JP2004305914A - Treatment of contaminated soil - Google Patents

Abstract

The present invention relates to a method for removing volatile chlorinated hydrocarbons from soil containing volatile chlorinated hydrocarbons, and to volatilize and purify the volatile chlorinated hydrocarbons by mixing an inorganic compound into the soil. The purpose is to reduce the time.
SOLUTION: A disturbing step of stirring the soil, a mixing step of adding and mixing an inorganic compound to the soil containing the volatile chlorinated hydrocarbon-based substance, a granulating step of granulating the mixture, and granulating are performed. Performing a transpiration step of aerating the mixture to promote volatilization of the volatile chlorinated hydrocarbon-based material.
[Selection diagram] Fig. 1

Description

【００１８】
実験の結果より本発明による揮発性塩素化炭化水素系物質が含まれる掘削土を乱し、水と発熱反応する無機化合物と混合し、混合物を造粒して養生した場合、揮発性塩素化炭化水素系物質の揮発による浄化時間が短縮されることが明らかになった。
【００１９】
【発明の効果】
以上述べたように本発明は、請求項１によると土壌を粒状化して粒体間の空隙へ通気させることで、揮発性塩素化炭化水素系物質の揮発が促され、短時間で浄化処理を行うことができる。請求項２によると、造粒工程以前で土壌の性状を造粒に適した性状へ変更するので、造粒工程での粒状化が容易となり、短時間で造粒工程を行うことができる。 請求項３によると、ひとつの装置で３つの工程に対応でき、混合物を効率良く粒状化できるので、浄化処理を省スペース、短時間で行うことができる。請求項４によると、添加物として無機化合物を用いることで発熱作用と土壌の含水調整をひとつの材料で行うことができる。 請求項５、７によると、混合物をさらに粒状化し易くすることが可能となり、造粒工程が容易となる。請求項６によると、粒体間の通気を強制的に行うことにより、通気性を更に向上させ、揮発作用をより促進させる。請求項８によると、乱し工程において、最適な攪拌を行うことができる。
【図面の簡単な説明】
【図１】本発明の実施例に用いる装置を一部破断した平面図。
【図２】図１のＺ−Ｚ部の断面図
【図３】本発明の汚染土壌の処理の手順を示す工程図。
【図４】乱し工程における攪拌翼が逆回転方向での攪拌翼、ロータ、混合物の動きを示す模式図。
【図５】乱し工程における攪拌翼が正回転方向での攪拌翼、ロータ、混合物の動きを示す模式図。
【図６】混合工程における攪拌翼、ロータ、混合物の動きを示す模式図。
【図７】造粒工程における攪拌翼、ロータ、混合物の動きを示す模式図。
【図８】攪拌翼の各回転方向における作用図。
【図９】回転羽根の正回転方向における作用図。
【符号の説明】
１ ドラム
２ 攪拌翼
３ ロータ
４ 攪拌具
１５ 回転羽根
１６ 混合物[0001]
[Industrial applications]
The present invention relates to a method for removing volatile chlorinated hydrocarbons from soil containing volatile chlorinated hydrocarbons.
[0002]
[Prior art]
In recent years, soil contamination by VOCs, heavy metals, and the like has become a problem, and purification methods have been studied. Under such circumstances, a method of volatilizing and purifying volatile chlorinated hydrocarbon-based substances by mixing an inorganic compound that reacts exothermically with water in soil containing volatile chlorinated hydrocarbon-based substances has been shown as one effective means. (For example, see Patent Document 1).
Examples of the volatile chlorinated hydrocarbon-based substance include those having a normal pressure boiling point of about 60 to 120 ° C. in which part or all of the hydrocarbon is replaced with chlorine. For example, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene , Chloroform, carbon tetrachloride, ethane dichloride and the like.
As the inorganic compound (hereinafter, referred to as inorganic compound) that generates an exothermic reaction with water used in the present invention, an oxide of an alkali metal or an alkaline earth metal, a sulfate of an alkaline earth metal, or the like is suitable. For example, quicklime, magnesium oxide , Barium oxide, strontium oxide, sodium oxide, potassium oxide, and anhydrides of calcium sulfate and magnesium sulfate. Among them, it is preferable to use quicklime in terms of safety, price, heat generation efficiency and the like.
[0003]
[Patent Document 1]
JP-A-6-168727
[Problems to be solved by the invention]
However, in Patent Document 1, after the inorganic compound is put into the soil containing the volatile chlorinated hydrocarbon-based material, the volatilization or stirring with a scoop or the like is performed to shorten the volatilization purification time. Has the disadvantage that the permeability of the soil decreases.
In addition, stirring with a scoop or the like only increases the area open to the atmosphere, but is insufficient in terms of improving air permeability. As a result, there is a problem that the time required to volatilize and purify volatile chlorinated hydrocarbon-based materials is long.
Accordingly, the present invention has been made in view of such circumstances, and has an object to reduce the time for volatilizing and purifying a volatile chlorinated hydrocarbon-based material by mixing an inorganic compound with soil containing a volatile chlorinated hydrocarbon-based material. I do.
[0005]
[Means for Solving the Problems]
An inorganic compound that reacts exothermically with water is added to and mixed with contaminated soil containing volatile chlorinated hydrocarbon-based substances. Step, a mixing step of adding an inorganic compound to the soil and mixing, a granulation step of granulating the mixture, and a transpiration step of aerating the granulated mixture to promote volatilization of the volatile chlorinated hydrocarbon-based material. This solves the problem.
[0006]
Embodiment
In the method for treating contaminated soil according to the present invention, first, in the disturbing step, the structure of the soil is changed before the addition of the inorganic compound, and the volatile chlorinated hydrocarbon-based material in the lump of the excavated soil is more air-conditioned. In addition to the action of opening to the atmosphere by touching, there is an action of forming a base for uniform mixing with the inorganic compound in the next step.
In the next mixing step, an inorganic compound necessary for volatilizing the volatile chlorinated hydrocarbon-based substance is introduced, uniformly mixed with the soil, and has the effect of adjusting the granulation conditions of the next step over the entire soil.
In the granulation step, the mixture is formed into a granulated structure composed of granules and aggregates of granules to improve air permeability.
Further, an evaporation step of evaporating the volatile chlorinated hydrocarbon-based material from the mixture of the granules and the aggregate structure produced in the granulation step is performed.
The synergistic effect of the above series of processes promotes the release of volatile chlorinated hydrocarbon-based materials to the atmosphere in the process, and creates granules that generate heat from the inside near the volatile chlorinated hydrocarbon-based materials, forming an aggregate structure By doing so, the air permeability is improved. Therefore, the conventional volatile chlorinated hydrocarbon-based material can be reduced in volatilization time.
[0007]
Hereinafter, as an embodiment of the present invention, an apparatus used when performing a disturbing step, a mixing step, and a granulating step as a series of operations in the same container will be described with reference to the drawings. FIG. 1 is a plan view of the present apparatus, and FIG. 2 is a cross-sectional view taken along the line ZZ of FIG.
In FIG. 1, a cylindrical drum 1 includes a stirring blade 2 that revolves and a rotor 3 that revolves while revolving. The first rotating shaft 4 provided with the revolving agitating blades 2 is provided with a motor A5 provided outside the drum 1 via a transmission mechanism A13, and the rotation direction and the rotation speed revolved by the operation of the transmission mechanism A13 are free. Can be changed to In addition, the rotor 3 that rotates while revolving is attached to an arm 6 provided integrally with the first rotating shaft 4 above the first rotating shaft 4. The rotation direction and speed of rotation of the rotating blades 15 of the rotor 3 can be freely changed by a motor B7 via a transmission mechanism B14 provided.
The vertical cut surface of the rotary blade 15 is a polygon as shown in FIG. 9, and the front side of the upper surface of the rotary blade 15 at the time of forward rotation is inclined by an angle α. A plurality of pins 24 projecting toward the drum inner wall 9 are provided at the lowermost stage of the rotary blade 15 so as to form a gap Y between the pins 24 and the drum inner wall 9. Further, the stirring tool 8 provided on the stirring blade 2 includes a gap changing mechanism 10 that can change the gap between the stirring tool 8 and the inner wall 9 of the drum 1.
The gap changing mechanism 10 includes a pin 19, a bracket A20, a bracket B21, and a stopper 22, and the bracket B21 can swing about the pin 19. As shown in FIG. 8, the gap changing mechanism 10 has a structure in which the swing angle of the bracket B21 is changed by changing the mounting position of the stopper 22, and the gap X between the agitator 8 and the drum inner wall 9 can be changed. ing.
[0008]
The present apparatus having such a structure can rotate and rotate the rotating direction and the rotating speed of the stirring blade 2 by operating the motors A5 and B7 while operating the transmission mechanism A13 and the transmission mechanism B14. It is possible to arbitrarily adjust the clearance with the drum inner wall 9 and arbitrarily adjust the rotation direction and rotation speed of the rotor 3 which rotates while revolving, thereby changing the functions of the agitator 8 and the rotary blade 15. It becomes.
[0009]
The process of treating the contaminated soil of the present invention using this apparatus will be described step by step with reference to the drawings.
FIG. 3 shows a process diagram, and FIGS. 4 to 7 are schematic diagrams showing the movement of the mixture in each process.
The black arrows in the figure indicate the direction in which the mixture relatively moves due to the rotation of the stirring blade 2 and the rotor 3, and the white arrows indicate the rotation direction of the stirring blade 2 and the rotor 3.
[0010]
The disturbing step, which is the first step, will be described. FIG. 4 and FIG. 5 are views showing a turbulence process. FIG. 4 shows a case where the stirring blade 2 is rotated in reverse to transmit a compressive force to the soil, and the soil is compressed at a high speed with the stirring tool 4 at the tip as shown in FIG. 8B. The shearing force is transmitted by the rotating rotor 3. In FIG. 5, the stirring blade 2 is rotated forward to loosen the soil, and the shearing force is transmitted by the rotor 3 rotating at a high speed while loosening the soil with the agitator 4 at the tip as shown in FIG. 8A. This is a step of repeatedly performing the above.
In the disturbance step, which is the first step, the soil contaminated with the volatile chlorinated hydrocarbon-based material is charged into the cylindrical drum 1 and the rotation direction of the stirring blade 2 is reversed to knead the soil. A barber is provided, and the soil is given to the soil by the rotor 3. The combination of the two actions disturbs the soil and simultaneously exposes the volatile chlorinated hydrocarbon-based material to the atmosphere.
Disturbing the soil changes its structure by applying external forces. In particular, the structure of clayey soil cannot be changed by vibration. The structure can be changed by giving the above-mentioned large shear deformation or kneading action to the soil.
[0011]
In order to agitate and disturb a large amount of soil as in the treatment of contaminated soil, it is effective to apply shear deformation or kneading to the soil using the rotating blades 15. In particular, in order to impart shear deformation to the soil, the peripheral speed of the rotary blade 15 is 100 m / min or more, and the rotation speed is most preferably 100 rpm or more. It is also an effective means to crush the soil and repeat the peeling operation.
Disturbing the soil facilitates mixing in the next step and enables uniform mixing. Further, by making the soil lump smaller, the chance of the volatile chlorinated hydrocarbon-based material in the soil coming into contact with the air is increased, and the volatile transpiration effect is enhanced.
[0012]
The mixing step, which is the second step, will be described.
FIG. 6 is a view showing a mixing step, in which an inorganic compound that generates an exothermic reaction with water is added to the soil disturbed in the disturbing step. Quicklime, which is an inorganic compound, is charged into the drum 1. In the mixing process, it has a role of mixing the inorganic compound by mixing the inorganic compound by rotating the rotor 3 at a high speed, and simultaneously sending air into the soil.
In FIG. 6, the stirring blade 2 is rotated in the reverse direction in order to mix both the soil, which is a mixture, and the inorganic compound. As a result, the mixture, which is a mixture, can be sufficiently mixed. In addition, the rotor 3 can be rotated at a high speed in the normal rotation direction to sufficiently mix the two components.
By thoroughly mixing the soil and the inorganic compound, the inorganic compound spreads evenly to the inside of the soil and reacts with water closer to the volatile chlorinated hydrocarbon-based substances to generate heat, thereby shortening the volatilization time. be able to.
[0013]
As another embodiment of the mixing step, in addition to the inorganic compound in the mixing step, an additive that changes the property of the soil to a property that can be easily granulated in the next granulation step is further added and mixed.
When the soil has a water content below the plastic limit water content ratio (see JIS-A-1205), the properties of the soil are changed from a plastic state to a semi-solid state, and the soil is broken into pieces by stirring and easily granulated. Therefore, granulation in the next granulation step can be easily performed by adding the additive to the soil and adjusting the water content of the soil.
Further, the composition ratio of the particle diameter of the soil is such that the particle diameter of 2 to 75 mm is 50% or less, and the particle diameter of less than 75 μm is 50% or more. (According to engineering classification) has an optimum viscosity for granulation, and the soil is easily granulated.
The additives change the properties of the soil into properties that facilitate granulation. When the water content is reduced or the viscosity is increased, the soil is likely to be divided into small agglomerates (granules) and to be easily granulated. As an additive for soil having the above properties, an inorganic compound that reacts exothermically with water to reduce moisture, or a stone powder that reduces the moisture content by adding a solid material having a low moisture content, cement, or in soil There is an aggregating material that increases the viscosity of the material.
In particular, when an inorganic compound is used as an additive, the exothermic action for volatilization and the adjustment of water content in the soil can be performed at the same time, and quick lime of the inorganic compound, which is effective in terms of economy and handling, can be used as the additive.
[0014]
The granulation step, which is the third step, will be described.
The mixture uniformly mixed in the mixing step is granulated. The granulation makes the soil a collection of granules, and the voids between the granules enhance the permeability of the mixture.
FIG. 7 is a diagram showing a granulation process, in which the stirring blade 2 is rotated in the forward direction at a high speed while kneading by rotating the stirring blade 2 at a low speed in the normal rotation, so that the mixture is reduced into small agglomerates (granules). Divide into
The granules produced through the above steps have a porous structure with small bubbles inside the granules, and the granules themselves have excellent air permeability. In addition, the inorganic compound spreads to the inside, and the inorganic compound reacts with water exothermically with water near the volatile chlorinated hydrocarbon-based material, thereby promoting volatilization and shortening the purification time.
[0015]
The transpiration step, which is the fourth step, will be described.
In the transpiration step, the mixture granulated in the granulation step is blown or sucked, thereby forcibly generating a flow of air between the granules and ventilating the volatile chlorinated hydrocarbon-based material. Promote.
The granules discharged from the drum are placed on a mesh belt feeder, and air is forcibly blown from a lower portion of the feeder by a blower. The feeder portion is covered by the case, and the air containing the evaporated volatile chlorinated hydrocarbon-based material is discharged out of the case through a filter that adsorbs the volatile chlorinated hydrocarbon-based material.
Supplying air using a blower and aerating between the particles as described above is effective in promoting the volatilizing action. In addition, by using an existing suction device for recovering the volatile volatile chlorinated hydrocarbon-based material and using the air flow effectively, it is economical without providing a new blower.
As a method of evaporation in a stock yard where the granules discharged from the drum 1 are stored, steam may be sprayed on the granules. Further, ventilation may be performed by performing intake or blowing. In particular, ventilation by inhalation can also serve to recover volatile chlorinated hydrocarbon-based substances. As a specific example, the floor surface of the stock yard is formed in a mesh shape so as to allow ventilation from under the floor of the stock yard. For example, air piping can be used to perform ventilation by a blower.
There is also a method in which ventilation is performed when the particles discharged from the drum 1 are transported by a belt conveyor or the like. A ventilation hole is provided in the belt, and ventilation of intake air and ventilation is performed from below the belt. Alternatively, air may be ventilated to the entire casing covering the belt conveyor.
[0016]
Hereinafter, experimental results according to the present example will be shown.
7% by weight of quicklime was added as an inorganic compound to a soil contaminated with trichlorethylene, a volatile chlorinated hydrocarbon-based substance, and mixed in a mixer, and the volume was kept constant in a container having a width of 230 mm × depth 220 mm × height 200 mm. It was cured. Experimental Example 1 disturbs the soil and adds only 7% by weight of quicklime without performing the process, and only performs mixing, while Experimental Examples 2 and 3 disturb the entire soil and performs a process of adding quicklime at 7% by weight. Through the mixing and granulation step, the soil was converted into granular soil having a particle size of 20 mm or less and 70% of 5 mm or less. In Experimental Example 1, curing was performed by separately rolling the container, and in Experimental Example 2, natural curing was performed in a drum. In Experimental Example 3, air was forced into the drum using a blower. Thereafter, the concentration of trichlorethylene (TCE) in the soil was measured. The results are shown in Table 1 below.
[0017]
[Table 1]

[0018]
From the results of the experiment, when the excavated soil containing the volatile chlorinated hydrocarbon-based material according to the present invention is disturbed, mixed with water and an inorganic compound which reacts exothermically, and the mixture is granulated and cured, the volatile chlorinated carbonized It became clear that the purification time by the volatilization of hydrogen-based substances was shortened.
[0019]
【The invention's effect】
As described above, according to the first aspect of the present invention, by volatilizing volatile chlorinated hydrocarbon-based substances by granulating the soil and aerating the pores between the granules, the purification treatment can be performed in a short time. It can be carried out. According to the second aspect, since the property of the soil is changed to a property suitable for granulation before the granulation step, granulation in the granulation step becomes easy, and the granulation step can be performed in a short time. According to the third aspect, three processes can be performed by one apparatus, and the mixture can be efficiently granulated, so that the purification process can be performed in a small space and in a short time. According to the fourth aspect, by using an inorganic compound as an additive, the exothermic effect and the water content adjustment of the soil can be performed with one material. According to the fifth and seventh aspects, the mixture can be further easily granulated, and the granulation step is facilitated. According to the sixth aspect, by forcibly performing the ventilation between the particles, the air permeability is further improved, and the volatilizing action is further promoted. According to the eighth aspect, optimal stirring can be performed in the disturbance step.
[Brief description of the drawings]
FIG. 1 is a partially cutaway plan view of an apparatus used in an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line ZZ in FIG. 1. FIG. 3 is a process diagram showing a procedure for treating contaminated soil according to the present invention.
FIG. 4 is a schematic view showing the movement of the stirring blade, the rotor, and the mixture in the direction of reverse rotation of the stirring blade in the disturbance step.
FIG. 5 is a schematic view showing the movement of the stirring blade, the rotor, and the mixture in the forward rotation direction of the stirring blade in the disturbance step.
FIG. 6 is a schematic diagram showing movements of a stirring blade, a rotor, and a mixture in a mixing process.
FIG. 7 is a schematic diagram showing movements of a stirring blade, a rotor, and a mixture in a granulation step.
FIG. 8 is an operation diagram in each rotation direction of the stirring blade.
FIG. 9 is an operation diagram of a rotary blade in a forward rotation direction.
[Explanation of symbols]
Reference Signs List 1 drum 2 stirring blade 3 rotor 4 stirring tool 15 rotating blade 16 mixture

Claims (8)

An inorganic compound that reacts exothermically with water is added to and mixed with contaminated soil containing volatile chlorinated hydrocarbon-based substances. Step, a mixing step of adding an inorganic compound to the soil and mixing, a granulation step of granulating the mixture, and a transpiration step of aerating the granulated mixture to promote volatilization of the volatile chlorinated hydrocarbon-based material. A method for treating contaminated soil. The method for treating contaminated soil according to claim 1, wherein in the mixing step, an additive that changes the property of the soil to a property that easily granulates is further added. A drum for storing the material therein, a stirring blade that revolves in the drum, and a rotor that rotates while revolving, using a device in which the rotation direction and the rotation speed of the stirring blade and the rotor are arbitrarily selected. 3. The method for treating contaminated soil according to claim 1, wherein the three steps of the mixing step, the mixing step, and the granulation step are performed as a series of continuous operations in the same drum, and are performed under the following restriction conditions. (A) the disturbing step is performed by repeatedly changing the rotation direction of the stirring blade; (B) the mixing step is performed by rotating the rotation direction of the stirring blade in reverse. C) The granulation step is performed by rotating the rotation speed of the stirring blade at a low speed. In the mixing step, the input amount of the inorganic compound is an amount necessary for volatilization of the volatile chlorinated hydrocarbon-based material, and is a sum of an amount to make the water content of the mixture equal to or less than the water content of the plastic limit. The method for treating contaminated soil according to claim 1. 3. The method for treating contaminated soil according to claim 2, wherein in the mixing step, the amount of the additive added is such that the water content of the mixture is equal to or less than the water content of the plastic limit. 4. The method for treating contaminated soil according to claim 1, wherein said evaporating means forcibly passes steam or air between the granules. In the mixing step, the composition ratio of the particle diameter of the soil is such that the particle diameter of 2 to 75 mm is 50% or less, and the particle diameter of less than 75 μm is 50% or more. The method for treating contaminated soil according to the above. 4. The method for treating contaminated soil according to claim 3, wherein in the disturbing step, a rotor is provided with a rotating blade, a peripheral speed of the rotating blade is 100 m / min or more, and a rotation speed is 100 rpm or more. .

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