论文中文题名: | 液化烃泄漏诱发气体扩散与蒸气云爆炸数值仿真 |
姓名: | |
学号: | 18220214108 |
保密级别: | 保密(2年后开放) |
论文语种: | chi |
学科代码: | 085224 |
学科名称: | 工学 - 工程 - 安全工程 |
学生类型: | 硕士 |
学位级别: | 工学硕士 |
学位年度: | 2021 |
培养单位: | 西安科技大学 |
院系: | |
专业: | |
研究方向: | 气体与粉尘爆炸防控 |
第一导师姓名: | |
第一导师单位: | |
第二导师姓名: | |
论文提交日期: | 2021-06-16 |
论文答辩日期: | 2021-05-31 |
论文外文题名: | Gas dispersion induced by liquefied hydrocarbon leakage and vapor cloud explosion obtaining using numerical simulation |
论文中文关键词: | |
论文外文关键词: | Liquefied hydrocarbon ; FLACS ; Leakage and dispersion ; Vapor cloud explosion ; Safety distance ; Blast wall |
论文中文摘要: |
石油化工厂区可能会因各种原因导致泄漏事故发生,引发一系列次生衍生事故,事故后果极为严重。通过事故统计分析,发现液化烃(在15 °C时,蒸气压大于0.1 MPa的烃类液体及其他类似的液体,包括液化石油气在内,同时还涉及乙烯、乙烷、丙烯等单组分液化烃类)泄漏扩散形成蒸气云,遇到点火源发生蒸气云爆炸后导致火灾是石化厂区最为常见的多米诺事故。然而,目前国家石化厂区建设防火规范和相关研究,都主要从防止火灾热辐射和满足消防操作的角度,规定和研究相关设计参数。此外,对泄漏物质的研究主要集中在二氧化碳、液化氢气、液化石油气和液化天然气等,对液化烃类研究有限。因此,基于CFD模型FLACS开展液化烃气体泄漏扩散和气云爆炸数值仿真,定性和定量评价典型的液化烃类燃料泄漏和爆炸事故危险性,研究常见安全防控措施对液化烃泄漏扩散和气云爆炸的防护作用。主要研究结论如下: (1) 通过理论分析,将影响液化烃泄漏扩散的原因,在传统的泄漏和环境条件的基础上,提出泄漏条件、几何条件和环境条件三类。参考事故发生规律和挪威风险和应急准备分析标准,讨论了泄漏速率的选取,分析了乙烷、丙烷、丁烷、乙烯和丙烯的泄漏扩散结果,综合气体层流燃烧速度、爆炸极限和密度等因素综合判定乙烯危险性最高。通过泄漏速率和气体组成的正交实验结论,建立了可燃气云体积和泄漏速率与液化烃气体密度的理论预测模型,发现了泄漏气体在高于或低于临界泄漏速率48 kg/s时,由重气驱动与浮力驱动的气体泄漏扩散机制的不同。发现泄漏源附近和泄漏方向上的几何障碍物阻塞率是影响气云形成的关键,乙烯在较低阻塞率储罐组的泄漏,气云体积显著低于阻塞率较高的复杂油气管网。通过理论分析,将风速小于3 m/s的天气定义为微风条件,研究得出微风条件下泄漏气体就会被强烈稀释,特别对于以浮力驱动为主的气体,会大幅降低泄漏危险性。 (2) 基于液化烃泄漏扩散的仿真结果,从气云形成条件和气云分布条件两个方面开展气云爆炸研究。发现随着乙烯气云体积在复杂油气管网内增大,最大爆炸超压(Pmax) 增强,当气云高度高于油气管网,爆炸火焰传播到开敞空间后,障碍物对火焰传播的加速作用中止,Pmax不再进一步增强。在多种液化烃类中,乙烯层流燃烧速度最快,在当量比为1.2时对应Pmax最强,气云爆炸事故危险性最高。研究气云覆盖多个模块的爆炸现象,发现两模块之间的无障碍区域能够有效中断湍流反馈,火焰在几何障碍物内加速,无几何障碍区域减速,因此火焰燃烧速度在两个模块之间呈现加速‒减速‒加速过程。多个模块之间蒸气云爆炸的变化规律,为安全间距效应研究提供了理论依据。 (3) 基于泄漏扩散-爆炸的最危险场景和概率分析方法,研究储罐之间安全间距,模块之间安全间距和防爆墙高度改变对泄漏扩散-爆炸后果的影响。储罐安全间距增大,大幅降低丙烯气云整体浓度和可燃气云体积,减弱爆炸超压。随着油气管网模块之间安全间距从50 m增大到60 m,被保护模块的可燃气云被稀释,气云体积降低。通过超压概率曲线分析得知,安全间距60 m对应的乙烯爆炸超压频率分布显著低于50 m对应的乙烯爆炸超压频率。在重要建筑物或区域前增设防爆墙,能有效降低被保护区域的泄漏扩散-爆炸风险,但需要针对具体场景进行泄漏扩散-爆炸评估,才能确定防爆墙高度参数。 本文的研究结果提供了典型的设计参数和完整的评价方案,对于工程项目风险评估和安全设计有一定借鉴意义。 |
论文外文摘要: |
Leakage accidents may occur in petrochemical plants due to various reasons, resulting in a series of secondary and derivative accidents, and the consequences of the accidents are tremendously serious. By statistical analysis on accidents, it found that the most common domino accidents in the petrochemical plant was that vapor cloud explosion and followed a fire caused by liquefied hydrocarbon leakage and dispersion (Liquefied hydrocarbon refers to hydrocarbon liquids and other similar liquids with a vapor pressure greater than 0.1 MPa at 15 °C, including liquefied petroleum gas, also involving single component such as ethylene, propylene, ethane liquefied hydrocarbon). However, the current national petrochemical plant construction-related fire codes and related studies stipulate the design parameters, were principally from the point of fire operation and fire heat radiation model. Additionally, the research on leakage materials mainly focuses on carbon dioxide, liquefied hydrogen, liquefied petroleum gas, and liquefied natural gas, and research on liquefied hydrocarbons is limited. Therefore, a CFD-based numerical simulation of liquefied hydrocarbon gas leakage, dispersion, and vapor cloud explosion was conducted. The risk of typical liquefied hydrocarbon leaks was evaluated. The protective effect of common safety prevention and control measures on the leakage, dispersion, and vapor cloud explosion of liquefied hydrocarbons was researched. The main conclusions are as follows: (1) Through theoretical analysis of the causes affecting the leakage and dispersion of liquefied hydrocarbon, three categories of leakage conditions, geometric conditions, and environmental conditions were proposed. Refer to the cases of the accidents and the risk and emergency preparedness analysis code, the selection of leak rate was discussed. Results of leakage and dispersion of the ethane, propane, butane, ethylene, and propylene were analyzed. The ethylene with the highest risk was determined by the factors of laminar burning velocity, explosion limit, and density. The theoretical model, describing the mathematical relationship between the combustible gas cloud volume and leak rate and liquefied hydrocarbon gas density, was established. The critical leakage velocity of liquefied hydrocarbon was defined as 48 kg/s. When the leak rate was higher than or lower than 48 kg/s, the different mechanism of the leakage and dispersion between the gas driven by heavy gas and buoyancy was obtained. The blockage rate of geometric obstacles near the leakage source and in the direction of the leakage played a great role in the formation of the gas cloud. The gas cloud volume in ethylene leak at the tank group with a lower blockage rate was significantly lower than that in the complex oil and gas pipeline network with a higher blockage rate. The wind speed below 3 m/s was the breeze condition was defined theoretically. The research has shown that under the breeze condition, the released gas will be strongly diluted and the leak risk will be momentously reduced. (2) Based on the simulation results of liquefied hydrocarbon leakage and dispersion, the experiments of gas cloud explosion were carried out from the two aspects of gas cloud formation conditions and gas cloud distribution conditions. It was found that the maximum explosive overpressure (Pmax) increased with the increase in the volume of ethylene gas cloud in the complex oil and gas pipe network. When the height of the gas cloud was higher than the oil and gas pipe network, the Pmax did not further increase, which proved that obstacles are the main reason for the acceleration of flame propagation. Among various liquefied hydrocarbons, ethylene has the fastest laminar burning velocity, corresponding explosion overpressure on the strongest, and the highest corresponding risk. When the equivalence ratio was 1.2, Pmax reached the maximum. It was found that the blank area before the two modules can interrupt the turbulent feedback. The flame accelerates in the geometric obstacle and decelerates in the barrier-free area. Therefore, the flame propagation velocity between the two modules shown a process of acceleration-deceleration-acceleration. The research resulted provide a theoretical basis for the following research on the safety distance effect. (3) Based on the most dangerous scenario and probability analysis method of leakage, dispersion, and explosion, the effects of safety distance between storage tanks, between modules, and blast wall height on the leakage and dispersion-explosion consequences were studied. With the increase in safety distance between storage tanks, the overall concentration and the volume of propylene gas cloud were significantly reduced, and the explosion overpressure was weakened. As the safety distance between the oil and gas network modules increased from 50 m to 60 m, the combustible gas cloud in the protected module was diluted and the volume of the gas cloud decreased. The overpressure probability curve analysis presented that the overpressure frequency distribution of ethylene explosion corresponding to the safety distance of 60 m was significantly lower than that corresponding to 50 m. A blast wall in front of important buildings or areas can effectively reduce the risk of leakage, dispersion, and explosion in the protected areas. However, the height parameters of a blast wall can only be determined by the assessment of leakage, dispersion, and explosion in specific scenarios. The research results of this paper provided typical design parameters and a complete evaluation scheme, which can be employed as a reference for risk assessment and safety design of engineering projects. |
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中图分类号: | X932 |
开放日期: | 2023-06-18 |