大型LNG储罐安全存储影响因素分析

Analysis of Factors Affecting Secure LNG Storage in Large LNG Tanks

LNG在储罐内长时间存储过程中,受外部热源的侵扰会发生蒸发,罐内压力升高,安全存储时间缩短并可能导致其分层翻滚,乃至LNG大量急剧蒸发,不仅浪费资源且造成安全隐患。建立密闭LNG储罐内静态蒸发模型,对初始充满率、储罐容积、环境温度、罐壁导热系数、LNG含氮量等影响因素进行研究,结论如下:其一,在同一初始充满率下,在储罐最大工作压力范围内,罐内压力随安全存储时间呈正比例关系增长。其二,在储罐最大工作压力范围内存在最优充满率,在最优充满率时储罐有最大的安全存储时间;当初始充满率小于最优充满率时,安全存储时间随初始充满率的减小而减小;当初始充满率大于最优充满率时,安全存储时间随初始充满率的增大而减小。其三,储罐的尺寸越小,储罐所具有的最大承压能力越大,最优充满率越大,安全存储时间越长。其四,外界环境温度越高以及罐壁导热系数越大,罐内压力随时间增长率越大,储罐的安全存储时间越短。其五,LNG组分中含氮量越高,罐内压力随时间增长率越大,储罐的安全存储时间越短。

In the process of lasting storage,the liquid in LNG tank gets influence from external heat source to become stratified which is related to the evaporation in the tank.The pressure in tank will rise up to shorten the secure storage time,and the stratification and rollover will cause great waste of resource as well as security threats.This paper constructs a model of static evaporation in airtight LNG tank to analyze the influencing factors of static evaporation such as initial filling rate,volume of tank,ambient temperature,thermal conductivity and nitrogen content,and provides theoreticalbasis forpreventing stratification.The conclusions are as follows：（1）With the same initial filling rate,the pressure oftank rises proportionately to the time within the range of maximum operating pressure.（2） There exists an optimal filling rate within the maximum operating pressure at which the tank acquires the longest secure storage time.When the initial filling rate is less than the optimal one,the secure storage time would decrease with the decrease of the initial filling rate.Similarly,a greater filling rate would lead to an increase of secure storage time with the increase of the initial filling rate.（3） Tank of smaller volume has the higher pressure capacity,larger optimal filling rate and longer secure storage time.（4） The higher the ambient temperature and the larger the thermal conductivity of insulation layer of tank are,the fasterthe pressure inside the tankrises,so as to a shorter secure storage time.（5） Alargernitrogen content in LNG leads to a fasterrising of pressure inside the tank as wellas a shorter secure storage time.