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Development of biomarker-based proxies for paleo sea-ice reconstructionsSmik, Lukas January 2016 (has links)
The analysis of the sea-ice diatom biomarker IP25 (a mono-unsaturated Highly Branched Isoprenoid (HBI) alkene) in Arctic marine sediments has previously been shown to provide a useful qualitative proxy measure for the past spring sea-ice occurrence. In the Southern Ocean the occurrence and variable abundance of a structurally similar di-unsaturated HBI (HBI diene II) has previously been proposed as a proxy measure of paleo sea-ice extent. However, the use of such biomarker proxies remains under development. In the current study, a number of additional palaeoceanographic developments of HBIs as sea-ice biomarkers in both polar regions has been undertaken. For the Arctic, an investigation into the combined analysis of IP25 and certain phytoplankton biomarkers has been conducted with the aim of providing more detailed and semi-quantitative descriptions of sea-ice conditions in the Barents Sea. In contrast, analysis of HBIs and other lipids within water column, surface sediment and sea-ice samples has been undertaken to provide further insights into the use of HBIs as proxies for Antarctic sea-ice. Analysis of surface sediments from across the Barents Sea has shown that the relative abundances of IP25 and a tri-unsaturated HBI lipid (HBI triene IIIa) are characteristic of the overlying surface oceanographic conditions, most notably, the location of the seasonal sea-ice edge. A semi-quantitative approach, in the form of the PIP25 index, showed a good positive linear relationship between PIP25 indices and spring sea-ice concentration, with a particularly strong relationship found when using HBI triene IIIa (PIIIaIP25) as the open-water counterpart to IP25. The quality of the linear fits were not especially dependent on the balance factor c, used in the PIP25 calculation, which may have important positive consequences for down-core sea-ice reconstruction, and when making comparisons between outcomes from different Arctic regions or climatic epochs. Further, a lower limit threshold for PIIIaIP25 (0.8) might represent a useful qualitative proxy for the past occurrence of summer sea-ice. The re-evaluation of biomarker data from three dated marine sequences in the Barents Sea suggests that the combined analysis of IP25 and HBI triene IIIa can provide information on temporal variations in the position of the maximum (winter) Arctic sea-ice extent, together with more quantitative sea-ice reconstructions. In the Southern Ocean, the distributions of di- and tri-unsaturated HBIs (HBI diene II and HBI trienes IIIa and IIIb) in surface waters were shown to be extremely sensitive to the local sea-ice conditions, consistent with significant environmental control over their biosynthesis by sea-ice diatoms and open water phytoplankton, respectively. Within the water column, the apparent alteration to HBI and other lipid abundances was evident between the photic and benthic parts of the water column, which, along with additional local factors (e.g. polynya formation), may have important implications for paleo sea-ice reconstructions. The sedimentary occurrence and distribution of HBI diene II (termed here as IPSO25) were consistent with the recent identification of the diatom Berkeleya adeliensis Medlin as a source of IPSO25. The tendency for B. adeliensis to flourish in platelet ice, the formation of which is strongly associated with super-cooled freshwater inflow, means that sedimentary IPSO25 may provide a potentially sensitive proxy indicator of landfast sea-ice influenced by meltwater discharge from nearby glaciers and ice shelves. Re-examination of some previous IPSO25 down-core records supports this suggestion, although further down-core analysis is required to confirm this hypothesis. The similar sedimentary distribution relationship between phytoplankton-derived HBI trienes and IPSO25, further indicates that the former may reflect production of these biomarkers by certain diatoms that flourish within the region of the retreating ice edge; however, the source identification of the HBI trienes is still needed to place this interpretation on a firmer footing.
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Agglomerationstechnologien für Reststoffe aus Midrex-DirektreduktionsanlagenLohmeier, Laura 31 May 2023 (has links)
Bei der Herstellung von direkt reduziertem Eisen im Midrex-Direktreduktionsprozess fallen zahlreiche eisenhaltige, feinkörnige Hüttenreststoffe an. Um eine Deponierung der Reststoffe zu vermeiden wurden zwei verschiedene Varianten zur Aufbereitung dieser Reststoffe durch Brikettierung anhand von Laborversuchen erprobt und hinsichtlich ihrer resultierenden Eigenschaften bewertet. Variante I umfasst die Brikettierung der Reststoffe zum erneuten Einsatz als Ausgangsmaterial im Midrex-Direktreduktionsprozess. Variante II untersucht die Einbindung der Reststoffe bei der ohnehin stattfindenen Heißbrikettierung der reduzierten Pellets zu heiß brikettiertem Eisen (HBI). Die vorliegende Arbeit zeigt für beide Varianten, dass mit geeigneten Mischungszusammensetzungen und Brikettierbedingungen Briketts mit ausreichenden mechanischen, thermischen und metallurgischen Eigenschaften hergestellt werden können. Die zugrunde liegenden Bindemechanismen werden anhand von optischer Mikroskopie, Vickershärtebestimmungen und REM/EDX-Untersuchungen qualitativ beurteilt.:1 Einleitung
2 Stand der Technik
2.1 Direktreduktion, Midrex-Prozess und Reststoffproblematik
2.2 Agglomeration von eisenhaltigen Reststoffen und Feinerzen
2.2.1 Brikettierung von Hüttenreststoffen aus dem Midrex-Prozess
2.2.2 Brikettierung von Reststoffen aus dem Hochofen
2.2.3 Aufbauagglomeration von Feinerzen
2.2.4 Sintern von Feinerzen
2.2.5 Auswahl einer geeigneten Agglomerationsmethode
2.2.6 Anforderungen an die Briketts für den Einsatz im Midrex-Prozess
2.2.7 Anforderungen an HBI-Briketts
2.3 Zielstellung
3 Anwendungsbezogene Grundlagen
3.1 Bindemechanismen
3.2 Pressverdichtung
3.3 Bindemittel
3.3.1 Vorbemerkungen
3.3.2 Bentonit
3.3.3 Stärke und Cellulose
3.3.4 Sulfitablaugen
3.3.5 Zement
3.3.6 Löschkalk
4 Versuchsaufbau und Versuchsdurchführung
4.1 Charakterisierung des Einsatzmaterials und der Bindemittel
4.1.1 Hüttenreststoffe
4.1.2 Eisenerzpellets
4.1.3 DRI-Pellets
4.1.4 Bindemittel
4.2 Brikettierung mit Bindemittel
4.2.1 Statistische Versuchsplanung
4.2.2 Mischen
4.2.3 Vorwärmen
4.2.4 Brikettieren
4.2.5 Aushärten und Lagerung
4.2.6 Mechanische und metallurgische Beurteilung der Briketts
4.3 Heißbrikettierung
4.3.1 Mischen
4.3.2 Aufheizen
4.3.3 Brikettieren
4.3.4 Beurteilung der Briketteigenschaften
4.4 Betrachtung der Bindemechanismen
5 Ergebnisse und Diskussion
5.1 Brikettierung der Reststoffmischung mit Bindemitteln (Variante I a)
5.1.1 Mechanische Eigenschaften der Briketts
5.1.2 Metallurgische Eigenschaften der Briketts
5.1.3 Chemische Eigenschaften der Reststoffbriketts mit Bindemittel
5.1.4 Zusammenfassung Brikettierung mit Bindemitteln
5.2 Heißbrikettierung der Reststoffmischung (Variante I b)
5.2.1 Einfluss der Mischungszusammensetzung
5.2.2 Einfluss der Pressbedingungen
5.2.3 Mikroskopische Betrachtung
5.2.4 Zusammenfassung Heißbrikettierung der Reststoffmischung
5.3 Gemeinsame Brikettierung der Reststoffmischung mit DRI-Pellets (Variante II)
5.3.1 Einfluss der Reststoffmischung auf die HBI Qualität
5.3.2 Einfluss der Pressbedingungen (Vorwärmtemperatur, Pressdruck)
5.3.3 Mikroskopische Betrachtung
5.3.4 Zusammenfassung Brikettierung Reststoffmischung mit DRI-Pellets
5.4 Beurteilung der Methoden zur Klärung der Bindemechanismen
5.5 Vergleichende Beurteilung der verschiedenen Verwertungsvarianten
6 Zusammenfassung und Ausblick
7 Literaturverzeichnis
Abbildungsverzeichnis
Tabellenverzeichnis
Abkürzungs- und Symbolverzeichnis
Anhang
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Briquetting and Reduction of DRI/HBI Fines for Next-Generation Iron and Steel Making TechnologyNITUNGA, Eddy-Nestor January 2024 (has links)
The current transition from Blast Furnace (BF) to Hydrogen-Direct Reduction (H-DR) is an initiative to reduce the carbon footprint in Iron and Steel production. The shift from traditional coke-based Iron and Steel making to a green H-DR requires new innovative technologies, underscoring the importance of collective efforts in this field. The production of DRI/HBI fines, which account for 1-2% wt. of DR production, poses a significant challenge for the iron and steel industries. These fines, rich in iron, are generated inside the plant during the handling, production, and transportation process. Their recycling in the DR process is difficult without proper agglomeration. Here, briquetting emerges as a promising solution to this challenge. This research work is dedicated to exploring the use of innovative binders in briquetting the DRI/HBI fines. It aims to understand the H2 -based reduction behaviour of the briquettes and the role of embedded biocarbon in enhancing resource efficiency. The study also investigates the impact of binders on the mechanical strength, moisture content, and compaction pressure of the briquettes. The optimized briquettes are then subjected to H2-based reduction using a thermogravimetric technique (TGA) followed by characterization by XRF, XRD, and LECO analysis, and mechanically evaluated to assess their potential in the next-generation H2-based Iron and Steel Making. Keywords: DRI/HBI Fines, Organic binders, Briquetting, H2 Reduction, Biocarbon, Recycling, Resource Efficiency
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Theoretical Considerations and Experimental Observations on Heat Transfer in Hydrogen Direct Reduced IronGöttfert, Felix January 2023 (has links)
Steel has played an indispensable role in shaping our contemporary world and will persist to play that role for the foreseeable future. However, the steel industry currently is responsible for 7% of the global CO2-emissions, primarily due to the conventional carbon-based reduction process of iron ore. Fossil-free steel manufacturing, such as hydrogen direct reduction, could essentially make the CO2-emissions from primary steel production obsolete. The product from hydrogen-based direct reduction of iron ore is H-DRI, which subsequently are molten in an EAF to produce crude steel. Due to H-DRI being a novel product, its thermophysical properties are not well documented, which are essential when investigating the heating and dissolution behavior. When feeding H-DRI to an EAF, ferrobergs may form, which consist of unmolten material that interrupts the continuous melting process. It is not established whether the heat transfer of the pellets or the heat transfer to the pellets is the leading cause of ferroberg-formation. Modelling the melting process in an EAF is considered near impossible, therefore a simplified heating model of H-DRI was required. In the present thesis, H-DRI pellets were examined with heating experiments in a lab-scale vertical tube furnace to 1500°C while the surface- and center temperatures of the pellets were measured. The measured surface temperatures were applied as varying boundary conditions in COMSOL Multiphysics heat transfer simulations of H-DRI and H-HBI. The thermal conductivity function was utilized as an adjustable parameter to fit the theoretical center temperatures from the heat transfer simulations with the experimental center temperatures to acquire the temperature dependent effective heat conductivity and thermal diffusivity of H-DRI. By establishing an estimate correlation between the heat conductivity of H-DRI and H-HBI, the thermal conductivity and thermal diffusivity of H-HBI could also be obtained. The experiments together with the heat transfer simulations proved to be effective and yielded successful results of the effective heat conductivity and thermal diffusivity of H-DRI and H-HBI, which can be used in process design, future models, and simulations. Furthermore, it is unlikely that ferroberg-formation is caused by slow heat transfer of the H-DRI. It is more likely that it is due to slow heat transfer to the H-DRI. Therefore, the focus should be to increase the heat transfer to the H-DRI pellets while melting in an EAF to avoid ferrobergs. / Stål har haft en oumbärlig roll i att forma vår samtida värld och kommer att fortsätta att inneha den rollen under en överskådlig framtid. Men stålindustrin ansvarar närvarande för 7% av den totala globala CO2-utsläppen, främst på grund av den konventionella kolbaserade reduktionsprocessen av järnmalm. Fossilfri ståltillverkning, som direktreduktion av järnmalm med vätgas, kan i princip göra CO2-utsläppen från primärståltillverkning föråldrat. Produkten från vätgasbaserad direktreduktion av järnmalm är H-DRI, som sedan smälts i en ljusbågsugn för att producera råstål. Eftersom H-DRI är en ny produkt så är dess termofysiska egenskaper, som är väsentliga när man undersöker dess uppvärmnings- och smältbeteende, inte väl dokumenterat. Vid matning av H-DRI till en ljusbågsugn kan det bildas ferroberg som består av osmält material som hindrar den kontinuerliga smältningsprocessen. Det är inte fastställt om det är värmeöverföringen i pelletsen eller värmeöverföringen till pelletsen som är den främsta orsaken till att ferroberg bildas. Modellering av smältprocessen i en ljusbågsugn anses nästintill omöjlig, därför krävdes en förenklad uppvärmningsmodell av H-DRI. I detta examensarbete undersöktes H-DRI-pellets med uppvärmningsexperiment i en vertikal rörugn till 1500°C samtidigt som yt- och centrumtemperaturerna för pelletsen mättes. De uppmätta yttemperaturerna användes som varierande randvillkor i COMSOL Multiphysics värmeöverföringssimuleringar av H-DRI och H-HBI. Den termiska konduktiviteten användes som en justerbar parameter för att anpassa de teoretiska centrumtemperaturerna från värmeöverföringssimuleringarna med de experimentella centrumtemperaturerna för att erhålla den temperaturberoende effektiva termiska konduktiviteten och termiska diffusiviteten för H-DRI. Genom att fastställa en uppskattad korrelation mellan värmeledningsförmågan för H-DRI och H-HBI, kunde även den termiska konduktiviteten och termiska diffusiviteten för H-HBI erhållas. Experimenten tillsammans med värmeöverföringssimuleringarna visade sig vara effektiva och gav framgångsrika resultat av den effektiva termiska konduktiviteten och termiska diffusiviteten hos H-DRI och H-HBI, som kan användas i processdesign, framtida modeller och simuleringar. Det är osannolikt att ferrobergbildning orsakas av långsam värmeöverföring i H-DRI, utan det är mer troligt att det beror på långsam värmeöverföring till H-DRI. Därför bör fokus vara att öka värmeöverföringen till H-DRI pellets i en ljusbågsugn för att undvika ferrobergbildning.
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