Integrated biomethane liquefaction using exergy from the discharging end of a liquid air energy storage system

Ali Rehman, Muhammad Abdul Qyyum, Kinza Qadeer, Fatima Zakir, Yulong Ding, Moonyong Lee and Li Wang

Applied Energy, 2020, vol. 260, issue C, No S0306261919319476

Abstract: Biomethane (BM) is one of the most promising bio-energy sources for reducing global dependency on fossil fuels. Liquefied biomethane (LBM) is the form of biomethane best suited for exporting to remote locations worldwide, as well as for storage. However, the liquefaction of biomethane (like conventional natural gas) is an energy- and cost-intensive process owing to considerable power consumption by compression units involved in the liquefaction process. Furthermore, unlike conventional natural gas, biomethane is produced at almost atmospheric pressure, making liquefaction more energy-intensive because pressure of produced BM is significantly lower than its critical pressure. Thus, we propose an energy- and cost-efficient biomethane liquefaction process integrated with the discharging end of a liquid air energy storage (LAES) unit. During the discharging phase of LAES, the cold exergy of liquid air is used to facilitate the subcooling and liquefaction of biomethane, which ultimately reduces the duty of the refrigeration cycle. In contrast, the heat exergy of a compressed single-mixed refrigerant (SMR) is used to aid the expansion phase of liquid air. Energy and exergy analyses, composite curve analysis, and economic analysis were performed to evaluate the commercial feasibility of the proposed integrated process. Thermodynamics analyses revealed that exergy efficiency of the integrated LBM process is 42% higher than that of the conventional (without LAES integration) SMR-LBM process, with 33.5% total annualized cost (TAC) savings. Moreover, the electricity generated from LAES has been used as a power source for compression units of the SMR refrigeration cycle in LBM plants. Therefore, the proposed integrated process is a promising candidate for small-scale applications.

Keywords: Liquid biogas; Liquefied natural gas; Integrated energy systems; LNG-LAES; Optimization; Economic evaluation (search for similar items in EconPapers)
Date: 2020
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Citations: View citations in EconPapers (9)

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DOI: 10.1016/j.apenergy.2019.114260

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