Abstract
The cryogenic industry has been experiencing continuous progress in recent years, primarily due to the global development of oil and gas activities. Natural gas liquefaction is a cryogenic process, with the refrigeration system being crucial to the overall process. The objective of the study presented herein is to carry out an exergoeconomic assessment for a dual nitrogen expander process used to liquefy natural gas, employing the SPecific Exergy COsting (SPECO) methodology. The air coolers and throttling valve are dissipative components, which present fictitious unit cost rates that are reallocated to the final product (Liquefied Natural Gas). The liquefaction process has an exergy efficiency of 41.89%, and the specific cost of liquefied natural gas is 292.30 US$/GJ. It was verified that this cost increased along with electricity. The highest exergy destruction rates were obtained for Expander 1 and Air cooler 2. The highest average cost per exergy unit of fuel was obtained for the vertical separator, followed by Air coolers 1 and 2. An assessment of the exergoeconomic factor indicated that both expanders could benefit from a decrease in exergy destruction, improving the exergoeconomic performance of the overall system. Regarding the relative cost difference, all compressors presented high values and can be enhanced with low efforts.
Highlights
The results indicated 47.83% energy savings with 55.25% less exergy destruction, and 24.12% less total costs than the reference nitrogen single expander process
The results demonstrated that the consideration of exergy within optimization yielded better results, with 7.1% less energy consumption, 9.5% less exergy destruction, and exergy efficiency 4.4% higher
Recognizing that liquefied natural gas (LNG) production is a cryogenic process and that the refrigeration system is the most critical section, the objective of this study is to carry out a thermodynamic assessment, with detailed explanations and correction of data found in existing scientific literature, followed by an exergoeconomic assessment based on the SPecific Exergy COsting (SPECO) method
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Energy transition refers to significant structural changes in how energy is used; throughout history, these changes have been driven by the availability of different fuels (and the associated demands). Recognizing that the widespread, indiscriminate use of fossil fuels is the major contributor to climate change, collective global efforts must focus on changing how energy is utilized [1]. The energy transition process has deaccelerated due to the crisis associated with the COVID-19 pandemic, but there is still pressure to shift energy systems away from carbon-intensive hydrocarbons towards low-carbon sources. The strategies to mitigate ever-increasing carbon emissions include incorporating renewable resources, combined energy production schemes, and improving the energy efficiency of current fossil fuel processes through economic and ecological strategies
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