燃煤细颗粒水汽相变长大特性实验研究

发布时间：2018-01-22 13:16

本文关键词： 燃煤细颗粒过饱和润湿性水汽相变长大　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：我国大气颗粒物污染状况严重,给人们的生活及健康带来了很大的危害。燃煤产生的细颗粒物是我国大气中细颗粒物的主要来源之一,这是由于目前燃煤电厂常用的电除尘器对大颗粒脱除效率高但对细颗粒物的脱除效率很低,因此控制燃煤电厂细颗粒物排放迫在眉睫。利用水汽相变促进细颗粒核化凝结长大,再用传统除尘设备脱除,可以达到经济、有效控制燃煤细颗粒物排放的目的。目前对于水汽相变促进细颗粒物脱除的应用研究已有不少,但对具有复杂物化性质的燃煤细颗粒物的水汽相变长大特性仍不清楚。针对研究长大特性的要求,本文采用在生长管壁上覆盖流动的热水,管内从下至上流动饱和气流的方式构建了过饱和场,并采用激光测量仪实现了含液颗粒尺寸的在线测量。通过对气流与热水之间的热值计算,分析了生长管内的过饱和度分布,表明在本文研究的参数范围内管内形成的过饱和度在1--2之间。实验考察了实验平台的同相凝结特性,结果表明在本文参数范围内未有同相凝结形成的液滴生成。为了解燃煤颗粒物物化特性对颗粒长大的影响,首先通过压片测接触角的方法对燃煤颗粒物的润湿性进行了表征,并采用XRF对燃煤颗粒物组分进行了分析,考察了燃煤颗粒物及其主要组分的润湿性,并研究了润湿剂的影响。研究表明,燃煤产生的灰颗粒中硅铝质化合物所占比例很高,达70%以上,接触角在40度左右,多为中等亲水性；含有较多的硫、钙元素时颗粒的亲水性好。对莫来石、石英、氧化铁、硫酸钙等四种煤灰中主要成分的润湿性研究结果显示,硅铝质化合物莫来石、石英等为中等亲水,氧化铁润性较差,硫酸钙润湿性好；燃煤产生的颗粒物润湿性与莫来石、石英等润湿性相近,但整体接触角与其氧化物成分所占比例并不是线性关系。通过对烧失前后燃煤颗粒的润湿性的测量探究了残碳的影响,结果表明烧失后燃煤灰颗粒润湿性稍许增强,烧失后的生物质灰润湿性增强明显。添加非离子型润湿剂吐温20后可以降低水与燃煤颗粒物的接触角。以燃煤灰中主要组分颗粒莫来石、石英、氧化铁、硫酸钙等单成分颗粒为研究对象,通过气溶胶发生器使颗粒物成为气溶胶状态,进入生长管中长大,并采用DP-02测量颗粒长大前后的粒径分布,考察了不同组分颗粒的长大特性,研究了颗粒粒径的影响、工艺参数等对颗粒长大的影响。结果表明：不同组分颗粒长大效果不同,润湿性越好长大效果越好；颗粒初始粒径是影响长大的一个重要因素,初始粒径越小的颗粒被激发后粒径长大的倍数越大；随着热水温度的增加,颗粒长大效果越好：数量浓度越小有利于组分颗粒的长大：长大时间越长小颗粒长得越大。以润湿性差的氧化铁颗粒为研究对象,通过在热水中添加吐温20来研究润湿剂对颗粒长大的影响,实验结果表明,这种润湿剂其可以促进颗粒的长大,但采用这种添加方式需要的润湿剂浓度较大。在对单成分颗粒长大特性研究的基础上,选取来自燃煤电厂三四电场的南京灰和内蒙灰、生物质电厂袋式除尘器器中的细灰以及被磨煤机研磨过的嘉兴电厂灰研究了燃煤灰颗粒长大的长大特性。研究结果表明：燃煤灰颗粒中较多粗颗粒会对其中的细颗粒长大产生很大的水汽竞争；南京灰颗粒和内蒙灰颗粒未旋风前大于10gm的颗粒占数量比例的20%左右,水汽相变实验后,小颗粒未长大；掺混质量比70%的南京灰颗粒和30%细石英颗粒,水汽相变实验后小颗粒没有长大；被研磨后的嘉兴电厂灰、粗颗粒较少的生物质灰及旋风除尘后的南京灰和内蒙灰在水汽相变实验后小颗粒都发生了长大；热水温度为323K时,嘉兴灰颗粒、生物质灰颗粒及旋风后的南京和内蒙灰颗粒都可以长大到2μm以上,且随数浓度的降低及长大时间的增加长大效果更好,润湿剂的添加可以明显促进灰颗粒的长大,平均几何粒径可以长大到3μm以上。
[Abstract]:The status of atmospheric particulate pollution is serious in China, has brought great harm to the life and health of the people. The fine particles from coal combustion is one of the main sources of fine particles in the atmosphere in China, this is due to the electrostatic precipitator in coal fired power plant commonly used on large particles removal efficiency but high removal efficiency of fine particles is very low, so the control of combustion emissions of fine particles by using water vapor phase of coal-fired power plant is imminent. Promote the fine particle nucleation growth, then the traditional dedusting equipment removal, can achieve economic, effective control of coal combustion emissions of fine particles. The vapor phase has been applied research for promoting the removal of fine particles by many, but the vapor transformation of coal fine particles on complex physicochemical properties of growth characteristics remains unclear. To study the growth characteristics of demand, the growth in the pipe wall covering the flow of hot water pipe. In the first way to build a saturated air flow saturation field, and the use of laser measuring instrument realizes the on-line measurement of liquid particle size. Through the calculation of calorific value between air and water, analyzes the growth of supersaturation distribution in the pipe, show that the parameters range in this study of the inner tube is formed in a saturation between 1--2. Experimental study of the experimental platform of homogeneous condensation characteristics, results show that in this range of parameters not in-phase condensed droplets formation. In order to understand the influences of coal particles on physicochemical characteristics of the particles grew up, first by wetting contact angle measuring method of pressed coal particles were characterized. And the XRF of coal particles were analyzed. The effects of wettability of coal particles and its main components, and study the influence of wetting agents. The results show that coal ash particles in Silicon aluminum compound proportion is very high, more than 70%, the contact angle of 40 degrees, more moderate hydrophilicity; containing more sulfur, good hydrophilic particles of calcium. Of mullite, quartz, iron oxide, wettability results of main components such as calcium sulfate four ash display silicon aluminum compounds, mullite, quartz and other medium hydrophilic iron oxide, run less calcium sulfate wettability; particle wettability of coal and mullite, quartz etc. but the wetting Their natures are much the same., accounting for the overall contact angle and its oxide composition ratio is not a linear relationship. By measuring the wettability of burning loss before and after the influence of the coal particles of carbon residue, results show that the burning loss of coal ash particles slightly enhanced, burning of biomass ash wetting loss obviously. Adding nonionic wetting agent Twain 20 can reduce the water and coal particles The contact angle of coal ash. The main components of particles of mullite, quartz, iron oxide, calcium sulfate single component particles as the research object, through the aerosol generator to become aerosol particles, enter the growth tube grow up and the use of DP-02 for measurement of particle size distribution before and after grow up, on Growth characteristics of different components the effects of particles, particle size, influence of process parameters on the grain growth. The results show that the different components of particle growth effect, better wettability grow better; particle initial particle size is an important factor affecting the initial growing up, the smaller the particle size of the particles can be excited particle diameter ratio grow up more; with the increase of water temperature, the better the effect of particle growth: the smaller the number concentration of particles was to grow up, grow longer small particles grows older. In the poor wettability of oxidation Iron particles as the research object, through the effect of adding Twain in hot water for 20 to study the wetting agent on the particle growth, the experimental results show that the wetting agent can promote the growth of particles, but the way to add greater concentration of wetting agent. Based on the research of characteristics of long single component particles, selected from three or four coal-fired power plants in Nanjing and Inner Mongolia electric field ash ash, biomass power plant bag type dust collector for fine ash and coal mill grinding of Jiaxing power plant ash on the growth characteristics of coal ash particle growth. The results show that the coarse particles more fuel ash particles can cause great competition of fine particles in water vapor grow up; Nanjing and Inner Mongolia ash ash particles is not greater than 10GM before cyclone accounted for about 20% of the proportion of the number of particles, water vapor phase after the experiment, the small particles grew up; mixing ratio of 70% in Nanjing Ash particles and 30% fine quartz particles, water vapor phase after the experiment of small particles are not grown up; Jiaxing power plant ash after grinding, biomass ash and cyclone coarse particles less after ash and ash in Inner Mongolia Nanjing small particles of water vapor phase after the experiment had grown up; hot water temperature is 323K, Jiaxing Nanjing ash particles. Inner Mongolia and ash of biomass ash particles and the cyclone can grow to more than 2 m, and with the decrease and increase of time grow better grow number concentration, the addition of wetting agent can significantly promote the growth of the ash particles, the average particle size of geometry can grow up to more than 3 mu m.

【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773

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