Analysis And Application On Improving The Loading Capacity For Liquefied Ethane Carrier

As a new type ship,liquefied ethane carrier is increasingly important in demands for the new raw material of petrochemical industry in recent years.When liquefied ethane carrier absorbing heat,a lot of Boil-Off Gas will be generated.There was a serious risk of leakage,burning,explosion if temperature and pressure of the liquefied ethane continue to rise uncontrollable.Thus,the loading limit was restrained by the international norm IGC code.This thesis studies how to improve the ocean transportation capacity by improving the loading limit of the cargo tank in liquefied ethane carrier.Firstly,the basic requirements of IGC code on the loading limit of liquefied gas carrier are introduced.And the nature and characteristics of ethane gas are introduced.The general methods of handling and utilization of Boil-Off Gas in LEG transfer chain are presented.Attention is given to the issue of LEG energy content transferred during loading and unloading of cargo tankers,as well as to the Boil-Off Gas generated by evaporation of the cargo during maritime transport.At the meantime,the tank material properties and insulation properties of LEG carrier are analyzed.The design and the monitoring configuration and the calculation of the thermal transfer of the cargo tank is presented.Then founded on the properties of the liquefied ethane and the two factors that affecting the loading limit,the methods of raising the cargo relative density and the filling limit under the reference temperature are researched.The different recovery and utilization ways of the boil off gas impacting on the relative density control are analyzed,such as reliquefaction system and gas combustion unit.Meanwhile,the factors that impact on loading limit,such as the level measurement,temperature measurement,start pressure setting of reliquefaction equipment,response cycle of emergency shutdown,size of cargo tank are considered.Finally,the method of how to increase the loading limit under a given condition is performed through the theoretical calculating and practical project validation.The results show that the loading limit of the liquefied ethane carrier can be improved effectively using the proposed method,and the achievements have been implemented in the actual project.