Title: Exergy analysis of an industrial air separation unit for liquefied natural gas production

Authors: Ali Ghazikhani; Asghar Baradaran Rahimi; Mojtaba Mamourian

Addresses: Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran ' Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran ' Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

Abstract: The idea of adding compressed natural gas to the main heat exchanger of an industrial air separation unit to produce liquefied natural gas in small scale is studied. The unit effectiveness is selected as the objective function to compare air separation unit and combined LNG and air separation unit. The results indicate that 1 kg/h dry air can also produce 0.013-0.027 kg/h liquid natural gas for different operating conditions of the air separation unit. Comparing with the base air separation unit, the cold box irreversibility of the combined unit reduces approximately 5-11%, while the process effectiveness increases about 35-60% for different operating conditions.

Keywords: air separation unit; ASU; liquid oxygen; compressed natural gas; CNG; liquefied natural gas; LNG; exergy analysis; effectiveness; irreversibility; combined unit.

DOI: 10.1504/IJEX.2020.105483

International Journal of Exergy, 2020 Vol.31 No.2, pp.172 - 185

Received: 12 Jan 2019
Accepted: 11 Aug 2019

Published online: 24 Feb 2020 *

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