【作者】 张国瑞；

【导师】 何伯述；

【作者基本信息】 北京交通大学 ， 动力机械及工程， 2011， 硕士

【摘要】 近年来,环境保护越来越受到重视。火力电站的燃煤锅炉在生产时产生大量的废气,包括氮氧化物、硫氧化物、飞灰等,因此,火力电站是颗粒污染物的重要来源之一。目前,电除尘器是电站的主要除尘设备之一,当烟气没有经过预除尘时烟气中粉尘颗粒的含量较多,电除尘器的除尘效率较低,能量损失大。为提高电站的除尘效率,减少能量损失,减少烟气的颗粒物对于空气预热器等的磨损,在省煤器下增设灰斗对烟气进行预除尘,能够很好的满足生产要求。为较大限度地提高除尘效率、减少压力损失,对省煤器灰斗系统进行优化,包括对灰斗的形状以及在转向室中所布置的导流板。通过冷态锅炉实验与数值模拟相结合的方法研究系统的性能,研究过程中对于冷态实验的搭建及改进提出了一些建议,并验证了模拟的可行性。实验中为保证流动相似采用了欧拉相似准则,在满足第二自模区要求的同时能够降低对动力设备的要求,减少风机的给风量。本文采用了商业软件fluent,应用颗粒轨道模型对系统进行数值模拟计算,并与实验结果进行对比。通过对多种情况下的气相流场性能、颗粒运动轨迹、除尘效率及压力损失的分析,发现导流板的布置位置对于系统的性能有很大的影响。研究发现,颗粒的大小以及颗粒进入系统的位置对于颗粒的运动轨迹有着重要影响,直接影响系统的除尘效率,初始位置距离出口较远及直径较大的颗粒容易被灰斗系统所收集；导流板可以优化出口的流场分布,减轻由于速度分布不均而对烟道某一侧面造成的磨损；导流板的角度、位置、数量等对于系统的性能有重大影响,且存在一定的规律,通过这些规律能够很快为实际生产提供一个可行的方案。更多还原

【Abstract】 Recently, more and more attention were paid on environmental protection. A large number of emissions, including Nitrogen oxides, Sulfur oxides and fly ash, were produced during Coal-fired power stations operation. The power plants were the sources of particle pollution. The electrostatic precipitator (ESP) was widely used in power plant. But the ESP has low efficiency and needs more energy when it dealt with flue without precollection. In order to increase the separation efficiency and reduce the wear and of air preheater, one easy way is the precollection of fly ash before ESP by adding ash-hoppers downstream the economizer.To obtain higher separate efficiency with lower pressure loss, it is necessary to optimize the ash-hopper’s structure to find reasonable arrangements for the baffles which were used to change the flow direction of flow gas in the flue. The results of system performance were obtained from the iso-thermal experiments and simulation. There were some advises mentioned for the iso-thermal model experiment, and the rationalization of the simulation result were verified by the iso-thermal experiments. The Euler similarity criterion was adopted in experiment, so the iso-thermal experiments could enter the second self-modeling region to be similar to the flow characteristics of prototype. In this case, less energy was needed for the power of experiment and less air from fans.The numerical simulation was carried out by the commercial CFD software, Fluent. It was found that the system structure, especially the baffles and the baffle arrangements, is important to the performance. The most suitable structure was found through simulation results including the velocity and pressure fields of gas phase, the pathlines of particles, the pressure drop and the separation efficiency. The diameter and the release location of particles had great influence to their pathlines. Particles far from the exit and with large diameter were easily trapped. The baffles could used to optimize the velocity field, decreasing the wear of flue from particles. The angles, arrangement, quantity of baffles were all important for the system performance. There were some laws for the system performance when they changed. Though the laws, the most valuable structure was picked quickly.更多还原