Dissertations / Theses on the topic 'Sulphur cycle'

The demand for energy is increasing throughout the world, and fossil fuel resources are diminishing. At the same time, the use of fossil fuels is slowly being reduced because it pollutes the environment. Research into alternative energy sources becomes necessary and important. An alternative fuel should not only replace fossil fuels but also address the environmental challenges posed by the use of fossil fuels. Hydrogen is an environmentally friendly substance considering that its product of combustion is water. Hydrogen is perceived to be a major contender to replace fossil fuels. Although hydrogen is not an energy source, it is an energy storage medium and a carrier which can be converted into electrical energy by an electrochemical process such as in fuel cell technology. Current hydrogen production methods, such as steam reforming, derive hydrogen from fossil fuels. As such, these methods still have a negative impact on the environment. Hydrogen can also be produced using thermochemical cycles which avoid the use of fossil fuels. The production of hydrogen through thermochemical cycles is expected to compete with the existing hydrogen production technologies. The sulphur iodine (SI) thermochemical cycle has been identified as a high-efficiency approach to produce hydrogen using either nuclear or solar power. A sound foundation is required to enable future construction and operation of thermochemical cycles. The foundation should consist of laboratory to pilot scale evaluation of the process. The activities involved are experimental verification of reactions, process modelling, conceptual design and pilot plant runs. Based on experimental and pilot plant data presented from previous research, this study presents the simulation of the sulphur iodine thermochemical cycle as applied to the South African context. A conceptual design is presented for the sulphur iodine thermochemical cycle with the aid of a process simulator. The low heating value (LHV) energy efficiency is 18% and an energy efficiency of 24% was achieved. The estimated hydrogen production cost was evaluated at $18/kg.
Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.

Anthropogenic greenhouse gas emissions and rising oil prices call for a sustainable transportable energy source. Hydrogen is a promising replacement for carbon based fuels in vehicles. The HyS cycle, proposed by the Westinghouse Corporation, is a route to hydrogen production on a scale large enough to satisfy the requirements of the transport industry. The process is a hybrid thermochemical cycle based on the decomposition of sulphuric acid.

A simple flowsheet of the hybrid sulphur cycle was devised and a steady state simulation thereof was built in Aspen. A sensitivity analysis was done and the snowball effect was identified as a significant process control issue. The flowsheet will become more complex as other process alternatives are investigated and optimisation and heat integration are done. This will probably result in further process control complications that need to be identified and dealt with. A detailed literature study was done and future research needed was identified. This includes further research to be done into the electrolyser and the thermodynamics of the mixtures involved in the hybrid sulphur cycle. The control related lessons learned were summarised in a very preliminary control strategy.
Thesis (M.Ing. (Nuclear Engineering))---North-West University, Potchefstroom Campus, 2010.

The discovery of sulphur-deficient agricultural soils has focussed concern on the dynamics of sulphur transformations in soils and on the important role of the soil microbial population in mineralising organic sulphur to forms more available to plants. This thesis reports a study carried out to investigate the dynamics of supply of plant available sulphur from soils and includes development of a method for determination of microbial biomass S, comparison of a perfusion system with a plant bioassay to assess soil S-supply, characterisation of a fertilizer S budget for a crop-soil system and assessment of the role of VA mycorrhizas in plant S uptake. The first experiment was carried out to investigate the factors involved in determination of microbial biomass S in soil in order to develop a more reliable assay. Biomass S-concentrations were determined by chloroform fumigation/direct extraction (with determination of the Ks calibration constant using 35S labelled microorganisms). The effects of period of fumigation, the need for chloroform evacuation, the type of extractant, and the time of extraction were investigated. The optimium values for biomass-S were obtained using a 5 day fumigation period without chloroform evacuation (use of 35S labelled microorganisms demonstrated that there is a vacuum sensitive non-biomass S pool), with CaC12 as an extractant over a 1 h extraction period. The second experiment consisted of a simple, open perfusion system for studying the S-supplying capacity of soils. A range of soils were perfused at frequent intervals and the leachates analysed for inorganic and total sulphur. Results were compared with plant S-offtake from the same soils. Although greater amounts of sulphur were removed in the perfusion system, data from the techniques correlated strongly, suggesting the perfusion system can be effectively used to estimate the S-supplying capacity of soils.

Since mankind's adoption of fossil fuels as its primary energy carrier for heating, elec- tricity and transportation, the release of greenhouse gases into the atmosphere has increased constantly . A potential replacement energy carrier is hydrogen. Current industrial techniques for dissociating hydrogen from its common substances are con- ventionally reliant on fossil fuels and thus greenhouse gases are still released. As a mechanism to develop a hydrogen economy current industrial techniques will suffice; however, a long-term sustainable solution to hydrogen mass production that does not release greenhouses gases is desired. The United States of America Government be- lieves that the Sulphur-Iodine thermochemical hydrogen production cycle, thermally powered by a nuclear source, is the most likely long-term solution. A critical part of the Sulphur-Iodine cycle is the point of interaction between the thermal source and sulphuric acid used within the cycle. A novel bayonet heat exchanger made from silicon carbide is theoretically applied to the point of interaction. Through a combination of experiments and theoretical modelling, the bayonet heat exchanger is characterised. The bayonet model is then modified to simulate the intended nuclear reactor favoured by the United States Department of Energy. In addition, the bayo- net heat exchanger is analysed for a solar thermal application. An advanced design of the bayonet is also presented and theoretically analysed for its increased thermal efficiency.

Les cultures intermédiaires multi-services (CIMS) implantées en interculture entre deux cultures de rente permettent de produire de nombreux services écosystémiques. Parmi les familles d’espèces utilisées comme CIMS, les crucifères réduisent efficacement la lixiviation de nitrate et de sulfate en captant l’azote (N) et le soufre (S) minéral du sol (services de piège à N et à S). Les crucifères ont aussi la capacité de contrôler les pathogènes via des composés biocides issus de l’hydrolyse de métabolites secondaires appelés glucosinolates (GSL). L’objectif de nos travaux de recherche est d’évaluer les performances en termes de services écosystémiques liés à l’azote, au soufre et au potentiel de bio-contrôle d’une grande diversité de mélanges bispécifiques de crucifères et de légumineuses en comparaison aux CIMS pures. Nous avons réalisé des expérimentations sur 2 sites contrastés (région de Toulouse et Orléans, France) et sur 2 années pour tester les performances de mélanges crucifère-légumineuse en comparaison aux espèces pures. Les espèces testées sont i) pour les crucifères : colza, moutarde blanche, moutarde brune, moutarde éthiopienne, navet, navette, radis, roquette, et ii) pour les légumineuses : trèfle Egyptien, trèfle incarnat, vesce commune, vesce pourpre, vesce velue, pois, soja, féverole et lupin blanc. Nos travaux de recherche montrent que les mélanges crucifère-légumineuse peuvent produire simultanément divers services écosystémiques avec un haut niveau d’expression, allant de 2/3 (production de GSL, engrais vert à N et S), à quasiment 100% (piège à N et S) du service produit par la famille d’espèce pure la plus performante. La concentration et les types de GSL ne changeant pas en mélanges, les interactions des crucifères avec leurs pathogènes restent identiques. Via une revue de littérature nous concluons également que le service de bio-contrôle des cultures pures de crucifères peut être maintenu en mélanges crucifère-légumineuse sur une grande diversité de pathogènes et adventices tout en réduisant les potentiels dis-services sur les auxiliaires et sur le cycle de l’azote
Multi-services cover crops (MSCC) grown during fallow period between two cash crops provide various ecosystem services. Among species used as MSCC, crucifers can efficiently prevent nitrate and sulphate leaching by catching residual soil mineral nitrogen (N) and sulphur (S) afterthe preceding cash crop (N and S catch crop services). Crucifers also have a unique capacity to suppress pathogens due to the biocidal hydrolysis products of endogenous secondary metabolites called glucosinolates (GSL). The aim of our study was to assess the provision of various ecosystem services linked to N, S cycles and biocontrol potential for a wide range of bispecific crucifer-legume mixtures in comparison to sole cover crops of legume and crucifer. We carried out experiments in 2 contrasted sites (Toulouse and Orléans regions, France) during 2 years in order to assess these services and the compatibility of various bi-specific crucifer-legume mixtures. We tested a great diversity of species, such as i) crucifers : rape, white mustard, Indian mustard, Ethiopian mustard, turnip, turnip rape, radish and rocket, and ii) legumes: Egyptian clover, crimson clover, common vetch, purple vetch, hairy vetch, pea, soya bean, faba bean, and white lupin. Our study demonstrated that crucifer-legume mixtures can provide and mutualize various ecosystem services by reaching from 2 thirds (GSL production, S and N green manure) to the same level ofservice (N and S catch crop) than the best sole family of species. GSL profile and concentration did not change in mixtures meaning that crucifer-pests interactions were identical. Through a literature review we also illustrated that biocontrol services of crucifers could be largely maintained in crucifer-legume mixtures for a wide range of pathogens and weeds while reducing potential disservices on beneficials and increasing N related service

Dimethylsulphoniopropionate (DMSP) and dimethylsulphoxide (DMSO) (collectively DMSP/O) are produced by marine algae, including symbiotic algae within corals. These sulphur compounds are important not only in sulphur cycle dynamics but also in potentially mediating atmospheric conditions, alleviating the effects of climate change and contributing to reef health. Most research has focused on the production of DMSP and its major degradation product, the climatically active gas, dimethylsulphide (DMS) by Acropora corals in the Great Barrier Reef. However, mechanisms for the production and release of DMSP/O by different reef taxa is poorly understood. Recently the importance of mesophotic reefs as refugia for shallow water corals has been postulated, however their role in the marine sulphur cycle is unknown. This research aimed to improve our understanding of the contemporary and climate change induced seawater and tissue production of DMSP/O in a range of reef environments and taxa. This was achieved through a combination of laboratory and field - based studies, using modern and established techniques. An effect of both elevated temperature and OA on increased tissue and seawater concentrations of DMSP/O production is reported in field and laboratory studies. Contrasting effects of benthic cover on tissue DMSP/O distributions and seawater DMSP are also noted. The importance of the physical and hydrodynamic environment on biogeochemical connectivity both within a reef and between neighbouring reefs is also focussed on. Crucially, however, the novel tissue and seawater data from mesophotic sites suggests that deeper reefs could affect the biogeochemistry of their shallow water counterparts. The key finding from this work is that climate change will result in increased seawater DMSP concentrations via two mechanisms; through the increase of cellular production of DMSP/O in all reef taxa, and by increasing the biomass of prolific DMSP producers as reefs transition to a fleshy/macroalgal assemblage. Whilst this could potentially mediate the effects of climate change, it will probably also worsen overall reef health, lead to a restructuring of reef communities from the microbial level upwards and will have possibly permanent and deleterious effects on overall ecosystem function.

Dans l’objectif d’évaluer le devenir de sédiments subduits variablement enrichis en soufre dans des conditions P-T (pression – température) correspondant au toit de la plaque sous un arc volcanique, des expériences de fusion et de cristallisation ont été réalisées en conditions hydratées en presse piston-cylindre(3 GPa ; 650 – 1000°C ; ƒO2 ~ NNO) sur des sédiments naturels (pélite et marne), non dopés en éléments en traces et variablement enrichis en soufre (0, 1 et 2 wt% Sin). Lors de la fusion du sédiment pélitique, des liquides trondhjémitiques à granitiques sont produits en équilibre avec un résidu composé de grenat +disthène ± phengite ± quartz + rutile. Lors de la fusion du sédiment marneux, des liquides granodioritiques sont produits en équilibre avec un résidu constitué de grenat ± épidote ± clinopyroxène ± disthène ± quartz +rutile. L’ajout de soufre dans le système pour une ƒO2 ~ NNO conduit à une précipitation de sulfures. La quantité de fer (Fe2+) disponible dans le système diminue fortement (augmentation du Mg#) et impactegrandement les relations de phases : le grenat, l’épidote et la phengite sont déstabilisées au profit des pyroxènes, de la biotite ou encore de l’amphibole. La distribution des éléments en traces dans le liquide silicaté par rapport au sédiment de départ est également très affectée pour les systèmes dopés en soufre(ex : fractionnement des terres rares). Nous proposons, à partir des données obtenues dans des xénolites mantelliques (Grenade, Petites Antilles) et lors de modélisations géochimiques, que la contribution dans lecoin mantellique de 1 à 3 % de liquides trondhjémitiques/granitiques issus de la fusion de sédiments pélitiques modérément enrichis en soufre (≤ 1 wt% Sin) peut expliquer la variabilité de composition des basaltes du sud de l’arc des Petites Antilles (Grenade et Grenadines)
The main issue of this study is to constrain the fate of subducted sediments variably enriched in sulphur for P-T (pressure – temperature) relevant for the slab at sub-arc depth. Using piston-cylinder apparatus, we performed melting and crystallisation experiments (3 GPa; 650 – 1000°C; ƒO2 ~ NNO) on natural, trace elementundoped and volatile-rich sediments (pelite and marlstone). Experiments were conducted with variable water (5 to 10 wt% H2Oin) and sulphur (0, 1 and 2 wt% Sin) contents. Silicate melts produced by the fluid-present melting of pelite range from trondhjemitic to granitic compositions, are broadly peraluminous and coexist with garnet + kyanite ± phengite ± quartz + rutile. Those produced by the fluid-present melting of marlstone are sodic (granodioritic composition), metaluminous to slightly peraluminous and coexist with garnet ± epidote ± clinopyroxene ± kyanite ± quartz + rutile. Sulphur addition at ƒO2 ~ NNO leads to sulphide precipitation. Thus, iron (Fe2+) contents decrease (Mg# increase) in the system and this strongly impacts phase relationships: garnet, epidote and phengite are consumed in favour of pyroxens, biotite and amphibole. Trace-element distribution between silicate melt and starting bulk for S-doped systems is largely impacted (e.g. rare earth elements fractionation). On the basis of data obtained in mantle xenoliths(Grenada, Lesser Antilles) and from geochemical modelisations, we are suggesting that a contribution in the mantle wedge of 1 to 3 % of trondhjemitic/granitic melts derived from pelitic sediments (≤ 1 wt% Sin) mayaccount for the composition of basalts in the southern part of Lesser Antilles (Grenada and Grenadines)

[Truncated abstract] Biogeochemical processes in seagrass sediments influence growth and nutrition of seagrasses. This thesis investigates the below-ground interactions between biotic and abiotic factors that influence seagrass nutrition and growth, with focus on a small species of seagrass, Halophila ovalis (R. Br.) Hook ƒ., from the Swan River Estuary, Western Australia. Seagrass showed significantly lower growth and an increase in leaf nitrogen and phosphorus concentrations with increased organic matter loading. With maximal light reduction, lower growth rates and average leaf weights were observed, and leaf nitrogen and phosphorus concentrations were higher. Light reduction was also shown to increase bioavailability of inorganic nutrients within porewater of seagrass sediment . . . Sulphide was hypothesised to have an inhibitory effect on nutrient uptake of Halophila ovalis. Below-ground sulphide inhibits the photosynthetic efficiency of photosystem II at sulphide concentrations greater than 1 mM. Sulphide exposure enhanced phosphate uptake, with no significant effect on ammonium uptake of H. ovalis. This thesis demonstrates that biogeochemical processes both constrain the potential growth of seagrasses and influence the nutrient status of seagrass tissue. Consideration of the influence of sulphide stress on seagrasses is likely to be particularly important for anthropogenically influenced aquatic systems, where inputs of organic matter are enriched relative to pristine ecosystems. A better understanding of biogeochemical processes will allow researchers to predict how future changes in sediment chemistry will influence seagrass meadows.

Si la modification actuelle du climat est attribuée aux émissions anthropiques, les émissions volcaniques ont toujours représenté un des moteurs principaux de son évolution. Elles correspondent à l'une des sources naturelles les plus importantes de soufre sur Terre, qui peut entrainer des perturbations du climat pendant plusieurs années. Cela est dû à l'oxydation du SO2 volcanique en aérosols de sulfate, qui ont la propriété d'interagir avec le rayonnement solaire incident. Cette étude vise à améliorer notre compréhension du devenir du soufre dans l’atmosphère au cours du temps, à partir d'une approche multi-isotopique sur les sulfates présents dans des dépôts volcaniques anciens et les encroutements noirs. L'étude conduite sur des dépôts volcaniques montre qu'à l'échelle des temps géologiques, les ignimbrites représentent une archive intéressante des oxydants de l'atmosphère. La différence de signature en ∆17O entre les sulfates anatoliens et péruviens suggère une implication différente de l'ozone dans leur formation. L'étude des encroutements noirs formés à différentes périodes a permis de comparer les voies d'oxydation du soufre en zone urbaine de nos jours et durant la période pré-industrielle. Leurs compositions isotopiques suggèrent que les contributions relatives des différentes voies d'oxydation ont changé depuis l’ère pré-industrielle. Enfin, de larges quantités de nitrate ont été découvertes dans des dépôts volcaniques. L'étude de ces nitrates a permis de montrer qu'ils résultent principalement de la fixation d'azote atmosphérique par les éclairs volcaniques
Present-day climate change is attributed to anthropogenic emissions, however, volcanic emissions have always played an essential role in climate evolution. They represent one of the most important natural sources of sulphur on Earth, that can lead to climate perturbation over years. This is due to volcanic SO2 oxidation into sulphate aerosols, which interact with incident solar radiations, thus modifying the Earth's radiative balance.Present-day sulphur oxidation pathways are relatively well-known, but they remainpoorly constrained in the past. This study aims to improve our understanding of the fate of atmospheric sulphur over geological times using a multi-isotopic approach on sulphates originating from volcanic deposits and black crusts.The study conducted on ancient volcanic deposits shows that ignimbrites represent an interesting archive of atmospheric oxidants, and certainly more reliable than volcanic ashfalls. The difference in ∆17O signature between Anatolian and Peruvian sulphates suggests a different involvement of ozone in their formation.The study of black crusts from the Parisian region and formed at different periods,leads to the comparison of sulphur oxidation pathways in urban area between the preindustrial era and the present-day. Their differences in isotopic composition suggest that the relative contributions of each oxidation channel have changed from pre-industrial to modern times.Finally, large amounts of nitrate have been found in volcanic deposits in Turkey andPeru. Our results show that most of the nitrates in volcanic deposits represent the end-product of atmospheric nitrogen fixation by volcanic lightning, occurring during explosive eruptions

The global oil refining industry with its present shift inproduct distribution towards fuels such as gasoline and dieselwill most likely hold the fort for many years to come. However,times will change and survival will very much depend onprocessing flexibility and being at the frontiers of refiningtechnology, a technology where catalysts play leading roles.Today oil refiners are faced with the challenge to producefuels that meet increasingly tight environmentalspecifications, in particular with respect to maximum sulphurcontent. At the same time, the quality of crude oil is becomingworse with higher amounts of polyaromatics, heteroatoms(sulphur and nitrogen) and heavy metals. In order to staycompetitive, it is desirable to upgrade dense streams withinthe refinery to value-added products. For example, upgradingthe fluid catalytic cracking (FCC) by-product light cycle oil(LCO) into a high quality diesel blending component is a veryattractive route and might involve a two-step catalyticprocess. In the first step the LCO is hydrotreated andheteroatoms are removed and polyaromatics are saturated, in thesecond step naphthenic rings are selectively opened to improvethe cetane number of the final product.

The present research is devoted to the second catalytic stepof LCO upgrading and was carried out within the framework of aEuropean Union project entitled RESCATS.

From the patent literature it is evident that iridium-basedcatalysts seem to be good candidates for ring-opening purposes.A literature survey covering ring opening of naphthenicmolecules shows the need for extending investigations toheavier model substances, more representative of the dieselfraction than model compounds such as alkylated mono C5 and C6-naphthenic rings frequently employed in academic studies.

Ring-opening catalysts, mainly Pt-Ir based, were synthesisedat KTH by two different methods: the microemulsion and theincipient wetness methods. Characterization of the catalystswas performed using a number of techniques including TPR,TEM-EDX, AFM and XPS etc. Catalytic screening at atmosphericpressure using pure indan as model substance was utilized todetect ring-opening activity and the magnitude of selectivityto desired cetane-boosting products. The development of suchring-opening catalysts is the topic of Paper I.

When designing a catalytic system aimed at refiningpetroleum, it is crucial to monitor the evolution of thesulphur distribution throughout the different stages of theprocess so that catalyst properties and reaction parameters canbe optimised. The final section of this thesis and Paper II arethus devoted to high-resolution sulphur distribution analysisby means of a sulphur chemiluminescence detector (SCD).

Keywords:ring opening, naphthenes, cetane numberimprovement, indan, light cycle oil (LCO), Pt-Ir catalyst,catalyst characterization, aromatic sulphur compounds, GC-SCD,distribution, analysis.

The global oil refining industry with its present product distribution essentially shifted towards fuels such as gasoline and diesel will most likely hold the fort for considerable time. However, conditions are changing and refinery survival will very much depend on long-term planning, process and product flexibility and being at the frontiers of refining technology, a technology where catalysts play leading roles. Today oil refiners are faced with the challenge of producing fuels that meet increasingly tight environmental specifications, in particular with respect to maximum sulphur content. At the same time, the average quality of crude oil is becoming poorer with higher amounts of aromatics, heteroatoms (sulphur and nitrogen) and heavy metals. In order to stay competitive, it is of decisive importance for refiners to upgrade dense petroleum fractions of low quality to highly value-added products. A practicable route, for example, is upgrading the catalytic cracking by-product Light Cycle Oil (LCO) into a high-quality diesel-blending component in a two-step catalytic process. In the first step the LCO is hydrotreated over a Pt Pd based acidic catalyst bringing about heteroatom and aromatic reduction and isomerization of C6 to C5 naphthenic structures. In the second step these naphthenic structures are selectively opened over an Ir-based catalyst to improve the cetane value. The present thesis is mainly devoted to the second catalytic step of LCO upgrading and was partly conducted within the framework of the European Union project RESCATS. From the patent literature it is evident that iridium-based catalysts could be good candidates for ring-opening purposes. A literature survey covering ring opening of naphthenic structures made in the beginning of the project (in 2001), showed the need for extending investigations to heavier hydrocarbons, more representative of the diesel fraction than model compounds such as alkylated mono C5 and C6 naphthenic rings frequently employed in previous academic studies. Ring-opening catalysts, mainly Pt-Ir based, were synthesised at KTH by two different techniques: the microemulsion and the incipient wetness techniques. Paper I is a review of the microemulsion technique and its applications in heterogeneous catalysis. Characterization of catalysts was performed employing a multitude of techniques including quantitative TPR, TEM-EDX, XPS, CO FT-IR, NH3-DRIFTS and XRF etc. Catalytic screening at 325 oC and atmospheric pressure with hydrogen and pure indan as model substance was conducted to investigate ring-opening activity in terms of conversion and selectivity to desired cetane-boosting products. This development process is the topic of Papers II-IV. The possible industrial implementation of the best catalyst candidate is demonstrated in Paper V. When designing a catalytic system aimed at refining petroleum, it is crucial to monitor the evolution of the sulphur distribution throughout the different stages of the process so that catalyst properties and reaction parameters may be optimised. The final section of this thesis and Paper VI are devoted to high-resolution sulphur-distribution analysis by means of a sulphur chemiluminescence detector (SCD) following gas chromatographic separation.
QC 20101014

The continuous and expected increase of electrification in the transport sector, the so-called "electromobility" revolution, is one of the main drivers of progress in energy storage for vehicle propulsion. Today's electric vehicles (EVs) use lithium-ion (Li-ion) batteries due to their high energy density compared to other types of batteries. Current rechargeable lithium-ion (Li-ion) batteries for EVs are capable of storing around 180 Wh/kg of energy density at cell level and 120 Wh/kg at battery level, while the typical consumption of one kg of petrol produces 3350 Wh of useful work. There is still a factor of 19 between the energy delivered by a kilo of petrol and 1 kg of battery (for example, the autonomy of a car with a similar weight that is powered by batteries is 5-10 times less than with petrol). Therefore, if we want to reach, or even approach, the goal of a 500 km autonomy with battery powered vehicles in the short term, it is necessary to research new materials and battery configurations. In this respect, lithium-Sulphur (Li-S) batteries are the closest battery technology capable of meeting these expectations. Despite the fact that solutions exist at a technical level, or are in the process of being implemented, to overcome the technological barriers which electric energy storage presents for EVs, their implementation on our roads remains a challenge and is below the expectations set out. One of the reasons why this implementation is not satisfactory is the high cost of electric vehicles, mainly due to the high cost of batteries. New electric storage technologies such as Li-S batteries must therefore take into account not only the technical factor for their design, but also strategies to be able to reuse them in a second life in order to reduce their potential cost and thus help reduce the price of the EV paid by the end user. Furthermore, in addition to offering a suitable technological solution and presenting itself as an economically viable alternative, it is necessary to study the impact on the environment produced throughout the life cycle of Li-S batteries. For this reason, this doctoral thesis focuses on the environmental analysis of all the stages of the life cycle of these batteries, from the scaling of Li-S button cells produced in the laboratory to a 50 kWh battery. The methodology used to calculate the environmental impacts of the batteries is the Life Cycle Assessment (LCA) according to ISO 14040 and 14044:2006, which allows a quantitative evaluation of the environmental profile of the batteries for all the stages of their life cycle, emphasizing the most critical aspects that can be improved. In addition, the thesis has also dealt with issues related to the suitability of the batteries for use in second life, based on current experience with Li-ion batteries. To this end, on the one hand, ageing tests have been carried out on the cells to determine their behaviour and longevity. On the other hand, an economic evaluation has been made of the actions taken to dismantle a battery once its first life in the vehicle has ended, this being the first stage to prepare the battery for its second life in a secondary energy storage system. The results obtained from these analyses have served as a basis for establishing a framework for adding more information on the environmental performance of these batteries in Li-S. In addition, information has been provided in order to determine the feasibility of using this type of battery, not only in a first life in the electric vehicle, but also in its second life in a stationary application, and in this way to be able to follow the principles of the Circular Economy.
El crecimiento continuo y previsto de la electrificación en el sector del transporte, la así llamada revolución de la "electromobilidad", es uno de los principales motores de los avances en el almacenamiento de energía destinado para la propulsión de vehículos. Los vehículos eléctricos (VE) actuales utilizan baterías de ion de litio (Li-ion) debido a su alta densidad energética respecto a otros tipos de baterías. Las actuales baterías de Li-ion recargables para VE son capaces de almacenar alrededor de 180 Wh / kg de densidad de energía a nivel de la celda y 120 Wh / kg a nivel de batería, mientras que el consumo típico de un kg de gasolina produce 3350 Wh de trabajo útil. Todavía hay un factor de 19 entre la energía entregada por un kilo de gasolina y 1 kg de batería (por ejemplo, una autonomía del automóvil con un peso similar que es impulsado por batería es 5-10 veces menor que con gasolina). Por lo tanto, si se quiere alcanzar, o incluso acercar, el objetivo de autonomía de 500 kilómetros con vehículos de baterías en el corto plazo es necesario investigar sobre nuevos materiales y configuraciones de baterías. A tal propósito, las baterías de litio-azufre (Li-S) son la tecnología de batería candidata a satisfacer estas expectativas. A pesar de que a nivel técnico existan soluciones, o estén en vías de implantación para superar las barreras tecnológicas que el almacenamiento de energía eléctrica presenta para VE, la implantación del VE en nuestras carreteras sigue siendo un reto y está por debajo a las expectativas previstas. Uno de los motivos por los cuales dicha implantación no está siendo satisfactoria es el alto coste de los vehículos eléctricos debido principalmente al alto coste de las baterías. Las nuevas tecnologías de almacenamiento eléctrico como las baterías de Li-S deben pues tener en cuenta no sólo el factor técnico para su diseño, sino también estrategias para poder ser reutilizadas en una segunda vida con el objetivo de reducir su coste potencial y de esta manera ayudar a la reducción del precio del VE que paga el usuario final. Por otro lado, además de ofrecer una solución tecnológica adecuada y de presentarse como una alternativa económicamente viable, debido al gran volumen de producción que se espera asociado a este sector en los próximos años, es necesario estudiar el impacto sobre el medio ambiente producido a lo largo del ciclo de vida de las baterías de Li-S. Por este motivo, esta tesis doctoral se centra en el análisis ambiental de todas las etapas del ciclo de vida de dichas baterías, a partir del escalado de celdas botón en Li-S producidas en laboratorio hasta una batería de 50 kWh. La metodología que se ha utilizado para calcular los impactos ambientales de las baterías es el Análisis de Ciclo de Vida (ACV) según las ISO 14040 y 14044:2006, que permite evaluar cuantitativamente el perfil ambiental de las baterías para todas las etapas de su ciclo de vida, haciendo hincapié en aquellos aspectos más críticos y que pueden ser sujetos a mejora. Además, la tesis también aborda los temas relativos a la adecuación de las baterías para su uso en segunda vida, partiendo de la experiencia actual con baterías de Li-ion. Para ello, por un lado, se han llevado a cabo ensayos de envejecimiento sobre las celdas para determinar su comportamiento y su longevidad. Por otro lado, se ha evaluado económicamente las acciones de desmontaje de una batería una vez que termina su primera vida en el vehículo, siendo esta la primera etapa para poder preparar la batería para su segunda vida en un sistema de almacenamiento energético secundario.

Hydrogen is a promising element for the transition from fossil fuels, even though the majority of industrial hydrogen production methods are not carbonneutral. There are, however, alternatives which could produce this CO2 free fuel on a massive scale. In particular, thermochemical cycles, including the Hybrid Sulfur (HyS) and Sulfur-Iodine (SI) cycles, which share a common sulphuric acid decomposition step. This project continues the work done by Shaw (2008), which involved the acquisition of experimental data relevant to the production of Hydrogen in the sulphur family of thermochemical cycles. This also lays the framework needed to continue the thermodynamic calculations needed for the design of equipment relevant to the SO2/O2/H2O separation. The model was developed simultaneously with the design of the next generation equilibrium still that was able to incorporate in-situ analysis. Several technical design milestones were achieved in the process, including the development of a sapphire liquid gas cell, a glass reinforced single pass 10 cm Zinc Selenide gaseous cell, several iterations of Raman Spectroscopy probes with ranging capabilities for different purposes, mostly high pressures and temperatures. It was also confirmed that with the low temperature separation approach, materials become an important factor for the success or failure of the process. Based on the results comparison between the calculations of the Mathematica® model, the GFE model, the available experimental data and general tendencies in the literature, it is concluded that the calculations, as well as the experimental techniques used throughout this project, are successful for their purpose, which is the aiding of equipment design for the HyS and SI cycle. Further efforts can be done to implement this model into process modelling software.

This diploma thesis is concerned with the design of the machinery with an extraction steam condensing turbine in Precheza corp. The theoretical part of this thesis describes the energetical situation in the company and the primary consideration about recovery of the heat, released at sulphuric acid production, for electrical power production. There is also presented brief description of the sulphuric acid production and the fundamental principles of the steam production at this process. In the practical part of this thesis there is performed the calculation of the heat-flow diagram of the steam turbine and the calculation of heat and producted electrical power at the basic operational states. There is presented the source code for the calculation of the heat-flow diagram using Matlab software. In the end there is mentioned the economical evaluation of the whole project, using the fundamental economical methods, such as net present value method, or profitability index, including the calculation of the pay-back period.