Gestión del boil off gas en la planta de regasificación de Cartagena

Este proyecto trata sobre la gestión del boil-off gas, o BOG (vapor de gas natural que se produce en las instalaciones de gas natural licuado de las plantas de regasificación), generado en la planta de regasificación de Gas Natural Licuado de Cartagena, tanto en las situaciones en las que se opera por debajo del mínimo técnico, 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 envía a los vaporizadores para ser regasificado y emitido a la red. De forma complementaria cuentan también con una antorcha/venteo donde se quema el exceso de boil-off que no puede ser tratado por el relicuador. Se procede a un análisis de la situación actual, y de cómo la baja demanda de regasificación dificulta la gestión del boil-off. Se simula el proceso de relicuación actual en distintas situaciones de operación. Ante la situación de baja demanda, ha aumentado considerablemente el número de días en los que las plantas españolas en general, y la planta de Cartagena en particular, operan por debajo del mínimo técnico, que es el nivel de producción mínimo para recuperar todo el boil-off generado en cualquier situación de operación al tiempo que mantiene en frío todas las instalaciones, y garantiza el 100% de disponibilidad inmediata del resto de los equipos en condiciones de seguridad de funcionamiento estable. Esta situación supone inconvenientes tanto operativos como medioambientales y acarrea mayores costes económicos, a los cuales da solución el presente proyecto, decidiendo qué alternativa técnica es la más adecuada y definiéndola. 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.

Influence of the composition of natural gas-hydrogen blends (HCNG) on performance an CO2 emissions of a spark ignition engine

Addition of hydrogen to natural gas could be a short-term alternative to nowadays fossil fuels as the emissions of greenhouse gases may be reduced. The aim of this study is to evaluate the performance and emissions of a park ignition engine fuelled with pure natural gas, pure hydrogen and different blends of hydrogen and natural gas (HCNG). The increase of the hydrogen fraction leads to variations in the cylinder pressure and CO2 emissions. In this work, a combustion model based on thermodynamic equations is used considering separated zones for the burned and unburned gases. The results show that the maximum cylinder pressure gets higher as the fraction of hydrogen in the blend increases. The presence of hydrogen in the blend leads to a drecrease in the CO2 emissions. Due to hydrogen properties, leaner fuel-air mixtures can be used along with the appropiate spark timing, leading to an engine emissions improvement without a performance worsening.

Life cycle assessment of concentrated solar power (CSP) and the influence of hybridising with natural gas

Purpose Concentrating Solar Power (CSP) plants based on parabolic troughs utilize auxiliary fuels (usually natural gas) to facilitate start-up operations, avoid freezing of HTF and increase power output. This practice has a significant effect on the environmental performance of the technology. The aim of this paper is to quantify the sustainability of CSP and to analyse how this is affected by hybridisation with different natural gas (NG) inputs. Methods A complete Life Cycle (LC) inventory was gathered for a commercial wet-cooled 50 MWe CSP plant based on parabolic troughs. A sensitivity analysis was conducted to evaluate the environmental performance of the plant operating with different NG inputs (between 0 and 35% of gross electricity generation). ReCiPe Europe (H) was used as LCA methodology. CML 2 baseline 2000 World and ReCiPe Europe E were used for comparative purposes. Cumulative Energy Demands (CED) and Energy Payback Times (EPT) were also determined for each scenario. Results and discussion Operation of CSP using solar energy only produced the following environmental profile: climate change 26.6 kg CO2 eq/KWh, human toxicity 13.1 kg 1,4-DB eq/KWh, marine ecotoxicity 276 g 1,4-DB eq/KWh, natural land transformation 0.005 m2/KWh, eutrophication 10.1 g P eq/KWh, acidification 166 g SO2 eq/KWh. Most of these impacts are associated with extraction of raw materials and manufacturing of plant components. The utilization NG transformed the environmental profile of the technology, placing increasing weight on impacts related to its operation and maintenance. Significantly higher impacts were observed on categories like climate change (311 kg CO2 eq/MWh when using 35 % NG), natural land transformation, terrestrial acidification and fossil depletion. Despite its fossil nature, the use of NG had a beneficial effect on other impact categories (human and marine toxicity, freshwater eutrophication and natural land transformation) due to the higher electricity output achieved. The overall environmental performance of CSP significantly deteriorated with the use of NG (single score 3.52 pt in solar only operation compared to 36.1 pt when using 35 % NG). Other sustainability parameters like EPT and CED also increased substantially as a result of higher NG inputs. Quasilinear second-degree polynomial relationships were calculated between various environmental performance parameters and NG contributions. Conclusions Energy input from auxiliary NG determines the environmental profile of the CSP plant. Aggregated analysis shows a deleterious effect on the overall environmental performance of the technology as a result of NG utilization. This is due primarily to higher impacts on environmental categories like climate change, natural land transformation, fossil fuel depletion and terrestrial acidification. NG may be used in a more sustainable and cost-effective manner in combined cycle power plants, which achieve higher energy conversion efficiencies.

Hybridizing concentrated solar power (CSP) with biogas and biomethane as an alternative to natural gas: Analysis of environmental performance using LCA

Concentrating Solar Power (CSP) plants typically incorporate one or various auxiliary boilers operating in parallel to the solar field to facilitate start up operations, provide system stability, avoid freezing of heat transfer fluid (HTF) and increase generation capacity. The environmental performance of these plants is highly influenced by the energy input and the type of auxiliary fuel, which in most cases is natural gas (NG). Replacing the NG with biogas or biomethane (BM) in commercial CSP installations is being considered as a means to produce electricity that is fully renewable and free from fossil inputs. Despite their renewable nature, the use of these biofuels also generates environmental impacts that need to be adequately identified and quantified. This paper investigates the environmental performance of a commercial wet-cooled parabolic trough 50 MWe CSP plant in Spain operating according to two strategies: solar-only, with minimum technically viable energy non-solar contribution; and hybrid operation, where 12 % of the electricity derives from auxiliary fuels (as permitted by Spanish legislation). The analysis was based on standard Life Cycle Assessment (LCA) methodology (ISO 14040-14040). The technical viability and the environmental profile of operating the CSP plant with different auxiliary fuels was evaluated, including: NG; biogas from an adjacent plant; and BM withdrawn from the gas network. The effect of using different substrates (biowaste, sewage sludge, grass and a mix of biowaste with animal manure) for the production of the biofuels was also investigated. The results showed that NG is responsible for most of the environmental damage associated with the operation of the plant in hybrid mode. Replacing NG with biogas resulted in a significant improvement of the environmental performance of the installation, primarily due to reduced impact in the following categories: natural land transformation, depletion of fossil resources, and climate change. However, despite the renewable nature of the biofuels, other environmental categories like human toxicity, eutrophication, acidification and marine ecotoxicity scored higher when using biogas and BM.

Desenvolvimento de um método para diagnose de falhas na operação de navios transportadores de gás natural liquefeito através de redes bayesianas.

O Gás Natural Liquefeito (GNL) tem, aos poucos, se tornado uma importante opção para a diversificação da matriz energética brasileira. Os navios metaneiros são os responsáveis pelo transporte do GNL desde as plantas de liquefação até as de regaseificação. Dada a importância, bem como a periculosidade, das operações de transporte e de carga e descarga de navios metaneiros, torna-se necessário não só um bom plano de manutenção como também um sistema de detecção de falhas que podem ocorrer durante estes processos. Este trabalho apresenta um método de diagnose de falhas para a operação de carga e descarga de navios transportadores de GNL através da utilização de Redes Bayesianas em conjunto com técnicas de análise de confiabilidade, como a Análise de Modos e Efeitos de Falhas (FMEA) e a Análise de Árvores de Falhas (FTA). O método proposto indica, através da leitura de sensores presentes no sistema de carga e descarga, quais os componentes que mais provavelmente estão em falha. O método fornece uma abordagem bem estruturada para a construção das Redes Bayesianas utilizadas na diagnose de falhas do sistema.

Testing co-volatility spillovers for natural gas spot, futures and ETF spot using dynamic conditional covariances

There is substantial empirical evidence that energy and financial markets are closely connected. As one of the most widely-used energy resources worldwide, natural gas has a large daily trading volume. In order to hedge the risk of natural gas spot markets, a large number of hedging strategies can be used, especially with the rapid development of natural gas derivatives markets. These hedging instruments include natural gas futures and options, as well as Exchange Traded Fund (ETF) prices that are related to natural gas stock prices. The volatility spillover effect is the delayed effect of a returns shock in one physical, biological or financial asset on the subsequent volatility or co-volatility of another physical, biological or financial asset. Investigating volatility spillovers within and across energy and financial markets is a crucial aspect of constructing optimal dynamic hedging strategies. The paper tests and calculates spillover effects among natural gas spot, futures and ETF markets using the multivariate conditional volatility diagonal BEKK model. The data used include natural gas spot and futures returns data from two major international natural gas derivatives markets, namely NYMEX (USA) and ICE (UK), as well as ETF data of natural gas companies from the stock markets in the USA and UK. The empirical results show that there are significant spillover effects in natural gas spot, futures and ETF markets for both USA and UK. Such a result suggests that both natural gas futures and ETF products within and beyond the country might be considered when constructing optimal dynamic hedging strategies for natural gas spot prices.

Potential Adverse Effects of the Alaska Natural Gas Pipeline on Arctic Caribou and Proposed Mitigation

The Alaska Natural Gas Pipeline (ANGP) is proposed for construction on the North Slope in 2016. It will be aligned through Arctic caribou habitat and evidence shows that caribou are negatively affected by human development. This Capstone identifies potential adverse affects of ANGP on Arctic caribou using interviews from expert caribou biologists and the 1977 Trans-Alaska Pipeline System (TAPS) as a model. Based on a synthesis of the interviews and TAPS analysis, this capstone proposes and examines a set of seventeen conservation measures to be implemented during construction and operation of ANGP to minimize adverse impacts on caribou herds. These conservation measures can be used as a baseline for future developments on the North Slope to promote caribou herd management.

Climate Change Policy & the Natural Gas Transmission Sector

Various emission reduction strategies are proposed to manage climate change in the U.S. This applied capstone evaluates the most likely policy options considering impacts and benefits to the natural gas transmission sector (NGT). It examines a case-study including a comparison of policy options to recommend the most beneficial program to the NGT sector. Two conclusions of major importance are: a federally preempted cap-and-trade program would be the most cost-effective for the NGT sector and the NGT sector should not be the point of regulation of any climate policy. Recommendations, strategies, and costs for implementation of a compliance plan for a federally preempted cap-and-trade program were developed as a tool for NGT companies as part of this applied capstone project.

La Région Méditerranéenne en 2020 et son Rôle dans le Réseau Energétique Européen, Vol. II: La production et les eschanges de petrole, de gaz naturel et d'electricite: Situation actuelle et perspectives dans les PSEM et les pays du golfe. May 1994 = The Mediterranean region in 2020 and its Role in European Energy Network, Vol. II: Production and eschanges of oil, natural gas and electricity: Current situation and prospects in MENA countries and the countries of the Gulf. May 1994

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