JP2002263633A - Cleaning device for contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning device for contaminated soil which suitably performs heating/cleaning of the contaminated soil. SOLUTION: A rotary kiln 1 of a parallel flow heating type which heat-treats contaminated soil is provided with a soil supplying means 5 for supplying contaminated soil at a burner 6 arrangement side. An exhaust duct 8 of the rotary kiln 1 is provided with a gas temperature sensor 17. Amount of burner combustion is controlled by a burner combustion controller 18 so that the detected value of the gas temperature sensor 17 may become equal to or more than the boiling point of volatile contaminant in the contaminated soil, or the prescribed value near the boiling point. Thereby, the volatile contaminant in the dust entrained with the waste gas and scattered is exposed to high temperature atmosphere, and is subjected to volatilization-separation or decomposition during the period until the contaminant reaches a dust collector or during the period it is being captured by the dust collector 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for purifying contaminated soil containing volatile organic compounds such as oil and volatile contaminants such as mercury by heating.

[0002]

2. Description of the Related Art In recent years, soil in the premises of each business site and the surrounding area has been contaminated with wastewater of volatile contaminants such as oil due to industrial activities, and the groundwater flowing under the soil has been contaminated. It has been a problem that it has been talked about. In order to treat soil contaminated in this way, the soil is excavated and thrown into a rotary kiln for heating, and the soil is heated above the boiling point of volatile contaminants, for example,
If the volatile contaminant is kerosene, the boiling point is 180-300 ° C,
In the case of heavy oil, the soil is purified by heating and raising the temperature up to or near the boiling point of 350 ° C. to volatilize and separate or decompose volatile contaminants permeating the soil.

[0003]

However, when the contaminated soil containing oil was heated to a boiling point or higher in a rotary kiln and the contaminated concentration of the scattered dust was measured, for example, the contaminated soil having a contaminated concentration of 500 ppm was heated and purified. It was measured that the dust trapped by the inertial dust collector downstream of the rotary kiln had a high concentration of 1000 ppm, and the dust trapped by the bag filter had a high concentration of 3000 ppm. Most of the volatile pollutants were entrained in the gas flow of the rotary kiln. And found that it had been scattered.
Therefore, it was thought that there would be a problem, including the economical aspect, that heating and raising the temperature of a soil containing a high-boiling fuel oil or the like to a temperature higher than the boiling point, as in the past, would be a problem.

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide an apparatus for purifying contaminated soil by appropriately heating and purifying the contaminated soil with a rotary kiln for heating.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventor has conducted a stepwise heating of a contaminated soil containing volatile contaminants to a temperature higher than the boiling point of the contaminants using a heating rotary kiln. Even if the dust concentration in the dust collector is small, the wind speed in the rotary kiln is so high that the volatile contaminants contained in the fine particles are scattered without being separated or decomposed. In the dust collected by the dust collector is not sufficiently purified, and contaminated soil, especially soil containing high boiling point heavy oil, is heated up to or near the boiling point. It was concluded that priority should be given to effectively purifying volatile contaminants.

Therefore, it is considered that the exhaust gas temperature of the rotary kiln is more important than the heating temperature of the contaminated soil as in the prior art, and if the exhaust gas temperature is maintained at a high temperature equal to or higher than the boiling point of the volatile contaminants, scattering will occur. During the time that the collected dust reaches the dust collector and is further trapped by the dust collector, it is heated to volatilize and separate volatile pollutants in the dust, and the volatilized pollutants are collected in the dust collector. It was thought that the dust concentration could be reduced without coagulation. In addition, in order to maintain the exhaust gas temperature at a high temperature and control the burner combustion amount at the exhaust gas temperature, the heating method in the rotary kiln uses a cocurrent heating method in which contaminated soil and hot air flow in parallel from the countercurrent heating method. I thought it was better.

That is, in order to solve the above-mentioned problems, the present invention relates to a contaminated soil purification apparatus according to claim 1, wherein a heating rotary kiln provided with a burner for heat-treating the contaminated soil is provided. A dust collector for capturing dust in exhaust gas derived from the rotary kiln is provided, and a soil supply means for supplying contaminated soil is provided on the burner arrangement side of the heating rotary kiln. A gas temperature sensor for detecting the temperature is provided, and a burner combustion amount controller for controlling the burner combustion amount based on the exhaust gas temperature detected by the gas temperature sensor is provided.

Further, in the apparatus for purifying contaminated soil according to claim 2, the exhaust gas temperature detected by the burner combustion amount controller by a gas temperature sensor is equal to or higher than the boiling point of volatile contaminants contained in the contaminated soil. In this manner, the burner combustion amount is controlled.

Further, in the apparatus for purifying contaminated soil according to claim 3, the dust collected by the dust collector is thrown into a heating rotary kiln and exposed to a high-temperature atmosphere.

[0010]

According to the apparatus for purifying contaminated soil according to the first aspect of the present invention, the contaminated soil is heated by supplying the contaminated soil in parallel with the hot air from the burner fed to the rotary kiln for heating. In this co-current heating method, the contaminated soil supplied to the heating rotary kiln comes into contact with high-temperature hot air in the initial heating stage, and fine particles in the contaminated soil are scattered before being scattered along with the gas flow. Volatile pollutants can be effectively separated off or decomposed.

Further, the temperature of the exhaust gas discharged from the heating rotary kiln is detected by a gas temperature sensor and taken into a burner combustion controller, and the burner combustion amount is controlled by the burner combustion controller so that the exhaust gas temperature is preset. If the exhaust gas temperature is appropriately maintained at or near the temperature at which volatile pollutants can be volatilized and separated, if the dust content in the exhaust gas reaches the dust collector,
In addition, while being trapped by the dust collector, the dust is heated to volatilize and separate volatile contaminants in the dust, and the volatilized contaminants do not solidify in the dust collector. Contamination concentration can be reduced.

Further, according to the apparatus for purifying contaminated soil according to the second aspect of the present invention, burner combustion control is performed so that the temperature of the exhaust gas is equal to or higher than the boiling point of volatile pollutants contained in the contaminated soil. The contaminants in the dust scattered along with it can be exposed to a high-temperature atmosphere having a boiling point or higher to be volatilized and separated or decomposed, so that the concentration of the dust can be reduced, and the apparatus is suitable for purifying the contaminated soil.

[0013] According to the apparatus for purifying contaminated soil according to claim 3 of the present invention, the dust captured by the dust collector is supplied to the rotary kiln for heating and exposed to the high-temperature atmosphere in the rotary kiln, thereby remaining on the dust. Volatiles are separated or decomposed. This makes it possible to further reduce the dust contamination concentration without a separate heating device.

[0014]

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

In the figure, reference numeral 1 denotes a rotary kiln that heats excavated contaminated soil. The rotary kiln rotatably supports a cylindrical drum 2 having a large number of raising blades provided therein. It is rotated at a predetermined speed by a device (not shown). A charging hopper 3 is provided at one end of the drum 2.
At the other end, a discharge hopper 4 is provided. Contaminated soil is charged into the drum 2 by a conveyor 5 which is a soil supply means disposed on the input hopper 3 side. While rolling down the inside, the contaminated soil is heated by hot air supplied from the burner 6 disposed on the input hopper 3 side to volatilize or decompose volatile contaminants contained in the soil, thereby purifying the soil. Is discharged from the discharge port 7 of the discharge hopper 4.

An exhaust duct 8 for discharging exhaust gas is connected to the upper part of the discharge hopper 4 of the rotary kiln 1, and a dust collector 9 such as a bag filter for removing dust in the exhaust gas is interposed in the exhaust duct 8. At the same time, an exhaust fan 10 for sucking exhaust gas is interposed downstream of the deodorizing furnace 1.
1 is connected to the entrance side.

The deodorizing furnace 11 is provided with a burner 12 for maintaining the temperature in the furnace at a predetermined value. By exposing the exhaust gas introduced into the furnace to a high temperature atmosphere, the volatile pollutants in the exhaust gas are burned and decomposed. I am trying to do it. The deodorizing furnace 11 is designed to completely burn and decompose volatile pollutants.
The combustion amount of the burner 12 is controlled so as to maintain the furnace temperature at, for example, a high temperature of about 750 ° C. or more, and the furnace length is secured such that it takes at least 1 to 2 seconds or more for exhaust gas to pass through the furnace. Is preferred.

The exhaust gas discharged from the deodorizing furnace 11 has a high temperature, and a heat exchanger 13 is disposed at the outlet side of the deodorizing furnace 11 in order to effectively use the heat of the exhaust gas. The heat exchanger 13 is connected to a supply duct 15 of a fan 14 for supplying combustion air to the burner 12 of the deodorizing furnace 11. Exhaust gas from the deodorizing furnace 11 that has passed through the heat exchanger 13 is released into the atmosphere from a chimney 16.

A gas temperature sensor 17 is attached to the exhaust duct 8 at the outlet of the rotary kiln 1, and the gas temperature sensor 17 is connected to a burner combustion controller 18. The burner combustion amount controller 18 is provided with exhaust gas temperature setting means, and compares a temperature set value set by the exhaust gas temperature setting means with a detection value taken in by the gas temperature sensor 17 to obtain a difference value. , The combustion amount of the burner 6 is controlled to maintain the exhaust gas temperature at a set value.

The dust captured by the dust collector 9 is supplied to the discharge hopper 4 of the rotary kiln 1 by the screw feeder 19, so that the dust can be exposed to the high temperature atmosphere in the drum 2.

Since the soil and dust discharged from the rotary kiln 1 are difficult to handle because they are hot and dry, the soil and dust are supplied to the soil water cooling device 20 to be immersed in water, wet and cooled to make them easy to handle. In the soil water cooling device 20, both ends are rotatably supported by penetrating a shaft 23 in which a stirring blade 22 is attached at an appropriate interval in a casing 21, and is rotated at a predetermined speed by a driving device (not shown). In addition, a casing supply port 24 is provided at one end of the casing 21 and a discharge port 25 is provided at the other end.

The casing 21 has a water jet nozzle 2
6, water supplied from a water supply source (not shown) is sprayed toward the heated soil to wet and cool the heated soil. The amount of water to be injected from the injection nozzle 26 is determined by detecting the amount and temperature of the supplied soil by an appropriate detecting means such as a measuring conveyor or a temperature sensor, and determining the optimal amount of water to be injected. Even if is changed, it is possible to prevent adhesion and clogging due to excessive humidification and also to prevent generation of dust due to insufficient humidification.

When the contaminated soil is to be treated by the above apparatus, first, the contaminated soil is supplied into the drum 2 from the charging hopper 3 side of the rotary kiln 1 by the conveyor 5, and the contaminated soil is tumbled down the drum 2. Burner 6
And contact with the hot air sent. At this time, the contaminated soil flows in parallel with the hot air and is heated, so that the contaminated soil comes into contact with the high-temperature hot air in the initial heating stage, so that the fine particles in the contaminated soil are converted into a gas flow passing through the drum 2. Volatile pollutants in contaminated soil can be effectively volatilized or separated before being accompanied and scattered.

Exhaust gas discharged from the rotary kiln 1 flows through an exhaust duct 8 to a dust collector 9. The temperature of the exhaust gas flowing through the exhaust duct 8 is detected by a gas temperature sensor 17 and taken in by a burner combustion controller 18 so that the temperature of the exhaust gas is set to an exhaust gas set value set by an exhaust gas temperature setting means of the burner combustion controller 18. 6 is controlled.

If the set value of the exhaust gas temperature is equal to or higher than the boiling point of the volatile contaminants contained in the contaminated soil, the volatile contaminants in the scattered dust can be volatilized or separated. If the temperature is around the boiling point, the volatile contaminants are not solidified by the dust collector 9. For example, kerosene has a boiling point of 180 to 300 ° C, and heavy oil has a boiling point of 35.
Since there is a wide range above 0 ° C and these various oils are often mixed in the soil, the boiling point of the main volatile contaminants contained in the soil is focused on and the exhaust gas temperature is adjusted. It is preferable to determine the degree of purification of soil or dust by performing a test operation or the like while controlling the temperature at or above the boiling point, and determine the exhaust gas temperature set value appropriately based on this.

When the temperature of the exhaust gas at the outlet of the rotary kiln 1 is maintained at a predetermined high temperature by the burner combustion control by the burner combustion controller 18, the volatile contaminants contained in the dust in the exhaust gas are volatilized or separated while being separated. And the contamination concentration of the dust collected by the dust collector 9 is reduced.

The exhaust gas that has passed through the dust collector 9 is introduced into the deodorizing furnace 11, where it comes into contact with the high-temperature gas in the deodorizing furnace 11, whereby the volatile pollutants in the gas are completely burned, and the odor and dioxin are decomposed. It becomes harmless and is released into the atmosphere from the chimney 16 after passing through the heat exchanger 13.

The combustion air supplied from the fan 14 exchanges heat while passing through the heat exchanger 13 to increase the air temperature, and is supplied to the burner 12 of the deodorizing furnace 11 to be effectively used as combustion air. You. The air that has passed through the heat exchanger 13 may be supplied to the burner 6 of the rotary kiln 1 as combustion air.

Although the volatile contaminants still remain in the dust collected by the dust collector 9, the dust is supplied to the discharge hopper 4 of the rotary kiln 1 by a screw feeder 19 to purify the volatile contaminants. Exposed to the high-temperature atmosphere inside, and further volatile separation or decomposition of volatile contaminants remaining in the dust.

The heated soil and dust discharged from the rotary kiln 1 are supplied to a soil water cooling device 20, where the water is jetted from a water jet nozzle 26 while being mixed by a stirring blade 22, so that the soil is wetted and cooled to lower the temperature. And increase the water content to make it easy to handle. The water vapor generated at this time is preferably led to the exhaust duct 8.

As described above, in the above-described apparatus, since the contaminated soil supplied to the rotary kiln 1 is brought into contact with the high-temperature hot air in the initial heating stage by adopting the co-current heating method, fine particles in the contaminated soil are converted into gas. The volatile contaminants in the contaminated soil can be effectively volatilized or decomposed before being scattered in the stream. In addition, the exhaust gas temperature can be easily controlled by the co-current heating method. If the exhaust gas temperature is maintained at a high temperature, the dust in the exhaust gas is heated even before reaching the dust collector 9 to volatilize volatile pollutants in the dust. The dust can be separated, and the contaminants that have volatilized are not solidified in the dust collector 9, so that the dust contamination concentration can be reduced.

In addition, since it is not necessary to heat the contaminated soil itself to a temperature higher than the boiling point, it is possible to suppress the fuel cost when purifying a substance having a high boiling point, such as heavy oil, so that the fuel cost can be reduced. Device.

In addition, if the dust containing high-concentration volatile contaminants captured by the dust collector 9 is supplied to the rotary kiln 1 and heated, a separate heating device becomes unnecessary, and further dust can be produced at low cost. Purification process can be performed.

Although the apparatus of the above embodiment is based on the premise that the volatile contaminants are volatile organic compounds of oils, the apparatus can also be applied when the contaminants are mercury.
At this time, it is preferable to employ a wet type washer instead of the deodorizing furnace 11 to recover mercury.

[0035]

As described above, according to the apparatus for purifying contaminated soil according to the first aspect of the present invention, a heating rotary kiln having a burner for heat-treating contaminated soil, and an exhaust gas derived from the heating rotary kiln A dust collector is provided for capturing dust inside, and a soil supply means for supplying contaminated soil is disposed on the burner side of the rotary kiln for heating. On the other hand, a gas temperature for detecting exhaust gas temperature is provided at an exhaust gas discharge section of the rotary kiln for heating. A contaminated soil supplied to the heating rotary kiln is provided with a high temperature in the initial heating stage because the sensor has a burner combustion amount controller for controlling the burner combustion amount based on the exhaust gas temperature detected by the gas temperature sensor. Effectively removes volatile pollutants in contaminated soil before coming into contact with hot air and causing fines in the contaminated soil to fly away with the gas stream It can be issued separation or decomposition. In addition, by controlling the exhaust gas temperature to a high temperature, until the dust in the exhaust gas reaches the dust collector,
In addition, while being trapped by the dust collector, the dust is heated to volatilize and separate volatile contaminants in the dust, and the volatilized contaminants do not solidify in the dust collector. Contamination concentration can be reduced.

Further, according to the apparatus for purifying contaminated soil according to the second aspect, the burner combustion controller controls the exhaust gas temperature detected by the gas temperature sensor to be equal to or higher than the boiling point of volatile contaminants contained in the contaminated soil. Since the burner combustion amount is controlled, volatile pollutants in dust scattered along with exhaust gas can be exposed to an atmosphere above the boiling point to promote volatilization and separation. Is not coagulated in the dust collector, the concentration of dust trapped by the dust collector can be reduced, and the apparatus is suitable for purifying contaminated soil.

According to the apparatus for purifying contaminated soil according to the third aspect of the present invention, the dust captured by the dust collector is introduced into the heating rotary kiln and exposed to a high-temperature atmosphere. Even by heating the volatile contaminants in the dust captured by the dust collector, the contamination concentration can be further reduced.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing one embodiment of a device for purifying contaminated soil according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotary kiln for heating 2 ... Drum 5 ... Conveyor (soil supply means) 6 ... Burner 9 ... Dust collector 11 ... Deodorizing furnace 17 ... Gas temperature sensor 18 ... Burner combustion controller 20 ... Soil water cooling device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F27D 17/00 105 B09B 3/00 303P 303L F-term (Reference) 2E191 BA02 BA11 BA12 BB00 BB01 BD11 BD12 4D004 AA37 AA41 AB02 AB03 AB07 CA22 CB34 CB36 DA01 DA02 DA06 DA20 4K056 AA19 BB01 CA06 CA20 DB07 DB12 DB21 4K061 AA08 BA03 DA01 FA05 FA06 GA02

Claims (3)

[Claims] 1. A heating rotary kiln having a burner for heat-treating contaminated soil, a dust collector for capturing dust in exhaust gas derived from the heating rotary kiln, and contamination on a side of the heating rotary kiln where a burner is disposed. While providing soil supply means for supplying soil, the exhaust gas discharge part of the heating rotary kiln is provided with a gas temperature sensor for detecting the temperature of the exhaust gas, and the combustion amount of the burner is determined based on the exhaust gas temperature detected by the gas temperature sensor. An apparatus for purifying contaminated soil, comprising a burner combustion amount controller for controlling. 2. The burner combustion amount controller according to claim 1, wherein the burner combustion amount is controlled so that the exhaust gas temperature detected by a gas temperature sensor is equal to or higher than the boiling point of volatile pollutants contained in the contaminated soil. The apparatus for purifying contaminated soil according to claim 1. 3. The apparatus for purifying contaminated soil according to claim 1, wherein the dust trapped by said dust collector is thrown into a heating rotary kiln and exposed to a high-temperature atmosphere.