Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-01-04T20:02:52Z No. of bitstreams: 1 AnaPaulaDaSilvaPeres_TESE.pdf: 6039953 bytes, checksum: dab3721993c73bd25b03fa484535a768 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-01-05T20:52:08Z (GMT) No. of bitstreams: 1 AnaPaulaDaSilvaPeres_TESE.pdf: 6039953 bytes, checksum: dab3721993c73bd25b03fa484535a768 (MD5) / Made available in DSpace on 2016-01-05T20:52:08Z (GMT). No. of bitstreams: 1 AnaPaulaDaSilvaPeres_TESE.pdf: 6039953 bytes, checksum: dab3721993c73bd25b03fa484535a768 (MD5) Previous issue date: 2014-09-08 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Nos ?ltimos anos, transportadores s?lidos de oxig?nio adequados t?m sido desenvolvidos para serem utilizados em diferentes processos de Recircula??o Qu?mica. O sucesso desta tecnologia est? diretamente relacionado com a reatividade qu?mica e a capacidade de armazenamento de oxig?nio do transportador. Desta forma, a pesquisa no desenvolvimento de novos materiais que possam ser aplicados ao processo torna-se de fundamental import?ncia. Entre os poss?veis candidatos est?o os transportadores baseados em n?quel e cobre por apresentarem propriedades termodin?micas favor?veis. Neste trabalho, aluminatos do tipo MAl2O4 (M=Mg e Ca) e M0,9B0,1Al2O4 (B=Ni e Cu) usados como suportes, foram sintetizados pela rea??o de combust?o assistida por microondas e calcinados a 900?C/2h. Em seguida, os suportes foram impregnados com 10% (m/m) de n?quel ou cobre e, posteriormente calcinados a 600?C/2h para obten??o dos transportadores s?lidos de oxig?nio, que foram caracterizados por Difra??o de raios X (DRX), Microscopia eletr?nica de varredura (MEV) e Redu??o a temperatura programada (RTP). Rea??es simulando o processo de combust?o por recircula??o qu?mica foram realizados atrav?s de ciclos de redu??o/oxida??o, com o objetivo de avaliar a reatividade dos transportadores. A an?lise de DRX mostrou picos de difra??o de estruturas tipo espin?lio. Nos suportes dopados n?o foram verificadas a presen?a de fases secund?rias, sugerindo que todo o metal foi incorporado ? estrutura do espin?lio. Nos transportadores s?lidos de oxig?nio, as fases NiO e CuO foram observadas ap?s a impregna??o das fases ativas sobre os diferentes suportes. Os resultados das avalia??es dos ciclos qu?micos de redu??o/oxida??o revelaram que os TSO?s impregnados com n?quel em diferentes suportes mostraram-se mais ativos, sendo potenciais candidatos para a aplica??o na tecnologia de Recircula??o Qu?mica. / In recent years, solid carriers suitable oxygen have been developed for use in different chemical processes recirculation. The success of this technology is directly related to the chemical reactivity and the oxygen storage capacity of the carrier. Thus, research into the development of new materials that can be applied to the process becomes extremely important. Possible candidates are the carriers based on nickel and copper for presenting favorable thermodynamic properties. In this work, aluminates type MAl2O4 (M = Mg and Ca) and M0,9B0,1Al2O4 (B = Ni and Cu) that are used as supports were synthesized by combustion reactions assisted by microwave and calcined at 900?C/2h. Then, the carriers were impregnated with 10% (m/m) of nickel or copper, and subsequently calcined at 600?C/2h to obtain the solid oxygen carriers, which were characterized by X-ray diffraction (XRD) Microscopy scanning electron microscopy (SEM) and temperature programmed reduction (TPR). Reactions simulating the combustion process by chemical recirculation were performed by cycles reduction/oxidation, in order to evaluate the reactivity of carriers. XRD analysis revealed diffraction peaks of the spinel type structures. In the doped substrates were verified the presence of secondary phases, suggesting that all the metal was incorporated into the spinel structure. In solid oxygen carriers, the NiO and CuO phases were observed after impregnation of active phases on different media. The results of evaluations of chemical cycles reduction/oxidation revealed that TSO's impregnated with nickel in various media were more active and are potential candidates for use in the chemical recirculation technology

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-04-02T13:00:25Z No. of bitstreams: 1 AdolfoLopesDeFigueredo_DISSERT.pdf: 1684722 bytes, checksum: ef8ee8ddf2d878e79c97573773aa969e (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-04-04T16:28:07Z (GMT) No. of bitstreams: 1 AdolfoLopesDeFigueredo_DISSERT.pdf: 1684722 bytes, checksum: ef8ee8ddf2d878e79c97573773aa969e (MD5) / Made available in DSpace on 2018-04-04T16:28:07Z (GMT). No. of bitstreams: 1 AdolfoLopesDeFigueredo_DISSERT.pdf: 1684722 bytes, checksum: ef8ee8ddf2d878e79c97573773aa969e (MD5) Previous issue date: 2016-01-29 / Tecnologias existentes para a captura e sequestro de CO2 tornam o processo muitas vezes invi?vel industrialmente, pois exige um alto consumo de energia, levando a uma redu??o na efici?ncia da planta e aumentando o custo de produ??o. Por isso, a fim de amenizar a emiss?o de gases de efeito estufa, tem-se focado na utiliza??o de energias alternativas e no aumento da efici?ncia na convers?o e utiliza??o de energia. Recircula??o Qu?mica para Combust?o (RQC) e reforma (RQR) est?o entre as melhores alternativas para reduzir a emiss?o de CO2, pois facilitam sua captura com baixo custo e sem perda de efici?ncia energ?tica substancial. O sistema reacional baseia-se na transfer?ncia de oxig?nio do ar para um combust?vel, atrav?s de um transportador s?lido de oxig?nio (TSO) que circula entre dois reatores de leito fluidizado. As rea??es de combust?o ocorrem na superf?cie dos TSO, sendo este, quest?o chave para o desenvolvimento e dimensionamento da tecnologia de RQC. Tendo em vista que ainda h? a necessidade de se estudar o comportamento dos TSOs a fim de obter um transportador adequado para a tecnologia de recircula??o qu?mica, o presente trabalho teve como objetivo realizar um estudo dos TSOs para RQC e RQR, utilizando hidrog?nio, metano e etanol como combust?vel. Dois TSOs, ? base de Ni e Cu, foram avaliados quanto as suas reatividades, bem como o estudo termodin?mico foi realizado para esse processo. Para esse estudo, uma caracteriza??o do TSO ? base de Cu, foi realizada utilizando diferentes concentra??es m?ssicas de Cu. Os resultados mostraram que o aumento da concentra??o de cobre a ser adicionado no suporte diminuiu o tamanho dos poros provocado por uma aglomera??o do metal ativo, restando apenas um percentual na superf?cie. Mudan?as significativas na temperatura de redu??o n?o foram observadas com o a aumento da concentra??o de Cu. Em geral, todos os TSO ? base de Cu atingiram convers?o m?xima, utilizando etanol como combust?vel, mostrando ser bastante reativos. Verificou-se ainda que quanto maior o teor de ?xido met?lico, menor ? a velocidade de rea??o. Para as baixas concentra??es de adi??o de cobre, o modelo de nuclea??o apresentou melhor descri??o dos dados experimentais. J? para as maiores concentra??es de adi??o de cobre e com adi??o de 1% de c?rio, o modelo shrinking core correlacionou melhor os dados experimentais. Com rela??o ao sistema redox CuO/Cu, observou-se que valores altos da constante de equil?brio (Keq) foram obtidos para as temperaturas investigadas, mostrando que a convers?o praticamente completa dos combust?veis ? obtida. O aumento da temperatura provocou uma diminui??o da Keq, por?m altas temperaturas foram necess?rias para a completa redu??o do TSO. A varia??o da energia de Gibbs foi m?nima para as temperaturas relevantes para RQC, indicando que a rea??o de combust?o ocorre de maneira espont?nea. Para o TSO ? base de Ni, amostras comerciais foram utilizadas. Este mostrou ser bem reativo, apresentando convers?es superiores a 90% utilizando como combust?veis H2 e CH4 e CH4 + H2O. Temperaturas altas, em torno de 900 ?C foram necess?rias para uma alta convers?o. O modelo shrinking core obteve uma boa descri??o dos dados experimentais, apresentando baixo erro para convers?es menores que 0,8, enquanto que o modelo de difus?o descreveu melhor os dados experimentais com convers?es superiores a 0,8. / Existing technologies for CO2 capture and sequestration oftentimes make the process industrially infeasible because it demands a high power consumption, leading to a reduction in plant efficiency and increasing the cost of production. Therefore, in order to mitigate the emission of greenhouse gases, has focused on the use of alternative energy and increased efficiency in conversion and use of energy. Chemical Looping Combustion (CLC) and Reform (CLR) are among the best alternatives to reduce CO2 emissions, because they facilitate his capture with low cost and without substantial loss of energy efficiency. The reaction system is based on oxygen transfer on the air into a fuel through a solid oxygen carrier (SOC) which circulates between two fluidized bed reactors. Combustion reactions occur on the surface of the SOC, which is, key issue for the development and sizing from CLC technology. In view of that there is still the necessity of study the behavior of SOCs in order to obtain a suitable carrier for the chemical looping technology, this work had as objective carry out a study of the SOCs for CLC and CLR using hydrogen, methane and ethanol as fuels. Two SOCs, to the based on Ni and Cu, were assessed according their reactivities, as well as the thermodynamic study was performed for this process. For this study, an characterization of SOC to Cu base was perfomed different mass concentrations of Cu. The results showed that the concentration of copper to be added to the support decreased size pore inflict on by sintering of the active metal, leaving only a percentage at the surface. Significant changes in the reduction temperature were not observed with the increase in Cu concentration. In general, all the SOC to Cu base reached maximum conversion using ethanol as fuel, showing to be quite reactive. It was also found that the higher the metal oxide content, the lower the reaction rate. For the addition of low concentrations of copper, the nucleation model showed better description of the experimental data. Already for the higher concentrations of copper addition and with addition of 1% cerium, the shrinking core model correlated better to experimental data. Regarding the redox system CuO / Cu, it was observed that high values of equilibrium constant (Keq) were obtained for the temperatures investigated, showing virtually complete conversion of the fuel is obtained. Increasing the temperature resulted in a decrease of Keq, but higher temperatures are required for complete reduction of the SOC. The variation of Gibbs energy was minimal for the relevant temperatures for CLC, indicating that the combustion reaction occurs spontaneously. For Ni-based SOC, commercial samples were used. This proved to be very reactive, with conversions greater than 90% using CH4 and H2 and CH4 + H2O as fuels. High temperatures, around 900 ?C were required for a high conversion. The shrinking core model obtained a good description of the experimental data presenting low error for lower conversions than 0.8, while the diffusion model described better the experimental data with conversions greater than 0.8.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-03-28T19:07:36Z No. of bitstreams: 1 TiagoRobertoDaCosta_TESE.pdf: 4624767 bytes, checksum: b882489e2f56b6e0d740f5f1aaf85b08 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-03-28T23:57:17Z (GMT) No. of bitstreams: 1 TiagoRobertoDaCosta_TESE.pdf: 4624767 bytes, checksum: b882489e2f56b6e0d740f5f1aaf85b08 (MD5) / Made available in DSpace on 2017-03-28T23:57:17Z (GMT). No. of bitstreams: 1 TiagoRobertoDaCosta_TESE.pdf: 4624767 bytes, checksum: b882489e2f56b6e0d740f5f1aaf85b08 (MD5) Previous issue date: 2016-08-05 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A matriz energ?tica mundial ? basicamente constitu?da a base de combust?veis f?sseis, sendo que diferentes estudos indicam que nas pr?ximas d?cadas n?o haver? mudan?as significativas nesse cen?rio e isso impacta de modo significativo no meio ambiente, pois a queima desses combust?veis para gera??o de energia produz bastante CO2. Sendo o di?xido de carbono o principal g?s de origem antropog?nica, respons?vel pela intensifica??o do efeito estufa. Devido a isso, cientistas e pol?ticos de todo mundo tem sugerido diversas medidas e tecnologias que objetivam a diminui??o das emiss?es de CO2 na atmosfera para as pr?ximas d?cadas. Entre as tecnologias, a Captura e Armazenamento de CO2 (CAC) tem tido um destaque especial nos ?ltimos anos. Estudos realizados pela Ag?ncia Internacional de Energia (International Energy Agency-IEA) quanto o Painel Intergovernamental sobre Mudan?as Clim?ticas (IPCC), sugerindo diversos cen?rios de crescimento econ?micos e de demanda energ?tica, indicam que na maioria dos casos as tecnologias de captura e armazenamento do CO2 contribuem entre 10-55% do esfor?o mundial para reduzir as concentra??es de CO2 na atmosfera at? 2100. Nesse contexto, a combust?o indireta com transportadores s?lidos de oxig?nio (processo Chemical-Looping Combustion-CLC), ? considerada uma das melhores alternativas para reduzir os custos da captura do CO2, principalmente quando comparadas aos processos convencionais, pois n?o necessita da separa??o do CO2 do N2, pois o combust?vel n?o ? misturado diretamente com ar ou oxig?nio. Esta tese de doutorado est? focada no desenvolvimento de cinco transportadores de oxig?nio ? base de mangan?s, os quais foram primeiramente caracterizados com objetivo de determinar quais deles s?o mais promissores para serem avaliados em processos de CLC. As t?cnicas e metodologias de caracteriza??es utilizadas durante a primeira etapa foram: porosimetria por inje??o de merc?rio, resist?ncia ? fratura, difra??o de raios X (DRX), redu??o e oxida??o ? temperatura programada (TPR e TPO), capacidade de transporte de oxig?nio (Roc), composi??o qu?mica, reatividade por termogravimetria e ?ndice de velocidade. Conclu?da essas etapas, verificou-se que os transportadores Mn-ZrMF e Mn-ZrSG apresentaram propriedades apropriadas para serem avaliados em um reator de leito fluidizado descont?nuo, onde os experimentos se assemelham ?s condi??es de CLC. Ao fim dos testes no reator, os transportadores de oxig?nio foram submetidos a algumas t?cnicas de caracteriza??o: DRX, TPR e MEV (Microscopia Eletr?nica de Varredura). O transportador Mn-ZrMF apresentou problemas de aglomera??o durante os testes no reator, sendo considerado inapropriado para prosseguir com os experimentos. Por outro lado, o Mn-ZrSG apresentou elevada reatividade com os combust?veis utilizados (CO > H2 > CH4), n?o sendo verificado o problema da aglomera??o, tendo baixa perda por atrito, com vida m?dia superior a 11.000 horas. Esse material ? bastante promissor para seu uso em CLC de combust?veis s?lidos. / The world?s energy matrix is essentially composed of fossil fuels and different studies show indicate that in the next decades there will be no significant changes in this scenario, which impacts significantly on the environment, since the burning of fossil fuels for power generation gives there main contibution to antropogenic CO2 emissions produces greatest amount of CO2. Carbon dioxide is the main anthropogenic gas responsible for intensifying the greenhouse effect. Because of this, scientists and politicians around the world have suggested a number of strategies and technologies to reduce CO2 emissions to the atmosphere for the next decades. Among these technologies, CO2 capture and storage (CCS) has gained attention in recent years. Studies conducted by the International Energy Agency (IEA) and the Intergovernmental Panel on Climate Change (IPCC) suggest various scenarios of economic growth and energy demand, indicating that in most cases the CO2 capture and storage technologies will contribute between 10-55% of the global effort to reduce CO2 concentrations in the atmosphere by 2100. In this context, the Chemical-Looping Combustion is considered one of the better alternatives to reduce the cost of CO2 capture, especially when compared to conventional capture processes, since it does not require the separation of CO2 from N2, once fuel is not mixed directly with air or oxygen. This doctoral thesis is focused in the development of five manganese-based oxygen carriers, which were first characterized in order to determine which of them are most promising to be evaluated in CLC processes. The techniques and characterization methods used during the first stage were: mercury porosimetry, fracture resistance, X-ray diffraction (XRD), temperature programmed reduction and oxidation (TPR and TPO), oxygen transport capacity (Roc), chemical composition, redox by thermogravimetry and rate index. Completed these steps, it was found that the carriers Mn- ZrMF and ZrSG presented appropriate properties to be evaluated in a discontinuous fluidized bed reactor, where the experiment conditions are subject to the CLC conditions. After the testing reactor, the oxygen carriers were submitted to the following characterization techniques: DRX, TPR and SEM (Scanning Electron Microscopy). Mn-ZrMF carrier presented problems of agglomeration during testing in the reactor, being considered inappropriate for CLC. On the other side, the Mn-ZrSG carrier showed high reactivity with the fuels used (CO> H2> CH4). Due this Mn-ZrSG is appropriate for CO + H2 combustion, but suffer deactivation during CH4 combustion. Do not showed agglomeration problems. The attrition rate was low and the lifetime was than 11.000 hours. Thus this material can be considered suitable to be used in solid fuels CLC.

Made available in DSpace on 2014-12-17T15:42:13Z (GMT). No. of bitstreams: 1 TiagoRC_DISSERT.pdf: 2194143 bytes, checksum: 2a20949c899c91ba3e574d7f71d319d4 (MD5) Previous issue date: 2012-04-11 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Oxygen carriers are metal oxides which have the ability to oxidize and reduce easily by various cycles. Due to this property these materials are widely usedin Chemical-Looping Reforming processes to produce H2 and syngas. In this work supports based on MCM-41 and La-SiO2 were synthesized by hydrothermal method. After the synthesis step they were calcined at 550?C for 2 hours and characterized by TG, XRD, surface area using the BET method and FTIR spectroscopy. The deposition of active phase, in this case Nickel, took place in the proportions of 5, 10 and 20% by weight of metallic nickel, for use as oxygen carriers.The XRD showed that increasing in the content of Ni supported on MCM-41 resulted in a decrease in spatial structure and lattice parameter of the material. The adsorption and desorption curves of the MCM-41 samples exhibited variations with the increase of Ni deposited. Surface area, average pore diameter and wall density of silica showed significant changes , due to the increase of the active phase on the mesoporous material. By other hand, in the samples with La-SiO2 composition was not observed peaks characteristic of hexagonal structure, in the XRD diffractogram. The adsorption/desorption isotherms of nitrogen observed are type IV, characteristic of mesoporous materials. The catalytic test indicates that the supports have no influence in the process, but the nickel concentration is very important, because the results for minor concentration of nickel are not good. The ratio H2/O2 was close to 2, for all 15 cycles involving the test storage capacity of O2, indicating that the materials are effective for oxygen transport / Transportadores de oxig?nio s?o ?xidos met?licos que possuem a capacidade de oxidar e reduzir facilmente por diversos ciclos. Devido a essa propriedade estes materiais s?o bastante utilizados nos processos de Chemical-Looping Reforming para a produ??o de H2 ou g?s de s?ntese (H2 mais CO). Neste trabalho foram sintetizados os suportes MCM-41 e La-SiO2 pelo o m?todo hidrot?rmico. Os materiais resultantes foram calcinados a 550 ?C por 2 horas e, posteriormente, caracterizados por TG, DRX, ?rea superficial pelo m?todo BET e FTIR. Ap?s a caracteriza??o dos suportes foi feita a deposi??o da fase ativa (Ni) com as propor??es de 5, 10 e 20% em massa de n?quel met?lico, para aplica??o como transportadores de oxig?nio. As an?lises de DRX mostraram que o aumento do teor de Ni suportado em MCM-41 deu origem a uma diminui??o no ordenamento estrutural e no par?metro de rede do material. As amostras MCM-41 apresentaram varia??es quanto ?s curvas de adsor??o/dessor??o de nitrog?nio, ?rea superficial, di?metro m?dio de poros e espessura da parede de s?lica, em fun??o do aumento da fase ativa no material mesoporoso. Enquanto que nas amostras com La-SiO2 n?o se observou picos caracter?sticos da estrutura hexagonal, nos difratogramas de DRX. Entretanto, as curvas de adsor??o/dessor??o de nitrog?nio observadas s?o do tipo IV, caracter?stico de materiais mesoporosos. Os resultados dos testes dos transportadores indicam que o suporte n?o influenciou no processo catal?tico. A raz?o H2/O2 foi pr?xima de 2, durante todos os 15 ciclos envolvendo o teste de capacidade de armazenamento de O2 , indicando que os materiais s?o eficientes para o transporte de oxig?nio estrutural e no par?metro de rede do material. As amostras MCM-41 apresentaram varia??es quanto ?s curvas de adsor??o/dessor??o de nitrog?nio, ?rea superficial, di?metro m?dio de poros e espessura da parede de s?lica, em fun??o do aumento da fase ativa no material mesoporoso. Enquanto que nas amostras com La-SiO2 n?o se observou picos caracter?sticos da estrutura hexagonal, nos difratogramas de DRX. Entretanto, as curvas de adsor??o/dessor??o de nitrog?nio observadas s?o do tipo IV, caracter?stico de materiais mesoporosos. Os resultados dos testes dos transportadores indicam que o suporte n?o influenciou no processo catal?tico. A raz?o H2/O2 foi pr?xima de 2, durante todos os 15 ciclos envolvendo o teste de capacidade de armazenamento de O2 , indicando que os materiais s?o eficientes para o transporte de oxig?nio