JP5288623B2 - Heat purification method for contaminated soil - Google Patents

Description

  The present invention relates to a method and apparatus for heating and purifying contaminated soil containing pollutants such as light oil, heavy oil, VOC (volatile organic compound), dioxin, and PCB.

If the soil in the premises of each business site or the surrounding area is contaminated with waste liquids of pollutants such as oil due to industrial activities, it is necessary to purify the contaminated soil. As one method of purifying contaminated soil, there is a method of purifying by volatilizing and decomposing volatile organic compounds that have soaked in the soil using a rotary kiln for heating. In the contaminated soil purification treatment apparatus described in Patent Document 1, a heat treatment kiln having a refractory material is provided on the inner peripheral wall, and the contaminated soil containing dioxin is heated at a high temperature in the heat treatment kiln to volatilize dioxins in the soil. The gasified dioxin is decomposed by heating and exposed to high-temperature gas atmosphere in an oxidative decomposition furnace, and the exhaust gas that has passed through the oxidative decomposition furnace is quenched in a cooling tower to reprecipitate dioxin. By suppressing the above, it is possible to purify contaminated soil containing dioxins and the like.
JP 2008-62168 A

  However, in the purification processing apparatus that heats at a high temperature as described above, a large amount of fossil fuel is used as a heat source, so how to conserve energy such as reduction of fuel cost and suppression of carbon dioxide generation amount. It will be a problem.

  This invention makes it a subject to provide the heating purification method and purification apparatus of contaminated soil which can heat-purify contaminated soil suitably, aiming at energy saving in view of said point.

  In order to solve the above problems, the present inventor has made extensive studies, and as a result, the basic principle of purification is to desorb the toxic substances such as oil by increasing the vapor pressure by heating the contaminated soil. Therefore, the influence of the moisture content of the contaminated soil has a great influence on the fuel consumption, and it is necessary to reduce the moisture content of the contaminated soil in advance to save energy. Supplying is essential to stabilize the quality (purification level). For this reason, contaminated soil is pretreated from the hopper feeder to a state where it can be cut out quantitatively, removing gravel and foreign materials, as well as clay and silt. Currently, it takes a lot of labor and time for pre-treatment, such as reducing the water content by adding quick lime and increasing the size of soil particles. To simplify Can save energy, and the high-temperature exhaust gas derived from the heating rotary kiln that heats contaminated soil is rapidly cooled in the cooling tower, but energy can be saved if this exhaust gas heat is used effectively, etc. Thus, the present invention has been achieved.

That is, in the method for heating and purifying contaminated soil according to claim 1 of the present invention, the heat treatment kiln for heating and purifying the contaminated soil by directly contacting the contaminated soil and high-temperature hot air sent from a burner, and the heat treatment An indirect heating preheating device that indirectly heats the contaminated soil before purification by the retained heat of the exhaust gas discharged from the kiln; and a supply means that supplies the contaminated soil discharged from the preheating device to the heat treatment kiln. And between the high-temperature exhaust gas discharged from the heat treatment kiln and the low-temperature gas including water vapor and volatile harmful gas discharged by heating the contaminated soil, downstream of the exhaust duct of the indirect heating type preheating device. A heat exchanger for exchanging heat, supplying quick lime together with the contaminated soil before purification to the preheating device of the indirect heating method to reduce the moisture content of the contaminated soil with quick lime. Indirectly heated by the exhaust gas potential heat of the heat treatment kiln while granulating the advance and soil particles, after the pretreatment for reducing the water content ratio of the contaminated soil, and a reduced contaminated soil water content to the heat treatment kiln While supplying and heating and purifying, the high temperature exhaust gas discharged from the heat treatment kiln is led to the heat exchanger via the indirect heating type preheating device, while the indirect heating type preheating device is heated by the contaminated soil. A low-temperature gas containing discharged steam and volatile harmful gas is introduced into the heat exchanger to exchange heat with the high-temperature exhaust gas, and a gas containing heated steam and volatile harmful gas is provided in the heat treatment kiln. It is characterized by being directed to a burner and used as combustion air for the burner.

Further, in the method for heating and purifying contaminated soil according to claim 2, the preheating device has a double cylinder structure comprising an inner cylinder that is rotatably supported to be inclined and an outer cylinder that covers the inner cylinder, It is characterized by being a preheating kiln of an indirect heating system in which contaminated soil is supplied into the inner cylinder and the exhaust gas of the heat treatment kiln is passed through the outer cylinder .

According to the method for heating and purifying contaminated soil according to claim 1 of the present invention, the heat treatment kiln that heats and purifies the contaminated soil by directly contacting the contaminated soil and high-temperature hot air fed from a burner, and the heat treatment kiln A preheating device of an indirect heating method that indirectly heats contaminated soil before purification with retained heat of exhaust gas discharged, and supply means for supplying contaminated soil discharged from the preheating device to the heat treatment kiln In addition, heat is generated between the high-temperature exhaust gas discharged from the heat treatment kiln and the low-temperature gas including water vapor and volatile harmful gas discharged by heating the contaminated soil downstream of the exhaust duct of the indirect heating preheating device. Equipped with a heat exchanger that performs replacement, and supplies quick lime along with the contaminated soil before purification to the preheating device of the indirect heating method to promote the reduction of the moisture content of the contaminated soil with quick lime Indirectly heated by the exhaust gas potential heat of the heat treatment kiln while granulating soil particles, after the pretreatment for reducing the water content ratio of contaminated soil to supply a reduced contaminated soil water content to the heat treatment kiln The high-temperature exhaust gas discharged from the heat treatment kiln is led to the heat exchanger via the indirect heating type preheating device, while being discharged from the indirect heating type preheating device by heating the contaminated soil. A low-temperature gas containing water vapor and volatile harmful gas is introduced into the heat exchanger to exchange heat with the high-temperature exhaust gas, and a burner provided with a gas containing heated water vapor and volatile harmful gas in the heat treatment kiln Because it is used as combustion air for burners, it is necessary for soil purification by reducing the moisture content of the contaminated soil before purification using the heat stored in the exhaust gas of the heat treatment kiln. Therefore energy savings can be made, such as suppression of reduction and carbon dioxide emissions of fuel costs. Moreover, since the water content ratio of the contaminated soil can be reduced by the preheating device, it is possible to eliminate the need for a pretreatment such as the conventional adjustment of the water content ratio of the contaminated soil before charging into the heat treatment kiln.

According to the method for heating and purifying contaminated soil according to claim 2 of the present invention, the preheating device has a double cylinder structure comprising an inner cylinder that is rotatably supported in an inclined manner and an outer cylinder that covers the inner cylinder. supplies the contaminated soil into the inner cylinder, since the pre-heating kiln structure as the indirect heating method of passing the exhaust gas heat treatment kiln into the barrel, efficiently preheated continuous feed to simplify the device structure Can be done .

It is a schematic explanatory drawing which shows one Example of the purification apparatus of the contaminated soil which concerns on this invention.

  According to the method and apparatus for heating and purifying contaminated soil according to the present invention, the contaminated soil is heated by heat treatment kiln and the contaminated soil before purification is heated by the retained heat of the exhaust gas discharged from the heat treatment kiln. A preheating device and supply means for supplying contaminated soil discharged from the preheating device to the heat treatment kiln are provided. In addition, a heat exchanger, a cooling tower, a bag filter dust collector and the like are provided downstream of the exhaust gas of the heat treatment kiln.

  When the heat-treated kiln also treats contaminated soil containing dioxin, a fireproof material is applied to the inner peripheral wall, and for example, a heat-resistant kiln that can withstand a high temperature of about 1800 ° C. is used. Further, downstream of the heat treatment kiln, the exhaust gas derived from the heat treatment kiln is retained for about 2 seconds, for example, and the exhaust gas temperature is maintained at about 800 ° C., whereby the gasified pollutant is thermally decomposed. An oxidative decomposition furnace (secondary combustion furnace) is provided.

  In addition, the preheating device employs, for example, an indirect heating type preheating kiln having a double cylinder structure including an inner cylinder that is rotatably supported to be inclined and an outer cylinder that covers the inner cylinder. And while putting the contaminated soil into the inner cylinder, the high temperature exhaust gas led out from the heat treatment kiln and passed through the oxidative decomposition furnace is passed through the gas passage formed between the inner cylinder and the outer cylinder, and the contaminated soil Indirect heating while rolling down the inner cylinder reduces the moisture content of the contaminated soil. In addition, a feeding means such as a screw feeder for placing quick lime into the inner cylinder of the preheating kiln is provided.

  Further, a grid-like cylindrical body is connected to the discharge end of the inner cylinder of the preheating kiln, and the contaminated soil that has passed through the openings of the grid-like cylindrical body is subjected to lower heating treatment by an appropriate supply means, for example, a supply chute. A recovery chute is provided that allows supply to the kiln and takes out the lump that has not passed through the openings.

  In addition, a heat exchanger is disposed downstream of the preheating kiln of the exhaust duct that guides the high-temperature exhaust gas discharged from the heat treatment kiln, and a low-temperature gas containing water vapor and volatile harmful gas discharged from the inner cylinder of the preheating kiln. Gas is passed through the bag filter dust collector into the heat exchanger, heat exchanged with the high-temperature exhaust gas, and the heated preheating kiln gas is supplied as combustion air for the burner provided in the heat treatment kiln. I am doing so.

  And when purifying the contaminated soil, the contaminated soil stored in the stock yard is scooped up by, for example, an excavator loader and put into the inner cylinder of the preheating kiln, while the gas passage between the inner cylinder and the outer cylinder The heat treatment kiln's high temperature, about 800 ° C exhaust gas is passed through and indirectly heated while the contaminated soil rolls down the inner cylinder, reducing the moisture content of the contaminated soil and supplying it to the next heat treatment kiln. Pre-process as much as possible. At this time, if it is a soft contaminated soil having a high water content such as clay and silt, quick lime is appropriately put into the inner cylinder of the preheating kiln simultaneously with the contaminated soil. Moisture in the contaminated soil is absorbed by the input quick lime, and the water content ratio is further reduced, and the increase of soil particles is also promoted, so that stable supply to the heat treatment kiln in the next step becomes possible.

  If the contaminated soil reaches the grid cylinder at the discharge end of the inner cylinder of the preheating kiln, it is sieved by the rotating grid cylinder, and the contaminated soil passing through the openings of the grid cylinder is heated through the supply chute. Gravel and foreign matters that have been supplied into the treatment kiln and have not passed through the mesh are taken out by the recovery chute.

  When the contaminated soil is supplied to the heat treatment kiln, the contaminated soil is exposed to a high temperature atmosphere of about 1800 ° C. while rolling down in the drum, and when the soil temperature reaches about 300 to 400 ° C. Dioxins volatilize and thermally decompose to gasify. Furthermore, the soil is heated as it is, and is heated to about 600 ° C. to be purified.

  In addition, the exhaust gas derived from the heat treatment kiln is guided to an oxidative decomposition furnace, and is exposed to a high-temperature atmosphere at about 800 ° C. for about 2 seconds in the oxidative decomposition furnace, so that the gasified dioxins present in the exhaust gas are removed. Heat decomposition. High-temperature exhaust gas that has passed through the heat treatment kiln and the oxidative decomposition furnace is guided to the heat exchanger through the preheating kiln. In addition, a low-temperature gas containing water vapor and volatile harmful gas discharged from the inner cylinder of the preheating kiln is introduced into the heat exchanger via a bag filter dust collector, and heat exchange with the high-temperature exhaust gas is performed. The gas of the preheating kiln heated up to 0 degreeC is led to the burner with which the heat processing kiln was equipped, and is used as combustion air of a burner.

  In this way, the water content ratio of the contaminated soil before purification is reduced by using the heat stored in the exhaust gas of the heat treatment kiln, so that energy savings such as reduction in fuel costs required for purification treatment and suppression of carbon dioxide generation are to be achieved. Can do. In addition, since the water content of the contaminated soil is reduced by the preheating kiln before the purification treatment by the heat treatment kiln, pretreatment such as adjustment of the water content of the contaminated soil before the introduction to the heat treatment kiln is unnecessary. You can also

  In addition, if quick lime is added to the preheated kiln at the same time as the contaminated soil, the moisture content of the soft soil with high water content is reduced, and the increase of soil particles is promoted. Supply becomes possible and the purification level can be stabilized. In addition, by arranging a grid-like cylindrical body at the discharge end of the inner cylinder of the preheating kiln, gravel and foreign matters having a large particle size can be recovered and removed without being supplied to the heat treatment kiln in the next step. Pre-processing for removing foreign substances is also unnecessary.

  Furthermore, a low temperature gas containing water vapor and volatile harmful gas discharged from the inner cylinder of the preheating kiln is heated and heated with a heat exchanger, and the heated gas is used as combustion air for the burner of the heat treatment kiln. If used, the fuel cost of the burner can be reduced, energy saving can be achieved, and volatile harmful gas discharged from the preheating kiln can be burned and detoxified.

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

  1 in the figure is a heat treatment kiln that heats and purifies contaminated soil. For example, a drum 2 with a refractory material applied to the inner peripheral wall so as to withstand a high temperature atmosphere of about 1800 ° C. is rotated on the machine base 3. It is tilted and supported freely, and is rotated at a predetermined speed by a drive motor (not shown). A flame is formed in the drum 2 from the burner 5 arranged on the charging hopper 4 side at one end of the drum 2 and hot air is sent into the drum 2, while contaminated soil is supplied into the drum 2 from the supply chute 6 of the charging hopper 4. The contaminated soil is exposed to a high temperature atmosphere while rolling down in the drum 2 to purify the pollutants in the contaminated soil by volatilization or thermal decomposition.

  In the lower part of the discharge side of the heat treatment kiln 1, a stock bin 7 for temporarily storing heated soil is disposed, and the heated soil is temporarily stored in the stock bin 7 so that aeration is performed in the soil. A small amount of contaminants remaining in the gas are gasified and removed. The purified soil is supplied to a soil cooling device 9 described later by the transfer means 8.

  An oxidative decomposition furnace in which exhaust gas at a high temperature of the heat treatment kiln 1, for example, about 800 ° C. is introduced and retained for about 2 seconds, and the pollutants in the exhaust gas are exposed to a high temperature atmosphere and thermally decomposed above the stock bin 7. 10 is disposed. In order to maintain the furnace temperature of the oxidative decomposition furnace 10 at a predetermined temperature, for example, 800 ° C., the furnace temperature is detected, and the combustion amount of the burner 5 is controlled based on the detected value. When the furnace temperature cannot be properly maintained by controlling the combustion amount of the burner 5, an auxiliary burner (not shown) is disposed in the oxidative decomposition furnace 10, and the auxiliary furnace is controlled so as to make the furnace temperature appropriate. You may make it maintain to.

  A cyclone dust collector 11 for capturing dust is disposed downstream of the exhaust gas from the oxidative decomposition furnace 10, and a preheating kiln 12 for preheating the contaminated soil is disposed downstream of the exhaust gas of the cyclone dust collector 11. The preheating kiln 12 has a double cylinder structure including an inner cylinder 13 that is rotatably supported to be inclined and an outer cylinder 14 that covers the inner cylinder 13, and allows exhaust gas to pass between the inner cylinder 13 and the outer cylinder 14. A gas passage 15 is formed. In addition, a charging hopper 16 for charging contaminated soil is disposed on one end side of the inner cylinder 13, and quick lime can be quantitatively charged by a screw feeder (not shown) or the like. The contaminated soil is indirectly heated by the high-temperature exhaust gas passing through the gas passage 15 while the contaminated soil is introduced from the introduction hopper 16 of the preheating kiln 12 and tumbles down the inner cylinder 13.

  Further, a grid-like cylindrical body 17 is connected to the discharge end of the inner cylinder 13, and the contaminated soil that has passed through the openings of the grid-like cylinder 17 is discharged from the discharge port 18 a of the discharge hopper 18. While being guided by the supply chute 6 to be supplied into the drum 2, gravel and foreign matters that have not passed through the mesh are taken out from the recovery chute 19 to the outside.

  In addition, the contaminated soil may be input into the preheating kiln 12 by scooping up the uncontaminated contaminated soil A stored in the stock yard 20 with an unillustrated shovel loader and directly inputting it into the input hopper 16. Moreover, you may make it throw in using a conveyance conveyor. At this time, if contaminated soil having a high water content ratio is introduced, it is preferable to appropriately attach means for forcibly feeding the contaminated soil into the inner cylinder 13. In addition, after performing pretreatments such as adjusting the water content ratio of contaminated soil as in the past, it may be put into the preheating kiln 12 while being cut out by a hopper feeder.

  The high-temperature exhaust gas that has passed through the gas passage 15 of the preheating heating kiln 12 passes through the exhaust duct 21 and is introduced into the heat exchanger 22. Heat exchange is performed with the low-temperature gas discharged from the inner cylinder 13 of the heating kiln 12. A water-cooled cooling tower 23 for cooling the exhaust gas is disposed downstream of the heat exchanger 22, and water is sprayed on the exhaust gas to rapidly cool the gas temperature to about 180 ° C. Dioxin reprecipitation is suppressed.

  A bag filter dust collector 24 is disposed downstream of the cooling tower 23, while slaked lime for neutralizing sulfur oxides and hydrogen chloride, which are harmful substances generated in the heating and purification process of heavy oil and VOC, is provided. A slaked lime storage bottle 25 for storing the slaked lime is provided, and includes a screw feeder 26 for cutting out a predetermined amount of slaked lime, a blower (not shown) for blowing slaked lime into the exhaust duct 21, and the like. Is appropriately blown into the exhaust duct 21 on the inlet side of the bag filter dust collector 24 so that sulfur oxide and hydrogen chloride are neutralized in the bag filter dust collector 24. In addition, activated carbon may be mixed into slaked lime, blown into the bag filter dust collector 24 and covered with a filter cloth, and dioxins in the exhaust gas may be adsorbed and removed by activated carbon. Alternatively, a bag filter dust collector (not shown) for capturing activated carbon may be provided downstream of the bag filter 24, and activated carbon may be blown alone upstream of the bag filter dust collector.

  Downstream of the bag filter dust collector 24, an exhaust fan 27 for sucking and exhausting exhaust gas is disposed. In order to suck the combustion gas supplied from the burner 5 into the heat treatment kiln 1 without excess or deficiency, a corner of the charging hopper 4 is provided. The suction amount is adjusted by controlling the opening degree of the air volume adjusting damper (not shown) in the exhaust duct 21 or the rotational speed of the exhaust fan 27 so that the static pressure detected by the air outlet becomes approximately atmospheric pressure. . The exhaust gas that has passed through the exhaust fan 27 is released from the chimney 28 into the atmosphere.

  The discharge hopper 18 of the preheating kiln 12 is connected to an exhaust duct 29 for exhausting low-temperature gas including water vapor and volatile harmful gas discharged from the inner cylinder 13, and a bug is disposed downstream of the exhaust duct 29. A filter dust collector 30 and exhaust fans 31 and 32 are disposed, and the end of the exhaust duct 29 passes through the heat exchanger 22 and is connected to the burner 5 of the heat treatment kiln 1. And the low-temperature gas containing the volatile harmful gas exhausted from the inner cylinder 13 is cleaned by the bag filter dust collector 30 and passed through the heat exchanger 22, so that it is discharged from the gas passage 15 of the preheating kiln 12. A gas that is heat-exchanged with high-temperature exhaust gas and heated to about 500 ° C. is used as combustion air for the burner 5. In this way, the gas containing water vapor and volatile harmful gas discharged from the inner cylinder 13 of the preheating kiln 12 is burned in the burner 5 of the heat treatment kiln 1 to detoxify the volatile harmful gas. By using combustion air that has been heated, burner fuel costs are reduced.

  The soil cooling device 9 is a well-known device that cools the high-temperature soil stored in the stock bin 7 so that it can be easily handled. For example, a rotary kiln type is used, and a scraping blade is used inside. A cylindrical drum 33 is provided on the machine base 34 so as to be rotatable and is rotated at a predetermined speed by a driving device (not shown).

  A charging hopper 35 is disposed at one end of the drum 33, and a discharging hopper 36 is disposed at the other end. In the meantime, the water stored in the water storage tank 37 is sprayed from the water spray nozzle 38 to cool the heated soil, and the moisture content is increased to such an extent that dust is not easily produced, thereby making it easy to handle. Further, dust and water vapor generated in the soil cooling device 9 are sucked and exhausted by the exhaust fan 40 disposed at the end of the exhaust duct 39, captured by the bag filter dust collector 41, and then introduced into the atmosphere from the chimney 28. It is trying to release.

  Next, the case where the contaminated soil containing dioxin is purified by the purification device will be described. When purifying the contaminated soil, first, the burner 5 of the heat treatment kiln 1 is burned while operating the exhaust fans 27, 31, 32, and the refractory material applied to the inner peripheral wall is heated to bring the drum 2 into a high temperature atmosphere. maintain. As a result, the preheating kiln 12 and the heat exchanger 22 downstream of the exhaust gas of the heat treatment kiln 1 are also heated, and preparation for purification is completed.

  Subsequently, when the contaminated soil A stored in the stock yard 20 is scooped up by, for example, an excavator loader and introduced into the charging hopper 16 of the preheating kiln 12, the contaminated soil is in a gas passage 15 while rolling down the inner cylinder 13. The moisture content of the contaminated soil is gradually reduced by the high-temperature exhaust gas passing through the inner cylinder 13, and when it reaches the discharge end of the inner cylinder 13, it is sieved by the grid cylinder 17. The contaminated soil that has passed through the opening is discharged from the discharge port 18 a of the discharge hopper 18, guided to the supply chute 6 of the heat treatment kiln 1, and supplied into the drum 2. Further, gravel and foreign matters that have not passed through the openings are taken out from the collection chute 19 to the outside.

  Note that when a contaminated soil having a high water content is charged into the preheating kiln 12, a predetermined amount of quicklime is simultaneously charged. As a result, the moisture content of the contaminated soil is further reduced by the action of quick lime while the contaminated soil flows down the inner cylinder 13, and the increase of the soil particles is promoted, so that the heat treatment kiln 1 in the next process can be heated and purified. Pretreatment can be performed effectively.

  When the contaminated soil supplied from the preheating kiln 12 to the heat treatment kiln 1 is heated to about 300 to 400 ° C., dioxins in the soil volatilize and thermally decompose to gasify. The soil is heated as it is to raise the temperature to about 600 ° C. and then put into the stock bin 7 at the outlet of the heat treatment kiln 1 for storage. In the stock bottle 7, the heated soil at about 600 ° C. is stored for a while, for example, for about 1 hour, and aerated, whereby a small amount of dioxin remaining in the soil is gasified and separated.

  The dioxins gasified in the heat treatment kiln 1 and the stock bin 7 are guided to the oxidative decomposition furnace 10 along with the exhaust gas, and are exposed to a high temperature atmosphere of about 800 ° C. in the oxidative decomposition furnace 10 for about 2 seconds. Thus, the gasified dioxin is thermally decomposed. At this time, the gas temperature in the oxidative decomposition furnace 10 is sequentially measured by a temperature sensor, and the combustion amount of the burner 5 is controlled so as to reach a temperature at which dioxins can be thermally decomposed, for example, about 800 ° C. In addition, when it is difficult to appropriately control the furnace temperature of the oxidative decomposition furnace 10 by the combustion amount of the burner 5, the furnace temperature is controlled by an auxiliary burner (not shown).

  The high-temperature exhaust gas derived from the oxidative decomposition furnace 10 is guided to the gas passage 15 of the preheating kiln 12 through the cyclone dust collector 11, and indirectly heats the contaminated soil that tumbles down in the inner cylinder 13, and then the exhaust duct. 21 is introduced into the heat exchanger 22.

  In the heat exchanger 22, low temperature gas including water vapor and volatile harmful gas discharged from the discharge hopper 18 of the preheating kiln 12 passes through the exhaust duct 29 and is introduced via the bag filter dust collector 30. Heat exchange is performed with the high-temperature exhaust gas that has passed through the gas passage 15 of the preheating kiln 12. And the gas containing the volatile harmful gas heated up to about 500 degreeC is introduce | transduced into the burner 5 of the heat processing kiln 1, and is used as combustion air.

  Further, the exhaust gas led out from the exhaust duct 21 of the heat exchanger 22 is guided to the cooling tower 23, and water is injected to rapidly cool the exhaust gas temperature to about 180 ° C. where the dioxin does not reprecipitate, thereby reprecipitation of the dioxin. After being suppressed, it is guided to the bag filter dust collector 24.

  In front of the bag filter dust collector 24, slaked lime mixed with activated carbon is blown with a slaked lime supply device so as to cover the filter cloth surface of the bag filter dust collector 24, and dioxins in the exhaust gas are adsorbed by the activated carbon. In addition, if heavy oil is contained in the soil, sulfur oxides are produced by sulfur components during the heating process, and if VOC is contained, phosgene is produced in the process of oxidative decomposition and thermal decomposition, and water vapor is added to this. When added, hydrogen chloride is generated by hydrolysis, so acid gases (SOx, HCL, etc.) in these exhaust gases are neutralized with slaked lime. Then, the bag filter dust collector 24 removes slaked lime, activated carbon, and dust fine particles and releases the gas, which has been cleaned, from the chimney 28 to the atmosphere.

  In addition, the heated soil stored in the stock bin 7 is supplied to the soil cooling device 9 in order to cool it to a temperature that is easy to handle because it is hot. The soil supplied to the soil cooling device 9 is cooled by being sprayed with water from the water spray nozzle 38 while rolling down in the drum 33, becomes easy to handle, is discharged from the discharge hopper 36, and is piled up. It will be processed later. Further, dust and water vapor generated in the drum 33 are sucked and exhausted by the exhaust fan 40 and guided to the downstream bag filter dust collector 41, where the dust is trapped and exhausted from the chimney 28.

  Thus, since the water content ratio of the contaminated soil before purification is reduced by using the heat stored in the exhaust gas of the heat treatment kiln 1 in the preheating kiln 12, the fuel cost required for the purification treatment and the generation amount of carbon dioxide are suppressed. Energy saving. Moreover, since the water content ratio of the contaminated soil can be reduced by the preheating kiln 12, it is possible to eliminate the need for pretreatment such as adjustment of the water content ratio before charging into the heat treatment kiln.

  Although the indirect heating type preheating kiln 12 is used as the preheating device, the present invention is not limited to this. In short, the contaminated soil before purification is preliminarily preserved by the retained heat of the exhaust gas derived from the heat treatment kiln 1. Any device capable of heating can be used, and various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Heat processing kiln 5 ... Burner 6 ... Supply chute (supply means) 7 ... Stock bottle 9 ... Soil cooling device 10 ... Oxidation cracking furnace 12 ... Preheating kiln (preheating device) 13 ... Inner cylinder 14 ... Outer cylinder 15 ... Gas passage 16 ... Input hopper 17 ... Grid-shaped cylinder 18 ... Discharge hopper 18a ... Discharge port 19 ... Recovery chute 22 ... Heat exchanger 23 ... Cooling tower 24 ... Bag filter dust collector 25 ... Slaked lime storage bottle 26 ... Screw feeder (slaked lime supply) apparatus)

Claims (2)

Heat treatment kiln that heats and purifies the contaminated soil by directly contacting the contaminated soil and high-temperature hot air sent from the burner, and indirect heating that indirectly heats the contaminated soil before purification by the retained heat of the exhaust gas discharged from the heat treatment kiln And a supply means for supplying contaminated soil discharged from the preheating device to the heat treatment kiln, and a heat treatment kiln downstream of the exhaust duct of the indirect heating preheater It has a heat exchanger that exchanges heat between the high-temperature exhaust gas discharged from the high-temperature exhaust gas and the low-temperature gas including water vapor and volatile harmful gas discharged by heating the contaminated soil. The heat treatment kiln's exhaust gas holding heat is used to promote the reduction of the moisture content of the contaminated soil with quick lime and increase the size of the soil particles by supplying it to a preheating device of the heating system. Indirectly heated Te, after pretreatment for reducing the water content ratio of contaminated soil, performs heat cleaning treatment by supplying a reduced contaminated soil water content to the heat treatment kiln, is discharged from the heat treatment kiln The high-temperature exhaust gas is led to the heat exchanger via the indirect heating type preheating device, while the low temperature gas including water vapor and volatile harmful gas discharged from the indirect heating type preheating device by heating the contaminated soil is heated. It was introduced into the exchanger and heat exchanged with the high-temperature exhaust gas, and the gas containing water vapor and volatile harmful gas whose temperature was increased was led to the burner provided in the heat treatment kiln and used as combustion air for the burner. A method for heating and purifying contaminated soil.   The preheating device has a double cylinder structure comprising an inner cylinder that is rotatably and tiltably supported and an outer cylinder that covers the inner cylinder, supplies contaminated soil into the inner cylinder, and heat-treats the kiln in the outer cylinder. The method for heating and purifying contaminated soil according to claim 1, wherein a preheating kiln of an indirect heating system configured to allow the exhaust gas to pass through is used.

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