Energy and exergy analyses of five conventional liquefied natural gas processes

Abstract

SUMMARY 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. Copyright © 2014 John Wiley & Sons, Ltd.

Conceptual design and energy analysis of novel integrated liquefied natural gas and fuel cell electrochemical power plant processes

“…Table 2 shows specifications of the liquefaction process equipment. Table 3 presents the required power in the compressors of this process and conventional dual mixed refrigerant process [2,3]. Using absorption refrigeration system decreases the total power consumption up to 26% and accordingly SPC can be decreased from 0.26 kWh kg-1 LNG to 0.19 kWh kg À1 LNG.…”

“…They are divided into three categories: single stage, multi stage and cascade. Five of the most conventional LNG processes are investigated by energy and exergy analysis methods [2,3]. High value of the required power in the refrigeration cycle compressors is the most important point which can be investigated for improving the liquefaction efficiency.…”

Advanced exergoeconomic analysis of the multistage mixed refrigerant systems

“…where e ph is physical exergy and e ch is chemical exergy. Physical exergy (e ph ) of a material stream can be defined as the maximum work (useful energy) that can be obtained from when it is taken to physical equilibrium state with the environment [2]:…”

“…Chemical exergy (e ch ) is equal to the maximum amount of work obtainable when the substance under consideration is brought from the environmental state to the dead state. Chemical exergy is obtained from the following equation [2]:…”

“…The results show the single mixed refrigerant (SMR) process has the best exergy efficiency. Energy and exergy analyses method are applied on five conventional liquefied natural gas processes [2]. The results indicate that the maximum coefficient of performance of the process and exergy efficiency is related to the mixed fluid cascade (MFC).…”