The global use of natural gas is growing quickly. This is primarily attributed to its favorable characteristics and to the environmental advantages it enjoys over other fossil fuels such as oil and coal. One of the key challenges in supplying natural gas is the form (phase) at which it should be delivered. Natural gas may be supplied to the consumers as a compressed gas through pipelines. Another common form is to be compressed, refrigerated and supplied as a liquid known as liquefied natural gas (LNG). When there is a considerable distance involved in transporting natural gas, LNG is becoming the preferred method of supply because of technical, economic, and political reasons. Thus, LNG is expected to play a major role in meeting the global energy demands. This work addresses the simulation and optimization of an LNG plant. First, the process flowsheet is constructed based on a common process configuration. Then, the key units are simulated using ASPEN Plus to determine the characteristics of the various pieces of equipment and streams in the plant. Next, process integration techniques are used to optimize the process. Particular emphasis is given to energy objectives through three activities. First, the synthesis and retrofitting of a heat-exchange network are considered to reduce heating and cooling utilities. Second, the turbo-expander system is analyzed to reduce the refrigeration consumption in the process. Third, the process cogeneration is introduced to optimize the combined heat and power of the plant. These activities are carried out using a combination of graphical, computeraided, and mathematical programming techniques. A case study on typical LNG facilities is solved to examine the benefits of simulation and integration of the process. The technical, economic, and environmental impact of the process modifications are also discussed.

Liquefied Natural Gas (LNG) is a commonly used flammable fuel that has safety concerns associated with vapor dispersion and radiation emitted from pool fires. The main objective of this effort is to advance the knowledge of pool fires and to expand the data that is commonly used to validate semi-empirical models. This includes evaluation of the methods that are utilized to obtain experimental values of mass burning rates, which are used in models where semi-empirical correlations cannot be applied. A total of three small-size experiments designed to study the radiative characteristics of LNG pool fires were carried out at Texas A & M University's Brayton Fire Training Field (BFTF). This set of experiments was designed to study how the heat feedback from the fire to the pool surface is subsequently distributed through the liquid volume and the validity of different methods for measuring burning rates. In this work, a number of semi-empirical correlations were used to predict the characteristics of the flame and examine the predictive accuracy of these correlations when compared to the values obtained experimentally. In addition, the heat transferred from the energy received at the pool's surface to the surroundings was investigated. Finally, the parameters that influenced the measurement of radiative head feedback to the liquid pool were analyzed to investigate potential causes of calibration drift in the instrumentation. The results of this work provided information regarding the validity of certain techniques for the measurement of mass burning rates and the use of correlations to predict the characteristics of an LNG pool fire on a small-scale. The findings from this work indicate that the energy received at the liquid surface was used entirely for evaporation and no indications of transmission to the surroundings were observed. Lastly, it was found that during the experiments, the sink temperature of the sensor was not constant, and therefore, the readings of the radiative heat were unreliable. This was due to the insufficient cooling effect of the water circulated. It was later shown in the laboratory that through a series of qualitative tests, a change of 20°C in the cooling water resulted in a calibration drift.

The evaluation of the potential hazards related with the operation of an LNG terminal includes possible release scenarios with the consequent flammable vapor dispersion within the facility; therefore, it is important to know the behavior of this phenomenon through the application of advanced simulation tools. Computational Fluid Dynamic (CFD) tools are often used to estimate the exclusion zones in an event of accidental LNG spill. In practice these releases are more likely to occur in the confines of complex geometries with solid obstacles such as LNG terminals, and LNG processing plants. The objective of this research is to study the effects that different obstacles have over the LNG vapor dispersion and the safety distance reduction caused by enhanced mixing. Through parametric analysis it is demonstrated that height, width and shape of the obstacles play an important role in the vapor concentration reduction. The findings of this research may be applied in the design stage of an LNG terminal, to improve the design of passive barriers, and for designing better layout configurations for storage tanks. Simulations results performed with FLACS (Flame Acceleration Simulator), a CFD solver, confirmed that these applications help to reduce safety distances.

No description available.

Os progestagênios isolados são contraceptivos indicados que em trombofílicas e/ou com passado de tromboembolismo venoso (TEV). Algumas dessas mulheres, também utilizam anticoagulantes orais (ATCO) o que pode implicar em alterações no padrão de sangramento menstrual associado ao uso de progestagênios isolados. Objetivo: avaliar os efeitos do uso de ATCO no padrão de sangramento associado ao sistema intrauterino liberador de levonorgestrel (SIU-LNG) em mulheres trombofílicas e/ou com passado de TEV . Métodos: Trata-se de um estudo de coorte prospectiva que dividiu as mulheres trombofílicas e/ou com passado de TEV em dois grupos, usuárias de ATCO e não-usuárias de ATCO. Padrão de sangramento, peso, índice de massa corpórea (IMC) e circunferência abdominal foram comparados entre os grupos antes, 6 e 12 meses após a inserção do SIU-LNG. Resultados: Foram incluídas 33 mulheres, entre 18 e 45 anos, 16 usuárias de ATCO e 17 não-usuárias. Houve aumento de 3,9% do peso e 3,8% do IMC em das usuárias de ATCO após 12 meses da inserção do SIU-LNG (p<0,01). Houve aumento de hemoglobina e hematócrito em ambos os grupos. Não se observou diferença entre o padrão de sangramento de ambos os grupos, sendo a amenorréia o padrão mais frequente nos dois grupos (41,2% em ambos) 12 meses após a inserção do SIU-LNG. Utilizar ATCO não aumentou a freqüência e a duranção de sangramento genital. Conclusão: As usuárias e não-usuárias de ATCO tiveram padrão de sangramento semelhante após a inserção do SIU-LNG. Os níveis de hemoglobina e hematócrito aumentaram em ambos os grupos / Background: Progestogen-only contraceptives (POCs) are suitable for women with thrombophilia and/or a history of venous thromboembolism (VTE). Several of these women, however, use oral anticoagulant therapy (OAT), which can impair the bleeding pattern associated with POC use. We evaluated the effects of OAT use on the bleeding pattern associated with the levonorgestrel-releasing intrauterine system (LNG-IUS) in women with thrombophilia and/or a history of VTE. Study Design: This prospective cohort study followed 2 groups of women, all of whom were thrombophilic and/or had a history of VTE: OAT users and non-users. Bleeding patterns, blood pressure, body mass index (BMI), weight, complete blood count and waist circumference were compared between the 2 groups before and 6 and 12 months after LNG-IUS insertion. Results: The patient cohort consisted of 33 women aged 18 to 45 years old, including 16 OAT users and 17 non-users. Body weight increased by 3.9% and BMI by 3.8% in OAT users 12 months after LNG-IUS insertion (p< 0,01). Hemoglobin and hematocrit levels increased by approximately 10% in both groups. There was no difference between the groups in bleeding patterns, with amenorrhea being the most frequent pattern in both groups (41.2% each) 12 months after LNG-IUS insertion. OAT did not increase the frequency of prolonged and/or frequent bleeding. Conclusion: OAT users and non-users had similar bleeding patterns after insertion of the LNG-IUS. Hemoglobin and hematocrit levels increased in both groups

Sjöfarten står idag inför allt strängare miljökrav. För att uppnå miljövänligare resultat har allt fler rederier börjat se sig om efter ett miljövänligare bränsle. Östersjön är ett stort handelsområde där striktare krav från SECA träder i kraft den 1 januari 2015. Fartyg med LNG-drift diskuteras flitigt som ett alternativt bränsle inom den svenska sjöfartsnärningen, då utsläppen av NOx, svavel och partiklar är mindre än tjockoljan (HFO). Ett av problemen med LNG i Sverige är att det i dagsläget inte finns ett tillräckligt utvecklat infrastrukturnät för flytande naturgas. I denna rapport har vi med hjälp av kvalitativa intervjuer kartlagt svenska aktörer inom LNGs infrastrukturutveckling och vad det är som hämmar utvecklingen. Vår analys av intervjuerna visade att utvecklingen bromsades av att ingen vågat ta första steget. Hamnarna vill inte bygga terminaler om det inte finns en marknad för distribution och rederierna vill inte bygga fartyg om det inte finns tillgänglighet av LNG. Det har också framkommit att intresset från den svenska staten har varit mycket svagt, näst intill obefintligt. Det finns även en del tomrum i de svenska regelverken kring hanteringen av LNG, vilket är en av faktorerna till att LNGs utveckling hämmas. / Shipping today faces stricter environmental requirements for pollution from vessels. Shipping companies have started to look for alternative fuel to achieve better environmental outcome. The Baltic Sea today is a major trading area for shipping . On 1 of January 2015 a new set of brand new and stricter regulation is getting implemented and these regulations are called SECA. Vessel running on LNG as an alternative fuel is today discussed extensively within the Swedish Maritime forum where emissions of NOx, sulfur and particles are less recipients than in heavy fuel oil (HFO). One of todays problems with a LNG distribution in Sweden are that the infrastructure is incomplete and outdated. This report has been built upon qualitative interviews with important actors within the Swedish maritime forum and also what impedes the development of the LNG’s infrastructure. The outcome of the interviews showed that the development has been slowed down because none within the Swedish martime forum have dared to take the first step. The ports does not want to develop terminals when there is no market demand and the shipping companies does not want to build vessel that runs on LNG when there is no market for distribution. Swedish governments involvement has been very weak, almost non-existing. There are also gaps in the Swedish regulations and restrictions of LNG cargo handling. This is aslo one of the factors that the development of LNG has been impeded.

Os progestagênios isolados são contraceptivos indicados que em trombofílicas e/ou com passado de tromboembolismo venoso (TEV). Algumas dessas mulheres, também utilizam anticoagulantes orais (ATCO) o que pode implicar em alterações no padrão de sangramento menstrual associado ao uso de progestagênios isolados. Objetivo: avaliar os efeitos do uso de ATCO no padrão de sangramento associado ao sistema intrauterino liberador de levonorgestrel (SIU-LNG) em mulheres trombofílicas e/ou com passado de TEV . Métodos: Trata-se de um estudo de coorte prospectiva que dividiu as mulheres trombofílicas e/ou com passado de TEV em dois grupos, usuárias de ATCO e não-usuárias de ATCO. Padrão de sangramento, peso, índice de massa corpórea (IMC) e circunferência abdominal foram comparados entre os grupos antes, 6 e 12 meses após a inserção do SIU-LNG. Resultados: Foram incluídas 33 mulheres, entre 18 e 45 anos, 16 usuárias de ATCO e 17 não-usuárias. Houve aumento de 3,9% do peso e 3,8% do IMC em das usuárias de ATCO após 12 meses da inserção do SIU-LNG (p<0,01). Houve aumento de hemoglobina e hematócrito em ambos os grupos. Não se observou diferença entre o padrão de sangramento de ambos os grupos, sendo a amenorréia o padrão mais frequente nos dois grupos (41,2% em ambos) 12 meses após a inserção do SIU-LNG. Utilizar ATCO não aumentou a freqüência e a duranção de sangramento genital. Conclusão: As usuárias e não-usuárias de ATCO tiveram padrão de sangramento semelhante após a inserção do SIU-LNG. Os níveis de hemoglobina e hematócrito aumentaram em ambos os grupos / Background: Progestogen-only contraceptives (POCs) are suitable for women with thrombophilia and/or a history of venous thromboembolism (VTE). Several of these women, however, use oral anticoagulant therapy (OAT), which can impair the bleeding pattern associated with POC use. We evaluated the effects of OAT use on the bleeding pattern associated with the levonorgestrel-releasing intrauterine system (LNG-IUS) in women with thrombophilia and/or a history of VTE. Study Design: This prospective cohort study followed 2 groups of women, all of whom were thrombophilic and/or had a history of VTE: OAT users and non-users. Bleeding patterns, blood pressure, body mass index (BMI), weight, complete blood count and waist circumference were compared between the 2 groups before and 6 and 12 months after LNG-IUS insertion. Results: The patient cohort consisted of 33 women aged 18 to 45 years old, including 16 OAT users and 17 non-users. Body weight increased by 3.9% and BMI by 3.8% in OAT users 12 months after LNG-IUS insertion (p< 0,01). Hemoglobin and hematocrit levels increased by approximately 10% in both groups. There was no difference between the groups in bleeding patterns, with amenorrhea being the most frequent pattern in both groups (41.2% each) 12 months after LNG-IUS insertion. OAT did not increase the frequency of prolonged and/or frequent bleeding. Conclusion: OAT users and non-users had similar bleeding patterns after insertion of the LNG-IUS. Hemoglobin and hematocrit levels increased in both groups

Worldwide concern on reducing global warming consequences has motivated the development of power generation technologies to move towards renewable and sustainable energy. The process takes time and currently, a significant percentage of the world’s electricity systems are driven by fossil fuels. The transition phase from fossil fuel to renewable technology has allowed the combined cycle gas power plant to play an essential role in our global energy mix. This investigation aims to develop scenarios to improve its performance and reduce the carbon footprint during its operation. A baseline scenario of the natural gas combined cycle has been developed using Aspen Hysys software, and the simulation performance is validated with ASME PTC 4-4. The analytical validation results in a 1.13% difference in air and fuel flow rate of 642.95 kg/s compared with 650.28 kg/s as simulation input. Four scenarios are developed following the baseline scenario: seawater cooling and intercooling with LNG cold energy utilization, carbon capture, and hydrogen blending. Those scenarios are compared with three key performance indicators such as system efficiency (%), levelized cost of electricity (USD/MWh), and specific carbon dioxide emissions (gr-CO2/kWh). The analysis shows that sea water cooling with LNG cold energy achieves the highest efficiency of 56.46%, a 0.12% increase compared with the baseline scenario. Hydrogen blending with natural gas achieves the lowest LCOE and specific carbon dioxide footprint of 46.97 USD/MWh and 351.23 gr-CO2/kWh, respectively. The reduction of 12.58 kTon annual carbon dioxide is achieved by implementing 5% hydrogen blending by volume into the combined cycle power generation system. / Världsomfattande oro att minska konsekvenserna av den globala uppvärmningen har motiverat kraftgenereringsteknik att gå mot förnybar och hållbar energiutveckling. Processen tar tid och förnuvarande drivs en betydande andel av världens elsystem av fossila bränslen. Övergångsfasen från fossilt bränsle till förnybar teknik har gjort det möjligt för kombikraftverk att spela en viktig roll i vår globala energimix. Denna rapport syftar till att utveckla scenarier för att förbättra dess prestanda och minska koldioxidavtrycket under dess drift. Ett utgångsscenario för naturgasens kombinerade cykel har utvecklats med hjälp av Aspen Hysys programvara, och simuleringsprestandan är validerad med ASME PTC 4-4. Den analytiska valideringen resulterar i en skillnad på 1,13 % i luft- och bränsleflöde på 642,95 kg/s jämfört med 650,28 kg/s som simuleringsindata. Fyra scenarier utvecklas efter baslinjescenariot: havsvattenkylning och mellankylning med LNG kall energianvändning, kolavskiljning och väteblandning. Dessa scenarier jämförs med tre nyckeltal som systemeffektivitet (%), utjämnad kostnad för el (USD/MWh) och specifika koldioxidutsläpp (gr-CO2/kWh). Analysen visar att havsvattenkylning med LNG kall energi uppnår den största verkningsgraden på 56,46 %, en ökning med 0,12 % jämfört med utgångsscenariot. Vätgasblandning med naturgas uppnår lägsta LCOE och specifika koldioxidavtryck på 46,97 USD/MWh respektive 351,23 gr-CO2/kWh. Minskningen av 12,58 kTon årlig koldioxid uppnås genom att implementera 5 % vätgasblandning i volym i det kombinerade kraftgenereringssystemet.

This thesis evaluates the possibilities of application of LNG (liquefied natural gas) in the Czech Republic. LNG is a relatively new commodity, which has broad use in the world, but as of now, the Czech Republic hasn't entered its market. The main objective of this thesis is to determine whether there exists suitable use for LNG in the Czech Republic today. By analysis and calculation I came to the conclusion, that there are applications that would be economically advantageous and would, in addition, bring other significant benefits, such as reducing emissions. The most perspective is the use of LNG as an alternative truck fuel. Under certain conditions suitable applications are also LNG satellite stations, cogeneration or bus transport. The conclusion of this thesis is that liquefied natural gas has a great potential to expand to the Czech Republic.

<p>This thesis describes a new general purpose dynamic process simulator applied to a natural gas liquefaction plant. More specifically, the Multi Fluid Cascade Process (MFCP). MFCP is the “Statoil Linde LNG Technology Alliance” - a proprietary and patented process for LNG production. This utilizes plate fin and spiral wound heat exchangers, produced by Linde AG, and Nuovo Pignone’s centrifugal compressors. This LNG technology is now being implemented for the Hammerfest baseload LNG project, Snøhvit.</p><p>The simulator is based on first principle conservation laws for energy and mass, and a simplified quasi-steady state momentum equation. Unit models for the process equipment (tanks/pipes, separation tanks, valves, liquid expanders, pumps, compressors, heat exchangers, and PI controllers) are described using rigorous thermodynamics. Equilibrium is assumed for all unit models, and equilibrium and physical properties are predicted with the Swoave-Redlich-Kwong or the Peng-Robinson equation of state.</p><p>Two different model approaches are compared in this work. One approach conserves energy in an enthalpy state, and the other conserves internal energy, the HP formulation and UV formulation respectively. The HP formulation defines a dynamic state for the pressure, and splits the integration of the fast and slow dynamics. The pressure states and the algebraic flow relations are solved by a fully implicit Euler method, while the internal unit model equation is solved locally with tailormade integration routines. The UV formulation, utilizes an analytical Jacobian, and is integrated with both a 1-stage Rosenbrock and freeware BDF codes.</p><p>The UV formulation generates an analytical Jacobian from physical property partial differentials. These property differentials are calculated from a first order approximation of the equilibrium. The equilibrium equations are linearized in dynamic state variables to produce partial differentials of the internal flash variables.</p><p>The simulator is tested on a portable PC. The full MFCP LNG plant is simulated with a fixed time step of 1.0 seconds, for both the HP and UV formulations.</p><p>The HP formulation has 611 ODE states. The UV formulation uses the 1-stage Rosenbrock method integrating a system with 1025 ODE states. The case simulated is a set point step for the LNG temperature controller. The plant is simulated over 9000 seconds. The major process dynamics are sampled every second, and plotted. The average performance of both formulation is better that 7 times real time. The worst local performance of the UV formulation is 1.7 times faster than the HP formulation, but more than 6 times faster than real time. The HP and UV formulations gave significantly different dynamic predictions.</p><p>The BDF codes proved too slow for practical use on the MFCP configuration.</p><p>The dynamic simulators in industry today are typically using a HP formulation, with precalculated thermodynamic data stored in look-up tables. The simulations of the full LNG plant show that simulators, utilizing EOS equilibrium descriptions, soon will be able to compare with modern industry simulators.</p>