Energy recovery and utilization from the regasification of LNG

Abstract

The accelerating impacts of climate change demand urgent advancements in energy efficiency and resource optimization across industries. LNG liquefaction is a particularly energy-intensive process, yet LNG retains part of this energy in the form of "cold energy." Much of this potential energy is often wasted during regasification. This thesis explores methods to recover this residual energy, primarily focusing on power generation, while also discussing potential applications in seawater desalination, carbon capture, NGL (natural gas liquids) recovery, and air separation. Using the Revithousa LNG import terminal as a case study, a combined ORC-DE system was modeled and optimized in MATLAB, incorporating the CoolProp library to utilize both the cold energy and waste heat from the installed CHP system. The model analyzed various ORC working fluids and configurations, applying multi-objective optimization to identify setups that maximize power output and efficiency. Leveraging the CoolProp library for precise thermodynamic properties, the MATLAB model accurately captured the interactions between the LNG cycle and ORC components under a range of operational conditions. The optimized system demonstrated the potential to produce up to 18 MW of power, achieving a thermal efficiency of 16.49% and a second-law efficiency of 32.79%. Specific power efficiencies reached 311 kW per kg of LNG, while also reducing seawater pumping requirements, offering a more sustainable approach to LNG regasification. An economic analysis highlighted the system’s viability, with an internal rate of return (IRR) of 33.51% and a profitability index of 5.11. Overall, this system provides an effective solution for reducing the carbon footprint of LNG processing while delivering economic value.