Thermodynamic analysis of an integrated gas turbine power plant utilizing cold exergy of LNG

Abstract

The main concerns in energy from petroleum-based fuels are the scarcity, cost, and pollution the fuels. Now, natural gas is considered as a better alternative. The process of converting natural gas into liquefied natural gas (LNG) is highly energy intensive and consumes about 10-15% of the total energy spent on natural gas production. Novel methods for regasification of LNG (converting back to NG) exist and are being used in various applications; mainly in power generation and refrigeration. One such method in power generation, the cold associated with LNG (cold exergy) can be utilized efficiently for improving the performance of power plants based on the Brayton cycle by precooling the working fluid. The study investigated such a possibility of precooling the inlet working fluid and to bring out the various factors influencing the overall efficiency of the power plant and regasification of LNG. Exergy analysis is the tool used for this study. The combined power plant is modeled using Aspen Hysys process simulation tool, and the results show that there is 35-135% improvement in the exergy efficiency of the power plant. This study also intends to find a suitable working fluid based on the objective functions such as exergy efficiency of the power plant and a regasification parameter (mass flow ratio). The gas turbine cycle gives maximum exergy efficiency when air is used as working fluid and Helium is the best working fluid candidate where regasification is the prime objective. Helium can gasify LNG about ten times more than other three working fluids