Chemical looping combustion (CLC) is a technique for separating pure carbon dioxide from the combustion of fuels. The oxygen to burn the fuel comes from the lattice oxygen contained in solid particles of an inorganic oxide (the 'oxygen carrier'), instead of from oxygen in the air. Thus only CO2 and water leave the combustor, or fuel reactor. Next, the water is condensed, leaving pure CO2. The oxygen carrier is regenerated by oxidising it in air in a second reactor, called the air reactor. Accordingly, a stream of pure carbon dioxide can be produced, uncontaminated with gases such as nitrogen, normally present when the fuel burns in air. This intrinsic separation with CLC enables CO2 to be separated more efficiently than with other techniques, such as post-combustion scrubbing of carbon dioxide from stack gases with amine-based solvents. The design of a CLC system and its performance within an electricity system represents a multi-scale problem, ranging from the behaviour of single particles of oxygen carrier within a reactor to how a CLC-based power plant would perform in an electricity grid. To date, these scales have been studied in isolation, with little regard for the vital interactions and dependences amongst them. This Dissertation addresses this problem by considering CLC holistically for the first time, using a multi-scale approach. A stochastic model was developed, combining the particle-and reactor-scales of CLC. It included an appropriate particle model and can be coupled to a detailed reactor model. The combination represented a significant change from existing approaches, uniquely accounting for all the important factors affecting the assemblage of particles performing in the CLC reactors. It was used to determine the regimes of operation in which CLC is sensitive to factors such as the manner in which the particles are reacting, the residence time distribution of particles in the two reactors, the particle size distribution and the reaction history of particles. To demonstrate that the approach could simulate specific configurations of CLC, as well as a general system, the model was compared with results from experiments in which CLC with methane was conducted in a laboratory-scale circulating fluidised bed. The long-term performance of oxygen carrier materials is important, because, in an industrial process, they would be expected to function satisfactorily for many thousands of hours of operation. Long-term experiments were conducted to evaluate the resistance of different oxygen carrier materials to physical and chemical attrition. The evolution of their chemical kinetics was also determined. The results were used to evaluate the impact of different oxygen carrier materials in a fuel reactor at industrial-scale. Finally, a theoretical approach was developed to simulate how a fleet of CLC-based power plants would perform within the UK's national grid. By understanding how different parameters such as capital cost, operating cost and measures of efficiency, compared with other methods of generation offering carbon reduction, desirable design modifications and needs for improvement for CLC were identified by utilising the theoretical and experimental work conducted at the particle- and reactor-scales.

The thesis, entitled 'Investigation of the conversion of fuels in the presence of solid oxygen carriers and the development of a plasma-assisted chemical looping system for H2 production', presents the work of Yaoyao Zheng in the Department of Engineering, University of Cambridge, for the degree of Doctor of Philosophy. The thesis focused on chemical looping conversion of fuels, which employ oxygen carriers to supply oxygen, followed by the regeneration of the reduced oxygen carriers in air. Combustion of a Polish coal-derived char was first carried out in a fluidised bed reactor in the presence of Fe2O3 or ZrO2-supported Fe2O3. CO2 was introduced to the fluidised bed, to allow the char to be gasified in situ, prior to the reaction with the oxygen carriers. The presence of Fe2O3 did not alter the gasification step, given that the gasification of the char was free of external mass transfer limitation. A numerical model was developed to describe the gasification behaviour, as well as predicting the effect of CO on gasification. The inhibition effect of CO on char gasification was found more significant than expected. Combustion of biomass (wood pellets), by Fe2O3 or mayenite-supported CuO was studied in a fluidised bed. This was to understand how efficient the wood pellets were combusted by the oxygen carriers, as well as the distribution of the products. A tar measurement system, based on a plasma reactor, was first developed. With the developed measuring system, it was found that both Fe2O3 and mayenite-supported CuO were efficient for combusting wood pellets. Particularly, the CLOU nature of CuO makes mayenite-supported CuO a promising candidate for direct combustion, without introducing any reactive gaseous oxidant. The final part of the dissertation was focused on developing a plasma-assisted chemical looping system for H2-rich gas production (PCLH) from CH4 at mild temperatures (~ 673 K). SrFeO3-, Fe2O3, and Ni-doped SrFeO3- and Fe2O3 were investigated as the packing material. Total combustion of CH4 was observed in SrFeO3-. The addition of Ni onto SrFeO3- significantly improved the selectivity towards H2; whilst it was only active in the fresh cycle. Fe2O3 was found to be inert for converting CH4; however, the addition of Ni to form NiO/Fe2O3 dramatically improved H2 production and the reactivity maintained high for three redox cycles. The energy cost of such PCLH was comparable to that of water electrolysis.

This thesis encompasses CO2 mitigation using three different processes: i) natural gas-fired combined cycle with chemical looping combustion (CLC), ii) trigeneration of electrical power, hydrogen and district heating with extended CLC, iii) steam-based gasification of biomass integrated in an advanced power cycle. In CLC, a solid oxygen carrier circulates between two fluidised-bed reactors and transports oxygen from the combustion air to the fuel; thus, the fuel is not mixed with air and an inherent CO2 separation occurs. In this thesis, CLC has been studied as an alternative process for CO2 capture in a natural gas-fired combined cycle (NGCC). The potential efficiency of such a process using a turbine inlet temperature of 1200 °C and a pressure ratio of 13 is between 52 and 53 % when including the penalty for CO2 compression to 110 bar. It is shown that this efficiency cannot be further improved by including an additional CO2 turbine. Two conceivable reactor designs for CLC in an NGCC are presented. Top-firing has been studied as an option to overcome a temperature limitation in the CLC reactor system. The degree of CO2 capture is shown versus the temperature in the CLC reactor and its combustion efficiency. CLC has the potential to reach both a higher efficiency and a higher degree of CO2 capture than conventional post combustion CO2 capture technique. However, further research is needed to solve technical problems as, for example, temperature limitations in the reactor to reach this potential. Extended CLC (exCLC) is introduced, in which hydrogen is not only produced but also inherently purified. The potential efficiency of a novel tri-generation process for hydrogen, electricity and district heating using exCLC for CO2 capture is investigated. The results show that a thermal efficiency of about 54% might be achieved. A novel power process named evaporative biomass air turbine (EvGT-BAT) for biomass feedstock is presented. This process contains a steam-based gasification of biomass, which is integrated in an externally fired gas turbine cycle with top-firing. In the EvGT-BAT process, the steam-based gasification is conducted in an entrained-flow tubular reactor that is installed in the SFC as a heat exchanger. The EvGT-BAT process has the potential to generate electrical power from biomass with an efficiency of 41 %.

Chemical-looping combustion is an indirect oxygen combustion strategy, considered to be the most cost-effective power generation technology with the CO2 inherently concentrated. In this process, a solid oxygen carrier is used to transfer oxygen from the air reactor to the fuel reactor, which completely isolates nitrogen in air to meet with fuels. The oxygen carriers in the combustion process are subjected to the severe environments, such as high temperatures, multi-cycle operations, and thermodynamic limitations. Thus, the preparation of an oxygen carrier with high durability and better kinetics under harsh environment could be an essential part of Chemical-looping combustion development. In this study, modified wet impregnation and co-precipitation methods have been developed. The active ingredient is copper(II) oxide, and the supporting material is either directly from titanium(IV) oxide (anatase 99%) or that prepared from other titanium resources such as titanium tetrachloride and tetrabutyl titanate. Preliminary results showed the prepared oxygen carriers functioned properly in the multi-cycles of oxidization and reduction in TGA at different temperatures. Characterization of used oxygen carriers was carried out using techniques of XRD, and SEM-EDS, which provide information for the difference between oxygen carriers from different preparation methods. Through the comparison, the oxygen carrier from the sol-gel preparation method has better dispersion and oxidation activity than those from mechanical mixing, wet-impregnation, and cox precipitation method. Moreover, towards the oxygen carrier from sol-gel method, nucleation model and diffusion models were determined at different reaction periods.

Posttraumatic stress disorder (PTSD) is a debilitating condition that results from the experience of a traumatic event. Natural kinds are mind-independent entities found in nature and are the objects of scientific inquiry. It is common to deny that PTSD is a natural kind, but extant denials assume a thesis of natural kinds that can be called “essentialism”. According to essentialism, many entities are not natural kinds that one would expect should be natural kinds. The homeostatic cluster view of natural kinds offers an alternative that accommodates these cases, including, superficially, the claim that PTSD is a natural kind. I introduce two novel objections to this claim and recommend a distinction aimed to resolve the newly introduced problems.

<p>This thesis encompasses CO₂ mitigation using three different processes: i) natural gas-fired combined cycle with chemical looping combustion (CLC), ii) trigeneration of electrical power, hydrogen and district heating with extended CLC, iii) steam-based gasification of biomass integrated in an advanced power cycle. </p><p>In CLC, a solid oxygen carrier circulates between two fluidised-bed reactors and transports oxygen from the combustion air to the fuel; thus, the fuel is not mixed with air and an inherent CO₂ separation occurs. In this thesis, CLC has been studied as an alternative process for CO₂ capture in a natural gas-fired combined cycle (NGCC). The potential efficiency of such a process using a turbine inlet temperature of 1200 °C and a pressure ratio of 13 is between 52 and 53 % when including the penalty for CO₂compression to 110 bar. It is shown that this efficiency cannot be further improved by including an additional CO₂ turbine. Two conceivable reactor designs for CLC in an NGCC are presented. Top-firing has been studied as an option to overcome a temperature limitation in the CLC reactor system. The degree of CO₂ capture is shown versus the temperature in the CLC reactor and its combustion efficiency. CLC has the potential to reach both a higher efficiency and a higher degree of CO₂capture than conventional post combustion CO₂ capture technique. However, further research is needed to solve technical problems as, for example, temperature limitations in the reactor to reach this potential. </p><p>Extended CLC (exCLC) is introduced, in which hydrogen is not only produced but also inherently purified. The potential efficiency of a novel tri-generation process for hydrogen, electricity and district heating using exCLC for CO₂capture is investigated. The results show that a thermal efficiency of about 54% might be achieved. </p><p>A novel power process named evaporative biomass air turbine (EvGT-BAT) for biomass feedstock is presented. This process contains a steam-based gasification of biomass, which is integrated in an externally fired gas turbine cycle with top-firing. In the EvGT-BAT process, the steam-based gasification is conducted in an entrained-flow tubular reactor that is installed in the SFC as a heat exchanger. The EvGT-BAT process has the potential to generate electrical power from biomass with an efficiency of 41 %.</p>

Varje dag utförs riskbedömningar inom rättspsykiatri och kriminalvård. Syftet med denna uppsats är att undersöka det vetenskapliga underlaget för riskbedömningar. Uppsatsen inleds med en kort beskrivning av i vilka sammanhang riskbedömningar används och den traditionella uppfattningen av hur området och instrumenten har utvecklats. Sedan följer en genomgång av olika studier som behandlar bedömningarnas träffsäkerhet generellt samt mellan olika generationer av bedömningar. Därnäst redovisas och framförs kritik mot validiteten i Psychopathy Checklist Revised (PCL-R, Hare, 1991) och dess tillämpning inom riskbedömningar. Avslutningsvis analyseras psykopatibegreppet utifrån Ian Hackings teorier om ”human kinds” och ”loopingeffekter” och det förs en kort diskussion av tänkbara konsekvenser av och farhågor kring användningen av PCL-R och psykopatibegreppet generellt. / Every day, forensic risk assessments are carried out. The aim of this thesis was to evaluate their scientific grounds. Initially, a short description of the contexts in which risk assesments are carried out, as well as a description of the historical development of risk assesment instruments are provided. A summary of evaluations of different types of risk assessments and their predictive validity is presented, followed by a critique on the validity of the Psychopathy Checklist Revised (PCL-R, Hare, 1991) and its use in risk assesments. The psychopathy construct is analysed in relation to Ian Hacking’s theories of human kinds and looping effects and potential risks and consequences of the application of PCL-R and the psychopathy construct are discussed.

Environmental concerns and energy security are two major forces driving the fossil fuel based energy system towards renewable energy. In this context, hydrogen is gaining more and more attention in this 21st century. Presently, hydrogen is produced from reformation of fossil fuels, a process that could not address above two problems. For this it needs to be produced from a renewable carbon neutral energy source. Biomass has been identified as such a renewable energy source. Conversion of biomass through thermo-chemical gasification process in the presence of steam could provide a viable renewable source of hydrogen. This thesis presents an innovative system based on chemical looping gasification for producing hydrogen-enriched gas from biomass. The other merit of this system is that it produces a pure stream of carbon dioxide by conducting in-process capture and regeneration of sorbent. A laboratory scale chemical looping gasification (CLG) system based on a circulating fluidized bed (CFB) is developed and tested. Experiments conducted to gasify sawdust in CFB-CLG system shows that it could produce a gas with as much as 80% hydrogen and as little as 5% carbon dioxide. A kinetic model is developed to predict the performance of the gasifier of a CFB-CLG system, and is validated against experimental results. To understand the science of biomass gasification in the presence of steam and CaO, a number of additional studies are conducted. It show that for higher hydrogen and lower carbon dioxide concentration in the product gas, the optimum values of steam to biomass ratio, sorbent to biomass ratio, and operating temperature are 0.83, 2.0 and 670oC respectively. In CFB-CLG system the sorbent goes through a series of successive calcination-carbonation cycles. Calcination studies in presence of three alternate media, nitrogen, carbon dioxide and steam show, that steam calcination is best among them. An empirical relation for calcination in presence of three media is developed. Owing to the sintering, irrespective of medium used for calcination, the conversion of CaO reduces progressively as it goes through alternate calcination-carbonation cycles. An additional empirical equation is developed to predict the loss in sorbent’s ability during carbonation.

Thesis (D.Eng.)--University of Delaware, 2006. / Principal faculty advisor: Dennis L. Loftus, School of Education. Includes bibliographical references.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-02-29T21:50:23Z No. of bitstreams: 1 JoseAntonioBarrosLealReisAlves_TESE.pdf: 5550413 bytes, checksum: 4c1d98761f0c020539c60eca7d324bf6 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-03-01T21:55:58Z (GMT) No. of bitstreams: 1 JoseAntonioBarrosLealReisAlves_TESE.pdf: 5550413 bytes, checksum: 4c1d98761f0c020539c60eca7d324bf6 (MD5) / Made available in DSpace on 2016-03-01T21:55:58Z (GMT). No. of bitstreams: 1 JoseAntonioBarrosLealReisAlves_TESE.pdf: 5550413 bytes, checksum: 4c1d98761f0c020539c60eca7d324bf6 (MD5) Previous issue date: 2014-06-09 / O aumento da demanda energ?tica est? sendo atendida em grande parte por reservas de combust?veis f?sseis, que emitem CO2, SOx e v?rios outros gases poluentes. Cresce tamb?m a busca por combust?veis que emitam menos poluentes e que possuam a mesma efici?ncia energ?tica. Neste contexto, o hidrog?nio (H2) vem sendo cada vez mais reconhecido como um potencial carreador de energia para um futuro pr?ximo. Isso ocorre porque o H2 pode ser obtido por diversas rotas e tem uma vasta ?rea de aplica??o, al?m de possuir queima limpa, gerando apenas H2O como produto da queima, e a maior densidade de energia por unidade de massa. O processo de reforma com recircula??o qu?mica (RRQ) vem sendo bastante investigado nos ?ltimos anos, pois ? poss?vel regenerar o carreador de oxig?nio por meio da aplica??o de ciclos de redu??o e oxida??o. Este trabalho tem como objetivo geral desenvolver carreadores de oxig?nio a base de n?quel e cobalto para estudar a reatividade em processo de reforma com recircula??o qu?mica. Os carreadores de oxig?nio foram preparados por tr?s m?todos diferentes: combust?o assistida por microondas, impregna??o por via ?mida e coprecipita??o. Todos os materiais sintetizados possuem a mesma quantidade em massa das fases ativas (60%m/m). Os 40%m/m restantes s?o de La2O3 (8%m/m), Al2O3 (30%m/m) e MgO (2%). Os carreadores de oxig?nio foram nomeados da seguinte forma: N ou C, n?quel ou cobalto, seguido do n?mero 3 ou 6, que significa 30 ou 60% de fase ativa na forma de ?xido e C, CI ou CP, que significa combust?o assistida por micro-ondas, combust?o assistida por micro-ondas seguida de impregna??o por via ?mida e co-precipita??o. Os carreadores de oxig?nio foram ent?o caracterizados atrav?s das t?cnicas de difra??o de raios X (DRX), ?rea espec?fica (BET), redu??o ? temperatura programada (RTP) e microscopia eletr?nica de varredura (MEV). Os resultados de caracteriza??o mostraram que os diferentes m?todos de s?ntese levaram ? obten??o de diferentes estruturas e morfologias. Os testes de redu??o/oxida??o utilizando CH4 como redutor e ar sint?tico como oxidante foram realizados com os carreadores de oxig?nio N6C e C6C, N6CI e C6CI e N6CP e C6CP. Os testes revelaram diferentes comportamentos e que estes dependem do tipo de fase ativa bem como do tipo de s?ntese. O carreador de oxig?nio N6C foi o que produziu mais H2, ao passo que o carreador de oxig?nio C6CI foi o que produziu mais CO2 e H2O, sem ocorr?ncia da forma??o de coque. / Increasing energy demand is being met largely by fossil fuel reserves, which emit CO2, SOx gases and various other pollutants. So does the search for fuels that emit fewer pollutants and have the same energy efficiency. In this context, hydrogen (H2) has been increasingly recognized as a potential carrier of energy for the near future. This is because the H2 can be obtained by different routes and has a wide application area , in addition to having clean burning, generating only H2O as a product of combustion , and higher energy density per unit mass . The Chemical Looping Reforming process (CLR) has been extensively investigated in recent years, it is possible to regenerate the catalyst by applying cycles of reduction and oxidation. This work has as main objective to develop catalysts based on nickel and cobalt to study the reactivity of reform with chemical recycling process. The catalysts were prepared by three different methods: combustion assisted by microwave, wet impregnation and co-precipitation. All catalysts synthesized have the same amount by weight of the active phases (60% w / w). The other 40 % m/m consists in La2O3 (8% w / w), Al2O3 (30% w / w) and MgO (2%). Oxygen carriers have been named as follows: N or C, nickel or cobalt, followed by the number 3 or 6, meaning 30 to 60% of active phase in the oxide form and C, CI or CP, which means self-combustion assisted by microwave, self-combustion assisted by microwave followed by wet impregnation and co-precipitation. The oxygen carriers were then characterized by the techniques of X-ray diffraction (XRD), surface area (BET), temperature programmed reduction (TPR) and scanning electron microscopy (SEM). The characterization results showed that the different synthesis methods have led to obtaining different morphologies and structures. Redox tests using CH4 as reducing agent and sintetic air as oxidant agent was done with N6C and C6C, N6CI and C6CI and N6CP and C6CP oxygen carriers. The tests revealed different behaviors, depending on active phase and on synthesis procedure. N6C oxygen carrier produced high levels of H2. The C6CI oxygen carrier produced CO2 and H2O without carbon deposits.