Dissertations / Theses on the topic 'Carbon upgrading'

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, February, 2021
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 219-233).
Electrochemical carbon dioxide reduction (CO2R) is increasingly recognized as a viable technology for the generation of chemicals using carbon dioxide (CO₂) recovered from industrial exhaust streams or directly captured from air. If powered with low-carbon electricity, CO2R processes have the potential to reduce emissions from chemicals production. Historically, three-electrode analytical cells have been used to study catalyst activity, selectivity, and stability with a goal of incorporating proven materials into larger devices. However, it has been recognized that the limited CO₂ flux through bulk volumes of liquid electrolyte limit the effective reaction rate of CO₂ when using promising catalyst systems.
Gas-fed electrolyzers adapted from commercial water electrolyzer and fuel cell technologies have motivated researchers to explore combinations of porous electrodes, catalyst layers, and electrolytes to achieve higher areal productivity and favorable product selectivities. Present art demonstrates that high current density production (>200 mA cm₋²) of valuable chemicals at moderate cell voltages (ca. 3-4 V) is achievable at ambient conditions using electrolysis devices with catalyst-coated gas diffusion electrodes (GDEs). However, beyond short durations (1-10 h) stable performance outcomes for flowing electrolyte systems remain elusive as electrolyte often floods electrode pores, blocking diffusion pathways for CO₂, diminishing CO2R selectivity, and constraining productivity. Systematic study of the driving forces that induce electrode flooding is needed to infer reasonable operational envelopes for gas-fed electrolyzers as full-scale industrial devices are developed.
In this thesis, I investigate GDE wettability as a prominent determinant of gas-fed flowing electrolyte CO₂ electrolyzer durability. To do this, I combine experimental and computational approaches. First, I use a flow cell platform to study transient evolution of activity, selectivity, and saturation to identify failure modes, including liquid pressurization, salt precipitation, electrowetting, and liquid product enrichment. Next, I use material wettability properties and reactor mass balances to estimate how enriched liquid product streams might defy non-wetting characteristics of current GDE material sets. Finally, I construct computational electrode models and vary surface chemistry descriptors to predict transport properties in partially saturated electrodes. Specifically, I consider how saturation evolves in response to relevant scenarios (i.e., electrowetting and liquid products) that challenge CO₂ electrolyzer durability.
by McLain E. Leonard.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering

Durante los últimos años, la investigación y el desarrollo de tecnologías para la reducción de las emisiones de gases de efecto invernadero (GEI) en nuestro planeta ha incrementado. Varias soluciones se han propuesto, incluyendo la captura y secuestro de carbono (CCS en inglés). La aplicación de CCS se ha focalizado en las tecnologías de producción de energía a gran escala que utilizan combustibles fósiles. Recientemente, se ha trabajado en el uso de CCS en tecnologías de enriquecimiento de biogás. Esta práctica consiste en la eliminación del CO2 del biogás emitido por digestores anaeróbicos y vertederos con el fin de incrementar la concentración de CH4 en el biogás, generando así un potencial sustituto de gas natural. Dos innovadoras tecnologías en desarrollo almacén además el CO2 eliminado en una forma sólida, a través de un proceso llamado mineralización de carbono. Este proceso utiliza óxido cálcico de los residuos industriales para fijar el CO2 en forma de carbonato cálcico. Idealmente estas tecnologías innovadoras de enriquecimiento deberían mostrar mayores beneficios ambientales en comparación con las tecnologías convencionales ya que almacenan inmediatamente el CO2. La primera tecnología analizada es la regeneración de alcalino (AwR) que consiste en el uso de una solución alcalina para eliminar el CO2 y que es regenerada mediante su exposición a un residuo industrial rico en CaO. La segunda tecnología es enriquecimiento de biogás con cenizas (BABIU), basada en la interacción directa del biogás con las cenizas resultantes de incineradores de residuos municipales. Esta tesis pretende determinar si estas tecnologías innovadoras muestran beneficios ambientales respecto a las tecnologías convencionales de enriquecimiento de biogás, mediante la aplicación de herramientas de la ecología industrial. El análisis de ciclo de vida, el análisis de flujos materiales y el análisis de exergía son aplicadas para el análisis ambiental y de recursos. Asimismo, la viabilidad a largo plazo de las tecnologías es examinada desde el punto de vista económico y material. En general, los resultados indican que las tecnologías innovadoras no muestran un perfil ambiental notablemente mejor que las convencionales, especialmente para AwR donde el uso de la solución alcalina da lugar a un elevado impacto ambiental. Aún así, ambas tecnologías consiguen un significante ahorro de CO2 respecto a las tecnologías convencionales. Asimismo, dado que las dos tecnologías analizadas se encuentran en un período de prueba piloto, se identifican las potenciales mejoras para optimizar el perfil ambiental y económico, como incrementar la eficiencia de la regeneración de la solución alcalina en la tecnología AwR. El análisis económico realizado para AwR resaltó que reducir sus costes operacionales incrementaría la oportunidad de su implementación como negocio. Los resultados pueden ser usados tanto por promotores de estas innovadoras tecnologías para mejorar su viabilidad económica y ambiental a largo plazo, como por promotores y fabricantes de tecnologías similares, como aplicaciones de CCS o enriquecimiento de biogás.
Our world has been increasingly looking for solutions to reduce the greenhouse gas (GHG) emissions of our planet. Various solutions have been proposed, including carbon capture and sequestration (CCS). Focus for application of CCS has normally centered on large scale energy production that burns fossil fuel. Recently, developers have been working on applying CCS to biogas upgrading technology. This entails removing CO2 from biogas emitted from anaerobic digestors and landfills while also increasing the CH4 concentration to render the biogas suitable as natural gas substitute. Two novel technologies under review also stores the removed CO2 in a solid form, through a process called carbon mineralization. This process uses calcium oxides found in industrial waste to fix CO2 by forming calcium carbonate. Ideally these novel upgrading technologies should have more environmental benefit over conventional ones based on the fact that they immediately store CO2, while conventional ones do not. The first technology is called alkaline with regeneration (AwR) and consists of using an alkaline solution to strip the CO2. The alkaline solution is then regenerated by exposing it to a waste rich in CaO. The second is called bottom ash for biogas upgrading (BABIU) which relies on a direct gas-solid phase interaction with bottom ash from municipal solid waste incinerators. This thesis examines whether or not these two novel technologies have an environmental benefit over conventional upgrading technologies, based on industrial ecology tools. Life cycle assessment, material flow analysis, and exergy analysis were applied for the environmental and resource assessments. The thesis also examines the long term feasibility of applying these technologies, both from a material and economic point of view. Overall it was determined that the novel technologies generally do not have a better environmental performance over conventional technologies, especially AwR which was found to have a higher impact due to the use of the alkaline solution. Despite this, both novel technologies had significant CO2 savings over conventional technologies. As well since both novel processes are in the pilot plant stage it is possible to pinpoint what can be improved in order to increase the all around environmental benefit, for example by increasing the regeneration rate of the alkaline solution in AwR. The economic assessment was conducted on AwR and it was found that improving its operational costs would help create a business case for potential application. The results not only help the developers of the novel technologies to improve their long term environmental and economic viability but also can be used by developers and manufactures of similar technologies, such as other biogas upgrading or CCS technologies.

Biogas is a renewable energy source, consisting primarily of methane and carbon dioxide (CO2), which can be upgraded by stripping the CO2 to produce biomethane. One of the standard industrial solvents used in biogas upgrading is monoethanolamine (MEA). Despite the effective CO2 capture capability of MEA, it is energy intensive to regenerate since it requires heating the solvent to approximately 120 oC. Additional issues with MEA include material losses due to degradation and evaporation. This work investigates methods for improving the biogas upgrading process by utilising microbubbles and comparing ionic liquid solvents to MEA. It is also examined whether CO2 can be released from a solvent with high enough purity to be utilised directly in conjunction with carbon dioxide utilisation (CDU) processes. The study experimentally investigates factors influencing bubble size and absorption of CO2 by ionic liquids with a view to biogas upgrading. It was found that bubble size in the majority of ionic liquids tested was far greater than that in aqueous glycerol mixtures of similar viscosity; however, three of the ionic liquids tested had a similar bubble size. Further analysis showed that rather than viscosity, the surface tension of the ionic liquid has the most significant influence on bubble size due to its stabilising effect on the homogeneous regime in bubble columns. 30 wt.% aqueous MEA solution was shown to have a significantly greater rate of mass transfer than the ionic liquids tested due to its greater absorption capacity, greater diffusivity and tendency to form smaller bubbles. Of the ionic liquids tested, the greatest absorption capacity was exhibited by [C2mim][NTf2] and the greatest volumetric mass transfer coefficient by [C2mim][EtSO4].

Hydrocracking and hydrotreating are bitumen upgrading technologies designed to enhance fuel quality by decreasing its density, viscosity, boiling point and heteroatom content via hydrogen addition. The aim of this thesis is to model and simulate an upgrading and integrated gasification combined cycle then to evaluate the feasibility of integrating slurry hydrocracking, trickle-bed hydrotreating and residue gasification using the Aspen HYSYS® simulation software. The close-coupling of the bitumen upgrading facilities with gasification should lead to a hydrogen, steam and power self-sufficient upgrading facility with CO2 capture. Hydrocracker residue is first withdrawn from a 100,000 BPD Athabasca bitumen upgrading facility, characterized via ultimate analysis and then fed to a gasification unit where it produces hydrogen that is partially recycled to the hydrocracker and hydrotreaters and partially burned for power production in a high hydrogen combined cycle unit. The integrated design is simulated for a base case of 90% carbon capture utilizing a monoethanolamine (MEA) solvent, and compared to 65% and no carbon capture scenarios. The hydrogen production of the gasification process is evaluated in terms of hydrocracker residue and auxiliary petroleum coke feeds. The power production is determined for various carbon capture cases and for an optimal hydrocracking operation. Hence, the feasibility of the integration of the upgrading process and the IGCC resides in meeting the hydrogen demand of the upgrading facility while producing enough steam and electricity for a power and energy self-sufficient operation, regardless of the extent of carbon capture.

Questions that were answered in the dissertation: Which process is suitable to desulphurize biogas knowing that chemical absorption will be used to separate CO2? Which absorption solvent is suitable to separate CO2 from concentrated gases such as biogas at atmospheric pressure? What properties of the selected solvent, namely aqueous diglycolamine (DGA), are already known? How to determine solvent properties such as equilibrium CO2 solubility under absorption and desorption conditions using simple, but robust apparatuses? What values do solvent properties such as density, viscosity and surface tension take at various DGA contents and CO2 loadings? How do primary alkanolamine content and CO2 loading influence solvent properties? What is the optimal DGA content in the solvent? What is the optimal desorption temperature at atmospheric pressure? How can equilibrium CO2 solubility in aqueous DGA solvents be simulated? What is the uncertainty in the results? How to debottleneck an absorber and increase its gas-treating capacity? How to determine the optimal lean loading of the absorption solvent? What are the characteristics of the absorption process that uses aqueous DGA as the solvent to separate CO2 from biogas and is more energy efficient and safer than the state-of-the-art processes? How to quantitatively compare the hazards of absorption solvents? What is the disposition of the German population towards hazards from biogas plants? What are the favourable and adverse environmental impacts of biomethane?
Fragen, die in der Dissertation beantwortet wurden: Welches Verfahren ist zur Entschwefelung von Biogas geeignet, wenn die chemische Absorption zur CO2-Abtrennung genutzt wird? Welches Absorptionsmittel ist geeignet, um CO2 aus konzentrierten Gasen, wie Biogas, bei atmosphärischem Druck abzutrennen? Welche Eigenschaften des ausgewählten Absorptionsmittels, wässriges Diglykolamin (DGA), sind bereits bekannt? Wie wird die CO2-Gleichgewichtsbeladung unter Absorptions- und Desorptionsbedingungen mit einfachen und robusten Laborapparaten bestimmt? Welche Werte nehmen die Absorptionsmitteleigenschaften wie Dichte, Viskosität und Oberflächenspannung bei verschiedenen DGA-Gehalten und CO2-Beladungen? Wie werden die Absorptionsmitteleigenschaften durch den Primäramin-Gehalt und die CO2-Beladung beeinflusst? Was ist der optimale DGA-Gehalt im Absorptionsmittel? Was ist die optimale Desorptionstemperatur bei atmosphärischem Druck? Wie wird die CO2-Gleichgewichtsbeladung im wässrigen DGA simuliert? Welche Ungenauigkeit ist zu erwarten? Wie wird eine Absorptionskolonne umgerüstet, um die Kapazität zu erweitern? Wie wird die optimale CO2-Beladung des Absorptionsmittels am Absorbereintritt (im unbeladenen Absorptionsmittel) bestimmt? Was sind die Prozesseigenschaften eines Absorptionsverfahrens, das wässriges DGA als Absorptionsmittel nutzt sowie energieeffizienter und sicherer als Verfahren auf dem Stand der Technik ist? Wie kann das Gefahrenpotenzial von Absorptionsmittel quantitativ verglichen werden? Wie werden Gefahren aus einer Biogasanlage durch die deutsche Bevölkerung wahrgenommen? Welche positive und negative Umweltauswirkung hat Biomethan?

A geraÃÃo de ResÃduos SÃlidos Urbanos (RSU) vem aumentando a cada ano no PaÃs, sendo a fraÃÃo orgÃnica normalmente responsÃvel por mais da metade da quantidade total de RSU gerada. Entre as alternativas existentes para o aproveitamento dos resÃduos sÃlidos orgÃnicos, destaca-se a digestÃo anaerÃbia, uma soluÃÃo atrativa, tendo em vista que hà produÃÃo de biogÃs durante o processo. Entretanto, para que suas possibilidades de aplicaÃÃo sejam mais abrangentes, à necessÃrio que o biogÃs seja purificado e posteriormente submetido a um processo de upgrade, a fim de que adquira caracterÃsticas similares ao do gÃs natural. O presente trabalho teve como objetivo sintetizar Carbonos Ativados (CAs) a partir de endocarpo de coco seco (Cocos nucifera), de coco babaÃu (Orbignya speciosa) e a partir de vagem de flamboyant (Delonix regia) por meio de ativaÃÃo com diÃxido de carbono em Ãnica etapa. As caracterÃsticas texturais das amostras foram determinadas por meio de isotermas de adsorÃÃo de N2 a -196 ÂC. Os maiores valores de Ãrea superficial especÃfica e volume de microporos foram obtidos para o bioadsorvente sintetizado a partir do coco seco, com valores de 1452 m2/g e 0,60 cm3/g, respectivamente. Foram selecionados os CAs de coco seco e de coco babaÃu para a anÃlise de suas eficiÃncias na separaÃÃo de misturas CO2/CH4 para aplicaÃÃo no upgrade de biogÃs. Para tanto, ensaios de equilÃbrio de adsorÃÃo dos componentes puros (CO2 e CH4) e da mistura (30% vol. CO2, 70% vol. CH4) foram realizados a 20 ÂC utilizando uma balanÃa de suspensÃo magnÃtica. A capacidade de adsorÃÃo de CO2 pouco se diferenciou entre as duas amostras, apresentando o CA de coco seco melhores resultados. Essa amostra apresentou valores bem maiores de captura de metano a pressÃes acima de 3,0 bar. Os dados experimentais foram comparados com os obtidos pelo ajuste do modelo de TÃth e da IAST (Teoria da SoluÃÃo Adsorvida Ideal) para os dados mono e multicomponentes, respectivamente. Os ajustes de TÃth foram bastante precisos, enquanto os da IAST se adequaram moderadamente. As seletividades das amostras para o CO2 em relaÃÃo ao CH4 foram determinadas e comparadas com a de outros adsorventes comerciais. O CA do coco seco apresentou resultados melhores que o coco babaÃu a baixas pressÃes, com valor de seletividade de 4,2 a 1,0 bar, indicando ser um material competitivo para a aplicaÃÃo proposta.
The generation of Municipal Solid Waste (MSW) is increasing every year in Brazil, being the organic matter responsible for more than half of the total MSW generated. Among the current alternatives to the use of organic solid waste, the anaerobic digestion is the most attractive as biogas production occurs in the process. Nevertheless, to increase its usage possibilities, biogas has to be purified and upgraded, in order to acquire characteristics similar to that of natural gas. The present work aims to prepare activated carbons (ACs) from coconut endocarp (Cocos nucifera), babassu coconut (Orbignya speciosa) and flamboyant pods (Delonix regia) by one step CO2 activation. The textural characteristics were determined by N2 adsorption isotherm at -196 ÂC. The best results of BET surface area and micropore volume were obtained for bioadsorbent synthesized from coconut shell, with values of 1452 m2/g and 0.6 cm3/g, respectively. ACs from coconut shell and babassu coconut were selected to analyze their efficiency in CO2/CH4 separation mixture for biogas upgrading application. Therefore, pure component (CO2 and CH4) and mixture (30% vol. CO2, 70% vol. CH4) adsorption equilibria were performed at 20 ÂC using a magnetic suspension balance. The CO2 adsorption capacity slightly differed between samples, presenting the AC from coconut shell better results. This sample had higher methane uptake above pressures of 3.0 bar. The experimental data were compared with the fit of Toth and IAST (Ideal Adsorbed Solution Theory) models for mono and multicomponent data, respectively. The Toth fitting was fairly accurate, while the IAST fit was moderate. The samples selectivity to CO2 over CH4 were calculated and compared with another commercial adsorbent. The AC from coconut shell presented better results than babassu coconut at low pressures, with a selectivity value of 4.2 at 1.0 bar, indicating to be a competitive material for the proposed application.

Cette thèse s'articule autour des zéolithes, plus particulièrement leur synthèse, leur caractérisation et leur application comme catalyseurs hétérogènes. Dans certains cas, la compréhension des phénomènes encontrés au cours de ce processus nécessitait un travail de rationalisation. Ce dernier ingrédient permet une réelle amélioration continue, ou une conception sur mesure d'un catalyseur pour une réaction. Les zéolithes sont des aluminosilicates, microporeux et cristallins, qui se définissent et se différencient de part leur arrangement 3D de tétraèdres (SiO4 et AlO4) . Il a été essayé d'utiliser des zéolithes conçues sur mesures en tant que catalyseurs pour des réactions faisant partie d'une chimie renouvelable. Ainsi, ces travaux s'inscrivent dans le cadre des concepts de la chimie verte et de l'addition graduelle de complexité moléculaire. Au cours de cette thèse, la boucle itéative de l'amélioration continue a mené à deux reprises à un catalyseur très adapté au processus catalytique en question: d'une part l'halogènation d'aromatiques a été effectuée en phase liquide, il s'agit d'un procédé liquide-solide pour lequel le meilleur catalyseur résulte en une zéolithe béta (H-*BEA) avec une porosité hiérarchisée. Au contraire, la réaction de la conversion du méthanol en oléfines (MTO) une réaction gas-solide semble avoir comme catalyse uroptimal des zéolithes de type ZSM-5 sans porosité hierarchisée, mais ayant des tailles cristallines élevées, une qualité cristalline proche de la perfection (sans défauts) et une densité de sites acides très disperses
This work revolved around the synthesis, characterisation and application of zeolites in heterogeneous catalysis. In some cases, counterintuitive observations and results needed a thorough rationalisation, which allowed a truly continuous improvement, or rational design of a catalyst for a given reaction. Zeolites are crystalline and microporous aluminosilicates, which are defined and differ one from another through their 3D arrangement of tetrahedra (SiO4 and AlO4).It has been aimed to design heterogeneous catalysts for reactions that fit in the concepts of a sustainable chemistry. Thus, this works describes and tried to respect the concepts of green chemistry and carbon upgrading. Remarkably, during this thesis the feedback looped continuous improvement approach has led twice to adapted catalysts for a catalytic chemical transformation: the liquid-solid continuous flow halogenation of aromatics was best performed with nanosized H-*BEA zeolites exhibiting a hierarchical porosity. In contrast, the gas-solid Methanol-to-Olefins (MTO) process needed an unusual catalyst. Indeed based on our study, large and perfectly crystalline H-ZSM-5 crystals with a disperse Brønsted acidity were the optimum catalyst

Carbon dioxide from biogas production is currently considered to be without value and isbecause of this released into the atmosphere in the biogas upgrading process. The residualgas is a potential carbon source and can create value in the biogas manufacturing process.By finding a suitable value-creating process that utilizes carbon dioxide, it can be possibleto provide both economic and environmental incentives for companies to develop theiroperations. This project explored the possibility to create value from this CO2. Through anevaluation of the technical maturity of CCU technologies, a recommendation could be givenat the end of the project. An analysis of technical barriers, such as pollutants in the gas, aswell as barriers in the form of competence and corporate culture were examined in orderto provide a reasoned recommendation. The project mapped which value-creating systemswould be suitable for biogas producers in a Swedish context. This included established methaneand carbon dioxide upgrading techniques currently in use and suitable CCU techniquesthat can interact with the selected upgrading processes and serve as value creators. Based onthis survey, it was then possible to identify common, critical variables for these systems. Thereafter,a recommendation of an appropriate CCU technology could be given depending onthe CO2 composition produced. One conclusion from the study was that carbon dioxide concentrationsfrom the residual gas was often high (approx. 97-98 %) and did not contain anycorrosive or toxic components, and that this largely depends on how the digestion reactor ishandled in the production process. Thus, questions were raised about what the actual limitationsof the CCU are, as they did not seem to be technical. CCU techniques that proved to beof particular interest were pH regulation of sewage plants, CO2 as a nutrient substrate for thecultivation of microalgae, and manufacturing of dry-ice for refrigerated transports. All of thesetechnologies currently have a sufficiently high degree of technical maturity to be installedalready today. Other CCU techniques, such as "’Power to gas”, require a high CO2 concentrationand were discarded as the literature review did not suggest the economic potential forthem as they require additional CO2 upgrading steps. Instead, CCU techniques were chosenthat could be implemented directly with the existing CO2 quality. Furthermore, it was concludedthat one reason why CCU technologies have not been widely implemented is internalbarriers between distributors and manufacturers (or users) of CCU technologies. Thus, theuse of carbon dioxide from biogas production and implementation of CCU technologies canbe promoted by eliminating barriers in companies, such as a lack of both knowledge andfinancial incentives.
Koldioxid från biogasproduktion betraktas i dagsläget som utan värde och släpps ut i atmosfärenvid uppgradering av biogas. Restgasen är en potentiell kolkälla och kan vara värdeskapandeför biogasprocessen. Genom att finna en lämplig värdeskapande process som utnyttjarkoldioxid går det att ge både ekonomiska och miljömässiga incitament till företag att utvecklasin verksamhet. I detta projekt undersöktes möjligheten att skapa värde av denna CO2.Genom en utvärdering av den tekniska mognadsgraden hos CCU-tekniker kunde en rekommendationges vid projektets slut. En analys av tekniska hinder, såsom föroreningar i gassammansättningen,såväl som hinder i form av kompetens och företagskultur undersöktes för attkunna ge en motiverad rekommendation. I projektet kartlades vilka värdeskapande systemsom skulle passa för biogasproducenter i en svensk kontext. Detta inkluderade etableradeuppgraderingstekniker för metan- och koldioxid som används i dagsläget. I projektet undersöktesäven lämpliga CCU-tekniker som kan samverka med de valda uppgraderingsprocessernaoch och agera värdeskapande. Utifrån denna kartläggning kunde det sedan anges vilkagemensamma, kritiska variabler som finns för dessa system. Därefter kunde en rekommendationav lämplig CCU-teknik ges beroende på den producerade CO2 sammansättningen. Enslutsats i projektet var att koldioxid från restgasen ofta var av hög koncentration (ca. 97-98 %)och ej innehöll några korrosiva eller toxiska komponenter, och att detta till stor del beror påhur rötkammaren är hanterad i produktionsprocessen. Således väcktes frågor kring vilka defaktiska begränsningarna för CCU är, då de inte torde vara tekniska. CCU-tekniker som visadesig vara av särskilt intresse var pH-reglering av avloppsverk, CO2 som näringssubstratför odling av mikroalger, samt tillverkning av kolsyreis för kyltransporter. Samtliga dessatekniker har tillräckligt hög teknisk mognadsgrad för att kunna installeras i dagsläget. AndraCCU-tekniker, såsom ”Power to gas”, kräver en hög CO2-koncentration och avfärdades dålitteraturstudien inte talade för den ekonomiska potentialen i dessa eftersom de kräver ytterligareuppgraderingssteg för CO2. Således valdes istället CCU-tekniker som skulle gå attimplementera direkt med den befintliga CO2 kvalitén. Vidare drogs slutsatsen att en anledningtill att CCU-tekniker inte har blivit vida implementerade till stor del är interna hindermellan distributörer och tillverkare (eller utnyttjare) av CCU-tekniker. Således kan användandetav koldioxid från biogasproduktion och implementering av CCU-tekniker främjasgenom att eliminera hinder hos företag. I projektet yttrade sig detta som bristande ekonomiskaincitament och okunskap. Ett ökat användande av CCU-tekniker kan också uppnås genomatt införa lagar och regler som begränsar användandet av föråldrade tekniker som drivs avfossila bränslen, och som kan ersättas av klimatvänliga CCU-tekniker.

Le biogaz issu de la dégradation anaérobie de matières organiques peut remplacer le gaz naturel dans plusieurs applications. Pour une meilleure valorisation énergétique du biogaz, ce travail s’intéresse à l’élimination des composés organiques volatils du silicium (siloxanes) dans biogaz par l’adsorption sur des matériaux poreux. Trois charbons actifs (CA) commerciaux ont été utilisés pour l’adsorption des siloxanes. Leurs propriétés physicochimiques sont caractérisées par plusieurs techniques. Un CA montre excellent capacité d’adsorption d’octaméthylcyclotétrasiloxane (D4) ce qui est bien supérieur que l’autre. En présence de la vapeur, les capacités d’adsorption des CA peuvent être réduites plus ou moins fort dépendant de dégrée d’humidité relative et la présence des sites hydrophiles sur la surface de CA. Ainsi, la capacité des échantillons possédant ces sites spécifiques est réduite après la thermodésorption à cause de la formation des espèces non volatiles sur la surface de CA. Tests avec d’autres siloxanes ont montré que le phénomène de polymérisation s’est produit avec de réactivité et de mécanisme différent, dépendant de la nature du CA et de siloxane. La polymérisation est toujours plus importante pour le CA qui présent plus de sites hydrophiles, conduisant également à sa plus faible régénérabilité
Biogas issued from the anaerobic digestion of organic materials is a renewable energy source that can replace natural gas in many applications. For a better energy recovery of biogas, this work focuses on the elimination of the volatile organic compounds of silicon (siloxanes) in biogas by the adsorption onto porous materials. Three commercial activated carbons (CA) were used for the adsorption of siloxanes. Their physicochemical properties are characterized by several techniques. Measurement of adsorption capacity of octamethylcyclotetrasiloxane (D4) revealed a CA that works better than the others. In presence of water vapor, the adsorption capacities of all AC can be reduced more or less depending on the degree of relative humidity and the presence of the hydrophilic sites on the surface of AC. Also, D4 adsorption capacity of samples with these specific sites is reduced after thermodesorption due to formation of nonvolatile species on the surface of AC. Tests with other siloxanes showed that the polymerization phenomenon occurred with different reactivity and mechanism, depending on the nature of the CA and siloxane. The polymerization is always more important for the CA which has more hydrophilic sites, thus leading to its lower regenerability

CASTRILLON, M. Y. D. M. C. Dados fundamentais para projeto de processos de dessulfuração e upgrading de gases combustíveis por adsorção. 2017. 112 f. Tese (Doutorado em Engenharia Química)-Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2017.
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In this study, the adsorption of CH4, CO2 and H2S has been studied on commercial activated carbon samples in order to assess its potential for upgrading and desulphurization of Biogas or contaminated natural gas. Different characterization techniques such as Fourier Transform Infrared Absorption Spectroscopy (FTIR), X-ray fluorescence (XRF), pH measurements and textural analysis (by N2 (196 oC) adsorption/desorption isotherms and CO2 (0 oC) adsorption isotherms) were used to study the porous structure of the material and detect the presence of K, Na and Fe and other elements in the samples. Gravimetric experiments were used to measure adsorption capacity of CO2 and selectivity with respect to CH4. Breakthrough curves under dry conditions were performed to evaluate H2S adsorption under dynamic conditions. The materials under study showed high adsorption capacities for both gases in the range of 0.013-0.28 mmol g-1 for H2S and 1.61-2.16 mmol g-1 CO2 under dry conditions, 25 ºC and 1 bar. In addition, selectivity of the samples with respect to CH4 was found to be in the range of 1.2-2.4 mmol g-1, with Desorex K43-BG being the material with the highest retention of H2S and Sorbonorit B4, the material with the greatest adsorption capacity of CO2 and CH4. The data obtained from adsorption experiments were correlated with the textural characteristics and the surface chemistry of the materials. The best compromise between adsorption capacity of H2S and selectivity of CO2 in the presence of CH4 were found for the sample containing Na (Desorex K43-Na), which benefited from both a basic surface chemistry and pore size distribution restricted to the micropore range. Breakthrough curves of H2S in the presence of CO2 have shown that the adsorption capacity of H2S in materials impregnated with alkali metals is considerably reduced: 37% for Desorex K43-BG and 65% for Desorex K43-Na sample. This loss of capacity may be due to the competition for the active sites (linked to the presence of metals) by the gases being co-adsorbed. For the non-impregnated Sorbonorit B4 material, the presence of CO2 in these tests did not cause appreciable loss in H2S adsorption capacity.
Neste estudo, foi investigada a adsorção de CH4, CO2 e H2S em carbonos ativados comerciais com o intuito de avaliar o seu potencial para o uso em "upgrading" e dessulfurização de biogás ou gás natural contaminado. Diferentes técnicas de caracterização, tais como Espectroscopia de Absorção no Infravermelho com Transformada de Fourier (FTIR), Fluorescência de Raios X (XRF), medições de pH e análise textural (por isotermas de adsorção/dessorção de N2 (196 oC) e isotermas de adsorção De CO2 (0 oC)) foram utilizadas para estudar a estrutura porosa do material e indicar a presença de K, Na e Fe e outros elementos nos materiais. Experimentos gravimétricos foram utilizados para a obtenção das isotermas de adsorção de gases individuais e misturas binárias a fim de avaliar a capacidade de retenção de CO2 e a seletividade dos adsorventes em relação ao CH4. Curvas de ruptura sob condições anidras foram medidas para avaliar a adsorção do H2S em condições dinâmicas. Os materiais estudados mostraram capacidades de adsorção elevadas para ambos os gases: na faixa de 0,013-0,28 mmol g-1 para H2S e 1,61-2,16 mmol g-1 de CO2, em condições secas, a 25ºC e 1 bar. Além disso, observou-se uma seletividade dos carbonos ativados para o CO2 em relação ao CH4 na faixa de 1,2-2,4, sendo o Desorex K43-BG o material com maior capacidade de retenção de H2S e o Sorbonorit B4 o material com maior capacidade de adsorção do CO2 e CH4. Os dados obtidos com os ensaios de adsorção foram correlacionados com as características texturais e as propriedades químicas dos materiais.. A melhor capacidade de adsorção de H2S, e seletividade pelo CO2 na presença de CH4, foi encontrada para a amostra contendo Na (Desorex K43-Na), graças à combinação da química da superfície do material (básica) e a distribuição de tamanho dos poros restritos ao intervalo de microporos. Os testes de H2S na presença de CO2 demonstraram que a capacidade de adsorção do H2S nos materiais impregnados com metais alcalinos é reduzida consideravelmente: redução de 37% para Desorex K43-BG e de 65% para amostra Desorex K43-Na. Esta perda de capacidade pode ser devido a competição pelos sítios ativos relacionados à presença de metais, em que H2S e CO2 são co-adsorvidos. Para o carbono ativado não impregnado Sorbonorit B4, a presença de CO2 nestes testes não provoca perda considerável na capacidade de adsorção de H2S.

Research the Selexol, Rectisol, Fluor and Purisol technologies for the treatment of biogas to natural gas quality is the main job. The purified biogas must meet quality requirements, which sets out legislation Czech Republic. An important point is to build models of technology in the ChemCad software. Methods are analyzed with these models for the same output requirements. The result is to determine whether the technologies are suitable for biogas purification and implement, through research, simplified technical and economic evaluation.

Detta är ett examensarbete som genomförts hos Göteborg Energi AB och syftar till att utreda omkryogen uppgradering av biogas med fördel kan ske genom att producera nödvändig kyla medvärmedriven absorptionskylmaskin. Göteborg Energi är en av tre parter som tillsammans ska bygga enbiogasanläggning i Lidköping som ska vara i drift 2010. Anläggningen ska producera 30 GWhflytande biogas per år.

Arbetet utreder om det är fördelaktigt ur ekonomiskt, energimässigt och miljömässigt perspektiv attuppgradera biogas med kryogen teknik med värmeproducerad kyla. En jämförelse görs först medkryogen teknik där kylan är producerad med el och sen med andra uppgraderingstekniker. Som stödhar två olika processimuleringsprogram används, Hysys och DESIGN II.

Resultatet visar att energianvändningen ökar då värmedriven kyla används i jämförelse med kylaproducerad med el. 0,47 kW/Nm3 rågas för kryo med absorptionskyla och 0,29 kW/Nm3 rågas medel. Om det finns avsättning för spillvärmen kan energianvändningen i uppgraderingen minska till 0,29kW/Nm3 rågas och 0,15 kW/Nm3 rågas för systemet med värmedriven respektive eldriven kyla. Ijämförelse med andra uppgraderingstekniker ligger 0,47 kW/Nm3 bland de teknikerna med högstenergianvändning medans 0,29 kW/Nm3 placerar sig bland de teknikerna med lägstenergianvändning.

Resultat visar att klimatpåverkan från uppgraderingen, som kommer av metanslip och elanvändningen,minskar marginellt om kylan produceras med värme istället för el. Resultatet varierar mycket beroendepå hur koldioxidutsläppen från marginalelen beräknas. I jämförelse med andra uppgraderingsteknikerligger kryo lägre än de flesta andra. Undantaget är COOAB-tekniken som är överlägset bäst tack varalågt metanslip och liten elanvändning.

Ekonomisk jämförelse med andra uppgraderingstekniker visar att kostnaden för energianvändningenligger i samma nivå som övriga uppgraderingstekniker i jämförelsen, ca 0,03 kr/kWh uppgraderad gas.Om det finns avsättning för spillvärmen sjunker kostnaden till 0,024 och 0,02 kr/kWh uppgraderad gasför kryoteknik med kyla ifrån värme respektive el.

Min slutsats är att utnyttjande av spillvärmen är av stor vikt för att få god ekonomi och lågenergianvändning med kryogen uppgradering. En marginellt förbättrad miljöprestanda kan erhållas omnödvändig kyla produceras med värme istället för el då kryogen uppgradering används. Annars är detalltid mer fördelaktigt att använda el för att producera nödvändig kyla.

This is a master thesis that has been carried out at Göteborg Energi AB. It refers to investigate ifcryogenic upgrading of biogas with advantage can be done by producing necessary cold with a heatdriven absorption cooling machine. Göteborg Energi is one of three actors that together will build abiogas plant in Lidköping that will be up and running in 2010. The plant will produce 30 GWhliquefied biogas annually.

This thesis investigastes whether it is advantageous, to upgrade biogas with heat driven cooling, in aperspective of economy, energy use and environment. It compares cryogenic upgrading with coldproduced by electricity, but also by other techniques. Two different process simulation softwares havebeen used as support to this thesis; Hysys and DESIGN II.

The result shows that energy usage increases when the necessary cold is produced with heat instead ofelectricity; 0,47 kW/Nm3 rawgas for cryo upgrade with absorptions cooling and 0,29 kW/Nm3 rawgaswith cold produced by electricity. If it’s possible to use the waste heat to warm the digester, the energyconsumption for the upgrading can be reduced to 0,29 kW/Nm3 for the system with heat-driven cold,and 0,15 kW/Nm3 rawgas for cold produced by electricity. In comparison with other techniques forupgrading, 0,47 kW/Nm3 rawgas is a high value while 0,29 kW/Nm3 rawgas is among the lowestvalues for energy use.

The impact on the climate emerges from the use of electricity and when methane slips out from theupgrading plant. The result shows that the impact on the climate is slightly decreased for cryogenicupgrading when the cold is produced with a heat driven absorption machine instead of electricity. Theresult varies a lot due to how one calculate the emission of carbon dioxide from the electricity on themargin. In comparison with other upgrading techniques, the climate impact from cryogenic upgradingis less, other than the COOAB-technique that is superior because of its low methane slip and lowdemand of electricity.

An economical comparison shows that the cost for energy usage is about the same for cryogenic as forother techniques; approximately 0,03 SEK/kWh upgraded gas. If one can utilize the waste heat, thecost would be decreased to 0,024 and 0,02 SEK/kWh upgraded gas for the system with cryogenicupgrading with cooling from absorption machine respectively cooling produced with electricity.

My conclusion is that the utilization of the waste heat is essential if one wishes to get good economyand low energy use for the upgrading of biogas with cryogenic methods. A slightly increasedenvironmental improvement can be received if one change the cold production from electricity to heat,otherwise it is always more advantageous to use electricity for cryogenic methods.

Les systèmes cryogéniques sont l’une des technologies les plus prometteuses et toujours en progrès pour valoriser le biogaz, car elles permettent son épuration sans solvants et possiblement à pression atmosphérique. Dans ce travail, un nouveau concept de récupération de froid par sublimation contrôlée est présenté. Un gaz froid est utilisé en tant que gaz de dégivrage. Il sublimera le givre en utilisant le gradient de pressions partielles entre le givre et la teneur de CO2 dans le gaz au lieu de gaspiller le froid par transfert de chaleur par convection. Avant cette étape, les dépôts de CO2 doivent être étudiés. La formation et la croissance de givre de CO2 sont détaillées et un modèle est présenté pour mieux expliquer comment le CO2 est séparé du biogaz et des dépôts sur une surface froide. Une comparaison entre les configurations de plaque plane et de tube a montré que cette dernière était meilleure pour la capture de CO2 dans un système cryogénique en termes de transfert de chaleur et de masse. Cependant, elle pose un problème de colmatage lorsque le givre augmente à l'intérieur du tube. L'étude de la formation de givre le long du tube a montré un décalage de temps pour le dépôt de givre le long du tube. Un processus d’épuration cryogénique du biogaz et de liquéfaction de biométhane a été présenté avec des calculs pour tous les composants inclus dans le système. Les résultats de la simulation montrent que la récupération de froid est possible par sublimation contrôlée et que la température du tube a atteint des valeurs inférieures à la température initiale, ce qui n'est pas possible par le simple transfert de chaleur par convection. Le concept de vaporisation contrôlée fonctionne mieux pour les faibles concentrations de CO2 dans le biogaz si les phases de givrage et de dégivrage doivent être terminées à durée égale. Enfin, une expérience a été menée pour valider le concept de récupération à froid par sublimation contrôlée. Les résultats montrent que cette technique a le potentiel d’éliminer complètement les utilités froides de certains procédés cryogéniques d’élimination de CO2
Cryogenic systems are one of the most promising and still rising technologies for upgrading biogas as it is solvent free and can operate at atmospheric pressure. In this work a new concept for cold recovery by controlled sublimation is presented. A cold gas flow is used as a defrosting gas that will sublimate the frost using the partial pressure gradient between the frost and the gas flow instead of wasting the cold by convective heat transfer. Prior to this step, CO2 deposition should be studied. CO2 frost formation and growth is thoroughly detailed and a model is presented to better explain how CO2 is separated from biogas and deposits on a cold surface. A comparison between the flat plate and the tube configurations showed that the latter was better for CO2 capture in a cryogenic system in terms of heat and mass transfer but it presents a problem of clogging as frost increases inside the tube. The study of frost formation along the tube showed a delay in the starting time of deposition at position further from the biogas inlet. A process for biogas cryogenic upgrading and biomethane liquefaction was presented with calculations for all the components included in the system. Simulation results show that cold recovery is possible by controlled sublimation and the tube temperature reached values lower to the gas flow temperature which is not possible by single convective heat transfer. The concept works best for lower CO2 concentrations in the inlet biogas if the frosting and defrosting phases are to be completed at the same time. Finally, an experiment was conducted to validate the concept of cold recovery by controlled sublimation, for which results have shown the potential to totally avoid cold utilities use in the cryogenic capture of CO2

Fossil resources provide the raw materials for manufacturing a majority of commodity chemicals and fuels, but the release of this buried carbon accelerates environmental crises related to rising levels of atmospheric CO2. Engineering direct and energy-efficient pathways to synthesize chemicals and fuels from sustainable reagents and using CO2-free renewable energy could mitigate these challenges. Promising strategies for developing such reaction processes utilize non-precious metal catalysts to address kinetic challenges and non-thermal plasma activation to circumvent thermodynamic constraints. Non-precious bimetallic catalysts were employed to selectively convert CO2 with H2 to the building block chemical CO, and in situ X-ray and infrared techniques revealed the properties of the catalytic components. Significant oxygen exchange between the ceria catalyst support material and gas-phase CO2 was quantified under reaction conditions, and NiFe bimetallic catalysts tuned the reaction selectivity while maintaining high activity. In order to eliminate H2 as a reagent, ethane (an underutilized shale gas fraction) was reacted with CO2 to produce alcohols. This reaction is not thermodynamically feasible under mild conditions, so non-thermal/non-equilibrium plasma activation was implemented in order to achieve a one-step, H2-independent process to synthesize alcohols and other oxygenates under ambient temperature and pressure. The ability to use non-thermal plasma to activate N2 at mild conditions introduces the possibility of moving beyond the carbon-based paradigm for chemicals and fuels. Non-thermal plasma has been used to synthesize ammonia under mild conditions, but the dearth of fundamental understanding of plasma-catalyst interactions handicaps the development of plasma catalytic N2 conversion processes. Therefore, an in situ FTIR reactor was employed to identify the surface reaction intermediates during plasma catalytic ammonia synthesis. These results provide the first direct evidence of catalytic surface reactions under plasma activation and reveal the presence of reaction pathways that are distinct from analogous thermocatalytic reactions. Finally, an energy-based analysis evaluates the environmental and economic outlook for plasma-activated nitrogen fixation processes.

碩士
國立臺灣科技大學
化學工程系
107
The storage capability of lithium ion hybrid capacitor can be upgraded through adjusting the mismatched rate qualities between positive and negative electrodes, since the positive electrode of electrostatic double layer (EDL) stores and releases electricity in a lesser quantity, yet much faster than the negative battery electrode. To increase the EDL capacity, a nitrogen-doped carbon (KP-N-900) of hollow-polygon structure is prepared with para-phenylphenol, achieving a surface area above 3000 m2g-1. 　　CNT must be oxidized and electrodepositing metallic antimony on Multi-wall carbon nanotubes, Sb/CNT, evidenced by a capacity approximating 220 mAh g-1 at 5.0 A g-1. 　　On the other hand, The capacitance of KP-N-900 displays a diffusive component 56.8 F g-1 exceeding its capacitive counterpart at 10 mV s-1. And its total capacitance increases to 168 F g-1 at 1 mV s-1 　　Hence, the full cell, with a 2:1 mass ratio of KP-N-900 to Sb/CNT exhibits an effectual trade-off between its energy and power, quite different from the one-sided dependence on the carbon electrode of most hybrid capacitors. Specifically, this 2:1 full cell stores 90 Wh kg-1 at a power level 0.13 kW kg-1, and 4.5Wh kg-1. at power 23.4 kW kg-1

Maize Cob Waste (MCW) is available in high amounts, as maize is the most produced cereal in the world. MCW is generally left in the fields despite its negligible impact in soil fertility. It can be used as substrate in Anaerobic co-Digestion (AcoD) and as precursor to produce Activated Carbons (ACs). In this context, a biorefinery concept was developed based on two purposes: 1) the pretreated MCW can be valorised as co-substrate in the AcoD with Organic Fraction of Municipal Solid Wastes (OFMSW), and 2) MCW can be used as a precursor of ACs for biomethane (bioCH4) conditioning. The AcoD of OFMSW with chemically pre-treated MCW in presence of H2O2 at 23 ºC increased the biogas and CH4 yields by 65% and 48%, respectively, when compared to AD of standalone OFMSW., providing higher biogas quality and a more stable AcoD process than with non-pre-treated MCW. Among the ACs produced, the physically MCW(PA)3h AC performed better in H2S removal than commercial and impregnated by liquid digestate ACs. Textural properties seemed to be more important than the mineral content for H2S removal and the presence of O2 on MCW(PA)3h surface may have favoured H2S catalytic oxidation. The MCW(PA)3h AC was also the most suitable candidate for CO2 separation due to its more favourable textural properties, sufficient selectivity and higher working capacity than the others ACs produced. The adsorption equilibrium measurements of CO2 and CH4 showed that the Sips isotherm model and the Adsorption Potential Theory (APT) can be confidently employed to correlate the experimental data, as well as the axial dispersed plug-flow and Linear Driving Force (LDF) model is able to correlate the fixed bed experimental data. The environmental Life Cycle Assessment of a biorefinery case study was performed on the hypothesis of implementing, at an existing Portuguese Anaerobic Digestion plant processing OFMSW, (i) an AcoD unit using MCW as co-substrate; (ii) an H2S unit using MCW(PA)3h as adsorbent, and (iii) a Pressure Swing Adsorption (PSA) upgrading unit. The cogeneration of the biogas produced during AcoD with non-pre-treated MCW is more sustainable than with pre-treated MCW. The environmental impacts associated with biogas upgrading to bioCH4 at optimized H2S adsorption capacity of MCW(PA)3h, if fossil natural gas used for the OFMSW transport is substituted by the produced bioCH4, decreased significantly, giving lower impacts than cogeneration in five categories.