ASPEN PLUS simulation and optimization on the process flow of reliquefaction in LNG carrier

To reduce the power consumption in the BOG reliquefaction process of a LNG carrier, appropriate thermodynamic method and equipment modules are selected by means of ASPEN PLUS for modeling of BOG reliquefaction process in a LNG carrier. Through simulation calculation of operating parameters of the process equipment, including outlet temperature of propylene pre-cooling exchanger, outlet pressure of compressor, outlet pressure of throttle valve and outlet pressure of BOG compressor, the rules of parameter impact upon power consumption of BOG reliquefaction process have been obtained. Targeting at the process system optimization, the optimized parameters are calculated for optimization by use of cyclic variable method. As a result, the relevant parameters at the key nodes of the BOG reliquefaction system, the parameters for optimized performances of compressors and heat exchangers and parameters for equipment design at certain sea water temperature in given range of BOG pressure in the cargo tank have been obtained. The total power consumption post optimization is reduced by 8.82% than that prior to optimization.