| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 98 === Liquefied natural gas (LNG), as a clean fossil energy, is the current mainstream energy utilized in Taiwan. As the global environmental consciousness, the government implemented "Expansion of the use of natural gas", and the "carbon reduction" policy, the campaign becomes very important. However, studies of the LNG cold energy utilization are very few in Taiwan. Most studies are conducted in Japan and China. The studies of LNG cold energy in Taiwan have focused on the components analysis. Not many studies have been done on system performance analysis.
In this paper, analysis of an existing LNG terminal with given operating conditions were performed, including the applications of power generation and warehouse refrigeration. According to the study, the joint method is the most efficient way for power generation. However, the highest value of efficiency obtained in this study is 44.2%, still lower than the value of 50% that has been reported in literature. As in the application of warehouse, it was found that the capacioty of single freezer is too low. Multiple freezers should be used to fully recover the cold energy of LNG. It is not suitable to use warehouse solely for cold energy recovery.
Finally, a complete system for the recovery of LNG cold energy for the Taichung liquefied natural gas plant of CPC Corporation was designed in this paper as an example to show how to fully utilize the cold energy. It was found that 113.45% of the cold energy could be utilized as LNG flow rate in the range of 0 ~ 13.572 T/hr. It was also found that cold energy applied in liquefied air separation has the highest payback as 658 NTs per ton of LNG. The indoor air conditioning has the lowest payback as only 3.8 NTs per ton of LNG.
However at excessive LNG flow rate, some of the recovery methods could not completely recover LNG cold energy, recycling way back in the installation of heaters, due to large flow blow out excess cold energy of air condition and could influence all the way to recovery and yield performance. This could approach the demand of the factory satisfaction.
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