FIELD OF THE INVENTION

The present invention relates to a composition for in-situ remediation of contaminated soil and groundwater.

The present invention pertains to the technical field of thermal soil and groundwater remediation.

BACKGROUND

There are numerous techniques employed for the remediation of contaminated subsurface material. The mechanisms for clean-up may be physical, chemical or biological. Common physical remediation methods include excavation and disposal of contaminated soil and pumping and treatment of contaminated groundwater.

This invention relates to the remediation of contaminated subsurface material. More specifically, the invention relates to a method of remediation of subsurface material through use of thermal desorption. More specifically, the invention relates to a method of fixing problematic elements such as sulfur, halogens and/or mercury mobilized by thermal desorption before they exit the soil package, under an inert form, enhancing said thermal desorption remediation overall efficiency and reducing its cost.

In-situ treatment of contaminated subsurface material is often a less expensive approach because it eliminates the need for physical removal of the contaminated material. Common in-situ treatment approaches include aerobic and anaerobic bioremediation, chemical oxidation and reduction, soil vapor extraction, air sparging, in-situ stabilization— immobilization and in-situ thermal desorption, which itself can be either conductive or resistive heating.

In-Situ Thermal Desorption (ISTD) is considered a highly effective treatment technology, as it mobilizes contaminants by vaporizing them in-situ and collecting said generated vapors to the surface for further treatment; said further treatment occurs either in ad-hoc treatment devices comprising condensation, adsorption, oxidation and/or even biological steps. Some ISTD technologies, such as in DI, are even using said vapors as fuel source for their own heating by injecting them directly into the burners for heating the soil. Such a beneficial reuse of contaminant vapors can, however, only be done of said vapors are exempt from toxic elements for the combustion itself or for the equipment or for further atmospheric emissions.

Such a method according to the preamble is also known from EP2632616A2 (DI). DI further describes the heating of soil by means of thermal desorption through inserted heating elements, with separate perforated pipes for recovering the vapors. Said heating elements are heated with individual burners which can also handle the combustion of extracted vapors if they do not contain sulfur, halogens or mercury; said heating elements and perforated pipes are surrounded by inert gravel.

Also known is the device/method/use from FR3056421A1 (D2). D2 relates to a control device for reusing the vapors as fuel by controlling stoichiometry.

EP1751775A1(D3) describes a method for handling mercury vapors to transform them into HgS (cinnabar) in a specific off-site chemical reactor;

Also known is FR2620056(D4) which describes the reactions of granulated quicklime with hydrocarbon sludges;

These known devices and methods do not take care of the problem posed by sulfur, halogens or mercury or other similar compounds before they exit the soil pack. Indeed, all those methods and devices require either specific equipment outside the soil pack to neutralize those vapors or even to physically condense or excavate the soils.

The present invention aims to resolve at least some of the problems and disadvantages mentioned above.

The invention thereto aims to provide the chemical neutralization of the vapors mobilized by in-situ thermal desorption before they exit the soil itself.

There remains a need in the art for an improved vapor in-situ handling, as current technologies handle those vapors once they are at the surface, which causes higher costs and risks of corrosion and other chemical alterations of surface equipment. Accordingly, a need arises for a composition that can successfully neutralize said vapors in-situ and maintain the effectiveness of thermal desorption technologies for the other targeted contaminants, also without having to generate waste at the surface.

Additionally, some thermal desorption technologies, such as in DI, use a re-burn system in which vapors containing energy and fully combustibles are used as an energy source for heating the soil. In the case where the contaminated material contains high levels of energy, such as hydrocarbons, but also contains sulfur, halogens or other non-combustibles. These cannot be recycled as fuel, because of the corrosive effect of halogens and/or sulfur, and because of the further neutralization needed of said halogens and/or sulfur. The present invention enables in-situ neutralization of the halogens and/or sulfur and subsequent ability for those highly energetic vapors to be recycled in the burners, which procures a double benefit in energy savings as well as avoidance of waste production.

Quicklime is often mixed with soil to dry soil or improve its mechanical properties. When used in granulated form, it can handle hydrocarbon contamination as well by using the exothermic reaction provoked by said mixing, as in FR2620056B1. This, however, requires mechanical treatment and excavation of said soil. It cannot be done in-situ. Quicklime is not, in its granulated form, used to react with other chemical elements such as sulfur or halogens in vapor form.

SUMMARY OF THE INVENTION

The present invention and embodiments thereof serve to provide a solution to one or more of above-mentioned disadvantages. To this end, the present invention relates to a composition according to claim 1.

Preferred embodiments of the device are shown in any of the claims 2 to 9. A specific preferred embodiment relates to an invention according to claim 2.

DESCRIPTION OF FIGURES

The following numbering refers to:

(1) contaminated soil

(2) heating element

(3) vapor extraction tube (4) composition mix of variable size and shapes of inert and reactive grains

(5) granules of quicklime

(6) granules of zeolites

(7) granules of gravel

(8) reaction product between quicklime and water and/or sulphur or halogens

(9) open reactive surface of quicklime

(10) borehole

(11) concrete layer

The following description of the figures detailing the specific features of the invention is merely exemplary in nature and is not intended to limit the present teachings, their application or uses. In the drawings, corresponding reference numerals indicate identical or corresponding parts and features.

Figure 1 schematically presents the process of In-Situ Thermal Desorption of soil (1), where the presence of the composition (4) is shown around the vapor extraction wells (3) co-located with the heating elements (2).

Figure 2 presents in more detail an example of composition where quicklime grains (5) are mixed with zeolites (6) and gravel (7) in variable shapes, forms and dimensions to form the composition.

Figure 3 presents a zoom view of an active quicklime granule (5) where some parts of the product have already reacted (8) and forms an inert element, while other parts (9) have been eroded and expose new active surfaces to react with the next reagents from the soil.

Figure 4 schematically presents the process of In-Situ Thermal Desorption, where the presence of the composition (4) is shown around the vapor extraction wells (3) when they are located at a substantial distance from the heating wells (2).

Figure 5 schematically presents the process, where the presence of the composition (4) is shown around the vapor extraction wells (3) co-located with the heating elements (2) and on the top surface of soil (1)

DETAILED DESCRIPTION OF THE INVENTION

The present invention concerns a composition of reactive and non-reactive minerals, natural or previously coated by reactive products, in variable proportions, shapes and forms, which are applied around vapor extraction tubes in In-Situ or On Site thermal desorption processes and serve to increase permeability for vapor recovery and neutralize reactive components such as sulfur, halogens or mercury. Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

As used herein, the following terms have the following meanings:

"A", "an", and "the" as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more than one compartment.

"About" as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of +/- 20% or less, preferably +/-10% or less, more preferably +/-5% or less, even more preferably +/-1% or less, and still more preferably +/-0.1% or less of and from the specified value, in so far such variations are appropriate to perform in the disclosed invention. However, it is to be understood that the value to which the modifier "about" refers is itself also specifically disclosed.

"Comprise", "comprising", and "comprises" and "comprised of" as used herein are synonymous with "include", "including", "includes" or "contain", "containing", "contains" and are inclusive or open-ended terms that specifies the presence of what follows e.g. component and do not exclude or preclude the presence of additional, non-recited components, features, element, members, steps, known in the art or disclosed therein.

Furthermore, the terms "first", "second", "third" and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints. The expression "% by weight", "weight percent", "%wt" or "wt%", here and throughout the description unless otherwise defined, refers to the relative weight of the respective component based on the overall weight of the formulation.

Whereas the terms "one or more" or "at least one", such as one or more or at least one member(s) of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any >3, >4, >5, >6 or >7 etc. of said members, and up to all said members.

Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention. The terms or definitions used herein are provided solely to aid in the understanding of the invention.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art of this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some, but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art.

For example, in the following claims, any of the claimed embodiments can be used in any combination.

Reference to "halogens" includes a group of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

Reference to "gravel" refers to a loose aggregation of rock fragments, occurring mainly naturally as a result of sedimentary and erosive geological processes or as crushed stones produced commercially. It is defined by particle range size and can vary from 2 to 70 mm.

In a first aspect, the invention relates to a composition for surrounding vapor extraction wells from contaminated soil, at temperatures in excess of 80°C, in which a mixture of at least 20% of inert gravel with dimensions comprised between 2 and 70 mm are mixed with an active solid and granular alkaline mineral such as calcium hydroxide, hydrated calcium carbonate or sodium bicarbonate, or with zeolites with dimensions comprising between 2 and 70 mm and in these proportions:

Min 20% gravel

Min 20% quicklime (CaO)

Max 40% hydrated lime (Ca(OH)2)

Max 80% zeolites where the mixture can be adapted to the application.

This composition will react with vaporous sulfur, which appears as H2S for example, and form inert salts which are harmless to the environment.

The granulometry is important, as it allows for enough permeability for the vapors to move towards the vapor extraction tubes. As the neutralization reaction will progress over the course of the treatment, which can last for several weeks or months, the inert material formed by the neutralization reaction will slowly reduce permeability by clogging the spaces between the individual grains. Therefore, the dimensions are designed to allow for sufficient residual permeability during the complete treatment and the variability in those granular sizes will have to be determined based on the expected duration of the treatment and the initial quantities of contaminants, sulfur, halogens or other reagents present in the soil.

State of the art of in-situ thermal desorption (ISTD) vapor treatment is found in DI and D2.

In the various current ISTD applications, heating elements are inserted in the soil. In some applications, not all, co-located vapor extraction wells are placed, i.e. vapor extraction is carried out in the same hole than where the heating element is placed. Gravel is placed around both elements, in order to create enough permeability to collect the vapors, while at the same time keeping enough matter density to ensure good thermal conduction of the heat generated by the heating elements.

That gravel material is always inert and does not react with the extracted vapors. It is mineral and granulated, so that both permeability and resistance at higher temperatures, varying from 80 to 600°C, preferably from 200 to 500°C and more preferably from 350 to 450°C.

The invention consists of providing the same benefits as currently provided, i.e. maintain permeability, good thermal conduction and temperature resistance and integrity, while providing additional benefits such as chemical reactions in favorable temperature ranges.

Temperature resistance is an essential element, as the composition will be reactive in the ISTD application at temperatures in excess of 200°C and preferably between 250°C and 450°C. At those temperatures, the kinetics for the neutralization reactions for halogens, sulfur or the cinnabar formation from vapor mercury through contact with metallic sulfur. The area around the heating tubes in the ISTD process (4) presents the necessary conditions for a favorable chemical reaction, with high surface contact between reagents and high temperature, increasing kinetics for all aimed neutralization reactions.

Treating vapors over calcium hydroxide fixed bed is commonly applied in many vapor treatment systems to neutralize said vapors. However, this is done usually at the end of the treatment process prior to release into the atmosphere. When applied, this is also mostly done with pure powder CaO rather than granulated. The powder materials are indeed more readily available and can easily be replaced when they are no longer reactive. Even when using granulated CaO, it is applied pure (i.e., with >95% CaO), as it would provide no benefit to mix said granulate with inert materials, such as granite or sandstone.

As contaminants often contain hydrocarbons, said hydrocarbons react with granulated quicklime, at higher temperatures than in D4, which increases the speed of reaction and release of energy contained in said exothermic reactions. Hence the vapors exiting to the surface will contain less if any hydrocarbon chains, and the heat generated by their oxidation reaction with the quicklime will directly contribute to the overall energy balance of the thermal desorption processes.

In the present invention, the size of the granules of calcium hydroxide is between 2 and 70mm, preferably between 2 and 15mm, more preferably between 3 and 10mm. Contrary to more commonly used powder calcium hydroxide, the granulated form allows for much longer reaction times, as the reaction will occur on the outer surface of each grain, producing inert salts, which themselves will turn into powder form, blocking voids and reducing permeability. Therefore, a fraction of the grains must remain inert, hence regular gravel, so that the total volume of voids in the composition is high enough to maintain permeability after quicklime has reacted with the vapors.

The size of the gravel particles, as well as the proportion between gravel and quicklime can therefore be customized and adapted to the specifics of the contamination to be treated and the expected duration of the remediation.

It is important to note that the fact that quicklime is in granular form, rather than in the more usual powder form, is critical for the efficiency of the composition. Indeed, the powder form would react very quickly with the water present in the material, as water will vaporize before the other elements, and once the reaction has taken place, there will be almost no reagents left to handle the critical elements such as sulfur, halogens and others. By using granular quicklime, the reaction will occur at the surface of each grain, generating a layer of gypsum for example, as a reaction between quicklime and water. That layer will slowly erode from the grain of quicklime, exposing more active quicklime to react with the next flow of reagents such as sulfur or halogens. Hence, the gypsum formed, under powder form, will move downwards the composition and remain in the soil.

Therefore, the granular element is essential to assure a longer reaction time, in line with the length of the ISTD treatment itself.

Additionally, give that in vapor extraction wells are located elsewhere than next to the heating wells, the composition will contain a larger portion of active quicklime, while still maintaining a minimum fraction of gravel. By having more quicklime, the exothermic reaction will be more intense, generating an extra heating source in the treatment area, thereby increasing heating, and reducing treatment time. The composition will also act in a lower temperature range, from 20 to 300°C, preferably from 50 to 250°C and more preferably from 80 to 200°C.

In another preferred embodiment, a specific solid reagent is mixed with the main composition to react with vaporized mercury and form HgS and/or HgO. Indeed, mercury is present under various forms in the soil and the most toxic forms are the most mobile and least stable ones, such as metallic mercury, organic mercury, etc. However, some forms of mercury, such as mercury oxide (HgO) or sulfide (HgS) are much less mobile, hence much less toxic. A known detoxication of mercury is to react with sulfur to form a stable HgS, which in itself has a much lower toxicity and can be considered environmentally safe. Where those known methods occur in reactors and at low (ambient) temperatures, the present invention allows for a higher temperature reaction, in gas phase for the reagents that need sulphuration and with no physical mixing of solids. In the present invention, the mercury vapors are brought in contact thanks to the granular characteristics of the composition, as well as their reactive nature, so that a better combination of contact time, high temperature and proper reagents can produce similar results than in a solid reactor. This composition of solid reagents forms a fixed permeable bed through which the other reagents have to flow, the whole reactor being heated by the soil heating elements in the immediate vicinity.

In another preferred embodiment, the composition is spread at the surface of the contaminated area, under the thermal insulation layer, and serves both as neutralization media for eventual fugitive emissions as well as a secondary heating source for reducing the thermal losses through the surface.

However, it is obvious that the invention is not limited to this application. The method according to the invention can be applied in all sorts of contaminated soil treatment and other equivalent materials to be treated by thermal desorption.

For example, some solid waste containing high sulfur content and high hydrocarbon content (acid tars) can be treated by state-of-the-art thermal desorption with great difficulty at high cost due to the presence of high sulfur concentrations, which cause corrosion issues in the system, and high vapor treatment costs.

In an embodiment, the mixture is amended by adding at least one of liquid and dissolved alkaline materials including NaOH, Na2CO3, NaHCO3, NH4OH, (NH4)2CO3, Na5P3O10, Na2HPO4 and Na3PO4. In another embodiment, the mixture is amended by adding a solid mineral selected from the group consisting of Zero-valent Iron, MgO, Mg(OH)2, MgCO3 and CaCO3.

In another embodiment, the mixture is amended by adding at least one of liquid and dissolved alkaline materials including NaOH, Na2CO3, NaHCO3, NH4OH, (NH4)2CO3, Na5P3O10, Na2HPO4 and Na3PO4.

In another embodiment, the mixture is amended by adding chemical oxidants including hydrogen peroxide, metal peroxides, peroxygens, persulfates, permanganate, and other oxidizing compounds to enhance contaminant degradation.

In another embodiment, the exact granular dimension limits are adapted in function of the expected duration of the remediation and its total initial acid load.

In another embodiment, granulated sulfur is added to the mixture in order to react with vaporized mercury compounds and form HgS and/or HgO.

In another embodiment, granular mineral acids are added to the mixture in order to react with alkaline vapors.

In another embodiment, zero-valent iron is added to the mixture in order to react with organic vapors.

In another aspect the invention relates to a method for treating contaminated soil comprising : digging extraction wells; applying in the extraction wells a mixture of (a) at least 20% of inert gravel with dimensions of 2 to 70 mm, (b) at least 20% quicklime (CaO) and (c) a granular alkaline mineral such as calcium hydroxide, hydrated calcium carbonate or sodium bicarbonate, or (d) with zeolites with dimensions comprising between 2 and 70 mm, wherein the mixture comprises of at least 20% (a), at least 20% (b), at most 40% (c) and at most 80% (d); applying a concrete layer in the surroundings of the extraction wells; heating the soil; allowing vapors produced from the soil to enter the extraction wells.

In an embodiment, the mixture further comprises at least one of liquid comprising NaOH, Na ₂ CO ₃ , NaHCO ₃ , NH ₄ 0H, (NH ₄ ) ₂ CO ₃ , Na ₅ P ₃ Oio, Na ₂ HPO ₄ , Na ₃ PO ₄ , Zero- valent Iron, MgO, Mg(OH) ₂ , MgCO ₃ or CaCO ₃ . In an embodiment, the vapors are combusted and at least 50% of the heat released during this combustion is transferred to the soil. This heat transfer reduces the energy requirements to remediate the contaminated soil.

In an embodiment, the granular dimension limits are adapted in function of the expected duration of the remediation and its total initial acid load. By adjusting the granular dimension in function of the expected duration of the remediation and its total initial acid load, a continuous flow of neutralizing compounds can be provided. This flow will sustain throughout the length of the remediation process. Furthermore, not too much materials should be supplied either.

A person skilled in the art, will realize that features of the first aspect can be used in the method according to the second aspect. Each feature described in this document, both above and below can be applied to any aspect of the invention.

The invention is further described by the following non-exhaustive list of examples which further illustrate the invention, and are not intended to, nor should they be interpreted to, limit the scope of the invention.

EXAMPLES AND/OR DESCRIPTION OF FIGURES

With as a goal illustrating better the properties of the invention the following presents, as an example and limiting in no way other potential applications, a description of several preferred applications of the method for examining the state of the grout used in a mechanical connection based on the invention, wherein:

FIG. 1 schematically presents the process of In-Situ Thermal Desorption of soil (1), where the presence the composition (4) is shown around the vapor extraction wells (3) co-located with the heating elements (2).

FIG. 2 presents in more detail an example of composition where quicklime grains (5) are mixed with zeolites (6) and gravel (7) in variable shapes, forms and dimensions to form the composition.

FIG. 3 presents a zoom view of an active quicklime granule (5) where some parts of the product have already reacted (8) and forms an inert element, while other parts (9) have been eroded and expose new active surfaces to react with the next reagents from the soil.

FIG. 4 schematically presents the process of In-Situ Thermal Desorption, where the presence the composition (4) is shown around the vapor extraction wells (3) when they are located far away from the heating wells (2). FIG. 5 schematically presents the process of In-Situ Thermal Desorption of soil (1), where the presence the composition (4) is shown around the vapor extraction wells (3) co-located with the heating elements (2) and on the top surface of the contaminated soil (1).

The present invention will now be further exemplified with reference to the following examples. The present invention is in no way limited to the given examples or to the embodiments presented in the figures.

Example 1

In example 1, ISTD treatment is carried out on a former dry cleaning site, containing chlorinated solvents such as PCE and TCE. At that site, inert gravel is replaced by the composition as invented, with a specific composition as follows:

Inert gravel: 45%, with granulometry 2 to 10 mm;

Quicklime (CaO): 35%, with granulometry 4 to 15 mm;

Hydrated lime (Ca(OH)2): 20% with granulometry 4 to 15 mm.

The composition is placed around heating elements and vapor extraction pipes, both placed in the same whole, as presented in Figure 1.

During heating, inert gravel will not change chemical nor physical shape, keeping high permeability to vapors throughput the process. The percentage of 45% has therefore been defined to keep said permeability at a high level.

The expected heating time is 25 days, and the target temperature at cold points is expected to reach 100°C. The site has high humidity content, as it is close to the groundwater.

Given the expected high humidity, a 35/20 ratio has been determined to be favorable to best react with water while leaving active grains with lime to react with vapor Cl passing through the composition.

Example 2

In the second example, a horizontal pile has been built to handle soil contaminated with mercury, chlorinated solvents and with high sulfur content. In this case, the following composition has been defined to best capture and neutralize all vapors:

Inert gravel: 30%, with granulometry 2 to 20 mm;

Quicklime (CaO): 30%, with granulometry 4 to 15 mm;

Hydrated lime (Ca(OH)2): 10% with granulometry 4 to 15 mm; Zeolites impregnated with solid sulfur: 30% with granulometry 2 to 10 mm.

This composition was chosen to be optimal, as treatment time is expected to be longer (at least 60 days), with lower moisture content. Quicklime/hydrated lime ratio is defined to capture Cl and S compounds while zeolites impregnated with S at a 30% ratio are destined to capture mercury vapors passing through the composition and transform them in HgS, which is considered mostly inert and can remain in the soil.

Example 3

In this example, the excavated soil is placed in thermal piles, as per an embodiment in DI. The soil contains low levels of moisture, but high concentrations of S next to high concentrations of hydrocarbons.

By using the composition as invented, the soil can be treated with a full reburn of all hydrocarbons, generating 20% to 25% fuel savings, without having sulfur corrosion issues (formation of H2SO4 in presence of water) nor H2S excess atmospheric emissions.

The composition is composed of 50% CaO with granularity between 2mm and 15mm and 50% inert gravel with the same granulometry.

This composition is focused solely on fixing S, with additional benefits of generating an exothermic reaction, which contributes positively to the overall heating of the contaminated soil.

Example 4

In example 4, a groundwater pack is contaminated with chlorinated solvents such as TCE and PCE. ISTD is applied to heat the groundwater package to temperatures between 60°C and 95°C, mobilizing the Dense Non-Aqueous Phase Liquids (DNAPL) and further vaporizing them in the vadose zone.

Parts of the TCE/PCE are evacuated through Multi-Phase extraction wells, while the remaining fraction (under TCE/PCE form or under degraded form) are vaporized and collected through specific vapor extraction wells located in the vadose zone. Those extraction wells are surrounded by the composition, composed of 40% inert gravel, 30% CaO, 20% Ca(OH)2 and 10% zero-valent iron, all with granulometries between 2 and 10mm. Example 5

In this example, a sensitive area is treated with ISTD, in a densely populated zone. On top of the composition being used around extraction wells, a layer of 20cm of specific composition has been spread on top of the area to capture any fugitive vapors before they might be released into the atmosphere. The composition of 80% CaO with granulometry 2 to 8mm and 20% gravel is designed to maximize reaction, with less focus on permeability, as the goal is to make sure that any passing vapor has reacted. Lower permeability over time is not deemed a problem in this specific application, as vapor will be extracted through the normal channels (vapor extraction wells).

Example 6

In example 6, ISTD treatment is carried out on a former petrol station site, containing hydrocarbons such as diesel and gasoline. At that site, inert gravel is replaced by the composition as invented, with a specific composition as follows: Inert gravel: 35%, with granulometry 2 to 10 mm;

Quicklime (CaO): 45%, with granulometry 4 to 15 mm;

Hydrated lime (Ca(OH)2): 20% with granulometry 4 to 15 mm.

The composition is placed around heating elements and vapor extraction pipes, both placed in the same whole, as presented in Figure 1.

During heating, inert gravel will not change chemical nor physical shape, maintaining high permeability to vapors throughput the process. The percentage of 35% has therefore been defined to maintain said permeability at a high level.

The expected heating time is reduced from 35 to 32 days as additional heating from the exothermic reaction generated quicker heating of the soil. Consequently, overall energy consumption is also reduced for the treatment.

As shown in those examples, the variability both in proportions and granulometry size in important to guarantee optimal efficiency of the composition, as it is customized for each application, based on the time of heating, moisture content, products to vaporize and further vapor treatment installed.

It is supposed that the present invention is not restricted to any form of realization described previously and that some modifications can be added to the presented example of fabrication without reappraisal of the appended claims. For example, the present invention has been described referring to contaminated soil, but it is clear that the invention can be applied to other solid waste with a mineral matrix and organic contamination for instance, or to similar products such as lagunes, tars and various solid waste streams.

The present invention is in no way limited to the embodiments described in the examples and/or shown in the figures. On the contrary, methods according to the present invention may be realized in many different ways without departing from the scope of the invention.

In another example, the application will create an exothermic reaction in the system, generating heat, which will be beneficial to the overall thermal desorption process, as said heat will propagate by conduction into the contaminated body and help remediate said body.

In another preferred embodiment, the mixture of gravel and granular quicklime is completed with a porous solid such as zeolites.

In another preferred embodiment, the mixture of gravel is mixed with zero-valent iron, KMnO3, Sodium Persulfate such that organics can react and be oxidized in-situ at higher temperature; even if some of those compounds can be unstable at temperatures above 60°C, they will react with organics in the soil, contained in vapors and their reaction will be exothermic, enhancing the thermal desorption itself and saving energy.

It is clear that the method and composition according to the invention, and its applications, are not limited to the presented examples.