| 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. |
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