燃煤烟气细颗粒物湍流团聚的研究

发布时间：2018-01-05 11:30

本文关键词：燃煤烟气细颗粒物湍流团聚的研究　出处：《哈尔滨工业大学》2014年硕士论文　论文类型：学位论文

【摘要】：细颗粒物（简称PM2.5）对环境和健康的影响已成为公众和政府关注的焦点。燃煤电厂排烟是大气中PM2.5的主要来源之一。由于PM2.5粒径过小，传统的除尘方式如采用电除尘器或布袋除尘器等均难以有效控制PM2.5的排放，所以在除尘器前设置预处理阶段，即通过物理或化学的作用使PM2.5团聚成粒径较大的颗粒，然后再通过除尘器加以清除的方法成为除尘技术发展的新方向。在众多新技术中，湍流团聚因操作简单，投资、运行成本低，具有较好的发展前景。在物理作用导致的细颗粒物团聚过程中，同时存在着几种不同的团聚机理，即布朗团聚、湍流团聚和电团聚（或称库仑团聚），其中电团聚只有在颗粒带电荷的情况下存在。根据这3种团聚机理的作用范围，并结合颗粒的初始粒径分布，本文首先确定了团聚核函数，然后研究了颗粒尺度和烟气温度对团聚核函数的影响，结果表明：随着烟气温度的升高，团聚核增大，但变化幅度不大；在单分散系统中，布朗团聚效果最差，在多分散系统中，布朗团聚核随着颗粒粒径差值的增大而增大；而电团聚则是随着颗粒粒径的增大而增大，与粒径差值无关。在确定了团聚核函数后，本文结合气固两相流动和颗粒团聚过程分析了两种扰流装置（即扰流圆柱和涡片）的结构及其参数对团聚效果和系统压降的影响。结果表明：对于扰流圆柱而言，垂直于流动方向并列布置时具有较好的团聚效果，且随着圆柱间距的增大，颗粒团聚效果逐渐增强，但增量很小；对于涡片而言，“+”字形结构比“ ”字形结构具有更好的团聚效果，大体上，随行（列）间距的增大团聚效果逐渐减弱；但系统压降随行间距的增大而减少，随列间距的增大而增加。综合颗粒团聚和压力损失这两方面的因素，涡片的行间距为250mm、列间距为100mm时，效果较好。基于扰流圆柱和涡片的扰流特点，本文将两者相结合，构造了一种新型湍流凝聚器。通过数值模拟，研究了新型湍流凝聚器的团聚效果，并探讨了烟气流速对团聚结果的影响。结果表明：新型湍流凝聚器中产生的大尺度湍流明显有利于较小颗粒（小于1μm）的团聚，产生的小尺度湍流明显有利于较大颗粒（大于1μm）的团聚；烟气流速越大，，团聚效果越差，同时系统压降也越高。
[Abstract]:Fine particulate matter (PM2.5). The impact on environment and health has become the focus of public and government attention. Coal fired power plant exhaust smoke is one of the main sources of PM2.5 in the atmosphere. Because of PM2.5 particle size is too small. Traditional dust collection methods such as electric precipitator or bag dust collector are difficult to effectively control the emission of PM2.5, so the pre-treatment stage is set before the dust collector. That is to say, the method of agglomeration of PM2.5 into larger particles by physical or chemical action and then cleaning by dust remover becomes a new direction in the development of dust removal technology. Turbulence agglomeration has a good prospect because of its simple operation, investment and low operating cost. In the process of fine particle agglomeration caused by physical action, there are several different agglomeration mechanisms, i.e. Brownian agglomeration, turbulent agglomeration and electric agglomeration (or Coulomb agglomeration). Electric agglomeration exists only in the case of charged particles. According to the range of the three agglomeration mechanisms and the initial particle size distribution, the agglomeration kernel function is first determined. The effect of particle size and flue gas temperature on the agglomeration kernel function is studied. The results show that the agglomeration nucleus increases with the increase of flue gas temperature, but the change is not significant. In the monodisperse system, the effect of Brownian agglomeration is the worst. In the polydisperse system, the Brownian agglomeration nucleus increases with the increase of particle size difference. The electric agglomeration increases with the increase of particle size, which is independent of the particle size difference. After determining the aggregation kernel function. Combined with gas-solid two-phase flow and particle agglomeration process, two kinds of scrambling devices (i.e. scrambling cylinder and vortex plate) are analyzed in this paper. The effect of the structure and its parameters on the agglomeration effect and the pressure drop of the system is obtained. The agglomeration effect is better when parallel arrangement is perpendicular to the flow direction, and the agglomeration effect increases gradually with the increase of cylinder spacing, but the increment is very small. For the vortex sheet, the "zigzag" structure has a better agglomeration effect than the "zigzag" structure. On the whole, the agglomeration effect of the increase of the accompanying (column) spacing gradually weakens. However, the pressure drop of the system decreases with the increase of the spacing, and increases with the increase of the spacing of the columns. When the row spacing is 250mm and the column spacing is 100mm, considering the two factors of particle agglomeration and pressure loss. The effect is good. Based on the scrambling characteristics of a turbulent cylinder and a vortex, a new type of turbulent condenser is constructed by combining them. The agglomeration effect of the new turbulence condenser is studied by numerical simulation. The effect of flue gas velocity on agglomeration results is discussed. The results show that the large scale turbulence produced in the new turbulent condenser is obviously beneficial to the agglomeration of smaller particles (less than 1 渭 m). The small scale turbulence is obviously favorable for the agglomeration of larger particles (> 1 渭 m). The higher the flue gas velocity, the worse the agglomeration effect and the higher the pressure drop of the system.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：X773

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