Optimization model and application for the recondensation process of boil-off gas in a liquefied natural gas receiving terminal

In a liquefied natural gas (LNG) receiving terminal, the recirculation flow rate and the branch flow rate entering the tank are important operating parameters that affect the amount of produced boil-off gas (BOG) in the system. However, the operating variables are generally kept unchanged when the flow rate of the external transportation LNG changes, resulting in additional power consumption and poor flexibility. Therefore, a total power consumption optimization model of the recondensation process was constructed for the varied flow rates of the external transportation. The total power consumption of the recondensation process was regarded as the objective function, and the recirculation flow rate and the branch flow rate were regarded as independent variables. Operating strategies for varied flow rates of the external transportation can be proposed using the model. The application of the research results at the Rudong LNG receiving terminal in Jiangsu, China indicated that the optimized operating strategy resulted in 2.93% annual energy reduction compared with the previous strategy, of which the energy reducing rate from June to October was 9.55%.