JPH08173947A - Method and device for purifying soil - Google Patents

Abstract

PURPOSE: To effectively remove even contaminants existing in the area at a long distance from an extracting well. CONSTITUTION: A high pressure air is injected by a compressor 24 into an underground contaminated area 11 through a suction pipe 12 provided for an extracting well 10, and thereby producing fissures 26 in the soil is generated. Upon occurrence of the fissures 26, the interior pressure of the extracting well 10 is reduced to atmospheric pressure, the interior of the extracting well 10 is thereafter sucked into a negative pressure by a vacuum pump 30 and the gas streams as shown by the arrows 40 are thus produced in the soil, whereby the contaminated gas in the soil is sucked out for removal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soil purification method for removing pollutants in soil, and more particularly to a soil purification method and device for sucking and removing volatile pollutants existing in the ground.

[0002]

2. Description of the Related Art At present, many factories use volatile organic chlorine compounds such as trichloroethylene, tetrachloroethylene, and 1,1,1-trichlororetylene as cleaning agents. Then, factory wastes containing these compounds may leak and penetrate into the ground to contaminate soil and groundwater. Therefore, it has been attempted to purify the soil by removing volatile organic chlorine compounds present in the soil.

The pollutants in the soil composed of volatile organic chlorine compounds are present in the soil or groundwater in the liquid phase or the gas phase, that is, in the unsaturated zone or the saturated zone. Therefore, conventionally, a vacuum extraction method has been adopted as a method for removing the contaminants composed of such a volatile organic chlorine compound. In this vacuum extraction method, an extraction well is drilled from the surface of the ground to a contaminated area in the ground, a suction pipe for gas extraction is placed in this well, and the inside of the suction pipe is sucked by a vacuum pump placed above the ground to create a negative pressure. Then, the pollutant (contaminant gas) in the soil is removed by suction. And, JP-A-3-2
In Japanese Patent No. 02586, it is proposed that a plurality of air introduction wells are drilled around the extraction well to promote the flow of air in the soil and facilitate the suction of pollutants.

[0004]

However, in the method of providing the air introducing well described in the above publication, since the air introducing well is opened to the atmosphere, air is sucked into the ground through the suction pipe. Since the air easily flows into the ground from the introduction well, the influence radius of the extraction well (the negative pressure reach distance from the extraction well) is only up to the air introduction well, and pollutants in the area far from the extraction well are effective. There is a problem that it cannot be sucked and removed. Moreover, since it is necessary to drill a plurality of air introduction wells around the extraction well, it takes a lot of time and cost, and the purification cost becomes high.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and provides a soil purification method and apparatus capable of effectively removing pollutants in a region far from an extraction well. It is an object.

[0006]

In order to achieve the above-mentioned object, the soil purification method according to the present invention forms an extraction well reaching the contaminated region in the ground from the surface of the earth, and through this extraction well In the soil purification method of sucking and removing pollutants, a space communicating with the lower suction port of the extraction well, through which at least gas can pass, is formed in the ground to expand the reach range of suction negative pressure. At least the space through which the gas can pass may be formed by injecting a high-pressure fluid into the ground through an extraction well, or another physical method, or a mechanical method such as an excavator, or even a scientific method. You may form by a conventional method. Further, it is desirable that at least the space through which the gas can pass is formed in the horizontal direction. As the high-pressure fluid, high-pressure air, high-pressure water or the like can be used.

Further, the soil purifying apparatus according to the present invention comprises a fluid injecting means for injecting a high-pressure fluid into the ground through an extraction well which communicates the ground surface with the contaminated region to generate a crack in the ground,
The suction means for sucking the pollutants by applying a negative pressure to the ground through the extraction well and the purifying means for separating or decomposing the pollutants from the gas sucked by the suction means are provided.

[0008]

According to the present invention constructed as described above, the space for at least gas passage is formed in the ground by communicating with the lower suction port of the extraction well to which the suction pump is connected, so that there is almost no pressure loss. Negative pressure can be transmitted to the tip of the space. Therefore, if at least a space through which gas can pass is formed farther from the extraction well, the suction negative pressure can reach a very large distance, and pollutants in a region far from the extraction well can be efficiently removed. Can be aspirated and removed. In particular, if at least a space through which gas can pass is formed in the horizontal direction, the projected area of the space on the ground surface becomes large, and the suction and removal range of contaminants can be greatly expanded. Then, when high-pressure fluid is injected into the ground through the extraction well, high pressure acts on the soil around the extraction well to cause cracks in the ground, so that at least a space through which gas can pass is easily formed at low cost. be able to.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the soil remediation method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG.
FIG. 3 is an explanatory diagram of a soil purification device according to an example of the present invention.

In FIG. 1, an extraction well 10 is excavated from the surface of the ground to a contaminated region 11 in the ground, and a suction pipe 12 is embedded inside. The suction pipe 12 has a suction opening 14 at the lower end, and a strainer 16 is arranged at the suction opening 14, so that when the inside of the pipe 12 is sucked, the soil around the pipe is It does not flow into the pipe. Further, a sealing plug 18 is attached to the upper end of the suction pipe 12, and an injection pipe 20 and a suction pipe 22 are connected to the plug 18.

A compressor 24, which is an injection means, is connected to the injection pipe 20, and by driving the compressor 24, the injection pipe 20, the suction pipe 12,
High-pressure compressed air is applied to the underground contamination area 11 through the strainer 16 so that cracks 26 can be generated in the ground. On the other hand, the suction tank 22 is connected to the suction pipe 22.
A vacuum pump 30 as a suction means is connected via 8 to suck gas components in the soil through the suction pipe 12 and the strainer 16. A processing tank 32, which is a purifying unit, is connected to the discharge side of the vacuum pump 30 so that the polluted gas composed of a volatile organic chlorine-based compound can be removed from the gas discharged by the vacuum pump 30. Further, in the processing tank 32,
The exhaust pipe 34 is connected, and the purified gas is sent to the exhaust pipe 3
It is designed to be released into the atmosphere via 4.

In the embodiment constructed as described above,
First, the extraction well 10 is excavated from the ground surface toward the contaminated region 11, and when the lower end of the extraction well 10 reaches the contaminated region 11, the pipe 12 is embedded in the extraction well 10. And
The strainer 1 is attached to the lower end suction port 14 of the suction pipe 12.
6 is arranged, and a sealing plug 18 is provided on the upper end of the suction pipe.
Is attached to connect the injection pipe 20 and the suction pipe 22. Then, the compressor 24 is driven to drive the suction pipe 1.
2. Inject high-pressure air into the contaminated area 11 in the ground via the strainer 16. The high-pressure air injected into the polluted area 11 exerts pressure on the soil in the polluted area 11, and the strainer 1
A large number of cracks 26, which are spaces centering on the portion 6 and communicating with the suction port 14 and through which gas can pass, are generated.

When the crack 26 is generated in the soil in this way, the inside of the extraction well 10, that is, the inside of the suction pipe 12 is depressurized to the atmospheric pressure, and then the vacuum pump 30.
To suck air in the extraction well 10 through the suction tank 28, the suction pipe 22, and the suction pipe 12 to make the inside of the extraction well 10 negative pressure. This negative pressure is strainer 16
To act on the contaminated soil in the surroundings to create a negative pressure in the crack 26 and generate a gas flow 40 in the soil as shown by the solid line.

The volatile organochlorine compound existing in the contaminated region 11 becomes a gas (contaminant gas), rides on the gas flow 40, and is sucked into the extraction well 10 through the crack 26. Further, the groundwater in which the pollutants are dissolved flows toward the suction pipe 12 due to the flow of the gas, is vaporized by the action of the negative pressure, and becomes gas to flow into the extraction well 10. At this time, the soil around the extraction well 10 is prevented from flowing into the extraction well 10 by the strainer 16. Then, the gas containing the contaminated gas flowing into the extraction well 10 is sucked into the suction pipe 2
2, processing tank 3 through suction tank 28 and vacuum pump 30
Inflow to 2. The gas flowing into the processing tank 32 is released into the atmosphere through the exhaust pipe 34 after the polluted gas component is adsorbed and removed by the activated carbon in the processing tank 32 to be purified.

As described above, in the embodiment, since the crack 26 communicating with the suction port 14 of the extraction well 10 is formed in the ground, the crack 26 located far from the extraction well 10 is formed.
The suction negative pressure can be transmitted to the tip of the crack 26 with a small pressure loss, and the degree of vacuum at the tip of the crack 26 can be made approximately the same as the inside of the extraction well 10. ) Can be greatly expanded. Therefore, it is possible to efficiently suck and remove pollutants existing at a distance from the extraction well 10.

That is, when the cracks 26 are not provided in the ground, the suction negative pressure generated by the vacuum pump 30 is conventionally the extraction well 10 as shown by the one-dot chain line 42 in FIG.
However, by forming the crack 26 as in the embodiment, the reach range of the negative pressure is greatly expanded as shown by the solid line 40, and a wide range of soil is purified. It becomes possible. Then, from the fact that a wide range of soil can be purified, it is possible to reduce the number of excavation wells 10 to be excavated to purify the soil.
The cost required for soil purification can be significantly reduced.

Although the case where the pollutant gas is adsorbed and removed has been described in the above embodiment, the pollutant gas may be decomposed by a method such as thermal decomposition. Further, in the above-described embodiment, the case where the compressor 24 injects high pressure air into the ground to generate the crack 26, but the air in the cylinder filled with the compressed air may be injected. The operation of pressurizing the soil (injecting high-pressure air) and depressurizing it to generate the crack 26 may be repeated a plurality of times. In addition, as long as there is no problem with the surrounding environment, an inert gas such as nitrogen or carbon dioxide may be used as a gas for injection, and if there is no influence of a high-pressure liquid such as water or secondary pollution. Other liquids may be used. In addition, in the above-mentioned embodiment, the case where at least a space through which high-pressure air can be injected to form a gas (crack) is formed has been described. However, for example, the inside of a well is blasted to generate a crack, Other physical methods such as softening the soil by blasting and removing the soil from the ground, or mechanical methods such as inserting a manipulator from the ground deep into the well and horizontally excavating the inside of the well to expand the space. Alternatively, a space may be formed by a chemical method such as putting a solvent, a solvent, or the like in a well, making a deep soil into a slurry and sucking it up above the ground with a pump, and creating a space under the ground.

2 to 4 show another embodiment of a space formed in the ground at least for allowing gas to pass therethrough. In the embodiment shown in FIG. 2, a plurality of spaces (holes) 50 are formed radially around the extraction well 10. To form the space 50, first, the extraction well 10 is excavated until it reaches the contaminated region 11. And the extraction well 1
When 0 reaches the contaminated area 11, four holes (spaces) 50 are radially formed in the soil from the bottom of the extraction well 10 in parallel with the ground surface 52, that is, in the horizontal direction by a mechanical or physical method using an excavator or the like. Form. Since the space 50 formed in this way communicates with the extraction well 10, the negative pressure in the extraction well 10 acts up to the tip of the space 50 with almost no pressure loss. Therefore, the vacuum degree can be made substantially the same over the entire area of the radially formed space 50, and a wide range of contaminants can be sucked and removed. In the embodiment shown in FIG. 2, the case where the four spaces 50 are formed has been described, but the number of the spaces 50 radially formed may be any number.

FIG. 3 shows a disk-shaped space 54 formed parallel to the surface of the earth with the lower end of the extraction well 10 as the center. Further, FIG. 4 shows that a spherical space 5 is provided under the extraction well 10.
6 is formed. These spaces 54, 56 also
It can be formed in the same manner as the space 50 in FIG.

[0020]

As described above, according to the present invention, since at least a space through which gas can pass is formed in the ground by communicating with the lower suction port of the extraction well to which the suction pump is connected, almost no pressure is applied. Since the negative pressure can be transmitted to the tip of the space without causing a loss, the contaminants in the region far from the extraction well can be efficiently sucked and removed. In particular, if at least a space through which gas can pass is formed in the horizontal direction, the projected area of the space on the ground surface becomes large, and the suction and removal range of contaminants can be greatly expanded. Then, when high-pressure fluid is injected into the ground through the extraction well, the high pressure acts on the soil around the extraction well to cause cracks in the ground, so at least a space through which gas can pass is easily formed at low cost. can do.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a soil purifying apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an embodiment in which a space through which a gas can pass is radially formed.

FIG. 3 is an explanatory diagram of an embodiment in which a space through which gas can pass is formed in a disk shape.

FIG. 4 is an explanatory diagram of an embodiment in which a space through which gas can pass is formed into a spherical shape.

[Explanation of symbols]

 10 Extraction Well 12 Suction Pipe 14 Suction Port 24 Compressor 26 Space (Crack) 30 Vacuum Pump 32 Processing Tank 50, 54, 56 Space

Claims (4)

[Claims] 1. In a soil purification method of forming an extraction well from the surface to reach a contaminated area in the ground, and sucking and removing underground pollutants through the extraction well, the extraction well is connected to a lower suction port of the extraction well. A soil purification method characterized by forming a space through which at least gas can pass in the ground to expand the reach of suction negative pressure. 2. The soil purification method according to claim 1, wherein the space through which at least gas can pass is formed in a horizontal direction. 3. The soil purification method according to claim 1, wherein the space through which at least the gas can pass is formed by injecting a high-pressure fluid into the ground through the extraction well. 4. A fluid injecting means for injecting a high-pressure fluid into the ground through an extraction well that connects the surface of the ground and a contaminated region to generate a crack in the ground, and a negative pressure in the ground through the extraction well. And a cleaning means for separating or decomposing the pollutant from the gas sucked by the suction means.