Simulation Model of Regenerative LNG Refrigeration System for Re-Liquification of BOG

Abstract

Boil-off gas (BOG) disposal in liquefied natural gas (LNG) tankers has long been considered inevitable owing to the constant vaporization of the LNG in the storage tanks, but results in energy waste and environmental pollution. To address these challenges, we developed a re-liquification system that can condense the BOG and return it to the storage tank. The re-liquification system was modeled, and a case study was conducted to evaluate the viability of the system. The energy waste, which was quantified by tonnes of oil equivalent (TOE), greenhouse-gas emissions in tonnes of carbon dioxide (TCO2), and cost reduction in millions of U.S. dollars (MUSD), was evaluated for five different tanker cruising speeds. The re-liquification system significantly reduced the average TOE, TCO2, and cost by up to 9120.40 TOE/year, 19,474.33 TCO2/year, and 1.9765 MUSD/year, respectively, for five different tanker speeds with multi-stage compression.

Thermoeconomic Analysis and Optimization of a Combined Supercritical CO2 Recompression Brayton/Kalina Cycle Driven by Boil‐Off Gas Combustion and Liquefied Natural Gas Cold Energy

“…Kurle et al [ 7 ] investigated the influence of the heat leakage in holding mode, the initial temperature of the LNG vessel tank and other parameters on the Jetty BOG (JBOG) profile, and discussed several JBOG utilization strategies. Son and Kim [ 8 ] proposed a regenerative LNG refrigeration system to condense and recover the BOG generated in storage tanks and evaluated the viability of the reliquification system by process modeling and case study. Liu et al [ 9 ] presented an LNG regasification superstructure for minimizing BOG flare.…”