【作者】 王伟云；

【导师】 李爱民；

【作者基本信息】 大连理工大学 ， 能源与环境工程， 2012， 博士

【摘要】 市政污泥是城市污水处理过程中产生的固体废弃物,经机械脱水后含水率在75%-87%之间,具有含水率高、体积大等特点,需采用干燥方法进一步去除水分。当前常用的传导干燥设备具有连续运行困难,进料需干污泥返混、水分蒸发量低等特点。本文在污泥固液结合形式及胶粘相机理研究基础上,进行了污泥间接干燥特性研究及机理探讨,并基于此开发了转鼓式压膜污泥干燥机,可实现液体水分脱除、设备连续运行且无需干污泥返混,从而为污泥干燥处理提供了一种新的设备和方法。首先论文重点介绍了污泥干燥类型、设备及各种新型深度脱水方法,并对现有污泥干燥研究理论、方法、模型进行了综述。对实验用污泥进行了性质分析,包括元素分析、工业分析等。采用热重、差热、扫描电镜、核磁共振成像等分析方法分析了不同含水率污泥的水分分布特点,得出了污泥胶粘相对应含水率区间。并基于不同含水率污泥特点分析了胶粘相成因。粘度测试结果表明高含水率污泥属于触变性流体。结合污泥干燥曲线、干燥速率曲线、表面温度与干燥时间关系曲线分析了污泥卤素干燥及间壁干燥特性。引入多重分形理论分析污泥干燥速率曲线及不同厚度污泥干燥裂纹分布,计算结果显示干燥速率曲线和干燥产生裂纹均具有多重分形特性。分析了污泥间接干燥冷凝水COD (Chemical Oxygen Demand)浓度值变化趋势,结果表明污泥干燥过程中污染物析出浓度不仅随干燥温度及厚度增加而增加,也随着干燥时间持续增长。基于污泥干燥试验数据确定污泥密度、比热、有效导热系数、有效扩散系数等物理参数与干燥温度及过程含水率的关系式,根据得到的参数表达式采用扩散模型对污泥干燥传热传质过程进行模拟,得到的含水率曲线与实际实验曲线比较吻合。采用白行设计实验设备对污泥进行热压力脱水干燥研究,发现在常压环境对污泥同时作用以热和压力,能实现部分水分以液体形式脱除。热压力脱水干燥后污泥粒径变小,污泥提取EPS中核酸量大幅增加,证明热压力脱水能使污泥中部分微生物细胞破坏,实现胞内水分析出团聚,进而以液体形式析出。基于间接干燥机理及热压力脱水干燥机理研制开发了转鼓式压膜污泥脱水干燥机,并进行针对性试验为设备选取最适宜滤布作为覆膜介质。不同掺入料试验显示,添加与污泥颗粒尺度相当的无机颗粒,能提高污泥脱水干燥效率。工业成分分析表明,干燥后污泥出现了分层现角,贴近鼓面和滤布的污泥有机质含量明显高于进料有机质含量。厌氧后污泥有机质含量低,粘鼓粘带现象明显低于原始脱水污泥。在12吨/天转鼓式压膜污泥干燥机上进行的示范实验表明,设备运行稳定,可实现污泥间接干燥设备的低能耗连续运行。更多还原

【Abstract】 Sewage sludge, also known as biosolid, is remainder left behind as water is cleaned in municipal wastewater treatment. Sludge treated by mechanical dewatering, can be called dewatered sludge, always has moisture content between75%and85%and should be dried for further moisture removal.In this paper, based on moisture distribution researches on municipal sewage sludge with different water content, drying characteristics and principles are experimentally studied, which offer basic theory for development of the rotary drum sludge drier, an innovative indirect drier for sludge with high moisture content.Firstly,the definition, classifications and hazards of sewage sludge are introduced,the treatment and disposal technologies are sorted described, and drying technologies, drying theories, as well as drying equipment, methods and models are summarized in this study.Ultimate analysis and proximate analysis of experimental sludge are obtained.And several different methods are used to analyze moisture distribution of sludge with different water content and conclusions can be drawn that the sticky phase is caused by EPS (Extra Celluar Polymers) in sludge which can adhere to one another since it is saturated hydrophilic colloid.Apparent viscosity of sludge with high water content shows its properties as thixotropic fluid.Halogen drying and indirect drying characteristics of sludge are studied by drying curves, drying rate curves and drying temperature curves.Multifractal theory are adopted for modelling drying rate curves and crack distribution for different thickness of sludge and it can be proved that they all have obvious multifractality.COD(Chemical Oxigen Demand) value of condensate from indirect sludge drying shows that, the higher the temperature is, the higher pollutant concentration is, and also the thicker sludge and longer drying duration may induce higher pollutant concentration.The physical parameters include density,specific heat, effective heat conductivity coefficients and effective mass transfer coefficients are determined based on experimental data. Diffusion models based on the obtained parameters are built for heat and mass transfer of sludge indirect drying and the simulation results are in good agreement with the experimental data.Thermal press dewatering and drying characteristics of sludge are studied by self-made equipment and the results show that coupling between heat and stress can make water remove from dewatered sludge in liquid phase.Particle size analysis shows that sludge treated by thermal press has finer particle size distribution.EPS extracted from sludge shows that nucleic acid concentration increases obviously, which proves that the thermal press can cause partial cell to be ruptured, which make water in sludge separated out and removed in liquid phase.The rotary drum sludge drier are developed based on indirect drying principles and thermal press theories. Key experiments indicate that polyester filter cloth with pore diameter of50μm is better for the drier. Different admixture trials indicate that inorganic additive with similar diameter of sludge can increase the dewatering efficiency.Proximate analysis shows that layering phenomena appear in sludge treated by rotary drum drier and more organic substance in sludge is close to the surfaces of drum and filter cloth.Since anaerobic digested sludge has less organic substances,less sludge adheres to drum and filter cloth, which is more suitable for the sludge drier. Continuous experiments show that rotary drum drier with processing capacity of12tons/day can operated stably.更多还原