Numerical Simulation of External Fire Condition of Small Gas Storage Tank

doi:10.3969/j.issn.1006-396X.2021.05.011

Abstract

Abstract:

Taking the gas storage tank in a gas?liquid linkage actuator of a gas transmission pipeline as an example, the software Ansys Fluent was used to establish a 3D model with the same proportion, to simulate the change of pressure and temperature with continuous heat input when external fire occur. Aspen Hysys was used to calculate the minimum PSV diameter required for safe discharge under fire conditions. The results show that the temperature and pressure of the tank rise sharply, reaching to the steel tank collapse temperature and design pressure in a very short time, when the external fire occurs. The time to reach the collapse temperature of steel tank is lagged behind the time to reach the design pressure of the gas tank. From a security perspective, the PSV should be set, which can also help to reduce the damage of the accidents even if the tanks collapse. The minimum diameter of the PSV calculated by Aspen Hysys is 0.13 cm², and the recommended diameter of the PSV is no less than 0.15 cm².

Key words: Gas storage tank, Fire, Ansys Fluent, Over?pressure, Pressure safety valve

摘要：

以某输气管线气液联动执行机构中的储气罐为例，利用Ansys Fluent软件建立同比例三维模型，模拟火灾工况下，外部热量不断输入，罐内压力和罐体温度随时间的变化情况。利用Aspen Hysys软件模拟计算该小型储气罐在火灾工况下安全泄放所需的最小安全阀口径。结果表明，当钢制储气罐外部发生火灾时，罐体温度和罐内压力急剧升高，在很短的时间内就能达到储气罐坍塌温度和储气罐设计压力；达到钢制储气罐坍塌温度的时间滞后于达到储气罐设计压力的时间；从安全的角度，设置安全阀可安全有效泄放气体，即使储气罐发生坍塌，也有助于降低事故发生的危害程度；确定的安全阀最小口径为0.03 cm²，建议选型的安全阀口径不低于0.05 cm²。

关键词: 储气罐, 火灾, Ansys Fluent, 超压, 安全阀

CLC Number:

TE88

Yufei Wan, Jianling Chen, Liwan Li, Rui Zhu, Wenguang Wang, Yinglei Liu. Numerical Simulation of External Fire Condition of Small Gas Storage Tank[J]. Journal of Petrochemical Universities, 2021, 34(5): 68-73.

万宇飞, 陈建玲, 李立婉, 朱睿, 王文光, 刘英雷. 小型储气罐火灾工况数值模拟分析[J]. 石油化工高等学校学报, 2021, 34(5): 68-73.

Figures/Tables 5

Table 1 Composition of natural gas

组分	摩尔分数
CH₄	0.925 47
C₂H₆	0.039 58
C₃H₈	0.003 35
i⁃C₄H₁₀	0.001 16
n⁃C₄H₁₀	0.000 86
i⁃C₅H₁₂	0.002 21
N₂	0.008 46
CO₂	0.018 90
H₂S	0.000 01

Fig.1 Pressure and temperature distribution in vessel after different time of fire when the pressure in vessel reaching 12.0 MPa

Fig.2 Pressure and temperature distribution in vessel after different time of fire when the temperature of vessel reaching 593.3 ℃

Fig.3 Dynamic model of PSV

Fig.4 Pressure of gas tank and discharge flow of different PSV

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