DESCRIPTION

FIELD OF THE INVENTION

The present invention relates to a system for sampling and monitoring in a process for the thermal remediation of contaminated soils. In particular, the invention relates to a method and devices for extracting a hot soil sample during or at the end of the treatment in order to subsequently analyse the chemical composition of this sample.

CONTEXT OF THE INVENTION

Soil contamination has become a major concern in many places. Soil can become contaminated with chemical, biological and/or radioactive contaminants. Material spills, leaking storage tanks and seepage from material dumps are just a few examples of the many ways that soil can become contaminated. If left in place, many of these contaminants will find their way into aquifers, the air or the food supply and could pose risks to public health.

There are many proposed methods for removing surface contaminants, such as excavation followed by incineration, in-situ vitrification, biological treatment, chemical additives for deactivation, radio frequency heating, etc. Although these methods work in some applications, they can be very expensive and are not practical if many tonnes of soil have to be treated. Although working in some applications, these methods can be very expensive and are not practical if many tonnes of soil need to be treated.

A process frequently used to remove contaminants from subsurface soil is in situ thermal desorption, which is used to increase the efficiency of a soil vapour extraction process. In-situ thermal desorption involves heating the soil without excavation to raise the temperature of the soil while simultaneously removing soil gas. The heat added to the contaminated soil can raise the soil temperature above the vaporisation temperatures of the contaminants in the soil and cause the contaminants to vaporise. A vacuum applied to the soil removes the vaporised contaminant from the soil. Another method of heating a soil containing contaminants comprises injecting a heated fluid into the soil. Such a process is for example described in US Patent No. 6,000,882. The process described here consists of introducing a system of perforated pipes into the soil. A flow of hot air is sent through the pipes. The hot air is injected into the soil through perforations in the pipes at the pipe perforations. A contaminant vapour is formed in the soil, which can be removed from the soil through the pipe perforations and discharged to an off-gas treatment unit.

Another way of heating a floor is to heat a floor by thermal conduction using electrical resistors or to heat the floor by injecting electrical current into the floor and dissipating it by Joule effect.

Thermal conductive heating of contaminated soil in combination with removal of contaminating gases from the soil by means of a vapour extraction system is old in the art.

During in-situ thermal desorption, all surfaces in contact with the atmosphere are usually covered with concrete and an insulation layer after the concrete layer.

There are therefore many soil treatment systems that involve, in one way or another, heating the soil to mobilise the contaminants and then extracting them.

All these systems face a common difficulty in measuring the progress of clearance on the one hand and in checking that it is complete on the other. Indeed, conventional sampling techniques are not designed to sample hot soils, in particular soils with temperatures above 100°C.

The main difficulties associated with hot sampling are related to the texture and structure of the soil, which loses its cohesion due to drying, and to ensuring that changes in physical and chemical conditions do not influence the quality of the recovered sample, particularly due to the volatilisation of the most volatile elements during sampling.

At the same time, it is important, when sampling said soil which not only is very hot but has lost all structure, to make sure that the sampling method itself does not affect the sample by for example releasing volatile components as it is exposed to colder atmosphere and different pressures when extracted;

Additionally, it is also essential to make sure that the exact depth/location of the sample is known and secured.

However, knowledge of the composition of the soil being processed is an asset that will allow the performance of the process to be evaluated and its operation to be improved. Conventional sampling techniques (augers, gouges, liners, etc.) are ineffective in such a process because the treated material literally "flows" through them. In addition, the high temperature (>>120°C) prevents the use of formed plastics such as check valves, advancing casing parts, etc.

The present invention therefore aims to provide a solution to be implemented to extract several samples from this processing volume in order to be able to know the composition of the soil after a certain processing time and in this way define the progress of the processing.

It also allows a hot sample of equivalent quality to a cold sample to be taken, enabling the objectives of thermal depollution to be validated.

The particulars of a hot sampling device as invented is that it can address all types of soils, heated at high temperature, while avoiding that the sample is exposed to different pressures and temperature while collected, and also guaranteeing the exact depth and location of the sample taken.

CN 107462439 and JP402120524 are known as prior art and present systems for the extraction of samples in soils, consisting of two coaxial tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached drawings illustrate the invention:

Figure 1 : Heat sampler - internal and external exploded view

Figure 2: Sampler - external appearance

Figure 3: Detail of the internal and external sampler

Figure 4: Sampling sequence with lost tip

Figure 5: External and internal sampler exploded

Figure 6: Perspective view lost point sampling

The legend of the figures is as follows:

1. Heat sampler: external tube

2. Internal coaxial cylinder

3. Crank handle

4. Tapered tip (lost or not)

5. External opening window

6. Scraper

7. Internal sampler cap

8. Internal opening window 9. Internal sampler

10. Internal sampler rod

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a hot soil sampling system for extracting samples representative of the subsoil condition at different depths. It allows the extraction of hot soils that have lost their cohesion due to heating. Thus, during thermal decontamination, which consists of heating the soil, often above 100°C, control samples can be taken as the decontamination progresses, in order to give a representative view of the actual state of the decontamination.

It consists of two coaxial cylinders that slide into each other and allow a sampling window to be opened and closed at a defined depth, thus ensuring a representative sample in warm soil.

The hot sampling system is a system for extracting a representative sample of hot soil during or after heat treatment.

The system consists of a hot sampler (1), an auger or equivalent system for drilling to the required depth for sampling and a set of rods for extending the borehole to the required depth and for handling the hot sampler.

The hot sampler (1) consists of two coaxial cylinders ( land2 ), each of which has an opening window (5 and 8) of comparable size at the top of the cylinder and of a height corresponding to the required depth window for sampling; the inner cylinder (2) is connected to the operator through the rod (10) which allows the operator to rotate the inner cylinder when it is positioned at the correct depth. The rod also allows the operator to establish the correct sampling depth.

The system consists of inserting a hot sampler (1) into the soil at the chosen depth for representative sampling. When the hot sampler (1) is placed at the correct depth, the rod (10) is rotated until the inner (8) and outer (5) windows are facing each other.

The sampling element inserted at the determined depth consists of two cylindrical elements sliding in each other around a radial axis.

In a preferred embodiment, the said sampling technique is made possible by placing reservation tubes (RT) of diameter between 30 and 70mm, preferably between 40 and 60mm at the same time as the placement of the heating elements of the in situ thermal desorption treatment, in the treatment area. The position and length of these tubes depends on the location of points equidistant from the heating elements. In a preferred embodiment, said sampling technique comprises the following steps:

1. The two tubes (1)(2) are pushed together into the soil or material to be sampled through the reservation tubes (TR) by arm force or with a sledgehammer. They are expandable by screwing one length of 0.7 to 2m, preferably 0.9 to 1.2m, onto the other to achieve the desired depth.

Depending on the type of soil, the introduction of this device into the soil can be complicated, it is necessary to first introduce a tube with a screw thread into the soil or the material to be sampled.

2. Once the sampling depth has been reached, the crank (3) must be turned half a turn to open the window (8) and sample the soil in the inner tube window (5 and 8).

3. To complete the filling of the window, both tubes are rotated about 5 turns.

4. Once filled, the window should be closed by turning the inner tube half a turn (8).

5. The inner tube (2) is extracted with a digger or pulling device or by arm power. The 1 m lengths are unscrewed gradually one by one to obtain the soil sample. The soil is immediately collected in a suitable container.

In another preferred embodiment, the outer window (5) is provided with a scraper (6) to force the soil to be sampled into the sampler (1) when it has been heated significantly and has become too hard to flow naturally into the sampler.

The collected soil sample is then sent to an accredited laboratory to analyse the targeted pollutants.

In another preferred embodiment, the said sampling technique consists of introducing the tube (1) into the ground through the TR tubes with a hammer. Again, in some cases the use of a tube with a screw thread is required before the sampling tube (1 and 9) is inserted.

In a preferred embodiment, the rod connected to the sampler (10) is provided with depth indications corresponding to the exact depth of the sample. In a preferred embodiment, the rod consists of 2 coaxial rods. The outer one is connected to the sampler (1) and the inner one to the inner sliding element (9).

In a preferred embodiment, the hot sampler is placed on a conical tip (4), which may or may not be attached to the sampler;

In a preferred embodiment, one or more windows of different sizes depending on the type of material to be sampled (variable inner window - large and fixed outer window).

In an embodiment, the crank handle (3) comprises an insulation layer of at least 1 cm, preferably 2 cm. To protect the hands of the operator, the handles comprise an insulation layer of at least 1 cm, preferably 2 cm. The insulation layer is resistant to temperatures up to at least 600°C.

In a preferred embodiment, the inner and outer cylinders are made of heat resistant metal, suitable to withstand temperatures up to 600°C. In an embodiment, the soil sampling system is made of heat resistant materials, suitable to withstand temperatures up to 600°C.

In an embodiment, the soil sampling system does not comprise any materials not resistant to temperatures up to 600°C, by preference, the soil sampling system does not comprise any plastic parts. The temperature at which polymers deform is in general low. Under a pressure of 0.46 MPa, polypropylene (PP) and polyethylene (PE) deform at, respectively, 100 and 85°C. Even when comprising 30% glass fibres, PE and PP are not suitable to be used in a hot soil sampling system because it is not stable at temperatures higher than 250°C.

In a preferred embodiment, the outer cylinder is provided with spiral or fractional spiral shaped fins to improve the introduction of the tool into the soil. The fins are defined as an additional part to the tube, which may be in the form of a spiral or a fraction of a spiral, composed, in a preferred embodiment, of the same material as the outer cylinder, which is intended to improve the introduction of the tool into the soil.

In a preferred embodiment, the outer shaft is provided with metric indications to determine the exact location of the sample. In a preferred embodiment, the outer cylinder is provided with metric indications, suitable to determine the exact location of the sampler.

In a preferred embodiment, the inner and outer cylinders are threaded.

In another preferred embodiment, the outer cylinder is provided with fins in the form of a full or partial spiral and allowing better penetration into the ground.

In an embodiment, the inner and outer cylinders allow a sampling window to be opened and closed.

In an embodiment, the soil samples inside the soil sampling system are stored airtight when the window is closed. During treatment to remove contaminants using in situ thermal desorption, temperatures higher than 500°C are applied. Soil sampling systems according to the prior art are not able to prevent loss of volatile organic compounds after sampling. This reduces the accuracy of the soil sampling and the analysis. Being able to follow-up the concentration of the contaminants at different depths, allows a good prediction of the required remaining treatment time.

The invention relates to a soil sampling system for extracting a hot soil sample, comprising at least one cylindrical element inserted in another cylindrical element of larger diameter allowing rotation of the inner element in the outer element, and wherein the inner element comprises at least one opening allowing entry of the solid to be sampled when positioned such that the openings in the inner and outer cylinder are aligned and allow the solid to be sampled to flow into the inner cylinder and such that the outer cylinder is provided with a scraper to force the entry of soils into the sampler upon rotation thereof.

The invention relates to a soil sampling system for extracting a hot soil sample up to 600°C, comprising (a) at least one inner cylinder comprising a sampler and (b) an outer cylinder of larger diameter allowing rotation of the inner cylinder in the outer cylinder, and wherein the inner cylinder and the outer cylinder comprise at least one opening suitable for entry of the hot soil sample when positioned such that the openings in the inner and outer cylinder are aligned and allow the sample to flow into the inner cylinder and such that the outer cylinder can rotate to seal the inner cylinder containing the sample airtight from the outside, and where the outer cylinder is provided with a scraper to force the entry of soil into the sampler upon rotation thereof and where the outer cylinder is provided with spiral or fractional spiral shaped fins to improve the introduction of the soil sampling system into the soil. In order to seal two sides from each other airtight, it means that no air can escape or pass through when the pressure on both sides is 1 atm. In an embodiment, the window is capable to prevent air from entering if the pressure inside remains higher than 0.5 atm., and preferably 0.2 atm. In an embodiment, the window is capable to prevent loss of volatiles if the pressure inside remains lower than 2.0 atm. and preferably 4 atm.