液氨泄漏扩散数值模拟及疏散研究

发布时间：2018-05-02 19:54

本文选题：数值模拟 + 氨气　；参考：《天津理工大学》2017年硕士论文

【摘要】：随着“十二五”经济规划的发展实施,化工行业成为了国民经济发展的热点行业,具有着重要的地位和作用。绝大多数化工企业内都设置有液氨储罐,储罐内的氨是在高压状态下以液态形式密封储存的。经过长时间的运行,压力储罐在储存介质的电化学腐蚀、内部高压、外部操作破坏的共同作用下极易发生储罐泄漏事故,泄漏的气体往往会导致周围的人员急性中毒或者死亡,甚至可能引起火灾及爆炸的危险。为此国内外学者针对氨气泄漏扩散进行了大量的试验和数值模拟工作,主要的研究方向是泄漏口大小、泄漏口形状、储罐压力、大气稳定度、障碍物等因素对氨气扩散的影响,但是氨气在扩散的过程中相变的研究一直是该研究领域的难点。此外,关于液氨储罐发生泄漏事故后的应急疏散也是该研究领域的热点之一。本文针对液氨储罐泄漏事故,采用数值模拟的方法研究不同因素对氨气扩散的影响。主要工作和结论如下:本文基于FLUENT软件建立液氨储罐三维全尺寸模型,模拟了风速、风向、障碍物对氨气扩散的影响。氨气在泄漏口附近由于受到罐内压力的作用呈水平扩散,并且随着时间的推移向下风向扩散的距离逐渐增大;氨气在远离泄漏口时由于密度小于空气密度而受到浮力的作用,呈现显著地上扬。在不同风速下,氨气在Y轴上的扩散距离随着风速的逐渐增加由大变小,因此,风速可以加剧氨气向下风向的扩散速度增大气体扩散的影响区域,也可以加剧气体在大气中的稀释速度,防止了氨气在扩散过程中浓度的堆积。在不同风向下,氨气在风向与储罐泄漏口水平时由于动力的作用将沿着垂直于泄漏口的方向进行扩散;在远离泄漏口一定距离后由于浮力和风力的作用主要沿着平行于泄漏口的方向进行扩散,即顺着风向进行扩散。氨气向下风向扩散的速度和影响区域由于有障碍物存在明显减小;正前方的氨气一部分顺着障碍物边缘向两侧蔓延扩散,一部分在障碍物正前方产生回流进行反方向扩散;障碍物上方的气体攀爬过障碍物后继续向下风向进行扩散并且伴随有上扬现象。基于FLUENT软件开发了液氨蒸发相变模型,通过软件用户自定义功能(UDF)导入到模拟计算中,模拟了液氨蒸发相变过程,将液氨蒸发扩散的模拟结果与氨气扩散时的模拟结果进行对比值找出其中的规律所在。分析液氨与氨气不同体积比条件下,液氨蒸发相变对氨气扩散的影响。当扩散的氨气中伴随有液氨时,气体的扩散速度和影响区域明显减小。这是因为气云中的液滴使得气云的质量变大,减小了气云的扩散速度和影响区域。利用GIS软件模拟计算某化肥厂液氨储罐发生泄漏后,在不同风向影响下周围群众向附近的安置点进行紧急疏散时的最佳路径。
[Abstract]:With the development and implementation of the 12th Five-Year Plan, the chemical industry has become a hot industry in the development of the national economy and plays an important role. Liquid ammonia storage tanks are installed in most chemical enterprises. The ammonia in storage tanks is sealed in liquid form under high pressure. After running for a long time, the pressure storage tank is prone to leakage accident under the combined action of electrochemical corrosion of storage medium, internal high pressure and external operation damage, and the leaking gas will often lead to acute poisoning or death of the people around it. It may even cause the danger of fire and explosion. For this reason, scholars at home and abroad have carried out a lot of experiments and numerical simulation work on ammonia leakage diffusion. The main research direction is the influence of leakage port size, leakage port shape, tank pressure, atmospheric stability, obstacles and other factors on ammonia diffusion. However, the study of phase transition in the process of ammonia diffusion has been a difficulty in this field. In addition, emergency evacuation after liquid ammonia tank leakage is also one of the hotspots in this field. In this paper, the effect of different factors on ammonia diffusion is studied by numerical simulation for the leakage accident of liquid ammonia storage tank. The main work and conclusions are as follows: based on FLUENT software, the three-dimensional full-scale model of liquid ammonia storage tank is established, and the effects of wind speed, wind direction and obstacles on ammonia diffusion are simulated. Ammonia diffuses horizontally in the vicinity of the leak due to pressure in the tank, and the distance of downward wind diffusion increases gradually with time, while ammonia gas is buoyant when it is far away from the leak because the density is less than the air density. Showing a significant upswing. At different wind speeds, the diffusion distance of ammonia on the Y-axis changes from large to small with the increasing of the wind speed. Therefore, the wind speed can aggravate the diffusion velocity of ammonia gas downward wind direction and increase the influence area of the gas diffusion. It can also increase the dilution rate of the gas in the atmosphere and prevent the accumulation of ammonia in the diffusion process. Under different wind directions, ammonia diffuses along the direction perpendicular to the leakage outlet due to the effect of dynamic force. After a certain distance away from the leak, the buoyancy and wind force mainly diffused along the direction parallel to the leak, that is, along the direction of the wind. The velocity of ammonia diffusion down the wind direction and the influence area are obviously reduced due to the presence of obstacles, and the ammonia gas in front of the barrier spreads along the edge of the barrier, and partly reflux in the front of the obstacle to spread in the reverse direction. The gas above the barrier climbs over the barrier and continues to spread down the wind with an upturn. Based on FLUENT software, the liquid ammonia evaporation phase change model is developed, and the process of liquid ammonia evaporation phase change is simulated by importing it into the simulation calculation by software user defined function. The simulation results of liquid ammonia evaporation diffusion are compared with those of ammonia diffusion to find out the law. The effect of liquid ammonia evaporation phase transition on ammonia diffusion was analyzed under different volume ratio of ammonia to ammonia. When there is liquid ammonia in the diffused ammonia, the diffusion velocity and the influence area of the gas decrease obviously. This is because the droplets in the gas cloud increase the mass of the gas cloud and reduce the diffusion speed and the influence area of the gas cloud. GIS software was used to simulate and calculate the optimal path of emergency evacuation of the surrounding people to nearby settlements under the influence of different wind directions after leakage of liquid ammonia storage tanks in a fertilizer plant.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ113.5

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