Abstract:
An efficient high-temperature water vapor generator is used to de-contaminate soil. The vapor generator includes a combustion chamber and a surrounding structure, wherein a cavity is located therebetween. Water is routed through the cavity and into the combustion chamber, where water vapor and heat are generated in the presence of fuel, ignition and air. The generated heat pre-heats the water in the cavity, thereby creating an efficient system. The water vapor is forced into a vapor tube (which has openings for emitting the vapor), thereby heating the vapor tube to temperatures of 800° F. or greater. A soil tube having lifting paddles located therein surrounds the vapor tube. Contaminated soil enters one end of the soil tube. The soil tube is rotated, thereby moving the contaminated soil into contact with the vapor tube (decontaminating the soil). The lifting paddles move the soil toward the second end of the rotating soil tube.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an environmental clean-up system. More specifically, the present invention relates to an efficient system for removing contaminants from soil.  
       BACKGROUND OF THE INVENTION  
       [0002]     Soil pollution is becoming a significant problem in this country. In numerous locations around the country, hazardous wastes, such as MTBE&#39;s, volatile organic compounds (VOCs), poisons and other chemicals have been inadvertently released, thereby contaminating the surrounding soil. Such soil contamination can be caused, for example, by leaking underground storage tank sites (LUST sites). The hazardous waste may leak through the soil, eventually contaminating water supplies.  
         [0003]     Cleaning up contaminated soil is both difficult and costly. Typically, the owner of a site containing contaminated soil is responsible for this soil. However, because there is no cost effective manner of cleaning the soil, the owners of contaminated soil typically pay to have the soil removed and stored at a remote location. One such location is the Kettleman Hazardous Waste Landfill, located near Fresno, Calif. The cost for removing and storing contaminated soil is typically about $65/cubic yard.  
         [0004]     It would therefore be desirable to have a cost efficient method and apparatus for cleaning contaminated soil. It would further be desirable if this method and apparatus were portable, such that contaminated soil could be de-contaminated on-site, without requiring that the contaminated soil be transported a significant distance.  
       SUMMARY  
       [0005]     Accordingly, the present invention provides an efficient high-temperature water vapor generator, which is used to de-contaminate soil. The vapor generator includes a generally cylindrical combustion chamber and a surrounding structure, wherein a cavity is located between the combustion chamber and the surrounding structure. Water is routed through the cavity and into the combustion chamber, where water vapor and heat are generated in the presence of fuel, ignition and air. The heat generated inside the combustion chamber causes the water in the cavity to pre-heat. As a result, the water that is introduced to the combustion chamber is pre-heated, thereby improving the efficiency of the water vapor generator.  
         [0006]     The high-temperature water vapor is forced into a vapor tube, which includes openings for emitting the vapor. The vapor heats the heating the vapor tube to temperatures of 600° F. or greater. In one embodiment, the vapor tube is mounted in a horizontal configuration over a fixed platform.  
         [0007]     A cylindrical soil tube is supported such that this soil tube surrounds the vapor tube. Contaminated soil in introduced to a first end of the soil tube. The soil tube is rotated along its central axis by a drive assembly. Lifting paddles are located on the inner surface of the soil tube, thereby lifting the contaminated soil into contact with the vapor tube. The soil is decontaminated by coming into contact with the high temperature vapor tube. That is, hydrocarbons in the soil are cracked by the high temperature. The lifting paddles move the soil toward the second end of the rotating soil tube, such that decontaminated soil is expelled at the second end of the soil tube.  
         [0008]     The decontamination process results in waste gases being emitted from within the soil tube. In one embodiment, these waste gases are routed into the vapor generator, thereby burning these waste gases and providing a more efficient system.  
         [0009]     The soil remediation unit of the present invention is compact, and can easily be mounted on a truck bed, a trailer or a barge. Moreover, the vapor generator and drive assembly can be operated in response to one or more portable batteries, a portable fuel supply and a portable (or non-portable) water supply. Thus, the soil remediation unit can be brought to the location where the contaminated soil resides. Because the soil remediation unit decontaminates the soil on-site, there is no need to remove any contaminated soil to a remote location.  
         [0010]     The present invention will be more fully understood in view of the following description and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a cross sectional diagram of a vapor generator in accordance with one embodiment of the present invention.  
         [0012]      FIG. 2  is a block diagram illustrating a vapor generating system that uses the vapor generator of  FIG. 1  in accordance with one embodiment of the present invention.  
         [0013]      FIG. 3  is a schematic side view of a soil remediation system, which uses the vapor generator system of  FIG. 2  to de-contaminate soil in accordance with one embodiment of the present invention.  
         [0014]      FIG. 4  is a schematic top view of the soil remediation system of  FIG. 3  in accordance with one embodiment of the present inventions.  
         [0015]      FIG. 5  is an end view of a portion of the soil remediation system of  FIG. 3  in accordance with one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0016]      FIG. 1  is a cross sectional diagram that illustrates a vapor generator  100  in accordance with one embodiment of the present invention. Vapor generator  100  is illustrated with an X-Y-Z coordinate system, as illustrated. Vapor generator  100  is generally cylindrical in nature, with the central axis of the cylinder parallel with the Z-axis.  
         [0017]     Vapor generator  100  includes outer cylindrical section  101 , inner cylindrical section  102 , a pair of inner conical structures  103 - 104 , a pair of outer conical structures  105 - 106 , an air coupling element  107 , a vapor coupling element  108 , an ignition coupling element  111 , a fuel coupling element  112 , vapor baffle element  113 , and water coupling elements  120 - 123 .  
         [0018]     In the described embodiment, the elements of vapor generator  100  are made of 304-stainless steel. However, it is understood that vapor generator  100  can be made of other materials in other embodiments. In the described embodiment, vapor generator  100  has a height (H 0 ) of about 43¼ inches. Outer cylindrical section  101  is a tube having an outside diameter of six inches and a height (H 1 ) of 32 inches. The walls of outer cylindrical section  101  have a thickness of 0.120 inches. Outer conical element  105  is connected to the upper end of outer cylindrical section  101 , and outer conical element  106  is connected to the lower end of outer cylindrical section. The ends of outer conical elements  105 - 106  that are connected to the ends of outer cylindrical section  101  have outside diameters equal to 6 inches. The walls of outer conical elements have a thickness of 0.120 inches. Thus, the ends of outer conical elements  105 - 106  have the same dimensions as the ends of outer cylindrical section  101 . In accordance with one embodiment, the outer conical elements  105 - 106  are connected to the ends of outer cylindrical section  101  by a conventional welding process. Each of the outer conical elements  105 - 106  tapers down from a maximum diameter of 6 inches to a minimum diameter of 4 inches. Each of the outer conical elements  105 - 106  has a height (H 4 ) of about 4 inches along the Z-axis.  
         [0019]     Inner cylindrical section  102  is a pipe having an outside diameter of 5{fraction (9/16)} inches and a height (H 2 ) of  30  inches. The walls of outer cylindrical section  101  have a thickness of 0.40 inches. Inner conical element  103  is connected to the upper end of inner cylindrical section  102 , and inner conical element  104  is connected to the lower end of inner cylindrical section  102 . The ends of inner conical elements  103 - 104  that are connected to the ends of inner cylindrical section  102  have outside diameters equal to 5 inches. The walls of inner conical elements  103 - 104  have a thickness of 0.40 inches. Thus, the ends of inner conical elements  103 - 104  have the same dimensions as the ends of inner cylindrical section  102 . In accordance with one embodiment, the inner conical elements  103 - 104  are connected to the ends of inner cylindrical section  102  by a conventional welding process. Each of the inner conical elements  103 - 104  tapers down from a maximum diameter of 5 inches to a minimum diameter of 3 inches. Each of the inner conical elements  103 - 104  has a height (H 3 ) of about 5 inches along the Z-axis.  
         [0020]     The smaller ends of inner conical element  103  and outer conical element  105  are connected to air coupling element  107 . In the described embodiment, the smaller ends of inner conical element  103  and outer conical element  105  are welded to the underside of the cylindrical air coupling element  107 , such that these conical elements are concentrically located around a central axis (which is parallel with the Z-axis). In the described embodiment, air coupling element  107  is a cylindrical element having an inside diameter of 3 inches, an outside diameter of 4.5 inches, and a height (H 5 ) of about 1⅝ inches. As described in more detail below, the opening of air coupling element  107  is subsequently configured to receive an inflow of air.  
         [0021]     Vapor baffle  113  is also connected to the lower surface of air coupling element  107 . In the described embodiment, vapor baffle  113  is a pipe having an inside diameter of  3  inches, a wall thickness of about 0.118 inches, and a height (H 8 ) of about 4 inches (along the Z-axis). The bottom edge of this pipe has a flange that extends outward from the central axis of the pipe. In the described embodiment, this flange has an outer diameter of about 5 inches. As described in more detail below, vapor baffle  113  regulates the flow of gasses within vapor generator  100 .  
         [0022]     The smaller ends of inner conical element  104  and outer conical element  106  are connected to vapor coupling element  108  in the same manner that inner conical element  103  and outer conical element  105  are connected to air coupling element  107 . In the described embodiment, vapor coupling element  108  is identical to air coupling element  107 . As described in more detail below, the opening of vapor coupling element  108  is subsequently configured to provide an outflow of heated water vapor.  
         [0023]     A cavity  131  is formed between the inner conical elements  103 - 104 /inner cylindrical element  102  and the outer conical elements  105 - 106 /outer cylindrical element  101 . As described in more detail, this cavity  131  is used to store (and pre-heat) water during normal operating conditions of vapor generator  100 . Cavity  131  is capable of storing approximately 200 gallons of water.  
         [0024]     A combustion chamber  130  is defined by inner conical elements  103 - 104 , inner cylindrical element  102 , air coupling element  107  and vapor coupling element  108 . As described in more detail below, a fuel/air mixture is ignited in the combustion chamber  130 , thereby heating water that has been injected into the combustion chamber  130 .  
         [0025]     Ignition coupling element  111  is a cylindrical element that extends through inner and outer conical elements  103  and  105 , as illustrated. In the described embodiment, ignition coupling element  111  has an outside diameter of 1 inch, an inside diameter of 14 mm, and a length of 1⅛ inches. The cylindrical opening through ignition coupling element  111  is threaded for receiving an ignition element (e.g., a spark plug). As described in more detail below, the ignition element introduces sparking within combustion chamber  130 . The opening of ignition coupling element  111  is located about 2 inches below the lower surface of air coupling element  107 .  
         [0026]     Fuel coupling element  112  is also a cylindrical element that extends through inner and outer conical elements  103  and  105 , as illustrated. In the described embodiment, fuel coupling element  112  has an outside diameter of {fraction (3/8)} inches, an inside diameter of {fraction (5/16)} inches and a length of about 1¼ inches. The cylindrical opening through fuel coupling element  112  is configured to receive a fuel line. The opening of fuel coupling element  112  is located about 2 inches below the lower surface of air coupling element  107 . As described in more detail below, a fuel, such as propane or natural gas, is introduced to combustion chamber  130  via fuel coupling element  112 . This fuel is ignited by sparks provided by the ignition element. As described in more detail below, vapor baffle  113  helps to contain the fuel in the same general vicinity as the ignition element, thereby improving the burn of the fuel.  
         [0027]     Water coupling elements  120 - 123  are also cylindrical elements. In the described embodiment, these elements  120 - 123  each have an outer diameter of 1 inch, an inner diameter of ½ inches. Water coupling element  120 , which has a length of about 1½ inches, extends through both outer cylindrical section  101  and inner cylindrical section  102 . As described in more detail below, water coupling element  120  is configured to receive a water injection device, such that water can be injected into inner chamber  130 . Water coupling elements  121 - 123 , each of which has a length of about 1½ inches, extends through outer cylindrical section  101  (but not through inner cylindrical section  102 ). The central axes of water coupling elements  121 - 122  are located at a height (H 6 ) of about 1½ inches above the lower edge of outer cylindrical section  101 . The central axes of water coupling elements  120  and  123  are located at a distance (H 7 ) of about 2½ inches below the upper edge of outer cylindrical section  101 .  
         [0028]     As described in more detail below, water is introduced into cavity  131  via one or both of water coupling elements  121  and  122 . The water level in cavity  131  is maintained at a level that is higher than water coupling element  123 . As described in more detail below, water is removed from cavity  131  via water coupling element  123 .  
         [0029]     Although vapor generator  100  has been described with particular dimensions and shapes, it is understood that other dimensions and shapes can be used in other embodiments.  
         [0030]      FIG. 2  is a block diagram illustrating a vapor generating system  200  that uses vapor generator  100  in accordance with one embodiment of the present invention. In addition to vapor generator  100 , system  200  includes air supply line  201 , blower  202 , ignition element  211 , ignition controller  212 , fuel supply line  221 , fuel supply  222 , water supply line  231 , water supply  232 , water injector  233 , pre-heated water supply line  234 , water plug  235  and vapor exhaust line  241 .  
         [0031]     In general, system  200  operates as follows to produce high temperature steam (vapor). As described in more detail below, this high temperature vapor is subsequently used to decontaminate a material, such as soil. Air, water, fuel and sparks are introduced to vapor generator  100  by air blower  202 , water injector  233 , fuel supply  222  and ignition element  211 , respectively. The sparks ignite the fuel and air to heat the injected water. In response, vapor generator  100  generates super-heated steam (vapor) having a temperature of about 400 to 1000° F. The high temperature water vapor is forced out through vapor exhaust line  241 . As described in more detail below, exhaust line  241  carries the high temperature water vapor to a soil moving device. The high temperature water vapor is then used to remove contaminants from soil that is forced through the soil moving device.  
         [0032]     In the described embodiment, air supply line  201  is flexible aluminum tubing having an inside diameter of 3 inches and a length of about 20 inches. Air supply line  201  can be coupled to air coupling element by a clamp. When air blower  202  is turned on, air is forced through air supply line  201  and into combustion chamber  130 . In the described embodiment, air blower  202  is a 10 horsepower (hp) high-speed hydraulic motor available from Spencer Industries, as part number EAT104-1006-006. This hydraulic motor is capable of operating at about 2000 rpm in response to a 24 Volt supply battery. In the described embodiment, air blower  202  provides an air flow in the range of about 200 to 700 cubic feet per minute (cfpm) at a maximum pressure in the range of about 2 to 5 pounds/square inch (psi).  
         [0033]     In the described embodiment, both fuel coupling element  112  and fuel supply line  221  have an inside diameter of about {fraction (3/8)} inch. Fuel supply line  221 , which is made of stainless steel, is coupled to fuel coupling element with a conventional metal sealed connector. Fuel supply  222  is controlled to provide a flow of fuel through fuel supply line  221  and fuel coupling element  112  into combustion chamber  130 . In the described embodiment, the fuel supply  222  is a 100-gallon fuel tank containing either propane or natural gas. Fuel supply  222  can be controlled manually or automatically in various embodiments of the present invention. The maximum fuel flow into combustion chamber  130  is on the order of 40 to 80 standard cubic feet per hour (scfh). In one embodiment, the fuel flow is about 2 gallons per hour, for a daily (8 hour) fuel cost of about $20. In the described embodiment, a control valve is inserted into fuel coupling element  112 , thereby limiting the fuel pressure to about 8 psi.  
         [0034]     In the described embodiment, ignition element  211  is located at the same height as fuel coupling element  112 , with a 180 degree separation between ignition element  211  and fuel coupling element  112 . Ignition element  211  can be, for example, a spark plug available from Bosch as part number W6DC. Other spark plugs can be used in other embodiments. Ignition controller  212  transmits electrical control signals to ignition element  211 . These electrical control signals are selected such that ignition element  211  fires (sparks) continuously while these electric control signals are being transmitted. The electrodes of ignition element  211  are located inside of combustion chamber  130 , such that the sparks are created within combustion chamber  130 . The expected life of ignition element  211  under these conditions is on the order of about 5000 hours. In the described embodiment, ignition controller  212  is a spark generator available from Dongan Electric Manufacturing Company as part number A06SAG. Ignition controller  212  is capable of operating in response to a 24 Volt battery supply.  
         [0035]     Water supply line  231  couples water supply  232  to water coupling element  121 . In the described embodiment, water supply line  231  is a rubber hose having an inside diameter of about 1 inch. In one embodiment, a {fraction (3/8)} inch Nupro ball valve is included in water coupling element  121 . Water supply line  231  is coupled to water coupling element  121  by a ½ inch pipe nipple. In one embodiment, water supply  232  is supplied by a water pump, available from Shurflo as part number 52063-B979. In the described embodiment, water coupling element  122  is sealed by plug  235 . In this embodiment water coupling element  122  provides redundancy, in case water coupling element  121  is (or becomes) defective. In an alternate embodiment, water supply  232  can be coupled to both water coupling elements  121  and  122 .  
         [0036]     Water from water supply  232  flows into cavity  131 . The water level  226  within cavity  131  is controlled such that this water level  226  is higher than water coupling element  123 . In a particular embodiment, water level  226  is controlled such that cavity  131  is substantially full during normal operation of system  200 .  
         [0037]     The water in cavity  131  is heated due to the proximity to combustion chamber  130 . That is, heat from the combustion chamber  130  heats the water in cavity  131  via the thermally conductive inner cylindrical section  102  and inner conical structures  103 - 104 . In one embodiment, the water in cavity  131  is heated to a temperature of about 60 to 212° F. Water supply  232  forces the heated water to exit cavity  131  and enter pre-heated water supply line  234 . From pre-heated water supply line  234 , the heated water enters water injection element  233 . In response, water injection element  233  causes the heated water to enter combustion chamber  130  as a spray. In the described embodiment, water injection element  233  injects water at a rate of 2 to 5 gallons/minute (gpm). Water injection element  233  can be, for example, part number 137-155, available from Delaven.  
         [0038]     Within combustion chamber  130 , the sparks introduced by ignition element  211  ignite the fuel introduced by fuel supply  222  and the air introduced by blower  202 , thereby generating heat, which in turn, causes the pre-heated water introduced by water injection element  233  to become super-heated. Air blower  202  forces the burnt fuel/water mixture (hereinafter referred to as the “vapor”) toward the bottom of combustion chamber  130 . The vapor pressure is increased as the combustion chamber  130  narrows.  
         [0039]     Locating ignition element  211  and fuel coupling element  221  near the top of the combustion chamber  130  advantageously allows a long time for the fuel to burn. That is, the fuel is allowed to burn down the entire length of the combustion chamber  130 . This allows the fuel to burn completely. The length of the combustion chamber  130  is selected to be long enough to allow the fuel to burn completely.  
         [0040]     The force introduced by air blower  202  further causes the vapor to flow through vapor supply line  241 . The vapor in vapor supply line  241  has a temperature in the range of about 200 to 1400° F. and a pressure in the range of about ½ to 5 psi. In none embodiment, vapor supply line  241  is stainless steel tubing, having a diameter of about 2 inches. The exhaust provided at vapor supply line  241  is relatively clean. It is estimated that the vapor will consist of about 20 water vapor 5% CO, 10% O 2 , 63% CO 2  and 2% NO.  
         [0041]     In accordance with one embodiment, system  200  is started as follows. First, air blower  202  and ignition controller  212  are turned on. As a result, any residual fuel in combustion chamber  130  will be safely burnt and blown out of vapor supply line  241 . About ten seconds later, fuel supply  222  is turned on, thereby providing fuel flow to combustion chamber  130 . At this time, fuel begins burning, thereby pre-heating combustion chamber  130 . About ten seconds after fuel supply  222  is turned on, water supply  232  is turned on, thereby introducing water to combustion chamber  130 . Vapor is then generated in combustion chamber  130  in the manner described above.  
         [0042]     In accordance with another embodiment, system  200  is turned off by turning off fuel supply  222 , ignition controller  212  and water supply  232  at about the same time. Blower  202  is allowed to run for about 30 seconds longer, thereby clearing combustion chamber  130  and vapor supply line  241 .  
         [0043]      FIG. 3  is a schematic side view of a soil remediation system  300 , which uses vapor generator system  200  to de-contaminate soil in accordance with one embodiment of the present invention.  FIG. 4  is a schematic top view of soil remediation system  300 . Note that vapor generator system  200  is not shown in  FIG. 4  for reasons of clarity. Soil remediation system  300  includes a base assembly  301 , which is formed from steel. In the described embodiment, base assembly  301  has a height of about 4 inches, a length of about 276 inches and a width of about 40 inches. Base assembly  301  is supported by ten support legs, including support legs  302 - 306 . Note that five support legs (not shown) are hidden behind support legs  302 - 306  in the side view of  FIG. 3 . Each support leg is made of steel. In the described embodiment, each of the support legs has a height of about 18 inches and a square cross section of about 4 inches by 4 inches. The support legs are welded to base assembly  301 .  
         [0044]     The support legs are also welded to an underlying platform  307 . In the described embodiment, platform  307  is the bed of a large truck or trailer. In the described embodiment, platform  307  is supported by four or more wheels of the truck/trailer, including wheels  308 - 309 , by conventional means. Note that two wheels (not shown) are hidden behind wheels  308 - 309  in the side view of  FIG. 3 . In other embodiments, platform  307  can be a raised stationary structure.  
         [0045]     System  300  further includes a front support assembly  311  and a rear support assembly  312 , each having an L-shaped cross section. The bases of front and rear support assemblies  311 - 312  are bolted down to base assembly  301 . In the described embodiment, front and rear support assemblies  311 - 312  are made of steel having a thickness of about 1 inch. The bases of front and rear support assemblies  311 - 312  each have a length of about 8 inches and a width of about 36 inches. Front support assembly  311  has a height of about 57½ inches, and rear support assembly  312  has a height of about 31 inches. An inner tube rear support  314  is welded to rear support assembly  312  as illustrated. Inner tube rear support  314  is a cylindrical steel tube having a length of about 18 inches, and an outside diameter of about 3½ inches.  
         [0046]     A vapor tube  313  extends between, and is supported by, front and rear support assemblies  311 - 312 . A first end of vapor tube  313  extends through an opening in front support assembly  311 . In one embodiment, the first end of vapor tube  313  is welded in this opening. The first end of vapor tube  313  is open. As described in more detail below, this opening in vapor tube  313  is coupled to receive the high temperature vapor provided by vapor generator  100 .  
         [0047]     The second end of vapor tube  313  fitted over inner tube support assembly  314 , as illustrated. As a result, inner tube support assembly  314  supports the second end of vapor tube  313 . The second end of vapor tube  313  is welded to rear support assembly  312 . As a result, the second end of vapor tube  313  is effectively sealed. In the described embodiment, vapor tube  313  is schedule  40  type  347  stainless steel cylindrical tube, having a 4 inch outside diameter, a wall thickness of 0.237 inches, and a length of 216¼ inches. In other embodiments, vapor tube  313  can have other shapes. For example, vapor tube  313  can have a triangular cross section, with a vertex of the vapor tube pointing straight up.  
         [0048]     A plurality of vapor openings  315  extend through a sidewall of vapor tube  313 . These vapor openings  315  are located along the length of vapor tube  313 . In a particular embodiment, these vapor openings  315  are all located along a straight line that extends along the length of vapor tube  313 . Vapor tube  313  is positioned such that these vapor openings  315  are located on the underside of vapor tube  313 . In the described embodiment, there are about  29  vapor openings located on the underside of vapor tube  313 , each having a diameter of about {fraction (3/8)} inches. As described in more detail below, the high temperature vapor from vapor generating system  200  enters the first end of vapor tube  313  and exits through vapor openings  315 . The high temperature vapor heats vapor tube  313  to a temperature that is sufficiently high to remove contaminants from soil.  
         [0049]     A drive assembly  331  and an idler assembly  332  are also mounted on base assembly  301 . Drive assembly  331  and idler assembly  332  support a main auger assembly  320 , which surrounds, but does not contact, vapor tube  313 . Main auger assembly  320  includes wear cylinders  321 - 322 , gear element  323 , soil tube  324 , and internally located lift paddles  1 - 4 . In the described embodiment, soil tube  324  is a schedule  40  C/S pipe having an outside diameter of 20 inches and a length of 216 inches. In other embodiments, soil tube  324  can have other dimensions. For example, soil tubes having diameters of 30 or 40 inches can be used to provide more soil throughput. The location of soil tube  324  is maintained by gear element  323 , which engages a corresponding gear element  333  on drive assembly  331 . Soil tube  324  is positioned such that a ½ inch clearance is maintained between a first end of soil tube  324  and front support assembly  311 .  
         [0050]     During normal operation, soil tube  324  is rotated along its central axis, around the stationary vapor tube  313 . This rotation is facilitated by drive assembly  331 , idler assembly  332  and motor  337 . As shown in  FIG. 4 , drive assembly  331  includes a rotating drive element  335  and a rotating support element  336 . Rotating drive element  335  includes two wear rings  401 - 402 , which contact wear ring  321 , and a recessed gear element  333 , which engages raised gear element  323 . Rotating support element  336  includes wear rings  411 - 412 , which contact wear ring  321 , and a recessed channel  413 , which is located between wear rings  411 - 412 . Recessed channel  413  receives, but does not contact gear element  323 . In the described embodiment, wear rings  401 - 402  and  411 - 412  are made of the same material as wear ring  323 .  
         [0051]     Idler assembly  332  includes a first rotating idler assembly  421  and a second rotating idler assembly  422 . The first rotating idler assembly  422  includes a first rotating wear ring  431 , which contacts wear ring  322 . The second rotating idler assembly  422  includes a second rotating wear ring  432 , which contacts wear ring  322 . The first and second rotating wear rings  431 - 432  rotate about a pair of corresponding axles, which are supported by a corresponding pair of brackets, which are connected to base assembly  301 .  
         [0052]      FIG. 5  is an end view of wear ring  321 , gear element  323  and drive assembly  331 . Note that gear element  323  extends above wear ring  321 . In the described embodiment, gear element  323  has a height of 24 inches and a width of 1⅛ inches. In the described embodiment, gear element  323  is formed by one or more laser cut pieces of A 36  steel, which are welded to wear ring  321 . As described above, gear element  333  is slightly recessed with respect to wear rings  401 - 402 , such that gear element  333  engages with gear element  323 , and wear rings  401 - 402  contact wear ring  321 . Also, as described above, wear rings  411 - 412  contact wear ring  321 , but gear  323  does not contact assembly  201  within channel  413 . Both rotating drive element  335  and rotating support element  336  are suspended by axles that are supported by brackets that are mounted on base assembly  301 . Both rotating drive element  335  and rotating support element  336  are free to rotate about their central axes. The drive shaft of motor  337  is attached to a coupling element  334 , thereby enabling motor  337  to turn rotating drive element  335  of drive assembly  331 . Rotating drive element  335  thereby rotates main auger assembly  320  via gear elements  333  and  323 . In the described embodiment, motor  337  is a 10 hp hydraulic motor capable of turning main auger assembly  320  at a rate of 0-10 rotations per minute (rpm). In the described example, motor  337  is part number EAT104-1006-006, available from Spencer Industries.  
         [0053]     Idler assembly  332  supports main auger assembly  301  as the main auger assembly is rotated. More specifically, wear ring  322  rotates on first rotating wear ring  431  and second rotating wear ring  432 . In the described embodiment, each of wear rings  431 - 432  has an outside diameter of 21 inches. Wear ring  322  rests on wear rings  431 - 432 . Wear ring  322  rotates freely on wear rings  431 - 432 , thereby enabling the entire auger assembly  320  to rotate in response to motor  337 . Wear rings  321 - 322  and  431 - 432  are made of a material that is more resistant to wear than soil tube  324 . For example, wear rings  321 - 322  and  431 - 432  can be made of A36 steel having a thickness of ½ inch.  
         [0054]     A soil feed chute  341  is attached to front support element  311 . Chute  341  includes an upper opening for receiving contaminated soil, and a lower opening for feeding contaminated soil through front support element  311  into tube  324 . The contaminated soil can be loaded into the upper opening of chute  341  in a controlled manner by various means, including a conveyor belt  351 .  
         [0055]     A set of four lifting paddles  1 - 4  are located inside soil tube  324 . The ends of these lifting paddles  1 - 4  are shown in  FIG. 5 . Lifting paddles  1 - 4  have angled ends, which help to hold soil as the soil tube is rotated. The direction of rotation, R, is illustrated in  FIG. 5 . Lifting paddles  1 - 4  each follow a spiral pattern along the length of soil tube  324 . This spiral pattern is shown schematically by line  325  in  FIG. 3 . Note that the lifting paddles maintain a spacing of about 90 degrees throughout this spiral pattern. This spiral pattern helps to move soil from the first end of soil tube  324  to the second end of soil tube  324 , as soil tube  324  is rotated. Lifting paddles  1 - 4  also cause the contaminated soil to be lifted over, and then dropped down upon, vapor tube  313 . As a result, the soil does not clog the vapor openings  315  in vapor tube  313 . As described in more detail below, vapor tube  313  is heated to a temperature of about 500 to 1200° F. by vapor produced by vapor generator  100 . When the contaminated soil comes into contact with vapor tube  313 , the hydrocarbons and volatile organic compounds (VOC&#39;s) present in the contaminated soil are cracked, thereby eliminating the hydrocarbons, and providing one or more by-product gasses (CO and CO 2 ). The high temperature vapor tube  313  also eliminates other contaminants from the soil, such as mercury.  
         [0056]     Decontaminated soil exits the second end of soil tube  324 , and falls through exit chute  342 , which extends through base assembly  301  and platform  307 . The decontaminated soil can then be removed, for example, by a conveyor belt assembly  352 .  
         [0057]     In accordance with one embodiment, a cover  360  extends over main auger assembly  320 , as illustrated in  FIG. 3 . This cover  360  is used to collect the gases that are expelled from soil tube  324 . These gases include water vapor that is expelled through the holes  315  in the bottom of vapor tube  313 . These gases also include the by-product gases created by decontaminating the soil. The air supply line  201  of vapor generator  100  is attached to cover  360 , such that air blower  202  pulls in air present under cover  360 . As a result, remaining contaminants in the by-product gases are burned when returned to vapor generator  100 .  
         [0058]     In the foregoing manner, the soil remediation system  300  is capable of efficiently cleaning contaminated soil. Soil remediation system  300  can easily be moved to job sites, thereby eliminating the need to transport contaminated soil over long distances. Soil remediation system  300  can advantageously be run in remote locations, because the motor  337 , blower  202 , ignition control unit  212  all run from battery power, fuel supply  222  can be provided in portable tanks, and water is either readily available or can be provided by portable tanks.  
         [0059]     The various embodiments of the structures and methods of this invention that are described above are illustrative only of the principles of this invention and are not intended to limit the scope of the invention to the particular embodiments described. For example, although soil tube  324  has been described as having a horizontal arrangement, it is understood that one end of soil tube  324  may be elevated with respect to the other end. Thus, the invention is limited only by the following claims.