Treatment system and treatment method for radioactive waste

Abstract

The invention discloses a radioactive waste treatment system and method. The radioactive waste treatment system comprises a feeding module, a reforming reaction module, an oxidation treatment module and a tail gas treatment module which are sequentially connected. The feeding module comprises a solid waste feeding unit and a liquid waste feeding unit; the reforming reaction module comprises a reforming reaction furnace, the reforming reaction furnace comprises an upper cooling area and a lower reaction area which are communicated with each other, the oxidation treatment module comprises a thermal oxidation furnace, and the thermal oxidation furnace comprises an upper oxidation chamber and a lower alkali wash quenching chamber which are communicated with each other; a gas outlet of the quenching chamber is connected with the tail gas treatment module. The treatment method based on the radioactive waste treatment system can meet the high efficiency and the high volume reduction ratio at the same time, and can meet the treatment requirements of various forms of radioactive waste.

Description

Technical Field

[0001] The present invention relates to a treatment system and a treatment method for radioactive waste. Background Art

[0002] Radioactive wastes such as waste resins, waste oils, waste organic solvents and chemical waste liquids generated by the nuclear industry are technically difficult to treat. Especially for units with a small amount of waste generated, centralized treatment with large-scale treatment devices will cause waste of resources, and there are difficulties in transporting them out. Therefore, at present, the method of temporary storage in the factory is mostly adopted, but this method is not conducive to the safe treatment of waste. At the same time, with the development of the nuclear energy industry, the problem of treatment and disposal of radioactive waste has become increasingly prominent, and the R & D demand for new waste treatment technologies has become increasingly urgent. Summary of the Invention

[0003] The technical problem to be solved by the present invention is the problem of low volume reduction ratio and low treatment efficiency in the prior art when treating radioactive waste, and a treatment system and a treatment method for radioactive waste are provided. The treatment method based on the treatment system for radioactive waste can simultaneously meet high efficiency and high volume reduction ratio, and can meet the treatment requirements of various forms of radioactive waste.

[0004] The present invention solves the above technical problems through the following technical solutions:

[0005] The present invention provides a treatment system for radioactive waste, which includes a feeding module, a reforming reaction module, an oxidation treatment module and a tail gas treatment module connected in sequence;

[0006] The feeding module includes a solid waste feeding unit and a liquid waste feeding unit;

[0007] The reforming reaction module includes a reforming reaction furnace, and the reforming reaction furnace includes a cooling zone in the upper part and a reaction zone in the lower part that are interconnected. The cooling zone is provided with a cooling zone gas outlet; the reaction zone is provided with a waste feeding port at the lower end and a first solid waste outlet at the bottom, which are respectively used for inputting radioactive waste and discharging the first solid waste; the waste feeding port is inclined upward and forms an acute angle of 30° - 75° with the axis of the reaction zone; the waste feeding port is respectively connected to the solid waste feeding unit and the liquid waste feeding unit;

[0008] The oxidation treatment module includes a thermal oxidation furnace, which includes an oxidation chamber in the upper part and an alkali washing and quenching chamber in the lower part that are interconnected. The oxidation chamber is also provided with an oxidation chamber inlet, and the outlet of the temperature reduction zone is connected to the oxidation chamber inlet for delivering the mixed gas obtained by the reforming reaction module to the thermal oxidation furnace. The oxidation chamber is used to oxidize the mixed gas to form flue gas and allow the flue gas to enter the alkali washing and quenching chamber for cooling and washing. The alkali washing and quenching chamber is provided with a quenching chamber outlet; the quenching chamber outlet is connected to the tail gas treatment module.

[0009] In the present invention, a parallel solid waste feeding unit and liquid waste feeding unit are provided, which can meet the treatment of various forms of radioactive waste (such as solid form and liquid form), and in cooperation with the acute angle formed between the waste feeding port and the axis of the reaction zone being 30° - 75°, it can ensure that there is no material loss when various forms of radioactive waste are input into the reaction zone. For example, when radioactive waste is input in liquid form, this angle can ensure that the radioactive waste does not spray on the furnace wall, so that the radioactive waste can fully react and improve the treatment efficiency of the radioactive waste treatment system.

[0010] The radioactive waste treatment system of the present invention has a compact floor area, convenient installation, and simple interfaces; with a compact containerized design, the main equipment can be moved or installed in a skid-mounted manner, and shielding facilities can be added according to radiation protection requirements; it meets the conditions for transportation, long-term storage, and disposal.

[0011] In the present invention, the size of the acute angle formed between the waste feeding port and the axis of the reaction zone is preferably 30° - 60°, more preferably 45°.

[0012] In the present invention, the waste feeding port preferably includes a solid waste feeding port and a liquid waste feeding port. The solid waste feeding port is connected to the solid waste feeding unit, and the liquid waste feeding port is connected to the liquid waste feeding unit.

[0013] Among them, both the solid waste feeding port and the liquid waste feeding port are inclined upward. The acute angle formed between the solid waste feeding port and the axis of the reaction zone is preferably 30° - 60°; the acute angle formed between the liquid waste feeding port and the axis of the reaction zone is preferably 30° - 60°.

[0014] In the present invention, the liquid waste feeding unit preferably includes a feeding tank and a feeding pump. The feeding tank, the feeding pump, and the waste feeding port are connected in sequence. The feeding tank is used to receive radioactive liquid waste. Among them, the feeding pump can continuously and evenly transport the radioactive liquid waste into the reforming reaction furnace.

[0015] Among them, the feed tank preferably includes a stirrer, and the stirrer is preferably an electric stirrer. Among them, the stirrer can make the radioactive liquid waste more uniform, which is beneficial to the transportation of the radioactive liquid waste.

[0016] Among them, the effective volume of the feed tank is preferably 0.5 m 3 .

[0017] Among them, the feed pump is preferably a peristaltic pump, a screw pump or a diaphragm pump.

[0018] In the present invention, the solid waste feeding unit preferably includes a low-temperature evaporation dryer and a screw feeder, and the low-temperature evaporation dryer, the screw feeder and the waste feeding port are connected in sequence. Among them, the low-temperature evaporation dryer can evaporate the free water and bound water in the radioactive solid waste, making the radioactive solid waste drier and facilitating transportation; the screw feeder can transport the dried radioactive solid waste into the reforming reaction furnace regularly and quantitatively.

[0019] Among them, the bottom of the low-temperature evaporation dryer is preferably equipped with a filter screen for filtering and recovering free water.

[0020] In the present invention, the first solid waste outlet is preferably connected in sequence with a discharge valve, a dust lock hopper, an ash discharge hopper and a discharge tank through a nitrogen blowing pipeline for discharging and collecting the first solid waste, or for sampling the first solid waste.

[0021] In the present invention, the reaction zone preferably further has a bed material feeding port for introducing inert bed material and / or reforming additives.

[0022] Among them, the acute angle preferably formed between the bed material feeding port and the axis of the reaction zone is 30°-60°.

[0023] Among them, the bed material feeding port and the waste feeding port are preferably on the same horizontal line.

[0024] Among them, the bed material feeding port and the waste feeding port preferably form an angle of 180° with the axis of the reaction zone.

[0025] In the present invention, the reforming reaction furnace is preferably a fluidized bed reactor or a fixed bed reactor.

[0026] In the present invention, the bottom of the reforming reaction furnace preferably further has an electric heating rod for heating the reforming reaction furnace.

[0027] In the present invention, the outer periphery of the reforming reaction furnace is preferably wrapped with heat insulating cotton.

[0028] In the present invention, the shell of the reforming reaction furnace is preferably made of alloy material. Using alloy material can enhance the heat resistance of the reforming reaction furnace.

[0029] In the present invention, the reforming reaction furnace preferably further includes a sight glass and a camera for observing the situation inside the furnace.

[0030] In the present invention, the outlet of the cooling zone is preferably connected to the inlet of the oxidation chamber through a high-temperature filter, and the high-temperature filter is used to separate solid particles in the mixed gas and form a second solid waste.

[0031] Among them, the filtration accuracy of the high-temperature filter is preferably 1 μm. Using a high-temperature filter can separate more than 99% of the second solid waste, and the particle size of the separated second solid waste is greater than 1 μm.

[0032] Among them, the bottom of the high-temperature filter is preferably connected to an ash-locking hopper and an ash-discharging hopper for discharging and collecting the second solid waste, or for sampling the second solid waste.

[0033] Among them, the filter element material of the high-temperature filter is preferably made of ceramic fiber or metal.

[0034] Among them, the temperature tolerance of the filter element material of the high-temperature filter is preferably ≤600°C.

[0035] Among them, a silicon-aluminum fiber thermal insulation layer is preferably provided on the inner side wall of the high-temperature filter, or the high-temperature filter preferably adopts a stainless steel outer shell. More preferably, heat-insulating cotton is provided on the outer periphery of the stainless steel outer shell. This way can reduce heat loss.

[0036] Among them, a sampling point can be set between the high-temperature filter and the inlet of the oxidation chamber for sampling the mixed gas.

[0037] In the present invention, the oxidation chamber preferably further includes an electric heating rod.

[0038] In the present invention, a high-temperature resistant material is preferably provided on the inner side wall of the oxidation chamber, and an air insulation layer is preferably provided on the outer periphery of the oxidation chamber. This way can enable the oxidation chamber to have good heat preservation and heat storage capabilities to maintain the stable temperature of the combustion chamber and reduce energy consumption.

[0039] In the present invention, preferably, the alkali washing and quenching chamber includes an alkali washing liquid inlet provided at the upper end of the alkali washing and quenching chamber and an alkali washing liquid outlet provided at the lower end of the alkali washing and quenching chamber. The alkali washing liquid inlet and the alkali washing liquid outlet are connected through a pipeline provided outside the thermal oxidation furnace, thereby forming an external circulation loop of the alkali washing liquid. The present invention sets an external circulation loop to more fully wash some impurities in the flue gas and make the emission of the tail gas meet the standards.

[0040] Preferably, a circulation pump, a washing liquid cooler and a washing liquid filter are further provided on the outer circulation loop, and the alkali washing liquid outlet, the circulation pump, the washing liquid cooler, the washing liquid filter and the alkali washing liquid inlet are connected in sequence. In the present invention, by providing the washing liquid cooler on the outer circulation loop, the alkali washing liquid can be cooled in time to keep the temperature of the alkali washing liquid always within a suitable range, so as to cool the flue gas in time and further reduce the impurities in the tail gas.

[0041] Preferably, an on-line pH meter and a salt solution concentration meter are further provided on the outer circulation loop.

[0042] Preferably, a liquid sampling port is provided at the outlet of the circulation pump.

[0043] In the present invention, preferably, the tail gas treatment module includes a demister, and the outlet of the quench chamber is connected to the demister for recovering the moisture in the tail gas; more preferably, the tail gas treatment module further includes a tail gas exhaust fan, and the tail gas exhaust fan is arranged downstream of the demister, and the tail gas exhaust fan is used for discharging the tail gas and maintaining the system negative pressure during the normal operation of the device.

[0044] For example, a chimney can be arranged downstream of the tail gas exhaust fan, and the chimney is used for discharging the tail gas.

[0045] The present invention also provides a method for treating radioactive waste, which uses the above-mentioned radioactive waste treatment system and includes the following steps:

[0046] S1. The radioactive solid waste and radioactive liquid waste are respectively passed through the solid waste feeding unit and the liquid waste feeding unit and introduced into the reaction zone through the waste feeding port, and then a reforming reaction is carried out to form a first solid waste and a mixed gas; the mixed gas is discharged from the outlet of the cooling zone to the oxidation chamber after being cooled in the cooling zone; the temperature of the reforming reaction is 500-800 °C, and the pressure of the reforming reaction is -5 to -1 kPa;

[0047] S2. The mixed gas is introduced into the oxidation chamber for an oxidation reaction to form flue gas, the flue gas is washed in the alkali washing and quenching chamber to form tail gas and alkali washing liquid, and the tail gas is introduced into the tail gas treatment module; the pressure of the oxidation reaction is -3.5 to -5.5 kPa.

[0048] The method for treating radioactive waste in the present invention uses steam reforming technology to treat radioactive waste, pyrolyzing and breaking the chains of organic macromolecular substances in the radioactive waste to make them inorganic. The resulting mixed gas (such as nitrogen, hydrogen, carbon monoxide, and methane) contains a large amount of combustible substances, which are burned with excess oxygen to generate carbon dioxide and water. The high-temperature flue gas generated by combustion contains impurities such as a small amount of soot and acidic gas components. After alkali washing, it forms tail gas, which enters the tail gas treatment system for purification and then is discharged. Compared with traditional treatment processes, it has the following advantages: (1) The volume reduction ratio is as high as more than 6, enabling efficient volume reduction. The formed inert solid waste is convenient for storage; (2) The impurity content in the tail gas is low, and no highly toxic substances such as dioxins are generated, having little impact on the environment and equipment; (3) The treatment is simple, the amount of secondary waste is small, the treatment process is highly safe, and it can meet the treatment requirements of various forms of radioactive waste.

[0049] This method can effectively treat radioactive waste with medium and low radiation dose rates generated in the nuclear industry. At the same time, it can also meet the treatment of various forms of radioactive waste, overcoming the difficulties of long-distance transportation of radioactive solid waste and radioactive liquid waste. This treatment method has the advantages of high efficiency, low transportation risk, and low transportation cost; for the selection of treatment sites, it has more flexibility.

[0050] In the present invention, the radioactive waste preferably includes radioactive solid waste and / or radioactive liquid waste.

[0051] Among them, the radioactive solid waste includes, for example, waste resin. The waste resin preferably includes anion exchange resin and / or cation exchange resin. The chemical formula of the anion exchange resin is C 25 H 25 S3O9, and the chemical formula of the cation exchange resin is C 34 H 52 N3O3.

[0052] Among them, the types of radioactive elements contained in the waste resin are, for example, cesium, strontium, and cobalt.

[0053] Among them, the content of cesium in the waste resin is preferably 0.2 g / m 3 .

[0054] Among them, the content of strontium in the waste resin is preferably 0.2 μg / m 3 .

[0055] Among them, the content of cobalt in the waste resin is preferably 0.01 g / m 3 .

[0056] In the present invention, the feeding rate of the radioactive solid waste is preferably 10 L / h.

[0057] In the present invention, the radioactive liquid waste preferably includes organic waste liquid and / or chemical waste liquid.

[0058] In the present invention, the feeding rate of the radioactive liquid waste is preferably 10 L / h.

[0059] Among them, the organic waste liquid preferably includes waste oil and / or waste organic solvent.

[0060] Among them, the waste oil is, for example, waste kerosene.

[0061] Among them, the waste organic solvent is, for example, waste tributyl phosphate (TBP), and the molecular formula of TBP is C 12 H 27 O4P.

[0062] Among them, the chemical waste liquid preferably includes nitrate waste liquid containing sodium ions.

[0063] In the present invention, the types of radioactive elements contained in the radioactive liquid waste are, for example, cesium, strontium, and cobalt.

[0064] In the present invention, the radioactive dose rate of the radioactive waste is preferably less than 10 mSv / h, and more preferably less than 2 mSv / h.

[0065] In the present invention, preferably, after the radioactive solid waste is evaporated and dried in a low-temperature evaporation dryer, it is transported to the waste feeding port through a screw feeder.

[0066] Among them, the temperature of the evaporation and drying is preferably 100 - 150 °C, and more preferably 120 - 150 °C.

[0067] Among them, the effective loading capacity of the low-temperature evaporation dryer is preferably 100 L.

[0068] Among them, after the evaporation and drying, the water content of the radioactive solid waste is preferably less than 6%.

[0069] In the present invention, after the radioactive solid waste is evaporated and dried, it is introduced into a reforming reaction furnace, which can avoid the problems that wet radioactive solid waste is not easy to transport and transfer, and improve the transport efficiency.

[0070] In the present invention, preferably, after the radioactive liquid waste is mixed with a raw material additive, it is introduced into the reaction zone. Among them, the raw material additive is preferably aluminum hydroxide and iron hydroxide.

[0071] Among them, the mass ratio of the radioactive liquid waste to the raw material additive is preferably 10:1.

[0072] In the present invention, in step S1, the temperature of the mixed gas discharged from the outlet of the cooling zone is preferably lower than 600 °C.

[0073] In the present invention, in step S1, the mixed gas preferably passes through a high-temperature filter and is then discharged into the oxidation chamber, so that solid particles with a particle size greater than 1 μm in the mixed gas are filtered out and form a second solid waste.

[0074] Among them, the temperature of the filtration is preferably 200-600 °C, for example, 550 °C.

[0075] Among them, the pressure of the filtration is preferably -2.5 to -4 kPa, for example, -3.5 kPa.

[0076] In some specific embodiments of the present invention, all the heat required for the filtration comes from the mixed gas. Since the inlet pipeline is relatively short, the high-temperature filter can be heated by the high-temperature mixed gas after reforming to maintain the required temperature.

[0077] In the present invention, in step S1, an inert bed material and / or a reforming additive are preferably introduced into the reaction zone.

[0078] Among them, the inert bed material is, for example, silica and / or alumina. The inert bed material does not chemically react with radioactive waste, and its temperature tolerance is higher than the reaction temperature of the reforming reaction furnace.

[0079] Among them, the shape of the alumina is preferably spherical, and the diameter of the alumina is preferably 0.5 mm.

[0080] Among them, the reforming additive is preferably a metal compound, more preferably a metal oxide and / or a metal hydroxide, for example, one or more of iron hydroxide, aluminum hydroxide, and kaolin. Among them, the kaolin is, for example, kaolin containing a silicon-aluminum compound. The reforming additive can react with radioactive elements in radioactive waste, thereby fixing acidic and / or basic radioactive elements in radioactive waste in the reforming additive to form an inert compound.

[0081] In the present invention, in step S1, the temperature of the reforming reaction is preferably 600-800 °C, more preferably 650-750 °C, for example, 700 °C.

[0082] In the present invention, in step S1, when the radioactive solid waste is waste resin, the temperature of the reforming reaction is preferably 725-750 °C.

[0083] In the present invention, in step S1, when the radioactive liquid waste is organic waste liquid, the temperature of the reforming reaction is preferably 500-700 °C.

[0084] In the present invention, in step S1, when the radioactive liquid waste is chemical waste liquid, the temperature of the reforming reaction is preferably 700 - 750 °C.

[0085] In the present invention, in step S1, the gas output of the mixed gas is preferably 18 Nm 3 / h.

[0086] In the present invention, in step S1, the heating method of the reforming reaction furnace is preferably electric heating. Using electric heating can improve safety and at the same time reduce the complexity of installation and operation processes.

[0087] In the present invention, in step S1, the mass of the first solid waste discharged each time is preferably 2 kg, and the time interval between each discharge is preferably 24 h.

[0088] In the reforming reaction occurring in step S1 of the present invention, the organic matter in the radioactive waste can be mineralized, nitrate can be reduced to harmless nitrogen gas, and at the same time, metal cations and anions (such as Cl, P, S, etc.) in the radioactive waste react with the reforming additive to fix the acidic and / or alkaline radioactive elements in the radioactive waste in the reforming additive, generating inert compounds.

[0089] The reforming reaction of the present invention mainly includes the following reactions:

[0090] Decomposition of organic matter: C x H y O z →C + CH4 + CO + H2;

[0091] Water - gas reaction: H2O + C → H2 + CO;

[0092] CO shift reaction: CO + H2O → CO2 + H2;

[0093] Carbon oxidation reaction: C + O2 → CO2;

[0094] CO oxidation reaction: 2CO + O2 → 2CO2;

[0095] H2 oxidation reaction: 2H2 + O2 → 2H2O;

[0096] First nitrate conversion reaction: 2NO3 + 3C → N2 + 3CO2;

[0097] Second nitrate conversion reaction: 2NO3 + 6H2 → N2 + 6H2O;

[0098] First hydrocarbon reforming reaction: C2H4 + 2H2O → 2CO + 4H2;

[0099] Second hydrocarbon reforming reaction: C6H6 + 6H2O → 6CO + 9H2.

[0100] In step S2 of the present invention, a mineralization reaction is also involved, that is, a new mineralized phase is formed between the reforming additive and the inorganic substances in the reforming residue in the reforming reaction furnace, which can well envelop the radionuclides in the radioactive waste in the mineralization products. For example, the following reactions are included:

[0101] Na + Al2O3 - 2SiO2 → Na2O - Al2O3 - 2SiO;

[0102] Na + K + Al2O3 - 2SiO2 → NaKO - Al2O3 - 2SiO;

[0103] Na + SO4 + Al2O3 - 2SiO2 → NaSO4 - (Na2O - Al2O3 - 2SiO2)6;

[0104] Na + Cl + Al2O3 - 2SiO2 → 2NaCl - (Na2O - Al2O3 - 2SiO2)6;

[0105] Na + F + Al2O3 - 2SiO2 → 2NaF - (Na2O - Al2O3 - 2SiO2)6;

[0106] Na + Al2O3 → NaAlO2.

[0107] In the present invention, the mixed gas includes, for example, nitrogen, hydrogen, carbon monoxide and methane.

[0108] In the present invention, in step S2, preferably natural gas and air are also introduced to fully oxidize and burn the mixed gas.

[0109] In the present invention, in step S2, the flue gas includes, for example, nitrogen, carbon dioxide and water vapor.

[0110] In the present invention, in step S2, the heating method of the oxidation chamber is preferably electric heating. Using electric heating can improve safety and at the same time reduce the complexity of the installation and operation process.

[0111] In the present invention, in step S2, the temperature of the oxidation reaction is preferably above 850 °C, more preferably 1100 - 2000 °C.

[0112] In the present invention, in step S2, the time of the oxidation reaction is preferably above 2 s, more preferably 5 - 10 s.

[0113] In the present invention, in step S2, the temperature of the tail gas is preferably below 85 °C, for example 70 - 85 °C.

[0114] In the present invention, in step S2, the volume fraction of oxygen in the tail gas is preferably greater than 3%.

[0115] In the present invention, in step S2, the temperature of the washing is preferably 55 - 60 °C.

[0116] In the present invention, in step S2, the washing liquid used for washing is preferably a sodium hydroxide solution, and the volume fraction of the sodium hydroxide solution is preferably 0.5% - 10%.

[0117] In step S2 of the present invention, preferably, the alkali washing liquid is cooled through an external circulation loop and then recycled.

[0118] Among them, the temperature of the alkali washing liquid after being cooled through the external circulation loop is preferably 50 - 65 °C.

[0119] In the present invention, in step S2, the temperature of the outer surface of the thermal oxidizer is preferably lower than 80 °C.

[0120] In the present invention, the tail gas is preferably discharged to the atmosphere by a tail gas exhaust fan after demisting or connected to other exhaust systems and then discharged to the atmosphere.

[0121] Among them, the inlet pressure of the tail gas exhaust fan is preferably -6.5 to -9 kPa.

[0122] In the present invention, the content of nitrogen oxides in the tail gas is preferably not more than 100 mg / Nm 3 .

[0123] In the present invention, the content of solid particulate matter in the tail gas is preferably not more than 20 mg / Nm 3 .

[0124] In the present invention, the treatment capacity of the radioactive waste is preferably 5 - 15 L / h.

[0125] When electric heating is used as the heat source in the present invention, since flammable fuels such as fuel oil or natural gas are not used, the installation of the treatment system is more flexible, and the size and occupied space of the equipment are significantly reduced.

[0126] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0127] The reagents and raw materials used in the present invention are all commercially available.

[0128] The positive and progressive effects of the present invention are as follows:

[0129] The present invention provides a treatment system and method for radioactive waste, which can effectively treat radioactive waste with medium and low radiation dose rates generated in the nuclear industry, and at the same time can also meet the treatment of various forms of radioactive waste, overcoming the difficulties of long-distance transportation of radioactive solid waste and radioactive liquid waste; this treatment method has the advantages of high efficiency, low transportation risk and low transportation cost;

[0130] Compared with the traditional treatment process, the present invention has the following advantages: (1) The volume reduction ratio is as high as more than 6, which can achieve efficient volume reduction, and the formed inert solid waste is convenient for storage; (2) The impurity content in the tail gas is low, and no highly toxic substances such as dioxins are generated, which has little impact on the environment and equipment; (3) The treatment is simple, the amount of secondary waste is small, and the safety of the treatment process is high. Description of the Drawings

[0131] Figure 1 It is a schematic diagram of the treatment system for radioactive waste in Example 1.

[0132] The reference numerals are as follows:

[0133] 1 - Low-temperature evaporation dryer; 2 - Screw feeder; 3 - Feed tank; 4 - Feed pump; 5 - Stirrer; 6 - Cooling zone; 7 - Reaction zone; 8 - Solid waste feed inlet; 9 - Liquid waste feed inlet; 10 - High-temperature filter; 11 - Oxidation chamber; 12 - Alkaline washing and quenching chamber; 13 - External circulation loop; 14 - Circulation pump; 15 - Wash liquor cooler; 16 - Demister; 17 - Tail gas exhaust fan. Detailed Embodiments

[0134] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0135] Example 1

[0136] The schematic diagram of the treatment system for radioactive waste in this example is as Figure 1 shown.

[0137] It includes a feeding module, a reforming reaction module, an oxidation treatment module and a tail gas treatment module connected in sequence;

[0138] The feeding module includes a solid waste feeding unit and a liquid waste feeding unit; the solid waste feeding unit includes a low-temperature evaporation dryer 1 and a screw feeder 2, and the low-temperature evaporation dryer 1, the screw feeder 2 and the waste feed inlet are connected in sequence; the liquid waste feeding unit includes a feed tank 3 and a feed pump 4, and the feed tank 3, the feed pump 4 and the waste feed inlet are connected in sequence, and the feed tank 3 is used to receive radioactive liquid waste; the feed tank 3 includes a stirrer 5, and the stirrer 5 is an electric stirrer;

[0139] The reforming reaction module includes a reforming reaction furnace, which includes a cooling zone 6 in the upper part and a reaction zone 7 in the lower part that are interconnected. There is an air outlet in the cooling zone 6; in the reaction zone 7, there is a waste feed port at the lower end and a first solid waste outlet at the bottom, which are respectively used for inputting radioactive waste and discharging the first solid waste; the waste feed port includes a solid waste feed port 8 and a liquid waste feed port 9. The solid waste feed port 8 is connected to the solid waste feed unit, and the liquid waste feed port 9 is connected to the liquid waste feed unit; both the solid waste feed port 8 and the liquid waste feed port 9 are inclined upward and form an acute angle of 45° with the axis of the reaction zone 7.

[0140] The air outlet of the cooling zone is connected to the air inlet of the oxidation chamber through a high-temperature filter 10. The high-temperature filter 10 is used to separate solid particles in the mixed gas and form a second solid waste; among them, the filtration accuracy of the high-temperature filter 10 is 1 μm; among them, the bottom of the high-temperature filter 10 is connected to an ash-locking hopper and a dust-discharging hopper, which are used to discharge and collect the second solid waste, or to sample the second solid waste.

[0141] The oxidation treatment module includes a thermal oxidation furnace, which includes an oxidation chamber 11 in the upper part and an alkali-washing and rapid-cooling chamber 12 in the lower part that are interconnected. The oxidation chamber 11 is also provided with an air inlet of the oxidation chamber. The air outlet of the cooling zone is connected to the air inlet of the oxidation chamber, which is used to transport the mixed gas obtained by the reforming reaction module to the thermal oxidation furnace. The oxidation chamber 11 is used to oxidize the mixed gas to form flue gas and make the flue gas enter the alkali-washing and rapid-cooling chamber 12 for cooling and washing. The alkali-washing and rapid-cooling chamber 12 is provided with an air outlet of the rapid-cooling chamber; the air outlet of the rapid-cooling chamber is connected to the tail gas treatment module.

[0142] The alkali-washing and rapid-cooling chamber 12 includes an alkali washing liquid inlet at the upper end of the alkali-washing and rapid-cooling chamber 12 and an alkali washing liquid outlet at the lower end of the alkali-washing and rapid-cooling chamber 12. The alkali washing liquid inlet and the alkali washing liquid outlet are connected through a pipeline arranged outside the thermal oxidation furnace, so as to form an external circulation loop 13 of the alkali washing liquid; among them, a circulation pump 14 and a washing liquid cooler 15 are also provided on the external circulation loop 13. The alkali washing liquid outlet, the circulation pump 14, the washing liquid cooler 15 and the alkali washing liquid inlet are connected in sequence; among them, an on-line pH meter and a salt liquid concentration meter are also provided on the external circulation loop 13; among them, a liquid sampling port is provided at the outlet of the circulation pump 14.

[0143] The tail gas treatment module includes a demister 16 and a tail gas exhaust fan 17. The air outlet of the rapid-cooling chamber is connected to the demister 16, which is used to recover the moisture in the tail gas; the tail gas exhaust fan 17 is arranged downstream of the demister 16. The tail gas exhaust fan 17 is used to discharge the tail gas and maintain the system negative pressure during the normal operation of the device.

[0144] Example 2

[0145] Example 2 uses the radioactive waste treatment system of Example 1, which includes the following steps:

[0146] S1. The radioactive solid waste and radioactive liquid waste are respectively passed through the solid waste feeding unit and the liquid waste feeding unit and introduced into the reaction zone through the waste feeding port, and then a reforming reaction is carried out to form the first solid waste and a mixed gas; the mixed gas is discharged from the outlet of the cooling zone to the oxidation chamber after being cooled in the cooling zone; the temperature of the reforming reaction is 700 °C, and the pressure of the reforming reaction is -3 kPa;

[0147] S2. The mixed gas is introduced into the oxidation chamber for oxidation reaction to form flue gas, and the flue gas is washed in the alkali washing and quenching chamber to form tail gas and alkali washing liquid, and the tail gas is introduced into the tail gas treatment module; the pressure of the oxidation reaction is -5 kPa, the temperature of the oxidation reaction is 1100 °C; the time of the oxidation reaction is 5 s;

[0148] Among them, the radioactive solid waste is waste resin, and the waste resin includes anion exchange resin and cation exchange resin. The chemical formula of the anion exchange resin is C 25 H 25 S3O9, and the chemical formula of the cation exchange resin is C 34 H 52 N3O3; the types of radioactive elements contained in the waste resin are cesium, strontium and cobalt; the radioactive dose rate of the waste resin is less than 10 mSv / h; the feeding rate of the radioactive solid waste is 10 L / h; the waste resin contains 20%-40% of free water, and after evaporation and drying, the water content of the radioactive solid waste is less than 6%.

[0149] Among them, the radioactive liquid waste includes organic waste liquid and chemical waste liquid, and the feeding rate of the radioactive liquid waste is 10 L / h; the organic waste liquid includes waste oil and waste organic solvent, the waste oil is waste kerosene, and the waste organic solvent is waste tributyl phosphate (TBP), and the molecular formula of TBP is C 12 H 27 O4P. The types of radioactive elements contained in the radioactive liquid waste are cesium, strontium and cobalt. The radioactive dose rate of the radioactive liquid waste is less than 10 mSv / h; after the radioactive liquid waste is mixed with the raw material additive, it is introduced into the reaction zone; among them, the raw material additive is aluminum hydroxide and iron hydroxide; among them, the mass ratio of the radioactive liquid waste to the raw material additive is 10:1.

[0150] Among them, the temperature of evaporation and drying is 120 °C, the effective loading capacity of the low-temperature evaporation dryer is 100 L; the effective volume of the feeding tank is 0.5 m 3 ;

[0151] In step S1, an inert bed material and / or a reforming additive are also introduced into the reaction zone; the inert bed material is alumina, the shape of the alumina is spherical, and the diameter of the alumina is 0.5 mm; in step S1, the temperature of the mixed gas discharged from the outlet of the cooling zone is lower than 600 °C; the gas output of the mixed gas is 18 Nm 3 / h; in step S1, after the mixed gas is filtered by a high-temperature filter, it is discharged into the oxidation chamber, so that solid particles with a particle size larger than 1 μm in the mixed gas are filtered and form a second solid waste; wherein, the temperature of the filtration is 550 °C; wherein, the pressure of the filtration is -3.5 kPa; in step S1, the mass of the first solid waste discharged each time is 2 kg, and the time interval between each discharge is 24 h;

[0152] In step S2, the temperature of the tail gas is 70 - 85 °C; the temperature of the washing is 55 - 60 °C; the alkali washing solution is cooled through an external circulation loop and then recycled, wherein the temperature of the alkali washing solution after being cooled through the external circulation loop is 50 - 65 °C.

[0153] After the tail gas is demisted, it is discharged to the atmosphere by a tail gas exhaust fan, and the inlet pressure of the tail gas exhaust fan is -8 kPa.

[0154] The power consumption of the entire set of devices in this embodiment is about 100 - 150 kW; this embodiment can achieve efficient volume reduction, and the formed inert solid waste is convenient for storage; the impurity content in the tail gas is low, and no highly toxic substances such as dioxins are generated, which has little impact on the environment and equipment; the treatment is simple, the amount of secondary waste is small, and the treatment process is highly safe, and it can meet the treatment requirements of various forms of radioactive waste.

[0155] The volume reduction ratio of this embodiment is 6, and the content of nitrogen oxides in the tail gas does not exceed 100 mg / Nm 3 ; the content of solid particles in the tail gas does not exceed 20 mg / Nm 3 .

Claims

1. A radioactive waste treatment system, characterized in that, It includes a feeding module, a reforming reaction module, an oxidation treatment module, and a tail gas treatment module that are connected in sequence; The feeding module includes a solid waste feeding unit and a liquid waste feeding unit; The reforming reaction module includes a reforming reaction furnace, and the reforming reaction furnace includes a cooling zone in the upper part and a reaction zone in the lower part that are interconnected. A cooling zone gas outlet is provided on the cooling zone; a waste feeding port is provided at the lower end of the reaction zone and a first solid waste outlet is provided at the bottom, which are respectively used for inputting radioactive waste and discharging the first solid waste; the waste feeding port is inclined upward and forms an acute angle of 30°-75° with the axis of the reaction zone; the waste feeding port is respectively connected to the solid waste feeding unit and the liquid waste feeding unit; The oxidation treatment module includes a thermal oxidation furnace, and the thermal oxidation furnace includes an oxidation chamber in the upper part and an alkali washing and quenching chamber in the lower part that are interconnected. An oxidation chamber air inlet is further provided in the oxidation chamber. The cooling zone gas outlet is communicated with the oxidation chamber air inlet for delivering the mixed gas obtained from the reforming reaction module to the thermal oxidation furnace. The oxidation chamber is used for oxidizing the mixed gas to form flue gas and enabling the flue gas to enter the alkali washing and quenching chamber for cooling and washing. An emergency cooling chamber gas outlet is provided in the alkali washing and quenching chamber; the emergency cooling chamber gas outlet is connected to the tail gas treatment module.

2. The radioactive waste treatment system according to claim 1, characterized in that, The radioactive waste treatment system satisfies one or more of the following conditions: (a) The acute angle formed between the waste feeding port and the axis of the reaction zone is 30°-60°, preferably 45°; (b) The waste feeding port includes a solid waste feeding port and a liquid waste feeding port. The solid waste feeding port is connected to the solid waste feeding unit, and the liquid waste feeding port is connected to the liquid waste feeding unit; (c) The liquid waste feeding unit includes a feeding tank and a feeding pump. The feeding tank, the feeding pump, and the waste feeding port are connected in sequence, and the feeding tank is used for receiving radioactive liquid waste; (d) The solid waste feeding unit includes a low-temperature evaporation dryer and a screw feeder. The low-temperature evaporation dryer, the screw feeder, and the waste feeding port are connected in sequence; (e) The first solid waste outlet is connected to a discharge valve, a dust locking hopper, a dust discharging hopper, and a discharging tank through a nitrogen blowing pipeline in sequence for discharging and collecting the first solid waste, or for sampling the first solid waste.

3. The radioactive waste treatment system according to claim 2, characterized in that, The radioactive waste treatment system satisfies one or more of the following conditions: (f) The feeding tank includes a stirrer, and the stirrer is preferably an electric stirrer; (g) The effective volume of the feed tank is 0.5 m 3 ; (h) The feeding pump is a peristaltic pump, a screw pump, or a diaphragm pump; (i) The bottom of the low-temperature evaporation dryer is equipped with a filter screen for filtering and recovering free water.

4. The radioactive waste treatment system according to claim 1, characterized in that, The radioactive waste treatment system satisfies one or more of the following conditions: (j) A bed material feeding port is further provided in the reaction zone, and the bed material feeding port is used for introducing inert bed material and / or reforming additives; (k) The reforming reaction furnace is a fluidized bed reactor or a fixed bed reactor; (l) An electric heating rod is also provided at the bottom of the reforming reaction furnace for heating the reforming reaction furnace; (m) A sight glass and a camera are also provided on the reforming reaction furnace for observing the situation inside the furnace; (n) The outlet of the cooling zone is connected to the inlet of the oxidation chamber through a high-temperature filter, and the high-temperature filter is used to separate solid particles in the mixed gas and form a second solid waste; wherein, the filtration accuracy of the high-temperature filter is preferably 1 μm; wherein, the bottom of the high-temperature filter is preferably connected to an ash-locking hopper and a dust-discharging hopper for discharging and collecting the second solid waste, or for sampling the second solid waste; (o) An electric heating rod is also provided in the oxidation chamber; (p) A high-temperature resistant material is provided on the inner side wall of the oxidation chamber, and an air heat insulation layer is preferably provided on the outer periphery of the oxidation chamber; (q) The tail gas treatment module includes a demister, and the outlet of the quench chamber is connected to the demister for recovering moisture in the tail gas; preferably, the tail gas treatment module further includes a tail gas exhaust fan, and the tail gas exhaust fan is arranged downstream of the demister, and the tail gas exhaust fan is used for discharging the tail gas and maintaining the system negative pressure during normal operation of the device.

5. The radioactive waste treatment system according to claim 4, characterized in that, When a bed material feed port is further provided in the reaction zone, the radioactive waste treatment system satisfies one or more of the following conditions: (r) The acute angle formed between the bed material feed port and the axis of the reaction zone is 30°-60°; (s) The bed material feed port and the waste feed port are on the same horizontal line; (t) The bed material feed port, the waste feed port and the axis of the reaction zone form an angle of 180°.

6. The radioactive waste treatment system according to claim 1, characterized in that, The alkali-washing quench chamber includes an alkali washing liquid inlet provided at the upper end of the alkali-washing quench chamber and an alkali washing liquid outlet provided at the lower end of the alkali-washing quench chamber. The alkali washing liquid inlet and the alkali washing liquid outlet are connected through a pipeline provided outside the thermal oxidation furnace, so as to form an external circulation loop of the alkali washing liquid; Among them, preferably, a circulation pump, a washing liquid cooler and a washing liquid filter are further provided on the external circulation loop, and the alkali washing liquid outlet, the circulation pump, the washing liquid cooler, the washing liquid filter and the alkali washing liquid inlet are connected in sequence; Among them, an on-line pH meter and a salt solution concentration meter are preferably further provided on the external circulation loop; Among them, a liquid sampling port is preferably provided at the outlet of the circulation pump.

7. A method for treating radioactive waste, characterized in that, The method for treating radioactive waste adopts the radioactive waste treatment system according to any one of claims 1-6, and includes the following steps: S1. Respectively pass the radioactive solid waste and radioactive liquid waste through the solid waste feeding unit and the liquid waste feeding unit and introduce them into the reaction zone through the waste feed port, and then carry out a reforming reaction to form a first solid waste and a mixed gas; the mixed gas is cooled in the cooling zone and discharged from the outlet of the cooling zone to the oxidation chamber; the temperature of the reforming reaction is 500-800 °C, and the pressure of the reforming reaction is -5 to -1 kPa; S2. The mixed gas is introduced into the oxidation chamber for an oxidation reaction to form flue gas. The flue gas is introduced into the alkali scrubbing and quenching chamber for washing to form tail gas and alkali scrubbing liquid. The tail gas is introduced into the tail gas treatment module; the pressure of the oxidation reaction is -3.5 to -5.5 kPa.

8. The method for treating radioactive waste according to claim 7, characterized in that, The radiation dose rate of the radioactive waste is less than 10 mSv / h, preferably less than 2 mSv / h; and / or, the radioactive solid waste contains 20%-40% free water; And / or, the radioactive solid waste includes waste resin, and the waste resin preferably includes anion exchange resin and / or cation exchange resin. The chemical formula of the anion exchange resin is C 25 H 25 S3O9, and the chemical formula of the cation exchange resin is C 34 H 52 N3O3; wherein, the types of radioactive elements contained in the waste resin are, for example, cesium, strontium, and cobalt; And / or, the radioactive liquid waste includes organic waste liquid and / or chemical waste liquid; wherein, the organic waste liquid preferably includes waste oil and / or waste organic solvent; wherein, the waste oil is, for example, waste kerosene; wherein, the waste organic solvent is, for example, waste tributyl phosphate, and the molecular formula of tributyl phosphate is C 12 H 27 O4P; wherein, the chemical waste liquid preferably includes nitrate waste liquid containing sodium ions; and / or, the feeding rate of the radioactive liquid waste is 10 L / h; and / or, the types of radioactive elements contained in the radioactive liquid waste are cesium, strontium, and cobalt; and / or, after the radioactive solid waste is evaporated and dried in a low-temperature evaporation dryer, it is transported to the waste feeding port through a screw feeder; wherein, the temperature of the evaporation and drying is preferably 100-150 °C, more preferably 120-150 °C; wherein, the effective loading capacity of the low-temperature evaporation dryer is preferably 100 L; wherein, after the evaporation and drying, the water content of the radioactive solid waste is preferably less than 6%; and / or, after the radioactive liquid waste is mixed with a raw material additive, it is introduced into the reaction zone; wherein, the raw material additive is preferably aluminum hydroxide and iron hydroxide; wherein, the mass ratio of the radioactive liquid waste to the raw material additive is preferably 10:

1.

9. The method for treating radioactive waste according to claim 7, characterized in that, In step S1, the temperature of the mixed gas discharged from the outlet of the cooling zone is lower than 600 °C; and / or, in step S1, the mixed gas is filtered through a high-temperature filter and then discharged to the oxidation chamber, so that solid particles with a particle size greater than 1 μm in the mixed gas are filtered and form a second solid waste; wherein, the temperature of the filtration is preferably 200-600 °C, such as 550 °C; wherein, the pressure of the filtration is preferably -2.5 to -4 kPa, such as -3.5 kPa; and / or, in step S1, an inert bed material and / or a reforming additive are also introduced into the reaction zone; wherein, the inert bed material is preferably silica and / or alumina; wherein, the shape of the alumina is preferably spherical, and the diameter of the alumina is preferably 0.5 mm; wherein, the reforming additive is preferably a metal compound, more preferably a metal oxide and / or a metal hydroxide, such as one or more of iron hydroxide, aluminum hydroxide, and kaolin; wherein, the kaolin is preferably kaolin containing a silicon-aluminum compound; and / or, in step S1, the temperature of the reforming reaction is 600-800 °C, preferably 650-750 °C, such as 700 °C; and / or, in step S1, when the radioactive solid waste is waste resin, the temperature of the reforming reaction is 725-750 °C; and / or, in step S1, when the radioactive liquid waste is organic waste liquid, the temperature of the reforming reaction is 500-700 °C; and / or, in step S1, when the radioactive liquid waste is chemical waste liquid, the temperature of the reforming reaction is 700-750 °C; and / or, in step S1, the gas outlet volume of the mixed gas is 18 Nm 3 / h; And / or, in step S1, the heating method of the reforming reactor is electric heating; And / or, the mixed gas includes nitrogen, hydrogen, carbon monoxide and methane.

10. The method for treating radioactive waste according to claim 7, characterized in that, Natural gas and air are also introduced in step S2 to fully oxidize and burn the mixed gas; And / or, the flue gas includes nitrogen, carbon dioxide and water vapor; And / or, the heating method of the oxidation chamber is electric heating; And / or, the temperature of the oxidation reaction is above 850 °C, preferably 1100 - 2000 °C; And / or, the time of the oxidation reaction is above 2 s, preferably 5 - 10 s; And / or, the temperature of the tail gas is below 85 °C, for example 70 - 85 °C; And / or, the volume fraction of oxygen in the tail gas is greater than 3%; And / or, the temperature of the washing is 55 - 60 °C; And / or, the washing liquid used for washing is sodium hydroxide solution, and the volume fraction of the sodium hydroxide solution is 0.5% - 10%; And / or, the alkali washing liquid is cooled through an external circulation loop and then recycled; wherein, the temperature of the alkali washing liquid after being cooled through the external circulation loop is preferably 50 - 65 °C; And / or, the temperature of the outer surface of the thermal oxidation furnace is lower than 80 °C; And / or, the tail gas is discharged to the atmosphere by a tail gas exhaust fan after demisting or connected to other exhaust systems and then discharged to the atmosphere; wherein, the inlet pressure of the tail gas exhaust fan is preferably -6.5 to -9 kPa; And / or, the content of nitrogen oxides in the tail gas does not exceed 100 mg / Nm 3 ; and / or, the content of solid particulate matter in the tail gas does not exceed 20 mg / Nm 3 .

Images