O objetivo desse trabalho foi o de obter-se fios de cobre em três composições químicas distintas da liga Cu-Mg a partir de cobre eletrolítico e de magnésio. Foram avaliadas as etapas envolvidas, começando com a fusão de botões em forno a arco na composição do eutético Cu-Mg, diluição destes botões em forno resistivo, vazamento em lingoteira de cobre, seguido de tratamento térmico de homogeneização em forno resistivo a 910 ºC por 2 h. Os tarugos foram posteriormente trabalhados mecanicamente por forjamento rotativo seguido de um passe final de acabamento por trefilação, para obtenção do fio. As análises químicas realizadas nos lingotes indicaram que a rota de preparação dos fios mostrou-se adequada aos estudos em escala de laboratório, suficiente para a confecção de fios com área de seção transversal de 4 mm2 por 10 m de comprimento, para cada composição de liga. Os fios foram caracterizados mecanicamente por ensaio de tração e de dureza após tratamento térmico de recristalização a 510 ºC por 1 h. Os fios também tiveram as condutividades elétricas medidas na condição recristalizada e os resultados foram comparados com dados experimentais da literatura. Os materiais obtidos mostraram-se adequados à utilização como fio condutor de energia elétrica. Os limites de escoamento e de resistência a tração tiveram seus valores melhorados com o aumento do teor de magnésio na liga, 11 % e 24 %, respectivamente, enquanto houve queda nos valores de condutividade elétrica para cerca de 60 % IACS (International Annealed Copper Standard). / The aim of this work was to obtain copper wires in three different chemical compositions starting from electrolytic copper and magnesium. The mains steps were evaluated, starting from the melting of small eutectic cooper-magnesium specimens in an electric arc furnace, followed by further dilution of this buttons in a resistive furnace and casting it in a copper mould. The as cast billets were homogenized in a resistive furnace at 910 ºC for 2 h. The billets were mechanically cold worked by swaging and a final drawing step to attain a round shape and a reasonable surface quality. The cast ingots chemical analysis indicated that the processing route showed to be adequate, in laboratory scale, to obtain wires with cross sectional area of 4 mm2 and 10 m in length. The wires in both conditions as cold worked and after a recovering heat treatment at 510 ºC for 1 h, were mechanically characterized by tensile testing and hardness. The wires had also the electric conductivity assessed in the recovered heat-treated state and the results were compared to the literature data. The obtained material showed to be adequate to be used as electric conductor. The yield strain and ultimate tensile strength were improved with the increasing amount of Mg in the alloy, 11 % and 24 %, respectively, while the electric conductivity decreased to 60 % IACS (International Annealed Copper Standard).

O ferro-esponja ou DRI (Direct Reduced Iron) é obtido pelo processo de redução direta onde o minério de ferro é transformado em ferro metálico através de reações químicas envolvendo o estado sólido (minério) e o gasoso (gases redutores). Neste processo o minério de ferro não passa pelo estado líquido como ocorre com o ferro-gusa. Isto confere ao ferro-esponja algumas desvantagens que prejudicam o seu desempenho nas aciarias. Pode-se citar a redução no rendimento metálico e o maior consumo de energia elétrica como principais impactos de sua utilização intensiva. O ferro-esponja apresenta menor quantidade de ferro total (maior quantidade de impurezas) do que o ferro-gusa e também apresenta óxidos de ferro remanescentes em sua estrutura (menor metalização). Para torná-lo mais competitivo, inúmeras melhorias no processo têm sido promovidas para aumento da metalização. No entanto, o limite superior alcançado na prática tem ficado ao redor de 95%. Visando contribuir para melhorar a qualidade do ferro-esponja este trabalho apresenta uma proposta inovadora a partir da técnica de auto-redução. O objetivo é aumentar o grau de metalização do ferro-esponja através de seu aquecimento. Para isso, foram realizadas análises termogravimetrias e aquecimentos em forno mufla; análises químicas por via úmida, difração de raios-x, espectroscopia mössbauer e análise de microssonda de raios-x. As análises estruturais foram realizadas utilizando microscópio eletrônico de varredura para confirmar a efetividade da técnica apresentada. Nesta dissertação pode-se comprovar que, através da técnica de auto-redução, o ferro-esponja alcança metalizações acima de 98% em detrimento da queda do teor de carbono total. Um aumento de 4% na metalização traz um ganho estimado de 5 a 10% no consumo de energia elétrica nos fornos de fusão e um acréscimo proporcional na produção horária das aciarias. / The direct reduced iron is obtained by direct reduction process, where iron ore is transformed in metallic iron via chemical reactions involving solid (ore) and gaseous (reductant gases) states. In this process the iron ore does not pass by liquid state like pig iron. This become to direct reduced iron some disadvantages, which decrease its performance in the steelmaking process. It can be mentioned the reduction of metallic yield and the higher consumption of electric energy as the main impacts of its intensive use. The direct reduced iron presents lower amount of total iron (higher amount of impurities) than pig iron and presents iron oxides remained in its structure (lower metallization). To become more competitive, several improvements in the reduction process have been carried out to increase its metallization. However, the highest level of metallization, which has been reached, is 95%. To improve the direct reduced iron quality, the present work evaluates, in an innovative way, using the technique of self reduction. The objective is increase of metallization of the direct reduced iron through its heating. Thermal, chemical and structural characterization was carried out to check the effectiveness of the investigated technique. The research confirms that the direct reduced iron can reach a metallization higher than 98% with a decrease of total carbon amount using the technique presented in this work. An improvement of 4% in the metallization brings savings of 5 to 10% in the electric energy consumption of the electric arc furnaces and a proportional increase of the production in the steelmaking plants.

Direct Reduced Iron (DRI) is used as an alternative feedstock in electric arc furnaces, making up 50% or more of the total iron charge. DRI produced with coal based reductants (for example in rotary kilns) make up roughly 25% of DRI produced in the world. It was found that SL/RN DRI samples from a kiln cooler had high nitrogen contents (50-250ppm, depending on particle size), higher than DRI from gas-based reduction. The higher nitrogen content of SL/RN DRI would increase the levels of nitrogen of liquid steel produced in the EAFs. The problem is exacerbated by the fact that the SL/RN DRI contains virtually no carbon (which would aid in preventing nitrogen pickup). The proposed mechanism of nitrogen pick-up by the SL/RN DRI is one where nitrogen present within the atmosphere of the rotary cooler (where hot DRI, discharged at 1000°C from the rotary kiln, is cooled to approximately 100 °C in ca. two hours) penetrates the solids bed and nitrides DRI particles. Possible rate-determining steps for nitriding in the cooler have been evaluated. Nitriding of DRI particles is predicted to be rapid: the most plausible location for rapid nitrogen pickup is the first 5 meters of the rotary cooler, where the high temperature, nitrogen-rich gas atmosphere and rapid solids bed mixing are conducive to nitriding; solid-state and pore diffusion of nitrogen into DRI particles are predicted to be rapid too. The most plausible rate determining step for nitriding of DRI particles is that of nitrogen dissociation on the DRI surface, which can be further retarded by the presence of sulphur. A strong correlation was found between the amount of “melt-in” carbon in the liquid steel and the final tap nitrogen content, with 0.3% C resulting in nitrogen levels as low as 50 ppm (80 ppm or less is desired on the plant in question) at tap, even with DRI material that is high in nitrogen and contains virtually no carbon. Proposals to increase the melt-in carbon are included. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Materials Science and Metallurgical Engineering / unrestricted

Sandvik produces about 230 000 tonnes of steel annually by melting in an electric arc furnace, where more than 90% of this steel is casted via continuous casting. When the strands are cast, these strands will be cuts to specific lengths with 2 cm thick cuts by using gas and iron powder. This generates approximately 750 tonnes of steel chips (cutting residues) each year, with a composition from the entire annual production of steel that falls as a residual. The purpose of the work was to review a possible reuse of the cutting residues as a raw material in the electric arc furnace. The problem with the cutting residue is the large reactive surface area, which could cause the material to burn in the electric arc furnace during operation. Since there are a high gas flow in the electric arc furnace during operation, the cutting residue that has a small particle size can also disappear from the furnace with the gas flow to the particle filters. By briquetting the cutting residue, these problems could be minimized and a reuse of the cutting slag as raw material could thus be possible. Therefore the cutting residue was transported to a company that sieved, dried and briquetted the cutting residue.  37 tonnes of cutting residue briquettes have been reused into 18 charges under normal operations with 2 tonnes of cutting residue briquettes in each charge (one charge with only 1 tonne of cutting slag). In order to measure how efficient, the reuse of the cutting residue was, a reference was needed. The reference was based on how the yield of steel for the elements, molybdenum, nickel, copper, cobalt and chromium in the electric arc furnace behaves in daily operation. This yield was used as a basis for calculating the yield when reusing the cutting residue. The results showed that nickel and molybdenum had a consistently good yield. The results for the cobalt and copper was not as clear, but the yields were generally good. In the case of chromium the results are naturally varied, as chromium reacts with the slag during the process. However, the predominant conclusion of the work was that it is possible to reuse the cutting residue as a raw material in the electric arc furnace with an acceptable yield by briquetting it. Analysis of the slag was also done to see any deviations from daily operations. The results showed that the slag was not affected when the cutting residue was reused as raw material in the electric arc furnace. / Varje år producerar Sandvik ungefär 230 000 ton stål genom nedsmältning av stålskrot i ljusbågsugnen där mer än 90 % av stålet gjuts via stränggjutning. När strängarna gjuts kapas de till specifika längder med ett 2 cm tjockt snitt med hjälp av syrgas och järnpulver. Detta resulterar i en restprodukt (skärslagg) om ca 750 ton per år, med sammansättningen från den årliga produktionen av stål. Syftet med arbetet var att se över en möjlig återanvändning av skärslaggen som råvara i ljusbågsugnen. Problematiken med skärslaggen är den stora reaktiva ytan vilket kan medföra att materialet börjar brinna i ljusbågsugnen under drift. Skärslaggen har en liten partikelstorlek och kan således följa med till gas- och partikelfilter då det är ett högt gasflöde i ljusbågsugnen under drift. Genom att brikettera skärslaggen kan dessa problem minimeras och en återföring av skärslaggen som råvara kan således vara möjlig. Skärslaggen transporterades till ett företag som siktade, torkade och briketterade skärslaggen. 37 ton skärslaggsbriketter har återförts i 18 försökscharger under normal drift med 2 ton skärslaggsbriketter i varje charge (en charge med enbart 1 ton skärslagg). För att mäta hur effektivt återföringen av skärslaggen var behövdes en referensnivå. Referensnivån baserades på hur utbytet till stål för elementen, molybden, nickel, koppar, kobolt och krom i ljusbågsugnen förhåller sig vid daglig drift. Detta utbyte användes som bas för att beräkna utbytet vid återföringen av skärslaggen. Av resultaten framgår det att nickel och molybden visade genomgående goda utbyten. Utfallet för elementen kobolt och koppar var inte lika tydliga men utbytena var till övervägande del goda. Beträffande krom var resultaten av naturliga skäl varierande, då krom reagerar med slaggen under processens gång. Den övervägande slutsatsen av arbetet var emellertid att det går att återföra skärslagg som råvara i ljusbågsugnen med godtagbara utbyten genom att brikettera den. Analysering av ljusbågsugnsslaggen gjordes också för att se eventuella avvikelser ifrån den dagliga driften. Resultaten visade att slaggen inte påverkas när skärslaggen återförs som råvara i ljusbågsugnen.

SSAB i Oxelösund ska bygga en ljusbågsugn för konvertering av verksamheten från huvudsakligen malmbaserad produktion till skrotbaserad produktion. I samband med byggandet av ljusbågsugnen kommer en ny 130 kV linje byggas och från denna linje kommer ett nytt 30 kV nät byggas för att mata ljusbågsugnen och två stycken skänkugnar. En av dessa skänkugnar är idag (2019) i drift med 10 kV men ska konverteras till 30 kV medan den andra är en ny elektriskt sett identisk ugn. Anslutningen av dessa tre ugnar till det avskilda 30 kV nätet är till för att begränsa spridning av övertoner och flimmer till övriga laster. Ugnarna ska sedan anslutas till ett gemensamt elektriskt filter, för 30 kV nätet. Ljusbågsugnen och skänkugnarna ska vara i drift första kvartalet 2024, på grund av att det är några år in i framtiden är kortslutningsimpedanser osäkra. För att uppfylla termisk- och korttidsströmsdimensionering för kabeln mellan huvudställverk (OT40) och skänkugnsställverk (SU2) fodras enledarkabel med 300 mm2 aluminiumledare och PEX-isolering. Denna dimensionering förutsätter att förläggning sker i triangelformation, temperaturen är högst 35 °C och kabeln förläggs på sådant sätt att den inte påverkas av andra kablar. Maximal kortslutningsström som kabeln klarar av under den maximala bortkopplingstiden är 32,5 kA. Kortslutnings- och spänningsfallsberäkningar är utförda iprogrammet GNU Octave. Högsta och lägsta kortslutningström i respektive ställverk är beräknad. Överströmsskydden ställs in så att selektiv bortkoppling erhålls, med maximal bortkopplingstid 0,9 sekunder. En blockeringslogik används för att försäkra anläggning enmot oselektiv utlösning. Logiken innebär, enligt SSAB:s praxis, att skyddet närmast felstället ska blockera överordnat skydds kortslutningsströmsteg (>> I). Jordfelsskydd dimensioneras efter en nollpunktsresistor om 10 A. Jordfelsskydden är riktade och friges av nollpunktsspänningsskydd för att säkerställa att okynnesutlösning av jordfelsskydden inte uppstår i samband med omkopplingar eller fel i nätet. Frigivningen fungerar upp till en maximal snedavstämning om cirka 21 A. / SSAB in Oxelösund will build an electric arc furnace to transform business from a mainly ore-based production, with blast furnaces, to a scrap based production. Together with the construction of the electric arc furnace, a new 130 kV overhead line and a 30 kV substation will be built. The 30 kV substation will feed one electric arc furnace and two ladle furnaces. One of these ladle furnaces is currently (2019) being fed with 10 kV, but is going to be converted to 30 kV, while the other one is a new electrically identical furnace. The connection of these three furnaces to the 30 kV grid is done in order to limit the distribution of harmonic distortions and flicker to the other loads. The furnaces on the 30 kV grid will be connected to a common electrical filter. The electric arc furnace and the ladle furnaces will be operational and produce steel in the first quarter of 2024. Since the installation will be performed some years ahead the short circuit impedance is not known. The cable between the main substation (OT40) and the ladle furnace substation (SU2) was being selected according to thermals and short time currents which determined the cable to consist of a single core cable with 300 mm2 aluminium conductor isolated by XLPE-isolation. This is provided that the cable is mountedin a triangle formation along a path with temperatures at maximum 35 C and is placed in such a way that the cable is not influenced thermally by other cables. Short circuit and voltage drop calculations are made in the program GNU Octave. The highest three phase and the lowest two phase short circuit current is calculated in every substation. The overcurrent protection is set to a maximum disconnection time of 0.9 seconds. A blocking logic is being used to further ensure a selectivity in the facility. The logic means, according to SSAB praxis, that the protection closest to the fault blocks the upstream short circuit protection ( I). The earth fault protection is designed around using a neutral grounding resistor of 10 A. The earth fault protection is directional and is being released by the neutral displacement protection to asure no unwanted tripping of the earth fault protection by change-over switching or faults in the grid. The release of the protection works with detuning up to about 21 A.

The landfilling of slag obtained from the high alloyed Electric Arc Furnace (EAF) steel making process, constitutes an environmental treat for society as well as an economical problem for the companies producing it, due to the costs related to waste management practices. Conventional methods of slag recycling are abundantly used among the steelmaking business, but due to their particular physical properties, high- alloyed EAF slags cannot be properly valorized. Moreover, the pickling process that high-alloyed EAF steels undergo to, generates acidic wastewaters, that need to be collected and neutralized, before they can be recirculated into the natural water streams. For such a task, steel mills currently utilize slaked lime (a Ca rich mineral) to raise the pH and to remove any metal particles dissolved into the wastewaters. Slag contains high amount of Ca; therefore, it has already been tested as a slaked lime replacement. In fact, previous studies conducted at the Material Science and Engineering department at KTH Royal Institute of Technology showed, on a laboratory scale, that slag has the potential to replace lime for the neutralization and purification of the acidic wastewaters. This Master’s thesis project aims at upscaling the volumes of wastewaters to be tested, about 70 to 90 folds of the one from previous research, bridging the gap between laboratory tests and the industrial scale. The thesis is divided into three tranches, a first part where a water-salt solution conductivity trials were carried out, to model the behavior or slag dispersion in the acidic wastewaters. After the results obtained from the conductivity trials, neutralization trials with slag and the lime product currently in use by the company, were carried out at the neutralization plant in Outokumpu Stainless, Avesta (Sweden). The neutralization trials were carried out with 70 and 90 liters of acidic wastewaters and in order to perform the trials on site, the slag sample was dried and later sieved to a particle size of less than 350μm. Moreover, data was analyzed and compared to previous studies in order to have a clearer understanding regarding the neutralization efficiency of the slag, especially whether or not the technology would had worked on upscaled volumes. Additionally, the project checked if it was possible to find a generalized relationship between the mass of slag and volume of wastewaters required for the neutralization process. Slag demonstrated to be able to buffer the pH to the target values of 9, while also showing an almost linear trend compared to previous studies. The reaction progress between slag, lime, and the acidic wastewaters was also analyzed. / Deponering av slagg som erhållits från den höglegerade ljusbågsugn (EAF) stålframställningsprocessen utgör en miljömässig behandling för samhället och ettekonomiskt problem för de företag som producerar den på grund av kostnaderna för avfallshantering. Konventionella metoder för återvinning av slagg används i storutsträckning bland stålindustrin, men på grund av deras speciella fysiska egenskaper kan höglegerade EAF-slaggen inte värderas ordentligt. Dessutom produceras sura avloppsvatten av betningsprocessen som höglegerade EAF-stål genomgår som sedan måste samlas in och neutraliseras innan de kan återcirkuleras i det naturliga vattnet. För en sådan uppgift använder stålfabriker för närvarande släckt kalk (ett Ca-rikt mineral) för att höja pH-värdet och för att avlägsna alla metallpartiklar som löses upp i avloppsvattnet. Slaggen innehåller hög mängd Ca och därför har den testats som en ersättning till släckt kalk. Tidigare studier utförda vid avdelningen materialvetenskap och teknik vid Kungliga Tekniska Högskola visade på laboratorieskala att slagg har potential att ersätta kalk för neutralisering och rening av sura avloppsvatten. Detta examensarbete syftar till att skala upp volymerna av avloppsvattnet som ska testas till cirka 70–90 gånger av den från tidigare forskning, och därav fylla ut bryggan mellan laboratorietester och industriell skala. Avhandlingen är uppdelad i tre delar, Första delen innehåller försök på ledningsförmåga i en vatten-saltlösning som genomfördes för att modellera beteende eller slaggspridning i sura avloppsvatten. Efter de resultat som erhållits från konduktivitetsmätningarna genomfördes neutraliseringsförsök med slagg och kalk som för närvarande används av företaget vid neutraliseringsanläggningen i Outokumpu Stainless, Avesta (Sverige). Neutraliseringsförsöken genomfördes med 70 och 90 liter sura avloppsvatten och för att utföra experimenten på plats torkades slagg provet och siktades senare till en partikelstorlek på mindre än 350 μm. Dessutom analyserades data och jämfördes med tidigare studier för att få en tydligare förståelse för slaggens neutraliseringseffektivitet, särskilt huruvida tekniken skulle ha fungerat på större volymer, och även om det också var möjligt att hitta ett generaliserat samband mellan mängden slagg och volym avloppsvatten som krävs för neutraliseringsprocessen. Slagget visade sig kunna buffra pH till målvärdena 9, samtidigt som den visade en nästan linjär trend jämfört med tidigare studier. Reaktionsförloppet mellan slaggkalk och de sura avloppsvattnen analyserades också.

Without a doubt, there is a consensus around the international community which suggests that our current way of life is unsustainable for a healthy planet, society and economy. One focal point that should be taken deeply into consideration is the steel industry as, globally, it accounts for 8% of global emissions. Thus, there is a dire need to incorporate drastic measures, if one wishes to reach net-zero emissions by 2050, in accordance with the Paris Agreement of 2015. Electric Arc Furnaces are seeing a rapid implementation in the steel industry. However, at 0.5 tonnes of CO2 emitted per tonne of liquid steel produced, this emissions rating is still significant considering the amount of steel being produced annually. Additionally, these furnaces emit off-gases which must be treated from the dust. This leaves operators with a conundrum as the dust content compromises the use of waste heat recovery boilers for energy recovery, due to constant breakdowns. Therefore, this study aims to analyse the feasibility of using bioenergy and carbon capture and utilisation (CCU) concepts to capitalise on the high off-gas energy and emissions content to remedy the dust issue, whilst producing higher value products. The proposed concept evaluates the effectiveness of using the off-gas as the energy carrier and feed-stock for a biogasificaiton unit. Three different cases based on different EAF off-gas compositions have been investigated. Case 1 suggested that the off-gas composition is very CO2-heavy, whichled to investigating the option of adopting a CO2 biogasification concept to directly use the CO2. Case 1 performed the best in terms of CO2 utilisation efficiency; being 0.293. The system energy utilisation also noted that 49.3% of the inlet streams energy was transferred to the desired product. On a broader picture, this means that around 11% of the total energy coming out of the EAF would be utilised in producing a value-added product in the form of syngas. This contrasts with allowing around 33% of the energy in the EAF either being completely dissipated to the environment or converting it into electricity via waste heat recovery. The following two cases, Case 2 and 3, indicate EAF off-gas composition containing 72% and 40% nitrogen respectively. For Cases 2 and 3, a steam biogasification process was integrated which did not yield positive results for CO2 utilisation, since is a more promising gasifying agent. In addition, significant energy from EAF off-gas is used in raising the temperature of steam to the design temperature of the gasifier. However, although the CO2 was not directly used in this part of the process, it allows for other opportunities of process integration, for example the reverse water-gas shift step.

<p>The electric arc furnace (EAF) is a highly energy intensive process used to convert scrap metal into molten steel. The aim of this research is to develop a dynamic model of an industrial EAF process, and investigate its application for optimal EAF operation. This work has three main contributions; the first contribution is developing a model largely based on MacRosty and Swartz (2005) to meet the operation of a new industrial partner (ArcelorMittal Contrecoeur Ouest, Quebec, Canada). The second contribution is carrying out sensitivity analyses to investigate the effect of the scrap components on the EAF process. Finally, the third contribution includes the development of a constrained multi-rate extended Kalman filter (EKF) to infer the states of the system from the measurements provided by the plant.</p> <p>A multi-zone model is developed and discussed in detail. Heat and mass transfer relationships are considered. Chemical equilibrium is assumed in two of the zones and calculated through the minimization of the Gibbs free energy. The most sensitive parameters are identified and estimated using plant measurements. The model is then validated against plant data and has shown a reasonable level of accuracy.</p> <p>Local differential sensitivity analysis is performed to investigate the effect of scrap components on the EAF operation. Iron was found to have the greatest effect amongst the components present. Then, the optimal operation of the furnace is determined through economic optimization. In this case, the trade-off between electrical and chemical energy is determined in order to maximize the profit. Different scenarios are considered that include price variation in electricity, methane and oxygen.</p> <p>A constrained multi-rate EKF is implemented in order to estimate the states of the system using plant measurements. The EKF showed high performance in tracking the true states of the process, even in the presence of a parametric plant-model mismatch.</p> / Master of Applied Science (MASc)

Thesis (MScEng) --University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis deals with the development of a new process for the production of Direct Reduced Iron (DRI), intended for use specifically by small scale Electric Arc Furnace (EAF) based steel mills, who require small volumes of DRI. The term development as used here is taken to include such aspects as conceptual design, theoretical verification and initial practical testing. The rise of EAF steelmaking brought about the metamorphosis of steel scrap from a waste product into a valuable raw material. Scrap prices rose steeply during the period 1995 to 2009 compelling EAF steelmakers, wishing to have more control over the cost of their input material, to seek for scrap supplements or alternatives. DRI has become an accepted and sought after supplement, or even complete alternative, to steel scrap. Adding DRI to an EAF charge has a range of advantages, including the dilution of tramp elements and possible cost benefits, but it does have negative effects. These include the lowering of the scrap to liquid metal yield and an increase in power consumed. The effect of charging DRI to a small EAF is quantified. The maximum DRI that may be added to the burden whilst still maintaining the present steelmaking volume, is shown to be as high as 50% if charged continuously, and the maximum price payable for DRI, is shown to be approximately 80% of base grade scrap price. Finally other requirements unique to small scale EAF operators are considered in order to prepare a schedule of requirements for a DRI plant specifically for small scale EAF steel mills. A review of published information on existing DRI production technology, processes and plants is undertaken is establish the fit of existing processes to the requirements set. Initially the thermodynamics and kinetics of iron ore reduction and coal gasification, specifically downdraft gasification are reviewed. Thereafter existing processes are reviewed. Shaft based processes and rotary kiln based processes are identified as possible suitors to the requirements. Limitations of these processes, specifically heat transfer in rotary kilns and the pressure drop over a reduction shafts are investigated. Finally a typical process in each of the main process classes is adjudicated against the set requirements. None is found to match the set requirements. A new process is proposed that is claimed to better suit to small scale operation. The uniqueness of the process is embodied in the combination of existing technologies of downdraft gasification and iron ore reduction in a shaft, in a single reactor. The process consists of two shafts, one placed above the other. Iron ore is charged into the top shaft, called the pre-heat shaft, where it is pre-heated and lightly reduced to wustite with gas from the bottom shaft, called the reduction shaft. The pre-heated ore is then charged together with coal into the reduction shaft. Gasification air is drawn into the top of the reduction shaft where the coal is gasified in a downdraft gasifier, generating reduction gas which reduces the ore as the gas moves concurrently with the iron ore. The exit gas is cleaned and pumped to the pre-heat shaft where it combusted with air to pre-heat the iron ore in the pre-heat shaft. The concept is analysed thermodynamically using amongst others, FactSage, and is shown to be thermodynamically viable. To test the concept process concept practically, an extremely small pilot plant with a production rate of 2kg DRI/h, consisting of only a gasifier/reduction shaft, was designed and constructed using reduction rate data obtained from literature supplemented with data obtained from thermogravimetric analysis of CO reduction of lump Sishen hematite. Pilot Plant trials were performed using various reductant sources. The degree of metallizaion was analysed using visual inspection of cut and polished samples compared to calibrated standards. Analysis of the results indicate that coal rate and production rate influence the degree of reduction positively and negatively. The conclusions arrived at include the fact that the process is thermodynamically viable, that it was possible to reduce iron ore in a simplified pilot plant, and that the process was found to be stable and controllable. It is recommended that a larger scale pilot plant, embodying the full proposed flow sheet be erected to test the process more completely. / AFRIKAANSE OPSOMMING: Die tesis handel oor die the ontwikkeling van ‘n nuwe proses vir die vervaardiging van sponsyster. Die proses is beoog spesifiek vir gebruik deur kleinskaalse Elektriese Boogoond (EBO) gebaseerde staal aanlegte, wat kleiner hoeveelhede sponsyster benodig. Die term ontwikkeling soos hier gebruik word aanvaar om aspekte soos konseptuele ontwerp, teoretiese verifikasie en aanvanklike toetsing te behels. Die vinnige groei van EBO staalvervaardiging het skroot getransformeer van weggooiproduk tot waardevolle grondstof. Die prys van skroot het skerp gestyg gedurende die periode 1995 to 2009. EBO gebaseerde staal produsente, in ‘n poging om meer beheer te hê oor die koste van hul insetmateriaal, het hul in ‘n toenemende mate tot skrootalternatiewe gewend. Sponsyster het ‘n aanvaarde en gewaardeerde byvoeging, en selfs alternatief tot staalskroot geword. Die byvoeging van sponsyster by die lading van ‘n tipiese EBO het besliste voordele, maar het dit ook nadelige effekte. Die voordele sluit die verdunning van reselemente en moontlike kostevoordele in, terwyl van die nadele die verlaging van die skroot tot vloeistaal opbrengs, en ‘n verhoging in kragverbruik, is. Die effek van die byvoeging van sponsyster tot ‘n EBO lading word gekwantifiseer. Daar word getoon dat die maksimum hoeveelheid sponsyster wat by ‘n EBO lading gevoeg kan word terwyl die hoeveelheid staal geproduseer konstant gehou word, ongeveer 50% is indien die sponsyster kontinue gelaai word, en die maksimum prys wat vir die sponsyster betaal kan word, word bereken op ongeveer 80% van die prys van basisgraad skroot. Ander vereistes uniek aan kleinskaal EBO bedrywers word oorweeg ten einde ‘n lys van vereistes vir ‘n sponsysteraanleg, uniek aan kleinskaal EBO bedrywers, te kan bepaal. ‘n Oorsig van gepubliseerde inligting oor sponsysterproduksietegnologie word onderneem ten einde die passing van bestaande prosesse met die gestelde vereistes te kan bepaal. Nadat die termodinamika en kinetika van ysterertsreduksie en steenkoolvergassing be-oordeel is, word bestaande sponsysterprosesse beskou. Skag- en Roterende oond gebaseerde prosesse word as moontlik gepaste prosesse identifiseer. Hitte-oordrag en die drukval oor gepakte beddens, synde tipiese beperkings eie aan die twee prosesse, woord beskou. Tipiese prosesse in elk van die hoofklasse van prosesse word ten laaste be-oordeel aan die gestelde kriteria. Daar word bevind dat geeneen van die bestaande prosesse aan die vereistes voldoen nie. ‘n Nuwe proses, wat skynbaar die behoefte van kleinskaalse EBO gebaseerde staalprodusente beter bevredig, word voorgestel. Bestaande tegnolgie word in ‘n unieke opstelling geïntegreer. Reduksie word in ‘n reduksiekag gedoen as gevolg van die ooglopende massa- en hitte-oordragvoordele van ‘n skag. Reduksiegas word verkry van steenkoolvergassing in ‘n afstroomvergasser ten einde teerverwydering in ‘n naverwerkingsstap oorbodig te maak. Die uniekheid van die proses is beliggaam in die kombinasie van ‘n steenkoolvergasser en reduksieskag in ‘n enkele reaktor. Die proses bestaan uit twee skagte, een bo die ander. Ystererts word in die boonste skag, wat die voorverhitskag genoem word, gelaai. Hier word die erts voorverhit en moontlik lig gereduseer tot wustiet met gas van die onderste skag, wat die reduksieskag genoem word. Die voorverhitte erts word saam met steenkool in die reduksieskag gelaai. Vergassingslug, word in die reduksieskag gesuig waar die steenkool in ‘n afstroomvergasser vergas word. Hierdeur word reduksiegas gegenereer wat die erts verder reduseer soos dit saamstromend met die erts af beweeg. Die uitlaatgas word gesuiwer en na die voorverhitskag gepomp waar dit verbrand word om die erts te voorverhit. Die konsep is termodinamies analiseer met gebruikmaking van onder andere FactSage, en werkbaar bevind. ‘n Baie klein, vereenvoudigde proefaanleg, met ‘n produksievermoë van 2kg DRY/uur, bestaande uit slegs ‘n reduksiekag, is ontwerp en gebou met gebruikmaking van kinetika inligting uit die literatuur aangevul met inligting uit termogravimetriese analise van die CO reduksie van Sishen hematiet. Proefaanleglopies is uitgevoer met ‘n reeks reduktantbronne. Die metallisasiegraad is bepaal deur visuele inspeksie van gesnyde, gepoleerde monsters wat vergelyk is met gekalibreerde standaarde. Analise van die resultate toon dat die steenkoolkoers ‘n positiewe verband, en die produksiekoers ‘n negatiewe verband met die metallisasiegraad het. Die slotsom waartoe gekom is, is dat die proses termodinamies werkbaar is, dat reduksie van ystererts in ‘n vereenvoudigde proefaanleg bewerk kon word, en dat die prose stabiel en beheerbaar voorgekom het. Die aanbeveling word gemaak dat ‘n groter proefaanleg wat die volledige voorgestelde vloeiskema verteenwoordig, opgerig behoort te word, ten einde die proses meer volledig te kan toets.

Eine umweltverträgliche Methode der Rückgewinnung anorganischer industrieller Abfallprodukte bietet die thermische Behandlung im elektrischen Lichtbogenofen. Hierbei wird der Abfallstoff geschmolzen und die enthaltenen Schwermetalloxide reduziert und von der mineralischen Phase abgetrennt. Der Prozess ist sehr energieaufwändig und noch nicht vollständig verstanden. Die laserinduzierte Plasmaspektroskopie (LIBS) soll als in situ-Messtechnik dabei helfen, das Verständnis zu verbessern und die Methode zu optimieren. In theoretischen Untersuchungen wurde gezeigt, dass die Güte von LIBS-Messungen durch Normierung auch mit einer gesättigten Linie eines Matrixelementes verbessert werden kann. Für LIBS-Messungen im elektrischen Lichtbogenofen wurde ein mobiles Doppelpuls-LIBS-System für industrielle Bedingungen entwickelt, getestet und optimiert. Als Modellsystem für Schlacken wurden dotierte Glasproben verwendet. Für festes und flüssiges Glas wurden Nachweisgrenzen im ppm-Bereich erreicht, was für die Gehalte in Schlackeproben ausreicht. Ferner wurden zwei Methoden entwickelt, Flüssigkeiten mit Hilfe von festen Standards zu quantifizieren. Um die Empfindlichkeit von LIBS zu verbessern, wurde Doppelpuls-LIBS untersucht. Es konnte eine Verstärkung des Signals um das 5,1-fache erreicht werden. Es konnten Emissionen der Moleküle CaCl, MgO, YO und ZrO in LIBS-Plasmen identifiziert und simuliert werden. Eine mögliche Verwendung der Molekülemissionen stellt die Quantifizierung sehr hoher Elementgehalte dar. Trotz der schwierigen experimentellen Bedingungen erwies sich das LIBS-System als empfindlich genug. Es wurde schrittweise Mangan- und Chromoxid zur Schmelze gegeben, was in einen linearen Anstieg der LIBS-Signale resultierte. Die Reduktion und Separation von Chrom gelang und konnte mit LIBS verfolgt werden, was durch die Referenzanalysen bestätigt wurde. / The reduction process in the electric arc furnace offers a sustainable method to recover industrial inorganic waste materials. The material is molten and the containing heavy metals are reduced and separated from the mineral phase. The energy consumption of the process is very high and the detailed reactions and dynamics are not yet fully understood. Laser induced breakdown spectroscopy can provide online-measurements inside a furnace, enabling us to increase understanding and optimize the process. In a theoretical investigation it has been shown that intensity fluctuations of LIBS can be compensated by normalizing the line used for analysis with a saturated line from a matrix element. For LIBS-measurements inside the electric arc furnace, a mobile double pulse LIBS-system designed for an industrial environment was built and tested. Glass was used as a model system for slags due to its lower melting point. Limits of detection in the ppm-region were achieved for solid and liquid glass, which is sufficient sensitivity for recycling slags. Furthermore, two methods were developed to quantify a liquid using solids as standards. To improve the sensitivity of LIBS, double-pulse measurements were conducted. Signal enhancements of up to 5.1 were achieved compared to single pulse. In the LIBS plasma emissions of molucules CaCl, MgO, YO and ZrO were identified and their emissions simulated. These emissions could be used to quantify large element concentrations. Despite the difficult experimental conditions the sensitivity of the LIBS-System has been found to be sufficient for recycling-slags. When stepwise adding manganese and chromium oxide to the melt, the respective LIBS intensity increased linearly. The reduction and separation of chromium was successful, which was confirmed by reference analysis.