天然气长输管道阀室冷放空风险分析与控制

发布时间：2018-03-16 10:10

本文选题：天然气长输管道　切入点：阀室　出处：《西南石油大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着国家经济快速发展,对天然气的需求量逐年增加,但考虑到天然气资源分布不均的情况,我国石油公司修建了大量的天然气长输管道。阀室在天然气长输管道系统中具有重要作用,当管道出现事故或需要改造时,需要利用阀室截断来气,并放空特定管段内天然气,以保证维修维护操作能够安全地进行。我国天然气管道阀室数量较多,所处地形多种多样,影响阀室放空作业的外部因素复杂多变,加上长输管道内的天然气本身具有高压、易燃易爆等特性,由立管直接排放天然气的过程具有一定风险。在近几年的天然气长输管道放空作业中,由于放空方式不当和障碍物的影响等导致了一些放空事故的发生,造成了巨大的经济损失,威胁到相关人员的生命安全,并给周边环境带来了污染和破坏。论文利用故障树分析原理,识别了阀室冷放空主要危害,通过对故障树的定性和定量分析,找出阀室冷放空过程中与“人—机—环境”有关的风险。运用流体力学、射流力学等理论分析了气体扩散主要影响因素,并分别确定了计划性和事故性放空量的计算方法。分别考虑有/无障碍物两种环境情况,建立了天然气冷放空物理模型；运用PHAST软件和FLUENT软件进行数值模拟,定性和定量地分析了风速、大气稳定度、初始出口压力、出口直径以及障碍物情况等变量对扩散过程和范围的影响规律,划分出不同工况下放空时气体扩散危险区域。运用HYSYS软件计算了不同压力和温度条件下放空阀处的温降大小,分析了温降效应对放空阀性能的影响；计算了作业过程中立管出口位置气体动能增加引起的气体焓降低量,分析了气体与管壁的对流换热引起的放空立管处的低温效应。最后,在所得结果的基础上提出了相关的风险控制措施。论文得到的气体扩散的数值模拟结果与气体扩散理论相符,并且与放空现场实测数据的偏差在可接受的范围内,对于放空阀和放空立管处的温降计算结果能较好解释阀室冷放空作业现场出现的相关现象。研究成果具有较好的工程实用价值,对天然气长输管道阀室冷放空作业的风险控制和后果预测具有一定指导意义。
[Abstract]:With the rapid development of the national economy, the demand for natural gas has increased year by year, but considering the uneven distribution of natural gas resources, The valve chamber plays an important role in the long distance natural gas pipeline system. When the pipeline happens or needs to be reformed, it is necessary to use the valve chamber to cut off the gas and empty the natural gas in the specific section. In order to ensure that the maintenance and maintenance operation can be carried out safely, the number of valve chambers in natural gas pipelines in China is relatively large, the topography is varied, the external factors affecting the emptying of valve chambers are complex and changeable, and the natural gas in the long distance pipeline has high pressure. The process of discharging natural gas directly from riser has certain risks due to the characteristics of flammability and explosive. In recent years, during the long distance pipeline emptying operation, some emptying accidents occurred due to improper emptying mode and the influence of obstacles, etc. It has caused huge economic losses, threatened the safety of the relevant personnel, and brought pollution and damage to the surrounding environment. Based on the principle of fault tree analysis, this paper identifies the main hazards of cold emptying in valve chamber. By qualitative and quantitative analysis of fault tree, the risks related to "man-machine-environment" in cold emptying process of valve chamber are found out. The main influencing factors of gas diffusion are analyzed in the theory of jet mechanics, and the calculation methods of planned and accidental emptying are determined respectively. The physical model of natural gas cold emptying is established by considering the two kinds of environmental conditions with or without obstacles. The effects of wind speed, atmospheric stability, initial outlet pressure, outlet diameter and obstacle on the diffusion process and range are analyzed qualitatively and quantitatively by using PHAST and FLUENT software. The dangerous area of gas diffusion under different conditions is divided. The temperature drop of the valve under different pressure and temperature is calculated by using HYSYS software, and the effect of temperature drop on the performance of the valve is analyzed. The gas enthalpy decrease caused by the increase of gas kinetic energy at the exit position of riser during operation is calculated, and the low temperature effect at emptying riser caused by convection heat transfer between gas and tube wall is analyzed. On the basis of the obtained results, the related risk control measures are proposed. The numerical simulation results of gas diffusion obtained in this paper are consistent with the gas diffusion theory, and the deviation from the field measured data is acceptable. For the temperature drop calculation results of the emptying valve and the emptying riser, the related phenomena in the cold emptying operation field of the valve chamber can be better explained. The research results have good engineering practical value. It has certain guiding significance for risk control and consequence prediction of valve chamber cold emptying operation in long distance natural gas pipeline.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE88

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