JP2005177593A - Technique for purifying soil contaminated with volatile organic compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To treat soil contaminated with a VOC at a purification yard, highly efficiently, in a short time, and at a low cost. <P>SOLUTION: The soil contaminated with the VOC is passed through a treating apparatus provided with the introduction part and the derivation part of out door air and also mounted with a plurality of conveyers by the plurality of conveyers while carrying out aeration, is repeatedly dried by air, is micronized to less than 0.1 to 4 cm or smaller, and is brought in contact with a large amount of air to accelerate gasification of the VOC contained in the soil contaminated with the VOC and reduce a VOC concentration of less than a targeted value or lower. Hot air is brought in contact with that as a counter current to a passage direction of the soil contaminated with the VOC. As pre-treatment, the soil contaminated with the VOC is passed through a volatile acceleration area constituted of a vibration screen having a passage aperture of 0.1 cm to 4 cm and an air blower, and falls while micronizing the soil contaminated with the VOC, or is subjected to reduction treatment of a moisture ratio or heat treatment at 40 to 100°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for purifying soil contaminated with a volatile organic compound (hereinafter referred to as VOC).

Conventionally, for purification of soil contaminated with VOC, various techniques are known as shown below, for example.
・ Hot soil method that mixes 100-150 kg of quicklime etc. and volatilizes VOC (for example, refer to Patent Document 1)
・ Aluminum clean method that mixes aluminum powder and alkaline agent with soil, purifies VOC by gas suction, and backfills in the field (for example, see Patent Documents 2 and 3)
・ A method of heating the soil with an electric heater and vacuuming VOCs (electric heating + vacuum suction method)
・ Method of extracting VOC as soil gas with vacuum pump (vacuum gas suction method)
・ Method of volatilizing VOC by mechanical stirring ・ Low-temperature heating method of heating VOC by external heating kiln or the like (for example, see Patent Document 4)
・ A method that mixes acid and alkali with soil and generates heat by heat of neutralization (for example, see Patent Document 5)
-Method and apparatus for removing VOC in soil that removes VOC by evaporation (see, for example, Patent Document 6)
-A method for removing VOCs in soil by aeration of muddy water obtained by mixing soil mixed with VOC and water and volatilizing the VOC from the muddy water (see, for example, Patent Document 7)
・ Decomposition method using oxidant mixture that decomposes VOC by mixing oxidants such as ozone, potassium permanganate and hydrogen peroxide ・ Microorganisms such as methane-utilizing bacteria, toluene / phenol-degrading bacteria, anaerobic microorganisms Method of disassembling VOC by the method (for example, see Patent Document 8)
A method of supplying a hydrogen donor and decomposing VOCs by the action of microorganisms (see, for example, Patent Document 9)
Japanese Patent No. 2589002 JP 2001-087410 A JP 2002-079232 A JP 2002-205050 A Japanese Patent No. 3438004 JP 2000-107741 A JP 2002-59151 A JP 2001-347280 A JP 2000-107743 A JP 2001-219155 A Japanese Patent No. 3324139 Japanese Patent No. 3269901

However, the hot-soil method increases the amount of quicklime used in order to reduce it to a predetermined concentration in a short time, so the soil after treatment becomes excessively high alkalinity, making it unsuitable for backfilling, and increasing disposal costs. In addition, there is a problem that the amount of unloading soil is large and the load on the environment is high.
In the aluminum clean method, it takes 1 to several days to suck the soil gas after heating. There is a problem that facility costs are high for small-scale soil treatment.

The electric heating + vacuum suction method has a problem that the processing speed is low and the processing cost is high in equipment that can be installed locally.
The vacuum gas suction method is difficult to purify to the environmental standard value in a short period of time. Uniform purification is difficult due to variations in the air permeability of the original ground. In the case of clay soil and soil with high adsorptivity, there are problems such as that there are places that do not fall below the environmental standard value even after several years.

The method of volatilizing VOC by mechanical agitation involves simply agitating the contaminated soil with a machine (such as a backhoe), and thus has a problem that the purification rate is slow and it cannot cope with high-concentration contamination.
The low-temperature heating method has a problem that it is applicable only at a site that requires a large amount of processing because the processing cost is high and the installation cost of the processing device is high.

In the method of generating VOCs with heat of neutralization, it is difficult to remove and separate VOCs from soil in a very short time.
In the method for removing VOC in soil, it is difficult to remove and separate VOC from soil in a very short time.
The decomposition treatment method using oxidant mixing is high in processing cost and has low removal efficiency for relatively low concentrations of contamination. Due to the high risk of the chemicals used, there is a problem that it may flow out of the target area due to improper use and may have an adverse effect on the surrounding environment due to the toxicity of the oxidizing agent itself.

In the method of removing VOC by evaporation, soil and an inorganic compound are uniformly mixed in the presence of moisture in a state where they are in sufficient contact to cause an exothermic reaction, and then the mixture heated by the exothermic reaction is subjected to VOC. This requires a process of evaporating VOCs while granulating them in a state where volatilization into the atmosphere is prevented, and is not suitable for ordinary VOC removal.
The decomposition treatment method using microorganisms requires a long period of time for purification. Microbial treatment is greatly affected by soil quality, and there are problems such as limited application locations.

  In addition, a contaminated soil pretreatment method and an apparatus for detrimental substances with low volatility such as dioxins and PCBs, and a contaminated soil detoxification treatment method are known (for example, see Patent Document 10). However, in Patent Document 9, since the soil is only dried, dioxins and PCBs adsorbed in the soil cannot be volatilized and separated. Moreover, it cannot cope with high concentration contamination. There is a problem that it cannot be applied at a site that requires a large amount of processing.

Further, a gas phase reductive decomposition method (for example, see Patent Document 11) of gasified VOC and a method for thermally oxidizing and decomposing an organic chlorine compound contained in a gas (for example, see Patent Document 12) are known. However, these are not inventions related to the purification of soil contaminated with VOCs.
The present invention has been made in order to solve such a conventional problem, and its purpose is to achieve a VOC that can be processed efficiently and in a short time at a low cost in a purification yard of soil contaminated with VOC. The purpose is to provide a method for the purification of contaminated soil.

  According to the first aspect of the present invention, the soil contaminated with VOC by the plurality of belt conveyors is allowed to pass through the processing apparatus provided with the outside air introduction section and the outlet section and provided with a plurality of belt conveyors. Repeated air drying, refined the soil contaminated with VOC to 0.1cm ~ 4cm or less, contact with a large amount of air, promote the gasification of VOC contained in the soil contaminated with VOC, the concentration of VOC Is reduced below the target value.

The invention according to claim 2 is a method for purifying soil contaminated with VOC according to claim 1,
It is characterized in that warm air is brought into contact with the passage direction and countercurrent of soil contaminated with VOC.
According to a third aspect of the present invention, in the method for purifying soil contaminated with VOC according to claim 1 or claim 2, before the soil contaminated with VOC is carried into a plurality of belt conveyors, the opening is 0.1 cm. It is characterized by passing through a volatilization promoting area constituted by a vibration sieve of ˜4 cm and a blower, and dropping soil contaminated with VOC while being subdivided.

According to a fourth aspect of the present invention, in the method for purifying soil contaminated with VOC according to any one of the first to third aspects, the water content ratio is reduced before the soil contaminated with VOC is carried into a plurality of belt conveyors. Or a process of heating the soil to 40 ° C to 100 ° C.
The invention according to claim 5 is the method for purifying soil contaminated with VOC according to any one of claims 1 to 4, wherein the VOC is a VOC having a boiling point of 150 ° C. or less at normal pressure. And

According to the present invention, the following effects can be obtained.
Purification that reduces the VOC concentration to a target value or less in a very short time can be realized.
By making the soil thickness 40 mm or less and improving the contact efficiency with the outside air, purification treatment at a heating temperature of 40 ° C. to 100 ° C. was made possible. Compared to heat treatment using an externally heated kiln that heats the soil to 200 ° C. to 800 ° C., the system configuration is simple, and initial and running costs are greatly reduced.

The soil excavated from the countermeasure area can be both transferred to the treated soil temporary storage yard and purified, saving labor greatly and enabling continuous treatment of contaminated soil.
Since the contaminated soil is treated in a treatment device sealed at or near the excavation site, the work environment is good, the outside air diffusion due to the movement and treatment of contaminants is suppressed to the maximum, and the burden on the environment is reduced. small.

The treated soil is well agitated and homogenized by the treatment. Furthermore, the purification status can be checked in the temporary storage yard, and reliable purification can be realized.
The purification system has a simple configuration according to the purification object and the purification target value, so that the apparatus cost is reduced and the processing cost is low.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
First, the processing apparatus 1 used for the purification method of the soil (henceforth contaminated soil) contaminated with VOC which concerns on this embodiment is demonstrated.
The processing apparatus 1 includes a plurality of belt conveyors 5 therein, and includes a tunnel-shaped processing unit 2 having an outside air introduction unit 3 and a lead-out unit 4 at both ends. The processing unit 2 is surrounded by a wall member on a floor member via a framework except for the outside air introduction unit 3 and the outlet unit 4 provided at both ends. In addition, in order to arrange | position the many belt conveyors 5 according to the object process soil, the tunnel-shaped process part 2 may be made to be able to arrange the belt conveyors 5 in a meandering manner.

  In the plurality of belt conveyors 5, only the first belt conveyor 5 a on the outside air deriving unit 4 side of the processing unit 2 is horizontally disposed, and the remaining belt conveyors 5 are configured to remove contaminated soil during delivery to the next belt conveyor 5. It is inclined at a predetermined angle so that it can be dropped. If necessary, the arrangement of the belt conveyor 5 is not limited to a linear arrangement, and may be meandering.

A hopper 7 for taking in contaminated soil is provided in the upper part of the room 6 where the first belt conveyor 5a is arranged. The room 6 also serves as the outside air deriving unit 4.
Further, a passage 8 communicating with the blower 9 is provided at the side or the lower portion of the room 6. The blower 9 communicates with an air purification chamber 11 containing activated carbon through a passage 10.
A belt conveyor 13 that conveys the treated soil to the yard 12 where the treated soil is temporarily placed is disposed at the subsequent stage of the last belt conveyor 5b of the processing unit 2.

Next, the contaminated soil purification method according to this embodiment will be described.
First, the blower 9 is driven to introduce outside air into the processing unit 2.
Next, the countermeasure area 14 where the contaminated soil exists is excavated, and the contaminated soil is put into the processing apparatus 1 from the hopper 7.
Next, after the received contaminated soil is received by the first belt conveyor 5a, it is dropped to the next belt conveyor 5, and then dropped and transferred to a plurality of successive belt conveyors 5 repeatedly. receive. At the time of the fall in each delivery, it is contacted with the passing direction of the contaminated soil and the outside air ventilated in a countercurrent, and is dried and subdivided. In this delivery, the contaminated soil is refined to 0.1 cm to 4 cm or less, and by contacting with a large amount of air, the VOC adsorbed in the contaminated soil and the contaminated soil is gasified, and the VOC concentration is the target value (soil environmental standard or Reduce to below the final disposal site acceptance standard value). The gasified VOC is sucked by the blower 9 and adsorbed on the activated carbon in the air purification chamber 11.

Next, the treated soil having a VOC concentration equal to or lower than the target value is conveyed from the final belt conveyor 5 of the processing apparatus 1 to the yard 12 where the treated soil is temporarily placed by the belt conveyor 13.
Next, the treated soil temporarily placed in the yard 12 is disposed of by backfilling or carrying out of the field after confirmation of purification.
As described above, according to the present embodiment, the contaminated soil is agitated and subdivided when the contaminated soil is dropped between the plurality of belt conveyors 5 at the delivery stage, and when the falling, by the ventilation in the processing apparatus 1 Since the contaminated soil is dried and VOCs adsorbed in and in the contaminated soil are easily gasified, the VOC concentration of the contaminated soil can be purified to a target value or less in a short time.

(Second embodiment)
This embodiment is different from the VOC purification method according to the first embodiment in that hot air is blown against the contaminated soil conveyed by the plurality of belt conveyors 5.
FIG. 2 shows a processing apparatus 1A used in this embodiment. In this processing apparatus 1 </ b> A, a hot air generator 15 is provided to blow hot air against the contaminated soil conveyed by the plurality of belt conveyors 5. Other configurations are the same as those of the processing apparatus 1 shown in FIG.

  The hot air generator 15 warms the air by heating due to heat generated from a chemical reaction, microwave heating, heating by an electric heater, heating by fuel such as kerosene, gas, etc., blows hot air by a fan, and blows contaminated soil at 40 ° C. to 100 ° C. It is a device that can be heated. Since the hot air generator 15 sucks the air in the processing apparatus 1A and heats it, the atmospheric temperature in the processing apparatus 1A also increases, and the contaminated soil can be easily heated.

Therefore, according to the present embodiment, when the contaminated soil is transported by the plurality of belt conveyors 5, hot air contacts with the outside air in the direction and countercurrent of the contaminated soil, and gasification of VOCs adsorbed in the contaminated soil and the contaminated soil is obtained. Can be promoted.
In the present embodiment, the hot air generator 15 is provided at a rate of one for the two belt conveyors 5, but the present invention is not limited to this and may be provided individually. Further, hot air may be blown from the outside air introduction unit 3 side toward the derivation unit 4 in order to increase the ambient temperature in the processing unit 2.

(Third embodiment)
This embodiment is different from the VOC purification method according to the first embodiment in that a vibrating screen 16 is provided at the input portion of the contaminated soil.
FIG. 3 shows a processing apparatus 1B used in this embodiment. In the processing apparatus 1B, a vibrating screen 16 is provided in a room 6 in which the first belt conveyor 5a is disposed. The vibration sieve 16 includes a hopper 17 and a plurality of nets 18 having an opening of 0.1 cm to 4 cm, for example.

  An intake port 19 for supplying hot air is provided on the lower side of the vibration sieve 16. The intake port 19 is provided with a hot air generator similar to that of the second embodiment. Since the VOC gas enters the room 6 as the contaminated soil is heated, the room 6 is enclosed by a sheet 20 or the like, and after the VOC gas is sucked by the blower 9 and purified in the air purification chamber 11 containing activated carbon. , Is supposed to exhaust.

According to this embodiment, before processing by the plurality of belt conveyors 5 in the processing apparatus 1C, the contaminated soil can be subdivided and dropped, and the VCO adsorbed in the contaminated soil and the contaminated soil by hot air can be gasified. Therefore, since the VCO adsorbed in the contaminated soil and the contaminated soil can be easily gasified, the purification degree can be improved.
In addition, although this embodiment demonstrated the case where a hot air generator was provided in the lower part of the vibration sieve 16, this invention is not restricted to this, It is also possible to process only with the vibration sieve 16. FIG.

(Fourth embodiment)
In the present embodiment, before the contaminated soil is treated in the first to fourth embodiments, for example, cement, quicklime, dry sand, and the like are mixed in order to reduce the moisture content.
Table 1 shows the necessity of moisture content adjustment.
In the present embodiment, adjustment is performed so that VOC can be efficiently removed according to the water content ratio of the contaminated soil, so that VOC can be removed in a short time.

In Table 1, the determination of whether the moisture content is high or low is based on the assumption that the moisture content is 22 or higher (the moisture content adjustment is necessary), and below that the moisture content is low (the moisture content adjustment is unnecessary).
(Fifth embodiment)
In this embodiment, Table 2 shows the selection of the purification method for each substance to be purified to which the first to fourth embodiments are applied.

In Table 2, “1” indicates a processing method according to the first embodiment. “2” indicates a processing method according to the second embodiment. “3” indicates a processing method according to the third embodiment. “4” indicates a processing method in which the processing method according to the fourth embodiment is applied to the processing method according to the third embodiment.
(Sixth embodiment)
In this embodiment, it was confirmed that it is desirable to crush the contaminated soil with an opening of the vibrating screen of 4 cm or less.

The present invention achieves purification in a short time by adjusting the conditions for promoting the volatilization of VOC contained in the soil. In the contact between the outside air and the soil for volatilizing the VOC, it is necessary to reduce the size of the soil.
The calculation result at the time of heating the upper layer of a sand layer with 50 degreeC warm air is shown. When the soil is heated with warm air, heat is transferred from the surface to the inside of the soil layer. In order to promote the purification effect, it is necessary to raise the temperature by 10 ° C. or more. Therefore, it can be judged that the soil thickness is effective up to 2 cm from the graph shown in FIG.

Heat is supplied from the top and bottom of the soil by refining the soil and stirring it with a belt conveyor. Therefore, the size of the soil is suitably 4 cm or less, which is twice 2 cm.
6 and 7 show the examination results of the soil thickness effective for heating.
Calculation of the rate of increase in soil temperature when the upper layer of the 5 cm sand layer was 50 ° C. revealed that the soil thickness was required to be 2 cm or less.

In this example, purification treatment of sandy soil contaminated with trichlorethylene and tetrachlorethylene was performed.
<conditions>
・ Target soil: Sandy soil, moisture content 17%, treated soil amount 180L (300kg)
-Pollutants: Trichlorethylene (TCE), Tetrachlorethylene (PCE)
-Purification method: The contaminated soil was treated by the method (1) or (2), and the purification effect was confirmed.

-A soil thickness of 4 cm was passed through a plurality of belt conveyors arranged in the tunnel-shaped processing section shown in the above embodiments.
The experimental conditions are as shown in Table 3.
The experimental results are as shown in Tables 4 and 5.
In the experimental results, Control 1 shows a case of 60 minutes left at 20 ° C. (1 kg of soil as a lump), and Control 2 shows a case of 60 minutes left at 50 ° C. (1 kg of soil as a lump).

<Discussion>
About method (1):
By passing the contaminated soil, which is about three times the environmental standard value, through a belt conveyor in a tunnel-shaped treatment section ventilated at 20 ° C, 73% of TCE and 70% of PCE are separated from the soil in just 2 minutes. It was below the environmental standard value.

On the other hand, as a control, the concentration of both TCE and PCE hardly decreased even when left as a lump at 20 ° C. for 60 minutes.
From the above, the removal rate in the method (1) is about 70 to 74%, and it was possible to purify the concentration 3 to 4 times the target value.
About method (2):
By setting the inside of the tunnel-like treatment part to 50 ° C with a hot air generator, the contaminated soil, which is about 6 to 7 times the environmental standard value, is passed through the belt conveyor in the tunnel-like treatment part, so that the soil is only about 2 minutes. Furthermore, 89% was separated by TCE and 87% by PCE, and the environmental standard value or less was set.

On the other hand, as a control, the removal rate of 1 kg at 50 ° C. for 60 minutes remains at a removal rate of 23% for TCE and 17% for PCE, and the effect of passing through the tunnel-like treatment part is obvious.
From the above, the removal rate in the method (2) is about 87 to 89%, and the concentration 7 to 8 times the target value could be purified.

In this example, a purification treatment of clay mixed with sand contaminated with trichlorethylene and tetrachlorethylene was performed.
<conditions>
-Target soil: sand-mixed clay, water content 19%, treated soil volume 2m ³
-Pollutants: Trichlorethylene (TCE), Tetrachlorethylene (PCE)
-Purification method: The contaminated soil was treated by the method (3), and the purification effect was confirmed.

-As a pretreatment, quick lime was added at 75 kg / m ³ to reduce the moisture content of the soil, and then the soil was warmed.
・ After curing for 2 to 3 hours after mixing, a vibration sieve was applied to pass through a belt conveyor in the tunnel-shaped processing section for purification. The opening of the vibrating screen was 4 cm or less.
Experimental conditions are as shown in Table 6.

The experimental results are as shown in Table 7.
<Discussion>
Contaminated soil that is 10 to 30 times the environmental standard value is mixed with quick lime in advance to reduce the moisture content and make it easier to refine, heat it to close to 60 ° C, and then pass through a vibrating sieve and flue belcon. By doing so, TCE and PCE were separated from the soil in only about 2 minutes, and the environmental standard value or less was achieved.

  In the method (3) for adjusting the moisture content ratio of soil, the removal rate is improved and stable treatment is possible as compared with the methods (1) and (2) in which the pretreatment is not performed.

In this example, purification treatment of high water content silt contaminated with tetrachloroethylene and trichlorethylene was performed.
<conditions>
-Target soil: sand-mixed clay, moisture content 22-27%, treated soil volume 1m ³
-Pollutants: Trichlorethylene (TCE), Tetrachlorethylene (PCE)
・ As a pretreatment, quick lime was added at ³⁰ , 50, 75, 100 kg / m ³ to reduce the moisture content of the soil and warm the soil.

・ After mixing for 2 to 3 hours after mixing, contact with the outside air with a blower, pass through a vibrating screen while promoting soil separation by volatilization, and treat the subsequent soil as treated soil to determine the moisture content and VOC elution concentration. It was measured.
Passing time 1 minute <Result>
-Shown in Table 8.

As shown in Table 8, the initial density was stratified and compared at 10 times or less and 10 times or more of the reference value. In the above initial concentration range, the VOC removal rate by the pretreatment was determined by the water content after the treatment and the temperature at the time of heating, and the influence of the initial concentration was small.
Therefore, the results in Table 8 were summarized, and the water content after the treatment and the VOC removal rate against the temperature at the time of warming were plotted, and are shown in FIGS.

A removal rate of 90% or more is required to make a contaminated soil whose initial concentration is 10 times or more the reference value as the environmental reference value. When the initial concentration is high, by sufficiently reducing the concentration in the pretreatment, it is possible to completely and reliably purify the environmental standard value or less by the next belt conveyor processing.
Therefore, it is reasonable to set the target values for pretreatment of high moisture content silt contaminated soil separately depending on the initial level of contamination. Table 9 shows the target values when adjusting the moisture content by mixing quick lime with high moisture content silty contaminated soil.

  As described above, as a method for treating silty soil with a high water content in a short time and reliably, pretreatment of mixing quick lime shown in Table 8 is performed to adjust the water content suitable for purification. Thereafter, as shown in the third embodiment, vibration sieve → belt conveyor processing is performed, and the VOC component can be gasified and separated to be processed to a reference value or less.

In this example, purification treatment of silt contaminated with trichlorethylene and tetrachloroethylene was performed.
<conditions>
-Target soil: sand-mixed clay, moisture content 27% (first experiment), 22.5% (second experiment), treated soil volume 2m ³
-Pollutants: Trichlorethylene (TCE), Tetrachlorethylene (PCE)
-Purification method: The contaminated soil was treated by the method (4) to confirm the purification effect.

・ As a pretreatment, quick lime was added at 75 kg / m ³ to reduce the moisture content of the soil, and then the soil was warmed.
・ After curing for 2 to 3 hours after mixing, a vibration sieve was applied to pass through a belt conveyor in the tunnel-shaped processing section for purification. The opening of the vibrating screen was 4 cm or less.
Experimental conditions are as shown in Table 10.

  The experimental results are as shown in Table 11.

<Discussion>
Contaminated soil that is about 10 times the environmental standard value is mixed with quick lime in advance to reduce the water content and make it finer, and heat it to about 50 ° C. By passing through the conveyor, TCE and PCE were separated from the soil in just about 2 minutes, and the environmental standard value was reached.

  Since the soil quality is different from that of Example 2, the moisture content of the treated soil is slightly high, but an almost equivalent removal rate can be expected.

It is explanatory drawing which shows the purification method of VOC which concerns on 1st embodiment of this invention. It is explanatory drawing which shows the purification construction method of VOC which concerns on 2nd embodiment of this invention. It is explanatory drawing which shows the purification method of VOC which concerns on 3rd embodiment of this invention. It is explanatory drawing for examination of the soil thickness effective for a heating. It is a figure which shows the relationship between the soil temperature rise based on FIG. 4, and contact time. It is a figure which shows the relationship between the soil temperature rise based on FIG. 4, and soil thickness. It is a figure which shows the relationship between the last time moisture content in Example 3, and a VOC removal rate. It is a figure which shows the relationship between the soil warming temperature in Example 3, and a VOC removal rate.

Explanation of symbols

1, 1A, 1B, 1C Processing device 2 Processing unit 3 Introducing unit 4 Deriving unit 5, 13 Belt conveyor 6 Room 7, 17 Hopper 8, 10 Passage 9 Blower 11 Air purification chamber 12 Yard 14 for temporarily placing processing soil 14 Countermeasure area 15 Hot Air Generator 16 Vibrating Sieve 18 Net 19 Intake Port 20 Sheet

Claims (5)

  Inside the processing apparatus having a plurality of belt conveyors with an outside air introduction part and a lead-out part, passing the soil contaminated with volatile organic compounds by the plurality of belt conveyors while ventilating, repeated air drying, The soil is refined to 0.1 cm to 4 cm or less, brought into contact with a large amount of air, promotes gasification of the volatile organic compound contained in the soil, and the concentration of the volatile organic compound is reduced to a target value or less. A method for purifying soil contaminated with volatile organic compounds, characterized by reducing it.   2. A method for purifying soil contaminated with a volatile organic compound according to claim 1, wherein warm air is brought into contact with the direction of passage of the soil and countercurrent to the soil. Method.   In the purification method of the soil contaminated with the volatile organic compound according to claim 1 or 2, before the soil is carried into the plurality of belt conveyors, a vibrating screen having an opening of 0.1 cm to 4 cm and a blower are used. A method for purifying soil contaminated with a volatile organic compound, which comprises passing through a configured volatilization promoting region and dropping the soil while being subdivided.   In the purification method of the soil contaminated with the volatile organic compound according to any one of claims 1 to 3, before the soil is carried into the plurality of belt conveyors, the moisture content is reduced or the soil is subjected to 40 ° C. A method for purifying soil contaminated with volatile organic compounds, characterized by performing a treatment of heating to -100 ° C.   5. The method for purifying soil contaminated with the volatile organic compound according to claim 1, wherein the volatile organic compound is a volatile organic substance having a boiling point of 150 ° C. or less at normal pressure. A method for the purification of soil contaminated with volatile organic compounds.

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