JP2002282837A - Purification method of oil contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a purification method of oil contaminated soil that not only can continuously remove the contaminant from the oil contaminated soil but also restrain the amount of soil which should be discharged requiring a high cost incineration to minimum. SOLUTION: In a rotary cylindrical vessel with no opening part in the peripheral surface and equipped with an agitation vane and a carrier vane therein, contaminated soil as a processing object and water are mixed and agitated. Then the admixture of the processing object and water is separated into three parts, a floating oil content, a solid phase, and a suspension liquid phase, respectively, and the separated floating oil content and the solid phase are recovered separately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a technique for purifying soil contaminated with petroleum compounds.

[0002]

2. Description of the Related Art There are a number of places and factories that handle a large number of petroleum products where the soil is contaminated with oil due to leakage or disposal. At present, laws and regulations are being prepared by the government, and the number of cases where local governments provide their own regulations and cleanup guidance is increasing.
Under such circumstances, there is a need to establish a method for remediating soil contaminated with oil. BACKGROUND ART Conventionally, in order to purify soil contaminated with oil, it has been proposed to perform a cleaning treatment using a chemical cleaning agent such as sodium hydroxide, hydrogen peroxide, an organic solvent, and a surfactant.

[0003]

However, these methods have the following problems. In the case of washing using a strong alkali such as sodium hydroxide, it is necessary to neutralize both the waste liquid and the soil after the treatment. The method of floating oil using hydrogen peroxide requires a pretreatment with an alkali such as sodium hydroxide, so that a neutralization treatment is required after washing as described above, and the cost is increased because expensive chemicals are used. high. In a treatment using a chemical cleaning agent such as an organic solvent or a surfactant, the separated oil is emulsified, so that it is difficult to separate the separated oil from an aqueous solution.

On the other hand, JP-A-2000-202422, 20
00-202423 proposes a washing method in which a soil contaminated with petroleum compounds and a washing liquid (sodium silicate, organic solvent) are stirred in a rotary sieve having an opening on the peripheral surface and the contaminated part is separated. I have. However, in this method, clogging of the rotary sieve occurs quickly, so that continuous processing is difficult. In addition, since the washing water immediately flows out from the opening in the peripheral surface, the water ratio of the contaminated soil and water is not stable, and it is difficult to control. Furthermore, there is no detailed description of the treatment of the soil fine-grain portion in the wash water which always occurs during the treatment.
Contamination is often concentrated in the soil fines, and in that case, it is inevitable to incinerate. Therefore, the amount of soil fines generated has a great effect on the treatment cost.

The present invention has been made to solve the above-mentioned problems of the prior art, and it is possible to continuously remove contaminants from soil contaminated with oil, and to discharge as high-cost incineration. It is an object of the present invention to propose a method of purifying oil-contaminated soil that can minimize the amount of soil to be removed.

[0006]

According to the present invention, oil-contaminated soil is stirred in a cylindrical container having no opening on the peripheral surface, and then separated into a floating oil component, a solid phase, and a suspended aqueous phase, and each of them is treated. Is a method for purifying oil-contaminated soil while reducing the amount of soil fines to be finally discarded. The first invention does not have an opening on the peripheral surface and a container is provided inside the container. In a rotating cylindrical container having a plurality of stirring blades having a height equal to or more than 1/15 of the inner diameter and having a plurality of stirring blades parallel to the rotation axis, and having a plurality of blades for transporting soil toward the cylindrical axis direction of the container inside the container, 50% of contaminated soil and water to be treated as solid concentration of soil
Mixing and stirring in the range of ~ 80%, separating the mixture of water to be treated and water into three parts, a floating oil component, a solid phase and a suspension phase, And a method of purifying oil-contaminated soil having a step of separately recovering oil. In a rotating cylindrical container having a plurality of stirring blades parallel to the rotation axis, having no, and having a height of 1/15 or more of the inner diameter of the container inside the container,
The contaminated soil and water to be treated are 50% -8
A step of mixing and stirring in a range of 0%, a step of separating a mixture of the object to be treated and water into three parts of a floating oil component, a solid phase and a suspension phase, and a step of separating the separated floating oil component and the solid phase. A method of purifying oil-contaminated soil having a step of separately recovering the oil-contaminated soil. A plurality of agitating blades having a height equal to or more than 1/15 of the inner diameter of the container inside the container and parallel to the rotation axis, and a plurality of blades for transporting the soil toward the cylindrical axis of the container inside the container. Mixing and stirring the contaminated soil to be treated and water in the range of 50% to 80% in the solid concentration of the soil in a rotating cylindrical container having;
Purification of oil-contaminated soil, comprising the steps of separating a mixture of water to be treated and water into three parts, a floating oil component, a solid phase, and a suspension phase, and recovering the separated floating oil component and the solid phase, respectively. A method according to a fourth aspect of the present invention, characterized in that the direction of the blade for transporting the soil in the rotary cylindrical container toward the cylindrical axis direction of the container is opposite to the inclination direction of the bottom of the peripheral surface. According to a fifth aspect of the present invention, the length of the blade for transporting the soil in the rotary cylindrical container in the cylindrical axis direction of the container is 60 to 270 ° as a central angle, and the distance between the adjacent blades is According to a sixth aspect of the present invention, a mixture of contaminated soil and water is shaken, a movable rod sieve, or the like, before being separated into three parts of a floating oil, a solid phase, and a suspension phase. Use either a cyclone classifier or a hydraulic classifier to set the soil size The seventh invention is characterized in that the solid phase after separation is returned to a rotating cylindrical container, and the eighth invention is characterized in that the solid phase adheres to the suspended components in the suspension phase. The oil component is separated and floated by performing pH adjustment or ultrasonic treatment.
The invention is characterized in that the floating oil and the liquid phase separated from the solid phase are circulated and reused as water to be mixed with the contaminated soil to be treated in the rotating cylindrical container. It is characterized by heating to a temperature range of 50 ° C.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a process diagram showing an embodiment of the method for purifying oil-contaminated soil according to the present invention, and FIG. 2 is an illustration of a rotary cylindrical container in a mixing / stirring step of the above-mentioned purification method. (A) is a schematic longitudinal sectional side view partially omitted, and (b) is a schematic longitudinal sectional front view, wherein 1 is a mixing / stirring step, 2 is a separation step,
3 is an oil recovery step, 4 is a solid phase recovery step, 5 is a soil separation step, 6 is an oil separation step, 7 is a heating step, 8 is an oil separator, and 11 is a rotary cylindrical container.

The mixing / stirring step 1 shown in FIG. 1 is a step of mixing and stirring the contaminated soil to be treated and water in a rotary cylindrical container. The rotary cylindrical container used here is shown in FIG. As schematically shown, a plurality of agitating blades 11-parallel to a rotating shaft 11-1 having a height equal to or more than 1/15 of the inner diameter of the container are provided in a cylindrical container 11 having a closed structure having no opening on the peripheral surface. 2, and a rotating cylindrical container 11a provided with a blade 11-3 for transporting soil in the cylindrical axis direction of the container inside the container 11. Although not shown in the drawing, it is needless to say that the cylindrical container 11a is provided with an inlet for charging the soil to be treated and water, and an outlet for a mixture of contaminated soil and water. In addition, the said conveyance blade 11-3 may be attached in the direction opposite to the inclination direction of the peripheral surface bottom part of the cylindrical container 11. The reason is that the residence time of the soil to be treated in the cylindrical container 11a is lengthened to sufficiently mix and stir the water with the soil to be treated. The length of the blade 11-3 is 60 to 27 as the central angle.
0 °, 30 as the center angle of each interval between adjacent blades
It is preferable to open up to 60 °. The reason is that both the transport blade 11-3 and the stirring blade 11-2 disposed between the transport blade 11-3 work efficiently.

The separation step 2 is a step of separating the mixture of the contaminated soil and water mixed in the mixing / stirring step 1 into three parts: a floating oil component, a solid phase, and a suspension phase. Oil recovery process 3
Is a step of recovering the floating oil separated in the separation step 2, and a solid phase recovery step 4 is a step of collecting the solid phase separated in the separation step 2. The soil separation step 5 is a step of separating coarse particles of soil in a mixture of contaminated soil and water at a stage before separation into three parts of a floating oil component, a solid phase, and a suspension phase in the separation step 2. The oil separation step 6 is a step of collecting the oil adhering to the suspension separated in the separation step 2.

When the soil contaminated by oil is to be repaired in the above-mentioned treatment step, first, the contaminated soil to be treated and water are put into a cylindrical container 11 having no opening in the mixing / stirring step 1, and the container is rotated. Let it. In the step of rotating the soil, the attrition effect is enhanced by rubbing the entire soil, and the cleaning effect is dramatically improved. With this technique,
Attrition can be effectively performed without a step requiring high power energy such as mechanical compression.

[0011] The amount of water to be supplied is as follows.
% To 80%, preferably 60% to 75%. The reason for this is that if the solid concentration is less than 50%, not only the attrition efficiency is reduced and the purification effect is reduced, but also the amount of washing water used is increased. This is because, when the slurry is separated into the soil having a diameter of not less than the diameter and the slurry having the diameter of not more than the diameter, the separation becomes insufficient and the purification effect is lowered.

When the cylindrical container 11 is installed horizontally, the soil can be advanced at a constant speed in the cylindrical container 11 by attaching blades 11-3 for conveying the soil to the peripheral surface to enable continuous treatment. Becomes Further, by attaching the stirring blade 11-2 parallel to the rotating shaft 11-1, the attraction effect is further improved by lifting the soil to a high place and falling when rotating. At this time, the height of the stirring blade 11-2 is preferably at least 1/15 of the diameter of the cylindrical container 11. The reason is that if it is less than 1/15, the soil is not lifted to a high place by the stirring blade 11-2, and the effect of the attrition is reduced. Further, the cylindrical container 11 can be installed with an inclination. In this case, since the soil is transported by the inclination, the transport blade 11-3 may not be provided.

According to the cylindrical container 11, since the container peripheral surface has no opening, the optimum solid-liquid ratio can always be kept constant during the rotation process, and the attrition effect can be kept high. Can be. The mixture is introduced directly into the separation step 2 or through the soil separation step 5 into the separation step 2. In this case, since the fine particles of the soil generated during the stirring in the mixing / stirring step 1 are highly contaminated, if the particles are separated as a slurry in the soil separation step 5, high oil removal efficiency can be obtained. . At this time, in the soil separation step 5, it is desirable to separate the coarse flow portion using any of a vibration sieve, a movable bar sieve, a cyclone classifier, and a hydraulic classifier. When the initial contamination concentration is high, the stirring-separation step may be performed in multiple stages.

In the separation step 2, the mixture or slurry is separated into a floating oil component, a solid phase and a suspension phase. Of these, the floating oil is collected in an oil recovery step 3, and the solid phase is recovered in a solid phase recovery step 4. In recovering the floating oil, an oil adsorbent such as a sheet, a belt type oil / water separator, or a float liquid level suction type oil / water separator can be used as an oil removing method.
If it is necessary to further purify the solid phase recovered in the solid phase recovery step 4, it is desirable to return the solid phase to the cylindrical container 11. Suspended components are dispersed in the separated suspension phase. Although the proportion of this suspended component in the whole treated soil is about several percent in general, the concentration of contamination is high because oil is adsorbed. Therefore, in order to reduce the contamination concentration of the suspended component, it is desirable to separate and collect the suspended component and the oil component by using a pH treatment or an ultrasonic treatment in the oil component separation step 6. Further, it is desirable that the water phase (liquid phase) after solid-liquid separation is passed through an oil separator 8 or the like to reduce the oil concentration in the treated water and reused as water mixed with the contaminated soil to be treated (wash water). . At this time, it is desirable that this water be heated to a water temperature of 30 to 50 ° C. during circulation. This is because increasing the water temperature lowers the viscosity of the oil, thereby increasing the cleaning effect. However, if the water temperature is too high, the volatile components in the oil will diffuse into the gas phase, and the odor may spread to the surrounding area. In addition, large equipment is required for heating and the cost is high. desirable. If the temperature is lower than 30 ° C., the cleaning effect is not improved. The heating step 7 is a step of heating the water to a temperature of 30 to 50C.

[0015]

EXAMPLES Example 1 5000 g of oil-contaminated soil (contamination concentration: 5 wt%) was used with a diameter of 3
Put into a cylindrical container of 00 mm and length of 400 mm and add 2 L of water.
Was sprinkled on contaminated soil with a pipe inserted into the cylindrical container, and the cylindrical container was rotated at a speed of 12 rpm. At this time, the soil and the washing water which came out of the cylindrical container about 10 minutes after the introduction were separated into soil having a particle diameter of 0.7 mm or more and soil having a particle diameter of less than 0.7 mm by a vibrating sieve. Of the slurry separated under the sieve, the suspended oil separated in the receiving tank was recovered by an oil absorption mat, and the precipitated soil was pulled out from the bottom of the receiving tank and returned to the cylindrical container. The intermediate aqueous phase was reused as washing water after oil separation treatment and solid-liquid separation treatment using an ultrasonic homogenizer. When the oil content in the soil as a whole of the soil in which the particle diameter after treatment was 0.7 mm or less and both of them were analyzed, the oil content was reduced to 0.2 wt%, and the oil removal rate was 96%. The processing cost was reduced to about 1/3 compared with the general incineration method. No large blockage was observed in the vibrating sieve, and there was no change in the sieving efficiency to the end.

Example 2 5000 g of oil-contaminated soil (contamination concentration: 5 wt%) was treated with a diameter of 3
00mm, put in a cylindrical container of 400mm length, 40 ℃
While heating 2 L of water heated to the contaminated soil through a pipe inserted into the cylindrical container, the cylindrical container was
at a speed of m. Approximately 10 minutes after charging, the soil and washing water that came out of the cylindrical container were washed with a vibrating sieve to a particle size of 0.7.
The soil was separated into soil of mm or more and soil of less than mm. In the slurry separated under the sieve, the suspended oil separated in the receiving tank was recovered by an oil absorption mat, and the precipitated soil was pulled out from the bottom of the receiving tank and returned to the cylindrical container. The middle aqueous phase was subjected to oil separation using an ultrasonic homogenizer.
A solid-liquid separation treatment was performed and reused as washing water. Analysis of the oil content in the soil as a whole of the combined soil having a particle size of 0.7 mm or less after treatment and 0.1 mm or less showed 0.1%.
wt%, and the oil removal rate was 98%.

Example 3 One end has a diameter of 300 mm and the other end has a diameter of 400 mm and a length of 5 mm.
In a 00mm trumpet-shaped container, water is placed at one end 5 in a cylindrical container.
Flow rate 0.3L / m from pipe inserted at 0mm
The cone-shaped container was rotated at a speed of 12 rpm while sprinkling oil-contaminated soil (contamination concentration: 5 wt%) continuously charged from the other end of the container in. At this time, the solid concentration of the soil in the rotary container was always 65 to 75%. Approximately 10 minutes after the introduction, the soil and the suspended water that came out of the cylindrical container were separately collected. In the separated suspension water, the suspended oil was recovered by an oil absorption mat, and the precipitated soil was withdrawn from the bottom of the receiving tank and returned to the conical vessel. The intermediate aqueous phase was reused as washing water after oil separation treatment and solid-liquid separation treatment using an ultrasonic homogenizer. Analysis of the oil content in the soil as a whole of the soil having a particle diameter of 0.7 mm or less after the treatment and a combination of the above both showed that the oil content was reduced to 0.2 wt%, and the oil removal rate was 96%. In addition, no large blockage was observed in the vibrating sieve, and there was no change in treatment efficiency until the end.

[0018]

As described above, according to the present invention,
The pollutants can be continuously removed from the oil-contaminated soil, and the amount of soil discharged as high-cost incineration can be minimized. Therefore, the present invention provides an excellent low-cost treatment technique for contaminated soil and can contribute to environmental protection.

[Brief description of the drawings]

FIG. 1 is a process diagram showing one embodiment of a method for purifying oil-contaminated soil according to the present invention.

FIG. 2 is a schematic view illustrating a rotating cylindrical container in a mixing / stirring step of the above purification method, in which (a) is a schematic vertical sectional side view partially omitted, and (b) is a schematic vertical sectional front view.

[Explanation of symbols]

 1 is a mixing / stirring step 2 Separation step 3 Oil recovery step 4 is a solid phase recovery step 5 Soil separation step 6 Oil separation step 7 Heating step 8 Oil separator 11 Rotating cylindrical container 11-1 Rotating shaft 11-2 Stirrer blade 11 -3 blades for transport

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B03B 5/00 B03B 5/00 Z 5/28 B 5/28 5/66 5/66 7/00 7 / 00 9/06 9/06 B09B 5/00 ZABS B09C 1/02 3/00 304K 1/08 F term (reference) 4D004 AA41 AB02 CA10 CA13 CA15 CA22 CA35 CA40 CB09 CB28 CB34 CB45 CC03 DA03 DA06 DA09 4D056 AB01 AB13 AC22 BA13 CA06 CA13 CA17 DA01 DA05 4D071 AA04 AA05 AA53 AA64 4G036 AA04

Claims (10)

[Claims] 1. A method for purifying soil contaminated with oil, wherein the method has no opening on the peripheral surface and is parallel to a rotating shaft having a height of at least 1/15 of the inner diameter of the container inside the container. In a rotating cylindrical container having a plurality of stirring blades and a plurality of blades for transporting soil toward the cylindrical axis of the container inside the container, the contaminated soil to be treated and water are reduced to 50% by solid concentration of the soil.
Mixing and stirring in the range of ~ 80%, separating the mixture of water to be treated and water into three parts, a floating oil component, a solid phase and a suspension phase, Recovering oil separately from the soil. 2. A method for purifying soil contaminated with oil, wherein the peripheral surface is installed at an angle of 5 to 30 ° with respect to a horizontal plane, and the peripheral surface has no opening, In a rotary cylindrical container having a plurality of agitating blades parallel to the rotation axis and having a height of 1/15 or more of the inner diameter of the container inside the container, the contaminated soil and water to be treated are reduced to a solid concentration of 50% to 50%. 80
%, A step of separating the mixture of water to be treated and water into three parts of a floating oil, a solid phase, and a suspension phase, and a step of separately separating the floating oil and the solid phase. And a method of purifying oil-contaminated soil. 3. A method for purifying soil contaminated with oil, wherein the peripheral surface is installed at an angle of 5 to 30 ° with respect to a horizontal plane, and the peripheral surface has no opening, A rotation having a plurality of stirring blades having a height of 1/15 or more of the inner diameter of the container inside the container and parallel to the rotation axis, and having a plurality of blades inside the container for transporting soil toward the cylindrical axis of the container. Mixing and agitating the contaminated soil and water to be treated in a cylindrical container in a solid concentration range of 50% to 80% in a solid concentration of the soil; and suspending the mixture of the contaminated soil and water to be treated with a floating oil component and a solid phase. A method for purifying oil-contaminated soil, comprising a step of separating into three parts of a liquid phase and a step of recovering the separated floating oil component and solid phase, respectively. 4. A blade for transporting soil in a rotating cylindrical container in a cylindrical axis direction of the container is oriented in a direction opposite to an inclination direction of a bottom portion of a peripheral surface. The method for purifying oil-contaminated soil according to the above. 5. The length of a blade for transporting soil in a rotating cylindrical container in the cylindrical axis direction of the container is 60 to 270 ° as a central angle, and the distance between adjacent blades is centered. The method for purifying oil-contaminated soil according to any one of claims 1 and 3 to 4, wherein the corner is opened by 30 to 60 degrees. 6. A method for separating a mixture of contaminated soil and water using a vibrating sieve, a movable rod sieve, a cyclone classifier, or a hydraulic classifier before separating the mixture into three parts, a floating oil, a solid phase, and a suspension phase. The method for purifying oil-contaminated soil according to any one of claims 1 to 5, wherein the soil is separated into a soil having a certain particle size or more and a slurry having a particle size not more than a predetermined particle size. 7. The method for purifying oil-contaminated soil according to claim 1, wherein the separated solid phase is returned to a rotating cylindrical container. 8. The method according to claim 1, wherein the oil adhering to the suspended components in the suspension phase is separated and floated by performing pH adjustment or ultrasonic treatment. The method for purifying oil-contaminated soil according to the above. 9. The method according to claim 1, wherein the floating oil and the liquid phase separated from the solid phase are circulated and reused as water mixed with the contaminated soil to be treated in the rotary cylindrical container. The method for purifying oil-contaminated soil according to claim 1. 10. The method according to claim 9, wherein the water is heated to a temperature range of 30 to 50 ° C. during circulation.