Abstract:
A soil venting system driven by air thermal property is developed to deaf with tow concentration gaseous hazard materials in unsaturated zone of soil. A process utilizes the thermal driven soil venting system to create air gradient in the unsaturated zone of soil and force the gaseous hazard materials out the contaminated soil.

Description:
DESCRIPTION OF FIGURES 
       [0001]      FIG. 1  is a schematic cross section view of the present invention for removal gaseous contamination of unsaturated zone 
         [0002]      FIG. 2  is a schematic plant view of the present invention for removal gaseous contamination of unsaturated zone 
         [0003]      FIG. 3  is a schematic of injection function of heating chamber 
         [0004]      FIG. 4  a schematic of extraction function of heating chamber 
         [0005]      FIG. 5  a schematic of inlet check valve detail of heating chamber as injection apparatus 
         [0006]      FIG. 6  a schematic of outlet check valve detail of heating chamber as injection apparatus 
         [0007]      FIG. 7  a schematic of inlet check valve detail of heating chamber as extraction apparatus 
         [0008]      FIG. 8  a schematic of outlet check valve detail of heating chamber as extraction apparatus 
       FIELD OF INVENTION 
       [0009]    This invention relates to a system employing thermal properties of air for controlling and reducing volatile organics compounds (VOCs), semi-volatile compound (sVOCs) and other gaseous hazard materials in unsaturated zone of soil. 
       BACKGROUND OF THE INVENTION 
       [0010]    There are quite a few mature methods for clean up VOCs, sVOCs and other gaseous hazard materials in contaminated unsaturated zone (EPA, 2004). The methodologies involve technologies either use air movement in the porous materials to drive the contaminations out or apply chemical or biological agents to degrade molecular structure of hazardous materials into harmless chemicals. Since fate of 70s, the remediation processes have developed and been used to treat thousands and thousands contaminated sites. 
         [0011]    Generally, existing methodologies require expensive machinery or costly chemical agent as weft as intensive maintenance and monitoring. With price tag of tens thousands dollars, it is not economically feasible to install the remediation system when the contamination is tow or to operate a system for tong period of time. Under such circumstance, tow concentration sites are in disadvantage when the resources are limited and some remediation systems have to shut down before the soil really free of hazard materials. Since the hazard materials at tow concentration either exist in small pores or are absorbed on surface of soil particles, the release rate of the contaminations is relatively stow. In other words, it is not efficient to use existing methodologies to remedy the tow contaminated area even if the economical feasibility is not in consideration. It is objective for the invention to provide a tow cost and tow maintenance system to deaf with gaseous contamination in unsaturated zone. 
       SUMMARY OF THE INVENTION 
       [0012]    A heating chamber  5  is designed to drive fresh air  10  into contaminated unsaturated soil  20  and/or extract air  30  with hazard materials through the injection wefts  40  and extraction wefts  50  installed in the contaminated area ( FIG. 1  and  FIG. 2 ). The chambers are operated by thermal property of the air. A pair of check valves  60  are used to assure the air only flow one direction ( FIG. 3  and  FIG. 4 ). It is object for the invention to form an air pressure gradient in the porous media so as for the air contained in the porous media to flow at a desired direction and remove gas phased contaminations. It is also object for the invention to provide a means to deliver gaseous decontamination agents into the porous media with contamination to accelerate natural attenuation. 
     
    
     DESCRIPTION OF THE INVENTION 
       [0013]    The invention use air thermodynamic properties as driving force. Special designed chambers  5  are coupled on wefts installed in the concerned area ( FIG. 1  and  FIG. 2 ). The chambers are consisted of a seated container  70 , a pair of check valves  60  and a set of heating apparatus  90  with temperature control device  100  ( FIG. 3  and  FIG. 4 ). The check valves are arranged as such that the air flow in the chamber will only flow one direction ( FIG. 3  and  FIG. 4 ). 
         [0014]    Heating process of the chamber is in sequence of heating and cooling. When discharge valve of the heating chamber is connected with underground pipes, it serves injection function to push the fresh air or/and decontamination agents into the unsaturated zone. When recharge valve of the heating chamber is connected with the underground pipes, however, it serves extraction function to extract gaseous contamination out from the unsaturated zone. 
         [0015]    During the injection function, the air  15  inside the heating chamber is expanded in the heating cycle. With increased pressure, the gate  110  is pushed open. Air  15  flows out the heating chamber  80  from opening  120  to opening  130  through gate  110 . When the preset temperature is reached, the temperature control device will disable the heating apparatus. Duo to dropped temperature, tow pressure is created in the chamber. The tow pressure will close the gate  110  and open gate  150 . Air  10  with ambient temperature recharges into the chamber from opening  130  to opening  140  through gate  150 . The air will further coot down the chamber. White either the preset tow temperature is reached or preset time period is elapsed, the heating process starts again. 
         [0016]    When serving extraction function, the cooling cycle is working cycle. During the heating cycle, expanded air  95  pushes gate  180  open. The air  95  flows out the heating chamber  85  from opening  160  to opening  170 . The heating apparatus will be disabled at a preset temperature. The dropped temperature will create tow pressure in the heating chamber  85  and close the gate  180 . In the mean time, the gate  190  is pushed open. The tow pressure draw the air  30  in the casing of extraction weft  50  from opening  200  to opening  210  through gate  190 . When the heating cycle starts again, the expanded air will push close gate  190  and reopen the gate  180 . 
         [0017]    By adjusting the size of the heating chamber and power of the heating apparatus, the volume of injected air can be adjusted. The bigger the heating chamber and the more powerful the heating apparatus, the more air is pushed. The injection pressure will depend on the preset maximum temperature of the heating chamber. With higher temperature setting, the heated air in the chamber can achieve higher pressure. 
         [0018]    The injection/extraction through the underground pipes will create air pressure gradient in concerned unsaturated zone of the soil. To achieve better clean up result, some accessory devices can be used. An oxygen diffuser can be added into the chamber. The oxygen rich air will be pushed into the unsaturated zone to increase the rate of the VOCs and SVOCs biodegrading. An ozone generator can also be attached to the chamber. The air flow created by heating chamber will enhance the diffusion of ozone and boost the clean up process. 
         [0019]    For some application requiring only limited amount air passing through, a solar panel may be used as heating apparatus. The daily temperature fluctuation will proceed as natural heating/cooling system.