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Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-07-26T20:04:29Z No. of bitstreams: 1 RODRIGO ALBUQUERQUE BATISTA – DISSERTAÇÃO (PPGEQ) 2009.pdf: 1371116 bytes, checksum: e83cb01217e145c19452e17728123ea0 (MD5) / Made available in DSpace on 2018-07-26T20:04:29Z (GMT). No. of bitstreams: 1 RODRIGO ALBUQUERQUE BATISTA – DISSERTAÇÃO (PPGEQ) 2009.pdf: 1371116 bytes, checksum: e83cb01217e145c19452e17728123ea0 (MD5) Previous issue date: 2009-03-31 / A destilação é um dos processos de separação mais importantes e que também, mais consomem energia em indústrias químicas e petroquímicas. Portanto sua operação otimizada é condição sine qua non para viabilidade dos negócios. Além do alto consumo, em alguns processos ocorre a formação de compostos azeotrópicos que se mantêm presentes na destilação; estes se classificam entre homogêneos e heterogêneos. Este trabalho abordou a otimização do sistema de purificação de solvente (trem de destilação) de uma das unidades da Braskem, o qual é constituído por duas colunas de destilação e um vaso de flash. A planta onde está localizado o sistema de purificação produz polietilenos de Alta Densidade (PEAD) e de Ultra Alto peso Molecular (PEUAPM) através da tecnologia Slurry. A polimerização é realizada em suspensão de solvente e utiliza reatores do tipo mistura perfeita (CSTR). A perda de solvente e o consumo de vapor representam 80% do custo variável após matérias primas da planta de produção de polietileno de alta densidade tecnologia slurry da MCI – Mitsubishi Chemical Inc. A otimização das colunas de destilação da Planta PE2 da Braskem utilizando modelo termodinâmico de Peng Robinson através do simulador comercial Aspen Plus demonstrou potencial de economia de 1.200.000 R$/ano. / The distillation is the most important separation process in chemical engineer, on the other hand it is the highest industry energy consumer. Therefore, optimized operation is essential to business feasibility. In some process happen the azeotropic moisture is formed that is hold in the distillation section, they can be classified as homogeneous or heterogeneous. This work approached the optimization of the Solvent Purification System (distillation train) from Braskem PE2 unit who is built up from to two distillation columns and one flash drum. The PE2 unit who produce High Density Polyethylene and Ultra High Molecular Weight Polyethylene by slurry process from Mitsubishi Chemical Corporation is localized in Camacari, Brazil. The polymerization is conduced in a solvent suspension and use Continuous Stirred Tank Reactor (CSTR) type. The solvent lost and the steam consumer together the 80% from the variable cost, before raw material, in High Densit y Polyethylene and Ultra High Molecular Weight Polyethylene by slurry process from Mitsubishi Chemical Corporation. The optimization from Braskem PE2 Unit distillation system, using thermodynamic model Peng Robinson through the Aspen Plus commercial simulator presented 1.200.000 R$/y.

Differences in water dynamics between deciduous aspen (Populus tremuloides) and co-occurring evergreen conifer species in the Northern Rocky Mountains result from complex physical and biological interactions. A comprehensive evaluation of individual water transfer mechanisms was used to elucidate the relative importance of several components of the hydro logic cycles of aspen and conifer, and determine which water transfer mechanisms have potential to cause differences in net water yield. Adjacent aspen and conifer stands were monitored to determine snow accumulation and ablation (snow survey), soil moisture recharge (capacitance probes), snowpack sublimation (sublimation pan), transpiration period (thermal dissipation probes), and evapotranspiration (soil water content). Snow accumulation was 34 and 44% higher in aspen during springs of 2005 and 2006, respectively. Ablation rates in aspen (9.58 mm day-1 ) were nearly double that of conifer (4.9 mm day-1). When changes in soil moisture (due to over winter snowmelt) were combined with snow accumulation in 2006, aspen had greater potential (42-83%) for runoff and groundwater recharge. Snowpack sublimation during the ablation period was not different between open, aspen, and conifer sites and comprised -1). Summertime ET rate was higher in an aspen stand (3.6 mm day-1) than in an adjacent conifer stand (2.7 mm day-1) amounting to ~126 mm more water lost over the growing season, but largely reflected post-ablation differences in stored soil water. The net effects of these water transfer processes could result in more watershed water yield from aspen than conifer forests. However, the difference in water yield between these two forests will largely depend on the fate of snow lost from the conifer canopy. Snow intercepted by conifer branches can be removed by the processes of sublimation (reduces water yield) and redistribution (does not affect water yield). Future studies should focus on partitioning the ratio of sublimation to redistribution to predict hydro logic response of vegetation conversions for water yield augmentation in snow-dominated watersheds.

Aspen is a key resource in the Rocky Mountain Region for wildlife forage and habitat, lumber products, scenery, and plays important roles in fire ecology and hydrological processes. There is evidence of aspen decline over much of the Intermountain West for approximately 100 years. In Dixie and Fishlake National Forests, UT, aspen distribution has decreased by nearly half. Causes of this decline are not well understood, although wildlife browsing by ungulates has been implicated as playing a major role. The objective of this research was to examine what soil or plant factors might be involved in wildlife browse choice in aspen. Twenty-two pairs of moderately and intensively browsed sites were studied to identify factors related to browse preferences over two field seasons. In the summer of 2008, sites were sampled in June, July, and August, and in the summer of 2009 sites were sampled in August only. Soils were analyzed for pH, EC, total nitrogen and carbon, and mineral nutrients. Leaf tissue samples were analyzed for defense chemical (tannin and phenolic glycoside) concentrations, mineral nutrients (via acid digestion), acid-detergent fiber, water content, carbon:nitrogen ratio, and non-structural carbohydrate (sugar) concentration. No significant difference in phenolic glycoside concentrations between moderately and intensively browsed sites was found. Tannins were highest in sites with intensive levels of browsing. Iron was significantly higher and zinc lower in intensively than moderately browsed sites. Leaf moisture was also significantly lower in intensively browsed sites. In the absence of differences in phenolic glycosides, ungulates may be selecting browse sites based on iron requirements. Seasonal changes in the studied factors could be identified in 2008. Over the course of the summer, we found significant decreases in nitrogen, phosphorus, potassium, sulfur, zinc, iron, copper, phenolic glycosides, and moisture concentration. Seasonal increases in calcium, sodium, tannins, sugars, acid-detergent fiber, and carbon:nitrogen ratios were observed. The need for large ungulates to obtain specific nutrients may indicate that aspen is in higher demand as a forage at different times of the year, particularly in areas with forages low in these nutrients. Our data suggest that aspen high in iron may be at risk since other factors explaining browsing choice were not significantly different in our study. This information can help identify clones that are at risk and direct resources where and when they are needed most.

With the Paris agreement calling to limit global warming to 2°C below pre-industrial levels, with further efforts to ensure it stays below 1.5°C, the Finnish government passed the Lakihiilen energiakäytön kieltämisestä (416/2019), i.e., Act of Prohibition of Coal Energy,which stipulates that the use of coal as a fuel for heat/electricity production to be bannedfrom 1 May 2029. This affects Helsinki’s energy industry and a key concern to this work is the Salmisaari Combined Heat and Power plant, which is set to be decommissioned. This plant currently generates heat and electricity by using wood pellets and coal to cater toaround 25-45% of the District Heating consumption of the city of Helsinki. To compensate for this decommissioning, there arises a need for more heat production,around 300-500MW of capacity. One alternative is the heat recovery of seawater by utilising the phase change heat of freezing. The present project investigates a technical feasibility study of a system to generate ice slurry, which is then used to extract heat fromseawater at ~0°C via a heat pump. The competitiveness of an ice-slurry based system to state-of-the-art water or ice-based storage is analysed as well. The proposed system is then modelled in Aspen Plus, and the pressure drop characteristics of the generated ice slurry are studied. Finally, a sensitivity analysis of the pressure ratio of the compressor on the performance of the system is studied. Based on prior works, level of commercialisation and technical feasibility, it was found that a vacuum ice generation method, in combination with heat pumps, is a viable solution to cater to the district heating demand of the city. Further, it is concluded that the pressure drop occurring during transport of the ice slurry is quite minimal – less than 0.5% of the total power consumed whilst producing 300MW of district heat. The COP of the system varies between 2.6-2.8 depending on the pressure ratio of the compressor and thus is energy efficient. Overall, the proposed solution seems to be promising and with further socio-techno-economic analysis, this could be the potential alternative to bridge the deficit. / Med Parisavtalet som kräver att den globala uppvärmningen ska begränsas till 2 °C under förindustriella nivåer, med ytterligare ansträngningar för att säkerställa att den håller sigunder 1,5 °C, antog den finska regeringen Laki hiilen energiakäytön kieltämisestä (416/2019), dvs. Förbud mot kolenergi, som föreskriver att användningen av kol som bränsle för värme-/elproduktion ska förbjudas från och med den 1 maj 2029. Detta påverkar Helsingfors energiindustri och en central fråga för detta arbete är Salmisaarikraftvärmeverk, som är planlagt på att avvecklas. Denna anläggning genererar för närvarande värme och elektricitet genom att använda träpellets och kol för att tillgodosecirka 25–45 % av Helsingfors stads fjärrvärmeförbrukning. För att kompensera för denna avveckling uppstår ett behov av mer värmeproduktion, cirka 300-500MW kapacitet. Ett alternativ är värmeåtervinning från havsvatten genom att utnyttja fasförändringsvärmen från frysning. Detta projekt skall undersöka genom en teknisk förstudie olika system för att generera isslurry (en blandning av is och vatten), som sedan används för att utvinna värme från havsvatten vid ~0°C med hjälp av en värmepump. Konkurrenskraften hos ett isslurrybaserat system jämfört mot toppmoderna vatten- eller isbaserad lagrings system analyseras också. Det föreslagna systemet modelleras sedan i Aspen Plus, och tryckfallsegenskaperna hos den genererade isslurryn studeras. Slutligengörs en känslighetsanalys av kompressorns tryckförhållande och dess påverkan på systemets prestanda. Baserat på tidigare arbeten, kommersialiseringsnivå och teknisk genomförbarhet fann denna rapport att genom en metod för att generera vakuumis, i kombination med värmepumpar att en hållbar lösning för att tillgodose stadens fjärrvärmebehov finns. Vidare dras slutsatsen att tryckfallet som inträffar under transport av isslurryn är minimalt- mindre än 0,5 % av den totala energiförbrukningen samtidigt som den producerar 300MW fjärrvärme. Systemets COP varierar mellan 2,6–2,8 beroende på kompressorns tryckförhållande och är därmed energieffektivt. Sammantaget verkar den föreslagna lösningen vara lovande och med ytterligare socio-teknoekonomisk analys kan detta vara ett potentiellt alternati för att brygga underskottet av fjärrvärme.

Hard carbon is an important material for future fossil-free transport systems, as it is a popular choice for the production of anodes for sodium-ion batteries. Biomass is a popular carbonaceous raw material for making hard carbon. It was only noticed at first because it is a renewable energy source, but with the wide application of carbon materials in several fields, industrial manufacturing using biomass as raw material has also been studied a lot. Process simulation of biomass pyrolysis and carbonization to produce hard carbon, pyrolysis gas, and bio-oil are investigated in this thesis work. The model simulation is assumed based on the current operating data and previous literature review, where the first two models use heat exchangers, and the last case uses by-products to generate heat. Economic analysis based on operating expenses and total capital investment is given based on simulated results. The results show that the yield of hard carbon is about 17% under 1000kg/h biomass feedstock, and the economic performance of using heat exchangers is better than that of pyrolysis gas combustion to supply energy. The economic results and break-even point are used to calculate the minimum selling price, payback period, and sensitivity analysis. The calculated minimum selling price for hard carbon is about SEK 20/kg, which is within the range of the current market price, and the payback period is about 16 years. From the sensitivity analysis results, if electricity prices continue to rise, the economics of using cracked gas may become more significant. / Hårt kol är ett viktigt material för framtida fossilfria transportsystem, eftersom det är ett populärt val för tillverkning av anoder till natriumjonbatterier. Biomassa är en populär kolhaltig råvara för att tillverka hårt kol. Det märktes först bara för att det är en förnybar energikälla, men med den breda användningen av kolmaterial inom flera områden har även industriell tillverkning med biomassa som råvara studerats mycket. Processimulering av biomassa pyrolys och karbonisering för att producera hårt kol, pyrolysgas och bioolja undersöks i detta examensarbete. Modellsimuleringen antas baserat på nuvarande driftdata och tidigare litteraturgenomgång, där de två första modellerna använder värmeväxlare och det sista fallet använder biprodukter för att generera värme. Ekonomisk analys baserad på driftskostnader och totala kapitalinvesteringar ges utifrån simulerade resultat. Resultaten visar att utbytet av hårt kol är cirka 17 % under 1000 kg/h biomassaråvara, och den ekonomiska prestandan för att använda värmeväxlare är bättre än för pyrolysgas förbränning för att leverera energi. De ekonomiska resultaten och brytpunkten används för att beräkna lägsta försäljningspris, återbetalningstid och känslighetsanalys. Det beräknade lägsta försäljningspriset för hårt kol är cirka 20 kr/kg, vilket ligger inom intervallet för gällande marknadspris, och återbetalningstiden är cirka 16 år. Om elpriserna fortsätter att stiga från resultaten av känslighetsanalysen kan ekonomin med att använda krackad gas bli mer betydande.

Fresh water resources in many of the world's oil producing regions, such as western Texas, are scarce, while produced water from oil wells is plentiful, though unfit for most applications due to high salinity and other contamination. Disposing of this water is a great expense to oil producers. This research seeks to advance a technology developed to treat produced water by reverse osmosis and other means to render it suitable for agricultural or industrial use, while simultaneously reducing disposal costs. Pilot testing of the process thus far has demonstrated the technology's capability to produce good-quality water, but process optimization and control were yet to be fully addressed and are focuses of this work. Also, the use of renewable resources (wind and solar) are analyzed as potential power sources for the process, and an overview of reverse osmosis membrane fouling is presented. A computer model of the process was created using a dynamic simulator, Aspen Dynamics, to determine energy consumption of various process design alternatives, and to test control strategies. By preserving the mechanical energy of the concentrate stream of the reverse osmosis membrane, process energy requirements can be reduced several fold from that of the current configuration. Process control schemes utilizing basic feedback control methods with proportional-integral (PI) controllers are proposed, with the feasibility of the strategy for the most complex process design verified by successful dynamic simulation. A macro-driven spreadsheet was created to allow for quick and easy cost comparisons of renewable energy sources in a variety of locations. Using this tool, wind and solar costs were compared for cities in regions throughout Texas. The renewable energy resource showing the greatest potential was wind power, with the analysis showing that in windy regions such as the Texas Panhandle, wind-generated power costs are approximately equal to those generated with diesel fuel.

Les risques sont inhérents à l’activité industrielle. Les prévoir et les maîtriser sont essentiels pour la conception et la conduite en sécurité des procédés. La réglementation des risques majeurs impose aux exploitants la réalisation d’études de sécurité quantitatives. La stratégie de maîtrise des risques repose sur la pertinence des analyses de risques. En marche dégradée, la dynamique des événements est déterminante pour quantifier les risques. Toutefois, de nos jours cette connaissance est difficilement accessible. Ce travail propose une méthodologie d’analyse de risques quantitative qui combine la méthode HAZOP, le retour d’expérience et la simulation dynamique de dérives de procédés. Elle repose sur quatre grandes étapes : La première étape est l’étude du fonctionnement normal du procédé. Pour cela, le procédé est décrit de façon détaillée. Des études complémentaires de caractérisation des produits et du milieu réactionnel sont menées si nécessaires. Ensuite, le procédé est simulé dynamiquement en fonctionnement normal. Lors de la seconde étape, parmi les dérives définies par l’HAZOP et le retour d’expérience, l’analyste discrimine celles dont les conséquences ne sont pas prévisibles et/ou nécessitent d’être quantifiées. La troisième phase fournit une quantification du risque sur la base de la simulation dynamique des scenarii retenus. Lors de la dernière étape, des mesures de maîtrise des risques sont définies et ajoutées au procédé lorsque le niveau de risque est supérieur au risque tolérable. Le risque résiduel est ensuite calculé jusqu’à l’atteinte de la cible sécurité. Le logiciel Aspen Plus Dynamics est sélectionné. Trois études de cas sont choisies pour démontrer d’une part, la faisabilité de la méthodologie et d’autre part, la diversité de son champ d’application : · la première étude de cas porte sur un réacteur semi-continu siège d’une réaction exothermique. L’oxydation du thiosulfate de sodium par le peroxyde d’hydrogène est choisie. Ce cas relativement simple permet d’illustrer la diversité des causes pouvant être simulées (erreur procédurale, défaut matériel, contamination de produits, …) et la possibilité d’étudier des dérives simultanées (perte de refroidissement du milieu et sous dimensionnement de la soupape de sécurité). · le deuxième cas concerne un réacteur semi-batch dans lequel une réaction exothermique de sulfonation est opérée. Elle est particulièrement difficile à mettre en œuvre car le risque d’emballement thermique est élevé. Cette étude montre l’intérêt de notre approche dans la définition des conditions opératoires pour la conduite en sécurité. · le troisième cas d’étude porte sur un procédé continu de fabrication du propylène glycol composé d’un réacteur et de deux colonnes de distillation en série. L’objectif est ici d’étudier la propagation de dérives le long du procédé. Sur la base du retour d’expérience, deux dérives au niveau du rebouilleur de la première colonne sont étudiées et illustrent les risques de pleurage et d’engorgement. La simulation dynamique illustre la propagation d’une dérive et ses conséquences sur la colonne suivante. / Risks are inherent to industrial activity. Predicting and controlling them is essential to the processes design and safe operation. Quantitative safety studies are imposed by the major hazard regulations. The risk management strategy relies on the relevance of risk analyzes. In degraded conditions, the dynamics of events are decisive for risks quantification. However, nowadays this knowledge is a real challenge. This work proposes a methodology of quantitative risk analysis, which combines the HAZOP method, the lessons learned from previous accidents and the dynamic simulation of process deviations. It is based on four main stages: The first stage is the study of the process normal operation. For this, the process is described in detail. Additional studies to characterize the products and the reaction are carried out if necessary. Then, the process is dynamically simulated in normal operation conditions. During the second step, among all the deviations defined by the HAZOP and lessons learned, the analyst discriminates those whose consequences are not predictable and/or need to be quantified. The third phase provides a risk quantification based on the dynamic simulation of the selected scenarios. In the last step, safety barriers are defined and added to the process when the risk level is greater than the tolerable risk. The residual risk is then calculated until the safety target is reached. Aspen Plus Dynamics software is selected. Three case studies are chosen in order to demonstrate, on the one hand, the feasibility of the methodology and, on the other hand, the diversity of its scope: · the first case study is a semi-continuous reactor with an exothermic reaction study. The oxidation of sodium thiosulfate by hydrogen peroxide is selected. This relatively simple case illustrates the diversity of causes that can be simulated (procedural error, material defect, product contamination …) and the possibility of studying simultaneous deviations (loss of cooling and under sized safety valve for example). · the second case concerns a semi-batch reactor in which an exothermic reaction of sulphonation is carried out. This reaction is particularly difficult to conduct because of the thermal runaway high risk. This study shows our approach’s interest in the definition of the operating conditions for safe operation. · the third case study concerns a continuous process of propylene glycol production. It is composed of a reactor and two distillation columns in series. The objective is to study the propagation of deviations along the process. Based on lessons learned, two deviations in the first column reboiler are studied and illustrate the flooding and weeping risks. Dynamic simulation illustrates the propagation of a deviation and its consequences on the second column

Orientadores: Maria Regina Wolf Maciel, Betânia Hoss Lunelli / Tese (doutorado) ¿ Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-26T13:48:19Z (GMT). No. of bitstreams: 1 Ardila_YuranyCamacho_D.pdf: 7705979 bytes, checksum: 19a2840a168991456944a44d857667ee (MD5) Previous issue date: 2015 / Resumo: A produção de biocombustíveis a partir da biomassa apresenta-se como uma alternativa para suprir as limitadas reservas de petróleo. A biomassa, atualmente, está sendo usada para diferentes processos termoquímicos, entre os quais a gaseificação é o de maior destaque. A gaseificação produz gás de síntese que é uma mistura, principalmente, de CO, H2 e CO2. Este gás serve para produzir energia, diferentes produtos químicos e biocombustíveis, como por exemplo, o bioetanol. A partir do gás de síntese, a produção de bioetanol pode ser realizada usando catalisadores químicos ou biocatalisadores, sendo este último processo conhecido como fermentação do gás de síntese. Para o processo integrado de gaseificação da biomassa e posterior fermentação para produção de bioetanol, as informações na literatura são escassas, o que dificulta avaliar a viabilidade desta nova tecnologia, em termos de condições operacionais. O uso de modelos matemáticos e sua simulação computacional podem auxiliar neste estudo. A literatura dispõe de vários estudos envolvendo simulações computacionais aplicadas à gaseificação de diferentes biomassas. Porém, poucos abordam a caracterização real do processo e as propriedades da biomassa utilizada, considerando apenas as propriedades para o carvão mineral, o que acaba gerando divergência nos resultados. Além disso, a maioria fundamenta suas simulações em modelos simples com base na caracterização elementar-imediata, que acaba limitando o desenvolvimento de plantas virtuais, que são baseadas na análise composicional da biomassa quando focadas na produção de bioetanol como etapa final ou como integração do processo. Assim, este trabalho tem como objetivos estudar o processo completo de gaseificação e realizar um estudo preliminar da fermentação do gás de síntese, mediante simulações computacionais, para definir as melhores condições e variáveis que afetam o processo global quando o bagaço de cana-de-açúcar é utilizado como matéria-prima. As simulações foram desenvolvidas utilizando o simulador comercial Aspen Plus¿ e os resultados validados com dados experimentais da literatura e dados obtidos nos Laboratórios LDPS/LOPCA/BIOEN/FEQ/UNICAMP. Para a completa simulação do processo, várias etapas foram estudadas e divididas para melhor entendimento. Foram desenvolvidos modelos matemáticos para predizer propriedades necessárias para o desenvolvimento de processos termoquímicos. Simulações baseadas nas análises elementar-imediata e composicional da biomassa foram realizadas para definir a decomposição inicial da biomassa, demonstrando os diferentes rendimentos e produtos que são gerados e que são a base da etapa inicial da gaseificação. Simulações completas da gaseificação foram desenvolvidas para estudar a gaseificação em diferentes tipos de reatores. A influência das condições de operação na gaseificação como temperatura, razão de equivalência (ER), injeção de vapor e temperatura do pré-aquecedor do ar no desempenho do gaseificador foram avaliadas. Com as condições operacionais da gaseificação definidas foi proposta uma simulação para representar a fermentação do gás de síntese. A partir dos resultados obtidos foi constatado que a composição do gás de síntese é alterada pelo aumento do ER e pela injeção de vapor no processo, e diferentes concentrações de bioetanol são obtidas quando a pressão de entrada do gás de síntese é alterada / Abstract: The production of biofuels from biomass is presented as an alternative to save the limited oil reserves. Currently, biomass is being used for different thermochemical processes, including gasification which is the most prominent. Gasification produces synthesis gas which is a mixture mainly of CO, H2 and CO2. This gas is used to produce energy, several chemicals and biofuels, such as ethanol. The ethanol from synthesis gas may be produced using chemical catalysts or biocatalysts, this latter process is known as fermentation of syngas. The information in the literature is scarce for the integrated gasification of biomass and subsequent fermentation to produce ethanol, making it difficult to see the feasibility of this new technology, in terms of operating conditions. The use of mathematical models and their computer simulation can help this study. Typically, numerous studies involving computer simulations, applied to different biomass gasification, are found in the literature. However, few of them approach the real characterization of process and properties for used biomass, considering only the properties for coal, which ends up generating divergence in the results. Moreover, most of the simulations are grounded on simple models based on proximate-ultimate characteristics, which end up limiting the development of virtual plants, which are based on biomass compositional analysis when focused on the production of ethanol as the final step or as integration process. Thus, the aims of this work are to study the complete gasification process and to carry out a preliminary study of synthesis gas fermentation, through computer simulations, in order to define the best conditions and variables that affect this global process when sugarcane bagasse is used as raw material. The simulations were developed using Aspen Plus ¿ simulator and the results validated with experimental data from literature and data obtained in the laboratories LDPS / LOPCA / BIOEN / FEQ / UNICAMP. For the full simulation of the process, several steps were studied and divided for a better understanding. Mathematical models were developed to predict properties required for the development of thermochemical processes. Simulations based on biomass analysis as proximate-ultimate and compositional were done to define the initial decomposition of biomass, demonstrating the different yields and products that are generated and which are the basis of the initial stage of the gasification. Complete simulations of gasification were carried out to study different types of gasification reactors. The influence of operating conditions at gasification performance was investigated; variables such as temperature, equivalence ratio (ER), steam injection and preheater temperature were evaluated. With the set conditions of gasification was proposed a simulation to represent the fermentation of syngas. It was demonstrated that the synthesis gas composition is changed when increased the ER and steam injection; and different ethanol concentrations are obtained when the input pressure of the synthesis gas is changed / Doutorado / Desenvolvimento de Processos Químicos / Doutora em Engenharia Quimica

One of the most crucial issues nowadays is the protection of the environment and the replacement of fossil fuels, which are abundantly used around the world, with more efficient and renewable sources. The highest portion of global energy demands today is used in heating and cooling purposes. One way of alleviating the fossil-based thermal energy uses is to harvest excess thermal energy using thermochemical storage materials (TCMs) for use at heating/cooling demands at different times and locations. Along this, in this master’s thesis, a bench-scale thermochemical heat storage (TCS) system is numerically designed, as a part of a collaborative project: Neutrons for Heat Storage (NHS), funded by Nordforsk. The TCS system that is designed herein employs the reversible chemical reaction of ammonia with a metal halide (MeX) for a heat storage capacity of 0.5 kWh, respectively releasing and storing heat during absorption and desorption of ammonia into and from the MeX. This system is designed for low temperature heat applications, around 40-80 °C. SrCl2 is chosen as the metal halide to be used, based on the research outcomes in determining the most suitable materials conducted by NHS project partners. In the ammonia-SrCl2 system, only the absorption and desorption between SrCl2∙NH3 and SrCl2∙8NH3 are considered. The main reason is because absorption/desorption between the last ammine and SrCl2 undergoes at a significantly higher/lower reaction pressure (for a given temperature), with a significant volume change compared to the rest of the ammines, and therefore is practically less cost effective. This thesis also includes a detailed discussion of four different thermochemical storage designs from literature, found as the most relevant to the present TCS system study, which use the reaction between ammonia and metal halides. The first system that was examined is a TCS system built by the NHS project partners at Technical University of Denmark (DTU), owing to its similarities with the desired project, regarding the design and parameters the system uses. This system works in batch mode, only allowing either absorption (i.e. heat release) or desorption (i.e. heat storage) at a given cycle. Thus, upgrading the design of this TCS system at DTU is considered as a most-likely solution to the research objectives of this current thesis project. Moreover, the TCS system at DTU uses storage conditions and desorption temperature similar to the current project’s desired low temperature range of 40-80 °C. The second system discussed herein from literature uses two reactors for cold and heat generation, which means that both charging and discharging processes occur simultaneously. This simultaneous operability is the main reason that this particular system was examined in this thesis. The next discussed system from literature also uses two reactors, for absorption and desorption processes, which work reversibly when each process is completed, like in the desired concept of this project. These two systems (i.e., the secondly and the thirdly discussed systems) use the reversible solid-gas reaction for absorption and desorption between SrCl2∙NH3 and SrCl2∙8NH3, however, the conditions of pressure and temperature between them differ. The second system from literature operates at desorption and absorption at respective conditions of 96 °C, 15 bar and 87 °C, 11 bar while the third system discussed operates at 103 °C, 16 bar and 59 °C, 3 bar during desorption and absorption respectively. The last system from literature that is discussed herein provides the same desorption temperature of 80 °C. Inaddition this particular study suggests that the reaction of solid with gaseous NH3 is better (than the solid with liquid NH3 reaction) based on results derived from several different low-pressure experiments of the reactions. The main differences between all these discussed systems from literature, as opposed to the desired TCS system design in this thesis project, concern the systems’ operating mode and the pressure and temperature-conditions. The first difference is that only one of the examined systems pumps the solid VIII powder salt around the system in contrast to the others that keep the salt static inside the reactors and pumped only the ammonia around the system, as chosen in the current system. The second difference concerns the operating conditions during absorption and desorption reactions, where these different systems operate at a widely different pressure and temperature conditions as compared to the current system expectations. Thus, there are four main lessons that were learnt via this literature analysis, to improve the TCS system at DTU to the desired new system in this work. The first lesson is related to the reactants’ transportation mechanism that should be used in this system. Regarding this, it was decided to maintain the solid salt (metal halide) stationary inside each reactor (but not pumping it instead of ammonia), similar to the majority of designs discussed from literature. According to the second and third lessons, the solid-gas reaction is the most suitable solution and only the reactions of absorption and desorption between SrCl2∙NH3 and SrCl2∙8NH3 are considered, following the experience from literature (for the reasons explained earlier). The last lesson regards the system’s suitable operating conditions and more specifically the TCS system’s temperatures that should match the district heating temperatures. Thus, the temperature point that was chosen as a priority was 80 °C, from the range 40- 80 °C set in the partner project NHS. To maintain this condition, therefore, the most suitable condition of pressure of both reactions (according to the equilibrium pressure vs temperature curve) was chosen to be at around 8 bar. This same pressure was chosen for both reactions, since the pressure difference between these reactors and the storage of ammonia (i.e. from 8 to 10 bar) should be as small as possible due to the high costs that can arise in the case of a higher pressure difference (i.e. requiring more compressors and heat exchangers). Inspired by these literature cases, firstly a conceptually suitable TCS system was proposed in this project and after that the final desired system was designed and was implemented and evaluated numerically. The numerical design and optimization of the chosen TCS system was performed herein by using the software Aspen Plus (version 9), which contains both fluids and solids in a simulation environment, using consistent physical properties. This TCS system is designed to store and release heat at around 80 °C and 8 bar through absorption and desorption by using two identical reactors respectively. Each reactor includes the amount of around 1 kg (more specifically 0.985 kg) strontium chloride salt reacting with 1.7 kg of ammonia. A verification system is also modelled in Aspen, using available experimental data from literature. Here, the modelled novel system design was adapted to this chosen other system layout from literature which uses the same reaction pair, yet at different operating conditions. This adapted system design in Aspen was then used to verify the chosen configuration and the reliability of the constructed system for the NHS project. Good agreements between the modelled results in Aspen against the available experimental data of this verification model are obtained. A sensitivity analysis is also conducted herein on the proposed novel TCS system to identify the optimum operating conditions and the behaviour of the chosen most important parameters of the system. The designed system provides an energy storage capacity of 0.5 kWh for the specific amounts (in volumetric flow rates) of ammonia and monoammine of strontium chloride, that comes from the analysis, of 1.08696 e-05 kmol/s and 1.5528 e-06 kmol/s respectively. For these specific values of the HTF, the analysis showed that the volumetric flow rates of the heat and cold external sources must be 1.56 l/min (which is decreasing with the increase of the inlet HTF temperature) and 0.42 l/min (which is increasing with the increase of the inlet HTF temperature) respectively. In conclusion, this study presents an ammonia-SrCl2 TCS benchscale system design that allows continuous heat storage and release, in an easy-to-scale up design, also suggesting optimum operating conditions. / En av de mest avgörande frågorna i dag är skyddet av miljön och utfasningen av fossila bränslen som används allmänt över hela världen för mer effektiva och förnybara resurser. Den största delen av den globala energibehovet idag avser uppvärmnings- och kylapplikationer. Ett sätt att minska fossilbaserad termiskenergianvändning är att lagra överskottsvärmeenergi genom termokemiska lagringsmaterial (TCM) och använda den för värme- och kylbehov vid olika tidpunkter och platser. I samband med detta är ett termokemiskt värmelagringssystem numeriskt utformat i detta mastersexamensprojekt, som en del av ett samarbetsprojekt Neutrons for Heat Storage (NHS) finansierat av Nordforsk. Det termokemiska lagringssystemet (TCS) som är konstruerat utnyttjar den reversibla kemiska reaktionen av ammoniak med en metallhalogenid (MeX) för en värmelagringskapacitet på 0.5 kWh, och frigör och lagrar värme respektive under absorption och desorption av ammoniak till och från MeX. Systemet är designat för lågtemperaturuppvärmningstillämpningar runt 40-80 °C. SrCl2 väljs som det mest lämpliga metallhalogeniden för systemet, baserat på studier som utförts av NHS-projektpartnerna. I ammoniak SrCl2-systemet beaktas endast absorption och desorption mellan SrCl2NH3 och SrCl28NH3. De huvudsakliga orsakerna till detta är att absorptionen/desorptionen mellan den sista aminen och SrCl2 kräver ett betydligt högre/lägre reaktionstryck (för en given temperatur), och resulterar i en betydande volymförändring jämfört med resten av aminerna, och är därför praktiskt taget mindre kostnadseffektivt. Detta mastersexamensprojekt inkluderar en detaljerad genomgång av fyra olika TCS-system från litteratur som använder reaktionen mellan ammoniak och metallhalogenider. Dessa väljs här eftersom dessa anses vara de mest relevanta (från litteratur) jämfört med det valda systemet i denna studie. Det första undersökta systemet är ett system byggt av NHS-projektpartnerna vid Danmarks Tekniska Universitet (DTU). Detta har valts på grund av likheterna med det önskade systemet i det aktuella mastersexamensprojektet, vad gäller systemdesign och parametrar. Detta system fungerar i batch-läge, vilket endast tillåter antingen absorption (dvs värmeavgivning) eller desorption (dvs värmelagring) under en specifik cykel. Således kan en uppgraderad design av detta TCS-system vid DTU möjligen vara en lämplig lösning på forskningsmålen för detta mastersexamensprojekt. Dessutom använder detta TCS-system från DTU ganska liknande driftsförhållanden (temperaturer och tryck) i nivå med det aktuella projektets önskade lågtemperaturintervall på 40-80 °C. Det andra systemet från den litteratur som diskuterats använder två reaktorer för kyla och värmeproduktion, vilket innebär att både laddningsoch urladdningsprocesser sker samtidigt. Denna samtidiga operation är främst anledningen till att systemet undersöktes, eftersom detta är en önskad funktion att uppnå i det aktuella projektet. Nästa system från den litteratur som diskuteras häri använder också två reaktorer för absorptions- och desorptionsprocesser, som fungerar reversibelt när varje process är klar, precis som önskat i detta projekt. Dessa två system (dvs det andra och det tredje diskuterade systemen) använder den reversibla fastgasreaktionen för absorption och desorption mellan SrCl2NH3 och SrCl28NH3, dock vid olika tryck- och temperaturförhållanden. Det andra systemet arbetar nämligen under kombinationer av absorption och desorption av 96 °C, 15 bar och 87 °C, 11 bar, medan det tredje systemet arbetar vid 103 °C, 16 bar respektive 59 °C, 3 bar. Det sista systemet som diskuterats från litteraturen arbetar vid samma temperatur som det önskade systemet gör (dvs. 80 ° C) och genom olika lågtrycksexperiment visar att den fasta salt-gasreaktionen är ett bättre val än reaktionen av det fasta saltet med flytande gasreaktion. De viktigaste skillnaderna mellan alla dessa diskuterade system från litteratur i motsats till det önskade TCS-system i detta mastersexamensprojekt, avser systemdriftläge samt deras tryck och X temperaturförhållanden. Den första skillnaden är att endast ett av alla undersökta system pumpar saltet i fast pulverform, till skillnad från de andra som håller saltet stillastående i reaktorerna och endast pumpar ammoniak. Den andra skillnaden gäller driftsförhållandena under absorptions- och desorptionsreaktioner där dessa system arbetar vid mycket olika tryck- och temperaturförhållanden jämfört med det nuvarande systemet. Således, från översynen av alla system, finns det fyra huvudsakliga lärdomar för att förbättra TCS-systemet vid DTU till det önskade nya systemet. Den första är relaterad till reaktanttransportmekanismen som bör användas i detta system. I detta avseende har det beslutats att hålla det fasta saltet (metallhalogenid) stillastående i varje reaktor (men inte pumpa det istället för ammoniak), till skillnad från de flesta system i litteraturen. Enligt dem andra och tredje lektionerna är den fasta gasreaktionen den mest lämpliga lösningen och endast reaktionerna på absorption och desorption mellan SrCl2∙NH3 och SrCl2∙8NH3 bör övervägas enligt erfarenheten från litteraturen (av de skäl som förklarats tidigare). Den sista lärdomen avser systemets lämpliga driftsförhållanden och mer specifikt TCS-systemets temperaturer för att matcha fjärrvärmetemperaturerna. Den temperaturpunkten valts som prioritet, från området 40-80 °C inställt av moderprojektet NHS, sattes till 80 °C. För att bibehålla detta tillstånd var det lämpligaste tryckvillkoret för båda reaktionerna (enligt jämviktstrycket kontra temperaturkurva) valdes att ligga på cirka 8 bar. Samma tryck valdes för båda reaktionerna, eftersom tryckskillnaden mellan dessa reaktorer och lagring av ammoniak (dvs. från 8 till 10 bar) borde vara så liten som möjligt på grund av de höga kostnaderna som kan uppstå vid högre tryckskillnad (dvs. fler kompressorer krävs och värmeväxlare). Inspirerad av denna litteratur föreslogs för det första ett konceptuellt lämpligt TCS-system i detta mastersexamensprojekt, varefter det slutliga systemet implementerades och utvärderades numeriskt för de önskade förhållandena. Den numeriska utformningen och optimeringen av det valda TCS-systemet utfördes här med hjälp av programvaran Aspen Plus (version 9), som innehåller både vätskor och fasta ämnen i en simuleringsmiljö, med konstant fysiska egenskaper. Detta TCS-system är utformat för att lagra och släppa värme vid cirka 80 °C och 8 bar genom absorption och desorption med användning av två identiska reaktorer respektive. Varje reaktor innefattar cirka 1 kg (närmare bestämt 0.985 kg) strontiumkloridsalt reagerande med 1.7 kg ammoniak. Ett verifieringssystem modelleras också i Aspen med hjälp av tillgängliga experimentella data från litteraturen. I detta anpassades den modellerade nya systemdesignen till denna valda andra verifieringssystemlayout från litteratur, som använder samma reaktionspar, men under olika driftsförhållanden. Denna anpassade systemdesign i Aspen användes sedan för att verifiera den valda konfigurationen och tillförlitligheten för det designade systemet för NHS-projektet. Här erhålls ett bra avtal för denna verifieringssystemdesign mellan Aspenmodellresultaten och experimentdata. Här utförs också en känslighetsanalys för det utformade TCSsystemet i det aktuella projektet för att identifiera de optimala driftsförhållandena och beteendet för de valda viktigaste parametrarna i systemet. Det konstruerade systemet ger en energilagringskapacitet på 0.5 kWh för de specifika mängderna (i volymflöde) av ammoniak och monoamin av strontiumklorid, som kommer från analysen, av 1.08696 e-05 kmol/s och 1.5528 e-06 kmol/s respektive. För dessa specifika värden på värmeöverföringsvätskan visade analysen att de volymetriska flödeshastigheterna för värme och kalla yttre källor måste vara 1.56 l/min (vilket minskar när temperaturen på värmeöverföringsvätskan ökar) och 0.42 l/min (som ökar när temperaturen på värmeöverföringsvätskan ökar). Sammanfattningsvis presenterar denna studie ett ammoniak-SrCl2 TCS-bänkskålsystem som möjliggör kontinuerlig värmelagring och frigöring, har en design som är lätt att anpassa och föreslår också optimala driftsförhållanden.