液化乙烷船液罐装载极限的提高方法

A method to improve the loading limit of cargo tank in liquefied ethane carrier

为了优化液化乙烷船远洋运输能力,根据液化气船液罐装载极限的基本要求和液化乙烷的货品属性,从提高基准温度下货物的对应密度和充装极限两个方面研究了提高液化乙烷船液罐装载极限的方法。将理论计算与液化乙烷船实际数据相结合,分析了BOG的不同回收利用方式对控制乙烷密度的影响;为了使主罐体充装极限达到99.5%,在液罐顶部设置气室,并将液罐压力释放阀安装于气室顶部;同时,对液位测量、温度测量、再液化设备启动压力设定、应急切断响应周期、液罐尺寸等修正裕量系数开展了研究,得出了在满足约束条件下提高装载极限的方法。结果表明:该方法可使得液化乙烷在基准温度下的对应密度、充装极限分别提高6.67%～8.89%、1.5%,可在其他液化乙烷船储运中推广应用。

In order to optimize the ocean transportation capacity of liquefied ethane carriers, a method to improve the loading limit of cargo tanks in liquefied ethane carriers was researched according to the basic requirements on the loading limit of cargo tank in liquefied gas carrier and properties of liquefied ethane. In the method, the loading limit of cargo tank in liquefied ethane carrier is improved by increasing the relative density and filling limit of cargo under the reference temperature. The effects of BOG recovery methods on the ethane density control were analyzed by combining the actual data of liquefied ethane carrier with its theoretical calculation. In order to make the filling limit of main tank up to 99.5%, a gas chamber was set at the top of the tank and a pressure release valve was installed at the top of the gas chamber. In addition, the effects on the loading limit from level measurement, temperature measurement, start pressure setting of reliquefaction unit, response cycle of emergency shutdown, tank size and other modification margin factors were investigated. Thus, the method to improve the loading limit while satisfying the constraint conditions was developed. It is shown that the relative density and filling limit of liquefied ethane under reference temperature are increased by 6.67%-8.89% and 1.5%, respectively, and this method can be applied and popularized to the storage and transportation of other liquefied ethane carriers.