天然气管道环境风险影响分析

对某市天然气输气管道工程不同气象、不同源高条件下事故环境风险的影响范围进行预测与分析.采用气体扩散多烟团模式预测天然气管道泄露及火灾事故的影响范围.结果表明：如果发生天然气泄漏、火灾事故,天然气管道泄漏处下风向的污染物危害范围呈圆环分布;各污染物的扩散多以小风1.5 m/s,稳定度为F类条件下的影响范围最大;在一定的风速和稳定度下,事故影响范围随源高的增高而降低.     

管道输运高压氢气与天然气的泄漏扩散数值模拟

基于有限体积法,建立了管道运输高压氢气及天然气的泄漏扩散模型,考虑到氢气与天然气的管道泄漏事故危险性不同,进行了数值模拟与对比,得出了管道泄漏后氢气与天然气的不同泄漏扩散特性.结果表明:高压氢气的泄漏扩散形成的危险云团较大而且集中;氢气初始的泄漏速度比天然气大得多,与周围环境达到压力平衡所需时间较天然气短;随着扩散时间的增加,氢气危险气体云团扩散最大高度较天然气增加得快;在近地面区氢气泄漏扩散产生的危险后果较天然气小.     

基于PHAST软件的液化天然气储罐泄漏事故模拟研究

利用PHAST软件对某大型LNG储罐建立事故模拟模型,进行泄漏事故模拟分析,定量计算了LNG储罐发生泄漏后的扩散、闪火、爆炸、池火影响范围,比较分析了不同风速条件下的事故影响能力。结果表明:风会加快气化后的LNG向空气的扩散,相同浓度的扩散气在高风速下的影响范围更小;风速低的气象条件不利于甲烷的扩散,甲烷浓度会比较高风速下更高,更有可能发生闪火爆炸事故;高风速会使LNG储罐扩散后引起的闪火热辐射范围更远,低风速不能有效降低LNG储罐扩散后引起的闪火热辐射范围;不同的风速对其垂直于风速的闪火热辐射影响区域基本没有影响;较高风速可减小爆炸发生影响区域,较好的风况条件有利于蒸汽云的扩散,将有效缩小爆炸事故的影响范围;较低的风速下池火灾影响范围较小,利于事故现场的应急控制,但是低风速工况不利于气体的扩散,将会生成较高热辐射值的区域。PHAST对泄漏事故的模拟分析有利于库区的安全运行和事故预防。     

输油圆管弯头段泄漏流场数值模拟

目前各国在役管道存在的老化及腐蚀等问题对人民生命财产安全构成了潜在的危害。如何及时准确地检测管道泄漏现象的发生,对管道安全运行及人民群众的生命财产安全具有重要意义.采用有限容积法,建立三维管道泄漏方程,分析了不同输送速度及泄漏孔径对泄漏后管内流场影响。研究发现：输送速度和泄漏孔径对管内压强、局部高压区、泄漏量、泄漏质量百分比的影响相反。管内压强和流量变化特性为高科技管道检测泄漏技术提供了可能性。     

天然气长输管道项目环境风险评价实例分析

环境风险评价是环境影响评价的重要组成部分。结合工程实例,旨在为长输天然气管道项目环境风险评价提供一种技术思路。以环境风险评价技术导则为指导,进行风险识别、源项分析、事故后果分析及风险值计算,确定长输管道(含阀室)和5个工艺站场为重大风险源,主要风险事故类型为长输管道和站场泄漏天然气引起的火灾和爆炸事故,针对性提出风险防范措施,要求制定事故应急预案,强化安全管理。     

浅析管道泄漏的原因及对策

鉴于目前我国很大一部分管道使用时间已超过20年,管网进入事故高发期,泄漏爆管事故频频发生.针对管网泄漏的原因进行了研究,认为主要是由外力破坏、管道腐蚀、设计不合理、安装质量及检测验收不合格等原因造成,并对每一项进行了深入分析,在此基础上给出相应解决方法.     

阴极保护在埋地管道中的应用

就目前情况而言,输送天然气石油的钢质管道基本上全部埋置在土壤中,输送的介质具有强烈的腐蚀性,不仅腐蚀管道的内壁,还对外壁有一定的腐蚀,若管道腐蚀得严重出现孔洞,那么会引发事故,产生危害的机率是非常高的.重点探讨阴极保护技术在埋地钢质管道中的应用情况,其参考意义重大.     

川东北高含硫天然气采输全流程中水合物生成及抑制研究进展

川东北高含硫气藏在开采、生产和集输过程中,极易形成天然气水合物,严重制约了高含硫气井的安全高效开发。水合物的形成需要满足一定的热力学和动力学条件,实际生产中,天然气组分、温度、压力及地层水矿化度等都会对水合物形成的相平衡条件产生影响,其中硫化氢含量的影响最为显著,低温高压和高硫化氢含量是水合物生成的重要原因。高含硫天然气一旦生成水合物,水合物颗粒会快速运移和聚集,极易在井筒、井口、场站、集输管线节流部位形成冰堵。自由水、硫化氢含量、节流效应、温度、压力及残余物等都会对水合物堵塞造成影响,其中自由水是形成高含硫天然气水合物堵塞的关键因素。高含硫天然气水合物防治措施主要分为热力学防治和动力学防治,破除水合物生成的热力学条件是水合物防治的关键,开发高效水合物动力学抑制剂是水合物防治的热门思路。     

元坝超深高含硫生物礁大气田安全有效开发技术

元坝气田是目前世界上气藏埋藏最深、开发风险最大、建设难度最高的酸性大气田,国内外没有成功先例,缺乏相应理论、技术、方法。针对元坝气田长兴组气藏超深、高温、高压、高含硫、礁体储层复杂、气水关系复杂、天然气组分复杂、压力系统复杂、地形地貌复杂等"一超、三高、五复杂"的特点,以及面临的地质规律不清、气藏描述太难、有效开发不易、钻完井瓶颈多、安全环保压力大等五大开发难题,创新了生物礁发育与储层分布开发地质理论,提出了超深条带状小礁体气藏有效开发模式,形成了超深层小礁体气藏精细描述技术、超深高含硫水平井钻完井技术、高含硫天然气深度净化技术、复杂山区高含硫气田安全集输技术等开发关键技术体系,建成了世界上第一个7000m超深高含硫生物礁大气田,突破了7000m超深高含硫生物礁气藏开发禁区,突破了7000m超深高含硫水平井钻完井技术瓶颈,实现了高含硫天然气深度净化技术国产化,实现了复杂山区高含硫气田安全集输技术智能化,确保了大型超深高含硫生物礁气田安全环保有效开发。     

川东地区高含硫气井元素硫沉积分析及防治措施探索

近年来,川东地区长兴、飞仙关等高含硫气藏气井的投产,为弥补天然气产量递减起到了关键作用。但是,高含硫气井在生产过程中,天然气中的硫会随气体状态的变化而析出,堵塞气流通道,影响气井正常生产。结合高含硫气藏生产特征及气质组分,分析认为,元素硫沉积的主要影响因素是气流速度和压力、温度,而压力、温度的影响主要表现在硫的溶解度上。对典型高含硫生产井峰X井进行元素硫沉积分析。提出相应的防治措施:通过适当提高采气速度,控制井筒压力和温度的变化,并采取加注化学硫溶剂等措施,可以防治元素硫沉积;特别提到了采用高抗硫材质小直径管加注工艺,这是结合川东地区高含硫气井完井管柱特点(油套环空安装有永久封隔器)采用的药剂加注工艺。通过对高含硫气井元素硫沉积的影响因素分析和防治措施的推荐,为高含硫气井的稳定开采提供借鉴。     

Study on leakage and explosion consequence for hydrogen blended natural gas in urban distribution networks

It appears to be the most economical means of transporting large quantities of hydrogen over great distances by the existing natural gas pipeline network. However, the leakage and diffusion behavior of urban hydrogen blended natural gas and the evolution law of explosion characteristics are still unclear. In this work, a Computational Fluid Dynamics three-dimensional simulation model of semi-confined space in urban streets is developed to study the diffusion process and explosion characteristics of hydrogen-blended natural gas. The influence mechanism of hydrogen blending ratio and ambient wind speed on the consequences of explosion accident is analyzed. And the dangerous area with different environmental wind effects is determined through comparative analysis based on the most dangerous scenarios. Results indicate that the traffic flow changes the diffusion path of the jet, the flammable gas cloud forms a complex profile in many obstacles, high congestion level lead to more serious explosion accidents. Wind effect keeps the flammable gas cloud near the vehicle flow, the narrow gaps between the vehicles aggravate the expansion of the flammable gas cloud. When the wind direction is consistent with the leakage direction, hydrogen blended natural gas is gathered in the recirculation zone due to the vortex effect, which results in more serious accident consequences. With the increase in hydrogen blending ratio, the higher content of H and OH in the gas mixture significantly increases the premixed burning rate, the maximum overpressure rises rapidly when the hydrogen blend level increases beyond 40%. The results can provide a basis for construction safety design, risk assessment of leakage and explosion hazards, and emergency response in hydrogen blended natural gas distribution systems.     

A numerical study of hydrogen leakage and diffusion in a hydrogen refueling station

Studies focused on the behavior of the hydrogen leakage and diffusion are of great importance for facilitating the large scale application of the hydrogen energy. In this paper, the hydrogen leakage and diffusion in six scenarios which including comparison of different leakage position and different wind effect are analyzed numerically. The studied geometry is derived from the hydrogen refueling station in China. Due to the high pressure in hydrogen storage take, the hydrogen leakage is momentum dominated. The hydrogen volume concentration with the variation of the leakage time in different scenarios is plotted. More importantly, profiles of the flammable gas cloud at the end of the leakage are quantitatively studied. Results indicate that a more narrow space between the leakage hole and the obstacle and a smaller contact area with the obstacle make the profile of the flammable gas cloud more irregular and unpredictable. In addition, results highlight the wind effect on the hydrogen leakage and diffusion. Comparing with scenario which the wind direction consistent with the leakage direction, the opposite wind direction may result in a larger profile of the flammable gas cloud. With wind velocity increasing, the profile of the flammable gas cloud is confined in a smaller range. However, the presence of the wind facilitates the form of the recirculation zone near the obstacle. With an increase of the wind velocity, the recirculation zone moves downward along the obstacle. Thus, the hydrogen accumulation is more prominent near the obstacle.     

Safety analysis of leakage in a nuclear hydrogen production system

Due to its unique advantages, such as clean and pollution-free, hydrogen energy has gradually improved its energy transition position. Constructing nuclear hydrogen production systems is a necessary means to achieve large-scale hydrogen production, and the study of hydrogen leakage and diffusion behavior is critical to commercializing hydrogen production systems. In engineering practice, the distance between the hydrogen storage device and the nuclear power plant is an important indicator to measure the safety of nuclear hydrogen production. To study the influence of gas storage tank's own conditions and external environmental conditions on leakage diffusion, influencing factors such as wind speed, leakage direction, leakage diameter, leakage height, and leakage angle are discussed in the present study. By calculating severe working conditions combined with the above multiple factors, the longest distance of hydrogen diffusion is determined. Finally, peak overpressure impact generated by hydrogen explosion was evaluated, and the minimum separation distance required to avoid safety risks was predicted. The results demonstrate that when the wind direction is consistent with the leakage direction, and the leakage angle is 0°, the higher the wind speed, the larger the leakage diameter and the lower the leakage height, resulting in a longer diffusion distance. Under more extreme and severe working conditions, the diffusion distance of combustible hydrogen cloud can reach as far as 237 m. Once hydrogen diffusion explodes, the minimum separation distance required is about 338 m. This research provides an effective method for safety risk assessment of a nuclear hydrogen production system.     

薄叶气封流场结构与密封、扭矩特性的数值研究

采用CFX商业软件,数值模拟了薄叶气封内的三维流动,分析了薄叶气封的流场结构和密封特性以及扭矩随转速和抬起量的变化。结果表明,由于薄叶间距很狭窄,壁面对气体的黏性阻抗大于气流的膨胀加速,气体同时降低速度与密度,泄漏流量明显减小。此外,转子转数与薄叶抬起量的变化几乎不影响泄漏量。在转子转数一定时,薄叶上抬量愈小,转子承受的摩擦扭矩愈大。而当薄叶上抬量一定,转子转数增加,摩擦扭矩增大。     

变形对小型Wankel转子发动机端面漏气的影响研究

以计算得到理想状态下的缸内压力、温度、传热系数为初始边界条件,用有限元方法计算发动机温度场,用试验测得的温度场校核计算的准确性,然后将温度场结果作为已知条件计算变形,得到漏气面积并计算端面漏气初值。用漏气后转子发动机状态更新计算边界条件,进行循环计算,最终得到端面漏气量。之后,用此方法研究了转速对端面漏气量的影响,得出如下结论:发生变形后,转子与端盖之间的漏气面积在曲轴转角约630°时达到最大值,最大漏气面积随转速的增加呈拟线性下降趋势;漏气率在上止点附近达到最大值,在上止点附近端面漏气量约占端面总漏气量的50%。漏气率随发动机转速的增加逐渐减小,最大漏气率所对应的曲轴转角随转速的增加而减小。     

Framework design of a hybrid energy system by combining wind farm with small gas turbine power plants

Owing to the stochastic characteristic of natural wind speed, the output fluctuation of wind farm has a negative impact on power grid when a large-scale wind farm is connected to a power grid. It is very difficult to overcome this impact only by wind farm itself. A novel power system called wind-gas turbine hybrid energy system was discussed, and the framework design of this hybrid energy system was presented in detail in this paper. The hybrid energy system combines wind farm with several small gas turbine power plants to form an integrated power station to provide a relatively firm output power. The small gas turbine power plant has such special advantages as fast start-up, shutdown, and quick load regulation to fit the requirement of the hybrid energy system. Therefore, the hybrid energy system uses the output from the small gas turbine power plants to compensate for the output fluctuation from the wind farm for the firm output from the whole power system. To put this hybrid energy system into practice, the framework must be designed first. The capacity of the wind farm is chosen according to the capacity and units of small gas turbine power plants, load requirement from power grid, and local wind energy resource distribution. Finally, a framework design case of hybrid energy system was suggested according to typical wind energy resource in Xinjiang Autonomous Region in China.     

Framework design of a hybrid energy system by combining wind farm with small gas turbine power plants

Owing to the stochastic characteristic of natural wind speed, the output fluctuation of wind farm has a negative impact on power grid when a large-scale wind farm is connected to a power grid. It is very difficult to overcome this impact only by wind farm itself. A novel power system called wind-gas turbine hybrid energy system was discussed, and the framework design of this hybrid energy system was presented in detail in this paper. The hybrid energy system combines wind farm with several small gas turbine power plants to form an integrated power station to provide a relatively firm output power. The small gas turbine power plant has such special advantages as fast start-up, shutdown, and quick load regulation to fit the requirement of the hybrid energy system. Therefore, the hybrid energy system uses the output from the small gas turbine power plants to compensate for the output fluctuation from the wind farm for the firm output from the whole power system. To put this hybrid energy system into practice, the framework must be designed first. The capacity of the wind farm is chosen according to the capacity and units of small gas turbine power plants, load requirement from power grid, and local wind energy resource distribution. Finally, a framework design case of hybrid energy system was suggested according to typical wind energy resource in Xinjiang Autonomous Region in China.     

Numerical Simulation on the Dispersion of Natural Gas Releases from a Buried Pipeline

Pipeline is a major way for natural gas transportation. Accidental gas release from a pipeline might lead to great economic losses and casualties. Therefore, it is important to investigate the dispersion characteristics of natural gas release from pipelines. Most previous studies on accidental natural gas release from pipelines mainly focused on bare pipelines and adopted simplified 2D models. This paper first established dispersion models of natural gas release from buried pipelines with high and low pressure, respectively. The numerical methods were validated by Trial 26 of the Thorney Island field experiment and the dispersion model was found to be reasonable and reliable. Then, comparative study between 2D and 3D dispersion model of released natural gas was carried out, which proved that 3D model had superiority upon the 2D model. Then the 3D model was employed to simulate dispersion process of released natural gas by changing pipeline pressure, orifice diameter, wind speed, and soil properties. Finally, the effect of leakage conditions on consequence distance was analyzed. The numerical results could provide technical supports for the design of emergency disposal equipments and urgent pipeline repairs.     

风电与燃气轮机互补发电系统发电成本分析

在采用风电场与小型燃气轮机组成的互补系统发电特性参数的基础上,详细分析了互补系统发电成本的构成和各自的计算方法。采用新疆达坂城风电场的风速数据,基于互补系统的发电特性参数和风电场与燃气轮机电站的发电成本构成,应用改进过的等额支付折算法,在当前的技术条件和价格下,计算了风电场子系统和燃气轮机电站子系统各自的折旧成本、燃料成本和运行维护成本,得到了整滚发电系统发电成本的计算方法,为在新疆地区实现这种互补发电系统提供经济分析基础。     

泄漏孔径对特高压GIL管SF6泄漏影响的混合数值模拟

  目的  为了分析具有6 km跨度特高压GIL内SF₆泄漏气体的泄压过程及其扩散形态,提出了一种一、三维混合CFD计算方法。利用1D Flowmaster研究具有不同孔径的泄漏口对SF₆泄压过程的影响。利用3D Fluent分析SF₆在管廊内的扩散形态、浓度分布。  方法  为了验证混合数值方法的准确性,对比了1D Flowmaster和3D Fluent对同一管廊结构SF₆泄压过程的计算结果。  结果  仿真对比结果表明,Flowmaster模拟泄压过程具有计算速度快、精度高的特点。  结论  结合通风设计要求,获得基于泄漏孔径区间的轻度、中度、重度泄漏事故分类及对应扩散形态、浓度分布等重要数据,可为实际应用设计、事故处理提供指导。