Analysis and assessment of partial re-liquefaction system for liquefied hydrogen tankers using liquefied natural gas (LNG) and H2 hybrid propulsion. (7th June 2019)

• Record Type: Journal Article
• Authors: Lee, Hyunyong; Shao, Yude; Lee, Seunghun; Roh, Gilltae; Chun, Kangwoo; Kang, Hokeun
• Is Part Of: International journal of hydrogen energy. Volume 44:Number 29(2019)
• Page Start: 15056
• Page End: 15071
• Publication Date: 2019-06-07
• Subjects: Hydrogen -- Boil-off gas -- Re-liquefaction -- Liquefied hydrogen tanker -- Exergy efficiency -- Specific energy consumption; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2019.03.277
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Boil-off gas (BOG) is inevitable on board liquefied hydrogen tankers and must be managed effectively, by using it as fuel, re-liquefying it or burning it, to avoid cargo tank pressure issues. This study aims to develop a BOG re-liquefaction system optimized for l60, 000 m 3 liquefied hydrogen tankers with an LNG and hydrogen hybrid propulsion system. The proposed system comprises hydrogen compression and helium refrigerant sections with 2 J–Brayton cascade cycles. Cold energy recovery from the fuels and feed BOG exiting the cargo tanks was used. The system exhibits a coefficient of performance (COP) of 0.07, a specific energy consumption (SEC) of 3.30 kWh/kgLH2, and exergy efficiency of 74.9%, with the hydrogen BOG entering the re-liquefaction system at a feed temperature of −220 °C. The theoretical COP and SEC values at ideal conditions were 0.09 and 2.47 kWh/kgLH2, respectively. The effects of varying the hydrogen compression pressure, inlet temperature of the hydrogen expander, feed hydrogen temperature and helium compression pressure were investigated. Additionally, the LNG-to-hydrogen fuel ratio was adjusted to satisfy the Energy Efficiency Design Index (EEDI) Phase 2 and 3 emission requirements. Highlights: Liquefied hydrogen tanker allows large quantities, international transport of hydrogen. Boil-off gas is inevitable on board liquefied hydrogen tanker and must be managed effectively. Hydrogen boil-off gas re-liquefaction system is proposed and evaluated through energy and exergy analyses. Energy analysis reveals that 3.30 kWh per kgLH2 is consumed for the re-liquefaction. The effective cold energy recovery from boil-off gas and LNG improved system efficiencies.