Plasma treatment device and method for removing nitrogen oxides and adsorbing radionuclides

Abstract

The invention relates to the field of radioactive waste treatment, in particular to a plasma treatment device and method for removing nitrogen oxides and adsorbing radionuclides. According to the device, a plasma furnace is connected with a secondary combustion chamber through a smoke exhaust pipe; a denitration furnace, a heat exchanger, a quench tower, a dust removal cloth bag, a washing tower, a flue gas cooler, a gas-liquid separator and an adsorber are connected behind the secondary combustion chamber; at least two adsorbers are arranged in parallel; one outlet of each adsorber is connected to the electric heater and the induced draft fan; and the other outlet of the adsorber is respectively connected to the plasma furnace and the smoke exhaust pipe. The method comprises the steps that the radioactive waste is incinerated; carrying out melting treatment on inorganic matters generated by incineration treatment; gas generated by incineration treatment enters a secondary combustion chamber to be subjected to secondary plasma incineration treatment; the generated flue gas is subjected to denitration treatment, heat exchange cooling treatment, extremely cold cooling treatment, dust removal treatment and at least two-stage washing treatment; and carrying out low-temperature cryogenic removal treatment, and discharging after heating. According to the invention, zero emission of nitrogen oxides is realized.

Description

Technical Field

[0001] The present invention relates to the field of radioactive waste treatment, and in particular to a plasma treatment device and method for removing nitrogen oxides and adsorbing radioactive nuclides. Background Art

[0002] With the continuous development of nuclear power in my country, the total amount of radioactive waste generated by the operation and decommissioning of future nuclear power plants will continue to increase. The development of high-volume and volume reduction treatment technologies for nuclear waste has become a major driver and challenge for nuclear safety. Compared to traditional treatment technologies, plasma incineration volume reduction and solidification technology offers advantages such as wide applicability, rapid reaction speed, minimal secondary pollution, low tail gas volume, and compact equipment. It can achieve the decomposition and gasification combustion of radioactive waste, high-temperature melting of inorganic waste, and solidification of radionuclides in a single system, significantly reducing waste volume and achieving a stable final waste form.

[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. The nitrogen oxide concentration measured at the outlet of the secondary combustion chamber is 2000~4000mg / m 3 , and its emissions pose potential harm to the environment.

[0004] Furthermore, the radioactive waste being treated contains a large number of volatile radionuclides, including Cs-137 and I-131. These nuclides, after entering the furnace during the pre-treatment process, are quickly volatilized into the flue gas during the pyrolysis and gasification process, which not only affects environmental quality but may also pose a threat to human health.

[0005] Therefore, there are relevant requirements for the total amount of radioactive nuclides in the flue gas finally emitted from the chimney, and it must not exceed the standard. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a plasma treatment device and method for removing nitrogen oxides and adsorbing radioactive nuclides, which can effectively remove nitrogen oxides, strongly adsorb radioactive nuclides, etc., reduce the total radiation dose in the flue gas, and thus ensure that radioactive emissions meet the standards.

[0007] The present invention provides a plasma treatment device for removing nitrogen oxides and adsorbing radioactive nuclides, comprising:

[0008] The L-shaped plasma furnace is connected to the secondary combustion chamber through a smoke exhaust pipe;

[0009] The top of the secondary combustion chamber is provided with a second plasma torch, and the upper part of the side wall is connected to the smoke exhaust pipe.

[0010] The second combustion chamber is connected in sequence to the desulfurization furnace, heat exchanger, quenching tower, dust bag, scrubber, flue gas cooler, gas-liquid separator and adsorber;

[0011] At least two adsorbers are arranged in parallel.

[0012] One outlet of the adsorber is connected to an electric heater, and the electric heater is connected to an induced draft fan;

[0013] Another outlet of the adsorber is connected to the annular air inlet of the L-shaped plasma furnace and the annular air inlet of the secondary combustion chamber of the smoke exhaust pipe through pipelines.

[0014] In a specific embodiment of the present invention, the furnace body of the L-shaped plasma furnace is divided into a vertical section and a horizontal section.

[0015] The first plasma torch is installed on the left side of the horizontal section.

[0016] A plurality of annular air inlets are arranged on the side wall of the vertical section.

[0017] In a specific embodiment of the present invention, at least two annular air inlets are vertically provided on the side wall of the smoke exhaust pipe close to the secondary furnace.

[0018] In a specific embodiment of the present invention, there are at least two dust removal bags, which are arranged in parallel.

[0019] In a specific embodiment of the present invention, the adsorption material in the adsorber is aluminum oxide, copper particles, a mixture of aluminum oxide and zeolite, or a mixture of copper particles and zeolite.

[0020] The present invention provides a plasma treatment method for removing nitrogen oxides and adsorbing radioactive nuclides, comprising the following steps:

[0021] Step 1: Incinerate the crushed and mixed radioactive waste in a plasma furnace;

[0022] The inorganic matter produced by incineration is melted;

[0023] Step 2: The gas generated by the incineration process enters the secondary combustion chamber for a second plasma incineration process;

[0024] Step 3: The flue gas generated by the second plasma incineration treatment is subjected to denitrification treatment, heat exchange and cooling treatment, extreme cooling treatment, dust removal treatment and at least two-stage washing treatment;

[0025] Step 4: The washed flue gas is subjected to low-temperature cryogenic removal treatment;

[0026] Low temperature cryogenic removal treatment specifically includes:

[0027] Use low-temperature refrigerant to cool the scrubbed flue gas and then separate the water vapor from it.

[0028] The dry flue gas produced is subjected to adsorption treatment;

[0029] Step 5: The gas after low-temperature cryogenic removal treatment is heated and then discharged.

[0030] In a specific embodiment of the present invention, in step 1, the plasma torch adopts a high current and low voltage operation mode;

[0031] In step 2, the second plasma incineration treatment adopts a low current and high voltage operation mode.

[0032] In a specific embodiment of the present invention, in step 3, the heat exchange and cooling treatment is performed to cool the flue gas temperature from 1100° C. to 600° C.;

[0033] During the extreme cold cooling treatment, the high temperature gas is cooled to 150-200°C within 1-5 hours.

[0034] In a specific embodiment of the present invention, in step 4, the scrubbed flue gas is cooled to below 0°C using a low-temperature refrigerant.

[0035] In a specific embodiment of the present invention, in step 4, two adsorbers arranged in parallel are used for adsorption treatment.

[0036] The first adsorber and the second adsorber work alternately; when the first adsorber has been adsorbing for a period of time, the adsorption capacity reaches saturation, and the switching valve switches to the second adsorber, and the first adsorber stops working;

[0037] During the operation of the second adsorber, the first adsorber is heated and regenerated and NO x The SO2 and NO originally adsorbed by the adsorption material are recycled and disposed of. x , after heating up, it enters the hot air, and the hot air returns to the plasma incinerator used in step 1 or the secondary combustion chamber described in step 2;

[0038] After regeneration, the first adsorber is ready for use and is ready for the next switch between the two adsorbers.

[0039] Compared with the prior art, the plasma treatment device and method for removing nitrogen oxides and adsorbing radionuclides of the present invention have the following beneficial effects:

[0040] (1) The combination of two-stage plasma incineration technology and cryogenic nitrogen oxide removal technology effectively solves the nitrogen oxide emission problem during the plasma disposal process and significantly reduces the risk of radioactive nuclides volatilization. Specifically, the addition of a low-temperature cryogenic removal system can adsorb and remove high-concentration nitrogen oxides, significantly reducing emissions. At the same time, through the special design of the adsorption material, the system can not only treat nitrogen oxides, but also specifically reduce the emission of radioactive nuclides, thereby ensuring that the final discharged radioactive waste meets national safety standards;

[0041] (2) Through the reduction treatment of the plasma furnace and the secondary combustion chamber, the treatment effect of nitrogen oxides is further optimized to ensure that the final emissions can achieve near-zero emissions. This technical improvement not only improves the environmental performance of plasma treatment, but also enhances the protection of public health by reducing the risk of secondary pollution;

[0042] (3) The adsorption material is regenerated and can be incinerated and cryogenically removed again after the pollutants are removed, forming a recycling process, further reducing the radiation dose in the flue gas and achieving zero pollutant emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram showing the structure of a plasma treatment device for removing nitrogen oxides and adsorbing radionuclides;

[0044] In the figure, 1-L-type plasma furnace, 2-feed port, 3-refractory material layer, 4-exhaust pipe, 5-1-first plasma torch, 5-2-second 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-second combustion chamber upper side annular air inlet Inlet; 16-2-annular air inlet on the lower side of the secondary combustion chamber, 17-secondary combustion chamber, 18-1-annular air inlet on the left side of the secondary combustion chamber, 18-2-annular air inlet on the right side of the secondary combustion chamber, 19-denitrification furnace, 20-heat exchanger, 21-quenching tower, 22-1-first dust bag, 22-2-second dust bag, 23-first scrubber, 24-secondary scrubber, 25-flue gas cooler, 26-gas-liquid separator, 27-1-first adsorber, 27-2-second adsorber, 28-electric heater, 29 induced draft fan. DETAILED DESCRIPTION

[0045] In order to further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than for limiting the present invention.

[0046] Low-temperature cryogenic pollutant removal technology is a near-zero emission technology. The main principle is to reduce the flue gas temperature to below 0°C, the SO2 adsorption capacity increases exponentially, and the NO adsorption capacity increases exponentially. Low-temperature catalytic oxidation is the key mechanism to promote the substantial increase in NO adsorption capacity. After the flue gas from the furnace is cooled to the sub-zero temperature zone, it enters the low-temperature adsorption tower, and NO x Deep adsorption and removal at low temperature achieves the two major goals of "integrated removal" and "near-zero emissions" of pollutants.

[0047] An embodiment of the present invention discloses a plasma treatment device for removing nitrogen oxides and adsorbing radioactive nuclides, comprising:

[0048] The L-shaped plasma furnace 1 is connected to the secondary combustion chamber 17 via a smoke exhaust pipe 4;

[0049] The L-shaped plasma furnace 1 is L-shaped as a whole, and the furnace body is divided into a vertical section and a horizontal section, wherein the vertical section serves as a gasification section and the horizontal section serves as a melting section. The vertical section and the horizontal section are detachable for easy maintenance and transportation;

[0050] The L-shaped plasma furnace 1 has a refractory material layer 3 on its inner wall. The refractory material layer 3 is in direct contact with the high-temperature molten pool and is a high-risk area. The refractory material layer 3 is made of high-temperature and corrosion-resistant materials such as silicon nitride, silicon carbide, or zirconium-chromium corundum. The surface temperature of the furnace shell is controlled at 80-100°C.

[0051] The vertical section of the L-shaped plasma furnace 1 is provided with a feed port 2 at the top, and a smoke exhaust port is provided on the upper side wall, which is connected to the secondary combustion chamber 17 through a smoke exhaust pipe 4;

[0052] The melting section is provided with a molten pool, and a first plasma torch 5-1 is provided above the left side of the melting section; an overflow outlet sealed chamber 6 is also provided adjacent to the melting section, a glass liquid overflow port 13 is provided in the middle and lower portion of the side wall shared by the molten pool and the overflow outlet sealed chamber 6, and the overflow outlet sealed chamber 6 is outside the glass liquid overflow port 13; a metal liquid drain port 12 is also provided at the bottom end of the side wall shared by the molten pool and the overflow outlet sealed chamber 6; an infrared thermometer is provided above the right side of the melting section for measuring the temperature of the molten pool surface; the melting section is also provided with a liquid level gauge for determining whether the glass liquid layer 10 formed by the melting of solid residue in the molten pool has accumulated beyond a set height;

[0053] The inner walls of the molten metal discharge port 12 and the molten glass overflow port 13 are both inclined at an angle of 10 to 15 degrees in the horizontal direction; the horizontal inclination angle of the electric heating plug located inside the molten metal discharge port 12 and the molten glass overflow port 13 is smaller than the inclination angle of the inner walls of the molten glass overflow port 13 and the molten metal discharge port 12, and is 5 to 10 degrees; the advantage of this is that the front end of the electric heating plug can be tightly combined with the contact surface of the molten glass overflow port, and it is not easy to get stuck in the front and back; the inclination angle between the electric heating plug and the molten glass overflow port and the horizontal direction solves the problem that the discharge port of the same type of furnace is easily blocked, resulting in poor discharge;

[0054] A detachable plug is provided in the glass liquid overflow port 13. The plug is L-shaped, and the volume of the front end of the L-shaped horizontal section is smaller than the volume of the rear end. The front end of the horizontal section of the L-shaped plug is sealed toward the glass liquid overflow port 13, so that the glass liquid overflow port can be tightly sealed by the electrically heated plug; the vertical section of the L-shaped plug passes through the top side wall of the overflow outlet sealing chamber 6 and extends to the outside of the L-shaped plasma furnace 1. A movable space for the plug is provided on the top side wall of the overflow outlet sealing chamber 6. The overflow outlet sealing chamber 6 and the vertical section of the L-shaped plug are movably connected through a sealing structure;

[0055] The shape of the metal liquid discharge port 12 is consistent with that of the glass liquid overflow port 13 and is also provided with a plug;

[0056] The L-shaped plasma furnace 1 is also equipped with an actuator for moving an electrically heated plug. The glass overflow port 13 is normally sealed by the plug. When the molten slag inside the molten pool forms a glass layer 10 that reaches a certain height, and the molten pool level significantly exceeds the overflow port, the actuator moves the plug from the left side, allowing it to be removed from the overflow port. The overflow port is now open, and the glass liquid flows out of the overflow port 13. This structure solves the problem of clogged discharge ports in similar furnaces, which can lead to poor discharge.

[0057] A water-cooled gate valve is provided at the bottom of the overflow outlet sealing chamber 6, and a hopper car 7 is provided just below the liquid outlet of the water-cooled gate valve;

[0058] After the material falls into the vertical section of the plasma furnace from the feed port 2, a gasification and pyrolysis layer 9 is formed. From top to bottom, this 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 to 1200°C from the upper surface to the high temperature section.

[0059] The side walls of the vertical section are provided with a right annular air inlet 8-1 and a left annular air inlet 8-2. In actual engineering use, 4 to 6 annular air inlets are provided as needed to supply oxygen to the gasification and pyrolysis layer 9. In the gasification and pyrolysis layer, most of the organic matter is gasified and pyrolyzed into synthesis gas at a temperature of 400 to 600°C. This gas is then discharged from the L-shaped plasma furnace exhaust pipe 4 to the secondary combustion chamber 17.

[0060] Synthesis gas is CO+H2.

[0061] The remaining inorganic matter in the gasification and pyrolysis layer 9 falls to the bottom of the vertical section and enters the horizontal melting section of the plasma furnace. A first plasma torch 5-1 is located above the melting section. During operation, this torch requires a high-power DC power supply and is cooled by cooling water. The torch uses nitrogen as the carrier air. The arc generated by the torch ionizes the nitrogen, forming a high-temperature jet that directly heats and melts the inorganic matter flowing from the vertical section, ultimately forming a glass liquid layer 10.

[0062] After the radioactive waste is treated by the L-shaped plasma furnace 1, most of the organic matter is gasified and decomposed into the secondary combustion chamber 17, and the remaining inorganic matter is melted at high temperature to form a glass body, which is a safe and stable medium that solidifies radionuclides and heavy metals inside the glass body, and preliminarily achieves the effect of harmless reduction of radioactive waste.

[0063] The smoke exhaust pipe 4 has a vertical opening on the side wall close to the secondary combustion furnace 17, and is provided with an annular air inlet 16-1 on the upper side of the secondary combustion chamber and an annular air inlet 16-2 on the lower side of the secondary combustion chamber;

[0064] A second plasma torch 5-2 is provided on the top of the secondary combustion chamber 17, and the upper part of the side wall is connected to the smoke exhaust pipe, the purpose of which 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;

[0065] The secondary combustion chamber 17 is provided with a left-side annular air inlet 18-1 and a right-side annular air inlet 18-2 in the middle of the sidewall. These inlets draw air from a horizontal opening in the middle of the secondary combustion chamber, increasing the oxygen required for combustion of the combustible components. In actual engineering use, four to six annular air inlets are provided as needed to enhance the treatment effect. The area from the middle air inlet to the exit of the secondary combustion chamber 17 is the burnout zone in the graded air distribution. This area has a low air volume and oxygen content, and the presence of unburned syngas from the middle and upper areas creates a reducing atmosphere. As described above, a two-stage air distribution scheme is implemented in the secondary combustion chamber 17. That is, a first-stage air inlet is set at the inlet of the secondary combustion chamber 17, forming a main combustion zone of syngas in the upper part of the secondary combustion chamber 17; a second-stage air inlet is set in the middle of the secondary combustion chamber 17, forming a burnout zone of combustible atmosphere in the lower middle part of the secondary combustion chamber 17, ensuring that the combustible components are completely burned 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 standards.

[0066] The bottom of the secondary combustion chamber 17 is funnel-shaped and is provided with a secondary combustion chamber ash discharge port 14;

[0067] Finally, the flue gas from the secondary combustion chamber 17 is discharged from the secondary combustion chamber exhaust port 15 to the downstream tail gas treatment system; the small amount of ash generated in the process is regularly discharged through the secondary combustion chamber ash discharge port 14 at the bottom;

[0068] The secondary combustion chamber 17 is connected to a desulfurization furnace 19, a heat exchanger 20, and a quenching tower 21;

[0069] The denitrification furnace 19 is provided with a gas inlet at the bottom and a gas outlet at the top; an alkaline solution spray port is also provided at the top;

[0070] The heat exchanger 20 is provided with a gas inlet at the bottom and a gas outlet at the top for the initial cooling of the flue gas;

[0071] The quenching tower 21 is provided with a gas inlet at the bottom and a gas outlet at the top for rapid cooling of the flue gas to avoid the generation of dioxins.

[0072] The rear end of the quenching tower 21 is connected to at least two dust removal bags, which are arranged in parallel to facilitate replacement without stopping the machine.

[0073] For example, the quenching tower 21 is connected to the first dust bag 22-1 and the second dust bag 22-2 respectively;

[0074] The outlet of the dust bag is connected to a washing tower, which includes at least two washing towers, such as a primary washing tower 23 and a secondary washing tower 24 connected in sequence;

[0075] The scrubber is followed by a flue gas cooler 25, a gas-liquid separator 26 and an adsorber;

[0076] The adsorber includes at least two, and several adsorbers are arranged in parallel to facilitate replacement and regeneration without stopping the machine;

[0077] One outlet of the adsorber is connected to an electric heater 29, which is then connected to an induced draft fan 30;

[0078] The other outlet of the adsorber is connected to the annular air inlet of the L-shaped plasma furnace 1 and the horizontal annular air inlet of the second combustion chamber of the exhaust pipe 4 through pipelines;

[0079] For example: including a first adsorber 27 - 1 and a second adsorber 27 - 2 in parallel;

[0080] The first adsorber 27-1 and the second adsorber 27-2 operate alternately, i.e., the first adsorber 27-1 operates first, while the second adsorber 27-2 is not in operation. After a period of adsorption, the adsorption capacity reaches saturation, and the switching valve switches the operation to the second adsorber 27-2, while the first adsorber 27-1 stops.

[0081] During the operation of the second adsorber 27-2, the first adsorber 27-1 is heated and regenerated. x The treatment process is as follows: In addition, a separate blower is used to supply air to the first adsorber 27-1. Electric heating is used in the process. After the heated air passes through the first adsorber 27-1 and is heated, the SO2 and NO originally adsorbed by the adsorption material are x , after heating up, it enters the hot air. As the temperature rises and time increases, the SO2 and NO contained in the first adsorber 27-1 itself x The amount is gradually decreasing, and most of it enters the hot air. At this time, the first adsorber 27-1 is ready for use after regeneration, waiting for the next time the two adsorbers are switched for use;

[0082] One outlet of the adsorber is connected to an electric heater 29, which is then connected to an induced draft fan 30;

[0083] The other outlet of the adsorber is connected to the annular air inlet of the L-shaped plasma furnace 1 and the annular air inlet of the secondary combustion chamber of the smoke exhaust pipe 4 through pipelines.

[0084] The embodiment of the present invention discloses a plasma treatment method for removing nitrogen oxides and adsorbing radionuclides, comprising the following steps:

[0085] Step 1: Incinerate the crushed and mixed radioactive waste in a plasma furnace.

[0086] The inorganic matter produced by incineration is melted.

[0087] Specifically include:

[0088] The arc generated by the plasma torch ionizes the nitrogen to form a high-temperature jet, which directly heats and melts the inorganic matter, and then forms a glass liquid layer 10 and a metal liquid layer 11.

[0089] High temperature jet is adjustable from 1500 to 2000℃;

[0090] During the working process of the plasma torch, a high-power DC power supply is used for power supply, and cooling water is passed through it for cooling. The plasma torch uses nitrogen as the carrier wind.

[0091] The plasma torch adopts a high current and low voltage operation mode. For example, with an output power of 150kw, a current of 350A and a voltage of 430V can be used, and a high-temperature jet length of 300mm can be used. The purpose of this is to use a shorter arc length and a smaller amount of nitrogen, increase the outlet high-temperature plasma jet temperature, provide high-temperature energy to the treated object, and make it easier to melt into glass. At the same time, the active radicals generated by the plasma high-temperature jet, such as H + , N + Charged particles such as radioactive substances also enter the vertical gasification section from the plasma furnace melting section and enter the gasification pyrolysis layer 9. These active groups have a greater activation and 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, in the oxidation area inside the gasification pyrolysis layer 9, the organic matter is pyrolyzed and gasified into synthesis gas. In the process of escaping from the oxidation area to the top, this part of the synthesis gas also passes through the drying and pyrolysis areas. The temperature of the synthesis gas is 1100℃~1200℃. Since the synthesis gas itself carries a certain reducing atmosphere, the middle and upper parts of the gasification pyrolysis layer 9 belong to the reducing area.

[0092] The slag is melted by high temperature and becomes liquid. Components such as silicon and calcium form a glassy liquid layer. Some metals such as iron, copper, and silver have higher densities and are deposited at the bottom to form a metal liquid layer.

[0093] The glass liquid and metal liquid should be discharged and collected regularly.

[0094] Step 2: The gas generated by the incineration treatment enters the secondary combustion chamber for a second plasma incineration treatment.

[0095] 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 it for cooling. 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, which directly burns the synthesis gas from the plasma furnace and burns out its combustible components. During use, due to its high temperature and high enthalpy characteristics, the plasma technology, under the condition of inert gas as the carrier, produces NO x Higher, 2000-4000 mg / m 3 ;

[0096] High temperature jet is adjustable from 1500 to 2000℃;

[0097] The plasma torch adopts a low current and high voltage operation mode. For example, for an output power of 150 kW, a current of 250 A and a voltage of 600 V can be used, and a high-temperature jet length of 500 mm can be used. The purpose of this is to adopt a longer arc length and a larger nitrogen dosage, thereby increasing the concentration and coverage of active groups generated by the nitrogen plasma, thereby improving the high-temperature combustion effect.

[0098] During the second plasma incineration treatment, a two-stage air distribution scheme is adopted. That is, a first-stage air inlet is set at the entrance of the second combustion chamber 17, and a second-stage air inlet is set in the middle of the second combustion chamber 17. A burnout zone with a combustible atmosphere is formed in the lower middle part of the second combustion chamber to ensure that the combustible components are completely burned in the second combustion chamber. 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.

[0099] Step 3: The flue gas generated by the second plasma incineration treatment is subjected to denitrification treatment, heat exchange and cooling treatment, extreme cooling treatment, dust removal treatment and at least two-stage washing treatment;

[0100] The denitration treatment is carried out in a denitration furnace 19, where ammonia water is sprayed into the furnace to react with nitrogen oxides to generate nitrogen gas and water.

[0101] The heat exchange and cooling process is carried out in the heat exchange gas, and the flue gas temperature is cooled from 1100°C to 600°C.

[0102] The extreme cooling treatment is carried out in an extreme cooling tower 21, where the high-temperature flue gas is cooled to 175°C within 2 seconds to avoid the generation of dioxins.

[0103] The dust removal process specifically refers to dust removal through bag filters.

[0104] The washing treatment specifically refers to spraying sodium hydroxide solution for deacidification.

[0105] Step 4: The washed flue gas is subjected to cryogenic removal treatment.

[0106] The principle of low-temperature cryogenic removal is: when the flue gas temperature drops below 0℃, the SO2 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, the high-performance low-temperature adsorption material preparation technology can be used to remove SO2 and NO. x Perform low-temperature adsorption removal.

[0107] Specifically include:

[0108] The scrubbed flue gas is cooled using a low-temperature refrigerant, and the water vapor therein is then separated to ensure dry flue gas.

[0109] The temperature of the flue gas after cooling is -20℃~0℃.

[0110] The dry flue gas produced is adsorbed using aluminum oxide or copper particles to remove SO2 and NO in the flue gas. x Low temperature adsorption removal, most of the SO2 and NO in the flue gas x All are removed;

[0111] The adsorption material also adds radioactive adsorption materials, such as zeolite, to adsorb Cs-137, I-131, etc., reducing the radiation dose in the flue gas and thus meeting the radioactive emission standards.

[0112] After the adsorption material reaches saturation, replace it with new adsorption material;

[0113] The saturated adsorption material is heated and regenerated, and the SO2 and NO x After being heated, it enters the hot air and is re-added to the plasma furnace.

[0114] The regenerated adsorption material can be used again.

[0115] The adsorption material that has reached the critical point after long-term adsorption will eventually be broken and mixed, and then enter the plasma furnace again for glass solidification process, or directly enter the cement solidification line for solidification treatment.

[0116] During the cryogenic removal process, not only nitrogen oxides are effectively removed, but also radioactive substances are removed, simplifying the pollutant removal process. At the same time, the adsorption material in the saturated state is regenerated to remove SO2 and NOx Incineration is carried out again to realize the recycling treatment of pollutants, improve the treatment effect and achieve zero pollutant emissions

[0117] Step 5: The gas after low-temperature cryogenic removal treatment is heated and then discharged.

[0118] After experimental verification, the gas NO treated by the present invention x The concentration was kept below 1 mg / Nm 3 , SO2 concentration is kept below 3mg / Nm 3 ; Basically meet the national near-zero emission requirements.

[0119] In order to further understand the present invention, the plasma treatment device and method for removing nitrogen oxides and adsorbing radioactive nuclides provided by the present invention are described in detail below with reference to the embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0120] Example 1

[0121] a. First, the crushed and mixed radioactive waste passes through the feeding device and enters the L-shaped plasma furnace 1 from the top feeding port 2.

[0122] b. The plasma furnace 1 is arranged in an L-shape, and the furnace body can be structurally divided into a vertical section and a horizontal section;

[0123] c. After the material falls from the feed port 2 into the vertical section of the L-shaped plasma furnace 1, a gasification and pyrolysis layer 9 is formed. From top to bottom, this 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 to 1200°C from the upper surface to the high temperature section.

[0124] d. The gasification and pyrolysis layer 9 is provided with a right annular air inlet 8-1 and a left annular air inlet 8-2 to supplement oxygen to the gasification and pyrolysis layer 9; in the gasification and pyrolysis layer, most of the organic matter is gasified and pyrolyzed into synthesis gas, which is then discharged from the exhaust pipe 4 to the secondary combustion chamber 17;

[0125] e. The remaining inorganic matter in the gasification and pyrolysis layer 9 falls to the bottom of the vertical section and enters the horizontal melting section of the L-shaped plasma furnace 1. A first plasma torch 5-1 is located above the melting section. During operation, this torch requires a high-power DC power supply and is cooled by cooling water. The torch uses nitrogen as the carrier air. The arc generated by the torch ionizes the nitrogen to form a high-temperature jet, which directly heats and melts the inorganic matter flowing from the vertical section, thereby forming a glass liquid layer 10.

[0126] The first plasma torch 5-1 here adopts a high current and low voltage operation mode, using a current of 350A, a voltage of 430V, and a high-temperature jet length of 300mm.

[0127] In the glass liquid layer 10, the slag is melted into liquid by the high temperature generated by the first plasma torch 5-1, wherein components such as silicon and calcium form a glass liquid layer here; some metals such as iron, copper, and silver have a large density and are deposited at the bottom to form a metal liquid layer 11. This is the stratification phenomenon inside the molten pool.

[0128] f. A glass liquid overflow port 13 is provided on the left side of the molten pool. Normally, it is sealed by a plug. When the glass liquid layer formed by the melted slag inside the molten pool reaches a certain height and the molten pool liquid level exceeds the overflow port by a large margin, the plug is moved from the left side through 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.

[0129] The slag usually contains a small amount of metal. 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, the metal liquid drain port 12 is opened to drain the metal liquid at the bottom.

[0130] The right side of the furnace bottom 11 is usually reserved with an inclined section to facilitate the glass liquid on the right to flow to the left under the action of gravity, making it easier to discharge;

[0131] After flowing out of the glass overflow port 13, the vitreous liquid enters the overflow outlet sealed chamber 6. This overflow outlet sealed chamber 6 is constructed with an outer steel shell and an inner lining of refractory material, which can prevent both high temperatures from the overflow port and the leakage of radioactive materials. A water-cooled gate valve is provided at the bottom of the overflow outlet sealed chamber 6. When the overflow port is not discharging material, the water-cooled gate valve is closed. Before the overflow port is discharging material, the water-cooled gate valve is opened, and the lower portion is prepared to receive the material hopper car 7. 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, undergoes a water quenching process, and then cools to form a vitreous body.

[0132] g. After a certain period of time, the molten glass from the overflow port has completely flowed out. The water-cooled gate valve is closed, and the plug, moved by the actuator, re-blocks the overflow port. Simultaneously, the upper portion of the receiving hopper car 7 undergoes an automatic sealing operation to ensure the car's airtightness. Upon completion of these operations, the overflow port, the outlet of the water-cooled gate valve, and the upper portion of the receiving hopper car are all sealed, ensuring no radioactive leakage. The lower portion of the receiving hopper car 7 is equipped with a pulley, which automatically transports the material to the adjacent finished product storage area via rails for temporary storage in accordance with radiation protection requirements.

[0133] h. After the radioactive waste is processed by the L-shaped plasma furnace 1, the organic matter inside the L-shaped plasma furnace 1 is gasified and decomposed to form mainly CO and H2, which enter the secondary combustion chamber 17 through the exhaust pipe 4;

[0134] A vertical hole is opened in the exhaust pipe near the secondary combustion chamber pipe, and an annular air inlet 16-1 on the upper side of the secondary combustion chamber and an annular air inlet 16-2 on the lower side of the secondary combustion chamber are provided. The purpose is to supply air and oxygen to the upper part of the secondary combustion chamber to promote the combustion of synthesis gas inside the secondary combustion chamber;

[0135] A second plasma torch 5-2 is provided above the top of the second combustion chamber 17. During operation, the plasma torch is also powered by a high-power DC power supply and cooled by cooling water. 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, which directly burns the synthesis gas from the plasma furnace and burns out its combustible components. During use, due to its high temperature and high enthalpy characteristics, the plasma technology, under the condition of inert gas as the carrier, produces NO x Concentration is 2000~4000mg / m 3 ;

[0136] The second plasma torch 5-2 here adopts a high voltage and low current operation mode, that is, a current of 250A, a voltage of 600V, and a high temperature jet length of 500mm;

[0137] In the middle of the secondary combustion chamber 17, there are two annular air inlets 18-1 on the left side and 18-2 on the right side. These air inlets are opened horizontally in the middle of the secondary combustion chamber to increase the oxygen required for the combustion of the combustible components.

[0138] i. The flue gas from the secondary combustion chamber 17 is completely burned and discharged from the secondary combustion chamber exhaust port 15 to the downstream exhaust treatment system; a small amount of ash generated during the process is regularly unloaded through the bottom secondary combustion chamber ash discharge port 14;

[0139] j. After the flue gas comes out of the secondary combustion chamber 17, it first passes through the denitrification furnace 19, where denitrification is carried out in the furnace. That is, ammonia is sprayed from the inside to react with nitrogen oxides to produce nitrogen and water.

[0140] k. The flue gas then enters the heat exchanger 20 for cooling, from 1100°C to 600°C. It then enters the quenching tower 21, where the high-temperature flue gas is cooled to 175°C in a relatively short period of time.

[0141] After being extremely cooled, the flue gas enters a bag filter for dust removal. A redundant configuration is used here, with a first bag filter 22-1 and a second bag filter 22-2. The flue gas then enters a two-stage scrubber, where NaOH solution is sprayed in for deacidification.

[0142] m. After washing, the flue gas enters the low-temperature cryogenic removal system, including a flue gas cooler 25, a gas-liquid separator 26, a first adsorber 27-1, and a second adsorber 27-2;

[0143] After washing, the flue gas enters the flue gas cooler 25, where the cooling method is usually a refrigerator, which uses a low-temperature refrigerant to cool the flue gas to -20℃~0℃;

[0144] After cooling, it enters the gas-liquid separator 26 to separate the water vapor generated in the scrubbing tower to ensure that dry flue gas is generated.

[0145] After gas-liquid separation, it enters the adsorber, where the adsorber adopts an alternating working mechanism, that is, the first adsorber 27-1 starts working first, while the second adsorber 27-2 is not put into operation. The adsorption material inside the first adsorber is used to absorb SO2 and NO in the flue gas. x Low temperature adsorption removal, most of the SO2 and NO in the flue gas x After all of the adsorbents are removed, the first adsorber 27-1 adsorbs for a period of time and its adsorption capacity reaches saturation. At this time, the first adsorber 27-1 can be switched to the second adsorber 27-2 through a switching valve. At this time, the second adsorber 27-2 starts working and the first adsorber 27-1 stops working.

[0146] During the whole process, the flue gas NO discharged from the adsorber is adsorbed x The concentration was kept below 1 mg / Nm 3 , SO2 concentration is kept below 3mg / Nm 3 ; Basically meet the national near-zero emission requirements.

[0147] aa. During the adsorption operation of the second adsorber 27-2, we heat the first adsorber 27-1 for regeneration and NO x The treatment process is as follows: In addition, a separate blower is used to supply air to the first adsorber 27-1. Electric heating is used in the process. After the heated air passes through the first adsorber 27-1 and is heated, the SO2 and NO originally adsorbed by the adsorption material are x , after heating up, it enters the hot air. As the temperature rises and time increases, the SO2 and NO contained in the first adsorber 27-1 itself x The amount is gradually decreasing, and most of it enters the hot air. At this time, the first adsorber 27-1 is ready for use after regeneration, waiting for the next time the two adsorbers are switched for use;

[0148] bb. Absorbed a large amount of SO2 and NO x Hot air is recycled:

[0149] The return operation path 1 is to enter the horizontal annular air inlet of the secondary combustion chamber, and enter the secondary combustion chamber 17 furnace from the entrance section of the secondary combustion chamber 17. According to the previous description, the two-level air distribution scheme is implemented in the secondary combustion chamber 17, that is, a main combustion zone with a first-level air inlet is set at the inlet of the secondary combustion chamber 17 and a burnout zone formed by a second-level air inlet is set in the middle of the secondary combustion chamber 17; after the returned hot air enters the secondary combustion chamber 17 furnace, it is partially reduced after passing through the reduction area of the burnout zone.

[0150] Recycling route 2 enters the annular air inlet of the vertical section of the L-shaped plasma furnace 1. This section is located within the gasification and pyrolysis layer 9. As described above, due to the inherent reducing atmosphere of the syngas, the upper and middle portions of the gasification and pyrolysis layer are considered reducing zones. After entering the L-shaped plasma furnace 1, the recycled hot air passes through the reducing zone of the upper and middle portions of the gasification and pyrolysis layer before entering the secondary combustion chamber 17 and the tail gas treatment process.

[0151] cc. After the hot air returned to the furnace is mixed with the hot flue gas generated in the original furnace, it enters the exhaust gas treatment link uniformly, so the SO2 and NO in the flue gas x In the process, it is adsorbed at low temperature, desorbed by heating, returned to the furnace, and then enters the exhaust system, forming a reciprocating cycle.

[0152] dd. After low-temperature adsorption in the adsorber, the flue gas reaches near-zero emission and is heated by the electric heater 29, and then passes through the induced draft fan 30 before meeting emission standards;

[0153] ee. Meanwhile, during the low-temperature adsorption process, selecting suitable adsorbent materials, such as zeolite, can strongly adsorb Cs-137, I-131, and other substances, reducing the total radiation dose in the flue gas and ensuring that radioactive emissions meet standards. Adsorbent materials that have reached a critical point through long-term adsorption ultimately undergo relevant processing steps before entering the plasma furnace for glass curing or directly entering the cement curing line for curing.

[0154] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0155] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A plasma treatment device for removing nitrogen oxides and adsorbing radioactive nuclides, characterized in that: include: The L-shaped plasma furnace is connected to the secondary combustion chamber through a smoke exhaust pipe; The top of the secondary combustion chamber is provided with a second plasma torch, and the upper part of the side wall is connected to the smoke exhaust pipe. The second combustion chamber is connected in sequence to the desulfurization furnace, heat exchanger, quenching tower, dust bag, scrubber, flue gas cooler, gas-liquid separator and adsorber; At least two adsorbers are arranged in parallel. One outlet of the adsorber is connected to an electric heater, and the electric heater is connected to an induced draft fan; Another outlet of the adsorber is connected to the annular air inlet of the L-shaped plasma furnace and the annular air inlet of the secondary combustion chamber of the smoke exhaust pipe through pipelines.

2. The plasma treatment device for removing nitrogen oxides and adsorbing radioactive nuclides according to claim 1, characterized in that: The L-shaped plasma furnace body is divided into a vertical section and a horizontal section. The first plasma torch is installed on the left side of the horizontal section. A plurality of annular air inlets are arranged on the side wall of the vertical section.

3. The plasma treatment device for removing nitrogen oxides and adsorbing radioactive nuclides according to claim 1, characterized in that: At least two annular air inlets are vertically provided on the side wall of the smoke exhaust pipe close to the secondary furnace.

4. The plasma treatment device for removing nitrogen oxides and adsorbing radionuclides according to claim 1, characterized in that: There are at least two dust removal bags, which are arranged in parallel.

5. The plasma treatment device for removing nitrogen oxides and adsorbing radionuclides according to claim 1, characterized in that: The adsorption material in the adsorber is aluminum oxide, copper particles, a mixture of aluminum oxide and zeolite, or a mixture of copper particles and zeolite.

6. A plasma treatment method for removing nitrogen oxides and adsorbing radioactive nuclides, characterized in that: The following steps are involved: Step 1: Incinerate the crushed and mixed radioactive waste in a plasma furnace; The inorganic matter produced by incineration is melted; Step 2: The gas generated by the incineration process enters the secondary combustion chamber for a second plasma incineration process; Step 3: The flue gas generated by the second plasma incineration treatment is subjected to denitrification treatment, heat exchange and cooling treatment, extreme cooling treatment, dust removal treatment and at least two-stage washing treatment; Step 4: The washed flue gas is subjected to low-temperature cryogenic removal treatment; Low temperature cryogenic removal treatment specifically includes: Use low-temperature refrigerant to cool the scrubbed flue gas and then separate the water vapor from it. The dry flue gas produced is subjected to adsorption treatment; Step 5: The gas after low-temperature cryogenic removal treatment is heated and then discharged.

7. The plasma treatment method for removing nitrogen oxides and adsorbing radioactive nuclides according to claim 6, characterized in that: In step 1, the plasma torch adopts a high current and low voltage operation mode; In step 2, the second plasma incineration treatment adopts a low current and high voltage operation mode.

8. The plasma treatment method for removing nitrogen oxides and adsorbing radionuclides according to claim 6, characterized in that: In step 3, the flue gas temperature is cooled from 1100° C. to 600° C. during the heat exchange and cooling process; During the extreme cold cooling treatment, the high temperature gas is cooled to 150-200°C within 1-5 hours.

9. The plasma treatment method for removing nitrogen oxides and adsorbing radionuclides according to claim 6, characterized in that: In step 4, the washed flue gas is cooled to below 0° C. using a low-temperature refrigerant.

10. The plasma treatment method for removing nitrogen oxides and adsorbing radioactive nuclides according to claim 6, characterized in that: In step 4, two adsorbers arranged in parallel are used for adsorption treatment. The first adsorber and the second adsorber work alternately; when the first adsorber has been adsorbing for a period of time, the adsorption capacity reaches saturation, and the switching valve switches to the second adsorber, and the first adsorber stops working; During the operation of the second adsorber, the first adsorber is heated and regenerated and NO x The SO2 and NO originally adsorbed by the adsorption material are recycled and disposed of. x , after heating up, it enters the hot air, and the hot air returns to the plasma incinerator used in step 1 or the secondary combustion chamber described in step 2; After regeneration, the first adsorber is ready for use and is ready for the next switch between the two adsorbers.

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