A nuclear industry process tail gas treatment device

Abstract

This invention provides a nuclear industry process tail gas treatment device, which can treat waste gas and flue gas generated in the nuclear industry with relatively low energy consumption. It first uses a GGH heat exchanger to treat NO-containing gases in the temperature range of 25~50℃. X The process exhaust gas to be treated is first-stage heated; then, the high-temperature ammonia gas discharged from the urea pyrolysis furnace is mixed with the process exhaust gas in the flue gas mixer for second-stage heating; this effectively utilizes thermal energy and reduces overall operating costs. At the same time, this application uses a two-stage heating method to raise the temperature of the low-temperature process exhaust gas to the process reaction temperature range of 230~260℃ for low-temperature SCR denitrification, and the heat source of the GGH heat exchanger can use the flue gas discharged from the SCR reactor in the range of 230~260℃, making full use of the heat source generated in the system and reducing system operating costs.

Description

Technical Field

[0001] This utility model relates to the field of flue gas denitrification technology, specifically a nuclear industry process tail gas treatment device. Background Technology

[0002] Nitrogen oxides (NOx) in the nuclear industry x The main source is the dissolved waste gas from nuclear fuel reprocessing plants, which contains high concentrations of NO produced by the decomposition of HNO3. x The waste / flue gas generated in the nuclear industry is characterized by low temperature (25~50℃), small volume, high concentration, and strong corrosivity. Currently, the main treatment technologies are alkaline absorption and selective catalytic reduction (SCR). While alkaline absorption is technically mature, highly reliable, and effectively removes high concentrations of NOx and neutralizes acidity, and can simultaneously remove some acidic aerosols and soluble radionuclides, the resulting salt / radionite-containing waste liquid requires further treatment through evaporation solidification, cement solidification, etc., resulting in high absorbent consumption and operating costs. Furthermore, equipment corrosion during the reaction process necessitates the use of equipment made of materials such as titanium alloys and high-grade stainless steel, further increasing costs. While SCR has high denitrification efficiency (up to 90% or more), a single-stage SCR cannot meet the demand for even higher denitrification efficiencies (99%). Additionally, it typically uses electric heaters or burners to raise the temperature to the required SCR temperature, resulting in high energy consumption and increased system operating costs. Summary of the Invention

[0003] To address the issue of high operating costs in existing waste gas and flue gas treatment systems in the nuclear industry, this invention provides a nuclear industry process tail gas treatment device that can treat waste gas and flue gas generated in the nuclear industry with relatively low energy consumption.

[0004] The structure of this utility model is as follows: a nuclear industry process tail gas treatment device, characterized in that it includes: a GGH heat exchanger, a urea pyrolysis furnace, a flue gas mixer and an SCR reactor group;

[0005] The low-temperature flue gas inlet of the GGH heat exchanger is connected to a NO-containing... X The inlet pipe of the process exhaust gas to be treated is connected to the high-temperature flue gas outlet of the GGH heat exchanger and the flue gas mixer; the exhaust port of the urea pyrolysis furnace is connected to the flue gas mixer through a pipe.

[0006] The exhaust port of the flue gas mixer is connected to the SCR reactor group; the SCR reactor group includes: a first SCR reactor and a second SCR reactor;

[0007] The exhaust port of the flue gas mixer is connected to the first SCR reactor and the second SCR reactor respectively through parallel valves; the exhaust ports of the first SCR reactor and the second SCR reactor are respectively connected to the high-temperature flue gas inlet of the GGH heat exchanger.

[0008] The exhaust port of the first SCR reactor is connected to the flue gas inlet of the second SCR reactor through a series flue gas duct, and a series control valve is installed on the series flue gas duct.

[0009] Its further features are:

[0010] A temperature measuring device is installed at the exhaust port of the flue gas mixer;

[0011] An electric heater is installed at the air inlet of the flue gas mixer;

[0012] A nitrogen oxide detector is installed on the pipeline connecting the GGH heat exchanger to the process exhaust gas to be treated.

[0013] The urea pyrolysis furnace is equipped with a dilution air electric heater at the dilution air inlet;

[0014] The parallel valves include: a first parallel valve and a second parallel valve, wherein the first parallel valve is disposed on the flue gas inlet duct of the first SCR reactor, and the second parallel valve is disposed on the flue gas inlet duct of the second SCR reactor; the second parallel valve is disposed between the series control valve and the flue gas inlet of the second SCR reactor.

[0015] It also includes: a heat exchange regulating valve, wherein the heat exchange regulating valve includes: a first heat exchange valve and a second heat exchange valve;

[0016] The first heat exchange valve is installed between the exhaust port of the first SCR reactor and the high-temperature flue gas inlet of the GGH heat exchanger.

[0017] The second heat exchange valve is installed between the exhaust port of the second SCR reactor and the high-temperature flue gas inlet of the GGH heat exchanger.

[0018] This application provides a nuclear industry process tail gas treatment device, which first treats NO-containing gases at temperatures ranging from 25 to 50°C using a GGH heat exchanger. XThe process tail gas to be treated undergoes a first-stage heating process; then, high-temperature ammonia gas discharged from the urea pyrolysis furnace is mixed with the process tail gas in a flue gas mixer for a second-stage heating process. Because the process tail gas generated in the nuclear industry is characterized by low temperature and small volume, this application fully utilizes the heat from the high-temperature ammonia gas required in the SCR denitrification process to heat the process tail gas, effectively utilizing thermal energy and reducing overall operating costs. This application uses a two-stage heating method to raise the temperature of the low-temperature process tail gas to the process reaction temperature range of 230~260℃ for low-temperature SCR denitrification, while the heat source for the GGH heat exchanger can be the flue gas discharged from the SCR reactor in the 230~260℃ range, fully utilizing the heat generated in the system. The heat source reduces system operating costs. Compared with the existing technology of heating low-temperature flue gas through a GGH+ burner, the two-stage heating method of this application is more energy-efficient and has lower system operating costs. At the same time, this application sets up two SCR reactors, which are connected in series by valves. The flue gas outlet of the flue gas mixer is connected to both SCR reactors simultaneously through valves. According to actual needs, either SCR reactor can be selected for denitrification reaction by opening and closing the valves, or the two SCR reactors connected in series can be selected to form a two-stage SCR reactor for denitrification reaction. This ensures that the solution of this application can more flexibly adjust the use of SCR reactors according to the exhaust gas concentration, making the solution more practical. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the nuclear industry process tail gas treatment device of this application. Detailed Implementation

[0020] like Figure 1 As shown, this application includes a nuclear industry process tail gas treatment device, which includes: a GGH heat exchanger 1, a urea pyrolysis furnace 2, a flue gas mixer 3, and an SCR reactor group.

[0021] The low-temperature flue gas inlet connection of GGH heat exchanger 1 contains NO X The inlet pipe of the exhaust gas to be treated is connected to the high-temperature flue gas outlet of the GGH heat exchanger 1, which is connected to the flue gas mixer 3; the exhaust port of the urea pyrolysis furnace 2 is connected to the flue gas mixer 3 through a pipe.

[0022] A dilution air heater 6 is installed at the dilution air inlet of the urea pyrolysis furnace 2. The dilution air is sent into the urea pyrolysis furnace 2 via a blower 10. The urea pyrolysis dilution air utilizes ambient air, is pressurized by the dilution blower, and then heated to 600-650℃ by the dilution air heater 6 before entering the urea pyrolysis furnace 2. The urea pyrolysis furnace 2 decomposes the urea solution and dilutes it into diluted ammonia gas with a concentration of less than 5%. The temperature of the diluted ammonia gas discharged from the urea pyrolysis furnace 2 is approximately 500℃. In ordinary chemical plant process systems or SCR reactors in large-capacity hazardous waste treatment systems, the heat from the diluted ammonia gas is insufficient to heat the process gas due to the large volume of process gas to be treated. However, the characteristics of nuclear industry process tail gas are low temperature (25-50℃), small flue gas volume, and high concentration, so the heat in the diluted ammonia gas can be fully utilized to reduce system operating costs.

[0023] The exhaust gas from the process to be treated, with a temperature of 25~50℃, is heated to about 160~185℃ by heat exchange in GGH heat exchanger 1, and then heated to 230~260℃ by diluted ammonia gas of about 500℃ emitted from urea pyrolysis furnace 2 in flue gas mixer 3, which meets the temperature requirements for medium and low temperature SCR denitrification.

[0024] To ensure that the flue gas entering the SCR reactor meets the low-temperature SCR denitrification temperature requirement of 230~260℃ and that the denitrification reaction occurs fully, this application includes a temperature measuring device and an auxiliary heating device. Specifically, a temperature measuring device 8 is installed at the exhaust port of the flue gas mixer 3 to measure the temperature of the flue gas exiting the flue gas mixer 3. The temperature measuring device can be implemented using various devices and sensors available in the prior art that can perform temperature measurement. In this embodiment, it is based on a temperature measuring resistor. The temperature measuring device 8 is used in conjunction with a process tail gas electric heater 9 for thermal auxiliary heating. Once the temperature measuring device 8 detects that the inlet temperature of the SCR reactor is lower than 230℃, the process tail gas entering the flue gas mixer 3 is heated by the process tail gas electric heater 9, which is located between the GGH heat exchanger 1 and the flue gas mixer 3.

[0025] Because of NO in the exhaust gas from nuclear industry processes X The flow rate is relatively high and unstable, so this application incorporates a flexibly adjustable SCR reactor group. The exhaust port of the flue gas mixer 3 is connected to the SCR reactor group; the SCR reactor group includes: a first SCR reactor 4 and a second SCR reactor 5.

[0026] The exhaust port of the flue gas mixer 3 is connected to the first SCR reactor 4 and the second SCR reactor 5 respectively through parallel valves; the exhaust ports of the first SCR reactor 4 and the second SCR reactor 5 are respectively connected to the high-temperature flue gas inlet of the GGH heat exchanger 1.

[0027] The exhaust port of the first SCR reactor 4 is connected to the flue gas inlet of the second SCR reactor 5 through a series flue gas duct, and a series control valve 52 is installed on the series flue gas duct.

[0028] The parallel valves include a first parallel valve 41 and a second parallel valve 51. The first parallel valve 41 is installed on the flue gas inlet duct of the first SCR reactor 4, and the second parallel valve 51 is installed on the flue gas inlet duct of the second SCR reactor 5. In this application, the second parallel valve 51 is positioned between the series control valve 52 and the flue gas inlet of the second SCR reactor 5, ensuring that the closure of the series control valve 52 does not affect the use of the second parallel valve 51. That is, in this application, either the first SCR reactor 4 or the second SCR reactor 5 can be selected for the denitrification reaction independently. This ensures that even if one SCR reactor fails, the system can still operate normally.

[0029] A nitrogen oxide detector 7 is installed on the pipeline connecting the GGH heat exchanger 1 to the process tail gas to be treated. When the nitrogen oxide detector 7 detects a low inlet nitrogen oxide concentration, the flue gas can be treated by passing through an SCR reactor and undergoing a first-stage denitrification process. At this time, the series control valve 52 can be closed to put the first SCR reactor 4 and the second SCR reactor 5 into parallel mode, and either SCR reactor can be selected for the denitrification reaction.

[0030] If the nitrogen oxide detector 7 detects a high concentration of nitrogen oxides at the inlet, the series control valve 52 is opened and the second parallel valve 51 is closed, putting the first SCR reactor 4 and the second SCR reactor 5 in series mode. The mixture of process tail gas and ammonia emitted from the flue gas mixer 3 passes through the two SCR reactors in series, undergoing two stages of denitrification reaction, ensuring that the high concentration of NO in the flue gas can be eliminated. X Complete removal is carried out to meet emission requirements.

[0031] In order to control the flue gas volume and inlet velocity of the high-temperature inlet flue gas in the GGH heat exchanger 1, this application also provides a heat exchange regulating valve, which includes: a first heat exchange valve 42 and a second heat exchange valve 43;

[0032] The first heat exchange valve 42 is located between the exhaust port of the first SCR reactor 4 and the high-temperature flue gas inlet of the GGH heat exchanger 1.

[0033] The second heat exchange valve 43 is located between the exhaust port of the second SCR reactor 5 and the high-temperature flue gas inlet of the GGH heat exchanger 1.

[0034] The SCR reactor emits process tail gas that has been denitrified and purified, with a temperature of approximately 230-260℃. This gas is sent to GGH heat exchanger 1 to exchange heat with the process tail gas to be treated. After heat exchange, the exhaust gas is cooled to approximately 140℃ and then discharged into the chimney by an induced draft fan.

[0035] All valves in this application can be operated manually or electrically.

[0036] In this application, both the first SCR reactor 4 and the second SCR reactor 5 adopt a multi-layer fixed-bed design, and each SCR reactor is equipped with a spare layer as a concentration buffer. Specifically, each SCR reactor includes: a multi-layer catalyst bed 11 and a spare catalyst layer 12. At the same time, to prevent the leakage of untreated flue gas, there are sealing designs between the catalyst modules and between the modules and the reactor shell.

Claims

1. A nuclear industry process tail gas treatment device, characterized in that, It includes: GGH heat exchanger, urea pyrolysis furnace, flue gas mixer and SCR reactor group; The low-temperature flue gas inlet of the GGH heat exchanger is connected to a NO-containing... X The inlet pipe of the process exhaust gas to be treated is connected to the high-temperature flue gas outlet of the GGH heat exchanger and the flue gas mixer; the exhaust port of the urea pyrolysis furnace is connected to the flue gas mixer through a pipe. The exhaust port of the flue gas mixer is connected to the SCR reactor group; the SCR reactor group includes: a first SCR reactor and a second SCR reactor; The exhaust port of the flue gas mixer is connected to the first SCR reactor and the second SCR reactor respectively through parallel valves; the exhaust ports of the first SCR reactor and the second SCR reactor are respectively connected to the high-temperature flue gas inlet of the GGH heat exchanger. The exhaust port of the first SCR reactor is connected to the flue gas inlet of the second SCR reactor through a series flue gas duct, and a series control valve is installed on the series flue gas duct.

2. The nuclear industry process tail gas treatment device according to claim 1, characterized in that: A temperature measuring device is installed at the exhaust port of the flue gas mixer.

3. The nuclear industry process tail gas treatment device according to claim 1, characterized in that: An electric heater is installed at the air inlet of the flue gas mixer.

4. The nuclear industry process tail gas treatment device according to claim 1, characterized in that: A nitrogen oxide detector is installed on the pipeline connecting the GGH heat exchanger to the process exhaust gas to be treated.

5. The nuclear industry process tail gas treatment device according to claim 1, characterized in that: The urea pyrolysis furnace is equipped with a dilution air electric heater at the dilution air inlet.

6. The nuclear industry process tail gas treatment device according to claim 1, characterized in that: The parallel valves include: a first parallel valve and a second parallel valve, wherein the first parallel valve is disposed on the flue gas inlet duct of the first SCR reactor, and the second parallel valve is disposed on the flue gas inlet duct of the second SCR reactor; the second parallel valve is disposed between the series control valve and the flue gas inlet of the second SCR reactor.

7. The nuclear industry process tail gas treatment device according to claim 1, characterized in that: It also includes: a heat exchange regulating valve, wherein the heat exchange regulating valve includes: a first heat exchange valve and a second heat exchange valve; The first heat exchange valve is installed between the exhaust port of the first SCR reactor and the high-temperature flue gas inlet of the GGH heat exchanger. The second heat exchange valve is installed between the exhaust port of the second SCR reactor and the high-temperature flue gas inlet of the GGH heat exchanger.

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