LNG加注趸船的池火危险距离分析

Assessment of the Hazard Distance of Pool Fire for LNG Bunkering Pontoon

液化天然气(LNG)加注趸船是一种适用于为长江上航行的LNG动力船实施燃料补给的工作船。低温损伤和火灾损伤是LNG泄漏后产生的对船舶造成的主要风险。为了控制LNG加注趸船的风险,论文分析了LNG加注趸船泄漏后可能产生的低温重气扩散、快速燃烧、喷射火、池火等不利后果;由于池火的风险较高,因此需要分析为趸船设计布置的池火危险距离。论文还讨论了人员、船上钢结构建筑物及储罐的热辐射通量接受准则,选取了合适的热辐射通量接受准则并且用于论文中的计算。热辐射危险距离计算采用简化的点源模型和实体火焰模型;以加注口泄漏LNG为例,当泄漏量为0.5m3时,计算了在尺寸为1m×1m×0.6m的立方体的集液盘中发生池火所应采取的危险距离布置。计算结果表明:在不采取热辐射隔绝措施下,对于人员露天作业的危险距离为14m,对于控制室等建筑物的危险距离为12m,对于储罐的危险距离为9m;并且建议应采用可考虑环境因素的实体火焰模型来计算池火危险距离。

Liquefied Natural Gas（LNG）bunkering pontoon provides an option of fuel supply for LNG-fuelled ships on Yangtze River. Cryogenic damage and fire damage are main risks of LNG spills. With respect to the control of the risk of LNG bunkering pontoon, unfavorable consequences after LNG spills are discussed, including heavy gas dispersion, flash vapor fire, jet fire and pool fire. Since pool fire takes high risk, an assessment of hazard distance at pontoon is necessary. Acceptable thermal radiation flux limit criteria for the people, pontoon＇s steel superstructure and storage tank are discussed, while appropriate criteria are selected to calculate the hazard distances. The calculation of hazard distance is based on simplified Point Source Model and simplified Solid Flame Model. Taking the spill of the pontoon＇s bunkering joint as an example, the spill volume is up to 0.5m3, and the spilled LNG is contained in a cubical drip tray whose size is lmxlmx0.6m. The calculation results show that, when no thermal radiation isolation measures are taken, hazard distance of the people working outdoor is 14m, hazard distance of the control room is 12m, and hazard distance of the storage tank is 9m. It is recommended to use the simplified Solid Flame Model, in which environmental factors are considered for the calculation of hazard distance of pool fire.