【作者】 陈梅倩；

【导师】 贾力；

【作者基本信息】 北京交通大学 ， 车辆工程， 2009， 博士

【摘要】 城市生活垃圾水分含量高,其湿分迁移特性对整个垃圾焚烧过程有重要影响,基于垃圾是一种具有含湿多孔介质特性的燃料,因此垃圾的热、质传递是研究干燥过程的热点问题之一。本文主要对典型城市生活垃圾基元中温湿分迁移过程的动力学特性进行了实验和模拟研究。本文完成了以下几方面的工作。利用马弗炉进行垃圾基元中温湿分迁移特性的实验研究,得到了温度、垃圾基元种类和块状垃圾基元几何尺寸等因素对典型城市生活垃圾基元中温湿分迁移特性的影响规律。结果表明,干燥时间和干燥温度之间关系呈t=aT~b的规律,初始含湿量较高的垃圾基元和弱各向异性垃圾基元在较低温度下均有明显的初始段、恒速段和降速段,在较高温度下,只有初始段和降速段,初始含湿量较低的强各向异性垃圾基元在所有温度下只呈现初始段和降速段。实验研究结果表明初始含湿量较高的生物质垃圾基元在第一降速段会出现明显的收缩现象,垃圾基元的含湿量、厚度、骨架的移动性以及湿分迁移速率等对其收缩特性均有不同程度的影响,在一定温度下,垃圾基元在第一降速段的收缩率与水分比近似呈线性关系。通过在流化床实验台中进行垃圾基元中温湿分迁移过程的实验研究,得到了相关因素对流化床中典型城市生活垃圾基元中温湿分迁移特性的影响规律。分析垃圾基元几何尺寸、干燥温度、床层厚度和风速对流化床中垃圾基元湿分迁移特性的影响程度,并对中温条件下垃圾基元在流化床和马弗炉中的湿分迁移特性进行了比较和分析。基于对实验结果的进一步分析,得到了典型城市生活垃圾基元中温湿分迁移过程的动力学参数。研究发现温度对垃圾基元湿分迁移过程有效湿分扩散系数的影响均可以用Arrhenius方程描述,典型垃圾基元中温湿分迁移过程所需表观活化能较小,可以在较低的温度下进行干燥。对垃圾基元在马弗炉中的中温湿分迁移过程进行了数值模拟,用收缩模型模拟初始含湿量较高生物质垃圾基元的湿分迁移过程,用不收缩模型模拟非生物质垃圾基元的湿分迁移过程,计算结果与实验结果吻合较好。研究结果表明当考虑高水分生物质垃圾基元的收缩特性时,计算误差会大大减少,高水分生物质垃圾基元收缩特性增大了垃圾基元表面的传热性质。本文的研究成果对进一步深入认识高水分城市生活垃圾湿分迁移特性、改进或设计新型焚烧炉适应我国高水分、低热值的固体废弃物焚烧技术提供参考。更多还原

【Abstract】 High moisture in MSW leads to low heat value , low combustion efficiency, and frequent and serious erosion during incinerating. As a crucial treatment for incineration, MSW should be dried first. Due to its extreme complicated components and microstructure, the drying of MSW is quite dififerent from normal cases. Particularly, the moisture migration would be a highly coupled heat and mass transfer under transient conditions. It is of critical importance to investigate the drying efficiency and key factors for the development or design of incinerators to incinerate MSW with high moisture and low heat value in China. The experiments and simulation on kinetics of moisture migration of MSW matrixes at medium temperature were carried out.The main contributions of this dissertation are as follows.Experiments on moisture migration of the high moisture MSW at medium temperature were conducted in muffle.The influences of drying temperature, variety of waste matrixes, and dimension of waste matrixes on drying characteristics of waste matrixes in muffle at medium temperature were gained.The results showed that the time required for drying and temperature were inversely with the relationship t = aT~b, the process of moisture migration for waste matrixes with high initial moisture content and weak-anisotropy abiological ones at low temperature can be divided into three phases including initial phase, constant-rate phase and falling-rate phase , without constant-rate phase at high temperature, only initial phase and falling-rate phase at any temperature for strong-anisotropy waste matrixes with low initial moisture content.Obvious shrinkage during moisture migration of biological waste matrixes with high initial moisture content can be observed, The results showed that the effects of moisture content and thickness of waste matrixes, mobility of framework and rate of moisture migration on shrinkage, linear relationships between shrinkage and moisture content ratio of waste matrixes during the first falling-rate phase at certain drying temperature were established.Experiments on moisture migration of the high moisture MSW at medium temperature were conducted in a fluidized bed . The influences of correlation factors on characteristics of moisture migration of waste matrixes in fluidized bed were analyzed. The influences of drying temperature, dimension of waste matrixes and wind speed on drying characteristics of waste matrixes were gained; rate of moisture migration in muffle is much higher than one in fluidized bed.Based on experimental results, the kinetics parameters of moisture migration of waste matrixes at medium temperature were gained. The results showed that effect of drying temperature on effective moisture diffusivity can be described with Arrhenius equation, and low energy is needed for completely drying of waste matrixes.Characteristics of moisture migration of typical MSW matrixes at medium temperature in muffle were simulated. Characteristics of moisture migration of biological waste matrixes were simulated using shrinkage model, characteristics of moisture migration of abiological waste matrixes were simulated using non-shrinkage model. The results show good agreement with experiment values. The shrinkage of biological waste matrixes can enhance surface heat transfer of matrixes.It provides theory fundament for realize the drying characteristics of MSW in incinerator, and scientific reference for design and improve of incinerator.更多还原