JP2012061374A - Method and device of remediating contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device of remediating contaminated soil capable of collecting contamination substance at a high yield.SOLUTION: Soil particles 8, containing contamination substance and constituted of coarse soil particles having particle diameters of 0.075 mm or more and fine soil particles having particle diameters less than 0.075 mm, are subjected to grinding treatment for converting 2 to 40 mass% of the coarse soil particles to the fine soil particles. Water is added to the coarse soil particles and the fine soil particles after the grinding treatment to form soil slurry 9. The soil slurry 9 is supplied into a remediation tank (columnar separation collection machine) 4. Some of the soil particles 8 together with bubbles 10 are floated and collected by supplying air from a lower part of the remediation tank 4 toward the soil slurry 9. The residue of the fine soil particles and the coarse soil particles included in the soil particles 8 is settled in the remediation tank 4.

Description

  The present invention relates to a purification method and a purification device for purifying soil contaminated with heavy metals or oil.

  Conventionally, a foam flotation method that applies the principle of flotation is used to select soil and heavy metals. As the apparatus, since a mine facility can be used, a general flotation machine using the rotation of an impeller has been used (for example, Patent Document 1). However, there is a problem that the construction cost and the operation cost are high and a large installation floor area is required.

  For this reason, in the field of beneficiation, column flotation machines have been introduced in recent years, in which ore pulp and air are brought into countercurrent contact in a reaction tower. The column flotation machine has a cylindrical or prismatic outer shape, and is equipped with a bubble generating device at the bottom, a feed section at the middle, and a float discharge at the top. Wash water is sprayed from the top and tailings are discharged from the bottom. The column flotation machine has a cleaning zone (selection zone) where soil is carefully cleaned by spraying water on the upper side of the supply section, and particles that are likely to float in the supply area on the lower side of the supply section. It has a recovery zone (collection area) that collects with bubbles and sends it to the top.

Japanese Patent Laid-Open No. 2005-186056

  However, the column flotation machine is improved mainly in the refinement process because the yield of the concentrate is improved but the yield is inferior to that of the conventional flotation machine. However, when the mine facility is used as a soil purification device, the concentrate concentration effect is not important, and it is required to increase the yield of pollutants. In general, the finer the finer, the higher the efficiency of the selection, so the column flotation machine is intended for slurries in which the ore is finely divided, for example, slurries with a 50% classification point of about 130 μm. Is used.

  This invention is made | formed in view of the said subject, The objective of this invention is providing the purification method and purification apparatus of the contaminated soil which can collect | recover a pollutant with a higher yield.

  In the present invention, the surface of the soil particles having a predetermined particle size range containing the pollutant is strongly ground and pulverized by using a grinding medium in an attritor, and the contaminated soil as the slurry raw material is relatively fine. Divide into pollutant particles and relatively coarse soil particles from which the pollutants have been stripped. In addition, by using a septic tank with a height, and using the difference in sedimentation speed between coarse and fine soil particles in the soil slurry, fine soil particles that are enriched in pollutants from the top. It has the function of overflowing and classifying. Furthermore, by introducing air bubbles into the septic tank, the surface-activated fine soil particles and a part of the coarse soil particles are attached to the air bubbles and allowed to overflow, so that the coarse effect is classified into coarse particles only by the classification effect. Even soil particles are effectively levitated and recovered. Or when the pollutant of the soil made into purification object is restricted only to oil or another hydrophobic chemical substance, you may use only a separation collection machine without using a grinder.

  That is, the present invention provides soil particles composed of coarse soil particles containing a contaminant and having a particle size of 0.075 mm or more and fine soil particles having a particle size of less than 0.075 mm. ~ 40% by mass is transferred to the fine-grained soil particles, water is added to the coarse-grained and fine-grained soil particles after the grinding treatment to form a soil slurry, and the soil slurry is placed in the septic tank. Supplying air from the lower part of this septic tank toward the soil slurry, and collecting and recovering a part of the soil particles together with foam, fine soil particles and coarse soil particles contained in the soil particles A method for purifying contaminated soil is provided, wherein the remaining portion is settled in the septic tank.

  In this purification method, the soil slurry is supplied from the upper part of the septic tank into the septic tank, the settled soil slurry is discharged from the lower part of the septic tank, and the supply rate of the soil slurry at this time is made larger than the discharge rate. Overflow may be generated.

  In the soil slurry, it is preferable to adjust the concentration of soil particles to 10 to 70% by mass. Furthermore, it is preferable that 5 to 30% by mass of the coarse soil particles are transferred to the fine soil particles by the grinding treatment. The contaminant may be a heavy metal.

  Furthermore, the present invention is a contaminated soil purification apparatus in which a grinding means, a soil slurry storage tank, and a septic tank are sequentially connected, the septic tank comprising a slurry supply means, an air supply means, and an upper discharge means. And a lower discharge means, wherein the grinding means grinds soil particles containing contaminants, and the soil slurry storage tank stores soil slurry obtained by adding water to the ground soil particles. In the septic tank, the soil slurry is supplied from the slurry supply means, air is supplied from the air supply means, foam and / or overflow water is discharged from the upper discharge means, and sediment is generated from the lower discharge means. Disclosed is a contaminated soil purification apparatus characterized by being discharged.

The air supply means may be an air diffuser having a plurality of holes having a hole diameter of 0.005 mm to 50 mm. Moreover, 1 to 400 m < ³ > / m < ² > / h may be sufficient as the air diffusion speed by the said air supply means with respect to the cross-sectional area of the said septic tank.

  According to the present invention, a part of contaminated soil is ground to a certain particle size, so that pollutants and soil particles are efficiently separated, and effective purification becomes possible. In addition, even in contaminated soil containing coarse particles, pollutant particles can be recovered with a high yield, so it is possible to purify large volumes of slurry-like contaminated soil containing coarse particles in a small area. It becomes.

  Furthermore, according to the present invention, the columnar separation and recovery machine does not require a large rotary impeller drive or a large installation floor area, can be realized at a low cost, and has an excellent ability to separate and recover contaminant particles. ing.

It is the schematic of the purification apparatus of the contaminated soil by this invention. It is a figure which shows the processing balance in Example 1. FIG. It is a graph which shows the transfer rate of the rough flow soil in Examples 2-5 and the comparative example 1. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The present invention is a method for purifying soil contaminated with heavy metals such as lead or oil, and can be widely implemented regardless of the place of use. The principle of the present invention is that the soil containing the pollutant is supplied to the purification device in a state in which water is added in advance to form a slurry.

  FIG. 1 shows an example of a purification apparatus 1 according to the present invention, a grinder 2 for grinding soil particles 8 containing pollutants, and a soil slurry 9 which is slurried by adding water after grinding the soil particles 8. Is provided with an air supply device 5 for supplying air to the columnar separation / recovery machine 4 and a columnar separation / recovery machine 4 used as a purification tank for purifying the soil slurry 9.

  Although omitted in FIG. 1, the soil particles before entering the grinder 2 include fine soil particles having a particle size of less than 0.075 mm and coarse soil particles having a larger particle size. As these soil particles, for example, particles having a particle size difference between the largest particles of 25 to 30 times can be used.

  In the grinder 2, the grinding medium 12 is used for grinding so that 2 to 40% by mass of the coarse soil particles are transferred to the fine soil particles. From the viewpoint of further improving the removal efficiency of pollutants, it is preferable that the rate of transfer to fine soil particles is 5 to 30% by mass. For example, coarse soil particles within a particle size range of 2 mm to 0.075 mm are ground to be separated into contaminant particles and clean soil particles from which the contaminant particles have been separated. By performing the grinding treatment in this way, contaminants can be efficiently removed, and the treated soil particles can be reused. In addition, the ratio of the soil mass contained in each particle size range is JIS standard-standard sieve (nominal mesh 0.075mm, 0.15mm, 0.3mm, 0.5mm, 1.0mm, 2.0mm, 5.0mm , 10.0 mm is used). As the classifier, for example, a wet cyclone or a high mesh separator can be used.

  The grinder 2 is a grinder main body 11 made of, for example, a cylindrical rotating body, in which a required amount of grinding media 12 is placed, and is a general apparatus having a mechanism for grinding contaminated soil particles 8. Wet mills such as various mills and scrubbers can be used. Examples of the grinding medium 12 include metal (preferably iron) balls having a diameter of 10 mm to 300 mm (preferably 15 mm to 150 mm), and metal (preferably iron) having a diameter of 20 mm to 300 mm (preferably 30 mm to 200 mm). The rod is used. The amount of the grinding medium 12 put into the grinder 2 is, for example, 500 kg to 150,000 kg. In addition, you may use the grinder 2 combining several units | sets, and it is preferable to determine the kind and magnitude | size of the grinding medium 12 to be used according to the contaminated soil made into object. Further, depending on the situation, a closed circuit can be used by using a wet cyclone in combination.

  The shape and material of the soil slurry storage tank 3 are not limited as long as the soil slurry storage tank 3 has a function of temporarily storing the soil slurry 9. The soil slurry storage tank 3 is preferably provided with a slurry stirrer using stirring means such as an impeller having a general stirring function and an underwater mixer.

  Further, the soil slurry storage tank 3 is provided with a supply pump 13 for supplying the soil slurry 9 to the columnar separation and recovery machine 4 and a slurry supply pipe 14 serving as a transfer path for the soil slurry 9.

  In the columnar separation and recovery machine 4, the main body 21 is preferably a column having a height of 1 m or more (more preferably 3 m to 15 m), and the shape may be a cylinder, a square column, or any other column shape. The main body 21 of the columnar separation and recovery machine 4 is provided with a slurry supply port 25 for supplying the soil slurry 9 transferred through the slurry supply pipe 14 into the columnar separation and recovery machine 4. The slurry supply port 25 is preferably provided above the middle of the main body 21 in order to perform efficient separation and recovery. Below the main body 21, a drawing pump 22 having a function of discharging a certain amount of slurry-like sedimentation product from the bottom of the columnar separation and recovery machine 4 is provided, and an aeration device 23 is disposed at the bottom of the main body 21. In addition, a foam discharge port 24 is provided at the uppermost end of the columnar separation and recovery machine 4 to overflow and collect the foam 10 that has collected the contaminant. In addition to these basic structures, the soil slurry 9 containing particles of a predetermined particle size of, for example, about 0.5 mm or less is extracted from the lower side surface of the main body 21 and introduced again into the columnar separation and recovery machine 4 above. A closed circuit system 26 may be provided.

As the air supply device 5, a compressor or a roots blower, which is a general air diffuser, can be used, but is not limited to these types. Air supply amount, per cross-sectional area 1 m ² of the columnar separation and recovery device 4 1~400m ³ / h (preferably ^{10m 3 / m 2 / h~300m 3} / m 2 / h) and. In addition to being supplied to the air diffuser 23, the air from the air supply device 5 can be supplied to the slurry supply pipe 14 and the closed circuit system 26, and the arrangement position is not limited to the example of FIG.

  As the air diffuser 23, an air diffuser having a plurality of holes having a hole diameter of 0.005 mm to 50 mm, a diffuser such as a membrane, or a jet aerator of air or air and water is used, and a bubble diameter of 5 μm to 50 mm (preferably Generates bubbles of 0.1 mm to 20 mm). The air diffuser 23 is not limited to any one of the above, and a plurality of devices may be used in combination.

  Further, a rotary paddle or the like may be provided at the uppermost end of the columnar separation / recovery machine 4 in order to promote the overflow property of the foam 10 attached with contaminant particles to the foam outlet 24.

  The purification method of the contaminated soil by the purification apparatus 1 having the above configuration will be described.

  For example, coarse soil particles 8 having a particle size range of 2 mm to 0.075 mm, for example, containing contaminants due to heavy metals such as lead are supplied to the grinder 2. In the grinder 2, the soil particles 8 are ground by the grinding medium 12, and the ground soil is sent to the soil slurry storage tank 3. Depending on the type of pollutant, coarse particles are removed by classification so that the particles become 10 mm or less (preferably 2 mm or less) in the soil slurry storage tank 3, or coarse particles are pulverized by the grinder 2. From the soil.

  In the soil slurry storage tank 3, the soil is diluted with water as necessary to become a soil slurry 9 adjusted to a slurry concentration of 10% to 70% by mass, via a supply pump 13 and a slurry supply pipe 14. Then, it is transferred to the columnar separation and recovery machine 4. In the soil slurry storage tank 3, the foaming agent is added to the soil slurry 9. The foaming agent to be used may be a general foaming agent, and a conditioner, an activator, a scavenger, an inhibitor and the like may be added as necessary.

  The soil slurry 9 is supplied from a slurry supply port 25 provided above the middle of the columnar separation and recovery machine 4, and bubbles are blown from the diffuser 23 at the lower part of the columnar separation and recovery machine 4, so that the soil slurry 9 And bubbles come into contact. Thereby, fine soil particles containing contaminants, for example, fine soil particles containing hydrophobic or hydrophobicized contaminants, and colloids float above the columnar separation and recovery machine 4 together with foam. The foam 10 containing this pollutant is discharged from the foam outlet 24 and recovered as a floss. On the other hand, coarse soil particles in the soil slurry 9 gradually settle and are discharged from the bottom of the columnar separation / recovery machine 4 as a sedimentation product via the extraction pump 22. Here, the floss refers to a silky floating substance in which contaminants floating in the cleaning liquid or fine particles of earth and sand containing the same are adsorbed (collected) by the foaming agent.

  In addition, the water level in the columnar separation and recovery machine 4 is kept constant by adjusting and managing the supply amount of the soil slurry 9 by the supply pump 13 and the extraction amount of the sediment product by the extraction pump 22. Alternatively, the amount of the soil slurry 9 supplied by the supply pump 13 is increased more than the amount of the sedimentation product extracted by the extraction pump 22, so that the coarse soil particles having a high settling rate are rapidly settled, and the fine soil having a low settling rate is set. By collecting the particles together with the overflow water, the fine particles of the contaminants separated from the particles in the soil slurry 9 can be removed.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this example. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

Example 1
Based on the conditions described above, the contaminated soil was purified by the purification apparatus according to the present invention.

First, classification treatment was applied to the contaminated soil to remove over 2 mm of gravel. As the grinder 2 used for the grinding treatment, a first scrubber having a diameter of 1800 mm and a length of 4000 mm filled with 1750 kg of iron balls having a diameter of 40 mm or less, and a diameter of 1800 mm and a length of 4300 mm filled with 4000 kg of iron balls having a diameter of 40 mm or less. A second scrubber was placed in series. With this mill, contaminated soil particles with a slurry concentration of 50% were ground at 25 m ³ / h. The grinding treatment was performed such that the migration rate of coarse soil particles within a particle size range of 0.075 mm to 2 mm to less than 0.075 mm was 16% by mass.

After the grinding treatment, in the soil slurry storage tank 3, a trapping agent and a foaming agent and 18 m ³ / h of diluted water are added to the columnar separation and recovery machine 4 as a contaminated soil slurry having a slurry concentration of 32%, 45 m ³ / h. Supplied with. The columnar separation / recovery machine 4 is a square column having a side of 2200 mm and a height of 5800 mm, and a slurry supply port 25 is provided at a position of 5400 mm in height to supply soil slurry into the main body 21, and a sedimentation product by the extraction pump 22. The amount of the drawn material was 37 m ³ / h, and the amount of floss collected from the foam outlet 24 was 8 m ³ / h. Under these conditions, a contaminated soil having a lead content of 618 mg / kg was treated. FIG. 2 shows the material balance of the contaminated soil slurry supplied to the columnar separation and recovery machine 4 and the floating recovered contaminants and sedimentation products recovered as floss.

  As shown in FIG. 2, 5.8% by mass of the supplied soil particles of 2 mm or less was separated and recovered together with foam, and 94.2% by mass was obtained as precipitated particles. The resulting precipitated particles had a lead content of 294 mg / kg, and the floating particles had a lead content of 5913 mg / kg, and 55.2% of lead could be separated and recovered from the contaminated soil slurry.

  Of 55.2% of the lead separated and recovered by levitation recovery, fine particles less than 0.075 mm account for 43.8% and about 80%, and the finely divided lead particles are effectively used in the grinder. It was possible to recover. Although the levitated recovery weight of coarse particles of 0.075 mm or more is as small as about 1% of the supplied weight, 8800 mg / kg lead-rich particles could be selectively separated and recovered.

  The standard that is evaluated as an excellent soil purification device is not the concentration (selection) of lead particles, but simply the separation and recovery of more lead. As shown in FIG. 2, the lead particles levitated and collected by the purification method of this example not only have a particularly high recovery rate from fine particles of less than 0.075 mm, but also coarse particles in the range of 0.075 mm to 2 mm. Lead-containing particles can also be effectively recovered from the particles. Thus, the purification device of the present invention can effectively recover heavy metal particles regardless of the particle size range, and can be said to be excellent as a soil purification device.

  In addition, the columnar separation and recovery machine used in the present invention does not require driving of a large-sized rotary impeller or the like, and can reduce the installation floor area, so that it is necessary for construction and operation, which has been a problem of conventional flotation machines. Cost can be reduced. Therefore, it is possible to achieve both the improvement in the ability to separate and recover the contaminant particles and the cost reduction.

(Examples 2 to 5, Comparative Example 1)
In grinding the soil particles used in Example 1, by changing the operating conditions in the grinding machine 2, the transition rate of coarse soil particles within a particle size range of 0.075 mm to 2 mm to less than 0.075 mm is obtained. 0% by mass (Comparative Example 1), 2% by mass (Example 2), 7% by mass (Example 3), 16% by mass (Example 4), and 38% by mass (Example 5). did. Otherwise, the contaminated soil was treated under the same conditions as in Example 1.

The reduction rate of the lead content from the supply soil in these treatments is shown in the graph of FIG. In addition, the reduction rate of lead content is the following formula (lead content reduction rate) = [(lead content of supplied soil−lead content of treated soil) / (lead content of supplied soil)] × 100
I asked more. It shows that the lead removal effect from the soil accompanying a process is so high that this reduction rate is large.

  As shown in FIG. 3, in Comparative Example 1 (migration rate 0% by mass), the reduction rate of lead content with respect to the entire particle size range of the treated soil reaches 20%, but only for coarse soil of 0.075 mm or more. As a result, the lead content was reduced by 3% and almost no lead was removed. On the other hand, in Examples 2 to 5 (migration rate of 2% by mass or more), it was possible to reduce the lead content even from coarse soil of 0.075 mm or more. In other words, it can be said that the lead particles recovered by the columnar separation and recovery machine 4 are limited to fine particles of 0.075 mm or less when the grinding treatment using the coarse-grained soil as the fine-grained soil is not performed.

  INDUSTRIAL APPLICABILITY The present invention is widely used as a contaminated soil purification device, and can be applied as an economical soil purification device particularly for high-concentration heavy metal-contaminated soil and oil-contaminated soil.

DESCRIPTION OF SYMBOLS 1 Purification apparatus 2 Grinding machine 3 Soil slurry storage tank 4 Columnar separation collection | recovery machine 5 Air supply apparatus 8 Soil particle 9 Soil slurry 10 Foam 11 Grinding machine main body 12 Grinding medium 13 Supply pump 14 Slurry supply piping 21 Main body 22 Extraction pump 23 Aeration Device 24 Foam discharge port 25 Slurry supply port 26 Closed circuit system

Claims (8)

Soil particles composed of coarse soil particles containing a pollutant and having a particle size of 0.075 mm or more and fine soil particles having a particle size of less than 0.075 mm, 2 to 40% by mass of the coarse soil particles are Performing the grinding treatment to transfer to fine soil particles, adding water to the coarse soil particles and fine soil particles after the grinding treatment to make a soil slurry,
The soil slurry is supplied into a septic tank, air is supplied from the lower part of the septic tank toward the soil slurry, and a part of the soil particles are levitated and collected together with foam, and the fine particles contained in the soil particles A method for purifying contaminated soil, wherein the remainder of soil particles and coarse soil particles are allowed to settle in the septic tank. The soil slurry is supplied into the septic tank from the upper part of the septic tank, and the settled soil slurry is discharged from the lower part of the septic tank,
The method for purifying contaminated soil according to claim 1, wherein the supply rate of the soil slurry at this time is made larger than the discharge rate to generate overflow.   3. The method for purifying contaminated soil according to claim 1, wherein a concentration of soil particles is adjusted to 10 to 70 mass% in the soil slurry.   The method for purifying contaminated soil according to any one of claims 1 to 3, wherein 5 to 30% by mass of the coarse soil particles are transferred to the fine soil particles in the grinding treatment.   The method for purifying contaminated soil according to any one of claims 1 to 4, wherein the pollutant is a heavy metal. A device for purifying contaminated soil in which grinding means, a soil slurry storage tank, and a septic tank are sequentially connected,
The septic tank comprises a slurry supply means, an air supply means, an upper discharge means, and a lower discharge means,
In the grinding means, soil particles containing pollutants are ground,
In the soil slurry storage tank, soil slurry obtained by adding water to the ground soil particles is stored,
In the septic tank, the soil slurry is supplied from the slurry supply means, air is supplied from the air supply means, foam and / or overflow water is discharged from the upper discharge means, and sediment is discharged from the lower discharge means. A device for purifying contaminated soil.   The contaminated soil purification apparatus according to claim 6, wherein the air supply means is an air diffuser having a plurality of holes having a hole diameter of 0.005 mm to 50 mm. The apparatus for purifying contaminated soil according to claim 6 or 7, wherein an air diffusing speed by the air supply means is 1 to 400 m ³ / m ² / h with respect to a cross-sectional area of the septic tank. .

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