Dynamic simulation and response analysis of LNG-based BOG re-liquefaction coupled with ORC power generation

Abstract

The utilization of liquefied natural gas (LNG) cold energy represents an important approach to improving the efficiency of the LNG value chain. Existing research on LNG cold energy utilization has mainly focused on steady-state simulations and key parameter optimization, while studies on dynamic simulation remain relatively limited. To address this gap, this study develops a dynamic model of a boil-off gas (BOG) re-liquefaction system coupled with an Organic Rankine Cycle (ORC) power generation unit driven by LNG cold energy, with particular emphasis on system dynamic stability. The effects of disturbances in certain parameters, such as temperature and mass flow rate, on system stability and dynamic response are investigated. The results indicate that when the LNG mass flow rate increases by 5%, the BOG re-liquefaction rate rises from 2,006 kg/h to approximately 2,100 kg/h (about 5%), while the ORC power output even increases from 60 kW to around 65 kW (about 8%), demonstrating the importance of sufficient cold energy for the ORC system. In contrast, a ±1 °C variation in BOG temperature has a limited impact on ORC power output (generally less than 2%), but it significantly affects the BOG re-liquefaction rate, which can increase by up to 10%. This study provides valuable insights into the dynamic operational characteristics of the BOG-ORC system and highlights the potential of utilizing LNG cold energy for both BOG re-liquefaction and power generation.

Keywords

Dynamic simulation / LNG cold energy / power generation / organic rankine cycle / BOG re-liquefaction

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