喷射雾滴烟气流动蒸发特性

Evaporation Characteristics of Atomized Droplets Sprayed in Flue Gas Flow

电站锅炉烟气脱硫废水喷入烟道蒸发是电厂废水零排放最经济可行的技术途径之一。针对该技术实际应用中存在的在烟道壁面上结垢腐蚀问题,以单台300 MW机组为对象,将针对连续相烟气的湍流流动传热欧拉方法,以及离散相雾化液滴群流动蒸发的拉格朗日方法相结合,建立物理数学模型。通过数值模拟方法,研究脱硫废水喷射雾滴在烟气中的流动蒸发特性及其影响因素,获得不同运行条件下喷雾的扩散范围和液滴在烟气内的运动轨迹。结果表明:烟气温度越高、雾化液滴群的直径越小,其完全蒸发所需的时间和距离越短;采用多喷嘴小流量的布置方式可以提高雾化液滴群的蒸发质量;喷嘴喷射方向的选择应该保证雾化液滴群与烟气相对运动增强的同时,保证液滴能在规定距离和时间内完全扩散并与烟气进行充分接触和换热,实现雾化液滴群蒸发质量的最大化;而液滴初速度、喷嘴的喷射全锥角、烟气速度对蒸发率的影响不大。研究结果可为火电厂脱硫废水烟气蒸发的工艺设计及性能调控提供依据。

Spraying flue gas desulfurization(FGD)wastewater into flue duct is an economical and feasible technology to achieve zero discharge in power plant.To deal with the scale and corrosion on flue walls that exist in the practical application of this technology,the physical and mathematical models are established based on a 300 MW power plant.The Eulerian-Lagrangian approach is used to describe the thermo-fluid behavior of FGD wastewater in flue gas,by which the turbulent flow heat transfer of flue gas is described by the Eulerian framework and the evaporation of water droplets is described using the Lagrangian framework.By numerical simulation the flow evaporation characteristics and influencing factors of FGD wastewater droplets sprayed in flue gas were studied.The diffusion range and trajectories of atomized droplets under different operating conditions were obtained.The following results were gained:higher flue gas temperature and smaller diameter of the atomized droplets contribute to shorter time and distance for complete evaporation.Besides,the arrangement of small-flow-multi nozzles can improve the evaporation of atomized droplets.The spray direction must ensure that the relative movement between atomized droplets and flue gas is enhanced,while the droplets can fully diffuse and contact with the flue gas within a specified distance and time,achieving maximum evaporation of the atomized droplets.However,the initial velocity of atomized droplets,the spray full cone angle of nozzles,and the velocity of flue gas have little influence on atomized droplets evaporation.These research results can provide process design and performance regulation of the FGD wastewater evaporation in flue duct of thermal power plants.