Добірка наукової літератури з теми "Power to Fuels"

The insatiable—and ever-growing—demand of both the developed and the developing countries for power continues to be met largely by the carbonaceous fuels comprising coal, and the hydrocarbons natural gas and liquid petroleum. We review the properties of the chemical elements, overlaid with trends in the periodic table, which can help explain the historical—and present—dominance of hydrocarbons as fuels for power generation. However, the continued use of hydrocarbons as fuel/power sources to meet our economic and social needs is now recognized as a major driver of dangerous global environmental changes, including climate change, acid deposition, urban smog and the release of many toxic materials. This has resulted in an unprecedented interest in and focus on alternative, renewable or sustainable energy sources. A major area of interest to emerge is in hydrogen energy as a sustainable vector for our future energy needs. In that vision, the issue of hydrogen storage is now a key challenge in support of hydrogen-fuelled transportation using fuel cells. The chemistry of hydrogen is itself beautifully diverse through a variety of different types of chemical interactions and bonds forming compounds with most other elements in the periodic table. In terms of their hydrogen storage and production properties, we outline various relationships among hydride compounds and materials of the chemical elements to provide some qualitative and quantitative insights. These encompass thermodynamic and polarizing strength properties to provide such background information. We provide an overview of the fundamental nature of hydrides particularly in relation to the key operating parameters of hydrogen gravimetric storage density and the desorption/operating temperature at which the requisite amount of hydrogen is released for use in the fuel cell. While we await the global transition to a completely renewable and sustainable future, it is also necessary to seek CO 2 mitigation technologies applied to the use of fossil fuels. We review recent advances in the strategy of using hydrocarbon fossil fuels themselves as compounds for the high capacity storage and production of hydrogen without any CO 2 emissions. Based on these advances, the world may end up with a hydrogen economy completely different from the one it had expected to develop; remarkably, with ‘Green hydrogen' being derived directly from the hydrogen-stripping of fossil fuels. This article is part of the theme issue ‘Mendeleev and the periodic table'.

By adding water to fuels, several objectives are pursued, with the main ones being to stabilize combustion, minimize the anthropogenic gaseous emissions, homogenize and stabilize the fuel, as well as improve its fire and explosion safety. Water can be injected into the furnace as droplets or vapor and introduced as part of fuel samples. Water often serves as a coupling or carrier medium for the delivery of the main fuel components. In this paper, we compare the combustion behaviors of high-potential slurry fuels and gas hydrates. We also analyze the contribution of in slurries and gas hydrates to the combustion process. The values of relative combustion efficiency indicators are determined for gas hydrates and slurry fuels. The conditions are identified in which these fuels can be burned effectively in power plants. The research findings can be used to rationalize the alternative ways of using water resources, i.e., gas hydrate powder and promising composite fuel droplets. The results can also help predict the conditions for the shortest possible ignition delay, as well as effective combustion of gas hydrates as the most environmentally friendly new-generation alternative fuel.

Ultrasound was adopted to prepare emulsion fuels between bio-oil and 0# diesel. The effects of ultrasound power and treating time on the stability of emulsion fuels were investigated. Excellent stability with stable time as long as 35 hours was obtained under an ultrasound power of 80W and a treating time of 3 minutes. Malvern nanometer particle size analyzer (Zetasizer Nano S90) was used to study the droplet size of emulsion fuels. The emulsion fuels with smaller droplet size had longer stable time. And the droplet size of the optimal emulsion fuel was around 0.4 um.

A comparative experimental investigation was conducted to evaluate the performance and exhaust emissions of an agricultural tractor engine when fueled with sunflower oil, rapeseed oil, and cottonseed oil and their blends with diesel fuel (20/80, 40/60 and 70/30 volumetrically). Tests were also carried out with diesel fuel to be used as a reference point. Engine power, torque, BSFC, thermal efficiency, NOx and CO2 were recorded for each tested fuel. All vegetable oils resulted in normal operation without problems during the short-term experiments. The 20/80 blends showed unstable results, in comparison to higher oil content fuels. Power, Torque and BSFC were higher as oil content was increased in the fuel. Rapeseed oil fuels showed increased power, torque and thermal efficiency with simultaneous lower BSFC in comparison to the other two vegetable oils. Cottonseed oil fuels gave better engine performance than sunflower oil fuels. In all oil types, NOx emissions were augmented when fuel oil percentage was increased. Cottonseed oil fuels led to higher NOx emission increase compared to rapeseed oil fuels. CO2 emissions showed a tendency to be increased as the oil content was evolved. The highest CO2 emissions were given by cottonseed oil fuels, followed by rapeseed and sunflower oil.

Abstract. The use of alternative fuels for aviation is likely to increase due to concerns over fuel security, price stability, and the sustainability of fuel sources. Concurrent reductions in particulate emissions from these alternative fuels are expected because of changes in fuel composition including reduced sulfur and aromatic content. The NASA Alternative Aviation Fuel Experiment (AAFEX) was conducted in January–February 2009 to investigate the effects of synthetic fuels on gas-phase and particulate emissions. Standard petroleum JP-8 fuel, pure synthetic fuels produced from natural gas and coal feedstocks using the Fischer–Tropsch (FT) process, and 50% blends of both fuels were tested in the CFM-56 engines on a DC-8 aircraft. To examine plume chemistry and particle evolution with time, samples were drawn from inlet probes positioned 1, 30, and 145 m downstream of the aircraft engines. No significant alteration to engine performance was measured when burning the alternative fuels. However, leaks in the aircraft fuel system were detected when operated with the pure FT fuels as a result of the absence of aromatic compounds in the fuel. Dramatic reductions in soot emissions were measured for both the pure FT fuels (reductions in mass of 86% averaged over all powers) and blended fuels (66%) relative to the JP-8 baseline with the largest reductions at idle conditions. At 7% power, this corresponds to a reduction from 7.6 mg kg−1 for JP-8 to 1.2 mg kg−1 for the natural gas FT fuel. At full power, soot emissions were reduced from 103 to 24 mg kg−1 (JP-8 and natural gas FT, respectively). The alternative fuels also produced smaller soot (e.g., at 85% power, volume mean diameters were reduced from 78 nm for JP-8 to 51 nm for the natural gas FT fuel), which may reduce their ability to act as cloud condensation nuclei (CCN). The reductions in particulate emissions are expected for all alternative fuels with similar reductions in fuel sulfur and aromatic content regardless of the feedstock. As the plume cools downwind of the engine, nucleation-mode aerosols form. For the pure FT fuels, reductions (94% averaged over all powers) in downwind particle number emissions were similar to those measured at the exhaust plane (84%). However, the blended fuels had less of a reduction (reductions of 30–44%) than initially measured (64%). The likely explanation is that the reduced soot emissions in the blended fuel exhaust plume results in promotion of new particle formation microphysics, rather than coating on pre-existing soot particles, which is dominant in the JP-8 exhaust plume. Downwind particle volume emissions were reduced for both the pure (79 and 86% reductions) and blended FT fuels (36 and 46%) due to the large reductions in soot emissions. In addition, the alternative fuels had reduced particulate sulfate production (near zero for FT fuels) due to decreased fuel sulfur content. To study the formation of volatile aerosols (defined as any aerosol formed as the plume ages) in more detail, tests were performed at varying ambient temperatures (−4 to 20 °C). At idle, particle number and volume emissions were reduced linearly with increasing ambient temperature, with best fit slopes corresponding to −8 × 1014 particles (kg fuel)−1 °C−1 for particle number emissions and −10 mm3 (kg fuel)−1 °C−1 for particle volume emissions. The temperature dependency of aerosol formation can have large effects on local air quality surrounding airports in cold regions. Aircraft-produced aerosols in these regions will be much larger than levels expected based solely on measurements made directly at the engine exit plane. The majority (90% at idle) of the volatile aerosol mass formed as nucleation-mode aerosols, with a smaller fraction as a soot coating. Conversion efficiencies of up to 2.8% were measured for the partitioning of gas-phase precursors (unburned hydrocarbons and SO2) to form volatile aerosols. Highest conversion efficiencies were measured at 45% power.

The article considers the main tendencies of development of alternative liquid fuels used in aviation, land transport, and for the needs of power generation sector. An overview of the main constraints to the development of alternative fuel technologies in these technical areas was carried out. The main groups of the most promising components and fuel compositions capable of effectively replacing conventional liquid fuels have been generalized. The basic criteria for evaluating alternative fuels are formulated. Environmental indicators of fuel combustion are of paramount importance for aviation. Rheological characteristics, calorific value, and environmental friendliness are critical for land transport engines. The effectiveness of alternative fuels for the power generation sector needs to be assessed in terms of such factors as economic, environmental, rheological, and energy to find an optimal balanced formulation. The list of potential components of alternative liquid fuels is extremely large. For a comprehensive analysis of the efficiency and selection of the optimal composition of the fuel that meets specific requirements, it is necessary to use multicriteria evaluation methods.

The limited resources of fossil fuels, as well as the search for a reduction in emissions of carbon dioxide and other toxic compounds to the atmosphere have prompted the search for new, alternative energy sources. One of the potential fuels which may be widely used in the future as a fuel is biogas which can be obtained from various types of raw materials. The article presents selected results as regards the effects of the proportion of biogas of various compositions on the course of combustion in a dual-fuel diesel engine with a Common Rail fuel system. The presented study results indicate the possibility for the use of fuels of this type in diesel engines; although changes are necessary in the manner of controlling liquid fuel injection.

Within the Euratom research and training program 2014–2018, three projects aiming at securing the fuel supply for European power and research reactors have been funded. Those three projects address the potential weaknesses – supplier diversity, provision of enriched fissile material – associated with the furbishing of nuclear fuels. First, the ESSANUF project, now terminated, resulted in the design and licensing of a fuel element for VVER-440 nuclear power plant manufactured by Westinghouse. The HERACLES-CP project aimed at preparing the conversion of high performance research reactor to low enriched uranium fuels by exploring fuels based on uranium-molybdenium. Finally, the LEU-FOREvER pursues the work initiated in HERACLES-CP, completing it by an exploration of the high-density silicide fuels, and including the diversification of fuel supplier for soviet designed European medium power research reactor. This paper describes the projects goals, structure and their achievements.

Abstract Power upgrade in nuclear reactors has been identified as one of the least costly options. This article focuses on how to further increase the thermal power and the possibility of using internally and externally cooled (I&EC) fuels instead of the solid fuels in the core of a Small Modular Reactor (SMR). In hence, The NuScale is chosen as the reference SMR. The core of NuScale is designed based on the use of a new 12 × 12 I&EC fuel assembly. This study is conducted throughout neutronic/thermal-hydraulic analysis. And many essential neutronic and thermal-hydraulic parameters such as variations of effective multiplication factor as a function of the pitch, neutron flux, power peaking factors, DNBRs and maximum temperature of the fuel were obtained. As one of the most important results of the analysis, I&EC fuel shows a sufficient margin available on DNBR and fuel pellet temperature compared with cylindrical solid fuel. The margin amount seems accommodating a 183% power-uprate seems viable. Also, the fuels axial temperature at different power levels were analyzed, and it was found that the proposed fuel at high power levels has a low peak temperature.

With the issue of the rise of anthropogenic CO2, global warming and rise of the primary energy demand, strong measures for the energy transition and the diversification with renewables and existing fossil-based infrastructure are required. Also, carbon capture and utilization of CO2 would also be needed. In that sense, thermochemical redox cycles gain particular interest to produce synthetic fuels, which can be used for energy generation and production of chemicals. In a two-step redox cycles, metal oxides acts as oxygen carriers and undergo looping between two reactors. In the reduction reactor, metal oxide is reduced with release of oxygen (solar-thermal) or produces syngas (for fuel reduction) whereas, in oxidation, CO2/H2O splits for form syngas when in contact with the metal oxide. Ceria being readily available at large scale and due to its nature of undergoing reduction non-stoichiometrically at low temperature makes it a good candidate. In the present thesis, a detailed investigation of thermochemical dissociation of CO2 and H2O considering solar thermal and fuel reduction with a focus on non-structured reactors is carried out. For the solar-driven cycle, an assessment of counter-current flow moving bed reactors for reduction and oxidation is performed and a chemical looping (CL) unit is added to a 100 MW power plant. With an operating temperature of 1600oC and 10-7 bar pressure, a maximum power output of 12.9 MW with solar to electricity efficiency of 25.4% is calculated. This additional power would bring down the efficiency loss due to carbon capture from 11.3 to 6%. Even though a considerable efficiency is obtained on very optimistic operating conditions, it still requires a huge solar field. Economics revealed that with a carbon tax of $40/tone of CO2 the levelized cost of electricity (LCOE) achieved is 17.8 times higher than the existing market price (without carbon capture). If a higher carbon tax of 80$/MWh is considered that it would still be 6.28 times higher for a plant with a carbon tax. As an alternative, methane-driven CL unit is integrated into a power plant to access the overall system efficiency and amount of efficiency regain after carbon capture. Since there exists no solid-state kinetic model in the literature for methane driven CO2/H2O splitting cycle, an experimental investigation was performed which revealed that an Avrami-Erofe’ev (AE3) model fit best to both oxidation and reduction, with activation energies of 283 kJ/mol and 59.7 kJ/mol, respectively. A comparative assessment was performed to investigate the influence of kinetics. A CL unit based on thermodynamics and kinetics (with moving bed reactors) were tested in a power plant. A drop of 20% in the efficiency of the CL unit was observed when the kinetic-based CL unit is considered. However, due to thermal balance within the system, a similar thermal efficiency of the overall plant was achieved as 50.9%. However, when the thermodynamic-based CL unit layout is considered there exists an excess heat which predicts the possibility of improving the efficiency. An economic assessment revealed a specific overnight capital cost of 2455$/kW, a levelized cost of CO2 savings of 96.25 $/tonneCO2, and a LCOE of 128.01 $/MWh. However, with a carbon tax of 6 $/tonneCO2, the LCOE would drop below 50 $/MWh. The methane-driven CL unit is later integrated as an add-on unit to a polygeneration plant that produces electricity and dimethyl ether. The results showed that the plant can produce 103 MWe and 2.15 kg/s of DME with energy and exergy efficiency of 50% and 44%, respectively. The capital investment required for the plantis about $534 million. With the carbon tax of $40/tonne of CO2, a current DME price of $18/GJ and an electricity price of $50/MWh would be achieved. Overall, the integration of the CL unit as an add-on unit to the power plant is more suitable than polygeneration with respect to the existing market price.
El aumento del CO2 antropogénico y el calentamiento global y el aumento de la demanda de energía primaria hace que se requieran medidas para la transición energética y la diversificación con energías renovables e infraestructuras existentes basadas en combustibles fósiles. Además de implementar medidas para la captura y el secuestro de carbono, también se necesita desarrollar métodos para la utilización de CO2. En ese sentido, los ciclos redox termoquímicos son particularmente interesantes para producir combustible sintético que, a su vez, pueden utilizarse para la producción de otras substancias químicas. La rotura de CO2 / H2O (CL) mediante una vía termoquímica de dos pasos está compuesta por dos reacciones redox con un óxido metálico. El primer paso es la reducción de los óxidos metálicos al perder oxígeno y crear vacantes en la red a una temperatura más alta y convertirse en óxido de metal de valencia más baja. Durante la etapa de oxidación, los gases reactivos CO2 / H2O reaccionan con el óxido metálico reducido formando CO y H2. Se ha investigado el uso de diferentes óxidos metálicos en función de su capacidad de transporte de oxígeno y sus propiedades para realizar ciclos redox continuos a distintos valores de temperatura y presión. Después de un examen cuidadoso, se ha seleccionado a la ceria para la división de CO2 / H2O a gran escala. En el presente trabajo, se investigan las divisiones termoquímicas de CO2 / H2O impulsadas por energía solar y la reducción de metano para la producción de gas de síntesis, con especial atención a su aplicación en reactores no estructurados. Se evalúa el uso de reactores de lecho móvil basado en flujo contracorriente y reactores de lecho fluidizado que funcionan en diferentes regímenes de fluidización. Es un reactor de lecho móvil tanto para la etapa de reducción como para la etapa de oxidación se obtienen altas selectividades de CO y H2 con volúmenes óptimos del reactor, mientras que en un reactor de lecho fluidizado el volumen requerido es mucho más alto, lo que lo hace inviable. Los modelos de reactor se han desarrollado en Aspen plus y se validan a partir de la literatura. Un análisis de sensibilidad ha revelado que la unidad CL depende en gran medida de la temperatura y la presión. El análisis se ha ampliado integrando la unidad desarrollada de CL como una unidad adicional a una central eléctrica de 100 MW con captura de carbono. La eficiencia de la planta se ha investigado considerando sólo la división de CO2, sólo la del H2O y la mezcla de CO2 y H2O como alimentación al reactor de oxidación de la unidad CL. El resultado es de una potencia máxima de 12.9 MW con una eficiencia de energía solar a eléctrica de 25.4%. Esta potencia adicional reduciría la pérdida de eficiencia debido a la captura de carbono de 11.3 a 6%. Para lograr esto, el reactor de reducción de la unidad CL debe funcionar a 1600 ° C y 10-7 bar de presión. Estas condiciones necesitarían un enorme campo solar y la operación, en ausencia de almacenamiento térmico, se limitaría a unas pocas horas durante el día. El análisis técnico-económico ha revelado que el coste nivelado de la electricidad es de 1321 $/MWh sin incluir incentivos ni impuestos sobre el carbono. Posteriormente, se ha considerado la reducción del metano como una alternativa a la reducción térmica. Al principio, se realizaron análisis termodinámicos de la unidad de CL impulsada por metano. A partir del análisis, se ha demostrado que la temperatura mínima requerida es de 900°C con 50% de exceso de metano para la reducción, lo que supone una eficiencia de la unidad CL de 62% con un rendimiento óptimo de CO y H2. La división de CO2/H2O en el reactor de oxidación a una mayor temperatura de salida beneficiaría considerablemente la eficiencia energética del ciclo redox CL completo. La variación de la relación H2/CO en la salida con respecto a los parámetros de entrada variables que incluyen la composición del gas al reactor de oxidación se ha estudiado con el fin de especificar las condiciones operativas idóneas. Posteriormente, la unidad CL impulsada por metano se ha integrado como una unidad adicional a una central eléctrica de 500 MW alimentada por oxígeno. Se ha investigado el rendimiento de un sistema con un ciclo combinado de gas natural convencional con o sin captura de carbono. Se ha obtenido una eficiencia de sistema y eficiencia energética de 50.7 y 47.4%, respectivamente. La eficiencia del sistema podría mejorarse a 61.5%, sujeto a la optimización del sistema. La evaluación tecno-económica ha revelado un coste de capital durante la noche de 2455 $/kW con un coste de ahorro de CO2 de 96.25 $/tonelada CO2 y un LCOE de 128.01 $/MWh. Sin embargo, con créditos de carbono de 6 $/tonelada CO2, el LCOE caería por debajo de 50 $/MWh.
Con l'aumento delle emissioni di CO2 antropogenica che contribuiscono al riscaldamento globale e l'incremento della domanda mondiale di energia primaria, sono richieste significative misure per favorire la diversificazione delle fonti e la transizione energetica tramite fonti rinnovabili a partire dalle infrastrutture esistenti basate su combustibili fossili. Prima ancora degli interventi per la cattura e il sequestro dell’anidride carbonica, anche l’utilizzo della CO2 rappresenta una misura necessaria al raggiungimento degli obiettivi di decarbonizzazione. In questo senso, i cicli redox termochimici hanno acquisito particolare interesse per la produzione di combustibile sintetico da utilizzare come intermedio nella produzione di altri prodotti chimici. La separazione chimica di CO2/H2O attraverso un ciclo termochimico – chemical looping splitting (CL) – in due fasi è composta da due reazioni redox con un ossido di metallo. La prima fase del ciclo avviene alla temperatura più elevata e consiste nella riduzione dell’ossido di metallo, che cede ossigeno creando vacanze nel reticolo e diventando ossido di metallo a bassa valenza. Durante la fase di ossidazione, i gas reagenti CO2/H2O reagiscono con l'ossido di metallo ridotto che forma CO e H2. Una mappatura dettagliata dei diversi ossidi di metallo è stata effettuata in base alla loro capacità di trasporto dell’ossigeno e alle proprietà nei cicli di ossido-riduzione a funzionamento continuo in condizioni di variazione di temperatura e pressione. Dopo un attento esame, l’ossido di Cerio - ceria - è stato selezionato per l'applicazione che può essere disponibile per la scissione CO2 / H2O su larga scala. In questo lavoro, sia la separazione termochimica di CO2/H2O alimentata tramite energia solare, sia i cicli con riduzione tramite metano, entrambi finalizzati all produzione di syngas sono stati studiati con particolare attenzione ai reattori non strutturati. Per il ciclo termochimico basato su energia solare, è stata effettuata la valutazione dei reattori a letto mobile a flusso in controcorrente e a letto fluido che operano in diversi regimi di fluidizzazione. Il reattore a letto mobile è stato individuato come il più performante sia per la riduzione che l’ossidazione, con elevate selettività verso CO e H2 e volumi ottimali del reattore, mentre una resa analoga con reattori a letto fluidizzato potrebbe essere ottenuta solo con volumi di reattore molto alti, rendendo questa scelta irrealizzabile nella pratica. I modelli di reattore sono stati sviluppati in Aspen plus e sono stati validati dalla letteratura. Un'analisi di sensitività ha rivelato che la performance dell'unità CL è in larga misura dipendente dalla temperatura e dalla pressione di riduzione. L'analisi è stata estesa integrando l'unità CL sviluppata come unità aggiuntiva di una centrale elettrica a ossicombustione da 100 MW con cattura di carbonio. L'efficienza dell'impianto è stata studiata considerando di alimentare il reattore di ossidazione dell'unità CL sia con CO2, sia con H2O, sia con una miscela di CO2 e H2O. I risultati indicano una potenza massima di 12,9 MW con un rendimento da solare a elettricità del 25,4% generabile grazie all’unità di CL. Questa potenza aggiuntiva ridurrebbe la perdita di efficienza dovuta alla cattura di carbonio dall'11,3 al 6%. Per ottenere ciò, il reattore di riduzione dell'unità CL deve operare a 1600 ° C con una pressione di 10-7 bar. Queste condizioni avrebbero bisogno di un enorme campo solare e l'operazione sarebbe limitata a poche ore durante il giorno senza l’integrazione di un accumulo termico. L'analisi tecno-economica ha rivelato che il costo livellato (levelizad cost) dell'elettricità era di 1321 $ / MWh, senza includere incentivi o tassazione sul carbonio. Successivamente, è stata considerata la riduzione della ceria con metano come alternativa alla riduzione termica. Inizialmente, sono state condotte analisi termodinamiche dell'unità CL con riduzione a metano. Dall'analisi è emerso che la temperatura minima richiesta era 900 °C per la riduzione con un eccesso di metano del 50%, che ha prodotto un'efficienza dell'unità CL del 62% con una resa ottimale di CO e H2. In questo caso, la scissione di CO2/H2O nel reattore di ossidazione consisteva nell'ossidazione completa esotermica della ceria, per cui una temperatura di uscita più elevata avrebbe notevolmente migliorato l'efficienza energetica del ciclo CL redox completo. La variazione del rapporto H2 / CO all'uscita rispetto ai vari parametri di input, compresa la composizione del gas inviato al reattore di ossidazione, è stata studiata per specificare le condizioni operative necessarie. Successivamente, l'unità CL a metano è stata integrata come unità aggiuntiva in una centrale elettrica a ossicombustione da 500 MW. Sono state studiate le prestazioni del sistema in una valutazione comparativa con un ciclo combinato convenzionale a gas naturale, un ciclo a ossicombustione con cattura di carbonio e l'impianto proposto. Sono stati ottenuti per l’impianto rispettivamente un rendimento del sistema e un'efficienza energetica del 50,7% e del 47,4%. L'efficienza del sistema potrebbe essere migliorata fino al 61,5% tramite l'ottimizzazione del recupero termico del sistema, valutata attraverso la pinch analysis del sistema. Una dettagliata valutazione tecno-economica ha rivelato un costo specifico del capitale di 2455 $ / kW (overnight cost), un costo livellato delle emissioni di CO2 evitate 96,25 $ / tonnellata di CO2, e un costo dell’elettricità (LCOE) di 128,01 $ / MWh. Tuttavia, considerando un incentivo di 6 $ / tonnellata di CO2 evitata, il LCOE scenderebbe sotto i 50 $ / MWh. L'unità CL a metano viene successivamente integrata come unità aggiuntiva in un impianto di poligenerazione che produce elettricità e dimetil-etere. I risultati hanno mostrato che l'impianto può produrre 103 MWe e 2,15 kg/s di DME con un’efficienza energetica ed exergetica del 50% e del 44% rispettivamente. L'investimento di capitale richiesto per l'impianto ammonta a 534 M$. Con un valoré per la carbon tax di $ 40 / tonnellata di CO2, il DME e l’elettricità raggiungerebbero la parità con gli attuali prezzi di mercato, pari a $18/GJ per il DME e $50/MWh per l’elettricità. I costi risultanti sono dovuti all'unità di separazione dell'aria richiesta per la centrale elettrica a ossicombustione e può essere ridotta sostituendo l'unità di separazione dell'aria con una tecnologia a membrana per la separazione dell'ossigeno. Poiché in letteratura non esiste un modello completo per cinetica dello stato solido che descriva la riduzione con metano della ceria, esso è stato ricavato per via sperimentale. Sono stati condotti esperimenti in un reattore tubolare orizzontale a letto fisso in un intervallo di temperatura di 900-1100 °C. E’ stata studiata la cinetica della scissione della CO2, essendo una reazione più complessa rispetto alla scissione dell'acqua, la cui cinetica è stata invece ottenuta dalla letteratura. In base all’analisi sperimentale condotta, il modello cinetico Avrami-Erofe'ev (AE3) è risultato essere il migliore per entrambe le reazioni, con le rispettive energie di attivazione ottenute rispettivamente come 283 kJ/mol e 59,68 kJ/mol. L'ordine della reazione è stato ricavato come relazione tra temperatura e concertazione dei reagenti. L'analisi è stata effettuata seguendo un approccio termodinamico, ma la reazione eterogenea dell'ossido di metallo e dei gas reagenti limita il raggiungimento dell'equilibrio durante la reazione e dipende sempre dal tipo di reattore scelto per x l'applicazione. Pertanto, un modello di reattore a letto mobile è stato sviluppato considerando la riduzione del metano ottenuta sperimentalmente e la cinetica di splitting della CO2 è stata incorporata per valutare i due impianti proposti: la centrale elettrica e l'impianto di poligenerazione. È stata osservata una riduzione del 20% nell'efficienza dell'unità CL. Tuttavia, grazie all’integrazione termica interna al sistema, l’efficienza termica dell'impianto complessivo è molto simile a quella raggiunta nell’analisi termodinamica, con un valore del 50,9%. Tuttavia, a differenza del layout termodinamico, non è disponibile calore in eccesso per migliorare ulteriormente l'efficienza del sistema. Oltre al riciclo e all'utilizzo della CO2, come criteri di valutazione della sostenibilità per il layout proposto sono stati analizzati anche l’occupazione del suolo terreno e il fabbisogno idrico. Sia il fabbisogno di terra che di acqua aumentano di 2,5 volte rispetto ad una centrale convenzionale a ciclo combinato a gas naturale. Inoltre, anche l’impianto di poligenerazione con produzione di energia elettrica e dimetil etere (DME) è stato studiato considerando un modello dell’unità CL basato sulla cinetica e ha rilevato che la produzione di DME scenderebbe da 2,15 kg/s a 1,48 kg/s e la potenza elettrica prodotta da 103 a 72 MW. Pertanto, la cinetica ha una forte influenza sulla prestazione complessiva del sistema, e considerarla nell’analisi porta a ridurre la produzione di energia e DME di circa il 30% con un aumento di costo del 30%. Complessivamente, l'integrazione dell'unità CL come unità aggiuntiva ad una centrale elettrica a ossicombustione risulta più adatta rispetto alla poligenerazione, considerando il prezzo di mercato attuale per le commodities prodotte.

Thesis (M.S. in Operations Research)--Naval Postgraduate School, March 2007.
Thesis Advisor(s): Daniel A. Nussbaum. "March 2007." Includes bibliographical references (p. 95-99). Also available in print.

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IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

The main objective of this thesis is to investigate the fundamental combustion process of ammonia-based fuels and the application on swirl-stabilised flames in the context of engineering type gas turbine combustion. The present study begins with a fundamental validation and mechanism reduction for chemical kinetics of ammonia/methane combustion. Different-sized reduced mechanisms of the well-known Konnov’s mechanism were compared at high-pressure conditions relevant to gas turbine devices. The reduced models can benefit the future simulation work with considerably less computational cost. Then characteristics of ignition delay time, laminar flame speed and emissions were obtained over a wide range of equivalence ratios and ammonia fractions. Prediction results showed a good potential of ammonia/methane to be used in gas turbine engines with relatively low emission. In the second part of this dissertation, in order to identify reaction mechanisms that can accurately represent ammonia/hydrogen kinetics at industrial conditions, various mechanisms were tested in terms of flame speed, combustion products and ignition delay against experimental data. It was preliminarily found that the Mathieu mechanism and Tian mechanism are the best suited for ammonia/hydrogen combustion chemistry under practical industrial conditions. Based on the Mathieu mechanism, an improved chemical mechanism was developed. Verification of the established model was quite satisfying, focusing particularly on elevated conditions which are encountered during gas turbine operation. Finally, a first assessment of the suitability of a chosen 70%NH3-30%H2 (%vol) blend was performed for utilisation within a gas turbine environment. It was found that stable flames can be produced with low NOx emissions at high equivalence ratios. Also, results showed that high inlet temperature conditions representative of real gas turbine conditions can significantly improve the combustion efficiency and reduce NOx emissions. A numerical gas turbine cycle calculation was performed indicating more research are required to enable higher efficiencies using ammonia/hydrogen.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 55-63).
The thesis is divided into two parts - 1) assessing the energy return on investment for alternative jet fuels, and 2) quantifying the tradeoffs associated with the aviation and non-aviation use of agricultural residues. We quantify energy return on energy investment (EROI) as one metric for the sustainability of alternative jet fuel production. Lifecycle energy requirements are calculated and subsequently used for calculating three EROI variants. EROI₁ is defined as the ratio of the lower heating value (LHV) of the liquid fuel produced, to lifecycle (direct and indirect) process fossil fuel energy inputs and fossil feedstock losses during conversion. EROI₂ is defined as the ratio of fuel LHV to total fossil fuel energy input, inclusive of the fossil energy embedded in the fuel. EROI₃ is defined as the ratio of fuel LHV to the sum of renewable and non-renewable process fuel energy required and feedstock energy losses during conversion. We also define an approximation for EROI₁ using lifecycle CO₂ emissions. This approach agrees to within 20% of the actual EROI₁ and can be used as an alternative when necessary. Feedstock-to-fuel pathways considered include jet fuel from conventional crude oil; jet fuel production from Fischer-Tropsch (FT) processes using natural gas, coal and/or switchgrass; HEFA (hydroprocessed esters and fatty acids) jet fuel from soybean, palm, rapeseed and jatropha; and advanced fermentation jet (AF-J) fuel from sugarcane, corn grain and switchgrass. We find that ERO₁ 1 for conventional jet fuel from conventional crude oil ranges between 4.9-14.0. Among the alternative fuel pathways considered, FT-J fuel from switchgrass has the highest baseline EROI₁ of 9.8, followed by AF-J fuel from sugarcane at 6.7. Jet fuel from oily feedstocks has an EROI₁ between 1.6 (rapeseed) and 2.9 (palm). EROI₂ differs from EROI₁ only in the case of fossil-based jet fuels. Conventional jet from crude oil has a baseline EROI₂ of 0.9, and FT-J fuel from NG and coal have values of 0.6 and 0.5, respectively. EROI 3 values are on average 36% less than EROI₁ for HEFA pathways. EROI₃ for AF-J and FT-J fuels considered is 50% less than EROI₁ on average. All alternative fuels considered have a lower baseline EROI₃ than conventional jet fuel. Using corn stover, an abundant agricultural residue, as a feedstock for liquid fuel or power production has the potential to offset anthropogenic climate impacts associated with conventional utilities and transportation fuels. We quantify the environmental and economic opportunity costs associated with the usage of corn stover for different applications, of which we consider combined heat and power, ethanol, Fischer-Tropsch (FT) middle distillate (MD) fuels, and advanced fermentation (AF) MD. Societal costs comprise of the monetized attributional lifecycle greenhouse gas (GHG) footprint and supply costs valued at the shadow price of resources. The sum of supply costs and monetized GHG footprint then provides the societal cost of production and use of corn stover for a certain application. The societal costs of conventional commodities, assumed to be displaced by renewable alternatives, are also calculated. We calculate the net societal cost or benefit of different corn stover usages by taking the difference in societal costs between corn stover derived fuels and their conventional counterparts, and normalize the results on a feedstock mass basis. Uncertainty associated with the analysis is captured using Monte-Carlo simulation. We find that corn stover derived electricity and fuels reduce GHG emissions compared to conventional fuels by 21-92%. The mean reduction is 89% for electricity in a CHP plant, displacing the U.S. grid-average, 70% for corn stover ethanol displacing U.S. gasoline and 85% and 55% for FT MD and AF MD displacing conventional U.S. MD, respectively. Using corn stover for power and CHP generation yields a net mean societal benefit of $48.79/t and $131.23/t of corn stover, respectively, while FT MD production presents a mean societal benefit of $27.70/t of corn stover. Ethanol and AF MD production from corn stover result in a mean societal cost of $24.86/t and $121.81/t of corn stover use, respectively, driven by higher supply costs than their conventional fuel counterparts. Finally, we note that for ethanol production, the societal cost of CO₂ that would need to be assumed to achieve a 50% likelihood of net zero societal cost of corn stover usage amounts to approximately -$100/tCO₂, and for AF MD production to ~$600/tCO₂.
by Parthsarathi Trivedi.
S.M.

The purpose of this presentation is to qualify a method of continuously and efficiently burning “dirty” solid fuels. Thus, the fuel cost is reduced and a significant savings is realized. Looking back on the many years of burning coal, a Preparation Plant was always involved in its supply. The delivered price took into account the extra cost for cleaning the 2″ × 0 “steam coal”. Following a request issued by the DOE in Illinois, Kinergy aligned with Riley Power in Massachusetts to develop an improved Vibrating Stoker Grate. Delivered in 2006, and “started up” in 2007, it has been in productive use for about 5 years. One of the most significant gains was the successful, continuous burning of “Run of Mine” (ROM) Coal. If this so-called “dirty” coal can be burned, then most of the cleaning done by a “Prep Plant” can be set aside, which is said to lower the cost of the coal by at least 35%. Further, other “dirty” solid fuels derived from waste, such as wood bark, shredded rubber tires, municipal solid waste (MSW and RDF) can also be burned. Usually the Power Plant is paid to accept these waste fuels. The maintenance of this Vibrating Stoker Grate is minimal and its productive availability is about 95%. Thus, it deserves attention. To observe the Vibrating Stoker Grate that successfully burns ROM Coal, it is located in the southern part of Illinois.

The paper presents experimental measurements of flashback propensity of H2-CO mixtures (primary constituents of syngas fuels). Effects of H2 concentration, external excitation and swirl on the flashback propensity of H2-CO flames are discussed. The flashback behavior of H2-CO flames changes nonlinearly with the increase in H2 contents in the mixture. The critical velocity gradient (gF) values of 5%–95% and 15%–85% H2-CO mixtures somewhat agree with the scaling relation (gF = c(SL2/α)) and yield an average c value of 0.035. However, the gF values of 25%–75% H2-CO mixture show higher order variations with the SL2/α ratio (especially for SL2/α < 19,000 s−1). At a lower SL2/α ratio, burner diameters have small effects on critical velocity gradient measurements; however, the effect is significant at higher SL2/α ratio. The effect of external excitation on the flashback propensity of H2-CO flames with more than 5% H2 is not significant. Flashback through two mechanisms and their dependence on combustor parameters were also identified for swirl stabilized H2-CO flames.

Use of opportunity fuels can provide cost-effective business deals for utilities. Successful use of these fuels is based on meeting fuel supply needs of the utility. These needs are specific to the particular power plant under consideration and can present significant challenges. Plant needs can be determined through an evaluation process based on a common set of fuel supply requirements. Results of this evaluation identify what is required for a successful fuel-supply business deal. The cost-benefits from this evaluation process are helpful in determining if the opportunity fuel will support a win-win business deal between the fuel supplier and the fuel user. This paper presents a framework for this evaluation process followed by case study reviews. This evaluation process can be helpful to fuel suppliers in understanding how to meet power plant fuel-supply needs and to power plant operators in clearly defining the needs that opportunity fuel suppliers must meet.

The paper presents the experimental measurements of the laminar burning velocity of H2-CO mixtures. Hydrogen (H2) and carbon monoxide (CO) are the two primary constituents of syngas fuels. Three burner systems (nozzle, tubular, and flat flame) are used to quantify the effects of burner exit velocity profiles on the determination of laminar flame propagation velocity. The effects to N2 and CO2 diluents have been investigated as well, and it is observed that the effects of N2 and CO2 on the mixture burning velocity are significantly different. Finally, the burning velocity data of various syngas compositions (brown, bituminous, lignite and coke) are presented.

A meso-scale heat recirculating combustor was used to examine the combustion characteristics of two specific synthetic fuels. One of the fuels was made via a Fischer-Tropsch (F-T fuel) process, while the other was produced from tallow (bio-jet fuel). The two fuels were burned in the meso-scale combustor using pure oxygen in a non-premixed injection configuration. The extinction behavior at the fuel-rich and fuel-lean combustion conditions has been investigated for each fuel. The results showed that although the two fuels showed some similarities, the F-T fuel exhibited stable, non-sooting combustion behavior at higher equivalence ratios than the bio-jet fuel. The lean stability limit for the bio-jet fuel was found to be lower (lower equivalence ratio) than that of the F-T fuel. The results were compared with conventional JP-8 jet fuel to provide a comparative analysis of combustion characteristics using the same combustor. A fuel characterization analysis was performed for each fuel, and their respective thermal efficiencies calculated. The F-T and bio-jet fuels both reached a maximum thermal efficiency of about 95% near their respective rich extinction limits.

<div class="section abstract"><div class="htmlview paragraph">Power options for off-road vehicles differ substantially from other commercial vehicles. Battery electrification is suitable for urban construction and light agriculture, but remote mining, forestry, and road building operations will require alternative fuels.</div><div class="htmlview paragraph"><b>Decarbonized Power Options for Non-road Mobile Machinery</b> discusses these domains as well as the potential benefits and challenges of implementing fuels and energy sources such as bioenergy, e-fuels, and alcohol, as well as hydrogen, hydrocarbon, and direct methanol fuel cells.</div><div class="htmlview paragraph"><a href="https://www.sae.org/publications/edge-research-reports" target="_blank">Click here to access the full SAE EDGE</a>^TM<a href="https://www.sae.org/publications/edge-research-reports" target="_blank"> Research Report portfolio.</a></div></div>

This article considers the role of activism and politics to restrict the supply of fossil fuels as a key means to prevent further climate injustices. We firstly explore the historical production of climate injustice through extractive economies of colonial control, the accumulation of climate debts, and ongoing patterns of uneven exchange. We develop an account which highlights the relationship between the production, exchange, and consumption of fossil fuels and historical and contemporary inequalities around race, class, and gender which need to be addressed if a meaningful account of climate justice is to take root. We then explore the role of resistance to the expansion of fossil-fuel frontiers and campaigns to leave fossil fuels in the ground with which we are involved. We reflect on their potential role in enabling the power shifts necessary to rebalance energy economies and disrupt incumbent actors as a prerequisite to the achievement of climate justice