Device for cold start of silver-loaded zeolite and use method thereof

Abstract

The invention provides a device for cold start of silver-loaded zeolite and a use method of the device, and belongs to the technical field of research on filtering characteristics of gaseous methyl iodide by a nuclear power station based on the silver-loaded zeolite. The problems that an existing cold-state starting scheme is not suitable for the silver-loaded zeolite, and the methyl iodide adsorption characteristic of the silver-loaded zeolite in the cold-state starting stage cannot be researched are solved. The device comprises a carrier gas system, a methyl iodide gas distribution system, a silver-loaded zeolite column assembly, a pipeline carrier gas flow path and a sampling and measuring system, the carrier gas system comprises a nitrogen source and a steam generator, the output end of the nitrogen source is connected with the input end of the steam generator, the methyl iodide gas distribution system comprises a gas cylinder, and the silver-loaded zeolite column assembly comprises a silver-loaded zeolite bed. Mixed gas output by the steam generator and methyl iodide gas output by the gas cylinder are mixed and conveyed to the silver-loaded zeolite column assembly through a main flow path of the pipeline carrier gas flow path, and the silver-loaded zeolite column assembly is connected with the sampling and measuring system. The device is mainly used for testing the adsorption characteristic of the silver-loaded zeolite.

Description

Technical Field

[0001] The invention belongs to the technical field of research on filtering characteristics of gaseous methyl iodide based on silver-loaded zeolite in nuclear power plants, and in particular relates to a device for cold starting of silver-loaded zeolite and a method for using the device. Background Art

[0002] When a serious accident occurs in a nuclear power plant reactor, in order to cool the temperature of the reactor core, a large amount of coolant will be sprayed into the containment. These coolants will absorb a large amount of reactor heat in a very short time and form steam in the containment with lower pressure. At the same time, after the reactor core melts, the molten core will destroy the pressure vessel and fall into the pile pit, reacting with the concrete floor to produce a large amount of non-condensable gas. The production of these steam and non-condensable gases in the containment will increase the temperature and pressure in the containment, which may eventually cause the containment to be destroyed due to internal pressure exceeding its pressure limit, causing radioactive substances to leak into the environment, causing serious radioactive pollution and endangering public safety. In order to protect the integrity of the containment, the containment needs to be actively discharged and depressurized as soon as the accident occurs. However, due to the large amount of radioactive substances in the containment, it cannot be discharged directly to the outside. The discharged gas needs to be filtered and treated for radioactive substances first to reduce the radioactive pollution discharged into the environment.

[0003] At present, for the filtration of radioactive materials in the containment, silver-loaded zeolite has been considered as a new material to filter the main methyl iodide gas in the radioactive materials. The adsorption performance of silver-loaded zeolite to methyl iodide gas is related to multiple parameters. In order to explore its adsorption performance, it is necessary to design relevant methods and devices.

[0004] The existing Chinese invention patent with publication number CN101238275B proposes a heating system for a liquid delivery system, the structure of which includes at least one first heating device for thawing the liquid, and at least one filter heating device for heating the filtered liquid, connecting wires, etc. The invention patent is particularly capable of heating the exhaust gas purification catalyst of the internal combustion engine to a working ready state more quickly when the temperature is below the freezing point. The system disclosed in the invention can well complete the heating function of the liquid delivery system, but compared with the present invention, although both belong to directional heating of a certain device or part, the present invention can keep the heated part warm while heating and keep the temperature constant at a certain temperature. The invention patents with publication numbers CN113847621A and CN111042882A all provide cold start methods or systems in some fields, but there are few patents related to the cold start of the silver zeolite bed, and due to the unique structure of the silver zeolite, these cold start methods and systems are not applicable.

[0005] In summary, the existing cold start scheme and heating system are of little help in studying the adsorption characteristics of silver-loaded zeolite for methyl iodide during the cold start stage. Summary of the invention

[0006] In view of this, the present invention aims to propose a device for cold start of silver-loaded zeolite and a method of using the same, so as to solve the problem that the existing cold start scheme is not applicable to silver-loaded zeolite and it is impossible to study the adsorption characteristics of silver-loaded zeolite for methyl iodide during the cold start stage.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A device for cold starting of silver-loaded zeolite comprises a carrier gas system, a methyl iodide gas distribution system, a silver-loaded zeolite column assembly, a pipeline carrier gas flow path and a sampling and measuring system. The carrier gas system comprises a nitrogen source and a steam generator, the output end of the nitrogen source is connected to the input end of the steam generator, the methyl iodide gas distribution system comprises a gas cylinder, the silver-loaded zeolite column assembly comprises a silver-loaded zeolite bed, the mixed gas output by the steam generator is mixed with the methyl iodide gas output by the gas cylinder and transported to the silver-loaded zeolite column assembly through the main flow path of the pipeline carrier gas flow path, and the silver-loaded zeolite column assembly is connected to the sampling and measuring system.

[0009] Furthermore, the silver-loaded zeolite column assembly further comprises a heat-insulating layer and a constant temperature box, the silver-loaded zeolite bed is arranged in the heat-insulating layer, and the heat-insulating layer is arranged in the constant temperature box.

[0010] Furthermore, the air inlet of the silver-loaded zeolite bed is connected to the first three-way valve through a main flow path, and the air outlet of the silver-loaded zeolite bed is connected to the third three-way valve through a main flow path.

[0011] Furthermore, a plurality of thermocouples are arranged at the side ends of the silver-loaded zeolite bed.

[0012] Furthermore, a main flow path between the output end of the nitrogen source and the output end of the steam generator is provided with a pressure relief valve, a flow meter and a regulating valve in sequence along the gas delivery direction, and a pressure gauge is provided on the steam generator.

[0013] Furthermore, an electric heating device is provided in the steam generator.

[0014] Furthermore, the sampling and measuring system includes a condenser and a gas chromatograph connected to each other, a second three-way valve is provided on the main flow path between the first three-way valve and the third three-way valve, and the second three-way valve is connected to the condenser.

[0015] Furthermore, a first stop valve is provided at a connection port between the first three-way valve and the bypass flow path of the pipeline carrier gas flow path, and a second stop valve is provided at a connection port between the third three-way valve and the bypass flow path.

[0016] Furthermore, the output ends of the first stop valve and the second stop valve are both equipped with condensate measuring instruments.

[0017] A method for using a device for cold starting of silver-carrying zeolite, comprising the following steps:

[0018] Step 1: Turn on the steam generator and the thermostat, and set the liquid phase temperature in the steam generator and the temperature in the thermostat to predetermined values;

[0019] Step 2: Start the nitrogen source, pass nitrogen into the steam generator, and discharge it through the bypass flow path;

[0020] Step 3: When the temperature of the steam generator reaches the set value, the flow rate of the nitrogen source is also increased to the set value, and at the same time, a condensate measuring instrument is connected after the first stop valve and the second stop valve;

[0021] Step 4: After the working condition is confirmed to be correct, the first three-way valve and the third three-way valve are connected to the bypass flow path, the second three-way valve is connected to the path flowing to the third three-way valve, the first stop valve is closed, and a path consisting of the steam generator, the first three-way valve, the second three-way valve, the third three-way valve and the second stop valve is formed, the gas cylinder is opened, and the methyl iodide concentration at the inlet of the silver-loaded zeolite bed is measured through the bypass flow path;

[0022] Step 5: switching the carrier gas to the silver-loaded zeolite bed through the first three-way valve, recording the temperature change of the silver-loaded zeolite bed, and measuring the methyl iodide gas concentration at the gas outlet of the silver-loaded zeolite bed;

[0023] Step 6: Gradually increase the temperature of the incubator from the cold state and repeat the above steps;

[0024] Step 7: After the test, switch the carrier gas to the bypass flow path, then turn off the gas cylinder, steam generator and nitrogen source in turn, and finally turn off the power of the thermostat.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention can well study the adsorption characteristics of silver-loaded zeolite for methyl iodide during the cold start-up phase, and can clearly reflect the change of bed temperature and methyl iodide adsorption efficiency over time after the carrier gas is switched to the silver-loaded zeolite bed, thereby well determining the adsorption efficiency of the silver-loaded zeolite under different temperature conditions.

[0027] 2. The present invention can provide good data support for studying the relationship between the adsorption of silver-loaded zeolite and other parameters, and ensure that steam condensation will not occur during the ventilation process during other characteristic research processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 This is a schematic structural diagram of a device for cold starting of silver-loaded zeolite according to the present invention;

[0030] Figure 2 It is a structural schematic diagram of the steam generator of the present invention;

[0031] Figure 3 is a schematic diagram of the structure of a silver-loaded zeolite column;

[0032] Figure 4 Schematic diagram of the distribution of pipeline carrier gas flow path.

[0033] 1-nitrogen source, 2-pressure relief valve, 3-flow meter, 4-pressure gauge, 5-gas cylinder, 6-insulation layer, 7-first three-way valve, 8-first stop valve, 9-condenser, 10-gas chromatograph, 11-second three-way valve, 12-second stop valve, 13-third three-way valve, 14-constant temperature box, 15-silver-loaded zeolite bed, 16-steam generator, 17-electric heating device, 18-regulating valve, 21-air inlet, 22-thermocouple, 23-air outlet, 24-main flow path, 25-bypass flow path. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict, and the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0035] Specific implementation method 1: See Figure 1-4The present embodiment is described as a device for cold starting of silver-loaded zeolite, characterized in that it includes a carrier gas system, a methyl iodide gas distribution system, a silver-loaded zeolite column assembly, a pipeline carrier gas flow path, and a sampling and measuring system. The carrier gas system includes a nitrogen source 1 and a steam generator 16. The output end of the nitrogen source 1 is connected to the input end of the steam generator 16. The methyl iodide gas distribution system includes a gas cylinder 5. The silver-loaded zeolite column assembly includes a silver-loaded zeolite bed 15. The mixed gas output by the steam generator 16 and the methyl iodide gas output by the gas cylinder 5 are mixed. The mixed body is transported to the silver-loaded zeolite column assembly through the main flow path 24 of the pipeline carrier gas flow path, and the silver-loaded zeolite column assembly is connected to the sampling and measuring system. The air inlet 21 of the silver-loaded zeolite bed 15 is connected to the first three-way valve 7 through the main flow path 24, and the air outlet 23 of the silver-loaded zeolite bed 15 is connected to the third three-way valve 13 through the main flow path 24. A first stop valve 8 is provided at the connecting port of the first three-way valve 7 and the bypass flow path 25 of the pipeline carrier gas flow path, and a second stop valve 12 is provided at the connecting port of the third three-way valve 13 and the bypass flow path 25.

[0036] Before use, the steam generator 16 and the thermostat 14 are turned on, and the liquid phase temperature in the steam generator 16 and the temperature in the thermostat 14 are set to predetermined values. Then, the nitrogen source 1 is started, and nitrogen is passed into the steam generator 16 and discharged through the bypass flow path 25. When the temperature of the steam generator 16 reaches the set value, the flow rate of the nitrogen source 1 is also increased to the set value. After the working condition is confirmed to be correct, the first three-way valve 7 and the third three-way valve 13 are connected to the bypass flow path 25, and the second three-way valve 11 is connected to the passage flowing to the third three-way valve 13. The first stop valve 8 is closed to form a passage consisting of the steam generator 16, the first three-way valve 7, the second three-way valve 11, the third three-way valve 13 and the second stop valve 12. The gas cylinder 5 is turned on, and the silver-loaded zeolite is measured through the bypass flow path 25. The methyl iodide concentration at the inlet of the bed 15 is measured by switching the carrier gas to the silver-loaded zeolite bed 15 through the first three-way valve 7, recording the temperature change of the silver-loaded zeolite bed 15, and measuring the methyl iodide gas concentration at the gas outlet 23 of the silver-loaded zeolite bed 15. The temperature of the thermostat 14 is gradually increased from the cold state, and the above steps are repeated. After the test, the carrier gas is switched to the bypass flow path 25, and then the gas cylinder 5, the steam generator 16 and the nitrogen source 1 are turned off in turn, and finally the power supply of the thermostat 14 is turned off. The device is used to study the adsorption characteristics of methyl iodide in the cold start-up stage of the silver-loaded zeolite, and can clearly reflect the change of the bed temperature and the methyl iodide adsorption efficiency with time after the carrier gas is switched to the silver-loaded zeolite bed, thereby well determining the adsorption efficiency of the silver-loaded zeolite under different temperature conditions.

[0037] Specific implementation method 2: See Figure 1-4To illustrate this embodiment, the main flow path 24 between the output end of the nitrogen source 1 and the output end of the steam generator 16 is provided with a pressure relief valve 2, a flow meter 3 and a regulating valve 18 in sequence along the gas delivery direction, the steam generator 16 is provided with a pressure gauge 4, the sampling and measuring system includes a condenser 9 and a gas chromatograph 10 connected to each other, the main flow path 24 between the first three-way valve 7 and the third three-way valve 13 is provided with a second three-way valve 11, the second three-way valve 11 is connected to the condenser 9, and each system is connected through a pipeline carrier gas flow path. Under normal working conditions of the device, the high-purity nitrogen gas from the high-purity nitrogen source 1 passes through the pipeline, flows through the pressure relief valve 2, the flow meter 3, and then enters the steam generator 16 through the regulating valve 18, and the high-purity nitrogen enters from the bottom of the generator and leaves from the upper liquid surface. The mixed gas leaving the steam generator 16 is then mixed with the methyl iodide gas from the high-pressure gas cylinder 5 through the pipeline and continues to be transmitted to the rear. When the stop valve 8 and the stop valve 12 are in the closed state, the three-way valve 13 is connected to the main flow path 24, and the sampled gas passes through the silver zeolite column 15, enters the condenser 9 through the three-way valve 11, and after condensation, enters the gas chromatograph 10 for final testing.

[0038] Specific implementation method three: see Figure 1-4 To illustrate this embodiment, the steam generator 16 is provided with an electric heating device 17, which has a temperature control function, and the pressure of the steam internal space can be monitored by the pressure gauge 4. The steam generator 16 is filled with deionized water, and high-purity nitrogen enters from the bottom of the generator and passes through the liquid phase in the form of bubbles. During this process, due to the low initial steam partial pressure in the bubble, the steam will be transferred from the gas-liquid interface to the inside of the bubble, and reach a mass transfer equilibrium state before leaving the liquid surface. Based on this principle, the steam mass fraction in the carrier gas can be achieved by adjusting the nitrogen flow rate and the evaporator heating power.

[0039] The pressure of the air flow into the carrier gas flow path of the pipeline can be controlled by the pressure relief valve 2 to ensure the safe operation of the device. The regulating valve 18 can adjust the air flow rate of the carrier gas flow path of the pipeline. The air flow rate of the carrier gas flow path of the pipeline can be measured by the flow meter 3, thereby providing a reference for the air flow rate control of the carrier gas flow path of the pipeline. The methyl iodide gas is supplied by the high-pressure gas cylinder 5, and the high-pressure gas cylinder 5 contains 3000ppm of high-concentration standard methyl iodide gas.

[0040] Specific implementation method four: see Figure 1-4To illustrate this embodiment, the silver-loaded zeolite column assembly also includes a thermal insulation layer 6 and a constant temperature box 14, the silver-loaded zeolite bed 15 is arranged in the thermal insulation layer 6, and the thermal insulation layer 6 is arranged in the constant temperature box 14. The silver-loaded zeolite column 15 is a cylindrical structure with an inner diameter of 25 mm, an air inlet 21 at the top, an air outlet 23 at the bottom, and an allowable filler height range inside of 0 to 12 mm. Three armored thermocouples 22 with a diameter of 1 mm are arranged along the height direction of the column to measure the temperature changes of the upper air space and the zeolite bed. The silver-loaded zeolite column 15 is installed as a whole in a constant temperature box 14. The temperature can be controlled, adjusted and monitored by the constant temperature box 14. The methyl iodide gas concentration at the inlet and outlet of the silver-loaded zeolite column 15 is measured and analyzed by a GC-2010 gas chromatograph 10. When the carrier gas contains water vapor, the sampled gas passes through a condenser 9 to remove the water vapor in the carrier gas before entering the chromatograph. At the same time, the steam share in the carrier gas can be calibrated by measuring the condensation rate. The experiment was carried out under the condition that the absolute pressure of the silver-loaded zeolite column 15 was 0.5 MPa. The inlet gas temperature of the silver-loaded zeolite column 15 was 145°C, the superheat was 10°C, and the initial conditions of the silver-loaded zeolite column 15 were close to normal temperature and pressure.

[0041] Specific implementation method five: see Figure 1-4 To illustrate this embodiment, the output ends of the first stop valve 8 and the second stop valve 12 are both equipped with condensate measuring instruments for measuring the amount of condensate.

[0042] Specific implementation method six: see Figure 1-4 The present embodiment is described as a method for using a device for cold starting of silver-loaded zeolite, which comprises the following steps:

[0043] Step 1: Turn on the steam generator 16 and the thermostat 14, and set the liquid phase temperature in the steam generator 16 and the temperature in the thermostat 14 to predetermined values;

[0044] Step 2: Start the nitrogen source 1, pass the nitrogen into the steam generator 16, and discharge it through the bypass flow path 25;

[0045] Step 3: When the temperature of the steam generator 16 reaches the set value, the flow rate of the nitrogen source 1 is also increased to the set value, and at the same time, a condensate measuring instrument is connected after the first stop valve 8 and the second stop valve 12;

[0046] Step 4: After the working condition is confirmed to be correct, the first three-way valve 7 and the third three-way valve 13 are connected to the bypass flow path 25, the second three-way valve 11 is connected to the path flowing to the third three-way valve 13, the first stop valve 8 is closed, and a path consisting of the steam generator 16, the first three-way valve 7, the second three-way valve 11, the third three-way valve 13 and the second stop valve 12 is formed, the gas cylinder 5 is opened, and the methyl iodide concentration at the inlet of the silver-loaded zeolite bed 15 is measured through the bypass flow path 25;

[0047] Step 5: Switch the carrier gas to the silver-loaded zeolite bed 15 through the first three-way valve 7, record the temperature change of the silver-loaded zeolite bed 15, and simultaneously measure the methyl iodide gas concentration at the gas outlet 23 of the silver-loaded zeolite bed 15;

[0048] Step 6: gradually increase the temperature of the thermostat 14 from the cold state, and repeat the above steps;

[0049] Step 7: After the test, switch the carrier gas to the bypass flow path 25, then turn off the gas cylinder 5, the steam generator 16 and the nitrogen source 1 in sequence, and finally turn off the power of the thermostat 14.

[0050] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

Claims

1. A device for cold starting of silver-loaded zeolite, characterized in that: The invention comprises a carrier gas system, a methyl iodide gas distribution system, a silver-loaded zeolite column assembly, a pipeline carrier gas flow path and a sampling and measuring system. The carrier gas system comprises a nitrogen source (1) and a steam generator (16). The output end of the nitrogen source (1) is connected to the input end of the steam generator (16). The methyl iodide gas distribution system comprises a gas cylinder (5). The silver-loaded zeolite column assembly comprises a silver-loaded zeolite bed (15). The mixed gas output by the steam generator (16) is mixed with the methyl iodide gas output by the gas cylinder (5) and is transported to the silver-loaded zeolite column assembly through a main flow path (24) of the pipeline carrier gas flow path. The silver-loaded zeolite column assembly is connected to the sampling and measuring system.

2. A device for cold starting of silver-loaded zeolite according to claim 1, characterized in that: The silver-loaded zeolite column assembly further comprises a heat-insulating layer (6) and a thermostatic box (14); the silver-loaded zeolite bed (15) is arranged in the heat-insulating layer (6), and the heat-insulating layer (6) is arranged in the thermostatic box (14).

3. A device for cold starting of silver-loaded zeolite according to claim 2, characterized in that: The air inlet (21) of the silver-loaded zeolite bed (15) is connected to the first three-way valve (7) via a main flow path (24), and the air outlet (23) of the silver-loaded zeolite bed (15) is connected to the third three-way valve (13) via a main flow path (24).

4. A device for cold starting of silver-loaded zeolite according to claim 2, characterized in that: A plurality of thermocouples (22) are arranged at the side end of the silver-loaded zeolite bed (15).

5. A device for cold starting of silver-loaded zeolite according to claim 1, characterized in that: A main flow path (24) between the output end of the nitrogen source (1) and the output end of the steam generator (16) is provided with a pressure relief valve (2), a flow meter (3) and a regulating valve (18) in sequence along the gas delivery direction, and a pressure gauge (4) is provided on the steam generator (16).

6. A device for cold starting of silver-loaded zeolite according to claim 5, characterized in that: An electric heating device (17) is provided in the steam generator (16).

7. A device for cold starting of silver-loaded zeolite according to claim 3, characterized in that: The sampling and measuring system comprises a condenser (9) and a gas chromatograph (10) which are connected to each other, a second three-way valve (11) is provided on the main flow path (24) between the first three-way valve (7) and the third three-way valve (13), and the second three-way valve (11) is connected to the condenser (9).

8. A device for cold starting of silver-loaded zeolite according to claim 3, characterized in that: A first stop valve (8) is provided at the connection port between the first three-way valve (7) and the bypass flow path (25) of the pipeline carrier gas flow path, and a second stop valve (12) is provided at the connection port between the third three-way valve (13) and the bypass flow path (25).

9. A device for cold starting of silver-loaded zeolite according to claim 8, characterized in that: The output ends of the first stop valve (8) and the second stop valve (12) are both equipped with condensate measuring instruments.

10. A method for using the device for cold starting of silver-loaded zeolite as claimed in claim 1, characterized in that: It includes the following steps: Step 1: Turn on the steam generator (16) and the thermostat (14), and set the liquid phase temperature in the steam generator (16) and the temperature in the thermostat (14) to predetermined values; Step 2: Start the nitrogen source (1), pass the nitrogen into the steam generator (16), and discharge it through the bypass flow path (25); Step 3: When the temperature of the steam generator (16) reaches the set value, the flow rate of the nitrogen source (1) is also increased to the set value, and at the same time, a condensate measuring instrument is connected after the first stop valve (8) and the second stop valve (12); Step 4: After the working condition is confirmed to be correct, the first three-way valve (7) and the third three-way valve (13) are connected to the bypass flow path (25), the second three-way valve (11) is connected to the path flowing to the third three-way valve (13), the first stop valve (8) is closed, and a path is formed by the steam generator (16), the first three-way valve (7), the second three-way valve (11), the third three-way valve (13) and the second stop valve (12), the gas cylinder (5) is opened, and the methyl iodide concentration at the inlet of the silver-loaded zeolite bed (15) is measured through the bypass flow path (25); Step 5: switching the carrier gas to the silver-loaded zeolite bed (15) through the first three-way valve (7), recording the temperature change of the silver-loaded zeolite bed (15), and measuring the methyl iodide gas concentration at the gas outlet (23) of the silver-loaded zeolite bed (15); Step 6: gradually increase the temperature of the thermostat (14) from the cold state, and repeat the above steps; Step 7: After the test is completed, the carrier gas is switched to the bypass flow path (25), and then the gas cylinder (5), the steam generator (16) and the nitrogen source (1) are turned off in sequence, and finally the power supply of the thermostat (14) is turned off.

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