Carbon dioxide CO₂capture through hydrate formation is a novel technology under consideration as an efficient means of separating CO₂from flue/fuel gas mixtures for sequestration and enhanced oil recovery operations. This thesis examines post-combustion capture of CO₂from fossil-fuel power plant flue-gas streams through hydrate formation in a silica gel column. Power plant flue-gas contains essentially CO₂and nitrogen (N2) after suitable pre-treatment steps, thus a model flue-gas comprising 17% co₂and 83% N2 was used in the study. Previous studies employed a stirred-tank reactor to achieve water-gas contact for formation of hydrates; recent microscopic studies involved using water dispersed in silica gel to react with gas, showing potential for improved hydrate formation rates without the need for agitation. This study focuses on macroscopic kinetics of hydrate formation in silica gel to evaluate hydrate formation rates, CO₂separation efficiency and determining optimal silica gel properties as a basis for a CO2 capture process. Spherical silica gels with 30.0 and 100.0 nm pore sizes and 40-75 and 75-200 μm particle sizes were studied to determine pore size and particle size effects on hydrate formation. 100.0 nm pores achieved higher gas uptake and CO₂recovery over the 30.0 nm case. Improved CO₂separation was obtained when 75-200 μm particles with 100.0 nm pores were used. The two effects observed are due to improved gas diffusion occurring with larger pore and particle size, favouring increased hydrate formation. Compared to stirred-tank experiments, results in this study show a near four-fold increase in moles of gas incorporated in the hydrate per mole of water, showing that improved water-to-hydrate conversion is obtained with pore-dispersed water. At similar experimental conditions, CO₂recovery improved from 42% for stirred-tank studies to 51% for the optimum silica (100.0 nm 75-200 μm) determined in this study. Finally, effects of tetrahydrofuran (THF) - an additive that reduces operating pressure were evaluated. Experiments with 1 mol% THF, the optimum determined from previous stirred tank studies, showed improved gas consumption in silica but reduced CO₂recovery, indicating that the optimum concentration for use in silica is different from that in stirred-tank experiments.

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Carbon dioxide CO₂capture through hydrate formation is a novel technology under consideration as an efficient means of separating CO₂from flue/fuel gas mixtures for sequestration and enhanced oil recovery operations. This thesis examines post-combustion capture of CO₂from fossil-fuel power plant flue-gas streams through hydrate formation in a silica gel column. Power plant flue-gas contains essentially CO₂and nitrogen (N2) after suitable pre-treatment steps, thus a model flue-gas comprising 17% co₂and 83% N2 was used in the study. Previous studies employed a stirred-tank reactor to achieve water-gas contact for formation of hydrates; recent microscopic studies involved using water dispersed in silica gel to react with gas, showing potential for improved hydrate formation rates without the need for agitation. This study focuses on macroscopic kinetics of hydrate formation in silica gel to evaluate hydrate formation rates, CO₂separation efficiency and determining optimal silica gel properties as a basis for a CO2 capture process. Spherical silica gels with 30.0 and 100.0 nm pore sizes and 40-75 and 75-200 μm particle sizes were studied to determine pore size and particle size effects on hydrate formation. 100.0 nm pores achieved higher gas uptake and CO₂recovery over the 30.0 nm case. Improved CO₂separation was obtained when 75-200 μm particles with 100.0 nm pores were used. The two effects observed are due to improved gas diffusion occurring with larger pore and particle size, favouring increased hydrate formation. Compared to stirred-tank experiments, results in this study show a near four-fold increase in moles of gas incorporated in the hydrate per mole of water, showing that improved water-to-hydrate conversion is obtained with pore-dispersed water. At similar experimental conditions, CO₂recovery improved from 42% for stirred-tank studies to 51% for the optimum silica (100.0 nm 75-200 μm) determined in this study. Finally, effects of tetrahydrofuran (THF) - an additive that reduces operating pressure were evaluated. Experiments with 1 mol% THF, the optimum determined from previous stirred tank studies, showed improved gas consumption in silica but reduced CO₂recovery, indicating that the optimum concentration for use in silica is different from that in stirred-tank experiments.

Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia e Ciência de Alimentos, Escola de Química e Alimentos, 2007. / Submitted by Caroline Silva (krol_bilhar@hotmail.com) on 2012-09-25T21:54:08Z No. of bitstreams: 1 cultivo de microalgas com gases de combusto formados da gerao termeltrica.pdf: 1291931 bytes, checksum: 947e8e39923ea39e3dd24f11490dae18 (MD5) / Approved for entry into archive by Bruna Vieira(bruninha_vieira@ibest.com.br) on 2012-11-07T00:58:29Z (GMT) No. of bitstreams: 1 cultivo de microalgas com gases de combusto formados da gerao termeltrica.pdf: 1291931 bytes, checksum: 947e8e39923ea39e3dd24f11490dae18 (MD5) / Made available in DSpace on 2012-11-07T00:58:29Z (GMT). No. of bitstreams: 1 cultivo de microalgas com gases de combusto formados da gerao termeltrica.pdf: 1291931 bytes, checksum: 947e8e39923ea39e3dd24f11490dae18 (MD5) Previous issue date: 2007 / O aumento da concentração de gás carbônico na atmosfera tem sensíveis conseqüências ambientais. Nos últimos anos a emissão de CO2 na atmosfera aumentou de 280ppm (1800) para 380ppm (2004), sendo cerca de 22% dessas emissões causadas por plantas de energia termelétrica. Dentre as várias alternativas para captura e utilização de CO2, uma abordagem particularmente interessante é o emprego de microalgas. As microalgas se destacam por apresentarem diversas potencialidades, como fonte de alimento e fonte para obtenção de bioprodutos, e também podem contribuir na redução do efeito estufa, fixando CO2. As microalgas Chlorella e Spirulina apresentam em sua composição alto teor de proteínas, ácidos graxos, sais minerais e pigmentos, e além disso, possuem certificado GRAS(Generally Recognized As Safe), podendo ser utilizadas como alimento sem oferecer risco à saúde humana. A captura do CO2 do gás de combustão de carvão é possível usando microalgas, tanto por separação como por uso direto do gás de combustão, sendo este último mais vantajoso, em função de uma maior economia de energia. Alguns agravantes podem influenciar no uso direto do gás de combustão como a alta temperatura, concentração de CO2 acima de 15% e a presença de SOx, NOx e material particulado (em especial cinzas), dificultando assim, o método direto, a menos que a microalga suporte condições extremas. O objetivo deste trabalho foi estudar a utilização de gases de combustão do carvão provenientes da geração termelétrica, para cultivo de microalgas. Previamente foi realizada seleção de microalgas quanto à resistência a SO2 que pode ser formado da combustão do carvão para geração de energia elétrica. As microalgas estudadas foram Chlorella homosphaera, Scenedesmus obliquus e Spirulina sp. expostas a de 6% de CO2 e 30ppm de SO2. A máxima produtividade de biomassa alcançada foi 0,19 g.L-1.d-1 e concentração celular máxima 2,92 g.L-1, ambos para microalga Spirulina sp. Após estudou-se as microalgas S. obliquus e Spirulina sp. em um sistema de FBRs em série em diferentes concentrações de CO2, SO2, NO e diferentes temperaturas. Foi alcançada concentração celular média máxima de 3,29 g.L-1 e fixação de CO2 máxima de 35,87%, ambos resultados para Spirulina sp. Seguindo o estudo em biofixação de CO2 por microalgas, foram isoladas as microalgas Synechococcus nidulans e Chlorella vulgaris da lagoa de estabilização da Usina Termelétrica Presidente Médici – UTPM/CGTEE, sul do Brasil. As microalgas isoladas foram cultivadas e comparadas com as microalgas Spirulina sp e S.s obliquus, em relação a biofixação de CO2. As microalgas foram expostas a 12% CO2, 60 ppm de SO2 e 100 ppm de NO, simulando um gás de combustão de carvão. A C. vulgaris apresentou comportamento semelhante a Spirulina sp., alcançando 13,43% de fixação diária máxima. Foi determinado o conteúdo lipídico e a composição em ácidos graxos das microalgas Spirulina sp., S. obliquus, S. nidulans e C. vulgaris cultivadas em meio contendo 12% de CO2, 60 ppm de SO2 e 100 ppm de NO à 30ºC. A microalga S. obliquus apresentou o maior teor lipídico (6,18%). Para as demais microalgas o conteúdo lipídico variou de 4,56 a 5,97%. O maior conteúdo em AGMI foi 66,01% para a S. obliquus. Os ácidos graxos poliinsaturados (PUFA) foram alcançados em maior quantidade pelas microalgas Spirulina sp. (29,37%) e S. nidulans (29,54%). Os resultados mostraram que o cultivo de microalgas enriquecido com os gases CO2, SO2 e NO, apresentaram uma biomassa rica em ácidos graxos, podendo estes ser utilizados tanto para a alimentação (ácidos graxos insaturados), quanto para produção de biocombustíveis(ácidos graxos saturados). Além disso, as microalgas estudadas podem contribuir na redução do aquecimento global. / The increasing concentration of carbon dioxide in the atmosphere has sensible environmental consequences. In the recent years the concentration of CO2 in the atmosphere increased from 280ppm (1800) to 380ppm (2004), around 22% of these emissions caused by coal fired power plants. Amongst several alternatives for the capture and application of the CO2, one of the most interesting overviews it is the use of microalgae. Microalgae are gain eminence for presenting potentiality, like a source of nutrients and for biofuels production, besides, they can contribute with the greenhouse gas abatement, fixing CO2. Chlorella and Spirulina presents a high amount of proteins, fatty acids, minerals and pigments in their composition, besides, they have the GRAS certificate (Generally Recognized As Safe), allowing them to be used like food without offer any risk to the human health. The CO2 capture from the coal fired flue gas is possible, as by the separation of the CO2 as by the direct use of the flue gas, being the last one advantageous, due to the major energy economy. Some bottlenecks can influence the direct use of the flue gas like the high temperature of the gas, high CO2 concentration and the presence of SOx, NOx and particulate matter(specially ashes), becoming hard, thus the direct method, unless that the microalga could tolerate extreme conditions. The aim of this work was to study the utilization of coal fired flue gas from power plants in microalgal cultures. Previously, was carried out the selection of the microalgae resistant to SO2, witch can be formed in the coal fired power generation. The studied microalgae were Chlorella homosphaera, Scenedesmus obliquus and Spirulina sp. LEB-18 exposed to 6% CO2 and 30ppm SO2. The maximum biomass productivity was 0.19 g.L-1.d-1 and the maximum cell concentration was 2,92 g.L-1, both for Spirulina sp LEB-18. Later, S. obliquus and Spirulina sp. LEB-18 were studied in a serial FBRs system, at different concentration of CO2, SO2, NO and different temperatures. The average maximum cell concentration obtained was 3,29g.L- 1 and maximum CO2 fixation 35,87%, both results for Spirulina sp. Following the CO2 biofixation study by microalgae, the strains Synechococcus nidulans and Chlorella vulgaris were isolated from Presidente Médici’s wastewater treatment station, south of Brazil. The isolated strains were cultivated and their CO2 biofixation was compared with Spirulina sp and S. obliquus. The microalgae were exposed to 12% CO2, 60ppm SO2 and 100ppm NO, simulating the flue gas. C. vulgaris showed similar behavior to that of Spirulina sp LEB-18, reaching 13,43% of maximum daily fixation. The lipid content and the fatty acids composition were determined for Spirulina sp. LEB-18, S. obliquus, S. nidulans e C. vulgaris, cultivated in a medium with 12% CO2, 60ppm SO2 and 100ppm NO at 30°C. S. obliquus showed the major lipid content (6,18%). For the other microalgae the lipid content ranged from 4,56 to 5,97%. The major AGMI content was 66,01% for S. obliquus. The PUFA were obtained in major amount by Spirulina sp. LEB-18 (29,37%) and S. nidulans (29,54%). The results showed that microalgae cultures enriched with CO2, SO2 and NO, presented a fatty acids rich biomass, being able to be used as like a nutrient source (unsaturated fatty acids), as for biofuels production (saturated fatty acids). Besides, the studied microalgae can contribute for the global warm reduction.

Abstract Non-linear methods have been utilised in modelling the processes on a flue-gas oxygen-content control system of a power plant. The ultimate objective is to reduce NOx and CO emissions by enhancing the control system. By investigating the flue-gas emission control strategy, the major factors affecting the flue-gas emissions have been determined. A simulator has been constructed, and it emulates a real process automation system and its physical processes. The process models of the simulator are: a flue-gas oxygen-content model, a secondary air flow model, a primary air flow model and a fuel feeding screw model (a fuel flow). The effort has been focused on two plant models: the flue-gas oxygen-content model and the secondary air flow model. Combustion is a non-linear, timevariant, multi-variable process with a variable delay. The secondary air model is a non-linear, timeinvariant (in principle), multi-variable system. Both phenomenological modelling (mass and energy calculations) and black-box modelling (neural networks) have been utilised in the Wiener/Hammerstein structures. It is possible to use a priori knowledge in model modifying, and therefore the model of flue-gas oxygen-content can be tuned on site. The simulator with precalculated parameters was tested in a full-scale power plant and a pilot-scale circulating fluidised bed boiler. The results in the power plant were remarkable since NOx emissions decreased significantly without increasing CO emissions.

Carbon dioxide CO₂capture through hydrate formation is a novel technology under consideration as an efficient means of separating CO₂from flue/fuel gas mixtures for sequestration and enhanced oil recovery operations. This thesis examines post-combustion capture of CO₂from fossil-fuel power plant flue-gas streams through hydrate formation in a silica gel column. Power plant flue-gas contains essentially CO₂and nitrogen (N2) after suitable pre-treatment steps, thus a model flue-gas comprising 17% co₂and 83% N2 was used in the study. Previous studies employed a stirred-tank reactor to achieve water-gas contact for formation of hydrates; recent microscopic studies involved using water dispersed in silica gel to react with gas, showing potential for improved hydrate formation rates without the need for agitation. This study focuses on macroscopic kinetics of hydrate formation in silica gel to evaluate hydrate formation rates, CO₂separation efficiency and determining optimal silica gel properties as a basis for a CO2 capture process. Spherical silica gels with 30.0 and 100.0 nm pore sizes and 40-75 and 75-200 μm particle sizes were studied to determine pore size and particle size effects on hydrate formation. 100.0 nm pores achieved higher gas uptake and CO₂recovery over the 30.0 nm case. Improved CO₂separation was obtained when 75-200 μm particles with 100.0 nm pores were used. The two effects observed are due to improved gas diffusion occurring with larger pore and particle size, favouring increased hydrate formation. Compared to stirred-tank experiments, results in this study show a near four-fold increase in moles of gas incorporated in the hydrate per mole of water, showing that improved water-to-hydrate conversion is obtained with pore-dispersed water. At similar experimental conditions, CO₂recovery improved from 42% for stirred-tank studies to 51% for the optimum silica (100.0 nm 75-200 μm) determined in this study. Finally, effects of tetrahydrofuran (THF) - an additive that reduces operating pressure were evaluated. Experiments with 1 mol% THF, the optimum determined from previous stirred tank studies, showed improved gas consumption in silica but reduced CO₂recovery, indicating that the optimum concentration for use in silica is different from that in stirred-tank experiments. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Thesis is focused on calculation of the condenser of flue gas, which is created by burning of natural gas. In the first part is theoretical overview of equations describing film condensation and physical properties of the flue gas. The second part deals with practical thermal calculation of the specified condenser. In third part parametric study is done in which a tempature of cooling water at inlet and the coefficient of excess air are changed. The last part of the thesis is dedicated to geometric design of the flue gas condenser whose required power is 8 MW.

This master`s thesis is focused on possibility of use of flue gas as source of CO2 for algae cultivation in bioreactors. The first part of the master`s thesis is devoted to a qualitative and quantitative description of flue gas sources as CO2 source for algae cultivation. In the thesis industry sectors with the largest share of CO2 emissions on a global scale and in the Czech republic are summarized. On the basis of these data it was possible to determine cheap sources of CO2 for algae cultivation producing valuable biomass and other bio-products. The composition of flue gas from these sources was discussed in this section also with given expected outlook within the following years. The next part of the thesis is devoted to the influence of flue gas properties on algae cultivation. The impact of flue gas individual parameters on cell growth rate, quality and composition of biomass is described there. The description and design of the bioreactor is processed in the next part of the thesis. The experimental part of the thesis was performed on a bioreactor with similar properties. The next part of the thesis describes the effect of light on algae cultivation and the design of a regulation scheme for bioreactor light source. The experimental part of the thesis describes methods used to determine the concentrations of flue gas substances that could pass from flue gas into cultivation medium for algae cultivation to measure the changing composition of the flue gas in the closed experimental bioreactor system. The processed data from experimental measurements are presented and are discussed. The change in the composition of the culture medium for algae (without the presence of algae) due to flue gas aeration was monitored in the experimental part. It includes also the measurement of the change in the composition of the flue gas in time. All obtained and collected information are then summarized and discussed in the final part of the master`s thesis.

Performance testing methods of boilers in transient operating conditions (start, stop and combustion power modulation sequences) need the combustion rate quantified to allow for the emissions to be quantified. One way of quantifying the combustion rate of a boiler during transient operating conditions is by measuring the flue gas flow rate. The flow conditions in chimneys of single family house boilers pose a challenge however, mainly because of the low flow velocity. The main objectives of the work were to characterize the flow conditions in residential chimneys, to evaluate the use of the Pitot-static method and the averaging Pitot method, and to develop and test a calibration method for averaging Pitot probes for low 𝑅𝑅𝑅𝑅.A literature survey and a theoretical study were performed to characterize the flow conditions in in single family house boiler chimneys. The flow velocities under normal boiler operating conditions are often below the requirements for the assumptions of non-viscous fluid justifying the use of the quadratic Bernoulli equation. A non-linear calibration coefficient is required to correct for these viscous effects in order to avoid significant measurement errors. The flow type in the studied conditions changes from laminar, across the transition regime, to fully turbulent flow, resulting in significant changes of the velocity profile during transient boiler operation. Due to geometrical settings occurring in practice measurements are often done in the hydrodynamic entrance region, where the velocity profiles are neither fully developed nor symmetrical. The predicted changes in velocity profiles are also confirmed experimentally in two chimneys.Several requirements set in ISO 10780 and ISO 3966 for Pitot-static probes are either met questionably or not met at all, meaning that the methods cannot be used as such. The main issues are the low flow velocity, viscous effects, and velocity profiles that change significantly during normal boiler operation. The Pitot-static probe can be calibrated for low 𝑅𝑅𝑅𝑅, but is not reliable because of the changing velocity profiles.The pressure averaging probe is a simple remedy to overcome the problems with asymmetric and changing velocity profiles, but still keeping low the irrecoverable pressure drop caused by the probe. However, commercial averaging probes are not calibrated for the characterized chimney conditions and the information available on the performance of averaging probes at low 𝑅𝑅𝑅𝑅 is scarce. A literature survey and a theoretical study were done to develop a method for calibrating pressure averaging probes for low 𝑅𝑅𝑒 flue gas flows in residential chimneys.The experimental part consists of constructing a calibration rig, testing the performance of differential pressure transducers, and testing a prototype pressure averaging probe. The results show good correlation over a wide operation range, but the low 𝑅𝑅𝑅𝑅 characteristics of the probe could not be identified due to instability in the chosen pressure transducer, and temperature correlation for one of the probes while not for the other. The differential pressures produced are close to the performance limitations of readily available transducers and it should be possible to improve the method by focusing on finding or building a suitable pressure transducer. The performance of the averaging method can be improved further by optimizing the geometry of the probe. Another way of reducing the uncertainty would be to increase the probe size relative to the conduit diameter to produce a higher differential pressure, at the expense of increasing the irrecoverable pressure drop.

The Diploma’s work deals with design to use new methods of cleaning the combustion products for the incinerator of biomass, which guarantees removal of dioxins from the combustion products. Thesis depicts methods of cleaning the combustion products, like ADIOX, using ceramic filters, catalytically filters and methods REMEDIA. Thesis compares constituent methods in terms of effectiveness and according to economic analysis applicable to incinerator of biomass-power output 1 MW. Thesis acquaints with the conception of biomass and with thermic processing, which produces dioxins. Thesis processes using biomass in Czech Republic and plan for using in the future. Thesis processes detailed model of filter using the fabric filters REMEDIA. Suggestion of position of the filter and it is connection to original products line of cleaning the combustion products. Increased pressure loss of the new pipework way and increased consumption of ventilator incinerator is calculated for the new connection. In quest of decreasing the thermal loss of combustion products and in quest of increasing safety of operation is calculated and in quest of increasing safety of operation is calculated proposal of isolation for the filter and pipework. In the end of the thesis is depicted using the technology for decreased amount of dioxins from the fly ash from dioxin filter.