JP2014124624A - Method for treating low concentration pcb and contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of surely treating contaminant included in contaminated soil and low concentration PCB in the same treating apparatus without adhering the low concentration PCB to the contaminated soil including a contaminant, such as heavy metal.SOLUTION: The method comprises the steps of: burning main fuel and liquid auxiliary fuel containing a low concentration PCB in a rotary kiln 10 to heat contaminated soil including a contaminant at 800-1200°C in the rotary kiln 10; and heating an exhaust gas exhausted from the rotary kiln 10 at a temperature of 850°C or more in a secondary combustion chamber 20 connected with the rotary kiln 10. The auxiliary fuel is supplied into the rotary kiln 10 in a state mixed with spray air and atomized.

Description

  The present invention relates to detoxification of low-concentration PCB and a treatment method for purifying contaminated soil contaminated with heavy metals.

  Contaminated soil contaminated with toxic substances such as heavy metals is purified in a contaminated soil treatment facility in a combustion furnace such as a rotary kiln. As an example of the purification treatment, Japanese Patent Application Laid-Open No. 2004-261700 (Patent Document 1) discloses that contaminated soil is heated (baked) at 800 ° C. to 1200 ° C. with a rotary kiln, and unburned components in the exhaust gas of the rotary kiln are It has been proposed to purify by burning in a secondary combustion furnace.

  On the other hand, PCB (polychlorinated biphenyl), which is a kind of harmful substance, has been used as an insulating material for transformers and the like because it is chemically stable and excellent in insulation. However, since its harmfulness has become a social problem, manufacturing, distribution and new use are prohibited by law, and used PCBs have been detoxified. In recent years, the existence of insulating oil containing low-concentration PCB has been newly found, and the construction of a treatment system for detoxifying low-concentration PCB has been promoted by the country.

  The low-concentration PCB is detoxified by high-temperature incineration in a combustion furnace such as a rotary kiln in an industrial waste treatment facility. About the detoxification process of PCB (or low concentration PCB), Unexamined-Japanese-Patent No. 2002-147722 (patent document 2), Unexamined-Japanese-Patent No. 2010-075848 (patent document 3), etc. are proposed. Specifically, in Patent Document 2, PCB is mixed with fuel and is thermally decomposed in a rotary kiln by burning at a temperature of 1000 ° C. or higher with a burner. Moreover, in patent document 3, the solid containing a low concentration PCB is thrown in in a rotary kiln, maintaining the inside of a rotary kiln at the temperature of 300 to 1000 degreeC with the fuel and the liquid auxiliary agent containing a low concentration PCB. Then, after incineration or calcination treatment, the exhaust gas discharged from the rotary kiln is introduced into the secondary combustion chamber maintained at a temperature of 850 ° C. or more and retained for 2 seconds or more, so that the low concentration contained in the exhaust gas PCB is disassembled and detoxified.

JP 2004-261700 A JP 2002-147722 A JP 2010-075848 A

  By the way, as mentioned above, the purification treatment of the contaminated soil is carried out in the contaminated soil treatment facility, and the detoxification treatment of the low-concentration PCB is carried out in the industrial waste treatment facility. However, the treatment of contaminated soil containing pollutants such as heavy metals and low-concentration PCBs in the same treatment facility has not yet been implemented.

  In the purification treatment of contaminated soil described in Patent Document 1, no consideration is given to the treatment of low-concentration PCB, and in the detoxification process of PCB described in Patent Document 2, contaminated soil containing heavy metals. No consideration is given to the purification process. On the other hand, Patent Document 3 describes the treatment of contaminated soil and a liquid containing low-concentration PCB, but the contaminated soil here is limited to soil containing low-concentration PCB, such as heavy metals No consideration is given to the treatment of contaminated soil containing other pollutants. Furthermore, at the treatment temperature of 300 ° C. to 1000 ° C. set in Patent Document 3, the contamination cannot be decomposed if contaminants such as heavy metals are contained in the contaminated soil, especially when a low treatment temperature is used. There is a risk that the soil purification process will be insufficient.

  In addition, in the purification apparatus described in Patent Document 1, if low-concentration PCB is introduced into the rotary kiln for processing, the low-concentration PCB is attached to the inside of the rotary kiln or soil during purification due to the low-concentration PCB being introduced. May not be purified. Here, the soil purified in the contaminated soil treatment facility is generally reused, for example, sold or used as a backfill material. Therefore, for example, a reliable purification process is necessary so that the contaminants such as heavy metals contained in the contaminated soil are not sufficiently purified or further contaminated by the low-concentration PCB.

  This invention made | formed in view of the said situation makes it a technical subject to process reliably low concentration PCB and the contaminated soil containing contaminants, such as a heavy metal, in the same processing apparatus.

  In order to solve the above-described problems, the low concentration PCB and the method for treating contaminated soil according to the present invention combust main fuel and liquid auxiliary fuel containing low concentration PCB in the rotary kiln, and in the rotary kiln, Including a step of heat-treating contaminated soil containing pollutants at 800 ° C. to 1200 ° C. and a step of heat-treating exhaust gas discharged from the rotary kiln at 850 ° C. or higher in a secondary combustion chamber connected to the rotary kiln. The fuel is supplied into the rotary kiln in a state of being atomized by mixing with the atomized air. Here, the low concentration PCB means a PCB having a concentration of PCB of 5000 mg / kg (5000 ppm) or less.

  According to such a method, for example, contaminated soil containing contaminants such as heavy metals can be purified by heat treatment at 800 ° C to 1200 ° C. On the other hand, low-concentration PCB can be contained in exhaust gas discharged from a rotary kiln and detoxified by heating (combustion) at 850 ° C. or higher in the secondary combustion chamber. In this way, it is possible to reliably perform the purification treatment of the contaminated soil and the detoxification treatment of the low-concentration PCB in the same processing apparatus. Further, the low-concentration PCB is easily combusted because it is supplied as auxiliary fuel into the rotary kiln in a state of being atomized by mixing with spray air. Therefore, since it is difficult to generate low-concentration PCBs that are not burned (unburned), it is possible to reliably prevent contamination due to adhesion of low-concentration PCBs to contaminated soil.

  By the way, when supplying low-concentration PCB as an auxiliary fuel, it is necessary to continue the detoxification process of the low-concentration PCB contained in the auxiliary fuel being supplied even if the supply of the auxiliary fuel is interrupted. Therefore, in the above processing method, when the supply of auxiliary fuel is interrupted, it is preferable to continue supplying the atomized air for a predetermined time after the auxiliary fuel is interrupted. As a result, even if the supply of auxiliary fuel is interrupted during the purification treatment of contaminated soil, the remaining auxiliary fuel is atomized and supplied to the rotary kiln for combustion by continuing the supply of spray air. Can do. Therefore, the remaining auxiliary fuel does not drip into the rotary kiln, and the low concentration PCB contained in the remaining auxiliary fuel can be prevented from adhering to the contaminated soil.

  In the above processing method, the main fuel and the auxiliary fuel may be mixed and burned by a burner having a main fuel supply path and an auxiliary fuel supply path. In this case, the auxiliary fuel including the main fuel and the low concentration PCB supplied into the rotary kiln can be burned by one burner port. As a result, it is possible to perform low-concentration PCB processing in addition to purification processing of contaminated soil simply by replacing the conventional burner. As a result, the cost for repairing the rotary kiln is reduced.

  Furthermore, in the above processing method, the pollutant contained in the contaminated soil may be at least one of first to third type specific harmful substances, dioxins, and oils. Thereby, even if it is the contaminated soil containing these contaminants, since it heat-processes at 800 to 1200 degreeC in a rotary kiln, it can be purified | cleaned reliably. Therefore, it becomes possible to sell the purified soil as a product.

  As described above, according to the present invention, the contaminant contained in the contaminated soil and the low-concentration PCB can be reliably treated in the same processing apparatus without attaching the low-concentration PCB to the contaminated soil containing the contaminant such as heavy metal. Can be processed.

It is the schematic of the contaminated soil purification apparatus concerning embodiment of this invention. It is sectional drawing which shows the principal part of the contaminated soil purification apparatus of FIG. It is sectional drawing which shows the principal part of the burner used for the contaminated soil purification apparatus of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. A contaminated soil purification apparatus 1 shown in FIG. 1 is installed in a contaminated soil treatment facility, and includes a rotary kiln 10 that heats contaminated soil containing heavy metals, a secondary combustion chamber 20 connected to the rotary kiln 10, and a secondary combustion chamber 20. An exhaust / exhaust gas cooling mechanism 30 connected, a contaminated soil supply mechanism 40 for supplying contaminated soil to the rotary kiln 10, a purified soil recovery mechanism (not shown) for recovering purified soil, and a main fuel tank 50 for storing main fuel , And an auxiliary fuel tank 60 for storing auxiliary fuel containing low-concentration PCB.

  Here, the exhaust / exhaust gas cooling mechanism 30 includes a first temperature reducing tower 31 and a second temperature reducing tower 32 that cool the exhaust gas exhausted from the secondary combustion chamber 20, a bag filter 33 that collects fly ash, and an induced draft. It comprises a machine 34 and a chimney 35.

  FIG. 2 shows a rotary kiln 10, a secondary combustion chamber 20 (shown by hatched lines in FIG. 2), and a first burner 11 as a heating means, which constitute the main part of the contaminated soil purification apparatus according to the present invention. Show. The rotary kiln 10 is a cylindrical incinerator, and is rotated by a rotating mechanism (not shown) when contaminated soil is treated. In the present embodiment, as shown in FIG. 2, the secondary combustion chamber 20 is connected to one end side of the rotary kiln 10, and the first burner 11 as heating means is disposed on the other end side. A main fuel tank 50 and an auxiliary fuel tank 60 are connected to the first burner 11, and main fuel and auxiliary fuel are supplied by a main fuel supply pump and an auxiliary fuel supply pump (not shown). In this embodiment, natural gas is used as the main fuel, and waste oil containing low-concentration PCB is used as the auxiliary fuel. A main fuel supply valve 51 and an auxiliary fuel supply valve 61 are provided in the middle of the main fuel and auxiliary fuel supply paths, respectively, and the supply amounts of the main fuel and auxiliary fuel are controlled by a control device (not shown).

  Moreover, the contaminated soil inlet 12 into which the contaminated soil is introduced by the contaminated soil supply mechanism 40 (see FIG. 1) is formed on one end side of the rotary kiln 10, and the purified soil not shown is purified on the other end side. A purified soil outlet 13 is formed for discharge to the soil recovery mechanism. In FIG. 2, X indicates the contaminated soil in the rotary kiln 10. In addition, the rotary kiln 10 is inclined and disposed so that the purified soil discharge port 13 is located below the contaminated soil input port 12 (see FIG. 2).

  The secondary combustion chamber 20 is a cylindrical combustion furnace having a lower end connected to the rotary kiln 10 and arranged in a vertical posture, and burns exhaust gas discharged from the rotary kiln 10. A second burner 21 is provided below the secondary combustion chamber 20. The second burner 21 includes a burner gun (not shown) that burns only the main fuel, and the main fuel tank 50 is connected to the second burner 21. A main fuel supply valve 52 is provided in the middle of the main fuel supply path. Further, the upper end of the secondary combustion chamber 20 is connected to the exhaust / exhaust gas cooling mechanism 30 via a cylindrical connecting portion 22. Further, a thermometer 23 for measuring the temperature in the secondary combustion chamber 20 is disposed downstream of the secondary combustion chamber 20 and between the connection portion 22.

  In FIG. 3, sectional drawing of the principal part of the 1st burner 11 is shown. The first burner 11 includes a burner gun 110 having a quadruple structure, a nozzle cap 120, and a burner shield 130. Inside the burner gun 110, a straight traveling main fuel supply path 111, a radiant main fuel supply path 112, an atomizing air supply path 113, and an auxiliary fuel supply path 114 are formed in order from the outside. The straight main fuel supply path 111 and the radiant main fuel supply path 112 are connected to the main fuel tank 50 and supplied with the main fuel. The front end 111a of the main fuel supply passage 111 for straight travel is open toward a direction (indicated by L1 in FIG. 3) parallel to the axial direction of the burner gun 110, and injects the main fuel straight. Further, the distal end portion 112a of the radiant main fuel supply passage 112 opens in a direction inclined with respect to the radial direction of the burner gun 110 (indicated by L2 in FIG. 3), and extends in a direction spreading outward from the burner gun 110. Inject main fuel.

  The spray air supply path 113 is connected to an air pump (not shown), and is supplied with high-pressure air. The auxiliary fuel supply path 114 is connected to the auxiliary fuel tank 60 and supplied with auxiliary fuel. The supplied spray air and auxiliary fuel are mixed in the mixer 115 and injected into the rotary kiln 10 from the tip 120a of the nozzle cap 120 in a state where the auxiliary fuel is atomized. Here, atomization is the particle size at which all of the auxiliary fuel is burned in the rotary kiln 10. The appropriate particle size of the auxiliary fuel is determined by the axial length of the rotary kiln 10, the pressure of the atomizing air, the supply amount of the auxiliary fuel, and the like. In the present embodiment, the particle size is set to be 100 μm or less. The auxiliary fuel combustion mechanism including the spray air supply passage 113, the auxiliary fuel supply passage 114, the mixer 115, and the nozzle cap 120 inside the burner gun 110 is detachable from the first burner 11.

  The burner shield 130 is a member that shields the flame radiated from the burner gun 110, and is attached around the tip of the burner gun 110. Further, an ignition device (not shown) is provided in the vicinity of the first burner 11.

  In the present embodiment, the supply of main fuel and the supply of auxiliary fuel to the first burner 11 are controlled independently. Thereby, even if the supply of the auxiliary fuel is stopped, the fuel is supplied to the main fuel and the combustion is continued. On the other hand, in the burner gun 110, since the main fuel is burning around the tip 120a of the nozzle cap 120 from which the auxiliary fuel is ejected, the auxiliary fuel can be burned. Therefore, the auxiliary fuel can be prevented from dripping and reliably burned, so that the low-concentration PCB can be processed safely.

  Then, the purification method of the contaminated soil concerning this invention is demonstrated. First, the first burner 11 of the rotary kiln 10 is ignited. The first burner 11 is ignited by a control mechanism (not shown) that opens the main fuel supply valve 51 and drives a main fuel supply pump (not shown) to start supplying the main fuel amount, and an ignition device (not shown). ). In the present embodiment, the temperature is controlled so that the inside of the rotary kiln 10 is 800 ° C to 1200 ° C. Here, the temperature in the rotary kiln 10 is preferably set to 900 ° C to 1000 ° C. If the inside of the rotary kiln 10 is 800 ° C. or lower, there is a possibility that heavy metals contained in the contaminated soil cannot be sufficiently decomposed. If the temperature is 1200 ° C. or higher, the soil itself is melted and purified. Since it is not preferable when reusing soil, the above temperature range is set. Further, in the rotary kiln 10, the temperature distribution is not uniform. Specifically, the temperature is high in the region close to the first burner 11, and the temperature decreases as the distance from the first burner 11 increases.

  Here, the shape of the flame radiated from the first burner 11 can be changed to an arbitrary shape by controlling the main fuel to be supplied. Specifically, the burner gun 110 has a straight-travel main fuel supply path 111 and a radiant main fuel supply path 112, but the radiant fuel is supplied to the main fuel supplied to the straight-travel main fuel supply path 111. When the ratio supplied to the main fuel supply path 112 is increased, the flame radiated from the first burner 11 has a widened shape. Thus, by changing the ratio and supply amount of the main fuel supplied to the straight-traveling main fuel supply path 111 and the radiating main fuel supply path 112, the spread and flame of the flame radiated from the first burner 11 are changed. The size of the flame can be changed as appropriate, and the shape of the flame can be appropriately set according to the size and length of the diameter of the rotary kiln 10.

  Next, the main fuel supply valve 52 provided in the secondary combustion chamber 20 is opened, the main fuel is also supplied to the second burner 21, and the second burner 21 is similarly ignited by an ignition device (not shown). In the present embodiment, the temperature is controlled from the measurement result of the thermometer 23 so that the inside of the secondary combustion chamber 20 becomes 850 ° C. or higher. Here, in the secondary combustion chamber 20, it is necessary to set the temperature to be sufficient to decompose the low-concentration PCB, and the temperature is set to be 850 ° C. or higher. In the present embodiment, the upper limit of the temperature of the secondary combustion chamber 20 is set to 860 ° C.

  When the rotary kiln 10 and the secondary combustion chamber 20 reach the set temperature, the purification process for the contaminated soil containing heavy metals and the purification process for the low-concentration PCB are started. The contaminated soil purification treatment and the low-concentration PCB detoxification treatment may be performed simultaneously or separately.

  First, the detoxification process of the low concentration PCB will be described. The low concentration PCB contained in the auxiliary fuel stored in the auxiliary fuel tank 60 is heat-treated in the rotary kiln 10 and the secondary combustion chamber 20 and detoxified. Specifically, the auxiliary fuel supply valve 61 is opened, and auxiliary fuel containing low concentration PCB is supplied to the first burner 11 by driving an auxiliary fuel supply pump (not shown). In the first burner 11, the auxiliary fuel is mixed with the atomized air and burned in the rotary kiln 10 together with the main fuel. In the present embodiment, the auxiliary fuel is atomized to have a particle size of 100 μm or less. Here, if the particle size of the auxiliary fuel is large, it is not burned by the first burner 11, so that the unburned auxiliary fuel adheres to the inner wall of the rotary kiln 10 or contaminated soil to be added separately. This is not preferable because the soil purified in the rotary kiln 10 may be contaminated with the low-concentration PCB contained in the auxiliary fuel.

  The low concentration PCB in the auxiliary fuel burned in the rotary kiln 10 is transferred into the exhaust gas and sent into the secondary combustion chamber 20. Subsequently, the exhaust gas is heated in the secondary combustion chamber 20. At this time, in the secondary combustion chamber 20, the low concentration PCB contained in the exhaust gas can be made harmless by retaining the exhaust gas at 850 ° C. or more for 2 seconds or more.

  Next, a purification process for contaminated soil will be described. In the present embodiment, the contaminated soil contains heavy metals, which are the second type specified harmful substances defined by laws and regulations (Soil Contamination Countermeasures Law, etc.), and performs pretreatment such as dehydration as necessary. The contaminated soil to be purified is introduced into the rotary kiln 10 maintained at 800 ° C. to 1200 ° C. from the contaminated soil inlet 12 formed on one end side of the rotary kiln 10 by the contaminated soil supply mechanism 40. Here, the rotary kiln 10 is rotated by the power of a rotation mechanism (not shown) and is inclined downward from the contaminated soil inlet 12. Therefore, the contaminated soil in the rotary kiln 10 moves toward the purified soil discharge port 13 as it rotates while being heated. In the present embodiment, the contaminated soil in the rotary kiln 10 is heated for about 1 hour. The purified soil purified in the rotary kiln 10 is discharged from the purified soil discharge port 13 and is appropriately recovered by a purified soil recovery mechanism (not shown). The purified soil is reused by being sold as a product or used as a backfill material.

  In this embodiment, since the 1st burner 11 which is a heating means is formed in the same side as the purification | cleaning soil discharge port 13 of the rotary kiln 10, the temperature in the rotary kiln 10 is high toward the purification | cleaning soil discharge port 13. It becomes. Therefore, even if contaminated soil having a low temperature is put into the rotary kiln 10 and the ambient temperature decreases, as the heat treatment proceeds, the contaminated soil increases in temperature as it moves toward a high-temperature region. Can be heated. The contaminated soil may contain PCB. The PCB here is not limited to a low concentration PCB, and may be a high concentration PCB. The PCB contained in the contaminated soil is transferred into the exhaust gas by the heat treatment in the rotary kiln 10 and is detoxified in the secondary combustion chamber 20 like the auxiliary fuel.

  Further, the exhaust gas discharged by heat-treating the contaminated soil and the exhaust gas from which the low-concentration PCB has been rendered harmless in the secondary combustion chamber pass through the connection portion 22 and pass through the first temperature-reducing tower 31 and the second reduction chamber. It is sent to the warm tower 32. Here, the recombination of dioxins is prevented by rapidly cooling the exhaust gas. Thereafter, fly ash is collected in the bag filter 33 and further exhausted from the chimney 35 through the induction fan 34.

  Here, the control when the supply of auxiliary fuel is interrupted in the first burner 11 will be described. The supply of the auxiliary fuel is controlled by the auxiliary fuel supply pump (not shown) and the auxiliary fuel supply valve 61 as described above. When the supply of auxiliary fuel is interrupted, the auxiliary fuel supply valve 61 is closed, so that no new supply is performed. However, on the downstream side of the auxiliary fuel supply valve 61, auxiliary fuel is supplied into the auxiliary fuel supply path 114. Remains. Therefore, the remaining auxiliary fuel may drip from the tip of the burner gun 110 into the rotary kiln 10 and contaminate the soil being purified with low-concentration PCB.

  Therefore, in the present embodiment, control is performed so that the supply of atomized air is continued for a predetermined time even when the supply of auxiliary fuel is stopped. Thereby, atomization can be continued for the remaining auxiliary fuel, and the remaining low-concentration PCB can be burned together with the main fuel. Therefore, even if the supply of auxiliary fuel is interrupted, it is possible to prevent soil contamination during purification due to the remaining auxiliary fuel dripping into the rotary kiln 10. The interruption of the auxiliary fuel supply includes an emergency supply stop due to some trouble or the like, as well as a case where the auxiliary fuel supply is stopped at the end of the normal processing.

  As described above, according to the present invention, in addition to contaminated soil containing heavy metals, low-concentration PCBs can be treated in a contaminated soil treatment facility. Therefore, the detoxification treatment of the low-concentration PCB, which has been conventionally performed in an industrial waste treatment facility, can be performed also in a contaminated soil treatment facility. As a result, it is possible to increase the number of facilities capable of processing the low-concentration PCB, and it is possible to proceed with the construction of a processing system for rendering the low-concentration PCB harmless.

  Moreover, in this embodiment, it becomes possible to process low concentration PCB by changing the first burner 11 and installing an auxiliary fuel tank in a conventional contaminated soil treatment facility. Therefore, it is possible to perform the detoxification process of the low-concentration PCB while suppressing an increase in the cost for repairing the rotary kiln 10.

  In the above-described embodiment, the first burner 11 includes the burner gun 110 having a quadruple structure inside, and forms the straight main fuel supply passage 111 and the radiant main fuel supply passage 112, thereby reducing the flame. The shape can be arbitrarily set. However, the present invention is not limited to this, and only a single main fuel supply path having one end opened at an appropriate angle may be provided, and the flame shape may be fixed. In the above embodiment, the main fuel and auxiliary fuel are supplied and burned in a single burner. However, the present invention is not limited to this, and the main fuel and auxiliary fuel are separated into separate burners. You may supply and burn.

  In the said embodiment, as shown in FIG. 2, the secondary combustion chamber 20 was connected to the one end side of the rotary kiln 10, and the example by which the 1st burner 11 was arrange | positioned at the other end side was shown. However, the present invention is not limited to this, and the secondary combustion chamber 20 and the first burner 11 may be provided on the same side of the rotary kiln.

  Moreover, although the contaminated soil inlet 12 was formed in the one end side of the rotary kiln 10, and the purification | cleaning soil discharge port 13 was formed in the same side as the 1st burner 11, the 1st burner was not restricted to this. The contaminated soil inlet 12 may be formed on the same side as 11 and the purified soil outlet 13 may be formed on the opposite side. In this case as well, the rotary kiln 10 is disposed so as to be inclined such that the purified soil discharge port 13 is located below the contaminated soil input port 12. Thus, various variations are appropriately employed for the arrangement of the secondary combustion chamber 20 and the first burner 11 and the positional relationship between the first burner 11 and the contaminated soil inlet 12 or the purified soil outlet 13. Can do.

  Furthermore, in the said embodiment, although the example which contains the heavy metal which is a 2nd kind specific harmful substance prescribed | regulated by law (Soil Contamination Countermeasures Law) as a pollutant contained in contaminated soil was shown, it is not restricted to this. It may contain 1st-3rd class specific harmful substance, dioxin, oils, etc. which are stipulated by law. In any case, it can be purified by the treatment of the present invention.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention. The method for treating contaminated soil according to the present invention has been described as an example in a contaminated soil treatment facility. However, the present invention is not limited to this, and it may be possible to treat contaminated soil in an industrial waste treatment facility. A facility having new equipment may be newly established.

DESCRIPTION OF SYMBOLS 1 Contaminated soil purification apparatus 10 Rotary kiln 11 1st burner 20 Secondary combustion chamber

Claims (4)

Burning main fuel and liquid auxiliary fuel containing low-concentration PCB in a rotary kiln, and heat-treating contaminated soil containing pollutants at 800 ° C. to 1200 ° C. in the rotary kiln;
Heat treating exhaust gas discharged from the rotary kiln at 850 ° C. or higher in a secondary combustion chamber connected to the rotary kiln,
A method for treating low-concentration PCB and contaminated soil, wherein the auxiliary fuel is supplied into the rotary kiln in a state of being atomized by mixing with spray air.   2. The low-concentration PCB and contaminated soil treatment according to claim 1, wherein when the supply of the auxiliary fuel is cut off, the supply of the sprayed air is continued for a predetermined time after the auxiliary fuel is cut off. Method.   The low-concentration PCB and the contaminated soil according to claim 1 or 2, wherein the main fuel and the auxiliary fuel are mixed and burned by a burner including the main fuel supply path and the auxiliary fuel supply path. Processing method.   The low-concentration PCB and the pollution according to any one of claims 1 to 3, wherein the pollutant contains at least one of the first to third class specific harmful substances, dioxins, and oils. Soil treatment method.

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