JP4406347B2 - Pollutant decomposition device and soil contaminant treatment device - Google Patents

Description

  The present invention relates to a decomposing apparatus for decomposing organic pollutants in soil vaporized by heating, and an apparatus for treating pollutants in soil.

  In recent years, environmental pollution caused by organic pollutants (organic pollutants) has attracted social attention. For example, pollutants have been removed from soil contaminated with organic pollutants such as PCB, dioxin, trichlorethylene, benzene and oil. Is required to be detoxified. One method of removing organic pollutants is to remove the soil from the soil by heating the soil to vaporize the pollutants. The detoxification treatment of the pollutants that have been vaporized from the soil is carried out by the catalytic method or the combustion method. Such processing methods have been known. However, the catalyst method or combustion method has catalyst deterioration, difficulty in controlling the furnace temperature and exhaust gas volume, etc., and even if it is possible to remove harmful substances from the soil (cleaning the soil), the detoxification treatment of the pollutant itself is not possible. The problem of being difficult remains.

  Therefore, a method of detoxifying a pollutant vaporized from contaminated soil by a steam decomposition method by indirect heating has been disclosed (see Patent Document 1). This is a method using indirect heating method so that a large amount of exhaust gas is not released when organic pollutants such as PCBs and dioxins are volatilized from contaminated soil, and the volatilized organic pollutant is a method using water vapor. This is a method for treating contaminated soil that can be stably decomposed into hydrogen halide and carbon dioxide. Furthermore, in order to facilitate handling of exhaust gas, a method of converting a gas treated by steam decomposition into an incombustible gas using an oxidizing agent is also known. In the decomposition process using water vapor, for example, when organic pollutants such as dioxins are decomposed, combustible components such as carbon monoxide, hydrogen, and methane may be generated as products after decomposition. This is because the combustible component is more preferably converted into a non-combustible component by adding an oxidizing agent such as air.

  However, when steam decomposition and oxidation treatment are performed in a single furnace, back mixing of the oxidant (a phenomenon in which the oxidant mixes in the first half by flowing back the gas flow in the furnace) occurs. A low temperature oxidizer lowers the temperature in the furnace, making it difficult to maintain a predetermined temperature during steam cracking treatment, or de novo synthesis occurs due to the presence of oxygen during steam cracking and harmful by-products May occur, and control of the decomposition process is very difficult. Therefore, it is desirable to divide the oxidation treatment process from the decomposition treatment process, and generally, a furnace is divided into a furnace for decomposition treatment and a furnace for oxidation treatment with a plurality of furnaces.

  On the other hand, when soil is treated, problems such as the fact that fine components of the soil tend to become dust inevitably occur. In particular, when dust is present in a high-temperature furnace, there is a problem that sintering is likely to occur. When a plurality of furnaces are used, the furnace connection portion is likely to be blocked.

Further, in the treatment of contaminated soil, an apparatus that is more compact and has good operability is desired due to restrictions on the place of use. However, in the case of multiple furnaces, the size of the apparatus itself becomes enormous. In addition, since a plurality of furnaces are provided, there are problems such as a large heat radiation area and poor thermal efficiency.
JP 2004-57911 A

  The present invention has been made to solve the above problems, and when decomposing pollutants evaporated from soil, it prevents clogging with dust and the like, and safely and reliably without releasing a large amount of exhaust gas. An object of the present invention is to provide an apparatus for decomposing pollutants that can be decomposed.

To achieve the above object, the device for decomposing pollutants according to the present invention includes a pressurized thermal furnace you heated decompose organic pollutants contained in the gas obtained by vaporizing by heating a soil containing organic contaminants, the disposed within the heating furnace, to convert the organic pollutants combustible decomposition products generated in the heating decompose decomposition zone and the decomposition ku zone by water vapor contained in the gas by an oxidizing agent to the non-combustible material and having a specification cut plate that divide the transition area.

  The partition plate is preferably installed in a direction perpendicular to the flow direction of the gas containing the organic pollutant, having an area of 50% or more of the flow path cross-sectional area in the heating furnace.

  The oxygen concentration in the decomposition zone is preferably 5% by volume or less.

  Moreover, it is preferable that the said heating furnace has one or more radiant tube type heaters and a heat insulating material inside.

Also, pollutant processing apparatus in soil according to the present invention, vaporized by heating by heating a soil containing organic contaminants, a first heating furnace Ru vaporized organic contaminants, a soil containing organic contaminants A second heating furnace for thermally decomposing organic pollutants contained in the gas that has been vaporized, and the second heating furnace includes water vapor contained in the gas containing the organic pollutants contained in the vaporized gas. An apparatus for treating a pollutant in soil, comprising: a partition area that separates a decomposition area that decomposes by the process and an area that converts a combustible product generated by the decomposition into an incombustible substance by an oxidant .

  The partition plate is preferably installed in a direction perpendicular to the flow direction of the gas containing the organic pollutant, having an area of 50% or more of the flow path cross-sectional area in the heating furnace.

  According to the present invention, there is provided a pollutant decomposing apparatus that can prevent clogging with dust and the like when decomposing pollutants evaporated from soil, and can safely and reliably decompose without releasing a large amount of exhaust gas. Can be provided.

  Hereinafter, embodiments according to the present invention will be described in detail.

  The schematic diagram of the contaminated soil processing apparatus which concerns on one Embodiment of this invention was shown in FIG.

  The treatment apparatus for contaminated soil (including sludge) is vaporized by the volatilization apparatus 101 for vaporizing contaminants from the contaminated soil, the cooling apparatus 102 for cooling the contaminated soil treated by the volatilization apparatus 101, and the volatilization apparatus 101. A decomposing apparatus 103 for treating the pollutant gas, an exhaust gas treating apparatus 104 for cooling the exhaust gas decomposed and detoxified by the decomposing apparatus 103, and the decomposing apparatus 103 And a blower 105 for discharging as exhaust gas.

  The volatilization device 101 is a device that uses a screw feeder, a kiln or the like, and indirectly heats the soil to vaporize the pollutant gas from the contaminated soil. Screw feeders or kilns can easily heat the soil indirectly, can be continuously treated, and can adjust the number of rotations, so that the amount of contaminated soil can be changed as appropriate. However, since the generation amount of dust can be suppressed, a screw feeder is preferably used.

  The decomposition treatment of the contaminated soil and pollutant gas is performed as follows.

  The contaminated soil is put into the volatilization apparatus 101. The volatilization apparatus 101 heats the input soil to 200 ° C to 600 ° C. The pollutant contained in the soil is vaporized as pollutant gas, and the treated soil is transported to the cooling device 102 as clean soil and cooled to near room temperature.

  On the other hand, the vaporized pollutant gas is sent to the decomposition apparatus 103 by the suction force of the blower 105. The pollutant gas is heated to 600 ° C. to 1300 ° C. and decomposed by reaction with water vapor in an area where the decomposition apparatus 103 decomposes with water vapor (hereinafter referred to as a decomposition area). The decomposition products generated by the steam decomposition process are converted into non-combustible gas by an oxidant (hereinafter referred to as conversion zone) and react with an oxidant such as air in a non-combustible substance (hereinafter referred to as non-combustible component). ). The treated gas is cooled by the exhaust gas treatment device 104. For example, when the exhaust gas is a highly acidic gas containing a large amount of hydrogen chloride or the like, an alkaline water shower scrubber device or the like is used. The cooled gas is discharged as exhaust gas through the blower 105.

  Here, the present inventors divided one heating furnace into two zones, a decomposition zone and a conversion zone, with a partition plate, thereby preventing clogging with dust mixed in pollutant gas without dividing the furnace. High thermal efficiency is possible, and at the same time, the temperature change in the furnace due to the addition of oxidant and the introduction of oxygen into the decomposition zone are suppressed, so that the proper decomposition of the pollutants evaporated from the contaminated soil is realized. Invented an apparatus for decomposing pollutants.

  A method for decomposing the pollutant gas will be described.

  First, in order to efficiently decompose the pollutant gas, it is preferable to perform steam decomposition in which the pollutant gas is indirectly heated and decomposed. Here, indirect heating refers to heating the pollutant gas so that the heat source (such as a heater) does not come into direct contact with the pollutant gas, and the heat source is isolated by a partition made of metal or ceramic. This is a method in which the pollutant gas is heated by heat transfer by radiant heat or the like through the partition wall. Indirect heating reduces the amount of exhaust gas generated compared to direct heating, so that the apparatus does not become enormous and the expansion of the heat radiation area (surface area of the heating furnace) can be prevented, so that the thermal efficiency is improved. The direct heating is a method in which the pollutant gas is directly heated by a heat source such as a burner. For example, the combustion gas generated by burning fuel and the pollutant gas are mixed to increase the temperature. In the case of direct heating, the temperature in the vicinity of a heat source such as a burner is locally high and is likely to be low in the vicinity of the furnace wall (hereinafter referred to as temperature unevenness), and unintentionally harmful by-products may be generated. Therefore, it is preferable to use an indirect heating method for detoxifying the pollutant gas.

  The principle that organic pollutants are decomposed (detoxified) is considered as follows.

  Organic pollutants have a carbon skeleton and are bonded with atoms such as hydrogen, oxygen, and nitrogen. In the steam decomposition step, when the organic pollutant is heated to 600 ° C. or higher, it reacts with the steam to break the bonds of carbon, hydrogen, oxygen, nitrogen and the like. Depending on the heating temperature, over time, the pollutants are converted to harmless substances with smaller molecules. For example, when organic pollutants such as dioxins are indirectly heated to 600 ° C. or higher in the presence of water vapor, they are finally converted into gases such as carbon monoxide, hydrogen, methane, carbon dioxide, and hydrogen chloride.

  Here, the temperature of the heating furnace is preferably 600 ° C. to 1300 ° C. in order to decompose the contaminants. In the decomposition of the pollutant gas, if the temperature in the heating furnace is lower than 600 ° C., the pollutant gas may remain without being sufficiently decomposed, and if the heating temperature exceeds 1300 ° C., the heating furnace The service life limit of the normal heat-resistant material to be constructed will be exceeded. Further, if the temperature is excessively higher than that required for decomposition, the thermal efficiency is also poor.

  Moreover, it is preferable that the time for staying in the heating furnace to decompose the pollutant gas is 2 to 10 seconds. If the residence time in the heating furnace is shorter than 2 seconds, there is a possibility that the pollutant gas remains without being sufficiently decomposed. On the other hand, if the residence time is longer than 10 seconds, the apparatus becomes too large, the thermal efficiency is poor, and the temperature unevenness of the heating furnace tends to occur.

Next, combustible components such as carbon monoxide, hydrogen, and methane are converted into incombustible components by an oxidant such as air. Degradation treatment (detoxification treatment) of pollutants is a treatment that converts harmful pollutants into harmless materials, but the treated gas contains combustible components such as carbon monoxide, hydrogen, and methane. In this state, if the pollutant is discharged out of the decomposition device, there is a risk of ignition and the like, and it is difficult to handle the exhaust gas. Therefore, it is preferable to convert the combustible component produced | generated by steam decomposition into an incombustible component with an oxidizing agent etc. For example, an oxidant such as air is added to convert a combustible component into an incombustible component.

  In the decomposition apparatus 103 shown in FIG. 1, the inside of a single heating furnace serving as the decomposition apparatus is subjected to a decomposition area where steam decomposition is performed by a partition plate, and a process (hereinafter referred to as a conversion process) for converting decomposition products into incombustible components. Divide into 2 zones with conversion zone. This is a structure that makes it possible to secure a residence time sufficient for processing in the decomposition zone.

  Next, it is possible to prevent the occurrence of back-mixing due to the addition of an oxidant by dividing the conversion area for converting the combustible component generated in the decomposition zone into an incombustible component by an oxidant or the like by a partition plate. Become. Oxidant reverses the flow of gas in the furnace from backmixing and enters the pollutant gas, for example, because de novo synthesis such as dioxin occurs, so the decomposition area and conversion area are placed in the same furnace. It is not preferable to provide it. However, in the decomposition apparatus 103, since the conversion process is separated from the steam decomposition process by the partition plate, problems such as de novo synthesis associated with back mixing or the like do not occur. Moreover, since the temperature change in the furnace accompanying the addition of the oxidant can be suppressed from reaching the steam decomposition zone, the temperature control in the furnace becomes easy.

  Therefore, it is possible to maintain the decomposition performance of pollutants even in a single heating furnace, further improve the safety of the gas discharged outside the decomposition apparatus, and improve workability.

  For example, when steam decomposition and conversion treatment are performed in the same heating furnace without a partition plate, a large temperature difference may occur in the vertical direction in the heating furnace. As a result of the temperature difference in the vertical direction in the heating furnace, the temperature reaches a temperature higher than necessary in one local area and does not reach the temperature necessary for decomposition in another local area. It can happen that the temperature is low even near the outlet.

  Furthermore, a phenomenon that the pollutant gas moves to the next process, for example, the conversion process, while the temperature of the pollutant gas does not reach the required temperature may occur, and a part of the pollutant gas that has not been decomposed. Will be discharged out of the disassembly unit.

  Therefore, it is preferable to provide a partition plate in the decomposition apparatus 103, and pollutant gas can be retained in the heating furnace for a predetermined residence time, thereby enabling stable decomposition processing of the contaminant.

  An apparatus capable of performing such a steam cracking process has, for example, a cylindrical shape or a rectangular parallelepiped shape, an apparatus that indirectly heats a pollutant gas through a furnace core tube made of metal or ceramics, or a heating furnace A heat source (such as a heater) is installed in the apparatus, and a device provided with a heat insulating material can be used to maintain the temperature in the heating furnace.

If Ru using a heating furnace inside adiabatic example, it is possible to adopt a sealed structure in refractory metal skin on the outside of the insulation, even airtightness in differences due to the change is small high temperature coefficient of thermal expansion of the material Can be secured. In addition, since the radiant tube type heater is distributed throughout the furnace, temperature unevenness is unlikely to occur even when scaled up, and since there are no narrower channels, the maintainability of the apparatus is good and clogging with dust is less likely to occur. Therefore, it is more preferable to use an internal heat insulation type heating furnace as the pollutant gas decomposition apparatus.

  Next, details of the decomposition apparatus 103 will be described with reference to FIG.

  The pollutant gas decomposition apparatus shown in FIG. 2 includes a heating furnace 10 that is covered with a metal shell 11 and has a heat insulating material 12 provided in order to maintain a predetermined temperature. Partition plates 13 and 14 provided in a direction perpendicular to the flow path direction are provided inside the heating furnace 10.

  The heating furnace 10 further introduces a pollutant gas (treated gas) vaporized from the soil, and discharges an inlet 20 and a gas (treated gas) after being treated at a predetermined temperature inside the heating furnace 10. A discharge port 30 is provided.

  The heating furnace 10 is divided into three sections by a first partition plate 13 and a second partition plate 14, and the section from the inlet 20 to the first partition plate 13 is a first decomposition section, a first partition section. The area from the first partition plate 13 to the second partition plate 14 is a second disassembly area. An oxidant addition device 40 including a preheating device 41 is provided after the second partition plate 14, and an oxidant such as air is supplied into the heating furnace 10 by the oxidant addition device. The area to which this oxidant is supplied is the conversion area.

  In the first decomposition zone, the second decomposition zone, and the conversion zone, respectively, heaters 51, 52, and 53 that serve as heat sources, and control means 61, 62, and 63 that control the temperature of the heaters 51, 52, and 53, In order to feed back to the control means 61, 62, 63, temperature sensors 71, 72, 73 that measure the temperature of the gas to be processed that has been heated in each zone are provided.

  The outer skin 11 is preferably formed of a steel material such as iron or stainless steel (SUS). The heating furnace 10 is an inner heat insulation type furnace, and the internal shape of the heating furnace 10 can be selected as appropriate, such as a cylinder or a rectangular parallelepiped. The heat insulating material 12 covering the inner wall of the heating furnace 10 is preferably formed of heat-resistant bricks, ceramic boards, or the like. In the inner heat insulation type heating furnace, high-temperature pollutant gas in the furnace is in direct contact with the heat insulating material, and gas contact with the outer heat-resistant metal outer skin 11 can be avoided. In the inner heat insulation type furnace, a sealed structure can be easily realized and thermal expansion of the outer skin itself can be suppressed.

  In particular, by providing the second partition plate 14, it is possible to divide into a decomposition zone and a conversion zone in the heating furnace 10. This makes it possible to shut off the pollutant gas that passes through the low temperature part and is discharged without being decomposed, and raises the gas flowing into the decomposition device to a predetermined temperature, compared to the device without a partition plate. It is possible to make it. That is, it is possible to realize residence at a temperature of 600 to 1300 ° C. for 2 to 10 seconds in a steam decomposition step necessary for decomposing the pollutant gas.

  For example, the first partition plate 13 is provided perpendicularly from the furnace bottom of the heating furnace 10 so as to correspond to 50% or more of the flow path cross-sectional area in the furnace, more preferably, 2/3 or more. And good. Further, the second partition plate 14 corresponds to a channel cross-sectional area of 50% or more, more preferably two-thirds or more of the channel cross-sectional area from the upper wall side of the heating furnace 10 vertically to the lower side of the furnace. It is good to provide. The first partition plate 13 and the second partition plate 14 may be any material that can withstand the temperature of the heated pollutant gas (treated gas), but the heat insulating material 12 such as a heat-resistant brick or a ceramic board. It is preferable to use the same material as that used in the above. For example, when dioxins are treated as pollutants, if oxygen is present in the low-temperature part of the decomposition zone due to the phenomenon that oxidant is mixed in the first half of the furnace (back mixing), dioxin synthesis can be used. May be synthesized. Although this may significantly degrade the decomposition performance, back mixing can be prevented by closing 50% or more of the flow path cross-sectional area of the gas flowing in the heating furnace and restricting the flow path. Also, by preventing back-mixing, it is possible to prevent uneven temperature such as a reaction between the oxidant and pollutant gas, resulting in a partial increase in temperature, or a decrease in temperature due to mixing of low-temperature oxidants. Become.

The heaters 51, 52, and 53 that serve as heat sources are preferably radiant tube heaters that are suspended from the top of the heating furnace 10 into the furnace. For example, the outer skin 11 and the radiant tube heaters 51, 52, and 53 are connected to each other. Connecting through a flange is effective for maintaining airtightness.

  A radiant tube type heater is a heater that heats the surroundings by radiating and transferring heat from the outer surface of the tube by passing a heat source through the inside of a heat resistant tube made of metal or ceramics. As a heat source that passes through the inside, a combustion gas of fuel such as an electric heater, kerosene, heavy oil, or city gas may be used.

  When using an electric heater, a heating element is inserted into the radiant tube.

  When using kerosene, heavy oil, city gas, or the like, a combustion burner suitable for the fuel used is provided outside the end of the radiant tube, and the high-temperature gas generated from the combustion burner is passed through the radiant tube.

  The shape of the radiant tube heater may be a straight tube type or a U-shaped tube type. In the case of the straight tube type, it is preferable to use a radiant tube having a double tube structure in which a combustion gas blower tube is inserted in the outer tube to the vicinity of the tip. The combustion gas from the combustion burner passes through the inside of the combustion gas blower pipe, is folded at the tip of the radiant tube, and is returned through the outside of the combustion gas blower pipe. The returned gas may be discharged out of the system as exhaust gas, or may be sent to a heat exchanger to utilize the exhaust heat to improve the thermal efficiency of the entire apparatus. The radiant tube type heater may be any method such as a method of hanging from the upper part of the heating furnace, a method of inserting sideways from the side of the heating furnace, or a method of inserting upward from the bottom of the heating furnace. Since the tube may be deformed at high temperatures, when inserting the radiant tube heater horizontally, it is recommended that the radiant tube heater be installed so that it does not come into contact with the outer wall of the furnace or other radiant tube heaters. . When a plurality of radiant tube heaters are arranged inside the heating furnace 10, the heat transfer surface is widely distributed in the furnace, so that the uniformity of the furnace temperature can be improved. Moreover, since the volatilization apparatus which vaporizes the pollutant from the soil conveys the contaminated soil while stirring, fine soil particles are contained in the gas as dust. When the soil particles are exposed to a high temperature of 1000 ° C. or higher, they may melt and form a clumped clinker. When the clinker grows, problems such as blockage in the furnace occur. By connecting a radiant tube type heater via the flange, the radiant tube type heater can be removed even if the clinker adheres to the radiant tube type heater. The mold heater can be pulled out and cleaned. Compared with the direct cleaning of the inner surface of the furnace core tube, the operation becomes much easier. In addition, the connection of each radiant tube type heater should just be a connection structure which can draw out a radiant tube type heater from a heating furnace.

  It is further preferable to provide a dust scraping feeder or the like in case dust or clinker accumulates at the bottom of the heating furnace.

    The control of the radiant tube heater is performed by a control means, and feedback control is performed so that the temperature detected by the temperature measuring instrument approaches the set temperature. The installation position of the temperature measuring device is not particularly limited as long as it can be installed at a position where the atmosphere in the heating furnace where the temperature of the radiant tube heater rises can be captured. For example, the radiant tube heater disposed in the first decomposition section 51 is provided with a temperature sensor 71 as a temperature measuring device between the first decomposition section and the second decomposition section, and the temperature detected by the temperature sensor 71 is fed back to the heater output control device 61 for output control. preferable.

  Similarly, the radiant tube heater 52 arranged in the second decomposition zone is provided with a temperature center 72 between the second decomposition zone and the conversion zone, and the temperature detected by the temperature center 72 is used as the heater output control device 62. The radiant tube heater 53 disposed in the conversion zone is fed back to the heater and provided with a temperature sensor 73 in the vicinity of the discharge port 30 of the heating furnace 10, and the temperature detected by the temperature sensor 73 is supplied to the heater output control device 63. Feedback control is performed.

  The control method of the output of the radiant tube type heater is a control method in which the output is turned on when the detected temperature does not reach the set temperature, and is turned off when the detected temperature is exceeded, or the output is PID by comparing the set temperature with the detected temperature. A method of controlling (Proportional-Integral-Deriva control), for example, a method of performing PID control on the amount of fuel supplied to the burner can be selected as appropriate.

  About the installation method of a partition plate and a heater, as shown in FIG. 3, the inlet 20 and the discharge port 30 are provided in the same side surface of the heating furnace 10, and the flow of pollutant gas is provided by providing the partition plate 15 horizontally. It is also possible to circulate the inside of the furnace. In this case, the lower part of the partition plate 15 becomes a decomposition zone, and an oxidant addition device 40 having a preheating device 41 is provided after the partition plate 15, and an oxidant such as air is introduced into the heating furnace 10 by the oxidant addition device. Supplied. The area where the oxidant is supplied is the conversion area. Further, as shown in FIG. 4, the inlet 20 is provided on the vertically lower side surface and the outlet 30 is provided on the upper side surface, and the partition plate 16 and the partition plate 17 are arranged in a direction perpendicular to the flow direction of the gas to be processed. It may be provided. The partition plate is provided so as to be positioned between the heaters 51, 52, 53 serving as heat sources, and an oxidant addition device 40 including a preheating device 41 is provided after the second partition plate 17. In this case, the area from the introduction port 20 to the second partition plate 17 is a decomposition area, and the area from the second partition plate 17 to the discharge port 30 to which the oxidant is supplied by the oxidant addition device 40 is a conversion area. is there. FIG. 4 shows the case where the heaters 51, 52 and 53 are inserted sideways from the side of the heating furnace. However, when a radiant tube heater is inserted sideways, it is sufficient for deformation of the tube at high temperatures. It is necessary to pay attention. Moreover, you may insert upward from a bottom part other than the type suspended from the heating furnace upper part.

  Furthermore, the pollutant can be stably and sufficiently decomposed by reducing the oxygen concentration in the steam decomposition process. When the oxygen concentration in the steam decomposition step is 5% by volume or less, preferably 1% by volume or less, resynthesis of dioxins can be prevented. Water vapor contained in the soil is mainly used as the water vapor used for decomposition, but water may be added to the decomposition apparatus 103 separately.

The processing method of the pollutant gas in the decomposition apparatus shown in FIG. 2 is as follows.

  The pollutant gas is introduced into the heating furnace 10 through the introduction port 20. In addition to organic pollutants, the pollutant gas contains moisture and low-boiling organic substances contained in the soil.

  In the heating furnace 10, the output of the radiant tube heater 51 is controlled by the first controller 61 based on the temperature detected by the first temperature sensor 71, and the pollutant gas is heated to the target reaction temperature.

  The pollutant gas that has been heated in the first decomposition zone and has reached a predetermined temperature flows into the second decomposition zone. In the second decomposition zone, the output of the radiant tube heater 52 is controlled by the second controller 62 based on the temperature detected by the second temperature sensor 72. The pollutant gas and water vapor are maintained at a predetermined reaction temperature and are retained for a predetermined time, thereby decomposing and detoxifying the pollutant gas.

  The treated gas flows into the conversion zone. In the conversion zone, an oxidant such as air preheated by the preheater heater 41 is supplied from the oxidant supply nozzle 40, and based on the temperature detected by the third temperature sensor 73, the third controller 63 performs a radiant tube type. The output of the heater 53 is controlled. Since the gas after processing contains combustible components generated by steam decomposition, these are converted into incombustible components by an oxidizing agent. At this time, it is preferable to use a substance capable of converting a combustible component such as air or oxygen into an incombustible component as the oxidizing agent.

  Hereinafter, an example of the pollutant gas decomposition apparatus and the contaminated soil treatment apparatus according to the present invention will be described based on examples.

  The treatment apparatus used in the present example is a treatment apparatus for contaminated soil having a soil treatment capacity of 300 kg / hr. After polluting the contaminated soil into a volatilizer to vaporize the contaminants, the contaminant gas shown in FIG. Was introduced into the decomposition apparatus and the decomposition process was performed.

  5, FIG. 6, and FIG. 7 are a longitudinal sectional view, a top view, and a sectional view in the width direction from the inlet side of the pollutant gas (processed gas) in the pollutant gas decomposition apparatus, respectively. Here, the same components as those in FIG.

  In FIG. 5, the heating furnace 10 of the pollutant gas decomposition apparatus is an inner heat insulation type heating furnace in which a ceramic board is provided as a heat insulating material 12 inside an outer skin 11 made of steel, and the inside dimension of the furnace is high. It is a rectangular parallelepiped shape of 1950 mm, length 2400 mm, and width 700 mm. The thickness of the ceramic board as the heat insulating material 12 is about 300 mm, and the temperature of the outer skin 11 can be prevented from reaching 100 ° C. in a steady state in the pollutant gas treatment. Therefore, the occurrence of accidents such as fires and burns due to the high temperature of the outer skin surface, and the decrease in thermal efficiency due to excessive heat escaping from the outer skin are prevented.

  In the heating furnace 10, the 1st partition plate 13 and the 2nd partition plate 14 are arrange | positioned, and the inside of a furnace is divided into three areas by these partition plates. The first partition plate is provided at a position 800 mm away from the introduction port 20 in the longitudinal direction so that the inside of the heating furnace 10 is equally divided into three sections, and the second partition plate is disposed in the longitudinal direction from the discharge port 30. It was provided at a position 800 mm away.

  Three radiant tube heaters 51, 52, and 53 were provided in each area.

  FIG. 6 is a top view of the pollutant gas decomposition apparatus, and a total of nine radiant tube heaters are provided in the heating furnace 10. A first partition plate 13 and a second partition plate 14 are provided at intervals of 800 mm from the introduction port 20. The upper ends of the individual radiant tube heaters 51, 52 and 53 are attached to the outer skin 11 by flanges 80, thereby ensuring an airtight structure. Since the flange 80 can be removed and the radiant tube heater can be pulled upward, the clinker attached to the tube can be easily cleaned.

  The radiant tube heaters 51, 52 and 53 are made of a heat-resistant metal, and the outer tube has an outer diameter of 150 mm and a length of 2000 mm. It has a double tube structure in which a combustion gas blower tube is inserted to the vicinity of the tip inside the outer tube of the radiant tube type heaters 51, 52, 53, and a gas burner is provided outside the furnace on the outer skin 11 side. . A high-temperature combustion gas is generated from the gas burner so that indirect heating can be performed by radiant heat transfer from the outer tube through the inside of the combustion gas blowing tube. The combustion gas flows through the blower pipe so as to be folded back at the tip of the radiant tube, and returns through the outside of the combustion gas blower pipe having a double pipe structure. The returned combustion gas is discharged out of the system as exhaust gas. Since this exhaust gas is a gas combustion gas, an exhaust gas treatment device is not particularly required.

  FIG. 7 is a cross-sectional view seen from the inlet side 20 of the gas to be treated. The heat insulating material 12 covered with the outer skin 11 is provided in the heating furnace 10, and the dimensions in the furnace are 1950 mm in height and 700 mm in width. The radiant tube type heater 51 is provided with another radiant tube type heater behind the two radiant tube type heaters shown in FIG. The radiant tube heater provided at the rear is located at the center of the two radiant tube heaters in FIG.

  The temperature of the pollutant gas flowing into the heating furnace is measured by the temperature sensors 71, 72, 73, and the radiant tube heaters 51, 52, 53 are controlled by the temperature control means so as to reach a predetermined temperature. In the case of this example, the temperature was adjusted by a gas burner so that the detected temperatures by the temperature sensors 71, 72 and 73 as temperature measuring instruments were close to 1000 ° C. Specifically, an LPG (liquefied petroleum gas) burner was used, and the amount of LPG supplied to the burner was PID controlled (Proportional-Integral-Deriva control) to control the temperature of the pollutant gas flowing into the heating furnace. .

  An oxidant addition device 40 having a preheating device 41 is provided after the second partition plate 14, and an oxidant such as air is supplied into the heating furnace 10 by the oxidant addition device 40. The third zone to which this oxidant is supplied becomes the conversion zone.

  Next, a method for decomposing the pollutant gas vaporized from the contaminated soil will be described.

  The soil used as the contaminated soil is a soil containing 10% by weight of water and 5% by weight of organic matter, and contains dioxins as contaminants at a concentration of 8000 pg-TEQ / g.

  This contaminated soil was introduced from the hopper of the volatilizer 101 in the soil treatment apparatus and heated to 500 ° C. to vaporize moisture, low-boiling organic substances and dioxins from the contaminated soil. By the suction force of the blower 105 in the soil treatment apparatus, the pollutant gas is sent into the heating furnace 10 of the above-described decomposition apparatus 103, and the pollutant gas is heated to about 1000 ° C. and held in the first zone and the second zone. And decomposed the pollutants.

Thereafter, air is supplied as an oxidant from the supply nozzle of the oxidizer addition apparatus 40 to the third zone at a flow rate of 150 Nm ³ / hr, and the product generated in the steam cracking process in the first zone and the second zone. Was converted. The treated exhaust gas was exhausted by removing dust and cooling with an exhaust gas treatment device 104.

  Measurement of the temperature distribution in the heating furnace 10, the oxygen concentration distribution in the heating furnace 10 and the concentration of the pollutant after the treatment when the pollutant gas vaporized from the contaminated soil is decomposed by the decomposition method as described above. did. The results are as follows.

The total amount of gas generated by introducing contaminated soil containing dioxins into the volatilization apparatus 101 and vaporizing with the volatilization apparatus was about 350 Nm ³ / hr. The main component in the vaporized gas is water vapor.

  Dioxin density | concentration of the contaminated soil processed with the volatilizer 101 was 2pg-TEQ / g. Since the concentration before being charged into the volatilization apparatus 101 was 8000 pg-TEQ / g, the removal rate of dioxins was 99.99% or more, and sufficient removal from the soil was possible.

  FIG. 8 shows the temperature distribution in the heating furnace 10. In the first decomposition zone immediately after the pollutant gas flows in, the temperature gradually changes to reach around 800 ° C., and after the second zone, the temperature is over 800 ° C. The temperature of the gas flowing after the second zone was 800 ° C. or higher. It is clear that there is no temperature difference in the apparatus shown in Example 1.

  FIG. 9 shows the oxygen concentration distribution in the heating furnace 10. A portion indicated by an arrow in FIG. 9 is a portion (air blowing port) into which air as an oxidizing agent flowing from the oxidizing agent adding device 40 is blown. As shown in FIG. 9, it is clear that the oxygen concentration in the first and second decomposition zones is 0% and almost no oxygen is mixed. The absence of oxygen in the first and second decomposition zones means that pollutants such as dioxins are not likely to be re-synthesized by de novo synthesis at low temperatures, and is a device that can perform stable treatment. It can be said that there is.

As a result of measuring the concentration of dioxins in the pollutant gas at the introduction port 20 where the pollutant gas evaporated from the volatilizer 101 flows into the heating furnace 10, it was 3000 ng-TEQ / Nm ³ . When the concentration of dioxins in the gas was measured at the end of the steam cracking step in the cracking apparatus, that is, at the outlet of the second zone, the decomposition rate was 0.06 ng-TEQ / Nm ³ and the decomposition rate was 99.99% or more. The exhaust gas discharged to the atmosphere through the exhaust gas treatment device 104 had a dioxin concentration of 0.03 ng-TEQ / Nm ³ . In addition, the hydrogen chloride concentration in the exhaust gas released to the atmosphere was 0.3 mg / Nm ³ , which satisfied the exhaust gas standards of the Air Pollution Control Law.

  The cracking apparatus according to the first embodiment can be configured with a single furnace for the steam cracking process and the conversion process. Therefore, in addition to stabilizing the decomposition performance of the pollutant gas and suppressing temperature unevenness in the heating furnace, the apparatus cost and release Compared to the multi-furnace configuration, it is a more effective device in terms of heat efficiency in terms of heat quantity and maintainability. The pollutant gas decomposition apparatus according to the present embodiment is an internal heat insulation system, suitable for scale-up, and effective as a pollutant gas decomposition apparatus.

(Comparative Experiment 1)
In the heating furnace in the pollutant gas decomposition treatment apparatus, a pollutant gas decomposition test was conducted using a heating furnace without a partition plate. FIG. 10 is a longitudinal sectional view of the heating furnace used in the test. This heating furnace is obtained by removing the partition plate from the heating furnace shown in the first embodiment, and the dimensions in the furnace are the same as those in the heating furnace shown in the embodiment.

  The oxidant addition device 40 provided with the preheating device 41 and the oxidant addition device 43 provided with the preheating device 42 are provided with an air blowing port as an oxidant at a location 800 mm away from the discharge port 30 in the longitudinal direction. Two places were provided.

  The treatment of the contaminated soil and the decomposition treatment of the pollutant gas are performed in the same procedure except for the configuration of the used heating furnace, and the composition of the contaminated soil used in the experiment is the same. Contaminated soil containing dioxins was put into a volatilizer, and the temperature distribution in the heating furnace, the oxygen concentration distribution in the heating furnace, and the concentration of the pollutant after treatment were measured when the pollutant gas was introduced into the heating furnace. . The results are as follows.

  FIG. 11 shows the temperature distribution in the heating furnace. As is clear from FIG. 11, there was a large temperature difference in the vertical direction in the heating furnace, and in particular, a low temperature of 400 ° C. or lower was shown in a wide range from the pollutant gas inlet to the bottom of the heating furnace. It is difficult to keep the temperature necessary for decomposing pollutants at 600 ° C. or higher.

  FIG. 12 shows the oxygen concentration distribution in the heating furnace. A portion indicated by an arrow in FIG. 12 is a portion (air blowing port) into which air as an oxidizing agent flowing from the oxidizing agent adding device 40 is blown. From FIG. 12, it was found that oxygen was detected up to the vicinity of the introduction port, and it was found that oxygen entered into the front half part (back mixing) from the air blowing port. In particular, when the pollutant is dioxins or the like, if the oxygen concentration is high in a low temperature region, there is a possibility of a resynthesis reaction by de novo synthesis, so it is preferable that oxygen enters the first half of the air inlet. Absent.

Next, as a result of conducting a treatment test for contaminated soil under the same conditions as in Example 1, the concentration of dioxins in the pollutant gas at the inlet of the heating furnace was 3000 ng-TEQ / Nm ³ , whereas air was blown in The dioxin concentration in the gas immediately before the mouth was 380 ng-TEQ / Nm ³ , and the exhaust gas discharged to the atmosphere through the exhaust gas treatment device had a dioxin concentration of 2 ng-TEQ / Nm ³ . The decomposition rate of dioxins concentration just before the air inlet is about 90%, and the concentration of dioxins in the exhaust gas discharged through the exhaust gas treatment device greatly exceeds the allowable emission limit value. It was unacceptable as a decomposition processing apparatus.

Schematic of the contaminated soil processing apparatus which concerns on one Embodiment of this invention. 1 is a schematic diagram of a pollutant gas decomposition apparatus according to an embodiment of the present invention. 1 is a schematic diagram of a pollutant gas decomposition apparatus according to an embodiment of the present invention. 1 is a schematic diagram of a pollutant gas decomposition apparatus according to an embodiment of the present invention. The schematic of the pollutant gas decomposition processing apparatus which concerns on a present Example. The top view of the pollutant gas decomposition processing apparatus which concerns on a present Example. Sectional drawing of the decomposition processing apparatus of the pollutant gas which concerns on a present Example. The figure which shows the temperature distribution in a heating furnace. The figure which shows oxygen concentration distribution in a heating furnace. Sectional drawing of the heating furnace which concerns on a comparative example. The figure which shows the temperature distribution in the heating furnace which concerns on a comparative example. The figure which shows oxygen concentration distribution in the heating furnace which concerns on a comparative example.

Explanation of symbols

10 ... heating furnace,
11. The outer skin,
12 ... heat insulating material,
13, 14, 15, 16, 17 ... partition plates,
20 ... introduction port,
30 ... discharge port 40, 43 ... oxidizer addition device,
41, 42 ... Preheating device,
51, 52, 53 ... heater,
61, 62, 63 ... control means,
71, 72, 73 ... temperature sensors,
80 ... flange,
101 ... Contaminated soil volatilizer,
102 ... Cooling device,
103 ... disassembly device,
104 ... Processing device,
105 ... Blower

Claims (6)

A pressurized heat furnace heated decompose organic pollutants contained in the gas obtained by vaporizing by heating a soil containing organic contaminants,
Wherein disposed in the heating furnace, converting the organic contaminant heating decomposed decomposed by water vapor contained in the gas zone and decomposition products of the combustible to be generated in the decomposition ku domain into non-combustible material with an oxidizing agent cracker contaminants and having a transition area was divided that specification cut plate for. The partition plate has an area of 50% or more of a flow path cross-sectional area in the heating furnace,
The pollutant decomposition apparatus according to claim 1, wherein the pollutant decomposition apparatus is installed in a direction perpendicular to a flow direction of the gas containing the organic pollutant.   2. The pollutant decomposition apparatus according to claim 1, wherein the oxygen concentration in the decomposition zone is 5% by volume or less.   2. The pollutant decomposition apparatus according to claim 1, wherein the heating furnace includes at least one radiant tube heater and a heat insulating material. The soil containing organic contaminants is heated, the first heating furnace which Ru is vaporized organic contaminants,
A second heating furnace for thermally decomposing the organic pollutant contained in the gas vaporized by heating the soil containing the organic pollutant;
Have
In the second heating furnace, the organic pollutant contained in the vaporized gas is decomposed by water vapor contained in the gas, and the combustible decomposition product generated in the decomposition area is incombustible by an oxidizing agent. An apparatus for treating a pollutant in soil, comprising a partition plate that separates an area to be converted into a natural substance. The partition plate has an area of 50% or more of a flow path cross-sectional area in the heating furnace,
6. The apparatus for treating pollutants in soil according to claim 5, wherein the apparatus is disposed in a direction perpendicular to a flow direction of the gas containing the organic pollutants.

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