The dust particles generated due to mechanical wear of iron ore pellets and clusters formed in molten stainless steel alloyed with rare earth metals (REM) are considered in this study. Firstly, the influence of the characteristics of iron ore pellets, applied load on a pellet bed and partial reduction of the pellets on the size distribution of the generated dust was investigated. Secondly, REM clusters are investigated to evaluate the size distribution of the clusters. Also, an extreme value distribution (EVD) analysis has been applied for the observed REM clusters. The large sized pellets showed 10-20% higher wear rate than small sized pellets during wear in a planetary mill. Moreover, an increase of ~67% was observed in the friction and dust generation in the pellet bed as the applied load increased from 1 to 3 kg. Also, it was observed that a higher friction in the pellet bed can lead to an increased amount of airborne particles. The mechanical wear experiments of pellets reduced at 500 °C (P500) and 850 °C (P850) showed that P500 pellets exhibit ~16-35% higher wear rate than unreduced pellets. For the P850 pellets, the wear is inhibited by formation of a metallic layer at the outer surface of the pellets. The mechanism of dust generation has been explained using the obtained results. A reliable cluster size distribution of REM clusters was obtained by improving the observation method and it was used to explicate the formation and growth mechanism of REM clusters. The results show that the growth of clusters is governed by different types of collisions depending on the size of the clusters. For EVD analysis three different size parameters were considered. Moreover, using the maximum length of clusters results in a better correlation of EVD regression lines compared to other size parameters. Moreover, a comparison of predicted and observed maximum lengths of clusters showed that further work is required for the application of EVD analyses for REM clusters. / Studien fokuserar på två olika typer av mikropartiklar som är valda från olika delar av järn- och ståltillverkningsprocessen. Dessa partiklar är dels stoft som genereras på grund av mekanisk nötning av partiklar och dels klusters som bildas i flytande rostfria stål legerade med sällsynta jordartsmetaller (REM). Inledningsvis så undersöktes inverkan av tre faktorer på storleksfördelningen hos stoft som bildas vid hantering av järnoxidpellets. De undersökta faktorerna inkluderade karakteristiken hos järnoxidpellets, det applicerade trycket på pelletsbädden och den partiella reduktionen av järnoxidpellets. Därefter så utfördes tredimensionella undersökningar av REM kluster som extraherats med hjälp av elektrolytisk extraction för att bestämma storleksfördelningen hos klustren. Dessutom så utfördes en extremvärdesdistribution (EVD) studie för de studerade klustren. En planetkvarn användes för att undersöka inverkan of karakeristiken hos pellets på stoftbildningen. Resultaten visade att storleken på pellets kan påverka nötningshastigheten under dessa försöksförhållanden. Pellets som hade en större storlek (13.5&lt; Deq &lt;15.0 mm) uppvisade en 10 till 20% högre nötningshastighet i jämförelse med mindre pellets (9.5&lt; Deq &lt;12.5 mm). Baserat på analyserna av stoftet som genererades under nötningsexperimenten så konstaterades att nötningsmekanismerna för dessa pellets var abrasions- och kollisionsnötning. En pelletsbädd skapades för att möjliggöra studier av inverkan av ett applicerat tryck på stoftbildningen och friktionskrafterna i en pelletsbädd. Ett varierat tryck på mellan 1 till 3 kg applicerades på pelletsbädden. Resultaten visade att en ökning på ~67% av friktionskraften och stoftbildningen ägde rum när det applicerade trycket ökades från 1 till 3kg. Dessutom så visade resultaten att en högre friktionskraft i pelletsbädden kan resultera in en ökad mängd luftburna partiklar. Den mekaniska nötningen av pellets som reducerats vid 500 °C (P500) och 850 °C (P850) studerades också genom användande av en planetkvarn. Resultaten visade att P500 pellets uppvisade en ~ 16 till 35% högre nötningshastighet i jämförelse med oreducerade referenspellets.  Resultaten för P850 pellets visade att den mekaniska nötningen motverkades genom bildningen av ett metalliskt skikt på den yttre delen av pelletsen. Resultaten visade också att stoftet som bildats pga mekanisk nötning av reducerade pellets innehöll 3 till 6 gånger mer grova partiklar  (&gt;20µm) i jämförelse med stoft som bildats från oreducerade pellets. Slutligen så diskuterades hur dessa resultat kan relateras till industriella förhållanden med avseende på mekanismerna som är involverade i den mekaniska nötningen av pellets samt med avseende på relationen mellan hastigheten av de utgående gaserna och storlken och morfologin hos stoftpartiklarna. Klusters innehållande REM-oxider som extraherats från en 253MA rostfri stålsort undersöktes med användande av en tredimensionell teknik. En trovärdig storleksfördelning av klusters (CSD) erhölls genom att förbättra undersökningsmetoden och denna användes för att studera bildningen och tillväxten av REM oxider. Dessutom så användes cirkularitetsfaktorn hos klusters för att dela in klustren i två olika grupper, vilka bildas och tillväxer enligt olika mekanismer. Resultaten visade också att tillväxten av klusters gynnas av olika typer av kollisioner som beror av av storleken på klusters. För REM-klusters så drogs slutsatsen att turbulenta kollisioner är den huvudsakliga mekanismen som påverkar tillväxten. Avhandlingen behandlar även problemet om hur det är möjligt att hantera synfält där det inte förekommer kluster vid en extremvärdesdistribution (EVD) analys. Tre olika parametrar undersöktes i EVD analysen. Resultaten visar att om den maximala längden på kluster (LC) används i analysen så erhålls den bästa korrelationen gällande regressionslinjen för en EVD analys. Specifikt så var R2 värdet upp till 0.9876 i jämförelse med de andra storleksparametrarna som har värden i intervallet 0.9656 – 0.9774. Slutligen så visar resultaten från en jämförelse mellan beräknade och observerade maximala klusterlängder att EVD analyser för studier av REM kluster behöver undersökas ytterligare i framtiden. / <p>QC 20161128</p>

<p>In the early 1860s three Swedes, Nils Wilhelm Mitander,Julius Ramsay and Gustaf Wittenström, were engaged by theBritish to build and run charcoal-based ironworks in India.These works, the Burwai Iron Works of the British Government inthe case of Mitander and the privately owned Kumaon Iron Worksin the case of Ramsay and Wittenström, were both to bebased on the most modern European technology. The projects werepioneering in Indian ironmaking. The ambitions were high andstakes big, but after only a few years the projects were closedand the Swedes returned home.<i>Landscapes of Technology Transfer</i>presents a detailedstudy of the Kumaon and Burwai Iron Works, from their firstconception to their final closure. The investigation isbasically empirical and a fundamental question is: Why were theworks never brought into full and continuous production?</p><p>The ironworks projects should be considered as processes oftechnology transfer rather than fully fledged and completedtransfers. In spite of this lack of success, or maybe becauseof it, the history of the ironworks and the Swedes also forms afruitful case to put other questions of wide relevance. Itexposes workings and effects of colonialism and offers anexplanation of the late development of India's iron and steelindustry and analyses of the complex totality forming theprerequisites for a successful transfer of technology. The longtraditions of bloomery ironmaking in India and ismarginalisation is also discussed.</p><p><i>Landscapes of Technology Transfer</i>is a comprehensiveempirical study. From a local and individual perspective ittraces lines of connection across boundaries of time andgeography. The historical landscapes of technology transfer aredescribed in their cultural, social, economic and politicaldimensions and the thesis underlines the importance of a closeacquaintance with local settings and conditions, where historyis manifested in a physical presence. The remains of theironworks and theirlocal landscapes in present-day India areused as a central source for writing their histories. There isalso a strong emphasis on the use of photographs and drawingsas sources.</p><p>The outcome of the projects was the result of the interplaybetween the local and the global, between a diversity ofconcrete factors influencing the construction of the works andtheir running and their colonial character. The studyemphasises the importance of technological systems andnetworks, both on a micro and a macro level. On a local leveldemanding logistics, a sometimes adverse climate, theprocurement of charcoal and iron ore in sufficient quantitiesand the build up of knowledge of ironmaking posed serious butnot insurmountable difficulties. Most obstacles were overcomealready during the first few years of the 1860s, the period ofthe Swedes, but to put the works into full and continuousproduction would have needed perseverance and purposefulefforts to support and protect the iron production, at leastduring an initial period. In the end the position of India as acolonial dependency, subjected to the primacy of Britishinterests, set the limits of the projects.</p><p><b>Key words:</b>History of technology, industrial heritagestudies, industrial archaeology, technology transfer,diffusion, technological systems, landscapes of technology,iron and steel, charcoal iron, direct and indirect ironmaking,bloomeries, 19th century, industrial history,industrialisation, de-industrialisation, underdevelopment,colonialism, India, Sweden, Great Britain, global history,annales.</p>

Ce travail de thèse est consacré à la modélisation du procédé de réduction directe du minerai de fer, un procédé alternatif intéressant dans le contexte de la réduction des émissions de CO2 de la sidérurgie. Le four à cuve, réacteur central du procédé, est divisé en trois zones (réduction, transition et refroidissement). Le modèle mathématique mis au point pour simuler l’ensemble repose sur une description détaillée et fidèle des principaux phénomènes physico-chimiques et thermiques intervenant. C’est un modèle bidimensionnel, en régime permanent et multi-échelle. Le lit mobile est constitué de boulettes, elles-mêmes supposées composées de grains et de cristallites. Huit réactions chimiques hétérogènes et deux réactions chimiques homogènes sont prises en compte. Les équations de conservation locales de la masse, l'énergie et de la quantité de mouvement ont été résolues numériquement en utilisant la méthode des volumes finis. Ce modèle a été appliqué avec succès pour simuler le four à cuve de deux usines de réduction directe de capacités différentes. Les résultats obtenus renseignent sur le fonctionnement interne du four et mettent en évidence des zones aux performances inégales. Le modèle a ensuite été exploité, après l’ajout et le couplage d’un modèle du reformeur, pour des calculs paramétriques, en particulier lorsque les caractéristiques des gaz réducteurs sont modifiées. Enfin des pistes sont présentées pour optimiser une installation de réduction directe en augmentant la capacité de production et le degré de métallisation du produit / This thesis is dedicated to the modelling of the iron ore direct reduction process, an attractive alternative process for making steel in the context of the reduction in CO2 emissions. The shaft furnace, the core reactor of the process, is divided into three sections (reduction, transition and cooling). The mathematical model developed to simulate this reactor is based on a detailed and faithful description of the main physical-chemical and thermal phenomena involved. The model is a two-dimensional, steady state and multi-scale. The moving bed is comprised of pellets of grains and crystallites. Eight heterogeneous chemical reactions and two homogeneous chemical reactions were taken into account. The local mass, energy and momentum balances were solved numerically using the finite volume method. The model was successfully applied to simulate the shaft furnace of two direct reduction plants of different capacities. The results obtained provide new insights on the internal behaviour of the furnace and highlight zones of uneven performance. After the addition and coupling of a reformer model, the shaft furnace model was used for parametric calculations, in particular when considering changes in the composition of the reducing gases. Finally, new possibilities are presented for optimizing the direct reduction process, e.g. for increasing the production capacity and the degree of metallization of the produced iron

Abstract A blast furnace is the dominant process for making iron in the world. Iron ore pellets are commonly used as iron burden materials in a blast furnace, in which iron oxides are reduced to metallic molten iron. While descending, the charge faces various stresses, which affect the gas flows in the shaft and the energy efficiency of the process. Charge material testing on a laboratory scale is of crucial importance in regard to the development of material quality. This doctoral thesis presents a couple of advanced novel experimental methods: a novel camera imaging method to determine the amount of swelling during reduction; a novel reducibility test to determine the reducibility in a solid state under simulated blast furnace conditions; and a novel experimental program for the ARUL reduction-softening test to more accurately simulate blast furnace conditions. Swelling tests under conditions of fixed temperature and gas composition showed that isothermal tests do not give a realistic insight into the material behaviour in a blast furnace. As a result, it is suggested that dynamic gas composition – temperature programmes simulating actual process conditions should be used. Additionally, the test results showed that circulating elements (sulphur and potassium) also affect the pellet volume change during reduction, however no abnormal swelling was observed in any of the swelling experiments. The factors affecting the high-temperature properties of iron burden materials for blast furnace use were evaluated by both the experimental methods and computational thermodynamics. It was shown that none of the studied pellet grades has as good reduction-softening properties as the fluxed sinter because of the differences in the chemistry and macro-porosity. FeO-SiO2-CaO-MgO-Al2O3 system examinations with FactSage was found to be a useful tool for predicting the softening of an iron burden material using the original chemical composition. FactSage computations suggest that the softening properties of an iron burden material can be improved either by decreasing the proportion of SiO2, increasing the proportion of MgO or introducing an appropriate amount of CaO in relation to the proportion of SiO2. / Tiivistelmä Masuuni on merkittävin raakaraudan valmistusprosessi maailmassa. Masuunissa käytetään yleisesti rautamalmipellettejä rautapanosmateriaalina. Masuunissa raudanoksidit pelkistetään metalliseksi rautasulaksi. Vajotessaan panos kohtaa monenlaisia rasitteita, joilla on vaikutusta kuilun kaasuvirtauksiin ja masuuniprosessin energiatehokkuuteen. Panosmateriaalien testaus laboratoriomittakaavassa on merkittävässä roolissa, kun niiden laatua kehitetään. Väitöskirjassa esitetään useita kehittyneitä koemenetelmiä: uusi kamerakuvausmenetelmä, jolla voidaan määrittää turpoaminen pelkistyksen edetessä; uusi pelkistyvyystesti, jolla voidaan määrittää rautapanosmateriaalin pelkistyminen kiinteässä tilassa masuunia jäljittelevissä olosuhteissa; ja uusi koeohjelma, jolla voidaan jäljitellä aiempaa tarkemmin masuuniolosuhteita sulamis-pehmenemiskokeessa. Turpoamistestit vakioiduissa olosuhteissa osoittivat, että isotermiset testit eivät anna realistista kuvaa materiaalin käyttäytymisestä masuunissa. Tämän vuoksi dynaamisia kaasukoostumus–lämpötila-ohjelmia tulisi suosia. Lisäksi tutkimustulokset osoittavat, että myös masuunissa kiertävillä komponenteilla (rikillä ja kaliumilla) on vaikutusta pelletin tilavuuden muutokseen pelkistyksessä. Yhdessäkään turpoamiskokeessa ei kuitenkaan havaittu katastrofaalista turpoamista. Masuunin rautapanosmateriaalien korkealämpötilaominaisuuksiin vaikuttavia tekijöitä arvioitiin sekä kokeellisin menetelmin että termodynaamisin laskelmin. Yhdelläkään tutkitulla pellettilaadulla ei havaittu sintterin veroisia korkealämpötilaominaisuuksia, mikä johtuu eroista kemiallisessa koostumuksessa ja makrohuokoisuudessa. FeO-SiO2-CaO-MgO-Al2O3 systeemitarkastelut rautapanosmateriaalin lähtökoostumuksella todettiin toimivaksi menetelmäksi arvioida panosmateriaalin pehmenemiskäyttäytymistä. FactSage-laskennat antavat ymmärtää, että rautapanosmateriaalin pehmenemisominaisuuksia voidaan parantaa joko vähentämällä SiO2:n osuutta, lisäämällä MgO:n osuutta tai lisäämällä CaO:ta sopiva määrä SiO2:n osuuteen nähden.

In the early 1860s three Swedes, Nils Wilhelm Mitander,Julius Ramsay and Gustaf Wittenström, were engaged by theBritish to build and run charcoal-based ironworks in India.These works, the Burwai Iron Works of the British Government inthe case of Mitander and the privately owned Kumaon Iron Worksin the case of Ramsay and Wittenström, were both to bebased on the most modern European technology. The projects werepioneering in Indian ironmaking. The ambitions were high andstakes big, but after only a few years the projects were closedand the Swedes returned home.Landscapes of Technology Transferpresents a detailedstudy of the Kumaon and Burwai Iron Works, from their firstconception to their final closure. The investigation isbasically empirical and a fundamental question is: Why were theworks never brought into full and continuous production? The ironworks projects should be considered as processes oftechnology transfer rather than fully fledged and completedtransfers. In spite of this lack of success, or maybe becauseof it, the history of the ironworks and the Swedes also forms afruitful case to put other questions of wide relevance. Itexposes workings and effects of colonialism and offers anexplanation of the late development of India's iron and steelindustry and analyses of the complex totality forming theprerequisites for a successful transfer of technology. The longtraditions of bloomery ironmaking in India and ismarginalisation is also discussed. Landscapes of Technology Transferis a comprehensiveempirical study. From a local and individual perspective ittraces lines of connection across boundaries of time andgeography. The historical landscapes of technology transfer aredescribed in their cultural, social, economic and politicaldimensions and the thesis underlines the importance of a closeacquaintance with local settings and conditions, where historyis manifested in a physical presence. The remains of theironworks and theirlocal landscapes in present-day India areused as a central source for writing their histories. There isalso a strong emphasis on the use of photographs and drawingsas sources. The outcome of the projects was the result of the interplaybetween the local and the global, between a diversity ofconcrete factors influencing the construction of the works andtheir running and their colonial character. The studyemphasises the importance of technological systems andnetworks, both on a micro and a macro level. On a local leveldemanding logistics, a sometimes adverse climate, theprocurement of charcoal and iron ore in sufficient quantitiesand the build up of knowledge of ironmaking posed serious butnot insurmountable difficulties. Most obstacles were overcomealready during the first few years of the 1860s, the period ofthe Swedes, but to put the works into full and continuousproduction would have needed perseverance and purposefulefforts to support and protect the iron production, at leastduring an initial period. In the end the position of India as acolonial dependency, subjected to the primacy of Britishinterests, set the limits of the projects. Key words:History of technology, industrial heritagestudies, industrial archaeology, technology transfer,diffusion, technological systems, landscapes of technology,iron and steel, charcoal iron, direct and indirect ironmaking,bloomeries, 19th century, industrial history,industrialisation, de-industrialisation, underdevelopment,colonialism, India, Sweden, Great Britain, global history,annales. / <p>Qc 20170119</p>

Abstract Most of the steel produced in the world is based on the integrated blast furnace-converter route, which is based on the use of virgin raw materials. Large amounts of fossil-based, carbon containing reductants are used in blast furnaces, which results in carbon dioxide emissions into the atmosphere. Fossil carbon dioxide emissions from steel production can be reduced by new technologies or moving from non-renewable to renewable energy sources. Biomass-based reductants could be one way to reduce the specific emissions from blast furnace-based steel production. The aim of this thesis was to examine the techno-economic and CO₂ mitigation potentials of using bioreducers in blast furnace ironmaking. Bioreducer feasibility was analyzed in the Finnish context, but the research methods used can be applied more widely. The metallurgical properties of bioreducers were evaluated and compared to fossil-based reductants. The impact of bioreducers on blast furnace behavior and on other steel plant processes was evaluated, with an emphasis on the reductions achieved in CO₂ emissions at the plant scale. The CO₂ emissions, energy consumption and production costs of bioreducers were evaluated, as was the availability of energy wood for bioreducer production. The results show that solid, liquid and gaseous bioreducers can be produced with thermochemical conversion technologies. However, their suitability for blast furnace use varies greatly. The highest substitution of fossil-based reductants in a blast furnace is achieved with charcoal injection. The carbon footprint of torrefied wood, charcoal and Bio-SNG is moderate compared to fossil-based reducing agents and their production is energetically feasible. The economic feasibility of bioreducers is currently weak in comparison to fossil-based reducing agents, but competitive when compared to other CO₂ emission reduction measures such as carbon capture and storage. The biomass availability assessment revealed that sufficient amount of energy wood could be available for bioreducer production in the areas where Finnish steel plants are situated. The feasibility of bioreducer production could be improved by producing a number of products from the biomass and taking advantage of the process of integration possibilities. / Tiivistelmä Suurin osa maailmassa tuotetusta teräksestä valmistetaan integroidulla masuuni-konvertteri reitillä, joka perustuu neitseellisten raaka-aineiden käyttöön. Masuuniprosessissa käytetään suuri määrä fossiilisia, lähinnä hiilipohjaisia pelkistimiä, jotka aiheuttavat hiilidioksidipäästöjä ilmakehään. Fossiilisia hiilidioksidipäästöjä voidaan teräksenvalmistuksessa vähentää uusilla teknologioilla tai siirtymällä uusiutumattomista energialähteistä uusiutuviin. Biomassasta valmistetut pelkistimet voisivat olla yksi mahdollinen keino alentaa masuunipohjaisen teräksenvalmistuksen ominaispäästöjä. Tämän työn tavoitteena oli tarkastella biopelkistimien käytön teknistaloudellista potentiaalia masuunikäytössä ja aikaansaatavia hiilidioksidipäästövähenemiä eri systeemirajauksilla. Työssä keskityttiin tarkastelemaan biopelkistimien hyödynnettävyyttä lähinnä Suomen tasolla, vaikka käytetyt tutkimusmetodit ovat sovellettavissa myös laajemmin. Työssä arvioitiin biopelkistimien metallurgisia ominaisuuksia, niiden vaikutusta masuuniprosessiin ja laajemmin muihin terästehtaan prosesseihin, pääpainon ollessa saavutettavan CO₂ päästövähenemän tarkastelussa. Työssä tarkasteltiin biopelkistimien valmistuksen CO₂ päästöjä, energiankulutusta ja tuotantokustannuksia sekä energiapuun saatavuutta biopelkistimien tuotantoon. Tulokset osoittavat, että biomassasta voidaan valmistaa kiinteitä, nestemäisiä ja kaasumaisia pelkistimiä termokemiallisilla konversioteknologioilla, joiden soveltuvuus masuunikäyttöön vaihtelee suuresti. Masuuniprosessissa suurin fossiilisten pelkistimien korvaavuus saavutetaan käyttämällä puuhiili-injektiota. Torrefioidun puun, puuhiilen ja Bio-SNG:n hiilijalanjälki on varsin maltillinen verrattuna fossiilisiin pelkistimiin ja niiden tuotanto on energeettisesti järkevää. Biopelkistimien taloudellinen kannattavuus verrattuna fossiilisiin pelkistimiin on tällä hetkellä heikko, mutta kilpailukykyinen verrattuna muihin CO₂ päästöjen vähennyskeinoihin, kuten hiilidioksidin talteenottoon ja -varastointiin. Energiapuun saatavuus biopelkistimien valmistukseen on suurin alueilla, jotka sijaitsevat lähellä Suomen terästehtaita. Biopelkistimien tuotannon kannattavuutta voitaisiin parantaa tuottamalla useita tuotteita ja hyödyntämällä prosessi-integraatiota.

<p>  </p> <p>Direct reduction ironmaking has gained popularity as a low carbon alternative to the typical blast furnace ironmaking route. A popular method of producing direct reduced iron is through the reduction of iron ore pellets in a reduction shaft furnace. Critical to this process is the use of a reliable continuous pellet feed system to provide a steady flow of pellets to the furnace. Therefore, any disruption in pellet flow can have a significant negative impact on the production rate of iron. </p> <p><br></p> <p>An iron ore pellet feed system for a direct reduction ironmaking furnace is jamming during winter operation. The pellets are jamming in a hopper at the top of the feed system above the furnace, and a hot gas, that seals off the furnace flue gas, flows counter to the pellets. A computational model of the feed system is built utilizing the discrete element method and computational fluid dynamics, using Siemen’s commercial multiphysics software Star-CCM+, to study the conditions that cause the jam to occur. The study is divided into six parts: pellet bulk flow calibration, computational cost reduction, modeling of the baseline operation, modeling the effect of moisture, development of a thermal model, and investigation of the minimal amount of icy and wet material to jam the system. The findings show that the location of jamming during operation matches the area in the simulation where it is most likely to occur, and that moisture alone is unlikely to result in jamming. Results indicate that the system will jam when charged with a minimum of 15% icy pellets, and when charged with 10% icy together with 5% wet pellets. Experimental work is recommended to validate the findings and to calibrate the simulations accordingly.</p>

This master's thesis covers an investigation of the reduction behavior of different iron oxides when electrolytically reduced with molten salt electrolysis (MSE). The tested iron oxides were wüstite (FeO), hematite (Fe2O3), magnetite (Fe3O4) and magnetite ore concentrate from the Tapuli deposit in Pajala, Norrbotten, Sweden. The properties of the Tapuli magnetite ore and magnetite ore concentrate were analysed from a mineralogical perspective to evaluate how the raw ore material influences the concentrate and its reduction by the MSE technology. The electrolytic experiments were performed in an Inconel 625 cell body within a pit-furnace. The different iron oxides were tested separately. The reduction samples were constructed of one or three iron oxide briquettes of 20 g each within a molybdenum mesh attached on a molybdenum tray with molybdenum wires. The molten electrolyte was kept at 500°C with an applied voltage of 1.7 or 2.1 V. The used electrolyte was sodium hydroxide (NaOH). The mineralogical examination shows that the Tapuli ore varies in composition between different locations of the deposit with respect to magnetite grain size and skarn composition and grain size. Point analyses with Laser Ablation Single Collector Inductively Coupled Plasma Mass Spectrometry (LA-SC-ICP-MS) on magnetite grains in thin sections from five drill cores fromdifferent parts of the deposit show that the element composition in the magnetite grains vary between the samples. Core-to-rim analyses for Fe, Mg, Mn and Al reveal relatively homogenous grades throughout the grains, with a few exceptions. Phase analysis with XRD shows that reduction has occurred in all tested iron oxides. Without prevention, the reduction products from trials on Fe2O3, Fe3O4 and magnetite ore concentrate show distinct XRD peaks of the by-product NaFeO2. According to XRD, the addition of Na2O seems to have reduced the NaFeO2 formation. Interestingly, no NaFeO2 was formed in the FeO trials. This might be explained by the absence of Fe3+ in FeO. The variation of the current-time curves of the trials is interpreted to depend on the voltage applied, the number of briquettes, briquette decomposition and Na2O addition. Electrolysis in molten NaOH can be used to reduce iron oxides. Despite this, NaOH might not be a suitable electrolyte for this process due to its interaction with Fe2O3 and Fe3O4 resulting information of NaFeO2. Na2O can be used as an additive to prevent formation of NaFeO2 but sharply decreases the current response, thus having an apparent negative effect on the process efficiency. Another preventive measure that can be tested is to calibrate the process voltage to decompose the NaFeO2 but not NaOH. Due to the shown interaction tendency of NaOH, other electrolytes should however be considered for this process. Regarding the Tapuli ore concentrate, more tests are needed to draw conclusions about how the trace elements effects its electrolytic behavior. / Denna masteruppsats avhandlar en undersökning av reduktionsbeteendet hos olika järnoxider vid elektrolytisk reduktion i saltsmälta (molten salt electrolysis (MSE)). Järnoxiderna som har testats är wüstit (FeO), hematit (Fe2O3), magnetit (Fe3O4) och magnetitmalmkoncentrat från malmfyndigheten Tapuli i Pajala, Norrbotten, Sverige. Malmkoncentratets egenskaper har analyserats ur mineralogisk synvinkel för att utvärdera hur den råa malmens mineralogi påverkar koncentratet och dess reduktionsbeteende vid elektrolys i saltsmälta. Elektrolysexperimenten utfördes i cellkropp av Inconel 625 placerad i en gropugn. De olika järnoxiderna testades separat. Reduktionsproverna utgjordes av en eller tre järnoxidbriketter på 20 g inuti ett molybdennät, fastvirade på en molybdenbricka med molybdentråd. Den smälta elektrolyten hölls vid en temperatur av 500°C med en applicerad spänning av 1.7 eller 2.1 V. Elektrolyten som användes var natriumhydroxid (NaOH). Den mineralogiska undersökningen visar att tapulimalmens sammansättning varierar mellan olika delar av fyndigheten med avseende på magnetitens kornstorlek och skarnets sammansättning och kornstorlek. Punktanalyser med Laser Ablation Single Collector Inductively Coupled Plasma Mass Spectrometry (LA-SC-ICP-MS) på magnetitkorn i tunnslip från fem olika borrkärnor visar att elementkoncentrationerna i magnetitkornen varierar mellan proverna. Core-to-rim-analyser på magnetitkornen visar att halterna av Fe, Mg, Mn och Al är tämligen homogena genom hela magnetitkornet med undantag av några få avvikande punkter. Fasanalys med XRD indikerar att reduktion har skett i alla försök. Utan prevention visar reduktionsprodukterna från försöken på Fe2O3, Fe3O4 och magnetitmalmkoncentrat klara indikationer av biprodukten NaFeO2. Enligt XRD verkar tillsats av Na2O ha minskat bildningen av Na2O för Fe2O3, Fe3O4 och Tapuli magnetitmalmkoncentrat. Intressant är att ingen NaFeO2 bildades i försöken med FeO. Förklaringen till detta skulle kunna vara avsaknaden av Fe3+ i FeO. De varierande ström-tidkurvorna från försöken tolkas bero på den applicerade spänningen, antalet briketter, brikettsönderdelning och tillsats av Na2O. Elektrolys i smält NaOH kan användas för att reducera järnoxider. Trots detta kanske NaOH inte är lämplig som elektrolyt i denna process, detta på grund av dess påvisade interaktion med Fe2O3 och Fe3O4 som resulterar i bildning av NaFeO2. Na2O kan tillsättas för att förhindra bildning av NaFeO2 men har en kraftigt negativ effekt på strömstyrkan i processen vilket minskar processens effektivitet. En annan preventiv åtgärd som kan testas är att kalibrera processens spänning så att NaFeO2 sönderdelas men inte NaOH. På grund av den konstaterade interaktionstendensen hos NaOH bör andra elektrolyter tas i beaktande för denna process. Angående magnetitmalmskoncentratet från Tapuli behövs fler tester för att dra slutsatser kring hur spårelementen påverkar dess uppförande vid smältelektrolys.