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Momentum transfer from Arc to slag bath in an ilmenite smelting DC Arc furnace - a computational analysis
Thesis (MEng)--Stellenbosch University, 2021.
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Stellenbosch : Stellenbosch University
2021
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| _version_ | 1867613818717208576 |
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| access_status_str | Open Access |
| author | Makgoale, Tumelo |
| author2 | Akdogan, Guven |
| author_browse | Akdogan, Guven Makgoale, Tumelo |
| author_facet | Akdogan, Guven Makgoale, Tumelo |
| author_sort | Makgoale, Tumelo |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2021. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/123937 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:42:11.774Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2021 |
| publishDateRange | 2021 |
| publishDateSort | 2021 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/123937 Momentum transfer from Arc to slag bath in an ilmenite smelting DC Arc furnace - a computational analysis Makgoale, Tumelo Akdogan, Guven Bogaers, Alfred Zietsman, Johan Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering. Ilmenite UCTD Plasma arc melting Turbulent gas jet Momentum transfer Thesis (MEng)--Stellenbosch University, 2021. ENGLISH ABSTRACT: Direct current (DC) arc furnaces are used for a variety of applications, including steelmaking, chromite smelting, ilmenite smelting, and nickel laterite smelting. Understanding the behaviour of DC plasma arcs is essential, as they are central to the operation of DC arc furnaces. The intent of this research project was to study and understand the interaction between the arc jet and slag bath in terms of momentum transfer to assist in furnace design and operation, particularly for ilmenite smelting processes. In an electric smelting furnace, there are a number of driving forces resulting in flow of the molten slag and alloy baths, and which influence the melting rate and temperature distribution. These include carbon monoxide bubbling, electromagnetic forces, arc jetting, and natural convection. The purpose of this research project was to find a computationally efficient and representative modelling method to describe an arc, and use this method to understand momentum transfer from arc to slag bath in DC arc furnaces. The first objective was to identify and investigate modelling methods that have been developed to describe plasma arcs, and to also select the most appropriate method to incorporate the description of an arc into multiphysics models. The criteria for an appropriate model includes: equivalence to arc behaviour, ability to reliably describe the interaction between plasma arc jet and molten bath, computational efficiency, and numerical stability during simulations. A steady-state turbulent gas jet was selected as an appropriate representation of an arc as it is capable of accounting for the thrust generated by an arc, yet is computationally simple enough to be included within a full multiphysics model suitable for furnace design. The second objective was to develop an understanding of the turbulent gas jet modelling method so that it can be applied effectively in simulations to provide an accurate and reliable arc description. A sensitivity study of the various parameters that can be modified when formulating a turbulent jet was performed. The analysis included: jet inlet velocity, gas density and viscosity, inlet nozzle diameter, jet length, as well as arc thrust. The idea was to isolate and highlight which of these parameters have significant influences on the impingement forces, and thereby highlighting which of these parameters should be chosen with care. An important finding from this investigation was the influence of the ρ 1 2 /μ ratio in maintaining Reynolds number equivalence. This approximation allows us to work with lower arc jet velocities without changing momentum transfer rate to the slag bath, while improving numerical stability and reducing computational cost. This investigation also showed that the inlet nozzle diameter has an influence on both momentum transfer to the slag bath and indentation size on the bath surface. Since there is no real physical argument to base the choice of inlet nozzle diameter, this parameter should be chosen with care. The last objective was to perform steady-state pilot plant scale simulations for a DC arc furnace to investigate the impact of furnace design and operating parameters using the turbulent jet approxi- mation as an arc. From these simulations, a 10 kA arc, with a length of 0.2 m, resulted in an average slag bath velocity of 0.0311 m s−1, an average transferred momentum of 3.342 × 10−3 kg m s−1, and a total slag bath kinetic energy of 9.3727 × 10−7 kW h. The results obtained in this study confirm that arc jetting can potentially be a major momentum driver within open bath furnaces, but the exact magnitudes may differ significantly for industrial scale furnaces. AFRIKAANSE OPSOMMING: Direkte stroom (DC) boogoonde word gebruik vir ’n verskeidenheid toepassings, insluitend staalver- vaardiging, chromietsmelting, ilmenietsmelting, en nikkellaterietsmelting. Om die gedrag van DC- plasmaboë te verstaan is essensieel, omdat dit sentraal tot die bedryf van DC-boogoonde is. Die doel van hierdie navorsingsprojek was om die interaksie tussen die boogstraal en slakbad te bestudeer en verstaan in terme van momentumoordrag om oondontwerp en -bedryf by te staan, veral vir ilmenietsmeltingprosesse. In ’n elektriese smeltoond, is daar ’n aantal stukragte wat vloei van gesmelte slak- en allooi- baddens tot gevolg het, en wat die smelttempo en temperatuurverspreiding beïnvloed. Hierdie sluit in koolstofmonoksiedborreling, elektromagnetiese kragte, boogstraling, en natuurlike konveksie. Die doel van hierdie navorsing was om ’n rekenkundige doeltreffende en verteenwoordigende modelleringmetode te vind wat ’n boog beskryf, en hierdie metode te gebruik om momentumoordrag van boog na slakbad in DC-oonde te verstaan. Die eerste doel was om modelleringmetodes te identifiseer en ondersoek wat ontwikkel is om plasmaboë te beskryf, en om ook die mees gepaste metode te kies om die beskrywing van ’n boog in multifisika-modelle te inkorporeer. Die kriteria vir ’n gepaste model sluit in: ekwivalensie aan booggedrag, vermoë om die interaksie tussen plasmaboogstraal en gesmelte bad betroubaar te beskryf, rekenkundige doeltreffendheid, en numeriese stabiliteit gedurende simulasies. ’n Bestendige toestand turbulente gasstraal is gekies as ’n gepaste verteenwoordiging van ’n boog omdat dit in staat is om die stootkrag gegenereer deur ’n boog in rekening te bring, maar is rekenkundig eenvoudig genoeg om ingesluit te word in ’n vol multifisika-model gepas vir oondontwerp. Die tweede doel was om die turbulente gasstraal modelleringsmetode te verstaan sodat dit ef- fektief in simulasies toegepas kan word om ’n akkurate en betroubare boogbeskrywing te verskaf. ’n Sensitiwiteitstudie van verskeie parameters wat aangepas kan word wanneer ’n turbulente straal gefor- muleer word, is uitgevoer. Die analise het ingesluit: straalinlaatsnelheid, gasdigtheid en -viskositeit, inlaatspuitstukdeursnit, straallengte, sowel as boogstootkrag. Die idee was om die parameters wat beduidende invloed op die botsende kragte het te isoleer en uit te lig, en hierdeur te beklemtoon watter parameters versigtig gekies moet word. ’n Belangrike bevinding van hierdie ondersoek was die invloed van die ρ 1 2 /μ ratio in die handhawing van Reynolds-nommer-ekwivalensie. Hierdie benadering laat ons toe om met laer straalsnelhede te werk sonder om die slakbad se momentumoordragtempo te verander, terwyl numeriese stabiliteit verbeter en rekenkundige kostes verminder word. Hierdie ondersoek het ook gewys dat die inlaatspuitstukdeursnit beide momentumoordrag na die slakbad en inkepinggrootte op die badoppervlak beïnvloed. Aangesien daar geen werklike fisiese argument is om die keuse van inlaatspuitstukdeursnit op te baseer nie, moet hierdie parameter met sorg gekies word. Die laaste doel was om bestendige toestand loodsaanlegsimulasies vir ’n DC-boogoond uit te voer om die impak van oondontwerp en bedryfsparameters te ondersoek deur die turbulente straalbenader- ing as ’n boog te gebruik. Vanuit hierdie simulasies het ’n 10 kA-boog, met lengte 0.2 m, ’n gemid- delde slakbadsnelheid van 0.0311 m s−1, ’n gemiddelde oordragmomentum van 3.342×10−3 kg m s−1, en ’n totale slakbad kinetiese energie van 9.3727 × 10−7 kW h, opgelewer. Die resultate in hierdie studie bevestig dat boogstraling potensieel ’n belangrike momentemdrywer binne oopbadoonde kan wees, maar die presiese groottes kan beduidend verskil vir industriële-skaal oonde. Masters 2021-12-06T10:48:43Z 2021-12-22T14:30:12Z 2021-12-06T10:48:43Z 2021-12-22T14:30:12Z 2021-12 Thesis http://hdl.handle.net/10019.1/123937 en_ZA Stellenbosch University 92 pages application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Ilmenite UCTD Plasma arc melting Turbulent gas jet Momentum transfer Makgoale, Tumelo Momentum transfer from Arc to slag bath in an ilmenite smelting DC Arc furnace - a computational analysis |
| title | Momentum transfer from Arc to slag bath in an ilmenite smelting DC Arc furnace - a computational analysis |
| title_full | Momentum transfer from Arc to slag bath in an ilmenite smelting DC Arc furnace - a computational analysis |
| title_fullStr | Momentum transfer from Arc to slag bath in an ilmenite smelting DC Arc furnace - a computational analysis |
| title_full_unstemmed | Momentum transfer from Arc to slag bath in an ilmenite smelting DC Arc furnace - a computational analysis |
| title_short | Momentum transfer from Arc to slag bath in an ilmenite smelting DC Arc furnace - a computational analysis |
| title_sort | momentum transfer from arc to slag bath in an ilmenite smelting dc arc furnace a computational analysis |
| topic | Ilmenite UCTD Plasma arc melting Turbulent gas jet Momentum transfer |
| url | http://hdl.handle.net/10019.1/123937 |
| work_keys_str_mv | AT makgoaletumelo momentumtransferfromarctoslagbathinanilmenitesmeltingdcarcfurnaceacomputationalanalysis |