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S.T. Abrahami
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1
Reduction mechanisms of goethite-rich iron ore fines under suspension smelting conditions
Influence of H2-enrichment, ore mineralogy and morphology
The steel industry is one of the major contributors to anthropogenic CO2-emissions, necessitating significant changes to achieve carbon neutrality in the future. Considerable efforts in recent years have focused on developing alternatives to the traditional blast furnace (BF) process, aiming for more sustainable ironmaking pathways. Within the framework of the ULCOS initiative in the early 2000s, the HIsarna® process was developed as a promising alternative ironmaking process. HIsarna produces liquid hot metal and slag, similar to the blast furnace, but enables rapid pre-reduction of fine iron ores in a suspension environment, often referred to as flash reduction due to the short reaction times and high temperatures, followed by a final smelting reduction step. Owing to its design, HIsarna offers several process advantages compared to the conventional BF. These are, for example, the elimination of material pre-treatment steps like ore agglomeration and coking, as well as the ability to use low-grade iron ores and secondary Fe-bearing materials.
This PhD project investigated the fundamental mechanisms of suspension smelting (flash ironmaking) in the pre-reduction stage of the HIsarna process, with a particular focus on the influence of ore mineralogy and H2-enriched reducing atmospheres. The primary objective was to understand how these factors affect the pre-reduction kinetics and particle behaviour, providing relevant insights for optimizing the HIsarna process. To achieve this, a combination of thermogravimetric analysis (TGA) and high-temperature drop tube furnace (HTDF) experiments was carried out. TGA enables a detailed kinetic analysis under controlled non-isothermal or isothermal conditions and long residence times, while the HTDF simulates isothermal in-flight particle reduction at very short residence times (hundreds of milliseconds), which is much closer to the actual conditions in the upper part of the HIsarna furnace. Incorporation of both techniques provides a comprehensive understanding of the in-flight single particle reduction behaviour, and of molten particle films, which undergo longer reduction times.
The study begins with a comprehensive characterization of three potential iron ore fines for HIsarna ironmaking (OreA, OreB, OreC) using SEM-EDS, XRD, XRF for compositional analysis, Raman spectroscopy for Fe-phase distribution, light scattering for particle size distribution, He-pycnometer for true particle density, and BET analysis to assess specific surface area and porosity. Throughout the thesis, different size fractions were investigated. For OreA, the < 63 and (63-125) μm fractions were studied, for OreB < 63, (63-125) and (125-250) μm fractions, and for OreC the < 63 and (63-125) μm fractions. The primary mineralogical difference among the three types of iron ores is the goethite content, which is absent in OreA, intermediate in OreB, and high in OreC, influencing physical properties such as porosity, true particle density, specific surface area, and reactivity. Due to the lower iron content in goethite compared to hematite, OreB (58.80-61.60 total-Fe) and OreC (56.80-58.00 total-Fe) are considered low-grade ores, whereas OreA (60.10-64.00 total-Fe) can still be classified as a medium-grade ore. For all ores, SiO2 and Al2O3 are the main gangue components. Additional mineralogical differences between the ores are the dolomite phase present in OreA and kaolinite phase in OreB.
Thermal decomposition of the ores in the TGA revealed that goethite decomposition occurs in a two-stage process. The initial stage is the chemically reaction-controlled decomposition of nearly pure goethite particles within the ore. The following second stage is the decomposition of goethite-hematite intertwined phases, which is diffusion controlled. Hematite thermal decomposition in the TGA is consistently chemical reaction controlled for all ores. Higher goethite content leads to higher reduction degrees during thermal decomposition, highlighting the mineralogical impact on the pre-reduction behaviour. Hence, at the end of the non-isothermal heating zone at 1773 K OreC reached the highest reduction degrees (11.91-13.81 %), followed by OreB (11.90-12.90 %), and OreA reached the lowest reduction degrees (9.48-10.75 %). While OreB and OreC were completely converted to magnetite during the heating period, OreA required additional holding times at 1773 K to fully convert to magnetite. HTDF experiments indicated that under in-flight conditions, thermal decomposition alone resulted in much lower pre-reduction due to extremely short particle residence times. Goethite-containing ores exhibited significant cracking, followed by fragmentation, altering particle size and density, which then influenced the extent of pre-reduction and its kinetics. OreC, with the highest goethite content, showed more extensive fragmentation, whereas OreB primarily expanded before fragmentation. Reducing gas enrichment (at low CO or H2 levels) slightly enhanced pre-reduction under flash conditions, but its effect was more pronounced in the TGA experiments, where small amounts of wustite have formed. EBSD analysis confirmed that reduction under both rapid thermal decomposition and low reducing gas-enriched atmospheres proceeded via a mixed mechanism of product-layer and internal pore diffusion.
Further isothermal TGA studies of OreB with varying H2-levels (7.5-37.5 %) demonstrated that increasing H2 in the atmosphere significantly accelerates reduction rates, reducing the overall reduction time even though the total reduction extent is only moderately affected. For example, at a post-combustion ratio (PCR) of 60% and at a temperature of 1773 K, the reduction in 7.5 % H2 took 502 s to achieve a PRD (pre-reduction degree) of 24.2 %. When the H2-content in the atmosphere was increased to 22.5 %, the reaction took only 375 s to achieve a PRD of 25.0 %. By further decreasing the PCR to 40 % and, therefore, increasing the H2-content to 37.5 %, the reaction only needed 206 s to reach a PRD of 27.1 %. SEM-EDS analysis indicated that the reduction was controlled by the diffusion of the reducing gas through a developing product layer. Within the same PCR, the activation energy decreased from 77.60 kJ/mol to 69.12 kJ/mol by increasing the H2 content, but increased to 79.91 kJ/mol at a lower PCR. Non-isothermal experiments confirmed that mineralogy, especially the goethite content, enhances hematite to wustite reduction, while under isothermal conditions these effects were limited after initial magnetite formation. The water-gas shift reaction was observed at higher temperatures, impacting the extent of available H2 during in-flight reduction. In HTDF experiments with 7.5 % H2, OreA exhibited higher pre-reduction at the particle surface, whereas OreB showed more bulk reduction, indicating surface-controlled interfacial reaction for OreA and a likely more mixed control of nucleation and surface control for OreB. Testing higher H2 levels under flash conditions was limited by rapid water-vapour formation via the water-gas shift reaction, which caused excessive condensation in the quenching zone. This condensation prevented reliable sample collection after the experiments.
Overall, this thesis provides a comprehensive understanding of how ore mineralogy and H2-enrichment influence reaction fundamentals under in-flight suspension smelting conditions. The findings highlight that under in-flight flash pre-reduction, goethite-containing ores perform better compared to ores containing only hematite due to favorable physical and morphological properties. H2-enrichment offers a promising approach to accelerate reduction, potentially decreasing the amounts of coal injection needed in the HIsarna smelting stage. However, its application must consider issues arising from the water-gas shift reaction, which consumes H2 and generates large amounts of water-vapour. This work establishes critical mechanistic insights for optimizing the HIsarna ironmaking process, demonstrating that control of ore selection and gas composition can enhance pre-reduction efficiency and support the development of more sustainable iron production processes.
...
This PhD project investigated the fundamental mechanisms of suspension smelting (flash ironmaking) in the pre-reduction stage of the HIsarna process, with a particular focus on the influence of ore mineralogy and H2-enriched reducing atmospheres. The primary objective was to understand how these factors affect the pre-reduction kinetics and particle behaviour, providing relevant insights for optimizing the HIsarna process. To achieve this, a combination of thermogravimetric analysis (TGA) and high-temperature drop tube furnace (HTDF) experiments was carried out. TGA enables a detailed kinetic analysis under controlled non-isothermal or isothermal conditions and long residence times, while the HTDF simulates isothermal in-flight particle reduction at very short residence times (hundreds of milliseconds), which is much closer to the actual conditions in the upper part of the HIsarna furnace. Incorporation of both techniques provides a comprehensive understanding of the in-flight single particle reduction behaviour, and of molten particle films, which undergo longer reduction times.
The study begins with a comprehensive characterization of three potential iron ore fines for HIsarna ironmaking (OreA, OreB, OreC) using SEM-EDS, XRD, XRF for compositional analysis, Raman spectroscopy for Fe-phase distribution, light scattering for particle size distribution, He-pycnometer for true particle density, and BET analysis to assess specific surface area and porosity. Throughout the thesis, different size fractions were investigated. For OreA, the < 63 and (63-125) μm fractions were studied, for OreB < 63, (63-125) and (125-250) μm fractions, and for OreC the < 63 and (63-125) μm fractions. The primary mineralogical difference among the three types of iron ores is the goethite content, which is absent in OreA, intermediate in OreB, and high in OreC, influencing physical properties such as porosity, true particle density, specific surface area, and reactivity. Due to the lower iron content in goethite compared to hematite, OreB (58.80-61.60 total-Fe) and OreC (56.80-58.00 total-Fe) are considered low-grade ores, whereas OreA (60.10-64.00 total-Fe) can still be classified as a medium-grade ore. For all ores, SiO2 and Al2O3 are the main gangue components. Additional mineralogical differences between the ores are the dolomite phase present in OreA and kaolinite phase in OreB.
Thermal decomposition of the ores in the TGA revealed that goethite decomposition occurs in a two-stage process. The initial stage is the chemically reaction-controlled decomposition of nearly pure goethite particles within the ore. The following second stage is the decomposition of goethite-hematite intertwined phases, which is diffusion controlled. Hematite thermal decomposition in the TGA is consistently chemical reaction controlled for all ores. Higher goethite content leads to higher reduction degrees during thermal decomposition, highlighting the mineralogical impact on the pre-reduction behaviour. Hence, at the end of the non-isothermal heating zone at 1773 K OreC reached the highest reduction degrees (11.91-13.81 %), followed by OreB (11.90-12.90 %), and OreA reached the lowest reduction degrees (9.48-10.75 %). While OreB and OreC were completely converted to magnetite during the heating period, OreA required additional holding times at 1773 K to fully convert to magnetite. HTDF experiments indicated that under in-flight conditions, thermal decomposition alone resulted in much lower pre-reduction due to extremely short particle residence times. Goethite-containing ores exhibited significant cracking, followed by fragmentation, altering particle size and density, which then influenced the extent of pre-reduction and its kinetics. OreC, with the highest goethite content, showed more extensive fragmentation, whereas OreB primarily expanded before fragmentation. Reducing gas enrichment (at low CO or H2 levels) slightly enhanced pre-reduction under flash conditions, but its effect was more pronounced in the TGA experiments, where small amounts of wustite have formed. EBSD analysis confirmed that reduction under both rapid thermal decomposition and low reducing gas-enriched atmospheres proceeded via a mixed mechanism of product-layer and internal pore diffusion.
Further isothermal TGA studies of OreB with varying H2-levels (7.5-37.5 %) demonstrated that increasing H2 in the atmosphere significantly accelerates reduction rates, reducing the overall reduction time even though the total reduction extent is only moderately affected. For example, at a post-combustion ratio (PCR) of 60% and at a temperature of 1773 K, the reduction in 7.5 % H2 took 502 s to achieve a PRD (pre-reduction degree) of 24.2 %. When the H2-content in the atmosphere was increased to 22.5 %, the reaction took only 375 s to achieve a PRD of 25.0 %. By further decreasing the PCR to 40 % and, therefore, increasing the H2-content to 37.5 %, the reaction only needed 206 s to reach a PRD of 27.1 %. SEM-EDS analysis indicated that the reduction was controlled by the diffusion of the reducing gas through a developing product layer. Within the same PCR, the activation energy decreased from 77.60 kJ/mol to 69.12 kJ/mol by increasing the H2 content, but increased to 79.91 kJ/mol at a lower PCR. Non-isothermal experiments confirmed that mineralogy, especially the goethite content, enhances hematite to wustite reduction, while under isothermal conditions these effects were limited after initial magnetite formation. The water-gas shift reaction was observed at higher temperatures, impacting the extent of available H2 during in-flight reduction. In HTDF experiments with 7.5 % H2, OreA exhibited higher pre-reduction at the particle surface, whereas OreB showed more bulk reduction, indicating surface-controlled interfacial reaction for OreA and a likely more mixed control of nucleation and surface control for OreB. Testing higher H2 levels under flash conditions was limited by rapid water-vapour formation via the water-gas shift reaction, which caused excessive condensation in the quenching zone. This condensation prevented reliable sample collection after the experiments.
Overall, this thesis provides a comprehensive understanding of how ore mineralogy and H2-enrichment influence reaction fundamentals under in-flight suspension smelting conditions. The findings highlight that under in-flight flash pre-reduction, goethite-containing ores perform better compared to ores containing only hematite due to favorable physical and morphological properties. H2-enrichment offers a promising approach to accelerate reduction, potentially decreasing the amounts of coal injection needed in the HIsarna smelting stage. However, its application must consider issues arising from the water-gas shift reaction, which consumes H2 and generates large amounts of water-vapour. This work establishes critical mechanistic insights for optimizing the HIsarna ironmaking process, demonstrating that control of ore selection and gas composition can enhance pre-reduction efficiency and support the development of more sustainable iron production processes.
...
The steel industry is one of the major contributors to anthropogenic CO2-emissions, necessitating significant changes to achieve carbon neutrality in the future. Considerable efforts in recent years have focused on developing alternatives to the traditional blast furnace (BF) process, aiming for more sustainable ironmaking pathways. Within the framework of the ULCOS initiative in the early 2000s, the HIsarna® process was developed as a promising alternative ironmaking process. HIsarna produces liquid hot metal and slag, similar to the blast furnace, but enables rapid pre-reduction of fine iron ores in a suspension environment, often referred to as flash reduction due to the short reaction times and high temperatures, followed by a final smelting reduction step. Owing to its design, HIsarna offers several process advantages compared to the conventional BF. These are, for example, the elimination of material pre-treatment steps like ore agglomeration and coking, as well as the ability to use low-grade iron ores and secondary Fe-bearing materials.
This PhD project investigated the fundamental mechanisms of suspension smelting (flash ironmaking) in the pre-reduction stage of the HIsarna process, with a particular focus on the influence of ore mineralogy and H2-enriched reducing atmospheres. The primary objective was to understand how these factors affect the pre-reduction kinetics and particle behaviour, providing relevant insights for optimizing the HIsarna process. To achieve this, a combination of thermogravimetric analysis (TGA) and high-temperature drop tube furnace (HTDF) experiments was carried out. TGA enables a detailed kinetic analysis under controlled non-isothermal or isothermal conditions and long residence times, while the HTDF simulates isothermal in-flight particle reduction at very short residence times (hundreds of milliseconds), which is much closer to the actual conditions in the upper part of the HIsarna furnace. Incorporation of both techniques provides a comprehensive understanding of the in-flight single particle reduction behaviour, and of molten particle films, which undergo longer reduction times.
The study begins with a comprehensive characterization of three potential iron ore fines for HIsarna ironmaking (OreA, OreB, OreC) using SEM-EDS, XRD, XRF for compositional analysis, Raman spectroscopy for Fe-phase distribution, light scattering for particle size distribution, He-pycnometer for true particle density, and BET analysis to assess specific surface area and porosity. Throughout the thesis, different size fractions were investigated. For OreA, the < 63 and (63-125) μm fractions were studied, for OreB < 63, (63-125) and (125-250) μm fractions, and for OreC the < 63 and (63-125) μm fractions. The primary mineralogical difference among the three types of iron ores is the goethite content, which is absent in OreA, intermediate in OreB, and high in OreC, influencing physical properties such as porosity, true particle density, specific surface area, and reactivity. Due to the lower iron content in goethite compared to hematite, OreB (58.80-61.60 total-Fe) and OreC (56.80-58.00 total-Fe) are considered low-grade ores, whereas OreA (60.10-64.00 total-Fe) can still be classified as a medium-grade ore. For all ores, SiO2 and Al2O3 are the main gangue components. Additional mineralogical differences between the ores are the dolomite phase present in OreA and kaolinite phase in OreB.
Thermal decomposition of the ores in the TGA revealed that goethite decomposition occurs in a two-stage process. The initial stage is the chemically reaction-controlled decomposition of nearly pure goethite particles within the ore. The following second stage is the decomposition of goethite-hematite intertwined phases, which is diffusion controlled. Hematite thermal decomposition in the TGA is consistently chemical reaction controlled for all ores. Higher goethite content leads to higher reduction degrees during thermal decomposition, highlighting the mineralogical impact on the pre-reduction behaviour. Hence, at the end of the non-isothermal heating zone at 1773 K OreC reached the highest reduction degrees (11.91-13.81 %), followed by OreB (11.90-12.90 %), and OreA reached the lowest reduction degrees (9.48-10.75 %). While OreB and OreC were completely converted to magnetite during the heating period, OreA required additional holding times at 1773 K to fully convert to magnetite. HTDF experiments indicated that under in-flight conditions, thermal decomposition alone resulted in much lower pre-reduction due to extremely short particle residence times. Goethite-containing ores exhibited significant cracking, followed by fragmentation, altering particle size and density, which then influenced the extent of pre-reduction and its kinetics. OreC, with the highest goethite content, showed more extensive fragmentation, whereas OreB primarily expanded before fragmentation. Reducing gas enrichment (at low CO or H2 levels) slightly enhanced pre-reduction under flash conditions, but its effect was more pronounced in the TGA experiments, where small amounts of wustite have formed. EBSD analysis confirmed that reduction under both rapid thermal decomposition and low reducing gas-enriched atmospheres proceeded via a mixed mechanism of product-layer and internal pore diffusion.
Further isothermal TGA studies of OreB with varying H2-levels (7.5-37.5 %) demonstrated that increasing H2 in the atmosphere significantly accelerates reduction rates, reducing the overall reduction time even though the total reduction extent is only moderately affected. For example, at a post-combustion ratio (PCR) of 60% and at a temperature of 1773 K, the reduction in 7.5 % H2 took 502 s to achieve a PRD (pre-reduction degree) of 24.2 %. When the H2-content in the atmosphere was increased to 22.5 %, the reaction took only 375 s to achieve a PRD of 25.0 %. By further decreasing the PCR to 40 % and, therefore, increasing the H2-content to 37.5 %, the reaction only needed 206 s to reach a PRD of 27.1 %. SEM-EDS analysis indicated that the reduction was controlled by the diffusion of the reducing gas through a developing product layer. Within the same PCR, the activation energy decreased from 77.60 kJ/mol to 69.12 kJ/mol by increasing the H2 content, but increased to 79.91 kJ/mol at a lower PCR. Non-isothermal experiments confirmed that mineralogy, especially the goethite content, enhances hematite to wustite reduction, while under isothermal conditions these effects were limited after initial magnetite formation. The water-gas shift reaction was observed at higher temperatures, impacting the extent of available H2 during in-flight reduction. In HTDF experiments with 7.5 % H2, OreA exhibited higher pre-reduction at the particle surface, whereas OreB showed more bulk reduction, indicating surface-controlled interfacial reaction for OreA and a likely more mixed control of nucleation and surface control for OreB. Testing higher H2 levels under flash conditions was limited by rapid water-vapour formation via the water-gas shift reaction, which caused excessive condensation in the quenching zone. This condensation prevented reliable sample collection after the experiments.
Overall, this thesis provides a comprehensive understanding of how ore mineralogy and H2-enrichment influence reaction fundamentals under in-flight suspension smelting conditions. The findings highlight that under in-flight flash pre-reduction, goethite-containing ores perform better compared to ores containing only hematite due to favorable physical and morphological properties. H2-enrichment offers a promising approach to accelerate reduction, potentially decreasing the amounts of coal injection needed in the HIsarna smelting stage. However, its application must consider issues arising from the water-gas shift reaction, which consumes H2 and generates large amounts of water-vapour. This work establishes critical mechanistic insights for optimizing the HIsarna ironmaking process, demonstrating that control of ore selection and gas composition can enhance pre-reduction efficiency and support the development of more sustainable iron production processes.
This PhD project investigated the fundamental mechanisms of suspension smelting (flash ironmaking) in the pre-reduction stage of the HIsarna process, with a particular focus on the influence of ore mineralogy and H2-enriched reducing atmospheres. The primary objective was to understand how these factors affect the pre-reduction kinetics and particle behaviour, providing relevant insights for optimizing the HIsarna process. To achieve this, a combination of thermogravimetric analysis (TGA) and high-temperature drop tube furnace (HTDF) experiments was carried out. TGA enables a detailed kinetic analysis under controlled non-isothermal or isothermal conditions and long residence times, while the HTDF simulates isothermal in-flight particle reduction at very short residence times (hundreds of milliseconds), which is much closer to the actual conditions in the upper part of the HIsarna furnace. Incorporation of both techniques provides a comprehensive understanding of the in-flight single particle reduction behaviour, and of molten particle films, which undergo longer reduction times.
The study begins with a comprehensive characterization of three potential iron ore fines for HIsarna ironmaking (OreA, OreB, OreC) using SEM-EDS, XRD, XRF for compositional analysis, Raman spectroscopy for Fe-phase distribution, light scattering for particle size distribution, He-pycnometer for true particle density, and BET analysis to assess specific surface area and porosity. Throughout the thesis, different size fractions were investigated. For OreA, the < 63 and (63-125) μm fractions were studied, for OreB < 63, (63-125) and (125-250) μm fractions, and for OreC the < 63 and (63-125) μm fractions. The primary mineralogical difference among the three types of iron ores is the goethite content, which is absent in OreA, intermediate in OreB, and high in OreC, influencing physical properties such as porosity, true particle density, specific surface area, and reactivity. Due to the lower iron content in goethite compared to hematite, OreB (58.80-61.60 total-Fe) and OreC (56.80-58.00 total-Fe) are considered low-grade ores, whereas OreA (60.10-64.00 total-Fe) can still be classified as a medium-grade ore. For all ores, SiO2 and Al2O3 are the main gangue components. Additional mineralogical differences between the ores are the dolomite phase present in OreA and kaolinite phase in OreB.
Thermal decomposition of the ores in the TGA revealed that goethite decomposition occurs in a two-stage process. The initial stage is the chemically reaction-controlled decomposition of nearly pure goethite particles within the ore. The following second stage is the decomposition of goethite-hematite intertwined phases, which is diffusion controlled. Hematite thermal decomposition in the TGA is consistently chemical reaction controlled for all ores. Higher goethite content leads to higher reduction degrees during thermal decomposition, highlighting the mineralogical impact on the pre-reduction behaviour. Hence, at the end of the non-isothermal heating zone at 1773 K OreC reached the highest reduction degrees (11.91-13.81 %), followed by OreB (11.90-12.90 %), and OreA reached the lowest reduction degrees (9.48-10.75 %). While OreB and OreC were completely converted to magnetite during the heating period, OreA required additional holding times at 1773 K to fully convert to magnetite. HTDF experiments indicated that under in-flight conditions, thermal decomposition alone resulted in much lower pre-reduction due to extremely short particle residence times. Goethite-containing ores exhibited significant cracking, followed by fragmentation, altering particle size and density, which then influenced the extent of pre-reduction and its kinetics. OreC, with the highest goethite content, showed more extensive fragmentation, whereas OreB primarily expanded before fragmentation. Reducing gas enrichment (at low CO or H2 levels) slightly enhanced pre-reduction under flash conditions, but its effect was more pronounced in the TGA experiments, where small amounts of wustite have formed. EBSD analysis confirmed that reduction under both rapid thermal decomposition and low reducing gas-enriched atmospheres proceeded via a mixed mechanism of product-layer and internal pore diffusion.
Further isothermal TGA studies of OreB with varying H2-levels (7.5-37.5 %) demonstrated that increasing H2 in the atmosphere significantly accelerates reduction rates, reducing the overall reduction time even though the total reduction extent is only moderately affected. For example, at a post-combustion ratio (PCR) of 60% and at a temperature of 1773 K, the reduction in 7.5 % H2 took 502 s to achieve a PRD (pre-reduction degree) of 24.2 %. When the H2-content in the atmosphere was increased to 22.5 %, the reaction took only 375 s to achieve a PRD of 25.0 %. By further decreasing the PCR to 40 % and, therefore, increasing the H2-content to 37.5 %, the reaction only needed 206 s to reach a PRD of 27.1 %. SEM-EDS analysis indicated that the reduction was controlled by the diffusion of the reducing gas through a developing product layer. Within the same PCR, the activation energy decreased from 77.60 kJ/mol to 69.12 kJ/mol by increasing the H2 content, but increased to 79.91 kJ/mol at a lower PCR. Non-isothermal experiments confirmed that mineralogy, especially the goethite content, enhances hematite to wustite reduction, while under isothermal conditions these effects were limited after initial magnetite formation. The water-gas shift reaction was observed at higher temperatures, impacting the extent of available H2 during in-flight reduction. In HTDF experiments with 7.5 % H2, OreA exhibited higher pre-reduction at the particle surface, whereas OreB showed more bulk reduction, indicating surface-controlled interfacial reaction for OreA and a likely more mixed control of nucleation and surface control for OreB. Testing higher H2 levels under flash conditions was limited by rapid water-vapour formation via the water-gas shift reaction, which caused excessive condensation in the quenching zone. This condensation prevented reliable sample collection after the experiments.
Overall, this thesis provides a comprehensive understanding of how ore mineralogy and H2-enrichment influence reaction fundamentals under in-flight suspension smelting conditions. The findings highlight that under in-flight flash pre-reduction, goethite-containing ores perform better compared to ores containing only hematite due to favorable physical and morphological properties. H2-enrichment offers a promising approach to accelerate reduction, potentially decreasing the amounts of coal injection needed in the HIsarna smelting stage. However, its application must consider issues arising from the water-gas shift reaction, which consumes H2 and generates large amounts of water-vapour. This work establishes critical mechanistic insights for optimizing the HIsarna ironmaking process, demonstrating that control of ore selection and gas composition can enhance pre-reduction efficiency and support the development of more sustainable iron production processes.
Lithium-ion batteries (LiBs) play a key role in the electrification of our society, and contain materials that are associated with supply risks, rendering them critical- or strategic raw materials (CRMs and SRMs, respectively). Examples of such materials are Li, Co, and Mn (CRMs), or Ni and Cu (SRMs). Recycling is a key contributor to relieve some of the pressure on the supply of these materials. This dissertation focuses on mixed battery waste streams of complex and varying chemistries, and on how this end-of-life product influences hydrometallurgical recycling, with the ultimate goal of designing a flexible, closed loop recycling process that combines
high product quality with minimal environmental footprint.... ...
high product quality with minimal environmental footprint.... ...
Lithium-ion batteries (LiBs) play a key role in the electrification of our society, and contain materials that are associated with supply risks, rendering them critical- or strategic raw materials (CRMs and SRMs, respectively). Examples of such materials are Li, Co, and Mn (CRMs), or Ni and Cu (SRMs). Recycling is a key contributor to relieve some of the pressure on the supply of these materials. This dissertation focuses on mixed battery waste streams of complex and varying chemistries, and on how this end-of-life product influences hydrometallurgical recycling, with the ultimate goal of designing a flexible, closed loop recycling process that combines
high product quality with minimal environmental footprint....
high product quality with minimal environmental footprint....
The increasing electrification of our world drives a demand for energy storage solutions, especially for electric vehicles. As they reach their end of life, recycling them becomes vital to recover the critical raw materials in these batteries. However, traditional recycling routes have high energy consumption or require high quantities of chemicals. To mitigate this need and drive more sustainable recycling routes, new methods must be investigated to allow for a green recycling process. In this thesis, the simultaneous leaching of LiNixMnyCozO2 and LiFePO4 was investigated in a mildly acidic solution to extract Li, Ni, Mn, Co, Fe, and PO4 , limiting the use of additional reagents, leaching efficiencies achieved over 90% for Li, Ni, Mn and Co, with significant amounts of impurities also leaching in the solution. Electrochemical purification methods were investigated to remove contaminants such as Fe, Cu, and Al to facilitate purification of the extracted leach solution. This was done by employing an electro-oxidation method on simpler solutions of FeSO4 and industrial LiFePO4 to oxidise the generated Fe2+ after leaching, with more than 99% oxidation achieved. This method was also used on more complex, multimetallic systems, with oxidation percentages reaching 73% in similar conditions. Furthermore, an electrodeposition step was added to mitigate the interference of Cu with the electro-oxidation step, with a moderate effect on improving the efficiency of the Fe2+ oxidation. Moreover, a pH adjustment step was also added to evaluate the influence of the solution acidity on the electrochemical methods, with pH 4 solutions achieving high impurity removal by combining all of the mentioned methods.
...
The increasing electrification of our world drives a demand for energy storage solutions, especially for electric vehicles. As they reach their end of life, recycling them becomes vital to recover the critical raw materials in these batteries. However, traditional recycling routes have high energy consumption or require high quantities of chemicals. To mitigate this need and drive more sustainable recycling routes, new methods must be investigated to allow for a green recycling process. In this thesis, the simultaneous leaching of LiNixMnyCozO2 and LiFePO4 was investigated in a mildly acidic solution to extract Li, Ni, Mn, Co, Fe, and PO4 , limiting the use of additional reagents, leaching efficiencies achieved over 90% for Li, Ni, Mn and Co, with significant amounts of impurities also leaching in the solution. Electrochemical purification methods were investigated to remove contaminants such as Fe, Cu, and Al to facilitate purification of the extracted leach solution. This was done by employing an electro-oxidation method on simpler solutions of FeSO4 and industrial LiFePO4 to oxidise the generated Fe2+ after leaching, with more than 99% oxidation achieved. This method was also used on more complex, multimetallic systems, with oxidation percentages reaching 73% in similar conditions. Furthermore, an electrodeposition step was added to mitigate the interference of Cu with the electro-oxidation step, with a moderate effect on improving the efficiency of the Fe2+ oxidation. Moreover, a pH adjustment step was also added to evaluate the influence of the solution acidity on the electrochemical methods, with pH 4 solutions achieving high impurity removal by combining all of the mentioned methods.
This study investigates the effect of repeated recycling processes on the properties of PLA matrix 3D printed filaments mixed with 20 wt.% Fe₃O₄ magnetic particles. The recycling process of the composite was simulated by using extrusion and manual cutting to achieve multiple closed-loop recycling processes. The research studied the 1st, 3rd, 5th, and 6th cycles, while the initial batch virgin materials (0 cycles) was used as a baseline.
Visual observations revealed that surface defects increase with each cycle, along with diameter inconsistencies and brittleness. The analysis showed that the 5th cycle had the highest diameter variation (range = 2.37 mm, standard deviation = 0.44 mm). The 6th cycle was unusable filament with a disoriented shape and chaotic flow behavior, which made it impossible to inject or print into the 3D printing machine. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis indicated significant morphological changes, agglomeration of magnetic particles, and content reduction along cycles. GPC analysis confirmed that the molecular weight of the PLA decreased and that the polydispersity increased, while NMR identified the absence of dichloromethane as a solvent, confirming that the degradation indicated by PLA molecular weight reduction was solely caused by thermomechanical reprocessing effects.
The findings suggest that PLA/Fe₃O₄ filaments can be processed up to five times, but the practical usability of the reprocessed filament is limited due to surface defects and poor filament diameter consistency. During the first cycle, the filament frequently stuck in the 3D printer feeder due to diameter inconsistencies, and by the third cycle, attempts to print resulted in improperly shaped parts, highlighting significant processing challenges. Additionally, repeated processing cycles lead to loss of magnetic particles, significantly affecting the filament’s functionality. Characterization using the Vibrating Sample Magnetometer (VSM) demonstrates a reduction in magnetic properties, with a 28.62% decrease in Cycle 3, a 51.41% decrease in Cycle 5, and a 73.91% decrease in Cycle 6 compared to Cycle 1. Moreover, the thermal stability of PLA is also compromised, as evidenced by the decrease in degradation temperature recorded in the Thermogravimetric Analysis (TGA), highlighting the declining performance of the filament after multiple recycling cycles. Further improvements in processing methods, material quality, and testing are recommended to enhance recyclability and ensure consistent print results in future applications. ...
Visual observations revealed that surface defects increase with each cycle, along with diameter inconsistencies and brittleness. The analysis showed that the 5th cycle had the highest diameter variation (range = 2.37 mm, standard deviation = 0.44 mm). The 6th cycle was unusable filament with a disoriented shape and chaotic flow behavior, which made it impossible to inject or print into the 3D printing machine. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis indicated significant morphological changes, agglomeration of magnetic particles, and content reduction along cycles. GPC analysis confirmed that the molecular weight of the PLA decreased and that the polydispersity increased, while NMR identified the absence of dichloromethane as a solvent, confirming that the degradation indicated by PLA molecular weight reduction was solely caused by thermomechanical reprocessing effects.
The findings suggest that PLA/Fe₃O₄ filaments can be processed up to five times, but the practical usability of the reprocessed filament is limited due to surface defects and poor filament diameter consistency. During the first cycle, the filament frequently stuck in the 3D printer feeder due to diameter inconsistencies, and by the third cycle, attempts to print resulted in improperly shaped parts, highlighting significant processing challenges. Additionally, repeated processing cycles lead to loss of magnetic particles, significantly affecting the filament’s functionality. Characterization using the Vibrating Sample Magnetometer (VSM) demonstrates a reduction in magnetic properties, with a 28.62% decrease in Cycle 3, a 51.41% decrease in Cycle 5, and a 73.91% decrease in Cycle 6 compared to Cycle 1. Moreover, the thermal stability of PLA is also compromised, as evidenced by the decrease in degradation temperature recorded in the Thermogravimetric Analysis (TGA), highlighting the declining performance of the filament after multiple recycling cycles. Further improvements in processing methods, material quality, and testing are recommended to enhance recyclability and ensure consistent print results in future applications. ...
This study investigates the effect of repeated recycling processes on the properties of PLA matrix 3D printed filaments mixed with 20 wt.% Fe₃O₄ magnetic particles. The recycling process of the composite was simulated by using extrusion and manual cutting to achieve multiple closed-loop recycling processes. The research studied the 1st, 3rd, 5th, and 6th cycles, while the initial batch virgin materials (0 cycles) was used as a baseline.
Visual observations revealed that surface defects increase with each cycle, along with diameter inconsistencies and brittleness. The analysis showed that the 5th cycle had the highest diameter variation (range = 2.37 mm, standard deviation = 0.44 mm). The 6th cycle was unusable filament with a disoriented shape and chaotic flow behavior, which made it impossible to inject or print into the 3D printing machine. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis indicated significant morphological changes, agglomeration of magnetic particles, and content reduction along cycles. GPC analysis confirmed that the molecular weight of the PLA decreased and that the polydispersity increased, while NMR identified the absence of dichloromethane as a solvent, confirming that the degradation indicated by PLA molecular weight reduction was solely caused by thermomechanical reprocessing effects.
The findings suggest that PLA/Fe₃O₄ filaments can be processed up to five times, but the practical usability of the reprocessed filament is limited due to surface defects and poor filament diameter consistency. During the first cycle, the filament frequently stuck in the 3D printer feeder due to diameter inconsistencies, and by the third cycle, attempts to print resulted in improperly shaped parts, highlighting significant processing challenges. Additionally, repeated processing cycles lead to loss of magnetic particles, significantly affecting the filament’s functionality. Characterization using the Vibrating Sample Magnetometer (VSM) demonstrates a reduction in magnetic properties, with a 28.62% decrease in Cycle 3, a 51.41% decrease in Cycle 5, and a 73.91% decrease in Cycle 6 compared to Cycle 1. Moreover, the thermal stability of PLA is also compromised, as evidenced by the decrease in degradation temperature recorded in the Thermogravimetric Analysis (TGA), highlighting the declining performance of the filament after multiple recycling cycles. Further improvements in processing methods, material quality, and testing are recommended to enhance recyclability and ensure consistent print results in future applications.
Visual observations revealed that surface defects increase with each cycle, along with diameter inconsistencies and brittleness. The analysis showed that the 5th cycle had the highest diameter variation (range = 2.37 mm, standard deviation = 0.44 mm). The 6th cycle was unusable filament with a disoriented shape and chaotic flow behavior, which made it impossible to inject or print into the 3D printing machine. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis indicated significant morphological changes, agglomeration of magnetic particles, and content reduction along cycles. GPC analysis confirmed that the molecular weight of the PLA decreased and that the polydispersity increased, while NMR identified the absence of dichloromethane as a solvent, confirming that the degradation indicated by PLA molecular weight reduction was solely caused by thermomechanical reprocessing effects.
The findings suggest that PLA/Fe₃O₄ filaments can be processed up to five times, but the practical usability of the reprocessed filament is limited due to surface defects and poor filament diameter consistency. During the first cycle, the filament frequently stuck in the 3D printer feeder due to diameter inconsistencies, and by the third cycle, attempts to print resulted in improperly shaped parts, highlighting significant processing challenges. Additionally, repeated processing cycles lead to loss of magnetic particles, significantly affecting the filament’s functionality. Characterization using the Vibrating Sample Magnetometer (VSM) demonstrates a reduction in magnetic properties, with a 28.62% decrease in Cycle 3, a 51.41% decrease in Cycle 5, and a 73.91% decrease in Cycle 6 compared to Cycle 1. Moreover, the thermal stability of PLA is also compromised, as evidenced by the decrease in degradation temperature recorded in the Thermogravimetric Analysis (TGA), highlighting the declining performance of the filament after multiple recycling cycles. Further improvements in processing methods, material quality, and testing are recommended to enhance recyclability and ensure consistent print results in future applications.
Carbon fibre reinforced polymer (CFRP) composites have become integral to modern day society, forming the backbone of lightweight, high performance structures in aerospace, renewable energy and automotive applications amongst other. Their exceptional strength-to-weight ratio, stiffness and corrosion resistance in such applications make them indispensable for improving fuel efficiency, thereby contributing to lower greenhouse gas emissions. However, their end-of-life management and recycling remains a critical challenge. The thermoset polymer matrix used in most high-performance CFRP composites, makes fibre-matrix separation difficult leading to limited recyclability and continues reliance on energy- and cost- intensive virgin carbon fibre production.
Among the emerging approaches for CFRP recycling, electrochemical processes have gained attention as promising low-energy and environmentally friendly alternatives to traditional thermal or chemical processes. The electrochemical recycling of CFRP operates under mild conditions, without the need of hazardous solvents or external heating. Despite these advantages, current literature focuses predominantly on fibre recovery efficiency with limited understanding of the gaseous, liquid and solid by-products formed during such process. These by-products may significantly influence the true environmental footprint and industrial feasibility of this technique.
To address this gap, this study systematically investigated the influence of constant applied voltage (4, 6 and 8 V) on by-product generation and CFRP degradation behaviour in an alkaline saline electrolyte composed of 3wt.% NaCl and 0.01M KOH. The by-products were characterised using gas chromatography and proton nuclear magnetic resonance spectroscopy. Additionally, the pH of the electrolytes after electrolysis was monitored and surface analysis techniques were employed to evaluate the degradation mechanisms and fibre integrity.
Results revealed that higher voltages increase current density, gas evolution and epoxy degradation, but also produced greater quantities of CO2, hydrocarbons and liquid by-products, alongside visible fibre damage. Conversely, lower voltages achieved sufficient resin removal while maintaining fibre integrity and reducing emissions. Liquid-phase analysis identified ethanol, acetone and formate, whose decomposition correlated with increasing CO2 evolution at higher potentials.
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Among the emerging approaches for CFRP recycling, electrochemical processes have gained attention as promising low-energy and environmentally friendly alternatives to traditional thermal or chemical processes. The electrochemical recycling of CFRP operates under mild conditions, without the need of hazardous solvents or external heating. Despite these advantages, current literature focuses predominantly on fibre recovery efficiency with limited understanding of the gaseous, liquid and solid by-products formed during such process. These by-products may significantly influence the true environmental footprint and industrial feasibility of this technique.
To address this gap, this study systematically investigated the influence of constant applied voltage (4, 6 and 8 V) on by-product generation and CFRP degradation behaviour in an alkaline saline electrolyte composed of 3wt.% NaCl and 0.01M KOH. The by-products were characterised using gas chromatography and proton nuclear magnetic resonance spectroscopy. Additionally, the pH of the electrolytes after electrolysis was monitored and surface analysis techniques were employed to evaluate the degradation mechanisms and fibre integrity.
Results revealed that higher voltages increase current density, gas evolution and epoxy degradation, but also produced greater quantities of CO2, hydrocarbons and liquid by-products, alongside visible fibre damage. Conversely, lower voltages achieved sufficient resin removal while maintaining fibre integrity and reducing emissions. Liquid-phase analysis identified ethanol, acetone and formate, whose decomposition correlated with increasing CO2 evolution at higher potentials.
...
Carbon fibre reinforced polymer (CFRP) composites have become integral to modern day society, forming the backbone of lightweight, high performance structures in aerospace, renewable energy and automotive applications amongst other. Their exceptional strength-to-weight ratio, stiffness and corrosion resistance in such applications make them indispensable for improving fuel efficiency, thereby contributing to lower greenhouse gas emissions. However, their end-of-life management and recycling remains a critical challenge. The thermoset polymer matrix used in most high-performance CFRP composites, makes fibre-matrix separation difficult leading to limited recyclability and continues reliance on energy- and cost- intensive virgin carbon fibre production.
Among the emerging approaches for CFRP recycling, electrochemical processes have gained attention as promising low-energy and environmentally friendly alternatives to traditional thermal or chemical processes. The electrochemical recycling of CFRP operates under mild conditions, without the need of hazardous solvents or external heating. Despite these advantages, current literature focuses predominantly on fibre recovery efficiency with limited understanding of the gaseous, liquid and solid by-products formed during such process. These by-products may significantly influence the true environmental footprint and industrial feasibility of this technique.
To address this gap, this study systematically investigated the influence of constant applied voltage (4, 6 and 8 V) on by-product generation and CFRP degradation behaviour in an alkaline saline electrolyte composed of 3wt.% NaCl and 0.01M KOH. The by-products were characterised using gas chromatography and proton nuclear magnetic resonance spectroscopy. Additionally, the pH of the electrolytes after electrolysis was monitored and surface analysis techniques were employed to evaluate the degradation mechanisms and fibre integrity.
Results revealed that higher voltages increase current density, gas evolution and epoxy degradation, but also produced greater quantities of CO2, hydrocarbons and liquid by-products, alongside visible fibre damage. Conversely, lower voltages achieved sufficient resin removal while maintaining fibre integrity and reducing emissions. Liquid-phase analysis identified ethanol, acetone and formate, whose decomposition correlated with increasing CO2 evolution at higher potentials.
Among the emerging approaches for CFRP recycling, electrochemical processes have gained attention as promising low-energy and environmentally friendly alternatives to traditional thermal or chemical processes. The electrochemical recycling of CFRP operates under mild conditions, without the need of hazardous solvents or external heating. Despite these advantages, current literature focuses predominantly on fibre recovery efficiency with limited understanding of the gaseous, liquid and solid by-products formed during such process. These by-products may significantly influence the true environmental footprint and industrial feasibility of this technique.
To address this gap, this study systematically investigated the influence of constant applied voltage (4, 6 and 8 V) on by-product generation and CFRP degradation behaviour in an alkaline saline electrolyte composed of 3wt.% NaCl and 0.01M KOH. The by-products were characterised using gas chromatography and proton nuclear magnetic resonance spectroscopy. Additionally, the pH of the electrolytes after electrolysis was monitored and surface analysis techniques were employed to evaluate the degradation mechanisms and fibre integrity.
Results revealed that higher voltages increase current density, gas evolution and epoxy degradation, but also produced greater quantities of CO2, hydrocarbons and liquid by-products, alongside visible fibre damage. Conversely, lower voltages achieved sufficient resin removal while maintaining fibre integrity and reducing emissions. Liquid-phase analysis identified ethanol, acetone and formate, whose decomposition correlated with increasing CO2 evolution at higher potentials.
This study explores the potential of metal oxide fluorides as cathode materials for solid-state fluoride-ion batteries (FIBs), aiming to combine the stability of intercalation-based electrode materials with the high energy density of conversion-based materials. Through comprehensive experimental investigations using techniques such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), linear sweep voltammetry (LSV), and X-ray diffraction (XRD), the compatibility and electrochemical performance of transition metal oxides (Cu2O, FeO, and Mn2O3) with CsPb0.9K0.1F2.9 (PK10) solid electrolyte and Pb/PbF2 composite anode are evaluated. Results indicate negligible room temperature capacity for Cu2O, FeO, and Mn2O3, suggesting potential limitations related to the cathode fluorination reaction. Additionally, PK10 electrolyte displays slight instability at room temperature, indicating potential electrochemical activity. Symmetric cell testing using Pb/PbF2 composite electrodes confirms the suitability of the Pb/PbF2 composite as both counter and reference electrodes. Notably, Cu2O full cells show enhanced specific capacity at elevated temperatures (60 °C), reaching 310.24 mAh/g during the first cycle, equivalent to 82.96% of the theoretical specific capacity. This considerable increase in capacity due to only a slightly higher temperature is attributed to reduced overpotential and enhanced fluoride ions diffusion rates. However, observation of capacity fade between cycles for the Cu2O cell at 60 °C suggests irreversible reactions, necessitating further investigation. In conclusion, this study highlights the potential of metal oxide cathode materials in solid-state FIBs, emphasizing the importance of understanding electrolyte stability and cathode compatibility for battery performance enhancement.
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This study explores the potential of metal oxide fluorides as cathode materials for solid-state fluoride-ion batteries (FIBs), aiming to combine the stability of intercalation-based electrode materials with the high energy density of conversion-based materials. Through comprehensive experimental investigations using techniques such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), linear sweep voltammetry (LSV), and X-ray diffraction (XRD), the compatibility and electrochemical performance of transition metal oxides (Cu2O, FeO, and Mn2O3) with CsPb0.9K0.1F2.9 (PK10) solid electrolyte and Pb/PbF2 composite anode are evaluated. Results indicate negligible room temperature capacity for Cu2O, FeO, and Mn2O3, suggesting potential limitations related to the cathode fluorination reaction. Additionally, PK10 electrolyte displays slight instability at room temperature, indicating potential electrochemical activity. Symmetric cell testing using Pb/PbF2 composite electrodes confirms the suitability of the Pb/PbF2 composite as both counter and reference electrodes. Notably, Cu2O full cells show enhanced specific capacity at elevated temperatures (60 °C), reaching 310.24 mAh/g during the first cycle, equivalent to 82.96% of the theoretical specific capacity. This considerable increase in capacity due to only a slightly higher temperature is attributed to reduced overpotential and enhanced fluoride ions diffusion rates. However, observation of capacity fade between cycles for the Cu2O cell at 60 °C suggests irreversible reactions, necessitating further investigation. In conclusion, this study highlights the potential of metal oxide cathode materials in solid-state FIBs, emphasizing the importance of understanding electrolyte stability and cathode compatibility for battery performance enhancement.
Neodymium (Nd) recycling plays a significant role in rare earth elements (REEs) reproduction and spent neodymium-iron-boron (NdFeB) permanent magnets is a crucial resource for Nd. This study aims at investigating the anodic behaviour and dissolution properties of NdFeB magnets during electroleaching in four biodegradable organic acids to indicate a suitable environmentally friendly and safe reagent that promotes electroleaching. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) characterization revealed that the metallic coating of the magnet was made of zinc. SEM-EDS analysis of polished sample surface showed the Nd-rich phases were surrounded by the matrix. Then open circuit potential (OCP) and linear scanning voltammetry (LSV) measurements were carried out to study the anodic behaviour of NdFeB. The comparison among the four organic acids at 1 M resulted in that citric acid and tartaric acid achieved the highest corrosion current with least negative OCP, as they have more carboxylic groups and higher acidities, while the lower OCP of formic acid compared to acetic acid which shows the lowest acidity revealed that the chemical leaching properties are not only dominated by acidity. But the higher corrosion current density of formic acid stated that the external potential reduced the influence of the factors other than acidity. Next, citric acid and formic acid were selected for studying the impact of concentration on anodic behaviours for their high corrosion current density and low price. Along the test that monitored the concentrations, 0.25 M citric acid was selected as the desired electrolyte for the higher corrosion current density compared to all groups of formic acid and low difference between citric acid at higher concentrations. The chronopotentiometry experiment for observing the influence of applied current density on the dissolved mass of NdFeB was failed to carry out due to the limited voltage range of the potentiostat. SEM-EDS characterization displayed that the NdFeB matrix formed a rough and porous surface after electroleaching, and the increase in test time and acid concentration promotes dissolution. The semi-quantitative composition analysis showed good dissolution properties of Nd-rich phases and praseodymium (Pr) when undergoing electroleaching in citric acid.
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Neodymium (Nd) recycling plays a significant role in rare earth elements (REEs) reproduction and spent neodymium-iron-boron (NdFeB) permanent magnets is a crucial resource for Nd. This study aims at investigating the anodic behaviour and dissolution properties of NdFeB magnets during electroleaching in four biodegradable organic acids to indicate a suitable environmentally friendly and safe reagent that promotes electroleaching. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) characterization revealed that the metallic coating of the magnet was made of zinc. SEM-EDS analysis of polished sample surface showed the Nd-rich phases were surrounded by the matrix. Then open circuit potential (OCP) and linear scanning voltammetry (LSV) measurements were carried out to study the anodic behaviour of NdFeB. The comparison among the four organic acids at 1 M resulted in that citric acid and tartaric acid achieved the highest corrosion current with least negative OCP, as they have more carboxylic groups and higher acidities, while the lower OCP of formic acid compared to acetic acid which shows the lowest acidity revealed that the chemical leaching properties are not only dominated by acidity. But the higher corrosion current density of formic acid stated that the external potential reduced the influence of the factors other than acidity. Next, citric acid and formic acid were selected for studying the impact of concentration on anodic behaviours for their high corrosion current density and low price. Along the test that monitored the concentrations, 0.25 M citric acid was selected as the desired electrolyte for the higher corrosion current density compared to all groups of formic acid and low difference between citric acid at higher concentrations. The chronopotentiometry experiment for observing the influence of applied current density on the dissolved mass of NdFeB was failed to carry out due to the limited voltage range of the potentiostat. SEM-EDS characterization displayed that the NdFeB matrix formed a rough and porous surface after electroleaching, and the increase in test time and acid concentration promotes dissolution. The semi-quantitative composition analysis showed good dissolution properties of Nd-rich phases and praseodymium (Pr) when undergoing electroleaching in citric acid.
Master thesis
(2023)
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N. RAMACHANDRAN, Siddhant Kumar, Luis Cutz , S.T. Abrahami, Michiel de Rapper
Pressurized liquid Tin finds application in the generation of Extreme Ultra-Violet light for semiconductor lithography. In order to improve the throughput of the lithography systems, tin must be pressurized to higher levels, and in turn, new pressurization methods are needed.
A phase change tin pump is an innovative system that pressurizes and pumps liquid Tin by harnessing the expansion and contraction during phase changes, without the need for any moving parts. The pump needs to pressurize liquid tin up to 2000 bars, with a pumping capacity of 4 ml/hr. Since this system relies heavily on control over the temperatures of tin, this study is set up to address the thermal constraints in the system by investigating three aspects of temperature distribution in the system.
Firstly, the heaters in the pump are placed at discrete locations, but the working volume is continuous. Thus, it is challenging to define a temperature control function that can facilitate uniform melting and continuous flow of tin. The relation between rate of heat input to the pump and the rate of heat transfer in tin is estimated using an analytical model. From the analytical model, it is found that heating rates of the order of 0.1 K/s are required in order to melt tin in a reasonably uniform fashion over a zone length of 5 mm.
Secondly, the number of heaters are limited, and it is hard to achieve precise control over the temperature of tin at any given location. In order to establish a good basic control, the free design parameters are optimized so that a steady state gradient of 50 K is achieved between solid (200°C) and liquid (250°C) tin in the working volume. This is done by evaluating the thermal profile of the system for different combinations of the design variables, using Finite Element Analysis. The two objectives of this optimization problem (maximum temperature gain and minimum crosstalk) are seen to have contrasting requirements of the design variables. An optimal combination of the variables is found such that a gradient of 50 K is possible, but with a little trade-off on both the objectives.
Thirdly, a direct measurement of temperature of tin inside the pump is not feasible, and tin temperatures are estimated analytically. The accuracy of estimation is impacted by changes in local temperatures due to the non-linear properties of tin like absorption/release of latent heat, pressure-dependent melting point. The effect of non-linear tin properties on local temperature distribution is studied by setting up a finite difference model. It is seen that the absorption of latent heat during melting of tin results in a temperature that is 12 K lower than what would have been without the effect of latent heat. ...
A phase change tin pump is an innovative system that pressurizes and pumps liquid Tin by harnessing the expansion and contraction during phase changes, without the need for any moving parts. The pump needs to pressurize liquid tin up to 2000 bars, with a pumping capacity of 4 ml/hr. Since this system relies heavily on control over the temperatures of tin, this study is set up to address the thermal constraints in the system by investigating three aspects of temperature distribution in the system.
Firstly, the heaters in the pump are placed at discrete locations, but the working volume is continuous. Thus, it is challenging to define a temperature control function that can facilitate uniform melting and continuous flow of tin. The relation between rate of heat input to the pump and the rate of heat transfer in tin is estimated using an analytical model. From the analytical model, it is found that heating rates of the order of 0.1 K/s are required in order to melt tin in a reasonably uniform fashion over a zone length of 5 mm.
Secondly, the number of heaters are limited, and it is hard to achieve precise control over the temperature of tin at any given location. In order to establish a good basic control, the free design parameters are optimized so that a steady state gradient of 50 K is achieved between solid (200°C) and liquid (250°C) tin in the working volume. This is done by evaluating the thermal profile of the system for different combinations of the design variables, using Finite Element Analysis. The two objectives of this optimization problem (maximum temperature gain and minimum crosstalk) are seen to have contrasting requirements of the design variables. An optimal combination of the variables is found such that a gradient of 50 K is possible, but with a little trade-off on both the objectives.
Thirdly, a direct measurement of temperature of tin inside the pump is not feasible, and tin temperatures are estimated analytically. The accuracy of estimation is impacted by changes in local temperatures due to the non-linear properties of tin like absorption/release of latent heat, pressure-dependent melting point. The effect of non-linear tin properties on local temperature distribution is studied by setting up a finite difference model. It is seen that the absorption of latent heat during melting of tin results in a temperature that is 12 K lower than what would have been without the effect of latent heat. ...
Pressurized liquid Tin finds application in the generation of Extreme Ultra-Violet light for semiconductor lithography. In order to improve the throughput of the lithography systems, tin must be pressurized to higher levels, and in turn, new pressurization methods are needed.
A phase change tin pump is an innovative system that pressurizes and pumps liquid Tin by harnessing the expansion and contraction during phase changes, without the need for any moving parts. The pump needs to pressurize liquid tin up to 2000 bars, with a pumping capacity of 4 ml/hr. Since this system relies heavily on control over the temperatures of tin, this study is set up to address the thermal constraints in the system by investigating three aspects of temperature distribution in the system.
Firstly, the heaters in the pump are placed at discrete locations, but the working volume is continuous. Thus, it is challenging to define a temperature control function that can facilitate uniform melting and continuous flow of tin. The relation between rate of heat input to the pump and the rate of heat transfer in tin is estimated using an analytical model. From the analytical model, it is found that heating rates of the order of 0.1 K/s are required in order to melt tin in a reasonably uniform fashion over a zone length of 5 mm.
Secondly, the number of heaters are limited, and it is hard to achieve precise control over the temperature of tin at any given location. In order to establish a good basic control, the free design parameters are optimized so that a steady state gradient of 50 K is achieved between solid (200°C) and liquid (250°C) tin in the working volume. This is done by evaluating the thermal profile of the system for different combinations of the design variables, using Finite Element Analysis. The two objectives of this optimization problem (maximum temperature gain and minimum crosstalk) are seen to have contrasting requirements of the design variables. An optimal combination of the variables is found such that a gradient of 50 K is possible, but with a little trade-off on both the objectives.
Thirdly, a direct measurement of temperature of tin inside the pump is not feasible, and tin temperatures are estimated analytically. The accuracy of estimation is impacted by changes in local temperatures due to the non-linear properties of tin like absorption/release of latent heat, pressure-dependent melting point. The effect of non-linear tin properties on local temperature distribution is studied by setting up a finite difference model. It is seen that the absorption of latent heat during melting of tin results in a temperature that is 12 K lower than what would have been without the effect of latent heat.
A phase change tin pump is an innovative system that pressurizes and pumps liquid Tin by harnessing the expansion and contraction during phase changes, without the need for any moving parts. The pump needs to pressurize liquid tin up to 2000 bars, with a pumping capacity of 4 ml/hr. Since this system relies heavily on control over the temperatures of tin, this study is set up to address the thermal constraints in the system by investigating three aspects of temperature distribution in the system.
Firstly, the heaters in the pump are placed at discrete locations, but the working volume is continuous. Thus, it is challenging to define a temperature control function that can facilitate uniform melting and continuous flow of tin. The relation between rate of heat input to the pump and the rate of heat transfer in tin is estimated using an analytical model. From the analytical model, it is found that heating rates of the order of 0.1 K/s are required in order to melt tin in a reasonably uniform fashion over a zone length of 5 mm.
Secondly, the number of heaters are limited, and it is hard to achieve precise control over the temperature of tin at any given location. In order to establish a good basic control, the free design parameters are optimized so that a steady state gradient of 50 K is achieved between solid (200°C) and liquid (250°C) tin in the working volume. This is done by evaluating the thermal profile of the system for different combinations of the design variables, using Finite Element Analysis. The two objectives of this optimization problem (maximum temperature gain and minimum crosstalk) are seen to have contrasting requirements of the design variables. An optimal combination of the variables is found such that a gradient of 50 K is possible, but with a little trade-off on both the objectives.
Thirdly, a direct measurement of temperature of tin inside the pump is not feasible, and tin temperatures are estimated analytically. The accuracy of estimation is impacted by changes in local temperatures due to the non-linear properties of tin like absorption/release of latent heat, pressure-dependent melting point. The effect of non-linear tin properties on local temperature distribution is studied by setting up a finite difference model. It is seen that the absorption of latent heat during melting of tin results in a temperature that is 12 K lower than what would have been without the effect of latent heat.
The production of plastic materials has experienced incredible growth over the past decades. Polyethylene constitutes the largest part (25%) of plastic production, finding its application mostly as film in industrial and food packaging and agricultural use. However, since packaging materials are getting increasingly complex, polyethylene waste is nearly always mixed with other polymers, making direct recycling impossible. Compatibilization of polymer blends can be used to convert an immiscible polymer blend into a homogeneous material with synergistic properties. When this compatibilization is carried out inside an extruder, one less reaction step is needed and the material can directly be processed according to its application.
This study addresses the reactive compatibilization of recycled LDPE (rLDPE) originating from industrial film waste with its polymer impurities, as well as virgin low-density polyethylene (LDPE)/polyamide 6 (PA6) blends of various compositions through reactive extrusion with PE grafted with MA (PE-g-MA). A literature review was carried out, summarising the current state-of-the-art of reactive compatibilization and reactive extrusion. The composition of the recycled stream was identified through various characterisation methods. Through a wide variety of characterisation techniques, the mechanical properties of the extruded sample pellets were investigated, as well as the mechanical and optical properties of the blown film.
The compatibilizing effect on the virgin LDPE/PA6 blends was found to grow in importance with increasing PA6 content. For 1 wt%, the samples did not exhibit any improvement upon compatibilization. The samples containing 5 wt% showed their improvements predominantly in the optical properties. The 10 wt% samples showed large enhancements overall, after being treated with the compatibilizer. Both the optical and mechanical properties of rLDPE saw a significant amelioration as a result of compatibilization. This study thus achieved compatibilization through reactive extrusion for an extensive variety of polymer samples.
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This study addresses the reactive compatibilization of recycled LDPE (rLDPE) originating from industrial film waste with its polymer impurities, as well as virgin low-density polyethylene (LDPE)/polyamide 6 (PA6) blends of various compositions through reactive extrusion with PE grafted with MA (PE-g-MA). A literature review was carried out, summarising the current state-of-the-art of reactive compatibilization and reactive extrusion. The composition of the recycled stream was identified through various characterisation methods. Through a wide variety of characterisation techniques, the mechanical properties of the extruded sample pellets were investigated, as well as the mechanical and optical properties of the blown film.
The compatibilizing effect on the virgin LDPE/PA6 blends was found to grow in importance with increasing PA6 content. For 1 wt%, the samples did not exhibit any improvement upon compatibilization. The samples containing 5 wt% showed their improvements predominantly in the optical properties. The 10 wt% samples showed large enhancements overall, after being treated with the compatibilizer. Both the optical and mechanical properties of rLDPE saw a significant amelioration as a result of compatibilization. This study thus achieved compatibilization through reactive extrusion for an extensive variety of polymer samples.
...
The production of plastic materials has experienced incredible growth over the past decades. Polyethylene constitutes the largest part (25%) of plastic production, finding its application mostly as film in industrial and food packaging and agricultural use. However, since packaging materials are getting increasingly complex, polyethylene waste is nearly always mixed with other polymers, making direct recycling impossible. Compatibilization of polymer blends can be used to convert an immiscible polymer blend into a homogeneous material with synergistic properties. When this compatibilization is carried out inside an extruder, one less reaction step is needed and the material can directly be processed according to its application.
This study addresses the reactive compatibilization of recycled LDPE (rLDPE) originating from industrial film waste with its polymer impurities, as well as virgin low-density polyethylene (LDPE)/polyamide 6 (PA6) blends of various compositions through reactive extrusion with PE grafted with MA (PE-g-MA). A literature review was carried out, summarising the current state-of-the-art of reactive compatibilization and reactive extrusion. The composition of the recycled stream was identified through various characterisation methods. Through a wide variety of characterisation techniques, the mechanical properties of the extruded sample pellets were investigated, as well as the mechanical and optical properties of the blown film.
The compatibilizing effect on the virgin LDPE/PA6 blends was found to grow in importance with increasing PA6 content. For 1 wt%, the samples did not exhibit any improvement upon compatibilization. The samples containing 5 wt% showed their improvements predominantly in the optical properties. The 10 wt% samples showed large enhancements overall, after being treated with the compatibilizer. Both the optical and mechanical properties of rLDPE saw a significant amelioration as a result of compatibilization. This study thus achieved compatibilization through reactive extrusion for an extensive variety of polymer samples.
This study addresses the reactive compatibilization of recycled LDPE (rLDPE) originating from industrial film waste with its polymer impurities, as well as virgin low-density polyethylene (LDPE)/polyamide 6 (PA6) blends of various compositions through reactive extrusion with PE grafted with MA (PE-g-MA). A literature review was carried out, summarising the current state-of-the-art of reactive compatibilization and reactive extrusion. The composition of the recycled stream was identified through various characterisation methods. Through a wide variety of characterisation techniques, the mechanical properties of the extruded sample pellets were investigated, as well as the mechanical and optical properties of the blown film.
The compatibilizing effect on the virgin LDPE/PA6 blends was found to grow in importance with increasing PA6 content. For 1 wt%, the samples did not exhibit any improvement upon compatibilization. The samples containing 5 wt% showed their improvements predominantly in the optical properties. The 10 wt% samples showed large enhancements overall, after being treated with the compatibilizer. Both the optical and mechanical properties of rLDPE saw a significant amelioration as a result of compatibilization. This study thus achieved compatibilization through reactive extrusion for an extensive variety of polymer samples.
Recycling permanent magnets from offshore wind turbines
An e-waste approach
OWTs and WEEEs have both been found to contain NdFeB permanent magnets, which are both valuable sources for the recovery of REEs. At the same time, OWTs have been found to contain many electrical components that may not officially fall under the WEEE direct but share many similarities with WEEE. While there is little known about the recycling of OWTs and their electrical components due to their recent introduction, the recycling of WEEE has been studied more extensively and is a more mature industry.
To determine the preferred recycling route for permanent magnets from OWTs, a comparison was made with the characteristics and the recycling routes of permanent magnets from WEEE. The disassembly was found to be the most critical part to enable an efficient recycling process, leading to the objective of how can permanent magnets be disassembled from OWT generators. It was found that the disassembly of magnetised magnets at the scale of OWTs is challenging due to the forces required to move them and the brittleness of the materials. For efficient disassembly, the permanent magnets need to be locally and thermally demagnetised. Through a series of interviews, desk research, a lab visit and a site visit to Cuxhaven a concept for the disassembly of permanent magnets from OWTs was developed.
It was found that induction heating a copper coil wrapped around U shaped core to transfer heat to the permanent magnet via conduction is a potential scalable, automatable and time-efficient solution for demagnetisation. The power required to heat the coil depended predominantly on the time taken to heat the core as well as the contact surface area of the core with the permanent magnet, the mass of the conductor and the material chosen for the conductor. After thermal demagnetisation, the magnet can be removed while the magnetic is still hot or after cooling, dependent on the thermal expansion coefficient, effect of re-magnetisation and remanence of the magnet. Depending on the acceptable remanence to be able to handle the magnet, it may not be necessary to heat the magnet up all the way to the Curie temperature. The solution proposed in this study is just one of many options towards the recycling of permanent magnets, thus alternative solutions such as direct induction of complete thermal demagnetisation should also be considered. ...
To determine the preferred recycling route for permanent magnets from OWTs, a comparison was made with the characteristics and the recycling routes of permanent magnets from WEEE. The disassembly was found to be the most critical part to enable an efficient recycling process, leading to the objective of how can permanent magnets be disassembled from OWT generators. It was found that the disassembly of magnetised magnets at the scale of OWTs is challenging due to the forces required to move them and the brittleness of the materials. For efficient disassembly, the permanent magnets need to be locally and thermally demagnetised. Through a series of interviews, desk research, a lab visit and a site visit to Cuxhaven a concept for the disassembly of permanent magnets from OWTs was developed.
It was found that induction heating a copper coil wrapped around U shaped core to transfer heat to the permanent magnet via conduction is a potential scalable, automatable and time-efficient solution for demagnetisation. The power required to heat the coil depended predominantly on the time taken to heat the core as well as the contact surface area of the core with the permanent magnet, the mass of the conductor and the material chosen for the conductor. After thermal demagnetisation, the magnet can be removed while the magnetic is still hot or after cooling, dependent on the thermal expansion coefficient, effect of re-magnetisation and remanence of the magnet. Depending on the acceptable remanence to be able to handle the magnet, it may not be necessary to heat the magnet up all the way to the Curie temperature. The solution proposed in this study is just one of many options towards the recycling of permanent magnets, thus alternative solutions such as direct induction of complete thermal demagnetisation should also be considered. ...
OWTs and WEEEs have both been found to contain NdFeB permanent magnets, which are both valuable sources for the recovery of REEs. At the same time, OWTs have been found to contain many electrical components that may not officially fall under the WEEE direct but share many similarities with WEEE. While there is little known about the recycling of OWTs and their electrical components due to their recent introduction, the recycling of WEEE has been studied more extensively and is a more mature industry.
To determine the preferred recycling route for permanent magnets from OWTs, a comparison was made with the characteristics and the recycling routes of permanent magnets from WEEE. The disassembly was found to be the most critical part to enable an efficient recycling process, leading to the objective of how can permanent magnets be disassembled from OWT generators. It was found that the disassembly of magnetised magnets at the scale of OWTs is challenging due to the forces required to move them and the brittleness of the materials. For efficient disassembly, the permanent magnets need to be locally and thermally demagnetised. Through a series of interviews, desk research, a lab visit and a site visit to Cuxhaven a concept for the disassembly of permanent magnets from OWTs was developed.
It was found that induction heating a copper coil wrapped around U shaped core to transfer heat to the permanent magnet via conduction is a potential scalable, automatable and time-efficient solution for demagnetisation. The power required to heat the coil depended predominantly on the time taken to heat the core as well as the contact surface area of the core with the permanent magnet, the mass of the conductor and the material chosen for the conductor. After thermal demagnetisation, the magnet can be removed while the magnetic is still hot or after cooling, dependent on the thermal expansion coefficient, effect of re-magnetisation and remanence of the magnet. Depending on the acceptable remanence to be able to handle the magnet, it may not be necessary to heat the magnet up all the way to the Curie temperature. The solution proposed in this study is just one of many options towards the recycling of permanent magnets, thus alternative solutions such as direct induction of complete thermal demagnetisation should also be considered.
To determine the preferred recycling route for permanent magnets from OWTs, a comparison was made with the characteristics and the recycling routes of permanent magnets from WEEE. The disassembly was found to be the most critical part to enable an efficient recycling process, leading to the objective of how can permanent magnets be disassembled from OWT generators. It was found that the disassembly of magnetised magnets at the scale of OWTs is challenging due to the forces required to move them and the brittleness of the materials. For efficient disassembly, the permanent magnets need to be locally and thermally demagnetised. Through a series of interviews, desk research, a lab visit and a site visit to Cuxhaven a concept for the disassembly of permanent magnets from OWTs was developed.
It was found that induction heating a copper coil wrapped around U shaped core to transfer heat to the permanent magnet via conduction is a potential scalable, automatable and time-efficient solution for demagnetisation. The power required to heat the coil depended predominantly on the time taken to heat the core as well as the contact surface area of the core with the permanent magnet, the mass of the conductor and the material chosen for the conductor. After thermal demagnetisation, the magnet can be removed while the magnetic is still hot or after cooling, dependent on the thermal expansion coefficient, effect of re-magnetisation and remanence of the magnet. Depending on the acceptable remanence to be able to handle the magnet, it may not be necessary to heat the magnet up all the way to the Curie temperature. The solution proposed in this study is just one of many options towards the recycling of permanent magnets, thus alternative solutions such as direct induction of complete thermal demagnetisation should also be considered.