A device and method for efficient capture of iodine-containing exhaust gas.

Abstract

This invention relates to an apparatus and method for the efficient capture of iodine-containing exhaust gas, comprising a tower system, a gas supply system, an absorbent system, an exhaust gas detection system, and a control system. Iodine-containing exhaust gas enters from the bottom of the tower system via the gas supply system and flows upward within the tower. The absorbent system enters from the top of the tower system via a nozzle and flows downward. The two gases come into countercurrent contact within the tower. Sodium hydroxide in the absorbent reacts with iodine in the exhaust gas to form iodide, thus converting iodine from the gas phase to the liquid phase, achieving iodine absorption and capture. After absorption and capture, the exhaust gas passes through a demisting section to capture entrained droplets before being discharged from the top of the tower system. The exhaust gas detection system measures the concentration of iodine in the exhaust gas. This method enables efficient gas-liquid contact and mass transfer, and achieves constant-temperature circulation and composition control of the alkaline solution. Through optimized tower structure and control system, it achieves stable and efficient capture of iodine from iodine-containing exhaust gas, possessing good potential for scientific research verification and engineering scale-up.

Description

Technical Field

[0001] This invention belongs to the field of radioactive waste gas treatment, specifically relating to a device and method for the efficient capture of iodine-containing tail gas. Background Technology

[0002] During nuclear fuel reprocessing, spent fuel dissolution exhaust gases contain substances such as... 129 I and 131 Class I radioactive iodine is highly volatile and toxic; direct emission would pose a serious threat to the environment and human health. Currently, methods for treating iodine-containing exhaust gases mainly include adsorption, chemical absorption, and cryogenic condensation. Among these, alkaline absorption is widely studied due to its simplicity and low cost. However, existing laboratory absorption devices generally suffer from uneven gas-liquid distribution, low mass transfer efficiency, insufficient precision in controlling operating parameters, and poor stability during continuous operation, making it difficult to meet the needs of engineering scale-up and process validation.

[0003] Especially in the spray-bubbling combined absorption process, the flow field distribution within the tower, droplet size, and gas-liquid contact efficiency significantly affect the capture effect, while existing devices often lack systematic monitoring and optimization of key hydrodynamic parameters. Furthermore, iodine-containing exhaust gases often contain nitrogen oxides, methyl iodine, and other components, whose influence on the absorption process is complex and requires systematic study using reliable equipment.

[0004] Therefore, there is an urgent need to develop an iodine-containing exhaust gas capture device that is structurally sound, precisely controlled, provides reliable data, and has good repeatability and engineering reference value. Summary of the Invention

[0005] To address the technical shortcomings of existing technologies, such as low gas-liquid mass transfer efficiency and uneven distribution, the present invention aims to provide a device and method for the efficient capture of iodine-containing tail gas. This device is suitable for wet capture and process verification of iodine-containing tail gas in spent fuel reprocessing. By designing a spray-bubbling composite absorption tower structure and optimizing the gas distributor and multi-layer nozzle arrangement within the tower, the gas-liquid two-phase flow state is improved, increasing the contact area and mass transfer efficiency. This overcomes the problems of low capture efficiency and unstable operation caused by uneven flow field distribution in traditional absorption towers. A high-precision temperature, pressure, flow rate, and liquid level monitoring and control unit is integrated to achieve precise control of key process parameters such as absorbent temperature (control accuracy ±1℃), gas flow rate (control accuracy ±0.1 m³ / h), and liquid-to-gas ratio, ensuring the repeatability of the experimental process and the reliability of the data.

[0006] By integrating functional modules such as absorption reaction, tail gas detection and data processing, a complete wet capture research platform for iodine-containing tail gas is formed, which supports kinetic research, process optimization and fluid dynamics verification, improves the system integration and scientific research applicability of the device, and provides direct basis for subsequent engineering scale-up.

[0007] For radioactive exhaust gas treatment environments, a control system with safety interlocks, over-limit alarms, and remote operation functions is designed. Key components adopt modular structures and corrosion-resistant materials, supporting rapid disassembly and remote maintenance, reducing personnel operation risks, and enhancing operational safety and equipment reliability in radioactive environments.

[0008] With replaceable nozzles, adjustable gas distribution structure and multi-section tower design, it supports performance testing and optimization under different operating conditions and structural configurations, providing a scalable and optimizable equipment platform with good adaptability, scalability and engineering transformation potential.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: Firstly, the present invention discloses a device for the efficient capture of iodine-containing tail gas. The system includes: a tower system, a gas supply system, an absorbent system, a tail gas detection system, and a control system. The tower system is used to achieve wet capture of iodine-containing tail gas; the gas supply system is used to transport the iodine-containing tail gas at a preset flow rate; the absorbent system is used to transport the absorbent and recycle it; the tail gas detection system is used to analyze the concentration of the iodine-containing tail gas after absorption and capture by the absorbent and to treat the tail gas; the control system is used to regulate the flow rate of the iodine-containing tail gas and the absorbent, control the temperature of the storage tank, and... The system controls valve switching, monitors temperature and liquid level, displays equipment operating status and data, stores data, and provides fault alarms. Iodine-containing tail gas enters from the bottom of the tower system via the gas supply system and is delivered to the gas distributor, flowing upwards within the tower. The absorbent enters the nozzle from the top of the tower system via the absorbent system and flows downwards. The two react counter-currently within the tower, where sodium hydroxide in the absorbent reacts with iodine in the tail gas to form iodide, thus converting iodine from the gas phase to the liquid phase, achieving iodine absorption and capture. After absorption and capture, the tail gas passes through a demisting section to capture entrained droplets before being discharged from the top of the tower system. The tail gas concentration is measured by a tail gas detection system.

[0010] Furthermore, the tower system includes an absorption tower, a gas inlet, a gas outlet, and an absorbent inlet. The absorption tower has a spray section, a bubbling section, and a demister section. A gas distributor and multiple layers of spray nozzles are installed inside the tower. The gas inlet is located at the bottom of the absorption tower, allowing the iodine-containing tail gas supplied by the gas supply system to enter from the bottom of the absorption tower and connect to the gas distributor at the bottom of the absorption tower via a connecting pipe. The gas outlet is located at the top of the tower, for discharging the absorbed tail gas. The absorbent inlet is located at the top of the tower, for allowing the absorbent supplied by the absorbent system to enter the absorption tower from the top of the tower system and spray downwards through nozzles located at the top of the absorption tower.

[0011] Furthermore, the absorbent system includes an absorbent storage tank, a constant flow pump, a heating device, and a piping system. The absorbent storage tank is connected to the constant flow pump and is used for preparing, temporarily storing, heating, and supplying the absorbent. The constant flow pump is used for conveying and metering the absorbent. The heating device is used to heat the absorbent to a set temperature. The piping system is used to connect the various components. The absorbent in the absorbent storage tank is heated to a set temperature by the heating device and then conveyed by the constant flow pump to the liquid inlet at the top of the tower to capture iodine in the tail gas. After capture, it is discharged from the liquid outlet at the bottom of the tower and enters the absorbent storage tank for recycling.

[0012] Furthermore, the exhaust gas detection system includes an exhaust gas sampling port, an absorption tank, and an ion chromatograph. The exhaust gas sampling port is located on the exhaust gas outlet pipeline, and the absorption tank is connected to the exhaust gas outlet pipeline. The exhaust gas sampling port is used to sample the exhaust gas after it has been captured. The absorption tank is used to absorb the sampled exhaust gas and convert it into a liquid for easy detection of iodine concentration. The ion chromatograph is used to analyze the sample after absorption.

[0013] Furthermore, after absorbing iodine, the absorbent is discharged from the bottom of the tower system and recycled through the absorbent system. The concentration is monitored regularly, and the absorbent is replaced when necessary.

[0014] Furthermore, the spray section is equipped with multiple layers of nozzles, including hollow cone nozzles, spiral nozzles, fan-shaped nozzles, and solid cone nozzles; the bubbling section is equipped with a gas distributor.

[0015] Furthermore, the absorbent system is composed of a mixed solution of 0.05~1 mol / L NaOH and 0~0.05 mol / L N2H4•H2O, with a temperature control accuracy of ±1℃ and a flow control accuracy of ±0.1 m³ / h.

[0016] Secondly, the present invention discloses a device for the efficient capture of iodine-containing exhaust gas. The device for the efficient capture of iodine-containing exhaust gas, as described in the first aspect of the present invention and any optional embodiment thereof, is used to capture the iodine-containing exhaust gas. The method includes the following steps:

[0017] S1. Start the absorption liquid system and control the temperature of the absorption liquid within the range of 60~80℃, preferably 65℃;

[0018] S2. Introduce iodine-containing exhaust gas at the preset flow rate;

[0019] S3. Perform gas-liquid countercurrent contact absorption under the set liquid-to-gas ratio of 28~556 L / m³.

[0020] S4. After the exhaust gas is demisted, it is sampled and tested to achieve real-time monitoring and verification of iodine capture efficiency.

[0021] The beneficial technical effects of this invention are as follows: This invention discloses a device and method for efficient capture of iodine-containing exhaust gas, which addresses the shortcomings of existing experimental devices in terms of gas-liquid mass transfer efficiency, parameter control accuracy, operational stability, and data reliability. Specifically, the beneficial effects are reflected in:

[0022] (1) Through the spray-bubbling composite absorption structure, efficient contact and mass transfer between the gas and liquid phases are achieved, and the iodine capture rate reaches 97%-99%.

[0023] (2) It adopts a multi-layer replaceable nozzle design to support research on different atomization characteristics and adapt to various operating conditions.

[0024] (3) Integrating high-precision detection and control units ensures that process parameters are accurate and controllable and experimental data are reliably repeatable.

[0025] (4) Modular structure design, which facilitates disassembly, maintenance and functional expansion.

[0026] (5) A complete safety protection system to ensure long-term stable operation of the equipment.

[0027] It is particularly suitable for scientific research work such as process research, kinetic parameter determination, and operating condition optimization of wet capture of iodine-containing tail gas, providing reliable technical basis for engineering scale-up. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a device for efficient capture of iodine-containing exhaust gas, as shown in Embodiment 1 of the present invention. Detailed Implementation

[0029] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] like Figure 1 As shown, this embodiment of the invention provides a device for efficient capture of iodine-containing exhaust gas, including a tower system, a gas supply system, an absorbent system, an exhaust gas detection system, and a control system.

[0032] The tower system is used for wet capture of iodine-containing tail gas; the gas supply system is used to deliver iodine-containing tail gas at a preset flow rate; the absorbent system is used to deliver the absorbent and recycle it; the tail gas detection system is used to analyze and detect the concentration of iodine-containing tail gas after absorption and capture by the absorbent and to treat the tail gas; the control system is used to regulate the flow rate of iodine-containing tail gas and absorbent, control the temperature of the storage tank, control the valve opening and closing, monitor the temperature and liquid level, display the equipment operating status and data, store data, and provide fault alarms.

[0033] Iodine-containing exhaust gas enters from the bottom of the tower system via the gas supply system and is delivered to the gas distributor, flowing upwards within the tower. The absorbent liquid enters the nozzle from the top of the tower system via the absorbent liquid system and flows downwards. The two gases come into countercurrent contact within the tower. Sodium hydroxide in the absorbent liquid reacts with iodine in the exhaust gas to form iodides, thus converting the iodine from the gas phase to the liquid phase, achieving iodine absorption and capture. After absorption and capture, the exhaust gas passes through a demister section to capture entrained droplets before being discharged from the top of the tower system. The exhaust gas concentration is measured by an exhaust gas detection system. The absorbent liquid, after absorbing iodine, is discharged from the bottom of the tower system and recycled through the absorbent liquid system. The concentration is monitored periodically, and the absorbent liquid is replaced when necessary.

[0034] (1) Tower system

[0035] The tower system includes an absorption tower, a gas inlet, a gas outlet, a top cover, an absorbent inlet, a demister, and nozzles. The gas inlet is located at the top of the absorption tower, allowing gas to enter from the top and connecting to a gas distributor at the top of the tower via a connecting pipe. The gas outlet is located at the top of the tower to discharge the absorbed tail gas. The top cover is detachably connected to the absorption tower. All vulnerable components, such as the gas distributor, demister, and nozzles, are fixed to the top cover and can be lifted out for remote maintenance and replacement. The absorbent inlet is connected to the nozzles. The demister captures liquid droplets entrained in the gas, and the nozzles are connected to the absorbent to disperse the absorbent. The nozzles are arranged in three layers to avoid channeling and ensure full contact between the absorbent and the gas. The gas distributor is located at the bottom of the absorption tower and connected to the gas inlet, ensuring uniform dispersion of the iodine-containing tail gas and allowing it to fully react with the iodine in the absorbent.

[0036] The tower system adopts a vertical spray bubbling absorption tower structure, with a total height of 2060±10 mm and an inner diameter of 100±2 mm. The tower body is made of 316L stainless steel, which is corrosion-resistant and high-temperature resistant. The tower body is divided into three functional sections from top to bottom:

[0037] Demisting section: 160 mm high, with a built-in demister to effectively remove liquid droplets entrained in the exhaust gas;

[0038] Spray section: 1400 mm high, equipped with three layers of spray devices, each layer is equipped with a replaceable nozzle. The nozzle types include hollow cone nozzles, spiral nozzles, fan nozzles and solid cone nozzles. The spray density can be adjusted within the range of 10-60 m³ / m² / h.

[0039] Bubbling section: 500 mm in height, with a gas distributor at the bottom. The distributor has an aperture of 2 mm and an opening rate of 30% to ensure uniform gas distribution.

[0040] (2) Gas supply system

[0041] The gas supply system is used to deliver iodine-containing exhaust gas at a preset flow rate.

[0042] (3) Absorption liquid system

[0043] The absorbent system includes an absorbent storage tank, a constant flow pump, a heating device, and a piping system. The absorbent storage tank is used for preparing, temporarily storing, heating, and supplying the absorbent, and is connected to the constant flow pump; the constant flow pump is used for transporting and metering the absorbent; the heating device heats the absorbent to a set temperature; and the piping system connects the pipes of each component.

[0044] The absorbent in the absorbent storage tank is heated to a set temperature by a heating device, and then pumped to the liquid inlet at the top of the tower by a constant flow pump to capture iodine in the tail gas. After capture, it is discharged from the liquid outlet at the bottom of the tower and enters the absorbent storage tank for recycling.

[0045] The absorption liquid system includes:

[0046] Absorbent storage tank: 100 L capacity, with liquid level display and heating function;

[0047] Constant flow pump: flow range 0.1-1.0 m³ / h, control accuracy ±0.01 m³ / h;

[0048] Heating device: Temperature control range: room temperature - 90℃, control accuracy: ±1℃;

[0049] Piping system: All piping is made of 316L stainless steel and covered with an external insulation layer.

[0050] (4) Exhaust gas detection system

[0051] The exhaust gas detection system includes an exhaust gas sampling port, an absorption tank, and an ion chromatograph. The exhaust gas sampling port is located on the exhaust gas outlet pipeline to sample the exhaust gas after it has been captured; the absorption tank is used to absorb the sampled exhaust gas, converting it into a liquid for easy detection of iodine concentration; and the ion chromatograph is used to analyze the sample after absorption.

[0052] The exhaust gas detection system includes:

[0053] Exhaust gas sampling port: located on the outlet pipe at the top of the tower;

[0054] Absorption tanks: two connected in series, each containing 200 ml of 0.01 mol / L NaOH absorption solution;

[0055] Ion chromatograph: Equipped with an AS16 anion analysis column, detection limit 0.1 mg / m³.

[0056] (5) Control system

[0057] The control system is used to realize temperature monitoring, pressure monitoring, flow monitoring, liquid level monitoring, data recording, safety interlocking and remote operation of the device.

[0058] The control system adopts a PLC + touch screen architecture and has the following functions:

[0059] Temperature monitoring: 8 temperature measuring points, accuracy ±0.5℃;

[0060] Pressure monitoring: 4 pressure measurement points, accuracy ±0.5%;

[0061] Flow monitoring: 3 flow meters, accuracy ±1%;

[0062] Liquid level monitoring: 2 liquid level sensors, accuracy ±10 mm;

[0063] Data logging: Automatically records all process parameters, with an adjustable storage interval of 1-60 minutes;

[0064] Safety interlock: Automatic alarm and shutdown for over-temperature, over-pressure, and leakage;

[0065] Remote operation: Supports remote computer monitoring.

[0066] Example 2

[0067] An experiment was conducted using a device for efficient capture of iodine-containing exhaust gas provided in this embodiment of the invention. Specific parameters are as follows: absorbent composition: 1 mol / L NaOH + 0.05 mol / L N2H4•H2O; absorbent temperature: 65℃; gas composition: NO2 500 mg / m³, total iodine 100 mg / m³ (99.5% gaseous iodine, 0.5% methyl iodine); gas flow rate: 6 m³ / h; spray density: 35 m³ / m² / h.

[0068] Results: The iodine capture rate remained stable at 98.8%, and the system operated continuously for 72 hours without failure.

[0069] Example 3

[0070] The effect of absorbent temperature on iodine capture rate was investigated using a device for efficient capture of iodine-containing exhaust gas provided in an embodiment of the present invention: absorbent temperatures were 60℃, 65℃, 70℃, 75℃, and 80℃, and other conditions were the same as in Embodiment 2;

[0071] Results: The iodine capture rate first increased and then decreased with increasing temperature, reaching the highest capture rate of 98.9% at 65℃.

[0072] Example 4

[0073] The effect of gas throughput (liquid-to-gas ratio) on iodine capture rate was investigated using a device for efficient capture of iodine-containing exhaust gas provided in an embodiment of the present invention: gas flow rates were 6, 7, 8, 9, and 10 m³ / h (liquid-to-gas ratios of 46, 40, 34, 30, and 28 L / m³); other conditions were the same as in Embodiment 2.

[0074] Results: As the gas flow rate increased (liquid-to-gas ratio decreased), the iodine capture rate gradually decreased, but it still reached 97.4% at 10 m³ / h.

[0075] Example 5

[0076] The nozzle atomization characteristics were studied using the device for efficient capture of iodine-containing exhaust gas provided in Embodiment 1 of the present invention: four types of nozzles, namely hollow cone, spiral, fan-shaped, and solid cone, were selected respectively; the atomization angle and droplet size distribution were measured under the same hydraulic conditions.

[0077] Results: The hollow cone nozzle has the best atomization effect, with an atomization angle of 90~100° and uniform droplet size distribution, making it suitable for this device.

[0078] As can be seen from the above embodiments, the device and method for efficient capture of iodine-containing tail gas disclosed in this invention can achieve high-precision coordinated control of multiple parameters, achieve efficient gas-liquid contact and mass transfer, and achieve constant temperature circulation and composition regulation of alkaline solution. Through optimized tower structure and control system, it can achieve stable and efficient capture of iodine in iodine-containing tail gas, and has good potential for scientific research verification and engineering scale-up.

[0079] The apparatus and method described in this invention are not limited to the embodiments described in the specific implementation. Other implementation methods derived by those skilled in the art based on the technical solution of this invention also fall within the scope of technical innovation of this invention.

Claims

1. A device for efficient capture of iodine-containing exhaust gas, characterized in that: The system includes a tower system, a gas supply system, an absorbent system, a tail gas detection system, and a control system. The tower system is used for wet capture of iodine-containing tail gas. The gas supply system is used to deliver iodine-containing tail gas at a preset flow rate. The absorbent system is used to deliver the absorbent and recycle it. The tail gas detection system is used to analyze the concentration of the iodine-containing tail gas after absorption and capture by the absorbent and to treat the tail gas. The control system is used to regulate the flow rate of iodine-containing tail gas and absorbent, control the temperature of the storage tank, control valve opening and closing, monitor temperature and liquid level, and monitor equipment operation. The system displays status and data, stores data, and provides fault alarms. Iodine-containing exhaust gas enters from the bottom of the tower system via the gas supply system and is delivered to the gas distributor, where it flows upwards. The absorbent liquid enters the nozzle from the top of the tower system via the absorbent liquid system and flows downwards. The two gases come into countercurrent contact within the tower. The sodium hydroxide in the absorbent liquid reacts with the iodine in the exhaust gas to form iodide, thus converting the iodine from the gas phase to the liquid phase, achieving iodine absorption and capture. After absorption and capture, the exhaust gas passes through a demisting section, where entrained droplets are captured, and it is discharged from the top of the tower system. The exhaust gas concentration is measured by the exhaust gas detection system.

2. The device for efficient capture of iodine-containing exhaust gas according to claim 1, characterized in that: The tower system includes an absorption tower, a gas inlet, a gas outlet, and an absorbent inlet. The absorption tower has a spray section, a bubbling section, and a demister section. A gas distributor and multiple layers of spray nozzles are installed inside the tower. The gas inlet is located at the bottom of the absorption tower, allowing the iodine-containing tail gas supplied by the gas supply system to enter from the bottom of the absorption tower and connect to the gas distributor at the bottom of the absorption tower via a connecting pipe. The gas outlet is located at the top of the tower, used to discharge the absorbed tail gas. The absorbent inlet is located at the top of the tower, used to allow the absorbent supplied by the absorbent system to enter the absorption tower from the top of the tower system and spray downwards through nozzles located at the top of the absorption tower.

3. The device for efficient capture of iodine-containing exhaust gas according to claim 1, characterized in that: The absorbent system includes an absorbent storage tank, a constant flow pump, a heating device, and a piping system. The absorbent storage tank is connected to the constant flow pump and is used for preparing, temporarily storing, heating, and supplying the absorbent. The constant flow pump is used for conveying and metering the absorbent. The heating device is used to heat the absorbent to a set temperature. The piping system is used to connect the various components. The absorbent in the absorbent storage tank is heated to a set temperature by the heating device and then conveyed by the constant flow pump to the liquid inlet at the top of the tower to capture iodine in the tail gas. After capture, it is discharged from the liquid outlet at the bottom of the tower and enters the absorbent storage tank for recycling.

4. The device for efficient capture of iodine-containing exhaust gas according to claim 1, characterized in that: The exhaust gas detection system includes an exhaust gas sampling port, an absorption tank, and an ion chromatograph. The exhaust gas sampling port is located on the exhaust gas outlet pipeline, and the absorption tank is connected to the exhaust gas outlet pipeline. The exhaust gas sampling port is used to sample the exhaust gas after it has been captured. The absorption tank is used to absorb the sampled exhaust gas and convert it into a liquid for easy detection of iodine concentration. The ion chromatograph is used to analyze the sampled and absorbed exhaust gas.

5. The device for efficient capture of iodine-containing exhaust gas according to claim 1, characterized in that: After absorbing iodine, the absorbent is discharged from the bottom of the tower system and recycled through the absorbent system. The concentration is monitored regularly and replaced when necessary.

6. The device for efficient capture of iodine-containing exhaust gas according to claim 2, characterized in that: The spray section is equipped with multiple layers of nozzles, including hollow cone nozzles, spiral nozzles, fan-shaped nozzles and solid cone nozzles; the bubbling section is equipped with a gas distributor.

7. A device for efficient capture of iodine-containing exhaust gas according to any one of claims 1-6, characterized in that: The absorbent system consists of a mixed solution of 0.05~1 mol / L NaOH and 0~0.05 mol / L N2H4•H2O. The temperature control accuracy of the absorbent is ±1℃, and the flow control accuracy is ±0.1 m³ / h.

8. A method for efficient capture of iodine-containing exhaust gas, comprising capturing the iodine-containing exhaust gas using a device for efficient capture of iodine-containing exhaust gas as described in any one of claims 1-7, characterized in that: The method includes the following steps: S1. Start the absorption liquid system and control the temperature of the absorption liquid within the range of 60~80℃, preferably 65℃; S2. Introduce iodine-containing exhaust gas at the preset flow rate; S3. Perform gas-liquid countercurrent contact absorption under the set liquid-to-gas ratio of 28~556 L / m³. S4. After the exhaust gas is demisted, it is sampled and tested to achieve real-time monitoring and verification of iodine capture efficiency.

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