Ageing of liquified natural gas during marine transportation and assessment of the boil-off thermodynamic properties

Peruško, Dalibor (author), Karabaić, Damir (author), Bajsič, Ivan (author), Kutin, Jože (author)

During LNG storage and transportation by ship, a fraction of the LNG in the cryogenic tanks evaporates due to heat ingress through the insulation, resulting in boil-off gas (BOG) production and a change in LNG composition, a phenomenon known as LNG ageing. Common practice is to assume that BOG composition and related density are identical to the initial LNG or pure methane, resulting in inaccuracy in BOG mass flow measurements. This is particularly important regarding LNG shipping economics and the utilization of BOG as a fuel for ship propulsion. This work investigates the influence of LNG ageing on the produced BOG thermodynamic properties relevant to the mentioned inaccuracies’ estimation and correction. An established, simplified, dynamic boil-off model is utilized for the simulation of LNG and BOG properties’ changes during the voyage. Four cases represented by limiting the minimum and maximum values of methane and nitrogen content are used to estimate the general influence of the compositional variability over the whole range of practically possible LNG source mixtures. Research results provide an insight into the relevant BOG properties’ variability and confirm that BOG flow measurements should be corrected with dynamic model simulations results due to significant differences between the total BOG mixture and forced BOG mixture corresponding to the LNG composition.

• Language: English
• Keywords: LNG shipping, LNG ageing, boil-off gas (BOG), LNG fueled vessel, gas flow measurement
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2023
• Number of pages: 23 str.
• Numbering: Vol. 11, iss. 10, art. 1980
• PID: 20.500.12556/RUL-151702
• UDC: 629.5.03:627.133
• ISSN on article: 2077-1312
• DOI: 10.3390/jmse11101980
• COBISS.SI-ID: 168777219
• Publication date in RUL: 17.10.2023

Record is a part of a journal

• Title: Journal of marine science and engineering
• Shortened title: J. mar. sci. eng.
• Publisher: Multidisciplinary Digital Publishing Institute
• ISSN: 2077-1312
• COBISS.SI-ID: 523219993

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: ladijski transport, staranje LNG, uparjeni plin, LNG pogon, merjenje pretoka plina