US20060180043A1

US20060180043A1 - System and method for remediation of explosive contamination using convective heat

Info

Publication number: US20060180043A1
Application number: US11/045,690
Authority: US
Inventors: John Coughlin; Mark Sylvester; Charles Irvin
Original assignee: Plexus Scientific Corp
Current assignee: Plexus Scientific Corp
Priority date: 2005-01-28
Filing date: 2005-01-28
Publication date: 2006-08-17

Abstract

According to the present teachings, a system and method are provided for decontaminating a conduit or vessel contaminated with residual explosive material. The system can include a heated gas flow source for heating a gas and providing a flow of the heated gas into the interior of a conduit or vessel. The temperature of the heated flow of gas can be at or in excess of the break down temperature of the residual explosive material.

Description

INTRODUCTION

The present teachings relate to a system and method for decontaminating a sewer line or other conduit, or a storage tank or other vessel, contaminated with residual explosive material.

SUMMARY

According to various embodiments, a system is provided that can comprise a conduit such as a sewer line, or a vessel such as a storage tank, having an inner surface comprising residual explosive material deposited thereon, and a heated gas flow source in fluid communication with the inner surface. The residual explosive material can have a break down temperature, and the heated gas flow source can be adapted to produce a flow of heated gas into the conduit or vessel sufficient to heat the inner surface to a temperature at or in excess of the break down temperature.
According to various embodiments, a system is provided that can comprise a heated gas flow source. The heated gas flow source can comprise one or more burner units. The heated gas flow source can comprise one or more fan or blower units in communication with one or more burner units and can be adapted to introduce gas, heated by the burner unit, into a sewer line at a flow rate. The heated gas flow source can comprise a fuel source. When the fuel source is a liquid, the heated gas flow source can comprise a vaporizer in communication with the fuel source and the burner unit. The vaporizer can be adapted to receive liquid fuel from the fuel source, vaporize the liquid fuel to produce a gas fuel, and provide the gas fuel to the burner unit.
According to various embodiments, a method is provided that can comprise: connecting a heated gas flow source to a conduit or vessel comprising residual explosive material deposited on an inner surface thereof, the residual explosive material having a break down temperature at which the residual explosive material chemically decomposes or breaks down; introducing a heated gas flow into the conduit or vessel; and maintaining a flow of heated gas through the conduit or vessel until the temperature of the inner surface reaches a temperature at or in excess of the break down temperature of the residual explosive material.
According to various embodiments, the method according to the present teachings can comprise maintaining the internal surface of a conduit or vessel at or in excess of the break down temperature of a residual explosive material or materials, for a period of time. The period of time can be, for example, one minute or longer, 10 minutes or longer, or 30 minutes or longer.
According to various embodiments, the method according to the present teachings can comprise maintaining the internal surface of a conduit or vessel at or in excess of the break down temperature of a residual explosive material or materials deposited therein, for a period of time that can comprise a period of time sufficient to ensure break down of the residual explosive material or materials.
According to various embodiments, the method according to the present teachings can comprise providing a heated gas flow at an initial temperature to a conduit or vessel comprising an inlet, an outlet, and an interior surface comprising residual explosive material having a break down temperature, deposited thereon, wherein the interior surface is in fluid communication with the heated gas flow, and maintaining the heated flow of gas at or above the initial temperature at least until the temperature of the heated flow of gas at the outlet is at or above the break down temperature of the residual explosive material.
Additional features and advantages of the present teachings are set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of the present teachings. The objectives and other advantages of the present teachings will be realized and attained by means of the elements and combinations particularly pointed out in the description that follows.
It is to be understood that both the foregoing summary and the following description are exemplary and explanatory only and are intended to provide a further explanation of the present teachings.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present teachings are exemplified in the accompanying drawings. The teachings are not limited to the embodiments depicted in the drawings, and include equivalent structures and methods as set forth in the following description and as would be known to those of ordinary skill in the art in view of the present teachings. In the drawings:
FIG. 1 illustrates a heated gas flow source connected to a sewer line in accordance with various embodiments of the present teachings;
FIG. 2 is a graph illustrating temperatures recorded by thermocouples during a convective heat decontamination method according to various embodiments of the present teachings;
FIG. 3 illustrates a graph of the temperatures reached during a convective heat decontamination method according to various embodiments of the present teachings.

DESCRIPTION

Definitions: The below definitions serve to provide a clear and consistent understanding of the present teachings.
The term “break down” is herein defined as the temperature at which a particular residual explosive material chemically decomposes or breaks down and is no longer explosive or otherwise volatile. The break down temperature of the explosive material is the temperature at which a chemical change in the composition of the explosive material occurs, for example, the temperature at which the explosive material ignites, combusts, explodes, deflagrates, oxidizes, reduces, decomposes, or otherwise breaks down.
The term “heated gas flow source” is herein defined as any device or combination of devices, capable of producing a heated flow of gas. The heated gas flow source can comprise a heating unit. The heating unit can comprise a gas burner, an electrical device, a solar heater, a light emitting device, or a combination thereof. A gas burner can comprise a propane burner, for example, a conventional propane burner. A propane burner can comprise a tube-type burner. The heated gas flow source can comprise a blower unit, for example a centrifugal blower. The heated gas flow source can comprise a vaporizer. The burner unit, blower unit and vaporizer, can each be a separate device, or any two of or all three of, the burner unit, blower unit and vaporizer, can be provided in a single device.
The term “heated flow of gas” is herein defined as a flow of gas at a temperature above ambient temperature. The heated flow of gas can comprise an initial temperature which can be increased to a target temperature. The heated flow of gas can comprises a temperature sufficient to break down one or more residual explosive materials. The heated flow of gas can comprise a temperature and flow rate sufficient to break down one or more residual explosive materials. The flow of gas can comprise a heated flow of gas provided at sufficient temperature, a sufficient flow rate, and for a sufficient time, to break down one or more residual explosive materials. The flow of gas can be introduced into a conduit or vessel at atmospheric pressure or greater.
The heated flow of gas can comprise a positive-pressure mediated flow of heated gas where the heated flow of gas is introduced into the conduit or vessel at a pressure greater than one atmosphere. The gas of the heated flow of gas, can comprise, for example, air, combustion products, or a combination thereof. The term “heated gas flow” is used synonymously with the term “heated flow of gas” as defined herein.
The term “internal surface” is herein defined as the entire interior surface of a conduit, for example, a sewer line, or a vessel, for example, an aboveground or underground storage tank. The internal surface can comprise the interior surface only, or can comprise the interior surface and a thickness of the conduit or vessel wall. An interior surface including a wall thickness can comprise a region from the interior surface to a depth of up to 0.5 inch into the material of the wall. The depth can comprise a depth of from about greater than 0 inch to about three inches, a depth of from about greater than 0 inch to about 0.5 inch, a depth of from about greater than 0 inch to about 0.25 inch, or a depth of about 0.25 inch. In the case where the wall of the conduit or sewer line comprises a porous material, the internal surface can comprise a thickness, for example, to ensure that any residual explosive material penetrating the porous interior surface is completely decomposed or broken down during convective heat treatment.
The term “residual explosive material” is herein defined as any material having explosive properties. Such residual materials can comprise one or more of nitroguanidine, dinitrotoluene (DNT), trinitrotoluene (TNT), hexogene, octogene, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), Pentaerythritol tetranitrate (PETN), cyclotetramethylene-tetranitramine (HMX), tetryl, nitrocellulose (NC), nitroglycerine (NG), ammonium nitrate, lead azide, lead styphnate, and a combination thereof.
The term “conduit or vessel” is herein defined as any structure used to carry a material from a source to a disposal site. The conduit or vessel can comprise a storm water drain line, a sewer line, an industrial waste line, a sanitary waste line, or a pipe. A conduit or vessel can comprise any material capable of maintaining thermal stability or remaining intact, at a temperature at or in excess of, a residual explosive material's break down temperature. For example, the conduit or vessel material can comprise one or more of terracotta, concrete, brick, monel, and a combination thereof.
The term “source of alkane” is herein defined as any alkane source. An alkane source can comprise one or more of ethane, propane, butane, pentane, hexane, heptane, octane, and a combination thereof. The term “alkane source” is used synonymously with the term “source of alkane” as defined herein.
The term “initial temperature” is herein defined as the temperature at which a heated flow of gas is first introduced into a conduit or vessel. The initial temperature can comprise a target gas flow temperature.
The term “target gas flow temperature” is herein defined as a gas flow temperature of the gas flow entering the gas inlet at or above the initial temperature that is sufficient to achieve break down of a residual explosive material. The target gas flow temperature can be at or in excess of the break down temperature of any residual explosive material present in a conduit or vessel being decontaminated.
According to various embodiments, the present system and method provides for break down of residual explosive material using convective heat where a source of heat energy is placed at one end of a section of a conduit or vessel, hereforth exemplified as a sewer line, while a blower pushes heated gas, for example, heated air, through the sewer line to heat up the sewer line including the internal surface of the sewer line. The system can be operated for a time and at a temperature, sufficient to achieve decomposition or break down of residual explosive material deposited in or on the internal surface.
According to various embodiments, the heated flow of gas is provided at a temperature, a flow rate, and for a time period, sufficient to heat an internal surface of a length of sewer line to a target temperature at or in excess of the break down temperature of one or more residual explosive materials. Once the internal surface of the sewer line is at or above the break down temperature, the heated flow of gas can be maintained at the target temperature for period of time sufficient to ensure complete break down of the residual explosive material, for example, for about 2.0 hours or more.

Thermal properties of common explosives are shown in the table below. The break down temperatures discussed herein with respect to such explosives as shown in the table, can be understood, for example, as the “deflagration temperature.”

TABLE I


THERMAL PROPERTIES OF COMMON EXPLOSIVES

Material	Melting Point	Deflagration Temperature

Tri Nitro Toluene	178° F.	537°-572° F.
Hexahydro-1,3,5-Trinitro-	392° F.	500° F.
1,3,5-Triazine
Pentaerythritol Tetranitrate	286° F.	394° F.
Nitro-Gylcerine	56.3° F.	432° F.
Nitrocellulose	275° F.	338° F.

According to various embodiments, and in view of the break down temperatures of residual explosive materials, in the event that a sewer line is contaminated with explosive materials, where the composition of the explosive material is not known, decontamination of the sewer line can be achieved by heating the inner surface of the sewer line to at or in excess of the break down temperature of TNT, i.e., at or in excess of 572° F., according to various embodiments of the present teachings.
According to various embodiments, the convective heating method can comprise discharging combustion products of a gas burner into an opening of a section of a sewer line while a blower induces a gas flow through the sewer line from the opening of the section. The temperature of the exhaust gas leaving an opposite end or section of the sewer can be measured and recorded. As the interior of the sewer line is heated, the exhaust temperature rises. When the exhaust temperature reaches the desired break down temperature, for example, 572° F. or greater, the burner can continue to be fired for a given period of time (“soak” time) and at a rate sufficient to maintain this temperature, for example, for about 2 hours. Thereafter, the burner can be shut down and the blower can be turned off. The sewer line can then be allowed to cool down slowly through conduction to the material surrounding the sewer line, for example, to the surrounding soil or atmosphere.
A gas burner can be used to combust a fuel to produce the heated gas, for example, to produce heated air. A fuel source can comprise one or more liquid or vapor fuels. A vapor fuel can comprise one or more vaporized liquid fuels. A liquid fuel can comprise one or more alkanes including for example, one or more of ethane, propane, butane, pentane, hexane, heptane, octane, and a combination thereof.
The gas burner unit can comprise a sensor capable of detecting the absence of a flame, for example, if the flame goes out, the supply of fuel would automatically cut-off. Suitable sensors can comprise an ultraviolet sensor or a bimetallic switch.
The method can comprise vaporizing a liquid gas fuel source using a vaporizer. The vaporized fuel source, for example, vaporized propane, can then be provided to the burner unit, for example, a propane burner. The vaporizer can be part of the burner unit, or can be a device provided separate from the burner unit. The vaporizer can comprise a liquid bath vaporizer.
Ignition of the vaporized gas can comprise ignition using a spark plug type of ignition device, for example an ignition wire. Other suitable ignition devices can include a lighter or an electric match. Other ignition devices are known and can be readily selected and employed by one of ordinary skill in the art to which the present teachings pertain, without undue experimentation.
One or more burner units can be used to heat a gas, for example, air, to a desired temperature. The heated air can then be blown into a sewer line using one or more blower units, through at least one gas inlet. The heated gas can be introduced into the sewer line through two or more gas inlets. The gas inlet can comprise an existing opening in the sewer line, for example an opening in a street through a drain or a manhole, or can comprise a break made in the sewer line for the purpose of accessing the sewer line.
The heated gas flow source can be connected to the gas inlet by any means sufficient to provide a seal between the heated gas flow source and an opening in the sewer line being decontaminated. A seal can be provided, for example, by fitting the heated gas flow source into an opening in a sewer line and sealing the heated gas flow source with mineral wool. The heated gas flow source can be fitted into the opening in the sewer line via any means capable of withstanding temperatures at or in excess of a desired target temperature. For example, the heated gas flow source can be fitted into an opening in a sewer line via a duct or a hose, for example a flexible hose. Similar fittings can be used for other conduits or vessels.
The blower unit can be part of the burner unit or can be a unit separate from the burner unit. The heated gas can be continually blown into the sewer line through one or more gas inlets, the heated gas then travels the length of the sewer line, and exhausts the sewer line through one or more gas outlets. The temperature of the heated gas can be monitored at, at least the gas inlet and the gas outlet, using temperature sensors, which sensors can comprise a thermocouple. The temperature of the sewer line can be monitored at, for example, the inner surface, the inner surface to a depth of about 0.25 to about 0.5 inch, and/or the outer surface or skin of the sewer line.
A blower unit can comprise, for example, a centrifugal blower, a fan unit, a turbine, or the like. According to various embodiments, the blower unit can be connected to the burner end of the burner unit via a duct. A duct can comprise a flexible hose. A flexible hose can comprise a reinforced, flexible hose. The reinforced, flexible hose can comprise a spiral-reinforced, flexible hose.
According to various embodiments, during operation, heated gas can be generated by the burner unit. The burner unit can discharge the heated gas into the opening of a section of a sewer line while one or more blower units can induce flow of the heated gas through the sewer line from the opening section via one or more gas inlets.
When the sewer line comprises a material, for example terracotta, that is susceptible to thermal shock, for example, as evidenced by cracking or collapse due to a rapid increase in temperature, the heated gas can be initially supplied to the opening section at an initial temperature below the break down temperature of any residual explosive material present in the sewer line being decontaminated. The initial temperature can comprise a temperature of less than about 400° F., of less than about 300° F., of less than about 200° F., of from about 100° F. to about 300° F., of from about 125° F. to about 225° F., or of about 150° F. The temperature of the heated gas can be increased slowly in order to avoid thermal shock to the sewer line, for example, in order to avoid cracking of the sewer line.
The initial temperature can be increased slowly to a target gas flow temperature, for example, the initial temperature can be increased at a rate of from about 1.5° F./min to about 10.0° F./min., of from about 2.0° F./min to about 8.0° F./min., of from about 2.5° F./min to about 6.0° F./min., of from about 3.0° F./min to about 5.0° F./min., or of from about 3.5° F./min to about 4.5° F./min.
The target gas flow temperature can be a temperature at or in excess of a break down temperature of one or more explosive materials present in the sewer line being decontaminated. Depending on the residual explosive material or materials present, the target temperature can be greater than about 400° F., greater than about 500° F., greater than about 572° F., greater than or equal to about 572° F., of from about 400° F. to about 3,000° F., of from about 500° F. to about 3,000° F., of from about 572° F. to about 3,000° F., of from about 600° F. to about 3,000° F., of from about 700° F. to about 3,000° F., of from about 900° F. to about 3,000° F., of from about 1,000° F. to about 3,000° F., of from about 1,500° F. to about 3,000° F., of from about 2,000° F. to about 3,000° F., or of from about 2,200° F. to about 3,000° F.
For sewer line materials susceptible to thermal shock, for example, terracotta, the heated gas can be introduced into the sewer line at an initial temperature that can be slowly increased until a target gas flow temperature is achieved. The time necessary to achieve an increase in temperature from the initial temperature to the target temperature can depend on the rate of temperature increase, and can comprise a period of time of from about 1.0 hour to about 8.0 hours, of from about 1.5 hours to about 8.0 hours, of from about 2.0 hours to about 6.0 hours, of from about 2.0 hours to about 5.0 hours, of from about 2.5 hours to about 4.0 hours, of from about 2.0 hours to about 3.5 hours, or of from about 2.0 hours to about 3.0 hours.
For sewer line materials not susceptible to thermal shock, the heated gas flow can be introduced into the sewer line as described above for materials susceptible to thermal shock, or the heated gas flow can be introduced at about the target gas flow temperature.
According to various embodiments, once the heated gas flow is at or about the target gas flow temperature and the outlet gas temperature is at or is in excess of the break down temperature of the residual explosive material present, whereby the internal surface of the sewer line is at or in excess of the break down temperature of the residual explosive material, the heated flow of gas can be maintained at about that target gas flow temperature for a period of time. The period of time can be a period of time sufficient to ensure complete breakdown the explosive material present in the sewer line. This amount of time is referred to herein as the “soak” time.
Chemical decomposition or break down of the residual explosive materials can be determined by monitoring the temperature of the heated gas at the burner outlet, or at both the gas inlet and at the gas outlet. For example, once the heated flow of gas at the gas inlet is at the target gas flow temperature, the temperature of the heated flow of gas can be periodically monitored at the burner outlet, or at both the gas inlet and at the gas outlet. As the temperature of the internal surface of a sewer line increases, the temperature of the gas exiting the gas outlet increases. Once the outlet gas temperature reaches a temperature at or in excess of the break down temperature of the residual explosive material or materials, the heated flow of gas can be maintained at the target gas flow temperature for a period of time (soak time).
Sufficient temperatures of gas exiting the sewer line at the gas outlet, depend on the residual explosive material or materials present in the sewer line being decontaminated. For example, an exit gas temperature can comprise a temperature of at least about 200° F., of at least about 300° F., of at least 400° F., of from about 300° F. to about 3,000° F., of from about 400° F. to about 3,000° F., of from about 500° F. to about 3,000° F., of from about 550° F. to about 3,000° F., of from about 572° F. to about 3,000° F., of from about greater than 572° F. to about 2,000° F., or at a temperature greater than about 572° F. Once the exit gas reaches a temperature in excess of the break down temperature, the heated flow of gas can be maintained at the target gas flow temperature for a period of time (soak time) sufficient to ensure break down the residual explosive material.
A sufficient period of time for maintaining the heated gas flow at about the target gas flow temperature to ensure break down of the residual explosive material can be readily determined by the skilled artisan without undue experimentation based on the presently taught parameters including, for example, the sewer line material, the internal diameter of the sewer line, the thickness of the sewer line, the length of the sewer line, the flow rate of the heated gas at the target temperature, the target temperature, the temperature of the gas exiting the sewer line at the gas outlet, and the potential amount of, and break down temperature of, the residual explosive material. For example, as the target gas flow temperature and/or flow rate of the heated gas is increased, the inner surface of the sewer line heats up faster, and the soak time can be shorter. For example, the longer the length of the sewer line, the greater the amount of soak time that might be required. The greater the temperature of the gas exiting the sewer line at the gas outlet, the shorter the soak time that might be required.
When the temperature of the outlet gas is at or in excess of the break down temperature, the heated flow of gas at the target gas flow temperature can be maintained for a period of time (soak time) sufficient to ensure complete break down the residual explosive material. A sufficient period of time can comprise at least about 1.0 hour, at least about 2.0 hours, from about 1.0 hour to about 8.0 hours, from about 1.0 hour to about 6.0 hours, from about 1.0 hour to about 4.0 hours, from about 1.5 hours to about 3.0 hours, from about 1.5 hours to about 2.5 hours, from about 2.0 to about 3.0 hours, or about 2.0 hours. Maintaining the heated flow of gas as described above can ensure that the entire internal surface of a sewer line is maintained at or in excess of the break down temperature of any residual explosive material or materials present in the sewer line.
According to various embodiments, the heated flow of gas can be provided at a flow rate sufficient to achieve chemical decomposition or break down of any residual explosive material or materials present in the sewer line being decontaminated. An appropriate flow rate can be readily determined and used by one of ordinary skill to which the present invention applies, without undue experimentation, based on the parameters presently taught. Such parameters can include the particular residual explosive material present, the break down temperature of the residual explosive material, and/or the composition and physical dimensions of the sewer line including internal diameter, length, and thickness of the sewer line wall. For example, the flow rate can comprise a flow rate of from about 100 to about 6,000 cubic feet per minute (hereinafter CFM), of from about 200 to about 5,000 CFM, of from about 300 to about 4,500 CFM, of from about 6000 to about 3,000 CFM, or of from about 800 to about 1,200 CFM.
For example, a slower flow rate can be selected for sewer lines having a smaller internal diameter, and a faster flow rate can be selected for sewer lines having a larger internal diameter. For sewer lines having an internal diameter of from about four inches to about 10 inches, a flow rate of from about 100 to about 2,000 CFM, of from about 200 to about 1,500 CFM, or of from about 250 to about 1,000 CFM, can be used. For sewer lines having an internal diameter of from about 10 inches to about 12 inches, a flow rate of from about 500 to about 3,000 CFM, of from about 600 to about 2,500 CFM, or of from about 750 to about 1,500 CFM, can be used. For sewer lines having an internal diameter of from about 12 inches to about 24 inches, a flow rate of from about 800 to about 6,000 CFM, of from about 900 to about 5,500 CFM, or of from about 1,000 to about 5,000 CFM, can be used.
According to various embodiments, the flow rate can be adjusted or modulated during the convective decontamination method according to various embodiments of the present teachings. For example, when the heated flow of gas is supplied at an initial temperature lower than the target gas flow temperature, the initial flow rate can be slower than a target flow rate, and the initial flow rate can be increased to the target flow rate in accordance with the increase in temperature from the initial temperature to the target gas flow temperature.
According to various embodiments, a heated flow of gas can be provided to a terracotta sewer line having a length of, for example, from about 300 feet to about 400 feet, and having an internal diameter of from about 6 inches to about 10 inches. If the sewer line comprises residual explosive material having a break down temperature of about 572° F., heated gas can be supplied according to various embodiments at an initial temperature of from about 100° F. to about 300° F., of from about 125° F. to about 225° F., or at about 150° F. The initial temperature can be slowly increased at a rate of from about 2.0° F./min to about 8.0° F./min, and the target gas flow temperature can be from about 575° F. to about 3,000° F. The temperature of the heated flow of gas at the gas inlet and gas outlet can be periodically monitored. Once the temperature of the gas flow at the gas outlet is at or greater than the break down temperature, the heated flow of gas entering the inlet can be maintained at about the target gas flow temperature for a soak time of about 2.0 hours or more.
Referring to FIG. 1, a system 10 is provided. The system 10 can comprise a heated gas flow source 12 comprising a burner unit 14 for producing heated air 16. The burner unit 14 can comprise an ignition device 18, for example, a pilot light and sensor 22, for example, an ultraviolet sensor. The heated gas flow source 12 can comprise a blower unit 24 for inducing a flow of heated gas through a sewer line 26 via a gas inlet 28 to heat up the sewer line 26, from the burner unit 14 end. The blower unit 24 can be connected to the burner unit 14 via a flexible duct or hose 30. The heated flow of gas 16 travels from the gas inlet 28 through the interior of the sewer line 26 heating an internal surface 32 thereof, and exits the sewer line 26 at a gas outlet 34. Residual explosive contamination is depicted as reference numeral 35. The heated gas flow source can comprise a fuel source 36 for providing fuel to the burner unit 14. The heated gas flow source can comprise a vaporizer unit 38 for vaporizing liquid fuel from the fuel source 36 to produce a gas fuel and for providing it to the burner unit 14. The vaporizer unit 38 is in fluid communication with both the fuel source 36 and the burner unit 14 via a flexible duct or hose 40. Liquid fuel is provided from the fuel source 36 to the vaporizer unit 38 where the fuel is vaporized. The vaporized fuel is provided to the burner unit 14 where a heated gas is produced upon combustion.

EXAMPLES

Example 1

Thermal Calculations for Convective Heating of Terracotta Pipes of Various Diameters

The following calculations were performed to illustrate the feasibility of using convective heat for explosive decontamination. Using the specific heat of clay used in terracotta sewer line and thermodynamic calculations, Table II was used to project the theoretical time required to raise the temperature of 300 feet of terracotta sewer line to 600° F., at a depth of 0.25 inch into the terracotta material from the inside surface of the sewer line, using an internal temperature of 1,200° F. The total time represents the time required to reach 600° F. plus a two-hour soak time.

TABLE II

THERMAL CALCULATIONS FOR CONVECTIVE HEATING

OF TERRACOTTA PIPES OF VARIOUS DIAMETERS

Internal

Diameter Time Soak Total Flow

Sample (in.) (min.) (min.) (min.) CFM Total BTU

1 6 100 120 220 295 527,968

2 10 70 120 190 820 1,267,449

3 12 65 120 185 1,180 1,775,892

4 24 45 120 165 4,700 6,308,770
The above shows that the convective heating method according to various embodiments of the present teachings is capable of decontaminating residual explosive materials contained in a sewer line. Based on these calculations, convective heating was then tested in the field.

Example 2

Prepared Test Bed Evaluation

Convective heat treatment was evaluated on a Prepared Test Bed including, a 100-foot long length of sewer line. The test bed consisted of 12-inch diameter terracotta pipe and was seeded with explosive materials at six locations approximately 50, 52, 54, 90, 92 and 94 feet from the propane burner. The locations were identified as Prepared Test Bed Locations A through F. Each location was seeded with approximately two to three grams of Composition B. The explosive materials contained in Composition B included a mixture of explosive materials. The melting point of Composition B was 378° F. and the deflagration temperature (break down temperature) was 532° F. Locations A and D were seeded with Composition B explosives set into the joint (not covered by soil or mud). Locations B and E were seeded with Composition B and covered top and bottom with soil and set in a joint. Locations C and F were seeded with Composition B and covered top and bottom with mud and set in a joint. After the test bed was seeded with explosives, the terracotta line was covered with approximately two feet of soil on all sides to simulate the actual heat sink the convective heat treatment would experience under subsurface conditions.
Hot air for heating the sewer line was generated by burning propane in a tube-type burner. The hot exhaust gas from the combustion was directed into the sewer line to provide thermal energy and heat the line to above the deflagration temperatures of the explosive materials present, that is, above 532° F. The propane fuel was delivered to the site in a trailer-mounted tank. Liquid propane was pulled from the bottom of the tank and then run through a liquid bath vaporizer to change the liquid to a vapor prior to being burned. Ignition of the gas at the burner was through a spark plug igniter. The existence of a flame was determined with an ultraviolet sensor (hereinafter “UV” sensor) so that if the flame went out, the supply of propane gas would automatically shut off. Air for combustion was supplied to the burner by a centrifugal blower. The blower was connected to the burner by a spiral-reinforced flexible hose.
The tube burner was fitted into the end of the sewer line and sealed in place using mineral wool. The combustion air hose, fuel hose, igniter wire, and UV sensor, were each connected to the burner assembly. Besides monitoring the temperatures at the inlet and outlet of the sewer line, temperatures were recorded at 0.25 inch into the terracotta material from the inside surface of the sewer line, 0.50 inch into the terracotta line from the inside surface of the sewer line, and on the outer skin of the 1.0 inch thick terracotta line at a location approximately 90 feet from the inlet. The temperature was slowly increased by increasing the volume of propane gas supplied to the burner, to avoid thermal shock to the terracotta sewer line. Thermal shock can cause a terracotta sewer line to crack and/or collapse. The heated gas flow was started at an initial temperature of 300° F. At 300° F., some cracking of the terracotta sewer line occurred. To eliminate further cracking of the sewer line, the temperature was reduced to 150° F. and then slowly increased.
After completion of the above, the Prepared Test Bed was inspected to confirm whether the convective heating was effective for explosive decontamination of sewer lines. It was determined that all of the Composition B explosive material seeded in the sewer line was broken down during the convective heat treatment.
FIG. 2 is a graph of the temperatures recorded by thermocouples after the convective heat treatment of Example 2. In FIG. 2, the “★” symbol represents the temperature of the outer skin of the sewer line; the “♦” symbol represents the temperature of the heated flow of gas; the “▪” symbol represents the temperature of the sewer line at a depth of 1.0 inch; the “Δ” symbol represents the temperature of the sewer line at a depth of 0.5 inch into the sewer line from the inside surface; and the “x” symbol represents the temperature of the sewer line at a depth of 0.25 inch into the sewer line from the inside surface of the sewer line. The “X” axis indicates the time and the “Y” axis indicates temperature.
The seeded explosives were tested for the presence of explosives using a calorimetric reagent and an MO-2M explosive vapor detector. None of the soils or joints at the seeded locations tested positive for the presence of explosives. The convective heat treatment successfully decontaminated explosive material.

Example 3

Field Evaluation

Convective heat treatment according to various embodiments of the present teachings was tested on an existing 365-foot long terracotta sanitary sewer line having an eight-inch inner diameter. While running the field evaluation on the existing sewer line it became apparent that groundwater elevations in the area were above the sewer line, and ground water was infiltrating into the sewer line. The sewer line at this location was between four feet and eight feet below the surface of the ground. At the inlet gas flow temperature of 1,200° F., enough heat energy could not be applied to evaporate all of the infiltrating groundwater and heat the entire 365-foot length of sewer line.
Thereafter, convective heat treatment according to various embodiments of the present teachings, was tested on an existing 395-foot long terracotta sanitary sewer line having an eight-inch internal diameter. The sewer line at this location ranged from 10 feet to 16 feet below the surface of the ground. The sewer line also contained infiltrating groundwater.
In order to treat the entire length of the sewer line, a hole was excavated at approximately the center of the 395-foot long line. When the sewer line was encountered at the bottom of the excavated hole, the eight inch terracotta pipe was broken to form an inlet and access the pipe. This effectively split the sewer line into two lengths, length A and length B. Two burner units and two blower units were placed in the two lengths at the bottom of the excavated hole, and convective heat was blown in opposite directions (A and B) towards the manholes (outlets). Simultaneously therewith, the burner outlet temperature was slowly increased to approximately 2,300° F. instead of 1,200° F. At this rate of energy use, all of the infiltrating groundwater was evaporated, and enough additional energy was supplied to accomplish the goal of raising the exhaust temperature to above 572° F. The higher temperature assured that the interior surface temperature of the entire length of the sewer line, and any void spaces along the line, were above the break down temperature.
In addition to monitoring the temperatures at the inlet and outlet of each 200-foot length of line lengths A and B, temperatures were monitored at the outer skin of the one-inch thick terracotta sewer line at one location in each of lengths, each temperature monitor approximately 190 feet from the two burners. FIG. 3 illustrates a graph of the temperatures reached during the convective heat treatment.
In FIG. 3, the “♦” symbol indicates the temperature of the heated gas flow in length A; the “▪” symbol represents the temperature of the heated gas flow in length B; the
symbol represents the temperature of the heated gas flow out of length A; the “●” symbol represents the temperature of the skin of length B of the sewer line; the “Δ” symbol represents the temperature of the skin of length A of the sewer line; and the
symbol represents the temperature of the heated gas flow out of length B. The “X” axis indicates time and the “Y” axis indicates temperature.
To summarize, after evaporating infiltrating ground water, a 395-foot sewer line having an eight-inch internal diameter, was successfully decontaminated. Inlet temperatures were in excess of 2,300° F. with final exhaust temperatures of approximately 820° F. Temperatures in excess of 572° F. were maintained over the entire 395 feet of sewer line for a soak period of more than two hours.
Other embodiments of the present teachings will be apparent to those skilled in the art from consideration of the present specification and practice of the present teachings disclosed herein. It is intended that the present specification and examples be considered as exemplary only.

Claims

1. A system comprising:

a conduit or vessel comprising an internal surface including a residual explosive material deposited in or on the internal surface; and

a heated gas flow source in fluid communication with the internal surface, wherein the residual explosive material has a break down temperature and the heated gas flow source is adapted to produce a flow of heated gas into the sewer line sufficient to heat the internal surface to a temperature at or in excess of the break down temperature.

2. The system of claim 1, wherein the conduit or vessel comprises a sanitary waste line.

3. The system of claim 1, wherein the conduit or vessel comprises an industrial pipeline.

4. The system of claim 1, wherein the conduit or vessel comprises a storm water drain line.

5. The system of claim 1, wherein the internal surface has an internal diameter of from about one inch to about 100 inches.

6. The system of claim 5, wherein the inner diameter is from about six inches to about 36 inches.

7. The system of claim 1, wherein the residual explosive material deposited on the internal surface comprises one or more of nitroguanidine, dinitrotoluene, trinitrotoluene, hexogene, octogene, tetryl, nitrocellulose, nitro-glycerine, ammonium nitrate, lead azide, lead styphnate, and a combination thereof.

8. The system of claim 1, wherein the heated gas flow source comprises a heater to heat a gas and a blower to introduce the heated gas into the conduit or vessel.

9. The system of claim 1, wherein the heated gas flow source comprises a gas burner and a source of an alkane.

10. The system of claim 9, wherein the source of an alkane comprises one or more of ethane, propane, butane, pentane, hexane, heptane, octane, and a combination thereof.

11. The system of claim 1, wherein the conduit or vessel comprises an inlet and an outlet, the heated gas flow source is in fluid communication with the inlet, and the heated gas flow source is capable of increasing the temperature of all points along the internal surface from the inlet to the outlet, to a temperature at or in excess of the break down temperature.

12. The system of claim 1, wherein the heated gas flow source is capable of producing from about 500,000 British Thermal Units (BTU) to about 10,000,000 BTUs of energy.

13. The system of claim 1, wherein the heated gas flow source is capable of producing a heated gas at a flow rate of from about 200 cubic feet per minute (CFM) to about 5,000 CFM.

14. The system of claim 1, wherein the heated gas flow source is capable of producing a gas flow having a temperature of from about 150° F. to about 3,000° F.

15. The method of claim 14, wherein the heated gas flow source is capable of producing a gas flow having a temperature of from about 1,000° F. to about 3,000° F.

16. A method comprising:

connecting a heated gas flow source to a conduit or vessel, the conduit or vessel including an internal surface and comprising residual explosive material deposited in or on the internal surface, the residual explosive material having a break down temperature at which the residual explosive material chemically breaks down;

introducing a heated gas flow into the conduit or vessel; and

maintaining a heated gas flow into the conduit or vessel at least until the temperature of the internal surface reaches a temperature at or in excess of the break down temperature.

17. The method of claim 16, wherein the heated gas flow is introduced at a temperature of from about 150° F. to about 3,000° F.

18. The method of claim 16, wherein the heated gas flow is introduced at a temperature of from about 1,000° F. to about 3,000° F.

19. The method of claim 16, wherein the conduit or vessel comprises at least one inlet and at least one outlet, the heated gas flow is introduced at the at least one inlet, and the heated gas flow has a temperature at the outlet of at least about 200° F.

20. The method of claim 16, further comprising producing the heated gas flow by burning a fuel in the presence of oxygen gas.

21. The method of claim 16, wherein the heated gas flow comprises heated air and combustion products.

22. The method of claim 16, wherein the conduit or vessel comprises a sewer line.

23. The method of claim 16, wherein the conduit or vessel comprises an aboveground or underground storage tank.

24. A method, comprising:

providing a heated gas flow at an initial temperature to a conduit or vessel that comprises an inlet, an outlet, and an internal surface, the internal surface comprising residual explosive material having a break down temperature, deposited at least therein or thereon, the internal surface being in fluid communication with the heated gas flow; and

maintaining the heated gas flow at or above the initial temperature at least until the temperature of the heated gas flow at the outlet is at or above the break down temperature of the residual explosive material.

25. The method of claim 24, further comprising periodically monitoring the temperature of the heated gas flow at the inlet, at the outlet, or at both the inlet and the outlet.

26. The method of claim 24, further comprising increasing the initial temperature to a target temperature that is at or above the break down temperature of the residual explosive material.