF ECO- AND ENERGY-EFFICIENT LUBRICATION STRATEGIES FOR THE DRILLING OF LIGHT METAL ALLOYS

Energy use will be one of the main drivers for the achievement of more eco-efficient drilling processes in the automotive industry. Industry awareness of the environmental impact of used cutting emulsions, and the negative effect on worker health, has increased sharply. This has led to innovative lubrication methods such as through-spindle minimal quantity lubrication (MQL) for drilling aluminium-silicon alloys. In this work the performance of MQL at different cutting speeds and feed rates has been investigated using infrared temperature measurements. The results indicate that MQL is a feasible ecoefficient alternative to conventional flood cooling when drilling aluminium-silicon alloys. OPSOMMING Energiebenutting maak een van die hoofdryfvere uit om eko-doeltreffendheid te behaal in boorprosesse in die motornywerheid. Nywerheidsbewustheid van die omgewingsimpak van gebruikte sny-vloeistowwe, en die negatiewe effek daarvan op werkergesondheid, het skerp toegeneem. Hierdie bewustheid het aanleiding gegee tot die ontwikkeling van smeringsmetodes soos deur-spil minimale hoeveelheid smering (Engels: Minimal Quantity Lubrication, MQL) vir die boor van aluminium-silikon legerings. In hierdie werk word die prestasie van MQL ondersoek teen verskillende snyspoed- en voertempo-kondisies deur middel van infra-rooi temperatuurmeting. Die resultate dui daarop dat MQL ’n lewensvatbare eko-vriendelike alternatief tot konvensionele vloedverkoeling is, wanneer aluminium-silikon legerings geboor word.

Numerical Investigation of Combined Top and Lateral Blowing in a Peirce-Smith Converter

Abstract Typical current operation of lateral-blown Peirce-Smith converters (PSCs) has the common phenomenon of splashing and slopping due to air injection. The splashing and wave motion in these converters cause metal losses and potential production lost time due to intermittent cleaning of the converter mouth and thus reduced process throughput. Understanding of the effect of combined top and lateral blowing could possibly lead to alternative technology advancement for increased process efficiency. In this study, computational fluid dynamics (CFD) simulations of conventional common practice (lateral blowing) and combined (top and lateral blowing) in a PSC were carried out, and results of flow variables (bath velocity, turbulence kinetic energy, etc.) were compared. The two-dimensional (2-D) and three-dimensional (3-D) simulations of the three-phase system (air–matte–slag) were executed utilizing a commercial CFD numerical software code, ANSYS FLUENT 14.0. These simulations were performed employing the volume of fluid and realizable turbulence models to account for multiphase and turbulent nature of the flow, respectively. Upon completion of the simulations, the results of the models were analysed and compared by means of density contour plots, velocity vector plots, turbulent kinetic energy vector plots, average turbulent kinetic energy, turbulent intensity contour plots and average matte bulk velocity. It was found that both blowing configuration and slag layer thickness have significant effects on mixing propagation, wave formation and splashing in the PSC as the results showed wave formation and splashing significantly being reduced by employing combined top- and lateral-blowing configurations.

The Effect of Granulated Nickel Converter Matte Mineralogy on Phase-Specific Hardness and Associated Breakage Characteristics

There is very little in-depth study on the processing behavior of granulated nickel converter matte as an intermediate product, particularly related to downstream comminution and hydrometallurgical processing. The measurement of fundamental phase-specific physical properties would assist in understanding grinding and leaching processing behavior. The aim of this study was to investigate a possible dependence between phase-specific hardness, microstructures, and breakage characteristics. Relevant to the investigation is the application of a novel combination of micro-analytical techniques. The phase-specific hardness and breakage characteristics were sequentially tested with a CSM Nano-Indentation Tester. Phase-breakage characteristics were further tested in a laboratory ball mill at a specific energy input. Comparative phase-breakage analysis was additionally performed using a field-emission scanning electron microscope. It was found that the softest phase is copper sulfide with an average hardness of 1975 MPa. The harder phases are NiCu-alloy and nickel sulfide with average hardness values of 4981 MPa and 4456 MPa, respectively. Indentation-induced micro-cracks are common along curving copper-sulfide phase boundaries while there is a notable smaller degree of breakage attainable with respect to the harder nickel-sulfide phases. In addition, there is a comparative lack of breakage attainable with respect to NiCu-alloy phases, suggesting possible ductility under both the compressive indentation loads and during grinding events in a laboratory ball mill.

Selection of Suitable Turbulence Models for Numerical Modelling of Hydrocyclones

The capability of Computational Fluid Dynamics (CFD) alternates the interest of researcher from the empirical models into the numerical approaches for studying hydrocyclones. This paper presents a comprehensive survey on the influences of turbulence model options in the 3D simulation of the hydrocyclone flow pattern. The required grid resolution was selected through a grid independency study. Four categories of turbulence models involving models based on the Boussinesq hypothesis, the Reynolds Stress Model (RSM), the Large Eddy Simulation (LES) model, and the Detached Eddy Simulation (DES) model were investigated for prediction of velocity components within the hydrocyclone. The methodology was validated by experimental data. The results confirm that both RSM and LES models are efficient turbulent model choices for the simulation of swirling flow of hydrocyclones.

Matte converting in copper smelting

ABSTRACT Copper matte converting is the key step to ensure high primary copper recovery in the smelting chain. Its development and the fundamental research carried out over the past decades will be reviewed. The operational challenges and environmental concern of batch-wise Peirce-Smith Converting vessel have induced more than 50 years ago attempts to continuous converting process which have materialised in the last two decades in the flash converting technology, utilised currently in one smelter in USA and three smelters in China. Their annual copper production is in excess of 1.5 Mt, and selected fundamental studies behind this major technological invention will be examined.

South African iron and steel industrial evolution : an industrial engineering perspective

The paper focuses on the evolution of the South African iron and steel industry from the industrial engineering perspective. The earliest ironmaking in South Africa dates to the fifth century CE; but the major evolution of the industry began in 1882 and, by the year 1934, steel production from native ore was in full swing. The study highlights the major developments in South Africa’s iron and steel industry, and ends by exploring the extent of the application of industrial engineering techniques to published research into the steel industry.

Lean applications : a survey of publications with respect to South African industry

CITATION: Dondofema, R. A., Matope, S. & Akdogan, G. 2017. Lean applications : a survey of publications with respect to South African industry. South African Journal of Industrial Engineering, 28(1):103-113, doi:10.7166/28-1-1660.