Threshold of equivalent gas cloud size based on explosion load of control room

doi:10.11949/j.issn.0438-1157.20170458

Abstract

Abstract:

Fire alarm and gas detector system (FGS) is the important safety barrier to prevent gas leakage. Combustible gas leaks and forms combustible gas cloud mixing with air, and its explosion belongs to volume explosion. The gas cloud has complexity and variability subject to a variety of factors, so it is converted into equivalent gas cloud and the threshold size calculation method is proposed. The threshold is key input index to realize the quantitative layout of detector network of FGS. The control room is selected as a receptor for analysis. Based on the critical value of shock wave overpressure which takes load of control room, the corresponding equivalent gas cloud size is calculated as the detecting threshold of combustible gas cloud by using multi-energy method in reverse order. Then the critical detecting time of the FGS is calculated by using equivalent air cloud computing method and Gaussian diffusion model. Through one LNG tank industry case analysis, the maximum cloud size which can be carried by the industry and the critical time of diffusion can be quantitatively determined. The numerical calculation shows that the equivalent gas cloud size threshold can not only be used as the quantitative input indicators for detector design of FGS, but also provide theoretical support for the detection time setting and the prevention and control measures of gas leakage and explosion.

Key words: gas cloud, explosion, fire alarm and gas detector system, explosive load, equivalent gas cloud size, threshold size, safety, simulation

摘要：

火气系统是防控气体泄漏灾害的重要安全屏障。可燃气体泄漏后与空气混合形成可燃气云，其爆炸属于体积爆炸，具有复杂性和多变性，因此将其折算为等价气云并提出阈值尺寸计算方法，是实现火气系统探测器网络量化布设的关键输入指标。选取控制室为受体，以载荷作为爆炸冲击波超压的临界值，运用多能法倒序计算，逆推得到对应的等价气云尺寸作为探测阈值，进而利用等价气云方法与高斯扩散模型得到火气系统探测临界时间。通过某LNG罐区案例分析，定量确定了该罐区可承载的气云尺寸最大值及扩散临界时间。数值计算表明，等价气云尺寸阈值不仅可以作为火气系统探测设计的量化输入指标依据，并可对探测时间设置以及气体泄漏及爆炸的防控措施提供理论支持。

关键词: 气云, 爆炸, 火气系统, 爆炸载荷, 等价气云尺寸, 阈值, 安全, 模拟

CLC Number:

X937

QI Xinge, WANG Haiqing, SONG Xiansheng, CHEN Guoming. Threshold of equivalent gas cloud size based on explosion load of control room[J]. CIESC Journal, 2017, 68(12): 4857-4864.

齐心歌, 王海清, 宋贤生, 陈国明. 基于控制室爆炸载荷的可燃气云等价尺寸阈值[J]. 化工学报, 2017, 68(12): 4857-4864.

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