JP2003080226A - Cleaning method for contaminated soil and asphalt plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform cleaning of contaminated soil by utilizing an asphalt plant at low cost. SOLUTION: A drier 1 for a heating means of the asphalt plant is utilized for heating and cleaning of the contaminated soil. The drier is also equipped with a deodorizing furnace 24, dust cleaning treatment equipment 31, soil cooling equipment 39, by which a dual purpose plant capable of cleaning both of the asphalt plant and the contaminated soil is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating contaminated soil containing oil such as light oil and heavy oil, and in particular, a method for purifying contaminated soil using an asphalt plant for producing road paving materials, and Regarding the device.

[0002]

2. Description of the Related Art In recent years, along with industrial activities, the soil in the premises of each business establishment and the surrounding area has been contaminated by waste liquid of volatile pollutants such as oil, and the groundwater flowing underground in the soil has also been contaminated. It has been a problem since it was said that it was in trouble. In order to treat oil-containing soil in this way, the soil is excavated and heat-treated in a contaminated soil purification treatment plant to burn and decompose volatile pollutants that have soaked into the soil to purify soil. It is carried out.

[0003]

However, when a contaminated soil purification treatment plant is newly installed, it is necessary to secure a site of a certain area in consideration of the environment, and the cost of the equipment becomes high. Therefore, there is a problem that the economical burden is large when a dedicated plant factory is installed.

In view of the above points, it is an object of the present invention to provide a method for cleaning contaminated soil and a device for cleaning contaminated soil at low cost.

[0005]

[Means for Solving the Problems] The present inventors have focused on an asphalt plant for producing road paving materials as a device for heating and purifying contaminated soil. The installation plant of the asphalt plant has its own site area in consideration of the environment,
In addition, a heating device that can also be used as a soil pollution treatment plant is installed. We thought that if the asphalt plant was also used as a plant for the purification treatment of contaminated soil using this site and equipment, the purification treatment of contaminated soil could be realized at low cost.

That is, according to the present invention, the dryer for heating the aggregate of the asphalt plant is constituted as a heating means for both heating the aggregate and for cleaning and purifying the contaminated soil, and a dust collector interposed in the exhaust flue of the dryer. It is characterized in that a deodorizing furnace for burning and decomposing volatile pollutants in exhaust gas is disposed downstream of the above.

Further, the present invention is characterized in that a dust purification processing device is provided for receiving the dust captured by the dust collector and burning and decomposing the volatile pollutants contained in the dust.

Further, the present invention is characterized by being provided with a soil cooling device which receives the soil which has been heated and purified to have a high temperature and cools it to a predetermined temperature.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, a contaminated soil is purified by using equipment of an asphalt plant, and a dryer for heating an aggregate, that is, a new aggregate installed in the asphalt plant. Contaminated soil is heated using either a dryer for heating or a dryer for heating asphalt pavement waste. In addition, necessary equipment such as a deodorizing furnace is additionally installed so that contaminated soil can be purified in an asphalt plant.

When the contaminated soil is purified, the contaminated soil is continuously fed into the dryer. The contaminated soil put into the dryer is exposed to the hot air from the burner while rolling down in the dryer, and some of the volatile pollutants such as oil in the soil are volatilized or combusted and decomposed, while the soil The fine particles containing a large amount of volatile pollutants inside are entrained in the gas flow of the dryer and scattered to the downstream of the dryer. Due to the volatilization and scattering of pollutants in the dryer, the soil discharged from the dryer has a low pollutant concentration and is purified.

On the other hand, the fine particles scattered on the gas flow of the dryer are guided to and collected by the dust collector. Then, the exhaust gas that has passed through the dust collector is guided to the deodorizing furnace, where the volatile components of the pollutants contained in the exhaust gas are exposed to a high temperature, burned and decomposed, and purified.

As described above, if the asphalt plant is also used as a contaminated soil remediation treatment plant, the capital investment can be suppressed and the contaminated soil remediation treatment can be carried out at a low cost as compared with the case where a new dedicated contaminated soil remediation treatment plant is installed. Can be realized.

Further, since the dust purifying processing device for receiving the dust captured by the dust collector and burning and decomposing the volatile pollutants contained in the dust is provided, the dust captured by the dust collector is supplied to the dust cleaning treatment device. Then, the volatile pollutants adhering to it can be decomposed by combustion. As a result, the contaminated soil can be completely purified, and the plant becomes suitable for the purification treatment of the contaminated soil.

Further, since the soil cooling device for receiving and cooling the heat-purified soil is provided, it is possible to supply the high temperature soil to the soil cooling device and cool it to a predetermined temperature.
This makes it easy to handle soil immediately after purification, and makes the plant more suitable for purification of contaminated soil.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an asphalt plant that also serves as a contaminated soil remediation treatment. First, a device configuration of a known asphalt plant will be explained. In the figure, 1 is a dryer for heating a new aggregate, and an inner peripheral portion thereof. A cylindrical drum 2 around which a large number of blades (not shown) are installed
It is rotatably supported on the upper side and is rotated at a predetermined speed by a driving device (not shown). Hot air is introduced into the drum 2 from a burner 5 provided in a hot hopper 4 at one end of the drum 2. While feeding, cold hopper 6 at the other end
An exhaust flue 7 is connected to the exhaust flue 7. The exhaust fan 8 interposed in the exhaust flue 7 sucks the exhaust gas to maintain a high-temperature gas flow passing through the inside of the drum 2, and a dust collector 9 such as a bag filter. The dust in the exhaust gas is captured via the exhaust gas and discharged from the stack 10.

Then, a predetermined amount of aggregate is dispensed from an aggregate hopper group (not shown) that stores new aggregate according to grain size, and the dispensed aggregate is fed into the drum 2 via the belt conveyor 11, While being rolled up by the scraping blades, the drum 2 is brought into contact with the high-temperature gas flow while rolling down, and the temperature is raised to a desired temperature and discharged from the hot hopper 4.

The aggregate discharged from the drum 2 is thrown into a bucket elevator 13 which is a vertical transfer device through a discharge chute 12 and lifted up to the upper part of the plant body 14 by the bucket elevator 13 to discharge the chute 15 above the bucket elevator 13. Through the plant body 14
The mixture is put into the uppermost vibrating screen 16, screened according to particle size, and stored in each compartment of the aggregate storage bin 17.

A discharge gate (not shown) for discharging aggregate is provided at the lower end of each compartment of the aggregate storage bin 17, and an aggregate measuring tank 1 supported by a weight detector is provided below the discharge gate.
The stone powder measuring tank 2 for arranging 8 and measuring the stone powder supplied by the screw feeder 20 of the stone powder storage bottle 19
1. An asphalt measuring tank 22 for measuring asphalt is arranged, and a mixer 23 is arranged below it.
A predetermined amount of each material is weighed in each of the above-mentioned weighing tanks, and the mixer 23
The desired asphalt mixture is produced by mixing and adjusting.

In addition to the configuration of the above-mentioned known asphalt plant, a deodorizing furnace 24 is interposed between the exhaust fan 8 and the stack 10 of the exhaust flue 7, and the furnace temperature is provided at one end of the deodorizing furnace 24. The chimney 10 is provided with a burner 25 for maintaining a predetermined value, exposing exhaust gas from the dryer 1 introduced into the furnace to a high temperature atmosphere to combust and decompose volatile pollutants such as oil contained in the exhaust gas. I try to exhaust more. In the deodorization furnace 24, the combustion amount of the burner 25 is controlled so that the temperature inside the furnace is maintained at a high temperature of, for example, approximately 750 ° C. or more so that the volatile pollutants can be completely combusted and decomposed, and the exhaust gas is discharged into the furnace It is preferable to secure a furnace length such that it takes at least 1 to 2 seconds or more to pass through.

Reference numerals 26 and 27 denote heat exchangers for effectively utilizing exhaust gas heat contained in the high-temperature exhaust gas discharged from the deodorization furnace 24. The heat exchanger 26 is provided from the dryer 1 to the deodorization furnace 24. The preheat of the exhaust gas to be introduced into the deodorizing furnace 24 from the combustion air supply fan 28 and the heat exchanger 27.
The preheating of the combustion air supplied to the burner 25 of FIG.

A branch chute 29 is arranged in the middle of the discharge chute 15 of the bucket elevator 13.
At the branch portion of the branch chute 29, there is rotatably arranged a path changing damper 30 for allocating the discharge direction depending on whether the material flowing through the discharge chute 15 is an aggregate for producing an asphalt mixture or the soil purified by heating. When it is located as shown by the solid line in the figure, it is toward the branch chute 29 side, and when it is located as shown by the chain double-dashed line, the vibrating sieve 1
It is designed to flow to the 6 side. And branch shoot 2
The soil flowing to the 9th side is collected as purified soil.

Further, the dust captured by the dust collector 9 contains a large amount of volatile pollutants, and a dust purification processing device 31 is installed to purify this dust. This dust purification processing device 31 has substantially the same structure as the dryer 1 that heats the new aggregate, and a cylindrical drum 32 having a large number of scraping blades around its inner periphery is rotatably mounted on a machine base 33. The drum 3 is tilted and is rotated at a predetermined speed by a driving device (not shown). The drum 3 is rotated by a burner 35 provided in a hot hopper 34 at one end of the drum 2.
2, while blowing hot air into the cold hopper 3 at the other end
An exhaust flue 37 is connected to the exhaust pipe 6, and exhaust gas is sucked by an exhaust fan 38 interposed in the exhaust flue 37 to maintain a high-temperature gas flow passing through the inside of the drum 32. It is connected to the exhaust flue 7 in front of the dust collector 9.
Then, the dust captured by the dust collector 9 is introduced into the hot hopper 34 side of the dust purification processing device 31, and heating is performed by a co-current heating method.

A soil cooling device 39 is provided as a means for cooling the soil heated and purified to a high temperature, and the tip of the branch chute 29 is connected to the soil cooling device 39. The soil cooling device 39 is provided with a drum 40 having substantially the same configuration as the drum 2 of the dryer 1, and a cylindrical drum 40 having a large number of scraping blades (not shown) around its inner peripheral portion. It is rotatably supported on the machine base 41 so that it can be rotated at a predetermined speed by a driving device (not shown).

A water spray nozzle 43 is provided in the charging hopper 42 at one end of the drum 40 in place of the burner, and water is sprayed on the high temperature soil charged in the drum 40 so as to be appropriately wetted and cooled. To make it suitable for handling. The amount of water sprayed from the water spray nozzle 43 is
When the amount and temperature of the soil to be put into the soil cooling device 39 are appropriately detected by the detection means to determine the optimum amount of water for spraying, even if the amount or temperature of the soil to be input changes, adhesion due to excessive humidification will occur. In addition to preventing clogging, it is possible to prevent dust generation due to insufficient humidification. Further, an exhaust duct 45 is connected to the discharge hopper 44 of the soil cooling device 39, the end of the exhaust duct 45 is connected to the exhaust flue 7, and water vapor generated in the soil cooling device 39 is exhausted via the exhaust duct 45. It is arranged to lead to the flue 7.

Although the soil heated and purified by the dryer 1 is supplied to the soil cooling device 39 through the bucket elevator 13 and the branch chute 29, the discharging chute 12 of the dryer 1 is provided with a distribution means or the like. Alternatively, the heated soil may be supplied to the soil cooling device 39 as shown by a dotted arrow.

Therefore, when the contaminated soil is purified by the asphalt plant having the above-mentioned structure, first, the contaminated soil is removed from the oversized ones and the foreign matters by a pretreatment device such as a sieve or a magnetic separator, which is not shown. It is put into the dryer 1 through the belt conveyor 11 and exposed to hot air from the burner 5 to heat the contaminated soil to a predetermined temperature. By this heating, the volatile pollutants in the contaminated soil are volatilized, separated or burned and decomposed, while the fine particles containing a large amount of the volatile pollutants in the soil are carried on the gas stream passing through the dryer 1 and downstream of the dryer 1. It scatters and the soil is purified.

Then, the exhaust gas discharged from the dryer 1 is guided to the dust collector 9, and the dust collector 9 captures fine particles containing a large amount of pollutants. The exhaust gas that has passed through the dust collector 9 is guided to the deodorizing furnace 24 and exposed to the high temperature atmosphere in the furnace, and the volatile pollutants remaining in the exhaust gas are completely combusted and decomposed.

On the other hand, the soil in the dryer 1 is sequentially discharged from the hot hopper 4 side, lifted to the upper position of the plant main body 14 via the bucket elevator 13, and discharged from the discharge chute 15. At this time, the path changing damper 30 is rotated to the solid line position in FIG. 1, and the soil flowing down from the discharge chute 15 is branched into the chute 29.
It is dropped to the side and thrown into the soil cooling device 39.
Then, the soil put into the soil cooling device 39 is sprayed with water from the water spray nozzle 43 while being tumbled down by the stirring blade, and is appropriately wetted and cooled to be in a state suitable for handling.

Further, a large amount of volatile pollutants are attached to the dust captured by the dust collector 9, and the dust is supplied to the dust purification processing device 31 in order to purify the dust.
The dust supplied into the dust purification processing device 31 is exposed to the hot air of the burner 35, and the volatile pollutants in the dust are burned and decomposed. The dust heated and purified by the dust purification processing device 31 is supplied to the soil cooling device 39 and cooled to a predetermined temperature.

In this way, if the asphalt plant is additionally equipped with the deodorizing furnace 24, the dust purification treatment device 31, the soil cooling device 39, etc., and the asphalt plant is made into a plant capable of contaminated soil purification treatment, a dedicated contaminated soil purification treatment is carried out. Capital investment can be reduced compared to setting up a plant, and a contaminated soil can be purified at low cost. Further, if the asphalt plant is also used as a plant for cleaning polluted soil, the operating rate of the plant is improved and the plant can be used efficiently.

FIG. 2 shows another embodiment of the dust purification processing device 31 and the soil cooling device 39. In FIG. 2, the same reference numerals as those in FIG. Omit it.

The dust purification processing device 31 in FIG. 2 will be briefly described. The dust purification processing device 31 has a structure for indirectly heating the dust captured by the dust collector 9 using the exhaust gas, and the screw 4 for transferring the dust into the casing 46.
7 is provided, and the periphery of the casing 46 is covered by the cylinder 4
Surrounded by 8. A hot air duct 49 for introducing the hot air of the deodorizing furnace 24 is connected to one end of the cover cylinder 48, and an exhaust duct 51 having a fan 50 for sucking and exhausting the hot air is connected to the other end. Further, an exhaust duct 53 with a fan 52 for exhausting generated volatile components is connected to the casing 46.

Then, the dust captured by the dust collector 9 is put into the casing 46, hot air is passed through the cover cylinder 48 while being transferred by the screw 47, and volatile pollutants in the dust are burned by indirect heating. Disassemble. Although the indirect heating method is adopted in order to avoid dust scattering at the time of heating, hot air may be introduced into the casing 46 to directly heat the dust. In this case, the exhaust gas is collected by the dust collector 9
It is good to lead to.

In the soil cooling device 39 shown in FIG. 2, a shaft 56 having agitation blades 55 mounted at appropriate intervals in a casing 54 is penetrated to rotatably support both ends of the shaft 56, and a drive device (not shown). The casing 54 is provided with a soil supply port 57 at one end and a discharge port 58 at the other end, and the tip of the branch chute 29 is connected to the supply port 57. ing.

The casing 54 has a water spray nozzle 5
9, the high temperature soil put into the casing 54 is sprayed with water from a water spray nozzle 59 while being stirred by a stirring blade 55, and is appropriately moistened and cooled to be in a state suitable for handling and an outlet 58. It discharges sequentially. Further, the water vapor generated in the casing 54 is led to the exhaust flue 7 via the exhaust duct 60.

As described above, when the continuous mixer system is adopted as the soil cooling device 39, the dried soil and the water can be mixed more uniformly by the stirring blade 55, and the soil suitable for handling can be stably obtained. it can.

FIG. 3 shows a type in which a dryer 61 for heating waste asphalt pavement is installed in parallel in an asphalt plant. In this type of asphalt plant, a contaminated soil is purified by a dryer 1 for heating a new aggregate. Although it can be treated, it is also possible to perform purification treatment using a dryer 61 that heats asphalt pavement waste. Hereinafter, the process of purifying contaminated soil using the dryer 61 will be described. Note that, in FIG. 3, the same reference numerals as those in FIG. 1 denote the same components, and the description thereof will be omitted.

Dryer 6 for heating asphalt pavement waste
1 has almost the same structure as the dryer 1 for heating the new aggregate, and a cylindrical drum 62 having a large number of scraping blades (not shown) around its inner circumference is rotated on the machine base 63. It is freely tilted and supported, and is rotated at a predetermined speed by a driving device (not shown). While hot air is sent into the drum 62 from a burner 65 arranged in a hot hopper 64 at one end of the drum 62, An exhaust flue 67 is connected to the storage bin 66 at the other end, and exhaust gas is sucked by an exhaust fan 68 interposed in the exhaust flue 67 to maintain a high-temperature gas flow passing through the inside of the drum 62. In addition, the exhaust gas is guided to the deodorizing furnace 24 via a dust collector 69 such as a cyclone dust collector.

Then, the waste asphalt pavement material is thrown into the drum 62 through the belt conveyor 70, exposed to the hot air from the burner 65 while it is rolling down and heated to be stored in the storage bin 66, and then the lower measurement is carried out. The asphalt pavement waste is reused by being dispensed to the tank 71, weighed appropriately, dispensed to the mixer 23 of the plant body 14 via the discharge chute 72, and mixed in a new asphalt mixture at a predetermined ratio. In the figure, the discharge chute 72 is used for the mixer 2
Although it is supplied to No. 3, it may be conveyed by a conveyor or the like.

In order to supply the soil heated and purified by the dryer 61 to the soil cooling device 39, the discharge chute 7
A branch chute 73 is arranged in the middle of 2, and a path changing damper 74 is freely rotatable at the branch part of the branch chute 73 as a means for allocating the discharge direction depending on whether it is waste asphalt pavement material or heat-purified soil. When it is located as shown by the solid line in the figure, it flows to the branch chute 73 side, and when it is located as shown by the chain double-dashed line, it flows to the mixer 23 side.

The tip of the branch chute 73 is connected to the charging hopper 42 of the soil cooling device 39 so that the purified soil is fed to the soil cooling device 39. Although the soil heated and purified by the dryer 61 is supplied to the soil cooling device 39 via the discharge chute 72 and the branch chute 73, the present invention is not limited to this, and the point is that the dryer 61 is used. What is discharged may be distributed and supplied to the mixer 23 and the soil cooling device 39.

The dust captured by the dust collector 69 is
Similar to the above, the dust purification treatment device 31 is supplied, and the exhaust duct 37 of the dust purification treatment device 31 is connected to the exhaust flue 67 in front of the dust collector 69.

When the contaminated soil is purified by the above apparatus, the contaminated soil is put into the dryer 61 via the belt conveyor 70 and heated to a predetermined temperature. By this heating, volatile pollutants such as oil in the polluted soil are volatilized and separated, or decomposed by combustion, while fine particles containing a large amount of volatile pollutants in the soil are carried on the gas flow passing through the drum 62. It is led to the downstream of the dryer 61,
Contaminated soil is cleaned.

After the exhaust gas discharged from the dryer 61 is guided to the dust collector 69 to capture the dust, the deodorizing furnace 2
4 is exposed to the high temperature atmosphere in the furnace, and the volatile pollutants remaining in the exhaust gas are completely combusted and decomposed and released from the chimney 10 into the atmosphere.

On the other hand, the soil which has been subjected to the purification treatment is dried by a dryer 6
It is appropriately paid out from the discharge chute 72 on the downstream side. At this time, the path changing damper 74 is rotated to the position shown by the solid line in FIG. 3, and the soil flowing down from the discharge chute 72 is thrown into the soil cooling device 39 via the branch chute 73 to spray water. To obtain a suitable state for handling by appropriately wetting and cooling.

As described above, in the case of the type in which the dryer 61 for heating the asphalt pavement waste material is arranged in parallel in the asphalt plant, the dryer 61 for heating the asphalt pavement waste material is used instead of the dryer 1 for heating the new aggregate. Then, the contaminated soil can be purified.

[0048]

As described above, according to the present invention, the dryer for heating the aggregate of the asphalt plant is configured as a heating means for both heating the aggregate and heating and cleaning the contaminated soil.
A deodorizing furnace that burns and decomposes volatile pollutants in exhaust gas is installed downstream of the dust collector interposed in the exhaust flue of the dryer.
The contaminated soil is heated and purified by a dryer, and the pollutants in the scattered exhaust gas are captured by a dust collector, and the volatile pollutants that could not be captured are burned and decomposed in a deodorization furnace. Can be carried out using the equipment of the asphalt plant, and the equipment investment can be suppressed compared to the installation of a dedicated contaminated soil purification treatment plant, and the contaminated soil purification treatment can be realized at low cost.

Further, since the dust purifying processing device for receiving the dust captured by the dust collector and burning and decomposing the volatile pollutants contained in the fine particles is disposed, the dust captured by the dust collector can also be purified and polluted. The plant is suitable for soil purification treatment.

Further, since the soil cooling device for cooling the high temperature soil discharged from the dryer is provided, the high temperature soil can be cooled to be easy to handle, and the plant is more suitable for the purification treatment of contaminated soil. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an asphalt plant that also serves as a contaminated soil purification treatment according to the present invention.

FIG. 2 is a diagram showing another embodiment of FIG.

FIG. 3 is a diagram showing another embodiment of FIG.

[Explanation of symbols]

1 ... Dryer (for heating new aggregate) 9 ... Dust collector 13 ... Bucket elevator 14 ... Plant body 23 ... Mixer 24 ... Deodorizing furnace 29 ... Branch chute 30 ... Route change damper 31 ... Dust cleaning device 39 ... Soil cooling device 61 ... Dryer (for heating asphalt pavement waste) 69 ... Dust collector 72 ... Ejection chute 73 ... Branch chute 74 ... Route change damper

Claims (6)

[Claims] 1. A contaminated soil is supplied to a dryer for heating aggregates of an asphalt plant for heating and purification, and at the same time, exhaust gas generated from the dryer is guided to a dust collector to capture fine particles containing pollutants and from the dust collector. A method for purifying contaminated soil, characterized in that the discharged exhaust gas is guided to a deodorizing furnace, and volatile pollutants in the exhaust gas are burned and decomposed in the deodorizing furnace. 2. The method for purifying contaminated soil according to claim 1, wherein the dust captured by the dust collector is taken out and heated to burn and decompose volatile pollutants in the dust. 3. The method for purifying contaminated soil according to claim 1 or 2, wherein the soil heated to a high temperature is guided to a soil cooling device to be cooled to a predetermined temperature. 4. A dryer for heating aggregates of an asphalt plant is constituted as a heating means for both heating aggregates and for cleaning and cleaning contaminated soil, and is provided downstream of a dust collector interposed in an exhaust flue of the dryer. An asphalt plant for cleaning and treating contaminated soil, comprising a deodorizing furnace for burning and decomposing volatile pollutants in exhaust gas. 5. A dust purification treatment device for accepting dust captured by a dust collector and burning and decomposing volatile pollutants contained in the dust is also provided. Asphalt plant. 6. The asphalt plant for contaminated soil cleaning and combined use according to claim 4 or 5, further comprising a soil cooling device for receiving the heated and purified soil and cooling it to a predetermined temperature.