BE1021572B1 - METHOD AND SYSTEM FOR CLEANING A SOIL CONTAINING CONTAMINANTS - Google Patents

Abstract

The present invention relates to a method and system for cleaning soil containing contaminants.

Description

METHOD AND SYSTEM FOR CLEANING A SOIL CONTAINING

CONTAMINANTS

FIELD OF THE INVENTION

The present invention relates to the field of soil remediation. The present invention relates to methods and systems for cleaning contaminant-containing soils, and more particularly to a method and system for volatilizing contaminants in soil by thermal conduction and for efficiently removing such contaminants.

BACKGROUND OF THE INVENTION

Soil contamination has become a subject of great concern in many places. The soil may be contaminated with chemicals, biologicals and / or radioactive contaminants. Spills of material, leaking storage tanks, and seepage from improperly buried materials are just a few examples of the many ways in which soil can be contaminated. If left in place, many of these contaminants end up in aquifers, the air, or the food supply, and could become public health risks.

There are many proposed methods for the removal of soil contaminants, such as excavation followed by incineration, in situ vitrification, biological treatment, chemical additives for deactivation, radiofrequency heating, etc. Despite the success in some applications, these methods can be very expensive and are not practical if several tons of soil have to be treated.

A process that can be used to remove contaminants from the soil is a process of extracting soil vapors. In such a process, a vacuum is applied to the soil so as to draw air and vapors through the soil. The vacuum can be applied to the soil / air interface or the vacuum can be applied by vacuum wells placed in the soil. Air and steam can entrain and transport volatile contaminants to the vacuum source. Gaseous effluents extracted from the soil by vacuum that include contaminants in the soil are then directed to a treatment facility in which they are treated to remove or reduce contaminants to acceptable levels.

In situ thermal desorption can be used to increase the efficiency of a soil vapor extraction process. In situ thermal desorption involves in situ heating of the soil to increase soil temperature while simultaneously removing soil release gases. The heat added to the contaminated soil can raise the soil temperature above the vaporization temperature of the contaminants and cause the vaporization of contaminants. A void applied to the ground allows to extract the vaporized contaminant from the ground.

A method of heating a soil containing contaminants includes injecting a heated fluid into the soil. A major disadvantage of the type of method described above is that the injection of hot air into the soil tends to create vapor flow paths in the soil. In addition, the percolation of hot air through the soil can be hindered by the nature of the soil, such as clay. As a result, hot air is not distributed homogeneously in the contaminated soil, but it accumulates rather at its level of injection into the ground, ie inside and around the perforations of the soil. pipes.

Another means of heating a soil is to heat a soil by thermal conduction. Thermal conduction heating, in combination with the removal of pollutant gases from the soil by means of a steam extraction system, is one of the tried and tested techniques. Thermal blankets and / or floor heaters that are placed above the contaminated soil were applied for conductive heating of the soil. Alternatively, systems have been described in which heat-conduction heating of the soil may include resistive heating (electrically) of well casing, which condenses the surrounding soil by conduction. A vacuum source in coincidence with the heat source or separated may be applied.

A common disadvantage of the methods mentioned above is that they may be relatively inefficient from an energy point of view. In addition, the heat produced by the combustion of contaminants is usually lost. In these methods, contaminated soil is heated, vaporized soil contaminants are extracted from the soil and decomposed or destroyed on site, for example in a heat treatment system. However, both soil heating and heat treatment of soil-derived contaminants are two processes that require the input of a significant amount of energy. The methods mentioned above therefore require a large input of energy and therefore induce significant operating costs.

EP 1 604 749 B1 discloses a system in which heat from the vaporized contaminants is reused. However, this system requires a fan to induce low pressure (vacuum) zones, so that the heated fluid can pass through the fan. This fan will suffer mechanically from the heat. Usually, these fans are limited in operating temperature. Often, they are not practical to use because of their weight and size.

The present invention aims to provide a solution to the aforementioned problems by providing a method and system for cleaning a soil containing contaminants that is more energy efficient, and at the same time offers less pressure on mechanical parts. In addition, the present invention aims to provide a method and system that is easier to install, less expensive to use, and / or more efficient to maintain. In addition, the present invention aims to provide a method and system that can be applied to a wide range of configurations.

SUMMARY OF THE INVENTION

The present invention relates to a method and system for cleaning a soil containing contaminants. The methods and systems described herein are intended to clean the soil of volatile and semi-volatile contaminants. The methods and systems of the present invention can be applied for cleaning contaminated soils in situ and ex situ.

The inventors have found that the methods and systems of the present invention are easier to install, less expensive to use, and / or more efficient to maintain. Furthermore, the inventors have found that the methods and systems of the present invention can be applied to a wide range of configurations. The inventors have also found that the methods and systems of the present invention are flexible, for example, heat can be supplied to a selected area without large changes in configuration. Therefore, the methods and systems of the present invention provide improved modularity and improved flexibility.

In a first aspect, the present invention relates to a method of cleaning a soil containing contaminants, wherein the method comprises the following steps: - introducing at least one heat pipe into said soil; the introduction of at least one perforated pipe; heating said ground by thermal conduction by circulating a heated fluid through said thermally conductive heat pipe so as to obtain a contaminant vapor, so that said contaminant vapor is directed to the perforated pipe due to the pressure negative present; transporting contaminant vapor from the ground to said perforated pipe, and incinerating said contaminant vapor to at least partially remove said contaminants from the soil; characterized in that the negative pressure in the perforated tube is created by a venturi.

In a preferred embodiment, the method further comprises the step of: - partially purging the contaminant vapor.

The vapor contaminant can be purged before or after incineration.

Preferably, the method comprises the step of: - Partially purging steam from incinerated contaminants.

In a preferred embodiment, the venturi has a diameter of 1.0 to 10.0 mm, preferably 2.0 to 7.5 mm, preferably 3.0 to 5.0 mm, preferably about 4.0 mm.

In a preferred embodiment, the compressed air has a pressure of 0.5 to 10.0 bar, preferably 2.0 to 8.0 bar, preferably 4.0 to 7.0 bar.

In a preferred embodiment, the compressed air has a relative humidity (as measured under standard conditions) of at most 20.0%, preferably at most 10.0%, preferably at most 5.0%, preferably at most 2.0%, preferably at most 1.0%, preferably at most 0.5%, preferably at most 0.2%, preferably not more than 0.1%.

In a preferred embodiment, the heat pipe and the perforated pipe are the same.

In a preferred embodiment, the heat pipe comprises an outer tube and an inner tube, wherein the inner tube receives the heated fluid, which is returned through the outer tube. Preferably, when the heat pipe and the perforated pipe are the same, a negative pressure is created by the flow of the heated fluid into said heat conducting pipe, which can extract the contaminating vapor from the soil.

In a preferred embodiment, the method comprises the step of reusing thermal energy obtained by incinerating said vapor to heat said contaminated soil to vaporize remaining contaminants in said soil.

In a preferred embodiment, the method comprises incinerating said contaminant vapor by: - incinerating soil contaminants in said contaminant vapor so as to obtain incineration gases and thermal energy; the recovery of this thermal energy, and the reuse of said recovered thermal energy to heat said fluid.

According to a second aspect, the invention relates to a system for cleaning a soil containing contaminants, wherein the system comprises: - means for heating said soil to produce a contaminant vapor, comprising at least one thermally conductive pipe comprising preferably an inner tube (8), through which the heating fluid is introduced into the ground, and an outer tube (6), through which the heated fluid is recovered; means for removing contaminants from said soil vapor, comprising at least one perforated pipe; means for forcing said contaminant vapor into said perforated pipe, and means for incinerating said contaminant vapor to at least partially remove said soil contaminants present in said contaminant vapor; wherein said means for forcing said contaminant vapor into said perforated pipe comprises a venturi.

In a preferred embodiment, the system further comprises: - means for purging the vapor phase contaminants (eg by one or more purges), wherein the vapor contaminant can be incinerated prior to the steam purge or wherein the contaminant may not be incinerated prior to purging.

In a preferred embodiment, the venturi has a diameter of 1.0 to 10.0 mm, preferably 2.0 to 7.5 mm, preferably 3.0 to 5.0 mm, preferably about 4.0 mm.

In a preferred embodiment, the venturi is supplied with compressed air, wherein the compressed air has a pressure of 0.5 to 10.0 bar, preferably 2.0 to 8.0 bar, of preferably from 4.0 to 7.0 bar.

In a preferred embodiment, the compressed air has a relative humidity (as measured under standard conditions) of at most 20.0%, preferably at most 10.0%, preferably at most 5.0%, preferably at most 2.0%, preferably at most 1.0%, preferably at most 0.5%, preferably at most 0.2%, preferably not more than 0.1%.

In a preferred embodiment, the heat conducting pipe and the pipe with at least one perforation are the same, preferably the outer pipe of the heat conducting pipe is perforated.

In a preferred embodiment, the system further comprises means for reusing thermal energy obtained by incinerating said vapor to heat said contaminant to the soil to vaporize remaining contaminants in said soil.

These and other objects, features, and advantages of the invention will become more apparent from the following detailed description of the preferred embodiments that proceed in accordance with the accompanying drawings.

DETAILED DESCRIPTION OF THE FIGURES

Fig. 1 is an illustration of an embodiment of a floor cleaning system according to the present invention, comprising a venturi (1), powered by compressed air (2), a fan (3) for a burner (7). ), a purge (4), a thermally conductive pipe (5) and a perforated pipe (6), wherein the thermally conductive pipe (5) and the perforated pipe (6) are the same, and wherein the thermally conductive pipe comprises a pipe interior (8) connected to the burner (7).

Fig. 2 is an illustration of an embodiment of a floor cleaning system according to the present invention, comprising a venturi (1), powered by compressed air (2), a fan (3) for a burner ( 7), two purges (4), a heat-conducting pipe (5) and a perforated pipe (6), wherein the heat-conducting pipe (5) and the perforated pipe (6) are the same, and wherein the heat-conducting pipe comprises a inner pipe (8) connected to the burner (7).

Fig. 3 is a photograph of an embodiment of a soil decontamination system according to the present invention.

Fig. 4 shows four stages of soil water treatment, using the soil decontamination system and method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Although the invention is susceptible to various modifications and variations, specific embodiments thereof are presented by way of example in the drawings and will be described in detail. The drawings are not necessarily to scale. It is to be understood that the drawings and the detailed description are not intended to limit the invention to the particular form described, but on the contrary, the intention is to cover all the modifications, equivalents and variants falling within the spirit and scope of the invention. scope of the present invention as defined by the appended claims.

The terms "contaminated soil" and "contaminant-containing soils" are used here synonymously and should be understood to include all types of soils that may be contaminated with chemical or biological pollutants, including, but not limited to, frozen soils, very wet soils, groundwater, soils with high clay content, saturated and unsaturated soil areas, soil residues containing coal, sediments, sludge, contaminated wastes, cakes filtration or others, etc.

Conduction heat occurs when two material media or objects are in direct contact, and the temperature of one is greater than the temperature of the other. Heat conduction (thermoconduction) consists of a kinetic energy transfer from a warmer medium to a colder medium. The term "(thermo) conduction" as used herein therefore refers to all types of heat transfer in which heat is moved from one (warmer) object to another (colder) object through direct contact. It is understood that in the present invention, where conductive heat transfer is described, there is also a very small amount of heat which is generally transferred to the ground by radiation. It must therefore be clear that the term "(thermo) conduction" as used herein refers to a situation in which the soil is heated by conduction, without introducing or injecting a heated fluid into the soil itself.

The present invention relates to a method and system for cleaning a soil containing contaminants in which a negative pressure zone (vacuum) is created by a venturi. In one embodiment, the invention relates to a substantially closed loop system that utilizes vacuum to extract contaminating gases from the heated soil so that the vacuum is created by a venturi. The present method is characterized in that the soil is heated by thermal conduction, that is to say without direct injection of a heated fluid into the soil. In one embodiment, the present method is also characterized in that the energy, which is obtained by heat treatment of soil contaminants is at least partially recovered and reused.

In one embodiment, the method according to the invention is also used to treat nonaqueous phase light liquids (LNAPL) or nonaqueous phase dense liquids (DNAPL). The viscosity of LNAPL products can be significantly reduced by increasing the temperature. In the particular case of groundwater polluted by phase layers, reducing the viscosity of the contaminated fluid improves its mobility and considerably speeds up the extraction process. Extraction processes at higher temperatures are therefore much faster than conventional methods. The method according to the invention provides a method for extracting LNAPL at high temperature under negative pressure, which leads to an improved extraction of LNAPL.

At least one perforated pipe may be partially perforated or, in some embodiments, even non-perforated, eg when used to extract DNAPL or LNAPL materials.

In one embodiment, the present invention relates to a method comprising heating said self by thermal conduction at a temperature sufficient to cause vaporization of said soil contaminant. Preferably, the soil is heated by thermal conduction by circulation of a heated fluid through the thermo-conductive pipe (s) which has (have) been introduced into said soil. In addition to allowing for greater removal of soil contaminants, increased soil heat may result in the destruction of contaminants in situ, for example, contaminants such as hydrocarbons and / or chlorinated hydrocarbon contaminants.

In another embodiment, the present invention relates to a method of reusing thermal energy obtained by incinerating said contaminating vapor, to heat the soil and to vaporize remaining contaminants in said soil.

In yet another embodiment, the present invention relates to a method which comprises extracting said contaminant vapor from said soil by creating a pressure difference in said soil (negative pressure or vacuum). The method preferably requires forcing said pollutant vapor into a perforated pipe by creating a negative pressure in said perforated pipe. A pressure difference is preferably achieved by imposing negative ground pressure to remove contaminants from the contaminated soil.

According to the invention, such a pressure difference is obtained by a venturi. Preferably, this venturi is placed in a pipe section connected to the pipe comprising at least one perforation. More particularly, one or more perforated pipes that will be subjected to a negative pressure in the working conditions are introduced into the ground. The present method includes the step of forcing said contaminant vapor into one or more perforated pipes, creating a negative pressure in said perforated pipes. Advantageously, in view of the present descriptions, the present process does not require the direct injection of a heated fluid into the soil. The remaining fluids heated in the tubes and contaminating gases formed in the soil are drawn into the tubes by the pressure difference between the soil and the pipes, with a lower pressure in the tubes than in the soil. In addition, the venturi suffers less mechanical fatigue and wear by the heated fluid than a traditional fan. As used herein, the term "negative pressure" or "vacuum" refers to a pressure below atmospheric pressure. Preferably, the pipes are under negative pressure, and the pressure in the pipes is lower than the pressure in the ground. The combined efficiency of heat and steam flow gives nearly 100% scanning efficiency, leaving no untreated area, and gives a destruction / suppression efficiency of almost 100%. This occurs because the colder locations in the treatment zone can be heated, where appropriate, to the boiling points of the compounds, and maintained at these temperatures for several days.

In addition, the increase in soil heat and the pressure difference imposed also allows the at least partial incineration of soil contaminants in situ. In particular, contaminants are not only vaporized in the soil, but they are also partly inflamed and automatically destroyed already in the soil, greatly improving their removal from the soil.

The present invention provides a method for cleaning contaminated soil that is very energy efficient and mechanically efficient. In particular, the method may include energy recovery, which is achieved by incineration of soil contaminants and reuse of that energy in the system. The present invention therefore requires less energy input compared to traditional methods, and is therefore more energy efficient, and reduces operating and / or maintenance costs. In one embodiment, the invention relates to a method of incinerating said contaminating vapor comprising: - incinerating soil contaminants in said contaminant vapor so as to obtain incineration gases and thermal energy, recovering said thermal energy, and reusing said recovered thermal energy to heat said fluid.

The present process is preferably characterized in that the heated fluid and the contaminant vapor are mixed and treated together so as to at least partially remove said contaminants from the soil, and to provide thermal energy. The thermal energy obtained is recovered and reused to heat the contaminants that may have remained in the. In one embodiment, the recovered thermal energy is at least partially reused to heat the fluid that is sent through the thermally conductive pipe (s) to conductively heat the soil. Preferably, the present method comprises recirculating at least a portion of the heated fluid and at least a portion of said incineration gas into the thermally conductive pipe (s) for heating the soil to be treated. In particular, the incineration gases from the incineration of the contaminant vapor are preferably at least partly (as much as possible) recirculated in the thermally conductive pipe (s).

In still another embodiment, the present invention relates to a method of circulating said heated fluid through the soil by introducing one or more thermally conductive pipes (possibly perforated) into said soil and circulating the heated fluid in said pipes. . In another embodiment, the present method further comprises extracting said contaminant vapor from the ground by forcing said contaminant vapor through the perforations in the perforated pipes, and further conveying said contaminant vapor into said pipes in the ground. The thermally conductive hoses can be threaded or unthreaded. In one embodiment, the present method comprises introducing one or more heat conducting and / or perforated pipes into said soil by screwing said heat conducting pipes into said soil.

The temperature reached by the soil is an important parameter for the evaluation of the cleaning potential of this method, as it is a determining factor for the decomposition of pollutants. For this, the present invention provides in another embodiment, a method which consists of monitoring the temperature in the ground and at different locations of the almost closed loop system.

In yet another embodiment, the present invention relates to a method of covering said soil containing soil contaminants with an insulation sheet and / or placing an insulation sheet under said soil containing soil contaminants. A protective sheet on the floor surface minimizes heat loss. An insulating sheet covering the soil surface reduces heat loss from the soil surface.

In another aspect, the invention relates to a system, preferably an almost closed loop system, for cleaning a soil containing contaminants comprising: - means for heating said soil, preferably comprising at least one thermally conductive pipe, possibly perforated, means for extracting a contaminant vapor, preferably comprising at least one perforated pipe, which may, or may not be the same as the thermally conductive pipe, means for forcing the vapor of a contaminant into said perforated pipe, wherein the means for forcing the vapor of a contaminant into said perforated pipe comprises at least one venturi, and - means for incinerating said contaminant vapor in view of at least partially removing said soil contaminants present in said vapor phase.

Preferably, said thermally conductive pipe comprises an inner open pipe, and a closed outer pipe at the end of the pipe (preferably where the closed external pipe is closed at the bottom and opened upwards). The heated fluid can then be forced through the inner tube and collected by the space between the inner and outer tubes. If the outer tube is perforated, this allows the collection of the heated contaminant vapor from the soil, due to the negative pressure created by the heated fluid flowing in the space between the two tubes. Alternatively, a separate perforated conduit may be used to collect the contaminant vapor, when said separate tube is placed in close proximity (e.g., about 10 to 50 cm) of the heat pipe and when a negative pressure is created, e.g. the connection with the system almost closed loop or by the use of a fan or a venturi.

In one embodiment, the system of the invention further comprises means for reusing the thermal energy obtained by the incineration of said vapor, for heating said contaminant to the soil in order to vaporize the remaining contaminants in said soil.

In another embodiment, the invention relates to a system wherein the means for heating the soil comprises at least one perforated pipe in communication with an oxidation chamber.

In another embodiment, the invention relates to a system, wherein said means for forcing said contaminant vapor of said soil into said heat conducting tube (s) comprise a vacuum system which is connection with said heat conducting tube (s). Preferably, this suction system comprises at least one venturi.

In another embodiment, the invention relates to a system, wherein said means for incinerating said contaminant vapor comprises an oxidation chamber which is in communication with said heat conducting pipe (s). ) and / or with the said perforated tube (s).

In yet another embodiment, the invention relates to a system, wherein said means for reusing the thermal energy obtained by the incineration of said contaminant vapor comprises a piping system connecting the said (s) thermally conductive pipe (s) and / or said perforated pipe (s) with said oxidation chamber.

According to one embodiment, the invention relates to a system further comprising means for pressure measurement, temperature measurement and / or flow control.

According to another embodiment, the invention relates to a system which further comprises one or more insulation blankets for covering and / or being positioned below said floor containing said contaminants.

The present invention relates to a system, preferably an almost closed loop system, one or more heat pipes and one or more perforated pipes driven into the ground, wherein one or more of the pipes can be both heat conducting and perforated. For the sake of clarity, the following description will be described by a system comprising at least two pipes. However, it should be clear that the current system may also include the use of a single pipe. The heat pipes are in communication with a heat source that circulates a heated fluid through the pipes. The method includes placing the pipes in the contaminated soil, circulating a heated fluid through the heat conductive tubes, raising the temperature of the soil surrounding the pipes to a temperature sufficient to cause vaporization of the soil contaminants; Extrude the vapor of contaminants from the ground in the perforated pipes, and treat the vapor of contaminants to remove contaminants from the soil. Contaminants are attracted to the perforated pipes, by imposing a negative pressure in the pipes, for example by connecting the pipes of a vacuum system, in which the negative pressure is created by a venturi.

The present method is preferably characterized in that vaporized soil contaminants and heated fluid are mixed in the piping system and collected on the soil during processing. Mixing the heated fluid improves the removal of vaporized contaminants from the soil: contaminants are entrained in the heated fluid stream and transported from the ground. The present process is also characterized in that preferably the energy, which is obtained by heat treatment of the vaporized contaminants is at least partially recovered and reused. In one embodiment, the present method comprises a closed-loop system, wherein the energy that is obtained by the incineration of soil contaminants is at least partially reused for heating the fluid that is sent through the system. piping for conductive floor heating. The gases from the incineration of the contaminant vapor can also be at least partly recycled and reintroduced into the system for heating the contaminated soil. Part of the incineration gases may be present in the substantially closed loop system.

The tubes can be arranged in a configuration in the contaminated soil so as to achieve more uniform heating in the floor assembly. Each regular configuration of tubes may be used, such as triangular, square, rectangular, hexagonal, etc., chosen to substantially cover the contaminated area. Triangular configurations are preferred because they provide the best thermal efficiency and, in practice, are easy to locate on the soil surface or in a pile of lands to be treated. The temperature in the soil rises through the circulation of a heated fluid through the tubes. A thermal front moves outside the tubes in the soil by thermal conduction, allowing the vaporization of water and contaminants in the soil. Superimposing heat flow from all pipes results in a more uniform temperature increase within the pattern.

It is clear that the number of pipes applied in the ground, the distance, the relative position of the pipes, the distance between the base and the pipes, and the distance between the pipes and the lateral sides of a pile of soil can be modified. depending on the degree of contamination and / or the desired duration to complete the process and / or soil type and / or economic considerations. In a preferred embodiment, the distance between the base of the pile of soil and the tubes is between 0.25 and 1 m, and preferably between 0.35 and 0.6 m. In another preferred embodiment, the distance between two thermally conductive pipes in a layer is between 0.5 and 2 m, and preferably between 0.7 and 1.2 m. In yet another preferred embodiment, the distance between the heat pipes in two superposed layers is between 0.5 and 2 m, and preferably between 0.7 and 1.2 m. In a preferred embodiment, said at least one heat-conducting pipe and said at least one perforated pipe are the same pipes. In one embodiment, said at least one heat pipe and said at least one perforated pipe are two separate tubes. In one embodiment, said at least one heat-conducting pipe and said at least one perforated pipe are two separate tubes, wherein the distance between the two tubes is at most 100 cm, preferably at most 75 cm, preferably at least plus 50 cm, preferably at most 25 cm, preferably at most 20 cm, preferably at most 15 cm, preferably at most 10 cm. The distance between the two tubes is considered as the distance between the central axes of the two tubes.

In a preferred embodiment, the heat pipe comprises an inner pipe. Preferably, the inner tube is connected to a burner and configured to introduce a heated fluid into the heat conducting tube. Preferably, there is a gap between the inner and outer pipe of the heat pipe, along which the heated fluid can pass. Such a configuration has the advantage of allowing the heated fluid to flow along the thermoconductive pipe. In one embodiment, the inner and outer tubes of the heat pipe are coaxial. In one embodiment, the cross-sectional area of the inner tube is from 0.30 to 0.70 times the cross sectional area of the heat-conducting pipe, preferably from 0.40 to 0.60 times, preferably about 0 to , 50 times.

The hoses are preferably made of a heat resistant material such as, but not limited to, steel, metal or ceramic. The pipes may be of any desired cross-sectional shape, including, but not limited to, triangular, rectangular, square, hexagonal, ellipsoidal, round, or oval. Preferably, the pipes have a substantially ellipsoidal, round, or oval section. In a particularly preferred embodiment, the heat conducting tubes are substantially round in cross-sectional shape and have a diameter which is between 50 and 200 mm and preferably between 80 and 180 mm. In one embodiment in which the heat pipes and the perforated pipes are separated, the perforated pipes preferably have a substantially round cross-sectional shape and have a diameter which is between 5 and 80 mm, preferably between 10 and 50 mm. .

The tubes preferably have a length of between 2.0 and 20.0 m, and preferably between 4.0 and 16.0 m. In an embodiment in which the heat pipes and the perforated pipes are separated, the perforated pipes preferably have a length of between 2.0 m and 20.0 m, preferably between 4.0 m and 16.0 m.

In another embodiment, pipes of different diameters may be introduced into contaminated soil. For example, a first layer of tubes may have a diameter that is greater (or smaller) than the diameter of the tubes of a second layer. Ideally, larger diameter tubes are at the base of a pile of soil to generate greater thermal conductivity at the base of the soil pile.

In another embodiment, one or more pipes may also be introduced vertically into the contaminated soil. However, according to other embodiments, the pipe can be placed in any orientation between 0 ° (horizontal) and 90 ° (vertical) by contribution to the surface of the ground. For example, in one embodiment of the soil remediation system, a pipe may be oriented at about 45 ° to sanitize soils adjacent to a geological layer that descends to about 45 °. Orientation can be chosen to result in a relatively low cost of rapid and effective soil remediation. The tube can also be placed in the soil so that part of the pipe is below the contaminated soil, and part of the pipe is above the contaminated soil. Heating a portion of the uncontaminated soil below the contaminated soil can prevent the temperature at the interface from falling. The cross-sectional area of the tube adjacent to the contamination may be small, or may be made of a different material, so that more heat is diffused into the soil in the vicinity of the interfaces. Spreading more heat adjacent to the interface can promote a more uniform temperature distribution across the contaminated soil. The pipe can be driven into contaminated soil at depths that extend slightly below the contaminated area. Alternatively, the pipe may be driven into the ground by conventional threshing techniques, such as hammers or ultrasonic devices. The tubes are not necessarily cemented into the ground and therefore can be removed and reused as soon as the cleaning process is complete. Depending on the geometry of the contaminated area, the perforated pipe should not be placed vertically, but can be tilted, or horizontal, or the perforated pipe could consist of a combination of vertical and horizontal sections. Alternatively, the perforated pipe may be drilled in straight sections at an inclined angle. In the alternative, when the soil is already dug, the pipes can be simply laid on a layer of soil, then covered with another layer of soil and this type of procedure is repeated until all the cuttings have been removed. placed in the stack.

It will be apparent to one skilled in the art that the number of pipes may vary depending on the size and amount and condition of the soil to be cleaned of contaminants.

Perforations in the perforated pipes may be, but are not limited to, holes and / or slots. Preferably, between 0.5% and 5.0% of the surface of a tube is provided with holes and / or slots, preferably between 1.0 and 2.5%. It is particularly preferred that a large amount of small perforations be provided on the pipe. The pipes may have several perforated zones at different positions along a length of the pipe. When the pipes are inserted into the ground, the perforated areas may be located next to contaminated soil layers. Alternatively, the perforations may be provided along the entire length of the perforated pipes.

The heat conducting tubes are heated by sending and circulating a fluid such as heated air at high temperature and / or gas through the piping. Preferably, the high temperature of the air / gas is heated to a temperature between 300 and 800 ° C, and more preferably between 500 and 750 ° C. Very high temperatures can also be used mainly depending on the limits of temperature of perforated pipes and / or inner pipes. Thus, in the case where the heat conducting pipes that are used can withstand extremely high temperatures, ie from 1000 to 1500 ° C, an extremely high temperature corresponding air / gas can be used. The heat is transferred to the earth by thermal conduction and gradually raises the temperature of the soil. A small amount of heat is also transferred to the ground by radiation. The high temperature of the soil allows contaminants in the contaminated soil to volatilize thereby producing a contaminant vapor.

According to the present invention, the soil is mainly heated by conductive heating, which is particularly advantageous because the temperatures that can be achieved by such heating are not limited by the amount of water present in the soil. The soil temperature significantly above the boiling point of water can be obtained by using heat conduction heating. Soil temperatures of at least about 100 ° C., 125 ° C., 150 ° C., 200 ° C., 400 ° C., 500 ° C., or more can be obtained using conductive heating.

A vacuum system is connected to the pipes to put the pipes under negative pressure. The suction system must be able to exert a vacuum appropriate to the particular configuration of the soil permeability, and perforated pipes in the treatment system. The suction system may be capable of creating a vacuum of between 50 Pa and 5000 Pa. The vacuum system includes a venturi. Even if the heat pipes and the perforated pipes are the same, as a result of the pressure difference imposed on the ground, the heated fluid which is sent through the tubes is not injected into the ground through the perforations of the pipes, but will remain in the piping system. Therefore, there will be no mixing of the heated fluid and the vapor of contaminants in the soil. Unlike direct injection of fluid into the soil, conductive heating will be very uniform in its vertical and horizontal sweep and will result in a homogeneous dispersion of heat in the soil. This is because the thermal energy injected into the ground by pipes is uniform on each pipe. In addition, conductive heating creates permeability as a result of drying and cracking of the overheated soil (ie> 100 ° C) that develops around each pipe. Very close steam flow paths are created even in fine silt and clay layers.

By putting the perforated pipes under negative pressure, the vaporized contaminants are sucked from the ground to the piping system. Contaminated vapors do not move from the soil to the soil surface, but rather through the perforated pipes and are directed by these pipes into a flue gas treatment unit. However, some vapors may move to the soil surface in a vapor retention chamber that forms between the soil and a coating applied to the top of the soil surface.

Vacuum is maintained throughout the heating period and for a sufficient time after heat conduction to avoid loss of contaminants or dispersion. Vacuum decreases the vapor pressure of the water in the soil and causes boiling at a temperature below the normal boiling temperature at atmospheric pressure.

In the perforated pipes, the vaporized contaminants may be mixed with the heated fluid circulating in the pipes. Advantageously, the mixture of the heated fluid with vaporized contaminants not only promotes the transport of contaminants from the ground to an effluent treatment unit, such as an oxidation chamber, as described below.

Advantageously, an elevated soil temperature, imposed vacuum and mixing with at least partially heated fluid initiates incineration of soil contaminants in situ. Contaminants from the soil in the contaminant vapor can at least partly ignite and be automatically destroyed already in the soil.

In a preferred embodiment, the soil surface is covered by an insulating sheet. Creating a vacuum below the sheet can cause the sheet to be sucked to the soil surface, but in any case reduce the amount of air that is drawn to the piping system from the atmosphere. Thus, almost exclusively air, soil moisture and contaminants in the soil will be evacuated by perforated pipes driven into the ground. By drawing moisture and contaminants to the pipes, the risk of contaminant spread is greatly reduced. The insulation sheet also reduces heat loss. A protective sheet / insulation is also provided under the pile of soil to be treated, to reduce heat loss in the underlying soil.

When the contaminated vapor is removed from the soil, the moisture level in the contaminated soil is substantially reduced, preferably to an average moisture content of less than about 5% by weight, preferably to an average moisture content of less than about 2% by weight, and preferably at an average moisture content of less than about 1% by weight.

Soil contaminants are extracted from the soil and treated through a combination of spraying, thermal decomposition in situ and oxidation in a combustion chamber. The perforated pipes and the surrounding soil are extremely hot and most of the contaminants entrained in the perforated pipes decompose with a residence time of the order of one second. An oxidation chamber may be further used for the collection and / or destruction (incineration) of vaporized contaminants. The system of the present invention may further include means for controlling and controlling the amount of contaminated vapor flowing through the perforated pipes in the oxidizer. In the oxidation chamber, the contaminants are recomposed into CO 2 and water. Preferably, the temperature in the oxidation chamber is between 600 ° C and 1200 ° C and preferably 700 ° C to 900 ° C.

Another preferred embodiment of the present system comprises a fluid introduction piping system which transports heated fluid to the perforated pipe system in the soil. In addition, the invention also preferably includes supply pipes for connecting the perforated pipes introduced into the pile of land to be treated with the fluid introduction piping system. These feed pipes are preferably flexible hoses.

The system of the invention also includes a vapor collection piping system that transports the heated fluid along with the vaporized contaminants into the soil to a treatment facility. In addition, the invention also preferably includes supply pipes for connecting the perforated pipes introduced into the pile of land to be treated with the collection pipe system. These feed pipes are preferably flexible hoses. The collection piping is connected to the system of perforated pipes driven into the ground and can be coupled to a vacuum system. In one embodiment, the piping may be unheated and / or uninsulated. Steam containing vaporized contaminants produced in the soil may first rise vertically and then be redirected downward into a treatment facility (oxidation chamber, for example). The initial rise and downward movement allows the contaminating vapor to condense and pass through a liquid trap or process system separator without blocking the lines of the collection system. In alternative embodiments, the piping is thermally insulated and heated. Insulated and heated piping prevents condensation of contaminant vapor inside the piping.

Heated fluids and vapor contaminant streams are directed to a treatment facility to reduce airborne contaminants to acceptable levels. The treatment facility may include a mass transfer system such as activated carbon, a reactor system such as a thermal oxidation reactor, a catalyst system, or a combination thereof. Preferably, the treatment plant is a thermal oxidation device.

In a particularly preferred embodiment, the thermal energy that is obtained by incinerating soil contaminants in the oxidizer is at least partially recovered and reused, particularly for heating the fluid to be passed through the tubes. The present invention thus provides an effective method for deeply cleaning contaminated soils: in one embodiment of the present process it is a substantially closed system, wherein at least a portion of the heating energy of a fluid is provided by the incineration of soil contaminants. In another particularly preferred embodiment, the heated fluid and the treated vapor in the oxidation chamber are reused to circulate the heat in the heat pipes. For this, they are preferably collected at the outlet of the oxidation device, and forced to the inlet of the inner pipes. Thus, the injection of hot air / gas is conveyed through the loop and returns to the oxidation chamber for reheating and reinjection into the heat pipes. In particular, the present invention also includes a piping system for at least partially recirculating the treated contaminant vapor, and in particular the incineration gases obtained after incineration of the contaminant vapor, to the thermally conductive hoses. Part of the incineration gases can be reintroduced into the substantially closed loop system via an additional circuit or piping system. Part of the incineration gases obtained may be present in the system, for example via an exhaust pipe on a collector.

In yet another preferred embodiment, the present invention relates to a method which comprises improving the incineration of soil contaminants by providing a surplus of energy and / or a gas, a solid, or a combustible liquid. In order to obtain an optimal incineration process, additional equipment such as combustible waste of high heat capacity, such as cokes, coals etc. and / or a gas, a solid, or a combustible liquid, can be introduced into the oxidation chamber.

In a preferred embodiment, the present invention relates to a method of accelerating the incineration of soil contaminants by providing a catalyst material that improves thermal degradation of contaminants and accelerates high temperature decomposition into simpler molecules. The catalyst may be a metal, metal oxide, or other type of catalyst that enhances the pyrolysis or oxidation of contaminants. In one embodiment, the catalyst is alumina.

The present system is preferably designed to allow soil treatment of 10 to 10,000 m3 of volume. The entire system can be loaded on one or more trailers for transportation to the site.

Referring to Figure 1, a system for remediation of soil contaminants according to one embodiment of the invention is schematically described. In this particular embodiment, the heat pipe (5) and the perforated pipe (6) are identical (5,6), but the invention also covers systems in which these pipes (5,6) are separated. The system shown in Figure 1 further comprises a burner (7), powered by an optional burner fan (3), which provides heat along an inner tube (8) in the heat pipe (5). The depression in the perforated tube (6) is created by the venturi (1), which is fed with compressed gas (2). A purge (4) in the piping system is a means for removing incinerated contaminants and for regulating the pressure in the system.

Fig. 2 shows an alternative system with two purges: one for incinerated vapors and one for non-incinerated vapors. The burner fan (3) airflow, while the Venturi (I) is powered by compressed air (2).

Figure 3 shows a photograph of a system according to one embodiment of the invention.

Fig. 4 shows several steps of groundwater treatment according to one embodiment of the invention. In a first step (a), a pipe system according to the invention is introduced into the soil, usually penetrating through an unsaturated soil section (II), a saturated soil section (12), and a floating layer (13) with for example contaminants in the unsaturated section (11). Preferably, the tube system comprises a perforated pipe or pipe section (6) in the unsaturated soil portion (11), while the pipe system comprises a non-perforated pipe or pipe section, in the part of the saturated soil (12). Preferably, the piping system comprises a thermally conductive tube (5) in unsaturated (11) and saturated soil sections (12). In a second step (b), the heat provided by the heat pipe (5) causes the evaporation of the groundwater and contaminants, which can be removed by the pipe or the perforated pipe section (6). The destruction zone will generally form a heat sink (14), which is free of liquids. In a third step (c), the soil and groundwater are further heated, resulting in further removal of groundwater and contaminants, increasing the heat sink (14) and decreasing the floating layer (13) contaminants. In a final step (d), the floating layer (13) of contaminants has been completely removed from the soil.

For other systems that could be modified using the venturi system according to the invention, reference is made to EP 1 604 749 B1 and WO 2012/055818, which are incorporated in their entirety by reference.

The following embodiments are also possible according to the invention: The invention also comprises a method for cleaning a soil containing contaminants, comprising the steps of: introducing at least one heat-conducting pipe into said soil, said pipe preferably being under negative pressure in the operating state and comprising a perforated outer pipe provided with a non-perforated inner pipe of a smaller diameter, so that a gap is created between the inner pipe and the pipe externally, in said soil, heating said soil by thermal conduction, circulating a heated fluid through said heat pipe, thereby obtaining a contaminant vapor, and then forcing said contaminant vapor into the perforated pipe, by means of a negative pressure therein, said heated fluid flowing through the inner pipe and being forced to pass through the open end of said inner pipe towards the space between the inner pipe and the outer pipe, and said contaminant vapor being forced from the ground towards the perforated pipe, incineration of said contaminant vapor in order to at least partially extracting said contaminants from the soil, and optionally reusing the heat energy obtained by incinerating said contaminant vapor, to heat said soil to vaporize the remaining contaminants in said soil, characterized in that the negative pressure is created by a venturi.

According to a particular embodiment, the method comprises the incineration of said contaminant vapor, by: incineration of said soil contaminants in said contaminant vapor, to thereby obtain incineration gases and heat energy, recovery of said calorific energy, and reuse of said recovered heat energy, for heating said fluid.

According to a particular embodiment, the method comprises the recirculation of at least a portion of said heated fluid and at least a portion of said incineration gas in the soil to be treated.

According to a particular embodiment, the method comprises accelerating the incineration of said soil contaminants by the addition of a catalyst.

According to a particular embodiment, the method further comprises the step of controlling the temperature.

According to a particular embodiment, the method further comprises the step of covering said soil containing soil contaminants with an insulating sheet.

In a particular embodiment, the method further comprises the step of disposing the insulating sheet below said soil containing soil contaminants. The invention also includes a system for cleaning a soil containing soil contaminants, comprising means for heating said soil to a temperature sufficient to generate vaporization of said soil contaminants, thereby obtaining a contaminant vapor, said means comprising at least one heat-conducting pipe being under negative pressure in the operating state and comprising a perforated outer pipe provided with a non-perforated inner pipe of a smaller diameter, so that a space is created between the inner pipe and the outer pipe, a means for forcing said contaminant vapor out of the ground and into said thermally conductive pipe, comprising a vacuum system connected to said thermally conductive pipe, a means for incinerating said contaminant vapor, in order to at least partially extracting said contaminants from the soil, and optionally a means for reusing the Heat energy obtained by the incineration of said contaminant vapor, for heating said sol to vaporize the remaining contaminants in said soil, the vacuum system comprising a venturi.

According to a particular embodiment, said means for heating said floor comprises at least one thermoconductive pipe communicating with an oxidation device.

According to a particular embodiment, said means for the incineration of said contaminant vapor comprises an oxidation device communicating with said thermoconductive pipe.

According to a particular embodiment, said means for reusing the heat energy obtained by the incineration of said contaminant vapor comprises a pipe system (6, 7) connecting said thermoconductive pipe (3) to said oxidation device (8). ).

According to a particular embodiment, the system further comprises one or more insulating sheets intended to cover said floor and / or to be placed above said floor containing said contaminants.

Claims (17)

A method of cleaning a soil containing contaminants comprising the steps of: - introducing at least one heat pipe into said soil; the introduction of at least one perforated pipe; heating said ground by thermal conduction by circulating a heated fluid through said thermally conductive heat pipe so as to obtain a contaminant vapor, so that said contaminant vapor is forced into the perforated pipe by a negative pressure present at inside of it; transporting contaminant vapor from the ground to said perforated pipe, and incinerating said contaminant vapor to at least partially remove said contaminants from the soil; characterized in that the negative pressure in the perforated tube is created by a venturi. The method of claim 1, further comprising the step of: - partially purging the contaminant vapor, before or after being incinerated. The method of claim 1 or 2, wherein the venturi has a diameter of 1.0 to 10.0 mm, preferably 2.0 to 7.5 mm, preferably 3.0 to 5.0 mm. preferably about 4.0 mm. 4. Process according to any one of claims 1 to 3, wherein the compressed air has a pressure of 0.5 to 10 bar. The process according to any one of claims 1 to 4, wherein the compressed air has a relative humidity of at most 20.0%, preferably at most 10.0%, preferably at most 5.0%, preferably at most 2.0%, preferably at most 1.0%, preferably at most 0.5%, preferably at most 0.2%, preferably not more than 0.1%. The method of any one of claims 1 to 5, wherein the heat pipe and the perforated pipe are the same. The method of any one of claims 1 to 6, wherein the heat pipe comprises an outer tube and an inner tube, wherein the inner tube receives the heated fluid or gas, which is returned through the outer tube. The method of any one of claims 1 to 7 including the step of reusing thermal energy obtained by incinerating said vapor to heat said contaminated soil to vaporize contaminants remaining in the soil. The process according to any of claims 1 to 8, comprising incinerating said contaminant vapor by: - incinerating the soil contaminants in said contaminant vapor so as to obtain incineration gases and 'thermal energy; the recovery of this thermal energy, and the reuse of said recovered thermal energy to heat said fluid. A system for cleaning a soil containing contaminants, wherein the system comprises: - means for heating said soil to produce a contaminant vapor, comprising at least one thermally conductive pipe; means for removing contaminants from said soil vapor, comprising at least one perforated pipe; means for forcing said contaminant vapor into said perforated pipe, and means for incinerating said contaminant vapor to at least partially remove said soil contaminants present in said contaminant vapor; wherein said means for forcing said contaminating vapor into said perforated pipe comprises a venturi. The system of claim 10, further comprising: - means for purging the vapor contaminants, before or after being incinerated. The system of claim 10 or 11, wherein the venturi has a diameter of 1.0 to 10.0 mm, preferably 2.0 to 7.5 mm, preferably 3.0 to 5.0 mm. preferably about 4.0 mm. 13. System according to any one of claims 10 to 12, wherein the venturi is fed with compressed air, wherein the compressed air has a pressure of 0.5 to 10 bar. The system of any one of claims 10 to 13, wherein the compressed air has a relative humidity of at most 20.0%, preferably at most 10.0%, preferably at most 5.0%, preferably at most 2.0%, preferably at most 1.0%, preferably at most 0.5%, preferably at most 0.2%, preferably not more than 0.1%. 15. System according to any one of claims 10 to 14, wherein the heat pipe and the perforated pipe are the same. The system of any one of claims 10 to 15, wherein said heat pipe comprises an outer tube and an inner tube, wherein the inner tube receives the heated fluid or gas, which is returned through the outer tube. 17. System according to any one of claims 10 to 16, comprising means for reusing the thermal energy obtained by the incineration of said contaminating vapor, for heating the soil to vaporize contaminants remaining in the soil.