大型LNG储罐翻滚的数值模拟与影响因素分析

Numerical Simulation and Influencing Factor Analysis of Large LNG Storage Tank Rollover

大型LNG储罐在储存与充装LNG过程中,储罐内LNG因密度差异可能会产生分层和翻滚现象,导致罐内液体短时间内大量蒸发,压力增加,顶部的安全阀释放大量沸腾气体,从而在储罐周围形成爆炸性的LNG蒸气云,遇到点火源引发爆炸,严重威胁LNG储罐及接收站的运行安全。基于FLUENT计算流体软件建立二维数学物理模型,对LNG储罐分层与翻滚的传质传热过程进行模拟,通过研究初始密度差、初始临界密度差和翻滚系数找出LNG储罐分层与翻滚的主要因素。结果表明:LNG初始密度差的存在是导致翻滚发生的主要原因,初始密度差越大,越容易发生翻滚;应选用组分和性质相同或相近的LNG,采用合理的方式进行充装,增强储罐的保温措施以减小漏热;初始临界密度差和翻滚系数可作为储罐翻滚的有效判据。研究成果对于防止储罐翻滚,提前预警并采取有效措施具有一定指导意义。

The LNG stratification and rollover may occur due to the density difference in the process of storing and filling in large LNG storage tank.The phenomenon directly results a large amount of boil off gas(BOG)and sharp pressure increase inside the tank.The safety valve releases a host of BOG,thereby,the explosive LNG heavy gas cloud is formed around the LNG storage tank.When it encountered ignition source,a heavy explosion will happen.Based on FLUENT software,a two-dimensional mathematical physics model was established to simulate the stratification and rollover mass and heat transfer process of the LNG storage tank.The main factors of stratification and rollover are found out by studying the initial density difference,the critical density difference and rollover coefficient.The result shows that the main cause of rollover is the LNG initial density difference.The larger the initial density difference,the easier it is to rollover.The reasonable way to fill the LNG storage tank is to select same or similar component and quality,enhance tank insulation to reduce heat leakage.The critical density difference and rollover coefficient can be seen as effective criterion.The results of this paper have important guiding significance for preventing tanks from rollover and early warning with effective measures.