JPH09164381A - Extraction method for extracting contaminant from contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soil contaminant extraction method capable of extracting the contaminant from a wide contaminated region with one extraction well. SOLUTION: The soil 22 on the circumference of a strainer 12 is heated, by which the moisture in the soil is reduced and the soil is fissured to a porous form. As a result, the soil contaminant existing in a gaseous form or liquid form in the soil 22 is more easily attracted to the strainer 12 in a negative pressure state. Since the soil 22 is made porous, the arrival distance of the negative pressure prolongs and, therefore, the soil contaminant existing at a far distance from the circumference of the strainer 12 is extracted as well. In the case of the soil contaminant existing in the gaseous state, the gaseous pressure in the soil is increased by heating by which the contaminant is easily moved into the pipe which is the vent port of the gaseous pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extraction method for extracting pollutants from contaminated soil, and in particular to extracting pollutants existing in gaseous or liquid form in polluted soil contaminated with industrial wastes. It relates to an extraction method for extracting contaminants from contaminated soil for removal.

[0002]

2. Description of the Related Art Soil pollutants discarded from factories such as trichlorethylene, tetrachloroethylene, 1,
Volatile organochlorine compounds such as 1,1 trichloroethane penetrate into the soil and exist in the gas state or liquid state in the soil. Therefore, in order to purify the contaminants that have penetrated into the soil, conventionally, the method described below has been used.

That is, first, a vertical hole (hereinafter referred to as an extraction well) is dug from the ground surface to the ground in the contaminated area. Next, a pipe for extracting contaminants having a large number of suction holes is fitted in the extraction well with airtightness. Next, a negative pressure is applied to the inside of the pipe by a vacuum pump through a connecting pipe connected to the end portion of the pipe on the ground surface side so that contaminants existing in the soil are sucked into the pipe. The sucked contaminants are adsorbed on activated carbon or the like in a treatment tank provided after the pump, or treated into a harmless substance by thermal decomposition or the like and then discharged.

As described above, the conventional extraction method for extracting contaminants from contaminated soil is to extract the contaminants by sucking the contaminants in a gas state or a liquid state into the soil by applying a negative pressure in the pipe. It is a thing.

[0005]

However, in the conventional extraction method for extracting contaminants from contaminated soil, when the soil has poor gas or liquid permeability, the negative pressure does not easily reach a long distance. There is a drawback that only nearby contaminants can be extracted. For this reason, one extraction well cannot cover a wide contaminated area, so that there is a problem that a large number of extraction wells must be excavated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a soil contamination extraction method capable of extracting contaminants from a wide contamination area with one extraction well.

[0007]

In order to achieve the above-mentioned object, the present invention provides an extraction method for extracting contaminants from contaminated soil for extracting soil contaminants existing in a gaseous or liquid state in soil. , A long hole-shaped extraction well drilled from the surface of the soil to the soil contaminated area, a contaminant extraction pipe having a strainer at the tip is inserted, and the soil inside the strainer is made negative by setting a negative pressure inside the pipe. When the soil contaminants are sucked from the inside and extracted from the strainer into the pipe, the soil around the strainer is heated.

According to the present invention, by heating the soil around the strainer, the water content in the soil is reduced and the soil is cracked and becomes porous. As a result, the soil contaminants existing in the soil in the form of gas or liquid are easily attracted to the strainer in the negative pressure state. In addition, since the soil becomes porous and the negative pressure reaches a long distance, it is possible to extract soil pollutants far from the strainer. In the case of soil pollutants existing in the gas state,
By heating and increasing the gas pressure in the soil, it becomes easier to move into the pipe, which is the gas pressure outlet.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a method for extracting contaminants from contaminated soil according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a diagram for explaining an extraction device for applying the method for extracting contaminants from contaminated soil according to the present invention, and shows a state in which soil contaminants in soil are extracted using the extraction device. .

As shown in FIG. 1, the extraction device 10 is provided with a strainer 12 at the tip end thereof and a pipe 1 for extracting contaminants.
4, a trapping tank 16, and a vacuum pump 18 are connected in order by respective conduits 20A and 20B, and are connected to each other. The extraction means includes a heating means for heating the soil and a processing means for detoxifying the extracted contaminants. It In the extraction means, when the vacuum pump 18 is operated, the inside of the pipe 14 is depressurized and a negative pressure is exerted in the soil 22 around the strainer 12. In addition, the strainer 1 is operated by the operation of the vacuum pump 18.
Gas and liquid are sucked from 2 but the soil 22 is cut by the strainer 12 so as not to be sucked into the pipe 14.

The heating means comprises a heating section 24 and a heating source 26, and FIG. 2 is a view showing one mode of the heating means. As shown in FIG. 2, a heater 24A is spirally wound around the outer circumference of the strainer 12 so that the stitches (mesh) of the strainer 12 are not blocked, and both ends of the heater 24A are provided on the ground surface via a cord wire 28. The heating source 26 is connected to a power supply device. As a result, when the power supply device is operated, the heater 24A is heated to heat the soil 22 around the strainer 12.

FIG. 3 is a view showing another mode of the heating means. As shown in FIG. 3, the pipe 14 and strainer 12
Is formed into a double pipe structure by the outer cylinders 12A and 14A and the inner cylinders 12B and 14B.
And form a U-shaped tubular steam passage 29. In this case, as a material for forming the strainer 12, a porous material such as porous ceramics may be processed into a double pipe structure, or a strainer 12 having a double pipe structure may be formed from a metal such as stainless steel, A large number of holes may be formed in the outer cylinder 12A and the inner cylinder 12B so as to function as the strainer 12. Then, the soil 22 around the strainer 12 is heated by supplying steam from the steam supply device, which is the heating source 26, to the steam passage 29.

As shown in FIG. 1, the processing means comprises a processing tank 30 and an exhaust pipe 32, and contaminants extracted by the vacuum pump 18 are sent to the processing tank 30 via a connecting pipe 33. In the processing tank 30, for example, the pollutants are rendered harmless by adsorbing the pollutants on activated carbon or the like or decomposing them by thermal decomposition or the like, and discharge the pollutants out of the system through the exhaust pipe 32. Next, the operation of the extraction device 10 configured as described above will be described.

When the extraction device 10 is used, an extraction well having a diameter substantially the same as that of the pipe 14 is dug from the surface to the ground in the contaminated region and the pipe 14 is placed in the extraction well, as described in the prior art. Insert with airtightness. Then, the vacuum pump 18 is operated to reduce the pressure in the pipe 14 to make the inside of the strainer negative. In parallel with this, the heating means is operated to heat the soil around the strainer 12. As a result, as shown in FIG. 1, heat is transferred from around the strainer 12 into the soil 22, and a high temperature region 34, a medium temperature region 36, and a low temperature region 38 are formed as the distance from the strainer 12 increases.

Since the soil 22 contains water, the water in the soil is evaporated by the negative pressure by the vacuum pump 18 and the heating by the heating means, and is extracted as steam into the pipe 14 through the strainer 12, As a result, the drying progresses in order from the soil 22 near the strainer 12. At this time, of the contaminants in the soil 22, those dissolved in water are extracted into the pipe 14 together with the water. By drying the soil 22, the high temperature region 34 around the strainer 12 to the low temperature region 3
The soil 22 cracks in order to 8 and becomes porous. As a result, the soil contaminants present in the soil 22 in the form of gas or liquid are easily attracted to the strainer 12 in the negative pressure state. Further, since the soil 22 becomes porous, the reaching distance of the negative pressure becomes long, so that soil contaminants located at a long distance from the periphery of the strainer 12 can also be extracted. In the case of soil pollutants existing in the gas state,
By heating and increasing the gas pressure, it moves into the pipe 14 which is a gas pressure release port.

Next, the extracted soil contaminants are treated in the treatment tank 3
When it is 0, it is rendered harmless and discharged. Thus, the method for extracting contaminants from the contaminated soil of the present invention has the following effects as compared with the conventional methods. Since the water content in the soil is likely to be extracted due to the synergistic effect of negative pressure and heating, the contaminants can be quickly extracted along with the extraction of the water content.

By extracting water in the soil, the soil is dried and becomes porous, and contaminants easily permeate through the soil. Therefore, the extraction efficiency is improved, and the porous makes it possible to reduce the reach distance of negative pressure. Being extended, one extraction well can cover a large contaminated area. As a result, the work efficiency of extraction is significantly improved. In this embodiment, as the heating means for heating the soil, the strainer 12 is heated by the heater or the steam is passed through the steam passage 29 to heat the strainer 12. However, the strainer 12 can be rotated so that the strainer 12 can be rotated. The periphery of the strainer 12 may be heated by the frictional heat between the soil and the soil.

[0018]

EXAMPLE FIG. 4 shows the construction of an experimental apparatus for experimentally confirming the effect of heating in the method for extracting contaminants from contaminated soil according to the present invention. As shown in FIG. 4, each length is 6
Three 0 mm columns A, B, and C were connected in series so as to communicate with each other. One end of the connected columns A, B, and C and the vacuum pump 18 were connected by a pipe-like conduit 40, and a mesh dish (not shown) was arranged at the other end so that air could pass through. Hereinafter, the column on the conduit 40 side is referred to as column A, the middle column as column B, and the column in which the mesh dish is arranged as column C.

Further, a vacuum gauge 42 and a valve 44 for adjusting the degree of vacuum are provided in the middle of the conduit 40 to set the degree of vacuum for extracting contaminants from the soil. As the contaminated soil used in the experiment, trichlorethylene was added to 1 kg of soil in an amount of 0.
While containing 25 mg, soil having a water content of 30.4% was densely packed in the connected columns A, B, and C. In this configuration, the right end of the column A is a strainer 1 provided at the tip of the above-mentioned pipe 14 fitted in the extraction well.
Since it can be assumed that there are two parts, column A is heater 2
The heater 24A can be heated by winding it around 4A and operating a power source (not shown). In addition, in the experiment, the vacuum condition was 10To while heating with the heater 24A.
It was sucked by the vacuum pump 18 so as to be rr for 90 minutes.

FIG. 5 shows the results of the residual rate of trichlorethylene in each of the columns A, B and C after 90 minutes and the water content in the soil at that time. The residual rate of trichlorethylene in the soil is shown by a bar graph, and the water content in the soil is shown by a line graph. As can be seen from FIG. 5, the residual rate of trichlorethylene decreased from the heated portion in a short time. That is, not only the residual amount of trichlorethylene in the soil packed in the column A where vacuum is easily reached was significantly reduced, but also the trichlorethylene in the soil of column C where vacuum was difficult to reach was significantly reduced. In addition, it was observed that the cracks in the soil became larger in the order of column A> column B> column C in which heat from the heater 24A was easily transmitted, and the state became porous.

On the other hand, although not shown in FIG. 5, when not heated by the heater 24A, the residual rate of trichlorethylene in the soil of the column A where the vacuum is easily reached is reduced to the same level as in this embodiment. However, the residual rate of trichlorethylene in the soil of column B and column C where the vacuum is hard to reach was twice as high as that of this example. Further, the degree of reduction of the water content in the soil is smaller than that of this example, and as a result, the soil hardly cracks,
It didn't become porous.

[0022]

As described above, according to the extraction method of the present invention for extracting contaminants from contaminated soil, the soil is heated to a porous state and then vacuum-extracted. As a result, a single extraction well can extract contaminants from a wide contamination area.

Therefore, since it is not necessary to drill many extraction wells, contaminants in the soil can be efficiently extracted.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an extraction device to which an extraction method for extracting contaminants from contaminated soil according to the present invention is applied.

FIG. 2 is an explanatory diagram when a heater is used as a heating means for heating soil.

FIG. 3 is an explanatory diagram when steam is used as a heating means for heating the soil.

FIG. 4 is a block diagram of an experimental apparatus for an extraction method for extracting contaminants from contaminated soil according to the present invention.

FIG. 5 is a diagram showing experimental results of an extraction method for extracting contaminants from contaminated soil according to the present invention.

[Explanation of symbols]

 10 ... Extraction device 12 ... Strainer 14 ... Pipe 16 ... Trap tank 18 ... Vacuum pump 22 ... Soil 24 ... Heating part 26 ... Heating source 30 ... Processing tank

Claims (1)

[Claims] 1. A method for extracting pollutants from polluted soil, which extracts soil pollutants existing in the form of gas or liquid in the soil, comprising a long hole drilled from the ground surface to the soil-contaminated area in the ground. A pipe for extracting contaminants having a strainer at the tip is inserted into the extraction well, and the inside of the pipe is made a negative pressure to draw in soil contaminants from the soil around the strainer and extract from the strainer into the pipe. A method for extracting contaminants from contaminated soil, characterized in that the soil around the strainer is heated when performing.