This thesis investigates the feasibility and benefits of integrating Thermochemical heat Storage (THS) into a CHP (Combined Heat and Power) plant. A case study is done for the CHP-plant in Sala, Sweden, with a maximum heat output of 20.9 MW and maximum electricity output of 9.6 MW. The THS type considered is calcium oxide in a hydroxide system. The fluctuations in electricity price for years 2020, 2030 and 2040 are considered and low-price electricity is used as a charging source for THS. During charging the superheated steam (endothermic reaction) is used to cover some of the district heating demand. The high temperature discharge from the THS is used as reheat in the Rankine cycle. The operations are modeled in Ebsilon and optimization is done in MATLAB using genetic algorithm with the objective to achieve maximum annual revenue. The results suggest that it is not feasible to introduce THS with electricity as a charging source in year 2020, but in 2030 and 2040 THS shows promising potential. The biggest increase in revenue comes from reduced fuel consumption, and, to a lesser extent, increased income from electricity. It is concluded that Calcium hydroxide is a promising candidate for integration into CHP during large electricity price fluctuation. The main drivers for the feasibility of this combination are high fuel price and large fluctuations of electricity price.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-04-08T12:32:34Z No. of bitstreams: 0 / Made available in DSpace on 2016-04-08T12:32:34Z (GMT). No. of bitstreams: 0 / A casca da castanha de caju (CCC), um resíduo agrícola da produção de castanha, proveniente da região nordeste do Brasil foi caracterizada e submetida ao processo de pirólise lenta. As propriedades do bio-carrvão, do bio-óleo e dos gases produzidos foram investigados e potenciais aplicações foram propostas. A CCC foi caracterizada pela seguintes técnicas: análise elementar CHNS, umidade total, conteúdo de cinzas, matérias voláteis, poder calorífico superior e por análise termogravimétrica. A análise termogravimétrica sob fluxo de nitrogênio mostrou que a decomposição é dominada pela degradação da hemicelulose e celulose na faixa de 250 a 350oC e pela decomposição da lignina na faixa de 400 a 500oC. Na presença de ar, o perfil de degradação é semelhante, porém observa-se uma maior degradação da lignina. A pirólise lenta da casca da castanha de caju foi realizada em um reator tipo batelada aquecido por chama ar-GLP sob diferentes fluxos (mL min-1) de nitrogênio ou ar. O sólido obtido (bio-carvão), líquido (fase aquosa + bio-óleo) e a fase gás foram quantificados e caracterizados por diferentes técnicas. Os experimentos realizados sob fluxo de nitrogênio apresentaram um rendimento de cerca de 30, 40 e 30% em massa paras as fases sólido, líquida e gás, respectivamente. Sob fluxo de ar ocorreu uma diminuição no rendimento da fase líquida, principalmente na produção de bio-óleo, e um aumento da fase gás. Os bio-carvões produzidos apresentaram elevados teores de carbono, na faixa de 70-75% em massa, poder calorífico na faixa de 25 a 28 MJ kg-1, características de carbono amorfo, sem morfologias definidas e ausência de poros. Os espectros FTIR de bio-óleos produzidos sob fluxo de nitrogênio apresentaram um aumento da intensidade relativa das bandas cerca de 1700 cm-1 (ν C=O) e 1230 cm-1 (ν C-O) em comparação com os produzidos sob fluxo de ar, o que sugere a presença de grandes quantidades de compostos oxigenados de carbono, como aldeídos, cetonas e ácidos carboxílicos. As análises das fases gás mostraram a predominância de CO2 e CO a temperaturas inferiores a 400ºC e a formação preferencial de H2 acima desta temperatura. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

The replacement of fossil resources through renewable alternatives is one way to mitigate global climate change. Biomass is the only renewable source of carbon available for replacing oil as a refining feedstock. Therefore, it needs to be utilized not just as a fuel but for both biochemical and thermochemical conversion through biorefining. Optimizing and combining various conversion processes using a system perspective to maximize the valorization, biomass usage, and environmental benefits is of importance. This thesis work has evaluated the integration opportunities for various thermochemical conversion processes within a biorefinery system. The aim for all evaluated concepts were syngas production through gasification or reforming. Two potential residue streams from an existing biorefinery were evaluated as gasification feedstocks, thereby combining biochemical and thermochemical conversion. Torrefaction as a biomass pretreatment for gasification end-use was evaluated based on improved feedstock characteristics, process benefits, and integration aspects. A system concept, “Bio2Fuels”, was suggested and evaluated for low-temperature slow pyrolysis as a way to achieve simultaneous biomass refinement and transport driven CO2 negativity. Syngas was identified as a very suitable intermediate product for residue streams from biochemical conversion. Resulting syngas composition and quality showed hydrolysis residue as suitable gasification feedstock, providing some adjustments in the feedstock preparation. Gasification combined with torrefaction pretreatment demonstrated reduced syngas tar content. The co-gasification of biogas and wood in a FBG was successfully demonstrated with increased syngas H2/CO ratio compared to wood gasification, however high temperatures (≥1000°C) were required for efficient CH4 conversion. The demonstrated improved feedstock characteristics for torrefied biomass may facilitate gasification of biomass residue feedstocks in a biorefinery. Also, integration of a torrefaction unit on-site at the biorefinery or off-site with other industries could make use of excess low-value heat for the drying step with improved overall thermal efficiency. The Bio2Fuels concept provides a new application for slow pyrolysis. The experimental evaluation demonstrated significant hydrogen and carbon separation, and no significant volatilization of ash-forming elements (S and Cl excluded)  in low-temperature (<400°C) pyrolysis. The initial reforming test showed high syngas CH4 content, indicating the need for catalytic reforming. The collective results from the present work indicate that the application of thermochemical conversion processes into a biorefinery system, making use of by-products from biochemical conversion and biomass residues as feedstocks, has significant potential for energy integration, increased product output, and climate change mitigation.

Ce travail de thèse porte sur l’étude de la réduction de CO 2 et H 2 O en CO et H 2 au moyen de cycles thermochimiques. Ces cycles utilisent des oxydes métalliques pour réaliser ces réductions en deux étapes, permettant de diminuer la température nécessaire. Dans une première étape endothermique, l’oxyde métallique est réduit à haute température (>1200°C) grâce à un apport d’énergie solaire concentrée. Dans une seconde étape exothermique réalisée à plus basse température (<1200°C), cette espèce réduite est ré-oxydée en présence d’eau ou de CO 2 , produisant H 2 ou CO et régénérant l’oxyde métallique pour un autre cycle. Le mélange de H 2 et CO (syngas), ainsi produit uniquement grâce à de l’énergie solaire peut ensuite être transformé en carburant liquide conventionnel par un procédé catalytique de type Fischer-Tropsch. Cette étude s’intéresse particulièrement aux cycles à base d’oxydes volatiles, ZnO/Zn et SnO 2 /SnO, dont le produit de la première étape de réduction est sous forme gazeuse à la température de réaction, puis se condense sous forme de nanoparticules. Tout d’abord, des moyens et méthodes ont été développés pour l’étude de la cinétique des réactions de réduction à hautes températures, en particulier une méthode inverse utilisant la mesure en ligne de l’oxygène produit dans un réacteur solaire, et un dispositif de thermogravimétrie solaire. Par ailleurs, différents moyens de diminuer la température des réactions de réduction ont été étudiés, à savoir la diminution de la pression et l’emploi d’un agent réducteur carboné. L’impact de la diminution de la pression sur la cinétique de réduction a été quantifié pour SnO 2 et ZnO.Une étude de l’évolution physico-chimique de poudres de SnO durant la deuxième étape d’oxydation du cycle a ensuite été réalisée, montrant l’importance de la réaction de dismutation de SnO en Sn et SnO 2 sur la réactivité des poudres dans la gamme de température étudiée. / This PhD thesis focuses on the study of the CO2 and H2O reduction into CO and H2 using thermochemical cycles. These cycles use metal redox pairs for stepwise reduction at lower temperature. The first step consists of the endothermic high temperature reduction of the metal oxide (>1200°C) using concentrated solar energy. The second step, operated at a lower temperature (<1200°C), uses the reduced specie to reduce CO2 or H2O, yielding CO or H2 and regenerating the metal oxide. The CO and H2 mixture (syngas), produced using solar energy, can then be converted into liquid fuel using a conventional Fischer-Tropsch catalytic process. The study considers more specifically the volatile oxide cycles, ZnO/Zn and SnO2/SnO, for which the reduced specie is obtained in gaseous phase at the reaction temperature, and is then condensed as nanoparticles. First, means and methods for studying the kinetics of reduction reactions at high temperatures were developed, namely an inverse method based on the online analysis of O2 production in a solar reactor and a solar-driven thermogravimeter. In addition, the study of reduced pressure operation and the use of a carbonaceous reducer were considered as efficient means to decrease the operating temperature and to promote a fast reaction. The impact of reduced pressure was quantified for SnO2 and ZnO reduction. A study of the evolution of the morphology and chemistry of the SnO powder during the second oxidation step was then conducted, emphasizing the importance of SnO disproportionation on the powder reactivity.

Les procédés de stockage de chaleur haute température par voie thermochimique solide/gaz présentent un grand intérêt pour des applications à des centrales solaires thermodynamiques. Le couple réactif CaO/Ca(OH)2 est adapté à cette application pour des déstockages entre 350 et 550°C sous des pressions de vapeur entre 0,2 et 2bar. Les paramètres de transferts de chaleur et de masse de lits de Ca(OH)2+GNE ont été évalués au travers de corrélations et d'expérimentations. Des expérimentations ont permis d'atteindre des puissances en réaction de déstockage supérieures à 200kW.m-3 pour des durées compatibles avec les centrales solaires (1 à 15h). Un modèle 2D a été développé, validé et exploité afin d'étudier les influences couplées des différents paramètres sur les performances du TCS. Enfin, l'intérêt de différentes configurations d'intégration du TCS dans la centrale solaire ont été mis en évidence en termes de performances et de puissances thermiques échangées avec les sources et puits. / High-temperature heat storage processes using thermochemical solid/gas reaction exhibit great interest for applications in solar thermodynamic power plants. The reactive pair CaO/Ca(OH)2 is suitable for this recovery step application ranging from 350 to 550°C within steam pressures from 0.2 to 2 bar. Heat and mass transfer Ca(OH)2+GNE beds parameters were evaluated through correlations and experimentations. Experiments achieved recovery reaction powers above 200kW.m-3 for compatible durations with solar power plants (1 to 15 hours). A 2D model was developed, validated and exploited to study the coupled influences of different parameters on the performance of TCS. Finally, the benefit of different configurations of TCS integration within the solar power plant have been highlighted in terms of thermal performances and sources and sinks power exchanges.

Le grippage dans le cas des aciers inoxydables est un phénomène complexe nécessitant une approche multi-échelle et multi-physique. Les 6 nuances d’aciers inoxydables sélectionnées au cours de cette thèse (316L, 316LN, Nitronic60, AISI660, Uranus45N et 17-4PH) ont été étudiées à l’état de réception et après traitements thermochimique de surface de type S3P. Ces matériaux ont subi un essai de grippage selon la norme ASTM G98 et les échantillons qui en résultent ont été caractérisés selon une approche d’abord surfacique (évolution de la morphologie de la surface, observations MEB…) puis en volume, notamment par le biais de l’approche originale de la microstructure (EBSD, DRX et MET notamment). Cette thèse a ainsi permis d’étudier les différents mécanismes intervenant lors du grippage des aciers inoxydables ainsi que d’étudier l’impact de différentes microstructures et composition chimiques sur ce phénomène. / Galling is a complex phenomenon requiring a multi-scale and multi-physical approach. During this thesis, 6 stainless steel grades (316L, 316LN, Nitronic60, AIS1660, Uranus45N et 17-4PH) are studied, both untreated and after S3P thermochemical heat surface treatment. These materials are tested according to ASTM G98 galling test and resulting samples are then characterized. This characterization is at first realized on the surface (surface morphology evolution, SEM investigations...), then on the bulk material, consisting mainly into a microstructural characterization based on EBSD, XRD and TEM investigations. It results from this thesis a better comprehension of the galling mechanisms in the case of stainless steel. The various effects of material composition, microstructure and material properties in general are also discussed.

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[pt] Pelo presente trabalho, buscou-se desenvolver uma ferramenta capaz de analisar e otimizar o uso de pelotas de minério de ferro em processos tradicionais de redução direta do tipo forno cuba. A criação de um modelo termoquímico do processo MIDREX foi proposta e elaborada dentro da PUC-Rio, levando-se também em conta alguns aspectos cinéticos relativos à redução dos minérios e à carburização do ferro-esponja, bem como alguns parâmetros operacionais. Este modelo foi subseqüentemente adaptado para interagir com um segundo modelo termoquímico de forno elétrico a arco da RS Consultants, representando assim a cadeia de fabricação de aço líquido primário pela rota redução direta - forno elétrico a arco. Para o gerenciamento computacional do processo de otimização e interação com os dois modelos acima citados, desenvolveu-se, adicionalmente, um terceiro modelo, o qual foi designado neste trabalho como modelo GESTOR. Um máximo uso de ferro-esponja ― e de pelotas, conseqüentemente ― é objetivado sempre que possível, sob determinadas condições operacionais pré-estabelecidas. A avaliação econômica destes processos foi embasada em conceitos de valor de uso. Alguns resultados são apresentados neste trabalho, para demonstrar a efetividade e o poder de análise da ferramenta e espera-se que os profissionais da Samarco possam fazer uso deste instrumento de trabalho, dando o devido suporte à tomada de decisão à comercialização e ao desenvolvimento de produtos existentes ou novos. / [en] The study at issue searched for developing an innovative tool able to effectively analyze and optimize the industrial usage of iron ore pellets undergoing traditional gas-based direct reduction processes. The creation of a thermochemical model for MIDREX process was proposed and carried out by PUC-Rio, taking into account relevant characteristics related to DRI carburization and reduction kinetics, as well as some important operating parameters. Subsequently, this model was adapted in order to interact with a second thermo-chemical model owned by RS Consultants and able to represent an electric arc furnace operation. In this sense, it has been possible to represent thereby the iron and steelmaking route based on direct reduction and electric arc furnace. For the computational management of the optimization methodology and interaction involving the two models above-mentioned, a third model was developed and referred to as GESTOR model. It was built to maximize the DRI usage ¯ and pellets utilization, consequently ¯ respecting certain operating conditions previously established. Economic assessments shall be made premised upon value in use concepts. Some results are shown in this study, based on a hypothetical scenario, aiming at proving the effectiveness of this tool. Its adoption by Samarco´s experts is expected as an important supportive methodology to help them to make decisions properly concerning both marketing strategies and product development activities.

Increased amounts of available biomass residues from agricultural food production are present widely around the globe. These biomass residues can find essential applications as bioenergy feedstock and precursors to produce value-added materials. This study assessed the production of biogenic silica (SiO2) from different biomass residues in Africa, including cornhusk, corncob, yam peelings, cassava peelings and coconut husks. Two processes were performed to synthesize the biogenic silica. First, the biomass fuels were chemically pre-treated with 1 and 5% w/v citric acid solutions. In the second stage, combustion at 600 °C for 2 h in a muffle oven was applied. The characterization of the untreated biomasses was conducted using Inductively coupled plasma—optical emission spectrometry (ICP-OES), thermal analysis (TG-DTA) and Fourier-transform infrared spectroscopy (FTIR). The resulting ashes from the combustion step were subjected to ICP, nitrogen physisorption, Energy dispersive X-ray spectroscopy (EDX) as well as X-ray diffraction (XRD). ICP results revealed that the SiO2 content in the ashes varies between 42.2 to 81.5 wt.% db and 53.4 to 90.8 wt.% db after acidic pre-treatment with 1 and 5 w/v% acid, respectively. The relative reductions of K2O by the citric acid in yam peel was the lowest (79 wt.% db) in comparison to 92, 97, 98 and 97 wt.% db calculated for corncob, cassava peel, coconut husk and cornhusk, respectively. XRD analysis revealed dominant crystalline phases of arcanite (K2SO4), sylvite (KCl) and calcite (CaCO3) in ashes of the biomass fuels pre-treated with 1 w/v% citric acid due to potassium and calcium ions present. In comparison, the 5 w/v% citric acid pre-treatment produced amorphous, biogenic silica with specific surface areas of up to 91 m2/g and pore volumes up to 0.21 cm3/g. The examined biomass residues are common wastes from food production in Africa without competition in usage with focus application. Our studies have highlighted a significant end-value to these wastes by the extraction of high quality, amorphous silica, which can be considered in applications such as catalyst support, construction material, concrete and backing material.

No description available.