【作者】 王健；

【导师】 潘伶；

【作者基本信息】 福州大学 ， 除尘系统、大气污染治理（专业学位）， 2020， 硕士

【摘要】 为了应对日益严重的雾霾问题,我国对烟尘颗粒物的排放标准要求越来越高,而传统除尘器对颗粒的脱除效率随颗粒的粒径减小而降低。如何有效控制超细颗粒物的排放,对我国燃煤电厂除尘系统提出了很大的挑战。本文首先建立颗粒碰撞聚并核函数数学模型,将颗粒组分以及通风因子考虑在内,改进蒸汽异质核化凝结生长率核函数数学模型;其次将建立的数学模型写入颗粒群平衡模型,耦合欧拉多相流、组分运输和k-ε双方程湍流模型;利用FLUENT软件模拟烟气在生长管中过饱和度分布以及超细颗粒在生长管中长大特性,并与现有试验对比验证改进后的数学模型精确性;最后模拟超细颗粒在普通生长管、旋流生长管、管束型相变凝并器以及波纹板型相变凝并器长大特性和脱除超细颗粒的效率,对波纹板型相变凝并器结构进行了优化。研究结果表明:(1)利用改进后蒸汽异质核化凝结生长率核函数模拟颗粒长大特性的模拟精度为88.2%,比原蒸汽异质核化凝结生长率核函数模拟精度提高了11.3%,改进后凝结生长率核函数更能准确的模拟颗粒长大特性。(2)流速和有无传质对生长管过饱和度影响较大,而生长管壁面温度和颗粒添加量对生长管过饱和度影响较小。与利用饱和湿空气流过冷壁生长管构建过饱和环境的方法相比,利用低温干空气中添加高温蒸汽构建过饱和环境方法获得的过饱和度更均匀,而且促进颗粒长大效果更明显。(3)在普通生长管内加装旋流装置后,旋流生长管更容易获得较高且均匀的过饱和度。旋流装置不仅对超细颗粒凝并长大有很好的促进作用,而且旋流生长管对超细颗粒数量浓度脱除效率高达65.8%。(4)模拟优化得出波纹板型相变凝并器波纹板间距为39mm、波纹型正弦曲线振幅为129mm、烟气流速为1.4 m/s时,相变凝并器经济与适用性最高。(5)与波纹板型相变凝并器相比:管束型相变凝并器对烟气冷却效果更好,更容易获得较高且均匀的过饱和度;管束型相变凝并器促进颗粒长大7.71倍,明显高于波纹板型相变凝并器的5.52倍;管束型相变凝并器对颗粒数量浓度脱除效率高达64.7%,比波纹板型相变凝并器脱除率高37.5%。两种相变凝并器对提高超精细分离器脱除颗粒效率具有明显的促进作用。更多还原

【Abstract】 In order to deal with the increasingly serious haze problem,China’s emission standards for soot particles are getting higher and higher,however,the efficiency of traditional filter to remove particles decreases as the particle size decreases.How to effectively control the emission of ultrafine particles poses a great challenge to the filter system of coal-fired power plants in China.In this paper,the mathematical model of particle collision and coalescence kernel function is firstly established,and the mathematical model of the kernel function of condensation growth rate of heterogeneous nucleation of steam is improved by taking the particle components and ventilation factors into consideration.Secondly,the established mathematical model is written into the population balance model,coupled with Euler multiphase flow,component transport and k-ε two-equation turbulence model;FLUENT software was used to simulate the supersaturation distribution of flue gas in the growth tube and the growth characteristics of ultrafine particles in the growth tube,and the accuracy of the improved mathematical model was verified by comparison with existing experiments.Finally,the growth characteristics and removal efficiency of ultrafine particles in ordinary growth tube,swirl growth tube,tube bundle type phase-transition agglomerator and corrugated plate type phase-transition agglomerator are simulated,the structure of corrugated plate type phase-transition agglomerator is optimized.The results show that:(1)Using the improved steam heterogeneous nucleation condensation growth rate kernel function to simulate particle growth characteristics,the simulation accuracy is 88.2%,which is 11.3% higher than the original steam heterogeneous nucleation condensation growth rate kernel function simulation accuracy.The improved kernel function of condensation growth rate can simulate particle growth characteristics more accurately.(2)The influence of velocity and mass transfer on the supersaturation of growth tube is greater,while the influence of wall temperature and the amount of particles added to the growth tube on supersaturation of growth tube is less.Compared with the method of constructing the supersaturated environment by using saturated wet air into the cold-wall growth tube,the supersaturated environment obtained by using the method of adding high-temperature steam in the low-temperature dry air is more uniform,and the effect of promoting particle growth is more obvious.(3)After the swirling device is installed in the ordinary growth tube,the swirling growth tube is easier to obtain a high and uniform supersaturation.The swirling device not only has a good promoting effect on the agglomeration and growth of ultrafine particles,but also has a high removal efficiency of 65.8% for the number of ultrafine particles by the swirling growth tube.(4)The simulation and optimization show that the corrugated plate type phase-transition agglomerator has the highest economy and applicability when the corrugated plate spacing is 39 mm,the corrugated sinusoidal curve amplitude is129 mm,and the flue gas flow rate is 1.4 m/s.(5)Compared with corrugated plate type phase-transition agglomerator: Tube bundle type phase-transition agglomerator have better cooling effect on flue gas,and it is easier to obtain high and uniform supersaturation;The tube bundle type phase-transition agglomerator promotes particle growth by 7.71 times,which is significantly higher than the corrugated plate type phase-transition agglomerator by5.52 times;The tube bundle type phase-transition agglomerator has a high removal efficiency of 64.7%,which is 37.5% higher than the corrugated plate type phase-transition agglomerator.The two kinds of phase-transition agglomerator can obviously improve the particle removal efficiency of the ultrafine separator.更多还原