Soot and dust treatment method and soot and dust treatment device

Abstract

To provide a dust processing method that removes mercury from the dust containing an active charcoal and radioactive substance adsorbing the mercury, and can reduce volume of the mercury.SOLUTION: A dust processing method, which melts a radioactive substance-containing object in a melting furnace in the presence of chlorine, performs volume reduction processing of dust recovered by bringing exhaust gas including a volatilized radioactive substance into contact with an assistant and active charcoal adsorption material with a dust recovery device, and removes the radioactive substance included in the dust, includes: an active charcoal separation step of separating an active charcoal included in the dust; a solid-liquid separation step of dissolving the dust in water, and recovering a remaining solid object; and a radioactive substance adsorption step of adsorbing and removing the radioactive substance from an aqueous solution having the dust dissolved in the water.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a dust treatment method and a dust treatment device. [Background technology]

[0002] In order to restore natural environments such as soil, vegetation, oceans, and rivers that have been contaminated with radioactive materials leaked from equipment that utilizes nuclear fission reactions at nuclear power plants and other facilities, various methods have been researched for separating and concentrating radioactive materials from materials that contain radioactive materials.

[0003] Among radioactive substances, cesium-134, cesium-137 are water-soluble, easily absorbed into the body, and have a significant impact on health, so they are said to be one of the three major nuclides along with iodine-131. Cesium-137 in particular has a long half-life of 30 years, and once adsorbed into soil it cannot be easily decontaminated.

[0004] There is a limit to the storage facilities for such temporarily accumulated large amounts of contaminated soil, vegetation, waste materials, etc., contaminated with radioactive materials, and there is an urgent need to reduce their volume. For example, combustible materials such as vegetation and waste materials, and sludge generated at sewage treatment plants, are incinerated and reduced in volume as incineration bottom ash and incineration fly ash, which contain concentrated radioactive materials, and then stored under strict management, but there is also a limit to the capacity of the storage facilities for these.

[0005] Patent Document 1 proposes a method for separating and concentrating radioactive cesium in a material to be treated, including soil, by melting the material to be treated. This method for separating and concentrating radioactive cesium includes a basicity adjustment step of adding a basicity adjustment assistant containing a chlorine-based basicity adjustment assistant to the material to be treated, a separation step of heating the material to which the basicity adjustment assistant has been added to 1200°C to 1500°C to volatilize and separate radioactive cesium from the material to be treated, and a collection step of collecting the radioactive cesium volatilized and separated in the separation step, and the remaining material from which the radioactive material has been removed in the separation step is reduced in volume as molten slag.

[0006] By adopting the method for separating and concentrating radioactive cesium as described in Patent Document 1, it is possible to melt incineration bottom ash, incineration fly ash, and even soil contaminated with radioactive substances to volatilize and separate the radioactive substances, and to reduce the volume of the remaining material from which the radioactive substances have been removed by turning it into molten slag. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2016-011924 A Summary of the Invention [Problem to be solved by the invention]

[0008] For example, by adopting a method for separating and concentrating radioactive cesium as described in Patent Document 1, it becomes possible to melt incineration bottom ash, incineration fly ash, and even soil contaminated with radioactive substances to volatilize and separate the radioactive substances, and to reduce the volume of the remaining substances from which the radioactive substances have been removed as molten slag. Then, by separating the radioactive substances contained in the exhaust gas by volatilization and separation as ash processing dust (hereinafter simply referred to as "dust") via a dust collector, it becomes possible to significantly reduce the volume of the radioactive substances, and there is also a reduced need to install additional storage facilities.

[0009] There is also a demand to further reduce the volume of such soot and dust in which radioactive materials are concentrated, and specific treatment methods are being considered. For example, focusing on the water-soluble nature of radioactive materials recovered as chlorides, it is conceivable to build water treatment facilities that dissolve the radioactive materials in water and separate them.

[0010] Incidentally, it is expected that the exhaust gas generated during the melting process may contain heavy metals and dioxins. Mercury, which has a particularly low boiling point, cannot be completely removed by the dust collector, so a separate mercury removal device must be installed in the flue downstream of the dust collector.

[0011] However, in melting furnaces and other equipment not equipped with a mercury removal device, it was necessary to inject and supply fine powdered activated carbon to adsorb and remove mercury in addition to auxiliary agents (strippers) such as calcium carbonate to protect the filter cloth in the dust collector. The fine powdered activated carbon adsorbs not only mercury but also dioxins.

[0012] When radioactive materials are separated from the soot separated by such a dust collection device and the remaining material from which the radioactive materials have been removed is re-melted, for example, in a melting furnace to reduce its volume, there is a risk that low-boiling point inorganic substances such as mercury adsorbed to the activated carbon will volatilize and become concentrated in the melting furnace.

[0013] In view of the above-mentioned problems, an object of the present invention is to provide a dust treatment method and dust treatment device that can remove mercury and radioactive substances from dust containing mercury-adsorbed activated carbon and radioactive substances, thereby reducing the volume. [Means for solving the problem]

[0014] In order to achieve the above-mentioned object, a first characteristic configuration of a dust treatment method according to the present invention is a dust treatment method which comprises melting radioactive material-containing material in a melting furnace in the presence of chlorine, contacting exhaust gas containing the volatilized radioactive material with an auxiliary agent and an activated carbon adsorbent in a dust collector, thereby reducing the volume of the recovered dust and removing the radioactive material contained in the dust, Solids Soot from The method includes an activated carbon separation process for separating activated carbon, a solid-liquid separation process for dissolving the dust in water and recovering the remaining solid matter, and a radioactive substance adsorption process for adsorbing and removing radioactive substances from the aqueous solution in which the dust is dissolved in water.

[0015] By melting radioactive materials in a melting furnace in the presence of chlorine, the radioactive materials are volatilized and separated from the molten slag and flow into the dust collector together with the exhaust gas, where the radioactive materials that have become chlorides and the heavy metals that have become solid fine particles are separated as soot and dust. The concept of "in the presence of chlorine" includes cases where the radioactive material contains chlorine or where chlorine is added as an auxiliary agent to the radioactive material. Solids Soot from The activated carbon is separated and removed together with mercury and dioxins in the activated carbon separation process, and is dissolved in water, dissolving water-soluble radioactive substances and the like. The undissolved solid matter remaining is recovered in the solid-liquid separation process, and the dissolved radioactive substances are removed in the radioactive substance adsorption process.

[0016] The second characteristic configuration is that, in addition to the first characteristic configuration described above, the activated carbon separation step uses either a wet method such as flotation separation, floatation or gravity separation, or a dry method such as air classification or electrostatic separation.

[0017] In order to separate the activated carbon from the soot and dust, any of the wet methods such as flotation, floatation or gravity separation, or the dry methods such as air classification or electrostatic separation can be suitably used. By separating the activated carbon that has adsorbed mercury and dioxins from the soot and dust, subsequent treatment such as reducing the volume of the soot and dust can be facilitated.

[0018] The third characteristic configuration of the present invention is, in addition to the first or second characteristic configuration described above, further comprising a heavy metal removal step of removing water-soluble heavy metals as insoluble heavy metals by adjusting the pH of the aqueous solution between the solid-liquid separation step and the radioactive substance adsorption step or after the radioactive substance adsorption step.

[0019] Heavy metals can be dissolved by dissolving them in water under acidic conditions, and if the pH of the aqueous solution is adjusted to neutral, for example, after the solid-liquid separation process and before the radioactive material adsorption process or after the radioactive material adsorption process, the dissolved heavy metals become insoluble and precipitate. For example, a heavy metal fixing agent (chelating agent) can be added to separate them as metal complexes, or a coagulant can be added to cause coagulation and precipitation.

[0020] The fourth characteristic configuration of the present invention is, in addition to the third characteristic configuration described above, further including a concentration process of evaporating to dryness the high-concentration salt water from which radioactive substances have been removed in the radioactive substance adsorption process and from which heavy metals have been removed in the heavy metal removal process.

[0021] The aqueous solution after the radioactive materials and heavy metals have been removed is highly saline, making it difficult to discharge into rivers from an environmental protection standpoint. Even in such cases, the saltwater can be reduced in volume by evaporating and drying it in the concentration process, making subsequent treatment easier.

[0022] The fifth characteristic configuration of the present invention is that, in addition to any one of the first to fourth characteristic configurations described above, it includes a circulation melting step of re-melting the solid material recovered in the solid-liquid separation step in the melting furnace.

[0023] The solid material recovered in the solid-liquid separation process can be remelted in a melting furnace, thereby reducing the volume and producing slag.

[0024] The sixth characteristic configuration of the present invention is that, in addition to any one of the first to fifth characteristic configurations described above, the radioactive substance-containing material is incineration bottom ash, incineration fly ash and / or fine-grained soil obtained by separating soil removed by decontamination according to grain size.

[0025] The radioactive material-containing materials suitable for treatment are incineration bottom ash, incineration fly ash, and / or fine-grained soil obtained by separating the soil by particle size after removal from the decontamination process.

[0026] A first characteristic configuration of the dust treatment apparatus according to the present invention is a dust treatment apparatus which melts radioactive material-containing material in a melting furnace in the presence of chlorine, and brings the exhaust gas containing the volatilized radioactive material into contact with an auxiliary agent and an activated carbon adsorbent in a dust collector, thereby reducing the volume of the collected dust and removing the radioactive material contained in the dust, Solids Soot from An activated carbon separator that separates activated carbon and dust To The system includes a dissolving device that dissolves the contained radioactive materials in water, a solid-liquid separation device that dissolves the dust in water and recovers the remaining solid matter, and a radioactive material adsorption device that adsorbs and removes the radioactive materials from the aqueous solution in which the dust is dissolved in water.

[0027] The second characteristic configuration is that, in addition to the first characteristic configuration described above, the activated carbon separation device is composed of either a flotation separation device, a flotation device or a gravity separation device that employs a wet method, or an air classifier or an electrostatic separator that employs a dry method.

[0028] The third characteristic configuration of the present invention is, in addition to the first or second characteristic configuration described above, further comprising a heavy metal removal device between the solid-liquid separation device and the radioactive substance adsorption device, or after the radioactive substance adsorption device, which adjusts the pH of the aqueous solution to remove water-soluble heavy metals as insoluble heavy metals.

[0029] The fourth characteristic configuration of the same is that, in addition to the third characteristic configuration described above, it further includes a concentrating device that evaporates and drys the high-concentration salt water from which radioactive substances have been removed by the radioactive substance adsorption device and from which heavy metals have been removed by the heavy metal removal device.

[0030] The fifth characteristic configuration of the present invention is that, in addition to any one of the first to fourth characteristic configurations described above, it includes a circulating melting mechanism that re-melts the solid material recovered in the solid-liquid separation device in the melting furnace.

[0031] The sixth characteristic configuration of the present invention is that, in addition to any one of the first to fifth characteristic configurations described above, the radioactive substance-containing material is incineration bottom ash, incineration fly ash and / or fine-grained soil obtained by separating soil removed by decontamination according to grain size. Effect of the Invention

[0032] As described above, according to the present invention, it is possible to provide a dust treatment method and dust treatment device that can remove mercury and radioactive substances from dust containing mercury-adsorbed activated carbon and radioactive substances, thereby reducing the volume of the dust. [Brief description of the drawings]

[0033] [Figure 1] An explanatory diagram of a method and a treatment device for materials containing radioactive substances [Diagram 2] An explanatory diagram of a dust processing method and a dust processing device [Diagram 3] An explanatory diagram of another embodiment of the dust treatment method and the dust treatment device DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, embodiments of the dust processing method and dust processing device according to the present invention will be described.

[0035] [Configuration of the treatment system for items containing radioactive materials] A treatment system 1 for radioactive material containing materials incorporating a dust treatment device is shown in Fig. 1. The treatment system 1 includes a melting furnace 2, a secondary combustion chamber 3, an air preheater 4, a temperature reducing tower 6, a first dust collector 7, a second dust collector 8, a neutralization product recovery device 9, a catalytic reaction tower 10, an induced draft blower 13, a chimney 14, and a dust treatment device 20 that treats the dust captured by the first dust collector 7 and the second dust collector 8.

[0036] Materials to be melted, such as incineration bottom ash and incineration fly ash, containing radioactive materials leaked from equipment that utilizes nuclear fission reactions, mainly cesium Cs and strontium Sr, are fed into the melting furnace 2 together with chlorine-containing auxiliary agents and melting point depressants that promote the volatilization of radioactive materials. Materials containing radioactive materials fed into the melting furnace 2 are not limited to incineration bottom ash and incineration fly ash generated by incinerating vegetation, waste materials, sewage sludge, etc. contaminated with radioactive materials in an incinerator, but may also include fine-grained soil with a grain size of 0.075 mm or less, which is obtained by separating the soil removed by decontamination. This is because fine-grained soil contains high concentrations of radioactive materials.

[0037] As chlorine-containing auxiliary agents, materials such as calcium chloride, chlorine-containing plastics and resins, sodium chloride, potassium chloride, and iron chloride are preferably used, but if the material to be melted contains the necessary amount of chlorine, there is no need to add chlorine-containing auxiliary agents. As the melting point depressant, calcium compounds, alkali metal salts, alkaline earth metal salts, boron compounds, and iron compounds are preferably used. For example, basicity regulators such as calcium oxide, calcium hydroxide, calcium carbonate, sodium carbonate, lithium carbonate, potassium carbonate, magnesium carbonate, magnesium hydroxide, magnesium oxide, boron oxide, borax, boric acid, ferrous oxide, triiron tetroxide, and ferric oxide are usable as the melting point depressant.

[0038] In the melting furnace 2, radioactive materials are melted in a high-temperature environment of 1200°C to 1500°C. During this process, chlorides and alkali salts of mercury and heavy metals are volatilized, and cesium chloride (CsCl) and strontium chloride (SrCl) are formed as chlorides by the aid of chlorine. 2 Radioactive materials such as fluorine, tin, and arsenic are vaporized and flow down into the secondary combustion chamber together with the exhaust gas, and the remaining solid matter is melted in the melting furnace 2 and collected as slag. The melting method of the melting furnace 2 is not particularly limited, and a rotary surface melting furnace or the like is preferably used.

[0039] The exhaust gas discharged from the melting furnace 2 undergoes secondary combustion in the secondary combustion chamber 3, where the unburned gas components are heated to approximately 1100°C, and then flows down the flue gas path, passing through the air preheater 4, which preheats the combustion air supplied to the melting furnace 2, and the temperature reduction tower 6, and at the inlet of the dust collectors 7, 8, the temperature is reduced to a temperature range of approximately 160 to 200°C, which can suppress the resynthesis of dioxins.

[0040] A bag filter in which a filter cloth is spray-coated with a release agent such as calcium carbonate is used as the first dust collector 7 and the second dust collector 8. In addition, activated carbon fine powder is sprayed and supplied to the dust collectors 7 and 8 to adsorb and remove mercury.

[0041] The exhaust gas passes through the temperature reducing tower 6 etc. and is cooled to about 160-200°C, causing radioactive salts, mineral elements and heavy metals to turn into solid fine particles, which then flow into the first dust collector 7 and the second dust collector 8 together with the exhaust gas and are captured as soot and dust. The first dust collector 7 and the second dust collector 8 are installed in a redundant manner to ensure reliability in case one of them breaks down. The first dust collector 7 and the second dust collector 8 may be connected in series or in parallel.

[0042] The fly ash from molten steel contains cesium chloride (CsCl) and strontium chloride (SrCl 2 ), sodium chloride (NaCl), potassium chloride (KCl), ferric chloride (FeCl 3 ), silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), calcium oxide (CaO), ferric oxide (Fe 2 O 3 ), heavy metal compounds including elements such as lead (Pb), cadmium (Cd), zinc (Zn), arsenic (As), and mercury (Hg), calcium carbonate (CaCO 3 ), and activated carbon powder C sprayed for mercury adsorption. Activated carbon powder C adsorbs mercury and dioxins contained in the exhaust gas.

[0043] The neutralized product recovery device 9 is also composed of a bag filter, and by blowing calcium hydroxide, a neutralizing agent, into the bag filter together with the exhaust gas, corrosive gas components such as hydrogen chloride contained in the exhaust gas are captured by the filter cloth as calcium chloride, etc. The calcium chloride (CaCl 2 The neutralized products such as chlorine-containing sulphur dioxide are recycled to the melting furnace 2 as auxiliary agents containing chlorine, and the surplus neutralized products are taken out and disposed of.

[0044] The catalytic reaction tower 10 is provided with a catalytic metal such as titanium or vanadium, and dioxins contained in the exhaust gas that has passed through the first dust collector 7 and the second dust collector 8 are decomposed by a catalytic reaction with the catalytic metal.

[0045] The exhaust gas that has passed through the catalytic reaction tower 10 is exhausted from a chimney 14 via an induced draft fan 13 provided downstream.

[0046] As shown in Figures 2 and 3, the dust treatment device 20 is an advanced treatment device that aims to reduce the volume of dust, which is molten fly ash captured by the first dust collector 7 and the second dust collector 8, and is equipped with an activated carbon separation device 21 that separates and removes activated carbon contained in the dust, a dissolution device 22 that dissolves radioactive materials contained in the dust from which the activated carbon has been separated into water, a solid-liquid separation device 24 that recovers solid materials from the aqueous solution that has passed through the dissolution device 22, and a radioactive material adsorption device 26 that adsorbs and removes radioactive materials from the aqueous solution from which the solids have been separated in the solid-liquid separation device 24.

[0047] The treatment system 1 for radioactive material must include at least the above-mentioned melting furnace 2, dust collection devices 7, 8, catalytic reaction tower 10, and dust treatment device 20, and preferably includes a circulation mechanism 25 for transporting solids recovered in the solid-liquid separation device 24 for re-melting in the melting furnace 2.

[0048] For example, in the case of a wet method, the activated carbon separation device 21 can be a flotation separation device that utilizes the difference in hydrophilicity and hydrophobicity between the surfaces of activated carbon particles and inorganic particles by putting dry dust in water, stirring the mixture, and leaving it for a predetermined time to float only the activated carbon particles, and then selectively recovering and separating only the activated carbon particles using a scraper or the like, or, in the case of a wet dust, a flotation device (foam separation device) can be used that puts the dust in water and brings it into contact with fine air bubbles, so that only the hydrophobic activated carbon particles adhere to the air bubbles and are separated. Also, a specific gravity separation device using a rotor, such as a wet centrifugal separator, can be used.

[0049] As the activated carbon separation device 21, for example, in the case of a dry method, an air flow classification device can be used that takes advantage of the difference in particle size between activated carbon particles and inorganic particles, creates a swirling air flow using a rotor or blades to apply centrifugal force to the particles, and separates and recovers them due to the difference in centrifugal force between the two.

[0050] In addition, an electrostatic separation device can be used that takes advantage of the difference in conductivity between activated carbon particles and inorganic particles, generates an electrostatic field between a rotor electrode and an electrostatic electrode, and separates and recovers the particles by utilizing the difference in conductivity between the two.

[0051] 2 and 3 show an embodiment in which a dry method is adopted for the activated carbon separation device 21 and the device is disposed in front of the dissolution device 22. When a wet method is applied to the activated carbon separation device 21, the activated carbon separation device 21 may be disposed in either the front or rear of the dissolution device 22, or may be configured as the same device as the dissolution device 22.

[0052] The dust treatment apparatus 20 further includes a heavy metal removal apparatus 28 between the solid-liquid separation apparatus 24 and the radioactive substance adsorption apparatus 26 (see FIG. 3), or downstream of the radioactive substance adsorption apparatus 26 (see FIG. 2), which adjusts the pH of the aqueous solution to remove water-soluble heavy metals as insoluble heavy metals.

[0053] The radioactive material adsorption device 26 is provided with an adsorption tower filled with a radioactive material adsorbent, and the radioactive material is adsorbed and removed by the radioactive material adsorbent. It further includes a concentrating device 29 that evaporates and dries the high-concentration brine from which heavy metals and radioactive materials have been removed. The heat contained in the exhaust gas passing through the flue can be used as a heat source for the concentrating device 29. For example, a waste heat recovery device can be provided between the air preheater 4 and the temperature reducing tower 6 or downstream of the mercury adsorption tower, and the recovered waste heat can be used as a heat source. The concentrating device 29 can also be configured as the temperature reducing tower 6, which is installed upstream of the dust collectors 7 and 8 and to which a portion of the high-concentration brine is supplied and sprayed.

[0054] [Method of treating materials containing radioactive materials and method of reducing the volume of soot and dust] The method for treating material containing radioactive substances of the present invention is carried out by the above-mentioned system 1 for treating material containing radioactive substances, which will be described in detail below.

[0055] In the above-mentioned melting furnace 2, a melting process is carried out in which radioactive substances are volatilized from the radioactive substance-containing material, and in the first dust collector 7 and the second dust collector 8, a dust collection process is carried out in which soot containing radioactive substances is recovered from the exhaust gas containing the radioactive substances volatilized in the melting process.

[0056] Furthermore, in the catalytic reaction tower 10, a dioxin decomposition step is carried out in which dioxins are decomposed.

[0057] Furthermore, a volume reduction process for reducing the volume of the dust is carried out in the dust treatment device 20. The activated carbon separation device 21 carries out an activated carbon separation process to separate the activated carbon contained in the dust, and the separated activated carbon and the mercury and dioxins adsorbed by the activated carbon are disposed of as industrial waste, or are disposed of as industrial waste after the mercury is separated and recovered.

[0058] Next, the dissolving device 22 performs a dissolving process in which radioactive materials contained in the dust are dissolved in water, the solid-liquid separator 24 performs a solid-liquid separation process in which solids remaining undissolved in the aqueous solution that has been subjected to the dissolving process are collected, and the radioactive material adsorption device 26 performs a radioactive material adsorption process in which radioactive materials are adsorbed and removed from the aqueous solution that has been subjected to the solid-liquid separation process. When a wet activated carbon separation process is employed, the activated carbon separation process may be performed before the dissolving process, or before the solid-liquid separation process in the dissolving process. Therefore, the order of the activated carbon separation process and the dissolving process is not particularly limited. Furthermore, when a wet activated carbon separation process is employed, the activated carbon separation process and the dissolving process may be performed in the same device by adding a function for collecting the floating activated carbon particles (such as a scraper) to the dissolving device 22.

[0059] In other words, the exhaust gas containing radioactive materials that have been volatilized and separated from the molten slag in the melting process is collected as dust through a dust collection process. The exhaust gas from which the dust has been removed is detoxified in a dioxin decomposition process, for example, to decompose dioxins, before being released into the atmosphere.

[0060] As described above, the soot and dust collected in the dust collection process contains radioactive chlorides, mineral elements such as oxides of aluminum and iron, and compounds of heavy metals such as lead. In the dissolution process included in the volume reduction process, the radioactive materials are dissolved in water, the solid matter that remains insoluble in water is removed in the solid-liquid separation process, and the radioactive materials dissolved in water are adsorbed and removed in the radioactive material adsorption process.

[0061] In the dissolution process, a pH adjuster is added to the water to make it acidic, so that the radioactive materials and heavy metals are adjusted to a solubilized state. In other words, the radioactive materials, heavy metals, and some salts are dissolved in the water.

[0062] As shown in Figure 2, the solid-liquid separation process is a process in which the pH of the aqueous solution that has been through the dissolution process is maintained at an acidic level, and thereby insoluble silica-based agents (stripping agents) and mineral elements are separated from water-soluble heavy metals and radioactive materials. Usually, the solution is adjusted to an acidic level to solubilize heavy metals and water-soluble materials such as cesium, and the insoluble silica-based or alumina-based auxiliary is separated. Alternatively, lead may be adjusted to an alkaline level to solubilize it together with water-soluble cesium, and the insoluble silica-based or alumina-based auxiliary may be separated.

[0063] In the solid-liquid separator 24A in the front stage, a dehydrator such as a filter press or a screw press is used, and in the solid-liquid separator 24B in the rear stage, a coagulant is added to the aqueous solution to coagulate and precipitate insoluble calcium carbonate (stripping agent) and mineral elements, which are then dehydrated in the solid-liquid separator 24 (24C). Note that dehydration may also be performed in the solid-liquid separator 24 (24A).

[0064] The solid matter recovered in the solid-liquid separation process is transported by the circulation mechanism 25 to the melting furnace 2, where it is melted again in the circulating melting process. Insoluble mineral elements, etc. are melted again in the melting furnace and turned into slag, which enables further reduction in the volume of soot and dust.

[0065] In the radioactive material adsorption device 26, a radioactive material adsorption process is carried out in which radioactive materials are adsorbed and removed from the aqueous solution that has been subjected to the solid-liquid separation process, and the radioactive materials adsorbed by adsorption materials such as zeolite, ferrocyanide compounds, and silicic titanates are stored under strict management in storage facilities outside the area (outside the prefecture).

[0066] As shown in Fig. 2, the aqueous solution from which the radioactive materials have been removed is sent to a heavy metal removal device 28 filled with a metal chelate, where the heavy metal removal process is carried out in which the heavy metals are captured by the metal chelate by adjusting the pH to neutral with a pH adjuster. The heavy metals captured by the metal chelate are reduced at the source and reused, or are treated as industrial waste.

[0067] The high-concentration salt water from which heavy metals have been removed in the heavy metal removal process is sent to the concentrating device 29, where the concentrating process is carried out and the salt water is evaporated to dryness. As described above, the heat contained in the exhaust gas passing through the flue can be used as the heat source for the concentrating device 29. Note that, as the concentrating process, a part of the high-concentration salt water may be supplied to the temperature reducing tower 6 installed upstream of the dust collector 7 and concentrated by spraying.

[0068] As shown in Fig. 3, in the heavy metal removal step, a pH adjuster is added to the aqueous solution that has been subjected to the solid-liquid separation step to adjust the solution from acidic to neutral, thereby making it possible to coagulate and precipitate the heavy metals that have been dissolved under acidic conditions in the dissolution step. In this case, it is preferable to add a coagulant in addition to the pH adjuster. In this case, the radioactive material adsorption step is carried out after the heavy metal removal step.

[0069] In other words, the heavy metal removal process is a process in which water-soluble heavy metals are removed as insoluble heavy metals by adjusting the pH of the aqueous solution between the solid-liquid separation process and the radioactive substance adsorption process, or after the radioactive substance adsorption process.

[0070] Heavy metals can be dissolved by carrying out the dissolution step under acidic conditions, and the dissolved heavy metals become insoluble and precipitate if the pH of the aqueous solution is adjusted to neutral, for example, after the solid-liquid separation step and before the radioactive material adsorption step or after the radioactive material adsorption step. A heavy metal fixing agent (chelating agent) is added to separate the heavy metals as a metal complex, or a coagulant is added to cause coagulation and precipitation.

[0071] The above-described embodiment is one example of the present invention, and the description is not intended to limit the scope of the present invention. It goes without saying that the configuration can be appropriately modified and designed within the scope in which the effects of the present invention are achieved. [Explanation of symbols]

[0072] 1: Processing system for items containing radioactive materials 2: Melting furnace 3: Secondary combustion chamber 4: Air preheater 6: Cooling tower 7: First dust collector 8: Second dust collector 9: Neutralized product recovery device 10: Catalytic reaction tower 20: Soot and dust treatment equipment 21: Activated carbon separation device 22: Dissolving device (water dissolving tank) 24:Solid-liquid separator 24A: Solid-liquid separator (dehydrator) 24B: Solid-liquid separator (coagulation sedimentation tank) 24C: Solid-liquid separator (dehydrator) 25: Circulation mechanism 26: Radioactive material adsorption device (cesium adsorption tower) 28: Heavy metal removal equipment (heavy metal chelating tower) 29: Concentrator

Claims

1. A dust treatment method comprising melting a radioactive material in a melting furnace in the presence of chlorine, contacting an exhaust gas containing the volatilized radioactive material with an auxiliary agent and an activated carbon adsorbent in a dust collector, thereby reducing the volume of the collected dust and removing the radioactive material contained in the dust, an activated carbon separation step of separating activated carbon from the solid particulate matter; a solid-liquid separation step of dissolving the soot and dust in water and recovering the remaining solid matter; a radioactive material adsorption process for adsorbing and removing radioactive materials from an aqueous solution in which soot and dust are dissolved in water; A dust treatment method comprising the steps of:

2. 2. The method for treating soot and dust according to claim 1, wherein the activated carbon separation step employs any one of a wet method such as flotation separation, floatation or gravity separation, and a dry method such as air classification or electrostatic separation.

3. 3. The dust treatment method according to claim 1, further comprising a heavy metal removal step of removing water-soluble heavy metals as insoluble heavy metals by adjusting the pH of the aqueous solution between the solid-liquid separation step and the radioactive substance adsorption step or after the radioactive substance adsorption step.

4. 4. The dust treatment method according to claim 3, further comprising a concentrating step of evaporating to dryness the high-concentration salt water from which radioactive materials have been removed in said radioactive material adsorption step and from which heavy metals have been removed in said heavy metal removal step.

5. 5. The method for treating soot and dust according to claim 1, further comprising a circulation melting step of remelting the solid matter recovered in the solid-liquid separation step in the melting furnace.

6. 6. The method for treating soot and dust according to claim 1, wherein the material containing radioactive substances is incineration bottom ash, incineration fly ash and / or fine-grained soil obtained by separating soil removed by decontamination according to grain size.

7. A dust treatment device which melts radioactive material in a melting furnace in the presence of chlorine, and brings the exhaust gas containing the volatilized radioactive material into contact with an auxiliary agent and an activated carbon adsorbent in a dust collector, thereby reducing the volume of the collected dust and removing the radioactive material contained in the dust, an activated carbon separator for separating activated carbon from solid dust; A dissolving device that dissolves radioactive materials contained in soot and dust into water; a solid-liquid separator that dissolves soot and dust in water and recovers the remaining solid matter; a radioactive material adsorption device that adsorbs and removes radioactive materials from an aqueous solution of soot and dust; A dust treatment device including:

8. 8. The dust treatment device according to claim 7, wherein the activated carbon separation device is composed of any one of a flotation separation device, a floatation device or a specific gravity separation device employing a wet method, and an air classifier or an electrostatic separator employing a dry method.

9. 9. The dust treatment device according to claim 7 or 8, further comprising a heavy metal removal device disposed between the solid-liquid separation device and the radioactive material adsorption device or after the radioactive material adsorption device, for removing water-soluble heavy metals as insoluble heavy metals by adjusting the pH of the aqueous solution.

10. 10. The dust treatment apparatus according to claim 9, further comprising a concentrating device for evaporating and drying the high-concentration salt water from which radioactive materials have been removed by the radioactive material adsorption device and from which heavy metals have been removed by the heavy metal removal device.

11. 11. The dust treatment apparatus according to claim 7, further comprising a circulation melting mechanism for remelting the solid matter recovered in the solid-liquid separator in the melting furnace.

12. 12. The dust treatment apparatus according to claim 7, wherein the material containing radioactive materials is incineration bottom ash, incineration fly ash, and / or fine-grained soil obtained by separating soil removed by decontamination and sorting it by particle size.

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