Numerical Simulation Of Landfill Gas Migration With Water

Increasing with the municipal solid waste, society-wide became extensive attention to the safety and environmental problems of landfill gas. Therefore, LFG pollution resource utilization have been become the focus both at home and abroad. LFG movement through the refuse is a largely complex kinetics process. The whole process of LFG migration and evolvement were subjected to water. Landfill is regarded as the unsaturated zone in this paper, and quantitation research of gas pressure, saturation and flow rate with water was presented in the process of LFG extraction. It provides theoretical evidence and technique support for LFG pollution control and resource utilization. The primary produce including:(1) On the base of unsaturated seepage and biodegradation, two dimensions gas-water two phase transient non-linear mathematics model has been developmented for LFG migration.(2) Numerical scheme of model is given by using Galerkin finite element method, and the reliability of non-linear arithmetic is validated.(3) The numerical simulation results show:1.The moisture increases with the decreasing gas effective permeability, which gas migration path is compressed leading to gas flux down. Difference of water saturation equal to 0.175, error of annual gas flux achieve 8760 m3/hr. Therefore, do not ignore the water saturation in LFG evaluation.2. LFG emission to atmosphere was prevented with final cover, at the same time, interior system gas pressure increases with the decreasing depth.3.Gas flow rate gradually decays when time,T0, elapsed since landfill was capped, is longer. The flow rate (45 m3/hr) for T0 = 20 years is 70% of that (65 m3/hr) for T0 = 10 year. The gas pressure for T0 = 20 years is also 70% of that for T0 = 10 year. This indicates that the gas pressure is important to flow rate.4. The comparison of computation and evaluation datas of gas well production was presented on JinKou landfill, the results of variation with elapsed year is anastomotic, and reliability of the model is further verified .