EFFECTS OF SOIL PROPERTY AND AIR INJECTION CONDITION ON AIRFLOW BEHAVIOR DURING AIR SPARGING

Laboratory experiments of air sparging were conducted in a model column to investigate the effects of grain size and air flow rate on airflow behavior. Basically two types of airflow patterns including channel flow and bubble flow are observed. The channel flow generally occurs in the sand with grain size of less than 1.0 mm, while the bubble flow occurs in the sand with grain size of larger than 2.0mm, and there did exist a transition state between them. With the growth of air flow rate, the air saturation is increased until to reach a relatively steady state, and the smaller the grain size is, the higher air saturation of the sand will be. The air flow rate almost increases linearly with increasing air injection pressure. Through extrapolation and empirical formula, the minimum air injection pressure and shape factor C were derived respectively. Air sparging simulations were also performed to study airflow behavior by T2VOC and compared with the experimental results. The influence of intrinsic permeability, air flow rate, air injection depth, and air permeability ratio between horizontal direction and vertical direction on airflow pattern, radius of influence (ROI) and distribution of air saturation were discussed. ROI is decreased with the increase of intrinsic permeability. Except for high intrinsic permeability, the increase of air flow rate has significant influence on ROI, and ROI increases linearly with the increasing permeability ratio permeability ratio. However, ROI increases limitedly with increasing sparging depth.