Analysis of the Behaviour of Biofuel-Fired Gas Turbine Power Plants

The utilisation of biofuels in gas turbines is a promising alternative to fossil fuels for power generation. It would lead to significant reduction of CO2 emissions using an existing combustion technology, although significant changes seem to be needed and further technological development is necessary. The goal of this work is to perform energy and exergy analyses of the behaviour of gas turbines fired with biogas, ethanol and synthesis gas (bio-syngas), compared with natural gas. The global energy transformation process (i.e. from biomass to electricity) has also been studied. Furthermore, the potential reduction of CO2 emissions attained by the use of biofuels has been determined, considering the restrictions regarding biomass availability. Two different simulation tools have been used to accomplish the aims of this work. The results suggest a high interest and the technical viability of the use of Biomass Integrated Gasification Combined Cycle (BIGCC) systems for large scale power generation.

Gesti��n del boil off gas en la planta de regasificaci��n de Cartagena

Este proyecto trata sobre la gesti��n del boil-off gas, o BOG (vapor de gas natural que se produce en las instalaciones de gas natural licuado de las plantas de regasificaci��n), generado en la planta de regasificaci��n de Gas Natural Licuado de Cartagena, tanto en las situaciones en las que se opera por debajo del m��nimo t��cnico, como en las cargas y descargas de buques, en las cuales se ha de gestionar una cantidad del boil-off adicional. Para recuperar el boil-off, las plantas cuentan con un relicuador (intercambiador de calor) en el que el BOG es relicuado por el GNL que se env��a a los vaporizadores para ser regasificado y emitido a la red. De forma complementaria cuentan tambi��n con una antorcha/venteo donde se quema el exceso de boil-off que no puede ser tratado por el relicuador. Se procede a un an��lisis de la situaci��n actual, y de c��mo la baja demanda de regasificaci��n dificulta la gesti��n del boil-off. Se simula el proceso de relicuaci��n actual en distintas situaciones de operaci��n. Ante la situaci��n de baja demanda, ha aumentado considerablemente el n��mero de d��as en los que las plantas espa��olas en general, y la planta de Cartagena en particular, operan por debajo del m��nimo t��cnico, que es el nivel de producci��n m��nimo para recuperar todo el boil-off generado en cualquier situaci��n de operaci��n al tiempo que mantiene en fr��o todas las instalaciones, y garantiza el 100% de disponibilidad inmediata del resto de los equipos en condiciones de seguridad de funcionamiento estable. Esta situaci��n supone inconvenientes tanto operativos como medioambientales y acarrea mayores costes econ��micos, a los cuales da soluci��n el presente proyecto, decidiendo qu�� alternativa t��cnica es la m��s adecuada y defini��ndola. Abstract This project is about the management of the boil-off gas (BOG), natural vapour gas that is produced in liquefied natural gas (LNG) regasification plants. Specifically, the study is focused on the LNG regasification plant located in Cartagena, when it operates both below the technical minimum level of regasification and in the loading/unloading of LNG carriers, situations when it is needed to handle additional BOG. In order to make the most of BOG, the plants have a re-condenser (heat exchanger). Here, the BOG is re-liquefied by the LNG that is submitted to the vaporizers and delivered to the grid. The plants also have a flare/vent where the excess of BOG that cannot be treated by the re-condenser is burned. An analysis of the current situation of the demand is performed, evaluating how low markets demand for regasification difficult the BOG management. Besides, it is simulated the current re-liquefaction operating in different environments. Due to the reduction of the demand for natural gas, the periods when Spanish LNG regasification plants (and particularly the factory of Cartagena) are operating below the technical minimum level of regasification are more usual. This level is the minimum production to recover all the BOG generated in any operating situation while maintaining cold all facilities, fully guaranteeing the immediate availability from other equipment in a safely and stable operation. This situation carries both operational and environmental drawbacks, and leads to higher economic costs. This project aims to solve this problem, presenting several technical solutions and deciding which is the most appropriate.

Evaluaci��n ambiental de las tecnolog��as de recuperaci��n de gas en formaciones no convencionales

Este proyecto pretende ofrecer una visi��n general de una de las tecnolog��as m��s actuales de recuperaci��n de gas en formaciones no convencionales: fracturaci��n hidr��ulica o ���fracking���. El proyecto est�� motivado por la necesidad de responder a diferentes cuestiones sobre los efectos ambientales, sociales y en la salud humana derivados de la utilizaci��n de esa tecnolog��a. Ofrece, adem��s, una descripci��n del proceso y utilizaci��n de la tecnolog��a haciendo especial menci��n de los riesgos inherentes de su uso, aunque tambi��n se intenta establecer una v��a de aceptaci��n para su desarrollo cuyo fin ��ltimo, a parte de los beneficios econ��micos de quienes la usan, es el de posibilitar la transici��n hacia el uso de unos recursos (energ��as f��siles de extracci��n no convencional) que requieren de dichas t��cnicas para mantener, a lo largo del tiempo, el suministro de una energ��a que se supone m��s respetuosa con el medio ambiente: el gas natural. En primer lugar se expone, a modo introductorio, la necesidad de utilizaci��n de nuevas t��cnicas de estimulaci��n de pozos y su utilizaci��n para satisfacer las necesidades energ��ticas mundiales en los pr��ximos a��os. A continuaci��n se hace una revisi��n del marco regulatorio aplicable al gas no convencional. Seguidamente, se hace una descripci��n de los recursos y fuentes no convencionales de gas y la descripci��n del proceso de fracturaci��n hidr��ulica. Se analizan los incidentes relacionados con su desarrollo y las posibilidades y mecanismos que pueden adoptarse para reducirlos. Finalmente, se proponen v��as alternativas basadas en las mejores t��cnicas aplicables al uso de la tecnolog��a, cuya finalidad sea la mayor consideraci��n ambiental posible y el menor riesgo posible en la salud de las personas. ABSTRACT This project aims to provide an overview of the latest technologies in gas recovery unconventional formations: hydraulic fracturing or "fracking". The project is motivated by the need to respond to various questions on the environmental, social and human health arising from the use of this technology. It also offers a description of the process and use of technology with special mention of the inherent risks of their use, but also tries to establish a path of acceptance for development whose ultimate goal, apart from the economic benefits of those who use is of enabling the transition to the use of certain resources (fossil energy extraction unconventional) which require such techniques to maintain, over time, of an energy supply which is more environmentally friendly: natural gas. First discussed the need to use new well stimulation techniques and their use to meet the world's energy needs in the coming years. Below is a review of the regulatory framework applicable to unconventional gas. Next, there is a description of resources and unconventional sources of gas, and the description of the process of hydraulic fracturing. We analyze the incidents related to its development and the possibilities and mechanisms that can be taken to reduce them. Finally, we suggest alternative routes based on the best techniques applicable to the use of technology, aiming at the highest possible environmental consideration and the least possible risk to the health of people.

Identificaci��n de los riesgos ambientales y sanitarios de la producci��n de gas mediante fracturaci��n hidr��ulica y bases para una propuesta metodol��gica de vulnerabilidad de las aguas subterr��neas

Hasta ahora, la gran mayor��a de los recursos explotados de gas natural proced��an de acumulaciones convencionales de gas aislado y de gas asociado y disuelto en el petr��leo. Sin embargo, el gas natural se encuentra tambi��n en yacimientos que, debido a su baja porosidad y permeabilidad, tienen unas caracter��sticas que hacen que hasta muy recientemente no hayan sido econ��micamente rentables y que s��lo puedan ser explotados mediante t��cnicas no convencionales, dando lugar al denominado gas no convencional. Las t��cnicas utilizadas para su extracci��n son la fracturaci��n hidr��ulica o ���fracking��� y la perforaci��n horizontal. Entre los diversos tipos de gas no convencional, es de prever que el gas de pizarra sea el que sufra mayor desarrollo a medio plazo en nuestro pa��s, por lo que se est��n generando grandes debates, debido al riesgo de contaminaci��n de las aguas superficiales y subterr��neas del entorno, provocados por la elevada cantidad de agua utilizada, los aditivos empleados, los fluidos de retorno, por la alteraci��n del medio f��sico, as�� como por la dificultad de monitorizaci��n de estos procesos. En este proyecto se identifican los riesgos ambientales y sanitarios asociados a la extracci��n de gas no convencional. El trabajo se basa principalmente en experiencias ocurridas en pa��ses donde el fracking se ha convertido en una pr��ctica habitual. Se trata adem��s de establecer las bases necesarias para la estimaci��n de la vulnerabilidad de los acu��feros frente a la contaminaci��n inducida por la fracturaci��n hidr��ulica. Abstract Until now, most of the natural gas resources exploited were from isolated conventional gas accumulations and associated and dissolved gas in oil. However, the natural gas is also in reservoirs that, due to their low porosity and permeability, have characteristics that make until recently not been economically profitable and can be exploited only by unconventional techniques, leading to the so called unconventional gas. The techniques used for extraction are hydraulic fracturing or "fracking" and horizontal drilling. Among the various types of unconventional gas, it is expected that shale gas is the suffering greater medium-term development in our country, so it is generating much debate, due to the risks of contamination in surface waters and subterranean environment, caused by the high amount of water used, the additives used, the return fluid, by altering the physical environment, and the difficulty of monitoring these processes. In this project identifies the environmental and health risks associated with unconventional gas extraction. The work is mainly based on experiences that occurred in countries where fracking has become a common practice. This is for establish the necessary basis for estimating the vulnerability of aquifers from contamination induced by hydraulic fracturing.

Optimizaci��n del coste de aprovisionamiento de gas en el mercado mayorista espa��ol para una comercializadora

Los precios de compra de gas natural en el mercado mayorista espa��ol son los m��s altos de toda Europa. Este escenario provoca que haya que buscar alternativas para minimizar los costes de aprovisionamiento para una comercializadora de gas. En este proyecto se analizan distintas oportunidades de compra de gas en los mercados europeos y su importaci��n al sistema gasista espa��ol para el suministro final a clientes, con el fin de optimizar los costes del gas natural para una comercializadora. En la b��squeda de nuevas oportunidades se incluye tambi��n un an��lisis del impacto econ��mico en el mercado, de la producci��n de ���shale gas��� en Espa��a a medio - largo plazo. ABSTRACT The gas prices in the Spanish gas market are the highest in Europe. This scenario leads the Spanish gas trading companies to look for alternatives to minimize gas supply costs. In this project it is analyzed different opportunities of gas supply in the European markets and the gas import to the Spanish gas system, in order to optimize the costs of the natural gas for a gas trading company. Along with this, it is also studied, the economic impact of the ���shale gas��� production in Spain in a medium - long term on the Spanish gas market

CO2 emissions from a spark ignition engine operatin on natural-hydrogen blends (HCNG)

The addition of hydrogen to natural gas could be a short-term alternative to today���s fossil fuels, as greenhouse gas emissions may be reduced. The aim of this study is to evaluate the emissions and performance of a spark ignition engine fuelled by pure natural gas, pure hydrogen, and different blends of hydrogen and natural gas (HCNG). Increasing the hydrogen fraction leads to variations in cylinder pressure and CO2 emissions. In this study, a combustion model based on thermodynamic equations is used, considering separate zones for burned and unburned gases. The results show that the maximum cylinder pressure rises as the fraction of hydrogen in the blend increases. The presence of hydrogen in the blend leads to a decrease in CO2 emissions. Due to the properties of hydrogen, leaner fuel���air mixtures can be used along with the appropriate spark timing, leading to an improvement in engine emissions with no loss of performance.

Co2 capture in power plants-using the oxy-combustion principle

In the C02 capture from power generation, the energy penalties for the capture are one of the main challenges. Nowadays, the post-combustion methods have energy penalties 10wer than the oxy combustion and pre-combustion technologies. One of the main disadvantages of the post combustion method is the fact that the capture ofC02at atmospheric pressure requires quite big equipment for the high flow rates of flue gas, and the 10w partial pressure of the CO2generates an important 10ss of energy. The A1lam cyc1e presented for NETPOWER gives high efficiencies in the power production and 10w energy penalties. A simulation of this cyc1e is made together with a simulation of power plants with pre-combustion and post-combustion capture and without capture for natural gas and forcoa1. The simulations give 10wer efficiencies than the proposed for NETPOWER For natural gas the efficiency is 52% instead of the 59% presented, and 33% instead of51% in the case of using coal as fuel. Are brought to light problems in the CO2compressor due the high flow ofC02that is compressed unti1300 bar to be recyc1ed into the combustor.

An Empirical Analysis of the Spanish Gas Price Structure

We can say without hesitation that in energy markets a throughout data analysis is crucial when designing sophisticated models that are able to capture most of the critical market drivers. In this study we will attempt to investigate into Spanish natural gas prices structure to improve understanding of the role they play in the determination of electricity prices and decide in the future about price modelling aspects. To further understand the potential for modelling, this study will focus on the nature and characteristics of the different gas price data available. The fact that the existing gas market in Spain does not incorporate enough liquidity of trade makes it even more critical to analyze in detail available gas price data information that in the end will provide relevant information to understand how electricity prices are affected by natural gas markets. In this sense representative Spanish gas prices are typically difficult to explore given the fact that there is not a transparent gas market yet and all the gas imported in the country is negotiated and purchased by private companies at confidential terms.

Potential effects of gas hydrate on human welfare

For almost 30 years. serious interest has been directed toward natural gas hydrate, a crystalline solid composed of water and methane, as a potential (i) energy resource, (ii) factor in global climate change, and (iii) submarine geohazard. Although each of these issues can affect human welfare, only (iii) is considered to be of immediate importance. Assessments of gas hydrate as an energy resource have often been overly optimistic, based in part on its very high methane content and on its worldwide occurrence in continental margins. Although these attributes are attractive, geologic settings, reservoir properties, and phase-equilibria considerations diminish the energy resource potential of natural gas hydrate. The possible role of gas hydrate in global climate change has been often overstated. Although methane is a ���greenhouse��� gas in the atmosphere, much methane from dissociated gas hydrate may never reach the atmosphere, but rather may be converted to carbon dioxide and sequestered by the hydrosphere/biosphere before reaching the atmosphere. Thus, methane from gas hydrate may have little opportunity to affect global climate change. However, submarine geohazards (such as sediment instabilities and slope failures on local and regional scales, leading to debris flows, slumps, slides, and possible tsunamis) caused by gas-hydrate dissociation are of immediate and increasing importance as humankind moves to exploit seabed resources in ever-deepening waters of coastal oceans. The vulnerability of gas hydrate to temperature and sea level changes enhances the instability of deep-water oceanic sediments, and thus human activities and installations in this setting can be affected.

Desenvolvimento de um m��todo para diagnose de falhas na opera����o de navios transportadores de g��s natural liquefeito atrav��s de redes bayesianas.

O G��s Natural Liquefeito (GNL) tem, aos poucos, se tornado uma importante op����o para a diversifica����o da matriz energ��tica brasileira. Os navios metaneiros s��o os respons��veis pelo transporte do GNL desde as plantas de liquefa����o at�� as de regaseifica����o. Dada a import��ncia, bem como a periculosidade, das opera����es de transporte e de carga e descarga de navios metaneiros, torna-se necess��rio n��o s�� um bom plano de manuten����o como tamb��m um sistema de detec����o de falhas que podem ocorrer durante estes processos. Este trabalho apresenta um m��todo de diagnose de falhas para a opera����o de carga e descarga de navios transportadores de GNL atrav��s da utiliza����o de Redes Bayesianas em conjunto com t��cnicas de an��lise de confiabilidade, como a An��lise de Modos e Efeitos de Falhas (FMEA) e a An��lise de ��rvores de Falhas (FTA). O m��todo proposto indica, atrav��s da leitura de sensores presentes no sistema de carga e descarga, quais os componentes que mais provavelmente est��o em falha. O m��todo fornece uma abordagem bem estruturada para a constru����o das Redes Bayesianas utilizadas na diagnose de falhas do sistema.

High-Pressure Methane Storage in Porous Materials: Are Carbon Materials in the Pole Position?

Natural gas storage on porous materials (ANG) is a promising alternative to conventional on-board compressed (CNG) or liquefied natural gas (LNG). To date, Metal���organic framework (MOF) materials have apparently been the only system published in the literature that is able to reach the new Department of Energy (DOE) value of 263 cm3 (STP: 273.15 K, 1 atm)/cm3; however, this value was obtained by using the ideal single-crystal density to calculate the volumetric capacity. Here, we prove experimentally, and for the first time, that properly designed activated carbon materials can really achieve the new DOE value while avoiding the additional drawback usually associated with MOF materials (i.e., the low mechanical stability under pressure (conforming), which is required for any practical application).