Hydrodynamic Characterization of Physicochemical Process in Stirred Tanks and Agglomeration Reactors

A short review of the state of the art in experimental and computational fluid dynamics (CFD) characterization of micro-hydrodynamics and physicochemical processes in stirred tanks and agglomeration reactors is presented. Results of experimental and computational studies focusing on classical mixing tanks as well as other innovative reactors with various industrial applications are briefly reviewed. The hydrodynamic characterization techniques as well as the influence of the fluid dynamics on the efficiency of the physicochemical processes have been highlighted including some of the limitations of the reported modeling approach and solution strategy. Finally, the need for specialized CFD codes tailored to the specific needs of fluid-particle reactor design and optimization is advocated to advance research in this field

The Role of Micro Vortex in the Environmental and Biological Processes

This work presents a short review of the theoretical developments in the application of vortex dynamics to the processing of environmental and biological systems. The mechanisms of complex fluid-particle interaction in vortex dominated and non-vortex dominated flows are briefly discussed from theoretical and practical perspectives. Micro vortex propagation, characteristics and their various applications in environmental process engineering are briefly discussed. Several existing and potential applications of vortex dynamics in turbulent flows are highlighted and as well as the knowledge gaps in the current understanding of turbulence phenomenon with respect to its applications in the processing of solid-liquid suspension and biological systems

Investigating the Physicochemical Property Changes of Plastic Packaging Exposed to UV Irradiation and Different Aqueous Environments

A wide range of weathering processes contributes to the degradation of plastic litter items which leads to the formation of microplastics that may be detrimental to marine ecosystems and the organisms inhabiting them. In this study, the impact of UV exposure on the degradation of clear polypropylene (CPP), black polypropylene (BPP), and polyethylene terephthalate (PET) packaging materials was investigated over a period of 6 weeks under dry air conditions representing the terrestrial environment. The exposure was conducted using differently sized and shaped samples at irradiation intensities of 65 W/m2 and 130 W/m2. Results indicated that UV irradiation led to changes in the properties of PET, BPP, and CPP that were proportional to the intensity delivered, leading to a higher level of mass loss, carbonyl indices, crystallinities, and microhardness in all polymer types at 130 W/m2 relative to 65 W/m2. However, material shape and size did not have a significant influence on any property for any of the test materials. Increased mass loss over time was accompanied by considerable increases in carbonyl index (CI) for both PPs. Clear PP (CPP) underwent the most severe degradation, resulting in the highest mass loss, increase in crystallinity, and CI. BPP was less degraded and modified by the UV irradiation than the CPP, indicating that the colorant, carbon black, provided some degree of protection to the bulk polymer material. PET was the least degraded of the three materials, suggesting this polymer type is more resistant to UV degradation. The differences in the degradation behaviours of the three test materials under dry environmental conditions indicate that the UV exposure history of plastic litter might play an important role in its potential for further degradation once it reaches the marine environment. Furthermore, analysis of samples exposed to UV in aqueous media reveals a more irregular set of trends for most material properties measured. Overall, the degree of degradation resulting from UV irradiation in dry environments was more pronounced than in aqueous environments, although the most significant property changes were observed for materials without previous UV exposure histories. Samples with previous UV histories showed higher resistance to further crystallinity changes, which appeared to be due to crosslinking in the pretreatment exposures inhibiting chain alignment into crystalline structures. The effect of solution medium was insignificant, although the presence of water allowed hydrolytic degradation to proceed simultaneously with UV degradation for PET. The reduction of CI in pretreated materials in the aqueous exposures, combined with the mass loss, suggest that the degraded surface layer erodes or products dissolve into surrounding solution medium, leaving a fresh surface of plastic exposed.publishedVersio

Phase equilibria and thermodynamic evaluation of the Fe-Ti-V-O system in air

In this study, the iron-titanium-vanadium-oxygen (Fe-Ti-V-O) system in equilibrium with air was studied experimentally by high-temperature equilibration, quenching, scanning electron microscope and microprobe analysis coupled with critical assessment and thermodynamic evaluation. The properties of the liquid phase were successfully described with the quasichemical model by optimizing parameters only related to the Fe-Ti-O system; remaining parameters for the Fe-V-O and Ti-V-O sub-systems were adopted from recent optimisations. The model for the rutile and hematite solid solutions were described with the compound energy formalism. The ferropseudobrookite solid solution was modelled with a simple polynomial model to include a small solubility . A final set of self-consistent thermodynamic parameters was estimated within acceptable error limits. Calculated isothermal projections at 1000 °C, 1100 °C, 1200 °C, 1300 °C, and 1400 °C of the Fe-Ti-V-O system in equilibrium with air are presented and compared to experimental observations.The raw data required to reproduce these findings are available to download from [https://data.mendeley.com/submissions/evise/edit/nvpgs2vjmr?submission_id=S0364-5916(18)30217-7&token=6bc0021a-85ab-4ea8-85c1-4f774cda067e].The processed data required to reproduce these findings are available to download from [https://data.mendeley.com/submissions/evise/edit/nvpgs2vjmr?submission_id=S0364-5916(18)30217-7&token=6bc0021a-85ab-4ea8-85c1-4f774cda067e].The Glencore Chair in Pyrometallurgical Modelling at the University of Pretoria.https://www.elsevier.com/locate/calphad2020-06-01hj2019Materials Science and Metallurgical Engineerin

Experimental and CFD Studies of the Hydrodynamics in Wet Agglomeration Process

In this study, an experimentally validated computational model was developed to investigate the hydrodynamics in a rotor-stator vortex agglomeration reactor RVR having a rotating disc at the centre with two shrouded outer plates. A numerical simulation was performed using a simplified form of the reactor geometry to compute the 3-D flow field in batch mode operations. Thereafter, the model was validated using data from a 2-D Particle Image Velocimetry (PIV) flow analysis performed during the design of the reactor. Using different operating speeds, namely 70, 90, 110, and 130 rpm, the flow fields were computed numerically, followed by a comprehensive data analysis. The simulation results showed separated boundary layers on the rotating disc and the stator. The flow field within the reactor was characterized by a rotational plane circular forced vortex flow, in which the streamlines are concentric circles with a rotational vortex. Overall, the results of the numerical simulation demonstrated a fairly good agreement between the Computational Fluid Dynamics (CFD) model and the experimental data, as well as the available theoretical predictions. The swirl ratio β was found to be approximately 0.4044, 0.4038, 0.4044, and 0.4043 for the operating speeds of N = 70, 90, 110, and 130 rpm, respectively. In terms of the spatial distribution, the turbulence intensity and kinetic energy were concentrated on the outer region of the reactor, while the circumferential velocity showed a decreasing intensity towards the shroud. However, a comparison of the CFD and experimental predictions of the tangential velocity and the vorticity amplitude profiles showed that these parameters were under-predicted by the experimental analysis, which could be attributed to some of the experimental limitations rather than the robustness of the CFD model or numerical code

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.The original publication is available at http://sajie.journals.ac.zaENGLISH ABSTRACT: South African industry faces immense global competition from developed countries such as Germany probably because of the adoption of lean manufacturing techniques by the latter. This study is a survey on publications concerning implementation and adoption of lean manufacturing in South Africa. To assess South Africa with regards to research publications on lean manufacturing, a benchmark exercise was conducted with Germany for the period 2014 to 2015. The study concludes by highlighting the gaps identified during this survey and recommendations.AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse industrie staar hewige globale mededinging vanaf ontwikkelde lande soos Duitsland in die gesig, waarskynlik as gevolg van die aanneming van lenige vervaardigingstegnieke deur die laasgenoemde. Hierdie navorsing is ʼn beskouing van die publikasies oor die implementering en aanneming van lenige vervaardiging in Suid-Afrika. Om Suid-Afrika te beoordeel aan die hand van navorsingsuitsette met lenige vervaardiging as die onderwerp, is ʼn maatstaf oefening uitgevoer met soortgelyke publikasies in Duitsland in die periode van 2014 tot 2015. Die navorsing lig die gapings só geïdentifiseer uit en maak aanbevelings hieroor.http://sajie.journals.ac.za/pub/article/view/1660Publisher's versio

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

CITATION: Dondofema, R. A., Matope, S. & Akdogan, G. 2017. South African iron and steel industrial evolution : an industrial engineering perspective. South African Journal of Industrial Engineering, 28(4):1-13, doi:10.7166/28-4-1683.The original publication is available at http://sajie.journals.ac.zaENGLISH ABSTRACT: 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.AFRIKAANSE OPSOMMING: Hierdie artikel fokus op die evolusie van die Suid-Afrikaanse yster- en staalindustrie vanuit ʼn bedryfsingenieurswese perspektief. Die vroegste yster produksie in Suid-Afrika dateer terug na die vyfde eeu VC, maar die hoofsaaklike ontwikkeling vind sy oorsprong in 1882 en staalproduksie vanaf ystererts was teen 1934 in volle swang. Hierdie studie lig die hooftrekke van ontwikkelings in Suid-Afrika se yster- en staalindustrie uit en sluit af deur die omvang van die toepassing van bedryfsingenieurswesetegnieke tot gepubliseerde navorsing in hierdie industrie te ondersoek.http://sajie.journals.ac.za/pub/article/view/1683Publisher's versio

Phase equilibria and thermodynamic evaluation of the Fe-Ti-V-O system in air

In this study, the iron-titanium-vanadium-oxygen (Fe-Ti-V-O) system in equilibrium with air was studied experimentally by high-temperature equilibration, quenching, scanning electron microscope and microprobe analysis coupled with critical assessment and thermodynamic evaluation. The properties of the liquid phase were successfully described with the quasichemical model by optimizing parameters only related to the Fe-Ti-O system; remaining parameters for the Fe-V-O and Ti-V-O sub-systems were adopted from recent optimisations. The model for the rutile and hematite solid solutions were described with the compound energy formalism. The ferropseudobrookite solid solution was modelled with a simple polynomial model to include a small solubility V 2 O 5 . A final set of self-consistent thermodynamic parameters was estimated within acceptable error limits. Calculated isothermal projections at 1000 °C, 1100 °C, 1200 °C, 1300 °C, and 1400 °C of the Fe-Ti-V-O system in equilibrium with air are presented and compared to experimental observations.Peer reviewe