Comparative evaluation of LNG – based cogeneration systems using advanced exergetic analysis (original) (raw)
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Liquefied natural gas (LNG) will contribute more in the future than in the past to the overall energy supply in the world. The paper discusses the application of advanced exergy-based analyses to a recently developed LNG-based cogeneration system. These analyses include advanced exergetic, advanced exergoeconomic, and advanced exergoenvironmental analyses in which thermodynamic inefficiencies (exergy destruction), costs, and environmental impacts have been split into avoidable and unavoidable parts. With the aid of these analyses, the potentials for improving the thermodynamic efficiency and for reducing the overall cost and the overall environmental impact are revealed. The objectives of this paper are to demonstrate (a) the potential for generating electricity while regasifying LNG and (b) some of the capabilities associated with advanced exergy-based methods. The most important subsystems and components are identified, and suggestions for improving them are made.
LNG – Based Cogeneration Systems: Evaluation Using Exergy-Based Analyses
Natural Gas - Extraction to End Use, 2012
Natural Gas-Extraction to End Use 236 360 vessels (the oldest is in operation since the year 1969), and 83 LNG regasification plants (including 10 floating structures) with a total storage capacity of 38.5 million m 3 of LNG in 363 tanks. The oldest regasification plants are in operation since 1969 in Spain and Italy, and since 1972 in France and Japan. Many of the old regasification plants have been reconstructed during the last decade. The newest regasification plants include those completed in 2009 (in China, UK and Canada), and 2010 (in USA, Japan and Chile).
Advanced exergetic analysis of five natural gas liquefaction processes
Conventional exergy analysis cannot identify portion of inefficiencies which can be avoided. Also this analysis does not have ability to calculate a portion of exergy destruction which has been produced through performance of a component alone. In this study advanced exergetic analysis was performed for five mixed refrigerant LNG processes and four parts of irreversibility (avoidable/unavoidable) and (endogenous/exogenous) were calculated for the components with high inefficiencies. The results showed that portion of endogenous exergy destruction in the components is higher than the exogenous one. In fact interactions among the components do not affect the inefficiencies significantly. Also this analysis showed that structural optimization cannot be useful to decrease the overall process irreversibilities. In compressors high portion of the exergy destruction is related to the avoidable one, thus they have high potential to improve. But in multi stream heat exchangers and air coolers, unavoidable inefficiencies were higher than the other parts. Advanced exergetic analysis can identify the potentials and strategies to improve thermodynamic performance of energy intensive processes.
Energy and exergy analyses of five conventional liquefied natural gas processes
International Journal of Energy Research, 2014
In this paper, five conventional LNG processes were investigated by energy and exergy analysis methods. On the basis of the energy analysis, three-stage process of Linde AG and Stat oil (mixed fluid cascade [MFC]) has less energy consumption than the other ones (0.254 kWh/kg liquefied natural gas). Also, coefficient of performance of the cycles of this process is higher compared with the other ones. Exergy analysis results showed that the maximum exergy efficiency is related to the MFC process (51.82%). However, performance of the MFC process in terms of quality and quantity of energy consumption is considerable. But using three cycles in this process needs more components and consequently more fixed costs. In this study, sensitivity of coefficient of performance, specific energy consumption, and indexes of exergy analysis were also analyzed versus important operating variables for all cases.
Exergy Analysis of an LNG Bog Re-Liquefaction Plant
The purpose of this study is to perform a rigorous and detailed exergy analysis of an LNG BOG re-liquefaction plant using nitrogen as the Claude cycle working fluid. Thermodynamic properties of the refrigerant are calculated using a set of equations of state developed on the basis of available data. Virial equation of state has been used to calculate thermodynamic properties of nitrogen and the energy and exergy analysis of the Claude cycle have been adopted to calculate the thermodynamic performances. Simulation results show the influence of operating conditions on the exergy losses and the exergy efficiency of the system.
Thermodynamic Analysis of an Integrated System for LNG Regasification and Power Production
Asian Journal of Engineering and Technology, 2015
Today, natural gas is used in domestic as well as for various industrial purposes. Natural gas being found in remote and specific locations, it has to be transported for long distance before supplied to customers around the globe. Producing liquefied natural gas (LNG) is a highly energy intensive process and consumes about 10 – 15% of total energy spent for LNG production. However, eventually for the end use, natural gas need to be supplied in its gaseous form and the process is known as regasification. Energy spent for the liquefaction of natural gas is wasted unless it is recovered during this regasification process. Cold exergy of LNG can be utilized for improving the performance of Rankine cycle based power plants. This paper has proposed a power system in which low temperature waste heat can be effectively recovered and LNG can be vaporized to atmospheric conditions. The system consists of propane Rankine cycle and LNG power generation system using direct expansion. It is mod...
Concepts for Regasification of LNG in Industrial Parks
Advances in Natural Gas Emerging Technologies, 2017
The exponentially growing markets of liquefied natural gas (LNG) require efficient processes for LNG regasification within import terminals. Usually, the regasification of LNG is accomplished by direct or indirect heating. However, integrating LNG regasification into different processes within industrial parks (mainly processes involving low temperatures) is an efficient approach because of the utilization of the low-temperature energy. In some LNG import terminals, integration technologies are already being used. Previous publications showed an increase in the thermodynamic efficiency for systems combining air separation (as an example) and LNG regasification. In addition, the variation in the efficiency as well as the capital investment depends on the schematic and operation conditions. This fact creates great potential for improving the systems. In this chapter, different schematics are evaluated using exergy-based methods in order to improve the effectiveness of complex industrial processes that can involve LNG regasification.
Energy Recovery from the LNG Regasification Process
InTech eBooks, 2017
The global request of natural gas (NG) is continuously increasing, consequently also the regasification of liquefied natural gas (LNG) is becoming a process largely employed. Liquefied natural gas at a temperature of around 113 K at atmospheric pressure has to be regasified for its transportation by pipeline. The regasification process makes the LNG exergy available for various applications, particularly for the production of electrical energy. Different possibilities to exploit the thermal energy released during regasification are available. New plant configurations whose functioning does not constrain the processes of the regasification terminal are proposed. A possible solution is LNG exploitation as a cold source for ocean thermal energy conversion (OTEC) power plants. Electric energy can be produced also by the exploitation of heat released from hot sources, for instance, the condensation heat of power plants by means of consecutive thermodynamic cycles. The rational use of the cold source (LNG) allows the increment of electrical production and growth of the thermodynamic efficiency, with corresponding environmental benefits.