JPH09192531A - Cleaning method of polluted soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently clean a soil polluted by petroleum and sea water and separate and recover an oil or a salt by shredding the polluted soil, then lowering its viscosity by heat, mixing and stirring it with kerosene, dissolving the petroleum to separate it, and extracting a cleaning water after mixing and stirring the cleaning water to dehydrate the soil. SOLUTION: A soil polluted by petroleum and sea water is shredded to the specified grain diameter or less using a shredding tank 2 having a heat source S, and the shredded soil is heated to 50-100 deg.C so that it is of such a low viscosity as enabling it to be transported by pump. Next, kerosene is mixed and stirred while heating it to 50-100 deg.C, using a treating tank 40 having a mixing and stirring means and the thermal source S. After that, the petroleum contained in the feedstock soil is dissolved into the kerosene and is kept still to separate and extract the kerosene. Further, the salt is dissolved in a cleaning water and is kept still, so that it is separated and the cleaning water containing the salt is extracted. In addition, the feedstock soil cleaned with hot water using the treating tank 40 having a centrifugal dehydrating means is dehydrated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying contaminated soil, and more specifically, it enables efficient purification of soil contaminated with petroleum such as crude oil and heavy oil and seawater, and also contaminated soil. The present invention relates to a method for cleaning contaminated soil in which oil and salt are separately separated and recovered.

[0002]

2. Description of the Related Art Conventionally, the treatment of soil near the coast contaminated with spilled crude oil due to an oil field or tanker accident, or soil contaminated with oil and seawater for fire extinguishing due to a fire in a refinery, should be done with the best possible oil. However, in the end, it depends on the evaporation of the volatile components and the weathering of the residuals, so the volatile components diffuse into the atmosphere and cause air pollution. There was an inconvenience, such as requiring years.

[0003]

In recent years, as a purification method for hydrocarbon-contaminated soil, a bio-remedication method utilizing microorganisms having a decomposition function for hydrocarbons has been rapidly developed. However, in such a bioreduction method, the hydrocarbon decomposition rate of the microorganism is slow, and a high concentration of salt is harmful to the microorganism. Therefore, in the case of cleaning the contaminated soil as described above, if the bioreduction method is applied after removing the petroleum and salt by a simple operation in advance, it is possible to more efficiently clean the contaminated soil. is there.

The present invention has been made as a result of various studies from the above viewpoints, and an object thereof is to enable efficient purification of soil contaminated by petroleum such as crude oil and heavy oil and seawater, and further An object of the present invention is to provide a method for purifying contaminated soil, which can separate and recover oil and salt from soil separately.

[0005]

That is, the gist of the present invention is to purify soil contaminated with petroleum such as crude oil and heavy oil and seawater by the following steps (A) to (D). It lies in the method of cleaning contaminated soil. (A) The viscosity of the raw material soil is pumped by using a crushing tank equipped with a heating means to crush the raw material soil containing petroleum and seawater into particles having a predetermined particle size or less and heating to 50 to 100 ° C. A crushing process that reduces the viscosity to a possible level. (B) Using a treatment tank as a washing tank provided with a mixing and stirring means and a heating means, and mixing and stirring the raw material soil treated in the crushing step and kerosene as a solvent while heating to 50 to 100 ° C After dissolving petroleum in the raw material soil with kerosene, the kerosene washing step is performed by allowing the petroleum-containing kerosene layer and the raw material soil layer to be separated by standing and then extracting the separated kerosene containing petroleum. (C) By using a treatment tank as a cleaning tank equipped with a mixing and stirring means and a heating means, and mixing and stirring the raw material soil treated in the kerosene cleaning step with the cleaning water at 50 to 100 ° C., A warm water washing step in which the salt in the raw material soil is dissolved in the wash water and then allowed to stand to separate into a wash water layer containing the salt and the raw material soil layer, and then the separated wash water containing the salt is extracted. (D) A dehydration step of using a treatment tank as a dehydration tank provided with a centrifugal dehydration means to dehydrate the raw material soil treated in the warm water washing step.

Further, in the above method, in order to further reduce the processing cost, one processing tank provided with a mixing and stirring means, a heating means and a centrifugal dehydration means is used as a cleaning tank and a dehydration tank to wash kerosene. It is preferable to perform the step, the warm water washing step and the dehydration step.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method for purifying contaminated soil according to the present invention will be described with reference to the drawings. FIG. 1 is a system diagram showing an example of a treatment process by the method for purifying contaminated soil according to the present invention. Hereinafter, the method for cleaning contaminated soil will be abbreviated as “cleaning method”.

The purification method of the present invention is a method for purifying soil contaminated with petroleum such as crude oil and heavy oil and seawater, and comprises a crushing step, a kerosene washing step, a hot water washing step and a dehydration step described below. Includes 4 steps. Examples of the contaminated soil include soil contaminated with crude oil (hereinafter, referred to as petroleum) and spilled seawater due to an accident in an oil field on the coast.

(A) Crushing step: In the crushing step, a crushing tank (2) equipped with a heating means is used to crush the raw material soil containing petroleum and seawater into particles having a predetermined particle size or less and 50 By heating to ~ 100 ° C, the viscosity of the raw material soil is reduced to a viscosity that allows pumping.

The general composition of the raw material soil is, for example, 1
When 00 is set, it is as follows.

[0011]

[Table 1] Petroleum content: 20-40% by weight Salt content: 9-14% by weight Moisture content: 3% by weight Soil: 68-43% by weight

Since the above-mentioned raw material soil has low fluidity,
First, it is collected in a soil pit (1) which is a storage facility using a dump truck or the like. Then, using a carrying-in means (11) such as a shovel loader, the soil pit (1) is put into the crushing tank (2). The crushing tank (2) has a hopper shape, and a rotary crusher is attached to the bottom thereof.
Further, the crushing tank (2) is provided with a jacket (heating means), and is configured to be heated by using a heat source (S) such as steam or hot water.

In the crushing tank (2), it is necessary to crush the input raw material soil into, for example, 10 mm or less in order to enhance the extraction effect of oil and salt and to enable pumping. At the same time, in order to further increase the fluidity, the raw material soil is preheated to 65 to 75 ° C. to reduce its viscosity. In the crushing step, kerosene in the kerosene tank (3) is injected into the crushing tank (2) through the pipe line (31) to adjust the viscosity of the raw material soil, if necessary.

(B) Kerosene washing step: In the kerosene washing step, the treatment tank (40) of the washing machine (4) as a washing tank provided with a mixing and stirring means and a heating means is used, and the above crushing step is carried out. The raw material soil treated in step 5 and kerosene as a solvent
The petroleum in the raw material soil is dissolved in kerosene by mixing and stirring while heating to 0 to 100 ° C., and the mixture is left to stand to separate into a kerosene layer containing petroleum and a raw material soil layer, and then the petroleum Extract the separated kerosene containing.

First, for the slurry-like raw material soil treated in the crushing step, a screw type sludge pump (22) directly connected to the lower part of the crushing tank (2) is used, and a washing machine is provided through a pipe line (21). Supply to (4). As the washing machine (4), various devices can be used as long as they have a structure capable of stirring and mixing the raw material soil and the solvent.

As the washing machine (4), in order to enhance the mixing and stirring effect and to smoothly discharge the washed soil, for example,
An apparatus in which the processing tank (40) can be tilted by mounting the rotating basket type processing tank (40) equipped with stirring blades (stirring and mixing means) on the tilting device (41) is suitable. The treatment tank (40) is an inner tank disposed inside a casing that substantially constitutes a container, and a jacket (heating means) is attached to the outer peripheral portion of the casing of the treatment tank (40). It is configured to be able to be heated by steam or other heat medium (S).

Kerosene pump (32) prior to the addition of soil
The kerosene is supplied from the kerosene tank (3) to the treatment tank (40) through a pipe (31) including the kerosene, and a necessary amount of kerosene is put into the casing surrounding the treatment tank (40). The required amount of kerosene is optimally around 30 in weight ratio with respect to 100 soil. If the amount is less than this, there is a problem in terms of stirring effect and solvent power, which is not practical.

The soil put in the treatment tank (40) is first washed with kerosene as a solvent to dissolve the petroleum component adhering to the soil in the kerosene. Kerosene is the most suitable solvent for extraction. The reason for using kerosene is, for example, that naphtha, which is lighter than kerosene, has a dissolving power but is highly volatile and may catch fire, which is not preferable for safety. In addition, light oil, which is heavier than kerosene, has a small dissolving power and is not suitable for practical use.

When washing kerosene, a jacket is used to heat kerosene and soil to 65 to 75 ° C. Then, the tilting device (41) tilts the treatment tank (40) with respect to the horizontal plane by about 30 degrees and rotates. Due to the inclined rotation of the treatment tank (40), soil components having a large specific gravity can be treated in the treatment tank (40).
Since it oscillates inside, the kerosene and the petroleum component can be sufficiently brought into contact with each other by stirring efficiently, and the petroleum component can be dissolved in a short time. At this time, if the circulation passage (46) provided with the circulation pump (47) is used and the kerosene is circulated, it can be more efficiently dissolved.

As described above, for example, after mixing and stirring for about 30 minutes, the treatment device (40) is operated by the operation of the tilting device (41).
Is returned to a horizontal position and allowed to stand still to separate into a kerosene layer containing petroleum and a raw material soil layer. Then, using the circulation pump (47) of the circulation passage (46), the kerosene solution constituting the kerosene layer is extracted from the bottom of the treatment tank (40) through the pipe passage (42) branched from the circulation passage (46). Collect in the recovered oil tank (5). The recovered oil in the recovered oil tank (5) is transferred to the refinery by the tank truck (51), processed in the atmospheric distillation device like ordinary crude oil, and recovered as a petroleum product.

(C) Hot water washing step: In the hot water washing step, a treatment tank (40) as a washing tank provided with a mixing and stirring means and a heating means is used to wash the raw material soil treated in the kerosene washing step. By mixing and stirring while heating to 50 to 100 ° C. with water, the salt in the raw material soil is dissolved in the wash water, and then left to stand to separate into a wash water layer containing the salt and the raw material soil layer, Then, the separated wash water containing salt is withdrawn.

In the warm water washing step, the treatment tank (40) of the washing machine (4) is used as a washing tank. That is, with respect to the treatment tank (40) containing the soil after washing kerosene, first, the washing water previously stored in the washing water tank (6) is passed through the pipe line (61) provided with the washing water pump (62). Is supplied, and washing water is poured into the casing of the treatment tank (40). At that time, the washing water is heated to about 70 ° C. by passing steam through the jacket. The amount of wash water is preferably 100 wash water with respect to 100 soil.

Next, the processing tank (40) is tilted by the tilting device (41), and the soil is stirred and mixed while rocking,
Removes salt from soil. The inside of the treatment tank (40) is maintained at about 70 ° C. by the jacket during the washing with warm water. This is to move the oil remaining in the soil into warm water to reduce the residual oil as much as possible. Also, during washing with warm water,
By driving the circulation pump (47) of the circulation path (46), the mixing efficiency of hot water and soil can be further enhanced.

After the above-mentioned washing with warm water is carried out for about 20 minutes, for example, the treatment tank (40) is returned to the horizontal state and allowed to stand still, and the oil content is floated on the liquid surface by utilizing the difference in specific gravity. Then, the tilting device (4
The treatment tank (40) is tilted by the operation of 1), and the oil component floating on the liquid surface is transferred to the oil-water separation tank (9) through the flow path (45). The oil-water separation tank (9) has a two-tank structure inside,
This is a tank for separating oil and water by overflowing the recovered oil component of the upper layer portion stored in one tank to the other layer.

The recovered oil recovered in the oil / water separation tank (9) is
The oil is recovered in the recovered oil tank (5) through a pipe (91) provided with a recovered oil pump (92). In addition, the hot water remaining in the casing of the treatment tank (40) flows through the pipe line (46).
Using the circulation pump (47) inside, draw it out and
It collects in the collection | recovery water tank (7) through the pipe line (43) branched from 6).

After removing the residual oil containing kerosene by washing with warm water as described above, subsequently, the main purpose is to remove salt.
Perform the second warm water wash. The washing operation is almost the same as the above-described first washing, but since it is not necessary to collect the surface floating oil, it is not necessary to perform the inclined discharge of warm water. That is, after the salt content is dissolved in warm water by the same stirring and washing as above, the circulation pump (47) is used to draw the washing waste water into the recovered water tank (7) through the pipe (43).

Incidentally, a considerable amount of salt is dissolved in the recovered water, and in some cases, in order to recover the salt, the recovered wastewater is collected through a pipe (71) equipped with a recovered water pump. ) To a salt recovery device (72).

(D) Dehydration step: After the oil and salt are removed to a predetermined concentration or less by passing through each of the above steps, a dehydration operation is performed to remove the wash water adhering to the soil. That is, in the dehydration step, the treatment tank (40) of the washing machine (4) as a dehydration tank provided with the centrifugal dehydration means is used to dehydrate the raw material soil treated in the warm water washing step.

The treatment tank (40) is a rotating basket having a fine mesh wire mesh attached to its inner peripheral surface, and the mesh structure of the treatment tank (40) and the treatment tank (40).
A drive mechanism for rotating the squid around its axis at high speed constitutes centrifugal dehydration means. Therefore, by rotating the treatment tank (40) in which the soil remains in the cleaning step at a predetermined speed, the cleaning water adhering to the soil is moved outward in the radial direction of the treatment tank (40) by a centrifugal effect. , Processing tank (40)
It can be collected on the casing side, which is the outer tank, through the wire mesh.

The collected water is collected in the pipe (4
Take out to the recovered water tank (7) through 3). And
After the dehydration operation is finished, the treatment tank (40) is tilted by the tilting device (41), and the substantially dewatered soil in the treatment tank (40) is discharged. Further, in discharging from the treatment tank (40), a transport mechanism (44) such as a conveyor is used to carry the purified soil to the recovery yard (8).

In the purification method of the present invention, by the above-mentioned four steps, it is possible to remove the petroleum content and salt content in the soil in a relatively simple operation and in a short time. When the purification method of the present invention is carried out, the contaminated soil can be purified more efficiently. Further, in the purification method of the present invention, various effects can be obtained, such as oil and salt can be separately separated and recovered from the contaminated soil, and the recovered oil and salt can be effectively used. I can.

In the present invention, as in the above embodiment, among the four steps (A) to (D), (B) to
By performing the three steps of (D) by the same apparatus, it is possible to prevent retention due to transportation and reduce the apparatus scale. That is, in the purification method of the present invention, one treatment tank (40) equipped with the mixing and stirring means, the heating means and the centrifugal dehydration means is used as the cleaning tank and the dehydration tank, and the kerosene cleaning step (B) and the hot water cleaning are performed. By performing the step (C) and the dehydration step (D), the processing cost can be further reduced. Of course, it is also possible to separately provide a cleaning tank and a dehydration tank.

[0033]

According to the method for purifying contaminated soil of the present invention, the following effects can be obtained. (1) Oil and salt in polluted soil can be separated and recovered separately, and the recovered oil can be used as a petroleum product by processing at an oil refinery, and salt can be used as a raw material for salt. Can be effectively used. (2) The residual oil content of the soil can be easily adjusted by increasing or decreasing the amount of kerosene used as a solvent for washing the soil. (3) Kerosene, which is a solvent used for cleaning, is not toxic at all, and therefore even if it remains in the soil, there is no fear of adversely affecting the environment. (4) Since each operation of kerosene cleaning, warm water cleaning, and dehydration can be performed by one device, the facility cost is economical, and the entire device can be skided to be carried into the optimum place of the contamination site.
Soil transfer costs can be saved.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of a treatment process by a method for purifying contaminated soil according to the present invention.

[Explanation of symbols]

 1: Soil pit 2: Crushing tank 3: Kerosene tank 4: Washing machine 40: Treatment tank 41: Tilt device 5: Collected oil tank 6: Washing water tank 7: Recovered water tank 8: Recovery yard 9: Oil-water separation tank

 ─────────────────────────────────────────────────── --- Continuation of front page (72) Inventor Toyoaki Kuwahara 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Tomio Kondo 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction (72) Inventor Kazuyuki Nishida 2-1, Okawa-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Sanryo Kakoki Co., Ltd. (72) Fumio Nishimura 2-1-1, Okawa-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Sanryo Within Kakoki Co., Ltd. (72) Inventor Masataka Noguchi 2-1, Okawa-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Sanryo Kakoki Co., Ltd.

Claims (2)

[Claims] 1. A method for purifying contaminated soil, which comprises purifying soil contaminated with petroleum such as crude oil and heavy oil and seawater by the following steps (A) to (D). (A) Using a crushing tank equipped with a heating means, the raw material soil containing petroleum and seawater is crushed to have a particle size of not more than a predetermined value and 50 to 10
A crushing process that lowers the viscosity of the raw material soil to a viscosity that allows pumping by heating to 0 ° C. (B) Using a treatment tank as a washing tank provided with a mixing and stirring means and a heating means, and mixing and stirring the raw material soil treated in the crushing step and kerosene as a solvent while heating to 50 to 100 ° C After dissolving the petroleum in the raw material soil with kerosene, the kerosene washing step of separating the kerosene layer containing the petroleum and the raw material soil layer by allowing to stand and then extracting the separated kerosene containing the petroleum. (C) By using a treatment tank as a cleaning tank equipped with a mixing and stirring means and a heating means, and mixing and stirring the raw material soil treated in the kerosene cleaning step with the cleaning water at 50 to 100 ° C., A warm water washing step in which the salt in the raw material soil is dissolved in the wash water and then allowed to stand to separate into a wash water layer containing the salt and a raw material soil layer, and then the separated wash water containing the salt is extracted. (D)
A dehydration step of dehydrating the raw material soil treated in the warm water washing step using a treatment tank as a dehydration tank provided with a centrifugal dehydration means. 2. The kerosene cleaning step, the hot water cleaning step and the dehydration step are performed by using one processing tank equipped with a mixing and stirring means, a heating means and a centrifugal dehydration means as a cleaning tank and a dehydration tank. Method for cleaning contaminated soil.