Gas conversion apparatus and method

Abstract

The present application relates to spectrum technology, and specifically provides a gas conversion device and method, the conversion device comprising a flow cell and a light source, the flow cell having an inlet, a channel and an outlet in sequence, and the light source emitting excitation light through the channel; a gas inlet joint is arranged at the inlet and has an inner diameter increasing section allowing gas to pass through. The present application has the advantages of high conversion efficiency.

Description

Technical Field

[0001] This invention relates to spectroscopy, and more particularly to gas conversion apparatus and methods. Background Technology

[0002] Nitrogen oxides (NOx) are key components of atmospheric chemistry, and their environmental effects involve multiple dimensions, including ozone layer dynamics, regional climate change, and human health. NOx is mainly composed of nitric oxide (NO) and nitrogen dioxide (NO2), and their spatiotemporal distribution in the atmosphere is influenced by multiple factors, including biological emissions, industrial activities, traffic sources, and photochemical reactions. NO2, as a core participant in the atmospheric photochemical cycle, is crucial for accurately monitoring not only to elucidate the mechanisms of secondary pollutant formation but also for formulating scientific emission reduction policies.

[0003] Currently, NOx measurement methods can be divided into two technical paths based on their detection principles: 1. The first category of technologies based on direct NO2 detection and NO to NO2 conversion includes the Saltzman method, the Luminox method, the Tunable Diode Laser Absorption Spectroscopy (TDLAS), the Differential Absorption Spectroscopy (DOAS), the Cavity Ring-down Spectroscopy (CRDS), and the Laser-Induced Fluorescence (LIF) method.

[0004] 2. The second category is based on direct NO detection and NO2 to NO conversion technology, including molybdenum catalytic conversion-chemiluminescence method and photolysis-chemiluminescence method (P-CL).

[0005] Photolysis-chemiluminescence (P-CL) works by utilizing the principle that NO2, when irradiated with light in a specific wavelength range (λ < 420 nm), photolyzes into NO and O atoms. The NO product is then detected using chemiluminescence to determine the NOx concentration. This method effectively avoids cross-interference by selecting a light source in a specific wavelength range, thereby improving the accuracy of NOx concentration measurements.

[0006] The photolysis device is the core component of a nitrogen oxide analysis instrument based on photolysis conversion-chemiluminescence method. Many scholars have conducted relevant research on the design and implementation of this device.

[0007] US Patent 7238328 discloses a photoconverter based on a solid-state light source. This converter mainly includes a reaction chamber made of a high diffuse reflectance material (such as polytetrafluoroethylene or barium sulfate), at least one ultraviolet solid-state light source (such as an LED or diode laser) with an emission wavelength in the 350-420 nm range, gas inlet and outlet pipes, and optional heat dissipation devices or thermoelectric cooling modules. The patent also explicitly proposes a single-channel system for nitrogen oxide detection, the principle of which is: using the same gas path and the same reaction chamber, nitric oxide and nitrogen oxides are measured separately by switching the illumination state. However, this scheme does not consider the airflow within the reaction chamber and does not include any device to homogenize the airflow. Turbulence occurs in the airflow within the reaction chamber, resulting in inconsistent residence times of gas molecules and low conversion efficiency.

[0008] US Patent 11435291 discloses a photolysis converter for converting reactant molecules in a fluid sample into product molecules using electromagnetic radiation. The converter includes a reaction chamber, an electromagnetic radiation source, an inlet pipe, and an outlet pipe. At least one of the pipes extends into the reaction chamber, allowing for orderly airflow within the chamber. This orderly flow reduces the likelihood of recombination reactions between photolysis products, thus improving conversion efficiency. However, extending the inlet or outlet pipe into the reaction chamber not only increases the complexity and manufacturing cost of the photolysis device, but the flow guiding structure within the reaction chamber can also obstruct electromagnetic radiation and airflow, thereby affecting the photolysis conversion efficiency. Furthermore, the pipes used as flow guiding structures are typically made of glass, which is fragile and requires careful installation and handling.

[0009] Chinese patent CN102445415B discloses a nitrogen dioxide photolysis device. This device includes a light source system, a gas path system, and a heat dissipation system. The photolysis of nitrogen dioxide is achieved by arranging the light source system opposite to each other on the upper and lower sides of the quartz gas path system, supplemented by a heat dissipation system for the light source. The axial direction of the quartz tube used in the gas path system is the same as the airflow direction, resulting in orderly airflow within the device. However, to ensure sufficient residence time of the gas under electromagnetic radiation, multiple LEDs need to be arranged axially, leading to a complex heat dissipation system, large size, and high cost. Furthermore, the gas path system uses a quartz tube, which is relatively fragile, requiring careful installation and handling.

[0010] Based on the above technical solutions, existing photolysis devices have the following drawbacks: 1. Some existing devices do not consider the issue of gas flow uniformity, resulting in turbulence in the reaction chamber, inconsistent residence time of gas molecules, and low conversion efficiency.

[0011] 2. Some photolysis devices improve conversion efficiency by extending the inlet / outlet pipes into the reaction chamber to achieve orderly airflow. However, this extension increases the structural complexity and manufacturing cost of the device. Furthermore, the pipes extending into the reaction chamber as flow guides can obstruct radiation and airflow, thus affecting photolysis conversion efficiency. To reduce the obstruction of radiation by the flow guide structure, these photolysis devices typically use quartz as the flow guide material. However, quartz is fragile and requires careful installation and handling.

[0012] 3. Some photolysis devices employ a design that arranges multiple light sources along the axial direction of the quartz tube. While this effectively avoids turbulence issues, it increases the complexity of the heat dissipation system and raises costs. Furthermore, the quartz tube itself is relatively fragile, requiring careful installation and handling. Summary of the Invention

[0013] To address the shortcomings of the existing technical solutions, the present invention provides a gas conversion device.

[0014] The objective of this invention is achieved through the following technical solution: A gas conversion device includes a flow cell and a light source. The flow cell has an inlet, a channel, and an outlet. Gas flows sequentially through the inlet, the channel, and the outlet. Excitation light emitted by the light source passes through the channel. The conversion device further includes: A vent connector is provided at the inlet and has an internally enlarged section that allows gas to pass through.

[0015] Another objective of this invention is to provide a gas conversion method, which is achieved through the following technical solution: The gas conversion method includes the following steps: The gas enters the larger inner diameter section of the gas connector, expands, and then passes through the inlet into the channel in the flow pool. Excitation light emitted from the light source passes through the channel, causing the components in the gas to transform, and then it is discharged from the outlet.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This application introduces a conical ventilation connector, which eliminates the need for a flow guide structure extending into the reaction chamber, thereby guiding the airflow to achieve orderly flow and significantly improving the conversion efficiency of the photolysis reaction. This avoids obstructing radiation and airflow, ensuring a more uniform distribution of the radiation field and airflow within the reaction chamber, and further guaranteeing efficient conversion; The reaction chamber made of metal has higher mechanical strength than that made of glass, which greatly reduces the risk of breakage. Attached Figure Description

[0017] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are merely illustrative of the technical solutions of this invention and are not intended to limit the scope of protection of this invention. In the drawings: Figure 1 This is a schematic diagram of the conversion device according to the present invention; Figure 2 This is a streamlined schematic diagram of the conversion device according to the present invention.

[0018] In the attached diagram, 11-flow pool, 111-inlet, 112-outlet, 113-channel, 21-light source, 31-heat sink, 41-ventilation connector, 411-first section, 412-inner diameter increasing section, 413-second section. Detailed Implementation

[0019] Figures 1-2 The following description illustrates optional embodiments of the invention to teach those skilled in the art how to implement and reproduce the invention. Some conventional aspects have been simplified or omitted to explain the technical solutions of the invention. Those skilled in the art should understand that variations or substitutions derived from these embodiments will be within the scope of the invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the invention. Therefore, the invention is not limited to the following optional embodiments, but is defined only by the claims and their equivalents.

[0020] Example 1

[0021] The gas conversion device of this invention, such as Figure 1 As shown, it includes: The flow cell 11 and the light source 21 are provided. The flow cell 11 has an inlet 111, a channel 113 and an outlet 112. Gas passes through the inlet 111, the channel 113 and the outlet 112 in sequence. The excitation light emitted by the light source 21 passes through the channel 113, thereby converting some components in the gas in the channel 113, such as nitrogen dioxide.

[0022] The vent connector 41 is located at the inlet 111 and has a first section 411, an inner diameter increasing section 412, and a second section 413 that allow gas to pass through sequentially. The cone angle of the inner diameter increasing section 412 is no greater than 14 degrees.

[0023] To avoid turbulence, the inner diameter of the first section 411 is the same as the inner diameter of the gas pipe connecting the first section 411, the inner diameter of the second section 413, the inner diameter of the inlet 111, and the inner diameter of the channel 113 are the same, and the depth of the inlet 111 is less than the wall thickness of the flow pool 11.

[0024] The conversion efficiency CE of nitrogen dioxide in the flow cell 11 satisfies: CE=Aexp(-k2·B)[1-exp(-k1·B)]+C, B=0.785D 2 ·L / Q.

[0025] D is the inner diameter of the flow cell 11, Q is the gas flow rate entering the vent connector 41, L is the length of the hollow interior of the flow cell 11, and A, k1, k2 and C are all constants.

[0026] Within a certain range, the conversion efficiency CE increases with the increase of parameter B. However, an excessively large parameter B will increase the recombination reaction between photolysis products, thus leading to a decrease in conversion efficiency. With a fixed volume of the flow cell 11, parameter B can be adjusted by adjusting the inlet / outlet flow rate Q to optimize the conversion efficiency. Conversely, with a fixed inlet / outlet flow rate Q, parameter B can be adjusted by adjusting the volume of channel 113 (reaction chamber) to optimize the conversion efficiency.

[0027] To further reduce the risk of breakage, the flow cell 11 is made of metal and has an internal polishing treatment.

[0028] The gas conversion method of this invention, i.e., the working method of the conversion device of this embodiment, includes the following steps: Gas enters the inner diameter-enlarging section 412 of the gas connector 41, expands, and then passes through the inlet 111 and enters the channel 113 in the flow pool 11.

[0029] The excitation light emitted by the light source 21 passes through the channel 113, the components in the gas are transformed, and then discharged from the outlet 112.

[0030] Example 2

[0031] Application examples of the gas conversion apparatus and method according to Embodiment 1 of the present invention.

[0032] In this application example, such as Figure 1 As shown, the flow cell 11 is made of metal and is cylindrical in shape. Inside is a cylindrical channel 113, and the inner wall of the flow cell 11 adjacent to the channel 113 is polished.

[0033] The toothed radiators 31 are fixed at both ends of the flow pool 11.

[0034] The two light sources 21 are narrowband LEDs with a center wavelength of 395nm, and the power is adjustable from 10W to 100W.

[0035] A vent connector 41 is located at the inlet 111 and has a first section 411, an inner diameter-enlarging section 412, and a second section 413 (depth h1) that allows gas to pass through sequentially. The cone angle β(2α) of the inner diameter-enlarging section 412 is no greater than 14 degrees. The inner diameter d of the first section 411 is the same as the inner diameter of the gas pipe connecting the first section 411. The inner diameter D1 of the second section 413, the inner diameter D1 of the inlet 111, and the inner diameter D of the channel 113 are the same. The depth h2 of the inlet 111 is 0.5 times the wall thickness of the flow pool 11.

[0036] In this embodiment, d=4.35mm, cone angle β=10 degrees, h1+h2=16mm, and D=16mm.

[0037] Under the illumination of the light emitted from light source 21, the photolysis reaction of NO2 is as follows: NO2 + hv → NO + O.

[0038] The conversion efficiency CE of nitrogen dioxide in the flow cell 41 satisfies: CE=Aexp(-k2·B)[1-exp(-k1·B)]+C, B=0.785D 2 ·L / Q.

[0039] Q is the gas flow rate, L is the length of the flow cell 11, A≈11.1585, k1≈1.2079, k2≈0.1761, C≈89.0019.

[0040] In this embodiment, when parameter B is between 1.4s and 1.8s, the conversion efficiency reaches over 96%.

[0041] The nitrogen oxide conversion method based on the conversion device of this embodiment is as follows: The gas passes sequentially through the first section 411, the inner diameter increasing section 412, and the second section 413, then through the inlet 111 and into the channel 113 within the flow cell 11. The gas expands as it passes through the inner diameter increasing section 412.

[0042] The reverse light emitted by the first light source 11 and the second light source 12 enters the channel 113, and the nitrogen dioxide in the gas undergoes a photolysis reaction to generate nitric oxide.

[0043] The generated nitric oxide is discharged from outlet 112 and sent downstream for analysis.

[0044] To characterize the uniformity of the airflow trajectory distribution, a uniformity index U is established.

[0045] U=0.165713·Q-0.000349·α-0.003081·k-0.080835·Q 2+0.000310·α 2 +0.000228·k 2 -0.044652·Q·α-0.008629·Q·k-0.000218·α·k, k=(D / d) 2 .

[0046] When the uniformity index U>0.65, the flow trajectory is smooth, with no obvious dead zones or backflow, and the overall airflow is relatively uniform.

[0047] When the uniformity index U ≤ 0.65, significant backflow zones or local turbulence often appear in the flow trajectory, indicating non-uniformity. U = 0.65 is used as the threshold for judging the quality of airflow uniformity.

[0048] In this embodiment, when the intake flow rate Q = 0.3 L / min, U = 0.7029 > 0.65, indicating that the airflow of the conversion device in this embodiment is relatively uniform.

[0049] like Figure 2 As shown, the airflow in the reaction chamber (channel 113) is highly ordered, ensuring that the airflow traces in the reaction chamber are almost equal in length, which fundamentally guarantees the uniformity of the residence time of gas molecules.

[0050] Example 3

[0051] An application example of the gas conversion apparatus and method according to Embodiment 1 of the present invention differs from Embodiment 2 in that: d=4.35mm, cone angle β=8 degrees, h1+h2=12mm, D=14mm.

Claims

1. A gas conversion device, comprising a flow cell and a light source, wherein the flow cell has an inlet, a channel, and an outlet, and gas sequentially passes through the inlet, the channel, and the outlet, and excitation light emitted by the light source passes through the channel; characterized in that, The conversion device further includes: A vent connector is provided at the inlet and has an internally enlarged section that allows gas to pass through.

2. The conversion apparatus according to claim 1, characterized in that, The vent connector also has a first section and a second section that allow gas to pass through. Gas passes through the first section, the inner diameter increasing section and the second section in sequence. The cone angle of the inner diameter increasing section is no greater than 14 degrees.

3. The conversion apparatus according to claim 2, characterized in that, The inner diameter of the first section is the same as the inner diameter of the gas pipe connecting the first section, and the inner diameter of the second section, the inner diameter of the inlet, and the inner diameter of the channel are the same.

4. The conversion apparatus according to claim 1, characterized in that, The conversion efficiency CE of nitrogen dioxide in the flow cell satisfies: CE=Aexp(-k2·B)[1-exp(-k1·B)]+C,B=0.785D 2 ·L / Q; D is the inner diameter of the flow cell, Q is the gas flow rate into the vent, L is the length of the hollow interior of the flow cell, and A, k1, k2 and C are all constants.

5. The conversion apparatus according to claim 2, characterized in that, The uniformity index U > 0.65; U=0.165713·Q-0.000349·α-0.003081·k-0.080835·Q 2 +0.000310·a 2 +0.000228·k 2 -0.044652·Q·α-0.008629·Q·k-0.000218·α·k,k=(D / d) 2 ; Q is the gas flow rate entering the vent connector, α is 0.5 times the cone angle, D is the inner diameter of the flow cell, and d is the inner diameter of the first section.

6. The conversion apparatus according to claim 1, characterized in that, The flow cell is made of metal and has an internal polishing treatment.

7. A gas conversion method, characterized in that, The conversion method includes the following steps: The gas enters the larger inner diameter section of the gas connector, expands, and then passes through the inlet into the channel in the flow pool. Excitation light emitted from the light source passes through the channel, causing the components in the gas to transform, and then it is discharged from the outlet.

8. The conversion method according to claim 7, characterized in that, The gas passes sequentially through the first section, the inner diameter increasing section, and the second section inside the vent connector, wherein the cone angle of the inner diameter increasing section is no greater than 14 degrees.

9. The conversion method according to claim 8, characterized in that, The inner diameter of the first section is the same as the inner diameter of the gas pipe connecting the first section, and the inner diameter of the second section, the inner diameter of the inlet, and the inner diameter of the channel are the same.

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