垃圾填埋产生、迁移规律及其资源化利用研究

Pollution control of landfill gas and its recovery is a urgent problem in China, .because over 90% municipal solid waste were disposed by landfill. Landfill gas production and migration were investigated by jointed methods of theory analysis and experimental tests in this project. .(1) Waste decomposition and landfill gas generation process under different composition and temperature conditions was investigated by a MSW landfill lysimeter. The experiment results show that higher temperature and adding wastewater sludge to MSW can accelerate organic wastes decomposition and landfill gas production. In experimental period, accumulation gas production is 2.04 and 3.4 times of contrast group. The gas production rate declines rapidly is the significant feature of gas production process of MSW which major content is kitchen waste. This results is quite different from that reported by abroad researchers. So the rapid decline of gas production after landfill closure will cause a deep effect on LFG recovery practice. . (2) An experimental method for measuring air permeability Kh、Kv of compacted MSW under different compacted densities, water contents and decomposition stage by a landfill lysimeter has been proposed. The experimental results indicate that compacted MSW is a typical heterogeneous porous media, the average air permeability in the horizontal direction is 7.5~20.0 times of in the vertical direction (compacted direction); Air permeability Kh、Kv decline with the increase of compacted density in exponential relation and with water content in liner relation; Air permeability of moderate decomposed MSW is close to the fresh MSW, and both are much lower than the air permeability of decomposed MSW..(3) A mathematical model for LFG migration under a vertical extraction well was proposed. By using the model, pressure distribution of LFG around a vertical extraction well in a landfill can be calculated, and effects of permeability, radius of influence of extraction well, LFG flow and the buried depth of the well for collection system design also be analyzed. The calculating results for the given LFG extraction system show that landfilled MSW is a typical heterogeneous porous media, it cannot be taken as isotropy, else will cause significant errors; It was concluded that the reasonable radius of influence of a extraction well is 35.0~40.0m for most landfill sites, and the optimal buried depth of extraction well is about 80% of total depth of waste for vertical extraction system.(4) A Numerical model for LFG migration within the landfill with multi-walls recovery system was established. The model allows systems composed of any number of wells to be assessed before installing them on a landfill, and can predict the effect of LFG recovery rate, optimum distribution of extraction wells..

垃圾填埋气是一种有用的资料，如不有效加以利用，不仅会浪费资源，更会对环境造成污染和破坏。本项目通过理论分析与实验相结合的方法，对垃圾填埋气的产生与迁移规律进行研究，建立填埋气产生、迁移模型并找出有关基础数据，为填埋气的资源化利用提供理论依据。本项目的研究结果将对国内数百座填埋场的填埋气回收利用具有重要的理论与实际价值。