LNG池火热辐射预测模型及防火间距评价研究

发布时间：2018-06-28 14:50

本文选题：LNG池火灾 + 数值模拟　；参考：《西南石油大学》2017年硕士论文

【摘要】：液化天然气(Liquefied Natural Gas,LNG)相比于传统能源,具有清洁、高效、无毒害、无腐蚀性以及储存率高等优势,被广泛应用于汽车、轮船、制冷、化工等领域。随着我国对LNG需求量的逐年上升,LNG站场的数量日益增多,随之带来的安全问题,也越来越受到高度重视。LNG在常压下的沸点为-161.5℃,一旦发生泄漏,LNG会快速蒸发,使得周围温度骤降,若遇到明火,极易引发火灾。而对于LNG站场而言,因储罐泄漏引发的池火灾最为常见。目前,我国相关规范已对LNG站场储罐之间和储罐区与其他建(构)筑物之间的防火间距作出了明确规定。但这些规定值的确定主要参考国内外天然气站场的选址数据及经验分析,相关规范没有明确规定适用于我国LNG站场工程的火灾事故后果计算模型。此外,相关规范在规定站场内设施受到的热辐射限值时,涉及的事故场景为风速0级、温度21℃、相对湿度为50%。该事故场景没有考虑到风速、围堰尺寸等因素对LNG池火热辐射分布的影响,从而导致对防火间距的确定过于保守或不足等问题。因此,调研国内外LNG池火实验以及热辐射预测模型现状,分析常用LNG池火热辐射解析模型的适用范围,并建立能够适用于不同事故场景的LNG池火热辐射预测模型,对LNG站场选址、布局设计、事故后果影响评价与风险管理等具有重要指导意义。对此,本文开展了以下研究工作:(1)为了准确地预测LNG池火的火焰特征及其对周围设施的热辐射强度,建立了LNG池火热辐射CFD模型,并采用有限体积法对模型进行求解。同时,采用LNG燃烧实验数据对CFD模型的准确性进行验证。采用该CFD模型对LNG池火灾的主要影响因素(包括环境风速、围堰直径)进行分析。结果表明,该CFD模型对LNG池火的火焰特征参数以及目标监测点处热辐射强度预测结果的平均相对误差分别为8.4%和9.1%,预测精度较高。(2)通过大量文献调研,对LNG池火燃烧实验数据进行归纳和整理,并采用这些实验数据对目前LNG行业常用的火焰长度、火焰倾斜角、火焰拖曳比以及热辐射强度的计算关联式的适用范围分别进行评价,进而提出一种能够适用于不同池火灾事故场景的LNG池火热辐射预测多场景解析模型。同时,将该模型与建立的CFD模型、目前常用解析模型的预测精度进行对比。结果表明,CFD模型的预测精度最高,其次是多场景解析模型和POOLFIRE3模型,它们各自平均相对误差分别为11%、17%、20%。由于CFD模型和多场景解析模型的相对误差均在±20%以内,故模型计算结果可靠。(3)基于C语言编程和多场景解析模型,开发了 LNG池火热辐射影响范围评价软件。该软件能够针对不同事故场景(包括环境风速、围堰直径),自动将推荐的火焰长度、火焰倾斜角、火焰拖曳比计算关联式以及热辐射强度预测模型进行组合,从而得到相应事故场景的池火特征参数和目标监测点热辐射强度预测值。同时,该程序还可以用于评价LNG站场内各设施与储罐之间防火间距,判断一旦发生池火灾时,站场内设施所受热辐射强度值是否超过相关规范的规定值。此外,通过将软件的计算值与手算值进行对比,二者结果吻合,验证了软件的准确性。(4)以四川省某典型LNG站场为例,采用本文开发的LNG池火热辐射影响范围评价软件,对不同池火灾事故场景中,各设施所受的热辐射强度值进行预测,并结合国内相关规范对各设施与储罐之间的防火间距进行评价。结果表明,在不同LNG火灾事故场景中,均存在设施安全间距不足的情况。同时,对不符合要求的情形,提出相应的优化方案,包括:1)增大围堰与其周围设施之间的距离;2)减小围堰面积,采用高围堰或双容罐和全容罐;3)在LNG储罐的围堰与周围设施之间安装喷射水幕。
[Abstract]:Compared with traditional energy, Liquefied Natural Gas (LNG) has the advantages of clean, high efficiency, no poison, no corrosion, and high storage rate. It is widely used in the fields of automobile, ship, refrigeration, chemical industry and so on. With the increasing demand of LNG in China, the number of LNG stations is increasing, and the safety problems brought with it are also the more. More attention is paid to.LNG's boiling point at normal pressure at -161.5 C. Once the leakage occurs, the LNG will evaporate rapidly, causing a sudden drop in the surrounding temperature. If a clear fire is encountered, fire is easily triggered. For the LNG station, the tank fire caused by the tank leakage is the most common. At present, the relevant specifications of our country have already been to the storage tank and storage area between the LNG station and the storage tank. The fireproof spacing between other building structures is clearly defined. However, the determination of these values is mainly based on the location data and experience analysis of natural gas stations at home and abroad. The relevant specifications do not specify the model for the calculation of the consequences of the fire accident, which is applicable to the LNG station in China. When the thermal radiation limits are reached, the accident scene involves the wind speed 0, the temperature 21, the relative humidity of 50%., which does not take into account the influence of wind speed, the cofferdam size and other factors on the thermal radiation distribution of the LNG pool, thus causing the determination of the fire spacing to be too conservative or insufficient. Therefore, the investigation of the LNG pool fire experiment at home and abroad and the heat are investigated. The present situation of the radiation prediction model is to analyze the applicable scope of the LNG pool fire thermal radiation analytical model, and to establish the LNG pool fire radiation prediction model which can be applied to different accident scenes. It has important guiding significance for the site site selection, layout design, the impact assessment and risk management of the accident consequences, and the following research work has been carried out in this paper. (1) in order to accurately predict the flame characteristics of LNG pool fire and the thermal radiation intensity to the surrounding facilities, a CFD model of LNG pool fire heat radiation is established, and the finite volume method is used to solve the model. At the same time, the accuracy of the CFD model is verified by the experimental data of LNG combustion. The main influencing factors of the CFD model on the LNG pool fire are obtained. The results show that the average relative error of the CFD model to the flame characteristic parameters of the LNG pool fire and the prediction results of the thermal radiation intensity at the target monitoring point is 8.4% and 9.1% respectively, and the prediction accuracy is higher. (2) through a large number of literature investigation, the experimental data of the fire combustion in the LNG pool are summarized and arranged. These experimental data are used to evaluate the applicable range of the correlation formula of flame length, flame tilt angle, flame drag ratio and thermal radiation intensity in LNG industry, and then a multi scene analysis model of LNG pool fire thermal radiation prediction can be applied to the scene of different pool fire accidents. The CFD model is established, and the prediction accuracy of the usual analytical models is compared. The results show that the prediction accuracy of the CFD model is the highest, followed by the multi scene analysis model and the POOLFIRE3 model, their average relative errors are 11%, 17% respectively, and the relative error of the CFD model and the multi scene model is within the range of + 20%, so the model meter is calculated. The results are reliable. (3) based on the C language programming and multi scene analysis model, the LNG pool fire radiation impact range evaluation software is developed. The software can automatically apply the recommended flame length, flame tilt angle, flame drag ratio and thermal radiation intensity prediction model for different accident scenes (including ambient wind speed, cofferdam diameter). In addition, the program can also be used to evaluate the fire-proof distance between the facilities and the tanks in the LNG station, and determine whether the thermal radiation intensity of the facilities in the station is more than the prescribed value of the relevant specifications when a pool fire occurs. In addition, by comparing the calculated value of the software with the hand calculation value, the results of the two are in agreement, and the accuracy of the software is verified. (4) taking a typical LNG station of Sichuan Province as an example, using the LNG pool fire radiation impact range evaluation software developed in this paper, the thermal radiation intensity values of various facilities are predicted, and the value of the thermal radiation intensity is predicted in the scene of different pool fire accidents, The fire spacing between the facilities and the storage tanks is evaluated with the relevant domestic specifications. The results show that there are insufficient safety gaps in the facilities of different LNG fire accidents. At the same time, the corresponding optimization schemes are proposed for the cases that are not in conformity with the requirements, including: 1) increase the distance between the cofferdam and its surrounding facilities; 2) reduce the circumference. The area of weir is high cofferdam or double capacity tank and full capacity tank. 3) spray water curtain is installed between cofferdam and surrounding facilities of LNG storage tank.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE88

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