The Dynamic Law Of Landfill Gas Transport And Heat Release

The catastrophe control and resource exploitation of landfill gas have been the important research subject in international Geo-engineering field. It have been the fundamental environmental and catastrophic problem needed to be solved about how to effective perform the reduce discharge and catastrophe control. The ultimate mechanics and evaluation of the quantity describe of gas transport is the key scientific question to settle this puzzle. Based on the intersect theory of the porous media seepage mechanics, bio-chemical dynamic, thermal-chemical dynamic and transport dynamic, the research achievements by laboratory testing as the basis, the numerical simulation as the leading, the systematic analysis and evaluation of landfill gas generation, reaction and transport with the coupling effect of the multi-physics. The main research results show:(1)The anaerobic treated waste was sampled at a plant for different organic fraction(the readily, moderately, and the slowly biodegradable fractions, respectively, 55%:30%:15%(case A), 30%:55%:15%(case B) and 15%:30%:55%(case C). The evaluation of potential gas generation and the gas generation rate coefficients have been completed. At the first stage, the gas generation rate coefficient, which are 0.0151, 0.0079 and 0.00756(day(-1)). At the second stage, the gas generation rate coefficient, which are0.0317, 0.0181 and 0.0145 (day-1).The gas generation rate model of three different waste components is given by the test data. The evaluation of the effect of gas generation rate coefficient on the temperature is performed, and the equation of k (T) is developed. It will provide the theoretical evidence for the simulation of the effect of gas generation on temperature.(2)Based on the coupling model of gas generation, transport and heat release, and the potential gas generation and coefficient data, the simulation of coupling effect for gas generation, transport and heat release was show to analysis the gas and heat variation process of dynamic behavior. The primary results including:1) The final cover has not significantly effect on temperature passing. The very of the season has the largely effect on the near-surface temperature. But the effect range is limited. And the temperature almost had no fluctuation in depth at 10m.2) The gas flux increased with the permeability increasing, so as to enlarge the radius; The gas flow rate is greatly differential in radial direction, induced by the gas diffusion, this is the main factor leading to the variation of the radius of influence with different diffusion coefficient. The radius of influence is increased with the readily biodegradable fractions decreased. The simulation result will provide the evidence for pumping well design, pollution control and resource utilization of landfill gas.(3)Based on the background of the section III of the ErFeishan landfill, the evaluation of the landfill gas resource utilization at the whole running stage was proposed. The result show: 1) The waste degradation have the significant effect on the total amount of gas generation. The gas generation rate is increased with temperature increasing during the bio-degradation with heat generation, leading to the increase of the decomposition of the organic. The simulation result of gas generation rate and heat generation rate during the whole running phase is also given the same viewpoint of waste generation rate accelerated by coupling effect. It will provide the basis data for the evaluation of ErFeishan landfill gas utilization.2) The evaluation result of electric power generation of section III running limit at ErFeishan landfilll by coupling model is about 9.2 year, less than 4 years of the result of the non-coupling model. So, the evaluation result of the electric power generation running time is exorbitant by the non-coupling model. Therefore, the coupling effect of the biologic- chemistry-heat must be considered about the feasibility evaluation of landfill gas electric power generation.The results in this paper will provide the theoretical evidence for revealing the reaction and transport mechanics. It will also provide the technological support for the quantity evaluation of gas productivity and exploitation potential of CDM project during landfill running, which have the important theoretical significance and application value.