【作者】 邓文义；

【导师】 严建华； 李晓东； 池涌；

【作者基本信息】 浙江大学 ， 能源环境工程， 2009， 博士

【摘要】 污泥是一种量大面广且对人体和环境都具有很大危害作用的固体废弃物,广泛来源于市政污水、工业污水、水体疏浚等污水处理过程。机械脱水污泥的主要成分为约80%的水分、5-12%的有机质和8-15%的灰分。目前污泥的处置方法主要为填埋、农用和焚烧,其中干化结合焚烧的污泥处理处置技术已被公认为能最大限度地实现污泥的减量化和资源化。但有关污泥干化机理的研究并不多,基于此背景,本文将开展污泥干化特性及其影响参数和污染物排放的相关研究,通过理论和实验研究建立可指导工业应用的理论体系。论文的第一章是对论文背景相关知识的文献综述。首先介绍了污泥的定义、分类、危害和现有的处理处置技术,以及污泥干化技术的概念、污泥干化技术工艺类型和污泥干化技术的主要流派,并对污泥干化的研究现状、污泥干化和焚烧污染物排放研究现状进行了综述。在此章节中,还包括了对全文系统和框架的介绍。论文的第二章是污泥水分分布特性研究。首先介绍了各种不同的水分分布测定方法,重点介绍了本文所采用的热干燥法、热重—示差热分析法(Thermogravimetric-differential thermal analysis, TG-DTA)、热重—差示扫描量热法(Thermogravimetric-differential scanning calorimetry, TG-DSC)和水活度法的检测原理和方法。然后通过上述4种方法对不同污泥的水分分布特性进行了实验研究,根据实验结果对比不同污泥水分分布特性的差异和不同检测方法的优缺点。论文的第三章是污泥在空心桨叶式干化机内干化特性及影响因素研究。结合常压渗透模型和实验结果对城市污水污泥和造纸污泥的干化机理进行了研究。根据模型要求对污泥的物性参数进行了检测,这些参数包括热扩散系数、导热系数、污泥比热和污泥粒径等,同时给出了检测方法。通过实验结果和理论模拟计算结果之间的对比,分析了干化温度、热轴搅动速率和载气流量对污泥干化特性的影响。本章最后还开展了不同添加剂和干化热源对污泥干化的影响研究,所用添加剂包括污泥燃烧辅助燃料如煤和废油、CaO脱硫剂和干污泥,研究发现当CaO添加剂的质量百分比高于0.5%时即能明显促进污泥干化速率的提高。通过实验测定了烟气热源在空心热轴内的对流换热系数,研究发现当烟气流速为3.5～13m/s时,烟气换热系数为18.6～53.0 W/(m2K)。最后对比分析和讨论了烟气热源、导热油热源和饱和水蒸汽热源对污泥干化的影响。论文的第四章是污泥间壁式真空搅动干化特性研究。首先结合真空渗透模型分析了城市污水污泥真空条件下的间壁式搅动干化机理,在此基础上以城市污水污泥为例研究了真空压力、干化温度、搅动速率和容积负荷对污泥干化特性的影响,同时探讨了干化机内刮条的功用。最后,对比研究了污泥真空干化特性和污泥常压干化特性,并对真空和常压干化条件下的干化冷凝液进行了对比分析。论文的第五章是污泥干化过程挥发性化合物排放特性研究。首先通过管式炉试验结合红外光谱分析研究了城市污水污泥和造纸污泥干化气体中挥发性化合物的主要成分为NH3、CH4、C7H16、CO2和挥发性有机酸,并根据实验结果对各种污染物的生成机理进行了分析。然后,在干化面积为2 m2桨叶式干化机上对污泥的干化气体污染物以及冷凝液的排放进行了研究,研究发现城市污水污泥干化冷凝液呈弱碱性,而造纸污泥干化冷凝液呈若酸性。论文的第六章是流化床内污泥焚烧污染物排放特性研究。本章的第一部分内容是城市污水污泥在小型流化床实验台内焚烧污染物排放特性研究,主要针对焚烧烟气中多环芳烃和二噁英的排放特性进行了研究,同时还研究了煤和生石灰等辅助燃料和添加剂对污染物排放的影响。本章的第二部分内容是在0.5 MW大型流化床焚烧炉上对滇池污泥焚烧过程污染物排放特性进行了研究,结果表明焚烧烟气中的重金属、二噁英和氮氧化物的排放浓度均符合国家标准。论文的第七章是计算机辅助污泥干化焚烧系统设计计算研究。首先对常见的干化辅助计算软件进行了详细的介绍。然后,以卧型桨叶式污泥干化机为例研究了间歇式污泥干化向连续式污泥干化转化的方法,并利用Excel Spreadsheet建立了污泥干化过程模型和可视化操作界面,研究了干化气体余热利用对污泥干化能量利用率的影响。模拟计算结果表明,如果对干化气体进行余热回收利用,污泥干化能量利用率将由69.8%提高至83.3%。最后,利用Excel Spreadsheet建立了污泥干化焚烧系统过程模型和可视化操作界面,并以杭州城市污水污泥为例,开展了干化焚烧系统优化方面的计算研究。计算结果表明：当杭州污泥入炉含水率不高于60%时,污泥焚烧系统不需要添加辅助燃料,而且当入炉污泥含水率等于60%时,污泥干化焚烧系统辅助燃料消耗量最低。论文的第八章是60吨／天污泥干化焚烧工程实例。该工程由污泥干化和污泥焚烧两部分组成,污泥焚烧产生的蒸汽用于污泥干化,污泥干化至含水率60%后投入焚烧炉进行焚烧。利用Excel Spreadsheet对污泥干化焚烧系统进行了设计计算,计算结果表明当制革污泥干化至含水率60%时,系统辅助燃料消耗量最低,为2.32吨煤／天。论文的第九章是全文总结及工作展望。主要包括对全文结论的总结归纳,论文创新点介绍,以及在未来需要进一步加强或开展的研究工作。更多还原

【Abstract】 Sludge is particularly burdensome for both the natural environment and human health. It is widely emitted from the treatment processes of municipal wastewater, industrial wastewater and urban waterbody sediment. Mechanically dewatered sludge usually contains about 80% of water,10% of organic matter and 10% of ash. Land-filling, agricultural utilization and incineration are the most widely used method for sludge disposal in the world. Drying and incineration has been recognized as the most effective method for sludge volume reduction and energy recovery. However, the drying mechanism of sludge is not well studied in the published documents. Based on above, in current dissertation the drying and pollutants emission mechanisms of sludge is studied:a theoretical system which can be used for the guidance of industrial application is built based on the theoretical analysis and experimental researchs.Chapter one is the background review, mainly including the definitions of sludge, the categories of sludge, the harm of sludge, the available sludge disposal methods, the concept of sludge drying, the types of sludge drying technologies, the research status of sludge drying mechanism, and the research status of pollutants emission during sludge drying and incineration processes, etc. In this chapter, the framework of the full text and the structure of this dissertation are also introduced.Chapter two is the researches on moisture distribution characteristics in sludges. Different methods for determination of moisture distribution in sludge are introduced. Thermal drying method, thermogravimetric-differential thermal analysis method (TG-DTA), thermogravimetric-differential scanning calorimetry method (TG-DSC), and water activity method have been paid a lot of attentions, focusing on their measuring principles and methods. The moisture distribution characteristics of different sludges are studied by these four methods respectively. The differences in moisture distributions of different sludges are compared, as well as the advantages and disadvantages of the four measuring methods.Chapter three is on the sludge drying characteristics in a nara-type paddle dryer. The drying mechanisms of sewage sludge and paper mill sludge are studied based on the laboratory experiments and penetration model. Physical parameters of sludge, including thermal diffusivity, thermal conductivity, specific heat capacity, and particle diameter, are experimentally determined for theoretical calculation. The experimental results are compared with those from theoretical calculation. The effects of drying temperature, stirrer speed and gas flowrate on drying characteristics of sludge are also studied. Furthermore, the effects of additives, including coal, waste oil, CaO, and dried sludge, on sludge drying are studied. The result indicates that the drying rate of sewage sludge increases significantly when CaO content in sludge is higher than 0.5%. The effects of heat-transfer media, including saturated water vapor, thermal oil and flue gas, on sludge drying are also studied. The heat transfer coefficient of flue gas in the hollow shaft of paddle dryer is measured. The effects of flue gas temperature and flowrate on the heat transfer coefficient of flue gas in are studied. The result indicates that when the flowrate increases from 3.5 to 13 m/s, the heat transfer coefficient will increase from 18.6 to 53.0 W/(m2 K). A comparison of overall heat transfer resistances from flue gas heated, thermal oil heated and saturated water vapor heated paddle dryers is presented.Chapter four is on drying characteristics of sludge under partial vacuum condition. The agitated drying mechanism of sewage sludge under partial vacuum condition based on penetration model is presented. The effects of system pressure, drying temperature, stirrer speed, and filling ratio on sludge drying characteristics are experimentally studied. The role of the scrappers in sludge dryer is also discussed. Furthermore, comparisons of drying characteristics and condensate properties between partial vacuum contact drying and atmospheric contact drying are presented.Chapter five is on emission characteristics of volatile compounds during sludge drying process. The drying experiments of sewage sludge and paper mill sludge are conducted on a tubular furnace, and the main components of drying gas are identified to be NH3、CH4、C7H16、CO2 by an infra-red spectrum analyzer. The formation mechanism of these compounds are also analysed. Furthermore, sludge drying experiments are carried out in a nara-type paddle dryer with 2m2 heating area. The drying gas and condensate from the dryer are analysed. The result indicates that condensate from sewage sludge drying is weakly alkaline, while the condensate from paper mill sludge drying is weakly acidic.Chapter six is on emission characteristics of pollutants during sludge combustion in a fluidized bed incinerator. In the first part, the emission characteristics of PAHs and dioxins, and the effects of coal and CaO on PAHs and dioxins emissions during sewage sludge combustion are studied, are also studied. In the second part, pollutants emission during incineration of Dianchi sludge in a 0.5 MW pilot-scale fluidized bed are studied. The result indicates that the heavy metal, dioxins and nitrogen oxide concentration in flue gas can meet the national standards.Chapter seven is on computer-aided sludge drying system and sludge drying incineration system design. The drying softwares available in the market are introduced. The method for sludge batch drying transferring to sludge continuous drying is presented. The process model of sludge drying and visualizing window are developed based on Excel spreadsheet software. Based on numerical simulation of spreadsheet software, it is found that energy utilization ratio of sludge drying system will increase from 69.8% to 83.3%, when the waste heat in drying gas is utilized. The process model of sludge drying and incineration system and visualizing are also developed based on Excel spreadsheet software. Optimizational calculation of the drying and incineration system is carried out based on the sewage sludge from Hangzhou city. The result indicates that, during incineration process, no auxiliary fuel is needed when the moisture content of sludge incinerated is not more than 60%; and that the sludge drying and incineration system consumes minimal auxiliary fuel when moisture content of sludge is 60%.Chapter eight is on a 60 t/d sludge drying and incineration project built in Wenzhou city. The project is composed of a sludge drying system and a sludge incineration system. Saturate water vapor produced from sludge incineration is supplied for sludge drying, and sludge is dried to a water content of 60% before being incinerated. The sludge drying and incineration system design is carried out based on Excel Spreadsheet software. The result indicates that the sludge drying and incineration system consumes minimal auxiliary fuel (2.32 t coal/d) when moisture content of sludge is 60%.Chapter nine mainly includes the conclusions of full text, the innovative point of this dissertation, and the prospect of future work.更多还原