【作者】 董希良；

【导师】 刘泽常； 刘静；

【作者基本信息】 山东建筑大学 ， 环境工程， 2011， 硕士

【摘要】 目前,大气微粒子已成为我国许多大中城市环境空气中的首要污染物,对环境和人体健康危害严重。大气微粒子的来源非常广泛,主要来源可分为固定源、开放源、移动源等,各种源类对城市环境空气中微粒子的贡献率不同。以济南为例,环境空气中首要污染物可吸入颗粒物浓度超过国家环境空气质量二级标准,在空气污染中的分担率为49.1%。在部分北方城市,开放源在可吸入颗粒物污染中的分担率达到了40-80%,是环境空气中可吸入颗粒物的主要来源。开放源类是一种复合源类,具有源强不确定、排放随机和排放位置不定等特点。不同城市工业布局、能源结构、地理环境、气象条件和地形条件不同,开放源的组成也不同。因此,了解开放源类微粒子排放特性,对于改善城市人居环境、控制城市空气颗粒物污染具有重要的理论意义；对于落实可持续发展战略、实现国家“十二五”时期继续加强一次颗粒物排放控制的规划目标具有重要的现实意义。以往的研究主要体现在对微粒子的基本理化特性、毒理学性质和微粒子的来源等方面,对于城市开放源类微粒子产生机理方面的研究较少。国内研究大多还是跟随国外的研究成果,研究水平停留在适应性研究方面。此外,国内针对有规律性、有组织性的微粒子污染源研究较多,特别是对电力、钢铁、采矿等行业的大型固定微粒子释放源的研究比较充分,而对城市开放源类释放的微粒子污染物研究相对薄弱。本文选择对济南市大气颗粒物贡献较大的建筑尘、道路尘、黄河沙、裸露地面尘四种开放源作为研究对象,利用与维也纳工业大学合作开发建立的实验室微粒子控制模拟实验装置,采用粉体物料自由下落逸出随机粉尘的实验研究方法,讨论了在开放源类粉体物料自由下落过程中微粒子排放特性。并在一定动力因素条件下,探讨了物料微粒子含量、质量流量、含水率、样品种类、空气湿度、加湿流量、加湿压力等因素对开放源物料中微粒子排放率的影响。实验结果表明,下落物料质量流量、空气湿度与微粒子排放率成幂指函数关系,随着质量流量、空气湿度的增加,微粒子排放率减小,且这种减小速度逐渐变慢。微粒子的粒径不同是对微粒子排放率影响最大的因素,粒径与微粒子排放率之间呈现指数关系。不同物料对微粒子排放率也有影响,裸露地面尘含有的微粒子最多,黄河沙最少,但裸露地面尘微粒子排放率最低,黄河沙微粒子排放率最高。含水率越高的样品,微粒子排放率越低,但含水率增加到1.34%之后物料物理特性发生明显变化,不再适用本项研究设定的条件。加湿方式是降低物料自由下落过程中微粒子排放率简单且有效的方法,在线加湿时,雾化喷头的空气压力和加水流量不同,微粒子排放率不同：当采用气水两相喷嘴,空气压力为0.3MPa时,微粒子排放率函数值最小；当加水流量为40mL/min时,微粒子排放率最低。本文研究了在一定动力因素条件下开放源物料自由下落过程中微粒子的排放率；建立了微粒子含量、质量流量、含水率、样品种类、空气湿度、加湿流量、加湿压力等影响因素与微粒子排放率之间的数学模型,并利用SigmaPlot数学分析软件对方程进行优化；通过研究发现粒径是对样品自由下落过程中微粒子排放率影响最大的因素。所获结论对开放源类物料在转运、装卸、堆放等操作过程中大气微粒子的排放估算和综合防治具有重要的理论意义和应用价值。更多还原

【Abstract】 Fine particulate matter of air,which have become the main pollutants of many medium-sized and large cities in China, is seriously harmful to environment and human health.Sources of them are widely distributed and mainly divided into stationary source, open source and mobile source according to their different contribution rates to air. Take the city of Jinan for example, the concentration of respirable particulate matter(RPM) of air beyond the corresponding requirements of ambient air quality standard(GB3095-1996). Open-sources materials,which takes 40-80% contents in the RPM(converse 49.1% of air pollutants),is the main source of RPM of air pollutants.Open-sources materials with its characteristics of uncertain source strength, various discharge location and random emission is classified for a compound-source one. It owns different composition with different urban industrial distribution energy structure, geographical location, weather conditions and terrain conditions. Therefore, it is necessary to understand the fine particle emission characteristics of the open source. Becauseit not only has theoretical significance for improving the urban living environment and controlling pollution in air,but also has important practical significance for the full implementation of the sustainable development strategy and achievement of national pollutants emissions planning objectives in the next five years.Previous studies have focused on fine particles (RPM) of the basic physical and chemical properties, toxicological properties and sources of fine particles,but few research about the producing mechanism of fine particles for urban open-sources materials and the domestic research were always follow the foreign results and just remain in the adaptation of the level of research. In addition the domestic research have mainly focused on the laws, and organized fine particles especially for the release of large fixed sources of fine particles which were produced by power steel, mining and other industries but less focused on the release of urban fine particle pollutants of open source.In this experiment, four kinds of open-sources materials as subjects(construction dust, road dust, the yellow river sand, ground dust)were selected. Computer measurement and control platform with powder material free-falling dust overflow experimental methods were used to research the fine particulate matter emission in free-fall process under online humidifying condition of open-sources materials. Under certain dynamic conditions(horizontal wind speed), the relationship between rate of the emission and water flow, nozzle pressure type of material, size distribution, moisture content, mass flow had been discussed.As the results shows, there exsits exponential relationship between emission rate and free-falling material mass flow, moisture content. With increasing of mass flow and moisture content, the rate of fine particle emissions rate decreased, and the reducing speed gradually slows down. Fine particle size is the most important factor which can affect its emission rate and their exsits a exponential function relationship between them. Different materials can also affect the emission rate of fine particle size. In this experiment, ground dust discharged the most RPM but with the least emission rate and the yellow river sands discharged the least but with the most emission rate. The higher the moisture content of samples have,the lower fine particle emissions rate have, but it is not applicable to the situation above when moisture content is beyond 1.34%, physical properties of materials will change significantly. Humidification is a simple and effective method to reduce the fine particle emissions rate of free-fall materials.When Online humidification were used, the particle emissions rate are different with the different air pressure of atomizing nozzle and water flow. When gas-water two-phase nozzle is used and the air pressure is 0.3MPa, fine particle emissions rate have minimum function value. When the water flow rate is 40mL/min, the fine particulate emissions rate is the lowest.In this paper, the rate of emission of fine particulate in the free-fall process of open-sources materials under uncertain dynamic conditions was studied. The mathematical model had been established between the rate of fine emission and water flow, nozzle pressure type of material, size distribution, moisture content, mass flow. Then the models were modified by SigmaPlot mathematical analysis software.It was found that the fine particle size is the most important factor which can affect its emission rate in the materials free-fall process. The operating conditions of water line was optimized. It can provide a reference by the results for making source control programs of fine particles and selection of technical measures to control open-sources fine particle emissions.更多还原