Numerical Simulation Of Sanitary Landfill's Gas Control System And It's Application

Landfill gas (LFG), originating from the anaerobic biodegradation of the organic content of waste, consists mainly of methane and carbon dioxide. LFG is a mixed gas witch contributes to the greenhouse effect greatly. In the other hand, methane in LFG is a renewable energy source. So, modern sanitary landfills always have landfill gas recovery system. But with the absence of reliable theory and handle tools to forecast or estimate the efficiency of LFG control systems, only experiential parameters be used in landfill gas recovery system design. The CFD method is suitable in these areas. LFG flow in waste can be treated to gas flow in porous media. Based on the analysis of generation and migration of LFG, a one phase mathematic model of LFG migration was being established. And, in this paper, PHOENICS was utilized for simulate LFG steady migration within landfill. The following is main conclusions got from the simulations:1) The relative pressure beyond 700Pa inside the landfill with no gas control system installed.2) Two different LFG control system was been compared in the landfill by the simulations. Results show that vertical control system is more suitable than horizontal control system in this landfill.3) In vertical control system, O2 concentrations of venting gas of wells in the shallower margin zone are more than those in centrically deeper zone.4) Results of simulations was be utilized to optimize vertical system in different venting zone. Low suction wells are arranged in the shallow margin zone. After the optimization, the control systems become more effective. Venting efficiency raised to 90.1%, O2 concentration in vented gas decreased to 0.6%.5) Results of the simulations indicate that the effective of gas venting decreased when permeability of top cover increased.