Silver-loaded zeolite filter and containment filtration and exhaust system of nuclear power plant

Abstract

A silver-loaded zeolite filter, and a nuclear power plant containment filtering and discharging system comprising the silver-loaded zeolite filter. The silver-loaded zeolite filter comprises a pressur

Description

05 06 25 SILVER-LOADED ZEOLITE FILTER AND CONTAINMENT FILTRATION AND EXHAUST SYSTEM OF NUCLEAR POWER PLANT $ The present disclosure claims priority from Chinese patent application entitled "SILVER-LOADED ZEOLITE FILTER AND CONTAINMENT FILTRATION AND EXHAUST SYSTEM OF NUCLEAR POWER PLANT", with an application date of April 12, 2021 and an application No. CN 202110389118.8. 10 Technical Field The present disclosure relates to a silver-loaded zeolite filter and a containment filtration and exhaust system of a nuclear power plant including the silver-loaded zeolite filter. 15 Background Art With the increasing worldwide shortage of energy and the increasing problem of environmental pollution, new clean energy has got more and more attention, of which nuclear power, as a clean and efficient energy, is widely 20 applied around the world. To prevent radioactive leakage, a nuclear power plant is provided with three safety “barriers”, among which nuclear power plant containment is the last safety barrier to prevent release of radioactive products to the environment. After the Fukushima nuclear accident in Japan, the overpressure problem of the containment at a later stage of a severe accident of 25 the nuclear power plant has gained extensive attention. When a core-melt severe accident (beyond design basic accident) occurs, a molten reactor core may continuously react with the bottom concrete to generate numerous non-condensable gas, causing a pressure in the containment to be continuously increased and finally exceed a pressure limitation of the containment to damage 30 integrity of the containment, and leading to leakage of the radioactive substances and pollution of the environment. In order to prevent such cases, a containment filtration and exhaust system is installed in the nuclear power plant, the pressure in the containment is reduced by active discharge, and meanwhile, a filtering 05 06 25 equipment on the system is used for filtering radioactive substances in the 5 discharged gas. In severe accidents, fission products in the containment mainly include aerosol, elemental iodine (I2) and gaseous organic iodine. A great deal of research documents show that the existing wet type containment filtration and exhaust system has excellent filtering capacity for aerosol and elemental iodine, 10 but has insufficient filtering capacity for organic iodine gas. This is mainly due to a low chemical reaction rate of organic iodine with aqueous solution, and an inadequate contact time with liquid phase. As a result, only a small part of organic iodine is retained in the process of flowing through the containment filtration and exhaust system. 15 Research on methods and apparatus for gaseous organic iodine filtration in nuclear power plants began in the 60's of the last century. A company in Western Europe designs a passive sliding pressure operation filtration and exhaust system, which adopts a wet water washing and filtering mode to filter radioactive substances in the containment after a nuclear power plant accident, but the 20 filtering efficiency of the system on gaseous organic iodine is less than 50%. In the US patent No. US8142665B2, it is mentioned that a removal efficiency of the solution for organic iodine gas is increased by adding a phase transfer catalyst, Aliquat 336, into the solution. However, it is difficult to achieve engineering applications due to the flammable and caking properties of Aliquat 336. Tests 25 currently performed on removal of radioactive iodine from nuclear facility exhaust gases, such as KI, TEDA (triethylenediamine) and silver impregnates, all have improved the efficiency of radioactive iodine removal. Activated carbon has also been successfully used in nuclear power plants, but in a high temperature system, TEDA impregnated activated carbon cannot serve as the 30 main adsorbent, mainly because the activated carbon has a low ignition point and 05 06 25 is resistant to nitrogen o Therefore, this method is not applicable to high temperature conditions. To remove radioactive iodine under high temperature conditions, an inorganic adsorbent which allows radioactive iodine to form a stable iodine compound is required. The activated carbon iodine adsorbers used 5 in nuclear power plants mainly include an iodine adsorber I type (a foldable type), an iodine adsorber II type (a drawer type) and an iodine adsorber III type (a deep bed type). A typical activated carbon adsorber in the non-nuclear industry further includes a cylinder type (a straw hat type). Among others, the foldable type and drawer type filter structures are relatively complicated, and is 10 difficult for sealing under a high pressure condition, while the deep bed type filter is a monolithic structure that is unfavorable for actual installation, maintenance and exchange. Summary 15 The technical problem to be solved by the present disclosure is to, in view of the above deficiencies in the background art, provide a silver-loaded zeolite filter that can effectively filter out organic iodine in the gas to be filtered, and a containment filtration and exhaust system of the nuclear power plant including the silver-loaded zeolite filter. 20 In order to solve the above technical problem, the present disclosure adopts the following technical solutions: A silver-loaded zeolite filter according to claim 1 is provided. Preferably, the silver-loaded zeolite filter further includes a gas inlet pipe and a gas outlet pipe, wherein the gas inlet pipe is disposed in the inlet of the 25 pressure-bearing tank and configured to convey the gas to be filtered into the pressure-bearing tank, and the gas outlet pipe is disposed in the outlet of the pressure-bearing tank and connected to the gas collection header, and is configured to discharge the filtered gas in the gas collection header out of the pressure-bearing tank. 30 Preferably, the silver-loaded zeolite filter further includes a beam disposed 05 06 25 in the pressure-bearing tank and above the silver-loaded zeolite filtering unit, wherein each end of the beam is fixed on a side wall of the pressure-bearing tank, and the beam is configured for compacting the silver-loaded zeolite filtering unit; the gas outlet pipe is connected to a bottom of the gas collection header, and the 5 gas outlet pipe is further configured to support the gas collection header and the silver-loaded zeolite filtering unit so that the silver-loaded zeolite filtering unit is fixed under clamping of the beam, the gas collection header and the gas outlet pipe. Preferably, a ratio of a distance between the beam and the top of the 10 pressure-bearing tank to a height of the pressure-bearing tank is in a range of 0.15 to 0.4. Preferably, the silver-loaded zeolite filter further includes a throttle orifice plate, wherein the throttle orifice plate is disposed at an input end of the gas inlet pipe, and is configured to obtain a dry gas to be filtered in an overheated state. 15 Preferably, the silver-loaded zeolite filter further includes a gas flow baffle assembly including a baffle, wherein the baffle is disposed in the pressure-bearing tank and above the silver-loaded zeolite filtering unit, and opposite to the gas inlet pipe. Preferably, a ratio of a distance between the baffle and the top of the 20 pressure-bearing tank to a height of the pressure-bearing tank is in a range of 0.05 to 0.3. Preferably, the gas flow baffle assembly further includes connection rods, wherein a plurality of connection rods are arranged in parallel, one end of each connection rod is fixedly connected to the top of the pressure-bearing tank, and 25 the other end is connected to the baffle. Preferably, the porous web is embedded on a bottom surface and at least one side surface of the frame, other surfaces of the frame form a closed structure. Three filter cartridge structures are provided, preferably consisting of a middle filter cartridge structure and two side filter cartridge structures, wherein 30 each filter cartridge structure has a flat plate shape with a square cross section, 05 06 25 and the middle filter cartridge structure has a length longer than each of the side filter cartridge structures. Preferably, the middle filter cartridge structure is located in the middle of the pressure-bearing tank, and the two side filter cartridge structures are 5 symmetrically distributed on two sides of the middle filter cartridge structure. Preferably, a gap is provided between the middle filter cartridge structure and each of the side filter cartridge structures, wherein a ratio of a width of the gap to a diameter of the pressure-bearing tank is in a range of 0.05 to 0.15. Preferably, a filling density of the silver-loaded zeolite bed layer is 10 obtained by precisely filling by means of a mechanical vibration platform. Preferably, the pressure-bearing tank is a pressure vessel composed of a cylindrical barrel, an upper head and a lower head, wherein the gas inlet pipe is provided on the upper head, and the gas outlet pipe is provided on the lower head. 15 The present disclosure further provides a containment filtration and exhaust system of a nuclear power plant, including a silver-loaded zeolite filter as described above, wherein the silver-loaded zeolite filter is configured to filter high-temperature organic iodine gas discharged from the containment. In the present disclosure, by using silver-loaded zeolite to filter organic 20 iodine gas, radioactive iodine elements in the organic iodine can be effectively removed. Further, with the reasonable and optimized arrangement of filter cartridge structures, gas flow distribution on the silver-loaded zeolite filter is uniform and the filtering effect is excellent. 25 Brief Description of the Drawings FIG. lisa schematic structural diagram of a silver-loaded zeolite filter in the embodiments of the present disclosure; FIG. 2 is a schematic structural diagram of a silver-loaded zeolite filtering unit in the embodiments of the present disclosure; 30 FIG. 3 is a schematic structural diagram of a throttle orifice plate in the 05 06 25 second embodiment of the present disclosure; FIG. 4 is a top view of a gas collection header in the second embodiment of the present disclosure; and FIG. 5 is a side view of the gas collection header in the second 5 embodiment of the present disclosure. In the drawings: 1 - pressure-bearing tank, 2 - baffle, 3 - silver-loaded zeolite filtering unit, 4 - gas collection header, 5 - gas outlet pipe, 6 - gas inlet pipe, 11 - connection rod, 12 - beam, 31 - frame, 32 - porous web, 33 -silver-loaded zeolite bed layer, and 7 - throttle orifice plate. 10 Detailed Description of the Embodiments The technical solution of the present disclosure will now be described clearly and completely with the help of accompanying drawings of the disclosure. Obviously, the described embodiments are part, but not all, of the 15 embodiments of the disclosure. Based on the embodiments of the disclosure, all the other embodiments obtained by those ordinary skilled in the art without any creative labor fall into the scope of the disclosure. In the description of the present disclosure, it should be noted that orientations or positional relationships, such as "above" or the like, are based on 20 the orientations or positional relationships shown in the drawings, and are merely for facilitating and simplifying the description, but not intended to indicate or imply that the referred device or element must be in a specific orientation, or constructed and operated in the specific orientation, and therefore, they should not be construed as limitations to the present disclosure. 25 In the description of the present disclosure, terms "first", "second", and the like are used for the purpose of illustration only but cannot be construed as indicating or implying a relative importance. In the description of the present disclosure, it should be noted that terms "connect", "dispose", "install", "fix" and the like should be understood broadly, 30 and may refer to, for example, a fixed connection or a detachable connection or 05 06 25 an integral connection; or may refer to a direct connection, an indirect connection via an intermedium, or an internal communication between two elements, unless explicitly stated or defined otherwise. The specific meanings of the above terms in the present disclosure can be understood by those skilled in 5 the art according to the specific context. The present disclosure provides a silver-loaded zeolite filter, including a pressure-bearing tank (or pressurized tank), a silver-loaded zeolite filtering unit, and a gas collection header. An inlet is provided on the top of the pressure-bearing tank, an outlet is provided on the bottom of the 10 pressure-bearing tank. The gas to be filtered enters the pressure-bearing tank from the inlet. The silver-loaded zeolite filtering unit is disposed in the pressure-bearing tank and configured to remove organic iodine in the gas to be filtered. The gas collection header is disposed below the silver-loaded zeolite filtering unit and connected to a bottom end of the silver-loaded zeolite filtering 15 unit, and is configured to collect the filtered gas. The outlet of the pressure-bearing tank is connected to a bottom end of the gas collection header. The present disclosure further provides a containment filtration and exhaust system of a nuclear power plant, which includes the silver-loaded zeolite filter as described above. The silver-loaded zeolite filter is configured to filter an 20 organic iodine gas (such as methyl iodide gas) discharged from a containment. First Embodiment As shown in FIG. 1, this embodiment of the present disclosure provides a silver-loaded zeolite filter which mainly consists of a cylindrical 25 pressure-bearing tank 1, a gas flow baffle 2, a silver-loaded zeolite filtering unit 3, a gas collection header 4, a gas outlet pipe 5 and a gas inlet pipe 6. In this embodiment, the cylindrical pressure-bearing tank 1 is a stainless steel pressure vessel with the gas inlet pipe 6 welded on the top thereof. The discharged gas enters the pressure-bearing tank 1 via the gas inlet pipe 6 on the 30 top. A gas flow entering the pressure-bearing tank 1 firstly impacts an upper 05 06 25 surface of the gas flow baffle 2. The gas flow baffle 2 is hung on the upper portion of the pressure-bearing tank 1 through connection rods 11. The connection rods 11 consists of four stainless steel support rods with threaded structures, and each rod has one end fixed on an upper head of the 5 pressure-bearing tank 1 by welding, and a lower end being a free end. Bolt holes are provided in the gas flow baffle 2, through which the connection rods 11 may penetrate to be fixed by nuts, and a spatial position of the gas flow baffle 2 on the pressure-bearing tank 1 may be adjusted according to design. In this embodiment, the silver-loaded zeolite filtering unit 3 consists of 10 three filter cartridge structures arranged in parallel. Each filter cartridge is a flat plate type filter structure consisting of a filler region and a gas flow channel. A porous web 32 made of sintering stainless steel is embedded on a surface of a stainless steel frame 31 by welding. The frame 31 is filled with silver-loaded zeolite particles to form a silver-loaded zeolite bed layer 33, and a filling density 15 is precisely controlled through a mechanical vibration platform. The porous web 32 forms a gas intake surface of the filter cartridge structure. An organic iodine gas, after entering from the porous web 32, chemically reacts with silver ions in the silver-zeolite loaded particles while passing through the silver-zeolite loaded bed layer 33, and thus organic iodine 20 (such as methyl iodide) is adsorbed and removed. Then the filtered gas enters the gas collection header 4. An upper end of the silver-zeolite loaded filtering unit 3 is fixedly connected to a middle portion of the pressure-bearing tank 1 via a beam 12. The beam 12 is made of a metal, and has a lower end matched with the gas collection 25 header 4 through a flange and bolt structure. The beam 12 is a stainless steel flat plate structure, each end of which is fixed on a side wall surface of the pressure-bearing tank 1 by bolts. In design of a horizontal height of the beam 12, a sum of heights of the silver-loaded zeolite filtering unit 3, the gas collection header 4 and the gas outlet pipe 5 is 30 sufficiently considered, and a compression margin is designed on this basis. The 05 06 25 beam 12 functions to compact the silver-loaded zeolite filtering unit 3 tightly to restrict displacement thereof in height, and to prevent gas leakage from the silver-loaded zeolite filtering unit 3 due to mechanical vibration during operation in accident or earthquake conditions. 5 The gas collection header 4 has a structure of a stainless steel box body matched with the bottom of the silver-loaded zeolite filtering unit 3. The gas collection header 4 is manufactured by welding, and the upper portion of the gas collection header 4 is of a special-shaped flange structure having a size in consistence with a flange at the bottom of the silver-loaded zeolite filtering unit 10 3. Below the flange at the upper portion of the gas collection header 4, a straight-section channel is provided. The height of the straight-section channel can ensure that the gas discharged from the filter cartridge does not accumulate or stagnate in the gas collection header 4, thereby preventing a pressure from being generated in the filter and influencing flow distribution characteristics. 15 The straight-section channel of the gas collection header 4 is matched in size with and welded on the gas outlet pipe 5, so as to reduce local pressure loss generated in flowing of the fluid, and the gas outlet pipe 5 is connected to the bottom of the pressure-bearing tank 1 through a flange to form a gas outlet channel. 20 Meanwhile, the gas outlet pipe 5 is also a support member for supporting the filtering unit 3 and the gas collection header 4, and together with the metal beam (with holes) 12, the gas outlet pipe 5 fixes the spatial position of the filtering unit 3, so as to prevent the silver-loaded zeolite bed layer 33 from being immersed by the condensed steam in the pressure-bearing tank 1 and influencing 25 the overall filtering efficiency of the filter. With such new structural design of the silver-loaded zeolite filter, it is ensured that the upper gas flow is uniformly distributed in the vessel, passes through the silver-loaded zeolite bed layer 33 at a low speed, and finally is discharged from the bottom of the pressure-bearing tank 1, resulting in little flow 30 resistance, high filtration efficiency and good flow stability. 05 06 25 The beneficial technical effects of this embodiment lie in that: The silver-loaded zeolite filtering unit 3 of the silver-loaded zeolite filter according to the present disclosure adopts a symmetrical flat-plate structure design, in which the plate-to-plate spacing can ensure uniform flow distribution 5 on the filter and thus ensure the filtering efficiency of the filter. Meanwhile, such a structure has good extensibility, can flexibly change a length size in the horizontal or vertical direction according to the actual gas treatment amount requirement without causing non-uniform flow distribution. In the present disclosure, with the optimized design of the filtering 10 structure and the arrangement, the filter has optimal flow distribution characteristics as a whole, thereby ensuring the filtering efficiency while reducing the flow resistance of equipment. The present disclosure innovatively provides a structural design of the gas collection header, which solves the problem of filter immersion failure caused by 15 steam condensation at the starting stage of the filter. The present disclosure adopts a compact arrangement of multiple filter units, and thus has the minimum equipment space volume on the premise of ensuring the organic iodine adsorption capacity. The present disclosure can realize high and stable filtration efficiency on 20 gaseous organic iodine in a high-temperature, high-pressure and high-humidity environment. Second Embodiment As shown in FIG. 1, this embodiment provides a silver-loaded zeolite filter 25 which include a pressure-bearing tank 1, a silver-loaded zeolite filtering unit 3, and a gas collection header 4. In this embodiment, the pressure-bearing tank 1 is cylindrical, and an interior of the pressure-bearing tank 1 is a cavity configured to provide an installation space for the silver-loaded zeolite filtering unit 3. An inlet is provided on the top of the pressure-bearing tank 1, an outlet is provided 30 on a bottom of the pressure-bearing tank 1, and the gas to be filtered enters the 05 06 25 pressure-bearing tank 1 from the inlet. The silver-loaded zeolite filtering unit 3 is disposed in the pressure-bearing tank 1 located between the inlet and the outlet of the pressure-bearing tank 1, and is configured to remove organic iodine in the gas to be filtered. The gas collection header 4 is disposed below the silver-loaded 5 zeolite filtering unit 3 and connected to the bottom end of the silver-loaded zeolite filtering unit 3, and is configured to collect the filtered gas. The outlet of the pressure-bearing tank 1 is connected to a bottom end of the gas collection header 4. In this embodiment, the gas inlet pipe 6 is disposed in the inlet of the 10 pressure-bearing tank 1 and configured to convey the gas to be filtered into the pressure-bearing tank 1, and the gas outlet pipe 5 is disposed in the outlet of the pressure-bearing tank 1 and connected to the gas collection header 4, and is configured to discharge the filtered gas in the gas collection header 4 out of the pressure-bearing tank 1. 15 As shown in FIGs. 4 and 5, in this embodiment, the silver-loaded zeolite filter further includes beams 12 disposed in the pressure-bearing tank 1 and above the silver-loaded zeolite filtering unit 3. Each end of each beam 12 is fixed on a side wall of the pressure-bearing tank 1, and each beam 12 is configured for compacting the silver-loaded zeolite filtering unit 3. The beams 12 are made of a 20 metal, and two beams 12 are provided and are disposed in parallel. Each beam 12 has a flat plate-shaped rod structure provided with an installation hole, and is connected to the silver-loaded zeolite filtering unit 3 therebelow through a bolt structure. A special-shaped flange is disposed on the top of the gas collection header 4, a bottom flange is disposed on the bottom of the silver-loaded zeolite 25 filtering unit, and the special-shaped flange of the gas collection header is matched with the bottom flange so that the gas collection header 4 can be connected to the silver-loaded zeolite filtering unit 3 through the special-shaped flange. The lower portion of the gas collection header 4 includes a straight-section channel with a height not less than 10% (in the embodiment, a 30 height of 20%) of a height of the pressure-bearing tank, so that the 05 06 25 straight-section channel of the gas collection header 4 has a relatively large space, thereby ensuring that the filtered gas will not accumulate or stagnate in the gas collection header 4, and can quickly and smoothly flow to the gas outlet pipe 5. The straight-section channel has the same diameter as the gas outlet pipe 5 5, and is connected to an input end of the gas outlet pipe 5 by welding. The upper portion of the gas outlet pipe 5 extending into the pressure-bearing tank 1 is configured to support the gas collection header 4 and the silver-loaded zeolite filtering unit 3 so that the silver-loaded zeolite filtering unit 3 is fixed under clamping of the beam 12, the gas collection header 4 and the gas outlet pipe 5. 10 Specifically, since temperature is relatively low at the starting stage of the silver-loaded zeolite filtering unit 3, the gas to be filtered (for example, an organic iodine gas containing a large amount of steam) entering the pressure-bearing tank 1 may condense in the silver-loaded zeolite filtering unit 3 to form a condensate and cause failure of the silver-loaded zeolite. With the gas 15 collection header 4, however, the organic iodine gas entering the silver-loaded zeolite filtering unit 3 will rapidly pass through the gas collection header 4. As a result, the organic iodine gas at the starting stage is condensed in the gas collection header 4, or falls into the gas collection header 4 after being condensed, instead of being retained in the silver-loaded zeolite bed layer, 20 thereby effectively solving the problem that the silver-loaded zeolite is immersed to fail by the condensate generated at the starting stage. In this embodiment, when setting the height of the beam 12, a sum of heights of the silver-loaded zeolite filtering unit 3, the gas collection header 4 and the gas outlet pipe 5 extending into the pressure-bearing tank 1 need to be 25 considered to ensure that the beam 12, the gas collection header 4 and the gas outlet pipe 5 can fix the silver-loaded zeolite filtering unit 3 and limit displacement of the silver-loaded zeolite filtering unit 3 in height. Specifically, a ratio of a distance between the beam 12 and the top of the pressure-bearing tank 1 to a height of the pressure-bearing tank 1 is in a range of 0.15 to 0.4. The 30 preferred height ratio is 0.26. In this embodiment, since a space in the 05 06 25 pressure-bearing tank 1 is sufficiently utilized to provide the silver-loaded zeolite filtering unit 3, the height of the silver-loaded zeolite filtering unit 3 in the pressure-bearing tank needs to be higher than a horizontal center line of the pressure-bearing tank (i.e. higher than the center of the pressure-bearing tank), 5 and thus, the beam should be disposed at a relatively upper position of the pressure-bearing tank 1. Because silver ions chemically react with the organic iodine (such as methyl iodide) at a higher rate under a high-temperature condition, a silver zeolite material formed by combining silver ions and a porous zeolite through a 10 displacement reaction has a good removal effect on the organic iodine gas. However, in the current situation, conditions for the chemical reaction between silver zeolite and organic iodine are harsh. On one hand, a high-temperature environment is required, on the other hand, the requirement on humidity is critical. When steam is contained in the carrier gas, condensation of the steam 15 may cause filtering failure of porous zeolite construction. Therefore, the steam is required to be kept in an overheated state to prevent a situation in which water molecules occupy the organic iodine replacement space of the silver zeolite due to condensation, which will greatly reduce the filtration efficiency of the organic iodine. As shown in FIG. 3, in this embodiment, in order to ensure that the 20 organic iodine gas in the gas to be filtered is always kept in an overheated state to avoid water molecules in the silver zeolite that may affect the absorption effect, the silver-loaded zeolite filter further includes a throttle orifice plate 7 which is disposed at an input end of the gas inlet pipe 6 and configured for obtaining a high-temperature and dry gas to be filtered in an overheated state, 25 thereby preventing filtering failure of the porous zeolite construction due to condensation of steam. Optionally, the silver-loaded zeolite filter further includes a gas flow baffle assembly including a baffle 2. The baffle 2, having a circular plate-shaped structure, is disposed in the pressure-bearing tank 1, above the silver-loaded 30 zeolite filtering unit 3 and opposite to the gas inlet pipe 6, and is configured to 05 06 25 obstruct a gas flow from the gas inlet pipe 6 and reduce a flow velocity of the gas flow so that the gas is uniformly distributed in the pressure-bearing tank 1. Therefore, the gas can fully react with a reaction medium in the silver-loaded zeolite filtering unit 3 to remove radioactive organic iodine in a gas discharged 5 in an accident. Specifically, a ratio of a distance between the baffle 2 and the top of the pressure-bearing tank 1 to a height of the pressure-bearing tank 1 is in a range of 0.05 to 0.3, so as to ensure optimal effects in reducing the gas flow velocity and improving the gas flow distribution by the baffle 2. In this embodiment, the 10 baffle 2 is disposed in the pressure-bearing tank 1 at a height 800 mm away from the top of the pressure-bearing tank 1. In this embodiment, the gas flow baffle assembly further includes connection rods 11. Specifically, four connection rods 11 are provided and are arranged in parallel, one end of each connection rod 11 is fixedly connected to 15 the top of the pressure-bearing tank 1 by welding, and the other end is connected to the baffle 2 via a bolt structure so that the baffle 2 can adjust a spatial position of the baffle 2 in the pressure-bearing tank 1 through the bolt structure. In this way, the baffle 2 can be adjusted to an optimal position in the pressure-bearing tank 1 according to actual conditions. 20 In this embodiment, the silver-loaded zeolite filtering unit 3 includes a plurality of filter cartridge structures arranged side by side. As shown in FIG. 2, specifically three filter cartridge structures, consisting of a middle filter cartridge structure and two side filter cartridge structures, are provided. The middle filter cartridge structure in the middle of the 25 pressure-bearing tank 1 has a length longer than each of the side filter cartridge structures at two sides of the middle filter cartridge structure. The two side filter cartridge structures are same in size and dimension, and are arranged about the middle filter cartridge structure symmetrically. Each cartridge structure has a flat plate shape with a square cross section (square plate face) and a rectangular top 30 surface. A side surface of each filter cartridge structure adjacent to the 05 06 25 pressure-bearing tank 1 is provided as close to the side wall of the pressure-bearing tank 1 as possible, so as to increase a space volume of the filter cartridge structure and provide more silver-loaded zeolite bed layers 33. The three filter cartridge structures are arranged compactly so that an occupied space 5 volume of the equipment can be effectively reduced. A gap is provided between the middle filter cartridge structure and each of the side filter cartridge structures. Many tests show that a ratio of a width of the gap to a diameter of the pressure-bearing tank 1 in the range of 0.05 to 0.15 is optimal because a gap with a width in this range can make flow distribution of 10 the gas to be filtered more uniform, and ensure the filtration efficiency while reducing flow resistance to the gas to be filtered. Meanwhile, the structure has good extensibility, and a size thereof can be flexibly changed according to the actually processed gas amount to adapt to the flow distribution of the gas to be filtered. In this embodiment, the ratio of the width of the gap to the diameter of 15 the pressure-bearing tank is 0.075. In this embodiment, each filter cartridge structure includes a frame 31, porous webs 32 and silver-loaded zeolite bed layers 33. The porous webs 32 are embedded on a bottom surface and at least one side surface of the frame 31, respectively, other surfaces of the frame 31 have a closed structure, and the 20 silver-loaded zeolite bed layers 33 are laid inside the frame 31. Specifically, the frame 31 is a rectangular frame structure made of stainless steel. Likewise, the porous webs 32 are made of stainless steel, and a plurality of tiny through holes are provided in the surface of each porous web 32 so that the surface of the porous web 32 forms a web shape, and thus forms an 25 inlet channel for a gas to flow into the frame 31. The frame 31 is formed by bending a stainless steel plate, the porous webs 32 are installed on two opposite side surfaces and a bottom surface of the frame 31, and the silver-loaded zeolite bed layer 33 is formed by paving silver-loaded zeolite particles having a size larger than the through holes in the porous webs 32 so that the silver-loaded 30 zeolite bed layer can be paved on the porous web 32 at the bottom. A support 05 06 25 web may be further provided at the bottom of the porous web 32. The support web has a relatively high structural strength and is configured to support the porous web 32 at the bottom and the silver-loaded zeolite bed layer. Specifically, each filter cartridge structure is provided with a support web below the frame of 5 the filter cartridge structure, the support web has a side length of 20mm and a batten width of 2mm, and forms a multi-grid-shaped net plate structure to ensure structural stability of the porous web at the bottom of the frame. The gas to be filtered (organic iodine gas) enters an interior of the frame 31 through the porous webs 32 to contact and react with the silver-loaded zeolite bed layer 33, and 10 remove the radioactive organic iodine gas in the gas to be filtered. Specifically, a filling density of the silver-loaded zeolite bed layer 33 is obtained by precisely filling by means of a mechanical vibration platform. In this embodiment, the pressure-bearing tank 1 is a pressure vessel composed of a cylindrical barrel, an upper head and a lower head. The gas inlet pipe 6 is 15 provided on the upper head, the gas outlet pipe 5 is provided on the lower head, and the cylindrical barrel is made of stainless steel. The silver-loaded zeolite filter of this embodiment can effectively filter the radioactive organic iodine gas in the gas to be filtered, remove radioactive iodine elements in the gas, and with a reasonable arrangement of filter cartridge 20 structures, ensure uniform and reasonable distribution of the gas flow while obtaining a good filtering effect, so that the filtering can be performed at a higher speed, with smaller gas flow resistance and good stability. Third Embodiment 25 This embodiment provides a containment filtration and exhaust system of a nuclear power plant, which includes the silver-loaded zeolite filter as described in the first or second embodiment. The silver-loaded zeolite filter is configured to filter a high-temperature organic iodine gas discharged from the containment. In this embodiment, an operation process of the containment filtration and 30 exhaust system of the nuclear power plant is as described below. 05 06 25 Firstly, connect the gas discharge port in the containment of a nuclear power plant with the gas inlet pipe 6 of the silver-loaded zeolite filter. An organic iodine gas (steam) discharged from the containment passes through the throttle orifice plate 7 and is in an overheated state. The organic iodine gas then 5 enters the interior of the pressure-bearing tank 1 through the gas inlet pipe 6. The organic iodine gas moves downwards at a reduced speed under the action of the baffle 2, and is uniformly distributed inside the pressure-bearing tank 1. The organic iodine gas enters the interior of the filter cartridge structure 10 through the porous webs 32 of the filter cartridge structure, and reacts with the silver-loaded zeolite bed layers 33 to remove radioactive iodine elements in the organic iodine gas. The filtered gas enters the gas collection header 4, passes through the straight-section channel of the gas collection header 4 to an exhaust pipe where 15 the gas is discharged. According to the containment filtration and exhaust system of the nuclear power plant in this embodiment, the radioactive organic iodine gas discharged from the containment is treated through the silver-loaded zeolite filter to effectively remove the radioactive organic iodine in the discharged gas, and 20 reduce the pollution to the environment. It will be appreciated that the above implementations are merely exemplary implementations for the purpose of illustrating the principle of the present disclosure, and the present disclosure is not limited thereto. It will be apparent to one of ordinary skill in the art that various modifications and 25 variations can be made to the present disclosure without departing from the spirit or essence of the present disclosure. Such modifications and variations should also be considered as falling into the protection scope of the present disclosure.

Claims

What is claimed is:

1. A silver-loaded zeolite filter, characterized in that, the silver-loaded zeolite filter comprises a pressure-bearing tank (1), a silver-loaded zeolite filtering unit (3), and a gas collection header (4), wherein an inlet 1s provided on a top of the pressure-bearing tank (1), an outlet is provided on a bottom of the pressure-bearing tank (1), and the gas to be filtered enters the pressure-bearing tank (1) from the inlet, the silver-loaded zeolite filtering unit (3) is disposed in the pressure-bearing tank (1) and configured to remove organic iodine in the gas to be filtered, the gas collection header (4) is disposed below the silver-loaded zeolite filtering unit (3) and connected to a bottom end of the silver-loaded zeolite filtering unit (3), and is configured to collect the filtered gas, and the outlet of the pressure-bearing tank (1) is connected to a bottom end of the gas collection header (4).

2. The silver-loaded zeolite filter according to claim 1, characterized by further comprising a gas inlet pipe (6) and a gas outlet pipe (5), wherein the gas inlet pipe (6) is disposed in the inlet of the pressure-bearing tank (1) and configured to convey the gas to be filtered into the pressure-bearing tank (1), and the gas outlet pipe (5) is disposed in the outlet of the pressure-bearing tank (1) and connected to the gas collection header (4), and is configured to discharge the filtered gas in the gas collection header (4) out of the pressure-bearing tank (1).

3. The silver-loaded zeolite filter according to claim 2, characterized by further comprising a beam (12) disposed in the pressure-bearing tank (1) and above the silver-loaded zeolite filtering unit (3), wherein each end of the beam (12) is fixed on a side wall of the pressure-bearing tank (1), and the beam (12) is configured for compacting the silver-loaded zeolite filtering unit (3), and the gas outlet pipe (5) is connected to a bottom of the gas collection header (4), and the gas outlet pipe (5) is further configured to support the gas collection header (4) and the silver-loaded zeolite filtering unit (3) so that the silver-loaded zeolite filtering unit (3) is fixed under clamping of the beam (12), the gas collection header (4) and the gas outlet pipe (5).

4. The silver-loaded zeolite filter according to claim 3, characterized in that, a ratio of a distance between the beam (12) and the top of the pressure-bearing tank (1) to a height of the pressure-bearing tank (1) is in a range of 015t0 04.

5. The silver-loaded zeolite filter according to claim 1, characterized by further comprising a throttle orifice plate (7), wherein the throttle orifice plate (7) is disposed at an input end of the gas inlet pipe (6), and is configured to obtain a dry gas to be filtered in an overheated state.

6. The silver-loaded zeolite filter according to claim 1, characterized by further comprising a gas flow baffle assembly comprising a baffle (2), wherein the baffle (2) is disposed in the pressure-bearing tank (1) and above the silver-loaded zeolite filtering unit (3), and opposite to the gas inlet pipe (6).

7. The silver-loaded zeolite filter according to claim 6, characterized in that, a ratio of a distance between the baffle (2) and the top of the pressure-bearing tank (1) to a height of the pressure-bearing tank (1) is in a range of 005t0 03 8. The silver-loaded zeolite filter according to claim 6, characterized in that, the gas flow baffle assembly further comprises a plurality of connection rods (11), wherein the plurality of connection rods (11) are arranged in parallel, one end of each connection rod (11) is fixedly connected to the top of the pressure-bearing tank (1), and the other end is connected to the baffle (2).

9. The silver-loaded zeolite filter according to any one of claims 1 to 8, characterized in that, the silver-loaded zeolite filtering unit (3) comprises a plurality of filter cartridge structures arranged side by side, wherein each filter cartridge structure comprises a frame (31), a porous web (32) and a silver-loaded zeolite bed layer (33), wherein the porous web (32) is embedded on a bottom surface and at least one side surface of the frame (31), other surfaces of the frame (31) form a closed structure, and the silver-loaded zeolite bed layer (33) is laid inside the frame (31).

10. The silver-loaded zeolite filter according to claim 9, characterized in that, three filter cartridge structures, consisting of a middle filter cartridge structure and two side filter cartridge structures, are provided, wherein the three filter cartridge structures each have a flat plate shape with a square cross section, and the middle filter cartridge structure has a length longer than each of the side filter cartridge structures.

11. The silver-loaded zeolite filter according to claim 10, characterized in that, the middle filter cartridge structure is located in the middle of the pressure-bearing tank (1), and the two side filter cartridge structures are symmetrically distributed on two sides of the middle filter cartridge structure.

12. The silver-loaded zeolite filter according to claim 10, characterized in that, a gap is provided between the middle filter cartridge structure and each of the side filter cartridge structures, wherein a ratio of a width of the gap to a diameter of the pressure-bearing tank (1) is in a range of 0.05 to 0.

15.

13. The silver-loaded zeolite filter according to claim 9, characterized in that, a filling density of the silver-loaded zeolite bed layer (33) is obtained by precisely filling by means of a mechanical vibration platform.

14. The silver-loaded zeolite filter according to any one of claims 1 to 8, characterized in that, the silver-loaded zeolite filtering unit (3) is connected to the gas collection header (4) via a bottom flange, wherein the top of the gas collection header (4) adopts a structure matched with the bottom flange.

15. The silver-loaded zeolite filter according to any one of claims 2 to 8, characterized in that, the pressure-bearing tank (1) is a pressure vessel composed of a cylindrical barrel, an upper head and a lower head, wherein the gas inlet pipe (6) is provided on the upper head, and the gas outlet pipe (5) is provided on the lower head.

16. A containment filtration and exhaust system of a nuclear power plant, characterized by comprising a silver-loaded zeolite filter according to any one of claims 1 to 15, wherein the silver-loaded zeolite filter is configured to filter a high-temperature organic iodine gas discharged from the containment.

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