声波团聚控制燃煤电厂细颗粒物排放研究

发布时间：2018-07-17 02:47

【摘要】：近几年,随着经济的快速增长,细微颗粒PM2.5的污染越来越严重,对人们的生活环境造成了巨大影响。煤炭等化石燃料的燃烧是这些颗粒污染物主要来源之一。对于燃烧源颗粒物的控制和脱除已成为能源和环境领域急需解决的重要问题。声波团聚作为一种应用在除尘器前的预处理技术,因其易于操作、效果比较明显而备受研究者的关注。鉴于此,本文对声波团聚技术开展了实验和模拟两方面的研究。在实验方面,设计并搭建燃煤电厂颗粒物低频声波团聚实验台,采用某电厂不同的燃煤飞灰作为实验所用气溶胶。研究了在声压级从133d B-146d B,频率从1000Hz-2400Hz,气溶胶初始数目浓度从1.33?105cm-3-3.55?105cm-3条件下声波团聚细微颗粒物的效果,分析不同参数对团聚效果的影响。结果表明:当频率为1400Hz,声压级为146d B时,团聚效率最高。随着声压级和气溶胶初始浓度的增加,团聚效果也不断增强。但是考虑到能耗问题,声压级和气溶胶初始浓度都应适度选择。在理论方面,探索细微颗粒物声波团聚的机理并进行数值模拟研究。首先对不同团聚机理的团聚核函数进行模拟,表明同向团聚核函数值远高于其它作用机理下的数值。对于粒径为1μm和2.5μm的亚细微颗粒,其最佳团聚频率都在10k Hz以上。其次,采用改进后的分组法对声波团聚气溶胶过程进行数值模拟,在频率、声压级及气溶胶初始浓度影响下,模拟所得结果基本与实验结果相符。在对温度的模拟中发现,团聚效果随着温度的升高而减缓,特别是温度高于300℃。最后,将几种不同团聚机理组成的模型进行数值模拟,并与实验结果作对比分析,从而表明不同机理对于颗粒团聚的影响,得到适用于燃煤电厂细微颗粒声波团聚的最适合模型。结果表明:四种不同数值模型模拟后的颗粒粒径分布趋势与实验结果相符,仅在部分粒径段出现些微偏差。在与实验值的对比中发现,布朗团聚主要作用于粒径小于0.1μm以下的颗粒,而对大于0.1μm以上的颗粒其影响几乎可以忽略。
[Abstract]:In recent years, with the rapid growth of economy, the pollution of PM2.5 is becoming more and more serious, which has a great impact on people's living environment. The combustion of fossil fuels such as coal is one of the main sources of these particulate pollutants. The control and removal of particulate matter from combustion source has become an important problem in the field of energy and environment. Acoustic agglomeration, as a pretreatment technique applied in front of dust catcher, has attracted much attention because of its easy operation and obvious effect. In view of this, the acoustic agglomeration technology has been studied in both experimental and simulation aspects. In the aspect of experiment, the low frequency acoustic wave agglomeration test table of particles in coal-fired power plant is designed and built. Different fly ash from coal burning in a power plant is used as the aerosol in the experiment. The effect of acoustic agglomeration of fine particles at sound pressure level from 133d B-146dB, frequency from 1000Hz to 2400Hz and initial concentration of aerosol from 1.33?105cm-3-3.55?105cm-3 was studied. The effect of different parameters on agglomeration effect was analyzed. The results show that when the frequency is 1400Hz and the sound pressure level is 146dB, the agglomeration efficiency is the highest. With the increase of the sound pressure level and the initial concentration of aerosol, the agglomeration effect is enhanced. However, considering energy consumption, sound pressure level and initial aerosol concentration should be appropriately selected. In theory, the mechanism of acoustic agglomeration of fine particles was explored and numerical simulation was carried out. Firstly, the agglomeration kernel function of different agglomeration mechanism is simulated, which shows that the value of codirectional agglomeration kernel function is much higher than that of other mechanisms. The optimum agglomeration frequency is above 10kHz for subfine particles with particle sizes of 1 渭 m and 2.5 渭 m. Secondly, the acoustic agglomeration aerosol process is numerically simulated by the improved grouping method. Under the influence of frequency, sound pressure level and initial concentration of aerosol, the simulated results are basically consistent with the experimental results. In the simulation of temperature, it is found that the agglomeration effect slows down with the increase of temperature, especially when the temperature is higher than 300 鈩，

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