JP5311007B2 - Heat treatment system and heat treatment method - Google Patents

Description

  The present invention relates to a system and a heat treatment method for pretreating soil contaminated with a pollutant such as dioxin and then heat treating it to make it harmless, and to a pretreatment apparatus used in the system.

  Incineration ash generated after incineration of plastic products contains dioxins, and the incineration ash contaminates the soil by being buried in the soil. Wastewater discharged from mines, factories, and industrial waste disposal sites contains heavy metals, organic solvents, etc., and they are sent to wastewater treatment facilities to treat them. Contaminate. Furthermore, the soil is contaminated by illegally dumping products containing pollutants such as dioxins, heavy metals and organic solvents. Since these pollutants are highly toxic and have a serious effect on the human body, environmental standard values are specified, and they must be removed to concentrations below the environmental standard values.

  Heavy metals include cadmium, lead, hexavalent chromium, arsenic, mercury, etc., and their environmental standard values are 0.01 mg, 0.01 mg, 0.05 mg, 0.01 mg,. 0005 mg. Volatile organic compounds used in organic solvents include dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, trichloroethylene, tetrachloroethylene, benzene, etc. It is set as 0.02 mg, 0.002 mg, 0.004 mg, 0.02 mg, 0.03 mg, 0.01 mg, 0.01 mg per 1L. About dioxins, it is 1000 pg-TEQ / g or less in terms of the toxicity of 2,3,7,8-tetrachlorodibenzo-para-dioxin.

  In order to detoxify contaminated soil, a method of cleaning with a purifier or water has been proposed (for example, see Patent Document 1). This method decontaminates contaminated soil while supplying purification agent and return water, sorts the soil while supplying return water and makeup water, and reuses a portion of the selected soil as washing soil, The remaining soil is classified while supplying return water, and is divided into washed soil and dirty soil or pollutants.

  Another method for washing is to add water to the contaminated soil, classify it with a wet sieve, separate gravel and coarse sand into slurry-like soil, add a dispersant to this soil and mix and agitate. After separating contaminants from the surface of the soil, the soil is hydrocyclone treated and classified into sand, fine sand, and fine particles containing contaminants, then subjected to gravity separation to separate the metal contaminants and dehydrate There exists a thing which obtains a washing processing soil by processing.

  In these methods, contaminants attached to gravel, coarse sand, sand, and fine sand are washed with water, etc., and separated using a dispersant to separate the contaminants. However, it is difficult to remove contaminants attached to small clay or silt, and washing alone is not sufficient.

  As another method, a method has been proposed in which soil contaminated with a hardly decomposable organic compound such as dioxin is heat-treated using superheated steam (see Patent Document 3).

  In this method, the contaminated soil is heated to evaporate moisture contained in the contaminated soil, and further heated to generate superheated steam. The superheated steam heats the contaminated soil and adheres to fine sand and the like. By degassing the decomposable organic compound, it is desorbed from the surface of fine sand and the like, and detoxified soil is obtained.

In this method, it is possible to separate and remove the hard-to-decompose organic compounds just by putting the contaminated soil into the gasifier as it is, so it can be easily treated and adhered to clay or silt having a particle size smaller than fine sand. Persistent organic compounds can also be removed.
JP 2008-43879 A Japanese Patent Laid-Open No. 2006-11697 JP 2007-296410 A

  In the above conventional heat treatment method, the contaminated soil is left as it is or after the removal of stones having a large particle diameter, the contaminated soil is placed in a gasifier and heated to a predetermined temperature in a superheated steam atmosphere to make it difficult to decompose. Organic compounds are separated and removed. In this contaminated soil, there are various large and small particles having different particle sizes from clay to gravel, and therefore there is a portion that is not sufficiently heated due to different heat conduction depending on the particle size.

  In particular, clay and silt having a small particle diameter to which a large number of hardly decomposable organic compounds are attached are put into a high-temperature gasifier, and when heated and stirred, they rapidly dry and harden to form a clot. Heat is gradually transferred from the surface to the inside of this clot, but the speed is slow, and it takes a considerable amount of time to transfer heat to the inside and gasify and desorb the attached persistent organic compounds. Cost. In this case, the amount of energy required for heating is also great.

  Moreover, in the gasifier, although it stirs and conveys with a screw, the dried and hardened earth lump is hard and there is also a problem that the screw is damaged.

  On the other hand, if it can be sufficiently dehydrated before being put into the gasifier, no earth clumps will be formed, and each particle can be rendered harmless by applying the necessary heat in a short time, and the energy required for heating Consumption can be reduced.

  However, when the dehydration process is performed using the dehydrator, the limit is to reduce the moisture content of the contaminated soil to about 45%. In this case, formation of a clot cannot be suppressed in the heat treatment at a high temperature, and the treatment time cannot be shortened, the energy consumption can be reduced, and damage to the screw cannot be prevented.

  Therefore, it has been desired to provide a system and a method that can make the contaminated soil harmless by sufficiently separating and removing the attached contaminants without taking time, so that no soil mass is formed.

  As a result of intensive studies, the inventors of the present invention classify the contaminated soil into pre-treatment before putting it into the gasifier and divide it into soil particles of each size. Therefore, in order to make the particle size uniform for the remaining particles of less than the predetermined size, granulate particles smaller than the specified particle size, specifically, powdery materials (clay and silt). As a result, it has been found that, by making it difficult for the lump to be formed in the gasifier, the contaminants can be sufficiently volatilized and removed in a short time by making the particle diameter uniform.

  Further, it has been found that by adding quick lime and cement and granulating, the moisture content can be reduced, and it can be a countermeasure for the contained heavy metals, and the energy consumption for heating can be reduced.

  This invention is made | formed by discovering these things, The said subject is solved by providing the pre-processing apparatus of this invention, the heat processing system containing the pre-processing apparatus, and the heat processing method. it can.

  That is, according to the present invention, a pretreatment apparatus used in a heat treatment system for pretreating contaminated soil and detoxifying it by heat treatment in an overheated steam atmosphere, the contaminated soil is classified into a plurality of particle size ranges. Pre-treatment, and a granulating means for granulating the contaminated soil classified into a particle size range smaller than the specified particle size so that a dry and hardened lump is not formed in the heat treatment after the pre-treatment. An apparatus is provided.

  The granulating means is preferably granulated by adding quick lime and / or cement.

  Further, in order to efficiently perform the heat treatment, it is preferable that the moisture contained in the contaminated soil is as small as possible. Therefore, the pretreatment device can further include a dehydrating means for removing moisture contained in the contaminated soil classified into a particle size range smaller than the specified particle size.

  According to the present invention, the pretreatment device described above and the contaminated soil having a particle diameter in a predetermined range obtained by classification and granulation by the pretreatment device are received, heated and heated in a superheated steam atmosphere with stirring. There is also provided a heat treatment system including a gasifier that volatilizes contaminants contained in the soil and separates the contaminants into treated soil.

  This heat treatment system further cools the organic compound contained in the volatilized pollutant and reacts it with superheated steam to decompose the organic compound, cools the decomposition product discharged from the reaction apparatus, and gas components. And a bubbling tank for separating the gas.

  The heat treatment system may further include a coagulation tank that receives a liquid containing solids and coagulates and precipitates the solids floating in the liquid in order to reprocess the solids remaining in the bubbling tank. . As a result, the waste is not discharged out of the heat treatment system, and the waste treatment cost becomes unnecessary.

  Moreover, in this invention, the heat processing method which pre-processes contaminated soil and heat-processes in a superheated steam atmosphere and detoxifies can also be provided. In this method, the contaminated soil is classified into a plurality of particle size ranges, and the contaminated soil is classified into a particle size range smaller than the specified particle size so that no dried and hardened lump is formed in the heat treatment after the pretreatment. A pollutant contained in the contaminated soil by heating in a superheated steam atmosphere while stirring the contaminated soil having a particle size in a predetermined range obtained in the granulation step, the classification step and the granulation step. And a purification step of separating the pollutant into treated soil.

  In this granulation step, granulation is performed by adding quick lime and / or cement to reduce the moisture content of the contaminated soil.

  Moreover, the dehydration process which removes the water | moisture content contained in the contaminated soil classified into the particle diameter range smaller than the designated particle diameter is further included after the classification process.

  Furthermore, the organic compound contained in the volatilized pollutant is further heated and reacted with superheated steam to decompose the organic compound, and a separation step of cooling the decomposed substance after the reaction and separating the gas component is included. .

  In addition, it includes an agglomeration step of aggregating and precipitating solids floating in the liquid that is separated and removed from the gas components, and the agglomerated and precipitated solids can be collected and pretreated and heated with contaminated soil .

  By providing the pretreatment device, the heat treatment system, and the heat treatment method of the present invention, it is possible to efficiently and sufficiently remove the contaminants attached to the contaminated soil. Moreover, damage to the stirring means of the gasifier can be prevented.

  Further, by providing the pretreatment device, the heat treatment system, and the heat treatment method of the present invention, the heat treatment time can be shortened in the gasification device, and the energy consumption can be reduced.

  Contaminated soil to be treated by the heat treatment system and heat treatment method provided with the pretreatment device of the present invention is due to leakage of waste water and waste from mines, factories, waste disposal sites, mass spraying of agricultural chemicals, illegal dumping, etc. This soil contains contaminants such as heavy metals, organic solvents, dioxins, and sulfuric acid pitch, and these contaminants are included to such an extent that they affect the natural environment and human body.

  As described above, heavy metals include lead, hexavalent chromium, cadmium, mercury, arsenic, etc., and organic solvents include dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, trichloroethylene, tetrachloroethylene. , Benzene, toluene, xylene, diethyl ether, chloroform, ethyl acetate and the like. Other contaminants include polychlorobiphenyl (PCB) used in paints and the like.

  These pollutants are present in a state of adhering to soil particles in soil having various particle sizes. The soil particles are, in descending order of size, stones, gravel, sand, and mud (silt, clay), which are debris made from broken rocks. Stone means particles with a particle diameter of 75 mm or more, gravel means particles with a particle diameter of 2 to 75 mm, sand means 0.074 to 2 mm, and mud means 0.074 mm or less. Say.

  If contaminants are equally attached to any size of soil particles, all particles must be supplied to the gasifier described below. In the present invention, it has been found that the smaller the particle size, the more pollutants are attached, and almost no stone or gravel is attached to a large particle size.

  Stones and gravel with a large particle size are preferable if they can be removed in advance because they may damage the screw, which is a stirring means in the gasifier described later. Is advantageous because it is hardly attached and can be classified and removed before being put into the gasifier.

  The remaining gravel, sand and mud with a small particle size are strongly contaminated and cannot be removed by washing. Therefore, these must be supplied to the gasifier and volatilized to be separated and removed.

  However, even if it is supplied as it is, there are various sizes of particles contained in the supplied contaminated soil, heat conduction varies depending on the particle size, and there is a lot of moisture, including powdered materials such as clay and silt. Therefore, it is heated rapidly in a high-temperature gasifier and a dry and hardened mass is formed, heat is transferred to the inside of the mass, and it is considerable that the contaminants adhering to the inside volatilize. It takes time.

  Therefore, as a pretreatment before putting into the gasifier, after removing a part of stones and gravel with a large particle size in the contaminated soil, clay and silt with a small particle size are granulated to make the particle size uniform. As a result, since there is no powdery material such as clay or silt, even if it is put into the gasifier, no clot is formed, and since the particle diameter is almost uniform, it can be heated uniformly. Time can be shortened and energy consumption can be reduced.

  Therefore, in the present invention, a pretreatment device is provided on the upstream side of the gasifier. The preprocessing apparatus will be described with reference to FIG. This pretreatment apparatus includes classification means 10 a and 10 b and granulation means 11.

  The contaminated soil is sent to the classifying means 10 a using the mud pump 12. The mud pump 12 can directly send the contaminated soil to the classification means 10a, but the cleaning means 13 can be provided between them to clean the contaminated soil. Examples of the cleaning means 13 include those capable of cleaning the surface by spraying a high-pressure shower onto contaminated soil on the screen. By this cleaning, a trace amount of contaminants attached to a large particle size such as pebbles or gravel can be removed.

  The classification means may be one stage, but it is divided into two stages like the classification means 10a and 10b shown in FIG. 1, and in the first classification means 10a, the contaminated soil after washing has a particle diameter of 5 mm. The above can be separated from the less. Those with a particle size of 5 mm or more have some stones and gravel, and these are almost free of contaminants, so they can be transported to the designated location after being separated here. . These stones and gravel can be used for aggregates and backfilling when making concrete.

  The classification means 10b in the next stage can be divided into those having a particle diameter of 0.074 mm or less and those having a particle diameter exceeding it. This is because contaminants adhere to particles having a particle diameter of more than 0.074 mm, but the amount of adhesion is overwhelmingly larger than particles with a particle size of 0.074 mm or less, and is dried and hardened in the gasifier. The reason why the clot is formed is that there are powdery materials such as clay and silt having a particle size of 0.074 mm or less.

  Here, clay and silt, which are powdery substances, are particles having a very small particle diameter, viscosity, and low water permeability, and are soft when they contain moisture but hard when heated. It is. For this reason, when the contaminated soil containing clay and silt is rapidly heated at a high temperature, the surface is dried and hardened to form a soil mass in which moisture is confined. This clot is very hard because the particles are in close contact with each other and is not crushed by the blades of the screw. Therefore, when a clot is formed, heat is slowly transferred to the inside through the particles, and evaporation of moisture held inside and volatilization of contaminants are also slowly performed through a slight gap between the particles. .

  Therefore, the classifying means 10b separates the clay and silt into sand, gravel and mud in order to send the clay and silt to the granulating means 11.

  Examples of the classifying means 10a and 10b include an apparatus equipped with a sieve and a classifying cyclone. When the sieve is rotated or vibrated, particles having a particle size smaller than the mesh size fall through the mesh, and vice versa, the larger particles remain on the mesh to be separated. The classification cyclone has a higher specific gravity due to centrifugal force, the larger the particle diameter, the more the particle diameter goes to the peripheral wall, the smaller the specific gravity, the smaller the particle diameter, the more the center, and the larger the specific gravity and particle diameter, the lower the specific gravity from the bottom nozzle. Those having a small particle size are discharged from the top nozzle. FIG. 1 shows a classification cyclone.

  The particles separated by the classifying means 10a and 10b are sent to the gasifier as they are for sand and gravel, and the mud is sent to the granulating means 11 after dehydrating as necessary.

  The granulating means 11 produces granules having a particle diameter of 0.074 mm or less and a particle having a particle diameter of more than 0.074 mm and less than 5 mm. As the granulating means 11, this mud is degassed and compressed to form flakes of about 1 to 7 mm, and the flakes are roughly crushed and sized, and the mud is pressurized and compressed. For example, an extrusion granulation device that forcibly advances while extruding continuously from a hole of a die (wire net), an agitation granulation device that grows particles by adding a binder (binder) while stirring and mixing mud, etc. be able to. The crushing and granulating apparatus includes a plurality of knives arranged around the rotor and a blade that repeatedly compresses and scrapes the contaminated soil. And an apparatus for granulating.

  In the granulating means 11, the mud preferably contains an additive so that the granulated particles are not crushed immediately, and preferably has an appropriate amount of water.

  Contaminated soil exists in various places, and its moisture content is high and is about 60 to 70%. Here, the moisture content is a numerical value obtained by dividing the mass of water contained by the sum of the mass of the water and the mass of dry soil and multiplying by 100. At this moisture content, since the amount of water contained in the mud is too large, it can be dehydrated by the dewatering means 14 to obtain the amount of water necessary for granulation. Examples of the dehydrating unit 14 include a centrifugal dewatering unit and a pressure dehydrating unit. The solid after being dehydrated by the dehydrating means 14 is called a dehydrated cake and has a moisture content of about 45 to 50%.

  The dehydrated cake placed on the lower side can be stored and stored after being dehydrated by the dehydrating means 14, and the dehydrated cake placed on the lower side is compressed by the dehydrated cake placed on the upper side and interposed between the particles. Moisture oozes out and water content can be reduced.

  The granulating means 11 is charged with a dehydrated cake and added with an additive. As the additive, the above binder can be added, but quicklime, cement, fly ash, gypsum, blast furnace slag, stone powder, and the like can be added. Quick lime, cement, fly ash, gypsum, and blast furnace slag are preferable in that they react with moisture contained in the dehydrated cake to reduce the moisture content.

  For example, quick lime can be added by about 10% with respect to the mass of the dehydrated cake, and cement can be added by, for example, about 5% with respect to the mass of the dehydrated cake. In addition, since cement can fix heavy metals, it is also effective as a countermeasure against contained heavy metals.

  The dehydrated cake and the additive added are repeatedly kneaded and crushed in the granulating means 11 to produce particles having a predetermined diameter. This particle | grain is the particle | grains exceeding 0.074 mm mentioned above and less than 5 mm, The moisture content is about 35%. Moreover, this particle | grain has no viscosity and has high water permeability compared with clay and silt. The granulated product produced by the granulating means 11 is stored and stored until it is put into the gasifier. Further, sand and gravel exceeding 0.074 mm and less than 5 mm classified by the classifying means 10 are also put into the gasifier, but after draining, they are stored and stored together with this granulated product until thrown. .

  If the moisture content is as high as about 60 to 70% as in the case of the collected contaminated soil, it is sent to the gasifier. Water has a large latent heat of vaporization, and steam has a large sensible heat compared to air. It takes a long time to heat up to the temperature, and energy consumption becomes great. However, by adding dehydration and quicklime, cement and the like in this manner, the moisture content can be greatly reduced, the heating time in the gasifier can be shortened, and the energy consumption can also be reduced.

  The contaminated soil is dehydrated by putting the contaminated soil in a bag having a large number of pores, stacking the bags and leaving them for several days, so that the weight of the upper bag causes water to flow out from the contaminated soil in the lower bag. be able to. By putting the dehydrated cake after dehydration in this way into the granulating means 11 that can be pulverized at the same time, pulverization, kneading and granulation can be performed. However, in this case, the granulating means 11 must include crushing means such as a knife because the contaminated soil includes pebbles and gravel with a large particle diameter.

  Next, the gasifier will be described with reference to FIG. The gasifier heats to about 700-900 ° C. to volatilize contaminants such as dioxins. This gasifier can also be divided into two units according to temperature. One unit can be used as a preheating device and the second unit can be used as a gasifier. In this case, the gasifier installed on the upstream side is used as a device for heating to about 300 to 500 ° C. in order to evaporate all the water contained in the contaminated soil, and is installed on the downstream side. Can be used as a device that heats to about 700-900 ° C. to volatilize contaminants. In FIG. 2, the gasifier divided into two units is illustrated.

  The gasifier shown in FIG. 2 receives a pretreated hopper 20 for receiving contaminated soil composed of soil particles having a particle size range of more than 0.074 mm and less than 5 mm, and receives the contaminated soil from the hopper 20 and is not shown. A container 21 for receiving superheated steam from the superheated steam generator and evaporating moisture contained in the contaminated soil, and receiving contaminated soil from the container 21 and receiving superheated steam from a superheated steam generator (not shown) to be contained in the contaminated soil. A container 22 for volatilizing the contaminants and separating and removing the contaminants from the soil, and a treated soil storage container 23 for storing the treated soil after the contaminants are removed by the container 22 are provided.

  The container 21 constitutes a first gasifier, and includes a receiving nozzle 24 that receives the contaminated soil and superheated steam discharged from the hopper 20, a discharge nozzle 25 that discharges the contaminated soil to the container 22, and an inside of the container 21. A screw 26 that conveys the received contaminated soil while stirring from a receiving nozzle 24 provided at one end to a discharge nozzle 25 disposed adjacent to the other end, and a motor that rotates the screw 26 27.

  The container 21 is provided with an electric heater (not shown) that is provided around the outer periphery and heats the container 21. In addition to the outer periphery, the electric heater can be attached to any one or two or all of the floor, ceiling, and side walls inside the container. Although the electric heater is used here, it may be other than the electric heater. For example, the container 21 can be a double pipe, and the contaminated soil put into the inner pipe can be heated through the combustion gas between the inner pipe and the outer pipe.

  The container 22 constitutes a second gasifier, and received a nozzle 28 that receives the contaminated soil and superheated steam discharged from the container 21, a discharge nozzle 29 that discharges the treated soil to the treated soil storage container 23, and volatilized. A gas delivery nozzle 30 for sending pollutants to the reaction apparatus, which will be described later, and a discharge provided in the container 22 and disposed in the vicinity of the other end from the receiving nozzle 28 provided at one end. A screw 31 that is conveyed while stirring to the nozzle 29 and a motor 32 that rotates the screw 31 are provided. The container 22 also includes an electric heater (not shown), and may be other than the electric heater in order to heat the contaminated soil inside.

  Heating in the gasifier can be performed by an electric heater, but in a method in which only the electric heater is used and the contaminated soil is heated by heated air, heat does not reach every corner of the contaminated soil. Therefore, the contaminated soil is heated by supplying superheated steam having a larger specific heat than air.

  This superheated steam has a specific heat twice that of air, has a larger convective heat transfer effect than air, and has a heat transfer effect due to heat radiation and condensed water. A necessary amount of heat can be given to the object to be heated in a short time.

  Heating with the electric heater and the superheated steam is performed while stirring the contaminated soil with the screws 26 and 31. Agitation of the contaminated soil provides heat evenly and enables efficient heating. The superheated steam diffuses in the gasifier, gives heat to the contaminated soil, enters between the soil particles, and gives heat to the soil particles inside. The contaminants adhering to the soil particles are volatilized and desorbed by the applied heat and separated from the soil particles. The soil particles are conveyed below the container 22 by the screw 31, and the separated contaminants move above the container 22 by the screw 31. The pollutant is discharged from the gas delivery nozzle 30 provided at the upper part of the container 22, and the soil after the pollutant is separated and removed is provided at the lower part of the container 22 as treated soil containing almost no pollutant. It is discharged from the discharge nozzle 29.

  The treated soil discharged from the discharge nozzle 29 is a soil containing only contaminants having a value lower than the environmental standard value, but cannot be used as it is because it is heated to about 700 to 900 ° C. Therefore, the cooling water can be used for indirect cooling, the cooling water can be sprayed for direct cooling, or the natural water can be left for natural cooling. After cooling, the treated soil is analyzed and confirmed that it is below the environmental standard value. Then, it contains soil for backfilling, quicklime and cement, and aggregates such as gravel and sand. It can be used as a material.

  The containers 21 and 22 of the gasifier have a high sealing property so that the superheated steam does not leak, and have a high heat retaining property so that the temperature can be maintained by heating for several tens of minutes to several hours. . The containers 21 and 22 can be made of ceramic, brick, stainless steel, titanium, nickel alloy or the like. The heat insulation property can be enhanced by attaching the heat insulating material so as to surround them.

  The superheated steam in the gasifier can be generated from moisture contained in the contaminated soil to be charged, or can be supplied from the superheated steam generator. It should be noted that superheated steam can be supplied from this superheated steam generator when the system is started up or when the moisture content is low.

  FIG. 3 is a diagram illustrating a configuration example of the superheated steam generator. The superheated steam generator includes a water storage tank 35 for storing water, a boiler 36 for evaporating water, a water supply pump 37 for supplying water from the water storage tank 35 to the boiler 36, and a steam heater 38 for generating superheated steam. It is configured.

  The steam heater 38 may be one that burns fuel and heats it with a high-temperature combustion gas, but it may also be one that uses electromagnetic induction heating. Here, electromagnetic induction heating means that a strong current is passed through a coil to generate a strong magnetic field, and a metal such as iron or stainless steel that is easy to conduct electricity is placed on it, and an eddy current is generated by electromagnetic induction. This is a heating method utilizing the principle that metal generates heat by resistance. When steam is heated by electromagnetic induction heating, it can be used as an electromagnetic induction heating device in which a cylindrical tube made of iron or stainless steel or the like and a conductor wire wound around the outer periphery thereof.

  The superheated steam generated by the superheated steam generation apparatus is steam at a temperature exceeding about 100 ° C. at almost atmospheric pressure. However, when the gasifier is supplied at a temperature lower than 700 ° C. such as 300 ° C. or 400 ° C., the temperature inside the gasifier once heated to about 700 to 900 ° C. is lowered and heated to that temperature again. It takes time to do. In addition, energy for heating to that temperature is consumed. Therefore, in order not to lower the temperature in the gasifier once heated, it is preferable to heat and supply at about 700 to 900 ° C.

  Volatilized contaminants include organic compounds such as organic solvents, paints, volatile organic compounds (VOC) used as adhesives, and dioxins. These organic compounds are one of the causes of health damage caused by photochemical oxidants, are air pollutants, and cannot be directly released into the atmosphere.

  Therefore, these organic compounds are decomposed into carbon dioxide gas, water and the like by a reaction apparatus and then released into the atmosphere. FIG. 4 is a diagram illustrating a configuration example of a gas processing apparatus including a reaction apparatus. In addition to the reaction device 40, the gas processing device includes a bubbling tank 41, a coagulation tank 42, a wastewater treatment device 43, an activated carbon tower 44, and a blower 45.

  In addition to the volatile organic compounds and dioxins generated in the gasifier, the reactor 40 is supplied with superheated steam and, if necessary, air. In the reaction apparatus 40, these are heated to a predetermined temperature, volatile organic compounds and dioxins are reacted with superheated steam, and decomposed into hydrogen, carbon monoxide, etc. by hydrolysis and thermal decomposition. Moreover, it oxidizes by supplying air, and produces | generates a carbon dioxide and water. The reactor 40 is heated to a temperature of about 900 to 1200 ° C. Examples of the reactor 40 include a reactor equipped with an electric heater in a cylindrical tube, an electromagnetic induction heating device in which a conducting wire is wound around the outer periphery of the cylindrical tube, and the like.

The bubbling tank 41 rapidly cools the cracked gas, heavy metal, clay, silt or the like, which has been discharged from the reactor 40, and separates gas components. The bubbling tank 41 contains an alkaline aqueous solution, and the decomposition gas is allowed to react with the alkali by passing through the aqueous solution to recover a halogen such as chlorine in hydrogen chloride, a part of carbon dioxide, SO _{x and the} like. Remove. As the alkali, potassium hydroxide, sodium hydroxide, or calcium hydroxide can be used. In the bubbling tank 41, carbon dioxide that has not reacted with the alkali and air that has not been used in the reaction in the reaction apparatus are moved into bubbles in the alkaline aqueous solution and moved upward, and are sucked by the blower 45 to cause the activated carbon tower 44 to enter. After passing, it is released into the atmosphere.

The activated carbon tower 44 adsorbs and removes hydrogen chloride, SO _{x and the} like discharged from the bubbling tank 41 without being reacted. Thereby, it is possible to prevent these pollutants from being released into the atmosphere. The blower 45 holds the inside of the gasifier, the reactor 40, the bubbling tank 41, and the activated carbon tower 44 at a negative pressure by sucking, and even if these devices are damaged, pollutants are released into the atmosphere. I'm trying not to be.

  The agglomeration tank 42 extracts a part of the liquid in the bubbling tank 41 and agglomerates and precipitates solids floating in the liquid. A flocculant is added in the agglomeration tank 42, and when the liquid is extracted from the bubbling tank 41, solid matter floating in the liquid is agglomerated by the flocculant and precipitates as a large lump. After dewatering, the sediment is sent to the pretreatment device together with the newly treated contaminated soil. Then, the heat treatment is performed again, and the heavy metals contained in the precipitate and the contaminants adhering to the clay and silt are reprocessed. Specifically, the precipitate is sent to the dehydrating unit 14 and granulated by the granulating unit 11 after dehydration.

  The supernatant liquid of the coagulation tank 42 is drained and then used as makeup water for the bubbling tank 41 or as washing water. If the amount of water used is low and water remains, it will be drained into rivers after water quality analysis. On the other hand, if water runs short, it is replenished. The wastewater treatment is performed by a wastewater treatment device, and the wastewater treatment device includes a sand filtration tank, an activated carbon tank, and a reuse tank.

  With reference to FIG. 5, the heat processing method which pre-processes contaminated soil and heat-processes in a superheated steam atmosphere is demonstrated. This method is performed by the above-described pretreatment apparatus and gasification apparatus. First, in step 500, the process is started, and in step 510, the contaminated soil is received by the classifying means 10a and 10b and divided into particle diameter ranges. That is, the particle size is divided into those of 5 mm or more, those of more than 0.074 mm and less than 5 mm, and those of 0.074 mm or less. Although it is divided into three ranges here, it can be divided into two ranges or four or more ranges.

  For those with a thickness of 5 mm or more, the heat treatment is not performed because the contaminants are hardly attached. Those exceeding 0.074 mm and less than 5 mm are drained, stored and stored until they are put into the gasifier.

  Those having a small particle diameter of 0.074 mm or less are sent to the granulating means 11 and granulated in step 520 so as to have a particle diameter of more than 0.074 mm and less than 5 mm. This is to eliminate the powdery material and make the particle size of the contaminated soil to be introduced into the gasifier uniform. The granulated product after granulation is stored and stored until it is put into the gasifier.

  In step 530, the contaminated soil stored and stored using the hopper 20 is introduced into the gasifier, and heated with an electric heater while supplying superheated steam into the gasifier, thereby heating the contaminated soil. In the gasifier, superheated steam spreads between the soil particles by stirring and is heated almost uniformly, and the contaminants attached to the soil particles are volatilized and desorbed from the soil particles. The treated soil from which the pollutants have been detached is recovered from the discharge nozzle 29, and the volatilized pollutants are sent to the reactor through the gas delivery nozzle 30, and the processing is terminated in step 540.

  The pretreatment apparatus and the heat treatment system of the present invention have been described in detail with reference to the embodiments shown in the drawings, but the present invention is not limited to the above-described embodiments, and other embodiments are described. It can be modified within the range that can be conceived by those skilled in the art, such as addition, change, deletion, etc., and any embodiment is included in the scope of the present invention as long as the operation and effect of the present invention are exhibited. is there. Therefore, the pretreatment apparatus includes at least a classification unit and a granulation unit, but can further include a cleaning unit and a dehydration unit. The heat treatment system includes at least a pretreatment device and a gasification device, but may further include an adsorption tower such as a superheated steam generation device, a reaction device, a bubbling tank, a coagulation tank, a wastewater treatment device, and an activated carbon tower, and a blower.

  In the above, the heat treatment method is finished when the treatment is performed up to step 530, but the subsequent treatment apparatus, bubbling tank, coagulation tank, waste water treatment apparatus, treatment with activated carbon tower can be included, and the coagulation tank is coagulated. The precipitate thus precipitated can be dehydrated again, granulated and introduced into the gasifier.

The figure which showed the structural example of the pre-processing apparatus. The figure which showed the structural example of the gasifier. The figure which showed the structural example of the superheated steam production | generation apparatus. The figure which showed the structural example of the gas processing apparatus. The flowchart which showed the flow of the pretreatment and heat processing of contaminated soil.

Explanation of symbols

10a, 10b ... Classification means, 11 ... Granulation means, 12 ... Mud pump, 13 ... Cleaning means, 14 ... Dehydration means, 20 ... Hopper, 21, 22 ... Container, 23 ... Treated soil storage container, 24, 28 ... Receiving nozzle, 25, 29 ... discharge nozzle, 26, 31 ... screw, 27, 32 ... motor, 30 ... gas delivery nozzle, 35 ... water storage tank, 36 ... boiler, 37 ... feed pump, 38 ... steam heater, 40 ... Reaction device 41 ... Bubbling tank 42 ... Coagulation tank 43 ... Waste water treatment device 44 ... Activated carbon tower 45 ... Blower

Claims (10)

A heat treatment system for pre-treating contaminated soil and detoxifying it by heat treatment in an overheated steam atmosphere,
The contaminated soil includes a first particle size range that is less than or equal to a first particle size, a second particle size range that is greater than or equal to a second particle size that is greater than the first particle size, and that exceeds the first particle size, and that the second particles Classifying means for classifying into a third particle size range less than the diameter, and the contaminated soil classified into the first particle size range so as not to form a dry-cured soil mass in the heat treatment after the pretreatment, A pretreatment device comprising a granulation means for granulation so as to obtain a particle size in the range of three particle sizes, and contamination having a particle size in the third particle size range obtained by classification and granulation by the pretreatment device A heat treatment system comprising: a gasification device that receives soil, heats it in a superheated steam atmosphere while stirring, volatilizes the contaminant contained in the contaminated soil, and separates the contaminant into treated soil.   The heat treatment system according to claim 1, wherein the granulating means granulates by adding quick lime and / or cement. The heat treatment system according to claim 2 , wherein the pretreatment device further includes a dehydrating unit that removes moisture contained in the contaminated soil classified into the first particle size range. The organic compound contained in the volatilized pollutant is further heated to react with superheated steam to decompose the organic compound, and the bubbling that cools the decomposed product discharged from the reactor and separates the gas components further comprising a tank, a heat treatment system according to any one of claims 1 to 3. 5. The coagulation tank according to claim 4 , further comprising a coagulation tank that receives the liquid containing the solid matter and coagulates and precipitates the solid matter floating in the liquid in order to reheat the solid matter remaining in the bubbling tank. Heat treatment system. A heat treatment method of pretreating contaminated soil and detoxifying by heat treatment in an overheated steam atmosphere,
The contaminated soil includes a first particle size range that is less than or equal to a first particle size, a second particle size range that is greater than or equal to a second particle size that is greater than the first particle size, and that exceeds the first particle size, and that the second particles A classification step of classifying into a third particle diameter range less than the diameter;
Granulation for granulating the contaminated soil classified into the first particle size range so as to have a particle size in the third particle size range so that a dry and hardened mass is not formed in the heat treatment after the pretreatment. Process,
The contaminated soil having a particle size in the third particle size range obtained in the classification step and the granulation step is heated in a superheated steam atmosphere while stirring to volatilize the contaminant contained in the contaminated soil, A heat treatment method comprising a purification step of separating the pollutant into treated soil. The heat treatment method according to claim 6 , wherein in the granulation step, quick lime and / or cement is added for granulation. The heat treatment method according to claim 7 , further comprising a dehydration step of removing water contained in the contaminated soil classified into the first particle size range after the classification step. The organic compound contained in the volatilized pollutant is further heated and reacted with superheated steam to decompose the organic compound, and the separation step of cooling the decomposition product after the reaction and separating the gas component is further performed The heat processing method of Claim 8 containing. A coagulation step of coagulating and precipitating solids floating in the liquid remaining after the gas component is separated and removed, and collecting the coagulated and precipitated solids and causing the pretreatment and the heat treatment together with contaminated soil; Item 10. The heat treatment method according to Item 9 .

Images