Research On LNG Custody Transfer By Sea

Along with the development of Liquefied Natural Gas(LNG) transportation at sea,the accuracy of LNG custody transfer is increased.LNG custody transfer by volume has been adopted for a long time in China,which could not meet with the international trade requirements.It is essential to make necessary research on LNG custody transfer by energy.Due to the fact that LNG transportation by sea is at its primary stage,the causes of error in the custody transfer are not properly acknowledged.The boil off gas which is unavoidable during LNG transportation at sea is affected by the ship's condition, trade route,weather and sea conditions.With a view to further enhance the level of LNG custody transfer,researches have been made in this thesis with the following achievements:â—†LNG cargo containment system and cargo operation procedure have been reviewed;â—†The Energy is obtained by the volume measurement,density calculation and gross heating value of LNG loaded or discharged calculation with reference to the standards of ISO,API and the related measurement organizations;â—†It is pointed out that the calibration of the tanks is necessary based on the measurement uncertainty evaluation;â—†The quantitative analysis has been made on the measurement device error, measurement operation error and error affected by the ambient temperature and sea temperature,and the corresponding error correction method has been provided;â—†The data of LNG custody transfer have been processed for calculating the Vessel Experience Factors(VEF) based on the principle of the mathematical statistics;â—†The measurement data have been processed and corrected in combination of a case of LNG custody transfer for MV Senshu Maru.