Plasma treatment device and method for radioactive waste

Abstract

The invention discloses a plasma treatment device and method for radioactive waste, and relates to the technical field of radioactive waste treatment device.The device comprises a plasma furnace body and a secondary combustion chamber which communicate with each other, and the rear end of a smoke outlet of the secondary combustion chamber is sequentially connected with a denitration device, a heat exchanger, a quench tower, a bag-type dust collector, a first-stage washing tower and a second-stage washing tower; the rear end of the secondary washing tower is connected with a low-temperature cryogenic removal system; the low-temperature cryogenic removal system comprises a flue gas cooler, a gas-liquid separator, an adsorber, an electric heater and an induced draft fan which are communicated with one another, and the flue gas cooler is communicated with the secondary washing tower; the adsorbers comprise the first adsorber and the second adsorber which are connected in parallel, the first adsorber and the second adsorber are both connected with remelting pipes, each remelting pipe is provided with two branch pipes, and the two branch pipes are connected with an annular air inlet of the plasma furnace body and an annular air inlet of the secondary combustion chamber respectively. And the near-zero emission of the flue gas finally exhausted by the chimney is ensured, so that the radioactive emission reaches the standard.

Description

Technical Field

[0001] The present invention relates to the technical field of radioactive waste treatment devices, and in particular to a plasma treatment device and a treatment method for radioactive waste. Background Art

[0002] With the continuous development of nuclear power, the total amount of radioactive waste generated by the operation and decommissioning of nuclear power plants will continue to increase in the future. The research and development of high-volume reduction and volume reduction treatment technologies for nuclear waste has become one of the main driving forces and challenges for nuclear safety. Compared with traditional treatment technologies, plasma incineration volume reduction and solidification technology has the advantages of wide application range, fast reaction speed, low secondary pollution, small tail gas volume and compact equipment. It can realize the decomposition and gasification combustion of radioactive waste, high-temperature melting of inorganic waste and solidification of radioactive nuclides in one system, greatly reducing the volume of waste and obtaining a stable final waste body.

[0003] However, due to the high temperature and high enthalpy characteristics of plasma itself, the nitrogen oxides produced in the process of treating radioactive waste are very high (2000-4000 mg / m 3 ), so it will have a certain impact on environmental emissions.

[0004] In addition, the radioactive waste being treated contains a large amount of volatile radioactive nuclides, including Cs-137, I-131, etc. After these nuclides enter the furnace during the pre-treatment process, they will quickly evaporate into the flue gas during the pyrolysis and gasification process. The total amount of radioactive nuclides in the flue gas finally discharged from the chimney is subject to relevant requirements and must not exceed the standard. Therefore, it is necessary to adsorb the nuclides in the flue gas to control the total amount. Summary of the invention

[0005] Based on the problem of high nitrogen oxides and radioactive substances in flue gas emissions pointed out in the background technology, the purpose of the present invention is to provide a plasma treatment device and method for radioactive waste, adding a low-temperature deep-cold removal system to the tail gas treatment system to adsorb high-concentration NO x After that, it returns to the first and second combustion chambers for reduction treatment, thus ensuring that the flue gas discharged from the chimney can reach near-zero emission, solving the problem of high nitrogen oxides and failure to achieve near-zero emission in the past. At the same time, the selection of suitable adsorption materials can strongly adsorb radionuclides, reduce the total radiation dose in the flue gas, and thus make the radioactive emission meet the standard.

[0006] The present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present application provides a plasma treatment device for radioactive waste, comprising a plasma furnace and a secondary combustion chamber which are interconnected, wherein the rear end of the smoke exhaust port of the secondary combustion chamber is sequentially connected with a denitration device, a heat exchanger, a quenching tower, a bag filter, a primary washing tower, and a secondary washing tower, wherein the rear end of the secondary washing tower is connected with a low-temperature deep-cold removal system;

[0008] The low-temperature deep-cold removal system includes a flue gas cooler, a gas-liquid separator, an adsorber, an electric heater, and an induced draft fan which are interconnected, and the flue gas cooler is connected to the secondary scrubbing tower;

[0009] The adsorber includes a No. 1 adsorber and a No. 2 adsorber connected in parallel, and the No. 1 adsorber and the No. 2 adsorber are both connected with a return furnace pipe, and the return furnace pipe has two branch pipes, and the two branch pipes are respectively connected to the annular air inlet of the plasma furnace body and the annular air inlet of the second combustion chamber.

[0010] Furthermore, the plasma furnace includes a vertical section and a horizontal section, arranged in an L shape; a No. 1 plasma torch is arranged directly above the horizontal section of the plasma furnace; a glass liquid overflow port is arranged above the side of the horizontal section of the plasma furnace, and a metal liquid drain port is arranged below.

[0011] Furthermore, after the material enters the vertical section of the plasma furnace from the feed port of the plasma furnace, a gasification and pyrolysis layer is formed, and an annular air inlet is arranged on the plasma furnace at the gasification and pyrolysis layer.

[0012] Furthermore, the plasma furnace uses high temperature resistant, corrosion resistant and fire resistant materials as the internal working layer.

[0013] Furthermore, an inclined section is provided on the right side of the furnace bottom of the plasma furnace.

[0014] Furthermore, a No. 1 plasma torch is arranged on the top of the secondary combustion chamber.

[0015] Furthermore, the bag dust collector adopts a redundant configuration, including a No. 1 bag dust collector and a No. 2 bag dust collector.

[0016] Furthermore, the plasma furnace body and the secondary combustion chamber are provided with a plurality of annular air inlets.

[0017] In a second aspect, the present application provides a method for treating radioactive waste, comprising the following steps:

[0018] The radioactive waste is added into the plasma furnace to form a gasification and pyrolysis layer, in which the organic matter is gasified and pyrolyzed into synthesis gas, which is then discharged from the plasma furnace exhaust pipe into the secondary combustion chamber;

[0019] After the flue gas is burned in the secondary combustion chamber, it is discharged from the secondary combustion chamber and enters the denitration device for denitration. After denitration, the flue gas enters the heat exchanger for cooling, and then enters the quenching tower for cooling. After quenching, the flue gas enters the bag filter for dust removal, and then enters the secondary washing tower, where alkali solution is sprayed for deacidification.

[0020] The flue gas after washing enters the cooler of the low-temperature deep-cold removal system for cooling, and then enters the gas-liquid separator to separate the water vapor generated in the washing tower to ensure that dry flue gas is generated;

[0021] After gas-liquid separation, the gas enters the adsorber for adsorption treatment. The exhaust gas NO x The concentration was kept below 1mg / Nm 3 , SO 2 The concentration was kept below 3 mg / Nm 3 .

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) The plasma treatment device of the present invention adds a low-temperature deep-cold removal system to the tail gas treatment system to absorb high-concentration NO x After that, it returns to the plasma furnace and the secondary combustion chamber for reduction treatment, so as to ensure that the flue gas discharged from the chimney can reach near-zero emission, solving the problem of high nitrogen oxides and failure to achieve near-zero emission in the past. At the same time, the selection of suitable adsorption materials can strongly adsorb radionuclides, reduce the total radiation dose in the flue gas, and thus make the radioactive emission meet the standard.

[0024] (2) The low temperature deep cold removal system of the plasma treatment device of the present invention reduces the flue gas temperature to below 0°C, SO 2 The adsorption capacity increases exponentially, and the NO adsorption capacity grows exponentially. Low-temperature catalytic oxidation is the key mechanism to promote a substantial increase in the NO adsorption capacity. In this way, the high-concentration flue gas coming out of the plasma furnace can be recycled through the process of low-temperature adsorption-heating desorption-return to the furnace to reduce the final concentration of nitrogen oxides emitted from the chimney and solve some inherent problems of the plasma furnace.

[0025] (3) The low temperature and deep cold removal system of the present invention can treat SO 2 , HCl, HF and other pollutants can be removed simultaneously; in this way, the goal of "integrated removal" of pollutants can be achieved.

[0026] (4) The adsorption material in the present invention can strongly adsorb Cs-137, I-131, etc., reducing the total radiation dose in the flue gas, thereby ensuring that the radioactive emissions meet the standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0028] Figure 1 It is a schematic structural diagram of a plasma treatment device for radioactive waste in the present invention;

[0029] Figure 2 It is a schematic diagram of the structure of the plasma furnace in the present invention;

[0030] Figure 3 It is a structural schematic diagram of the secondary combustion chamber in the present invention;

[0031] Figure 4 It is a schematic diagram of the structure of the low-temperature deep-cold removal system of the present invention.

[0032] Reference numerals:

[0033] 1-plasma furnace, 2-feeding port, 3-refractory material, 4-plasma furnace exhaust pipe, 5-1-No. 1 plasma torch, 5-2-No. 1 plasma torch, 6-overflow outlet sealing chamber, 7-receiving hopper car, 8-1-right annular air inlet, 8-2-left annular air inlet, 9-gasification pyrolysis layer, 10-glass liquid layer, 11-metal liquid layer, 12-metal liquid emptying port, 13-glass liquid overflow port, 14-second combustion chamber ash discharge port, 15-second combustion chamber exhaust port, 16-1-No. 1 second combustion chamber horizontal annular air inlet, 1 6-2-Horizontal annular air inlet of No. 2 secondary combustion chamber, 17-secondary combustion chamber, 18-1-Middle annular air inlet of No. 1 secondary combustion chamber, 18-2-Middle annular air inlet of No. 2 secondary combustion chamber, 19-induced draft fan, 20-denitrification device, 21-heat exchanger, 22-quenching tower, 23-1-No. 1 bag dust collector, 23-2-No. 1 bag dust collector, 24-first-stage washing tower, 25-second-stage washing tower, 26-flue gas cooler, 27-gas-liquid separator, 28-1-No. 1 adsorber, 28-2-No. 2 adsorber, 29-electric heater. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0035] The following detailed description specifically discloses the implementation methods of the plasma treatment device and treatment method for radioactive waste of the present application with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0036] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range.

[0037] In addition, the terms "number one" and "number two" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "number one" and "number two" may explicitly or implicitly include at least one of the features.

[0038] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0039] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0040] Unless otherwise specified, the terms "include" and "comprising" mentioned in this application may be open-ended or closed-ended. For example, the terms "include" and "comprising" may mean that other substances not listed may also be included or only the listed substances may be included.

[0041] Example 1

[0042] like Figures 1 to 4 As shown, this embodiment provides a plasma treatment device for radioactive waste, including a plasma furnace 1 and a secondary combustion chamber 17 which are interconnected, and a denitrification device 20, a heat exchanger 21, a quenching tower 22, a bag filter, a primary washing tower 24, and a secondary washing tower 25 are sequentially connected to the rear end of the smoke exhaust port of the secondary combustion chamber 17, and a low-temperature deep-cold removal system is connected to the rear end of the secondary washing tower 25;

[0043] The low temperature deep cold removal system includes a flue gas cooler 26, a gas-liquid separator 27, an adsorber, an electric heater, and an induced draft fan 19 which are interconnected, and the flue gas cooler 26 is connected to a secondary scrubber 25;

[0044] The adsorber includes a No. 1 adsorber 28-1 and a No. 2 adsorber 28-2 connected in parallel. Both the No. 1 adsorber 28-1 and the No. 2 adsorber 28-2 are connected with a return furnace pipe. The return furnace pipe has two branch pipes, which are respectively connected to the annular air inlet of the plasma furnace body and the annular air inlet of the second combustion chamber 17.

[0045] Specifically, the plasma furnace 1 includes a vertical section (gasification section) and a horizontal section (melting section), which are arranged in an L shape; a No. 1 plasma torch 5-1 is arranged directly above the horizontal section of the plasma furnace 1; a glass liquid overflow port 13 is arranged above the side of the horizontal section of the plasma furnace 1, and a metal liquid drain port 12 is arranged below.

[0046] A plasma torch No. 1 5-1 is arranged above the melting section. During the operation of the plasma torch, a high-power DC power supply is required for power supply, and cooling water is passed through the plasma torch for cooling. The plasma torch uses nitrogen as the carrier wind. The arc generated by the plasma torch ionizes the nitrogen to form a high-temperature jet (adjustable at 1500-2000°C), which directly heats and melts the inorganic matter coming from the vertical section, and then forms a glass liquid layer 10.

[0047] Among them, the No. 1 plasma torch 5-1 can adopt a high current and low voltage operation mode, such as 150kw output power, 350A, 430V, and a high-temperature jet length of about 300mm. The purpose of this is to use a shorter arc length (smaller nitrogen consumption), increase the outlet temperature of the plasma jet, provide high-temperature energy to the treated material (slag and ash) and make it easier to melt into glass. At the same time, the active radicals (H + 、N + Charged particles (such as charged particles) also enter the vertical gasification section from the melting section of the plasma furnace 1 and enter the gasification pyrolysis layer 9. These active groups have a greater activation catalytic effect and have a greater promoting effect on the pyrolysis reaction, which can accelerate the decomposition of organic matter in radioactive waste and the combustion of carbon; at the same time, the organic matter is pyrolyzed and gasified in the oxidation area inside the gasification pyrolysis layer 9 to become synthesis gas (CO+H 2 ), in the process of escaping upward from the oxidation area (1200°C), this part of the synthesis gas also has to pass through the drying and pyrolysis areas. Since the synthesis gas itself carries a certain reducing atmosphere, the middle and upper part of the gasification pyrolysis layer 9 belongs to the reducing area.

[0048] In the glass liquid layer 10, the slag is melted into liquid by the high temperature generated by the No. 1 plasma torch 5-1, wherein components such as silicon and calcium form the glass liquid layer 10 here, and some metals such as iron, copper, and silver have a relatively high density and are deposited at the bottom to form a metal liquid layer 11. This is the stratification phenomenon inside the molten pool.

[0049] Among them, a glass liquid overflow port 13 is arranged on the left side of the molten pool, which is usually blocked and sealed by a plug. When the glass liquid layer 10 formed by the melting of the slag in the molten pool reaches a certain height and the molten pool liquid level exceeds the overflow port by a large amount, the plug is moved from the left side by the actuator to move it out of the overflow port. At this time, the overflow port is opened, and the glass liquid flows out from the glass liquid overflow port 13. This structure solves the problem that the discharge port of the same type of furnace is easily blocked, resulting in poor discharge.

[0050] The slag usually contains a small amount of metal (such as iron, copper, etc.). This part of the metal liquid cannot form a glass body and usually accumulates at the bottom of the molten pool. After waiting for a certain period of time (such as about a month), the metal liquid drain port 12 is opened to drain the metal liquid at the bottom.

[0051] After the vitreous liquid flows out from the glass liquid overflow port 13, it enters the overflow outlet sealing chamber 6; the overflow outlet sealing chamber 6 is a structure of an outer steel shell and an inner lining of refractory material, which can not only prevent the high temperature coming out of the overflow port, but also prevent the leakage of radioactive substances; a water-cooled gate valve is arranged at the bottom of the overflow outlet sealing chamber 6, and when the overflow port is not discharging material, the water-cooled gate valve is in a closed state; before the overflow port is discharged, the water-cooled gate valve is opened, and the lower part is prepared for the receiving hopper car 7, and a water pool is arranged at the bottom of the receiving hopper car 7. When the overflow port is opened, the glass liquid flows into the water pool at the bottom of the hopper car, and then undergoes a water quenching process and then cools to form a glass body.

[0052] After a certain period of time, the glass liquid at the overflow port has flowed out. At this time, the water-cooled gate valve is closed, and the plug is moved by the actuator to block the overflow port again. At the same time, the upper part of the receiving hopper car 7 performs an automatic sealing operation to ensure the airtightness of the hopper car. After completing the above operations, the overflow port, the outlet of the water-cooled gate valve, and the upper part of the receiving hopper car 7 are all in a sealed state to ensure that there is no radioactive leakage. There is a pulley at the bottom of the receiving hopper car 7, which is automatically transferred to the finished product warehouse next to it through the track and temporarily stored in accordance with radiation protection requirements.

[0053] Specifically, after the material enters the vertical section of the plasma furnace 1 from the feed port 2 of the plasma furnace 1 , a gasification and pyrolysis layer 9 is formed. An annular air inlet is provided on the plasma furnace 1 at the gasification and pyrolysis layer 9 .

[0054] Among them, the gasification pyrolysis layer 9 forms a drying layer, a pyrolysis layer, an oxidation layer, a slag layer and other cross-sections from top to bottom in the vertical direction, and its temperature ranges from 400°C to 1200°C from the upper surface to the high temperature section.

[0055] The gasification pyrolysis layer 9 is provided with a right annular air inlet 8-1 and a left annular air inlet 8-2 (only two air inlets are marked in the figure, and in actual engineering applications, 4 to 6 annular air inlets can be provided as needed to supplement oxygen to the gasification pyrolysis layer 9). In the gasification pyrolysis layer 9, most of the organic matter is gasified and pyrolyzed into synthesis gas (CO+H 2 ), the temperature is about 400℃~600℃, and then this part of gas is discharged from the exhaust pipe 4 of the plasma furnace 1 to the secondary combustion chamber 17.

[0056] Among them, the inorganic matter (bottom slag and ash) remaining in the gasification and pyrolysis layer 9 falls to the bottom of the vertical section and then enters the horizontal melting section of the plasma furnace 1.

[0057] Specifically, the plasma furnace 1 uses a high temperature resistant, corrosion resistant, refractory material 3 as an internal working layer.

[0058] Among them, the refractory material 3 can be selected from silicon nitride, silicon carbide, zirconium chromium corundum and other related materials according to different positions, and the surface temperature of the furnace shell is controlled at about 80°C to 100°C.

[0059] Specifically, an inclined section is provided on the right side of the furnace bottom of the plasma furnace 1 .

[0060] This structure makes it easier for the glass liquid on the right to flow to the left under the action of gravity, making it easier to discharge.

[0061] Specifically, a No. 1 plasma torch 5 - 2 is disposed on the top of the second combustion chamber 17 .

[0062] A No. 1 plasma torch 5-2 is arranged above the top of the second combustion chamber 17; during the operation of the plasma torch, a high-power DC power supply is also used for power supply, and cooling water is passed through to cool it. Here, the plasma torch uses nitrogen as the carrier wind; the arc generated by the plasma torch ionizes the nitrogen to form a high-temperature jet (adjustable at 1500-2000°C), which directly burns the synthesis gas from the plasma furnace 1 and burns out its combustible components. During use, due to its high temperature and high enthalpy characteristics, the plasma technology produces a high NOx (about 2000-4000 mg / m3) under the condition of inert gas as a carrier.

[0063] No. 1 plasma torch 5-2 Here, we can adopt high voltage and low current operation mode, such as 150kw output power, 250A, 600V, and high-temperature jet length of about 500mm. The purpose is to adopt a longer arc length (larger nitrogen consumption) to increase the concentration and coverage of active groups generated by nitrogen plasma, thereby improving the high-temperature combustion effect.

[0064] Specifically, the bag dust collector adopts a redundant configuration, including a No. 1 bag dust collector 23-1 and a No. 2 bag dust collector 23-2.

[0065] Specifically, the plasma furnace body and the secondary combustion chamber 17 are provided with a plurality of annular air inlets.

[0066] Among them, a vertical hole is opened in the smoke exhaust pipe 4 near the secondary combustion chamber 17 pipe, and a horizontal annular air inlet 16-1 for the secondary combustion chamber No. 1 and a horizontal annular air inlet 16-2 for the secondary combustion chamber No. 2 are provided. The purpose is to supply air and oxygen to the upper part of the secondary combustion chamber 17 to promote the combustion of the synthesis gas inside the secondary combustion chamber 17.

[0067] Among them, we set the middle annular air inlet 18-1 of the No. 1 second combustion chamber and the middle annular air inlet 18-2 of the No. 2 second combustion chamber in the middle of the second combustion chamber 17. The air inlet is opened horizontally in the middle of the second combustion chamber 17 to increase the oxygen required for the combustion of the combustible components; similarly, only two air inlets are marked on the figure, and 4 to 6 annular air inlets can be set as needed in actual engineering use to improve the treatment effect; from the middle air inlet position to the outlet of the second combustion chamber 17, it belongs to the burnout area in the graded air distribution. This part has a low air volume and low oxygen content. In addition, there is unburned synthetic gas from the middle and upper parts, so this area belongs to a reducing atmosphere. As mentioned above, we have implemented a two-stage air distribution scheme in the secondary combustion chamber 17, that is, a first-stage air inlet is set at the inlet of the secondary combustion chamber 17 to form a main combustion zone of the synthesis gas in the upper part of the secondary combustion chamber 17; a second-stage air inlet is set in the middle part of the secondary combustion chamber 17 to form a burnout zone of the combustible atmosphere in the lower middle part of the secondary combustion chamber 17 to ensure that the combustible components are burned out in the secondary combustion chamber 17. At the same time, the strategy of graded air distribution can effectively reduce the concentration of nitrogen oxides and ensure that pollutant emissions meet the standards; graded air distribution and low-nitrogen combustion is a mature technology and will not be elaborated in this article.

[0068] Example 2

[0069] Based on Example 1, this example provides a method for treating radioactive waste, using the plasma treatment device in Example 1 to treat radioactive waste, and the method is carried out according to the following steps:

[0070] S1. First, the crushed and mixed radioactive waste (including waste resin, PE, clothing, etc.) enters the plasma furnace 1 from the feed port 2 at the top of the plasma furnace 1 through the feeding device.

[0071] S2. After the material falls from the feed port 2 into the vertical section of the plasma furnace 1, a gasification pyrolysis layer 9 is formed. From top to bottom, the layer forms a drying layer, a pyrolysis layer, an oxidation layer, a slag layer and other cross-sections in the vertical direction. The temperature varies from 400°C to 1200°C from the upper surface to the high temperature section.

[0072] S3, the organic matter in the plasma furnace 1 is gasified and decomposed to form synthesis gas (CO+H 2 ), enters the secondary combustion chamber 17 through the exhaust pipe 4 of the plasma furnace 1, and the flue gas that is completely burned in the secondary combustion chamber 17 is discharged from the secondary combustion chamber exhaust port 15 to the downstream exhaust gas treatment system; a small amount of ash generated in the process is regularly discharged through the secondary combustion chamber ash discharge port 14 at the bottom.

[0073] S3. After the flue gas comes out of the secondary combustion chamber 17 (1100°C), it first passes through the denitration device, where denitration is carried out in the furnace, that is, ammonia water is sprayed from the inside to react with nitrogen oxides to produce nitrogen and water.

[0074] S4, the flue gas enters the heat exchanger 21 for cooling from 1100°C to 600°C, and then enters the quenching tower 22, where the high-temperature flue gas is cooled to 175°C in a relatively short time, avoiding the secondary production area of ​​dioxins.

[0075] S5. After rapid cooling, the flue gas then enters the bag filter for dust removal. Redundancy configuration is considered here, that is, bag filter No. 1 23-1 and bag filter No. 23-2 are configured; then the flue gas enters the secondary washing and is sprayed with sodium hydroxide solution for deacidification.

[0076] S6. After washing, the flue gas enters the low-temperature deep-cold removal system. When the flue gas temperature drops below 0°C, SO 2 The adsorption capacity increases exponentially, and the NO adsorption capacity increases exponentially. Therefore, low-temperature catalytic oxidation is the key mechanism to promote the substantial increase in NO adsorption capacity. Therefore, after cooling the flue gas, high-performance low-temperature adsorption materials can be used to adsorb SO 2 and NO x Carry out low temperature adsorption removal.

[0077] S7. After washing, the flue gas enters the flue gas cooler 26, where a refrigerator is used for cooling the flue gas to a desired temperature (about -20°C to 0°C, depending on the removal situation) using a low-temperature refrigerant.

[0078] S8. After cooling, the flue gas enters the gas-liquid separator 27 to separate the water vapor generated in the scrubbing tower to ensure that dry flue gas is generated.

[0079] S9, after gas-liquid separation, enters the adsorber, where the adsorber adopts an alternating working mechanism, that is, the first adsorber 28-1 starts working, and the second adsorber 28-2 is not put into operation at this time. The adsorption material (alumina or copper particles) inside the first adsorber 28-1 is used to absorb SO in the flue gas. 2 and NO x Low temperature adsorption removal, most of the SO in the flue gas 2 and NO xAfter all are removed, after a period of adsorption, the adsorption capacity of adsorber No. 1 28-1 reaches saturation state, and then the switching valve can be used to switch to adsorber No. 2 28-2. At this time, adsorber No. 1 28-1 starts working and adsorber No. 2 28-2 stops working. x The concentration was kept below 1mg / Nm 3 , SO 2 The concentration was kept below 3 mg / Nm 3 ; Basically meet the national near-zero emission requirements.

[0080] S10, during the adsorption operation of the No. 1 adsorber 28-1, the No. 1 adsorber 28-1 is heated, regenerated and NO x The treatment process is as follows: a separate blower is used to supply air to the adsorber No. 1 28-1, and electric heating is used in the process. After the heated air passes through the adsorber No. 1 28-1 and is heated, the SO2 originally adsorbed by the adsorbent material is 2 and NO x , and then enters the hot air after being heated. As the temperature rises and the time increases, the SO contained in adsorber No. 1 28-1 itself 2 and NO x The amount is gradually decreasing, and most of it enters the hot air. At this time, the first adsorber 28-1 is ready for use after regeneration, waiting for the next time the first adsorber 28-1 and the second adsorber 28-2 are switched for use.

[0081] S11, absorbed a lot of SO 2 and NO x The hot air is operated in the circuit in the following two ways:

[0082] Loop operation route 1: Enter the horizontal annular air inlet of the secondary combustion chamber 17, enter the secondary combustion chamber 17 furnace from the entrance section of the secondary combustion chamber 17, and implement a two-level air distribution scheme in the secondary combustion chamber 17 as described above, that is, a main combustion zone with a primary air inlet is set at the inlet of the secondary combustion chamber 17 and a burnout zone formed by a secondary air inlet is set in the middle of the secondary combustion chamber 17; after the hot air returned to the furnace enters the secondary combustion chamber 17 furnace, it is partially reduced after passing through the reduction area of ​​the burnout zone.

[0083] Recycling operation path 2: Entering the annular air inlet of the vertical section of the plasma furnace body, this part belongs to the gasification pyrolysis layer 9. As described above, since the synthesis gas itself has a certain reducing atmosphere, the middle and upper parts of the gasification pyrolysis layer 9 belong to the reducing area. After entering the plasma furnace body, the recycled hot air passes through the middle and upper reducing area of ​​the gasification pyrolysis layer 9 and enters the secondary combustion chamber 17 and the tail gas treatment link.

[0084] S12. The hot air returned to the furnace is mixed with the hot flue gas originally generated in the furnace and then enters the exhaust gas treatment link. Therefore, SO 2 and NO x In this process, it is adsorbed at low temperature, desorbed by heating, returned to the furnace, and then enters the exhaust system, forming a reciprocating cycle.

[0085] S13. After low-temperature adsorption in the adsorber, the flue gas reaching near-zero emission is heated by the electric heater 29 and then passes through the induced draft fan 19 to meet emission standards.

[0086] Among them, in the low-temperature adsorption process, selecting a suitable adsorption material (such as zeolite, etc.) can strongly adsorb Cs-137, I-131, etc., reduce the total radiation dose in the flue gas, and thus make the radioactive emission meet the standard. The adsorption material that has been adsorbed to the critical point for a long time will eventually enter the plasma furnace 1 again for the glass solidification process after relevant processing steps (crushing, compatibility, etc.), or directly enter the cement solidification line for solidification treatment.

[0087] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A plasma treatment device for radioactive waste, comprising a plasma furnace (1) and a secondary combustion chamber (17) connected to each other, characterized in that: The rear end of the smoke outlet of the secondary combustion chamber (17) is connected in sequence to a denitration device (20), a heat exchanger (21), a quenching tower (22), a bag filter, a primary washing tower (24), and a secondary washing tower (25), and the rear end of the secondary washing tower (25) is connected to a low-temperature deep-cold removal system; The low-temperature deep-cold removal system comprises a flue gas cooler (26), a gas-liquid separator (27), an adsorber, an electric heater (29), and an induced draft fan (19) which are interconnected, and the flue gas cooler (26) is connected to the secondary scrubbing tower (25); The adsorber comprises a No. 1 adsorber (28-1) and a No. 2 adsorber (28-2) connected in parallel, and the No. 1 adsorber (28-1) and the No. 2 adsorber (28-2) are both connected to a return furnace pipe, and the return furnace pipe has two branch pipes, and the two branch pipes are respectively connected to the annular air inlet of the plasma furnace (1) and the annular air inlet of the second combustion chamber (17).

2. The plasma treatment device for radioactive waste according to claim 1, characterized in that: The plasma furnace (1) comprises a vertical section and a horizontal section, arranged in an L shape; a No. 1 plasma torch (5-1) is arranged directly above the horizontal section of the plasma furnace (1); a glass liquid overflow port (13) is arranged above the side of the horizontal section of the plasma furnace (1), and a metal liquid drain port (12) is arranged below.

3. The plasma treatment device for radioactive waste according to claim 2, characterized in that: After the material enters the vertical section of the plasma furnace (1) from the feed port (2) of the plasma furnace (1), a gasification and pyrolysis layer (9) is formed. An annular air inlet is provided on the plasma furnace (1) at the gasification and pyrolysis layer (9).

4. The plasma treatment device for radioactive waste according to claim 1, characterized in that: The plasma furnace (1) uses high temperature resistant, corrosion resistant and fire resistant materials (3) as the internal working layer.

5. The plasma treatment device for radioactive waste according to claim 1, characterized in that: The right side of the furnace bottom of the plasma furnace (1) is provided with an inclined section.

6. The plasma treatment device for radioactive waste according to claim 1, characterized in that: A No. 1 plasma torch (5-2) is arranged on the top of the secondary combustion chamber (17).

7. The plasma treatment device for radioactive waste according to claim 1, characterized in that: The bag dust collector adopts a redundant configuration, including a No. 1 bag dust collector (23-1) and a No. 2 bag dust collector (23-2).

8. The plasma treatment device for radioactive waste according to claim 1, characterized in that: The plasma furnace (1) is provided with a plurality of annular air inlets and the secondary combustion chamber (17) has a plurality of annular air inlets.

9. A method for treating radioactive waste, characterized in that: The process is carried out using the plasma processing apparatus according to any one of claims 1 to 8.

10. A method for treating radioactive waste according to claim 9, characterized in that: The following steps are involved: Radioactive waste is added into a plasma furnace (1) to form a gasification and pyrolysis layer (9), in which organic matter is gasified and pyrolyzed into synthesis gas, and then the gas is discharged from a plasma furnace exhaust pipe (4) into a secondary combustion chamber (17); After the flue gas is burned in the secondary combustion chamber (17), it is discharged from the secondary combustion chamber (17) and enters the denitration device (20) for denitration. The flue gas after denitration enters the heat exchanger (21) for cooling, and then enters the quenching tower (22) for cooling. The flue gas after quenching and cooling then enters the bag filter for dust removal, and then enters the secondary washing tower (25) to be sprayed with alkali solution for deacidification. The flue gas after washing enters the cooler of the low temperature deep cold removal system for cooling, and after cooling enters the gas-liquid separator (27) to separate the water vapor generated in the washing tower to ensure that dry flue gas is generated; After gas-liquid separation, the gas enters the adsorber for adsorption treatment. The exhaust gas NO x The concentration was kept below 1mg / Nm 3 , SO2 concentration is kept below 3mg / Nm 3 .

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