Dissertations / Theses on the topic 'Electric furnaces Electric furnaces Steel-works Steel'

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.

A series of model steels containing copper levels up to 0.48wt%, nickel up to 0.22wt% and silicon levels of 0.52wt% were oxidised in air at 1050 and 1150??C, and in a CO2-N2 mixture at 1250??C for times of up to 3 hours. The scaling kinetics were measured and the behaviour of copper-rich phase formation at the scale/metal interface was investigated. When oxidised at 1050/1150??C, significant quantities of copper-rich phase were observed for most model steels. The relatively high oxidation rate under these conditions led to the rapid development of a copper-rich layer with little copper diffusing into the metal. However, when oxidised at 1250??C, the copper-rich phase did not form for a significant amount of time; and for some model steels, not at all. This was attributed to the considerably lower oxidation rate and the fact that more copper was found to have diffused into the metal. Alloying additions of nickel and silicon were found to be beneficial in reducing the amount of copper-rich phase measured at the scale/metal interface under the conditions investigated at 1150??C and 1250??C. This occurred because nickel and silicon addition promoted the occlusion of copper-rich phase into the scale. Copper enrichment during oxidation was modelled using a numerical description of the diffusion processes involved. Predictions of the time for commencement of copper-rich phase formation at 1250??C were in close agreement with observation. Agreement between predicted and observed copper-rich layer thickness was less successful under conditions where occlusion was significant, and the measured thickness varied non-uniformly with time. The cracking susceptibility of the model steels was examined using a hot compression test. Oxidation was performed in air at 1050, 1150 and 1250??C and most specimens were compressed at 1050??C. The amount of cracking was found to increase with the amount of copper-rich phase precipitated at the scale/metal interface during oxidation. In general, nickel addition reduced the amount of cracking at all temperatures; and under some conditions prevented cracking altogether. Silicon reduced or completely suppressed cracking when the subscale formed was liquid. The beneficial effects of nickel and silicon addition were attributed to their effect of promoting copper occlusion.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Along with the essential importance of the metallurgical sector, one must recognise that it is also one of the largest sources of environmental pollution. In particular, the problem of electric arc furnace (EAF) dusts is of a growing concern due to the increase in popularity of EAF steelmaking. This dust is classified as a hazardous product due to the elevated content of toxic metals (e.g., Cr).
Studies on the properties of EAF dusts are sparse. Experiments were performed in order to determine the chemical and physical characteristics of the dust. It was determined that EAF dust is constituted of randomly distributed agglomerations of homogeneously nucleated particles and entrained particles. The main elements present within the particular dust were iron and chromium, the latter due to the fact that the dust used was formed within a stainless steel mini-mill. The main phases present within the dust were Fe2O3/Fe 3O4 and Cr2O3.
Thermal remediation experiments were then carried out in a computer controlled thermogravimetric system. The parameters studied during the tests included temperature, residence time and heating rate. In addition, the behaviour of the EAF dust during remediation was studied; in terms of weight and volume loss, gas evolution, particle morphology and resulting leachability of the treated product. Furthermore, it was observed that at temperatures greater than 1200°C metal leachability decreased significantly due to a decrease in toxic metal concentration within the treated product and the formation of a resistant, dense, plate-like morphology. At 1600°C, no toxic metals leached out of the remediated EAF dust and volume reduction was significant, resulting in a product that would be safe and more economical to landfill.

In steel production, an electric arc furnace (EAF) is most commonly used to melt raw material in order to produce liquid steel. Scrap is the main raw material which differs in regard to the content of iron and of some chemical elements. The price of scrap depends on these attributes. In order to obtain the desired quality and quantity, each melting bath unit of steel has either its own material constraints or the constraints for electric arc furnace such as the capacity of EAF. In addition, the availability and transportation of scrap are also restricted because they need space. The research in this thesis is to create an optimization model which minimizes the cost of raw material and charges the EAF efficiently while meeting the constraints of the scrap recipe and scrap transportation system. This problem is a combinational optimization problem and the model is developed based on linear programming theory. The running speed of the model is reasonably guaranteed by properly designing the combinatorial structure with branch and bound rules and heuristics. Finally, a software is created by representing the model in the spreadsheet, which can be used in real, everyday production. Simulation results show significant improvement compared to the strategy applied today at ArcelorMittal(Contrecoeur, Quebec): the cost of scrap steel is reduced by 2 to 6% and the time of charging buckets is 2 to 10 minutes faster.
Dans la production d'acier, four à arc électrique (FEA) est la technologie la plus couramment utilisée pour faire fondre les matières premières afin de obtenir de l'acier liquide. La ferraille est la matière première principale dont les types se diffèrent selon le contenu de fer et d'autres éléments chimiques. Le prix de la ferraille dépend de ces attributs. Afin d'obtenir la qualité et la quantité souhaitées, chaque unité bain de fusion de l'acier a subi à ses propres contraintes matérielles ou des contraintes liées au four à arc électrique, telles que la capacité du FEA. En outre, la disponibilité et la capacité à transporter de la ferraille sont également limitées, en raison d'espace limité. L'objectif dans cette thèse est de créer un modèle d'optimisation qui minimise le coût des matières premières et charge le FEA efficacement afin de satisfaire des contraintes de la recette de ferraille et de transport de ferraille. Le modèle est développé sur la base de théorie de la programmation linéaire. La vitesse de l'exécution du modèle est raisonnablement garantie par une bonne conception de la structure combinatoire avec les règles de 'branch and bound' et heuristiques. Enfin, un logiciel qui applique le modèle est créé. Celui-ci peut être utilisé dans la production réelle quotidienne. Les résultats des simulations montrent une amélioration significative par rapport aux pratiques actuelles de planification de production appliquée aujourd'hui dans ArcelorMittal (Contrecoeur, Quebec): le coût de la ferraille est réduite de 2 à 6 pour cent et le temps de godets de charge est de 2 à 10 minutes plus vite.

This thesis centers around an electric arc furnace (EAF) at a steel mini-mill in Wilton, IA. First, the thesis replicates previous optimization attempts. Next, the modeling is greatly altered to produce a much improved steel-melting model. Then, a new optimal control system is created and used to reduce energy and fuel costs over the melting process. Finally, results are presented. This thesis shows that when the new optimal control is simulated, the system shows significant energy and fuel savings.

The carbon footprint from the iron, steel and other metal sectors has become a problem both environmentally and economically. The purpose of this report is to propose a concept of an electrified reheat furnace for the steel industry in the making of sheet metal. The aim is to reduce the environmental impact from the steel industry. The approach in this report has been to analyse relevant facts to propose a fully electrified concept. The concept is divided into two sections. The first section of the concept consists of a preheating furnace with the purpose to heat the slabs to 850 °C before it enters the second section. The preheating furnace contains 1447 – 2412 MoSi2 heating elements due to considering different efficiencies. The second section consists of 13 induction heating modules heating the slabs to a homogenous temperature of 1250 °C. By applying electrical heating in a walking beam furnace approximately 100 000 tonne carbon dioxide can be reduced annually. In conclusion, the proposed concept could be a feasible solution in order to avoid carbon emission and obtain the same production rate as the existing reheating furnaces. However, it is suggested that further investigations and analysis are performed regarding this concept to verify the total efficiency of the reheating furnace and to theoretically determine the required power input
Koldioxidutsläppen från järn, stål och andra metallindustrier har blivit ett problem både urmiljö och ekonomisk synpunkt. Syftet med denna rapport är att föreslå ett koncept av en heltelektrifierad uppvärmningsugn för stålindustrin i processen för att skapa plåt. Målet meddenna studie är att reducera stålindustrins påverkan på växthuseffekten. Metoden i denna rapport har varit att analysera relevant fakta för att sedan kunna föreslå ettkoncept av en helt elektrifierad ugn. Det föreslagna konceptet är uppdelad i två delar. Denförsta delen består av en förvärmningsugn med målet att värma stålet till 850 °C innan ståletgår in i den andra delen. Förvärmningsugnen består av 1447 – 2412 stycken MoSi2värmeelement med hänsyn till ugnens verkningsgrad. Den andra delen består utav 13 styckeninduktionsvärmemoduler som värmen stålet till en homogentemperatur på 1250 °C. Genomatt använda elektricitet för att värma ugnen minskar koldioxidutsläppen med 66 kg per tontillverkas stål. Sammanfattningsvis, det föreslagna konceptet kan vara en möjlig lösning för att minskakoldioxidutsläpp och samtidigt bibehålla samma produktionshastighet som existerandeuppvärmningsugnar. Däremot är det förslaget att vidare studier och analyser görs påkonceptet för att verifiera den totala verkningsgraden av ugnen och för att bestämma denexakta energiförbrukningen.

This study explores the possibility of prediction and modification of some of the physicochemical properties of non-metallic inclusions by considering top slag-steel-ladle equilibria in an ASEA-SKF ladle furnace. To test the reliability of an available computational thermodynamic computer program, the first sub project was done. It was concluded that LiMeS, an interface for Thermo-Calc, is a useful tool for slag-steel equilibrium calculations. The second sub project was set out to find some model/s that could calculate the most accurate oxygen activity of molten steel compared to the measured one. This study concluded that both Wagner’s and Turkdogan's equations are useful. It was further seen that increasing the Al contents in the molten steel, increasing the CaO/Al2O3 ratio in the top slag, and reducing the temperature, resulted in reduction of the oxygen activity of the molten steel. In the third sub project a comparison was made between measured CaO and Al2O3 (normalised to CaO-Al2O3) in top slag, calcium aluminate inclusions, and the results of theoretical calculations. The average contents of CaO and Al2O3 in all inclusions were close to the composition of the phase Ca12Al14O33 and the contents of CaO and Al2O3 in the slags were close to the composition of the phase Ca3Al2O6 in the binary phase diagram of CaO-Al2O3. The forth sub project set out to study the effect of vacuum degassing time on non-metallic inclusions. It was concluded that during the vacuum degassing process the share of calcium aluminates compared to spinels, Ca content of the oxides, and the average equivalent circle diameters of the oxides were increasing, and oxides tended to form spherical shapes. Finally, based on the preceding four sub projects, the fifth sub project aimed to optimize the steel treatment in an ASEA-SKF ladle furnace. The final results showed that by adding 200 kg fluorite to the top slag of 1200 kg, it was possible to achieve a sulphur content of less than 10 ppm in the steel and a sulphur ratio between slag and steel of 1570, and at the same time reduce the oxygen activity of the molten steel and the degassing time.

QC 20120917

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.

In this thesis the relationship between the spread of technology and the extent of economic development is analysed. The quantitative dimension of the spread of technology is usually analysed in studies on the speed and extent of diffusion across countries and industries. The qualitative dimension concerns the adoption and use of technology which is usually studied in the literature on technology adoption and adaptation by firms. A process technology in two countries that differ considerably in their level of development, viz. UK and India, is considered. This controls for the technological and industrial specificity of the spread process allowing the influence of the development factor to be seen more clearly. The study is conducted at the industry/economy level, as well as the firm level. In this way the effects of the studying the different levels of aggregation together, and the relation between adoption and diffusion are clarified. The study indicates a wide diversity of patterns in the spread of technology across countries. Differences in both the coefficients of the diffusion curve and in the underlying functional form are identified. A deeper analysis of the patterns of spread in India and Britain reveals the greater influence of supply and infrastructure constraints in India, while in Britain the entire process was largely consumption constrained. If it can be assumed that capacity and production side constraints are more likely in industrialising economies, these dynamics could be inferred as more typical in influencing the spread of technology in developing countries. A study of the use and adoption of the technology by firms shows the importance of existing market structures, defined broadly to include the structure and organisation of production and consumption. In fact the composition of consumption in terms of users and user sectors was vital in defining rules of competition and in what way technology was harnessed as a competitive force. In the purely technological sense of operational efficiency it is shown that Indian firms performed more poorly than British firms. Furthermore this poor performance could be traced back to diversification strategies of Indian firms which in turn were a response to poorer levels of market formation in the economy.

Lake Champlain is a major economic driver for Vermont's tourism economy, as well as a primary source of drinking water for many of the state's residents but nutrient pollution represents a potential threat to ecosystem health and economic well-being. From December 2011 to December 2012 a field trial of an EAF steel slag filter was assessed for its feasibility in treating wastewater originating from Swan Valley Cheese (SVC), in Swanton, VT. The study focuses on a period of the filter's operation from May 4 to October 10, 2012. The plant generates approximately 20,000 gallons per day of high P concentration wash water which is treated in an open aerated lagoon. The filter treated effluent from this lagoon. The major goals of this research were to conduct a field trial of an EAF steel slag filter to evaluate its effect on total P (TP), dissolved reactive P (DRP), and total suspended solids (TSS). Research was also conducted on pH reduction for filter effluent. Results indicate that the filter removed 95.83% of TP, 96.65% of DRP, and 52.25% of TSS. Average pH effluent was measured at 10.12 ±1.55. Additionally, a field study was conducted on sampling two unlined bioretention systems treating urban stormwater runoff. Methods used are presented and methodological considerations for future studies are presented to guide researchers in more effective and efficient methods for obtaining influent and effluent samples from bioretention systems that are not necessarily designed for sampling.

A method of producing steel that is not used in Sweden today is direct reduction using natural gas, a method which could has enormous potential in the future of steelmaking. Historically, steelmaking prioritized productivity and profitability. However, other aspects such as safety, sustainability, and environmentally friendliness have become increasingly important to Swedish steelmakers. This study evaluates the usage of natural gas to  directly reduce iron ore into the porous form known as iron sponge, then finally processing that sponge into crude steel. The technology available today is assessed through a literature review, then two calculative data-based model: using DRI sponge in a traditional integrated steelmaking line or replacing steel scrap with it in an electric arc furnace. While this technology is used in many regions where natural gas is plentiful, it has not yet been used in Sweden. Now, when the Swedish natural gas network is expanding and the vehicular transportation of liquid natural gas is becoming more and more viable, it is a prime situation to evaluate direct reduction in Sweden. While models require assumptions and estimations, they suggest that DRI will absolutely be a viable option in the years to come. Integrated plant operators can reduce their immense carbon emissions for a reasonable price, while DRI sponge melting in an electrical arc furnace can either help steelmakers escape the volatile scrap market or be used to replace the blast furnace as a whole in the future.
En metod för att producera stål som inte används i Sverige idag är direkt reduktion med hjälp av naturgas, en metod som har en enorm potential i framtida ståltillverkning. Historiskt har ståltillverkningen prioriterat produktivitet och vinst, men säkerhet, hållbarhet, och miljövänlighet har blivit områden mer och mer viktiga för svenska ståltillverkare. Den här studien utvärderar användningen av naturgas för att direkt reducera järnmalm till den porösa formen känd som järnsvamp, och sen bearbeta den till primärt stål. Teknologin som flnns idag utvärderas genom en litteraturstudie, vars data beräknas till två scenariomodeller: användningen av järnsvamp i ett traditionellt integrerat stålverk eller genom att ersätta stålskrot med järnsvamp i ljusbågsungen. Den här teknologin används redan idag i regioner där naturgas är lättillgängligt, men har hittills inte använts i Sverige. Men nu när Sveriges naturgasnät byggs ut och fordonstransporterad flytande naturgas blir mer och mer kostnadseffektiv så är det lämpligt att utvärdera direkt reduktion i Sverige. Modellerna kräver antaganden och uppskattningar, men de pekar på att direkt reducering av järnmalm kommer att vara en genomförbar metod för ståltillverkning i en nära framtid. Integrerade masugnslinjer kan minska sina enorma koldioxidutsläpp till ett rimligt pris, och järnsvampssmältning i ljusbågsugn kan hjälpa ståltillverkare att undanfly den instabila stålskrotsmarknaden eller användas för att helt ersätta masugnsproduktion i framtiden.

Orientador: Pedro Magalhães Sobrinho
Resumo: O aço é um dos materiais mais utilizados em todo o mundo, é possível ser 100% reciclado, obtendo novo aço sem perda de qualidade e quantas vezes for necessário. O setor siderúrgico é o maior consumidor de energia final destinado a indústria. Para produção do aço existem diversas alternativas possíveis. Neste trabalho é destacada a do forno elétrico a arco, a mais eficiente em termos de energia consumida e a única a qual pode-se utilizar como matéria-prima até 100% de material reciclado. Sendo o aço uma commodity, uma mercadoria básica facilmente intercambiável e utilizada como insumo para produção de outros produtos, tem seu preço regulado pelo mercado e trabalhos em eficiência energética são essenciais para a competitividade das empresas. O presente trabalho visa elaborar sugestões de métodos e tecnologias que possibilitem a redução do consumo específico de energia elétrica em kWh/t (quilowatt hora por tonelada de aço) para o processo de fusão do aço de um forno elétrico a arco, localizado na região do Vale do Paraíba. A metodologia empregada foi a pesquisa-ação, tendo um forno elétrico a arco real, disponível para estudos e captura de dados. As soluções encontradas estão desde técnicas operacionais de produção, até tecnologias em reaproveitamento de gases de exaustão, utilizados para o pré-aquecimento de sucata. Como resultado da pesquisa, obteve-se um conjunto de possibilidades tecnológicas com ganhos de até 143 kWh/t, o que representa cerca de 34% de redução no consumo es... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Steel is one of the most widely used materials worldwide, and it is possible to recycle 100% of it so as to generate new steels without quality loss and as many times as needed, however, the steel sector is the largest final energy consumer. There are several possible routes for steel production, but the Electric Arc Furnace has been selected for the present work due to being the most efficient in terms of energy consumption and it is the only one that can use up to 100% of recycled matter as raw material. As steel is a commodity, a basic goods easily interchangeable and used as input for the production of other products, its price is set by the market and energy efficiency studies are essential for the competitiveness of companies. The present work aims to elaborate suggestions of methods and technologies that allow the reduction of the specific electric energy consumption in kWh/t (kilowatt hour per ton of steel) by the steel melting process of an electric arc furnace located in the region of the Paraíba Valley. The methodology used was the action research, having an electric arc furnace, available for studies and data capture. The identified solutions range from operational production techniques to exhaust gas recovery technologies for scrap preheating. As a result, a set of technological possibilities with savings of up to 143 kWh/t have been obtained, which represents about 34% reduction in specific electric energy consumption by taking into account an average consumptio... (Complete abstract click electronic access below)
Mestre

Steel heating and melting processes consume the majority of the energy used in advanced short-process steelmaking practices. Economic and environmental pressures from energy consumption drive the research to improve the furnace operation efficiency and energy efficiency. The goal of this research is to utilize computational fluid dynamics (CFD) modeling to provide useful tools and recommendations on the steel heating and melting practices in the steelmaking process. The steel slab reheating process, the steel scrap preheating process and the steel scrap melting process are studied.

A transient three-dimensional (3-D) CFD model was developed to simulate the flow characteristics, combustion process and multi-scale, multi-mode heat transfer inside the reheating furnace. The actual geometry of an operating industrial furnace was used and typical operating conditions were simulated. Specific walking speeds of slabs in production were modeled using a dynamic mesh model which is controlled by a user-defined function (UDF) solved using ANSYS Fluent. Fuel variations at different zones with respect to time were also considered. The model was validated with instrumented slab trials conducted at the SSAB Mobile (Alabama) mill. The temperature field in the furnace and the temperature evolution of a slab predicted by the CFD model are in good agreement with those obtained from the instrumented slab trials. Based on the simulation results, the slab reheating process and the temperature uniformity of a slab at discharge were able to be properly evaluated. In addition, a comprehensive two-dimensional (2-D) numerical heat transfer model for slab reheating in a walking beam furnace was developed using the finite difference method. An in-house code was developed. The model is capable of predicting slab temperature evolution during a reheating process based on real time furnace conditions and steel physical properties. The model was validated by using mill instrumented slab trials and production data. The results show that the temperature evolution predicted by the model is in good agreement with that measured by the thermocouples embedded in the instrumented slab. Compared with 3-D CFD simulation of a reheating process, this 2-D heat transfer model used for predicting slab temperature evolution requires less computing power and can provide results in a few seconds. A graphical user interface was also developed to facilitate the input and output process. This is a very convenient and user-friendly tool which can be used easily by mill metallurgists in troubleshooting and process optimization.

CFD models for steel scrap preheating and melting processes by the combined effects of the heat source from both oxy-fuel combustion and electric arc were also developed. The oxy-fuel burners firing natural gas (NG) are widely used in EAF operation during the scrap preheating and melting stages. In order to understand the role of oxy-fuel combustion and potentially increase the energy input from NG while decreasing the electricity consumption, numerical simulation of scrap preheating by oxy-fuel combustion in an EAF was firstly conducted. A 3-D CFD model was developed with detailed consideration of gas flow, oxy-fuel combustion, heat transfer between gas and solid scrap and scrap oxidation. The model was validated by a small-scale experimental study and applied onto a real-scale EAF.

Scrap melting in bath is comprehensively studied with a CFD model developed to simulate the melting in bath process under given operating conditions. Two sub-models were developed for model integration: steel melting model and coherent jet model. The multiphase volume of fluid (VOF) model and the enthalpy-porosity technique are applied to describe the steel melting process. The coherent jet model calculates the gas jet momentum and is integrated into the flow model to calculate its effect on the fluid flow in the bath. The electric arc was treated as a heat flux to represent the heat transfer from the electric arc during the melting process. Model validations were conducted for each sub-model to ensure their accuracy. Parametric studies were also carried out to obtain useful information for real practice.

Overall, the CFD models developed in this research work have demonstrated value in improving energy efficiency in the energy-intensive steelmaking processes. The developed CFD models also provide insights for better understanding of the multi-physics processes.

碩士
國立高雄應用科技大學
化學工程與材料工程系
97
Electric arc furnace (EAF) contains mainly zinc ferrite(ZnFe2O4) and zincite(ZnO). There are still problems for recovery Zn for the EAF dusts between the pyrometallurgical and/or hydrometallurgical processes. In the thesis, a low temperature caustic leaching process was investigated for the extraction Zn from EAF dust. NaOH was chosen as leaching agent combining either NH4OH or citric acid. In this thesis, different alkaline leaching agent were used to find out the maximum zinc extraction ratio: (i) NaOH leaching agent; the highest zinc recovery ratio was about 42 % under treatment for 2 hours, 1:10 S/L ratio, NaOH of 4 N. (ii) NH4OH leaching agent; the highest zinc recovery ratio was about 14 %. (iii) NH4OH add into NaOH leaching agent: the experimental results showed that the ratio of zinc extraction was 54 %, under the leaching agent (1:4 NH4OH/NaOH(aq)) treatment for 1 hour, 1:8 S/L ratio, at room temperature. (iv) citric acid add into NaOH leaching agent; the highest Zn recovery ratio (54 %) were found under these condition :30 g citric acid , 100℃, 1:10 S/L ratio, 8 N NaOH(aq) and 2h leaching time.

碩士
國立中央大學
環境工程研究所在職專班
106
With the advancement of technology, more stringent regulation in environmental protection and the trend of implementing circular economy policies, how to recycle valuable metals from fly ash has become a big challenge. The aim of this study is to evaluate the effectiveness of electric smelting reduction furnace (ESRF) to recover valuable metals from the fly ash collected from stainless steel industry. Analysis of the compositions of stainless steel fly ash indicates that four elements including iron, chromium, nickel, and zinc, are of the most recovery value; and they account for 30-68% of the total compositions. The granulated pellet of ash is put into the electric smelting reduction furnace with a temperature of 1550℃ and reducing agent such as coke is applied to reduce the metallic oxide in the fly ash to recover iron, chromium, nickel, and zinc. Moreover, the impact of varying basicity on the recovery rate of of the targent metals is also evaluated and the results reveal that the best recovery rates of iron, chromium, and nickel can be obtained if the basicity is controlled at 1-1.09. The recovery rates of iron, chromium, and nickel reach≧90%. The results of toxicity characteristic leaching procedure (TCLP) reveal that leaching concentrations of nickel and chromium are 0.16 and 0.1 mg/L, respectively. The results also indicate that as the basicity is controlled between 1.1 and 1.3, the leaching concentrations of nickel and chromium are the lowest, demonstrating that operation under this condition results in the best stability of slag. Analysis of the ash collected by baghouse during manufacturing process reveals the zinc oxide content in the secondary ash is around 34%. The total solid input for the test run is 2175 tons with the total output of 1158 ton. The decrease in mass is caused by the oxidation and reduction of metallic oxide in ESRF, which turn into CO2 and is discharged into the atmosphere. The electricity consumed for treating one ton of stainless steel fly ash is 3050 kWh, indicating that the process is energy-intensive. How to reduce electricity consumption and reduce operating cost remains a big challenge. Overall the result reveals the electric smelting reduction furnace can effectively recycle valuable metals from stainless steel ash and this process can turn stainless steel fly ash into harmless, recyclable, and reusable products.

碩士
朝陽科技大學
環境工程與管理系
105
The environmental concepts on people have been improved in recent years. The reuse of waste, such as reuse of slag was carried out. Therefore, this research main discuss about reuse of slag. Then propose the correct management measures to industry. This research report be able to increase cognition and safety of slag industry. The people worried about the slag expansion with water. This reason cause safety problems when using. If the slag via stability test that has environmental protection and energy saving features. This study case was Cheng Sheng Environmental Protection Co., Ltd. There are three reasons for the instability of the ballast: 1. unstable composition; 2. high pH of slag; 3. particle size influences. When obtain the safety slag have been 3 steps. First step was raw material classification. Second step was stability. Third step was select products (quality control). This study evaluation the process program and product quality of slag in the Cheng Sheng Co. The application were concrete building materials. Therefore, slag was classify that about crude and fine. Using the slag to make permeable brick and brick. At permeable brick part testing result as follows: 1. Compressive strength (kgf/cm2) were 653, 447 and 210 when cement and slag ratio were 0:1, 7:3, 1:1, respectively. 2. Permeability coefficient (cm/sec) were 32.76×10-2, 8.15×10-2 and 7.54×10-2 when cement and slag ratio were 0:1, 7:3, 1:1, respectively. The other experiment at brick part testing result as follows: 1. Compressive strength (kgf/cm2) were 1245 and 1055 when cement and slag ratio were 0:1 and 1:1, respectively. 2. Water absorption (%) were 6.6 and 6.2 when cement and slag ratio were 0:1 and 1:1, respectively. The testing results all standards compliant in accordance with CNS14995 and CNS13295 regulations. Therefore, the results prove the slag have hard and wear characteristics. When the product could be selectivity in classification management. The slag could create safety use by people.

碩士
國立高雄第一科技大學
環境與安全衛生工程所
91
The purpose of this study is to explore the feasibility of recycling stainless steel EAF slag as a resource. The valuable contents of oxidized slag of stainless steel EAF are mainly the stainless steel slag iron and steel drops, which accounted for about 14﹪of oxidized slag. Since they are with magnetism, they can be magnetically selected in mechanical and physical methods for remelting. After removing stainless steel slag iron and steel drops, the oxidized slag is a brittle material and its TCLP and pH values are under the determining standard of hazardous waste and may be regarded as general industrial waste. The micro-structure is smooth and free of pore, and is different from the porous carbon steel water-quenched slag. The breaking test results indicated the bearable load of oxidized slag is as high as 3,947 kg/kg of slag that shows their higher pressure and abrasion resisting properties. The ICP and EDS analysis confirmed that he stainless steel oxidized slag is mainly comprised of CaO、SiO2 and Cr2O3, and is similar to the composition of Portland cement. Therefore, it may be used as admixture to cement. In the aggregate durability test, the specific gravity of oxidized slag（3.29） is higher than the standard of river sand （2.5） and water content （0.93﹪） is far lower than the standard of river sand （3.0﹪）. The solved silicon (Sc) of the oxidized slag is 2.23mmol/L, smaller than the 10mmol/L of the river sand. The alkali reaction consumption (Rc) of the oxidized slag is 950mmol/L, higher than the 700mmol/L of the standard of river sand. The solved silicon (Sc) and alkali reaction consumption (Rc) are both harmless, i.e. the quantity of reaction between SiO2 and alkali is insufficient to damage the strength of concrete. The test for sieve soundness of analysis of aggregate durability indicated the loss rate is 9.96%, and the fine aggregate tolerable loss rate is within 12% range, which confirms to durability test standards. After breaking oxidized slag, screened, grounded to substitute raw and fine aggregate, then mixed with cement paste in different ratio. The compression strength test after curing indicated that the test piece with 5% oxidized slag of raw aggregate has the pressure resistance strength confirming to ASTM C109 standard. In fine aggregate, in the same water/cement ratio, mixed with oxidized slag, the compression strength of the test piece is better than the conventional mixing with standard sand. Conclusion drawing from the above, it is found that the oxidized slag is an artificial mineral and may be used to replace natural size gradation raw material after treatment.

碩士
國立中央大學
土木工程學系
107
With the increase of the piling of the waste materials in Taiwan, it is relevant to take actions following the sustainable development norms and find ways to introduce the recycling materials into the civil engineering work such as the pavements construction. The electric arc furnace (EAF) steel slag is one of the recycling materials piling in the nature produced from the steel refining industry. Reclaimed asphalt pavement (RAP) is another recycling material resulted from the roads milling for roads maintenance and rehabilitation. This study aimed at evaluating hot mix asphalt mixtures containing of both the EAF fine steel slag aggregate and RAP. The first mix design contains the EAF with 30% and the second mix design contains the hybrid EAF and RAP with 20% each. Laboratory mixed and compacted specimens are designed and carried for a chain of experimental tests to evaluate their physical properties performance as they are compared to a control mix design. The EAF and EAF+RAP exposed less Marshall stability compared to the control mix yet performed better in terms of rutting resistance and moisture susceptibility. For the second phase of the study, a road test was paved into three distinct sections each presenting one of the previously designed mixtures in the lab. The paving plant’s mixtures were investigated and showed critical quality control: the air voids within the mixtures containing EAF showed very critical air voids percentages. Nevertheless, after the road paving, in-site tests were carried out on three different dates with one-month interval between each date. The EAF section, next to the section with the hybrid EAF+RAP, showed the best rutting resistance and skid resistance while all of the three sections displayed a satisfying smoothness. Thus, the incorporation of one to two recycling materials yielded in satisfying results and the investigation to introducing new recycling materials to the civil engineering work should carry on for the sake of the sustainable development.

碩士
逢甲大學
環境工程與科學學系
106
The steel industry is the foundation of industrial development and is therefore often regarded as an indicator of national power. According to the statistics of Taiwan Environmental Protection Administration, the declared amounts of steel dust ash in Taiwan is about 250,000 metric tons in recent years. The steel dust/ash contains a lot of heavy metal compounds, so it is more difficult to disposal. At present, most of steel dust/ash are treated by thermal methods to recover the zinc oxides and the cost of the treatment is considerable. In order to effectively improve the reuse benefits of steel dust/ash and increase the values of reuse products, this study mainly investigates the characteristics, treatment and reuse technology of steel electric arc furnace dust. The chemical metallurgy method was used to recover the metals of steel electric arc furnace dust, and then the coprecipitation method was used to synthesize the zinc-ferrite. The influences of different synthesis factors were investigated and the optimum operating conditions were determined. The synthetic zinc-ferrite was further used as a catalyst for air pollution control, and the catalytic activity and optimal reaction conditions for different pollutants were explored. The zinc-ferrite was synthesized from the steel electric arc furnace dust with the optimum metal recovery conditions. The catalytic activity of the synthetic zinc-ferrite catalyst was tested. The results showed that the best recovery efficiency of zinc and iron was obtained as the reagent was hydrochloric acid, the reagent concentration was 12 M, the microwave reaction temperature was 120 °C, and the reaction holding time was 25 minutes. Among these operation factors, the reagent type had the most important influence and followed by the microwave reaction temperature, the reagent concentration and the reaction holding time. The optimum synthesis condition of zinc-ferrite was occurred as the Zn/Fe molar ratio was 1/2.5, the pH of coprecipitation solution was 10, the aeration time was 3 hours and the calcination was operated at 500 °C for 2 hours. Among these synthesis factors, the Zn/Fe molar ratio had the most important influence and followed by the pH of coprecipitation solution, the calcination temperature and the aeration time. The results of catalytic activity tests show that most of the zinc-ferrites synthesized at different conditions had good performance. When the space velocity was controlled at 10,000 hr-1 and the reaction temperature was 300°C, the conversion rate of propylene could reach 98% and the conversion rate of nitric oxide could reach 85-92% when the reaction temperature was 400°C. As a result, reuse of steel electric arc furnace dust for the synthesis of zinc-ferrite was feasible and the application of zinc-ferrite as a catalyst for the removals of propylene and nitric oxide was effective. Moreover, the leachability of different heavy metals from the synthesized zinc-ferrite were very low and far below the limits of Toxicity Characteristic Leaching Procedure. Through this recycling method, the goal of harmless and reusable of steel dust can be achieved.

碩士
國立中央大學
土木工程學系
107
With the increasing amount of construction waste in Taiwan. How to effectively reuse it became the goal of the engineering field in recent years. Electric arc furnace steel slag (EAF) is a by-product of steelmaking. Taiwan produces about 1.16 million tons of EAF per year. It is a major issue to solve the stockpiling and space occupation problem. Taiwan had used EAF in pavement construction in recent years. This study will evaluate the effectiveness of EAF in replacing fine aggregate of asphalt concrete by laboratory evaluation. First, this study will investigate whether the granulated properties of the crushed and magnetically selected EAF meet the relevant specifications of CNS 15310 and other related specifications. Whether it can replace the fine granules of dense graded asphalt concrete. Second, a conventional aggregate substitute by 30% EAF has been used to design 3 kinds of grading curves. Third, Superpave Gyratory Compactor (SGC) was used to simulate the compaction situation in the field, and reverent performance tests are carried out in order to find the most reliable design. The EAF’s aggregate and toxic dissolution, dioxin and other environmental tests have to reach the requirement of the related specification. Mix design result shows by adding EAF it will increase the optimum asphalt content while EAF can’t effectively absorb the additional asphalt. It has the same absorption as conventional aggregate. Then slightly rust has been observed during the performance test. EAF-lower displayed the most unsatisfying performance results. In summary, EAF can be used in dense graded asphalt concrete. The gradation curve should be closed to the upper and middle grading curve. In addition, the EAF vary greatly depending on the source (differ from plants), and the basic properties are highly unstable. It is recommended to use the same EAF which is from the same plants in order to prevent poor performance.

碩士
國立臺灣科技大學
化學工程系
106
The steel reducing slag (SRS) from electric arc furnace (EAF), byproduct of the steel industry, exhibits high potential for carbon dioxide absorption due to its plenty content of free-calcium oxide (f-CaO). The SRS will be stable after carbonization reaction, can be further applied as the additive of cement with low expansion ratio. The process is able to achieve the goal of resource recycle and CO2 utilization. In this study, SRS of different electric arc furnaces in steel factory was evaluated in the gas-solid-liquid reaction in semi-batch and packed bed reactor, respectively. The SRS reacted with pure carbon dioxide stream continuously under ambient condition. The effects of water contents, temperature, and reaction time on the carbonation efficiency for this process were systematically investigated in detail, where the degree of carbonization was determined by thermogravimetric analyzer (TGA), nondispersive infrared CO2 detector, and Field-emission scanning electron microscope equipped with energy dispersive spectroscopy. (FE-SEM-EDS). The results indicated that the CO2-absorption capacity of the pre-washed SRS was 0.1338 gCO2/gSRS in the small semi-batch reactor. A packed bed reactor was further designed and established for SRS raw material to simulate the filed condition. The largest CO2-absorption capacity of different SRS (US and DS) was obtained with adjusting the water content to 20±3 wt%, where the slag diameter is about 0.5 mm and reaction time is 2 hours. The maximum CO2 adsorption was 0.1 g CO2/g SRS-US and 0.075 g CO2/g SRS-DS under room temperature. Moreover, the properties of autoclave expansion and compressive strength for blended cement with using 20 wt% SRS as additive was examined according to CNS standards (CNS1258 and CNS 15286). The expansion ratio of carbonated US sample was only 11.1 %, which was much less than that of the raw material. The test result of compressive strength also met the requirement of regulation. Finally, the system was magnified to 20 liters semi-batch reactor to ensure the practicability of utilization of SRS from different EAF for CO2 absorption and the economic potential of carbonated product.

碩士
國立中山大學
環境工程研究所
91
In this work, feasibility of utilizing municipal incinerator fly ash (MIFA) of different sources as a substitute of raw materials for steel-making in a mini-mill was studied. Also studied included the efficacy of this mode of melting treatment and recycling. Under the condition of adding 1 wt% MIFA to scrap iron/scrap steel for partial replacement of lime, the L9 orthogonal arrays of Taguchi methods were utilized to investigate the effects of MIFA melting treatment of different sources by an electric arc furnace (EAF). Four experimental factors (i.e., scrap iron mass, lime mass, coke mass, and MIFA mass) were selected to study their effects on Pb leaching of EAF dust and slag. Test results for MIFA obtained from Plants K1, K2, and K3 show that EAF dust remains hazardous as it is originally a listed waste. On the other hand, slag so generated remains nonhazardous based on the TCLP results. The experimental results of EAF dust and slag were further subjected to the analysis of variance (ANOVA) and regular analysis. Using this process, the optimal operating conditions with respect to the leached Pb concentration would be as follows: (1) Plant K1(injection mode operation)--87 tons of scrap iron, 1.4 tons of lime, 0.4 ton of coke, and 0.9 ton of MIFA; (2) Plant K2(injection mode operation)--90 tons of scrap iron, 1.4 tons of lime, 0.7 ton of coke, and 1.1 tons of MIFA; (3) Plant K2(one-time-charge mode operation)--90 tons of scrap iron, 1.4 tons of lime, 0.9 ton of coke, and 0.7 ton of MIFA; (4) Plant K3(injection mode operation)--85 tons of scrap iron, 1.4 tons of lime, 0.7 ton of coke, and 0.9 ton of MIFA; and (5) Plant K3(one-time-charge mode operation)--87 tons of scrap iron, 1.5 tons of lime, 0.4 ton of coke, and 0.7 ton of MIFA. In this study, using MIFA from Plant K2 as an example, it was found that it required 29-35 kg of lime per ton of steel billets produced when MIFA was added. Under a normal operation of EAF steel-making, however, it required 35-45 kg of lime per ton of steel billets produced based on the past experience. In average, when MIFA is added, it needs only 32 kg of lime per ton of steel billets produced as compared to 40 kg of lime for regular steel-making. In other words, it would result in a reduction of 8 kg of lime per ton of steel billets produced by using this novel process. Based on an average monthly production of 20,973 tons of steel billets and a unit cost of 2,200 NT$ per ton of lime, a monthly saving of lime cost would be 369,125 NT$. Namely, about 4.4 million NT$ per year. In addition, it was also found that using this novel process to melt MIFA would not deteriorate the quality of steel billets and bars produced.

碩士
國立雲林科技大學
環境與安全衛生工程系
102
The steel production process is characterized by high pollution levels and high energy consumption. Waste products and air pollutants such as electric arc furance slag and dust, greenhouse gases, particulate pollutants, and sulfur oxides are generated in large amounts during the smelting and rolling process and have complex properties. The steel industry therefore generates a huge impact on the environment. In recent years, the concept of sustainable development of the earth has received growing attention all over the world. The steel industry should therefore not only strive for operational efficiency but rather make a serious effort to reduce environmental impacts and implement sustainable development. This study conducts a case study of a steel plant in central Taiwan by adopting the eco-efficiency indicator quantitative framework which has been developed by the World Business Council for Sustainable Development (WBCSD). Based on the concept of eco-efficiency, the author selected two indicators in the financial dimension (crude steel production amount and output value) and 10 indicators in the environmental dimension (water consumption, GHG emissions, raw material consumption, power consumption, oxygen consumption, natural gas consumption, amounts of electric arc slag and dust, sulfur oxide emissions, and particulate pollutant emissions). Eco-efficiency ratios were established for two steel-making processes of an individual company and eco-efficiency quadrant charts were designed to analyze eco-efficiency performance over the years. These tools were used to assess the eco-efficiency performance of the steel-making process characterized by continuous blast furnace operations and electric arc furnace processes as well as the environmental impact of the capacity expansion of blast furnaces over the past four years and trend changes over the years. The results of this study indicate that the crude steel production amount and output value of the studied company have greatly increased through the adoption of a steel-making process characterized by continuous blast furnace operations within the past four years which has been accompanied by a rising environmental impact. The company should therefore make a firm commitment to an increase of product quality and quantity, an effective utilization of energy resources, and an adoption of pollution control and improvement measures to reduce environmental impacts and thereby enhance the eco-efficiency of production processes. Electric arc furnace steel-making processes have exhibited a greatly increased eco-efficiency as far as power consumption and particulate pollutant emissions are concerned. The most likely reason for this phenomenon is that a larger amount of molten iron was added to the electric arc furnace steel-making process after the two blast furnaces were commissioned due to the high demands of electric arc furnace products which in turn led to significantly decreased power consumption and particulate pollutant emissions. Crude steel output value as a main indicator for eco-effectiveness tends to be affected by the national and international economic climate and the supply and demand fluctuations of the steel market.

博士
國立臺灣科技大學
營建工程系
97
The feasibility of reducing slag as cement-based cementing material was studied in this paper. The activity and replaceability of reducing slag in Taiwan Electric-Arc Furnace (EAF) Steel-Making Factory as cement-based cementing material were studied. Samples, which were from Electric-Arc Furnace Steel-Making Factories producing carbon steel and stainless steel, were sieved and dried without physical or chemical excitation after field sampling, and their physical and chemical properties as well as activities were tested. The samples were mixed according to the percentage of output and the activities of reducing slag before and after storing were studied. Then the application of reducing slag as elastic conductive coating and water conducting paint where water dispersing type acrylate copolymer emulsion as base and cement, reducing slag, graphite and conductive black as packing were studied. There are two types of conductive materials in the elastic conductive coating: one is traditional conductive graphite; the other is the mixture of powdered carbon waste of laser printer and conductive graphite as a comparative material. The study showed that the reducing slag of electric-arc furnace was a hydraulic, cementing and white powder, and contained materials such as CaO, SiO2,MnO,MgO, Fe2O3 and so on,.When using reducing slag of electric-arc furnace producing conductive coating, cement was to disperse with the addition of more reducing slag. It was calculated that the coating was a good Electromagnetic interference(EMI) shielded. EMI shielded was above 40dB in 10kHz; heating power density in water can reach 7W/cm2 and the decay time of conductivity of the coating can last for 210 to 450 days.

碩士
國立中山大學
環境工程研究所
93
The objective of this study was to utilize an electric arc furnace （EAF）in a steel mill to melt municipal incinerator fly ash （MIFA）of different sources （Plants K1 and K2） and evaluate its effectiveness in aspects of environment and economy. The results of full-scale tests have shown that slag thus generated by the EAF was found to be non-hazardous based on the TCLP result and also met the standard of CNS 14602. However, EAF dust thus obtained remained hazardous as it was originally a listed waste by Taiwan EPA. Test results have indicated that this novel treatment technology would not deteriorate the quality of steel billets and bars produced. Moreover, when melting MIFAs from Plant K1（with 2.00 wt％ of MIFA） and Plant K2 （with 3.28 wt％ of MIFA）, the air quality in the steel mill surroundings and off-gas from the stack were all below the regulatory limits. Thus, it would not cause additional pollution problems from this practice. Based on the total capacity of EAFs in Taiwan, it was estimated that these EAFs would be capable of melting fly ash generated by municipal incinerators in Taiwan. From the economic perspective, this melting practice would not lower the production rate of EAF steel-making and increase the tap-to-tap cycle time, consumption of electrical energy, consumption of oxygen, and consumption of graphite electrodes. Furthermore, through this novel practice, the contents of MIFA have turned out to be able to replace some portions of quick-lime and coke powder required for steel-making. Test results have also shown that 1 wt％ of MIFA injection would generate additional 8.93 kg of slag and 2.76 kg of EAF dust. It was found that an additional cost of NT＄318 per ton of MIFA treated would be resulted through this practice. This treatment cost is very low as compared with NT＄8,000 per ton of waste treated by solidification and followed by landfilling. Assuming a melting cost of NT＄5,000 per ton of MIFA is charged by EAFs, it would save more than ten million NT＄ per year for a municipal incinerator with an annual generation of 5,840 tons of MIFA. On the other hand, for a mini-mill with an annual capacity of 264,000 tons of billets, it would have an additional income of 37 million NT＄ if 3 wt％ of MIFA is melted while making steel.

In South Africa, the ferrochromium industry produces approximately 100,000 t bag house filter dust and slurry, while the stainless steel industry produces 24,000 t of dust annually [17,39]. The toxic substances in these wastes potentially pose a threat to the environment and human health, especially Cr (VI) due to its toxic, carcinogenic, highly soluble and strongly oxidizing properties. Therefore, the existence and treatment of wastes from stainless steel and ferrochrome production remain a challenge and an issue of concern. The increase of environmental legislation globally and the trend towards sustainable development are drives for alternatives to landfill. In the present thesis, the characteristics, formation mechanisms, leachability and stabilisation of the Cr (VI)-containing electric furnace dust and filter cake were investigated using various techniques such as XRD, XRF, TG/DTA, XPS, SEM-EDS, FT-IR, Raman spectrometer and UV/Vis spectrometer. The electric furnace dust and filter cake are very fine particles. Stainless steel dust forms by the entrainment of charge materials, evaporation or volatilisation of elements and ejection of slag and metal by spitting or the bursting of gas bubbles. It was found that ferrochrome dust is formed by the ejection of slag and metals droplets from the electrode hole, the entrainment of charge materials, vaporisation as well as the formation and precipitation of compounds from vaporised species in the off-gas duct. Filter cake contains crystal phases (CaF2 and CaSO4 ) and metal rich amorphous phases. It is formed due to super saturation and precipitation. Leaching experiments on the wastes showed that Cr (VI) rapidly leaches out by distilled water. Bricks were produced by mixing wastes (stainless steel plant dust, ferrochrome dust and filter cake) and clay. The optimum sinter parameter was found to be 1100oC and 5 hours for a 50wt% SPD-50wt% AS mixture in the brick. The leachability of Cr(VI) is strongly influenced by the mass%CaO/mass%SiO2 ratio and alkali metal oxides content in the wastes. The emission factors from the stabilised wastes (SPD, FCD1, FCD2 and FC) are similar to those reported for the cement industry. Semi-dynamic leaching tests indicated that the predominant leaching mechanisms of chromium species are initial surface wash-off followed by matrix diffusion.
Thesis (PhD (Metallurgical Engineering))--University of Pretoria, 2007.
Materials Science and Metallurgical Engineering
unrestricted

碩士
國立中興大學
精密工程學系所
106
Steel making industry is an indispensable processes for modern infrastructures and industrial technology. The quality requirements for steel are becoming more and more important. In addition, due to the current increase in steel purity and low cost requirements, the steel industry are face to the issues such as resource conservation and environmental protection. In fact, in terms of saving resources and reducing slag discharge, it is possible to reactivate the refining slag through the implementation of multiple recycles and the cooperation with the EAF to rapidly crude steel technology, in which it can achieve the purpose of reducing slag and carbon emissions. In this thesis, there are six sets of dephosphorization agent formulation of the EAF reuse refining slag process and all sets were studied for their performance using computer simulation to find out the best of them. In the simulation, we used two-phase dynamics simulation analysis of ANYSYS CFD software. The dephosphorization formulation that made by different used refining slag formulations were compared with the actual experimental processes. The study build 3D models of the EAF to implement steel liquid dephosphorization processes and studying to find the best formulation of dephosphorization efficiency when using refining slag. The results of the study proof the effect of refining slag on phosphorus content during dephosphorization and show it could reuse 50% of refining slag. Accordingly, it has more than 60% efficiency on dephosphorization after 20 minutes of crude.

碩士
臺灣大學
職業醫學與工業衛生研究所
96
Objectives：(1) to measure airborne particulate metal concentrations in the major steel manufacturing departments, (2) to explore the relationship between work environmental metal exposure and blood metal levels of workers, (3) to explore the effects of blood lead level and occupational noise on hearing loss. Method：Study subjects included 412 employees from a steel plant. Environmental monitoring consisted of total and respirable airborne particulate metal levels, average and maximum noise levels. Information collected for study subjects includes blood metal levels, hearing loss, demographic data, and work history. Airborne particulate samples and blood samples of workers were analyzed for Cr, Mn, Ni, Cu, Zn, As, Cd, Pb with inductively coupled plasma mass spectrometry . Results：Results of total airborne particulate sample analyses showed that electric arc furnace area had the highest levels of Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, and Pb. Results of respirable airborne particulate sample analyses showed that material-supplying area had the highest levels of Cr, Mn, Fe, and Cu, and electric arc furnace area had the highest levels of Ni, Zn, Cd, and Pb. Total and respirable airborne particulate lead levels were shown highly correlated with the blood lead levels with correlation coefficients of 0.475 and 0.383（p<0.0001）, respectively. All subjects were categorized into high lead level group and low lead level group at the cut point of 7 μg/dL, and classified into high and low noise exposure groups at the environmental noise level of 85 dB. Hearing loss was defined as both ears with average hearing loss greater than 25 dB. After adjusting the effect of age, the odds ratio for hearing loss for the high blood lead level group were 4.8 (95% CI：1.6~14.4) at 3K Hz and 2.7 (95% CI：1.2~5.7) at 4K Hz. Conclusion：Blood lead levels of workers were highly correlated with the work environmental lead particulate exposure. Relatively low blood lead level was founded correlated with hearing loss, and, however, the mechanism still need to be further explored. Key words：electric arc furnace, lead dust, blood lead, hearing loss.