JP2003275738A - Method for treating contaminant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating a contaminant in soil, by which the contaminated soil can be decontaminated efficiently without causing the contaminant to leak to the outside while saving expenditures and labor. <P>SOLUTION: The contaminant and an organic carbon compound contained in the contaminated soil are vaporized by heating the soil. The gas containing the vaporized contaminant and organic carbon compound is heated in an oxygen- lowered atmosphere so that the organic carbon compound is carbonized to produce carbon particles. The produced carbon particles are collected and the contaminant adsorbed on the collected carbon particles is recovered. Otherwise, the contaminant contained in the soil is vaporized by heating the soil. The vaporized contaminant is cooled to obtain a condensate. The contaminant is recovered from the obtained condensate, namely, the condensate is separated into a hydrophilic phase and an oleophilic phase, the dust contained in the hydrophilic phase is separated and the contaminant is removed from the hydrophilic phase by making the hydrophilic phase pass through a separation membrane. <P>COPYRIGHT: (C)2003,JPO

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 pollutants that contaminate soil, and more particularly, to collect and treat pollutants with high accuracy by preventing incomplete collection of pollutants and leakage from a treatment system. The present invention relates to a method for treating soil pollutants.

[0002]

2. Description of the Related Art In recent years, soil pollution due to harmful substances has become a serious problem. Examples of pollutants are cadmium, all-cyan, organic neighbors, lead, hexavalent chromium, arsenic, total mercury, alkylmercury, PCB, copper, dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene. , Cis-1,2-dichloroethylene, 1,1,1
-Trichloroethane, 1,1,2-trichloroethane,
Trichlorethylene, tetrachloroethylene, 1,3-
There are substances that are harmful to living organisms, such as dichloropropene, thiuram, simazine, thiobencarb, benzene, selenium, and dioxin (DXN), and substances that have low toxicity such as oil but make soil use difficult. In particular, many soil pollutions due to DXNs and PCBs, which are highly harmful even at low concentrations, have been found, which is a serious problem.

Traditionally, to remove pollutants from soil,
In many cases, incinerators and cement kilns were used to gasify pollutants in the soil at high temperature and at the same time to decompose them by combustion. In this case, the combustion gas after combustion decomposition is exhausted from the chimney as it is. Although decomposition by combustion is a cheap method, it is extremely difficult to maintain stable decomposition capacity, so in order to obtain stable decomposition capacity, a large amount of fuel is injected to stabilize the combustion state. However, the advantage of being inexpensive is lost.

Therefore, a method has been proposed in which the soil is heated and gasified pollutants are not burned and decomposed but separated from the soil and then collected once. Therefore, the decomposition treatment is performed by using various known decomposition techniques.

[0005]

However, in the above method for recovering the pollutant, it is necessary to reliably recover the pollutant in order to prevent the pollutant gas separated from the soil from leaking out of the processing apparatus. For this reason, activated carbon and other special scavengers and additives (hereinafter collectively referred to as chemicals) are used. However, the treatment by using these chemicals or the like causes an increase in cost. Further, the adsorption efficiency of these chemicals is improved as the contact time with the pollutant is longer, so that the actual processing apparatus is inevitably large in order to effectively act the chemicals, and the apparatus structure becomes complicated. . Furthermore, sufficient treatment is necessary to keep the concentration of pollutants in the exhaust gas or wastewater discharged from the treatment equipment below the environmental standard, but the increase in treatment labor and cost poses a problem, and the treatment procedure must be constructed efficiently. It has been strongly desired to reduce processing labor and cost.

[0006] DXNs and PCBs have been noted as harmful substances even before the problem of soil pollution and many decomposition techniques have been proposed. However, chelating agents conventionally used for separating and recovering pollutants. Scavengers such as often inhibit the degradation of pollutants. Therefore, when the decomposition technique is applied to soil purification, it is necessary to separate the scavenger that inhibits decomposition from the collected pollutants, which is troublesome. For this reason, there is a demand for a method for treating pollutants in soil that can collect pollutants without externally adding a scavenger that inhibits decomposition.

[0007] The present invention is capable of efficiently purifying contaminated soil without leaking pollutants from the treatment equipment, and can reduce the cost and labor of the purification treatment, so that the pollutants can be efficiently treated. An object is to provide a method for treating a substance.

[0008]

According to one aspect of the present invention, there is provided a method for treating pollutants, which comprises a vaporization step of vaporizing pollutants and organic carbon compounds contained in soil, and the vaporized pollutants and organic compounds. A carbonization step of heating a gas containing a carbon compound in a low oxygen atmosphere to carbonize the organic carbon compound to generate carbon particles, and a recovery step of recovering the contaminants adsorbed by the carbon particles together with the carbon particles. It is a gist to have.

Further, according to one aspect of the present invention, a method for treating a pollutant includes a vaporizing step of vaporizing the pollutant contained in the soil, and a condensing step of cooling the vaporized pollutant to obtain a condensate. A phase separation step of separating a hydrophilic phase and a lipophilic phase of the condensate, a dust separation step of separating dust contained in the hydrophilic phase separated in the phase separation step, and the hydrophilic phase And a membrane separation step of removing the contaminants from the hydrophilic phase through a separation membrane.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION When a pollutant is vaporized and separated from the soil by heating the polluted soil, an organic carbon compound in the soil is vaporized together with the pollutant. When the vaporized gas is heated under conditions such that the organic carbon compound is carbonized, carbon particles are generated and act as an adsorbent for pollutants, and the adsorbed pollutants are collected together by collecting the carbon particles.
Degradation of pollutants progresses according to the heating temperature, and the carbon particles act as a catalyst for the decomposition to promote the decomposition, so that the pollutants can be sufficiently removed from the exhaust gas and waste water after the treatment. In the vaporization of pollutants and organic carbon compounds, the polluted soil is preferably heated to about 400 ° C. or more and about 600 ° C. or less, and the carbonization of the organic carbon compounds involves generating a gas containing the pollutants and the organic carbon compounds in a low oxygen environment. About 7 below
00 ° C or higher, preferably about 800 ° C or higher and about 1200
Heating to a temperature of ℃ or less, carbonization of the organic carbon compound produces carbon particles. By cooling the carbon particles to a temperature of about 200 ° C. or lower and collecting the carbon particles, the carbon particles in which the pollutants in the atmosphere are sufficiently taken in are recovered. In this way, soil remediation with maximum leakage and re-emission of pollutants can be carried out at low cost.

The soil treatment of the present invention will be described in detail below.

The pollutants to be treated in the soil treatment of the present invention are organic compounds and metals that are harmful to the living body or the environment and are vaporized (or sublimated) by heating or depressurization. A substance that evaporates by heating at ℃ or by vacuum is suitable as an object to be treated. Examples of the organic compound include PCB, dioxins (DXN), dichloromethane, carbon tetrachloride, 1,2
-Dichloroethane, 1,1-dichloroethylene, cis-
1,2-dichloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene, tetrachloroethylene, 1,3-dichloropropene, thiuram, simazine, thiobencarb, benzene,
There are compounds harmful to the human body such as naphthalene and anthracene. Examples of the metals include cadmium, phosphorus,
Lead, chromium, arsenic, mercury, selenium, etc. can be mentioned,
The soil is not particularly limited to these substances, and the soil containing the vaporizable pollutant as described above can be purified, that is, the pollutant can be removed.

In the present invention, pollutants can be treated by using organic matter contained in soil such as trees, flowers, carcasses of animals and plants, and feces as a carbon source. Therefore, the soil to be treated may be a soil containing an organic carbon compound that produces carbon under carbonization conditions. That is, it is possible to treat soil in which rocks constituting the land are crushed into fine grains and biological remains or decomposed products thereof are mixed without particular limitation. For example, soil that contains a large amount of organic matter (humus) in agricultural land, horticultural fields and mountains; soil that contains a relatively small amount of humus such as roads, residential land, factories, lakes,
It also includes bottom sediment, which is a constituent material of the bottom of the sea and rivers, and sludge mixed with any of the above. Further, the organic carbon compound is not limited to those naturally contained in the soil as described above, it may be artificially added to the soil, for example, oils and fats soil contaminants are not particularly harmful to the human body, etc. When such an organic compound is included, such an organic compound serves as a carbon source in carbonization. The soil containing water is
In the present invention, water vapor is generated in the vaporization of pollutants, and the hydrocarbons remaining on the surface of the carbon particles generated in the carbonization of the organic compound are removed by the water vapor to activate the carbon particles to generate activated carbon having a high adsorption ability. It is advantageous.

The vaporizing means for vaporizing and separating the pollutants from the soil is not particularly limited as long as it is a means capable of vaporizing the pollutants by heating the soil and removing them from the soil. For example, a kiln furnace, a fluidized bed A heating furnace such as a furnace or a vacuum heating furnace can be used. By using such a heating furnace as a vaporizing means and introducing the contaminated soil and heating it to vaporize the pollutants, the organic carbon compound and the water in the soil are also vaporized.
The heating temperature required for vaporizing the pollutants varies depending on the atmospheric pressure, and at atmospheric pressure, it is generally about 400 ° C. or higher.

The vaporization of the pollutant itself can be carried out in an oxygen-containing atmosphere. At this stage, if the pollutant is heated to a high temperature in a low-oxygen atmosphere, the pyrolysis reaction of the organic matter occurs simultaneously with the gasification of the pollutant. A high molecular weight component having a molecular weight of about 100 to 3000 is generated. That is, it is possible to generate a component having a high molecular weight suitable for generating carbon particles used as an adsorbent. To cause such thermal decomposition,
The heating temperature is 150 ° C. or higher, preferably 400 ° C. or higher, and the higher the temperature, the more the thermal decomposition proceeds. Further, since the generated high molecular weight gas is decomposed by oxygen, in order to obtain the above high molecular weight component, the oxygen concentration in the atmosphere needs to be low, and the oxygen concentration at the outlet of the vaporizing means is 5 vol.
% (Volume ratio) or less, preferably 0% is important.

The gas to be treated containing pollutants and organic carbon compounds vaporized from the soil contains a high molecular weight component depending on the vaporization conditions as described above, and further, depending on the state of the soil,
It contains mineral particles mainly composed of water contained in soil and fine particles (less than about 75 μm) in which a part of soil is scattered by gas flow. Such a gas to be treated is further heated to a higher temperature in a low oxygen atmosphere (oxygen concentration: 5 vol% or less) to carbonize the organic carbon compound. The heating temperature for promoting carbonization is 800 ° C. or higher, preferably 1000 ° C. or higher. However, if the temperature is higher than this, the production efficiency of carbon particles decreases, and therefore, it is specifically preferably 1200 ° C. or lower.
At this temperature, the decomposition reaction of pollutants also proceeds. Further, the produced carbon particles have a catalytic action on the decomposition reaction of the pollutant, particularly the dehalogenation reaction of the halogen compound, and the decomposition of the pollutant proceeds. If the ratio of the organic carbon compound to the pollutant in the soil is about 1/1 or more, the effect of the carbon particles can be remarkably obtained.

The method of heating the gas to a high temperature includes a method of heating with a heater, an indirect heating method with a burner, a method of indirectly heating the gas to be treated with a high-temperature heating medium using a heat exchanger, There are methods such as heating the mixed gaseous medium with the gas to be treated and heating it, and using a reactant that causes an exothermic reaction by contact with the gas to be treated or the components contained in it. There is no particular limitation as long as it can be heated. However, the method of adding preheated high-temperature steam is particularly effective in that the effect of water derived from soil can be supplemented. In other words, when the high molecular weight component in the heated gas to be treated is pyrolyzed to lower molecular weight and solid carbon is deposited, water vapor removes the hydrocarbons remaining on the carbon surface and adds carbon particles to remove harmful substances. Increase the ability to collect. When only the amount of water contained in the soil is sufficient, it is not necessary to use a heating method using steam, and it can be suitably carried out by the above-mentioned method such as indirect heating, and if necessary, it may be added to the gas to be treated. Good.

The gas to be treated after the completion of carbonization by heating is cooled, and the carbon particles are collected at a temperature of about 200 ° C. or lower. During the cooling process, the carbon particles reach a temperature suitable for adsorbing and collecting the pollutants, and sufficiently adsorb the pollutants remaining in the gas to be treated. If the cooling temperature of the gas to be treated is equal to or higher than the boiling point of water, the carbon particles can be collected by a dry method. If the cooling temperature is lower than the boiling point of water, the water is condensed because the water is condensed.

Examples of the collecting means include, but are not limited to, filter media such as bag filters and wet separation membranes that can separate carbon particles from the gas to be treated.
When the carbon particles filtered out from the gas are deposited on the surface of the filter medium to form a layer, the carbon particles themselves also constitute a filter, and a further collection effect can be expected. In addition, the longer the contact time of the gas to be treated with the carbon particles, the more the decomposition of pollutants, especially the dechlorination of organic chlorine compounds progresses. Has the effect of promoting.

FIG. 1 shows an example of an apparatus for performing the above processing. The contaminated soil is put into the soil heating furnace 1 and heated to vaporize the pollutants, the organic carbon compounds and the water. The gas to be treated vaporized from the soil is further heated in the gas heating furnace 2 to carbonize the organic carbon compound. Steam is supplied from the steam supply unit 2a to the gas heating furnace 2 as needed, and the heating temperature of the gas heating furnace 2 is controlled by the temperature control unit 2b. The gas to be treated after carbonization is cooled by the cooler 3. If the cooling temperature is equal to or higher than the boiling point of water, the carbon particles are separated from the gas by passing through the carbon recovery device 4 equipped with a filter according to the dry process of FIG. Cool to condense water vapor and separate as wastewater. If the cooling temperature of the gas to be treated is lower than the boiling point of water, water containing carbon particles that is condensed and separated by cooling in the cooler 3 is separated and collected by the moisture collecting device 5 according to the wet process of FIG. 2B. , The condensed water is passed through a carbon recovery device 4 ′ equipped with a filter to separate and collect carbon particles and waste water.

Since the natural soil generally contains various organic compounds, the gas generated when the contaminated soil is heated, the high-molecular-weight component is directly captured by the activated carbon and the like unless carbonized by high temperature heating. Contact with chemicals such as scavengers and additives, especially tar-like substances cover the surface of the chemicals, which may interfere with the collection of target pollutants, and if the chemical is a packed tower type, the pressure of the packed tower itself This increases the loss and interferes with normal driving. However, in the present invention, the high-molecular-weight component that becomes tar-like is carbonized and used as carbon particles, so that it is possible to avoid damage to chemicals and treatment facilities and increase in treatment cost.

Further, as a technique for decomposing pollutants such as PCBs, there is a method of irradiating with ultraviolet rays. However, if tar components are present together with the contaminants, the energy absorption of the aromatic compounds in the tar components causes the decomposition of the contaminants. . In this embodiment, since the tar content is used as the raw material of the carbon particles, the effect of removing the tar content that interferes with the decomposition of PCB at the same time as the production of the carbon particles can be obtained.

In the purification of soil for heating polluted soil to remove pollutants from the soil, if the gas containing pollutants, water vapor and organic matter generated from the soil is condensed and collected without further heating, the pollutants and soil It becomes a condensate in which decomposition products of organic matter are mixed. When recovering pollutants, especially organic compound-based pollutants such as PCB and DXN from this condensate, it is necessary to devise a treatment procedure in order to efficiently collect pollutants in exhaust gas and wastewater so that the pollutant concentration becomes low. Become. In the present invention, as the treatment process, phase separation (separation of a plurality of liquid phases that spontaneously separates), solid separation (separation of liquid and solid) and membrane separation (separation of substances in a liquid phase at a molecular level) are performed. Is mainly applied, and if necessary, oil-water separation (forcibly collecting the dispersed phase of the dispersion liquid by an external stimulus to separate into separate liquid phases for liquid separation) or liquid-liquid extraction is incorporated.

A description will be given below with reference to FIGS.

The condensate obtained by condensing the gas obtained from the contaminated soil heated in the soil heating furnace 1 in the scrubber 6 is used in the liquid separating tank 7
In the above, due to the difference in specific gravity, there are three liquid phases, an upper phase, a middle phase and a lower phase. The middle phase is a hydrophilic liquid phase in which a trace amount of contaminants are dissolved or turbid in water. The upper and lower phases are liquid phases that are poorly soluble in water, and are separated into those with a low specific gravity and those with a high specific gravity. In addition, in the upper phase, pollutants are often dissolved in decomposition products of organic matter in soil, and in the lower phase, pollutants are often the main components. Phase separation is a process of separating pollutants from the condensate by taking out these liquid phases for each phase, and the pollutants are recovered from the upper phase and the lower phase. The lower phase also contains dust that has a relatively large particle size and tends to settle. Phase separation is possible without using special equipment. For example, it can be used also as a water tank attached to a scrubber provided to prevent atmospheric release of gas and mist generated when soil is heated.

The middle phase obtained by removing the upper and lower phases by phase separation is the dust (sludge) existing in the liquid by the filter medium 8.
Is separated (dust removal). As the filter material, an ordinary filter membrane or sand filter can be used. Pollutants are adsorbed on the separated dust. A part of the permeated liquid that has permeated through the filter medium 8 may be used as spray water or the like in the scrubber of the previous operation.

When the soil is relatively slightly contaminated and the organic component contained in the middle phase obtained by phase separation is small, the contaminants contained in the middle phase can be removed by membrane separation using the separation membrane 9. Although it is possible (see Fig. 3), when the medium phase organic component is relatively large or the composition of the organic component is complex and thus it is in a dispersed liquid state, the treatment by membrane separation tends to cause malfunction, so oil-water separation (See FIG. 4 or FIG. 5) is efficient.

Oil-water separation is performed using a liquid separation tank 10 provided with a permeable membrane having a fine flow path. When the aqueous phase liquid in which fine oil droplets are dispersed is permeated, the oil droplets are captured by the membrane while permeating through the permeable membrane, and are repeatedly coalesced with other oil droplets to form coarse particles.
As a result, the lipophilic liquid phase can be formed separately from water by the difference in specific gravity. The material of the permeable membrane is preferably lipophilic. By the oil-water separation, it is possible to separate into three liquid phases of an upper phase, a middle phase and a lower phase, similarly to the above-mentioned phase separation process. Similar to the above, the hydrophilic phase from which the lipophilic phase containing contaminants has been removed is detoxified by membrane separation.

Membrane separation is a process in which contaminants are removed from an aqueous phase liquid containing water as a main component that has undergone oil-water separation to reduce the concentration to a level satisfying environmental standards and drainage standards. A membrane separator having a separation membrane is provided. Remove at 9. The separation membranes that can be used include reverse osmosis membrane (RO), ultrafiltration membrane (UF), microfiltration (MF).
and so on. By such membrane treatment, it is possible to obtain permeated water from which contaminants have been removed and concentrated water in which contaminants have been concentrated. A plurality of types of membranes may be used in combination. When a plurality of membranes are used in combination, it is effective to configure the membrane separator 9 so as to circulate the liquid concentrated in the downstream membrane ML to the upstream membrane MU for reprocessing as shown in FIG. is there. The permeated water obtained by membrane separation can be discharged as drainage if it is removed to a concentration that meets environmental standards and drainage standards. Alternatively, it may be used for regenerating the soil in addition to the soil after the purification treatment that loses water by heating. The concentrated water is
The contaminants can be separated by recycling to the oil-water separation or phase separation process.

Alternatively, as shown in FIG. 7, the treatment process can be configured to perform liquid-liquid extraction using a solvent instead of the oil-water separation described above. In this case, the middle phase obtained by phase separation is preferably liquid-liquid extracted in the extraction tank 11 before removing dust. As a result, the contaminants contained in the dust separated by the filter medium 8 after the liquid-liquid extraction are extremely small, so that the dust can be directly discarded. In liquid-liquid extraction, a solvent that is sparingly soluble in water and capable of extracting contaminants from a condensate is brought into contact with the hydrophilic phase (middle phase) to extract and separate contaminants. However, the solvent used here must be a solvent that does not interfere with the decomposition of pollutants. For example, n-hexane is poorly soluble in water and easily dissolves PCB and DXN. Further, since it has a linear structure, there is no problem even if it coexists when decomposing contaminants by the UV decomposition method.

The pollutants collected by the above treatment process are decomposed in the decomposition device 12.
Decomposition of pollutants can be performed, for example, by photolysis by UV irradiation
Catalyst decomposition method using a catalyst, S using metallic sodium
It is possible by the D method or the like. In the case of dioxins, combustion decomposition can also be used.

In the treatment process of FIG. 4, the upper and lower liquid phases generated in the phase separation and the oil-water separation and the sludge generated in the dust removal are processed by sequentially performing the phase separation, the dust separation, the oil-water separation and the membrane separation. By collecting the pollutants, the pollutants can be directly supplied to the decomposition means. It should be noted that, for example, if the order of the steps is changed as shown in FIG. 8, the processing efficiency is lowered, and thus it becomes difficult to process high-concentration contamination.

In phase separation and oil-water separation, the higher the initial concentration of pollutants, the greater the total amount of pollutants that can be separated and the higher the separation efficiency. On the other hand, in the process of membrane separation, the separation rate can be improved by increasing the ratio of concentrated water to permeated water. Therefore, in the treatment process of FIG. 5, considering that the gas generated in the early stage of heating the soil contains less pollutants,
Gas with little pollutant generated in the early stage of soil heating and gas with many pollutant in the latter stage of heating are processed by different routes (hereinafter, the condensate derived from the initial gas is the condensate A and the latter one is the condensate B. And). Since most of the condensate A in the initial stage of heating is water, the condensate B has a high concentration of pollutants as much as water is removed in the initial stage of heating, so phase separation,
The efficiency in oil-water separation can be improved. Therefore, if necessary, the condensate A from which the dust is removed by the filter medium 13
By performing detoxification treatment by membrane separation after mixing with the aqueous phase after oil-water separation, it is possible to maintain the removal efficiency of pollutants high for a long time and reduce the maintenance frequency of the treatment system. In addition, it is necessary to detoxify leachate generated during excavation for heat treatment of contaminated soil, rain, etc., but in this case, Si, Na, Ca, etc. dissolved in leachate There is a problem that the mineral substances of (3) are deposited on the surface of the membrane during the membrane separation and interfere with the permeability of the membrane. On the other hand, the above problem can be solved by mixing the condensed water A to reduce the concentrations of these components and then performing the detoxification treatment. In order to effectively separate the condensed water A and the condensed water B, the soil heating temperature is set to 300 at the initial stage.
Condensed water A may be fractionated at a temperature of not higher than 0 ° C, preferably 200 ° C or lower, and then the temperature may be raised to take condensed water B.

In FIG. 7, the liquid-liquid extraction is performed between the phase separation and the dust removal, and the intermediate-phase liquid containing dust taken in from the phase separation is extracted as it is. As a result, a trace amount of pollutants in the water are extracted, and the pollutants adsorbed on the dust are also extracted. Therefore, since the dust pollutants can be removed, the sludge recovered by the dust removal can be returned to the soil and used. No oil-water separation is required in this process.

In the present invention, since it is not necessary to add a scavenger from the outside to use, the processing cost can be reduced.

[0036]

EXAMPLES Example 1 Using the apparatus shown in FIG. 1, according to the treatment conditions shown in Table 1, soil purification treatment (experiment Nos. 1 to 20) was performed on soils of various soils containing pollutants. The evaluation was performed by measuring the concentration of pollutants in wastewater and exhaust gas from the purification treatment. The results are shown in Table 1. The processing procedure and evaluation of the results are as follows.

The contaminated soil was charged into the soil heating furnace at a predetermined treatment rate and heated, the generated gas was introduced into the gas heating furnace, and then the gas was cooled by the cooler 3 to collect carbon particles in the gas. . When the carbon particles were collected by a dry method, the cooling temperature of the cooler 3 was 170 ° C., and in the case of a wet method, the cooling temperature was atmospheric temperature. In the case of dry collection, as shown in FIG. 2 (a), the cooling gas is passed through the filter of the carbon recovery device 4 to separate the carbon particles from the gas, and then the gas is cooled to room temperature in the moisture collection device 5 to vaporize it. Was condensed and separated as waste water. In the case of wet collection, water containing carbon particles that is condensed and separated by cooling in the cooler 3 is collected by the moisture collector 5, and the condensed water is passed through the filter of the carbon recovery device 4 ′ to generate carbon particles and waste water. Separated and collected.

The pollutant concentrations of the waste water and the exhaust gas obtained by the above treatment were measured, and the legal standards (PCB: [waste water] 0.0005 mg / L or less, [exhaust gas] 0.1 mg) were measured.
/ M ³ or less, dioxin: [drainage] 10 pg-TEQ
/ L or less, [exhaust gas] 0.1 ng-TEQ / m ³ or less)
It was evaluated according to whether or not

In Table 1, the soil quality is in accordance with the soil engineering classification method (JGS M111), and the amount of treated soil is the amount of treated soil per hour (wet weight). Units of soil pollutant concentration are mg / kg for PCBs and ng-TEQ / g for dioxins.
The amount of organic matter is converted to the content per wet weight as a heat loss reduction.

[0040]

[Table 1] In the results shown in Table 1, there is a difference in the amount of weight loss even if the soil quality is the same, which is considered to be due to the difference in the soil sampling location.

As can be seen from Experiment 1, the pollutants can be collected by the carbon particles by producing the carbon particles, and therefore the pollutants are treated so that the pollutant concentrations in the waste water and exhaust gas satisfy the legal regulations. be able to. In Experiment 2,
For comparison, carbonization was not performed by heating the gas to be treated. In this case, carbon particles were not generated, the pollutant concentration in the wastewater and exhaust gas was extremely high, and the legal regulations were not satisfied. Experiments 3 to 20 are examples in which the treatment conditions were changed, and it was shown that carbonization also proceeds favorably in these cases and effectively acts on the treatment of pollutants.

Example 2 Soil of various soil types shown in Table 2 was heated in a soil heating furnace to cool gas produced by a scrubber, and the obtained condensate was subjected to FIGS. 3 to 5 and 7 to 8. The treatment of Experiments 21 to 41 is performed according to the procedure shown in any one of 1. to measure the pollutant concentration in the wastewater, and the pollutant concentration in the wastewater is a legal standard (PCB: [wastewater] 0.0005 mg /
L or less, [exhaust gas] 0.1 mg / m ³ or less, dioxin: [drainage] 10 pg-TEQ / L or less, [exhaust gas]
0.1 ng-TEQ / m ³ or less), the removal efficiency of pollutants was evaluated depending on whether or not it complies with. The results are shown in Table 2.

In Table 2, the soil quality is in accordance with the soil engineering classification method (JGS M111), and the amount of treated soil is the amount of treated soil per hour (wet weight). The water content is indicated by the ratio of the weight of water to the weight of wet soil. The soil heating temperature indicates the temperature heated by the soil heating furnace in order to vaporize and separate pollutants from the soil. Units of soil pollutant concentration are mg / kg for PCBs and ng-TEQ / g for dioxins.

[0044]

[Table 2] In the results of Table 2, it is considered that the difference in the weight reduction amount occurs even if the soil quality is the same because the sampling location is different.

As can be seen from Experiments 21, 22, and 23, the treatment procedures shown in FIGS. 4, 5, and 7 are suitable for treating the condensate so that the pollutant removal efficiency is good and the pollutant concentration in the wastewater meets the legal regulations. I know what I can do. When the order of the treatment process is different (Experiment 24) or when oil-water separation is not performed (Experiment 2)
In 6), the removal efficiency decreases. In Experiment 24, a tar-like substance adhered to the filter medium during the dust removal process, and even if the filter medium was washed, the permeation capacity could not be restored and the treatment of condensed water could not be continued. In Experiment 26, the condensed water in which fine oil droplets were dispersed was directly treated in the detoxification treatment process, so the membrane surface was covered with the oil droplets, and even if the membrane was washed, the permeation capacity could not be restored and the condensed water treatment was continued I couldn't. However, the procedures of Experiments 24 and 26 can be applied when the contamination concentration is low (for example, Experiment 25). Furthermore, Experiment 2
The contaminants can be preferably removed even under the various conditions shown in 7 to 41.

[0046]

INDUSTRIAL APPLICABILITY According to the present invention, in the purification of soil in which pollutants are gasified and separated by heating the soil, carbon powder is produced by utilizing organic matter contained in the soil, which is simple, inexpensive and highly efficient. A method for collecting pollutants can be provided.

The present invention relates to a method for purifying soil in which pollutants are gasified and separated by heating the soil, and the pollutants contained in the condensate obtained by condensing and collecting the gas containing the generated water vapor and the pollutants are collected. Since it is possible to separate and collect and concentrate without using, it becomes possible to directly use it as a means for decomposing pollutants.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a soil treatment apparatus according to the present invention.

FIG. 2 is a diagram showing dry collection (a) and wet collection (b) of carbon particles in the soil treatment according to the present invention.

FIG. 3 is a schematic configuration diagram showing a first embodiment of an apparatus for performing treatment of a condensate in soil treatment according to the present invention.

FIG. 4 is a schematic configuration diagram showing a second embodiment of the apparatus for carrying out the treatment of the condensate in the soil treatment according to the present invention.

FIG. 5 is a schematic configuration diagram showing a third embodiment of an apparatus for performing treatment of a condensate in soil treatment according to the present invention.

FIG. 6 is a schematic configuration diagram showing an embodiment of a membrane separator used in the treatment of the condensate in the soil treatment according to the present invention.

FIG. 7 is a schematic configuration diagram showing a fourth embodiment of the apparatus for carrying out the treatment of the condensate in the soil treatment according to the present invention.

FIG. 8 is a schematic configuration diagram showing a fifth embodiment of the apparatus for carrying out the treatment of the condensate in the soil treatment according to the present invention.

[Explanation of symbols]

1 soil heating furnace, 2 gas heating furnace, 3 cooler 4,4 'carbon recovery device 5 Moisture collector, 6 Scrubber, 7 Separation tank 8,13 Filter material, 9 Membrane separator, 10 Separation tank 11 extraction tanks, 12 decomposition devices

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01D 53/06 B01J 20/20 B 4G066 B01J 20/20 C02F 1/26 B C02F 1/26 1/44 K 1/44 9/00 502D 9/00 502 502E 502Z 503Z 503 504B 504 B09B 3/00 303P (72) Inventor Tomohiro Tokidoki 8 Shinsugita-cho, Isogo-ku, Yokohama, Kanagawa Prefecture Toshiba Corporation Yokohama Works (72) Inventor Hajime Nako 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Incorporated company Toshiba Yokohama Office (72) Inventor Yoshio Hananaka, Shin-Sugita-cho, Isogo-ku, Yokohama, Kanagawa Prefecture F-term (in Toshiba Corporation, Yokohama office) Reference) 4D004 AA41 AB02 AB03 AB05 AB06 AB07 AC04 CA22 CA42 4D006 GA03 GA06 GA07 KA01 KA52 KA63 KB14 KB30 LA08 M B10 PA01 PB12 PB14 PC23 4D012 CA20 CC13 CG01 CH06 CH10 4D037 AA11 AB14 BA11 4D056 AB18 AB19 AC02 4G066 AA04B AA75B CA21 CA25 CA27 CA33 CA46 CA50 CA51 DA01 FA22

Claims (4)

[Claims] 1. A vaporization step of vaporizing pollutants and organic carbon compounds contained in soil, and heating the gas containing the vaporized pollutants and organic carbon compounds in a low oxygen atmosphere to carbonize the organic carbon compounds. A method for treating a pollutant, comprising: a carbonization step of producing carbon particles and a recovery step of recovering the pollutants adsorbed by the carbon particles together with the carbon particles. 2. The vaporizing step is a step of heating the soil to 400 ° C. or more and 600 ° C. or less, and the heating temperature of the gas in the carbonizing step is 800 ° C. or more and 12 ° C. or more.
The temperature is not higher than 00 ° C., and the carbon particles are not
The processing method according to claim 1, which is a step of cooling to below 00 ° C and collecting. 3. A vaporization step of vaporizing a pollutant contained in soil, a condensing step of cooling the vaporized pollutant to obtain a condensate, and a liquid separation of a hydrophilic phase and a lipophilic phase of the condensate. Phase separation step, a dust separation step for separating dust contained in the hydrophilic phase separated in the phase separation step, and a membrane for removing the contaminants from the hydrophilic phase through a separation membrane. A method for treating pollutants, comprising a separation step. 4. The method further comprises, before the membrane separation step, a step of removing the dispersed phase dispersed in the hydrophilic phase by oil-water separation using a permeable membrane or liquid-liquid extraction using a lipophilic extract. The processing method according to claim 3.